JP2815469B2 - Asbestos scattering prevention coating composition and method for producing the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coating composition for asbestos scattering prevention used for preventing asbestos scattering and a method for producing the same.

[Problems to be Solved by Conventional Techniques and Inventions] Asbestos has been used in large amounts in buildings as a heat insulating material, a fireproof material, and a sound absorbing material. However, in recent years, the harm of asbestos to the human body has become a problem, and its use has been restricted. Then, asbestos that has already been constructed is required to be removed. To meet such demands, various asbestos removal methods or solidification methods have been proposed. For example, JP-A-1-301571 discloses an asbestos scattering prevention method in which an aqueous emulsion paint containing a foamable silicate is sprayed on the surface of a layer containing asbestos (hereinafter simply referred to as "asbestos layer"). Have been. However, it is generally difficult for water-based emulsion-type paints to achieve both film formability and water resistance and flexibility of the film. That is, in this method, when the polymer particles in the aqueous emulsion are composed of a polymer having a low glass transition point in order to enhance the film forming property, the water resistance of the coating film is reduced. Further, the coating has adhesiveness, and dust easily adheres. On the other hand, when the glass transition point of the polymer particles is increased, not only does the film-forming property deteriorate, but also the flexibility of the film decreases, and cracks are likely to occur. When cracks occur in the coating, asbestos is scattered.

Japanese Patent Application Laid-Open No. 1-160887 discloses an aqueous emulsion,
A method using an asbestos scattering inhibitor to which a urethane prepolymer excellent in water retention is added is disclosed. This method retains moisture with the urethane prepolymer and prevents asbestos from scattering during the painting operation. However, this method also has the same problem as described above because an aqueous emulsion is used. Furthermore, since the applied asbestos scattering inhibitor is kept in a wet state for a long time by the urethane prepolymer having high water retention, it takes a long time to form a film, and dust easily adheres in the film forming process.

In addition, since the dispersion medium of the aqueous emulsion-type coating composition is water, generally, the substrate surface from which the asbestos layer or asbestos has been removed (hereinafter, simply referred to as “asbestos-removed surface”).
Low wettability and permeability. For this reason, the coating formed by the aqueous emulsion-type coating composition cannot not only solidify the entire asbestos layer, but also has low adhesion to the asbestos-removed surface. Therefore, the coating may peel off from the asbestos layer or the asbestos removal surface, and the asbestos may be scattered again.

An object of the present invention is to form a polymer having a high glass transition point as a constituent component, yet have high film-forming properties, high flexibility and water resistance of a film, and excellent permeability and adhesion to an asbestos layer and an asbestos-removed surface. The object of the present invention is to provide a coating composition for preventing asbestos scattering which can prevent asbestos from scattering.

Another object of the present invention is to provide a coating composition for preventing asbestos scattering which can form a coating film having even better adhesion, water resistance and flexibility.

Still another object of the present invention is to provide a method for producing a coating composition for asbestos scattering prevention having the above-mentioned excellent properties.

[Constitution of the Invention] As a result of intensive studies, the present inventors include polymer particles having a core / shell structure having a core made of a polymer having a low glass transition point and an outermost layer of a shell made of a polymer having a high glass transition point. The addition of an organic solvent to an aqueous emulsion has been found to be excellent in film-forming properties, water resistance and flexibility of a coating film, excellent permeability and adhesion to an asbestos layer and a surface from which the asbestos layer has been removed, and can prevent asbestos from being scattered. did. That is, the present invention is an aqueous emulsion-type coating composition containing polymer particles composed of a core and a shell composed of at least one layer covering the core, wherein the core has a glass transition point of 20 ° C. or lower. Wherein the outermost layer of the shell is formed of a polymer having a glass transition point of higher than 20 ° C. and contains an organic solvent.

Further, the present invention is a method of multiply emulsion-polymerizing monomers having different compositions in an aqueous medium and adding at least an organic solvent to the obtained aqueous emulsion, wherein a polymer having a glass transition point of 20 ° C. or lower is formed. At least one type of monomer is emulsion-polymerized, and in the presence of the obtained polymer emulsion, at least in the final stage of emulsion polymerization, the glass transition point is
Provided is a method for producing a coating composition for asbestos scattering prevention by emulsion polymerization of at least one monomer constituting a polymer having a temperature exceeding 20 ° C.

The aqueous emulsion contained in the coating composition of the present invention,
A multilayer emulsion containing multilayer polymer particles composed of a core and a shell made of at least one layer covering the core. The polymer particles of the aqueous emulsion may be any of the conventional monomers such as styrenic monomers; acrylates, methacrylates;
A monomer having a hydroxy group; a monomer having an amide group; a monomer having an amino group; a monomer having a glycidyl group; a monomer having an N-methylol group or an N-alkoxymethyl group; a vinyl monomer; .

Examples of the styrene-based monomer include styrene, α
-Methylstyrene, p-methylstyrene, m-methylstyrene, p-chlorostyrene, m-chlorostyrene, p
-Methoxystyrene and the like. A preferred styrenic monomer is styrene.

Examples of the acrylate and methacrylate include, for example, methyl acrylate, ethyl acrylate, propyl acrylate, isopropyl acrylate, butyl acrylate, isobutyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, dodecyl acrylate ,
Examples include acrylates such as stearyl acrylate, α-chloroethyl acrylate, cyclohexyl acrylate, phenyl acrylate, methoxyethyl acrylate, ethoxyethyl acrylate, methoxypropyl acrylate, and ethoxypropyl acrylate, and corresponding methacrylates. Preferred acrylates and methacrylates are methyl acrylate, ethyl acrylate, butyl acrylate, acrylate-2-
Ethylhexyl and the corresponding methacrylate.

Examples of the acidic monomer include a monomer having a carboxyl group such as acrylic acid, methacrylic acid, crotonic acid, itaconic acid, itaconic acid half ester, maleic acid, and maleic acid half ester, and a monomer having a sulfonic acid group. Preferred acidic monomers are acrylic acid and methacrylic acid.

Examples of the monomer having a hydroxy group include, for example, 2
-Hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, allyl alcohol, monoacrylates of polyhydric alcohols, polyhydric alcohols And the like.

Examples of the monomer having an amide group include acrylamide, methacrylamide, and maleamide. A preferred monomer having an amide group is acrylamide.

Examples of the monomer having an amino group include 2-aminoethyl acrylate, 3-aminopropyl acrylate, dimethylaminoethyl acrylate, 2-butylaminoethyl acrylate, methacrylate and vinylpyridine corresponding thereto.

Examples of the monomer having a glycidyl group include, for example, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, monomers and oligomers obtained by reacting an epoxy compound having two or more glycidyl groups with a monomer having an active hydrogen atom. Can be Examples of the monomer having an active hydrogen atom include the above-mentioned acidic monomer, a monomer having a hydroxy group, and a monomer having an amino group. Preferred monomers having a glycidyl group are glycidyl acrylate and glycidyl methacrylate.

Examples of the monomer having an N-methylol group or an N-alkoxymethyl group include N-methylol acrylamide,
Examples include N-methoxymethylacrylamide, N-ethoxymethylacrylamide, N-propoxymethylacrylamide, N-isopropoxymethylacrylamide, N-butoxymethylacrylamide, and methacrylamide corresponding thereto. Among these, a preferred monomer is N-methylolacrylamide.

Examples of the vinyl monomer include a vinyl monomer generically referred to as VeoVa such as vinyl acetate, vinyl chloride, vinyl caproate, vinyl propionate, and vinyl versatate, and methyl vinyl ketone. Preferred vinyl monomers are vinyl acetate and VeoVa.

Examples of the other monomers include ethylene, butadiene, isoprene, chloroprene, acrylonitrile, methacrylonitrile, crotonaldehyde, diethyl fumarate, dipropyl fumarate, dibutyl fumarate, and di (2-ethylhexyl) fumarate. Among these, preferred monomers are acrylonitrile and dialkyl fumarate.

The core of the polymer particles in the aqueous emulsion is formed of a polymer having a glass transition point of 20 ° C. or lower, preferably −80 to 20 ° C., and more preferably about −50 to 0 ° C. The outermost layer of the shell is formed of a polymer having a glass transition point of more than 20 ° C, preferably a polymer having a glass transition point of 40 to 130 ° C, and more preferably about 50 to 110 ° C.
When the shell is formed of a multilayer polymer,
The glass transition point of the polymer layer interposed between the core and the outermost layer of the shell is not particularly limited, and is, for example, about -50 to 110 ° C. Further, when the shell has such a structure, the composition of the polymer layer interposed between the core and the outermost layer of the shell may be continuously changed,
The outermost layer of the shell may be formed of a polymer having a composition that varies continuously from the intervening polymer layer.

The core and shell can easily adjust the glass transition point,
It is preferably formed of an acrylic polymer or a styrene-acrylic polymer from which an emulsion having a multilayer structure can be easily prepared.

The core and shell having the glass transition point can be formed by emulsion polymerization using one or two or more monomers in combination. In combining the monomers, usually at least one hard component monomer and at least one soft component monomer are used. Examples of the hard component monomer include monomers constituting a homopolymer having a glass transition point of 70 ° C. or higher, such as acrylonitrile, methyl methacrylate, t-butyl methacrylate, and styrene. As the soft component monomer, a monomer constituting a homopolymer having a glass transition point of 0 ° C. or lower,
For example, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate and the like can be mentioned.

When a core is formed by combining a plurality of monomers, the ratio of the hard component monomer to the soft component monomer is, for example, about 10 to 60% by weight of the hard component monomer and about 90 to 40% by weight of the soft component monomer. If the amount of the hard component monomer is less than 10% by weight, the water resistance of the coating tends to decrease, and
If the amount is more than 10% by weight, the flexibility of the coating tends to decrease.

When the outermost layer of the shell is formed by combining a plurality of monomers, the ratio of the hard component monomer to the soft component monomer is, for example, about 60 to 100% by weight of the hard component monomer and about 40 to 0% by weight of the soft component monomer. It is.
If the amount of the hard component monomer is less than 60% by weight, the water resistance and adhesion of the coating are likely to be reduced.

The monomer may be selected based on the actually measured glass transition point, or may be selected based on the glass transition point estimated by the following Tobolsky formula.

1 / Tg = Wa / Tga + Wb / Tgb + ... [wherein, Tg: glass transition point of copolymer (K) Tga: glass transition point of homopolymer of monomer a (K) Tgb: glass transition point of homopolymer of monomer b Point (K) Wa: weight fraction of monomer a Wb: weight fraction of monomer b] In order to improve the adhesion, water resistance and flexibility of the coating,
The polymer forming at least the outermost layer of the shell preferably has a crosslinkable functional group. More preferably, both polymers constituting the core and the shell have a crosslinkable functional group. The crosslinkable functional group can be introduced by copolymerizing a monomer having a crosslinkable functional group with the monomer. The amount of the monomer having a crosslinkable functional group is about 0.1 to 20% by weight, preferably about 0.5 to 15% by weight, based on the total amount of the constituent monomers of the core and / or shell. If the amount of the monomer having a crosslinkable functional group is less than 0.1% by weight, the water resistance and the like of the formed film are not significantly improved, and if it exceeds 20% by weight, the film becomes hard.

The type of the monomer having a crosslinkable functional group is not particularly limited as long as it can constitute a crosslinkable system. Preferred monomers having a functional group are monomers forming a self-crosslinking polymer, for example, (1) a combination of at least a monomer having a glycidyl group and a monomer having an active hydrogen atom, and (2) at least an N-methylol group. Or a monomer having an N-alkoxymethyl group. Examples of the monomer having an active hydrogen atom include a monomer having a carboxy group, a hydroxy group, an amide group, or an amino group.

Monomers that form self-crosslinking polymers include N-
Methylol acrylamide; a combination of glycidyl acrylate or glycidyl methacrylate with a monomer having a carboxy group and a monomer having a hydroxy group is preferred.

Further, in order to enhance the stability of the emulsion, it is preferable that 0.2 to 8% by weight of an acidic monomer is copolymerized with respect to at least the outermost layer of the shell, preferably the total amount of the constituent monomers of both the core and / or the shell.

The emulsion containing the polymer particles having the above structure is obtained by emulsion polymerization of at least one monomer constituting a polymer having a glass transition point of 20 ° C. or lower in an aqueous medium, for example, in a multistage polymerization method in which monomers having different compositions are emulsion-polymerized. Then, in the presence of the obtained polymer emulsion, at least at the final stage of emulsion polymerization, it can be prepared by emulsion polymerization of at least one monomer constituting a polymer having a glass transition point exceeding 20 ° C.

More specifically, for example, when producing an emulsion containing a polymer particle having a two-layer structure composed of a core and a shell composed of one layer, first, at least one type of monomer constituting the core is: It can be prepared by a two-stage polymerization method in which emulsion polymerization is carried out in an aqueous medium, and in the presence of the obtained polymer emulsion, at least one monomer constituting the shell is added and emulsion polymerization is carried out. In the case of producing an emulsion containing polymer particles having a multilayer structure, a core is formed in the same manner as described above, and in the presence of the obtained polymer emulsion, monomers having different compositions are sequentially fed stepwise to emulsion polymerization. Then, at the final stage of the emulsion polymerization, it can be prepared by a multi-stage polymerization method in which at least one monomer constituting the outermost layer of the shell is fed and emulsion polymerization is performed. Further, the emulsion containing the polymer particles having a continuous layer structure,
For example, after forming a core in the same manner as described above, feed is performed while continuously changing the monomer composition in the presence of the obtained polymer emulsion so that the monomer composition finally constitutes the outermost layer of the shell. And can be prepared by a power feed polymerization method.

In the emulsion polymerization, conventional components, for example, anionic surfactants, nonionic surfactants, cationic surfactants, surfactants such as amphoteric surfactants, and water-soluble polymers, water-soluble oligomers and the like At least one emulsifier selected from protective colloids; a buffer; a polymerization initiator; a chain transfer agent, and the like can be used.

By adding at least an organic solvent to the aqueous emulsion obtained as described above, the coating composition for asbestos scattering prevention of the present invention can be obtained.

Organic solvents include conventional solvents, for example, aromatic solvents such as benzene, toluene and xylene; alicyclic solvents such as cyclohexane; aliphatic solvents such as hexane; methyl alcohol, ethyl alcohol, isopropyl alcohol and the like. Alcohols; polyhydric alcohols such as ethylene glycol and acetylene glycol; methyl cellosolve;
Cellosolve solvents such as ethyl cellosolve and butyl cellosolve; esters such as ethyl acetate and butyl acetate; ketones such as acetone and methyl ethyl ketone; mixed solvents thereof.

By adding an organic solvent, not only can the polymer having a high glass transition point be used as a constituent polymer, but not only the film-forming properties, and thus the water resistance and flexibility, can be improved,
The permeability and adhesion of the coating composition to the asbestos layer and the asbestos-removed surface can be increased. The amount of the organic solvent to be added is 1 to 20 parts by weight, preferably about 2.5 to 15 parts by weight, based on 100 parts by weight of the solid content of the aqueous emulsion. When the amount of the organic solvent is less than 1 part by weight, the permeability and adhesion to the asbestos layer and the asbestos-removed surface decrease, and when the amount exceeds 20 parts by weight, the odor becomes strong or the emulsion becomes unstable. May be impaired.

The asbestos scattering prevention paint composition of the present invention may contain, if necessary, conventional additives such as a plasticizer, a colorant, a rust inhibitor, a dispersant, a defoamer, a thickener, a neutralizer, and a preservative. Agents, antifreezing agents and the like.

The amount of the plasticizer to be added is usually the solid content of the aqueous emulsion.
0 to 15 parts by weight, preferably about 1 to 10 parts by weight, per 100 parts by weight. By adding this plasticizer, the film forming property and plasticity can be improved even if the polymer constituting the shell has a high glass transition point. As a plasticizer,
For example, phthalic acid esters such as dibutyl phthalate and dioctyl phthalate, phosphoric acid esters such as trichlorophosphate, and 2,2,4-trimethylpentanediol-1 are used.

As the colorant, organic and inorganic dyes and pigments are used. The addition amount is usually 0 to 40 parts by weight, preferably 2 to 30 parts by weight based on 100 parts by weight of the solid content of the aqueous emulsion.
It is about parts by weight.

The amount of rust inhibitor added is usually the solid content of the aqueous emulsion.
0 to 50 parts by weight, preferably about 0.1 to 2 parts by weight, per 100 parts by weight. Addition of a rust inhibitor can prevent corrosion of reinforcing bars and the like exposed on the asbestos-removed surface.

The amount of the dispersant added is usually the solid content of the aqueous emulsion.
0 to 10 parts by weight, preferably about 0.5 to 5 parts by weight, per 100 parts by weight.

The order and method of adding these additives are not particularly limited, but the colorant can be added by dispersing in advance with a dispersant such as a water-soluble polymer or a surfactant.

The coating composition of the present invention prevents scattering of asbestos by directly applying to the asbestos layer and the asbestos removal surface. The application of the coating composition can be performed by a usual application method, for example, means such as spraying, brushing, and roller brushing. When the polymer particles in the aqueous emulsion have a crosslinkable functional group, they can be cured after application to form a film having excellent water resistance, flexibility, adhesion and the like. In the case of using an emulsion containing the self-crosslinkable polymer particles, particularly a room temperature-curable emulsion, the coating may be cured without heating.

The coating composition for asbestos scattering prevention of the present invention can be applied to an asbestos layer or an asbestos-removed surface such as a ceiling of a gymnasium, a ceiling of an auditorium, and a wall.

[Effects of the Invention] The coating composition for preventing asbestos scattering of the present invention contains an emulsion containing polymer particles of a specific structure and an organic solvent, so that a film having a high glass transition point is used as a constituent component while forming a film. It has high properties, high plasticity and water resistance of the coating, and has excellent permeability and adhesion to the asbestos layer and the asbestos-removed surface, and can prevent asbestos from scattering.

Further, when the polymer particles in the aqueous emulsion have a crosslinkable functional group, a coating film having more excellent adhesion, water resistance and flexibility can be formed.

Further, according to the production method of the present invention, a coating composition for asbestos scattering prevention having the above-mentioned excellent properties can be obtained.

EXAMPLES Hereinafter, the present invention will be described in more detail based on examples.

Example 1 In a flask containing 26 parts by weight of water, 20 parts by weight of water, 1 part by weight of polyoxyethylene nonylphenyl ether, 3 parts by weight of polyoxyethylene lauryl sulfate, 9 parts by weight of styrene, 21 parts by weight of butyl acrylate, An emulsion obtained by mixing 1 part by weight of glycidyl methacrylate and 0.3 part by weight of methacrylic acid, and a polymerization initiator aqueous solution consisting of 4 parts by weight of water and 0.2 part by weight of potassium persulfate were mixed in a nitrogen gas atmosphere.
Emulsion polymerization was carried out at 85 ° C. for 3 hours while sequentially adding to obtain a polymer emulsion. The glass transition point of the polymer in the emulsion is -20C.

The obtained polymer emulsion was heated to 90 ° C., and then a monomer mixture for forming a polymer having a glass transition point of 98 ° C., ie, 11 parts by weight of styrene, 1 part by weight of glycidyl methacrylate, and 0.7 part by weight of methacrylic acid was used. While successively adding a monomer mixture solution in a nitrogen gas atmosphere,
Emulsion polymerization was carried out for 2 hours to obtain an aqueous emulsion.

The solid content of the obtained aqueous emulsion was about 46% by weight, the viscosity was about 200 cps, and the pH was 9.0.

For 100 parts by weight of the solid content of this aqueous emulsion,
5 parts by weight of butyl cellosolve acetate as an organic solvent,
2 parts by weight of dibutyl phthalate as a plasticizer, 15 parts by weight of titanium dioxide as a coloring pigment, 1 part by weight of sodium hexametaphosphate as a rust inhibitor, 1 part by weight of sodium tripolyphosphate as a dispersant, 0.1 part by weight of an antifoaming agent, a thickener 0.1 parts by weight of hydroxyethyl cellulose, aqueous ammonia 0.1
Parts by weight, 0.1 part by weight of formalin as a preservative, and 1 part by weight of ethylene glycol as an antifreeze were added and mixed to obtain a coating composition for preventing asbestos scattering.

Examples 2 to 4 Asbestos scattering prevention coating compositions were obtained in the same manner as in Example 1 except that the organic solvents shown in the table were used instead of butyl cellosolve acetate.

Comparative Example 1 A coating composition for asbestos scattering prevention was obtained in the same manner as in Example 1 without adding an organic solvent.

Comparative Examples 2 and 3 Emulsions of all monomers used in Example 1 (20 parts by weight of water, 1 part by weight of polyoxyethylene nonylphenyl ether, 3 parts by weight of polyoxyethylene lauryl sulfate) were placed in a flask containing 26 parts by weight of water. Parts, 20 parts by weight of styrene, 21 parts by weight of butyl acrylate, 2 parts by weight of glycidyl methacrylate, and 1 part by weight of methacrylic acid), and a polymerization initiator aqueous solution comprising 4 parts by weight of water and 0.2 part by weight of potassium persulfate. Emulsion polymerization was carried out at 85 ° C. for 5 hours while sequentially adding in a nitrogen gas atmosphere to prepare an aqueous emulsion.

A coating composition for asbestos scattering prevention was obtained in the same manner as in Example 1 except that the amount of butyl cellosolve acetate shown in the table was added to the obtained aqueous emulsion.

The adhesion and stability of the coating compositions obtained in Examples and Comparative Examples were evaluated by the following methods.

Adhesion The coating composition obtained in each of Examples and Comparative Examples was spray-coated on a concrete plate so as to be 0.3 kg / m ² in a wet state, and then naturally dried at room temperature for 7 days. A peel test was performed in which the adhesive surface of the cloth adhesive tape was adhered to the coating, and the cloth adhesive tape was peeled off. From the peeling state of the coating, the adhesion was evaluated according to the following criteria.

Excellent: No peeling at all Good: Less than 5% peeling off Acceptable: 5 to 30% peeling off Impossible: Peeling off at least 30% Stability 200g of the paint composition packed in a glass bottle is kept at a constant temperature of 60 ° C It was left in a bath for 7 days and examined for high-temperature stability. The state of the composition after standing was observed, and its stability was evaluated based on the following criteria.

 Excellent: No change was observed in the composition. Good: Viscosity of the composition changed slightly. Bad: The composition gelled. The results are shown in the table.

As can be seen from the table, the coating composition for asbestos scattering prevention of the present invention is superior to the coating composition of the comparative example in adhesion and high-temperature stability.

Incidentally, the coating composition for asbestos scattering prevention of the present invention,
Despite using a polymer having a high glass transition point as a constituent polymer, the film was excellent in film-forming properties, water resistance and flexibility of the film, and the film was not contaminated by dust.

Claims (4)

(57) [Claims] 1. An aqueous emulsion-type coating composition comprising polymer particles composed of a core and a shell comprising at least one layer, wherein the core has a glass transition point of 20 ° C.
An asbestos scattering prevention coating composition formed of the following polymer, wherein the outermost layer of the shell is formed of a polymer having a glass transition point of higher than 20 ° C., and contains an organic solvent. 2. The coating composition according to claim 1, wherein at least the outermost layer of the shell has a crosslinkable functional group. 3. The coating composition for asbestos scattering prevention according to claim 1, which comprises 1 to 20 parts by weight of an organic solvent based on 100 parts by weight of the solid content of the aqueous emulsion. 4. A method in which monomers having different compositions are emulsion-polymerized in an aqueous medium in a multistage manner, and at least an organic solvent is added to the obtained aqueous emulsion, wherein the glass transition point is 20 ° C.
Emulsion polymerization of at least one monomer constituting the following polymer, and in the presence of the obtained polymer emulsion, at least in the final stage of emulsion polymerization, at least one monomer constituting a polymer having a glass transition point exceeding 20 ° C. A method for producing a coating composition for preventing asbestos scattering which undergoes emulsion polymerization.