JP2007153628A - Powdery cement dispersant and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a powdery cement dispersant having good workability and an excellent cement water reducing property and to provide its manufacturing method. <P>SOLUTION: In the powdery cement dispersant containing a polycarboxylic acid-based copolymer (I), the polycarboxylic acid-based copolymer (I) has at least a part (A) represented by general formula (1) and a part (B) represented by general formula (2). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

TECHNICAL FIELD The present invention relates to a powdery cement dispersant and a method for producing the same, and more specifically, a powdery cement dispersant that can provide a cement composition that exhibits high water reduction performance and is easy to handle, and a method for producing the same. About.

Cement dispersants containing polycarboxylic acid copolymers are widely used in cement compositions such as cement paste, mortar, and concrete, and are indispensable for building civil engineering and building structures from cement compositions. It is not possible to. Such a cement dispersant has the effect of improving the strength and durability of the cured product by increasing the fluidity of the cement composition and reducing the water content of the cement composition. As such a dispersant, a polycarboxylic acid-based dispersant mainly composed of a polycarboxylic acid-based copolymer that exhibits high water-reducing performance as compared with a conventional naphthalene-based dispersant has recently been frequently used. It has become like this. However, many of the polycarboxylic acid-based dispersants are aqueous solutions. When applying by adjusting cement mortar made of cement, water, and sand, the polycarboxylic acid-based dispersant is an aqueous solution, so it is mixed immediately before the installation. There is a strong demand for a dispersant that can be mixed with cement or sand in advance because it must be complicated. Under such circumstances, attempts have been made to pulverize several polycarboxylic acid-based dispersants. However, polycarboxylic acid-based copolymers in the molecular weight region useful as cement dispersants have low molecular weight. It was not easy to make a powder that was not sticky and easy to handle. For example, Patent Document 1 discloses a method in which an aqueous solution of a polycarboxylic acid copolymer and a slurry solution of an inorganic powder are simultaneously put into a spray dryer to form a powder, and the inorganic powder is used in combination. By doing so, the stickiness of the powder is eliminated. Patent Document 2 discloses a powdery cement dispersant that uses, in part, an alkyl (meth) acrylate represented by methyl methacrylate as a monomer component constituting a polycarboxylic acid copolymer. .
Japanese Patent Laid-Open No. Hei 6-239652 JP 2001-294463 A

The present invention has been made in view of the above situation, and provides a powdered cement dispersant without impairing the dispersibility of the cement. Furthermore, the powdery cement dispersant without stickiness The manufacturing method which can manufacture easily is provided.

The present inventors have found that a specific polycarboxylic acid-based copolymer is useful as a powdery cement dispersant, and further, by powdering under specific conditions, a powdery form without stickiness The present inventors have found a production method capable of easily producing a cement dispersant. That is,
The first invention is a powdery cement dispersant comprising a polycarboxylic acid copolymer (I), wherein the polycarboxylic acid copolymer (I) is represented by the following general formula (1);

(In the formula, R ¹ and R ² are the same or different and represent a hydrogen atom or a methyl group. R ³ is the same or different and represents an alkylene group having 2 to 5 carbon atoms. X represents a number of 0 to 2. M represents the average number of added moles of the oxyalkylene group, and is a number from 3 to 200. R ⁴ represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. The following general formula (2);

(Wherein, R ⁵ represents a hydrogen atom or a methyl group, and M represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, an ammonium group, or an organic amino group). At least the mass proportion of the total of the site (A) and the site (B) to the polycarboxylic acid copolymer (I) is 70% by mass to 100% by mass, and the site (A) And the part (B) is 4 to 40% by mass with respect to the total mass of the part (B).
Furthermore, the manufacturing method of the powdery cement dispersant which is the second invention is the following general formula (3);

(In the formula, R ⁶ is the same or different and represents an alkylene group having 2 to 5 carbon atoms, R ⁷ represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and n is an average added mole number of an oxyalkylene group. And is a number of 10 to 200.) Powdered cement dispersant for converting an aqueous solution of a polycarboxylic acid copolymer (II) having a polyalkylene oxide chain represented by the formula The method for producing a powdery cement dispersant is characterized in that the temperature of hot air introduced into the drying chamber of the spray dryer is 60 ° C to 130 ° C. Further, the production method is characterized in that the inside of the drying chamber of the spray dryer is powdered under a reduced pressure atmosphere of 9.9 × 10 ⁴ Pa or less, and further has the polyalkylene oxide chain. The polycarboxylic acid copolymer (II) is represented by the following general formula (1);

(In the formula, R ¹ and R ² are the same or different and represent a hydrogen atom or a methyl group. R ³ is the same or different and represents an alkylene group having 2 to 5 carbon atoms. X represents a number of 0 to 2. M represents the average number of added moles of the oxyalkylene group and is a number of 3 to 200. R ⁴ represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms.)
A site (A) represented by the following general formula (2);

(Wherein, R ⁵ represents a hydrogen atom or a methyl group, and M represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, an ammonium group, or an organic amino group). It is this manufacturing method characterized by having at least.
The present invention is described in detail below.

The powdery cement dispersant according to the first aspect of the present invention is a polycarboxylic acid having at least a part (A) represented by the general formula (1) and a part (B) represented by the general formula (2). -Based copolymer (I) is included, and the mass proportion of the total of site (A) and site (B) in the polycarboxylic acid copolymer (I) is 70% by mass to 100% by mass. And a powdery cement dispersant characterized in that the part (B) is 4% by mass to 40% by mass with respect to the total mass of the part (A) and the part (B), Includes a copolymer obtained by copolymerizing a monomer (A-1) that forms part (A) and a monomer (B-1) that forms part (B) in the presence of a solvent. It can be obtained by drying and pulverizing the polymer solution.

The average added mole number of the alkylene oxide represented by m in the part (A) is from 3 to 200, preferably from 10 to 150, more preferably from 25 to 150. When m is in this range, there is almost no stickiness of the powdered cement dispersant and the cement dispersibility is excellent.
The mass ratio of the total of the site (A) and the site (B) to the polycarboxylic acid copolymer (I) is 70% by mass to 100% by mass, preferably 90% by mass to 100% by mass. Most preferably, it is 95% by mass to 100% by mass.

As the monomer (A-1), 3 to 200 mol of alkylene oxide is added to alkenyl alcohol such as vinyl alcohol, allyl alcohol, hydroxybutyl vinyl ether, methallyl alcohol, and 3-methyl-3-buten-1-ol. It can also be obtained by an etherification reaction of an adduct obtained by the above, or a compound having an alkenyl group and a halogen and a terminal alkylpolyalkylene glycol, such as an etherification reaction product of allyl chloride and methoxypolyethylene glycol. May be used in combination of two or more.

Specific examples of the monomer (B-1) include methacrylic acid, acrylic acid, and their alkali metal salts, alkaline earth metal salts, ammonium salts, and salt-forms with organic amines. Acrylic acid is preferred. Further, in the case of a salt-forming product, a monovalent alkali metal salt is preferable, and in the case of a divalent or higher such as an alkaline earth metal, crosslinking with a carboxyl group occurs, and when powdered, cement and water The solubility in the mixture is inferior, and the dispersion performance may not be sufficiently exhibited.

As a component other than the part (A) and the part (B), the monomer (C-1) may be copolymerized together with the monomer (A-1) and the monomer (B-1). Monomer (C-1) includes monomers (A-1) such as styrene, alkyl (meth) acrylate, and acrylamide, or monomers copolymerizable with monomer (B-1). It is done.

The part (B) is 4% by mass to 40% by mass with respect to the total mass of the part (A) and the part (B), which are components forming the polycarboxylic acid copolymer (I), preferably It is 6 mass%-30 mass%, More preferably, it is 6 mass%-16 mass%, and it exists in this range, and it is excellent in cement dispersibility. The ratio of the part (B) to the total mass of the part (A) and the part (B), which are the components forming the polycarboxylic acid copolymer (I), is based on the use ratio of each monomer donated to the polymerization. Can be sought. That is, the monomer (B-1) is preferably 4% by mass to 40% by mass with respect to the total mass of the monomer (A-1) and the monomer (B-1), and 6% by mass to 30%. % By mass is more preferable, and 6% by mass to 16% by mass is more preferable.

According to a second aspect of the present invention, there is provided a method for producing a powdery cement dispersant using a spray drier for an aqueous solution of a polycarboxylic acid copolymer (II) having a polyalkylene oxide chain represented by the general formula (3). When the hot air inlet temperature to be introduced into the drying chamber is adjusted to a powder by a spray dryer adjusted to 60 ° C. to 130 ° C., and the hot air inlet temperature is higher than 130 ° C., the polycarboxylic acid copolymer (II) Degradation occurs, and cement dispersibility is poor. On the other hand, when the temperature is lower than 60 ° C., a dry product with stickiness remains and a good powder product cannot be obtained. The hot air inlet temperature is preferably 80 ° C to 125 ° C, more preferably 90 ° C to 110 ° C. Moreover, 85 degreeC or less is preferable and the exhaust air temperature which hits the exit of a drying chamber has more preferable 85 to 30 degreeC. When the hot air inlet temperature or the exhaust air temperature is within this range, the polycarboxylic acid copolymer (II) is less deteriorated and has excellent cement dispersion performance.

In the spray dryer, only the aqueous solution of polycarboxylic acid copolymer (II) which may contain impurities such as polymerization initiator, chain transfer agent, unreacted monomer, etc. required for polymerization is introduced and dried, powdered It is preferable to form. If the inorganic substance is spray-dried at the same time, disproportionation of the polycarboxylic acid copolymer (II) occurs, and when added to cement, the dispersion performance may not be constant. The content of the polycarboxylic acid copolymer (II), which is a cement dispersion effect component, is reduced, and the dispersion effect is reduced.

In the method for producing a powdery cement dispersant which is the second invention of the present invention, in order to efficiently obtain a powdery material without good stickiness, the inside of the drying chamber is 9.9 × 10 ⁴ Pa or less. and it is effective to maintain the reduced pressure atmosphere, it is preferable that the pressure in the drying chamber is ^{9.9 × 10 4 Pa~6.7 × 10 4} Pa, still more 9.6 × ¹⁰ 4 Pa~8 It is preferably 0.0 × 10 ⁴ Pa. By reducing the pressure, the powdery cement dispersant can be obtained quickly and without stickiness, but if the pressure is reduced too much, the recovery rate of the powdery material will be reduced. By setting the pressure range in the drying chamber to this range, it can be manufactured with high productivity.

The polycarboxylic acid copolymer (II) has a polyalkylene oxide chain represented by the general formula (3), but n, which is the average number of added moles of oxyalkylene groups, is 10 to 200. Yes, preferably 40-160, more preferably 40-120, and most preferably 40-80. When the average added mole number of the oxyalkylene group is shortened, the powdery material becomes more sticky and the handleability is inferior. Further, even if the average added mole number of the oxyalkylene group is larger than this range, the improvement in cement dispersibility is small and it is not economical.

The polycarboxylic acid copolymer (II) may be in any form as long as it is a polycarboxylic acid copolymer having a polyoxyalkylene chain represented by the general formula (3). Preferably, the following general formula (4);

(In the formula, R ⁸ and R ⁹ are the same or different and represent a hydrogen atom or a methyl group. R ¹⁰ is the same or different and represents an alkylene group having 2 to 5 carbon atoms. Q represents a number of 0 to 2) P represents an average addition mole number of the oxyalkylene group, and is a number of 3 to 200. R ¹¹ represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. -1) and the following general formula (5);

(Wherein R ¹² , R ¹³ and Z are the same or different and each represents a hydrogen atom, a methyl group, or — (CH ² ) eCOOQ, and e represents a number of 0 to ^2. — (CH ² ) eCOOQ is -COOY or other ^- (CH 2) ^eCOOQ and good .Y and Q may form a anhydrides are the same or different, a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, an ammonium group, an organic amino And a copolymer containing at least the monomer (E-1) represented by the above group, and more preferably the same copolymer as the polycarboxylic acid copolymer (I). .

Examples of the monomer (D-1) include adducts obtained by adding an alkylene oxide of an unsaturated alcohol or an unsaturated carboxylic acid in a predetermined repeating amount, a halide having an unsaturated group, and a polyhydride. Examples include etherification reaction products with alkylene oxides and esterification products of unsaturated carboxylic acids with polyalkylene oxides. Specific examples include vinyl alcohol, allyl alcohol, hydroxybutyl vinyl ether, methallyl alcohol, 3-methyl-3- Examples include adducts obtained by adding 10 to 200 mol of alkylene oxide to alkenyl alcohols such as buten-1-ol, and esterified products of (meth) acrylic acid and terminal alkyl polyalkylene glycol. These are used in combination of two or more. You may do it.

Examples of the monomer (E-1) include (meth) acrylic acid, maleic acid, itaconic acid and their anhydrides, alkali metal salts, alkaline earth metal salts, ammonium salts, and salt-forming products with organic amines. These may be used in combination of two or more, preferably acrylic acid or methacrylic acid. Further, in the case of a salt-forming product, a monovalent alkali metal salt is preferable, and in the case of a divalent or higher such as an alkaline earth metal, crosslinking with a carboxyl group occurs, and when powdered, cement and water The solubility in the mixture is inferior, and the dispersion performance may not be sufficiently exhibited.

Although the use ratio of the monomer (D-1) and the monomer (E-1) can be arbitrarily set, preferably (D-1) / (E-1) = 95/5 to 60/40. It is a mass ratio. The ratio of the total amount of the monomer (D-1) and the monomer (E-1) in the total monomers used for forming the polycarboxylic acid copolymer (II) is 50 masses. % To 100% by mass is preferable, and 80% to 100% by mass is more preferable.

Both the polycarboxylic acid copolymer (I) and the polycarboxylic acid copolymer (II) can be obtained by the same polymerization method. That is, as the polymerization method, a known method such as aqueous solution polymerization, polymerization in an organic solvent, emulsion polymerization, or bulk polymerization can be used by using a polymerization initiator and, if necessary, a chain transfer agent. As the polymerization initiator, known ones can be used. Persulfates such as ammonium persulfate, sodium persulfate and potassium persulfate; hydrogen peroxide; azobis-2-methylpropionamidine hydrochloride, azoisobutyronitrile Suitable are azo compounds such as benzoyl peroxide, lauroyl peroxide, cumene hydroperoxide and the like. In addition, as a promoter, reducing agents such as sodium bisulfite, sodium sulfite, Mohr's salt, sodium pyrobisulfite, formaldehyde sodium sulfoxylate, ascorbic acid and erythorbic acid; amine compounds such as ethylenediamine, sodium ethylenediaminetetraacetate and glycine It can also be used together. These polymerization initiators and accelerators may be used alone or in combination of two or more.

In the polymerization method, a chain transfer agent can be used as necessary. As such a chain transfer agent, one or more known ones can be used, but as a hydrophobic chain transfer agent, butanethiol, octanethiol, decanethiol, dodecanethiol, hexadecanethiol, octadecanethiol, cyclohexyl mercaptan , Thiophenol, octyl thioglycolate, octyl 2-mercaptopropionate, octyl 3-mercaptopropionate, 2-ethylhexyl mercaptopropionate, 2-mercaptoethyl ester octanoate, 1,8-dimercapto-3,6-di Thiol chain transfer agents such as oxaoctane, decane trithiol, dodecyl mercaptan; Halides such as carbon tetrachloride, carbon tetrabromide, methylene chloride, bromoform, bromotrichloroethane; α-methylstyrene Mer, alpha-terpinene, .gamma.-terpinene, dipentene, and unsaturated hydrocarbon compounds such as terpinolene. These can use 1 type (s) or 2 or more types. In addition, as the hydrophilic chain transfer agent, thiol chain such as mercaptoethanol, thioglycerol, thioglycolic acid, mercaptopropionic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, thiomalic acid, 2-mercaptoethanesulfonic acid, etc. Transfer agents; primary alcohols such as 2-aminopropan-1-ol; secondary alcohols such as isopropanol; phosphorous acid, hypophosphorous acid and salts thereof (sodium hypophosphite, potassium hypophosphite, etc.) Sulfurous acid, bisulfite, dithionite, metabisulfite and its salts (sodium sulfite, sodium bisulfite, sodium dithionite, sodium metabisulfite, potassium sulfite, potassium bisulfite, potassium dithionite, metabisulfite Lower oxides of potassium sulfite and the like and salts thereof These may be used alone or in combination.

As a method for adding the chain transfer agent to the reaction vessel, a continuous charging method such as dropping or divided charging can be applied. Further, the chain transfer agent may be introduced alone into the reaction vessel, or may be mixed in advance with a monomer, a solvent or the like. The polymerization method can be carried out either batchwise or continuously. In addition, a known solvent can be used as necessary during the polymerization, and water; alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol; benzene, toluene, xylene, cyclohexane, n-heptane Aromatic or aliphatic hydrocarbons such as; esters such as ethyl acetate; ketones such as acetone and methyl ethyl ketone, and one or more of these may be used in combination. Among these, from the solubility point of the monomer and the resulting polycarboxylic acid copolymer, one or more solvents selected from the group consisting of water and lower alcohols having 1 to 4 carbon atoms are used. It is preferable to use it.

In the above polymerization method, as a method for adding a monomer, a polymerization initiator or the like to the reaction vessel, all the monomers are charged into the reaction vessel, and copolymerization is performed by adding the polymerization initiator into the reaction vessel. Method: A method in which a part of a monomer is charged into a reaction vessel and polymerization is performed by adding a polymerization initiator and the remaining monomer components into the reaction vessel, a polymerization solvent is charged in the reaction vessel, A method of adding the entire amount of the polymerization initiator is suitable. The polymerization conditions such as the polymerization temperature are appropriately determined depending on the polymerization method used, the solvent, the polymerization initiator, and the chain transfer agent. The polymerization temperature is usually preferably 0 ° C. or higher, and 150 ° C. or lower. Preferably there is. More preferably, it is the range of 40 degreeC-120 degreeC.

The polymer obtained by the above method is used as it is as a main component of the cement admixture, but may be further neutralized with an alkaline substance as necessary. As the alkaline substance, it is preferable to use inorganic salts such as hydroxides, chlorides and carbonates of monovalent metals and divalent metals; ammonia; organic amines.

The weight average molecular weight of the polycarboxylic acid copolymer that is an essential component of the present invention is preferably 3000 to 100,000 in terms of polyethylene glycol equivalent weight average molecular weight (Mw) by gel permeation chromatography (hereinafter referred to as “GPC”). More preferably, it is 5000-50000, More preferably, it is 7000-40000. Within this molecular weight range, there is little stickiness when powdered, and the cement dispersibility is also excellent. If the molecular weight is set higher, the powder is more easily formed, but the cement dispersibility may be inferior.

The solution of the polycarboxylic acid copolymer (I) can be made into a powdery cement dispersant by various drying and pulverizing methods. For example, it can be powdered by a mill after drying and pulverizing with a kneader. Can be used, such as a method of pulverizing with a mill after drying with a drum dryer or a disk dryer, a method of pulverizing with a spray dryer, etc. It is preferable to use a powdery cement dispersant. For both the polycarboxylic acid copolymer (I) solution and the polycarboxylic acid copolymer (II) solution, 0.1% by mass to 5% by mass of an antifoaming agent is added to the polymer in advance. In this case, if the powdered cement dispersant is used for mortar, concrete, etc., the air content is reduced and the strength is improved.

The powdery cement dispersant of the present invention can be used in addition to a cement composition such as cement paste, mortar, concrete and the like, as well as known cement dispersants. It can also be used for ultra high strength concrete. As the cement composition, those usually used including cement, water, fine aggregate, coarse aggregate and the like are suitable. Moreover, what added fine powders, such as a fly ash, blast furnace slag, a silica fume, and a limestone, may be used. As the cement, portland cement such as normal, early strength, super early strength, moderate heat, white, etc .; mixed portland cement such as alumina cement, fly ash cement, blast furnace cement, silica cement and the like are suitable. As the blending amount and unit water amount per 1 m ³ of concrete of the cement, for example, in order to produce highly durable and high strength concrete, the unit water amount is 100 to 185 kg / m ³ , and the water / cement ratio is 10 to 70. % Is preferable. More preferably, the unit water amount is 120 to 175 kg / m ³ and the water / cement ratio is 20 to 65%.

The proportion of the powdery cement dispersant of the present invention added to the cement composition is such that the polycarboxylic acid-based copolymer, which is an essential component of the present invention, is 0.1% relative to the total cement mass of 100% by mass. It is preferable to be at least 01% by mass, and it is preferable to be at most 10% by mass. If it is less than 0.01% by mass, the performance may be insufficient, and if it exceeds 10% by mass, the economical efficiency will be inferior. More preferably, they are 0.05 mass% or more and 8 mass% or less, More preferably, they are 0.1 mass% or more and 5 mass% or less.

Since the cement dispersant having a specific structure defined in the present invention is in a powder form, it is excellent in handling workability and has high cement dispersion performance. Further, the powder production of the cement dispersant can be easily performed by the specific production method defined in the present invention, and a powdery cement dispersant having high cement dispersion performance can be provided.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to these examples. Note that “%” means “mass%” unless otherwise specified.
(Method for measuring weight average molecular weight of polymer)
Column used: TSK guard column SWXL + TSKge1 G4000SWXL + G3000SWXL + G2000SWXL manufactured by Tosoh Corporation
Eluent: An eluent solution prepared by dissolving 115.6 g of sodium acetate trihydrate in a mixed solvent of 10999 g of water and 6001 g of acetonitrile and adjusting the pH to 6.0 with acetic acid is used.
Implanted amount: 100 μL of eluent solution with polymer concentration of 0.5%
Eluent flow rate: 0.8 mL / min
Column temperature: 40 ° C
Standard material: polyethylene glycol, peak top molecular weight (Mp) 272500, 219300, 85000, 46000, 24000, 12600, 4250, 7100, 1470.
Calibration curve order: Tertiary detector: 2414 made by Japan Waters Differential refraction detector analysis software: Empower software made by Japan Waters

(Production Example 1)
A reactor equipped with a thermometer, a stirrer, a dripping device, a nitrogen introduction tube and a cooling tube was charged with 76.9 g of distilled water and 149.3 g of 3-methyl-3-buten-1-ol ethylene oxide 50 mol adduct, The temperature was raised to 60 ° C. Subsequently, a mixed solution of 0.23 g of hydrogen peroxide and 11.7 g of water was added, and 20.2 g of acrylic acid was added dropwise over 3 hours. At the same time, 40.7 g of water, 0.79 g of 3-mercaptopropionic acid, and L- A solution mixed with 0.3 g of ascorbic acid was added dropwise over 3.5 hours. Stirring was continued for 1 hour after the dropwise addition, and 14.0 g of 30% NaOH aqueous solution was added to partially neutralize to obtain a polycarboxylic acid copolymer aqueous solution (I-1) having a weight average molecular weight of 30000. It was.

(Production Example 2)
A reactor equipped with a thermometer, a stirrer, a dripping device, a nitrogen introduction tube and a cooling tube, 136.5 g of distilled water, 200.0 g of 3-methyl-3-buten-1-ol ethylene oxide 50 mol adduct, and malee The acid 20.8g was prepared and it heated up at 65 degreeC. Subsequently, 0.18 g of hydrogen peroxide was added, and a solution prepared by mixing 9.8 g of water and 0.23 g of ascorbic acid was added dropwise over 1 hour. Stirring was further continued for 1 hour after the dropping, and then 22.0 g of 30% NaOH aqueous solution was added to partially neutralize to obtain a polycarboxylic acid copolymer aqueous solution (IFC-1) having a weight average molecular weight of 37000. It was.

(Production Example 3)
Into a reactor equipped with a thermometer, a stirrer, a dropping device, a nitrogen introducing tube and a cooling tube, 149.3 g of distilled water was charged and the temperature was raised to 75 ° C. A solution prepared by mixing 158.3 g of methoxypolyethyleneglycol (EO repetition number 6) methacrylate, 41.8 g of methacrylic acid, 2.3 g of 3-mercaptopropionic acid, and 41.3 g of water was added dropwise over 5 hours, and at the same time 11.1 mass % Aqueous ammonium persulfate solution was added dropwise over 6 hours. Stirring was continued for 1 hour after the dropping, and then 65.0 g of 30% NaOH aqueous solution was added to partially neutralize to obtain a polycarboxylic acid copolymer aqueous solution (C-1) having a weight average molecular weight of 15000. It was.

The aqueous solution of the polycarboxylic acid copolymer shown in each production example was made into a dry powder form with a spray dryer under the conditions shown in Table 1, and the spray drying property and the cement dispersibility were evaluated by the following methods.
<Spray drying>
During spray drying, the degree of powder adhesion in the drying chamber was evaluated as follows.
Almost no adhesion ◎
There is a little adhesion ○
Adhesion size ×
If the degree of adhesion is large, the resulting powdery cement dispersant remains sticky, resulting in poor workability.

<Cement dispersibility>
Cement mortar to which the powdery cement dispersant of the present invention was added was prepared, and fluidity, which is an index of dispersion performance, was evaluated. That is, 0.714 g of powdered cement dispersant, 240 g of water, 595 g of ordinary Portland cement, and 1350 g of ISO standard sand were mixed with a Hobart mixer to prepare a cement mortar. Similarly, the mortar flow value was measured.
Table 1 shows the spray drying conditions and the performance evaluation results.

FIG. 1 is a schematic view showing an example of a spray dryer.

Explanation of symbols

a Polycarboxylic acid copolymer solution inlet b Hot air inlet c Drying chamber d Pressurized air inlet e Vacuum outlet f Cyclone g Product collector

Claims (4)

A powdery cement dispersant comprising a polycarboxylic acid copolymer (I), wherein the polycarboxylic acid copolymer (I) is represented by the following general formula (1);

(In the formula, R ¹ and R ² are the same or different and represent a hydrogen atom or a methyl group. R ³ is the same or different and represents an alkylene group having 2 to 5 carbon atoms. X represents a number of 0 to 2. M represents the average number of added moles of the oxyalkylene group, and is a number from 3 to 200. R ⁴ represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. The following general formula (2);

(Wherein, R ⁵ represents a hydrogen atom or a methyl group, and M represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, an ammonium group, or an organic amino group). At least the mass proportion of the total of the site (A) and the site (B) to the polycarboxylic acid copolymer (I) is 70% by mass to 100% by mass, and the site (A) And the part (B) is 4% by mass to 40% by mass with respect to the total mass of the part (B). The following general formula (3);

(In the formula, R ⁶ is the same or different and represents an alkylene group having 2 to 5 carbon atoms, R ⁷ represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms, and n is an average added mole number of an oxyalkylene group. And is a number of 10 to 200.) Powdered cement dispersant for converting an aqueous solution of a polycarboxylic acid copolymer (II) having a polyalkylene oxide chain represented by the formula A method for producing a powdery cement dispersant, characterized in that the hot air temperature introduced into the drying chamber of the spray dryer is 60 ° C to 130 ° C. The manufacturing method according to claim 2, wherein the inside of the drying chamber of the spray dryer is powdered in a reduced-pressure atmosphere of 9.9 x 10 ⁴ Pa or less. The polycarboxylic acid copolymer (II) having the polyalkylene oxide chain is represented by the following general formula (1);

(In the formula, R ¹ and R ² are the same or different and represent a hydrogen atom or a methyl group. R ³ is the same or different and represents an alkylene group having 2 to 5 carbon atoms. X represents a number of 0 to 2. M represents the average number of added moles of the oxyalkylene group, and is a number from 3 to 200. R ⁴ represents a hydrogen atom or a hydrocarbon group having 1 to 20 carbon atoms. The following general formula (2);

(Wherein, R ⁵ represents a hydrogen atom or a methyl group, and M represents a hydrogen atom, an alkali metal atom, an alkaline earth metal atom, an ammonium group, or an organic amino group). The manufacturing method according to claim 2, comprising at least.

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