JP2001062973A - Multilayer oriented polyamide film and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oriented multilayer polyamide film of superior pinhole resistance, transparency, tensile strength, interlaminar release strength, gas barrier properties and retort resistance and also provide a manufacturing method thereof. SOLUTION: A polyamide film is formed of at least three layers including a resin layer X of a polyamide A composed of a xylenediamine component and a 4-12C aliphatic dicarboxylic acid component and a resin layer Z formed of a mixture of the polyamide A and an aliphatic polyamide B on the middle of a resin layer Y containing 0.5-3 wt.% polymer compound P in the aliphatic polyamide B. The polymer compound P is a modified polyethylene composed of 95-50 wt.% ethylene, 0.1-10 wt.% unsaturated dicarboxylic acid and/or its derivative and 4.9-40 wt.% unsaturated carboxylic acid and/or its low alkyl ester derivative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has excellent pinhole resistance, transparency, tensile strength, delamination strength, gas barrier property, dimensional stability, and excellent retort resistance (hot water treatment resistance). The present invention relates to a multilayer stretched polyamide film suitable for packaging applications.

[0002]

2. Description of the Related Art Various plastic film packaging bags are used in large quantities for packaging foods, medicines, miscellaneous goods, etc. Usually, a biaxially stretched plastic film is used as a base film and a heat sealable sealant film ( For example, a laminated film obtained by laminating a non-oriented film) is used. The base film is required to have excellent properties such as pinhole resistance, transparency, gas barrier properties, dimensional stability, and tensile strength, and also has excellent delamination strength with the sealant film. It is necessary. However, recent demands for long-term preservation of the contents of the package require the quality of the packaging materials to be improved, and in order to provide advanced gas barrier properties, the surface of the biaxially stretched polyamide film is coated with a vinylidene chloride-based polymer latex. Such films are widely used, but have drawbacks of environmental problems and clouding due to hot water treatment.

[0003] Further, a film using polymetaxylylene adipamide (hereinafter referred to as MXD6) synthesized from adipic acid and metaxylylenediamine as a raw material has excellent gas barrier properties, but has poor pinhole resistance. For this reason, multilayer films have been proposed which are mixed with another polyamide resin, coextruded with a resin layer of polyamide, polyester, polyolefin or the like, or laminated.

[0004] For example, a biaxially stretched film formed from a mixture of MXD6 and an aliphatic polyamide (Japanese Patent Laid-Open No.
JP-A-54176), a biaxially stretched film obtained by laminating MXD6 and an aliphatic polyamide by a tubular method (JP-A-57-51427), a surface layer composed of a mixture of MXD6 and an aliphatic polyamide, and mainly composed of MXD6. Three-layer film having an intermediate layer (JP-A-56-155)
No. 762), a multilayer film comprising at least one layer of MXD6 and / or a mixture of an aliphatic polyamide and an amorphous polyamide (Japanese Patent Laid-Open No. 4-59244), and a multilayer film in which MXD6 is mixed with a flexing agent ( Japanese Patent Application Laid-Open No. 6-255054) has been proposed.

However, in a biaxially stretched film using a mixture of MXD6 and an aliphatic polyamide as a raw material, it is difficult to provide both pinhole resistance and gas barrier properties. In this case, there was a disadvantage that the layers were easily delaminated. Further, even in the case of the configuration disclosed in JP-A-56-155762, the pinhole resistance was insufficient. According to the method disclosed in Japanese Patent Application Laid-Open No. 4-59244, although the problem of the delamination phenomenon is improved, the pinhole resistance performance is insufficient when applied to a wide range of uses. . Even with the configuration disclosed in JP-A-6-255054, the pinhole resistance performance was insufficient when applied to a wide range of packaging applications.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned drawbacks and has excellent pinhole resistance, transparency, gas barrier properties, delamination strength, tensile strength, and dimensional stability. An object of the present invention is to provide a multilayer stretched polyamide film having excellent retort resistance and suitable for packaging. Specifically, no delamination phenomenon occurs between the aliphatic polyamide resin layer and the MXD6 resin layer, and in addition to the excellent mechanical properties, pinhole resistance, and transparency of the aliphatic polyamide resin layer, An object of the present invention is to provide a multilayer stretched polyamide film suitable as a packaging material having both heat resistance and gas barrier properties of an MXD6 resin layer, and a method for producing the same.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a multilayer stretched film having a composition composed of a specific component and a specific layer constitution has solved these problems. They have found that they can be solved and have reached the present invention.

That is, the gist of the present invention is as follows. (1) A resin layer (X) of a polyamide (A) formed from a xylylenediamine component and an aliphatic dicarboxylic acid component having 4 to 12 carbon atoms, and an aliphatic polyamide (B) formed of the following polymer compound P , A resin layer (Z) comprising a mixture of polyamide (A) and polyamide (B) in the middle of a resin layer (Y) containing 0.5 to 3% by weight of a multilayer stretched polyamide film comprising at least three layers . Polymer compound P: 95 to 50% by weight of ethylene, 0.1 to 10% by weight of unsaturated dicarboxylic acid and / or a derivative thereof,
A modified polyethylene comprising 4.9 to 40% by weight of an unsaturated carboxylic acid and / or a lower alkyl ester derivative thereof. (2) A resin layer (X) of a polyamide (A) formed from a xylylenediamine component and an aliphatic dicarboxylic acid component having 4 to 12 carbon atoms, and the above-described polymer compound P on an aliphatic polyamide (B). , A resin layer (Z) comprising a mixture of polyamide (A) and polyamide (B) in the middle of a resin layer (Y) containing 0.5 to 3% by weight of a multilayer stretched polyamide film comprising at least three layers Wherein the polyamide (A) and the polyamide (B) are co-extruded using a resin in which the polyamide (A) and the polyamide (B) are melt-kneaded in advance as the polyamide for forming the resin layer (Z). Method.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The polyamide (A) in the present invention comprises
Or, it is a polyamide obtained by a polycondensation reaction from paraxylylenediamine and an aliphatic dicarboxylic acid having 4 to 12 carbon atoms, and in particular, MXD6 synthesized from metaxylylene and adipic acid is preferable.

In the present invention, the aliphatic polyamide (B)
Examples thereof include nylon 6, nylon 66, nylon 46, nylon 610, nylon 612, nylon 12, nylon 11, copolymerized polyamides thereof, and mixed polyamide resins, and nylon 6 is particularly preferred.

The polyamide (A) and the polyamide (B)
Although the adhesiveness is generally not good, by laminating a resin layer (Z) composed of a molten mixture of polyamide (A) and polyamide (B) as an intermediate layer, the delamination strength of the resin layers (A) and (B) is increased. Is improved. Further, as the resin layer (Z),
Multi-layer co-extrusion using a resin in which polyamide (A) and polyamide (B) are melt-mixed in advance further improves the delamination strength of each resin layer. As a condition for mixing the polyamide (A) and the polyamide (B), it is preferable to extrude the mixture in a temperature range of 250 to 300 ° C. using a twin-screw extruder. If the temperature is lower than 250 ° C., the delamination strength becomes insufficient, and if it exceeds 300 ° C., the resin does not bite into the extruder.

The resin layer (Z) has a mixing ratio of the polyamide (A) and the polyamide (B) of 50 to 80.
It is more preferable to set the content of the polyamide (B) to 50 to 20% by weight because the delamination strength is further improved.

The polymer compound P in the present invention comprises 95 to 50% by weight of ethylene, 0.1 to 10% by weight of an unsaturated dicarboxylic acid and / or a derivative thereof, and an unsaturated carboxylic acid and / or a derivative thereof.
Or an ethylene-based terpolymer composed of 4.9 to 40% by weight of a lower alkyl ester derivative having a melt index of 0.1 to 60 g / 10 minutes, preferably 1 to 50
g / 10 minutes.

The unsaturated dicarboxylic acids and derivatives thereof include, for example, maleic acid, fumaric acid, itaconic acid,
Derivatives such as citraconic acid, mesaconic acid and their metal salts and acid anhydrides are included. Among these, maleic anhydride is most preferred from the viewpoint of cost performance and the like.

Examples of the unsaturated carboxylic acid and its lower alkyl ester derivative include acrylic acid, methacrylic acid and the like, methyl acrylate, methyl methacrylate, ethyl acrylate, n-propyl acrylate, and the like.
Isopropyl acrylate, n-butyl acrylate,
Examples thereof include isobutyl acrylate and t-butyl acrylate, and methyl acrylate is particularly preferable.

The compounding amount of the polymer compound P in the resin layer (Y) is 0.5 to 3% by weight, preferably 1 to 2% by weight. If the effect of improving the properties is insufficient, and if it exceeds 3% by weight, the delamination strength tends to decrease, which is not preferable.

Further, talc is added to the resin layer (X) in an amount of 0.01 to
By adding 0.5% by weight, preferably 0.05 to 0.3% by weight, the strength of the obtained multilayer stretched polyamide film can be improved. If the amount of talc to be blended is less than 0.01% by weight, the effect of improving strength is not exhibited,
Addition of more than 0.5% by weight is not preferred because not only the effect of improving strength is saturated but also the haze of the film is impaired.

The structure of the multilayer stretched polyamide film in the present invention needs to have at least a three-layer structure of X / Z / Y, but the structure of the layers can be appropriately combined depending on the application and purpose.

As a typical layer structure, for example, a five-layer structure such as Y / Z / X / Z / Y is used in view of the pinhole property, transparency, tensile strength, gas barrier property and the like of the obtained multilayer film. The above product is particularly suitable in terms of the balance of physical properties.

The multilayer stretched polyamide film of the present invention comprises:
Tensile strength 23 ~ 35kg / mm ² , Number of pinholes 3 or less, Hot water shrinkage 0.5 ~ 3.5%, Haze 6% or less, Oxygen permeability 6cc / atm / m ²・ day or less, Delamination strength 350
It preferably has physical properties of g / 15 mm or more. Note that the tensile strength and the hot water shrinkage are both average values in the machine direction (MD) of the film and in each direction (TD).

If the tensile strength is less than 23 kg / mm ^{2, the} strength of the packaging bag will be insufficient, and if it exceeds 35 kg / mm ² , not only will the quality be excessive, but rather the workability during film production will deteriorate, Not preferred. If the number of pinholes exceeds three, the strength of the packaging bag becomes insufficient, which is not preferable. If the hot water shrinkage rate exceeds 3.5%, problems such as curling in the process of manufacturing a packaging bag occur. It is not preferable because it lowers.

If the haze exceeds 6%, the commercial value of the packaging bag is reduced, which is not preferable, and the oxygen permeability is 6 cc / a.
If it is greater than tm / m ² · day, the protection of the contents as a packaging bag will be insufficient. In addition, the delamination strength is desirably larger than 350 g / 15 mm from the viewpoint of practical performance when used as a packaging bag. The tensile elongation is usually 80 to 130% (MD and T
(Average value of D).

As the method for producing the multilayer polyamide film in the present invention, any known method can be employed. That is, a method in which each resin constituting each layer is melted using a separate extruder, extruded from a die after being superimposed by a feed block method, and several types of molten resins are extruded after being superimposed in a multi-manifold die. A method, a method of laminating each resin layer by lamination, a method of combining these, and the like can be adopted.

Further, as a stretching method of the multilayer film,
Flat type sequential biaxial stretching method, flat type simultaneous biaxial stretching method, tubular method and the like can be used,
The flat simultaneous biaxial stretching method is most preferable in order to obtain the uniformity of the thickness of the multilayer film and the uniformity of the physical properties in the vertical and horizontal directions.

Next, a production method by the flat simultaneous biaxial stretching method will be described. For example, first, using a three-type, five-layer co-extrusion T-die, a composition comprising nylon 6 and modified polyethylene is used from an extruder (A), and a mixture of MXD6 and, if necessary, talc is used from an extruder (B). (C) The compositions consisting of nylon 6 and MXD6 were added in amounts of 230 to 28, respectively.
The multilayer unstretched sheet is extruded in a temperature range of 0 ° C., and is rapidly cooled by being closely adhered to a cooling drum whose temperature is adjusted to room temperature or lower.

Next, the obtained sheet is passed through a hot water bath whose temperature is controlled at 40 to 70 ° C., the moisture content is adjusted to 3 to 7% by weight, and then preheated at 140 to 210 ° C. ~
After being simultaneously biaxially stretched at a stretching ratio of 2 to 4 times at 220 ° C. at a stretching ratio of 2 to 4 times, and then subjected to a 1-5% relaxation treatment in the transverse direction, 150
Heat treatment is performed at a temperature of about 220 ° C. for several seconds to obtain a multilayer stretched film having a desired thickness.

[0027] If the temperature of the hot water bath is lower than 40 ° C, the impregnation time required for the unstretched multilayer sheet to have a constant moisture content becomes longer, and if it is higher than 70 ° C, the sheet is deformed during impregnation. Also, if the moisture content is lower than 3% or higher than 7%, the stretchability decreases. On the other hand, if the preheating temperature and the stretching temperature are out of the above-mentioned ranges, unevenness in stretching occurs and the film breaks during stretching, which is not preferable.

The larger the stretching ratio, the higher the strength of the film. However, from the viewpoint of stretching stability, it is preferably about 2 to 4 times in each of length and width. The stretching ratio in the longitudinal and transverse directions is preferably equal in view of the balance in the longitudinal and transverse directions such as tensile strength.However, in consideration of the shrinkage of the film in the transverse direction due to the relaxation treatment in the heat treatment process, the stretching ratio in the transverse direction is set to be vertical. Preferably, it is about 1 to 1.2 times the direction.

By setting the manufacturing conditions in the above range, it is possible to obtain a multi-layer stretched film having a difference in tensile strength and hot water shrinkage of 10% or less and 70% or less in the longitudinal direction and the transverse direction, respectively. The difference between the longitudinal direction and the transverse direction of the tensile strength and the hot water shrinkage is the value obtained by removing the absolute value of the difference between the physical values in the longitudinal direction and the lateral direction by the average value of the physical values in the longitudinal direction and the lateral direction. . If the difference between the tensile strength and the hot water shrinkage in the vertical and horizontal directions exceeds 10% and 70%, respectively, the bag may be deformed or broken when pressure or impact is applied to the packaging bag. Occurs.

When the multilayer stretched film of the present invention is used for a packaging bag, it is usually provided with a heat seal property. Further, in order to further increase the gas barrier property and mechanical strength depending on the use, polypropylene, polyethylene, or the like is used.
It is used by laminating with a plastic film such as an ethylene-vinyl acetate copolymer or polyester, paper, or a metal foil such as aluminum.

The thickness of the multilayer stretched film in the present invention is not particularly limited, but when it is used as a flexible packaging material, the thickness is 300 μm or less, usually 5 to 50 μm.

In order to improve the productivity of the film, usually, an inorganic lubricant such as silica, alumina, kaolin and calcium carbonate and an organic lubricant such as ethylenebisstearylamide are added to improve the slip property of the film surface.

Next, the present invention will be described more specifically with reference to examples. In addition, the raw materials and measuring methods used in the evaluation of Examples and Comparative Examples are as follows.

1. Raw materials (1) Nylon 6 (N6); Unitika A1030B
RF (2) MXD6; MX nylon 60 manufactured by Mitsubishi Gas Chemical Company
11 (relative viscosity 2.64) (3) Modified polyethylene (P
E); Lexpearl ET 183B manufactured by Nippon Polyolefin Co. Terpolymer of ethylene, n-methyl acrylate, maleic anhydride (4) Talc (TL); UPNHS-T0.5 manufactured by Hayashi Kasei

2. Measurement method (1) Tensile strength, elongation Measured according to ASTM-D882 using a sample having a width of 10 mm and a length of 10 cm. (2) Hot water shrinkage A sample having a width of 10 mm and a length of 10 cm was immersed in boiling water for 30 minutes, the dimensional change before and after the treatment was measured, and the rate of change relative to the original length was determined. (3) Haze Measurement was performed using a fully automatic haze meter (TC-H3DPK) manufactured by Tokyo Denshoku Co., Ltd. in accordance with JIS K-6714. Haze (%) = [Td (diffuse transmittance%) / (total light transmittance)] × 100 (4) Pinhole resistance MIL-B Me of Fed.Test Method Std.101c shown in 131F
According to thod 2017, a 12 inch x 8 inch sample is made into a cylindrical shape with a diameter of 3.5 inch, gripping both ends, the initial gripping interval is 7 inches, the gripping interval at the maximum bending is 1 inch, and the speed is 40 times / min. The number of pinholes generated after bending 1,000 times at 5 ° C. was counted using a so-called gel botester (manufactured by Rigaku Corporation). (5) Oxygen permeability Using OX-TRAN10-50A manufactured by Modern Control,
The measurement was performed under the conditions of ° C. and 65% RH. (Unit: cc / atm / m ²・
day) (6) Delamination strength After peeling off the edge of the multilayer film with a width of 15mm at the interface, 20
The peeling strength was measured at a peeling rate of 300 mm / min by a T-peel method using an autograph manufactured by Shimadzu Corporation in an atmosphere at 65 ° C and 65% RH. (7) Moisture content About 20 g of the unstretched multilayer sheet impregnated in a hot water bath is sampled in a weighing bottle and precisely weighed. Next, in a constant temperature dryer at 120 ± 2 ° C.,
After drying for an hour, the weight after cooling slowly to room temperature in a calcium chloride desiccator was precisely weighed, and the weight loss rate (%) was determined. (8) Hot water treatment resistance Unstretched polypropylene (Toray's Tolephan ZK-93K, 60 μm
), Heat seal in three directions and lengthen 14c
A rectangular filling bag measuring mx 12 cm wide was manufactured. Next, the bag is filled with 50 ml of water, and the remaining one is heat-sealed,
The appearance of the bag after the hot water treatment at 120 ° C. for 30 minutes was visually observed, and evaluated on a scale of A to C according to the following criteria. A: good B: only a small part (5% or less of the surface area of the filling bag) has poor appearance. C: Appearance defects are observed on the entire surface.

Example 1 MXD using an extruder (a) using a three-type, five-layer coextrusion die
6 was mixed with 0.2% by weight of talc at a temperature of 280.
At a temperature of 250 ° C. (Y layer) at a temperature of 250 ° C. (Y layer).
Layer) and a melt-mixed pellet of N6 and MXD6 from an extruder (C) at a temperature of 280 ° C. (Z layer), respectively, melt extruded, and extrude a sheet laminated in the order of Y / Z / X / Z / Y from a die. And quenched by closely contacting it on a cooling drum controlled to a surface temperature of 18 ° C., and the thickness of each layer is Y / Z / X / Z.
/ Y = 45/5/50/5/45 (μm) to obtain an unstretched sheet having a total thickness of 150 μm. 6
The mixture was sent to a hot water tank whose temperature was controlled at 0 ° C., and was subjected to a soaking treatment for 1.5 minutes to adjust the water content to 4.7%. The end of this sheet is gripped by clips of a tenter type simultaneous biaxial stretching machine,
After preheating at 5 ° C., the film was simultaneously biaxially stretched at a stretching temperature of 190 ° C., a stretching ratio of 3.0 times and a width of 3.3 times, and then the film was cooled and wound up.
Z / X / Z / Y = 4.5 / 0.5 / 5.0 / 0.5 /
A multilayer stretched film having a thickness of 15 μm and a thickness of 4.5 (μm) was obtained. Next, the obtained raw roll was slit, and the results of evaluating various film properties are shown in Table 1. As shown in Table 1, the pinhole resistance and the delamination strength were good, and the film had good suitability as a packaging film.

Examples 2 to 7 The same as Example 1 except that the mixing ratio of N6 and PE constituting the Y layer and the mixing ratio of N6 and MXD6 constituting the Z layer were changed as shown in Table 1. Table 1 shows the results of measuring the performance.

Comparative Examples 1-2 A multilayer stretched film was produced in the same manner as in Example 1 except that the mixing ratio of N6 and PE constituting the Y layer was changed as shown in Table 1, and the performance was measured. The results are shown in Table 1.

Comparative Examples 3 to 5 A multilayer stretched film was produced in the same manner as in Example 1 except that the compositions of the X layer and the Y layer were changed as shown in Table 1.
The results of measuring the performance are shown in Table 1.

[0040] ★

[Table 1]

[0041]

The multilayer stretched polyamide film of the present invention has excellent pinhole resistance, transparency, tensile strength, delamination strength, gas barrier properties, and dimensional stability, and can be processed when used for retorts. It is also excellent in nature and economy,
The industrial utility value is extremely high.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 77/06 C08L 77/06 // (C08L 77/00 23:08) B29K 23:00 77:00 B29L 7:00 F term (reference) 4F100 AC10A AK04B AK04D AK47A AK47C AK47E AK48B AK48C AK48D AK48E AK70B AK70D AL06B AL06D BA03 BA05 BA06 BA07 BA10A BA10C BA10E EH20 EH20C EH20E02A00 J02 Y02 J01 Y02 CL031 CL051 DJ046 GF00 GG02

Claims (5)

[Claims] 1. A xylylenediamine component having 4 to 4 carbon atoms.
A resin layer (X) of a polyamide (A) formed from an aliphatic dicarboxylic acid component and an aliphatic polyamide (B)
A resin layer (Z) comprising a mixture of polyamide (A) and polyamide (B) in the middle of a resin layer (Y) containing 0.5 to 3% by weight of the following polymer compound P; Multi-layer stretched polyamide film composed of layers. Polymer compound P: 95 to 50% by weight of ethylene, 0.1 to 10% by weight of an unsaturated dicarboxylic acid and / or a derivative thereof, and 4.9 to 40% by weight of an unsaturated carboxylic acid and / or a lower alkyl ester derivative thereof. Modified polyethylene. 2. The method according to claim 1, wherein the resin layer (Z) is made of polyamide (A) 50.
The multilayer stretched polyamide film according to claim 1, comprising from 80 to 80% by weight and from 50 to 20% by weight of the polyamide (B). 3. The resin layer (X) is coated with talc in an amount of 0.01 to 0.1.
3. The multilayer stretched polyamide film according to claim 1, which contains 5% by weight. 4. The method according to claim 1, wherein the multilayer stretched film is Y / Z / X / Z /
The multilayer stretched polyamide film according to any one of claims 1 to 3, comprising five layers of Y. 5. A xylylenediamine component having 4 to 4 carbon atoms.
A resin layer (X) of a polyamide (A) formed from an aliphatic dicarboxylic acid component and an aliphatic polyamide (B)
A resin layer (Z) comprising a mixture of polyamide (A) and polyamide (B) in the middle of a resin layer (Y) containing 0.5 to 3% by weight of the following polymer compound P; A method for producing a multilayer stretched polyamide film comprising layers, wherein a polyamide (A) and a polyamide (B) are co-extruded using a resin in which a polyamide (A) and a polyamide (B) are melt-kneaded in advance as a polyamide for forming the resin layer (Z). For producing a multilayer stretched polyamide film. Polymer compound P: 95 to 50% by weight of ethylene, 0.1 to 10% by weight of unsaturated dicarboxylic acid and / or derivative thereof, 4.9 of unsaturated carboxylic acid and / or lower alkyl ester derivative thereof
-40% by weight of a modified polyethylene.