HK1147973B

HK1147973B - Process for producing polyamide resin film and polyamide resin film obtained by the process

Info

Publication number: HK1147973B
Application number: HK11102078.8A
Authority: HK
Inventors: 坪内健二; 野田敦子; 桑田秀树
Original assignee: 尤尼吉可株式会社
Priority date: 2007-11-08
Filing date: 2008-11-07
Publication date: 2015-09-25

Description

Method for producing polyamide resin film and polyamide resin film obtained by the method

Technical Field

The present invention relates to a method for producing a polyamide resin film and a polyamide resin film obtained by the method.

Background

Biaxially oriented polyamide resin films mainly composed of nylon are tough, excellent in gas barrier properties, pinhole resistance, transparency, printability and the like, and therefore are widely used as packaging materials for various foods such as liquid foods, water-containing foods, frozen foods, retort pouch foods, paste foods, livestock meat-aquatic foods and the like. In particular, in recent years, it has been widely used for packaging retort pouch foods.

Generally, a biaxially oriented polyamide resin film is laminated with a polyethylene resin film or a polypropylene resin film (sealant) without being used alone, and processed into a bag-like shape to form a packaging material. If necessary, the packaging material may be formed by applying a treatment such as an adhesive coating, an antistatic coating, or a coating exhibiting barrier properties, or a treatment such as a metal vapor deposition process, or a corona treatment, followed by laminating the resultant with a sealant layer and forming a bag.

However, if the physical properties of the polyamide resin film are not uniform in the transverse direction (also referred to as "width direction") and the longitudinal direction (also referred to as "longitudinal direction") of the film, the thickness of the coating layer or the metal deposition layer tends to be non-uniform, or the adhesive strength with the coating layer or the metal deposition layer tends to be non-uniform. As a result, the film has uneven easy adhesion performance, antistatic performance, and gas barrier performance. Further, when laminating the sealant, the film is deformed into a curved S-shaped curl, which is problematic.

Generally, as a method for producing a biaxially stretched polyamide resin film, a method is employed in which a substantially non-oriented unstretched film is continuously molded in an extrusion step, and then the unstretched film is stretched in both the longitudinal and transverse directions of the film to obtain a high-strength biaxially oriented film having sufficient molecular orientation. The biaxial stretching method includes a sequential biaxial stretching method in which longitudinal stretching is performed and then transverse stretching is performed, and a simultaneous biaxial stretching method in which stretching is performed simultaneously in the longitudinal direction and the transverse direction.

For the successive stretching, the following method is proposed in JP 3671978B: a biaxially oriented polyamide resin film free from S-shaped curling is obtained by adjusting the boiling water shrinkage ratio, the difference in boiling water shrinkage directions, the thickness unevenness, the refractive index in the thickness direction, and the like of a polyamide resin film roll to specific numerical ranges and specifying the change rate in the longitudinal direction thereof.

However, JP3671978B focuses only on the variation in the length direction of the polyamide resin film. Generally, the values of mechanical properties of a polyamide resin film are different between the transverse direction and the longitudinal direction of the film at the time of production. Therefore, in the technique described in JP3671978B, when the film is processed into a product such as a packaging material, anisotropy occurs in the product performance, and there is a problem that applicability is deteriorated.

The simultaneous biaxial stretching method has an advantage that a film having a uniform orientation in the film plane direction can be obtained as compared with the sequential biaxial stretching method, and is therefore an effective method for solving the technical problem of JP 3671978B. However, since the stretching apparatus is accompanied by a physically complicated stretching mechanism, that is, a longitudinal stretching mechanism for accelerating and controlling the operation speed of a jig for holding the end portion of the unstretched film in a mechanical or electrical manner, it is difficult to uniformly stretch and deform the unstretched film in the stretching step.

Conventionally, studies have been made to uniformize the deformation behavior in the stretching step by studying the locus of the longitudinal stretching magnification in the simultaneous biaxial stretching method. The stretch ratio trace refers to the change in stretch ratio from the start of stretching to the time when the maximum stretch ratio is reached.

For example, as a method for suppressing the bowing phenomenon, a method of stretching in the transverse direction while performing a relaxation treatment in the longitudinal direction (JP2000-309051a), a method of performing a stretch magnification trajectory in the longitudinal direction before a stretch magnification trajectory in the transverse direction (JP2002-370278A), and the like have been proposed. The longitudinal stretching magnification trajectory before the transverse stretching magnification trajectory means that, when normalizing the change in magnification, the change value of the longitudinal stretching magnification becomes larger than the change value of the transverse stretching magnification at an arbitrary point from the start of stretching to the time when the maximum stretching magnification is reached. In other words, the longitudinal stretching magnification ratio trace performed before the transverse stretching magnification ratio trace means that, at any time during stretching, the maximum stretching magnification ratio of the longitudinal stretching magnification ratio to the longitudinal stretching ratio at that time is higher than the maximum stretching magnification ratio of the transverse stretching magnification ratio to the transverse stretching ratio at that time.

However, when the longitudinal stretching magnification trajectory cannot be controlled well in particular, there is a problem that stretching unevenness due to stress relaxation occurs in the film and the thickness unevenness is enlarged. The stretching unevenness generated in the stretching step is first expressed as thickness unevenness, and causes unevenness in film properties due to difference in molecular orientation. This variation in physical properties is not directly related to the disadvantage of the film production process, but is also related to the occurrence of problems such as a shift in printing pitch, meandering, defective sealing, and bag making variation in the processing steps such as printing lamination processing and bag making filling processing of film products, which are examples of packaging applications. Moreover, this results in deterioration of the quality of the film processed product. In applications where a balance of physical properties is particularly required, it is not possible to use the entire width of the stretched film as a film having the same physical properties.

Disclosure of Invention

The present invention aims to provide a polyamide resin film which is uniform and has excellent quality stability, while suppressing as much as possible the expansion of stretching unevenness and thickness unevenness due to stress relaxation, which are problems in the simultaneous biaxial stretching method.

That is, the present invention is characterized as follows.

(1) A method for producing a polyamide resin film, which is a simultaneous biaxial stretching method by a tenter method in which an end portion in a width direction of an unstretched film is sandwiched by clips and simultaneously biaxially stretched in a longitudinal direction and a transverse direction, characterized in that the longitudinal stretching magnification expressed by a linear distance between the adjacent clips is not reduced by 5% or more of the maximum stretching magnification of the longitudinal stretching from the start of the transverse stretching to the maximum stretching magnification of the transverse stretching.

(2) The method for producing a polyamide resin film according to (1), wherein a longitudinal stretching ratio represented by a linear distance between the adjacent jigs and jigs is not decreased by more than 3% of a maximum stretching ratio of the longitudinal stretching from the start of the transverse stretching to the maximum stretching ratio of the transverse stretching.

(3) The method for producing a polyamide resin film according to (1) or (2), wherein at any point in the stretching, a maximum stretch ratio of a ratio of the longitudinal stretch to the longitudinal stretch at that point in time is higher than a maximum stretch ratio of a ratio of the transverse stretch to the transverse stretch at that point in time.

(4) The process for producing a polyamide resin film according to any one of (1) to (3), wherein the simultaneous biaxial stretching is carried out at a longitudinal stretching magnification of 2.5 to 4.5 times and at a ratio of the longitudinal stretching magnification to the transverse stretching magnification of 1: 0.5 to 1.5.

(5) The process for producing a polyamide resin film according to any one of (1) to (4), wherein the tenter simultaneous biaxial stretching machine is driven by a linear motor system.

(6) The method for producing a polyamide resin film according to any one of (1) to (5), wherein the laminate section is formed by a coating method on at least one surface of an unstretched film obtained by pressing a polyamide resin sheet melt-extruded from a die against a casting roll, and both ends in the width direction of the laminate obtained thereby are sandwiched by a jig and biaxially stretched in both the longitudinal direction and the transverse direction.

(7) A polyamide resin film characterized in that the film has a thickness unevenness expansion ratio of 3.5 times or less and a variation ratio of the refractive index in the film thickness direction across the entire plane of 0.5% or less.

(8) A polyamide resin film characterized in that the film has a thickness unevenness expansion ratio of 2.5 times or less and a variation ratio of the refractive index in the film thickness direction across the entire plane of 0.25% or less.

(9) The polyamide resin film according to (7) or (8), wherein the rate of change in the adhesion strength of the surface layer of the film over the entire surface is 10% or less.

(10) The polyamide resin film according to (7), wherein the film has a thickness unevenness expansion ratio of 2.5 times or less, a refractive index variation ratio across the entire plane of the film in the thickness direction of 0.25% or less, and a variation ratio across the entire plane of the adhesion strength of the surface layer of the film of 8.0% or less.

(11) The polyamide resin film according to (9) or (10), which is characterized by having a laminate portion formed from a product of at least one of a polyvinylidene chloride copolymer resin, a polyester resin, a polyurethane resin, a polyacrylic resin, a polyvinyl alcohol resin, a polycarboxylic acid resin, an olefin-polycarboxylic acid copolymer resin, and an ethylene-vinyl acetate copolymer resin laminated on the polyamide resin film of the base portion.

(12) The polyamide resin film according to (7) is a laminated film in which the 2 nd resin layer (Z) is laminated on at least one surface of the 1 st resin layer (X), wherein the 1 st resin layer (X) is composed of one of a polyamide resin (A) composed of a xylylenediamine component and an aliphatic dicarboxylic acid component having 4 to 12 carbon atoms and an ethylene-vinyl acetate copolymer saponified product, and the 2 nd resin layer (Z) is composed of a polyamide resin B.

According to the present invention, a uniform polyamide resin film having excellent quality stability can be obtained.

Drawings

Fig. 1 is a diagram showing an example of a longitudinal stretch magnification trajectory according to the present invention.

Fig. 2 is a diagram showing an actual mechanism of the draw-initial portion (extended order portion).

Fig. 3 is a view showing an actual mechanism of the stretching tail portion (extended pan).

Fig. 4 is a diagram showing tensile stress applied to the jig.

Detailed Description

In the present invention, a simultaneous biaxial stretching method by a tenter method is used in which both ends in the width direction of an unstretched film are sandwiched by a plurality of clips and simultaneously biaxially stretched in the longitudinal direction and the transverse direction of the film. In this simultaneous biaxial stretching method, it is most important not to decrease the longitudinal stretching magnification trajectory expressed by the distance between the clamps by 5% or more of the maximum stretching magnification until the transverse stretching magnification trajectory reaches the maximum magnification. Preferably, it is not reduced by more than 3%, and more preferably, it is not reduced by more than 2%.

The longitudinal stretching magnification trajectory in the present invention means a change in stretching magnification in a section of the stretching apparatus from a position at a stretching start point along the longitudinal direction of the film to a position at which a maximum stretching magnification along the longitudinal direction reaches a point. Further, the stretch ratio trace in the film transverse direction is referred to as transverse direction stretch ratio trace.

In the known technique, for example, as shown in JP2-131920a (especially, page 2, bottom left column, lines 15 to 17) and the like, a stretch ratio locus is determined by the shape of a guide rail for guiding a tenter. In contrast, in the present invention, the stretch ratio locus is determined based on the movement locus of the jig. As the longitudinal stretching magnification trajectory, (i) a linear distance between adjacent clips, and (ii) a distance obtained by projecting the inter-clip distance in the longitudinal direction (film movement) can be considered. In the present invention, (i) is used and is referred to as "longitudinal stretch magnification trajectory expressed by the distance between the clips".

The reason why the stretch ratio locus is determined based on the movement of the jig is as follows. In the tenter type simultaneous biaxial stretching apparatus, the clips are attached to a support body guided by a guide rail and run, but are provided on the film side at a position away from the support body, i.e., the guide rail, in order to prevent the film from being contaminated by oil splashed from the support body and the rail. Therefore, the moving track of the jig and the running track of the support body, that is, the shape of the guide rail are different. That is, the moving track of the jig is deformed with respect to the shape of the guide rail.

Fig. 1 shows an example of a longitudinal stretch magnification trajectory. When the film is stretched, the respective steps of preheating, stretching, and heat treatment are performed. The longitudinal stretching ratio trace in fig. 1 indicates the stretching ratio trace when the film having passed through the preheating step on the left side of the drawing is subjected to the stretching treatment in the stretching step. The stretched film is subjected to a heat treatment process on the right side of the drawing. As in the above-described known technique, when the stretch ratio locus is determined by the shape of the guide rail, the stretch ratio locus corresponds to the shape of the guide rail. In fig. 1, 11 denotes a stretching start point, and 12 denotes a maximum stretching magnification reaching point. Reference numeral 13 denotes an initial stretching section which moves from a parallel linear traveling section of a preheating zone of the simultaneous biaxial stretching machine to a gradually expanding stretching traveling section. The drawing tail 14 indicates a parallel straight running portion which moves from the drawing gradually-expanding running portion to the heat treatment zone.

Fig. 2 shows an actual mechanism of the stretching initial portion 13. Reference numeral 21 denotes a guide rail, 22 denotes a support body, and 23 denotes a jig. In the initial stretching portion 13, the guide rail 21 is curved, and the support body 22 is guided by the guide rail 21 and travels along a track having a shape similar to that of the guide rail 21. On the other hand, since the jig 23 is attached to the support 22 at a position away from the guide rail 21 on the film side, the movement path thereof is deformed with respect to the shape of the guide rail 21. Here, as shown in the drawing, the linear distance D between the jigs is larger than the shape of the guide rail 21. That is, the inter-jig linear distance D expands, and deformation occurs based on this.

Fig. 3 shows a practical mechanism for stretching the tail 14. In which the guide rail 21 is bent and the moving track of the gripper 23 is deformed with respect to the shape of the guide rail 21. Here, as shown in the drawing, the inter-jig linear distance D is smaller than the shape of the guide rail 21. That is, the inter-jig linear distance D contracts, and deformation occurs based on this.

Fig. 2 and 3 show one end portion in the width direction of the film. In fact, the same processing is performed also at the other end portions in the width direction of the film by a mechanism symmetrical to them. That is, the film is simultaneously biaxially stretched by pulling both ends in the width direction thereof in the longitudinal and transverse directions.

As can be seen from the above, when the stretch ratio locus is defined according to the shape of the guide rail 21, the actual stretch ratio locus is deformed. As described above, this deformation mainly occurs in two places, namely, the curved trajectory of the stretching initial portion 13 moving from the parallel straight running in the preheating zone to the gradually expanding stretching running shown in fig. 2, and the reverse curved trajectory of the stretching tail portion 14 moving from the gradually expanding stretching running to the parallel straight running in the heat treatment zone shown in fig. 3. That is, the inter-clip distance D changes so as to expand and recover first in the curved trajectory of the initial stretching portion 13, and the inter-clip distance D changes so as to contract and recover first in the curved trajectory of the tail stretching portion 14. In particular, the stretch tail portion 14 is a stage in which a film tensile stress is strongly applied to the film surface, and therefore, the operation of temporarily relaxing the film in the longitudinal direction during stretching and then restoring the film to stretching has a great adverse effect on the tensile deformation behavior of the entire film surface in the stretching region.

This point will be explained in detail. The simultaneous biaxial stretching has a mechanism for simultaneously stretching the film in biaxial directions of the longitudinal direction and the transverse direction. That is, the stretching method is a stretching method in which, as longitudinal stretching, the distance between the adjacent clips of the clip row disposed on the right and left sides in the film running direction and running so as to sandwich the film end is gradually increased to stretch (accelerate) in the film running direction, and as transverse stretching, the distance between the clips of the clips facing each other on the right and left sides in the film running direction is gradually increased to stretch in the width direction. In this case, the mechanical expansion in the longitudinal direction and the transverse direction of the stretch ratio change mutually affects the actual film deformation. The reason for this is that when the uniaxial longitudinal (or transverse) tensile deformation occurs, the contraction stress acts in the transverse (or longitudinal) direction, which is the orthogonal direction. That is, this is because, in addition to the tensile stress in the longitudinal (or transverse) uniaxial direction, a contraction stress in the orthogonal direction is applied to the film surface, and both of them act simultaneously with each other.

If the longitudinal stretch ratio exhibits a change such that it temporarily decreases and then increases again during stretching, a decrease in tensile stress is temporarily caused, and this decrease in stress affects the stress relaxation in the longitudinal direction and the stress relaxation in the transverse direction. Since the transverse stretching magnification has already been performed, stretching unevenness with different surface magnifications exists in a stress balance manner in a stretching portion where materials constituting a film are bonded to each other (see つり and う). Particularly, if the film has a thickness unevenness, a thick portion having a low tensile stress is caused to pass through the stretching zone of the stretching apparatus directly below the maximum stretching magnification. Therefore, the uneven thickness expansion rate of the film after stretching increases. The details of the "uneven thickness expansion ratio" are as follows. This phenomenon is particularly remarkable in a polyamide resin film.

In the films having different surface magnifications (large uneven thickness expansion ratios), the refractive index in the thickness direction of the portion having a low surface magnification is low, and the refractive index in the thickness direction of the portion having a high surface magnification is high. In particular, if there is a difference in refractive index between the film roll at the center and at the ends in the film thickness direction, the result is that the shrinkage difference in the oblique direction becomes large, and a bag with a pronounced S-shaped curl is formed during bag making, which causes filling leakage and the like.

The manufacturing method of the present invention is characterized in that the stress reduction caused by the deformation of the longitudinal stretching magnification trajectory during the simultaneous biaxial stretching does not exceed the allowable limit.

The stress in this tensile zone can be analyzed by, for example, measuring the tensile stress of the film applied to the fixture. Fig. 4 shows the relationship between the film tensile stress component and the vector resultant stress applied to the jig and the slope thereof.

Here, the stress F applied to the jig 23 in the tangential traveling direction of the traveling movement_RD(in the reverse direction-F)_RD) And a stress F applied to the normal direction of the traveling movement of the jig_VDSince the actual measurement can be performed, the stress component F in the longitudinal traveling direction can be calculated from the traveling angle α of the jig 23_MD(in the reverse direction-F)_MD) And a transverse stress component F_TDAnd its vector resultant stress F_CPAnd F_CPThe slope phi of (c). Stress F_CPIt refers to the magnitude of the stress applied to the clamp 23 from the film, i.e., if viewed from the opposite perspective, the magnitude of the stress applied to the film.

In the present invention, until the transverse stretching magnification trajectory reaches the maximum magnification, the longitudinal stretching magnification trajectory is not reduced by 5% or more of the maximum stretching magnification, so that the vector resultant stress F is caused_CPIt is important not to reduce the amount of the solvent to such an extent that the quality of the resulting film is adversely affected.

The actual tensile stress can be detected by mounting a sensor such as a strain gauge or a piezoelectric element on a pedestal connecting the jig 23 holding the film end or an arm connecting a unit of the bearing device of the support body 22 running along the rail 21 and the jig 23, and performing computer analysis of the sensor signal.

In order not to decrease the longitudinal stretch magnification factor trajectory beyond the allowable limit, the deformation of the longitudinal stretch magnification factor trajectory may be corrected.

If the longitudinal stretch ratio trajectory is not reduced beyond the allowable limit, a movement is usually performed in which a portion having a low surface ratio (having a low tensile stress) is sequentially stretched from a portion having a high surface ratio (having a high tensile stress) of the film, and a film having a uniform stretching process is obtained.

The specific correction method is as follows. For example, in the linear motor type simultaneous biaxial stretching apparatus described in JP51-33590B, the jig supporting part which travels alone is moved by being pulled by a moving magnetic field generated by the fixed inductors of a plurality of linear motors provided along the rail. Since the traveling speed of each jig support portion can be individually adjusted to be accelerated or decelerated by changing the ac frequency of the exciting coil supplied to the fixed inductor, the distortion of the longitudinal stretching magnification locus can be corrected by correcting the frequency of each linear motor driver.

In a mechanical simultaneous biaxial stretching machine, for example, a pantograph type simultaneous biaxial stretching machine described in JP45-6785B (utility model), an endless ring device for seamlessly connecting ring units is constrained to a pair of guide rails provided at one end and the other end in the width direction of the film and driven by sprocket teeth. The longitudinal stretching mechanism for extending the inter-jig distance between the jigs fixed to the ring unit is configured to adjust by gradually narrowing the interval between the pair of guide rails. Therefore, by correcting the rail track or continuously changing the curvature radius of the curved track of the rail, the deformation of the longitudinal stretching magnification locus can be corrected.

The method of correcting the distortion of the longitudinal stretching magnification trajectory may be other than the above method, and is not limited to the above method. For example, it is effective to make the mounting position of the jig 23 very close to the running rail of the support body 22.

The method for preventing the decrease of the longitudinal stretching magnification trajectory of the present invention can be applied in combination with a countermeasure for bowing of the longitudinal stretching magnification trajectory prior to the transverse stretching magnification trajectory. The longitudinal stretching magnification trajectory is performed before the transverse stretching magnification trajectory, and is a trajectory in which, at an arbitrary timing during stretching, the maximum stretching magnification of the longitudinal stretching in the longitudinal direction at that timing is higher than the maximum stretching magnification of the transverse stretching in the transverse direction at that timing. In other words, the longitudinal stretching magnification trajectory prior to the transverse stretching magnification trajectory means that the stretching magnification is normalized such that the stretching magnification at the stretching start point is 0 and the stretching magnification at the stretching end point is 1, and that the longitudinal stretching magnification is higher than the transverse stretching magnification at any point in the film longitudinal direction in the stretching step, that is, at any point in the film longitudinal direction in the stretching step. The technique of this bow countermeasure is described in detail in the aforementioned JP2002-370278A filed by the present applicant.

In the present invention, it is preferable that the longitudinal stretching magnification of the simultaneous biaxial stretching is 2.5 to 4.5 times, and the ratio of the longitudinal stretching magnification to the transverse stretching magnification is 0.5 to 1.5. This range is a range of biaxial stretching magnification of the simultaneous biaxial stretched film which is practically used for imparting sufficient orientation, and is a range in which the effect of not reducing the longitudinal stretching magnification trajectory by 5% or more of the maximum magnification, which is the gist of the present invention, that is, the effect for uniformly stretching can be remarkably exhibited. The present invention is particularly useful in this stretch ratio range.

The curve of the transverse stretching magnification trajectory related to the deformation of the longitudinal stretching magnification trajectory is not particularly limited, and may be set by a quadratic or cubic function, a trigonometric function, a circular arc and a straight line, a curve, or a combination thereof.

The simultaneous biaxial stretching of the present invention can be performed using a pantograph system tenter, a screw system tenter, a linear motor system tenter, or the like. As a specific example of this apparatus, a tenter in which each clip is individually driven by a linear motor system as described above is most preferable because it has flexibility that allows the longitudinal stretching magnification to be arbitrarily controlled by controlling a variable frequency driver. That is, the tenter of this mode has the following advantages: the distortion of the longitudinal stretch ratio locus can be easily corrected and adjusted, and the longitudinal stretch ratio and the locus curve can be delicately and freely selected.

The polyamide resin film of the present invention will be explained.

The polyamide resin film of the present invention must have a nonuniform thickness expansion ratio of 3.5 times or less. Preferably 2.5 times or less.

The uneven thickness expansion ratio as used herein means an expansion ratio obtained by comparing the thickness variation coefficient of an unstretched film per unit length with the thickness variation coefficient of a stretched film after stretching. The coefficient of variation is a statistical expression representing the degree of fluctuation of data by a ratio of standard deviation from the mean value.

More specifically, the thickness variation coefficient of the film in the present invention is defined as follows. That is, the thickness of the unstretched film is measured at n intervals of a predetermined pitch p in the width direction of the film, at m intervals of a predetermined distance d along the longitudinal direction of the film, and at n × m — nm in total. Then, the standard deviation and the arithmetic mean were obtained from all the obtained data, and the coefficient of variation was obtained as the coefficient of variation C in the thickness of the unstretched film_AD. Then, the resultant was stretched in the width direction at [ p X transverse stretching magnification X relaxation rate]The thickness of the biaxially stretched film at n points was measured at intervals of n, and the film was subjected to longitudinal stretching at intervals of [ d ] x longitudinal stretching magnification x relaxation rate]And measuring the position m. Then, the coefficient of variation was similarly determined from all the obtained data (at n × m) and used as the coefficient of variation C in the thickness of the stretched film_BO. Then, C is obtained_BORelative to C above_ADMultiplying power (C)_BO/C_AD) This was defined as the rate of uneven thickness expansion.

The thickness unevenness enlargement rate indicates how much the thickness of the film deviates depending on the position of the film when the film is stretched. When the uneven thickness expansion ratio is 3.5 times or less, a film free from sag or wrinkle during film processing is obtained, and no defects are generated in the vapor deposition processing step and the lamination step, and a product can be produced with good productivity. Further, with such a film, almost the entire width of the manufactured film can be a product, and productivity is high.

When the thickness unevenness expansion ratio exceeds 3.5 times, it is difficult to form a long film roll exceeding 30000 m. Even if it can be formed, looseness and wrinkles are likely to occur at the time of processing such as vapor deposition processing, printing processing, lamination processing, and the like.

Therefore, it is necessary to measure and evaluate the uneven thickness spread rate of the total width of the film roll during processing such as vapor deposition and printing.

Next, the rate of change of the refractive index in the thickness direction of the film over the entire plane will be described. The polyamide resin film of the present invention is required to have a refractive index in the film thickness direction, and a change rate in the entire plane including a change rate in the film length direction and a change rate in the film width direction of 0.5% or less. Preferably 0.25% or less, more preferably 0.19% or less.

The rate of change of the refractive index of the film in the thickness direction over the entire plane as referred to in the present invention means the following. That is, samples were cut at a plurality of positions across the entire width of the stretched film, and the cutting operation was performed at a plurality of positions at regular intervals along the longitudinal direction of the film to obtain a plurality of test pieces. Next, the refractive index in the thickness direction of the obtained test piece was measured, the average refractive index, the maximum refractive index, and the minimum refractive index were obtained from a plurality of data, and the value having a larger difference from the average value was obtained by the following equation, and used as the change rate of the refractive index.

Rate of change (| maximum refractive index or minimum refractive index-average refractive index | × 100)/average refractive index

The variation of the refractive index in the thickness direction of the film over the entire plane indicates the degree of non-uniformity of stretching depending on the position of the film.

That is, the refractive index in the thickness direction differs depending on the resin constituting the film, and it does not make much sense to specify the value itself. This is because, for example, if nylon 6 is used, the refractive index is 1.504 to 1.505, and when poly (m-xylylene adipamide) or the like is added to nylon 6, the refractive index increases. However, the refractive index in the thickness direction gradually decreases when the unstretched film is stretched, and therefore, this becomes one of the indexes of stretching. That is, the change in the refractive index of the film is significant, and the change in the refractive index in the longitudinal direction of the film and the change in the refractive index in the width direction of the film are reduced, whereby a film having an excellent balance between the longitudinal and lateral physical properties is formed. As a result, a good product free from printing offset at the time of printing bag making and warping of a bag-made product can be obtained.

When the amount is outside the above range, the film has a poor physical property balance between the machine direction and the transverse direction. Such a film causes printing displacement when a bag is printed, distortion of a bag product, and the like, and the defective rate of bag manufacturing processing is increased.

From such a viewpoint, the rate of change of the refractive index in the thickness direction over the entire plane must be measured and evaluated for the total width of the film roll when processing such as vapor deposition or printing is performed.

The polyamide resin used in the present invention includes, for example, nylon 6 mainly composed of epsilon-caprolactam. Examples of the other polyamide resin include polyamide resins obtained by polycondensation of a lactam having a 3-membered or higher ring, an ω -amino acid, a dibasic acid, and a diamine.

Specifically, the lactams include enantholactam, caprylolactam, laurolactam and the like, in addition to the epsilon-caprolactam described above. Examples of the omega-amino acids include 6-aminocaproic acid, 7-aminoheptanoic acid, 9-aminononanoic acid, and 11-aminoundecanoic acid. Examples of the dibasic acids include adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, hexadecanedioic acid, eicosanedioic acid, 2, 4-trimethyladipic acid, terephthalic acid, isophthalic acid, 2, 6-naphthalenedicarboxylic acid, and xylenedicarboxylic acid. Examples of the diamines include ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, pentamethylenediamine, undecamethylenediamine, 2, 4 (or 2, 4, 4) -trimethylhexamethylenediamine, cyclohexanediamine, bis- (4, 4' -aminocyclohexyl) methane, and m-xylylenediamine.

Further, a polymer obtained by polycondensing these or a copolymer thereof, for example, nylon 6, 7, 11, 12, 6.6, 6.9, 6.11, 6.12, 6T, 6I, MXD6 (m-xylylene adipamide), 6/6.6, 6/12, 6/6T, 6/6I, 6/MXD6 and the like can be used. In the production of the polyamide resin film of the present invention, the polyamide resins may be used singly or in combination of 2 or more or in a multilayer form.

Among the above polyamide resins, the polyamide resin having a relative viscosity of 2.0 to 3.5 is particularly preferable in the present invention. This is because the relative viscosity of the polyamide resin affects the toughness, the elongation and the like of the obtained biaxially stretched film, and when the relative viscosity is less than 2.0, the impact strength feeling is insufficient, whereas when the relative viscosity exceeds 3.5, the biaxial stretchability tends to be deteriorated as the tensile stress increases. The relative viscosity used herein means a value obtained by measuring at 25 ℃ a solution prepared by dissolving a polymer in 96% sulfuric acid and having a concentration of 1.0 g/dl.

The polyamide resin film of the present invention may contain various additives such as a lubricant, an anti-blocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, and an impact resistance improver, as long as the properties thereof are not impaired. In particular, in order to improve the lubricity of the biaxially stretched film, various inorganic particles are preferably contained as the lubricant. In addition, the addition of an organic lubricant such as ethylene bis stearamide, which exerts an effect of reducing the surface energy, is preferable because the lubricity of the film constituting the film roll becomes excellent. The amount of the lubricant added is preferably in the range of 0.01 to 1 mass%.

Further, the polyamide resin film of the present invention may be subjected to heat treatment and humidity conditioning treatment in order to improve dimensional stability according to the application. Further, in order to improve the adhesiveness of the film surface, corona treatment, coating treatment, flame treatment, or the like, or printing or the like may be performed.

The film of the present invention may have a structure in which a laminate portion is laminated on a polyamide resin film of a base portion. Hereinafter, the 1 st embodiment of laminating a polyamide resin film will be described.

When the polyamide resin film is laminated, if the uneven thickness expansion ratio is large, the uneven thickness expansion ratio of the laminated portion is also large. As a result, the film surface has unevenness in adhesion strength, electrification performance, gas barrier performance, and the like, and a stable product cannot be obtained.

The adhesion strength of the film surface layer will be described. In the laminated polyamide resin film of the present invention, the rate of change in the adhesion strength of the film surface layer over the entire plane including changes in the film length direction and changes in the film width direction is preferably 10% or less. More preferably 8.0% or less, and still more preferably 5.0% or less.

The adhesion strength was measured by using a laminated polyamide resin film, in which a laminated portion was laminated on a polyamide resin film constituting a base portion of the laminated film, as a test film, laminating a non-stretched polypropylene film on a surface layer of the laminated portion of the test film via a laminating adhesive, and then peeling the polyamide resin film and the polypropylene film of the base portion between the layers while sandwiching them.

In the present invention, the adhesion strength of the film surface layer means the strength at which peeling occurs at any of (i) the interface between the polyamide resin film constituting the base material portion in which the polyamide resin film is laminated and the laminated portion in which the polyamide resin film is laminated, (ii) the interface between the laminated portion and the lamination adhesive layer, and (iii) the interface between the adhesive layer and the polypropylene film.

In this case, peeling occurs at any of the above interfaces (i), (ii), and (iii), and the measured value is regarded as the adhesion strength between the polyamide resin film of the substrate portion and the laminated portion of the present invention. This is because, when peeling occurs at the interface (ii) or the interface (iii), the interface (i) is estimated to adhere with a strength at least larger than the adhesion strength measured at that time.

In the measurement, when the polyamide film or the laminated polypropylene film of the substrate portion was broken, an adhesive tape (No. 31B, manufactured by hitto polyester tape company) was attached to the back surface of one or both of the films to reinforce the film, and the adhesion strength of the present invention was determined by taking the value obtained in a state where the breakage of the material did not occur.

The rate of change of the adhesion strength over the entire surface of the film was determined as follows. The test pieces were cut at a plurality of positions across the entire width of the stretched film, and the cutting operation was performed at a plurality of positions at regular intervals along the longitudinal direction of the film, to obtain a plurality of test pieces. Next, the peel strength of the obtained test piece was measured, and the average adhesion strength, the maximum adhesion strength, and the minimum adhesion strength were obtained from a plurality of data, and the value having a larger difference from the average value was obtained by the following formula, and used as the change rate of the adhesion strength.

The rate of change (| maximum adhesion strength or minimum adhesion strength-average adhesion strength | × 100)/average adhesion strength

If the rate of change in the adhesion strength exceeds 10%, stress concentration occurs in a portion having low adhesion strength when an impact such as dropping is applied after the contents are filled in the film-processed bag-made product printed and laminated, and the bag breakage rate increases.

The gas barrier properties of the film will be explained. In the laminated polyamide resin film of the present invention, when the laminated portion laminated on the polyamide resin film as the base layer is a layer exhibiting barrier properties, the rate of change in the oxygen permeability of the film over the entire plane including a change in the film longitudinal direction and a change in the film width direction is preferably 15% or less. More preferably 10% or less, and still more preferably 5.0% or less.

If the rate of change in oxygen permeability exceeds 15%, it becomes difficult to obtain the required content storage performance in the portion where the oxygen permeability is poor after filling the contents in the film-processed bag-made product.

Examples of the resin used in the laminated portion of the polyamide resin film of the present invention include polyvinylidene chloride copolymer resins, polyester resins, polyurethane resins, polyacrylic resins, polyvinyl alcohol resins, polycarboxylic acid resins, olefin-polycarboxylic acid copolymer resins, ethylene-vinyl acetate copolymer resins, and the like. The resin may be used alone, or at least 1 or more of the above resins may be used in combination with other resins. Among the above resins, polyvinylidene chloride copolymer resins, olefin-polycarboxylic acid copolymer resins, polyurethane resin, and the like are particularly preferable in the present invention.

The resin used in the laminated portion is preferably applied as a solution or emulsion to a polyamide resin film constituting the base layer, thereby forming the laminated portion.

When using the latex, it is preferable to use a so-called precoating method in which treatment is performed by utilizing high heat during film stretching, from the viewpoint of improving the gas barrier property of the formed latex film and the adhesion to the film of the base layer after the latex is applied to the base layer film before completion of the oriented crystallization. The latex is applied to a film of the base layer and dried, thereby evaporating the solvent to form a densely packed structure. Further, by stretching the film of the base layer, the latex itself is deformed and fused while being stretched, and changes to a continuous film state.

In this stretching process, the latex film is very easily affected by the tensile stress of the film itself of the base material layer. When a decrease in tensile stress occurs in the polyamide resin film of the base layer, stress deformation occurs between the polyamide resin film and the latex film, and adhesion failure is likely to occur between the polyamide resin film and the latex film. On the other hand, if the polyamide resin film has stretching unevenness of different surface magnifications, the latex film itself naturally also has stretching unevenness, and the uniformity of the latex such as the degree of thermal fusion and the state of continuous film is poor. Therefore, when a printing ink layer or a laminating adhesive layer is formed on the latex film, the adhesion strength to the printing ink layer or the laminating adhesive layer is also affected.

The polyvinylidene chloride copolymer that can be used in the present invention can be obtained as a latex dispersed in a solvent by polymerizing 50 to 99 mass% of vinylidene chloride and 1 to 50 mass% of 1 or more other monomers copolymerizable with vinylidene chloride by a known emulsion polymerization method. When the proportion of the copolymerizable monomer is less than 1% by mass, plasticization inside the resin becomes insufficient and film-forming properties of the film are degraded, and when the proportion of the monomer exceeds 50% by mass, gas barrier properties are degraded.

Examples of the monomer copolymerizable with vinylidene chloride include vinyl chloride; acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate; methacrylic acid esters such as methyl methacrylate and glycidyl methacrylate; acrylonitrile, methacrylonitrile; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid. These monomers may be used in the form of 1 or 2 or more.

The polyvinylidene chloride copolymer may be used in combination with other resins. Examples of the other resin include an ethylene-vinyl acetate copolymer, a (meth) acrylate copolymer, a methyl methacrylate-butadiene-styrene copolymer, an acrylonitrile copolymer, a methyl vinyl ether-maleic anhydride copolymer, and the like. These resins may be used in the form of 1 or 2 or more.

The solid content concentration of the polyvinylidene chloride copolymer latex can be changed as appropriate depending on the type of the coating apparatus and the drying/heating apparatus. However, too dilute solutions tend to cause a problem in that a long time is required for the drying step. On the other hand, if the latex concentration is too high, a coating film is formed during storage, and the liquid pot life (pot life) becomes short, or a problem tends to occur in coatability. From such a viewpoint, the solid content concentration of the polyvinylidene chloride copolymer latex is preferably in the range of 10 to 70 mass%, more preferably in the range of 30 to 55 mass%.

The application of the polyvinylidene chloride copolymer latex to the base film may be carried out at any stage in the production process of the unstretched film for obtaining the base film. For example, a method in which a polyvinylidene chloride copolymer latex is applied to a base film and then a stretching treatment and a film forming treatment are simultaneously performed as it is exemplified. Alternatively, there may be mentioned a method in which, after the step of applying the coating composition, the moisture content of the polyvinylidene chloride copolymer latex is evaporated and dried by blowing hot air with a dryer or the like or by irradiation with infrared rays, and then the stretching treatment and the film-forming treatment are simultaneously performed. The temperature in the water evaporation and drying step is preferably 70 to 150 ℃, and more preferably 80 to 120 ℃ which is excellent in film forming properties of the polyvinylidene chloride copolymer latex. When the drying temperature is less than 70 ℃, the film forming property is lowered, and when the drying temperature exceeds 150 ℃, the temperature of the latex rapidly rises to cause a phenomenon such as bumping, and a uniform film cannot be obtained. The moisture evaporation drying process can be cut into different temperature profiles. The time required for the treatment step to exhibit the highest temperature is arbitrarily selected depending on the thickness of the base film and the polyvinylidene chloride copolymer layer, the amount of solid content in the latex, the specific heat of the latex, and the like. Usually, the time is 0.01 to 120 seconds, preferably 1 to 80 seconds. When the time is less than 0.01 second, the water evaporation property of the polyvinylidene chloride copolymer latex tends to be poor, or the film formation of the polyvinylidene chloride copolymer film tends to be insufficient. On the other hand, if the time exceeds 120 seconds, crystallization of the polyamide resin is excessively promoted, and thus a stretched film may not be produced, or adhesiveness to the latex film may be poor.

The method of applying the material constituting the laminated portion of the laminated polyamide resin film of the present invention to the polyamide resin film constituting the base material layer is not particularly limited. For example, a common method such as gravure roll coating, reverse roll coating, wire bar coating, air knife coating, die coating, curtain die coating, or the like can be used.

In the laminated polyamide resin film of the present invention, the thickness of the laminated portion is preferably 0.1 to 3.0 μm, more preferably 0.5 to 2.0 μm. When the film thickness is less than 0.1 μm, the adhesiveness and gas barrier property are liable to be deteriorated. On the other hand, if it exceeds 3.0. mu.m, the film formability is lowered and the appearance of the film is easily deteriorated.

The following describes embodiment 2 in which a polyamide resin film is laminated.

The polyamide resin laminated film of the present invention has the following configuration 2: the second resin layer (Z) is laminated on at least one side of the first resin layer (X) which is used as a barrier layer, wherein the first resin layer (X) is composed of one of a polyamide resin (A) and an ethylene-vinyl acetate copolymer saponified product, the polyamide resin (A) is composed of a xylylenediamine component and an aliphatic dicarboxylic acid component with 4-12 carbon atoms, and the second resin layer (Z) is composed of a polyamide resin (B).

The polyamide resin (a) contained in the first resin layer (X) 1 includes a polyamide resin obtained by a polycondensation reaction of m-and/or p-xylylenediamine, which is a xylylenediamine component, and an aliphatic dicarboxylic acid having 4 to 12 carbon atoms. Particularly preferred is m-xylylene adipamide (MXD6) synthesized from m-xylylenediamine and adipic acid. In addition, the 1 st resin layer (X) may contain less than 20 mass% of the polyamide resin (B) constituting the 2 nd resin layer (Z) in order to improve the interlayer peel strength with the 2 nd resin layer (Z) as a base material layer.

An ethylene-vinyl acetate copolymer saponified product (EVOH) preferably has an ethylene content of 20 to 50 mol%, preferably 27 to 44 mol%, and a saponification degree of a vinyl acetate component of 96 mol% or more, preferably 99 mol% or more, because it has excellent gas barrier properties and strength. Resins having affinity with EVOH, antioxidants, plasticizers, antistatic agents, lubricants, colorants, fillers, and the like may be added to EVOH as long as the properties thereof are not impaired.

The polyamide resin (a) or EVOH is preferably contained in an amount of 80 mass% or more of the resin constituting the 1 st resin layer (X) as the barrier layer. When the content is less than 80% by mass, it is difficult to exert the desired barrier performance. Therefore, it is more preferable to contain 90 mass% or more

Examples of the polyamide resin (B) constituting the 2 nd resin layer (Z) as the base layer include the polyamide resins described above including nylon 6 and the like.

The relative viscosity of the polyamide resin (a) and the polyamide resin (B) constituting the laminated polyamide resin film of the present invention is preferably 2.0 to 3.5 in the same manner.

The polyamide resin (B) and the polyamide resin (a) may contain other polyamide and thermoplastic resin. In this case, the amount of the resin layer (Z) or the resin layer (X) is preferably 20% by mass or less. In particular, since the impact resistance of the entire laminated film may be lowered by laminating the polyamide resin (a) functioning as a barrier layer, it is preferable to add 0.5 to 20 mass% of a thermoplastic elastomer to the resin layer (X) or/and the resin layer (Z) in order to compensate for this. Examples of the thermoplastic elastomer include polyamide elastomers such as block or random copolymers of polyamide resins such as nylon 6 and nylon 12 and PTMG (polytetramethylene glycol) and PEG (polyethylene glycol); polyolefin elastomers such as ethylene- (meth) acrylate copolymers, ethylene-butene copolymers, and styrene-butadiene copolymers; and ionomers of olefin resins such as ethylene ionomers.

The polyamide resin (a) and the polyamide resin (B) may contain various additives such as a lubricant, an anti-blocking agent, a heat stabilizer, an antioxidant, an antistatic agent, a light resistance agent, and an impact resistance improver, as long as the properties thereof are not impaired. In particular, in order to improve the lubricity of the biaxially stretched film, various inorganic particles are preferably contained as the lubricant. Further, the addition of an organic lubricant such as ethylene bisstearic acid, which exerts an effect of reducing the surface energy, is preferable because the lubricity of the film constituting the film roll becomes excellent. For these purposes, the amount of the lubricant added is preferably in the range of 0.01 to 1 mass%.

In particular, when the 1 st resin layer (X) as the barrier layer is made of the polyamide resin (a), it is preferable to add an adhesive layer (Y) between them in order to increase the interlayer peeling force with the 2 nd resin layer (Z) as the base layer. As the resin constituting the adhesive layer (Y), a mixture of the polyamide resin (a) and the amorphous polyamide resin, or a mixture of the polyamide resin (a) and the polyamide resin (B) is preferable. The proportion of the amorphous polyamide resin or polyamide resin (B) in the adhesive layer (Y) is preferably 5 to 90% by mass, more preferably 20 to 80%, and still more preferably 40 to 70%.

The amorphous polyamide resin referred to herein is a generic term for polyamide resins having no crystallinity or having no crystallinity. The polymer is not particularly limited as long as it has a low crystallinity, and generally, a polymer composed of a monomer component having a structure inhibiting crystallization, that is, a side chain or a ring structure is exemplified. Examples of such polymers include polyamides obtained by the reaction of dicarboxylic acids such as terephthalic acid and isophthalic acid with diamines such as hexamethylenediamine, 4 ' -diamino-3, 3 ' -dimethyl-dicyclohexylmethane, 4 ' -diamino-dicyclohexylpropane, and isophoronediamine. Alternatively, the polyamide may be obtained by copolymerizing an isocyanate component such as a lactam component or 4, 4' -diphenylmethane-diisocyanate, among the above components.

The laminated polyamide resin film according to claim 2 of the present invention is a film in which a 2 nd resin layer (Z) as a base layer containing a polyamide resin (B) as a main component is laminated on at least one surface of a1 st resin layer (X) as a barrier layer containing a polyamide resin (a) or EVOH as a main component. Examples of the lamination method include Z/X, Z/X/Z, X/Z/X, and Z/Y/X/Y/Z, X/Y/Z/Y/X in which an adhesive layer (Y) is added. Among them, Z/X/Z or Z/Y/X/Y/Z with the barrier layer (X) as an intermediate layer is preferable.

The thickness of each layer of the laminated polyamide resin film of the 2 nd aspect of the present invention is usually 2 to 35 μm, preferably about 3 to 20 μm, of the 2 nd resin layer (Z) made of the polyamide resin (B). The 1 st resin layer (X) as the barrier layer is usually about 1 to 20 μm, preferably about 2 to 15 μm. The thickness of the adhesive layer (Y) is usually about 0.3 to 10 μm, preferably about 0.5 to 5 μm.

The laminated polyamide resin film according to embodiment 2 of the present invention is required to have a thickness unevenness expansion ratio of 3.5 times or less, preferably 2.5 times or less.

In the laminated polyamide resin film according to embodiment 2 of the present invention, the refractive index in the thickness direction of the film, and the rate of change in the entire plane including the rate of change in the film length direction and the rate of change in the film width direction need to be 0.5% or less. Preferably 0.25% or less, more preferably 0.19% or less.

The laminated polyamide resin film according to embodiment 2 of the present invention may be subjected to a heat treatment or a humidity control treatment in order to improve dimensional stability according to the application. Further, in order to improve the adhesiveness of the film surface, corona treatment, coating treatment, flame treatment, or the like, or printing or the like may be performed.

The polyamide resin film of the present invention may be a laminate in which a pressure-sensitive adhesive layer is laminated directly or via a printing ink layer, and a heat-seal layer is further laminated thereon. In order to improve the adhesion between the film and the laminating adhesive layer or the printing ink layer, surface treatment such as corona treatment or ozone treatment may be applied.

Examples of the printing ink layer include those formed by adding various pigments, extender pigments, plasticizers, drying agents, stabilizers and other additives to conventionally used ink binder resins such as urethane-based, acrylic-based, nitrocellulose-based, rubber-based, vinyl chloride-based, and the like. The printing ink layer can display characters, patterns and the like by the above ink. As a method for forming the printing ink layer, for example, a known printing method such as an offset printing method, a gravure printing method, a screen printing method, or a known coating method such as roll coating, knife edge coating (knife edge coat), gravure coating, or the like can be used.

As the coating agent used for forming the laminating adhesive layer, known coating agents can be mentioned. Examples of the coating agent include isocyanate-based, urethane-based, polyester-based, polyethyleneimine-based, polybutadiene-based, polyolefin-based, and alkyl titanate-based coating agents. Among them, in view of effects such as adhesion, heat resistance, and water resistance, isocyanate-based, polyurethane-based, and polyester-based coating agents are preferable. Particularly preferred are isocyanate compounds; 1 or more than 2 mixtures and reaction products of polyurethane and urethane prepolymers; mixtures and reaction products of 1 or more than 2 of polyesters, polyols and polyethers with isocyanates; or a solution or dispersion thereof. The laminating adhesive layer is preferably thicker than at least 0.1 μm in order to sufficiently improve the adhesion to the heat seal layer. The method for forming the laminating adhesive layer is not particularly limited, and a general method such as gravure roll coating, reverse roll coating, wire bar coating, air knife coating, or the like can be used.

The heat seal layer is used as a heat seal layer when forming a packaging bag or the like using the polyamide resin film of the present invention, and is formed of a material that can be heat sealed, high-frequency sealed, or the like. Examples of such a material include low-density polyethylene, linear low-density polyethylene, high-density polyethylene, ethylene-vinyl acetate copolymer, polypropylene, ethylene-acrylic acid copolymer, ethylene-acrylate copolymer, and ethylene-acrylate copolymer. The thickness is determined according to the purpose, and is preferably 15 to 200 μm.

As a method for forming the laminating adhesive layer, a known method can be used. Examples of the lamination method include a lamination method such as a dry lamination method, a wet lamination method, a solvent-free dry lamination method, and an extrusion lamination method, a coextrusion method in which two or more resin layers are simultaneously extruded and laminated, and a coating method in which a film is formed by a coater or the like. Among them, dry lamination is preferable in view of adhesion, heat resistance, water resistance, and the like.

Examples

The following examples and comparative examples are provided to evaluate various physical properties.

(1) Rate of differential thickness expansion

The thickness of the unstretched film was measured at 5mm intervals in the width direction of the unstretched film. The coefficient of variation was determined from all the data at 10 points at 10m intervals in the longitudinal direction, and the coefficient of variation was determined as the coefficient of variation C in the thickness of the unstretched film_AD. Then, the biaxially stretched film was stretched at [ 5X transverse stretching magnification X relaxation rate in the width direction]The thickness was measured at mm intervals, and the thickness was measured at intervals of [ 10X longitudinal stretch ratio X relaxation rate in the longitudinal direction]m at 10, the coefficient of variation was determined from all the data and used as the coefficient of variation C in the thickness of the stretched film_BO。

Find C_BORelative to the C_ADMultiplying power (C)_BO/C_AD) The thickness unevenness enlargement rate is defined as a thickness unevenness enlargement rate.

The thickness was measured using FILM THICKNESS TESTER (KG601A) manufactured by Anritsu corporation.

(2) Measurement component (mu-liter) stretch ratio (area ratio)

The whole surface of the unstretched film was printed with a measurement component of 10mm square, and then continuously stretched. The area of the square of the measurement component after biaxial stretching was determined, and the substantial stretch ratio (area ratio) of the film to each measurement component was measured. The total width of the wound film was measured in the longitudinal direction at 5m, and the surface magnification distribution was obtained from the array matrix of the substantial stretching magnification. It was measured at 10 points every 100m in the longitudinal direction. The coefficient of variation was determined from all the area magnification data.

(3) Refractive index in thickness direction

A10 cm × 10cm square sample was cut out with the sides of the sample aligned in the longitudinal direction and the width direction of the film, centered at 5 points in total along the width direction of the stretched film, the center, the inner side (end) 5cm away from both ends of the film, and the center of the center and both ends. This cutting operation was performed at 40 points per 100m in the longitudinal direction of the film, and a total of 5 × 40 to 200 test pieces were obtained.

The test piece was left to stand at a temperature of 20 ℃ and a humidity of 65% for 2 hours or more, and then the refractive index in the thickness direction was measured at a temperature of 20 ℃ and a humidity of 65% by using an Abbe refractometer (1T) manufactured by Atago. The number of measurement points for each test piece was 3, and the average of the 3 points was used as data.

The average refractive index, the maximum refractive index, and the minimum refractive index were obtained from the data of 200 points, and the value having a larger difference from the average was obtained as the change rate of the refractive index by the following equation.

(4) Tensile stress (F) applied to the jig_CP)

A strain gauge is attached to a connection portion between the support body 22 and the jig 23 shown in fig. 4, and a component force of tensile stress applied to the jig (bending stress applied in the traveling direction and tensile stress applied in a direction perpendicular thereto) is measured. The stress signal is wirelessly transmitted by a microminiature remote controller NK7690D (manufactured by Sanyo corporation of Japan), and the resultant force F is calculated by performing computer analysis from the traveling position of the jig to be measured_CPAnd an angle phi.

(5) S-shaped curling phenomenon

Biaxially stretched polyamide resin film and sealant film (CP; unstretched polypropylene film RX-21, thickness 40 μm, manufactured by Tohcello Co., Ltd.) were dry-laminated (adhesive coating amount 3 g/m) with urethane adhesive (Takerac A-525/A-52 two-pack type, manufactured by Sandi chemical polyurethane Co., Ltd.)²) Thereby producing a laminated film.

The resulting laminated film was cut into a width of 400 mm. The resulting cut film was folded into 2 pieces in such a manner that creases were formed along the longitudinal direction thereof, while both edge portions were continuously heat-sealed at 180 ℃ per 20mm using a test sealant, and a wide width of 10mm was intermittently heat-sealed at 150mm intervals in a direction perpendicular thereto, to obtain a semi-finished bag having a wide width of about 200 mm. The half-finished bags were cut so that the seal portions at both edges in the longitudinal direction became 10mm, and then cut at the boundary of the seal portions in the direction perpendicular to the cut portions to produce 10 sealed bags with 3 sides. These 3-side sealed bags were heat-treated in boiling water for 30 minutes, and then kept for one day and night in an atmosphere of 20 ℃ and 65% RH, and further 10 of these 3-side sealed bags were stacked and a load of 9.8N (1kgf) was applied to the entire surface of the bag from above, and after keeping for one day and night, the load was removed, and the degree of reverse buckling (S-shaped curling) of the bag was observed. Next, evaluation was performed using the following criteria.

Very good: 10 of the cells have no inflection

O: with pockets having slight retroflections visible

X: with clearly visible retroflection

X: the retroflection is obvious.

(6) Adhesion strength of film surface layer and rate of change thereof

A test piece was prepared by the following method, and the adhesion strength of the surface layer of the laminated polyamide resin film was evaluated.

First, the surface of the laminate part of the polyamide resin film of the present invention on which the polyamide resin film is laminated is coated by a gravure roll in a dry coating amount of 2.5g/m²A dry laminating adhesive (Takerac A-525/A-52 two-pack type manufactured by Mitsui chemical polyurethane Co., Ltd.) was applied, and then heat treatment was performed at 80 ℃. Next, a non-stretched polypropylene film (RXC-21, 70 μm, manufactured by Tohcello Co., Ltd.) was dry-laminated on a metal roll heated to 80 ℃ with a nip pressure of 490 kPa. Followed by the adhesive recommended aging to give a laminated film.

The sampling method of the test piece was the same as the above-described method for measuring "(3) refractive index in the thickness direction", and 200 samples were obtained.

In the measurement of the adhesion strength, a test piece having a width of 15mm was taken out from the cut sample, and after the polypropylene film and the laminated polyamide resin film at the end of the test piece were peeled off in an environment of 20 ℃ and 65% RH, the polypropylene film was pulled at a pulling speed of 300mm/min by using a pull tester (AGS-100G manufactured by shimadzu corporation) in a state where the polypropylene film was bent at 180 ° with respect to the laminated polyamide resin film, and the adhesion strength was measured. The number of measurement points is 3, and the average of the three points is used as data.

The average adhesion strength, the maximum adhesion strength, and the minimum adhesion strength were obtained from the data of 200 test pieces, and the value having a larger difference from the average value was obtained by the following formula and used as the change rate of the adhesion strength.

(7) Gas barrier property (oxygen permeability and rate of change thereof)

The oxygen gas barrier property was measured as the oxygen permeability of a test piece in which a polyamide resin film was laminated under an environment of 20 ℃ and 85% relative humidity using an oxygen barrier measuring instrument (OX-TRAN 2/20) manufactured by MOCON corporation. The number of measurement points was 3, and the average of three points was used as data.

The sampling method of the test piece was the same as the above-described method for measuring "(3) refractive index in the thickness direction", and 200 test pieces were obtained.

From the data of the 200 test pieces, the average oxygen permeability, the maximum oxygen permeability, and the minimum oxygen permeability were determined, and the value having a larger difference from the average value was obtained as the change rate of the oxygen permeability by the following equation.

Rate of change (| maximum oxygen permeability or minimum oxygen permeability-average oxygen permeability | × 100)/average oxygen permeability

[ preparation of Main chip ]

6 parts by mass of a nylon 6 resin (A1030-BRF, manufactured by Youngco Co., Ltd.) having a relative viscosity of 3.0 measured in 96% concentrated sulfuric acid at 25 ℃ and a concentration of 1.0g/dl was dried, and silica (SYLYSIA 310P having an average particle diameter of 2.7 μm: manufactured by Fuji Silysia chemical Co., Ltd.) was melt-mixed in 100 parts by mass to prepare a master chip.

[ preparation of polyvinylidene chloride copolymer (PVDC) latex ]

In a pressure-resistant reaction vessel to which enamel glass was applied, 85 parts by mass of water, 0.15 part by mass of sodium alkylsulfonate and 0.10 part by mass of sodium persulfate were charged, and after degassing, the temperature of the contents was maintained at 55 ℃. In a separate container, 97 parts by mass of vinylidene chloride, 2 parts by mass of methyl acrylate, and 1 part by mass of acrylic acid were weighed and mixed to prepare a monomer mixture. The reaction vessel was charged with 10 parts by mass of the monomer mixture, and the reaction was allowed to proceed with stirring. After confirming that the reaction was almost completely carried out by the decrease in the internal pressure of the reaction vessel, 10 parts by mass of sodium alkylsulfonate as a 15 mass% aqueous solution was introduced thereinto by pressure, and the remaining total amount of the monomer mixture was continuously added in a fixed amount for 15 hours. To the latex thus obtained was added sodium alkylsulfonate in a 15 mass% aqueous solution so that the surface tension of the liquid at 20 ℃ reached 42 mN/m.

The polymerization yield at this time was 99.9%. Therefore, the composition of the vinylidene chloride copolymer latex (A) obtained was substantially equal to the charging ratio. The solid content concentration of the latex (a) was 51 mass%. In the measurement of the melting point of crystals by DSC, the melting point was 190 ℃.

As compared with the above, a monomer mixture was prepared by changing vinylidene chloride to 90 parts by mass, methyl acrylate to 9 parts by mass, and acrylic acid to 1 part by mass. Then, a vinylidene chloride copolymer latex (B) was obtained in the same manner as described above except for the above. The solid content concentration of the latex was 51 mass%. In the measurement of the melting point of crystals by DSC, the melting point was 140 ℃.

The latex (a) and the latex (B) were stirred and mixed to obtain a mixed latex. In this case, the amount of the vinylidene chloride-based copolymer (a) was 35 parts by mass per 100 parts by mass of the total vinylidene chloride-based copolymer contained in the mixed latex.

[ other raw materials ]

Nylon 6(Ny 6): yougikuka A1030BRF (relative viscosity 3.0)

MXD 6: MX Nylon 6907 (relative viscosity 2.40) manufactured by Mitsubishi gas chemical company

Amorphous polyamide (amorphous Ny): grivory XE3038, EMS Inc

EVOH (3) in the following ratio: EVAL F101B (32 mol% ethylene, degree of saponification 99% or more) manufactured by KURARAAY corporation

Ethylene-butene copolymer: TAFMER-A4085, manufactured by Mitsui Chemicals Inc

Example 1

Nylon 6 resin was melt-extruded from a T-die having a width of 600mm, cooled and solidified on a cooling roll into a sheet, and an unstretched polyamide film having a thickness of 150 μm was formed, followed by water absorption treatment in a warm water bath having a temperature adjusted to 50 ℃. Then, the film was fed to a simultaneous biaxial stretching tenter driven by a linear motor, both ends in the width direction were held by clips, and simultaneous biaxial stretching was performed at 190 ℃ at a longitudinal stretching magnification of 3.0 times and a transverse stretching magnification of 3.3 times. At this time, the frequency of the linear motor driver is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and the longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig linear distance is not decreased is used. Fig. 1 shows a graph of the longitudinal stretch magnification trajectory as a.

Further, the film was heat-treated at 215 ℃ in a tenter oven, subjected to a 2% relaxation treatment in the longitudinal and transverse directions, cooled, trimmed at both ends in the width direction of the film, and then wound up by a winder. Thus, a simultaneous biaxially stretched polyamide film product roll having a thickness of 15 μm was obtained. The take-up speed was 120 m/min.

The rate of uneven thickness expansion in the width direction in example 1 was 2.1 times. That is, the coefficient of thickness variation of the stretched film was 2.1% and 1.0% with respect to the unstretched film. The coefficient of variation of the surface magnification is 2% or less, and the film is uniformly stretched. The rate of change in refractive index in the film thickness direction was 0.07%. F shown in FIG. 1_CPHas no reduction at all。

That is, a film uniformly stretched in both the width direction and the length direction was obtained. Almost the entire total width of the film can be practically used as a product.

Example 2

Under the same conditions as in example 1, a longitudinal stretching magnification factor trace in which the longitudinal stretching magnification factor represented by the distance between the jigs decreases, as shown in B of fig. 1, was used. The reduction rate was set to 3%. The rate of uneven thickness expansion in the width direction in example 2 was 3.5 times. That is, the coefficient of thickness variation of the stretched film was 3.5% and 1.0% with respect to the unstretched film. The coefficient of variation of the surface magnification is 4% or less, but the thickness unevenness is large. The rate of change in refractive index in the film thickness direction was 0.29%. F_CPThe equilibrium state is temporarily formed without dropping.

As a result, a film which was uniformly stretched and had no practical problem was almost all obtained. Can be used as a film product.

Example 3

Under the same conditions as in example 1, a longitudinal stretching magnification trace of a graph shown by B in fig. 1, in which the longitudinal stretching magnification represented by the inter-jig linear distance was reduced by 2%, was used.

The uneven thickness spread rate in the width direction in example 3 was 3.4 times. That is, the coefficient of thickness variation of the stretched film was 3.4% and 1.0% with respect to the unstretched film. The coefficient of variation of the surface magnification is 4% or less, but the thickness unevenness is large. The rate of change in refractive index in the film thickness direction was 0.24%. F_CPThe equilibrium state is temporarily formed without dropping.

Example 4

Under the same conditions as in example 1, the unstretched polyamide film was fed to a pantograph type simultaneous biaxial stretcher, and both ends in the width direction of the film were sandwiched by clamps to carry out simultaneous biaxial stretching at a longitudinal stretching magnification of 3.0 times and a transverse stretching magnification of 3.3 times. At this time, the rail interval is adjusted, the deformation of the longitudinal stretching magnification trajectory is corrected, and the longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig linear distance is not decreased is used. Fig. 1 shows a graph of the longitudinal stretch magnification trajectory as a.

The rate of uneven thickness expansion in the width direction in example 4 was 2.2 times. That is, the coefficient of thickness variation of the stretched film was 2.2% and 1.0% with respect to the unstretched film. The coefficient of variation of the surface magnification is 2% or less, and the film is uniformly stretched. The rate of change in refractive index in the film thickness direction was 0.08%. F_CPThere was no drop at all.

By the above operation, in examples 1 to 4, films uniformly stretched in both the width direction and the length direction were obtained. Almost the entire total width of the film can be used as a product.

Comparative example 1

Under the same conditions as in example 1, a longitudinal stretching magnification trace of a graph indicated by B in fig. 1, in which the longitudinal stretching magnification represented by the inter-jig straight line distance was reduced by 5%, was used.

In comparative example 1, the rate of uneven thickness spread in the width direction was 9.5 times. That is, the coefficient of thickness variation of the stretched film was 9.5% and 1.0% with respect to the unstretched film. The coefficient of variation of the surface magnification was 10% or more, and significant stretching unevenness was observed. The rate of change in refractive index in the film thickness direction was 1.2%. F_CPTemporarily decreased by 30%.

Cannot be used as a film product.

Example 5

Dried nylon 6 resin (A1030-BRF, manufactured by YOUGHIKEKO Co., Ltd.) and the above master chips were mixed so that the compounding ratio of silica was 0.05% by mass, and the mixture was fed into an extruder, melt-extruded through a T-die having a width of 600mm, cooled and solidified on a cooling roll into a sheet-like form, and an unstretched polyamide film having a thickness of 150 μm was molded. Then, water absorption treatment was carried out in a warm water tank in which the temperature was adjusted to 50 ℃. Then, the film was fed to a simultaneous biaxial stretching tenter driven by a linear motor, both ends in the width direction thereof were held by clips, and simultaneous biaxial stretching was performed at 190 ℃ at a longitudinal stretching magnification of 3.0 times and a transverse stretching magnification of 3.3 times. At this time, the frequency of the linear motor driver is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and the longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance does not decrease as shown in fig. 1a is used.

Further, the film was subjected to a heat treatment at 215 ℃ in a tenter oven, and subjected to a relaxation treatment of 2% in terms of the longitudinal and lateral directions, and after cooling, both ends of the film in the width direction were trimmed, and then wound up by a winder. A simultaneously biaxially stretched polyamide film product roll having a thickness of 15 μm was thus obtained. The take-up speed was 120 m/min.

The measurement results of the properties of the obtained film are shown in table 1. As is clear from table 1, the thickness unevenness enlargement ratio in example 5 was 2.1 times. Specifically, the coefficient of thickness variation of the unstretched film was 1.0%, and the coefficient of thickness variation of the stretched film was 2.1%. The average value of the refractive index in the thickness direction was 1.504, and the rate of change thereof was 0.07%, and the film was uniformly stretched. F in drawing shown in FIG. 4_CPThere was no drop at all. That is, a film uniformly stretched in both the width direction and the length direction was obtained. Therefore, almost the entire film total width can be used as a product.

[ Table 1]

Example 6

As compared with example 5, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was employed. Further, the reduction rate was 2%. Otherwise, a simultaneous biaxial stretching polyamide film product roll was obtained in the same manner as in example 5.

The measurement results of the properties of the obtained film are shown in table 1. As is clear from table 1, in example 6, the thickness unevenness expansion ratio was 3.4 times (the thickness variation coefficient with respect to the unstretched film was 1.0%, and the thickness variation coefficient of the stretched film was 3.4%), and the thickness unevenness was larger than that in example 5. The average value of the refractive index in the thickness direction was 1.503, and the rate of change thereof was 0.24%, and the film was uniformly stretched. F shown in FIG. 4_CPThe equilibrium state is temporarily formed without dropping. That is, a film which is almost entirely uniformly stretched and has no problem in practical use is obtained. Therefore, it can be used as a film product.

Example 7

As compared with example 5, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was employed. Further, the reduction rate was 1%. Except for this, a simultaneous biaxial stretching polyamide film product roll was obtained in the same manner as in example 5.

The measurement results of the properties of the obtained film are shown in table 1. As is clear from table 1, in example 7, the thickness unevenness expansion ratio was 2.9 times (the thickness variation coefficient with respect to the unstretched film was 1.0%, and the thickness variation coefficient of the stretched film was 2.9%), and the thickness unevenness was slightly increased as compared with example 5. The average value of the refractive index in the thickness direction was 1.504, and the rate of change was 0.18%. F_CPThere is no drop. That is, almost all of the resulting fiber is uniformly stretched and practically noneProblematic films. Therefore, the film can be used as a film product.

Example 8

The unstretched polyamide film produced under the same conditions as in example 5 was supplied to a pantograph type simultaneous biaxial stretching machine, and both ends in the width direction thereof were sandwiched by clamps, and simultaneous biaxial stretching was carried out at a longitudinal stretching ratio of 3.0 times and a transverse stretching ratio of 3.3 times. At this time, the rail interval is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and as shown in fig. 1a, the longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance does not decrease is used. Except for this, a simultaneous biaxial stretching polyamide film product roll was obtained in the same manner as in example 5.

The measurement results of the properties of the obtained film are shown in table 1. As is clear from table 1, the uneven thickness growth rate in example 8 was 2.2 times (the thickness variation coefficient with respect to the unstretched film was 1.0%, and the thickness variation coefficient of the stretched film was 2.2%). The average value of the refractive index in the thickness direction was 1.504, the rate of change was 0.08%, and the film was uniformly stretched. F_CPThere was no drop at all. That is, a film stretched uniformly in both the width direction and the length direction is obtained, and almost all of the total width of the film can be used as a product.

Example 9

Dried nylon 6 resin (A1030-BRF, manufactured by YOUGHIKEKO Co., Ltd.) and the above master chips were mixed so that the compounding ratio of silica was 0.05% by mass, and the mixture was fed into an extruder, melt-extruded through a T-die having a width of 600mm, cooled and solidified on a cooling roll into a sheet-like form, and an unstretched polyamide film having a thickness of 250 μm was molded. Then, water absorption treatment was carried out in a warm water tank in which the temperature was adjusted to 50 ℃. Then, the film was fed to a pantograph type simultaneous biaxial stretching machine, both ends were held by a jig, and simultaneous biaxial stretching was performed at 200 ℃ at a longitudinal stretching magnification of 3.0 times and a transverse stretching magnification of 3.3 times. At this time, the rail interval is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and as shown in fig. 1a, the longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance does not decrease is used.

Further, the film was subjected to a heat treatment at 215 ℃ in a tenter oven to perform a 2% relaxation treatment in the longitudinal and transverse directions, cooled, trimmed at both ends in the width direction of the film, and then wound up by a winder. A simultaneous biaxially stretched polyamide film product roll having a thickness of 25 μm was thus obtained. The take-up speed was 120 m/min.

The measurement results of the properties of the obtained film are shown in table 1. As is clear from table 1, the uneven thickness growth rate in example 9 was 2.3 times (the thickness variation coefficient with respect to the unstretched film was 1.0%, and the thickness variation coefficient of the stretched film was 2.3%). The average value of the refractive index in the thickness direction was 1.505, the rate of change was 0.07%, and the film was uniformly stretched. F_CPThere was no drop at all. That is, a film uniformly stretched in both the width direction and the length direction was obtained. Therefore, almost the entire total width of the film can be used as a product.

Example 10

A dried nylon 6 resin (A1030-BRF available from Youngko K.K.) and MXD6 (trade name: MXnylon S6907, relative viscosity 2.40 available from Mitsubishi gas chemical) were mixed at a mass ratio of 80: 20 to obtain a polyamide composition. The polyamide composition and the main chip were mixed so that the compounding ratio of silica was 0.05 mass%, and the mixture was fed into an extruder, melt-extruded through a T die having a width of 600mm, cooled and solidified on a cooling roll into a sheet form, and an unstretched polyamide film having a thickness of 150 μm was molded. Then, water absorption treatment was performed in a warm water tank adjusted to 60 ℃. Then, the film was fed to a pantograph type simultaneous biaxial stretching machine, and both ends in the width direction thereof were sandwiched by a jig, and simultaneous biaxial stretching was carried out under conditions of a stretching temperature of 185 ℃, a longitudinal stretching magnification of 3.0 times, and a transverse stretching magnification of 3.3 times. At this time, the rail interval is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and as shown in fig. 1a, the longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance does not decrease is used.

Further, the film was subjected to a heat treatment at 205 ℃ for 4 seconds in a tenter oven to perform a 5% relaxation treatment in the vertical and horizontal directions, and after cooling, both ends of the film in the width direction were trimmed and then wound up by a winder. A simultaneously biaxially stretched polyamide film product roll having a thickness of 15 μm was thus obtained. The take-up speed was 120 m/min.

The measurement results of the properties of the obtained film are shown in table 1. As is clear from table 1, the uneven thickness spread rate in example 10 was 2.4 times (the thickness variation coefficient with respect to the unstretched film was 1.0%, and the thickness variation coefficient of the stretched film was 2.4%). The average value of the refractive index in the thickness direction was 1.517, the rate of change was 0.09%, and the film was uniformly stretched. F_CPThere was no drop at all. That is, a film uniformly stretched in both the width direction and the length direction was obtained. Therefore, almost the entire total width of the film can be used as a product.

Comparative example 2

As compared with example 5, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was employed. Further, the reduction rate was 5%. Except for this, a simultaneous biaxial stretching polyamide film product roll was obtained in the same manner as in example 5.

The measurement results of the properties of the obtained film are shown in table 1. As is clear from table 1, the uneven thickness spread rate in this comparative example 2 was 9.5 times (the thickness variation coefficient with respect to the unstretched film was 1.0%, and the thickness variation coefficient of the stretched film was 9.5%). The average value of the refractive index in the thickness direction was 1.504, the rate of change was 1.2%, and significant stretching unevenness was observed. F shown in FIG. 4_CPA temporary decrease of 30%. As is clear from Table 1, it was not possible to use the film as a film product.

Comparative example 3

As compared with example 9, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was employed. Further, the reduction rate was 5%. Except for this, a simultaneous biaxial stretching polyamide film product roll was obtained in the same manner as in example 9.

The measurement results of the properties of the obtained film are shown in table 1. As is clear from table 1, the uneven thickness spread rate in this comparative example 3 was 9.8 times (the thickness variation coefficient with respect to the unstretched film was 1.0%, and the thickness variation coefficient of the stretched film was 9.8%). The average value of the refractive index in the thickness direction was 1.504, the rate of change was 1.4%, and significant stretching unevenness was observed. F_CPTemporarily decreased by 30%. As is clear from Table 1, it was not possible to use the film as a film product.

Comparative example 4

As compared with example 10, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was employed. Further, the reduction rate was 5%. Except for this, a simultaneous biaxial stretching polyamide film product roll was obtained in the same manner as in example 10.

The measurement results of the properties of the obtained film are shown in table 1. As is clear from table 1, the uneven thickness spread rate in this comparative example 4 was 10.1 times (the thickness variation coefficient with respect to the unstretched film was 1.0%, and the thickness variation coefficient of the stretched film was 10.1%). The average value of the refractive index in the thickness direction was 1.519, the rate of change was 2.9%, and significant stretching unevenness was observed. F_CPTemporarily decreased by 30%. As is clear from Table 1, it was not possible to use the film as a film product.

Example 11

Dried nylon 6 resin (A1030-BRF, manufactured by YOUGHIKEKO K.K., relative viscosity 3.0) and the above main chips were mixed so that the compounding ratio of silica was 0.05% by mass, and the mixture was fed into an extruder, melt-extruded through a T die having a width of 600mm, cooled and solidified on a cooling roll into a sheet-like shape, and an unstretched polyamide film having a thickness of 150 μm was molded. Then, water absorption treatment was performed in a warm water tank in which the temperature was adjusted to 50 ℃.

Next, the polyvinylidene chloride copolymer latex was coated on the untreated surface of the unstretched polyamide film by an air knife coating method, and dried by an infrared irradiation machine at a temperature of 110 ℃ for 30 seconds to evaporate and dry the water in the latex, thereby obtaining an unstretched laminated film.

Then, the unstretched laminate film was supplied to a simultaneous biaxial stretching tenter driven by a linear motor, both ends in the width direction thereof were held by clips, and simultaneous biaxial stretching was carried out at 190 ℃ at a longitudinal stretching magnification of 3.0 times and a transverse stretching magnification of 3.3 times. At this time, the frequency of the linear motor driver is adjusted to correct the distortion of the longitudinal stretching magnification locus, and the condition that the longitudinal stretching magnification locus does not decrease in the inter-jig distance as shown in fig. 1a is adopted.

Further, relaxation treatment was performed at 2% in the longitudinal and transverse directions by heat treatment at 215 ℃ for 5 seconds in a tenter oven, and after cooling, both ends of the film in the width direction were trimmed and then wound up by a winder. The polyamide film of the base layer thus obtained was biaxially stretched and laminated to obtain a product roll of a polyamide resin film, the thickness of the polyamide film being 15 μm and the thickness of the laminated portion being 1.2 μm. The take-up speed was 120 m/min.

The measurement results of the properties of the obtained film are shown in table 2. As is clear from table 2, the uneven thickness spread ratio in example 11 was 2.1 times. Specifically, the coefficient of thickness variation of the unstretched film was 1.0%, and the coefficient of thickness variation of the stretched film was 2.1%. The average value of the refractive index in the thickness direction was 1.5035, and the rate of change was 0.1%, and the film was uniformly stretched. F shown in FIG. 4_CPThere was no drop at all.

That is, a film uniformly stretched in both the width direction and the length direction was obtained. Almost the entire total width of the film can be used as a product.

[ Table 2]

Example 12

As compared with example 11, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was employed. The reduction rate was 2%. A laminated polyamide resin film was obtained in the same manner as in example 11 except for the above.

The measurement results of the properties of the obtained film are shown in table 2. As is clear from table 2, in example 12, the thickness unevenness expansion ratio was 3.4 times (the thickness variation coefficient of the unstretched film was 1.0% and the thickness variation coefficient of the stretched film was 3.4%), and the thickness unevenness was larger than that in example 11. The average value of the refractive index in the thickness direction was 1.5033, and the rate of change was 0.5%. F shown in FIG. 4_CPThe equilibrium state is temporarily formed without dropping. That is, a biaxially stretched laminate film which is uniformly stretched and has no practical problem is obtained almost entirely. Therefore, the film can be used as a film product.

Example 13

As compared with example 11, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was employed. Further, the reduction rate was set to 1%. A laminated polyamide resin film was obtained in the same manner as in example 11 except for the above.

The measurement results of the properties of the obtained film are shown in table 2. As is clear from table 2, in example 13, the thickness unevenness expansion ratio was 2.9 times (the thickness variation coefficient with respect to the unstretched film was 1.0%, and the thickness variation coefficient of the stretched film was 2.9%), and the thickness unevenness was slightly increased as compared with example 11. The average value of the refractive index in the thickness direction was 1.5042, and the rate of change was 0.3%. F shown in FIG. 4_CPThere is no drop. That is, a film which is uniformly stretched and has no problem in practical use is almost all obtained. Thus can be used as a film productThe preparation is used.

Example 14

In comparison with example 11, the unstretched laminated film was fed to a pantograph type simultaneous biaxial stretching machine, and both ends in the width direction thereof were sandwiched by clamps to carry out simultaneous biaxial stretching. Other conditions were the same as in example 11. In this case, the distance between a pair of guide rails provided in the width direction of the film for guiding the running of the pantograph is adjusted, and the deformation of the longitudinal stretching magnification trajectory is corrected so as not to decrease the longitudinal stretching magnification trajectory represented by the inter-jig distance as in a of fig. 1.

In example 14, the rate of uneven thickness expansion was 2.2 times (the coefficient of thickness change with respect to the unstretched film was 1.0%, and the coefficient of thickness change with respect to the stretched film was 2.2%). The average value of the refractive index in the thickness direction was 1.5038, and the rate of change was 0.2%, and the film was uniformly stretched. F shown in FIG. 4_CPDoes not drop.

The measurement results of the properties of the obtained film are shown in table 2. As is clear from table 2, films uniformly stretched in both the width direction and the longitudinal direction were obtained. Almost the entire total width of the film can be used as a product.

Example 15

A dry nylon 6 resin (A1030-BRF available from Youngko Co., Ltd.) and the above master chips were mixed, and the mixture was fed into an extruder so that the compounding ratio of silica was 0.05% by mass, melt-extruded through a T die having a width of 600mm, cooled and solidified on a cooling roll into a sheet form, and an unstretched polyamide film having a thickness of 250 μm was molded. Then, water absorption treatment was performed in a warm water tank adjusted to 50 ℃.

Subsequently, the vinylidene chloride copolymer latex was applied to the untreated surface of the unstretched film by air knife coating, and dried by evaporation of water in the latex for 30 seconds by an infrared irradiation machine at a temperature of 110 ℃.

Then, the film was fed to a pantograph type simultaneous biaxial stretching machine, both ends in the width direction were sandwiched by clamps, and simultaneous biaxial stretching was carried out at 200 ℃ at a longitudinal stretching magnification of 3.0 times and a transverse stretching magnification of 3.3 times. At this time, the distance between the pair of rails is adjusted to correct the distortion of the longitudinal stretching magnification locus, and the condition that the longitudinal stretching magnification locus represented by the distance between the jigs does not decrease as in fig. 1a is adopted.

Further, the film was subjected to a heat treatment at 215 ℃ for 5 seconds in a tenter oven to perform a 2% relaxation treatment in the vertical and horizontal directions, and after cooling, both ends of the film in the width direction were trimmed, and then wound up by a winder. The polyamide film of the substrate layer thus obtained was a product roll of a biaxially stretched polyamide film having a thickness of 25 μm and a thickness of the laminated portion of 1.2. mu.m. The take-up speed was 120 m/min.

The measurement results of the properties of the obtained film are shown in table 2. As is clear from table 2, the rate of uneven thickness expansion in the width direction in example 15 is 2.3 times. Specifically, the coefficient of thickness variation of the unstretched film was 1.0%, and the coefficient of thickness variation of the stretched film was 2.3%. The average value of the refractive index in the thickness direction was 1.5045, and the rate of change was 0.2%, and the film was uniformly stretched. F shown in FIG. 4_CPThere was no drop at all.

Example 16

A polyamide resin composition obtained by mixing a dried nylon 6 resin (A1030-BRF available from Unix corporation) and MXD6 (MXnylon S6907 available from Mitsubishi gas chemical Co., Ltd., relative viscosity: 2.40) at a mass ratio of 80: 20 and the above main chips were charged into an extruder so that the compounding ratio of silica was 0.05 mass%, melt-extruded through a T die having a width of 600mm, cooled and solidified on a chill roll into a sheet, and an unstretched polyamide film having a thickness of 150 μm was molded. Then, water absorption treatment was performed in a warm water tank adjusted to 60 ℃.

Subsequently, the vinylidene chloride copolymer latex was applied to the untreated surface of the unstretched film by air knife coating, and dried by an infrared irradiation machine at a temperature of 110 ℃ for 30 seconds to evaporate and dry the water in the latex.

The film was then fed to a pantograph type simultaneous biaxial stretching machine, and both ends in the width direction were sandwiched by clamps, and simultaneous biaxial stretching was carried out at a stretching temperature of 185 ℃, a longitudinal stretching magnification of 3.0 times, and a transverse stretching magnification of 3.3 times. At this time, the interval between the rails is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and the condition that the longitudinal stretching magnification trajectory represented by the inter-jig distance does not decrease as in fig. 1a is adopted.

Further, the film was heat-treated at 205 ℃ for 5 seconds in a tenter oven, subjected to 5% relaxation treatment in the longitudinal and transverse directions, cooled, trimmed at both ends in the width direction of the film, and then wound up by a winder. The polyamide film of the substrate layer thus obtained was biaxially stretched into a roll of a polyamide film product having a thickness of 15 μm and a thickness of the laminated portion of 1.2. mu.m. The take-up speed was 120 m/min.

The measurement results of the properties of the obtained film are shown in table 2. As is clear from table 2, the rate of uneven thickness expansion in the width direction in example 16 was 2.4 times. That is, the coefficient of thickness change of the stretched film was 2.3% and 1.0% for the unstretched film. The average value of the refractive index in the thickness direction was 1.5170, and the rate of change was 0.2%, and the film was uniformly stretched. F shown in FIG. 4_CPThere was no drop at all.

Example 17

Polyvinyl alcohol (PVA) (Poval 105 (polyethylene has a saponification degree of 98 to 99% and an average polymerization degree of about 500) manufactured by KURARAY corporation) was dissolved in hot water, and then cooled to room temperature, thereby obtaining an aqueous PVA solution having a solid content of 15 mass%. An aqueous EMA solution having a solid content of 15 mass% was prepared by dissolving ethylene-maleic acid copolymer (EMA) (weight average molecular weight 60000, maleic acid unit 45 to 50 mol%) and sodium hydroxide in hot water, and then cooling to room temperature to neutralize 10 mol% of the carboxyl groups with sodium hydroxide.

Next, the PVA aqueous solution and the EMA aqueous solution were mixed so that the mass ratio (solid content) of the PVA to the EMA was 30/70, to obtain an olefin-carboxylic acid copolymer mixed aqueous solution having a solid content of 10 mass%.

Next, the above-mentioned olefin-carboxylic acid copolymer mixed solution was applied to the untreated surface of the unstretched polyamide film obtained by the same formulation as in example 11 by air knife coating, and dried by an infrared irradiation machine at a temperature of 110 ℃ for 30 seconds to evaporate and dry the water in the mixed solution, thereby obtaining an unstretched laminated film.

Then, the unstretched laminate film was supplied to a simultaneous biaxial stretching tenter driven by a linear motor, both ends in the width direction thereof were held by clips, and simultaneous biaxial stretching was carried out at 190 ℃ at a longitudinal stretching magnification of 3.0 times and a transverse stretching magnification of 3.3 times. At this time, the frequency of the linear motor driver is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and the condition that the longitudinal stretching magnification trajectory expressed by the inter-jig distance does not decrease as shown in a of fig. 1 is adopted.

Further, relaxation treatment was performed at 2% in the longitudinal and transverse directions by heat treatment at 215 ℃ for 5 seconds in a tenter oven, and after cooling, both ends of the film in the width direction were trimmed and then wound up by a winder. The polyamide film of the base layer thus obtained was biaxially stretched and laminated to obtain a product roll of a polyamide resin film, the thickness of the polyamide film being 15 μm and the thickness of the laminated portion being 0.3 μm. The take-up speed was 120 m/min.

The measurement results of the properties of the obtained film are shown in table 2. As is clear from table 2, the uneven thickness spread ratio in example 17 was 2.1 times. Specifically, the coefficient of thickness variation of the unstretched film was 1.0%, and the coefficient of thickness variation of the stretched film was 2.1%. The average value of the refractive index in the thickness direction was 1.5036, and the rate of change was 0.1%, and the film was uniformly stretched. F shown in FIG. 4_CPThere was no drop at all. Further, the laminated adhesion strength was improved and the gas barrier property was lowered compared with the laminated PVDC resins of examples 11 to 16 because the EMA-based resin was laminated, but the rate of change of these properties was the same as those of examples 11 to 16 and the uniformity of the properties was excellent.

Example 18

An urethane emulsion TakeraccWS-5100 manufactured by Mitsui chemical polyurethane corporation was diluted with water to obtain an aqueous solution of easily bondable substance adjusted to a concentration of 10% by mass.

Next, the above-mentioned aqueous solution susceptible to adhesion was applied to the untreated surface of the unstretched polyamide film obtained by the same formulation as in example 11 by air knife coating, and dried by an infrared irradiation machine at a temperature of 110 ℃ for 30 seconds to evaporate and dry the water in the mixed solution, thereby obtaining an unstretched laminated film.

Then, the unstretched laminate film was supplied to a simultaneous biaxial stretching tenter driven by a linear motor, both ends in the width direction thereof were held by clips, and simultaneous biaxial stretching was carried out at 190 ℃ at a longitudinal stretching magnification of 3.0 times and a transverse stretching magnification of 3.3 times. At this time, the frequency of the linear motor driver is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and the condition shown in fig. 1a that the longitudinal stretching magnification trajectory is not decreased as indicated by the inter-jig distance is adopted.

Further, relaxation treatment was performed at 2% in the longitudinal and transverse directions by heat treatment at 215 ℃ for 5 seconds in a tenter oven, and after cooling, both ends of the film in the width direction were trimmed and then wound up by a winder. The polyamide film of the base layer thus obtained was biaxially stretched and laminated to obtain a product roll of a polyamide resin film, the thickness of the polyamide film being 15 μm and the thickness of the laminated portion being 0.1 μm. The take-up speed was 120 m/min.

The measurement results of the properties of the obtained film are shown in table 2. As is clear from table 2, the uneven thickness spread ratio in example 18 was 2.1 times. Specifically, the coefficient of thickness variation of the unstretched film was 1.0%, and the coefficient of thickness variation of the stretched film was 2.1%. The average value of the refractive index in the thickness direction was 1.5036, and the rate of change was 0.1%, and the film was uniformly stretched. F shown in FIG. 4_CPThere was no drop at all. Further, since the urethane resin was laminated, the laminated adhesion strength was improved as compared with the PVDC resin laminated in examples 11 to 16, and the change rate was equal to those in examples 11 to 16, and the uniformity of the performance was excellent. Among them, since it is not a urethane-based resin, that is, a gas barrier resin, the oxygen permeability is not evaluated.

Comparative example 5

As compared with example 11, the condition of decreasing the longitudinal stretching magnification factor locus expressed by the inter-jig distance as shown in B of fig. 1 was employed. The reduction rate was adjusted to 5%. Except for this, a laminated polyamide resin film was obtained under the same conditions as in example 11.

The measurement results of the properties of the obtained film are shown in table 2. As is clear from table 2, the uneven thickness spread rate in this comparative example 5 is 9.5 times. That is, the coefficient of thickness variation of the stretched film was 9.5% and 1.0% with respect to the unstretched film. The average value of the refractive index in the thickness direction was 1.5037, and the rate of change was 1.2%, indicating significant stretching unevenness. F shown in FIG. 4_CPTemporarily decreased by 30%. And thus cannot be used as a film product.

Comparative example 6

As compared with example 15, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was employed. Further, the reduction rate was 5%. A laminated polyamide resin film was obtained in the same manner as in example 15 except for the above.

The measurement results of the properties of the obtained film are shown in table 2. As is clear from table 2, in comparative example 6, the rate of uneven thickness expansion in the width direction was 9.8 times (the coefficient of thickness change with respect to the unstretched film was 1.0%, and the coefficient of thickness change of the stretched film was 9.8%). The average value of the refractive index in the thickness direction was 1.5042, and the rate of change was 1.4%, indicating significant stretching unevenness. F shown in FIG. 4_CPTemporarily decreased by 30%. And thus cannot be used as a film product.

Comparative example 7

As compared with example 16, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was employed. Further, the reduction rate was 5%. Except for this, a laminated polyamide resin film was obtained in the same manner as in example 16.

The measurement results of the properties of the obtained film are shown in table 2. As is clear from table 2, in comparative example 7, the rate of uneven thickness expansion in the width direction was 10.1 times (the coefficient of thickness change with respect to the unstretched film was 1.0%, and the coefficient of thickness change of the stretched film was 10.1%). The average value of the refractive index in the thickness direction was 1.5191, and the rate of change was 2.9%, indicating significant stretching unevenness. F shown in FIG. 4_CPTemporarily decreased by 30%. And thus cannot be used as a film product.

Example 19

Using a 5-layer coextrusion T die, MXD6 constituting the resin layer (X) was melt-extruded at 280 ℃ by A1 st extruder, a mixture of a nylon 6 resin (a 1030-BRF manufactured by yunigaku corporation) and the main chip so that the compounding ratio of silica constituting the resin layer (Z) was 0.05 mass% was melt-extruded at 270 ℃ by a 2 nd extruder, and a resin composed of 30 parts by mass of MXD6 and 70 parts by mass of XE3038 constituting the resin layer (Y) was melt-extruded at 280 ℃ by a 3 rd extruder. Subsequently, the laminated unstretched sheet obtained by stacking the sheets in the order of Z/Y/X/Y/Z was extruded from a die, adhered to a cooling drum having a surface temperature of 20 ℃ and quenched to obtain an unstretched laminated sheet having a thickness of 150 μm. Then, water absorption treatment was carried out in a warm water tank in which the temperature was adjusted to 50 ℃. Then, the film was fed to a simultaneous biaxial stretching tenter driven by a linear motor, both ends in the width direction thereof were held by clips, and simultaneous biaxial stretching was performed at 190 ℃ at a longitudinal stretching magnification of 3.0 times and a transverse stretching magnification of 3.3 times. At this time, the frequency of the linear motor driver is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and the longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance does not decrease as shown in fig. 1a is used.

Further, the relaxation rate in the transverse direction was adjusted to 5%, and the film was subjected to heat treatment at 210 ℃ for 4 seconds and then gradually cooled to room temperature to obtain a product roll of a laminated stretched film having a thickness of 4.5/0.5/5.0/0.5/4.5 μm. The take-up speed was 120 m/min.

The measurement results of the properties of the obtained film are shown in table 3. As is clear from table 3, the rate of uneven thickness expansion in the width direction in example 19 was 2.2 times. Specifically, the coefficient of thickness variation of the unstretched film was 1.0%, and the coefficient of thickness variation of the stretched film was 2.2%. The average value of the refractive index in the thickness direction was 1.497, and the rate of change thereof was 0.04%, and the film was uniformly stretched. In the drawing, F shown in FIG. 4_CPNot dropping at all. That is, a film uniformly stretched in both the width direction and the length direction was obtained. Therefore, almost the entire total width of the film can be used as a product.

[ Table 3]

Example 20

As compared with example 19, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was used. The reduction rate was 2%. Except for this, a product roll obtained by simultaneously biaxially stretching and laminating a polyamide resin film was obtained in the same manner as in example 19.

The measurement results of the properties of the obtained film are shown in table 3. As is clear from table 3, in example 20, the rate of expansion of the thickness unevenness in the width direction was 3.4 times (the thickness variation coefficient with respect to the unstretched film was 1.0%, and the thickness variation coefficient of the stretched film was 3.4%), and the thickness unevenness was larger than that in example 19. The average value of the refractive index in the thickness direction was 1.500, and the rate of change thereof was 0.26%, and the film was uniformly stretched. F shown in FIG. 4_CPThe equilibrium state is temporarily formed without dropping. That is, a film which is uniformly stretched and has no problem in practical use is almost all obtained. Therefore, the film can be used as a film product.

Example 21

As compared with example 19, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was used. Further, the reduction rate was set to 1%. Except for this, a simultaneous biaxial stretching polyamide film product roll was obtained in the same manner as in example 19.

The measurement results of the properties of the obtained film are shown in table 3. As is clear from table 3, in example 21, the rate of expansion of the thickness unevenness in the width direction was 3.1 times (the thickness variation coefficient with respect to the unstretched film was 1.0%, and the thickness variation coefficient of the stretched film was 3.1%), and the thickness unevenness was slightly larger than that in example 19. The average value of the refractive index in the thickness direction was 1.498, the rate of change was 0.22%. F_CPDoes not drop. That is, a film which is uniformly stretched and has no problem in practical use is almost all obtained. Therefore, the film can be used as a film product.

Example 22

The unstretched polyamide film produced under the same conditions as in example 19 was fed to a pantograph type simultaneous biaxial stretching machine, and both ends in the width direction thereof were sandwiched by clamps, and simultaneous biaxial stretching was carried out at a longitudinal stretching ratio of 3.0 times and a transverse stretching ratio of 3.3 times. At this time, the rail interval is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and as shown in fig. 1a, the longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance does not decrease is used. Except for this, a simultaneous biaxial stretching polyamide film product roll was obtained in the same manner as in example 19.

The measurement results of the properties of the obtained film are shown in table 3. As is clear from table 3, in example 22, the rate of uneven thickness expansion in the width direction was 2.4 times (the coefficient of thickness change with respect to the unstretched film was 1.0%, and the coefficient of thickness change of the stretched film was 2.4%). The average value of the refractive index in the thickness direction was 1.496, and the rate of change was 0.11%, and the film was uniformly stretched. F_CPThere was no drop at all. That is, a film stretched uniformly in both the width direction and the length direction is obtained, and almost the entire width of the film can be used as a product.

Example 23

Using a 5-layer coextrusion T die, MXD6 constituting the resin layer (X) was melt-extruded at 280 ℃ by A1 st extruder, a mixture of a nylon 6 resin (a 1030-BRF, manufactured by yunigaku corporation) and the above main chip in a silica blending ratio of 0.05 mass% constituting the resin layer (Z) was melt-extruded at 270 ℃ by a 2 nd extruder, and a mixture of 30 parts by mass of MXD6 and 70 parts by mass of XE3038 constituting the resin layer (Y) was melt-extruded at 280 ℃ by a 3 rd extruder. Subsequently, the laminated undrawn sheet obtained by stacking the layers in the order of Z/Y/X/Y/Z was extruded from a die, and the resultant was closely adhered to a cooling drum having a surface temperature of 18 ℃ for quenching, thereby obtaining an undrawn laminated sheet having a thickness of 250 μm. Then, water absorption treatment was carried out in a warm water tank in which the temperature was adjusted to 50 ℃. Then, the film was fed to a simultaneous biaxial stretching tenter driven by a linear motor, both ends in the width direction thereof were held by clips, and simultaneous biaxial stretching was performed at 190 ℃ at a longitudinal stretching magnification of 3.0 times and a transverse stretching magnification of 3.3 times. At this time, the frequency of the linear motor driver is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and the longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance does not decrease as shown in fig. 1a is used.

Further, the relaxation rate in the transverse direction was adjusted to 5%, and the film was subjected to a heat treatment at 210 ℃ for 4 seconds and then gradually cooled to room temperature to obtain a product roll of a laminated stretched film having a thickness of 8.0/0.5/8.0/0.5/8.0 μm. The take-up speed was 120 m/min.

The measurement results of the properties of the obtained film are shown in table 3. As is clear from table 3, the rate of uneven thickness expansion in the width direction in example 23 is 2.4 times. Specifically, the coefficient of thickness variation of the unstretched film was 1.0%, and the coefficient of thickness variation of the stretched film was 2.4%. The average value of the refractive index in the thickness direction was 1.499, and the rate of change thereof was 0.33%, and the film was uniformly stretched. In the drawing, F shown in FIG. 4_CPNot dropping at all. That is, a film uniformly stretched in both the width direction and the length direction was obtained. Therefore, almost the entire total width of the film can be used as a product.

Example 24

Using a 3-layer coextrusion T die, MXD6 and an ethylene-butene copolymer as an impact resistance-improving resin for constituting the resin layer (X) were melt-extruded at 280 ℃ by a1 st extruder so as to be MXD 6/ethylene-butene copolymer (mass ratio) of 97/3. Further, a mixture of a nylon 6 resin (A1030-BRF available from Youngko Co., Ltd.) and the main chip, which constitutes the resin layer (Z) and had a silica content of 0.05 mass%, was melt-extruded at 270 ℃ by a 2 nd extruder. Subsequently, the laminated undrawn sheet stacked in the order of Z/X/Z was extruded from a die, adhered to a cooling drum having a surface temperature of 19 ℃ and quenched to obtain an undrawn laminated sheet having a thickness of 150 μm. Then, water absorption treatment was carried out in a warm water tank in which the temperature was adjusted to 50 ℃. Then, the film was fed to a simultaneous biaxial stretching tenter driven by a linear motor, both ends in the width direction thereof were held by clips, and simultaneous biaxial stretching was performed at 180 ℃ at a longitudinal stretching magnification of 3.0 times and a transverse stretching magnification of 3.3 times. At this time, the frequency of the linear motor driver is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and the longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance does not decrease as shown in fig. 1a is used.

Further, the relaxation rate in the transverse direction was adjusted to 5%, and the film was subjected to a heat treatment at 210 ℃ for 4 seconds and then gradually cooled to room temperature to obtain a product roll of a laminated stretched film having a thickness Z/X/Z of 5.0/5.0/5.0 μm. The take-up speed was 120 m/min.

The measurement results of the properties of the obtained film are shown in table 3. As is clear from table 3, the rate of uneven thickness expansion in the width direction in example 24 was 2.1 times. Specifically, the coefficient of thickness variation of the unstretched film was 1.0%, and the coefficient of thickness variation of the stretched film was 2.1%. The average value of the refractive index in the thickness direction was 1.496, and the rate of change thereof was 0.07%, and the film was uniformly stretched. In the drawing, F shown in FIG. 4_CPNot dropping at all. That is, a film uniformly stretched in both the width direction and the length direction was obtained. Therefore, almost the entire total width of the film can be used as a product.

Example 25

EVOH (F101B, manufactured by KURARAAY corporation) constituting the resin layer (X) was melt-extruded at 270 ℃ by A1 st extruder, a nylon 6 resin (A1030-BRF, manufactured by YOU NIGHT CORPORATION) in which the blend ratio of silica to the resin layer (Z) was 0.05 mass% and the main chip were melt-extruded at 270 ℃ by a 2 nd extruder, and a laminated unstretched sheet constituted by nylon 6/EVOH/nylon 6 was melt-extruded from a T die having a width of 600mm, and was cooled while being in close contact with a cooling drum having a surface temperature of 18 ℃ to form an unstretched polyamide film having a thickness of 150 μm. Then, water absorption treatment was carried out in a warm water tank in which the temperature was adjusted to 50 ℃. Then, the film was fed to a simultaneous biaxial stretching tenter driven by a linear motor, both ends in the width direction thereof were held by clips, and simultaneous biaxial stretching was carried out at 170 ℃ at a longitudinal stretching magnification of 3.0 times and a transverse stretching magnification of 3.3 times. At this time, the frequency of the linear motor driver is adjusted to correct the distortion of the longitudinal stretching magnification trajectory, and the longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance does not decrease as shown in fig. 1a is used.

Further, after heat treatment at 210 ℃ for 4.0 seconds, the film was directly heat-treated at 170 ℃ for 10 seconds, cooled at 90 ℃ for 2.0 seconds, and then both widthwise ends of the film were trimmed and wound up by a winder. Thus, a product roll of a simultaneously biaxially laminated stretched polyamide film having a nylon 6/EVOH/nylon 6 ratio of 5.0/5.0/5.0 μm was obtained. The take-up speed was 120 m/min.

The measurement results of the properties of the obtained film are shown in table 3. As is clear from table 3, the rate of uneven thickness expansion in the width direction in example 25 was 2.5 times. Specifically, the coefficient of thickness variation of the unstretched film was 1.0%, and the coefficient of thickness variation of the stretched film was 2.5%. The average value of the refractive index in the thickness direction was 1.495, and the rate of change thereof was 0.23%, and the film was uniformly stretched. In the drawing, F shown in FIG. 4_CPNot dropping at all. That is, a film uniformly stretched in both the width direction and the length direction was obtained. Therefore, almost the entire total width of the film can be used as a product.

Comparative example 8

As compared with example 19, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was used. Further, the reduction rate was 5%. Except for this, a product roll of a simultaneous biaxial stretching polyamide film was obtained in the same manner as in example 19.

The measurement results of the properties of the obtained film are shown in table 3. As is clear from table 3, in comparative example 8, the rate of uneven thickness expansion in the width direction was 9.5 times (the coefficient of thickness change with respect to the unstretched film was 1.0%, and the coefficient of thickness change of the stretched film was 9.5%). The average value of the refractive index in the thickness direction was 1.501, the rate of change was 1.3%, and significant stretching unevenness was observed. F shown in FIG. 4_CPTemporarily decreased by 30%. It is understood from Table 3 that the film could not be used as a film product.

Comparative example 9

As compared with example 23, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was employed. Further, the reduction rate was 5%. Except for this, a product roll of a simultaneous biaxial stretching polyamide film was obtained in the same manner as in example 23.

The measurement results of the properties of the obtained film are shown in table 3. As is clear from table 3, in comparative example 9, the rate of uneven thickness expansion in the width direction was 9.7 times (the coefficient of thickness change with respect to the unstretched film was 1.0%, and the coefficient of thickness change of the stretched film was 9.7%). The average value of the refractive index in the thickness direction was 1.498, the rate of change was 1.5%, and significant stretching unevenness was observed. F_CPTemporarily decreased by 30%. It is understood from Table 3 that the film could not be used as a film product.

Comparative example 10

As compared with example 25, a longitudinal stretching magnification trajectory in which the longitudinal stretching magnification represented by the inter-jig distance was decreased as shown in B of fig. 1 was employed. Further, the reduction rate was 5%. Except for this, a product roll of a simultaneous biaxial stretching polyamide film was obtained in the same manner as in example 25.

The measurement results of the properties of the obtained film are shown in table 3. From Table 3 canIt is understood that the width-directional uneven thickness spread rate in this comparative example 10 is 11.1 times (the thickness variation coefficient with respect to the unstretched film is 1.0%, and the thickness variation coefficient of the stretched film is 11.1%). The average value of the refractive index in the thickness direction was 1.499, the rate of change was 3.2%, and significant stretching unevenness was observed. F_CPTemporarily decreased by 30%. It is understood from Table 3 that the film could not be used as a film product.

Claims

1. A method for producing a polyamide resin film, which is a simultaneous biaxial stretching method by a tenter method in which an end portion in a width direction of an unstretched film is sandwiched by clips and biaxially stretched simultaneously in a longitudinal direction and a transverse direction, characterized in that a support portion to which the clips are attached is driven to travel along a guide rail,

the support part runs at a bending part which is a bending part of a running track of a transverse stretching section and comprises a bending track of a stretching initial part and a reverse bending track of a stretching tail part,

in the bending track at the initial stretching part, the linear distance between the adjacent clamps is changed in a manner of expanding and recovering,

in the reverse bending track at the stretching tail part, the linear distance between the adjacent clamps is changed in a mode of shrinking and recovering,

the longitudinal stretching magnification, which is expressed by the linear distance between the adjacent clips, is not reduced by 5% or more of the maximum stretching magnification of the longitudinal stretching from the start of the transverse stretching until the maximum stretching magnification of the transverse stretching is reached.

2. The method for producing a polyamide resin film according to claim 1, wherein a longitudinal stretching ratio represented by a linear distance between the adjacent clamps is not decreased by more than 3% of a maximum stretching ratio of the longitudinal stretching from the start of the transverse stretching to the maximum stretching ratio of the transverse stretching.

3. The method for producing a polyamide resin film according to claim 1, wherein at any point in time during stretching, the maximum stretch ratio of the stretch ratio in the longitudinal direction to the stretch ratio in the longitudinal direction at that point in time is higher than the maximum stretch ratio of the stretch ratio in the transverse direction to the stretch ratio in the transverse direction at that point in time.

4. The method for producing a polyamide resin film according to claim 1, wherein the longitudinal stretching magnification of the simultaneous biaxial stretching is 2.5 to 4.5 times, and the ratio of the longitudinal stretching magnification to the transverse stretching magnification is 1: 0.5 to 1.5.

5. The method for producing a polyamide resin film according to claim 1, wherein the tenter method simultaneous biaxial stretching machine is driven by a linear motor system.

6. The method for producing a polyamide resin film according to claim 1, wherein a laminate portion is formed by a coating method on at least one surface of an unstretched film obtained by pressing a polyamide resin sheet melt-extruded from a die against a casting roll, and both ends in the width direction of the laminate obtained thereby are sandwiched by jigs and biaxially stretched in both the longitudinal direction and the transverse direction.

7. A polyamide resin film obtained by the production method according to claim 1, wherein the film has a thickness unevenness expansion ratio of 3.5 times or less and a refractive index variation ratio across the entire plane in the film thickness direction of 0.5% or less.

8. The polyamide resin film according to claim 7, wherein the film has a thickness unevenness expansion ratio of 2.5 times or less and a change ratio of a refractive index in a thickness direction of the film over the entire plane of 0.25% or less.

9. The polyamide resin film according to claim 7, wherein the rate of change in the adhesion strength of the surface layer of the film over the entire surface is 10% or less.

10. The polyamide resin film according to claim 7, wherein the film has a thickness unevenness expansion ratio of 2.5 times or less, a change ratio of a refractive index in a thickness direction of the film over the entire plane of the film is 0.25% or less, and a change ratio of an adhesion strength of a surface layer of the film over the entire plane of the film is 8.0% or less.

11. The polyamide resin film according to claim 9, wherein a laminate portion formed from a product of at least one of a polyvinylidene chloride copolymer resin, a polyester resin, a polyurethane resin, a polyacrylic resin, a polyvinyl alcohol resin, a polycarboxylic acid resin, an olefin-polycarboxylic acid copolymer resin, and an ethylene-vinyl acetate copolymer resin is laminated on the polyamide resin film of the base portion.

12. The polyamide resin film according to claim 7, wherein a 2 nd resin layer Z is laminated on at least one surface of a1 st resin layer X, the 1 st resin layer X is composed of one of a polyamide resin A and an ethylene-vinyl acetate copolymer saponified product, the polyamide resin A is composed of a xylylenediamine component and an aliphatic dicarboxylic acid component having 4 to 12 carbon atoms, and the 2 nd resin layer Z is composed of a polyamide resin B.