HAYASHIYA TOSHIO (JP)
JPH09132445A | 1997-05-20 | |||
JPH05125114A | 1993-05-21 | |||
JPH0545611A | 1993-02-26 | |||
JPH0539322A | 1993-02-19 | |||
JPS5620007A | 1981-02-25 |
1. | A copolymer formed by polymerizing a monomer component containing (A) which are any one or more of the monomers represented by the following formulas (1) (3) , and (B)which is amonomer representedby the following formula ( 4 ) wherein R1O and R2O either identically or not identically denote an oxyalkylene having a carbon number in the range of. |
2. | 4, m pieces of R1O may be identical or no identical, and, when two or more kinds of oxyalkylene are contained, they may be added in a blocked form or a random form, n pieces of OR2 may be identical or not identical, and, when two or more kinds of oxyalkylene are contained, they may be added inablockedformor a randomform, R. |
3. | ndR4 either identically or not identically denote a hydrogen atom, an aliphatic hydrocarbon group having a carbon number in the range of 1 20, a substituted or not substituted aryl group or aralkyl group having a carbon number in the range of 6 14, m denotes a number in the range of 1 300, and n denotes a number in the range of 1 300. wherein R5, R6, and R7 either identically or not identically denote a hydrogen atom, methyl, or (CH2)PCOOM2, the (CH2)pCOOM2 may form an anhydride with COOM1 or another (CH2)pCOOM2 and, in that case, the groups are devoid of M1 and M2, and M1 and M2 either identically or not identically denote a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, ammonium, alkylene ammonium, or alkyl ammonium substituted with a hydroxyl group, and p denotes a number in the range of 0 2. 2. Acopolymeraccordingtoclaim1, whereinsaidmonomer (A) is a monomer represented by the formula (1) mentioned above. 3. A copolymer according to claim 1 or claim 2, which contains the monomer (A) and the monomer (B) mentioned above and, when the total of the monomers (A) and (B) mentioned above is taken as 100 mol%, the monomer (A) is contained in a ratio in the range of 0.5 99.5 mol% and the monomer (B) is contained in a ratio in the range of 0.5 99.5 mol% in the copolymer. 4. A copolymer according to claim 1 or claim 2, which further contains another monomer (C) copolymerizable with said monomer (A) and monomer (B) and, when the total of said monomers (A) , (B) , and (C) is taken as 100 mol%, the monomer (A) is contained in a ratio in the range of 0.5 99 mol%, the monomer (B) in the range of 0.5 99 mol%, and the monomer (C) in the range of 0.5 50 mol%. 5. A dispersant containing a copolymer set forth in any of claims 1 4. |
COPOLYMER AND DISPERSANT
Technical Field This invention relates to a copolymer of a polyalkylene glycol diester of itaconicacid, citraconic acid, oritiesaconic acid and a specific (meth) acrylic acid and a dispersant containing the copolymer. Background Art Cement is used abundantly at the sites of civil engineering works and building constructions. The cement paste formed by adding water to cement, the mortar formed by adding sand as a fine aggregate thereto, and the concrete formed by further mixing pebbles therewith are used as in structural members, groundsills, and fireproof walls and in large quantities. The cement paste, mortar, and concrete are caused by the reaction of hydration between cement and water to generate strength via coagulation and solidification. As a result, the workability thereof is degraded with the elapse of time after the addition of water. This phenomenon in the raw concrete is generally called a slump loss. The slump loss increases in accordance as the unit amount of water present in the cement paste decreases. Since an addition to the unit amount of water in the raw concrete for the sake of improving the workability results in inducing the concrete, etc. to lose strength, the material necessitating cement and water is required to decrease the amount of water to be used to the fullest possible extent from the viewpoint of strength and durability. Thus, various cement dispersants and water-reducing admixtures are being developedwiththe object of maintaining the workability without sacrificing the fluidity in spite of a decrease in the amount of water. For example, a cement dispersant which is formed of a copolymer obtained by polymerizing an alkoxypolyalkylene glycol mono (meth) acrylic ester type monomer (monomer A) resulting from the transesterification of an alkoxypolyalkylene glycol and (meth) acrylic ester in the presence of a basic catalyst has been known (EPO799807B1) . The aforementioned monomer A obtained by the transesterification in the presence of a basic catalyst is rated to excel in commercial superioritybecause it is capable of substantially enhancing the water-reducing property and substantially reducing the reaction time elapsing till the monomer A is obtained. As the copolymerization component (monomerB), (meth) acrylicacids (salts) areavailable. Most copolymers used as a cement dispersant adopt the esters of polyalkylene glycolswithapolymeric carboxylicacidas their monomers. This adoption resides in utilizing the fact that the relevant copolymer is capable of forming a carboxylic acid with elapse of time owing to the hydrophilic property of the polyalkylene glycol and the hydrolysis with an alkali. As the polymeric carboxylic acid, therefore, such a dicarboxylic acid as itaconic acid may be additionally used in the place of (meth) acrylic acid. In EPO799807B1 mentioned above, as typical examples of the monomer C which can be arbitrarily incorporated, dicarboxylic acids such as maleic acid, fumaric acid, citraconic acid, mesaconic acid, and itaconicacid, andmonoesters ordiesters of suchdicarboxylic acids and uniterminal alkoxy bodies of polyalkylene oxide are cited. In the working examples cited herein, however, no ester of the aforementioned dicarboxylic acid and the uniterminal alkoxy body of polyalkylene oxide was produced as the monomer C. A concrete admixture which is formed of a vinyl copolymer of an ethylenically unsaturated monomer (monomer A) possessing an oxyalkylene and an alkyl ester monomer (monomer B) of an ethylenically unsaturtedmono- or di-carboxylic acid is also disclosed (US000005911820A) . The concrete admixture has resulted from a study which was pursued with a view to enabling a hydraulic composition to excel in the ability to retainthe fluidityandenhancingthe slumpretainingproperty with an insignificant delay of curing. As typical examples of the monomer A, polyalkylene glycol monoallyl ethers and dicarboxylic acid type compounds adding oxyalkylene groups having a carbon number in the range of 2 - 3 such as maleic anhydride, itaconic anhydride, citraconic anhydride, maleic acid, itaconic acid, and citraconic acid are cited besides the esters of uniterminal alkyl hindered polyalkylene glycol and acrylic acid or methacrylic acid. It has a mention to the effect that the other monomer C may be contained besides the monomers A and B mentioned above. As the monomer C, such unsaturatedcarboxylic acidmonomers as acrylicacidare cited. In the working example of the US000005911820A, a copolymer ofanEOadduct ofmaleic acidandmethyl acrylatewasproduced. As regards the utilization of the hydrophilic property ofapolyalkyleneglycol, acompoundformedbytheesterlinkage of one molecule of polyalkylene glycol with an itaconic acid monoalkylate having a carbon number in the range of 1 - 22 is used as an emulsifier (US3, 689, 532) . It is disclosed that the compound is prepared by causing an epoxide to act on itaconic acid inthe presence of quaternaryammoniumandboron fluoride and, when used in combination with boron fluoride, is transformed into a long-chain polyalkylene glycol ester. As concerns the way of producing the ester of itaconic acid and a polyalkylene glycol, a method which resides in reacting itaconic acid with polyethylene glycol monododecyl ether in thepresenceoftoluene sulfonicacidandamethodwhichresides in reacting itaconic acidwithpolyethylene glycolmonomethyl ether in the presence of 2-chloro-l-methyl pyridinium iodide have been known (Hideyuki Hama et al, Synthesis of Polystyrene/Itaconic acid Long-chain Ester type Graft Copolymer, Science and Industry, pp. 456 - 462, 1994) . Disclosure of the Invention The conventional dispersants generally contain polyalkylene glycol esters of (meth) acrylic acidandmanifest prescribed results in the dispersing property and the water-reducing property. Some of them even contain polyalkylene glycol diesters of dicarboxylic acid such as maleic acid in the place of such monocarboxylic acids as (meth) acrylic acid. The desirability of developing a new dispersant which is further excellent in dispersing property and workability, however, has been finding recognition. Generally, the dispersant is required not only for the cement but also for coating materials, paper coating agents, binders to be used in molding ceramic sinters, and the like. For the purpose of producing the copolymer to be used in such a wide range, the improvement of the efficiency of production and the excellence of the reaction stability in the process of production are important. Thus, the desirability of developing a novel dispersant which is easy to produce and can be produced in a high yield has been has been finding approval. Inthe light of the true state of affairsmentionedabove, this invention is aimed at providing a novel copolymer excellingindispersingpropertyandwater-reducingproperty. It is also aimed at providing a dispersant which is easy to produce and excellent in efficiency of production. The present inventors have made a detailed study concerning monomers heretofore used as a dispersant and copolymers derived therefrom. They have consequently found that copolymers containing a polyalkylene glycol diester of itaconicacidasamonomercomponentareusefulasadispersant. This invention has been perfected as a result. It has been heretofore known that the esters of such monocarboxylic acids as (meth) acrylic acid and polyalkylene glycols are used as a dispersant. Since (meth) acrylic acid has low thermal stability, it has not been easily esterified at elevated temperatures. A search for substances excelling inthermal stabilityhas revealedthat suchdicarboxylic acids as itaconic acid, citraconic acid, and mesaconic acid answer the requirement and that the polyalkylene glycol diesters of these dicarboxylic acids excel in the ability to copolymerize with (meth) acrylic acid. The copolymer of this invention contains the polyalkylene glycol diester of itaconic cid, citraconic acid and/ormesaconic acidas amonomer component and canbe ideally usedas adispersant. Particularly, itiscapableofuniformly dispersing an inorganic substance or an organic substance which is insoluble in a liquid medium. As a result, it can be used as a cement dispersant, a coating material, a pigment dispersant for a paper coating operation, a dispersant for molding a ceramic sinter, etc. Moreover, since themonomer excels inthermal stability, it can decrease the amount of the catalyst to be added and can yield the monomer at a high productivity rate. Best Mode of Embodying the Invention This invention primarily is directed toward a copolymer whichis formedbypolymerizingamonomer component containing (A) which are any one or more of the monomers represented by the following formulas (1) - (3), and (B) which is a monomer represented by the following formula (4)
wherein -R1O- and -R2O- either identically or not identically denote an oxyalkylene having a carbon number in the range of 2 - 4, m pieces of -R1O- may be identical or no identical, and, when two or more kinds of oxyalkylene are contained, they may be added in a blocked form or a random form, n pieces of -OR2- may be identical or not identical, and, when two or more kinds of oxyalkylene are contained, they may be added inablockedformorarandomform, R3 andR4 eitheridentically or not identically denote a hydrogen atom, an aliphatic hydrocarbon group having a carbon number in the range of 1 - 20, a substituted or not substituted aryl group or aralkyl group having a carbon number in the range of 6 - 14, m denotes a number in the range of 1 - 300, and n denotes a number i the range of 1 - 300.
wherein R5, R6, and R7 either identically or not identically denote a hydrogen atom, methyl, or - (CH2)PCOOM2, the -(CH2)PCOOM2 may form an anhydride with -COOM1 or another - (CH2)pCOOM2 and, in that case, the groups are devoid of M1 and M2, and M1 and M2 either identically or not identically denote a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, ammonium, alkylene ammonium, or alkyl ammonium substituted with a hydroxyl group, and p denotes a number in the range of 0 - 2. The foregoingformula (1) representspolyalkyleneglycol diesters of itaconic acid and the foregoing formula (2) and formula (3) represent polyalkylene glycol diesters respectively of citraconic acid and mesaconic acid. The citraconic acid and the mesaconic acid are both isomers of itaconicacid. Asapolymerizable dicarboxylicacid, maleic acid exists. The copolymer having this polyalkylene glycol diester as a copolymer component is used as a dispersant. As describedinthe foregoingpublicationScience and Industry (pp.456-462, 1994), however, thepolyalkyleneglycol diester of itaconic acid has never been isolated because the reaction of itaconic acid with a polyalkylene glycol forms a monoester body as a main component and this monoester body is separated fromtheby-produceddiesterbodywithdifficulty. Asaresult, the copolymer of the diester body of itaconic acid and (meth) acrylic acid has never been synthesized because the copolyitierizability thereof remains yet to be clarified. The present inventors, by actually synthesizing a polyalkylene glycol diester of itaconic acid, have been ascertained that since the itaconic acid excels in the thermal stability of the double bond thereof, it enables the esterification to proceed at a higher temperature than ever and excels in the yield of the monomer. Further, by investigating the copolymerizability of the monomer with (meth) acrylic acid, they have been ascertained that the monomer possesses high copolymerizability and that the produced copolymermanifests an extremely excellent mortar flow value as compared with the alkylene glycol diester of maleic acid. Now, this invention will be explained in detail below. Themonomer (A) tobeusedinthis inventionis represented by the aforementioned formulas (1) - (3) . In the formulas (1) - (3) , -R1O- and -R2O- severally represent an oxyalkylene having a carbon number in the range of 2 - 4. Preferred oxyalkylenes are oxyethylene, oxypropylene, oxytrimethylene, oxyisobutylene, etc. Oxyethylene and oxypropylene are particularly preferable, m pieces of -R1O- may be identical or not identical. When two or more kinds of oxyalkylene are included, they may be added in a blocked form or in a random form. The same holds good with n pieces of -OR2-. When -R1O- and -R2O- both denote oxyethylenes, the monomer excels in dispersing property in an aqueous medium When m pieces of -R1O- and n pieces of -R2O- severally contain an oxypropylene in a ratio in the range of 0 - 30 mol%, preferably in the range of 5 - 25 mol%, and particularly preferably in the range of 10 - 20 mol%, the produced copolymer excels in the balance between the water-solubility and the hydrophobic property. The aliphatic hydrocarbon groups of carbon numbers of 1 - 20 denoted by R3 and R4 include branched alkyl groups such as isopropyl, sec-butyl, tert-butyl, and 2-methyl octane and alicyclic hydrocarbons such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, andcyclooctylbesides linearalkylgroups suchasmethyl, ehyl, propyl, butyl, pentyl, octyl, tetradecyl, and octadecyl. The substituted or unsubstituted aryl groups of a carbon number of 6 - 14 include phenyl, o-,m-, orp-tolyl, 2, 3- or2, 4-xylyl, cumenyl, mesityl, naphthyl, antholyl, phenanthryl, biphenyl, andpyrenyl. The substituted or unsubstituted aralkyl groups of carbon number of 6 - 14 include benzyl, phenethyl, benzhydryl, and trityl. In this invention, R3 and R4 severally denote preferably hydrogen, an alkyl group of a carbon number of 1 - 20, an alicyclic hydrocarbon of a carbon number of 1 - 20, and a substituted or unsubstituted aryl group or aralkyl group of a carbon number of 6 - 14 and more preferably a hydrogen atom, methyl, ethyl, propyl, butyl, phenyl, and benzyl. m and n severally denote the degree of polymerization of an alkylene oxy, m is in the range of 1 - 300, preferably 1 - 150, more preferably 4 - 150, further preferably 4 - 100, and particularly preferably 4 - 50 and n is in the range of 1 - 300, preferably 1 - 150, more preferably 4 - 50, further preferably 4 - 100, and particularly preferably 4 - 50. If they deviate from the ranges specified above, the deviation will possibly result in lowering the polymerizability and lowering the dispersing property as well. In this invention, the monomer (A) may properly adopt any of the aforementioned monomers of the formulas (1) - (3) . It does not need to adopt any one of them exclusively but may adopt two or more of them together. Incidentally, the polyalkylene glycol diester of itaconic acidproves favorable since it excels in copolymerizability with the monomer (B) . It is the monomer represented by the following formula (I1) that proves particularly favorable.
wherein -R1O- and -R2O- each denote an oxyethylene or an oxypropylene, mpieces of-R1O- andnpieces of-R2O- severally contain 0 - 30mol% ofoxypropylene, R3andR4eitheridentically or not identically denote a hydrogen atom, an aliphatic hydrocarbon group of a carbonnumber of 1 - 20, or a substituted or unsubstitutedaryl group or aralkyl group of a carbonnumber of 6 - 14, m denotes a number of 1 - 300, and n denotes a number of 1 - 300. Themonomer (B) tobeusedinthis inventionis represented by the foregoing formula (4) . In the formula (4) , M1 and M2 each denote a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, • ammonium, an alkyl ammonium, or an alkyl ammonium substituted with a hydroxyl group. Sodium and potassium are preferred alkali metal atoms, magnesium and calcium are preferred alkaline earth metal atoms, methyl ammonium, ethylammonium, dimethyl ammonium, diethylammonium, propyl ammonium, n-butyl ammonium, sec-butyl ammonium, and tert-butyl ammonium are preferred alkyl ammoniums, and hydroxymethyl ammonium, hydroxyethyl ammonium, hydroxydimethyl ammonium, hydroxydiethyl ammonium, hydroxy-propyl ammonium, hydroxy-n-butyl ammonium, hydroxy-sec-butyl ammonium, andhydroxy-tert-butyl ammonium are preferred alkyl ammoniums substituted with a hydroxyl group. This invention prefers M1 and M2 each to be a hydrogen atom, sodium, or potassium. The -(CH2)pCOOM2 which is definedby R5, R6, and R7 include sodium salt and potassium salt of carboxyl besides the carboxyl; and anhydrides with other -COOM1. Incidentally, when M1 and/or M2 is an alkaline earth metal atom in the foregoing formula (4) , the COOM1 may form a salt with other - (CH2)pCOOM2. In this case, M2 is not present. R5, R6, and R7 are each preferred to be a hydrogen atom or methyl. As typical examples of the monomer (B) which is used in this invention, unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid, unsaturated dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid, mesaconic acid, and citraconic acid, and anhydrides thereof, and further salts of these unsaturated carboxylic acids and unsaturated dicarboxylic acids such as, for example, alkali metal salts, alkalineearthmetal salts, ammoniumsalts, alkyl ammonium salts, and alkyl ammonium salts substituted with a hydroxyl group may be cited. One or more members selected from among acrylic acid, methacrylic acid, and sodium salts and calciumsalts thereof are particularlypreferred examples of the monomer (B) . The compositional ratioofthemonomer (A) andthemonomer (B) mentioned above for obtaining the copolymer contemplated by this invention does not need to be particularly restricted but may be properly selected to suit the purpose of use of the copolymer. When the copolymer is used as a dispersant, for example, the monomer (A) is in a proportion of 0.5 - 99.5 mol% and the monomer (B) in a proportion of 0.5 - 99.5 mol%, preferably the monomer (A) in a proportion of 3 - 85 mol% and the monomer (B) in a proportion of 15 - 97 mol%, and more preferably the monomer (A) in a proportion of 5 - 70 mol% and the monomer (B) in a proportion of 30 - 95 mol%, on the assumption that the total of the monomer (A) and the monomer ( B) is 100 mol% . The copolymer of this invention is allowed to contain further another monomer (C) which is copolymerizable with the monomer (A) or the monomer (B) As typical examples of this monomer (C) , half esters of unsaturated dicarboxylic acids such as maleic acid mono (methoxypolyethylene glycol) esters and itaconic acid mono (methoxypolyethylene glycol) esters; (meth) acrylic acid alkyl esters such as methyl (meth) acrylate and ethyl (meth) acrylate; (meth) acrylic acid hydroxyalkyl esters such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate; and styrene, acrylamide, 2-hydroxy-3-allyloxy~l-propane sulfonic acid and sodium salts thereof may be cited. The amount of the aforementioned monomer (C) to be incorporateddoes not needtobe restrictedbutmaybeproperly selected to suit the purpose of use. In this case, themonomer (C) may be incorporated in an amount of not more than 40 mol% on the assumptionthat the total of the aforementionedmonomer (A), monomer (B), and monomer (C) is 100 mol%. Preferably, the aforementioned monomer (A) is in the range of 0.5 - 99 mol%, the aforementioned monomer (B) in the range of 0.5 - 99 mol%, and the aforementioned monomer (C) in the range of 0.5 - 40 mol%, more preferably the aforementioned monomer (A) in the range of 4 - 80 mol%, the aforementioned monomer (B) inthe range of 20 - 90mol%, andthe aforementionedmonomer (C) in the range of β - 30 mol%, and particularly preferably the aforementioned monomer (A) in the range of 5 - 70 mol%, the aforementioned monomer (B) in the range of 30 - 80 mol%, and the aforementioned monomer (C) in the range of 15 - 30 mol% (providing that the total amount of the monomers (A) + (B) + (C) is 100 mol%) . If they are shown by mass%, when the total of the monomer (A) , the monomer (B) and the monomer (C) is 100 mass%, the monomer (A) is preferably 55-95 mass%, especially preferable 65-90 mass%. By copolymerizing these monomers in the amounts falling in the respective ranges, it is made possible to obtain the copolymer which excels in dispersibility. Incidentally, the copolymer of this invention which is obtained by polymerizing the aforementioned monomers does not need to be restricted to themethodofproductionwhich is disclosedbythis invention. It is only required to contain the component units originating in the aforementioned monomers. The expression "component units originating in the aforementioned monomers" refers to the configuration (-C-C-) in which the polymerizing double bond (C = C) of each of the monomers is opened by the polymerization reaction. The copolymer of this invention can be used in its unaltered form as a varying dispersant. It may be dissolved in a solvent such as water and used in the form of an aqueous solution. Though the concentration of the copolymer in the aqueous solution may be properly selected to suit the use and the molecular weight of the polymer, it is generally in the range of 5 - 60 mass%. The objects for which the dispersant is intended are cement, coating material, paper manufacture, pigment, moldingofceramic sinter, etc. The copolymerisparticularly useful for cement dispersant. When the dispersant is used as a cement dispersant, it may be used together with other cement admixture. As typical examples of the admixture, the AE agent, water-reducing admixture, AE water-reducing admixture, high-performance water-reducing admixture, high-performance AE water-reducing admixture, retardingagent, fluidizingagent, shrinkage-reducing agent, defoaming agent, etc. which are enumerated in Chapter 4 of "Handbook of Concrete Admixtures (published by N.T.S. K.K. on April 23, 2004) " may be cited. Though the amount of such an admixture to be incorporated can be decided in view of the performance to be expected, it is preferably in the range of 0 - 50 mass% based on 100 mass% of the copolymer of this invention. When the cement dispersant using the polymer thus obtained as a main component is compounded in a cement composition formed of at least cement and water, it promotes the dispersion of cement. The cement dispersant of this invention can be used for hydraulic cements such as portland cement, cement of high belite content, alumina cement, and variousmixedcement andhydraulicmaterials otherthan cement such as gypsum. The cement dispersant to be used in this invention manifests an excellent effect even when it is added in a small amount as compared with the conventional cement dispersant. Whenit isusedformortarorconcreteusingahydrauliccement, for example, it is only required to be added during the course of kneading in an amount computed to account for a ratio in the range of 0.02 - 3.0% and preferably 0.1 - 2.0%, based on the mass of cement. This addition results in bringing various favorable effects such as accomplishing a high water-reducing ratio, enhancing the ability to prevent slump loss, reducing the unit amount of water, exalting strength, and enhancing durability. If the amount of-the addition falls short of 0.02%, the shortage will prevent the performance from being manifested sufficiently. Conversely, if this amount exceeds 30%, the overage will prove disadvantageous from the economic point of view because the effect thereof substantially reaches its ceiling. The cement composition formed of the aforementioned cement dispersant, cement, andwater does not needto restrict particularly the amount of cement to be used and the unit amount of water per 1 m3 of the composition. The unit amount of water is in the range of 150 - 190 kg/m3 and the water/cement mass ratio is in the range of 0.10 - 0.65. Preferably, the unit amount of water is in the range of 160 - 185 kg/m3 and the water/cement mass ratio is in the range of 0.2 - 0.5. The cement composition, when necessary, incorporates therein sand and aggregate such as small pebbles. The monomer (A) to be used in this invention may be produced by any method available at all. The monomer represented by the aforementioned formula (1) is preferred to be synthesized by Method 1: the reaction of esterification of itaconic acid or itaconic anhydride and a polyalkylene glycol, Method2: the reactionofesterificationofanitaconic alkylate and a polyalkylene glycol, Method 3: the addition of an alkylene oxide to itaconic acid, and Method 4: the addition of an alkylene oxide to an itaconic acidhydroxyalkyl ester. Incidentally, the compounds represented by the aforementioned formulas (2) and (3) can be similarly synthesized by using citraconic acid and mesaconic acid in the place of itaconic acid. Method 1: Reaction of esterification of itaconic acid or itconic anhydride and a polyalkylene glycol. The polyalkylene glycols available for this reaction are required to be transformed by the reaction of esterification with itaconic acid or itaconic anhydride into compounds represented by the aforementioned formula (1) and they are varied in a wide range. As typical examples of thepolyalkylene glycol of this description, polyalkylene glycols such as polyethylene glycol, polypropylene glycol, ethylene oxide-propyleneoxiderandomcopolymer, andethylene oxide-propylene oxide block copolymer; uniterminal alkoxy bodies ofpolyalkyleneglycol suchasmonomethoxypolyethylene glycol, monoethoxypolyethylene glycol, monobutoxypolyethylene glycol, monomethoxypolypropylene glycol, and uniterminal alkyl bodies of ethyleneoxide-propylene oxide randomcopolymer; uniterminal aryloxy bodiesof polyalkylene glycol such as monophenoxypolyethylene glycol, monophenoxypolyethylene glycol, monophenoxy-polyethylene glycol, monophenoxypolypropylene glycol, and uniterminal body of ethylene oxide-propylene oxide random copolymer; and uniterminal aryl alkoxybodies such as monobenzyloxyethylene glycol, monobenzyloxypolyethylene glycol, monobenzyloxypoly-ethylene glycol, monobenzyloxypolyethylene glycol, monobenzyloxypolypropylene glycol, and uniterminal benzyloxy body of ethylene oxide-propylene oxide random copolymer may be cited. Incidentally, when the ethylene oxide-propylene oxide copolymer is used, it is preferred to contain 1 - 30 mol% of propylene oxide. This invention uses preferablythe uniterminal alkoxybodyofpolyalkylene glycol, the uniterminal aryloxy body of polyalkylene glycol, or the uniterminal aryl alkoxy body of polyallynene glycol and more preferably the uniterminal alkoxy body of polylkylene glycol from the viewpoint of the excellence in reactivity and the excellence of the dispersibility of the copolymer to be obtained. Though the amount of the polyalkylene glycol to be incorporated per mol of itaconic acid or itaconic anhydride is theoretically 2 mols, it is preferably in the range of 1.5 - 2.5 mols, more preferably in the range of 1.7 - 2.1 mols, and particularly preferably in the range of 1.8 - 2.0 mols. If this amount falls short of 1.5 mols, the shortage willpossiblyresult inincreasingthemixingratioofitaconic acid and polyalkylene glycol monoester and degrading the dispersibility of the produced copolymer. Conversely, if this amount exceeds 2.5 mols, the overage will prove disadvantageous economically because it brings only a small change in the yield of itaconic acid polyalkylene diester. The reaction is allowed to use an esterifying catalyst. Thecatalysts available forthe reactioninclude suchsulfonic acid type compounds as toluene sulfonic acid and methyl sulfonic acid. At least one compound selected from the group consistingofphenothiazine, N-oxyl compound, phenol compound, manganese salts such as manganese acetate, copper salts of dialkyl dithiocarbamic acid such as copper dibutylthiocarbamate, and nitroso compounds and amine compounds may be used for the purpose of preventing itaconic acid from being polymerized. Since the thermal stability is high, the production can be accomplished without using this compound. When the compound is used at all, it may be used in the smallest possible amount. For example, it may be not more than 200 ppm based on the total mass of itaconic acid and polyalkylene glycol. The reaction may be carried out in the presence of a solvent such as benzene, toluene, xylene, or cyclohexane. The reaction ideally proceeds when the reaction substrate concentration (the total amount of itaconic acid or itaconic anhydride and polyalkylene glycol) in the solvent is in the range of 50 - 98 mass% and more preferably in the range of 70 - 95 mass%. The synthesis of a polyalkylene glycol ester of itaconic acid has been tried heretofore, though with an extremely low yield. In the publication Science and Industry (PP 456-462, 1994), for example, the reaction of itaconic acid with polyethylene glycol monododecyl ether by the use of toluene sulfonic acid as a catalyst failed to produce the target diester body in a high yield and the use of 2-chloro-l-methyl pyridinium iodide in the place of toluene sulfonic acid resulted in producing a monoester body as a main component. Though the cause for this low yield remains yet to be elucidated, it may be logically explained by a supposition that owing to the use of benzene in a large amount as an azeotropic solvent, the reaction temperature was elevated barely to the neighborhood of 1200C and consequently the yield was low. This invention has originated in the particular notice directed to the excellence of itaconic acid in thermal stability and culminated in the discovery that the temperature of esterification can be set at a higher level than ever and the yield can be enhanced by limiting the amount of the solvent in the range mentioned above. Incidentally, the product of publication Science and Industry (PP 456-462, 1994) has a monoester body and a diester body existing in a mixed state. The polyalkylene glycol diester body of itaconic acid, however, has not been substantially isolated from this product because these two bodies do not permit easy separation. The reaction temperature is in the range of 50° - 2200C, preferably in the range of 100° - 2000C, and particularly preferably in the range of 130° - 1800C. The polyalkylene glycol ester of (meth) acrylic acid has low thermal stability. When the reaction temperature surpasses 1300C, the reaction solution suffers the viscositythereof to rise after the start of polymerization, with the possible result that the solution will allow no easy agitation any longer and incur a decline in the yield. The itaconic acid, however, excels in thermal stability and enables the temperature to be elevated to the range mentioned above and permits the esterification to be accomplished within a short time in a high yield. If the temperature falls short of 500C, the shortage will suffer the reaction to consume an unduly long time. Conversely if this temperature exceeds 22O0C, the overage will be at a disadvantage in not allowing the reaction to be accelerated any further. As this reaction of esterification advances, it by-produces water. When this reaction is continued while the water is expelled by distillation, it gives rise to the polyalkylene glycol diester of itaconic acid. Method 2: The reaction of transesterificaation of itaconic alkylate and polyalkylene glycol The polyalkylene glycol to be used in this reaction is required to be transformed by the reaction of transesterificationwith an itaconic alkylate into a compound represented by the aforementioned formula (1) . It is varied in a wide range. The polyalkylene glycols cited in the Method 1 mentioned above can be advantageously used. As the itaconic alkylate, the diester bodies of itaconic acidandalcohols havingcarbonnumbers of 1 - 8 canbe favorably- used. As typical examples of the itaconic alkylate, itaconic dimethyl ester, itaconic diethyl ester, itaconic dipropyl ester, itaconicmethylethyl ester, and itaconicmethylpropyl ester may be cited. Though the amount of the polyalkylene glycol to be incorporatedpermol of itanconic dialkylate is theoretically 2 mols, it is preferably in the range of 1.5 - 2.5 mols, more preferably in the range of 1.7 - 2.1 mols, and particularly preferably in the range of 1.5 - 2.0 mols. If this amount falls short of 1.5 mols, the shortage will prevent the transesterification from proceeding sufficiently. Conversely, if this amount exceeds 2.5 mols, the overage will bring only a small change in the yield of the itaconic polyalkylene glycol diester. The reaction can be carried out in the presence of such a solvent as benzene, toluene, xylene, or cyclohexane. The reaction ideally proceeds when the reaction substrate concentration (the total amount of itaconic dialkylate and polyalkylene glycol) in the solvent is in the range of 50 - 98 mass% and more preferably in the range of 70 - 95 mass%. Thereactionmayuseanacidiccatalystorabasiccatalyst. Preferably, however, the basic catalyst is used because the copolymer using the produced diester body excels in dispersibility. As typical examples of the preferred basic catalyst, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, and lithium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide; alkali metal alkoxides such as sodium methoxide, sodium ethoxide, sodium isopropoxide, potassium methoxide, potassium ethoxide, andpotassium isopropoxide; and strongly basic ion-exchange resins having an ammonium salt type amine as an exchange group may be cited. In these basic catalysts, the alkali metal ydroxides and the metal alkoxides prove preferable and sodium hydroxide and sodium methoxide prove particularly preferable. The amount of the basic catalyst to be used is preferably in the range of 0.05 - 5 mass% and particularly preferably in the range of 0.1 - 2.0 mass%, based on the mass of the itaconic alkylate. If this amount falls short of 0.05 mass%, the shortage will prevent the effect of catalysis from being manifested sufficiently. If this amount exceeds 0.5 mass%, the overage will prove only uneconomical. The basic catalyst canbe addedto the reaction system either all at once or continuously or piecemeal. The addition made continuously or piecemeal proves preferable from the viewpoint of preventing the surface of catalyst from being inactivated within the system or the catalytic action from being deactivated. The reaction temperature is preferably in the range of 50° - 2200C, more preferably in the range of 100° - 2000C, and particularly preferably in the range of 100° - 1900C. If this reaction temperature falls short of 500C, the shortage will sufferthereactiontorequireanundulylongtime. Conversely, if the temperature exceeds 2200C, the overage will be at a disadvantage in preventing the ratio of esterification from being increased any further. The reaction of transesterification can be carried out either batchwise or continuously. In the batchwise reaction, for example, when the bulk temperature is gradually elevated till it reaches the allowable limit, the termination of the reaction is confirmed by the cessation of the flowage of an alkyl alcohol. Then, the polyalkylene glycol diester of itaconic acid aimed at by the reaction is obtained by expelling the itaconic alkylate as an unaltered raw material by distillation under a vacuum. Incidentally, also in this method, the diester can be produced in a short time in a high yield because itaconic acid excels (meth) acrylic acid in thermal stability. Method 3: Addition of alkylene oxide to itaconic acid The alkylene oxide to be added to itaconic acid is an alkylene oxide having a carbon number in the range of 2 - 4. As typical example of the alkylene oxide, ethylene oxide, propylene oxide, trimethylene oxide, and isobutylene oxide may be cited. Preferably, ethylene oxide or propylene oxide is used alone or ethylene oxide and propylene oxide are used in combination. The amount of the alkylene oxide to be added to 1 mol of itaconic acid is theoretically m + n mol. It is preferably in the range of 2 - 400 mols, more preferably in the range of 8 - 200 mols, and particularly preferably in the range of 16 - 130 mols. In this case, when propylene oxide is additionally used, it is preferable to use the propylene oxide in an amount in the range of 1 - 30 mol%. The reaction is allowed to use a catalyst. As typical examples of the preferred catalyst, quaternary ammonium compounds, boron fluoride, sodium hydroxide, and potassium hydroxide may be cited. Among other catalysts enumerated above, boron fluoride proves ideal because it is capable of efficiently promoting the non-aqueous reaction. As typical examples of the quaternary ammoniumcompound, 4- (4, β-dimethoxy-l,3,5-triazin-2-yl) -4-methyl morpholinium chloride, 4- (4, 6-diethoxy-l, 3, 5-triazin-2-yl) -4-methyl morpholinium chloride, 4- (4, β-dipropoxy-1, 3, 5~triazin-2-yl) -4-methyl morpholinium chloride, 4- (4, 6-diisopropoxy-l, 3, 5~triazin-2-yl) -4-methyl morpholinium chloride, 4- (4, 6-dibutoxy-l, 3, 5-triazin-2-yl) -4-methyl morpholinium chloride, 4- (4, β-biphenoxy-1, 3, 5-triazin-2-yl) -4-methyl morpholinium chloride, 4- (4, 6-dimethoxy-l, 3, 5-triazin-2-yl) -4-ethyl morpholinium chloride, 4- (4, 6-diethoxy-l, 3, 5-triazin-2-yl) -4-ethyl morpholinium chloride, 4- (4, 6-dipropoxy-l, 3, 5-triazin-2-yl) -4-ethyl morpholinium chloride, 4- (4, 6-diisopropoxy-l, 3, 5-triazin-2-yl) -4-ethyl morpholinium chloride, 4- (4, 6-dipropoxy-l, 3, 5-triazin-2-yl) -4-ethyl morpholinium chloride, 4- (4, 6-diisopropoxy-l, 3, 5-triazin-2-yl) -4-ethyl morpholinium chloride, 4- (4, 6-dibutoxy-l, 3, 5-triazin-2-yl) -4-ethyl morpholinium chloride, 4- ( 4 , β-biphenoxy-1 , 3 , 5-triazin-2-yl ) -4 -ethyl morpholinium chloride, 4- (4, 6-dimethoxy-l, 3, 5-triazin-2-yl) -4-isobutyl morpholinium chloride, 4- (4, β-diethoxy-1, 3, 5-triazin-2-yl) -4-isobutyl morpholinium chloride, 4- (4, 6-dipropoxy-l, 3, 5-triazin-2-yl) -4-isobutyl morpholinium chloride, 4- (4, 6-diisopropoxy-l, 3, 5-triazin-2-yl) -4-isobutyl morpholinium chloride, 4- (4, 6-dibutoxy-l, 3, 5-triazin-2-yl) -4-isobutyl morpholinium chloride, and 4- (4, 6-biphenoxy-l, 3, 5-triazin-2-yl) -4-methyl morpholinium chloride may be cited. By using a quaternary ammonium compound and boron fluoride in combination, it is made possible to increase the degree of polymerization of polyalkylene oxide up to a long chain of 300. The reaction temperature is preferably in the range of 40° - 2200C, more preferably in the range of 100° - 2000C, and particularly preferably in the range of 100° - 1500C. If the reaction temperature falls short of 400C, the shortage will sufferthereactiontoconsumeanundulylongtime. Conversely, if this temperature exceeds 22O0C, the overage will be at a disadvantage in possibly inducing a polymerization reaction. The reaction time of 2 - 20 hours suffices to produce the polyalkylene glycol diester of itaconic acid. This reaction is at an advantage in enabling the target product to be easily isolated because it can be effectively carried out without requiring use of a solvent. Also in this method, the diester canbe produced in a short time in a high yieldbecause itaconic acid excels (meth) acrylic acid in thermal stability. Method 4: Addition of alkylene oxide to itaconic hydroxyalkyl ester The itaconichydroxyalkylestertobeusedforthismethod is an ester body of itaconic acid and a monohydroxy alcohol possessing a linear chain or a branched chain having a carbon number in the range of 2 - 4. Such diester bodies as hydroxy ethanol and hydroxy butanol are preferred examples. When an alkylene oxide and itaconic hydroxyalkyl ester are mixed, since the itaconic hydroxyalkyl ester functions as a polymerization initiator, the oxyalkylene is polymerized with the hydroxyl group of the itaconic hydroxyalkyl ester. As a result, the produced polyalkylene glycol diester body of itaconic acid has a hydroxyl group as the terminal thereof. For the reaction, such catalysts as quaternary ammonium compounds, boron fluoride, and sodium hydroxide which have been enumerated in the aforementioned Method 3 are favorably usable. The reaction temperature is preferably in the range of 40° - 2200C, more preferably in the range of 100° - 2000C, and particularly preferably in the range of 100° - 15O0C. If this temperature falls short of 400C, the shortage will suffer the reaction to consume an unduly long time. Conversely, if this temperature exceeds 22O0C, the overage will be at a disadvantage in inducing a polymerization reaction. The reaction time in the range of 2 - 20 hours suffices to obtain the polyalkylene glycol diester of itaconic acid. Even in this method, the diester can be produced in a short time in a high yield because itaconic acid excels (meth) acrylic acid in thermal stability. The copolymer of this invention merely requires the monomer component containing the aforementioned monomer (A) and monomer (B) and optionally adding the monomer (C) to be copolymerized by the use of a polymerization initiator. The copolymerization may be effected by polymerization in a solvent or by a method of bulk polymerization. The polymerization in a solvent canbe carried out either batchwiseorcontinuously. Astypicalexamplesofthe solvent to be used in the polymerization, water; lower alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol; aromatic oraliphatichydrocarbons suchas benzene, toluene, xylene, cyclohexane, and n-hexane; ester compounds such as ethyl acetate; and ketone compounds such as acetone and methylethyl ketone may be cited. From the viewpoint of the solubility of the raw material monomer and the produced copolymer and the convenience of the copolymer during the course of use, it is preferable to use at least one member selected fromthe group consisting ofwater and lower alcohols having carbon numbers of 1 - 4. Among other lower alcohols having carbon numbers of 1 - 4, methyl alcohol, ethyl alcohol, and isopropyl alcohol prove particularly effective. When the polymerization is carried out in an aqueous medium, a water-soluble polymerization initiator such as a persulfate of ammoniumor an alkalimetal or hydrogenperoxide is used. In this case, an accelerator such as sodiumhydrogen sulfite or Mohr' s salt may be additionally used. Then, in the polymerization using a lower alcohol, an aromatic hydrocarbon, an aliphatic hydrocarbon, an ester compound, or a ketone compound as a solvent, peroxides such as benzoyl peroxide and lauroyl peroxide, hydroperoxides such as cumene hydroperoxide; and aromatic azo compounds such as azobisisobutylonitrile can be used as polymerization initiators. In this case, an accelerator such as an amine compoundmaybeadditionallyused. Whenawater-loweralcohol mixed solvent is used, the aforementioned various polymerization initiators and combinations of such polymerization initiators and accelerators are available for proper selection. The polymerization temperature is properly decided, depending on the solvent and the polymerizationinitiatortobeactuallyused. Itis generally in the range of 0° - 1200C. The bulk polymerization is carried out by using a polymerization initiator selected from among peroxides such as benzoylperoxide andlauroylperoxide; hydroperoxides such as cumene hydroperoxide; and aliphatic azo compounds such as azobisisobutyronitrile at a temperature in the range of 50° - 2000C. Further, for the purpose of adjusting the molecular weight of the produced copolymer, a thiol type chain transfer agentmaybe additionallyused. The weight average molecular weight of the copolymer of this invention is preferably in the range of 4,000 - 80,000, more preferably in the range of 6,000 - 50,000, and particularly preferably in the range of 10,000 - 30,000. If the weight average molecular weight falls short of 4,000, the shortage will possibly result in deteriorating the dispersibility. Conversely, if it exceeds 80, 000, the overage will be at a disadvantage in deteriorating the water-reducing property and the slump loss-preventing property of the cement dispersant when the copolymer is used as the cement dispersant. Incidentally, the weight average molecular weight is the magnitude which is obtained by the method of gel permeation chromatography/polyethylene glycol conversion. Now, this inventionwillbe specifically explainedbelow with reference to the working examples cited herein. These working examples do not restrict this invention in any way. The term "parts" used herein means "parts by mass" unless otherwise specified. Synthesis Example 1 (Synthesis of itaconic acid (methoxypolyethylene glycol) ester) Ina reactionvesselprovidedwithanitrogen introducing tube, a thermometer, and a Dean Stark type water separating device, 52 g (0.4 mol) of itaconic acid, 340 g (0.72 mol) of monomethoxypolyethylene glycol (adduct of 10 mols of ethylene oxide of methanol), 0.078 g of phenothiazine, 7.1 g of toluene sulfonic acid monohydrate, and 30 g of toluene wereplacedandheatedand stirredunder a current ofnitrogen. The reaction solution began a reflux when the temperature thereof reached 137°C. When the temperature was further elevatedwhilethe removalofthe formedwaterfromthereaction vessel was continued, it reached 1800C within 5 hours of startingthereflux. Thereactionwas completedatthispoint. The amount of the water so removed totaled 12.O g (0.67 mol) . The ratio of esterification computed from the amount of the removed water was found to be 93%. The subsequent removal of toluene at 1600C under a vacuum resulted in forming 381 g of a reaction mixture (IT-I) having an acid number of 18.3 mgKOH/g and containing 84.1 mass% of itaconic di (methoxypolyethylene glycol) ester and 13.3 mass% of itaconic mono (methoxypolyethylene glycol) ester. Synthesis Example 2 (Synthesis of itaconic di (methoxypolyethylene glycol) ester) In a reactionvesselprovidedwith anitrogenintroducing tube, a thermometer, and a Dean Stark type water separating device, 42 g (0.32 mol) of itaconic acid, 302 g (0.64 mol) of monomethoxypolyethylene glycol (adduct of 10 mols of ethylene oxide of methanol) , 6.2 g of toluene sulfonic acid monohydrate, and 30 g of toluene were placed and heated and stirred under a current of nitrogen. The reaction solution began a reflux when the temperature thereof reached 147°C. When the temperature was further elevated while the removal of the formed water from the reaction vessel was continued, it reached 1850C within 6 hours of starting the reflux. The reaction was completed at this point. The amount of the water so removed totaled 10.5 g (0.58 mol) . The ratio of esterification computed from the amount of the removed water was found to be 91%. The subsequent removal of toluene at 1600C under a vacuum resulted in forming 334 g of a reaction mixture (IT-2) having an acid number of 13.4 mgKOH/g and containing 84.7 weight% of itaconic di (methoxypolyethylene glycol) ester and 8.2 weight% of itaconic mono- (methoxypolyethylene glycol) ester. Synthesis Example 3 (Synthesis of itaconic di (methoxypolyethylene glycol) ester) Ina reactionvesselprovidedwitha nitrogen introducing tube, a thermometer, and a Dean Stark type water separating device, 21 g (0.16 mol) of itaconic acid, 326 g (0.29 mol) of monomethoxypolyethylene glycol (adduct of 25 mols of ethylene oxide of methanol), 0.035 g of phenothiazine, 5.2 g of toluene sulfonic acid monohydrate, and 60 g of toluene wereplacedandheatedandstirredunder a current of nitrogen. The reaction solution began a reflux when the temperature thereof reached 1380C. When the temperature was further elevatedwhiletheremovaloftheformedwaterfromthereaction vessel was continued, it reached 1500C within 19 hours of startingthereflux. Thereactionwascompletedatthispoint. The amount of the water so removed totalled 3.8 g (0.21 mol) . The ratio of esterification computed from the amount of the removed water was found to be 73%. The subsequent removal of toluene at 1600C under a vacuum resulted in forming 348 g of a reaction mixture (IT-3) having an acid number of 11.9 mgKOH/g and containing 76.9 weight% of itaconic di (methoxypolyethylene glycol) ester and 16.4 weight% of itaconic mono (methoxypolyethylene glycol) ester. Comparative Synthesis Example 1 (Synthesis of maleic di (methoxypolyethylene glycol) ester) In the same apparatus as used in Synthesis Example 1, 46 g (0.4 mol) of maleic acid, 340 g (0.72 mol) of monomethoxypolyethylene glycol (adduct of 10 mols of ethylene oxide ofmethanol) , 0.072 g ofphenothiazine, 6.95 g of toluene sulfonic acid monohydrate, and 30 g of toluene were placed and heated and stirred under a current of nitrogen. The reaction solution began a reflux when the temperature thereof reached 1400C. When the temperature was further elevated while the removal of the formedwater from the reaction vessel was continued, it reached 164°C within 2.2 hours of starting the reflux. The reaction was completed at this point. The amount of the water so removed totaled 12.3 g (0.68 mol) . The ratio of esterification computed from the amount of the removed water was found to be 95%. The subsequent removal of toluene at 600C under a vacuum resulted in forming 386 g of a reaction mixture (MA-I) having an acid number of 25.5 mgKOH/g and containing 68.5 weight% of maleic di (methoxypolyethylene glycol) ester and 20.5 weight% of maleic mono (methoxypolyethylene glycol) ester. Comparative Synthesis Example 2 In the same apparatus as used in Synthesis Example 1, 34.4 g (0.4 mol) of methacrylic acid, 170 g (0.36 mol) of monomethoxypolyethylene glycol (adduct of 10 mols of ethylene oxideofmethanol) , 3.68 goftoluene sulfonicacidmonohydrate, and 16 g of toluene were placed and heated and stirred under a current of nitrogen. When the temperature of the reaction solution reached 125°C, a solid substance which seemed to be a polymer was separated. The reaction was stopped because the separated solid substance did not allow easy stirring any longer. Example 1 (Synthesis of polymer) Inareactionvesselprovidedwithanitrogenintroducing tube, a condenser, and a stirring device, 8.5 g of IT-I obtained in Synthesis Example 1, 1.5 g of acrylic acid, 40 gofwater, 0.23 gof aqueous 30mass% sodiumhydroxide solution, 0.2 g of ammonium persulfate, and 0.1 g of mercapto propionic acid were placed and heated in an oil bath at 8O0C under a current of nitrogen for 2 hours. Subsequently, the resultant solution added 2.45 g of an aqueous 30 mass% sodium hydroxide solution to give rise to an aqueous solution of copolymer (P-I) having a pH value of 6.3. This aqueous solution had a solid content of 19.5 mass%. The weight average molecular weight of P-I was 14,800. Example 2 (Synthesis of polymer) Ina reactionvesselprovidedwith anitrogen introducing tube, a condenser, anda stirringdevice, 8.5 gof IT-2 obtained in Synthesis Example 2, 1.5 g of acrylic acid, 40 g of water, 0.23 g of an aqueous 30 weight% sodium hydroxide solution, 0.2 g of ammonium persulfate, and 0.1 g of mercapto propionic acid were placed and heated in an oil bath at 800C under a current of nitrogen for 2 hours. Subsequently, the resultant solution added2.20 g of anaqueous 30 weight% sodiumhydroxide solution to give rise to an aqueous solution of a polymer (P-2) having a pH value of 6.2. The solid content of this aqueous solution was 19.7 weight% and the weight average molecular weight of P-2 was 22800. Example 3 (Synthesis of polymer) Ina reactionvesselprovidedwithanitrogenintroducing tube, a condenser, and a stirring device, 13 g of water was placed and heated to 600C under a current of nitrogen. To thewater, asolutionAformedbymixing4.38 gofIT-3 obtained in Synthesis Example 3, 3.10 g of an aqueous 20% acrylic acid solution, 0.1 g of mercapto propionic acid, and 5.00 g of an aqueous 0. IN sodium hydroxide solution was added dropwise over a period of one hour and, at the same time, 2.06 g of an aqueous 5% 2,2-azobis [2- (5~methyl-2-imidazolin-2-yl)propane] dihydro-chloride was added dropwise over a period of one hour and 30 minutes. After completion of the dropwise addition, the resultant mixed solution was further heated for one hour and subsequently combined with 0.7 g of an aqueous 30 weight sodium hydroxide solution and 15 g of water to give rise to an aqueous solution of a polymer (P-3) having a pH value of 6.3. The solid content of this aqueous solution was 11.0 weight% and the weight average molecular weight of P-3 was 26000. Comparative Example 1 (Synthesis of polymer) Ina reactionvesselprovidedwithanitrogenintroducing tube, a condenser, anda stirringdevice, 8.5 gofMA-I obtained in Comparative Synthesis Example 1, 1.5 g of acrylic acid, 40 gof water, 0.23 g of an aqueous 30 weight% sodiumhydroxide solution, and 0.2 g of ammonium persulfate and heated in an oil bath at 800C under a current of nitrogen for 2 hours. Subsequently, the resultantmixture added 2.53 g of an aqueous 30 weight% sodiumhydroxide solutionto give rise to an aqueous solution of a polymer (C-I) having a pH value of 6.2. The solid content of this aqueous solution was 22.2 weight% and the weight average molecular weight of C-I was 31000. (Evaluation as cement dispersant) The test of evaluation was performed in accordance with the method for mortar flow test specified in JIS (Japanese Industrial Standard) R5201-1997 by using a kneader of the machine mixing grade specified in the same standard. In the mortar flow test, the magnitude of flow was determined by simply causing a cone to rise and omitting a falling motion. The mortar for the test was composed of 240 g of water, 595 g of ordinary portland cement, and 1350 g of standard sand. Incidentally, the polymer of this invention and the product of Pozorisu Bussan K.K. sold under the trademark designation ofMA404 andusedhereinas a defoaming agent were incorporated in the mortar by having them dissolved in advance in the water used for the composition of the mortar. The amounts of the polymer and the defoaming agent to be added are indicated in Table 1 in weight% based on the weight of the cement. Table 1
Industrial Applicability
The polyalkylene glycol diester of itaconic acid to be
used in this invention excels in thermal stability and,
therefore, can be produced in a high yield. The copolymer
of this diester and (meth) acrylic acid exhibits an excellent
dispersibility and is useful as a dispersant.
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