Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Patent
1995-07-29
1997-07-15
Merriam, Andrew E. C.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
524178, 524512, 523408, 523410, 523523, 525166, 525176, 525441, C09D16700, C09D13314, C08K 519, C08K 557
Patent
active
056484178
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a color coating composition having excellent mar resistance, acid resistance and superior appearance which is useful in top coats for automobiles as well as coil coatings.
PRIOR ART
Solid color coating compositions employing aminoplast as a curing agent are well known. However, when the aminoplast is employed as a sole curing agent, acid resistance of the coating film is poor at the site of the crosslinking, resulting in a coating film defect especially due to acid rain which is one of recent concern.
We have already proposed a curable resin composition which comprises (a) a polymer containing acid anhydride half ester groups and (b) a polymer having hydroxyl groups and epoxy groups. Since this coating composition employs an acid anhydride curing system, excellent acid resistance is achieved and the coating film defect due to the acid rain can be significantly improved. Nevertheless, this coating system is intended to be used basically as a clear coating, and no studies have been made with regard to a solid color coating composition containing pigments.
It is desired that a coating film obtained from a solid color coating composition has not only acid resistance mentioned above, but also superior appearance performance and excellent mar resistance. In addition, a coating composition should also be a high content of nonvolatile components. On the other hand, it is essential that the coating film has high crosslink density to achieve both of excellent acid resistance and excellent mar resistance. As a result, strain at the curing by baking is accumulated in the interface of the coating, resulting in the problem of reduced adhesion to an undercoat.
SUMMARY OF THE INVENTION
The present invention provides a solid color coating composition which provides a coating film having excellent mar resistance, excellent acid resistance, excellent adhesion to an undercoat and superior appearance which are achieved by incorporating a pigment dispersed in a particular pigment dispersing resin and a particular resin in particular amounts to the clear coating system already suggested by us.
Accordingly, the present invention provides a color coating composition which comprises:
(1) 10 to 60% by weight of one or more pigment dispersing resins selected from the group consisting of a polyester resin and derivatives thereof which are modified with a basic substance, wherein said resin has an acid value from 5 to 300 mgKOH/g(solid), a hydroxyl value from 5 to 300 mgKOH/g(solid), a number average molecular weight from 400 to 6,000, said polyester resin is prepared from acid component and alcohol component and said acid component contains not more than 25% by weight of an acid having a straight carbon chain with 12 or more carbon atoms based on the total monomer weight of the polyester resin;
(2) 1 to 40% by weight of an aminoplast;
(3) 5 to 60% by weight of a polymer having carboxyl groups and carboxylic ester groups, which is obtained by reacting (i) an acid anhydride-containing polymer obtained by copolymerizing (a) 15 to 40% by weight of an acid anhydride-containing ethylenically unsaturated monomer with (b) 60 to 85% by weight of other copolymerizable ethylenically unsaturated monomer, with (ii) a hydroxyl group-containing compound having 1 to 12 carbon atoms in the molar ratio of the acid anhydride/the hydroxyl group of 1/10 to 1/1;
(4) 5 to 60% by weight of a polymer having hydroxyl groups and epoxy groups obtained by copolymerizing (i) 5 to 70% by weight of a hydroxyl group-containing ethylenically unsaturated monomer having the structure of the formula (i): ##STR1## wherein R represents hydrogen or methyl group, X represents ##STR2## (Y is a straight or branched alkylene group having 2 to 8 carbon atoms, m is an integer from 3 to 7, and q is an integer from 0 to 4) or ##STR3## (R' represents hydrogen or methyl group and n is an integer of 2 to 50), (ii) 10 to 60% by weight of an epoxy group-containing ethylenically unsaturated monomer, and optionally (iii) 0 to
REFERENCES:
patent: 4339365 (1982-07-01), Becher et al.
patent: 4461870 (1984-07-01), Kanda et al.
Fushimi Akira
Miyazoe Seigo
Okude Yoshitaka
Yamada Atsushi
Merriam Andrew E. C.
Nippon Paint Co. Ltd.
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