WO2001010920A1

WO2001010920A1 - Process for producing (meth)acrylic acid polymer

Info

Publication number: WO2001010920A1
Application number: PCT/JP1999/004277
Authority: WO
Inventors: Kengo Shibata; Haruya Minou; Haruyuki Sato; Toshinao Ukena; Yoshinao Kono
Original assignee: Kao Corporation
Priority date: 1999-08-06
Filing date: 1999-08-06
Publication date: 2001-02-15

Abstract

A process for producing a (meth)acrylic acid polymer suitable for use as a cement dispersant of stable quality. The process comprises: a step (1) in which (meth)acrylic acid and a polyalkylene glycol monoalkyl ether are subjected to esterification in a molar ratio of 5/1 to 50/1 in the presence of an acid catalyst and a polymerization inhibitor, the acid catalyst is subsequently deactivated with an alkali, and unreacted (meth)acrylic acid is then distilled off to obtain an esterification product containing a (meth)acrylic ester and the residual unreacted (meth)acrylic acid; and a step (2) in which the (meth)acrylic ester and the residual unreacted (meth)acrylic acid in the esterification product are copolymerized in the pH range of 1.5 to 3.5.

Description

Specification

Method for producing (meth) acrylic acid polymer

The present invention relates to a method for producing a (meth) acrylic acid-based polymer useful as a dispersant for cement for improving the dispersibility of cement particles in a hydraulic composition such as cement paste, mortar, and concrete. Background art

Polycarboxylic acid polymers are useful as dispersants for cement, and various techniques have been proposed. As such a dispersant for cement, Japanese Patent Publication No. 59-183338 discloses polyalkylene glycol mono (meth) acrylate monomer and (meth) acrylic monomer, Further, a polymer containing a copolymer produced by reacting these monomers with a copolymerizable monomer at a specific ratio is disclosed, and Japanese Patent Application Laid-Open No. Hei 5-238795 discloses. Discloses a copolymer containing a copolymer obtained by polymerizing a polyalkylene dalicol diester monomer having an unsaturated bond and a monomer having a dissociation group. Japanese Patent Application Laid-Open Publication No. H11-163,086 discloses a polymer containing a copolymer of a polyalkylene glycol ester monomer having an unsaturated bond and a specific monomer. However, these prior arts do not describe specific polymerization conditions. For example, in the fourth column of JP-A-8-123966, the polymer of the present invention is known. It can be manufactured by the method described in Disclosure of the invention

ADVANTAGE OF THE INVENTION This invention can obtain the (meth) acrylic-acid type polymer suitable as a dispersing agent for cement with a stable quality by setting polymerization conditions concretely. It is intended to provide a method.

The inventors of the present invention deactivated the acid catalyst by adding an alcohol catalyst to the esterification reaction product containing the acid catalyst and the polymerization inhibitor, and further caused the polymerization reaction in a specific range of pH. The inventors have found that the object can be achieved, and have completed the present invention. In the present invention, (meth) acrylic acid and polyalkylene glycol monoalkyl ether are added in a molar ratio of 3 ::! To 50: 1, and an esterification reaction is performed in the presence of an acid catalyst and a polymerization inhibitor. Then, a step 1 of deactivating the acid catalyst with an alkali agent to obtain an esterification reactant containing (meth) acrylate ester and (meth) acrylic acid residue, and a pH in the range of pH 3.5 to 3.5. And a step (2) of copolymerizing (meth) acrylic acid ester with (meth) acrylic acid. A monomer copolymerizable with these monomers may be included.

The monomer of step 2 may include the reactants of step 1, residues, and newly added monomers. The monomer (meth) acrylate of Step 2 includes the reactant of Step 1. Further, it may contain a newly added monomer. The (meth) acrylic acid may include the residue of step 1 and further newly added monomers.

The reaction product of step 1 may be polymerized as it is, or (meth) acrylic acid may be removed by distillation. Polymerization may be carried out by adding a monomer. These may be combined and polymerized. It polymerizes in the range of pH 3.5 to 3.5. Polymerization may be performed without adding an acid.

Either all or part of the unreacted (meth) acrylic acid is distilled off in step 1, and Z or (meth) acrylic acid ester and (meth) acrylic acid can be copolymerized with (meth) acrylic acid in step 2. By adding a functional monomer, a copolymer having a desired monomer ratio can be obtained. That is, the polymer monomer includes the reactant in step 1 and the monomer added in step 2.

In step 2, an acid may be added to the esterification reaction product to adjust the pH to a range of from 5 to 3.5.

The monomer copolymerizable with the (meth) acrylic ester added in step 2 may be (meth) acrylic acid, methyl (meth) acrylate or methoxypolyethylene glycol mono (meth) acrylate. preferable.

In the present invention, “(meth) acrylic acid” means both acrylic acid and methacrylic acid. BEST MODE FOR CARRYING OUT THE INVENTION

In step 1, first, (meth) acrylic acid and polyalkylene glycol monoalkyl ether are subjected to an esterification reaction in the presence of an acid catalyst and a polymerization inhibitor. The (meth) acrylic acid used in the esterification reaction is not particularly limited, and a commercially available one containing a polymerization inhibitor in advance can be used.

Examples of the polyalkylene glycol monoalkyl ether used in the esterification reaction include those in which the polyalkylene moiety consists of an alkylene oxide adduct such as an adduct of ethylene oxide alone or a mixed adduct of ethylene oxide and propylene oxide. Preferably, the total number of moles of the alkylene oxide is from 1 to 300. The alkyl group constituting the monoalkyl ether moiety is preferably an alkyl group having 1 to 3 carbon atoms.One or more kinds of polyalkylene alkylenes having different addition mole numbers of alkylene oxides and different carbon numbers of no or alkyl groups. Mixtures of recall monoalkyl ethers can be used. The mixing ratio of the (meth) acrylic acid and the polyalkylene glycol monoalkyl ether in the reaction system is in a molar ratio of 3: 1 to 50: 1, preferably 10: 5, in order to further increase the esterification reaction rate. 1 to 40: 1

Examples of the acid catalyst used in the esterification reaction include sulfonic acids such as p-toluenesulfonic acid, methanesulfonic acid and benzenesulfonic acid, and mineral acids such as sulfuric acid and phosphoric acid.

The acid catalyst is preferably used in an amount of 0.1 to 10 parts by weight based on 100 parts by weight of the polyalkylene glycol monoalkyl ether. When the amount is 0.1 part by weight or more, the reaction speed can be maintained at an appropriate level, and when the amount is 10 parts by weight or less, it is economical, without cleaving the alkylene oxide chain of the polyalkylene glycol monoalkyl ether. This is preferable because the reaction can smoothly proceed.

Examples of the polymerization inhibitor used in the esterification reaction include a combination of one or more selected from hydroquinone, benzoquinone, methoquinone, BHT, and the like in an arbitrary ratio. Further, by passing a gas containing oxygen through the reaction system, the polymerization inhibiting effect can be further enhanced.

The polymerization inhibitor is preferably used in an amount of 0.001-1 part by weight based on 100 parts by weight of the polyalkylene glycol monoalkyl ether.

The reaction temperature in the esterification reaction is preferably from 80 to 130 ° C. If the temperature is 80 ° C or higher, an appropriate reaction rate can be maintained.If the temperature is 130 ° C or lower, deterioration of the quality of the polyalkylene glycol monoalkyl ether can be prevented, and the viscosity of the reaction system is maintained at an appropriate level. It is preferable because it can be performed.

The pressure of the reaction system in the esterification reaction is not particularly limited, but is preferably a reduced pressure from the viewpoint of distilling water generated by the reaction out of the system.

In step 1, after the esterification reaction, an alkali agent is added to deactivate the acid catalyst. Let Examples of the alkaline agent include alkaline metal hydroxides such as sodium hydroxide and potassium hydroxide, and alkaline earth metal hydroxides such as calcium hydroxide. The amount of the alkali agent to be used is preferably 0.9 to 1.5 equivalent times, more preferably 1.0 to 1.3 equivalent times, based on the acid catalyst used. In step 1, after deactivating the acid catalyst, unreacted (meth) acrylic acid is distilled off, and mainly contains (meth) acrylic acid ester represented by the following general formula (I). Further, an esterification reaction product containing a (meth) acrylic acid residue represented by the following general formula (II) is obtained.

R,

rl ₂ = C (R

C 00 (A0) nR ₂

CH ₂ = C (II)

C 0 0 M

Wherein R represents a hydrogen atom or a methyl group, R ₂ represents an alkyl group having 1 to 3 carbon atoms, AO represents an oxyalkylene group having 2 to 3 carbon atoms, and n represents 1 to 30. R ₃ represents a hydrogen atom or a methyl group, M represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom or the like].

In the esterification reaction in step 1, a large excess amount of (meth) acrylic acid is used to make the reaction proceed smoothly. Therefore, if an excess amount of (meth) acrylic acid is present in excess of the desired amount of (meth) acrylic acid in step 2, unreacted (meth) acrylic acid is distilled off in step 1. is there. The degree of distillation of the unreacted (meth) acrylic acid is appropriately set according to the molar ratio of copolymerization of (meth) acrylate and (meth) acrylic acid in the next step 2. Methods for removing unreacted (meth) acrylic acid include vacuum distillation and steam evaporation. A distillation method or a method of distilling together with the carrier gas at normal pressure can be applied.

In step 2, the (meth) acrylic ester and the (meth) acrylic acid residue contained in the esterification reaction product obtained in step 1 are combined with each other in a pH range of 5 to 3.5. The copolymerization reaction is performed.

In the copolymerization reaction, a monomer copolymerizable with (meth) acrylic acid ester and Z or (meth) acrylic acid represented by the general formula (I) can be further added. Examples of this monomer include acrylic acid, methacrylic acid, crotonic acid, and (meth) acrylic monomers such as alkali metal salts, alkaline earth metal salts, ammonium salts and amine salts thereof; maleic anhydride, Unsaturated dicarboxylic acid monomers such as maleic acid, itaconic anhydride, itaconic acid, citraconic anhydride, citraconic acid, fumaric acid and their alkali metal salts, alkaline earth metal salts, ammonium salts or amine salts; (Meth) alkyl acrylate, (meth) hydroxy phenol acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypolyethylene polypropylene glycol (meth) acrylate, styrene, (meth) atalide , Atarilonitrile, Styrenesulfonic acid and Salts, sulfoalkyl (meth) Atari rate and its salts, and 2-acrylamide one 2- methylation propanesulfonic acid and its salts.

In order to add in step 2, the monomer copolymerizable with the (meth) acrylic ester must be (meth) acrylic acid, methyl (meth) acrylate or methoxypolyethylene glycol mono (meth) acrylate. Is preferred.

The amount of such a monomer copolymerizable with the (meth) acrylic ester is 0.3 to 100 parts by weight of the (meth) acrylic ester represented by the general formula (I). It is preferably 170 parts by weight, particularly preferably 0.3 to 100 parts by weight. The pH of the reaction system is in the range of 1.5 to 3.5, preferably pH 2.0 to 3.0. It is possible to suppress the occurrence of a hydrolysis reaction of the (meth) acrylate during the polymerization reaction in which 1¾ is 1.5 or more. When the pH is 3.5 or less, the copolymerization rate can be kept high, and the structure of each monomer in the copolymer can be appropriately controlled. As a result, stable quality can be obtained. A (meth) acrylic acid polymer useful as a dispersant for cement can be obtained. Here, the pH in step 2 is the pH of a 5% by weight aqueous solution of the polymerization reaction mixture.

If the pH of the esterification reaction product is outside or within the range of 1.5 to 3.5, it is preferable to add an acid or a base for preparing the pH, if desired.

Examples of the acid used for adjusting the pH include phosphoric acid, sulfuric acid, nitric acid, alkylphosphoric acid, alkylsulfuric acid, alkylsulfonic acid, alkylbenzenesulfonic acid, and benzenesulfonic acid. Among these, phosphoric acid is preferred because it has a pH buffering action, easily adjusts pH to a predetermined range, and can suppress foaming of the polymerization reaction system. Examples of the base include sodium hydroxide and a hydroxylating rhine.

In step 2, the reaction can be performed in the presence of a solvent to reduce the viscosity of the polymerization reaction system. Examples of the solvent include water, lower alcohols such as methanol, ethanol, isopropanol and butanol; aromatic hydrocarbons such as benzene, toluene and xylene; alicyclic hydrocarbons such as cyclohexane; and fats such as n-hexane. Group hydrocarbons; esters such as ethyl acetate; ketones such as acetone and methyl ethyl ketone; Of these, water and lower alcohols are preferred because they are easy to handle and easy to evaporate.

In step 2, a polymerization initiator can be added. Examples of the polymerization initiator include organic peroxides, inorganic peroxides, nitrile compounds, azo compounds, diazo compounds, and sulfinic acid compounds. The amount of the polymerization initiator The molar ratio is preferably 1 to 50 times the total of the general formula (1), the general formula (II) and other monomers.

In step 2, a chain transfer agent can be added. Examples of the chain transfer agent include lower alkali mercaptan, lower mercapto fatty acid, thioglycerin, thiolingoic acid, 2-mercaptoethanol and the like. Particularly when water is used as the solvent, the molecular weight can be adjusted more stably by adding these chain transfer agents.

The reaction temperature of the copolymerization reaction in step 2 is preferably from 0 to 120 ° C.

The (meth) acrylic acid-based polymer obtained through the above-mentioned processes 1 and 2 can be further subjected to a deodorizing treatment, if necessary. In particular, when a thiol such as mercaptoethanol is used as the chain transfer agent, an unpleasant odor remains in the polymer.

As a deodorizing treatment method when thiol is used as a chain transfer agent, a method of converting thiol to disulfide with an oxidizing agent can be exemplified. Examples of the oxidizing agent used in this method include hydrogen peroxide, air, oxygen and the like, but hydrogen peroxide is preferred because of its high deodorizing effect by oxidation. The amount of hydrogen peroxide added is preferably from 100 to 2000 ppm, particularly preferably from 100 to 1000 ppm, based on the polymer. If it is 100 ppm or more, sufficient deodorizing treatment can be performed, and if it is 2000 ppm or less, excess hydrogen peroxide remains, which acts as a polymerization initiator to promote polymerization, or hydrogen peroxide is generated. It does not decompose to generate oxygen or cause problems such as gelation of the polymer solution in the metal container. The deodorizing temperature is preferably from 70 to 100 ° C, particularly preferably from 80 to 90 ° C. When the temperature is 70 ° C or more, the deodorizing effect is enhanced, and when the temperature is 100 ° C or less, generation of by-products due to thermal decomposition of the polymer can be prevented.

The (meth) acrylic acid-based polymer obtained by the production method of the present invention is an acid Can also be used as a dispersant for cement, but from the viewpoint of suppressing the hydrolysis of the ester by an acid, it is preferable to form a salt by neutralization with an alkali. Examples of the alkali include a hydroxide of an alkali metal or an alkaline earth metal, ammonium, alkylammonium, alkanolamine, N-alkyl-substituted polyamine, ethylenediamine, polyethylenepolyamine and the like. When a (meth) acrylic acid polymer is used as a dispersant for cement, the pH is preferably adjusted to 5 to 7 by neutralization.

Weight average molecular weight of (meth) acrylic acid-based polymer obtained by the production method of the present invention (gel permeation chromatography. Eluent: 0.2 M buffer monoacetonitonyl phosphate = 73. Polyethylene oxide equivalent) ) Is preferably 100,000 to 200,000 in order to obtain sufficient dispersibility as a dispersant for cement, and 200,000 to: 100,000. But especially preferred.

The (meth) acrylic acid-based polymer obtained by the production method of the present invention may be used as a dispersant for hydraulic cement other than cement, such as portland cement, alumina cement, various mixed cements, and gypsum. it can. Industrial applicability

According to the production method of the present invention, it is possible to obtain a (meth) acrylic acid-based polymer that is stable in quality and has high cement dispersibility and is suitable as a dispersant for cement. Example

In the following examples, “%” represents “% by weight”.

Example 1 (Process 1)

Ethylene oxide melted at 80 ° C Addition of 120 moles of polyethylene daricol monomethyl ether (weight average molecular weight: 5344) 100 parts by weight of a thermometer, stirrer, dropping funnel, and introduction of nitrogen It was charged into a glass reactor equipped with a tube and a cooling condenser. Next, 3 parts by weight of hydroquinone and 32 parts by weight of p-toluenesulfonic acid were added. Here, air was introduced into the reaction solution at a flow rate of 6 ml / min per 1 kg of the total weight of polyethylene glycol monomethyl ether and methacrylic acid, and nitrogen was further introduced into the gas phase of the reaction vessel at a flow rate of 12 ml min. During the introduction, 483 parts by weight of methacrylic acid (an amount that was 30 mol times the amount of polyethylene dalicol monomethyl ether) was charged, and heating and depressurization in the reaction vessel were started. The pressure was controlled at 26.7 kPa, the reaction start time was when the reaction solution temperature reached 105 ° C, and the reaction was continued while heating to maintain the reaction solution temperature at 11 ° C. The reaction was performed while distilling off water and methacrylic acid. The pressure was reduced to 12 to 13.3 kPa one hour after the start of the reaction, and was maintained as it was. Six hours after the start of the reaction, the pressure was returned to normal pressure, neutralized by adding 1.05 times equivalent of a 48% aqueous sodium hydroxide solution to p-toluenesulfonic acid, and the reaction was terminated. .

After completion of the reaction, the temperature of the reaction solution was maintained at 130 ° C. or lower, and unreacted methacrylic acid was recovered by a vacuum distillation method to obtain an esterification reaction product (A) -1. This (A) -1 has a methacrylate concentration of 91.2%, an unreacted polyethylene glycol monomethyl ether concentration of 2.8%, a polymerization inhibitor concentration of 0.3%, and a catalyst salt (sodium p-toluenesulfonate) concentration. The concentration was 3.4% and the methacrylic acid concentration was 2.3%.

(Process 2)

In the same glass reaction vessel as in step 1 in which the cooling condenser was replaced with a reflux condenser, 485 parts by weight of water was charged, and while stirring, the gas phase of the reaction vessel was replaced with nitrogen. The temperature was raised to 80 ° C. Next, 600 parts by weight of esterification reaction product (A) -1; 21 parts by weight of methacrylic acid; Dequest (phosphonic acid chelating agent; manufactured by Nippon Monsanto Co.) 0.7 parts by weight, 85% A solution prepared by mixing and dissolving 5 parts by weight of phosphoric acid and 400 parts by weight of water and 3 parts by weight of 3 parts by weight of 2-mercaptoethanol and 39 parts by weight of a 15% aqueous solution of ammonium persulfate were simultaneously added dropwise. The dropping was completed over 0 minutes. Next, 15 parts by weight of a 15% aqueous solution of ammonium persulfate was added dropwise over 30 minutes, and the mixture was aged at 80 ° C. for about 1 hour. During the polymerization reaction, the pH at the time of dropping and aging was 2.5. Further, after neutralizing by adding 30 parts by weight of a 48% aqueous sodium hydroxide solution, 0.7 parts by weight of 35% hydrogen peroxide was added dropwise, and the mixture was aged at 90 ° C for 1 hour. A (meth) ataryl acid polymer was obtained. The viscosity of the (meth) acrylic acid polymer was measured (B-type viscometer manufactured by Tokyo Keiki Seisakusho, rotor No. 2, 30 rpm) and found to be 420 mPa's.

Using the (meth) acrylic acid-based polymer thus obtained, an evaluation test as a cement dispersant was performed by the following method. Table 1 shows the results.

(Measurement of past flow value)

To 700 g of ordinary Portland cement and 210 g of water, add 0.9 g of a 40% aqueous solution of a (meth) acrylic acid polymer, and use a mortar mixer (manufactured by Sanei Seisakusho) at 63 rpm. The mixture was mixed for 1 minute, and further mixed at 126 rpm for 2 minutes. After mixing, the mixture is poured from the upper opening of the paste flow measurement cone (top diameter 76 mm, lower diameter 86 mm, height 40 mm) with the lower opening pressed against a flat surface. After the cone for measurement was pulled up in the direction perpendicular to the plane and removed, the diameter of the cement paste spread in a circle on the plane was measured at two points, and the average value was used as the paste flow value (mm). When the paste flow value is 240 to 260, it indicates that the dispersibility is excellent. Example 2

In Step 2 of Example 1, a (meth) acrylic acid-based polymer was obtained in the same manner as in Example 1, except that 5 parts by weight of phosphoric acid was used instead of 5 parts by weight of phosphoric acid. The pH during the polymerization reaction in Step 2 was 2.2 to 2.8. The viscosity of the obtained (meth) atalylic acid polymer was 450 mPa's. The paste flow value of this (meth) acrylic acid-based polymer was determined in the same manner as in Example 1. Table 1 shows the results.

Example 3

In step 2 of Example 1, 485 parts by weight of water was charged into the same glass reaction vessel as in step 1, and the gas phase of the reaction vessel was replaced with nitrogen while stirring, and the temperature was raised to 80 ° C under a nitrogen atmosphere. The temperature rose. Next, 269 parts by weight of the esterification reaction product (A) -1 was added, 76 parts by weight of metadallylic acid, methoxypolyethylene glycol monomethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., average number of moles of ethylene oxide 9 1) 3 parts by weight of a mixture of 18 parts by weight, 2 parts by weight of 85% phosphoric acid and 200 parts by weight of water, 3 parts by weight of 2-mercaptoethanol and 19 parts by weight of a 15% aqueous solution of ammonium persulfate Was simultaneously dropped, and the dropping of all three solutions was completed in 90 minutes. Next, 9 parts by weight of a 15% aqueous solution of ammonium persulfate was added dropwise over 30 minutes, and the mixture was aged at 80 ° C. for 1 hour. The pH during the polymerization reaction was 2.6. Further, after neutralizing by adding 34 parts by weight of a 48% aqueous sodium hydroxide solution, 0.7 parts by weight of 35% hydrogen peroxide was added dropwise, and the mixture was aged at 90 ° C for 1 hour to give (meth) acrylic acid. An acid polymer was obtained. The viscosity of this (meth) acrylic acid polymer was 380 mPa's. For this (meth) acrylic acid-based polymer, a paste mouth opening peak value was determined in the same manner as in Example 1. Table 1 shows the results.

Example 4

In step 2 of Example 1, water 485 weight was added to the same glass reaction vessel as in step 1. The gas phase of the reaction vessel was replaced with nitrogen while stirring, and the temperature was raised to 80 ° C under a nitrogen atmosphere. Next, 600 parts by weight of the esterification reaction product (A) -1, 3.6 parts by weight of methacrylic acid, 61 parts by weight of methyl acrylate, 2.5 parts by weight of 85% phosphoric acid, and 400 parts by weight of water The mixed solution, 3 parts by weight of 2-mercaptoethanol, and 46 parts by weight of a 15% aqueous solution of ammonium persulfate were simultaneously dropped at a time, and the dropping was completed over 90 minutes. Next, 15 parts by weight of a 15% aqueous solution of ammonium persulfate was added dropwise over 30 minutes, and the mixture was aged at 80 ° C. for about 1 hour. The pH during the polymerization reaction was 3.0. Further, 15 parts by weight of a 48% aqueous sodium hydroxide solution was added for neutralization to obtain a (meth) acrylic acid polymer. The viscosity of this (meth) acrylic acid polymer was 4500 mPa-s. With respect to this (meth) acrylic acid-based polymer, a peak value was determined in the same manner as in Example 1. Table 1 shows the results.

Example 5

(Process 1)

In step 1 of Example 1, the same procedures as in Example 1 were carried out except that 1,000 parts by weight of polyethylene glycol monomethyl ether (average number of moles of added ethylene 200, weight average molecular weight 8864) and 291 parts by weight of methacrylic acid were used. As a result, an esterification reaction product (A) -2 was obtained. This (A) -2 is the concentration of methacrylic acid ester 90.5%, unreacted polyethylene glycol monomethyl ether 2.7%, polymerization inhibitor concentration 0.3%, catalyst salt (sodium p-toluenesulfonate) concentration 3.0% and methacrylic acid concentration was 3.5%.

(Process 2)

(Meth) acrylic acid polymer was obtained in the same manner as in Example 1 except that 21 parts by weight of methacrylic acid was not used in Step 2 of Example 1 using the esterification reaction product (A) -2. Was. The pH during the polymerization reaction in step 2 was 3.1. Profit The viscosity of the obtained (meth) acrylic acid polymer was 455 mPa's. The paste flow value of this (meth) acrylic acid polymer was determined in the same manner as in Example 1. Table 1 shows the results.

Example 6

(Process 1)

In Step 1 of Example 1, polyethylene glycol monomethyl ether (average number of moles added of ethylene: 9, weight average molecular weight: 429) 1000 parts by weight, methacrylic acid 1200 parts by weight and p-toluenesulfonic acid 40 parts by weight were used. In the same manner as in Example 1, esterification reaction product (A) -3 was obtained. This (A) -3 has a methacrylate concentration of 91.5%, an unreacted polyethylene glycol monomethyl ether concentration of 2.4%, a polymerization inhibitor concentration of 0.2%, and a catalyst salt (sodium p-toluenesulfonate). The concentration was 3.4% and the methacrylic acid concentration was 2.5%.

(Process 2)

546 parts by weight of water was charged into the same glass reaction vessel as in Step 1, and the gas phase of the reaction vessel was replaced with nitrogen while stirring, and the temperature was raised to 80 ° C under a nitrogen atmosphere. Next, a liquid obtained by mixing 585 parts by weight of the esterification reaction product (A) -3, 158 parts by weight of methacrylic acid and 550 parts by weight of water, 4 parts by weight of 2-mercaptoethanol and a 15% aqueous solution of ammonium persulfate 19 Parts by weight of the three liquids were simultaneously dropped, and the dripping of all three liquids was completed in 90 minutes. Next, 5 parts by weight of a 15% aqueous solution of ammonium persulfate was added dropwise over 30 minutes and aged at 80 ° C for 1 hour. The pH during the polymerization reaction was 2.8. The mixture was neutralized by adding 116 parts by weight of a 48% aqueous sodium hydroxide solution to obtain a (meth) acrylic acid-based polymer. The viscosity of this (meth) acrylic acid polymer was 320 mPa's. The paste flow value of this (meth) acrylic acid polymer was determined in the same manner as in Example 1. Table 1 shows the results. Comparative Example 1

In step 2 of Example 1, except that 16 parts by weight of 48% sodium hydroxide was used instead of 5 parts by weight of 85% phosphoric acid, a (meth) acrylic acid-based polymer was prepared in the same manner as in Example 1. A coalescence was obtained. The pH during the polymerization reaction in step 2 was 4.4. The viscosity of the obtained (meth) acrylic acid polymer was 480 mPa's. The paste flow value of this (meth) acrylic acid-based polymer was determined in the same manner as in Example 1. Table 1 shows the results.

Comparative Example 2

In Step 2 of Example 5, a (meth) acrylic acid-based polymer was obtained in the same manner as in Example 5, except that 5 parts by weight of phosphoric acid was not used. The pH during the polymerization reaction in step 2 was 4.1. The viscosity of the obtained (meth) acrylic acid-based polymer was 500 mPa's. The paste flow value of this (meth) acrylic acid polymer was determined in the same manner as in Example 1. Table 1 shows the results.

table 1

* 1: Indicates parts by weight.

The (meth) acrylic acid-based polymers obtained by the production methods of Examples 1 to 5 all had high paste flow values, and as a result, it was confirmed that a high-quality cement dispersant could be provided. Was done.

On the other hand, the (meth) acrylic acid-based polymers obtained by the production methods of Comparative Examples 1 and 2 had a lower pace because the pH of the polymerization reaction system in Step 2 was outside the range specified in the present invention. The flow rate value was significantly inferior. Therefore, it was confirmed that when the production method of the present invention was not applied, a (meth) acrylic acid-based polymer having a low paste flow value was obtained, and a high-quality cement dispersant could not be provided.

Claims

The scope of the claims

1. (Meth) acrylic acid and polyalkylene glycol monoalkyl ether are added in a molar ratio of 3: 1 to 50: 1, and the esterification reaction is carried out in the presence of an acid catalyst and a polymerization inhibitor. Deactivating the acid catalyst with an agent to obtain an esterification reactant containing (meth) acrylic acid ester and (meth) acrylic acid residue, and in the range of pH 1.5 to 3.5, A process for producing a (meth) acrylic acid-based polymer, comprising a step 2 of copolymerizing a (meth) acrylic acid ester with (meth) atalylic acid.

2. Evaporating unreacted (meth) acrylic acid in step 1 and / or adding a monomer copolymerizable with (meth) acrylic acid ester and di- or (meth) acrylic acid in step 2 The method according to claim 1, wherein a copolymer having a desired monomer ratio is obtained by the above method.

3. The production method according to claim 1, wherein in step 2, an acid is added to the esterification reaction product to adjust the esterification reaction product to a pH in the range of 5 to 3.5.

4. The method according to claim 3, wherein the acid is phosphoric acid.

5. The monomer that can be copolymerized with (meth) acrylate and Z or (meth) acrylic acid added in step 2 is (meth) acrylic acid, methyl (meth) acrylate or methoxypolyethylene glycol mono ( The production method according to any one of claims 2 to 4, wherein the (meth) is acrylate.