Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Patent
1988-12-02
1990-06-12
Welsh, Maurice J.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
252351, 252357, C08G 1871
Patent
active
049334174
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a pigment dispersing agent used when a pigment is mixed with a coating composition in the manufacture of paints.
BACKGROUND ART
In the manufacture of paints, it is important to mix the pigment with the coating composition In this case, the pigment is dispersed into a vehicle to form a dispersion paste, and then the paste is mixed with the coating composition to obtain a pigment dispersing composition. However, a greatest problem in such a pigment dispersing composition lies in that the pigment particles are apt to be agglomerated. This agglomeration may occur in the dispersion step, dissolution step, storing step or painting step. As a result, the gloss, sharpness and color strength of the finally obtained paint film are injured.
In order to improve the above drawbacks, therefore, there are proposed various pigment dispersing agents and grinding aids and also methods for improving dispersion of the pigment are attempted. For instance, there are known (1) a method of dispersing the pigment by using non-ionic, anionic or cationic surfactant or a wetting agent such as aliphatic polyvalent carboxylic acid or the like as a grinding aid; (2) a method of dispersing the pigment by using an amphipathic substance obtained by bonding a pigment-affinitive substance disclosed in British Pat. Nos. 1108261, 1159252 and 1346298 to a medium-affinitive substance; (3) a method of reducing surface tension with a surfactant such as alkyl silicone to prevent the occurrence of pigment floating; (4) a method of mixing the pigment with a certain substituted derivative of the pigment to conduct the dispersion of the pigment as disclosed in Japanese Patent laid open No. 51-18736; (5) a method of using as a dispersing agent a compound obtained by reacting an organic compound having two or more isocyanate groups, an organic compound having one or more functional group (amino group or hydroxyl group) capable of reacting with the isocyanate groups, and a polymer having substantially one functional group capable of reacting with the isocyanate group as disclosed in U.S. Pat. No. 3,684,771, British Pat. No. 1393401 and the like; (6) a method of dispersing the pigment by using a dispersing agent obtained by bonding a basic substance disclosed in European Patent laid open No. 208041, U.S. Pat. No. 4,647,647 and the like to a polyester compound; and the like.
However, the grinding aids or dispersing agents used in the methods (1).about.(3) do not sufficiently improve the aforementioned drawbacks, and the harmful effects derived from the use of these agents, i.e. secondary evil influences of degrading the paint film performances or painted state should be encountered. The pigment derivative used in the method (4) is naturally colored, so that it can not generally be used. Further, the basic thought of the dispersing agent used in the methods (5) and (6) is a technical idea of making a block structure to a polymer portion capable of solvating with a solvent as described by A. Topham in Progress in Organic Coatings, vol. 5, (1977) pp 237.about.243. In this technique, it is important that the polymer portion capable of solvating with the solvent is excellent in the compatibility with a resin used as a film forming component of the paint film and has adsorption point to the pigment as much as possible. When the polymer portion capable of solvating with the solvent is poor in the compatibility with the resin added as a film forming component of the paint film, the solvated polymer portion agglomerates to cause the degradation of pigment dispersing performances. Further, when the number of adsorption points to the pigment is small, the desorption of the dispersing agent from the pigment is apt to be caused to degrade the pigment dispersing performances. From these reasons, it is most important how to make the polymer portion having excellent compatibility with a wide range of resins, and further how to give many adsorption points to the pigment. And also, the polymer portion solvating with the solvent i
Matsubara Yoshiro
Yamamoto Toshio
Nippon Oil and Fats Co. Ltd.
Welsh Maurice J.
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