JP2024050820A - Polyamide Film - Google Patents

Abstract

To provide a polyamide film having excellent pinhole resistance.SOLUTION: A polyamide film at least comprises a polyamide layer (B). The polyamide layer (B) comprises an aliphatic polyamide and a polyester elastomer. The total number of pinholes, as measured by a rotary drum test during the production of a packaging bag, is 10 or fewer in a 100 mm×100 mm sheet.SELECTED DRAWING: None

Description

The present invention relates to a polyamide film.

Films containing nylon resin are widely used in various fields as films with gas barrier properties, toughness, etc., and are particularly widely used for product packaging. This film is preferably used as a packaging film for food products distributed on the market. However, pinholes can occur during transportation and handling, and various improvements are being made from the perspective of protecting the contents.

The applicant has developed a polyamide-based film having at least a polyamide layer containing 86% to 98% by weight of polyamide and 2% to 14% by weight of a bending resistance agent (Patent Document 1). This polyamide-based film has excellent pinhole resistance due to bending and pinhole resistance due to repeated contact, and also exhibits excellent puncture resistance.

Japanese Patent No. 6573487 (JP 2017-2114 A)

The objective of the present invention is to provide a polyamide film with excellent pinhole resistance.

The inventors conducted extensive research to solve the above problems and discovered that a specific polyamide film can solve the above problems, which led to the completion of the present invention.

The present invention provides the following polyamide-based film:

Item 1.
A polyamide-based film,
The polyamide film includes at least a polyamide layer (B),
The polyamide layer (B) contains an aliphatic polyamide and a polyester-based elastomer,
A polyamide-based film having a total number of pinholes of 10 or less in a 100 mm x 100 mm sheet, as measured according to a rotating drum test when a packaging bag is made.

Item 2.
2. The polyamide film according to item 1, further comprising a polyamide layer (A) containing an aliphatic polyamide.

Item 3.
3. The polyamide film according to item 1 or 2, further comprising a barrier layer (C) containing an ethylene-vinyl alcohol copolymer or polymetaxylylene adipamide.

Item 4.
4. The polyamide film according to any one of items 1 to 3, further comprising a sealant layer (D).

Item 5.
A polyamide-based film,
The polyamide-based film includes at least a polyamide layer (A), a polyamide layer (B), a barrier layer (C), and a sealant layer (D),
The polyamide layer (A) contains an aliphatic polyamide,
The polyamide layer (B) contains an aliphatic polyamide and a polyester-based elastomer,
The barrier layer (C) is a polyamide film containing an ethylene-vinyl alcohol copolymer or polymetaxylylene adipamide.

The polyamide film of the present invention has excellent pinhole resistance.

1 is a diagram for explaining a method for performing a rotating drum test using the packaging bag of the present invention. FIG. 1 is a diagram illustrating a method for performing a rotating drum test using the packaging bag of the present invention. A rotating drum containing three cardboard cases is shown. FIG. 1 is a diagram illustrating a method for performing a rotating drum test using the packaging bag of the present invention. FIG. 2 is a diagram illustrating a method for producing a packaging bag using the polyamide film of the present invention.

The present invention will be described in detail below.

[1] Polyamide-based film The polyamide-based film of the present invention includes the following aspects.

The polyamide film of the present invention includes at least a polyamide layer (B), which contains an aliphatic polyamide and a polyester-based elastomer, and the total number of pinholes measured according to a rotating drum test when packaging bags (3 bags) are produced is 10 or less in a 100 mm x 100 mm sheet.

The polyamide film of the present invention preferably further comprises a polyamide layer (A) containing an aliphatic polyamide.

The polyamide film of the present invention preferably further comprises a barrier layer (C) containing ethylene-vinyl alcohol copolymer (EVOH) or polymetaxylylene adipamide (MXD-nylon).

The polyamide film of the present invention preferably further comprises a sealant layer (D).

The polyamide film of the present invention includes at least a polyamide layer (A), a polyamide layer (B), a barrier layer (C) and a sealant layer (D), the polyamide layer (A) contains an aliphatic polyamide, the polyamide layer (B) contains an aliphatic polyamide and a polyester-based elastomer, and the barrier layer (C) contains an ethylene-vinyl alcohol copolymer (EVOH) or polymetaxylylene adipamide (MXD-nylon).

When packaging bags are made using the polyamide film of the present invention, pinholes do not form in the packaging bags or the occurrence of pinholes is minimized, making it possible to reduce food waste.

The polyamide-based film of the present invention (film containing nylon resin) has excellent pinhole resistance. When the polyamide-based film of the present invention is used as a packaging bag for food, etc., even if the packaging bag repeatedly comes into contact with the cardboard during long-distance transportation by truck or the like at room temperature or low temperature after packaging in the cardboard, pinholes are not generated in the packaging bag or the generation of pinholes is suppressed to a minimum.

When a packaging bag is made using the polyamide film of the present invention, pinholes do not occur in the packaging bag or the occurrence of pinholes is minimized, so leakage of contents and odors is suppressed, acid deterioration of the contents due to oxygen inflow is suppressed, and spoilage due to bacterial intrusion is suppressed. This prevents the food contents of the packaging bag from being discarded, and does not lead to food loss or minimizes food loss.

The polyamide film of the present invention does not cause pinholes in packaging bags or minimizes the occurrence of pinholes, making it possible to reduce food waste.

In the present invention, "room temperature" refers to transporting or storing food, raw materials, etc. at a temperature of, for example, about 10°C to 35°C. In the present invention, "low temperature" refers to cooling, freezing, and storing food, raw materials, etc. at a temperature of, for example, less than 10°C.

(1) Polyamide layer (A)
The polyamide film of the present invention contains at least a polyamide layer (B) described below, and preferably further contains a polyamide layer (A) containing an aliphatic polyamide.

The polyamide layer (A) preferably contains an aliphatic polyamide.

The polyamide layer (A) preferably contains, as the polyamide, an aliphatic polyamide, an aromatic polyamide, etc. As the polyamide, it is more preferable to use an aliphatic polyamide in terms of being more excellent in pinhole resistance.

Aliphatic Polyamide The polyamide layer (A) preferably uses aliphatic nylon or a copolymer thereof as the aliphatic polyamide.

Specific examples of aliphatic polyamides that may be used include polycapramide (nylon-6), poly-ω-aminoheptanoic acid (nylon-7), poly-ω-aminononanoic acid (nylon-9), polyundecaneamide (nylon-11), polylauryl lactam (nylon-12), polyethylenediamineadipamide (nylon-2,6), polytetramethyleneadipamide (nylon-4,6), polyhexamethyleneadipamide (nylon-6,6), polyhexamethylenesebacamide (nylon-6,10), polyhexamethylenedodecamide (nylon-6,12), polyoctamethyleneadipamide (nylon-8,6), and polydecamethyleneadipamide (nylon-10,8).

Specific examples of aliphatic polyamides that may be used include caprolactam/lauryl lactam copolymer (nylon-6/12), caprolactam/ω-aminononanoic acid copolymer (nylon-6/9), caprolactam/hexamethylenediammonium adipate copolymer (nylon-6/6,6), lauryl lactam/hexamethylenediammonium adipate copolymer (nylon-12/6,6), ethylenediamine adipamide/hexamethylenediammonium adipate copolymer (nylon-2,6/6,6), caprolactam/hexamethylenediammonium adipate/hexamethylenediammonium sebacate copolymer (nylon-6,6/6,10), and ethyleneammonium adipate/hexamethylenediammonium adipate/hexamethylenediammonium sebacate copolymer (nylon-6/6,6/6,10).

These aliphatic polyamides may be used alone or in combination of two or more.

As the aliphatic polyamide, nylon-6, nylon-6,6, nylon-6/6,6 (copolymer of nylon 6 and nylon 6,6) are preferred, nylon-6, nylon-6/6,6 are more preferred, and nylon-6 is particularly preferred. As the two or more kinds of aliphatic polyamide, a combination of nylon-6 and nylon-6/6,6 is preferred. In the above combination, for example, the weight ratio of nylon-6:nylon-6/6,6 is preferably about 50:50 to 95:5.

Relative Viscosity of Polyamide In the polyamide-based film of the present invention, the aliphatic polyamide used preferably has a relative viscosity of 3.0 to 5.5, more preferably 3.2 to _4.2 , measured by a measurement method conforming to JIS K6920-2:2009 under the conditions of a sample concentration of 1.0 wt% in 96% _H2SO4 as a solvent and a temperature of 25°C.

The polyamide-based film of the present invention can further improve pinhole resistance by using a polyamide having the above relative viscosity as the polyamide.

When two or more polyamides are mixed together in the polyamide-based film of the present invention, the relative viscosity of the polyamide is determined by measuring the relative viscosity of each polyamide to be mixed, and taking the weighted average of the measured values.

In the polyamide-based film of the present invention, the relative viscosities of the aliphatic polyamides used in each layer may be the same or different.

The polyamide film of the present invention may contain polyamides other than aliphatic polyamides.

Aromatic Polyamide The polyamide may contain an aromatic polyamide in addition to an aliphatic polyamide.

Examples of aromatic polyamides include crystalline aromatic polyamides obtained by polycondensation reaction of aromatic diamines such as metaxylylenediamine and paraxylylenediamine with dicarboxylic acids or derivatives thereof such as adipic acid, suberic acid, sebacic acid, cyclohexanedicarboxylic acid, terephthalic acid, and isophthalic acid. Preferred aromatic polyamides are crystalline aromatic polyamides such as polymetaxylyleneadipamide (MXD-nylon). Specific examples of aromatic polyamides include S-6007 and S-6011 (both manufactured by Mitsubishi Gas Chemical Company, Inc.).

Examples of aromatic polyamides include amorphous aromatic polyamides (amorphous nylons) obtained by polycondensation reaction of aliphatic diamines such as hexamethylenediamine with dicarboxylic acids such as terephthalic acid and isophthalic acid or derivatives thereof. A preferred example of an aromatic polyamide is a copolymer of hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid. A specific example of the aromatic polyamide is Sealer PA (manufactured by DuPont-Mitsui Polychemicals Co., Ltd.).

Combinations of Polyamides Preferred combinations of aliphatic polyamides and aromatic polyamides include, for example, a combination of nylon-6 and MXD-nylon, a combination of nylon-6 and non-crystalline aromatic polyamide (amorphous nylon), and the like.

When aliphatic polyamide and aromatic polyamide are mixed as the polyamide, the content of aliphatic polyamide in the polyamide is preferably 80% by weight to 100% by weight, and more preferably 90% by weight to 100% by weight, assuming the amount of polyamide to be 100% by weight.

When the polyamide contains both an aliphatic polyamide and an aromatic polyamide, the content of the aromatic polyamide in the polyamide is preferably 0% to 20% by weight, and more preferably 0% to 10% by weight, assuming the amount of polyamide to be 100% by weight.

The polyamide-based film of the present invention can exhibit better stretch-film-forming properties when it contains an aliphatic polyamide and an aromatic polyamide as the polyamide.

(2) Polyamide layer (B)
The polyamide film of the present invention includes at least a polyamide layer (B), and the polyamide layer (B) contains an aliphatic polyamide and a polyester elastomer.

The polyamide layer (B) preferably contains 80% to 99.5% by weight of an aliphatic polyamide and 20% to 0.5% by weight of a polyester elastomer.

Polyamide The polyamide used in the polyamide layer (B) is preferably the same as that used in the polyamide layer (A).

The polyamide layer (B) contains aliphatic polyamides, aromatic polyamides, etc. as polyamides. It is preferable to use aliphatic polyamides as the polyamides, since they have superior pinhole resistance at room temperature and in low temperature environments.

The polyamide layer (B) preferably contains 80% to 99.5% by weight of aliphatic polyamide.

Polyester elastomer Polyester elastomer is a thermoplastic material having rubber-like elasticity. Polyester elastomer gives flexibility to polyamide film at room temperature and low temperature.

The polyamide layer (B) contains a polyester-based elastomer, preferably at 20% to 0.5% by weight.

As the polyester-based elastomer, a modified polyester-based elastomer is preferably used. In this specification, the term "polyester-based elastomer" includes modified polyester-based elastomers.

The modified polyester elastomer is a modified thermoplastic elastomer, and examples of modifications in the thermoplastic elastomer include modifications by copolymerization or graft modification, and modifications by the addition of polar groups. The addition of polar groups may be performed by graft modification. Examples of such polar groups include epoxy groups, carboxyl groups, acid anhydride groups, hydroxyl groups, amino groups, and oxo groups. Polar groups can be added by one type or by combining multiple types. Therefore, modified products to which polar groups have been added include, for example, epoxy modified products, carboxy modified products, acid anhydride modified products, hydroxy modified products, and amino modified products of thermoplastic elastomers.

Modified polyester elastomers are modified polyester elastomers, in which saturated polyester thermoplastic elastomers containing polyalkylene ether glycol segments are modified with unsaturated carboxylic acids or their derivatives.

Specifically, the polyester elastomer is a modified polyester elastomer obtained by modifying a saturated polyester thermoplastic elastomer having a polyalkylene ether glycol segment content of 58% by weight to 73% by weight with an unsaturated carboxylic acid or a derivative thereof in the presence of a radical generator. Reactive groups are introduced by the graft reaction and terminal addition reaction of the unsaturated carboxylic acid or a derivative thereof, improving the chemical bonding and hydrogen bonding properties with various resins.

The saturated polyester-based thermoplastic elastomer is a block copolymer consisting of soft segments containing polyalkylene ether glycol segments and hard segments containing polyester, and the content of polyalkylene ether glycol segments in the polyester-based elastomer is approximately 58% to 73% by weight.

Preferable examples of polyalkylene ether glycols constituting the soft segment include polyethylene glycol, poly(1,2 and 1,3-propylene ether) glycol, poly(tetramethylene ether) glycol, and poly(hexamethylene ether) glycol. The number average molecular weight of the polyalkylene ether glycol is preferably about 400 to 6,000.

Preferably, the unsaturated carboxylic acid or its derivative is, for example, an unsaturated carboxylic acid such as acrylic acid, maleic acid, or fumaric acid, an acid anhydride thereof, an ester thereof, or a metal salt thereof.

Preferably, the radical generator is, for example, a peroxide such as t-butyl hydroperoxide or cumene hydroperoxide, or an azo compound such as 2,2'-azobisisobutyronitrile (AIBN).

The blending ratio of each of the above components is preferably 0.01 to 30 parts by weight of the unsaturated carboxylic acid or its derivative and 0.001 to 3 parts by weight of the radical generator per 100 parts by weight of the saturated polyester thermoplastic elastomer.

The method for preparing the modified polyester elastomer is not particularly limited, but it can be prepared, for example, by the method described in JP-A-2002-155135. The melt flow rate (MFR) of the resulting modified polyester elastomer is preferably 40 g/10 min to 300 g/10 min.

Melt flow rate (MFR) is a value measured under conditions of 230°C and 2.16 kg using a measurement method conforming to JIS K7210.

As a commercially available polyester elastomer, specifically, TEFABLOC (manufactured by Mitsubishi Chemical Corporation) is preferably used.

The polyamide layer (B) may contain, in addition to the polyester-based elastomer (including modified polyester-based elastomer), a thermoplastic elastomer selected from the group consisting of polyamide-based elastomers, polyolefin-based elastomers, polystyrene-based elastomers, polyurethane-based elastomers, polyvinyl chloride-based elastomers, and ionomer polymers.

The polyamide layer (B) may be made of a single polyester elastomer, or may be made of a combination of two or more other thermoplastic elastomers.

Composition of Polyamide Layer (B) The polyamide layer (B) preferably contains 80% by weight to 99.5% by weight of aliphatic polyamide and 20% by weight to 0.5% by weight of polyester elastomer, with the weight of the entire polyamide layer (B) being 100% by weight.

The content of the aliphatic polyamide in the polyamide layer (B) is more preferably 85% to 99% by weight, and even more preferably 88% to 98% by weight, with the weight of the entire polyamide layer (B) being 100% by weight.

The content of the polyester-based elastomer in the polyamide layer (B) is more preferably 15% by weight to 1% by weight, and even more preferably 12% by weight to 2% by weight, with the weight of the entire polyamide layer (B) being 100% by weight.

The polyamide film of the present invention has excellent pinhole resistance at room temperature and in low temperature environments. By setting the content of the thermoplastic elastomer in the polyamide layer (B) within the above range, the pinhole resistance of the polyamide film at room temperature and in low temperature environments can be further improved.

(3) Barrier layer (C)
The polyamide film of the present invention includes at least a polyamide layer (B), and preferably further includes a barrier layer (C) containing an ethylene-vinyl alcohol copolymer or polymetaxylylene adipamide.

The polyamide-based film of the present invention can exhibit better gas barrier properties by having a barrier layer (C). When normal barrier properties are required, the polyamide-based film of the present invention can use the resin of the polyamide layer (B).

Ethylene-vinyl alcohol copolymer (EVOH)
The barrier layer (C) preferably uses an ethylene-vinyl alcohol copolymer.

The ethylene-vinyl alcohol copolymer preferably has an ethylene content of about 55 mol% or less, more preferably about 20 mol% to 50 mol%, and even more preferably about 25 mol% to 44 mol%.

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

The ethylene-vinyl alcohol copolymer may further contain, as necessary and preferably, a small amount of a comonomer such as an α-olefin such as propylene, isobutene, α-octene, α-dodecene, or α-octadecene; an unsaturated carboxylic acid or a derivative thereof (e.g., a salt, a partial alkyl ester, a complete alkyl ester, a nitrile, an amide, or an anhydride); or an unsaturated sulfonic acid or a salt thereof.

The melt index (MI) of the ethylene-vinyl alcohol copolymer is preferably 0.5 g/10 min to 50 g/10 min (210°C, 2,160 g load), and more preferably 1 g/10 min to 35 g/10 min (210°C, 2,160 g load).

The ethylene-vinyl alcohol copolymer can be melt-extruded well when its viscosity is preferably 0.5 g/10 min or more. The ethylene-vinyl alcohol copolymer has a MI of 50 g/10 min or less, which allows for good film-forming properties.

Commercially available ethylene-vinyl alcohol copolymers that can be preferably used include DC3203FB and DT2904RB (manufactured by Mitsubishi Chemical Corporation).

Polymetaxylylene adipamide (MXDNY)
The barrier layer (C) is preferably made of polymetaxylylene adipamide.

Aromatic nylons such as polymetaxylylene adipamide (MXD-nylon). Aromatic polyamides are crystalline aromatic polyamides obtained by polycondensation reaction of aromatic diamines such as metaxylylene diamine and paraxylylene diamine with dicarboxylic acids or derivatives thereof such as adipic acid, suberic acid, sebacic acid, cyclohexanedicarboxylic acid, terephthalic acid, and isophthalic acid. Examples of aromatic nylons that can be preferably used include S-6007 and S-6011 (manufactured by Mitsubishi Gas Chemical Co., Inc.).

Other Components The barrier layer (C) may contain other components such as modified ethylene vinyl acetate copolymer, methacrylic acid copolymer ionomer, etc., as necessary. When the thermoplastic resin layer (C) contains other components, the content of these other components is usually about 15 parts by weight or less, and preferably about 1.0 to 7.5 parts by weight, based on 100 parts by weight of the ethylene-vinyl alcohol copolymer or polymetaxylylene adipamide.

(4) Other Components of Each Layer Each layer may contain other additives as necessary, such as a lubricant, a nucleating agent, and an antioxidant.

(5) Layer Structure The polyamide film of the present invention contains at least a polyamide layer (B) (B layer), and preferably further contains a polyamide layer (A) (A layer) and a barrier layer (C) (C layer).

The polyamide film of the present invention is at least a single layer of layer B, and preferably has two layers of layer A/layer B, three layers of layer A/layer B/layer A, three layers of layer B/layer A/layer B, five layers of layer A/layer B/layer C/layer B/layer A, five layers of layer B/layer A/layer C/layer A/layer B, etc.

The polyamide film of the present invention more preferably includes layer A in addition to layer B, with each layer being symmetrical.

The polyamide film of the present invention exhibits excellent pinhole resistance at room temperature and in low temperature environments. The polyamide film of the present invention does not break even if the contents of the product are solidified (frozen) and the film is subjected to a strong impact during transportation of the product.

Thickness of Each Layer The total thickness of the polyamide film of the present invention is preferably about 10 μm to 50 μm, more preferably about 12 μm to 30 μm, further preferably about 13 μm to 25 μm, and particularly preferably about 15 μm.

In the polyamide film of the present invention, the polyamide layer (A) preferably has a thickness of about 6.15 μm to 8.85 μm, more preferably about 6.45 μm to 8.55 μm, even more preferably about 6.75 μm to 8.25 μm, and particularly preferably about 6.8 μm to 7 μm, in total when it is one layer or two or more layers.

In the polyamide film of the present invention, the polyamide layer (B) has a thickness of one layer or a total thickness of two or more layers, which is preferably about 3.75 μm to 8.55 μm, more preferably about 4.35 μm to 7.95 μm, even more preferably about 4.95 μm to 7.35 μm, and particularly preferably about 6.4 μm to 6.8 μm.

In the polyamide film of the present invention, the barrier layer (C) has a thickness of preferably about 0.3 μm to about 2.4 μm, more preferably about 0.6 μm to about 2.1 μm, even more preferably about 0.9 μm to about 1.8 μm, and particularly preferably about 1.4 μm to about 1.6 μm.

The polyamide film of the present invention can exhibit excellent pinhole resistance in a freezing environment when used for packaging frozen foods that are transported at low temperatures. The polyamide film of the present invention has excellent stretchability and the film rarely breaks due to stretching. The polyamide film of the present invention is suitable for packaging food, portioning, packaging food that contains moisture, etc., and can be suitably used for packaging frozen foods that are transported at low temperatures.

[2] Method for Producing Polyamide Film The method for producing the polyamide film of the present invention is not particularly limited, and preferably, a conventionally known method for forming a laminate can be adopted.

A manufacturing method is adopted in which the resin compositions of the layers of the polyamide-based film of the present invention are co-extruded from a T-die onto a chill roll through which cooling water circulates, for example, in an embodiment that includes at least a polyamide layer (B) (single layer), preferably including a polyamide layer (A) and a polyamide layer (B), and further including a barrier layer (C), for example, in the order of polyamide layer (A)/polyamide layer (B)/barrier layer (C)/polyamide layer (B)/polyamide layer (A), to prepare a flat multi-layer polyamide-based film.

The resulting polyamide film may be uniaxially or biaxially stretched (simultaneous biaxial stretching or sequential biaxial stretching). The stretching ratio is, for example, 2.5 to 4.5 times in the longitudinal direction (MD) and 2.5 to 5.0 times in the transverse direction (TD).

For example, in the case of sequential biaxial stretching, the film is stretched longitudinally 2.5 to 4.5 times using a roll stretching machine at 50°C to 80°C, then stretched transversely 2.5 to 5.0 times using a tenter stretching machine in an atmosphere of 80°C to 140°C, and then heat-treated using the same tenter in an atmosphere of 180°C to 220°C to obtain the film.

The polyamide film of the present invention may be uniaxially or biaxially stretched (simultaneous biaxial stretching or sequential biaxial stretching), and the resulting polyamide film may be subjected to a corona discharge treatment on both surfaces or on one surface, if necessary.

The polyamide film of the present invention contains a polyester elastomer and has excellent pinhole resistance, and is particularly effective in improving pinhole resistance in low temperature environments.

[3] Manufacturing method of packaging bag The polyamide film of the present invention is preferably processed into a bag to manufacture a packaging bag.

Sealant layer (D)
The polyamide film of the present invention contains at least a polyamide layer (B), preferably contains a polyamide layer (A) and a barrier layer (C), and further, as a preferred embodiment, has a sealant layer (D).

Another embodiment of the polyamide-based film of the present invention includes at least a polyamide layer (A), a polyamide layer (B), a barrier layer (C) and a sealant layer (D), in which the polyamide layer (A) contains an aliphatic polyamide, the polyamide layer (B) contains an aliphatic polyamide and a polyester-based elastomer, and the barrier layer (C) contains an ethylene-vinyl alcohol copolymer or polymetaxylylene adipamide.

The sealant of the sealant layer (D) is preferably a thermoplastic resin that exhibits sealing suitability. For example, the sealant is preferably a low-density, medium-density, high-density, linear low-density polyethylene, a propylene homopolymer, a propylene copolymer such as a propylene-ethylene copolymer, or a polypropylene. For example, the sealant is preferably an olefin-based sealant of a polyvinyl acetate resin, or an ethylene-vinyl alcohol copolymer (EVOH)-based sealant.

The thickness of the sealant layer (D) is preferably 10 μm to 200 μm.

To produce a packaging bag, a laminate film is preferably used in which a sealant layer is laminated on one side of a packaging film. The sealant layer is the part (sealant layer) that closes the bag using the packaging film of the present invention and the seal bar, and is the innermost layer of the bag, and is the layer on the opposite side to the seal bar via the resin layer (A).

The packaging film of the present invention is processed into a bag shape to produce a packaging bag.

The packaging bag can be formed by using an automatic filling and packaging machine or the like, using a laminate film in which a sealant layer (D) (sealant film) is laminated on one side of the polyamide film of the present invention.

Devices that process polyamide film into bags and automatically package food include, but are not limited to, horizontal pillow type packaging machines, vertical pillow type packaging machines, three-sided seal packaging machines, four-sided seal packaging machines, stick packaging machines, etc.

The present invention includes a method for suppressing the occurrence of pinholes using a film used in food packaging bags, which includes a step of packaging food using the polyamide film of the present invention, and is a method for suppressing the occurrence of pinholes in the packaging bag after freezing and thawing the packaged food. The method for suppressing the occurrence of pinholes in packaging bags of the present invention can effectively suppress the occurrence of pinholes in packaging bags for frozen foods that are transported at low temperatures.

The polyamide film of the present invention can also exhibit excellent pinhole resistance when used to package frozen foods that are transported at low temperatures. The polyamide film of the present invention is suitable for packaging heavy items, servings, and foods such as rice cakes and sausages, and can be used effectively to package frozen foods that are transported at low temperatures.

[4] Physical properties of polyamide films
Rotating Drum Test The polyamide-based film of the present invention contains at least a polyamide layer (B), and the total number of pinholes measured according to the rotating drum test when packaging bags (3 bags) were produced is 10 or less in a 100 mm x 100 mm sheet (polyamide-based film).

The rotating drum test is conducted on packaging bags (size: 100 mm x 100 mm) made of the polyamide film of the present invention, using a rotating drum testing machine with 50 g of polypropylene (PP) pellets as the contents, at a temperature of 23°C (normal temperature) and humidity of 50% RH, at a rotation speed of 9,000 revolutions (50 rpm x 180 minutes).

First, in the production of packaging bags (Figure 4), for example, a polyamide film is cut lengthwise in the MD direction. Next, the sample sheet is folded in half and both ends are heat sealed. Next, a specified amount of PP pellets is inserted through the opening, and the opening is heat sealed.

Next, to set it up in the rotating drum test machine, one sample packaging bag (containing PP pellets) is placed into one cardboard case (Figure 3). The lid of the cardboard case is then closed. Three such cases are made. Three of these cardboard cases are placed inside the rotating drum of the rotating drum test machine (n=3) (Figure 2).

A rotation test is performed (Figure 1) to measure the number of pinholes that occur in the polyamide film that makes up the packaging bag.

The polyamide film of the present invention has excellent pinhole resistance and is particularly useful for packaging frozen foods that are transported at low temperatures.

When the food to be packaged is a relatively sharp-edged item (food), the packaging bag must be able to prevent pinholes from forming due to the contents during transportation, handling, etc. In particular, when the contents are frozen foods, the packaging bag must have excellent pinhole resistance. When the food to be packaged is a frozen food that is liquid at room temperature, it may be heavy, and the packaging bag must have excellent pinhole resistance.

The polyamide film of the present invention is a film that has excellent pinhole resistance, for example, pinhole resistance at low temperatures, when used as a food packaging film, particularly for packaging products filled at low temperatures and products distributed at low temperatures. The polyamide film of the present invention is a film that shows excellent toughness and is less likely to develop pinholes when packaging food and transporting, carrying, etc., food not only under normal temperature environments but also under low temperature environments. Improvements in cooling technology have made it possible to freeze various foods, enabling the transportation of foods over long distances. The polyamide film of the present invention is useful when transporting food over long distances at low temperatures.

The present invention will be described in more detail below using examples and comparative examples.

The present invention is not limited to these examples.

(1) Raw material of polyamide-based film PA6: aliphatic polyamide, nylon 6 (NY6), relative viscosity 4.08, melting point 220°C
Modified polyester thermoplastic elastomer: melting point 145°C
Unmodified polyester thermoplastic elastomer: Melting point 163°C
EVOH: Ethylene-vinyl alcohol copolymer

(2) Production of polyamide film Using the above-mentioned raw materials, resin compositions for forming each polyamide layer were prepared according to the formulations shown in the table.

Polyamide layer (A): PA6
Polyamide layer (B):
PA6 + modified polyester-based thermoplastic elastomer PA6 + unmodified polyester-based thermoplastic elastomer Barrier layer (C): EVOH

The resin compositions constituting each polyamide layer were fed into an extruder at 250°C and co-extruded from a T-die at 250°C onto a chill roll through which cooling water was circulating, in the order of a single layer or A layer/B layer/C layer/B layer/A layer, to obtain a flat single-layer or five-layer polyamide film.

This film was stretched longitudinally 3.0 times using a roll stretching machine at 65°C, then stretched transversely 4.0 times using a tenter stretching machine in an atmosphere of 100°C, and further heat-treated in an atmosphere of 210°C using the same tenter to obtain a single-layer or five-layer polyamide-based film with a thickness of 15 μm.

(3) Manufacturing of packaging bags using polyamide-based films The polyamide film was cut to A4 size, coated with a mixture of ethyl acetate/fatty acid ester-based adhesive, and dried with a dryer. Next, a sealant film was attached using a hand roller, and dried again with a dryer. After that, it was aged (cured) at 40°C for 2 days or more.

The film was folded in half and both ends were heat sealed to produce a 100 mm x 100 mm packaging bag (Figure 4). 50 g of contents (polypropylene (PP) pellets) were stuffed into the bag, and the opening was heat sealed (Figure 4).

The following evaluations were carried out using packaging bags made from polyamide-based films.

(4) Evaluation of polyamide films
Pinhole resistance measurement method (rotating drum test)
Equipment used in rotating drum testing: Rotating drum testing machine (Figure 1)
The rotating drum tester is a regular hexagonal drum with a side length (C in FIG. 1) of 250 mm and a width (depth, B in FIG. 1) of 280 mm, made of metal (stainless steel). The diameter of the regular hexagonal drum (A in FIG. 1) is 435 mm. Three cardboard cases (FIG. 3) are set and the lids are placed (FIG. 2).

Rotation speed: 9,000 rpm (50 rpm x 180 min)
Ambient temperature: 23°C (normal temperature), 50% RH
Contents: Polypropylene (PP) pellets PP pellet model number: PC412A manufactured by SunAllomer Co., Ltd.
Packaging bag: A 100 mm x 100 mm packaging bag (made of polyamide film) is filled with 50 g of PP pellets as the contents (Figure 4).

Packaging format: The sample (packaging bag filled with contents) is packed in a cardboard case of 150 mm x 150 mm x 260 mm (cardboard case in Figure 3). One packaging bag is packed in the cardboard case.

Cardboard model number:
The inner liner is OFK-EM210 (material: K6) manufactured by Oji Materia Co., Ltd.
The core is HM120 (material: S120) manufactured by Marusan Paper Co., Ltd.
The outer liner is FMKS170 (material: K5) manufactured by Marusan Paper Co., Ltd.
Thickness of cardboard: A flute Three cardboard cases (cardboard cases containing one packaging bag) are set on a rotating drum testing machine (stainless steel drum) and the lids are closed (Figure 2).

The rotating drum test is carried out at the above rotation speeds (Figure 1).

After the rotating drum test, remove the cardboard case from the rotating drum test machine and remove the packaging bag filled with the contents (50 g of PP pellets) from the cardboard case.

The seal checker is used to check the number of pinholes in packaging bags (100mm x 100mm in size).

Measurement criteria for pinhole resistance Pinhole resistance: ○: The total number of pinholes measured in accordance with the rotating drum test for three packaging bags is 10 or less on the 100 mm × 100 mm sheet (front or back) that constitutes the packaging bag.

Pinhole resistance: The total number of pinholes measured in a rotating drum test on three packaging bags exceeds 10 on the 100 mm x 100 mm sheet (front or back) that makes up the packaging bag.

(5) Summary of Effects of the Polyamide Film of the Present Invention When the polyamide film of the present invention was used, the total number of pinholes in three bags in a 100 mm x 100 mm sheet (front or back) of the packaging bag was 10 or less, even after 9,000 rotations in a rotating drum test.

Packaging bags made using the polyamide-based film of the present invention can be evaluated as not generating pinholes during transportation. The polyamide-based film of the present invention can be evaluated as having excellent pinhole resistance, even when used for packaging frozen foods that are transported at low temperatures. The polyamide-based film of the present invention is suitable for packaging food, portioning, packaging foods that contain moisture, etc., and can be evaluated as being suitable for packaging frozen foods that are transported at low temperatures.

The polyamide-based film of the present invention (film containing nylon resin) has excellent pinhole resistance. When the polyamide-based film of the present invention is used as a packaging bag for food, etc., even if the packaging bag repeatedly comes into contact with the cardboard during long-distance transportation by truck or the like at room temperature or low temperature after packaging in the cardboard, pinholes are not generated in the packaging bag or the generation of pinholes is minimized.

When a packaging bag is made using the polyamide film of the present invention, pinholes do not occur in the packaging bag or the occurrence of pinholes is minimized, so leakage of contents and odors is suppressed, acid deterioration of the contents due to oxygen inflow is suppressed, and spoilage due to bacterial intrusion is suppressed. This prevents the food contents of the packaging bag from being discarded, and does not lead to food loss or minimizes food loss.

The polyamide film of the present invention does not cause pinholes in packaging bags or minimizes the occurrence of pinholes, making it possible to reduce food waste.

Claims (5)

A polyamide-based film,
The polyamide film includes at least a polyamide layer (B),
The polyamide layer (B) contains an aliphatic polyamide and a polyester-based elastomer,
A polyamide-based film having a total number of pinholes of 10 or less in a 100 mm x 100 mm sheet, as measured according to a rotating drum test when a packaging bag is made. The polyamide film according to claim 1, further comprising a polyamide layer (A) containing an aliphatic polyamide. The polyamide film according to claim 1 or 2, further comprising a barrier layer (C) containing an ethylene-vinyl alcohol copolymer or polymetaxylylene adipamide. The polyamide film according to any one of claims 1 to 3, further comprising a sealant layer (D). A polyamide-based film,
The polyamide-based film includes at least a polyamide layer (A), a polyamide layer (B), a barrier layer (C), and a sealant layer (D),
The polyamide layer (A) contains an aliphatic polyamide,
The polyamide layer (B) contains an aliphatic polyamide and a polyester-based elastomer,
The barrier layer (C) is a polyamide film containing an ethylene-vinyl alcohol copolymer or polymetaxylylene adipamide.