JP2005162869A - Heat-shrinkable polyester-based resin film and label using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a heat-shrinkable polyester-based film resin that has a sufficiently high heat shrinkage percentage, causes no shrinkage unevenness of film in heat shrinkage, has a beautiful appearance and impact resistance to control fracture in processing, stably keeps its appearance even under a high-temperature condition, has excellent tearability and unsealability in distribution and use after heat shrinkage and fitting as a packaging bag or a label and excellent perforation cutting necessary for a label releasing process in a recycling process. <P>SOLUTION: The heat-shrinkable polyester-based film is a polyester-based film having ≥20 maximum heat shrinkage percentage at least in one direction, ≤50% haze value and ≥2.0 J impact strength, has perforation cutting to make ≤1 mm maximum width in the direction perpendicular to the tear direction of the film and contains 0.1-20 wt.% of a styrenic thermoplastic elastomer. The heat-shrinkable polyester-based label is produced by using the heat-shrinkable polyester-based resin film. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polyester film suitable as a packaging material used for coating, binding, exterior, and the like.

  The heat-shrinkable film of the present invention has particularly low shrinkage unevenness, gives a shrinkage result excellent in heat resistance, stably maintains a beautiful finished appearance, is excellent in impact resistance, hardly breaks, and further lightly shrinks. It has excellent tearability and perforation cutability, and is suitably used for container barrel labels.

  Since heat-shrinkable film has a function of shrinkability, it does not use fixing means such as adhesives and fasteners for the object to be applied, and it is laminated and integrated with the object by the shrinkage force and shapeability generated from the film. I can do it. For example, a design that takes advantage of the shape of the bottle can be applied by processing the film into a tube shape, covering the bottle, and allowing the film to pass through a heat-shrinkable tunnel for shrinkage and adhesion. Therefore, it has not only mechanical protection of the object by laminating or coating, but also functions such as binding and sealing.

  Further, when the shrink film itself has a special function, the special function can be freely added to the target object after the lamination by laminating. This property is effectively used in the packaging field where the main purposes are content preservation, protection and display during distribution, and design.

  For example, various types of containers such as bottles (including glass and plastic bottles) and cans and long objects (pipes, rods, wood, various rods, etc.), or single sheets such as films, sheets, plates, etc. Used for bundling, exterior or sealing.

  Specifically, it is used for applications that cover part or all of the cap part, shoulder part, and body part of the bottle for the purpose of improving the commercial value by displaying, protecting, binding, and functionalizing. Here, functionalization refers to the provision of shielding properties such as ultraviolet rays, visible light, infrared light and other electromagnetic waves, provision of gas barrier properties, and other methods such as coating, lamination, and kneading on the base shrink film. In other words, a shrinkable film having various functions is prepared, and a new function is imparted to, for example, a container having no function by shrinking and attaching the film.

  Furthermore, it is also used for applications such as stacking and packaging a plurality of boxes, bottles, plates, sticks, notebooks, etc., and packaging (skin package) with a film in close contact with an object to be packaged. At this time, when the film is preliminarily displayed and shaped for the purpose of design, the product is a shrinkable label.

  As the material for the film, polyvinyl chloride, atactic polystyrene, polyester, polyamide, aliphatic polyolefin, derivatives thereof, hydrochloric acid rubber, and the like are used. Usually, these films are formed into a tube shape and, for example, covered with a bottle or pipes are collected, and then packaged or bound by heat shrinking.

  As a result of using materials with various properties in this way, there is a common or unique advantage for each material.

  That is, all of the above conventional films have poor heat resistance and cannot withstand high temperature boil processing and retort processing, so that when applied to foods, hygiene products, pharmaceutical applications, high temperature disinfection is not possible. There is. For example, when a retort process is performed, the conventional film is easily damaged during the process.

  Referring to the polyvinyl chloride film, this film has very good heat shrinkage properties, but it has poor adhesion to ink during printing, and moreover, it tends to form a gel-like additive characteristic of the resin. Therefore, it is easy to generate a pinhole on the printing surface of the film. Furthermore, there is a problem of environmental pollution when discarded and incinerated.

  Polystyrene film has a low density and is advantageous for separation in the recycling process, but has poor heat resistance. In addition, since it shrinks with time after production, a change in printing pitch due to shrinkage occurs, and high-precision printing cannot be performed. Furthermore, it was partly dissolved or swollen in the solvent contained in the printing ink, and good printing was difficult.

  The polyester film is excellent in heat resistance, dimensional stability, solvent resistance, and the like. However, in order to achieve desirable shrinkage characteristics, adhesion, etc., precise manufacturing condition control technology is required. It has also been pointed out that the impact resistance for preventing breakage during processing is inferior.

  Furthermore, it is said that general heat-shrinkable polyester films are inferior to tear-opening properties during distribution and perforation cuts necessary for the label peeling process in the recycling process after being heat-shrinked as packaging bags or labels. In some cases, not only in the cutting direction but also in the orthogonal direction.

  The present invention solves the problems of conventional heat-shrinkable polyester films and labels, and the object of the present invention is that the heat shrinkage rate is sufficiently large, and the film has uneven shrinkage when heat-shrinked. It does not occur, has a beautiful appearance, has impact resistance that suppresses breakage during processing, stably maintains its appearance even under high temperature conditions as experienced later, and is heat shrink-fitted as a packaging bag or label Then, it is providing the heat-shrinkable polyester-type film and label excellent in the tear openability at the time of distribution | circulation and use, and the perforation cutting property required for the label peeling process in a recycling process.

  In order to achieve the above object, the heat shrinkable polyester resin film of the present invention has a maximum heat shrinkage of 20% or more in at least one direction, a haze value of 50% or more and less than 80%, and an impact resistance. This is a polyester resin film with a strength of 2.0 J or more, and a perforation with a spacing of 4.72 mm is linearly inserted into the film and torn by hand. The film is placed between the polarizing plates so as to be a dark field, and has a perforation cut property in which the value when the maximum width in the direction perpendicular to the tear direction of the brightened portion within the field scale range is measured is 1 mm or less. It is characterized by that.

  Moreover, in order to achieve the said objective, the heat-shrinkable polyester-type resin film of this invention contains 0.1-20 weight% of styrene-type thermoplastic elastomers, It is characterized by the above-mentioned.

  Furthermore, in order to achieve the above object, the heat-shrinkable polyester-based label of the present invention is manufactured using the above-described heat-shrinkable polyester-based resin film.

  The heat-shrinkable label of the present invention and the film comprising the same have a maximum heat shrinkage rate of 20% or more in at least one direction, a haze value of 50% or more and less than 80%, and an impact strength of 2.0 J. Since it has a perforation cut property of 1 mm or less, it has a heat shrinkage rate sufficient for practical use, has few breaks during processing, and is heat shrunk for use in coating or binding. Provides a uniform shrinkage result regardless of temperature fluctuations and non-uniformity in the shrinking process, and is excellent in cutability, so that it is easy to separate the object to be attached and the label in light shrinkage label fields such as body labels. Yes, its recyclability is demonstrated.

  The film material used in the present invention is a polyester resin composition. As the polyester-based resin, a known (copolymerized) polyester obtained by polycondensation with a polyhydric alcohol component using one or more of aromatic dicarboxylic acids, their ester-forming derivatives, and aliphatic dicarboxylic acids as dicarboxylic acid components. Can be used.

  Examples of the aromatic dicarboxylic acid include terephthalic acid, isophthalic acid, naphthalene-1,4- or -2,6-dicarboxylic acid, and 5-sodium sulfoisophthalic acid. Examples of these ester derivatives include derivatives such as dialkyl esters and diaryl esters.

  Examples of the aliphatic dicarboxylic acid include dimer acid, glutaric acid, adipic acid, sebacic acid, azelaic acid, oxalic acid, and succinic acid. Further, an oxycarboxylic acid such as p-oxybenzoic acid, and a polyvalent carboxylic acid such as trimellitic anhydride and pyromellitic anhydride may be used in combination as necessary.

  Examples of the polyhydric alcohol component include ethylene glycol, diethylene glycol, dimer diol, propylene glycol, triethylene glycol, 1,4-butanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, 1,6-hexanediol, 3- Alkylene glycols such as methyl 1,5-pentanediol, 2-methyl-1,5-pentanediol, 2,2-diethyl-1,3-propanediol, 1,9-nonanediol, 1,10-decanediol, Examples include alkylene oxide adducts of bisphenol compounds or derivatives thereof, trimethylolpropane, glycerin, pentaerythritol, polyoxytetramethylene glycol, polyethylene glycol and the like. Moreover, although it is not a polyhydric alcohol, (epsilon) -caprolactone can also be used.

  The polyester raw material which comprises a polyester-type heat-shrinkable film may be individual, and may mix and use 2 or more types. When used alone, homopolyesters other than polyethylene terephthalate such as polybutylene terephthalate, polycyclohexylene dimethyl terephthalate, and polyethylene naphthalate are preferable. This is because polyethylene terephthalate alone does not exhibit heat shrinkability.

  From the viewpoint of adjusting heat shrinkage characteristics, specifically adjusting the heat shrink temperature range, shrinkage speed and shrinkage stress, it is possible to blend two or more polyesters having different glass transition temperatures (Tg). preferable. In particular, it is preferable to use a mixture of polyethylene terephthalate and a copolyester (may be two or more types), but a combination of copolyesters may also be used. Moreover, polybutylene terephthalate, polycyclohexylene dimethyl terephthalate, and polyethylene naphthalate can be combined, or these can be used in combination with other copolyesters.

  The most preferable heat shrinkage property is suitable for adjustment of crystallinity, glass transition point, etc., and is a copolymer composed of polyethylene terephthalate, polybutylene terephthalate, a mixed diol component of ethylene glycol and neopentyl glycol, and terephthalic acid. Three types of blends with polyester.

  Polyesters can be produced by melt polymerization in the usual way, but the so-called direct polymerization method in which oligomers obtained by direct reaction of dicarboxylic acids and glycols are polycondensed, dimethyl ester of dicarboxylic acid and glycol are transesterified. Examples include a so-called transesterification method in which polycondensation is performed after the reaction, and any production method can be applied. Moreover, the polyester obtained by another polymerization method may be sufficient.

  The degree of polymerization of the polyester is preferably an intrinsic viscosity of 0.3 to 1.3 dl (deciliter) / g from the viewpoint of mechanical properties and moldability.

  In addition to polymerization catalysts such as antimony oxide, germanium oxide, and titanium compounds, polyesters such as Mg salt, Ca salt, Mn salt, Zn salt, Co salt, etc. are used in order to prevent problems such as coloring and gel generation. Metal salts may be added. Moreover, you may add phosphorus compounds, such as a phosphate ester derivative.

  Further, if necessary, fine particles such as silica, titanium dioxide, kaolin, calcium carbonate may be added, and an antioxidant, an ultraviolet absorber, an antistatic agent, a colorant, an antibacterial agent, etc. may be added. it can.

  As a method of imparting impact resistance and cutability to the heat-shrinkable polyester resin film and label in the present invention, blending a cutability improving material into the raw material resin can be mentioned. A styrenic thermoplastic elastomer is suitable as the cutting property improving material. A preferable addition amount is 0 to 20% by weight.

  By adding such a cutting property improving material, a complete or semi-complete “sea-island structure” is generated, and the stress due to film deformation concentrates on the “island” part made of styrenic thermoplastic elastomer. It is considered that the cutting property is improved by the stress at the time of cutting being concentrated on the thermoplastic elastomer.

  The polyester-based composition is formed into a film by a known method (for example, an extrusion method or a calendar method). The shape of the film is, for example, a flat shape or a tube shape, and is not particularly limited.

  A normal method is adopted as the stretching method. Examples thereof include a roll stretching method, a long gap stretching method, a tenter stretching method, and a tubular stretching method. In any of these methods, stretching is performed by sequential biaxial stretching, simultaneous biaxial stretching, uniaxial stretching, and combinations thereof. In the biaxial stretching, stretching in the vertical and horizontal directions may be performed at the same time, but sequential biaxial stretching in which one of them is performed first is effective, and either of the vertical and horizontal orders may be performed first.

  The draw ratio is arbitrarily set in the range of 1.0 to 6.0 times, and the magnification in one predetermined direction and the magnification in the direction orthogonal to the direction may be the same or different. In the stretching step, preheating is preferably performed at a temperature not lower than the glass transition temperature of the polymer constituting the film, for example, not higher than Tg + 50 ° C.

  In the heat setting after stretching, for example, it is recommended to pass through a heating zone of 30 ° C. to 150 ° C. for about 1 second to 30 seconds after stretching. Further, after the film is stretched and before or after heat setting, the relaxation treatment may be performed at a predetermined degree.

  Further, after the stretching, a step of cooling while applying a stress to the film while keeping the stretched or tensioned state, or a cooling step after releasing the tensioned state following the treatment may be added. The thickness of the obtained film is preferably in the range of 10 to 100 μm.

  The heat-shrinkable polyester resin film and label in the present invention are required to have a maximum heat shrinkage of at least 20% in one direction.

  This performance can be used for general barrel labels. If it is 50% or more, it can be attached to a general PET bottle. Furthermore, if it is 60% or more, even a container having a complicated shape can be mounted. If it is 70% or more, it can be suitably used as a full label of a container having a complicated shape.

  Examples of methods for improving the maximum heat shrinkage include increasing the draw ratio, reducing heat setting, and adjusting the compatibility state of the mixed resin.

  The heat-shrinkable polyester resin film and label in the present invention must have a haze value of 50% or more and less than 80%. As a result, a semi-transparent texture can be obtained, and an optimum value can be adjusted in consideration of the cut property depending on the application. Specifically, for example, the addition of inorganic particles and organic particles can be performed in addition to the amount of the cutting property improving material.

  When the haze value is 50% or less, the color of the ink at the time of printing becomes unclear, and when it exceeds 80%, the watermark portion becomes cloudy, which is not preferable in either case.

  The haze value can be adjusted by adjusting the blending amount of the rubber particles described above and adjusting the addition amount of inorganic particles and organic particles.

  The heat-shrinkable polyester resin film and the label in the present invention have impact strength and cut property.

  The impact resistance referred to here is a characteristic necessary for preventing bag breakage during processing, and can be represented by, for example, a piercing impact strength measured by an impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.).

  As the impact strength, the above film impact tester (manufactured by Toyo Seiki Seisakusho Co., Ltd.) was used to measure a 0.5 inch φ weight and convert it to a film thickness of 25 μm (= measured value × 25 / actual film film) Thickness) is preferably 2.0 J (joule) or more.

  If the impact strength is 2.0 J or less, bag breakage during processing tends to occur, leading to a decrease in yield, which is not preferable.

  In addition, cutability means that when tearing with a notch, it can be cut stably in the direction that you would most likely manually (tearability), and the perforation is straight and you can do it manually along your eyes. It shows the property (perforation cut ability) that can be stably cut when it is torn.

Of the cutting properties, the tearing property indicates the degree of deviation from the intended direction of the tearing direction when a 5 mm cut is made with scissors, the direction is determined, and tearing is performed manually.

  The perforation cutability is a measure of how the perforated film can be torn along the perforation when the film is perforated manually. A straight line of 72mm perforations, teared by hand, and inserted into the projector (10x objective) between the polarizing plates made of crossed Nicols so that it becomes a dark field, bright within the field scale range The maximum width in the direction orthogonal to the tearing direction of the part that became (that is, the part that thinned by extending when tearing) was measured, and when the value was 1 mm or less, it was determined as OK.

  When the perforation cut property is 1 mm or more, the transition from one hole to the next hole at the time of tearing becomes unstable, and this causes the crack to spread in an unexpected direction.

  Examples of the method for imparting cutability to the heat-shrinkable polyester resin film and the label in the present invention include blending a styrene-based thermoplastic elastomer into the raw material resin as a cutability improving material. The content is preferably 0.1 to 20% by weight.

  If the content of the styrene-based thermoplastic elastomer is 0.1% by weight or less, the effect of addition cannot be obtained, the impact resistance becomes insufficient, and the haze value also decreases. On the other hand, if the content of the styrenic thermoplastic elastomer exceeds 20%, the thermal shrinkage rate is lowered, which is not preferable in any case.

  The heat-shrinkable film and label thus obtained are finished with a beautiful appearance as compared with the case of using the conventionally proposed heat-shrinkable film. A tear-opening property that can be stably cut in the direction that you want when you put it and tear it, and when you peel off the label with a perforation manually as part of the recycling process, along the perforation It is suitable for strict fractional recycling because it has the perforation cutability that can be cut stably and stably.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited only to these examples. The evaluation method of the film performed by this invention is shown below.

(1) Maximum heat shrinkage rate The direction of shrinking the film is the long side, and the film is cut out to have a width of 15 mm. Marks are marked at intervals of 200 mm in the long side direction. This sample is suspended in a gear oven, heated by applying 100 ° C. hot air for 1 minute, and the amount of change in the distance between the marked lines is measured. The percentage of the change amount with respect to the original length is defined as a heat shrinkage rate (%), and the temperature is increased by 5 ° C., and the measurement is performed up to 150 ° C. The maximum value of the heat shrinkage rate of these samples is adopted.

(2) Perforation cut ability (Ripple distance)
A perforation with an eye spacing of 4.72 mm is placed in a straight line on the film, and it is torn by hand (created with every other roulette tooth marked CLOVER). A projector (Nikon PROFILE PROJECTOR, V-12, objective lens magnification 10 ×) was used as transmitted light, and the film was placed between the polarizing plates made of crossed Nicols so as to be in a dark field, and the brightness was within the visual field scale range. Measure the maximum width in the direction perpendicular to the tear direction of the part. A value of 1 mm or less was accepted.

(3) Tearability Use a scissors to cut a 5mm cut, determine the direction, and tear manually. The tearability was evaluated by setting a standard as follows.
○: Can be cut stably in the desired direction △: Cutting direction is not determined ×: Cutting in an unintended direction

(4) Using an intrinsic viscosity Ubbelohde type viscosity tube, the sample was dissolved in a mixed solvent of phenol / tetrachloroethane in a weight ratio of 6/4 at a solution concentration of 0.4 g / dl and reduced from the value measured at a temperature of 30 ° C. The viscosity was determined and converted to the intrinsic viscosity.

(5) Haze value Measured according to JIS K-7105.

(6) Impact strength The impact strength measured by using a film impact tester (manufactured by Toyo Seiki Co., Ltd.) in an atmosphere of 23 ° C.-60% RH. However, the diameter of the weight was 0.5 inch φ, and the data was a value converted to a film thickness of 25 μm (= measured value × 25 / actual film thickness).

(Example 1)
PET resin (PEs-A: limiting viscosity 0.75), copolymerized PET resin (PEs-B: limiting viscosity 0.725) copolymerized with 30 mol% of neopentyl glycol, PBT resin (PEs-C: NV5010 / Mitsubishi Rayon) 3% by weight of a styrene-based thermoplastic elastomer (Tuftec H1052 manufactured by Asahi Kasei Co., Ltd.) as a cutting property improving material mixed with each of the pellets of 35:50:15, manufactured by Kogyo Co., Ltd. It was put into a 30 mmφ biaxial extruder, melted at 275 ° C., extruded onto a cooling roll from a die, and adhered and cooled and solidified by an electrostatic application method to obtain an amorphous sheet having a thickness of about 160 μm. The amorphous sheet was first preheated to 84 ° C. using a stenter type horizontal uniaxial stretching machine, and stretched in the transverse direction at a stretching temperature of 76 ° C. at a magnification of 4.0. Then, after heat-setting at 79 ° C. for 10 seconds, it was rapidly cooled to room temperature. The thickness of the obtained film was 40 μm. The obtained film was used as a heat shrink label. The maximum heat shrinkage rate, haze value, cutability, and impact strength of this product were measured. The results are shown in Table 1.

(Example 2)
A film and a label were obtained and measured in the same manner as in Example 1 except that a styrene-based thermoplastic elastomer (Tuftec M1943 manufactured by Asahi Kasei) was used instead of the cutting property improving material used in Example 1. The results are shown in Table 1.

  As can be seen from Table 1, the heat shrink films and labels of Examples 1 and 2 have a maximum shrinkage of 68% to 77%, a haze value of 54% to 68%, and a perforation cut property of 0.73 mm to 0.81 mm. In addition, impact resistance strength 2.3J to 2.6J, showing a good value in each measurement, and also showed the result that it was possible to tear in the intended direction in terms of tearability. It can be seen that the heat-shrinkable films and labels of Examples 1 and 2 are heat-shrinkable films and labels having extremely desirable properties.

(Comparative Example 1)
A film and a label were obtained and measured in the same manner as in Example 1 except that a polyamide resin (T-600 manufactured by Toyobo Co., Ltd.) was used instead of the cutting property improving material used in Example 1. The results are shown in Table 1.

Since the heat-shrinkable film and label of Comparative Example 1 used a polyamide resin instead of a thermoplastic elastomer, they lacked flexibility like a thermoplastic elastomer and resulted in inferior impact strength compared to the Examples. With respect to the other items, almost the same results as in the example were obtained.

(Comparative Example 2)
A film and a label were obtained in the same manner as in Example 1 except that polymethyl methacrylate resin (PMMA) was used in place of the cutting property improving material used in Example 1, and measurement was performed. The results are shown in Table 1.

The heat-shrinkable film and label of Comparative Example 2 used polymethylmethacrylate resin instead of thermoplastic elastomer, so lacked flexibility like thermoplastic elastomer and absorbed impact energy by “islands” of “sea-island structure”. It did not occur, and all the measurement items were inferior to those of the examples.

  The heat-shrinkable label of the present invention, and the film comprising the same, have a practically sufficient heat shrinkage rate, have few breaks during processing, are heat-shrinked, and are used in coating or binding applications. It provides uniform shrinkage results regardless of temperature fluctuations and non-uniformity, and is excellent in cutability, so it is easy to separate the object to be attached and the label, especially in the field of light shrinkage labels such as body labels, and its recyclability is Demonstrated.

Claims (3)

  A polyester-based resin film having a maximum heat shrinkage of 20% or more in at least one direction, a haze value of 50% or more and less than 80%, and an impact strength of 2.0 J or more. A straight line of 72 mm perforation is manually cut and teared manually, and the film is placed between the polarizing plates of crossed Nicols of the projector (10x objective) so that it is in the dark field, and is within the field scale range. A heat-shrinkable polyester-based resin film having a perforation-cutting property that gives a value of 1 mm or less when the maximum width in the direction orthogonal to the tearing direction of the brightened portion is measured.   The heat-shrinkable polyester resin film according to claim 1, wherein the heat-shrinkable polyester resin film contains 0.1 to 20% by weight of a styrene thermoplastic elastomer.   A heat-shrinkable polyester-based label produced using the heat-shrinkable polyester-based resin film according to claim 1.