JP2002348465A - Biaxially oriented polyamide film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biaxially oriented polyamide film which maintains transparency and has an excellent sliding property at a high humidity condition. SOLUTION: The biaxially oriented polyamide film contains an inorganic particle and a bisamide of a long chain fatty acid. The inorganic particle consists of (A) silica with an average particle size of 1-2 μm and (B) silica with an average particle size of 2-3 μm. The total content of (A) and (B) is 0.1-0.3 mass %, the mass ratio (A)/(B) is 3/1 or above, the bisamide of a long chain fatty acid is a bisamide consisting of a fatty acid with 20C or more and the bisamide content is 0.1-0.3 mass %.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a polyamide film having excellent slipperiness. More specifically, the present invention relates to a polyamide film having excellent sliding properties, particularly under high humidity, while maintaining transparency.

[0002]

2. Description of the Related Art Generally, a polyamide resin film is
Mechanical properties, optical properties, thermal properties, gas barrier properties,
Excellent in toughness, pinhole resistance, bending resistance, etc.
It is widely used mainly for packaging applications, especially food packaging applications. Packaging films are required to have excellent slipperiness in order to increase workability and processing speed during processing such as printing, vapor deposition, lamination, and bag making. Particularly, in the packaging of foods containing a large amount of water, slipperiness under high humidity is regarded as important because the food is used in a high humidity environment. However, the polyamide resin film tends to have poor slipperiness in a high humidity environment, and has been required to be improved.

Conventionally, various methods for improving the slipperiness of a polyamide resin film include a method of forming surface projections by adding an inorganic filler, a coating of a projection-forming substance on a film surface, and a method of adding an organic lubricant. Have been tried.

[0004] However, the method of forming surface projections by adding an inorganic filler is an effective means. However, if the amount of the inorganic filler is small, sufficient lubricity cannot be obtained. However, polyamide films having sufficient slip properties, particularly under high humidity, have not been obtained due to the problem that the properties are reduced and the commercial value as a packaging film is lost.

On the other hand, a method of adding an organic lubricant such as a bisamide compound is known as a method capable of improving the slipperiness while maintaining the transparency of the obtained film. There is a drawback that the adhesion of the printing ink is reduced and printing defects are likely to occur. For this reason, the upper limit of the amount added is restricted, and the slipperiness under high humidity cannot be brought to a satisfactory level.

For this reason, in general, transparency, slipperiness and printability have been optimized by the combined use of an inorganic filler and an organic lubricant, but the transparency required for a packaging film and the printability have been improved. The fact is that a polyamide film satisfying the properties and excellent in slipperiness under high humidity has not been industrially obtained.

For example, in Japanese Patent Application Laid-Open No. 10-168310, the number of projections on the film surface is set to a specific range,
A method has been proposed to improve the slipperiness under high humidity by making the surface hydrophobic by adding an organic lubricant.
Satisfactory sliding properties and transparency could not be obtained.

[0008]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and to maintain excellent transparency, especially under high humidity, while maintaining the transparency, print processability and post-processability of the film. It is to provide a polyamide film.

[0009]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that the purpose can be achieved by blending a specific size of silica and a specific fatty acid-based bisamide into a polyamide film, The present invention has been reached.

That is, the gist of the present invention is to provide a polyamide film containing inorganic particles and a long-chain fatty acid-based bisamide, wherein the inorganic particles are silica (A) having an average particle size of 1 to 2 μm, Of silica (B) having a total content of 0.1 to 0.3 μm.
% By mass, and the mass ratio of silica (A) to (B) A / B
Is at least 3/1, and the long-chain fatty acid-based bisamide is C
A biaxially stretched polyamide film excellent in slipperiness under high humidity, characterized in that it is a bisamide composed of 20 or more fatty acids and has a content of 0.1 to 0.3% by mass.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below. Examples of the polyamide resin used in the present invention include a lactam having three or more rings, a polymerizable ω-amino acid,
A polyamide resin obtained by polycondensation of a dibasic acid and a diamine can be used. Specifically, ε-caprolactam, aminocaproic acid, enantholactam,
7-aminoheptanoic acid, 11-aminoundecanoic acid, 9
Polymers such as aminononanoic acid, α-pyrrolidone and α-piperidone, diamines such as hexamethylenediamine, nonamethylenediamine, undecamethylenediamine, dodecamethylenediamine, meta-xylylenediamine, and terephthalic acid, isophthalic acid, and adipic acid , Sebacic acid,
Polymers obtained by polycondensing a salt with a dicarboxylic acid such as dodecane dibasic acid or glutaric acid or copolymers thereof, for example, nylon 4, 6, 7, 8, 11, 1
2, 6, 6, 6, 10, 6, 11, 6, 12, 6T, 6
/6.6, 6/12, 6 / 6T, 6I / 6T and the like. Nylon 6 and nylon 66 are used as packaging polyamide films because of their excellent mechanical and thermal properties.
Is preferable.

The silica contained in the polyamide resin is amorphous silicon dioxide, which comprises silica (A) having an average particle size of 1 to 2 μm and silica (B) having an average particle size of 2 to 3 μm,
0.1-0.4% by mass in total and their mass ratio A
/ B needs to be 3/1 or more.

As the silica (A) to be mainly used, one having an average particle size of 1 to 2 μm is selected. Average particle size is 1μm
Below, the ability to form surface protrusions on the film is low,
Slipperiness is not improved. When the average particle size exceeds 2 μm,
Although the effect of improving the slipperiness is exhibited, the transparency of the film is deteriorated. In particular, when attention is paid to the slipperiness under high humidity, a film excellent in transparency and slipperiness can be obtained by using one having an average particle size of 1 to 2 μm.

The film of the present invention has an average particle size of 1 to 2 μm.
Of silica (A) and a small amount of silica (B) having an average particle size of 2 to 3 μm, whereby the sliding performance under high humidity is improved. The content of the silica (B) having an average particle diameter of 2 to 3 μm needs to be 1/3 or less of the mass of the silica (A) having an average particle diameter of 1 to 2 μm, and more than 1/3. When blended, transparency and sliding performance cannot be simultaneously satisfied. In addition, average particle size 3μ
m or more of silica, the effect of improving the slip property is small,
It is better not to contain it because it deteriorates the transparency.

The long-chain aliphatic bisamide compound to be contained must be a bisamide composed of a fatty acid having C20 or more, and a bisamide composed of a fatty acid having less than C20 has a sufficient slip-improving effect in a low humidity region. There is
The effect of improving the slipperiness under high humidity is small and insufficient. Specific examples of C20 or higher fatty acids include saturated fatty acids such as behenic acid (C22) and unsaturated fatty acids such as erucic acid (C22). Specific examples of bisamides composed of these fatty acids include commercially available ethylene amides such as ethylene bisbehenamide, ethylene bis erucamide, hexamethylene bis behenamide, and hexamethylene bis erucamide. Hexamethylene bisamide such as acid amide can be mentioned. In particular, ethylene bisamide is
It is preferable because it has an excellent effect of improving the slipperiness under high humidity.

The content of the long-chain aliphatic bisamide compound is 0.1 to 0.3% by mass. If it is less than 0.1%,
The effect of improving slipperiness under high humidity is too low. On the other hand, 0.3
%, Problems such as poor printability of the obtained film are likely to occur.

The method for adding silica and fatty acid bisamide to the polyamide is not particularly limited, and it can be prepared according to a commonly used method. For example, a silica resin pellet and a bisamide compound may be dry blended at a predetermined ratio to a polyamide resin pellet and used. As for the silica particles, it is preferable to mix an inorganic filler with a raw material for forming a polyamide resin when the polyamide resin is polymerized and to disperse the inorganic filler in the resin before use.

In the present invention, by containing the above silica and fatty acid bisamide, it has become possible to provide a polyamide film having excellent transparency and excellent slipperiness under high humidity. As slipperiness, under a high humidity of 90% RH, the static friction coefficient and the dynamic friction coefficient are both 0.45 or less, preferably 0.40 or less,
Further, as the transparency, haze is 6% or less, preferably 5%.
%, More preferably 4% or less.

In the present invention, if necessary,
Various additives and modifiers usually blended, for example, heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, tackifiers, sealability improvers, antifoggants, crystals A nucleating agent, a release agent, a plasticizer, a cross-linking agent, a flame retardant, a colorant (a pigment, a dye, etc.) may be blended.

The polyamide resin thus prepared can be formed into the polyamide film of the present invention by a known film forming method. For example, after extruding a molten polymer from a T-die, it is cooled with a casting roll to prepare an unstretched sheet, and this sheet is biaxially stretched simultaneously or sequentially. The stretched film is subjected to a short-time heat treatment at a temperature of about 200 ° C. in order to improve dimensional stability.

The polyamide film of the present invention may be a single-layer film or a laminated film formed by coextrusion or lamination.

[0022]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these without departing from the gist thereof. In addition, each physical property of the film was calculated | required by the method shown below. (1) Haze: Using Tokyo Denshoku haze meter,
The haze value was measured. (2) Static friction coefficient: JIS K under the conditions of a relative humidity of 65%, a temperature of 20 ° C., and a relative humidity of 90% and a temperature of 20 ° C.
According to 7125, the static friction coefficient of the film / film was measured. (3) Dynamic friction coefficient: JIS K under the conditions of 65% relative humidity, 20 ° C temperature, and 90% relative humidity, 20 ° C temperature.
The dynamic friction coefficient of the film / film was measured according to 7125. (4) Number of surface protrusions: Using a surface roughness shape measuring device Surfcom 550A type manufactured by Tokyo Seimitsu Co., Ltd., and the tip radius of the stylus: 5 μm
m, load: 400 mg, measurement length: 1 mm, measurement speed:
0.06 mm / sec and cut-off value: 0.05 m
m, measure the surface roughness of the polyamide film sample,
A surface roughness curve was obtained. The number of protrusions can be determined by an arbitrary method such that, after crossing a line parallel to the center line of the surface roughness curve and having a predetermined height (0.06 μm from the center line) on the + side and then crossing on the − side, one count is performed. The total number of counts per mm measured in the direction was determined. The measurement was performed 20 times, and the average value was defined as the “number of protrusions”. In addition, the polyamide film sample
After conditioning in an atmosphere at 20 ° C. and a relative humidity of 65% for 24 hours or more, the surface roughness was measured.

In the examples, the following silica and fatty acid bisamide were used. (1) Silica Sea Hoster KE-P50 (manufactured by Nippon Shokubai Co., Ltd., average particle size 0.5 μm) Sylysia 310P (manufactured by Fuji Silysia Chemical Ltd., average particle size 1.4 μm) Mizukasil P73 (manufactured by Mizusawa Science Co., Ltd., average particle size 2. 5μ
m) Mizukasil P78A (manufactured by Mizusawa Science Co., Ltd., average particle size 3.3)
μm) (2) Fatty acid bisamide Ethylene bislauric amide (Nippon Kasei Co., Slipax L, fatty acid carbon number 12) Ethylene bisstearic amide (Nippon Kasei Co., Slipax E, fatty acid carbon number 18) Hexamethylene bis Stearamide (Nippon Kasei Co., Slipax ZHS, fatty acid having 18 carbon atoms) Ethylene bisbehenamide (Nippon Kasei Co., Slipax B, fatty acid having 22 carbon atoms) Hexamethylenebisbehenamide (Nippon Kasei Co., Ltd.
Slipax ZHB, fatty acid having 22 carbon atoms) Ethylene biserucamide (Nippon Kasei Co., Slipax R, fatty acid having 22 carbon atoms)

Preparation of silica master chip 10 kg of ε-
Caprolactam, 1 kg of water, and 500 g of silica (trade name: Sylysia 310, manufactured by Fuji Silysia Chemical Ltd.)
P, average particle size: 1.4 μm), and the mixture was kept at 100 ° C. and stirred at this temperature until the inside of the reaction system became uniform.
Subsequently, the mixture was heated to 260 ° C. while stirring, and the pressure was increased to 1.5.
The MPa was maintained for 1 hour, the pressure was released to normal pressure over 1 hour, and the polymerization was continued for 1 hour. At the end of the polymerization,
The reaction product was discharged into a strand, cooled, solidified, and then cut to obtain a pellet made of a polyamide resin. Next, the pellets were refined with hot water at 95 ° C. for 8 hours to remove unreacted monomers and the like, and then dried. The relative viscosity of the obtained polyamide resin was 2.7. Each silica master was similarly prepared.

Preparation of fatty acid bisamide master chip Nylon 6 resin (manufactured by Unitika, trade name: A1030B)
RF and a relative viscosity of 2.7) were dry-blended with ethylene bisbehenamide (Slipax B, manufactured by Nippon Kasei Co., Ltd.) at a concentration of 1%, and the resulting mixture was subjected to 30 m at a cylinder temperature setting of 250 ° C.
The mixture was melt-kneaded with an m2-screw extruder, extruded into strands, cooled, solidified, and then cut to obtain master chips. Each fatty acid bisamide master was similarly prepared.

Examples 1 to 7 and Comparative Examples 1 to 9 Nylon 6 resin (trade name: A1030B, manufactured by Unitika Ltd.)
RF, relative viscosity of 2.7), a silica master chip and a fatty acid bisamide master chip were mixed so that the silica particles and the fatty acid bisamide had the compounding amounts shown in Table 1, and 90 mm single screw extrusion was performed at a cylinder temperature of 260 ° C. The sheet was extruded from a T-die and was brought into contact with a cooling roll having a set temperature of 20 ° C. to obtain an unstretched sheet having a thickness of 140 μm. The obtained unstretched sheet is immersed in a warm water layer adjusted to 50 ° C. for 1 minute, stretched 3 times vertically and 3.3 times horizontally at a stretching temperature of 190 ° C. by a simultaneous biaxial stretching machine, and heat-treated at 210 ° C. for 5 seconds. And a 5% relaxation treatment in the transverse direction was performed, followed by cooling to obtain a biaxially stretched film having a thickness of 15 μm. The obtained film was subjected to physical property measurement. The results are shown in Table 1.

[0027]

[Table 1]

In the case of the embodiment, the transparency is good and the sliding property under high humidity (90% RH) is excellent. In the case of Comparative Examples outside the range of the present invention, there were problems such as poor slipperiness under high humidity or poor transparency, and no excellent film was obtained.

[0029]

According to the present invention, mechanical properties, thermal properties,
Provided is a biaxially stretched polyamide film which has not only barrier properties but also excellent abrasion resistance, impact resistance and pinhole resistance, and also has excellent slipperiness especially under high humidity while maintaining transparency. You.

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Claims (3)

[Claims] 1. A polyamide film containing inorganic particles and a long-chain fatty acid-based bisamide, wherein the inorganic particles are silica (A) having an average particle size of 1 to 2 μm, and an average particle size of 2 to 3 μm.
m of silica (B), the total content of silica (A) and (B) is 0.1 to 0.3% by mass, and the mass ratio A / B of silica (A) and (B) is: 3/1 or more, wherein the long-chain fatty acid-based bisamide is a bisamide comprising a C20 or more fatty acid, and the content thereof is 0.1 to 0.3% by mass. Excellent in character 2
Axial stretched polyamide film. 2. The biaxially stretched polyamide film according to claim 1, wherein the bisamide comprising a C20 or more fatty acid is ethylene bisbehenamide or ethylene biserucamide. 3. The biaxially stretched polyamide film according to claim 1, wherein the main component of the polyamide is nylon 6.