Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-12-17
2001-10-16
Sellers, Robert E. L. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C523S415000, C524S558000, C524S571000, C524S589000, C524S590000, C524S591000, C525S330500, C525S332500, C525S440030, C528S045000
Reexamination Certificate
active
06303707
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a novel resin composition for electrodeposition paint and, in more detail, relates to a resin composition for electrodeposition paint capable of forming a coating film excellent in anticorrosivity and further excellent in low temperature curability.
2. Description of the Prior Art
As an electrodeposition paint is excellent in throwing power and capable of forming a coating film excellent in performances such as durability, anticorrosivity etc., it has been widely adopted conventionally in application fields where these performances are required, for example, coating of motorcar body, coating of electric appliances etc.
An electrodeposition paint generally consists of a resin containing hydroxyl group as a base resin and a polyisocyanate compound blocked with a blocking agent as a curing agent.
Conventional blocked polyisocyanates dissociate the blocking agent usually at a higher temperature than 160° C., due to the structure of their blocking agent, and the freed isocyanate groups react with the hydroxyl groups of the base resin.
However, in recent years, plastics parts have been used together in case of coating of metal plates for car body in automobile industry and therefore a development of such a blocked polyisocyanate compound that dissociates the blocking agent at a low baking temperature, at which said plastics parts do not melt, and can react with the base resin.
As a method to dissociate the blocking agent from a blocked polyisocyanate compound at a relatively low baking temperature, for example, a process to block a polyisocyanate compound with an oxime has been known. However, there is a problem that an electrodeposition paint composition containing a polyisocyanate compound blocked with an oxime dissociates oxime blocking agent during storage, increases the paint viscosity and the smoothness of the electrodeposition coating surface deteriorates to a great extent.
The present inventors have been intensively conducting research aiming at developing a composition for electrodeposition paint, capable of solving problems such as mentioned above, excellent in storage stability and capable of forming a coating film excellent in low temperature curability. As a result, this time, they found that the above-mentioned purpose could be achieved by a resin composition for electrodeposition paint consisting of a resin containing hydroxyl group and a polyisocyanate compound blocked with an amidoalcohol having amide bond and alcoholic hydroxyl group in the molecule and completed the present invention.
SUMMARY OF THE INVENTION
Thus, according to the present invention, there is provided a resin composition for electrodeposition paint characterized by comprising
(A) a resin containing hydroxyl group, and
(B) a polyisocyanate compound blocked with an amidoalcohol having at least one amide bond and at least one alcoholic hydroxyl group in the molecule.
DESCRIPTION OF SPECIFIC EMBODIMENTS
Then the resin composition for electrodeposition paint of the present invention is described in more detail.
The electrodeposition paint composition of the present invention may be either anionic type or cationic type. Generally, however, a catoinic type one is preferable from a viewpoint of anticorrosivity etc.
Resin Containing Hydroxyl Group (A):
The resin containing hydroxyl groups (A) used in the present invention can be any resin which is used generally as base resin in a composition for electrodeposition paint, contains hydroxyl groups and anionizable groups (for example, carboxyl group, sulfonic acid group etc.) or cationizable groups (for example, amino group, quaternary ammonium group etc.) and is dispersible in water and there can be used resins of, for example, epoxy type, acrylic type, polybutadiene type, alkyd type, polyester type etc. Above all, a polyamine resin containing hydroxyl group represented by an amine-added epoxy resin containing hydroxyl group is preferable
As the above-mentioned amine-added epoxy resin containing hydroxyl group there can be mentioned, for example, (i) an adduct of polyepoxide compound containing hydroxyl groups and primary mono- or polyamine, secondary mono- or polyamine or primary/secondary mixed polyamines (cf for example, U.S. Pat. No. 3,984,299); (ii) an adduct of polyepoxide compound containing hydroxyl group and secondary mono- or polyamine having a ketiminized primary amino group (cf. for example, U.S. Pat. No. 4,017,438); (iii) a reaction product obtained by etherification of a polyepoxide compound containing hydroxyl group and hydroxy compound having a ketiminized primary amino group (cf. for example, Japanese Laid-open Patent Publication No. 43013/1984).
The polyepoxide compound containing hydroxyl groups used in the preparation of the above-mentioned amine-added epoxy resin containing hydroxyl groups is a compound having two or more of each hydroxyl group and epoxy group in the molecule. It is preferable genrally to have a number-average molecular weight in the range of at least 200, preferably 400-4,000, more preferably 800-2,000 and an epoxy equivalent in the range of at least 150, preferably 180-2200, more preferably 400-1100. Particularly preferable is a product obtained by a reaction of a polyphenol compound and epichlorohydrin. As a polyphenol compound usable to form said polyepoxide compound containing hydroxyl group there can be mentioned, for example, bis-(4-hydroxyphenyl)-2,2-propane, 4,4-dihydroxybenzophenone, bis-(4-hydroxyphenyl)-1,1-ethane, bis-(4-hydroxyphenyl)-1,1-isobutane, bis-(4-hydroxy-tert-butyl-phenyl)-2,2-propane, bis-(2-hydroxynaphthyl)methane, 1,5-dihydroxynaphthalene, bis(2,4-dihydroxyphenyl)methane, tetra(4-hydroxyphenyl)-1,1,2,2-ethane, 4,4-dihydroxydiphenylsulfone, phenol novolac, cresol novolac etc.
Said polyepoxide compound containing hydroxyl groups may be modified by partially reacting with a polyol, polyetherpolyol, polyesterpolyol, polyamidoamine, polycarboxylic acid, or polyisocyanate compound etc. and may be further graft-polymerized with &egr;-caprolactone, acrylic monomer etc.
Blocked Polyisocyanate Compound (B):
The blocked polyisocyanate compound (B) used in the present invention can be a product of an addition reaction of a polyisocyanate compound and an isocyanate-blocking agent and is used as a curing agent for the above-mentioned resin containing hydroxyl groups (A). Usually said blocked polyisocyanate compound is preferably of completely blocked type wherein substantially all the existing isocyanate groups are blocked.
As a polyisocyanate compound used for the preparation of said blocked polyisocyanate compound (B) there can be mentioned, for example, an aromatic polyisocyanate compound such as tolylene diisocyanate, diphenylmethane-4,4′-diisocyanate, diphenylmethane-2,4-diisocyanate, crude diphenylmethane diisocyanate, xylylene diisocyanate, phenylene diisocyanate etc.; alicyclic polyisocyanate compound such as isophorone diisocyanate, bis(isocyanatomethyl)cyclohexane etc.; aliphatic polyisocyanate compound such as tetra-methylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate etc., and compounds containing terminal isocyanate obtained by reacting excess amount of these isocyanate compounds with a low molecular active hydrogen compound such as ethylene glycol, propylene glycol, trimethylolpropane, hexanetriol, castor oil etc. Among them, particularly an aromatic polyisocyanate compound is preferable from the viewpoint of anticorrosivity etc.
On the other hand, the isocyanate-blocking agent is to temporarily add and block the isocyanate groups of a polyisocyanate compound and the blocked polyisocyanate compound formed by addition is a substance which is stable at normal temperature and can reproduce free isocyanate groups through dissociation of the blocking agent at the baking temperature of a coating film.
The characteristic of the present invention lies in the point of using an amidoalcohol having at least one, preferably only one, amide bond (—NHCO—) and at least one, preferably only one,
Hirato Sinzi
Nishida Reijiro
Nishiguchi Shigeo
Kansai Paint Co. Ltd.
Sellers Robert E. L.
Wenderoth , Lind & Ponack, L.L.P.
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