Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Patent
1997-10-24
2000-04-25
Dawson, Robert
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
427410, 523501, 524832, 524839, 524845, C08K 320, C08L 6302
Patent
active
060545089
DESCRIPTION:
BRIEF SUMMARY
INDUSTRIAL FIELD
The present invention relates to a water dispersible resin composition, particularly a water dispersible resin composition which can be suitably used for a coating composition.
Prior Art
A coating composition generally comprises a coloring agent such as a dye and pigment, a binder which fixes the coloring agent to a surface to be coated, and a liquid medium for making a uniform coated film. The binder is generally water insoluble, since they are a high-molecular weight polymer or resin, and an organic solvent such as a thinner has been primarily used as a liquid medium for a coating composition which contains such a water insoluble binder.
Recently, however, a waterborne coating composition is highly desired which makes no bad influence on the environment and is not harmful for workers. Many water soluble or water dispersible coating compositions have been reported so far, however, the water soluble coating composition has a defect that it is essentially inferior in water resistance and the water dispersible coating composition has a defect that the coating composition thereof is inferior in stability.
The reason of the bad stability of the water dispersible coating composition mainly consists in poor stability of the water dispersible resin composition which is used for the water dispersible coating composition.
For example, Japanese Patent Kokai Publication No. 47029/1977 discloses a water dispersible resin composition obtained by neutralizing a copolymer obtained by polymerizing a mixture of alkoxymethylacrylamide, .alpha., .beta.-ethylenically unsaturated carboxylic acid and the other copolymerizable ethylenically unsaturated monomers in the presence of a waterborne resin. However, since compatibility between the water soluble resin and the copolymer is insufficient, the resulting resin composition is inferior in dispersed stability in water. Therefore, a coating composition obtained by using the resin composition is inferior in painting workability, and it is apt to sag. Further, the resulting coated film is inferior in transparency, smoothness, chemical resistance, water resistance and mechanical strength.
Further, Japanese Patent Kokai Publication 504138/1991 discloses a water dispersible resin composition obtained by polymerizing alternately (a) a monomer mixture comprising an acrylic monomer having a carboxyl group and (b) a monomer mixture comprising an acrylic monomer having a hydroxyl group, and by neutralizing them. However, this resin composition is inferior in dispersed stability in water due to insufficient compatibility between a polymer having acid value and a polymer having no acid value. Therefore, the coating composition comprising this resin composition does not show sufficient structural viscosity.
SUMMARY OF THE INVENTION
The present invention solves the above-described problems. The object thereof is to provide a water dispersible resin composition which can realize a waterborne coating composition which forms a coated film having excellent transparency, smoothness, chemical resistance, water resistance and mechanical strength, and which has excellent painting workability and dispersed stability, and to provide a method for producing the same.
The present invention provides a method for producing a water dispersible resin composition, comprising the steps of:
radically polymerizing, in the presence of a polymerization initiator, a starting mixture comprising (a) 10 to 95% by weight of a water insoluble resin having a solubility in water of not more than 1; and (b) 5 to 90% by weight of a monomer mixture which comprises of (1) 2 to 75% by weight of an ethylenically unsaturated monomer having an acid group, and (2) 25 to 98% by weight of the ethylenically unsaturated monomer other than (1); and
neutralizing the resulting resin composition containing an acid group by adding a neutralizing agent. This method accomplishes the above-mentioned object.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 is a sectional view which shows an example of a multi-layered coated film f
REFERENCES:
patent: 4916181 (1990-04-01), Maska et al.
patent: 5015688 (1991-05-01), Bederke et al.
patent: 5034275 (1991-07-01), Pearson et al.
patent: 5114993 (1992-05-01), Scherping et al.
patent: 5322865 (1994-06-01), Inoue et al.
Kuwajima Teruaki
Miwa Hiroshi
Suzuki Satoshi
Watanabe Masakazu
Aylward D.
Dawson Robert
Nippon Paint Co. Ltd.
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