JPS5880361A - Resin composition for powder coating - Google Patents

Abstract

PURPOSE:To provide the titled compsn. excellent in rapid curing, capable of forming a film excellent in mechanical strength at low temp. baking (about 140-160 deg.C), by mixing a polyepoxy compd., a polycarboxy compd., a phosphonate compd., and the like. CONSTITUTION:0.01-5pts.wt. phosphonate compd. of formulaI(wherein R is alkyl, aryl) and/or of formula II is added to 100pts.wt. mixt. (equiv. ratio of epoxy to carboxy group of about 0.5-1.5) of polyepoxy compd. (e.g., a bisphenol A diglycidyl ether type epoxy resin) and polycarboxy compd. (e.g., trimellitic acid or maleic anhydride) and mixed together. Then, the resulting mixt. is melt- kneaded at about 70-120 deg.C. Next, the kneaded mixt. is cooled and pulverized to yield a resin compsn. for powder coating.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a new and useful 11N composition for powder coatings, and particularly to a composition for forming powder coatings with excellent low-temperature curability.

Trial coating requires heating in a baking oven, as the powder coating is heated to melt and smooth it, while at the same time crosslinking and hardening it.

By the way, in response to the current demands for saving resources and energy, attempts have been made to lower the baking temperature as well as the furnace temperature, that is, to improve the curing properties of powder coatings.

If an attempt is made to improve the curing properties of the paint in order to satisfy such demands, the smoothness of the paint film will drop significantly, or the paint itself will react during storage, resulting in extreme cases. It is easy to cause various defects such as gelation, and it is extremely difficult to improve the curing properties of the paint while maintaining a balance between these various performances.

However, as a result of intensive research in view of the current situation as described above, the present inventors have developed a powder coating that has excellent curability, can be sufficiently crosslinked and cured even at low temperature baking of 140 to 160°C, and has excellent performance. The present invention was completed based on the discovery of a resin composition for use in the present invention.

That is, in the present invention, at least one compound selected from the group consisting of phosphonate compounds and phosphite compounds is added to 100 parts by weight of the resin component consisting of the polyepoxy compound^ and the polycarboxy compound B).
The object of the present invention is to provide a resin composition for a powder coating, which contains 01 to 5 parts by weight and has excellent low-temperature curability.

The polyepoxy compound referred to in the present invention is a compound having an average of at least two epoxy groups per molecule, and includes conventionally known epoxy lIwiI and glycidyl acrylate,
Glycidyl methacrylate, β-methyl! Examples include copolymers of glycidyl group-containing vinyl monomers such as lyxidyl methacrylate and other copolymerizable heptamers. Specific examples of the epoxy resin include bisphenol diglycidyl ether type epoxy resin, hydrogenated bisphenol type epoxy resin, ester type epoxy resin, P-oxybenzoic acid glycidyl ester ether, triglyfudylisocyanurate, and the like.

The polycarboxy compound referred to herein is a compound having an average of at least two carboxyl groups or at least one acid anhydride group per molecule, and includes low molecular weight polycarboxylic acids and their acid anhydrides, carboxyl groups, or Examples include polyester resins containing acid anhydride groups, and copolymers of carboxyl group-containing monomers such as acrylic acid, methacrylic acid, itaconic acid, and crotonic acid with other copolymerizable heptamers. Specific examples of these include trimellitic acid, pyromellitic acid, maleic acid, benzophenonetetracarboxylic acid, tetrahydroheptalic acid, methyltetrahydrophthalic acid or anhydrides thereof, cepacic acid,
Examples include aliphatic dibasic acids such as decanesiazide.

The polyepoxy compound and the polycarboxy compound can be arbitrarily combined to obtain a curable resin, but the equivalent ratio of the epoxy group to the carboxyl group is α5 to t5.
It is preferable to use the ratio within the range of .

On the other hand, the above-mentioned phosphonate compound and phosphite compound Q are compounds represented by the general formula % () and the general formula P - (OR)s (■) [However, R is as described above], respectively. Typical examples of 8 in the above formulas include alkyl groups such as methyl, ethyl, butyl, pentyl, hexyl, and octyl, and nuclear substituted or unsubstituted aryl groups such as phenyl, isopropylphenyl, and cresyl. It is.

In this case, R may be the same or different.

Further, R may be an alkoxyalkyl group such as ethoxyethyl or butoxybutyl, or a halogenated alkyl group such as chloropropyl or bromopropyl.

These compounds 4mC) can be used alone or in a mixture, but in the case of a mixture of 211[11], the total amount is 101 to 5 parts by weight per 100 parts by weight of the above-mentioned respective compounds and B). , preferably within a range of 0.5 to 11 parts by weight.

The powder coating of the present invention is prepared by tri-blending a polyepoxy compound, a polycarboxy compound, a flow control agent, a pigment, and other fillers, melting the mixture preferably at a temperature of 70 to 120"C, cooling it, and pulverizing it. obtained by

Apply the obtained powder coating to the substrate,
A coating film with excellent mechanical strength can be obtained by baking at 0°C.

The present invention will be explained below according to examples.
The lid is shown.

Synthesis Example 1 (Synthesis of Polyester Resin P-1) A mixture consisting of neopentyl glycol 1046@, 119 parts of 1,4-cyclohexane dimetatool, 1000 parts of dimethyl terephthalate and 11 parts of zinc acetate was added to the reaction system with methanol to be produced. Heat at 150℃ for 1 hour, 2 hours while removing it outside.
After reaction at 10°C for 2 hours, 47 parts of trimethylolpropane,
61,800 parts of terephthal and 15 parts of dibutyltin oxide were added and heated at the same temperature for 4 hours and then at 240°C for 10 hours to conduct dehydration condensation. Then, the temperature of the reaction mixture was lowered to 180°C, 613 parts of trimellitic anhydride was added, and the mixture was reacted at the same temperature for 3 hours to obtain polyester resin P-1 having a softening point of 125°C and an acid value of 62.

Synthesis Example 2 (Synthesis of Vinyl Polymer V-1) A mixture of 70 parts of xylene and 50 parts of butyl acetate was heated to 120°C, and 30 m of styrene, 20 parts of isobutyl methacrylate, 20 parts of methyl methacrylate, and glycidyl were added to the mixture. 30 parts of methacrylate, 3 parts of azobisisobutyronitrile
and 1 part of cumene hydroperoxide was added dropwise over 2 hours and kept at the same temperature for an additional 15 hours. After removing common agents until the non-volatile content was 995%, the softening point was 108°C, number average. A polymer v-1 with a molecular weight of 800 was obtained.

Examples 1 to 4, Comparative Example 1

Claims (1)

[Scope of Claims] Consisting of (A) a polyepoxy compound, (B) a polycarboxy compound, and at least one compound selected from the group consisting of (Q phosphonate compound and phosphite compound), and the above compound (4) A resin composition for a powder coating, characterized in that the above compound VQ is used in a range of 101 to 5 parts by weight based on 100 parts by weight of the total amount of the above compound (5).