JPH11157896A - Admixture for cement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an admixture for cement excellent in easiness in working and excellent in mechanical strength enhancing effect even when a small amt. is added. SOLUTION: This admixture for cement contains a PVA modified body having an ether bond and a carbonyl group in a side chain and a PVA modified body having at least one structural unit represented by the formula [where X is -NHR<2> , -N(R<2> )2 , -O-, -NH-C(CH3 )2 -CH2 -SO3 <-> , -NH-R<3> -N(CH3 )2 or -NH-R<3> -N (CH3 )3 <+> , R<1> is a 1-4C alkylene bond, R<2> is H or a 1-4C alkyl group and R<3> is a 1-4C alkylene bond].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an admixture for cement, and more particularly, to an admixture for cement having an excellent effect of improving mechanical strength such as bending strength and compressive strength. The present invention relates to a cement admixture containing a modified polyvinyl alcohol having a carbonyl group (hereinafter also referred to as a “modified PVA”).

[0002]

2. Description of the Related Art Conventionally, when producing pastes, mortars, concretes, etc. using cement, latex, polymer emulsion, PVA, A method of adding methylcellulose or the like is widely used.

[0003] In the case of latex, polymer emulsion and the like, in order to improve the mechanical strength of cement, it is necessary to add a large amount thereof, and the effect is insufficient.

[0004] On the other hand, PVA, methylcellulose and the like can be handled in a powder form and thus are excellent in simplicity at the time of operation. However, sufficient mechanical strength cannot be expected.

[0005] Therefore, there has been a long-felt need for a cement admixture which is excellent in simplicity at the time of operation and which has an excellent effect of improving mechanical strength even when added in a small amount.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a cement for cement which is excellent in simplicity at the time of operation and excellent in improving the mechanical strength even when added in a small amount. To provide an admixture.

[0007]

Means for Solving the Problems In view of such a situation, the present inventors have made intensive studies and have found that an admixture for cement containing a modified PVA having an ether bond and a carbonyl group in a side chain has been developed. The present invention was found to be excellent in simplicity at the time of use, and was also excellent in the effect of improving mechanical strength even with a small amount of addition.

That is, the admixture for cement according to the first aspect comprises a modified polyvinyl alcohol having an ether bond and a carbonyl group in a side chain.

The admixture for cement according to claim 2 is the admixture for cement according to claim 1, which contains a modified polyvinyl alcohol having one or more structural units represented by the following general formula (I). It is made.

[0010]

Embedded image (Wherein, X is _{^{-NHR 2, -N (R 2)}} 2, -O -, -
_{NH-C (CH 3) 2} -CH 2 -SO 3 -, -NH-R
^{_{3 -N (CH 3) 2,}} -NH-R 3 -N (CH 3) 3 +
And R ¹ represents an alkylene bond having 1 to 4 carbon atoms;
R ² is H or an alkyl group having 1 to 4 carbon atoms, ^{R 3}
Represents an alkylene bond having 1 to 4 carbon atoms. ).

The cement admixture according to claim 3 is a modified polyvinyl alcohol obtained by subjecting the ethylenically unsaturated monomer to a Michael addition reaction to polyvinyl alcohol in the cement admixture according to claim 1 or 2. Is contained.

A cement admixture according to a fourth aspect of the present invention contains a modified polyvinyl alcohol obtained by subjecting the admixture for a cement according to the third aspect to Michael addition, followed by partial or complete hydrolysis. It is made.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION As a method for producing a modified PVA of the present invention, a monomer having an ether bond and a carbonyl group (for example, methacrylic acid monoester of polyethylene glycol) and a monomer such as vinyl acetate are used. Copolymerize,
A so-called copolymer modification method and a so-called post-modification method in which another agent is reacted with PVA to introduce an ether bond and a carbonyl group into a side chain are conceivable.

Examples of the post-modification method include a method of reacting PVA with monochloroacetic acid or the like to carry out carboxymethylation, a method of subjecting an ethylenically unsaturated monomer to a PVA Michael addition reaction, or a method of graft polymerization. Here, the denaturation by the Michael addition reaction will be described in detail.

Although the degree of saponification of PVA is not particularly limited,
When a strong alkali is used as the catalyst, it is preferably at least 80 mol%, more preferably at least 95 mol%. This is to prevent the alkali of the catalyst from being consumed by saponification and to suppress the amount of by-products (acetate) generated by saponification.

The degree of polymerization of PVA is 100 to 10,000.
00 is preferable, and 300 to 5,000 is more preferable. If it is less than 100, a sufficient mechanical strength effect may not be obtained, and it may be difficult to obtain a final product as a powder. If the amount exceeds 10,000, the flowability may decrease as the amount added increases, and PVA having a degree of polymerization exceeding 10,000 is not practical because the production cost increases.

Further, in addition to the above-mentioned PVA, a modified PVA such as an ethylene-vinyl alcohol copolymer, carboxy-modified, sulfone-modified, cation-modified, or silyl-modified may be used as a raw material. In this case, the modification rate of the modified PVA used as a raw material is, for example, 10 mol% or less.

Examples of the ethylenically unsaturated monomer which can provide an alkylene group having 2 carbon atoms to R ¹ in the above formula (I) include acrylonitrile, acrylamide, N-methylolacrylamide, N, N-dimethyl. Nonionics such as acrylamide N-methylacrylamide, N-isopropylacrylamide, acrylic acid or a salt thereof, acrylate, 2-acrylamido-2-methylpropanesulfonic acid (hereinafter referred to as “AMPS”) or a salt thereof, and anionic ethylenic compounds In addition to the saturated monomers, cationic ethylenically unsaturated monomers such as N, N-dimethylaminoethyl acrylate or a quaternary salt thereof, and N, N-dimethylaminopropylacrylamide or a quaternary salt thereof are exemplified. Moreover, these can also be used in combination of 2 or more types.

Examples of the monomer which can provide an alkylene group having 3 carbon atoms to R ¹ in the formula (I) used in the present invention include 4-chlorobutyric acid and the like. Examples of the obtained monomer include 5-chlorovaleric acid.

The amount of the above-mentioned monomer such as an ethylenically unsaturated monomer is preferably 1 to 150 mol% with respect to PVA (even when the modified PVA is contained), more preferably 5 to 100 mol%. Mol%.

When the number of carbon atoms in R ¹ in the above formula (I) exceeds 4, there is a problem that the cost is extremely high.

It is preferable to use a basic catalyst such as caustic soda, caustic potash, sodium methoxide, triethylamine and the like in order to smoothly carry out the Michael addition reaction. The amount of the basic catalyst to be added is preferably 0.5 to 100 mol% based on PVA, more preferably 2 to 100 mol%.
50 mol%.

In the presence of an appropriate basic catalyst, an ethylenically unsaturated monomer is added and the mixture is added at 5-95 ° C. for 30 minutes.
By subjecting Michael addition reaction for 20 hours, the desired P
A VA variant can be obtained. In addition, for example, when acrylonitrile or acrylamide is used as the ethylenically unsaturated monomer, the modified polyvinyl alcohol having a carboxyl group in the side chain is further partially or completely hydrolyzed after Michael addition. Obtainable. The hydrolysis is generally carried out at 50 to 95 ° C. in the presence of a basic compound such as caustic soda. As the basic compound, a basic catalyst remaining in the reaction system after Michael addition is used. And caustic soda may be additionally added.

The modification rate of the thus obtained modified PVA of the present invention is preferably from 0.5 to 40 mol%, more preferably from 1.0 to 40 mol%. If the modification ratio is less than 0.5 mol%, sufficient improvement in mechanical strength cannot be obtained. In addition, even if it is modified at more than 40 mol%, an effect corresponding to the modification is often not obtained, and the production cost is high, which is disadvantageous. In that sense, 30 mol% or less is more preferable.

In the present invention, the amount of the modified PVA is preferably 0.01 to 30% by weight based on cement, and is preferably 0.1 to 30% by weight.
More preferably, the content is from 0.05 to 10% by weight. If it is less than 0.01% by weight, the effect of the present invention cannot be sufficiently obtained. 30% by weight
If added in excess of this, not only the effect corresponding to the addition is not obtained, but also other physical properties such as fluidity of the cement may be affected.

The method for adding the modified PVA of the present invention is not particularly limited, and may be either a powder or an aqueous solution. Since the modified PVA of the present invention has a higher dissolution rate in cement paste than unmodified PVA, this feature works advantageously when added and used in powder form. The improvement of the dissolution rate is particularly remarkable when an anionic group such as a carboxyl group or a sulfone group is introduced.

Although the modified PVA of the present invention exhibits high effects even when used alone, PVA, copolymerized modified PVA, latex, polymer emulsion, methylcellulose, etc. are used as long as the physical properties are not affected. There is no problem even if other admixtures such as cellulose derivative of the above are used in combination. In addition, an AE agent, a water reducing agent, a fluidizing agent, an antifoaming agent, a foaming agent, a setting / hardening modifier, and the like can be added according to the intended use.

The cement of the present invention includes hydraulic cements such as portland cement, alumina cement, and mixed cement, as well as hydraulic materials such as gypsum that are hardened by water. The hydraulic cement is used as concrete, mortar, and paste for civil engineering and construction.

[0029]

The present invention will be described in more detail with reference to the following examples. In the following description, “parts” or “%” is based on weight unless otherwise specified.

Production Example 1 PVA (degree of polymerization: 50) was placed in a 4-liter horizontal blender.
0, saponification degree 98.8 mol%) 400 parts, 30% -Na
50 parts of an OH aqueous solution and 200 parts of a 50% -acrylamide aqueous solution were added, and the mixture was stirred at 35 ° C for 7 hours. When the reaction product was analyzed by NMR, the amide modification rate was 11.5 mol% and the carboxyl modification rate was 0.8 mol%.

Preparation Example 2 In the same manner as in Preparation Example 1, after stirring at 35 ° C. for 7 hours, 50 parts of a 30% aqueous solution of NaOH was added, and hydrolysis was carried out at 80 ° C. for 1 hour. When the reaction product was analyzed by NMR, the amide modification rate was 5.2 mol% and the carboxyl modification rate was 6.7 mol%.

Production Example 3 In the same manner as in Production Example 1, the mixture was stirred at 35 ° C. for 7 hours, and then 130 parts of a 30% NaOH aqueous solution was added.
For 3 hours. When the reaction product was analyzed by NMR, the amide modification rate was 0.9 mol% and the carboxyl modification rate was 11.2 mol%.

Production Example 4 PVA (polymerization degree: 170) was placed in a 4-liter horizontal blender.
0, saponification degree 98.8 mol%) 400 parts, 30% -Na
70 parts of an OH aqueous solution, 200 parts of acrylonitrile 200 and 200 parts of isopropyl alcohol were added, and the mixture was stirred at 25 ° C. for 5 hours. Then, 287 g of 45% -NaOH was added, and hydrolysis was performed at 70 ° C. for 6 hours. When the reaction product was analyzed by NMR, the carboxyl modification ratio was 36.
It was 2 mol%.

Production Example 5 PVA (degree of polymerization 2,4) was placed in a 4-liter horizontal blender.
00, degree of saponification 95.8 mol%) 440 parts, 50% -N
280 parts of aOH aqueous solution and 50% -AMPS aqueous solution 8
28 parts were added and stirred at 80 ° C. for 7 hours. When the reaction product was analyzed by NMR, the sulfone group modification rate was 13.1.
Mole%.

Production Example 6 PVA (degree of polymerization 4,0) was placed in a 4-liter horizontal blender.
00, degree of saponification 99.8 mol%) 440 parts, 30% -N
70 parts of an aOH aqueous solution and 284 parts of a 50% -acrylamide aqueous solution were added, and the mixture was stirred at 60 ° C for 4 hours. Then 5
125 parts of 0% -NaOH was added, and the mixture was hydrolyzed at 70 ° C. for 1 hour. Next, 460 parts of a 50% -AMPS sodium salt aqueous solution was added, and the mixture was stirred at 80 ° C for 4 hours. When the reaction product was analyzed by NMR, the amide modification rate was 3.2.
Mol%, carboxyl modification rate was 12.4 mol%, and sulfone group modification rate was 6.5 mol%.

Production Example 7 PVA (degree of polymerization: 50) was placed in a 4-liter horizontal blender.
0, saponification degree 98.8 mol%) 400 parts, 30% -Na
70 parts of an OH aqueous solution, 200 parts of a 50% -acrylamide aqueous solution, and 52 parts of an aqueous solution of a 75% -N, N-dimethylaminopropylacrylamide methyl chloride quaternary salt were added, followed by stirring at 50 ° C. for 7 hours. NMR of reaction product
As a result, the amide modification ratio was 6.5 mol%, the carboxyl modification ratio was 4.8 mol%, and the cationic group modification ratio was 1.3 mol%.

Production Example 8 PVA (degree of polymerization: 50) was placed in a 4-liter horizontal blender.
0, saponification degree 98.8 mol%) 400 parts, 35% -Na
390 parts of an aqueous OH solution and 331 parts of a 40% aqueous sodium monochloroacetate solution were added, and the mixture was stirred at 60 ° C for 8 hours. When the reaction product was analyzed by NMR, the rate of carboxyl modification was 4.2 mol%.

[0038]

[Table 1]

Examples 1 to 8 and Comparative Examples 1 to 4 (cement
Physical properties test of tmortar) Using the modified PVA obtained in Production Examples 1 to 8, the following Table 2
To prepare a cement mortar. Various tests were performed using the prepared cement mortar.

These were powders which were easy to handle, and were extremely excellent in simplicity at the time of operation because they were very quickly dispersed and dissolved in cement paste. For comparison, an example in which nothing was added (Comparative Example 1), an example in which PVA having an average degree of polymerization of 500 and a saponification degree of 88 mol% was blended (Comparative Example 2), and an example in which commercially available methylcellulose for a building material was blended (Comparative Example) Example 3) and an example (Comparative Example 4) in which an ethylene-vinyl acetate copolymer emulsion (EVA) having an ethylene content of 15 mol% was blended, the same test was performed.

(Flow value) Measured according to JIS-R5201, and adjusted so that the flow value was 160 ± 20 mm.

(Compression strength and bending strength)
A mortar specimen was molded according to SR-5201 and then cured in water at 20 ° C., and the strength after 28 days was measured.

The results are also shown in Table 2.

[0044]

[Table 2]

[0045]

According to the present invention, the simplicity of operation is excellent,
In addition, even with a small amount of addition, it is possible to provide a cement admixture excellent in the effect of improving mechanical strength.

Claims (4)

[Claims] An admixture for cement comprising a modified polyvinyl alcohol having an ether bond and a carbonyl group in the side chain. 2. The admixture for cement according to claim 1, which comprises a modified polyvinyl alcohol having one or more structural units represented by the following general formula (I). Embedded image (Wherein, X is _{^{-NHR 2, -N (R 2)}} 2, -O -, -
_{NH-C (CH 3) 2} -CH 2 -SO 3 -, -NH-R
^{_{3 -N (CH 3) 2,}} -NH-R 3 -N (CH 3) 3 +
And R ¹ represents an alkylene bond having 1 to 4 carbon atoms;
R ² is H or an alkyl group having 1 to 4 carbon atoms, ^{R 3}
Represents an alkylene bond having 1 to 4 carbon atoms. ) 3. The admixture for cement according to claim 1, which comprises a modified polyvinyl alcohol obtained by subjecting an ethylenically unsaturated monomer to a Michael addition reaction with polyvinyl alcohol. 4. The admixture for cement according to claim 3, comprising a modified polyvinyl alcohol obtained by partial or complete hydrolysis after Michael addition.