JPH07292313A - Automotive coating agent composition - Google Patents

Abstract

PURPOSE:To obtain the subject composition excellent in adhesiveness scratch resistance, water resistance, weatherability, contamination resistance and gloss, comprising a copolymer containing side chain unsaturated group-contg. ladder silicone oligomer, organic solvent, ultraviolet light absorber, oxidation stabilizer and crosslinking agent. CONSTITUTION:This automotive coating agent composition comprises an organic solvent, ultraviolet light absorber, oxidation stabilizer, crosslinking agent, and a copolymer 300-5000 in number-average molecular weight (Mn), 400-50000 in weight-average molecular weight (Mw) and <=10 in Mw/Mn, produced by copolymerization between a ladder silicone oligomer containing 1-50mol% of (meth)acryloxyalkyl group at the side chain group in the molecule and at least one kind of monomer among (meth)acrylic esters, (meth)acrylamide, methylol (meth)acrylamide, alkoxymethylol (meth)acrylamides, unsaturated carboxylic acids, styrene and vinyltoluene. This composition is in good balance between the adhesiveness to substrate, scratch resistance, water resistance, oil resistance, weatherability, contamination resistance and gloss.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention provides a composition having excellent gloss, weather resistance, water resistance, oil resistance, scratch resistance, and adhesion to a substrate as a coating agent for clear tops of painted surfaces of automobiles. To do.

[0002]

2. Description of the Related Art The surface coating of automobiles is subjected to pretreatment and electrodeposition coating, followed by intermediate coating and topcoating, and a clear topcoat is applied on top of high-grade vehicles. The purpose of the clear top coat is to protect the painted surface and to give it a vivid impression.
As a result, it is intended to give the car itself a high-class image. Conventionally, clear top coats have been applied to acrylic, urethane, fluorine, silicon, etc. coating agents, all of which have been used in luxury cars, but some have weather resistance. There is nothing perfect yet, because the coating film is insufficient, the coating film is soft and easily scratched, and the stain resistance is insufficient.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a clear topcoat for automobile surface coating, which has been conventionally regarded as a drawback, such as adhesion to a substrate, scratch resistance, water resistance, oil resistance, weather resistance and stain resistance. , Aims to develop a coating agent with a well-balanced gloss.

[0004]

The present invention has a number average molecular weight Mn of 300 to 5,000 and a weight average molecular weight Mw of 40.
0 to 50,000, Mw / Mn is 10 or less, and the content of the (meth) acryloxyalkyl group in the side chain group in the molecule is 1 to 50 mol% of a ladder silicone oligomer and a (meth) acrylic acid ester, (Meth) acrylamide, methylol (meth) acrylamide, alkoxymethylol (meth) acrylamide, unsaturated carboxylic acid,
By developing a copolymer prepared by copolymerizing at least one monomer selected from styrene and vinyl ester, an organic solvent thereof, an ultraviolet absorber, an oxidation stabilizer and a cross-linking agent, the above-mentioned coating agent for automobiles is developed. Achieved the purpose.

Ladder silicone has been found to have excellent weather resistance, water resistance and heat resistance when used as a coating agent (see, for example, JP-A-62-132575).
No.), it has been used for coating various products used outdoors, but it has excellent effect, but the material, shape, and size of the base material to be coated are small because the elongation of the coating film is small.
Particularly in metal surface coating, cracks are likely to occur on the coated surface due to the difference in coefficient of thermal expansion from the base material due to the difference in temperature.

Acrylic resin coating agents can produce coating films with various variations from hard to soft depending on the composition. Generally, the weather resistance and water resistance of silicone resin-based and fluororesin-based coating agents are improved. Inadequate in comparison. On the other hand, although silicone resin-based and fluororesin-based coating agents have excellent weather resistance, it has been pointed out that the adhesion of the coating film to the substrate and the stain resistance are insufficient.

The present invention solves these problems by using a copolymer obtained by copolymerizing a ladder silicone oligomer having a specific structure and a specific polymerizable monomer as a clear top coating agent, thereby providing a conventional coating agent. We have completed a new coating agent that overcomes the above-mentioned drawbacks.

That is, the ladder silicone copolymer used in the coating agent of the present invention has an Mn of 300 to 300.
5,000, Mw is 400 to 50,000, Mw / Mn
Is 10 or less, and the (meth) acryloxyalkyl-based content in the side chain group is 1 to 50 mol%, preferably 3 to
30 mol% of ladder silicone oligomer and at least one selected from (meth) acrylic acid ester, (meth) acrylamide, methylol (meth) acrylamide, alkoxymethylol (meth) acrylamide, unsaturated carboxylic acid, styrene and vinyl ester. It is a copolymer with one or more monomers selected from the monomers.

Mn of ladder silicone oligomer used
If the Mw is less than 300 or the Mw is less than 400, the weather resistance, water resistance, and stain resistance of the coating film are poor. When the Mn exceeds 5,000 or the Mw exceeds 50,000, the workability and sprayability of the coating agent, etc. Is bad and the viscosity increase during storage is large and unsuitable. Mw / Mn is 10
If it exceeds, there is an increase in viscosity during storage and gelation tends to occur.

The content of the (meth) acryloxyalkyl group in the side chain group in the ladder silicone is 1 to 50 mol%, preferably 3 to 30 mol%. When the content is less than 1 mol%, the copolymerizability is poor, and unreacted ladder silicone oligomer remains in the coating agent, resulting in insufficient weather resistance and stain resistance. Moreover, this content is 5
When it exceeds 0 mol%, it is unsuitable because gelation occurs during the production of the ladder silicone oligomer, and the viscosity remarkably increases.

The content of the substituent other than the (meth) acryloxyalkyl group of the ladder silicone oligomer is 99 to 50.
Mol%, preferably 97 to 70 mol%, and as the substituent, an alkyl group having 1 to 18 carbon atoms, a substituted alkyl group, a phenyl group, and a substituted phenyl group are used, and particularly a methyl group and a phenyl group are excellent. ing. In this case, 5 mol% or less of epoxy group and amino group may be added to the side chain group.

The compounding ratio of the ladder silicone oligomer and the polymerizable monomer is 1:99 to 50:50 by weight, preferably 3:97 to 30:70. When the content of the ladder silicone oligomer in the copolymer is less than 1% by weight, the weather resistance, water resistance and stain resistance are insufficient, and when it exceeds 50% by weight, the increase in viscosity during storage is large and unstable.

The ladder silicone oligomer is synthesized by post-hydrolysis condensation of trialkoxysilane or trichlorosilane.

As the trialkoxysilane, trimethoxymethacryloxypropylsilane, triethoxyacryloxybutylsilane, trichloromethacryloxypropylsilane and triethoxymethylsilane, trimethoxyphenylsilane, trichloromethylsilane, trichlorophenylsilane and the like are mixed. Used.

The thus-synthesized ladder silicone oligomer has a terminal group of a hydroxyl group or an alkoxy group and reacts with a hydroxyl group or an alkoxy group of another molecule during storage or upon heating to condense to increase the viscosity and finally to gel. Therefore, it is desirable to substitute the silicone atom of the terminal group with a non-reactive alkyl group and / or phenyl group (trimethylsilyl group and / or triphenylsilyl group). For this purpose, monofunctional silanes such as trimethylalkoxysilane, triphenylalkoxysilane, trimethylchlorosilane, and triphenylchlorosilane are added at the end of the ladder silicone synthesis reaction to substitute the terminal with a methyl group or a phenyl group, or a hexamethyl group. It can be stabilized by reacting an alkyldisiloxane and converting the terminal to a trialkyl group.

The monomers copolymerizable with the ladder silicone oligomer include methyl acrylate as a (meth) acrylic acid ester, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, glycidyl acrylate, glycidyl methacrylate, aminoethyl acrylate, aminoethyl methacrylate and the like can be mentioned.

Other unsaturated monomers as polymerizable monomers include acrylic acid, methacrylic acid, maleic acid, crotonic acid and itaconic acid, and vinyl esters include vinyl formate, vinyl acetate and vinyl propionate.
Examples of (meth) acrylamide monomers such as vinyl versatate and vinyl stearate include (meth) acrylamide, methylol (meth) acrylamide, and alkoxymethylol (meth) acrylamide, and other monomers include styrene.

The copolymerization is carried out by solution polymerization, and the solvent is mainly an ester such as ethyl acetate or butyl acetate, an aromatic hydrocarbon such as toluene or xylene, cellosolve, cellosolve acetate, butyl cellosolve, carbitol, butyl carbitol. Ethylene glycol-based, propylene glycol acetate, such as
Propylene glycol-based compounds such as propylene glycol methyl ether acetate, ketone-based compounds such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, and other alcohols such as ethanol and butanol can be conveniently used. Polymerization is benzoyl peroxide,
It is carried out by adding a polymerization initiator such as azobisisobutyronitrile and heating. The copolymer of the present invention is excellent in weather resistance, but further contains a UV absorber and an oxidation stabilizer to prevent deterioration due to ultraviolet rays and oxidative decomposition.
Must be stabilized for long term outdoor use.

Benzotriazole-based, benzophenone-based, salicylic acid-based, and cyanoacrylate-based UV absorbers are used, and hindered amine-based, phenol-based, sulfur-based, and phosphorus-based UV stabilizers are used.

Although the as-polymerized copolymer is thermoplastic, a cross-linking agent is added to cross-link it to make it thermoset. As the cross-linking agent, an alkoxymethylol melamine, an amino compound such as a melamine resin initial condensate, a polyglycidyl compound, and a blocked polyisocyanate are used.

For example, alkoxymethylol melamine reacts with OH or COOH in the copolymer to crosslink, polyglycidyl compound reacts with OH, NH ₂ etc. in the polymer to crosslink, and blocked polyisocyanate releases isocyanate by heating. , OH in polymer, NH
It reacts with ₂ and crosslinks to become a thermosetting resin, which improves properties such as heat resistance, hardness, chemical resistance, water resistance, and oil resistance.
In order to improve the workability, defoaming and leveling properties of the coating agent, a cellulose ester, silicone-based, fluorine-based, acrylic-based defoaming agent or leveling agent may be added.

The coating agent of the present invention is mainly coated by spraying, but roll coating, brush coating, etc. are also possible. A surface treatment, an undercoat, an intermediate coat, and a top coat are applied, and a clear coat is performed thereon by using the coating agent of the present invention as a clear top coat agent.

The thickness of the clear coat film is about 2 to 30 μm, though it depends on the desired properties.
It is heated at 0 to 180 ° C. for 10 to 60 minutes, dried and baked to finish. The topcoat and clear topcoat can be painted and baked by the 2coat 1bake method.

[0024]

The coating agent for automobiles of the present invention is a clear top coating agent for coating surfaces of automobiles and is for improving the gloss, weather resistance, water resistance, oil resistance and abrasion resistance of the coating surface.

Particularly as a ladder silicone oligomer,
The number average molecular weight Mn is 300 to 5,000, the weight average molecular weight Mw is 400 to 50,000, Mw / Mn is 10 or less, and the content of the (meth) acryloxyalkyl group in the side chain group in the molecule is 1 A coating agent mainly composed of a copolymer obtained by copolymerizing a polymerizable monomer with 50 to 50 mol% of a ladder silicone oligomer can be used for a metal base material having a difference in thermal expansion coefficient, which is a problem that a conventional clear top coating agent has. It was possible to improve without lowering the performance such as adhesion.

Furthermore, the stability of the coating agent is greatly improved by using a siloxane in which the end group of the ladder silicone oligomer is bonded to an alkyl group and / or a phenyl group substituent.

[0027]

EXAMPLES Examples are shown to specifically explain the present invention. (Test method) A galvanized steel sheet is pretreated with a phosphate, then undercoated by cationic electrodeposition, then an intermediate coating with a polyester pigment colored white and dried. Acrylic paint colored with titanium white is applied on this, and 150 ℃
The product baked for 20 minutes was used as a substrate.

On top of this, the clear top coating agents obtained in Examples and Comparative Examples were spray coated to a dry film thickness of 15 μm, dried at 70 ° C., and then baked at 150 ° C. for 20 minutes for finishing. The following tests were conducted.

(Adhesion) A cross-cut test was conducted in accordance with JIS K 5400 (General paint test method). Those that did not peel at all were set to 100/100, and those that completely peeled off were set to 0/100, and the values were written according to the number of peeled.

(Pencil scratch test) JIS D 020
According to 2 (General Rules for Coating Films for Automobile Parts), the hardness is shown as the upper limit of scratch resistance with a pencil.

(Water resistance) According to JIS K 5400,
It was immersed in deionized water at 30 ° C. for 72 hours and pulled up to observe swelling and peeling.

(Oil resistance) According to JIS D 0202,
After soaking in gear oil at 20 ° C. for 1 hour, the oil was wiped off with absorbent cotton soaked with benzine, and left in the air for 1 hour. Then, changes in blistering, peeling, gloss and the like were examined.

(Gasoline resistance) According to JIS D 0202, after immersing in No. 1 gasoline for 1 hour, changes in blistering, peeling, gloss and the like were examined.

(Weather resistance) According to JIS D 0202,
2000 using a sunshine carbon weather meter
After the time test, changes in blistering, peeling, gloss, etc. were examined.

(Stain resistance) The coated plate was exposed to the outdoors in the Kawasaki area for 3 months, washed with running water, and the degree of stain was observed. The one that is completely clean is ◎, and the one that is completely clean is ×.
Intermediate ones are indicated by Δ.

Example 1 In a 2 L flask equipped with a thermometer, a stirrer, and a backflow condenser, 50 g (0.2 mol) of 3-methacryloxypropyltrimethoxysilane and 125 g (0.7 mol of methyltriethoxysilane) were added. ), Phenyltrimethoxysilane 20 g (0.1 mol), acetone 80
g, 0.01 mol of hydrochloric acid, 20 g of water were charged, and the temperature was adjusted to 60
The temperature was raised to 0 ° C., and the temperature was maintained for 3 hours with stirring. Subsequently, the temperature was raised to 70 ° C., and the reaction was carried out for 1 hour. Then, butylamine was added to neutralize, the mixture was washed with water and toluene, and the solvent and water were removed using a rotary evaporator.

20 mol% of the substituent R in the side chain of the obtained ladder silicone oligomer is a methacryloxypropyl group, 70 mol% is a methyl group, 10 mol% is a phenyl group, and the molecular weight is Mn = 3,200. Mw = 16,0
00 and Mw / Mn = 5.0.

10 parts by weight of this ladder silicone oligomer, 20 parts by weight of methyl methacrylate, 15 parts by weight of butyl acrylate, 2 parts by weight of methacrylic acid and 3 parts by weight of 2-hydroxyethyl methacrylate were mixed, and butyl acetate and toluene (1: Copolymerization in 1 mixed solvent)
%, A copolymer solution having a molecular weight Mn of 36,000 was obtained.

To 200 g of this polymer solution, 10 g of butoxymethylol melamine, 1.0 g of a benzotriazole type ultraviolet absorber and 0.5 g of a hindered amine type stabilizer were added and dissolved to obtain a coating liquid.

The above-mentioned undercoating, intermediate coating, and topcoating were applied on the zinc steel sheet diluted with thinner and spray-coated to form a clear film having a thickness of 15 μm, dried at 70 ° C., and baked at 150 ° C. for 20 minutes. After finishing, the coating film test was performed. The results are shown in Table 1.

Example 2 To 10 parts by weight of the ladder silicone oligomer produced in Example 1, 0.2 parts by weight of hexamethyldisiloxane was added, and hydrochloric acid was added to adjust the pH to 4,
The reaction was carried out at 50 ° C. for 2 hours to synthesize a ladder silicone oligomer having a terminal trimethylsilyl group. Thereafter, in the same manner as in Example 1, copolymerized with an acrylic monomer, to 200 g of the obtained polymer, 4.7 g of a trimer of hexamethylene diisocyanate was used instead of butoxymethylolmelamine.
(OH: NCO molar ratio 1: 1.2) and 0.01 g of dibutyltin dilaurate were added, and a similar ultraviolet absorber,
A stabilizer was added to obtain a coating liquid.

The above-mentioned undercoating, intermediate coating, and topcoating were applied to the above-mentioned zinc steel sheet by diluting the coating solution with a thinner and spray-coating to form a clear film having a thickness of 15 μm, followed by drying at 70 ° C. and baking at 150 ° C. for 20 minutes. Finishing and coating film test. The results are shown in Table 1.

(Example 3) 24 g (0.1 mol) of 3-glycidoxypropyltrimethoxysilane and 50 g of 3-methacryloxypropyltrimethoxysilane were placed in a 2 L flask equipped with a thermometer, a stirrer and a backflow condenser. (0.2 mol), 125 g (0.7 mol) of methyltrimethoxysilane, 80 g of acetone, 0.01 mol of hydrochloric acid, and 20 g of water were charged, the temperature in the flask was raised to 60 ° C., and while stirring, Temperature to 70 ° C and react for 1 hour,
Butylamine was added for neutralization, and after washing with water and toluene, the solvent and water were removed using a rotary evaporator.

During the reaction, some of the epoxy groups were hydrolyzed and converted to hydroxyl groups, but most of them remained as epoxy groups. Substituent R of the obtained ladder silicone oligomer
20% by mole was a methacryloxypropyl group, 8% by mole was an epoxy group, 2% was a hydroxyl group, and 70% by mole was a methyl group. The molecular weight is Mn = 2,600, Mw = 12,000.
0 and Mw / Mn = 4.6.

To 10 parts by weight of this ladder silicone oligomer, 5 parts by weight of styrene, 5 parts by weight of methyl methacrylate,
5 parts by weight of glycidyl methacrylate, 15 parts by weight of 2-ethylhexyl acrylate, 3 parts by weight of methacrylic acid, 2 parts by weight of 2-hydroxyethyl methacrylate and 5 parts by weight of butoxymethylolacrylamide were mixed with a toluene / butyl acetate mixed solvent ( Solution polymerization was carried out in a mixing ratio of 1: 1) 50 parts by weight. The produced copolymer has a solid content concentration of 50.
%, And the molecular weight Mn was 41,000.

To 200 g of this solution, 1.0 g of cellulose acetate butyrate, 1.0 g of benzotriazole type ultraviolet absorber and 0.5 g of hindered amine type stabilizer were added and dissolved to obtain a coating liquid.

The same substrate as in Example 1 was spray-coated to the same thickness to form a clear coating film having a thickness of 15 μm.
After drying at ℃, it was baked at 150 ℃ for 20 minutes to finish. The coating film test is shown in Table 1.

Comparative Example 1 In Example 1, the ladder silicone oligomer was omitted, and 20 parts by weight of methyl methacrylate, 15 parts by weight of butyl acrylate, 2 parts by weight of methacrylic acid and 3 parts by weight of 2-hydroxyethyl methacrylate were added to butyl acetate. Was copolymerized with toluene (1: 1 mixed solvent) to obtain a polymer solution having a solid content concentration of 50% and a molecular weight Mn of 42,000.

In the same manner as in Example 1, butoxymethylolmelamine, an ultraviolet absorber and a stabilizer were added to prepare a coating solution. The results of the coating test are shown in Table 1, which is unsatisfactory as compared with Example 1.

(Comparative Example 2) In Example 1, 50 g of 3-methacryloxypropyltrimethoxysilane, 125 g of methyltriethoxysilane, 20 g of phenyltrimethoxysilane, 80 g of acetone, 0.01 mol of hydrochloric acid, and 20 of water.
After charging g, the mixture was reacted at 60 ° C. for 3 hours, 0.05 mol of butylamine was added, and the temperature was raised to 80 ° C. and kept for 3 hours. After washing with water and toluene, the solvent and water were removed using a rotary evaporator.

The molecular weight of the obtained ladder silicone oligomer is Mn = 9,200, Mw = 120,000, Mw
/ Mn = 13. This oligomer was treated with methyl methacrylate, butyl acrylate, methacrylic acid, 2-hydroxyethyl methacrylate and butyl acetate as in Example 1.
Upon copolymerization in a toluene mixed solution (1: 1), the viscosity rapidly increased during the reaction, and finally gelation occurred, whereby a coating solution could not be obtained.

Comparative Example 3 The same amount of 3-methacryloxypropyltrimethoxysilane, methyltriethoxysilane and phenyltrimethoxysilane as in Example 1 was added to acetone,
Mix with water, 80 ℃ without adding hydrochloric acid as a reaction catalyst
After reacting for 5 hours, the water and acetone were removed by a rotary evaporator.

The molecular weight of the obtained ladder silicone oligomer was Mn = 180, Mw = 360, Mw / Mn = 2.
It was 0. This oligomer was solution copolymerized with methyl methacrylate, butyl acrylate and 2-hydroxyethyl methacrylate in the same manner as in Example 1. Butoxymethylol melamine, an ultraviolet absorber and a stabilizer were added to the obtained polymer solution to prepare a coating liquid. Spray coat,
As shown in Table 1, the physical properties of the coating film after drying and baking were inferior to those of the Examples.

(Comparative Example 4) 10 g of butoxymethylolmelamine was added to the copolymer solution of the ladder silicone oligomer and the acrylic monomer prepared in Example 1, and the ultraviolet absorber and the stabilizer were omitted to prepare a coating solution. A steel plate treated in the same manner as in Example 1 was similarly coated.
As shown in Table 1 for the coating film test results, various physical properties are shown in Example 1.
However, the weather resistance was inferior, choking occurred in the accelerated weathering test for 2000 hours, and the effects of the ultraviolet absorber and the oxidation stabilizer were obvious.

[0055]

[Table 1]

[0056]

The coating composition for automobiles of the present invention comprises a solution of a copolymer of a ladder silicone oligomer and a monomer copolymerizable therewith in an organic solvent, an ultraviolet absorber, an oxidation stabilizer and a crosslinking agent. It is a clear topcoat agent that contains the following substances, and solves problems such as adhesion to metal base materials with different thermal expansion coefficients of ladder silicone oligomer-based paints and cracking. Compared with the agent, the gloss, weather resistance, water resistance, oil resistance, scratch resistance, and stain resistance of the coated surface were significantly improved.

Claims (4)

[Claims] 1. A number average molecular weight Mn of 300 to 5,000.
0, weight average molecular weight Mw is 400 to 50,000, Mw
/ Mn is 10 or less, and the content of the (meth) acryloxyalkyl group in the side chain group in the molecule is 1 to 50 mol%.
Ladder silicone oligomer and (meth) acrylic acid ester, (meth) acrylamide, methylol (meth)
A copolymer obtained by copolymerizing at least one monomer selected from acrylamide, alkoxymethylol (meth) acrylamide, unsaturated carboxylic acid, styrene and vinyl ester, an organic solvent thereof, an ultraviolet absorber, an oxidation stabilizer and a cross-linking agent. A coating composition for an automobile, which is characterized by being 2. A ladder silicone oligomer in a copolymer and selected from (meth) acrylic acid ester, (meth) acrylamide, methylol (meth) acrylamide, alkoxymethylol (meth) acrylamide, unsaturated carboxylic acid, styrene and vinyl ester. The copolymerization compounding ratio with at least one kind of monomer is 1: by weight.
The coating composition for automobiles according to claim 1, which is 99 to 50:50. 3. A coating agent for automobiles according to claim 1, wherein the end group of the ladder silicone oligomer is a siloxane bonded to a total of three substituents having 1 to 18 carbon atoms and / or phenyl groups. Composition. 4. The coating composition for automobiles according to claim 1, wherein the crosslinking agent is at least one of amino resin, blocked polyisocyanate and polyglycidyl compound.