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

Abstract

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 aid. The film formation aid is a water-insoluble organic compound.SELECTED DRAWING: None

Description

[Technical Field]

[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. [Background technology]

[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, and the installation must also be done by workers, which hinders automation and prevents 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 water-based emulsion paints contain a large amount of water, depending on the drying conditions, volume shrinkage occurs when the water evaporates, which can cause cracks in the coating, or swelling occurs due to the bumping of water, which can lead to coating defects. In particular, to achieve vibration-damping effects, the coating must be thick, but if the coating is made thick, the coating dries and hardens from the surface, which can easily cause swelling and cracks in the coating when the water remaining inside the coating evaporates. Therefore, in order to prevent such coating defects, foaming agents such as inorganic hollow particles (thermally expandable resin balloons, etc.) are used, as disclosed in Patent Documents 1 to 3. Furthermore, in this type of water-based emulsion paint, inorganic fillers such as mica are also used to improve vibration damping and rigidity. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-145331 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-115740 [Patent Document 3] Japanese Patent Application Laid-Open No. 2008-291077 Summary of the Invention [Problem to be solved by the invention]

[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. [Means for solving the problem]

[0008] The aqueous emulsion vibration-damping coating composition of the invention of claim 1 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 ester resin (including methacrylic 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 milky state in a liquid (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, commonly used sense of "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 coalescent 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 according to claim 5 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 two or more types of resin emulsions are blended, the minimum film-forming temperature of the resin emulsion refers to the minimum film-forming temperature measured for the entire mixture (JIS K6828:200).

[0019] The inorganic filler in the aqueous emulsion-based 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-based 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 contains at least a resin and an inorganic filler as coating film components. [Effects of the Invention]

[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, and the film-forming aid is a water-insoluble organic compound. As a result of extensive experimental research, the inventors have discovered that by blending a film-forming aid made of a water-insoluble organic compound with an aqueous emulsion vibration-damping coating composition containing a resin emulsion and an inorganic filler, it is possible to reduce the thickness of the coating film while maintaining 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 invention of claim 2, the boiling point of the film-forming aid is preferably within the range of 140 to 250°C. If the boiling point of the coalescent is too low, it will evaporate easily, resulting in poor film-forming properties and difficulty in preventing blistering of the coating.On the other hand, if the boiling point is too high, the coalescent will likely remain even after baking (usually at 100-200°C), resulting in poor coating performance such as vibration damping. If the coalescing aid is a water-insoluble organic compound having a boiling point within the above range, it is possible to ensure high vibration-damping properties and high film-forming properties, and further reduce coating blistering, in addition to the effect described in claim 1. More preferably, if the boiling point of the coalescing aid is within the range of 140 to 225°C, and even more preferably 160 to 220°C, the coalescing aid is less likely to remain even at low baking temperatures, so it is possible to achieve higher vibration-damping properties and also to achieve energy savings during baking.

[0024] According to the aqueous emulsion-based vibration-damping coating composition of the invention of claim 3, the film-forming 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, relative to 100 parts by mass of the resin emulsion. If the amount of coalescing agent is too small, film-forming properties and thin film formation will be reduced, while if the amount is too large, the coalescing agent will tend to remain even after baking and drying, reducing film properties such as vibration damping. If the blending amount of the film-forming 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 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. In the case of a film-forming aid made of a water-insoluble organic compound, if the solubility 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, whereas if the solubility in water is too low, it is difficult to obtain the thin film effect. If the film-forming aid is a water-insoluble organic compound whose solubility in water at 25°C is within the above range, in addition to the effect described in claim 1, high thin film properties can be ensured and the coating film is less likely to blister.

[0026] According to the aqueous emulsion vibration-damping coating composition of 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 minimum film-forming temperature is preferably within the range of 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-based vibration-damping coating composition of the invention of claim 7, 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, relative to 100 parts by mass of the resin emulsion. If the amount of inorganic filler blended is too small, sufficient vibration damping properties cannot be obtained, whereas if the amount blended is too large, thin film formation and application workability decrease. If the amount of inorganic filler blended is within the above range, in addition to the effect of claim 1, vibration damping properties and coating workability can both be achieved, and a high degree of thin film formation can be obtained.

[0029] According to the cured coating film of the invention of claim 8, the cured coating film is formed from an aqueous emulsion-based vibration-damping coating composition containing a resin emulsion, an inorganic filler, and a film-forming aid, and the film-forming aid is a water-insoluble organic compound. As a result of extensive experimental research, the inventors have discovered that by blending a film-forming aid made of a water-insoluble organic compound with an aqueous emulsion vibration-damping coating composition containing a resin emulsion and an inorganic filler, it is possible to reduce the thickness of the coating film while maintaining 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. That is, the cured coating film according to the invention of claim 8 can be made thinner while maintaining vibration-damping properties, and coating defects such as coating blistering are less likely to occur. DETAILED DESCRIPTION OF THE INVENTION

[0030] [Embodiment Mode] Hereinafter, an embodiment of the present invention will be described. The aqueous emulsion vibration-damping coating composition according to an embodiment 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 ester 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. Acids may also be alkali metal salts, alkaline earth metal salts, or the like. Furthermore, polymers and copolymers of the above-mentioned (meth)acrylic acid and the like may be modified with urethane resins, such as urethane-modified (meth)acrylic acid, or polymers of epoxy-, phenol-, or melamine-modified (meth)acrylic acid, such as those modified with epoxy resins, phenolic resins, melamine resins, 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 acrylic-styrene emulsions are particularly preferred because they can improve 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 good, evaporation of water can be reduced, and a uniform coating film can be obtained. Furthermore, even if a large amount of inorganic filler is blended, the inorganic filler can be retained, and good coating film performance such as vibration damping and rigidity can be achieved. The blending amount of the resin emulsion is preferably within the range of 10 to 70 mass%, more preferably 20 to 60 mass%, and even more preferably 25 to 40 mass%, of the entire aqueous emulsion vibration-damping coating composition, and is preferably within the range of 5 to 50 mass%, more preferably 8 to 40 mass%, and even more preferably 10 to 30 mass%, calculated as the resin content (solid content). The weight-average molecular weight of the resin emulsion as a whole, measured by GPC (gel permeation chromatography), is preferably in the range of Mw = 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. If it is within this range, a coating film that exhibits 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, and preferably within 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, and wollastonite, and one or more of these are used. Preferably, a combination of two or more types can provide good vibration damping properties over a wide temperature range.

[0039] Among these, calcium carbonate, mica, talc, diatomaceous earth, barium sulfate, zeolite, magnesium carbonate, and other materials that do not have a biaxially oriented shape are preferred because they facilitate the evaporation of water in the paint during baking and drying, making it less likely for the paint film to blister. Furthermore, inorganic fillers such as calcium carbonate, mica, talc, diatomaceous earth, barium sulfate, zeolite, and magnesium carbonate are relatively compatible with resin emulsions, and therefore can exhibit high vibration-damping properties in coating films obtained by applying aqueous emulsion-based vibration-damping coating compositions. In particular, mica is scaly and entangles with the resin in the resin emulsion during baking and drying, thereby improving the vibration-damping properties and rigidity of the coating film. Preferably, mica has an aspect ratio of approximately 10 to 35 and an average median diameter of approximately 3 μm to 35 μm, which makes it possible to further improve vibration-damping properties and rigidity while maintaining good application workability and dispersibility. Calcium carbonate is inexpensively available, allowing for cost reduction, and can also slow down the rate of close-packing, facilitating the evaporation of water from the paint during baking and drying, preventing the occurrence of blistering in the coating film. Barium sulfate has a high specific gravity, which is advantageous for the sound insulation properties of the coating film.

[0040] The amount of inorganic filler to be blended 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 the resin emulsion. The content of the inorganic filler in the aqueous emulsion vibration-damping coating composition 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 small, sufficient vibration-damping properties and rigidity cannot be obtained when the film is formed, while if the amount is too large, the film formation properties may be reduced, the viscosity may increase, making application work easier, and the coating may be more susceptible to cracking during baking and drying. If the amount of inorganic filler blended is within the above range, the coating workability is good, the film thickness is high, high vibration-damping properties and rigidity are obtained, and the coating film is less likely to crack. The above blending amount of inorganic filler indicates the total amount when two or more types are blended.

[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 achieve higher thin film properties while suppressing coating blistering and the like.

[0042] The film-forming aid consisting of an ether-based water-insoluble organic compound preferably has a solubility in water at 25°C within 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. In the case of an ether-based water-insoluble organic compound, if the solubility in water is too high, it is difficult to suppress blistering of the coating film and to obtain the thin film effect, whereas if the solubility is too low, it is difficult to obtain the thin film effect. If the film-forming aid is an ether-based, water-insoluble organic compound whose solubility in water at 25°C is within the above range, a high degree of thin film formation can be ensured and the coating is less likely to blister.

[0043] Furthermore, the boiling point of such a film-forming aid made of a water-insoluble organic compound is preferably within the range of 140 to 250°C, more preferably 140 to 225°C, and even more preferably 160 to 220°C. If the boiling point of the coalescent is too low, it will evaporate easily, resulting in poor film-forming properties and difficulty in preventing blistering of the coating.On the other hand, if the boiling point is too high, the coalescent will likely remain even after baking (usually 100-250°C), resulting in poor coating performance such as vibration damping. If the coalescing aid is a water-insoluble organic compound having a boiling point within the above range, high vibration-damping properties and high film-forming properties can be ensured, and the coating is less likely to blister. More preferably, if the boiling point of the coalescing aid is within the range of 140 to 225°C, and even more preferably 160 to 220°C, it is less likely to remain even at low baking and drying temperatures, so that higher vibration-damping properties can be achieved and energy savings can be achieved.

[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's resin solids content. 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. 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 will be reduced, while if the amount is too large, the coalescing agent will tend to remain even after baking and drying, reducing coating film performance such as vibration damping. If the blending amount of the film-forming aid 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 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, UV 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 with 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 when heated. The unexpanded microcapsules preferably have an average median diameter in the range of approximately 10 to 20 μm and an expansion initiation temperature in the range of approximately 80 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, and is preferably thermally expandable organic hollow particles. 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 it hardens, which 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 the water-retaining agent 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 is less likely to crack, and dry bumps are less likely to form at the tip of the nozzle of the coating device. 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. The content of the water retention agent in the aqueous emulsion-based vibration-damping coating composition is preferably within the range 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 ranges, both water drainage and suppression of electrodeposition blisters during baking can be achieved.

[0052] Examples of the defoaming agent include silica-based (hydrophobic silica-based, etc.), metal soap-based, wax-based, polyether-based, silicone-based, and acrylic-based defoaming agents. The inclusion of an antifoaming agent can reduce the generation of bubbles due to stirring, even when the viscosity is low. The antifoaming agent is preferably blended in an amount of 0 to 1.0 part 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. The content of the antifoaming agent in the aqueous emulsion vibration-damping coating composition 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 (such as sodium polycarboxylic acid salts), phosphonic acid-based, naphthalene sulfonic acid-based, cationic polymers, and sodium polyphosphate. The inclusion of a dispersant can improve the dispersibility of the blended materials. The dispersant is blended in an amount of preferably 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 dispersant 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.

[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 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 (finely powdered silica), 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 the resin emulsion. The content of the anti-sagging agent in the aqueous emulsion-based vibration-damping coating composition 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, control of the coating film surface, etc. The pigment is preferably blended in an amount of 0 to 1.5 parts by mass, more preferably 0.1 to 1.0 parts by mass, and even more preferably 0.2 to 0.5 parts by mass, per 100 parts by mass of the resin emulsion. The content of the pigment in the aqueous emulsion-based vibration-damping coating composition is preferably 0 to 2.0% by mass, more preferably 0.01 to 1.0% by mass, and even more preferably 0.05 to 0.5% by mass.

[0057] Examples of water-absorbing agents (anti-swelling agents) include water-absorbing synthetic resins, cellulose derivatives, and starches of polysaccharides (for example, 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 bumping 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 the 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., and polyacrylic acid-based agents are preferred. The inclusion of a thickener can adjust the viscosity to an appropriate level and improve the dispersibility of the inorganic filler. 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 the resin emulsion. The content of the thickener in the aqueous emulsion-based vibration-damping coating composition is preferably 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 the mixture using a mixer such as a Banbury mixer, a planetary mixer, a butterfly mixer, a Henschel mixer, a super mixer, a static mixer, a dynamic mixer, or a spiral mixer, or a known mixer / disperser such as a dissolver, a roll mill, a grain mill, an open kneader, a vacuum kneader, or an attritor, and then degassing the mixture. For example, a resin emulsion is placed in a mixer having a degassing and stirring function, and additives (e.g., dispersants, wetting agents, antifoaming agents, etc.) are added as needed and stirred, followed by addition of an inorganic filler and a film-forming aid consisting of a water-insoluble organic compound, which is stirred and mixed until uniform. Further, other additives (e.g., thickeners, water retention agents, anti-sagging agents, foaming agents, etc.) and water are added as needed to adjust the viscosity to a predetermined level, and the mixture is then degassed and stirred (vacuum degassing, etc.) to produce an 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), whereby the composition is bake-cured to form 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 has a dry specific gravity of preferably 1.03 or more and 1.30 or less, more preferably 1.05 or more and 1.25 or less, and even more preferably 1.05 or more and 1.25 or less. 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 for a given applied weight.Within this range, both sound insulation and thin film properties will be achieved.

[0064] [Example] Next, examples of the aqueous emulsion vibration-damping coating composition according to the embodiment of the present invention will be described. The aqueous emulsion vibration-damping coating compositions of Examples 1 to 5 were prepared by blending 100.0 parts by mass (50 to 51 parts by mass in terms of resin solids) of an acrylic emulsion (Dow Chemical's "ACOUSTICRYL SD-380 (acrylic copolymer emulsion)"; resin solids content: 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 1.0 to 5.0 parts by mass of a water-insoluble ether-based organic compound (Dow Chemical's "DOWANOL Dpnp (dipropylene glycol-n-propyl ether)"; boiling point: 213°C, solubility in water at 25°C: 19.6 g / 100 g H2O) as the film-forming aid. In addition, the additives included 2.0 parts by mass of a foaming agent (heat-expandable balloon), 4.3 parts by mass of a water retention agent (propylene glycol), 2.7 parts by mass of an anti-sagging 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 film-forming aid made of a water-insoluble ether-based organic compound, as shown in the top row of Table 1 below. That is, a water-insoluble ether-based organic compound (Dow Chemical's "DOWANOL Dpnp (dipropylene glycol-n-propyl ether)", boiling point: 213°C, solubility in water at 25°C: 19.6 g / 100 g-H2O) was used as a film-forming aid 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 Example] Furthermore, for comparison, aqueous emulsion coating compositions of Comparative Examples 1 to 3 were also prepared. Comparative Example 1 did not use any coalescent, but otherwise had the same blending materials and composition as those of Examples 1 to 5. In other words, it was a composition in which no coalescent was blended compared to the blending of Examples 1 to 5. In Comparative Example 2, instead of the film-forming aid used in Examples 1 to 5, 2.0 parts by mass of a water-soluble ether-based organic compound (Butyl CARBITOL (diethylene glycol monobutyl ether) from Dow Chemical Company, boiling point: 230.6°C, solubility in water at 25°C: miscible) was blended as the film-forming aid; otherwise, the blending materials and blending amounts were the same as those in Examples 1 to 5 above. In Comparative Example 3, instead of the film-forming 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) from Dow Chemical Company, boiling point: 230.6°C, solubility in water at 25°C: miscible) was used as the film-forming aid; otherwise, the same materials and amounts were used as in Examples 1 to 5 above.

[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 row of Table 1. The values ​​in the same column in the upper row of Table 1 indicate the quantity (parts by mass). The aqueous emulsion coating compositions of each Example and Comparative Example were prepared by mixing ingredients according to the formulation shown in the top row of Table 1 and degassing and stirring using a high-speed stirrer.

[0068] [Table 1]

[0069] For each of the aqueous emulsion coating compositions of Examples 1 to 5 and Comparative Examples 1 to 3, evaluation tests were carried out on the vibration-damping properties of the coating film, thin coating film thickness, coating film blistering, and film-forming properties. Regarding vibration damping, a water-based emulsion paint composition was applied to an electrodeposited steel plate measuring 10 mm wide x 220 mm long x 1.6 mm thick with an area of ​​10 mm x 200 mm, with a surface density of 4 kg / m 2 The test piece (evaluation panel) was prepared by baking and drying the coated surface in a drying oven (dryer) adjusted to 130°C for 30 minutes. The secondary resonance frequency of the test piece was measured using the cantilever beam method, and the loss factor at the secondary resonance point at each temperature of 20°C, 40°C, and 60°C was calculated using the half-value width method. If the loss factor is 0.04 or more, it is determined that vibration damping properties are ensured. As a result of measurements using the cantilever beam method, loss factors of 0.04 or more at temperatures of 20°C, 40°C, and 60°C were evaluated as ○ (pass), and those less than 0.04 were evaluated as × (fail).

[0070] Regarding thin film properties, the aqueous emulsion coating composition was applied to an electrodeposited steel plate measuring 70 mm x 150 mm x 0.8 mm thick so that the wet film thickness was 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 dry specific gravity of the cured coating film formed on the electrodeposited coated plate was measured. If the mass of the coating components is about the same, the higher the dry specific gravity at this time, the thinner the film will be. Therefore, coatings with a dry specific gravity of 1.10 or more were judged to have excellent thin coating film properties and were rated as ◎ (good, passed), coatings with a dry specific gravity of 1.05 or more but less than 1.10 were rated as 〇 (fair, passed) because the coating film was sufficiently thin, and coatings with a dry specific gravity of less than 1.05 were rated as × (unacceptable, failed).

[0071] To check for blistering of the coating film, the aqueous emulsion coating composition was applied to an electroplated steel plate measuring 70 mm in length, 150 mm in width, and 0.8 mm in thickness so that the wet film thickness was 3 mm. 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 electroplated coated plate was checked. Those with no blistering of the coating were evaluated as ◎ (good, passed), those with blistering of less than 3 mm were judged to be within the range of practical use and evaluated as 〇 (fair, passed), and those with blistering of 3 mm or more were judged to be coating defects and evaluated as × (unacceptable, failed).

[0072] Regarding film-forming properties, an aqueous emulsion-based paint composition was applied to an electroplated 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 the plate was left wet at room temperature for 72 hours. Thereafter, the plate was 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 base material was confirmed. Those in which no cracks reached the substrate were evaluated as ◯ (pass), and those in which cracks reached the substrate were evaluated as × (fail). The results of these evaluations are shown in the lower part of Table 1.

[0073] As shown in Table 1, in Comparative Example 1, in which no coalescing 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 ◯, and no coating blistering occurred during baking, earning a rating of ⊚, but the dry specific gravity of the cured coating 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 before being baked, cracks occurred in the cured coating film reaching the base material of the substrate, and the film formability was also rated as x. That is, the aqueous emulsion coating composition of Comparative Example 1 does not use a film-forming aid made of a water-insoluble organic compound, so the coating film formed after baking and drying is thick, and film formation is poor when left at room temperature after application.

[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 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, 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 paint 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 paint 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 blistered less than 3 mm during high-temperature baking drying, 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 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 Good. In addition, the dry specific gravity of the cured coating film after baking drying was 1.05 or more, resulting in a rating of Good or Excellent for thin film properties. Furthermore, the coating film blistering during high-temperature baking drying was less than 3 mm, resulting in a rating of Good or Excellent. 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, resulting in a rating of Good for film-forming properties.

[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] In this way, the aqueous emulsion vibration-damping coating compositions of Examples 1 to 5, which use a film-forming aid made of a water-insoluble organic compound, can form coatings with low specific gravity and thin films 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 agent 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 increasing the fusion of the resin particles and resulting in a thinner film.Furthermore, if the coalescing agent is a water-insoluble organic compound, its low affinity with water makes it difficult to capture water, which is thought to make the coating less likely to blister 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 thin-film effect, 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 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 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 coalescing agent 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 reduced film-forming properties and a reduced thin-film effect. On the other hand, if the amount of coalescing agent added is too large, vibration-damping properties at high temperatures (60°C) will be reduced, 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 coalescing agent, and further from the fact that, as the amount of coalescing agent 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 experimental research conducted by the present inventors, it has been confirmed that, as long as the blending amount of the film-forming aid 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 achieved, 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 film-forming aid added increased, the loss factor at 20°C became higher than the loss factor at 60°C.

[0084] Thus, the aqueous emulsion vibration-damping coating composition according to the above example can form a thin coating (reduced film thickness) while maintaining vibration-damping properties by combining a resin emulsion, an inorganic filler, and a film-forming aid consisting of a water-insoluble organic compound, and can also form a coating that is less likely to blister. Furthermore, in the aqueous emulsion vibration-damping coating composition according to the above examples, the minimum film-forming temperature of the film-forming aid is 0°C or higher and 40°C or lower, so that even if the composition is left wet at or below room temperature after application and before baking and drying, no cracks will occur (no film formation failure will occur), and film-forming properties will be ensured. Furthermore, the aqueous emulsion vibration-damping coating composition according to the above example allows the coating thickness to be reduced without reducing the coating weight, and therefore allows the coating thickness to be reduced without impairing sound insulation properties. Furthermore, according to the aqueous emulsion vibration-damping coating composition of the above example, an acrylic copolymer emulsion is used as the resin emulsion, and mica, barium sulfate, and calcium carbonate are used in combination 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 storage at 40°C for two weeks, 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, and the film-forming aid is a water-insoluble organic compound. According to the aqueous emulsion vibration-damping coating composition of the above embodiment, 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 ensuring vibration-damping properties, and that is less likely to produce coating defects such as coating film blistering.

[0088] In the aqueous emulsion-based vibration-damping coating composition according to the above embodiment, the boiling point of the film-forming 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. If the boiling point of the coalescent is too low, it will evaporate easily, resulting in poor film-forming properties and making it difficult to prevent blistering of the coating, whereas if the boiling point is too high, the coalescent will remain even after baking and drying, resulting in poor coating performance such as vibration damping. If the film-forming aid is a water-insoluble organic compound having a boiling point within the above range, it is possible to ensure high vibration-damping properties and high film-forming properties, and it is also possible to make the coating less susceptible to blistering.

[0089] In the aqueous emulsion-based vibration-damping coating composition according to the above embodiment, the film-forming aid is preferably blended in an amount of 0.3 parts by mass or more and 10.0 parts by mass or less, more preferably 0.5 parts by mass or more and 10.0 parts by mass or less, even more preferably 0.5 parts by mass or more and 8.0 parts by mass or less, and particularly preferably 1.0 parts by mass or more and 5.0 parts by mass or less, relative to 100 parts by mass of the resin emulsion. If the blending amount of the film-forming 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 film-forming 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 solubility of the coalescent in water at 25°C is within the above range, high thin film properties can be ensured and the coating is less likely to blister. Furthermore, if the coalescent is an ether-based water-insoluble organic compound, the viscosity change rate after aging is small and storage stability can be ensured.

[0091] In the aqueous emulsion-based 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.

[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 parts by mass or more and 250 parts by mass or less, more preferably 120 parts by mass or more and 230 parts by mass or less, and even more preferably 150 parts by mass or more and 200 parts by mass or less, relative to 100 parts by mass of the resin emulsion. When the amount of inorganic filler is within the above range, vibration damping properties and coating workability can be achieved at the same time, and a high degree of thin film formation can be achieved.

[0093] The above-described embodiment can also be understood as an invention of 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, wherein the film-forming aid is a water-insoluble organic compound. The cured coating film of the above embodiment can be made thinner while maintaining vibration-damping properties, and coating defects such as coating blistering are less likely to occur.

[0094] When carrying out the present invention, other compositions, components, blending amounts, materials, sizes, production methods, etc. of the aqueous emulsion vibration-damping coating composition are not limited to those in this embodiment. Furthermore, the numerical values ​​given in the embodiments of the present invention do not indicate critical values, but rather indicate preferred values ​​suitable 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, 1. A water-based emulsion vibration-damping coating composition, wherein the film-forming aid is a water-insoluble organic compound.

2. 2. The water-based 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. 2. The water-based emulsion vibration-damping coating composition according to claim 1, wherein the film-forming aid is blended in an amount within a range of 0.3 to 10.0 parts by mass per 100 parts by mass of the resin emulsion.

4. 2. 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. in the range of 5 to 40 g / 100 g.

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

6. 2. The water-based emulsion vibration-damping coating composition according to claim 1, wherein the resin emulsion has a minimum film-forming temperature within the range of 0 to 40°C.

7. 2. The water-based emulsion vibration-damping coating composition according to claim 1, wherein the inorganic filler is blended in an amount within a 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 vibration-damping coating composition containing a resin emulsion, an inorganic filler, and a film-forming aid, A cured coating film characterized in that the film-forming aid is a water-insoluble organic compound.

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