JP7735257B2 - Cement additive, cement admixture, and cementitious composition - Google Patents

Description

The present invention relates to cement additives, cement admixtures, and cementitious compositions.

Cement paste is a material composed of cement and water. Cement mortar is a material composed of cement, water, and fine aggregate (sand), and concrete is a material that contains the above and also coarse aggregate (gravel). In this application, cement paste, cement mortar, and concrete are collectively referred to as cementitious compositions.

Generally, small amounts of admixtures are added to cementitious compositions to improve flowability and adjust air content. Known admixtures include air-entraining agents (such as carboxylates and ABS soaps), water-reducing agents or air-entraining water-reducing agents (such as lignin sulfonates, naphthalenes, melamines, and polyols), and high-performance air-entraining water-reducing agents (such as naphthalenes, polycarboxylic acids, melamines, and aminosulfonic acids).

In addition, polymers (polymer cement admixtures) are often blended into cementitious compositions to improve their bending strength. Known examples of such polymers include EVA, SBR, and acrylic latex.

Patent document 1 describes the use of an aqueous dispersion containing a core-shell polymer in adhesive mortar or repair mortar, and describes that the core portion contains 45 to 95% by weight of a vinyl ester of a monocarboxylic acid, and the shell portion contains 3 to 15% by weight of an aromatic vinyl benzene and 1 to 10% by weight of an unsaturated carboxylic acid having 3 to 4 carbon atoms.

Patent Document 2 describes the use of polymer microparticles having a core-shell structure as an additive for cement mortar and/or concrete, and describes that the core polymer contains 55 to 100% by weight of an acrylic acid alkyl ester having an alkyl group with 1 to 8 carbon atoms, and the shell polymer contains 5 to 49.9% by weight of an acrylic acid alkyl ester having an alkyl group with 1 to 8 carbon atoms, 45 to 90% by weight of a methacrylic acid alkyl ester having an alkyl group with 1 to 4 carbon atoms, and 0.1 to 5% by weight of an ethylenically unsaturated carboxylic acid or a salt thereof.

Patent Document 3 describes an acrylic resin emulsion used in a polymer cement composition, which is obtained by emulsion polymerization of 25 to 99.8% by weight of an alkyl (meth)acrylate ester, 0.1 to 5 parts by weight of (meth)acrylic acid, 0.1 to 5 parts by weight of a di(meth)acrylate such as alkylene glycol, and 0 to 60 parts by weight of an aromatic vinyl compound.

Japanese Patent Application Publication No. 1-121351 Patent No. 2932574 Patent No. 4930966

When polymer particles having a core-shell structure as described in Patent Document 1 or 2, or the acrylic resin emulsion as described in Patent Document 3, are blended into a cementitious composition, the fluidity of the cementitious composition before hardening may decrease, the adhesive strength to the substrate may be insufficient, and the compressive strength may also tend to decrease, leaving room for improvement in these respects.

In view of the above-mentioned current situation, the present invention aims to provide a cement additive that is added to cementitious compositions, which improves compressive strength and achieves good adhesion to substrates without reducing the unit water content, and can form cementitious compositions that have good fluidity before hardening.

The inventors discovered that the above problems can be solved by adding polymer particles having a specific core-shell structure to a cementitious composition, and thus arrived at the present invention.

That is, the present invention relates to a cement additive comprising polymer particles having a core-shell structure including a core layer and a shell layer located outside the core layer, wherein the core layer is formed from a crosslinked polymer, the content of the core layer in the polymer particles is 20 to 85% by weight, and the shell layer is formed from a copolymer of an aromatic vinyl compound and a carboxyl group-containing monomer and/or a hydroxyl group-containing monomer, the content of the carboxyl group-containing monomer and/or the hydroxyl group-containing monomer in the copolymer is 1 to 45% by weight.
Preferably, the aromatic vinyl compound is a substituted or unsubstituted styrene.
Preferably, the crosslinked polymer is formed from at least one monomer selected from the group consisting of conjugated dienes, aromatic vinyl compounds, (meth)acrylic acid esters, and organosiloxanes.
Preferably, the crosslinked polymer is formed from a (meth)acrylic acid ester.
Preferably, the polymer particles have a volume average particle size of 70 to 2500 nm.
Preferably, the additive is in the form of a latex or powder.
Preferably, the content of the carboxyl group-containing monomer or the hydroxyl group-containing monomer in the copolymer is 1 to 40% by weight.
The present invention also relates to a cement admixture containing the additive and a flow improver and/or a water reducing agent.
The present invention also relates to a cementitious composition containing cement, water, and the additive or admixture.

The present invention provides a cement additive that is added to a cementitious composition, which improves compressive strength and achieves good adhesion to the substrate without reducing the unit water content, and can form a cementitious composition that has good fluidity before hardening. According to a preferred embodiment of the present invention, it is also possible to improve the flexural strength and waterproofing of the cement after hardening.

Embodiments of the present invention are described in detail below.

(Cement additive)
The cement additive according to this embodiment includes polymer particles having a core-shell structure, each of which includes a core layer and a shell layer located outside the core layer.

The core layer refers to the polymer layer located inside the polymer particle relative to the shell layer, and is composed of a crosslinked polymer. The core layer may consist of only one layer, or it may consist of two or more layers with different monomer compositions.

The shell layer refers to a polymer layer located on the surface side of the polymer particle, and is also called a graft layer. The shell layer is preferably graft-bonded to the core layer.
The shell layer covers the surface of the core layer, but is not limited to covering the entire surface of the core layer, as long as it covers at least a part of the surface of the core layer.

The polymer particles may further have an intermediate layer between the core layer and the shell layer, as long as the effects of the invention are achieved. The intermediate layer is preferably a layer composed of a polymer and is graft-bonded to the core layer. When such an intermediate layer is present, the intermediate layer will cover at least a portion of the surface of the core layer, and the shell layer will cover at least a portion of the surface of the intermediate layer.

(Core layer)
The core layer of the polymer particle is formed from a crosslinked polymer. By forming the core layer from a crosslinked polymer, the cementitious composition to which the additive according to the present embodiment is added can have high adhesion strength to a substrate and ensure good fluidity. Furthermore, according to a preferred embodiment, the bending strength of the cementitious composition after hardening can also be improved. The crosslinked polymer is preferably formed from at least one monomer selected from a conjugated diene, an aromatic vinyl compound, a (meth)acrylic acid ester, and an organosiloxane, and more preferably formed from a (meth)acrylic acid ester.

Examples of the crosslinked polymer include polybutadiene, poly(butadiene-styrene), acrylic rubber, polysiloxane rubber elastomers, and aromatic vinyl crosslinked polymers. Among these, acrylic rubber is preferred from the standpoints of weather resistance and ease of handling.

Polybutadiene or poly(butadiene-styrene) may contain or not contain vinyl monomers other than butadiene and styrene. Examples of such vinyl monomers include aromatic vinyl monomers (excluding styrene) such as α-methylstyrene; (meth)acrylic acid and (meth)acrylic acid alkyl esters such as acrylic acid, methacrylic acid, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-hydroxyethyl methacrylate, and glycidyl methacrylate; and unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile.

Furthermore, polybutadiene or poly(butadiene-styrene) may be polymerized using multifunctional monomers such as divinylbenzene, allyl methacrylate, ethylene glycol dimethacrylate, and 1,3-butylene dimethacrylate.

Furthermore, polybutadiene or poly(butadiene-styrene) may be polymerized without the use of a chain transfer agent, or may be polymerized in the presence of a chain transfer agent. Usable chain transfer agents are not particularly limited, but examples include alkyl mercaptans such as n-dodecyl mercaptan, t-dodecyl mercaptan, t-decyl mercaptan, n-decyl mercaptan, and n-octyl mercaptan, and alkyl ester mercaptans such as 2-ethylhexyl thioglycolate.

The acrylic monomer that constitutes the acrylic rubber is not particularly limited, but examples include alkyl acrylates such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, dodecyl acrylate, stearyl acrylate, and behenyl acrylate; aromatic ring-containing acrylates such as phenoxyethyl acrylate and benzyl acrylate; hydroxyalkyl acrylates such as 2-hydroxyethyl acrylate and 4-hydroxybutyl acrylate; glycidyl acrylates such as glycidyl acrylate and glycidyl alkyl acrylate; and alkoxyalkyl acrylates. Of these, alkyl acrylates are preferred, with butyl acrylate being particularly preferred.

In addition, monomers other than acrylic monomers may or may not be used in combination. Examples of other monomers include methacrylic monomers, aromatic vinyl compounds such as styrene, vinyl cyanide compounds such as acrylonitrile, vinyl halides such as vinyl chloride, vinyl acetate, alkenes such as ethylene and propylene, etc. The polymerization ratio of acrylic monomers to the total acrylic rubber is preferably 50% by weight or more, more preferably 70% by weight or more, even more preferably 80% by weight or more, and particularly preferably 90% by weight or more.

The acrylic rubber has a cross-linked structure. To introduce a cross-linked structure, for example, a cross-linkable monomer such as a multifunctional monomer may be used when polymerizing the monomer components to synthesize the core layer polymer.

Examples of the polyfunctional monomer include allyl alkyl (meth)acrylates such as allyl (meth)acrylate and allyl alkyl (meth)acrylate; allyloxyalkyl (meth)acrylates; polyfunctional (meth)acrylates having two or more (meth)acrylic groups such as (poly)ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, ethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, and tetraethylene glycol di(meth)acrylate; diallyl phthalate, triallyl cyanurate, triallyl isocyanurate, and divinylbenzene. Allyl methacrylate, triallyl isocyanurate, butanediol di(meth)acrylate, and divinylbenzene are preferred, with allyl methacrylate being particularly preferred.

The total proportion of polyfunctional monomers used in acrylic rubber is preferably 0.01 to 10 parts by weight, more preferably 0.05 to 5 parts by weight, and even more preferably 0.1 to 3 parts by weight, per 100 parts by weight of the total monomer components (monomers other than polyfunctional monomers) that make up the acrylic rubber.

The polysiloxane rubber-based elastomer may be, for example, a polysiloxane rubber composed of alkyl or aryl di-substituted silyloxy units, such as dimethylsilyloxy, methylphenylsilyloxy, or diphenylsilyloxy. Furthermore, it is more preferable for the polysiloxane rubber-based elastomer to have a crosslinked structure introduced, for example, by partially using a multifunctional alkoxysilane compound during polymerization or by subjecting a silane compound with a vinyl-reactive group to a radical reaction.

Examples of the aromatic vinyl crosslinker include copolymers of an aromatic vinyl compound and a crosslinkable monomer. Examples of aromatic vinyl compounds include unsubstituted vinyl aromatic compounds such as styrene and 2-vinylnaphthalene; substituted vinyl aromatic compounds such as α-methylstyrene; ring-alkylated vinyl aromatic compounds such as 3-methylstyrene, 4-methylstyrene, 2,4-dimethylstyrene, 2,5-dimethylstyrene, 3,5-dimethylstyrene, and 2,4,6-trimethylstyrene; ring-alkoxylated vinyl aromatic compounds such as 4-methoxystyrene and 4-ethoxystyrene; ring-halogenated vinyl aromatic compounds such as 2-chlorostyrene and 3-chlorostyrene; ring-ester-substituted vinyl aromatic compounds such as 4-acetoxystyrene; and ring-hydroxylated vinyl aromatic compounds such as 4-hydroxystyrene.

From the viewpoint of achieving both fluidity and adhesive strength, the content of the core layer in the polymer particles is 20% by weight or more and 85% by weight or less. It is preferably 30% by weight or more, more preferably 40% by weight or more, even more preferably 50% by weight or more, even more preferably 60% by weight or more, and particularly preferably 65% by weight or more. It is also preferably 80% by weight or less, more preferably 75% by weight or less.

(shell layer)
The shell layer is formed from a copolymer of an aromatic vinyl compound and a carboxyl group-containing monomer and/or a hydroxyl group-containing monomer. By using a carboxyl group-containing monomer and/or a hydroxyl group-containing monomer as the polymer forming the shell layer, the hydrophilicity of the shell layer is improved, and the dispersibility of the polymer particles in the hydrophilic cementitious composition is improved. However, if the hydrophilicity of the shell layer is too high, the fluidity of the cementitious composition decreases, and the density of the cementitious composition after hardening decreases due to the interaction between the cement and the polymer particles, which tends to reduce the compressive strength.
By using an aromatic vinyl compound in addition to a carboxyl group-containing monomer and/or a hydroxyl group-containing monomer in the polymer forming the shell layer, the interaction between the cement and the polymer particles can be controlled to an appropriate level, ensuring good fluidity of the cementitious composition and, without inhibiting the dense structure of the cementitious composition after hardening, making it even denser and improving the compressive strength of the cementitious composition after hardening. Only the carboxyl group-containing monomer or only the hydroxyl group-containing monomer may be used. Furthermore, the carboxyl group-containing monomer and the hydroxyl group-containing monomer may be used in combination.

The aromatic vinyl compound is not particularly limited and the compounds described above can be used, but substituted or unsubstituted styrene is preferred, styrene and/or α-methylstyrene is more preferred, and styrene is particularly preferred. Aromatic vinyl compounds may be used alone or in combination of two or more.

The carboxyl group-containing monomer is not particularly limited, and examples thereof include acrylic acid, methacrylic acid, itaconic acid, crotonic acid, maleic acid, maleic anhydride, etc. The carboxyl group-containing monomers may be used alone or in combination of two or more.
The hydroxyl group-containing monomer is not particularly limited, and examples thereof include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, etc. The hydroxyl group-containing monomers may be used alone or in combination of two or more.
Of these, it is preferable to use a carboxyl group-containing monomer, and among these, acrylic acid and/or methacrylic acid are more preferable, with methacrylic acid being particularly preferable.

The copolymer forming the shell layer may or may not contain constituent monomers other than the aromatic vinyl compound and the carboxyl group-containing monomer and/or the hydroxyl group-containing monomer. Examples of such monomers include vinyl cyanide monomers such as (meth)acrylonitrile and substituted (meth)acrylonitrile, (meth)acrylamide, and maleimide.

The content of the carboxyl group-containing monomer and/or hydroxyl group-containing monomer in the copolymer forming the shell layer is 1% by weight or more and 45% by weight or less, from the viewpoint of achieving both fluidity and adhesive strength and improving compressive strength. From the same viewpoint, the content of the carboxyl group-containing monomer or hydroxyl group-containing monomer is preferably 1% by weight or more and 40% by weight or less. It is preferably 2% by weight or more, more preferably 3% by weight or more, even more preferably 5% by weight or more, and particularly preferably 10% by weight or more. It is also preferably 35% by weight or less, more preferably 30% by weight or less, even more preferably 25% by weight or less, and particularly preferably 20% by weight or less.

In addition, from the viewpoint of achieving both fluidity and adhesive strength and improving compressive strength, the content of the aromatic vinyl compound in the copolymer forming the shell layer is preferably 55% by weight or more and 99% by weight or less, and more preferably 60% by weight or more and 99% by weight or less. It is more preferably 65% by weight or more, even more preferably 70% by weight or more, particularly preferably 75% by weight or more, and most preferably 80% by weight or more. It is also more preferably 98% by weight or less, even more preferably 97% by weight or less, particularly preferably 95% by weight or less, and most preferably 90% by weight or less.

Furthermore, the content of constituent monomers other than the aromatic vinyl compound and the carboxyl group-containing monomer and/or the hydroxyl group-containing monomer in the copolymer forming the shell layer is not particularly limited, but is preferably 0% by weight or more and 30% by weight or less, more preferably 20% by weight or less, even more preferably 10% by weight or less, particularly preferably 5% by weight or less, and most preferably 1% by weight or less.

(Volume average particle diameter of polymer particles)
From the viewpoint of achieving both polymerization stability and latex stability, the polymer particles preferably have a volume average particle diameter of 70 nm or more and 2,500 nm or less. It is more preferably 80 nm or more, even more preferably 90 nm or more, and even more preferably 100 nm or more. It may also be 110 nm or more, 120 nm or more, 130 nm or more, or 140 nm or more. It is particularly preferably 150 nm or more, 160 nm or more, 170 nm or more, 180 nm or more, or 190 nm or more. It is most preferably 200 nm or more. It is also more preferably 2,000 nm or less, even more preferably 1,500 nm or less, even more preferably 1,000 nm or less, particularly preferably 500 nm or less, and most preferably 300 nm or less. The volume average particle diameter of the polymer particles is a value measured in the state of the polymer particles in a latex state using a particle size measuring device, as shown in the Examples section. The particle size of the polymer particles can be controlled by the types and amounts of the polymerization initiator, chain transfer agent, oxidation-reduction agent, emulsifier, etc., the polymerization temperature, the polymerization time, etc.

(Method for producing polymer particles)
The method for producing the polymer particles is not particularly limited, but for example, emulsion polymerization, mini-emulsion polymerization, micro-emulsion polymerization, and emulsifier-free (soap-free) emulsion polymerization can be used.

The emulsifier that can be used in emulsion polymerization is not particularly limited, and examples thereof include anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, etc. Dispersants such as polyvinyl alcohol, alkyl-substituted cellulose, polyvinylpyrrolidone, and polyacrylic acid derivatives may also be used in combination.
Among the above-mentioned emulsifiers, the anionic surfactant is not particularly limited, and examples thereof include the following compounds: fatty acid soaps such as potassium laurate, potassium coconut fatty acid, potassium myristate, potassium oleate, potassium oleate diethanolamine salt, sodium oleate, potassium palmitate, potassium stearate, sodium stearate, mixed fatty acid soda soap, semi-hardened beef tallow fatty acid soda soap, and castor oil potassium soap; alkoxylated surfactants such as sodium dodecyl sulfate, higher alcohol sodium sulfate, triethanolamine dodecyl sulfate, ammonium dodecyl sulfate, sodium polyoxyethylene alkyl ether sulfate, triethanolamine polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate, and sodium 2-ethylhexyl sulfate; alkyl sulfate salts; sodium alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate; sodium dialkylsulfosuccinates such as sodium di-2-ethylhexyl sulfosuccinate; sodium alkylnaphthalenesulfonates; sodium alkyldiphenyletherdisulfonates; potassium alkylphosphate salts; phosphate ester salts such as sodium polyoxyethylene lauryl ether phosphate; sodium salts of naphthalenesulfonate formalin condensates; polycarboxylic acid type polymeric anions; sodium acyl (beef tallow) methyl taurate; sodium acyl (coconut) methyl taurate; sodium cocoyl isethionate; sodium α-sulfofatty acid ester salts; sodium amidoethersulfonate; oleyl sarcosine; sodium lauroyl sarcosine; rosin acid soap, etc.

Furthermore, among the above-mentioned emulsifiers, nonionic surfactants are not particularly limited, but examples include the following compounds: polyoxyethylene alkyl allyl ethers or polyoxyethylene alkyl ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene oleyl ether, and polyoxyethylene lauryl ether; polyoxyethylene sorbitan esters such as polyoxyethylene sorbitan monolaurate and polyoxyethylene sorbitan monostearate; polyoxyethylene fatty acid esters such as polyethylene glycol monolaurate, polyethylene glycol monostearate, and polyethylene glycol monooleate; oxyethylene/oxypropylene block copolymers, etc.

Furthermore, among the above emulsifiers, cationic surfactants are not particularly limited, but examples include the following compounds: alkylamine salts such as coconut amine acetate, stearyl amine acetate, octadecyl amine acetate, and tetradecyl amine acetate; quaternary ammonium salts such as lauryl trimethyl ammonium chloride, stearyl trimethyl ammonium chloride, cetyl trimethyl ammonium chloride, distearyl dimethyl ammonium chloride, alkyl benzyl dimethyl ammonium chloride, hexadecyl trimethyl ammonium chloride, and behenyl trimethyl ammonium chloride.

Furthermore, among the above emulsifiers, amphoteric surfactants are not particularly limited, but examples include the following compounds: alkyl betaines such as lauryl betaine, stearyl betaine, and dimethyl lauryl betaine; sodium lauryl diaminoethyl glycine; amido betaine; imidazoline; lauryl carboxymethyl hydroxyethyl imidazolinium betaine, etc.

These emulsifiers may be used alone or in combination of two or more. Among emulsifiers, sodium dialkyl sulfosuccinate or a surfactant having an oxyethylene structure is preferred from the viewpoint of improving the fluidity of the cementitious composition, and sodium polyoxyethylene lauryl ether phosphate is particularly preferred. The average particle size of the polymer particles can be controlled by adjusting the amount of emulsifier used.

When emulsion polymerization is used, known polymerization initiators, such as 2,2'-azobisisobutyronitrile, hydrogen peroxide, potassium persulfate, and ammonium persulfate, can be used as thermal decomposition initiators.

Redox initiators can also be used that combine peroxides such as organic peroxides such as t-butylperoxyisopropyl carbonate, paramenthane hydroperoxide, cumene hydroperoxide, dicumyl peroxide, t-butyl hydroperoxide, di-t-butyl peroxide, and t-hexyl peroxide; or inorganic peroxides such as hydrogen peroxide, potassium persulfate, and ammonium persulfate with at least one selected from the group consisting of reducing agents such as sodium formaldehyde sulfoxylate and glucose; transition metal salts such as iron (II) sulfate; chelating agents such as disodium ethylenediaminetetraacetate; and phosphorus-containing compounds such as sodium pyrophosphate.

When a redox initiator is used, polymerization can be carried out at low temperatures where the peroxide does not substantially decompose thermally, making it possible to set the polymerization temperature over a wide range, making it preferable. Among these, organic peroxides such as cumene hydroperoxide, dicumyl peroxide, and t-butyl hydroperoxide are preferably used as redox initiators. The amount of the initiator used, and when a redox initiator is used, the amount of the reducing agent, transition metal salt, chelating agent, phosphorus-containing compound, etc. used, can be within known ranges. Furthermore, when polymerizing a monomer having two or more radically polymerizable double bonds, known chain transfer agents can be used within known ranges. Surfactants can also be used, but these amounts are also within known ranges.

The solvent used during emulsion polymerization may be any solvent that allows the emulsion polymerization to proceed stably, and for example, water can be suitably used.

The temperature during emulsion polymerization is not particularly limited as long as the emulsifier is dissolved uniformly in the solvent, but is, for example, 40 to 75°C, preferably 45 to 70°C, and more preferably 49 to 65°C.

When the polymer particles are produced by emulsion polymerization, for example, the latex of the polymer particles can be spray-dried to obtain a powder that can be redispersed in water, and this can be used as the polymer particles.

The cement additive according to this embodiment may be in the form of a latex of the polymer particles, or in the form of a powder of the polymer particles. Because this has excellent dispersibility in cementitious compositions, it is preferable that the additive be in the form of a latex of the polymer particles.

The cement additive of this embodiment is used by adding it to a cementitious composition before hardening and mixing and dispersing it. This allows the cementitious composition to have good adhesion to the substrate after hardening and even improved compressive strength without reducing the fluidity of the cementitious composition before hardening.

The amount of the additive to be added to the cementitious composition may be, for example, such that the solid content of the polymer particles is approximately 0.1% by weight or more and 20% by weight or less relative to the cement, preferably 0.5% by weight or more and 10% by weight or less, and more preferably 1% by weight or more and 5% by weight or less.

A cement admixture can also be provided by mixing the cement additive of this embodiment with a fluidity improver and/or a water-reducing agent. This cement admixture is also used by adding it to a cementitious composition before hardening, mixing, and dispersing it. This makes it possible to achieve the effects of good adhesion to substrates and even improved compressive strength after hardening, without reducing the fluidity of the cementitious composition before hardening.

The flow improver, air-entraining water-reducing agent, high-performance air-entraining water-reducing agent, and other water-reducing agents can be any known agent. For example, lignin sulfonate, hydroxy acid salt, and other air-entraining water-reducing agents can be used in combination with high-performance air-entraining water-reducing agents, such as naphthalene-based, melamine-based, aminosulfonic acid-based, and polycarboxylic acid-based high-performance water-reducing agents.

Cementitious compositions containing the additives or admixtures of this embodiment have the advantage that the compressive strength of the cementitious composition is improved by adding the additives or admixtures of this embodiment, even without reducing the unit water content.

A cementitious composition containing the additive or admixture according to this embodiment is also one aspect of this embodiment. A cementitious composition is a composition containing at least cement and water, and as described above, is a concept that encompasses any of cement paste, cement mortar, and concrete. The cementitious composition according to this embodiment may be either pre-hardened or hardened.

The application method for the cementitious composition containing the additive or admixture according to this embodiment is not particularly limited, and it can be applied in the same way as conventional cementitious compositions.

The cement mortar containing the additive or admixture according to this embodiment has good adhesion to substrates, particularly concrete substrates, and can form a cement mortar layer on the substrate concrete by applying it to the substrate concrete. When applying the cement mortar containing the additive or admixture according to this embodiment to the substrate concrete, the application may be performed after forming a polymer layer (a polymer layer not containing cement) on the surface of the substrate concrete. In addition, a protective layer such as a tile can be laminated on the top surface of the cement mortar layer.
Concrete or cement paste containing the additive or admixture according to this embodiment also has good adhesion to substrates, particularly concrete substrates, and can be used in the same manner as the cement mortar described above.

Cementitious compositions containing the additives or admixtures of this embodiment can be used to manufacture interior and exterior wall substrates for building structures, tile adhesives, tile joint materials, flooring materials, anticorrosion lining materials such as ACL rebar corrosion protection, waterproofing materials for water storage tanks, pools, silos, tennis court bases, and other applications, deck covering materials for ship decks, pedestrian bridge floors, bridge decks, and other applications, acid-resistant Hume pipes, special concrete molded products for GRC products, semi-rigid roads for bus terminals, tunnels, expressways, factories, and other applications, spray-applied protective coating materials for mortar and concrete structures that combine inorganic and organic fibers such as glass fiber, carbon fiber, polyester fiber, and polyvinyl alcohol fiber, conductive coating materials that combine carbon fiber and metal powder (flakes), electromagnetic wave shielding materials, ultra-high-strength molded products, heavy-duty anticorrosion coating materials for ship ballast tanks, etc., mortar float repair materials, cable-stayed bridge wire materials, decorative bottles, interlocking, and other chemical molded products.

The present invention will be explained in more detail below with reference to the following examples, but the present invention is not limited to these examples. Hereinafter, "parts" and "%" refer to "parts by weight" and "% by weight" unless otherwise specified.

(Method for measuring average particle size of polymer particles)
The average particle size of the polymer particles was measured as a volume average particle size in the state of polymer particle latex. The measuring device used was Nanotrac Wave manufactured by Nikkiso Co., Ltd. The calculation mode was set to UPA compatible mode.

Example 1
(Formation of Core Layer)
3832.3 g of deionized water and 30.0 g of Pelex OT-P (Kao Corporation: sodium dialkyl sulfosuccinate, solid content 70%) were charged into an 8 L polymerization reactor, the temperature was raised to 60° C., and nitrogen was flowed through.
A mixture of 100 g (5 parts) of butyl acrylate, 0.5 g (0.03 parts) of allyl methacrylate, and 0.3 g of t-butyl hydroperoxide (solid content 69%) was added to the polymerizer, and a solution of 0.05625 g of ferrous sulfate (FeSO ₄ ·7H ₂ O) and 0.09375 g of disodium ethylenediaminetetraacetate in 29.85 g of deionized water was added, followed by the addition of 60.0 g of sodium formaldehyde sulfoxylate (solid content 5%), and stirring for 30 minutes.
4.7 g of Perex OT-P (Kao Corporation: sodium dialkyl sulfosuccinate, solids content 70%) was added, and a mixture of 1,300 g (65 parts) of butyl acrylate, 6.5 g (0.32 parts) of allyl methacrylate, and 3.8 g of t-butyl hydroperoxide (solids content 69%) was added to the polymerizer over 185 minutes. During the addition, 23.0 g of Perex OT-P (Kao Corporation: sodium dialkyl sulfosuccinate, solids content 70%) was added, and at the end of the addition, 1.4 g of t-butyl hydroperoxide (solids content 69%) was added, and the mixture was stirred for 30 minutes.

(Shell layer formation)
20.0 g of sodium formaldehyde sulfoxylate (solid content 5%) was added to the polymerizer, and a mixture of 200 g (10 parts) of methacrylic acid, 400 g (20 parts) of styrene, and 8.7 g of t-butyl hydroperoxide (solid content 69%) was added to the polymerizer over 90 minutes.
Pelex OT-P, sodium formaldehyde sulfoxylate, and t-butyl hydroperoxide were added appropriately, and the polymerization was completed after 120 minutes, yielding a latex of core-shell structure-containing polymer particles with a conversion rate of 100% and a solids concentration of 32.9%.

(Examples 2, 4 to 6, 8 to 10, Comparative Examples 1 to 18)
Latices of core-shell structure-containing polymer particles were obtained in the same manner as in Example 1, except that the type or amount of monomer or the particle size of the polymer particles was changed according to the descriptions in Tables 1 to 3.

Example 3
A latex of core-shell structure-containing polymer particles was obtained in the same manner as in Example 1, except that the amount of PELLEX OT-P (manufactured by Kao Corporation: sodium dialkyl sulfosuccinate, solid content 70%) added at the initial stage of preparing the core layer was changed to 100.0 g.

Example 7
(Formation of Core Layer)
571.4 g of sodium hydrogen phosphate (1% solids content) was added to 3,600 g of deionized water, and a solution of 0.237 g of ferrous sulfate (FeSO ₄ · 7H ₂ O) and 0.395 g of disodium ethylenediaminetetraacetate dissolved in 125.8 g of deionized water was further added, followed by deoxidation at −0.01 MPa for 15 minutes.
19.4 g of Neopelex G-15 (manufactured by Kao Corporation: sodium dodecylbenzenesulfonate, solid content 16.2%) and 20,000 g of butadiene were charged into a 100 L polymerization reactor, and the internal temperature was raised to 45°C.
200.0 g of sodium formaldehyde sulfoxylate (solid content 5%) and 10.8 g of paramenthane hydroperoxide (solid content 52%) were added to initiate polymerization.
Thirty hours after the start of polymerization, the mixture was degassed under reduced pressure to remove the remaining monomers that had not been used in the polymerization, thereby terminating the polymerization. A latex with a solid content of 35.0% was obtained.
During the polymerization, sodium formaldehyde sulfoxylate, paramenthane hydroperoxide, ferrous sulfate (FeSO ₄ ·7H ₂ O) and disodium ethylenediaminetetraacetate were each added to the 100 L polymerizer in any amount and at any time.

(Shell layer formation)
2000 g of the obtained rubber latex (solid content 35.0%) was charged into an 8 L polymerization reactor, and the shell layer was polymerized in the same manner as in Example 1 thereafter to obtain a latex of core-shell structure-containing polymer particles.

(Evaluation method)
The latexes obtained in each example and comparative example were used to carry out the following evaluations. In Reference Example 1, the evaluations were carried out without adding any latex. In Reference Example 2, the evaluations were carried out using EVA (ethylene vinyl acetate copolymer emulsion, Hiflex-1000, manufactured by Nippon Kasei Chemical Co., Ltd.) as the polymer.

(Fluidity: Cement paste (simple mixing))
C: Ordinary Portland cement (manufactured by Taiheiyo Cement Corporation)
W: Dilution water + water content in latex P: Polymer = solid content of latex C = 50 g, P = 0.5 g (P/C = 1%), W = 25 g (W/C = 50%)
The solution of latex and dilution water was added to 50 g of cement and stirred by hand with a wooden spatula for 1 minute. The resulting cement paste was packed into a cylinder 5 cm in diameter and 4 cm in height, the surface was smoothed, the cylinder was slowly removed, and the width of the spread cement paste was measured. The flow value was calculated using the following formula.
Flow value [%] = (width of spread cement paste) [cm] / (diameter of cylinder) [cm]
Those showing a flow value of 50% or more were evaluated as ◯.

(Fluidity: Premixed mortar (simple mixing))
PM: Premix mortar: NS Zeroyon #20 manufactured by Nippon Kasei Co., Ltd.
W: Dilution water + water content in latex P: Polymer = solid content of latex PM = 50 g, P = 2.26 g, W = 27.7 g
A solution of latex and dilution water was added to 50 g of premix mortar and stirred by hand with a wooden spatula for 1 minute. The resulting mortar was packed into a 5 cm diameter cylinder, the surface was smoothed, the cylinder was slowly removed, and the width of the mortar spread was measured. The flow value was calculated according to the above formula. A flow value of 50% or more was evaluated as good.

(Fluidity: Premixed mortar (mixed with a mixer))
PM: Premix mortar: NS Zeroyon #20 manufactured by Nippon Kasei Co., Ltd.
W: Dilution water + water content in latex P: Polymer = solid content of latex PM = 3000 g, P = 135 g, W = 945 g
All materials were added to a mortar mixer (High Power Mixer manufactured by Marutosha) and mixed at low speed (rotation 140 rpm, revolution 62 rpm) for 1 minute, then scraped off and further mixed at high speed (rotation 285 rpm, revolution 125 rpm) for 1 minute to obtain mortar.
The slump value of the mortar was measured using a slump cone (top inner diameter 50 mm, bottom inner diameter 100 mm, height 150 mm). Mortars showing a slump value of 5 cm or more were evaluated as good.
In addition, for those with a slump value of less than 5 cm, 1% of a high-performance air-entraining water-reducing agent Masterglanium SP8SV (manufactured by BASF) was added to the premix mortar, and mortar was obtained in the same manner as above, and the slump value was measured.Those with a slump value of 5 cm or more were also evaluated as good.

(Adhesion strength)
The surface of the substrate concrete was sanded with a #100 file. An amount equivalent to 150 g/ ^m2 of the latex of each Example or Comparative Example diluted to a solids concentration of 8.7% was applied to the substrate with a brush and air-dried for 24 hours.
The premixed mortar mixed under the conditions of the mixer mixing test was applied to a thickness of 2 mm on the substrate concrete after the latex coating. The mortar was then subjected to 48 hours of moist air curing at 20°C and 80% RH or higher, and then left to stand at 20°C and 60% RH until the material was 14 days old. On the 13th day, a 40 mm x 40 mm incision was made in the mortar surface. An epoxy adhesive (Cemedine Hi-Quick) was applied to the mortar surface, which was the test surface, and a tensile jig was attached. After 24 hours of rest, the bond strength was measured using a Construction Research Institute adhesion tester. Four measurements were performed, and the average value is shown.

(Compressive strength)
Premixed mortar mixed under the conditions of the mixer mixing test was poured into a cylindrical specimen measuring 50 mm in diameter and 100 mm in height, and the specimen was cured for 48 hours in an environment of 20°C and 80% RH or higher. The specimen was then left to stand in an environment of 20°C and 60% RH until the age of 14 days. A compressive strength test was conducted on the 14th day. The loading rate was 0.6 N/ ^mm2 per second. Three measurements were taken, and the average value of these measurements is shown.

Table 1 shows that Examples 1 to 10, which used additives that meet the requirements of the present invention, had good fluidity and adhesive strength, and also had better compressive strength than Reference Example 1, which did not contain the additive. It can also be seen that Reference Example 2, which contained EVA as the polymer, had lower compressive strength than Reference Example 1, which did not contain the polymer.

From Tables 2 and 3, it can be seen that in Comparative Examples 1 to 18, which used additives that did not satisfy the requirements of the present invention, at least one of the fluidity, adhesive strength, and compressive strength was insufficient.
Comparative Examples 1 and 2 have a high content of MAA, a carboxyl group-containing monomer, while Comparative Example 3 does not use MAA. Comparative Example 4 does not have a core layer formed from a crosslinked polymer, while Comparative Examples 5, 13, and 14 have a high content of MAA in the core layer. Comparative Examples 6 and 13 do not crosslink the polymer in the core layer. Comparative Example 7 does not have a shell layer. Comparative Examples 8 to 12 and 15 to 17 do not use an aromatic vinyl compound in the shell layer. Comparative Example 18 has only one layer formed from a crosslinked polymer.
Comparative Example 13 corresponds to the polymer particles disclosed in JP-A-1-121351, Comparative Example 17 corresponds to the polymer particles disclosed in Japanese Patent No. 2,932,574, and Comparative Example 18 corresponds to the polymer particles disclosed in Japanese Patent No. 4,930,966.

When a water permeability test was conducted on Reference Example 2 and Example 6 in accordance with JIS A 6916, the water permeability was 0.125 mL for Reference Example 2 and 0.10 mL for Example 6. This shows that Example 6 has better waterproofing properties than Reference Example 2.

Claims (9)

An additive for cement,
The polymer particles have a core-shell structure including a core layer and a shell layer located outside the core layer,
the core layer is formed from a crosslinked polymer;
the cross-linked polymer is polybutadiene, poly(butadiene-styrene), acrylic rubber, or polysiloxane rubber elastomer;
the content of the core layer in the polymer particles is 20 to 85% by weight,
the shell layer is formed from a copolymer of an aromatic vinyl compound and a carboxyl group-containing monomer and/or a hydroxyl group-containing monomer,
The content of the carboxyl group-containing monomer and/or the hydroxyl group-containing monomer in the copolymer is 1 to 45% by weight. The additive according to claim 1, wherein the aromatic vinyl compound is a substituted or unsubstituted styrene. 3. The additive according to claim 1, wherein the cross-linked polymer is polybutadiene, poly(butadiene-styrene), or acrylic rubber . The additive according to claim 1 or 2, wherein the crosslinked polymer is an acrylic rubber . The additive according to any one of claims 1 to 4, wherein the polymer particles have a volume average particle diameter of 70 to 2500 nm. The additive according to any one of claims 1 to 5, in the form of a latex or powder. The additive according to any one of claims 1 to 6, wherein the content of the carboxyl group-containing monomer or hydroxyl group-containing monomer in the copolymer is 1 to 40% by weight. The additive according to any one of claims 1 to 7, and
Flow improver and / or water reducer,
Admixture for cement. A cementitious composition containing cement, water, and the additive described in any one of claims 1 to 7 or the admixture described in claim 7.