JPH01149862A - Clear varnish composition - Google Patents

Abstract

PURPOSE:To obtain the title composition, containing a modified polyester resin prepared by reacting a specific saturated polyester resin with an ethylenically unsaturated bifunctional carboxylic acid and amino resin as a resin component and useful for external top coating of metallic cans, etc. CONSTITUTION:A composition obtained by containing (A) a modified polyester resin prepared by reacting (i) 100 pts.wt. hydroxyl group-containing saturated polyester resin with (ii) 0.5-30 pts.wt. ethylenically unsaturated bifunctional carboxylic acid or acid anhydride thereof in the presence of (iii) preferably 3-15 pts.wt. radical forming agent (e.g., benzoyl peroxide) and (B) an amino resin (e.g., melamine resin) as a resin component. Furthermore, the component (B) is blended in an amount of preferably 100-250 pts.wt. based on 100 pts.wt. component (A).

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention provides a clear coating with excellent paint gloss, retort resistance, and processability, useful as a top coating paint for the outer surface of metal cans, etc. The present invention relates to varnish compositions.

(Prior Art) Conventionally, clear varnish compositions used on the outer surface of metal cans include paint systems made of saturated polyester, oil-free alkyd resins, a combination of alkyd resins and amino resins, and acrylic resins and amino resins. Combination paint systems are known.

Among these, for acrylic-amino paints, the film hardness.

Although it has excellent gloss, the coating film has poor flexibility, which limits its use as a top coating for metal cans.

Furthermore, although paints using saturated polyester resins have excellent coating film flexibility, they are inferior to acrylic-amino paints in hardness, gloss, retort resistance, and the like. In addition, paints using alkyd resin have good gloss, but
It has the drawback that it has poor weather resistance and paint baking sometimes causes discoloration.

(Problems to be Solved by the Invention) The present invention eliminates the above-mentioned drawbacks of conventional clear varnish compositions, and improves coating film gloss, coating film flexibility that can withstand metal can processing, and retortability. The present invention provides a clear varnish composition with excellent water resistance.

[Structure of the invention]

(Means for Solving the Problems) That is, the first invention of the present application is based on 100 parts by weight of a saturated polyester resin containing a hydroxyl group.

A clear varnish characterized in that the resin component is a modified polyester resin and an amino resin obtained by reacting 0.5 to 30 parts by weight of an ethylenically unsaturated dicarboxylic acid or its acid anhydride in the presence of a radical generator. The second invention is a composition in which 0.5 to 30 parts by weight of an ethylenically unsaturated dihydric carboxylic acid or an acid anhydride thereof is added as a radical generator to 100 parts by weight of a saturated polyester resin containing a hydroxyl group. This is a clear varnish composition characterized in that the resin components are a modified polyester resin, a bisphenol type epoxy resin, and an amino resin reacted in the presence of the present invention.

In the present invention, the saturated polyester resin is a linear polyester having a molecular weight of 500 to 100,000 synthesized by an esterification reaction or transesterification reaction of a polyhydric carboxylic acid or its lower alkyl ester or anhydride with a polyhydric alcohol.

Polyvalent carboxylic acids that need to contain hydroxyl groups in order to carry out crosslinking reactions with saturated polyester resins and amino resins include succinic acid, adipic acid, pimelic acid, speric acid, and azelaic acid.

Cepatic acid, maleic acid, fumaric acid, itaconic acid.

It is selected from one or more aliphatic or aromatic divalent carboxylic acids such as phthalic acid, terephthalic acid, and isophthalic acid, and may also be used in combination with trivalent carboxylic acids such as trimellitic acid.

Polyhydric alcohols include 5, for example, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-
Propylene glycol, 1. 3-butylene glycol, tetramethylene glycol.

hexamethylene glycol, neopentyl glycol,
Trimethylolpropane, pentaerythritol, etc.1
Selected from one species or two or more species.

In the present invention, the modified polyester resin is one in which carboxyl groups are introduced into the polyester resin by reacting a saturated polyester with an ethylenically unsaturated dicarboxylic acid or its acid anhydride in the presence of a radical generator. Examples of ethylenically unsaturated dicarboxylic acids include itaconic acid,
Maleic acid.

Fumaric acid, etc., and acid anhydrides of these can also be used.

The ethylenically unsaturated dihydric carboxylic acid or its acid anhydride is used in an amount of 0.00 parts by weight per 100 parts by weight of the saturated polyester resin.
5 to 30 parts by weight are used. If the amount used is less than 0.5 parts by weight, the gloss of the coating film will not improve, and if the amount used is more than 30 parts by weight, the flexibility of the coating film will tend to decrease.

As the radical generator, peroxides such as benzoyl peroxide or a redox system in which these are combined with a reducing agent can be preferably used.

The amount of radical generator used is 10% of the saturated polyester raw material.
0.1 to 25 parts by weight, preferably 3 parts by weight
~15 parts by weight. If it is less than 0.1 part by weight,
Ethylenically unsaturated carboxylic acid or its acid anhydride cannot react sufficiently.

As a method for modifying the resin, a saturated polyester resin and an ethylenically unsaturated dihydric carboxylic acid or its acid anhydride are preferably dissolved in an organic solvent.

It can be obtained by sequentially adding a radical generator. The reaction temperature is higher than the temperature necessary to generate radicals, and preferably 200° C. or lower in order to suppress the esterification reaction between the hydroxyl groups in the polyester resin and the carboxylic acid. It is preferable to proceed with the reaction under reflux of an organic solvent having an appropriate boiling point in order to keep the reaction temperature constant. Examples of organic solvents include aromatic hydrocarbons such as toluene and xylene, ketone solvents such as methyl ethyl ketone and cyclohexanone, ester solvents such as ethyl acetate and butyl acetate, and their derivatives such as 2-ethoxyethanol and 2-ethoxyethyl acetate. There is an ether solvent,
A mixed solvent of these may be used.

The amino resin of the present invention is a melamine resin.

Examples include benzobunaamine resin. The amount of amino resin used is preferably 20 to 300 parts by weight per 100 parts by weight of the modified polyester resin.

It ranges from 100 to 250 parts by weight.

In the present invention, a bisphenol type epoxy resin can be blended in order to improve the processability of the coating film. These epoxy resins are bisphenol A type epoxy resins,
It is an epoxy resin such as bisphenol F type epoxy resin, and preferably has an epoxy equivalent of 180 to 700.

These epoxy resins include 7, for example Epicote 1001.
Commercially available products such as 828 can be used. The amount of bisphenol type epoxy resin used is 80 parts by weight or less, preferably in the range of 25 to 65 parts by weight, based on 100 parts by weight of the modified polyester resin.

The clear varnish composition of the present invention can be used as an organic solvent solution by blending a predetermined amount of a modified polyester resin, an amino resin, and, if necessary, a bisphenol type epoxy resin as a binder component. It is used by blending paint additives such as wax.

For coating, a conventional coating machine such as a natural coater or a reverse coater can be used, and the coating is applied to an aluminum substrate with a dry coating thickness of 3 to 20 μm.

The curing time is appropriately selected from 150 to 270°C and 0.5 to 20 minutes.

Examples will be described below. In the examples, "parts" indicate "parts by weight" and "%" indicate "% by weight."

(Example) Synthesis of saturated polyester resin (a) 18.5 parts of phthalic anhydride, 6.3 parts of adipic acid, 13.7 parts of ethylene glycol, 19 parts of neopentyl glycol
．． Two parts were placed in a reaction vessel and heated to 160 to 200° C. with stirring under a nitrogen stream to perform a transesterification reaction.

Gradually reduce the pressure in the reaction vessel at oxidation of 20 or less, and reduce the pressure to 1wHg or less.
Polyester resin (a) having hydroxyl groups at both ends was obtained by polymerizing under reduced pressure at 200° C. for 2 hours. Polyester resin (
The hydroxyl value of a) is 60. Acid value is 1.09, molecular weight is approximately 10
It was 00.

Synthesis of saturated polyester resin (b) 13.0 parts of isophthalic acid, 11.7 parts of phthalic anhydride.

10.0 parts of adipic acid, 19.0 parts of neopentyl glycol.
0 parts, 2.0 parts of 1,6-hexanediol, and 5.0 parts of trimethylolpropane were charged into a reaction vessel.

The transesterification reaction was carried out by heating to 160 to 200° C. while stirring under a nitrogen stream. The reaction was carried out until the acid value became 10 or less to obtain a mono-branched type saturated polyester resin (b). The hydroxyl value of the polyester resin (b) is 120. The acid value was 8.

Synthesis of Modified Polyester Resin (C) 100 parts of saturated polyester resin (a) and 2 parts of maleic anhydride were dissolved in 70 parts of a mixed solvent of equal amounts of butyl cellosolve and Tsurupez 150, and then 0.5 parts at 110°C.
A solution of 150 parts of benzoyl peroxide dissolved at a concentration of 10 parts was added dropwise.

After the completion of the stirring, the mixture was further stirred for 60 minutes to obtain a modified polyester resin (C).

Synthesis of modified polyester resin (d) Same procedure as for the synthesis of modified polyester resin (c) except that 5 parts of maleic anhydride and 10 parts of benzoyl peroxide were used for 100 parts of saturated polyester resin (a). A modified polyester resin (d) was obtained.

Synthesis of modified polyester resin (e) 100 parts of saturated polyester resin (b) and 10 parts of maleic anhydride are dissolved in 180 parts of cellosolve acetate, followed by dissolving 1 part of benzoyl peroxide to a concentration of 10 parts at 110°C. The cellosolve acetate solution obtained was added dropwise, and after the completion of the addition, the mixture was stirred for an additional 60 minutes to obtain a modified polyester resin (e).

Synthesis of modified polyester resin (f) Same procedure as for the synthesis of modified polyester resin (e) except that 5 parts of itaconic acid and 1 part of benzoyl peroxide were used for 100 parts of saturated polyester resin (b). A modified polyester resin (f) was obtained.

Example 1 100 parts of modified polyester resin (C), benzoguanamine resin (trade name, Hitachi Chemical Co., Ltd.).

Melan 326B) 100 parts, 30 parts of epoxy resin (Yuka Shell Epoxy Co., Ltd. trade name Epicote 1001) and 0.5 part of curing accelerator paratoluenesulfonic acid were mixed and prepared in a Ford cup #4 with butyl cellosolve for 100 seconds. It was coated with clear varnish.

E printed with this clear varnish using metal printing ink.
It was painted on a T plate and baked at 200°C for 5 minutes. The coating film thickness was 5μ.

Examples 2 to 7 and Comparative Examples 1 to 4 A clear varnish composition was prepared in the same manner as in Example 1 using a modified polyester resin, an epoxy resin, and an acrylic resin at the resin blending ratios shown in Table 1 below. It was created.

The gloss of the coating film was observed for the coated ET plates obtained on each side.

O...good △・・・Possible ×...Poor It was expressed as

Further, each coated plate was subjected to a retort treatment test at 125° C. for 30 minutes and a 3×3 camp punching test as a processing test, and the results were shown using the same criteria as above.

The test evaluations are shown in Table 1.

〔Effect of the invention〕

The clear varnish composition of the present invention can be formed into a coating film with excellent gloss and retort resistance without impairing the flexibility of the coating film, which is a characteristic of clear varnishes using polyester resin. .

Therefore, the clear varnish composition of the present invention is as follows.

It has all the physical properties required as an external top coating for metal cans and has high practical value.

Claims (1)

[Claims] 1. 0.5 to 30 parts by weight of an ethylenically unsaturated dihydric carboxylic acid or its acid anhydride is added to 100 parts by weight of a saturated polyester resin containing a hydroxyl group in the presence of a radical generator. A clear varnish composition comprising a modified polyester resin and an amino resin as resin components. 2. A modified polyester obtained by reacting 0.5 to 30 parts by weight of an ethylenically unsaturated dicarboxylic acid or its acid anhydride with 100 parts by weight of a saturated polyester resin containing a hydroxyl group in the presence of a radical generator. A clear varnish composition comprising a resin, a bisphenol type epoxy resin, and an amino resin as resin components.