JP4262128B2 - Damping emulsion - Google Patents

Description

  The present invention relates to a copolymer emulsion for vibration damping materials. More specifically, the present invention relates to a copolymer emulsion for vibration damping materials having excellent vibration damping properties and drying properties.

  Damping materials are used to prevent vibrations and noises in various structures and keep quiet. They are used under the interior floors of automobiles, as well as railway vehicles, ships, aircraft, electrical equipment, and buildings. It may also be used for structures and construction equipment. As such a damping material, for example, an asphalt sheet containing inorganic powder has been used under the interior floor of an automobile, etc., but since it is necessary to heat-seal, improvement in workability and the like can be achieved. Desirably, various compositions for damping materials and polymers for forming damping materials have been studied.

  However, with these techniques, it has not been possible to obtain a vibration damping material that achieves both excellent heat drying properties and vibration damping properties. That is, when using a conventional synthetic resin emulsion or asphalt emulsion, when the film is dried by heating, the surface is dried and the moisture in the undried film tends to evaporate, so dandruff is likely to occur. There was room for improvement in improving heat drying properties. In addition, as a vibration damping property, the loss factor (tan δ) of a steel plate provided with a 2 mm thick asphalt sheet that is currently used is about 0.1, and a value higher than that is required. However, when a copolymer latex formed from a conjugated diene monomer and other monomers is used, the monomer unit of the conjugated diene monomer has sufficient vibration damping properties. There was room for improvement to improve vibration control because it was not demonstrated.

  Therefore, in order to solve such a problem, it is a copolymer emulsion for a vibration damping material obtained by copolymerizing a monomer mixture containing an acrylic monomer as an essential component. It contains less than 10% by mass of unsaturated monomers having functional groups and 32% by mass or more of ethylenically unsaturated carboxylic acid alkyl ester monomers with respect to the total monomer mixture. A characteristic copolymer emulsion for damping material has been proposed (Patent Document 1).

However, such copolymer emulsions still have insufficient vibration damping properties, and satisfactory results have not been obtained. In particular, there was a change in the vibration damping properties accompanying changes in temperature, and it was impossible to maintain high vibration damping properties.
JP 2003-206382 A

  Accordingly, an object of the present invention is to provide a novel copolymer emulsion for vibration damping materials.

  Another object of the present invention is to provide a copolymer emulsion for a vibration damping material having high vibration damping properties, particularly high vibration damping properties over a wide temperature range.

The above objects are achieved by the following (1) to (6) .

(1) A copolymer emulsion for a vibration damping material, which is obtained by copolymerizing a monomer mixture containing an acrylic monomer as an essential component .
(A) 0.1 to 10% by mass of an ethylenically unsaturated carboxylic acid,
(B) 25-90% by weight methyl methacrylate, and
(C) 5 to 74.9% by mass of other copolymerizable ethylenically unsaturated monomers (however, the total of the respective monomers is 100% by mass), and the copolymerizable ethylene The unsaturated copolymerizable monomer (c) contains 20% by mass or more of an acrylic monomer having an ester residue having 4 to 8 carbon atoms as an essential component .

(2) The copolymer for a damping material according to (1), wherein the copolymerizable ethylenically unsaturated monomer (c) contains butyl acrylate and / or 2-ethylhexyl acrylate as an essential component. Polymerized emulsion.

(3) The copolymer emulsion for vibration damping materials as described in (2 ) above, wherein the copolymerizable ethylenically unsaturated monomer (c) further contains an aromatic unsaturated monomer.
(4) The monomer mixture is
(A) 0.5 to 10% by mass of ethylenically unsaturated carboxylic acid,
(B) 25-80% by weight methyl methacrylate, and
(C) Any of the above (1) to (3), which is 20 to 70% by mass of another copolymerizable ethylenically unsaturated monomer (however, the total of the respective monomers is 100% by mass) A copolymer emulsion for a vibration damping material according to any one of the above .
(5) The copolymer emulsion for vibration damping materials according to any one of (1) to (4), wherein the ethylenically unsaturated carboxylic acid (a) is acrylic acid.
(6) The copolymer emulsion for vibration damping materials according to any one of (3) to (5), wherein the aromatic unsaturated monomer is styrene.

  Since the present invention has the configuration as described above, the vibration damping material using the emulsion has high vibration damping properties, particularly high vibration damping properties in a wide temperature range. Therefore, compared with the damping material using the conventional emulsion, not only the damping effect is high, but the thickness can be reduced by that amount, the mass can be reduced, and the drying time is shortened. There is an advantage that the cost is reduced.

The present invention is a copolymer emulsion for a vibration damping material obtained by copolymerizing a monomer mixture essentially comprising an acrylic monomer, the monomer mixture comprising:
(A) 0.1 to 10% by mass of an ethylenically unsaturated carboxylic acid,
(B) 25-90% by weight methyl methacrylate, and
(C) 5 to 74.9% by mass of other copolymerizable ethylenically unsaturated monomers (however, the total of the respective monomers is 100% by mass), and the copolymerizable ethylene The unsaturated unsaturated monomer (c) is a copolymer emulsion for a vibration damping material characterized by containing 20% by mass or more of an acrylic monomer having 4 to 8 carbon atoms in an ester residue as an essential component. is there.

  The copolymer emulsion for vibration damping material of the present invention is obtained by copolymerizing a monomer mixture having an acrylic monomer as an essential component. The above-mentioned copolymer emulsion for damping material is a water-based one in which water is a continuous phase and a copolymer essentially containing an acrylic monomer is dispersed. Usually, the vibration damping material is formed by applying a vibration damping material blend which essentially requires such a copolymer emulsion for the vibration damping material. In addition, the damping material formed with an emulsion is also called an aqueous damping material.

  The acrylic monomer means (meth) acrylic acid derivatives such as (meth) acrylic acid and (meth) acrylic acid esters. As content of the acryl-type monomer in the said monomer mixture, it is preferable to set it as 50 mass% or more with respect to all the monomer mixtures, for example, More preferably, it is 60-99.9 mass%. Most preferably, it is 65-99.5 mass%. As such a monomer mixture, the content of the conjugated diene monomer is preferably 10% by mass or less with respect to the total monomer mixture, more preferably 5% from the viewpoint of vibration damping properties. It is not more than mass%, and most preferably, it does not contain a conjugated diene monomer.

In the present invention, the monomer mixture preferably contains an unsaturated monomer having a functional group. Based on all the monomers mixture, the unsaturated monomer having a functional group preferably contains 0.1-10 wt%, more preferably 0.5 to 5 mass%. Moreover, methyl methacrylate which is an essential component is 25-90 mass%, Preferably it is 25-80 mass%, More preferably, it is 25-75 mass%. That is, when methyl methacrylate is less than 25% by mass, it is difficult to obtain vibration damping properties, particularly high vibration damping properties in a wide temperature range. On the other hand, when it exceeds 90 mass%, it becomes unstable at the time of emulsion polymerization and may cause gelation. Alternatively, the mechanical stability becomes unstable, and there is a risk of gelation during coating.

  The functional group in the unsaturated monomer having a functional group may be any functional group that can be crosslinked when the damping emulsion copolymer emulsion is obtained by copolymerization. The film forming property and heat drying property of the copolymer emulsion for vibration damping material can be improved by the action of the unsaturated monomer having a functional group.

  In the present invention, by appropriately setting the mass ratio of the unsaturated monomer having a functional group and methyl methacrylate in the monomer mixture, these synergistic effects are sufficiently exerted so that the copolymer for damping material can be obtained. The emulsion has excellent vibration damping properties. More preferably, the unsaturated monomer which has a functional group is 0.1-3.0 mass%. In addition, the said mass ratio is a mass ratio with respect to 100 mass% of all-mer mixture.

  Examples of the functional group include an epoxy group, an oxazoline group, a carbodiimide group, an aziridinyl group, an isocyanate group, a methylol group, a vinyl ether group, a cyclocarbonate group, and an alkoxysilane group. One kind of these functional groups may be present in one molecule of the unsaturated monomer, or two or more kinds thereof may be present.

  Examples of the unsaturated monomer having a functional group include divinylbenzene, ethylene glycol di (meth) acrylate, N-methoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, and Nn-butoxymethyl. (Meth) acrylamide, Ni-butoxymethyl (meth) acrylamide, N-methylol (meth) acrylamide, diallyl phthalate, diallyl terephthalate, polyethylene glycol di (meth) acrylate, propylene glycol di (meth) acrylate, polypropylene glycol di ( (Meth) acrylate, tetramethylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl Polyfunctional unsaturated monomers such as Koruji (meth) acrylate; glycidyl (meth) acrylate, glycidyl group-containing unsaturated monomers such as acrylic glycidyl ether. Among these, it is preferable to use an unsaturated monomer (polyfunctional unsaturated monomer) having two or more functional groups. These may be used alone or in combination of two or more.

  In the present invention, in addition to methyl methacrylate, other ethylenically unsaturated carboxylic acid alkyl ester monomers can also be used. Such an ethylenically unsaturated carboxylic acid alkyl ester monomer is not particularly limited. For example, the above-described unsaturated monomer having a functional group, methyl (meth) acrylate, ethyl (meth) acrylate, butyl ( 1 type, or 2 or more types, such as (meth) acrylic acid esters, such as (meth) acrylate, 2-ethylhexyl (meth) acrylate, and cyclohexyl (meth) acrylate, are mentioned. 5-74.9 mass% is preferable with respect to the whole monomer mixture, and, as for the quantity of this ethylenically unsaturated carboxylic acid ester, More preferably, it is 20-70 mass%.

In the present invention, the monomer mixture preferably contains 0.1 to 10% by mass of the ethylenically unsaturated carboxylic acid monomer. By containing an ethylenically unsaturated carboxylic acid monomer, the dispersibility of fillers such as inorganic powder is improved in the vibration damping composition that requires the copolymer emulsion for vibration damping material, and the vibration damping property is improved. It will be improved. Moreover, it becomes easy to adjust Tg, a physical property, etc. of the copolymer emulsion for damping materials by including the other copolymerizable ethylenically unsaturated monomer. In the monomer mixture, even if the ethylenically unsaturated carboxylic acid monomer is less than 0.1% by mass or more than 10 % by mass, the emulsion may not be stably copolymerized. In the copolymer emulsion for damping material of the present invention, the synergistic effect of the monomer units formed from these monomers makes it possible to more fully exhibit excellent damping properties in an aqueous damping material. Become. In addition, the said mass ratio is a mass ratio with respect to 100 mass% of all monomer mixtures.

  The ethylenically unsaturated carboxylic acid monomer is not particularly limited. For example, (meth) acrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, monomethyl fumarate, monoethyl fumarate, monomethyl mayate, 1 type, or 2 or more types, such as unsaturated carboxylic acids, such as monoethyl mayate, or its derivative (s) are mentioned.

  The other copolymerizable ethylenically unsaturated monomer is not particularly limited. For example, in addition to the above-described unsaturated monomer having a functional group and ethylenically unsaturated carboxylic acid alkyl ester monomer, styrene 1 type (s) or 2 or more types, such as aromatic unsaturated monomers, such as (alpha) -methylstyrene and vinyltoluene.

  When the number average molecular weight of the copolymer emulsion for vibration damping material of the present invention is small, in the vibration damping composition that essentially requires the copolymer emulsion for vibration damping material of the present invention, a filler such as an inorganic powder and vibration damping are used. Affinity with the copolymer emulsion for materials is improved and dispersibility is improved. Moreover, it is preferable that a glass transition point (Tg) is -50-60 degreeC. Even if Tg is less than −50 ° C. or exceeds 60 ° C., vibration damping may not be sufficient. More preferably, it is -30-40 degreeC. In addition, Tg of the copolymer emulsion for vibration damping materials can be calculated by Tg of the homopolymer of each monomer forming the copolymer emulsion for vibration damping materials.

  The above-mentioned copolymer emulsion for damping material preferably has a loss coefficient (tan δ) of 7% or more when formed into a damping material blend. That is, it is preferable that a damping material composition is prepared using the copolymer emulsion for damping material of the present invention, and a loss coefficient (tan δ) of a film formed from this damping material composition is 7% or more. . The damping property, that is, the loss factor correlates with the tan δ of the coating film used, and the higher the tan δ, the higher the loss factor and the better the damping property. If the loss factor (tan δ) is less than 7%, the water-based vibration damping material may not be able to exhibit excellent vibration damping properties. More preferably, it is 10% or more, More preferably, it is 13% or more.

  As a method for measuring the loss factor (tan δ) when the vibration damping composition is used, it is preferable to prepare and measure the vibration damping composition as described below, for example.

Damping material composition:
100 parts by weight of copolymer emulsion for vibration damping material, 250 parts by weight of calcium carbonate: NN # 200 (trade name, manufactured by Nitto Flour Chemical Co., Ltd.), 1 part by weight of dispersant: Demall EP (trade name, manufactured by Kao Corporation) , Thickener: Acreset AT-2 (trade name, manufactured by Nippon Shokubai Co., Ltd.) 2 parts by mass, antifoaming agent: Nopco 8034L (trade name, manufactured by San Nopco Co., Ltd.) 0.3 parts by mass.

Method for measuring loss factor (tan δ):
The damping material composition was poured into a 3 mm thick mold on a cationic electrodeposition coated steel sheet (15 width × 250 length × thickness 1.5 mm) and dried at 150 ° C. for 30 minutes to obtain a test piece. About this test piece, the loss factor of the measurement environment of each temperature is measured using the loss factor measurement system and the cantilever method by Ono Sokki Co., Ltd.

  The method for producing the copolymer emulsion for vibration damping material of the present invention will be described below. The copolymer emulsion for a vibration damping material of the present invention is obtained by copolymerizing a monomer mixture essentially containing an acrylic monomer. Examples of a method for copolymerizing the monomer mixture include, for example, emulsion weight Legal methods can be suitably applied. The form for carrying out the emulsion polymerization is not particularly limited, and for example, the emulsion polymerization can be carried out by appropriately adding a monomer mixture, a polymerization initiator and a surfactant to an aqueous medium for copolymerization. Moreover, you may use a polymerization chain transfer agent etc. for molecular weight adjustment.

  The aqueous medium is not particularly limited, and for example, water, one or more mixed solvents that can be mixed with water, and a mixed solvent in which water is a main component mixed with such a solvent. Etc. Among these, it is preferable to use water.

  The polymerization initiator is not particularly limited, and examples thereof include known water-soluble or oil-soluble initiators such as ammonium persulfate, potassium persulfate, hydrogen peroxide, and butyl hydroperoxide. In order to promote emulsion polymerization, sodium hydrogen sulfite, L-ascorbic acid or the like may be used as a reducing agent to form a redox initiator. These may be used alone or in combination of two or more.

  The amount of the polymerization initiator used is not particularly limited, and may be set as appropriate according to the type of the polymerization initiator. For example, 0.1 to 2 masses per 100 mass parts of the total monomer mixture. Part. More preferably, it is 0.2-1 mass part.

  It does not specifically limit as said surfactant, For example, any emulsifier of an anionic emulsifier, a nonionic emulsifier, and a nonionic anionic emulsifier can be used. Among these emulsifiers, it is preferable to use a nonionic emulsifier and a nonionic anionic emulsifier from the viewpoint of emulsion polymerization stability, and it is more preferable to use a nonionic emulsifier and a nonionic anionic emulsifier in combination. Examples of the anionic emulsifier include fatty acid soap, rosin acid soap, alkyl sulfonic acid soap, dialkyl aryl sulfonate, alkyl sulfo succinate, polyoxyethylene alkyl sulfate, and the like. Examples of the nonionic emulsifier include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene sorbitan fatty acid ester, oxyethylene oxypropylene block copolymer, and the like. These surfactants may be used alone or in combination of two or more.

  Although it does not specifically limit as the usage-amount of the said surfactant, What is necessary is just to set suitably according to the kind of emulsifier, etc., for example, 0.05-5.0 mass with respect to 100 mass parts of all monomer mixtures. Part. More preferably, it is 0.1-3.0 mass parts.

  The polymerization chain transfer agent is not particularly limited. For example, alkyl mercaptans such as hexyl mercaptan, octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecyl mercaptan, n-tetradecyl mercaptan; carbon tetrachloride , Halogenated hydrocarbons such as carbon tetrabromide and ethylene bromide; mercaptocarboxylic acid alkyl esters such as mercaptoacetic acid 2-ethylhexyl ester, mercaptopropionic acid 2-ethylhexyl ester, mercaptopyropionic acid tridecyl ester; mercaptoacetic acid methoxybutyl Mercaptocarboxylic acid alkoxyalkyl ester such as ester, mercaptopropionic acid methoxybutyl ester; carboxylic acid mercaptoal such as octanoic acid 2-mercaptoethyl ester Glycol ester or, alpha-methylstyrene dimer, terpinolene, alpha-terpinene, .gamma.-terpinene, dipentene, anisole, allyl alcohol and the like. These may be used alone or in combination of two or more. Among these, alkyl mercaptans such as hexyl mercaptan, octyl mercaptan, n-dodecyl mercaptan, t-dodecyl mercaptan, n-hexadecyl mercaptan, and n-tetradecyl mercaptan are preferably used. As the usage-amount of a polymerization chain transfer agent, it is 0-1 mass part normally with respect to 100 mass parts of all monomer mixtures, Preferably it is 0-0.5 mass part.

  The emulsion polymerization may be performed in the presence of a chelating agent such as sodium ethylenediaminetetraacetate, a dispersing agent such as sodium polyacrylate, an inorganic salt, or the like, if necessary. Moreover, as addition methods, such as a monomer mixture and a polymerization initiator, methods, such as a batch addition method, a continuous addition method, a multistage addition method, are applicable, for example. Moreover, you may combine these addition methods suitably.

  What is necessary is just to set suitably as reaction conditions in the said emulsion polymerization according to the composition of a monomer mixture, the polymerization initiator to be used, etc. For example, the polymerization temperature is preferably 5 to 90 ° C. More preferably, it is 20-85 degreeC. The polymerization time is preferably 3 to 8 hours, for example. Moreover, it is preferable that superposition | polymerization and dripping are performed under stirring.

  In the said manufacturing method, after manufacturing a copolymer emulsion by emulsion polymerization, it is preferable to neutralize an emulsion with a neutralizing agent. Thereby, a copolymer emulsion will be stabilized. The neutralizing agent is not particularly limited, and for example, tertiary amines such as triethanolamine, dimethylethanolamine, diethylethanolamine and morpholine; ammonia water; sodium hydroxide and the like can be used. These may be used alone or in combination of two or more. Among these, it is preferable to use a volatile base that volatilizes when the coating film is heated, because the water resistance and the like of the coating film formed from the vibration damping composition that requires the copolymer emulsion is improved. More preferably, an amine having a boiling point of 80 to 360 ° C. is preferably used because heat drying properties are improved and vibration damping properties are improved. As such a neutralizing agent, for example, tertiary amines such as triethanolamine, dimethylethanolamine, diethylethanolamine and morpholine are suitable.

  The addition amount of the neutralizing agent is not particularly limited. For example, the acid value of the damping emulsion copolymer emulsion, that is, the neutralizing agent base is equivalent to 1 equivalent of the acid group of the damping emulsion copolymer emulsion. It is preferable to add so that it may become 0.3-1.4 equivalent. More preferably, it is 0.5 to 1.2 equivalents.

  The copolymer emulsion for damping material of the present invention can constitute a damping material blend together with an additive, a solvent and the like as required. Such a damping material composition essentially comprising the copolymer emulsion for damping material of the present invention is one of the preferred embodiments of the present invention, and exhibits excellent damping properties. Can be formed. Moreover, the copolymer emulsion for damping material of the present invention has good performance as a damping material and is suitable for damping material. The damping material formed by using the copolymer emulsion for damping material formed from such a damping material blend is one of the preferred embodiments of the present invention.

  The blending amount of the copolymer emulsion for damping material in the damping material composition that forms the damping material is, for example, for damping material with respect to 100% by mass of the solid content of the damping material composition. It is preferable that the solid content of the copolymer emulsion is 15 to 40% by mass. Moreover, as solid content concentration of a damping material compound, it is preferable to set it as 60-90 mass% with respect to 100 mass% of a damping material compound, for example.

  Examples of the additives include fillers, colorants, preservatives, dispersants, thickeners, thixotropic agents, antifreeze agents, pH adjusters, antifoaming agents, wetting agents, rust preventive agents, and adhesion imparting agents. Etc. These may be used alone or in combination of two or more. Among these, it is preferable that a filler is included.

  The filler is not particularly limited, and examples thereof include inorganic fillers such as calcium carbonate, kaolin, silica, talc, barium sulfate, alumina, iron oxide, titanium oxide, and glass talk; scale-like inorganic substances such as glass flakes and mica. Fillers: Metal oxide whiskers, fibrous inorganic fillers such as glass fibers, and the like.

  As a compounding quantity of the filler in the said damping material mixture, it is preferable to set it as 50-400 mass parts with respect to 100 mass parts of solid content of the copolymer emulsion for damping materials, for example. More preferably, it is 100-350 mass parts.

  The solvent is not particularly limited as long as the effects of the present invention are exerted, and one or more can be used. Moreover, what is necessary is just to set suitably as a compounding quantity of a solvent so that the solid content concentration of a damping material compound may become the range mentioned above, for example.

  It is preferable that the said damping material formulation also contains a polyvalent metal compound with the copolymer emulsion for damping materials. Thereby, stability of a damping material compound, dispersibility, heat drying property, and damping property of a damping material formed from a damping material compound can be improved. It does not specifically limit as a polyvalent metal compound, For example, zinc oxide, zinc chloride, zinc sulfate etc. are mentioned, 1 type (s) or 2 or more types can be used. Among these, it is preferable to use zinc oxide in the present invention.

  It does not specifically limit as a form of the said polyvalent metal compound, For example, a powder, an aqueous dispersion, an emulsion dispersion, etc. can be used. Among these, since the dispersibility of the vibration damping composition improves, it is preferably used in the form of an aqueous dispersion or an emulsified dispersion. More preferably, it is an emulsified dispersion. Moreover, as a usage-amount, it is preferable that a polyvalent metal compound shall be 0.05-5.0 mass parts with respect to 100 mass parts of solid content of the copolymer emulsion for damping materials, for example. More preferably, it is 0.05 to 3.5 parts by mass.

  The solvent is not particularly limited as long as the effects of the present invention are exerted, and one or more can be used. Moreover, what is necessary is just to set suitably as a compounding quantity of a solvent so that the solid content concentration of a damping material compound may become the range mentioned above, for example.

  The damping material composition that forms the damping material can be produced by mixing the damping emulsion copolymer emulsion with the above-described additives, solvents, and the like. The apparatus used for mixing is not particularly limited, and examples thereof include a butterfly mixer, a planetary mixer, a spiral mixer, a kneader, and a dissolver.

  The said damping material composition forms the film used as a damping material, for example by apply | coating to a base material and drying. The substrate is not particularly limited. Moreover, as a method of apply | coating a damping material compound to a base material, it can apply | coat using a brush, a spatula, an air spray, an airless spray, a mortar gun, a lysing gun etc., for example.

  The coating amount of the damping material composition may be set depending on the application, desired performance, etc. For example, if the damping material composition is applied to form the damping material, The thickness of the coating is preferably 1 to 10 mm, more preferably 2 to 6 mm.

  The condition for applying the damping material composition and then drying to form a film may be, for example, heat drying or room temperature drying, but heat drying is preferable in terms of efficiency. In the present invention, the heat drying property is excellent, which is preferable. For example, when the damping material is formed, the heat drying temperature is preferably 80 to 210 ° C. More preferably, it is 110-160 degreeC.

  The use of the damping material composition that essentially requires the copolymer emulsion for damping material of the present invention is not particularly limited, and can exhibit excellent heat drying properties and damping properties. The present invention can be suitably applied to railway vehicles, ships, aircraft, electrical equipment, building structures, construction equipment, etc. in addition to indoor floors.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited only to these examples. Unless otherwise specified, “part” means “part by mass” and “%” means “% by mass”.

1. Synthesis of emulsion Example 1
210.4 parts of deionized water 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. On the other hand, 236 parts of methyl methacrylate, 251 parts of butyl acrylate, 5.0 parts of acrylic acid, and Haitenol N-08 (trade name, polyoxyethylene alkyl ether sulfate ester salt prepared in advance in a 20% aqueous solution in the dropping funnel) A monomer emulsion consisting of 37.5 parts (Daiichi Kogyo Seiyaku Co., Ltd.) and 57.5 parts deionized water was charged. Next, the above monomer emulsion was uniformly dropped over 2 hours while maintaining the internal temperature of the polymerization vessel at 70 ° C., and at the same time, 54 parts of 5% potassium persulfate aqueous solution and 2% sodium hydrogensulfite aqueous solution 40 An emulsion was formed by uniformly dropping the portions over 2 hours. After completion of the dropping, aging was continued at 75 ° C. for 1 hour to completely consume each monomer. Then, it cooled, added 5.1 parts of 25% ammonia water, filtered through a 100 mesh stainless steel wire net, and took out. Thereby, an aqueous resin was obtained. As shown in Table 2, the nonvolatile content of the obtained aqueous resin was 55.2%, the pH was 8.8, and the viscosity was 500 mPa · s. The composition of the monomer composition is summarized in Table 1.

Examples 2-4 and Comparative Examples 1-5
A damping material emulsion was obtained in the same manner as in Example 1 except that the composition of the aqueous resin in Example 1 was changed to the composition shown in Table 1. The physical properties are shown in Table 2.

  The following evaluation tests were performed on the emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 5. The results were as shown in Table 3, respectively.

2. Loss coefficient The acrylic resin emulsions obtained in Examples 1 to 4 and Comparative Examples 1 to 5 were blended as follows, and the vibration damping property was confirmed as a vibration damping water-based coating composition.

・ Acrylic copolymer emulsion 100 parts ・ Calcium carbonate NN # 200 ^{* 1} 250 parts ・ Dispersant Demole EP ^{* 2} 1 part ・ Thickener Acreset AT-2 ^{* 3} 2 parts ・ Antifoamer Nopco 8034L ^{* 4} 0.3 * 1: Filler made by Nitto Flour Chemical Co., Ltd. * 2: Special polycarboxylic acid type polymer surfactant made by Kao Corporation * 3: Alkali-soluble acrylic thickener made by Nippon Shokubai Co., Ltd. * 4: Sannopco Defoaming agent (main component: hydrophobic silicone + mineral oil)

  The above damping material composition is poured into a 3 mm-thick mold on a cold-rolled steel sheet (SPCC 15 width × 250 length × thickness 1.5 mm), dried at 150 ° C. for 30 minutes, and then on the cold-rolled steel sheet. A damping material film was formed on the surface. The vibration damping property was measured using a cantilever method (loss factor measurement system manufactured by Ono Sokki Co., Ltd.), and the loss factor at each temperature (20 ° C. to 60 ° C.) was measured by a resonance method (3 dB method). The results are shown in Table 1. The larger the loss factor, the better the damping performance. Further, with respect to the temperature dependence of the vibration damping property, the temperature width at a predetermined loss coefficient (7% and 10%) was measured. The results shown in Table 3, Table 5 and Table 7 were obtained. It shows that the damping property is expressed in a wide temperature range, so that this temperature range is large.

  The vibration suppression test results shown in Table 3 are plotted on the graph as shown in FIG. Table 4 shows the temperature dependence of the loss coefficient calculated from this graph.

  The vibration suppression test results shown in Table 5 are plotted in the graph as shown in FIG. Table 6 shows the temperature dependence of the loss coefficient calculated from this graph.

  The vibration suppression test results shown in Table 7 are plotted on a graph as shown in FIG. Table 8 shows the temperature dependence of the loss coefficient calculated from this graph.

It is a graph which shows the temperature dependence of the loss factor of the damping material using the emulsion by this invention. It is a graph which shows the temperature dependence of the loss coefficient of the damping material which uses the conventional emulsion. It is a graph which shows the temperature dependence of the loss factor of the damping material which uses the emulsion by the other Example of this invention.

Claims (3)

A copolymer emulsion for a vibration damping material obtained by copolymerizing a monomer mixture essentially containing an acrylic monomer, the monomer mixture comprising:
(A) 0.1 to 10% by mass of an ethylenically unsaturated carboxylic acid,
(B) 25 to 90% by mass of methyl methacrylate, and (c) 5 to 74.9% by mass of other copolymerizable ethylenically unsaturated monomers and aromatic unsaturated monomers And the copolymerizable ethylenically unsaturated monomer (c) comprises an acrylic monomer having an ester residue of 4 to 8 carbon atoms as an essential component. both further aromatic unsaturated monocyclic mer for vibration damping materials copolymer emulsion characterized in that it contains a containing more than 20% by mass.   The copolymerizable ethylenically unsaturated monomer (c) other than the aromatic unsaturated monomer contains butyl acrylate and / or 2-ethylhexyl acrylate as an essential component. Copolymer emulsion for damping material.   The copolymer emulsion for vibration damping materials according to claim 1 or 2, wherein the aromatic unsaturated monomer is styrene.

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