JP2000327384A - Dispersant for powdery cement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dispersant not causing change in quality in itself, capable of imparting high fluidity and suppressing deterioration with the lapse of time and capable of imparting early strength in the hardening initial stage by drying an aqueous mixture of (A) a water-soluble vinyl copolymer having specific structural units and a specific number average molecular weight with (B) a reducing inorganic compound selected from the group consisting of a sulfurous acid compound and a thiosulfuric acid compound, and then by crushing the dried mixture. SOLUTION: The ingredient A contains structural units of formula I to formula V, wherein R1-R3 are each H or methyl; R4 is a 1-3C alkyl; M1 is H, an alkali (or alkaline earth) metal, ammonium or an organic amine; M2 is M1 is except H; (m) is 40-109 and; (n) is 5-30 in respective contents of 50-75 mol%, 2-20 mol%, 1-18 mol%, 2-15 mol% and 0.5-15 mol% and in the total of 100 mol%. The number average molecular weight of the ingredient A is 3,500-70,000. The mixing weight ratio of the ingredient A to the ingredient B is 100/0.01 to 100/3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a powdery cement dispersant. A powdery cement dispersant is used in the production of a cement-based premix product in which various admixtures are blended with cement, or in the preparation of a mortar or concrete mixture. The present invention relates to an improvement of such a powdery cement dispersant.

[0002]

2. Description of the Related Art Hitherto, a high-condensate salt of naphthalenesulfonic acid formalin and a high condensate of melaminesulfonic acid formalin have been proposed as a powdery cement dispersant as described above (Japanese Patent Application Laid-Open No. 60-221354). However, these powdery cement dispersants have the disadvantage that the fluidity of cement formulations prepared using them is greatly reduced over time. In order to improve such a decrease in fluidity over time, a pulverized mixture of a water-soluble vinyl copolymer and lime or cement has been proposed (Japanese Patent Application Laid-Open No. Sho 62-4).
1743, JP-A-6-239652). However, these powdery cement dispersants have the disadvantage that the water-soluble vinyl copolymer deteriorates during the production process, and when a cement compound is prepared using these powdery cement dispersants, naphthalene sulfone Compared to the case of using a high-condensate salt of acid formalin or a high-condensate salt of melamine sulfonic acid, there is less decrease in fluidity over time, but there is a disadvantage that coagulation delay is increased and early strength is poorly expressed. .

[0003]

The problem to be solved by the present invention is that the conventional powdery cement dispersant has a large decrease in the fluidity of the prepared cement composition with time or is deteriorated by itself. It is easy and the prepared cement compound is inferior in early strength.

[0004]

Means for Solving the Problems Thus, the present inventors have
As a result of research to solve the above problems, a water-based mixture of a water-soluble vinyl copolymer having a specific molecular structure and a specific reducing inorganic compound is dried, and a pulverized powdery cement dispersant is suitably used. I found that.

That is, the present invention relates to the following components A and B
And a powdery cement dispersant obtained by drying and pulverizing an aqueous mixture of the above. Component A: 50 to 75 mol% of the structural unit A represented by the following formula 1 and 2 to 20 mol% of the structural unit B represented by the following formula 2 in all the structural units, represented by the following formula 3 1 to 18 mol% of the structural unit C, a structural unit D represented by the following formula 4
And a structural unit E represented by the following formula 5:
Is a water-soluble vinyl copolymer having a number average molecular weight of 3500 to 70,000 having a ratio of 0.5 to 15 mol% (total 100 mol%) Component B: at least one reducing inorganic compound selected from a sulfite compound and a thiosulfate compound

[0006]

(Equation 1)

(Equation 2)

(Equation 3)

(Equation 4)

(Equation 5)

In the formulas (1) to (5), R ¹ , R ² , R ³ : H or CH ₃ R ⁴ : an alkyl group having 1 to 3 carbon atoms M ¹ : hydrogen, an alkali metal, an alkaline earth metal, ammonium or organic amine X: -SO ₃ M ² or -O-C ₆ H ₄ organic groups represented by -SO ₃ M ² (M ^2; an alkali metal, alkaline earth metal, ammonium or organic amine) m: forty to one hundred and nine integer n: an integer of 5 to 30

The component A to be used in the present invention is a water-soluble vinyl copolymer having a predetermined ratio of each of the structural units A to E represented by the formulas 1 to 5, and the structural unit represented by the formula 4 in the molecule. It is a specific water-soluble vinyl copolymer having a relatively long polyoxyethylene graft chain derived from D and a relatively short polyoxyethylene graft chain derived from the structural unit E represented by Formula 5. The structural units AE constituting the water-soluble vinyl copolymer are formed by copolymerizing the corresponding vinyl monomers.

The vinyl monomer which forms the structural unit A represented by the formula 1 includes: 1) methacrylic acid, acrylic acid, 2) an alkali metal salt, an alkaline earth metal salt or an organic amine salt of methacrylic acid. 3) There are alkali metal salts, alkaline earth metal salts and organic amine salts of acrylic acid. Of these, alkali metal salts of methacrylic acid such as sodium and potassium are preferred.

The vinyl monomer which forms the structural unit B represented by the formula 2 includes: 1) an alkali metal salt, an alkaline earth metal salt or an organic amine salt of methallyl sulfonic acid; There are alkali metal salts, alkaline earth metal salts or organic amine salts of riloxybenzenesulfonic acid. Among them, alkali metal salts of methallylsulfonic acid such as sodium and potassium are preferable.

The vinyl monomer which forms the structural unit C represented by the formula 3 includes methyl acrylate and methyl methacrylate.

The vinyl monomer which forms the structural unit D represented by the formula 4 includes alkoxypolyethoxyethyl (meth) having 1 to 3 carbon atoms and having 40 to 109 repeating oxyethylene units. There are acrylates.
This includes, for example, methoxypolyethoxyethyl (meth)
Acrylate, ethoxypolyethoxyethyl (meth) acrylate, n-propoxypolyethoxyethyl (meth) acrylate, isopropoxypolyethoxyethyl (meth) acrylate and the like are mentioned, and among them, the number of repeating oxyethylene units is 55 to 100. Certain methoxypolyethoxyethyl methacrylates are preferred.

The vinyl monomer which forms the structural unit E represented by the formula 5 includes methoxypolyethoxyethyl methacrylate in which the number of repeating oxyethylene units is 5 to 30. Among them, methoxypolyethoxyethyl methacrylate having a repeating number of oxyethylene units of 7 to 25 is preferable.

The water-soluble vinyl copolymer used in the present invention is:
It is obtained by radical copolymerization of the above-mentioned vinyl copolymer which forms the structural units A to E in the presence of a radical initiator so as to have a predetermined copolymerization ratio. Such radical copolymerization is usually carried out by aqueous solution polymerization using water as a solvent. More specifically, first, each vinyl monomer is dissolved in water, and the total amount of each vinyl monomer is 1%.
An aqueous solution containing 0 to 45% by weight is prepared. Next, a radical initiator is added to the aqueous solution under a nitrogen gas atmosphere,
A radical copolymerization reaction is performed at 0 to 70 ° C. for 5 to 8 hours to obtain a water-soluble vinyl copolymer. The type of the radical initiator used is not particularly limited as long as it decomposes at the temperature of the copolymerization reaction and generates a radical, but a water-soluble radical initiator is preferably used. Examples of such a water-soluble radical initiator include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate.

The water-soluble vinyl copolymer thus obtained contains 50 to 75 mol%, preferably 55 to 72 mol% of the structural unit A and 2 to 5 mol% of the structural unit B in all the structural units.
20 mol%, preferably 3 to 18 mol%, structural unit C
Is 1 to 18 mol%, preferably 3 to 15 mol%, the structural unit D is 2 to 15 mol%, preferably 3 to 12 mol%, and the structural unit E is 0.5 to 15 mol%, preferably 1 to 12 mol%.
Mol% (100 mol% in total). The number average molecular weight is 3500 to 70000 (G
PC method, pullulan conversion, the same applies hereinafter), but preferably in the range of 5000 to 45000.

The reducing inorganic compound of component B used in the present invention includes: 1) a sulfite compound such as an alkali metal sulfite or an alkaline earth metal sulfite; 2) an alkali metal thiosulfate or an alkaline earth metal thiosulfate. Thiosulfate compounds such as
3) Mixtures of the above 1) and 2) are mentioned, among which alkali metal sulfites are preferred, and sodium sulfites are particularly preferred.

The powdery cement dispersant of the present invention comprises a component A
Drying the aqueous mixture of the water-soluble vinyl copolymer as the above and the reducing inorganic compound as the component B,
It is made by grinding.

The aqueous mixture in this case is a mixture of a water-soluble vinyl copolymer as the component A and a reducing inorganic compound as the component B in a system mainly containing water, usually an aqueous solution. means. Therefore, when the water-soluble vinyl copolymer as the component A is obtained as an aqueous solution by the above-described aqueous solution polymerization, it can be used as it is and mixed with the reducing inorganic compound as the component B.

In the present invention, the aqueous mixture ratio of the component A and the component B is not particularly limited, but the component A / component B = 10
It is preferable to carry out aqueous mixing so as to have a ratio of 0 / 0.01 to 100/3 (weight ratio), and component A / component B = 100 /
It is more preferable to carry out aqueous mixing so as to have a ratio of 0.5 to 100 / 2.5 (weight ratio).

The aqueous mixture of component A and component B is dried,
The means for pulverizing include: 1) when both are aqueous-mixed and then dried, and then pulverized; 2) when both are aqueous-mixed and dried; when pulverized; 3) when both are aqueous-mixed and then dried. 4) In some cases, both aqueous mixing, drying and grinding are performed in parallel. More specifically, for example, when the solid content concentration of the mixture of the aqueous solution of the water-soluble vinyl copolymer as the component A and the reducing inorganic compound as the component B is 5 to 40% by weight, A reducing inorganic compound is added to the aqueous solution of the copolymer,
And then dried using a spray drier or a flash jet drier, etc., and pulverized to obtain a powdery cement dispersant. Further, for example, when the solid content concentration of the mixture of the aqueous solution of the water-soluble vinyl copolymer as the component A and the reducing inorganic compound as the component B exceeds 40% by weight, the water-soluble vinyl copolymer may be used. A reducing cement compound is added to the aqueous solution of the above, and the mixture is dried while being mixed at a temperature of 60 to 120 ° C. using a stirring and kneading dryer or a band-type continuous vacuum dryer, and then pulverized to obtain a powdery cement dispersant.

The powdery cement dispersant thus obtained can be used as it is in the production of a cement premix product or in the preparation of a cement composition, but it is used to produce a cement premix product or the like. From the viewpoint of convenience at the time and convenience at the time of preparing a cement composition using the same, it is preferable to further classify the mixture to make the particle size uniform. In this case, classification may be performed while pulverizing, or may be performed after pulverizing. Component A
In the case where the aqueous mixture of component A and component B is dried and pulverized or further classified, the resulting powdery cement dispersant has a particle size of not more than 3000 μm and an average The diameter is preferably 5 to 2000 μm, more preferably 700 μm or less and the average particle diameter is 5 to 500 μm.

The cement to which the powdery cement dispersant of the present invention is applied includes various portland cements such as ordinary cement, early-strength cement and moderately heated portland cement, as well as blast furnace cement, fly ash cement, silica fume cement and the like. Various mixed cements are included. In addition to the powdery cement dispersant of the present invention, fine powder admixture materials such as silica fume, blast furnace slag fine powder, and fly ash, a hardening accelerator, a hardening retardant, and the like can be appropriately used as appropriate.

The powdery cement dispersant of the present invention is usually mixed in an amount of 0.01 to 5.0 parts by weight with respect to 100 parts by weight of a binder comprising cement or cement and a fine powder admixture. Although it is used, it is preferable to use it by mixing so as to have a ratio of 0.05 to 3.0 parts by weight.

The powdery cement dispersant of the present invention comprises a specific water-soluble vinyl copolymer having a relatively long polyoxyethylene graft chain and a relatively short polyoxyethylene graft chain in a predetermined ratio in a molecule; It is characterized in that an aqueous mixture with a reducing inorganic compound selected from a sulfite compound and a thiosulfate compound is dried and pulverized.
The powdery cement dispersant of the present invention having such features,
There is no deterioration, and it gives high flowability to the cement composition prepared using the same, and at the same time, suppresses the deterioration over time, and develops sufficient early strength at the initial stage of hardening.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention include the following 1) to 5). 1) 62 mol% of the constituent units formed from sodium methacrylate, 12 mol% of the constituent units formed from sodium methallylsulfonate, and 12 mol% of the constituent units formed from methyl acrylate in all the constituent units. Methoxypolyethoxy (repeating number of oxyethylene units: 6
8, hereinafter referred to simply as 68) by 8 mol% of a structural unit formed from methacrylate and methoxypolyethoxy (9)
Number average molecular weight of 1480 having 6 mol% (total 100 mol%) of structural units formed from methacrylate
A water-based mixture of 100 parts by weight of a water-soluble vinyl copolymer of No. 0 and 0.5 parts by weight of sodium sulfite is dried, pulverized, and classified to form a powder having a particle size of 700 μm or less and an average particle size of 450 μm. Cement dispersant.

2) 57 mol% of the structural unit formed from sodium methacrylate, 15 mol% of the structural unit formed from sodium methallylsulfonate, and the structural unit formed from methyl acrylate in all the structural units. 14
Number average having 10% by mole of the structural unit formed from methoxypolyethoxy (68) methacrylate and 4% by mole (total 100% by mole) of the structural unit formed from methoxypolyethoxy (23) methacrylate. An aqueous mixture of 100 parts by weight of a water-soluble vinyl copolymer having a molecular weight of 11,000 and 0.6 parts by weight of sodium sulfite is dried, pulverized and classified, and has a particle size of 700 μm or less and an average particle size of 220 μm. Cement dispersant.

3) Among all the structural units, 72 mol% of the structural unit formed from sodium methacrylate, 8 mol% of the structural unit formed from sodium methallylsulfonate, and the structural unit formed from methyl acrylate. 5 mol%, 4 mol% of a structural unit formed from methoxy polyethoxy (95) methacrylate and 1 mol of a structural unit formed from methoxy polyethoxy (9) methacrylate.
A water-based mixture of 100 parts by weight of a water-soluble vinyl copolymer having a number average molecular weight of 18500 at a ratio of 1 mol% (total 100 mol%) and 1.0 part by weight of sodium sulfite is dried, pulverized, and classified. A powdery cement dispersant having a particle size of 700 μm or less and an average particle size of 320 μm.

4) Among all the constituent units, 65 mol% of the constituent unit formed from sodium methacrylate, 5 mol% of the constituent unit formed from sodium methallylsulfonate, and the constituent unit formed from methyl acrylate. 10
Number average having 12 mol% of constituent units formed from methoxypolyethoxy (45) methacrylate and 8 mol% of constituent units formed from methoxypolyethoxy (23) methacrylate (total 100 mol%). A water-based mixture of 100 parts by weight of a water-soluble vinyl copolymer having a molecular weight of 37,000 and 1.0 part by weight of sodium sulfite is dried, pulverized, and classified, and has a particle diameter of 3000 μm or less and an average particle diameter of 950 μm. Cement dispersant.

5) In all the structural units, 58 mol% of the structural unit formed from methacrylic acid, 18 mol% of the structural unit formed from sodium p-methallyloxybenzenesulfonate, and methyl acrylate were used. 8 mol% of the structural unit, 10 mol% of the structural unit formed from methoxypolyethoxy (68) methacrylate, and 6 mol% of the structural unit formed from methoxypolyethoxy (23) methacrylate (100 mol% in total) Water-soluble vinyl copolymer 100 having a number average molecular weight of 8500
A water-based mixture of 1 part by weight and 1.2 parts by weight of sodium thiosulfate is dried, pulverized and classified, and has a particle size of 3000.
A powdery cement dispersant having a particle size of 1 μm or less and an average particle size of 1100 μm.

Hereinafter, examples and the like will be described in order to make the configuration and effects of the present invention more specific, but the present invention is not limited to these examples. In the following examples and the like, parts mean parts by weight and% means% by weight unless otherwise specified.

[0031]

EXAMPLES Test Category 1 (Production of Powdery Cement Dispersant) Example 1 107 parts (1.24 mol) of methacrylic acid, 38 parts (0.24 mol) of sodium methallylsulfonate, 21 parts of methyl acrylate ( 0.24 mol), 495 parts (0.16 mol) of methoxypolyethoxyethyl (68) methacrylate, 60 parts (0.12 mol) of methoxypolyethoxyethyl (9) methacrylate and 800 parts of water were charged into a reaction vessel. 165 parts of a 30% aqueous solution of sodium oxide was added to neutralize and uniformly dissolve, and then the atmosphere was replaced with nitrogen. The temperature of the reaction system was maintained at 60 ° C. in a warm water bath, and 55 parts of a 20% aqueous solution of sodium persulfate was charged to start polymerization, and the polymerization was continued for 6 hours to complete the polymerization. Thereafter, 6 parts of a 30% aqueous sodium hydroxide solution were added to neutralize the acidic decomposition product, and the water-soluble vinyl copolymer (A-1) was added.
Was obtained. When this water-soluble vinyl copolymer (A-1) was analyzed by NMR measurement, elemental analysis, titration analysis, gel permeation chromatography (GPC) measurement, etc., it was found that sodium methacrylate was formed in all constituent units. Structural unit formed from sodium methallyl sulfonate / Structural unit formed from methyl acrylate / methoxypolyethoxy (68)
Water having a number average molecular weight of 14,800 having a ratio of structural units formed from methacrylate / methoxypolyethoxy (9) structural units formed from methacrylate = 62/12/12/8/6 (mol%, total 100 mol%) It was a functional vinyl copolymer. An aqueous solution 60 containing 42% of the water-soluble vinyl copolymer (A-1) thus obtained.
Then, 1.3 parts of sodium sulfite was added to 0 parts, and the mixture was stirred and mixed with a hand mixer. While crushing, further open sieve 700μm
Classified with a vibrating sieve, powder cement dispersant (P-1)
I got

Examples 2 to 5 and Comparative Examples 1 to 4 In the same manner as in Example 1, the powdery cement dispersants (P-2 to P-5) of Examples 2 to 5 and Comparative Examples 1 to 4 Powdered cement dispersants (R-1 to R-4) were obtained.

Comparative Example 5 A water-soluble vinyl copolymer obtained in the same manner as in Example 1 (A-
An aqueous solution containing 42% of 1) was pulverized while drying in the same manner as in Example 1 and further classified to obtain a powdery cement dispersant (R-5).

Comparative Examples 6 and 7 In the same manner as in Comparative Example 5, a powdery cement dispersant (R-
6, R-7).

Comparative Example 8 A powdery cement dispersant (R-8) was obtained in the same manner as in Example 4 except that quicklime was used in place of the sodium sulfite of Example 4.

Comparative Example 9 A powdery cement dispersant (R-9) was obtained in the same manner as in Example 5, except that the ordinary Portland cement was used in place of the sodium thiosulfate of Example 5. Table 1 summarizes the contents of the powdery cement dispersants (P-1) to (P-5) and (R-1) to (R-9) obtained in each example.

[0037]

[Table 1]

In Table 1, am-1: sodium methacrylate bm-1: sodium methallylsulfonate bm-2: sodium p-methallyloxybenzenesulfonate cm-1: methyl acrylate dm-1: methoxypolyethoxyethyl (68) Methacrylate dm-2: Methoxypolyethoxyethyl (95) Methacrylate dm-3: Methoxypolyethoxyethyl (45) Methacrylate em-1: Methoxypolyethoxyethyl (9) Methacrylate em-2: Methoxypolyethoxyethyl (23 ) Methacrylate B-1: sodium sulfite B-2: sodium thiosulfate C-1: quicklime D-1: ordinary Portland cement

Test Category 2 (Evaluation of powdery cement dispersant) The powdery cement dispersant (P-
The particle diameters and average particle diameters of 1) to (P-5) and (R-1) to (R-9) were determined as follows. In addition, the presence or absence of alteration in these manufacturing processes is determined by examining the powdery cement dispersant 10
The mixture was added to 90 parts of water at room temperature, dissolved, and evaluated by the presence or absence of an insoluble gel in the aqueous solution. The results are summarized in Table 2. Particle size and average particle size The particle size was determined from the opening of the vibrating sieve. The average particle size is
The classified powder is photographed with a scanning electron microscope, and 100 particles are arbitrarily selected from the photographed image, and the major axis of each selected particle (the longest diameter passing through the center of the particle = _DL ). And minor axis (shortest diameter passing through the center of the particle = D _s )
Was measured, and the average value of (D _L + D _S ) / 2 was obtained.

[0040]

[Table 2]

Test Category 3 (Preparation and Evaluation of Cement Paste) 1000 parts of ordinary Portland cement (specific gravity = 3.16, Blaine value of 3300) was charged into a 2 liter Hobart mixer, and the paste flow value was adjusted to a range of 200 ± 10 mm. 0.20 of the powdery cement dispersant described in Table 1
~ 1.05 parts were added and dry mixed. Here, the dry-mixed product is a cement-based premix product. Next, 270 parts of water was added to the dry-mixed cement premix product, and the mixture was kneaded at a temperature of 20 ° C. for 3 minutes to prepare a cement paste. The paste flow value of the prepared cement paste was measured as follows. In addition, the paste flow value after 90 minutes of kneading was measured in the same manner while standing still at a temperature of 20 ° C., and the flow residual ratio was determined as follows. After 18 hours, the compressive strength was measured as follows. The results are summarized in Table 3.

Paste flow value: A vinyl chloride pipe (inner volume 1) having an inner diameter of 50 mm and a height of 51 mm was placed on a glass plate.
00 ml), and after filling the prepared paste, the pipe was pulled up. After the spread of the paste was stopped, the diameter in two perpendicular directions was measured, and the average value was taken as the flow value. -Residual flow rate: (Paste flow value after 90 minutes / Paste flow value immediately after kneading) x 100-Compressive strength: Filling the prepared paste into a steel mold having a diameter of 5 cm and a height of 10 cm to prepare a specimen did. 20 ℃
, And the compressive strength was measured according to JIS-A1108.

[0043]

[Table 3]

In Table 3, addition amount: added portion of powdery cement dispersant to 100 parts of cement R-10: powdered product of high-condensate of formalin naphthalenesulfonic acid *: measurement was not possible because it was not cured

[0045]

As is apparent from the above description, the present invention described above has no deterioration of its own, gives high fluidity to the cement composition, suppresses its deterioration over time, and has a sufficient effect in the early stage of curing. This has the effect of developing early strength.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // C04B 103: 40 (72) Inventor Masahiro Iida 2-5 Minatomachi, Gamagori-shi, Aichi Prefecture Takemoto Yushi Co., Ltd. (72) Inventor Kazuhisa Okada 2-5 Minatomachi, Gamagori-shi, Aichi Prefecture Inside Takemoto Yushi Co., Ltd. (72) Inventor Koichi Soeda 2-4-2 Daisaku, Sakura-shi, Chiba Pref. Person Hiroshi Hayashi 2-4-2 Daisaku, Sakura City, Chiba Prefecture Inside the Sakura Laboratory, Pacific Cement Co., Ltd. (72) Inventor Kazuhisa Tsukada 2-4-2 Daisaku, Sakura City, Chiba Prefecture, Japan Sakura Laboratory, Pacific Cement Co., Ltd. (72) Invention Person Hirotaka Isomura 2-4-2 Daisaku, Sakura City, Chiba Prefecture Pacific Term C Sakura Laboratory F-term (reference) 4G012 MB12

Claims (6)

[Claims] 1. A powdery cement dispersant obtained by drying and pulverizing an aqueous mixture of the following components A and B. Component A: 50 to 75 mol% of the structural unit A represented by the following formula 1 and 2 to 20 mol% of the structural unit B represented by the following formula 2 in all the structural units, represented by the following formula 3 1 to 18 mol% of the structural unit C, a structural unit D represented by the following formula 4
And a structural unit E represented by the following formula 5:
Is a water-soluble vinyl copolymer having a number average molecular weight of 3500 to 70,000 having a ratio of 0.5 to 15 mol% (total 100 mol%) Component B: at least one reducing inorganic compound selected from a sulfite compound and a thiosulfate compound (Equation 1) (Equation 2) (Equation 3) (Equation 4) (Equation 5) に お い て In the formulas 1 to 5, R ¹ , R ² , R ³ : H or CH ₃ R ⁴ : an alkyl group having 1 to 3 carbon atoms M ¹ : hydrogen, an alkali metal, an alkaline earth metal, ammonium or an organic amine X : —SO ₃ M ² or —OC ₆ H ₄
Organic group represented by —SO ₃ M ² (M ² ; alkali metal, alkaline earth metal, ammonium or organic amine) m: an integer of 40 to 109 n: an integer of 5 to 30 2. A powdery cement dispersant obtained by drying, pulverizing and classifying an aqueous mixture of the component A and the component B according to claim 1. 3. Component A has a number average molecular weight of 5,000 to 450.
The powdery cement dispersant according to claim 1 or 2, which is a water-soluble vinyl copolymer. 4. The powdery cement dispersant according to claim 1, wherein component B is an alkali metal sulfite. 5. The aqueous mixture according to claim 1, wherein component A and component B are aqueous-mixed in a ratio of component A / component B = 100 / 0.01 to 100/3 (weight ratio). , 3
Or the powdery cement dispersant according to 4 above. 6. The method according to claim 1, wherein the particle size is 3000 μm or less and the average particle size is 5 to 2000 μm.
Or a powdery cement dispersant according to 5 above.