JPH1171150A - Additive for cement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an additive for cement, capable of extremely improving a compression strength by a small amount addition by using a vinyl alcoholic polymer containing a specific amount of a specified structural unit obtained by an acetalizing reaction or a Michael addition reaction. SOLUTION: This additive for cement comprises a vinyl alcoholic polymer including 0.1-45 mol.% structural unit of formulas I and II [X is COOH, SO3 H, CONR<2> R<3> , N<+> R<4> R<5> R<6> .Y (Y is a halogen) or OH; R<1> to R<6> are each H, an alkyl or phenyl]. The polymerization degree thereof is preferably <=60 mPa.s expressed by the viscosity of an aqueous solution having 4 wt.% polymer concentration. The average saponification degree of the vinyl ester part of the polymer is preferably >=70 mol.%. The addition amount of the additive for the cement is preferably 0.01-10 pts.wt. based on 100 pts.wt. cement, though the amount is different according to the amount of a used aggregate and water, and the ratio of the water to the cement is preferably 0.1-2.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an additive for cement which is mixed with a cement composition, for example, concrete, mortar, cement paste, etc. to improve compressive strength.

[0002]

2. Description of the Related Art Conventionally, a polymer emulsion, a latex,
Alternatively, a method of mixing a water-soluble polymer such as methyl cellulose with cement has been widely used. However, in order to improve the compressive strength by using these admixtures, it is necessary to add an amount of the polymer itself until the strength develops, and it is not economically preferable because a large amount of the polymer cannot be denied.

[0003]

In recent years, a high-flow-high-strength concrete with a good mold filling property has been used in a large amount by using a high-performance AE water reducing agent to reduce the unit water amount. Such high-strength concrete is used,
For example, the lowermost layer of reinforced concrete for a high-rise house receives a very large stress, so that further strength and durability are desired. The present invention has been made in view of the above circumstances, to provide a cement additive that provides a cement composition having a significantly improved compressive strength with a small amount of addition.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to develop an additive for cement having the above-mentioned preferable properties, and as a result, at least one structural unit represented by Chemical Formula 3 is subjected to an acetalization reaction. Introducing more than one kind, or chemical 4
Using at least one of the structural units shown in (1) by a Michael addition reaction, and using a cement additive made of a vinyl alcohol polymer having a total content of those structural units of 0.1 to 45 mol%. It is found that the compressive strength is dramatically improved by adding a small amount,
The present invention has been completed.

[0005]

Embedded image

[0006] However, X is -COOH (or a salt thereof), - SO ₃ H (or a salt thereof), - CONR ² R ^{3,
-N + R 4 R 5 R 6} · Y - (Y: halogen), - represents ^{OH, R 1, R 2,} R 3, R 4, R 5 and R ⁶ represents H, alkyl group or a phenyl group .

[0007]

Embedded image

[0008] However, X is -COOH (or a salt thereof), - SO ₃ H (or a salt thereof), - CONR ² R ^{3,
-N + R 4 R 5 R 6} · Y - (Y: halogen), - represents ^{OH, R 1, R 2,} R 3, R 4, R 5 and R ⁶ represents H, alkyl group or a phenyl group .

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail. The cement additive of the present invention is obtained by acetalizing at least one aldehyde having a structural unit represented by Chemical Formula 3 in the same molecule based on a polyvinyl alcohol (hereinafter abbreviated as PVA) resin. The obtained PVA-based polymer and the PVA-based polymer obtained by subjecting at least one kind of substance having a structural unit represented by Chemical Formula 4 to a Michael addition reaction are also preferably used.

As the PVA resin used as a raw material of the present invention, various resins can be applied. For example, vinyl acetate is polymerized or copolymerized by a known polymerization method such as bulk, solution, suspension, emulsification and the like. Obtained by saponifying the obtained polyvinyl acetate or vinyl acetate copolymer by a known method. This PVA-based resin may be of one type, or two or more different types of PVA-based resins may be blended. Instead of this vinyl acetate or together with vinyl acetate, vinyl formate, vinyl propionate, vinyl valerate, vinyl caprate, vinyl pivalate, vinyl trifluoroacetate, vinyl 2-ethylhexanoate, or vinyl versatate And the like.

[0011] Further, within a range not to impair the gist of the present invention,
The PVA-based resin may contain other monomer units. Examples of such units include olefins such as ethylene, propylene, 1-butene and isobutene;
Unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, (phthalic anhydride), (maleic anhydride) maleic acid, (taricic anhydride) itaconic acid or salts thereof, or mono- or dialkyl esters having 1 to 18 carbon atoms; acrylamide, carbon Acrylamides such as N-alkylacrylamide, N, N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or a salt thereof, acrylamidopropyldimethylamine or an acid salt thereof or a quaternary salt thereof represented by Formulas 1 to 18; methacrylamide, carbon number 1-18 N
Methacrylamides such as -alkylmethacrylamide, N, N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid or a salt thereof, methacrylamidopropyldimethylamine or an acid salt thereof or a quaternary salt thereof; N-vinylpyrrolidone, N N-vinylamides such as vinyl formamide and N-vinylacetamide; vinyl cyanides such as acrylonitrile and methacrylonitrile; vinyl ethers such as alkyl vinyl ethers having 1 to 18 carbon atoms, hydroxyalkyl vinyl ethers and alkoxyalkyl vinyl ethers; Vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, and vinyl bromide; vinyl silanes such as trimethoxyvinyl silane; allyl acetate, allyl chloride, allyl alcohol Le, although dimethylallyl alcohol and the like are not limited thereto. There are no restrictions on the content of these monomer units.
It is sufficient that the obtained polymer is water-soluble or water-dispersible.

The degree of polymerization of the PVA resin used in the present invention is as follows:
60 mP expressed by the viscosity of an aqueous solution having a polymer concentration of 4% by weight
The value of a · s or less is desirable in view of workability of adding a product obtained by subjecting the PVA-based resin to an acetalization reaction or a Michael addition reaction to cement. More preferably,
30 mPa · s or less, most preferably 15 mP
a · s or less. However, these viscosities specified here were measured using a Brookfield type viscometer, using a rotor No. 1 is a value measured under the conditions of 60 rpm and 20 ° C. The average degree of saponification of the vinyl ester portion of the PVA-based resin is not particularly limited.
It is at least 0 mol%, preferably at least 80 mol%, more preferably at least 90 mol%. When the average degree of saponification is less than 70 mol%, the water solubility or water dispersibility is undesirably reduced.

Examples of the aldehydes having the structural unit shown in Chemical Formula 3 in the same molecule used in the acetalization reaction of the present invention include those having a carboxyl group, such as glyoxylic acid, succinic semialdehyde, and 4-carboxybenzaldehyde. And the like. Examples of those having a sulfonic acid group include, but are not limited to, benzaldehyde-2-sodium sulfonic acid. Aldehydes having the structural unit shown in Chemical Formula 3 need only use at least one kind.
The reaction may be carried out using a plurality of aldehydes simultaneously. As a reaction method, a conventional general acetalization reaction method may be used.
The aqueous solution of the resin is mixed and stirred in the presence of an acid with the aqueous solution of the above-mentioned aldehydes to cause an acetalization reaction.
A VA polymer can be obtained. Acids used at this time include hydrochloric acid, sulfuric acid, acetic acid and the like. The aldehyde is preferably used in an amount of about 80 to 300 mol% based on the PVA resin, and the acid is preferably used in an amount of about 50 to 200 mol% based on the aldehyde. In addition, there is a method of reacting while dissolving the PVA-based resin powder in the mixed aqueous solution of the aldehyde and the acid, but the method is not limited thereto.

In order to obtain various forms of the final product, the concentration of the reaction solution in the acetalization reaction may be changed. For example, in the case of a powder form, the reaction solution should be as high as possible to facilitate drying. It is desirable, but not limited, to proceed with the reaction at a concentration.

The total content of the structural units represented by Chemical Formula 3 in the PVA-based polymer synthesized by the acetalization reaction of the present invention is 0.1 to 45 mol%, preferably 0.5 to 35 mol. %, More preferably 2 to 30 mol%
It is necessary to be. When the content is less than 0.1 mol%, no effect of improving the compressive strength is obtained, and when it exceeds 45 mol%, the production cost is too high, which is not preferable. The viscosity of an aqueous solution having a polymer concentration of 4% by weight of the obtained PVA-based polymer is preferably 60 mPa · s or less in view of the workability of adding the present PVA-based polymer to cement. More preferably, it is 30 mPa · s or less, most preferably 15 mPa · s or less. However, these viscosities specified here were measured using a Brookfield type viscometer, using a rotor No. 6 in 1
This is a value measured under the conditions of 0 rpm and 20 ° C.

As the base polymer used in the Michael addition reaction of the present invention, the PVA resin used in the above acetalization reaction may be used. In order to introduce the structural unit shown in Chemical formula 4 using the Michael addition reaction, for example, for the introduction of a carboxyl group, after performing a Michael addition reaction using acrylamide or methacrylamide on a PVA-based resin, and then using an alkali. It is obtained by hydrolysis. In order to introduce a sulfonic acid group, a Michael addition reaction is performed by using 2-acrylamido-2-methylpropanesulfonic acid (or an alkali metal, alkaline earth metal, amine salt thereof) or the like on a PVA-based resin. can get. Acrylamide or methacrylamide is preferably used for the introduction of the amide group, and among them, acrylamide having high reactivity is more preferable. For the introduction of the cationic group, allyltriethylammonium chloride, (meth) acrylamidopropyl-trimethylammonium chloride and the like are used. Further, as the hydroxyl group, 2-hydroxyethyl-methacrylate and 2,3-dihydroxypropyl-methacrylate are used for Michael. Although it can be obtained by performing an addition reaction, the substance used in the Michael addition reaction used in the present invention is not limited to these.

According to the present invention, a PV into which at least one structural unit represented by Chemical Formula 4 is introduced by a Michael addition reaction.
The total content of these structural units in the A-based polymer must be 0.1 to 45 mol%, preferably 0.5 to 35 mol%, and more preferably 2 to 30 mol%. . When the content is less than 0.1 mol%, no effect of improving the compressive strength is obtained, and when it exceeds 45 mol%, the production cost is too high, which is not preferable. The obtained PVA-based polymer had a polymer concentration of 4% by weight.
The viscosity of the aqueous solution of 60 mPa · s or less is desirable in view of the workability of adding the present PVA-based polymer to cement.
More preferably, it is 30 mPa · s or less, most preferably 15 mPa · s or less. However, these viscosities specified here were measured using a Brookfield type viscometer, using a rotor No. 1 is a value measured under the conditions of 60 rpm and 20 ° C.

The PVA-based polymer of the present invention into which the structural unit shown in Chemical Formula 4 is introduced by the Michael addition reaction is further used for the PVA-based polymer into which the structural unit shown in Chemical Formula 3 is introduced by further performing an acetalization reaction. It doesn't matter. Alternatively, a PVA-based polymer synthesized by the reverse method may be used.

The additive for cement of the present invention is used by mixing with cement and, if necessary, fine aggregate or coarse aggregate (eg, sand, gravel, crushed stone, etc.). Further, in addition to cement and aggregate, it may be used together with siliceous powder or reinforcing fiber. Further, in recent years, a water reducing agent, a high performance water reducing agent, and a high performance A which are fluidity improvers of cement kneaded materials which have brought about the necessity of compaction after concrete injection have become unnecessary.
E A water reducing agent or the like may be used in combination.

In the present invention, the amount of the PVA-based additive varies depending on the amount of aggregate and water used.
Preferably, the amount is from 0.05 to 5 parts by weight, most preferably from 0.1 to 3 parts by weight. 0.0
If the amount is less than 1 part by weight, the effect of addition is not recognized. If the amount exceeds 10 parts by weight, problems such as deterioration of the fluidity of the cement occur.

There is no particular limitation on the method of adding the cement additive composed of the PVA-based polymer, and examples thereof include a method of adding an aqueous solution and a method of dry-blending a PVA-based polymer powder with a cement powder in advance. Can be In the case of using a PVA polymer powder, the particle size is preferably 8 mesh pass, more preferably 16 mesh pass, most preferably 60 mesh pass through a JIS standard sieve from the viewpoint of dispersibility and solubility in cement. Those prepared in a mesh path are preferred.

The cement composition to which the cement additive comprising the PVA polymer of the present invention is added may generate a large amount of bubbles during kneading, and the strength is reduced by entraining the bubbles in the molded product. May cause. In such a case,
It is desirable to add and use an antifoaming agent for the PVA-based polymer. The amount of the defoaming agent varies depending on the performance of the defoaming agent 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 the PVA-based polymer.
-5 parts by weight is more preferable, and 0.01-3 parts by weight is most preferable. The defoaming agent for the PVA-based polymer is not particularly limited, and examples thereof include silicone-based, amide-based, polyether-based, ester-based, urethane-based, (poly) alkylene glycol-based, and those in which an ionic group is introduced. It may be used, and one or more antifoaming agents may be used in combination.

The molding method of the cement molded product using the PVA polymer in the present invention is not limited, and it can be molded by, for example, a papermaking method, an extrusion method, a flow-on method, a casting method, or the like.
The curing method is not particularly limited. For example, a natural curing method, an underwater curing method, a steam curing method, an autoclave curing method, or the like can be employed. In particular, it exerts its performance effectively in the natural curing method.

The amount of water to be added to the cement composition in the present invention is determined by the mixing ratio of the cement composition, the strength and durability of the molded product, etc., and the water / cement ratio is 0.1 to 2.0.
It is generally used in the range of, preferably 0.2
It is used in the range of ~ 0.7, but is not limited to these values.

Various additives may be used in combination with the cement additive of the present invention as long as the effect is not impaired. Examples thereof include fluidity improvers such as methylcellulose, starch compounds, polyhydric alcohols, boric acid, borax, calcium borate, boron compounds such as borate esters, water repellents such as calcium stearate, paraffin, foam entrainers, Lubricants and the like.

[0026]

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples. In the following, “parts” and “%” mean “parts by weight” and “% by weight”, respectively, unless otherwise specified.

Example 1 Based on PVA105 (manufactured by Kuraray Co., Ltd .; degree of saponification: 98.5 mol%, viscosity at 20 ° C, 4% aqueous solution: 5.6 mPa · s), acetalization reaction using succinic semialdehyde was performed. Containing 15 mol% of carboxyl group units,
PV having an aqueous solution viscosity of 5.2 mPa · s at 0 ° C. and 4%
An A-based polymer was obtained. <Kneading method> Under 20 ° C and 65% RH conditions, 150 g of a 10% aqueous solution preparation of the PVA polymer obtained above (solid content: 0 g) was added to 3000 g of ordinary Portland cement (manufactured by Tokuyama Corporation). 0.5% / cement), 37.5 g of high-performance AE water reducing agent (Mighty 3000S (20% aqueous solution; manufactured by Kao Corporation) (0.25% in solid content / cement), and 735 g of water (final (So that the water / cement ratio becomes 0.3) with a mortar mixer for 3 minutes. <Measurement of viscosity of cement paste> The viscosity of the cement paste obtained by the above kneading method was measured by BL
Rotational speed 60 using a mold viscometer (manufactured by Tokimec)
rpm, rotor No. 4 at 20 ° C. and used as an index of fluidity. Table 1 shows the results. <Measurement of Air Volume> Using the cement paste obtained by the above-mentioned kneading method, it was calculated from the method of calculating from the unit volume mass and the specific gravity of the constituent material of the cement paste based on JIS A 1174. Table 1 shows the results. <Form filling and curing method> The cement paste obtained by the above kneading method was subjected to 5φ under the conditions of 20 ° C. and 65% RH.
After filling in a mold of × 10 cm and demolding after 48 hours (completely sealed in the mold until demolding), 20 ° C, 6
Cured under 5% RH. <Measurement of compressive strength>
After curing at 20 ° C. and 65% RH, the compressive strength was measured after 7 days and 28 days. The compressive strength was determined from the maximum load when loaded at a head speed of 1 mm / min using a universal testing machine manufactured by Shimadzu Corporation. Table 1 shows the results.

Example 2 Based on PVA105 (manufactured by Kuraray Co., Ltd .; saponification degree: 98.5 mol%, viscosity at 20 ° C., 4% aqueous solution: 5.6 mPa · s), sodium benzaldehyde-2-sulfonate was used. Acetalization reaction, containing 8 mol% of sulfonic acid group units, 20 ° C, 4% aqueous solution viscosity of 5.6 mPa ·
Thus, a PVA-based polymer s was obtained. The same test as in Example 1 was performed using this PVA-based polymer. Table 1 shows the results.

Example 3 A Michael addition reaction was carried out using acrylamide on the basis of PVA105 (manufactured by Kuraray Co., Ltd .; saponification degree: 98.5 mol%, viscosity of an aqueous solution at 20 ° C., 4%, 4%). Subsequently, the resultant was hydrolyzed with sodium hydroxide to contain 12 mol% of carboxyethyl group units.
PVA whose aqueous solution viscosity at 4 ° C and 4% is 5.0 mPa · s
A polymer was obtained. The same test as in Example 1 was performed using this PVA-based polymer. Table 1 shows the results.

Example 4 Example 1 was repeated except that the amount of addition was 1.0% / cement and that of the high-performance AE water reducing agent was 0.5% / cement, using the PVA-based polymer used in Example 3. The same test was performed.
Table 1 shows the results.

Example 5 A Michael addition reaction was carried out using acrylamide based on PVA117 (manufactured by Kuraray Co., Ltd .; saponification degree: 98.5 mol%, viscosity at 20 ° C., 4% aqueous solution: 28.0 mPa · s). Subsequently, by hydrolysis with sodium hydroxide, the carboxyl group unit was contained at 12 mol%,
A PVA-based polymer having a 4% aqueous solution viscosity of 20.8 mPa · s was obtained. The same test as in Example 1 was performed using this PVA-based polymer, except that the addition amount was 1.0% / cement and the high-performance AE water reducing agent was 0.5% / cement.
Table 1 shows the results.

Example 6 Acrylamide was added to Michael based on PVA105 (manufactured by Kuraray Co., Ltd .; saponification degree: 98.5 mol%, viscosity of aqueous solution at 20 ° C, 4%: 5.6 mPa · s), and the mixture was hydrolyzed with sodium hydroxide. After decomposition, 2-acrylamide-2
-By addition of sodium methylpropanesulfonate by Michael addition, a PVA-based polymer containing a total of 10 mol% of carboxyl groups and sulfonic acid group units, and having a viscosity of 4.8 mPa · s in a 4% aqueous solution at 20 ° C is obtained. Was.

Comparative Example 1 The same test as in Example 1 was carried out except that the system did not contain PVA and the amount of the high-performance AE water reducing agent was 0.1% / cement. Table 1 shows the results.

[0034]

[Table 1]

[0035]

Industrial Applicability The additive for cement of the present invention can provide a cement composition whose compressive strength is drastically improved with a small amount of addition.

Claims (3)

[Claims] 1. A cement additive comprising a vinyl alcohol polymer having at least one structural unit represented by Chemical Formula 1 introduced by an acetalization reaction and having a total content of 0.1 to 45 mol%. Embedded image However, X is -COOH (or a salt thereof), - SO ₃ H
(Or a salt thereof), -CONR ² R ³ , -N ⁺ R ⁴ R ⁵ R ⁶
· ^Y - (Y: halogen), - represents OH, R ^1, R ^2,
R ³ , R ⁴ , R ⁵ and R ⁶ represent H, an alkyl group or a phenyl group. 2. An additive for cement comprising a vinyl alcohol polymer having at least one structural unit represented by Chemical formula 2 introduced by a Michael addition reaction and having a total content of 0.1 to 45 mol%. Embedded image However, X is -COOH (or a salt thereof), - SO ₃ H
(Or a salt thereof), -CONR ² R ³ , -N ⁺ R ⁴ R ⁵ R ⁶
· ^Y - (Y: halogen), - represents OH, R ^1, R ^2,
R ³ , R ⁴ , R ⁵ and R ⁶ represent H, an alkyl group or a phenyl group. 3. The viscosity of a 4% aqueous solution at 20 ° C. is 60 mPa ·
An additive for cement comprising the vinyl alcohol-based polymer according to claim 1 or 2, which is not more than s.