JP7565069B2 - Method for producing aerosol coating composition - Google Patents

Description

The present invention relates to a method for producing an aerosol coating composition.

When painting machine parts or building components, a primer (undercoat) is applied to improve adhesion between the topcoat and the painted surface. Primers are required to have functionality such as rust prevention and water resistance in addition to adhesion, and pigments are blended in to impart these functions. In addition, a one-component primer can be made by blending a modified epoxy resin as a binder.

If the primer could be made into an aerosol, work efficiency could be improved and it would be possible to paint complex surfaces. Patent Document 1 describes an aerosol paint that is a mixture of modified epoxy resin, epoxy resin, pigment, solvent, etc. In addition, aerosol paints that do not contain pigments and paints that do not contain modified epoxy resins are known, but these aerosols cannot form a coating film that has excellent rust prevention, water resistance, and strength.

JP 2018-9121 A

The object of the present invention is to provide a method for producing a paint that contains a pigment and a modified epoxy resin and does not aggregate even when it comes into contact with a filler for aerosolization.

The inventors discovered that by dispersing the pigment with a dispersant beforehand and then adding a modified epoxy resin, it is possible to produce an aerosol coating composition that does not aggregate even when it comes into contact with a filler, and thus completed the present invention.

That is, the present invention relates to a method for producing an aerosol coating composition, which includes a step of dispersing a pigment in a solvent containing a dispersant, and a step of adding a modified epoxy resin.

It is preferable not to add modified epoxy resin during the dispersion process.

The dispersant is preferably a cationic dispersant.

Preferably the pigment is talc, precipitated barium sulfate, or kaolin.

The present invention also relates to an aerosol coating composition obtained by the above-mentioned production method.

The manufacturing method of the present invention makes it possible to produce a paint that contains a pigment and a modified epoxy resin and does not aggregate even when it comes into contact with a filler for aerosolization. By aerosolizing this paint, it is possible to efficiently apply a coating film that has excellent rust prevention, water resistance, and strength.

The flowability of Reference Example 8 is shown. The flowability of Reference Example 9 is shown. 1 shows the state of aggregation in Example 1 and Comparative Example 1. FIG. 2 is an enlarged view of the state of aggregation in Example 1 and Comparative Example 1.

The present invention relates to a method for producing an aerosol coating composition, which includes a step of dispersing a pigment in a solvent containing a dispersant and a step of adding a modified epoxy resin.

<Pigments>
The pigment is not particularly limited as long as it can be blended in the aerosol, and examples thereof include extender pigments, coloring pigments, rust-preventive pigments, and functional pigments. A major feature of the present invention is that the pigment is dispersed in advance with a dispersant, and then the modified epoxy resin is added.

Coloring pigments include titanium oxide, carbon black, yellow iron oxide, red iron oxide, phthalocyanine blue, phthalocyanine green, permanent red, naphthol red, quinacridone red, benzimidazolone yellow, isoindoline yellow, etc. These coloring pigments can be selected appropriately depending on the color required for the paint.

Examples of extender pigments include talc, precipitated barium sulfate, kaolin, silica, calcium carbonate, zinc stearate, etc. Among these, talc, precipitated barium sulfate, and kaolin are preferred.

Anti-rust pigments include aluminum tripolyphosphate, zinc oxide, zinc phosphate, etc.

Functional pigments include heat-shielding pigments, UV-reflecting pigments, conductive pigments, photochromic pigments, etc.

The average particle size of the pigment is preferably 5 to 50 μm, more preferably 20 to 30 μm. If the dispersed particle size exceeds 50 μm, the coating composition is more likely to aggregate. If the dispersed particle size is less than 5 μm, re-aggregation may occur in the solvent, resulting in large particles.

The amount of pigment to be used is not particularly limited, but is preferably 50 to 85% by weight, more preferably 60 to 80% by weight, based on the solid content of the aerosol coating composition. If it is less than 50% by weight, the coating film tends to sag easily, and if it exceeds 85% by weight, the physical properties of the coating film tend to deteriorate.

<Dispersant>
The dispersant is not particularly limited as long as it can disperse the pigment in the solvent. Examples of the dispersant include cationic dispersants, anionic dispersants, amphoteric dispersants, nonionic dispersants, and polymeric dispersants.

Cationic dispersants include alkylamine salts and quaternary ammonium salts such as lauryltrimethylammonium chloride and hexadecyltrimethylammonium bromide. Commercially available products include DISPERBYK-2164, DISPERBYK-164, and DISPERBYK-2155.

Anionic dispersants include sodium alkyl sulfates having alkyl groups, polyoxyethylene alkyl ether sulfates, alkylbenzene sulfonates, and polyester phosphates. Commercially available products include DISPERBYK-110 and BYK-P105.

Zwitterionic dispersants include alkyl betaines and alkyl amine oxides.

Nonionic dispersants include polyoxyethylene alkyl ethers, block copolymers composed of ethylene oxide and propylene oxide, alkylphenol polyethylene glycol ethers, and sorbitan fatty acid esters. Commercially available products include DISPERBYK-2152.

Examples of polymeric dispersants include polyvinylpyrrolidone, polyvinyl alcohol, hydroxycellulose, hydroxyalkylcellulose, carboxymethylcellulose, and carboxypropylcellulose. Commercially available products include DISPERBYK-145 and DISPERBYK-106.

Among the above, cationic dispersants are preferred from the viewpoint of dispersion stability after the addition of the modified epoxy resin. Dispersants that are compatible with the solvent described below are also preferred.

The amount of dispersant added is preferably 1.5 to 4.0 parts by weight, more preferably 2.0 to 3.0 parts by weight, in terms of solid content per 100 parts by weight of pigment. If it is less than 1.5 parts by weight, the pigment tends to aggregate and cause clogging when the aerosol is filled, and if it exceeds 4.0 parts by weight, the paint performance tends to decrease.

<Solvent>
Examples of the solvent include glycol ether solvents (cellosolves) such as propylene glycol monomethyl ether, ethylene glycol monobutyl ether, and diethylene glycol monobutyl ether, ketone solvents such as isophorone, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, and acetone, ester solvents such as normal butyl acetate, ethyl acetate, and butyl acetate, aromatic hydrocarbon solvents such as toluene, xylene, and ethylbenzene, and alcohol solvents such as methyl alcohol, ethyl alcohol, isopropyl alcohol, normal propyl alcohol, and normal butyl alcohol. These may be used alone or in combination of two or more.

Of the above solvents, glycol ether solvents, cyclohexanone, and isophorone are examples that can be used alone.

The mixed solvent may be a solvent in which an aromatic hydrocarbon solvent and an alcohol solvent are mixed in a ratio of aromatic hydrocarbon solvent:alcohol solvent = 60:40 to 80:20. Here, examples of the aromatic hydrocarbon solvent include toluene, xylene, ethylbenzene, and naphtha, and examples of the alcohol solvent include ethyl alcohol, isopropyl alcohol, and normal butyl alcohol.

The solvent may be added in the pigment dispersion process, or in the modified epoxy resin addition process or thereafter. The ratio of the amount added in the pigment dispersion process to the amount added in the modified epoxy resin addition process or thereafter is preferably 30:70 to 50:50 by weight. When the solvent is added in the modified epoxy resin addition process, it is preferable to mix and stir the pigment dispersion and the modified epoxy resin before adding the solvent.

If a solvent is added alone between the pigment dispersion step and the modified epoxy resin addition step, mixing of the paint composition with the filler may cause aggregation. Therefore, it is preferable not to add a solvent alone between the pigment dispersion step and the modified epoxy resin addition step.

The final solids concentration of the aerosol coating composition is preferably 30 to 50% by weight, more preferably 35 to 45% by weight. If it is less than 30% by weight, the pigment will tend to settle in the aerosol, and the pigment content necessary to exhibit coating performance will not be ejected. If it exceeds 50% by weight, the viscosity of the paint will increase, and nozzle clogging will tend to occur when the aerosol is sprayed.

<Dispersion process>
In the dispersion step, the pigment is dispersed in a solvent containing a dispersant. The machine used for dispersion is not particularly limited, but examples include a bead mill, a basket mill, a roll mill, a sand mill, and a high-pressure homogenizer. When dispersion is performed using a bead mill, the bead diameter is preferably 1.00 to 2.00 mm, and more preferably 1.00 to 1.40 mm. If the bead diameter is less than 1.00 mm, the pigment may be pulverized to a primary particle size or smaller and re-aggregated.

If the pigment is dispersed in the presence of a modified epoxy resin, the modified epoxy resin will preferentially adhere to the pigment, and the contents will tend to aggregate when the aerosol coating composition is mixed with the filler. Therefore, it is preferable not to add the modified epoxy resin in the dispersion process.

<Modified epoxy resin addition step>
In the production method of the present invention, a modified epoxy resin is added to a pigment dispersion.

The mass average molecular weight of the modified epoxy resin used in the present invention is preferably 10,000 or more, more preferably 12,000 or more, and even more preferably 14,000 or more. If the mass average molecular weight is less than 10,000, the hardness of the coating film formed using the aerosol coating composition tends to be insufficient. The upper limit of the mass average molecular weight is not particularly limited, but is generally 50,000 or less. The modified epoxy resin is preferably a resin obtained by polymerizing a bisphenol A type epoxy resin using a modifier.

Modified epoxy resins include urethane-modified epoxy resins, amine-modified epoxy resins, isocyanate-modified epoxy resins, acrylic-modified epoxy resins, phenol-modified epoxy resins, polyester-modified epoxy resins, and acid-modified epoxy resins.

Specific examples of modified epoxy resins include Arakawa Chemical Industries Co., Ltd.'s Arakid 9201N, Arakid 9203N, Arakid 9205, Arakid 9208, Arakid 9212, KA-1439A, KA-1492, KA-1550, and Modepix 401. Also included are Mitsui Chemicals' Epochy 871T, Epochy 810STS, Epochy 811, Epochy 813, Epochy 814, Epochy 818, Epochy 861, Epochy 863, Epochy 864, Epochy 872, Epochy 877, Epochy 891, Epochy 878, and Epochy 879. Other examples include DIC's H-301-35PX, H-303-45M, H-304-40, and H-601-55.

The glass transition temperature of the modified epoxy resin is preferably 25°C to 130°C, and more preferably 40°C to 90°C.

The amount of modified epoxy resin is not particularly limited, but is preferably 10 to 35% by weight, more preferably 25 to 30% by weight, based on the solid content of the aerosol coating composition. If it exceeds 35% by weight, the coating film tends to sag easily, and if it is less than 10% by weight, the physical properties of the coating film tend to deteriorate.

<Additives>
The aerosol coating composition may contain additives such as unmodified epoxy resin, modifier, curing agent, curing accelerator, defoamer, surface conditioner, etc. in addition to the solvent, dispersant, suspending agent, pigment, and modified epoxy resin.

As the unmodified epoxy resin, mainly bisphenol A type epoxy resin can be used. The mass average molecular weight of the unmodified epoxy resin is preferably less than 10,000, more preferably 8,000 or less, and even more preferably 6,000 or less. Although the unmodified epoxy resin is not essential, when the unmodified epoxy resin is added, the solids weight ratio of the above-mentioned modified epoxy resin to the unmodified epoxy resin is preferably 99.9:0.1 to 30:70, and more preferably 95:5 to 40:60. The timing of adding the unmodified epoxy resin is not particularly limited, but it is preferable to add it during the process of dispersing the pigment.

The modifier is not particularly limited as long as it is a material compatible with the modified epoxy resin, and examples thereof include acrylic resin, polyester resin, alkyd resin, epoxy ester resin, and silane coupling agent. Modified epoxy resins with a larger mass average molecular weight than the modified epoxy resins described above can also be used. Compatibility can be confirmed by the presence or absence of cloudiness when mixed with the modified epoxy resin.

When a hardener is used, examples of the hardener include amine compounds, blocked isocyanates, etc.

<Filler>
The aerosol coating composition is filled into an aerosol container together with a filler. The filler is not particularly limited as long as it is used in aerosols, and examples of the filler include liquefied petroleum gas (LPG), dimethyl ether, and fluorohydrocarbons. Among these, a solvent with a medium degree of hydrogen bonding compatibility with epoxy resins is recommended, and therefore dimethyl ether with a hydrogen bonding parameter of 1.0 is preferred.

The amount of filler used is preferably such that the volume ratio of the aerosol coating composition to the filler is 55:45 to 40:60, and more preferably 50:50 to 45:55.

In the present invention, a coating material that does not aggregate even when it comes into contact with a filler for aerosolization can be produced by dispersing the pigment and then adding a modified epoxy resin. Here, the aggregation property of the coating material composition can be evaluated after filling it into an aerosol container when dimethyl ether is used as the filler, but it can also be evaluated after mixing it with diethyl ether under atmospheric pressure. Diethyl ether, like dimethyl ether, has a moderate degree of intermolecular hydrogen bonding and has a similar SP value (the SP value of dimethyl ether is 7.3 cal/cm ³ , and the SP value of diethyl ether is 7.4 cal/cm ³ ). However, since diethyl ether is a liquid at room temperature, the aggregation property of the aerosol coating material composition produced by the method of the present invention can be evaluated without filling it at high pressure.

<Formation of coating film on substrate>
The aerosol coating composition produced by the method of the present invention has excellent adhesion to the substrate, and is also excellent in rust prevention and water resistance. The substrate can be wood or metal. Examples of metals include steel, galvanized steel, stainless steel, magnesium alloy, aluminum alloy, brass, etc., and among them, non-ferrous metals such as aluminum alloy and stainless steel are preferred.

A coating film can be formed by spraying the aerosol onto a substrate and drying. Drying can be carried out, for example, by leaving it to stand at room temperature (23°C) for 20 to 40 minutes. If the aerosol coating composition contains a curing agent, it can be cured under conditions that correspond to the type of curing agent. For example, drying at 120 to 140°C is used when melamine resin is used as the curing agent, and drying at 110 to 150°C is used when blocked isocyanate is used.

(1) Materials used (1-1) Pigment TITANIX JR-701 (Teika)
Mistron Paper (Imeris)
Precipitated Barium Sulfate HF (Tomatec)

(1-2) Dispersant DISPERBYK-2164 (BYK)
DISPERBYK-2155 (BYK)
(1-3) Suspension agent ASA DS-313 (Ito Oil Co., Ltd.)

(1-4) Epoxy resin Epicron H-601-55 (DIC, solid content 55%)
Arakied 9205 (Arakawa Chemical, solid content 40%)
KA-1550 (Arakawa Chemical, solid content 40%)
Modepics 401 (Arakawa Chemical, solid content 40%)
Epoxy 871T (Mitsubishi Chemical, solid content 45%)
Epicron 7050-60M (DIC, solid content 60%)
Epicron 1050-70X (DIC, solid content 70%)
Epicron 850 (DIC, solids content 100%)

(1-5) Solvent-mixed thinner (cyclohexanone: 77.6%, propylene glycol monomethyl ether: 10.1%, n-butyl acetate: 3.4%, methyl ethyl ketone: 9.0%)
Cyclohexanone

(2) Mixing Pigments, Additives, and Epoxy Resins All at Once (Comparative Examples 1 to 5, Reference Examples 1 to 3)
The pigment, additives, epoxy resin, and solvent listed in Table 1 were mixed and dispersed for 30 minutes using beads with a particle size of 1.0 to 1.4 mm to prepare a paint. The modified epoxy resin and diethyl ether (DEE), which has a SP value close to that of dimethyl ether used as a propellant, were mixed at a paint/DEE ratio of 1/1, and the dilutability of the mixture at room temperature was visually observed.

In all of Comparative Examples 1 to 5, solid aggregates were found at the bottom and around the test tube immediately after mixing (marked with an x in Table 1). No aggregates were found in Reference Examples 1 to 3. Since various functional groups are added to the modified epoxy resin, it is thought that it easily adheres to the pigment due to its similar function as a dispersant. When a solvent that is poorly compatible with the modified epoxy resin is added while the modified epoxy resin is attached to the pigment, the modified epoxy resin that escapes from the solvent interface takes the pigment with it, causing the pigments to aggregate together.

(3) Adhesion test between pigment and modified epoxy resin (Reference Examples 4 to 11)
The epoxy resin used in Comparative Examples 1 to 5 and Reference Examples 1 to 3 was mixed with the pigment at a weight ratio of 4% in terms of solid content. Specifically, the pigment was added to a solvent in which the resin had been dissolved while stirring with a disperser, and it was observed whether the fluidity could be maintained.

In Reference Examples 4 to 8, fluidity was maintained, and the pigment could be added until the end (marked with a circle in Table 2). In Reference Examples 9 to 11, fluidity was lost, and it became impossible to add the pigment halfway through (marked with an x in Table 2). From these results, it is presumed that the modified epoxy resin has high adhesion to the pigment, which caused the aggregation in Comparative Examples 1 to 5.

Figures 1 and 2 show photographs of the aerosol coating compositions of Reference Examples 8 and 9 during stirring. Reference Example 8 maintained fluidity due to its low viscosity, but Reference Example 9 had an extreme increase in viscosity, causing the stirring blades to spin freely, and the pigment remained in powder form without being stirred.

(4) Addition of epoxy resin in the finishing process (Examples 1 to 5)
The pigment, additives, and solvent shown in Table 3 were dispersed for 30 minutes using beads with a particle size of 1.0 to 1.4 mm (dispersion step). The modified epoxy resin and solvent shown in Table 3 were added to the dispersed mixture (finishing step) to produce a paint. As in Comparative Examples 1 to 5, the paint/DEE was mixed at a ratio of 1/1, and the dilutability of the mixture at room temperature was visually observed.

In all of Examples 1 to 5, no agglomerates were observed when observed a few minutes after mixing, and no agglomerates were observed even after 24 hours (marked with circles in Table 3). As shown in Reference Examples 4 to 8, these modified epoxy resins have high adhesion to pigments, so it is assumed that by adding them in the finishing process, the pigments are no longer affected by the resin.

The aerosol coating compositions of Example 1 and Comparative Example 1 were each placed in equal amounts together with DEE into a test tube, and the state after thorough shaking is shown in Figure 3A. An enlarged view of the composition is shown in Figure 3B. No aggregates were observed in Example 1, while aggregated pigment was confirmed on the inner wall of the test tube in Comparative Example 1.

(5) Production of aerosol (Example 6)
The pigment, additives, epoxy resin, and solvent shown in Table 4 were mixed (dispersion step). The modified epoxy resin and solvent shown in Table 4 were added to the dispersed mixture in this order (finishing steps (1) and (2)) to produce paint. In the finishing steps (1) and (2), the components were added and then stirred for several minutes using a disperser. Thereafter, dilution was confirmed with a paint/DEE ratio of 1/1, and the paint was filled with dimethyl ether using a filling machine.

When the paint was observed a few minutes after mixing with DEE, no agglomerates were found, and no agglomerates were found even after 24 hours. In addition, when the paint was aerosolized, it sprayed well and no clogging occurred.

(6) Addition of epoxy resin in the finishing process (Examples 7 to 8)
The pigment, dispersant, suspending agent, epoxy resin, and solvent shown in Table 5 were mixed (dispersion step). Modified epoxy resin and solvent were added to the mixture after dispersion (finishing step) to produce a paint. The paint/DEE was mixed at 1/1, and the mixture was visually observed at room temperature.

In all of Examples 7 to 8, no agglomerates were observed when observed a few minutes after mixing, and no agglomerates were observed even after 24 hours. (See circles in Table 5.) The dispersants used in Examples 7 to 8 also had good solubility in DEE.

In addition, when 10% by weight of the dispersant was added to diethyl ether (DEE) to check the compatibility of the dispersant itself with diethyl ether, it was confirmed that none of the dispersants of Examples 7 to 8 became cloudy after mixing with diethyl ether, and thus the dispersants were compatible ("10% dispersant/DEE" in Table 5).

Claims (2)

The method includes dispersing a pigment in a solvent containing a cationic dispersant, and adding a modified epoxy resin ;
No modified epoxy resin is added in the dispersion process.
A method for producing an aerosol coating composition. 2. The process of claim 1 , wherein the pigment is talc, precipitated barium sulfate, or kaolin.