KR20050071169A - Method for preparing an aqueous top coating for automobile - Google Patents

Abstract

The present invention relates to a method for producing a water-soluble topcoat for automobiles, and more specifically, to a method of preparing a core obtained by emulsion polymerization by mixing a monomer that is easy to swell when neutralized with seed particles; Providing a core-shell polymer obtained by emulsion polymerization by mixing monomers which are hardly swollen in alkali to the prepared cores; Swelling the inside of the core by adding a neutralizing agent to the core-cell polymer; And adding an organic co-solvent to the core-cell polymer to swell the outside of the hydrophobic shell layer and to further absorb water into the particles, thereby reducing the amount of water outside the particles. The paint of the present invention has excellent water resistance, adhesion and pigment dispersibility, has a sintering viscosity behavior, and can be coated in a wide range of temperature and humidity conditions, so that it is suitable for use as a coating for water-soluble automotive coatings / transparent coating systems.

Description

Method for preparing an aqueous topcoat for automobiles {Method for preparing an aqueous top coating for automobile}

The present invention relates to a method for producing a water-soluble topcoat for automobiles, and more specifically, to a water-soluble automobile because it has excellent water resistance, adhesion and pigment dispersibility, has a plasticity viscosity behavior, and can be coated in a wide temperature and humidity condition. The present invention relates to a water-soluble topcoat for automobiles suitable for use in top coats of solvent coatings / transparent coating systems.

From the environmental point of view of reducing the amount of volatile organic compounds, the aqueous solution of the conventional solvent type paint is spreading all over the world. However, the water-soluble automotive topcoat / transparent coating system has a problem that the physical properties such as appearance, water resistance, and adhesiveness are weaker than those of the conventional solvent-type automotive topcoat / transparent coating system, and are sensitive to temperature and humidity conditions. Therefore, the development of a water-soluble automotive topcoat / transparent coating system for overcoming the above problems continues.

U.S. Patent No. 4,403,003 discloses that core-shell particles composed of a shell composition comprising a crosslinked core and carboxylic acid can be synthesized by non-water dispersion and emulsion polymerization to be used as a coating for water-soluble automotive coatings / transparent coating systems. . When using the polymer particles described in the patent as a main resin, there is an advantage in showing a good orientation when using metallic pigments due to the excellent plasticity behavior, but it is sensitive to temperature and humidity conditions, causing low viscosity when spray coating in high humidity conditions sagging (sagging) phenomenon, in the dry conditions there is a disadvantage in that the appearance of poor appearance due to the inhibition of the film smoothness due to the high viscosity.

U. S. Patent No. 5,786, 417 also describes the use of water dispersible organic clay complex compounds as rheology modifiers. The above technique improves the water resistance of the paint and greatly lowers the high shear viscosity of the paint to facilitate spray workability and paint transfer. However, the viscosity of the arrived paint is delayed, causing a sagging during coating with the thick film.

On the other hand, US Patent No. 6,376,575 discloses a method of increasing the orientation of the rheology and metallic pigment of the applied paint by mixing the alkali non-swellable main resin with the alkali swellable viscosity regulator, but the method of mixing a separate rheology regulator There is a drawback of causing a sagging during coating with a thick coat by delaying the viscosity recovery, and if the water resistance of the viscosity modifier is poor, there is a disadvantage that the water resistance of the coating film is inferior.

In order to solve the above-mentioned problems, the present invention emulsifies and polymerizes a large amount of monomer mixture having a crosslinked composition which can be water swelled upon neutralization, and is relatively hydrophobic than the prepared core particles and hardly swells in alkali. The red shell composition was subsequently emulsion polymerized to prepare a core-shell polymer, and then a neutralizer (alkali) and an organic solvent were added to prepare a paint. As a result, the core is swelled by absorbing water into the particles by the neutralizing agent, and the hydrophobic shell layer is also swollen by the organic solvent, but the water in the shell layer is continuously absorbed into the core and the amount of the particles outside the particles decreases, thereby bringing the distance between particles closer. , The paints are found to have a very high viscosity in the low shear region, and exhibits excellent plasticity viscosity behavior in which the viscosity decreases drastically in the high shear region, and the paint is dried under high humidity conditions. It was found that the fast and the viscosity recovery is also fast exhibiting excellent sagging resistance even in the thick film, the present invention was completed based on this.

Accordingly, it is an object of the present invention to provide a method for producing a water-soluble topcoat for automobiles.

The production method of the present invention for achieving the above object comprises the steps of providing a core obtained by emulsion polymerization by mixing a monomer that is easy to swell water upon neutralization in the seed particles; Providing a core-shell polymer obtained by emulsion polymerization by mixing monomers which are hardly swollen in alkali to the prepared cores; Swelling the inside of the core by adding a neutralizing agent to the core-cell polymer; And adding an organic co-solvent to the core-cell polymer to swell the outside of the hydrophobic shell layer and to further absorb water into the particles, thereby reducing the amount of water outside the particles.

Hereinafter, the method of the present invention will be described in more detail.

The manufacturing method of the water-soluble topcoat for automobiles of the present invention is a step of preparing an alkali swellable hydrophilic core (first emulsion polymerization step), a step of preparing a core (hydrophilic) -shell (hydrophobic) composite having an alkali swellable core (second emulsion polymerization). Step), the neutralization step of the core and the swelling step of the shell.

1) Preparation of Alkali Swellable Cores

First, in the first emulsion polymerization step, the seed particles are easily mixed with monomers which are easily swelled upon neutralization, and the cores are prepared by emulsion polymerization.

The core may be prepared by polymerizing monomers without a seed. However, the core may be prepared by polymerizing monomers in the presence of seed particles in order to secure polymerization stability, proper particle size control, and polymerization reproducibility.

The amount of seed particles used is 1 to 20% by weight, preferably 2 to 15% by weight of the core composition. If the content of the seed particles is less than 1% by weight, the effect of using the seed is reduced, and if it exceeds 20% by weight, there is a disadvantage that the function as a core is reduced.

The particle size of the seed is 20 to 100 nm, preferably 30 to 85 nm. If the particle size of the seed is less than 20nm, the effect of using the seed is reduced, if the seed exceeds 100nm, there is a disadvantage that the size of the core is too large.

Monomers that are emulsion polymerized with the seed during core preparation are at least one acid monomer, at least one crosslinking monomer and at least one other ethylenically unsaturated monomer.

The acid monomer is preferably used at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, monoalkylmaleate, monoalkylfumalate, monoalkylitaconate and vinylbenzoic acid. Do.

The content of the acid monomer is preferably 15 to 40% by weight based on the total weight of the monomer, and if the content is less than 15% by weight, there is a problem in that sufficient water swellability is not added when the neutralizing agent is added. There is a problem in that new sites are generated without the particles growing due to the increased site.

The cross-linking monomer serves to ensure that the core has a stable form when the core is swelled with a neutralizing agent. For this purpose, two or more unsaturated double bonds must be present to enable polymerization in the molecule.

The crosslinking monomers are aryl acrylate, aryl methacrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, diaryl phthalate It is preferable to use one or more selected from the group consisting of tripropylene glycol dimethacrylate, trimethylolpropane trimethacrylate and triaryl isocyanurate.

The content of the crosslinking monomer is preferably 0.1 to 5% by weight relative to the total weight of the monomer, when less than 0.1% by weight is low crosslinking density of the resulting particles is difficult to produce a stable core / shell structure of particles solubilized during neutralization There is a problem, and when it exceeds 5% by weight there is a problem in ensuring the polymerization stability and high crosslinking density of the particles produced does not exhibit sufficient water swellability.

The other structural monomers are preferably selected from the group consisting of styrene, vinyltoluene, methylstyrene, ethylene, butadiene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, alkyl acrylate and alkyl methacrylate. Do.

The content of the other structural monomers is preferably 55 to 84.9% by weight relative to the total weight of the monomer, and when less than 55% by weight, the content of acid monomers or crosslinking monomers is too high, and when it exceeds 84.9% by weight. There is a problem that the content of the acid monomer or crosslinking monomer is too small.

According to the invention, the average particle size of the core is 50-250 nm, preferably 50-150 nm. If the particle size of the core is less than 50 nm, the resulting emulsion particle size is too small, the amount of emulsifier is increased to obtain a stable emulsion, the workability and coating properties of the paint is lowered, and if the particle size exceeds 250 nm, Since the thickness of the shell to be manufactured becomes relatively thin, the swelling becomes severe during neutralization, which causes difficulty in filtration and packaging.

2) Preparation of Core-Shell Composites with Alkali Swellable Cores

In the presence of the prepared cores, monomers which are relatively hydrophobic to the core and hardly swell in an alkali (neutralizing agent) are mixed and emulsion polymerized to prepare a core-shell polymer.

The shell may be a primary shell or synthesized as primary and secondary shells for retention of the core-shell morphology before and after polymerization.

The monomers used in the manufacture of the shell are at least one acid monomer and at least one other structural monomer, the amount of which is used so that the weight ratio of core to shell is 1: 1 to 100, preferably 1:10 to 60. It is preferable.

The acid monomer is preferably used at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, monoalkylmaleate, monoalkylfumalate, monoalkylitaconate and vinylbenzoic acid. In addition, the monomer mixture used in the shell copolymer is preferably hydrophobic and hardly swelled in an alkali (neutralizing agent) than the monomer used in the core polymerization.

In the present invention, it is preferable to use an acid monomer at 0 to 10% by weight of the total shell weight in order to ensure the water resistance of the final coating film and the viscosity stability at the neutralization of the product. There is a problem that the water resistance of the final coating film is lowered and the viscosity becomes too high after neutralization.

The other structural monomers are selected from the group consisting of styrene, vinyltoluene, methyl styrene, ethylene, butadiene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylonitrile, alkyl acrylate and alkyl methacrylate. desirable.

The content of the structural monomer is preferably used in 90 to 100% by weight of the total shell weight, if less than 90% by weight there is a problem that the water resistance of the final coating film is lowered and the viscosity is too high after neutralization.

The average molecular weight of the shell is a weight average molecular weight of 5,000 to 500,000, preferably 10,000 to 200,000, to facilitate swelling of the shell when the organic solvent is added. For this purpose, a molecular weight regulator is used in the emulsion polymerization. As the molecular weight modifier usable in the present invention, carbon tetrachloride, n-alkyl mercaptan, alkyl mercapto propionic acid, alkyl esters thereof, and the like are preferable.

The polymerization initiators usable in the core and shell preparation of the present invention are both water soluble and useful in the conventional emulsion polymerization, and may be used alone or in combination with a reducing agent.

Such polymerization initiators include, for example, ammonium persulfate, sodium persulfate, potassium persulfate, t-butyl hydroperoxide, 4,4'-azobis (4-cyano valeric acid) as water solubility, 2'-azobisbutyronitrile, 2,2'-azobis-2-methylbutyronitrile, cumene hydroperoxide, and the like, and reducing agents include ascorbic acid, sodium formaldehyde sulfoxide, sodium bisulfite, and the like. This is preferred.

The polymerization initiator may be added before the monomer composition is introduced or used simultaneously with the monomer. Since the type and the amount of the initiator have a large influence on the water resistance of the coating film, it is selected and used to satisfy the water resistance, but it is generally preferred to use 0.1 to 3.0% by weight of the monomer used.

The pH during the polymerization reaction is preferably maintained at a pH of 4 or less so as to increase the efficiency of the initiator when the water-soluble initiator is used and not to ionize the acid monomer.

In the present invention, the emulsifier that can be used when preparing cores and shells may be used in conventional emulsion polymerization, but it is preferable to use a reactive emulsifier that can be copolymerized with monomers to improve water resistance of the coating film, and to minimize the addition amount thereof. desirable.

Such emulsifiers include sodium alkylsulfate, sodium alkylbenzene sulfonic acid, ammonium salts of alkylphenoxy polyethylene oxide sulfonates, and non-reactive emulsifiers include, for example, allyl sulfo succinate-based eleminol JS-2 and Japanese kao Japan's Asahi Denka Kogyo, which is an aryl compound substituted with Aquaron HS-5, HS-10 and sulfonate of Daiichi Koyo Seiyaku Co., Ltd., which is an alkyl phenyl ether-based compound, S-120, S-180, S-180A, etc. Adecaria soap SE-1025 and the like can be used.

Since the amount of the emulsifier affects the water resistance of the coating film, the type and amount of use are preferably used in an amount of 0.1 to 0.3% by weight of the monomer used within a range that does not affect the water resistance and the synthetic stability. If the amount of the emulsifier used is too small, the synthetic stability is poor, if too large, there is a problem that the water resistance of the coating film is inferior.

3) neutralization of core

Neutralizer (alkali) is added to the emulsion particles of the final core-shell. The hydrophilic core layer is swollen by absorbing water by the neutralizing agent.

The neutralizing agent may be selected from ammonia and volatile lower amines which may react with the carboxyl group, or may be selected from metal bases, but is preferably volatilized for water resistance of the coating film. Specific examples of the neutralizing agent may be used ammonia and volatile lower alkyl tertiary amines.

The amount of neutralizing agent that can be used in the present invention is preferably used so that the pH of the emulsion polymerization liquid is in the range of 6 to 11, and when the pH is too low, the alkali swellability of the core is lowered, and when too high, the coating or subsequent coating is performed. It may interfere with the curing reaction of the transparent paint. In addition, it is preferable to perform addition of a neutralizing agent in a cooling process after shell polymerization is complete | finished.

4) Swelling of the shell and production of water-soluble topcoat for automobiles

After swelling the core of the present invention with a neutralizing agent, an organic co-solvent is added to swell the outside of the particles of the hydrophobic shell layer.

According to the present invention, water outside the swollen particles continues to penetrate into the particles, thereby decreasing the amount of the particles outside the particles, thereby making the distance between particles close. As the distance between particles gets closer, the viscosity in the low shear region is greatly increased, and at high shear, the interaction between particles decreases, resulting in a physicochemical viscosity behavior in which the viscosity is sharp. Therefore, the rheology control agent may be used separately or the amount thereof may be minimized to help the coating film of the main resin and to improve the low shear viscosity.

If the spray coating with the paint prepared above, the drying is faster even in high-humidity conditions due to the outside of the particles made of an organic solvent, the recovery speed is also faster and has excellent sagging resistance even in the thick film.

The organic solvent used in the present invention is preferably added at 20% by weight or less with respect to the total coating, there is a problem that the storage of the coating is lowered when added to the above range.

The type of organic solvent is preferably selected from the group consisting of butyl glycol, hexyl glycol, 2-ethylhexanol and ethylene glycol 2-ethylhexyl ether, and the type of the solvent and the content in the paint are used in the present invention. It is preferable to determine the solubility and hydrophilicity / hydrophobicity of the synthesized resin in consideration of the difference.

On the other hand, the main resin synthesized in the present invention can be used in combination with a curing agent. Suitable curing agents generally use amino resins, blocked isocyanates, epoxy compounds, aziridine compounds, carbodiimide compounds, oxazoline compounds and the like, or amino resins with low manufacturing costs.

In addition, the main resin synthesized in the present invention can be used in admixture with auxiliary resins such as urethane water-dispersion resin, polyester water-dispersion resin, acrylic urethane water-dispersion resin, etc. to improve adhesion and water resistance, pigment, which is a general paint additives, Dyes, dispersants, curing accelerators, and the like. At this time, it is preferable to adjust the solid content of paint to 10-40 weight%.

Hereinafter, the present invention will be described in more detail with reference to the following examples, but the scope of the present invention is not limited to the following examples.

Example 1

1) Preparation of Alkali Swellable Core Emulsion

The thermocouple, stirrer, and reflux were respectively mounted in a four-necked 2 L round flask, and 550 g of deionized water and 3.43 g of Latemal S-180A, which is a reactive emulsifier of Cao were added, and the reactor temperature was raised to 80 ° C. While heating up the reactor, a total emulsion consisting of 150 g of deionized water, 15.58 g of Lateral S-180A, 166.66 g of ethyl acrylate, 93.21 g of methacrylic acid, and 0.13 g of triarylisocyanurate was prepared, and this was added to separatory funnel A. Was added. In addition, separatory funnel B was prepared by adding an initiator solution consisting of 25.0 g of deionized water and 0.38 g of ammonium persulfate, and separating funnel C from an initiator solution consisting of 30.0 g of deionized water and 0.14 g of ammonium persulfate. When the reactor was maintained at 80 ° C., 21.78 g of the separatory funnel A in the total emulsion and the aqueous solution of the initiator of the separatory funnel B were simultaneously dropped and maintained for 40 minutes. After seed formation, the initiator aqueous solution of the separatory funnel C was added dropwise for 10 minutes, and the whole emulsion of the separatory funnel A was dropped for 3 hours. After holding for 1 hour, the mixture was cooled to 50 ° C. and packed with filtration through a 400 mesh filter. The particle diameter of the synthesized emulsion particles was 120nm, measured by LLS, the solid content was 26.0% by weight.

2) Preparation of Core-Shell Emulsion Polymers with Alkali Swellable Cores and Neutralization of Cores

A thermocouple, a stirrer, and a reflux were respectively mounted in a four-necked 2 L round flask, and 115.66 g of the core solution synthesized in Example 1 and 450.15 g of deionized water were added thereto, followed by heating to 85 ° C. 231.32 g of deionized water, 5.78 g of Lateral S-180A, 3.0 g of 2,2'-azobisisobutyronitrile, 46.3 g of styrene, 46.3 g of methyl methacrylate, 11.57 g of 2-hydroxyethyl methacrylate g, 196.62 g of ethyl methacrylate. A total emulsion consisting of 6.0 g of methacrylic acid and 3.0 g of n-dodecyl mercaptan is added. When the reactor temperature was maintained at 85 ℃ dropping the total emulsion of the separatory funnel for 3 hours and maintained for 1 hour. After the holding reaction, the mixture was cooled to 50 ° C. and packed with filtration through a 400 mesh filter. The particle size of the synthesized emulsion particles was 150 nm, and the solid content was 35.0% as measured by LLS.

3) Preparation of paint

A water-soluble automotive topcoat was prepared by using a silver metallic paint formulation using the synthesized emulsion.

In the above formulation, the solid content of the applied resin was 35% by weight to maintain the solid content of the paint and the pigment / resin ratio. First, 72 g of the emulsion resin solution prepared above was added to a 300 ml container, and 8.0 g of an aqueous 10% dimethylethanol amine solution was slowly mixed while stirring with a high speed stirrer. 6.9 g of aluminum paste (60 wt% solids) and 7.5 g of butyl glycol of Hydrolan 2154, which are aluminum flake pigments of Eckert Berke Co., Ltd., were mixed and stirred for 10 minutes with a high speed stirrer. While continuing to stir, 1.65 g of Disinfectant Surfinol, 5.5 g of hexyl glycol, and 5.0 g of 2-ethylhexanol were added. After stirring was stopped, 4.65 g of Cymel 325 (solid content 80 wt%), which is a melamine curing agent from Cytec, was added, and stirring was started again. 17.5 g of deionized water was added while stirring continued. A total amount of deionized water, an aqueous 10% dimethylethanol amine solution and Hv-30, an alkali swellable thickener of Ciba Specialty, was added at 18.3 g, and a paint was prepared in a Pod # 40 cup at a pH of 8.0 to 8.5 for 35 seconds.

4) Application of paint

The prepared silver metallic paint was coated on a steel panel specimen coated with an electrodeposition and a medium coating so that the coating thickness was approximately 15 microns thick at the time of drying, and was flash-dried for 4 minutes in an 80 ° C. oven. Keshisu paint, which is a solvent-type acrylic-melamine transparent paint manufactured by Kumkang Korea Chemical Co., Ltd., was coated to have a dry coating thickness of 45 microns and cured at 150 ° C. for 30 minutes.

Table 1 shows the test results of the paint and film properties.

Example 2

Use of non-reactive emulsifiers

In Example 1, the emulsifier was replaced with Rhodia's non-reactive anionic emulsifier CO-436 instead of the reactive emulsifier Lateral S-180A, and the amount of the emulsifier was 80% of the amount of S-180A. The particle diameter of the synthesized emulsion particles was 135 nm, and the solid content was 34.9% as measured by LLS.

Using the synthesized emulsion to prepare a water-soluble automotive topcoat with the same silver metallic paint formulation as in Example 1 was applied to the coating as in Example 1 and the paint and coating properties test results are shown in Table 1 below.

Example 3

Synthesis of Main Resin with Core-Shell1-Shell2

A thermocouple, a stirrer, and a reflux were respectively mounted in a four-necked 2 L round flask, and 115.66 g of the core solution synthesized in 1) of Example 1 and 450.15 g of deionized water were added thereto, and the temperature was increased to 85 ° C. Into the separatory funnel, a monomer mixture consisting of 1.0 g of 2,2'-azobisisobutyronitrile, 15.0 g of methyl methacrylate, 50.0 g of ethyl methacrylate, and 3.0 g of methacrylic acid was added dropwise for 2 hours and maintained for 1 hour. I was. Here, 231.32 g of deionized water, 5.78 g of Lateral S-180A, 2.0 g of 2,2'-azobisisobutyronitrile, 46.3 g of styrene, 31.3 g of methyl methacrylate, 11.57 g of 2-hydroxyethyl methacrylate A total emulsion containing 146.62 g of ethyl methacrylate, 3.0 g of methacrylic acid, and 3.0 g of n-dodecyl mercaptan was added thereto. When the reactor temperature was maintained at 85 ° C., the whole emulsion of the separatory funnel was added dropwise for 150 minutes and maintained for 1 hour. After the holding reaction was cooled to 50 ℃ and packaged while filtering with a 400 mesh filter. The particle size of the synthesized emulsion particles was 155 nm, and the solid content was 35.0% as measured by LLS.

Using the synthesized emulsion to prepare a water-soluble automotive topcoat with the same silver metallic paint formulation as in Example 1 was applied to the coating as in Example 1 and the paint and coating properties test results are shown in Table 1 below.

Comparative Example 1

Preparation of Homogeneous Alkali Non-Swellable Emulsion Polymers

Unlike Example 1 synthesized to have an alkali swellable core (high methacrylic acid content) -alkali non-swellable shell (low methacrylic acid content), alkali non-swellable composition (less methacrylic acid content) without the alkali swellable core The polymerization was carried out only.

The four-necked 2 L round flask was equipped with a thermocouple, a stirrer and a reflux reactor, and 479.64 g of deionized water was added thereto, and the temperature was increased to 85 ° C. An aqueous solution consisting of 38.49 g of deionized water, 2.0 g of Lateral S-180A and 0.18 g of ammonium persulfate was added to the separatory funnel A. Separation funnel B consists of 51.3 g of styrene, 51.3 g of methyl methacrylate, 12.8 g of 2-hydroxyethyl methacrylate, 218.2 g of ethyl methacrylate and 6.7 g of methacrylic acid, and 3.3 g of n-dodecyl mercaptan. The monomer mixture was added. When the reactor temperature was maintained at 85 ℃ was added all the amount of separatory funnel A and 17.2g of B at the same time and maintained for 40 minutes. After dissolving 3.3 g of 2,2'-azobisisobutyronitrile in separatory funnel B, the residue was added dropwise for 3 hours and maintained for 1 hour. After the holding reaction was cooled to 50 ℃ and packaged while filtering with a 400 mesh filter. The particle size of the synthesized emulsion particles was 170 nm, and the solid content was 35.0% as measured by LLS.

Using the synthesized emulsion to prepare a water-soluble automotive topcoat with the same silver metallic paint formulation as in Example 1 was applied to the coating as in Example 1 and the paint and coating properties test results are shown in Table 1 below.

Comparative Example 2

Preparation of Alkali Non-Swellable Core-Alkali Swellable Shell Emulsion Polymers

Unlike Example 1 synthesized to have an alkali swellable core (high methacrylic acid content) -alkali non-swellable shell (low methacrylic acid content), alkali non-swellable core (without methacrylic acid) -alkali swellable shell It was synthesized to have (high methacrylic acid content).

The thermocouple, stirrer and reflux were respectively mounted in a four-necked 1 L round flask, 448.4 g of deionized water, 1.5 g of CO-436, Rhodia's anionic emulsifier, 4.0 g of styrene, and 4.4 g of ethyl acrylate were added and the reactor temperature was maintained at 80 ° C. . When the temperature was maintained, an initiator solution in which 0.2 g of ammonium persulfate was dissolved in 4.4 g of deionized water was added thereto and maintained for 40 minutes. During the fat and oil reaction, 106.5 g of deionized water, 1.2 g of CO-436, 0.2 g of ammonium persulfate, 46.7 g of styrene, 88.4 g of ethyl acrylate, and 2.8 g of 1,6-hexanediol diacrylate were emulsified to prepare a total emulsion. The prepared whole emulsion was added dropwise for 2 hours and maintained for 60 minutes. During the holding time, 47.8 g of deionized water, 0.6 g of CO-436, 0.2 g of ammonium persulfate, 5.9 g of methacrylic acid, 7.9 g of 2-hydroxyethyl acrylate, 24.3 g of ethyl acrylate, and 4.8 g of methyl methacrylate were added. Emulsification gave a total emulsion. The prepared total emulsion was added dropwise for 60 minutes and maintained for 60 minutes. After the holding reaction was cooled to 50 ℃ and packaged while filtering with a 400 mesh filter. The particle diameter of the synthesized emulsion particles was 115nm, measured by LLS, the solid content was 25.8%.

Using the synthesized emulsion to prepare a water-soluble automotive topcoat with a silver metallic paint formulation as in Example 1 was applied to the coating as in Example 1 and the paint and coating properties test results are shown in Table 1 below.

Comparative Example 3

In the shell polymerization process of Examples 1 to 2, n-dodecyl mercaptan, which is a neutralizing agent, was not used. The particle diameter of the synthesized emulsion particles was 152 nm and the solid content was 35.0% as measured by LLS.

Using the synthesized emulsion to prepare a water-soluble automotive topcoat with the same silver metallic paint formulation as in Example 1 was applied to the coating as in Example 1 and the paint and coating properties test results are shown in Table 1 below.

Applicable Resin Hv-30 dosage Water resistance ¹⁾ Adhesion ²⁾ Rheological behavior ³⁾ High Humidity Workability ⁴⁾ Low Humidity Workability ⁵⁾ Appearance ⁶⁾ Example 1 0g Great Great Great Great Great Great Example 2 0g usually Great Great usually usually Great Example 3 1.0 g Great Great Very good Very good Great Great Comparative Example 1 3.5 g Great Great usually Bad usually Great Comparative Example 2 0g usually Great Great Bad usually usually Comparative Example 3 2.5g Great Great usually usually usually usually

1) Water resistance After the specimen was immersed in water at 40 ° C. for 10 days, discoloration, blistering, and water resistance were evaluated.

2) Adhesion was applied to the coating film of the transparent paint and the top coat and the transparent paint, respectively, and evaluated by cross hatch adhesion.

3) Rheological behavior was evaluated by observing the viscosity change in a reciprocating manner using a rheometer from ⁰ to 100 s ^-1 and observing the low point viscosity, the high shear viscosity and the viscosity recovery.

4) High Humidity Workability was evaluated by sagging resistance and popping resistance generated when coating was applied at a relative humidity of 22 ° C. and 85%.

5) Low Humidity Workability was evaluated by sagging resistance and popping resistance generated when coating was applied at 25 ° C and 60% relative humidity.

6) Appearance was evaluated by visual observation and a combination of light ratios at 25 ° and 75 ° angles measured using an X-Rite MA58 photometer.

As shown in Table 1, the water-soluble topcoat according to the embodiment of the present invention has a water resistance, adhesion and plasticity viscosity behavior, it was found that the workability is excellent in both low and high humidity conditions. In addition, the paint of the present invention was excellent in plasticity viscosity behavior without a thickener, excellent workability at high humidity, and when the thickener was added separately, the function was very excellent.

As can be seen from the test results, the method of preparing an emulsion resin according to the present invention was able to produce a main resin that can be used as a top coat of a water-soluble top coat / transparent coating system without the use of a separate thickener and rheology control agent, When it is used as a top coat, it has excellent water resistance, adhesiveness and pigment dispersibility, has a plasticity viscosity behavior, and can be coated in a wide temperature and humidity condition.

Claims (7)

Providing a core obtained by emulsion polymerization by mixing a seed particle with a monomer that is easily swelled upon neutralization; Providing a core-shell polymer obtained by emulsion polymerization by mixing monomers which are hardly swollen in alkali to the prepared cores; Swelling the inside of the core by adding a neutralizing agent to the core-cell polymer; And Adding an organic co-solvent to the core-cell polymer to swell the outside of the hydrophobic shell layer and to further absorb water into the particles to reduce the amount of water outside the particles; Method for producing a water-soluble coating for automotive, characterized in that it comprises a. The method of claim 1 wherein the weight ratio of core to shell of the core-shell polymer is from 1: 100 to 1 and the average molecular weight of the shell is from 5,000 to 500,000. The monomer of claim 1 wherein the monomers used in the core preparation comprise at least one acid monomer, at least one crosslinking monomer and at least one other ethylenically unsaturated monomer, the content of each of which is 15 relative to the total weight of the monomers. 40% by weight, 0.1-5% by weight and 55.0-8.9% by weight. The method of claim 1, wherein the monomer used in the manufacture of the shell comprises at least one acid monomer and at least one other ethylenically unsaturated monomer, the content of which is 0 to 10% by weight and 90 to 90% by weight of the shell, respectively. 100% by weight. The method of claim 3, wherein the acid monomer is at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, monoalkylmaleate, monoalkylfumalate, monoalkylitaconate and vinylbenzoic acid. Selected and used, the crosslinking monomers are aryl acrylate, aryl methacrylate, ethylene glycol dimethacrylate, ethylene glycol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, At least one selected from the group consisting of diaryl phthalate, tripropylene glycol dimethacrylate, trimethylolpropane trimethacrylate and triaryl isocyanurate, and other ethylenically unsaturated monomers are styrene, vinyltoluene, methylstyrene , Ethylene, butadiene, vinyl acetate, vinyl chloride, vinylidene chloride, acrylic Nitriles, characterized in that used is selected at least one from the group consisting of alkyl acrylates and alkyl methacrylates. The method of claim 4, wherein the acid monomer is at least one selected from the group consisting of acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, monoalkylmaleate, monoalkylfumalate, monoalkylitaconate and vinylbenzoic acid. One or more other ethylenically unsaturated monomers selected from the group consisting of styrene, vinyltoluene, methylstyrene, ethylene, butadiene, vinylacetate, vinylchloride, vinylidene chloride, acrylonitrile, alkyl acrylate and alkyl methacrylate Characterized in that it is selected and used. The method of claim 1 wherein the core neutralizer is used in a pH range of 6-11.