WO2018034487A1 - Electro-deposition paint composition - Google Patents

Abstract

The present invention provides a modified polyepoxide-amine resin for electro-deposition paint and an electro-deposition paint composition containing same, the modified polyepoxide-amine resin for electro-deposition paint having an epoxy-amine equivalent weight of 20,000-40,000 and being obtained by chain-extending, in the presence of a polyepoxide-amine resin containing a tertiary amine group, a polyepoxide resin having an epoxy equivalent weight of 800-1,200, and a polyol having a molecular weight of 100-500.

Description

Electrodeposition Paint Composition

The present invention relates to an electrodeposition coating resin and an electrodeposition coating composition comprising the same.

Electrodeposition coating is a method of depositing a coating object in an electrodeposition coating composition as an anode or a cathode, and depositing a coating film electrically on the surface of a to-be-coated object through a direct current on a to-be-painted object and its counter electrode, and forming a coating film. Recently, due to the rapid development and development of water-soluble paints to avoid pollution and fire problems, it is applied to automotive primers. Currently, most electrodeposition paint resins use a system in which the polyepoxide-amine reaction product is neutralized with an acid.

On the other hand, since the electrodeposition coating is a method of depositing a coating film by electric force, a metal substrate is mainly used as a substrate having electrical conductivity as the workpiece. In general, the metal substrate is a pre-treated metal substrate for improving the coating quality and rust prevention.

Currently, as a pretreatment method of a metal base for electrodeposition coating, there are a phosphate pretreatment method using phosphate as a coating agent and a non-phosphate pretreatment method using a non-phosphate compound such as zirconium compound as a coating agent. Among them, phosphate-based pretreatment uses phosphoric acid (H ₃ PO ₄ ), nitric acid (HNO ₃ ), zinc (Zn), nickel (Ni), etc., which is highly environmentally contaminated, and also contains heavy metals such as zinc. There is a drawback of cost.

Accordingly, in the field of electrodeposition coating, there is a trend to replace the conventional phosphate pretreatment with non-phosphate pretreatment such as environmentally friendly and low cost zirconium pretreatment.

In addition, automakers are trying to reduce the cost of automobile production. Among them, in the electrodeposition process, which is a coating process, in particular, the coating process, attention is focused on reducing the production cost by reducing the consumption of paint by setting the coating thickness low.

However, if you simply paint with a small amount of paint to reduce the thickness of the coating, there is a disadvantage in that the appearance and rust resistance of the coating is greatly reduced.

Therefore, there is a demand for the development of a new electrodeposition paint that can maintain excellent levels of physical properties, appearance and rust resistance even when a small amount of paint is applied onto a metal substrate pretreated with a non-phosphate compound.

The present invention is to provide a modified polyepoxide-amine resin for electrodeposition paint that can reduce the thickness of the coating film and ensure excellent physical properties, appearance and rust resistance.

On the other hand, this invention provides the cationic resin composition for electrodeposition paints containing the said modified polyepoxide amine resin for electrodeposition paints.

Moreover, this invention provides the cationic electrodeposition coating composition containing the said cationic resin composition for electrodeposition paints.

The present invention provides an epoxy-amine equivalent obtained by chain-extending a polyepoxide resin having an epoxy equivalent of 800 to 1,200 and a polyol having a molecular weight of 100 to 500 in the presence of a polyepoxide-amine resin containing a tertiary amine group. Provided is a modified polyepoxide-amine resin for electrodeposition paint having 20,000 to 40,000.

On the other hand, the present invention provides a cationic resin composition for electrodeposition paint comprising the modified polyepoxide-amine resin for the electrodeposition paint and a urethane curing agent.

The present invention also provides a cationic electrodeposition coating composition comprising the above cationic resin composition for electrodeposition paint, pigment and deionized water.

In another aspect, the present invention provides an automotive part comprising a paint layer formed using the electrodeposition paint composition.

The modified polyepoxide-amine resin for electrodeposition paint according to the present invention can reduce the thickness of the coating film to 20㎛ or less when electrodeposition coating is applied, and can form a coating film showing excellent physical properties, appearance and rust resistance.

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

1. Degeneration Polyepoxide - Amine  Suzy

One embodiment of the present invention provides a modified polyepoxide-amine resin for electrodeposition paint.

The modified polyepoxide-amine resin for electrodeposition paint is a polyepoxide resin having an epoxy equivalent of 800 to 1,200 and a polyol having a molecular weight of 100 to 500 in the presence of a polyepoxide-amine resin containing a tertiary amine group. The present invention relates to a modified polyepoxide-amine resin for electrodeposition paint, obtained by chain extension reaction, having an epoxy-amine equivalent of 20,000 to 40,000.

In the present invention, the epoxy equivalent means the value obtained by dividing the number average molecular weight of the polyepoxide resin by the number of epoxy groups per molecule.

In the present invention, the epoxy-amine equivalent means the value obtained by dividing the number average molecular weight of the polyepoxide-amine resin by the number of active hydrogens of the epoxy group and the amine per molecule. In this case, the active hydrogen of the amine refers to a highly reactive hydrogen bonded to nitrogen in the hydrogen of the polyepoxide-amine resin.

The polyepoxide resin is a resin having at least two epoxy groups.

Examples of the polyepoxide resin include polyglycidyl ethers of aromatic polyols such as bisphenol and polyphenol. Such polyepoxide resins can be prepared by ether reaction of aromatic polyols with epihalohydrin or dihalohydrin such as epichlorohydrin or dichlorohydrin in the presence of an alkali.

The polyepoxide resin may increase its molecular weight by reacting with the polyol in the presence of a chain extending catalyst. Through this process, the epoxy equivalent of the polyepoxide resin can be adjusted to 800 to 1,200. When the epoxy equivalent of the polyepoxide resin is less than 800, heat resistance may be poor, and when the epoxy equivalent of the polyepoxide resin is greater than 1,200, the coating film riseability may be reduced.

Benzyldimethylamine or the like may be used as the chain extension catalyst.

The polyol having a molecular weight of 100 to 500 may be an aromatic polyol having a molecular weight of 100 to 500. Specifically, the aromatic polyol may be bisphenol A, or modified bisphenol A such as ethoxylated bisphenol A.

The polyepoxide-amine resin comprising the tertiary amine group acts as a catalyst for the chain extension reaction to allow for further chain extension. That is, the polyepoxide-amine resin including the tertiary amine group acts as a catalyst for the chain extension reaction to react with the polyepoxide resin having an epoxy equivalent of 800 to 1,200 and the polyol having a molecular weight of 100 to 500. Accordingly, a modified polyepoxide-amine resin having an epoxy-amine equivalent of 20,000 to 40,000 can be obtained.

The polyepoxide-amine resin including the tertiary amine group may be formed by reacting a secondary amine having a primary hydroxy group with a polyepoxide resin having an epoxy equivalent of 800 to 1,200.

Specific examples of the secondary amine having the primary hydroxyl group include diethanol amine, dimethanol amine, dipropanol amine, ethyl monoethanolamine, mono-n-butyl monoethanolamine, mono-tert-butyl monoethanolamine, bis ( 2-hydroxypropyl) amine, mono-n-propyl monoethanolamine, N-methylethanolamine, etc. are mentioned.

The polyepoxide resin having an epoxy equivalent of 800 to 1,200 reacts with a secondary amine, part of which has a primary hydroxy group, to produce a polyepoxide-amine resin comprising the tertiary amine group, the remainder of the polyol and chain Prolonged reaction. At this time, the polyepoxide-amine resin containing the tertiary amine group produced acts as a catalyst of the chain extension reaction.

On the other hand, the modified polyepoxide-amine resin is a chain-extension reaction of the polyepoxide-amine resin containing the epoxy equivalent of 800 to 1,200 and the polyepoxide-amine resin containing a diketimine group with the polyol having a molecular weight of 100 to 500 It can also be obtained.

The polyepoxide-amine resin including the diketimine group may be formed by reacting diketimine with a polyepoxide resin having the epoxy equivalent of 800 to 1,200. That is, the diketimine with the secondary amine having the primary hydroxyl group is reacted with the polyepoxide resin having the epoxy equivalent of 800 to 1,200, and the diketimine group together with the polyepoxide-amine resin including the tertiary amine group. It is also possible to form a polyepoxide-amine resin to contain.

The diketimine group may be aminated by hydrolysis, and the amine group formed by the amination may participate in the curing of the coating film to help improve physical properties of the coating film.

The diketamine may be derived from the reaction of a ketone compound with a compound containing two primary amine groups. Specifically, the diketimine may be a compound of formula 1, which is a reaction product of diethylenetriamine and methyl isobutyl ketone.

[Formula 1]

The chain extension reaction temperature may be 100 to 120 ℃. If the reaction temperature is less than 100 ° C it may be difficult to extend the chain, if the reaction temperature is greater than 120 ° C may be degraded due to excessive chain extension.

The modified polyepoxide-amine resin has a very high epoxy-amine equivalent of 20,000 to 40,000, reducing the film thickness to 20 μm or less, and in particular, when coating on a non-phosphate based pretreated metal substrate such as zirconium pretreatment. It is possible to improve the appearance characteristics by reducing the deviation phenomenon and to exhibit excellent internal coating properties, thereby improving the rust resistance. When the epoxy amine equivalent weight is less than 20,000, external appearance such as uneven coating may occur. When the epoxy amine equivalent is more than 40,000, an overcoat may be formed, thereby deteriorating internal coating property.

2. Cationic Resin Composition

Another embodiment of the present invention provides a cationic resin composition for electrodeposition paint comprising the modified polyepoxide-amine resin and a urethane curing agent.

The urethane curing agent may include polyisocyanate with at least some isocyanate groups blocked. For example, the urethane curing agent may include a polyisocyanate in which an isocyanate group is completely blocked, that is, a polyisocyanate in which free isocyanate remains. In the present invention, the polyisocyanate means a compound having two or more isocyanate groups.

The blocked polyisocyanate can be obtained by reacting the polyisocyanate with a blocking agent.

The polyisocyanate may be an aliphatic or aromatic polyisocyanate including alicyclic, and typical examples thereof include tetramethylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate and isophorone diisocyanate. aliphatic polyisocyanates selected from the group consisting of diisocyanate); Polymethylene diphenyl diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylene diisocyanate, diphenylmethane-4,4'-diisocyanate and triphenylmethane-4,4 ', And aromatic polyisocyanates selected from the group consisting of 4 ''-triisocyanates.

The blocking agent may be a monohydric alcohol, a polyhydric alcohol (polyol) or a mixture thereof.

As the monohydric alcohol, 2- (2-butoxyethoxy) ethanol, ethanol, or the like can be used.

Examples of the polyhydric alcohol include trimethylol propane, polycaprolactone triol, 1,2,4-butane triol, ethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, neopentyl glycol, polycaprolactone Diol, 1,5-pentanediol, 1,2-butanediol, 1,2-hexanediol, bisphenol A (BPA), bisphenol F (BPF), modified bisphenol A, etoxylated bisphenol A, Benzenediol and the like can be used.

In the reaction of the polyisocyanate with the blocking agent, the equivalent ratio of the isocyanate group in the polyisocyanate group and the hydroxy group in the blocking agent may be 1: 1 to 1: 2.

The isocyanate group blocked as described above is stable to active hydrogen at room temperature, and may react with active hydrogen at a high temperature, for example, 150 to 200 ° C. which is a curing temperature.

The urethane curing agent may include a solvent for easy handling and use. Methyl isobutyl ketone may be used as the main solvent. In addition, as an auxiliary solvent, tripropylene glycol, 1,12-dodecanediol, triethylene glycol and the like may be used together.

In addition, the urethane curing agent may include a curing catalyst such as a tin catalyst. Examples of the curing catalyst include dibutyltin dilaurate, dibutyl tin oxide and silver tin catalyst, which are in an amount corresponding to 0.05-1% by weight of the tin component based on 100% by weight of total solids in the urethane curing agent. May exist.

The electrodeposition paint cationic resin composition may further include deionized water and a neutralized acid.

The neutralized acid reacts with an amine group in the cationic resin for electrodeposition paint to generate a cation. As the neutralized acid, inorganic acids such as hydrochloric acid, nitric acid, hypophosphoric acid, and organic acids such as acetic acid, lactic acid, formic acid, methanesulfonic acid, sulfonic acid, and acetylglycinic acid may be used.

In addition, the cationic resin composition for electrodeposition paint of the present invention may further include additives such as ACA (anticrater agent), microgel, antifoaming agent, surface conditioner, antibacterial agent.

3. Cationic Electrodeposition Coating Composition

Another embodiment of the present invention relates to a cationic electrodeposition coating composition comprising the above cationic resin composition for electrodeposition paint, a pigment, and deionized water.

The pigment may be dispersed in a pigment dispersing resin having a property capable of adsorbing the pigment properly and dissolving in water, and may be blended into the cationic electrodeposition coating composition in the form of a pigment paste.

Pigment components that can be used in the production of the pigment paste include titanium dioxide, antimony oxide, zinc oxide, barium carbonate, calcium carbonate, aluminum silicate, silica, magnesium carbonate and / or magnesium silicate, cadmium yellow, cadmium red, carbon black Colored pigments such as, phthalocyanine blue, chrome yellow, toluidine red and hydrated iron oxide can also be used.

The pigment dispersion resin may be stabilized so that the pigment component does not precipitate, and should be charged so that electrophoresis may occur in an electric field. Examples of the pigment dispersion resin mainly used include a polyepoxide-amine resin having a structure similar to that of an electrodeposited main resin, and in order to cover the surface of the pigment having hydrophobic properties to stabilize dispersion in an aqueous medium. It may have some hydrophobic group. Specifically, the pigment dispersion resin may be a primary, secondary, and / or tertiary amine salt-containing polyepoxide-amine resin, quaternary ammonium salt-containing polyepoxide-amine resin, beta hydroxyalkyl carbamate Group-containing polyepoxide-amine resins and the like can be used.

In addition to the pigment component and the resin component for pigment dispersion, the pigment paste may optionally contain components such as wetting agents, surfactants and antifoaming agents.

In addition to the above components, the cationic electrodeposition coating composition of the present invention may further include components that may be generally added to the electrodeposition coating composition, if necessary, such as a sub-resin, a solvent, an antioxidant, a surfactant, and the like. Can be.

Electrodeposition coating using the electrodeposition coating composition of the present invention can be carried out by conventional methods. For example, electrodeposition may be performed by applying the coating composition to the electrical cathode and the anode, respectively, and applying a DC voltage ranging from several V to several hundred V and a current density of 0.25 to 15 A / ft ² . After electrodeposition, it is possible to obtain a finished coating film through a washing process and a curing process, wherein the curing may be performed at a temperature of 150 to 200 ℃ for 15 to 60 minutes.

4. Auto parts

Another embodiment of the present invention relates to an automotive part including a coating layer formed by using the cationic electrodeposition coating composition. In particular, the automotive part may be an automotive part including a coating layer formed on a zirconium pretreatment metal substrate, such as a zirconium pretreatment steel sheet. In addition, the vehicle component may be an automobile body, an automobile bumper, or the like.

Hereinafter, the present invention will be described in more detail with reference to Examples, Comparative Examples and Experimental Examples. These examples, comparative examples and experimental examples are only for illustrating the present invention, it is apparent to those skilled in the art that the scope of the present invention is not limited thereto.

Production Example  1: Preparation of Urethane Curing Agent

A urethane curing agent was prepared according to the method described below with the composition as shown in Table 1 below.

ingredient	Parts by weight
PAPI2940 1)	1318.7
Methyl isobutyl ketone	687.5
Dibutyltin dilaurate	1.0
2- (2-butoxyethoxy) ethanol	1000.5
Trimethylol propane	133.5
2- (2-butoxyethoxy) ethanol	137.2

1) Polymethylene diphenyl diisocyanate commercially available from Dow Chemical Co.

PAPI2940, methyl isobutyl ketone and dibutyltin dilaurate were fed to the reaction flask, and heated to 30 ° C. under a nitrogen atmosphere, then the first portion of 2- (2-butoxyethoxy) was maintained at 60 to 65 ° C. Ethanol was added slowly. When the addition is complete the reaction mixture is left at 65 ° C. for 90 minutes, then trimethylol propane is added and the mixture is heated to 110 ° C. and left at this temperature for 3 hours before the second portion of 2- (2-butoxyethoxy) Ethanol was added. The reaction was continued until no unreacted NCO remained by infrared analysis.

Production Example  2: Dibutyltin Oxide Of paste  Produce

Dibutyl tin oxide paste was prepared according to the method described below with the composition as shown in Table 2 below.

ingredient	Parts by weight
Pigment Dispersion Resin	909.0
Dibutyltin oxide	577.6
Deionized water	1513.4

Pigment dispersion resin (CRQ00143, KCC) was added to the reaction flask and dibutyltin oxide was added while stirring. When the pigment content is high and the viscosity is high, some of the deionized water is gradually added and stirred well until the pigment is uniform, and finally, the remaining amount of deionized water is added and diluted. The resulting mixture was dispersed up to Hegman No. 8 with an SL-50 (BYK) disperser.

Production Example  3: pigment for electrodeposition paint Of paste  Produce

A pigment paste for electrodeposition paint was prepared according to the method described below with the composition as shown in Table 3 below.

ingredient	Weight part
Pigment Dispersion Resin	196.2
Dibutyltin oxide paste of Preparation Example 2	398.0
Carbon black	6
Deionized Water (Primary)	440.0
ASP200 1)	307.3
Titanium dioxide	461.0
Surfynol 104 / BC (50%) 2)	20.8
Deionized Water (Secondary)	170.7

1) Aluminum silicate (BASF)

2) 50% diluent of butyl cellosolve with hexanediol-based wetting agent (Air Products)

The pigment dispersion resin (CRQ00143, KCC) was placed in a reaction flask, and dibutyltin oxide paste, carbon black, deionized water (primary), ASP200, and titanium dioxide of Preparation Example 2 were added thereto while stirring sequentially. . When the pigment content increased and the viscosity increased, the mixture was stirred well until Surfynol104 / BC (50%) was added to homogenize the pigment component, and finally diluted with secondary deionized water. The resulting mixture was dispersed up to Hegman number 8 with an SL-50 disperser.

Example  1: di Ethanolamine  Preparation of Applied Cationic Electrodeposition Resin Compositions

A cationic electrodeposition resin composition was prepared according to the method described below with the composition as shown in Table 4 below.

ingredient	Weight part
EPON 828 1)	133.67
Bisphenol A	54.27
Methoxypropanol	9.36
Benzyldimethylamine	0.53
Ethoxylated BPA 2)	10.8
Urethane Curing Agent of Preparation Example 1	173.93
Diethanolamine	17.76
KT-22 3)	15.73
Solvent vacuum recovery	-39.87
Deionized water	368.44
70% methanesulfonic acid	4.14
Deionized water	251.25

1) Diglycidyl ether of bisphenol A (epoxy equivalent: 188) (Kukdo Chemical)

2) bisphenol A ethoxylate (CECA BELGIUM S.A.)

3) A 73% methyl isobutyl ketone solution of diketamine in which diethylene triamine is capped with methyl isobutyl ketone (Air Products)

EPON828, bisphenol A, ethoxylated BPA and methoxy propanol were fed to a reaction vessel and heated to 140 ° C. under a nitrogen atmosphere. Benzyldimethylamine was added when the reaction was heated to 140 ° C. and the reaction mixture was left for 30 to 60 minutes and then maintained at 145 ° C. until the epoxy equivalent reached 830 to 860. Upon reaching the epoxy equivalent, the urethane curing agent of Preparation Example 1 was added and the reaction mixture was cooled while stirring for 30 minutes. When the temperature of the reactant was 120 ° C. or lower, diethanolamine was added first, followed by reaction for 25 minutes, and KT-22 was continuously added. It was found that the epoxy-amine equivalent of the mixture was 25,000 after 90 minutes of reaction while the mixture was exothermic and the temperature was maintained at 120 ° C. Vacuum was applied to the reaction to remove the organic solvent. The reaction product was then slowly added to and dispersed in a mixture of stirring methanesulfonic acid and first deionized water. Then, the second deionized water was gradually added to the dispersion to further dilute to prepare a cationic electrodeposition resin composition having a solid content of 36% by weight.

Example  2: dimethanol Amine  Preparation of Applied Cationic Electrodeposition Resin Compositions

Cationic electrodeposition resin composition was prepared in the same manner as in Example 1 with the composition as shown in Table 5 below. In the above composition, the reaction mixture was first added with di methanol amine for 30 minutes, followed by the reaction with KT-22 at 120 ° C. for 90 minutes, and the epoxy-amine equivalent weight of the mixture was found to be 25,000.

ingredient	Weight part
EPON 828 1)	133.65
Bisphenol A	55.52
Methoxypropanol	9.57
Benzyldimethylamine	0.55
Ethoxylated BPA 2)	10.80
Urethane Curing Agent of Preparation Example 1	173.93
Dimethanol amine	13.32
KT-22 3)	16.09
Solvent vacuum recovery	-40.36
Deionized water	368.44
70% methanesulfonic acid	4.14
Deionized water	192.08

1) Diglycidyl ether of bisphenol A (epoxy equivalent: 188) (Kukdo Chemical)

2) bisphenol A ethoxylate (CECA BELGIUM S.A.)

3) A 73% methyl isobutyl ketone solution of diketamine in which diethylene triamine is capped with methyl isobutyl ketone (Air Products)

Example  3: N- methyl Ethanolamine  Preparation of Applied Cationic Electrodeposition Resin Compositions

Cationic electrodeposition resin composition was prepared in the same manner as in Example 1 with the composition as shown in Table 6 below. In the above composition, N-methyl ethanolamine was added first, followed by 30 minutes of reaction, followed by KT-22 at 120 ° C for 90 minutes, and the epoxy-amine equivalent of the mixture was found to be 30,000.

ingredient	Weight part
EPON 828 1)	136.97
Bisphenol A	55.61
Methoxypropanol	9.59
Benzyldimethylamine	0.55
Ethoxylated BPA 2)	10.80
Urethane Curing Agent of Preparation Example 1	173.93
N-methyl ethanol amine	13.02
KT-22 3)	16.12
Solvent vacuum recovery	-40.40
Deionized water	368.44
70% methanesulfonic acid	4.14
Deionized water

1) Diglycidyl ether of bisphenol A (epoxy equivalent: 188) (Kukdo Chemical)

2) bisphenol A ethoxylate (CECA BELGIUM S.A.)

3) A 73% methyl isobutyl ketone solution of diketamine in which diethylene triamine is capped with methyl isobutyl ketone (Air Products)

Comparative example  1: di Methylamine  Preparation of Applied Cationic Electrodeposition Resin Compositions

Cationic electrodeposition resin composition was prepared in the same manner as in Example 1 with the composition as shown in Table 7 below. In the above composition, dimethylamine was added first, followed by 30 minutes of reaction, followed by KT-22, followed by reaction at 120 ° C for 90 minutes, and the epoxy-amine equivalent weight of the mixture was found to be 17,000.

ingredient	Weight part
EPON 828 1)	140.46
Bisphenol A	57.03
Methoxypropanol	9.83
Benzyldimethylamine	0.56
Ethoxylated BPA 2)	10.80
Urethane Curing Agent of Preparation Example 1	173.93
Dimethylamine	8.00
KT-22 3)	16.53
Solvent vacuum recovery	-40.15
Deionized water	368.44
70% methanesulfonic acid	4.14
Deionized water	192.08

1) Diglycidyl ether of bisphenol A (epoxy equivalent: 188) (Kukdo Chemical)

2) bisphenol A ethoxylate (CECA BELGIUM S.A.)

3) A 73% methyl isobutyl ketone solution of diketamine in which diethylene triamine is capped with methyl isobutyl ketone (Air Products)

Experimental Example  1: Preparation of Cationic Electrodeposit Coating Composition and Evaluation of Coating Properties

While mixing and stirring 888 parts by weight of the cationic electrodeposition resin composition prepared in Examples 1 to 3 and Comparative Example 1 and 957 parts by weight of deionized water, 155 parts by weight of the pigment paste prepared in Preparation Example 3 was added slowly to obtain a solid content of 20% by weight. A cationic electrodeposition coating composition was prepared. The cationic electrodeposition coating composition was passed through an ultrafilter to an amount of 20% by weight of the initial volume, and the ultrafiltrate was changed to deionized water. Thereafter, the mixture was left to stir for one day, followed by electrodeposition coating at a temperature of 28 ° C. for 3 minutes at a DC voltage of 220V. At this time, zirconium pretreatment steel plate was used, and zinc phosphate pretreatment steel plate and zirconium pretreatment steel plate were used only for corrosion resistance evaluation. The coated workpiece for 3 minutes was cured for 25 minutes at 160 ℃.

The coating film thickness of the cured coating film, specimen coating film deviation, gloss, roughness, internal paintability, and corrosion resistance (corrosion resistance) were measured by the method described below, and the results are shown in Table 8 below.

Coating Thickness: Coating Gauge

Intra-Piece Coating Deviation: Mapping (Using Coating Gauge, Minitest3100, ElektroPhysik)

-Gloss: Polisher (TRI-MICRO, Sheen), 60˚

-Illuminance: illuminometer (Surtronic 3P, Taylor-Hobson), cut off = 0.8㎜

-Internal paintability: 4Box method measurement (G / A surface,%)

Corrosion resistance (rust resistance): ASTM B117, X-cut, 1000 hours, one side mm

division	Coating thickness (μm)	Intra-film coating deviation (㎛)	Glossy (60 °)	Roughness (Ra: Cut off = 0.8mm)	Internal paintability	Corrosion Resistance
						Zinc Phosphate Pretreatment	Non-Phosphate Pretreatment (Zirconium Pretreatment)
Comparative Example 1	25-35	4 ~ 5	86	0.3	15%	1 mm	4 mm
Example 1	18-20	2 ~ 3	88	0.15	45%	1 mm	2.5 mm
Example 2	18-20	1 ~ 2	83	0.14	45%	1 mm	2.5 mm
Example 3	18-20	1 ~ 2	86	0.15	60%	1 mm	2 mm

As shown in the results of Table 8, the cationic electrodeposition coating composition comprising the cationic electrodeposition resin composition of Examples 1 to 3 according to the present invention is applied to the coating film compared to the cationic electrodeposition coating composition comprising the cationic electrodeposition resin composition of Although the thickness of the coating film was reduced, it was confirmed that the coating film deviation phenomenon in the specimen was reduced, thereby ensuring an excellent appearance and securing excellent internal paintability.

In addition, it was found that the rust resistance can be improved by increasing the molecular weight of the polyepoxide resin and the polyol by further chain extension. In particular, it was confirmed that when the cationic electrodeposition coating composition according to the present invention is applied to a non-phosphate-based pretreatment (zirconium pretreatment) steel sheet, corrosion resistance, that is, corrosion resistance can be improved.

Having described the specific part of the present invention in detail, it is apparent to those skilled in the art that this specific technology is only a preferred embodiment, which is not intended to limit the scope of the present invention. Do. Those skilled in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above contents.

Therefore, the substantial scope of the present invention will be defined by the appended claims and equivalents thereof.

Claims (10)

1. In the presence of a polyepoxide-amine resin containing a tertiary amine group, an epoxy-amine equivalent obtained by chain-extending a polyepoxide resin having an epoxy equivalent of 800 to 1,200 and a polyol having a molecular weight of 100 to 500 is from 20,000 to Modified polyepoxide-amine resin for electrodeposition paint of 40,000.
2. The modified polyepoxide-amine resin for electrodeposition paint according to claim 1, wherein the polyepoxide-amine resin serves as a catalyst for the chain extension reaction.
3. The modified polyepoxide-amine resin for electrodeposition paint according to claim 1, wherein the polyepoxide-amine resin is formed by reacting a secondary amine having a primary hydroxyl group with the polyepoxide resin.
4. The modified polyepoxide-amine resin for electrodeposition paint according to claim 1, wherein the polyepoxide-amine resin contains a diketamine group.
5. The modified polyepoxide-amine resin according to claim 4, wherein the polyepoxide-amine resin including the diketimine group is formed by reacting with a secondary amine having a primary hydroxy group, diketimine, and the polyepoxide resin. Epoxide-amine resins.
6. The modified polyepoxide-amine resin according to claim 1, wherein the chain extension reaction temperature is 100 to 120.
7. The method of claim 3, wherein the secondary amine having a primary hydroxyl group is diethanol amine, dimethanol amine, dipropanol amine, ethyl monoethanolamine, mono-n-butyl monoethanolamine, mono-tert-butyl monoethanolamine A modified polyepoxide-amine resin for electrodeposition paints selected from the group consisting of bis (2-hydroxypropyl) amine, mono-n-propyl monoethanolamine and N-methylethanolamine.
8. The cationic resin composition for electrodeposition paints containing the modified polyepoxide-amine resin for electrodeposition paints of any one of Claims 1-7, and a urethane hardening | curing agent.
9. The cationic electrodeposition coating composition containing the cationic resin composition, pigment and deionized water of Claim 8 electrodeposition paint.
10. An automotive part comprising a coating layer formed using the cationic electrodeposition coating composition of claim 9.