JPS59206457A - Coating composition for food packaging film - Google Patents

Abstract

PURPOSE:To provide the titled compsn. capable of imparting gas barrier properties, moisture proofness and printability to food packaging films, consisting of a polyester contg. sulfonate salt groups and a vinylidene chloride copolymer. CONSTITUTION:A filler, a crosslinking agent, a coupling agent, etc. are added if necessary, to a compsn. consisting of 90-10wt% sulfonate salt group-contg. polyester having a sulfonate salt group content of 0.0005-30mol% and an intrinsic viscosity of 0.1-2 and 10-90wt% vinylidene chloride copolymer composed of 95-60mol% of vinylidene chloride and 5-40mol% of other copolymerizable monomer such as acrylic acid to obtain a coating compsn. The compsn is dissolved in a solvent such as ethylene glycol and applied to a food packaging film in such a quantity as to give a film thickness of 0.5-5mu, and the film is then dried.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating composition that imparts gas barrier properties, moisture resistance, and printability to various food packaging films by coating or laminating them.

Polypropylene, polyester, and other films used for food packaging do not necessarily have sufficient gas barrier and moisture-proof properties when used alone, so it has long been possible to coat them with blends of vinylidene chloride copolymers and other resins. It is being said.

However, such conventionally known compositions do not necessarily have sufficient adhesion, and when used for food packaging, it is often required to directly print on the coated surface. However, in the food packaging industry, there are products with excellent printing aptitude,
There is a need for a coating material that also has adhesion to the substrate, gas barrier properties, and moisture proofing properties.

However, as a result of various studies in view of the above-mentioned problems, the inventor Zero has found that when using a composition mainly composed of a sulfonic acid group-containing polyester and a vinylidene chloride copolymer as a coating material, sufficient gas barrier properties and moisture proofing properties can be obtained. The present inventors have discovered that scales can be applied to a substrate, and that they can also improve adhesion to a substrate and provide excellent printability, leading to the completion of the present invention.

The composition of the present invention will be specifically explained.

First, the sulfonic acid group-containing polyester used in the present invention usually has an intrinsic viscosity of 0.1 to 2, preferably 0.6 to 1.
Any linear or branched 414 fat of 5 may be used. As a method for introducing a sulfonic acid group into polyester, conventionally known methods are used as appropriate, but representative methods are listed below: A method of reacting polyhydric alcohols.

2) A polybasic acid or a polyhydric alcohol having an unsaturated bond is reacted with a polybasic sulfite to form a polybasic acid or a polyhydric alcohol containing a sulfonic acid group, and this is mixed with a polybasic acid or a polyhydric alcohol containing an unsaturated bond. Method of reaction 1. 6) A method of adding acidic sulfite to unsaturated bonds in unsaturated polyester.

4) A method in which a compound having an epoxy group and an acidic sulfite are reacted to form a polyfunctional monomer containing a sulfonic acid group, and this is reacted with a polybasic acid or a polyhydric alcohol.

etc. can be mentioned. In the polyester, the sulfonic acid group in the resin is usually 0.0005 to 60 mol%, preferably 0.001% by mole, from the viewpoint of water resistance of the coating composition.
It is preferable to introduce it in a range of 10 mol %.

Next, vinylidene chloride-based copolymers generally have a molar ratio of vinylidene chloride monomer and other copolymerizable monomers of 95:
5-60: 40 is used. If the proportion of vinylidene chloride monomer is 95 mol % or more, the compatibility with the polyester containing the sulfonic acid group and the solvent decreases, and the composition becomes unusable. On the other hand, if it is less than 60 mol %, gas barrier properties and moisture proof properties deteriorate, making it undesirable. There are no particular restrictions on the copolymerizable monomer as long as it is copolymerizable with vinylidene chloride monomer, but generally acrylic acid, methacrylic acid, crotonic acid, incrotonic acid, etc. or alkyl esters thereof are used. , modified products such as acrylonitrile and methacrylonitrile, itaconic acid, maleic acid, fumaric acid, curtaconic acid, etc. or their monos, or dialkyl esters or anhydrides, as well as vinyl acetate, vinyl chloride, vinyl bromide, vinylidene bromide, etc. Any monomer of can be used.

In the present invention, the above-mentioned sulfonic acid group-containing polyester and vinylidene chloride copolymer are mixed in a ratio of 90:10 to +0:
90 (weight ratio), preferably 70:60 to '50 near 0
(weight ratio), it is possible to expect particularly excellent performance in various physical properties on average. However, the invention is not limited to this scope.

The pigment dispersibility of the coating composition of the present invention is also significantly improved by the introduction of the sulfonic acid group, so even if known fillers, crosslinking agents, and coupling agents are added, there will be no problem in coating workability. A uniform coating film can be obtained. Such fillers include colloidal silica, titanium oxide,
Lucium carbonate, talc, lithopone, baritum sulfate, lucium sulfate, alumina, clay, carbon black,
Phthalocyanine blue, navy blue, ultramarine, and lakey.

Examples include rho, yellow lead, orca yellow, hand yellow, Benkara, lake red, chrome permillion, phthalocyanine green, bentonite, organic hentonite, quartz powder, diatomaceous earth, glass powder, and asbestos. Further, as the crosslinking agent, known ones having functional groups such as incyanate group, carboxyl group, and epoxy group in the molecule, such as tolylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, trinotyrolpropane-tolylene diisocyanate adduct,
Polymethylene polypuenyl isocyanate, succinic acid,
Glucuric acid, adipic acid, pimelic acid, azelaic acid,
7Tallic acid, isophthalic acid, terephthalic acid, bisphenol
/l/A type diglycidyl ether, triglycidyl isocyanate, etc. are used. Furthermore, examples of the coupling agent include known coupling agents such as titanium, aluminum, and silicone.

Further, in the present invention, there is no problem in adding resins other than the sulfonic acid group-containing polyester and the vinylidene chloride copolymer as long as the effect is not lost. Such resins include vinyl chloride copolymers, acrylic copolymers, methalylic copolymers, styrene copolymers, acrylonitrile copolymers, polyamide resins, polyvinyl butyral, cellulose derivatives, and known resins that do not contain sulfonic acid groups. Examples include polyester, Aminoki 1"6, phenol umetsuji, epoxy epoxy, and silicone epoxy.

The composition of the present invention takes advantage of its gas barrier properties, moisture resistance, adhesion to substrates, and printability to coat substrate films used in the food packaging field. Examples of such base films include polyester films such as polypropylene, polyethylene, polyethylene terephthalate, polybutylene terephthalate, etc., and metal vapor-deposited films in which metal foil such as aluminum, gold, silver, tin, nickel, etc. is vapor-deposited on one or both sides of these films. can be used up.

When coating the base film with the coating composition, the coating method is arbitrary. Typically, there are two methods: one is to dissolve the coating composition in a solvent and apply it to the base film as a solution, and the other is to form a coating composition into a film and laminate it onto the base film, but the former is usually adopted from the viewpoint of workability. be done.

When coating a coating composition containing a sulfonic acid group-containing polyester or a vinylidene chloride copolymer as a main component, it is usually dissolved in a known solvent.

Such solvents are not particularly limited, but typically include methanol, ethanol, propatool, lower alcohols such as methanol, ethylene glycol, propylene glycol, gtylene gelylcol, 1,4-butanediol, and 1,5-butane. Polyhydric alcohols such as diols,
Ketones such as acetone, methyl ethyl ketone, dimethyl ketone, diethyl ketone, methyl isobutyl ketone, ethyl isobutyl ketone, lower alkyl esters such as methyl acetate, ethyl acetate, propyl acetate, aromatic hydrocarbons such as benzene, toluene, xylene, etc. Chlorine-containing solvents such as chloride, methylene chloride, chloroform, ethylene dichloride, trichloroethylene, and tetrachloroethane, and solvents such as dimethyl hexaran and tetrahydrofuran can also be used.

As a coating method, commonly known brush coating, roll coating, and spray coating can be arbitrarily employed. In addition, from the viewpoints of economical efficiency and coating film performance, it is usually preferable to apply the coating amount so that the film thickness is 0.5 to 5 .mu.m.

When the coating composition is formed into a film and then laminated onto a base film, a well-known method can be used, such as forming a sheet with a thickness of 5 to 20 μm and laminating it onto the base material using pressure bonding or a known adhesive. However, the composition and the base film may be coextruded and laminated.

However, the food packaging film coated with the above composition can be used for fish,
By packaging all kinds of food, including living things such as vegetables and meat, the freshness of the contents can be maintained, and the price, product name, etc. can be printed directly on the film, which is very useful.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, unless otherwise specified, "Chubu" or "%" refers to
It is based on weight.

Further, the intrinsic viscosity of the polyester resin is a value measured at 60° C. using a mixed solution of phenol and tetrachloroethane in a ratio of 1:1 (weight ratio).

Example 1 A composition consisting of a sulfonic acid group-containing polyester and a vinylidene chloride copolymer Saran R202 (trade name, manufactured by Asahi Kasei Corporation) as shown in Table 1 was used as a solvent to prepare a 1/1 (weight ratio) mixed solvent of toluene/methyl ketone. 80 parts were used for dissolution. Thereafter, additives as shown in the same table were added as necessary and dispersed using a high-speed disperser to obtain a coating composition.

The resulting coating composition was applied to a film (thickness: 20 .mu.m) made of the materials shown in Table 1 at a dry film thickness of 1 to 2 .mu.m. Coating was performed using a roll coater, and drying was performed by passing through a hot air oven at an oven temperature of 80° C. for 60 seconds.

Tests were conducted on the adhesion of the composition to the base film, suitability for printing with various inks, gas barrier properties, moisture resistance, and workability during coating.

The results are shown in Table 2.

Comparative Example The composition shown in Table 1 was used as a coating composition in the same manner as in Example 1, and was applied to a base film under the same conditions to examine various performances.

The results are also shown in Table 2.

Example 2 Sulfonic acid group-containing polynisdel (intrinsic viscosity: 0.8
, sulfone em group content: 0. + -e tv
%), 10 parts of the above Saran R202 was laminated as a 5μ thick film onto a biaxially oriented polypropylene film. When this film was tested in the same manner as in Example 1, excellent performance was obtained, with adhesion to substrates being 4, UV ink printability being 5, gas/clear properties being 2, and moisture proofing being 2.

Example 5 Sulfonic acid group-containing polynisdel (intrinsic viscosity: 0.5,
Sulfone em group-containing 9fk: 10 mol%) 10 parts,
10 parts of Saran R202 was blended and coextruded with biaxially oriented polypropylene to a thickness of 2μ to produce a 20μ extruded film. The physical properties of this film showed excellent performance such as adhesion to substrates: 5, UV ink: 5, gas barrier properties: 6, and moisture resistance: 7.

The performance test was conducted as follows.

Adhesion to the base film: Use a sharp blade to reach the base film by 2 tm x
100 base marks of 2 tnm are applied, and these are suitable for printing with various inks. For oil-based inks and water-based inks, after printing with each ink, it is released for 15 seconds, and the same base marks as in the case of adhesion are applied to the printed surface, This was peeled off with cellophane tape and evaluated on a five-point scale (5: no peeling, 4: peeling less than 10%, 3: peeling less than 10-20%, 2: peeling 0-less than 40%,
1: peeling of 50% or more).

Regarding the printing suitability of UV ink, print on the painted surface using commercially available acrylic Frethane type UV ink O...
) Irradiation was performed for 60 seconds using an irradiation device equipped with a filter lamp. This was subjected to the same treatment as in the case of the adhesion of the base film, and evaluated on a 5-point scale (5: base marks completely remained, 4: peeling 10
Less than %, 3: Peeling less than 20%, 2: Peeling 50-40
%, 1: peeling of 50% or more).

O Gas Barrier Property (Oxygen Permeability) The oxygen permeability was measured at 25° C. and 75% RH using a gas permeability measuring device manufactured by Mocon Oxtran.

0 moisture proof It was measured by the method shown in JIS-20208.

Claims (1)

[Claims] A coating composition for food packaging film comprising a sulfonic acid group-containing polyester and a vinylidene chloride copolymer as main components.