Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-06-13
2003-07-22
Sanders, Kriellion A. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S430000, C524S451000, C524S495000, C526S317100, C526S318400
Reexamination Certificate
active
06596793
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a copolymer excelling in dispersing ability of pigments, in particular, dispersibility of organic pigment such as diketopyrrolopyrrole; to a pigment dispersion in which said copolymer is used; and to a paint composition containing said pigment dispersion, which excels in stable color development.
2. Description of the Invention
Pigment dispersion pastes which are formed by dispersing pigment in a mixture of a dispersing resin, solvent and if necessary a dispersion promotor, have been widely used for paints and inks for coloring. In the field of paints and inks, social needs require further improvements in such properties as color developing ability and sharpness with increasing keenness, in addition to better performance of the paint film or printed matter per s. To meet the requirements, various organic pigments such as phthalocyanine pigments, quinacridone pigments, diketopyrrolopyrrole pigments and the like have been developed.
Whereas, even when a new pigment having excellent color developing property or sharpness meeting the social demands is developed, a dispersing resin and dispersion promotor matching the pigment must be used for preparing a dispersion showing the original innate color of the same pigment. The pigment dispersion, furthermore, must have sufficient stability to prevent reagglomeration of pigment particles, when it is used in a paint or ink. Hence, proposals have been made to develop dispersing resins and/or dispersion promotors which exhibit excellent pigment dispersibility, capacity for drawing forth the maximum color developing property of the available pigment and also excellent pigment dispersing stability to effectively inhibit re-agglomeration of the pigment particles in the formed pigment dispersion.
Such past proposals include, for example, (1) method of using a lubricant such as nonionic, cationic or anionic surfactant as the dispersion promotor (cf U.K. Patent Nos. 1108261 and 1159252), (2) method of using a pigment derivative as the dispersion promotor, which is mixed with a pigment to disperse the latter [cf. Sho 51(1976)-18736A1-JP], (3) method of using a nitrogen-containing compound as the dispersion promoter and a polyester oligomer as the dispersing resin, to improve dispersibility of the pigment and stability of the pigment dispersion by utilizing the affinity between the polyester oligomer and the nitrogen-containing compound [cf. Sho 58(1983)-145762A1-JP], (4) method of using a pigment dispersing agent comprising a component to form a steric repelling layer composed of a pigment-adsorbing component having nitrogen-containing substituent groups and polyester resin [cf. Hei 4(1992)-352882A1-JP] and (5) a method of using a copolymer which is obtained from a monomer having tertiary amino group and/or quaternary ammonium base and a polyalkyl (meth)acrylate macromonomer having a (meth)acryloyl group at its terminal [cf. Hei 8(1996)-253540A1-JP].
Where the dispersion promoter in the above method (1) is used, however, the adsorption layer adsorbed onto the particle surfaces is too thin to exhibit satisfactory stabilization effect, and no appreciable improvement in pigment dispersibility is achieved. In the above method (2), the pigment derivatives used are themselves essentially colored, and hence this method cannot be generally used for all pigments. In the method (3), the polyester oligomer used therein has poor compatibility with acrylic resins which are of particular importance as resins for paint. In consequence, it is difficult for this method to attain in acrylic resin-derived paints the color developing property inherent in individual pigments. Furthermore, although the methods (4) and (5) introduced a steric repelling component, adsorption of the dispersant onto pigment is insufficient and stability of pigment dispersion is unsatisfactory. In particular, in the occasion of dispersing diketopyrrolopyrrole pigments, the insufficient adsorption of the dispersant onto the pigments causes notably inferior color developing property and dispersing stability. An attempt was made to give a surface treatment to the pigment with the view to improve said defect, which, however, achieved neither any substantial improvement in dispersing stability of the pigment nor full exhibition of innate color-developing property. Where the pigment concentration was high, furthermore, troubles were caused by the surface treating agent of the pigment.
Thus, the main object of the present invention is to provide a pigment dispersion which excels in dispersibility and dispersion stability of a broad range of pigments, in particular, in those of difficulty dispersible pigments such as diketopyrrolopyrrole pigments, and is capable of drawing forth the innate color developing ability of individual pigments; dispersing resin useful for preparation of such a pigment dispersion; and also a paint composition using the pigment dispersion, which excels in color developing ability and appearance of the coat film.
SUMMARY OF THE INVENTION
This invention provides a copolymer which is characterized in that said copolymer is obtained through copolymerization of
(a) carboxyl-containing, polymerizable unsaturated macromonomer 5-50 parts by weight,
(b) at least one polymerizable unsaturated macromonomer selected from polyalkyl (meth)acrylate macromonomers and polystyrene macromonomers 30-70 parts by weight, and
(c) at least one other polymerizable unsaturated monomer which is co-polymerizable with above (a) and/or (b) component 5-65 parts by weight, said copolymer having a number-average molecular weight within a range of 2,000-100,000 and a resin acid value within a range of 10-200 mgKOH/g.
The invention also provides a pigment dispersion which contains said copolymer, pigment, organic solvent and optionally a dispersion promotor.
The invention furthermore provides a paint composition containing said paint dispersion.
Hereinafter the invention is explained in further details.
DETAILED DESCRIPTION OF THE INVENTION
A copolymer according to the invention is prepared by copolymerization of a carboxyl-containing macromonomer (a), a specific macromonomer (b) and other polymerizable unsaturated monomeric component (c), which are hereafter explained.
Carboxyl-containing Polymerizable Unsaturated Macromonomer (a):
The carboxyl-containing, polymerizable unsaturated macromonomer, which serves as the component (a) constituting a copolymer of the present invention, has at least one carboxyl group and at least one polymerizable unsaturated bond per molecule. This monomeric component is useful when said copolymer of the invention is used for dispersing pigment, for effectively adsorbing the copolymer onto the pigment. Because the component (a) is in the form of a macromonomer, it can assist localization of the pigment-adsorbing component in the copolymer of the invention, whereby improving the adsorbing ability of the copolymer to the pigment and preventing re-aggromeration of the pigment, to improve stability of the pigment dispersion.
The carboxyl-containing, polymerizable unsaturated macromonomer (a) can be prepared by a production method known per se, for example, by a process comprising synthesizing in advance a vinyl polymer having a carboxyl precursor group which is convertible to a carboxyl group by a post-treatment, and treating the vinyl polymer to introduce thereinto a polymerizable, unsaturated group and convert the carboxyl precursor group to a carboxyl group. More specifically, for example a carboxyl-containing macromonomer can be prepared through the steps of copolymerizing a monomeric mixture of tert-butyl (meth)acrylate and other vinyl monomer using a carboxyl-containing chain transfer agent represented by 3-mercaptopropionic acid and if necessary a radical polymerization initiator, in the presence of an organic solvent, to form a copolymer with carboxyl group-terminated polymer chain; reacting the resulting copolymer with an epoxy-containing monomer such as
Yamashita Fumio
Yukawa Yoshiyuki
Kansai Paint Co. Ltd.
Sanders Kriellion A.
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