JP7650820B2 - Cement Additives - Google Patents

Description

The present invention relates to a cement additive. More specifically, the present invention relates to a cement additive that can be suitably used in cement compositions, etc.

Polycarboxylic acid copolymers having polyalkylene glycol on the side chain of a polycarboxylic acid such as poly(meth)acrylic acid have become indispensable for constructing civil engineering and architectural structures from cement compositions such as cement paste, mortar, and concrete due to their excellent cement dispersing performance.
Cement admixtures containing such copolymers are used as water reducing agents, etc., and have the effect of improving the strength, durability, etc. of the hardened product by increasing the fluidity of the cement composition and reducing the water in the cement composition. Conventionally, naphthalene-based water reducing agents have been used as water reducing agents, but compared to these, cement additives containing copolymers such as polycarboxylic acid-based copolymers as the main component can exhibit high water reducing performance, and have been widely used as high-performance air-entraining water reducing agents.

Such cement additives are required not only to improve the initial dispersibility of cement but also to maintain the fluidity of cement for a long period of time, and various polycarboxylic acid copolymers have been developed so far. For example, Patent Documents 1 and 2 disclose a hydraulic composition dispersant containing a copolymer obtained by polymerizing a monomer containing a monomer 1 represented by a specific structure and a monomer 2 represented by a specific structure, and a monomer 3 represented by a specific structure, in which the ratios of the monomer 1, monomer 2, and monomer 3 among the constituent monomers of the copolymer are each within a specific range. Patent Document 3 discloses a dispersion-retaining agent for hydraulic compositions, which is composed of a copolymer having a weight-average molecular weight of 30,000 to 60,000 obtained by polymerizing a monomer 1 represented by a specific structure, a monomer 2 represented by a specific structure, and a monomer 3 represented by a specific structure, in which at least a part of the monomer 2 satisfies a predetermined relationship, and among the constituent monomers of the copolymer, the monomer 1 is 25 to 78% by weight and the monomer 3 is 0 to 18% by weight.

JP 2009-096672 A JP 2009-173527 A JP 2009-221025 A

However, conventional polycarboxylic acid copolymers did not have sufficient fluid retention. Furthermore, in recent years, due to the problem of depletion of natural aggregate resources, low-quality aggregates are sometimes used as concrete materials. In such cases, the viscosity of the cement composition, such as its plastic viscosity and yield value, increases, causing problems such as reduced workability in construction. For this reason, there is also a demand for reducing the viscosity of cement compositions.

The present invention has been made in consideration of the above-mentioned current situation, and aims to provide a cement additive that can improve the fluidity retention of cement and reduce the viscosity of cement.

The inventors conducted extensive research into polymers that can be used in cement compositions, etc., and found that a polyalkylene glycol monomer having an average added molar number of oxyalkylene groups within a specific range, an unsaturated monocarboxylic acid monomer, and a copolymer having a specific range of content of structural units derived from carboxylate hydroxyalkyl ester can improve the fluidity retention of a cement composition and reduce the viscosity of the cement composition. They then came to the conclusion that the above-mentioned problems can be solved brilliantly, and arrived at the present invention.

That is, the present invention provides a cement additive containing a polycarboxylic acid copolymer,
The polycarboxylic acid copolymer is represented by the following formula (1):

(wherein R ¹ , R ² and R ³ are the same or different and represent a hydrogen atom or a methyl group; R ⁴ is a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms; (R ⁵ O) are the same or different and represent an oxyalkylene group having 2 to 18 carbon atoms; n represents the average number of moles of oxyalkylene groups added and is a number from 5 to 24; x is a number from 0 to 4; and y is 0 or 1.) is a cement additive in which the contents of structural units (a) derived from a polyalkylene glycol monomer (A), structural units (b) derived from an unsaturated monocarboxylic acid monomer (B) and structural units (c) derived from a hydroxyalkyl carboxylate (C) are 50 to 99 mass%, 1 to 30 mass% and 0 to 20 mass%, respectively, relative to 100 mass% of all structural units.

In the above polycarboxylic acid-based copolymer, it is preferable that y in formula (1) is 0.

It is preferable that the above-mentioned carboxylic acid hydroxyalkyl ester (C) is a hydroxyalkyl (meth)acrylate.

It is preferable that the unsaturated monocarboxylic acid monomer (B) is at least one selected from the group consisting of (meth)acrylic acid, half esters of maleic acid and alcohols having 1 to 22 carbon atoms or glycols having 2 to 4 carbon atoms, half esters of fumaric acid and alcohols having 1 to 22 carbon atoms or glycols having 2 to 4 carbon atoms, and salts thereof.

In the above polycarboxylic acid copolymer, it is preferable that the proportion of structural units (e) derived from other monomers (E) other than the polyalkylene glycol monomer (A), the unsaturated monocarboxylic acid monomer (B), and the carboxylic acid hydroxyalkyl ester (C) is 0 to 10 mass% relative to 100 mass% of all structural units.

It is preferable that the above polycarboxylic acid copolymer has a weight average molecular weight of 3,000 to 100,000.

The present invention is also a cement composition comprising the above-mentioned cement additive and cement.

It is preferable that the above cement composition further contains other cement dispersants and/or water reducers other than the above cement additives.

The cement additive of the present invention has the above-mentioned configuration and can improve the fluidity retention of the cement composition and reduce the viscosity, and therefore can be suitably used in cement compositions, etc.

The preferred embodiments of the present invention are described in detail below, but the present invention is not limited to the following description, and can be modified and applied as appropriate within the scope that does not change the gist of the present invention. Note that a combination of two or more of the individual preferred embodiments of the present invention described below also falls under the preferred embodiments of the present invention.

[Polycarboxylic acid copolymer]
The polycarboxylic acid copolymer contained in the cement additive of the present invention (hereinafter also referred to as the copolymer of the present invention) has a structural unit (a) derived from the polyalkylene glycol monomer (A) represented by the above formula (1) and a structural unit (b) derived from the unsaturated monocarboxylic acid monomer (B).

In the polycarboxylic acid copolymer, the proportion of the structural unit (a) is 50 to 99% by mass, preferably 60 to 95% by mass, more preferably 65 to 95% by mass, even more preferably 70 to 90% by mass, and most preferably 75 to 90% by mass, based on 100% by mass of all structural units.
The proportion of each structural unit in the polycarboxylic acid copolymer can be calculated based on the remaining amount of each monomer measured by high performance liquid chromatography.

In the above polycarboxylic acid copolymer, the proportion of structural unit (b) is 1 to 30% by mass relative to 100% by mass of all structural units. It is preferably 5 to 30% by mass, more preferably 10 to 30% by mass, even more preferably 15 to 30% by mass, and most preferably 15 to 25% by mass. In the present invention, when calculating the mass proportion (mass%) of the above structural unit (b) relative to 100% by mass of all structural units, it is calculated in terms of the corresponding sodium salt. For example, the mass proportion of a structural unit derived from acrylic acid is calculated as the mass proportion (mass%) of a structural unit derived from the corresponding sodium salt, sodium acrylate.

The polycarboxylic acid copolymer may further have a structural unit (c) derived from a carboxylate hydroxyalkyl ester (C), and the content of the structural unit (c) is 0 to 20 mass% relative to 100 mass% of the structural units. It is preferably 0 to 18 mass%, which can further improve the fluidity retention of the cement composition. It is more preferably 0 to 15 mass%, even more preferably 0 to 12 mass%, and most preferably 0 to 10 mass%.

The polycarboxylic acid copolymer may have a structural unit (e) derived from a monomer (E) other than the polyalkylene glycol monomer (A), the unsaturated monocarboxylic acid monomer (B), and the hydroxyalkyl carboxylate (C).
The proportion of the structural unit (e) in the copolymer is preferably 0 to 10% by mass relative to 100% by mass of all structural units.
It is more preferably 0 to 8% by mass, further preferably 0 to 5% by mass, and most preferably 0% by mass.

The polycarboxylic acid copolymer preferably has a weight average molecular weight of 3,000 to 100,000. This can further improve the fluidity retention of the cement composition and further reduce the viscosity. It is more preferably 3,000 to 50,000, even more preferably 4,000 to 30,000, even more preferably 4,000 to 20,000, still more preferably 4,500 to 18,000, and particularly preferably 5,000 to 15,000.
The weight average molecular weight can be measured by the method described in the Examples.

<Polyalkylene glycol monomer (A)>
The polyalkylene glycol monomer (A) (hereinafter also referred to as monomer (A)) is a compound represented by the above formula (1).
In the above formula (1), R ¹ to R ³ are the same or different and each represents a hydrogen atom or a methyl group. Preferably, R ¹ and R ² are hydrogen atoms, and R ³ is a hydrogen atom or a methyl group. More preferably, R ¹ and R ² are hydrogen atoms, and R ³ is a methyl group.

R ⁴ in the above formula (1) represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. It is preferably a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, more preferably a hydrogen atom or a hydrocarbon group having 1 to 18 carbon atoms, even more preferably a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms, particularly preferably a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, and most preferably a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms.
Examples of the hydrocarbon group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, an isopentyl group, a neopentyl group, a 3-pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an undecyl group, a dodecyl group, an isooctyl group, a 2,3,5-trimethylhexyl group, a 4-ethyl-5-methyloctyl group, a 2-ethylhexyl group, a tetradecyl group, and an octadecyl group. linear or branched alkyl groups such as icosyl group, cyclic alkyl groups such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, and cyclooctyl, and aryl groups such as phenyl, benzyl, phenethyl, o-, m-, or p-tolyl, 2,3-, or 2,4-xylyl, mesityl, naphthyl, anthryl, phenanthryl, biphenylyl, benzhydryl, trityl, and pyrenyl. Of these, linear, branched, or cyclic alkyl groups are preferred.

In the above formula (1), R ⁵ O "may be the same or different" and represent an oxyalkylene group having 2 to 18 carbon atoms, which means that the n oxyalkylene groups of R ⁵ O present in the polyalkylene glycol may all be the same or different.
The oxyalkylene group preferably has 2 to 18 carbon atoms, more preferably 2 to 12 carbon atoms, further preferably 2 to 8 carbon atoms, and particularly preferably 2 to 4 carbon atoms.
In the above formula (1), the oxyalkylene group represented by R ⁵ O is an alkylene oxide adduct, and examples of such alkylene oxides include alkylene oxides having 2 to 8 carbon atoms such as ethylene oxide, propylene oxide, butylene oxide, isobutylene oxide, 1-butene oxide, 2-butene oxide, styrene oxide, etc. More preferred are alkylene oxides having 2 to 4 carbon atoms such as ethylene oxide, propylene oxide, butylene oxide, and even more preferred are ethylene oxide and propylene oxide.
In addition, when the polyalkylene glycol is an adduct of any two or more kinds of alkylene oxides selected from ethylene oxide, propylene oxide, butylene oxide, styrene oxide, etc., it may be in any form of random addition, block addition, alternating addition, etc. In order to ensure a balance between hydrophilicity and hydrophobicity, it is preferable that the oxyalkylene group in the polyalkylene glycol has an oxyethylene group as an essential component, more preferably 50 mol % or more of the oxyethylene group, and even more preferably 90 mol % or more of the oxyethylene group.

In the above formula (1), n represents the average number of moles of oxyalkylene groups added and is 5 to 24. This reduces the viscosity of the cement composition. n is preferably 5 to 22, more preferably 5 to 20, even more preferably 5 to 18, and particularly preferably 5 to 15.

In the above formula (1), x represents a number from 0 to 4, and y represents 0 or 1.
x is preferably 1 to 4. y is preferably 0. Since the monomer (A) in which y is 0 is inexpensive, the polycarboxylic acid copolymer of the present invention can be produced at low cost.
When y is 0, x is preferably 1 to 4, more preferably 1 or 2, and further preferably 2. When x is 1 to 4, ^R3 is preferably a methyl group.
When the above y is 1, x is preferably 0. In this case, ^R3 is more preferably a hydrogen atom or a methyl group.

Specific examples of the polyalkylene glycol monomer (A) include (poly)alkylene glycol (meth)acrylates such as polyethylene glycol (meth)acrylate and alkoxy (poly)alkylene glycol (meth)acrylates whose ends are hydrophobically modified with a hydrocarbon group having 1 to 30 carbon atoms; vinyl alcohol, allyl alcohol, methallyl alcohol, 3-methyl-3-buten-1-ol, 3-methyl-2-buten-1-ol, 2-methyl-3-buten-1-ol, 2-methyl-2-buten-1-ol, 3-allyloxy-1,2-propanediol, and other unsaturated alcohols having 2 to 8 carbon atoms, with 5 to 24 moles of alkylene oxide added thereto, and compounds whose ends are hydrophobically modified with a hydrocarbon group having 1 to 30 carbon atoms. Among these, compounds whose ends are hydrophobically modified with a hydrocarbon group having 1 to 30 carbon atoms and 5 to 24 moles of alkylene oxide added thereto are preferred. More preferred are compounds in which 5 to 24 moles of an alkylene oxide are added to an unsaturated alcohol having 2 to 8 carbon atoms, and even more preferred are compounds in which an alkylene oxide is added to methallyl alcohol or 3-methyl-3-buten-1-ol.

<Unsaturated monocarboxylic acid monomer (B)>
The unsaturated monocarboxylic acid monomer (B) (hereinafter also referred to as monomer (B)) may be any monomer having one unsaturated group and one group capable of forming a carbanion in the molecule, and examples thereof include (meth)acrylic acid, crotonic acid, isocrotonic acid, tiglic acid, 3-methylcrotonic acid, 2-methyl-2-pentenoic acid, α-hydroxyacrylic acid, etc.; monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts thereof; half esters of the following unsaturated dicarboxylic acid monomers and alcohols having 1 to 22 carbon atoms or glycols having 2 to 4 carbon atoms; and half amides of unsaturated dicarboxylic acid monomers and amines having 1 to 22 carbon atoms.
The unsaturated dicarboxylic acid monomer may be any monomer having one unsaturated group and two groups capable of forming a carbanion in the molecule, and examples thereof include maleic acid, itaconic acid, mesaconic acid, citraconic acid, fumaric acid, etc., their monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts, and their anhydrides.
The unsaturated monocarboxylic acid monomer (B) is preferably (meth)acrylic acid, a half ester of maleic acid with an alcohol having 1 to 22 carbon atoms or a glycol having 2 to 4 carbon atoms, a half ester of fumaric acid with an alcohol having 1 to 22 carbon atoms or a glycol having 2 to 4 carbon atoms, or a salt thereof, more preferably (meth)acrylic acid (salt), and even more preferably acrylic acid (salt).

Examples of the alcohols having 1 to 22 carbon atoms include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonaol, decanol, undecanol, dodecanol, tridecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol, and icosanol.

Examples of glycols having 2 to 4 carbon atoms include ethylene glycol, propylene glycol, diethylene glycol, etc.

Examples of the amines having 1 to 22 carbon atoms include methylamine, ethylamine, propylamine, butylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, pentylamine, dipentylamine, hexylamine, dihexylamine, heptylamine, diheptylamine, octylamine, dioctylamine, dodecylamine, etc.

<Carboxylic Acid Hydroxyalkyl Ester (C)>
The carboxylic acid hydroxyalkyl ester (C) (hereinafter also referred to as monomer (C)) may be an unsaturated carboxylic acid alkyl ester having a hydroxyl group on the alkyl group. The unsaturated carboxylic acid may be the unsaturated monocarboxylic acid monomer (B) or the unsaturated dicarboxylic acid monomer.
The unsaturated carboxylic acid is preferably an unsaturated monocarboxylic acid monomer (B), more preferably (meth)acrylic acid, and even more preferably acrylic acid. That is, the carboxylic acid hydroxyalkyl ester (C) is preferably a hydroxyalkyl (meth)acrylate.
The hydroxyalkyl carboxylate (C) preferably has a hydroxyalkyl group having 1 to 12 carbon atoms. The hydroxyalkyl group more preferably has 1 to 8 carbon atoms, further preferably has 1 to 6 carbon atoms, and particularly preferably has 1 to 4 carbon atoms.
Specific examples of the hydroxyalkyl group include a hydroxymethyl group, a hydroxyethyl group, a 2-hydroxy-1-methylethyl group, a hydroxypropyl group, a hydroxybutyl group, a hydroxypentyl group, a hydroxyhexyl group, a hydroxyoctyl group, a hydroxynonyl group, and a hydroxydecyl group.

Specific examples of the carboxylic acid hydroxyalkyl ester (C) include hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 2-hydroxy-1-methylethyl (meth)acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, hydroxypentyl (meth)acrylate, etc. Among these, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and 3-hydroxypropyl (meth)acrylate are preferred, and 2-hydroxyethyl (meth)acrylate is more preferred.

The copolymer of the present invention may have a structural unit (e) derived from a monomer (E) other than the monomers (A), (B) and (C).
The other monomer (E) is not particularly limited as long as it can be copolymerized with the monomers (A), (B), and (C). Examples of the other monomer (E) include 3-(meth)allyloxy-2-hydroxypropanesulfonic acid, 2-(meth)allyloxyethylenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, p-styrenesulfonic acid, α-methyl-p-styrenesulfonic acid, vinylsulfonic acid, vinylsulfamic acid, (meth)allyl sulfonic acid, isoprene sulfonic acid, 4-(allyloxy)benzenesulfonic acid, 1-methyl-2-propene-1-sulfonic acid, 1,1-dimethyl-2-propene-1-sulfonic acid, 3-butene-1- Unsaturated sulfonic acids and their salts, such as sulfonic acid, 1-butene-3-sulfonic acid, 2-acrylamido-1-methylpropanesulfonic acid, 2-acrylamidopropanesulfonic acid, 2-acrylamido-n-butanesulfonic acid, 2-acrylamido-2-phenylpropanesulfonic acid, and 2-((meth)acryloyloxy)ethanesulfonic acid; hydroxyl group-containing ethers, such as 3-(meth)allyloxy-1,2-dihydroxypropane and 1-allyloxy-3-butoxypropan-2-ol; N-vinyl lactam monomers, such as N-vinylpyrrolidone; methyl (meth)acrylate, ethyl (meth)acrylate, and (meth)acryloyloxy. (Meth)acrylic acid esters such as propyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, iso-nonyl (meth)acrylate, dodecyl (meth)acrylate, and stearyl (meth)acrylate; N-substituted or unsubstituted (meth)acrylamides such as (meth)acrylamide, N-monomethyl(meth)acrylamide, N-monoethyl(meth)acrylamide, and N,N-dimethyl(meth)acrylamide; styrene, α-methylstyrene, vinyltoluene, indene, vinylnaphthalene, phenylmaleimide, vinyl vinyl aryl monomers such as diphenyl aniline; alkenes such as ethylene, propylene, butadiene, isobutylene, octene, etc.; vinyl carboxylates such as vinyl acetate, vinyl propionate, etc.; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether, etc.; vinyl ethylene carbonate and derivatives thereof; unsaturated amines such as N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylamide, vinylpyridine, vinylimidazole, and salts or quaternized products thereof; and vinyl cyanide monomers such as acrylonitrile, methacrylonitrile, etc.

[Method for producing copolymer]
The production of the polycarboxylic acid copolymer of the present invention is not particularly limited, but can be produced by polymerizing a monomer component, and specific and preferred examples of the monomer component are as described above. The content ratio of each monomer component relative to 100% by mass of the total monomer components can be determined based on the ratio of the structural units (a) to (e) relative to 100% by mass of the total structural units described above. When y in formula (1) for the polyalkylene glycol monomer (A) is 0, it is preferable from the viewpoint of reactivity that the amount of the polyalkylene glycol monomer (A) used is greater than the desired ratio of the structural unit (a).

In the production of the copolymer, a chain transfer agent can be used to adjust the molecular weight of the resulting polymer. Examples of chain transfer agents include thiol-based chain transfer agents such as mercaptoethanol, thioglycerol, thioglycolic acid, 3-mercaptopropionic acid, thiomalic acid, and 2-mercaptoethanesulfonic acid; secondary alcohols such as isopropyl alcohol; and hydrophilic chain transfer agents such as lower oxides and salts of phosphorous acid, hypophosphorous acid, and salts thereof (sodium hypophosphite, potassium hypophosphite, etc.), sulfurous acid, hydrogen sulfite, dithionous acid, metabisulfite, and salts thereof (sodium sulfite, sodium hydrogen sulfite, sodium dithionite, sodium metabisulfite, etc.).

As the chain transfer agent, a hydrophobic chain transfer agent can also be used. As the hydrophobic chain transfer agent, for example, a thiol-based chain transfer agent having a hydrocarbon group having 3 or more carbon atoms, such as butanethiol, octanethiol, decanethiol, dodecanethiol, hexadecanethiol, octadecanethiol, cyclohexyl mercaptan, thiophenol, octyl thioglycolate, or octyl 3-mercaptopropionate, is preferably used.
In order to adjust the molecular weight of the copolymer, it is also effective to use, as the monomer (E), a monomer having high chain transfer property, such as (meth)allylsulfonic acid (salts).

The amount of the chain transfer agent used may be set appropriately, but is preferably 0.1 mol or more, more preferably 0.25 mol or more, and even more preferably 0.5 mol or more, per 100 mol of the total amount of monomer components, and is preferably 20 mol or less, more preferably 15 mol or less, and even more preferably 10 mol or less.

The above polymerization reaction can be carried out by a method such as solution polymerization or bulk polymerization, using a radical polymerization initiator as necessary. Solution polymerization can be carried out batchwise or continuously, or a combination thereof. Examples of the solvent used in this case include water; alcohols such as methyl alcohol, ethyl alcohol, and isopropyl alcohol; aromatic or aliphatic hydrocarbons such as benzene, toluene, xylene, cyclohexane, and n-hexane; ester compounds such as ethyl acetate; ketone compounds such as acetone and methyl ethyl ketone; and cyclic ether compounds such as tetrahydrofuran and dioxane. Among these, polymerization by the aqueous solution polymerization method is preferred.

When carrying out the aqueous solution polymerization, as the radical polymerization initiator, a water-soluble polymerization initiator, for example, persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate; hydrogen peroxide; azoamidine compounds such as 2,2'-azobis-2-methylpropionamidine hydrochloride, cyclic azoamidine compounds such as 2,2'-azobis-2-(2-imidazolin-2-yl)propane hydrochloride, and water-soluble azo-based initiators such as azonitrile compounds such as 2-carbamoylazoisobutyronitrile are used, and in this case, accelerators such as alkali metal sulfites such as sodium hydrogensulfite, metabisulfites, sodium hypophosphite, Fe(II) salts such as Mohr's salt, sodium hydroxymethanesulfinate dihydrate, hydroxylamine hydrochloride, thiourea, L-ascorbic acid (salt), and erythorbic acid (salt) may also be used in combination. Among these, preferred are persulfates such as ammonium persulfate, sodium persulfate, potassium persulfate, etc., and combinations of hydrogen peroxide with an accelerator such as L-ascorbic acid (salt), etc. These radical polymerization initiators and accelerators may be used alone or in combination of two or more kinds.
When solution polymerization is carried out using a lower alcohol, an aromatic or aliphatic hydrocarbon, an ester compound, or a ketone compound as a solvent, or when bulk polymerization is carried out, peroxides such as benzoyl peroxide, lauroyl peroxide, and sodium peroxide; hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide; and azo compounds such as azobisisobutyronitrile are used as radical polymerization initiators. In this case, accelerators such as amine compounds can also be used in combination. Furthermore, when a water-lower alcohol mixed solvent is used, the above-mentioned various radical polymerization initiators or combinations of radical polymerization initiators and accelerators can be appropriately selected and used.

The amount of the radical polymerization initiator used is preferably 0.001 mol or more, more preferably 0.01 mol or more, even more preferably 0.1 mol or more, and particularly preferably 0.2 mol or more, per 100 mol of the total amount of monomer components, and is preferably 20 mol or less, even more preferably 10 mol or less, particularly preferably 5 mol or less, and most preferably 3 mol or less.

In the above polymerization reaction, polymerization conditions such as polymerization temperature are appropriately determined depending on the polymerization method, solvent, polymerization initiator, and chain transfer agent used, but the polymerization temperature is preferably 0°C or higher and 150°C or lower. It is more preferably 30°C or higher, and even more preferably 50°C or higher. It is also more preferably 120°C or lower, and even more preferably 100°C or lower.

The method of feeding each monomer component into the reaction vessel is not particularly limited, and examples thereof include a method of feeding the entire amount into the reaction vessel at once at the beginning; a method of feeding the entire amount into the reaction vessel in portions or continuously; a method of feeding a part of the monomer component into the reaction vessel at the beginning and feeding the remainder into the reaction vessel in portions or continuously. In addition, the feeding speed of each monomer into the reaction vessel may be changed continuously or stepwise during the reaction, and the feeding weight ratio of each monomer per unit time may be changed continuously or stepwise, so that two or more copolymers having different monomer ratios are simultaneously synthesized during the polymerization reaction. The radical polymerization initiator may be charged into the reaction vessel from the beginning, or may be added dropwise to the reaction vessel, or these may be combined depending on the purpose.
The polymers obtained as described above can be used as dispersants as they are, but if necessary, they may be neutralized with an alkaline substance before use. Suitable alkaline substances include inorganic salts such as hydroxides and carbonates of monovalent or divalent metals, ammonia, and organic amines. After the reaction is completed, the concentration can be adjusted if necessary.

[Cement Additives]
The cement additive of the present invention essentially contains the copolymer of the present invention, but may contain two or more of the above copolymers, or may contain one or more copolymers different from the above copolymers.
The content of the copolymer in the cement additive (the total content when two or more types of copolymers are included) is not particularly limited, but is preferably 2% by mass or more and 50% by mass or less, more preferably 3% by mass or more and 40% by mass or less, even more preferably 4% by mass or more and 35% by mass or less, and particularly preferably 5% by mass or more and 30% by mass or less, based on 100% by mass of the solid content (i.e., non-volatile content) in the cement additive.
In this specification, the term "cement additive" refers to an additive added to cement compositions such as cement paste, mortar, and concrete, and may be an agent consisting of the above-mentioned copolymer alone, or may contain not only the above-mentioned copolymer but also other components, additives, and the like as necessary.

The above cement additive may further contain other commonly used cement dispersants and water reducing agents, and a combination of a plurality of them is also possible. The other cement dispersants (water reducing agents) are not particularly limited, and examples thereof include various sulfonic acid dispersants (water reducing agents) having a sulfonic acid group in the molecule, various polycarboxylic acid dispersants (water reducing agents) having a polyoxyalkylene chain and a carboxyl group in the molecule, and various phosphoric acid dispersants (water reducing agents) having a phosphoric acid group in the molecule.
When the copolymer of the present invention is used in combination with another commonly used cement dispersant (water reducing agent), the copolymer of the present invention particularly exerts the technical significance of the present invention as a fluidity retaining agent.
An embodiment in which the cement additive contains the copolymer of the present invention and another cement dispersant and/or water reducing agent is also one of the preferred embodiments of the present invention.
When the copolymer of the present invention is used in combination with another cement dispersant (water reducing agent), the content of the copolymer of the present invention is preferably 5 to 100 mass%, more preferably 5 to 40 mass%, based on 100 mass% of the content of the other cement dispersant (water reducing agent).

The sulfonic acid dispersant (water reducing agent) may be any compound having a sulfonic acid group or a sulfonic acid salt group in the molecule. The compound having a sulfonic acid group or a sulfonic acid salt group is preferably one having an aromatic ring in the molecule.
Examples of the sulfonic acid dispersant (water reducing agent) include polyalkylarylsulfonate dispersants (water reducing agents) such as naphthalenesulfonic acid formaldehyde condensates, methylnaphthalenesulfonic acid formaldehyde condensates, and anthracenesulfonic acid formaldehyde condensates; melamine formalin resin sulfonate dispersants (water reducing agents) such as melamine sulfonic acid formaldehyde condensates; aromatic aminosulfonate dispersants (water reducing agents) such as aminoarylsulfonic acid-phenol-formaldehyde condensates; lignin sulfonate water reducing agents such as lignin sulfonates and modified lignin sulfonates; and polystyrene sulfonate dispersants (water reducing agents).
As the sulfonic acid-based dispersant (water-reducing agent), polyalkylarylsulfonate-based dispersants (water-reducing agents) and ligninsulfonate-based dispersants (water-reducing agents) are preferred, and naphthalenesulfonate formaldehyde condensates are more preferred.

The polycarboxylic acid dispersant (water reducing agent) is preferably a polymer obtained by copolymerizing a monomer component containing an unsaturated carboxylic acid monomer and a (poly)alkylene glycol monomer.
The unsaturated carboxylic acid monomer may be the same as the monomer (B) described above.
Specific examples of the (poly)alkylene glycol monomer include compounds in which 1 to 300 moles of alkylene oxide are added to unsaturated alcohols having 2 to 8 carbon atoms and terminal hydrophobically modified products thereof; esters of unsaturated carboxylic acid monomers and (poly)alkylene glycols having an average added mole number of 1 to 300 and terminal hydrophobically modified products thereof; and the like.

In the polycarboxylic acid dispersant (water reducing agent), the proportion of structural units derived from unsaturated carboxylic acid monomers is preferably 5 to 45% by mass, more preferably 10 to 30% by mass, relative to 100% by mass of all structural units.
In the polycarboxylic acid dispersant (water reducing agent), the proportion of structural units derived from (poly)alkylene glycol monomers is preferably 55 to 95 mass%, more preferably 70 to 90 mass%, relative to 100 mass% of all structural units.
The polycarboxylic acid dispersant (water reducing agent) preferably has a weight average molecular weight of 5,000 to 500,000. More preferably, it is 7,000 to 200,000, and even more preferably, it is 8,000 to 100,000. The weight average molecular weight can be measured by gel permeation chromatography (GPC) under the conditions described in the examples described later.

Examples of the phosphoric acid-based dispersant (water-reducing agent) include phosphoric acid-based polymers containing polyalkylene glycol and phosphoric acid-based condensates.
The phosphoric acid polymer is preferably a polymer obtained by copolymerizing a monomer component containing a (poly)alkylene glycol monomer and a phosphoric acid monomer.
Examples of the phosphoric acid monomer include mono(2-hydroxyethyl)(meth)acrylic acid ester, di-{(2-hydroxyethyl)(meth)acrylic acid} ester, and (poly)alkylene glycol mono(meth)acrylate acid phosphoric acid ester.
As the phosphoric acid condensate, for example, a condensate of a phosphoric acid ester and an aldehyde compound is suitable. The phosphoric acid ester is not particularly limited as long as it is an esterification product of phosphoric acid (which may be a salt) and a hydroxyl group-containing compound, and one or more kinds can be used. In addition, any of phosphoric acid monoester, phosphoric acid diester, and phosphoric acid triester may be used.

Furthermore, the above cement additives may contain one or more of the following cement additives (materials): water-soluble polymer substances, polymer emulsions, retarders, early strengthening agents/accelerators, mineral oil-based defoamers, oil-based defoamers, fatty acid-based defoamers, fatty acid ester-based defoamers, oxyalkylene-based defoamers, alcohol-based defoamers, amide-based defoamers, phosphate ester-based defoamers, metal soap-based defoamers, silicone-based defoamers, AE agents, surfactants, waterproofing agents, rust inhibitors, crack reducing agents, expansion agents, cement wetting agents, thickeners, separation reducing agents, coagulants, drying shrinkage reducing agents, strength enhancing agents, self-leveling agents, rust inhibitors, colorants, mold inhibitors, blast furnace slag, fly ash, cinder ash, clinker ash, husk ash, silica fume, silica powder, gypsum, etc.

[Cement Composition]
The above-mentioned cement additive can be used in various hydraulic materials, i.e., cement compositions such as cement and gypsum, and other hydraulic materials. Specific examples of hydraulic compositions containing such hydraulic materials, water, and the above-mentioned cement additive, and further containing fine aggregates (sand, etc.) and coarse aggregates (crushed stone, etc.) as necessary, include cement paste, mortar, concrete, plaster, etc. Among these hydraulic compositions, the most preferred is a cement composition using cement as the hydraulic material, and a cement composition containing the above-mentioned cement additive and cement is also one aspect of the present invention.

In the cement composition of the present invention, the cement includes Portland cement (normal, early strength, super early strength, moderate heat, sulfate resistance and each low alkali form); various mixed cements (blast furnace cement, silica cement, fly ash cement); white Portland 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 cement (low heat type blast furnace cement, fly ash mixed low heat type blast furnace cement, belite high content cement); ultra-high strength cement; cement-based solidification material; ecocement (cement manufactured using one or more of urban waste incineration ash and sewage sludge incineration ash as raw materials), as well as those to which fine powders such as blast furnace slag, fly ash, cinder ash, clinker ash, husk ash, silica fume, silica powder, limestone powder, and gypsum have been added. The cement contained in the cement composition of the present invention may be only one type, or two or more types.
Examples of the aggregate include gravel, crushed stone, granulated slag, recycled aggregate, and the like, as well as refractory aggregate such as silica, clay, zircon, high alumina, silicon carbide, graphite, chrome, chromium-magnesium, and magnesia.

In the above cement composition, the unit water amount per 1 ^m3 , the amount of cement used, and the water/cement ratio are not particularly limited, and for example, the unit water amount is 100 to 185 kg/ ^m3 , the amount of cement used is 250 to 800 kg/ ^m3 , and the water/cement ratio (weight ratio) is 0.12 to 0.74. More preferably, the unit water amount is 120 to 175 kg/ ^m3 , the amount of cement used is 270 to 800 kg/ ^m3 , and the water/cement ratio (weight ratio) is 0.15 to 0.65. In this way, the cement composition of the present invention can be used widely from lean to rich mixes, and is effective for both high-strength concrete with a large unit cement amount and lean concrete with a unit cement amount of 300 kg/ ^m3 or less. In addition, the cement composition of the present invention can be used well in a relatively high water reduction ratio region, that is, a low water/cement ratio region such as a water/cement ratio (weight ratio) of 0.15 to 0.5 (preferably 0.15 to 0.4).

In addition, by using the cement additive of the present invention, the resulting cement composition has excellent workability for a long time in a wide range of blends, and is therefore particularly effective for ready-mixed concrete, shotcrete, etc. On the other hand, it can also be applied to concrete for secondary concrete products (precast concrete), concrete for centrifugal molding, concrete for vibration compaction, steam curing concrete, etc. The cement additive of the present invention is also effective for mortar and concrete that require high fluidity, such as medium-fluidity concrete (concrete with a slump value in the range of 22 to 25 cm), high-fluidity concrete (concrete with a slump value of 25 cm or more and a slump flow value in the range of 500 to 700 mm), self-compacting concrete, and self-leveling materials.

In the above cement composition, the blending ratio of the cement additive of the present invention is preferably set so that the copolymer (the total amount when multiple copolymers are included) which is an essential component of the present invention is 0.005 to 10 mass% based on 100 mass% of the total cement mass, calculated as solid content. If it is less than 0.005 mass%, the performance may not be sufficient, and conversely, if it exceeds 10 mass%, the effect may substantially plateau and may be disadvantageous from the economical point of view. It is more preferably 0.01 to 5 mass%, and even more preferably 0.02 to 3 mass%. In this specification, the solid content can be measured as follows.
<Solid content measurement method>
1. Accurately weigh the aluminum dish.
2. Accurately weigh the solids content measurement sample into the aluminum dish used in step 1.
3. The solid content measured in step 2 is placed in a dryer adjusted to 130° C. under a nitrogen atmosphere for 1 hour.
4. After 1 hour, remove from the dryer and allow to cool in a desiccator at room temperature for 15 minutes.
5. After 15 minutes, remove from the desiccator and accurately weigh the aluminum dish plus the sample.
6. The mass of the aluminum dish obtained in 1 is subtracted from the mass obtained in 5, and the result is divided by the mass of the solids measurement sample obtained in 2 to measure the solids content.

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. Unless otherwise specified, "parts" means "parts by mass" and "%" means "% by mass."

<Gel Permeation Chromatography (GPC)>
The weight average molecular weight of the polycarboxylic acid copolymer was measured by the following method.
Apparatus: Alliance (e2695) (Waters)
Analysis software: Empower2 Professional + GPC option (Waters)
Columns used: TSKguard columns SWXL (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) (all manufactured by Tosoh Corporation)
Detector: differential refractometer (RI) detector (Waters 2414, manufactured by Waters Corporation)
Eluent: A solution prepared by dissolving 115.6 g of sodium acetate trihydrate in a mixed solvent of 10,999 g of ion-exchanged water and 6,001 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=255000, 200000, 107000, 72750, 44900, 31400, 21300, 11840, 6450, 4020, 1470
Calibration curve: Prepared using a cubic equation using the Mp values of the above polyethylene glycol.

<High performance liquid chromatography (LC)>
The remaining amount of each monomer used as a reaction raw material was measured under the following conditions and used to calculate the composition of the polycarboxylic acid copolymer.
Apparatus: Alliance 2695 (Waters)
Analysis software: Empower Professional (Waters)
Column: Atlantis dC18 5 μm (inner diameter 4.6 mm × length 250 mm) × 2 (Waters)
Detector: differential refractometer (RI) detector (Waters 2414), multi-wavelength visible ultraviolet (PDA) detector (Waters 2996)
Solvent: A solution of 100 mM sodium acetate aqueous solution and acetonitrile mixed in 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: 1% by mass)

<Mortar test method>
The mortar test was carried out in an environment of a temperature of 20° C.±1° C. and a relative humidity of 60%±15%. The mortar was mixed with the materials shown below so that C/S/W=900/1260/270 (g).
C: Cement (ordinary Portland cement, manufactured by Taiheiyo Cement Corporation)
S: Fine aggregate (Oigawa land sand)
W: Ion-exchanged aqueous solution of sample (copolymer) and antifoaming agent W contained a predetermined amount of sample and 0.005% by mass of antifoaming agent (Microair 404, manufactured by BASF Pozzolith) based on the cement mass, and was sufficiently and uniformly dissolved in the ion-exchanged water. The amount of each sample added was shown as the mass % of the solid content of each sample based on the cement mass.

<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 S (fine aggregate) were charged into a mixing vessel and mixed at low speed for 10 seconds. While further mixing at low speed, W (an ion-exchanged aqueous solution of a sample and an antifoaming agent) was charged over 15 seconds. The mixer was stopped 40 seconds after the start of mixing, and the mortar adhering to the vessel wall was scraped off over 20 seconds. After that, mixing was continued at high speed for an additional 180 seconds to prepare the mortar.

<Method of measuring mortar flow value>
The mortar obtained as described above was half-filled into a slump cone (compliant with JIS-A-1171, upper end inner diameter 50 mm, lower end inner diameter 100 mm, height 150 mm) placed on a horizontally placed flow measurement plate (steel flat plate, 60 cm x 60 cm), and poked 15 times with a ramming rod. The mortar was further filled to the top of the slump cone and poked 15 times with a ramming rod, and the surface of the slump cone was smoothed. Then, 11 minutes after the first start of the mixer, the slump cone was lifted vertically, and the diameter of the spread mortar (the diameter of the longest part (major axis) and the diameter of the part at 90 degrees to the major axis) were measured at two points, and the average value was taken as the mortar flow value (initial flow value). The larger the mortar flow value, the better the dispersion performance. In the same manner, the mortar flow value was measured 60 minutes after the start of the mixer.

<Method of measuring funnel flow time>
The funnel flow time of the obtained mortar was measured using a J14 funnel in accordance with the Japan Society of Civil Engineers standard JSCE-F541. Similarly, the funnel flow time of the mortar was measured 60 minutes after the start of the mixer.

<Evaluation of water reduction performance, retention performance, and viscosity>
The performance of each sample was evaluated based on the mortar flow value and the funnel flow time.

<Water reduction performance>
Based on the amount of sample added necessary to give a flow value of 250 mm immediately after mixing (initial stage), the proportion of the sample in the cement (C) ([wt %/C]) was calculated.

<Retention performance>
The mortar having a flow value of 250 mm immediately after mixing (initial value) was used, and the flow value of the mortar was measured 60 minutes after mixing to calculate the flow retention (flow value after 60 minutes/initial flow value).

<Viscosity>
Mortar was prepared so that the flow value immediately after mixing (initial) was 250 mm, and the funnel flow time at the initial flow value (initial flow time) and the funnel flow time at which the flow value reached 280 mm 60 minutes after mixing (flow time after 60 minutes) were measured. The shorter the flow time, the lower the viscosity was evaluated to be.

<Production Example 1>
In a glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, 282 parts of ion-exchanged water, an unsaturated polyalkylene glycol (IPN-10) in which an average of 10 moles of ethylene oxide was added to 3-methyl-3-buten-1-ol, were charged, and the temperature was raised to 65 ° C., and then an aqueous hydrogen peroxide solution containing 1.47 parts of hydrogen peroxide and 2.72 parts of ion-exchanged water was added thereto. Next, acrylic acid was dropped into the reaction vessel over 5 hours, and at the same time, an aqueous solution in which 0.76 parts of L-ascorbic acid and 7.62 parts of 3-mercaptopropionic acid were dissolved in 93.1 parts of ion-exchanged water was dropped over 5.5 hours. Thereafter, the temperature was maintained at 65 ° C. for 1 hour to terminate the polymerization reaction. Thereafter, the reaction solution was neutralized to pH 7 using an aqueous sodium hydroxide solution at a temperature below the polymerization reaction temperature, and an aqueous solution of copolymer 1 having a weight average molecular weight of 5,000 was obtained. The total amount of IPN-10 and acrylic acid used was 408 parts, and the final monomer composition ratio in the copolymer was calculated based on the remaining amount of monomer measured by LC.

<Production Example 2>
In a glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, 272 parts of ion-exchanged water, an unsaturated polyalkylene glycol (IPN-10) in which an average of 10 moles of ethylene oxide was added to 3-methyl-3-buten-1-ol was charged, and the temperature was raised to 65 ° C., and then an aqueous hydrogen peroxide solution containing 1.47 parts of hydrogen peroxide and 2.72 parts of ion-exchanged water was added thereto. Next, acrylic acid was dropped into the reaction vessel over 5 hours, and at the same time, an aqueous solution in which 0.76 parts of L-ascorbic acid and 6.10 parts of 3-mercaptopropionic acid were dissolved in 105 parts of ion-exchanged water was dropped over 5.5 hours. Thereafter, the temperature was maintained at 65 ° C. for 1 hour to terminate the polymerization reaction. Thereafter, the reaction solution was neutralized to pH 7 using an aqueous sodium hydroxide solution at a temperature below the polymerization reaction temperature, and an aqueous solution of copolymer 2 having a weight average molecular weight of 6,000 was obtained. The total amount of IPN-10 and acrylic acid used was 408 parts, and the final monomer composition ratio in the copolymer was calculated based on the remaining amount of monomer measured by LC.

<Production Example 3>
In a glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, 287 parts of ion-exchanged water, an unsaturated polyalkylene glycol (IPN-10) in which an average of 10 moles of ethylene oxide was added to 3-methyl-3-buten-1-ol, were charged, and the temperature was raised to 65 ° C., and then an aqueous hydrogen peroxide solution containing 1.47 parts of hydrogen peroxide and 2.72 parts of ion-exchanged water was added thereto. Next, acrylic acid was dropped into the reaction vessel over 5 hours, and at the same time, an aqueous solution in which 0.76 parts of L-ascorbic acid and 4.58 parts of 3-mercaptopropionic acid were dissolved in 91 parts of ion-exchanged water was dropped over 5.5 hours. Thereafter, the temperature was maintained at 65 ° C. for 1 hour to terminate the polymerization reaction. Thereafter, the reaction solution was neutralized to pH 7 using an aqueous sodium hydroxide solution at a temperature below the polymerization reaction temperature, and an aqueous solution of copolymer 3 having a weight average molecular weight of 7,500 was obtained. The total amount of IPN-10 and acrylic acid used was 408 parts, and the final monomer composition ratio in the copolymer was calculated based on the remaining amount of monomer measured by LC.

<Production Example 4>
In a glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, 317 parts of ion-exchanged water, an unsaturated polyalkylene glycol (IPN-10) in which an average of 10 moles of ethylene oxide was added to 3-methyl-3-buten-1-ol was charged, and the temperature was raised to 65 ° C., and then an aqueous hydrogen peroxide solution containing 1.91 parts of hydrogen peroxide and 3.56 parts of ion-exchanged water was added thereto. Next, acrylic acid was dropped into the reaction vessel over 5 hours, and at the same time, an aqueous solution in which 2.32 parts of L-ascorbic acid and 3.10 parts of 3-mercaptopropionic acid were dissolved in 126 parts of ion-exchanged water was dropped over 5.5 hours. Thereafter, the temperature was maintained at 65 ° C. for 1 hour to terminate the polymerization reaction. Thereafter, the reaction solution was neutralized to pH 7 using an aqueous sodium hydroxide solution at a temperature below the polymerization reaction temperature, and an aqueous solution of copolymer 4 having a weight average molecular weight of 10,000 was obtained. The total amount of IPN-10 and acrylic acid used was 500.4 parts, and the final monomer composition ratio in the copolymer was calculated based on the remaining amount of monomer measured by LC.

<Production Example 5>
In a glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, 268 parts of ion-exchanged water, an unsaturated polyalkylene glycol (IPN-10) in which an average of 10 moles of ethylene oxide was added to 3-methyl-3-buten-1-ol, were charged, and the temperature was raised to 65 ° C., and then an aqueous hydrogen peroxide solution containing 2.12 parts of hydrogen peroxide and 3.94 parts of ion-exchanged water was added thereto. Next, acrylic acid and 2-hydroxyethyl acrylate (HEA) were dropped into the reaction vessel over 5 hours, and at the same time, an aqueous solution in which 2.56 parts of L-ascorbic acid and 4.32 parts of 3-mercaptopropionic acid were dissolved in 213 parts of ion-exchanged water was dropped over 5.5 hours. Thereafter, the temperature was maintained at 65 ° C. for 1 hour to terminate the polymerization reaction. Thereafter, the reaction solution was neutralized to pH 7 using an aqueous sodium hydroxide solution at a temperature below the polymerization reaction temperature, and an aqueous solution of copolymer 5 having a weight average molecular weight of 11,000 was obtained. The total amount of IPN-10, acrylic acid and HEA used was 500 parts, and the final monomer composition ratio in the copolymer was calculated based on the remaining amount of the monomer measured by LC.

<Production Example 6>
In a glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, 260 parts of ion-exchanged water, an unsaturated polyalkylene glycol (IPN-10) in which an average of 10 moles of ethylene oxide was added to 3-methyl-3-buten-1-ol, were charged, and the temperature was raised to 65 ° C., and then an aqueous hydrogen peroxide solution containing 2.24 parts of hydrogen peroxide and 4.16 parts of ion-exchanged water was added thereto. Next, acrylic acid and 2-hydroxyethyl acrylate (HEA) were dropped into the reaction vessel over 5 hours, and at the same time, an aqueous solution in which 2.71 parts of L-ascorbic acid and 4.86 parts of 3-mercaptopropionic acid were dissolved in 212 parts of ion-exchanged water was dropped over 5.5 hours. Thereafter, the temperature was maintained at 65 ° C. for 1 hour to terminate the polymerization reaction. Thereafter, the reaction solution was neutralized to pH 7 using an aqueous sodium hydroxide solution at a temperature below the polymerization reaction temperature, and an aqueous solution of copolymer 6 having a weight average molecular weight of 10,000 was obtained. The total amount of IPN-10, acrylic acid and HEA used was 507.6 parts, and the final monomer composition ratio in the copolymer was calculated based on the remaining amount of monomer measured by LC.

<Production Example 7>
In a glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, 293 parts of ion-exchanged water, an unsaturated polyalkylene glycol (IPN-10) in which an average of 10 moles of ethylene oxide was added to 3-methyl-3-buten-1-ol, were charged, and the temperature was raised to 65 ° C., and then an aqueous hydrogen peroxide solution containing 2.29 parts of hydrogen peroxide and 4.25 parts of ion-exchanged water was added thereto. Next, acrylic acid and 2-hydroxyethyl acrylate (HEA) were dropped into the reaction vessel over 5 hours, and at the same time, an aqueous solution in which 2.77 parts of L-ascorbic acid and 4.96 parts of 3-mercaptopropionic acid were dissolved in 178 parts of ion-exchanged water was dropped over 5.5 hours. Thereafter, the temperature was maintained at 65 ° C. for 1 hour to terminate the polymerization reaction. Thereafter, the reaction solution was neutralized to pH 7 using an aqueous sodium hydroxide solution at a temperature below the polymerization reaction temperature, and an aqueous solution of copolymer 7 having a weight average molecular weight of 10,000 was obtained. The total amount of IPN-10, acrylic acid and HEA used was 508.1 parts, and the final monomer composition ratio in the copolymer was calculated based on the remaining amount of monomer measured by LC.

<Production Example 8>
In a glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, 153 parts of ion-exchanged water, an unsaturated polyalkylene glycol (IPN-50) in which an average of 50 moles of ethylene oxide was added to 3-methyl-3-buten-1-ol was charged, and the temperature was raised to 65 ° C., and then an aqueous hydrogen peroxide solution containing 0.36 parts of hydrogen peroxide and 6.77 parts of ion-exchanged water was added thereto. Next, acrylic acid and 2-hydroxyethyl acrylate (HEA) were dropped into the reaction vessel over 3 hours, and at the same time, an aqueous solution in which 0.46 parts of L-ascorbic acid and 1.39 parts of 3-mercaptopropionic acid were dissolved in 29.0 parts of ion-exchanged water was dropped over 3.5 hours. Thereafter, the temperature was maintained at 65 ° C. for 1 hour to terminate the polymerization reaction. Thereafter, the reaction solution was neutralized to pH 7 using an aqueous sodium hydroxide solution at a temperature below the polymerization reaction temperature to obtain an aqueous solution of copolymer 8 having a weight average molecular weight of 30,000. The total amount of IPN-10, acrylic acid and HEA used was 254.9 parts, and the final monomer composition ratio in the copolymer was calculated based on the remaining amount of monomer measured by LC.

<Production Example 9>
In a glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, 106 parts of ion-exchanged water, an unsaturated polyalkylene glycol (IPN-50) in which an average of 50 moles of ethylene oxide was added to 3-methyl-3-buten-1-ol, was charged, and the temperature was raised to 65 ° C., and then an aqueous hydrogen peroxide solution containing 0.19 parts of hydrogen peroxide and 3.59 parts of ion-exchanged water was added thereto. Next, acrylic acid was dropped into the reaction vessel over 5 hours, and at the same time, an aqueous solution in which 0.24 parts of L-ascorbic acid was dissolved in 49.3 parts of ion-exchanged water was dropped over 5.5 hours. Thereafter, the temperature was maintained at 65 ° C. for 1 hour to terminate the polymerization reaction. Thereafter, the reaction solution was neutralized to pH 7 using an aqueous sodium hydroxide solution at a temperature below the polymerization reaction temperature, and an aqueous solution of copolymer 9 having a weight average molecular weight of 40,000 was obtained. The total amount of IPN-50 and acrylic acid used was 274.7 parts, and the final monomer composition ratio in the copolymer was calculated based on the remaining amount of monomer measured by LC.

<Production Example 10>
In a glass reaction vessel equipped with a thermometer, a stirrer, a dropping funnel, a nitrogen inlet tube and a reflux condenser, 277 parts of ion-exchanged water, an unsaturated polyalkylene glycol (IPN-50) in which an average of 50 moles of ethylene oxide was added to 3-methyl-3-buten-1-ol, were charged, and the temperature was raised to 65 ° C., and then an aqueous hydrogen peroxide solution containing 0.67 parts of hydrogen peroxide and 12.73 parts of ion-exchanged water was added thereto. Next, acrylic acid was dropped into the reaction vessel over 3 hours, and at the same time, an aqueous solution in which 0.87 parts of L-ascorbic acid and 1.57 parts of 3-mercaptopropionic acid were dissolved in 16.49 parts of ion-exchanged water was dropped over 3.5 hours. Thereafter, the temperature was maintained at 65 ° C. for 1 hour to terminate the polymerization reaction. Thereafter, the reaction solution was neutralized to pH 7 using an aqueous sodium hydroxide solution at a temperature below the polymerization reaction temperature, and an aqueous solution of copolymer 10 having a weight average molecular weight of 30,000 was obtained. The total amount of IPN-50 and acrylic acid used was 458.4 parts, and the final monomer composition ratio in the copolymer was calculated based on the remaining amount of monomer measured by LC.

The composition ratio (finished ratio) and weight average molecular weight of each structural unit in copolymers 1 to 10 obtained in production examples 1 to 10 are shown in Table 1.

<Examples 1 to 6 and Comparative Examples 1 and 2>
The fluidity retention and viscosity retention were evaluated by the above-mentioned methods for Copolymers 1 to 6, 8 and 9 obtained in Production Examples 1 to 6, 8 and 9. The results are shown in Table 2.

<Examples 7 to 13 and Comparative Examples 3 and 4>
The copolymers 1 to 9 obtained in Production Examples 1 to 9 were mixed with the copolymer 10 as a cement dispersant in a mass ratio of 7:3 to prepare samples. The fluidity retention and viscosity retention of these samples were evaluated by the above-mentioned methods. The results are shown in Table 3.
The amounts added in Table 3 are the amounts of samples added.

Claims (3)

A cement additive comprising a polycarboxylic acid copolymer,
The polycarboxylic acid copolymer is represented by the following formula (1):

(In the formula, R ¹ , R ² and R ³ are the same or different and each represents a hydrogen atom or a methyl group. R ⁴ represents a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. ⁾ O) are the same or different and represent an oxyalkylene group having 2 to 4 carbon atoms. n represents the average number of moles of oxyalkylene groups added and is a number from 5 to 18. x represents a number from 0 to 4. y represents 0. The content ratios of the structural unit (a) derived from the polyalkylene glycol monomer (A), the structural unit (b) derived from the unsaturated monocarboxylic acid monomer (B) and the structural unit (c) derived from the hydroxyalkyl carboxylate (C) represented by (a) to (c) are 65 to 95 mass%, 5 to 30 mass% and 0 to 18 mass%, respectively, relative to 100 mass% of all structural units; the content ratio of the structural unit (e) derived from another monomer (E) other than the polyalkylene glycol monomer (A), the unsaturated monocarboxylic acid monomer (B) and the hydroxyalkyl carboxylate (C) is 0 to 5 mass% relative to 100 mass% of all structural units; the weight average molecular weight is 3,000 to 15,000;
The cement additive further comprises a copolymer different from the polycarboxylic acid copolymer,
The different copolymers are polymers obtained by polymerizing monomer components including an unsaturated carboxylic acid monomer and a (poly)alkylene glycol monomer,
A cement additive, characterized in that the total content of the polycarboxylic acid copolymer and the different copolymer is 2 mass% or more and 50 mass% or less based on 100 mass% of the solid content of the cement additive (provided that the following formula (3);

(wherein R ¹⁰ and R ¹¹ are the same or different and are a hydrogen atom or a methyl group, Y is -(CH ₂ ) _m - or -Z-CHOH-, m is an integer from 1 to 10, Z is -COO-CH ₂ - or -(AO) _p -CH ₂ -, AO is an oxyalkylene group having 2 to 3 carbon atoms, and p is an integer from 1 to 500) , and a polymer (β) having a structural unit derived from a monomer represented by the following formula (4);

(wherein R ¹² , R ¹³ , and R ¹⁴ are the same or different and represent a hydrogen atom or a methyl group, R ¹⁵ represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms, R ^a O represents an oxyalkylene group having 2 to 18 carbon atoms, n3 represents the average addition mole number of the oxyalkylene group represented by R ^a O, n3 is an integer of 1 to 500, x2 is an integer of 0 to 2, and y2 is 0 or 1), and a structural unit (I) derived from an unsaturated polyalkylene glycol alkenyl ether monomer (a1) represented by the following formula (5);

(wherein R ¹⁶ and R ¹⁷ are the same or different and each represents a hydrogen atom or a methyl group, R ¹⁸ represents a hydrogen atom, and X ² represents a hydrogen atom, a methyl group, an ethyl group, an alkali metal, an alkaline earth metal, an ammonium group, an organic ammonium group, or an organic amine group), and a structural unit (II) derived from an unsaturated carboxylic acid monomer (b1) represented by the following formula (6);

(wherein R ¹⁹ is a hydrogen atom or a methyl group, Y ² is -NH- or -O-, R ²⁰ is an alkylene group having 1 to 10 carbon atoms, and M is a hydrogen atom, a metal atom, an ammonium group (forming an ammonium salt, i.e., SO ₃ NH ₄ ), or an organic amino group (forming an organic amine salt).) and the content of the structural unit (II) is more than 4 parts by mass and less than 30 parts by mass when the total of the structural unit (I), the structural unit (II), and the structural unit (III ) is 100 parts by mass is excluded.) The cement additive according to claim 1, characterized in that the carboxylic acid hydroxyalkyl ester (C) is a hydroxyalkyl (meth)acrylate. A cement composition comprising the cement additive according to claim 1 or 2 and cement.