JPH0422188B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a coating composition, and more particularly to a coating composition containing a specific acrylic graft copolymer as a binder component and having excellent drying properties and gloss. Acrylic thermosetting fuel or air-drying two-component urethane paints usually produce coatings with excellent gloss, hardness, water resistance, chemical resistance, weather resistance, etc., and are suitable for automobiles, vehicles, electrical equipment, furniture, etc. Widely used for painting enamel, metal seals, etc. In addition to the property of providing a good appearance, fast drying properties are strongly desired for applications such as automobile repair. Recently, the technology of blending cellulose derivatives to improve the drying properties of paints has been attracting attention, but in the case of acrylic paints, it is necessary to increase the styrene content in order to obtain high gloss and good chemical resistance. .
However, even if cellulose derivatives are tried to be blended to improve drying properties, if the styrene content of the acrylic resin is high, the compatibility of the resins is poor, resulting in poor appearance. Systems that do not contain cellulose derivatives have good appearance but poor drying properties. As described above, dryness and appearance are contradictory issues and it has been difficult to achieve both. However, in recent years, fields that require dryness and appearance have become more and more popular, such as automobile repair, woodworking, and ceramics. JP-A No. 56-157463 discloses a room-temperature-drying coating composition containing as a vehicle component a modified vinyl copolymer obtained by copolymerizing cellulose acetate butyrate (hereinafter referred to as CAB) and a vinyl monomer. However, it is said that there is a limit to the amount of styrene that can be copolymerized. This can be achieved through the conventional direct reaction of CAB and vinyl monomers, or by reacting CAB with maleic acid, fumaric acid, acid anhydride, acid chloride, etc., and then reacting with vinyl monomers. This is because the methods described in 8105 and the like all have poor grafting rates, and it is also impossible to copolymerize more than a certain limit amount of styrene monomer, for example, more than 35% by weight of the total monomers. If cellulose derivatives can be efficiently grafted into acrylic polymers to improve drying properties, and if the styrene content can be polymerized at a higher content than the 20% required for high gloss, both drying properties and appearance can be improved. It is expected that a solution and useful resin vehicle will be obtained at the same time. The present inventors previously focused on the ester bonds of acetate and butyrate in CAB as a means of grafting CAB onto an acrylic polymer.
We developed a macromer method to react CAB with mono- or diester of fumaric acid or maleic acid to obtain CAB with copolymerizable double bonds.
They discovered that the desired product could be obtained with a high grafting rate by copolymerizing a polymerizable monomer with a CAB macromer, and filed a patent application on September 10, 1981 for a method for producing a graft copolymer resin. The invention according to the above application aims to increase the grafting rate of CAB and obtain a resin composition that has good solubility and compatibility with solvents or other resins and does not become cloudy when formed into a coating film. The polymerizable monomer copolymerized with CAB macromer is α,
It was recognized as any vinyl monomer having a β-ethylenically unsaturated bond. In subsequent research, the present inventors found that the same method was applicable not only to cellulose acetate butyrate but also to other esters of cellulose such as cellulose acetate and cellulose acetate propionate (hereinafter referred to as cellulose derivatives), and that the styrene content It has been found that styrene has a high gloss, that is, styrene accounts for 20 to 50% of the monomers constituting the acrylic resin, and is particularly useful for obtaining a resin vehicle that can provide a high gloss coating surface. Therefore, in the present invention, the monomer to be copolymerized with the cellulose derivative macromer is preferably
A polymerizable monomer containing 25% to 40% styrene is copolymerized with a cellulose derivative macromer,
The high styrene cellulose derivative grafted acrylic copolymer thus obtained is used as an essential component of the resin vehicle. In addition to increasing the styrene content, it is desirable that the number average molecular weight of the main chain portion of the acrylic graft copolymer excluding the cellulose derivative is about 1,000 to 15,000. This is because if it is less than 1,000, the initial drying properties are poor, and if it exceeds 15,000, the flowability is poor, resulting in poor appearance, and both are recognized as being undesirable for the purpose of the invention. The glass transfer temperature of the main chain resin is 50 to 95℃.
It is preferable that the drying temperature is within the range of 100°C. If the temperature is lower than 50°C, the initial drying property will be low, and if the temperature exceeds 95°C, the weather resistance will tend to deteriorate. Furthermore, although it is not an absolute condition, the resin acid value should be designed within the range of 2 to 20, as if it is less than 2, the curing properties during crosslinking will be poor, and if it exceeds 20, the reaction will be too fast and there will be a tendency to cause distortion etc. Furthermore, if the hydroxyl value is less than 50, the crosslinking density will be low, the reactivity will be slow, and the drying property will be poor, and if it exceeds 150, the cost will be too high, so it is preferably set to 50 to 150. The coating composition of the present invention contains any organic or inorganic pigment used for top coating, intermediate coating, etc., and constitutes a stable dispersion system. The coating composition may further contain other resins, if desired.
Extender pigments, ultraviolet absorbers, antioxidants, surface conditioners, wetting agents and other optional paint additives can be added. The coating composition of the present invention thus obtained has excellent drying properties based on cellulose and high gloss, weather resistance, chemical resistance, etc. based on the high styrene content.
It is useful as a thermosetting paint, a two-component urethane paint, etc. in a wide range of paint fields including automobile repair, woodworking, nitriding, and others. The present invention will be explained below with reference to Examples. Unless otherwise specified, parts and percentages in the examples are by weight. Production example of CAB resin solution 1 In a reactor equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas introduction device, 500 parts of cellulose acetate butyrate "CAB-551-0.2" (manufactured by Eastman Chemical Products) and 500 parts of xylene prepare the department,
Gradually raise the temperature and after confirming that CAB has dissolved, add 150 parts of monobutyl maleate, 1.0 part of dibutyltin oxide, and 100 parts of xylene, and heat to 145-150℃.
The reaction was carried out under stirring for about 7 hours while blowing nitrogen gas. After the reaction was completed, 500 parts of toluene, 500 parts of xylene, and 1000 parts of butyl acetate were added to dilute the mixture to obtain a CAB resin solution having a double bond copolymerizable with other polymerizable monomers. The resulting resin solution was a transparent solution with a nonvolatile content of 20%, a viscosity of A ₂ -A _{, and} a color number of 1. Production Examples 2 to 4 of CAB Macromer CAB resin solutions of Production Examples 2 to 4 were obtained using the same method as Production Example 1 and the formulations shown in Table 1. The special values are shown at the bottom of Table 1.

[Table] Production Example 1 of CAB graft acrylic resin solution 40 parts of the CAB resin solution obtained in Production Example 1 of CAB resin solution, 25 parts of toluene, 25 parts of xylene, and 19 parts of butyl acetate were mixed with a thermometer, a stirrer, and cooled under reflux. The mixed solution of the vinyl monomer component and polymerization initiator shown below was heated and stirred while introducing nitrogen gas into a reactor equipped with a reactor, a nitrogen inlet tube, and a dropping funnel. The solution was added dropwise from the dropping funnel at a constant rate over 3 hours. 30 minutes after completion of dropping, add 0.8 parts of tertiary butyl peroxy 2-ethylhexanoate, 7 parts of butyl acetate.
Part of the mixed solution was added dropwise at a uniform rate over 30 minutes. After the dropwise addition was completed, the temperature was maintained at 120°C for 90 minutes, and the contents were taken out after cooling. The obtained graft copolymer solution has a non-volatile content
It was a homogeneous and transparent solution with 50.2%, a viscosity of X, and a color number of 1 or less. Other resin properties are shown in Table 3. Vinyl monomer component and polymerization initiator styrene...40.0 parts 2-hydroxyethyl methacrylate...16.2 parts Methacrylic acid...0.6 parts Methyl methacrylate...32.0 parts Isobutyl methacrylate...1.5 parts n-butyl acrylate... ...9.7 parts Tertiary butyl peroxy 2-ethylhexanoate ...2.0 parts Total 102.0 parts Production examples 2 to 7 of CAB graft acrylic resin solutions Vinyl monomer components shown in Table 2 by the same method as Production Example 1 above and a polymerization initiator to obtain CAB grafted acrylic resin solutions 2 to 7. The special values are shown in Table 3.

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[Table] Comparative structure example 1 Toluene 25 was placed in a reactor equipped with a stirrer, thermometer, reflux condenser, nitrogen gas inlet pipe, and dropping funnel.
1 part, xylene 25 parts, and butyl acetate 9 parts were heated and stirred while introducing nitrogen gas, and when the temperature reached 120°C, the vinyl monomer components and polymerization initiator shown in Production Example 1 of CAB grafted acrylic resin solution were added. 102 parts of the mixed solution was added dropwise at a constant rate of 120° C. from the dropping funnel over 3 hours. 30 minutes after completion of dropping, add 0.8 parts of tertiary butyl peroxy 2-ethylhexanoate, 7 parts of butyl acetate.
Part of the mixed solution was added dropwise at a uniform rate over 30 minutes. After the dripping was completed, the temperature was kept at 120℃ for 90 minutes, and then the “CAB-551-
0.2” (manufactured by Eastman Chemical Products) 6
15 parts xylene, 10 parts toluene,
A solution dissolved in 15 parts of butyl acetate was added, stirred for 30 minutes, cooled, and the contents were taken out. The varnish properties and resin characteristics are shown in Table 5. Comparative Production Example 2 6 parts of "CAB-551-0.2", 40 parts of xylene, 35 parts of toluene, and 24 parts of butyl acetate were charged into a reactor similar to that shown in Comparative Production Example 1, and the mixture was gradually heated while introducing nitrogen gas. When CAB is dissolved and the temperature reaches 120°C, the mixture 102 of the monomer and polymerization initiator shown in Example 1 is added from the dropping funnel at a constant temperature of 120°C.
It was dropped at a uniform rate over time. Thirty minutes after the completion of the dropwise addition, a mixed solution of 0.8 parts of t-butylperoxy 2-ethylhexanoate and 7 parts of butyl acetate was added dropwise at a constant rate over 30 minutes. After dropping, keep at 120℃ for 90 minutes and then cool.
I took out the contents. The varnish properties and resin characteristics are shown in Table 5. Comparative production example 3 Cellulose acetate butyrate “CAB-551
-0.2'' and 500 parts of xylene were charged, the temperature was gradually raised, and after confirming that cellulose acetate butyrate had dissolved, 150 parts of maleic anhydride, 1.0 part of dibutyltin oxide, and 100 parts of xylene were charged, and nitrogen gas was added. After about 10 hours, 500 parts of toluene, 500 parts of xylene, and 1000 parts of butyl acetate were added to form a cellulose acetate butyrate resin solution. I got it. The resulting resin solution was a transparent solution with a nonvolatile content of 20%, a viscosity of D, and a color number of 1. 40 parts of the obtained resin solution, 25 parts of toluene, 25 parts of xylene, and 19 parts of butyl acetate were charged into the same reactor as in Comparative Production Example 1, heated and stirred while introducing nitrogen gas, and when the temperature reached 120°C, CAB 102 parts of the mixed solution of the vinyl monomer component and polymerization initiator shown in Production Example 1 of Grafted Acrylic Resin Solution was added dropwise at a constant rate of 120° C. from the dropping funnel over 3 hours. Thirty minutes after the completion of the dropwise addition, a mixed solution of 0.8 parts of tert-butylperoxy-2-ethylhexanoate and 7 parts of butyl acetate was added dropwise at a constant rate over a period of 30 minutes. After dripping
The container was kept at 120° C. for 90 minutes, and after cooling, the contents were taken out. The varnish properties and resin characteristics are shown in Table 5. Varnish Comparative Production Examples 4 to 7 Varnish Comparative Production Examples 4 to 7 were obtained using the vinyl monomer components and polymerization initiators shown in Table 4 in the same manner as in CAB graft acrylic resin Production Example 1.

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[Table] Example 1 Preparation of white paint Using the varnish obtained in Production Example 1 of CAB graft acrylic resin solution, perform pigment dispersion according to the following dispersion blend to create a white dispersion paste, and then dissolve and blend to create a white primary color paint. It was created. Dispersed blended titanium white CR-95 (manufactured by Ishihara Sangyo Co., Ltd.) ...27.0 parts Varnish ...10.8 parts Toluene ...7.2 parts 45.0 parts Dissolved blended white dispersion paste ...45.0 parts Varnish ...49.2 parts Xylene ...5.8 parts 100.0 parts 100 parts of the above white primary color paint and 10 parts of Sumidyur-75 (manufactured by Sumitomo Bayer) were diluted to a specified viscosity with a thinner consisting of toluene/xylene/butyl acetate = 1/1/1 and heated at 25°C to a commercially available Lutker. Spray painted over the primer. The coating performance is shown in Table 6. Examples 2 to 7 and Comparative Examples 2 to 7 In the same manner as in Example 1, a white primary color paint was prepared and spray-painted. The coating film performance is shown in Table 6.

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Claims (1)

[Scope of Claims] 1 (a) A copolymerizable compound obtained by reacting a cellulose ester derivative selected from cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate with a mono- or diester of maleic acid or fumaric acid. An acrylic graft copolymer obtained by copolymerizing a cellulose derivative having a double bond and a polymerizable monomer containing at least 20 to 50% by weight of styrene, in which the main chain portion excluding the cellulose derivative is Number average molecular weight is about 1000~
15,000, a glass transition temperature of 50 to 95°C, a resin acid value of 2 to 20, and a hydroxyl value of 50 to 150; (b) an isocyanate prepolymer curing agent; , a solvent-type, air-drying two-component urethane coating composition in which the equivalent ratio of the NCO group of the curing agent to the HO group of the binder component is 0.5 to 2.0.