JPH0380184B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improved coating resin composition,
More specifically, the present invention relates to a resin composition for coating that provides a coating film with particularly excellent durability, which is made by blending a specific compound with orientation to the coating surface and ability to absorb ultraviolet rays. In recent years, from the perspective of saving resources, there has been a strong desire for paints with excellent weather resistance, and this demand is even stronger in the automobile industry, where paints that can maintain their luster even after being exposed outdoors for up to three years have been strongly desired. Therefore, in terms of accelerated weather resistance, it is desired that the gloss does not deteriorate over a long period of time. By the way, as resins for top coatings for automobiles, acrylic resins have been used in combination with melamine-formaldehyde resins mainly for metallics, and coconut oil has been used for solid colors. Short oil alkyd resins modified with synthetic or synthetic fatty acids have likewise been used in combination with melamine-formaldehyde resins. However, none of the resins listed above have a high degree of weather resistance. However, in view of these circumstances, the present inventors have conducted extensive research in order to obtain a coating composition that has a high degree of weather resistance. The present invention has now been completed by discovering a useful resin composition for coatings in which specific compounds as described below are blended. That is, the present invention uses an alkyl-substituted silicone resin having an amino group (hereinafter abbreviated as silicone oil) and 2-hydroxy-4-
0.01 to 3 parts by weight of the compound (A) obtained by reacting methoxybenzophenone-5-sulfonic acid with hydroxyl group-containing alkyd resin (B) having an oil length of 45% or less.
64.99 to 77 parts by weight, and 35 to 20 parts by weight of the melamine-formaldehyde resin (C) etherified with C ₁ to _{C 4} monohydric alcohol, and these (A), (B) and ( C) The sum of the essential components is 100
The object of the present invention is to provide a resin composition for coating that provides a coating film with particularly excellent durability, and which contains the following parts by weight: In general, in metallic finishes, the durability is significantly improved by incorporating a UV absorber into the clear topcoat layer, whereas in solid color coatings containing a large amount of pigment, the durability of the coating surface is significantly improved. Since the clear layer itself is thin, the effect of such a UV absorber cannot be expected. In other words, it is simply impossible to expect a large effect from the ultraviolet absorber, which exists in a form dispersed throughout the solid color coating. For this reason, current efforts are currently being made to improve the UV resistance of the resin itself; for example, changes to ultra-short oil or oil-free (alkyd) alkyd resins are being considered.
When such a method is used, pigment dispersibility and texture of the surface of the coating film, which affect the appearance of the coating film, tend to be rather inferior. On the other hand, when using the composition of the present invention, the ultraviolet absorber is concentrated in the clear layer on the surface of the coating film, so there is no need to select a special resin system, and it is a leap forward compared to conventional resin systems. This makes it possible to improve weather resistance. The compound (A), which is a particularly important constituent factor among the essential components constituting the composition of the present invention, is
It is obtained by reacting silicone oil with 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, and this reaction easily proceeds in a solvent such as dimethyl sulfoxide or dimethyl formamide. Here, the silicone oil mentioned above is
"Torre Silicone DC-536 or SH-3531"
Various amino group-containing silicone resins commercially available as silicone oil manufactured by Toray Silicone Co., Ltd. can be used. Since the compound (A) has the ability to orient to the coating film surface and absorb ultraviolet rays, the composition of the present invention obtained by blending the compound (A) with the compound (A) has the ability to absorb ultraviolet rays as well as the known and commonly used ultraviolet rays. It was confirmed that the same improvement in weather resistance was achieved when an absorbent was overcoated and a clear layer was applied. Furthermore, by incorporating an antioxidant into the composition of the present invention, the effect of improving weather resistance becomes even more remarkable. On the other hand, the above-mentioned hydroxyl group-containing alkyd resin (B) has an oil length of 45% or less, preferably 40%, modified with animal and vegetable oils or their constituent fatty acids, which have been conventionally used as solid color resins for automobiles. One or more resins appropriately selected from the following alkyd resins and/or oil-free alkyd resins are used. Next, the above-mentioned amino-formaldehyde resin
(C) refers to melamine resin, guanamine resin, acetoguanamine resin, or urea resin that has been etherified with C ₁ to _{C 4} monohydric alcohol, but melamine resin is used as a solid color resin. is most preferred. and (A), (B) and (C) as listed above.
The mixing ratio of each essential ingredient is (A):(B):(C)
A suitable ratio is 0.01 to 3:64.99 to 77:20 to 35 (parts by weight). Here, if the amount of component (A) used is less than 0.01 part by weight, the effect of improving weather resistance cannot be expected, and conversely, if it exceeds 3 parts by weight, the gloss and brightness of the solid color coating film will be reduced. Either case is unfavorable since the film resistance, acid resistance, moisture resistance, etc. will be significantly inferior. Furthermore, if the amount of component (C) used is less than 20 parts by weight, a coating film with sufficient hardness will not be obtained, and if it exceeds 35 parts by weight, weather resistance will be poor. However, the physical properties of the coating film become extremely brittle depending on the baking temperature, so either case is unfavorable. The resin composition for paint of the present invention obtained in this way has excellent durability such as weather resistance, so it can be used in inorganic materials such as slate and roof tiles in a form in which pigments are blended for purposes such as weather resistance. It is used in a wide range of applications, including paints for building materials and various other building materials such as colored galvanized iron.In particular, it is used as solid color paints for automobiles. Next, the present invention will be specifically explained with reference to Reference Examples, Examples, and Comparative Examples. In the following, all parts and percentages are based on weight unless otherwise specified. Reference example 1 [Preparation example of compound (A)] 1 equipped with a stirring device, thermometer and dropping funnel
In a flask, add 500 parts of dimethyl sulfoxide and 2-hydroxy-4-methoxybenzophenone.
50 parts of 5-sulfonic acid and
50 parts of ``Silicone DC-536'' were added and stirred at a temperature of 50°C for 1 hour to complete the reaction. Next, dimethyl sulfoxide was distilled under reduced pressure, and the target compound, which was a colorless and transparent liquid, was dissolved in methyl isobutyl ketone to obtain 1.
% solution. Reference Example 2 [Preparation example of hydroxyl group-containing oil-modified alkyd resin (B)] Charge 380 parts of coconut oil, 0.15 parts of lithium hydroxide, and 152 parts of trimethylolpropane to 230 parts.
After carrying out the alcohol exchange reaction at ℃ for 1 hour,
To this, 376 parts of phthalic anhydride, 94 parts of pentaerythritol, 48 parts of trimethylolethane and 40 parts of xylene were added and maintained at a temperature range of 160-180°C for 3 hours, then from 180°C to 22°C. 2
The temperature was gradually raised over time, and then heated to 220℃ for 3
A time dehydration reaction was carried out. Thereafter, the solution was diluted with xylene to adjust the non-volatile content to 60% to obtain a solution of the desired resin having a Gardner viscosity of V at 25°C, an acid value of 6.0, and a hydroxyl value of 77. Reference Example 3 [Preparation example of hydroxyl group-containing oil-free alkyd resin (B)] 180 parts of isophthalic acid, 180 parts of adipic acid, 120 parts of trimethylolpropane, and 180 parts of neopentyl glycol were stirred in an inert gas stream. The mixture was heated at 180°C for 2 hours and then at 220°C for about 7 hours to obtain a polyester resin having an acid value of 8. Next, this resin was treated with a mixed solvent of xylene/butyl cellosolve = 9/1 (weight ratio) to remove the nonvolatile content.
The solution was diluted to 60% to obtain a solution of the desired resin having a Gardner viscosity of UV, an acid value of 4.5, and a hydroxyl value of 70. Examples 1 to 6 Resin compositions of the present invention were prepared using the formulations shown in Table 1 and according to the procedure described below. That is, the hydroxyl group-containing alkyd resin of Reference Example 2 or 3
Part 87 “Fast Gen Super Red YE” [quinacridone pigment manufactured by Dainippon Ink and Chemicals Co., Ltd.] 13〃 “Solbenz 100” [mixture of aromatic hydrocarbons manufactured by Etsuso Petrochemical Co., Ltd.] 25〃 Naru After preparing a red base by kneading it in a sand mill for 2 hours, the specified amount of compound (A) obtained in Reference Example 1 and "Supervecamine L- 117-60'' (n-butyl etherified melamine resin manufactured by Dainippon Ink & Chemicals Co., Ltd.; non-volatile content = 60%) and its additives were blended to prepare a paint. Next, each paint was applied to a zinc phosphate steel plate treated with Bonderite #144 using an air spray paint machine (4 air) to a film thickness of 35 to 40 μm, and after setting for 10 minutes,
A cured coating film was obtained by baking in a hot air dryer at a temperature of 140°C for 30 minutes. Thereafter, the performance of each coating film was evaluated. The results are summarized in Table 2, and the methods and evaluation criteria for each performance test are as follows. Gloss: Measurement of 60-degree reflectance (%) Sharpness: Determined visually Hardness: Displayed as the hardness of the pencil before scratches using Uni, manufactured by Mitsubishi Pencil Co., Ltd. Weather resistance due to outdoor exposure: Expressed as gloss retention rate (%) after exposure for 1 year and 2 years, respectively, in Bangkok, Thailand, facing south at 5 degrees. Accelerated weather resistance...Gloss retention rate (%) after 1000 hours and 2000 hours of exposure, respectively, by Sunshine Weather-O-Meter (abbreviated as SWOM)
It is displayed as follows. Wax discoloration test: A piece of flannel cloth soaked in "Wilson Ten All" (a silicone wax manufactured by Wilson Co., Ltd.) was rubbed against a glass plate under a load of 500 g 30 times. _E1 is when measured with a color difference meter manufactured by Color Co., Ltd., and exposed under the specified conditions at the location and time shown in the table, and the exposed coating was rubbed 30 times in the same manner. The measured value was calculated as _E2 , and _E1 - _E2 was calculated as ΔE. Humidity resistance: Changes in the coating film were visually judged after being left in a high-temperature, humid atmosphere at 50°C and RH of 98% or higher for 72 hours. Acid resistance: 0.5 ml of a 5% sulfuric acid aqueous solution was dropped onto the coating film and left to stand for 24 hours, after which changes in the coating film were visually judged. Comparative Examples 1 to 6 Comparative compositions were prepared in the same manner as Examples 1 to 5, except that the composition was changed to the one shown in Table 1, and the compositions were made into paints, and then painted and cured. A membrane was obtained. Thereafter, the performance evaluation of each coating film is summarized in Table 2.

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Claims (1)

[Scope of Claims] 1 (A) 0.01 to 3 parts by weight of a compound obtained by reacting an alkyl-substituted silicone resin having an amino group with 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid, (B) 64.99 to 77 parts by weight of a hydroxyl group-containing alkyd resin with an oil length of 45% or less, and (C) 20 to 35 parts by weight of an amino-formaldehyde resin etherified with a C ₁ to C ₄ monohydric alcohol. A resin composition for a paint which provides a coating film with particularly excellent durability, which comprises the essential components (A), (B) and (C) in such a proportion that the total amount is 100 parts by weight.