JP2008163349A - Emulsion for vibration damper - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means to improve drying properties of a coating film formed as a vibration damper and to suppress cracking or expansion on the surface of the coating film. <P>SOLUTION: The emulsion for the vibration damper comprises particles comprising an acrylic copolymer (A) forming a core part and an acrylic copolymer (B) as a shell part coating the above core part, in which the acrylic copolymer (B) has a glass transition temperature of ≥-9°C and the glass transition temperature difference between the acrylic copolymer (B) and the acrylic copolymer (A) is ≥20°C. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an emulsion used for forming a vibration damping material. The emulsion of the present invention can be applied to members that require vibration damping properties such as vehicle chassis.

  In order to keep the place where vibration is transmitted quietly, a damping material that absorbs sound energy is used. For example, a vibration damping material disposed in a chassis of an automobile reduces vibration transmitted from a road surface or an engine, and improves the environment in the passenger compartment.

  As a material used for the damping material, rubber latex and acrylic copolymer have been proposed. In a device such as a vehicle that is used under a wide range of temperatures from below freezing to several tens of degrees, the function as a damping material needs to be manifested in a wide temperature range. As a technology to meet such a demand, for a damping material containing core-shell type particles having a core part made of an acrylic copolymer and a shell part made of an acrylic copolymer covering the core part. Emulsions have been proposed (see, for example, Patent Document 1 and Patent Document 2). The core-shell type particles have excellent vibration damping properties in a wide temperature range as compared with the case where an acrylic copolymer is used alone or when two or more kinds of acrylic copolymers are blended.

  However, when a vibration damping material is formed using an emulsion containing particles made of a polymer, the heat drying property of the coating film has been a problem.

  In order to act as a vibration damping material, the coating film needs to have a certain film thickness. However, when a thick coating film is dried, since there is a tendency to dry from the surface, the coating film in the vicinity of the surface is cured while the inner coating film still retains moisture. Since the coating film formed from the emulsion immediately melts to form a film when the amount of water around the particles decreases, this tendency is particularly remarkable when the coating film is formed using the emulsion.

When the moisture inside the coating film evaporates after the coating film in the vicinity of the surface is cured, there arises a problem that the coating film in the vicinity of the surface that has already been cured expands to the outside of the coating film and cracks occur in the coating film. When the coating film expands or cracks occur, the characteristics as a vibration damping material are greatly deteriorated. In this case, even if the particles contained in the emulsion are improved like the core-shell type particles, the characteristics cannot be fully utilized.
JP-A-53-78234 JP-A-5-148446

  Accordingly, an object of the present invention is to provide means for improving the drying property of a coating film formed as a vibration damping material and suppressing cracks and expansion on the coating film surface.

  An emulsion for a vibration damping material, comprising particles having a core part made of an acrylic copolymer (A) and a shell part made of an acrylic copolymer (B) covering the core part, wherein the acrylic copolymer The glass transition temperature of the union (B) is −9 ° C. or higher, and the difference between the glass transition temperature of the acrylic copolymer (B) and the glass transition temperature of the acrylic copolymer (A) is 20 It is an emulsion for vibration damping materials having a temperature of ℃ or higher.

  The coating film formed using the emulsion for vibration damping materials of the present invention is excellent in drying property, and the occurrence of cracks and expansion of the coating film during drying are suppressed. For this reason, the damping material which can be utilized in a wide temperature range in which the effect of the core-shell type particles is fully utilized is formed.

  The inventors improve the drying property of the coating film by controlling the glass transition temperature (hereinafter referred to as “Tg”) in the core-shell type particles blended in the emulsion for vibration damping materials. I found out.

  The emulsion for a vibration damping material of the present invention includes core-shell type particles having different Tg. In this particle, the difference between the Tg of the acrylic copolymer (B) constituting the shell portion and the Tg of the acrylic copolymer (A) constituting the core portion is 20 ° C. or more. Moreover, predetermined conditions are satisfy | filled about the range of Tg of the acrylic copolymer (B) which comprises a shell part. If the Tg of the acrylic copolymer (A) constituting the core part and the Tg of the acrylic copolymer (B) constituting the shell part satisfy the conditions defined in the present invention, the detailed mechanism is not clear. Although not, curing of the coating film surface during drying is suppressed. For this reason, the expansion | swelling and crack of a coating-film surface which are easy to generate | occur | produce when the water | moisture content inside a coating-film evaporates from the coating-film surface are suppressed.

  Further, when the core portion of low Tg and the shell portion of high Tg are compatible at the time of heat drying, particles having both high strength and flexibility having a Tg gradient from the inside to the outside are formed, Generation | occurrence | production of the crack in the coating-film surface and the fall of adhesiveness can also be suppressed.

  First, the components of the emulsion for vibration damping material of the present invention will be described.

  The emulsion of the present invention includes at least a medium and core-shell type particles dispersed in the medium.

  As the medium, an aqueous medium is usually used. Examples of the aqueous medium include water and a mixed solution of water and a solvent mixed with water. In consideration of safety and environmental impact when applying a paint containing an emulsion, water is preferable as the aqueous medium.

  The core-shell type particles are particles having a core part made of an acrylic copolymer (A) and a shell part made of an acrylic copolymer (B) covering the core part.

“Acrylic copolymer” is a copolymer composed of two or more monomer units, in which at least one of the monomer units is a copolymer derived from acrylic acid, methacrylic acid, a salt thereof, or an esterified product thereof. Refers to coalescence. That is, at least one monomer _{unit, CH 2 = CH-COOR '} , or _CH 2 ₌ C (CH 3) refers to a copolymer derived from a monomer represented by -COOR ". Here, R' and R "Is a hydrogen atom, an alkali metal atom, or a linear, branched or cyclic alkyl group. The other monomer units are selected from compounds copolymerizable with these compounds.

  Tg of the acrylic copolymer (A) constituting the core part is 20 ° C. or higher or 20 ° C. or higher higher than Tg of the acrylic copolymer (B) constituting the shell part. Thus, by providing a difference in Tg between the acrylic copolymer (A) and the acrylic copolymer (B), high vibration damping properties are exhibited in a wide temperature range.

  The monomer unit constituting the acrylic copolymer (A) is not particularly limited as long as the Tg of the acrylic copolymer (A) falls within the range defined in the present invention and can be used as a vibration damping material.

  As the monomer used for the synthesis of the acrylic copolymer (A), the following compounds may be used. However, the monomer as a raw material of the acrylic copolymer (A) is not limited to the compounds exemplified below.

  Acrylic acid, methacrylic acid, crotonic acid, citraconic acid, itaconic acid, maleic acid, maleic anhydride, fumaric acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl Acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, pentyl acrylate, pentyl methacrylate, isoamyl acrylate, isoamyl methacrylate, hexyl acrylate, hexyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, octyl acrylate, octyl acrylate Methacrylate, isooctyl acrylate, isooctyl methacrylate, nonyl acrylate, nonyl methacrylate, isononyl acrylate, isononyl methacrylate, decyl acrylate, decyl methacrylate, dodecyl acrylate, dodecyl methacrylate, tridecyl acrylate, tridecyl methacrylate, hexadecyl acrylate, hexa Decyl methacrylate, octadecyl acrylate, octadecyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, styrene, α-methylstyrene, vinyl toluene, ethyl vinyl benzene, acrylonitrile, methacrylonitrile, vinyl formate, vinyl acetate, vinyl propionate, acrylamide , Methacrylamide, diace Tonacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, divinylbenzene, diallyl phthalate, triallyl cyanurate, ethylene Glycol diacrylate, ethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, diethylene glycol diacrylate, diethylene glycol Dimethacrylate, allyl acrylate, allyl methacrylate.

  The ratio of each monomer which comprises an acrylic copolymer (A) is not specifically limited. Usually, 30 to 60% by mass of monomer units derived from acrylic acid, methacrylic acid, a salt thereof, or an esterified product thereof is contained based on the total of each monomer unit. In addition, mass% here means the average value of the particle | grains contained in an emulsion.

  The Tg of the acrylic copolymer to be synthesized may be determined based on the knowledge already obtained, or may be controlled by the type and use ratio of the monomer unit. The Tg of the acrylic copolymer to be synthesized can theoretically be calculated from the following calculation formula.

Where Tg ′ is the Tg (absolute temperature) of the acrylic copolymer to be synthesized, W ₁ ′, W ₂ ′,... W _n ′ is the mass fraction of each monomer relative to the total monomer, T ₁ , T ₂ ,... T _n are glass transition temperatures (absolute temperatures) of homopolymers composed of the respective monomers.

  The acrylic copolymer (B) constituting the shell portion has a Tg of −9 ° C. or higher. When the Tg of the acrylic copolymer (B) constituting the shell satisfies these conditions, the drying property of the coating film formed using the coating material containing the emulsion for vibration damping material of the present invention is improved, and the coating is performed. Expansion and cracks on the film surface can be suppressed. That is, a vibration damping material having excellent vibration damping properties is formed. Specifically, Tg of the acrylic copolymer (B) constituting the shell part is preferably −9 to 70 ° C., more preferably −9 to 50 ° C. The Tg of the acrylic copolymer (A) constituting the core part is designed to be different by 20 ° C. or more from the Tg of the acrylic copolymer (B) constituting the shell part.

  Moreover, the difference of Tg of the acrylic copolymer (B) which comprises a shell part, and Tg of the acrylic copolymer (A) which comprises a core part is 20 degreeC or more. By providing a difference between the Tg of the acrylic copolymer (A) constituting the core part and the Tg of the acrylic copolymer (B) constituting the shell part, a vibration damping material capable of supporting a wide temperature range is obtained. However, if the temperature difference is too large, the vibration damping property may be inferior at the actually used temperature. Considering these, the difference between the Tg of the acrylic copolymer (B) constituting the shell part and the Tg of the acrylic copolymer (A) constituting the core part is preferably 20 to 100 ° C., and more Preferably it is 20-90 degreeC, More preferably, it is 20-80 degreeC.

  The monomer unit constituting the acrylic copolymer (B) is not particularly limited as long as the Tg of the acrylic copolymer (B) falls within the range defined in the present invention and can be used as a vibration damping material. As the monomer used for the synthesis of the acrylic copolymer (B), the compounds exemplified for the acrylic copolymer (A) may be used. However, the monomer as a raw material of the acrylic copolymer (B) is not limited to the above compound.

  The ratio of each monomer constituting the acrylic copolymer (B) is not particularly limited. Usually, 40 to 70% by mass of monomer units derived from acrylic acid, methacrylic acid, a salt thereof, or an esterified product thereof is contained on the basis of the total of each monomer unit.

  The core-shell type particles have a structure in which an acrylic copolymer in the core part is coated with an acrylic copolymer in the shell part. The surface of the core part is preferably completely covered by the shell part, but in some cases, it may not be completely covered. For example, it may be a form covered with a mesh or a form in which the core is exposed in some places.

  In the core-shell type particles, the core part and the shell part may be clearly separated, but both may be mixed at the boundary between the core part and the shell part. If at least the core part existing in the center of the particle and the shell part made of an acrylic copolymer having a different Tg and an acrylic copolymer constituting the core part are present, it corresponds to a core-shell type particle. In some cases, an acrylic copolymer having a different Tg may be formed outside the shell portion. Moreover, the outer surface of the shell part may be surface-treated.

  In the core-shell type particles, there are a core portion made of an acrylic copolymer, and an acrylic copolymer constituting the core portion and a shell portion made of an acrylic copolymer having a different Tg. The mass ratio of the acrylic copolymer to the high Tg acrylic copolymer is preferably 1: 9 to 5: 5, more preferably 3: 7 to 5: 5. If the ratio of the low Tg acrylic copolymer is too small, cracks may occur after heat drying. On the other hand, when there are too many low Tg acrylic copolymers, there exists a possibility that a swelling (expansion of a coating film) may arise after heat drying.

  The average particle size of the core-shell type particles is not particularly limited, but is usually about 10 nm to 1 μm, preferably about 20 to 500 nm. If the average particle size of the emulsion is less than 10 nm, the viscosity of the emulsion becomes too high, and the dispersion stability may not be maintained and the particles may aggregate. On the other hand, when it exceeds 1 μm, it is no longer an emulsion.

  Next, the manufacturing method of the emulsion for vibration damping materials of this invention is demonstrated.

  The emulsion of the present invention can be prepared by a known emulsion polymerization method such as a seed method. For example, in the emulsion of the present invention, (1) a monomer is emulsion-polymerized in an aqueous medium in the presence of a surfactant and / or a protective colloid to form a core part composed of the acrylic copolymer (A). Step (2) The emulsion can be produced by a method comprising a step of adding a monomer to an emulsion containing a core portion and further emulsion-polymerizing it to form a shell portion comprising an acrylic copolymer (B).

  As a method for adding a monomer, a polymerization initiator and the like, a seed component method, a monomer component dropping method, a pre-emulsion method, a power feed method, a multistage addition method, and the like can be used.

  The emulsifier is not particularly limited, and various emulsifiers can be used. For example, anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, polymer surfactants, reactive surfactants thereof and the like can be used as emulsifiers. These may be used in combination.

  Examples of anionic surfactants include alkyl sulfate salts such as sodium dodecyl sulfate, potassium dodecyl sulfate, and ammonium alkyl sulfate; sodium dodecyl polyglycol ether sulfate; sodium sulforicinoate; alkyl sulfonate such as sulfonated paraffin salt; sodium dodecylbenzene Alkyl sulfonates such as sulfonates and alkali metal sulfates of alkali phenol hydroxyethylene; high alkyl naphthalene sulfonates; naphthalene sulfonic acid formalin condensates; fatty acid salts such as sodium laurate, triethanolamine oleate, triethanolamine abiates Oxyalkyl ether sulfate ester salt; Polyoxyethylene carboxylate sulfate ester Le salts; polyoxyethylene phenyl ether sulfate; dialkyl succinate sulfonate; and the like polyoxyethylene alkyl aryl sulfate salts. However, the anionic surfactant is not limited to these. Two or more anionic surfactants may be used.

  Nonionic surfactants include polyoxyethylene alkyl ethers; polyoxyethylene alkyl aryl ethers; sorbitan aliphatic esters; polyoxyethylene sorbitan aliphatic esters; aliphatic monoglycerides such as monolaurate of glycerol; polyoxyethyleneoxypropylene Copolymer; Condensation products of ethylene oxide and aliphatic amines, amides or acids are included. However, the nonionic surfactant is not limited to these. Two or more nonionic surfactants may be used.

  Cationic surfactants include dialkyldimethylammonium salts, ester-type dialkylammonium salts, amide-type dialkylammonium salts, dialkylimidazolinium salts, and the like. However, the cationic surfactant is not limited to these. Two or more cationic surfactants may be used.

  Amphoteric surfactants include alkyldimethylaminoacetic acid betaines, alkyldimethylamine oxides, alkylcarboxymethylhydroxyethyl imidazolinium betaines, alkylamidopropyl betaines, alkylhydroxysulfobetaines, and the like. However, the amphoteric surfactant is not limited to these. Two or more amphoteric surfactants may be used.

  Polymeric surfactants include polyvinyl alcohol and modified products thereof; (meth) acrylic acid-based water-soluble polymers; hydroxyethyl (meth) acrylic acid-based water-soluble polymers; hydroxypropyl (meth) acrylic acid-based water-soluble polymers Molecule; polyvinylpyrrolidone and the like are included. However, the polymer surfactant is not limited to these. Two or more kinds of polymer surfactants may be used.

  Among the emulsifiers, it is preferable to use a reactive emulsifier. From the environmental viewpoint, it is preferable to use a non-nonylphenyl emulsifier. In some cases, two or more emulsifiers may be used.

  The usage-amount of an emulsifier is adjusted according to the kind of emulsifier to be used, the kind of monomer, etc. In general, the amount of emulsifier used is about 0.3 to about 10 parts by weight, preferably about 0.5 to about 5 parts by weight, based on 100 parts by weight of the total amount of monomers used to form the acrylic copolymer. It is.

  Examples of protective colloids include polyvinyl alcohols such as partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, and modified polyvinyl alcohol; cellulose derivatives such as hydroxyethyl cellulose, hydroxypropyl cellulose, and carboxymethyl cellulose salt; natural polysaccharides such as guar gum; Etc.

  The protective colloid may be used alone or in combination with an emulsifier. The amount of the protective colloid used is usually 0 to about 3 parts by mass with respect to a total of 100 parts by mass of monomers used to form the acrylic copolymer, although it depends on the conditions of use.

  A polymerization initiator can be used to initiate the emulsion polymerization. The polymerization initiator is not particularly limited as long as it is a substance that decomposes by heat and generates radical molecules. In emulsion polymerization, a water-soluble initiator is preferably used. Examples of the polymerization initiator include persulfates such as potassium persulfate, ammonium persulfate, and sodium persulfate; 2,2′-azobis (2-amidinopropane) dihydrochloride, 4,4′-azobis (4-cyanopentanoic acid) Water-soluble azo compounds such as hydrogen peroxide; thermal decomposition initiators such as hydrogen peroxide; hydrogen peroxide and ascorbic acid, t-butyl hydroperoxide and rongalite, potassium persulfate and metal salts, ammonium persulfate and sodium bisulfite, etc. Redox polymerization initiators and the like are included. However, the polymerization initiator is not limited to these. Two or more polymerization initiators may be used.

  The usage-amount of a polymerization initiator is not specifically limited, What is necessary is just to set suitably according to the kind etc. of polymerization initiator. For example, when the total amount of all monomers is 100 parts by mass, it is preferably 0.1 to 2 parts by mass, more preferably 0.2 to 1 part by mass.

  In the emulsion polymerization, a reducing agent may be used in combination as necessary. Examples of the reducing agent that can be used include reducing organic compounds such as ascorbic acid, tartaric acid, citric acid, and glucose; for example, reducing inorganic compounds such as sodium thiosulfate, sodium sulfite, sodium bisulfite, and sodium metabisulfite. Can be mentioned.

  The amount of the reducing agent to be used is not particularly limited, but is usually about 0.05 to about 1 part by mass with respect to 100 parts by mass in total of the monomers used to form the acrylic copolymer.

  In the emulsion polymerization, a chain transfer agent may be used in an amount of 0.001 to 2 parts by mass per 100 parts by mass of the monomer in order to reduce the molecular weight. Chain transfer agents include halogen-substituted alkanes such as carbon tetrachloride, bromoform, bromotrichloroethane; alkyl mercaptans such as n-dodecyl mercaptan, tert-dodecyl mercaptan, octyl mercaptan, tetradecyl mercaptan, hexadecyl mercaptan; butyl thioglycolate, Examples include thioesters such as alkyl monothioglycolate such as isooctyl thioglycolate and dodecyl thioglycolate; alcohols such as methanol, ethanol and isopropanol; α-methylstyrene dimer, terpinol, terpinene and dipentene. However, the chain transfer agent is not limited to these. Two or more chain transfer agents may be used.

  The polymerization temperature in emulsion polymerization is not particularly limited. The polymerization temperature is preferably 0 to 100 ° C, more preferably 40 to 95 ° C. The polymerization time is not particularly limited. The polymerization time is usually 1 to 15 hours.

  The core part and the shell part can be basically formed by the same operation, but the additives and conditions to be used can be used as needed. For example, in the emulsion polymerization for forming the shell portion, it is not necessary to add a surfactant and / or a protective colloid.

  The nonvolatile content in the emulsion obtained after the emulsion polymerization reaction, that is, the core-shell type particles is preferably 60% by mass or less. When the non-volatile content exceeds 60% by mass, the viscosity of the emulsion is too high, so that the dispersion stability cannot be maintained and aggregation may occur.

  The pH of the emulsion is not particularly limited, but is usually in the range of 2 to 10, preferably 2 to 8. The pH of the emulsion can be adjusted by adding ammonia water, water-soluble amines, alkaline hydroxide aqueous solution and the like to the emulsion.

  The viscosity of the emulsion is usually in the range of about 10 to 10000 mPa · s, preferably about 50 to 5000 mPa · s. The viscosity can be measured using a B-type rotational viscometer under predetermined conditions such as 25 ° C. and 20 rpm.

  As shown in the Examples, the emulsion for vibration damping materials of the present invention is blended with other components to form a vibration damping composition, for example, a water-based coating composition for vibration damping materials. Other components blended in the vibration damping composition include: solvent; plasticizer; stabilizer; thickener; wetting agent; antiseptic agent; antifoaming agent; inorganic filler; coloring agent; Examples thereof include pigments, antifoaming agents, anti-aging agents, antifungal agents, ultraviolet absorbers, and antistatic agents. Preferably, the composition for damping material includes at least the emulsion for damping material of the present invention and an inorganic filler. That is, the vibration damping composition of the present invention is a water-based vibration damping composition obtained by mixing the vibration damping emulsion of the present invention and an inorganic filler. The emulsion for vibration damping materials, the inorganic filler, and other components blended as necessary can be mixed using, for example, a butterfly mixer, a planetary mixer, a spiral mixer, a kneader, a dissolver, and the like.

  These blends can be appropriately selected from known materials. For example, examples of the solvent include ethylene glycol, butyl cellosolve, butyl carbitol, and butyl carbitol acetate. Examples of the thickener include polyvinyl alcohol, cellulose derivatives, and polycarboxylic acid resins. Inorganic fillers include calcium carbonate, kaolin, silica, talc, barium sulfate, alumina, iron oxide, titanium oxide, glass talk, magnesium carbonate, aluminum hydroxide, talc, diatomaceous earth, clay, etc .; glass flakes And flaky inorganic fillers such as mica; fibrous inorganic fillers such as metal oxide whiskers and glass fibers. Examples of the colorant include organic or inorganic colorants such as titanium oxide, carbon black, dial, hansa yellow, benzine yellow, phthalocyanine blue, and quinacridone red. Examples of the dispersant include inorganic dispersants such as sodium hexametaphosphate and sodium tripolyphosphate, and organic dispersants such as polycarboxylic acid-based dispersants. Examples of the rust preventive pigment include a metal phosphate, a metal molybdate, and a metal borate. Examples of the antifoaming agent include silicon-based antifoaming agents.

  The composition for damping material preferably contains a solid content in the range of about 40 to 90% by mass, more preferably about 50 to 85% by mass, and still more preferably about 60 to 80% by mass. Moreover, the pH of the composition for vibration damping materials is preferably within the range of 7 to 11, more preferably 8 to 10.

  The compounding quantity of each component in the composition for vibration damping materials is not particularly limited. Usually used amounts are formulated taking into account the properties obtained. For example, the blending amount of the damping material emulsion is preferably 10 to 60 parts by weight, more preferably 15 to 55 parts by weight, and more preferably 15 to 55 parts by weight with respect to 100 parts by weight of the solid content of the damping material composition. Preferably it is 20-50 mass parts. The blending amount of the thickener is a solid content, preferably 0.01 to 2 parts by mass, more preferably 0.05 to 1.5 parts by mass with respect to 100 parts by mass of the solid content of the vibration damping composition. More preferably, it is 0.1 to 1 part by mass. The blending amount of the inorganic filler is preferably 40 to 90 parts by mass, more preferably 45 to 85 parts by mass, and further preferably 50 to 80 parts by mass with respect to 100 parts by mass of the solid content of the vibration damping composition. is there. However, the blending amount is not limited to this range.

  The composition for damping material may contain a polyvalent metal compound. By the polyvalent metal compound, stability, dispersibility, heat drying property of the vibration damping composition, and vibration damping of the vibration damping material formed from the vibration damping composition are improved. The polyvalent metal compound is not particularly limited, and examples thereof include zinc oxide, zinc chloride, and zinc sulfate. Two or more of these may be used in combination.

  The form of the polyvalent metal compound is not particularly limited, and may be, for example, a powder, an aqueous dispersion, an emulsion dispersion, or the like. In these, since the dispersibility in the composition for damping materials improves, it uses preferably in the form of an aqueous dispersion or an emulsified dispersion, More preferably, an emulsified dispersion. Moreover, the usage-amount of a polyvalent metal compound becomes like this. Preferably it is 0.05-5.0 mass parts with respect to 100 mass parts of solid content in the composition for damping materials, More preferably, it is 0.05-3. .5 parts by mass.

  When the vibration damping composition is applied to the substrate and dried, a coating film that acts as a vibration damping material is formed. The substrate is not particularly limited. In addition, a brush, a spatula, an air spray, an airless spray, a mortar gun, a ricin gun, or the like can be used to apply the vibration damping composition to the substrate.

  The composition for vibration damping materials prepared using the emulsion for vibration damping materials of the present invention is applied to the interior floors of automobiles, railway vehicles, ships, aircraft, electrical equipment, building structures, construction equipment, and the like. However, it is not limited to these.

  The coating amount of the damping material composition is set depending on the application, desired performance, and the like. Specifically, the thickness of the coating film when dried is preferably 0.5 to 5.0 mm, more preferably 1.5 to 4.5 mm. A coating film formed by applying the vibration damping composition prepared using the emulsion of the present invention is less likely to expand or crack when dried. For this reason, even if it is thickly coated, problems are unlikely to occur.

  In order to form a film by applying the vibration damping coating material, the film may be dried by heating or may be dried at room temperature. Heat drying is preferable from the viewpoint of efficiency. Even if the damping material coating formed using the damping material composition of the present invention is forcibly heated and dried, the coating material is excellent in drying properties, so that expansion and cracking are unlikely to occur. For this reason, it is particularly beneficial when heat drying is used. The temperature for heat drying is preferably 80 to 210 ° C, more preferably 110 to 160 ° C.

  The effects of the present invention will be described using examples and comparative examples. Unless otherwise specified, in the following examples, “%” and “part” mean “% by mass” and “part by mass”, respectively.

<Example 1>
Deionized water (170.5 parts) was charged into a polymerization vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen inlet tube and a dropping funnel. Thereafter, the internal temperature was raised to 70 ° C. while stirring under a nitrogen gas stream. Meanwhile, in the dropping funnel, methyl methacrylate (25 parts), styrene (111.5 parts), 2-ethylhexyl acrylate (108.5 parts), acrylic acid (2.5 parts), glycidyl methacrylate (2.5 parts) , A sulfate ester salt of polyoxyethylene alkyl ether (Daiichi Kogyo Seiyaku Co., Ltd., Hightenol N-08; 37.5 parts) previously adjusted to a 20% aqueous solution, and deionized water (57.5 parts). Charger emulsion 1 was charged.

  The reaction was started by dropping the monomer emulsion 1 into a polymerization vessel adjusted to 70 ° C., and after raising the temperature to 75 ° C., the monomer emulsion 1 was kept for 2 hours while maintaining the internal temperature at 75 ° C. The solution was dripped uniformly. At the same time, 5% aqueous potassium persulfate solution (27 parts) and 2% aqueous sodium hydrogen sulfite solution (20 parts) were uniformly added dropwise over 2 hours. The core part emulsion was formed by these dripping. After completion of the dropwise addition, the reaction was continued at 75 ° C. for 1 hour to completely consume each monomer.

  Next, in another dropping funnel, methyl methacrylate (50 parts), styrene (126 parts), 2-ethylhexyl acrylate (69 parts), acrylic acid (2.5 parts), glycidyl methacrylate (2.5 parts), 20% in advance Monomer emulsion 2 comprising a polyoxyethylene alkyl ether sulfate ester salt prepared in an aqueous solution (Hitenol N-08; 37.5 parts by Daiichi Kogyo Seiyaku Co., Ltd.) and deionized water (57.5 parts) Prepared.

  Reaction was started by dripping the prepared monomer emulsion 2 to the emulsion of a core part, and the monomer emulsion 2 was dripped over 2 hours, maintaining internal temperature at 75 degreeC. At the same time, 5% aqueous potassium persulfate solution (27 parts) and 2% aqueous sodium hydrogen sulfite solution (20 parts) were uniformly added dropwise over 2 hours. By dripping these, a shell part was formed and it was set as the core-shell type particle | grain. After completion of the dropwise addition, the reaction was continued at 75 ° C. for 1 hour to completely consume each monomer. Thereafter, the reaction solution was cooled to 25 ° C. and an appropriate amount of 25% ammonia water was added to obtain an aqueous emulsion for vibration damping materials. The obtained emulsion for vibration damping materials had a nonvolatile content of 55.1%, a pH of 8.8, and a viscosity of 500 mPa · s.

For reference, the composition of the monomer composition used is shown in Table 1. Table 3 shows the specifications of the formed emulsion for vibration damping materials. In Tables 1 and 2, MMA represents methyl methacrylate, St represents styrene, 2-EHA represents 2-ethylhexyl acrylate, AA represents acrylic acid, and GAA represents glycidyl methacrylate. Total Tg indicates the glass transition temperature of the entire core-shell type particle. M _(C) : M _(S) is a mass ratio between the mass M _(C) of the core part and the mass M _(S) of the shell part.

<Examples 2 to 9>
In Example 1, vibration control containing core-shell type particles was performed in the same manner as in Example 1 except that the composition of the monomer composition used for forming the core part and the shell part was changed to the composition shown in Table 1. An emulsion for the material was obtained. Table 3 shows the specifications of the formed emulsion for vibration damping materials.

<Comparative Example 1>
Deionized water (170.5 parts) was charged into a polymerization vessel equipped with a stirrer, a reflux condenser, a thermometer, a nitrogen inlet tube and a dropping funnel. Thereafter, the internal temperature was raised to 70 ° C. while stirring under a nitrogen gas stream. Meanwhile, in the dropping funnel, methyl methacrylate (75 parts), styrene (239 parts), 2-ethylhexyl acrylate (176 parts), acrylic acid (5 parts), glycidyl methacrylate (5 parts) were previously adjusted to a 20% aqueous solution. Monomer emulsion 3 consisting of polyoxyethylene alkyl ether sulfate (Daiichi Kogyo Seiyaku Co., Ltd. Hytenol N-08; 75 parts) and deionized water (115 parts) was charged.

  The reaction was started by dropping the monomer emulsion 3 into a polymerization vessel adjusted to 70 ° C., and after raising the temperature to 75 ° C., the monomer emulsion 3 was maintained while maintaining the internal temperature at 75 ° C. It was dripped uniformly over time. Simultaneously, 5% aqueous potassium persulfate solution (54 parts) and 2% aqueous sodium hydrogensulfite solution (40 parts) were uniformly added dropwise over 3 hours. By these droppings, acrylic copolymer particles having a glass transition temperature of 15 ° C. were formed. After completion of the dropwise addition, the reaction was continued at 75 ° C. for 1 hour to completely consume each monomer. Thereafter, the mixture was cooled to 25 ° C. and an appropriate amount of 25% ammonia water was added to obtain an aqueous emulsion for vibration damping materials. The obtained emulsion for vibration damping materials had a non-volatile content of 54.9%, a pH of 8.9, and a viscosity of 450 mPa · s. For reference, the composition of the monomer composition used is shown in Table 2. Table 3 shows the specifications of the formed emulsion for vibration damping materials.

<Comparative Examples 2 and 3>
In Comparative Example 1, an emulsion for damping material containing particles was obtained in the same manner as in Comparative Example 1 except that the composition of the monomer composition was changed to the composition shown in Table 2. Table 3 shows the specifications of the formed emulsion for vibration damping materials.

<Comparative Examples 4-6>
In Example 1, vibration control containing core-shell type particles was performed in the same manner as in Example 1 except that the composition of the monomer composition used for forming the core part and the shell part was changed to the composition shown in Table 2. An emulsion for the material was obtained. Table 3 shows the specifications of the formed emulsion for vibration damping materials.

The emulsion for damping materials of Examples 1 to 5 and Comparative Examples 1 to 3 were blended as shown below to obtain aqueous coating compositions for damping materials.
・ Emulsion for vibration damping material 100 parts ・ Inorganic filler (calcium carbonate; NN # 200 manufactured by Nitto Flour Industries Co., Ltd.) 250 parts ・ Dispersant (Demol EP manufactured by Kao Corporation) 1 part ・ Thickener (Japan Co., Ltd.) Catalyst Acre Reset AT-2) 2 parts, Antifoaming agent (Nopco 8034L, manufactured by San Nopco Co., Ltd.) 0.3 part About this water-based coating composition for damping material, heat drying property and loss factor were evaluated.

<Heat drying property>
The prepared aqueous coating composition was applied onto the cationic electrodeposition coated plate so that the dry film thicknesses were 1.5 mm, 3.0 mm, and 4.5 mm. Then, it dried for 30 minutes at 150 degreeC using the hot air dryer, and the swelling and crack generation | occurrence | production state of the obtained dried coating film were evaluated on the following references | standards.
・ Evaluation criteria (visual evaluation)
○: Occurrence of swelling / cracking has not been confirmed. △: Slight occurrence of swelling / cracking has been confirmed. ×: Many swelling / cracking has occurred. <Measurement method of loss factor>
The prepared water-based paint composition was poured into a 4 mm thick mold on a cold-rolled steel plate (SPCC-SD manufactured by Nippon Test Panel; width 15 mm x length 250 mm x thickness 0.8 mm), and dried at 150 ° C for 30 minutes. A damping material film was formed on the cold-rolled steel sheet. The damping property of the obtained damping material coating was evaluated using the loss factor. The loss factor was measured by tan δ at 25 ° C. and 40 ° C. by the resonance method (3 dB method) using a cantilever method (Ono Sokki Co., Ltd., loss factor measurement system). The larger the loss factor value, the better the damping performance.

  As shown in Table 4, the coating film formed using the emulsion for vibration damping materials of the present invention is excellent in drying properties, and the generation of cracks and the expansion of the coating film during drying are suppressed. Moreover, it turns out that it acts as a damping material in a wide temperature range.

Claims (1)

An emulsion for a damping material containing particles having a core part made of an acrylic copolymer (A) and a shell part made of an acrylic copolymer (B) covering the core part,
The glass transition temperature of the acrylic copolymer (B) is −9 ° C. or higher, and the glass transition temperature of the acrylic copolymer (B) and the glass transition temperature of the acrylic copolymer (A). The emulsion for damping materials whose difference is 20 degreeC or more.