JPS6254355B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a curing accelerator for chipping-resistant coatings (hereinafter referred to as accelerator) used in intermediate coatings for vehicles. Conventionally, xylene sulfonic acid, p-toluene sulfonic acid, dodecylbenzenesulfonic acid, and the like are known and widely used as this type of accelerator. All of these well-known promoters are acidic and have the property of reacting with chemicals having alkaline functional groups. On the other hand, it goes without saying that the intermediate coating paint is used by being applied onto an undercoating film that has been previously applied to the steel plate of the vehicle body or other vehicle parts. Conventionally, this undercoating paint has generally been an anionic electrodeposition coating, and anionic electrodeposition coatings have been widely used as the paint. Therefore, the undercoat film is
Since it is an acidic coating, the undercoat does not react with the sulfonic acid group of a well-known accelerator such as para-toluenesulfonic acid during baking formation of the intermediate coating, so the function of the accelerator does not deteriorate. However, in recent years, cationic electrodeposition coating, which has excellent antirust effects, has come to be widely used as an undercoat, and the coating film is a basic coating film. Therefore, this basic coating film and the sulfonic acid group of the well-known accelerator react with each other during baking, and its action as an accelerator is reduced, so that the resin does not undergo a sufficient curing reaction, resulting in a good intermediate coating film. A problem has arisen where it is not possible to obtain In this industry, there is an urgent need to solve this problem, and various developments have been attempted, but a good accelerator has not yet been obtained. As a countermeasure to this problem, it has been proposed to increase the baking temperature of the intermediate paint to a relatively high temperature, for example, 160℃ or higher.
A good effect is obtained by the action of the curing agent, with almost no need for an accelerator. However, baking at high temperatures requires high energy and is not a good method in these days of energy conservation, and there is an urgent need to develop an accelerator that allows baking at low temperatures, for example around 120°C. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an accelerator which eliminates all of the above-mentioned drawbacks. The object of the present invention is achieved by blending 0.1 to 5 parts by weight of dinonylnaphthalene disulfonic acid (hereinafter simply referred to as DNNDSA) to 100 parts by weight of resin in the intermediate coating. This invention will be explained in detail below. What is DNNDSA, which forms the main part of this invention? It is a compound with the chemical structural formula of
It is a structure with individuals. Also, this property has specific gravity:
0.8, appearance: transparent + liquid, hue: 8, flash point: 40
°C acid value is 115. The blending ratio of DNNDSA is 0.1 to 5 parts by weight based on 100 parts by weight of the resin, and preferably,
It is 1 to 3 parts by weight. The principle of this invention is that as the functional group of DNNDSA,
There are two sulfonic acid groups, and one each at positions 1 to 4 and 5 to 8 of the naphthalene ring, so one of the sulfonic acid groups reacts with the cationic electrodeposited undercoat film during baking. Also, since the other sulfonic acid group acts as an accelerator for the curing agent, it sufficiently functions as an accelerator and forms a good thick intermediate coating film. Next, a method for producing a thick film type intermediate coating composition using the accelerator of the present invention and other additives will be described. First, the manufacturing method involves blending the resin, two or more pigments DNNDSA, a solvent, and various compounding agents such as antifoaming agents and antisettling agents as necessary in a known stirrer such as a disper, stirring and mixing, and then using a ball mill.
After uniformly dispersing with a known dispersing machine such as a sand grinder or a roll mill, the product is defoamed. The above pigment is a general term for extender pigments and coloring pigments, and specifically includes calcium carbonate, silinica, alumina, iron oxide (including red iron oxide), aluminum silicate (clay, kaolin, etc.), asbestos, and hydrated silicic acid. Magnesium (including talc), barium sulfate, glass beads, zinc white and titanium oxide, and more preferably calcium carbonate, silica, iron oxide, aluminum silicate, titanium oxide and zinc white. When used, at least two or more of the above pigments are selected and used. What is important in this case is to adjust the particle size distribution range of the pigment, and if this adjustment is incorrect, the finished appearance and coating performance will be significantly impaired. This particle size distribution is
It should be distributed within the range of 0.001 to 70μ, and preferably in 100 parts by weight of the total pigment.
The amount of pigment distributed within the range of 0.001 to 5 μ is 30 parts by weight or less, and the amount of pigment distributed within the range of 5 to 70 μ is
The amount of pigment distributed within the range of 0.001 to 5 μ is preferably 30 parts by weight or less, and the amount of pigment distributed within the range of 5 to 30 μ is 35 parts by weight. A smooth coating film can be obtained by using a pigment with a small particle size of 25 parts by weight or less and a pigment with a large particle size distributed within the range of 30 to 70 μm. As a method for adjusting the pigment distribution width to this particle size, since soft pigments tend to become fine particles during the dispersion process using a roll mill or sand grinder, there is no problem in preparing a region with a fine particle size, but 5μ or more The particle size of silica, which is difficult to atomize in the dispersion process,
An effective method is to select and use at least one hard pigment from alumina, asbestos, glass beads, and the like, and to incorporate the pigment with a large particle size into the final thick-film intermediate coating. The proportion of pigment in the thick film intermediate coating is 100 to 500 parts by weight based on 100 parts by weight of resin, and preferably
It is 150 to 400 parts by weight. Although the pigments are generally as described above, the appearance, particle size distribution range, and blending ratio of each pigment suitable for the present invention are shown in Table 1 below.

[Table] Next, as the resin that can be blended with the accelerator of this invention, any well-known coating resin can be used, and there are no particular restrictions, but polyester resins are preferred, particularly urethane-modified polyester resins, oil-free alkyd resins, and urethane resins. , phenol-modified resin,
It is an acrylic resin or the like, and its blending ratio is 5 to 70 parts by weight, preferably 10 to 50 parts by weight, in 100 parts by weight of the total high film thickness type paint. Next, regarding the solvent, any known solvent can be used, but preferably
At least two or more selected from the group consisting of a low boiling point solvent of 120°C or lower and a high boiling point solvent of 120°C or higher are used, and most preferably the high boiling point solvent is 50 parts by weight per 100 parts by weight of the total solvent. The above is to be used. Specific examples of the low boiling point solvent are low molecular weight alcohol solvents such as methanol, normal butanol, and isobutanol, and specific examples of the high boiling point solvent are ethylene glycol monoethyl ether, ethylene glycol monobutyl, etc. These are glycol ethers such as ether, Kent-based solvents such as cyclohexanone and isophorone, and aromatic hydrocarbons. The blending ratio of these solvents is 20 to 100 parts by weight per 100 parts by weight of the resin, and preferably,
It is 30-80 parts by weight. As mentioned above, the three ingredients essential to this invention are resin, pigment, and solvent, but it is even more preferable to use antifoaming agents, leveling agents, anti-settling agents, etc. in addition to these ingredients as necessary. A thick film type intermediate coating paint can be obtained. Normally, if defoaming is complete, a smooth surface can be obtained for the coating film, so defoaming agents often double as leveling agents. The antifoaming agent is a copolymer-based antifoaming agent such as a silicone-based antifoaming agent, and preferably a non-silicone antifoaming agent. Examples of anti-settling agents include fatty acid ester polymers, synthetic waxes, and silica-based anti-settling agents. If these compounding agents are used in too large a quantity, other physical properties will be impaired, so it is better to limit the amount to 0.01 to 5 parts by weight per 100 parts by weight of the resin. The working viscosity of a suitable thick film intermediate coating using the accelerator of the present invention is then between 1000 and 4000 C.PS, most preferably between 2500 and 3500 C.PS.
The solid content is 60 to 90 parts by weight in 100 parts by weight of the total high film type paint, and most preferably 65 parts by weight.
~75 parts by weight. When painting, it is preferable to use a hot airless sprayer. As mentioned above, the above-mentioned compounding agent and method for producing a thick film type intermediate coating paint have shown the most preferable example for obtaining a thick film type intermediate coating paint using the accelerator of the present invention. Any compounding agent for thick film type intermediate coating paint, for example, each resin and each pigment can be blended together to obtain thick film type intermediate coating paint, and it exhibits a remarkable effect, and it can be used in any manufacturing method. Can be used. (Example 1) 24 parts by weight of polyester (oil-free alkyd) resin with 60% non-volatile content, 8.9 parts by weight of melamine resin (curing agent) with 70% non-volatile content, and calcium carbonate.
6.4 parts by weight (0.01~3μ) and titanium oxide (0.01~3μ)
1 μ), 2.0 parts by weight of silica (1 to 50 μ), 45.0 parts by weight of silica (1 to 50 μ), 1.2 parts by weight of antifoaming and leveling agent, 12.5 parts by weight of a mixed solvent of xylol, cyclohexanone and cellosolve acetate, and 1.3 parts by weight of DNNDSA are blended into the disper. The mixture was stirred and mixed for 15 minutes, passed through a three-roll mill three times to be dispersed, and then transferred to a degassing tank and defoamed at a reduced pressure of about 70 mmHg to obtain a thick film intermediate coating for vehicles. (Example 2) A thick film intermediate coating for vehicles was obtained in the same manner as in Example 1 except that the amount of DNNDSA was changed to 4 parts by weight. (Comparative Example 1) Example 1 except that 1.3 parts by weight of dodecylbenzenesulfonic acid was added instead of 1.3 parts by weight of DNNDSA.
A thick-film intermediate coating for vehicles was obtained in the same manner as above. (Comparative Example 2) A thick film intermediate coating for vehicles was obtained in the same manner as in Example 2, except that 4 parts by weight of dodecylbenzenesulfonic acid was blended instead of 4 parts by weight of DNNDSA. In order to examine the performance of the thick-film type intermediate coating paints for vehicles obtained in Examples 1 and 2 and Comparative Examples 1 and 2, we coated iron plates with anionic electrodeposition or cationic electrodeposition in advance. Apply 150 μ of thick film intermediate coating for vehicles, set for 2 minutes, and apply 100 μ
It was baked for 10 minutes in a furnace maintained at 110°C and then allowed to cool to room temperature. After that, apply 35μ of normal intermediate paint.
It was applied, set for 7 minutes, baked in a furnace maintained at 120°C for 30 minutes, and allowed to cool. Thereafter, 35μ of a regular top coat was applied, set for 7 minutes, baked in a furnace kept at 120°C for 30 minutes, and allowed to cool to obtain a test piece. This test piece was subjected to tests such as sagging film thickness type, armpit film thickness type, airless sprayability, smoothness, chipping resistance, and salt spray tests required for coating films, and all showed good characteristics. Next, in order to check the adhesion of the coating film on the test piece, an NT cutter (NT cutter S type A type) was applied perpendicularly to the coated surface of the test piece to reach the substrate. 2.0~2.3
Draw 11 parallel lines at mm intervals, draw 11 parallel lines at 2.0-2.3 mm intervals where they intersect, draw 100 squares surrounded by 4 straight lines, and apply adhesive tape (Nichiban) to these areas. The tape was removed from the test specimen by holding one end of the adhesive tape (industrial cellophane tape) and pulling it rapidly upwards, and the number of squares with 50% or more of the coating remaining was counted. The test results listed in Table 2 were obtained. In addition, regarding the adhesion after water deterioration, the above test piece was
After soaking in distilled water at 40±1℃ for 240 hours and taking it out, 3~
Adhesion was evaluated after 8 hours.

[Table] As is clear from Table 2 and other test results,
The present invention provides a curing agent for thick film type intermediate coatings for vehicles, which provides favorable results in all aspects of coating performance, and in particular provides good adhesion performance to cationic electrodeposited primer coatings.

Claims (1)

[Claims] 1. In the curing accelerator for vehicle intermediate coatings containing at least a resin, a solvent, a pigment, and a curing accelerator, the curing accelerator contains dinonylnaphthalene disulfonic acid in an amount of 0.1 to 5 parts by weight per 100 parts by weight of solid content of the resin. A curing accelerator for intermediate coatings for vehicles, characterized by containing part by weight.