Dispersant for gypsum slurry

Abstract

The present invention provides a dispersant for gypsum slurry that exhibits excellent low-temperature storage stability and imparts excellent fluidity to the gypsum slurry, as well as a gypsum slurry with excellent fluidity and a method for producing the same. [Solution] A dispersant for gypsum slurry containing the following component (A). (A) Component: A copolymer comprising a specific constituent monomer (A1) represented by general formula (A1) and a specific constituent monomer (A2) represented by general formula (A2) as constituent monomers, wherein the proportion of constituent monomer (A1) in the total amount of constituent monomer (A1) and constituent monomer (A2) is 5% by mass or more and 25% by mass or less, and the pH of the aqueous solution when dissolved in water to a concentration of 40% by mass is 4 or less.

Description

Technical Field

[0001] The present invention relates to a dispersant for gypsum slurry, as well as a gypsum slurry and a method for producing the same.

Background Art

[0002] For the gypsum slurry used in gypsum boards, a naphthalene sulfonic acid formaldehyde condensate has been used as a dispersant. In recent years, the use of polycarboxylic acid-based dispersants has been increasing from the perspective of reducing production costs. When manufacturing gypsum boards, after forming the gypsum slurry into a plate shape, it is dried with a drying dryer to remove excess water. By using a polycarboxylic acid-based dispersant with high water-reducing properties, it is possible to form the shape even with a small amount of water, and there is an advantage of reducing drying costs. As fuels for drying dryers, LPG, LNG, coal, petroleum, etc. are used. However, against the backdrop of the recent soaring fuel prices and the increasing importance of CO2 reduction, the advantages of using polycarboxylic acid-based dispersants have been increasing.

[0003] [[ID=十七]] However, when the pH of the raw gypsum slurry is low, there is a problem that the adsorbability of the polycarboxylic acid-based dispersant to gypsum decreases, and the dispersibility of the gypsum slurry decreases. To address this, in some patent documents, methods for adjusting the pH of the gypsum slurry to improve viscosity and fluidity have been introduced. In Patent Document 1, it contains hemihydrate gypsum with an average particle size of 50 μm or less, calcium carbonate with an average particle size of 50 μm or less, and a setting retarder. The content of the calcium carbonate is 10 to 400 parts by mass with respect to 100 parts by mass of the hemihydrate gypsum, and the content of the setting retarder is 0.1 part by mass or more. When water is added to make a gypsum-based coating material, a dry-curing type coating material for gypsum composition capable of forming a thin, smooth coating film with suppressed color unevenness is disclosed. In Patent Document 2, there is disclosed a one-component liquid dispersant composition for gypsum that contains (A) a specific polycarboxylic acid copolymer, a specific nitrogen-containing compound such as a specific alkylamine, and water, and has a pH at 20°C of 7.0 or higher and 13.0 or lower, and can obtain a gypsum slurry excellent in stability and excellent in fluidity.

Prior Art Document

Patent Document

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, a method for controlling the cohesiveness of a gypsum slurry using a retarder is disclosed, but the combined use with a dispersant is not described. In Patent Document 2, by using a liquid dispersant for gypsum that combines a polycarboxylic acid-based dispersant and a specific nitrogen-containing compound such as an alkylamine, the fluidity of the gypsum slurry can be improved. However, in the winter, crystallized substances occur at the bottom of the container containing the dispersant, and the solubility of the dispersant polymer decreases, resulting in the formation of a gel-like substance, and there are problems with storage stability.

[0006] The present invention provides a dispersant for a gypsum slurry that is excellent in low-temperature storage stability assuming winter (for example, -5°C to 5°C), can impart excellent fluidity to the gypsum slurry, and a gypsum slurry excellent in fluidity and a method for producing the same.

Means for Solving the Problems

[0007] The present invention relates to a dispersant for a gypsum slurry containing the following component (A). (A) Component: A copolymer containing, as constituent monomers, a constituent monomer (A1) represented by the following general formula (A1) and a constituent monomer (A2) represented by the following general formula (A2), wherein the proportion of the constituent monomer (A1) in the total amount of the constituent monomer (A1) and the constituent monomer (A2) is 5% by mass or more and 25% by mass or less, and the pH of the aqueous solution when dissolved to a concentration of 40% by mass with water is 4 or less.

[0008]

Chemical formula

[0009] [In the formula, R 1a 、R 2a 、R 3a : are the same or different and are a hydrogen atom, a methyl group or (CH2) r COOM 2a ; when (CH2) r COOM 2a forms an anhydride with COOM 1a or another (CH2) r COOM 2a , M 1a 、M 2a do not exist. M 1a 、M 2a : are the same or different and are a hydrogen atom, an alkali metal, an alkaline earth metal (1 / 2 atom), an ammonium group, an alkylammonium group, a substituted alkylammonium group, an alkyl group, a hydroxyalkyl group or an alkenyl group r: a number from 0 to 2 .]

[0010]

Chemical formula

[0011] [In the formula, R 4a 、R 5a : are the same or different and are a hydrogen atom or a methyl group R 6a : a hydrogen atom, a methyl group, (CH2)r COOM 3a , or (CH2) q1 (CO) p1 O(AO) n1 R 7a R 7a : Hydrogen atom or alkyl group having 1 to 4 carbon atoms AO: Alkylene oxy group with 2 to 4 carbon atoms n1: The average number of moles added to AO, a number between 50 and 150. q1: A number between 0 and 6 (inclusive) p1:0 or 1 M 3a : Hydrogen atom, alkali metal, alkaline earth metal (1 / 2 atom), ammonium group, alkylammonium group, substituted alkylammonium group, alkyl group, hydroxyalkyl group or alkenyl group r: A number between 0 and 2 (inclusive) This indicates...

[0012] The present invention also relates to a gypsum slurry containing the above-mentioned component (A), gypsum, and water.

[0013] The present invention also relates to a method for producing a gypsum slurry by mixing component (A), gypsum, and water.

[0014] The present invention also relates to the use of a dispersant containing component (A) in a gypsum slurry. [Effects of the Invention]

[0015] The present invention provides a dispersant for gypsum slurry that exhibits excellent low-temperature storage stability, assuming winter conditions (e.g., -5°C to 5°C), and can impart excellent fluidity to the gypsum slurry, as well as a gypsum slurry with excellent fluidity and a method for producing the same.

[0016] The dispersant for gypsum slurry of the present invention can impart excellent fluidity to the gypsum slurry, making it possible to form the gypsum slurry with a small amount of water in the gypsum board manufacturing process. This reduces the amount of fuel required to dry the gypsum board, achieving both reduced environmental impact and cost savings simultaneously. Furthermore, its excellent fluidity also allows for a reduction in the amount of setting retarder used. [Modes for carrying out the invention]

[0017] The dispersant for gypsum slurry of the present invention exhibits excellent low-temperature storage stability, assuming winter conditions (e.g., -5°C to 5°C), and can impart excellent fluidity to the gypsum slurry. Furthermore, the reasons why the gypsum slurry and its manufacturing method of the present invention exhibit excellent fluidity are not entirely clear, but are presumed to be as follows. When a polycarboxylic acid-based dispersant is neutralized, the polymer molecules expand, and the polyalkylene oxy chain portion, which is introduced as a steric repulsion, also expands. This causes intermolecular entanglement in water, increasing viscosity. Furthermore, it is presumed that when a polycarboxylic acid-based dispersant is neutralized, the adsorption groups repel each other electrostatically, causing the polymer main chain to expand. In this state, when preparing the slurry by incorporating it, the mixing time for the slurry is very short, making efficient adsorption impossible and resulting in weak fluidity. On the other hand, in this invention, by designing the degree of neutralization of the polycarboxylic acid-based dispersant of component (A) to be low (i.e., the pH of the aqueous solution when dissolved in water to a concentration of 40% by mass is designed to be 4 or less), it is not entirely certain, but it is expected that the entanglement between polymers will be resolved, the expansion of the polymer molecules themselves will be suppressed, and a compact structure will be adopted. In this case, it is presumed that the gypsum slurry containing component (A) of this invention can be efficiently adsorbed to gypsum immediately after contact with water, exhibiting excellent fluidity. Furthermore, although the details of why the dispersant for gypsum slurry of the present invention exhibits improved low-temperature stability, assuming winter conditions (e.g., -5°C to 5°C), are not entirely clear, it is speculated that lowering the degree of neutralization of the polycarboxylic acid-based dispersant component (A) suppresses the ionization of carboxyl groups, resulting in more compact polymer chains. This makes intermolecular entanglement and network formation less likely, thus maintaining a low base viscosity, reducing viscosity increases at low temperatures, and minimizing the effects of aggregation due to freeze-thickening, thereby improving low-temperature stability. However, the present invention is not limited to the above-described mechanism of action.

[0018] [Dispersant for gypsum slurry] <(A) component> The dispersant for gypsum slurry of the present invention contains a copolymer as component (A), comprising a constituent monomer (A1) represented by the following general formula (A1) and a constituent monomer (A2) represented by the following general formula (A2), wherein the proportion of constituent monomer (A1) in the total amount of constituent monomer (A1) and constituent monomer (A2) is 5% by mass or more and 25% by mass or less, and the pH of the aqueous solution when dissolved in water to a concentration of 40% by mass is 4 or less. In this specification, "a copolymer containing a constituent monomer (A1) represented by general formula (A1) and a constituent monomer (A2) represented by general formula (A2) as constituent monomers" may also mean "a copolymer having constituent units derived from the monomer represented by general formula (A1) and constituent units derived from the monomer represented by general formula (A2)." The same applies to the constituent monomer (A3) described later.

[0019] [ka]

[0020] [During the ceremony, R 1a , R 2a , R 3a : Identical or different, hydrogen atom, methyl group or (CH2) r COOM 2a (CH2) r COOM 2a COOM 1a or other (CH2) r COOM 2a When forming anhydrous compounds, the M of those groups 1a M 2a It does not exist. M 1a M 2a : Same or different hydrogen atoms, alkali metals, alkaline earth metals (1 / 2 atom), ammonium groups, alkylammonium groups, substituted alkylammonium groups, alkyl groups, hydroxyalkyl groups, or alkenyl groups r: A number between 0 and 2 (inclusive) This indicates...

[0021] [ka]

[0022] [During the ceremony, R 4a , R 5a : The same or different hydrogen atom or methyl group R 6a : Hydrogen atom, methyl group, (CH2) r COOM3a , or (CH2) q1 (CO) p1 O(AO) n1 R 7a R 7a : Hydrogen atom or alkyl group having 1 to 4 carbon atoms AO: Alkylene oxy group with 2 to 4 carbon atoms n1: The average number of moles added to AO, a number between 50 and 150. q1: A number between 0 and 6 (inclusive) p1:0 or 1 M 3a : Hydrogen atom, alkali metal, alkaline earth metal (1 / 2 atom), ammonium group, alkylammonium group, substituted alkylammonium group, alkyl group, hydroxyalkyl group or alkenyl group r: A number between 0 and 2 (inclusive) This indicates...

[0023] In general formula (A1), from the standpoint of availability, R 1a A hydrogen atom is preferred. In general formula (A1), R 2a The atom is preferably a hydrogen atom or a methyl group, and more preferably a methyl group. In general formula (A1), from the standpoint of availability, R 3a A hydrogen atom is preferred. (CH2) r COOM 2a Regarding COOM 1a or other (CH2) r COOM 2a They may also form anhydrous compounds, in which case the M of those groups 1a M 2a It does not exist. M 1a and M 2a These are identical or different hydrogen atoms, alkali metals, alkaline earth metals (1 / 2 atom), ammonium groups, alkylammonium groups, substituted alkylammonium groups, alkyl groups, hydroxyalkyl groups, or alkenyl groups. M 1a and M 2aThe alkyl group, hydroxyalkyl group, and alkenyl group each preferably have 1 to 4 carbon atoms. M 1a and M 2a Preferably, the same or different components are a hydrogen atom, alkali metal, alkaline earth metal (1 / 2 atom), ammonium group, or alkylammonium group; more preferably, a hydrogen atom, alkali metal, alkaline earth metal (1 / 2 atom), or ammonium group; even more preferably, a hydrogen atom, alkali metal, or alkaline earth metal (1 / 2 atom); and still more preferably, a hydrogen atom or alkali metal. (CH2) in general formula (A1) r COOM 2a r is preferably 0.

[0024] In general formula (A2), R 4a From the standpoint of availability, hydrogen atoms are preferred. In general formula (A2), R 5a From the viewpoint of availability and copolymerizability with constituent monomer (A1), a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred. In general formula (A2), R 6a From the standpoint of availability, hydrogen atoms are preferred. In general formula (A2), R 7a From the viewpoint of ease of manufacture and the quality stability of the product, a hydrogen atom or a methyl group is preferred, and a methyl group is more preferred. In general formula (A2), AO is preferably a group selected from an ethyleneoxy group and a propyleneoxy group, with an ethyleneoxy group being more preferred, from the viewpoint of availability and cost. It is preferable that AO contains an ethyleneoxy group. In general formula (A2), n1 is the average number of moles of AO added, and from the viewpoint of imparting dispersibility to gypsum slurry and low-temperature storage stability of the dispersant for gypsum slurry, it is 50 or more, preferably 70 or more, more preferably 90 or more, even more preferably 100 or more, even more preferably 110 or more, and 150 or less, preferably 140 or less, and even more preferably 130 or less. Furthermore, if the AO contains alkylene oxy groups with different numbers of carbon atoms in an average of n1 repeating units, these alkylene oxy groups with different numbers of carbon atoms may include random addition, block addition, or a mixture thereof. In the total AO, ethylene oxy groups are preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more, and it is preferable that the entire AO consists of ethylene oxy groups. For example, AO may also contain propylene oxy groups, butylene oxy groups, etc., in addition to ethylene oxy groups. In general formula (A2), from the viewpoint of availability, q1 is preferably 0, 1, or 2, more preferably 0 or 1, and even more preferably 0. In general formula (A2), from the viewpoint of availability, p1 is preferably 1. (CH2) in general formula (A2) r COOM 3a M 3a A preferred embodiment is M 1a M 2a This is the same as, and r is preferably 0.

[0025] In the total constituent monomers of component (A), the proportion of constituent monomer (A1) in the total amount of constituent monomer (A1) and constituent monomer (A2) is 5% by mass or more, preferably 7% by mass or more, more preferably 9% by mass or more, even more preferably 11% by mass or more, and 25% by mass or less, preferably 24% by mass or less, and more preferably 23% by mass or less, from the viewpoint of imparting dispersibility to the gypsum slurry.

[0026] In the total constituent monomers of component (A), the proportion of constituent monomer (A1) in the total amount of constituent monomer (A1) and constituent monomer (A2) is preferably 80 mol% or more, more preferably 85 mol% or more, even more preferably 87 mol% or more, and preferably 97 mol% or less, more preferably 96 mol% or less, and even more preferably 95 mol% or less.

[0027] In the total constituent monomers of component (A), the proportion of constituent monomer (A2) in the total amount of constituent monomer (A1) and constituent monomer (A2) is preferably 70% by mass or more, more preferably 75% by mass or more, even more preferably 80% by mass or more, even more preferably 85% by mass or more, and preferably 97% by mass or less, more preferably 95% by mass or less, even more preferably 92% by mass or less, and even more preferably 90% by mass or less.

[0028] In the total constituent monomers of component (A), the proportion of constituent monomer (A2) in the total amount of constituent monomer (A1) and constituent monomer (A2) is preferably 2 mol% or more, more preferably 4 mol% or more, even more preferably 6 mol% or more, even more preferably 8 mol% or more, and preferably 20 mol% or less, more preferably 16 mol% or less, and even more preferably 13 mol% or less.

[0029] (A) Of the total constituent monomers of component (A), the total amount of constituent monomer (A1) and constituent monomer (A2) is preferably 70% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and preferably 100% by mass or less, from the viewpoint of imparting dispersibility to the gypsum slurry. This total amount may be 100% by mass. (A) Of the total constituent monomers of component (A), the total amount of constituent monomer (A1) and constituent monomer (A2) is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and preferably 100 mol% or less, from the viewpoint of imparting dispersibility to the gypsum slurry. This total amount may be 100 mol%.

[0030] The copolymer of component (A) may contain constituent monomers other than constituent monomer (A1) and constituent monomer (A2) (hereinafter also referred to as constituent monomer (A3)). Examples of constituent monomer (A3) include 2-(methacryloyloxy)ethyl phosphate (HEMA-P), 2-hydroxyethyl acrylate (HEA), methyl acrylate, methyl methacrylate, 2-hydroxyethyl methacrylate (HEMA), allyl sulfonic acid, methallyl sulfonic acid, and salts thereof, such as alkali metal salts, alkaline earth metal salts, ammonium salts, or amine salts. Furthermore, constituent units using one or more monomers selected from (meth)acrylamide, N-methyl(meth)acrylamide, N,N-dimethyl(meth)acrylamide, 2-(meth)acrylamide-2-methasulfonic acid, 2-(meth)acrylamide-2-ethanesulfonic acid, 2-(meth)acrylamide-2-propanesulfonic acid, styrene, styrenesulfonic acid, etc. (Meth)acrylic means acrylic or methacrylic.

[0031] The weight-average molecular weight (Mw) of component (A) is preferably 20,000 or more, more preferably 25,000 or more, even more preferably 30,000 or more, even more preferably 35,000 or more, even more preferably 40,000 or more, and preferably 100,000 or less, more preferably 80,000 or less, even more preferably 60,000 or less, even more preferably 50,000 or less, and even more preferably 48,000 or less, from the viewpoint of imparting dispersibility to the gypsum slurry.

[0032] (A) The ratio Mw / Mn of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) of component (A) is preferably 1.0 or higher, more preferably 1.1 or higher, even more preferably 1.2 or higher, and preferably 2.0 or lower, more preferably 1.8 or lower, and even more preferably 1.6 or lower, from the viewpoint of imparting dispersibility to the gypsum slurry.

[0033] The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of component (A) were measured by gel permeation chromatography (GPC) under the following conditions. *GPC conditions Equipment: GPC (HLC-8320GPC), manufactured by Tosoh Corporation. Columns: G4000PWXL + G2500PWXL (manufactured by 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 substances: Polyethylene glycol equivalent (monodisperse polyethylene glycols with known molecular weights: 250,000, 145,000, 87,500, 46,000, 24,000)

[0034] (A) When component (A) is dissolved in water to a concentration of 40% by mass, the pH of the aqueous solution is 4 or less, preferably 3.5 or less, more preferably 3.0 or less, even more preferably 2.5 or less, and preferably 1.0 or higher, more preferably 2.0 or higher, from the viewpoint of imparting dispersibility to gypsum slurry and the low-temperature storage stability of the dispersant for gypsum slurry. The pH of component (A) is determined by the M in the general formula (A1) of the constituent monomer (A1). 1a This is adjusted by using a hydrogen atom and changing the proportion of the constituent monomer (A1). Furthermore, the temperature of the aqueous solution during pH measurement may be 20°C.

[0035] The content of component (A) in the dispersant for gypsum slurry of the present invention is preferably 1% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, even more preferably 30% by mass or more, even more preferably 35% by mass or more, from the viewpoint of imparting dispersibility to the gypsum slurry and the low-temperature storage stability of the dispersant for gypsum slurry, and preferably 60% by mass or less, more preferably 50% by mass or less, even more preferably 45% by mass or less, from the viewpoint of reducing production costs.

[0036] From the viewpoint of production stability, the dispersant for gypsum slurry of the present invention may contain a setting retarder as component (B). Examples of the coagulation retardant for component (B) include organic acids such as citric acid and oxycarboxylic acids and their salts, sugars such as glucose, maltose, and dextrin, sodium bicarbonate, and sodium phosphate, and one or more of these can be used. (B) Citric acid is more preferred from the viewpoint of availability and cost-effectiveness of the coagulation.

[0037] When the dispersant for gypsum slurry of the present invention contains component (B), the content of component (B) in the solid content other than water contained in the dispersant for gypsum slurry of the present invention is preferably 0.01% by mass or more, more preferably 0.02% by mass or more, even more preferably 0.03% by mass or more, and preferably 1.0% by mass or less, more preferably 0.09% by mass or less, and even more preferably 0.08% by mass or less, from the viewpoint of coagulation properties.

[0038] The dispersant for gypsum slurry of the present invention may contain water. When water is contained in the admixture for hydraulic compositions of the present invention, the water content is preferably 40% by mass or more, preferably 45% by mass or more, more preferably 50% by mass or more, and preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less.

[0039] The dispersant for gypsum slurry of the present invention may optionally contain thickeners, chelating agents, heavy metal scavengers, rust inhibitors, preservatives, colorants, fragrances, defoamers, solvents, flocculants, water-soluble polymers, etc. (except those corresponding to components (A) and (B)).

[0040] The dispersant for gypsum slurry of the present invention can be suitably used as a dispersant for gypsum slurry in which the pH of the gypsum slurry at 20°C is preferably 8.0 or higher, more preferably 8.5 or higher, and preferably 10.0 or lower, and more preferably 9.5 or lower, from the viewpoint of imparting dispersibility to the gypsum slurry. The pH of the gypsum slurry can be adjusted using the pH adjusting agent of component (C) described later in the gypsum slurry of the present invention.

[0041] [Method for producing a dispersant for gypsum slurry] The present invention relates to a method for producing a dispersant for gypsum slurry, comprising mixing the above-mentioned component (A). The method for producing the dispersant for gypsum slurry of the present invention may further involve mixing in component (B). The method for producing a dispersant for gypsum slurry according to the present invention may further involve mixing in water. Components (A) and (B) are the same as those described in the present invention for the dispersant for gypsum slurry. The method for producing the dispersant for gypsum slurry of the present invention can be appropriately applied to the embodiments described in the description of the dispersant for gypsum slurry of the present invention. In the method for producing the dispersant for gypsum slurry of the present invention, the mixing amounts of component (A), component (B), and water can be appropriately applied by substituting the content of each component with the mixing amount, as described in the gypsum slurry dispersant of the present invention.

[0042] [Use of dispersants in gypsum slurry] The dispersant for gypsum slurry of the present invention can be suitably used as a dispersant for gypsum slurry containing gypsum. In other words, the present invention relates to the use of a dispersant containing component (A) in a gypsum slurry. The dispersant may further contain component (B). The dispersant may further contain water. Components (A) and (B) are the same as those described in the present invention for the dispersant for gypsum slurry. The aforementioned dispersant is the same as the dispersant for gypsum slurry of the present invention, and the embodiments described in the dispersant for gypsum slurry and its manufacturing method of the present invention can be applied as appropriate.

[0043] [Gypsum slurry] The present invention provides a gypsum slurry containing component (A), gypsum, and water. The gypsum slurry of the present invention may further contain component (B). The gypsum slurry of the present invention can be appropriately adapted to the embodiments described in the dispersant for gypsum slurry and the method for producing the same of the present invention. Components (A) and (B) are the same as those described in the present invention for the dispersant for gypsum slurry. The gypsum slurry of the present invention is suitable for use with gypsum boards.

[0044] Gypsum comes in various forms, including anhydrous gypsum, hemihydrate gypsum, and dihydrate gypsum. Any type of gypsum can be used, including high-quality neutralized gypsum, phosphate gypsum (a by-product of phosphoric acid production), flue gas desulfurization gypsum (generated from thermal power plants), natural gypsum containing various impurities and clays, and mixtures thereof. One or more of these types of gypsum can be used.

[0045] The gypsum slurry of the present invention has a water / gypsum ratio of preferably 50% by mass or more, more preferably 55% by mass or more, and even more preferably 60% by mass or more, from the viewpoint of productivity, and preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less, from the viewpoint of reducing fuel costs during drying. Here, the water / gypsum ratio is the mass percentage (mass%) of the water content and gypsum content in the gypsum slurry, and is calculated as water / gypsum × 100. The same applies to other quantitative relationships with respect to gypsum in the gypsum slurry of this invention.

[0046] In the gypsum slurry of the present invention, the content of component (A) is preferably 0.005 parts by mass or more, more preferably 0.01 parts by mass or more, even more preferably 0.02 parts by mass or more, even more preferably 0.06 parts by mass or more, even more preferably 0.10 parts by mass or more, per 100 parts by mass of gypsum, from the viewpoint of imparting dispersibility to the gypsum slurry, and from the viewpoint of cost reduction, preferably 1.0 part by mass or less, more preferably 0.8 parts by mass or less, even more preferably 0.6 parts by mass or less, even more preferably 0.4 parts by mass or less, even more preferably 0.20 parts by mass or less, and even more preferably 0.15 parts by mass or less.

[0047] In the gypsum slurry of the present invention, if component (B) is included, the content of component (B) is preferably 0.01 parts by mass or more, more preferably 0.02 parts by mass or more, even more preferably 0.03 parts by mass or more, and preferably 0.1 parts by mass or less, more preferably 0.09 parts by mass or less, and even more preferably 0.08 parts by mass or less, per 100 parts by mass of gypsum, from the viewpoint of the setting properties of the gypsum slurry.

[0048] The pH of the gypsum slurry of the present invention at 20°C is preferably 8.0 or higher, more preferably 8.5 or higher, and preferably 10.0 or lower, and more preferably 9.5 or lower, from the viewpoint of imparting dispersibility to the gypsum slurry. pH can be measured using a pH meter. The pH of the gypsum slurry of the present invention at 20°C can be adjusted by including a pH adjusting agent as component (C).

[0049] Examples of pH adjusters for component (C) include inorganic acids such as hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid; organic acids such as formic acid, acetic acid, lactic acid, glycolic acid, oxalic acid, succinic acid, citric acid, maleic acid, fumaric acid, propionic acid, malonic acid, glutaric acid, adipic acid, malic acid, crotonic acid, benzoic acid, p-toluenesulfonic acid, cumenesulfonic acid, metaxylenesulfonic acid, and polyacrylic acid; inorganic bases such as sodium hydroxide and potassium hydroxide; and organic bases such as triethanolamine. One or more of these can be used. (C) Component is preferably one or more selected from sodium hydroxide, potassium hydroxide, and calcium hydroxide, and more preferably one or more selected from sodium hydroxide and calcium hydroxide, from the viewpoint of low cost and availability. The content of component (C) in the gypsum slurry of the present invention is adjusted so that the pH of the gypsum slurry of the present invention at 20°C falls within the aforementioned range.

[0050] The gypsum slurry of the present invention may contain a foaming agent as component (D) if the gypsum slurry contains air bubbles.

[0051] Examples of foaming agents for component (D) include sulfonic acid compounds, ether sulfate compounds, carboxylic acid compounds, phosphonic acid compounds, and phosphoric acid compounds having hydrocarbon groups with 8 to 18 carbon atoms. For example, one or more selected from alkyl or alkenyl sulfate esters having alkyl or alkenyl groups, alkyl or alkenyl sulfonic acids having alkyl or alkenyl groups, polyoxyalkylene alkyl or alkenyl ether sulfate esters having alkyl or alkenyl groups, polyoxyalkylene alkyl or alkenyl ether carboxylic acids having alkyl or alkenyl groups, and salts thereof. Examples of salts of these compounds include one or more selected from alkali metal salts such as sodium salts and potassium salts, ammonium salts, and organic ammonium salts.

[0052] Component (D) is preferably one or more selected from alkyl or alkenyl sulfate esters having an alkyl or alkenyl group having 8 to 18 carbon atoms, alkyl or alkenyl sulfonic acid having an alkyl or alkenyl group having 8 to 18 carbon atoms, polyoxyalkylene alkyl or alkenyl ether sulfate esters having an alkyl or alkenyl group having 8 to 18 carbon atoms, and salts thereof, particularly in terms of foaming performance in aqueous systems. Salts of these compounds include one or more selected from alkali metal salts such as sodium salts and potassium salts, ammonium salts, and organic ammonium salts.

[0053] Component (D) is preferably one or more selected from (D1) alkyl or alkenyl sulfate esters or salts thereof having an alkyl or alkenyl group having 8 to 18 carbon atoms (hereinafter referred to as (D1) component), and (D2) polyoxyalkylene alkyl or alkenyl ether sulfate esters or salts thereof having an alkyl or alkenyl group having 8 to 18 carbon atoms (hereinafter referred to as (D2) component).

[0054] Component (D1) preferably has an alkyl or alkenyl group having 8 or more carbon atoms, more preferably 10 or more, preferably 18 or fewer, more preferably 16 or fewer, even more preferably 14 or fewer, and even more preferably 12 or fewer carbon atoms, from the viewpoint of increasing the diameter of air bubbles in the hardened gypsum. The salt of component (D1) may be one or more selected from alkali metal salts such as sodium salts and potassium salts, ammonium salts, and organic ammonium salts.

[0055] Component (D1) specifically includes one or more selected from octyl sulfate, decyl sulfate, dodecyl sulfate, tetradecyl sulfate, hexadecyl sulfate, octadecyl sulfate, 2-ethylhexyl sulfate, 2-propylheptyl sulfate, and salts thereof. From the viewpoint of increasing the diameter of air bubbles in the hardened gypsum, it is preferable to include one or more compounds selected from decyl sulfate, dodecyl sulfate, tetradecyl sulfate, and salts thereof, and it is more preferable to include one or more compounds selected from decyl sulfate, dodecyl sulfate, and salts thereof.

[0056] Component (D) may include, in particular from the viewpoint of foaming performance in aqueous systems, two types of alkyl or alkenyl sulfate esters or salts thereof, having different numbers of carbon atoms in the alkyl or alkenyl group, as component (D1).

[0057] Component (D2) preferably has an alkyl group or alkenyl group having 8 or more carbon atoms, more preferably 10 or more, and preferably 16 or fewer carbon atoms, more preferably 14 or fewer, and even more preferably 12 or fewer carbon atoms, from the viewpoint of increasing the diameter of air bubbles in the hardened gypsum. The oxyalkylene group of component (D2) is an oxyethylene group or an oxypropylene group, preferably an oxyethylene group, and the average number of moles of oxyalkylene groups added is preferably 1 or more, more preferably 2 or more, and preferably 10 or less, more preferably 6 or less, and even more preferably 4 or less, from the viewpoint of foaming performance in aqueous systems. The salt of component (D2) may be one or more selected from alkali metal salts such as sodium salts and potassium salts, ammonium salts, and organic ammonium salts.

[0058] (D2) Component specifically consists of polyoxyethylene octyl ether sulfate, polyoxyethylene decyl ether sulfate, polyoxyethylene lauryl ether sulfate, polyoxyethylene tridecyl ether sulfate, polyoxyethylene myristyl ether sulfate, polyoxyethylene cetyl ether sulfate, polyoxyethylene stearyl ether sulfate, polyoxypropylene octyl ether sulfate, polyoxypropylene decyl ether sulfate, polyoxypropylene lauryl ether sulfate, polyoxypropylene tridecyl ether sulfate, polyoxypropylene myristyl ether sulfate, polyoxypropylene cetyl ether sulfate, polyoxypropylene stearyl ether sulfate, polyoxyethylene polyoxypropylene octyl ether sulfate, polyoxyethylene polyoxypropylene decyl ether sulfate, and polyoxyethylene polyoxypropylene lauryl ether sulfate. Examples include polyoxyethylene polyoxypropylene tridecyl ether sulfate, polyoxyethylene polyoxypropylene myristyl ether sulfate, polyoxyethylene polyoxypropylene cetyl ether sulfate, polyoxyethylene polyoxypropylene stearyl ether sulfate, and one or more selected from these salts. From the viewpoint of increasing the diameter of bubbles in the gypsum slurry, it is preferably polyoxyethylene decyl ether sulfate, polyoxyethylene lauryl ether sulfate, polyoxyethylene myristyl ether sulfate, polyoxypropylene decyl ether sulfate, polyoxyethylene polyoxypropylene lauryl ether sulfate, polyoxyethylene polyoxypropylene myristyl ether sulfate, and one or more selected from these salts.

[0059] In the gypsum slurry of the present invention, if component (D) is included, the content of component (D) is preferably 0.1 parts by mass or more, more preferably 0.2 parts by mass or more, even more preferably 0.3 parts by mass or more, and preferably 1.0 part by mass or less, more preferably 0.9 parts by mass or less, and even more preferably 0.8 parts by mass or less, with respect to 100 parts by mass of water.

[0060] The gypsum slurry of the present invention may contain additives used for gypsum boards and the like. Such additives include defoamers, foam stabilizers, hardening modifiers, water repellents, adhesives, retarders, etc. (excluding those corresponding to components (A), (B), (C), and (D)). Furthermore, glass fibers, carbon fibers, recycled paper, virgin pulp, etc. may be added as reinforcing fibers, or gypsum boards may be manufactured together with lightweight aggregates such as perlite and foamed steel.

[0061] The gypsum slurry of the present invention yields a hardened gypsum body when dried and cured. The specific gravity of the hardened gypsum slurry of the present invention is preferably 0.3 or higher, more preferably 0.4 or higher, and even more preferably 0.5 or higher, from the viewpoint of the strength of the hardened gypsum, and preferably 0.9 or lower, more preferably 0.8 or lower, and even more preferably 0.7 or lower, from the viewpoint of the ease of handling the hardened gypsum.

[0062] The gypsum slurry of the present invention preferably contains air bubbles. When it contains air bubbles, the average air bubble diameter of the hardened gypsum slurry of the present invention is preferably 230 μm or more, more preferably 250 μm or more, and even more preferably 300 μm or more, from the viewpoint of improving the strength of the hardened body, and preferably 800 μm or less, more preferably 700 μm or less, even more preferably 600 μm or less, even more preferably 500 μm or less, and even more preferably 400 μm or less, from the viewpoint of the cross-sectional aesthetics of the hardened gypsum. The average bubble diameter is calculated by preparing a hardened gypsum slurry, cutting out a cross-section from the hardened material, observing the cross-section with a digital microscope, measuring the diameter of 200 to 400 randomly selected bubble cross-sections, and then calculating the average (arithmetic mean) of these values. Note that when measuring the diameter of a bubble cross-section, if the cross-section is circular, the diameter is measured; if the cross-section is elliptical, the diameter is measured along the major axis; and if the cross-section is irregularly shaped, the diameter is measured along the longest part.

[0063] [Method for producing gypsum slurry] The present invention relates to a method for producing a gypsum slurry by mixing component (A), gypsum, and water. The method for producing gypsum slurry according to the present invention may further involve mixing in component (B). The method for producing gypsum slurry according to the present invention may further involve mixing in component (C). The method for producing gypsum slurry according to the present invention may further involve mixing in component (D). Components (A) and (B) are the same as those described in the present invention for the dispersant for gypsum slurry. The gypsum, component (C), and component (D) are the same as those described in the gypsum slurry of the present invention. The method for producing gypsum slurry of the present invention can appropriately apply the embodiments described in the present invention for the dispersant for gypsum slurry and its production method, as well as the gypsum slurry of the present invention. In the method for producing the hydraulic composition of the present invention, gypsum is mixed so that the water / gypsum ratio falls within the range described for the gypsum slurry of the present invention. In the method for producing gypsum slurry of the present invention, the mixing amounts of component (A), component (B), and component (D) can be appropriately applied by substituting the content of each component with the mixing amount in the gypsum slurry content of the present invention.

[0064] In the method for producing gypsum slurry of the present invention, from the viewpoint of productivity, it is preferable to pre-mix component (A), an optional component (B), and water, and then mix them with gypsum. Furthermore, in the method for producing gypsum slurry of the present invention, the addition of component (A) and any component (B) is preferably done using the gypsum slurry dispersant of the present invention, and it is more preferable to pre-mix the gypsum slurry dispersant of the present invention with water and then mix it with gypsum. In the method for producing gypsum slurry of the present invention, component (C) is mixed to adjust the pH of the slurry to preferably 8.0 or higher, more preferably 8.5 or higher, and preferably 10.0 or lower, and more preferably 9.5 or lower, from the viewpoint of imparting dispersibility to the gypsum slurry. The pH may be the pH of the gypsum slurry at 20°C. In the method for producing gypsum slurry of the present invention, if air bubbles are to be included in the gypsum slurry, foam obtained by foaming a liquid composition containing component (D) and water may be mixed separately into the gypsum slurry.

[0065] The gypsum slurry obtained by the method for producing gypsum slurry of the present invention is molded and hardened. Molding and hardening can be carried out by known methods. For example, gypsum board can be prepared by referring to "Gypsum Board Manufacturing" on pages 322-324 of the "Gypsum Lime Handbook" (edited by the Gypsum Lime Society).

[0066] [Method for producing gypsum slurry containing air bubbles] The gypsum slurry containing air bubbles according to the present invention can be manufactured using the dispersant for gypsum slurry according to the present invention. In other words, the present invention provides a method for producing a gypsum slurry containing air bubbles, comprising the following steps 1 and 2. <Process 1> A step of foaming a liquid composition containing the aforementioned component (D) and water to obtain foam. <Process 2> A step of mixing the dispersant for gypsum slurry of the present invention, gypsum, water, and the foam obtained in step 1. In addition, in step 2, a gypsum slurry containing the gypsum slurry dispersant of the present invention, gypsum, and water may be prepared, and this gypsum slurry may be mixed with the foam obtained in step 1.

[0067] This manufacturing method allows for the preparation of the gypsum slurry containing air bubbles according to the present invention. The method for producing a gypsum slurry containing air bubbles according to the present invention can appropriately apply the embodiments described in the dispersant for gypsum slurry and its production method, as well as the gypsum slurry and its production method according to the present invention. Component (D) is the same as described in the embodiment of the gypsum slurry of the present invention. The content of component (D) in the liquid composition in step 1 is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, and preferably 1.0% by mass or less, more preferably 0.9% by mass or less, with the remainder being water. In the method for producing a gypsum slurry containing air bubbles according to the present invention, the gypsum is mixed so that the water / gypsum ratio is within the range described in the gypsum slurry of the present invention. In the method for producing a gypsum slurry containing air bubbles according to the present invention, the mixing amounts of component (A) and component (B) can be appropriately applied by substituting the content of each component with the mixing amount, as described in the gypsum slurry of the present invention. The mixing amount of component (C) is adjusted to be within the pH range described in the method for producing a gypsum slurry of the present invention. The pH of the gypsum slurry may be the pH at 20°C. The temperatures of the foam and gypsum slurry used in mixing are preferably between 15°C and 40°C.

[0068] In step 1, the foaming ratio of the liquid composition depends on the intended use of the gypsum slurry, but from an economic standpoint, it is preferably 5 times or more, more preferably 7 times or more, and even more preferably 10 times or more. From the viewpoint of the kneadability of the gypsum slurry, it is preferably 30 times or less, more preferably 25 times or less, and even more preferably 20 times or less.

[0069] In step 2, depending on the intended use of the gypsum slurry, foam is mixed with the gypsum slurry in an amount of preferably 50% or more by volume, more preferably 100% or more by volume, and even more preferably 150% or more by volume, from the viewpoint of reducing the specific gravity of the hardened gypsum, and preferably 400% or less by volume, more preferably 300% or less by volume, and even more preferably 200% or less by volume, from the viewpoint of the strength of the hardened gypsum. In this manufacturing method, admixtures and additives known in the industry can be mixed in step 1 and / or step 2.

[0070] After step 2, step 3 is performed to manufacture a hardened gypsum slurry, i.e., gypsum board. Step 3: A step in which the gypsum slurry obtained in Step 2 is molded and hardened. Molding and hardening can be carried out by known methods. For example, gypsum board can be prepared by referring to "Gypsum Board Manufacturing" on pages 322-324 of the "Gypsum Lime Handbook" (edited by the Gypsum Lime Society). [Examples]

[0071] Table 1 shows the components (A) and (A') (comparative components of (A)) used in the examples and comparative examples.

[0072] [Table 1]

[0073] The constituent monomers used in Table 1 are as follows: • MEPEG(120): Methoxypolyethylene glycol (120) monomethacrylate (the number in parentheses represents the average number of moles of ethylene oxide added.) MEPEG(23): Methoxypolyethylene glycol(23) monomethacrylate (the number in parentheses represents the average number of moles of ethylene oxide added.)

[0074] <Manufacturing of Copolymer A-1> 317 g (17.6 mol) of water was charged into a reaction vessel equipped with a stirrer, and while stirring, the mixture was purged with nitrogen and heated to 75°C in a nitrogen atmosphere. A mixture of 323 g (0.06 mol) of MEPEG(120), 46.5 g (0.54 mol) of methacrylic acid (mass ratio = 87.4 / 12.6, molar ratio = 10 / 90), and 239 g (13.3 mol) of water was dissolved and simultaneously added dropwise to the reaction system over 2 hours: 41.7 g of 10% by mass aqueous solution of ammonium persulfate and 1.9 g of 2-mercaptoethanol. Next, 13.9 g of 10% by mass aqueous solution of ammonium persulfate was added dropwise over 30 minutes, and the mixture was aged at the same temperature (75°C) for 1 hour. After maturation, a 48% by mass NaOH aqueous solution was added to neutralize the mixture, and the pH of the aqueous solution, which was dissolved to a concentration of 40% by mass, was adjusted to 4.0 at 20°C, yielding a reaction product containing copolymer A-1 with a weight-average molecular weight of 44,000 and water. For the other copolymers in Table 1, the same method as described above was used, by changing the type and amount of constituent monomers, and the amount of NaOH used to neutralize the aqueous solution at 20°C so that the pH of the aqueous solution at a concentration of 40% by mass in water was as shown in Table 1.

[0075] In Table 1, the weight-average molecular weight (Mw) and the ratio of weight-average molecular weight (Mw) to number-average molecular weight (Mn), Mw / Mn, for each copolymer were measured by gel permeation chromatography (GPC) under the following conditions. *GPC conditions Equipment: GPC (HLC-8320GPC), manufactured by Tosoh Corporation. Columns: G4000PWXL + G2500PWXL (manufactured by 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 substances: Polyethylene glycol equivalent (monodisperse polyethylene glycols with known molecular weights: 250,000, 145,000, 87,500, 46,000, 24,000)

[0076] [Preparation of dispersant for gypsum slurry] Each gypsum slurry dispersant was prepared by mixing component (A) or (A') with water so that the amount of component (A) or (A') in the gypsum slurry dispersant was as shown in Tables 2 to 5 (effective amount, the remainder being water).

[0077] [Low-temperature storage stability test of dispersant for gypsum slurry] Each prepared dispersant for gypsum slurry was placed in a 100 mL screw-cap bottle, sealed, and stored in a constant temperature bath at -5°C for 7 days. After storage, each dispersant for gypsum slurry was visually inspected and evaluated according to the following criteria. The results are shown in Tables 2-5. A: No crystals formed, and no gelation occurred. B: Crystals have formed, or the gel has formed.

[0078] [Evaluation of the fluidity of gypsum slurry] 200g of gypsum (G) (Sakura brand A-grade gypsum, manufactured by Yoshino Gypsum Co., Ltd.), 114g of mixed water (W) (tap water) containing the prepared dispersants for each gypsum slurry, and the mixture was stirred for 10 seconds (900rpm) using a hand mixer (MK-H4, manufactured by Panasonic Corporation) to prepare a gypsum slurry. For each gypsum slurry dispersant, the content of component (A) or (A') in the gypsum slurry was adjusted to the amount (effective amount) shown in Tables 2 to 5 per 100 parts by mass of gypsum, and the mixture was stirred to prepare the mixed water. The content of powdered sodium hydroxide (component (C)) was adjusted so that the pH of the gypsum slurry at 20°C was the value shown in Tables 2 to 5. Furthermore, the W / G (mass%) values ​​in Tables 2-5 represent the mass percentage of water and gypsum in the gypsum slurry, and are calculated as water / gypsum × 100. Each gypsum slurry, immediately after preparation, was filled into a paste cone (50 mm in diameter x 100 mm in height), placed on a 30 cm x 30 cm plastic plate, and 30 seconds after the gypsum came into contact with water, the paste cone was lifted vertically. The maximum diameter of the gypsum slurry on the plastic plate and the diameter of the gypsum slurry positioned perpendicular to the maximum diameter on the plastic plate were measured, and the average value of these measurements was defined as fluidity. A higher fluidity value indicates better fluidity. The results are shown in Tables 2-5.

[0079] [Table 2]

[0080] [Table 3]

[0081] [Table 4]

[0082] [Table 5]

[0083] [Evaluation of the setting properties of gypsum slurry] A gypsum slurry was prepared by mixing 200g of gypsum (G) (Sakura brand A-grade gypsum, manufactured by Yoshino Gypsum Co., Ltd.), 114g of kneading water (W) (tap water) containing sodium hydroxide powder as a pH adjuster for component (C), and citric acid as a setting retarder for components (A) or (A') and (B) as described in Tables 6 and 7, and stirring for 10 seconds (900 rpm) with a hand mixer (MK-H4, manufactured by Panasonic Corporation). The content of component (A) or (A') and the content of component (B) were prepared by adding them to water and stirring so that the content (effective amount) per 100 parts by mass of gypsum in the gypsum slurry was the value described in Tables 6 and 7 (Note that the content of component (B) was adjusted so that the peak top position of the exothermic peak described later was the same). The amount of sodium hydroxide powder in component (C) was adjusted so that the pH of the gypsum slurry at 20°C was as shown in Tables 6 and 7. In Tables 6 and 7, W / G (mass%) represents the mass percentage of water and gypsum in the gypsum slurry, and is calculated as water / gypsum × 100. Each gypsum slurry was filled into a film case at a rate of 8g immediately after preparation, and the heat generation peak was confirmed using a calorimeter (TAMAir, TA Instrumental). Table 6 shows the amount of setting retarder to be reduced when adjusting the content of component (B) in Reference Examples 1 and 2 to the same position as Reference Comparative Example 1, and calculating the amount of setting retarder to be reduced when adjusting. Table 7 shows the amount of setting retarder to be reduced when adjusting the content of component (B) in Reference Examples 3 and 4 to the same position as Reference Comparative Example 2, and calculating the amount of setting retarder to be reduced when adjusting. The results are shown in Tables 6 and 7. When the position of the heat generation peak is the same, it can be said that the curing time is the same, and the gypsum slurry of the present invention, due to its excellent fluidity, can reduce the amount of setting retarder in component (B) without delaying the curing time.

[0084] [Table 6]

[0085] [Table 7]

Claims

1. A dispersant for gypsum slurry containing the following component (A). (A) Component: A copolymer comprising a constituent monomer (A1) represented by the following general formula (A1) and a constituent monomer (A2) represented by the following general formula (A2) as constituent monomers, wherein the proportion of constituent monomer (A1) in the total amount of constituent monomer (A1) and constituent monomer (A2) is 5% by mass or more and 25% by mass or less, and the pH of the aqueous solution when dissolved in water to a concentration of 40% by mass is 4 or less. 【Chemistry 1】 [During the ceremony, R １ａ 、R ２ａ 、R ３ａ : The same or different, a hydrogen atom, a methyl group or (CH ２ ) ｒ COOM ２ａ where (CH ２ ) ｒ COOM ２ａ is COOM １ａ or another (CH ２ ) ｒ COOM ２ａ forms an anhydride, M １ａ and M ２ａ of those groups do not exist. M １ａ M ２ａ : The same or different hydrogen atom, alkali metal, alkaline earth metal (half atom), ammonium group, alkylammonium group, substituted alkylammonium group, alkyl group, hydroxyalkyl group or alkenyl group r: A number between 0 and 2 (inclusive) This indicates... 【Chemistry 2】 [During the ceremony, R ４ａ , R ５ａ : The same or different hydrogen atom or methyl group R ６ａ : Hydrogen atom, methyl group, (CH ２ ) ｒ COOM ３ａ , or (CH ２ ) ｑ１ (CO) ｐ１ O (AO) ｎ１ R ７a R ７ａ : Hydrogen atom or alkyl group having 1 to 4 carbon atoms AO: Alkylene oxy group with 2 to 4 carbon atoms n1: The average number of moles of AO added, a number between 50 and 150. q1: A number between 0 and 6 (inclusive) p1: 0 or 1 M ３ａ : Hydrogen atom, alkali metal, alkaline earth metal (1 / 2 atom), ammonium group, alkylammonium group, substituted alkylammonium group, alkyl group, hydroxyalkyl group or alkenyl group r: A number between 0 and 2 (inclusive) This indicates...

2. The dispersant for gypsum slurry according to claim 1, wherein the slurry has a pH of 8.0 or higher and 10.0 or lower at 20°C.

3. The dispersant for gypsum slurry according to claim 1 or 2, further comprising the following component (B). (B) Component: Coagulation retarder

4. A gypsum slurry containing the following component (A), gypsum, and water. (A) Component: A copolymer comprising a constituent monomer (A1) represented by the following general formula (A1) and a constituent monomer (A2) represented by the following general formula (A2) as constituent monomers, wherein the proportion of constituent monomer (A1) in the total amount of constituent monomer (A1) and constituent monomer (A2) is 5% by mass or more and 25% by mass or less, and the pH of the aqueous solution when dissolved in water to a concentration of 40% by mass is 4 or less. 【Transformation 3】 [During the ceremony, R １ａ , R ２ａ , R ３ａ : The same or different, hydrogen atom, methyl group or (CH ２ ) ｒ COOM ２ａ (CH ２ ) ｒ COOM ２ａ COOM １ａ or other (CH ２ ) ｒ COOM ２ａ When forming an anhydrous, the M of those groups １ａ M ２ａ It does not exist. M １ａ M ２ａ : The same or different hydrogen atom, alkali metal, alkaline earth metal (half atom), ammonium group, alkylammonium group, substituted alkylammonium group, alkyl group, hydroxyalkyl group or alkenyl group r: A number between 0 and 2 (inclusive) This indicates... 【Chemistry 4】 [During the ceremony, R ４ａ , R ５ａ : The same or different hydrogen atom or methyl group R ６ａ : Hydrogen atom, methyl group, (CH ２ ) ｒ COOM ３ａ , or (CH ２ ) ｑ１ (CO) ｐ１ O (AO) ｎ１ R ７a R ７ａ : Hydrogen atom or alkyl group having 1 to 4 carbon atoms AO: Alkylene oxy group with 2 to 4 carbon atoms n1: The average number of moles of AO added, a number between 50 and 150. q1: A number between 0 and 6 (inclusive) p1: 0 or 1 M ３ａ : Hydrogen atom, alkali metal, alkaline earth metal (1 / 2 atom), ammonium group, alkylammonium group, substituted alkylammonium group, alkyl group, hydroxyalkyl group or alkenyl group r: A number between 0 and 2 (inclusive) This indicates...

5. The gypsum slurry according to claim 4, wherein the pH at 20°C is 8.0 or higher and 10.0 or lower.

6. The gypsum slurry according to claim 4 or 5, further comprising the following component (B). (B) Component: Coagulation retarder

7. The gypsum slurry according to claim 4 or 5, further containing the following component (C). (C) Ingredients: pH adjuster

8. A method for producing a gypsum slurry, comprising mixing the following component (A), gypsum, and water. (A) Component: A copolymer comprising a constituent monomer (A1) represented by the following general formula (A1) and a constituent monomer (A2) represented by the following general formula (A2) as constituent monomers, wherein the proportion of constituent monomer (A1) in the total amount of constituent monomer (A1) and constituent monomer (A2) is 5% by mass or more and 25% by mass or less, and the pH of the aqueous solution when dissolved in water to a concentration of 40% by mass is 4 or less. 【Transformation 5】 [During the ceremony, R １ａ , R ２ａ , R ３ａ : The same or different, hydrogen atom, methyl group or (CH ２ ) ｒ COOM ２ａ (CH ２ ) ｒ COOM ２ａ COOM １ａ or other (CH ２ ) ｒ COOM ２ａ When forming an anhydrous, the M of those groups １ａ M ２ａ It does not exist. M １ａ M ２ａ : The same or different hydrogen atom, alkali metal, alkaline earth metal (half atom), ammonium group, alkylammonium group, substituted alkylammonium group, alkyl group, hydroxyalkyl group or alkenyl group r: A number between 0 and 2 (inclusive) This indicates... 【Transformation 6】 [During the ceremony, R ４ａ , R ５ａ : The same or different hydrogen atom or methyl group R ６ａ : Hydrogen atom, methyl group, (CH ２ ) ｒ COOM ３ａ , or (CH ２ ) ｑ１ (CO) ｐ１ O (AO) ｎ１ R ７a R ７ａ : Hydrogen atom or alkyl group having 1 to 4 carbon atoms AO: Alkylene oxy group with 2 to 4 carbon atoms n1: The average number of moles of AO added, a number between 50 and 150. q1: A number between 0 and 6 (inclusive) p1: 0 or 1 M ３ａ : a hydrogen atom, an alkali metal, an alkaline earth metal (1 / 2 atom), an ammonium group, an alkylammonium group, a substituted alkylammonium group, an alkyl group, a hydroxyalkyl group or an alkenyl group r: A number between 0 and 2 (inclusive) This indicates...

9. The method for producing a gypsum slurry according to claim 8, further comprising mixing in component (C) below to adjust the pH of the slurry to 8.0 or higher and 10.0 or lower. (C) Ingredients: pH adjuster

10. A method for producing a gypsum slurry according to claim 8 or 9, further comprising mixing in component (B) below. (B) Component: Coagulation retarder

Images