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...
Reexamination Certificate
2000-01-13
2001-07-31
Michl, Paul R. (Department: 1714)
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...
Reexamination Certificate
active
06268429
ABSTRACT:
The present invention relates to an aqueous coating and a method for film formation using the aqueous coating.
There are known an aqueous coating comprising (a) a base resin having hydroxyl group and carboxyl group and (b) an alkyl-etherified methylolmelamine resin, and a method for film formation which comprises applying a powder coating on the uncured film of the above aqueous coating to form thereon a film of the powder coating and then heating the two films to cure them simultaneously (see U.S. Pat. No. 5,585,146).
When the above aqueous coating film and powder coating film are heated for simultaneous curing, however, the aqueous coating film gives rise to a reaction between the hydroxyl group and the alkyl ether group and generates an alcohol. This alcohol passes through the molten powder coating film, vaporizes into the air, allows the powder coating film to have depressions, popping, craters, etc., and consequently reduces the surface smoothness, distinctness of image gloss, physical performance of film, other properties, etc. of the powder coating film. Further, when the aqueous coating film contains a fake-like metallic pigment, the alignment of the metallic pigment is disturbed and the metallic feeling thereof is reduced.
The present inventors made a study in order to eliminate the above-mentioned problems caused by the alcohol generated as a by-product in heat-curing an aqueous coating comprising (a) a base resin having hydroxyl group and carboxyl group and (b) an alkyl-etherified methylolmelamine resin. As a result, the present inventors found out that by using an oxazoline group-containing compound in combination with the alkyl-etherified methylolmelamine, the amount of the alcohol generated as a by-product can be reduced and the above-mentioned problems can be alleviated. The present invention has been completed based on the above finding.
The present invention provides an aqueous coating (this coating is hereinafter referred to as the present invention coating) comprising:
(A) a resin having hydroxyl group and carboxyl group in the molecule,
(B) an alkyl-etherified methylolmelamine resin, and
(C) an oxazoline group-containing compound.
The present invention also provides a method for multilayered film formation (this method is hereinafter referred to as the present invention method), which comprises applying a powder coating or a powder slurry on the uncured film of an aqueous coating, to form thereon a film of the powder coating or powder slurry and then heating the two films to cure them simultaneously, wherein the aqueous coating is the present invention coating mentioned above.
The present invention coating and the present invention method are described in detail below.
RESIN (A) HAVING HYDROXYL GROUP AND CARBOXYL GROUP IN THE MOLECULE
The resin (A) used in the present invention coating is preferably an acrylic resin, a polyester resin or the like, each having hydroxyl group and carboxyl group in the molecule. The acrylic resin can be obtained by copolymerizing a hydroxyl group-containing unsaturated monomer, a carboxyl group-containing unsaturated monomer, an acrylic unsaturated monomer and, as necessary, other unsaturated monomer.
The hydroxyl group-containing unsaturated monomer is a compound having at least one hydroxyl group and at least one polymerizable unsaturated bond in the molecule and it includes, for example, C
2-20
-hydroxyalkyl (meth)acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate and the like. The carboxyl group-containing unsaturated monomer is a compound having at least one carboxyl group and at least one polymerizable unsaturated bond in the molecule and it includes, for example, monocarboxylic acids such as acrylic acid, methacrylic acid and the like; and dicarboxylic acids and modified products thereof, such as maleic acid, itaconic acid, fumaric acid, mesaconic acid, anhydrides thereof and half-esterified products thereof. As the acrylic unsaturated monomer, there can be used a C
1-22
-alkyl (meth)acrylates such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate, hexyl methacrylate, octyl acrylate, octyl methacrylate, lauryl acrylate, lauryl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate and the like.
The other unsaturated monomer used as necessary is a polymerizable unsaturated bond-containing compound other than the above-mentioned compounds. It includes, for example, C
2-18
-alkoxyalkyl (meth)acrylates such as methoxybutyl acrylate, methoxybutyl methacrylate, methoxyethyl acrylate, methoxyethyl methacrylate and the like; amino(meth)acrylic monomers such as N,N-dimethylaminoethyl acrylate, N,N-dimethylaminoethyl methacrylate, N,N-diethylaminoethyl acrylate, N,N-diethylaminoethyl methacrylate, N-t-butylaminoethyl acrylate, N-t-butylaminoethyl methacrylate, N,N-dimethylaminopropyl acrylate, N,N-dimethylaminopropyl methacrylate and the like; (meth)acrylamide type monomers such as acrylamide, methacrylamide, N-methylacrylamide, N-methylmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide, N-butylacrylamide, N-butylmethacrylamide, N-dimethylacrylamide, N-dimethylmethacrylamide and the like; glycidyl group-containing monomers such as glycidyl acrylate, glycidyl methacrylate and the like; vinyl aromatic compounds such as styrene, &agr;-methylstyrene, vinyltoluene and the like; acrylonitrile; vinyl acetate; and vinyl chloride.
The acrylic resin can be produced by polymerizing these monomers by an ordinary process such as solution polymerization, emulsion polymerization or the like.
The acrylic resin may be any of a water-soluble acrylic resin and a water-dispersible acrylic resin. However, combined use of a water-soluble acrylic resin and a water-dispersible acrylic resin is preferable because such use can prevent the unevenness of metallic pigment in film, sagging, etc. and further can enhance the intercoat adhesion between acrylic resin film (film of the aqueous coating of the present invention) and film of powder coating or powder slurry, the water resistance of final film, etc.
The water-soluble acrylic resin is an acrylic resin which is readily soluble in water when neutralized by a method described later. It preferably has a number-average molecular weight of 5,000-100,000, particularly 15,000-80,000; a hydroxyl value of 20-200 mg KOH/g, particularly 40-150 mg KOH/g; and an acid value of 10-150 mg KOH/g, particularly 20-100 mg KOH/g.
The water-dispersible acrylic resin is an acrylic resin which, when neutralized by a method described later, is not readily soluble in water but is stably dispersible in water in fine particles. It preferably has a number-average molecular weight of 150,000 or more, particularly 200,000-3,000,000; a hydroxyl value of 20-200 mg KOH/g, particularly 40-150 mg KOH/g; and an acid value of 10-100 mg KOH/g, particularly 20-80 mg KOH/g. The water-dispersible acrylic resin can be produced, for example, by emulsion polymerization or by solution polymerization in organic solvent and subsequent dispersion of resulting polymer in water.
Herein, “water-soluble resin” and “water-dispersible resin” is determined as follows. A finely ground resin powder is placed in water of 20° C. so that the solid content becomes 10% by weight; the resin powder is neutralized with a base of equivalent amount; the resulting material is stirred thoroughly for 10 minutes and then is put in a colorless transparent beaker placed on a white paper having a black letter printed thereon with a No. 4 type, so that the height of the material in the beaker becomes 5 cm; and the letter is seen from above the material surface. When the letter is readable clearly, the resin is judged as “water-soluble resin”. When the letter is not readable but the resin is stably dispersed and gives no precipitate, the resin is judged as “water-dispersible resin”.
When the water-soluble acrylic resin and the water-dispersible resin are used in combination, there is no particular
Kawamoto Yugen
Mitsuji Masaru
Numa Nobushige
Kansai Paint Co. Ltd.
Michl Paul R.
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Aqueous coating and method for film formation using the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Aqueous coating and method for film formation using the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Aqueous coating and method for film formation using the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2488444