JPH0575711B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to an additive for cement, and more specifically, it improves the fluidity of cement mixtures (cement paste, mortar, or concrete), suppresses deterioration of the fluidity over time, and improves workability. This invention relates to an additive for cement that improves the properties of cement. [Problems to be solved by the prior art and the invention] In cement mixtures such as cement paste, mortar, and concrete, the cohesive force of cement particles is strong, and therefore workability is good with the unit amount of water required to harden the cement. Unable to obtain cement mix. Therefore, in order to improve the workability of cement mixtures, it is necessary to increase the unit amount of water. However, increasing the unit amount of water leads to a decrease in strength, so in order to obtain the same strength, it is necessary to increase the unit amount of cement. However, when the unit amount of cement is increased, the curing calorific value increases, which causes the problem that cracks are more likely to occur. Further, after mixing the various materials, cement mixtures are often transported to the pouring site by mixer trucks, etc., but the time required for transportation tends to vary depending on the distance of transportation, the degree of traffic congestion, etc.
For this reason, the fluidity of the cement mixture varies at the pouring site, making it difficult to achieve a certain level of workability. Furthermore, when pumping a cement mixture using a pump, if the pumping is interrupted for some reason and then restarted, the fluidity of the cement mixture in the piping has decreased, so the pumping pressure after restarting is There were problems such as having to raise the pipes or partially blocking the pipes. As mentioned above, the simplest means to improve the fluidity of a concrete mixture is to increase the amount of water mixed, but increasing the amount of water causes cracks and spalling after construction. Therefore, it has water reduction hardening, improves the dispersibility of cement particles,
Additionally, there is a desire for an additive that can provide suitable fluidity and maintain this fluidity. Conventionally, a mixture of a formalin condensate of naphthalene sulfonate and a salt or ester of an acrylic acid polymer has been known as such an additive. Although this additive can impart relatively good fluidity to cement mixtures, it has the disadvantage that the fluidity cannot be maintained and its fluidity deteriorates markedly over time. SUMMARY OF THE INVENTION An object of the present invention is to provide a cement additive that can impart good fluidity to a cement mixture and suppress a decline in fluidity over time. [Means for Solving the Problems] As a result of intensive research to achieve the above object, the present inventors discovered that the above object could be achieved by using a combination of specific compounds,
The present invention was completed based on this knowledge. That is, the present invention provides a cement additive comprising (A) a saponified product of a sulfonated styrene-maleic acid copolymer and (B) a salt of an acrylic acid polymer and/or an ester of an acrylic acid polymer. It is. The saponified product of the sulfonated styrene-maleic acid copolymer, which is the component (A) of the cement additive of the present invention, has the following general formula:

[Chemical formula] (In the formula, X ¹ represents either Na, K, 1/2Ca, NH ₄ or an organic amino group.) A sulfonated styrene unit represented by the following general formula

[C] (In the formula, X ² and X ³ are respectively Na, K, 1/2Ca,
Indicates either _NH4 or an organic amino group. ), and there are various types such as random copolymers, block copolymers, alternating copolymers, etc. In the present invention, the copolymer preferably has a mole fraction of sulfonated styrene units in the saponified product of 20 to 85%, particularly preferably 30 to 70%. For example, this saponified product has the following general formula

[C] (In the formula, X ¹ , X ² , and X ³ are the same as above, li is an integer from 1 to 5, mi is an integer from 1 to 3,
ⁿ¹ is an integer from 4 to 10, and i represents a variable that changes to an integer from 1 to ⁿ¹ . ) can be expressed as A saponified product of a sulfonated styrene-maleic acid copolymer can be obtained by, for example, sulfonating a styrene-maleic acid copolymer by a conventional method, removing the unreacted copolymer, and then removing the remaining sulfuric acid using a conventional liming sodation. It can be obtained by saponification such as removing it as gypsum. Here, the styrene-maleic acid copolymer as a raw material may be a random copolymer, a block copolymer, or an alternating copolymer, but has a number average molecular weight of 1000 to 9000, particularly 1500 to 9000. It is preferable to use 2000. Also general formula ()
The sulfonation rate of the saponified copolymer (100 times the number of sulfone groups (SO ₃ X ¹ ) introduced per styrene unit) is 30% or more, preferably 50% or more Good to have. Next, as component (B) in the present invention, a salt of an acrylic acid polymer and/or an ester of an acrylic acid polymer is used. Here, the salt of the acrylic acid polymer has the following general formula:

[Chemical Formula] (In the formula, R ¹ represents hydrogen or a methyl group, Y represents any of an alkali metal, alkaline earth metal, or ammonium, and n ² is 5 to 100, preferably 10
Indicates an integer between ~80. ) can be expressed as Acrylic acid polymer salts are obtained by polymerizing (meth)acrylic acid or (meth)acrylic ester using a conventional method, and then polymerizing it directly with an aqueous alkali metal solution, an aqueous alkaline earth metal solution, or aqueous ammonia, or in an appropriate solvent. It can be obtained by dispersing and reacting. In addition, as an ester of acrylic acid polymer, the following general formula

[Formula, R ² represents hydrogen or a methyl group, R ³ represents an alkyl group having 1 to 3 carbon atoms, n ³ represents 5 to 100,
Preferably it represents an integer of 10 to 80. ) can be expressed as Esters of acrylic acid polymers can be produced by polymerizing (meth)acrylic esters in a conventional manner. As component (B) in the present invention, either the salt of the acrylic acid polymer described above or the ester of the acrylic acid polymer described above may be used alone, or a mixture of the two may be used. The above (B) component is usually 10 to 10 parts by weight per 100 parts by weight of component (A).
It is used in a proportion of 100 parts by weight, preferably 20 to 80 parts by weight. The cement additive of the present invention is added to cement mixtures such as cement paste consisting of cement and water; mortar consisting of cement, sand and water; concrete consisting of cement, sand, pebbles and water; , kneaded products may be added to these, or predetermined amounts of each component may be added to the cement mixture. The amount of the cement additive of the present invention added to the cement mixture is not particularly limited, but is preferably 0.01 to 1.00% by weight in terms of solid content based on the cement.
0.05-0.50% by weight is suitable. In addition, in addition to the cement additive of the present invention, other known cement additives such as water reducing agents,
Retarders, hardening accelerators, air entraining agents, air entraining water reducing agents, cement particle dispersants and other auxiliary ingredients may be added as appropriate. [Effect of the invention] By blending the cement additive of the present invention, excellent fluidity is imparted to the cement mixture,
Furthermore, it is possible to suppress the deterioration of the fluidity over time. Therefore, the workability and workability of the cement mixture are improved. Therefore, the cement additive of the present invention is extremely useful in fields such as civil engineering, architecture, and construction, as well as in fields that handle secondary concrete products. [Examples] Next, the present invention will be explained in detail by examples. Production example 1 Production of saponified product of sulfonated styrene-maleic acid copolymer Styrene-maleic acid copolymer (number average molecular weight
1900, manufactured by ARCO Chemical, "SMA-3000")
Dissolve 85g in 100ml of 98% concentrated sulfuric acid and add 80% of fuming sulfuric acid.
Add g over 1 hour while adjusting the temperature to 30-40℃,
Thereafter, the copolymer was reacted for 3 hours to sulfonate the copolymer. After the reaction is complete, water is added to the reaction product to separate the unreacted styrene-maleic acid copolymer, and then the remaining sulfuric acid is removed as a gypsum component by the usual liming sodation method at 70°C, and the saponified product ( 138g of sodium salt) was obtained. Production example 2 Production of formalin condensate of naphthalene sulfonate Add 600 g of 98% sulfuric acid to 500 g of naphthalene,
℃ for 1.5 hours to sulfonate. Then,
310 g of 37% formalin was added dropwise at 100°C and condensation was carried out for 5 hours. At this time, when the viscosity increased, a small amount of water was added to lower the viscosity and condensation was performed. The obtained cocondensate was made into a sodium salt by a conventional liming sodation method. Production Example 3 Production of polymethyl acrylate 30 g of methyl acrylate, 1.69 g of benzoyl peroxide as a polymerization initiator, and 120 g of benzene as a solvent were added to a three-necked flask, and a polymerization reaction was carried out at 70° C. for 5 hours. After the reaction was completed, benzene was distilled off from the reaction product, and the product was purified by reprecipitation using chloroform as a solvent and methanol as a precipitant, and dried under reduced pressure and heat until a constant weight was obtained to obtain polymethyl acrylate. Vapor pressure osmotic pressure method (benzene solvent) for this item
The molecular weight was 6850. Production Example 4 Production of polymethyl methacrylate Production Example 3 except that 30 g of methyl methacrylate was used instead of methyl acrylate in Production Example 3.
Polymethyl methacrylate was obtained in the same manner as above. Vapor pressure osmotic pressure method (benzene solvent) for this item
The molecular weight was 8500. Production Example 5 Production of Sodium Polymethacrylate The polymethyl methacrylate produced in Production Example 4 was heated and saponified in an autoclave with 1.5 times the equivalent of 20% sodium hydroxide aqueous solution at a temperature of 140°C for 5 days to produce sodium polymethacrylate. (saponification rate of 98%). Examples 1 to 4 and Comparative Examples 1 to 5 Cement, sand,
The predetermined amounts of pebbles and water were added and stirred for 1 minute. Thereafter, prescribed additives shown in Table 1 were added and stirred for an additional 30 seconds to prepare a concrete composition. The concrete composition thus obtained was also evaluated by measuring the air content, slump value, and compressive strength. The results are shown in Table 1.

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Claims (1)

[Scope of Claims] 1. A cement additive comprising (A) a saponified product of a sulfonated styrene-maleic acid copolymer and (B) a salt of an acrylic acid polymer and/or an ester of an acrylic acid polymer. 2. The additive according to claim 1, comprising 100 parts by weight of component (A) and 10 to 100 parts by weight of component (B).