JPS5933114B2 - Composite film for packaging - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite film for packaging that has low gas permeability and water vapor permeability, excellent low-temperature impact resistance, and high modulus.

Plastic films made from various synthetic resins or composite films made by combining these synthetic resin films are used as packaging films, but each has advantages and disadvantages in performance.

For example, nylon film has relatively low gas permeability but high water vapor permeability, and its gas permeability changes depending on the influence of moisture. Composite films of nylon and polyethylene are commercially available, but although they have good pinhole resistance, thermal adhesion, and oil resistance, they are poor in gas permeability and modulus. Composite films made of nylon and unstretched polypropylene are used as transparent retort packaging materials, but they have poor gas permeability, bag strength after retort,
Poor thermal stability etc. during retort. The present inventors previously developed a block polyether amide, which is made by copolymerizing polyether with metaxylylene group-containing polyamide, as an inner layer, and one outer layer with a melting point of 170°C or higher and an initial elastic modulus of 10 kg.
/1 or more, and the other outer layer is a thermoplastic resin having a melting point lower than the melting point of the block polyether amide by 50°C or more, but this film has poor durability after retort treatment. It has been found that gas permeability becomes extremely poor depending on the combination of resins, resulting in the disadvantage that the contents cannot be stored for a long period of time. The present invention improves these drawbacks. The present invention uses meta-xylylene diamine or mixed xylylene diamine containing para-xylylene diamine in an amount of 30% by weight or less based on the total amount of meta-xylylene diamine, and a mixed xylylene diamine having 6 to 12 carbon atoms.
A polymer (A) containing at least 70 mol% of each residue from one or more α, ω mono-aliphatic dicarboxylic acids in its molecular chain (hereinafter abbreviated as polyamide 4 containing meta-xylylene groups) ) is used as one outer layer, and a resin (B) having a melting point of 150°C or more and an initial elastic modulus of 10 kg/1 or more is used as the center layer, and the melting point is higher than the melting point of any of the resins in (2) or (2) above. This is a packaging composite film characterized in that the other outer layer is a thermoplastic resin (C) having a melting point lower than 50°C.

The composite film for packaging of the present invention has particularly low gas permeability and water vapor permeability, strong transparency and modulus, excellent thermal stability during retort processing, and overall excellent properties. be. The packaging composite film of the present invention is particularly suitable as a retort food packaging film.

These foods are heated at 120 to 160℃ for 17!1i to sterilize them.
A wet heat treatment is performed for 40 min. For this reason, packaging materials are required to be resistant to hot water and have gas parity properties in order to preserve the contents for a long period of time. Films having compositions such as polyethylene terephthalate/aluminum foil/polypropylene, nylon-6/polypropylene, and polyethylene terephthalate/polypropylene are generally used as packaging materials for retort applications.

Films with a composition of polyethylene terephthalate/aluminum foil/polypropylene have good gas barrier properties and have a longer shelf life, but because aluminum foil is used, it is not possible to check the contents from the outside, causing consumer anxiety. It is one of the elements that makes it so. Furthermore, since the seal portion cannot be seen through, it is difficult to identify bags with defective seals during bag manufacturing. In addition, since aluminum foil is used, pinholes are likely to occur when packaging protrusions, and it is unsuitable for applications that require bending resistance. In the case of nylon-6/polypropylene, it has good transparency and bending resistance, so it is possible to check the contents and identify defective seals, and it is suitable for packaging with protrusions and packaging that requires bending resistance. , there is a problem with the storage period due to poor gas barrier properties. Polyethylene terephthalate/polypropylene has good hot water resistance and transparency, but has drawbacks in gas barrier properties and bending resistance. An object of the present invention is to provide a film that can withstand high temperature sterilization treatment conditions, has good transparency, and has excellent gas barrier properties and bending resistance.

The composite film of the present invention is not limited to retort pouch applications.
It is also applicable to applications requiring mild hot water resistance, for example, treatment at 80 to 100°C for about 30 minutes. Examples of the polyamide containing a xylylene group used in the present invention include polymethaxylylene adipamide, polymethaxylylene pimeramide, polymethaxylylene speramide, polymethaxylylene azeramide, polymethaxylylene sebaamide, and polymethaxylylene homopolymers such as dodecanediamide, etc., and metaxylylene/paraxylylene adipamide copolymers, metaxylylene/paraxylylene pimeramide copolymers, metaxylylene/paraxylylene speramide copolymers, metaxylylene/para Copolymers such as xylylene azeramide copolymer, metaxylylene/paraxylylene sebacamide copolymer, metaxylylene/paraxylylene dodecanediamide copolymer, etc., and components of these homopolymers or copolymers. and aliphatic diamines such as hexamethylene diamine, alicyclic diamines such as piperazine, aromatic diamines such as para-bis-1(2-aminoethyl)benzene, aromatic dicarboxylic acids such as terephthalic acid, and lactams such as ε-caprolactam. ,
Examples include copolymers obtained by copolymerizing ω-aminocarboxylic acids such as 7-aminoheptanoic acid, aromatic aminocarboxylic acids such as para-aminomethylbenzoic acid, and the like.

In the above copolymer, para-xylylene diamine accounts for 30% or less of the total xylylene diamine, and the constituent units formed from xylylene diamine and aliphatic dicarboxylic acid account for at least 70 mol% or more in the molecular chain. It is. Furthermore, the xylylene group-containing polyamide of the present invention has metaxylylene diamine or a mixed xylylene diamine component containing metaxylylene diamine and paraxylylene diamine in an amount of 30% or less of the total diamine amount, and has 6 to 6 carbon atoms. A copolymer consisting of a polyamide-forming component whose main dicarboxylic acid component is 12 α, ω monoaliphatic dicarboxylic acids, and a polyether having a molecular weight of 2,000 to 20,000 and having at least one terminal amino group or terminal carboxyl group. and a block polyether amide (hereinafter sometimes abbreviated as block polyether amide) in which the polyether content in the block polyether amide is 0.2 to 10% (by weight).

Examples of block polyetheramides include block copolymers of polyamide-forming components and polyether residues as shown below. [Polyamide-forming components] Polymethaxylylene adipamide, polymethaxylylene pimeramide, polymethaxylylene speramide, polymethaxylylene azeramide, polymethaxylylene sebacamide,
Homopolymers such as polymethaxylylene dodecanediamide, and polymethaxylylene/paraxylylene adipamide, polymethaxylylene/paraxylylene pimeramide,
Polyamide formation to form copolymers such as polymethaxylylene/paraxylylene peramide, polymethaxylylene/paraxylylene azeramide, polymethaxylylene/paraxylylene sebaamide, polymethaxylylene/paraxylylene dodecanediamide, etc. components, and these polyamide-forming components further include hexamethylene diamine, 2,
Aliphatic diamines such as 4,4-trimethylhexamethylene diamine, heterocyclic or heteroatom-containing diamines such as piperazine bispropylamine, neopentyl glycol pispropylamine, and aromatic diamines such as parabis(2-aminoethyl)benzene. Diamines such as group diamines,
Nylon salts with α,ω-aliphatic dicarboxylic acids having 6 to 12 carbon atoms or aromatic dicarboxylic acids such as terephthalic acid and isophthalic acid, or lactams such as ε-caprolactam, ε-aminocaproic acid, para-aminomethyl A polyamide-forming component containing a copolymer component such as an ω-aminocarboxylic acid such as a copolymer with benzoic acid.

In addition, when para-xylylene diamine is present in the constituent components in addition to metaxylylene diamine, the amount of metaxylylene diamine in the total xylylene diamine is 70 mol% or more to improve the coloring of the polymer. It is useful from the viewpoint of melt moldability. [Polyether residue] Molecular weight is 200
The polyether of 0 to 20,000 may be any polyether, but specifically, it is preferably a residue of a compound mainly represented by the following general formula.

However, Y: an alkylene group or a cycloalkylene group having 1 to 6 carbon atoms.

X, basis)
or a group into which NH2 is introduced, and at least one of X and X7 is an alkyl, aryl, or aralkyl group containing -COOH, COOR, or -N
The H2 group is always introduced.

n: - The molecular weight of the compound represented by general formula [A] is 2000
A number set to ~20000.

Specific examples of the group Y include -CH2, -ClI2-CH
-H (R2, R3: the same or different groups, H or -CH3), etc.

Specific examples of X,
Ethyl phenyl, propylphenyl, butylphenyl,
Alkylaryl groups such as nonylphenyl and 2,4-dimethylphenyl groups, aralkyl groups such as phenylmethyl, phenylpropyl, phenylbutyl, and phenyloctyl groups, or aminoethyl groups and aminopropyl groups, 2
- A group having an amino group such as a methylaminopropyl group or an aminoethylphenyl group; a group having a carboxyl group such as carboxymethyl, carboxyethyl, 2-carboxypropyl, carboxybutyl, or carboxyphenyl group; or a group having the above carboxyl group; It can indicate a group in which the carboxyl group of the group is esterified with methyl, ethyl, etc.

In addition, at least one of X and X' is an alkyl, aryl or aralkyl group with -COOH,
-COOR or a group into which one NH2 group is introduced. In the block polyether amide of the present invention, a polyether having a structural formula that is an arbitrary combination of these groups is used.

Furthermore, in the present invention, in addition to the single polyether or copolymer polyether represented by the above general formula [E], this polyether is used as the main structure, and furthermore, ester groups, amide groups, Alternatively, a block polyether may be formed into which a heterocyclic ring or the like is introduced.

Representative examples of these polyethers include diethylamino-N-polyoxetane, piperazine-N,N'-polyethylene oxide, cyclohexylamino N,N'-polyethylene oxide, polyethylene glycol dipropylamine, and polypropylene glycol dipropionic acid. , polytetrahydrofuran diamine, dipropylamine of polytetrahydrofuran/polyethylene oxide block copolymer, caprolactam-N-polyethylene oxide, meta-aminophenol ethylene oxide adduct, ethylene oxide adduct of resorcin, ethylene oxide adduct of aminothiophenol polyalkylene glycol tricyanurate, 2,4-N,
N/-distearylpolyethyleneoxyamino-6-p
-(sodiumsulfophenylamino)-s-triazine, N-polyethyleneoxyalkyl-2-octadecylsuccinimide, 2-phenyl-3-polyoxyalkylene imidazole, and the like.

These polyethers are copolymerized with polyamide-forming components as block polyether amide, but they are usually dispersed in the polymer as island components with a particle size of 10 μm or less when observed under a microscope. . Further, the molecular weight of the polyether needs to be 2,000 or more in order to improve refractive fatigue resistance and low-temperature impact resistance, and it needs to be 20,000 or less in order to have appropriate dispersibility.

A more preferable molecular weight range is 3,000 to 8,000. Also, the amount of polyether in the polyamide is 0.2wt
If the amount is less than 10 wt%, it is difficult to fully achieve the purpose of the present invention, and if the amount is more than 10 wt%, there is a limit to the effect and deterioration of physical properties is also observed, so it is not preferable.
In addition to polyamides containing metaxylylene groups, other polymers such as nylon 6, nylon 6.6, nylon 6.
10. Polyethylene terephthalate, polyolefin, etc., antistatic agents, lubricants, antifogging agents, antiblocking agents, stabilizers, ultraviolet absorbers, dyes, pigments, etc. may be appropriately contained.

In the present invention, the film laminated with the metaxylylene group-containing polyamide film to form the inner layer of the composite film has an initial elastic modulus of 10 kg/Md or more and a melting point of 1.
It is necessary that the film has a temperature of 50°C or higher.

Specific examples include polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polypropylene, nylon-6, nylon 6.6, and polyimide. The metaxylylene group-containing polyimide layer, which is the outer layer material, has excellent breaking strength and yield strength, and particularly has extremely excellent gas barrier properties, which can prevent discoloration and deterioration of the contents. Furthermore, since it has good pinhole resistance, it can be applied to contents with uneven or sharp protrusions. Moreover, as a bag making method, it can be used not only for ordinary flat bags but also for cassette bags where pinholes are likely to occur due to the folding of films. Furthermore, the composite film of the present invention has excellent transparency. Conventionally, composite films composed of polyester/aluminum foil/polyethylene or polypropylene have been commonly used in retorts, but in this case, Aj foil has excellent gas barrier properties and heat resistance, but has the fatal drawback of being opaque. I have it. For this reason, it is difficult to determine seal defects during bag manufacturing based on the appearance, and consumers cannot confirm the contents. The polymer forming another outer layer of the composite film of the present invention is 50°C or more lower than the melting point of the resin with the lower melting point of the polymer (4) forming one outer layer and the polymer (8) forming the inner layer. It is a thermoplastic resin with a melting point.

When the difference between the melting point or softening point of the polymer (C) and the melting point of the polymer with the lower melting point of the polymer (4) forming the outer layer and the polymer (3) forming the inner layer is not 50°C or more. is undesirable because it causes deterioration and shrinkage due to heat during thermal bonding.

The melting point or softening point of the above thermoplastic resin is usually 170°C
The thermoplastic resin used in the present invention is a homopolymer of α-olefin such as ethylene, propylene, butene, benzene, or a copolymer mainly composed of these. For example, ethylene/
Propylene copolymer, ethylene/butene-1 copolymer,
Ethylene/vinyl acetate copolymer, propylene/butene
1 copolymer and (metal crosslinkable polymer of ethylene-α,β-unsaturated carboxylic acid copolymer, copolymerized polyester,
Examples include low softening point polyamides.

To manufacture the composite film of the present invention: (1) A so-called dry lamination method in which individually manufactured films are laminated together.

(2) Extrusion lamination of one type of polymer onto a pre-made laminated film of two types of films;
This is the so-called extrusion lamination method.

(3) Co-extrusion lamination method of three types of materials.

This is a method of bonding inside the die, outside the die, and at the adapter part.In the case of the inside of the die and the adapter part, it is laminated bonding in a molten state.Furthermore, there is also a method of bonding the film once solidified using a heated roll, belt, etc. It can be done. (4) A method in which a metaxylylene group-containing polyamide uniaxially stretched film is laminated with another material in a solidified or molten state, and then stretched perpendicular to the stretching direction of the metaxylylene group-containing polyamide uniaxially stretched film. It can be done in other ways.

The composite film of the present invention has the excellent properties of gas permeability, high modulus, and transparency that are possessed by a metaxylylene group-containing polyamide film, as well as oil resistance, pinhole resistance, low temperature resistance, thermal stability during retort processing, etc. It has excellent properties.

It also has good thermal adhesion. Composite films with such comprehensive properties are suitable for packaging products that require mold resistance, fragrance retention, moisture resistance, and vacuum retention, and are suitable for various packaging such as vacuum packaging and pole-in packs. used for.

The present invention will be specifically explained below with reference to Examples. In the Examples, various properties of the film were measured as follows. (1
) Base: Conforms to JIS-K67l4.

(2) Young's modulus: According to JIS-11073. (3)
Pinhole resistance: Tie the film in a bag shape to the tip of a glass tube with a diameter of 1071LT1L, and apply 1k9/C to the glass tube.
! Pressure of 7L and vacuum are repeatedly applied at a rate of 15 times/minute, and the number of times until holes are generated in the film is expressed as the number of times. (4) Water vapor transmission rate: 4 according to JIS-ZO2O8
Measurement was performed in an atmosphere of 0° C. and 90% RH.

(5) Oxygen permeability: Measured at 30°C using a dual gas permeability meter manufactured by Rika Seiki Kogyo Co., Ltd. in accordance with ASTM-Dl434-58. Example 1 100 parts of a copolymerized polyester resin (Vylon 300 manufactured by Toyobo Co., Ltd.) was added to a biaxially stretched film (12 μ) obtained from polymethaxylene adipamide copolymerized with 2.5 weight e of polyethylene glycol having a molecular weight of 4000. 4.4 parts of Coronate L (manufactured by Nippon Polyurethane Co., Ltd.) was diluted to 30%, applied with a gravure roll of 100 meshes, dried, and made into a biaxially stretched polyethylene terephthalate film (Toyobo Co., Ltd.) with a thickness of 12μ. Still film) was attached.

Further, a 50 μm polyethylene film was attached to the other side of the polyester film in the same manner. As comparison products, biaxially stretched polyethylene terephthalate film (12μ) / aluminum foil (11μ) / polyethylene film (50μ) were made using the same lamination method...Comparative film A Biaxially stretched polyethylene terephthalate film (12μ) / polyethylene film (70μ) Comparative Film B Biaxially stretched nylon film (15 μm: manufactured by Unitika)/Polyethylene (70 μm) A laminated film having the structure of Comparative Film C was prepared.

A bag was made from these composite films, and a commercially available edible ham was placed in the bag, and the discoloration of the contents was examined after storage for one month. The degree of discoloration was visually judged and compared with a blank stored in a cool and dark place, and evaluated using the following standards. 10; No discoloration 8; Slight discoloration 6
; Discoloration 4: Significant discoloration 2: Severe discoloration The physical properties and storage test results of the composite film are shown below.

Example 2 A biaxially stretched polyether amide film obtained from polymethaxylylene adipamide copolymerized with 2.5% by weight of polyethylene glycol having a molecular weight of 4000 (
12μ), a 10:1 mixture of Nipporan 3016 and Coronate L (both manufactured by Nippon Polyurethane) and diluted with a mixed solvent of ethyl acetate and toluene (1:1) was applied and dried to a thickness of 12μ. A biaxially stretched polyester film was bonded thereto.

Claims (1)

[Claims] 1 Meta-xylylene diamine or mixed xylylene diamine containing meta-xylylene diamine and para-xylylene diamine in an amount of 30% by weight or less of the total amount, and a carbon number of 6 to 1
One outer layer is a polymer (A) containing at least 70 mol% of each residue from one or more of two α,ω-aliphatic dicarboxylic acids in the molecular chain, and the melting point is 150°C or higher. Resin with an initial elastic modulus of 10 kg/mm^2 or more (B
) as a center layer, and a thermoplastic resin (C) having a melting point lower than the melting point of either resin (A) or (B) by 50°C or more as the other outer layer. .