JP5240411B2 - Dispersant for calcium carbonate and method for producing the same - Google Patents

Abstract

Provided is a dispersant for calcium carbonate with which the initial viscosity of a calcium carbonate slurry obtained by wet grinding is low and furthermore a marked rise in viscosity over time is prevented, and also provided is a method for producing the dispersant for calcium carbonate. The dispersant for calcium carbonate contains an acrylic polymer having a weight-average molecular weight between 4,500 and 8,500 that is obtained by: a polymerization step in which a monomer comprising acrylic acid is polymerized at a reaction temperature between 68 and 82ºC in the presence of 1.4 to 4.4 parts by mass of a hypophosphite and 0.3 to 1.5 parts by mass of a persulfate per 100 parts by mass of the monomer, using an isopropyl alcohol aqueous solution as a solvent; and a neutralization step in which 15 to 95 mol% of carboxyl groups having structural units derived from the monomer comprising the resulting polymer are neutralized.

Description

  The present invention relates to a dispersant for calcium carbonate and a method for producing the same. More specifically, the present invention relates to a calcium carbonate dispersant in which the initial viscosity of a calcium carbonate slurry obtained by wet pulverization is low and a significant increase in viscosity over time is suppressed, and a method for producing the same.

Calcium carbonate slurry obtained by wet pulverization of calcium carbonate is widely used for paper coating agents, paint pigments, and the like. In the production of the calcium carbonate slurry, a dispersant for calcium carbonate is used to lower the viscosity of the obtained calcium carbonate slurry.
As this calcium carbonate dispersant, a dispersant containing an acrylic polymer is used in order to obtain a slurry having a low viscosity.
As a method for obtaining this dispersant, for example, Patent Document 1 discloses a method for producing a polymer having a low molecular weight by using water as a solvent and using a large amount of a molecular weight regulator such as sodium hypophosphite. Has been. However, when the dispersant obtained by this method is used, the viscosity of the obtained calcium carbonate slurry is high, and the viscosity may increase remarkably with time.
On the other hand, as a method not using a molecular weight regulator such as sodium hypophosphite, for example, in Patent Document 2, the weight average molecular weight is 4,000 to 40,000, and Mw / Mn is 1.2 to 2. A method for producing a dispersant comprising a polymer containing a vinyl group-containing monocarboxylic acid (salt) as a constituent unit using 0 persulfate as a polymerization initiator and isopropyl alcohol as a reaction solvent and molecular weight regulator. It is disclosed. Patent Documents 3 and 4 also disclose a method for producing a dispersant using persulfate as a polymerization initiator and isopropyl alcohol as a reaction solvent and molecular weight regulator, as in Patent Document 2.

JP 60-174793 A JP 2004-306222 A JP 2004-315359 A WO 2004/087574

However, in the production methods described in Patent Documents 2 to 4 described above, since only a persulfate is used as a polymerization initiator, the performance of the resulting dispersant is still not fully satisfactory.
The present invention has been made in view of the above problems, and the calcium carbonate slurry obtained has a low initial viscosity, suppresses a significant increase in viscosity over time, and has excellent long-term dispersion stability. And it aims at providing the manufacturing method.

  As a result of intensive studies in view of the above problems, the present inventors have found that a calcium carbonate slurry obtained by wet pulverization or the like has a low initial viscosity and has a small increase in viscosity over time. Used as a polymerization step for polymerizing a monomer containing acrylic acid in the presence of hypophosphite and persulfate, and the structural unit derived from the monomer constituting the obtained polymer has And a neutralizing step for neutralizing 15 to 95 mol% of the carboxyl group, whereby a dispersant for calcium carbonate in which the initial viscosity of the obtained calcium carbonate slurry is low and a significant increase in viscosity over time is suppressed. I found out to get.

The present invention is as follows.
1. Derived from the above-described monomer constituting the polymer, and a polymerization step of polymerizing a monomer containing acrylic acid in the presence of hypophosphite and persulfate using an isopropyl alcohol aqueous solution as a solvent A neutralizing step of neutralizing 15 to 95 mol% of the carboxyl group of the structural unit, and an acrylic polymer obtained by comprising
The amount of the hypophosphite used is 1.4 to 4.4 parts by mass with respect to 100 parts by mass of the monomer.
The amount of the persulfate used is 0.3 to 1.5 parts by mass with respect to 100 parts by mass of the monomer.
The reaction temperature in the polymerization step is 68 to 82 ° C.
A dispersing agent for calcium carbonate, wherein the acrylic polymer has a weight average molecular weight of 4,500 to 8,500.
2. The said 1. provided with the concentration process which distills isopropyl alcohol after the said polymerization process. Dispersant for calcium carbonate as described in 1.
3. In the concentration step, the isopropyl alcohol recovered by the distillation is used in the polymerization step. Dispersant for calcium carbonate as described in 1.
4). The isopropyl alcohol concentration in the isopropyl alcohol aqueous solution is 15 to 55% by mass. To 3. The dispersing agent for calcium carbonate of any one of these.
5. The acrylic acid used in the polymerization step is contained in an amount of 80 to 100% by mass with respect to 100% by mass of the total amount of the monomers. To 4. The dispersing agent for calcium carbonate of any one of these.
6). A method for producing a dispersant for calcium carbonate containing an acrylic polymer,
A polymerization step of polymerizing a monomer containing acrylic acid in the presence of hypophosphite and persulfate using an aqueous isopropyl alcohol solution as a solvent;
A neutralization step of neutralizing 15 to 95 mol% of the carboxyl group of the structural unit derived from the monomer constituting the obtained polymer,
The amount of the hypophosphite used is 1.4 to 4.4 parts by mass with respect to 100 parts by mass of the monomer.
The amount of the persulfate used is 0.3 to 1.5 parts by mass with respect to 100 parts by mass of the monomer.
The reaction temperature in the polymerization step is 68 to 82 ° C.
A method for producing a dispersing agent for calcium carbonate, wherein the acrylic polymer has a weight average molecular weight of 4,500 to 8,500.
7. 5. The above-mentioned 6. comprising a concentration step for distilling off isopropyl alcohol after the polymerization step. The manufacturing method of the dispersing agent for calcium carbonate as described in any one of.
8). In the concentration step, the isopropyl alcohol recovered by the distillation is used in the polymerization step. The manufacturing method of the dispersing agent for calcium carbonate as described in any one of.
9. 6. The isopropyl alcohol concentration of the isopropyl alcohol aqueous solution is 15 to 55% by mass. To 8. The manufacturing method of the dispersing agent for calcium carbonate of any one of these.
10. The acrylic acid used in the polymerization step is contained in an amount of 80 to 100% by mass with respect to 100% by mass of the total amount of the monomers. Thru 9. The manufacturing method of the dispersing agent for calcium carbonate of any one of these.

According to the dispersant for calcium carbonate of the present invention, it is excellent in dispersibility of calcium carbonate, and particularly exhibits excellent dispersibility and long-term dispersion stability as a dispersant for wet grinding of calcium carbonate. The dispersant for calcium carbonate of the present invention uses isopropyl alcohol having the function of a molecular weight regulator as a solvent, and uses a hypophosphite as a molecular weight regulator and a persulfate as a polymerization initiator in combination. In addition, it is possible to provide a dispersant for calcium carbonate that contains fewer by-products such as phosphite and phosphate by-produced from hypophosphite and sulfate by-produced from persulfate. By using the dispersing agent for calcium carbonate of the present invention, the calcium carbonate slurry obtained can have a low initial viscosity and can be a calcium carbonate slurry that suppresses a significant increase in viscosity over time.
Moreover, when the acrylic acid used at the said polymerization process is contained 80-100 mass% with respect to 100 mass% of said monomer whole quantity, it is set as the dispersing agent for calcium carbonate which the dispersibility of calcium carbonate is further excellent. be able to.

The method for producing a dispersant for calcium carbonate of the present invention efficiently produces a dispersant for calcium carbonate that forms a calcium carbonate slurry in which the initial viscosity of the calcium carbonate slurry is low and a significant increase in viscosity over time is suppressed. Can do.
In addition, when a concentration step for distilling off isopropyl alcohol is provided after the polymerization step, a dispersant for calcium carbonate with reduced isopropyl alcohol can be efficiently produced.
In addition, in the concentration step, when isopropyl alcohol recovered by the distillation is used in the polymerization step, the distilled isopropyl alcohol is reused in the polymerization step, so that there is no need for disposal and cost can be reduced. Thus, it is possible to provide a method for producing a dispersant for calcium carbonate that is excellent in production efficiency and environmental conservation.
In addition, when the acrylic acid used in the polymerization step is contained in an amount of 80 to 100% by mass with respect to 100% by mass of the total amount of the monomer, the calcium carbonate dispersant is further improved in efficiency. Can be manufactured well.

Hereinafter, the dispersant for calcium carbonate of the present invention (hereinafter also simply referred to as “dispersant”) and the method for producing the dispersant for calcium carbonate of the present invention will be described in detail.
The present invention includes a polymerization step in which a monomer containing acrylic acid is polymerized in the presence of hypophosphite and persulfate using an aqueous isopropyl alcohol solution as a solvent, and an obtained polymer (hereinafter, “ And a neutralizing step for neutralizing 15 to 95 mol% of the carboxyl group of the structural unit derived from the monomer constituting the “first polymer”), and an acrylic polymer obtained by a production method The amount of the hypophosphite used is 1.4 to 4.4 parts by mass with respect to 100 parts by mass of the monomer, and the amount of persulfate used is the monomer. It is 0.3-1.5 mass parts with respect to 100 mass parts, The reaction temperature of the said superposition | polymerization process is 68-82 degreeC, The weight average molecular weight of the said acrylic polymer is 4,500-8, 500.
In this specification, “(meth) acryl” is used to mean one or both of acrylic and methacrylic.

  The dispersant of the present invention is obtained by including the polymerization step and the neutralization step. The raw materials used for forming the dispersant of the present invention will be described.

In the polymerization step, the monomer polymerized by the polymerization reaction is a monomer containing at least acrylic acid. Therefore, the total amount of the monomer may be acrylic acid, and the monomer may contain acrylic acid as part of the monomer.
The monomer other than acrylic acid (hereinafter also referred to as “other monomer”) is not particularly limited as long as it is a monomer copolymerizable with acrylic acid. Specifically, a vinyl monomer (polymerizable unsaturated compound) having radical polymerizability is exemplified. Examples of the vinyl monomers include ethylenically unsaturated carboxylic acids other than acrylic acid, neutralized salts of ethylenically unsaturated carboxylic acids, (meth) acrylic acid alkyl ester compounds, aromatic vinyl compounds, and acid anhydrides. , Amino group-containing vinyl compounds, amide group-containing vinyl compounds, sulfonic acid group-containing vinyl compounds, polyoxyalkylene group-containing vinyl compounds, alkoxyl group-containing vinyl compounds, cyano group-containing vinyl compounds, vinyl cyanide compounds, vinyl ether compounds, vinyl esters Examples thereof include compounds and conjugated dienes. These can be used alone or in combination of two or more.
Of these, (meth) acrylic acid alkyl ester compounds and polyoxyalkylene group-containing vinyl compounds are preferred from the viewpoint of the physical properties (dispersion stability, coloration suppression, etc.) of the resulting dispersant.

  Examples of ethylenically unsaturated carboxylic acids other than acrylic acid include methacrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, crotonic acid, phthalic anhydride half-esterified with alkyl alcohol, and itaconic anhydride And those obtained by half-esterification with alkyl alcohol.

  Examples of the neutralized salt of the ethylenically unsaturated carboxylic acid include ethylenically unsaturated carboxylic acids in which carboxyl groups such as acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, fumaric acid, itaconic acid, and crotonic acid are neutralized. Salt. Examples of the ethylenically unsaturated carboxylate include alkali metal salts, alkaline earth metal salts, ammonium salts, and organic amine salts.

  Examples of the (meth) acrylic acid alkyl ester compound include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and n-butyl (meth) acrylate. , Isobutyl (meth) acrylate, sec-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-pentyl (meth) acrylate, isoamyl (meth) acrylate, n-hexyl (meth) acrylate , 2-methylpentyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-decyl (meth) acrylate, n-dodecyl (meth) acrylate, (meth) N-octadecyl acrylate, isobornyl (meth) acrylate, cyclohexyl (meth) acrylate, Meth) phenyl acrylate include benzyl (meth) acrylate and the like.

  Examples of the aromatic vinyl compound include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, and 4-tert-butylstyrene. Tert-butoxystyrene, vinyltoluene, vinylnaphthalene, halogenated styrene, styrenesulfonic acid, α-methylstyrenesulfonic acid, and the like.

  Examples of the acid anhydride monomer include maleic anhydride, itaconic anhydride, citraconic anhydride, and the like.

  Examples of the amino group-containing vinyl compound include dimethylaminomethyl (meth) acrylate, diethylaminomethyl (meth) acrylate, 2-dimethylaminoethyl (meth) acrylate, 2-diethylaminoethyl (meth) acrylate, (meth) 2- (di-n-propylamino) ethyl acrylate, 2-dimethylaminopropyl (meth) acrylate, 2-diethylaminopropyl (meth) acrylate, 2- (di-n-propylamino) (meth) acrylate Propyl, 3-dimethylaminopropyl (meth) acrylate, 3-diethylaminopropyl (meth) acrylate, 3- (di-n-propylamino) propyl (meth) acrylate, and the like.

  Examples of the amide group-containing vinyl compound include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-methylol (meth) acrylamide and the like.

  Examples of the sulfonic acid group-containing vinyl compound include methallylsulfonic acid, acrylamide-2-methyl-2-propanesulfonic acid, and the like.

  Examples of the polyoxyalkylene group-containing vinyl compound include (meth) acrylic acid esters of alcohols having a polyoxyethylene group and / or a polyoxypropylene group.

  Examples of the alkoxyl group-containing vinyl compound include 2-methoxyethyl (meth) acrylate, 2-ethoxyethyl (meth) acrylate, 2- (n-propoxy) ethyl (meth) acrylate, and 2- (meth) acrylic acid 2- (N-butoxy) ethyl, 3-methoxypropyl (meth) acrylate, 3-ethoxypropyl (meth) acrylate, 2- (n-propoxy) propyl (meth) acrylate, 2- (n) (meth) acrylate -Butoxy) propyl and the like.

  Examples of the (meth) acrylic acid ester compound having a cyano group include cyanomethyl (meth) acrylate, 1-cyanoethyl (meth) acrylate, 2-cyanoethyl (meth) acrylate, 1-cyanopropyl (meth) acrylate, (Meth) acrylic acid 2-cyanopropyl, (meth) acrylic acid 3-cyanopropyl, (meth) acrylic acid 4-cyanobutyl, (meth) acrylic acid 6-cyanohexyl, (meth) acrylic acid 2-ethyl-6- And cyanohexyl and 8-cyanooctyl (meth) acrylate.

  Examples of the vinyl cyanide compound include acrylonitrile, methacrylonitrile, ethacrylonitrile and the like.

Examples of the vinyl ether compound include vinyl methyl ether, vinyl ethyl ether, vinyl-n-butyl ether, vinyl phenyl ether, vinyl cyclohexyl ether and the like. These may be used alone or in combination of two or more.
Examples of the vinyl ester monomer include vinyl formate, vinyl acetate, and vinyl propionate.

  Examples of the conjugated diene include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, 1,3-pentadiene, 2-methyl-1,3-pentadiene, 1,3-hexadiene, 4, 5-diethyl-1,3-octadiene, 3-butyl-1,3-octadiene, chloroprene and the like can be mentioned.

  Other maleimide compounds such as maleimide, N-methylmaleimide, N-butylmaleimide, N-phenylmaleimide, N-cyclohexylmaleimide; maleic acid ester compounds; itaconic acid ester compounds; N-vinyl heterocyclic compounds such as vinylpyridine Is mentioned.

  Of these other monomers, methyl acrylate and butyl acrylate are preferable. By using methyl acrylate, butyl acrylate or the like together with acrylic acid, a dispersant excellent in suppression of coloring can be obtained.

  In the polymerization step, when the monomer includes other monomers other than acrylic acid, the content of acrylic acid is preferably 70% by mass or more with respect to 100% by mass of the total monomer. More preferably, it is 80 mass% or more, More preferably, it is 90 mass% or more. Particularly preferred is the case where the total amount of monomers is 100% by mass and acrylic acid is used. When the content of acrylic acid is 70% by mass or more, the solubility of the resulting dispersant in water can be made sufficient.

  In the polymerization step, hypophosphite is used as a chain transfer agent. The hypophosphite is not particularly limited as long as it is a compound having a chain transfer action. Specifically, sodium hypophosphite, potassium hypophosphite, lithium hypophosphite, calcium hypophosphite, Examples thereof include magnesium phosphite and barium hypophosphite. These can be used alone or in combination of two or more. Of these, sodium hypophosphite is preferred.

  The usage-amount of the said hypophosphite is 1.4-4.4 mass parts with respect to 100 mass parts of monomers, Preferably it is 2.0-4.0 mass parts, More preferably, it is 2.5. -3.5 parts by mass. When the amount of hypophosphite used is within the above range, a polymer having a weight average molecular weight of 4,500 to 8,500 can be obtained efficiently. Further, when the amount of hypophosphite used is 4.4 parts by mass or less, a dispersant having a low content of by-product phosphite and phosphate can be obtained. The resulting calcium carbonate slurry has a low initial viscosity, a significant increase in viscosity over time can be suppressed, and a dispersant having excellent long-term dispersion stability can be obtained. In addition, when there is much usage-amount of hypophosphite (for example, it uses more than 4.4 mass parts), the initial viscosity of a calcium carbonate slurry will become high, and the viscosity will raise remarkably with time. This is presumed that the increase in viscosity is caused by the increase of phosphite and phosphate, which are by-products generated from hypophosphite, and this by-product forms a poorly soluble compound with calcium carbonate. The

  In the polymerization step, persulfate is used as a polymerization initiator (radical polymerization initiator). The persulfate is not particularly limited, and specific examples include sodium persulfate, ammonium persulfate, and potassium persulfate. These can be used alone or in combination of two or more. Among these, sodium persulfate and potassium persulfate are preferred because volatile components are unlikely to be generated in the neutralization step performed after the polymerization step.

  The persulfate is used in an amount of 0.3 to 1.5 parts by weight, preferably 0.4 to 1.4 parts by weight, more preferably 0.6 to 1 part per 100 parts by weight of the monomer. .2 parts by mass. When the amount of persulfate used is within the above range, unreacted monomers can be reduced. Furthermore, when the amount of persulfate used is 1.5 parts by mass or less, a dispersant having a low content of by-produced sulfate can be obtained. If the amount of persulfate used is large (for example, more than 1.5 parts by mass), the initial viscosity of the calcium carbonate slurry increases, and the viscosity increases with time. As in the case of hypophosphite, the by-product sulfate generated from persulfate increases, and this by-product forms a poorly soluble compound with calcium carbonate, resulting in an increase in viscosity. Inferred.

In the polymerization step, an aqueous solution of isopropyl alcohol is used as a solvent.
Isopropyl alcohol also acts as a chain transfer agent in the polymerization step. Therefore, the isopropyl alcohol aqueous solution is used as a reaction solvent and a chain transfer agent.
The isopropyl alcohol concentration of the aqueous isopropyl alcohol solution is preferably 5% by mass or more and 90% by mass or less, more preferably 10 to 80% by mass, still more preferably 15 to 60% by mass, and particularly preferably 15 to 55% by mass. %, And may be 20 to 50% by mass or 30 to 50% by mass.
When the concentration of isopropyl alcohol is 5% by mass or more, the chain transfer effect as a chain transfer agent possessed by isopropyl alcohol works effectively. Further, if the concentration of isopropyl alcohol is increased, the action of the chain transfer effect is also improved accordingly.

  Moreover, in the said polymerization process, the usage-amount of isopropyl alcohol becomes like this. Preferably it is 15-80 mass parts with respect to 100 mass parts of monomers, More preferably, it is 45-75 mass parts. When the amount of isopropyl alcohol used is 15 parts by mass or more, the chain transfer effect of isopropyl alcohol works effectively. Moreover, the solubility of a raw material improves that it is 80 mass parts or less.

  In the polymerization step, a monomer containing acrylic acid is polymerized with a monomer containing acrylic acid using an aqueous solution of isopropyl alcohol as a reaction solvent in the presence of hypophosphite and persulfate. And a step of obtaining a first polymer having a structural unit derived from the monomer.

  As reaction temperature in the said superposition | polymerization process, it is 68-82 degreeC, Preferably it is 70-80 degreeC. By setting the reaction temperature to 82 ° C. or lower, the polymerization can be smoothly advanced and the molecular weight modifier hypophosphorous acid can be prevented from being oxidized to phosphite or phosphate. It is possible to make a dispersant having a low content of phosphite and phosphate. Moreover, the dispersing agent with few unreacted monomers can be obtained by making reaction temperature 68 degreeC or more.

The polymerization step may be a batch polymerization method or a continuous polymerization method. In the case of the batch polymerization method, the time required for the step of supplying the raw material (raw material composition) containing the monomer is preferably 2 to 12 hours, more preferably 3 to 8 hours. If the required time is 2 hours or longer, it is easy to remove the heat of polymerization, and if it is 12 hours or shorter, the productivity is increased.
As the reaction apparatus, a known reaction apparatus can be used in batch polymerization, and it is preferable to have a stirrer and a temperature control apparatus. The stirrer is not particularly limited as long as a known stirring blade is installed, and examples of the stirring blade include an anchor blade, a paddle blade, a propeller blade, a turbine blade, a ribbon blade, and a large flat blade. Moreover, as said temperature control apparatus, a well-known internal and / or external heat exchanger, such as a jacket, an internal coil, or plate-type heat exchange, can be employed. Further, a baffle or the like may be provided in the reactor as necessary for the purpose of increasing the stirring efficiency and the like.
In the case of the continuous polymerization method, the process is preferably performed by a multistage CSTR (continuous stirred tank reactor having a plurality of reaction tanks). In this case, the average residence time of each reaction tank is preferably 60 to 240 minutes, and more preferably 80 to 180 minutes. When the average residence time is 60 minutes or longer, unreacted monomers can be reduced. Moreover, the size of a reaction tank can be made small as it is 240 minutes or less.
Also in the case of continuous polymerization, the same thing as the said batch type can be used for the stirrer, the apparatus for temperature control, etc.

The polymerization method for obtaining the first polymer in the polymerization step is not particularly limited. For example, the following aspects (1) to (3) may be mentioned.
(1) A predetermined amount of isopropyl alcohol aqueous solution is held in a reaction vessel. And the raw material mixture which consists of a monomer, isopropyl alcohol aqueous solution and hypophosphite, and persulfate are dripped at reaction container, and a polymerization reaction is performed.
(2) A raw material mixture composed of a monomer, an aqueous isopropyl alcohol solution and hypophosphite is prepared, and the above raw material mixture and persulfate are dropped into a reaction vessel to carry out a polymerization reaction.
(3) An aqueous isopropyl alcohol solution is charged into the reaction vessel and kept at the same temperature as the reaction temperature or a temperature close thereto. And a monomer, hypophosphite, and persulfate are dripped at the reaction container, and a polymerization reaction is performed.
Of these, the embodiment (1) is preferred because a uniform polymer is obtained.

  As a specific example of the above (1), a predetermined amount (20 to 80% by mass of the total amount used) of isopropyl alcohol aqueous solution is previously held in the reaction vessel at the same temperature as or close to the reaction temperature. . On the other hand, a raw material mixture composed of the remaining aqueous isopropyl alcohol solution, monomers, and hypophosphite charged into the reaction vessel is prepared. And it can be set as the method of dripping the said raw material mixture and persulfate to the said reaction container with which the isopropyl alcohol aqueous solution was hold | maintained, and performing a polymerization reaction.

  In the polymerization step, isopropyl alcohol having the function of a molecular weight regulator is used as a solvent, and the hypophosphite of the molecular weight regulator and the persulfate of the polymerization initiator are used in combination. When used, the resulting calcium carbonate slurry has a low initial viscosity and can be a calcium carbonate slurry in which a significant increase in viscosity over time is suppressed. This is because the amount of hypophosphite and persulfate used is reduced, and phosphite and phosphoric acid by-produced from hypophosphite and sulfate by-produced from persulfate. Therefore, the formation of a hardly soluble compound between the by-product and calcium carbonate is suppressed, whereby the initial viscosity of the slurry is low and a significant increase in viscosity over time is suppressed. .

  By the polymerization step, a first polymer formed from a monomer containing acrylic acid is obtained. The weight average molecular weight of the first polymer is preferably 4500-8500. The weight average molecular weight can be measured by a gel permeation chromatography (GPC) using a standard substance such as sodium polyacrylate. When the weight average molecular weight of the first polymer is 4500-8500, the weight average molecular weight of the acrylic polymer obtained after the subsequent neutralization step can be 4500-8500.

  The said neutralization process is a process of neutralizing the carboxyl group which the structural unit derived from the said monomer which comprises the 1st polymer obtained by the said polymerization process has. By this neutralization step, a part of the carboxyl group is neutralized, and an acrylic polymer contained in the dispersant can be obtained.

The neutralization of the carboxyl group in the neutralization step can be performed with a basic compound. Although it will not specifically limit as said basic compound if it is a compound which can neutralize a carboxyl group, For example, an inorganic basic compound and an organic basic compound are mentioned. These can be used alone or in combination of two or more.
Examples of the inorganic basic compound include alkali metal hydroxides such as sodium hydroxide, potassium hydroxide and lithium hydroxide, alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide, and ammonia water. It is done.
Examples of the organic basic compound include organic amine compounds such as monoethanolamine and triethanolamine. Of these basic compounds, alkali metal hydroxides that generate less volatile components are preferred, and sodium hydroxide is more preferred.

  In the neutralization step, the amount (neutralization rate) of neutralizing the carboxyl group of the first polymer is 15 to 95 mol%, preferably 20 to 90 mol%. It can be set as the dispersing agent excellent in the dispersion performance which disperse | distributes calcium carbonate as the said neutralization rate is 15-95 mol%.

The acrylic polymer is a polymer in which a monomer containing acrylic acid is polymerized, and a part of the carboxyl group derived from the monomer is neutralized. The composition derived from the hypophosphite and persulfate used in the above may be included.
The weight average molecular weight of the acrylic polymer is 4500-8500, preferably 5000-8000. The weight average molecular weight can be measured by GPC using a standard substance such as sodium polyacrylate as described above. When the weight average molecular weight of the acrylic polymer is within the above range, it becomes a dispersant having excellent dispersion performance for dispersing calcium carbonate, the initial viscosity of the resulting calcium carbonate slurry is low, and the viscosity increase with time is small. It can be a dispersant.

  Moreover, as a dispersing agent of this invention, in addition to the said polymerization process and the said neutralization process, a concentration process can be further provided after the said polymerization process. The concentration step is preferably provided between the polymerization step and the neutralization step.

  In the concentration step, isopropyl alcohol is distilled off from the reaction solution containing the first polymer obtained in the polymerization step to obtain a concentrated composition in which isopropyl alcohol is reduced.

  In the concentration step, isopropyl alcohol can be distilled out of the system by reducing the pressure of the reaction system and / or heating the reaction system. Thereby, isopropyl alcohol can be distilled off from the reaction solution. The isopropyl alcohol distilled off is usually an azeotrope with water. Therefore, in the concentration step, isopropyl alcohol is distilled off from the reaction solution as an aqueous solution, and a concentrated composition in which isopropyl alcohol and water are reduced is obtained.

  The method for distilling off isopropyl alcohol in the concentration step is not particularly limited. For example, water and isopropyl alcohol can be distilled out of the system by subjecting the reaction system to reduced pressure and keeping its internal temperature at or above the azeotropic temperature of isopropyl alcohol. Further, water and isopropyl alcohol may be distilled out of the system by passing the reaction solution through a thin film evaporator under reduced pressure.

  The content of isopropyl alcohol contained in the concentrated composition obtained by the concentration step is preferably 1% by mass or less, more preferably 5000 ppm or less, still more preferably 2000 ppm by mass or less, and particularly preferably 1000% by mass. ppm or less.

Moreover, the isopropyl alcohol aqueous solution distilled off in the concentration step can be recovered. And this collect | recovered isopropyl alcohol aqueous solution can be repeatedly used in a superposition | polymerization process. When the aqueous isopropyl alcohol solution is reused, it is not necessary to discard the distilled isopropyl alcohol, the cost is reduced, the production efficiency is excellent, and the dispersant for calcium carbonate, which is excellent in environmental conservation, and calcium carbonate It can be set as the manufacturing method of the dispersing agent.
When recovering an isopropyl alcohol aqueous solution, the concentration of the isopropyl alcohol aqueous solution may change before and after the recovery. This is because the recovered isopropyl alcohol is recovered as an azeotropic mixture of isopropyl alcohol and water after being distilled off, so even if a high concentration isopropyl alcohol aqueous solution is used in the polymerization step, This is because the isopropyl alcohol concentration of the recovered isopropyl alcohol aqueous solution is usually about 60% by mass or less.
On the other hand, in the above polymerization step, it is preferable to use the isopropyl alcohol aqueous solution at a constant concentration even when the recovered isopropyl alcohol aqueous solution is reused in order to increase the efficiency of the production process. That is, when the polymerization step is performed at a high concentration of 60% by mass or more of isopropyl alcohol, the concentration of the recovered isopropyl alcohol aqueous solution may be lower than that before the recovery due to distillation. In that case, it is necessary to concentrate the recovered aqueous isopropyl alcohol solution so as to have a high concentration. Depending on the concentration of the aqueous isopropyl alcohol solution, the concentration of the recovered aqueous isopropyl alcohol solution may be higher than before the recovery. When the concentration of the recovered isopropyl alcohol aqueous solution becomes higher than that before the recovery, water may be newly added to adjust the concentration. However, when the recovered aqueous isopropyl alcohol solution is concentrated so as to have a high concentration, a concentration facility is required, resulting in poor production efficiency.
Accordingly, the isopropyl alcohol aqueous solution can be recycled by making the concentration of isopropyl alcohol in the aqueous isopropyl alcohol solution lower than the concentration of isopropyl alcohol in the recovered isopropyl alcohol aqueous solution in the concentration step. The concentration of isopropyl alcohol for recovering and using this aqueous isopropyl alcohol solution is preferably 15 to 55% by mass, more preferably 20 to 50% by mass, and still more preferably 30 to 50% by mass. When the recovered isopropyl alcohol aqueous solution is reused, the isopropyl alcohol aqueous solution is preferably reused in the polymerization step by adjusting the isopropyl alcohol concentration.

  The concentrated composition obtained in the concentration step is subjected to the neutralization step to neutralize a part of the carboxyl groups of the first polymer to obtain an acrylic polymer contained in the dispersant. be able to.

  The dispersant of the present invention includes the acrylic polymer obtained by providing the polymerization step, the neutralization step, and the like, and a solution in which the acrylic polymer is dissolved in an aqueous medium, or an acrylic heavy polymer. It can be set as the dispersion liquid which united substance disperse | distributed to the aqueous medium. In addition, the said aqueous medium is a medium containing water, and may be only water or a mixture containing water.

  Moreover, as a dispersing agent of this invention, the reaction liquid (a) by the reaction product obtained by providing the said superposition | polymerization process and the said neutralization process, or the said superposition | polymerization process, the said concentration process, and the said neutralization process are included. The reaction liquid (b) obtained by providing can be used as the dispersant of the present invention. Among these, it is preferable to use the reaction liquid (b) as a dispersant from the viewpoint of efficiently obtaining a dispersant. Further, these dispersants may be further added with an aqueous medium.

The reaction liquid (b) is an aqueous solution in which an acrylic polymer is dissolved in an aqueous medium, and the hypophosphite and / or its by-products, persulfate, and In some cases, the by-product and the basic compound used in the neutralization step may be included. Furthermore, the reaction solution (b) may contain isopropyl alcohol in an amount corresponding to the content after the concentration step.
The content of isopropyl alcohol contained in the reaction liquid (b) can be 1% by mass or less, preferably 5000 ppm by mass or less, more preferably 2000 ppm by mass or less, and still more preferably 1000 ppm by mass. It is as follows.

  When the dispersing agent of this invention is the said reaction liquid (b), pH and solid content concentration are not specifically limited. As pH, Preferably it is 3-8, More preferably, it is 3-7. Moreover, as solid content concentration, Preferably it is 35-55%, More preferably, it is 40-50%.

Moreover, the dispersing agent of this invention can contain other components, such as an antifoamer and a preservative, further.
Examples of the antifoaming agent include polyethers, mineral oils, silicones, and amides. When the dispersant of the present invention contains the antifoaming agent, the content thereof is preferably 0.01 to 1.0% by mass with respect to 100 parts by mass of the acrylic polymer.

  Examples of the preservative include isothiazoline and parabens. When the dispersant of the present invention contains the preservative, the content thereof is preferably 0.001 to 1.0% by mass with respect to 100 parts by mass of the acrylic polymer.

The dispersant of the present invention may be a solution or dispersion in which an acrylic polymer and the above-described other components blended as necessary are contained in an aqueous medium.
Moreover, when the dispersing agent of this invention contains the said other component, another component is added and mixed. In addition, the said mixing is not specifically limited, It can carry out by a well-known method.

When obtaining a calcium carbonate slurry using the dispersant of the present invention, the amount of the dispersant is not particularly limited, but the acrylic polymer is 0.1 to 10.0 mass per 100 mass parts of calcium carbonate. It is preferable to mix | blend so that a part and an aqueous medium may be 25-100 mass parts.
And the calcium carbonate slurry can be obtained by wet-grinding the mixture of the dispersing agent containing calcium carbonate and acrylic polymer blended as described above by a known method.

  The dispersant of the present invention is excellent in the dispersibility of calcium carbonate, and is suitably used as a dispersant for calcium carbonate when calcium carbonate is wet pulverized to obtain a calcium carbonate slurry. The calcium carbonate slurry obtained using the dispersant of the present invention has a low initial viscosity, a remarkable increase in viscosity with time is suppressed, and a slurry having excellent long-term dispersion stability can be obtained.

  Moreover, when the dispersing agent of this invention contains the said other component, the other component added as needed can be mixed with an acrylic polymer. Moreover, when the dispersing agent of this invention is the aqueous solution or dispersion liquid by the aqueous medium containing an acrylic polymer, another component is added and mixed with this aqueous solution and dispersion liquid as needed. In addition, the said mixing is not specifically limited, It can carry out by a well-known method.

Examples of the present invention will be described below together with synthesis examples and comparative examples, but it goes without saying that the scope of the present invention is not limited to these examples. In the following, “part” and “%” are based on mass unless otherwise specified.
Further, “Mw” in Synthesis Examples, Examples and Comparative Examples means a weight average molecular weight. This “Mw” was measured by gel permeation chromatography (GPC). The GPC measurement conditions were as follows. As the GPC apparatus, an HLC8020 system (manufactured by Tosoh Corporation) was used, and the columns used were G4000PWxl, G3000PWxl, and G2500PWxl (all columns manufactured by Tosoh Corporation). The eluent was 0.1M NaCl + phosphate buffer (pH 7), and the calibration curve was prepared using polyacrylic acid Na (manufactured by Sowa Kagaku Co., Ltd.).

In the synthesis examples, examples and comparative examples, the viscosity of the slurry of heavy calcium carbonate after wet pulverization and the viscosity of the slurry after standing at 25 ° C. for 7 days are 25 ° C. using a B-type viscometer. , And measured at 60 rpm.
The median diameter of the heavy calcium carbonate slurry after the wet pulverization and the 1.32 μm under integrated value of the slurry after the wet pulverization of the slurry were measured by a laser diffraction scattering type particle size distribution measuring apparatus LA-910 (Horiba, Ltd.). ).

<Preparation of dispersant for calcium carbonate and preparation of heavy calcium carbonate slurry>
Example 1-1 (Preparation of Dispersant 1-1 and Preparation of Slurry Using Dispersant 1-1)
A flask equipped with a stirrer and a condenser was charged with 500 g of an aqueous solution having a isopropyl alcohol (hereinafter also simply referred to as “IPA”) concentration of 36% and maintained at 80 ° C. Next, a mixture of 600 g of acrylic acid (hereinafter also simply referred to as “AA”), 20 g of sodium hypophosphite, and 270 g of an aqueous solution having an IPA concentration of 36%, 40 g of a 15% aqueous sodium persulfate solution, Was supplied dropwise over 4 hours to cause reaction (polymerization). Furthermore, after completion | finish of dripping, the reaction liquid was hold | maintained at 80 degreeC for 1 hour, and was reacted (polymerization). Subsequently, about the obtained reaction liquid, IPA was depressurizingly distilled, throwing in deionized water until IPA density | concentration became 1000 mass ppm or less. Subsequently, the reaction solution obtained by distilling off IPA under reduced pressure was maintained at 80 ° C., and a 32% aqueous sodium hydroxide solution was supplied so that the neutralization rate was 22 mol%. As a result, a dispersant 1-1 containing an acrylic polymer 1-1 and having a solid content concentration of 40% and a pH of 4 was obtained. Mw of the acrylic polymer 1-1 contained in the dispersant 1-1 was 6000. Further, Table 1 shows the amount of each raw material used, the concentration of each raw material, the ratio of the raw material to 100 parts of the monomer, and the like used for preparing the dispersant.

17 g of the dispersant 1-1 obtained as described above, 320 g of ion-exchanged water, and 900 g of heavy calcium carbonate (manufactured by Maruo Calcium Co., Ltd., “Charcoal Cal A”) are put into a cylindrical container and stirred gently. Blended evenly. Next, 3000 g of media (1 mmφ ceramic beads) was put into the cylindrical container and stirred at 1000 rpm for 50 minutes to wet pulverize heavy calcium carbonate. Thereafter, the slurry was recovered through a 200-mesh filter cloth, and ion exchange water was added to adjust the solid content to 75%, thereby obtaining a heavy calcium carbonate slurry. And when the viscosity immediately after wet grinding of this slurry and the viscosity after standing for 7 days at 25 ° C. were measured as described above, the viscosity immediately after wet grinding was 210 mPa · s, and the viscosity after 7 days was 1800 mPa · s. s.
Moreover, when the median diameter of the slurry immediately after wet grinding and the 1.32 μm under integrated value were measured as described above, the median diameter was 0.67 μm, and the 1.32 μm under value was 100%. These results are shown in Table 1.
In the following Examples and Comparative Examples, Tables 1 to 6 show the amount of each raw material used, the concentration of each raw material, the ratio of the raw material to 100 parts of the monomer, and the like used for preparing the dispersant. Further, in the following Examples and Comparative Examples, in the same manner as in Example 1-1, the Mw of the acrylic polymer contained in the dispersant, the viscosity of the heavy calcium carbonate slurry after wet pulverization, and 7 at 25 ° C. The viscosity of the slurry after standing for one day, the median diameter of the heavy calcium carbonate slurry after wet pulverization, and the 1.32 μm under integrated value of the slurry after wet pulverization of the slurry were measured. Shown in ~ 6.

Example 1-2 (Preparation of Dispersant 1-2 and Preparation of Slurry Using Dispersant 1-2)
In Example 1-2, Dispersant 1-2 was prepared using the recovered IPA aqueous solution which was distilled off during preparation of Dispersant 1-1 in Example 1-1 above.
When the concentration of the IPA aqueous solution recovered in Example 1-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 1-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. And except having used this IPA aqueous solution which adjusted this density | concentration, it carries out similarly to Example 1-1, performs polymerization, pressure reduction distillation, and neutralization, and solid content density | concentration containing the acrylic polymer 1-2 is carried out. Dispersant 1-2 with 40% and pH 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 1-2.

Example 2-1 (Preparation of Dispersant 2-1 and Preparation of Slurry Using Dispersant 2-1)
Polymerization, distillation under reduced pressure and neutralization were carried out in the same manner as in Example 1-1 except that the aqueous solution having an IPA concentration of 36% in Example 1-1 was used instead of the aqueous solution having an IPA concentration of 48%. In addition, a dispersant 2-1 containing an acrylic polymer 2-1 and having a solid content concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 2-1.

Example 2-2 (Preparation of Dispersant 2-2 and Preparation of Slurry Using Dispersant 2-2)
In Example 2-2, Dispersant 2-2 was prepared using the IPA aqueous solution which was distilled off during the preparation of Dispersant 2-1, and recovered in Example 2-1. When the concentration of the IPA aqueous solution recovered in Example 2-1 was measured, the IPA concentration was 48%. Since the concentration of this IPA aqueous solution was the same as the concentration of IPA used in Example 2-1, the concentration was not adjusted. And except having used this collect | recovered IPA aqueous solution, it carried out similarly to Example 2-1, superposed | polymerized, depressurizingly distilled, and neutralized, and the solid content density | concentration containing acrylic polymer 2-2 is 40. Dispersant 2-2 with% and pH 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 2-1 using the obtained dispersing agent 2-2.

Example 3-1 (Preparation of Dispersant 3-1 and Preparation of Slurry Using Dispersant 3-1)
Except that the amount of sodium hypophosphite in Example 1-1 was changed from 20 g to 17 g, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1-1 to obtain an acrylic polymer 3 Dispersant 3-1 containing -1 and having a solid content concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 3-1.

Example 3-2 (Preparation of Dispersant 3-2 and Preparation of Slurry Using Dispersant 3-2)
In Example 3-2, Dispersant 3-2 was prepared using the IPA aqueous solution which was distilled off and recovered in Preparation of Dispersant 3-1, in Example 3-1.
When the concentration of the IPA aqueous solution recovered in Example 3-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 3-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, vacuum distillation and neutralization were performed in the same manner as in Example 3-1, and the solid content concentration containing the acrylic polymer 3-2 was reduced. Dispersant 3-2 with 40% and pH 4 was obtained.
And using the obtained dispersing agent 3-2, it carried out similarly to Example 3-1, and obtained the heavy calcium carbonate slurry.

Example 4-1 (Preparation of Dispersant 4-1 and Preparation of Slurry Using Dispersant 4-1)
Except that the amount of the sodium persulfate aqueous solution in Example 1-1 was changed from 40 g to 30 g, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1-1 to obtain an acrylic polymer 4- 1 and a dispersant 4-1 having a solids concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 4-1.

Example 4-2 (Preparation of Dispersant 4-2 and Preparation of Slurry Using Dispersant 4-2)
In Example 4-2, Dispersant 4-2 was prepared using IPA which was distilled off during the preparation of Dispersant 4-1, and recovered in Example 4-1.
When the concentration of the IPA aqueous solution recovered in Example 4-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 4-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. And except having used this IPA aqueous solution whose density | concentration adjustment was carried out, it carried out similarly to Example 4-1, and it superposed | polymerized, depressurizingly distilled, and neutralized, and solid content density | concentration containing the acrylic polymer 4-2 is carried out. Dispersant 4-2 with 40% and pH 4 was obtained.
And using the obtained dispersing agent 4-2, it carried out similarly to Example 4-1, and obtained the heavy calcium carbonate slurry.

Example 5-1 (Preparation of Dispersant 5-1 and Preparation of Slurry Using Dispersant 5-1)
Polymerization and depressurization were carried out in the same manner as in Example 1-1 except that the holding temperature of the IPA in the flask in Example 1-1, the reaction temperature in the polymerization, and the temperature in the neutralization were changed from 80 ° C to 75 ° C. Distillation and neutralization were performed to obtain Dispersant 5-1, which contains acrylic polymer 5-1, and has a solids concentration of 40% and a pH of 4.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 5-1.

Example 5-2 (Preparation of Dispersant 5-2 and Preparation of Slurry Using Dispersant 5-2)
In Example 5-2, Dispersant 5-2 was prepared using IPA which was distilled off during the preparation of Dispersant 5-1, and recovered in Example 5-1.
When the concentration of the IPA aqueous solution recovered in Example 5-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 5-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 5-1, and the solid content concentration containing the acrylic polymer 5-2 was reduced. Dispersant 5-2 with 40% and pH 4 was obtained.
And using the obtained dispersing agent 5-2, it carried out similarly to Example 5-1, and obtained the heavy calcium carbonate slurry.

Example 6-1 (Preparation of Dispersant 6-1 and Preparation of Slurry Using Dispersant 6-1)
In the same manner as in Example 1-1, except that the neutralization rate with the 32% aqueous sodium hydroxide solution in Example 1-1 was changed from 22 mol% to 40 mol%, polymerization, distillation under reduced pressure, and Summing was performed to obtain a dispersant 6-1 containing an acrylic polymer 6-1 and having a solid content concentration of 40% and a pH of 5.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 6-1.

Example 6-2 (Preparation of Dispersant 6-2 and Preparation of Slurry Using Dispersant 6-2)
In Example 6-2, the dispersant 6-2 was prepared using the recovered IPA which was distilled off during the preparation of the dispersant 6-1 in the above Example 6-1.
When the concentration of the IPA aqueous solution recovered in Example 6-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 6-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 6-1, and the solid content concentration containing the acrylic polymer 6-2 was reduced. Dispersant 6-2 with 40% and pH 5 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 6-1 using the obtained dispersing agent 6-2.

Example 7-1 (Preparation of Dispersant 7-1 and Preparation of Slurry Using Dispersant 7-1)
Polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1-1 except that the aqueous solution having an IPA concentration of 36% in Example 1-1 was used instead of the aqueous solution having an IPA concentration of 20%. A dispersant 7-1 containing an acrylic polymer 7-1 and having a solid content concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 7-1.

Example 7-2 (Preparation of Dispersant 7-2 and Preparation of Slurry Using Dispersant 7-2)
In Example 7-2, Dispersant 7-2 was prepared using the recovered IPA which was distilled off during preparation of Dispersant 7-1 in Example 7-1.
When the concentration of the IPA aqueous solution recovered in Example 7-1 was measured, the IPA concentration was 25%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 7-1, deionized water was added and it adjusted to the aqueous solution of IPA density | concentration 20%. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 7-1, and the solid content concentration containing the acrylic polymer 7-2 was reduced. Dispersant 7-2 with 40% and pH 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 7-1 using the obtained dispersing agent 7-2.

Example 8-1 (Preparation of Dispersant 8-1 and Preparation of Slurry Using Dispersant 8-1)
Polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1-1 except that the aqueous solution having an IPA concentration of 36% in Example 1-1 was used in place of the aqueous solution having an IPA concentration of 53%. Thus, a dispersant 8-1 containing an acrylic polymer 8-1 and having a solid content concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 8-1.

Example 8-2 (Preparation of Dispersant 8-2 and Preparation of Slurry Using Dispersant 8-2)
In Example 8-2, Dispersant 8-2 was prepared using the recovered IPA which was distilled off during preparation of Dispersant 8-1 in Example 8-1 above.
When the concentration of the IPA aqueous solution recovered in Example 8-1 was measured, the IPA concentration was 53%. Since the concentration of this IPA aqueous solution was the same as the concentration of the IPA aqueous solution used in Example 8-1, the concentration was not adjusted. Then, in the same manner as in Example 8-1, polymerization, distillation under reduced pressure, and neutralization were performed, and the dispersant 8-containing an acrylic polymer 8-2 and having a solid content concentration of 40% and a pH of 4 was used. 2 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 8-1 using the obtained dispersing agent 8-2.

Example 9-1 (Preparation of Dispersant 9-1 and Preparation of Slurry Using Dispersant 9-1)
Except that the amount of sodium hypophosphite in Example 1-1 was changed from 20 g to 9.5 g, polymerization, distillation under reduced pressure and neutralization were carried out in the same manner as in Example 1-1. Dispersant 9-1 containing solid 9-1 and having a solids concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 9-1.

Example 9-2 (Preparation of Dispersant 9-2 and Preparation of Slurry Using Dispersant 9-2)
In Example 9-2, Dispersant 9-2 was prepared using the recovered IPA aqueous solution which was distilled off during preparation of Dispersant 9-1 in Example 9-1.
When the concentration of the IPA aqueous solution recovered in Example 9-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 9-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 9-1, and the solid content concentration including the acrylic polymer 9-2 was reduced. Dispersant 9-2 with 40% and pH 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 9-1 using the obtained dispersing agent 9-2.

Example 10-1 (Preparation of Dispersant 10-1 and Preparation of Slurry Using Dispersant 10-1)
Except that the amount of sodium hypophosphite in Example 1-1 was changed from 20 g to 26.5 g, polymerization, distillation under reduced pressure and neutralization were carried out in the same manner as in Example 1-1. Dispersing agent 10-1 containing coalescence 10-1 and having a solid content concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 10-1.

Example 10-2 (Preparation of Dispersant 10-2 and Preparation of Slurry Using Dispersant 10-2)
In Example 10-2, the dispersant 10-2 was prepared using the recovered IPA aqueous solution which was distilled off during the preparation of the dispersant 10-1 in the above Example 10-1.
When the concentration of the IPA aqueous solution recovered in Example 10-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 10-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, distillation under reduced pressure and neutralization were carried out in the same manner as in Example 10-1, and the solid content concentration containing the acrylic polymer 9-2 was reduced. Dispersant 10-2 with 40% and pH 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 10-1 using the obtained dispersing agent 10-2.

Example 11-1 (Preparation of Dispersant 11-1 and Preparation of Slurry Using Dispersant 11-1)
Except that the amount of the sodium persulfate aqueous solution in Example 1-1 was changed from 40 g to 12 g, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1-1 to obtain an acrylic polymer 11- 1 and a dispersant 11-1 having a solid content concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 11-1.

Example 11-2 (Preparation of Dispersant 11-2 and Preparation of Slurry Using Dispersant 11-2)
In Example 11-2, the dispersant 11-2 was prepared using the recovered IPA which was distilled off during the preparation of the dispersant 11-1 in the above Example 11-1.
When the concentration of the IPA aqueous solution recovered in Example 11-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 11-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, vacuum distillation and neutralization were performed in the same manner as in Example 11-1, and the solid content concentration including the acrylic polymer 11-2 was reduced. Dispersant 11-2 with 40% and pH 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 11-1 using the obtained dispersing agent 11-2.

Example 12-1 (Preparation of Dispersant 12-1 and Preparation of Slurry Using Dispersant 12-1)
Except that the amount of the sodium persulfate aqueous solution in Example 1-1 was changed from 40 g to 60 g, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1-1 to obtain an acrylic polymer 12- 1 and a dispersant 12-1 having a solid content concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 12-1.

Example 12-2 (Preparation of Dispersant 12-2 and Preparation of Slurry Using Dispersant 12-2)
In Example 12-2, Dispersant 12-2 was prepared using IPA which was distilled off and recovered in Preparation of Dispersant 12-1 in Example 12-1.
When the concentration of the IPA aqueous solution recovered in Example 12-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 12-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. And except having used this IPA aqueous solution whose density | concentration adjustment was carried out, it carried out similarly to Example 12-1, and it superposed | polymerized, depressurizingly distilled, and neutralized, and solid content density | concentration containing the acrylic polymer 12-2 is carried out. Dispersant 12-2 with 40% and pH 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 12-1 using the obtained dispersing agent 12-2.

Example 13-1 (Preparation of Dispersant 13-1 and Preparation of Slurry Using Dispersant 13-1)
In the same manner as in Example 1-1, except that the neutralization rate with the 32% aqueous sodium hydroxide solution in Example 1-1 was changed from 22 mol% to 18 mol%, polymerization, distillation under reduced pressure, and Summing was performed to obtain a dispersant 13-1 containing an acrylic polymer 13-1 and having a solid content concentration of 40% and a pH of 3.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 13-1.

Example 13-2 (Preparation of Dispersant 13-2 and Preparation of Slurry Using Dispersant 13-2)
In Example 13-2, Dispersant 13-2 was prepared using IPA which was distilled off during the preparation of Dispersant 13-1 and recovered in Example 13-1.
When the concentration of the IPA aqueous solution recovered in Example 13-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 13-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 13-1, and the solid content concentration containing the acrylic polymer 13-2 was reduced. Dispersant 13-2 with 40% and pH 3 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 13-1 using the obtained dispersing agent 13-2.

Example 14-1 (Preparation of Dispersant 14-1 and Preparation of Slurry Using Dispersant 14-1)
In the same manner as in Example 1-1, except that the neutralization rate with the 32% aqueous sodium hydroxide solution in Example 1-1 was changed from 22 mol% to 90 mol%, polymerization, vacuum distillation, and Summing was performed to obtain a dispersant 14-1 containing an acrylic polymer 14-1 and having a solid content concentration of 40% and a pH of 7.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 14-1.

Example 14-2 (Preparation of Dispersant 14-2 and Preparation of Slurry Using Dispersant 14-2)
In Example 14-2, the dispersant 14-2 was prepared using the recovered IPA which was distilled off during the preparation of the dispersant 14-1 in the above Example 14-1.
When the concentration of the IPA aqueous solution recovered in Example 14-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 14-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. And except having used this IPA aqueous solution which adjusted this density | concentration, it carried out similarly to Example 14-1, and superposed | polymerized, depressurizingly distilled, and neutralized, and solid content density | concentration containing the acrylic polymer 14-2 is carried out. Dispersant 14-2 with 40% and pH 7 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 14-1 using the obtained dispersing agent 14-2.

Example 15-1 (Preparation of Dispersant 15-1 and Preparation of Slurry Using Dispersant 15-1)
The aqueous solution having an IPA concentration of 36% in Example 1-1 was replaced with an aqueous solution having an IPA concentration of 65%, and the amount of sodium hypophosphite was changed from 20 g to 15 g, as in Example 1-1. Polymerization, distillation under reduced pressure, and neutralization were performed to obtain a dispersant 15-1 containing an acrylic polymer 15-1 and having a solid content concentration of 40% and a pH of 4.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 15-1.

Example 15-2 (Preparation of Dispersant 15-2 and Preparation of Slurry Using Dispersant 15-2)
In Example 15-2, Dispersant 15-2 was prepared using the recovered IPA aqueous solution which was distilled off during the preparation of Dispersant 15-1 in Example 15-1. When the concentration of the IPA aqueous solution recovered in Example 15-1 was measured, the IPA concentration was 55%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 15-1, IPA was concentrated and it adjusted to the aqueous solution whose IPA density | concentration is 65%. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 15-1, and the solid content concentration containing the acrylic polymer 15-2 was reduced. Dispersant 15-2 with 40% and pH 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 15-1 using the obtained dispersing agent 15-2.

Example 16-1 (Preparation of Dispersant 16-1 and Preparation of Slurry Using Dispersant 16-1)
Polymerization was carried out in the same manner as in Example 1-1 except that 600 g of acrylic acid in Example 1-1 was used as 575 g of acrylic acid and 25 g of methyl acrylate, and methyl acrylate was also used in addition to acrylic acid. Then, vacuum distillation and neutralization were performed to obtain a dispersant 16-1 containing an acrylic polymer 16-1 and having a solid content concentration of 40% and a pH of 4.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 16-1.

Example 16-2 (Preparation of Dispersant 16-2 and Preparation of Slurry Using Dispersant 16-2)
In Example 16-2, the dispersant 16-2 was prepared using the recovered IPA which was distilled off during the preparation of the dispersant 16-1 in the above Example 16-1.
When the concentration of the IPA aqueous solution recovered in Example 16-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Example 16-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 16-1, and the solid content concentration containing the acrylic polymer 16-2 was reduced. Dispersant 16-2 with 40% and pH 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 16-1 using the obtained dispersing agent 16-2.
Um slurry was obtained.

Comparative Example 1-1 (Preparation of Dispersant 1-1C and Preparation of Slurry Using Dispersant 1-1C)
Polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1-1 except that the aqueous solution having an IPA concentration of 36% in Example 1-1 was used instead of the aqueous solution having an IPA concentration of 10%. A dispersing agent 1-1C containing an acrylic polymer 1-1C and having a solid content concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 1-1C.

Comparative Example 1-2 (Preparation of Dispersant 1-2C and Preparation of Slurry Using Dispersant 1-2C)
In Comparative Example 1-2, Dispersant 1-2C was prepared using the recovered IPA which was distilled off during preparation of Dispersant 1-1C in Comparative Example 1-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 1-1 was measured, the IPA concentration was 20%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Comparative Example 1-1, deionized water was added and it adjusted to the aqueous solution of 10% of IPA density | concentration. And except having used this IPA aqueous solution whose density | concentration adjustment was carried out, it carried out similarly to Comparative Example 1-1, superposed | polymerized, depressurizingly distilled, and neutralized, and solid content density | concentration containing acrylic polymer 1-2C was carried out. Dispersant 1-2C having 40% and pH of 4 was obtained.
And using the obtained dispersing agent 1-2C, it carried out similarly to the comparative example 1-1, and obtained the heavy calcium carbonate slurry.

Comparative Example 2-1 (Preparation of Dispersant 2-1C and Preparation of Slurry Using Dispersant 2-1C)
Polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1-1 except that the aqueous solution having an IPA concentration of 36% in Example 1-1 was used instead of the aqueous solution having an IPA concentration of 65%. Thus, a dispersing agent 2-1C containing an acrylic polymer 2-1C and having a solid concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 2-1C.

Comparative Example 2-2 (Preparation of Dispersant 2-2C and Preparation of Slurry Using Dispersant 2-2C)
In Comparative Example 2-2, Dispersant 2-2C was prepared using the recovered IPA which was distilled off during preparation of Dispersant 2-1C in Comparative Example 2-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 2-1 was measured, the IPA concentration was 55%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Comparative Example 2-1, IPA was concentrated and it adjusted to the aqueous solution of 65% of IPA density | concentration. And except having used this IPA aqueous solution which adjusted this density | concentration, it carried out similarly to Comparative Example 2-1, superposed | polymerized, depressurizingly distilled, and neutralized, and solid content density | concentration containing acrylic polymer 2-2C was carried out. Dispersant 2-2C having 40% and pH of 4 was obtained.
And using the obtained dispersing agent 2-2C, it carried out similarly to the comparative example 2-1, and obtained the heavy calcium carbonate slurry.

Comparative Example 3-1 (Preparation of Dispersant 3-1C and Preparation of Slurry Using Dispersant 3-1C)
Except that the amount of sodium hypophosphite in Example 1-1 was changed from 20 g to 6 g, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1-1 to obtain an acrylic polymer 3 Dispersant 3-1C containing -1C and having a solid content concentration of 40% and a pH of 4 was obtained.
And heavy calcium carbonate slurry was obtained like Example 1-1 using obtained dispersing agent 3-1C.

Comparative Example 3-2 (Preparation of Dispersant 3-2C and Preparation of Slurry Using Dispersant 3-2C)
In Comparative Example 3-2, Dispersant 3-2C was prepared using IPA which was distilled off during the preparation of Dispersant 3-1C and recovered in Comparative Example 3-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 3-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Comparative Example 3-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. And except having used this IPA aqueous solution which adjusted this density | concentration, it carried out similarly to Comparative Example 3-1, and it superposed | polymerized, depressurizingly distilled, and neutralized, and solid content density | concentration containing acrylic polymer 3-2C was carried out. Dispersant 3-2C with 40% and pH 4 was obtained.
And using the obtained dispersing agent 3-2C, it carried out similarly to the comparative example 3-1, and obtained the heavy calcium carbonate slurry.

Comparative Example 4-1 (Preparation of Dispersant 4-1C and Preparation of Slurry Using Dispersant 4-1C)
Acrylic polymer 4 was polymerized, distilled off under reduced pressure and neutralized in the same manner as in Example 1-1 except that the amount of sodium hypophosphite in Example 1-1 was changed from 20 g to 33 g. Dispersant 4-1C containing -1C and having a solids concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 4-1C.

Comparative Example 4-2 (Preparation of Dispersant 4-2C and Preparation of Slurry Using Dispersant 4-2C)
In Comparative Example 4-2, Dispersant 4-2C was prepared using the recovered IPA which was distilled off during the preparation of Dispersant 4-1C in Comparative Example 4-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 4-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Comparative Example 4-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. And except having used this IPA aqueous solution which adjusted this density | concentration, it carried out similarly to Comparative Example 4-1, and it superposed | polymerized, depressurizingly distilled, and neutralized, and solid content density | concentration containing acrylic polymer 4-2C was carried out. Dispersant 4-2C with 40% and pH 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Comparative Example 4-1 using the obtained dispersing agent 4-2C.

Comparative Example 5-1 (Preparation of Dispersant 5-1C and Preparation of Slurry Using Dispersant 5-1C)
Except that the amount of the sodium persulfate aqueous solution in Example 1-1 was changed from 40 g to 7 g, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1-1 to obtain an acrylic polymer 5- Dispersant 5-1C containing 1C and having a solids concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 5-1C.

Comparative Example 5-2 (Preparation of Dispersant 5-2C and Preparation of Slurry Using Dispersant 5-2C)
In Comparative Example 5-2, Dispersant 5-2C was prepared using the recovered IPA which was distilled off during preparation of Dispersant 5-1C in Comparative Example 5-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 5-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used by Comparative Example 5-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Comparative Example 5-1, and the solid content concentration containing acrylic polymer 5-2C was 40. Dispersant 5-2C with% and pH 4 was obtained.
And using the obtained dispersing agent 5-2C, it carried out similarly to the comparative example 5-1, and obtained the heavy calcium carbonate slurry.

Comparative Example 6-1 (Preparation of Dispersant 6-1C and Preparation of Slurry Using Dispersant 6-1C)
Except that the amount of the sodium persulfate aqueous solution in Example 1-1 was changed from 40 g to 80 g, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Example 1-1 to obtain an acrylic polymer 6- Dispersant 6-1C containing 1C and having a solid content concentration of 40% and a pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 6-1C.

Comparative Example 6-2 (Preparation of Dispersant 6-2C and Preparation of Slurry Using Dispersant 6-2C)
In Comparative Example 6-2, Dispersant 6-2C was prepared using the recovered IPA which was distilled off during preparation of Dispersant 6-1C in Comparative Example 6-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 6-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Comparative Example 6-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. And except having used this IPA aqueous solution whose density | concentration adjustment was carried out, it carried out similarly to Comparative Example 6-1, and it superposed | polymerized, depressurizingly distilled, and neutralized, and solid content density | concentration containing acrylic polymer 6-2C was carried out. Dispersant 6-2C having 40% and pH of 4 was obtained.
And heavy calcium carbonate slurry was obtained like Comparative Example 6-1 using the obtained dispersing agent 6-2C.

Comparative Example 7-1 (Preparation of Dispersant 7-1C and Preparation of Slurry Using Dispersant 7-1C)
Polymerization and depressurization were carried out in the same manner as in Example 1-1 except that the holding temperature of the IPA flask in Example 1-1, the reaction temperature in polymerization, and the temperature in neutralization were changed from 80 ° C. to 60 ° C. Distillation and neutralization were performed to obtain a dispersant 7-1C containing an acrylic polymer 7-1C and having a solid content concentration of 40% and a pH of 4.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 7-1C.

Comparative Example 7-2 (Preparation of Dispersant 7-2C and Preparation of Slurry Using Dispersant 7-2C)
In Comparative Example 7-2, Dispersant 7-2C was prepared using IPA which was distilled off during the preparation of Dispersant 7-1C and recovered in Comparative Example 7-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 7-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Comparative Example 7-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, vacuum distillation and neutralization were performed in the same manner as in Comparative Example 7-1, and the solid content concentration including the acrylic polymer 7-2C was increased. Dispersant 7-2C having 40% and pH of 4 was obtained.
And heavy calcium carbonate slurry was obtained like comparative example 7-1 using obtained dispersing agent 7-2C.

Comparative Example 8-1 (Preparation of Dispersant 8-1C and Preparation of Slurry Using Dispersant 8-1C)
Polymerization and depressurization were carried out in the same manner as in Example 1-1 except that the holding temperature of the IPA in the flask in Example 1-1, the reaction temperature in polymerization, and the temperature in neutralization were changed from 80 ° C. to 89 ° C. Distillation and neutralization were performed to obtain a dispersing agent 8-1C containing an acrylic polymer 8-1C and having a solid content concentration of 40% and a pH of 4.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 8-1C.

Comparative Example 8-2 (Preparation of Dispersant 8-2C and Preparation of Slurry Using Dispersant 8-2C)
In Comparative Example 8-2, Dispersant 8-2C was prepared using the recovered IPA which was distilled off during preparation of Dispersant 8-1C in Comparative Example 8-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 8-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Comparative Example 8-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. And except having used this IPA aqueous solution which adjusted the density | concentration, it carried out similarly to Comparative Example 8-1, and it superposed | polymerized, pressure reduction distillation, and neutralization, and solid content density | concentration containing acrylic polymer 8-2C was carried out. Dispersant 8-2C having 40% and a pH of 4 was obtained.
And using the obtained dispersing agent 8-2C, it carried out similarly to the comparative example 8-1, and obtained the heavy calcium carbonate slurry.

Comparative Example 9-1 (Preparation of Dispersant 9-1C and Preparation of Slurry Using Dispersant 9-1C)
In the same manner as in Example 1-1, except that the neutralization rate with the 32% aqueous sodium hydroxide solution in Example 1-1 was changed from 22 mol% to 10 mol%, polymerization, vacuum distillation, and Summing was performed to obtain a dispersant 9-1C containing an acrylic polymer 9-1C and having a solid content concentration of 40% and a pH of 2.
And heavy calcium carbonate slurry was obtained like Example 1-1 using obtained dispersing agent 9-1C.

Comparative Example 9-2 (Preparation of Dispersant 9-2C and Preparation of Slurry Using Dispersant 9-2C)
In Comparative Example 9-2, Dispersant 9-2C was prepared using IPA which was distilled off during the preparation of Dispersant 9-1C and recovered in Comparative Example 9-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 9-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used by Comparative Example 9-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. Then, except that this concentration-adjusted IPA aqueous solution was used, polymerization, vacuum distillation and neutralization were performed in the same manner as in Comparative Example 9-1, and the solid content concentration containing the acrylic polymer 8-2C was reduced. Dispersant 9-2C having 40% and pH of 2 was obtained.
And heavy calcium carbonate slurry was obtained like Comparative Example 9-1 using obtained dispersing agent 9-2C.

Comparative Example 10-1 (Preparation of Dispersant 10-1C and Preparation of Slurry Using Dispersant 10-1C)
In the same manner as in Example 1-1, except that the neutralization rate with the 32% aqueous sodium hydroxide solution in Example 1-1 was changed from 22 mol% to 98 mol%, polymerization, distillation under reduced pressure, and Summing was performed to obtain a dispersant 10-1C containing an acrylic polymer 10-1C and having a solid content concentration of 40% and a pH of 9.
And the heavy calcium carbonate slurry was obtained like Example 1-1 using the obtained dispersing agent 10-1C.

Comparative Example 10-2 (Preparation of Dispersant 10-2C and Preparation of Slurry Using Dispersant 10-2C)
In Comparative Example 10-2, Dispersant 10-2C was prepared using the recovered IPA which was distilled off during preparation of Dispersant 10-1C in Comparative Example 10-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 10-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Comparative Example 10-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. And except having used this IPA aqueous solution which adjusted the density | concentration, it carried out similarly to Comparative Example 10-1, and it superposed | polymerized, depressurizingly distilled, and neutralized, and solid content density | concentration containing acrylic polymer 10-2C was carried out. Dispersant 10-2C having 40% and pH 9 was obtained.
And using the obtained dispersing agent 10-2C, it carried out similarly to the comparative example 10-1, and obtained the heavy calcium carbonate slurry.

Comparative Example 11-1 (Preparation of Dispersant 11-1C and Preparation of Slurry Using Dispersant 11-1C)
Except for changing the aqueous solution having an IPA concentration of 36% in Example 1-1 to an aqueous solution having an IPA concentration of 10%, and changing the amount of the sodium persulfate aqueous solution from 40 g to 80 g, Polymerization, distillation under reduced pressure, and neutralization were performed to obtain a dispersant 11-1C containing an acrylic polymer 11-1C, having a solid content concentration of 40% and a pH of 4.
And the heavy calcium carbonate slurry was obtained like Example 11-1 using the obtained dispersing agent 11-1C.

Comparative Example 11-2 (Preparation of Dispersant 11-2C and Preparation of Slurry Using Dispersant 11-2C)
In Comparative Example 11-2, Dispersant 11-2C was prepared using the recovered IPA which was distilled off during preparation of Dispersant 11-1C in Comparative Example 11-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 11-1 was measured, the IPA concentration was 20%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Comparative Example 11-1, deionized water was added and it adjusted to the aqueous solution of 10% of IPA density | concentration. And except having used this IPA aqueous solution which adjusted this density | concentration, it carried out similarly to Comparative Example 11-1, superposed | polymerized, depressurizingly distilled, and neutralized, and solid content density | concentration containing acrylic polymer 11-2C was carried out. Dispersant 11-2C having 40% and pH of 4 was obtained.
And using the obtained dispersing agent 11-2C, it carried out similarly to the comparative example 11-1, and obtained the heavy calcium carbonate slurry.

Comparative Example 12-1 (Preparation of Dispersant 12-1C and Preparation of Slurry Using Dispersant 12-1C)
Polymerization and decompression were carried out in the same manner as in Example 1-1, except that the amount of sodium hypophosphite in Example 1-1 was changed from 20 g to 6 g, and the amount of the sodium persulfate aqueous solution was changed from 40 g to 80 g. Distillation and neutralization were performed to obtain a dispersant 12-1C containing an acrylic polymer 12-1C and having a solid content concentration of 40% and a pH of 4.
And heavy calcium carbonate slurry was obtained like Example 1-1 using obtained dispersing agent 12-1C.

Comparative Example 12-2 (Preparation of Dispersant 12-2C and Preparation of Slurry Using Dispersant 12-2C)
In Comparative Example 12-2, Dispersant 12-2C was prepared using the recovered IPA which was distilled off during preparation of Dispersant 12-1C in Comparative Example 12-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 12-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Comparative Example 12-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. And except having used this IPA aqueous solution which adjusted this density | concentration, it carried out similarly to the comparative example 12-1, and it superposed | polymerized, depressurizingly distilled, and neutralized, and solid content density | concentration containing acrylic polymer 12-2C was carried out. Dispersant 12-2C having 40% and pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Comparative Example 12-1 using the obtained dispersing agent 12-2C.

Comparative Example 13-1 (Preparation of Dispersant 13-1C and Preparation of Slurry Using Dispersant 13-1C)
The same procedure as in Example 1-1 was conducted, except that the aqueous solution having an IPA concentration of 36% in Example 1-1 was changed to an aqueous solution having an IPA concentration of 10%, and the amount of sodium hypophosphite was changed from 20 g to 33 g. Then, polymerization, distillation under reduced pressure and neutralization were performed to obtain a dispersant 13-1C containing an acrylic polymer 13-1C and having a solid content concentration of 40% and a pH of 4.
And the heavy calcium carbonate slurry was obtained like Example 13-1 using the obtained dispersing agent 13-1C.

Comparative Example 13-2 (Preparation of Dispersant 13-2C and Preparation of Slurry Using Dispersant 13-2C)
In Comparative Example 13-2, Dispersant 13-2C was prepared using the recovered IPA which was distilled off during preparation of Dispersant 13-1C in Comparative Example 13-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 13-1 was measured, the IPA concentration was 20%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Comparative Example 13-1, deionized water was added and it adjusted to the aqueous solution of 10% of IPA density | concentration. And except having used this IPA aqueous solution whose concentration was adjusted, polymerization, vacuum distillation and neutralization were carried out in the same manner as in Comparative Example 13-1, and the solid content concentration containing the acrylic polymer 13-2C was reduced. Dispersant 13-2C having 40% and pH of 4 was obtained.
And the heavy calcium carbonate slurry was obtained like Comparative Example 13-1 using the obtained dispersing agent 13-2C.

Comparative Example 14-1 (Preparation of Dispersant 14-1C and Preparation of Slurry Using Dispersant 14-1C)
Except that the holding temperature of the IPA flask in Example 1-1, the reaction temperature in polymerization, the temperature in neutralization were changed from 80 ° C. to 60 ° C., and the amount of aqueous sodium persulfate solution was changed from 40 g to 80 g. In the same manner as in Example 1-1, polymerization, distillation under reduced pressure, and neutralization were performed, and the dispersant 14-1C containing an acrylic polymer 14-1C having a solid content concentration of 40% and a pH of 4 was used. Got.
And the heavy calcium carbonate slurry was obtained like Example 14-1 using the obtained dispersing agent 14-1C.

Comparative Example 14-2 (Preparation of Dispersant 14-2C and Preparation of Slurry Using Dispersant 14-2C)
In Comparative Example 14-2, Dispersant 14-2C was prepared using the recovered IPA which was distilled off during the preparation of Dispersant 14-1C in Comparative Example 14-1.
When the concentration of the IPA aqueous solution recovered in Comparative Example 11-1 was measured, the IPA concentration was 40%. In order to make this collect | recovered IPA aqueous solution the same with the density | concentration of the IPA aqueous solution used in Comparative Example 14-1, deionized water was added and it adjusted to the aqueous solution of 36% of IPA density | concentration. And except having used this IPA aqueous solution which adjusted the density | concentration, it carried out similarly to Comparative Example 14-1, superposed | polymerized, depressurizingly distilled, and neutralized, and solid content density | concentration containing acrylic polymer 14-2C was carried out. Dispersant 14-2C having 40% and pH of 4 was obtained.
And heavy calcium carbonate slurry was obtained like comparative example 14-1 using obtained dispersing agent 14-2C.

In Examples 1-1 to 16-2, the amounts of sodium hypophosphite and sodium persulfate used were 1.4 to 4.4 parts and 0.3 to 1, respectively, with respect to 100 parts by weight of the monomer. In the range of 0.5 parts, the reaction temperature in the polymerization step is in the range of 68 to 82 ° C., and the acrylic polymer obtained has a weight average molecular weight of 4,500 to 8,500, and a carboxyl group. The sum was also 15 to 95 mol%. And from said result, the dispersing agent of Examples 1-1-16-2 is a dispersing agent with which the initial viscosity of the calcium carbonate slurry obtained by wet grinding is low, and the remarkable raise of the viscosity with time is suppressed. I understood that.
On the other hand, in Comparative Examples 1-1 and 1-2, since the weight average molecular weight of the acrylic polymer is as large as 11000, the slurry viscosity during pulverization of calcium carbonate is high, and the slurry viscosity after 7 days is also remarkable. An increase was seen. In Comparative Examples 2-1 and 2-2, the slurry viscosity at the time of pulverization of calcium carbonate is small, but the weight average molecular weight of the acrylic polymer is too small as 4300 and 4200, so that the slurry viscosity after 7 days is remarkable. The rise was seen. Moreover, Comparative Examples 1-1 and 1-2 have a large weight average molecular weight of the acrylic polymer, and Comparative Examples 2-1 and 2-2 have a small weight average molecular weight of the acrylic polymer. About the molecular weight of this acrylic polymer (1st polymer), when the usage-amount of a hypophosphite and a persulfate is specified, it can adjust with the quantity of IPA. That is, the amount of IPA used in Comparative Examples 1-1 and 1-2 was 13 parts with respect to 100 parts of the monomer, which was less than 46 parts of Example 1-1, and Comparative Examples 2-1 and 2- The amount of IPA used in No. 2 is as large as 83 parts, which affects the molecular weight of the acrylic polymer. In addition, since the IPA aqueous solution concentration used in Comparative Examples 2-1 and 2-2 is a high concentration of 65%, when the recovered IPA is reused, the recovered IPA aqueous solution (azeotrope) is Needed concentration.

Further, in Comparative Examples 3-1 and 3-2, the amount of sodium hypophosphite used is as small as 1 part with respect to 100 parts of the monomer, so that the weight average molecular weight of the acrylic polymer is 10900 and The slurry viscosity was increased to 10800, and the slurry viscosity during pulverization of calcium carbonate was high, and the slurry viscosity after 7 days was also markedly increased.
In Comparative Examples 4-1 and 4-2, the amount of sodium hypophosphite used is as large as 5.5 parts with respect to 100 parts of the monomer, so that the weight average molecular weight of the acrylic polymer is small. However, the slurry viscosity during pulverization of calcium carbonate was high, and the slurry viscosity after 7 days was significantly increased.

In Comparative Examples 5-1 and 5-2, the amount of sodium persulfate used was as small as 0.2 parts with respect to 100 parts of the monomer, so that the weight average molecular weight of the acrylic polymer was 9100 and 9900. In addition, the amount of unreacted acrylic acid increased, the slurry viscosity during pulverization of calcium carbonate was high, and the slurry viscosity after 7 days was significantly increased. And in the comparative example 5-1, mixing of acrylic acid was seen in the collect | recovered IPA aqueous solution, and it is thought that reuse of this collect | recovered IPA is unsuitable.
In Comparative Examples 6-1 and 6-2, the amount of sodium persulfate used is as large as 2.0 parts with respect to 100 parts of the monomer, so that the weight average molecular weight of the acrylic polymer is in an appropriate range. Although the slurry viscosity was high, the slurry viscosity during pulverization of calcium carbonate was high, and the slurry viscosity after 7 days was significantly increased.

In Comparative Examples 7-1 and 7-2, the reaction temperature in the polymerization process was as low as 60 ° C., so the weight average molecular weight of the acrylic polymer was slightly increased, and the amount of unreacted acrylic acid increased. The slurry viscosity during pulverization of calcium carbonate was high, and the slurry viscosity after 7 days was significantly increased. In Comparative Example 7-1, acrylic acid is mixed in the recovered IPA aqueous solution, and it is considered that the reuse of the recovered IPA is inappropriate.
Moreover, in Comparative Examples 8-1 and 8-2, the reaction temperature in the polymerization step was as high as 89 ° C., and thus the weight average molecular weight of the acrylic polymer was within an appropriate range. The slurry viscosity was high, and a significant increase was observed in the slurry viscosity after 7 days.

  In Comparative Examples 9-1 and 9-2, since the carboxyl group neutralization rate was as low as 10 mol%, calcium carbonate could not be pulverized, and no slurry was obtained. In Comparative Examples 10-1 and 10-2, since the carboxyl group neutralization rate was as high as 98 mol%, calcium carbonate could be pulverized, but the slurry viscosity during pulverization of calcium carbonate was high, and 7 There was also a noticeable increase in slurry viscosity after the day.

In Comparative Examples 11-1 and 11-2, the amount of sodium persulfate used was increased to 2 parts with respect to 100 parts of the monomer, while the weight average molecular weight of the acrylic polymer was within an appropriate range. Therefore, the amount of IPA used was 13 parts with respect to 100 parts of the monomer. Thereby, the weight average molecular weight of the obtained acrylic polymer was within an appropriate range of around 7400, but because the amount of sodium persulfate used is large, the slurry viscosity during pulverization of calcium carbonate is high, There was also a significant increase in slurry viscosity after 7 days.
In Comparative Examples 12-1 and 12-2, the amount of sodium persulfate used was increased to 2 parts with respect to 100 parts of the monomer, while the weight average molecular weight of the acrylic polymer was within an appropriate range. Therefore, the amount of sodium hypophosphite used was 1 part per 100 parts of monomer. Thereby, although the weight average molecular weight of the obtained acrylic polymer was within an appropriate range of around 6900, again, because the amount of sodium persulfate used is large, the slurry viscosity during pulverization of calcium carbonate is high, In addition, a remarkable increase was observed in the slurry viscosity after 7 days.

In Comparative Examples 13-1 and 13-2, the amount of sodium hypophosphite used was increased to 5.5 parts with respect to 100 parts of the monomer, while the weight average molecular weight of the acrylic polymer was increased. In order to make it within an appropriate range, the amount of IPA used was 13 parts with respect to 100 parts of the monomer. Thereby, the weight average molecular weight of the obtained acrylic polymer was within an appropriate range of around 7100, but because the amount of sodium hypophosphite used is large, the slurry viscosity during grinding of calcium carbonate is high, In addition, a remarkable increase was observed in the slurry viscosity after 7 days.
In Comparative Examples 14-1 and 14-2, the amount of sodium persulfate used was increased to 2 parts with respect to 100 parts of the monomer, while the reaction temperature in the polymerization step was set to 60 ° C. Thereby, the weight average molecular weight of the obtained acrylic polymer was within an appropriate range of around 7300, but again, because the amount of sodium persulfate used is large, the slurry viscosity during pulverization of calcium carbonate is high, In addition, a remarkable increase was observed in the slurry viscosity after 7 days.

As described above, since the calcium carbonate dispersant of the present invention exhibits excellent calcium carbonate dispersibility and long-term dispersion stability, it can be effectively used particularly as a wet grinding dispersant for calcium carbonate.
Moreover, according to the manufacturing method of the dispersing agent for calcium carbonate of this invention, the said dispersing agent for calcium carbonate can be manufactured efficiently. Furthermore, when the isopropyl alcohol recovered in the concentration step of the present invention is used in the polymerization step, it is not necessary to discard the distilled isopropyl alcohol, the cost can be reduced, the production efficiency is excellent, and the environmental conservation aspect. However, it can be an excellent method for producing a dispersant for calcium carbonate.

Claims (10)

Derived from the above-described monomer constituting the polymer, and a polymerization step of polymerizing a monomer containing acrylic acid in the presence of hypophosphite and persulfate using an isopropyl alcohol aqueous solution as a solvent A neutralizing step of neutralizing 15 to 95 mol% of the carboxyl group of the structural unit, and an acrylic polymer obtained by comprising
The amount of the hypophosphite used is 1.4 to 4.4 parts by mass with respect to 100 parts by mass of the monomer.
The amount of the persulfate used is 0.3 to 1.5 parts by mass with respect to 100 parts by mass of the monomer.
The reaction temperature in the polymerization step is 68 to 82 ° C.
A dispersing agent for calcium carbonate, wherein the acrylic polymer has a weight average molecular weight of 4,500 to 8,500.   The dispersant for calcium carbonate according to claim 1, further comprising a concentration step of distilling off isopropyl alcohol after the polymerization step.   The dispersant for calcium carbonate according to claim 2, wherein isopropyl alcohol recovered by the distillation is used in the polymerization step in the concentration step.   The dispersant for calcium carbonate according to any one of claims 1 to 3, wherein the isopropyl alcohol concentration in the aqueous isopropyl alcohol solution is 15 to 55 mass%.   The dispersant for calcium carbonate according to any one of claims 1 to 4, wherein acrylic acid used in the polymerization step is contained in an amount of 80 to 100% by mass with respect to 100% by mass of the total amount of the monomers. A method for producing a dispersant for calcium carbonate containing an acrylic polymer,
A polymerization step of polymerizing a monomer containing acrylic acid in the presence of hypophosphite and persulfate using an aqueous isopropyl alcohol solution as a solvent;
A neutralization step of neutralizing 15 to 95 mol% of the carboxyl group of the structural unit derived from the monomer constituting the obtained polymer,
The amount of the hypophosphite used is 1.4 to 4.4 parts by mass with respect to 100 parts by mass of the monomer.
The amount of the persulfate used is 0.3 to 1.5 parts by mass with respect to 100 parts by mass of the monomer.
The reaction temperature in the polymerization step is 68 to 82 ° C.
A method for producing a dispersing agent for calcium carbonate, wherein the acrylic polymer has a weight average molecular weight of 4,500 to 8,500.   The manufacturing method of the dispersing agent for calcium carbonate of Claim 6 provided with the concentration process of distilling off isopropyl alcohol after the said superposition | polymerization process.   The manufacturing method of the dispersing agent for calcium carbonate of Claim 7 which uses the isopropyl alcohol collect | recovered by the said distillation in the said concentration process at the said concentration process.   The method for producing a dispersant for calcium carbonate according to any one of claims 6 to 8, wherein the isopropyl alcohol concentration in the aqueous isopropyl alcohol solution is 15 to 55 mass%.   The manufacturing method of the dispersing agent for calcium carbonate of any one of Claims 6 thru | or 9 with which acrylic acid used at the said superposition | polymerization process is contained 80-100 mass% with respect to 100 mass% of said monomer whole quantity.