Aqueous aerosol coating composition and process for producing the same

Abstract

To provide a coating stock solution for an aqueous aerosol excellent in discharge stability, adhesion and water resistance of a coating film, and an aqueous aerosol coating composition using the same.SOLUTION: The aqueous aerosol coating composition contains a coating stock solution and a propellant, wherein the coating stock solution contains water, an emulsion resin and a dispersion resin. The propellant is preferably a hydrophilic propellant.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an aqueous aerosol coating composition and a method for producing the same. [Background technology]

[0002] Lacquer-based aerosol paints have traditionally been widely used as home paints and for repairing industrially painted products because they dry quickly and are easy to apply. However, in recent years, there has been a demand for water-based aerosol paints that contain less volatile organic solvents, in order to improve the painting work environment and to protect the natural environment. For example, Patent Document 1 discloses an aqueous aerosol coating composition containing an emulsion of a water-dilutable resin having a weight-average molecular weight (Mw) of 4000 to 50000 and a resin having a weight-average molecular weight (Mw) of 3000 to 80000. It is described that this aqueous aerosol coating composition has excellent adhesion to the substrate, non-brittleness, non-stickiness, and water resistance.

[0003] Patent Document 2 discloses an aqueous aerosol coating composition containing a urethane-modified water-dilutable resin obtained by copolymerizing a polyisocyanate resin with a water-dilutable resin having a weight-average molecular weight of 4000 to 50000. It is described that this aqueous aerosol coating composition provides a coating film with excellent drying properties, water resistance, gasoline resistance, adhesion, and impact resistance.

[0004] Patent Document 3 discloses a water-based aerosol paint containing a water-dispersible resin, water, and dimethyl ether as a water-soluble propellant. This water-based aerosol paint is described as being weakly flammable, has little odor, and is low in pollution.

[0005] Patent Document 4 discloses an aqueous emulsion aerosol composition containing a synthetic resin emulsion obtained by emulsion polymerization in the presence of a polymerizable emulsifier, water, and a propellant. It is described that this aqueous emulsion aerosol composition has excellent storage stability and sprayability.

[0006] Patent Document 5 discloses an aqueous aerosol paint concentrate containing 15% by mass or more and 45% by mass or less of a dispersion resin in terms of resin solid content and 40% by mass or more and 80% by mass or less of water. It is described that this aqueous aerosol paint concentrate allows the amount of organic solvent to be reduced and also provides excellent storage stability and coating film performance. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-82294 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-45028 [Patent Document 3] Japanese Patent Application Publication No. 54-31445 [Patent Document 4] Japanese Patent Application Publication No. 62-258738 [Patent Document 5] Japanese Patent Application Laid-Open No. 2011-219629 Summary of the Invention [Problem to be solved by the invention]

[0008] However, in the coating compositions described in Patent Documents 1 and 2, the main resin is a water-dilutable resin, and therefore the compositions may have poor water resistance and adhesion. Furthermore, the water-based aerosol paint described in Patent Document 3 may have poor storage stability because it uses a water-dispersible resin that thickens when aerosolized. Also, because the amount of solvent used is large, sagging may occur during application, resulting in poor appearance. Furthermore, the aqueous emulsion aerosol composition described in Patent Document 4 contains only an emulsion resin as the resin. Emulsion resins have poor compatibility with aerosol propellants and a high tendency to gel, resulting in poor ejection stability. Furthermore, paints using aqueous aerosol paint concentrates such as those described in Patent Document 5 can cause poor appearance due to the large amount of foaming that occurs during application. The present invention has been made in view of the above circumstances, and aims to provide a water-based aerosol paint concentrate that is excellent in discharge stability, adhesion, and water resistance of the coating film, and an water-based aerosol paint composition using the same. [Means for solving the problem]

[0009] The present inventors discovered that by using a dispersion resin in addition to an emulsion resin as the resin for a paint concentrate for an aqueous aerosol, compatibility with the propellant is improved, and the ejection stability, adhesion, and water resistance of the coating film are excellent, leading to the present invention. That is, the present invention provides the following paint concentrate and aqueous aerosol paint composition. [1] The present invention is an aqueous aerosol paint composition containing a paint concentrate and a propellant, wherein the paint concentrate is an aqueous aerosol paint composition containing water, an emulsion resin, and a dispersion resin. [2] The aqueous aerosol coating composition according to [1] above, wherein the propellant is a hydrophilic propellant. [3] The present invention also provides a method for producing an aqueous aerosol paint composition, comprising the steps of: mixing an emulsion resin, a dispersion resin, and water to prepare a paint concentrate; and adding a propellant to the paint concentrate to prepare an aqueous aerosol paint composition. [Effects of the Invention]

[0010] According to the present invention, it is possible to obtain a water-based aerosol paint concentrate which is excellent in discharge stability, adhesion, and water resistance of the coating film, and an water-based aerosol paint composition using the same. DETAILED DESCRIPTION OF THE INVENTION

[0011] The paint concentrate and aqueous aerosol paint composition of the present invention will be described in detail below.

[0012] [Water-based aerosol paint composition] The aqueous aerosol coating composition of the present invention contains a paint concentrate and a propellant, and the paint concentrate contains water, an emulsion resin, and a dispersion resin. First, the paint concentrate will be described in detail.

[0013] <Paint stock solution> The water, emulsion resin, and dispersion resin that make up the paint concentrate will now be described in detail. (water) The water used in the paint concentrate and the aqueous aerosol paint composition is not particularly limited, and examples thereof include pure water such as ion-exchanged water and distilled water, groundwater, tap water, industrial water, etc. Furthermore, when the aqueous aerosol paint composition is to be stored for a long period of time, water that has been sterilized by ultraviolet irradiation or the like may be used to prevent the growth of mold and bacteria. The water content in the paint concentrate is preferably 40% by mass or more and 80% by mass or less. By containing water in this range, the dispersion resin, the dispersion resin, and the pigment can be dispersed well while the drying property of the coating film can be ensured. The water content in the paint concentrate is more preferably 40% by mass or more and 70% by mass or less.

[0014] (organic solvent) The paint concentrate may contain an organic solvent. From the viewpoint of reducing volatile organic solvents (VOCs), the content of the organic solvent in the paint concentrate is preferably 10% by mass or less, more preferably 5% by mass or less. Although a small content of organic solvent is preferred, the use of a small amount of organic solvent can improve, for example, adhesion to the substrate, coating drying properties, and film-forming properties.

[0015] The organic solvent that can be used in the paint concentrate of the present invention is not particularly limited, and various organic solvents can be used. As the organic solvent, either a hydrophilic organic solvent or a hydrophobic organic solvent can be used, but among them, it is more preferable to include a hydrophilic organic solvent. As the organic solvent, it is preferable to use, for example, an alcohol-based solvent, a glycol ether-based solvent, etc. Examples of the alcohol-based solvent include n-butyl alcohol, isoamyl alcohol, n-amyl alcohol, hexyl alcohol, 2-ethylbutyl alcohol, methylamyl alcohol, cyclohexanol, 2-ethylhexyl alcohol, octyl alcohol, benzyl alcohol, dimethylaminoethanol, butanol, methyl alcohol, ethyl alcohol, isopropyl alcohol, isobutyl alcohol, and diacetone alcohol. Examples of the glycol ether-based solvent include ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, and tetraethylene glycol dimethyl ether. Only one organic solvent may be used, or two or more organic solvents may be used in combination.

[0016] (emulsion resin) The emulsion resin in the present invention refers to a water-dispersible resin obtained by emulsion polymerization. Conventionally, aqueous aerosol coating compositions using only a dispersion resin and a propellant have had the problem of poor water resistance of the coating film. The aqueous aerosol coating composition of the present invention can obtain a coating film with excellent water resistance by adding an emulsion resin, even if a dispersion resin is used. The emulsion resin preferably has excellent dispersion stability even when mixed with a propellant, and examples thereof include epoxy resins, acrylic resins, acrylic silicone resins, urethane resins, vinyl chloride resins, fluororesins, polyester resins, and modified resins thereof. Among these, from the viewpoint of compatibility with the dispersion resin and the propellant, it is preferable to use epoxy resins, acrylic resins, urethane resins, and modified resins thereof. The emulsion resin may be used alone or in combination of two or more.

[0017] Methods for improving dispersion stability when the emulsion resin is mixed with the propellant include increasing the amount of surfactant, using anionic and nonionic surfactants in combination, using reactive and non-reactive surfactants in combination, selecting a film-forming aid and selecting a water-soluble film-forming aid to increase compatibility with dimethyl ether, and mixing and polymerizing a hydrophobic film-forming aid during polymerization to suppress the generation of aggregates due to shock when mixed with dimethyl ether.

[0018] -Particle size- The particle size D50 of the emulsion resin is preferably 50 nm or more and 300 nm or less, more preferably 60 nm or more and 200 nm or less, from the viewpoint of improving the compatibility of the emulsion resin with the propellant and the dispersibility of the resin particles.

[0019] -Resin solids- The resin solids content of the emulsion resin in the paint concentrate is from 1% by mass to 40% by mass, and more preferably from 1% by mass to 30% by mass, from the viewpoint of improving compatibility and dispersion stability with the dispersion resin and propellant described below, and improving discharge stability and coating film properties.

[0020] (Dispersion resin) The dispersion resin in the present invention refers to a water-dispersible resin dispersed in water by a method other than emulsion polymerization, such as a forced emulsification type dispersion resin obtained by mechanically forcibly dispersing a water-insoluble resin in water, or a self-dispersible dispersion resin obtained by polymerizing a monomer mixture in the absence of a solvent or in the presence of an appropriate organic solvent, adding the resulting mixture dropwise to water, and optionally removing the excess organic solvent, or by adding water after the polymerization reaction and optionally removing the excess organic solvent. In the present invention, it is preferable to use a self-dispersible dispersion resin that is self-dispersed in an aqueous medium because it has excellent dispersion stability even when sprayed as an aerosol. Conventionally, aqueous aerosol coating compositions containing only an emulsion resin have had problems such as poor compatibility between the emulsion resin and the propellant, and a lack of discharge stability, etc. The aqueous aerosol coating composition of the present invention uses an emulsion resin and a dispersion resin in combination, thereby ensuring dispersion stability and exhibiting excellent compatibility with the propellant, discharge stability, etc.

[0021] Examples of dispersion resins include acrylic resins, urethane resins, epoxy resins, alkyd resins, polyester resins, polyolefin resins, vinyl chloride resins, vinyl chloride-vinyl acetate resins, silicone resins, and modified resins of these.

[0022] -Particle size- The average particle diameter D50 of the dispersion resin is preferably 20 nm or more and 500 nm or less, more preferably 30 nm or more and 400 nm or less, from the viewpoint of preventing gelation when mixed with the propellant. The average particle diameter can be determined from the particle size distribution measured using a particle size distribution measuring device (e.g., a laser diffraction / scattering particle size distribution measuring device). The particle diameter is expressed as the spherical equivalent diameter measured by the laser diffraction / scattering method.

[0023] -Resin solids- The resin solids content of the dispersion resin in the paint concentrate is preferably 3% by mass or more and 45% by mass or less, and more preferably 3% by mass or more and 40% by mass or less. By having the resin solids content of the dispersion resin in this range, good compatibility between the emulsion resin and the propellant can be achieved.

[0024] (Ratio of emulsion resin to dispersion resin) The ratio of emulsion resin to dispersion resin in the aqueous aerosol coating composition is preferably 10:90 or more and 90:10 or less, and more preferably 10:90 or more and 80:20 or less, based on the solid content. A high blending ratio of emulsion resin results in excellent coating film performance such as water resistance, while a high blending ratio of dispersion resin results in good discharge stability of the aerosol spray.

[0025] (pigment) The paint concentrate may contain at least one of a color pigment, an extender pigment, and an anti-rust pigment. These pigments are preferably selected appropriately depending on the color and gloss of the paint film, the ease of application, the strength and physical properties of the paint film, etc.

[0026] -Coloring pigments- Examples of color pigments include titanium oxide, iron oxide, carbon black, yellow lead, molybdate orange, ultramarine, Prussian blue, phthalocyanine blue, phthalocyanine green, quinacridone red, naphthol red, benzimidazolone yellow, Hansa yellow, benzimidazolone orange, dioxazine violet, etc. The color pigments may be used alone or in combination of two or more. The content of the color pigment in the paint concentrate is preferably 0.1% by mass or more and 25% by mass or less, and more preferably 1% by mass or more and 20% by mass or less.

[0027] -Extender pigment- The paint concentrate preferably contains an extender pigment. Examples of the extender pigment include silica, kaolin, talc, mica, calcium carbonate, barium sulfate, and clay. Of these, calcium carbonate, kaolin, talc, and barium sulfate are preferred. The extender pigment may be used alone or in combination of two or more. The content of the extender pigment in the paint concentrate is preferably 0.1% by mass or more and 25% by mass or less, and more preferably 0.1% by mass or more and 10% by mass or less.

[0028] -Anti-rust pigments- The paint concentrate of the present invention may contain an anti-rust pigment. In consideration of the environment, the anti-rust pigment preferably does not contain lead, chromium, or the like. Examples include zinc powder, zinc oxide, barium metaborate, calcium silicate, aluminum phosphate, condensed aluminum phosphate, aluminum tripolyphosphate, zinc phosphate, zinc phosphite, potassium phosphite, calcium phosphite, aluminum phosphite, calcium zinc phosphate, zinc aluminum phosphate, zinc phosphomolybdate, aluminum phosphomolybdate, magnesium phosphate, and vanadate / phosphate mixed pigments. Zinc oxide, zinc phosphate, barium metaborate, and the like are particularly preferred. The anti-rust pigment may be used alone or in combination of two or more. The content in the paint concentrate is preferably 1% by mass or more and 10% by mass or less.

[0029] The aqueous aerosol paint of the present invention contains an emulsion resin and a dispersion resin, and therefore can exhibit excellent discharge stability, adhesion, and water resistance even when used as an anti-rust paint containing an anti-rust pigment. The content of the anti-rust pigment in the paint concentrate is preferably 0.1% by mass or more and 10% by mass or less, and more preferably 1% by mass or more and 10% by mass or less.

[0030] (Other ingredients) The paint concentrate may contain various additives commonly used in the field of paints, such as crosslinking components, thixotropic agents, dispersants, thickeners, neutralizing agents, antifoaming agents, surface conditioners, emulsifiers, surfactants, silane coupling agents, pH adjusters, preservatives, rust inhibitors, antialgae agents, antiviral agents, antistatic agents, conductive materials, and low-fouling agents, within the range that does not impair the effects of the present invention. The aqueous aerosol coating composition of the present invention can be provided with a surface conditioner to reduce the surface tension, thereby improving compatibility with the propellant, improving coating workability, and providing a coating film with excellent appearance. Furthermore, organic solvents such as film-forming aids can be blended as appropriate, but if blended, the amount of organic solvent in the aqueous aerosol coating composition is preferably 5% by mass or less.

[0031] <Propellant> The aqueous aerosol paint composition contains the above-mentioned paint concentrate and a propellant. Examples of propellants include hydrophilic propellants such as dimethyl ether (DME), hydrocarbons (liquefied petroleum gas), fluorocarbons, compressed carbon dioxide, and compressed nitrogen. Hydrophilic propellants, particularly dimethyl ether, are suitable for use because they are easily liquefied and have good compatibility with water.

[0032] (Mixing ratio of paint concentrate and propellant) In the aqueous aerosol paint composition, the mixing ratio of the paint concentrate and the propellant is preferably 20 parts by mass or more and 66 parts by mass or less, and more preferably 25 parts by mass or more and 55 parts by mass or less, per 100 parts by mass of the paint concentrate, because this allows for good compatibility of the propellant with the paint concentrate and good discharge stability.

[0033] (Emulsion resin solids / propellant) The content of the resin solids of the emulsion resin relative to the propellant in the aqueous aerosol paint composition is preferably 1% by mass or more and 150% by mass or less, and more preferably 2% by mass or more and 120% by mass or less, from the viewpoint of achieving good compatibility and ejection stability.

[0034] (resin solids of dispersion resin / propellant) The resin solid content of the dispersion resin relative to the propellant in the aqueous aerosol paint composition is preferably 1% by mass or more and 80% by mass or less, and more preferably 5% by mass or more and 75% by mass or less, from the viewpoint of improving the water resistance of the coating film.

[0035] <Viscosity> The viscosity of the aqueous aerosol coating composition of the present invention can be adjusted to a range suitable for aerosol coating, for example, from 15 to 90 seconds using a Ford Cup #4 at a measurement temperature of 25° C. A diluent such as water can be used to adjust the viscosity. The viscosity of the aqueous aerosol coating composition is a value measured by the flow cup method at a measurement temperature of 25°C in accordance with JIS K 5600-2-2:1999.

[0036] [Method of manufacturing aqueous aerosol coating composition] The method for producing the aqueous aerosol paint composition of the present invention comprises the steps of mixing an emulsion resin, a dispersion resin, and water to prepare a paint concentrate, and adding a propellant to the paint concentrate to prepare the aqueous aerosol paint composition.

[0037] <Process for preparing the paint concentrate> The emulsion resin, dispersion resin, and water may be mixed to prepare the paint concentrate by any known mixing method. If necessary, the above-mentioned other components may be mixed.

[0038] <Step of preparing aqueous aerosol coating composition> The aqueous aerosol paint composition of the present invention contains the above-mentioned paint concentrate and propellant, and can be produced by mixing the paint concentrate and the propellant and filling the mixture into a pressure-resistant aerosol can.

[0039] [Object to be coated] Substrates to which the aqueous aerosol coating composition of the present invention is applied include plastic substrates such as epoxy resins, ABS resins, polycarbonate, polyvinyl chloride, polystyrene, acrylic resins, such as polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), and polyolefins, such as polypropylene (PP); metal substrates such as steel, galvanized steel, tinned steel, stainless steel, magnesium alloys, aluminum, aluminum alloys, titanium, and titanium alloys; inorganic substrates other than metals, such as cement, mortar, concrete, slate, gypsum, calcium silicate, glass, ceramics, calcium carbonate, marble, and artificial marble; wood substrates, and composite substrates combining two or more of these substrates. Examples of composite substrates include wood fiber-reinforced cement boards, fiber-reinforced cement boards, and fiber-reinforced cement-calcium silicate boards; metal substrates that have been subjected to various surface treatments, such as oxidation treatments; and plastic substrates whose surfaces are coated with inorganic substances (e.g., glass-coated plastic substrates). Furthermore, the substrate may be subjected to various surface treatments, and at least a portion of the substrate surface may have a primer coating film such as a conductive primer, or an old coating film (a coating film that has already been formed before the aqueous aerosol coating composition of the present invention is applied).

[0040] The dry film thickness of the coating film formed by applying the aqueous aerosol coating composition of the present invention is, for example, preferably 5 μm to 40 μm, more preferably 5 μm to 30 μm. A dry coating film of 5 μm or more makes it easier to obtain a continuous, uniform film that is not too thin, and when a color coating is made using a coloring pigment, it makes it easier to completely conceal the color of the base. On the other hand, a dry coating film of 40 μm or less makes it less likely to develop defects such as popping or sagging during drying, resulting in a normal dry coating film. [Example]

[0041] The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to these examples and comparative examples. In the examples and comparative examples, "parts" and "%" are based on mass unless otherwise specified.

[0042] [Examples 1 to 18, Comparative Examples 1 and 2] The paint concentrates 1 to 9 were prepared according to the following procedure, and then the paint concentrates were mixed with a propellant to prepare water-based aerosol paint compositions 1 to 20.

[0043] <1. Preparation of paint stock solution> The raw materials listed in Table 1 were mixed in order in a container, and by ordinary kneading and dispersion, paint concentrates 1 to 9 were prepared. The raw materials listed in Table 1 are as follows. (1) Emulsion resin (acrylic resin, weight average molecular weight of 300,000 or more, solid content concentration of 49% by mass) (2) Dispersion resin 1 (acrylic resin, weight average molecular weight 22,000, solid content 34% by mass) (3) Dispersion resin 2 (alkyd resin type, weight average molecular weight 9000, solid content concentration 42% by mass) (4) Color pigment 1 (titanium oxide) (5) Coloring pigment 2 (organic pigment (black)) (6) Coloring pigment 3 (organic pigment (blue)) (7) Anti-rust pigment (barium metaborate) (8) Extender pigment (calcium carbonate) (9) Additives (dispersants, antifoaming agents, film-forming agents, leveling agents, preservatives)

[0044] <2. Preparation of aqueous aerosol coating composition> Next, the concentrate paints 1 to 9 prepared above and a propellant (dimethyl ether) were mixed in the ratios shown in Table 1 to prepare aqueous aerosol paint compositions 1 to 20 of the examples and comparative examples.

[0045] [evaluation] The aqueous aerosol coating compositions of the above Examples and Comparative Examples were evaluated for discharge stability, adhesion, and water resistance.

[0046] <Rating 1> (Discharge stability) The resulting aqueous aerosol coating compositions were evaluated for ejection stability during spraying according to the following criteria, and the results are shown in Table 1. <Evaluation criteria> ◎: The discharge amount is stable and the particles are fine particles ○: Discharge volume is stable △: Discharge is possible and the discharge amount is within the acceptable range ×: Unable to eject or unable to eject midway

[0047] <Rating 2> First, test specimens were prepared as follows, and the adhesion and water resistance were evaluated. The results are shown in Table 1.

[0048] (Preparation of test specimen) The aqueous aerosol coating composition was applied to a test piece (SPCC-SD steel plate (JIS G3141) by aerosol so that the dry coating film would be 15 μm to 25 μm thick, and the test piece was prepared by drying at room temperature of 23°C and humidity of 50% RH for 7 days.

[0049] (Adhesive) The prepared test specimens were evaluated in accordance with JIS K5600-5-6 (cut interval: 1 mm, grid: 100). The evaluation criteria were as follows: <Evaluation criteria> ○:100 / 100 △:90~99 / 100 ×: Less than 90 / 100

[0050] (Water resistance (water immersion method)) The prepared test specimens were evaluated in accordance with JIS K5600-6-2 (23°C, 1 day). The evaluation criteria are as follows: <Evaluation criteria> ○: No blistering of the coating film ×: Blisters present in the coating

[0051] [Table 1]

[0052] [Table 2]

[0053] As shown in Table 1, the aqueous aerosol coating compositions of Examples 1 to 18 obtained good results in the evaluations of discharge stability during spraying, adhesion, and water resistance. Comparative Example 1 contained only an emulsion resin, and therefore clogging occurred during spraying, resulting in poor discharge stability. Comparative Example 2 contained only a dispersion resin, and therefore had good ejection stability but poor water resistance. From the above results, it was found that by using an emulsion resin and a dispersion resin in combination, an aqueous aerosol coating composition having excellent discharge stability when sprayed, as well as excellent adhesion and water resistance, can be obtained. In Examples 1 to 4, the spray state became a coarse mist when sprayed. This is thought to be due to the small amount of propellant (DME), and was not affected by changes in the ratio of emulsion resin to dispersion resin. From Examples 5 to 8, it was confirmed that the spray state of the mist was improved by adjusting the amount of DME to 25 parts by mass or more per 100 parts by mass of the concentrate paint. From Examples 9 to 12, it was found that when the amount of DME was increased to 55 parts by mass or more per 100 parts by mass of the concentrate paint, the higher the proportion of emulsion resin, the poorer the ejection stability, and the higher the proportion of dispersion resin, the finer the spray state became and the better the ejection stability. However, in Examples 13 to 15, when the DME content was adjusted to 66 parts by mass per 100 parts by mass of the concentrate paint, the amount of sprayed sometimes became unstable regardless of the proportion of the dispersion resin. This is thought to be due to the tendency for the dispersion state of the emulsion resin to become unstable as the amount of DME increased. It was confirmed that the systems using organic pigments in Examples 16 and 17, and the system in Example 18 to which an anti-rust pigment and an extender pigment were added also ensured ejection stability and water resistance.

Claims

1. An aqueous aerosol paint composition containing a paint concentrate and a propellant, The aqueous aerosol paint composition, wherein the paint concentrate contains water, an emulsion resin, and a dispersion resin.

2. 2. The aqueous aerosol coating composition of claim 1, wherein said propellant is a hydrophilic propellant.

3. a step of mixing an emulsion resin, a dispersion resin, and water to prepare a paint concentrate; adding a propellant to the paint concentrate to prepare an aqueous aerosol paint composition; A method for producing an aqueous aerosol coating composition comprising:

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