JP6851918B2 - Polyamide-based multilayer film - Google Patents

Description

The present invention relates to a polyamide-based multilayer film.

A multilayer film containing a nylon resin layer is tough and is widely used for packaging foods and the like. The food packaging film is also required to have pinhole resistance, that is, gas barrier property, so that pinholes do not occur during transportation, transportation, and the like.

The applicant has already developed a polyamide-based multilayer film having excellent pinhole resistance, which has softness to withstand bending and hardness to withstand abrasion due to repeated contact (Patent Document 1). This polyamide-based multilayer film has a structure in which a characteristic polyamide layer (A), a polyamide layer (B), and a barrier layer (C) are laminated in the order of A / B / C / B / A and the like. This polyamide-based multilayer film is excellent in processing suitability with little elongation of the film due to tension or heat during printing or laminating. This polyamide-based multilayer film is also excellent in stretchability, piercing strength, and impact strength, and is suitable for packaging heavy objects, especially foods such as rice cakes and wieners.

When used for food packaging, it is often used by printing on this polyamide-based multilayer film or by further laminating a polyolefin-based film or the like.

However, in the printing process and the laminating process, tension is applied to the film and further heat is applied, so that the film is stretched, causing misalignment and distortion in the printed pattern, and misalignment with the laminated film. During the bag making process, the design on the front surface and the design on the back surface of the bag sometimes deviated from each other.

The applicant has developed a polyamide-based multilayer film having extremely low elongation with respect to tension and heat in response to such defects (Patent Document 2).

Currently, food packaging films have good cutability for the purpose of improving the openability of bag-making products in addition to the above-mentioned toughness and gas barrier properties and dimensional stability against heat and tension. Is also required.

Japanese Patent Application Laid-Open No. 2008-188774 JP 2011-161682

An object of the present invention is to provide a polyamide-based multilayer film having improved cutability in order to improve the openability of a bag-making product.

As a result of diligent research to solve the above problems, the present inventor has made the polyamide-based multilayer film tough by being composed of a layer containing a specific polyamide and a layer containing an ethylene-vinyl alcohol copolymer. It was found that the cut property is also good in addition to the property and gas barrier property.

Based on this finding, further research has been carried out to complete the present invention.

The present invention provides the following polyamide-based multilayer film and a method for producing the same.

Item 1.
Polyamide-based multilayer film
(A) A layer containing 80-95% by weight of nylon-6 and 20-5% by weight of amorphous aromatic polyamide.
(B) A layer containing 80-95% by weight of nylon-6 and 20-5% by weight of crystalline aromatic polyamide, and (C) an ethylene-vinyl alcohol copolymer having an ethylene content of 20-35 mol%. Including the containing layer,
Stacked in the order of A / B / C / B / A,
A polyamide-based multilayer film characterized by this.

Item 2.
The polyamide according to claim 1, wherein the amorphous aromatic polyamide contained in the layer (A) is an amorphous aromatic polyamide obtained by a polycondensation reaction between an aliphatic diamine and a dicarboxylic acid or a derivative thereof. System multilayer film.

Item 3.
The polyamide-based multilayer film according to claim 1 or 2, wherein the amorphous aromatic polyamide contained in the layer (A) is a copolymer of hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid.

Item 4.
One of claims 1 to 3, wherein the crystalline aromatic polyamide contained in the layer (B) is a crystalline aromatic polyamide obtained by a polycondensation reaction between an aromatic diamine and a dicarboxylic acid or a derivative thereof. The polyamide-based multilayer film described.

Item 5.
The polyamide-based multilayer film according to any one of claims 1 to 4, wherein the crystalline aromatic polyamide contained in the layer (B) is polymethoxylylene adipamide.

The polyamide-based multilayer film of the present invention has good cutability in addition to toughness and gas barrier properties.

When the polyamide-based multilayer film of the present invention is used for a food packaging film, it is possible to produce a food packaging bag having good cutability in addition to toughness and gas barrier properties and better opening property of the bag-making product. it can.

The present invention relates to a polyamide-based multilayer film.

(1) Polyamide-based multilayer film The polyamide-based multilayer film of the present invention is
(A) A layer containing 80-95% by weight of nylon-6 and 20-5% by weight of amorphous aromatic polyamide.
(B) A layer containing 80-95% by weight of nylon-6 and 20-5% by weight of crystalline aromatic polyamide, and (C) an ethylene-vinyl alcohol copolymer having an ethylene content of 20-35 mol%. Including the containing layer,
It is characterized in that it is laminated in the order of A / B / C / B / A.

(A) The layer containing 80 to 95% by weight of nylon-6 and 20 to 5% by weight of amorphous aromatic polyamide exhibits pinhole resistance such as abrasion resistance, bending resistance, and puncture resistance. It is a layer (polyamide layer) that improves the laminate strength.

(B) The layer containing 80 to 95% by weight of nylon-6 and 20 to 5% by weight of crystalline aromatic polyamide exhibits pinhole resistance such as abrasion resistance, bending resistance, and puncture resistance, and is rigid. It is a layer (polyamide layer) that exhibits heat resistance and suppression of dry heat shrinkage.

(C) The layer containing the ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 35 mol% is a layer (barrier layer) exhibiting oxygen barrier properties and rigidity.

The polyamide-based multilayer film of the present invention has two layers (B) (polyamide layer) having pinhole resistance and the like on both sides of the oxygen barrier (C) layer and pinhole resistance and the like. It is sandwiched between two layers (A) (polyamide layer) and has a laminated structure of at least five layers.

When the polyamide-based multilayer film of the present invention is used for packaging, it is preferable to have an adhesive layer and a sealing layer on one surface.

The polyamide-based multilayer film of the present invention has good cutability in addition to toughness and gas barrier properties. The polyamide-based multilayer film of the present invention also has an advantage that it is excellent in processing suitability because the film does not stretch easily due to tension or heat.

(1-1) (A) layer (polyamide layer)
The layer (A) of the polyamide-based multilayer film of the present invention is a layer containing 80 to 95% by weight of nylon-6 and 20 to 5% by weight of amorphous aromatic polyamide.

The amorphous aromatic polyamide contained in the layer (A) is preferably an amorphous aromatic polyamide obtained by a polycondensation reaction between an aliphatic diamine and a dicarboxylic acid or a derivative thereof. The amorphous aromatic polyamide is preferably a copolymer of hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid. The layer (A) contains 80 to 95% by weight of nylon-6 (polycapramide). , Preferably containing 84-92% by weight, more preferably 86-90% by weight. When the layer (A) contains nylon-6, the polyamide-based multilayer film is provided with pinhole resistance such as abrasion resistance, bending resistance, and puncture resistance.

The layer (A) contains 20-5% by weight of amorphous aromatic polyamide, preferably 16-8% by weight, more preferably 14-10% by weight. Since the layer (A) contains an amorphous aromatic polyamide, when the polyamide-based multilayer film is used for packaging, the lamination strength with the adhesive layer and the sealing layer can be improved.

The amorphous aromatic polyamide (amorphous nylon) is an amorphous aromatic polyamide obtained by a polycondensation reaction between an aliphatic diamine such as hexamethylenediamine and a dicarboxylic acid such as terephthalic acid or isophthalic acid or a derivative thereof. Is preferable.

As the amorphous aromatic polyamide, preferred ones are a polymer of hexamethylenediamine-isophthalic acid, a polymer of hexamethylenediamine-terephthalic acid, a copolymer of hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid and the like. Is. For example, Sealer PA (copolymer of hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid) manufactured by Mitsui-DuPont Polychemical Co., Ltd. can be exemplified.

An anti-blocking agent can be appropriately added to the layer (A) for the purpose of forming microscopic irregularities on the film surface and imparting an anti-blocking effect. By appropriately blending an anti-blocking agent in the layer (A), processability such as film runnability is improved.

The layer (A) exhibits pinhole resistance such as wear resistance, bending resistance, and puncture resistance in a polyamide-based multilayer film, and improves the lamination strength.

(1-2) (B) layer (polyamide layer)
The layer (B) of the polyamide-based multilayer film of the present invention is a layer containing nylon-6 and a crystalline aromatic polyamide.

The layer (B) is preferably a layer containing 80 to 95% by weight of nylon-6 and 20 to 5% by weight of crystalline aromatic polyamide.

The crystalline aromatic polyamide contained in the layer (B) is preferably a crystalline aromatic polyamide obtained by a polycondensation reaction between an aromatic diamine and a dicarboxylic acid or a derivative thereof. The crystalline aromatic polyamide is preferably polymethoxylylen adipamide.

The layer (B) contains nylon-6 (polycoupled) in an amount of preferably 80 to 95% by weight, more preferably 82 to 93% by weight, still more preferably 84 to 91% by weight. When the layer (B) contains nylon-6, the polyamide-based multilayer film is provided with pinhole resistance such as bending resistance and puncture resistance.

The layer (B) contains preferably 20 to 5% by weight of crystalline aromatic polyamide, more preferably 18 to 7% by weight, and even more preferably 16 to 9% by weight. By including the crystalline aromatic polyamide in the layer (B), the polyamide-based multilayer film is imparted with rigidity, heat resistance, dry heat shrinkage resistance, and the like.

As the crystalline aromatic polyamide, polycondensation of aromatic diamines such as metaxylene diamine and paraxylene diamine with dicarboxylic acids such as adipic acid, suberic acid, sebacic acid, cyclohexanedicarboxylic acid, terephthalic acid and isophthalic acid or derivatives thereof. It is preferably a crystalline aromatic polyamide obtained by the reaction. Specifically, it is a xylylenediamine-based polyamide.

As the crystalline aromatic polyamide, a polyamide composed of metaxylylenediamine and adipic acid, that is, polymethaxylene adipamide or the like is preferable. For example, S-6007 and S-6011 (MX nylon) manufactured by Mitsubishi Gas Chemical Company, Inc. can be used.

The layer (B) exhibits rigidity, heat resistance, and dry heat shrinkage suppression in a polyamide-based multilayer film.

(1-3) (C) layer (barrier layer)
The (C) layer of the polyamide-based multilayer film of the present invention is a layer containing an ethylene-vinyl alcohol copolymer having an ethylene content of 20 to 35 mol%. The layer (C) imparts oxygen barrier properties and rigidity to the polyamide-based multilayer film.

Since the layer (C) is composed of an ethylene-vinyl alcohol copolymer (EVOH), a layer having low gas permeability such as oxygen, nitrogen, and carbon dioxide is provided on the polyamide-based multilayer film, that is, a gas barrier property is provided. Give.

The ethylene content of the ethylene-vinyl alcohol copolymer is 20 to 35 mol%, preferably 22 to 28 mol%, and more preferably 24-26 mol%.

The degree of saponification of the vinyl acetate component of the ethylene-vinyl alcohol copolymer is preferably 90 mol% or more, more preferably 95 mol% or more.

The melt indexer (MFR) (210 ° C., 2160 g) of the ethylene-vinyl alcohol copolymer is preferably 1 to 35 g / 10 min, more preferably 2 to 10 g / 10 min.

For example, V2504RB manufactured by Nippon Synthetic Chemistry Co., Ltd. can be used.

The layer (C) is a layer (barrier layer) that exhibits an oxygen barrier property.

(1-4) Layer Structure The polyamide-based multilayer film of the present invention comprises the above-mentioned (A) layer, (B) layer, and (C) layer laminated in the order of A / B / C / B / A. ..

The composition and blending amount of the two (A) layer (polyamide layer) and the two (B) layer (polyamide layer) may be the same or different, respectively, but from the viewpoint of simplicity in manufacturing a multilayer film, curl, and the like. , Preferably the same.

The total thickness of the polyamide-based multilayer film of the present invention is preferably 12 to 20 μm. The total thickness of the polyamide-based multilayer film is more preferably 14 to 18 μm, still more preferably 15 to 17 μm.

The thickness of the layer (A) is, for example, the total of the two layers, preferably 4 to 13 μm, more preferably 5 to 12 μm, and even more preferably 6 to 11 μm.

The thickness of the layer (B) is, for example, the total of the two layers, preferably 3 to 10 μm, more preferably 4 to 9 μm, and further preferably 5 to 8 μm.

The thickness of the layer (C) is, for example, one layer, preferably 0.5 to 3 μm, more preferably 1.0 to 2.5 μm, and further preferably 1.5 to 2.0 μm.

(2) Method for Manufacturing Polyamide-based Multilayer Film The polyamide-based multilayer film of the present invention is
(1) The resin composition for the (A) layer, the resin composition for the (B) layer, and the resin composition for the (C) layer are laminated by coextrusion in the order of A / B / C / B / A. Process,
By a manufacturing method including (2) a step of stretching the laminate obtained in the step (1) in two vertical and horizontal axes, and (3) a step of heat-treating the stretch obtained in the step (2).
It is preferably manufactured.

Process (1)
The (A) layer resin composition, the (B) layer resin composition, and the (C) layer resin composition can be laminated by coextrusion in the order of A / B / C / B / A. preferable. For example, it can be co-extruded from a T-die onto a chill roll in which cooling water circulates to obtain a flat multilayer film.

Process (2)
It is preferable to stretch the laminate obtained in the step (1) in two vertical and horizontal axes. The obtained stone structure (film) may be uniaxially stretched or biaxially stretched (simultaneous biaxial stretching, sequential biaxial stretching).

The stretching ratio is preferably, for example, a longitudinal stretching (MD) of 2.5 to 4.5 times and a transverse stretching (TD) of 2.5 to 5 times.

For example, in the case of sequential biaxial stretching, it is preferable to vertically stretch 2.5 to 4.5 times with a roll stretching machine at 50 to 80 ° C. and laterally stretch 2.5 to 5 times with a tenter stretching machine in an atmosphere of 80 to 140 ° C.

Process (3)
It is preferable to heat-treat the stretched product obtained in the step (2). Following the step (2), it is preferable to obtain by heat treatment with the same tenter in an atmosphere of 180 to 220 ° C.

The polyamide-based multilayer film of the present invention may be uniaxially stretched or biaxially stretched (simultaneously biaxially stretched, sequentially biaxially stretched), and if necessary, both surfaces or one surface thereof may be subjected to corona discharge treatment.

(3) Usage of Polyamide-based Multilayer Film The polyamide-based multilayer film of the present invention has good cutability in addition to toughness and gas barrier properties. The polyamide-based multilayer film of the present invention also has an advantage that it is excellent in processing suitability because the film does not stretch easily due to tension or heat.

The polyamide-based multilayer film of the present invention is preferably used as a base material for a packaging bag. The packaging bag is preferably for food packaging.

The polyamide-based multilayer film of the present invention is excellent in cutability when opening a bag, in addition to toughness and gas barrier properties.

When the polyamide-based multilayer film of the present invention is used for a food packaging film, it is possible to produce a food packaging having good cutability in addition to toughness and gas barrier properties, and opening of a bag-making product is better.

The polyamide-based multilayer film of the present invention is suitable for packaging foods that are easily affected by oxygen such as rice cakes and wieners. The polyamide-based multilayer film of the present invention is also suitable for packaging frozen foods transported at a low temperature. Since the polyamide-based multilayer film of the present invention has high transparency, the contents (food) can be easily visually observed when it is used as a food package.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

(1) Raw materials for polyamide-based multilayer films The raw materials for polyamide-based multilayer films are shown (Table 1).

(2) Production of Polyamide-based Multilayer Film The polyamide-based multilayer film was adjusted at the ratios shown in Tables 2 and 3.

The resin composition for the (A) layer, the resin composition for the (B) layer, and the resin composition for the (C) layer are put into an extruder having a barrel temperature of 180 to 260 ° C., respectively, and A / B / C / B. It was extruded from a multilayer die at 250 ° C. in the order of / A and cooled and solidified with a chill roll at 20 to 40 ° C. to obtain a flat 5-layer film.

Next, the obtained 5-layer film was stretched 2.8 times in the longitudinal direction (MD direction) with a roll stretcher at 50 to 60 ° C., and then laterally (TD direction) with a tenter stretcher at an ambient temperature of 110 ° C. It was stretched 4.0 times and further heat-treated in the same tenter in an atmosphere of 210 ° C. to obtain a 5-layer stretched film.

Layer A contains a silica-based anti-blocking agent.

(3) Evaluation of polyamide-based multilayer film
(A) Tear propagation strength
Preparation of measurement sample The obtained 5-layer stretched film was cut into a rectangle with a long side of 63.5 ± 0.5 mm along the film TD direction and a short side of 50 mm in the direction perpendicular to the film TD direction to prepare a measurement sample.

Next, a notch with a length of 12.7 ± 0.5 mm was made in the center of the short side of the measurement sample (25 mm from the end of the test piece) in parallel with the long side.

Measuring method As the measuring device, a light load tear tester D type manufactured by Toyo Seiki Seisakusho was used.

For each Example and Comparative Example, a total of 5 measurements were performed and the average value of each was calculated.

Evaluation Criteria When the average measurement value was 100 mN or less, it was evaluated as ◯ (good), and when it exceeded 100 mN, it was evaluated as × (defective).

(B) Laminate strength
Preparation of measurement sample Corona treatment was applied to one surface of the obtained 5-layer stretched film so that the wetting tension was 56 mN / m, and the film surface was coated with a sealant film (MC-S manufactured by Mitsui Chemicals Tohcello Corporation, thickness: 30 μm ) And the extrusion laminating process to prepare a laminated film. The thickness of the extruded laminate layer was 20 μm.

Next, the inner surfaces of the two films cut to a length of 7 cm in the MD direction and a length of 20 cm in the TD direction of the laminated film were subjected to a thermal tilt tester HG-100-2 manufactured by Toyo Seiki Seisakusho Co., Ltd. Heat fusion was performed under the conditions of sealing temperature: 150 ° C., pressure: 0.26 MPa, and pressurization time: 1 second. A measurement sample was prepared by cutting it into strips so that the heat-sealed portion had a width of 10 mm.

Measuring method As the measuring device, Strograph VE1D manufactured by Toyo Seiki Seisakusho Co., Ltd. was used.

The measurement sample cut into strips was pulled in the direction of the film MD, and the stress when the heat-sealed portion was peeled off was measured.

For each Example and Comparative Example, a total of 5 measurements were performed and the average value of each was calculated.

Evaluation Criteria When the average measurement value was 33 N / cm or more, it was evaluated as ◯ (good), and when it was less than 33 N / cm, it was evaluated as × (bad).

(C) Flex resistance
Preparation of measurement sample The obtained 5-layer stretched film was cut into a sample of about 35 cm in the MD direction and about 36 cm in the TD direction.

Next, the inner surface and the inner surface of the film were aligned, a measurement pattern was sandwiched inside, the film was bent and sealed in the MD direction with a sealing machine, and an excess portion was cut along the sealed portion to prepare a measurement sample.

Measuring method As the measuring device, a gelboflex tester BE-1006 with a constant temperature bath manufactured by Tester Sangyo was used.

The measurement sample was bent 1000 times. Then, a 10 cm marked line was placed in the center of the sample, one of the marked lines was sealed with a sealer, and then the number of pinholes generated was counted using a seal checker.

For each Example and Comparative Example, a total of 3 measurements were performed and the average value of each was calculated.

Evaluation Criteria When the average measurement value was less than 21, it was evaluated as ◯ (good), and when it was 21 or more, it was evaluated as × (defective).

(4) Evaluation Results of Polyamide-based Multilayer Films The results of each evaluation are shown in Tables 4 and 5.

The polyamide-based multilayer film of the present invention (Examples 1 to 8) is a layer containing (A) 80 to 95% by weight of nylon-6 and 20 to 5% by weight of amorphous aromatic polyamide, and (B) nylon-6. Contains a layer containing 80-95% by weight and 20-5% by weight of crystalline aromatic polyamide, and (C) a layer containing an ethylene-vinyl alcohol copolymer having an ethylene content of 20-35 mol%. The cuttability is good because the layers are laminated in the order of / B / C / B / A.

Further, the polyamide-based multilayer film of the present invention has high lamination strength.

When the polyamide-based multilayer film of the present invention is used as a food packaging film, it is possible to produce a food packaging bag having good cutability in addition to toughness and gas barrier properties and less peeling of the laminate.

Claims (5)

Polyamide-based multilayer film
(A) A layer containing 80-95% by weight of nylon-6 and 20-5% by weight of amorphous aromatic polyamide.
(B) A layer containing 80-95% by weight of nylon-6 and 20-5% by weight of crystalline aromatic polyamide, and (C) an ethylene-vinyl alcohol copolymer having an ethylene content of 20-35 mol%. Including the containing layer,
Stacked in the order of A / B / C / B / A,
A polyamide-based multilayer film characterized by this. The polyamide according to claim 1, wherein the amorphous aromatic polyamide contained in the layer (A) is an amorphous aromatic polyamide obtained by a polycondensation reaction between an aliphatic diamine and a dicarboxylic acid or a derivative thereof. System multilayer film. The polyamide-based multilayer film according to claim 1 or 2, wherein the amorphous aromatic polyamide contained in the layer (A) is a copolymer of hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid. One of claims 1 to 3, wherein the crystalline aromatic polyamide contained in the layer (B) is a crystalline aromatic polyamide obtained by a polycondensation reaction between an aromatic diamine and a dicarboxylic acid or a derivative thereof. The polyamide-based multilayer film described. The polyamide-based multilayer film according to any one of claims 1 to 4, wherein the crystalline aromatic polyamide contained in the layer (B) is polymethoxylylene adipamide.