Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-04-14
2002-04-16
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C204S489000, C204S501000, C204S502000, C204S504000, C204S506000
Reexamination Certificate
active
06372824
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a novel cationic electrodeposition paint composition and a process for preparing the same, and more particularly to a cationic electrodeposition coating composition in which the electrodeposited coating film of the electrodeposition paint composition has an epoxy-acrylic double-layered structure, and in which an organic solvent content can be minimized, and a process for preparing the same. Further, the present invention relates to a pigment grinding vehicle suitable for electrodeposition coating of the cationic electrodeposition paint composition.
The cationic electrodeposition paint is widely used for primer coating of cars, household electric appliances, and industrial machines. Recent research at home and abroad on a cationic electrodeposition paint have concentrated on paints related to energy saving, safety and environmental considerations. Also, research or binders of electrodeposition coating have concentrated on developing high functional and high efficient electrodeposition paint having various purposes and characteristics. Among the research, studies on reducing an organic solvent emissions from paint operations are being developed. The motive for these studies is the regulation of emission of organic solvents for the protection of the environment. As examples of regulations related to the regulation of emission of organic solvents, a regulation for volatile organic compounds (VOC) of the Environment Office in U.S. and an atmospheric purification law in Germany can be illustrated. The former establishes a guideline for the amount of organic solvents in a paint, while the latter restricts the amount of organic solvents discharged from the paint used for coating a car. Since 20% of the amount of carbon dioxide discharged in the whole world are due to the coating industry (for example, organic solvent and combustion by means of a drying oven), the coating industry is a major cause of environmental pollution. Hence, the coating industry has become the subject of supervision. Presently, as an electrodeposition coating for primer coating, epoxy cationic electrodeposition paints are mainly used. However, these epoxy cationic electrodeposition paints are rich in organic solvents and these solvents are evaporated from the electrodeposition tank, thereby emitting an offensive odor in a workpiece. Also, these solvents are emitted during baking, so environmental pollution problems occur. Though these epoxy cationic electrodeposition paints have excellent properties such as chemical resistance, corrosion-resistance, adhesion etc., they are lacking in properties such as weather-resistance, yellowing resistance, etc.
SUMMARY OF THE INVENTION
Accordingly, considering the problems described above, it is an object of the present invention to provide an improved cationic electrodeposition composition in which an organic solvent content can be minimized and the electrodeposited coating layer has an epoxy-acrylic double-layered structure for improving properties such as weather-resistance, yellowing resistance, etc.
It is a further object of the present invention to provide a process for preparing a cationic electrodeposition composition particularly suited for manufacturing cationic electrodeposition coating.
It is yet another object of the present invention to provide a pigment grinding vehicle suitable for electrodeposition coating of the cationic electrodeposition composition.
In accordance with the present invention, a cationic electrodeposition coating composition having a resinoid dispersed into an aqueous medium is provided. The cationic electrodeposition coating composition of the present invention essentially comprises a cationic electrodeposition resin prepared by a reaction of (a) 40-60 percent by weight of a cationic electrodeposition synthetic resin obtained by an epoxy-amino addition reaction, (b) 5-10 percent by weight of an acrylic cationic electrodeposition resin having an amino group, (c) 1-3 percent by weight of a fatty acid ester resin synthesized by an estrification reaction of styrene-allylalcohol copolymer and a fatty acid, and (d) 30-50 percent by weight of a blocked polyisocyanate crosslinking agent. A cationic electrodeposition coating composition is obtained by dispersing the cationic electrodeposition resin into an aqueous medium. At this time, an organic solvent is contained less than 2.0 percent by weight based on the dispersed solution of the cationic electrodeposition resin.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be explained in more detail.
The cationic electrodeposition resin according to the present invention is a major film forming resin in an electrodeposition coating composition. Some of these known film forming resins are illustrated in U.S. Pat. Nos. 3,663,839; 3,984,299; 3,947,338; and 3,947,339. These film forming resins represent a resin having an amino group formed by an addition reaction of polyepoxide with a primary, secondary or tertiary amine. As for the cationic electrodeposition synthetic resin formed by the addition reaction of polyepoxide and amine, a resin having the following structural formula can be illustrated:
wherein R
1
, R
2
and B are as follows, and n is an integer of 3 or 4.
R
1
R
2
B
N-
—CH
3
—(CH
2
)
2
OH
—[—(CH
2
)
5
—
methylethanol
CO—O—]—
amine
(—CH
2
)
5
—
diketimine
—CH
2
N═
R
2
═R
1
C(CH
3
)CH
2
CH(CH
3
)
2
If the amount of the cationic electrodeposition synthetic resin having an amino group used is less than 40 percent by weight, mechanical properties of the dried coating layer are weak, and if the amount of the cationic electrodeposition synthetic resin having a amino group used exceeds 60 percent by weight, the manufacture of a water-dispersed solution is difficult. Therefore, the amount of the cationic electrodeposition resin having an amino group used is preferably about 40-60 percent by weight, and more preferably about 45-55 percent by weight.
In addition, as an other cationic electrodeposition resin, an acrylic cationic electrodeposition resin having an amino group which is copolymerized with butyl acrylate, methyl acrylate, hydroxy ethyl acrylate, styrene, methyl methacrylate, (N,N-dimethyl)aminoethyl methacrylate, etc., can be illustrated. The structural formula of the acrylic cationic electrodeposition resin is as follows:
If the amount of the acrylic cationic electrodeposition resin used is less than 5 percent by weight, a dried coating film having an epoxy-acrylic double-layered structure cannot be obtained, and if the amount of the acrylic cationic electrodeposition resin used exceeds 10 percent by weight, the epoxy resin and acrylic resin are not compatible, thereby affecting the surface appearance and gloss. Therefore, the amount of the acrylic cationic electrodeposition resin used is preferably about 5-10 percent by weight, and more preferably about 7-9 percent by weight.
Usually these resins having an amino group are used together with a blocked polyisocyanate crosslinking agent. The isocyanate is so completely blocked that it can be mixed with the resin having an amino group. Otherwise, the isocyanate is partially blocked in such a manner that it can react with the backbone of a resin. As for the blocked polyisocyanate crosslinking, agent, a compound having the following structural formula can be illustrated:
If the amount of the blocked polyisocyanate crosslinking agent used is less than 30 percent by weight, properties such as pencil hardness, corrosion resistance, etc., are diminished. If the amount of the blocked polyisocyanate crosslinking, agent used exceeds 50 percent by weight, the preparation of a water-dispersed solution is difficult and properties such as impact-resistance, flexible-resistance, etc., are diminished. Therefore, the amount of the blocked polyisocyanate crosslinking agent used is preferably about 30-50 percent by weight, and more preferably 35-45 percent by weight.
Particularly, the composition of the present invention comprises a fatty acid ester sy
Back Seung-Jae
Chung Hoon
Hong Jong-Myung
Song Ki-Myong
Aylward D.
Daihan Paint & Ink Co., Ltd.
Dawson Robert
Ostrolenk Faber Gerb & Soffen, LLP
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