JPH0715082B2 - Baking paint with excellent adhesion to polyolefin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Field of Industrial Application) The present invention relates to a baking paint having adhesiveness to polyolefins such as polyethylene and polypropylene.
The present invention relates to a baking paint having excellent properties such as workability, adhesion to an aluminum base material, and adhesion to a polyolefin in the application of coating on an aluminum plate base material and laminating polyolefin as a packing material to form a cap of a container.

(Prior Art) Conventionally, a polyolefin packing material is mainly used for a metal cap of a soft drink container, and an organic solvent in which a polyolefin resin is dispersed in order to protect the metal base material and to impart the adhesiveness of the polyolefin. Mold metal coating compositions have been used. Such paint is disclosed, for example, in Japanese Patent Laid-Open No. 50-1083.
No. 79, JP-A-51-124181, JP-A-54-80383, JP-A-54-71180 and the like.

However, when the metal base material of these paints is aluminum, the adhesiveness to the base material is insufficient, and therefore sufficient adhesion strength cannot be obtained even if polyolefin is laminated,
In addition, when the cap is molded, it has the drawback that cracks and blisters in the coating film occur in the processed part. Therefore, in the case of manufacturing an aluminum cap, it is the current situation that an aluminum plate is undercoated and an adhesive coating is applied on the aluminum plate to supplement the adhesiveness with an aluminum substrate. In order to reduce the complexity of the process for manufacturing the aluminum cap and to reduce the cost, there has been a demand for a polyolefin adhesive baking coating which has excellent adhesion to an aluminum plate without being subjected to an undercoating treatment.

(Problems to be Solved by the Invention) An object of the present invention is to have excellent adhesion to an aluminum base material, and the baked coating film has a strong adhesion to polyolefin and can be molded into a cap or the like. It is an object of the present invention to provide a baking paint whose coating film adhesion strength does not decrease even when processed.

[Structure of Invention]

(Means for Solving Problems) The present invention relates to an organic solvent, a bisphenol A type epoxy resin (A) and a phenol resin (B) dissolved in the organic solvent, and an acid dispersed in the resin solution. TECHNICAL FIELD The present invention relates to a baking coating having excellent adhesion to a polyolefin, which is characterized in that phosphoric acid or phosphoric acid ester is mixed in a composition comprising a polyolefin resin (C) having a valency.

Bisphenol A type epoxy resin (A) in the present invention
Is obtained by condensing epihalohydrin and bisphenol A up to a high molecular weight in the presence of an alkali catalyst, or by condensing epihalohydrin and bisphenol A into a constant molecular weight epoxy resin in the presence of an alkaline catalyst, and by combining the low molecular weight epoxy resin with bisphenol A. Is produced by a polyaddition reaction. In the present invention, the bisphenol A type phenoxy resin, which is a higher molecular weight compound produced by the same method as described above, may be used by substituting a part of the bisphenol A type epoxy resin. Particularly for applications requiring processability, it is preferable to blend a bisphenol A phenoxy resin.

The phenol resin (B) in the present invention is a carboxylic acid, p-cresol, m-cresol, p-ethylphenol, p-tert.
-Butylphenol, p-nonylphenol, bisphenol A and other phenols are obtained by reacting with formaldehyde in the presence of a basic catalyst.

Polyolefin resin (C) having an acid value according to the present invention
Is a random copolymer of an olefin such as ethylene, propylene or butene and a polymerizable unsaturated carboxylic acid such as acrylic acid or methacrylic acid, a graft copolymer, a homopolymer such as polyethylene or polypropylene, or an olefin copolymer. Modified polyolefins formed from unsaturated carboxylic acids such as maleic acid, fumaric acid, and itaconic acid, or polyethylene oxides having a carbonyl group introduced into the polymer by oxidation treatment of polyethylene or a polyethylene-based copolymer is there. Especially when polyethylene is used as packing material,
Oxidized polyethylene or acid-modified polyethylene having an acid value of 1 to 35 and a molecular weight of 2000 to 150,000 can be preferably used.

Polyolefin resin (C) having oxidation in the present invention
Is incorporated as a dispersion in the solvent-soluble resin solution. The addition method is to add a dispersion finely dispersed in an organic solvent in advance to the composition of the solvent-soluble resin solution, or to add it as a solution dissolved by heating in the solution and disperse it in the paint. .

In the baking paint of the present invention, of the above resin components, the epoxy resin (A) and the phenol resin (B) are dissolved in an organic solvent, and the oxidized polyolefin resin (C) is dispersed in the solution. Examples of the organic solvent include cellosolve solvents such as ethyl cellosolve and butyl cellosolve, aromatic hydrocarbon solvents such as xylene and toluene, ketone solvent such as cyclohexanone and methyl isobutyl ketone, alcohol solvent such as n-butanol and isobutanol. A mixed solvent appropriately selected from is preferably used.

The mixing ratio of each resin component of the baking paint of the present invention is 40 to 95 parts by weight of epoxy resin (A) and 5 to 60 of phenol resin (B).
It is preferable to use the polyolefin resin (C) in an amount of 5 to 60 parts by weight based on 100 parts by weight of the synthesized amount of parts by weight. The epoxy resin (A) contributes to processability, the phenol resin (B) is a curable component of the epoxy resin (A), and contributes to the adhesion of the coating film to the base material and the adhesion to the polyolefin, The polyolefin resin (C) contributes to the adhesiveness with the polyolefin.

The greatest feature of the baking paint of the present invention is to add phosphoric acid or phosphoric acid ester to the composition containing the above resin. Here, the phosphoric acid ester is an alkyl ester or an aryl ester such as phosphoric acid monoalkyl ester or phosphoric acid dialkyl ester. Phosphoric acid or phosphoric acid ester contributes to the adhesion between the metal base material and the resin, and the preferable blending amount is 0.01 to 3 based on 100 parts by weight of the total amount of the epoxy resin (A) and the phenol resin (B). Parts by weight. Epoxy resin (A) and phenol resin (B) when used in excess of 3 parts by weight
As a result of increasing the cross-linking density, the flexibility of the coating film is deteriorated and the workability is adversely affected.

In the present invention, the epoxy resin (A) and the phenol resin (B) can be pre-condensed in the presence of phosphoric acid or a phosphoric acid ester, and this pre-condensation improves the adhesiveness with the polyolefin and allows long-term storage. Less adhesion deterioration. The conditions for this precondensation are the reaction temperature
90 to 110 ° C. and a reaction time of 2 to 4 hours are preferable.

The baking paint of the present invention can be applied to a base material such as a metal plate, a metal foil, a laminate of metal and paper or a plastic film, by a usual coating machine such as a roll coater. Examples of metal plates include aluminum plates, treated steel plates such as tin-free steel, and various plated steel plates. The coating film thickness is preferably 5 to 7 μ. 180-210 as baking conditions
The temperature can be selected from 8 to 15 minutes.

The base material coated with the baking paint according to the present invention has adhesiveness to a polyolefin film or a molten resin. Polyolefins that can be adhered include polyethylene, polypropylene, polybutene, poly-2-
In addition to polyolefin resins such as methyl 5-pentene, ethylene-vinyl acetate, ethylene-vinyl acetate partially saponified products and the like are available. When laminating as a film, it is necessary to heat the coating substrate or film to a temperature sufficiently high to soften the polyolefin film to be laminated and press-bond it. This temperature is 130-1 for polyethylene film
70 ° C.

If desired, the baking paint of the present invention may contain a silicone-based or acrylic-based additive in order to improve coating suitability.

Examples will be described below. In the examples, "part" and "%" are "part by weight" and "% by weight", respectively.

(Example) Preparation of Epoxy Resin (a1) Solution 100 parts of Epicoat 1009 (bisphenol A type epoxy resin manufactured by Shell Chemical Co., Ltd.) and 100 parts of butyl cellosolve, xylene
It was dissolved in 100 parts of the mixed solution.

Preparation of phenoxy resin (a2) solution 100 parts of phenoxy PKHH (Bisphenol A type phenoxy resin manufactured by Union Carbide Co.) was added to 100 parts of butyl cellosolve.
Parts and xylene 100 parts.

Preparation of phenol resin (b1) solution 288 parts of bisphenol A, 225 parts of 40% n-butanol solution of formaldehyde and 17 parts of 25% ammonia water were reacted at 100 ° C for 5 hours, and then xylene, n-butanol and cyclohexanone were added. And dilute, then dehydrate and resin content 33.3%
To obtain a phenol resin (b1).

Preparation of polyethylene oxide resin (c1) solution Polyethylene oxide with density 0.96, average molecular weight 6500, and oxidation 20
After mixing and stirring 15 parts and 85 parts of xylene, the mixture was heated and dissolved at 120 ° C.

Preparation of carboxyl group-modified polyethylene resin (c2) solution 15 parts of polyethylene resin having a density of 0.92 and an average molecular weight of 95,000 and 85 parts of xylene are mixed and stirred, and dissolved by heating at 120 ° C, 1 part of maleic anhydride and 0.2 part of benzoyl peroxide. And react at 120 ° C for 1 hour. Modified polyethylene resin (c2)
A solution was obtained.

Example 1 Phosphoric acid 0.5 was added to a solution of 85 parts of epoxy resin (a1) and 15 parts of phenol resin (b1) and reacted at 100 ° C for 2 hours. After cooling, 20 parts of the solution was mixed with polyethylene oxide (c1) as a resin component to obtain a paint.

Practical Examples 2 to 6 A coating material was obtained by the same operation as above with the blending ratio of the resin components shown in Table I below. In Examples 6 and 7, the epoxy resin and the phenol resin were simply pre-condensed without being mixed.

Comparative Example 1 A paint was prepared in Example 6 without adding phosphoric acid.

Comparative Example 2 A coating material was prepared in the same manner as in Example 7 except that phosphoric acid was not added.

Roll-coat the paint prepared in each example on a 0.24 mm thick aluminum plate to a coating thickness of 5μ
After baking for one minute, a coated plate was obtained. Next, using this coated plate, bending workability, cap punching workability, work adhesion, and polyethylene adhesion were tested, and the results are shown in Table II.

The evaluation methods for each test method are shown below.

Bending processability After the coated plate was bent 180 °, the state of cracking of the coating film when a load of 2 kg was dropped from the height of 50 cm to the bent portion was evaluated by measuring the amount of electricity (mA).

Cap punching workability A coated plate is punched into a cap shape with a diameter of 3.8 mm and a depth of 5 cm, and the cracked state of the coating film in the processed part and the floating of the coating film are observed with a magnifying glass.
Very good (⊚), good (∘), little change (△), and significant change (×) were used for the graded evaluation.

Processing adhesion The side surface of the cap was subjected to a peeling test with cellophane tape, and the peeled surface of the coating film was measured.

Polyethylene Adhesion A polyethylene sheet was thermocompression-bonded to an uncoated plate at 150 ° C. for 10 seconds to measure the adhesive strength when a polyethylene with an adhesion width of 1 cm was peeled in a 90 ° direction by a tensile test.

[Effect of the Invention] When the baking paint of the present invention is directly applied to a metal plate, particularly an aluminum plate, and a polyolefin such as polyethylene or polypropylene is laminated on the coated surface, the metal plate and the polyolefin are firmly bonded together. Further, even if the coated plate is bent or punched, peeling does not occur between the metal plate and the coating film. In particular, the baking paint of the present invention does not require the undercoating of an aluminum plate, which has been indispensable in the past, and thus is advantageous in the process and greatly contributes economically.

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Claims (4)

[Claims] 1. An organic solvent, a bisphenol A type epoxy resin (A) and a phenol resin (B) dissolved in the organic solvent, and a polyolefin resin (C) having an acid value dispersed in the resin solution. In the composition
A baking coating with excellent adhesion to polyolefin, which is characterized by being mixed with phosphoric acid or phosphoric acid ester. 2. The baking paint according to claim 1, wherein the polyolefin resin (C) having an acid value is polyethylene oxide. 3. The baking paint according to claim 1, wherein an aluminum plate and a polyolefin are adhered to each other. 4. The baking paint according to claim 1, which is obtained by precondensing the bisphenol A type epoxy resin (A) and the phenol resin (B) in the presence of phosphoric acid or a phosphoric acid ester.