Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
1999-02-09
2001-07-24
Nakarani, D. S. (Department: 1773)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C428S418000, C428S446000, C428S447000, C428S450000
Reexamination Certificate
active
06265073
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a curable composition for top coating favorable for cars, industrial machines, steel furniture, interior and exterior decorations for constructions, household electric appliances, plastic goods, etc., and to articles coated with the composition. More precisely, the invention relates to a curable composition for top coating, which forms coating films having high acid resistance and scratch resistance, good outward appearance, and extremely excellent stain resistance and which has good thermal curability, and also to articles coated with it. The composition is especially favorable to top coating for cars.
BACKGROUND ART
For coating cars, industrial machines, steel furniture, interior and exterior decorations for constructions, household electric appliances, plastic goods and others, coating compositions consisting essentially of melamine resins such as alkydmelamines, acrylic melamines and the like have heretofore been used.
However, the coating compositions consisting essentially of such melamine resins are problematic in that they generate harmful formalin when cured. In addition, it is a more serious problem that the cured films produced by such melamine resins have poor acid resistance. These melamine resins are therefore often corroded, or etched, whitened or stained, by the acid rain caused by recent air pollution.
In order to solve this problem, coating compositions not containing melamine resins have been proposed (Japanese Patent Application Laid-Open (JP-A) Hei-3-287650 and Hei-2-45577). In those coating compositions, formed are ester bonds that act as crosslinking points, through reaction of an acid group with an epoxy group. Therefore, as compared with coating compositions consisting essentially of melamine resins, those not containing melamine resins have the advantage of forming coating films with good acid resistance and weather resistance.
Apart from the above, other studies have been made for using blends of hydrolyzable silyl group-having vinylic copolymers and acrylic polyols, or copolymers of hydrolyzable silyl group-having vinyl monomers and alcoholic hydroxyl group-having vinylic monomers in coating compositions (see JP-A Sho-63-132977).
The coating compositions comprising blends of hydrolyzable silyl group-having vinylic copolymers and acrylic polyols, or copolymers of hydrolyzable silyl group-having vinyl monomers and alcoholic hydroxyl group-having vinylic monomers are characterized in that they cure through stable siloxane or siloxy bonding to be formed by the reaction of the hydrolyzable silyl group and the alcoholic hydroxyl group, and, therefore, as compared with coating compositions consisting essentially of melamine resins such as acrylic melamines, alkydmelamines and the like, they form coating films having better acid resistance and weather resistance.
Generally, any of two types of metallic color finishing and solid color finishing are employed for finishing car bodies by top coating.
For the metallic color finishing 2-coat 1-bake method of heating and curing a coating composition, is generally employed coating a substrate with a metallic base coat followed by overcoating it with a clear coat of an acrylic melamine resin composition in an wet-on-wet system.
For the other solid color finishing, generally employed is a 1-coat 1-bake method of using an alkydmelamine resin composition, in which the composition is heated and cured to form top coating. For recent severe requirements for the properties of coating films, including, for example, finish appearance, weather resistance, acid resistance, scratch resistance and stain resistance thereof, a method of overcoating a solid color-finished substrate with a clear coat of an acrylic melamine resin composition or the like has been proposed.
The present invention has been made in consideration of the current situation noted above, and its object is to provide a curable composition for top coating, which has good thermal curability to form good coating films having well-balanced physical properties including good acid resistance, scratch resistance, weather resistance, outward appearance and recoating adhesiveness, and additionally having extremely excellent stain resistance, and also to provide articles coated with the composition.
DISCLOSURE OF THE INVENTION
The curable composition for top coating of the invention, which solves the problems noted above, comprises;
(A) 100 parts by weight of an epoxy group-having resin,
(B) from 0.001 to 100 parts by weight of a carboxyl group-having compound or resin, and
(C) from 1.0 to 100 parts by weight of a silicon compound of the following general formula (I) and/or its partially-hydrolyzed condensate:
(R
1
O)
4-a
SiR
2
a
(I)
wherein R
1
represents a hydrogen atom, an alkyl group having from 1 to 10 carbon atoms, an aryl group having from 6 to 10 carbon atoms, or an aralkyl group having from 7 to 10 carbon atoms; R
2
represents an alkyl group having from 1 to 10 carbon atoms, an aryl group having from 6 to 10 carbon atoms, an aralkyl group having from 7 to 10 carbon atoms, or an alkoxy group having from 1 to 10 carbon atoms; a represents an integer of from 0 to 2; and plural R
1
's may be the same or different, and plural R
2
's, if any, may also be the same or different.
In the curable composition for top coating noted above, it is desirable that the resin of the component (A) has at least 2 epoxy groups in one molecule and has an epoxy equivalent of from 240 to 2,000 g/mol.
In the curable composition for top coating noted above, it is also desirable that the component (A) is a vinylic copolymer, of which the main chain is substantially a vinylic copolymer chain, and which has at least 2 epoxy groups in one molecule and has at least one hydrolyzable silyl group of the following general formula (II) as bonded to the carbon atom at the main chain terminals and/or in the side chains in the molecule, and which has an epoxy equivalent of from 240 to 2,000 g/mol and a hydrolyzable silyl equivalent of from 500 to 7,000 g/mol:
wherein R
3
represents a hydrogen atom, or an alkyl group having from 1 to 10 carbon atoms; R
4
represents a hydrogen atom, or a monovalent hydrocarbon residue selected from an alkyl group having from 1 to 10 carbon atoms, an aryl group having from 6 to 10 carbon atoms and an aralkyl group having from 7 to IO carbon atoms; b represents an integer of from 0 to 2; and plural R
3
's may be the same or different, and plural R
4
's, if any, may also be the same or different.
In the curable composition for top coating noted above, it is more desirable that the component (A) additionally has at least one alcoholic hydroxyl group at the main chain terminals and/or in the side chains, and has an alcoholic hydroxyl equivalent of from 500 to 3,000 g/mol.
In the curable composition for top coating noted above, the component (A) may additionally have a monovalent organic group of a polyoxyalkylene group of the following general formula (III):
wherein R
5
and R
6
may be the same or different, and each represents a hydrogen atom or an alkoxy group having from 1 to 4; R
7
represents a hydrogen atom, or an alkoxy group having from 1 to 4; p represents an integer of from 2 to 4; and q represents an integer of from 1 to 200.
In the curable composition for top coating noted above, it is desirable that the component (B) is an oligomer compound having a molecular weight of not larger than 2,000, which is prepared through half-esterification of a polyol compound and an acid anhydride, and has at least 2 carboxyl groups in one molecule.
It is also desirable that the molar ratio of the epoxy groups in the component (A) to the carboxyl groups in the component (B) falls between 0.2/1 and 3.0/1 in terms of epoxy groups/carboxyl groups.
It is also desirable that the component (C) is a partially-hydrolyzed condensate of tetraalkyl silicates.
It is more desirable that the component (C) is a partially-hydrolyzed condensate of tetramethyl silicate and/or tetraethyl silicate, and has a weig
Inoue Masaharu
Kouno Yoshiyuki
Nakamura Seigo
Nanbu Toshirou
Jackson Monique R.
Jordan and Hamburg LLP
Kaneka Corporation
Nakarani D. S.
LandOfFree
Curable composition for top coating and articles coated... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Curable composition for top coating and articles coated..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Curable composition for top coating and articles coated... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2464095