JPS6012894B2 - Dispersant for Sachin White - Google Patents

Description

[Detailed description of the invention] The present invention relates to a dispersant for satin white.

More specifically, the present invention relates to a dispersant that provides an aqueous satin white dispersion that has excellent dispersibility and stability and has a low viscosity even at high concentrations. Sachin white is a white pigment in the form of needle-like crystals, and is generally obtained by adding and reacting an aqueous solution of aluminum sulfate to a suspension of calcium hydroxide.
3.*aS04.31-3 is calcium sulfomate represented by the chemical formula 20. It is usually supplied as a hard cake-like satin white paste containing 70 to 75% water by weight, but it has been considered one of the pigments that is difficult to disperse. Traditionally, Sachin White has been used as a distinctive coating pigment together with kaolin gray, calcium carbonate, etc. For example, coated paper obtained using Sachin White has excellent whiteness, gloss, printability, etc. However, in this case, it is strongly required that the pigment particles have extremely fine particle diameters and excellent dispersibility. In particular, when coating at high speeds like the current one, if the dispersibility of the pigment is poor, the apparent viscosity of the coating solution will increase and the fluidity will deteriorate, making it difficult to achieve good coating. Physical properties deteriorate. Sodium pyrophosphate, sodium hexametaphosphate, sodium polyacrylate, and the like are conventionally known as dispersants for satin white. However, these dispersants require a large amount to be added in order to impart sufficient fluidity to the aqueous satin white dispersion, and they also have drawbacks such as extremely poor fluidity under high shear conditions. In order to overcome these drawbacks, a method using an inorganic fluorine compound as a dispersant has been proposed (Japanese Patent Application Laid-Open No. 117825/1982), but it is difficult to add a large amount of an inorganic fluorine compound, which is a readily water-soluble salt. This is not desirable. In addition, a copolymer of acrylic acid and itaconic acid (
Japanese Patent Publication No. 47-33055) and saponified products of polyacrylic acid esters (Japanese Patent Publication No. 47-45411) have been disclosed. However, all of these methods only show a dispersing effect at a low concentration of satin white of 20%. The present inventors have solved the above-mentioned problems in dispersants for sachin white.As a result of intensive research, a block copolymer consisting of a repeating structural unit (A) and a repeating horizontal unit (B) has been found to be a dispersant for satin white. The present invention was completed based on the discovery that it has excellent effects as an agent and can solve all of the problems mentioned above.

Therefore, an object of the present invention is to provide a dispersant suitable for paper coating, which allows easy production of a satin white aqueous dispersion with high concentration, low viscosity, and excellent dispersion stability by adding a small amount. It is. That is, the dispersant for satin white of the present invention has the general formula (where n is an integer of 5 to 100).

) and the general formula (wherein R represents hydrogen or a methyl group, and X represents hydrogen, a monovalent metal, a divalent metal, an ammonium group, or an organic amine group). It consists of a repeating structural unit (B) shown by, and the total amount of (A) and the total amount of (B) are 5:95 to
It consists of a block copolymer having a ratio of 40:60.

Such a block copolymer can be used as a dispersant for sachin white of the present invention, but such a block copolymer has, for example, a general formula (where n is 5 to 100). is an integer.

), and the general formula (wherein R represents hydrogen or a methyl group, and X represents hydrogen, a monovalent metal, a divalent metal, an ammonium group, or an organic Represents an amine group.

) It can be obtained by copolymerizing the (meth)acrylic acid monomer (0) represented by 0 using a polymerization initiator, and further neutralizing with an alkaline substance if necessary.

Polyethylene glycolyl monoallyl ether (1) is represented by the above general formula, and has an added mole number n of ethethylene oxide of 5 to 100. If the number of added moles n is less than 5, the resulting block copolymer will have poor performance as a dispersant for satin white, and if it exceeds 100, the zero copolymerization reactivity of such polyethylene glycol monoallyl ether will be low. , a block copolymer effective as a dispersant of the present invention cannot be obtained. Polyethylene glycoyl monoallyl ether (1) is KOH or Na
It can be synthesized by a known method of directly adding ethylene oxide to allyl alcohol using an alkali such as OH as a catalyst.

The (meth)acrylic acid monomer (0) is represented by the general formula above, and specifically includes acrylic acid, methacrylic acid, and their monovalent metal salts, divalent metal salts, and ammonium salts. and organic amine salts. One or more of these can be used. The block copolymer used as the dispersant for sachin white of the present invention has a weight ratio of the total amount of repeating structural units (A) to the total amount of repeating structural units (B) and 8- to 5:95 to 4.
It is necessary to be within the range of 0:60.

Therefore, when producing a block copolymer, polyethylene glycol monoacrylic ether (1) and (meth)
The charging ratio of the acrylic acid monomer (0) is such that the total amount of repeating structural units (A) and the total amount of repeating structural units (B) in the obtained block copolymer fall within the above ratio range. You must do so. If the ratio is outside this range, a dispersant with excellent performance will not be obtained. In order to produce the block copolymer used as the dispersant of the present invention from polyethylene glycoyl monoallyl ether (1) and (meth)acrylic acid monomer (0), copolymerization is performed using a polymerization initiator. That's fine. Copolymerization can be carried out by methods such as polymerization in a solvent or bulk polymerization. Polymerization in a solvent can be carried out either batchwise or continuously, and the solvents used in this case include water, lower alcohols, mixed solvents of water and lower alcohols, aromatic hydrocarbons, aliphatic hydrocarbons,
Examples include ketone compounds and ethyl acetate.

As the polymerization solvent, various water-soluble polymerization initiators, peroxides, hydroperoxides, combinations of these with polymerization accelerators, azo compounds, etc. are used depending on the solvent used. The polymerization temperature is appropriately determined depending on the solvent and polymerization initiator used, but is usually 0 to 120
This is done within the range of oo.

When water is used as a solvent, sodium hydrogen sulfite-oxygen may be used as a polymerization catalyst.

In this case, the polymerization is carried out by blowing oxygen gas or a mixed gas of oxygen and an inert gas into the solvent while adding sodium hydrogen sulfite to the solvent containing the raw material monomer, and adding 5 to 80 q.
The polymerization reaction can be carried out by proceeding the polymerization reaction within a temperature range of o. Bulk polymerization uses peroxide, hydroperoxide, or an azo compound as a polymerization initiator,
It is carried out within a temperature range of 50 to 15,000 °C.

When producing a block copolymer in this way,
polyethylene glycol monoallyl ether (1),
The block copolymer obtained depends on the charging ratio with the (meth)acrylic acid monomer (b), the amount of polymerization initiator used, the polymerization temperature, the type and amount of the solvent in the case of polymerization in a solvent, etc. The molecular weight of can be adjusted as appropriate. The molecular weight of the block copolymer used as the dispersant for sachin white of the present invention is from 500 to 100,000, preferably from 100 to 100,000.
Those in the range of 0 to 20,000 are particularly effective. The block copolymer thus obtained can be used as it is as a dispersant for satin white of the present invention, but if necessary, it may be further neutralized with an alkali compound. Preferred examples of such alkaline substances include hydroxides, chlorides, and carbonates of monovalent metals and divalent metals, ammonia, and organic amines. To obtain an aqueous dispersion of Sachin White using the dispersant for Sachin White of the present invention, Sachin White may be dispersed in water in the presence of the dispersant.

The amount of the dispersant used is 0.1 to 5 parts by weight, preferably 0.5 to 3 parts by weight, per 100 parts by weight of sachin white. As a method for dispersing Sachin White, for example, a method of adding Sachin White Base to an aqueous solution containing a dispersant and mixing it with a rope, or a method of adding a dispersant and water to Sachin White Base and mixing it with water. By these methods, a satin white aqueous dispersion can be easily obtained with good workability.

As a method for mixing the ropes, a commonly used rope mixing device such as a ribbon mixer, kneader, high-speed mixer, etc. can be used. However, the scope of the present invention is not limited by the method of adding the dispersant and satin white, or the method of adding the dispersant and satin white. The aqueous satin white dispersion thus obtained using the dispersant of the present invention exhibits low viscosity at a high solid content concentration of 25% by weight with a small amount added compared to conventional dispersants, and It has excellent dispersion stability and is extremely easy to handle.

The reason why the dispersant for satin white of the present invention provides such excellent effects is not yet clear, but it is thought to be as follows.

That is, the block copolymer constituting the dispersant of the present invention is
Contains two types of blocks with different properties in one molecule: an anionic block having a carboxyl group and/or a salt thereof, and a nonionic and hydrophilic block consisting of a high molar adduct of ethylene oxide. However, among these, the anionic block adsorbs to the surface of the Sachin White particles, helps disperse the Sachin White particles, prevents reagglomeration, and further reduces the viscosity. It is believed that the nonionic and hydrophilic block contributes to maintaining the stability of the reduced viscosity. However, the scope of the present invention is not limited by this reason. The present invention will be explained in more detail below using Examples and Comparative Examples, but it goes without saying that the present invention is not limited to these Examples.

Furthermore, all parts in the examples represent parts by weight. still,
The viscosity of the dispersant aqueous solution and the viscosity of the Sachin White aqueous dispersion in the examples were all measured using a Pismetron viscometer manufactured by Seiki Kogyo Research Institute under conditions of 25 qo and 6 ratio pm. In addition, the molecular weight was measured using gel permeation chromatography (24 ships manufactured by Waters). Furthermore, the residual rate of each monomer was also determined using gel permeation chromatography, and the polymerization rate and the weight ratio of the structural units constituting each copolymer were calculated. Example 1 Polyethylene glycolyl monoallyl ether (containing an IN solid ethylene oxide unit per molecule on average) was placed in a glass reaction vessel equipped with a thermometer, a base plater, a dropping funnel, a gas inlet pipe, and a reflux condenser. 20% of a monomer mixture aqueous solution consisting of 30 parts and 922 parts of a 18.4% sodium acrylate aqueous solution and 20% of 4 parts of a 5% ammonium persulfate aqueous solution were charged into the reaction vessel by dropping a rope. was replaced with nitrogen and heated to 9,500 ℃.

Thereafter, the remaining monomer mixture aqueous solution and ammonium persulfate aqueous solution were added in 12 portions each. After the addition was completed, add 8 parts of 5% ammonium sulfate aqueous solution for 20 minutes.
Added in minutes. After completing the addition of the sodium acrylate aqueous solution, the temperature was maintained at 9,500 ℃ for 12 minutes to complete the polymerization reaction, and an aqueous solution of floc copolymer {1} was obtained. Table 1 shows the pH, viscosity and molecular weight of this aqueous solution of copolymer {1-, residual monomer rate, polymerization rate, weight ratio in the copolymer, and charged weight ratio of monomers. Using the above copolymer m as a dispersant, the dispersibility of Sachin White (manufactured by Shiraishi Kogyo Co., Ltd.) was evaluated according to the following routine. That is, deionized water, Sachin White, and an aqueous solution of the copolymer {1-} in the amount shown in Table 2 were charged into a stainless steel beaker with an internal volume of 1, and a Lab Body Spar (manufactured by Tokushu Kika Kogyo Co., Ltd., M-Kin) was charged.
A 25% sachin white slurry was prepared by heating the slurry for 20 minutes using a L-shape, and the viscosity of each slurry was measured.
The results were as shown in Table 2. As shown in Table 2, the dispersant of the present invention has excellent dispersion ability even when added in a small amount compared to the low molecular weight sodium polyacrylate (molecular weight 5000) conventionally used in this branch. ing.

Example 2 Into the same reaction vessel as in Example 1, 54 parts of polyethylene glycol monoallyl ether (containing on average 2 solid ethylene oxide units per minute molecule), 126 parts of acrylic acid,
An azeotropic composition (IPA/
Water = 87.4/12.6 (weight ratio)) 20% of the 41 mixture was charged, the inside of the reaction vessel was purged with nitrogen under Azusa Taka, and heated to the boiling point.

The remainder of the above mixture was then added over 120 minutes. After the addition is complete, add an additional 0.4 parts of penzoyl peroxide to I
A PA-water azeotropic composition dispersed in 7.6 parts was added in two portions to every 3 females. After completing the addition of the above mixture,
The temperature was maintained at boiling point for 120 minutes to complete the polymerization reaction. After that, completely neutralize with aqueous caustic soda solution, m
A was removed to obtain an aqueous solution of copolymer [2]. The pH, viscosity and molecular weight of the aqueous solution of this copolymer [2], the residual rate of monomer, the polymerization rate, the weight ratio in the copolymer, and the charged weight ratio of monomers are as shown in Table 1. Ta.

Example 01 using the above copolymer [2' as a dispersant]
The dispersibility of Sachin White was evaluated using the same method as described above.

The results were as shown in Table 2. Example 3 60 parts of polyethylene glycotal monoallyl ether (containing 3 boxes of ethylene oxide units per molecule on average) and 524 parts of water were placed in the same reaction vessel as in Example 1, and the mixture was placed in the reaction vessel under Azusa Taka. was replaced with nitrogen and heated to 9,500 ℃.

Thereafter, 368 parts of a 38% sodium methacrylate aqueous solution and 40 parts of a 5% ammonium persulfate aqueous solution were each added over 120 minutes, and after the addition was completed, 8 parts of a 5% ammonium persulfate aqueous solution was further added over 20 minutes. After the addition of the monomers was completed, the temperature was maintained at 95q0 for 12 minutes to complete the polymerization reaction, and an aqueous solution of copolymer {3' was obtained. The pH, viscosity and molecular weight of the aqueous solution of this copolymer (3), residual rate of monomer, polymerization rate, weight ratio in the copolymer, and charged weight ratio of monomers were as shown in Table 1. The dispersion of Sachin White was evaluated in the same manner as in Example 1 using the above copolymer '3' as a dispersant.The results were as shown in Table 2.Example 4 Example 1 In the same reaction vessel as above, 70 parts of polyethylene glycol monoallyl ether (containing on average 1 solid ethylene oxide unit per molecule) and 54 parts of water were charged.
The inside of the reaction vessel was purged with nitrogen under clear conditions and heated to 95°C.

After that, total % sodium acrylate aqueous solution 342 groups and 5
4 parts of a 5% aqueous ammonium persulfate solution were added at 12 parts each, and after the addition was complete, an additional 8 parts of a 5% aqueous ammonium persulfate solution were added over 20 minutes. After the addition of the monomers was completed, the temperature was maintained at 95° C. for 120 minutes to complete the polymerization reaction, and an aqueous solution of copolymer 4 was obtained. The pH, viscosity and molecular weight of this aqueous solution of copolymer '4-, residual rate of monomer, polymerization rate, weight ratio in the copolymer, and charged weight ratio of monomers were as shown in Table 1. . The dispersibility of satin white was evaluated in the same manner as in Example 1 using the above copolymer [4' as a dispersant.

The results were as shown in Table 2. Example 5 Into the same reaction vessel as in Example 1, a monomer consisting of 36 parts of polyethylene glycol monoallyl ether (containing an average of 2 solid ethylene oxide units per molecule) and 82 parts of a 20% aqueous sodium acrylate solution was added. 20% of the aqueous mixture solution and 20% of 12 parts of a 5% aqueous ammonium sulfate solution per week were charged, and the inside of the reaction vessel was purged with nitrogen and heated to 95°C.

Thereafter, the remaining monomer mixture aqueous solution and catalyst solution were each added over a period of 120 minutes. After the addition was completed, 24 parts of 5% ammonium persulfate aqueous solution was added over 20 minutes. 95 for 120 minutes after completing the addition of the sodium acrylate aqueous solution.
The polymerization reaction is completed by maintaining the temperature at qo, and the copolymer [5
An aqueous solution of ' was obtained. The pH of the aqueous solution of this copolymer [5-
Table 1 shows the viscosity, molecular weight, monomer residual rate, polymerization rate, weight ratio in the copolymer, and monomer charge weight ratio. The dispersion of Sachin White was evaluated in the same manner as in Example 1 using the above copolymer field as a dispersant.
The results were as shown in Table 2. Example 6 40 parts of polyethylene glycol monoallyl ether (containing on average 1 solid ethylene oxide unit per molecule) and 491 parts of water were placed in the same reaction bath vessel as in Example 1, and reacted by dropping a rope. The inside of the container was directly flushed with nitrogen and heated to 990℃.

Thereafter, partially neutralized sodium acrylate (85 mol%
A total of 421 parts of a 5% aqueous solution of ammonium persulfate (neutralization) and 4 parts of a 5% aqueous solution of ammonium persulfate were each added over 120 minutes. After the addition was complete, 8 parts of 5% ammonium persulfate aqueous solution was added over 2 minutes. 95 for 120 minutes after monomer addition is complete.
The temperature was maintained at 0.degree. C. to complete the polymerization reaction. Thereafter, it was completely neutralized with a caustic soda aqueous solution to obtain an aqueous solution of English Polymer '61. The pH, viscosity and molecular weight of this aqueous solution of copolymer (1), residual rate of monomer, polymerization rate, weight ratio in the copolymer and charge weight ratio of monomers were as shown in Table 1. The dispersibility of Sachin White was evaluated in the same manner as in Example 1 using the copolymer '6' as a dispersant.

The results were as shown in Table 2. Comparative Example 1 Into the same reaction vessel as in Example 1, 4 parts of polyethylene glycol monoallyl ether (containing ethylene oxide units of IN solids per molecule on average) and 432 g of water were charged, and the inside of the reaction vessel was poured under a rope. The atmosphere was replaced with nitrogen and the mixture was heated to 95°C.

After that, 516 parts of 38% sodium acrylate aqueous solution and 5
% ammonium persulfate aqueous solution 4 and 120% each
Added in minutes. After the addition was complete, 8 parts of 5% ammonium persulfate aqueous solution was further added over 20 minutes. After the monomer addition was completed, the temperature was maintained at 95° C. for 120 minutes to complete the polymerization reaction, and an aqueous solution of comparative copolymer [1' was obtained. The pH, viscosity and molecular weight of this aqueous solution of Comparative Copolymer '11, residual rate of monomer, polymerization rate, weight ratio in the copolymer, and charge weight ratio of monomers were as shown in Table 1. . The dispersibility of satin white was evaluated in the same manner as in Example 1 using the above comparative copolymer [1-] as a dispersant. The results were as shown in Table 2. Comparative Example 2 Into the same reaction vessel as in Example 1, 150 parts of polyethylene glycol monoallyl ether (containing on average 1 unit of ethylene oxide per molecule) and 67 parts of water were charged into the reaction vessel using a hawk. was replaced with nitrogen and heated to 95 oo.

Then 38% sodium acrylate aqueous solution 132 and 5
% ammonium persulfate aqueous solution, 12% each
Added at 0 minutes. After the addition was complete, 8 parts of a 5% ammonium persulfate aqueous solution was added in 2 portions. After the addition of the monomers was completed, the temperature was maintained at 95 qo for 120 minutes to complete the polymerization reaction, and an aqueous solution of Z shark copolymer (2) was obtained. Table 1 shows the pH, viscosity, molecular weight, residual rate of monomer, polymerization rate, weight ratio in the copolymer, and charged weight ratio of monomers of the aqueous solution of comparative copolymer (1). A satin white aqueous dispersion was obtained in the same manner as in Example 1 using the comparative copolymer (1) as a dispersant.

The viscosity of this moisture content material was measured in the same manner as in Example 1. The results were as shown in Table 2. Comparative Example 3 A satin white slurry was prepared in the same manner as in Example 1 except that commercially available low molecular weight sodium polyacrylate (molecular weight 5000) was used as a dispersant,
The viscosity was measured.

The results were as shown in Table 2. Table 1 (Note 1) 4
Viscosity of aqueous solution with 0* concentration (B-type viscometer, 25℃, 60r
(Measured in pm) However, only the copolymer diagram was measured with a 45% concentration aqueous solution.

(Note 2) Measured using gel vermation chromatography-K. (Note 3) Acrylic acid was determined as sodium acrylate. Moreover, the weight ratio of the copolymer was also determined based on sodium acrylate. Table 2 (Note 1) Measured values are in cps (Note 2) Amount of dispersant (solid content) per 100 parts of sachin weight (unit: parts) Example 7 In the same reaction vessel as in Example 1, polyethylene glycol monomer was added. Allyl ether (containing on average 5 ethylene oxide units per molecule) 1
2 parts and 445 parts of water were charged, the inside of the reaction vessel was replaced with nitrogen under a vacuum cleaner, heated to 95oC in a nitrogen atmosphere, and then heated to 95oC in a nitrogen atmosphere.
495 parts of an 8% aqueous sodium acrylate solution and 4 parts of a 5% aqueous ammonium persulfate solution were each added over 120 minutes, and after the addition was complete, 8 parts of a 5% aqueous ammonium persulfate solution was added in 2 minutes.

After the addition of monomer 2 was completed, the temperature was maintained at 95 qC for 12 minutes to complete the polymerization reaction, and an aqueous solution of the copolymer was obtained. Table 3 shows the pH, viscosity, molecular weight, residual rate of monomer, polymerization rate, weight ratio in the English polymer, and charged weight ratio of monomers of this copolymer '7} aqueous solution. The dispersibility of satin white was evaluated in the same manner as in Example 1 using the above copolymer [71] as a dispersant. The results were as shown in Table 4. Example 8 Into the same reaction vessel as in Example 1, 76 parts of polyethylene glycol monoallyl ether (containing on average 1 solid ethylene oxide unit per molecule) and 55 parts of water were charged.
Before dropping the flies, the inside of the reaction vessel was replaced with nitrogen, and the temperature was increased to 95% in a nitrogen atmosphere.
It was heated to qo.

Then 326 parts of 8% sodium acrylate aqueous solution and 5
% ammonium persulfate aqueous solution and 12 parts each
After the addition was completed, 8 parts of 5% ammonium persulfate aqueous solution was added over 20 minutes. After the addition of the monomers was completed, the temperature was maintained at 95° C. for 120 minutes to complete the polymerization reaction, and an aqueous copolymer solution was obtained. The pH, viscosity, molecular weight, residual rate of monomer, polymerization rate,
Table 3 shows the weight ratio in the copolymer and the weight ratio of monomers charged. The dispersibility of satin white was evaluated in the same manner as in Example 1 using the above copolymer [8] as a dispersant.

The results are shown in Table 4, Table 3 (Note 1),
(Note 2) and (Note 3) are the same as Table 1K.

Table 4 (Note 1) The unit of face U' constant value is cps. (Note 2) Amount of dispersant (solid content) (unit: parts) per 100 parts of sachin powder.As shown in Tables 2 and 4, the present invention If this dispersant is used, excellent dispersion properties can be achieved even when used in small amounts.

Claims (1)

[Claims] 1 A repeating structural unit (A) represented by the general formula ▲ Numerical formulas, chemical formulas, tables, etc. (where n is an integer from 5 to 100) and the general formula ▲ Numerical formula, There are chemical formulas, tables, etc. ▼ (However, in the formula, R represents hydrogen or a methyl group, and X represents hydrogen, a monovalent metal, a divalent metal, an ammonium group, or an organic amine group.) Repeating structural unit ( B) and (A
) and (B) in a weight ratio of 5:95 to 40:
A dispersant for Sachin White comprising a block copolymer having a molecular weight within the range of 60.