JPH1087937A - Cement admixture - Google Patents

Abstract

(57) [Summary] [Objective] To provide a cement admixture that provides a cement molded product having excellent mechanical strength such as bending strength, compressive strength, and wear resistance. SOLUTION: A cement admixture comprising a polyvinyl alcohol-based polymer which is dissolved in a saturated calcium hydroxide aqueous solution at 40 ° C. at 60% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a cement admixture. More specifically, the present invention relates to a cement admixture which is excellent in mechanical strength such as flexural strength, compressive strength, and abrasion resistance (surface strength), and particularly provides a cement composition in which flexural strength is dramatically improved.

[0002]

2. Description of the Related Art Conventionally, a method of incorporating a water-soluble polymer such as a polymer emulsion, latex, or methyl cellulose into cement has been widely used for the purpose of improving mechanical properties of cement. However, even with these methods, at present, little improvement effect can be expected on bending strength and surface strength which are essential drawbacks of cement.

[0003]

Under such circumstances, the present invention is excellent in mechanical strength such as bending strength, compressive strength, and abrasion resistance (surface strength), and particularly, the bending strength is remarkable. The purpose of the present invention is to provide a cement admixture which gives a cement composition which is improved.

[0004]

The present inventors have conducted intensive studies to develop a cement admixture having the above-mentioned preferable properties, and as a result, have found that a polyvinyl alcohol-based polymer having a specific solubility (hereinafter referred to as PVA-based polymer). (Abbreviated as polymer) have been found to be suitable for the above purpose. The present invention has been completed based on such findings. That is, an object of the present invention is to provide a cement admixture comprising a PVA-based polymer that is dissolved in a saturated calcium hydroxide aqueous solution at 40 ° C. in an amount of 60% or more.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The cement admixture of the present invention comprises 40
It is necessary that the solubility in a saturated calcium hydroxide aqueous solution at 60 ° C. is 60% or more, and a more preferred range is 80%.
% Or more, and most preferably 90% or more. Solubility 6
If it is less than 0%, the dispersibility in the cement, particularly the dispersibility at the time of the hardening reaction of the cement, becomes poor, and the performance as an admixture cannot be sufficiently exhibited. Although the cause of this is not fully understood, if the solubility is less than 60%, PVA may be present in the cement matrix in the form of particles or PVA once dissolved.
Is presumed that the effect of addition is not exhibited due to uneven distribution due to salting out or the like. The method for obtaining a PVA-based polymer having a solubility in a saturated calcium hydroxide aqueous solution at 40 ° C. of 60% or more is not particularly limited, but a method of copolymerizing with a hydrophilic monomer described later, a degree of saponification and A method of adjusting the degree of polymerization, a method of drying at a low temperature during the production of a PVA-based polymer,
The adjustment can be made by a method of reducing the particle size or a method of adding a filler or a plasticizer to the PVA particles.

The degree of polymerization and the degree of saponification of the PVA polymer are not particularly limited, but the following ranges are preferred. The degree of polymerization is
Usually, it is selected between 100 and 10,000. Polymerization degree is 1
If it is less than 00, the effect as a cement admixture may not be exhibited.If the degree of polymerization exceeds 10,000, the solubility in an aqueous solution of calcium hydroxide, which is a feature of the present invention, is reduced, and the contribution to improving the performance of a cement molded product is reduced. descend. In addition, a PVA-based polymer having a degree of polymerization exceeding 10,000 is not practical from the viewpoint of supply of the PVA-based polymer because its production method is special. Therefore, the preferred range of the degree of polymerization is 200 to 8000, more preferably 400 to 500.
0. The degree of saponification is usually selected from between 60 and 100 mol%. If the saponification degree is less than 60 mol%, it is not preferable because problems such as a decrease in solubility in a saturated calcium hydroxide aqueous solution and an insufficient effect as a cement admixture occur. On the other hand, if the saponification degree is too high, the solubility in a saturated calcium hydroxide aqueous solution decreases, which is not preferable. Therefore, the preferred range of the degree of saponification varies depending on the modified species of PVA and the amount of modification, but 65 to 99 mol%.
Is preferable, and 70 to 98 mol% is most preferable.

The method for producing the PVA polymer in the present invention is not particularly limited. Generally, it is produced by hydrolysis or alcoholysis of polyvinyl ester. Modification by copolymerization or post-reaction of PVA or polyvinyl acetate (PVAc) may be performed within a range not to impair the features of the present invention. The polyvinyl ester includes a homopolymer of a vinyl ester, a copolymer of two or more vinyl esters, and a copolymer of a vinyl ester and another ethylenically unsaturated monomer. Here, vinyl esters include vinyl formate, vinyl acetate, vinyl propionate,
Vinyl versatate, vinyl pivalate and the like can be used, and among them, industrially inexpensive vinyl acetate is generally used. The PVA used in the present invention may be a copolymer with another monomer, or a polymer obtained by modifying the terminal of a polymer with a chain transfer agent may be used. The ethylenically unsaturated monomer copolymerized with the vinyl ester is not particularly limited as long as it can be copolymerized with the vinyl ester.
Olefins, halogen-containing monomers, carboxylic acid-containing monomers and their anhydrides or esters, (meth) acrylates, vinyl ethers, sulfonic acid-group-containing monomers, amide-group-containing monomers, amino-group-containing monomers Monomers, quaternary ammonium base-containing monomers, silyl group-containing monomers, hydroxyl group-containing monomers, acetyl group-containing monomers, and the like. Among these, those which are easy to obtain a PVA polymer having excellent solubility in saturated calcium hydroxide, which is a feature of the present invention, are preferable. Specifically, carboxylic acid-containing monomers and their anhydrides or esters, (meth) acrylates, vinyl ethers, sulfonic acid group-containing monomers, amide group-containing monomers, amino group-containing monomers, Copolymers with quaternary ammonium base-containing monomers and hydroxyl-containing monomers are preferred, especially itaconic acid and its salts, (anhydrous)
In addition to monomers having an anionic group such as maleic acid and its salts, allylsulfonic acid and its salts, acrylamidopropylsulfonic acid and its salts, acrylamide, N, N-dimethylacrylamide, N-vinylacetamide, -It is more preferable to modify with a monomer which promotes the solubility of the PVA-based polymer although it is nonionic, such as vinyl formamide, methyl vinyl ether and ethyl vinyl ether. There is no restriction on the composition of the copolymer,
The copolymerization can be performed within a range that does not impair the features of the present invention.

[0008] The cement admixture of the present invention is mixed with cement and, if necessary, fine aggregate or coarse aggregate (eg, sand, gravel, crushed stone, etc.). You may use together with a powder, a reinforcing fiber, etc. In the present invention, the addition amount of the admixture composed of a PVA-based polymer varies depending on the amount of aggregate and water used, but is preferably 0.01 to 60 parts by weight per 100 parts by weight of cement, and is preferably 0.05 to 60 parts by weight. The range is more preferably from 40 to 40 parts by weight, and most preferably from 0.1 to 20 parts by weight. If the amount is less than 0.01 parts by weight, no effect is observed,
Exceeding 0 parts by weight causes problems such as deterioration of the fluidity of the cement.

As a method of adding the admixture comprising the PVA polymer, a method of adding an aqueous solution can be used.
It is preferable to add the PVA-based polymer in the form of a powder from the viewpoint of workability and the like. In the case of powder, from the viewpoint of dispersibility in cement and the like, the particle size is preferably 8 mesh passes, more preferably 16 mesh passes, and most preferably 60 mesh passes using a JIS standard sieve.

[0010] The admixture comprising the PVA-based polymer of the present invention may generate bubbles in a cement slurry or paste, and the strength may be reduced by entraining the bubbles in the cement system. In such a case, the admixture comprising the PVA-based polymer is preferably used by adding an antifoaming agent to PVA. The amount of the defoamer added varies depending on the performance of the defoamer used, but is preferably 0.001 to 10 parts by weight, more preferably 0.005 to 10 parts by weight, per 100 parts by weight of PVA.
5 parts by weight is more preferable, and 0.01 to 2 parts by weight is most preferable. The defoaming agent for the PVA-based polymer is not particularly limited, and examples thereof include silicon-based, amide-based, polyether-based, ester-based, urethane-based, (poly) alkylene glycol-based, and those having an ionic group introduced therein. They may be used, and one or more antifoaming agents may be used in combination. Examples of these defoamers include the following. Examples of the silicone-based defoaming agent include Nopco-8034 and Nopco-8034 manufactured by Nopco.
L, SN-DF-483, SN-DF-475L, SN
-DF-369, SN-DF-5016, SN-DF-
381, SN-DF-382, SN-DF-305, S
N-DF-414, SN-DF-373, Formaster AP and the like. Particularly, Nopco-3034, Nopco-3034L and SN-DF-483 are preferable. Amide-based antifoaming agents include SN-DF-277, manufactured by Nopco.
SN-DF-5013, NOPCO-141-A, NOPCO-
267-A and the like. As a polyether type,
Nopco SN-DF-470, SN-DF-480,
SN-DF-458, SN-DF-260, SN-DF
-SN-DF-375, SN-DF-247, SN-D
F-224, SN-IX-2263, SN-IX-22
65, Formaster PC, and Formaster P. As special urethanes, there are JORUSIN-LBD, JORUSIN-LX, JORUSIN-P manufactured by Diafine.
B and the like.

The method of forming a cement molded product using a PVA-based polymer in the present invention is not limited. For example, it can be formed by a papermaking method, an extrusion method, a flow-on method, a casting method, or the like.
In particular, the admixture comprising the PVA-based polymer of the present invention exhibits its performance effectively in the extrusion method, the flow-on method, and the casting method. The curing method is not particularly limited. For example, a natural curing method, a steam curing method, an autoclave curing method, or the like can be used. In particular, it demonstrates its performance effectively against natural curing methods.

Various additives may be used together with the admixture of the present invention as long as the effects of the present invention are not impaired.
Examples include flow improvers such as methyl cellulose, starch compounds, polyhydric alcohols, boric acid, borax,
Examples include boron compounds such as calcium borate and borate ester, water repellents such as calcium stearate and paraffin, foam entrainers, lubricants and the like.

[0013]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited by the examples. In the following, "parts" and "%" are "parts by weight" and "% by weight" unless otherwise specified.

The methods for measuring the solubility of the PVA polymer and the properties of the cement are described below. (1) Solubility of PVA-based polymer Saturated calcium hydroxide aqueous solution 500 kept at a constant temperature of 40 ° C
While stirring, 20 g of PVA-based polymer powder is added to the mixture, and stirring is continued for 60 minutes. After 60 minutes, the solution was subjected to suction filtration (filter paper; Advantech 4A), and P in the filtrate was filtered.
The concentration of VA is quantified, and the solubility is calculated by the following equation 1. Solubility (%) = (dissolved PVA) / (prepared PVA) × 100 (Formula 1) (2) Physical properties of cement PVA-based polymer powder for a mixture of 100 parts by weight of ordinary Portland cement and 300 parts by weight of Toyoura standard sand Was added, and if necessary, an antifoaming agent was added. Next, after adding water and kneading so that the flow value becomes 170 mm, molding is performed in accordance with JIS R-5201 “Physical Properties Test of Cement”, and after curing for 4 weeks under standard conditions (20 ° C., 65% RH). And the strength was measured.

Example 1 A particle size having a degree of polymerization of 550 and a degree of saponification of 82.5 mol% was J
2 parts by weight of a PVA-based polymer powder of 32 mesh pass was added to 100 parts by weight of cement using an IS standard sieve. Further, 0.2 parts by weight of Nopco-8034L (San Nopco) as an antifoaming agent was used with respect to 100 parts by weight of the PVA-based polymer, and a molded product was obtained according to the above-described evaluation method and cement physical properties to measure physical properties. Table 1 shows the results.

Example 2 A particle size having a degree of polymerization of 620, a degree of saponification of 78.2 mol%, and a degree of modification of itaconic acid of 1.2 mol% is 32 using a JIS standard sieve.
5 parts by weight of a PVA polymer powder of a mesh pass was added to 100 parts by weight of cement. Further, 0.2 parts by weight of Nopco-8034L (San Nopco) as an antifoaming agent was added to 100 parts by weight of the PVA-based polymer, and a molded product was obtained according to the above-described evaluation method and cement physical properties to measure physical properties. Table 1 shows the results.

Example 3 A particle size having a degree of polymerization of 1800, a degree of saponification of 93.1 mol%, and a degree of maleic acid modification of 2.1 mol% was measured using a JIS standard sieve.
A 2-mesh pass PVA-based polymer powder was added to cement 100
2 parts by weight were added to parts by weight. Further, 0.2 parts by weight of Jorsin-LBD (Diafine) as an antifoaming agent was added to 100 parts by weight of the PVA-based polymer, and a molded product was obtained according to the above-described evaluation method and cement physical properties, and the physical properties were measured. Table 1 shows the results.

Example 4 A 10% aqueous solution of a PVA polymer having a degree of polymerization of 2,000 and a degree of saponification of 92.1 mol% was added in an amount of 20 parts by weight to 100 parts by weight of cement, and molded in accordance with the above-described evaluation method and cement properties. The product was obtained and the physical properties were measured. Table 1 shows the results.

Comparative Example 1 A molded product was obtained and the physical properties were measured in accordance with Example 1 except that no PVA polymer was used. Table 1 shows the results.

Comparative Example 2 2 parts by weight of a PVA polymer powder having a degree of polymerization of 1750 and a saponification degree of 99.7 mol%, based on a JIS standard sieve and having a mesh size of 32 mesh pass, based on 100 parts by weight of cement, used as a foaming agent 0.2 parts by weight of Nopco-8034L (San Nopco) was added to 100 parts by weight of the PVA-based polymer, and a molded product was obtained in accordance with the above-mentioned evaluation method and cement physical properties, and the physical properties were measured. Table 1 shows the results.

[0021]

[Table 1]

(Footnotes to Table 1) 1) Solubility: Solubility of PVA-based polymer in 40 ° C. saturated aqueous calcium hydroxide solution. 2) Nopco-8034L, SN-DF-483: An antifoaming agent manufactured by San Nopco Co., Ltd. Jorsin-LBD: Defoamer manufactured by Diafine Corporation. 3) Composition: Cement, Toyoura standard sand, water and PVA are values based on 100 parts by weight of cement. However, the amount of the defoamer added is
Values based on 100 parts by weight of PVA. 4) Physical properties: Flexural strength and compressive strength are JIS R-5201.
by. 5) In Example 4, a 10% aqueous solution of PVA was added (2 parts by weight based on cement in terms of solid content).

[0023]

As is apparent from the above results, the cement admixture of the present invention can provide a cement molded product having excellent mechanical strength such as flexural strength, compressive strength and abrasion resistance (surface strength). .

Claims (1)

[Claims] 1. A cement admixture comprising a polyvinyl alcohol-based polymer which is soluble in a saturated calcium hydroxide aqueous solution at 40 ° C. at 60% or more.