JP2000169206A - Powdery cement dispersant and its production and cement mixture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a dispersant suitable for producing highly fluid cement compositions by adjusting a dispersion consisting mainly of an acrylate- or methacrylate-based polymeric compound to a specific pH followed by adding a reducing agent to the dispersion and then evaporating the resultant dispersion to dryness. SOLUTION: This powdery cement dispersant is obtained by the following process: first a mixture is prepared so as to comprise, as the main component, a polymeric compound, i.e., an acrylate- or methacrylate-based one essentially having respective constitutive units of formula I and formula II (R1 to R3 are each H or methyl; R4 is a 1-3C alkyl; M is H, an alkali metal, alkaline earth metal, ammonium or an organic amine; Y is CH2O or COO; n is 20-109), pref. a polymeric compound composed of 40-80 mol% of the unit of formula I and 1-45 mol% of the unit of formula II, and water or a solvent, the mixture is adjusted to pH 7-9 and then incorporated with a reducing agent to deactivate the oxidative power of the radical reaction initiator left in the mixture; subsequently the resultant mixture is evaporated to dryness and then pulverized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a powdery cement dispersant suitable for producing a cement composition having excellent fluidity, a powdery cement dispersant produced by this production method, and a method for producing the same. The present invention relates to a cement mixture, and more particularly, to a cement dispersant which can be preliminarily incorporated into a premix product or the like, and a method for producing the same.

[0002]

2. Description of the Related Art The strength and durability of a composition using a cement such as concrete or mortar generally improve as the water-cement ratio (W / C) decreases. However, when the water-cement ratio is small, the fluidity and workability decrease.
Cement dispersants are used to ensure high fluidity even when the water-cement ratio (W / C) is small. As such a cement dispersant, a dispersant containing a polycarboxylic acid-based polymer compound such as acrylic acid or methacrylic acid as an active ingredient is widely used, and other examples include a naphthalene sulfonate formalin condensate. There are also known cement dispersants containing various kinds of sulfonate-based formalin condensates as active ingredients for dispersion.

[0003]

However, the dispersant containing a polycarboxylic acid-based polymer compound as a main component is generally in a liquid state, and therefore, for example, a premix product frequently used in plastering materials and the like. It is practically impossible to pre-mix it in advance, or it requires a lot of care in terms of transportation, containers and container treatment as compared with a powdered dispersant, and the cost for that is also expensive. Further, since formalin is a harmful substance in the sulfonate-based formalin condensate, handling and use thereof have necessarily been restricted.

[0004] For this reason, attempts have been made to powder a cement dispersant containing a polycarboxylic acid polymer as a main component, but generally, the polycarboxylic acid polymer is dissolved in water or a water-soluble solvent. Is a liquid product produced by a polymerization reaction using each monomer of polycarboxylic acid and a polymerization initiator as raw materials. A powdering technique of a known cement admixture from this liquid material (for example, Japanese Patent Publication No. Hei 7-14829 and Patent No. 2)
No. 669761), when an attempt is made to obtain a powdery dispersant having a high solubility in water, an insoluble gel may be formed during the powder production process, or caking or component deterioration may occur. It tends to lack stability in properties such as action, and the production yield tends to be low. That is, in order to easily perform a drying operation for forming a polycarboxylic acid-based polymer compound such as a methacrylate-based or acrylate-based polymer into a solid powder, the viscosity increases in a reaction system in which a high concentration is generated, and the raw material monomer is increased. The radical reaction initiator that causes the polymerization reaction of the above does not sufficiently diffuse, and the reaction tends to be uneven. In such a case or when the radical reaction initiator is excessively used to enhance the reaction efficiency, the radical reaction initiator is likely to remain, and in that case, the radical reaction initiator is formed in various powdering steps such as concentration, kneading, and drying. In some cases, the desired polymer was re-polymerized to form an insoluble gel, and furthermore, the produced desired polymer was chemically deteriorated by hydrolysis, so that the performance as a cement dispersant was liable to decrease.

[0005]

In order to powder a liquid dispersant containing an acrylate or methacrylate polymer as a main component, the present inventors have set the liquid dispersant to a specific hydrogen ion concentration. This can prevent the hydrolysis of the polycarboxylic acid-based polymer compound in the powdering step, thereby suppressing the deterioration of the polymer compound and the accompanying deterioration in properties, and the residual by adding a reducing agent. A single-grained powder can be easily obtained without deactivating the radical reaction initiator and causing gelation. Further, the present inventors have found that the dispersing action when this powder is blended with cement is not inferior to that of a conventional liquid dispersant, and has completed the present invention.

That is, the present invention provides a method for producing a powdery cement dispersant represented by the following (1) to (3), a powdery cement dispersant represented by (4), and (5) It is a cement mixture represented.

(1) At least one of the following formulas (I) and (II)

[0008]

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Wherein R ¹ , R ² and R ³ are the same or different and each represent a hydrogen atom or a methyl group, and R ⁴ has 1 to 3 carbon atoms.
And M represents a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or an organic amine;
Y represents a -CH ₂ O-or -COO-, n is 20 to 1
09 is shown. A powdery cement dispersant characterized by comprising adding a reducing agent to a mixture containing acrylate or methacrylate polymer having a structural unit represented by formula (1) as a main component, water or a solvent, and then drying the mixture. Manufacturing method. (2) The method for producing a powdery cement dispersant according to the above (1), wherein the pH of the mixture is adjusted to 7 to 9. (3) The method for producing a powdery cement dispersant according to the above (1) or (2), wherein the reducing agent is a readily soluble radical reaction terminator. (4) A powdery cement dispersant produced by the production method according to any one of (1) to (3).
(5) A powdery granule or a powdery cement mixture containing the powdery cement dispersant of the above (4) and cement.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The powdery cement dispersant of the present invention has a methacrylate or acrylate (hereinafter referred to as (meth) acrylate) having at least the structural units of the formulas (I) and (II) in the molecule. )) As a main component. The production of the polymer compound is not particularly limited as long as it is a known technique of copolymerizing a desired monomer in water or a solvent, but the most common production example is water-soluble such as water or a lower alcohol. In an organic solvent, a (meth) acrylate monomer having the formula (I) and a (meth) acrylate monomer having the formula (II) are decomposed as a polymerization initiator at a temperature lower than a copolymerization reaction temperature to generate radicals. An inorganic oxidizing agent represented by persulfates such as potassium persulfate and ammonium persulfate and peroxides such as hydrogen peroxide or 2,2'-azobis (2-amidinopropane) It is obtained by adding an organic oxidizing agent such as dihydrochloride and causing a copolymerization reaction.

The constituent amount of each constituent unit in the (meth) acrylate polymer compound which is the main component of the powdery cement dispersant of the present invention is such that the constituent unit represented by the above formula (I) is 40 to 40%.
It is preferably 80 mol%, more preferably 45 mol%.
The content of the structural unit represented by the formula (II) is preferably from 1 to 45 mol%, more preferably from 3 to 40 mol%. M in the formula (I) includes a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or an alkanolamine such as ethanolamine.
Further, n in the formula (II) represents a number of 20 to 109, and when n is less than 20, chemical stability in the air is deteriorated, and when n exceeds 109, the dispersion capacity is reduced. Are not preferred. The alkyl group represented by R ^4, a methyl group, an ethyl group, n- propyl group, i- propyl group.

In the structural unit (II), there are two types of units, in which Y is —CH ₂ O— or —COO—, but it is also possible for only one or both to be present. When both are present, the average molecular number n of one of the constituent units may be in the range of 20 to 109, and the abundance of Y is-
A is (II) is preferably one comprising from 1 to 30 mol%, Y is -CH ₂ O-(II) is 1 to 30 mol% COO-.

The (meth) acrylate polymer compound of the present invention contains not only the structural units represented by the above formulas (I) and (II) but also the following formula (III) or (IV)
May have one or more structural units represented by

[0014]

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(Wherein, R ⁵ represents a hydrogen atom or a methyl group, R ⁶ represents an alkyl group having 1 to 3 carbon atoms, and X represents —S
Showing a or _{-O-Ph-SO 3 M 2} - O 3 M 2. Here, M represents a hydrogen atom, an alkali metal, an alkaline earth metal, ammonium or an alkanolamine, and Ph represents a phenylene group. )

In the structural units (III) and (IV), examples of the alkyl group having 1 to 3 carbon atoms represented by R ⁶ include a methyl group, an ethyl group, an n-propyl group and an i-propyl group. Can be The constituent amount of the constituent unit represented by the formula (III) is preferably 2 to 25 mol%, more preferably 5 to 25 mol%.
１５15 mol%. In addition, mol% is (I)-(IV)
Are shown as mol% when the total of all the structural units is 100 mol%.

In the formulas (I) to (IV), R ¹
To R ⁶ is particularly preferably a methyl group, and M is sodium, X is -SO ₃ Na are particularly preferred. The (meth) acrylate-based polymer compound as the main component in the dispersant desirably contains all the structural units represented by the formulas (I) to (IV). Further, the number average molecular weight of such a (meth) acrylate polymer compound is preferably from 2000 to 2000.
50,000, more preferably 3500 to 30000.

The powdery cement dispersant of the present invention can be obtained by drying and pulverizing a liquid mixture containing such a (meth) acrylate polymer as a main component. Most of the remainder of the mixture is derived from the solvent used in the synthesis of the main component and by-products of the polymerization reaction.

Next, a method of pulverizing the liquid mixture will be described in detail. Since the liquid mixture is usually an acidic solution, the pH is adjusted to 7 to 9 by adding an aqueous solution of an alkali metal or alkaline earth metal such as sodium hydroxide, potassium hydroxide, or calcium hydroxide. I do. The reason for adjusting the pH is to prevent the polymer compound in the mixture from being easily hydrolyzed during the subsequent heating and drying treatment, and to prevent the deterioration and property deterioration due to the hydrolysis. pH 7
If the pH is less than 1, it is not preferable because a large amount of a reducing agent is required, and if the pH is more than 9, hydrolysis is liable to occur, and the COD value of water released during drying is not preferable. When the liquid mixture has a pH of 7 to 9 from the beginning, it is not necessary to adjust the pH by adding a pH adjuster or the like. Subsequently, a reducing agent is added to the mixture having a pH value of 7-9. The reducing agent may be a known reducing agent that hardly reacts with the polymer compound as a main component, and is preferably selected according to a radical reaction initiator used for polymerizing the polymer compound. In general, when a readily soluble peroxide is used, sulfites, nitrites, and thiosulfates are used as reducing agents. Shall have power. As such a reducing agent, a readily soluble radical reaction terminator that is generally used when terminating a copolymerization reaction is particularly preferable. The amount of the reducing agent to be added may be determined according to the type and the remaining amount of the radical reaction initiator remaining in the mixture, and usually, the amount of the solid content (mol%) of the radical reaction initiator used in the synthesis of the polymer compound is used. Value) or less, it is desirable that the amount is not less than an amount that can deactivate the oxidizing power of the residual radical reaction initiator.

After adding the reducing agent, the mixture is kneaded and stirred. The temperature for kneading and stirring is preferably about 40 to 120 ° C, more preferably about 60 to 100 ° C. The kneading / stirring can be performed in the air, but is preferably performed under reduced pressure or in an atmosphere of an inert gas such as nitrogen or argon from the viewpoint of preventing deterioration. The kneaded and agitated one is dried, but the drying is started by heating substantially during the kneading and agitating. Drying is not particularly limited as long as it is a convection type drying apparatus such as a hot air type or a heat conduction type drying apparatus. However, when the processed product is a 5 to 40% solution, the former drying apparatus, a spray dryer,
Flash jet dryers are suitable. When the processed product is a high-concentration solution exceeding 40% or a material having high viscoelasticity, the latter can be exemplified by a drying machine such as a stirring kneading drying machine type or a band type continuous vacuum drying machine. When the former is used, a large amount of drying can be performed in a relatively short time, and when the latter is used, drying can be performed while kneading and stirring. By performing such a drying operation, a powdery cement dispersant can be obtained. The dried powder may be agglomerated into small agglomerates, but the agglomerates are fragile and can be easily formed into single particles with a slight crushing force.

The powdered cement dispersant may have an average particle size of 5 to 2 by an arbitrary pulverizing / classifying method for convenience in use.
It is desirable to adjust the thickness to 000 μm, more preferably 10 to 500 μm.

The cement to which the powdery cement dispersant of the present invention can be applied is not particularly limited, and may be a mixed cement such as ordinary Portland cement, blast furnace cement, silica cement, fly ash cement, ultra-rapid hardening cement, or low alkali cement. Further, a spraying cement containing a quick-hardening agent, or a concrete composition containing blast furnace slag, fly ash, or the like as an aggregate component may be used. The compounding amount of the dispersant in the cement is 100
A suitable value is 0.01 to 5 parts by weight, based on 100 parts by weight of cement, of which 0.05 to 3 parts by weight of the present dispersant is contained in a powder or a cement mixture in powder form. It is particularly preferred that If the amount of the dispersant is less than 0.01 part by weight, the dispersing effect is poor, and if the amount exceeds 5 parts by weight, the dispersibility is not further improved.

[0023]

The present invention will be described below in more detail with reference to examples. It is produced using (NH ₄ ) ₂ S ₂ O ₈ as a polymerization initiator, and the molecular weight, the structural units (I) to (IV) and the structural ratio (mol%) are shown in Table 1 (A) to (A). (D)
(Meth) acrylate polymer compound as a main component, the solid content concentration is 45%, and the pH is 6.7 (Examples 1 and 5) or 6.1 (Examples 2 to 4, 6 to 9, Comparative Example) One in which 800 g each of the liquid mixture of 1) to 3) is subjected to pH adjustment (Example 1)
9 to 9 and Comparative Example 3), 75.2 g of a 10% by weight aqueous solution of sodium hydroxide was added to this solution, and the mixture was stirred at room temperature for about 3 minutes with a hand mixer, and then a reducing agent was added. The mixture was placed in a kneader-type kneader-stirring machine having a volume of 1 liter and concentrated and dried while kneading at a temperature of 90 ° C. under a reduced pressure of 30 torr.

[0024]

[Table 1]

The type of the main component (polymer compound) of the mixture used (indicated by using (A) to (D) shown in Table 1), the pH value of the liquid mixture, and the pH-adjusted one is adjusted. Table 2 below shows the pH value, and the type of reducing agent and the amount added (% by weight based on the weight of the solid content of the mixture). Table 2 also shows the state of the product obtained by the drying operation.

[0026]

[Table 2]

Next, 0.14 g of the dry powder thus obtained was added to 100 g of ordinary Portland cement (manufactured by Taiheiyo Cement Co., Ltd.) and dry-mixed to obtain a powdery cement mixture having an average particle size of 250 μm. Produced. 30 g of water was added to this cement mixture and kneaded for 3 minutes with a Hobart mixer, and the paste flow value of the kneaded product was measured. Table 2 also shows the dissolved state of the dried powder and the paste flow value (mm) when water was added and kneaded. Also,
As Comparative Example 4, a liquid cement dispersant mainly containing a commercially available naphthalene sulfonate formalin condensate, as a comparative example 5, a liquid cement dispersant mainly containing a commercially available polycarboxylic acid polymer compound, Comparative Example 6 was obtained by adding and kneading 0.88 g in terms of solids weight to 100 g of cement and 30 g of water using a powdery cement dispersant mainly containing a commercially available polycarboxylic acid polymer compound as a main component. The flow value of the paste was also measured. The paste flow value was measured by placing a hard resin cylindrical pipe (with an inner volume of 100 ml) having an inner diameter of 50 mm and a height of 51 mm vertically on a horizontally polished glass plate, and kneading the cement paste to the top of the pipe. Immediately after filling, the pipe was pulled up, and after the spread of the flowing paste stopped, the diameters in any two directions perpendicular to the spread were measured, and the average value was defined as the paste flow value.

[0028]

The method for producing a powdery cement dispersant of the present invention can be carried out by relatively simple steps and techniques, and can sufficiently improve the reduction in quality performance and production yield that has been seen in the past. . The powdery cement dispersant manufactured by this method is
As compared with a liquid cement dispersant, excellent dispersibility can be achieved with a small amount of use. In addition, since the present dispersant can be stored and transported as a powdery mixture in addition to cement or the like in advance, it can be used for so-called premix products.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C04B 103: 40 111: 00 (72) Inventor Koichi Soeda 2-4-2 Daisaku, Sakura City, Chiba Pref. Pacific Cement Inside Sakura Laboratory Co., Ltd. (72) Inventor Kenjiro Makino 2-517 Sakuragaoka, Nobeoka City, Miyazaki Prefecture F-term (reference) 4G012 MC00 PA01 PB31 PC01 4J002 BG011 BG071 BQ001 CH051 DF036 DG046 EE016 FD206 GL00 HA09

Claims (5)

[Claims] 1. A compound having at least the following formulas (I) and (II) in a molecule: (Wherein, R ¹ , R ² and R ³ are the same or different and represent a hydrogen atom or a methyl group, R ⁴ represents an alkyl group having 1 to 3 carbon atoms, M represents a hydrogen atom, an alkali metal, an alkaline earth, metal, shows the ammonium or organic amine, Y is -CH ₂
O- or -COO- is shown, and n shows 20-109. A powdery cement dispersant characterized by comprising adding a reducing agent to a mixture containing acrylate or methacrylate polymer having a structural unit represented by formula (1) as a main component, water or a solvent, and then drying the mixture. Manufacturing method. 2. The method for producing a powdery cement dispersant according to claim 1, wherein the pH of the mixture is adjusted to 7 to 9. 3. The method for producing a powdery cement dispersant according to claim 1, wherein the reducing agent is an easily soluble radical reaction terminator. 4. A powdery cement dispersant produced by the production method according to claim 1. 5. A powdery or powdery cement mixture comprising the powdery cement dispersant of claim 4 and cement.