JPH0159304B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a pigment dispersant made of a specific water-soluble polymer, and more specifically, a pigment dispersant made of a water-soluble polymer containing a specific functional group, which significantly improves the dispersibility and stability of pigments in aqueous media. This invention relates to a dispersant that can improve the properties of the dispersant. In various industries such as pigments, dyes, paints, inks, and plastics, it is an extremely important issue to uniformly disperse pigment particles in a medium, and the quality of the final product is greatly influenced by the quality of the dispersion. As such dispersants, alkaline inorganic salts such as sodium hexametaphosphate, cellulose derivatives such as carboxymethylcellulose and sodium alginate, polymer dispersants such as sodium polyacrylate, and ordinary low-molecular emulsifiers are well known. However, all of these dispersants require the use of large amounts, have poor stability, are subject to significant restrictions on the type of pigment, and do not have sufficient effects, so they are not always satisfactory. As a result of intensive studies aimed at providing a dispersant for pigments free from such defects, the present inventor found that a water-soluble polymer containing a specific functional group can be added in small amounts to a wide variety of pigments. discovered the fact that it can exhibit remarkable effects as a dispersion stabilizer,
We have arrived at the present invention. That is, an object of the present invention is to provide a pigment dispersant made of a specific water-soluble polymer that can significantly improve the dispersion stability of pigments in aqueous media. , to improve the quality of final products such as plastics. Further objects of the present invention will become apparent from the detailed description of the invention provided below. The pigment dispersant according to the present invention for achieving the above object is composed of a monomer unit consisting essentially of an ethylenically unsaturated carboxylic acid or a salt thereof and a sulfonated unsaturated aromatic hydrocarbon or a salt thereof. It is made of a water-soluble polymer containing bonded monomer units. Here, the water-soluble polymer according to the present invention is
A monomer unit (component A) consisting of an ethylenically unsaturated carboxylic acid or a salt thereof as the polymer constituent unit
A water-soluble polymer obtained by bonding a monomer unit (component B) consisting of a sulfonated unsaturated aromatic hydrocarbon or a salt thereof, and obtained by any method. However, in general, a water-soluble polymer containing both components A and B can be effectively used in the present invention. However, in general, components A and B are copolymerized by a well-known method (especially by copolymerization of components A and B). (preferably solution polymerization using water as the polymerization medium). In addition, component A may be introduced into the polymer by hydrolyzing a copolymer of unsaturated carboxylic acid esters such as acrylic acid esters, vinyl cyanide monomers, etc. It goes without saying that methods such as introducing component B through sulfonation can also be employed. In addition, the composition ratio of component A and component B in such a water-soluble polymer varies slightly depending on the type of pigment to be applied, etc., and is difficult to define unambiguously, but in general, component A/component B = 20~95%/80~5%
There is no particular restriction on the degree of polymerization of such a polymer, but within a practical molecular weight range, it is better to use one with a small molecular weight to improve the dispersion stability of the pigment. It seems so. Furthermore, depending on the type of pigment, in addition to components A and B, a small amount of a hydrophobic monomer such as acrylonitrile, styrene, ester of acrylic acid or methacrylic acid, vinylidene chloride, etc. may be copolymerized as a water-soluble polymer. Better results may be obtained by using water-soluble polymers, and such polymers are therefore also included within the scope of the water-soluble polymers according to the present invention. In addition, as the A component introduced into such a water-soluble polymer, unsaturated monohydric carboxylic acids such as acrylic acid, methacrylic acid, vinyl acetic acid, crotonic acid and their salts; maleic acid, fumaric acid, itacon Examples thereof include acids, unsaturated polycarboxylic acids such as aconitic acid, citraconic acid, and mesaconic acid, and salts thereof. In addition, as component B,
p-styrenesulfonic acid, isopropenylbenzenesulfonic acid, 2-chlorostyrenesulfonic acid,
Examples include sulfonated unsaturated aromatic hydrocarbons such as vinyloxybenzenesulfonic acid and salts thereof, and by introducing these monomer units, the pigment dispersion effect becomes even more remarkable. Next, pigments to which the dispersant of the present invention is suitably applied include zinc white, titanium oxide, antimony white,
Oxides such as iron black, red iron, red lead, and chromium oxide;
Sulfides such as lithopone, zinc sulfide, cadmium yellow; sulfates such as barium sulfate, gypsum, lead sulfate;
Carbonates such as barium carbonate, lime carbonate powder, white lead; hydroxides such as alumina white; chromates such as yellow lead, zinc yellow, barium chromate; silver vermilion, zinc powder,
Examples include metal powders such as aluminum powder, copper powder, and tin powder; carbon black; and organic pigments such as nitro, azo, and phthalocyanine, but especially oxides, sulfates, carbonates, and water. It exhibits a remarkable dispersion stabilizing effect on inorganic pigments such as oxides. The amount of the dispersant used in the present invention needs to be varied depending on the type of pigment to which it is applied, and it is difficult to define it unambiguously, but it depends on the solid content ratio of the water-soluble polymer to the pigment. approximately
It is appropriately selected and used within the range of 0.005 to 5% by weight, preferably 0.01 to 1% by weight. Note that the aqueous medium includes methanol, ethanol, propanol, 2-methoxyethanol,
- An aqueous mixed solvent of water and a water-miscible organic solvent such as ethoxyethanol, acetone, dimethylformamide, dimethyl sulfoxide, or water alone, or a polymer dispersed in the solvent (aqueous polymer emulsion), etc. In addition, small amounts of other organic or inorganic substances may coexist in these aqueous media. The water-soluble polymer containing a specific functional group according to the present invention described above does not have an amphiphilic structure consisting of a hydrophilic group and a lipophilic group like ordinary low-molecular emulsifiers, and also has foaming properties and Although it does not have any emulsifying effect such as emulsifying property, it exhibits a remarkable effect of improving dispersion stability when dispersing pigments in aqueous media. Although the details of this reason have not yet been elucidated, the polymer of the present invention helps the pigment particles to wet the aqueous medium, and also has a charge effect,
It is thought that steric protection or the like contributes in some way to the stabilization mechanism of the dispersion system. Pigment dispersants made of the above-mentioned specific water-soluble polymers can uniformly, finely and stably disperse pigments in aqueous media by adding only a small amount to a wide variety of pigments, making it possible to disperse pigments in paints. A characteristic advantage of the present invention is that it can improve the quality of final products such as, inks, plastics, etc. EXAMPLES The present invention will be described below in more detail with reference to Examples, but the scope of the present invention is not limited in any way by the description of these Examples. In the examples, parts and percentages are expressed on a weight basis unless otherwise specified. Example 1 To 70 parts of methacrylic acid (MAA) and 30 parts of sodium p-styrene sulfonate (SPSS), 2 parts of ammonium persulfate, 1.8 parts of acidic sodium sulfite, 0.0015 parts of ferrous chloride, and 230 parts of ion-exchanged water were added. Then, polymerization was carried out at 70°C for 1 hour under stirring conditions. The polymer () obtained by neutralizing this polymer with a 5% caustic soda aqueous solution was added to 100 parts of carbonated lime powder and 80 parts of water in the proportions shown in Table 1, and the dispersibility of carbonated lime powder was improved. The measurement results are listed in Table 1. As a comparative example, the results of evaluating the performance of Dispext-40 (sodium polyacrylate manufactured by Toagosei Co., Ltd.) are also listed in Table 1.

[Table] As is clear from the results in Table 1, it is understood that the product of the present invention exhibits an extremely excellent effect of improving dispersion stability even when added in a small amount. Example 2 A water-soluble polymer () neutralized according to the recipe described in Example 1 except that 80 parts of MAA and 20 parts of SPSS were used as monomers, and 2-acrylamide-2-methyl was used instead of SPSS. A water-soluble polymer () was prepared using 20 parts of propane sulfonic acid. A water-soluble polymer () was also prepared using 100 parts of SPSS as a monomer. The dispersion performance of Polymer (-) and Dispext-40 for various pigments shown in Table 2 was measured. The results are also listed in Table 2.

【table】

[Table] Note: ○ mark: Inventive product From the results in Table 2, it is clear that the inventive product exerts a remarkable dispersibility improving effect on various pigments when added in small amounts. Example 3 A water-soluble polymer () was produced according to the recipe described in Example 1, except that acrylic acid was used instead of MAA. When 0.01 part of this polymer () was added to 100 parts of barium sulfate and 30 parts of water, the viscosity was measured.
It was 100 CPS and had good dispersibility.

Claims (1)

[Claims] 1 Contains 20 to 95% by weight of monomer units consisting of ethylenically unsaturated carboxylic acid or its salt and 80 to 5% by weight of monomer units consisting of sulfonated unsaturated aromatic hydrocarbons or its salt. Pigment dispersant made of water-soluble polymer.