JPH0229621B2 - - Google Patents

Description

[Detailed description of the invention]

A Technical Field of the Invention The present invention relates to a cement admixture that is excellent in improving the mechanical strength of cement. B. Prior art and its problems In recent years, when using cement to manufacture concrete, mortar, paste, etc., improvements have been made to improve workability by improving fluidity, improving strength and durability, etc.
Various admixtures are used to improve crack resistance, adhesion, and other physical properties. Various polymer emulsions (latexes) are known as such admixtures. However, in the case of polymer emulsions, it is necessary to add large amounts to improve the mechanical properties of cement, which may delay hardening in some cases, resulting in a decrease in strength or Limited range. On the other hand, powdered admixtures are also known for use in premixed instant mortars, which are easy to work with. For example, re-emulsifying powder emulsions, methylcellulose, powdered water-soluble polymers such as polyvinyl alcohol (hereinafter referred to as PVA), etc., but although these are easy to work with, they are not as effective as the polymer emulsions mentioned above. The effect cannot be expected. Therefore, there is a strong need for a cement admixture that is a powdered admixture that is easy to work with and that has a large effect on improving the strength and physical properties of cement even when used in small amounts. C Structure, purpose, and effects of the present invention Under these circumstances, as a result of various studies, the present invention has been developed based on the following:
By using modified PVA as a cement admixture, which has a hydrocarbon group with a carbon number of 4 or more and a hydrophobic group unit without an ionic hydrophilic group, and an ionic hydrophilic group unit, even though it is a powdered admixture. First, the inventors discovered that a cement with excellent mechanical strengths such as adhesive strength, bending strength, and compressive strength can be obtained by adding a small amount of the compound, and thus completed the present invention. Premixed cement to which ordinary PVA has been added is conventionally used as a powdered admixture.
Water is poured into the cement at the site and used, but at that time saponification progresses due to the strong alkali of the cement, resulting in a decrease in the dispersion stabilizing effect on cement particles. Therefore, it becomes impossible to obtain cement with excellent mechanical strength. On the other hand, the modified PVA of the present invention has good workability in that it is extremely easily dissolved under the same water injection conditions as conventional PVA, and has a high dispersion stabilizing effect on cement particles even in the strongly alkaline environment of cement. does not change. This seems to be the reason why high-performance cement products with excellent mechanical properties can be manufactured. In other words, as mentioned above, the modified PVA of the present invention has an ionic hydrophilic group unit that quickly dissolves in water at room temperature, and a hydrophobic group unit that does not have an ionic hydrophilic group that does not cleave even in a strong alkaline environment. The effects of ionic hydrophilic groups, hydrophobic groups, and OH groups in PVA work synergistically to maintain good dispersibility of cement particles under strong alkali, and as a result, powdered admixtures Despite this, with a small amount of addition,
It is believed that a cement with excellent mechanical strengths such as adhesive strength, bending strength, and compressive strength can be obtained. D More detailed description of the present invention As the hydrophobic group unit having no ionic hydrophilic group in the modified PVA used in the present invention, a so-called large aliphatic hydrocarbon group having 4 or more carbon atoms is effective,
The preferred number of carbon atoms is 6-20, optimally 8-18. Moreover, an alkyl group is suitable as the hydrocarbon. If the number of carbon atoms is 3 or less, the effect that a cement with excellent mechanical strength can be obtained even when a small amount is used is not sufficiently exhibited. It is desirable that the amount of hydrophobic groups introduced is in the range of 0.1 mol% to 15 mol%; if it is less than 0.1 mol%, the amount of hydrophobic groups is too small and the strength improvement effect of cement will not be sufficiently exhibited; If more than 100% of the modified PVA is introduced, the water solubility of the modified PVA decreases and good results cannot be obtained, although it depends on the amount of hydrophilic groups introduced as described below. A more preferable amount of hydrophobic groups is 0.5 mol% ~
It is 10 mol%. Further, the amount of ionic hydrophilic groups introduced into the modified PVA used in the present invention is preferably in the range of 0.2 mol% to 15 mol%. If the amount of hydrophobic groups is small, it will be water soluble even without ionic hydrophilic groups, but it will be difficult to dissolve in water at room temperature. It is essential to introduce If the amount of hydrophobic groups is large, it is necessary to introduce a large amount of ionic hydrophilic groups, but even if they are introduced in excess of 15 mol%, the effect will already be saturated and no further performance improvement can be expected. Therefore, introduction of 15 mol% or more is economically disadvantageous. In the present invention, as a method for producing modified PVA having a hydrocarbon having a carbon number of 4 or more and having a hydrophobic group unit having no ionic hydrophilic group and an ionic hydrophilic group unit, for example, vinyl acetate and a carbon number of 4 or more are used. A method of copolymerizing and saponifying an ethylenically unsaturated monomer having a hydrocarbon group and no ionic hydrophilic group and an ethylenically unsaturated monomer having an ionic hydrophilic group is mentioned. It will be done. Examples of the ethylenically unsaturated monomer having a hydrocarbon group having 4 or more carbon atoms and no ionic hydrophilic group include alkyl vinyl ethers such as butyl vinyl ether, lauryl vinyl ether, and stearyl vinyl ether, heptene-1, Examples include α-olefins such as octene-1 and dodecene-1, and vinyl esters such as lauric acid vinyl ester and stearic acid vinyl ester. A monomer having a branched hydrocarbon group such as VeoVa-10) manufactured by Kagaku Co., Ltd. is preferably used. The ethylenically unsaturated monomer having an ionic hydrophilic group means an ethylenically unsaturated monomer having an anionic or cationic hydrophilic group. Examples of the ethylenically unsaturated monomer having an anionic hydrophilic group include ethylenically unsaturated carboxylic acids or their salts, such as crotonic acid, itaconic acid, monomethyl maleate, methyl acrylate, and maleic anhydride, or their salts. Examples include lower alkyl esters, acid anhydrides, ethylenically unsaturated sulfonic acids such as vinylsulfonic acid, allylsulfonic acid, N-(meth)acrylamidopropanesulfonic acid, and salts thereof. Examples of ethylenically unsaturated monomers having a cationic hydrophilic group include ethylenically unsaturated monomers represented by the following general formulas (), () and (). However, R ¹ , R ² ; hydrogen atom or lower alkyl group. A: A group that connects the nitrogen atom in B and the nitrogen atom of the amide group. B;

[expression] or

[Formula] R ³ , R ⁴ , R ⁵ ; Hydrogen atom or lower alkyl group (which may contain a substituent). X ^- ; anion R ⁶ , R ⁷ , R ⁸ , R ⁹ ; Hydrogen atom or lower alkyl group or phenyl group Y ^- ; Anion Specifically, N-(1,1 dimethyl-3 dimethylaminopropyl) acrylamide, trimethyl-
3-(1-acrylamido-1,1-dimethylpropyl)ammonium chloride, N-(1,1
-dimethyl-3-dimethylaminobutyl)acrylamide, trimethyl-3-(1-acrylamido-3-dimethylaminobutyl)ammonium chloride, N-(1-methyl-1,3-diphenyl-3-diethylaminopropyl)methacrylamide, N-(3-dimethylaminopropyl)acrylamide, trimethyl-3-(1-acrylamidopropyl)ammonium chloride, dimethylacrylamidopropyl-4-trimethylammoniumbutenyl-2-ammonium chloride, 2-(acrylamidomethoxy)ethyltrimethylammonium chloride , N-(3-dimethylaminopropyl)methacrylamide, trimethyl-3-(1-methacryl-aminopropyl)ammonium chloride, 1-vinylimidazole, 1-vinyl-2-methylimidazole,
1-vinyl-ethylimidazole, 1-vinyl-
2-phenylimidazole, 1-vinyl-2,3
-dimethylimidazole, 1-vinyl-2,4,
Examples include 5-trimethylimidazole and quaternized salts of these imidazoles. Other methods for obtaining the modified PVA of the present invention include a method in which both are contained by post-modification, for example, unmodified PVA is acetalized with an aliphatic monoaldehyde such as butyraldehyde or laurylaldehyde, and then sulfuric acid, chloride, etc. Examples include a method of esterification by reacting with sulfonic acid or the like. Alternatively, there may be a method in which a saponified copolymer of vinyl acetate and an ethylenically unsaturated monomer having an ionic hydrophilic group is made to contain a hydrophobic group having no ionic hydrophilic group by post-modification. The degree of saponification of the modified PVA used in the present invention is not particularly limited, and may be within a water-soluble range. The degree of polymerization is usually suitably in the range of 100 to 3000. The amount of the modified PVA of the present invention added is preferably 0.05 to 20% by weight, particularly 0.1 to 10% by weight, based on the cement. If the addition amount is less than 0.05% by weight, the effect of improving the strength and physical properties of cement will be small, and if the addition amount is less than 0.05% by weight, the effect of improving the strength and physical properties of cement will be small.
If added in excess of
Inconveniences arise, such as the need to add a large amount of water to maintain good fluidity. The cement of the present invention also includes hydraulic cements such as boltland cement, alumina cement, various mixed cements, and hydraulic materials that harden with water, such as gypsum. The cement admixture of the present invention is particularly suitable for Bortland cement,
It is highly effective against hydraulic cements such as alumina cement and various mixed cements. These are used as concrete, mortar, and paste for civil engineering and construction, and are also suitably used in the production of concrete products such as piles and blocks, and press-formed sheet products. Further, although the cement admixture of the present invention can be used alone to fully exhibit its effects, there is no problem in using it in combination with a small amount of other known admixtures. Hereinafter, the present invention will be explained by giving examples. In the examples, "parts" and "%" are based on weight.Example 1 and Comparative Examples 1 to 5 Fatty acid vinyl ester (Ciel Chemical, Veo
Va-10) 55 parts, 3600 parts of methyl alcohol, and 58 parts of sodium allylsulfonate as an ethylenically unsaturated sulfonate were used for polymerization in a conventional manner, unreacted vinyl acetate was expelled, and the resulting polymer solution was Saponification was carried out by a conventional method using caustic soda as a catalyst. The obtained modified PVA (A) contained 1.2 mol% of hydrocarbon groups (persic acid ester part), 2.0 mol% of sulfonic acid groups, saponification degree of 97.0 mol%,
The viscosity of the 4% aqueous solution at 20°C was 7 centipoise. (b) Physical property test of cement mortar The following items were tested: bending strength, compressive strength, adhesive strength, water absorption, water permeability, and length change rate.
JISA evaluated PVA(A) as a cement admixture.
- It was carried out according to 6203. In addition, the slump value
Adjusted to 35±5mm. Regarding the amount added, for 100 parts of ordinary Portland cement,
0.5 part of modified PVA (A) in powder form was added and evaluated as an admixture. Details of the results are shown in the Example 1 column of Table 1. For comparison, the average degree of polymerization is 1700, and the degree of saponification is 88.
Mol% of unmodified PVA (Kuraray Poval 217), methyl cellulose for mortar addition, and ethylene-vinyl acetate copolymer aqueous emulsion (EVA emulsion) with an ethylene content of 17% by weight were each added to 100 parts of ordinary Bortland cement. When using an ethylene-vinyl acetate copolymer aqueous emulsion with an ethylene content of 17% by weight, 0.5 parts (solid content) was added to ordinary Bortland cement.
When using a large amount of 10 parts (solid content) per 100 parts, and when no admixture is added,
Evaluation was made under the same conditions as in Example 1. The results are shown in the columns of Comparative Examples 1 to 5 in Table 1. Example 2 Production of modified PVA (B) 770 parts of vinyl acetate, 1370 parts of methyl alcohol,
25.1 parts of lauryl vinyl ether was charged into a polymerization reactor and polymerized by a conventional method, unreacted vinyl acetate was removed, and then saponification was performed using caustic soda as a catalyst. The obtained PVA was reacted with chlorosulfonic acid in a pyridine medium and then neutralized to obtain modified PVA (B). The analysis results show that the modified PVA (B) contains 0.9 mol% of lauryl ether groups and 1.0 mol% of sulfonic acid ester groups.
The saponification degree was 99.1 mol%, and the viscosity of a 4% aqueous solution at 20°C was 10 centipoise. The modified PVA (B) was used in powder form and evaluated as an admixture in the same manner as in Example 1. Table 1 shows the results.
Shown below. Example 3 Production of modified PVA (C) Modified PVA containing 2.0 mol% of persaccharic acid ester moiety and 1.0 mol% of trimethyl-3-(1-methacrylaminopropyl) ammonium chloride moiety was produced in the same manner as in Example 1. I got (C). said denaturation
Similar to Example 1, using PVA(C) in powder form,
It was evaluated as an admixture. The results are shown in Table 1.

[Table] As is clear from Table 1, when the modified polyvinyl alcohol of the present invention having a hydrophobic group having a hydrocarbon having 4 or more carbon atoms in the side chain and an ionic hydrophilic group is used as a cement admixture, , cement with excellent bending strength, compressive strength, and adhesive strength can be obtained by adding extremely small amounts. Moreover, the water absorption rate, water permeability, and length change rate are also extremely small and excellent. On the other hand, in the case of ethylene-vinyl acetate copolymer emulsion, as is clear from Comparative Example 3, no improvement in strength or the like is observed when the amount added is comparable to that of the modified PVA of the present invention. Also, as is clear from Comparative Example 4, in order to improve the strength etc. to some extent, it is necessary to add 100 parts of ordinary Portland cement to
It was necessary to add an extremely large amount of EVA emulsion (10 parts (solid content)), which caused disadvantages such as slow curing time and economic disadvantage.

Claims (1)

[Scope of Claims] 1. A modified polyvinyl alcohol having an ethylenically unsaturated monomer unit having a hydrocarbon group having 4 or more carbon atoms and having no ionic hydrophilic group, and a monomer unit having an ionic hydrophilic group. Cement admixture consisting of. 2 The ethylenically unsaturated monomer having a hydrocarbon group having 4 or more carbon atoms and having no ionic hydrophilic group is a fatty acid vinyl ester, an alkyl vinyl ether,
N-alkyl (meth)acrylamide and α-
The cement admixture according to claim 1, which is at least one monomer selected from olefins. 3. The cement admixture according to claim 1, wherein the ionic hydrophilic group is an anionic hydrophilic group. 4. The cement admixture according to claim 3, wherein the anionic hydrophilic group is an anionic hydrophilic group generated by a polymerized unit of an ethylenically unsaturated monomer having an anionic hydrophilic group. 5 The ethylenically unsaturated monomer having an anionic hydrophilic group is an ethylenically unsaturated carboxylic acid, a salt thereof, a lower alkyl ester thereof, an acid anhydride thereof,
The cement admixture according to claim 4, which is at least one monomer selected from ethylenically unsaturated sulfonic acids and salts thereof. 6. The cement admixture according to claim 1, wherein the ionic hydrophilic group is a cationic hydrophilic group. 7. The cement admixture according to claim 6, wherein the cationic hydrophilic group is a cationic hydrophilic group generated by a polymerized unit of an ethylenically unsaturated monomer having a cationic hydrophilic group. 8 The ethylenically unsaturated monomer having a cationic hydrophilic group has the following general formulas (), () and ()
The cement admixture according to claim 7, which is at least one of the monomers represented by: R ¹ , R ² ; Hydrogen atom or lower alkyl group A; Group B connecting the N atom in B and the N atom of the amide group; [Formula] or [Formula] R ³ , R ⁴ , R ⁵ ; Hydrogen atom or Lower alkyl group (may contain substituents) X ^- ; anion R ⁶ , R ⁷ , R ⁸ , R ⁹ ; Hydrogen atom, lower alkyl group or phenyl group Y ^- ; Anion