JPH10265665A - Biaxially oriented polyamide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a biaxially oriented film having excellent antistatic properties, slip properties and transparency and being highly valuable as especially a food packaging film by using a raw material prepared by melt-mixing a specified amount of a polyoxyethylene sorbitan fatty acid ester and a polyamide. SOLUTION: This film is made from a composition comprising 99.5-99.95 wt.% polyamide and 0.5-0.05 wt.% polyoxyethylene sorbitan fatty acid ester. It has a coefficient of dynamic friction of 0.5 or below, a haze of 5.0% or below and an ash test performance of 15 mm or below. The polyamide used is particularly desirably nylon 6 or nylon 66. The fatty acid of the polyoxyethylene sorbitan fatty acid used is oleic acid, stearic acid or lauric acid. The film is obtained by a film formation process such as a T-die process or a tubular process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a biaxially stretched polyamide film having excellent transparency and antistatic properties.

[0002]

2. Description of the Related Art Polyamide films, especially biaxially stretched polyamide films, have mechanical properties, optical properties, thermal properties,
It has excellent gas barrier properties, abrasion resistance, impact resistance, pinhole resistance, etc., and is widely used mainly in the field of food packaging. However, the polyamide film has a drawback that it easily absorbs moisture, the slip property decreases as the humidity increases, and wrinkles easily occur during the film processing step. In addition, despite the high hygroscopicity, a phenomenon that ink is repelled by static electricity in a printing process, so-called "print mustache" is liable to occur.

[0003] As a method for improving the slip property of a polyamide film, an inorganic lubricant such as silicon oxide, alumina, calcium carbonate or the like is used in order to reduce the frictional force between the films or a material in contact with the film. A method of adding an organic lubricant such as bisstearylamide or an organic high molecular compound such as polyolefin or polytetrafluoroethylene has been used.

[0004] However, when an inorganic compound is added, there is a problem that the particles tend to agglomerate to lower the transparency of the film, and the compatibility with the polymer base material is low, so that the particles are likely to be missing. In addition, when an organic lubricant or an organic polymer compound is added, the heat resistance of the film is reduced, the compatibility with the polyamide is low, the transparency of the obtained film is reduced, and a film forming problem occurs during sheet extrusion molding. This is problematic in that the problem is likely to occur.

As a method for preventing electrostatic trouble, there is a method of adding a hydrophilic compound such as polyethylene glycol or polyoxyethylene alkylphenyl ether or an organic sulfonate to polyamide, but the transparency of the film is impaired. And colored yellow. A method has been proposed in which an unstretched film obtained by melt-extruding a polyamide resin containing the above-mentioned hydrophilic compound or the like is subjected to a water absorption treatment before stretching (Japanese Patent Publication No. 5-64579). There has been a problem that the production method of the stretched polyamide film involves restrictions.

As a method for simultaneously improving the slip property and the electrostatic property of a polyamide film, a polyamide film in which a polyoxyethylene alkyl phenyl ether is coated on at least one surface of the film has been proposed (Japanese Patent Laid-Open No. 5-287709). Publication), when coating with vinylidene chloride to enhance gas barrier performance, or when performing treatment such as easy-adhesion coating for imparting ink adhesiveness, the effect of improving these properties and durability are reduced. There was a problem of doing.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide a biaxially stretched polyamide film having excellent antistatic properties, slip properties and transparency. Things.

[0008]

Means for Solving the Problems The present inventors have made intensive studies to solve such problems, and as a result, by forming a biaxially stretched film using a raw material obtained by melting and mixing a specific compound with polyamide, The inventors have found that the above problems have been solved and the object of the present invention has been achieved, and have reached the present invention.

That is, the gist of the present invention is to provide a polyamide 9
A biaxially stretched polyamide film comprising a composition of 9.5 to 99.95% by weight and a polyoxyethylene sorbitan fatty acid ester 0.5 to 0.05% by weight.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The polyamide in the present invention is
A polymer compound having an amide bond (-CONH-) in the molecule, such as polycapramid (nylon 6), polyhexamethylene adipamide (nylon 66), polyhexamethylene sebacamide (nylon 610), polyaminoundecanamid (Nylon 11), polylaurylamide (nylon
12), polymethaxylylenediadipamide, polyhexamethylene terephthalamide, and copolymers thereof, and the like. Nylon 6 and nylon 66 are particularly preferred from the viewpoint of cost performance.

The polyoxyethylene sorbitan fatty acid ester of the present invention is obtained by subjecting a polyhydric alcohol (referred to as sorbit) produced by hydrogen reduction of glucose to intramolecular dehydration of sorbitan, and esterifying the sorbitan with a fatty acid. Obtained by adding an oxide. As the fatty acid, oleic acid, stearic acid or lauric acid has good compatibility with the polyamide, and the resulting polyamide film has excellent performance and is suitable.

In the present invention, the content of the polyoxyethylene sorbitan fatty acid ester in the polyamide is from 0.05 to 0.05.
It is 0.5% by weight, preferably 0.05 to 0.3% by weight, more preferably 0.08 to 0.15% by weight. When the content of the polyoxyethylene sorbitan fatty acid ester is less than 0.05% by weight, the resulting polyamide film has insufficient slip properties and antistatic properties. Not only is the improvement effect saturated, but rather the transparency of the film is undesirably reduced.

In the present invention, as a method for obtaining a composition comprising a polyamide and a polyoxyethylene sorbitan fatty acid ester, a mixture of a polyamide and a polyoxyethylene sorbitan fatty acid ester is charged into an extruder in a film forming step. A method of melt extrusion, a method of melt-extruding a mixture of polyamide and polyoxyethylene sorbitan fatty acid ester in advance and mixing a polyamide with a master batch and a method of melt-extruding, or a hole for injection in a barrel of an extruder. There is a method of injecting polyoxyethylene sorbitan fatty acid ester into the extruder in a liquid state after opening, but the method is not particularly limited.

The film of the present invention has excellent properties in terms of antistatic properties, slip properties, and transparency. The indexes showing these properties include a dynamic friction coefficient of 0.5 or less, a haze of 5.0% or less, and an ash Test performance is 15mm or less.

The biaxially stretched polyamide film of the present invention comprises:
It can be manufactured using a known film forming method such as a T-die method and a tubular method.

For example, in the T-die method, a molten unstretched sheet extruded from the T-die is solidified by a cooling roll having a surface temperature of about 20 ° C., and then longitudinally drawn by sequential biaxial stretching or simultaneous biaxial stretching. And stretch in the transverse direction. The stretching temperature can be the same as that of a single polyamide film, and the stretching ratio may be appropriately changed as needed. Usually, the stretching is performed in a range of 1.2 to 6 times in both the vertical and horizontal directions. The biaxially stretched polyamide film is given heat-resistant dimensional stability by heat treatment usually at 190 to 220 ° C. The thickness of the biaxially stretched film is suitably from 1 to 50 μm, usually from 10 to 30 μm.

[0017]

The reason why the biaxially stretched polyamide film of the present invention has excellent antistatic properties and slip properties is that the polyamide and the polyoxyethylene sorbitan fatty acid ester are appropriately compatible and the polyoxyethylene sorbitan fatty acid ester is applied to the film surface. It is considered that the migration of the medium is appropriately controlled.

[0018]

EXAMPLES The present invention will be described more specifically with reference to examples. The measurement methods used in the examples and comparative examples are as follows.

Dynamic friction coefficient (slip property): ASTM-D-1894
The dynamic friction coefficient was measured by the method. Haze (transparency): Measured by the JIS-K-6714 method. Ash test: JIS0803 under conditions of 23 ° C and 50% RH
200mm on the specified cotton cloth (attached white cloth for dyeing fastness test)
Hold a × 30mm film sample with both hands, rub the film surface back and forth 20 times, charge the film, bring the tobacco ash closer and the distance at which the ash particles start to adhere to the film (unit: m)
m) was measured and regarded as the ash test performance.

Example 1 99.92% by weight of nylon 6 (A1030BRF manufactured by Unitika Ltd.)
And polyoxyethylene sorbitan monostearate 0.
After melting and mixing 08% by weight, coat hanger type T
Melt extrusion was performed using a 65 mmφ extruder equipped with a die. T
The sheet melt-extruded from the die was closely adhered to a cast roll adjusted to a surface temperature of 20 ° C. and rapidly cooled to obtain an unstretched sheet having a thickness of 150 μm. The obtained unstretched sheet was simultaneously biaxially stretched at a temperature of 80 ° C. with a stretching ratio of 3.0 times in the machine direction and 3.3 times in the transverse direction to obtain a biaxially stretched polyamide film having a thickness of 15 μm. About the obtained biaxially stretched film, the dynamic friction coefficient,
Table 1 shows the results of measuring the haze and the ash test.

Examples 2 to 8, Comparative Examples 1 to 7 Types of polyoxyethylene sorbitan fatty acid ester,
A biaxially stretched polyamide film having a thickness of 15 μm was obtained in the same manner as in Example 1, except that the amounts of the polyamide and nylon 6 were changed as shown in Table 1. Table 1 shows the results of measuring each performance of the obtained biaxially stretched film.

Example 9 and Comparative Example 8 The procedure of Example 1 was repeated except that nylon 66 was used instead of nylon 6 and the amount of polyoxyethylene sorbitan fatty acid ester to nylon 66 was changed as shown in Table 1. Thus, a biaxially stretched polyamide film having a thickness of 15 μm was obtained. Table 1 shows the results of measuring each performance of the obtained biaxially stretched film.

[0023]

[Table 1]

[0024]

According to the present invention, a biaxially stretched polyamide film having excellent antistatic properties, slip properties and transparency can be provided, and thus its use value as a food packaging film is extremely high.

Claims (4)

[Claims] 1. A biaxially stretched polyamide film comprising a composition of 99.5 to 99.95% by weight of a polyamide and 0.5 to 0.05% by weight of a polyoxyethylene sorbitan fatty acid ester. 2. The polyamide film according to claim 1, wherein the fatty acid of the polyoxyethylene sorbitan fatty acid ester is one of oleic acid, stearic acid and lauric acid. 3. The dynamic friction coefficient is 0.5 or less, and the haze is 5.0%.
The biaxially stretched polyamide film according to claim 1 or 2, wherein the ash test performance is 15 mm or less. 4. The biaxially stretched polyamide film according to claim 1, wherein the polyamide is nylon 6 or nylon 66.