JP6998221B2 - Cement Additives and Cement Compositions - Google Patents

Description

The present invention relates to cement additives and cement compositions.

For cement compositions such as cement paste, mortar, and concrete, the purpose is to improve properties such as fluidity immediately after kneading of the cement composition, fluid retention over time after kneading, and strength development after curing of the cement composition. Various additives are contained as. In recent years, the development of concrete and the like having higher strength and higher durability has been promoted, and reduction of the unit water amount and reduction of the water-cement ratio have become issues. Further, as the water content decreases, the viscosity such as the plastic viscosity and the yield value of the cement composition increases, which causes a problem that the construction workability decreases. Therefore, as an additive for reducing the viscosity of the cement composition, an additive for cement containing a polycarboxylic acid-based copolymer has been conventionally proposed (Patent Document 1).

Japanese Unexamined Patent Publication No. 2017-88470

In recent years, particularly cement compositions have been required to maintain the desired fluidity and viscosity even after a lapse of time after kneading, in addition to reducing the viscosity immediately after kneading. It was necessary to increase the amount of addition in order to obtain a sufficient effect, which caused problems such as a significant increase in cost.

The present invention has been made by paying attention to the above circumstances, and an object of the present invention is not only to reduce the viscosity of the cement composition immediately after kneading, but also to have excellent fluidity and viscosity over time after kneading. To provide additives for use.

（式（Ｉ）中、
Ｒ²は、水素原子又は炭素数１～１８のアルキル基を表し、
Ｒ³、Ｒ⁴、及びＲ⁵は、同一又は異なって、水素原子、又は、メチル基を表し、
Ｒ⁶は炭素数０～５のアルキレン基を表し、
Ｒ¹Ｏは、同一又は異なって、炭素数２～１８のオキシアルキレン基を表し、
ｍは、Ｒ¹Ｏで表されるオキシアルキレン基の平均付加モル数であって、５～３００を表す。）

（式（ＩＩ）中、
Ｒ⁷、Ｒ⁸、及びＲ⁹は、同一又は異なって、水素原子、炭素数１～８のアルキル基、または－（ＣＨ_２）ｚＣＯＯＭ²を表し（但し、Ｒ⁷～Ｒ⁹のいずれか１つが－（ＣＨ_２）ｚＣＯＯＭ²である）、
ｚは０～２の整数であり、
Ｍ¹、Ｍ²は、同一又は異なって、水素原子、一価金属、二価金属、アンモニウム基、又は有機アミン基を表す。 The present invention that has solved the above problems is an additive for cement containing a polycarboxylic acid-based copolymer, wherein the polycarboxylic acid-based copolymer has the following structural unit (I) and the following structural unit (II). ), And the structural unit (III) derived from the carboxylic acid hydroxyalkyl ester-based monomer, based on 100% by mass of the structural unit (I), the structural unit (II), and the structural unit (III) in total. The gist is that the structural unit (I) is 40 to 87% by mass, the structural unit (II) is 5 to 30% by mass, and the structural unit (III) is 8 to 30% by mass. Have.

(In formula (I),
R ² represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.
R ³ , R ⁴ , and R ⁵ represent the same or different hydrogen atom or methyl group.
R ⁶ represents an alkylene group having 0 to 5 carbon atoms.
R ¹ O represents an oxyalkylene group having 2 to 18 carbon atoms, which is the same or different.
m is the average number of moles of oxyalkylene group represented by R ¹ O, and represents 5 to 300. )

(In formula (II),
R ⁷ , R ⁸ and R ⁹ are the same or different and represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or-(CH ₂ ) zCOM ² (provided that any one of R ⁷ to R ⁹ is used. One is-(CH ₂ ) zCOMM ² ),
z is an integer of 0 to 2 and
M ¹ and M ² are the same or different and represent a hydrogen atom, a monovalent metal, a divalent metal, an ammonium group, or an organic amine group.

In the cement additive of the present invention, (1) one of R ⁸ and R ⁹ in the formula (II) is COM ² , and (2) in the formula (I), R ⁶ The alkylene group has 1 or 2 carbon atoms, (3) m is 5 to 100 in the formula (I), and (4) the carboxylic acid hydroxyalkyl ester from which the structural unit (III) is derived. It is a preferred embodiment that the system monomer is a (meth) acrylic acid hydroxyalkyl ester.

The present invention also includes cement, water, and a cement composition containing the above-mentioned additive for cement of the present invention. Further, it is preferable to include a cement dispersant, and it is also preferable that the dispersant is at least one selected from the group consisting of a sulfonic acid-based dispersant, a polycarboxylic acid-based dispersant, and a phosphoric acid-based dispersant. be.

The cement additive of the present invention has excellent properties of reducing the viscosity of the cement composition and the fluidity of the cement composition. In particular, the cement additive of the present invention has excellent properties of suppressing the increase in viscosity immediately after kneading the cement composition and after kneading, and also having excellent fluidity over time after kneading the cement composition. Hereinafter, the viscosity immediately after kneading may be referred to as "initial viscosity", the viscosity over time may be referred to as "viscosity over time", the two may be simply referred to as "viscosity", or the effects of both may be referred to as "suppression of increase in viscosity". Further, the fluidity immediately after kneading may be referred to as "initial fluidity", the fluidity over time may be referred to as "fluidity over time", and the combination of the two may be simply referred to as "fluidity". According to the present invention, it is possible to provide a cement composition containing the above-mentioned cement additive.

FIG. 1 is a schematic cross-sectional view of a J14 funnel according to the JSCE standard JSCE-F541 for measuring the funnel flow time. FIG. 2 is a graph showing the relationship between the funnel flow time immediately after kneading the mortar of Example 1 and Comparative Example 1 and the mortar flow value. FIG. 3 is a graph showing the relationship between the funnel flow time and the mortar flow value 30 minutes after kneading the mortars of Example 1 and Comparative Example 1. FIG. 4 is a graph showing the relationship between the funnel flow time and the mortar flow value 60 minutes after kneading the mortars of Example 1 and Comparative Example 1.

As used herein, "(meth) acrylic" means "acrylic and / or methacrylic". Further, "acid (salt)" means "acid and / or a salt thereof". Further, "mass" and "weight" may be read as "weight" and "mass", respectively.

(Polycarboxylic acid-based copolymer)
The cement additive of the present invention contains a specific polycarboxylic acid-based copolymer. By containing the specific polycarboxylic acid-based copolymer, it has an excellent effect of suppressing an increase in viscosity of the cement composition and also has an excellent property of fluidity with time.

If the cement additive of the present invention contains the polycarboxylic acid-based copolymer of the present invention satisfying the following constitution, the above effect can be obtained. Further, the cement additive of the present invention may contain one or more kinds of the polycarboxylic acid-based copolymer of the present invention.

The polycarboxylic acid-based copolymer of the present invention contains a structural unit (I), a structural unit (II), and a structural unit (III) derived from a carboxylic acid hydroxyalkyl ester-based monomer. The "monomer-derived structural unit" is a structural unit formed by polymerizing a monomer, and specifically, the polymerizable carbon-carbon double bond of the monomer becomes a single bond. It is a structure.

(Structural unit (I))

The polycarboxylic acid-based copolymer of the present invention may contain only one type of structural unit (I) represented by the following formula, or may contain two or more types.

In formula (I), R ³ , R ⁴ , and R ⁵ represent the same or different hydrogen atoms or methyl groups.

R ⁶ represents an alkylene group having 0 to 5 carbon atoms, and the preferred carbon number is 0 to 3, more preferably 1 or 2. The alkylene group having 1 to 5 carbon atoms may be either a linear group or a branched chain alkylene group. Examples of R ⁶ are methylene, ethanediyl, propanediyl, methylpropanediyl, ethylpropanediyl, butanediyl, methylbutanediyl, and pentanediyl, more preferably methylene, ethanediyl, propanediyl, butanediyl, and pentanediyl, and more preferably methylene. , Ethane-1,2-diyl, propane-1,3-diyl, butane-1,4-diyl, pentane-1,4-diyl.

In formula (I), R ¹ O represents the same or different oxyalkylene group having 2 to 18 carbon atoms. The oxyalkylene group preferably has 2 to 8 carbon atoms, more preferably 2 to 4 carbon atoms.

Examples of R ¹ O include an oxyethylene group, an oxypropylene group, an oxybutylene group and an oxystyrene group, preferably an oxyethylene group, an oxypropylene group and an oxybutylene group, and more preferably an oxyethylene group and an oxypropylene group. Is. When two or more different R ¹ O structures are present, the addition form of R ¹ O may be any form such as random addition, block addition, and alternate addition. In order to secure a balance between hydrophilicity and hydrophobicity, it is preferable that the oxyalkylene group contains an oxyethylene group as an essential component. Specifically, the oxyethylene group is preferably 80 mol% or more, more preferably 90 mol% or more, and further preferably 100 mol% with respect to 100 mol% of the total oxyalkylene group.

In formula (I), R ² represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. The alkyl group preferably has 1 to 10 carbon atoms, and more preferably 1 to 8 carbon atoms. The alkyl group may be a substituted alkyl group or an unsubstituted alkyl group. The alkyl group having 1 to 18 carbon atoms may be a linear, branched or cyclic alkyl group. The alkyl group having 1 to 18 carbon atoms is preferably a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group or an isobutyl group, and more preferably a methyl group, an ethyl group or n-. It is a propyl group and an n-butyl group.

In formula (I), m is the average number of moles of oxyalkylene group represented by R ¹ O, which is 5 to 300. m is preferably 5 to 100, more preferably 6 to 90, still more preferably 8 to 85, and particularly preferably 10 to 80. When m is within the above range, it is effective in suppressing the increase in viscosity of the cement composition, and it is possible to exert an excellent effect on fluidity, particularly fluidity with time. In the formula (I), the "average number of moles of substance added" of the oxyalkylene group represented by m is the oxyalkylene added in one unit of the structural unit represented by the formula (I) in one mole of the copolymer. It means the average value of the number of moles of a group.

(Structural unit (II))
The polycarboxylic acid-based copolymer of the present invention may contain only one type of structural unit (II) represented by the following formula, or may contain two or more types. When the structural unit (II) is combined with the structural unit (I) and the following structural unit (III), it is effective in suppressing the increase in viscosity of the cement composition and further contributes to the improvement of fluidity.

In formula (II), R ⁷ , R ⁸ and R ⁹ are the same or different, a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or-(CH ₂ ) zCOOM ² (provided that R ⁷ to R 7 to 2). Any one of R ⁹ is − (CH ₂ ) zCOMM ² ), preferably one of R ⁸ and R ⁹ is COMM ² .

In formula (II), z is an integer of 0 to 2. z is preferably 0 or 1, more preferably 0.

In formula (II), M ¹ and M ² represent a hydrogen atom, a monovalent metal, a divalent metal, an ammonium group, or an organic amine group, which are the same or different. Further, -COOM ¹ may form an anhydrate with another- (CH ₂ ) zCOOM ² .

The monovalent metal and the divalent metal may employ any suitable metal atom. The monovalent metal is preferably an alkali metal such as lithium, sodium or potassium; and the divalent metal is preferably an alkaline earth metal such as calcium or magnesium.

The ammonium group is a functional group represented by " ^-NH ₄₊ ". Further, as the organic amine group, any suitable organic amine group may be adopted as long as it is a protonated organic amine. Examples of the organic amine group include alkanolamine groups such as ethanolamine group, diethanolamine group and triethanolamine group; alkylamines such as monoethylamine, diethylamine and triethylamine group; and polyamines such as ethylenediamine and triethylenediamine.

(Structural unit (III))
The structural unit (III) is a structural unit derived from a carboxylic acid hydroxyalkyl ester-based monomer. The polycarboxylic acid-based copolymer of the present invention may contain only one type of structural unit (III), or may contain two or more types of structural unit (III). The structural unit (III) contributes to the manifestation of the above-mentioned effect of the present invention by being combined with the above-mentioned structural unit (I) and the above-mentioned structural unit (II) at a predetermined ratio.

The structural unit (III) is preferably a structural unit derived from a (meth) acrylic acid hydroxyalkyl ester, more preferably the number of carbon atoms in the alkyl moiety is preferably 1 to 8, and even more preferably 2 to 4 (meth). ) It is a structural unit derived from acrylic acid hydroxyalkyl ester. Specifically, a structural unit derived from (meth) acrylic acid hydroxyethyl ester, a structural unit derived from (meth) acrylic acid hydroxypropyl ester, or a structural unit derived from (meth) acrylic acid hydroxybutyl ester is preferable.

The content ratios of the structural unit (I), the structural unit (II), and the structural unit (III) contained in the polycarboxylic acid-based copolymer of the present invention are the structural unit (I), the structural unit (II), and the structure. The structural unit (I) is 40 to 87% by mass, the structural unit (II) is 5 to 30% by mass, and the structural unit (III) is 8 to 30% by mass with respect to the total 100% by mass of the unit (III). .. Preferably, the structural unit (I) is 45 to 86% by mass, the structural unit (II) is 5 to 25% by mass, and the structural unit (III) is 9 to 30% by mass. More preferably, the structural unit (I) is 50 to 85% by mass, the structural unit (II) is 5 to 20% by mass, and the structural unit (III) is 10 to 30% by mass. When the content ratios of the structural unit (I), the structural unit (II), and the structural unit (III) are within the above ranges, it is effective in suppressing the increase in viscosity of the cement composition and also has an excellent effect on fluidity. Play. The content ratios of the structural units (I) to (III) are calculated based on the reaction rate of the monomer described in the examples obtained by high performance liquid chromatography.

The total content ratio of the structural units (I) to (III) contained in the polycarboxylic acid-based copolymer is preferably 50 to 100% by mass, more preferably 50% by mass, based on 100% by mass of the polycarboxylic acid-based copolymer. It is 70 to 100% by mass, more preferably 80 to 100% by mass, particularly preferably 90 to 100% by mass, and most preferably 95 to 100% by mass. When the total content ratio of the structural units (I) to (III) of the present invention is within the above range, the increase in viscosity of the cement composition can be suppressed and the fluidity can be effectively enhanced. When the total of the structural units (I) to (III) is less than 100% by mass, the residual may contain the structural unit (IV) described later and / or various known additives.

(Structural unit (IV))
In addition to the structural units (I) to (III), the polycarboxylic acid-based copolymer of the present invention may contain a structural unit (IV) derived from the other monomer (d). The structural unit (IV) may be contained alone or in combination of two or more.

The other monomer (d) is a monomer other than the monomer from which the structural units (I) to (III) are derived. The structural unit (IV) derived from the other monomer (d) is preferably a structural unit derived from the following monomer.
Monocarboxylic acid-based monomers such as (meth) acrylic acid and crotonic acid or salts thereof; various (alkoxy) (poly) such as polyethylene glycol mono (meth) acrylate and methoxy (poly) ethylene glycol mono (meth) acrylate. Alkylene glycol mono (meth) acrylates; (poly) alkylene glycol di (meth) acrylates such as (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate; hexanediol di (meth) Polyfunctional (meth) acrylates such as acrylates and trimethylolpropane tri (meth) acrylates; (poly) alkylene glycol dimalates such as polyethylene glycol dimalates; vinyl sulfonates, (meth) allylsulfonates, 2-methylpropanesulfonic acid Unsaturated sulfonic acids (salts) such as (meth) acrylamide and styrene sulfonic acid; unsaturated amides such as (meth) acrylic (alkyl) amides, N-methylol (meth) acrylamides and N, N-dimethyl (meth) acrylamides. Classes; Amides of unsaturated monocarboxylic acids such as methyl (meth) acrylamide and amines having 1 to 30 carbon atoms; Vinyl aromatics such as styrene, α-methylstyrene and vinyltoluene; 1,4-butanediol Alcandiol mono (meth) acrylates such as mono (meth) acrylates; dienes such as butadiene and isoprene; unsaturated cyanides such as (meth) acrylonitrile; unsaturated esters such as vinyl acetate; amino (meth) acrylates. Unsaturated amines such as ethyl, dimethylaminoethyl (meth) acrylate, vinylpyridine; divinyl aromatics such as divinylbenzene; allyls such as (meth) allyl alcohol, glycidyl (meth) allyl ether; and the like. ..

The content ratio of the structural unit (IV) contained in the polycarboxylic acid-based copolymer of the present invention is preferably 0 to 100% by mass, based on 100% by mass of the total of the structural units (I) to (III). It is preferably 0 to 5% by mass. The polycarboxylic acid-based copolymer of the present invention can exert the above-mentioned effect as long as it is a predetermined amount of the structural unit (IV). The content ratio of the structural unit (IV) can also be specified in the same manner as in the structural units (I) to (III).

The weight average molecular weight (Mw) of the polycarboxylic acid-based copolymer of the present invention is 5,000 to 100 as the weight average molecular weight (Mw) in terms of polyethylene glycol by gel permeation chromatography (GPC) described in the examples. It is 000. The weight average molecular weight (Mw) is preferably 6,000 to 80,000, more preferably 7,000 to 50,000, still more preferably 8,000 to 30,000, and particularly preferably 9,000 to 25,000. be. When the weight average molecular weight (Mw) of the polycarboxylic acid-based copolymer is within the above range, it is effective in suppressing the increase in viscosity of the cement composition and has an excellent effect of fluidity.

(Method for producing polycarboxylic acid-based copolymer)
The method for producing the polycarboxylic acid-based copolymer of the present invention is not particularly limited, but an unsaturated polyalkylene glycol-based monomer (a), a dicarboxylic acid-based monomer (b), and a carboxylic acid hydroxyalkyl ester-based monomer are preferable. It can be produced by polymerizing a monomer component containing the monomer (c) in the presence of a polymerization initiator. Other monomers (d) may be contained if necessary.

The structural unit (I) is formed from the unsaturated polyalkylene glycol-based monomer (a) represented by the following formula (1).

In the above formula (1), R ³ , R ⁴ , and R ⁵ represent the same or different hydrogen atom or methyl group. R ⁶ represents an alkylene group having 0 to 5 carbon atoms. R ¹ O represents an oxyalkylene group having 2 to 18 carbon atoms, which is the same or different. R ² represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. m is the average number of moles of oxyalkylene group represented by R ¹ O, and is 5 to 300. The number of carbon atoms of the preferred oxyalkylene group represented by R ¹ O and a suitable example thereof; the number of carbon atoms of the preferred alkyl group represented by R ² and a preferred example thereof; the preferred alkylene represented by R ⁶ Since it is the same as the preferable range of the number of carbon atoms of the group; m, the description thereof will be omitted.

As the unsaturated polyalkylene glycol-based monomer (a), any unsaturated polyalkylene glycol ether-based monomer satisfying the structural unit (I) can be adopted. Specific examples of the unsaturated polyalkylene glycol ether-based monomer (a) represented by the formula (1) include hydroxyethyl vinyl ether, allyl alcohol, metallic alcohol, 3-butene-1-ol, and 3-. Methyl-3-butene-1-ol, 3-methyl-2-butene-1-ol, 2-methyl-2-butene-1-ol, 3-butene-2-ol, 3-methyl-3-butene- An alkylene oxide having 2 to 18 carbon atoms was added to an unsaturated alcohol having 2 to 10 carbon atoms such as 2-ol, 2-methyl-3-butene-1-ol, and 2-methyl-3-butene-2-ol. Examples thereof include unsaturated alcohol alkylene oxide adducts. A compound obtained by adding 5 to 300 mol of ethylene oxide or propylene oxide to any of allyl alcohol, methallyl alcohol, and 3-methyl-3-buten-1-ol is preferable, and methallyl alcohol or 3- is more preferable. It is a compound in which 5 to 300 mol of ethylene oxide is added to at least one selected from methyl-3-butene-1-ol.

The synthesis of the unsaturated polyalkylene glycol-based monomer (a) is not particularly limited, and the unsaturated polyalkylene glycol-based monomer (a) may be synthesized by various known methods. For example, it can be synthesized by adding an alkylene oxide to an unsaturated alcohol such as allyl alcohol, methallyl alcohol, 3-methyl-3-butene-1-ol (isoprenol), hydroxyethyl vinyl ether, and hydroxybutyl vinyl ether.

The structural unit (II) is formed from the dicarboxylic acid-based monomer (b) represented by the following formula (2).

In formula (2), R ⁷ , R ⁸ and R ⁹ represent the same or different hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or-(CH ₂ ) zCOOM ² (provided that R ⁷ to R 7 to). Any one of R ⁹ is-(CH ₂ ) zCOMM ² ). Preferably, either R ⁸ or R ⁹ is COM ² . z represents an integer of 0 to 2. M ¹ and M ² are the same or different and represent a hydrogen atom, a monovalent metal, a divalent metal, an ammonium group, an organic ammonium group, or an organic amine group. Since the preferred range of z and the preferred examples of M ¹ and M ² are the same as those of the structural unit (II), the description thereof will be omitted.

Examples of the dicarboxylic acid-based monomer (b) represented by the formula (2) include unsaturated dicarboxylic acid-based monomers such as maleic acid, itaconic acid, and fumaric acid, or salts thereof; maleic acid, itaconic acid, and fumaric acid. An anhydrides of unsaturated dicarboxylic acid-based monomers such as acids or salts thereof; and the like. Examples of the salt here include alkali metal salts, alkaline earth metal salts, ammonium salts, organic ammonium salts, and organic amine salts. Examples of the alkali metal salt include lithium salt, sodium salt, potassium salt and the like. Examples of the alkaline earth metal salt include calcium salt and magnesium salt. Examples of the organic ammonium salt include methylammonium salt, ethylammonium salt, dimethylammonium salt, diethylammonium salt, trimethylammonium salt, triethylammonium salt and the like. Examples of the organic amine salt include alkanolamine salts such as ethanolamine salt, diethanolamine salt and triethanolamine salt. Among these, maleic acid and fumaric acid are preferable, and by using the structural unit (II) derived from these, more excellent effects are exhibited by suppressing the increase in viscosity of the cement composition and improving the fluidity.

The structural unit (III) is formed from the carboxylic acid hydroxyalkyl ester-based monomer (c). Any carboxylic acid hydroxyalkyl ester-based monomer can be adopted, but it is preferably a (meth) acrylic acid hydroxyalkyl ester, and the number of carbon atoms in the alkyl moiety is preferably 1 to 8, more preferably 2 to 2. 4 is a (meth) acrylic acid hydroxyalkyl ester. Specifically, (meth) acrylic acid hydroxyethyl ester, (meth) acrylic acid hydroxypropyl ester, or (meth) acrylic acid hydroxybutyl ester is preferable.

An unsaturated polyalkylene glycol-based monomer (a), a dicarboxylic acid-based monomer (b), and a hydroxyalkyl carboxylic acid that can be used for producing the polycarboxylic acid-based copolymer contained in the cement additive of the present invention. The amount of each of the ester-based monomer (c) used may be appropriately adjusted so that the ratio of each structural unit in the total structural units constituting the polycarboxylic acid-based copolymer is within the above range.

If necessary, another monomer (d) may be used, and the structural unit (IV) is formed from the other monomer (d). The above-mentioned monomer corresponds to a specific example of the other monomer (d).

Polymerization of the monomeric components can be carried out by any suitable method. For example, solution polymerization and bulk polymerization can be mentioned. Examples of the solution polymerization method include batch type and continuous type. Solvents that can be used in solution polymerization include water; alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol; aromatic or aliphatic hydrocarbons such as benzene, toluene, xylene, cyclohexane, n-hexane; esters such as ethyl acetate. Compounds; ketone compounds such as acetone and methyl ethyl ketone; cyclic ether compounds such as tetrahydrofuran and dioxane; and the like can be mentioned.

When polymerizing a monomer component, the polymerization initiator is a water-soluble polymerization initiator, for example, persulfate such as ammonium persulfate, sodium persulfate, potassium persulfate; hydrogen peroxide; 2,2'-. Azobisin compounds such as azobis-2-methylpropionamidine hydrochloride, cyclic azoamidin compounds such as 2,2'-azobis-2- (2-imidazolin-2-yl) propane hydrochloride, 2-carbamoyl azoisobutyronitrile and the like. A water-soluble azo-based initiator such as the azonitrile compound of the above; etc. can be used. These polymerization initiators include alkali metal sulfites such as sodium hydrogen sulfite, Fe (II) salts such as metadiosulfate, sodium hypophosphite, and molle salts, sodium hydroxymethanesulfinate dihydrate, and hydroxylamine hydrochloride. Accelerators such as salt, thiourea, L-ascorbic acid (salt), and erythorbic acid (salt) can also be used in combination. Among the polymerization initiators, persulfates and hydrogen peroxide are preferable. Among the accelerators, Fe (II) salts such as moor salt and L-ascorbic acid (salt) are preferable. Each of these polymerization initiators and accelerators may be of only one type or of two or more types.

When solution polymerization is performed using a lower alcohol, aromatic hydrocarbon, aliphatic hydrocarbon, ester compound, or ketone compound as a solvent, or when bulk polymerization is performed, benzoylper oxide or lauroylper is used as a polymerization initiator. Hydrocarbons such as oxides and sodium peroxides; hydrocarbonates such as t-butylhydrocarbonates and cumenehydroperoxides; azo compounds such as azobisisobutyronitrile; and the like can be used. When such a polymerization initiator is used, an accelerator such as an amine compound can also be used in combination. Further, when a water-lower alcohol mixed solvent is used, it can be appropriately selected and used from the above-mentioned various polymerization initiators or combinations of the polymerization initiator and the accelerator.

The reaction temperature at the time of polymerization of the monomer component is appropriately determined by the polymerization method, solvent, polymerization initiator and chain transfer agent used. Such a reaction temperature is preferably 0 ° C. or higher, more preferably 30 ° C. or higher, still more preferably 50 ° C. or higher, preferably 150 ° C. or lower, more preferably 120 ° C. or lower, still more preferably 100 ° C. or lower. be.

Any suitable method can be adopted as the method for charging the monomer component into the reaction vessel.

When polymerizing the monomer component, a chain transfer agent may be preferably used. When a chain transfer agent is used, it becomes easy to adjust the molecular weight of the obtained copolymer. The chain transfer agent may be only one kind or two or more kinds.

As the chain transfer agent, any suitable chain transfer agent may be adopted. Examples of such a chain transfer agent include thiol-based chain transfer agents such as mercaptoethanol, thioglycerol, thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thioapple acid, and 2-mercaptoethanesulfonic acid; Secondary alcohols such as isopropanol; phosphite, hypophosphite, and salts thereof (sodium bisulfite, potassium hypophosphite, etc.), sulfite, hydrogen sulfite, dithionic acid, metabisulfite, And lower oxides of salts thereof (sodium bisulfite, potassium sulfite, sodium hydrogen sulfite, potassium hydrogen sulfite, sodium bisulfite, potassium bisulfite, sodium metabisulfite, potassium metabisulfite, etc.) and salts thereof; etc. Can be mentioned.

The produced cement additive can be used as it is as the cement additive of the present invention, but from the viewpoint of handleability, the pH of the reaction solution after the production of the cement additive is adjusted to 5 or more. It is preferable to keep it. However, in order to improve the polymerization rate, it is preferable to carry out the polymerization at a pH of less than 5, and adjust the pH to 5 or more after the polymerization. The pH can be adjusted, for example, by using an inorganic salt such as a hydroxide or carbonate of a monovalent metal or a divalent metal; ammonia; an organic amine; or an alkaline substance.

The concentration of the produced cement additive can be adjusted as necessary with respect to the solution obtained by the production.

The produced cement additive may be used as it is in the form of a solution, or may be powdered and used.

(Cement composition)
The cement composition of the present invention is a cement paste, mortar, concrete, etc., and contains the cement additive of the present invention.

The cement composition of the present invention comprises cement, water, and the cement additive of the present invention. Preferably, it contains cement, water, aggregate, and the cement additive of the present invention.

Cement includes Portorand cement (normal, early-strength, ultra-fast-strength, moderate heat, low heat, sulfate resistant and each low alkaline type), various mixed cements (blast furnace cement, silica cement, fly ash cement), white Portorand cement. , Alumina cement, ultra-fast-hardening cement (1 clinker fast-hardening cement, 2 clinker fast-hardening cement, magnesium phosphate cement), grout cement, oil well cement, low heat-generating cement (low-heat-generating blast furnace cement, fly-ash mixed low-heat-generating blast furnace) Cement (cement with high content of belite), ultra-high strength cement, cement-based solidifying material, eco-cement (cement manufactured from one or more of municipal waste incineration ash and sewage sludge incineration ash) are suitable, and further, a blast furnace. Fine powders such as slag, fly ash, cinder ash, clinker ash, husk ash, silica fume, silica powder, limestone powder and the like may be added. The cement contained in the cement composition of the present invention may be one kind or two or more kinds.

In addition to sand, gravel, crushed stone, recycled aggregate, granulated slag, etc., aggregates include silica stone, clay, zircone, high alumina, silicon carbide, graphite, chromium, chromog, magnesia, etc. The refractory aggregate of is also exemplified. The aggregate may be appropriately selected depending on the intended use, and for example, the mortar includes fine aggregate such as sand, cement, water, and the cement additive of the present invention. Further, for example, concrete contains coarse aggregate such as gravel, fine aggregate, cement, water, and the additive for cement of the present invention.

The cement additive of the present invention in the cement composition may adopt any appropriate content ratio depending on the purpose. For example, the polycarboxylic acid copolymer of the present invention has a solid content of preferably 0.001 part by mass to 10 parts by mass, more preferably 0.005 part by mass to 5 parts by mass, still more preferably, with respect to 100 parts by mass of cement. Is 0.01 parts by mass to 3 parts by mass, particularly preferably 0.01 parts by mass to 2 parts by mass, and most preferably 0.01 parts by mass to 1 part by mass. When the content of the polycarboxylic acid copolymer of the present invention in the cement composition is within the above range with respect to the cement, the unit water amount is reduced, the strength is increased, the durability is improved, and the effects peculiar to the present invention ( It can be expressed at the same time as suppressing increase in viscosity and fluidity).

The unit water amount, cement usage amount and water / cement ratio per 1 m ³ of the cement composition of the present invention containing the cement additive of the present invention can be appropriately set. The unit water amount is preferably 100 to 185 kg / m ³ , the cement amount used is 250 to 800 kg / m ³ , the water / cement ratio (mass ratio) is 0.1 to 0.7, and more preferably, the unit water amount is 120 to 175 kg / m ³ . , The amount of cement used is 270 to 800 kg / m ³ , and the water / cement ratio (mass ratio) = 0.15 to 0.65. The cement composition of the present invention can be widely used from poorly mixed to richly mixed, and is effective for both high-strength concrete having a large unit cement amount and poorly mixed concrete having a unit cement amount of 300 kg / m ³ or less.

In addition to the cement additive of the present invention, the cement composition of the present invention may contain any suitable other components as long as the effects of the present invention are not impaired.

Other components include, for example, cement dispersants, AE agents, defoamers, setting retarders, curing accelerators, curing retarders, waterproofing agents, rust preventives, crack reducing agents, and cement additives such as swelling agents. These may be added alone or in combination of two or more. In the present invention, it is preferable to add a cement dispersant.

The cement dispersant may have a function of adsorbing to the surface of the cement particles immediately after the addition of the cement dispersant or after a lapse of time, dispersing the cement particles by its repulsive action, and enhancing the fluidity of the cement composition, in particular. Not limited. Such a cement dispersant is preferably at least one selected from the group consisting of a sulfonic acid-based dispersant having a sulfonic acid group in the molecule, a polycarboxylic acid-based dispersant, and a phosphoric acid-based dispersant. When the cement dispersant is used in combination with the cement composition of the present invention, it is effective in suppressing the increase in viscosity of the cement composition and can exhibit an excellent effect of fluidity.

Examples of the sulfonic acid-based dispersant include polyalkylaryl sulfonate-based sulfonic acid-based dispersants such as naphthalene sulfonic acid formaldehyde condensate, methylnaphthalene sulfonic acid formaldehyde condensate, and anthracene sulfonic acid formaldehyde condensate; melamine sulfonic acid formaldehyde condensation. Melamine formalin resin sulfonate-based sulfonic acid-based dispersant; Aromatic aminosulfonate-based sulfonic acid-based dispersant such as aminoaryl sulfonic acid-phenol-formaldehyde condensate; Lignin sulfonate, modified lignin Lignin sulfonate-based sulfonic acid-based dispersants such as sulfonates; polystyrene sulfonate-based sulfonic acid-based dispersants; and the like can be mentioned.

As the polycarboxylic acid-based dispersant (excluding the polycarboxylic acid-based copolymer contained in the cement additive of the present invention, the same applies hereinafter), various known polycarboxylic acid-based copolymers can be used, which is preferable. Is preferably a polycarboxylic acid-based dispersant which is a monocarboxylic acid-based monomer alone or a copolymer, and a polycarboxylic acid-based copolymer having a polyalkylene glycol chain is more preferable. For example, a dispersant containing a structural unit derived from an unsaturated (poly) alkylene glycol ether-based monomer; a dispersant containing a structural unit derived from an unsaturated monocarboxylic acid-based monomer; a dispersant containing an unsaturated monocarboxylic acid ester-based single amount. Dispersant containing constituent units derived from the body; Dispersant containing constituent units derived from (poly) alkylene glycol mono (meth) acrylic acid ester-based monomer; Dispersant containing constituent units derived from unsaturated dicarboxylic acid-based monomer Agent; Dispersant containing a structural unit derived from a hydrophobic unsaturated monocarboxylic acid ester-based monomer and the like can be mentioned.

As the phosphoric acid-based dispersant, a dispersant having a phosphoric acid group in the molecule: a copolymer of a polyalkylene glycol mono (meth) acrylic acid ester-based monomer and a phosphoric acid ester-based monomer, aromatic poly Examples thereof include a formalin condensate of an alkylene glycol ether-based monomer and an aromatic phosphate ester-based monomer.

When a dispersant is used, the ratio of the polycarboxylic acid-based copolymer of the present invention to the cement dispersant can be set depending on the type of the cement dispersant used, the compounding conditions, the test conditions, etc., but the viscosity of the cement composition The ratio of the polycarboxylic acid-based copolymer of the present invention to the cement dispersant (polycarboxylic acid-based copolymer / dispersant of the present invention) in consideration of the effect of suppressing the increase and the effect of improving the initial fluidity and the flow retention over time. Is preferably 1/99 to 99/1, more preferably 10/90 to 90/10, still more preferably 20/80 to 80/20, particularly preferably 30/70 to 70/30, and most preferably 40/ It is 60 to 60/40.

The cement composition of the present invention may be effective for ready-mixed concrete, concrete for secondary concrete products, concrete for centrifugal molding, concrete for vibration compaction, steam curing concrete, sprayed concrete and the like. The cement composition of the present invention includes medium-fluidity concrete (concrete with a slump value of 22 to 25 cm), high-fluidity concrete (concrete with a slump value of 25 cm or more and a slump flow value of 50 to 70 cm), self-filling concrete, and self. It can also be effective for mortar and concrete that require high fluidity such as leveling materials.

The cement composition of the present invention may be prepared by blending the constituent components by any suitable method. For example, a method of kneading the constituents in a mixer may be mentioned.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited by the following examples as well as the present invention, and appropriate modifications are made to the extent that it can meet the purposes of the preceding and the following. Of course, it is possible to carry out, and all of them are included in the technical scope of the present invention. Unless otherwise specified, the term "part" means parts by mass, and the term "%" means% by mass.

(Measurement conditions for weight average molecular weight (Mw))
The weight average molecular weight (Mw) was determined by using GPC (gel permeation chromatography) under the following conditions.
Equipment: Alliance (2695) (manufactured by Waters)
Analysis software: Emper2 Professional + GPC option (manufactured by Waters)
Column used: TSKguardcoremsSWXL (inner diameter: 6.0 mm x 40 mm) + TSKgel G4000SWXL (inner diameter: 7.8 mm x 300 mm) + G3000SWXL (inner diameter: 7.8 mm x 300 mm) + G2000SWXL (inner diameter: 7.8 mm x 300 mm) (both manufactured by Tosoh Corporation) )
Detector: Differential refractometer (RI) detector (Waters 2414, manufactured by Waters)
Eluent: A solution prepared by dissolving 115.6 g of sodium acetate trihydrate in a mixed solvent of 10999 g of ion-exchanged water and 6001 g of acetonitrile, and further adjusting the pH to 6.0 with acetic acid.
Flow rate: 1 mL / min Column temperature: 40 ° C
Measurement time: 45 minutes Sample solution injection amount: 100 μL (eluent solution with sample concentration of 0.5% by mass)
GPC standard sample: Polyethylene glycol manufactured by Tosoh Corporation, Mp = 255,000, 200,000, 107,000, 72750, 44900, 31400, 21300, 11840, 6450, 4020, 1470.
Calibration curve: Prepared by a cubic formula using the Mp value of the above polyethylene glycol.

(High Performance Liquid Chromatography (LC))
The residual amount of each monomer used as the reaction raw material was confirmed under the following conditions.
Equipment: Waters Alliance 2695 (manufactured by Waters)
Analysis software: Emper Professional (manufactured by Waters)
Column: Atlantis dC18 5 μm (inner diameter 4.6 mm x length 250 mm) x 2 (manufactured by Waters)
Detector: Differential Refractometer (RI) detector (Waters 2414), multi-wavelength visible ultraviolet (PDA) detector (Waters 2996)
Solvent: A solution in which a 100 mM sodium acetate aqueous solution and acetonitrile are mixed at a ratio of 6: 4 Flow rate: 1 mL / min Column temperature: 40 ° C.
Measurement time: 30 minutes Sample solution injection amount: 100 μL (sample concentration is 1% by mass)

[Synthesis of copolymer (A-1)]
Ion-exchanged water: 109.3 parts was charged in a glass reaction vessel equipped with a thermometer, agitator, dropping device, nitrogen introduction tube and reflux condenser, and the inside of the reaction vessel was replaced with nitrogen under stirring to reach 58 ° C. The temperature was raised. Next, 159.6 parts of unsaturated polyalkylene glycol ether (IPN-50) to which an average of 50 mol of ethylene oxide was added to 3-methyl-3-butene-1-ol was dissolved in ion-exchanged water: 104.8 parts. An aqueous solution prepared by diluting 12.3 parts of maleic acid and 23.4 parts of 2-hydroxyethyl acrylate (HEA) with ion-exchanged water: 45 parts was added dropwise to the reaction vessel over 5 hours. At the same time, an aqueous solution in which 1.7 parts of ammonium persulfate is dissolved in 19.8 parts of ion-exchanged water and L-ascorbic acid: 0.5 parts and 3-mercaptopropionic acid in 21.8 parts of ion-exchanged water: An aqueous solution in which 1.7 parts were dissolved was added dropwise over 5 hours. Then, the temperature was maintained at 58 ° C. for 1 hour to complete the polymerization reaction. Then, the reaction solution was neutralized to pH 6 with an aqueous sodium hydroxide solution at a temperature equal to or lower than the polymerization reaction temperature to obtain an aqueous solution of the copolymer (A-1) of the present invention having a weight average molecular weight (Mw) of 12,500. rice field. The reaction rate of each raw material monomer was determined by measuring the residual amount by liquid chromatography (LC). As a result, the reaction rate of IPN-50 was 91.1%, and the reaction rate of maleic acid was 62. It was 5%, and the reaction rate of HEA was 99.0%. The obtained copolymer (A-1) is a mixture having the structural unit (I), the structural unit (II), and the structural unit (III) shown in Table 1. Table 1 shows the ratio of each structural unit of the copolymer (A-1) obtained from the reaction rate of each raw material monomer.

[Synthesis of copolymer (B-1)]
Ion-exchanged water: 100 parts was charged in a glass reaction vessel equipped with a thermometer, agitator, dropping device, nitrogen introduction tube and reflux condenser, and the inside of the reaction vessel was replaced with nitrogen under stirring to raise the temperature to 58 ° C. did. Next, 162.8 parts of unsaturated polyalkylene glycol ether (IPN-50) to which an average of 50 mol of ethylene oxide was added to 3-methyl-3-butene-1-ol was dissolved in 107.1 parts of ion-exchanged water. An aqueous solution prepared by diluting 13.3 parts of acrylic acid and 23.9 parts of 2-hydroxyethyl acrylate (HEA) with ion-exchanged water: 45 parts was added dropwise to the reaction vessel over 5 hours. At the same time, an aqueous solution in which 24.2 parts of ion-exchanged water: 2.1 parts of ammonium persulfate is dissolved, and 18.8 parts of ion-exchanged water: L-ascorbic acid: 0.6 parts and 3-mercaptopropionic acid: The aqueous solution in which 2.1 parts were dissolved was added dropwise over 5 hours. Then, the temperature was maintained at 58 ° C. for 1 hour to complete the polymerization reaction. Then, the reaction solution was neutralized to pH 6 with an aqueous sodium hydroxide solution at a temperature equal to or lower than the polymerization reaction temperature to obtain an aqueous solution of a comparative copolymer (B-1) having a weight average molecular weight (Mw) of 11,900. The reaction rate of each raw material monomer was determined by measuring the residual amount by liquid chromatography (LC). As a result, the reaction rate of IPN-50 was 83.0%, and the reaction rate of acrylic acid was 93. It was 6%, and the reaction rate of HEA was 95.3%. The obtained copolymer (B-1) is a mixture having a structural unit (I), a structural unit (II), and a structural unit (V) shown in Table 1. Table 1 shows the ratio of each structural unit of the copolymer (B-1) obtained from the reaction rate of each raw material monomer.

[Synthesis of copolymer (C)] (cement dispersant)
An average of 50 mol of ethylene oxide was added to 277 parts of ion-exchanged water and 3-methyl-3-buten-1-ol in a glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen introduction tube and a reflux condenser. 400 parts of unsaturated polyalkylene glycol ether (IPN-50) is charged, the temperature is raised to 65 ° C., and then a hydrogen peroxide aqueous solution containing 0.67 parts of hydrogen peroxide and 12.73 parts of ion-exchanged water is added thereto. did. Next, 58.4 parts of acrylic acid was added dropwise into the reaction vessel over 3 hours, and at the same time, 0.87 parts of L-ascorbic acid and 1.57 parts of 3-mercaptopropionic acid were added to 16.49 parts of ion-exchanged water. Was added dropwise over 3.5 hours. Then, the temperature was maintained at 65 ° C. for 1 hour to complete the polymerization reaction. The concentration of the polymerization component (concentration of all monomer components in mass% with respect to all raw materials) at the end of the polymerization reaction was 60%. Then, the reaction solution was neutralized to pH 7 with an aqueous sodium hydroxide solution at a temperature equal to or lower than the polymerization reaction temperature to obtain an aqueous solution of the copolymer (C) having a weight average molecular weight of 30,400. The reaction rate of each raw material monomer was determined by measuring the residual amount by liquid chromatography (LC). As a result, the reaction rate of IPN-50 was 94.1%, and the reaction rate of acrylic acid was 98. It was 2%.

[Example 1]
The copolymer (A-1) and the copolymer (C) were mixed at a ratio of 6: 4 to obtain a sample copolymer (1).

[Comparative Example 1]
The copolymer (B-1) and the copolymer (C) were mixed at a ratio of 6: 4 to obtain a sample copolymer (2).

<Mortar test>
The mortar test was carried out in an environment where the temperature was 20 ° C. ± 1 ° C. and the relative humidity was 60% ± 15%. The mortar was blended using the materials shown below so that C / S / W = 900/1260/270 (g).
C: Cement (ordinary Portland cement, manufactured by Taiheiyo Cement)
S: Fine aggregate (land sand from Oi River)
W: Ion-exchanged aqueous solution of sample (copolymer) and defoaming agent For W, 0.005% by mass of defoaming agent with respect to a predetermined amount of sample and cement mass (Microair 404, manufactured by BASF Pozoris). Was sufficiently uniformly dissolved in ion-exchanged water. The amount of each sample added was shown as the mass% of the solid content of each sample with respect to the mass of cement.

(Preparation of mortar)
The mortar was prepared as follows. Using a high power mixer (manufactured by Maruto Seisakusho, model number: CB-34), the above C (cement) and the above S (fine aggregate) were put into a kneading container and kneaded at a low speed for 10 seconds. W (an ion-exchanged aqueous solution of the sample and the defoaming agent) was added over 15 seconds while kneading at a lower speed. The mixer was stopped 40 seconds after the start of kneading, and the mortar adhering to the wall of the container was scraped off over 20 seconds. Then, kneading was performed at a higher speed for 180 seconds to prepare a mortar.

(Measurement method of mortar flow value)
The mortar obtained as described above is placed on a horizontally installed flow measuring plate (steel flat plate, 60 cm x 60 cm) with a slump cone (based on JIS-A-1171, upper end inner diameter 50 mm, lower end inner diameter 100 mm). , Height 150 mm), stuffed in half and stabbed with a stick 15 times, and mortar was stuffed to the full extent of the slump cone and stabbed with a stick 15 times, and then the surface of the slump cone was smoothed. Then, 11 minutes after starting the mixer for the first time, the slump cone is pulled up vertically to set the diameter of the expanded mortar (the diameter of the longest part (major diameter) and the diameter of the part 90 degrees to the long diameter). The points were measured and the average value was used as the mortar flow value (initial flow value). As for the mortar flow value, the larger the value, the better the dispersion performance. Similarly, the mortar flow values 30 minutes and 60 minutes after the start of the mixer were measured.

(Measuring method of funnel flow time)
The funnel flow time of the obtained mortar was measured using a J14 funnel as shown in FIG. 1 according to the JSCE standard JSCE-F541 of the Japan Society of Civil Engineers. Similarly, the roh flow time of the mortar was measured 30 minutes and 60 minutes after the start of the mixer. The amount of the copolymer (1) and the copolymer (2) added was No. 2 in Table 2. The flow value and the flow time were measured by changing as shown in (i) to (iii).

(Evaluation of water reduction performance, retention performance, and viscosity)
The characteristics of each sample were evaluated from the above mortar flow value and the above funnel flow time.

(Water reduction performance)
The ratio ([wt% / C]) to the cement (C) is calculated based on the amount (wt%) of the sample (copolymer) required for the flow value (initial flow value) immediately after kneading to be 250 mm. Calculated. The same test was performed three times, and the values calculated from the approximate formula are shown in Table 2. It should be noted that the smaller the required amount of addition, the higher the water reduction performance.

(Holding performance)
Using a mortar having a flow value (initial flow value) of 250 mm immediately after kneading, the flow value (flow value after 60 minutes) 60 minutes after kneading of the mortar is measured, and the flow retention rate (60 minutes later) is measured. Flow value / initial flow value) was calculated and shown in Table 2.

(viscosity)
Using a mortar adjusted so that the flow value (initial flow value) immediately after kneading is 220 mm, the rohto flow time (initial flow time) of the initial flow value and the flow value 60 minutes after kneading (60 minutes). The roh flow-down time (60 minutes back-flow time) at which the post-flow value) was 220 mm was measured. The same test was performed three times, and the values calculated from the approximate formula are shown in Table 2. It was evaluated that the shorter the flow time, the lower the viscosity.

From Tables 1 and 2 and FIGS. 2 to 4, in Example 1 using the copolymer (A-1) satisfying the requirements of the present invention, any of the initial viscosity, the viscosity with time, and the fluidity with time of the cement composition Was also excellent.

On the other hand, in Comparative Example 1 in which the copolymer (B-1) containing the structural unit (V) derived from acrylic acid, which is an unsaturated monocarboxylic acid-based monomer, was used instead of the structural unit (II), the viscosity was increased. The inhibitory effect was low. Further, in Example 1, the addition amount was smaller than that in Comparative Example 1, and excellent initial fluidity, aging fluidity, and suppression of viscosity increase could be exhibited.

From these results, the cement additive containing a polycarboxylic acid-based copolymer configured to satisfy the requirements of the present invention suppresses an increase in viscosity immediately after kneading the cement composition and after kneading with time. It can be seen that it also has excellent fluidity.

(Example 2, Comparative Example 2, Comparative Example 3)
[Synthesis of copolymer (A-2)]
The same procedure as for the above copolymer (A-1) was carried out except that the ratios of unsaturated polyalkylene glycol ether (IPN-50), maleic acid, and 2-hydroxyethyl acrylate (HEA) were changed, and the weight average molecular weight (weight average molecular weight) ( An aqueous solution of the copolymer (A-2) of Mw) 11,900 was obtained. The reaction rate of each raw material monomer was determined by measuring the residual amount by liquid chromatography (LC), and the ratio of each structural unit of the copolymer (A-2) is shown in Table 3.

[Synthesis of copolymer (B-2)]
The above, except that the ratio of unsaturated polyalkylene glycol ether (IPN-50) was changed, the ratio was changed by changing maleic acid to acrylic acid, and 2-hydroxyethyl acrylate (HEA) was not added. The same procedure as for the copolymer (A-1) was carried out to obtain an aqueous solution of the copolymer (B-2) having a weight average molecular weight (Mw) of 33,000. The reaction rate of each raw material monomer was determined by measuring the residual amount by liquid chromatography (LC), and the ratio of each structural unit of the copolymer (B-2) is shown in Table 3.

[Synthesis of copolymer (B-3)]
The same procedure as for the copolymer (B-1) was carried out except that the ratios of unsaturated polyalkylene glycol ether (IPN-50), acrylic acid, and 2-hydroxyethyl acrylate (HEA) were changed, and the weight average molecular weight (Mw) was increased. ) 28,800, an aqueous solution of the copolymer (B-3) was obtained. The reaction rate of each raw material monomer was determined by measuring the residual amount by liquid chromatography (LC), and the ratio of each structural unit of the copolymer (B-3) is shown in Table 3.

[Example 2]
The copolymer (A-2) and the copolymer (C) were mixed at a ratio of 6: 4 to obtain a sample copolymer (2).

[Comparative Example 2]
The copolymer (B-2) and the copolymer (C) were mixed at a ratio of 6: 4 to obtain a sample copolymer (4).

[Comparative Example 3]
The copolymer (B-3) and the copolymer (C) were mixed at a ratio of 6: 4 to obtain a sample copolymer (5).

The copolymers (3) to (5) were also subjected to a mortar test in the same manner, and the water reduction performance, retention performance, and viscosity were evaluated. The results are shown in Table 4.

From Tables 3 and 4, Example 2 using the polycarboxylic acid-based copolymer satisfying the requirements of the present invention was excellent in all of the initial viscosity, the viscosity with time, and the fluidity with time of the cement composition. Further, Example 2 in which the ratio of the structural unit (II) and the structural unit (III) was higher than that in Example 1 was further excellent in the effect of suppressing the increase in viscosity.

On the other hand, in Comparative Example 2 containing no structural unit (II) and structural unit (III), both the initial viscosity and the viscosity with time were poor.

Further, in Comparative Example 3 containing no structural unit (II), both the initial viscosity and the viscosity with time were poor as in Comparative Example 2.

Claims (9)

An additive for cement containing a polycarboxylic acid-based copolymer.
The polycarboxylic acid-based copolymer is
The following structural unit (I),
It contains the following structural unit (II) and a structural unit (III) derived from a carboxylic acid hydroxyalkyl ester-based monomer.
The structural unit (I) is 40 to 87% by mass with respect to a total of 100% by mass of the structural unit (I), the structural unit (II), and the structural unit (III), and the structural unit (II). ) Is 5 to 30% by mass, and the structural unit (III) is 10 to 30% by mass.

(In formula (I),
R ² represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.
R ³ , R ⁴ , and R ⁵ represent the same or different hydrogen atom or methyl group.
R ⁶ represents an alkylene group having 0 to 5 carbon atoms.
R ¹ O represents an oxyalkylene group having 2 to 18 carbon atoms, which is the same or different.
m is the average number of moles of oxyalkylene group represented by R ¹ O, and represents 5 to 300. )

(In formula (II),
R ⁷ , R ⁸ and R ⁹ are the same or different and represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms, or-(CH ₂ ) zCOM ² (provided that any one of R ⁷ to R ⁹ is used. One is-(CH ₂ ) zCOMM ² ),
z is an integer of 0 to 2 and
M ¹ and M ² are the same or different and represent a hydrogen atom, a monovalent metal, a divalent metal, an ammonium group, or an organic amine group ) . The cement additive according to claim 1, wherein either R ⁸ or R ⁹ in the formula (II) is COMM ² . The cement additive according to claim 1 or 2, wherein the alkylene group of R ⁶ has 1 or 2 carbon atoms in the formula (I). The cement additive according to any one of claims 1 to 3, wherein m is 5 to 100 in the formula (I). The cement additive according to any one of claims 1 to 4, wherein the carboxylic acid hydroxyalkyl ester-based monomer from which the structure (III) is derived is a (meth) acrylic acid hydroxyalkyl ester. A cement composition comprising cement, water, and the cement additive according to any one of claims 1-5. The cement composition according to claim 6, further comprising a cement dispersant. The cement composition according to claim 7, wherein the dispersant is at least one selected from the group consisting of a sulfonic acid-based dispersant, a polycarboxylic acid-based dispersant, and a phosphoric acid-based dispersant. The polycarboxylic acid-based dispersant is a dispersant containing a structural unit derived from an unsaturated (poly) alkylene glycol ether-based monomer.
The cement composition according to claim 8, wherein the dispersant containing a structural unit derived from the unsaturated (poly) alkylene glycol ether-based monomer contains a structural unit derived from acrylic acid.

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