JPS6011987B2 - Method for producing Sachin White aqueous dispersion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a sachin white aqueous dispersion.

More specifically, the present invention relates to a method for producing a high-concentration satin white microcrystalline water solution using an alkali neutralized product of a specific copolymer and a water-soluble phosphate. Sachin white is obtained by adding and reacting an aqueous solution of aluminum sulfate to an aqueous suspension of calcium hydroxide, and has the general formula: a○-AI203.
- It is a white pigment with length aS04-3140.

This Sachin White is used as a water-dispersed coating liquid in combination with kaolin clay, calcium carbonate, aluminum hydroxide, etc. as coating pigments, and a binder such as latex or starch. The coated paper obtained using such a coating liquid has good receptivity to printing ink,
It also has excellent smoothness, gloss, whiteness, etc. However, as a coating pigment, the particle size must be extremely small, and therefore, when coating at high speeds, a coating solution with a high content of Sachin White microcrystals exhibits strong dilatancy and is difficult to coat. Met. Conventionally, polyphosphates, polyacrylates, and the like have been known as dispersants used in the production of high-concentration pigment aqueous dispersions used for paper coating as described above.

However, polyphosphates such as sodium hexametaphosphate are not sufficiently effective, and polyacrylates are also not sufficiently effective. In order to overcome these drawbacks, for example, a method using an inorganic fluorine compound as a dispersant (Tokukan Sho 50
No. 117825) has been proposed, but this method requires the addition of a large amount of an inorganic fluorine compound, which is a readily water-soluble salt, and is not preferred. As another improvement method,
No. 7-133055 discloses a copolymer of acrylic acid and itaconic acid, and Japanese Patent Publication No. 47-145411 discloses a saponified polyacrylic acid ester.

However, in all these methods, Sachin White is 20
It merely shows the dispersion effect at low concentrations of %. The present inventors have attempted to solve the above-mentioned problems with highly concentrated aqueous dispersions of satin white.As a result of intensive research, the inventors have found a solution to the above-mentioned problems with highly concentrated aqueous dispersions of satin white. As a result, we have found that it is possible to easily obtain a satin white water solution that has a high concentration, low viscosity, and little change in viscosity over time, and has completed the present invention.

Therefore, the present invention provides a method for easily producing a satin white aqueous dispersion suitable for paper coating, which has high concentration, low viscosity, and excellent dispersion stability. That is, the method for producing the aqueous satin white dispersion of the present invention uses an unsaturated monomer selected from the group consisting of hydroxyalkyl acrylate and hydroxyalkyl methacrylate.
a} and unsaturated carboxylic acid 'b} are essential components, the unsaturated monomer 'a} is within the range of 80 to 5 mol%, and the unsaturated carboxylic acid [b- is within the range of 20 to 95 mol%. (hereinafter, alkali neutralized product of copolymer obtained using
Copolymers are called alkali neutralized products.

) is characterized in that satin white microcrystals are dispersed in water in the presence of a water-soluble monophosphate 'B) in an amount ranging from 5 to 4 parts. . The alkali-neutralized copolymer used in the present invention contains an unsaturated monomer 'a) and an unsaturated carboxylic acid {b' as essential components, and the unsaturated monomer 'a' is in the range of 80 to 5 mol%. and a copolymer obtained by using unsaturated carboxylic acid [b' in an amount ranging from 20 to 95 mol%] with an alkaline substance.

As the unsaturated monomer {a}, those whose alkyl group has 2 to 4 carbon atoms are used, such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate. , 2-hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, and the like.

Among these, 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate are particularly preferred.
Examples of the unsaturated carboxylic acid [b} include acrylic acid,
Methacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid and the like can be used, with acrylic acid, methacrylic acid and maleic acid being particularly preferred. Unsaturated monomer [a
' and unsaturated carboxylic acid {b}, the former is 80~
The amount used is within the range of 5 mol %, the latter in the range from 20 to 95 mol %. Unsaturated monomer (amount of a is 80
If the amount of unsaturated carboxylic acid [b} exceeds 2 mol% or the amount of unsaturated carboxylic acid [b}
If it is less than 0 mol %, the dispersion effect of the present invention will not be sufficient, which is not preferable. The amount of unsaturated monomer [a} is less than 5 mol% or the amount of unsaturated carboxylic acid 'b} is 95 mol%
If it exceeds this value, the effect of lowering the viscosity of the present invention will not be sufficient, and this is also undesirable. When obtaining the copolymer alkali neutralized product W of the present invention, the unsaturated monomer 'a you 80~
Other monomers copolymerizable with these monomers can be copolymerized as long as the amount of unsaturated carboxylic acid (b) is within the range of 20 to 95 mol%.

Examples of such monomers include alkyl acrylates, alkyl methacrylates, glycidyl acrylates, and glycidyl methacrylates having an alkyl group having 1 to 4 carbon atoms, and alkoxyalkyl acrylates and alkoxyalkyl having an alkyl group having 1 to 4 carbon atoms. Examples include methacrylate, alkylamide, N-methylolacrylamide, vinyl acetate, and the like. There are no particular restrictions on the polymerization method for obtaining the alkali neutralized copolymer of the present invention from these monomers, and various methods can be employed.

Further, neutralization with an alkaline substance may be carried out at any stage before the copolymerization reaction, during the copolymerization reaction, or after the copolymerization reaction. As a method for obtaining the alkali-neutralized copolymer of the present invention, for example, a mixed monomer consisting of an unsaturated monomer {a}, an unsaturated carboxylic acid 'b} and, if necessary, other copolymerizable monomers is used. There is a method in which unsaturated carboxylic acid [b
A method of copolymerizing by dropping an alkali neutralized product of ', an unsaturated monomer {a', and other copolymerizable monomers as necessary together with a polymerization initiator into an aqueous medium and heating the mixture, etc. be able to. In addition, the degree of polymerization of the copolymer is 10 to 50.
It is preferably in the range of 0, but is not particularly limited. As the alkaline substance for neutralizing the copolymer, ammonia or alkali metal hydroxides or carbonates can be used, but sodium hydroxide is particularly preferred.

The amount of the alkaline substance to be used may be such that the copolymer of the present invention becomes water-soluble, and for this purpose, the amount that makes the aqueous solution of the alkali-neutralized copolymer have a pH value of 6 to 9 may be used. . Examples of water-soluble phosphates include hexametaphosphoric acid,
Alkali salts of phosphoric acid such as tripolyphosphoric acid or pyrophosphoric acid are used, and sodium tripolyphosphate and potassium pyrophosphate are particularly preferred. In the present invention, the copolymer alkali neutralized product and water port phosphate (B) must be used together.

The excellent effects of the present invention can only be obtained when the copolymer alkali neutralized product (■) and the water-soluble phosphate [B] interact in an inseparable relationship, and cannot be obtained by using each alone. It is not possible. In order to produce a sachin white aqueous dispersion according to the present invention, commercially available sachin white microcrystals are dispersed in water in the coexistence of copolymer alkali neutralized product (1) and water-droptable phosphate [B] in the above-mentioned specific ratio. Just let it happen.

Such a method includes, for example, adding a mixture of copolymer alkali neutralized product and water-soluble phosphate 'B' to a paste composition consisting of Sachin White microcrystals and water, and mixing the mixture. Examples include a method in which Sachin White microcrystals are added to an aqueous solution containing alkali neutralized English polymer (1) and water-soluble phosphate [B'] and mixed together. However, the scope of the present invention is not limited by the order or method of addition of the copolymer alkali-neutralized arc, water-soluble phosphate {B}, and satin white microcrystals. The sachin white aqueous dispersion thus obtained based on the method of the present invention exhibits a significantly lower viscosity than the sachin white aqueous dispersion using a conventionally known dispersant,
It also has excellent physical properties such as good dispersion stability and little change in viscosity over time, and little change in viscosity even when subjected to heat treatment.

Hereinafter, the present invention will be explained in more detail with reference to Reference Examples, Examples, and Comparative Examples, but the present invention is not limited only to these examples. In these examples, % means % by weight, and parts mean parts by weight. Reference example 1 Initial water 24909 was charged into a 5- and 6-hole flask equipped with a reflux condenser, three dropping funnels, and a thermometer.
Heat to reflux.

The system was then charged with 2
- 560 g of hydroxyethyl acrylate, 800 g of a 30% aqueous solution of sodium acrylate, and 150 g of a 10% aqueous solution of ammonium persulfate were uniformly added dropwise over 4 hours to cause a polymerization reaction, and the mixture was further aged under reflux for 3 minutes. An aqueous solution of the alkali-neutralized copolymer [1} was obtained. Reference Examples 2 to 4 Polymerization reactions were carried out in the same manner as in Reference Example 1, except that the monomer compositions and amounts of water listed in Table 1 were used to obtain aqueous solutions of various alkali-neutralized copolymers.

These copolymer alkali-neutralized products are hereinafter referred to as copolymer alkali-neutralized product 1, copolymer alkali-neutralized product 31, and copolymer alkali-neutralized product 4', respectively. Table 1 Reference Example 5 A 6-hole flask similar to that used in Reference Example 1 was charged with 2,700 g of water and 160 g of disodium maleate, and the mixture was heated and dissolved.

The system was further heated to reflux the solvent, and 2-hydroxyethyl acrylate (44%) was added to each of the three addition funnels.
A monomer mixture of 1.0 ml and 150 ml of acrylic acid, 250 ml of a 10% aqueous solution of ammonium persulfate and 250 ml of 20% hydrogen peroxide solution were uniformly added dropwise over 5 hours to effect a polymerization reaction. After completion of the dropwise addition, the mixture was further aged for 30 minutes under reflux of the solvent to obtain an aqueous solution of the polymer. After cooling this system to room temperature,
Fifty grams of sodium hydroxide was added to prepare an aqueous solution of the alkali-neutralized copolymer {5). Comparative Reference Example 1 A copolymer alkali neutralized product was prepared in the same manner as in Reference Example 1, except that the initial water amount was 2810 m2, and the monomer composition was 700 m2 of 2-hydroxyethyl acrylate and 340 m2 of a 25% aqueous solution of potassium methacrylate. 6} was obtained.

Example 1 Copolymer alkali neutralized product obtained in Reference Example 1 [1
To an aqueous solution (solid content: 100 ml) of sodium hexametaphosphate, 20 ml of sodium hexametaphosphate was added and dissolved.

A mixed aqueous solution (solid content: 4.0%) of this copolymer alkali neutralized product {1} and sodium hexametaphosphate was placed in a beaker with an internal volume of 1, and while stirring slowly with a lab mixer, it was mixed with sachin white (major diameter 3 784 pieces of 25.5% paste (manufactured by Shiraishi Kogyo Co., Ltd.) of
Sachin white water dispersion with a high concentration of 25% was obtained by continuing to stir the fly for 18 minutes at m. The viscosity of this Sachin White aqueous dispersion as measured by a Hercules viscometer was 3 ps (110 ps, Bob A, hereinafter the same) as shown in Table 2. Further, even after 2 hours at room temperature, the increase in viscosity was extremely small and was only 3 ps. After preparing the Sachin White aqueous dispersion, it was heated at 75 oo for 10 minutes and then cooled to room temperature and the viscosity was measured in the same manner, but the viscosity increase was small, and the viscosity was measured in the same manner.
It was 7cps. Comparative Example 1 In Example 1, instead of using the mixed aqueous solution (solid content: 4.0 μm) of copolymer alkali neutralized product m obtained in Reference Example 1 and sodium hexametaphosphate, the solution obtained in Reference Example 1 was used. A sachin white aqueous dispersion having a concentration of 25% was obtained in the same manner as in Example 1, except that only an aqueous solution (solid content: 4.0%) of copolymer alkaline hydrate '1) was used.

The viscosity of this Sachin White aqueous dispersion measured by a Hercules viscometer was 4 ps as shown in Table 3.
After 24 hours at room temperature, the specific ps increased to 21 ps. In addition, when the sachin white aqueous dispersion was prepared and then heat-treated at 75 qo for 1 minute and then cooled to room temperature and the viscosity was measured in the same manner, the viscosity had increased to more than the measurement limit of 30 ps. Example 2 To an aqueous solution (solid content: 100%) of the alkali neutralized copolymer obtained in Reference Example 2, 40% of potassium pyrophosphate was added and dissolved.

An aqueous satinvite dispersion having a concentration of 25% was obtained in the same manner as in Example 1, except that this mixed aqueous solution (solid content: 5.0%) was used. The viscosity of this Sachin White aqueous dispersion was measured using a Hercules viscometer, and the results are shown in Table 2. Comparative Example 2 In Example 1, instead of using the mixed aqueous solution of copolymer alkali neutralized product '1} and sodium hexametaphosphate, the copolymer alkali neutralized product 1 obtained in Reference Example 2 (solid content: 5. Concentration 2 was prepared in the same manner as in Example 1 except that
A 5% sachin white aqueous dispersion was obtained.

The viscosity measurement results were as shown in Table 3. Example 3 5.0% sodium tripolophosphate was added to an aqueous solution (solid content: 100%) of the alkali-neutralized copolymer base obtained in Reference Example 3.
9 was added and dissolved.

A satin white aqueous dispersion having a concentration of 25% was obtained in the same manner as in Example 1 except that this mixed aqueous solution (solid content: 4.0%) was used. The viscosity measurement results were as shown in Table 2. Example 4 A powder obtained by drying the copolymer alkali neutralized aqueous solution {4} obtained in Reference Example 4 under reduced pressure: 100 yen and sodium pyrophosphate 1 yen
The mixture was uniformly mixed.

This mixture 4.0% was added to the same Sachin White 25.5% paste 784 as used in Example 1, and after stirring, stirring was continued for 15 minutes at 500 pm, and the Sachin White aqueous dispersion was I got it. The viscosity measurement results were as shown in Table 2. Example 5 To 100 g of the powder obtained by drying the aqueous solution of the copolymer alkali neutralized product obtained in Reference Example 5 under reduced pressure, 30 g of sodium xametaphosphate was added and mixed uniformly.

5.0% of this mixture was added with 784% of the same sachin white 25.5% paste used in Example 1, and Example 4
A sachin white aqueous dispersion was obtained in the same manner as above. The viscosity measurement results were as shown in Table 2. Comparative Example 3 40 g of potassium pyrophosphate was dissolved in an aqueous solution of the copolymer alkali neutralized product 6 obtained in Comparative Reference Example 1 (solid content: 100 g).

A sachin white aqueous dispersion was obtained in the same manner as in Example 1 except that this mixed aqueous solution (solid content: 5.0 mm) was used.
The viscosity measurement results were as shown in Table 3. Comparative example 4 Commercially available sodium polyacrylate (molecular weight 4000) 5
．． The same Sachin White 25.0 was used in Example 1.
A 5% paste 784 was added to obtain a sachin white aqueous dispersion in the same manner as in Example 4.

The viscosity measurement results were as shown in Table 3. Comparative Example 5 The same procedure was carried out as in Example 1, except that instead of the mixed aqueous solution of copolymer alkali neutralized product 1 and sodium hexametaphosphate, an aqueous solution prepared by dissolving only 5.0 g of potassium pyrophosphate in 20 g of water was used. Although a paste of Sachin White was added in the same manner as in Example 1, a low-viscosity aqueous dispersion was not obtained, and the viscosity immediately after production was 30 specific ps or more.

Furthermore, the viscosity after 2 hours at room temperature was 30 ps or more. Table 2 (Note) Viscosity (cps) measured with a Hercules viscometer (1,100 rpm, Bop A).

Table 3 (Note) Hercules type viscometer (1,100c
pm, viscosity (cps) according to Bob A).

Claims (1)

[Claims] 1 Unsaturated monomer (a) selected from the group consisting of hydroxyalkyl acrylate and hydroxyalkyl methacrylate and unsaturated carboxylic acid (b) are essential components, and the unsaturated monomer (a) is within the range of 80 to 5 mol%. and an alkali neutralized product of a copolymer obtained using unsaturated carboxylic acid (b) in an amount within the range of 20 to 95 mol% (
A) Sachin White aqueous dispersion characterized in that Sachin White microcrystals are dispersed in water in the presence of a water-soluble phosphate (B) in an amount ranging from 5 to 40 parts to 100 parts. manufacturing method.