JP2023178296A - Easily adhesive polyamide film - Google Patents

Abstract

To provide an easily adhesive polyamide film which is excellent in impact resistance, bending pinhole resistance, and friction pinhole resistance, has a reduced amount of deteriorated matter attached to a die slip outlet during production, also has reduced thickness spots, and is excellent in water-resistant adhesive strength to a sealant film.SOLUTION: An easily adhesive polyamide film has an adhesive modified layer (C layer) composed of any one resin of a polyester resin, a polyurethane resin and/or a polyacrylic resin as solid contents in a coating amount of 0.01-3 g/m2, on at least one surface of a laminated and stretched polyamide film formed by stacking surface layers (B layers) composed of a polyamide resin composition containing 99-100 mass% of a polyamide 6 resin as a polyamide-based resin and less than 1 mass% of a polyamide-based elastomer on both surfaces of a base material layer (A layer) composed of a polyamide resin composition containing a mixed resin of 97.5-80 mass% of a polyamide 6 resin and 2.5-20 mass% of a polyamide-based elastomer.SELECTED DRAWING: Figure 1

Description

The present invention relates to a laminated biaxially oriented polyamide film that has excellent impact resistance, bending pinhole resistance, and friction pinhole resistance, has little thickness unevenness, and has excellent water-resistant adhesive strength with a sealant film. The easily adhesive polyamide film of the present invention is suitably used for food packaging films and the like.

Conventionally, biaxially stretched films made of aliphatic polyamides such as nylon 6 have excellent impact resistance and pinhole resistance, and have been widely used as various packaging material films.

In addition, in order to further improve pinhole resistance and impact resistance for liquid filling packaging such as soups and seasonings, various elastomers (rubber components) are mixed with aliphatic polyamide to make it more flexible and pinhole resistant. Biaxially oriented polyamide films with improved properties are widely used.

As a means for improving the above-mentioned pinhole resistance, a film in which a polyamide elastomer is mixed with an aliphatic polyamide is known (see, for example, Patent Document 1). This film has good pinhole resistance and impact resistance in low-temperature environments, and pinholes due to bending fatigue are less likely to occur even in low-temperature environments.

However, pinholes are caused not only by bending but also by friction. Methods for improving pinholes caused by bending and pinholes caused by friction are often contradictory. For example, if the flexibility of the film is increased, bending pinholes are less likely to occur, but as the film becomes softer, pinholes due to friction tend to occur more easily. On the other hand, a packaging laminate has been proposed that has excellent bending resistance and friction pinhole resistance by providing a surface coating agent on the outer surface of a biaxially stretched polyamide film (for example, see Patent Document 2). However, this method is less effective in preventing the occurrence of friction pinholes. Additionally, a coating process is required.
Furthermore, in the case of a film made of aliphatic polyamide mixed with a polyamide elastomer, the polyamide elastomer added during film production deteriorates due to heat, which tends to produce a degraded product called grout at the lip exit of the die. It has also been found that the deteriorated substances cause deterioration in the accuracy of film thickness. In addition, the deteriorated products themselves fall down, resulting in defective products, which poses a problem of lowering production efficiency during continuous film production.

Furthermore, when a film obtained by laminating a polyamide film with a sealant film is used for a liquid soup bag or a water bag, the adhesive strength between the laminated films (also referred to as lamination strength) is required to be sufficiently high.

1695602633227_01695602633227_1 1695602633227_21695602633227_3

An object of the present invention is to provide an easily adhesive polyamide film that has excellent impact resistance, bending pinhole resistance, and friction pinhole resistance, and also has excellent water-resistant adhesive strength with a sealant film. Another object of the present invention is to provide an easily adhesive polyamide film which has less generation of lint (degraded material produced at the exit of the die lip) during film production, has excellent operability, and has less unevenness in film thickness.

That is, the present invention consists of the following configuration.
(1) Both sides of the base material layer (layer A) made of a polyamide resin composition containing a mixed resin of 97.5 to 80% by mass of polyamide 6 resin and 2.5 to 20% by mass of polyamide elastomer are coated with polyamide. A surface layer (layer B) made of a polyamide resin composition containing 100 to 80% by mass of 6 resin, less than 1% by mass of polyamide elastomer, and 0 to 20% by mass of polyamide resin other than polyamide 6 and polyamide elastomer is laminated. An adhesion-modifying layer (layer C) made of any one of polyester resin, polyurethane resin, and/or polyacrylic resin with a coating amount of 0.01 to 3 g/m ² as solid content on at least one side of the laminated stretched polyamide film. An easily adhesive polyamide film characterized by having.
(2) Impact strength is 0.75 J/15 μm or more, the number of Gelbo pinhole defects is 5 or less when the twisting and bending test using a Gelbo Flex Tester is performed 1000 times at a temperature of 1°C, and the friction pinhole test The easily adhesive polyamide film according to (1), wherein the distance to the occurrence of a pinhole is 3000 cm or more.
(3) The easily adhesive polyamide film according to (1) or (2), wherein the thickness of the B layer is at least 0.5 μm or more.
(4) Easy adhesion according to any one of (1) to (3), characterized in that the polyamide resin composition constituting layer B contains 0.01 to 0.3% by mass of an antioxidant. polyamide film.

The easily adhesive polyamide film of the present invention has impact resistance, puncture resistance, and pinhole resistance by dispersing polyamide elastomer into polyamide 6 resin, with polyamide 6 resin as the main component as the base layer (layer A). Make it manifest. Provides excellent bending pinhole resistance, especially in low-temperature environments. Then, a surface layer (layer B) made of a polyamide resin composition containing 100 to 80% by mass or more of polyamide 6 resin, less than 1% of polyamide elastomer, and 0 to 20% by mass of polyamide resin other than polyamide 6 and polyamide elastomer, By improving the friction pinhole resistance and preventing the polyamide elastomer from coming into contact with the die surface inside the die, it prevents deterioration from adhering to the inner surface of the die and dirt from attaching to the exit of the die slip over a long period of time. suppress. Thereby, deterioration of film thickness unevenness can be prevented. Furthermore, if thickness unevenness worsens due to deterioration matter adhering to the inner surface of the die or greasy residue adhering to the die slip outlet, production must be stopped and the die lip must be cleaned. The easily adhesive polyamide film of the present invention can enable continuous production over a long period of time. Further, at least one side of the laminated stretched polyamide film consisting of the base layer (A layer) and the surface layer (B layer) is coated with a polyester resin, a polyurethane resin, and/or a polyester resin with a coating amount of 0.01 to 3 g/m ² as solid content. By laminating an adhesion-modifying layer (C layer) made of one of the acrylic resins, when a film laminated with a sealant film is used for liquid soup bags or water bags, the adhesive strength between the laminated films can be improved. (Also referred to as lamination strength), it is possible to provide packaging bags that are less likely to tear.

Schematic diagram of friction pinhole resistance evaluation device

1: Head of the fastness tester 2: Cardboard board 3: Mount for holding the sample 4: Film sample folded in four 5: Rubbing amplitude direction

Hereinafter, the easily adhesive polyamide film of the present invention will be explained in detail.
The easily adhesive polyamide film of the present invention is a laminate in which a surface layer (B layer) made of a specific polyamide resin composition is laminated on both sides of a base layer (A layer) made of a specific polyamide resin composition. An adhesion modifying layer (C layer) is laminated on at least one side of the stretched polyamide film.

<Base material layer (A layer)>
The base material layer (layer A) in the present invention is a polyamide resin composition containing 97.5 to 80% by mass of polyamide 6 resin and 2.5 to 20% by mass of polyamide elastomer.
The base material layer (A layer) in the present invention contains 2.5 to 20% by mass of polyamide elastomer, so it has a structure in which polyamide elastomer as a pinhole-resistant material is dispersed, and has excellent bending pinhole resistance. In particular, a laminated and stretched polyamide film having good bending pinhole resistance in a low-temperature environment can be obtained.
The base material layer (A layer) in the present invention has a polyamide 6 resin content of 97.5 to 80% by mass, so that a laminated and stretched polyamide film with good mechanical strength such as impact strength can be obtained. .

The polyamide elastomer used for the base layer (layer A) in the present invention includes a polyamide block copolymer consisting of a hard segment composed of a polyamide component and a soft segment composed of a polyoxyalkylene glycol component. . The polyamide component of the hard segment is selected from the group consisting of (1) a lactam, (2) an aminoaliphatic carboxylic acid, (3) an aliphatic diamine and an aliphatic dicarboxylic acid, or (4) an aliphatic diamine and an aromatic dicarboxylic acid. be done. Specifically, (1) ω-lauryllactam, ε-caprolactam, (2) aminoheptanoic acid, (3) hexamethylenediamine, nonanediamine and adipic acid, sebacic acid, (4) hexamethylenediamine, nonanediamine and terephthalic acid. , isophthalic acid. Further, examples of the polyoxyalkylene glycol constituting the soft segment of the polyamide block copolymer include polyoxytetramethylene glycol, polyoxyethylene glycol, polyoxy-1,2-propylene glycol, and the like. In particular, a polyamide elastomer in which the hard segment is polyamide 6 or polyamide 12 and the soft segment is polyoxytetramethylene glycol is preferred because it has a high effect of improving bending pinhole resistance.

The melting point of the polyamide elastomer in the present invention is determined by the type and ratio of the hard segment composed of the polyamide component and the soft segment composed of the polyoxyalkylene glycol component, but is usually in the range of 120°C to 180°C. things are used.

In the present invention, by using a polyamide elastomer as a constituent component of the base layer of the laminated stretched polyamide film, the bending pinhole resistance of the laminated stretched polyamide film, particularly the bending pinhole resistance in a low temperature environment, can be improved.
The lower limit of the content of the polyamide elastomer in the polyamide resin composition of the base layer is 2.5% by mass. As a result, a laminated and stretched polyamide film having good bending pinhole resistance can be obtained.
The upper limit of the content of the polyamide elastomer in the polyamide resin composition of the base layer is 20% by mass. As a result, a laminated and stretched polyamide film having good bending pinhole resistance while maintaining other mechanical properties and transparency can be obtained.

The polyamide resin composition constituting layer A in the present invention may optionally contain other thermoplastic resins, such as polyester polymers such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, polyethylene, A polyolefin polymer such as polypropylene may be contained within a range that does not impair its properties.

The polyamide resin composition constituting layer A preferably contains 0.01 to 0.3% by mass of an antioxidant. If the antioxidant content exceeds the above range, whitening may occur due to precipitation on the surface of the laminated stretched polyamide film, and poor adhesion during lamination with polyethylene or polypropylene sealant may occur. When using recovered recycled raw materials such as scrap materials and recycled resin as the polyamide resin composition, poor film-forming operability may occur due to thermal deterioration of the recovered recycled raw materials.

As the antioxidant, phenolic antioxidants are preferred. The phenolic antioxidant is preferably a fully hindered phenolic compound or a partially hindered phenolic compound. For example, tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane, stearyl-β-(3,5-di-t-butyl-4-hydroxy phenyl)propionate, 3,9-bis[1,1-dimethyl-2-[β-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl]2,4,8,10- Examples include tetraoxaspiro[5,5]undecane.

By incorporating the above-mentioned phenolic antioxidant into the polyamide resin composition of layer A, the film forming operability of the laminated and stretched polyamide film is improved. In particular, in systems that mix recovered and recycled raw materials using film scraps, recycled resin, etc., thermal deterioration is likely to occur due to the recovery and recycling of thermoplastic elastomers, which can lead to poor film production operations, resulting in decreased operational efficiency. Due to the increase in production costs and the decrease in the amount of recovered and recycled raw materials used, the amount of virgin raw materials used tends to increase, leading to an increase in production costs. In contrast, by incorporating an antioxidant into the polyamide resin composition of layer A of a polyamide stretched film containing recovered recycled raw materials, thermal deterioration of various polymers including thermoplastic elastomers can be suppressed. , achieving stable film forming operability. Therefore, according to the present invention, it is possible to reduce production costs by improving operability and reducing raw material costs by increasing the amount of recovered and recycled raw materials used.

The polyamide resin composition constituting Layer A is a mixture of virgin raw material polyamide 6 and polyamide elastomer, as well as non-standard films and cut ends (edge trim) produced during the production of laminated stretched polyamide films. It is also possible to add virgin raw materials as recycled resin.

<Surface layer (B layer)>
The surface layer (B layer) in the present invention consists of 100 to 80% by mass of polyamide 6 resin, less than 1% by mass of polyamide elastomer, and 0 to 20% by mass of polyamide resin other than polyamide 6 resin and polyamide elastomer. By keeping the content of polyamide-based elastomer, which is the main cause of resin deterioration, in layer B to less than 1% by mass, it is possible to suppress resin deterioration inside the die during film production, and prevent deterioration from entering the die inner surface. It is possible to suppress adhesion and adhesion of eye grime to the die exit. Thereby, deterioration of film thickness unevenness can be prevented. Moreover, long-term continuous production can be made possible.
Further, by controlling the content of the polyamide elastomer to less than 1% by mass, the friction pinhole resistance can be improved, and the pinhole generation distance in the friction test can be increased to 3000 cm or more.

The surface layer (layer B) in the present invention has a structure in which it is laminated on both sides of the base material layer, but each side may have a different resin composition as long as it satisfies the above composition. .
For example, within the range that satisfies the above composition, one side of layer A is laminated with a polyamide resin composition containing fine particles and fatty acid amide to improve slipperiness, and the other side contains a copolymerized polyamide resin. This allows a polyamide resin composition with improved adhesiveness to be laminated.

As the polyamide 6 resin constituting the B layer in the present invention, the same polyamide 6 resin as the above-described polyamide 6 resin of the A layer can be used.
The polyamide elastomer constituting layer B in the present invention is a polyamide elastomer consisting of a hard segment composed of a polyamide component and a soft segment composed of a polyoxyalkylene glycol component, similar to that used for the above-mentioned layer A. It is a block copolymer. Most preferably, layer B does not contain a polyamide elastomer.

The polyamide resin composition of layer B in the present invention may contain polyamide resins other than polyamide 6 and polyamide elastomer in an amount not exceeding 20% by mass. Examples of polyamide resins other than polyamide 6 and polyamide elastomers include polyamide 11 resin, polyamide 12 resin, polyamide 66 resin, polyamide 6/12 copolymer resin, polyamide 6/66 copolymer resin, and polyamide MXD6 resin.

The polyamide resin composition constituting layer B in the present invention may include other thermoplastic resins as necessary, such as polyester polymers such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene-2,6-naphthalate, polyethylene, A polyolefin polymer such as polypropylene may be contained within a range that does not impair its properties.

The polyamide resin composition constituting the A layer and B layer of the laminated stretched polyamide film of the present invention preferably contains fine particles in order to improve slipperiness and make it easier to handle.
The fine particles can be appropriately selected from among inorganic lubricants such as silica, kaolin, and zeolite, and polymeric organic lubricants such as acrylic and polystyrene. Note that from the viewpoint of transparency and slipperiness, it is preferable to use silica fine particles.

The average particle diameter of the fine particles is preferably 0.5 to 5.0 μm, more preferably 1.0 to 3.0 μm. If the average particle diameter is less than 0.5 μm, a large amount is required to obtain good slipperiness, and if it exceeds 5.0 μm, the surface roughness of the film becomes too large to meet practical properties. So I don't like it.

The pore volume range of the fine particles is preferably 0.5 to 2.0 ml/g, more preferably 0.8 to 1.6 ml/g. When the pore volume is less than 0.5 ml/g, voids are likely to occur and the transparency of the film deteriorates, and when the pore volume exceeds 2.0 ml/g, it becomes difficult to form protrusions on the surface due to fine particles. This is not preferable because the film becomes less slippery.

The polyamide resin composition constituting layer A and layer B of the laminated stretched polyamide film of the present invention can contain fatty acid amide and/or fatty acid bisamide for the purpose of improving slipperiness. Examples of fatty acid amide and/or fatty acid bisamide include erucic acid amide, stearic acid amide, ethylene bis stearic acid amide, ethylene bis behenic acid amide, and ethylene bis oleic acid amide.

In this case, the content of fatty acid amide and/or fatty acid bisamide in the polyamide polymer is preferably 0.01 to 0.40% by mass, more preferably 0.05 to 0.30% by mass. If the content of fatty acid amide and/or fatty acid bisamide is less than the above range, slipperiness will be poor, resulting in poor processing suitability for printing, laminating, etc.; if it exceeds the above range, it will bleed onto the film surface over time, causing surface damage. It may cause spots, which is unfavorable in terms of quality.

When the laminated and stretched polyamide film of the present invention is processed into a packaging material (bag-made product), it often has a laminated structure in which the B layer side is the outermost surface of the bag-made product. When friction occurs with transport packaging, such as friction, the film may be scraped and the bag may break, or the bags may pierce when they come into contact with each other, increasing bending fatigue and causing the bag to break. In the configuration of the present invention, by improving the slipperiness of layer B, the factors of bag breakage due to friction are reduced, and high bag breakage prevention properties are achieved.

Various additives such as antistatic agents, antifogging agents, ultraviolet absorbers, dyes, and pigments may be added to the polyamide resin compositions constituting layers A and B of the laminated stretched polyamide film of the present invention, as necessary. It can be contained in one or both of the A layer and/or the B layer.

The addition method can be carried out by a known method such as adding it during resin polymerization or adding it during melt extrusion with an extruder to form a masterbatch, and adding this masterbatch to a polyamide polymer during film production. Can be done.

There are no particular restrictions on the method of mixing the various polyamide resins, polyamide elastomers, lubricants, etc. that make up the A and B layers, but there is a method in which chip-shaped polymers are mixed using a blender or the like, then melted and molded. is used.

The total thickness of the laminated stretched polyamide film in the present invention is not particularly limited, but when used as a packaging material, it is usually 100 μm or less, generally 5 to 50 μm thick, particularly 8 to 50 μm thick. A thickness of 30 μm is used.

Regarding the thickness structure of each layer of the laminated stretched polyamide film in the present invention, when the thickness of layer B occupies most of the total thickness of the film, the bending pinhole resistance decreases. On the other hand, when the thickness of layer A almost occupies the total thickness of the film, the bending pinhole resistance is excellent, but the friction pinhole resistance is poor, and deterioration of thickness unevenness cannot be suppressed. Therefore, in the present invention, the thickness of layer A is preferably 70 to 93%, particularly 80 to 93%, of the total thickness of layer A and layer B. Furthermore, by setting the thickness of the B layer to at least 0.5 μm or more, preferably 1 μm or more, it is possible to achieve both bending pinhole resistance, friction pinhole resistance, and suppression of thickness unevenness.

The laminated stretched polyamide film in the present invention preferably has an impact strength of 0.75 J/15 μm or more. A more preferable impact strength is 1.0 J/15 μm or more. Further, it is preferable that the laminated stretched polyamide film of the present invention has 10 or less Gelbo pinhole defects when subjected to a twist-bending test using a Gelbo flex tester 1000 times at a temperature of 1°C. More preferably, the number is 5 or less. Further, it is preferable that the laminated stretched polyamide film in the present invention has a distance to pinhole occurrence of 2900 cm or more in a friction pinhole resistance test. The length is more preferably 3000 cm or more, and even more preferably 3100 cm or more. The laminated and stretched polyamide film of the present invention preferably satisfies these properties at the same time. Stretched polyamide films with these properties are useful as packaging films that are less likely to generate pinholes during transportation.
<Adhesion modification layer (C layer)>
The easily adhesive polyamide film of the present invention has adhesive modification made of any one of polyester resin, polyurethane resin, and/or polyacrylic resin with a coating amount of 0.01 to 3 g/m ² as solid content on at least one side. It has layers.
The adhesion-modifying layer in the present invention is provided by applying and drying a coating liquid before winding up the film as a mill roll in the film manufacturing process.
The coating liquid can be applied to an unstretched film, a uniaxially stretched film, and/or a biaxially stretched film. When producing a film by a sequential biaxial stretching method, a coating liquid is usually applied to the uniaxially stretched film and dried. When producing a film by simultaneous biaxial stretching, a coating solution is usually applied to the unaxially stretched film and dried.

In the present invention, the coating liquid for providing the adhesion-modifying layer is applied and dried to form a coating film before the film is wound up as a mill roll in the film manufacturing process, ensuring safety and hygiene during manufacturing. Therefore, it is preferable to use an aqueous dispersion of resin.

(Polyester resin used for adhesive modification layer)
When a polyester resin is provided as the adhesion-modifying layer in the present invention, a copolymerized polyester resin can be selected as the polyester resin. The copolymerized polyester resin is a polycondensate of a dicarboxylic acid component, a diol component, and other ester-forming components. Examples of dicarboxylic acid components contained in the copolymerized polyester resin include terephthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, 4,4'-biphenylene dicarboxylic acid, and 5-sodium sulfoisophthalic acid. aromatic dicarboxylic acids, aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, and sebacic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid and 1,2-cyclohexanedicarboxylic acid; maleic acid; Examples include unsaturated dicarboxylic acids such as fumaric acid and tetrahydrophthalic acid.

In addition to the above dicarboxylic acid components, in order to impart water dispersibility, 5-sulfoisophthalic acid, sulfoterephthalic acid, 4-sulfoisophthalic acid, 4-sulfonaphthalene-2,6-dicarboxylic acid, 5(4-sulfophenoxy ) Salts of isophthalic acid can be used. Among these, it is preferable to use 5-sodium sulfoisophthalic acid in an amount of 1 to 10 mol%.

Diol components contained in the copolymerized polyester resin include ethylene glycol, diethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,6-hexanediol, polyethylene glycol, etc. Aliphatic diols such as 1,4-cyclohexanedimethal, aromatic diols such as 4,4'-bis(hydroxyethyl) bisphenol A, and bis(polyoxyethylene glycol) bisphenol ether. be able to.
The polyester resin is preferably used as a coating liquid for an aqueous dispersion.

(Polyurethane resin used for adhesive modification layer)
When a polyurethane resin is provided as the adhesion-modifying layer in the present invention, examples of the polyurethane resin include those obtained by reacting polyols having two or more active hydrogens with an organic polyisocyanate.
Examples of polyols include saturated polyester polyols; polyether polyols (e.g. polyethylene glycol, polytetramethylene glycol, etc.); amino alcohols (e.g. ethanolamine, diethanolamine, triethanolamine, etc.); unsaturated polyester polyols (e.g. For example, those obtained by polycondensing an unsaturated polycarboxylic acid alone or a mixture of this and a saturated polycarboxylic acid with a mixture of a saturated polyhydric alcohol and an unsaturated polyhydric alcohol), polybutadiene polyols (for example, 1,2-polybutadiene polyol, 1,4-polybutadiene polyol, etc.), acrylic polyols (having hydroxyl groups in the side chains obtained by copolymerizing various acrylic monomers and acrylic acid monomers having hydroxyl groups) Examples include polyols having unsaturated double bonds such as acrylic polyols).
Examples of organic polyisocyanates include aromatic polyisocyanates (for example, diphenylmethane diisocyanate, toluene diisocyanate, etc.), aliphatic polyisocyanates (for example, hexamethylene diisocyanate, etc.), alicyclic polyisocyanates (for example, isophorone diisocyanate, etc.), Examples include aromatic/aliphatic polyisocyanates (for example, kylylene diisocyanate) and polyisocyanates obtained by reacting these isocyanates with low molecular weight polyols in advance.

This polyurethane resin can be produced by a known method. During production, it is necessary to ensure that two or more unreacted isocyanate groups are present in the produced prepolymer. This isocyanate group is preferably blocked, and this blocking is especially essential when preparing an aqueous coating liquid. This blocking is well known as isocyanate blocking, and free isocyanate groups can be regenerated by heating. Examples of the blocking agent include bisulfites, alcohols, oximes, active methylene compounds, imidazoles, lactams, imine compounds, amide compounds, and imide compounds.

The reaction between these blocking agents and the isocyanate groups in the polyurethane prepolymer can be carried out at a temperature of room temperature to 100°C, and a urethanization catalyst can be used if necessary. Here, in order to impart stable water dispersibility and water solubility to the polyurethane prepolymer, it is preferable to introduce a hydrophilic group into the molecule. The hydrophilic groups include -SO ₃ M (where M is an alkali metal or alkaline earth metal), -OH, -COOR (where R is ammonia or a residue of a tertiary amine). Examples include. Among these, carboxyl groups neutralized with ammonia or tertiary amines are particularly preferred. In order to introduce a carboxyl group neutralized with ammonia or a tertiary amine into a polyurethane prepolymer, for example, a method using a carboxyl group-containing polyhydroxy compound as one of the reaction raw materials during polyurethane prepolymer synthesis, The isocyanate groups of a polyurethane prepolymer having isocyanate groups are reacted with a hydroxyl group-containing carboxylic acid or an amino group-containing carboxylic acid, and then the reaction product is neutralized by adding it to ammonia water or a tertiary amine aqueous solution under high-speed stirring. There are methods such as methods.
It is preferable to use the polyurethane resin in the form of an aqueous dispersion coating solution.

(Polyacrylic resin used for adhesive modification layer)
When a polyacrylic resin is provided as the adhesion-modifying layer in the present invention, examples of the polyacrylic resin include acrylic polymers obtained by polymerizing acrylic acid or methacrylic acid, or salts or esters thereof.
Examples of acrylic ester and methacrylic ester monomers include methyl acrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, glycidyl acrylate, methyl methacrylate, Examples include ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, 2-hydroxyethyl methacrylate, and glycidyl methacrylate. Examples of the salts of acrylic acid and methacrylic acid include sodium acrylate, sodium methacrylate, potassium acrylate, potassium methacrylate, ammonium acrylate, and ammonium methacrylate.
In addition to these essential components, acrylic acid monomers such as acrylamide, methacrylamide, aminoethyl methacrylate, aminomethyl methacrylate, N-methylolacrylamide, and N-methoxymethylacrylamide may be added.
In addition, monomers such as vinyl chloride, vinyl acetate, styrene, vinyl ether, butadiene, isoprene, and sodium vinylsulfonate can also be used as copolymerization components.
The acrylic polymer contains hydrophilic components such as an acrylate component, a methacrylate component, an acrylic acid component, an acrylamide component, a 2-hydroxyethyl acrylate component, and an N-methylolacrylamide component as copolymerized components. This is preferable in order to enhance the functionality of the coating film. It may also be a copolymer having a functional group in its molecular side chain. The acrylic polymer can also be obtained by copolymerizing a hard component such as methyl methacrylate or ethyl methacrylate as a main component and a soft component such as an acrylic ester as a copolymerization component.
It is preferable to use the polyacrylic resin in the form of an aqueous dispersion coating solution.

(Acrylic graft copolymerized polyester aqueous dispersion used in adhesion-modifying layer)
The coating liquid used for the adhesion-modifying layer in the present invention is particularly preferably an aqueous dispersion of a copolyester obtained by graft-polymerizing a polyacrylic resin onto a polyester resin.
The average particle diameter of the acrylic graft copolyester particles in the aqueous acrylic graft copolyester dispersion as measured by a laser light scattering method is 500 nm or less, preferably 10 nm to 500 nm, more preferably 10 nm to 300 nm. If the average particle diameter exceeds 500 nm, the strength of the coating film after application may decrease.

The content of the acrylic graft copolyester particles in the aqueous acrylic graft copolyester dispersion is usually 1% by mass to 50% by mass, preferably 3% by mass to 30% by mass.
The particles in the aqueous acrylic graft copolymerized polyester dispersion that can be used in the present invention have a core-shell structure with a polyester main chain as the core in the aqueous dispersion medium.

The coating film obtained from the aqueous acrylic graft copolymerized polyester dispersion has excellent adhesion to the polyamide film. Furthermore, since it has very good blocking resistance, it can be used without problems even in film base materials with a relatively low glass transition point. Furthermore, when it is made into a laminate, it has very good adhesion with the adhesive used when laminating printing ink and sealant layers. The resulting laminated film (also referred to as a laminate film) has significantly improved durability during retort treatment and boiling water treatment.

(Polyester main chain of acrylic graft copolyester)
The polyester that can be used as the main chain of the grafted polyester in the present invention is preferably a saturated or unsaturated polyester synthesized from at least a dicarboxylic acid component and a diol component. It can be a mixture of more than one type of polymer. Preferably, polyester is not naturally dispersed or dissolved in water by itself. The weight average molecular weight of the polyester that can be used in the present invention is from 5,000 to 100,000, preferably from 5,000 to 50,000. When the weight average molecular weight is less than 5,000, the physical properties of the dried coating film, such as post-processability, deteriorate. Further, if the weight average molecular weight is less than 5,000, the polyester itself as the main chain is easily water-solubilized, so that the acrylic graft copolyester does not form a core-shell structure. When the weight average molecular weight of the polyester exceeds 100,000, water dispersion becomes difficult. From the viewpoint of water dispersion, it is preferably 100,000 or less.
The glass transition temperature of the acrylic graph and the copolymerized polyester is 30°C or lower, preferably 10°C or lower. When the temperature is 30° C. or lower, preferably 10° C. or lower, the adhesiveness and durability with the ink layer and the sealant layer are improved.

The dicarboxylic acid component includes at least one aromatic dicarboxylic acid, at least one aliphatic and/or alicyclic dicarboxylic acid, and at least one dicarboxylic acid having a radically polymerizable unsaturated double bond. , a dicarboxylic acid mixture is preferred. The aromatic dicarboxylic acid contained in this dicarboxylic acid mixture is 30 to 99.5 mol%, preferably 40 to 99.5 mol%, and the aliphatic and/or alicyclic dicarboxylic acid is 0 to 70 mol%. The amount of the dicarboxylic acid having a radically polymerizable unsaturated double bond is preferably 0.5 to 10 mol%, preferably 2 to 7 mol%, and more preferably 3 to 6 mol%. If the content of the dicarboxylic acid containing a radically polymerizable unsaturated double bond is less than 0.5 mol %, it is difficult to effectively graft the radically polymerizable monomer onto the polyester, and it is difficult to graft the radically polymerizable monomer to the polyester. The dispersed particle size tends to increase, and the dispersion stability tends to decrease.

As the aromatic dicarboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, biphenyl dicarboxylic acid, etc. can be used. Furthermore, sodium 5-sulfoisophthalate may also be used if necessary.
As the aliphatic dicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedioic acid, dimer acid, acid anhydrides thereof, etc. can be used.
As the alicyclic dicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, acid anhydrides thereof, etc. can be used.

Examples of dicarboxylic acids containing radically polymerizable unsaturated double bonds include fumaric acid, maleic acid, maleic anhydride, itaconic acid, citraconic acid, and fats containing unsaturated double bonds as α,β-unsaturated dicarboxylic acids. As the cyclic dicarboxylic acid, 2,5-norbornene dicarboxylic anhydride, tetrahydrophthalic anhydride, etc. can be used. Among these, fumaric acid, maleic acid and 2,5-norbornenedicarboxylic acid (endo-bicyclo-(2,2,1)-5-heptene-2,3-dicarboxylic acid) are preferred.

The diol component comprises at least one of aliphatic glycols having 2 to 10 carbon atoms, alicyclic glycols having 6 to 12 carbon atoms, and ether bond-containing glycols.
Examples of aliphatic glycols having 2 to 10 carbon atoms include ethylene glycol, 1,2-propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6 -hexanediol, 3-methyl-1,5-pentanediol, 1,9-nonanediol, 2-ethyl-2-butylpropanediol, and the like can be used.
As the alicyclic glycol having 6 to 12 carbon atoms, 1,4-cyclohexanedimethanol and the like can be used.
Ether bond-containing glycols include diethylene glycol, triethylene glycol, dipropylene glycol, and glycols obtained by adding 1 to several moles of ethylene oxide or propylene oxide to two phenolic hydroxyl groups of bisphenols, such as 2,2 -bis(4-hydroxyethoxyphenyl)propane and the like can be used. Polyethylene glycol, polypropylene glycol, and polytetramethylene glycol may also be used if necessary.

In addition to the above dicarboxylic acid component and diol component, a trifunctional or higher functional polycarboxylic acid and/or polyol may be copolymerized.
Examples of trifunctional or higher-functional polycarboxylic acids include trimellitic acid (anhydride), pyromellitic acid (anhydride), benzophenonetetracarboxylic acid (anhydride), trimesic acid, ethylene glycol bis(anhydrotrimellitate), and glycerol tris(anhydride). hydrotrimelitate), etc. can be used.
As the trifunctional or higher functional polyol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, etc. can be used.
The trifunctional or higher functional polycarboxylic acid and/or polyol is 0 to 5 mol%, preferably 0 to 3 mol%, based on the total polycarboxylic acid component including the dicarboxylic acid component or the total polyol component including the diol component. Can be used within the range.

(Graft part of acrylic graft copolymerized polyester)
The graft portion of the acrylic graft copolyester that can be used in the present invention is a monomer containing at least one radically polymerizable monomer that has a hydrophilic group or a group that can be later converted into a hydrophilic group. It is an acrylic polymer derived from a mixture of

The weight average molecular weight of the polymer constituting the graft portion is 500 to 50,000, preferably 4,000 to 50,000. When the weight average molecular weight is less than 500, the grafting rate decreases and hydrophilicity cannot be sufficiently imparted to the polyester, and it is generally difficult to control the weight average molecular weight of the grafted portion to less than 500. be. The grafted portion forms a hydration layer of the dispersed particles. In order to provide the particles with a sufficiently thick hydration layer and obtain a stable dispersion, it is desirable that the weight average molecular weight of the graft portion derived from the radically polymerizable monomer is 500 or more. The upper limit of the weight average molecular weight of the graft portion of the radically polymerizable monomer is preferably 50,000 as described above from the viewpoint of polymerizability in solution polymerization. The molecular weight can be controlled within this range by appropriately selecting the amount of polymerization initiator, monomer dropping time, polymerization time, reaction solvent, and monomer composition, and by appropriately combining chain transfer agents and polymerization inhibitors as necessary. I can do it.
The glass transition point is 30°C or lower, preferably 10°C or lower.

As the hydrophilic group possessed by the radically polymerizable monomer, a carboxyl group, a hydroxyl group, a sulfonic acid group, an amide group, a quaternary ammonium salt, a phosphoric acid group, etc. can be used. As the group that can be converted into a hydrophilic group, acid anhydride, glycidyl, chlor, etc. can be used. The water dispersibility of the grafted polyester can be controlled by the hydrophilic groups introduced into the polyester by grafting. Among the above hydrophilic groups, the amount of carboxyl group introduced into the grafted polyester can be accurately determined using the acid value known in the art, so it controls the dispersibility of the grafted polyester in water. It is preferable to do so.

Examples of carboxyl group-containing radically polymerizable monomers include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, and maleic anhydride, which easily generates carboxylic acid when in contact with water/amine. Itaconic anhydride, methacrylic anhydride, and the like can be used. Preferred carboxyl group-containing radically polymerizable monomers are acrylic anhydride, methacrylic anhydride and maleic anhydride.

In addition to the hydrophilic group-containing radically polymerizable monomer, it is preferable to copolymerize at least one radically polymerizable monomer that does not contain a hydrophilic group. In the case of only a hydrophilic group-containing monomer, grafting to the polyester main chain does not occur smoothly, making it difficult to obtain a good copolymerized polyester aqueous dispersion. Highly efficient grafting can only be achieved by copolymerizing radically polymerizable monomers that do not contain at least one hydrophilic group.

As the radically polymerizable monomer not containing a hydrophilic group, one or more combinations of monomers having an ethylenically unsaturated bond and not containing a hydrophilic group as described above are used. Such monomers include acrylic acid esters such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, and hydroxypropyl acrylate; Methacrylic acid esters such as methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-hexyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, hydroxylpropyl methacrylate; acrylamide , N-methylolacrylamide, diacetone acrylamide, and other acrylic acid or methacrylic acid derivatives; acrylonitrile, methacrylonitrile, and other nitriles; vinyl acetate, vinyl propionate, vinyl benzoate, and other vinyl esters; vinyl methyl ether, vinyl ethyl Vinyl ethers such as ether and vinyl isobutyl ether; Vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, and methyl isopropenyl ketone; N- such as N-vinylpyrrole, N-vinyl carbazole, N-vinylindole, and N-vinylpyrrolidone. Vinyl compounds; vinyl halides such as vinyl chloride, vinyldene chloride, vinyl bromide, and vinyl fluoride; aromatic vinyl compounds such as styrene, α-methylstyrene, t-butylstyrene, vinyltoluene, and vinylnaphthalene; be able to. These monomers may be used alone or in combination of two or more.

The ratio of the hydrophilic group-containing monomer to the hydrophilic group-free monomer is determined by taking into account the amount of hydrophilic groups to be introduced into the grafted polyester, but usually the mass ratio (hydrophilic group The monomer content (monomer containing no hydrophilic group) is in the range of 95:5 to 5:95, preferably 90:10 to 10:90, and more preferably 80:20 to 40:60.

When a carboxyl group-containing monomer is used as the hydrophilic group-containing monomer, the total acid value of the grafted polyester is 600 to 4000 eq. /10 ⁶ g, preferably 700 to 3000 eq. /10 ⁶ g, most preferably 800-2500 eq. /10 ⁶ g. Acid value is 600eq. /10 ⁶ g or less, it is difficult to obtain an aqueous copolyester dispersion with a small particle size when the grafted polyester is dispersed in water, and furthermore, the dispersion stability of the aqueous copolyester dispersion decreases. Acid value is 4000eq. /10 ⁶ g or more, the water resistance of the adhesion-modified layer formed from the copolymerized polyester aqueous dispersion becomes low.

The mass ratio of the polyester main chain to the graft portion in the acrylic graft copolymerized polyester (polyester: radically polymerizable monomer) is 40:60 to 95:5, preferably 55:45 to 93:7, more preferably 60. :40 to 90:10.

When the mass ratio of the polyester main chain is 40% by mass or less, the excellent performance of the base polyester described above, namely high processability, excellent water resistance, and excellent adhesion to various substrates, cannot be fully exhibited. On the contrary, it adds undesirable properties of acrylic resin, such as low processability, gloss, and water resistance. If the mass ratio of the polyester is 95% by mass or more, the amount of hydrophilic groups in the grafted portion that imparts hydrophilicity to the grafted polyester is insufficient, making it impossible to obtain a good aqueous dispersion.

(Solvent for grafting reaction of acrylic graft copolyester)
The solvent for the grafting reaction is preferably composed of an aqueous organic solvent with a boiling point of 50 to 250°C. Here, the aqueous organic solvent refers to an organic solvent having a solubility in water at 20° C. of at least 10 g/L, preferably 20 g/L or more. Aqueous organic solvents with a boiling point exceeding 250° C. are unsuitable because their evaporation rate is slow and they cannot be sufficiently removed even by high-temperature baking of the coating after the coating is formed. In addition, when carrying out a grafting reaction using an aqueous organic solvent with a boiling point of 50°C or lower, an initiator that decomposes into radicals at a temperature of 50°C or lower must be used, which increases handling risks and is therefore not preferred. do not have.

Examples of aqueous organic solvents (first group) that dissolve polyester well and relatively well dissolve polymerizable monomers containing hydrophilic groups, especially carboxyl group-containing polymerizable monomers, and their polymers include esters. , such as ethyl acetate; ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; cyclic ethers such as tetrahydrofuran, dioxane, and 1,3-dioxolane; glycol ethers such as ethylene glycol dimethyl ether, propylene glycol methyl ether, Propylene glycol propyl ether, ethylene glycol ethyl ether, and ethylene glycol butyl ether; carbitols, such as methyl carbitol, ethyl carbitol, and butyl carbitol; lower esters of glycols or glycol ethers, such as ethylene glycol diacetate and ethylene Glycol ethyl ether acetate; ketone alcohols such as diacetone alcohol; N-substituted amides such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone; and the like.

In contrast, aqueous organic solvents (second group) that hardly dissolve polyester but relatively well dissolve polymerizable monomers containing hydrophilic groups, especially carboxyl group-containing polymerizable monomers, and their polymers. , water, lower alcohols, lower glycols, lower carboxylic acids, and lower amines. Preferred are alcohols and glycols having 1 to 4 carbon atoms.

If the grafting reaction is carried out in a single solvent, one of the first group of aqueous organic solvents may be used. When carrying out the reaction in a mixed solvent, a plurality of aqueous organic solvents of the first group or at least one aqueous organic solvent of the first group and at least one aqueous organic solvent of the second group may be used.

The grafting reaction can be carried out both in a single solvent from the first group of aqueous organic solvents and in a mixed solvent consisting of one type of each of the first and second group of aqueous organic solvents. However, from the viewpoint of the progress behavior of the grafting reaction, the appearance and properties of the grafting reaction product and the aqueous dispersion derived therefrom, a mixture consisting of one kind of aqueous organic solvent of the first group and the second group is recommended. Preference is given to using a solvent. The reason for this is that in the grafting reaction of polyester, gelation of the system tends to occur due to crosslinking between polyester molecules, but gelation can be prevented by using a mixed solvent as described below.

In the first group of solvents, the polyester molecular chains were in a stretched state with a large spread, whereas in the mixed solvent of the first group/second group, the polyester molecular chains were entangled in a thread-like state with a small spread. This was confirmed by measuring the viscosity of the polyester in these solutions. When the polyester molecular chain is extended, all the reactive points in the polyester main chain can contribute to the grafting reaction, so the grafting rate of the polyester increases, but at the same time, the rate of intermolecular crosslinking also increases. On the other hand, when the polyester molecular chain is in the form of a thread ball, the reaction points inside the thread ball cannot contribute to the grafting reaction, and at the same time, the rate at which intermolecular crosslinking occurs is low. Therefore, by selecting the type of solvent, the state of the polyester molecules can be controlled, thereby controlling the grafting rate and the intermolecular crosslinking caused by the grafting reaction.

Both a high grafting rate and gelation inhibition can be achieved in a mixed solvent system. The optimal mixing ratio of the first group/second group solvent mixture may vary depending on the solubility of the polyester used, etc., but the mass ratio of the first group/second group solvent mixture is usually 95:5 to 95:5. The range is 10:90, preferably 90:10 to 20:80, more preferably 85:15 to 30:70.

(Radical polymerization initiator and chain transfer agent for acrylic graft copolyester)
As the radical polymerization initiator that can be used in the present invention, organic peroxides and organic azo compounds known to those skilled in the art can be used.
As organic peroxides, benzoyl peroxide, t-butyl peroxypivalate, as organic azo compounds, 2,2'-azobisisobutyronitrile, 2,2'-azobis(2,4-dimethylvaleronitrile), etc. can be mentioned.
The amount of the radical polymerization initiator used for carrying out the grafting reaction is at least 0.2% by mass or more, preferably 0.5% by mass or more, based on the radically polymerizable monomer.
In addition to the polymerization initiator, a chain transfer agent such as octyl mercaptan, mercaptoethanol, 3-t-butyl-4-hydroxyanisole, etc. may be used as necessary to adjust the chain length of the graft portion. In this case, it is preferably added in an amount of 0 to 5% by mass based on the radically polymerizable monomer.

(Grafting reaction of acrylic graft copolymerized polyester)
The graft portion is formed by polymerization of the radically polymerizable unsaturated double bond in the polyester and the radically polymerizable monomer and/or by polymerization of the radically polymerizable unsaturated double bond in the polyester and the radically polymerizable monomer. The reaction proceeds by reaction between the active end of the polymer. The reaction product after the completion of the grafting reaction contains, in addition to the desired grafted polyester, a polyester having no graft moiety and a polymer of the radically polymerizable monomer that was not grafted with the polyester. When the production ratio of grafted polyester in the reaction product is low and the ratio of polyester without grafted moieties and polymers of radically polymerizable monomers that are not grafted is high, a dispersion with good stability is obtained. I can't get it.

Usually, the grafting reaction can be carried out by adding the radically polymerizable monomer and the radical initiator to a solution containing the polyester at the same time under heating, or separately over a certain period of time. After the addition, the reaction can be carried out by continuing to heat the mixture under stirring for a certain period of time to advance the reaction. Alternatively, if necessary, a portion of the radically polymerizable monomer is added first, then the remaining radically polymerizable monomer and polymerization initiator are separately added dropwise over a certain period of time, and then further The grafting reaction can be carried out by continuing heating with stirring for a period of time.

The mass ratio of the polyester to the solvent is selected in consideration of the reactivity between the polyester and the radically polymerizable monomer and the solubility of the polyester in the solvent, so that the reaction proceeds uniformly during the polymerization process. The ratio is usually 70:30 to 10:90, preferably 50:50 to 15:85.

(Water dispersion of acrylic graft copolyester)
The grafted polyester that can be used in the present invention can be water-dispersed by introducing it into an aqueous medium in a solid state, or by dissolving it in a hydrophilic solvent and then introducing it into an aqueous medium. In particular, when a monomer having an acidic group such as a sulfonic acid group or a carboxyl group is used as a radically polymerizable monomer having a hydrophilic group, the grafted polyester can be neutralized with a basic compound. A copolymerized polyester aqueous dispersion can be prepared by easily dispersing the grafted polyester in water as fine particles having an average particle diameter of 500 nm or less.

The basic compound is preferably a compound that volatilizes during coating film formation or, if a curing agent described below is added, during baking curing. As such basic compounds, ammonia, organic amines, etc. are preferable. Examples of organic amines include triethylamine, N,N-diethylethanolamine, N,N-dimethylethanolamine, aminoethanolamine, N-methyl-N,N-diethanolamine, isopropylamine, iminobispropylamine, ethylamine, diethylamine, 3-ethoxypropylamine, 3-diethylaminopropylamine, sec-butylamine, propylamine, methylaminopropylamine, dimethylaminopropylamine, methyliminobispropylamine, 3-methoxypropylamine, monoethanolamine, diethanolamine, triethanolamine etc. can be mentioned.
The amount of the basic compound to be used is preferably an amount that at least partially or completely neutralizes the carboxyl groups contained in the grafted portion and brings the pH value of the aqueous dispersion to a range of 5.0 to 9.0. .

A method for preparing a copolymerized polyester aqueous dispersion neutralized with a basic compound is to remove the solvent from the reaction solution under reduced pressure using an extruder or the like after the grafting reaction is completed to obtain a melt or solid (pellet) dispersion. , powder, etc.), and then pouring this into an aqueous basic compound solution and stirring while heating, or immediately pouring the aqueous basic compound solution into the reaction solution as soon as the grafting reaction is completed, and continuing to stir with heating ( Aqueous dispersions can be prepared by a one-pot method. The one-pot method is preferred from the point of view of convenience. In this case, if the boiling point of the solvent used in the grafting reaction is 100°C or lower, part or all of it can be easily removed by distillation.

(Crosslinking agent added to coating solution)
The above aqueous dispersion can be used as it is as a coating agent to form an adhesion-modifying layer, but by adding a cross-linking agent (curing resin) and curing it, the adhesive-modifying layer has a high degree of water resistance. can be granted.
Examples of crosslinking agents include phenol-formaldehyde resins, which are condensates of alkylated phenols, cresols, etc., and formaldehyde; adducts of formaldehyde with urea, melamine, benzoguanamine, etc., and alcohols having 1 to 6 carbon atoms with these adducts. Amino resins such as alkyl ether compounds consisting of; polyfunctional epoxy compounds; polyfunctional isocyanate compounds; blocked isocyanate compounds; polyfunctional aziridine compounds; oxazoline compounds, etc. can be used.
These crosslinking agents may be used alone or in combination of two or more. The amount of the crosslinking agent blended is preferably 5% by mass to 40% by mass based on the grafted polyester.

The method of blending the crosslinking agent is (1) when the crosslinking agent is water-soluble, directly dissolving or dispersing it in the aqueous dispersion, or (2) when the crosslinking agent is oil-soluble, after the grafting reaction is completed. Alternatively, a method may be used in which a crosslinking agent is added before or after water dispersion to coexist with the polyester in the core portion. These methods can be appropriately selected depending on the type and properties of the crosslinking agent. Furthermore, a curing agent or an accelerator may be used in combination with the crosslinking agent.

The adhesion-modifying layer used in the present invention further contains additives such as antistatic agents, inorganic lubricants, and organic lubricants in order to impart antistatic properties and slip properties within a range that does not impair the effects of the present invention. be able to. When applying antistatic agents, inorganic lubricants, organic lubricants, etc. to the film surface, it is preferable to include them in the adhesion-modifying layer in order to prevent these additives from being detached.

<Manufacturing method>
The laminated stretched polyamide film in the present invention can be manufactured by a known manufacturing method.
Examples include a sequential biaxial stretching method and a simultaneous biaxial stretching method. The sequential biaxial stretching method is preferable because it increases the film forming speed and is advantageous in terms of manufacturing cost. It may be a uniaxially stretched film formed by a uniaxial stretching method.

Before stretching the film, an unstretched sheet in which layer A and layer B are laminated is obtained. A preferred method for this is a coextrusion method using a feed block, multi-manifold, or the like. In addition to the coextrusion method, a dry lamination method, an extrusion lamination method, etc. can also be selected.
When laminating by coextrusion, the relative viscosities of the polyamides used for layer A and layer B are desirably selected so that the difference in melt viscosity between layer A and layer B is small.

A normal device is used as the sequential biaxial stretching device. The manufacturing conditions include a longitudinal stretching temperature of 50 to 100°C, a longitudinal stretching ratio of 2 to 5 times, a width direction stretching temperature of 120 to 200°C, a width direction stretching ratio of 3 to 5 times, and heat setting. Preferably, the temperature is in the range of 200°C to 230°C.
In order to increase the adhesive strength with the sealant film and the printed layer, the surface of the laminated stretched polyamide film and/or the surface of the adhesion modifying layer (C layer) may be subjected to corona treatment, flame treatment, etc. Furthermore, in order to increase the adhesive strength between the laminated and stretched polyamide film and the adhesion-modified layer, the surface of the laminated and stretched polyamide film on the adhesion-modified layer (layer C) side may be subjected to corona treatment, flame treatment, or the like.

The method for forming the adhesion-modifying layer (C layer) in the present invention includes a gravure method, a reverse method, and a laminated stretched polyamide film, in which a coating agent containing a polyester resin, a polyurethane resin, and/or a polyacrylic resin is applied. , a die method, a bar method, a dip method, and other known coating methods can be used.

The coating amount of the coating agent is preferably 0.01 to 3 g/m ² as solid content to the polyamide film after biaxial stretching. More preferably, the coating amount is 0.04 to 0.5 g/m ² . With the above coating amount, sufficient adhesive strength between the adhesion-modifying layer and other layers can be obtained, and blocking between the films can be suppressed.

The adhesion-modifying layer in the present invention is formed by applying a coating agent to a biaxially oriented polyamide film base material, or by applying a coating agent to an unstretched or uniaxially stretched polyamide film base material, and then drying the coating agent, and then applying the coating agent as necessary. It can be prepared by further performing heat setting after uniaxial stretching or biaxial stretching. The drying temperature after application of the coating agent is 150°C or higher, preferably 200°C or higher by drying and heat setting to strengthen the coating film and improve the adhesion between the adhesion-modifying layer and the polyamide film base material. do.

When stretching is performed after coating, it is necessary to control the moisture content of the coated film within the range of 0.1 to 2% during drying after coating so as not to impair the stretchability of the coated film. After stretching, by drying and heat-setting at 200° C. or higher, the coating film becomes strong and the adhesion between the adhesion-modifying layer and the polyamide film base material is dramatically improved.

The easily adhesive polyamide film of the present invention thus obtained can prevent the film from being scraped and the bag from breaking due to friction, even if friction occurs with transportation packaging such as cardboard during transportation of the bag-formed product. In addition, it is possible to prevent bags from breaking due to bending fatigue due to contact between bags. Furthermore, since the water-resistant adhesive strength between the polyamide film and the sealant film is high, it exhibits high bag breakage prevention properties.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples. The film was evaluated using the following measurement method. Unless otherwise specified, measurements were performed in a measurement room at 23° C. and 65% relative humidity.
(1) Haze value of film It was measured in accordance with JIS-K-7105 using a direct reading haze meter manufactured by Toyo Seiki Seisakusho Co., Ltd.
Haze (%) = [Td (diffuse transmittance %) / Tt (total light transmittance %)] × 100
(2) Impact strength of film It was measured using a film impact tester manufactured by Toyo Seiki Seisakusho Co., Ltd. The measured value was expressed as J (joule)/15 μm in terms of thickness per 10 μm.

(3-1) Bending pinhole resistance of film Using a Gelbo Flex Tester manufactured by Rigaku Kogyo Co., Ltd., the number of bending fatigue pinholes was measured by the following method.
After applying a polyester adhesive to the film produced in the example, a linear low-density polyethylene film (L-LDPE film: manufactured by Toyobo Co., Ltd., L4102) with a thickness of 40 μm was dry laminated, and the film was dried for 3 days at 40°C. It was aged and made into a laminate film. The obtained laminated film was cut into a 12 inch x 8 inch cylinder with a diameter of 3.5 inches, and one end of the cylindrical film was placed on the fixed head side of the Gelbo Flex Tester, and the other end was placed on the movable head side. and the initial gripping interval was set to 7 inches. The first 3.5 inches of the stroke are given a 440-degree twist, and the next 2.5 inches are subjected to a bending fatigue cycle of 1000 times at a rate of 40 times per minute, with the entire stroke completed in a straight horizontal motion. The number of pinholes that occurred was counted. Note that the measurements were performed in an environment of 1°C. The test film was placed on a filter paper (Advantech, No. 50) with the L-LDPE film side facing down, and the four corners were fixed with Sellotape (registered trademark). Ink (ink manufactured by Pilot (product number INK-350-Blue) diluted 5 times with pure water) was applied onto the test film and spread over the entire surface using a rubber roller. After wiping off unnecessary ink, the test film was removed and the number of ink dots on the filter paper was counted.

(3-2) Friction pinhole resistance of film Using a fastness tester (Toyo Seiki Seisakusho), a friction test was conducted according to the method below, and the distance at which pinholes occurred was measured.
A test sample was made by folding a laminate film similar to that made in the bending pinhole resistance evaluation above into four with sharp corners, and tested with a fastness tester at an amplitude of 25 cm and an amplitude speed of 30 times/ It was rubbed against the inner surface of the cardboard with a load of 100g. The cardboard used was K280 x P180 x K210 (AF) = (front material liner x core material x backing liner (type of flute)).

The pinhole occurrence distance was calculated according to the following procedure. The longer the pinhole generation distance, the better the friction pinhole resistance.
First, a friction test was conducted with an amplitude of 100 times and a distance of 2500 cm. If the pinhole did not open, a friction test was performed by increasing the number of vibrations by 20 times and increasing the distance by 500 cm. Further, if the pinhole did not open, a friction test was performed by increasing the number of vibrations by 20 times and increasing the distance by 500 cm. This was repeated and the distance at which the pinhole was opened was marked with an x to determine level 1. If a pinhole opened after 100 amplitudes and a distance of 2,500 cm, a friction test was conducted with the number of amplitudes reduced by 20 times and a distance of 500 cm. In addition, if a pinhole opened, a friction test was conducted by reducing the distance by 500 cm and 20 more vibrations. This process was repeated and the distance at which no pinhole was formed was marked with a circle and set as level 1.
Next, as level 2, if the final score was ○ in level 1, a friction test was performed by increasing the number of amplitudes by 20 times, and if a pinhole did not open, a ○ was marked, and if a pinhole did open, a × was marked. If the final score was × in level 1, a friction test was performed by reducing the number of vibrations by 20 times, and if a pinhole did not open, a mark was given as ○, and if a pinhole opened, a mark was given as ×.
Furthermore, for levels 3 to 20, if the previous level was ○, increase the number of amplitudes by 20 times and perform a friction test, and if the pinhole does not open, mark ○, and if the pinhole opens, mark ×. If the previous level was ×, reduce the number of vibrations by 20 times and perform a friction test, and if a pinhole does not open, mark ○, and if a pinhole opens, mark ×. Repeat this and mark ○ or × for levels 3 to 20.

For example, the results shown in Table 1 were obtained. How to determine the pinhole occurrence distance will be explained using Table 1 as an example.
Count the number of ○ and × trials for each distance.
The distance with the most number of tests is set as the median value, and the coefficient is set as zero. When the distance is longer than that, the coefficient is +1, +2, +3, etc. for every 500 cm, and when the distance is shorter, the coefficient is -1, -2, -3, etc. for every 500 cm.
In all tests from level 1 to level 20, we compared the number of tests in which no hole was formed and the number of tests in which a hole formed, and calculated the friction pinhole occurrence distance for the following cases A and B using the respective formulas. .
A: In all tests, if the number of tests in which no hole was formed is greater than the number of tests in which a hole was formed. Friction pinhole occurrence distance = median + 500 × (Σ (coefficient × number of tests in which no hole was formed) / hole was Number of exams that were not opened) + 1/2)
B: In all tests, when the number of tests in which no hole was formed is less than the number of tests in which a hole was formed Friction pinhole occurrence distance = median + 500 × (Σ (coefficient × number of tests in which a hole was formed) / hole was formed number of tests)-1/2)

(4) Thickness of the film Divide the film into 10 equal parts in the width direction (for narrow films, divide the film so that it has enough width to measure the thickness), and stack 10 films of 100 mm in length in the vertical direction. Cut out and condition for 2 hours or more at a temperature of 23°C and a relative humidity of 65%. The thickness at the center of each sample was measured using a thickness measuring device manufactured by Tester Sangyo, and the average value was taken as the thickness.
The thickness of the base layer (layer A) and the surface layer (layer B) is determined by measuring the total thickness of the laminated stretched polyamide film measured by the above method, the discharge amount of layer A and the discharge amount of layer B, and calculating the discharge amount. The thicknesses of layer A and layer B were calculated based on the ratio.
(5) Thickness unevenness after 15 hours (TV%)
The thickness of the film 15 hours after the start of film formation was measured in the same manner as above, and the value (%) obtained by dividing the difference between the maximum and minimum thicknesses at the center of each sample by the average value was calculated as the value (%) after 15 hours. It was calculated as thickness unevenness (TV%).

(6) Occurrence cycle of grain stain (degraded product generated at die lip outlet) After cleaning the lip of the die, film formation was started, and the time until grain stain appeared on the lip of the die was observed.

(7) Coating amount of adhesion-modifying layer A biaxially stretched polyamide film was cut into an area of 10 cm x 10 cm, and the surface of the adhesion-modifying layer of the film was wiped with a cloth impregnated with a mixed organic solvent of methyl ethyl ketone/toluene = 1/1. The weight before and after wiping was measured using a precision balance (AUW120D manufactured by Shimadzu Corporation). Based on the measured weight difference, the coating amount (g/m ² ) was calculated per square meter.

(8) Water-resistant laminate strength (laminate strength under water adhesion conditions)
A polyester adhesive [a mixture of TM-569 (product name) and CAT-10L (product name) manufactured by Toyo Morton Co., Ltd. in a mass ratio of 7.2/1 (solid content concentration 23%)] was applied to the film. After coating so that the resin solid content after drying is 3.2 g/m ² , a 40 μm linear low-density polyethylene film (L-LDPE film: manufactured by Toyobo Co., Ltd., RIX (registered trademark) L4102) was dry laminated. Then, aging was performed for 2 days in an environment of 40°C to obtain a laminate film.
The produced laminate film was cut into strips with a width of 15 mm and a length of 200 mm, and one end of the laminate film was peeled off at the interface between the biaxially stretched polyamide film and the linear low-density polyethylene film. Graph), the laminate strength was measured three times under the conditions of a temperature of 23°C, a relative humidity of 50%, a pulling speed of 200 mm/min, and a peeling angle of 90° while dropping water with a dropper onto the peeled interface of the strip-shaped laminate film. The average value was used for evaluation.

(9) Relative viscosity of raw material polyamide A polyamide solution in which 0.25 g of polyamide was dissolved in 96% sulfuric acid to a concentration of 1.0 g/dl in a 25 ml volumetric flask was measured for relative viscosity at 20°C.
(10) Melting point of raw material polyamide In accordance with JIS K7121, using a Seiko Instruments SSC5200 differential scanning calorimeter, sample weight: 10 mg, heating start temperature: 30°C, temperature rising in a nitrogen atmosphere. Measurement was performed at a rate of 20° C./min, and the endothermic peak temperature (Tmp) was determined as the melting point.
<Preparation of acrylic graft copolyester coating liquid for adhesive modification layer>
466 parts by weight of dimethyl terephthalate, 466 parts by weight of dimethyl isophthalate, 401 parts by weight of neopentyl glycol, 443 parts by weight of ethylene glycol, and tetra-n-butyl were placed in a stainless steel autoclave equipped with a stirrer, a thermometer, and a partial reflux condenser. 0.52 parts by mass of titanate was charged, and a transesterification reaction was carried out at 160 to 220°C over 4 hours. Next, 23 parts by mass of fumaric acid was added and the temperature was raised from 200°C to 220°C over 1 hour to perform an esterification reaction. Next, the temperature was raised to 255° C., the pressure of the reaction system was gradually reduced, and the reaction was carried out under a reduced pressure of 0.2 mmHg with stirring for 1 hour and 30 minutes to obtain a polyester. The obtained polyester was pale yellow and transparent, had a glass transition temperature of 60° C., and a weight average molecular weight of 12,000. The composition obtained by NMR measurement etc. was as follows.
・Dicarboxylic acid component Terephthalic acid 48 mol%
Isophthalic acid 48 mol%
Fumaric acid 4 mol%
・Diol component neopentyl glycol 50 mol%
Ethylene glycol 50 mol%

75 parts by mass of the above polyester resin, 56 parts by mass of methyl ethyl ketone, and 19 parts by mass of isopropyl alcohol were placed in a reactor equipped with a stirrer, a thermometer, a reflux device, and a quantitative dropping device, and the resin was dissolved by heating and stirring at 65° C. . After the resin is completely dissolved, a solution of a mixture of 17.5 parts by mass of methacrylic acid and 7.5 parts by mass of ethyl acrylate and 1.2 parts by mass of azobisdimethylvaleronitrile dissolved in 25 parts by mass of methyl ethyl ketone is The mixture was added dropwise into the polyester solution at a rate of 2 ml/min, and stirring was continued for an additional 2 hours after the dropwise addition was completed. After sampling for analysis (5 g) from the reaction solution, 300 parts by mass of water and 25 parts by mass of triethylamine were added to the reaction solution and stirred for 1 hour to prepare a dispersion of grafted copolymerized polyester. Thereafter, the temperature of the obtained dispersion was raised to 100° C., and methyl ethyl ketone, isopropyl alcohol, and excess triethylamine were distilled off to obtain a copolymerized polyester aqueous dispersion.
The obtained dispersion was diluted with water to a solid content concentration of 5% to obtain a coating liquid AEG for an adhesion-modifying layer. Note that parts by mass are values as solid content.

<Adjustment of polyester coating liquid for adhesive modification layer>
100 parts by mass of a water-dispersible polyester resin (Vylonal MD1930, manufactured by Toyobo Co., Ltd.) and 43 parts by mass of a reactive water-based urethane resin (Elastron BN11, manufactured by Daiichi Kogyo Yakuhin Co., Ltd.) were mixed, and then the solid content concentration was adjusted to 5%. The mixture was diluted with water to obtain a coating liquid PES for an adhesion-modifying layer. Note that parts by mass are values as solid content.
<Adjustment of polyurethane coating liquid for adhesive modification layer>
100 parts by mass of water-dispersible polyurethane resin (Hydran KU400SF, manufactured by DIC Corporation) is mixed with 20 parts by mass of trimethylolmelamine resin (Beccamin APM, manufactured by DIC Corporation), and the solid content is adjusted to 5%. The mixture was diluted with water to obtain a coating liquid PU for an adhesion-modifying layer. Note that parts by mass are values as solid content.

(Example 1)
Using a device consisting of two extruders and a coextrusion T-die with a width of 380 mm, the molten resin was laminated in a B layer/A layer/B layer configuration and extruded into a sheet form from the T die, and the temperature was controlled at 20 ° C. A laminated unstretched sheet having a thickness of 200 μm was obtained by closely contacting a cooling roll.
The resin compositions of layer A and layer B are as follows.
Resin composition constituting layer A: 97 parts by mass of nylon 6 (manufactured by Toyobo Co., Ltd., relative viscosity 2.8, melting point 220°C), and a polyamide elastomer in which nylon 12 is a hard segment and polytetramethylene glycol is a soft segment. (manufactured by Arkema, PEBAX4033SA02) A polyamide resin composition consisting of 3.0 parts by mass.
Resin composition constituting layer B: resin composition consisting of 100 parts by mass of nylon 6 (manufactured by Toyobo Co., Ltd., relative viscosity 2.8, melting point 220°C), 0.54 parts by mass of silica particles, and 0.15 parts by mass of fatty acid amide. thing.
In addition, the thickness of the laminated stretched polyamide film is such that the total thickness is 15 μm, the thickness of the base layer (A layer) is 12 μm, and the thickness of the front and back surface layers (B layer) is 1.5 μm each. The configuration and extruder output rate were adjusted.

The obtained laminated unstretched sheet was introduced into a roll-type stretching machine, and using the difference in circumferential speed of the rolls, it was stretched 1.7 times in the longitudinal direction at 80°C, and then further stretched 1.85 times at 70°C. .
Next, a coating liquid of an aqueous dispersion of acrylic graft copolymer polyester was applied to this longitudinally stretched film using a roll coater method, and the film was dried with hot air at 70°C.
Subsequently, this uniaxially stretched film is continuously introduced into a tenter type stretching machine, and after being preheated at 110°C, it is stretched in the transverse direction by 1.2 times at 120°C, 1.7 times at 130°C, and 2.0 times at 160°C. After stretching and heat-setting at 210°C, relaxation treatments were performed at 210°C for 3% and at 185°C for 2%, and then the surface to be dry laminated with the linear low-density polyethylene film was subjected to corona discharge treatment. A biaxially stretched polyamide film having two types and three layers laminated in the order of B layer/A layer/B layer was obtained.
The coating amount of the acrylic graft copolyester in the obtained biaxially stretched polyamide film was 0.3 g/m ² as solid content. Table 2 shows the characteristics evaluation results of the film.

(Examples 2 to 6 and Comparative Examples 1 to 4)
A biaxially stretched film was obtained in the same manner as in Example 1, except that the resin composition and thickness structure of the A layer and B layer were changed as shown in Table 2. Table 2 shows the characteristics evaluation results of the obtained biaxially stretched film.
Note that in Comparative Examples 1 to 3, no adhesion improving layer was applied.

The abbreviations for the types of adhesion-modifying layers in Table 2 are as follows.
AGE: Acrylic graft copolyester coating layer for adhesion modification layer.
PES: Polyester coating layer for adhesion modification layer.
PU: Polyurethane coating layer for adhesion modification layer.

As shown in Table 2, in Comparative Examples 1 to 3, in which the surface layer (layer B) contained 1% by mass or more of polyamide elastomer, the friction pinhole generation distance was shorter than 2900 cm, and the friction pinhole resistance was insufficient. Ta. Furthermore, as the content of polyamide elasmer in the surface layer (layer B) increased, unevenness in thickness became worse. The time it took for eye stains to appear on the lip surface of the die was also short.
On the other hand, in Examples 1 to 6 in which the content of the polyamide elastomer in the surface layer (layer B) was less than 1% by mass, the friction pinhole resistance was good. Furthermore, deterioration of film thickness unevenness could be suppressed. It took more than 24 hours for eye stain to appear on the lip surface of the die, and efficient production was possible. In Examples 1 to 6, since the base layer (layer A) contained 2.5% by mass or more of the polyamide elastomer, films with good bending pinhole resistance were obtained. Additionally, the presence of the adhesion-modifying layer provided a sufficiently strong waterproof laminate.

The easily adhesive polyamide film of the present invention has excellent impact resistance, bending pinhole resistance, and friction pinhole resistance, and has high quality with little thickness unevenness. Furthermore, since the film laminated with the sealant has high waterproof lamination strength, it can be suitably used as a packaging material for foods and the like.

Claims (4)

A polyamide-based resin is applied to both sides of a base layer (layer A) made of a polyamide resin composition containing a mixed resin of 97.5-80% by mass of polyamide 6 resin and 2.5-20% by mass of polyamide-based elastomer. A coating amount as a solid content is applied to at least one side of a laminated stretched polyamide film formed by laminating a surface layer (layer B) made of a polyamide resin composition containing 99 to 100% by mass of polyamide 6 resin and less than 1% by mass of polyamide elastomer. It has an adhesion-modifying layer (C layer) made of 0.01 to 3 g/m ² of polyester resin, polyurethane resin, and/or polyacrylic resin , and the thickness of A layer is the same as that of A layer and B layer. An easily adhesive polyamide film having a total thickness of 80 to 93% . The impact strength is 0.75J/15μm or more, the number of Gelbo pinhole defects is 5 or less when the twisting and bending test using the Gelbo Flex Tester is carried out 1000 times at a temperature of 1℃, and there are no pinholes in the friction pinhole test. The easily adhesive polyamide film according to claim 1, wherein the distance to occurrence is 3000 cm or more. The easily adhesive polyamide film according to claim 1 or 2, wherein the thickness of the B layer is at least 0.5 μm or more. The easily adhesive polyamide film according to any one of claims 1 to 3, wherein the polyamide resin composition constituting layer B contains 0.01 to 0.3% by mass of an antioxidant.