Powder coatings

Details Powder coatings Powder coatings

1995-03-28

1997-06-17

Short, Patricia A.

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Ethylenically unsaturated reactant admixed with either...

525167, 525170, 525176, 525186, 525190, 525438, 525449, 525530, 525533, 525934, C08L 3700, C08L 6300, C08L 6700, C08L 7302

Patent

active

056398212

DESCRIPTION:

BRIEF SUMMARY
The invention relates to powder coatings which provide coating films having excellent properties, and in particular coating films of high flexibility with a high degree of hardness.
Powder coatings are known. Since they contain no solvents, they can be used for coating in an especially environment-friendly manner. The coating films which can be produced using powder coatings, however, remain in need of further improvement in terms of their properties.
The object on which the present invention is based consists in the provision of new powder coatings which can be used to produce coating films which, in relation to the prior art, have improved properties, and in particular a higher flexibility and a higher degree of hardness.
This object is achieved, surprisingly, by the provision of powder coatings which contain as film-forming material a mixture of epoxide groups and may contain ethylenically unsaturated double bonds, or of a mixture of such epoxide group-containing synthetic resins, carboxyl groups and may contain ethylenically unsaturated double bonds, or of a mixture of such carboxyl group-containing compounds, ethylenically unsaturated double bonds and is different from (A) and (B), or of a mixture of such compounds, and polymerizations or of a mixture of initiators for free-radical polymerizations, mixture of components (A), (B), (C) and (D) containing from 0.1 to 6.0 mol of ethylenically unsaturated double bonds per 1000 g of mixture.
Using the powder coatings provided in accordance with the invention it has, surprisingly, been possible to produce coating films which, in relation to the prior art, have improved properties, and in particular higher flexibilities and higher degrees of hardness.
EP-A-38 635 describes powder coatings which contain, as film-forming material, a synthetic resin containing epoxide groups and a linear polyester containing carboxyl groups. Coating films prepared using these powder coatings possess, in comparison to coating films which have been produced using the powder coatings provided in accordance with the invention, poorer properties, and in particular poorer flexibilities and degrees of hardness.
The film-forming material of the powder coatings according to the invention comprises from 19.9 to 90.0 percent, preferably from 39.9 to 80.0 percent and particularly preferably from 49.9 to 70.0 percent by weight of component (A), from 9.9 to 80.0 percent, preferably from 19.9 to 60.0 percent and particularly preferably from 29.9 to 50.0 percent by weight of component (B), from 0 to 20 percent, preferably from 0.5 to 10.0 percent and particularly preferably from 1.0 to 5.0 percent by weight of component (C) and from 0.1 to 3.0 percent, preferably from 0.2 to 2.0 percent and particularly preferably from 0.5 to 1.5 percent by weight of component (D), the percentages by weight being based on (A)+(B)+(C)+(D)=100% by weight and the mixture of components (A), (B), (C) and (D) containing from 0.1 to 6.0 mol, preferably from 0.2 to 4.0 mol and particularly preferably from 0.3 to 2.5 mol of ethylenically unsaturated double bonds per 1000 g of mixture.
As component (A) it is possible in principle to employ any synthetic resin which contains epoxide groups and may contain ethylenically unsaturated double bonds, which can be employed for the production of powder coatings and has a melting point of from 20.degree. to 100.degree. C., preferably from 30.degree. to 80.degree. C. and particularly preferably from 30.degree. to 60.degree. C., or a mixture of such synthetic resins. Examples of epoxide group-containing synthetic resins which may be employed are epoxide group-containing polyacrylate resins, polyglycidyl ethers of aliphatic or cycloaliphatic alcohols such as ethylene glycol, diethylene glycol, 1,2-propylene glycol, 1,4-butylglycol, 1,2-cyclohexanediol, 1,4 cyclohexanediol, 1,2-bis(hydroxymethyl)cyclohexane and hydrogenated bisphenol A, or polyglycidyl ethers of polyphenols such as bisphenol A, 1,1-bis(4-hydroxyphenyl)ethane and 2-methyl-1,1-bis(4-hydroxyphenyl)propane, and the compou

REFERENCES:
patent: 3508951 (1970-04-01), Shimp
patent: 3660371 (1972-05-01), Johnson et al.
patent: 4891403 (1990-01-01), Farris

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