WO2006129883A1

WO2006129883A1 - Powdery cement dispersant

Info

Publication number: WO2006129883A1
Application number: PCT/JP2006/311473
Authority: WO
Inventors: Hirokatsu Kawakami
Original assignee: Nippon Shokubai Co., Ltd.
Priority date: 2005-06-01
Filing date: 2006-06-01
Publication date: 2006-12-07
Also published as: CN101189197A; JP2008542159A

Abstract

The present invention provides a polycarboxylic acid type powdery cement dispersant having superior dispersing performance. The present invention provides a powdery cement dispersant which contains a polycarboxylic acid type copolymer having a repeating unit (I) derived from an unsaturated polyalkyleneglycol ether type monomer (a) and a repeating unit (II) derived from an unsaturated carboxylic acid type monomer (b) and having neutralization degree of carboxyl groups contained in the polycarboxylic acid type copolymer is not higher than 50%. The present invention also provides a powdery cement dispersant which comprises a polycarboxylic acid type copolymer comprising a repeating unit (I) derived from an unsaturated polyalkyleneglycol ether type monomer (a) and a repeating unit (II) derived from an unsaturated carboxylic acid type monomer (b), and the unsaturated polyalkyleneglycol ether type monomer (a) comprising an alkenyl group having 4 to 8 carbon atoms.

Description

DESCRIPTION POWDERY CEMENT DISPERSANT

Technical Field The present invention relates to a powdery cement dispersant, and in particular, relates to a powdery cement dispersant containing a polycarboxylic acid type polymer having a polyalkylene oxide moiety at the side chain part thereof.

Background Art

Concrete has become one of indispensable materials in the modern society, and widely used for a variety of applications such as buildings, houses, bridges and tunnels. Concrete is usually formed through hardening a concrete composition containing cement, water and aggregates . In the concrete composition, various admixtures in addition to these materials are incorporated in order to enhance various performances of concrete composition such as fluidity, air-entraining property and freezing and thawing resistance.

As one of admixtures, cement dispersant has been known.

Since a concrete with less water content generally has higher durability, a quantity of water to be incorporated in a concrete composition is preferably as low as possible. However, too small quantity of water to be incorporated cannot ensure sufficient fluidity of the concrete composition resulting in lowering in workability. Cement dispersant has a function to reduce a quantity of water to be incorporated in a concrete composition to contribute to solve this problem. As one of the cement dispersants, a polycarboxylic acid type cement dispersant containing a carboxylic acid or a salt thereof in a repeating unit of the polymer has been known. In addition, it has also been known that fluidity of cement paste can be improved by introducing a polyalkyleneoxide (PAO: -(AO)_n-) into a polycarboxylic acid type polymer. A polycarboxylic acid type cement dispersant introduced with a polyalkyleneoxide is more superior in cement dispersibility, fluidity of cement composition in fresh state, fluidity retention property, segregation resistance and hardened material strength expressing property, compared with conventional naphthalene type or melamine type cement dispersant.

The polycarboxylic acid type cement dispersant introduced with a polyalkyleneoxide can be classified into several types depending on a monomer to be used as a rawmaterial and bonding form of polyalkyleneoxide. These types include, for example, a polymer in which (meth) acrylic acid or a salt thereof is used as one of raw material monomers and polyalkyleneoxide is bonded via an ether linkage to a main chain of another raw material monomer (alkenyl PAO ether / acrylic acid structure: see the following formula (1), wherein COOY represents a carboxyl group or a salt thereof) , a polymer in which maleic acid, fumaric acid or a salt thereof is used as one of rawmaterial monomers and polyalkyleneoxide is bonded via an ether linkage to a main chain of another raw material monomer (alkenyl PAO ether / maleic acid sutructure: see the following formula (2)), and a polymer in which (meth) acrylic acid or a salt thereof is used as one of raw material monomers and polyalkyleneoxide is bonded via an ester linkage to a main chain of another rawmaterial monomer (PAO (meth) acrylate ester / (meth) acrylic acid structure: see the following formula (3)). Further, the various polymers canbe classified into acid type, monovalent metal salt type, 'divalent metal salt type, trivalent metal salt type, and the like depending on whether the carboxylic acid moieties remain carboxylic acids or become metal salts.

Conventionally, for example, JP-A-2000-26145 discloses monovalent metal salt type polymers of a PAO

(meth) acrylate ester / (meth) acrylic acid structure and a

PAO (meth) acrylate ester / alkenyl PAO ether / (meth) acrylic acid structure. Also, for example, JP-A-2002-167255 discloses monovalent metal salt type polymers of a PAO (meth) acrylate ester / (meth) acrylic acid structure and an alkenyl PAO ether / acrylic acid structure. Further, for example, JP-A-2002-167256 discloses divalent metal salt type polymers of a PAO (meth) acrylate ester / .(meth) acrylic acid structure and an alkenyl PAO ether / acrylic acid structure. Still further, for example, JP-A-9-309756 discloses a divalent metal salt type polymer of an alkenyl PAO ether / maleic acid structure. In order to improve characteristics of cement dispersant, a technique in which the polycarboxylic acid type polymer is added with another component has been proposed. For example, a cement dispersant, in which a polycarboxylic acid type polymer and PEG are mixed, has been disclosed (see, for example, JP-A-2000-26146) . Further, a cement composition, in which alkyleneoxide is incorporated to a polycarboxylic acid type polymer and a polyalkylenepolyamine by addition polymerization, has been disclosed (see, for example, JP-A-2000-109357 ) .

Disclosure of the Invention

The polycarboxylic acid type cement dispersant as described above is usually used in a liquid form. However, in view of transporting cost, etc., cement dispersant is preferably in a powdery state. Cement dispersant is also required to have high dispersibility . However, the conventional polycarboxylic acid type cement dispersant, in which a polyalkyleneoxide moiety is present in a polymer, tends to be waxy or syrupy even when water is removed, and is hardly pulverized.

Therefore, an object of the present invention is to provide a means to express superior dispersibility and to be easily pulverized in the polycarboxylic acid type cement dispersant . The present inventors have found, after intensive study on a way to solve the problems, that in a polycarboxylic acid type polymer with specific structure having a polyalkylene oxide moiety at the side chain thereof, by means of controlling neutralization degree of carboxyl groups contained in the copolymer to not higher than a predetermined value or adopting an unsaturated polyalkyleneglycol ether type monomer containing an alkenyl group having predetermined number of carbon atoms as a monomer generating a repeating unit in the copolymer, a solution containing a polycarboxylic acid type polymer, which has conventionally been difficult to be pulverized, can easily be pulverized without losing dispersing performance thereof, and have completed the present invention based on such knowledge.

Specifically, according to an aspect of the present invention, a powdery cement dispersant which contains a polycarboxylic acid type copolymer having a repeating unit (I) derived from an unsaturated polyalkyleneglycol ether type monomer (a) and a repeating unit (II) derived from an unsaturated carboxylic acid type monomer (b) and having neutralization degree of carboxyl groups contained in the polycarboxylic acid type copolymer is not higher than 50% is provided.

Further, according to another aspect of the present invention, a powdery cement dispersant containing a specific copolymer which shows excellent dispersibility and can be easily pulverized. Specifically, a powdery cement dispersant which contains a polycarboxylic acid type copolymer having a repeating unit (I) derived from an unsaturated polyalkyleneglycol ether type monomer (a) and a repeating unit (II) derived from an unsaturated carboxylic acid type monomer (b) , and the unsaturated polyalkyleneglycol ether type monomer (a) containing an alkenyl group having 4 to 8 carbon atoms is provided.

The other objects, features and .advantages of the present invention will become clear by referring to and consideration of the preferred embodiments exemplified in the following explanation.

Brief Description of the Drawings

Fig. 1 is a photograph showing a cement dispersant of the present invention produced in Example 2.

Fig. 2 is a photograph showing a starch syrup-like composition obtained by drying a polycarboxylic acid type polymer composition produced in Comparative Example 1.

Detailed Description of the Embodiment

As a method for pulverization of a polycarboxylic acid type cement dispersant, for example, a method for neutralization of a cement dispersant to convert a part of or all of the carboxylic acid groups to a metal salt form has been well-known. However, by the study result by the present inventors, it has been clarified that dispersing performance of a cement dispersant decreases with increase in proportion of metal salts in a polymer.

As a result of further study by the present inventors, it has been clarified that introduction of a polyalkylene oxide moiety by an ether bond into a polycarboxylic acid type polymer makes pulverization of the polymer easier even in acid form state. In addition, it has also been clarified that in the case when a part of the carboxyl groups in a polymer is neutralized, a polycarboxylic acid type powdery cement dispersant having superior dispersing property can be obtained, even when the neutralization degree is low. Mechanism thereof is not clear, but the ether bond is estimated to have certain effect on volatilization ofmoisture. However, the mechanism is only estimation and technical scope of the present invention should by no means be limited by this mechanism.

Next, detailed explanation is given on a cement dispersant of the present invention.

An aspect of the present invention is a powdery cement dispersant which contains a polycarboxylic acid type copolymer having a repeating unit (I) derived from an unsaturated polyalkyleneglycol ether type monomer (a) and a repeating unit (II) derived from an unsaturated carboxylic acid type monomer (b) and having neutralization degree of carboxyl groups contained in the polycarboxylic acid type copolymer is not higher than 50%.

The cement dispersant containing the polycarboxylic acid type copolymer as amain component can be easilypulverized from a solution in production, and has high dispersing performance .

Hereinbelow, this aspect will be explained by exemplifying the repeating unit (I) and the repeating unit (II) . The structure of the polycarboxylic acid type copolymer contained in the powdery cement dispersant in this aspect is, for example, represented by the following Chemical Formula 1. [Chemical Formula 1]

In the Chemical Formula 1, R¹ represents a hydrogen atom or a methyl group. R¹ is preferably a methyl group in view of copolymerizability of monomers.

In the Chemical Formula 1, R² represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. Said hydrocarbon group includes, for example, alkyl group, alkenyl group, aryl group and alkylphenyl group. Such alkyl group includes, for example, methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group and cyclohexyl group . Further, "alkenyl group" means a monovalent group represented by the general formula C_nH_2n-_I in which one hydrogen atom is removed from an optional carbon atom in an alkene . Such alkenyl group includes, for example, vinyl group, allyl group, propenyl group and isopropenyl group. Further, aryl group includes, for example, phenyl group and naphthyl group, and alkylphenyl group includes, for example, methylphenyl group and ethylphenyl group. In view of fluidity, R² is preferably a hydrogen atom or a methyl group.

In the Chemical Formula 1, each of R³ and R⁴ independently represents a hydrogen atom, a methyl group or -COOM², provided that a case where both of R³ and R⁴ are -COOM² is excluded. Further, R⁵ represents a hydrogen atom, a methyl group or -CH₂COOM³, provided that when R⁵ is -CH₂COOM³, each of R³ and R⁴ independently represents a hydrogen atom or a methyl group and does not represent -COOM². Further, in the Chemical Formula 1, each of M¹, M² and M³ independently represents a hydrogen atom, a metal atom, an ammonium group or an organic ammonium group. When M¹, M² or M³ is a metal atom, said metal atom may be any of monovalent, divalent and trivalent, and specifically, a suitable metal atom includes a monovalent metal atom like an alkali metal atom such as lithium, sodium and potassium; a divalent metal atom like an alkaline earth metal atom such as calcium and magnesium; and a trivalent metal atom such as aluminum and iron. Among them, from the viewpoint to improve easiness of pulverisation, M¹, M² or M³ is preferably a monovalent metal atom or a divalent metal atom. Further, the ammonium group is a functional group represented by "-NH₃ ⁺". And the organic ammonium group includes, for example, a residual group derived from organic amines like an alkanol amine such as monoethanolamine, diethanolamine and triethanolamine; an alkylamine such as monoethylamine, diethylamine and triethylamine; and a polyamine such as ethylenediamine and triethylenediamine .

When each of R³ and R⁴ is a hydrogen atom, the repeating unit (II-a) on the right side in the Chemical Formula 1 can be a moiety derived from acrylic acid (when R⁵ is a hydrogen atom) and methacrylic acid (when R⁵ is a methyl group) . Also, when R⁴ is a carboxyl group and R³ and R⁵ is a hydrogen atom, the repeating unit (II-a) on the right side in the Chemical Formula 1 can be a moiety derived from maleic acid and fumaric acid. Further, when R³ and R⁴ is a hydrogen atom and R⁵ is a -CH₂COOH group, the repeating unit (II-a) on the right side in the Chemical Formula 1 can be a moiety derived from itaconic acid. In the the Chemical Formula 1, AO represents an oxyalkylene group having 2 to 18 carbon atoms. "A" constituting such oxyalkylene group includes, for example, ethylene, group, trimethylene group, methylethylene group, ethylethylene group, phenylethylene group, tetramethylene group and 1, 2-dimethylethylene group. Namely, "AO" in the Chemical Formula 1 is an oxyalkylene group containing the above-described functional group (for example, oxyethylene group) . Among them, from the viewpoint of superior fluidity, A is preferably an ethylene group or a methylethylene group. Further, 2 or more different types of AO structures may optionally be present in a repeating unit represented by (AO) _n. However, in view of easiness in producing t.he polyoxyalkylene chain and controlling the structure thereof, the repeating structure represented by (AO)_n is preferably a repeated structure of the same AO unit.

In the Chemical Formula 1, R^a represents an alkylene group having 0 to 2 carbon atoms. Here, "an alkylene group having 0 carbon atom" means a structure in which 0(AO)_nR² directly binds to a carbon atom constructing a main chain without any moiety represented by R^a. Further, R^a having 1 carbon atom means a structure in which a carbon atom of a main chain and0 (AO) _nR² are connectedthrough amethylene group, and R^a having 2 carbon atoms means a structure in which a carbon atom of a main chain and 0(AO)_nR² are connected through an ethylene group or a methylmethylene group.

In the Chemical Formula 1, n means an average addition mole number of the oxyalkylene group represented by "AO", and is an integer of 2 to 300. From the viewpoints of superior fluidity and easiness in pulverization, n is preferably 10 to 200, and more preferably 20 to 150.

In view of easiness of pulverization, weight average molecular weight (as converted to polyethylene glycol) of a polycarboxylic acid type copolymer having a repeating unit represented by Chemical Formula 1 preferably be 1,000 to 500,000 and more preferably 5,000 to 100,000. In this connection, for measurement of the weight average molecular weight value, a method described in Examples below is used.

As a monomer forming a repeating unit (I-a) on the left side of the Chemical Formula 1, an alkylene oxide adduct compound of an unsaturated alcohol, obtained by adding 2 to

300 moles of alkylene oxides to an unsaturated alcohol such as vinyl alcohol, allyl alcohol, methallyl alcohol, isoprene alcohol (3-methyl-3-butene-l-ol) , and the like are included. Two or more kinds thereof may be used in combination. In addition, as a monomer forming a repeating unit (I-a) on the left side of the Chemical Formula 1 , a compound available on the market may be used, or a compound may be prepared by synthesis by oneself. In the synthesis, knowledge having already been obtained may be referred to, as appropriate. For example, in adding an alkylene oxide to an unsaturated alcohol, an alkylene oxide such as ethylene oxide, propylene oxide, butylene oxide, and the like may be added to an unsaturated alcohol such as allyl alcohol, methallyl alcohol, isopreήe alcohol (3-methyl-3-butene-l-ol) . Temperature condition in carrying out an addition reaction of an alkylene oxide is not especially limited, however, preferably be 80 to 155°C, and more preferably be 90 to 150⁰C.

As a monomer forming a repeating unit (II-a) on the right side of the Chemical Formula 1, acrylic acid, methacrylic acid, maleic acid, and the like are included. Two or more kinds thereof may be used in combination.

As a monomer forming a repeating unit (II-a) on the right side of the Chemical Formula 1 also, a compound available on the market may be used, or a compound may be prepared by synthesis by oneself.

Content ratio of a repeating unit (I-a) on the left side of .the Chemical Formula 1 to a repeating unit (II-a) on the right side of the Chemical Formula 1 is not especially limited but determined appropriately taking desired dispersibility etc. into consideration. The ratio (I-a) /(II-a) is preferably in the ranger of 50 - 99 / 50 - 1 % by mass, more preferably in the ranger of 60- 95/ 4 - 5% by mass, and further preferably in the ranger of 70 - 95/ 30 - 5 % by mass, based on the total amount 100 % by mass of the repeating units (I-a) and (II-a) .

In addition, content ratio of an oxyalkylene unit (hereinafter also referred to as a "AO unit (a)") contained in the repeating unit (I-a) to a carboxylic acid (salt) unit

(hereinafter also referred to as a "COOH unit (a) ") contained in the repeating unit (II-a) is not especially limited. However, tomake the cement dispersant expressing goodbalance between absorption performance by a carboxyl group and dispersing performance by a polyoxyalkylene moiety, ratio of total number of AO units (a) : total number of COOH units

(a) is preferably in the range of 1 : 1 to 50 : 1, more preferably in the range of 4:1 to 30:1, and further more preferably 7:1 to 25:1. Total numbers of AO units (a) and COOH units (a) can be calculated by ¹H-NMR method or alkalimetry.

In a polycarboxylic acid type copolymer having the repeating unit represented by Chemical Formula 1, repeating units other than the repeating unit (I-a) and the repeating unit (II-a) may also be contained. As a monomer forming these other repeating units, for example, an unsaturated sulfonic acid having a sulfonic acid group, such as

2- (meth) acrylamide-2-methylpropanesulfonic acid, 2-hydroxy-3-allyloxypropanesulfonic acid, sulfoethyl

(meth) acrylate, sulfopropyl (meth) acrylate and styrenesulfonic acid; monovalent metal salt, divalent metal salt, ammonium salt, or organic-ammonium salt thereof; an unsaturated amide such as (meth) acrylamide and (meth) acrylalkylamide; vinyl esters such as vinyl acetate and vinyl propionate; styrene derivatives such as styrene and bromostyrene, and the like are included. These repeating units may be present by obtaining via random polymerization, block polymerization, alternate polymerization, or the like. However, to make the cement dispersant expressing superior dispersing performance and easiness in pulverization in. producing, these two repeating units represented by the Chemical Formula 1 are preferably major repeating units of a polycarboxylic acid type copolymer. Specifically, the two essential repeating units described above are contained preferably in the range of 50 to 100% and more preferably 80 to 100% based on total number of repeating units in a polycarboxylic acid type copolymer.

In this connection, in a polycarboxylic acid type copolymer having a repeating unit represented by the Chemical Formula 1, the repeating unit (I-a), the repeating unit (II-a) and the other repeating units may be copolymerized in a block form, or may be copolymerized randomly, ormay be copolymerized alternately.

The polycarboxylic acid type copolymer, which is a main component of the powdery cement dispersant of the present invention, can easily be pulverized even in acid form state in which carboxyl groups are not being neutralized. In this case, a part of the carboxyl groups contained in the polycarboxylic acid type copolymer may be present as a salt form by neutralization. A counter ion generated by the neutralization is preferably a monovalent ion and more preferably sodium ion. When the counter ion is divalent (for example, calcium ion) , trivalent or more, the copolymer can suffer from the disadvantage of difficulty in dissolving in water constituting a concrete composition or a mortar composition which essentially contain water and cement when added into these compositions, and delay in expression of dispersing effect. In addition, when the cement dispersant is used in an agueous solution after transported to a work site in a powdery form, which is advantageous in transportation, the copolymer is hard to dissolve in water, which results indecrease ofworkability. On the contrary, decrease in ratio of the carboxyl groups by neutralization r.esults in decrease in dispersing performance as a cement dispersant . Therefore, ratio of a neutralized portion is preferably smaller. Specifically, the present copolymer has features in having neutralization degree determined by the following equation of not higher than 50%, and the neutralization degree is preferably not higher than 30%, andmore preferably not higher than 10% . By suppressingneutralization degree to a lowvalue, a cement dispersant having superior dispersing performance can be obtained. Among others, in view of cement dispersing property and easiness of pulverization, neutralization degree particularly is preferably 0%. That is, as a polycarboxylic acid type copolymer, one in which a neutralized carboxyl group is not present, namely a complete acid form is particularly preferably used.

Neutralization degree (%)= [j/(j+k)] *100

wherein j represents total number of carboxyl groups present in a salt form in the polycarboxylic acid type copolymer; and k represents total number of carboxyl groups present in a non-neutralized acid form in the polycarboxylic acid type copolymer.

In this connection, the neutralization degree can be measured by pH measurement or alkalimetry. In addition, when a repeating unit containing a carboxyl group is included, as other repeating units, such carboxyl groups contained in the other repeating units are also counted in calculation of the neutralization degree. Therefore, in carboxyl groups contained in other repeating units also, ratio of an acid form is preferably higher and ratio of a salt form is preferably- lower . A method for producing a copolymer, which is a main component of the powdery cement dispersant of the present invention, is not especially limited and the copolymer can be synthesized based on conventionally well-known knowledge . The copolymer may be synthesized based on newly obtained knowledge. As raw materials, monomers corresponding to the repeating units may be prepared.

A drying means to obtain the powdery cement dispersant of the present invention by drying to pulverize the copolymer is also not especially limited. The drying means may be selected depending on property of the copolymer. Such drying means for a solution containing the copolymer includes, for example, drying andpulverizationmethod, salting-out method, coagulating sedimentation method, freeze-drying method, coagulation cracking and drying method, spray dryer method, drum dryer method and belt dryer method. Among them, from the viewpoint to prevent thermal degradation of the copolymer, a drying means by which the polymer is less heated (for example, freeze-drying method) can be preferably used. In the freeze-drying method, for example, a solution containing the copolymer is rapidly cooled to freeze up using liquid nitrogen, etc. , and the frozen copolymer solution is subsequently dried under reduced pressure using a freeze-dry machine. By such procedures, fine particles having a particle size of, for example, around 40 nm to 500 μm can be obtained. Also, in the spray dryer method, the copolymer solution is atomized using a spray dryer, and mixed with hot air to dry in air. By such procedures, fine particles having a average particle size of, for example, not more than 100 μm can be obtained. Further, in the drum dryer method or the belt dryer method, the copolymer solution is dried to a film so that a film thickness becomes not more than 100 μm using a drum dryer or a belt dryer, then this film is crushed and classified. By these procedures, fine particles having a average particle size of, for example, not more than 300 μm can be obtained. In this connection, particle size of the fine particles obtained through pulverization by drying may be further adjusted using an optional crushing / classification means to obtain the powdery cement dispersant having a desired particle size.

Average particle size of the polycarboxylic acid type copolymer, which is a main component of the powdery cement dispersant of the present invention, is preferably 1 to 500 μm, and more preferably 10 to 100 μm. An average particle size less than 1 μmhas a risk that the powdery cement dispersant tends to cohere, whereas an average particle size over 500 μm could lead to decrease solubility to water and lower dispersibility to cement.

Another aspect of the present invention is a powdery cement dispersant which contains a polycarboxylic acid type copolymer having a repeating unit (I) derived from an unsaturated polyalkyleneglycol ether type monomer (a) and a repeating unit (II) derived from an unsaturated carboxylic acid type monomer (b) , and the unsaturated polyalkyleneglycol ether type monomer (a) containing an alkenyl group having 4 to 8 carbon atoms. In this aspect, the number of carbon atoms of the alkenyl group contained in the monomer (a) forming the repeating unit (I) is preferably in the range of 4 to 6, and more preferably in the range of 4 to 5 in view of polymerizability of the monomer and availability of raw material. Hereinbelow, this aspect will be explained by exemplifying the repeating unit (I) and the repeating unit (I.I) . The structure of the polycarboxylic acid type copolymer contained in the powdery cement dispersant in this aspect is, for example, represented by the following Chemical Formula

2.

[Chemical Formula 2]

The Chemical Formula 2 has the structure similar to the Chemical Formula 1.

In the Chemical Formula 2, R¹, R², AO, n, R³, R⁴, R⁵ and M¹ are the same as defined in the Chemical Formula 1. Therefore, detailed explanation thereof is omitted here . Of course, specific modes of a repeating unit on the right side of the Chemical Formula 2 are the same as the Chemical Formula 1. In the Chemical Formula 2, R^b represents an alkylene group having 1 to 2 carbon atoms. The specific mode of R^b is the same as the R^a in the Chemical Formula 1, and therefore detailed explanation thereof is omitted here.

A .monomer forming a repeating unit (I-b) on the left side of the Chemical Formula 2 can be obtained by adding 2 to 300 moles of alkylene oxides to an unsaturated alcohol such as methallyl alcohol or isoprene alcohol (3-methyl-3-butene-l-ol) and the like.

In addition, as a monomer forming a repeating unit (I-b) on the left side of the Chemical Formula 2 , a compound available on the market may be used, or a compound may be prepared by synthesis by oneself, which is the same as the Chemical Formula 1. In this aspect of the present invention, the neutralization degree of carboxyl groups contained in the polycarboxylic acid type copolymer is not especially limited. In this connection, the neutralization degree in this aspect of the present invention is preferably not more than 80 %, more preferably not more than 50 % , and further more preferably not more than 30 %.

Other specific modes except for the neutralization degree in the powdery cement dispersant in this aspect of the present invention are also the same as the powdery cement dispersant in the above aspect of the present invention.

Therefore, detailed explanation thereof is also omitted here .

Content ratio of a repeating unit (I-b) on the left side of the Chemical Formula 2 to a repeating unit (II-b) on the right side of the Chemical Formula 2 is not especially limited but determined appropriately taking desired dispersibility etc. into consideration. The ratio (I-b) /(II-b) is preferably in the ranger of 50 - 99 / 50 - 1 % by mass, more preferably in the ranger of 60- 95/ 4 - 5% by mass, and further preferably in the ranger of 70 - 95/ 30 - 5 % by mass, based on the total amount 100 % by mass ^■ of the repeating units (I-b) and (II-b) .

In addition, content ratio of an oxyalkylene unit (hereinafter also referred to as a "AO unit (b)") contained in the repeating unit (I-b) to a carboxylic acid (salt) unit

(hereinafter also referred to as a "COOH unit (b) ") contained in the repeating unit (II-b) is not especially limited.

However, to make the cement dispersant expressing good balance between absorption performance by a carboxyl group and dispersing performance by a polyoxyalkylene moiety, ratio of total number of AO units (b) : total number of COOH units (b.) is preferably in the range of 1:1 to 50:1, and more preferably in the range of 4:1 to 30:1, and further more preferably 7:1 to 25:1. Total numbers of AO units (b) and COOH units (b) can be calculated by ¹H-NMR method or alkalimetry. The above-described powdery cement dispersant of the present invention is used for the purpose of improving dispersibility of cement compositions such as cement paste, mortar and concrete by adding to these compositions. The dispersant can also be used for ultra-high strength concrete. In the cement composition, materials usually used such as cement, water, sand and coarse aggregate can be incorporated. In the cement composition, fine particles such as fly ash, blast-furnace slag, silica fume and lime stone may be added. In this connection, super-high strength concrete means a concrete which is generally so termed, that is, a concrete whose hardened material shows equivalent or higher strength compared with the conventional concrete even when ratio of water / cement is reduced compared with the conventional concrete. For example, super-high strength concrete is a concrete which has workability not to have a problem for usual use and of which hardened material has compressive strength of preferably not less than 60 N/mm², more preferably not less than 80 N/.mm², further more preferably not less than 100 N/mm², still further more preferably not less than 120 N/mm², particularly preferably not less than 160 N/mm², and most preferably not less than 200 N/mm², even when ratio of water / cement is preferably not more than 25% by mass, more preferably not more than 20% by mass, further more preferably, not more than 18% by mass, particularly preferably not more than 14% by mass, and most preferably not more than 12% by mass .

As the cement, Portland cement suc.h as common, high early-strength, super early-strength, rapid hardening hydraulic, moderate-heat and white; mixed Portland cement such as alumina cement, fly ash cement, slag cement and silica cement are suitable. Amount of the cement to be incorporated and unit water quantity per 1 m³ of concrete are as follows. For example, for producing high durability and high-strength concrete, preferably unit water quantity is 100 to 185 kg/m³ and ratio of water / cement = 10 to 70%. More preferably, unit water quantity is 120 to 175 kg/m³ and ratio of water / cement = 20 to 65%.

When the powdery cement dispersant of the present invention is used, amount of the powdery cement dispersant of the present invention to be added to cement composition is preferably adjusted so that an amount of the powdery cement dispersant of the present invention becomes 0.01 to 1.0% by mass to 100% by mass of cement composition. When addition amount of the powdery cement dispersant is less than 0.01% by mass, performance thereof could be insufficient, and when the addition amount is over 1.0% bymass, economical efficiency thereof could be decreased without an improvement in dispersibility corresponding to increase in addition amount. Further, addition amount of the powdery cement dispersant is more preferably 0.05 to 0.5% by mass, and further more preferably 0.1 to 0.3% by mass to 100% by mass of cement composition. In this connection, the unit of % bymass means a value reduced to solid content.

The powdery cement dispersant of the present invention is added to a cement composition, and the powdery cement dispersant of the present invention may be added to a cement composition in combination of 2 or more members thereof. In the cement composition, another additive may be incorporated. Fςr example, in addition to the powdery , cement dispersant of the present invention, another cement dispersant, air-entraining agent, cement moistening agent, swelling agent, waterproof agent, retardant, quick-setting agent, water-soluble polymer material, thickening agent, flocculating agent, dry shrinkage reducing agent, strength enhancing agent, hardening accelerator, antifoaming agent, and the like can be added in a cement composition.

Suitable embodiment of a combination of the powdery cement dispersant of the present invention and another additive includes the following (1) to (7) .

(1) Combination containing, as essential components, <1> the powdery cement dispersant of the present invention and <2> oxyalkylene type antifoaming agent . As an oxyalkylene type antifoaming agent, polyoxyalkylenes, polyoxyalkylene alkyl ethers, polyoxyalkylene acetylene ethers, polyoxyalkylene alkylamines, and the like can be used. Among them, polyoxyalkylene alkylamines are particularly suitable . Incorporating ratio by mass of <2> oxyalkylene type antifoaming agent is preferably in a range of 0.01 to 20% by mass to 100% by mass of <1> the powdery cement dispersant.

(2) Combination containing, as essential components, 3 components of <1> the powdery cement dispersant of the present invention, <2> oxyalkylene type antifoaming agent and <3> AE agent. As an oxyalkylene type antifoaming agent, polyoxyalkylenes, polyoxyalkylene alkyl ethers, polyoxyalkylene acetylene ethers, polyoxyalkylene alkylamines, and the'- like can be used. Among them, polyoxyalkylene alkylamines are particularly suitable. As an AE agent, rasinate soap, alkylsulfonate esters and alkyl phosphate esters are particularly suitable. Incorporating ratio by mass of <2> oxyalkylene type antifoaming agent is preferably in a range of 0.01 to 20% by mags to 100% by mass of <1> the powdery cement dispersant. Incorporating ratio by mass of <3> AE agent is preferably in a range of 0.001 to 2% by mass to 100% by mass of cement composition.

(3) Combination containing, as essential components, 3 components of <1> the powdery cement dispersant of the present invention, <2> a copolymer composed of a polyalkyleneglycol mono (meth) acrylate type monomer having a polyoxyalkylene chain added with an alkyleneoxide having 2 to 18 carbon atoms in an average addition mole number of 2 to 300, (meth) acrylic acid type monomer and a monomer copolymerizable with these monomers (disclosed in JP-B-59-18338, JP-A-7-223852, JP-A-9-241056, etc.), and <3> an oxyalkylene type antifoaming agent . Incorporating ratio by mass of <1> the powdery cement dispersant and <2> a copolymer is preferably in a range of 5/95 to 95/5 (powdery cement dispersant / copolymer) , and more preferably in a range of 10/90 to 90/10. Incorporating ratio of <3> an oxyalkylene type antifoaming agent is preferably in a range of 0.01 to 20% by mass to 100% by mass in total of <1> the powdery cement dispersant and <2> a copolymer.

(4) Combination containing, as essential components, 2 components of <1> the powdery cement dispersant of the present invention and <2> a retardant. As a retardant, oxycarboxylic acids such as gluconic acid (salt thereof) and citric acid - (salt thereof) ; sucharides such as glucose; sugar alcohols such as sorbitol; and phosphonic acids such as amino-tri- (methylenephosphonic acid) can be used. Incorporating ratio by mass of <1> the powdery cement dispersant and <2> a retardant is preferably in a range of 50/50 to 99.9/0.1 (powdery cement dispersant / retardant), and more preferably in a range of 70/30 to 99/1.

(5) Combination containing, as essential components, 2 components of <1> the powdery cement dispersant of thepresent invention and <2> a accelerator. As an accelerator, soluble calcium salts such as calcium chloride, calcium nitrite and calcium nitrate; chlorides such as ferric chloride and magnesium chloride; thiosulfate salts; formic acid; and formate salts such as calcium formate can be used. Incorporating ratio by mass of <1> the powdery cement dispersant and <2> an accelerator is preferably in a range of 10/90 to 99.9/0.1 (powdery cement dispersant / accelerator) , and more preferably in a range of 20/80 to 99/1.

(6) Combination containing, as essential components, 2 components of <1> the powdery cement dispersant of the present invention and <2> a material separation reducing agent. As a material separation reducing agent, various thickening agents such as nonionic cellulose ethers and a compound having a hydrophobic substituent consisting of a hydrocarbon chain having 4 to 30 carbon atoms and a polyoxyalkylene chain added with an alkyleneoxide having 2 to 18 carbon atoms in an average addition mole number of 2 to 300 as partial structures, and the like can be used. Incorporating ratio by mass of <1> the powdery cement dispersant and <2> a material separation reducing agent is preferably in a range of 10/90 to 99.99/0.01 (powdery cement dispersant / material separation reducing agent) , and more preferably in a range of 50/50 to 99.9/0.1. A cement composition having this combination is suitable for high-flow concrete, self-compacting concrete and self-leveling material.

(7) Combination containing, as essential components, 2 components of <1> the powdery cement dispersant of the present invention and <2> a sulfonic acid type dispersant having a sulfonic acid group in a molecule. As a sulfonic acid type dispersant, lignin sulfonate salt, naphthalenesulfonic acid - formalin condensate, melaminesulfonic acid - formalin condensate, polystyrenesulfonate salt, aminosulfonic acid type dispersant such as aminoarylsulfonic acid - phenol - formaldehyde condensate, and the like can be used. Incorporating ratio by mass of <1> the powdery cement dispersant and <2> a sulfonic acid type dispersant is preferably in a range of 5/95 to 95/5 (powdery cement dispersant / sulfonic acid type dispersant) , and more preferably in a range of 10/90 to 90/10. Method for preparing the concrete composition is not particularly limited, and the similar method to that for the conventional cement composition can be used. For example, a method by which the powdery cement dispersant of the present invention and cement are mixed, and other incorporating materials are further mixed, if necessary, followed by addition of water and mixing; a method by which a solution containing the cement dispersant is prepared by dissolving the cement dispersant of the present invention in advance, and the solution is added and mixed to a composition containing cement and other incorporating materials, and the like are included.

EXAMPLES

Hereinafter, the present invention is explained inmore detail by using Examples, but the technical scope of the present invention is not limited only to the following Examples. In this connection, in the Examples described below, measurement of weight average molecular weight of a polycarboxylic acid type copolymer was conducted by GPC under the measuring conditions described below.

Model of apparatus: Waters LCMl;

Detector: Waters 410 Differential Refraction Detector;

Analysis Software: Waters Millennium Ver. 2.18;

Eluent : Eluent prepared by dissolving 115.6 g of sodium acetate trihydrate in a mixture of 10, 999 g of water and 6, 001 g of acetonitrile, and adjusting to pH 6 with a 30% sodium hydroxide aqueous solution;

Flow rate of eluent: 0.8 ml/min;

Column temperature: 35°C;

Column : TSKgel Guardcolumn SWXL + G4000SWXL + G3000SWXL + G2000SWXL produced from Tosoh Corp; and

Standard substance: Polyethylene glycol, weight average molecular weight (Mw): 272,500, 219,300, 85,000, 46,000, 24,000, 12,600, 4,250, 7,100 and 1,470.

Example 1-1

A glass reactor equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen introducing tube and a reflux condenser was prepared. Into this reactor, 76.91 g of water and 149.28 g of an unsaturated polyalkyleneglycol ether obtained by adding 50 moles, in average, of ethylene oxide (EO) to 3-methyl-3-butene-l-ol (3M3B1O) , as a monomer forming a repeating unit (I-a) in the Chemical Formula 1 or a repeating unit (I-b) in the Chemical Formula 2, were charged, and after replacing inside the reactor with nitrogen gas under stirring the aqueous solution, the solution was heated up to 60°C under nitrogen atmosphere . After inner temperature was stabilized at 60°C, an aqueous solution of hydrogen peroxide composed of 0.23 g of hydrogen peroxide and 11.71 g of water was added. Then, 20.17 g of acrylic acid (AA), as a monomer forming a repeating unit (II-a) in the Chemical Formula 1 or a repeating unit (II-b) in the Chemical Formula 2, and an aqueous solution dissolved with 0.3 g of L-ascorbic acid and 0.79 g of 3-mercaptopropionic acid into 40.74 g of water were dropped over 3 hours and 3.5 hours, respectively. Subsequently, by maintaining temperature of the polymerization reaction solution at 60⁰C, the polymerization reaction was continued for another 1 hour. After completion of the polymerization, a reaction product was diluted with water so that the solid content concentration is adjusted at 40% by mass to obtain an aqueous solution (1-1) . Weight average molecular weight

(Mw) of the polycarboxylic acid type copolymer (1-1) in the resultant aqueous solution (1-1) was 37,000 and pH of the aqueous solution (1-1) was 3.4. Polymer content was measured by GPC tobe 90% . In this connection, as for calculationmethod, the polymer content was calculated by the method in which an area corresponding to the polymer component obtained by a GPC chart was divided by the sum of the area corresponding to the polymer component and the area corresponding to the residual unsaturatedpolyalkyleneglycol ether component . In addition, ratio of total number of AO units ( (a) or (b) ) and total number of COOH units ( (a) or (b) ) in the polycarboxylic acid type copolymer (1-1) was calculated. As a result, the ratio was proved to be 10.5:1. In the meantime, the ratio was calculated according to following equations.

Total number of AO units = l^χm^χn =149.28/2286x90x50=293.86 Total number of COOH units = pxq =20.17/72x100=28.01 wherein, 1 represents a mole number of the unsaturated polyalkyleneglycol ether which is a monomer forming the repeating unit (I-a) or (I-b), m represents a polymerization ratio (%) of the unsaturated polyalkyleneglycol ether, and n represents an average addition mole number of ethylene oxide in the unsaturated polyalkyleneglycol ether. Further, p represents a mole number of the acrylic acid which is a monomer forming the repeating unit (II-a) or (II-b), and q represents a polymerization ratio (%) of the acrylic acid.

Using the aqueous solution (1-1) obtained as described above, pulverization was attempted as described later to evaluate whether the solution was pulverizable or not.

Example 1-2

By adjusting pH of the aqueous solution (1-1) obtained in the Example 1-1 with sodium hydroxide up to 5.0 ± 0.5, an aqueous solution (1-2) was obtained. Neutralizaiton degree of the polycarboxylic acid type copolymer (1-2) in the resultant aqueous solution (1-2) was 30%.

Using the aqueous solution (1-2) obtained as described above, pulverization was attempted as described later to evaluate whether the solution was pulverizable or not.

Example 1-3

By adjusting pH of the aqueous solution (1-1) obtained in the Example 1-1 with sodium hydroxide up to 6.5 ± 0.5, an aqueous solution (1-3) was obtained. Neutralizaiton degree of the polycarboxylic acid type copolymer (1-3) in the resultant aqueous solution (1-3) was 80%.

Using the aqueous solution (1-3) obtained as described above, pulverization was attempted as described later to evaluate whether the solution was pulverizable or not.

Example 1-4

By adjusting pH of the aqueous solution (1-1) obtained in the Example 1-1 with calcium hydroxide up to 6,5 ± 0.5, an aqueous solution (1-4) was obtained. Neutralizaiton degree of the polycarboxylic acid type copolymer (1-4) in the resultant aqueous solution (1-4) was 80%.

Using the aqueous solution (1-4) obtained as described above, pulverization was attempted as described later to evaluate whether the solution was pulverizable or not.

Example 2 A glass reactor equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen introducing tube and a reflux condenser was prepared. Into this reactor, 64.62 g of water and 120.00 g of an unsaturated polyalkyleneglycol ether obtained by adding 20 moles, in average, of ethylene oxide (EO) to 3-methy-3-butene-l-ol (3M3B1O), as a monomer forming an repeating unit (I-a) in the Chemical Formula 1 or a repeating unit (I-b) in the Chemical Formula 2, were charged, and after replacing inside the reactor with nitrogen gas under stirring the aqueous solution, the solution was heated up to 58 °C under nitrogen atmosphere . After inner temperature was stabilized at 58 °C, an aqueous solution of hydrogen peroxide composed of 0.60 g of hydrogen peroxide and 29.32 g of water was added. Then, an aqueous solution composed of 22.74 g of acrylic acid (AA), as a monomer forming a repeating unit (II-a) in the Chemical Formula 1 or a repeating unit (II-b) in the Chemical Formula 2, and 9.74 g of water, along with an aqueous solution dissolved with 0.78 g of L-ascorbic acid and 0.65 g of 3-mercaptopropionic acid into 51.55 g of water were dropped over 3 hours and 3.5 hours, respectively. Subsequently, by maintaining temperature of the polymerization reaction solution at 58°C, the polymerization reaction was continued for another 1 hour. After completion of the polymerization, solid content concentration of the reaction solution was 49% by mass. The reaction solution was named as an aqueous solution (2) . Weight average molecular weight of the polycarboxylic acid type copolymer (2) in the resultant aqueous solution (2) was 31, 000 and pH of the aqueous solution ( 2 ) was 3 . 2 .

Using the aqueous solution (2) obtained as described above, pulverization was attempted as described later to evaluate whether the solution was pulverizable or not.

Example 3

A glass reactor equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen introducing tube and a reflux condenser was prepared. Into this reactor, 150.00 g of water and 100.00 g of an unsaturated polyalkyleneglycol ether obtained by adding 150 moles, in average, of ethylene oxide (EO) , to a methallyl alcohol (MTA) as a monomer forming a repeating unit (I-a) in the Chemical Formula 1 or a repeating unit (I-b) in the Chemical Formula 2, were charged, and after replacing inside the reactor with nitrogen gas under stirring the aqueous solution, the solution was heated up to 60°C under nitrogen atmosphere . After inner temperature was stabilized at 60°C, an aqueous solution of hydrogen peroxide composed of 0.07 g of hydrogen peroxide and 3.37 g of water was added. Then, an aqueous solution composed of 6.21 g of acrylic acid (AA), as a monomer forming a repeating unit (II-a) in the Chemical Formula 1 or a repeating unit (II-b) in the Chemical Formula 2 , and 4.14 g of water, along with an aqueous solution dissolved with 0.09 g of L-ascorbic acid and 0.16 g of 3-mercaptopropionic acid into 12.26 g of water, were dropped over 3 hours and 3.5 hours, respectively. Subsequently, by- maintaining temperature of the polymerization reaction solution at 60°C, the polymerization reaction was continued for another 1 hour. After completion of the polymerization, solid content concentration of the reaction solution was 39% by mass. The reaction solution was named as an aqueous solution (3). Weight average molecular weight of the polycarboxylic acid type copolymer (3) in the resultant aqueous solution (3) was 69, 000 and pH of the aqueous solution (3) was 3.9.

Using the aqueous solution (3) obtained as described above, pulverization was attempted as described later to evaluate whether the solution was pulverizable or not.

Example 4

A glass reactor equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen introducing tube and a reflux condenser was prepared. Into this reactor, 144.34 g of water, 217.46 g of an unsaturated polyalkyleneglycol ether obtained by adding 50 moles, in average, of ethylene oxide (EO) to 3-methy-3-butene-l-ol (3M3B1O), as a monomer forming a repeating unit (I-a) in the Chemical Formula 1 or a repeating unit (I-b) in the Chemical Formula 2, and 22.53 g of maleic acid (MA) , as a monomer forming a repeating unit (II-a) in the Chemical Formula 1 or a repeating unit (II-b) in the Chemical Formula 2, were charged, and after replacing inside the reactor with nitrogen gas under stirring the aqueous solution, the solution was heated up to 63°C under nitrogen atmosphere. After inner temperature was stabilized at 63°C, an aqueous solution of hydrogen peroxide composed of 0.20 g of hydrogen peroxide and 0.46 g of water was added. Then, an aqueous solution composed of 14.75 g of water dissolved with 0.26 g of L-ascorbic acid was dropped over 1 hour. Subsequently, by maintaining temperature of the polymerization reaction solution at 63°C, the polymerization reaction was continued for another 1 hour. After completion of the polymerization, solid content concentration of the reaction solution was 60% by mass . The reaction solution was named as an aqueous solution (4) . Weight .average molecular weight of the polycarboxylic acid type copolymer (4) in the resultant aqueous solution (4) was 29, 000 and pH of the aqueous solution (4) was 2.7.

Using the aqueous solution (4) obtained as described above, pulverization was attempted as described later to evaluate whether the solution was pulverizable or not.

Example 5

A glass reactor equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen introducing tube and a reflux condenser was prepared. Into this reactor, 76.91 g of water and 149.28 g of an unsaturated polyalkyleneglycol ether obtained by adding 50 moles, in average, of ethylene oxide (EO) to allyl alcohol (ALA) , as a monomer forming a repeating unit (I-a) in the Chemical Formula 1, were charged, and after replacing inside the reactor with nitrogen gas under stirring the aqueous solution, the solution was heated up to 60⁰C under nitrogen atmosphere . After inner temperature was stabilized at 60⁰C, an aqueous solution of hydrogen peroxide composed of 0.23 g of hydrogen peroxide and 11.71 g of water was added. Then, 20.17 g of acrylic acid (AA), as a monomer forming a repeating unit (II-a) in the Chemical Formula 1, and an aqueous solution dissolved with 0.3 g of L-ascorbic acid and 0.79 g of 3-mercaptopropionic acid into 40.74 gof water were dropped over 3 hours and 3.5 hours, respectively. Subsequently, by maintaining temperature of the polymerization reaction solution at 60°C, the polymerization reaction was continued for another 1 hour. After completion of the polymerization, a reaction product was diluted with water so that the solid content concentration is adjusted at 40% by mass to obtain an aqueous solution (5) . Weight averagemolecular weight (Mw) of the polycarboxylic acid type copolymer (.5) in the resultant aqueous solution (5) was 16, 000 and pH of the aqueous solution (5) was 3.4. Polymer content was measured by GPC to be 53%. In addition, according to the same procedure as the Example 1-1, ratio of total number of AO units (a) and total number of COOH units (a) in the polycarboxylic acid type copolymer (5) was calculated. As a result, the ratio was proved to be 6.3:1. Using the aqueous solution (5) obtained as described above, pulverization was attempted as described later to evaluate whether the solution was pulverizable or not.

Comparative Example 1

A glass reactor equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen introducing tube and a reflux condenser was prepared. Into this reactor, 100.01 g of water was charged, and after replacing inside the reactor with nitrogen gas under stirring the water, the solution was heated up to 80°C under nitrogen atmosphere . After inner temperature was stabilized at 80°C, 169.99 g of an aqueous monomer solution obtained by mixing 112.59 g of methoxypolyethyleneglycol monomethacrylate (MPEGMA; average addition mole number of ethylene oxide: 25), 22.41 g of methacrylic acid (MAA), 33.40 g of water and 1.24 g of 3-mercaptopropionic acid, along with 30 g of an, aqueous solution dissolved with 1.55 g of ammonium persulfate were dropped over 4 hours and 5 hours, respectively. Subsequently, by maintaining temperature of the polymerization reaction solution at 80°C, the polymerization reaction was continued for another 1 hour. After completion of the polymerization, solid content concentration of the reaction solution was 47% by mass . The reaction solution was named as an aqueous solution (A) . Weight average molecular weight of the polycarboxylic acid type copolymer (A) in the resultant aqueous solution (A) was 23, 000 and pH of the aqueous solution (A) was 2.2.

Using the aqueous solution (A) obtained as described above, pulverization was attempted as described later to evaluate whether the solution was pulverizable or not.

Comparative Example 2

A glass reactor equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen introducing tube and a reflux condenser was prepared. Into this reactor, 99.52 g of water was charged, and after replacing inside the reactor with nitrogen gas under stirring the water, the solution was heated up to 70 °C under nitrogen atmosphere . After inner temperature was stabilized at 70°C, 170.48 g of an aqueous monomer solution obtained by mixing 106.68 g of methoxypolyethyleneglycol monomethacrylate (MPEGMA; average addition mole number of ethylene oxide: 10), 28.32 g of methacrylic acid (MAA), 33.31 g of water and 1.73 g of 3-mercaptopropionic acid, along with 30 g of an aqueous solution dissolved with 1.55 g of ammonium persulfate were dropped over 4 hours and 5 hours, respectively. Subsequently, by maintaining temperature of the polymerization reaction solution at 70°C, the polymerization reaction was continued for another 1 hour. After completion of the polymerization, a reaction product was diluted with water and solid content concentration of the reaction solution was adjusted at 40% by mass to obtain an aqueous solution (B) . Weight averagemolecular weight of a polycarboxylic acid- type copolymer (B) in the resultant aqueous solution (B) wasl4,000 and pH of the aqueous solution (B) was 3.9.

Using the aqueous solution (B) obtained as described above, pulverization was attempted as described later to evaluate whether the solution was pulverizable or not. Pulverization Test

Using aqueous solutions (1-1 to 1-4, 2 to 5, A, and B) obtained in each of the Examples and Comparative Examples, pulverization tests were conducted by the following procedures.

Each of the aqueous solutions was supplied to a glass-made petri dish having a diameter of 13 cm so that solid content became 20 g after drying. The solution was left to stand for 24 hours under an environment of 50⁰C and 50 Torr (about 6.7 x 10³ Pa) to remove water. After drying, the solid was left to stand for one day in a desiccator, and a resultant product was pulverized in a mortar. The pulverized powder was passed through a sieve of 16 meshes to obtain a powdery cement dispersant having a certain particle size distribution.

It was evaluated whether each of the above solutions can be pulverized or not by the above process. The results of evaluation are shown in the following Table 1. The evaluation was conducted according to the following criteria : O: A powdery cement dispersant having a fluidity was obtained;

X : Solid became a syrupy or a sticky film and could not be pulverized.

[Table 1]

Ul

As shown in the Table 1, in a polycarboxylic acid type copolymer having a polyalkylene oxide moiety as a main component of a cement dispersant, it is shown that by suppressing neutralization degree of carboxyl groups contained in the copolymer to a low level, an aqueous solution containing the copolymer can be easily pulverized by drying, and a powdery cement dispersant can be obtained.

In this connection, for reference, a photograph of a powder obtained by drying the resultant aqueous solution (2) in the Example 2 is shown in Fig.1. In addition, a photograph of a starch syrup-like composition obtained by drying the resultant aqueous solution (B) in the Comparative Example 1 is shown in Fig. 2.

Mortar Test

For the purpose of studying a dispersibility of the powdery cement dispersant of the present invention, mortar tests were conducted by adding powdery cement dispersants obtained by pulverizing the aqueous solution (1-1) to (1-4) and the aqueous solution (5) obtained in the Example 1-1 to 1-4 and the Example 5 were added to mortar, respectively. The mortar composition was as described below. TAIHEIYO ordinary Portland cement: 900 g Standard sand defined by JIS R 5201: 1,350 g Water: 270 g

Mortar flow was measured according to the flow test of JIS R 5201 by using a mixer and a mixing method similar to a mixing method according to Item 10.4.3 in JIS R 5201. In the connection, powdery cement dispersants were incorporated into the mortar compositions before mixing . The measurement results are shown in the following Table 2. In the Table 2, the addition amounts of the powdery cement dispersant is shown based on % based on cement as converted to solid content.

[Table 2]

As shown in the Table 2, the powdery cement dispersant (1-1) derived from Example 1-1, in which the copolymer is not neutralized and the powdery cement dispersant (1-2) derived from Example 1-2, which has a neutralization degree as low as 30% provide higher flow value compared with that of the powdery cement dispersant (1-3), which has a neutralization degree as high as 80%. Namely, the powdery cement dispersant (1-1) of Example 1-1 and the powdery cement dispersant (1-2) of Example 1-2 are found to provide higher cement dispersing property compared with that of the cement dispersant (1-3) of Example 1-3.

In addition, the cement dispersant (1-3) of Example 1-3 is found to provide higher cement dispersing property compared with that of the cement dispersant (1-4) of Example 1-4. It is expected that this is because sodium ion has greater ability to cause high solubility of the copolymer than calcium ion. Furthermore, the cement dispersant (1-1) of Example 1-1 is found to provide higher cement dispersing property compared with that of the cement dispersant (5) of Example 5. It is expected that this is because the cement dispersant (5) has polymer content at. lower level than the cement dispersant (1-1), which results in a decrease in content of active ingredient .

The present application is based on Japanese patent application No. 2005-162049, filed on June 1, 2005, whose disclosure content is incorporated herein by reference as its entirety.

Claims

1. A powdery cement dispersant which comprises a polycarboxylic acid type copolymer comprising a repeating unit (I) derived from an unsaturated polyalkyleneglycol ether type monomer (a) and a repeating unit (II) derived from an unsaturated carboxylic acid type monomer (b) and having neutralization degree of carboxyl groups contained in the polycarboxylic acid type copolymer is not higher than 50%.

2. A powdery cement dispersant according to claim 1, wherein the polycarboxylic acid type copolymer comprises a repeating unit represented by the following Chemical Formula

1:

[Chemical Formula 1]

wherein R¹ represents a hydrogen atom or a methyl group, R² represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, each of AO independently represents^' an oxyalkylene group having 2 to 18 carbon atoms, R^a represents an alkylene group having 0 to 2 carbon atoms, n represents an average addition mole number of an oxyalkylene group and is 2 to 300, each of R³ and R⁴ independently represents a hydrogen atom, a methyl group or -COOM² (provided that a case where both of R³ and R⁴ are -COOM² is excluded) , R⁵ represents a hydrogen atom, a methyl group or -CH₂COOM³ (provided that when R⁵ is -CH₂COOM³, each of R³ and R⁴ independently represents a hydrogen atom or a methyl group) , and each of M¹, M² and M³ independently represents a hydrogen atom, a metal atom, an ammonium group or. an organic ammonium group.

3. A powdery cement dispersant according to claim 1 or

2, wherein the R¹ is a methyl group.

4. A powdery cement dispersant of any one of claims 1 to

3, wherein the R³, the R⁴ and the R⁵ are hydrogen atoms.

5. A powdery cement dispersant of any one of claims 1 to

4, wherein the A is an ethylene group or a methylethylene group.

6. A powdery cement dispersant of any one of claims 1 to

5, wherein the neutralization degree is 0%.

7. A powdery cement dispersant which comprises a polycarboxylic acid type copolymer comprising a repeating unit (I) derived from an unsaturated polyalkyleneglycol ether type monomer (a) and a repeating unit (II) derived from an unsaturated carboxylic acid type monomer (b) , and the unsaturated polyalkyleneglycol ether type monomer (a) comprising an alkenyl group having 4 to 8 carbon atoms.

8. A powdery cement dispersant according to claim 7, wherein the polycarboxylic acid type copolymer comprises a repeating unit represented by the following Chemical Formula 2:

[Chemical Formula 2]

wherein R¹ represents a hydrogen atom or a methyl group, R² represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, R^b represents an alkylene group having 1 to 2 carbon atoms, each of AO independently represents an oxyalkylene group having 2 to 18 carbon atoms, n represents an. average addition mole number of an oxyalkylene group and is 2 to 300, each of R³ andR⁴ independently represents a hydrogen atom, a methyl group or -COOM² (provided that a case where both of R³ and R⁴ are -COOM² is excluded) , R⁵ represents a hydrogen atom, a methyl group or -CH₂COOM³ (provided that when R⁵ is -CH₂COOM³, each of R³ and R⁴ independently represents a hydrogen atom or a methyl group) , and each of M¹, M² and M³ independently represents a hydrogen atom, a metal atom, an ammonium group or an organic ammonium group.