KR100575684B1 - Automotive paint compositions - Google Patents

Abstract

The present invention relates to a coating composition for automobiles, and more particularly to a coating composition containing an acrylic resin including an acrylic, a melamine curing agent, and an acid catalyst as a binder component, wherein the acrylic resin contains at least two hydroxyl groups. Containing unsaturated monomer, acetonate group-containing polyol and ethylenically unsaturated monomer, it has excellent viscoelasticity and is excellent for aluminum pigment orientation and flow prevention, and has a beautiful appearance.It is suitable for automotive top coating, solid color and color-transparent paint. The present invention relates to a coating composition for automobiles suitable for maintenance paints and the like.

Description

Automotive paint compositions

The present invention relates to a coating composition for automobiles, and more particularly to a coating composition containing an acrylic resin including an acrylic, a melamine curing agent, and an acid catalyst as a binder component, wherein the acrylic resin contains at least two hydroxyl groups. Containing unsaturated monomer, acetonate group-containing polyol and ethylenically unsaturated monomer, it has excellent viscoelasticity and is excellent for aluminum pigment orientation and flow prevention, and has a beautiful appearance.It is suitable for automotive top coating, solid color and color-transparent paint. The present invention relates to a coating composition for automobiles suitable for maintenance paints and the like.

Recently, automotive top coats have been widely favored by color-transparent paints in the form of repainting transparent paints in solid color coatings, which are color finishing finishes for producing only color. Such color coating compositions are disclosed in US Patent Nos. 4,220,679 and 4,403,003. No. 4,147,569 and the like are well known. One of the reasons color-transparent paint is favored is that it is very good in terms of appearance, such as gloss and Distinctness of Image. In general, it is very important to minimize the phenomenon that the color coating is melted during the transparent coating in order to form a coating film showing the high quality and beautiful appearance. Generally, water or solvent is removed by leaving it at room temperature or heating for a short time. The proper drying conditions are different depending on the color paint composition, but the mixing of color paint and transparent paint is minimized while the color film and transparency are minimized. In order to increase the interlayer adhesion between the membranes, so-called wet on wet coating is commonly used, which is dried at room temperature and immediately repainted with a transparent paint.

In order to obtain a coating film having a high quality appearance during the coating operation by the wet-on-wet coating method, it is very important to control the drying rate of the solvent and the compatibility between the binders, but it is important to appropriately control the fluidity of the color paint and the transparent paint.

DESCRIPTION OF RELATED ART Conventionally, the method of using a cellulose-type fluidity regulator, such as cellulose acetate butyrate, is disclosed by Unexamined-Japanese-Patent No. 1-168388. The cellulose derivative is capable of improving the appearance to some extent by providing fast drying property and good leveling property, but there is a problem in that the solid content of the coating composition is lowered due to excessive viscosity increase, and often a tee is generated in the coating film. As another example, the method disclosed in US Pat. Nos. 4,055,607, 4,290,932, etc., suggests a method of forming and using crosslinked microparticles through an emulsion method or a non-aqueous dispersion method. These methods not only provide high solids content paint compositions, but also have a relatively sufficient anti-flow effect. However, in the case of the emulsion method, it is accompanied with the trouble of replacing the water in the system with an organic solvent, and also has the disadvantage of causing unstable storage property due to phase change and deterioration of physical properties by an emulsifier.

The non-aqueous dispersion method also had limitations in practical use due to problems such as excessive limitation of solvents and lack of compatibility in addition to the complicated process of preparing a separate dispersion resin. In addition to the above-described improvement in paint specifications and paint flow characteristics, improvement of scratch resistance due to rapid dissemination of automatic washing machine, acid rain, and development of acid resistant paint film due to deepening of air pollution are required. However, the scratches generated by the automatic washing machine appear to be very different from those of the hand washing machine. It is understood that it is due to the difference in the magnitude of the applied force, speed, direction and shape of the contact material, hardness, friction coefficient, etc. and adds to the difficulty of improvement. In addition, the problems of acid rain, air pollution, etc., which are getting worse day by day, are increasing the damage of the coating film, and the situation is encouraging the development of the coating film having excellent acid resistance.

Conventional cured coatings using acryl polyol-melamine have excellent appearance and are very advantageous in terms of economics, and although they have been widely used, they contain a large amount of ether sites that are easily dissociated by acid rain, thereby improving the acid resistance of coatings. This is required.

As another coating composition, the two-component coating composition which uses isocyanate as a hardener for polyols, such as a polyester polyol, a polyether polyol, a polyurethane polyol, and an acryl polyol, has been used industrially widely.

However, the two-part coating composition may provide excellent gloss, image clarity, and acid resistance, but has had problems such as difficulty in handling by using isocyanate as a hardener component, sensitive to moisture, and careful prevention of safety.

In order to solve this problem, a method of preparing a one-component coating composition by blocking an isocyanate group with a blocking agent has emerged. However, blocked isocyanates lead to the disadvantages of lowering solubility and compatibility and deteriorating coating interlayer adhesion and coating appearance. In addition, since the undissociated isocyanate remains after curing, hardness and scratch resistance are inferior to those of the two-component coating composition. In particular, damage to the coating film due to acid rain is also severe due to lack of acid resistance.

As an example for improving the acid resistance of the coating film, U.S. Patent No. 4,499,151 discloses γ-methacryloyloxypropyltrimethoxysilane, γ-methacryloyloxypropylmethyldimethoxysilane, and vinyltrimethoxysilane in the production of acrylic polyols. A method of copolymerizing reactive silane containing ethylenically unsaturated monomers such as the like is disclosed. However, the coating composition using the reactive silane-modified acrylic polyols can provide a cured coating film having excellent acid resistance due to the high binding energy of the siloxane bonding site, but the gloss, clearness, Appearance is greatly reduced, such as image sharpness.

In addition, in order to impart sufficient acid resistance to the coating film, an excessive amount of siloxane bonding site is required, so that the internal stress of the coating film remains large, and the probabilities that cracking occurs in the coating film in a long-term exposure greatly increase the storage stability. do.

An object of the present invention is to solve the above problems by containing an acrylic resin composed of an ethylenically unsaturated monomer containing at least two or more hydroxyl groups, a polyol containing an acetonate group, etc., exhibiting excellent viscoelasticity, resulting in excellent aluminum pigment orientation and flow prevention properties. It is to provide a coating composition for automobiles that can form an excellent and beautiful appearance coating film.

The present invention for achieving the above object is a coating composition containing an acrylic resin containing an acrylic, melamine curing agent, acid catalyst as a binder component, the acrylic resin is at least two or more in an amount such that the hydroxyl equivalent 30 to 180 It is characterized by the automotive coating composition containing 20-40 weight% of ethylenically unsaturated monomer containing a hydroxyl group, 5-30 weight% of acetonate group containing polyols, and 10-70 weight% of ethylenically unsaturated monomers.

The present invention will be described in more detail as follows.

Automotive coating composition according to the present invention is an ethylenically unsaturated monomer and acetonate for controlling two or more functional groups to show a high crosslink density, instead of reducing the polarity of chain length and branching degree which is a disadvantage of hydroxyacrylpolyol Polyols manufactured by using a group are manufactured using melamine, which is generally used as a curing agent, and exhibits the same physical properties as those of an isocyanate curing agent, which is suitable for automotive top coatings, and is a solid color and a base-coat & coating material. Clear-coat, Refinish coat is effective.

The ethylenically unsaturated monomer containing at least two or more hydroxyl groups contained in the acrylic resin in the coating composition according to the present invention contains two or more hydroxyl groups in the monomer molecule to react with more triazine-based curing agents to form a dense crosslinked product. In addition to being able to form a very high coating film reliability, it provides excellent viscoelasticity to form a beautiful coating film. As the ethylenically unsaturated monomer containing at least two hydroxyl groups as described above, 2,3-dihydroxypropyl methacrylate, 2,3-dihydroxypropyl acrylate, dimethylol propane acid, glycid methyl acryl and Macromolecular systems obtained by reacting an epoxy group-containing ethylenically unsaturated monomer with a hydroxyl group-containing copolymer derived from a condensation reactant with an acid-containing compound and a carboxyl group-containing chain transfer agent are used, i.e., cellulose methacrylate, cellulose acrylate, and the like. Can be. In the condensation reaction product of the glycid methyl acryl and the compound containing an acid component, examples of the compound containing an acid component include 3-mercaptopropionic acid, dimethylol butanoic acid, and polycaprolactone diol containing a carboxyl group (fraxel 205BA). However, the present invention is not limited thereto. Moreover, it can also be used by copolymerizing with a well-known ethylenically unsaturated monomer for the purpose of adjusting viscosity, solubility, hardness, gloss, glass transition temperature, etc. of a coating film as needed. At this time, known ethylenically unsaturated monomers used are hydroxyethyl methacrylate, hydroxyethyl acrylate, 2-hydroxypropyl methacrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate. , 3-hydroxypropyl acrylate, 4-hydroxybutyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl vinyl ether, 4-hydroxycyclohexyl vinyl ether, caprolactone addition type hydroxyl group-containing ethylene And unsaturated unsaturated monomers. Such ethylenically unsaturated monomers containing at least two or more hydroxyl groups are contained within a range such that the hydroxyl equivalent of the acrylic resin is 30 to 180. If the hydroxyl equivalent is less than 30, the degree of crosslinking is lowered and the acid resistance, durability, and resistance of the coating film are lowered. There is a disadvantage that the scratches are inferior, and if it exceeds 180, the viscosity is high, the fluidity is poor, and the internal stress of the coating is severe, so that the crack resistance is degraded.

In the present invention, it is usually preferred that the ethylenically unsaturated monomer containing at least two or more hydroxyl groups be contained in 20 to 40% by weight of the total coating composition.

On the other hand, in the present invention, the acetonate group-containing polyol is used for the purpose of improving acid resistance and scratch resistance, and such acetonate group-containing polyols include acetoethyl methacrylate; Acetoethyl acrylate; Ethyl acetonate; Butylacetonate; Reaction adducts of malonates and acrylpolyols; And reaction adducts of dimethylmethisopropylbenzyl isocyanate and acetoethyl methacrylate. Such acetonate group-containing polyol is contained in the acrylic resin at 5 to 30% by weight. If the content is less than 5% by weight, the acid resistance is lowered.

In addition, the acrylic resin of the present invention contains a conventional ethylenically unsaturated monomer, which is used for the purpose of improving physical properties such as flexibility, durability, hardness, glass transition temperature and coating film formation of the acrylic resin, such as ethylenically unsaturated monomer Methacrylate, methyl acrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, isobutyl methacrylate, isobutyl acrylate, ethylhexyl methacrylate, ethylhexyl acrylate, styrene, vinyl acetate, cyclohexyl Methacrylate, cyclohexyl acrylate, isobornyl methacrylate, isobornyl acrylate, lauryl methacrylate, lauryl acrylate and the like. Such ethylenically unsaturated monomer is good to contain in an acrylic resin in 10 to 70weight% of a range.

In addition, the melamine curing agent contained in the acrylic resin in the present invention is methoxy methyl melamine, methyl melamine, butyl melamine, isobutoxy melamine, butoxy melamine and the like. The melamine curing agent is preferably contained in a range such that the proportion of hydroxyl groups contained is 0.8 to 1.2 with respect to the acrylic resin. If the hydroxyl group content is less than 0.8, hydroxyl groups remain, resulting in poor water resistance and rough coating appearance. If there is more than 1.2, the paint viscosity is high, the coating film is hard and fragile, there is an uneconomical problem.

As the acid catalyst, it is preferable to use an organic acid catalyst obtained by reacting any amine salt or epoxy group selected from dodecylbenzenesulfonic acid, dinonylbenzenesulfonic acid, and paratoluenesulfonic acid. It is preferable to contain such an organic acid catalyst in the range of 0.5 to 5 weight% in an acrylic resin. If the content is less than 0.5% by weight, the hardness and chemical properties of the coating due to the curing failure is lowered, if the content exceeds 5% by weight there is a problem that can be a yellowing and shelf life of the coating and the price synergistic effect.

The acrylic resin of the present invention containing the above components is obtained by a polymerization method known in the art after each of the above components, or a hydroxyl group-containing ethylenically unsaturated monomer, an acetonate group-containing polyol and Two or more selected from ethylenically unsaturated monomers may be mixed in advance, followed by addition of an acid catalyst and the like, followed by polymerization. Among them, suitably, the number average molecular weight is adjusted to be in the range of 1,000 to 100,000 using a solution polymerization method prepared under a diluting solvent to prepare a coating composition. If the range of number average molecular weight is out of the above range, there is a problem of gelation. In addition, if necessary, auxiliary resins, diluents, and other components used in paints can be added to cure in a one-part form, and pigments can also be added thereto.

Auxiliary resins that can be added include amino resins, polyester resins, silicone modified polyester resins, silicone resins, vinyl resins, and the like, and diluents include xylene, toluene, butyl acetate, ethylcellulose, Hansol, and butanol. Solvents such as methyl ethyl ketone and methyl isobutyl ketone may be used.

In addition to the other components that can be added to the coating composition of the present invention as a component used in the paint additives such as limonene monooxide, limonene dioxide and the like and reaction catalysts such as organometallic salts, tertiary amines, amine salts can be used Known additives such as thickeners, rheology modifiers, wetting agents, pinhole removers, film smoothing agents and the like can be used.

Automotive coating composition according to the present invention can be applied as a solid paint, a color paint, a transparent paint, a repair paint composition, and after the color coating to improve the appearance, gloss, etc. of the coating film, the present invention in a wet state It is also possible to apply what is called a 2-coat 1 baking system which heat-hardens after repainting the coating composition of the coating composition. At this time, the heat curing conditions are suitable for about 15 to 60 minutes at 120 to 180 ℃, if the heating temperature is too high, the energy consumption is large, there is a problem such as yellowing coating film is generated.

Although this invention is demonstrated in detail based on an Example, this invention is not limited to an Example.

Preparation Example 1

50 parts by weight of xylene, 200 parts by weight of butyl acetate, and 10 parts by weight of 3-mercaptopropionic acid were placed in a four-necked flask equipped with a stirrer, a cooler, and a thermometer to be heated and stirred to maintain a solvent reflux, followed by 300 parts by weight of 2- Hydroxyethyl methacrylate, 270 parts by weight of styrene, 55 parts by weight of methyl methacrylate, 250 parts by weight of N-butyl methacrylate, 100 parts by weight of butylacrylate, 70 parts by weight of 2,2-azobis (1-dimethyl Valeronitrile) mixture was added dropwise uniformly over 3 hours, and then maintained for 2 hours. 20 parts by weight of triphenylphosphine and 15 parts by weight of glycidyl methacrylate mixed solution were added thereto, and the acid value thereof was measured to react until the carboxyl group was not detected. After cooling to room temperature, the content of solids was adjusted to 80% by weight using xylene to obtain an ethylenically unsaturated monomer containing two or more hydroxyl groups.

Preparation Example 2

In a four-necked flask equipped with a stirrer, a cooler, and a thermometer, 200 parts by weight of xylene and 148 parts by weight of dimethylolbutanoic acid were added, followed by heating and stirring to 135 ° C to maintain a temperature. At this time, a solution of 142 parts by weight of glycid methacrylate, 0.1 part by weight of triphenylphosphine and 0.1 part by weight of hydroquinone was added dropwise for 1 hour.

After dropping for 1 hour, the acid value was measured to terminate the reaction at 1 or less (solid state) to obtain an ethylenically unsaturated monomer containing two or more hydroxyl groups.

Preparation Example 3

In a four-necked flask equipped with a stirrer, a cooler and a thermometer, 200 parts by weight of xylene and 500 parts by weight of solvent were placed in a Pracel 205BA manufactured by Daicel Japan, and heated and stirred to 135 ° C to maintain a temperature. At this time, a solution of 142 parts by weight of glycid methacrylate, 0.1 part by weight of triphenylphosphine and 0.1 part by weight of hydroquinone was added dropwise for 1 hour.

After dropping for 1 hour, the acid value was measured to terminate the reaction at the carboxyl group of 1 or less (solid state) to obtain an ethylenically unsaturated monomer containing two or more hydroxyl groups.

Preparation Example 4

In a four-necked flask equipped with a stirrer, a cooler, and a thermometer, 100 parts by weight of butyl acetate and 300 parts by weight of xylene were added and kept under reflux while heating and stirring. Then, 4-hydroxybutyl acrylate 150, which is a hydroxyl group-containing ethylenically unsaturated monomer, was added. Parts by weight, 50 parts by weight of 2-hydroxypropyl acrylate and 200 parts by weight of methyl acrylate which is an ethylenically unsaturated monomer, 250 parts by weight of butyl acrylate, 200 parts by weight of 4-hydroxybutyl acrylate, 50 parts by weight of ethylhexyl acrylate A mixture of 50 parts by weight of tetra-butylperacetate was added dropwise and uniformly over 3 hours as a part and a radical initiator, and then maintained for 2 hours. After cooling to room temperature, an ethylenically unsaturated copolymer polyol solution prepared by adjusting xylene to 70% solids was prepared.

Preparation Example 5

In a four-necked flask equipped with a stirrer, a cooler, and a thermometer, 200 parts by weight of xylene and 100 parts by weight of Swagel # 100 of Yugyo Co., Ltd. were used as a solvent, and the reaction was maintained at 100 ° C., followed by 80 parts by weight of acetonate ethyl methacrylate. , 120 parts by weight of 2-hydroxypropyl acrylate which is a hydroxyl group-containing ethylenically unsaturated monomer, 200 parts by weight of methyl acrylate which is an ethylenically unsaturated monomer, 250 parts by weight of butyl acrylate, 70 parts by weight of 4-hydroxybutyl acrylate and a radical A mixture of 50 parts by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) was added dropwise uniformly over 3 hours as an initiator, and then maintained for 2 hours. After cooling to room temperature, the acetonate group-containing polyol was prepared by adjusting the content of solids to 70% by using xylene.

Preparation Example 6

In a four-necked flask equipped with a stirrer, a cooler, and a thermometer, 37 parts by weight of xylene was refluxed, followed by 40 parts by weight of dimethylmethisopropylbenzylacetonate, 200 parts by weight of ethyl hexyl acrylate, and 2,2-azobis (2, 10 parts by weight of 4-dimethylvaleronitrile) was added dropwise for 3 hours, maintained for 2 hours, and adjusted to a solid content of 65% by weight to prepare an acetonate group-containing polyol.

Then, 100 parts by weight of the acetonate group-containing polyol prepared above was heated to 70 ° C., and then 12 parts by weight of acetonate ethyl methacrylate and 20 parts by weight of xylene were added dropwise for 1 hour to maintain the free acetonate. At that point the reaction was terminated. After cooling to room temperature, the solid content was adjusted to 60% by weight with xylene to prepare acetonate group-containing polyol.

Preparation Example 7

Into a four-necked flask equipped with a stirrer, a cooler, and a thermometer, 40 parts by weight of Solver Solver # 100 by solvent was refluxed, followed by 210 parts by weight of methyl methacrylate, 96 parts by weight of butyl methacrylate, 140 parts by weight of styrene, 70 parts by weight of ethyl hexyl acrylate, 170 parts by weight of hydroxy ethyl acrylate and 14 parts by weight of acrylic acid were mixed, and 56 parts by weight of t-butylperbenzoate was added dropwise, followed by reaction for 3 hours to prepare an acetonate group-containing polyol. It was.

Then, 20 parts by weight of diethyl malonate was added to 200 parts by weight of the acetonate group-containing polyol prepared above, and the temperature was raised to 140 ° C. for about 6 hours for reaction and maintenance. This was terminated to prepare an acetonate group-containing polyol having a solid content of 70% by weight.

Production Examples 8-13

In a four-necked flask equipped with a stirrer, a cooler, and a thermometer, 150 parts by weight of solvent was added to Solsol # 100, 300 parts by weight of xylene, and heated to 100 ° C. A mixture of 70 parts by weight of 2,2'-azobis (2,4-dimethylvaleronitrile) and the components shown in the following Table 1 was added dropwise uniformly over 3 hours, then maintained for 2 hours and cooled to room temperature . Xylene was used to adjust the solids content to 70% by weight.

TABLE 1

Comparative Production Example 1

168 parts by weight of methyl methacrylate, 175 parts by weight of butyl methacrylate, 56 parts by weight of styrene, 21 parts by weight of methacrylic acid, 140 parts by weight of hydroxyethyl methacrylate, and mixed by mixing 7 parts by weight of benzyl peroxide, 510 parts by weight of xylene and 140 parts by weight of butanol were titrated over 3 hours, then maintained for 2 hours, and 1 part by weight of benzyl peroxide was added dropwise to 50 parts by weight of xylene for 10 minutes and maintained for 2 hours.

Comparative Production Example 2

210 parts by weight of methyl methacrylate, 70 parts by weight of butyl methacrylate, 140 parts by weight of styrene, 70 parts by weight of ethylhexyl acrylate, 196 parts by weight of hydroxyethyl acrylate and 14 parts by weight of acrylic acid and cumene hydroxyperoxide 70 The mixture was mixed by weight, and then titrated for 4 hours to 330 parts by weight of Solsol Solver # 100 by Yugong Co., Ltd. and maintained for 3 hours.

Examples 1-7 and Comparative Examples 1-2

The coating composition for automobiles was prepared with the resin prepared in Preparation Example and the composition shown in Table 2 below.

TABLE 2

Experimental Example

The coating properties of the automotive coating compositions prepared in Examples 1 to 7 and Comparative Example 2 and the automotive coating paints of the acrylic emulsion type without acetonate group in Comparative Example 3 were measured, and the results are shown in Table 3 below. It was.

TABLE 3

As described above, the automotive coating composition according to the present invention can improve acid resistance and the like at the same level of general physical properties such as appearance, price, productivity, adhesiveness, storage property, and the like in the conventional paint, and exhibit excellent aluminum viscosity and It is suitable for the top coat of automobiles by forming a coating film with excellent flow prevention property and beautiful appearance, and it is effective for solid color, color-transparent paint, and repair paint.

Claims (6)

In the coating composition which contains the acrylic resin containing acrylic, a melamine hardening | curing agent, and an acid catalyst as a binder component, The acrylic resin is 20 to 40% by weight of an ethylenically unsaturated monomer containing at least two or more hydroxyl groups in an amount such that a hydroxyl group equivalent of 30 to 180, 5 to 30% by weight of an acetonate group-containing polyol and 10 to 70 ethylenically unsaturated monomers. An automotive paint composition, characterized in that it contains a weight%. The method of claim 1, wherein the ethylenically unsaturated monomer containing at least two hydroxyl groups is 2,3-dihydroxypropyl methacrylate, 2,3-dihydroxypropyl acrylate, dimethylol propane acid, glycid methyl A coating composition for automobiles, characterized in that selected from macromas obtained by reacting an epoxy group-containing ethylenically unsaturated monomer with a hydroxyl group-containing copolymer derived from a condensation reaction product of an acryl and an acid component and a carboxyl group-containing chain transfer agent. The acetonate group-containing polyol is selected from the group consisting of acetoethyl methacrylate; Acetoethyl acrylate; Ethyl acetonate; Butylacetonate; Addition reactants of malonates and acrylpolyols; And an addition reactant of dimethylmethisopropylbenzyl isocyanate and acetoethyl methacrylate. The coating composition for automobiles according to claim 1, wherein the melamine curing agent is selected from methoxy methyl melamine, methyl melamine, butyl melamine, isobutoxy melamine and butoxy melamine. The coating composition for automobiles according to claim 1, wherein the acid catalyst is a reactant with any one amine salt or an epoxy group selected from dodecylbenzenesulfonic acid, dinonylbenzenesulfonic acid, and paratoluenesulfonic acid. The method of claim 1, wherein the acrylic resin is characterized in that the ethylenically unsaturated monomer containing at least two or more hydroxyl groups, acetonate group-containing polyol and ethylenically unsaturated monomers are each mixed or prepared by mixing two or more selected in advance Automotive paint compositions.