JP2869662B2 - Cement admixture - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a cement admixture having excellent performance as a dispersant, a water reducing agent, a superplasticizer and the like.

2. Description of the Related Art In recent years, cement compounds such as cement paste, mortar, and concrete have been used in large quantities in the fields of civil engineering, construction, concrete secondary products, and the like. These cement compounds are blended with admixtures called dispersants, water reducing agents, fluidizers and the like for the purpose of improving slump, workability and the like.

Conventionally, as such an admixture, those mainly composed of lignin sulfonate, those mainly composed of β-naphthalenesulfonic acid formalin condensate and the like are known, but all have advantages and disadvantages, and dispersion of cement. There was no admixture that exhibited good performance in all aspects of fluidity, slump retention, and curing properties.

JP-A-60-171256 discloses the copolymerization of an N-substituted-α, β-unsaturated monocarboxylic acid amide N-substituted with a sulfonic acid group-containing residue and an α, β-unsaturated monocarboxylic acid. It is described that the combined salt is used as an admixture for cement. Japanese Patent Publication No. 1-55210 discloses that a homopolymer of 2-acrylamido-2-methylpropanesulfonate or a copolymer of this monomer and acrylamide and / or acrylate is mixed with a hydraulic cement admixture. It has been proposed to use as

However, all of these admixtures, although improving the slump loss, required a large amount of addition to obtain the desired fluidity (slump). In addition, since α, β-unsaturated monocarboxylic acid such as acrylic acid is contained as a copolymer component, coagulation delay occurs, and workability is poor.

Problems to be Solved by the Invention The present invention is to provide a cement admixture which has excellent fluidity, prevents a decrease in the fluidity, and does not cause setting delay.

The cement admixture of the present invention comprises: (a) an N-substituted-α, β-unsaturated monocarboxylic amide derivative represented by the general formula (I); and (b) an unsaturated carboxylic acid ester or vinyl acetate. And a copolymerization ratio of (a) /
(B) It is characterized by containing a copolymer in the range of 95/5 to 40/60 and having a weight average molecular weight of 10,000 to 300,000.

(Wherein, R ₁ : hydrogen or a lower alkyl group R ₂ : a linear or branched alkyl group having 1 to 4 carbon atoms X: hydrogen, an alkali metal, an alkaline earth metal, an organic ammonium group) This will be described in detail.

Examples of the (a) N-substituted-α, β-unsaturated monocarboxylic amide derivatives include 2-acrylamido-2-methylpropanesulfonic acid, 2-acrylamidoethanesulfonic acid, 2-methacrylamidoethanesulfonic acid,
Methacrylamidopropanesulfonic acid or salts thereof can be mentioned.

As the salt, an organic ammonium salt such as an alkali metal salt, an alkaline earth metal salt, an ammonium salt, an amine salt, or an alkanolamine salt is used.

Examples of (b) the unsaturated carboxylic acid ester or vinyl acetate which is a copolymer component include methyl methacrylate, ethyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, dimethyl maleate, and diethyl maleate. , Methyl crotonate, ethyl crotonate, butyl crotonate, vinyl acetate and the like.

In the copolymer of the present invention, the copolymerization ratio of the above copolymer components (a) and (b) is (a) / (b) = 95/5 to 40/6 in molar ratio.
It must be in the range of 0, preferably 80/20 to 50/50. When the copolymerization ratio exceeds 95/5, the holding power of the slump is significantly deteriorated, and when it is less than 40/60, the air amount increases,
Poor in cement strength.

Further, the copolymer of the present invention has a weight average molecular weight of 10,000.
Must be in the range of ~ 300,000, preferably 5
It is between 0,000 and 150,000. If the weight average molecular weight exceeds 300,000, the viscosity of the aqueous solution becomes high, handling becomes difficult, and the deterioration of slump holding power is remarkable. Conversely, if the molecular weight is less than 10,000, the amount of air increases, and the slump holding power also deteriorates.

The copolymer of the present invention can be synthesized by, for example, radical polymerization or the like. However, as the radical initiator, a redox initiator obtained by combining a persulfate and a sulfite is used, and the above-mentioned ( Those obtained by copolymerizing components a) and (b) are preferred. As the persulfate, sodium persulfate, ammonium persulfate, potassium persulfate and the like are used. Further, as sulfites, sodium sulfite, potassium sulfite, ammonium sulfite, sodium bisulfite, potassium bisulfite, ammonium bisulfite, sodium pyrosulfite,
Potassium pyrosulfite, ammonium pyrosulfite and the like are used. In particular, a redox polymerization initiator obtained by combining ammonium persulfate and potassium bisulfite is preferable. In the copolymerization reaction, the component (a) and the component (b) may be simultaneously added to the reaction system, or the component (b) may be added to the component (a).

The concentration of persulfuric acid was 0.003 per mole of vinyl monomer.
~ 0.2 mol is suitable, preferably 0.007-0.03 mol. When the persulfate concentration exceeds 0.2 mol, the weight average molecular weight of the obtained copolymer decreases, the amount of air increases, and the slump holding power also deteriorates. Conversely, if it is less than 0.003 mol, the viscosity of the aqueous solution becomes high, handling becomes difficult, and the slump holding power also deteriorates.

Sulfites are used in an amount of 0.07 to 10 mol per mol of persulfate,
It is desirable to use them together in a ratio of preferably 0.35 to 1 mol. When the amount is more than 10 mol, the salt concentration of the obtained copolymer becomes high, and the durability of the cement is deteriorated. On the other hand, if the amount is less than 0.07 mol, the polymerization rate decreases, the amount of air increases, and the slump holding power is significantly deteriorated.

The polymerization temperature is preferably from 15 to 70C. If the polymerization temperature exceeds 70 ° C., thermal decomposition of persulfate occurs, and the polymerization rate decreases, leading to an increase in the amount of air and deterioration in slump holding power. Further, even when the polymerization temperature is lower than 15 ° C., the polymerization rate decreases, and the same phenomenon occurs.

The time required for the polymerization is usually about 20 minutes to 4 hours, but is appropriately selected depending on the ratio of the monomers, the concentration of the aqueous solution and the like.

Further, the pH of the polymerization reaction is preferably 2 or more. further,
As long as the effects of the present invention are not impaired, the copolymer components (a) and (b) are further copolymerized with other copolymer components such as styrene, acrylonitrile, acrylamide, acrylic acid, and methacrylic acid. Is also good.

The copolymer of the present invention is desirably added to the cement composition in an amount of 0.01 to 2.0% by weight based on the amount of cement.
The admixture of the present invention can be used in the form of an aqueous solution or powder, and can be added at any time between kneading and molding of the cement product. Also, if necessary, a known AE agent,
AE water reducing agent, high performance AE water reducing agent, curing accelerator, setting retarder,
Concrete admixture materials such as rust preventives, separation reducing agents, swelling agents, polymer admixtures and the like can be used in combination.

Effects of the Invention According to the present invention, an N-substituted compound represented by the general formula (I)
The copolymerization ratio of the α, β-unsaturated monocarboxylic acid amide derivative and (b) unsaturated carboxylic acid ester or vinyl acetate is (a) / (b) = 95/5 to 40/60, and the weight average molecular weight is 10 ,
By using a copolymer of 000 to 300,000 as a cement admixture, a polymer composed of only the component (a) or a copolymer composed of components other than the component (b), such as an unsaturated carboxylate and a component (a), As compared with the copolymer (1), the fluidity is excellent, the deterioration of the fluidity with time is prevented, and the setting is not delayed.

EXAMPLES Production Example A 0.29 mol (67 g) aqueous solution of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS.Na) was placed in a 300-ml reactor equipped with a stirrer equipped with a reflux condenser, a dropping funnel and a gas inlet tube. And 0.13 mol (13 g) of methyl methacrylate were added to replace with nitrogen, and the temperature was raised while flowing nitrogen. When the temperature reached 50 ° C, 0.005 mol (0.63 g) of potassium bisulfite dissolved in a small amount of water and 0.005 mol (1.20 g) of ammonium persulfate dissolved in a small amount of water were added.
The polymerization was carried out for 30 minutes while maintaining the polymerization temperature. At this time, the concentration of AMPS · Na and methyl methacrylate in the whole reaction system was 30% by weight.

The weight average molecular weight of the copolymer thus obtained was 110,000 as measured by gel permeation chromatography (GPC). This was used in Example 3 described below.

Hereinafter, the copolymers used in Examples 1 to 4 and Comparative Examples 1 and 2 were produced according to the above-mentioned production method, while appropriately changing the addition amounts of potassium bisulfite and ammonium persulfate.

The copolymers used in Examples 5 to 13 and Comparative Examples 4 to 5 were produced by changing the ratio or type of the copolymerized monomers.

Examples 1-4, Comparative Examples 1-3 Copolymers of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS · Na) / methyl methacrylate (MMA) = 70/30 (molar ratio) having different molecular weights were prepared. It was used as a hydraulic cement admixture and its performance was evaluated.

The mixture was weighed by mixing the composition A shown in Table 1 below so that the kneading amount became 50 l, and the whole amount and a predetermined amount of the cement admixture (0.6 wt% with respect to the cement as a pure component) were put into a 100 l Eirich mixer, and then 90 seconds. Kneading was performed.

The mixture was taken out of the mixer, the slump was measured in accordance with JIS A 1101, and the amount of air was measured in accordance with JIS A 1128. The measured value was taken as the value immediately after.

After exactly the same kneading with another mixer, the setting time was measured by the method described in Appendix 1 of JIS A 6204.

After the measurement, the mixture was transferred to a 100-l tiltable mixer, stirred at a low speed (2 rpm), and after a lapse of a predetermined time, the slump and air amount over time were measured by the same test method.

Further, a cement mixture of Comparative Example 3 was produced without adding the cement admixture, with the blended composition of the base concrete being the composition B of Table 1 so that the slump value immediately after kneading was 20.0 cm. In addition, when it mix | blends with the composition A of Table 1 without adding a cement admixture, a slump value becomes too high and it cannot mix substantially.

 The above results are shown in Table 2.

Examples 5 to 7, Comparative Examples 4 to 5 Copolymerization of 2-acrylamido-2-methylpropanesulfonic acid / Na (AMPS · Na) / methyl methacrylate (MMA) having a molecular weight of 30,000 and different molar ratios obtained by radical polymerization About the coalescence, the performance as a hydraulic cement admixture was evaluated similarly. The results are shown in Table-3.

Examples 8 to 13 and Comparative Example 6 For a copolymer of sodium 2-acrylamido-2-methylpropanesulfonate (AMPS · Na) / unsaturated carboxylic acid ester or vinyl acetate (second component) obtained by radical polymerization, Similarly, the performance as a hydraulic cement admixture was evaluated. The results are shown in Table-4.

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C04B 24/26

Claims (2)

(57) [Claims] (A) an N-substituted compound represented by the general formula (I):
an α, β-unsaturated monocarboxylic acid amide derivative, (Wherein, R ₁ : hydrogen or lower alkyl group R ₂ : linear or branched alkyl group having 1 to 4 carbon atoms X: hydrogen, alkali metal, alkaline earth metal, ammonium, organic ammonium) (b) Unsaturation A copolymer with a carboxylic acid ester or vinyl acetate, wherein the copolymerization ratio is (a) /
(B) = A cement admixture comprising a copolymer having a weight average molecular weight of 10,000 to 300,000 in the range of 95/5 to 40/60. 2. The cement admixture according to claim 1, wherein the unsaturated carboxylic acid ester is methyl methacrylate, ethyl methacrylate, methyl acrylate, ethyl acrylate, dimethyl maleate or diethyl maleate.