JP2009241375A - Polypropylene film for heat print lamination - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polypropylene film for heat print lamination in which surface activity is hardly deactivated even in the heat lamination process and which has stable suction affixing property. <P>SOLUTION: At least three layers of a layer A, a layer B, and a layer D each containing polyolefin are laminated in this order, the center line average roughness Ra of the surface of the layer A is 0.3 to 0.9 μm and the ration (O/C) of an oxygen atom number (O) to the carbon atom (C) in the surface of the layer A is 0.03 to 0.3, the layer B is the biaxially extended layer containing polypropylene base resin, the layer D is the layer containing polyethylene, in the polypropylene film for heat print lamination. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is used by attaching a hot roll to the surface of a printing paper or the like used for these applications in order to impart the beauty of the surface of a poster, a cover of this kind, a paper container, etc., and an antifouling property, The present invention relates to a so-called polypropylene film for print lamination. In particular, the present invention relates to a polypropylene film for thermal print lamination that is excellent in printability and adhesiveness when further printing is performed on the surface of the polypropylene film after bonding or other materials are bonded.

Biaxially stretched polypropylene films are widely used for industrial purposes such as food packaging and pressure-sensitive adhesive tapes because of their excellent mechanical properties, light weight, and excellent water resistance. In addition, the film is preferably used for the purpose of bonding the film to paper, improving water resistance, protecting the surface of a printed pattern, imparting design properties by controlling the surface glossiness, and the like. Specifically, a polypropylene film is bonded to the surface of a book cover / cover, shopping bag, packaging material, and paper constituting a paper container (hereinafter collectively referred to as print lamination). As a method of print lamination, a method in which paper and a film are bonded with a solvent-based adhesive (hereinafter referred to as “solvent bonding”) and a heat-melting resin layer having a low melting point is provided on the surface of the polypropylene-based film in advance. In addition, there are two methods of heat bonding to paper using a heat roll (hereinafter referred to as “thermal lami”), but for solvent application, release of volatile solvent used in the bonding process to the atmosphere Due to this problem, the thermal lamination method is gradually increasing. The thermal lamination method is a technology in which a low melting point polyolefin resin layer having a melting point of 60 to 80 ° C. is formed on one side of a polypropylene film, and the paper and the polypropylene film are bonded to each other with a hot roll of 100 to 120 ° C. Although it is patent documents 1, 2, and 3), since it is excellent also in terms of economy as well as environmental friendliness, the share as a bonding method is expanding, but there is a problem in process suitability for specific applications. It has been confirmed. The application is a so-called sack pasting application in which the film surface is further thermally bonded to the paper and then the surface of the film is further printed or an adhesive is applied to form a paper case. If the surface of the polypropylene film is subjected to a corona treatment or the like in advance, the treatment is deactivated or weakened in the heat lamination process, and the adhesive force is not stable. is there. This phenomenon originates from the fact that the corona discharge treatment applied as an activation treatment on the non-polar polypropylene film having a small surface energy is deactivated by heat.
JP-A-8-142277 JP 2005-306031 A JP 2004-276601 A

  An object of the present invention is to provide a polypropylene film for thermal printing lamination in a polypropylene film for thermal lamination, which is less susceptible to surface treatment even after a thermal laminating process, and has stable printability and sack pasting characteristics. To do.

  In order to achieve the above object, the present invention has the following configuration.

  (1) At least three layers A, B, and D containing polyolefin are laminated in this order, the center line average roughness Ra of the surface of the layer A is 0.3 to 0.9 μm, and the layers The ratio (O / C) of the number of oxygen atoms (O) to carbon atoms (C) on the surface A is 0.03 to 0.3, and the layer B is a biaxially stretched layer containing a polypropylene resin, A polypropylene film for thermal print lamination, wherein the layer D is a layer containing a polyethylene resin.

  (2) The polypropylene film for thermal print lamination according to the above (1), which has a layer C containing a polypropylene copolymer resin having a thickness of 0.3 to 3 μm between the layer B and the layer D.

  (3) The polypropylene film for thermal print lamination according to the above (1) or (2), wherein the layer A contains a polypropylene resin having a melting point of 150 to 165 ° C.

  (4) The ratio (N / C) of nitrogen atom (N) to carbon atom (C) on the surface of layer A is 0.01 to 0.2, according to any one of (1) to (3) above. Polypropylene film for thermal print lamination.

  (5) The polypropylene film for thermal print lamination according to any one of the above (1) to (4), wherein the layer A contains a polypropylene resin having a cold xylene soluble part of 3 to 15% by mass.

  The present invention has the following effects.

  (1) Since the surface treatment applied to the film surface is not easily attenuated even after a thermal history of 100 to 120 ° C., the sack sticking suitability is excellent.

  (2) Excellent printability on the film surface after thermal print lamination, print loss is less likely to occur, and the beauty is improved.

  The polypropylene film for thermal print lamination of the present invention will be described in detail below.

  The film of the present invention has at least three layers A, B, and D containing polyolefin, and these layers are laminated in this order (hereinafter sometimes referred to as A / B / D). ). Among these, the layer A is a surface forming layer, the layer B is a base film, and is a biaxially stretched layer (biaxially stretched polypropylene film) containing polypropylene, and the layer D is a thermal adhesive property with papers. A low melting point resin layer. As long as the function of each layer is not impaired, it may be combined with other resin layers. Below, the preferable structure of each layer is demonstrated.

  First, the layer A will be described.

  The layer A is a functional layer having a matte appearance and adhesiveness with printing ink, adhesive, and the like. The matte appearance is brought about by a large number of irregularities formed on the surface, and the center line average roughness (Ra) is preferably 0.3 to 0.9 μm. If Ra is too small, it may not be recognized as a matte appearance, and if Ra is too large, the film may slip too much and the winding property may deteriorate. Ra is appropriately selected within the above range depending on the purpose of use of the film of the present invention.

  Such surface roughness can be realized by appropriately combining a polymer blend of polypropylene and polyethylene and a copolymer of ethylene and propylene. That is, as the resin constituting the layer A, biaxial stretching is performed using a resin having a sea-island structure including a high-fluidity propylene-based resin phase (sea phase) and a low-fluidity ethylene-based resin layer (island phase). As a result, an appropriately roughened surface state with the island phase as a protrusion can be obtained. The resin used as the sea phase is isotactic polypropylene and copolymers thereof, and ethylene propylene copolymer, propylene butene copolymer, and ethylene propylene butene terpolymer are preferably used. As the island phase, high density polyethylene, low density polyethylene, ethylene propylene rubber, and the like can be appropriately selected.

  The layer A preferably contains a polypropylene resin as described above, but the cold xylene soluble part of the polypropylene resin is preferably 3 to 15% by mass, particularly preferably 4 to 13% by mass. It is preferable that If the cold xylene soluble part is too small, the surface state after the surface activation treatment such as corona discharge treatment is not stable, and the adhesiveness with the printing ink and the adhesive may be lowered. Moreover, when there are too many cold xylene soluble parts, there exists a possibility that a blocking phenomenon may arise or heat resistance may fall. The cold xylene soluble part is composed of the low crystalline component or low molecular weight component of the propylene-based resin phase, so comonomer is appropriately copolymerized with propylene, and an appropriate catalyst is selected to lower the regularity of the polypropylene phase. The content can be controlled by appropriately combining such techniques.

  However, when the comonomer is simply copolymerized or the regularity is lowered, the melting point of the polypropylene phase is lowered. The melting point of the polypropylene resin contained in the layer A is preferably 150 to 165 ° C., particularly preferably from the viewpoint of the deformation of the surface and the durability of the surface activation treatment in the thermal lamination process for bonding to printing paper or the like. Is 155 to 160 ° C. For this reason, the propylene homopolymer is selected based on a propylene polymer obtained by copolymerizing about 0.3 to 2% by mass of ethylene, and a low-crystalline polypropylene is appropriately added to adjust the cold xylene soluble part. It is preferable to use it. Specific examples of such a resin include F224V manufactured by Prime Polymer Co., Ltd.

  The layer A preferably has a ratio (O / C) of the number of oxygen atoms (O) to carbon atoms (C) on the surface of 0.03 to 0.3, for example, by surface activation treatment or the like. More preferably, it is 0.05-0.25. If O / C is too low, printability may be poor, and if O / C is too high, problems such as blocking may occur.

  Furthermore, it is preferable that the ratio (N / C) of the nitrogen atom (N) to the carbon atom (C) on the surface of the layer A is 0.01 to 0.2 because printability and adhesiveness are further improved.

  In the present invention, O / C and N / C are the number of oxygen atoms or nitrogen atoms constituting the polar group group such as carbonyl group, carboxyl group, amino group and the like bonded to the carbon skeleton constituting the surface polypropylene resin. The ratio is expressed as a percentage of the number of carbon atoms. A large value means that there are many polar groups added. Polyolefins such as polyethylene and polypropylene usually do not contain polar groups in their structures, so O / C and N / C are almost zero. In order to introduce such oxygen atoms and nitrogen atoms, a surface activation treatment such as corona treatment or plasma treatment is applied, or a technique in which a component containing a polar group is previously grafted in the resin structure. It is possible to control by applying.

  Examples of the surface activation treatment that can be applied to the present invention include corona discharge treatment, plasma treatment, and flame treatment. In the corona discharge treatment, a corona discharge is generated by applying a high-voltage AC voltage to an electrode having a specific gap from the film surface while the film is placed in an air on an insulating roll made of rubber or ceramic. The surface can be activated and the above polar group can be added to the surface layer. Since the processing intensity is proportional to the amount of power input per unit area of the film, it depends on the processing power and the processing speed. That is, in order to control O / C and N / C, the processing power and the line speed may be adjusted as appropriate. Moreover, as a polar group to be introduced, when a corona discharge treatment is performed in normal air, only a polar group containing oxygen can be introduced, N / C becomes almost zero, and the atmosphere is nitrogen gas or nitrogen gas and carbon dioxide gas. By substituting with the mixed gas, a polar group group containing nitrogen can be introduced together with a polar group group containing oxygen, and N / C can be controlled together with O / C. Further, in the method of graft polymerization of a component containing a polar group on a polyolefin resin in advance, a method of introducing an acid anhydride such as maleic anhydride or methacrylic acid is exemplified. Specifically, Admer manufactured by Mitsui Chemicals, Inc. Etc. can be added as a resin constituting the layer A.

  Next, the layer B will be described.

  Layer B forms the base layer of the film of the present invention, and consists of a biaxially stretched layer (biaxially stretched film) containing a polypropylene resin. The polypropylene resin contained preferably has a melting point of 158 to 168 ° C, particularly preferably 160 to 166 ° C. If the melting point is too low, the rigidity of the film is low, and the handling property of the film of the present invention may be deteriorated or the thermal dimensional stability may be deteriorated. On the other hand, if the melting point is too high, the stretchability is deteriorated, the uniformity of thickness is inferior, and problems such as uneven thickness may occur. Further, the melt mass flow rate (MFR) of the polypropylene resin is preferably 1 to 10 g / 10 min, and more preferably 2 to 6 g / 10 min. Is preferable. Examples of such polypropylene resins include Noblen FS2016, Prime Polymer F300SP manufactured by Sumitomo Chemical Co., Ltd., and the like. The polypropylene resin may be copolymerized with other α-olefins such as ethylene, butene-1, pentene-1, 3methylbutene-1, hexene-1,4methylpentene 1, and the like. Is 3% by mass or less, particularly preferably 2% by mass or less. If the amount of copolymerization is too large, the heat resistance and rigidity of the film may be reduced. In addition, the polypropylene resin may contain other olefin resins, specifically, high density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene, ethylene propylene copolymer. And ethylene propylene butene terpolymer, polybutene 1, poly 3 methyl butene 1, poly 4 methyl pentene 1 and the like.

  Moreover, it is preferable to add a stabilizer for the purpose of suppressing thermal decomposition and oxidative decomposition of the polypropylene resin, and examples include compounds such as hindered phenols, phosphites, and hindered amines. Specific examples include Irgafos 168 and Irganox 1010.

  It is preferable to add an antistatic agent to the film of the present invention for the purpose of imparting print laminate processing suitability and antistatic properties after bonding. The content of these antistatic agents is appropriately selected according to the purpose of use, but is preferably 1,000 to 5,000 ppm (mass basis), particularly preferably 2, based on the resin amount of the layer B. 000 to 4,000 ppm (mass basis).

  Next, the layer D will be described.

  The layer D is a functional layer that imparts adhesion to printing paper and the like, and includes a polyethylene resin. In the thermal lamination process, the temperature of the heating roll is about 100 to 120 ° C., and the printing paper or the like as the adherend has a heat insulating property and the surface is not smooth, so that the layer D has a melting point of 55 to 100 ° C. It is preferable to contain a polyethylene resin. The melting point is more preferably 60 to 95 ° C, particularly preferably 65 to 90 ° C. If the melting point is too low, blocking may occur after the film of the present invention has been wound into a roll, and the film may not be unwound. In addition, the solvent contained in the printing ink may remain on the printing paper, and if the resin constituting the layer D cannot adsorb the solvent well, there may be a problem that the adhesive force is not sufficient. There is sex. For this reason, it is preferable that the resin contained in the layer D has a low density and does not have a strong polarity, for example, it is preferably a polyethylene resin. Specifically, ultra-low density polyethylene, low density polyethylene, ethylene ethyl acrylate copolymer, ethylene vinyl acetate copolymer, ethylene methyl methacrylate copolymer, etc. are exemplified, especially ultra low density polyethylene, low density polyethylene, It is preferable to include at least one resin selected from ethylene ethyl acrylate copolymers.

  The layer D may have a multilayer structure of two or more layers as long as it does not contradict the object of the present invention. For example, the layer D has a two-layer structure of a layer D1 and a layer D2, and the layer D1 has an ultra-low density. It is also possible for the polyethylene layer D2 to be a layer composed of low density polyethylene.

  The thickness of the layer D is preferably 5 to 20 μm, more preferably 8 to 15 μm, from the viewpoints of adhesiveness and economy. In addition, the surface of the layer D preferably has a center line average roughness of 0.05 to 1 μm, particularly preferably 0.1 to 0.8 μm, in order to improve laminating suitability. is there.

  Although the thickness of this invention film is not specifically limited, From the point of the mechanical strength as laminated paper, it is preferable that it is 20-40 micrometers, Most preferably, it is 25-35 micrometers.

  Next, the case where the layer C is provided will be described.

  The layer C functions as a bonding layer between the layer D and the layer B described above. That is, the biaxially stretched polypropylene film constituting the layer B is hardly thermally bonded to other polyolefin-based resins due to stretch orientation. Therefore, by providing the layer C as a polyolefin layer having a relatively low melting point on the layer B, when the layer D is extruded and laminated, the layer C partially melts, so that the layer B passes through the layer C. And layer D can be integrated. When layer D contains a polyethylene-based resin, it is preferable that layer C is a polypropylene-based copolymer resin having a melting point of 110 to 140 ° C. because the adhesive force is good for both layer B and layer D. Particularly preferably, the melting point is 115 to 135 ° C. Specific examples of such a polypropylene copolymer resin include an ethylene propylene copolymer, a propylene butene copolymer, and an ethylene propylene butene copolymer.

  The thickness of the layer C may be 0.3 μm or more, preferably 0.5 μm or more, in order to provide a function as a bonding layer, and the upper limit is in consideration of economics and film handling properties. It is preferably 3 μm or less, more preferably 2 μm or less.

  In consideration of post-processing suitability, it is preferable to add an inorganic and / or organic filler to the layer C in order to impart appropriate slipperiness. As a preferable particle diameter, the average value is 0.5-5 micrometers, Most preferably, it is 1-3 micrometers. The particle shape may be either monodispersed or agglomerated. Examples of inorganic particles include calcium carbonate, silicon dioxide, calcium phosphate, titanium dioxide, aluminum oxide, barium sulfate, and the like. As the organic particles, resin particles insolubilized by taking a crosslinked structure are preferable because they are excellent in heat resistance, and examples thereof include silicone particles, polymethyl methacrylate particles, and benzoguanamine particles. These particles can be added alone or in appropriate combination, and the content is 500 to 5,000 ppm (mass basis) with respect to the resin amount of layer C. Is preferable for improving the slipperiness and the adhesion between the layer D and particularly preferably 1,000 to 3,000 ppm (mass basis).

  Subsequently, the manufacturing method of this invention film is demonstrated.

  Needless to say, the present invention is not limited to the following description. Hereinafter, a case where the layer C is provided to produce the film of the present invention will be described.

  Using three extruders (extruders a, b, and c, respectively), the resin A that forms the surface layer of the film of the present invention, the resin B that becomes the base layer, and the resin C that becomes the bonding layer are melt-extruded. The extrusion temperature can be appropriately selected according to the characteristics of the resin, but is preferably 230 to 280 ° C. In addition to the resin B, an antistatic agent or a masterbatch thereof can be appropriately added to the extruder b so as to have a predetermined addition amount. Next, each resin is led to a polymer filter, and after removing foreign substances, led to a T die having a merging device capable of forming a three-layer structure of A / B / C. Thus, the molten resin extruded from the T die becomes a sheet shape having a three-layer structure of A / B / C, and is cooled and solidified on a cooling drum at 20 to 70 ° C. Next, the temperature of the cooled and solidified sheet is sequentially increased by using a plurality of heating rolls, and after preheating to 120 to 140 ° C., the sheet is passed through a heating roll group having a difference in peripheral speed in the running direction of the film. Stretch 4 to 7 times to make a uniaxially stretched film. After grasping both ends of the uniaxially stretched film thus obtained with a clip, guiding it to a hot air oven, blowing hot air heated from 150 to 170 ° C. from a plurality of nozzles installed above and below the oven, and sufficiently preheating, The clip is stretched 7 to 15 times by widening in the width direction, and then heat-fixed at 150 to 170 ° C. while allowing relaxation of 1 to 20% by narrowing the clip width.

  The biaxially stretched film thus obtained was released from the clip that had gripped both ends, and then subjected to corona discharge treatment on the surface of layer A in the film transport process composed of the transport roll group, After removing the part (film edge), it is wound up as an intermediate product. The intermediate product thus obtained is subjected to aging treatment for 10 to 50 hours in an appropriately adjusted atmosphere, after removing strain during stretching, and then appropriately cut to a width suitable for the subsequent process using a slitting device. Product roll. Hereinafter, the three-layer laminated film thus obtained is designated as PF, and the wound product roll is designated as R. Next, the roll (R) is set in an unwinding portion of a laminator including an unwinding / winding device, an extruder (d), and a cooling drum. The polyethylene resin constituting the layer D from the extruder (d) is melt-extruded into a sheet form from a T die at 190 to 240 ° C., and the film (PF) unwound from the product roll (R) and the polyethylene resin layer are It is pressed by a nip device on the cooling drum so as to be integrated, and then cooled and solidified. At this time, the polyethylene resin is brought into contact with the surface of the layer C among the A / B / C layers constituting the film (PF). In addition, the surface of the cooling drum is roughened into a satin finish by sandblasting or the like, and the pattern of the drum surface is transferred by pressing the polyethylene resin against the drum during the above-described lamination, The surface shape of the resin surface is controlled. Next, after laminating the polyethylene-based resin, the edge is trimmed, and if necessary, the surface of the layer D is subjected to a corona discharge treatment and wound up. The layer structure of the film thus obtained (hereinafter referred to as (F)) is laminated in the order of A / B / C / D, the surface of layer A is roughened, and the wetting index is 36 by corona discharge treatment. The layer D is a thermal adhesive layer that adheres to paper. When the film (F) is bonded to the printing paper or the like, the roll of the film (F) is unwound from the unwinding part of the laminating apparatus, and the continuous paper or sheet paper unwound from the roll paper and 100 It is heated and pressurized between a metal roll heated to ˜120 ° C. and a rubber roll to integrate them to form a laminated paper. The laminated paper thus obtained is appropriately printed or further cut and used for making a paper container or the like.

  Hereinafter, based on an Example, this invention is demonstrated concretely. The measuring method and the like are as follows.

(1) Centerline average roughness (Ra) and ten-point average roughness (Rz)
Measured according to JIS B-0601 (1982) using a “non-contact three-dimensional fine shape measuring instrument (ET-30HK)” and “three-dimensional roughness analyzer (MODEL SPA-11)” manufactured by Kosaka Laboratory Ltd. . The number of measurements was 3, and the average value was used.

  The detailed conditions are as follows.

    Measurement surface treatment: Aluminum was vacuum-deposited on the measurement surface to obtain a non-contact method.

Measurement length: 1mm
Horizontal magnification: 200 times Vertical magnification: 20,000 times Cut off: 0.25 mm
Width direction feed speed: 0.1 mm / sec Length direction feed pitch: 10 μm
Number of feeds in length direction: 20 times (2) Melting point (Tm)
The measurement was performed under the following conditions using a Seiko RDC220 differential scanning calorimeter.

  Preparation of sample: Weigh 4 ± 1 mg as a resin amount in an aluminum pan for measurement, and sandwich the aluminum pan with a crimper.

  Measurement conditions: The temperature is raised from room temperature to 280 ° C. at a rate of 20 ° C./min and held for 5 minutes. Thereafter, the temperature is lowered to 25 ° C. at a rate of 20 ° C./min. At this time, an exothermic peak accompanying crystallization of the resin is taken as a melt crystallization peak (Tmc), and when there are a plurality of crystallization peak values, a melting peak having the largest peak area is adopted.

  The above measurement was repeated 5 times, and the average value of the remaining 3 points, excluding 2 points of the maximum value and the minimum value, was defined as Tm (° C.).

(3) Layer structure The cross section of the film was photographed with a transmission electron microscope (TEM) under the following conditions, and the thickness structure of the film was measured.

Apparatus: JEM-1200EX manufactured by JEOL Ltd.
Observation magnification: 1,000 times Acceleration voltage: 100 kV
(4) Film thickness 7.4.1.1. Of JIS C-2330 (2001). Thus, the average film thickness was obtained. The film thickness was measured with one sheet, and an average value of 10 points was obtained.

(5) MFR (Melt Mass Flow Rate)
JIS K-7210 (1999) 7.4.2. It was measured by.

(6) Ratio of oxygen atoms to carbon atoms on the film surface (O / C), and ratio of nitrogen atoms (N / C)
The film surface was measured under the following conditions using ESCA spectrometer model ES200 manufactured by Kokusai Electric Co., Ltd.

Excitation X-ray: Al Kα ray (1486.6 eV)
X-ray output: 10Kv 20mA
Temperature: 20 ° C
Kinetic energy correction: Neutral carbon (—CH ₂ —) kinetic energy was adjusted to 1202.0 eV.

  From the obtained energy value, the ratio of the peak area of C1s and the peak area of O1s was O / C, and the ratio of the peak areas of C1s and N1s was N / C.

(7) Cold xylene solubles (CXS)
10 g of a sample was dissolved in 1,000 ml of boiling xylene, then slowly cooled to 50 ° C., then immersed in ice water, cooled to 20 ° C. with stirring, allowed to stand overnight at 20 ° C., and the precipitated polymer was filtered off. Xylene was evaporated from the filtrate, dried under reduced pressure at 60 ° C., and a polymer soluble in xylene at 20 ° C. was recovered, and the mass thereof was determined by measurement.

(8) Wetting index It measured based on the measuring method prescribed | regulated to JISK-6768 (1999) by the liquid mixture of formamide and ethylene glycol monoethyl ether.

Example 1
F224V (mixture of ethylene propylene block copolymer and polyethylene) manufactured by Prime Polymer Co., Ltd. as the resin forming the A layer on the surface, and FS2016 (polypropylene) manufactured by Sumitomo Chemical Co., Ltd. as the resin forming the B layer WF345S (ethylene propylene butene random copolymer) manufactured by Sumitomo Chemical Co., Ltd. as a resin to be melted and extruded into an extruder, laminated and sheeted in a T-type die, and cooled on a casting drum set at 30 ° C Solidified to obtain an unstretched sheet. Next, after preheating the unstretched sheet with a preheating roll group heated to 140 ° C., the longitudinal direction is stretched 4.5 times at 135 ° C. to obtain a uniaxially stretched polypropylene film, and then the film is held by a clip, The film was led into an oven heated to 160 ° C., stretched 10 times in the transverse direction, and then heat-set at 155 ° C. while allowing 5% relaxation in the transverse direction to obtain a biaxially oriented polypropylene film. Next, Evaflex-EEA A725 (ethylene ethyl acrylate copolymer) manufactured by Mitsui DuPont Polychemical Co., Ltd. was melted with an extruder, and the molten sheet was contacted with the C layer of the film obtained at 25 ° C. The film was cooled and solidified while being pressed on the cooling drum with a nip roll to obtain a film having a Ra of 0.6 on the surface of the A layer. Subsequently, the edge portion of the laminated film is trimmed, and the A layer is wound up with corona discharge treatment in an air atmosphere at a treatment strength of 20 W / m ² / min. A polypropylene film for lamination was obtained. It had sufficient sacking characteristics and showed good printability even after thermal printing lamination.

(Example 2)
A biaxially stretched polypropylene film was produced in the same manner as in Example 1, and was subjected to corona discharge treatment at a treatment strength of 24 W / m ² / min to obtain a polypropylene film for print lamination having an O / C of 0.3 on the surface of the A layer. . It had sufficient sacking characteristics and showed good printability even after thermal printing lamination.

(Example 3)
A biaxially stretched polypropylene film was produced in the same manner as in Example 1, and the surface of the A layer was wound up with corona discharge treatment in a nitrogen atmosphere at a treatment strength of 45 W / m ² / min. Polypropylene films for print lamination having N / C of 0.2 and 0.1, respectively, were obtained. It had sufficient sacking characteristics and showed good printability even after thermal printing lamination.

Example 4
As a resin for forming the surface A layer, 80% by mass of Prime Polymer F224V and 20% by mass of Sumitomo Chemical Co., Ltd. FS2016 were used. Other than that, a biaxially stretched polypropylene film was produced under the same conditions as in Example 1 to obtain a polypropylene film for print lamination in which Ra on the surface of the A layer was 0.4. It had sufficient sacking characteristics and showed good printability even after thermal printing lamination.

(Example 5)
As a resin for forming the surface A layer, 65% by mass of Prime Polymer F224V and 35% by mass of Sumitomo Chemical Co., Ltd. FS2016 were used. Others produced the biaxially-stretched polypropylene film similarly to Example 1, and obtained the polypropylene film for print lamination whose Ra of the surface of A layer was 0.3 micrometer. Although the appearance was not so good, it was at a level where there was no problem in use.

(Example 6)
As a resin for forming the surface A layer, 80 mass% of F224V manufactured by Prime Polymer and 20 mass% of F218-0 (polyethylene) manufactured by Sumitomo Chemical Co., Ltd. were mixed and used. Others produced the biaxially-stretched polypropylene film similarly to Example 1, and obtained the polypropylene film for print laminations whose Ra of the A layer surface is 0.9 micrometer. Although the winding property was not so good, it was at a level where there was no problem in the process.

(Example 7)
As a resin for forming the D layer, Evaflex-EVA V431 (ethylene vinyl acetate copolymer) manufactured by Mitsui DuPont Polychemical Co., Ltd. was used. Others produced the biaxially-stretched polypropylene film similarly to Example 1, and obtained the polypropylene film for print lamination. It had sufficient sacking characteristics and showed good printability even after thermal printing lamination.

(Comparative Example 1)
A biaxially stretched polypropylene film was produced in the same manner as in Example 1 and wound up while performing corona discharge treatment at a treatment strength of 10 W / m ² / min, and a polypropylene film for print lamination having an O / C of A layer of 0.02. Although it was obtained, adhesion failure occurred in the process after thermal print lamination.

(Comparative Example 2)
A biaxially stretched polypropylene film was produced in the same manner as in Example 1 and wound up while performing corona discharge treatment at a treatment strength of 28 W / m ² / min, and a polypropylene film for print lamination having an O / C of 0.4 in the A layer was obtained. Although obtained, blocking occurred in the winding process.

(Comparative Example 3)
As a resin for forming the surface A layer, 70 mass% of F224V manufactured by Prime Polymer and 30 mass% of F218-0 manufactured by Sumitomo Chemical Co., Ltd. were mixed and used. Otherwise, a biaxially stretched polypropylene film was produced in the same manner as in Example 1, and when a polypropylene film for print lamination having an Ra of the surface of the layer A of 1.0 μm was obtained, winding deviation occurred in the winding process.

(Comparative Example 4)
As the resin forming the surface A layer, FSX41E4 (ethylene propylene block copolymer) manufactured by Sumitomo Chemical Co., Ltd. was used. Others produced a biaxially stretched polypropylene film in the same manner as in Example 1, and obtained a polypropylene film for print lamination with an Ra of the surface of the layer A of 0.1 μm. In this case, it was unable to withstand use because of blocking.

  The film of the present invention is preferably used for applications in which post-processing such as printing and adhesion is performed after laminating with printing paper or the like, but can also be used without any problem in ordinary print lamination applications in which no post-processing is performed. Moreover, since the layer D is excellent also in the adhesiveness with a metal, it can be bonded together and used for metal foil, such as aluminum foil, for the purpose of providing corrosion resistance or design properties.

Claims (5)

At least three layers A, B and D containing polyolefin are laminated in this order, the center line average roughness Ra of the surface of the layer A is 0.3 to 0.9 μm, and the surface of the layer A The ratio (O / C) of the number of oxygen atoms (O) to carbon atoms (C) is 0.03 to 0.3, layer B is a biaxially stretched layer containing a polypropylene resin, and layer D is A polypropylene film for thermal print lamination, which is a layer containing a polyethylene resin. 2. The polypropylene film for thermal print lamination according to claim 1, comprising a layer C containing a polypropylene-based copolymer resin having a thickness of 0.3 to 3 μm between the layer B and the layer D. 3. The polypropylene film for thermal print lamination according to claim 1 or 2, wherein the layer A contains a polypropylene resin having a melting point of 150 to 165 ° C. The polypropylene film for thermal print lamination according to any one of claims 1 to 3, wherein the ratio (N / C) of nitrogen atoms (N) to carbon atoms (C) on the surface of layer A is 0.01 to 0.2. . The polypropylene film for thermal print lamination according to any one of claims 1 to 4, wherein the layer A contains a polypropylene resin having a cold xylene soluble part of 3 to 15% by mass.