WO1998047704A1

WO1998047704A1 - Multilayer shrinkable polyamide film

Info

Publication number: WO1998047704A1
Application number: PCT/JP1998/001796
Authority: WO
Inventors: Hiroki Kuriu; Hidekazu Biwaki; Osamu Niwa
Original assignee: Gunze Limited
Priority date: 1997-04-21
Filing date: 1998-04-20
Publication date: 1998-10-29
Also published as: JPH10291286A; AU6854498A

Abstract

A heat-shrinkable, multilayer film possessing excellent pinhole resistance, transparency, and adhesion to a tray. Specifically, a heat-shrinkable, multilayer film comprising five layers of a polyamide layer, an EVOH layer, a polyamide layer, an adhesive resin layer, and a polyolefin layer, wherein the polyamide layer comprises 70 to 95 % by weight of nylon 6 and/or copolynylon 6-66 and 30 to 5 % by weight of noncrystalline nylon, the EVOH layer comprises a saponificate of an ethylene/vinyl acetate copolymer having an ethylene content of 20 to 65 % by mole, the polyolefin layer comprises a linear, low-density polyethylene (LLDPE) and/or a low-density polyethylene (LDPE), and the adhesive resin is a resin capable of bonding the polyamide layer to the polyolefin layer; and a process for preparing the same.

Description

Specification

Polyamide multilayer shrink film

Technical field

The present invention relates to a polyamide-based multilayer shrink film. The film of the present invention is applied to applications requiring gas barrier uniformity, such as shrink packs and lid materials for tray containers.

Background art

Conventionally, as a packaging film, a 5-layer structure of LLDPE adhesive resin EV0 adhesive resin LLDPE, which is made by sandwiching EVOH (genide of ethylene-vinyl acetate copolymer) with LLDPE (linear low-density polyethylene) Film is used. This film suffers from poor pinhole resistance and transparency.

As a solution to such a drawback, a multilayer film including a polyamide resin layer is known (JP-A-4-59244, JP-A-4-185322, US Pat. No. 5,562,996). This film has improved pinhole resistance and transparency, but has room for improvement in the adhesion to the tray.

An object of the present invention is to provide a heat-shrinkable multilayer film having excellent pinhole resistance, transparency, and adhesion to a tray.

Disclosure of the invention

The present invention relates to the following heat-shrinkable multilayer film.

Item 1. A heat-shrinkable multilayer film including five layers of a polyamide layer / EVOH layer / polyamide layer and an adhesive resin layer Z, wherein the polyamide layer is made of 6 nylon and / or 6-66 copoly nylon. The EVOH layer contains a saponified ethylene-vinyl acetate copolymer having an ethylene content of 20 to 65 mol%; the polyolefin layer contains a linear low-density 70 to 95% by weight and amorphous nylon 30 to 5% by weight. A heat-shrinkable multilayer film comprising polyethylene (LLDPE) and / or low-density polyethylene (LDPE); wherein the adhesive resin is a resin capable of bonding a polyamide layer and a polyolefin layer. -.

Item 2. If the EVOH layer is ethylene-vinyl acetate with ethylene content of 25-50 mol% Item 2. The heat-shrinkable multilayer film according to item 1, wherein the heat-shrinkable multilayer film comprises a polymer gent; the polyolefin layer comprises linear low density polyethylene (LL DPE); and the adhesive resin comprises LLDPE treated by a graft reaction.

Item 3. The heat-shrinkable multilayer film according to Item 1, wherein the polyamide layer is 1 to 15 m; the EVOH layer is 2 to 15 m; the adhesive resin layer is 1 to 5 / m; and the polyolefin layer is 2 to 40.

Item 4. The heat-shrinkable multilayer film according to Item 1 or 2, wherein the film has a heat shrinkage of 2 to 50% in the vertical direction and 2 to 50% in the horizontal direction when the film is treated with boiling water for 30 seconds. Item 5. The heat-shrinkable multilayer film according to items 1 to 4, wherein an antifogging agent is added.

Item 6. The heat-shrinkable multilayer film according to Item 1, wherein the two polyamide layers contain 70 to 95% by weight of 6-66 copolynylon and 30 to 5% by weight of amorphous nylon.

Item 7. Co-extrusion film formation in a flat shape using a T-die, followed by sequential biaxial stretching of about 1.2 to 5.0 times in the longitudinal direction and about 2.5 to 5.0 times in the horizontal direction. A method for producing a film including five layers, namely, a polyamide layer, a ZEVOH layer, a Z polyamide layer, a Z adhesive resin layer, and a polyolefin layer.

Clause 8. The method of clause 7, wherein the two polyamide layers comprise 70-95% by weight of 6-66 copolynairon and 30-5% by weight of amorphous nylon.

The heat-shrinkable multilayer film of the present invention is preferably a film having a five-layer structure of a polyamide layer, an EOH layer, a polyamide layer, an adhesive resin layer and a polyolefin layer, but a polyolefin layer, an adhesive resin layer, and a polyamide layer. Layer Polyamide layer Adhesive resin layer Polyolefin layer may be a seven-layer film.

The polyamide layer comprises 70-95% by weight, preferably 80-90% by weight, and 30-5% by weight, preferably 20-10% by weight, of nylon 6 and nylon 6-copolynylon. Including. 6-66 copolynylon is a copolymer of 6-nylon (poly-ε-force prolactam) and 66-nylon (polyhexamethylene adipamide). It is preferably at least 50%, more preferably at least 70 mol%. Nylon has a molecular weight (weight average molecular weight) of about 13,000-33,000. The two polyamide layers may be the same or different as long as they contain the above components. Polyamide layer thickness is l ~ 15m Degree, preferably about 3 to 11 ^ απι. Amorphous polyamides include copolymers or terpolymers of dicarboxylic acids such as terephthalic acid and isophthalic acid with diamines such as hexamethylenediamine.

The EVOH layer is a genoide of an ethylene-vinyl acetate copolymer, and the ethylene content is usually about 20 to 65 mol%, preferably about 25 to 50 mol%, more preferably about 25 to 45 mol%. is there. The degree of genification is about 90% or more, preferably about 95% or more. The thickness of the EVOH layer is about 2 to 15 m, preferably about 3 to 10 m.

The adhesive resin layer is not particularly limited as long as the EVOH layer and the polyolefin layer can be adhered, but is preferably LLDPE treated by a graft reaction. The thickness of the adhesive resin layer is about l to 5 m, preferably about 2 to 5 m. The polyolefin layer comprises a polyolefin, such as polyethylene or polypropylene, preferably linear low density polyethylene (LLDPE) and / or low density polyethylene (LDPE), especially LLDPE. The thickness of the polyolefin layer is about 2 to 40 m, preferably about 5 to 20 m.

The total thickness of the laminated film of the present invention is about 6 to 75 m, preferably about 20 to 40 m.

It is preferable to add an antifogging agent to the laminated film of the present invention. An anti-fog agent is preferably added to the polyolefin layer. Known antifogging agents are widely used, such as fatty acid esters of polyhydric alcohols, amines of higher fatty acids, amides of higher fatty acids, and ethylene oxide in amine amides of higher fatty acids. An added anti-fogging agent may be mentioned.

The polyamide-based multilayer shrinkable film of the present invention is preferably a flat film. This film may be co-extruded in a flat shape from a T-die and sequentially biaxially stretched. The film formation is not particularly limited, but can be generally performed by extrusion casting on a cooled chill roll. The film of the present invention is obtained by successively biaxially stretching the film thus formed. The stretching is carried out, for example, by longitudinal stretching using a roll stretching machine and transverse stretching using a tenter stretching machine.

The stretching ratio is preferably about 1.2 to 5 times in the vertical direction and about 2.5 to 5 times in the horizontal direction. Degrees. The stretching temperature is about 60 to 120 ° C in the longitudinal direction, preferably about 70 to 100 ° C, and about 70 to 100 in the horizontal direction; about L80 ° C, preferably about 100 ° C. It is about 160 ° C.

After stretching, heat treatment is performed as necessary, but when high heat shrinkability is required, heat treatment may not be performed. The heat treatment method is not particularly limited, but is generally performed in a continuous process following the transverse stretching using a tenter stretching machine. When heat treatment is performed, the force can be reduced (relaxed) within 20%, preferably 3 to 10% in the width direction. Of course, the width may be set to be the same as the width in the horizontal stretching. The width may be set to be equal to or greater than the width at the time of stretching. The heat treatment conditions are, for example, less than 150 ° C., preferably about 80 to 130 ° C. by a tenter stretching machine, and if necessary, within about 20% in the width direction, preferably 3 to It can be performed with the size reduced to about 10%. The heat treatment is performed for the purpose of preventing natural shrinkage.

Applications of the multilayer film according to the present invention include meat, processed meat, retort foods, water foods, microwave oven products, food packaging materials such as frozen foods, and other various packaging materials. Etc. can also be processed.

Examples of the packaging form include overwrap packaging, sleeve packaging, and the like.The packaging may be made into a bag by heat sealing, and is not particularly limited. Can be used as a packaging material simply by cutting it to a predetermined size.

The above has been a description of preferred embodiments of the present invention, and the present invention is not limited to the description and can take any embodiments.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples.

Example 1

Using the following raw materials, a five-layer laminated film was manufactured.

(1) Raw materials:

• Polyamide layer = 6-66 copoly nylon (80% by weight) and amorphous nylon (20% by weight)

• EVOH layer = ethylene content (32 mol%) and vinyl acetate content (68 mol%) Of ethylene-vinyl acetate copolymer consisting of: (Genification degree = 99% or more) • Polyamide layer = 6-66 copoly nylon (80% by weight) and amorphous nylon (20% by weight)

• Adhesive resin layer-based on LLDPE, grafted to introduce functional groups

'Polyolefin layer = LLDPE (100%)

The polyolefin layer was mixed with an anti-fogging agent at 5000 ppm.

When the above-described five-layer laminated film was continuously operated for eight hours under the condition of 60 m per minute, the number of breaks was zero.

(2) Test method

• Pinhole test I (Torsion bending test): A film formed into a cylindrical shape with a folding diameter of 150i and a length of 300 mm was mounted on a gelbo flex tester (manufactured by RIKEN KOGYO CO., LTD.), And a twist angle of 440 ° was used. Repeat the bending linear motion of Ocm 1000 times at 25 ° C and 5 ° C each, and check the number of pinholes using the permeate. The measurement is performed at a position of 300 cm ^{2 at} the center of the sample.

• Pinhole test II (Rotating drum test): After wrapping the square cake in a film so that it fits, place the ten cakes in a hexagonal pillar-shaped drum that rotates 50 times a minute for 20 minutes. After rotating for 30 minutes, or after 30 minutes, count the number of samples that generate pinhole force.

• Average thickness: At regular intervals, measure the thickness using a pointer micrometer (Gugami Co., Ltd.) and average the measured values.

• Haze: Measure according to ASTM D-1003.

• Tensile strength: Measure according to JIS K-6732.

• Tensile elongation: Measure according to JIS K-6732.

• Lubricity: Measure static friction Z dynamic friction according to ASTM D-1894.

'Thermal shrinkage: 60 ° C, 70 ° C, 80 ° C, 90 ° C ヽ 3 in hot water at each temperature of 100 ° C

Measure the shrinkage when immersed for 0 seconds.

• Natural shrinkage: Leave at 40 ° C and 0% RH for 7 days and measure the shrinkage. • Seal strength: The heat-sealing surface of the film and the heat-sealing surface Seals at temperature (150, 160, 170 ° C), pressure (2kg / cm ² ), and time (1 second) at Toyo Seiki Seisakusho. The obtained sample is put into a 1 cm-wide strip and pulled with a strograph (Toyo Seiki Seisaku-sho, Ltd.) to measure the stress until breaking.

• Oxygen permeability: Measure according to ASTM D-3985.

(3) Production of film

The components of the respective layers were co-extruded in a flat shape from a T-die and extruded on a chill roll to obtain a flat film. The obtained film was successively biaxially stretched (3.0 times in the longitudinal direction, 3.4 times in the transverse direction) and heat-treated at 100 ° C for 20 minutes to obtain a film of the present invention. The obtained film had a polyimide layer ZEVOH layer Z polyamide layer adhesive resin layer polyolefin layer = 5-3 / 5-2 / 10 Om.

Table 1 shows the physical property values of the obtained film.

The film was subjected to pinhole tests I and II. Table 2 shows the results.

Example 2

(1) Raw materials:

• Polyamide layer = 6-nylon (80% by weight) and amorphous nylon (20% by weight) • EVOH layer = ethylene-vinyl acetate consisting of ethylene content (32 mol%) and vinyl acetate content (68 mol%) Genized polymer (Genification degree = 99% or more) • Polyamide layer = 6-66 copoly nylon (80% by weight) and amorphous nylon (20% by weight)

• Adhesive resin layer = LLDPE based, grafted and functional groups introduced

• Polyolefin layer LLDPE (100%)

The polyolefin layer was mixed with an anti-fogging agent at 5000 ppm.

When the above-described five-layer laminated film was continuously operated for eight hours under the condition of 60 m per minute, the number of breaks was three.

The shrinkage (heat shrinkage) when immersed in 100 ° C warm water for 30 seconds is It was 20.3% in the MD direction and 29.6% in the D0 direction.

Comparative Example 1

LLD PE layer Z adhesive resin layer ZE V 0 H layer Z adhesive resin layer No. LLDPE layer = 1 2/3/2/11 m Five-layer film (brand name: Ecorap; manufacturer Okura Industries Co., Ltd.) Manufactured in the same manner as 1.

Test example 1

Physical properties of the films obtained in Example 1 and Comparative Example 1 were measured. Table 1 shows the results. In addition, the above films were subjected to pinhole tests I and II. The results are shown in Tables 1 and 2.

table 1

1: ccm 24 h20 ° CX 65% H

Table 2

Comparative Example 2

Polyamide ZEVOHZ Polyamide 3-layer laminated film (HEP TAX; manufactured by Gunze Co., Ltd.) is used as a seal layer. A polyolefin layer composed of LL DP E is used as a seal layer. Bonding was performed with the above-mentioned adhesive resin introduced to obtain a laminated film having a five-layer structure. The resulting film had a polyamide layer ZEVOH layer Z polyamide layer adhesive layer polyolefin layer = 63 Z 6/15/30 m.

Test example 2

A tray (125Mix200mni) is wrapped with the film obtained in Example 1 and Comparative Example 2 having a folded diameter of 155 and a length of 240πιιη, and the wrapped tray is passed through a tunnel at 120 ° C for 10 seconds to shrink the film. Then, the packaging condition was observed and evaluated.

In the laminated film obtained in Example 1, the film adhered to the tray, and no excess film was formed in the square of the tray. In addition, the film was fitted on the tray, and the film on the top of the tray was in a stretched state.

On the other hand, the five-layer film obtained in Comparative Example 2 adhered tightly to the tray. No film was left, especially in the square of the tray.

As described above, the film of the present invention has good shrink properties, and a packaged product in which the film is in close contact can be easily obtained.

Comparing the results of Example 1 and Example 2, it was found that the stretchability was improved by using two polyamide layers of 6-66 nylon. In the film of Example 1, the number of breaks during continuous operation for 8 hours was 0, the heat shrinkage was larger than that of the film of Example 2, and the adhesion to the tray was excellent. Therefore, as the crystalline polyamide component, 6-66 copolynylon is preferable to 6-nylon.

Claims

The scope of the claims

1. Polyamide layer ZE V 0 H layer Nopolyamide layer Adhesive resin layer A heat-shrinkable multilayer film containing five layers of polyolefin layers, where the polyamide layer is made of 6 nylon and Z or 6-66 copoly nylon 70 ~ 95% by weight and 30 to 5% by weight of amorphous nylon; E VOH layer contains genoates of ethylene monoacetate copolymer having an ethylene content of 20 to 65% by mole; Polyolefin layer contains linear low density polyethylene

(LLDPE) and / or low-density polyethylene (LDPE); a heat-shrinkable multilayer film in which the adhesive resin is a resin capable of bonding a polyamide layer and a polyolefin layer.

2. The E VOH layer contains an ethylene-vinyl acetate copolymer genide with an ethylene content of 25-50 mol%; the polyolefin layer contains linear low-density polyethylene (LLD).

The heat-shrinkable multilayer film according to claim 1, wherein the adhesive resin comprises LLDPE treated by a graft reaction.

3. The heat shrinkability according to claim 1, wherein the polyamide layer is 1 to 15 m; the EVOH layer is 2 to 15 m; the adhesive resin layer is 1 to 5 m; and the polyolefin layer is 2 to 40 m. Multilayer film.

4. The heat-shrinkable multilayer film according to claim 1, wherein the heat-shrinkage ratio when the film is treated with boiling water for 30 seconds is 2 to 50% in a vertical direction and 2 to 50% in a horizontal direction.

5. The heat-shrinkable multilayer film according to claim 1, further comprising an antifogging agent.

6. The heat-shrinkable multilayer film according to claim 1, wherein the two polyamide layers comprise 70-95% by weight of 6-66 copolynylon and 30-5% by weight of amorphous nylon.

7. Co-extrusion film is formed flat by T-die and then biaxially stretched about 1.2 to 5.0 times in the longitudinal direction and about 2.5 to 5.0 times in the horizontal direction. A method for producing a film that includes five layers: a polyimide layer, a ZEVOH layer, a polyamide layer, and an adhesive resin layer.

8. The method of claim 6, wherein the two polyamide layers comprise 70-95% by weight of 6-66 copolynylon and 30-5% by weight of amorphous nylon.