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
2001-04-24
2004-08-31
Yoon, Tae H. (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...
C524S604000, C524S832000, C524S901000, C523S426000, C525S374000
Reexamination Certificate
active
06784236
ABSTRACT:
The present invention relates to an electrodeposition coating composition which has an excellent film forming property and which is excellent in performances such as a smoothness and a rust preventive property even after storing over a long period of time.
Cationic type or anionic type electrodeposition coating composition scarcely contain organic solvents, and therefore they are suited to environmental countermeasure such as public pollution prevention and excellent in a throwing property. In particular, a cationic type electrodeposition coating composition forms a coating film which is excellent in a durability and a corrosion resistance and therefore is widely employed as an under coating composition for conductive metallic materials for car bodies.
In order to maintain a film-forming property of the coating film, an electrodeposition coating composition is usually blended with a low boiling organic solvent having a boiling point of about 120° C. or lower (for example, methyl isobutyl ketone (116° C.) and methyl ethyl ketone (80° C.)), a hydrophilic solvent having a boiling point of 120 to 200° C. (for example, butyl cellosolve (171° C.) and propylene glycol monomethyl ether (121° C.)), or a low molecular weight soft resin having a molecular weight of 4000 or less (for example, a xylene resin and polypropylene glycol). However, an electrodeposition coating composition containing such substances is slowly reduced in a film-forming property thereof (film-forming ability) if stored for long time, and it becomes difficult to coat the coating composition in a prescribed film thickness. In addition thereto, there involved is the defect that the coated surface thereof is gradually reduced in a smoothness. Further, blending of a low boiling organic solvent or a hydrophilic solvent goes against a reduction in VOC (a reduction in a content of a volatile organic compound) and therefore is not preferred.
On the other hand, a content of volatile components such as an organic solvent contained in an electrodeposition coating composition is removed to, for example, 1% by weight or less by distillation under reduced pressure in order to lower VOC, but this reduces the film-forming property and makes it difficult to coat the coating composition in a film thickness of 15 &mgr;m or more as a cured coating film. In addition thereto, the coating film is likely to be reduced in a smoothness and a corrosion resistance. If an electrodeposition coating composition is applied to alloy-plated steel plates (steel plates covered with an alloy plating of zinc and iron) which are used in many cases as base materials for an automobile outside plate and an applied voltage is elevated in order to coat it in a large film thickness, brought about is the problem that gas is produced to cause pin holes (usually called crater) to reduce a smoothness on the coating film.
A principal object of the present invention is to provide an electrodeposition coating composition, particularly a cationically electrodeposition coating composition which is reduced in a content of a volatile organic solvent and has a good film-forming property and which can readily be coated in a film thickness of 15 &mgr;m or more and makes it possible to coat in a large film thickness without bringing about crater even when electrodeposition coated on an alloy-plated steel plate.
Intensive researches repeated by the present inventors have resulted in finding that the object described above can be achieved by adding a specific ester compound to an electrodeposition coating composition, and they have come to complete the present invention.
Thus, the present invention provides an electrodeposition coating composition comprising an ester compound selected from the group consisting of:
(a) a diester compound of polyoxyalkylene glycol and aliphatic monocarboxylic acid,
(b) a diester compound of polyoxyalkylene alkyl ether monoalcohol and aliphatic dicarboxylic acid and
(c) a polyester compound obtained by reaction of aliphatic glycol having 2 or 3 carbon atoms, aliphatic dicarboxylic acid and aliphatic monoalcohol.
The electrodeposition coating composition of the present invention (hereinafter referred to merely as the present coating composition) shall be explained below in further details.
Diester Compounds
Diester Compound (a):
The diester compound (a) capable of being used in the present coating composition is a compound prepared by subjecting two terminal hydroxyl groups contained in polyoxyalkylene glycol (a-1) to esterification reaction with aliphatic monocarboxylic acid (a-2). An alkylene part in the polyoxyalkylene glycol (a-1) constituting the diester compound (a) includes, for example, linear or branched alkylene groups having 2 to 4 carbon atoms such as ethylene, propylene and butylene, and the polyoxyalkylene glycol (a-1) includes, to be specific, polyethylene glycol, polypropylene glycol and polybutylene glycol. These polyoxyalkylene glycols (a-1) have preferably a weight average molecular weight falling in a range of usually 150 to 1000, particularly 200 to 600. The aliphatic monocarboxylic acid (a-2) reacted with the polyoxyalkylene glycol (a-1) has most preferably 6 to carbon atoms, particularly 8 carbon atoms from operational and economical points of view and includes, to be specific, hexanoic acid, heptanoic acid, caprylic acid, nonanoic acid, decanoic acid, 2-ethyl-hexenoic acid, isooctylic acid and neodecanoic acid.
Diesterification reaction of these polyoxyalkylene glycols (a-1) with the aliphatic monocarboxylic acids (a-2) can be carried out by conventionally known methods. In this case, the glycols and the aliphatic carboxylic acids can be used alone or in combination of two or more kinds thereof respectively. The diester compounds thus obtained have preferably a weight average molecular weight falling in a range of usually 400 to 1200, particularly 450 to 1000.
Diester Compound (b):
The diester compound (b) capable of being used in the present coating composition is a diester compound of polyoxyalkylene alkyl ether monoalcohol (b-1) with aliphatic dicarboxylic acid (b-2). The polyoxyalkylene alkyl ether monoalcohol (b-1) used in this case can be obtained by, for example, a method in which alkylene oxide having 2 to 4 carbon atoms and monohydric alkylalcohol having 4 to 8 carbon atoms are subjected to etherification reaction in an equimolar ratio or one of hydroxyl groups at both ends contained in a polyether compound of alkylene oxide having 2 to 4 carbon atoms is subjected to etherification reaction with monohydric alkylalcohol having 4 to 8 carbon atoms. It has one hydroxyl group and at least one ether bond in a molecule.
The alkylene oxide having 2 to 4 carbon atoms described above includes, for example, ethylene oxide, propylene oxide and butylene oxide, and the monohydric alkylalcohol having 4 to 8 carbon atoms described above includes, for example, butyl alcohol, isobutyl alcohol, pentyl alcohol, isopentyl alcohol, hexyl alcohol, isohexyl alcohol, heptyl alcohol, isoheptyl alcohol, octyl alcohol, isooctyl alcohol and 2-ethylhexyl alcohol.
The etherification reaction of the alkylene oxide with the alkylalcohol described above, the polyetherification reaction of the alkylene oxide and the etherification reaction of hydroxyl groups contained in this polyether compound with the alkylalcohol can be carried out by conventionally known methods. The polyoxyalkylene alkyl ether monoalcohol (b-1) thus obtained has preferably a weight average molecular weight failing in a range of usually 100 to 500, particularly 150 to 400.
Capable of being used as the aliphatic dicarboxylic acid (b-2) reacted with this monoalcohol (b-1) is a compound which has two carboxyl groups in a molecule and in which a part excluding those of the carboxyl group has 2 to 6 carbon atoms, and it includes, for example, succinic acid, glutaric acid, adipic acid, pimelic acid and suberic acid. Among them, adipic acid is particularly preferred from economical and operational points of view.
The diesterification reaction of the monoalcohol (b-1) with the alipha
Aoki Kenji
Hirano Kouji
Mizoguchi Yoshitaka
Nakao Fumiaki
Sugisaki Katsuhisa
Kansai Paint Co. Ltd.
Wenderoth , Lind & Ponack, L.L.P.
Yoon Tae H.
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