Patent Publication Number: US-6043329-A

Title: Acrylic copolymers

Description:
1. DESCRIPTION OF THE INVENTION 
     The present invention relates to new acrylic copolymers and polymer compositions and their use as dispersants in the preparation of aqueous suspensions of inorganic materials such as cements, clays, talc, lime, calcium carbonate, silicates, calcium sulfate (anhydrous, Hemihydrate, or Dihydrate), ceramic slurries. The new copolymers are very effective in hydraulic cements as superplasticizers capable to impart an extended excellent workability to such mixtures with low air-entraining effect and to reduce the slump loss over a long period of time. 
     2. THE STATE-OF-THE-ART 
     Dispersants are useful in preventing settling, deposition, precipitation, agglomeration, flocculation, coagulation, adherence or caking of solid particles in a fluid medium. In aqueous medium, effective dispersants cause the solid particles to repell each other, inhibit their agglomeration or settling and influence the rheology. 
     The use of organic polymeric dispersants for the preparation of aqueous suspensions of inorganic materials is well known. Various polymeric compositions have been tested. Details of such products, by types and trademarks, are given, e. g., in &#34;Dispersants&#34;--Kirk-Othmer Encyclopedia of Chemical Technology--Fourth Edition 1993--Volume 8, page 302-303, published by John Wiley &amp; Sons Inc. 
     Dispersants are also used in compositions based on cement such as concrete, mortars and cement pastes. Concretes are made with cement, coarse and fine aggregates and water. Mortars consist of cement, special graded sand and water, while a paste contains only cement and water. Many of the useful properties of cementitious compositions stem from chemical reactions between cement and water, which cause the transformation of the initial aqueous suspension into a rigid solid. Since this transformation is slow, the cementitious composition may be processed, transported, or poured into moulds. Water is one reactant of the hydration reactions of cement and an excess is normally used to obtain a good workability of such mixtures. Because of decreasing strength and increasing permeability, an excess of added water is unfavorable to the properties of the hardened cementitious products. Preparing cement-based mixtures, an effective dispersant reduces the water demand without changing the workability of such mixtures. In cement-concrete technology, dispersants usually are classified as &#34;Chemical admixtures&#34;. Water reducers are chemical admixtures, capable of reducing the water requirement of mixtures by about 10 to 15% b.w. Superplasticizers (or High-Range-Water-Reducers) are chemical admixtures capable of reducing the water requirement by about 25-30% b.w. Known water reducers are based e. g. on salts of Lignosulfonic Acids, Hydroxicarboxylic Acids or processed Carbohydrates. Traditional superplasticizers are based on Sulfonated Naphthalene Formaldehyde polymers or Melamine Formaldehyde polymers. New types of superplasticizers are e.g. polycarboxylic polymers. A review of chemical admixtures is reported in &#34;Effect of admixtures&#34; Collepardi, M. and Ramachandran, V.S.--9th Int. Congr. Chem. Cem., 1992, page 529-568, by National Council of Chemical Building Material (New Delhi, India). Traditional superplasticizers impart a very good workability to fresh mixtures, but cannot maintain it for long periods. The workability decreases (hereinafter referred as &#34;slump loss&#34;) dramatically already after 20-30 minutes. Initial workability can be restored by adding fresh water to those mixtures, but the characteristics with regard to mechanical strength and durability of this type of retempered cementitious compositions are poor. New superplasticizers reduce the &#34;slump loss&#34; effects by applying compositions containing polyoxyalkylene groups in the polymer chains. Examples of these compositions are claimed in European Patent Application 601536/A1 or in European Patent Application 610699/A1. Cement compositions with good workability have been also made adding a polymer of a Hydroxialkyl(meth)acrylate as superplasticizer, as claimed e. g. in U.S. Pat. No. 4,792,360 or in U.S. Pat. No. 4,473,406. The former patents suggest the use of an antifoaming agent during the preparation of a cement mixture, to eleminate air-entrainig effects of a superplasicizer. Entrained air is a drawback since it occurs in form of macrovoids of uncontrollabe size in hardened concrete or mortar reducing their mechanical properties. 
     The object of the present invention was therefore, to find additives for dispersions and for cement compositions without the above-mentioned disadvantages and which, especially in cementitious mixtures, show favorable workability development with time and low air-entraining effects. The acrylic copolymers of the present invention solve these problems by acting as superplasticizers in cementitious compositions imparting a good workability to such mixtures over a long period of time combined with low or without air entrainment. 
     3. SUMMARY OF THE INVENTION 
     The present invention relates to acrylic copolymers, which can be obtained by reacting one or more monomers selected from the group consisting of compounds of formulas I and II: 
     
         CH.sub.2 ═C(R.sub.1)--CO--O R.sub.2                    I) 
    
     
         CH.sub.2 ═C(R.sub.1)--CO--O--R.sub.3                   II) 
    
     wherein each R 1  independently represents H or CH 3 , 
     R 2  represents H or a cation of Na, Li, 1/2 Ca or C 1  - to C 3  -alkylamine, 
     R 3  represents a hydroxyalkyl group --(CH 2 ) x  OH with x=2 to 10, 
     with one or more monomers of formula III 
     
         R.sub.4 --O--R.sub.5 --CO--NH--R.sub.6                     III) 
    
     wherein R 4  represents H or a group of the following formulas: ##STR2## R 5  represents an oxyalkenyl group of the following formulas: 
     
         --(CHR.sub.1 --CH.sub.2 --O).sub.m -- or --(CHR.sub.1 --CH.sub.2 --O).sub.m1 --(CH.sub.2 --CH.sub.2 --O).sub.n -- 
    
     with m=15 to 30; m1=5 to 15 and n=2to 6 
     R 6  represents a C 1  - to C 8  -alkyl group, a C 5  - to C 7  -cycloalkyl group, or a phenyl group, 
     and optionally one or more monomers selected from the group consisting of compounds of formulas IV or V 
     
         CH.sub.2 ═CR.sub.1 --R.sub.7                           IV) 
    
     wherein R 7  represents a sulfonic group --SO 3  H, 
     or a phenyl sulfonic group --C 6  H 4  --SO 3  H, 
     or a 2-amido-2-methyl-1-propane sulfonic group of the following formula: 
     
         --CO--NH--C(CH.sub.3).sub.2 --CH.sub.2 --SO.sub.3 R.sub.2 
    
     or a sulfoalkyl carboxylic ester group of the formula 
     
         --(CO)O--R--SO.sub.3 R.sub.2 
    
     with R respresenting a C 1  - to C 5  -alkyl group 
     
         CH.sub.2 ═C(R.sub.1)--CO--O--R.sub.8 --R.sub.9         V) 
    
     wherein R 8  represents a polyoxyethylene chain 
     
         --(--CH.sub.2 --CH.sub.2 --O--).sub.n1 -- 
    
     with n 1  being an integer from 2 to 50, 
     R 9  represents H or CH 3 . 
     These polymers are useful, e. g., as dispersants for aqueous suspensions of cements, clays, calcium carbonate, calcium sulfates (anhydrous, hemihydrate or dihydrate), talc, silicates, stone powders and porcelain slurries. More particularly they can be used in cementitious mixtures, such as concretes, mortars and cement pastes. 
     The invention further relates to a process of manufacturing of acrylic copolymers by the reaction of the monomers of formulas I and II with monomers of formula III, and optionally with monomers of formulas IV and V. 
     4. DETAILED DESCRIPTION OF THE INVENTION 
     Examples of the units represented by formula I include acrylic acid, methacrylic acid or crotonic acid and their alkali metal salts, alkaline earth salts, alkylamine salts and substituted alkylamine salts. The alkyl group of the alkylamine salt has preferably 1 to 3 carbon atoms. Examples of substituted alkylamines include monoethanolamine, diethanolamine and triethanolamine. Among them, alkali metal salts of methacrylic acid are preferred. 
     The monomers represented by formula II are acrylic or methacrylic monomers with hydroxialkyl substituents. Examples of such monomers are 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate. The most preferred is the 2-hydroxypropyl acrylate. 
     The units represented by formula III are preferably poly(oxyethylenepropylene)glycol mono urethanes or their (meth)acrylates, or alternatively mono maleate derivatives. The urethane group connects the strong hydrophobic and the more hydrophilic segments in the molecular structure of these units. 
     Examples of hydrophobic segments are alkyl or phenyl or cyclohexyl groups, while the hydrophilic segment may independently be oxyalkylene chains with oxypropylene or oxypropylene-oxyethylene repeating units. The number of the oxyalkylene groups constituting the chain varies from 15 to 30. The remaining hydroxyl group of the more hydrophilic segment can be reacted with maleic anhydride or with a (meth)acrylic functional group. The preferred unit of formula III is a poly(oxypropylene)glycol phenyl urethane or its monomaleate derivative. The preferred copolymers are reaction products of monoisocyanate-poly(oxypropylene)glycol-maleic anhydride with a molar ratio of about 1:1:1, or of monoisocyanate-poly(oxypropylene)glycol with a molar ratio of about 1:1. The preferred molecular weight of poly(oxypropylene)glycol is from about 200 to 5000, most preferred about 1000. 
     The units represented by formula IV are monomers with sulfonic acid end groups and their alkali metal salts, alkaline earth salts, alkylamine salts or substituted alkylamine salts, the same as described above for the units represented by formula 1. Examples of these monomers are vinyl sulfonic acid, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), 4-styrenesulfonic acid. Preferred is vinylsulfonic acid and AMPS. 
     The units represented by formula V are preferably poly(oxyethylene or oxypropylene)glycol mono(meth)acrylate or poly(oxyethylene or oxypropylene)mono methyl-ether-(meth)acrylate with molecular weights from about 200 to 2000. Most preferred is methoxy(polyoxyethylene)glycol methacrylate with an average molecular weigh of about 430 to 1000. 
     In the backbones of the copolymers, the main building blocks are the units of formulas I and II. The unit represented by formula III is very effective as air-detraining agent, when the copolymers of the invention are used in cementitious mixtures. 
     The molar ratios of the monomer units range from 30 to 79.95 mole %, preferred 40 to 65.95 mole % for units of formula I, from 20 to 69.95, preferred 30 to 55.95 mole % for units of formula II, from 0.05 to 2 mole %, preferred 0.05 to 1 mol % for units of formula III, from 0 to 5 mole %, preferred 3 to 5 mol % for units of formula IV, from 0 to 3 mole %, preferred 1 to 3 mole % for units of formula V. 
     The polymers according to the present invention can be prepared by known processes. An example is the radical polymerization, using water as a solvent. As solvents also methanol, ethanol, isopropanol, ethyl acetate, acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, toluene, xylene, aliphatic hydrocarbons, such as cyclohexane, n-hexane can be used. A water soluble polymerisation catalyst, such as a potassium or sodium or ammonium salt of persulfuric acid or hydrogen peroxide is preferred, when water is the solvent. For solvents other than water, the polymerization initiator can be selected e. g. among benzoyl peroxide, lauroyl peroxide, azo-bis-isobutyronitrile, azo-bis-2-methyl valeronitrile, dicyclohexylperoxidicarbonate, tert-butylperoxy-2-ethylhexanoate and butylperbenzoate. A polymerization accelerator may be used together with the initiator. Suitable e. g. is sodium hydrogensulfite, mercaptoethanol or sodium formaldehyde sulfoxylate. The polymerization reaction can be generally conducted at a temperature in the range of about 50 to 140° C., depending on the the boiling point of the selected solvents. When water is used, the more preferred range is about 70 to 100° C. The reaction time can vary over a wide range, depending on such factors as polymerization temperature, solvent and initiator concentrations. When using water as solvent and potassium persulfate as initiator at 95° C. for example, a reaction time of two to three hours is sufficient to obtain the claimed polymers. It is usually desirable to purge the reactor with nitrogen for a sufficient period to reduce the inhibition effect of the oxygen on the polymerization reaction. It is also preferred to conduct the polymerization under a continuous nitrogen blanket. In a preferred preparation method, the mixture of reactants is prepared by dissolving the reactive monomers in water, followed by pH adjustment with sodium hydroxide to approximately pH 5.5 to 6.5. Then the thus obtained aqueous mixture (preferably at room temperature) and the solution of polymerization initiator are gradually added, at a constant rate over 90 to 120 minutes, to the reactor containing water at 95° C. After the end of the initiator addition, the mixture is allowed to stand at, e. g. 95° C. for 15 minutes. The obtained acrylic polymer solutions are ready for use. 
     The claimed polymers can be used as additives or admixtures for improving the properties of construction materials. Thus, the present invention further relates to a process for improving the properties of construction materials, wherein polymers according to the invention are added to the construction materials. Preferred construction materials are, e. g. cementitous compositions. The term &#34;hydraulic binders&#34; is used herein in its ordinary sense and refers to any inorganic mixture, which sets and hardens when made into a paste with water. Examples of hydraulic binders include cementitous compounds like portland cements, alumina cements, fly ash, slags, any pozzolanic binder such as, silica fume, and any type of blended cement, and water-curable materials other then cement, such as gypsum, and/or mixtures of them. The acrylic copolymers of the present invention may be used together with known additives and/or known auxiliary materials for mortars, concretes or cement pastes. Examples of such additives include water reducing agents, fluidizing agents, high range water reducing agents, retarders, accelerators, air-entrainig agents, foaming agents, blowing agents, Theological additives, waterproofing agents. The formulation of cement mortars, concretes or pastes is not limited. The amount of the claimed acrylic copolymers applied to provide the desired effects of the present invention is typically 0.01-5 parts by weight, preferably 0.1-1.0 1,0 part by weight of acrylic polymers, calculated as dry matter in 100 parts of the dry construction material composition. The claimed acrylic copolymers can be dissolved in the blending water for the preparation of the cementitious composition or added to the already kneaded cement admixture. The invention further relates to construction materials, which contain one or more of the copolymers of the invention. 
     The acrylic copolymers of the present invention are also suitable as dispersing agents for, preferably aqueous slurries of inorganic mixtures other than cements. Thus, the invention further relates to the use of the copolymers according to the invention as additives or admixtures to improve the properties of dispersions, and to a process for improving the rheological properties of dispersions, wherein copolymers according to the invention are added to the dispersions. Preferred are dispersions of clays, talcum, lime, ceramic materials, calcium carbonate, calcium sulfate, silicates or mixtures of them. The invention further relates to dispersions, which contain one or more copolymers according to the invention as additives. The dispersions contain preferably 0.01 to 5% b.w., most preferred 0.05 to 1% b.w., of the copolymers according to the invention, calculated as dry matter referred to the dry inorganic components in the dispersion. The copolymers according to the invention mainly reduce the viscosity of, preferably aqueous, slurries based on e. g. clays, lime and talcum. It is necessary that the viscosity of the slurry is as low as possible during the preparation in order to afford ease of handling and application operations. The water demand of the aqueous slurries is reduced by the acrylic polymers, which are added in an amount ranging from e. g. 0.01 to 1% b.w. (as dry matter) referred to 100 parts of inorganic component. The acrylic polymer effect is thought to be based on the deflocculation of the small inorganic particles, preventing also their agglomeration. 
    
    
     5. EXAMPLES 
     The acrylic polymers of the present invention can be conveniently synthetized by many known polymerization methods. The present invention is explained by the following examples, which are given for illustrative purpose only and are not meant to limit the invention. 
     The following monomers were used in the examples: 
     AMA: Methacrylic acid (BASF), example for formula I 
     HPA: Hydroxypropylacrylate (BASF), example for formula II 
     VS: Vinyl sulfonic acid (Aldrich), example for formula IV 
     PPG Poly(oxypropylene)glycol (MW 1000) (SAPICI), example for formula V 
     PPO 1000: adduct Phenyl isocyanate--PPG (molar ratio 1:1), example for formula III 
     PPO 1000 MA: adduct PPO 1000-Maleic anhydride (molar ratio 1: 1), example for formula III 
     MPEG: Methoxy(polyoxyethylene)monomethacrylate (8 oxyethylene units). (Intern. Speciality Chemicals), example for formula V 
     Example 1 
     In a glass bottom-rounded reactor, equipped with mechanical stirrer, thermometer and reflux condenser, 500 g (0.5 mole) of poly(oxypropylene)glycol (average number of PO=17) are charged. Under stirring, the system is purged with nitrogen and heated up to 40° C. Then 59,5 g (0.5 mole) of phenylisocyanate are added dropwise during 15 minutes. After completion of the dropwise addition, the reaction system is raised to 85° C. and maintained at this temperature for 6 hours. About 550 g of an amber-coloured liquid are obtained, having a viscosity of about 940 mPa.s at 25° C. and being free of NCO-groups (Adduct A1). 
     Example 2 
     In a glass bottom-rounded reactor equipped with mechanical stirrer, thermometer and reflux condenser 500 g (0.5 mole) of poly(oxypropylene)glycol (average number of PO:17) are charged. Under stirring, the system is purged with nitrogen and heated up to 40° C. Then 59,5 g (0.5 mole) of phenylisocyanate are added dropwise during 15 minutes. After completion of the dropwise addition, the reaction system is raised to 85° C. and mantained at temperature for 6 hours. Then the temperature is decreased to 55° C. and 49 g (0.5 mole) of maleic anhydride are added. The reaction temperature is raised to 80° C. and is maintained at this temperature for 3 hours. About 590 g of a yellow liquid are obtained, with an acid number of 57 mg KOH/g of adduct, free of NCO-groups and with a viscosity of about 950 mPa.s at 25° C. (Adduct A2). 
     Example 3 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 90 g (1.046 mole) of methacrylic acid, 110 g (0.846 mole) of hydroxypropyl acrylate, 4 g (0.0035 mole) of adduct A1, 31.4 g (0.785 mole) of sodium hydroxide in 200 g of deionized water. 
     The initiator solution is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added dropwise, simultaneously and separately during 90 minutes into the reactor. Then, another solution of 1.17 g (0.0043 mole) of potassium persulfate in 37.8 g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 770 g of a polymer solution with a pH of 6, a total solids content of 29.1% b.w. and a viscosity of about 195 mPa.s at 25° C. are obtained. (Acrylic Polymer B1). 
     Example 4 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 90 g (1.046 mole) of methacrylic acid, 110 g (0.846 mole) of hydroxypropyl acrylate, 6 g (0.0054 mole) of adduct A1, 31.4 g (0.785 mole) of sodium hydroxide in 200 g of deionized water. 
     The initiator solution is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added dropwise, simultaneously and separately during 90 minutes into the reactor. Then, another initiator solution of 1.17 g (0.0043 mole) of potassium persulfate in 37.8 g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 775 g of a polymer with a pH of 5.9 , a total solids content of 29.3% b.w. and a viscosity of about 215 mPa.s at 25° C. are obtained (Acrylic Polymer B2). 
     Example 5 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 90 g (1.046 mole) of methacrylic acid, 110 g (0.846 mole) of hydroxypropyl acrylate, 10 g (0.009 mole) of adduct A1, 31.4 g (0.785 mole) of sodium hydroxide in 200 g of deionized water. 
     The initiator solution is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added dropwise, simultaneously and separately during 90 minutes into the reactor. Then, another solution of 1.17 g (0.0043 mole) of potassium persulfate in 37.8 g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 780 g of a polymer solution with a pH of 6, a total solids content of 28.7% b.w. and a viscosity of about 210 mPa.s at 25° C. are obtained (Acrylic Polymer B3). 
     Example 6 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 90 g (1.046 mole) of methacrylic acid, 110 g (0.846 mole) of hydroxypropyl acrylate, 2 g (0.0016 mole) of adduct A2, 31.4 g (0.785 mole) of sodium hydroxide in 200 g of deionized water. 
     The initiator solution is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added dropwise, simultaneously and separately during 90 minutes into the reactor. Then, another solution of 1.17 g (0.0043 mole) of potassium persulfate in 37.8 g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 770 g of a polymer solution with a pH of 6, a total solids content of 28.5% b.w. and a viscosity of about 210 mPa.s at 25° C. are obtained (Acrylic Polymer B4). 
     Example 7 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 90 g (1.046 mole) of methacrylic acid, 110 g (0.846 mole) of hydroxypropyl acrylate, 4 g (0.0033 mole) of adduct A2, 31.4 g (0.785 mole) of sodium hydroxide in 200 g of deionized water. 
     The initiator is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added dropwise, simultaneously and separately during 90 minutes into the reactor. Then another solution of 1.17 g (0.0043 mole) of potassium persulfate in 37.8 g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 770 g of a polymer solution with a pH of 6, a total solids content of 28.6% b.w. and a viscosity of about 220 mPa.s at 25° C. are obtained (Acrylic Polymer B5). 
     Example 8 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 90 g (1.046 mole) of methacrylic acid, 110 g (0.846 mole) of hydroxypropyl acrylate, 6 g (0.005 mole) of adduct A2, 31.4 g (0.785 mole) of sodium hydroxide in 200 g of deionized water. 
     The initiator is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added dropwise, simultaneously and separately during 90 minutes into the reactor. Then another solution of 1.17 g (0.0043 mole) of potassium persulfate in 37.8 g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 770 g of a polymer solution with a pH of 5.9, a total solids content of 29.2% b.w. and a viscosity of about 210 mPa.s at 25° C. are obtained (Acrylic Polymer B6). 
     Example 9 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 90 g (1.046 mole) of methacrylic acid, 110 g (0.846 mole) of hydroxypropyl acrylate, 10 g (0.008 mole) of adduct A2, 31.4 g (0.785 mole) of sodium hydroxide in 200 g of deionized water. 
     The initiator is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added dropwise, simultaneously and separately during 90 minutes into the reactor. Then another solution of 1.17 g 0.0043 mole) of potassium persulfate in 37.8 g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 780 g of a polymer solution with a pH of 6, a total solids content of 28.7% b.w. and a viscosity of about 210 mPa.s at 25° C. are obtained (Acrylic Polymer B7). 
     Example 10 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 118.8 g (1.381 mole) of methacrylic acid, 78.8 g (0.606 mole) of hydroxypropyl acrylate, 2.4 g (0.002 mole) of adduct A1, 41.4 g (1.035 mole) of sodium hydroxide in 200 g of deionized water. 
     The initiator is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added dropwise, simultaneously and separately during 90 minutes into the reactor. Then another solution of 1.17 g (0.0043 mole) of potassium persulfate in 37.8 g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 780 g of a polymer solution with a pH of 6.1, a total solids content of 29.3% b.w. and a viscosity of about 225 mPa.s at 25° C. are obtained (Acrylic Polymer B8). 
     Example 11 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 75.8 g (0.881mole) of methacrylic acid, 113.4 g (0.872 mole) of hydroxypropyl acrylate, 5.4 g (0.0044 mole) of adduct A2, 26.4 g (0.66 mole) of sodium hydroxide in 200 g of deionized water. 
     The initiator is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added, simultaneously and separately during 90 minutes dropwise into the reactor. Then another solution of 1.17 g (0.0043 mole) of potassium persulfate in 37.8 g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 765 g of a polymer solution with a pH of 6.1, a total solids content of 28.2% b.w. and a viscosity of about 210 mPa.s at 25° C. are obtained (Acrylic Polymer B9). 
     Example 12 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 80 g (0.93 mole) of methacrylic acid, 110 g (0.846 mole) of hydroxypropyl acrylate, 8.3 g (0.077 mole) of vinyl sulfonic acid, 4 g (0.0033 mole) of adduct A2, 26.4 g (0.66 mole) of sodium hydroxide in 200 g of deionized water. 
     The initiator is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added dropwise, simultaneously and separately during 90 minutes into the reactor. Then another solution of 1.17 g (0.0043 mole) of potassium persulfate in 37.8 g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 770 g a polymer solution with a pH of 1, a total solids content of 28.4% b.w. and a viscosity of about 170 mPa.s at 25° C. are obtained (Acrylic Polymer B10). 
     Example 13 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 90 g (1.046 mole) of methacrylic acid, 100 g (0.769 mole) of hydroxypropyl acrylate, 10 g (0.023 mole) of methoxy(polyoxyethylen) monomethacrylate (with about 8 oxyethylene units), 6 g (0.0054 mole) of adduct A1, 31.4 g (0.785 mole) of sodium hydroxide in 200 g of deionized water. 
     The initiator is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added dropwise, simultaneously and separately during 90 minutes into the reactor. Then another solution of 1.17 g (0.0043 mole) of potassium persulfate in 37.8g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 770 g of a polymer solution with a pH of 5.9, a total solids content of 29% b.w. and a viscosity of about 230 mPa.s at 25° C. are obtained (Acrylic Polymer B11). 
     Example 14 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 90 g (1.046 mole) of methacrylic acid, 90 g (0.692 mole) of hydroxypropyl acrylate, 20 g (0.046 mole) of methoxy(polyoxyethylene)monomethacrylate (with about 8 oxyethylene units), 6.6 g (0.0054 mole) of adduct A2, 31.4 g (0.785 mole) of sodium hydroxide in 200 g of deionized water. 
     The initiator is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added dropwise, simultaneously and separately during 90 minutes into the reactor. Then another solution of 1.17 g (0.0043 mole) of potassium persulfate in 37.8g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 770 g of a polymer solution with a pH of 6.1, a total solids content of 28 per cent and a viscosity of about 200 mPa.s at 25° C. are obtained (Acrylic Polymer B12). 
     Comparative Example 
     200 g of deionized water are charged into a glass bottom-rounded reactor fitted with a stirrer. Free oxygen is purged with nitrogen while stirring. The system is heated up to 96° C. A monomer solution is prepared by dissolving 90 g (1.04 mole) of methacrylic acid, 110 g (0.846 mole) of hydroxypropyl acrylate, 31.3 g (0.784 mole) of sodium hydroxide in 200 g of deionized water. The initiator solution is prepared by dissolving 3.5 g (0.013 mole) of potassium persulfate in 113.5 g of deionized water. The monomer and initiator solutions are added dropwise, simultaneously and separately during 90 minutes into the reactor. Then another solution of 1.17 g (0.0043 mole) of potassium persulfate in 37.8 g of deionized water is added dropwise to the reaction system during 30 minutes. After completion of the addition, the reaction system is maintained at 96° C. for 15 minutes. About 770 g of a polymer solution are obtained, with a pH of 5.9, a total solids content of 27.3 per cent and a viscosity of about 160 mPa.s at 25° C. (Acrylic Polymer B13). The obtained polymer is not according to the invention, a monomer according to formula III is missing. 
     In table 1 the amount of applied monomers in mole %, in table 2 the solids content in % b.w., the pH and the viscosities (measured according to Brookfield at 25° C.) of the polymer solutions are summarized. 
     Application Examples Ex 1 to Ex 9 
     The acrylic polymers B2, B4, B5, B7, B8, B12 obtained in examples 4, 6, 7, 9, 10, 14 were applied as superplasticizers for cement based mortars. Mortar samples were prepared with Portland Cement (Normo 4--Rekingen, Holderbank AG) and sand (CEN STANDARD SAND EN 196-1-Normensand GmbH) in a Hobart type mixer, according to European Standard EN 196-1. The polymer/cement ratio was 0.002, the water/cement ratio was 0.50 and the sand/cement ratio was 3 (Application examples Ex 1 to Ex 7). The blanks were prepared without acrylic polymers and with a water/cement ratio 0.50 and 0.60 (Application examples Ex 8 and Ex 9). Immediatly after mixing, the fresh mortar was tested for bulk density and consistency (spread on flow table), according to European Standard EN 196-1. In order to evaluate the workability loss of the mortar, the consistency (flow table mesurement) was determined 30, 60 and 90 minutes after the initial mixing. The results are given in Table 3. As displayed in Table 3, the acrylic polymers of the present invention impart workability to a mortar composition over a long time, even when used in a reduced amount without affecting the compressive strength (measured according to EN-196-1). Also the entrained air is very low, whereby the bulk density of the mortar is inversely proportional to the amount of entrained air. The density is a factor affecting the workability of the mortar. Mixtures containing more air (low bulk density) have better workability. Surprisingly, the acrylic polymers of the invention allow the preparation of cementitious mixtures with a low air content and with good workability over a long time, in comparison to acrylic polymer B13 (comparative example without the claimed monomer composition in Application example Ex 7), which shows a very low bulk density (air entraining effect). 
     Application Examples Ex 10 to Ex 25 
     The acrylic polymers B1, B2, B3, B5, B6, B8, B9, B10, B11 and B12 obtained in examples 3, 4, 5, 7, 8, 10, 11, 12, 13, 14 were used as dispersants for aqueous suspensions of clays or talcum or calcium carbonate. According to Tappi Official Test Method T 648 om-88 (Viscosity of coating clay slurry), aqueous dispersions of clay (Superclay M from English China Clays-Application examples Ex 10 to Ex 14),or of talcum (Finntalc from Finnminerals OY--Application examples Ex 16 to Ex 19), or calcium carbonate (from OMYA Italia-Application examples Ex 21 to Ex 24) were prepared with introduction of the claimed acrylic polymers as dispersing agent. The dispersing properties of the tested acrylic polymers were evaluated using viscosimetric determinations of the so obtained slurry. The testing equipment was a low-shear viscosimeter (Brookfield Engineering Laboratories Inc.) operated at 20 and 100 rpm spindle speed. The results are given in Table 4, Table 5 and Table 6. When using the acrylic polymers according to the invention, the low-shear viscosity of the slurry is reduced (compared with slurries without acrylic polymers--Application examples Ex 15 for Superclay M, Ex 20 for talcum and Ex 25 for calcium carbonate). 
     
                                           TABLE 1                                 
__________________________________________________________________________
Composition of the Copolymers                                             
            MONOMERS mole %                                               
Examples                                                                  
      Copolymer                                                           
            AMA HPA                                                       
                   VS  MPEG                                               
                           PPO 1000                                       
                                PPO 1000MA                                
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Comparative                                                               
      B13   55.30                                                         
                44.70                                                     
                   --  --  --   --                                        
  3 B1 55.20 44.61 -- -- 0.19 --                                          
  4 B2 55.10 44.62 -- -- 0.28 --                                          
  5 B3 55.00 44.53 -- -- 0.47 --                                          
  6 B4 55.20 44.72 -- -- -- 0.08                                          
  7 B5 55.20 44.63 -- -- -- 0.17                                          
  8 B6 55.10 44.65 -- -- -- 0.25                                          
  9 B7 55.00 44.57 -- -- -- 0.43                                          
  10 B8 69.00 30.50 -- -- 0.10 --                                         
  11 B9 50.00 49.50 -- -- -- 0.50                                         
  12 B10 50.10 45.60 4.10 -- -- 0.20                                      
  13 B11 56.70 41.70 -- 1.30 0.30 --                                      
  14 B12 58.40 38.70 -- 2.60 -- 0.30                                      
AMA      Methacrylic acid                                                 
  HPA Hydroxypropylacrylate                                               
  VS Vinyl sulfonic acid                                                  
  PPG Poly(oxypropylene)glycol (MW 1000)                                  
  PPO 1000 adduct Phenyl isocyanate-PPG (molar ratio 1/1)                 
  PPO 1000MA adduct PPO 1000-Maleic anhydride (molar ratio 1/1)           
  MPEG Methoxy (polyoxyethylene)monomethacrylate                          
   (8 oxyethylene units)                                                  
__________________________________________________________________________
 
    
     
                       TABLE 2                                                     
______________________________________                                    
Properties of Copolymer - Solutions                                       
                      solids    Viscosity mPa · s                
  Example Copolymer % pH (100 rpm Brookfield 25° C.)               
______________________________________                                    
Comparative                                                               
         B13      27.3    5.9 160                                         
  3 B1 29.1 6.0 195                                                       
  4 B2 29.3 5.9 215                                                       
  5 B3 28.7 6.0 210                                                       
  6 B4 28.5 6.0 210                                                       
  7 B5 28.6 6.0 220                                                       
  8 B6 29.2 5.9 210                                                       
  9 B7 28.7 6.0 210                                                       
  10  B8 29.3 6.1 225                                                     
  11  B9 28.2 6.1 210                                                     
  12   B10 28.2 6.1 170                                                   
  13   B11 29.9 5.9 230                                                   
  14   B12 28.0 6.1 200                                                   
______________________________________                                    
 Viscosity = Brookfield 25° C.                                     
 
    
     
                                           TABLE 3                                 
__________________________________________________________________________
Copolymers as superplasticizers                                           
              bulk                                                        
                  SPREAD         C S                                      
Application   density                                                     
                  zero                                                    
                     30 min                                               
                         60 min                                           
                             90 min                                       
                                 24 h                                     
                                     28 d                                 
  Example Additive W/C kg/m.sup.3 mm mm mm mm N/mm.sup.2 N/mm.sup.2       
__________________________________________________________________________
Ex 1  B2   0.50                                                           
              2335                                                        
                  225                                                     
                     219 203 190 11.1                                     
                                     48.6                                 
  Ex 2 B4 0.50 2225 220 205 192 183 10.3 44.7                             
  Ex 3 B5 0.50 2330 227 202 188 178 12.3 49.3                             
  Ex 4 B7 0.50 2335 223 216 208 200 9.3 49.2                              
  Ex 5 B8 0.50 2310 221 206 193 187 11.7 47.2                             
  Ex 6 B12 0.50 2292 230 203 185 172 9.7 48.0                             
  Ex 7 B13 0.50 1570 204 204 205 204 2.3 10.9                             
  Ex 8  0.50 2280 177 168 160 150 14.4 48.9                               
  Ex 9  0.60 2270 229 216 211 205 8.8 38.2                                
Cement                                                                    
      Normo 4 (Holderbank)                                                
  Sand CEN                                                                
  W/C Water/Cement ratio                                                  
  C S Compressive strength                                                
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                       TABLE 4                                                     
______________________________________                                    
Copolymers as Dispersants for Superclay M                                 
  Application                   Viscosity mPa · s                
Example Additive  P/S     Solids %                                        
                                  20 rpm 100 rpm                          
______________________________________                                    
Ex 10   B8        0.002   65.9     7400  5500                             
  Ex 11 B2 0.003 66.2 12000 6200                                          
  Ex 12 B5 0.003 66.4 12750 5200                                          
  Ex 13 B9 0.003 66.7 12750 6200                                          
  Ex 14  B10 0.005 66.1 17300 6000                                        
  Ex 15 -- -- 60.0 30000 9200                                             
______________________________________                                    
 Superclay M Clay from English China Clays                                
 P/S Acrylic polymer (as dry matter)/Superclay M weight ratio             
 Viscosity Brookfield 20° C.                                       
 
    
     
                       TABLE 5                                                     
______________________________________                                    
Copolymers as dispersants for talcum                                      
  Application                   Viscosity mPa · s                
Example Additive  P/T     Solids %                                        
                                  20 rpm 100 rpm                          
______________________________________                                    
Ex 16   B8        0.005   66.3    2450   3500                             
  Ex 17  B12 0.005 65.6 9500 6200                                         
  Ex 18 B6 0.005 65.3 9500 5200                                           
  Ex 19 B3 0.005 67.0 13000  6000                                         
  Ex 20 -- -- 56.2 12500  5100                                            
______________________________________                                    
 Talcum Finntalc from FINNMINERALS OY                                     
 P/T Acrylic polymer (as dry matter)/Talkum weight ratio                  
 Viscosity Brookfield 20° C.                                       
 
    
     
                       TABLE 6                                                     
______________________________________                                    
Copolymers as dispersants for calcium carbonate                           
  Application                   Viscosity mPa · s                
Example Additive  P/CC    Solids %                                        
                                  20 rpm 100 rpm                          
______________________________________                                    
Ex 21   B1        0.005   70       103   210                              
  Ex 22 B6  0.005 70   95 170                                             
  Ex 23 B11 0.003 70  420 336                                             
  Ex 24 B11 0.005 70  105 170                                             
  Ex 25 -- -- 65 23500 9500                                               
______________________________________                                    
 Calcium carbonate OMYA 1V (OMYA Italia)                                  
 P/CC Acrylic copolymer (as dry matter)/Calcium carbonate, weight ratio   
 Viscosity Brookfield 20° C.