JP2020200214A - Additive for cement, cement admixture, cement composition, molded body, and method for improving hardness of molded body - Google Patents

Abstract

To provide an additive for concrete, in which: a cement composition exhibits low viscosity and high flowability in an early stage of installation even if the additive is added; and long age strength of the concrete and the like is improved by the addition.SOLUTION: An additive for cement comprises a water-absorbing resin, wherein: the water-absorbing resin is formed by polymerizing a monomer mixture containing 75 mol% or more of a nonionic monomer; the monomer mixture comprises 0.01-1 mol% of a non-hydrolyzable cross-linking nonionic monomer and 25 mol% or more of a hydrolyzable cross-linking nonionic monomer.SELECTED DRAWING: None

Description

The present invention relates to cement additives, cement admixtures, cement compositions, molded articles, and methods for improving the strength of molded articles.

Cement compositions such as cement paste made by adding water to cement, mortar mixed with sand, which is a fine aggregate, and concrete mixed with pebbles are used for multiple purposes such as structural materials, foundations, and refractory walls. The amount is also large. These cement compositions undergo hydration reaction between cement and water to aggregate and harden to generate strength as a molded product.

Additives for cement are added to the cement composition for the purpose of improving various properties. A water-absorbent resin is known as such an additive. For example, Patent Document 1 discloses that a water-absorbent resin obtained by polymerizing a monomer component containing a sulfonic acid-based monomer is added to a cement composition. It is said that the addition of such a water-absorbent resin slows down the evaporation rate of water from the cement composition at the initial stage of construction and does not cause cracks.

Further, in Patent Document 2, when the water-absorbent resin is added to the cement composition, it takes a long time to transport the ready-mixed concrete before hardening from the ready-mixed concrete manufacturing factory to the construction site. Therefore, the water-absorbing resin is absorbed during the transportation. In view of the problem that the resin reaches the saturated water absorption amount, a technique for using a water-absorbent resin obtained by coating the surface of the water-absorbent resin with a slowly soluble / hydrolyzable resin as an additive for cement is disclosed. There is.

Further, Patent Document 3 describes that a water-absorbent resin having anionic / cationic properties and having a time-delayed swelling action is used for concrete and mortar.

JP-A-63-291840 Japanese Unexamined Patent Publication No. 1-261250 Special Table 2011-525556

One of the most important properties in the performance of the molded product obtained by molding the cement composition is strength. Strength is broadly classified into early strength and long-term strength. Early strength indicates strength with a curing period of mainly several days, and high early strength leads to shortening of construction period and labor saving of construction. On the other hand, the long-term strength shows the strength after the curing period is mainly 28 days, which is directly linked to the durability of concrete and is an indispensable performance for structures. Therefore, it is very important that the long-term strength of the molded product obtained by molding the cement composition is high.

In addition, the ready-mixed concrete before hardening is transported from the ready-mixed concrete manufacturing factory to the construction site, pumped at the casting site, and filled in the formwork. If the fluidity of the cement composition is too low or the viscosity is too high during pumping, it takes a long time to transport the cement composition, and in the worst case, the cement composition is clogged in the pipe. Therefore, from the viewpoint of workability, it is preferable that the cement composition at the time of casting has low viscosity and high fluidity.

Therefore, the present invention provides an additive for concrete in which the viscosity of the cement composition is low and the fluidity is high at the initial stage of addition such as at the time of casting, and the long-term strength of a molded product such as concrete is improved by the addition. The purpose is to do.

The present invention is an additive for cement containing a water-absorbent resin, wherein the water-absorbent resin is obtained by polymerizing a monomer mixture containing 75 mol% or more of a nonionic monomer, and the monomer mixture is formed. Is an additive for cement containing 0.01 to 1 mol% of non-hydrolytable crosslinkable nonionic monomer and 25 mol% or more of hydrolyzable crosslinkable nonionic monomer.

According to the cement additive of the present invention, the viscosity of the initial cement composition is unlikely to change even with the addition. Therefore, it is easy to handle the cement composition at the time of casting, and it is easy to pump it, and workability is improved. Further, according to the additive for cement of the present invention, the addition improves the long-term strength of a molded product such as concrete after a long-term curing period (for example, 28 days).

<Additives for cement>
The first embodiment of the present invention is an additive for cement containing a water-absorbent resin.
The water-absorbent resin is obtained by polymerizing a monomer mixture containing 75 mol% or more of nonionic monomer.
The monomer mixture is an additive for cement containing 0.01 to 1 mol% of non-hydrolyzable crosslinkable nonionic monomer and 25 mol% or more of hydrolyzable crosslinkable nonionic monomer. ..

By using the cement additive of the present embodiment, the initial cement composition has high fluidity and low viscosity, while the long-term strength of the molded product is remarkably improved. Such an excellent effect is that the water-absorbent resin of the present invention does not exhibit high water-absorbing performance immediately after water addition (for example, up to about 2 hours), exhibits water-absorbing ability after a lapse of time, and has a lapse of time. Later, it is considered that this is due to the high water absorption performance.

The water-absorbent resin used in the first embodiment is made by polymerizing a monomer mixture. The content of the nonionic monomer in the monomer mixture is 75 mol% or more. Further, the monomer mixture contains 0.01 to 1 mol% of non-hydrolyzable crosslinkable nonionic monomer and 25 mol% or more of hydrolyzable crosslinkable nonionic monomer. That is, the monomer mixture contains two or more crosslinkable nonionic monomers, one of which is hydrolyzable and the other is non-hydrolyzable. If such a configuration is deviated, the water absorption performance begins to appear in the initial stage, for example, 5 minutes after the addition of water (see Comparative Production Examples 1 and 2 described later). However, when water is absorbed by the water-absorbent resin, the viscosity of the cement composition rapidly increases, and it is necessary to significantly increase the amount of the dispersant added in order to improve the fluidity of the cement composition. Occurs.

On the other hand, by adopting the configuration of the present embodiment, the water absorption performance is not so high at the initial stage, for example, 5 minutes after the addition of water. In addition, it does not exhibit rapid water absorption performance even after 2 hours of addition (see Examples described later). Therefore, the amount of water absorbed by the water-absorbent resin in the cement composition is low, and the viscosity / fluidity of the cement composition at the initial stage of addition is maintained by adding a small amount of the cement dispersant. Therefore, the work efficiency of the builder is improved and the pumping is smoothly performed. Although the detailed mechanism by which such an effect is exhibited by adopting the configuration of the present embodiment is unknown, it is considered as follows. In an alkaline environment of the cement composition, the structural unit portion of the hydrolyzable crosslinkable nonionic monomer undergoes hydrolysis. As a result, the crosslink density is lowered, the water absorption performance is improved, and the presence of the structural unit derived from the non-hydrolyzable crosslinkable nonionic monomer can prevent the structure of the water-absorbent resin from collapsing. Conceivable.

On the other hand, the present inventor has found that the long-term strength of the molded product is improved by adopting the configuration of the present embodiment. The water-absorbent resin of the present embodiment gently absorbs the surrounding water during the period from the time of casting to the curing period in order to exhibit the water-absorbing performance slowly. This prevents the moisture from escaping from the molded product. In addition, since cement develops strength by a hydration reaction, a sufficient reaction is not carried out when water is insufficient, and the strength is not sufficiently developed as expected. It is thought that by storing water after the water-absorbent resin is cast, water is supplied from the water-absorbent resin to the residual unhydrate during the curing period, the hydration rate of cement is improved, and the strength of concrete is improved. Be done.

For example, Patent Document 3 discloses a water-absorbent resin having anionic properties. The finding that a polymer having a low content of anionic monomers and having a nonionic monomer as a main component can exhibit high water absorption performance as in the present embodiment constitutes a water-absorbent resin. This is a very surprising fact in view of the fact that it has been conventionally considered that the water absorption performance is exhibited by the repulsion of the anionic group in the anionic monomer. The detailed mechanism of why the polymer containing a nonionic monomer as a main component exhibits water absorption performance over time is unknown.

In addition, Patent Document 3 also discloses a polymer of a monomer that is stable in hydrolysis and a monomer that is easily hydrolyzed in the presence of a cross-linking agent. Patent Document 3 describes that "only a hydrolyzable cross-linking agent" is used as the cross-linking agent, and does not use a hydrolyzable cross-linking agent (monomer) as in the present embodiment.

Hereinafter, the cement additive will be described in detail.

In the present specification, "X to Y" indicating a range means "X or more and Y or less".

As used herein, "~ acid (salt)" means "~ acid and / or a salt thereof". "(Meta) acrylic" means "acrylic and / or methacrylic".

[Water-absorbent resin]
As used herein, the term "water-absorbent resin" refers to polymer gelation having a water swelling property (CRC) of 5 g / g or more and a soluble component of 50% by mass or less as defined by ERT441.2-02. Refers to an agent. "ERT" is a European standard (substantially world standard) method for measuring water-absorbent resin (EDANA Recommended Test Method) established by EDANA (abbreviation of European Nonwovens and Nonwovens Associations). It is an abbreviation. In this specification, unless otherwise specified, the physical properties of the water-absorbent resin are measured in accordance with the 2002 version of ERT.

The water-absorbent resin preferably has a water absorption ratio of less than 20 g / g, more preferably less than 18 g / g, and less than 15 g / g when immersed in 50 mL of an aqueous solution having a pH of 12.9 at 25 ° C. for 2 hours. It is more preferable to have. By having such characteristics, the viscosity is low at the initial stage of addition of the cement additive, the fluidity is high, and the workability is excellent. The water absorption ratio when immersed in an aqueous solution of pH 12.9 at 25 ° C. for 2 hours is preferably as low as possible, and the lower limit thereof is not particularly limited, but is usually 5 g / g or more.

Aqueous solution of pH12.9 _herein, mixed _{CaSO 4 · 2H 2 O1.72g, Na} 2 SO 4 6.96g, K 2 SO 4 4.76g, the KOH7.12g and deionized water 979.4g Is. The aqueous solution having a pH of 12.9 is a cement simulating solution that imitates becoming a strong alkali when it contains cement. Therefore, the aqueous solution can imitate the behavior of the water-absorbent resin when water is added to the cement composition containing the cement additive.

Further, the water absorption ratio of the water-absorbent resin when immersed in an aqueous solution of pH 12.9 at 25 ° C. for 1 day is preferably 10 g / g or more, preferably 15 g / g or more, from the viewpoint of improving long-term strength. Is more preferable, and 20 g / g or more is further preferable. The higher the water absorption ratio when immersed in an aqueous solution of pH 12.9 at 25 ° C. for 1 day, the more preferable, and the upper limit thereof is not particularly limited, but is usually 50 g / g or less, and 45 g / g. The following is preferable.

The water-absorbent resin is preferably a powder, and the shape of the powder may be a spherical shape or an agglomerate thereof, or an amorphous (crushed form) obtained by subjecting a hydrogel or a dry polymer to a pulverization step. It is preferably amorphous (crushed).

The particle size distribution of the water-absorbent resin (powder) preferably has 90% by mass or more in the range of 45 to 850 μm, more preferably in the range of 100 to 850 μm, and more preferably 250, because the long-term strength is further improved. Even more preferably, it is in the range of ~ 850 μm. It is considered that the sustained release of water is enhanced and the long-term strength is further improved by increasing the average particle size of the water-absorbent resin (powder).

The mass average particle size (D50) of the water-absorbent resin (powder) can be measured in the same manner as in "Average Particle Diameter and Distribution of Particle Sizeter" disclosed in European Patent No. 0349240. That is, using a JIS standard sieve (JIS Z8801-1 (2000)) having an opening of 850 μm, 710 μm, 600 μm, 500 μm, 420 μm, 300 μm, 212 μm, 150 μm, 106 μm, 45 μm or an equivalent sieve, 10 g of the particulate water absorbent. Is classified, and the masses of the water-absorbent resin remaining on each sieve and the water-absorbent resin that has passed through all the sieves are measured. Classification is performed for 5 minutes using a vibration classifier (IIDA SIEVE SHAKER, TYPE: ES-65 type, SER. No. 0501), and the residual percentage R is plotted on logarithmic probability paper. Then, the particle size corresponding to R = 50% by mass can be read as the mass average particle size (D50) and used as the read average particle size.

The amount of residual monomer in the water-absorbent resin is preferably 1000 mass ppm or less, more preferably 500 mass ppm or less, and even more preferably 400 mass ppm or less. When the amount of the residual monomer is not more than the above upper limit, the safety is high when added to the cement composition. The smaller the amount of residual monomer, the more preferable, but it is usually 5 mass ppm or more.

As a method for reducing the amount of residual monomer, a conventionally known method can be used, and for example, a method such as adding a reducing substance after polymerization can be used. Here, the amount of residual monomer means the amount of monomer remaining in the water-absorbent resin. Examples of the reducing substance include inorganic reducing agents such as phosphorus-based reducing agents and sulfur-based reducing agents (particularly oxygen-containing sulfur-based reducing agents); and organic reducing agents such as ascorbic acid.

The amount of residual monomer was determined by adding 1.0 g of a water-absorbent resin to 200 ml of a 0.9 wt% sodium chloride aqueous solution and stirring at 500 rpm for 1 hour according to ERT410.2-02, and then the amount of dissolved monomers ( Unit; mass ppm) is the value measured using HPLC (High Performance Liquid Chromatography).

The monomer mixture refers to the entire polymerizable monomer that forms the polymer that is the main component of the water-absorbent resin, and the total amount of the monomers that form the polymer is 100 mol%. The monomer mixture contains at least 75 mol% or more of nonionic monomer. Nonionic monomers are classified into non-crosslinkable nonionic monomers and crosslinkable nonionic monomers. The crosslinkable nonionic monomer is, for example, a monomer having two or more unsaturated double bonds and playing a role of crosslinking the main chains. On the other hand, the non-crosslinkable nonionic monomer refers to a monomer having one unsaturated double bond.

Further, the crosslinkable nonionic monomer is distinguished into a non-hydrolyzable crosslinkable nonionic monomer and a hydrolyzable crosslinkable nonionic monomer.

In other words, the water-absorbent resin contains 75 mol% or more of the constituent units derived from the nonionic monomer, and 0.01 to 1 mol% of the constituent units derived from the non-hydrolyzable crosslinkable nonionic monomer and water. Contains 25 mol% or more of structural units derived from degradable crosslinkable nonionic monomers. The structural unit derived from the nonionic monomer, the structural unit derived from the non-hydrolyzable crosslinkable nonionic monomer, and the structural unit derived from the hydrolyzable crosslinkable nonionic monomer are the production of each monomer. It may be considered that it matches the molar ratio at the time of preparation.

(Crosslinkable nonionic monomer)
The crosslinkable nonionic monomer is a monomer having two or more polymerizable unsaturated groups. A crosslinked structure (crosslinked body) is formed by the crosslinkable nonionic monomer, and water absorption at the initial stage of addition can be suppressed.

The crosslinkable nonionic monomer is preferably water-soluble because it can further exert the effects of the present invention. Hereinafter, the water-soluble crosslinkable nonionic monomer is also referred to as a water-soluble crosslinkable nonionic monomer. Here, the "water-soluble" in the water-soluble crosslinkable nonionic monomer refers to a monomer that dissolves 5 g or more in 100 g of water at 25 ° C. The water-soluble crosslinkable nonionic monomer is preferably dissolved in 10 g or more, more preferably 50 g or more, and further preferably 100 g or more in 100 g of water.

In the present embodiment, as the crosslinkable nonionic monomer, a hydrolyzable monomer (hydrolyzable crosslinkable nonionic monomer, hereinafter also simply referred to as a hydrolyzable monomer) and a non-hydrolyzable monomer are used. Two kinds of sex monomers (non-hydrolyzable crosslinkable nonionic monomer, hereinafter simply referred to as non-hydrolyzable monomer) are used.

Here, the hydrolyzable means that when the monomer is immersed in an aqueous solution (25 ° C.) having a pH of 12.9 for one day, 80% or more of the monomer is decomposed. Decomposition can be measured by analysis by methods such as LC (liquid chromatography) and GC (gas chromatography).

The non-hydrolytable monomer is not particularly limited as long as it is a compound having two or more polymerizable unsaturated groups, but for example, (N, N'-methylenebis (meth) acrylamide and the like ( Meta) Polyfunctional vinyl ethers such as acrylamide monomer, ethylene glycol divinyl ether, diethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, butylene glycol divinyl ether, hexanediol divinyl ether, and polyfunctional fragrance such as divinylbenzene. Examples include family vinyls. These can be used alone or in combination of two or more.

Among them, the non-hydrolyzable monomer preferably contains N, N'-methylenebisacrylamide. Furthermore, the non-hydrolyzable monomer may be only a (meth) acrylamide-based monomer or may be only N, N'-methylenebis (meth) acrylamide.

The content of the non-hydrolyzable monomer in the monomer mixture is 0.01 to 1 mol%. When the content of the non-hydrolyzable monomer is in such a range, the crosslinked structure in the water-absorbent resin can be maintained even in an alkaline environment after the addition of cement, so that the cement does not remain. Water can be gradually supplied to the hydrate. Therefore, the long-term strength is improved. Since the effects of the present invention are further exhibited, the content of the non-hydrolyzable monomer in the monomer mixture is more preferably 0.05 to 0.5 mol%, and 0.1 to 0.1. It is more preferably 0.3 mol%.

The hydrolyzable monomer is not particularly limited as long as it is a compound having two or more polymerizable unsaturated groups, but for example, (poly) ethylene glycol di (meth) acrylate, (poly). Polyfunctional (meth) acrylates such as propylene glycol di (meth) acrylates, trimethyllol propantri (meth) acrylates, ethylene oxide-modified trimethylol propantri (meth) acrylates, pentaerythritol hexa (meth) acrylates; triallyl cyanurate, Cyanuric acid such as triallyl isocyanurate or an allyl ester of isocyanuric acid; and the like. These can be used alone or in combination of two or more. Among them, the hydrolyzable monomer preferably has an ester bond, more preferably a polyfunctional (meth) acrylate, and (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol. Di (meth) acrylate is even more preferred, (poly) ethylene glycol di (meth) acrylate is even more preferred, polyethylene glycol di (meth) acrylate is particularly preferred, and polyethylene glycol diacrylate. Is most preferable.

The content of the hydrolyzable monomer in the monomer mixture is 25 mol% or more. When the content of the hydrolyzable monomer is in such a range, the crosslink density is high in the initial stage under an alkaline environment after the addition of cement, so that water absorption is suppressed. On the other hand, the hydrolyzable portion (for example, ester bond) of the hydrolyzable monomer is hydrolyzed with time, and the crosslink density becomes small, so that the water absorption performance is exhibited. Therefore, the long-term strength is improved. Since the effects of the present invention are further exhibited, the content of the hydrolyzable monomer in the monomer mixture is more preferably 45 mol% or more. The hydrolyzable monomer is preferably 25 to 99.9 mol%, more preferably 45 to 99.9 mol%, still more preferably 45 to 80 mol%, and 45 to 80 mol%. It is particularly preferably 60 mol%.

As the nonionic monomer, a non-crosslinkable monomer (non-crosslinkable nonionic monomer) may be used. The non-crosslinkable nonionic monomer refers to a monomer having one unsaturated double bond.

The non-crosslinkable nonionic monomer is preferably water-soluble because it can further exert the effects of the present invention. Hereinafter, the water-soluble non-crosslinkable nonionic monomer is also referred to as a water-soluble non-crosslinkable nonionic monomer. Here, "water-soluble" in the water-soluble non-crosslinkable nonionic monomer means that 5 g or more is dissolved in 100 g of water at 25 ° C. The water-soluble non-crosslinkable nonionic monomer is preferably dissolved in 10 g or more, more preferably 50 g or more, and further preferably 100 g or more in 100 g of water.

The non-crosslinkable nonionic monomer is not particularly limited as long as it has one unsaturated double bond in the monomer. The non-crosslinkable nonionic monomer preferably excludes N-vinylacylamide. Specific examples of the non-crosslinkable nonionic monomer include (meth) acrylamide, N-monomethyl (meth) acrylamide, N-monoethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide and the like (meth). ) Acrylamide-based monomer; N-vinyllactam-based monomer such as N-vinylpyrrolidone; hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, (meth) acrylic Hydroxy (meth) acrylates such as hydroxypentyl acid; unsaturated amines such as N- (2-dimethylaminoethyl) (meth) acrylamide, vinylpyridine, vinylimidazole; vinyl cyanide monomers such as acrylonitrile and methacrylonitrile An unsaturated polyalkylene glycol alkenyl ether-based monomer represented by the following general formula (1);

(In the general formula (1), R ¹ , R ² , and R ³ independently represent a hydrogen atom or a methyl group, and R ⁴ represents a hydrogen atom or a hydrocarbon group having 1 to 30 carbon atoms. represents, ^{R a} O represents an oxyalkylene group having 2 to 18 carbon atoms, n is a mean addition mol number of oxyalkylene groups represented by ^{R a} O, n represents a number from 1 to 500 , X is an integer of 0 to 2, and y is 0 or 1.) And the like. These can be used alone or in combination of two or more.

Further, since the non-crosslinkable nonionic monomer is excellent in water absorption performance after a lapse of time, it is preferable that the non-crosslinkable nonionic monomer contains a (meth) acrylamide-based monomer and / or a hydroxy (meth) acrylate, and (meth). It is more preferable to contain an acrylamide-based monomer, even more preferably to contain (meth) acrylamide, and particularly preferably to contain acrylamide. Furthermore, the non-crosslinkable nonionic monomer may be only (meth) acrylamide or may be only acrylamide.

The content of the non-crosslinkable nonionic monomer in the monomer mixture is preferably 10 mol% or more. When the content of the non-crosslinkable nonionic monomer is 10 mol% or more, it is easy to exhibit water absorption performance over time in an alkaline environment after cement addition, and the long-term strength of the molded product is further excellent. It becomes. The content of the non-crosslinkable nonionic monomer in the monomer mixture is preferably 10 to 60 mol%, more preferably 25 to 50 mol%, and 35 mol% or more and less than 50 mol%. Is even more preferable. For the content of each monomer in the monomer mixture, the value obtained up to the second decimal place is adopted.

In this embodiment, in addition to the nonionic monomer, an anionic monomer and / or a cationic monomer may be contained. The anionic monomer refers to a monomer having an anionic functional group or a salt group thereof in the monomer. The anionic functional group means a functional group in which counter ions are dissociated to become anions (anionized). The cationic monomer refers to a monomer having a cationic functional group or a salt group thereof in the monomer. The cationic functional group means a functional group in which counter ions are dissociated to become cations (cationized).

In the present embodiment, the content of the anionic monomer and the cationic monomer in the monomer mixture is preferably 25 mol% or less, preferably 10 mol% or less and 5 mol% or less. 4 mol% or less, 3 mol% or less, 2 mol% or less, 1 mol% or less, 0.5 mol% or less, 0 mol% (that is, it does not contain anionic and cationic monomers). Is most preferable.

In a preferred embodiment of the present invention, the water-absorbent resin does not contain ionic monomers (anionic and cationic monomers), that is, the water-absorbent resin is a non-crosslinkable nonionic monomer and It is a form obtained by polymerizing a monomer mixture composed of only crosslinkable nonionic monomers.

(Manufacturing method of water-absorbent resin)
The method for producing the water-absorbent resin is not particularly limited, and the water-absorbent resin can be produced by a conventionally known method. Examples of the polymerization method for obtaining the water-absorbent resin include spray polymerization, droplet polymerization, bulk polymerization, precipitation polymerization, aqueous solution polymerization, reverse phase suspension polymerization and the like, but here, aqueous solution polymerization is used as an example. List the manufacturing methods that were used.

(1) Preparation Step of Aqueous Monomer Mixture This step is a step of preparing an aqueous solution of a monomer mixture by dissolving each monomer constituting the polymer in water as a solvent.

Each monomer may be added all at once or in sequence. Here, the aqueous solution is a concept including an aqueous dispersion. If necessary, the aqueous solution of the monomer mixture may contain components constituting additives for cement such as trace components (chelating agent, surfactant, dispersant, etc.).

The "aqueous solution" in the monomer mixture aqueous solution means that 100% by mass of the solvent is not limited to water, and 0 to 30% by mass, preferably 0 to 5% by mass of a water-soluble organic solvent (for example, alcohol) is used in combination. These may be treated as an aqueous solution in the present invention.

(2) Aqueous Solution Polymerization Step Aqueous solution polymerization is a method of polymerizing a monomeric aqueous solution without using a dispersion solvent. For example, US Pat. Nos. 4,652,0099, 4873299, 4286082, 4973632, etc. It is disclosed in No. 4985518, No. 5124416, No. 5250640, No. 5264495, No. 5145906, No. 5380808, European Patent No. 0811636, No. 0955086, No. 0922717, etc. There is.

The concentration of the aqueous monomer solution at the time of the polymerization is not particularly limited, but is preferably 20% by mass to a saturation concentration or less, more preferably 25 to 80% by mass, and further preferably 30 to 70% by mass. When the concentration is 20% by mass or more, a decrease in productivity can be suppressed. In addition, since the physical properties of the monomer in a slurry (aqueous dispersion) are deteriorated, it is preferable to carry out the polymerization at a saturation concentration or less.

In the polymerization step, a polymerization initiator is added to the aqueous solution of the monomer mixture obtained above.

The polymerization initiator used is appropriately determined depending on the polymerization form, and is not particularly limited, and examples thereof include a photodegradable polymerization initiator, a thermal decomposition initiator, and a redox-based polymerization initiator. Polymerization is initiated by these polymerization initiators.

Examples of the photodegradable polymerization initiator include benzoin derivatives, benzyl derivatives, acetophenone derivatives, benzophenone derivatives, azo compounds and the like. Specifically, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, α-methylbenzoin, α-phenylbenzoin, anthraquinone, methylanthraquinone, acetophenone, 2,2-diethoxyacetophenone, 2,2-dimethoxy-2. -Phenylacetone, benzyldiacetylacetophenone, benzophenone, p-chlorobenzophenone, 2-hydroxy-2-methylpropiophenone, diphenyldisulfide, tetramethylthiuram sulfide, α-chloromethylnaphthalene, anthracene, hexachlorobutadiene, pentachlorobutadiene, Michelers ketone , 2-Chlorothioxanthone, 2,4-diethylthioxanthone, benzyldimethylketal, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide, 2-methyl-1- [4- (methylthio) phenyl] -2 -Mophorinopropanone-1,2-hydroxy-2-methyl-1-phenylpropane-1-one, 1- [4- (2-hydroxyethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane -1-On, etc. Such a photodegradable polymerization initiator may be a commercially available product, and the trade names of Ciba Specialty Chemicals are Irgacure (registered trademark) 184 (hydroxycyclohexyl-phenylketone) and Irgacure (registered trademark) 2959 (1- [4- (2-hydroxy). Ethoxy) -phenyl] -2-hydroxy-2-methyl-1-propane-1-one) and the like can be exemplified.

Examples of the thermally decomposable polymerization initiator include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; and peroxides such as hydrogen peroxide, t-butyl peroxide, and methyl ethyl ketone peroxide; 2 , 2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2- (2-imidazolin-2-yl) propane] dihydrochloride and the like.

Further, examples of the redox-based polymerization initiator include a system in which a reducing compound such as L-ascorbic acid or sodium bisulfite is used in combination with the persulfate or peroxide.

Further, the photodecomposition type polymerization initiator and the thermal decomposition type polymerization initiator may be used in combination. Further, active energy rays such as ultraviolet rays, electron beams, and γ rays may be used alone or in combination with the above-mentioned polymerization initiator.

The amount of the polymerization initiator used is preferably 0.0001 to 1 mol%, more preferably 0.0005 to 0.5 mol%, based on the monomer.

The polymerization step can be carried out at normal pressure, reduced pressure, or pressurization, but is preferably carried out at normal pressure (or its vicinity, usually ± 10 mmHg). The temperature at the start of polymerization is preferably 15 to 130 ° C, more preferably 20 to 120 ° C, although it depends on the type of polymerization initiator used.

In this way, a gel-like crosslinked polymer is obtained.

(3) Gel Crushing Step In this step, a gel-like crosslinked polymer (hereinafter referred to as "hydrous gel") obtained through the above polymerization steps and the like (particularly aqueous solution polymerization) is gel-crushed to form a particulate hydrogel (hereinafter referred to as "hydrous gel"). Hereinafter, it is an arbitrary step for obtaining (referred to as “particulate hydrogel”).

The gel crusher that can be used is not particularly limited. And so on. Among them, a screw type extruder having a perforated plate at the tip is preferable, and examples thereof include a screw type extruder disclosed in Japanese Patent Application Laid-Open No. 2000-063527.

(4) Drying Step This step is a step of drying the hydrogel obtained through the above polymerization steps and the like to obtain a dry polymer. When the above-mentioned polymerization step is aqueous solution polymerization, gel pulverization (fine granulation) is performed before and / or after drying the hydrogel. Moreover, the dried polymer (aggregate) obtained in the drying step may be supplied to the pulverization step as it is.

The drying method is not particularly limited, and various methods can be adopted. Specific examples thereof include heat drying, hot air drying, vacuum drying, infrared drying, microwave drying, co-boiling dehydration drying with a hydrophobic organic solvent, and high humidity drying using high-temperature steam. Alternatively, the two types can be used in combination. The drying temperature is preferably 100 to 300 ° C, more preferably 120 to 250 ° C. The drying time depends on the surface area and water content of the hydrogel, the type of dryer, and the like, but is preferably 1 minute to 5 hours, for example.

(5) Crushing / Classification Step This step is a step of pulverizing and / or classifying the dried polymer obtained in the above drying step to obtain a water-absorbent resin having a specific particle size. It is different from the above (3) gel crushing step in that the crushed object has undergone a drying step. Further, the water-absorbent resin after the pulverization step may be referred to as a pulverized product.

The particle size can be controlled in the pulverization / classification step of the polymerization step, the gel pulverization step, or the drying step, but it is particularly preferable to perform it in the classification step after drying.

[Other ingredients]
The additive for cement contains a water-absorbent resin as a main component. Here, the main component means that it is 80% by mass or more of the cement additive, preferably 90% by mass or more, more preferably 95% by mass or more, and most preferably 98% by mass or more (upper limit is 100% by mass, that is, an additive for cement consisting only of a water-absorbent resin). The water-absorbent resin referred to in the present invention also includes a water-absorbent resin in which the obtained polymer is chemically modified (surface-modified or the like). Preferably, the cement additive is a water-absorbent resin composed only of a polymer obtained by polymerizing the above-mentioned monomer mixture.

In addition to the absorbent resin, the cement additive contains 0 to 10% by mass, preferably 0.1 to 10% by mass, of a surfactant, a color inhibitor, a reducing agent, etc. for the purpose of stabilizing the water-absorbent resin. It may contain 1% by mass.

<Cement admixture>
A second embodiment of the present invention is a cement admixture containing the cement additive and cement dispersant of the first embodiment. By using both in combination, when added to the cement composition, the dispersibility of the cement is ensured and the viscosity of the cement composition is maintained low even in a region where the amount of the cement dispersant added is small. , The long-term strength of the molded body is improved.

As the cement dispersant, a conventionally known cement dispersant can be used. Examples of the cement dispersant include polyalkylaryl sulfonates such as naphthalene sulfonic acid formaldehyde condensate; melamine formalin resin sulfonates such as melamine sulfonic acid formaldehyde condensate; aminoaryl sulfonic acid-phenol-formaldehyde condensate. Aromatic amino sulfonates such as; lignin sulfonates such as lignin sulfonates and modified lignin sulfonates; various sulfonic acid-based dispersants having sulfonic acid groups in molecules such as polystyrene sulfonates; Polyalkylene glycol mono (meth) acrylic acid ester-based monomers, (meth) acrylic acid-based monomers, and these, as described in JP-A-59-18338 and JP-A-7-223852. Copolymers obtained from monomers copolymerizable with the monomer; JP-A-10-236858, JP-A-2001-220417, JP-A-2002-121055, JP-A-2002-121056. A (poly) oxyalkylene group in a molecule such as an unsaturated (poly) alkylene glycol ether-based monomer, a maleic acid-based monomer, or a copolymer obtained from a (meth) acrylic acid-based monomer as described. Various polycarboxylic acid dispersants having a carboxyl group and a (alkoxy) polyalkylene glycol mono (meth) acrylate as described in JP-A-2006-52381, a phosphoric acid monoester monomer, and a phosphoric acid. Various phosphoric acid-based dispersants having a (poly) oxyalkylene group and a phosphoric acid group in a molecule such as a copolymer obtained from a diester-based monomer, a phosphoric acid-based dispersion described in JP-A-2008-517080. Examples include agents. Above all, as the cement dispersant, it is preferable to use a polycarboxylic acid-based dispersant because the effects of the present invention are further exhibited. The cement dispersant may be only one kind or two or more kinds.

The content mass ratio of the cement dispersant in the cement admixture and the cement additive is preferably 1: 0.1 to 10, more preferably 1: 0.5 to 5.

<Cement composition>
A third embodiment of the present invention is a cement composition containing the cement additive and cement of the first embodiment.

Another embodiment of the present invention is a cement composition containing a water-absorbent resin and cement, wherein the water-absorbent resin polymerizes a monomer mixture containing 75 mol% or more of nonionic monomers. The monomer mixture is a cement composition containing 0.01 to 1 mol% of non-hydrolytable crosslinkable nonionic monomer and 25 mol% or more of hydrolyzable crosslinkable nonionic monomer. is there.

As the content ratio of the cement additive (or water-absorbent resin) in the cement composition, any appropriate content ratio can be adopted depending on the purpose. When used for mortar or concrete using hydrohard cement, the content ratio of the cement additive (or water-absorbent resin) to 100 parts by mass of the cement is preferably 0.01 to. It is 10 parts by mass, more preferably 0.02 to 5 parts by mass, and further preferably 0.05 to 3 parts by mass. Such a content ratio brings about various favorable effects such as low viscosity, high fluidity, and increased strength.

The cement composition preferably contains water. The cement composition preferably comprises aggregate.

As the cement, any suitable cement may be adopted. Examples of such cements include Portoland cements (normal, early-strength, ultra-fast-strength, moderate heat, sulfate-resistant and low-alkali forms of each), various mixed cements (blast furnace cement, silica cement, fly ash cement), and the like. White Portoland cement, alumina cement, ultra-fast-hardening cement (1 clinker fast-hardening cement, 2 clinker fast-hardening cement, magnesium phosphate cement), grout cement, oil well cement, low heat-generating cement (low-heat-generating blast furnace cement, fly ash mixed low) Heat-generating blast furnace cement, belite-rich cement), ultra-high-strength cement, cement-based solidifying material, eco-cement (cement manufactured from one or more of municipal waste incineration ash and sewage sludge incineration ash) and the like. Further, fine powder such as blast furnace slag, fly ash, cinder ash, clinker ash, husk ash, silica powder, limestone powder and gypsum may be added to the cement composition. The cement contained in the cement composition of the present invention may be only one kind or two or more kinds.

In the cement composition, any appropriate value can be set as the unit water amount per 1 m ³ of the cement composition, the amount of cement used, and the water / cement ratio. Such values, preferably, unit water is ^{100kg / m 3 ~185kg / m 3} , the amount of cement used is ^{250kg / m 3 ~800kg / m 3} , water / cement ratio (mass ratio) = is 0.1 to 0.7, more preferably, a unit water amount is ^{120kg / m 3 ~180kg / m 3} , the amount of cement used is ^{270kg / m 3 ~800kg / m 3} , water / cement ratio ( Mass ratio) = 0.12 to 0.65.

As the aggregate, any suitable aggregate such as fine aggregate (sand or the like) or coarse aggregate (crushed stone or the like) can be adopted. Examples of such aggregates include sand (land sand and the like), crushed stones, granulated slag, and recycled aggregates. Further, examples of such aggregates include refractory aggregates such as silica stone, clay, zircon, high alumina, silicon carbide, graphite, chromium, chromag, and magnesia.

The cement composition preferably comprises a cement dispersant. That is, a preferred embodiment of the present invention is a cement composition containing the cement additive, cement, and cement dispersant of the first embodiment. The cement dispersant is the same as that described in the column of the second embodiment.

The content mass ratio of the cement dispersant and the cement additive in the cement composition is preferably 1: 0.1 to 10, and more preferably 1: 0.5 to 5. The content ratio of the cement dispersant in the cement composition may be any appropriate content ratio depending on the intended purpose, and is, for example, 0.01 to 10 parts by mass with respect to 100 parts by mass of cement.

The cement composition may contain any other suitable cement additive as long as it does not impair the effects of the present invention. Examples of such other cement additives include other cement additives as exemplified in the following (1) to (12). (1) Water-soluble polymer substances: nonionic cellulose ethers such as methyl cellulose, ethyl cellulose, carboxymethyl cellulose; polysaccharides produced by microbial fermentation such as yeast glucan, xanthan gum, β-1,3 glucan; polyacrylamide, etc. .. (2) Polymer emulsion: A copolymer of various vinyl monomers such as alkyl (meth) acrylate. (3) Curing retardant: Oxycarboxylic acid such as gluconic acid, glucoheptonic acid, arabonic acid, malic acid, citric acid or a salt thereof; Sugars; disaccharides such as maltose, shoe cloth, lactose; trisaccharides such as raffinose; oligosaccharides such as dextrin erythritol, xylitol, D-arabinitol, L-arabinitol, rivitol, boremitol, persetol, sorbitol, mannitol, galactitol, D Sugar or sugar alcohols such as -traytoll, L-treitol, D-iditol, D-glycidol, D-erythro D-galactose-octitol; polyhydric alcohols such as glycerin; phosphonic acid such as aminotri (methylenephosphonic acid) and Its derivatives etc. (4) Fast-strengthening agent / accelerator: soluble calcium salts such as calcium chloride, calcium nitrite, calcium nitrate, calcium bromide, calcium iodide; chlorides such as iron chloride and magnesium chloride; sulfates; potassium hydroxide; Sodium hydroxide; carbonate; thiosulfate; formates such as formic acid and calcium nitrate; alkanolamine; alumina cement; calcium aluminate silicate and the like. (5) Oxyalkylene-based defoaming agent: polyoxyalkylene alkyl ethers such as diethylene glycol heptyl ether; polyoxyalkylene acetylene ethers; (poly) oxyalkylene fatty acid esters; polyoxyalkylene sorbitan fatty acid esters; polyoxyalkylene alkyl (Aryl) ether sulfate ester salts; polyoxyalkylene alkyl phosphate esters; polyoxypropylene polyoxyethylene laurylamine (addition of 1 to 20 mol of propylene oxide, addition of 1 to 20 mol of ethylene oxide, etc.) and alkylene oxide were added. Polyoxyalkylene alkylamines such as amines derived from fatty acids obtained from hardened beef fat (additions of 1 to 20 mol of propylene oxide, adduct of 1 to 20 mol of ethylene oxide, etc.); polyoxyalkylene amides and the like. (6) Defoamers other than oxyalkylene-based: Defoamers such as mineral oil-based, oil-based, fatty acid-based, fatty acid ester-based, alcohol-based, amide-based, phosphoric acid ester-based, metal soap-based, and silicone-based defoamers. (7) AE agent: resin soap, saturated or unsaturated fatty acid, sodium hydroxystearate, lauryl sulfate, ABS (alkylbenzene sulfonic acid), alkane sulfonate, polyoxyethylene alkyl (phenyl) ether, polyoxyethylene alkyl (phenyl) ether Sulfate ester or salt thereof, polyoxyethylene alkyl (phenyl) ether phosphate ester or salt thereof, protein material, alkenyl sulfosuccinic acid, α-olefin sulfonate, etc. (8) Other surfactants: Various anionic surfactants; various cationic surfactants such as alkyltrimethylammonium chloride; various nonionic surfactants; various amphoteric surfactants and the like. (9) Waterproofing agent: fatty acid (salt), fatty acid ester, fat, silicone, paraffin, asphalt, wax, etc. (10) Anticorrosive agent: nitrite, phosphate, zinc oxide, etc. (11) Crack reducing agent: polyoxyalkyl ether or the like. (12) Expansion material; ettringite-based, coal-based, etc.

Other known cement additives include cement wetting agents, thickeners, separation reducing agents, coagulants, drying shrinkage reducing agents, strength enhancers, self-leveling agents, rust inhibitors, coloring agents, fungicides and the like. Can be mentioned. These known cement additives (materials) may be only one type or two or more types. In addition, other cement additives are blended in an appropriate amount in the cement composition in consideration of the purpose of addition.

The cement composition may be effective for ready-mixed concrete, concrete for secondary concrete products, concrete for centrifugal molding, concrete for vibration compaction, steam curing concrete, sprayed concrete and the like. Cement compositions include medium-fluidity concrete (concrete with a slump value of 22 to 25 cm), high-fluidity concrete (concrete with a slump value of 25 cm or more and a slump flow value of 50 to 70 cm), self-filling concrete, self-leveling material, etc. It can also be effective for mortar and concrete that require high fluidity.

The cement composition may be prepared by blending the constituent components by any appropriate method. For example, a method of kneading the constituents in a mixer can be mentioned.

<Molded body>
A fourth embodiment of the present invention is a molded product obtained by molding the cement composition of the third embodiment.

The formation of the molded product is not particularly limited, and is performed by a conventionally known method. Examples of the molding method include a method in which the cement composition is poured into a mold, the mold is cured, and then the mold is removed, or a molded product in which the cement composition is poured into the mold and then removed from the mold. There is a method of curing the body.

The curing method is not particularly limited, and may be any of underwater curing, sealing curing, and aerial curing. Moreover, you may apply a curing agent and cure.

Since the molded product of the fourth embodiment can withstand long-term use, it can be used for various purposes. Specific examples thereof include structures such as buildings; concrete structures such as columns, piles, and gutters.

<Method of improving the strength of the molded product>
A fifth embodiment of the present invention is a method for improving the strength of a molded product obtained by molding a cement composition containing cement, which comprises incorporating the cement additive of the first embodiment into the cement composition. This is a method for improving the strength of a molded product.

The strength of the molded product may exceed 100%, preferably 105% or more, and more preferably 110% or more, as compared with the strength of the molded product before the addition of the cement additive. As the strength of the molded product, the value measured by the method described in the following Examples is adopted.

The effects of the present invention will be described with reference to the following examples and comparative examples. In the examples, the indication of "parts" or "%" may be used, but unless otherwise specified, it indicates "parts by mass" or "% by mass". Unless otherwise specified, each operation is performed at room temperature (25 ° C.) and normal pressure.

[Manufacturing Example 1]
In a 1000 ml cylindrical separable flask, 3.7 g of acrylamide, 26.27 g of diacrylate (hereinafter abbreviated as PEG9DA) of polyethylene glycol (with 9 mol of ethylene oxide), 0.0241 g of N, N-methylenebisacrylamide and water 60. 93 g was charged and dissolved uniformly. Here, in the monomer mixture composed of acrylamide, PEG9DA and N, N-methylenebisacrylamide, acrylamide is 49.9 mol%, PEG9DA is 49.9 mol%, and N, N-methylenebisacrylamide is 0.15 mol%. After replacing the inside of the flask with nitrogen, heat the flask to 45 ° C., add 4.656 g of a 1% aqueous sodium persulfate solution and 4.464 g of a 0.1% L-ascorbic acid aqueous solution, stop stirring and polymerize. I let you. Heat was generated after the start of polymerization, and the temperature rose to 80 ° C. 10 minutes later. When the rise in the liquid temperature stopped, the bath temperature was raised to 80 ° C. and aging was carried out for 30 minutes. The obtained gel-like polymer (hydrous gel) is subdivided using a cutter, dried with hot air at 130 ° C. for 3 hours, pulverized with a mixer, and then sieved using JIS standard sieves with openings of 500 μm and 250 μm. Then, it passed through a sieve having a mesh size of 500 μm, and the powdery water-absorbent resin remaining on the sieve having a mesh size of 250 μm was collected. 90% by mass or more of the powdered water-absorbent resin was in the range of 45 to 850 μm. This powdery water-absorbent resin was used as an additive for cement.

[Manufacturing Example 2]
In a 1000 ml cylindrical separable flask, 1.71 g of acrylamide, 28.27 g of diacrylate (hereinafter abbreviated as PEG9DA) of polyethylene glycol (with 9 mol of ethylene oxide), 0.0185 g of N, N-methylenebisacrylamide and water 62. 1 g was charged and dissolved uniformly. Here, in the monomer mixture composed of acrylamide, PEG9DA and N, N-methylenebisacrylamide, acrylamide is 30.0 mol%, PEG9DA 69.9 mol%, and N, N-methylenebisacrylamide is 0.15 mol%. After replacing the inside of the flask with nitrogen, heat the flask to 45 ° C., add 4.056 g of a 1% aqueous sodium persulfate solution and 3.888 g of a 0.1% L-ascorbic acid aqueous solution, stop stirring and polymerize. I let you. Heat was generated after the start of polymerization, and the temperature rose to 80 ° C. 10 minutes later. When the rise in the liquid temperature stopped, the bath temperature was raised to 80 ° C. and aging was carried out for 30 minutes. The obtained gel-like polymer (hydrous gel) is subdivided using a cutter, dried with hot air at 130 ° C. for 3 hours, pulverized with a mixer, and then sieved using JIS standard sieves with openings of 500 μm and 250 μm. Then, it passed through a sieve having a mesh size of 500 μm, and the powdery water-absorbent resin remaining on the sieve having a mesh size of 250 μm was collected. 90% by mass or more of the powdered water-absorbent resin was in the range of 45 to 850 μm. This powdery water-absorbent resin was used as an additive for cement.

[Manufacturing Example 3]
A 1000 ml cylindrical separable flask was charged with 29.99 g of polyethylene glycol (with 9 mol of ethylene oxide) diacrylate (hereinafter abbreviated as PEG9DA), 0.0138 g of N, N-methylenebisacrylamide and 63.1 g of water, and uniformly charged. Was dissolved in. Here, in the monomer mixture composed of PEG9DA and N, N-methylenebisacrylamide, PEG9DA is 99.9 mol% and N, N-methylenebisacrylamide is 0.15 mol%. After replacing the inside of the flask with nitrogen, heat the flask to 45 ° C., add 3.542 g of a 1% sodium persulfate aqueous solution and 3.396 g of a 0.1% L-ascorbic acid aqueous solution, stop stirring and polymerize. I let you. Heat was generated after the start of polymerization, and the temperature rose to 80 ° C. 10 minutes later. When the rise in the liquid temperature stopped, the bath temperature was raised to 80 ° C. and aging was carried out for 30 minutes. The obtained gel-like polymer (hydrous gel) is subdivided using a cutter, dried with hot air at 130 ° C. for 3 hours, pulverized with a mixer, and then sieved using JIS standard sieves with openings of 500 μm and 250 μm. Then, it passed through a sieve having a mesh size of 500 μm, and the powdery water-absorbent resin remaining on the sieve having a mesh size of 250 μm was collected. 90% by mass or more of the powdered water-absorbent resin was in the range of 45 to 850 μm. This powdery water-absorbent resin was used as an additive for cement.

[Comparative Manufacturing Example 1]
19.69 g of acrylamide, 8.23 g of acrylic acid, 1.99 g of diacrylate (hereinafter abbreviated as PEG9DA) of polyethylene glycol (with 9 mol of ethylene oxide), N, N-methylenebisacrylamide 0 in a 1000 ml cylindrical separable flask. .0915 g and 46.76 g of water were charged and dissolved uniformly. Here, in a monomer mixture consisting of acrylamide, acrylic acid, PEG9DA and N, N-methylenebisacrylamide, acrylamide 70.0 mol%, acrylic acid 28.9 mol%, PEG9DA 1 mol%, N, N-methylenebis Acrylamide is 0.15 mol%. After replacing the inside of the flask with nitrogen, heat the flask to 45 ° C., add 11.934 g of a 1% aqueous sodium persulfate solution and 11.441 g of a 0.1% L-ascorbic acid aqueous solution, stop stirring and polymerize. I let you. Heat was generated after the start of polymerization, and the temperature rose to 80 ° C. 10 minutes later. When the rise in the liquid temperature stopped, the bath temperature was raised to 80 ° C. and aging was carried out for 30 minutes. The obtained gel-like polymer (hydrous gel) is subdivided using a cutter, dried with hot air at 130 ° C. for 3 hours, pulverized with a mixer, and then sieved using JIS standard sieves with openings of 500 μm and 250 μm. Then, it passed through a sieve having a mesh size of 500 μm, and the powdery water-absorbent resin remaining on the sieve having a mesh size of 250 μm was collected. 90% by mass or more of the powdery water-absorbent resin was in the range of 45 to 850 μm. This powdery water-absorbent resin was used as an additive for cement.

[Comparative Manufacturing Example 2]
9.45 g of acrylamide, 1.35 g of acrylic acid, 19.15 g of diacrylate (hereinafter abbreviated as PEG9DA) of polyethylene glycol (with 9 mol of ethylene oxide), N, N-methylenebisacrylamide 0 in a 1000 ml cylindrical separable flask. .0439 g and 56.78 g of water were charged and dissolved uniformly. Here, in a monomer mixture consisting of acrylamide, acrylic acid, PEG9DA and N, N-methylenebisacrylamide, 70 mol% of acrylamide, 9.9 mol% of acrylic acid, 20 mol% of PEG9DA, N, N-methylenebisacrylamide 0. .15 mol%. After replacing the inside of the flask with nitrogen, heat the flask to 45 ° C., add 6.79 g of a 1% aqueous sodium persulfate solution and 6.509 g of a 0.1% L-ascorbic acid aqueous solution, stop stirring and polymerize. I let you. Heat was generated after the start of polymerization, and the temperature rose to 80 ° C. 10 minutes later. When the rise in the liquid temperature stopped, the bath temperature was raised to 80 ° C. and aging was carried out for 30 minutes. The obtained gel-like polymer (hydrous gel) is subdivided using a cutter, dried with hot air at 130 ° C. for 3 hours, pulverized with a mixer, and then sieved using JIS standard sieves with openings of 500 μm and 250 μm. Then, it passed through a sieve having a mesh size of 500 μm, and the powdery water-absorbent resin remaining on the sieve having a mesh size of 250 μm was collected. 90% by mass or more of the powdered water-absorbent resin was in the range of 45 to 850 μm. This powdery water-absorbent resin was used as an additive for cement.

[Water absorption test method]
CaSO ₄ · 2H ₂ O and 1.72 g, 6.96 g of _Na 2 SO _4, 4.76g of K 2 SO _4, 7.12g of KOH, deionized water were mixed 979.4G, solutions for water absorption test Was prepared (pH 12.9).

Approximately 0.2 g of powdered water-absorbent resin was accurately weighed (mass W1 (g)), placed in a 4 cm × 5 cm non-woven tea bag, and sealed by heat sealing. This tea bag is placed in a screw tube made of glass and having a specified volume of 50 mL, and is placed in 50 mL of a water absorption test solution at room temperature (25 ° C.) and at normal pressure for a predetermined time (5 minutes, 30 minutes, 2 hours, 1 day). ) Was immersed. Next, the end of the tea bag was grasped with tweezers, the tea bag was pulled up, placed on a Kim towel (manufactured by Nippon Paper Crecia Co., Ltd.) with one side of the tea bag facing down, and allowed to stand for 5 seconds. Next, the tea bag was placed on a Kim towel with the opposite side facing down and allowed to stand for 5 seconds to drain the liquid, and then the mass (W2 (g)) of the tea bag was measured. Separately, the same operation was performed without using a water-absorbent resin, and the mass (W3 (g)) of the tea bag at that time was determined as a blank. The water absorption ratio calculated according to the following formula was taken as the liquid absorption capacity.

Table 1 below shows the water absorption ratio of each powdered water-absorbent resin.

From the above results, the powdered water-absorbent resins of Production Examples 1 to 3 had a water absorption ratio of less than 15 g / g after 5 minutes, and even after 2 hours, the water absorption ratio was less than 15 g / g. On the other hand, after 1 day, it had a high water absorption ratio of 10 g / g or more. On the other hand, the powdery water-absorbent resin of Comparative Production Examples 1 and 2 had a water absorption ratio of 10 g / g or more after 5 minutes had passed. From this result, it can be seen that the powdered water-absorbent resins of Production Examples 1 to 3 do not have very high water-absorbing performance at the initial stage of water addition (up to about 2 hours), but exhibit high water-absorbing performance over time. ..

It is more preferable that the powdery water-absorbent resin has a water absorption ratio of less than 10 g / g after being immersed for 5 minutes according to the above-mentioned water absorption test method.

[Manufacturing Example A: Manufacture of cement dispersant]
80.0 parts of ion-exchanged water was placed in a glass reaction vessel equipped with a Dimroth condenser, a stirrer with a Teflon (registered trademark) stirring blade and a stirring seal, a nitrogen introduction tube, and a temperature sensor, and stirred at 250 rpm. The mixture was heated to 70 ° C. while introducing nitrogen at 200 mL / min. Next, a mixed solution of 133.4 parts of methoxypolyethylene glycol monomethacrylic acid ester (average number of moles of ethylene oxide added), 26.6 parts of methacrylic acid, 1.53 parts of mercaptopropionic acid and 106.7 parts of ion-exchanged water. Was added dropwise over 4 hours, and at the same time, a mixed solution of 1.19 parts of ammonium persulfate and 50.6 parts of ion-exchanged water was added dropwise over 5 hours. The polymerization reaction was completed by keeping the temperature at 70 ° C. for 1 hour after the completion of the dropping. Then, it was neutralized with an aqueous solution of sodium hydroxide to obtain an aqueous solution of a polycarboxylic acid-based copolymer containing a polymer as a cement dispersant (solid content of about 46.0% by mass).

[Evaluation method 1: Mortar test and strength test method]
A kneader for mechanical kneading, a spoon, a flow table, a flow cone and a thrust rod conforming to JIS-R5201-1997 were used. At this time, unless otherwise specified, a mortar test was conducted in accordance with JIS-R5201-1997.

The composition of the mortar (cement composition) is 587 g of ordinary Portland cement manufactured by Pacific Cement Co., Ltd., 1350 g of standard sand for cement strength test conforming to JIS-R5201-1997, and the copolymer aqueous solution (cement dispersant) obtained in Production Example A. ) And 264.1 g of ion-exchanged water containing a defoaming agent (the copolymer solid content content with respect to 100 parts by mass of cement is 0.11 to 0.19 parts by mass, Table 2 below). The powdery water-absorbent resins of Production Examples 1 to 3 and Comparative Production Examples 1 and 2 were added in advance by 0.3 parts by mass with respect to 100 parts by mass of cement and mixed with cement. The defoaming agent was added for the purpose of avoiding the influence of air bubbles on the dispersibility of the mortar composition, and the amount of air was adjusted to 4.0% or less. Specifically, an oxyalkylene defoaming agent was used in an amount such that it was 0.1% with respect to the copolymer. When the amount of air in the mortar was larger than 4.0%, the amount of antifoaming agent added was adjusted so that the amount of air was 4.0% or less.

The mortar was prepared at room temperature (20 ± 2 ° C.) in 4 minutes and 30 seconds using a Hobart type mortar mixer (model number N-50, manufactured by Hobart). Specifically, a specified amount of cement and powdered water-absorbent resin were placed in a kneading pot, attached to a kneader, and started at a low speed. Fifteen seconds after starting the paddle, water containing the specified amount of cement dispersant and defoamer was added in 15 seconds. Then, sand was added and kneaded at low speed for 30 seconds, then at high speed, and kneading was continued for 30 seconds. Remove the kneading bowl from the kneader, pause kneading for 120 seconds, attach the kneading bowl to the kneading machine again, knead at high speed for 60 seconds (start at low speed at the beginning, then start at low speed for 4 minutes and 30 minutes). After seconds), stir with a spoon 10 times each on the left and right. The mixed mortar is packed in two layers in a flow cone placed on a flow table. Each layer is thrust 15 times over the entire surface so that the tip of the thrust rod enters to a depth of about 1/2 of that layer, and finally the shortage is supplemented, the surface is smoothed, and the start is started at a low speed at the beginning. Six minutes later, after lifting the flow cone vertically, the diameter of the mortar spread on the table was measured in two directions, and this average value was taken as the flow value.

To measure the amount of mortar air, put the mortar into a 500 ml graduated cylinder, measure the weight and volume, and measure the difference between the measured volume and the volume when the amount of air in the mortar of the put weight is 0%. It was calculated as.

After measuring the flow value and the amount of air, a sample for a compression strength test was prepared, and the compression strength after 28 days was measured under the following conditions.

Specimen preparation: 50 mm x 100 mm
Specimen curing (28th): After performing constant temperature and humidity air curing at a temperature of about 20 ° C. and humidity of 60% for 24 hours, the specimen was wrapped in a plastic film so that water could not be exchanged between the mortar surface and the outside. After that, it was put in a plastic bag, sealed, and sealed and cured for 27 days.

Specimen polishing: Specimen surface polishing (using specimen polishing finishing machine)
Compression strength measurement: Automatic compression strength measuring device (Maekawa Mfg. Co., Ltd.)
[Evaluation method 2: Rohto flow test method]
A funnel flow test of mortar was carried out as an evaluation of pipe passability during pump pumping. If the mortar did not block in the middle and flowed down in a short time, it was judged that the pipe passage was good. The specific method of the Rohto flow test is as follows.

A rubber stopper was attached to the lower end of the J14 funnel (upper end inner diameter 70 mm, lower end inner diameter 14 mm, height 392 mm) specified in the Japan Society of Civil Engineers standard JSCE-F541, and the funnel was vertically supported by a stand. Next, an electronic scale for measuring the amount of mortar that flowed out was installed below the lower end of the J14 funnel.

The obtained mortar was poured to the upper surface of the J14 funnel to smooth the upper surface. Next, the rubber stopper was removed to allow the mortar to flow out, and the time from the start of the mortar outflow to the flow down of 1200 g was measured with a stopwatch, and this was taken as the funnel flow-down time.

The results of each Example and Comparative Example are shown in Table 2 below. In addition,% in the column of 28-day intensity is% of each intensity when the value of Comparative Example 1 is taken as 100%.

From the above results, in the cement composition using the cement additive of Example, the same flow value was obtained with the same amount of dispersant as in Comparative Example 1. Further, in the cement composition having the same flow value (fluidity), the cement composition using the cement additive of the example is the same as the cement composition using the cement additive of Comparative Examples 2 and 3. The amount of cement dispersant was smaller than that. Further, it was found that the cement composition using the cement additive of the example had a low viscosity and was excellent in pumping property because the flow time was short. In addition, the cement composition using the cement additive of the example had improved strength in the sealing cure on 28 days as compared with Comparative Example 1 in which the cement additive was not added.

On the other hand, in Comparative Examples 2 and 3 using the powdered water-absorbent resin which does not adopt the constitution of the present invention, it was necessary to add a large amount of dispersant in order to obtain the same flow value (fluidity). In addition, the cement compositions of Comparative Examples 2 and 3 had a high viscosity due to a long flow time, resulting in inferior work.

[Evaluation method 3: Concrete test and strength test method]
Ordinary Portland cement (manufactured by Pacific Cement Co., Ltd.) is used as cement, land sand from Oigawa water system is used as fine aggregate, crushed stone from Qinghai is used as coarse aggregate, and tap water is used as kneading water. Cement: 382 kg / m ³ , water: 172 kg / m ³ , Fine aggregate: 796 kg / m ³ , Coarse aggregate: 930 kg / m ³ , Fine aggregate ratio (fine aggregate / fine coarse aggregate + coarse aggregate) (volume ratio): 47%, cement dispersant and Water-absorbent resin powder A cement composition was prepared with a blending ratio shown in Table 3 below and a water / cement ratio (mass ratio) = 0.45. The powdery water-absorbent resins of Production Examples 1 to 3 and Comparative Production Examples 1 and 2 were previously added by 0.3 parts by mass with respect to 100 parts by mass of cement and mixed with cement.

The materials used for measurement, the forced kneading mixer, and the measuring instruments were adjusted under the above-mentioned measurement temperature atmosphere so that the temperature of the cement composition became the measurement temperature of 20 ° C., and the kneading and each measurement were carried out as described above. The measurement was performed in an atmosphere of temperature. In addition, in order to avoid the influence of air bubbles in the cement composition on the fluidity of the cement composition, an oxyalkylene defoaming agent is used as necessary so that the amount of air is 4.5 ± 0.5%. Adjusted to.

Under the above conditions, concrete was produced using a forced kneading mixer with a kneading time of 90 seconds, and the flow value and the amount of air were measured. The flow value and the amount of air were measured in accordance with the Japanese Industrial Standards (JIS-A-1101: 2014, 1128: 2014). The amount of the cement dispersant added was such that the flow value was 375 mm to 425 mm.

After measuring the flow value and the amount of air, a sample for a compression strength test was prepared, and the compression strength after 28 days was measured under the following conditions. Specimen preparation: 100 mm x 200 mm Specimen curing (28 days): After 24 hours of constant temperature and humidity air curing at a temperature of about 20 ° C and humidity of 60%, the concrete surface is provided so that water cannot be exchanged with the outside. After wrapping the specimen with a poly film, it was placed in a plastic bag, sealed, and sealed and cured for 27 days.

Specimen polishing: Specimen surface polishing (using specimen polishing finishing machine)
Compression strength measurement: Automatic compression strength measuring device (Maekawa Mfg. Co., Ltd.)
The results are shown in Table 3 below.

From the above results, the cement composition using the cement additive of the example obtained the same flow value with the same amount of dispersant as that of the comparative example. Further, in the cement composition having the same flow value (fluidity), the cement composition using the cement additive of the example is compared with the cement composition using the cement additive of the comparative example. The amount of cement dispersant was small. In addition, the cement composition using the cement additive of the example had improved strength in the sealing cure on 28 days as compared with Comparative Example 1 in which the cement additive was not added.

On the other hand, in Comparative Examples 2 and 3 using the powdery water-absorbent resin not adopting the constitution of the present invention, it was necessary to add a large amount of dispersant in order to obtain the same flow value (fluidity).

Claims (13)

An additive for cement containing a water-absorbent resin.
The water-absorbent resin is obtained by polymerizing a monomer mixture containing 75 mol% or more of nonionic monomer.
The monomer mixture is an additive for cement containing 0.01 to 1 mol% of non-hydrolyzable crosslinkable nonionic monomer and 25 mol% or more of hydrolyzable crosslinkable nonionic monomer. The water-absorbing resin, an aqueous solution of pH 12.9 (here, aqueous solution of pH 12.9 _{is, CaSO 4 · 2H 2 O1.72g,} Na 2 SO 4 6.96g, K 2 SO 4 4.76g, KOH7.12g The cement additive according to claim 1, wherein the water absorption ratio is less than 20 g / g when immersed in (an aqueous solution containing 979.4 g of deionized water) at 25 ° C. for 2 hours. The cement additive according to claim 1 or 2, wherein when the water-absorbent resin is immersed in the aqueous solution of pH 12.9 at 25 ° C. for 1 day, the water absorption ratio is 10 g / g or more. The cement additive according to any one of claims 1 to 3, wherein the content of the hydrolyzable crosslinkable nonionic monomer in the monomer mixture is 45 mol% or more. The cement additive according to any one of claims 1 to 4, wherein the hydrolyzable crosslinkable nonionic monomer has an ester bond. The cement additive according to any one of claims 1 to 5, wherein the monomer mixture contains 10 mol% or more of a non-crosslinkable nonionic monomer. The cement additive according to claim 6, wherein the non-crosslinkable nonionic monomer contains a (meth) acrylamide-based monomer. A cement admixture comprising the cement additive according to any one of claims 1 to 7 and a cement dispersant. A cement composition comprising the cement additive according to any one of claims 1 to 7 and cement. The cement composition according to claim 9, further comprising a cement dispersant. A cement composition containing a water-absorbent resin and cement.
The water-absorbent resin is obtained by polymerizing a monomer mixture containing 75 mol% or more of nonionic monomer.
The monomer mixture is a cement composition containing 0.01 to 1 mol% of non-hydrolyzable crosslinkable nonionic monomer and 25 mol% or more of hydrolyzable crosslinkable nonionic monomer. A molded product obtained by molding the cement composition according to any one of claims 9 to 11. A method for improving the strength of a molded product obtained by molding a cement composition containing cement.
A method for improving the strength of a molded product, which comprises incorporating the cement additive according to any one of claims 1 to 7 or the cement admixture according to claim 8 into the cement composition.