JPH0641384B2 - Admixture for cement - Google Patents

Description

TECHNICAL FIELD The present invention relates to a novel admixture for hydraulic cement, and more particularly, a novel water admixture having excellent performance as a dispersant, a water reducing agent, a fluidizing agent, etc. It relates to an admixture for hard cement.

(Prior Art) Generally, concrete using cement, mortar,
When manufacturing a paste or the like, an admixture called a dispersant, a water reducing agent or a fluidizing agent is used. This admixture is expected to have the following main effects. That is, (1) increase the workability of the cement composition that has not yet set. If the workability is the same, the amount of water used will be reduced. (2) Since the amount of water used can be reduced, the strength after construction is increased as a result. If the strength is the same, the amount of cement used will be reduced. (3) Increasing water tightness.

Conventionally, as such an admixture, an oxycarboxylic acid type, an olefin-α, β-unsaturated dicarboxylic acid copolymer type (hereinafter, may be simply referred to as a polycarboxylic acid type)
Are known.

(Problems to be Solved by the Invention) However, in these conventional techniques, it is hard to say that the performance required for the more advanced dispersion fluidity and slump retention is sufficiently satisfied in recent years, and the improvement thereof is strong. Was wanted.

Therefore, as a result of repeated intensive studies to overcome the above drawbacks, the present inventors used a polycarboxylic acid having a specific composition with a small high molecular weight portion as a polycarboxylic acid composition, and using this together with an oxycarboxylic acid-based admixture as a cement. The present inventors have found that a cement composition having good dispersion fluidity, good slump deterioration, and good workability can be obtained, and a cured product having high strength can be obtained, and thus the present invention has been completed.

(Means for Solving Problems) Thus, according to the present invention, (a) an admixture for oxycarboxylic acid cement of 95 to 5% by weight and (b) a number average molecular weight of 3
A copolymer of 60 to 85 mol% of α, β-unsaturated dicarboxylic acid and 40 to 15 mol% of olefin, in which a high molecular weight portion having a molecular weight of 20,000 to 10,000 and a molecular weight of 20,000 or more is controlled to 10 wt% or less, or There is provided an admixture for hydraulic cement, which comprises a mixture of 5 to 95% by weight of its salt as an active ingredient.

The oxycarboxylic acid cement admixture used as the first component in the present invention is a water-soluble oxycarboxylic acid and a water-soluble salt of oxycarboxylic acid, and specific examples thereof include gluconic acid, citric acid, and 2 -Ketogluconic acid, tartaric acid, heptgluconic acid, alkali metal salts such as ammonium salts, amine salts, sodium salts and potassium salts thereof, alkali metal salts and the like are exemplified, and among these, sodium gluconate and gluconate amine salts are preferable. Used in Moreover, what added ethylene oxide to the hydroxyl group and the carboxyl group as needed may be used.

The second component used in the present invention is (a) α, β-unsaturated dicarboxylic acid 60 to 85 mol%, preferably 65 to
It comprises a copolymer of 80 mol% and (b) olefin 40 to 15 mol%, preferably 35 to 20 mol% or a salt thereof, and has a number average molecular weight of 300 to 10,000, preferably 1.00.
In the range of 0 to 8,000, the high molecular weight portion having a molecular weight of 20,000 or more is controlled to 10% by weight or less, preferably 8% by weight or less of the whole.

Here, the number average molecular weight means a polystyrene equivalent value measured by a high performance liquid chromatograph (tetrahydrofuran solvent, measurement temperature 40 ° C.).

Such a copolymer has a large amount of α, β-unsaturated dicarboxylic acid units constituting the copolymer and a small content of a high molecular weight portion as compared with conventionally known polycarboxylic acid-based cement admixtures. By using such a copolymer in combination, excellent performance over the prior art is exhibited in terms of dispersion fluidity and slan retention.

Among them, the sharper the molecular weight distribution, the better the performance tends to be, and the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn) is 2.0 or less, and further 1.
It is preferably 9 or less.

Specific examples of the component (a) that constitutes the copolymer include maleic acid, itaconic acid, citraconic acid, and their anhydrides, with maleic anhydride being industrially advantageous.

On the other hand, specific examples of the component (b) include ethylene, propylene, isobutylene, butene-1, butene-2, pentene-1, pentene-2, 2-methylbutene-1,2-.
Chain olefins such as methylbutene-2, 4-methylpentene-1, hexene-1, etc., cyclobutene, cyclopentene, cyclohexene, cycloheptene, cyclooctene, cyclopentadiene, dicyclopentadiene, 2-ethyl-5-norbornene, 2-cyano -5
Examples thereof include cycloolefins such as norbornene and 2-acetyl-5-norbornene, and among them C
_{4 to 6} chain olefins, C _{4 to} C ₆ cycloolefins, especially C ₅ chain olefins are preferred.

Further, within the range that does not substantially impair the effects of the present invention,
A vinyl monomer such as acrylic acid, vinyl acetate, methyl methacrylate, methyl vinyl ether, acrylonitrile, or ethylene sulfonic acid may be copolymerized, and a part of the carboxyl group and / or acid anhydride group in the copolymer may be copolymerized. It can also be used after being esterified or amidated.

The method for producing the copolymer used in the present invention is not particularly limited, and any method may be used as long as the copolymer having the above properties can be obtained. As a specific example thereof, an excess amount of α, β-unsaturated dicarboxylic acid with respect to an olefin is charged and radically polymerized, and then a high molecular weight portion is extracted and separated using a solvent or a method of removing the high molecular weight portion by ultrafiltration. The method of doing is mentioned.

When the produced copolymer is water-soluble by itself, it can be used as it is, but usually, a part or all of the carboxyl groups and / or acid anhydride groups present in the copolymer are monovalent or It is used by forming a salt with a polyvalent cation to enhance the water-solubilizing ability. Specific examples of such salts include salts of alkali metals or alkaline earth metals such as sodium, potassium, magnesium, calcium, barium, ammonium salts, amine salts such as trimethylamine, triethylamine and triethanolamine, and salts of these salts. Examples thereof include complex salts. Among them, alkali metal salts are most favored from the viewpoints of economy, safety and dispersibility.

The mixing ratio (weight basis) of the first component and the second component is 95.
-5: 5-95, preferably 80-20: 20-80,
It is more preferably 70 to 30:30 to 70, and the amount of the mixture to be mixed at the time of kneading concrete, mortar, cement paste or the like is 0.01 to 2% by weight, preferably 0.05 to 1% by weight with respect to cement. . The admixture of the present invention is used as a dry powder or an aqueous solution, and if desired, it is used in combination with other admixtures to obtain a desired hydraulic cement composition.

The timing of addition to the cement mixture can be appropriately selected depending on the purpose of use. As a specific method thereof, for example, a method of premixing with cement, a method of simultaneously adding at the time of kneading a cement mixture such as concrete, a method of adding water or another admixture after starting stirring,
Examples include a method in which the compound is kneaded in advance and then added at an appropriate interval.

The type of cement to which the admixture for hydraulic cement of the present invention is applicable is not particularly limited, and specific examples thereof include ordinary Portland cement, early strength Portland cement, moderate heat Portland cement, and alumina cement,
Examples include fly ash cement, blast furnace cement, silica cement, slag cement, and various mixed cements.

(Effects of the Invention) Thus, according to the present invention, it is possible to obtain a cement composition having good dispersion fluidity of cement and excellent workability in which slump deterioration is significantly suppressed, and a cured product having high strength can be obtained.

(Example) Hereinafter, the present invention will be described more specifically with reference to Examples.
Parts and% in the examples and reference examples are based on weight unless otherwise specified.

Reference Example 1 98 parts of maleic anhydride under a nitrogen atmosphere in a 1-liter autoclave, 76 parts of a C ₅ olefin mixture shown in Table 1,
A mixture of 4 parts of benzoyl peroxide and 400 parts of benzene was heated and stirred at 70 to 75 ° C. for 8 hours to be reacted. After the completion of the polymerization reaction, the precipitated copolymer was separately collected and dried to obtain a C ₅ olefin-maleic anhydride copolymer.

Then, this copolymer was dissolved in methyl ethyl ketone and subjected to ultrafiltration using a membrane having a separation limit molecular weight of 20,000 to remove a high molecular weight portion.

The composition, the number average molecular weight, the weight average molecular weight, and the content of the high molecular weight portion having a molecular weight of 20,000 or more were measured for the copolymer thus obtained.

Further, 300 parts of water was added to 100 parts of this copolymer, and 600% of 10% sodium hydroxide aqueous solution was added with stirring.
A water solution of the water-soluble salt [I] was obtained by gradually adding and stirring the parts. The results are shown in Table 2.

Table 1 iso-pentane about 16% n-pentane about 15% 2-methylbutene-1 about 42% penten-1 about 27% isoprene 0.1% or less Reference Example 2 98 parts of maleic anhydride and C shown in Table 1. _A water-soluble salt [II] was obtained in the same manner as in Reference Example 1 except that 26 parts of a ₅ olefin mixture was used. The properties are shown in Table 2.

Reference Example 3 98 parts of maleic anhydride and 110 C ₅ olefin mixture shown in Table 1 under nitrogen atmosphere in a 1 l autoclave.
Parts, benzoyl peroxide 4 parts and benzene 40
0 parts of the mixture is heated and stirred at 70 to 75 ° C. for 8 hours,
It was made to react. After the completion of the polymerization reaction, the precipitated copolymer was separately collected and dried to obtain a C ₅ olefin-maleic anhydride copolymer.

Next, this copolymer was subjected to the same operation as in Reference Example 1 without undue ultrafiltration to obtain a water-soluble salt [III]. The results are shown in Table 2.

Example 1 The various water-soluble salts obtained in Reference Examples 1 to 3 and sodium gluconate were used alone or in mixture, and the performance as an admixture for hydraulic cement was evaluated according to the following mortar test conditions. The results are shown in Table 3.

[Mortar test]

A cement mortar with the following composition was prepared and a mortar test was carried out according to JIS-R-5201 (target flow-230 ± 5 mm
The amount of admixture added was adjusted so that The air entrainment amount was measured according to JIS-A-1116. The mortar temperature was 20 ± 2 ° C., and the temperature in water training for measuring the compressive strength was 20 ± 2 ° C.

Mixture Cement: 600 parts Asano ordinary Portland cement Sand: 1200 parts Oigawa-produced river sand Water: 210 parts (total amount including water in the admixture below) Cement admixture: As shown in Table 3 Cement / sand ratio = 1/2 Cement / water ratio = 1 / 0.35 From these results, it can be seen that the product of the present invention is added in a small amount and is excellent in slump retention as compared with the conventional system using a polycarboxylic acid-based admixture together (Experiment No. 9 to 10).

Example 2 The above water-soluble salts and gluconates were used alone or mixed to evaluate the composition for general concrete by the following concrete composition. For comparison, a system using water-soluble salt III was also evaluated in the same manner. The result is the fourth
Shown in the table.

Concrete mixture Cement: 300kg / m ³ Asano ordinary Portland cement Coarse aggregate: 1012kg / m ³ Ome crushed stone (maximum particle size 20mm) Fine aggregate: 815kg / m ³ Oigawa river sand water: 166.0kg / m ³ (with admixture Admixture for hydraulic cement: As shown in Table 4 Water / cement ratio: 55.3% Fine aggregate ratio: 44.6 Target slump: 10 ± 1 cm Target air volume: 4.5 ± 0.5% (Air volume adjustment Vinsol: Mountain) (Sou Kagaku) It can be seen from Table 4 that slump retention and air retention are better when added in small amounts than when used alone.

Further, it is understood that the strength of the combined use system with the gluconic acid triethanolamine salt greatly increases.

Claims (1)

[Claims] 1. An oxycarboxylic acid cement admixture for cement (95 to 5% by weight) and (b) a number average molecular weight of 300 to 1
A copolymer of 60 to 85 mol% of α, β-unsaturated dicarboxylic acid and 40 to 15 mol% of olefin in which the high molecular weight portion of 20,000 or more has a controlled high molecular weight portion of 10 wt% or less, or a copolymer thereof An admixture for hydraulic cement, which contains a mixture of 5 to 95% by weight of salt as an active ingredient.