KR100427706B1 - Method for producing acrylic resin for use in top coating for cars having excellent pigment dispersibility, clearness, heat resistance, chemical resistance and weather resistance, acrylic resin obtained therefrom and top coating for cars based on the same resin - Google Patents

Abstract

PURPOSE: Provided is a method for producing an acrylic resin for use in top coating for cars having balanced structural and formal changeability, molecular weight and crosslinking rate of the resin and showing excellent pigment dispersibility, clearness, chemical resistance, heat resistance and weather resistance. CONSTITUTION: The method comprises carrying out solution polymerization of: (a) a compound represented by the following formula 1; (b) a compound represented by the formula of R-C=CH2 (wherein R is an aromatic vinyl compound); and (c) a monomer mixture including at least one long-chain hydroxy-containing monomer selected from a functional monomer obtained by epoxy ring-opening of glycidyl ester with an active hydrogen compound and a monomer obtained by epoxy ring-opening of glycidyl ester with a mercaptan acid or polyester monomer, a hydroxy monomer, and a monomer having an acid or amino group, in the weight ratio of (a):(b):(c) of 50-85:5-20:10-30. In formula 1, R1 is H or CH3, and R2 is a C1-C14 alkyl.

Description

Method for producing acrylic resin, acrylic resin obtained therefrom and automotive top coat based on the same

The present invention relates to a coating material containing an acrylic resin, and more particularly, to a method for producing an acrylic resin having excellent high-performance coating properties, that is, pigment dispersibility, gloss retention, and the like without using a rheology modifier, It relates to a paint for automotive top coat.

There are various types of resins for automobile paints according to the intended use. However, rheology control agents are used to improve the orientation of pigment dispersion resins and pigment particles while using polyester, alkyd and thermosetting acrylic resins as main materials for automotive coatings. I use it.

However, when the rheology control agent is used in this way, the orientation of the pigment particles is good, but the storage property of the paint is poor, so that the appearance, ie, the selectivity of the coating film, is high. In addition, a process for dispersing the rheology control agent for each pigment should be introduced and a separate pigment dispersion resin should be used, thereby increasing the manufacturing cost.

Accordingly, the present invention is to solve the above disadvantages, the purpose is to balance the structure and shape of the resin, the molecular weight of the resin, the crosslinking reaction rate and the like, good pigment dispersibility, clarity of appearance, chemical resistance, It is to provide an automotive top coat with excellent heat resistance and weather resistance.

In addition, another object of the present invention to provide a method for producing an acrylic resin for automotive top coat.

Automotive topcoat paints to achieve the object of the present invention is limited to the conventional acrylic resin, so excellent pigment dispersibility, functional groups and quick-drying solvents and clear paints and wet-on-wet (wet-on-wet) coating The system is characterized by the production of resins in which the polymer structure and molecular weight of the resin are increased in order to give the orientation and appearance of the pigment particles without the rheology control agent.

More specifically, the acrylic resin used in the present invention is prepared by using a solvent having a low boiling point and mercaptans for molecular weight distribution control and radical reaction of a double bond of a monomer with an initiator, and an acid value of 5 to 30 mgKOH / g, The oxy group is 30-100 mgKOH / g, the number average molecular weight 5000-30000, and glass transition temperature (Tg) are 20-70 degreeC.

Automotive topcoat paints based on acrylic resins reduce the steric hindrance effect of long chain hydroxy monomers and long chain carboxylic acid and amine groups, i.e., pigments, in the manufacture of acrylic resins. We use resins with aromatic functional groups to minimize flocculation and increase the molecular weight to wet-on-wet paints and clear coatings for automotive topcoats without using rheology modifiers such as cellulose acetate butyrate systems and microgels. The system can be painted.

In addition, by applying the top coat paint in a quick-drying type during coating, the coating film has been given goodness, it has excellent characteristics such as pigment dispersibility, gloss retention, weather resistance, heat resistance, chemical resistance.

The present invention will be described in detail step by step.

1. Preparation of Acrylic Resin

There are various methods for producing the acrylic resin, but it is most preferable to use solution polymerization, which is the most common method.

The method for producing an acrylic resin according to the present invention can be broadly divided into two methods. Ultimately, all the methods are intended to introduce long chain hydroxyl groups into the acrylic resin.

(1) The first method

The first of the methods is a method of solution polymerization of an acrylic monomer represented by the following general formula (1), an acrylic monomer represented by the general formula (2) and a functional monomer, wherein the functional monomer is a long chain It is a mixture of the monomer which has a hydroxyl group, a hydroxyl monomer, and the monomer which has an acidic group or an amino group.

R ₁ is a hydrogen atom or a methyl group, and R ₂ is an alkyl group having 1 to 14 carbon atoms.

Wherein R is an aromatic vinyl compound.

Monomers corresponding to the general formula (1) are methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, 2-ethylhexyl acrylate, lauryl acryl Latex, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, cyclohexyl acrylate, Cyclohexyl methacrylate, cellosolve methacrylate, and the like, and an appropriate content thereof is 50 to 85% by weight, more preferably 60 to 80% by weight.

The reason for this is that when the acrylic monomers are used at least 50%, the adhesion to the substrate is improved and the acrylic basic physical properties are obtained. That is, the inherent physical properties of the acrylic monomer should be appropriately selected so as to complement the flexibility and hardness, appearance, pigment dispersibility, etc. by appropriately adjusting the glass transition temperature (Tg). If more than 85% of these monomers are used, the coating film becomes harder than necessary, resulting in insufficient flexibility and chipping problems.

Monomers corresponding to the general formula (2) include styrene, α-methylstyrene, benzyl (meth) acrylate, phenyl (meth) acrylate, vinyltoluene, and the like, which are used alone or in combination with others. And their proper content is 5 to 20% by weight. If it is used in more than 20% by weight, the weather resistance and pigment dispersibility of the coating film is rather reduced.

Functional monomers are suitably used in an amount of 10 to 30% by weight.

a) monomers with long chain hydroxyl groups

As a monomer having a long chain hydroxyl group, a monomer obtained through the following two methods can be used.

a-1) Monomer obtained by ring-opening an epoxy ring of glycidyl ester with an active hydrogen compound

It is prepared by reacting glycidyl ester with an acrylic monomer such as (meth) acrylic acid, crotonic acid, itaconic acid, fumaric acid, and an acid group such as paraaminobenzoic acid and paranitrobenzoic acid.

In this case, glycidyl ester may be glycidyl butyrate, glycidyl palmitate, glycidyl laurate, glycidyl stearate, and generally the CADURA E series manufactured by Shell. Series).

In the reaction, an equivalent ratio between an acid group and an epoxy group is 1: 0.8 to 1.2, and the reaction is carried out at 130 ° C. or less to prepare a monomer having a hydroxyl group.

a-2) Monomer obtained by ring-opening the epoxy ring of glycidyl ester with a mercaptanic acid or a polyester monomer

Mercaptanic acids such as mercaptan propionic acid, thioglycolic acid, and dimethyl are ring-opened with epoxy monomers of glycidyl esters using polyester monomers such as propionic acid, (methyl) hexaphthalic anhydride and the like.

In this case, as the glycidyl ester, glycidyl (meth) acrylate, methylglycidyl (meth) acrylate, allyl glycidyl ester, or the like can be used.

In the above reaction, the glycidyl ester is added to the acrylic resin skeleton in the first reaction and the mercaptanic acid and the polyester acid are reacted in the second reaction. In this case, an equivalent ratio of acid and epoxy is 1: 0.8 to 1.2, and the monomer is reacted at a temperature of 150 ° C. or less to prepare a monomer having a hydroxyl group.

The polymer thus prepared has a branch or graft structure.

In preparing the monomers of a-1) and a-2), the glycidyl ester serves to generate a long chain hydroxy group by reacting with an acid. Acids also react with the epoxy groups to produce long chain hydroxyl groups.

b) hydroxy monomer

The hydroxy monomer is used to give a site capable of reacting with the melamine curing agent when the acrylic resin is subsequently applied to the paint, specifically, hydroxy ethyl (meth) acrylate, hydroxy propyl (meth) acrylate, Hydroxybutyl (meth) acrylate etc. are mentioned.

c) monomers having an acid group or an amino group

As a monomer which has an acidic radical, the compound of following General formula (3) is included.

R ₁ is hydrogen or a methyl group, R ₂ is an aromatic ring or an alkyl group having 1 to 8 carbon atoms, and n is an integer of 1 to 4 here.

Specifically, examples of the monomer having an acid group or an amino group include (meth) acrylic acid, crotonic acid, itaconic acid, fumaric acid, monomethacryloyloxyethyl phthalate (BISOMER EMP manufactured by International Specialty Chemical), dimethylaminoethylmetha Acrylate, diethylaminoethyl methacrylate, isobutoxymethyl acrylate, n-butoxymethyl acrylamide, acrylamide and the like.

These reactive monomers will increase the pigment dispersion effect during paint preparation, increase corrosion resistance, improve compatibility and sleepability, scratch resistance. Moreover, it is suitable to use about 10-30 weight% of hydroxy groups, 1-10 weight% of acidic groups, and about 1-10 weight% of amino groups for resin.

(2) second method

As another method for introducing a long-chain hydroxy group into the acrylic resin according to the present invention, the acrylic monomer of the general formula (1) exemplified in the first method (1) above, the acrylic monomer of the general formula (2), hydroxy A method of producing an acid copolymer resin by solution polymerization of a monomer and a monomer having an acid group or an amino group in the above ratio, followed by branching or graft polymerization by adding an glycidyl ester to ring-open an epoxy ring.

The acid copolymer resin obtained by solution polymerization has an acid value of 40-80 mgKOH / g, and uses this to ring-open the epoxy ring of glycidyl ester, and manufactures resin which has a branch or graft structure. At this time, the equivalent ratio between acid and epoxy is 1: 0.8 to 1.2 and reacted at a temperature of 150 ° C. or less.

(Meth) acrylic acid, crotonic acid, itaconic acid, fumaric acid are used as the acidic monomer which is the main agent of the acid copolymer resin, and glycidyl butyrate, glycidyl palmitate, glycid as glycidyl ester Cydyl laurate, glycidyl stearate and the like can be used.

In preparing the acrylic resin through the first method or the second method, the initiators during solution polymerization include azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile, and fur such as benzoyl peroxide and laurodiperoxide. Oxide organic initiators are used.

As the solvent, an aliphatic or aromatic hydrocarbon solvent is used. Specifically, hydrocarbon solvents such as heptane, toluene and xylene, acetates such as ethyl acetate, n-butyl acetate and isobutyl acetate, ethanol, isopropanol and n-butanol alcohols such as, sec-butanol and isobutanol are used alone or in combination.

Solution polymerization usually reacts at the reflux temperature of the solvent, and the reaction time is generally about 5 to 15 hours. At this time, in order to prevent the molecular weight from increasing more than necessary, mercaptans can be used as a polymerization regulator. The mercaptans that can be used include n-butyl mercaptan, n-dodecyl mercaptan, t-butyl mercaptan, n-octyl mercaptan and the like, and are generally added at 0.05 to 0.1% by weight.

An acrylic resin having an acid value of 5 to 30 mgKOH / g, 1 to 2 of hydroxyl groups at the end, and a hydroxyl of 30 to 100 mgKOH / g prepared by the above method is applied to the paint. The reason is that if the acid value is 5 or less, problems occur in curing and adhesion strength, and if it is 30 or more, the water resistance becomes weak. If the hydroxyl value is 30 or less, the crosslinking density is low, and the hardness, chemical resistance and corrosion resistance are poor. This is because it may cause cracks in the coating film or chipping problems.

2. Paint manufacturer

Coating preparation may use the acrylic resin and hardening | curing agent in which the long-chain hydroxyl group was introduce | transduced through said 1st method or 2nd method, and may mix an inorganic and organic pigment, a leveling agent, a ultraviolet absorber, and a solvent.

Alkoxy methyl melamine resin is used as a curing agent in the production of paint. Examples thereof include methylated melamine resin, n-butylated melamine resin, isobutylated melamine resin and the like, and an ethoxy group, n-butoxy group and isobutoxy group are used as the alkoxy group. Most preferred of these is the use of n-butylated melamine resins and isobutylated melamine resins.

At this time, the solvent uses a quick-drying type, and when the coating is separated between the top coat and clear paint to excellent after clearing after curing.

Curing of the paint is carried out at a temperature of 160 ° C. or less for 50 minutes or less.

Since the paint of the present invention uses a long chain functional group, it is not necessary to use a pigment dispersible resin, and there is no need to use a rheology modifier such as a cap (CAB) or a microgel for the orientation of the pigment particles.

In addition, the paint of the present invention has a stronger coating film, excellent chipping, sleeping and scratching properties, and excellent weather resistance, heat resistance and acid resistance.

Hereinafter, the present invention will be described in detail with reference to the following Examples, the present invention is not limited by the Examples.

<Production of Monomer Having Long Chain Hydroxy Group>

Preparation Example 1 (C-1)

360 g of acrylic acid, 1250 g of CADURA E-10 (manufactured by Shell Company), and 3.2 g of hydroquinone were placed in a flask and maintained at a reaction temperature of 100 ° C. for 15 hours to terminate the reaction at an acid value of 1 mgKOH / g or less.

Preparation Example 2 (C-2)

480 g of mercaptopropionic acid, 568 g of glycidyl methacrylate, and 2.1 g of hydroquinone were placed in a flask and maintained at a reaction temperature of 100 ° C. for 15 hours to terminate the reaction at an acid value of 1 mgKOH / g or less.

Preparation Example 3 (C-3)

366 g of dimethylol propionic acid, 426 g of glycidyl methacrylate, 0.2 g of hydroquinone and 528 g of n-butanol were placed in a flask and maintained at a reaction temperature of 100 ° C. for 15 hours to terminate the reaction at an acid value of 1 mgKOH / g or less.

<Production of Acrylic Resin>

Preparation Example 1 (A-1)

240 g of methyl methacrylate, 150 g of n-butyl methacrylate, 90 g of styrene, 60 g of hydroxyethyl methacrylate, 60 g of acrylic acid, 12 g of benzoyl peroxide were mixed and added to 580 g of toluene over 3 hours and refluxed for 2 hours. After dissolving 0.3 g of benzoyl peroxide in 20 g of toluene, the mixture was added for 10 minutes and refluxed for 3 hours to prepare a primary reactant. After cooling the first reactant to room temperature, 145.8 g of Kadura E-10 was added thereto, maintained at a reaction temperature of 100 ° C. for 15 hours (secondary reaction), and the reaction was terminated at an acid value of 24 mgKOH / g or less. Its number average molecular weight is 10000.

Preparation Example 2 (A-2)

180 g of methyl methacrylate, 180 g of n-butyl methacrylate, 90 g of styrene, 30 g of hydroxyethyl methacrylate, 18 g of acrylic acid, 102 g of the product prepared in Intermediate Preparation Example (C-1) are mixed, and as an initiator 6 g of azobisisobutyronitrile was mixed and added to 580 g of toluene over 3 hours, and refluxed for 2 hours. Then, 0.3 g of azobisisobutyronitrile was added to 20 g of toluene, and maintained for 3 hours. To prepare. Its number average molecular weight is 12000.

Preparation Example 3 (A-3)

120 g of ethyl acrylate, 240 g of n-butyl acrylate, 90 g of styrene, 60 g of hydroxyethyl methacrylate, 24 g of methacrylic acid, 78 g prepared in Intermediate Preparation Example (C-2), dimethylaminoethyl methacrylate 18 g, 12 g of azobisisobutyronitrile was mixed and added to 580 g of toluene over 3 hours, and refluxed for 2 hours. Then, 0.3 g of azobisisobutyronitrile was added to 20 g of toluene, and maintained for 3 hours. To prepare. Its number average molecular weight is 10000.

Preparation Example 4 (A-4)

240 g of methyl methacrylate, 180 g of n-butyl acrylate, 90 g of hydroxyethyl methacrylate, 120 g of the one prepared in Intermediate Preparation Example (C-3), 12 g of methacrylate, 12 g of diethylaminoethyl methacrylate, n 0.4 g of octyl mercaptan and 14 g of benzoyl peroxide were mixed and added to 454 g of toluene over 3 hours and refluxed for 2 hours. Then, 0.3 g of benzoyl peroxide was added to 20 g of toluene, and maintained for 3 hours. Prepare a resin. Its number average molecular weight is 9000.

Preparation Example 5 (A-5)

90 g of styrene, 210 g of isobutyl methacrylate, 60 g of hydroxyethyl methacrylate, 60 g of the product prepared in Intermediate Preparation Example (C-1), 150 g of n-butyl methacrylate, BISOMER EMMP (EMP ) (Manufactured by International Specialty Chemical) 30g, 9g of benzoyl peroxide were added to 580g of toluene over 3 hours, refluxed for 2 hours, 0.3g of benzoyl peroxide was added to 20g of toluene, and added for 3 hours. To prepare an acrylic resin. Its number average molecular weight is 14000.

Comparative Example 1 (B-1)

180 g of methyl methacrylate, 240 g of n-butyl methacrylate, 90 g of styrene, 72 g of hydroxyethyl methacrylate, 18 g of methacrylate were mixed, 12 g of benzoyl peroxide was mixed and added to 580 g of toluene over 3 hours. After refluxing for 2 hours, 0.3 g of benzoyl peroxide was added to 20 g of toluene, and then maintained for 3 hours to prepare an acrylic resin.

Comparative Example 2 (B-2)

240 g of methyl methacrylate, 90 g of n-butyl acrylate, 120 g of styrene, 90 g of hydroxyethyl acrylate, 18 g of acrylic acid were mixed, 12 g of azobisisobutyronitrile were mixed and added to 580 g of toluene over 3 hours. After refluxing for an hour, 0.3 g of azobisisobutyronitrile was added to 20 g of toluene and dissolved for 3 hours to prepare an acrylic resin.

Millbase manufacturing

Preparation Example 1 (M-1)

A mill base is prepared by ball milling 150 g of carbon black pigment, 500 g of melamine resin (1), 400 g of solvent, and 150 g of rheology control agent for 10 hours.

Preparation Example 2 (M-2)

A mill base is prepared by ball milling 150 g of carbon black pigment, 500 g of melamine resin (1), and 400 g of a solvent for 10 hours.

Preparation Example 3 (M-3)

Millbase is prepared by ball milling 150 g of phthalocyanine blue, 500 g of melamine resin (2), and 400 g of a solvent for 10 hours.

Examples 1-5

Table 1 is an example of manufacturing a coating for automotive top coat with a composition ratio of the present invention.

Using the paints prepared in these Examples and Comparative Examples, the top coat was coated on the specimens coated with electrodeposition and the intermediate, and then the clear coat was applied. The top coat was coated at 25 ° C. with a pod-cup. After adjusting to 15 sec and sprayed to harden at 150 ℃ for 20 minutes to prepare a coating having a film thickness of 17 ± 3㎛. In this case, a clear paint was used as a paint of Korea Chemical, and the physical property test data thereof is shown in Table 2.

Appearance Test: Tested by visual inspection method with tension meter.

Gloss test: Tested at 60 ° using a Micro-Tri-Glassmeter manufactured by BYK.

Acid Resistance Test: After dropping 0.5 ml of 26% and 36% sulfuric acid on the specimen, and left for 1 hour at 70 ° C, the traces were checked (1: good, 2: fine trace, 3: color retention, 4 : corrosion).

Water resistance test: After immersion in water at 40 ℃ for 10 days to confirm the appearance of the coating film.

Cold resistance chipping test: After chipping at -40 ° C for 3 hours, chipping test is performed and compared with GM specification.

Storage test: After the paint was prepared with the viscosity of the stock solution and stored for 3 days at 60 ℃ to check the appearance of the paint.

Weatherability Test: Measured using Q-Pannel's Q.U.V.

As can be seen from the physical property test results of Table 2, it can be seen that the paint according to the present invention is superior to the conventional paint in terms of appearance, gloss, acid resistance, water resistance, storage resistance, cold resistance, weather resistance.

Claims (9)

A compound represented by formula (1); A compound represented by formula (2); And, 1 type selected from monomers obtained by ring-opening an epoxy ring of glycidyl ester with an active hydrogen compound as a functional monomer and monomers obtained by ring-opening an epoxy ring of glycidyl ester with a mercaptanic acid or polyester monomer A method of producing an acrylic resin, characterized by solution polymerization of a mixture of a monomer having a long chain hydroxyl group, a hydroxy monomer and a monomer having an acid group or an amino group in a proportion of 50 to 85: 5 to 20: 10 to 30 parts by weight. Here, R ₁ is a hydrogen atom or a methyl group, R <_2> is a C1-C14 alkyl group. Wherein R is an aromatic vinyl compound. The acrylic resin is prepared according to the production method of claim 1, the number average molecular weight 5000 ~ 30000, the hydroxy is 30 ~ 100mgKOH / g, the acid value 5 ~ 30mgKOH / g, the glass transition temperature 20 ~ 70 ℃. An automobile phase characterized in that the acrylic resin of claim 1 is used as a main material, and a melamine resin, an inorganic and organic pigment, a leveling agent, an ultraviolet absorber, and a solvent are mixed and cured at a temperature of 160 ° C. or less for 50 minutes or less as a curing agent. Pottery paints. The method of claim 1, The monomer having an acid group is a compound having a double bond of the following structural formula (3), and the monomer having an amino group is selected from dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, n-butoxymethylacrylamide and acrylamide. The manufacturing method of the acrylic resin characterized by using 1 or more types. Wherein R ₁ is hydrogen or a methyl group, R ₂ is an aromatic ring or an alkyl group having 1 to 8 carbon atoms, n is an integer of 1-4. A compound represented by formula (1); A compound represented by formula (2); And a solution copolymer of a mixture of a hydroxy monomer and an monomer having an acid group or an amino group as a functional monomer in a ratio of 50 to 85: 5 to 20: 10 to 30 parts by weight to prepare an acid copolymer resin, The branched or graft polymerization of an acrylic resin by ring-opening an epoxy ring by adding at least one glycidyl ester selected from dibutyl butyrate, glycidyl palmitate, glycidyl laurate and glycidyl stearate Manufacturing method. Here, R ₁ is a hydrogen atom or a methyl group, R <_2> is a C1-C14 alkyl group. Wherein R is an aromatic vinyl compound. The process for producing an acrylic resin according to claim 5, wherein the equivalent ratio between the acid and the epoxy of the glycidyl ester is 1: 0.8 to 1.2. The method of claim 5, wherein The monomer having an acid group is a compound having a double bond of the following structural formula (3), and the monomer having an amino group is selected from dimethylaminoethyl methacrylate, diethylaminoethyl methacrylate, n-butoxymethylacrylamide and acrylamide. The manufacturing method of the acrylic resin characterized by using 1 or more types. Wherein R ₁ is hydrogen or a methyl group, R ₂ is an aromatic ring or an alkyl group having 1 to 8 carbon atoms, n is an integer of 1-4. The acrylic resin is prepared according to the production method of claim 5, the number average molecular weight 5000 ~ 30000, the hydroxy is 30 ~ 100mgKOH / g, the acid value 5 ~ 30mgKOH / g, the glass transition temperature 20 ~ 70 ℃. An automobile phase characterized in that the acrylic resin of claim 8 is used as a main material, and the melamine resin and the inorganic and organic pigments, the leveling agent, the ultraviolet absorber and the solvent are mixed and cured at a temperature of 160 ° C. or less for 50 minutes or less as a curing agent. Pottery paints.