JPH06102766B2 - Clear varnish composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention is a clear coating having excellent gloss, retort resistance, and processability, which is useful as a top coating coating for the outer surface of a metal can. Varnish composition.

(Prior Art) Conventionally, as a clear varnish composition used on the outer surface of a metal can, a saturated polyester, an oil-free alkyd resin or a paint system in which an alkyd resin and an amino resin are combined, or an acrylic resin and an amino resin are used. Combined paint systems are known. Of these, acrylic-amino paints are excellent in coating film hardness and gloss, but are inferior in flexibility of the coating film and are actually limited in their use as top coatings for metal cans.

Further, a coating material using a saturated polyester resin is excellent in the flexibility of the coating film, but is inferior in terms of hardness, gloss and retort resistance to the acrylic-amino coating material. In addition, although the coating using the alkyd resin has good gloss, it has the drawback that the weather resistance is poor and color burning occurs when the coating is baked.

(Problems to be Solved by the Invention) The present invention eliminates the above-mentioned drawbacks of the conventional clear varnish composition, and makes the coating film glossy, the flexibility of the coating film resistant to metal can processing, and the retort treatment. The present invention provides a clear varnish composition having excellent water resistance, which is resistant to water.

[Structure of Invention]

(Means for Solving Problems) That is, the first invention of the present application is that the ethylenically unsaturated divalent carboxylic acid or its acid anhydride is contained in an amount of 0.5 to 30 parts by weight per 100 parts by weight of a saturated polyester resin containing a hydroxyl group. A second aspect of the present invention is a clear varnish composition comprising a modified polyester resin obtained by reacting a part of a resin in the presence of a radical generator and an amino resin as a resin component.
Modified polyester resin obtained by reacting 0.5 to 30 parts by weight of an ethylenically unsaturated divalent carboxylic 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 bisphenol type A clear varnish composition comprising an epoxy resin and an amino resin as resin components.

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

The saturated polyester resin needs to contain a hydroxyl group in order to carry out a crosslinking reaction with the amino resin.

Polycarboxylic acids include, for example, aliphatic or aromatic compounds such as succinic acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, itaconic acid, phthalic acid, terephthalic acid, and isophthalic acid. One or more divalent carboxylic acids may be selected, and a trivalent carboxylic acid such as trimellitic acid may be used in combination.

Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, trimethylolpropane and pentaerythritol. It is selected from two or more species.

In the present invention, the modified polyester resin is one in which a saturated polyester is reacted with an ethylenically unsaturated divalent carboxylic acid or an acid anhydride thereof in the presence of a radical generator to introduce a carboxyl group into the polyester resin. As the ethylenically unsaturated divalent carboxylic acid, itaconic acid,
Maleic acid, fumaric acid, etc., and these acid anhydrides can be used as well.

The ethylenically unsaturated divalent carboxylic acid or its acid anhydride is used in an amount of 0.5 to 30 per 100 parts by weight of the saturated polyester resin.
Parts by weight are used. When the amount used is less than 0.5 parts by weight, the gloss of the coating film does not improve, and when the amount used is more than 30 parts by weight, the flexibility of the coating film tends to decrease.

As the radical generator, a peroxide such as benzoyl peroxide or a redox system combining these with a reducing agent can be preferably used. The amount of the radical generator used is 0.1 per 100 parts by weight of the saturated polyester raw material.
-25 parts by weight, preferably 3-15 parts by weight. If the amount is less than 0.1 part by weight, the ethylenically unsaturated carboxylic acid or its acid anhydride cannot sufficiently react.

As a method of modifying the resin, it is possible to obtain a resin by dissolving a saturated polyester resin and an ethylenically unsaturated divalent carboxylic acid or an acid anhydride thereof, preferably in an organic solvent, and successively adding a radical generator. it can. The reaction temperature is above the temperature required to generate radicals,
The temperature is preferably 200 ° C. or lower in order to suppress the esterification reaction between the hydroxyl group in the polyester resin and the carboxylic acid. It is preferable to allow the reaction to proceed under reflux of an organic solvent having an appropriate boiling point in order to keep the reaction temperature constant. 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 ethers such as 2-ethoxyethanol and 2-ethoxyethyl acetate. There are system solvents, and mixed solvents of these may be used.

Examples of the amino resin of the present invention include melamine resin and benzognaamine resin. The amount of the amino resin used is 20 to 300 parts by weight, preferably 100 to 250 parts by weight, based on 100 parts by weight of the modified polyester resin.

In the present invention, the bisphenol type epoxy resin can be added in order to improve the processability of the coating film. These epoxy resins are bisphenol A type epoxy resins,
An epoxy resin such as a bisphenol F type epoxy resin, preferably having an epoxy equivalent of 180 to 700. These epoxy resins are, for example, Epicoat 100
Commercially available products such as 1,828 can be used. The amount of the bisphenol type epoxy resin used is 80 parts by weight or less, preferably 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 mixing a modified polyester resin, an amino resin and, if necessary, a bisphenol type epoxy resin in a predetermined amount as a binder component. , Blended with paint additives such as wax.

A normal coating machine such as a nachoral coater or a reverse coater can be used for coating, and a dry coating film thickness of 3 to 20 µ is coated on an aluminum substrate. Curing time is 150-270
The temperature is appropriately selected from 0.5 to 20 minutes.

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

(Example) Synthesis of Saturated Polyester Resin (a) Phthalic anhydride 18.5 parts, adipic acid 6.3 parts, ethylene glycol 13.7 parts, neopentyl glycol 19.2 parts were charged into a reaction vessel and stirred under a nitrogen stream at 160 to 200. It heated at 0 degreeC and transesterified. Gradually depressurize the reactor at oxidation of 20 or less and polymerize under reduced pressure of 1 mmHg or less at 200 ° C for 2 hours.
A polyester resin (a) having hydroxyl groups at both ends was obtained. The hydroxyl value of polyester resin (a) is 60 and the acid value is 1.
0, the molecular weight was about 1000.

Synthesis of saturated polyester resin (b) Isophthalic acid 13.0 parts, phthalic anhydride 11.7 parts, adipic acid
10.0 parts, neopentyl glycol 19.0 parts, 1,6-hexanediol 2.0 parts, and trimethylolpropane 5.0 parts were charged into a reaction vessel and heated to 160 to 200 ° C with stirring under a nitrogen stream to carry out a transesterification reaction. . The reaction was carried out until the acid value became 10 or less to obtain a branched type saturated polyester resin (b). The hydroxyl value of polyester resin (b) is 120 and the acid value is 8
Met.

Synthesis of modified polyester resin (c) 100 parts of saturated polyester resin (a) and maleic anhydride 2
Parts of butyl cellosolve and Solvesso 150 mixed solvent 7
Dissolve it in 0 part, and then add 110 parts of 0.5 parts benzoyl peroxide dissolved in 10% concentration of Solvesso 150 solution dropwise and stir for another 60 minutes after completion to obtain modified polyester resin (c). It was

Synthesis of modified polyester resin (d) By the same operation as the synthesis of modified polyester resin (c) except that maleic anhydride was changed to 5 parts and benzoyl peroxide was changed to 10 parts per 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 maleic anhydride 10
Part was dissolved in 180 parts of cellosolve acetate, and then 110 parts of benzoyl peroxide at 10% concentration of cellosolve acetate solution was added dropwise at 110 ° C.
The mixture was stirred as it was for minutes to obtain a modified polyester resin (e).

Synthesis of modified polyester resin (f) Modified by the same procedure as the synthesis of modified polyester resin (e) except that itaconic acid was changed to 5 parts and benzoyl peroxide was changed to 10 parts per 100 parts of saturated polyester resin (b). A polyester resin (f) was obtained.

Example 1 100 parts of modified polyester resin (c), benzoguanamine resin (trade name of Hitachi Chemical Co., Ltd., Melan 326B) 100
Part, an epoxy resin 30 parts (Yukaka Shell Epoxy Co., Ltd., trade name Epicoat 1001) and 0.5 parts of a curing accelerator paratoluene sulfonic acid were mixed, and butyl cellosolve was prepared in a Ford cup # 4 for 100 seconds to prepare a clear varnish.

ET printed with this clear varnish with metal printing ink
The board was painted 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 by the same procedure as in Example 1 using the modified polyester resin, epoxy resin and acrylic resin in the resin compounding ratios shown in Table 1 below, and then coated plates were prepared. Created.

The coated ET plate obtained in each example was observed for the gloss of the coating film, and was expressed as ○ ・ ・ ・ Good △ ・ ・ ・ Poor × ・ ・ ・ Poor.

In addition, each coated plate was subjected to a retort treatment test at 125 ° C for 30 minutes, and a 3 x 3 cap was punched as a processing test, and the results are shown on the same basis as above.

The test evaluations are shown in Table 1.

〔The invention's effect〕

The clear varnish composition of the present invention can be formed into a coating film excellent in gloss and retort resistance without impairing the flexibility of the coating film which is a characteristic of the clear varnish using a polyester resin. . Therefore, the clear varnish composition of the present invention has various physical properties required as an outer top coating of a metal can and has high practical value.

Claims (2)

[Claims] 1. A saturated polyester resin containing a hydroxyl group 10
A modified polyester resin and an amino resin obtained by reacting 0.5 to 30 parts by weight of an ethylenically unsaturated divalent carboxylic acid or its acid anhydride in the presence of a radical generator are used as resin components. A characteristic clear varnish composition. 2. A saturated polyester resin containing a hydroxyl group 10.
Modified polyester resin, bisphenol epoxy resin, and amino resin obtained by reacting 0.5 to 30 parts by weight of an ethylenically unsaturated divalent carboxylic acid or acid anhydride in the presence of a radical generator with respect to 0 parts by weight. A clear varnish composition characterized by being a component.