JP2007136873A - Biaxially stretched laminated polyamide film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a baxially stretched laminated polyamide film which holds transparency and has excellent slip properties under a high humidity condition. <P>SOLUTION: In the biaxially stretched laminated polyamide film constituted by laminating a layer (X) comprising a polyamide resin and a layer (Y) comprising a gas barrier resin in the order of X/Y/X, the X-layer contains 0.04-0.14 mass% of a bisamide comprising a 20C or above fatty acid, and the thickness of the X-layer is 3-9 μm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a laminated polyamide film excellent in slipperiness. More specifically, the present invention relates to a laminated polyamide film having high gas barrier properties and particularly excellent sliding properties under high humidity.

  In general, polyamide resin films are excellent in mechanical properties, optical properties, thermal properties, gas barrier properties, toughness, pinhole resistance, flex resistance, etc., mainly for packaging applications, especially food packaging applications. Widely used. The packaging film is required to have excellent slipperiness in order to increase workability and processing speed during processing such as printing, vapor deposition, lamination, and bag making. Especially in the packaging of foods containing a lot of water, slipperiness under high humidity is regarded as important because it is used in a high humidity environment. However, the polyamide-based resin film has a tendency to deteriorate slipperiness in a high humidity environment, and has been required to be improved.

  Conventionally, it has been proposed to use an inorganic filler and an organic lubricant in combination as means for improving the slipperiness of a polyamide-based resin film under high humidity. For example, Patent Document 1 proposes a method for improving the slipperiness under high humidity by setting the number of protrusions on the film surface in a specific range and hydrophobizing the surface by adding an organic lubricant. However, even with this method, satisfactory slipperiness and transparency cannot be obtained, the transparency required as a packaging film and the suitability for lamination with a sealant layer are satisfied, and the slipperiness under high humidity is excellent. In fact, the polyamide film was not obtained industrially.

In addition, the present inventors have proposed that a specific amount of silica and a specific fatty acid-based bisamide are mixed in a polyamide film (Patent Document 2), but a polyamide-based resin film layer and a gas barrier resin film layer are proposed. In the laminated film consisting of the above, the blending amount of the fatty acid-based bisamide is not necessarily optimal, and satisfactory slipping and transparency and suitability for lamination with the sealant layer have not been obtained.
JP-A-10-168310 JP 2002-348465 A

  An object of the present invention is to solve the above problems, and in a laminated film composed of a polyamide-based resin film layer and a gas barrier resin film layer, while maintaining the transparency and suitability of the film, excellent slipping particularly under high humidity. It is in providing the laminated polyamide film which has property.

As a result of intensive studies, the present inventors have found that the object can be achieved by blending a specific fatty acid-based bisamide in the polyamide layer and defining the layer structure, and have reached the present invention.
That is, the gist of the present invention is a laminated polyamide film in which a layer (X) made of a polyamide resin and a layer (Y) made of a gas barrier resin are laminated in the order of X / Y / X, and the X layer has 20 carbon atoms. A biaxially stretched laminated polyamide film excellent in slipperiness under high humidity, characterized in that it contains 0.04 to 0.14% by mass of a bisamide composed of the above fatty acids and the thickness of the X layer is 3 to 9 μm It is.

  According to the present invention, not only mechanical properties, thermal properties, and barrier properties, but also excellent wear resistance, impact resistance, and pinhole resistance, while maintaining transparency, particularly excellent under high humidity. A biaxially stretched polyamide film having slipperiness is provided.

Hereinafter, the present invention will be specifically described.
The laminated polyamide film of the present invention is a film in which a layer (X) made of a polyamide resin and a layer (Y) made of a gas barrier resin are laminated in the order of X / Y / X.

  As the polyamide resin used in the present invention, a polyamide resin obtained by polycondensation of a lactam having three or more members, a polymerizable ω-amino acid, a dibasic acid and a diamine can be used. Specifically, polymers such as ε-caprolactam, aminocaproic acid, enanthractam, 7-aminoheptanoic acid, 11-aminoundecanoic acid, 9-aminononanoic acid, α-pyrrolidone, α-piperidone, hexamethylenediamine, nonamethylene A polycondensation of a salt of a diamine such as diamine, undecamethylenediamine, dodecamethylenediamine, or metaxylylenediamine with a dicarboxylic acid such as terephthalic acid, isophthalic acid, adipic acid, sebacic acid, dodecane dibasic acid, or glutaric acid. Or a copolymer thereof, for example, nylon 4, 6, 7, 8, 11, 12, 6, 6, 6, 10, 6, 11, 6, 12, 6T, 6/6, 6 6/12, 6 / 6T, 6I / 6T, and the like. From the viewpoint of excellent mechanical properties and thermal properties, the polyamide film for packaging is preferably composed mainly of nylon 6 or nylon 66.

  In the present invention, the layer (X) made of a polyamide resin needs to contain a bisamide made of a fatty acid having 20 or more carbon atoms. Bisamides composed of fatty acids having less than 20 carbon atoms are sufficient in improving the slipperiness in the low humidity region, but are not sufficient because the effect of improving the slipperiness in the high humidity is small. Specific fatty acids having 20 or more carbon atoms 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 those that are generally commercially available, such as ethylene bisamides such as ethylene bisbehenamide, ethylenebiserucamide, hexamethylene bisbehenamide, hexamethylene biserca. Examples include hexamethylene bisamide such as acid amide. In particular, ethylene bisamide is preferable because it has an excellent effect of improving slipperiness under high humidity.

  The content of bisamide in the layer (X) made of the polyamide resin is required to be 0.04 to 0.14% by mass, and preferably 0.06 to 0.10% by mass. If it is less than 0.04% by mass, the effect of improving the slipperiness under high humidity cannot be obtained. On the other hand, if it exceeds 0.14% by mass, the effect of improving the slipperiness of the obtained film under high humidity is sufficient. However, problems such as a decrease in laminate strength with the sealant layer are likely to occur.

  In the present invention, the thickness of the layer (X) made of the polyamide resin is required to be 3 to 9 μm, and preferably 4 to 8 μm. If the thickness of the X layer is less than 3 μm, the excellent mechanical properties (toughness, pinhole resistance, flex resistance) of the polyamide resin may not be sufficiently exhibited, or stretching may not be possible. When the thickness exceeds 9 μm, the above-mentioned bisamide content does not provide the effect of improving the slipperiness under a sufficiently high humidity. That is, in the polyamide single layer film, it is necessary to bleed out the organic lubricant from a deep part in the thickness direction of the film, whereas in the laminated film as in the present invention, the organic lubricant is distributed on the surface layer. Only a small amount of organic lubricant is required.

  By specifying the thickness of the layer (X) made of polyamide resin and the content of bisamide in the present invention, it is possible to provide a laminated polyamide film having excellent gas barrier properties and excellent sliding properties under high humidity. It became. That is, as the slipperiness, a material having a static friction coefficient of 0.6 or less, preferably 0.55 or less under a high humidity of 20 ° C. and 90% RH can be obtained. Moreover, as the laminate suitability with the sealant layer, a laminate having a laminate strength of 4 N / cm or more, preferably 5 N / cm can be obtained.

  In the present invention, the layer (X) made of a polyamide resin preferably contains 0.1 to 0.4% by mass of silica. The silica is preferably composed of silica (A) having an average particle diameter of 1 to 2 μm and silica (B) having an average particle diameter of 2 to 3 μm, and the mass ratio A / B thereof is preferably 3/1 or more. . When the average particle diameter of silica (A) is less than 1 μm, the ability to form surface protrusions of the film is low and the slipperiness is not improved. When the average particle diameter exceeds 2 μm, the effect of improving the slipperiness appears. The transparency of the is reduced. In particular, when paying attention to slipperiness under high humidity, a film excellent in transparency and slipperiness can be obtained by using one having an average particle diameter of 1 to 2 μm. The content of silica (B) is preferably 1/3 or less with respect to the mass of silica (A), and if it exceeds 1/3, transparency and sliding performance cannot be satisfied at the same time. Addition of silica having an average particle size of 3 μm or more has little effect of improving the slipperiness and lowers the transparency.

  There is no restriction | limiting in particular about the method of adding bisamide and a silica to polyamide, It can prepare according to the method used normally. For example, polyamide resin pellets may be used by dry blending bisamide and silica at a predetermined ratio. As a method for adding silica, a method may be used in which silica is added to a polyamide resin forming raw material and the silica is dispersed in advance during polymerization of the polyamide resin.

The gas barrier resin in the present invention is not limited as long as it has a gas barrier property better than that of the polyamide resin, and an ethylene-vinyl acetate copolymer saponified product (EVOH), polymetaxylylenediamine azimuth having excellent coextrusion suitability with the polyamide resin. Pamide (MXD6) is a preferred example. By laminating these gas barrier resins, the laminated polyamide film can be given gas barrier properties, and the oxygen permeability at 20 ° C. and 65% RH is 100 ml / (m ² · day · MPa) or less, preferably 80 ml. / (M ² · day · MPa) or less can be obtained. The thickness of the layer (Y) made of the gas barrier resin is preferably 2 to 10 μm, and more preferably 3 to 8 μm. When the thickness of the Y layer is less than 2 μm, the gas barrier property may not be achieved. When the thickness exceeds 10 μm, not only the quality is increased, but the cost is increased.

  The film of the present invention needs to have a configuration in which a layer (X) made of a polyamide resin and a layer (Y) made of a gas barrier resin are laminated in the order of X / Y / X. / Y / X, X / Y / X / Y / X. The thickness of each X layer is preferably equal. If necessary, an adhesive layer and a recovery layer can be provided between the layers.

  In the present invention, various additives and modifiers that are usually blended as required, for example, heat stabilizers, ultraviolet absorbers, light stabilizers, antioxidants, antistatic agents, and tackifiers. Further, a sealing property improving agent, an antifogging agent, a crystal nucleating agent, a release agent, a plasticizer, a crosslinking agent, a flame retardant, a colorant (pigment, dye, etc.) and the like may be blended.

  The biaxially stretched laminated polyamide film of the present invention can be formed by a known film forming method. For example, a molten polymer is laminated from a T-die, extruded, cooled with a casting roll to produce an unstretched sheet, and this is simultaneously biaxially stretched or sequentially biaxially stretched. The stretched film is subjected to a short heat treatment at a temperature of around 200 ° C. in order to improve dimensional stability.

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples without departing from the gist thereof. In addition, each physical property of the film was calculated | required by the method shown below.
(1) Static friction coefficient: The static friction coefficient in a film / film was measured according to JIS K7125 under conditions of 90% relative humidity and a temperature of 20 ° C.
(2) Oxygen permeability: OX-TRAN 2/20 manufactured by Modern Control was used and measured under the conditions of 20 ° C. and 65% RH. Unit: ml / (m ² · day · MPa)
(3) Lamination strength: 4-5 g / m ^{2 of} polyurethane adhesive for dry lamination (A515 / A50, manufactured by Takeda Pharmaceutical Company Limited) is applied to a biaxially stretched laminated polyamide film, and unstretched polypropylene for dry lamination ( Tosero Co., Ltd., RXC-18, 60 μm) was laminated by a dry laminating method (temperature 80 ° C., pressure 490 kPa) to form a sealant layer. Using a film laminate having a width of 15 mm laminated with a sealant layer as a sample, the laminate was peeled off at a tensile rate of 300 mm / min in an environment of 20 ° C. × 65% RH, and the laminate strength was measured by a T-type peeling method. .

In the examples, the following raw materials were used.
(1) Nylon 6 resin: manufactured by Unitika, A1030BRF, relative viscosity 3.0
(2) Silica Silica A: manufactured by Fuji Silysia Chemical Ltd., Silicia 310P, average particle size 1.4 μm
Silica B: Mizusawa Chemical Co., Ltd., Mizukasil P73, average particle size 2.5 μm
(3) Fatty acid bisamide ethylene bislauric acid amide (Nippon Kasei Co., Ltd., SLIPAX L, fatty acid carbon number 12)
Ethylene bis-stearic acid amide (Nippon Kasei Co., Ltd., SLIPAX E, 18 carbon atoms of fatty acid)
Hexamethylenebisstearic acid amide (Nippon Kasei Co., Ltd., SLIPAX ZHS, carbon number 18 of fatty acid)
Ethylene bisbehenamide (Nippon Kasei Co., Ltd., SLIPAX B, C22 of fatty acid)
Hexamethylene bisbehenamide (Nippon Kasei Co., Ltd., SLIPAX ZHB, fatty acid 22 carbon atoms)
Ethylene bis erucamide (Nippon Kasei Co., Ltd., SLIPAX R, carbon number 22 of fatty acid)
(4) Gas barrier resin ethylene-vinyl acetate copolymer saponification product (EVOH) (Kuraray Co., Ltd., EP-F101BZ)
Polymetaxylylene adipamide (MXD6) (manufactured by Mitsubishi Gas Chemical Company, MX nylon 6007, relative viscosity 2.6)
(5) Adhesive amorphous nylon (manufactured by EMS, Grivory G21)
(6) Preparation of silica master chip:
An autoclave with an internal volume of 30 liters was charged with 10 kg of ε-caprolactam, 1 kg of water, 450 g of silica A and 150 g of silica B, maintained at 100 ° C., and stirred at this temperature until the reaction system became uniform. did. Subsequently, the mixture was heated to 260 ° C. with stirring, maintained at a pressure of 1.5 MPa for 1 hour, further released to normal pressure over 1 hour, and further polymerized for 1 hour. When the polymerization was completed, the reaction product was discharged into a strand, cooled, solidified, and then cut to obtain a polyamide resin pellet. Next, the pellets were refined with hot water at 95 ° C. for 8 hours to remove unreacted monomers and then dried. The relative viscosity of the obtained polyamide resin was 3.0.
(7) Preparation of bisamide master chip:
After 99 parts by mass of nylon 6 resin is dry blended with 1 part by mass of ethylene bisbehenamide, this is melt kneaded with a 30 mm twin screw extruder with a cylinder temperature setting of 250 ° C., extruded into a strand, cooled, solidified and then cut. To obtain a master chip. Each fatty acid bisamide master was prepared in the same manner.

Example 1
88 parts by mass of nylon 6 resin, 8 parts by mass of ethylene bisbehenamide amide master and 4 parts by mass of silica master are mixed and supplied to a single screw extruder set at a cylinder temperature of 260 ° C. The combined saponified product is supplied to a single screw extruder set at a cylinder temperature of 230 ° C., and is laminated and extruded in the order of nylon 6 / ethylene-vinyl acetate copolymer saponified product / nylon 6 using a multi-manifold die. An unstretched sheet having a thickness of 50/50/50 μm and a total thickness of 150 μm was obtained by contacting with a cooling roll at a temperature of 20 ° C. The obtained unstretched sheet is immersed in a warm water layer adjusted to 50 ° C. for 1 minute, stretched 3 times in length and 3.3 times in width at a stretching temperature of 175 ° C. with a simultaneous biaxial stretching machine, and heat-treated at 210 ° C. for 5 seconds. Then, a relaxation treatment of 5% was performed in the transverse direction and cooled 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.

Example 2
88 parts by mass of nylon 6 resin, 8 parts by mass of ethylene bisbehenamide amide master and 4 parts by mass of silica master are mixed and supplied to a single screw extruder set at a cylinder temperature of 260 ° C., while polymetaxylylene adipa The amide is supplied to a single screw extruder set at a cylinder temperature of 260 ° C, and the adhesive is supplied to a twin screw extruder set at 260 ° C. Using a multi-manifold die, nylon 6 / adhesive / polymeta Xylylene adipamide / adhesive / nylon 6 are laminated and extruded in order, brought into contact with a cooling roll at a set temperature of 20 ° C., and each layer has a thickness of 45/5/50/5/45 μm and a total thickness of 150 μm. Got. As an adhesive, an equivalent mixture of polymetaxylylene adipamide and amorphous nylon was used. The obtained unstretched sheet was dipped in a warm water layer adjusted to 50 ° C. for 1 minute, and stretched at a stretching temperature of 190 ° C. at a stretching speed of 3 times and a transverse speed of 3.3 times with a simultaneous biaxial stretching machine, and heat treatment at 210 ° C. for 5 seconds. Then, a relaxation treatment of 5% was performed in the transverse direction and cooled 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.

Examples 3-4, Comparative Examples 1-7
The same procedure as in Example 1 was conducted except that the layer structure, the type of bisamide, and the content were changed as shown in Table 1. The obtained film was subjected to physical property measurements, and the results are shown in Table 1. In Comparative Example 6, no film was obtained due to stretch fracture.

In the case of the examples, the transparency is good and the slipperiness under high humidity (90% RH) is excellent. In the case of the comparative example outside the scope of the present invention, there was a problem that the slipperiness under high humidity was poor or the laminate strength with the sealant layer was not good, and an excellent film could not be obtained.

Claims (6)

  A laminated polyamide film in which a layer (X) made of a polyamide resin and a layer (Y) made of a gas barrier resin are laminated in the order of X / Y / X, wherein the X layer contains 0 or less bisamide made of a fatty acid having 20 or more carbon atoms. A biaxially stretched laminated polyamide film excellent in slipperiness under high humidity, characterized by containing 0.04 to 0.14% by mass and the thickness of the X layer being 3 to 9 μm.   The biaxially stretched laminated polyamide film according to claim 1, wherein the bisamide composed of a fatty acid having 20 or more carbon atoms is ethylene bisbehenic acid amide or ethylene biserucic acid amide.   The biaxially stretched laminated polyamide film according to claim 1 or 2, wherein a static friction coefficient at 20 ° C and 90% RH is 0.6 or less.   The biaxial stretching according to any one of claims 1 to 3, wherein the gas barrier resin is saponified ethylene-vinyl acetate copolymer (EVOH) or polymetaxylylene adipamide (MXD6). Laminated polyamide film. 5. The biaxially stretched laminated polyamide film according to claim 1, wherein the oxygen permeability at 20 ° C. and 65% RH is 100 ml / (m ² · day · MPa) or less. The biaxially stretched laminated polyamide film according to any one of claims 1 to 5, wherein the main component of polyamide is nylon 6.