Dispersants for clay-containing gypsum composition

Abstract

To provide dispersants exhibiting good performance even for a gypsum composition.SOLUTION: Provided is gypsum slurry which comprises: (A) a dispersant containing a copolymer of (a) methacrylic acid, (b) a vinyl monomer having a cationic group, and (c) one monomer c of the general formula (1); (B) a dispersant containing a copolymer B of (d) a monomer of the general formula (2) and (e) a monomer of the general formula (3); (C) a gypsum powder; and (D) water.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a dispersant for a clay-containing gypsum composition. [Background technology]

[0002] In recent years, with the depletion of high-quality fine aggregates such as river sand, the proportion of aggregates that have not been actively used in the past, particularly natural gypsum, that are being used is increasing. Hydraulic compositions using such aggregates tend to have high viscosity in the fresh state, low fluidity, and low workability, even at normal water-cement ratios (W / C). In addition, the proportion of natural gypsum containing clay in the gypsum that is the raw material for gypsum boards is increasing. Hydraulic compositions using such natural gypsum tend to have low fluidity and low workability. To address the decrease in fluidity and workability, polycarboxylic acid-based water-reducing agents have been used up to now, but it is difficult to address this issue with conventional methods. For this reason, additives for hydraulic compositions containing cationic polymers containing quaternary nitrogen have been developed.

[0003] Patent Document 1 discloses an additive for hydraulic compositions containing a cationic polymer (A) containing a quaternary nitrogen atom to which is bonded a polyoxyalkylene group containing an alkyl group having 1 to 22 carbon atoms or an oxyalkylene group having 1 to 8 carbon atoms.

[0004] Patent Document 2 discloses an additive for hydraulic compositions containing a cationic polymer (A) that satisfies the following: (i) the polymer has a structure derived from a vinyl monomer (a) having a cationic group and a vinyl monomer (b) having no cationic group, (ii) the molar ratio of the monomer (a) to the monomer (b) is (a) / (b)=1 / 99 to 95 / 5, and (iii) the monomer (a) contains a vinyl monomer having a quaternary nitrogen cationic group.

[0005] Patent Document 3 discloses a copolymer having (a) 16 to 95 mol % of cationic structural units (A) and (b) 5 to 55 mol % of macromonomer structural units (B) as an additive for hydraulic compositions. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2006-45010 A [Patent Document 2] Special Publication No. 2014-503455 [Patent Document 3] JP 2014-205606 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, when low-quality aggregates, especially natural gypsum, are used, it has been found that a significant amount of the dispersant is adsorbed or absorbed by the clay contained therein. It has also been found that monomers having quaternary ammonium groups generally have poor polymerizability, do not improve yields, and do not provide sharp molecular weight distributions, resulting in problems with their performance as dispersants. [Means for solving the problem]

[0008] The present inventors have discovered the following (A) to (E): (A) (a) methacrylic acid, (b) a vinyl monomer having a cationic group, (c) one or more monomers selected from the monomers represented by general formula (1): [ka] [In the formula, R 1c and R 2c R may be the same or different and represent a hydrogen atom or a methyl group. 3c is a hydrogen atom or -C(O)O(A c O) nc R 4c A cO represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms. qc represents an integer of 0 to 2. pc represents 0 or 1. nc represents a molar average value of 5 to 150. R 4c represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. A dispersant (A) containing a copolymer A of the formula: Here, the weight average molecular weight (Mw) of the copolymer A contained in the dispersant (A) is 30,000 or more and 80,000 or less, and the ratio of Mw to number average molecular weight (Mn), Mw / Mn, is 1.0 or more and 2.0 or less. (B) (d) One or more monomers selected from the monomer d represented by general formula (2): [ka] [In the formula, R 1d and R 3d R may be the same or different and represent a hydrogen atom or a methyl group. 2d represents an alkyl group having 1 to 3 carbon atoms. d O represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms. qd represents an integer of 0 to 2. pd represents 0 or 1. nd represents a molar average value of 40 to 130. R 4d represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. (e) one or more monomers selected from the monomer e represented by general formula (3): [ka] [In the formula, R 1e , R 2e and R 3e are the same or different and represent a hydrogen atom or a methyl group. M represents a hydrogen atom, an alkali metal, or a (1 / 2) alkaline earth metal. A dispersant (B) containing a copolymer B of wherein the weight average molecular weight (Mw) of the copolymer B contained in the dispersant (B) is 35,000 or more and 100,000 or less, the ratio of Mw to the number average molecular weight (Mn), Mw / Mn, is 1.0 or more and 2.0 or less, and the weight content of the monomer e in the dispersant (B) is 10% by mass or more and 30% by mass or less; (C) Gypsum powder, (D) Water; It has been found that the above problems can be solved by using a gypsum slurry containing Effect of the Invention

[0009] According to the present invention, it is possible to provide a dispersant for a hydraulic composition which exhibits high dispersibility even in gypsum containing clay, particularly natural gypsum. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The gypsum slurry of the present application contains the following (A) to (E). (A) (a) methacrylic acid, (b) a vinyl monomer having a cationic group, (c) one or more monomers selected from the monomers represented by general formula (1): [ka] [In the formula, R 1c and R 2c R may be the same or different and represent a hydrogen atom or a methyl group. 3c is a hydrogen atom or -C(O)O(A c O) nc R 4c A c O represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms. qc represents an integer of 0 to 2. pc represents 0 or 1. nc represents a molar average value of 5 to 150. R 4c represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. A dispersant (A) containing a copolymer A of the formula: (B) (d) One or more monomers selected from the monomer d represented by general formula (2): [ka] [In the formula, R 1d and R 3d R may be the same or different and represent a hydrogen atom or a methyl group. 2d represents an alkyl group having 1 to 3 carbon atoms. d O represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms. qd represents an integer of 0 to 2. pd represents 0 or 1. nd represents a molar average value of 40 to 130. R 4d represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. (e) one or more monomers selected from the monomer e represented by general formula (3): [ka] [In the formula, R 1e , R 2e and R 3e are the same or different and represent a hydrogen atom or a methyl group. M represents a hydrogen atom, an alkali metal, or a (1 / 2) alkaline earth metal. A dispersant (B) containing a copolymer B of Here, the content of the monomer e in the dispersant (B) is 10% by mass or more and 30% by mass or less. (C) Gypsum powder, (D) Water.

[0011] The mass blending ratio (A) / (B) of the dispersant (A) to the dispersant (B) in the gypsum slurry is preferably 5 / 95 or more, more preferably 7 / 93 or more, and even more preferably 10 / 90 or more, in terms of good performance as a dispersant, and is preferably 95 / 5 or less, more preferably 93 / 7 or less, and even more preferably 90 / 10 or less.

[0012] The total content of dispersant (A) and dispersant (B) in the gypsum slurry is preferably 0.03 mass% or more, more preferably 0.04 mass% or more, and even more preferably 0.05 mass% or more, in terms of good performance as a dispersant, and is preferably 0.5 mass% or less, more preferably 0.4 mass% or less, and even more preferably 0.3 mass% or less.

[0013] The mass ratio of water to gypsum powder in the gypsum slurry is preferably 0.65 or less from the viewpoint of excellent water reducing property.

[0014] At 20°C of the gypsum slurry, a predetermined amount of copolymer was mixed with water relative to 100 parts by mass of clay-containing gypsum, and water was added to 0.256% dispersant to adjust the mixing water to a total amount of 150g. 150g of this mixing water was mixed with 250g of natural gypsum in a 500ml disposable cup and mixed with a hand mixer for 10 seconds to obtain a clay slurry. The obtained gypsum slurry was filled into a cone with an upper inner diameter of 50mm, a lower inner diameter of 50mm, and a height of 50mm, and the flow (mm) after drawing was measured. After measuring the flow, the gypsum slurry was collected in a disposable cup and the pH was measured using a pH meter. The pH is preferably 5.0 or more and 11.0 or less in terms of good performance as a dispersant.

[0015] Next, each of the components (A) to (E) will be described. First, each of the monomers that are constituent monomers of the copolymer A contained in the dispersant (A) will be described.

[0016] <(a) Methacrylic acid> The copolymer A contained in the dispersant (A) of the present invention contains methacrylic acid as an essential component as a constituent monomer.

[0017] <(b) Vinyl monomer having a cationic group> The copolymer A contained in the dispersant (A) of the present invention contains, as an essential component, one or more constituent monomers of vinyl monomers having a cationic group. As the vinyl monomer having a cationic group, a monomer represented by the general formula (4) [ka] [In the formula, R 1b R represents a hydrogen atom or a methyl group. 2b , R 3b and R 4b are the same or different and each represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. Y represents an oxygen atom or an -NH- group. m represents an integer of 1 to 6. X - indicates the counter anion. Ammonium salts represented by the following formula are preferred because they have good dispersing properties.

[0018] R in general formula (4) 1b As the alkyl group, a methyl group is preferred because of its good performance as a dispersant.

[0019] Examples of Y in the general formula (4) include an oxygen atom and an -NH- group. The oxygen atom is preferred because it has good performance as a dispersant.

[0020] In formula (4), m is preferably from 1 to 6, and more preferably 2, in that good performance as a dispersant is obtained.

[0021] R in general formula (4) 2b , R 3b and R 4b Examples of R include a hydrogen atom, a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a tert-butyl group, a hexyl group, a 2-ethylhexyl group, a cyclohexyl group, an octyl group, a cyclooctyl group, a decyl group, a dodecyl group, a tetradecyl group, a hexadecyl group, and an octadecyl group. 2b , R 3b and R 4b It is preferable that two of the groups are methyl groups and one is an ethyl group.

[0022] X in general formula (4) -Examples of the ion include halide ions such as chloride ion, bromide ion, and iodide ion, sulfate ion, nitrate ion, perchlorate ion, phosphate ion, methyl sulfate ion, ethyl sulfate ion, phenyl sulfate ion, tolyl sulfate ion, acetate ion, acetylacetonate ion, etc. In terms of easy availability, methyl sulfate ion or ethyl sulfate ion is preferred, and chloride ion is more preferred.

[0023] <(c) Monomer c> The constituent monomer of the copolymer A contained in the dispersant (A) of the present invention is one or more monomers c selected from the monomers represented by the general formula (1): [ka] [In the formula, R 1c and R 2c R may be the same or different and represent a hydrogen atom or a methyl group. 3c is a hydrogen atom or -C(O)O(AO) n R 4c AO represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms. qc represents an integer of 0 to 2. pc represents 0 or 1. nc represents a molar average value of 5 to 150. R 4c represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. Contains as an essential ingredient.

[0024] In the general formula (1), A c Examples of the alkyl group include an ethylene group, a propylene group, a butylene group, a methylethylene group, a 1-methylpropylene group, a 2-methylpropylene group, and a phenylethylene group. These groups may also be mixed. The ethylene group is preferred because of its excellent performance as a dispersant.

[0025] In the general formula (1), qc represents an integer of 0 or more and 2 or less. An integer of 0 is preferable in that the performance as a dispersant is good.

[0026] In the general formula (1), pc represents 0 or 1. It is preferably 1 in that it provides good performance as a dispersant.

[0027] In the general formula (1), nc represents the molar average value of the monomer c when the monomer c is one type. When two or more monomers are used as the monomer c, nc represents the molar average value calculated by taking into account the molar content of each monomer.

[0028] The nc value is preferably 1 or more, more preferably 3 or more, and even more preferably 5 or more, in terms of good performance as a dispersant, and is preferably 150 or less, more preferably 140 or less, and even more preferably 130 or less.

[0029] In the general formula (1), R 4c Specific examples of the alkyl group include methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, hexyl, 2-ethylhexyl, cyclohexyl, octyl, cyclooctyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl, etc. The methyl group is preferred because of its good performance as a dispersant.

[0030] The copolymer A contained in the dispersant (A) may be isolated after the polymerization reaction, but may not be isolated and may contain unreacted monomers (a) to (c). If the yield of the copolymer is more than 95%, the molar ratio of the constituent monomers charged in the production of the copolymer can be considered to be the molar ratio of the constituent monomers in the copolymer.

[0031] In addition, in the case where copolymer A is not isolated and contains unreacted monomers (a) to (c), the content of the unreacted monomers is preferably 5 mol % or less based on the total amount of each monomer charged, in terms of good dispersant performance.

[0032] The ratio of the constituent monomers is not particularly limited, but in terms of good dispersant performance, copolymer A contains methacrylic acid as a constituent monomer in an amount of preferably 1 mol % or more, more preferably 1.5 mol % or more, and preferably 50 mol % or less, more preferably 45 mol % or less.

[0033] The content of methacrylic acid as a constituent monomer contained in copolymer A is preferably 1 mol % or more, more preferably 1.5 mol % or more, and preferably 50 mol % or less, more preferably 45 mol % or less, in terms of good dispersant performance.

[0034] The content of component (b) as a constituent monomer contained in copolymer A is preferably 5 mol % or more, more preferably 10 mol % or more, and preferably 75 mol % or less, more preferably 70 mol % or less, in terms of good dispersant performance.

[0035] The content of component (c) as a constituent monomer contained in copolymer A is preferably 10 mol % or more, more preferably 15 mol % or more, and preferably 90 mol % or less, more preferably 85 mol % or less, in terms of good dispersant performance.

[0036] The weight average molecular weight (Mw) of copolymer A is preferably 20,000 or more, more preferably 30,000 or more, in terms of good performance as a dispersant, and is preferably 100,000 or less, more preferably 80,000 or less. In addition, the ratio of Mw to the number average molecular weight (Mn), Mw / Mn, is preferably 1.0 or more and 2.0 or less in terms of good performance as a dispersant.

[0037] Copolymer A of the present invention can be produced under the conditions for copolymerization of general-purpose vinyl polymers. For example, water can be used as the solvent. The reaction temperature is in the range of 50°C to 100°C. The reaction time varies depending on the reaction temperature, but can be in the range of 0.5 hours to 10 hours.

[0038] The production of Copolymer A of the present invention is preferably carried out at a pH of 2.9 or less in terms of good yield.

[0039] Next, each monomer serving as a raw material for the copolymer of the dispersant (B) will be described.

[0040] <(d) Monomer d> The dispersant (B) of the present invention includes a copolymer B having a monomer represented by the general formula (2): [ka] [In the formula, R 1d and R 3d R may be the same or different and represent a hydrogen atom or a methyl group. 2d represents an alkyl group having 1 to 3 carbon atoms. d O represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms. qd represents an integer of 0 to 2. pd represents 0 or 1. nd represents a molar average value of 40 to 130. R 4d represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. The copolymer contains one or more monomers d represented by the following formula (1) as essential components.

[0041] In the general formula (2), A d Examples of the alkyl group include an ethylene group, a propylene group, a butylene group, a methylethylene group, a 1-methylpropylene group, a 2-methylpropylene group, a phenylethylene group, etc. These may also be mixed. The ethylene group is preferred in that it provides good dispersant performance.

[0042] R in general formula (2) 1d and R 3d is preferably a hydrogen atom in terms of good dispersant performance. 2d is preferably a methyl group.

[0043] In the general formula (2), qd represents an integer of 0 or more and 2 or less. In terms of providing good dispersant performance, 0 or 2 is preferred.

[0044] In the general formula (2), pd represents 0 or 1. When qd is 0, 1 is preferred, and when qd is 2, 0 is preferred, in terms of good dispersant performance.

[0045] In the general formula (2), nd indicates the molar average value of the monomer when the monomer d is one type. When two or more monomers are used as the monomer d, nd indicates the molar average value calculated by taking into account the molar content of each monomer.

[0046] The nd value is preferably 40 or more, more preferably 45 or more, and even more preferably 50 or more, in terms of good performance as a dispersant, and is preferably 150 or less, more preferably 140 or less, and even more preferably 130 or less.

[0047] <(e) Monomer e> The constituent monomer of the copolymer B contained in the dispersant (B) of the present invention is one or more monomers selected from the monomer e represented by the general formula (3): [ka] [In the formula, R 1e , R 2e and R 3e are the same or different and represent a hydrogen atom or a methyl group. M represents a hydrogen atom, an alkali metal, or a (1 / 2) alkaline earth metal. The copolymer contains one or more monomers e represented by the following formula (1) as an essential component.

[0048] R in general formula (3) 1e and R 3e is preferably a hydrogen atom in terms of good dispersant performance. 2e is preferably a methyl group.

[0049] Examples of M in the general formula (3) include a hydrogen atom, alkali metals such as lithium, sodium, potassium, etc., and alkaline earth metals such as magnesium, calcium, etc. A hydrogen atom is preferred in terms of providing good dispersant performance.

[0050] Copolymer B may be isolated after the polymerization reaction, but may also be used without being isolated and containing unreacted monomers (d) and (e). If the yield of copolymer B is greater than 95%, the molar ratio of the constituent monomers charged in the production of the copolymer may be considered to be the molar ratio of the constituent monomers in copolymer B.

[0051] In addition, in the case where copolymer B is not isolated and contains unreacted monomers (d) and (e), the content of the unreacted monomers is preferably 5 mol % or less based on the total amount of each monomer charged, in terms of good dispersant performance.

[0052] The ratio of the constituent monomers is not particularly limited, but in terms of good dispersant performance, the monomer (e) in copolymer B is preferably 10 mass % or more, more preferably 12 mass % or more, and preferably 30 mass % or less, more preferably 25 mass % or less, of the constituent monomers.

[0053] The weight average molecular weight (Mw) of the copolymer B is preferably 35,000 or more, more preferably 40,000 or more, in terms of good dispersant performance, and is preferably 100,000 or less, more preferably 80,000 or less. In addition, the ratio of Mw to the number average molecular weight (Mn), Mw / Mn, is preferably 1.0 or more and 2.0 or less in terms of good performance as a dispersant.

[0054] The copolymer B of the present invention can be produced under the conditions for copolymerization of general-purpose vinyl polymers. For example, water can be used as the solvent. The reaction temperature is in the range of 50°C to 100°C. The reaction time depends on the reaction temperature, but can be in the range of 0.5 hours to 10 hours.

[0055] The production of the copolymer B of the present invention is preferably carried out at a pH of 2.9 or less in terms of good yield.

[0056] The weight average molecular weight of the copolymers A and B can be adjusted by adding a chain transfer agent. Examples of the chain transfer agent that can be used include general-purpose thiols such as β-mercaptopropionic acid, 2-mercaptoethanol, 2-ethylhexyl-β-mercaptopropionic acid, methoxybutyl β-mercaptopropionate, and octadecyl 3-mercaptopropionate, and carbon tetrachloride.

[0057] Next, the (C) gypsum powder will be described. The silicon atom content in the gypsum powder that can be used in the present application, as determined by ICP analysis, is preferably 100 ppm or more and 60,000 ppm or less, from the viewpoint of good dispersibility.

[0058] Next, (D) water will be described. The gypsum slurry of the present invention contains water as the (d) component. From the viewpoint of exhibiting good fluidity, water that does not contain impurities and is appropriately purified is preferably used, but well water and industrial water can also be used. From the viewpoint of exhibiting stable fluidity, tap water, purified water, and ion-exchanged water are preferred. EXAMPLES

[0059] <Examples and Comparative Examples> The present invention will be described in detail below with reference to examples and comparative examples, but the present invention is not limited to the following descriptions.

[0060] Copolymer 1 of the dispersant (A) was produced in the examples and comparative examples using the following components (a) to (c). <Component (a)> Methacrylic acid was used, and acrylic acid was also used for comparison.

[0061] <(b) Component> MOEDES: Ethyl [2-(methacryloyl)ethyl] dimethylammonium ethyl sulfate DMAEM-Q: 2-(acryloyl)ethyltrimethylammonium chloride

[0062] <(c) component> The ester of polyethylene glycol monomethyl ether and methacrylic acid shown in general formula (9) was used. [ka] The molar average value nc is as follows: MEPEG(9):nc=9 MEPEG(23):nc=23 MEPEG(120):nc=120

[0063] Furthermore, vinyloxybutyl polyethylene glycols 3000 and 5800 of the following formula (17) were used as comparative compounds. [ka] The molar average value n' is as follows: Vinyloxybutyl polyethylene glycol (66): n'=66 Vinyloxybutyl polyethylene glycol (130): n'=130

[0064] In the production of copolymer A, one type of component (c) was used, so the value of nc indicates the average number of ethylene oxide units added to each MEPEG. The molar average value n' of the vinyloxybutyl polyethylene glycol used in the comparative example is also shown.

[0065] Copolymer B contained in dispersant (B) was produced in the examples and comparative examples using the following components (d) and (e). <(d) component> Polyethylene glycol monomethyl ether (MEPEG) represented by general formula (12) and polyethylene glycol isoprenyl ether (TPEG) represented by general formula (15) were used. [ka] The molar average value nd is as follows: MEPEG(9):nd=9 MEPEG(23):nd=23 MPEG(120):nd=120 [ka] The molar average value nd is as follows: TPEG(45):nd=45 TPEG(60):nd=60 TPEG(70):nd=70 In addition, in the production of copolymer B of B-2 to B-5 in Table 2, two types of (d) components, (d-1) and (d-2), were used, so the value of nd indicates the average number of ethylene oxide additions taking into account the molar contents of these.

[0066] <(e) component> Methacrylic acid and acrylic acid were used.

[0067] <Production of Copolymers A and B by Copolymerization Reaction> In producing copolymer A, β-mercaptopropionic acid was added in an amount of 1.5 to 9.0 mol % based on the total amounts of components (a), (b), and (c) used in producing copolymer A. In addition, β-mercaptopropionic acid and 2-mercaptoethanol were added in an amount of 1.0 to 9 mol % based on the total amounts of components (d) and (e) used in producing copolymer B. The procedure will be explained below using the production of B-2 in Table 2 as an example. 354.71 g of water was placed in a glass reaction vessel equipped with a stirrer, and the inside of the vessel was replaced with nitrogen while stirring, and the temperature was raised to 80° C. in a nitrogen atmosphere. (i) A solution prepared by mixing and dissolving 379.34 g of an aqueous solution of MEPEG(120) (active ingredient: 87.89% by mass, water: 38.1% by mass), 114.05 g of an aqueous solution of MEPEG(23) (active ingredient: 93.13% by mass, water: 35.2% by mass), 82.2 g of methacrylic acid, and 3.71 g of 3-mercaptopropionic acid; (ii) A solution prepared by dissolving 4.81 g of ammonium persulfate in 25 g of water. These two solutions were each added dropwise into the said container over 1.5 hours. Next, a solution prepared by dissolving 1.76 g of ammonium persulfate in 10 g of water was added dropwise over 30 minutes, and then the mixture was aged at the same temperature (80 °C) for 1 hour. After the aging was completed, it was neutralized with 34.05 g of a 48% aqueous sodium hydroxide solution to obtain a reaction product containing a copolymer with a weight-average molecular weight of 62,000 and water. For the other copolymers in Table 1 and Table 2, they were produced in the same manner as above, except that the types and amounts of monomers used were changed.

[0068] Table 1 shows the average molecular weights and yields of copolymers A and A' obtained by the above production method.

[0069]

Table 1

[0070] Table 2 shows the average molecular weights and yields of copolymers B and B' obtained by the above production method.

[0071]

Table 2

[0072] As the gypsum powder, natural gypsums (1), (2), and (3) were used. Each natural gypsum was subjected to composition analysis by XRF analysis and quantification of the silicon and phosphorus contents by ICP analysis. The respective measurement methods are shown below. <XRF analysis> 50 mg of the sample was placed on filter paper, covered with a PET film, and pressed. The prepared sample was measured with a fluorescent X-ray analyzer under the following conditions. Analyzer: Rigaku wavelength-dispersive fluorescent X-ray PrmusII 2θ (θ: analytical angle): varies depending on the element to be measured Target: rhodium tube Tube voltage: 50 kV Tube current: 50 mA Spectrometer crystal: LiF(200), Ge, PET, RX25 Detector: SC, PC <ICP analysis> The reagents used are shown below. Sulfuric acid: for precision analysis, manufactured by FUJIFILM Wako Pure Chemical Corporation Hydrochloric acid: for metal analysis, manufactured by Kanto Chemical Co., Inc. Nitric acid: EL grade, manufactured by Kanto Chemical Co., Inc. Hydrogen peroxide: for atomic absorption spectrometry, manufactured by FUJIFILM Wako Pure Chemical Corporation Sodium carbonate: special grade, manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd. Boric acid: special grade, manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd. Standard solution for each element: 1000 mg / L for atomic absorption spectrometry, manufactured by Kanto Chemical Co., Inc. Ultra-pure water: Milli-Q water produced by an ultra-pure water manufacturing apparatus, manufactured by Millipore 1. Preparation of samples (i) Pretreatment method for Si Weigh 0.1 g of the sample precisely into a platinum crucible, add 2 g of an alkaline flux (sodium carbonate: boric acid = 1:0.4), and melt it in an electric furnace at 950 °C. Cover it with a watch glass, add 10 mL of ultra-pure water and hydrochloric acid (6 mol / L), heat and dissolve it on a hot plate at 70 - 80 °C. After cooling, make up the volume to 100 mL with ultra-pure water to obtain the measurement solution. Samples exceeding the calibration curve range were appropriately diluted to obtain the measurement solution. (ii) Pretreatment method for P Take 0.1 g of the sample into a decomposition container, add 2 mL of sulfuric acid, appropriate amounts of nitric acid and hydrogen peroxide for wet decomposition, make up the volume to 50 mL with ultra-pure water, and then use the supernatant obtained after precipitating the insoluble matter as the sample measurement solution. (iii) Preparation of calibration curve solution Using the standard solution for atomic absorption spectrometry (each element: 1000 mg / L), calibration curve solutions with concentrations of 0.1 - 20 mg / L were prepared. Alkaline flux and hydrochloric acid were added to the solution for Si quantification to be similar to the sample. Sulfuric acid was added to the solution for P quantification to a concentration of 4%. 2. Measurement The samples prepared in step 1 were subjected to measurement of each element using an ICP optical emission spectrometer under the following conditions. Analytical equipment: Thermo Fisher Scientific iCAP6500Duo Wavelength: Si 251.611nm, P 213.618nm RF power: 1150W Coolant gas flow rate: 12L / min Nebulizer flow rate: 0.70L / min Auxiliary gas: 0.5L / min Pump flow rate: 50 rpm

[0073] [Table 3] It should be noted that the values ​​from the XRF analysis are not quantitative values ​​but qualitative values ​​indicating peak intensities.

[0074] <Preparation of gypsum slurry and measurement of pH> 250 g of natural gypsum was mixed with mixing water containing a dispersant (0.256% dispersant was mixed with water to adjust the total to 150 g) and stirred with a hand mixer for 10 seconds. The pH of the resulting slurry was measured, and the results are shown in Table 4.

[0075] [Table 4]

[0076] The water reducing ability and setting ability were evaluated using gypsum slurries (slurries (1) to (3)) prepared by changing the amounts of dispersants (A) and (B). First, the evaluation method for water reducing ability and setting ability will be described. <Evaluation of water-reducing properties> Gypsum slurries prepared using each type of natural gypsum were filled into a paste cone (diameter 50mm x height 50mm), and 30 seconds after contact with water, the paste cone was lifted vertically to measure the fluidity at the maximum diameter and at the right angle, and the amount of water at which the average value was 125mm was defined as 0% water reduction, and the amount of water that could be reduced in the same system with dispersant added was defined as the water reduction rate and measured. In other words, for example, if the amount of water that can be obtained for 125mm using only water is 200g (W / G=80%), and the amount of water that can be obtained for 125mm using 0.256% dispersant is 160g (W / G=64%), 1-(160 / 200)=0.2 The water reduction rate is estimated at 20%.

[0077] <Evaluation of coagulation property> Setting time refers to the time from when each gypsum slurry is poured into the mixed water until it sets. As the setting progresses, the "initial setting time", "apparent final setting time" and "final setting time" are measured. Setting time is measured as follows. a) To measure the setting time, a Vicat needle apparatus specified in JIS R 5201 is used. The standard needle for gypsum is a metal needle with a length of 45 mm and a diameter of 2 mm, with its head cut flat. The total mass of the moving part that descends with it is 300±1g. b) The thermometer used is a thermometer with thermometer symbol C specified in JIS B 7411-1 or a temperature measuring device with an accuracy equal to or higher than that of the thermometer. c) The measurement method is to pour the gypsum paste obtained by pouring the gypsum slurry into the mixed water into a cylindrical mold with an inner diameter of 78±5 mm and a height of 40.0±0.5 mm placed on a glass plate, insert a thermometer into the center, and perform the following measurements. 1) Initial time: Measure the time it takes for the standard needle of the measuring device to stop at a height of about 1 mm from the bottom of the test piece. 2) Apparent final time: Measure the time it takes for the standard needle of the measuring device to stop at a depth of about 1 mm from the surface of the test piece. 3) Final time: Measure the time it takes for the thermometer to indicate the maximum temperature.

[0078] <Evaluation of water reducing and setting properties (1)> Table 5 shows the results of evaluation of the water reducing ability and coagulation ability of Slurry 1 prepared using A-7 and A-2 as dispersants (A) and B-1 as dispersant (B). [Table 5] It was found that Comparative Example 1, which did not contain the dispersant (A), had a lower water reducing property than Examples 1 and 2, and also showed a delayed start and end of setting.

[0079] <Evaluation of water reducing properties (1)> Table 6 shows the results of evaluating the water reducing ability of slurries prepared by adding 0.06 mass % of each of the dispersants (A) and (B) to the slurry 1. [Table 6] From Table 6, it is clear that the slurry 1 using the comparative dispersant (A') and the dispersant (B') is inferior in water reducing ability.

[0080] <Measurement of water reducing properties (2)> Table 7 shows the results of evaluating the water reducing ability of slurries prepared by adding 0.126 mass % of each of the dispersants (A) and (B) to the slurry 1.

[0081] [Table 7] From Table 7, it is clear that the slurry 1 using the comparative dispersant (A') and the dispersant (B') is inferior in water reducing ability.

[0082] <Measurement of water reducing properties (3)> Table 8 shows the results of evaluating the water reducing ability of slurries prepared by adding 0.256 mass % of each of the dispersants (A) and (B) to the slurry 1.

[0083] [Table 8]

[0084] <Measurement of strength> Next, the strength of Slurry 2 was measured. Slurry 2 was filled into a cylindrical plastic mold (bottom diameter: 5 cm, height: 10 cm) using a two-layer filling method based on JIS A 1132, and cured in air at 20°C. The 7-day strength of the hardened gypsum paste body removed from the mold after curing was measured for compressive strength based on JISA 1108. The results are shown in Table 9.

[0085] [Table 9] From Table 9, it was found that the slurry 2 using the comparative dispersant (A') and the dispersant (B') was clearly inferior in strength.

[0086] <Evaluation of water reducing and setting properties (2)> Table 10 shows the results of evaluation of water reducing ability and coagulation property of Slurry 3 prepared using A-10 and A-6 as dispersants (A) and B-1 as dispersant (B).

[0087] [Table 10] It was found that Comparative Example 21, which did not contain the dispersant (A), had a lower water reducing property than Examples 27 and 28, and also showed a delayed start and end of setting.

[0088] <Measurement of water reduction, initial setting time, and final setting time (3)> Table 11 shows the results of evaluation of water reducing ability and coagulation ability of slurries prepared using A-10, A-6 and A'-4 as dispersants (A) and B-1 as dispersant (B).

[0089] [Table 11] It was found that Comparative Example 22, which used A'-4 containing acrylic acid as component (a), and Comparative Example 23, which did not contain dispersant (A), had lower water reducing properties than Examples 29 and 30, and that both the onset and completion of coagulation were delayed.

[0090] <Measurement of water reducing properties (4)> Table 12 shows the results of evaluating the water reducing ability of slurries prepared by adding 0.06 mass % of each of the dispersants (A) and (B) to the slurry 1.

[0091] [Table 12] From Table 12, it is clear that the slurry 1 using the comparative dispersant (A') and the dispersant (B') is inferior in water reducing ability.

[0092] <Measurement of water reducing properties (5)> Table 13 shows the results of evaluating the water reducing ability of slurries prepared by adding 0.126 mass % of each of the dispersants (A) and (B) to the slurry 3.

[0093] [Table 13] From Table 13, it is clear that the slurry 1 using the comparative dispersant (A') and the dispersant (B') is inferior in water reducing ability.

[0094] <Measurement of water reducing properties (6)> Table 14 shows the results of evaluating the water reducing ability of slurries prepared by adding 0.256 mass % of each of the dispersants (A) and (B) to the slurry 3.

[0095] [Table 14] From Table 14, it is clear that Slurry 1 using the comparative dispersant (A') and dispersant (B') is inferior in water reducing ability.

Claims

1. A gypsum slurry comprising the following (A) to (E): (A) (a) methacrylic acid, (b) a vinyl monomer having a cationic group; (c) one or more monomers selected from the monomers represented by general formula (1): 【Chemical 1】 [In the formula, R １ｃ and R ２ｃ are the same or different and represent a hydrogen atom or a methyl group. ３ｃ is a hydrogen atom or -C(O)O(A ｃ O) ｎｃ R ４ｃ represents a group. ｃ O represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms. qc represents an integer of 0 to 2. pc represents 0 or 1. nc represents a molar average value of 5 to 150. R ４ｃ represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. a dispersant (A) containing a copolymer A of the formula: Here, the weight average molecular weight (Mw) of the copolymer A contained in the dispersant (A) is 30,000 or more and 80,000 or less, and the ratio of Mw to number average molecular weight (Mn), Mw / Mn, is 1.0 or more and 2.0 or less. (B) (d) One or more monomers selected from the monomer d represented by general formula (2): 【Chemistry 2】 [In the formula, R １ｄ and R ３ｄ are the same or different and represent a hydrogen atom or a methyl group. ２ｄ represents an alkyl group having 1 to 3 carbon atoms. ｄ O represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms. qd represents an integer of 0 to 2. pd represents 0 or 1. nd represents a molar average value of 40 to 130. R ４ｄ represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. (e) One or more monomers selected from the monomer e represented by general formula (3): 【Chemistry 3】 [In the formula, R １ｅ , R ２ｅ and R ３ｅ are the same or different and represent a hydrogen atom or a methyl group; M represents a hydrogen atom, an alkali metal, or a (1 / 2) alkaline earth metal. a dispersant (B) containing a copolymer B of the formula: wherein the weight average molecular weight (Mw) of the copolymer B contained in the dispersant (B) is 35,000 or more and 100,000 or less, the ratio of Mw to the number average molecular weight (Mn), Mw / Mn, is 1.0 or more and 2.0 or less, and the weight content of the monomer e in the dispersant (B) is 10% by mass or more and 30% by mass or less; (C) gypsum powder, (D) Water.

2. 2. The gypsum slurry according to claim 1, wherein a mass blending ratio (A) / (B) of the dispersant (A) to the dispersant (B) is 5 / 95 or more and 95 / 5 or less.

3. 2. The gypsum slurry according to claim 1, wherein the total content of the dispersant (A) and the dispersant (B) is 0.03% by mass or more and 0.5% by mass or less of the gypsum powder.

4. 2. The gypsum slurry according to claim 1, wherein the gypsum powder (C) has a silicon atom content determined by ICP analysis of 100 ppm or more and 60,000 ppm or less.

5. The gypsum slurry according to claim 1, wherein a mass ratio of the water (D) to the gypsum powder (C) is 0.65 or less.

6. 2. The gypsum slurry according to claim 1, wherein the pH at 20°C is 5.0 or more and 11.0 or less.

7. 2. The gypsum slurry according to claim 1, wherein the dispersant (A) contains (a) a copolymer A containing 1 mol % or more and 50 mol % or less of methacrylic acid as a constituent monomer.

8. 2. The gypsum slurry according to claim 1, wherein the vinyl monomer having a cationic group in the copolymer A contained in the dispersant (A) is one or more monomers b selected from vinyl monomers represented by general formula (4). 【Chemistry 4】 [In the formula, R １ｂ represents a hydrogen atom or a methyl group. ２ｂ , R ３ｂ and R ４ｂ are the same or different and represent a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. Y represents an oxygen atom or an -NH- group. m represents an integer of 1 to 6. X － indicates a counter anion.

9. 2. The gypsum slurry according to claim 1, wherein the vinyl monomer having a cationic group in the copolymer A contained in the dispersant (A) is one or more monomers b selected from vinyl monomers represented by general formula (5). 【Chemistry 5】 [In the formula, R ２ｂ , R ３ｂ and R ４ｂ each independently represents a hydrogen atom or a methyl group; Y represents an oxygen atom or an —NH— group; and m represents an integer of 1 or more and 6 or less. X － indicates a counter anion.

10. 2. The gypsum slurry according to claim 1, wherein the vinyl monomer having a cationic group in the copolymer A contained in the dispersant (A) is one or more monomers b selected from vinyl monomers represented by general formula (6). 【Chemistry 6】 [In the formula, X － indicates a counter anion.]

11. X － The gypsum slurry according to any one of claims 8 to 10, wherein is a methyl sulfate ion or an ethyl sulfate ion.

12. The gypsum slurry according to claim 1, wherein the monomer c in the copolymer A contained in the dispersant (A) is one or more monomers selected from monomers represented by general formula (7): 【Chemistry 7】 [In the formula, R １ｃ and R ２ｃ are the same or different and represent a hydrogen atom or a methyl group. ３ｃ is a hydrogen atom or -C(O)O(A ｃ O) ｎｃ R ４ｃ represents a group. ｃ O represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms. nc represents a molar average value of 5 to 150. R ４ｃ represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.

13. The gypsum slurry according to claim 1, wherein the monomer c of the copolymer A contained in the dispersant (A) is one or more monomers selected from monomers represented by general formula (8): 【Chemistry 8】 [In the formula, R ４ｃ represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. ｃ O represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms, and nc represents a molar average value of 5 to 150.

14. The gypsum slurry according to claim 1, wherein the monomer c of the copolymer A contained in the dispersant (A) is one or more monomers selected from monomers represented by general formula (9): 【Chemistry 9】 [In the formula, n c represents a molar average value of 5 to 150.]

15. 2. The gypsum slurry according to claim 1, wherein the total content of unreacted monomers (a) to (c) in copolymer A contained in dispersant (A) is 5 mol % or less with respect to the total amount of each monomer charged.

16. The gypsum slurry according to claim 1, comprising a copolymer A obtained by copolymerizing the copolymer A contained in the dispersant (A) at a pH of 2.9 or less.

17. 2. The gypsum slurry according to claim 1, wherein the monomer d of the copolymer B contained in the dispersant (B) is one or more monomers selected from the monomers represented by general formula (10): 【Chemistry 10】 [In the formula, R １ｄ and R ３ｄ are the same or different and represent a hydrogen atom or a methyl group. ２ｄ represents an alkyl group having 1 to 3 carbon atoms. ｄ O represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms. nd represents a molar average value of 40 to 130. R ４ｄ represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.

18. 2. The gypsum slurry according to claim 1, wherein the monomer d of the copolymer B contained in the dispersant (B) is one or more monomers selected from the monomers represented by general formula (11): 【Chemistry 11】 [In the formula, R ４ｄ represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms. ｄ O represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms, and nd represents a molar average value of 40 to 130.

19. The gypsum slurry according to claim 1, wherein the monomer d of the copolymer B contained in the dispersant (B) is one or more monomers selected from the monomers represented by general formula (12): 【Chemistry 12】 [In the formula, the molar average value is 40 or more and 130 or less.]

20. 2. The gypsum slurry according to claim 1, wherein the monomer d of the copolymer B contained in the dispersant (B) is one or more monomers selected from the monomers represented by general formula (13): 【Chemistry 13】 [In the formula, R １ｄ and R ３ｄ are the same or different and represent a hydrogen atom or a methyl group. ２ｄ represents an alkyl group having 1 to 3 carbon atoms. ｄ O represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms. qd represents an integer of 0 to 2. nd represents a molar average value of 40 to 130. R ４ｄ represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.

21. 2. The gypsum slurry according to claim 1, wherein the monomer d of the copolymer B contained in the dispersant (B) is one or more monomers selected from the monomers represented by general formula (14): 【Chemistry 14】 [In the formula, A ｄ O represents an oxyalkylene group or a phenylethylene group having 2 to 4 carbon atoms. qd represents an integer of 0 to 2. nd represents a molar average value of 40 to 130. R ４ｄ represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms.

22. The gypsum slurry according to claim 1, wherein the monomer d of the copolymer B contained in the dispersant (B) is one or more monomers selected from the monomers represented by general formula (15): 【Chemistry 15】 [In the formula, nd represents a molar average value of 40 or more and 130 or less.]

23. 2. The gypsum slurry according to claim 1, wherein the monomer e of the copolymer B contained in the dispersant (B) is one or more monomers selected from the monomers represented by general formula (16): 【Chemistry 16】 [In the formula, R ３ｅ represents a hydrogen atom or a methyl group.

24. 2. The gypsum slurry according to claim 1, wherein the total content of unreacted monomers (d) and (e) in copolymer B contained in dispersant (B) is 5 mol % or less with respect to the total charged amount of each monomer.

25. The gypsum slurry according to claim 1, further comprising a copolymer B obtained by copolymerizing the copolymer B contained in the dispersant (B) at a pH of 2.9 or less.

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