Aqueous emulsion-based vibration-damping coating composition and cured coating film thereof

Abstract

[Problem] To make it possible to form a thin film while ensuring vibration damping properties thereof and to make defects such as coating film swelling unlikely to occur in a coating film. [Solution] This aqueous emulsion-based vibration-damping coating composition comprises a resin emulsion, an inorganic filler, and a film formation assisting agent. The film formation assisting agent is a water-insoluble organic compound.

Description

Water-based emulsion vibration-damping coating composition and cured coating film thereof

[0001] The present invention relates to a water-based emulsion vibration-damping coating composition of application type that is applied to, for example, vehicle floors or the like to prevent vibrations, and to a cured coating film formed from the composition. In particular, the present invention relates to a water-based emulsion vibration-damping coating composition that is less likely to cause coating defects such as blisters and that can be made into a thin film while maintaining vibration-damping properties, and to a cured coating film formed from the composition.

[0002] Conventionally, to prevent vibrations, sheet-like vibration-damping materials (vibration-damping sheets) primarily composed of asphalt have been installed on the floors of vehicles such as automobiles. However, when used in vehicles, such vibration-damping sheets must be cut to fit the shape of the part to be installed for each vehicle model, making it difficult to apply to parts with complex shapes. In addition, the installation must be done by workers, which hinders automation and hinders the reduction of process time.

[0003] In recent years, paint-on vibration-damping materials have been developed as an alternative to vibration-damping sheets, and are already in practical use. These paint-on vibration-damping materials can be applied automatically by painting robots, shortening the process time. Most of these paint-on vibration-damping materials are water-based paints, such as emulsion-based paints, so they do not emit the asphalt smell of conventional vibration-damping sheets or the organic solvent smell of organic solvent-based paints during application, and they do not emit toxic gases during baking and drying, so they have little impact on environmental pollution.

[0004] However, because aqueous emulsion paints contain a large amount of water, depending on the drying conditions, volume shrinkage occurs when the water evaporates, which can lead to coating cracks, and swelling occurs due to the bumping of water, which can easily cause coating defects. In particular, to achieve a vibration-damping effect, a thick coating film is required. However, if the coating film is thick, the coating film dries and hardens from the surface, which can easily cause swelling and cracks when the moisture remaining inside the coating film evaporates. Therefore, to prevent such coating defects, foaming agents such as inorganic hollow particles (e.g., thermally expandable resin balloons) are used, as disclosed in Patent Documents 1 to 3. Furthermore, inorganic fillers such as mica are also used in this type of aqueous emulsion paint to improve vibration-damping properties and rigidity.

[0005] Japanese Patent Laid-Open No. 7-145331 Japanese Patent Laid-Open No. 2004-115740 Japanese Patent Laid-Open No. 2008-291077

[0006] However, adding materials to prevent these coating defects or to improve vibration-damping and rigidity further increases the coating thickness. This creates the problem of limiting the areas where the coating can be applied, as it can cause interference with other parts or problems with the assembly of components in later processes. While it is possible to reduce the coating thickness by reducing the weight of the coating through improved vibration-damping and rigidity, reducing the weight of the coating can lead to the risk of not being able to ensure sound insulation due to the law of mass.

[0007] SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an aqueous emulsion vibration-damping coating composition which can be thinned while maintaining vibration-damping properties and which is less likely to cause coating defects such as blistering.

[0008] The aqueous emulsion vibration-damping coating composition of the present invention is an aqueous emulsion vibration-damping coating composition containing a resin emulsion, an inorganic filler, and a film-forming aid, wherein the film-forming aid is a water-insoluble organic compound.

[0009] Examples of the resin emulsion include acrylic resin (including methacrylic resin) emulsions (for example, acrylic acid ester resin (including methacrylic acid ester resin) emulsions such as acrylic-styrene copolymer emulsions), styrene-butadiene emulsions, styrene-butadiene-latex (SBR) emulsions, vinyl acetate emulsions, ethylene-vinyl acetate emulsions, ethylene-acrylic emulsions, epoxy resin emulsions, urethane resin emulsions, phenolic resin emulsions, polyester resin emulsions, and acrylonitrile-butadiene-latex (NBR) emulsions. One type may be used alone, or two or more types may be used in combination.

[0010] The term "emulsion" is also called an emulsion, and its original meaning is a system in which liquid particles are in the form of colloidal particles or larger particles in a liquid, forming a milky state (dispersed system) (Nagakura Saburo et al., eds., Iwanami Dictionary of Physics and Chemistry (5th Edition), p. 152, published by Iwanami Shoten Co., Ltd. on February 20, 1998). However, in this specification and claims, the term "emulsion" is used in the broader sense, meaning "a system in which solid or liquid particles are dispersed in a liquid."

[0011] Examples of inorganic fillers that can be used include calcium carbonate, magnesium carbonate, barium sulfate, clay, talc, mica, diatomaceous earth, alumina, gypsum, cement, converter slag powder, shirasu powder, glass powder, glass flakes, graphite, vermiculite, kaolinite, and zeolite. One type may be used alone, or two or more types may be used in combination. Preferably, fillers that do not have a biaxially oriented shape, such as calcium carbonate, mica, barium sulfate, talc, and diatomaceous earth, are used, which facilitates evaporation of moisture during baking and drying, thereby preventing blistering of the coating film.

[0012] The film-forming aid is a water-insoluble organic compound, preferably an ether-based water-insoluble organic compound, and examples of the ether-based water-insoluble organic compound include dipropylene glycol-n-propyl ether, propylene glycol-n-butyl ether, propylene glycol methyl ether acetate, dipropylene glycol methyl ether acetate, propylene glycol diacetate, propylene glycol phenyl ether, dipropylene glycol dimethyl ether, tripropylene glycol-n-butyl ether, ethylene glycol phenyl ether, ethylene glycol hexyl ether, diethylene glycol monohexyl ether, etc. Among these, dipropylene glycol-n-propyl ether and propylene glycol-n-butyl ether are preferred.

[0013] Here, the term "water-insoluble" means a liquid other than a water-soluble liquid (a liquid that, when placed in an equal volume of pure water at 20°C under 1 atmosphere and stirred, maintains a uniform appearance even after the flow has subsided), and preferably has a solubility in water within the range of 5 to 40 g / 100 g (water), more preferably 5 to 30 g / 100 g, even more preferably 5 to 20 g / 100 g, and particularly preferably 5.5 to 20 g / 100 g.

[0014] The film-forming aid of the aqueous emulsion vibration-damping coating composition of the invention of claim 2 is preferably a water-insoluble organic compound having a boiling point in the range of 140 to 250°C, more preferably 140 to 225°C, and even more preferably 160 to 220°C.

[0015] The film-forming aid in the aqueous emulsion-based vibration-damping coating composition of the invention of claim 3 is preferably blended in an amount within the range of 0.3 to 10.0 parts by mass, more preferably 0.5 to 10.0 parts by mass, even more preferably 0.5 to 8.0 parts by mass, and particularly preferably 1.0 to 5.0 parts by mass, relative to 100 parts by mass of the resin emulsion.

[0016] The film-forming aid of the aqueous emulsion vibration-damping coating composition of the invention of claim 4 is preferably a water-insoluble organic compound having a solubility in water at 25°C in the range of 5 to 40 g / 100 g, more preferably 5 to 30 g / 100 g, even more preferably 5 to 20 g / 100 g, and particularly preferably 5.5 to 20 g / 100 g.

[0017] The film-forming aid of the aqueous emulsion vibration-damping coating composition of the invention is preferably an ether-based water-insoluble organic compound.

[0018] The resin emulsion of the aqueous emulsion-based vibration-damping coating composition of the invention of claim 6 preferably has a minimum film-forming temperature (MFT) in the range of 0 to 40° C., more preferably 5 to 35° C., and even more preferably 10 to 25° C. When the resin emulsion contains two or more types of resin emulsion, the minimum film-forming temperature refers to the minimum film-forming temperature measured for the entire mixture (JIS K6828:200).

[0019] The inorganic filler in the aqueous emulsion vibration-damping coating composition of the invention of claim 7 is preferably blended in an amount of 100 to 250 parts by mass, more preferably 120 to 230 parts by mass, and even more preferably 150 to 200 parts by mass, relative to 100 parts by mass of the resin emulsion. When two or more types of inorganic filler are blended, the blending amount indicates the total amount of the inorganic fillers.

[0020] The cured coating film of the invention of claim 8 is a cured coating film formed from an aqueous emulsion vibration-damping coating composition containing a resin emulsion, an inorganic filler, and a film-forming aid, wherein the film-forming aid is a water-insoluble organic compound. The cured coating film formed from the aqueous emulsion vibration-damping coating composition is obtained by baking and drying the aqueous emulsion vibration-damping coating composition, and has at least a resin and an inorganic filler as coating components.

[0021] The aqueous emulsion vibration-damping coating composition according to the invention of claim 1 contains a resin emulsion, an inorganic filler, and a film-forming aid, the film-forming aid being a water-insoluble organic compound. As a result of extensive experimental research, the inventors have discovered that by blending a water-based emulsion vibration-damping coating composition containing a resin emulsion and an inorganic filler with a film-forming aid consisting of a water-insoluble organic compound, it is possible to reduce the thickness of the coating film while ensuring the vibration-damping properties of the coating film, and also to make it less likely for the coating film to blister during baking and drying. Based on this finding, the present invention was completed.

[0022] That is, according to the aqueous emulsion vibration-damping coating composition of the invention of claim 1, by combining a resin emulsion, an inorganic filler, and a film-forming aid consisting of a water-insoluble organic compound, it is possible to form a coating film that can be made thin while maintaining vibration-damping properties, and that is less likely to produce coating defects such as coating film blistering.

[0023] According to the aqueous emulsion vibration-damping coating composition of the present invention, the boiling point of the coalescent is preferably within the range of 140 to 250°C. Coalescents with too low a boiling point tend to evaporate easily, resulting in poor film-forming properties and difficulty in suppressing coating blistering. On the other hand, if the boiling point is too high, the coalescent tends to remain even after baking (usually 100 to 200°C), resulting in poor coating performance, such as vibration-damping. In addition to the effects described in claim 1, a coalescent composed of a water-insoluble organic compound with a boiling point within the above range can ensure high vibration-damping properties and film-forming properties, and can further reduce coating blistering. More preferably, the boiling point of the coalescent is within the range of 140 to 225°C, and even more preferably 160 to 220°C, because the coalescent is less likely to remain even at low baking temperatures, the resulting coating exhibits better vibration-damping properties and also enables energy savings during baking.

[0024] According to the aqueous emulsion vibration-damping coating composition of the present invention, the coalescence aid is preferably blended in an amount of 0.3 to 10.0 parts by mass, more preferably 0.5 to 10.0 parts by mass, even more preferably 0.5 to 8.0 parts by mass, and particularly preferably 1.0 to 5.0 parts by mass, per 100 parts by mass of the resin emulsion. If the blending amount of coalescence aid is too small, film-forming properties and thin-film formation properties will be reduced, while if the blending amount is too large, the coalescence aid will tend to remain even after baking and drying, resulting in reduced film properties such as vibration damping. If the blending amount of coalescence aid is within the above range, in addition to the effect of claim 1, high vibration damping properties, high film-forming properties, and high thin-film formation properties can be ensured.

[0025] According to the aqueous emulsion vibration-damping coating composition of the invention of claim 4, the film-forming aid is a water-insoluble organic compound having a solubility in water at 25°C of preferably 5 to 40 g / 100 g, more preferably 5 to 30 g / 100 g, even more preferably 5 to 20 g / 100 g, and particularly preferably 5.5 to 20 g / 100 g. When the water-insoluble organic compound has a water-insoluble organic compound, if the water-solubility is too high, it is difficult to suppress blistering of the coating film and it is difficult to obtain the thin-film effect. On the other hand, if the water-solubility is too low, it is difficult to obtain the thin-film effect. If the film-forming aid is a water-insoluble organic compound having a water-solubility in water at 25°C within the above range, in addition to the effect of claim 1, it is possible to ensure high film-forming properties and to further reduce the occurrence of blistering of the coating film.

[0026] In the aqueous emulsion vibration-damping coating composition according to the invention of claim 5, the film-forming aid is preferably an ether-based organic compound, which reduces the rate of viscosity change after aging, thereby ensuring storage stability in addition to the effect of claim 1.

[0027] According to the aqueous emulsion vibration-damping coating composition of the invention of claim 6, the resin emulsion has a minimum film-forming temperature within the range of preferably 0 to 40°C, more preferably 5 to 35°C, and even more preferably 10 to 25°C, so that the film-forming properties are good even if the composition is left at a temperature below room temperature before baking and drying. Therefore, in addition to the effect of claim 1, the range of application of the coating can be expanded.

[0028] According to the aqueous emulsion vibration-damping coating composition of the invention of claim 7, the inorganic filler is preferably blended in a range of 100 to 250 parts by mass, more preferably 120 to 230 parts by mass, and even more preferably 150 to 200 parts by mass per 100 parts by mass of the resin emulsion. If the blending amount of inorganic filler is too small, sufficient vibration-damping properties cannot be obtained, while if the blending amount is too large, thin-film properties and application workability are reduced. If the blending amount of inorganic filler is within the above range, in addition to the effect of claim 1, vibration-damping properties and application workability can both be achieved, and high thin-film properties can be obtained.

[0029] According to the eighth aspect of the present invention, there is provided a cured coating film formed from an aqueous emulsion vibration-damping coating composition containing a resin emulsion, an inorganic filler, and a film-forming aid, wherein the film-forming aid is a water-insoluble organic compound. As a result of extensive experimental research, the present inventors discovered that by blending a water-based emulsion vibration-damping coating composition containing a resin emulsion and an inorganic filler with a film-forming aid consisting of a water-insoluble organic compound, the coating film can be made thinner while maintaining its vibration-damping properties, and blistering is less likely to occur during baking and drying. Based on this finding, the present invention was completed. That is, the cured coating film according to the eighth aspect of the present invention can be made thinner while maintaining its vibration-damping properties, and is less likely to suffer from coating defects such as blistering.

[0030] [Embodiments] The following describes embodiments of the present invention. The aqueous emulsion vibration-damping coating composition according to the embodiments of the present invention contains a resin emulsion, an inorganic filler, and a film-forming aid made of a water-insoluble organic compound.

[0031] Examples of resin emulsions include acrylic resin (including methacrylic resin) emulsions, vinyl acetate emulsions, ethylene vinyl acetate emulsions, vinyl acetate acrylic emulsions, styrene-butadiene-latex (SBR) emulsions, styrene-butadiene emulsions, ethylene acrylic emulsions, acrylonitrile-butadiene-latex (NBR) emulsions, urethane resin emulsions, epoxy resin emulsions, phenolic resin emulsions, and polyester resin emulsions, and one or more of these may be used.

[0032] The acrylic resin in the acrylic resin (including methacrylic resin) emulsion refers to a homopolymer or copolymer of (meth)acrylic acid (meaning acrylic acid or methacrylic acid; the same applies hereinafter) or a (meth)acrylic acid ester, or a copolymer of such a monomer copolymerizable with (meth)acrylic acid or the like.

[0033] Examples of the (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, ethylhexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 3-hydroxybutyl (meth)acrylate, 2,2-bis(hydroxymethyl)ethyl (meth)acrylate, 3-chloro-2-hydroxypropyl (meth)acrylate, glycidyl (meth)acrylate, aminoethyl (meth)acrylate, aminopropyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, diethylaminoethyl (meth)acrylate, methoxyethyl (meth)acrylate, methoxypropyl (meth)acrylate, methoxybutyl (meth)acrylate, and stearyl (meth)acrylate.

[0034] Monomers copolymerizable with (meth)acrylic acid and the like are preferably monomers having an ethylenically unsaturated group, such as ethylene, propylene, butylene, butadiene, styrene, α-methylstyrene, vinylphenol, vinyl chloride, vinylidene chloride, vinyl acetate, vinyl pivalate, vinyl benzoate, vinyl alcohol, allyl alcohol, crotonic acid, itaconic acid, maleic acid, fumaric acid, (meth)acrylamide, N-methylolacrylamide, N-butoxymethylol(meth)acrylamide, and (meth)acrylonitrile. Emulsion polymerization is a common copolymerization method, but the copolymerization method is not limited thereto. In addition, in the case of acids, their alkali metal salts, alkaline earth metal salts, and the like may also be used. Furthermore, polymers and copolymers of the above-mentioned (meth)acrylic acid and the like may be modified with a urethane resin, such as urethane-modified (meth)acrylic acid, or polymers of epoxy-modified, phenol-modified, or melamine-modified (meth)acrylic acid, modified with an epoxy resin, a phenol resin, a melamine resin, or the like.

[0035] As the resin emulsion, an acrylic resin emulsion of an acrylic copolymer or a styrene-butadiene-latex (SBR) emulsion is preferred because it is low cost and can form a coating film with high vibration-damping properties and rigidity. Acrylic resin emulsions are more preferred, and among them, acrylic styrene emulsions are preferred because they can enhance vibration-damping properties.

[0036] The resin emulsion preferably has a minimum film-forming temperature (MFT) in the range of 0 to 40° C., more preferably 5 to 35° C., and even more preferably 10 to 25° C. If the resin emulsion has a minimum film-forming temperature in the above range, cracks and the like are unlikely to occur and the film-forming properties are good even if the resin emulsion is left wet at a temperature below room temperature before baking and drying.

[0037] The concentration of the resin component (resin solids) in the resin emulsion is preferably 30 to 90% by mass, more preferably 40 to 80% by mass, and even more preferably 45 to 70% by mass. Within this range, coating workability is improved, the amount of water evaporated can be reduced, and a uniform coating film can be obtained. Furthermore, even when a large amount of inorganic filler is incorporated, the inorganic filler can be retained, resulting in excellent coating film performance such as vibration damping and rigidity. The amount of resin emulsion incorporated is preferably 10 to 70% by mass, more preferably 20 to 60% by mass, and even more preferably 25 to 40% by mass, based on the total aqueous emulsion vibration-damping coating composition. Furthermore, in terms of resin content (solids), the amount is preferably 5 to 50% by mass, more preferably 8 to 40% by mass, and even more preferably 10 to 30% by mass. The weight-average molecular weight (Mw) of the entire resin, as measured by GPC (gel permeation chromatography), is preferably in the range of 40,000 to 200,000. If the weight-average molecular weight of the resin emulsion is too small, the strength of the coating film will be weak and it will lack practicality, while if the weight-average molecular weight of the resin emulsion is too large, the vibration-damping properties will be reduced.Within this range, a coating film exhibiting appropriate coating strength and vibration-damping properties will be obtained.The particle size (median size) of the resin emulsion is about 100 to 300 nm, preferably in the range of 150 to 200 nm.

[0038] Examples of inorganic fillers include calcium carbonate, mica, talc, diatomaceous earth, barium sulfate, magnesium carbonate, iron oxide, zeolite, alumina, gypsum, cement, zeolite, clay, converter slag powder, shirasu powder, glass powder, glass flakes, graphite, calcium silicate, vermiculite, kaolinite, wollastonite, etc., and one or more of these may be used. Preferably, a combination of two or more types can provide good vibration damping properties over a wide temperature range.

[0039] Among these, inorganic fillers that do not have a biaxially oriented shape, such as calcium carbonate, mica, talc, diatomaceous earth, barium sulfate, zeolite, and magnesium carbonate, are preferred because they facilitate the evaporation of water from the paint during baking and drying, reducing the likelihood of blistering of the paint film. Furthermore, inorganic fillers such as calcium carbonate, mica, talc, diatomaceous earth, barium sulfate, zeolite, and magnesium carbonate are relatively compatible with resin emulsions, allowing the paint film obtained by applying an aqueous emulsion-based vibration-damping paint composition to exhibit high vibration-damping properties. In particular, mica is scaly, and by entangling with the resin of the resin emulsion during baking and drying, it can improve the vibration-damping properties and rigidity of the paint film. Preferably, mica with an aspect ratio of approximately 10 to 35 and an average median diameter of approximately 3 μm to 35 μm can further enhance vibration-damping properties and rigidity while maintaining good application workability and dispersibility. Calcium carbonate is inexpensive and therefore reduces costs, and its ability to slow down the formation of close-packed particles facilitates evaporation of water from the paint during baking and drying, preventing blistering of the paint film. Barium sulfate has a high specific gravity, which is advantageous for the sound insulation of the paint film.

[0040] The amount of inorganic filler is preferably 100 to 250 parts by mass, more preferably 120 to 230 parts by mass, and even more preferably 150 to 200 parts by mass per 100 parts by mass of resin emulsion. In the aqueous emulsion vibration-damping coating composition, the inorganic filler content is preferably 30 to 80% by mass, more preferably 40 to 70% by mass, and even more preferably 50 to 60% by mass. If the amount of inorganic filler is too low, sufficient vibration-damping properties and rigidity cannot be obtained when the coating is formed into a thin film. On the other hand, if the amount is too high, thin film formation is impaired, viscosity increases, coating workability is impaired, and the coating is more likely to crack during baking and drying. If the amount of inorganic filler is within the above range, coating workability is good, thin film formation is excellent, high vibration-damping properties and rigidity are obtained, and coating cracking is less likely to occur. Note that the above amount of inorganic filler refers to the total amount when two or more types of inorganic filler are combined.

[0041] The film-forming aid is a water-insoluble organic compound, and may be an ether or ester type, with an ether type being preferred. An ether-based water-insoluble organic compound can suppress viscosity changes, ensuring the storage stability of the aqueous emulsion vibration-damping coating composition. Examples of water-insoluble ether-based organic compounds that can be used include dipropylene glycol n-propyl ether, propylene glycol n-butyl ether, propylene glycol methyl ether acetate, dipropylene glycol methyl ether acetate, propylene glycol diacetate, propylene glycol phenyl ether, dipropylene glycol dimethyl ether, tripropylene glycol n-butyl ether, ethylene glycol phenyl ether, ethylene glycol hexyl ether, and diethylene glycol monohexyl ether. These compounds may be used alone or in combination of two or more. Among these, dipropylene glycol-n-propyl ether and propylene glycol-n-butyl ether are preferred from the viewpoints that they are unlikely to remain after baking and drying, can exhibit high vibration-damping properties, and can further enhance thin film properties while suppressing coating blistering and the like.

[0042] The coalescing aid made of an ether-based water-insoluble organic compound preferably has a water solubility at 25°C of 5 to 40 g / 100 g, more preferably 5 to 30 g / 100 g, even more preferably 5 to 20 g / 100 g, and particularly preferably 5.5 to 20 g / 100 g. If the solubility of an ether-based water-insoluble organic compound in water is too high, it is difficult to suppress blistering of the coating film, and it is difficult to obtain the thin-film effect. On the other hand, if the solubility is too low, it is difficult to obtain the thin-film effect. A coalescing aid made of an ether-based water-insoluble organic compound whose solubility in water at 25°C is within the above range can ensure high film-forming properties and is less likely to cause blistering of the coating film.

[0043] Furthermore, such coalescing aids made of water-insoluble organic compounds preferably have a boiling point in the range of 140 to 250°C, more preferably 140 to 225°C, and even more preferably 160 to 220°C. Coalescing aids with too low a boiling point tend to evaporate easily, resulting in reduced film-forming properties and difficulty in suppressing coating blistering. On the other hand, if the boiling point is too high, the coalescing aid tends to remain even after baking (usually 100 to 250°C), resulting in reduced coating performance, such as vibration damping. Coalescing aids made of water-insoluble organic compounds with a boiling point within the above range can ensure high vibration damping and film-forming properties, and also reduce the likelihood of coating blistering. Coalescing aids with a boiling point in the range of 140 to 225°C, even more preferably 160 to 220°C, tend to remain even at low baking temperatures, resulting in higher vibration damping and energy savings.

[0044] The blending amount of the coalescent is preferably 0.3 to 10.0 parts by mass, more preferably 0.5 to 10.0 parts by mass, even more preferably 0.5 to 8.0 parts by mass, and particularly preferably 1.0 to 5.0 parts by mass, per 100 parts by mass of the resin emulsion. The blending amount of the coalescent is preferably 0.5 to 20.0 parts by mass, more preferably 1.0 to 20.0 parts by mass, even more preferably 1.5 to 15.0 parts by mass, and particularly preferably 2.0 to 10.0 parts by mass, per 100 parts by mass of the resin solids content of the resin emulsion. In the aqueous emulsion-based vibration-damping coating composition, the content of the coalescent is preferably 0.1 to 3.5% by mass, more preferably 0.15 to 2.5% by mass, and even more preferably 0.3 to 1.6% by mass. If the amount of coalescing agent is too small, film-forming properties and thin film formation properties will be reduced, while if the amount is too large, the coalescing agent will likely remain even after baking and drying, resulting in reduced coating film performance such as vibration damping.If the amount of coalescing agent is within the above range, vibration damping properties can be ensured over a wide temperature range, and high vibration damping properties, high film-forming properties, and high thin film formation properties can be ensured.

[0045] The aqueous emulsion vibration-damping coating composition of this embodiment preferably further contains additives. Examples of additives include foaming agents, expanding agents, antifoaming agents, dispersants, plasticizers, thickeners, anti-sagging (anti-dragging) agents, anti-settling agents, water absorbents, wetting agents, water retention agents, pigments, ultraviolet absorbers, and antioxidants. In addition, water (solvent) may be added to adjust the viscosity to an appropriate level during application and to improve the finish of the coated surface.

[0046] As the foaming agent, organic or inorganic hollow particles such as thermally expandable resin balloons that expand when heated, or organic foaming agents that foam when heated are used.

[0047] Examples of heat-expandable organic hollow particles include unexpanded microcapsules (resin balloon particles) that contain a balloon having an outer shell made of a polymeric compound (e.g., polyvinylidene chloride, polyacrylonitrile, polystyrene, polyethylene, polyvinylidene chloride, polymethyl methacrylate, polyamide, polyester, polyurethane, or copolymers thereof) and an expanding agent (e.g., a liquid hydrocarbon, preferably a low-boiling hydrocarbon having 4 to 6 carbon atoms such as butane or isobutane) that volatilizes and expands upon heating, and that begin to expand when heated at a predetermined temperature (preferably 80°C to 100°C).The unexpanded microcapsules preferably have an average median diameter in the range of about 10 to 20 μm and a foaming initiation temperature in the range of about 80°C to 100°C.

[0048] Examples of organic blowing agents include nitroso-based blowing agents such as dinitrosopentamethylenetetramine, sulfonylhydrazide-based blowing agents such as benzenesulfonylhydrazide and p-toluenesulfonylhydrazide, and azo-based blowing agents such as azobisisobutylnitrile and azodicarbonamide. When using these blowing agents, a blowing assistant such as a urea-based blowing assistant, an organic acid-based blowing assistant, or a metal salt-based blowing assistant may be used in combination.

[0049] The blowing agent may be one of the above-mentioned types alone or two or more types may be used in combination, with thermally expandable organic hollow particles being preferred. The thermally expandable organic hollow particles are preferably blended in an amount of 0 to 5 parts by mass, more preferably 0.5 to 4.0 parts by mass, and even more preferably 1.0 to 3.0 parts by mass, per 100 parts by mass of the resin emulsion. The content of the thermally expandable organic hollow particles in the aqueous emulsion-based vibration-damping coating composition is preferably 0 to 3% by mass, more preferably 0.1 to 2% by mass, and even more preferably 0.3 to 1.0% by mass.

[0050] The inclusion of such a foaming agent causes the foaming agent to expand, creating cracks and micropores in the coating film before curing, which in turn allows moisture to be quickly expelled to the outside, improving water drainage and reducing the occurrence of swelling of the coating film during baking and drying due to the bumping of moisture (water vapor).

[0051] Examples of water retention agents include glycols (dihydric alcohols) such as ethylene glycol, propylene glycol, and diethylene glycol; polyethylene glycol; glycerols such as glycerin; and polyols such as polyglycerin. The inclusion of a water retention agent helps retain moisture in the resin emulsion, suppressing surface drying and skinning, thereby reducing the occurrence of coating blistering during baking. Furthermore, even when left wet before heating, the coating film is less likely to crack, and drying bumps are less likely to occur at the nozzle tip of the applicator. The water retention agent is preferably blended in an amount of 0 to 8.0 parts by mass, more preferably 1.0 to 7.0 parts by mass, and even more preferably 3.0 to 6.0 parts by mass per 100 parts by mass of resin emulsion. In aqueous emulsion-based vibration-damping coating compositions, the water retention agent is preferably present in an amount of 0 to 5.0% by mass, more preferably 0.5 to 3.0% by mass, and even more preferably 1.0 to 2.0% by mass. Within the above range, both water drainage and suppression of the occurrence of electrodeposition blisters during baking can be achieved.

[0052] Examples of defoaming agents include silica-based (e.g., hydrophobic silica-based), metal soap-based, wax-based, polyether-based, silicone-based, and acrylic-based defoaming agents. The inclusion of a defoaming agent can reduce the generation of foam during stirring, even at low viscosity. The defoaming agent is preferably blended in an amount of 0 to 1.0 parts by mass, more preferably 0.1 to 0.8 parts by mass, and even more preferably 0.2 to 0.5 parts by mass, per 100 parts by mass of the resin emulsion. In the aqueous emulsion-based vibration-damping coating composition, the content of the defoaming agent is preferably 0 to 0.3% by mass, more preferably 0.01 to 0.1% by mass, and even more preferably 0.05 to 0.15 parts by mass.

[0053] Examples of dispersants include polycarboxylic acid-based dispersants (such as sodium polycarboxylic acid salts), phosphonic acid-based dispersants, naphthalenesulfonic acid-based dispersants, cationic polymers, and sodium polyphosphate. The inclusion of a dispersant can improve the dispersibility of the blended materials. The dispersant is preferably blended in an amount of 0 to 2.0 parts by mass, more preferably 0.5 to 1.8 parts by mass, and even more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the resin emulsion. In the aqueous emulsion-based vibration-damping coating composition, the dispersant content is preferably 0 to 0.5% by mass, more preferably 0.05 to 0.2% by mass, and even more preferably 0.1 to 0.4% by mass.

[0054] Examples of wetting agents (emulsifiers) include nonionic surfactants and anionic surfactants. The inclusion of a wetting agent can stabilize the resin emulsion. The wetting agent is preferably blended in an amount of 0 to 2.0 parts by mass, more preferably 0.5 to 1.8 parts by mass, and even more preferably 0.5 to 1.5 parts by mass, per 100 parts by mass of the resin emulsion. The content of the wetting agent in the aqueous emulsion-based vibration-damping coating composition is preferably 0 to 0.5% by mass, more preferably 0.05 to 0.2% by mass, and even more preferably 0.1 to 0.4% by mass.

[0055] Examples of anti-sagging agents (thixotropic agents) include silica-based (fine silica powder), bentonite-based, sepiolite-based, and calcium carbonate-based agents. The inclusion of an anti-sagging agent can adjust viscosity and thixotropy. The anti-sagging agent is preferably blended in an amount of 0 to 4.0 parts by mass, more preferably 1.0 to 5.0 parts by mass, and even more preferably 2.0 to 3.0 parts by mass, per 100 parts by mass of resin emulsion. In the aqueous emulsion-based vibration-damping coating composition, the content of the anti-sagging agent is preferably 0 to 2.0% by mass, more preferably 0.1 to 1.5% by mass, and even more preferably 0.5 to 1.0% by mass.

[0056] Examples of pigments include color pigments such as carbon black, titanium oxide, iron oxide, and zinc oxide, organic azo chelate pigments, insoluble azo pigments, condensed azo pigments, diketopyrrolopyrrole pigments, benzimidazolone pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, quinacridone pigments, isoindolinone pigments, metal complex pigments, yellow lead, yellow iron oxide, red iron oxide, and titanium dioxide. The inclusion of a pigment enables cosmetic effects and control of the coating film surface. The pigment is preferably blended in an amount of 0 to 1.5 parts by mass, more preferably 0.1 to 1.0 part by mass, and even more preferably 0.2 to 0.5 parts by mass per 100 parts by mass of the resin emulsion. In the aqueous emulsion vibration-damping coating composition, the pigment content is preferably within the range of 0 to 2.0 mass %, more preferably 0.01 to 1.0 mass %, and even more preferably 0.05 to 0.5 mass %.

[0057] Examples of water-absorbing agents (anti-blister agents) include water-absorbing synthetic resins, cellulose derivatives, and starches of polysaccharides (e.g., corn starch, potato starch, wheat starch). The inclusion of a water-absorbing agent allows the moisture retained therein to gradually volatilize, preventing coating film blistering due to sudden boiling of moisture in the coating film. The anti-blister agent is preferably blended in an amount of 0 to 50.0 parts by mass, more preferably 10.0 to 40.0 parts by mass, and even more preferably 20.0 to 30.0 parts by mass, per 100 parts by mass of resin emulsion. The content of the anti-blister agent in the aqueous emulsion-based vibration-damping coating composition is preferably 0 to 15.0% by mass, more preferably 1.0 to 12.0% by mass, and even more preferably 5 to 10.0% by mass.

[0058] Examples of thickeners include methyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polycarboxylic acid amides, water-soluble polysaccharides, proteins, polyvinyl alcohol, polyacrylates, anhydrous silica, etc., with polyacrylic acid being preferred. The inclusion of a thickener can adjust the viscosity to an appropriate level and improve the dispersibility of inorganic fillers. The thickener is preferably blended in an amount of 0 to 4.0 parts by mass, more preferably 0.5 to 3.0 parts by mass, and even more preferably 1.0 to 2.0 parts by mass per 100 parts by mass of resin emulsion. In aqueous emulsion-based vibration-damping coating compositions, the thickener is preferably present in an amount of 0 to 2.0% by mass, more preferably 0.1 to 1.0% by mass, and even more preferably 0.3 to 0.8% by mass.

[0059] The aqueous emulsion vibration-damping coating composition of this embodiment is produced by uniformly stirring and then degassing using a mixer such as a Banbury mixer, planetary mixer, butterfly mixer, Henschel mixer, super mixer, static mixer, dynamic mixer, or spiral mixer, or a known mixer / disperser such as a dissolver, roll mill, grain mill, open kneader, vacuum kneader, or attritor. For example, the resin emulsion is placed in a mixer with a degassing / stirring function, and additives (e.g., dispersants, wetting agents, and antifoaming agents) are added as needed. After stirring, an inorganic filler and a film-forming aid consisting of a water-insoluble organic compound are added and stirred until uniform. Furthermore, other additives (e.g., thickeners, water retention agents, anti-sagging agents, and foaming agents) and water are added as needed to adjust the viscosity to a predetermined level, followed by degassing and stirring (vacuum degassing, etc.) to produce the aqueous emulsion vibration-damping coating composition.

[0060] The aqueous emulsion vibration-damping coating composition thus prepared is applied to a predetermined location on the surface of a steel plate (electrodeposition coated surface) or the like by a known coating method, for example, by coating means such as a spray gun for spray coating, an air spray gun, an airless spray gun, an air-assisted airless spray gun, a mortar gun, a lysine gun, a curtain flow coater, a dispenser, brush coating, roller coating, or electrostatic coating, and then baked and dried using a hot air circulation drying oven or the like at a predetermined temperature (usually in the range of 100°C to 200°C, preferably 100 to 160°C, more preferably 120 to 150°C, preferably for 5 to 40 minutes, more preferably 20 to 30 minutes), thereby curing the composition and forming a cured coating film.

[0061] The aqueous emulsion vibration-damping coating composition of this embodiment can be applied automatically using a coating robot or the like to, for example, the floor, trunk, dash, door, fender, floor tunnel, exhaust system panel, roof, etc. of a vehicle, and can also be applied to areas where application of a vibration-damping sheet has been difficult, such as areas with complex surface shapes, such as an automobile chassis, pillars, backbone, wheelhouse, etc. Of course, the application is not limited to automobile vehicles, and can also be applied to railway vehicles, ships, aircraft, electrical equipment, building structures, construction equipment, etc.

[0062] In particular, the aqueous emulsion vibration-damping coating composition of this embodiment contains a resin emulsion, an inorganic filler, and a film-forming aid, and because the film-forming aid is a water-insoluble organic compound, it is possible to form a coating film that can be made thin while maintaining vibration-damping properties and that is less likely to cause coating defects such as blistering. Thus, with the aqueous emulsion vibration-damping coating composition of this embodiment, the resulting thin cured coating film is less likely to cause interference with parts, and is less likely to cause assembly defects even when parts are assembled in a later process, making it possible to expand the range of application of the coating.

[0063] The cured coating film obtained by applying the aqueous emulsion vibration-damping coating composition of this embodiment and then baking and drying it preferably has a dry specific gravity in the range of 1.03 to 1.30, more preferably 1.05 to 1.25, and even more preferably 1.05 to 1.25. If the dry specific gravity of the cured coating film is too low, the sound insulation properties will be reduced, while if the dry specific gravity is too high, the film will have poor thinness when the application weight is approximately the same. If the dry specific gravity is within this range, both sound insulation and thin film properties will be achieved.

[0064] Examples Next, examples of aqueous emulsion-based vibration-damping coating compositions according to embodiments of the present invention will be described. The aqueous emulsion-based vibration-damping coating compositions according to Examples 1 to 5 contain 100.0 parts by mass (amount converted to resin solids: 50 to 51 parts by mass) of an acrylic emulsion (Dow Chemical's "ACOUSTICRYL SD-380 (acrylic copolymer emulsion)"; resin solids: 50 to 51%, minimum film-forming temperature: approximately 14 to 16°C) as the resin emulsion, 3.1 parts by mass of mica, 136.5 parts by mass of calcium carbonate (heavy calcium carbonate), and 33.8 parts by mass of barium sulfate as inorganic fillers, totaling 173 parts by mass, and a water-insoluble ether-based organic compound (Dow Chemical's "DOWANOL SD-380"; a water-insoluble ether-based organic compound) as a film-forming aid. The composition contains 1.0 to 5.0 parts by mass of dipropylene glycol-n-propyl ether (Dpnp), boiling point: 213°C, solubility in water at 25°C: 19.6 g / 100 g-H2O. The composition also contains additives such as 2.0 parts by mass of a foaming agent (thermal expansion balloon), 4.3 parts by mass of a water retention agent (propylene glycol), 2.7 parts by mass of a sagging prevention agent (bentonite), 0.3 parts by mass of a coloring pigment (carbon black), 23.7 parts by mass of a water absorbent (starch), and 1.6 parts by mass of a thickener, as well as 4.4 parts by mass of ion-exchanged water.

[0065] The only difference between the formulations of Examples 1 to 5 is the amount of the water-insoluble ether-based organic coalescent compound, as shown in the upper part of Table 1. That is, the water-insoluble ether-based organic coalescent compound ("DOWANOL Dpnp (dipropylene glycol-n-propyl ether)" from The Dow Chemical Company, boiling point: 213°C, solubility in water at 25°C: 19.6 g / 100 g-HO) was blended in an amount of 1.0 part by mass in Example 1, 2.0 parts by mass in Example 2, 3.0 parts by mass in Example 3, 4.0 parts by mass in Example 4, and 5.0 parts by mass in Example 5, relative to 100 parts by mass of the resin emulsion.

[0066] [Comparative Examples] Furthermore, for comparison, aqueous emulsion paint compositions of Comparative Examples 1 to 3 were also prepared. Comparative Example 1 did not use a coalescing aid, but otherwise had the same blended materials and formulation as Examples 1 to 5 above. That is, it is a composition in which no coalescing aid is blended compared to the blends of Examples 1 to 5. Comparative Example 2 blended 2.0 parts by mass of a water-soluble ether-based organic compound ("Butyl CARBITOL (diethylene glycol monobutyl ether)" from The Dow Chemical Company, boiling point: 230.6°C, solubility in water at 25°C: miscible) as a coalescing aid instead of the coalescing aid used in Examples 1 to 5 above, but otherwise had the same blended materials and amounts as Examples 1 to 5 above. In Comparative Example 3, instead of the coalescence aid used in Examples 1 to 5, 4.0 parts by mass of a water-soluble ether-based organic compound (Butyl CARBITOL (diethylene glycol monobutyl ether) manufactured by The Dow Chemical Company, boiling point: 230.6°C, solubility in water at 25°C: miscible) was blended as the coalescence aid. Other than that, the blending materials and blending amounts were the same as those of Examples 1 to 5.

[0067] The formulations of the aqueous emulsion coating compositions of each Example and Comparative Example are shown in the upper part of Table 1. The ingredients and amounts of ingredients other than the film-forming agent were all consistent throughout the formulations of Examples 1 to 5 and Comparative Examples 1 to 3, and the only differences between the formulations of Examples 1 to 5 and Comparative Examples 1 to 3 were the type and amount of film-forming agent shown in the upper part of Table 1. The numerical values ​​in the same column in the upper part of Table 1 indicate the quantity (parts by mass). The aqueous emulsion coating compositions of each Example and Comparative Example were prepared by mixing the ingredients according to the formulation shown in the upper part of Table 1 and degassing and stirring using a high-speed stirrer.

[0068]

[0069] Each of the aqueous emulsion coating compositions of Examples 1 to 5 and Comparative Examples 1 to 3 was subjected to evaluation tests for the vibration-damping properties of the coating film, the thinness of the coating film, the blistering of the coating film, and the film-forming properties. For the vibration-damping properties, the aqueous emulsion coating composition was applied to an electrodeposited steel plate measuring 10 mm wide x 220 mm long x 1.6 mm thick in an area of ​​10 mm x 200 mm, and the surface density was 4 kg / m 2 The test piece was placed in a drying oven (dryer) adjusted to 130°C for 30 minutes to be baked and dried, and used as a test piece (evaluation panel). The secondary resonance frequency of this test piece was measured by the cantilever method, and the loss factor at the secondary resonance point at each temperature of 20°C, 40°C, and 60°C was calculated by the half-width method. If the loss factor was 0.04 or more, it was determined that vibration damping properties were ensured, and as a result of the measurement by the cantilever method, a loss factor of 0.04 or more at each temperature of 20°C, 40°C, and 60°C was evaluated as ○ (pass), and one of less than 0.04 was evaluated as × (fail).

[0070] Regarding film thinning, the aqueous emulsion coating composition was applied to an electrodeposited steel plate measuring 70 mm x 150 mm x 0.8 mm thick to a wet film thickness of 3 mm, and immediately after application, the plate was placed in a drying oven (dryer) adjusted to 130°C for 30 minutes to dry by baking, and the dry specific gravity of the cured coating film formed on the electrodeposited plate was measured. Since it can be said that the higher the dry specific gravity at this time, the thinner the film, if the masses of the coating components are similar, a dry specific gravity of 1.10 or more indicates excellent film thinning and was evaluated as ◎ (good, pass); a dry specific gravity of 1.05 or more but less than 1.10 indicates that the coating film was sufficiently thin and was evaluated as ○ (fair, pass); and a dry specific gravity of less than 1.05 was evaluated as × (unacceptable, fail).

[0071] For coating blistering, the aqueous emulsion coating composition was applied to an electrodeposited steel plate measuring 70 mm long x 150 mm wide x 0.8 mm thick to a wet film thickness of 3 mm, and immediately after application, the plate was placed in a drying oven (dryer) adjusted to 130°C for 30 minutes to bake and dry, and the state of blistering of the cured coating film formed on the electrodeposited plate was checked. Coatings with no blistering were rated as ⊚ (good, pass); blistering of less than 3 mm was judged to be within the range of practical use and rated as ◯ (fair, pass); and blistering of 3 mm or more was judged to be a coating defect and rated as × (unacceptable, fail).

[0072] Regarding film-forming properties, an aqueous emulsion coating composition was applied to an electrodeposited steel plate measuring 150 mm long x 150 mm wide x 0.8 mm thick to a length of 100 mm x width of 100 mm x wet film thickness of 3 mm, and then left wet at room temperature for 72 hours. The plate was then placed in a dryer adjusted to 130°C for 30 minutes to bake and dry, and the presence or absence of cracks in the cured coating film reaching the substrate was confirmed. Those that did not have cracks reaching the substrate were evaluated as ◯ (pass), and those that had cracks reaching the substrate were evaluated as × (fail). The evaluation results are shown in the lower part of Table 1.

[0073] As shown in Table 1, in Comparative Example 1, in which no coalescence aid was used, the loss factor was 0.04 or more at all measurement temperatures of 20°C, 40°C, and 60°C, and the vibration damping was rated as ◯. Furthermore, no coating blistering occurred during baking, earning a rating of ⊚. However, the dry specific gravity of the cured coating film after baking was 1.01, and the thin film property was rated as x. Furthermore, when the aqueous emulsion coating composition was applied to a substrate and then left wet at room temperature and then baked, cracks occurred in the cured coating film reaching the substrate base, and the film-forming property was also rated as x. In other words, since the aqueous emulsion coating composition of Comparative Example 1 did not use a coalescence aid composed of a water-insoluble organic compound, the coating film after baking was thick. Furthermore, leaving the coating at room temperature after application resulted in poor film formation.

[0074] In addition, in Comparative Example 3, which used a film-forming aid but used a water-soluble ether-based organic compound (diethylene glycol monobutyl ether) at a blending rate of 2.0 parts by mass per 100 parts by mass of resin emulsion, the loss factor was 0.04 or more at all temperatures of 20°C, 40°C, and 60°C, and the vibration damping was rated as good, and the coating blister during high-temperature baking was less than 3 mm, and the film forming property was rated as good. When the aqueous emulsion-based coating composition was applied to a substrate and then left wet at room temperature and then baked, no cracks occurred in the cured coating film that reached the base material of the substrate, and the film forming property was rated as good, but the dry specific gravity of the cured coating film after baking was 1.03, and the thin film property was rated as bad.

[0075] On the other hand, in Comparative Example 4, which used a film-forming aid but which was a water-soluble ether-based organic compound (diethylene glycol monobutyl ether) at a blending rate of 4.0 parts by mass per 100 parts by mass of resin emulsion, the loss coefficient was 0.04 or more at all temperatures of 20°C, 40°C, and 60°C, and the vibration damping was rated as good, the dry specific gravity of the cured coating film after baking drying was 1.06, and the thin film property was rated as good, and when the aqueous emulsion-based coating composition was applied to a substrate and then left wet at room temperature and then baked, no cracks occurred in the cured coating film that reached the base material of the substrate, and the film-forming property was rated as good, but the coating blister during high-temperature baking drying was less than 3 mm, and the film was rated as bad.

[0076] That is, in the aqueous emulsion coating compositions of Comparative Examples 2 and 3, the film-forming aid is composed of a water-soluble organic compound, and therefore the coating cannot be thinned without causing coating defects such as blistering.

[0077] In contrast, in Examples 1 to 5, which used an ether-based water-insoluble film-forming aid, the loss factor was 0.04 or more at all measurement temperatures of 20°C, 40°C, and 60°C, resulting in a rating of ◯, and the dry specific gravity of the cured coating film after baking drying was 1.05 or more, resulting in a rating of ◯ or ◎ for thin film properties. Furthermore, the coating film blistering during high-temperature baking drying was less than 3 mm, resulting in a rating of ◯ or ◎. Furthermore, when the aqueous emulsion-based vibration-damping coating composition was applied to a substrate and then left wet at room temperature before being baked and dried, no cracks occurred in the cured coating film that reached the base material of the substrate, and the film-forming properties were also rated ◯.

[0078] That is, in the aqueous emulsion vibration-damping coating compositions of Examples 1 to 5, by blending a film-forming aid made of a water-insoluble organic compound, thin films were achieved without impairing vibration-damping properties or causing coating defects such as coating blister of 3 mm or more.

[0079] Thus, the aqueous emulsion vibration-damping coating compositions of Examples 1 to 5, which use a water-insoluble organic compound as a coalescing aid, can form thin coatings with low coating density without impairing vibration-damping properties, and which are less likely to develop coating defects such as blistering during baking and drying. This is thought to be because the coalescing aid is a water-insoluble organic compound, which is compatible with the resin particles and easily swells, softens, dissolves, and deforms (plasticizes) the resin particles, thereby enhancing the fusion between the resins, resulting in a thinner coating. Furthermore, if the coalescing aid is a water-insoluble organic compound, its low affinity with water makes it less likely to capture water, and therefore less likely to develop blistering during baking.

[0080] Here, if the solubility of a water-insoluble ether-based organic compound in water is too low, it will not reach the resin particles as efficiently, increasing the adhesion between the resins and reducing the effect of forming a thin film, while if the solubility in water is too high, it will have a high affinity with water and will be less likely to blister during baking. This can be seen from a comparison between Examples 1 to 5, where the dry specific gravity increases as the amount of film-forming aid added increases, improving the thin film properties, but also making the coating more susceptible to blistering.

[0081] According to experimental research by the present inventors, it has been confirmed that if the water-insoluble ether-based organic compound has a solubility in water at 25°C in the range of preferably 5 to 40 g / 100 g, more preferably 5 to 30 g / 100 g, even more preferably 5 to 20 g / 100 g, and particularly preferably 5.5 to 20 g / 100 g, then the presence of the compound in the aqueous phase and in the resin particles is balanced, thereby achieving both thin film formation and the effect of preventing blistering during baking.

[0082] Furthermore, if the amount of coal-forming aid added is too small, cracks will occur when the coating is left wet at or below room temperature and then baked to dry, resulting in a decrease in film-forming properties and a decrease in the film-thinning effect. On the other hand, if the amount of coal-forming aid added is too large, vibration-damping properties at high temperatures (60°C) will decrease, and as mentioned above, it will be difficult to suppress coating blistering. These facts can be seen from the fact that poor film formation occurred in Comparative Example 1, which did not use a coal-forming aid, and further from the fact that, as the amount of coal-forming aid added increases, the loss factor at 20°C increases, but the loss factor at high temperatures such as 40°C and 60°C decreases.

[0083] According to the experimental research of the present inventors, it has been confirmed that, when the blending amount of the coalescing agent is within the range of preferably 0.3 to 10.0 parts by mass, more preferably 0.5 to 10.0 parts by mass, even more preferably 0.5 to 8.0 parts by mass, and particularly preferably 1.0 to 5.0 parts by mass, relative to 100 parts by mass of the resin emulsion, film-forming properties are ensured, high vibration-damping properties are obtained, excellent thin film properties are obtained, and blistering of the coating film during baking and drying is reliably suppressed. In all of Examples 1 to 5, the loss factor was highest at 40°C, and as the amount of coalescing agent added increased, the loss factor at 20°C became higher than the loss factor at 60°C.

[0084] Thus, with the aqueous emulsion vibration-damping coating composition according to the above examples, the combination of a resin emulsion, an inorganic filler, and a film-forming aid consisting of a water-insoluble organic compound allows for a thinner coating (reduced film thickness) while maintaining vibration-damping properties, and also allows for the formation of a coating film that is less likely to blister. Furthermore, with the aqueous emulsion vibration-damping coating composition according to the above examples, the minimum film-forming temperature of the film-forming aid is between 0°C and 40°C, so that no cracks occur (no film formation failure) even if the coating is left wet at or below room temperature after application and before baking and drying, and film-forming properties are ensured. Furthermore, with the aqueous emulsion vibration-damping coating composition according to the above examples, the film thickness can be reduced without reducing the weight of the coating film, and therefore the thickness can be reduced without compromising sound insulation properties. Furthermore, the aqueous emulsion vibration-damping coating composition according to the above example uses an acrylic copolymer emulsion as the resin emulsion, and mica, barium sulfate, and calcium carbonate as the inorganic filler, thereby ensuring vibration-damping properties over a wide temperature range of 20 to 60°C.

[0085] The inventors measured the viscosity after aging of the aqueous emulsion vibration-damping coating compositions of Examples 1 to 5, which used a film-forming aid consisting of an ether-based water-insoluble organic compound. That is, they measured the initial viscosity and the viscosity after two weeks of storage at 40°C, and investigated the rate of viscosity change.

[0086] As a result, it was confirmed that the viscosity of the aqueous emulsion vibration-damping coating compositions of Examples 1 to 5, which used a film-forming aid consisting of an ether-based water-insoluble organic compound, after aging showed a viscosity change rate of less than 30%, ensuring storage stability. Therefore, it is unlikely that the coating workability will deteriorate after storage, or that the coating thickness will change during application, resulting in a deterioration in coatability, etc.

[0087] As explained above, the aqueous emulsion vibration-damping coating composition according to the above embodiment contains a resin emulsion, an inorganic filler, and a film-forming aid, the film-forming aid being a water-insoluble organic compound. The aqueous emulsion vibration-damping coating composition according to the above embodiment combines a resin emulsion, an inorganic filler, and a film-forming aid made of a water-insoluble organic compound, making it possible to form a coating film that is thin and less prone to film defects such as blistering while ensuring vibration-damping properties.

[0088] In the aqueous emulsion vibration-damping coating composition according to the above embodiment, the boiling point of the coalescing aid is preferably in the range of 140°C or higher and 250°C or lower, more preferably 140°C or higher and 225°C or lower, and even more preferably 160°C or higher and 220°C or lower. Coalescing aids with too low a boiling point tend to evaporate easily, resulting in poor film-forming properties and making it difficult to suppress coating blistering. On the other hand, if the boiling point is too high, the coalescing aid remains even after baking and drying, resulting in poor coating performance such as vibration damping. A coalescing aid made of a water-insoluble organic compound with a boiling point within the above range can ensure high vibration damping properties and high film-forming properties, and also makes it less likely for coating blistering to occur.

[0089] In the aqueous emulsion vibration-damping coating composition according to the above embodiment, the coalescence aid is preferably blended in an amount of 0.3 to 10.0 parts by mass, more preferably 0.5 to 10.0 parts by mass, even more preferably 0.5 to 8.0 parts by mass, and particularly preferably 1.0 to 5.0 parts by mass, per 100 parts by mass of the resin emulsion. If the blending amount of the coalescence aid is within the above range, high vibration-damping properties, high film-forming properties, and high thin film properties can be ensured.

[0090] In the aqueous emulsion vibration-damping coating composition according to the above embodiment, the coalescing aid is an ether-based, water-insoluble organic compound having a solubility in water at 25°C of preferably 5 g / 100 g or more and 40 g / 100 g or less, more preferably 5 g / 100 g or more and 30 g / 100 g or less, even more preferably 5 g / 100 g or more and 20 g / 100 g or less, and particularly preferably 5.5 g / 100 g or more and 20 g / 100 g or less. If the coalescing aid has a solubility in water at 25°C within the above range, high thin film properties can be ensured and blistering of the coating film is less likely to occur. Furthermore, if the coalescing aid is an ether-based, water-insoluble organic compound, the viscosity change rate after aging is small, ensuring storage stability.

[0091] In the aqueous emulsion vibration-damping coating composition according to the above embodiment, the resin emulsion has good film-forming properties even when left at room temperature or below before baking, so long as the minimum film-forming temperature is preferably within the range of 0° C. or higher and 40° C. or lower, more preferably 5° C. or higher and 35° C. or lower, and even more preferably 10° C. or higher and 25° C. or lower. This allows for a wider range of application for coating.

[0092] In the aqueous emulsion vibration-damping coating composition according to the above embodiment, the inorganic filler is preferably blended in an amount of 100 to 250 parts by mass, more preferably 120 to 230 parts by mass, and even more preferably 150 to 200 parts by mass, per 100 parts by mass of the resin emulsion. If the blending amount of the inorganic filler is within the above range, vibration-damping properties and coating workability can both be achieved, and high thin-film properties can be obtained.

[0093] The above-described embodiment can also be considered as an invention of a cured coating film formed from an aqueous emulsion vibration-damping coating composition containing a resin emulsion, an inorganic filler, and a film-forming aid, the film-forming aid being a water-insoluble organic compound. The cured coating film of the above-described embodiment can be made thin while maintaining vibration-damping properties, and is less likely to suffer from coating defects such as blistering.

[0094] When carrying out the present invention, the other compositions, components, blending amounts, materials, sizes, manufacturing methods, etc. of the aqueous emulsion vibration-damping coating composition are not limited to those of the present embodiment. Furthermore, the numerical values ​​given in the embodiments of the present invention do not indicate critical values ​​but indicate suitable values ​​for implementation, and therefore slight changes to the above numerical values ​​do not negate the implementation.

Claims

1. An aqueous emulsion vibration-damping coating composition containing a resin emulsion, an inorganic filler, and a film-forming aid, characterized in that the film-forming aid is a water-insoluble organic compound.

2. The aqueous emulsion vibration-damping coating composition according to claim 1, wherein the boiling point of the film-forming aid is within the range of 140 to 250°C.

3. The aqueous emulsion vibration-damping coating composition according to claim 1, characterized in that the film-forming aid is blended in an amount within the range of 0.3 to 10.0 parts by mass per 100 parts by mass of the resin emulsion.

4. The aqueous emulsion vibration-damping coating composition according to claim 1, wherein the film-forming aid is an organic compound having a solubility in water at 25°C within the range of 5 to 40 g / 100 g.

5. The water-based emulsion vibration-damping coating composition according to claim 1, wherein the film-forming aid is an ether-based organic compound.

6. The aqueous emulsion vibration-damping coating composition according to claim 1, characterized in that the resin emulsion has a minimum film-forming temperature within the range of 0 to 40°C.

7. The aqueous emulsion vibration-damping coating composition according to claim 1, characterized in that the inorganic filler is blended in an amount within the range of 100 to 250 parts by mass per 100 parts by mass of the resin emulsion.

8. A cured coating film formed from an aqueous emulsion-based vibration-damping coating composition containing a resin emulsion, an inorganic filler, and a film-forming aid, characterized in that the film-forming aid is a water-insoluble organic compound.

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