WO2000012576A1

WO2000012576A1 - Process for producing (meth)acrylic acid polymer

Info

Publication number: WO2000012576A1
Application number: PCT/JP1999/004276
Authority: WO
Inventors: Kengo Shibata; Haruya Minou; Haruyuki Sato; Toshinao Ukena
Original assignee: Kao Corporation
Priority date: 1998-08-27
Filing date: 1999-08-06
Publication date: 2000-03-09
Also published as: WO2000012577A1

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 an alkyl (meth)acrylate and a polyalkylene glycol monoalkyl ether are subjected to transesterification in a molar ratio of 5/1 to 50/1 and then the by-product alcohol and the remaining alkyl (meth)acrylate are distilled off to obtain an esterification product containing a PGMA (meth)acrylate; and a step (2) in which the PGMA (meth)acrylate in the esterification product is copolymerized with a monomer copolymerizable therewith 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 and Japanese Patent Application Laid-Open No. 8-12396 describe that a polyalkylene glycol ester monomer having an unsaturated bond is specified. One containing a copolymer with the following monomer is disclosed. However, these prior arts do not describe specific polymerization conditions. Disclosure of the invention

The present invention can produce a (meth) acrylic acid-based polymer suitable as a dispersant for cement with a stable quality by setting polymerization conditions specifically. The purpose is to provide the law.

The present inventors have found that the above object can be achieved by subjecting the esterification reaction product to a polymerization reaction at a specific pH range.

The present invention provides a process for producing a (meth) acrylic acid-based polymer comprising the following steps 1 and 2 Is the law.

Step 1: Alkyl (meth) acrylate and polyalkylene glycol monoalkyl ether are subjected to a transesterification reaction in a molar ratio of 3: 1 to 50: 1 to obtain a polyalkylene glycol monoalkyl ether (meth) acrylate (hereinafter, referred to as “polyalkylene glycol monoalkyl ether”). (PGMA (meta) acrylate)), and then removing the by-produced alcohol to obtain an esterification reaction product containing PGMA (meth) acrylate.

Step 2: A step of copolymerizing PGMA (meth) acrylate and a monomer copolymerizable with PGMA (meth) acrylate in the range of pH 1.5 to 3.5.

The reaction product of step 1 may be polymerized as it is, or the reaction product may be distilled off and polymerized. Polymerization may be carried out by adding a monomer. These may be combined for polymerization. It polymerizes in the range of pH 1.5 to 3.5. Polymerization may be performed without adding an acid. The pH may be adjusted with an acid and polymerized.

Removing unreacted alkyl (meth) acrylate in step 1 and / or adding a monomer copolymerizable with PGMA (meth) acrylate in step 2; Can have a ratio.

In step 2, the monomer copolymerizable with the PGMA (meth) acrylate to be added may be (meth) acrylic acid, methyl (meth) acrylate or methoxypolyethylene render glycol mono (meth) acrylate. ,.

Either distill off unreacted (meth) acrylic acid in step 1 or add a monomer copolymerizable with PGMA (meth) acrylate in step 2 if necessary It is preferred to obtain a copolymer having a ratio.

In the present invention, “alkyl (meth) acrylate” refers to both alkyl acrylate and alkyl methacrylate, and “PGMA (meth) acrylate” refers to both acrylate and methacrylate. means. BEST MODE FOR CARRYING OUT THE INVENTION

In step 1, first, an alkyl (meth) acrylate is subjected to an ester exchange reaction with a polyalkylene glycol monoalkyl ether (hereinafter, referred to as “glycol ether”).

The alkyl (meth) acrylate used in the transesterification is not particularly limited, and a commercially available product containing a polymerization inhibitor in advance is used. This alkyl group preferably has 1 to 4 carbon atoms.

Examples of the glycol ether used in the transesterification reaction include those in which the polyalkylene moiety is composed of an alkylene oxide adduct such as an adduct of ethylene oxide alone or a mixed adduct of ethylene oxide and propylene oxide. Is preferably 1 to 300. The alkyl group constituting the monoalkyl ether moiety preferably has 1 to 3 carbon atoms.One or more kinds of polyalkylene having one or more moles of an alkylene oxide and a different number of carbon atoms of the alkyl or alkyl group are used. Mixtures of glycol monoalkyl ethers can be used. .

The mixing ratio in the reaction system of alkyl (meth) acrylate and dalicol ether is in the range of 3: 1 to 50: 1, preferably 10: 1 in molar ratio, in order to further increase the transesterification rate. ~ 40: 1 range.

In the transesterification reaction of Step 1, it is preferable to use an acid catalyst or a basic catalyst. Examples of the acid catalyst include sulfonic acids such as p-toluenesulfonic acid, methanesulfonic acid and benzenesulfonic acid, and mineral acids such as sulfuric acid and phosphoric acid. Examples of the basic catalyst include those described in JP-A-9-132836, page 7, column 11, lines 15 to 26, and among these, alkaline catalysts such as sodium hydroxide are exemplified. Li metal hydroxide, Alkali metal alkoxides such as sodium methoxide are preferred.

The amount of the acid catalyst or the basic catalyst used is preferably from 0.1 to 10 parts by weight based on 100 parts by weight of dalicol ether. When the amount is 0.1 part by weight or more, the reaction rate can be maintained at an appropriate level, and when the amount is 10 parts by weight or less, it is economical.

It is preferable to use a polymerization inhibitor in the transesterification reaction, and examples thereof include hydroquinone, benzoquinone, methoquinone, BHT, phenothiazine, and catechol. Further, by passing a gas containing oxygen into the reaction system, the polymerization inhibiting effect can be further enhanced.

The amount of the polymerization inhibitor to be used is preferably from 0.001 to 1 part by weight based on 100 parts by weight of dalicol ether.

The reaction temperature in the transesterification is preferably 60 to 130 ° C. When the temperature is 60 ° C or higher, an appropriate reaction rate can be maintained.When the temperature is 130 ° C or lower, deterioration of the glycol ether quality can be prevented, and the viscosity of the reaction system can be maintained at an appropriate level. Preferred because it can.

The pressure of the reaction system in the transesterification reaction is not particularly limited, and is preferably a reduced pressure from the viewpoint of distilling off the alcohol generated by the reaction to the outside of the system.

When an acid catalyst is used in step 1, after the transesterification reaction, an alkali agent is added to deactivate the acid catalyst. Examples of the alkaline agent include alkali 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, relative to the acid catalyst used.

In the transesterification reaction of Step 1, a large excess amount of alkyl (meth) acrylate is used in order to make the reaction proceed smoothly. When a basic catalyst is used in step 1, unreacted alkyl (meth) acrylate is then distilled off. If an acid catalyst is used in step 1, after deactivating the acid catalyst, unreacted alkyl (meth) acrylate is distilled off, and the PGMA (meth) acrylate represented by the following general formula (I) is removed. Thus, an esterification reaction product is obtained which mainly contains an alkyl (meth) acrylate residue represented by the following general formula (II) and a by-product represented by the general formula (III). R,

H ₂ C = C ₍₁₎

C00 (A0) nR ₂

R3

H C = C II

COOR4 5

H ₂ C = C III)

COOM

Wherein, is a hydrogen atom or a methyl group, R ₂ is an alkyl group having 1 to 3 carbon atoms, AO is an oxyalkylene group having 2 to 3 carbon atoms, n is a number of 1 to 300; R ³ is hydrogen An atom or a methyl group, represents an alkyl group having 1 to 4 carbon atoms; R ₅ represents a hydrogen atom or a methyl group; and M represents a hydrogen atom, an alkali metal or an alkaline earth metal. ]

The content of alkyl (meth) Akuri rate residues is preferably 5 wt% or less, 0.5 wt ^_0/0 or less is particularly preferable. When the content is 5% by weight or less, a (meth) acrylic acid-based polymer having stable quality and useful as a dispersant for cement can be obtained. The above-mentioned by-products can be used as they remain because they copolymerize with the (meth) acrylate. Unreacted alkyl (meth) acrylate can be distilled off by vacuum distillation, A steam distillation method or a method of distilling together with a carrier gas at normal pressure can be applied. In step 2, the PGMA (meth) acrylate obtained in step 1 and the monomer copolymerizable with PGMA (meth) acrylate are copolymerized with pH 1.5 to 3.5. Polymerize.

Examples of monomers copolymerizable with PGMA (meth) acrylate include acrylic acid, methacrylic acid, crotonic acid, and (meth) acrylic acid such as alkali metal salts, alkaline earth metal salts, ammonium salts, and amine salts thereof. Acid monomers such as maleic anhydride, maleic acid, itaconic anhydride, itaconic acid, citraconic anhydride, citraconic acid, fumaric acid and their alkali metal salts, alkaline earth metal salts, ammonium salts or ammonium salts, etc. Unsaturated dicarboxylic acid monomer; alkyl (meth) acrylate, hydroxyalkyl (meth) acrylate, methoxypolyethylene glycol (meth) acrylate, methoxypolyethylene polypropylene diol (meth) Methoxypolyalkylene glycol (meth) acrylates such as atalylate Relate monomers, styrene, (meth) ataliamide, acrylonitrile, styrenesulfonic acid and its salts, sulfoalkyl (meth) acrylates and their salts, 2-acrylamide 2-methylpropanesulfonic acid and its salts ( Here, (meta) is as defined above. Among these, from the viewpoint of dispersibility when used as a cement dispersant, (meth) acrylic acid, methyl (meth) acrylate or methoxypolyethylene glycol mono (meth) acrylate is preferred, and methacrylic acid is preferred. Particularly preferred.

The amount of the monomer copolymerizable with the PGMA (meth) acrylate is 0.3 to 1 part by weight based on 100 parts by weight of the PGMA (meth) acrylate represented by the general formula (I). 70 parts by weight is preferred, and 0.3 to 100 parts by weight is particularly preferred.

The pH of the polymerization reaction system is in the range of 1.5 to 3.5, but ρΗ2.0 to 3.0 is preferable. Good. When the pH is 1.5 or more, the occurrence of hydrolysis of PGMA (meth) acrylate during the polymerization reaction can be suppressed. When the pH is 3.5 or less, the copolymerization rate can be kept high, and the composition of each monomer in the copolymer can be appropriately controlled.As a result, it is useful as a stable-quality cement dispersant. A (meth) acrylic acid-based polymer is obtained. The pH in step 2 was 5 weight of the polymerization reaction mixture. /. PH of aqueous solution.

Examples of the acid used for adjusting the pH include phosphoric acid, sulfuric acid, nitric acid, alkylphosphoric acid, alkynoleic acid, alkylsulfonic acid, alkylbenzenesulfonic acid, benzenesulfonic acid and the like. 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. 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; n-hexane and the like. Aliphatic 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 to be added is preferably 1 to 50 mole times the total of the general formula (1), the general formula (III) and other monomers.

In step 2, a chain transfer agent can be added. Examples of the chain transfer agent include lower alkyl mercaptan, lower mercapto fatty acid, thioglycerin, thiomalic acid, and 21-mercaptoethanol. Especially when water is used as the solvent, By adding these chain transfer agents, the molecular weight can be adjusted more stably. 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 deodorized if necessary. In particular, when a thiol such as mercaptoethanol is used as the chain transfer agent, it is desirable to perform a deodorizing treatment since an unpleasant odor remains in the polymer.

As a method of deodorizing when thiol is used as a chain transfer agent, a method of converting thiol to disulfide with an oxidizing agent can be mentioned. 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 to be added is preferably from 100 to 2000 ppm, more preferably from 100 to 100 ppm, based on the polymer. If it is 100 ppm or more, sufficient deodorizing treatment can be performed, and if it is 200 ppm or less, excess hydrogen peroxide remains, which acts as a polymerization initiator to promote polymerization, Hydrogen peroxide is not decomposed to generate oxygen, and problems such as gelation of the polymer solution in a metal container do not occur. The deodorizing temperature is preferably from 70 to 100 ° C, particularly preferably from 80 to 90 ° C. If the temperature is at least 70 ° C, the deodorizing effect will be enhanced. If the temperature is at most 100 ° C, 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 can be applied as a dispersant for cement even when it is in the form of an acid. However, from the viewpoint of suppressing the hydrolysis of the ester by the acid, the salt is neutralized with an alkali. Preferably, it is shaped. Examples of the alkali include hydroxides of alkali metals or alkaline earth metals, 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 adjusted to 5 to 7 by neutralization. Is preferred.

Weight average molecular weight of (meth) acrylic acid polymer obtained by the production method of the present invention

(Gel permeation chromatography method, in terms of polyethylene oxide) is preferably from 10,000 to 200,000, more preferably from 20,000 to 100,000, in order to obtain sufficient dispersibility as a dispersant for cement. I like it.

The (meth) acrylic acid-based polymer obtained by the production method of the present invention is used as a dispersing agent for hydraulic materials other than cement such as Portland cement, alumina cement, various mixed cements, and gypsum. Can be 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)

80. A glass reactor was charged with 1,000 parts by weight of polyethylene dalicol monomethyl ether (weight-average molecular weight: 5344) having ethylene oxide addition mole number of 120 melted in C. Next, 3 parts by weight of hydroquinone and 32 parts by weight of p-toluenesulfonic acid were added. While introducing air and nitrogen, 565 parts by weight of methyl methacrylate (an amount that was 30 mol times as much as polyethylene dalicol monomethyl ether) was charged, and heating and depressurization in the reaction vessel were started. Pressure is 40-90 kPa The reaction was performed while maintaining the temperature of the reaction solution at 110 ° C. Nine 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 kept at 130 ° C. or lower, and unreacted methyl (meth) acrylate was recovered by a vacuum distillation method to obtain an esterification reaction product (A) -1. The methacrylate concentration of this (A) -1 was 93.4. /. Met.

(Process 2)

The same glass reaction vessel as in step 1 was charged with 485 parts by weight of water, the gas phase of the reaction vessel was replaced with nitrogen while stirring, and the temperature was raised to 80 ° C. Next, 600 parts by weight of the esterification reaction product (A) -1; 36 parts by weight of methacrylic acid; 3 parts by weight of 2-mercaptoethanol; Dequest (phosphonic acid chelating agent; manufactured by Monsanto Japan Limited). A solution obtained by mixing and dissolving 7 parts by weight, 5 parts by weight of 85% phosphoric acid and 420 parts by weight of water and 39 parts by weight of a 15% aqueous solution of ammonium persulfate were added dropwise 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 1 hour. The pH during the polymerization reaction was 2.4. Further, 30 parts by weight of a 48% aqueous sodium hydroxide solution was added for neutralization, and 0.7 parts by weight of 35% hydrogen peroxide was added dropwise. The mixture was aged at 90 ° C. for 1 hour, (Meth) An acrylic acid polymer was obtained. this

When the viscosity of the (meth) acrylic acid-based polymer was measured (B-type viscometer manufactured by Tokyo Keiki Seisakusho Co., Ltd., data No. 2, 30 rpm), it was 425 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 paste flow value)

0.9 g of a 40% aqueous solution of a (meth) acrylic acid polymer was added to 700 g of ordinary Portland cement and 210 g of water, and the mixture was added to a mortar mixer (manufactured by Sanei Seisakusho). And mixed at 63 rpm for 1 minute, and further mixed at 126 rpm for 2 minutes. After mixing, pour the mixture 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 measuring cone is pulled up in the direction perpendicular to the plane and removed, the diameter of the cement paste that spreads out in a circle on the plane is measured at two points, and the average value is the average value of the paste toe mouth (mm). And The larger the past flow value, the better the dispersibility.

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 2.6. The viscosity of the obtained (meth) acrylic acid-based 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; 84 parts by weight of methacrylic acid; methoxypolyethylene glycol monomethacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., average number of moles of ethylene oxide added: 9) A solution prepared by mixing and dissolving 121 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 were mixed. At the same time, the dropping was completed over 90 minutes for all three solutions. Next, 10 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, add 34 parts by weight of a 48% aqueous sodium hydroxide solution to After the addition, 0.7 parts by weight of 35% hydrogen peroxide was added dropwise, and the mixture was aged at 90 ° C. for 1 hour to obtain a (meth) acrylic acid polymer. The viscosity of the (meth) acrylic acid-based polymer was 400 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 4

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, 600 parts by weight of the esterification reaction product (A) -1, 18 parts by weight of methacrylic acid, 63 parts by weight of methyl acrylate, 2.5 parts by weight of 85% phosphoric acid, and 400 parts by weight of water 3 parts of 2-mercaptoethanol and 15 parts of a 15% aqueous solution of ammonium persulfate (48 parts by weight) were simultaneously added dropwise to the three liquids, and the addition of all three liquids was completed in 90 minutes. Next, 16 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-based polymer. The viscosity of this (meth) acrylic acid polymer was 452 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 5

(Process 1)

In step 1 of Example 1, a catalyst was used at a reaction temperature of 290 using 1.5 parts by weight of 48% sodium hydroxide as a catalyst, 1.5 parts by weight of hydroquinone and 1.5 parts by weight of phenothiazine as a polymerization inhibitor. C. An esterification reaction product (A) -2 was obtained in the same manner as in Example 1 except that neutralization was not performed after the completion of the reaction. The methacrylate concentration of this (A) -2 was 93.7%. (Process 2)

(Meth) acrylic acid polymer was obtained in the same manner as in Example 1 except that 5 parts by weight of phosphoric acid was changed to 26 parts by weight using esterification reaction product (A) -2. The pH during the polymerization reaction in step 2 was 3.1. The viscosity of the obtained (meth) acrylic acid-based polymer was 449 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 6

(Process 1)

In Step 1 of Example 1, 100 parts by weight of polyethylene glycol monomethyl ether (number of moles of added ethylene oxide 9, weight average molecular weight 4229), 1200 parts by weight of methyl methacrylate and 40 parts by weight of p-toluenesulfonic acid An esterification reaction product (A) -3 was obtained in the same manner as in Example 1 except for using parts by weight. The methacrylate concentration of this (A) -3 was 93.4%.

(Process 2)

The same glass reaction vessel as in step 1 was charged with 546 parts by weight of water, 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 solution obtained by mixing and dissolving 574 parts by weight of the esterification reaction product (A) -3, 172 parts by weight of methacrylic acid and 550 parts by weight of water, 4 parts by weight of 2-mercaptoethanol and 15 parts by weight A solution of 19 parts by weight of an aqueous solution of ammonium persulfate (19 parts by weight) was simultaneously dropped, and the dropping of all three solutions 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 the mixture was aged at 80 ° C. for about 1 hour. The pH during the polymerization reaction was 2.8. Further, it was neutralized by adding 1 16 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-based polymer was 340 mPa • s. The same (meth) acrylic acid polymer as in Example 1 Past flow values were determined by the method. Table 1 shows the results.

Comparative Example 1

A (meth) acrylic acid-based polymer was obtained in the same manner as in Example 1, except that in Step 2 of Example 1, 16 parts by weight of 48% sodium hydroxide was used instead of 85% phosphoric acid. . The pH during the polymerization reaction in step 2 was 4.5. The viscosity of the obtained (meth) acrylic acid polymer was 490 mPa's. The paste flow value of this (meth) atalylic 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 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 not added. The pH during the polymerization reaction in step 2 was 4.0. The viscosity of the obtained (meth) acrylic acid-based polymer was 460 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.

Table 1 Example s Example Comparative example

1 o 4 o b 1

\ C

(A) -1 (A) -1 (A) -1 (A,)-1 (A) -2 (A) -3 (A) -1 (A) -1 Esterification reactant

600 bOO DUO bUO 574 60U bUU Methacrylic acid oon c

D i I O OD17 OD o Monomeric methoxyphenol ethylene glycol

121

Type Nometallate

Methyl acrylate 63

85% phosphoric acid 5 2 2.5 26

pH adjuster Sulfuric acid 5

48 <½ sodium hydroxide 16 pH during polymerization reaction 2.4 2.6 3.0 3.0 3.1 2.8 4.5 4.0 Viscosity of polymer (mPa-s) 425 450 400 452 449 340 490 460 Paste flow value (mm) 250 248 240 243 248 245 245 170 168

(Meth) acrylic acid-based polymers obtained by the production methods of Examples 1 to 5 all had a high paste flow value, and as a result, it was confirmed that a high-quality cement dispersant could be provided. In contrast, the obtained by the production method (meth) § acrylic acid polymer Comparative Example 1, since _P H of the polymerization reaction system in the step 2 is outside the range specified in the present invention, the pace Tofuro value Was greatly inferior.

Claims

Range of δ calculation

1. A method for producing a (meth) acrylic acid polymer, comprising the following steps 1 and 2. Step 1: An alkyl (meth) acrylate and a polyalkylene glycol monoalkyl ether are subjected to transesterification at a molar ratio of 3: 1 to 50: 1 to obtain a polyalkylene glycol monoalkyl ether (meth) acrylate (hereinafter referred to as PG). After producing MA (meta) acrylate, a by-product alcohol is distilled off to obtain an esterification reaction product containing GMA (meth) acrylate.

Step 2: a step of copolymerizing PGMA (meth) acrylate and a monomer copolymerizable with ΡGMA (meth) acrylate in the range of ρΗ1.5 to 3.5.

2. By distilling off unreacted alkyl (meth) acrylate in step 1 and adding a monomer copolymerizable with PGMA (meth) acrylate in step 2 or 2. The method according to claim 1, wherein a copolymer having a ratio of monomers is obtained.

3. The production method according to claim 1, wherein in step 2, an acid is added to the esterification reaction product to adjust the pH to a range of 1.5 to 3.5.

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

5. Claim that the monomer copolymerizable with PGMA (meth) acrylate added in step 2 is (meth) acrylic acid, (meth) methyl acrylate or methoxypolyethylene glycol mono (meth) acrylate. Item 5. The method according to any one of Items 2 to 4.