Additives for lean concrete compositions

Abstract

To provide an additive excellent in material separation resistance in a poorly mixed concrete composition.SOLUTION: An additive for a poorly mixed concrete composition according to the present invention is an additive used for a concrete composition having a water / hydraulic powder ratio of 50% or more, wherein the additive comprises a copolymer that has a structural unit (a) derived from a polyalkylene glycol-based monomer (A), represented by the following formula (1) (where R1, R2 and R3 are, identically or differently, hydrogen atoms or methyl groups; R4 is a hydrogen atom or a hydrocarbon group having from 1 to 30 carbons; (R5O) is, identically or differently, an oxyalkylene group having from 2 to 18 carbons; n represents the average number of additional moles of oxyalkylene groups, which is a number from 10 to 200; x is 0 to 4; and y is 0 or 1), and a structural unit (b) derived from an unsaturated carboxylic acid-based monomer (B), wherein the structural unit (b) is at least 35 mass% based on 100 mass% of the total structural units; and wherein the weight-average molecular weight of the copolymer is 5000 to 30,000.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to an additive for lean-mix concrete compositions. [Background technology]

[0002] Polycarboxylic acid copolymers, which have polyalkylene glycols in the side chains of polycarboxylic acids such as poly(meth)acrylic acid, have become indispensable for constructing civil engineering and building structures from cement compositions such as cement paste, mortar, and concrete, due to their excellent cement dispersion properties. Cement admixtures containing such copolymers are used as water-reducing agents, and by increasing the fluidity of the cement composition and reducing its water content, they improve the strength and durability of the hardened product. While naphthalene-based water-reducing agents were conventionally used, cement additives primarily composed of copolymers such as polycarboxylic acid copolymers exhibit superior water-reducing performance and have therefore gained a wide track record as high-performance AE water-reducing agents.

[0003] Regarding polycarboxylic acid copolymers, for example, Patent Document 1 discloses an ultrafine particle injection material composition comprising a polycarboxylic acid copolymer having repeating units derived from an unsaturated polyalkylene glycol monomer of a predetermined structure and repeating units derived from an unsaturated carboxylic acid monomer of a predetermined structure, wherein the ultrafine particle injection material composition comprises ultrafine particle cement having a particle size of 16 μm or more in amount of 10 volume% or less, and the ultrafine particle cement comprises blast furnace slag and gypsum. Patent Document 2 discloses a cement admixture containing in predetermined proportions a copolymer (A) having structural units derived from an unsaturated (poly)alkylene glycol ether monomer (a) and a saturated carboxylic acid monomer, and an unsaturated (poly)alkylene glycol ether monomer (a) and a non-polymerizable (poly)alkylene glycol (B) that does not have an alkenyl group. In addition, Patent Documents 3 and 4 disclose a method of plasticizing a hydraulic cementitious composition in a low to medium range or achieving water reduction in a low to medium range in a hydratable cementitious composition by using a comb-shaped polycarboxylate copolymer obtained by polymerizing a monomer component containing a polyoxyalkylene monomer having a predetermined structure, an unsaturated carboxylic acid monomer having a predetermined structure, and optionally a water-soluble and hydrophilic unsaturated monomer at a predetermined ratio.

[0004] In civil engineering, construction, etc., lean-mix concrete with a high water-cement ratio may be used from the viewpoints of crack prevention due to hydration heat and economy. Regarding the dispersant used for lean-mix concrete, Patent Document 5 discloses a dispersant for a hydraulic composition containing a copolymer (i) obtained by copolymerizing a first polyalkylene glycol (meth)acrylate (1-a) having a predetermined structure, a second polyalkylene glycol (meth)acrylate (1-b) having a predetermined structure, and a monomer (1-c) having a predetermined structure at a predetermined weight ratio.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0006] Lean mix concrete has a high water content, which makes it prone to material segregation. As mentioned above, polycarboxylic acid copolymers have been developed for use in lean mix concrete compositions, but they have not been sufficient in terms of resistance to material segregation.

[0007] This invention has been made in view of the above-mentioned circumstances, and aims to provide an additive that exhibits excellent resistance to material segregation in lean-mix concrete compositions. [Means for solving the problem]

[0008] The inventors of the present invention have investigated various polymers that can be used in lean concrete compositions and have found that copolymers having structural units derived from polyalkylene glycol monomers and unsaturated carboxylic acid monomers of a predetermined structure, and in which the content ratio of structural units derived from unsaturated carboxylic acid monomers and the weight-average molecular weight are within a predetermined range, exhibit excellent resistance to material segregation in lean concrete compositions. This led the inventors to the present invention, as they realized that the above problem could be successfully solved.

[0009] In other words, the present invention is as follows. [1] An additive used in a concrete composition having a water / hydraulic powder ratio of 50% or more, The additive is given by the following formula (1); [ka] (In the formula, R 1 , R 2 and R 3 R represents a hydrogen atom or a methyl group, either identical or distinct. 4 (R) represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. 5An additive for lean concrete compositions, characterized by containing a copolymer having structural units (a) derived from a polyalkylene glycol monomer (A) and structural units (b) derived from an unsaturated carboxylic acid monomer (B), wherein the content of structural units (b) is 35% by mass or more relative to 100% by mass of all structural units, and the weight-average molecular weight is 5000 to 30000. [2] The additive for lean concrete composition according to [1] above, characterized in that the content of the above structural unit (b) is 70% by mass or less with respect to 100% by mass of all structural units. [3] An additive for lean concrete compositions according to [1] or [2] above, characterized in that the hydraulic powder contains cement. [4] A concrete composition characterized by comprising the additive for lean concrete composition described in any of [1] to [3] above, cement, and aggregate. [5] A method for producing a concrete composition, characterized by comprising the step of mixing a lean-mix concrete composition additive described in any of [1] to [3] above with cement and aggregate. [Effects of the Invention]

[0010] The additive for lean-mix concrete compositions of the present invention has the above-described configuration and, because it exhibits excellent resistance to material segregation in lean-mix concrete compositions, it can be suitably used in lean-mix concrete and the like. [Modes for carrying out the invention]

[0011] Preferred embodiments of the present invention will be described below in detail, but the present invention is not limited to the following descriptions and can be modified and applied as appropriate without changing the gist of the present invention. Furthermore, embodiments combining two or more of the individual preferred embodiments of the present invention described below also constitute preferred embodiments of the present invention.

[0012] [Copolymer] The copolymer contained in the additive for lean concrete compositions of the present invention (hereinafter also referred to as the additive of the present invention) has a structural unit (a) derived from a polyalkylene glycol monomer (A) represented by the above formula (1) and a structural unit (b) derived from an unsaturated carboxylic acid monomer (B). In this invention, a monomer-derived structural unit refers to a structure (-CC-) in which the carbon-carbon double bond (C=C) portion of a monomer is replaced by a single bond and forms a bond with an adjacent carbon atom. In this invention, monomer-derived structural units are not limited to those formed by polymerization of monomers, but may also be formed by reactions other than polymerization.

[0013] In the copolymer described above, the proportion of structural unit (b) is 35% by mass or more relative to 100% by mass of all structural units. This ensures that the number of side chains of structural unit (a) is below a predetermined amount, preventing excessive cement dispersibility and maintaining a suitable range. As a result, it is possible to adequately hold water in the concrete composition and suppress material segregation. The proportion of structural unit (b) is preferably 80% by mass or less. This allows the additive of the present invention to exert its effect more sufficiently even when added in small amounts. More preferably it is 40 to 75% by mass, even more preferably 45 to 70% by mass, and particularly preferably 50 to 65% by mass. In the present invention, when calculating the mass percentage (mass%) of the above structural unit (b) relative to 100% by mass of all structural units, the calculation shall be performed on a basis of the corresponding sodium salt. For example, the mass percentage of structural units derived from acrylic acid shall be calculated as the mass percentage (mass%) of structural units derived from sodium acrylate, which is the corresponding sodium salt.

[0014] In the copolymer described above, the proportion of structural unit (a) is preferably 20 to 65% by mass relative to 100% by mass of the total structural units. More preferably 25 to 60% by mass, even more preferably 30 to 55% by mass, and particularly preferably 35 to 50% by mass.

[0015] The above copolymer may have structural units (c) derived from monomers (C) other than polyalkylene glycol monomers (A) and unsaturated carboxylic acid monomers (B). The proportion of structural unit (c) in the above copolymer is preferably 0 to 10% by mass relative to 100% by mass of the total structural units. More preferably 0 to 8% by mass, even more preferably 0 to 5% by mass, and most preferably 0% by mass.

[0016] In the copolymer described above, the proportion of structural unit (a) is preferably 1 to 30 mol% relative to 100 mol% of the total structural units. More preferably 1 to 25 mol%, even more preferably 1 to 20 mol%, even more preferably 1 to 15 mol%, and particularly preferably 1 to 10 mol%.

[0017] In the copolymer described above, the proportion of structural unit (b) is preferably 70 to 99 mol% relative to 100 mol% of the total structural units. More preferably 75 to 99 mol%, even more preferably 80 to 99 mol%, even more preferably 85 to 99 mol%, and particularly preferably 90 to 99 mol%. Furthermore, the proportion of structural unit (b) is preferably greater than 75 mol%, more preferably greater than 80 mol%, even more preferably greater than 85 mol%, and even more preferably greater than 90 mol% relative to 100 mol% of the total structural units.

[0018] In the copolymer described above, the proportion of structural unit (c) is preferably 0 to 10 mol% relative to 100 mol% of the total structural units. More preferably it is 0 to 5 mol%, even more preferably 0 to 1 mol%, and particularly preferably 0 to 0.1 mol%.

[0019] The above copolymer has a weight average molecular weight of 5000 to 30000. As a result, the cement dispersibility does not become too high and is within a suitable range, so that the water in the concrete composition can be sufficiently held and material separation can be suppressed. Preferably it is 5500 to 25000, more preferably 6000 to 20000, still more preferably 6500 to 18000, and particularly preferably 7000 to 15000. The above weight average molecular weight can be measured by the method described in the examples.

[0020] <Polyalkylene glycol monomer (A)> The above 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 ~R 3 represent, the same or different, a hydrogen atom or a methyl group. Preferably R 1 , R 2 are hydrogen atoms, and R 3 is a hydrogen atom or a methyl group. More preferably, R 1 , R 2 are hydrogen atoms, and R 3 is a methyl group.

[0021] R in the above formula (1) 4 represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. Preferably it is a hydrocarbon group having 1 to 18 carbon atoms or a hydrogen atom, more preferably a hydrogen atom or a hydrocarbon group having 1 to 8 carbon atoms, still more preferably a hydrogen atom or a hydrocarbon group having 1 to 6 carbon atoms, and particularly preferably a hydrogen atom or a hydrocarbon group having 1 to 3 carbon atoms. Examples of the hydrocarbon group include an alkyl group (linear, branched or cyclic), a phenyl group, an alkyl-substituted phenyl group, etc. Among them, an alkyl group (linear, branched or cyclic) is preferable, a methyl group, an ethyl group, and a propyl group are more preferable, and a methyl group is most preferable.

[0022] In the above formula (1), R 5O represents an oxyalkylene group having 2 to 18 carbon atoms, "identical or different," where n R groups exist in the polyalkylene glycol. 5 This means that the oxyalkylene groups of O may all be the same or they may all be different. The number of carbon atoms in the oxyalkylene group is preferably 2 to 18. More preferably 2 to 12, even more preferably 2 to 8, and particularly preferably 2 to 4. In the above equation (1), R 5 The oxyalkylene group represented by 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, and styrene oxide. More preferably, alkylene oxides having 2 to 4 carbon atoms, such as ethylene oxide, propylene oxide, and butylene oxide, and even more preferably, ethylene oxide and propylene oxide. Furthermore, if the polyalkylene glycol is any two or more alkylene oxide adducts selected from ethylene oxide, propylene oxide, butylene oxide, styrene oxide, etc., it may be in any form such as random addition, block addition, or alternating addition. In order to ensure a balance between hydrophilicity and hydrophobicity, it is preferable that the polyalkylene glycol contains oxyethylene groups as an essential component, more preferably 50 mol% or more being oxyethylene groups, and even more preferably 90 mol% or more being oxyethylene groups.

[0023] In formula (1) above, n represents the average number of moles of oxyalkylene groups added, and is between 10 and 200. Preferably, n is between 15 and 150, more preferably between 20 and 100, even more preferably between 25 and 90, even more preferably between 30 and 80, and particularly preferably between 35 and 70.

[0024] In equation (1) above, x represents a number from 0 to 4, and y represents 0 or 1. x is preferably between 1 and 4. y is preferably 0. Since monomer (A) with y = 0 is inexpensive, the copolymer of the present invention can be manufactured at low cost. When y is 0, x is preferably 1 to 4, more preferably 1 or 2, and even more preferably 2. When x is 1 to 4, R 3 It is preferable that it be a methyl group. When y is 1, it is preferable that x is 0. In this case, R 3 It is more preferable that it be a hydrogen atom or a methyl group.

[0025] Specific examples of the polyalkylene glycol monomer (A) include polyalkylene glycol (meth)acrylates such as polyethylene glycol (meth)acrylate and alkoxy polyalkylene glycol (meth)acrylates obtained by hydrophobically modifying these with hydrocarbon groups having 1 to 30 carbon atoms at their ends; compounds obtained by adding 10 to 200 moles of alkylene oxide to unsaturated alcohols having 2 to 8 carbon atoms such as vinyl alcohol, allyl alcohol, metharyl 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, and 3-allyloxy-1,2-propanediol; and compounds obtained by hydrophobically modifying these with hydrocarbon groups having 1 to 30 carbon atoms at their ends. Among these, compounds obtained by adding 10 to 200 moles of alkylene oxide to unsaturated alcohols having 2 to 8 carbon atoms and compounds obtained by hydrophobically modifying these with hydrocarbon groups having 1 to 30 carbon atoms at their ends are preferred. More preferably, the compound is obtained by adding 10 to 200 moles of alkylene oxide to an unsaturated alcohol having 2 to 8 carbon atoms, and even more preferably, the compound is obtained by adding alkylene oxide to 4-hydroxybutyl-1-monovine ether, (meth)allyl alcohol, or 3-methyl-3-buten-1-ol.

[0026] <Unsaturated carboxylic acid monomer (B)> The above unsaturated carboxylic acid monomer (B) is not particularly limited as long as it has a carboxyl group and an ethylenically unsaturated hydrocarbon group (unsaturated group), but the following formula (2);

[0027] [ka]

[0028] (In the formula, R 6 , R 7 , R 8 These are identical or different hydrogen atoms, C1-C10 alkyl groups, and -(CH2) p1 COOM 2 (-(CH2) p1 COOM 2 is, -COOM 1 or other (CH2) p1 COOM 2 (and may form an anhydrous product), -(CH2) p2 (CO) q1 -OR 9 , or -(CH2) p3 CONR 10 R 11 This represents p1, p2, and p3, which are either the same or different integers between 0 and 2, and q1 represents 0 or 1. 1 and M 2 R represents, either identically or distinctly, a hydrogen atom, a monovalent metal atom, a divalent metal atom, a trivalent metal atom, a quaternary ammonium group, or an organic amine group. 9 , R 10 , R 11 It is preferable that the compound is represented by (which is the same or different, and represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms).

[0029] The above R 6 , R 7 , R 8 The number of carbon atoms in the C1-C10 alkyl group is preferably 1-8, more preferably 1-4. The C1-C10 alkyl group is preferably a methyl group, an ethyl group, a propyl group, or a butyl group, more preferably a methyl group or an ethyl group, and particularly preferably a methyl group. The above R6 , R 7 , R 8 Preferably, at least one of them is a hydrogen atom, and more preferably, at least two are hydrogen atoms. 9 , R 10 , R 11 Examples of C1-C30 hydrocarbon groups in include C1-C30 aliphatic alkyl groups, C3-C20 alicyclic alkyl groups, C2-C30 alkenyl groups, C2-C30 alkynyl groups, C6-C30 aryl groups, etc. 1 and M 2 Examples of monovalent metal atoms include alkali metal atoms such as lithium, sodium, and potassium. Examples of divalent metal atoms include alkaline earth metal atoms such as calcium and magnesium. Examples of trivalent metal atoms include aluminum and iron. Examples of organic amine groups include alkanolamine groups such as ethanolamine, diethanolamine, and triethanolamine, and triethylamine. Above M 1 and M 2 Hydrogen atoms or alkali metal atoms are preferred.

[0030] Specific examples of the above-mentioned unsaturated carboxylic acid monomer (B) include the following unsaturated monocarboxylic acid monomers and unsaturated dicarboxylic acid monomers. Examples of unsaturated monocarboxylic acid monomers include (meth)acrylic acid, crotonic acid, isocrotonic acid, tigric 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 of these; half-esters of the following unsaturated dicarboxylic acid monomers with C1-22 alcohols or C2-4 glycols; and half-amides of unsaturated dicarboxylic acid monomers with C1-22 amines.

[0031] Examples of the above-mentioned C1-C22 alcohols include methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, nonaol, decanol, undecanol, dodecanol, tridecanol, pentadecanol, hexadecanol, heptadecanol, octadecanol, nonadecanol, and eicosanol.

[0032] Examples of the above-mentioned glycols having 2 to 4 carbon atoms include ethylene glycol, propylene glycol, and diethylene glycol.

[0033] Examples of the above-mentioned amines having 1 to 22 carbon atoms include methylamine, ethylamine, propylamine, butylamine, dimethylamine, diethylamine, dipropylamine, dibutylamine, pentylamine, dipentylamine, hexylamine, dihexylamine, heptylamine, diheptylamine, octylamine, dioctylamine, and dodecylamine.

[0034] Examples of unsaturated dicarboxylic acid monomers include maleic acid, itaconic acid, mesaconic acid, citraconic acid, fumaric acid, and their monovalent metal salts, divalent metal salts, ammonium salts, and organic amine salts, as well as their anhydrides. The unsaturated carboxylic acid monomer (B) is preferably (meth)acrylic acid (salt), maleic acid (salt), or maleic anhydride. From the viewpoint of improving polymerizability, (meth)acrylic acid (salt) is more preferred.

[0035] The copolymer of the present invention may have structural units (c) derived from monomers (A) and (B) other than monomer (C). Other monomers (C) are not particularly limited as long as they can copolymerize with monomers (A) and (B), but for example, 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)allylsulfonic acid, isoprenesulfonic acid, 4-(allyloxy)benzenesulfonic acid, 1-methyl-2-propene-1-sulfonic acid, 1,1-dimethyl Unsaturated sulfonic acids such as tyl-2-propene-1-sulfonic acid, 3-butene-1-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, 2-(meth)acryloyloxy)ethanesulfonic acid and their salts; hydroxyl group-containing ethers such as 3-(meth)allyloxy-1,2-dihydroxypropane, 1-allyloxy-3-butoxypropane-2-ol; N- N-vinyl lactam monomers such as vinylpyrrolidone; (meth)acrylic acid esters such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, iso-nonyl (meth)acrylate, dodecyl (meth)acrylate, stearyl (meth)acrylate; hydroxymethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate Hydroxyl group-containing (meth)acrylic acid esters such as rilate, 3-hydroxypropyl (meth)acrylate, 2-hydroxy-1-methylethyl (meth)acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and hydroxypentyl (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;Examples include vinylaryl monomers such as styrene, α-methylstyrene, vinyltoluene, indene, vinylnaphthalene, phenylmaleimide, and vinylaniline; alkenes such as ethylene, propylene, butadiene, isobutylene, and octene; vinyl carboxylates such as vinyl acetate and vinyl propionate; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, and butyl vinyl ether; vinyl ethylene carbonate and its derivatives; unsaturated amines such as N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethylaminoethyl (meth)acrylamide, vinylpyridine, vinylimidazole and their salts or quaternaries; and vinyl cyanide monomers such as acrylonitrile and methacrylonitrile.

[0036] [Method for producing copolymers] The preparation of the copolymer of the present invention is not particularly limited, but it can be prepared by polymerizing monomer components, and specific and preferred examples of monomer components are as described above. The proportion of each structural unit in a copolymer produced by polymerization can be calculated based on the proportion of each monomer used as a reaction material and the amount of remaining monomer measured by high-performance liquid chromatography.

[0037] In the production of the above 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 its salts (sodium hypophosphite, potassium hypophosphite, etc.), sulfurous acid, bisulfite, dithionite, metabisulfite and its salts (sodium sulfite, sodium bisulfite, sodium dithionite, sodium metabisulfite, etc.).

[0038] As the above-mentioned chain transfer agent, a hydrophobic chain transfer agent may also be used. Suitable hydrophobic chain transfer agents include thiol-based chain transfer agents having three or more carbon atoms, such as butanethiol, octanthiol, decanethiol, dodecanethiol, hexadecanethiol, octadecanethiol, cyclohexyl mercaptan, thiophenol, octyl thioglycolate, and octyl 3-mercaptopropionate. Furthermore, to adjust the molecular weight of the copolymer, it is also effective to use monomers with high chain mobility, such as (meth)allyl sulfonic acid (salts).

[0039] The amount of the above-mentioned chain transfer agent used can be set as appropriate, but is preferably 0.1 moles or more, more preferably 0.25 moles or more, even more preferably 0.5 moles or more, and also preferably 20 moles or less, more preferably 15 moles or less, and even more preferably 10 moles or less, per 100 moles of the total amount of monomer components.

[0040] The above polymerization reaction can be carried out by methods such as solution polymerization or bulk polymerization, using a radical polymerization initiator as needed. Solution polymerization can be carried out in batches, continuous processes, or a combination thereof, and examples of solvents used 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 aqueous solution polymerization is preferred.

[0041] When carrying out the above aqueous solution polymerization, water-soluble polymerization initiators such as persulfates (e.g., ammonium persulfate, sodium persulfate, 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 2-carbamoylazoisobutyronitrile can be used as radical polymerization initiators. In this case, accelerators such as alkali metal sulfites such as sodium bisulfite, metadisulfite, sodium hypophosphite, Fe(II) salts such as Mohr's salt, sodium hydroxymethanesulfinate dihydrate, hydroxylamine hydrochloride, thiourea, L-ascorbic acid (salt), and erythorbic acid (salt) can also be used in combination. In particular, combinations of persulfates such as ammonium persulfate, sodium persulfate, and potassium persulfate, and hydrogen peroxide with accelerators such as L-ascorbic acid (salt) are preferred. These radical polymerization initiators and accelerators may be used individually or in combination of two or more. Furthermore, when performing solution polymerization using lower alcohols, aromatic or aliphatic hydrocarbons, ester compounds, or ketone compounds as solvents, or when performing bulk polymerization, 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 may also be used in combination. Moreover, when using a water-lower alcohol mixed solvent, various radical polymerization initiators or combinations of radical polymerization initiators and accelerators can be appropriately selected and used from the above-mentioned options.

[0042] The amount of radical polymerization initiator used is preferably 0.001 moles or more, more preferably 0.01 moles or more, even more preferably 0.1 moles or more, particularly preferably 0.2 moles or more, and preferably 20 moles or less, even more preferably 10 moles or less, particularly preferably 7 moles or less, and most preferably 5 moles or less, based on 100 moles of the total amount of monomer components.

[0043] In the polymerization reaction described above, polymerization conditions such as polymerization temperature are appropriately determined by the polymerization method, solvent, polymerization initiator, and chain transfer agent used. However, the polymerization temperature is preferably 0°C or higher, and preferably 150°C or lower. More preferably 30°C or higher, and even more preferably 50°C or higher. Furthermore, it is even more preferably 120°C or lower, and even more preferably 100°C or lower.

[0044] The method of adding each monomer component to the reaction vessel is not particularly limited and includes methods such as adding the entire amount to the reaction vessel all at once at the beginning; adding the entire amount to the reaction vessel in installments or continuously; or adding a portion to the reaction vessel initially and then adding the remainder in installments or continuously. Furthermore, by continuously or stepwise changing the rate at which each monomer is added to the reaction vessel during the reaction, the weight ratio of each monomer added per unit time can be continuously or stepwise changed, thereby simultaneously synthesizing two or more copolymers with different monomer ratios during the polymerization reaction. The radical polymerization initiator may be added to the reaction vessel from the beginning, added dropwise to the reaction vessel, or a combination of these methods may be used depending on the purpose. The polymers obtained as described above can be used as dispersants as is, but may be further neutralized with an alkaline substance if necessary. Suitable alkaline substances include inorganic salts such as hydroxides or carbonates of monovalent or divalent metals; ammonia; and organic amines. After the reaction is complete, the concentration can be adjusted if necessary.

[0045] [Additives for lean-mix concrete compositions] The additive for lean concrete compositions of the present invention is essential for the copolymer of the present invention, but may contain two or more of the above copolymers, or one or more copolymers different from the above copolymers. The additive for lean concrete compositions of the present invention may consist solely of the copolymer described above, or it may contain not only the copolymer but also other components or additives as needed.

[0046] The above-mentioned additive for lean concrete compositions may also contain other commonly used cement dispersants and water-reducing agents, as long as they do not impair the effects of the present invention, and multiple combinations are also possible. Other cement dispersants (water-reducing agents) are not particularly limited and include, for example, various sulfonic acid-based dispersants (water-reducing agents) having sulfonic acid groups in their molecules, various polycarboxylic acid-based dispersants (water-reducing agents) having polyoxyalkylene chains and carboxyl groups in their molecules, and various phosphoric acid-based dispersants (water-reducing agents) having phosphoric acid groups in their molecules. When the copolymer of the present invention is used in combination with other cement dispersants (water-reducing agents), the content of the other cement dispersants (water-reducing agents) is preferably 1 to 50% by mass, and more preferably 1 to 40% by mass, relative to 100% by mass of the copolymer of the present invention.

[0047] The above-mentioned sulfonic acid-based dispersant (water-reducing agent) may contain any compound having a sulfonic acid group or a sulfonic acid salt group in its molecule. Preferably, the compound having a sulfonic acid group or a sulfonic acid salt group has an aromatic ring in its molecule. Examples of the above-mentioned sulfonic acid-based dispersants (water-reducing agents) include polyalkylaryl sulfonate-based dispersants (water-reducing agents) such as naphthalene sulfonate formaldehyde condensate, methylnaphthalene sulfonate formaldehyde condensate, and anthracene sulfonate formaldehyde condensate; melamine formalin resin sulfonate-based dispersants (water-reducing agents) such as melamine sulfonate formaldehyde condensate; aromatic amino sulfonate-based dispersants (water-reducing agents) such as aminoaryl sulfonate-phenol-formaldehyde condensate; lignin sulfonate-based water-reducing agents such as lignin sulfonate and modified lignin sulfonate; and polystyrene sulfonate-based dispersants (water-reducing agents). The above-mentioned sulfonic acid-based dispersants (water-reducing agents) are preferably polyalkylaryl sulfonate-based dispersants (water-reducing agents) and lignin sulfonate-based dispersants (water-reducing agents), and more preferably lignin sulfonate-based dispersants (water-reducing agents).

[0048] As the above-mentioned polycarboxylic acid-based dispersant (water-reducing agent), a polymer obtained by copolymerizing monomer components containing an unsaturated carboxylic acid monomer and a (poly)alkylene glycol monomer is preferred. Examples of unsaturated carboxylic acid monomers include monomers similar to monomer (B) mentioned above. Examples of (poly)alkylene glycol monomers include compounds obtained by adding 1 to 300 moles of alkylene oxide to an unsaturated alcohol having 2 to 8 carbon atoms, and their hydrophobic modified forms, as well as esterified compounds of an unsaturated carboxylic acid monomer with an average addition mole of 1 to 300 (poly)alkylene glycols, and their hydrophobic modified forms.

[0049] The above polycarboxylic acid-based dispersant (water-reducing agent) preferably has a proportion of structural units derived from unsaturated carboxylic acid monomers of less than 35% by mass relative to 100% by mass of all structural units. More preferably, it is 1 to 30% by mass, and even more preferably 1 to 25% by mass. The above polycarboxylic acid-based dispersant (water-reducing agent) preferably contains structural units derived from (poly)alkylene glycol monomers at a rate of 65% by mass or more, relative to 100% by mass of all structural units. More preferably, it is 70-99% by mass, and even more preferably 75-99% by mass. The above polycarboxylic acid-based 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, 8,000 to 100,000.

[0050] Examples of the above-mentioned phosphate-based dispersants (water-reducing agents) include phosphate-based polymers and phosphate-based condensates containing polyalkylene glycol. As a phosphoric acid-based polymer, a polymer obtained by copolymerizing monomer components containing a (poly)alkylene glycol monomer and a phosphoric acid-based monomer is preferred. Examples of the above-mentioned phosphate monomers include mono(2-hydroxyethyl)(meth)acrylic acid phosphate, di-{(2-hydroxyethyl)(meth)acrylic acid} phosphate, and (poly)alkylene glycol mono(meth)acrylate acid phosphate. Suitable phosphate condensates include, for example, condensates of phosphate esters and aldehyde compounds. The phosphate ester is not particularly limited as long as it is an esterified product of phosphates (which may also be salts) and a hydroxyl group-containing compound; one or more types can be used. Note that any of phosphate monoesters, phosphate diesters, or phosphate triesters may be used.

[0051] Furthermore, the additives of the present invention may include, for example, one or more of the following: water-soluble polymer substances (such as polyethylene glycol), polymer emulsions, retarders (such as oxycarboxylic acids like gluconic acid), 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, air-entraining agents, surfactants, waterproofing agents, rust inhibitors, crack reducing agents, expanding agents, cement wetting agents, thickeners, separation reducing agents, flocculants, drying shrinkage reducing agents, strength enhancers, self-leveling agents, rust inhibitors, colorants, and antifungal agents.

[0052] [Concrete Composition] The additive of the present invention is used in lean concrete compositions. The above lean concrete composition contains a hydraulic powder (hydraulic material) such as cement, water, and aggregates such as fine aggregate (sand, etc.) or coarse aggregate (crushed stone, etc.), and the ratio of water to hydraulic powder (water / hydraulic powder ratio) is 50% or more. Examples of the hydraulic powder mentioned above include cement, blast furnace slag, fly ash, silica fume, and gypsum, with cement being preferred. The above-mentioned hydraulic powder containing cement is one of the preferred embodiments of the present invention. A concrete composition comprising the additive of the present invention, cement, and aggregate is also one of the present inventions.

[0053] In the lean concrete composition of the present invention, the cement may include Portland cement (ordinary, rapid-hardening, ultra-rapid-hardening, moderate-heat, low-heat, sulfate-resistant, and their respective low-alkali forms); various blended cements (blast furnace cement, silica cement, fly ash cement, eco-cement, white Portland cement, alumina cement, etc.), 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, or gypsum are added. The lean-mix concrete composition of the present invention may contain only one type of cement, or two or more types of cement.

[0054] In addition to gravel, crushed stone, granulated slag, and recycled aggregates, other aggregates mentioned above include refractory aggregates such as silica, clay, zircon, high alumina, silicon carbide, graphite, chromium, chromium-magnesium, and magnesia.

[0055] The above lean concrete composition may have a water / hydraulic powder ratio of 50% or more, but is preferably 50-70%, more preferably 50-65%, and even more preferably 55-65%. On the other hand, the mass of the hydraulic powder is 190-350 kg / m³. 3 Preferably, it is 210-340 kg / m 3 It is more preferable that it be 230-330 kg / m 3 It is even more preferable that it be 250-320 kg / m 3 It is most preferable that this be the case.

[0056] In the lean concrete composition described above, the blending ratio of the additives of the present invention is preferably set such that the copolymer (total amount if multiple copolymers are included), which is an essential component of the present invention, is 0.005 to 10% by mass on a solid content basis, relative to 100% by mass of the total amount of hydraulic powder. Setting it to 0.005% by mass or more allows the performance of the present invention to be more fully exhibited, while setting it to 10% by mass or less allows the performance of the present invention to be fully exhibited while also being economically efficient. More preferably, it is 0.01 to 5% by mass, and even more preferably 0.02 to 3% by mass.

[0057] A method for producing a concrete composition, comprising the step of mixing the additive for lean concrete compositions of the present invention with cement and aggregate, is also one of the present inventions. In the method for producing the above-mentioned concrete composition, the mixing step preferably involves mixing the additive of the present invention with cement, aggregate, and water. Specific examples and preferred examples of additives, cement, and aggregates for lean-mix concrete compositions used in the above mixing process are as described in the sections on additives for lean-mix concrete compositions and concrete compositions of the present invention. Furthermore, the mixing ratio of the additives for lean-mix concrete compositions, cement, water, etc. is the same as the mixing ratio in the above-mentioned concrete composition.

[0058] In this specification, the solid content can be measured as follows. <Method for measuring solid content> 1. Weigh the aluminum tray accurately. 2.1 The solid content sample is accurately weighed into the aluminum pan prepared in step 2.1. 3. Place the solids measured in step 2 into a dryer heated 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 weigh the aluminum tray and the sample. The solid content is measured by subtracting the mass of the aluminum tray obtained in step 1 from the mass obtained in step 6.5, and then dividing by the mass of the solid content sample obtained in step 2. [Examples]

[0059] 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 "percent mass".

[0060] <Gel Permeation Chromatography (GPC)> The weight-average molecular weight of the copolymers produced in the polymerization examples below was measured using the following method. Equipment: Alliance (e2695) (manufactured by Waters) Analysis software: Empower2 Professional + GPC option (Waters) Columns used: TSKguardcolumnsSWXL (inner diameter: 6.0mm x 40mm) + TSKgel G4000SWXL (inner diameter: 7.8mm x 300mm) + G3000SWXL (inner diameter: 7.8mm x 300mm) + G2000SWXL (inner diameter: 7.8mm x 300mm) (all manufactured by Tosoh Corporation) Detector: Differential refractometer (RI) detector (Waters 2414) Eluent: A solution prepared by dissolving 115.6 g of sodium acetate trihydrate in a mixed solvent of 10999 g of deionized water and 6001 g of acetonitrile, and then adjusting the pH to 6.0 with acetic acid. Flow rate: 1mL / min Column temperature: 40℃ Measurement time: 45 minutes Sample injection volume: 100 μL (eluent solution with a sample concentration of 0.5% by mass) GPC standard samples: Polyethylene glycol manufactured by Tosoh Corporation, Mp = 255000, 200000, 107000, 72750, 44900, 31400, 21300, 11840, 6450, 4020, 1470 Calibration curve: Created using a cubic equation with the Mp values ​​of polyethylene glycol mentioned above.

[0061] <High-performance liquid chromatography (LC)> In the polymerization examples below, the remaining amounts of each monomer used as reaction raw materials were measured under the following conditions and used in the calculation of the copolymer composition. Equipment: Alliance 2695 (manufactured by Waters) Analysis software: Empower Professional (Waters Corporation) Column: Atlantis dC18 5μm (4.6mm inner diameter x 250mm length) x 2 (Waters Co., Ltd.) Detectors: Differential refractometer (RI) detector (Waters 2414), multi-wavelength visible ultraviolet (PDA) detector (Waters 2996) Solvent: Solution prepared by mixing 100 mM sodium acetate aqueous solution and acetonitrile in a 6:4 ratio. Flow rate: 1 mL / min Column temperature: 40℃ Measurement time: 30 minutes Sample injection volume: 100 μL (sample concentration: 1% by mass)

[0062] <Fluidity and resistance to separation> Concrete was manufactured under conditions of room temperature of 20°C ± 1°C and relative humidity of 60% ± 5%, using the mix proportions shown in Table 1 below. After adding coarse aggregate (G) to a forced twin-shaft mixer, fine aggregate (S) and cement (C) were added and mixing was started. Mixing water (W), a mixture of copolymer aqueous solution, air content adjuster, and tap water, was added simultaneously with the start of mixing in the mixer. Concrete was discharged from the mixer 120 seconds after the start. The air content adjuster was used by measuring the air content of the concrete in accordance with JIS A 1128, and adjusting the amount of the mix proportions as appropriate so that the air content immediately after discharge was 4.5 ± 1.0%. (Materials used) C: Ordinary Portland cement manufactured by Taiheiyo Cement Corporation (Specific gravity: 3.16 g / cm³) 3 )G: Hard crushed stone from Ome (Specific gravity: 2.65 g / cm³) 3 ) S: Kakegawa River system land sand (Specific gravity: 2.65 g / cm³) 3 Air volume regulators: MasterAir 404 and MasterAir 202 manufactured by Pozzolith Solutions. (1) Liquidity The slump flow value of the concrete was measured according to JIS A 1150. (2) Separation resistance After mixing, the concrete was discharged from the mixer onto a flat plate (steel plate), quickly mixed again with a shovel to form a mass approximately 50 cm in diameter, and left to stand. Ten minutes after the start of mixing, the degree to which mortar separated and flowed out from the edges of the standing concrete was evaluated according to the following criteria. ◎: The maximum distance from the edge of the concrete to the edge of the mortar that has flowed out is less than 10 mm. ○: The maximum distance from the edge of the concrete to the edge of the mortar that has flowed out is between 10mm and 20mm. △: The maximum distance from the edge of the concrete to the edge of the mortar that has flowed out is between 20mm and 30mm. ×: The maximum distance from the edge of the concrete to the edge of the mortar that has flowed out is 30 mm or more.

[0063] [Table 1]

[0064] [Polymerization Example 1] Deionized water was charged into a glass reaction vessel equipped with a thermometer, stirrer, dropper, nitrogen inlet tube, and reflux condenser. Subsequently, the reaction vessel was purged with nitrogen while stirring, and the temperature was raised to 60°C under a nitrogen atmosphere. Then, an aqueous solution of hydrogen peroxide was added. Next, aqueous solutions of an unsaturated polyalkylene glycol monomer (IPN-50) in which an average of 50 moles of ethylene oxide were added to 3-methyl-3-buten-1-ol, acrylic acid (AA), and 3-mercaptopropionic acid, each dissolved in deionized water, were added dropwise at a constant rate over 4 hours. An aqueous solution of L-ascorbic acid dissolved in deionized water was added dropwise at a constant rate over 4.5 hours. The temperature was kept constant at 60°C during this time, and after the dropwise addition was completed, the temperature was maintained at 60°C for 1 hour to complete the polymerization reaction. Subsequently, the pH of the reaction solution was neutralized to pH=6 using an aqueous sodium hydroxide solution at a temperature below the polymerization reaction temperature to obtain an aqueous polymer solution containing copolymer (1).

[0065] [Polymerization Examples 2-15] For each polymerization example 2 to 15, polymerization reactions were carried out in accordance with the method of polymerization example 1 using various polyalkylene glycol monomers (A) and unsaturated carboxylic acid monomers (B) listed in Table 2 below, to obtain aqueous copolymer solutions containing one of copolymers (2) to (15).

[0066] Table 2 below shows the content ratio (final ratio) and weight-average molecular weight (Mw) of each structural unit in copolymers (1) to (15) obtained in polymerization examples 1 to 15.

[0067] [Table 2] The abbreviations for monomers in Table 2 are as follows: IPN-5: Ethylene oxide adduct of 3-methyl-3-buten-1-ol (average number of moles added: 5 moles) IPN-10: Ethylene oxide adduct of 3-methyl-3-buten-1-ol (average number of moles added: 10 moles) IPN-50: Ethylene oxide adduct of 3-methyl-3-buten-1-ol (average number of moles added: 50 moles) MLA-150: Ethylene oxide adduct of metharyl alcohol (average number of moles added: 150 moles) PGM-25E: Methoxypolyethylene glycol (average addition number of moles: 25 moles) monomethacrylate PGM-40E: Methoxypolyethylene glycol (average addition number of moles: 40 moles) monomethacrylate AA: Acrylic acid MAA: Methacrylic acid

[0068] <Examples 1-11 and Comparative Examples 1-4> The fluidity (flow value) and separation resistance of each copolymer (1) to (15) obtained in polymerization examples 1 to 15 were evaluated using the method described above (these evaluations are referred to as Examples 1 to 11 or Comparative Examples 1 to 4, depending on the type of copolymer used, as shown in Table 3 below). The evaluation results are shown in Table 3 below. In the table, "% / C" represents the amount of copolymer solids added to the cement (mass%).

[0069] [Table 3]

[0070] The results in Table 3 above show that the examples all exhibited superior resistance to concrete segregation compared to the comparative examples. Therefore, it is suggested that the copolymer of the present invention exhibits excellent resistance to material segregation in lean concrete compositions.

Claims

1. An additive used in a concrete composition having a water / hydraulic powder ratio of 50% or more, The additive is given by the following formula (1): The following formula (1); 【Chemistry 1】 (In the formula, R １ , R ２ and R ３ R represents a hydrogen atom or a methyl group, either identical or distinct. ４ (R) represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. ５ O) represents an oxyalkylene group having 2 to 18 carbon atoms, which may be the same or different. n represents the average number of moles of oxyalkylene groups added, and is a number from 10 to 200. x represents a number from 0 to 4. y represents 0 or 1. It has a structural unit (a) derived from a polyalkylene glycol monomer (A) and a structural unit (b) derived from an unsaturated carboxylic acid monomer (B), The content of the structural unit (a) is 35 to 65% by mass relative to 100% by mass of all structural units. The content of the structural unit (b) is 35% by mass or more relative to 100% by mass of all structural units. An additive for lean concrete compositions, characterized by containing a copolymer having a weight-average molecular weight of 5,000 to 30,000.

2. The additive for lean concrete compositions according to claim 1, characterized in that the content of the structural unit (b) is 65% by mass or less with respect to 100% by mass of all structural units.

3. The additive for lean concrete compositions according to claim 1 or 2, characterized in that the hydraulic powder contains cement.

4. A concrete composition characterized by comprising the additive for lean concrete compositions according to claim 1 or 2, cement, and aggregate.

5. A method for producing a concrete composition, characterized by comprising the step of mixing the additive for lean concrete composition described in claim 1 or 2 with cement and aggregate.

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