Water-hardening components powder dispersant components

Abstract

To provide a powdery dispersant composition for a hydraulic composition which is excellent in heat resistance.SOLUTION: The powdery dispersant composition for a hydraulic composition contains a copolymer including, as constituent monomers, (A) one or more compounds selected from acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and maleic acid, and (B) one or more compounds selected from compounds represented by specific methacrylic acid ester compounds and specific acrylic acid ester compounds, and optionally an alkaline agent, in which a degree of neutralization of the copolymer is 0.7 or more and 1 or less, and the alkaline agent content is 0.3 molar equivalent or less with respect to the copolymer.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a powder dispersant composition for hydraulic compositions and a method for producing the same. [Background technology]

[0002] In recent years, there has been a trend toward environmentally friendly infrastructure development. Examples of this include the construction of new offshore wind turbines to utilize renewable energy, and the booming maintenance and repair of infrastructure established during the period of rapid economic growth. Developing infrastructure from this perspective is considered desirable from the perspectives of achieving the SDGs and evaluating companies based on ESG.

[0003] In the fields of construction and civil engineering that develop infrastructure, hydraulic compositions such as concrete are often used as repair materials, but because construction space at work sites is limited and it is difficult to transport ready-mixed concrete, the mainstream approach is to use premixes, which are powder mixtures of hydraulic compositions and organic compounds such as powdered dispersants (hereinafter referred to as powder dispersants). Powder dispersants that are premixed into repair materials include naphthalene sulfonic acid-based dispersants, polycarboxylic acid-based dispersants, and melamine sulfonic acid-based dispersants, and polycarboxylic acid-based dispersants in particular exhibit high dispersibility and contribute to improving the strength of structures by reducing the amount of water mixed in the hydraulic composition.

[0004] On the other hand, powder dispersants are obtained, for example, by drying a dispersant solution, and powdering methods are roughly divided into heat drying methods in which drying is performed by heating at room temperature and normal pressure, and reduced pressure drying methods in which drying is performed under reduced pressure. Depending on the method for spreading the dispersant solution, it can be divided into thin film drying methods represented by drum drying, disk drying, and belt drying, spray drying, kneader methods, inorganic powder supporting methods, etc.

[0005] Patent Document 1 describes a powder dispersant that contains a copolymer obtained by polymerizing a specific vinyl monomer (a), such as an ethylenically unsaturated carboxylic acid derivative having a polyoxyalkylene group, with a specific vinyl monomer (b), such as (meth)acrylic acid, in which the average number of moles of oxyalkylene groups or oxystyrene groups having 2 to 4 carbon atoms added is 50 to 300, the ratio of monomer (a) to monomer (b) is (a) / [(a)+(b)]×100=10 to 50 (mol %), and at least a portion of the copolymer is a monovalent metal salt.

[0006] Patent Document 2 provides a powdery cement dispersant that includes a polycarboxylic acid copolymer having repeating units (I) derived from an unsaturated polyalkylene glycol ether monomer (a) and repeating units (II) derived from an unsaturated carboxylic acid monomer (b), wherein the degree of neutralization of the carboxyl groups contained in the polycarboxylic acid copolymer is 50% or less. The present invention also describes a powdery cement dispersant that includes a polycarboxylic acid copolymer having repeating units (I) derived from an unsaturated polyalkylene glycol ether monomer (a) and repeating units (II) derived from an unsaturated carboxylic acid monomer (b), wherein the unsaturated polyalkylene glycol ether monomer (a) has an alkenyl group having 4 to 8 carbon atoms.

[0007] Patent Document 3 describes a powder dispersant composition for hydraulic compositions, which contains a copolymer having a structural unit (1) represented by a specific structural formula (1) and a structural unit (2) represented by a specific structural formula (2), and which has a median diameter of 1 μm or more and 90 μm or less, and a proportion of particles having a particle diameter of 1 μm or more and 250 μm or less of 90 mass % or more and 100 mass % or less. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-167255 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-542159 [Patent Document 3] Patent Publication No. 2021-102535 Summary of the Invention [Problem to be solved by the invention]

[0009] However, powdered polycarboxylic acid dispersants, particularly polycarboxylic acid dispersants copolymerized with unsaturated polyalkylene glycol ether compounds, have the problem that they can burn when exposed to high temperatures due to heating during drying, making powderization difficult. However, this problem of combustion due to heating has not been found with polycarboxylic acid dispersants copolymerized with unsaturated polyalkylene glycol ester compounds (polycarboxylic acid ester dispersants).

[0010] The present invention provides a powder dispersant composition for hydraulic compositions, which contains a polycarboxylic acid copolymer copolymerized with an unsaturated polyalkylene glycol ether compound and has excellent heat resistance, and a method for producing the same. [Means for solving the problem]

[0011] The present invention provides a powder dispersant composition for hydraulic compositions, which contains, as constituent monomers, a copolymer containing (A) one or more compounds selected from acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and maleic acid, and (B) one or more compounds selected from compounds represented by the following general formula (1) and compounds represented by the following general formula (2), and optionally an alkali agent: The degree of neutralization of the copolymer is 0.7 or more and 1 or less, The content of the alkaline agent is 0.3 molar equivalents or less relative to the copolymer. The present invention relates to a powdery dispersant composition for hydraulic compositions.

[0012] [ka]

[0013] (In the formula, R 1 is a hydrogen atom or a methyl group, and R 2 is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n is the average number of moles added, which is a number of 5 to 150.

[0014] The powder dispersant composition for hydraulic compositions of the present invention includes a powdery dispersant composition for hydraulic compositions obtained by heating and drying an aqueous solution having a pH of 6 to 13 and containing, as constituent monomers, a copolymer comprising (A) one or more compounds selected from acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and maleic acid, and (B) one or more compounds selected from compounds represented by the following general formula (1) and compounds represented by the following general formula (2), in a concentration of 20% by mass to 60% by mass:

[0015] The present invention also relates to a method for producing a powdery dispersant composition for hydraulic compositions, which comprises heating and drying an aqueous solution having a pH of 6 to 13 and containing, as constituent monomers, a copolymer comprising (A) one or more compounds selected from acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and maleic acid [hereinafter referred to as monomer (A)] and (B) one or more compounds selected from the compounds represented by general formula (1) and the compounds represented by general formula (2) [hereinafter referred to as monomer (B)] in a concentration of 20% by mass to 60% by mass, to obtain a powder of the copolymer. [Effects of the Invention]

[0016] According to the present invention, there are provided a powder dispersant composition for hydraulic compositions which contains a polycarboxylic acid copolymer copolymerized with an unsaturated polyalkylene glycol ether compound and has excellent heat resistance, and a method for producing the same. The present invention can easily produce powder by heat drying and reduce the labor required for the hydraulic powder mixing process when manufacturing hydraulic compositions, and is thought to be a technology that can contribute to SDGs Nos. 7, 9, 11, 12, and 13, for example. DETAILED DESCRIPTION OF THE INVENTION

[0017] The present inventors have found that the heat resistance of a polycarboxylic acid dispersant copolymerized with an unsaturated polyalkylene glycol ether compound can be improved by controlling the degree of neutralization of the polycarboxylic acid dispersant and the content of the alkali agent in the composition. The reason for this effect is not entirely clear, but is presumed to be as follows. The combustion of a substance is related to its ease of combining with oxygen and its molecular polarity. It is believed that molecules with higher polarity are less likely to combine with hydrophobic oxygen due to intermolecular interactions and interactions with water, making them less flammable. In the present invention, the polycarboxylic acid dispersant (a copolymer of monomers (A) and (B)) contains an unsaturated polyalkylene glycol ether compound (monomer (B)) with a large number of unsaturated alcohol-derived carbon atoms, which makes it more susceptible to oxygen combination. The polycarboxylic acid dispersant requires a relatively large amount of energy for combustion. By adjusting the degree of neutralization within a predetermined range, the ionization and hydration of the carboxyl groups are promoted, and the molecular polarity is enhanced, thereby inhibiting dehydration and improving heat resistance. Furthermore, in the present invention, the amount of an alkali agent (e.g., a neutralizing agent) in the powdered dispersant composition for hydraulic compositions is limited, thereby suppressing decomposition of the polycarboxylic acid dispersant and maintaining its performance as a dispersant.

[0018] <Powdered dispersant composition for hydraulic composition> The powdery dispersant composition for hydraulic compositions of the present invention contains, as constituent monomers, (A) one or more compounds selected from acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and maleic acid [monomer (A)], and (B) one or more compounds selected from the compounds represented by the general formula (1) and the compounds represented by the general formula (2) [monomer (B)], and contains a copolymer (hereinafter also referred to as the copolymer of the present invention) having a degree of neutralization of 0.7 or more and 1 or less.

[0019] The monomer (A) is one or more compounds selected from acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and maleic acid. The monomer (A) may be in the form of a salt (neutralized product) when charged in the production of the copolymer of the present invention. After copolymerization, maleic anhydride may undergo ring-opening and be incorporated into the copolymer as maleic acid.

[0020] The monomer (B) is one or more compounds selected from the compounds represented by the general formula (1) and the compounds represented by the general formula (2). In general formula (1) and general formula (2), R 1 is at least one of a hydrogen atom and a methyl group, and preferably contains a hydrogen atom, that is, is a hydrogen atom or a mixture of a hydrogen atom and a methyl group. In general formula (1) and general formula (2), R 2 is at least one of a hydrogen atom and an alkyl group having 1 to 3 carbon atoms, and is preferably a hydrogen atom. In general formula (1) and general formula (2), n is the average number of moles added, and is 5 or more, preferably 20 or more, more preferably 40 or more, and 150 or less, preferably 120 or less, more preferably 90 or less. The compound of general formula (1) includes an alkylene oxide adduct of 3-methyl-3-buten-1-ol, preferably an adduct of an alkylene oxide selected from ethylene oxide and propylene oxide. Examples of the compound of general formula (2) include alkylene oxide adducts of isoprene alcohol (isoprenol; 3-methyl-3-buten-1-ol), preferably adducts of alkylene oxides selected from ethylene oxide and propylene oxide.

[0021] In the copolymer of the present invention, the molar ratio of monomer (A) to monomer (B), monomer (A) / monomer (B), is preferably 1 or more, more preferably 3 or more, and 20 or less, more preferably 10 or less.

[0022] The copolymer of the present invention may contain, as constituent monomers, monomers other than the monomer (A) and the monomer (B), but it is desirable that the proportion of the monomer (A) and the monomer (B) is high. In the copolymer of the present invention, the total proportion of the monomer (A) and the monomer (B) in all the constituent monomers is preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 90 mol% or more, and preferably 100 mol% or less, and may be 100 mol%.

[0023] Furthermore, in the copolymer of the present invention, the proportion of monomer (A) in the total of monomer (A) and monomer (B) is preferably 60 mol % or more, more preferably 70 mol % or more, and preferably 95 mol % or less, more preferably 90 mol % or less.

[0024] The copolymer of the present invention may have a weight average molecular weight of, for example, 20,000 or more, further 25,000 or more, further 30,000 or more, and 70,000 or less, 60,000 or less, further 50,000 or less. This weight average molecular weight is measured by gel permeation chromatography (GPC) under the following conditions. *GPC conditions Apparatus: GPC (HLC-8320GPC) manufactured by Tosoh Corporation Column: G4000PWXL + G2500PWXL (Tosoh Corporation) Eluent: 0.2M phosphate buffer / CH3CN=9 / 1 Flow rate: 1.0mL / min Column temperature: 40℃ Detection: RI Sample size: 0.2 mg / mL Standard substance: Polyethylene glycol equivalent (monodisperse polyethylene glycol: molecular weight 87,500, 250,000, 145,000, 46,000, 24,000)

[0025] The copolymer of the present invention has a water content of preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less. The powdery dispersant composition for hydraulic compositions of the present invention preferably has a water content of 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less. These water contents are calculated based on the following formula from the masses before and after drying of the copolymer of the present invention or the powdery dispersant composition for hydraulic compositions (hereinafter collectively referred to as the sample) at 105°C for 2 hours. Drying can be carried out, for example, using a constant temperature air blower dryer FC-410 (manufactured by Advantec Toyo Co., Ltd.). A predetermined amount, for example, 2 g, of the sample can be used. Moisture content (mass%) = {sample mass before drying (g) - sample mass after drying (g)} / sample mass before drying (g)

[0026] The degree of neutralization of the copolymer of the present invention is 0.7 or more, preferably 0.8 or more and 1 or less, from the viewpoint of the heat resistance of the copolymer.

[0027] The powdery dispersant composition for hydraulic compositions of the present invention optionally contains an alkaline agent. The content of the alkaline agent is 0.3 molar equivalents or less, preferably 0.2 molar equivalents or less, and even more preferably 0.1 molar equivalents or less, relative to the copolymer. Examples of alkaline agents include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, ammonia, and alkanolamines. The alkaline agent may be, for example, the neutralizing agent used to neutralize the copolymer of the present invention. For example, an excess of neutralizing agent may be added to the copolymer of the present invention (unneutralized product) to neutralize it, thereby producing a copolymer with a neutralization degree of 1, and the remaining neutralizing agent may remain in the composition within the above-mentioned molar ratio range. When the copolymer of the present invention has a neutralization degree of less than 1, the alkaline agent may not be contained. Furthermore, when the copolymer of the present invention has a neutralization degree of 1, an alkaline agent may be optionally contained within the above-mentioned range.

[0028] The powder dispersant composition for hydraulic compositions of the present invention can contain the copolymer of the present invention in an amount of, for example, 40% by mass or more, further 60% by mass or more, further 80% by mass or more, and 99% by mass or less, further 95% by mass or less, or further 90% by mass or less.

[0029] The powder dispersant composition for hydraulic compositions of the present invention may contain any component other than the copolymer of the present invention, such as a hydraulic powder, a latent hydraulic powder, a fine aggregate, a powder antifoaming agent, a powder shrinkage reducing agent, a powder expanding agent, a powder effect accelerator, a powder effect retarder, a powder foaming agent, a powder waterproofing agent, and a powder rust inhibitor.

[0030] The median diameter (D50) of the copolymer of the present invention may be, for example, 20 μm or more, or even 70 μm or more, and 150 μm or less, or even 120 μm or less.

[0031] The median diameter (D50) of the powder dispersant composition for hydraulic compositions of the present invention may be, for example, 20 μm or more, or even 70 μm or more, and 150 μm or less, or even 120 μm or less.

[0032] The median diameter (D50) may be measured using a laser diffraction / scattering particle size distribution analyzer LA-920 (manufactured by Horiba, Ltd.) with ethanol (ethanol (95), manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a dispersion medium without ultrasonic irradiation.

[0033] <Method for producing powdery dispersant composition for hydraulic composition> The present invention relates to a method for producing a powdery dispersant composition for hydraulic compositions (hereinafter also referred to as the production method of the present invention), which comprises heating and drying an aqueous solution (also referred to as a raw material aqueous solution) containing a copolymer comprising a monomer (A) and a monomer (B) as constituent monomers at a concentration of 20% by mass or more and 60% by mass or less and having a pH of 6 or more and 13 or less, to obtain a powder of the copolymer. The matters described for the powdery dispersant composition for hydraulic compositions of the present invention can be applied as appropriate to the manufacturing method of the present invention.Specific examples and preferred examples of the monomer (A) and the monomer (B) in the manufacturing method of the present invention are the same as those for the powdery dispersant composition for hydraulic compositions of the present invention.

[0034] In the production method of the present invention, the concentration of the copolymer in the raw material aqueous solution is 20% by mass or more, further 30% by mass or more, and 60% by mass or less, further 40% by mass or less.

[0035] In the production method of the present invention, the pH of the raw material aqueous solution is adjusted to 6 or more, preferably 8 or more, and to 13 or less, preferably 11 or less. The pH of the raw material aqueous solution can be adjusted, for example, by a neutralizing agent (alkali agent) used to neutralize the copolymer.

[0036] In the present invention, a raw material aqueous solution to be subjected to heat drying can be prepared by adding 0.7 to 1.3 molar equivalents of a neutralizing agent (alkali agent) relative to the theoretical neutralization amount of the copolymer to an aqueous solution containing an unneutralized copolymer and water. After neutralizing the copolymer by adding a predetermined amount of neutralizing agent to the aqueous solution containing an unneutralized copolymer and water in this way, it is preferable to heat dry the aqueous solution.

[0037] The production method of the present invention may be a production method in which the raw material aqueous solution is heated and dried to obtain a powder containing the neutralized product of the copolymer.Furthermore, the production method of the present invention may be a production method in which the raw material aqueous solution is heated and dried to obtain a powder containing the neutralized product of the copolymer having a degree of neutralization of 0.7 to 1.

[0038] In the production method of the present invention, it is preferable to obtain a powder containing the copolymer of the present invention having a degree of neutralization of 0.7 to 1 and optionally an alkaline agent, wherein the content of the alkaline agent in the powder is 0.3 molar equivalents or less relative to the copolymer.

[0039] The heat drying of the raw material aqueous solution can be performed by spray drying and / or thin film drying. Preferably, the heat drying includes spray drying. The maximum temperature during spray drying may be 140°C or higher, preferably 150°C, and 200°C or lower, preferably 170°C or lower. Spray drying and thin film drying can each be performed according to a known method.

[0040] In the production method of the present invention, the heat drying is preferably carried out until the moisture content in the powder of the copolymer of the present invention is 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less.

[0041] The copolymer of the present invention obtained by the production method of the present invention and / or the powder dispersant composition for hydraulic compositions of the present invention preferably has a median diameter within the above range. [Example]

[0042] <Copolymer> Copolymer 1: A copolymer of acrylic acid / polyethylene glycol (50) isoprenyl ether = 80 mol / 20 mol (the number in parentheses is the average number of moles added, the same applies below), weight average molecular weight = 30,000, an aqueous solution containing 40 mass% of unneutralized copolymer was used as the raw material aqueous solution. Copolymer 2: A polymerization solution (unneutralized product) containing a polycarboxylic acid polymer synthesized according to Production Example C1 of JP 2009-161379 A was used as the raw material aqueous solution.

[0043] <Comparative copolymer> Comparative copolymer 1: acrylic acid / polyethylene glycol (50) allyl ether = 80 mol / 20 mol copolymer, weight average molecular weight = 50,000, an aqueous solution containing 40 mass% of unneutralized copolymer was used as the raw material aqueous solution. Comparative copolymer 2: acrylic acid / polyethylene glycol (50) methallyl ether = 80 mol / 20 mol copolymer, weight average molecular weight = 40,000, an aqueous solution containing 40 mass% of unneutralized copolymer was used as the raw material aqueous solution.

[0044] <Example 1 and Comparative Example 1> (1) Preparation of raw material aqueous solution A predetermined amount of 48% aqueous sodium hydroxide solution (manufactured by Kanto Chemical Co., Inc.) was added as an alkaline agent (neutralizing agent) to an aqueous solution containing the unneutralized copolymer described above and water, and the mixture was vigorously stirred with a magnetic stirrer to adjust the pH of the raw aqueous solution and the degree of neutralization (mol %) of the copolymer in the aqueous solution as shown in Table 1 to obtain a raw aqueous solution.

[0045] (2) Preparation of powder dispersant composition and measurement of water content 0.4 mg of the raw material aqueous solution prepared in (1) was weighed into an aluminum pan and subjected to measurement using a TG-DTA (Thermo plus EVO2, manufactured by Rigaku Corporation) under a nitrogen gas atmosphere at 200 mL / min under the temperature conditions described below. The powder dispersant composition was then prepared by drying, and the loss on ignition was calculated, and the water content (%) was calculated using the following formula. The results are shown in Table 1. The water content can be considered to be the water content in the copolymer after powderization. [1] 30℃ → 100℃(10.0℃ / min) [2] 100℃ → 30℃(-30.0℃ / min) Water content (%) = {mass of raw solution (mg) - loss on ignition (mg)} x 100 / mass of raw solution (mg)

[0046] (3) Heat resistance of copolymer The powder dispersant composition prepared in (2) was subjected to measurement using a TG-DTA (Thermo plus EVO2, manufactured by Rigaku Corporation) in a dry air atmosphere at 200 mL / min under the following temperature conditions, and the DTA exothermic peak temperature (Tm; °C) due to combustion was recorded. The results are shown in Table 1. Tm can be considered to be the Tm of the copolymer after powderization. [1] 30℃ → 500℃(10.0℃ / min) [2] 500℃ → 30℃(-30.0℃ / min)

[0047] [Table 1]

[0048] *1 Molar equivalent to copolymer (same below)

[0049] In Table 1, Examples 1-1 to 1-4, which are dried copolymers containing monomer (A) and monomer (B) as constituent monomers and have a degree of neutralization of 0.7 to 1, exhibited higher DTA exothermic peak temperatures (Tm; °C) than Comparative Examples 1-1 to 1-4, which used comparative copolymers. This is thought to be because monomer (B) contains a moiety with a relatively large number of carbon atoms derived from an unsaturated alcohol, and the degree of neutralization of the copolymer of the present invention is within a specified range, promoting ionization and hydration of the carboxyl groups of the relatively flammable copolymer of the present invention, increasing molecular polarity, and inhibiting dehydration, thereby improving heat resistance. However, the mechanism by which the effects of the present invention are exhibited is not limited to this.

[0050] <Example 2 and Comparative Example 2> (I) Production of powder dispersant composition for hydraulic composition by spray drying method The raw aqueous solution prepared in Example 1(1) or the raw aqueous solution with its pH varied (using the same neutralizer) was spray-dried in a pilot-type powdering facility, and heat resistance was evaluated. The powdering facility used was equipped with a disk atomizer, a blower, and a dryer. The dryer inlet temperature was 150°C, the outlet temperature was 80°C, the ambient temperature was 20°C, and the disk atomizer rotation speed was 18,000 rpm. When a powder dispersant composition was obtained, the moisture content of the composition was measured using an infrared moisture meter FD-660 (Kett Electric Laboratory Co., Ltd.). When a powder dispersant composition was obtained, particle size distribution was measured using a laser diffraction / scattering particle size distribution analyzer LA-920 (Horiba, Ltd.) using ethanol (95) (Fujifilm Wako Pure Chemical Industries, Ltd.) as the dispersion medium, and the median diameter (D50; μm) of the composition was calculated. The results are shown in Table 2. The water content can be regarded as the water content in the copolymer after pulverization, and the median diameter can be regarded as the median diameter of the copolymer after pulverization.

[0051] [Table 2]

[0052] In Table 2, Examples 2-1 and 2-2, which are dried copolymers containing monomer (A) and monomer (B) as constituent monomers and have a degree of neutralization of 0.7 or more and 1 or less, exhibit better heat resistance than Comparative Examples 2-1 and 2-2, which use comparative copolymers, and were obtained as high-quality powder dispersant compositions. This is also thought to be due to the improved heat resistance of the copolymer through a mechanism similar to that of Example 1, but the mechanism by which the effects of the present invention are exhibited is not limited to this.

Claims

1. A method for producing a powdery dispersant composition for a hydraulic composition, comprising: heating and drying an aqueous solution containing, as constituent monomers, a copolymer in a concentration of 20% by mass or more and 60% by mass or less, the copolymer comprising (A) one or more compounds selected from acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, and maleic acid, and (B) one or more compounds selected from compounds represented by the following general formula (1) and compounds represented by the following general formula (2): 【Chemistry 1】 (In the formula, R １ is a hydrogen atom or a methyl group, and R ２ is a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and n is the average number of moles added, which is a number of 5 to 150.

2. The method for producing a powdery dispersant composition for hydraulic compositions according to claim 1, wherein the heat drying is spray drying and / or thin film drying.

3. 3. The method for producing a powdery dispersant composition for hydraulic compositions according to claim 1 or 2, wherein the heat drying is spray drying.

4. The method for producing a powdery dispersant composition for hydraulic compositions according to claim 3, wherein the maximum temperature during spray drying is 140°C or higher and 200°C or lower.

5. The method for producing a powdery dispersant composition for hydraulic compositions according to any one of claims 1 to 4, wherein the aqueous solution is prepared by adding 0.7 molar equivalents or more and 1.3 molar equivalents or less of a neutralizing agent with respect to a theoretical neutralization amount of the copolymer.

6. The method for producing a powdery dispersant composition for hydraulic compositions according to any one of claims 1 to 5, wherein the heat drying is carried out until the moisture content in the copolymer powder becomes 5 mass% or less.

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