JP4428931B2 - Method for producing biaxially oriented polypropylene composite film - Google Patents

Description

【００３５】
＜比較例１＞
実施例１における変性プロピレン重合体を用いることなく、ポリプロピレンにポリアクリル酸とポリビニルアルコールの混合物水溶液をコーティングした以外は、実施例１と同様に行なった。
ただし、ガスバリア層としては、１０％の中和度のポリアクリル酸７：ポリビニルアルコール３の割合で混合した水溶液を用いた。
得られた複合フィルムは、外観は、良好であったが、基材剥離性は、１００％の剥離が見られ、包装材料として使用できるものではなかった。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a biaxially stretched polypropylene composite film having excellent barrier properties, and more specifically, a barrier comprising a mixture of poly (meth) acrylic acid and polyvinyl alcohol on one side of a biaxially stretched polypropylene film. The present invention relates to a method for producing a biaxially stretched polypropylene composite film in which a layer is formed.
[0002]
[Prior art]
Biaxially stretched polypropylene films are used in a wide range of fields including packaging materials because of their excellent transparency, mechanical strength, rigidity, and the like. However, the biaxially oriented polypropylene film has a slight property of permeating oxygen and water vapor, so that when it is used as a packaging material for foods, cosmetics, pharmaceuticals, etc., deterioration of the package is prevented. Therefore, a composite film in which a gas barrier layer for reducing oxygen permeability and water vapor permeability is usually laminated on one side of the film is used.
[0003]
[Patent Document 1]
For example, in JP-A-7-205379, a film formed from a mixture of polyvinyl alcohol and poly (meth) acrylic acid or a partially neutralized product thereof is laminated adjacent to a thermoplastic resin layer. A gas barrier laminate obtained by this is described.
Although it does not specifically limit as a thermoplastic resin layer seen in this patent document 1, For example, a polyethylene terephthalate (PET), nylon 6, nylon 66, nylon 12, nylon 6.66 copolymer, nylon 6.12 copolymer weight Polyamide such as coalescence, low density polyethylene, high density polyethylene, linear low density polyethylene, vinyl acetate copolymer, polypropylene, ethylene / acrylic acid copolymer, ethylene / acrylic acid copolymer, ethylene / ethyl acrylate copolymer Examples include polyolefins such as polymers, polyvinyl chloride, polyvinylidene chloride, and polyphenylene sulfide.
[0004]
However, it has been found that a mixture of polyvinyl alcohol and poly (meth) acrylic acid is excellent in gas barrier properties, but depending on the type of thermoplastic resin to be laminated, there are some which cannot be laminated as they are by coating.
For example, when the laminated substrate is a polypropylene film, the polypropylene film does not have a polar group in itself, so that there is a problem in adhesion, and the mixture cannot be coated as it is.
[0005]
[Problems to be solved by the invention]
Accordingly, an object of the present invention is to provide a method for producing a composite film in which a gas barrier layer composed of a mixture of poly (meth) acrylic acid and polyvinyl alcohol, which cannot be laminated by a usual method, is suitably laminated on the surface of a biaxially stretched polypropylene film. It is to provide.
[0006]
[Means for Solving the Problems]
The present invention has been proposed to achieve the above object, and is characterized by comprising the following requirements.
That is, according to the present invention, after a polypropylene and a modified propylene polymer (A) are coextruded to obtain a laminated sheet, the laminated sheet is stretched in the longitudinal direction, and then the modified propylene polymer (A). The layer side is coated with a mixture layer comprising a poly (meth) acrylic acid (B) partially neutralized product of 3 to 15% and polyvinyl alcohol (C) in a mixing ratio of 7: 3 to 5: 5. A method for producing a biaxially oriented polypropylene composite film is provided.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the invention will be described below.
<Biaxially stretched polypropylene film>
The biaxially stretched polypropylene film (hereinafter sometimes referred to as “OPP film”) used in the present invention is a small amount of a propylene homopolymer or a main amount of propylene, and usually α other than 5 mol% of propylene. -A film obtained by biaxially stretching a copolymer of olefins such as ethylene, 1-butene, 1-hexene, 4-methyl-1-pentene and 1-octene sequentially or simultaneously.
Since this biaxially stretched polypropylene film does not have a polar group itself, even if it is intended to coat a mixture layer of poly (meth) acrylic acid and polyvinyl alcohol, which is a gas barrier layer, on the film surface, it is laminated as it is. I can't.
[0012]
An important feature of the present invention is that a polypropylene film is unstretched or uniaxially stretched in the longitudinal direction, and a layer of a modified propylene polymer is formed on the film surface. "PAA") and polyvinyl alcohol (hereinafter also referred to as "PVA") mixture layer is coated, and then this is stretched to obtain a finally obtained biaxially stretched film And
Therefore, when the polypropylene film before forming the gas barrier layer is unstretched, the subsequent stretching is biaxial stretching. If the polypropylene film is uniaxially stretched in the longitudinal direction, the subsequent stretching is performed in the transverse direction. In any case, the final polypropylene film only needs to be biaxially stretched.
[0013]
<Modified propylene polymer (A)>
When the modified propylene polymer (A) of the present invention is interposed between the OPP film and the gas barrier layer composed of a mixture layer of PAA and PVA, a specific stretching means is used when laminating the gas barrier layer on the above OPP film. By combining them, a mixture layer of PAA and PVA as a gas barrier layer is suitably laminated with excellent adhesive strength on the surface of the OPP film in which the film itself does not have a polar group.
[0014]
The modified propylene polymer (A) according to the present invention is a homopolymer of propylene or a main amount of propylene, for example, a small amount of ethylene, 1-butene, 1-hexene, 4-methyl-1 of 5 mol% or less. A copolymer obtained by copolymerizing an α-olefin such as pentene and 1-octene is modified by adding a polar group. The method for imparting the polar group is not particularly limited, but a graft-modified unsaturated carboxylic acid or derivative thereof is preferable because it is excellent in the effect of improving the adhesion between the OPP film and the gas barrier layer.
[0015]
As unsaturated carboxylic acid, acrylic acid, maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, isocrotonic acid, endocis-bicyclo [2,2,1] hept-5-ene-2, Examples include 3-dicarboxylic acid (trade name: nadic acid), and examples of derivatives thereof include acid halamide, amide, imide, anhydride, and ester.
Specific examples of such derivatives include, for example, maleyl chloride, maleimide, maleic anhydride, citraconic anhydride, monomethyl maleate, dimethyl maleate, glycidyl maleate and the like. Among them, unsaturated dicarboxylic acid or its anhydride In particular, maleic acid, nadic acid or acid anhydrides thereof are preferably used.
[0016]
The modified propylene polymer graft-modified with an unsaturated carboxylic acid or derivative thereof is preferably 0.05 to 15% by weight, more preferably 0.1 to 10% by weight based on the propylene polymer before modification. Graft-modified with saturated carboxylic acid or its derivative.
The modified propylene polymer (A) preferably has a melt flate (MFR, 230 ° C.) of 0.1 to 50 g / 10 minutes, more preferably 0.3 to 30 g / 10 minutes. The modified propylene polymer is a modified propylene polymer modified with an unsaturated carboxylic acid or derivative thereof and an unmodified propylene polymer as long as the graft amount of the unsaturated carboxylic acid or derivative thereof is within the above range. It may be a composition.
[0017]
<Gas barrier layer>
In the present invention, a layer made of a mixture of PAA (B) and PVA (C) is used as the gas barrier layer formed on one side of the OPP film.
The mixture of PAA (B) and PVA (C) is mixed in the form of a solution using water or a solvent, and laminated on the propylene film surface. The thickness of the gas barrier layer is appropriately set depending on the application, but is usually 0.05 to 10 μm, and preferably about 0.1 to 5 μm.
[0018]
PAA (B) includes polyacrylic acid and / or polymethacrylic acid, copolymers of (meth) acrylic acid and ethyl or butyl ester of (meth) acrylic acid or (meth) acrylic amide, and alkali metals thereof. Salts or ammonium salts are used. Moreover, what neutralized by making some carboxyl groups of PAA into carboxylate using alkalis, such as sodium hydroxide, potassium hydroxide, lithium hydroxide ammonia, can be used more preferably, Those having a sum of less than 20%, particularly 3 to 15% are more preferably used.
The degree of polymerization of PAA (B) is usually in the range of 30 to 3000, and more preferably in the range of 50 to 1000. When the degree of polymerization of PAA is outside the above range, it may not be possible to follow the stretching when the polypropylene film is stretched after being coated on the polypropylene film.
[0019]
According to the experiments by the present inventors, as shown in Examples described later, depending on the mixing ratio of PAA and PVA, depending on the neutralization degree of PAA, the appearance of the obtained composite film, the substrate It was found to be affected by the adhesion of
The degree of neutralization is determined by the following formula known per se.
Degree of neutralization = (X / Y) × 100 (%)
Here, X is the total number of moles of neutralized carboxyl groups in 1 g of partially neutralized PAA, and Y is the total number of moles of carboxyl groups in 1 g of PAA before partial neutralization.
[0020]
PVA (C) is a polymer mainly composed of vinyl alcohol, and is usually a polymer obtained by saponifying polyvinyl acetate, and some of them are vinyl carboxylate, alkyl vinyl ether, (meth) acrylate, acrylamide, It may be a modified product with an unsaturated carboxylic acid (ester) or an anhydride thereof. As such PVA (C), those having a degree of polymerization of 100 to 3000, more preferably 300 to 2000 can be used. Further, when mixed with the PAA (B), those having a high saponification degree of 70 to 99% are preferably used from the viewpoint of water solubility, and those having a saponification degree of 85 to 99% are particularly preferred.
[0021]
A preferred mixing ratio of PAA (B) and PVA (C) is (B) :( C) of 1: 9 to 9: 1, preferably 2: 8 to 8: 2, more preferably 7: 3 to 5: 5.
By coating the gas barrier layer in which PAA (B) and PVA (C) are mixed in the above range, it is possible to follow the stretching (lateral or biaxial) after coating on the propylene film, and on the OPP film In addition, a gas barrier layer adheres, and a composite film excellent in both appearance and substrate adhesion can be obtained.
[0022]
At this time, when a PVA having a polymerization degree of less than 1000 is used alone, it cannot follow stretching after coating on a propylene film, and an OPP film finally coated with a gas barrier layer cannot be obtained. On the other hand, PAA alone is inferior in appearance and adhesion to the substrate film, and an OPP film coated with a suitable gas barrier layer cannot be obtained.
[0023]
<OPP composite film>
The final product of the present invention, the OPP composite film, is formed by forming a gas barrier layer comprising a mixture of PAA (B) and PVA (C) on the OPP film via the modified propylene polymer layer (A). It is.
However, simply coating the gas barrier layer on the OPP film cannot provide a composite film suitable for use for packaging or the like because the adhesion between the OPP and the gas barrier layer is poor.
[0024]
Therefore, in the present invention, a gas barrier layer made of a mixture of PAA and PVA is laminated on a non-stretched or longitudinally stretched OPP film through a layer of a modified propylene polymer, and then this is stretched at least in the transverse direction. By finally forming a biaxially stretched laminated film, a composite film in which a gas barrier layer composed of a mixture of PAA (B) and PVA (C) is firmly adhered onto the OPP film as the base material is obtained.
[0025]
The thickness of each layer in the OPP film on which the gas barrier layer of the present invention is laminated is appropriately determined in consideration of flexibility, mechanical strength, economics, etc. depending on the application, but is usually a base film. The thickness of the OPP film layer is 10 to 100 μm, preferably 15 to 60 μm, the thickness of the modified propylene polymer (A) layer is 0.2 to 10 μm, preferably 0.5 to 5 μm, PAA (B) and PVA ( The thickness of the gas barrier layer comprising the mixture of C) is in the range of 0.05 to 10 μm, preferably 0.1 to 5 μm.
[0026]
The OPP composite film of the present invention comprises at least a 3 to 15% portion of poly (meth) acrylic acid (B) via a modified propylene polymer layer (A) on one side of a biaxially stretched polypropylene film as a base material. It is necessary that the mixture layer of the neutralized product and the polyvinyl alcohol (C) has a mixture ratio of 7: 3 to 5: 5. However, the layer is not necessarily limited to this configuration. Accordingly, another plastic film layer can be laminated as the outer layer. In addition, a known compounding agent such as an ultraviolet absorber, an antifogging agent, a filler, an antioxidant, a lubricant, a pigment, and an antistatic agent can be added to any one of the layers in the composite film.
[0027]
<Method for producing OPP composite film>
The OPP composite film of the present invention is obtained by first coextruding a polypropylene serving as a base material and a modified propylene polymer (A) to obtain a sheet, and then 3 to 3 of PAA (B) on the modified propylene polymer layer side. A method of biaxially stretching the laminated film after coating a (water) solution of a mixture of 15% partially neutralized product and PVA (C) in a mixture ratio of 7: 3 to 5: 5 , or polypropylene and After coextrusion molding with the modified propylene polymer (A), the sheet was stretched in the machine direction to obtain a sheet, and then 3 to 15% partially neutralized product of PAA (B) on the modified propylene polymer layer side And a PVA (C) mixture ratio of 7: 3 to 5: 5, and after coating a (water) solution, the laminated film can be obtained by a method of stretching in the transverse direction.
That is, polypropylene and a modified propylene polymer that coat a (water) solution of a mixture of PAA (B) 3 to 15% partially neutralized product and PVA (C) in a mixture ratio of 7: 3 to 5: 5 The co-extruded sheet is unstretched or uniaxially stretched in the machine direction.
[0028]
The gas barrier layer that coats the non-stretched or uniaxially stretched coextruded film in the longitudinal direction is, for example, an air knife coater, a direct gravure coater, a gravure offset, an arc gravure coater, a gravure coater such as a gravure reverse and jet nozzle method, top Reverse roll coater such as feed reverse coater, bottom feed reverse coater and nozzle feed reverse coater, 5-roll coater, lip coater, bar coater, bar reverse coater, die coater, etc. The film was coated on the film so that the solid content in the (water) solution of the mixture of PAA (B) and PVA (C) was 0.5 to 100 g / m ² , preferably 1 to 50 g / m ² . After 50 10 seconds to at 140 ° C. and to it is possible to obtain by drying about 3 minutes.
[0029]
At this time, the layer side of the modified propylene polymer that coats the gas barrier layer may be subjected to surface treatment such as corona treatment in advance in order to improve wettability with the gas barrier layer.
The stretch temperature and stretch ratio for obtaining the OPP composite film are not particularly limited, and are generally performed, that is, if simultaneous biaxial stretching, the gas barrier layer is coated and then dried, If the stretching temperature is 150 to 190 ° C. and the stretching ratio is in the range of 3 to 10 times each in the length and width directions, the successive stretching is biaxial stretching, the longitudinal stretching temperature is 125 to 145 ° C., and the stretching ratio is 4.5 to 6 times. The stretching may be performed within the range, and the transverse stretching temperature after coating the gas barrier layer may be 150 to 190 ° C. and the stretching ratio may be 9 to 11 times.
[0030]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the composite film with which the gas barrier layer which consists of a mixture of specific PAA and PVA firmly adhere | attached on the biaxially stretched polypropylene film is provided.
This composite film has excellent properties for suppressing the permeability of gases such as oxygen in addition to the characteristics such as transparency, mechanical strength, rigidity, and water vapor barrier properties that are inherent properties of the OPP film. It can be suitably used as a packaging material for foods, cosmetics, pharmaceuticals and the like that are easily affected by oxygen and moisture.
[0031]
【Example】
EXAMPLES Hereinafter, although this invention is demonstrated further more concretely based on an Example, this Example illustrates the suitable aspect of this invention, This invention is not limited by this.
[0032]
<Example 1>
The following biaxially stretched polypropylene composite film was obtained using a biaxially stretched film molding machine.
Melting point: 162 ° C., MFR (230 ° C.): 2 g / 10 min of polypropylene as a base material layer, one surface of which was graft-modified with maleic anhydride, melting point: 165 ° C., MFR (230 ° C.): 3 g / 10 min The modified propylene polymer was coextruded to obtain a laminated film.
The obtained laminated film was stretched 5 times in the longitudinal direction, and then the modified propylene polymer was subjected to corona treatment. On the layer side of the modified propylene polymer, polyacrylic acid (trade name “Julimer AC10L”, concentration 20%) and After coating an aqueous solution in which polyvinyl alcohol (trade name “PVA103C”, concentration 20%) was mixed in the ratio shown in Table 1, it was dried at 140 ° C. for 30 seconds.
In addition, about polyacrylic acid, the thing of neutralization degree 0 degree, 5 degree | times, 10 degree | times, and 20 degree | times was used by each mixing ratio.
Next, the film was stretched 10 times in the transverse direction in a tenter in which hot air at 160 ° C. was circulated, and then fixed with hot air at 150 ° C. for 5 seconds to obtain a biaxially stretched polypropylene composite film. The thickness of each layer of the obtained composite film was 20 μm for the polypropylene base film layer, 1 μm for the modified propylene polymer layer, and 0.7 μm for the gas barrier layer.
[0033]
The appearance, adhesion to the substrate, and oxygen permeability of the obtained OPP composite film were evaluated by the following methods, and the results are shown in Table 1.
Appearance: The appearance of the obtained OPP composite film was visually evaluated.
○: Good Δ: White unevenness occurs ×: A continuous film (gas barrier layer) is not formed.
A cellophane tape made by Nichiban Co., Ltd. (width: 24 mm) was affixed to the gas barrier layer of the OPP composite film by 6 cm in length, and after strongly pressing with a finger, the affixed cellophane tape was peeled off at an angle of 180 degrees, and the state of the gas barrier layer was Observed.
◯: No peeling Δ: Peeling less than 10% is observed X: Peeling of 10% or more is observed Note that in FIG. 1, the locations indicated by-are based on cellophane tape because a continuous gas barrier layer was not formed. This means that the peel test was not performed.
Oxygen permeability;
An oxygen permeability measuring machine (OX-TRAN 2/20 manufactured by MOCON) was used, and measurement was performed under the conditions of 20 ° C. and RH 0%. The unit is ml / m ² · day · MPa.
In addition, the location shown by-in Table 1 means that the oxygen permeability measurement was not performed because the film appearance was poor.
[0034]
[Table 1]

[0035]
<Comparative Example 1>
The same procedure as in Example 1 was performed except that the modified propylene polymer in Example 1 was not used and the polypropylene was coated with a mixed aqueous solution of polyacrylic acid and polyvinyl alcohol.
However, as the gas barrier layer, an aqueous solution mixed in a ratio of polyacrylic acid 7: polyvinyl alcohol 3 having a neutralization degree of 10% was used.
The resulting composite film had good appearance, but the substrate peelability was 100% peelable and could not be used as a packaging material.

Claims (1)

After a polypropylene and a modified propylene-polymer (A) are coextruded to obtain a laminated sheet, the laminated sheet is stretched in the longitudinal direction, and then the modified propylene polymer (A) layer side has a poly (meth) A mixture layer comprising a partially neutralized product of 3 to 15% of acrylic acid (B) and polyvinyl alcohol (C) in a mixing ratio of 7: 3 to 5: 5 is coated and stretched in the transverse direction. A method for producing a biaxially oriented polypropylene composite film.