Stock material or miscellaneous articles – Composite – Of polyester
Reexamination Certificate
2002-10-29
2004-08-10
Short, Patricia A. (Department: 1712)
Stock material or miscellaneous articles
Composite
Of polyester
C428S458000, C525S131000, C525S176000, C525S166000
Reexamination Certificate
active
06773819
ABSTRACT:
This invention relates to paint compositions for motorcars, which are capable of forming cured coating excelling in resistance to scratches, mars caused by car-washing machines and acid.
Recently mars on motorcar bodies incurred by car-washing machines which now are more widely used, scratches around keyholes, and furthermore etching and stains caused by acid precipitation have emerged as problems in coatings for motorcars, and their solution is in demand. The demand is particularly strong among car users who place more importance on outer appearance of cars.
Consequently, in the field of automobile production, development of paint compositions for motorcars capable of forming cured coating concurrently meeting the three performance requirements, i.e., scratch resistance, resistance to mars incurred by car-washing machines (scrub resistance) and acid resistance, is now one of important subjects for raising commercial value of motorcars. A number of proposals have heretofore been made with the view to solve the problem.
For example, JP-Hei 2 (1990)-222753A disclosed improvement in scrub resistance of the coating by concurrent use of acrylic resin of high hydroxyl value and monomeric melamine resin, which are baked in the presence of acid catalyst to form coating of high crosslinking density. This crosslinked system, however, has a defect that the formed coating is inferior in acid resistance, due to the coating crosslinked with melamine resin is easily decomposed with acid.
As a crosslinking system intended to form a coating in which the scrub resistance and acid resistance are made compatible by introducing another acid-resistant crosslinking system into such weakly acid-resistant melamine resin crosslinking system, for example, a composite crosslinking system of carboxyl group(s)/epoxy group(s)/ hydroxyl group(s)/ melamine resin (U.S. Pat. No. 5,087,286, EP-A-388858) or a composite crosslinking system of hydroxyl group(s)/alkoxysilyl group(s)/melamine resin (WO91/16383) have been proposed, but the improvement in acid resistance achieved thereby is not necessarily satisfactory, because of the use of melamine resin in all of these.
On the other hand, proposals have also been made for crosslinking systems avoiding use of melamine resins whose weakpoint lies in low acid resistance, such as, for example, a crosslinking system composed of combination of carboxyl group(s)/epoxy group(s) or one composed of combinations of carboxyl group(s)/epoxy group(s)/hydroxyl group(s) (e.g., U.S. Pat. No. 4,764,430, EP-A-212457, EP-A-353734 and U.S. Pat. No. 5,270,392, EP-A-450963). Coatings formed through utilization of these crosslinking systems excel in acid resistance, but are subject to a defect that their resistance to scratches and scrubbing is insufficient because of insufficient crosslinking density.
Also as a crosslinking system composed of combination of carboxyl group(s)/epoxy group(s)/hydrolysable silyl group(s), resin compositions comprising carboxyl-containing vinyl polymer(s) and epoxy- and hydrolysable silyl-containing compound (U.S. Pat. No. 4,764,430, EP-A-275138) are known. The compositions, however, are subject to a defect that their curing reaction does not sufficiently progress, due to the steric hindrance attributable to concurrent presence of epoxy groups and hydrolysable silyl groups within a same molecule.
Furthermore, as a crosslinking system composed of combination of carboxyl group(s)/epoxy group(s)/hydroxyl group(s), resin compositions comprising a silicone polymer containing hydroxyl groups and carboxyl groups, polymer containing carboxyl groups and carboxylic acid ester groups and a polymer containing hydroxyl groups and epoxy groups have been proposed (JP-Hei 6 (1994)-166741A), which however are open to a problem that cured coatings formed therefrom are insufficient in crosslinking density.
As a paint composition to give coating exhibiting improved soiling resistance and scrub resistance, JP-2000-136332A proposed organic solvent-based, thermosetting paint composition comprising a thermosetting resin composition formed of a base resin such as acrylic resin, polyester resin, alkyd resin, urethane resin and the like; a crosslinker component for crosslinking said composition, selected from melamine resin, urea resin, guanamine resin, optionally blocked polyisocyanate compound and carboxyl-containing compound; and further a minor amount of colloidal silica added to said thermosetting resin composition. Cured coating formed from this paint composition, however, exhibits insufficient acid resistance.
As above, none of those paints for motorcars heretofore proposed is found to form cured coating concurrently exhibiting the three performances of satisfactory scratch resistance, resistance to mars incurred by car-washing machines and acid resistance in good balance.
The main object of the present invention is to provide paint compositions for motorcars, which are capable of forming cured coating excelling in all of scratch resistance, resistance to mars incurred by car-washing machines and acid resistance.
As a result of concentrative studies, we now have come to find that the above object could be accomplished by using as the base resin a carboxyl-containing polyester resin which contains a unit or units derived from alicyclic polybasic acid and/or alicyclic polyhydric alcohol. The present invention is whereupon completed.
Thus, according to the present invention, a paint composition for motorcars, which comprises
(A) a carboxyl-containing polyester resin also containing a unit or units derived from alicyclic polybasic acid (a) and/or alicyclic polyhydric alcohol (b), and
(B) a vinyl polymer having epoxy group(s) and hydroxyl group(s) within one molecule,
and which is capable of forming cured coating having Universal Hardness (HU) not higher than 500 N/mm
2
.
Hereinafter the paint composition for motorcars of the present invention (“present paint composition”) is explained in further details.
Polyester Resin (A)
Polyester resin (A) which is used as the base resin in the present paint composition is a carboxyl-containing polyester resin prepared by using an alicyclic polybasic acid (a) and/or an alicyclic polyhydric alcohol (b) as the essential monomeric components, if necessary in combination with other polybasic acid (c) and/or other polyhydric alcohol (d).
The alicyclic polybasic acid (a) is a compound containing at least one alicyclic ring, preferably a 4- to 6-membered alicyclic ring, and at least 2, preferably 2-3 carboxyl groups, per molecule, specific examples of which include cyclohexane-1,3-dicarboxylic acid, cyclohexane-1,4-dicarboxylic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, hexahydrotrimellitic acid, tetrahydrophthalic acid, methyl hexahydrophthalic acid, and anhydrides of those acids.
Other useful polybasic acids (c) include compounds containing at least two carboxyl groups per molecule, which are customarily used as acid component for polyester production. As examples of such acids, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, fumaric acid, itaconic acid, trimellitic acid, pyromellitic acid and anhydrides of those acids may be named.
Alicyclic polyhydric alcohol (b) is a compound containing at least one alicyclic ring, preferably a 4- to 6-membered alicyclic ring, and at least 2, preferably 2-3 hydroxyl groups, per molecule, specific examples including cyclohexane-1,4-dimethylol, hydrogenated bisphenol A, spiroglycol and dihydroxymethyltricyclodecane.
Other useful polyhydric alcohols (d) include those compounds containing at least two hydroxyl groups per molecule, which are customarily used as alcohol component for polyester production. As examples of such alcohols, glycols such as ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 1,2-pentanediol, 1,5-pentanediol, 1
Kato Kazuhiro
Kitazono Kazuaki
Matsuno Yoshizumi
Kansai Paint Co. Ltd.
Short Patricia A.
Wenderoth , Lind & Ponack, L.L.P.
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