WO2014185726A1

WO2014185726A1 - Method for preparing urethane hardener for electrodeposition paint, cationic electrodeposition resin composition for electrodeposition paint containing same, and electrodeposition paint composition

Info

Publication number: WO2014185726A1
Application number: PCT/KR2014/004362
Authority: WO
Inventors: 정하택; 정만용; 고봉성; 김홍렬; 김태호; 황영준
Original assignee: 주식회사 케이씨씨
Priority date: 2013-05-16
Filing date: 2014-05-15
Publication date: 2014-11-20
Also published as: CN105378009B; CN105378009A; KR20140135471A; KR101858272B1; RU2637029C2; RU2015153429A

Abstract

The present invention relates to a method for preparing a urethane hardener for electrodeposition paint, the method comprising a step of reacting one selected from aromatic dihydric alcohol, aliphatic dihydric alcohol, and a mixture thereof, and polyisocyanate; to a cationic resin composition containing the hardener for electrodeposition paint, and to an electrodeposition paint composition. The electrodeposition paint composition containing the hardener according to the present invention can reduce the bake off loss at the time of baking and have excellent surface roughness and interior paintability.

Description

Method for producing urethane curing agent for electrodeposition paint, cationic electrodeposition resin composition and electrodeposition paint composition for electrodeposition paint comprising the same

The present invention relates to a method for preparing a urethane curing agent for electrodeposition paint, and a cationic electrodeposition resin composition and electrodeposition paint composition for electrodeposition paint comprising the same, wherein an aromatic dihydric alcohol, an aliphatic dihydric alcohol or a mixture thereof is a polyisocyanate group. The present invention relates to a urethane curing agent free of free isocyanate, and a cationic electrodeposition resin composition and electrodeposition coating composition for electrodeposition paint comprising the same.

Electrodeposition coating refers to a technique in which a polymer having an electric charge moves to an electrode of opposite charge under a direct current, and a change in pH caused by decomposition of water at the electrode causes polymer precipitation to form a non-conductive coating film. The importance of these electrodeposition methods is increasing because they provide higher adhesion efficiency, significant corrosion resistance, and lower environmental pollution than non-electrophoretic means.

A general curing agent for electrodeposition resins is prepared by blocking polyisocyanates using monohydric alcohols and polyhydric alcohols as blocking agents. At this time, the equivalent ratio of the hydroxyl group of the alcohol and the NCO of the polyisocyanate is 1: 1 or 1.01: 1. Thus, the blocked curing agent has a smaller molecular structure compared to the main binder of the electrodeposition resin, and thus affects the appearance, baking temperature, and coating riseability of the electrodeposition coating film depending on the content of the curing agent in the electrodeposition resin composition and the molecular weight of the blocking agent. Gives.

Electrodeposited coatings generally form a finished coating after baking for 20 to 40 minutes at 140 ° C to 180 ° C. Alcohols blocked by the curing agent during the baking process dissociate from the polyisocyanate and evaporate to prevent loss of the coating during baking. Generate. In addition, when the content of the curing agent is increased in order to lower the baking temperature, there is a problem in that the internal coating property decreases due to the increase in coating film riseability.

In order to compensate for this, Korean Patent Application No. 10-2009-0027370 discloses a method of preparing a tertiary amine containing a hydroxyl group as a blocking agent by reacting a secondary amine having a hydroxyl group with a mono epoxy compound and a curing agent blocked therefrom. By reducing the loss of the coating film in the baking process, and describes the curing agent for the cationic electrodeposition paint to improve the internal coating property under the influence of the amine, there is a disadvantage that the baking temperature rises.

[Technical Document] Korean Patent Application No. 10-2009-0027370

An object of the present invention is to block the isocyanate using an aromatic dihydric alcohol, an aliphatic dihydric alcohol, or a mixture thereof, and to improve the internal coating property by increasing the molecular weight and to reduce the loss of the coating in the baking process by blocking the isocyanate. It is to provide a urethane curing agent for electrodeposition paint that can be reduced, and a cationic electrodeposition resin composition and electrodeposition paint composition for electrodeposition paint comprising the same.

In order to achieve the above object, the present invention uses an aromatic dihydric alcohol and an aliphatic dihydric alcohol or a mixture thereof as a blocking agent, the production of a polyurethane curing agent for electrodeposition paint comprising the step of reacting a polyisocyanate thereto Provide a method.

According to another aspect of the present invention, a urethane curing agent prepared according to the present invention; And it provides a cationic electrodeposition resin composition for electrodeposition paint comprising an amine-modified polyepoxy resin prepared by reacting a polyepoxy resin and an amine.

According to another aspect of the present invention, there is provided an electrodeposition coating composition comprising a cationic electrodeposition resin composition, a pigment paste and deionized water according to the present invention.

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

The method for preparing a urethane curing agent included in a cationic electrodeposition resin composition for electrodeposition paint includes reacting a polyisocyanate with a blocking agent including any one or a mixture of aromatic dihydric alcohols and aliphatic dihydric alcohols.

The blocker is a blocker for isocyanates in the curing agent and aliphatic, aromatic dihydric alcohols and mono-polyhydric alcohols may be included in the blocker. In the present invention, a blocking agent comprising one selected from aromatic dihydric alcohols, aliphatic dihydric alcohols and mixtures thereof is used. According to one embodiment of the present invention, by extending the polyisocyanate by using a dihydric alcohol of the blocking agent used in the urethane curing agent can be expected to improve the internal paintability according to the molecular weight increase, aromatics that do not evaporate even when dissociated during the baking process By using a dihydric alcohol and an aliphatic dihydric alcohol having a dissociation time point, it is possible to reduce the loss of the coating film generated during the baking process.

As a typical blocking agent for isocyanates, aliphatic dihydric alcohols having a molecular weight of 60 to 300 and having different reactivity of hydroxy groups can be used, and aromatic 2 is characterized by not evaporating at an appropriate baking temperature of 140-180 ° C. Alcohol can be used. Preferably, the aliphatic dihydric alcohol is selected from the group consisting of ethylene glycol, 1,2-propylene glycol, 1,4-propylene glycol, 1,5-pentanediol, 1,2-butanediol and 1,2-hexanediol Aromatic dihydric alcohol may be used, one selected from the group consisting of bisphenol A, bisphenol F, ethoxylate bisphenol A and benzene diol, and selected from aliphatic dihydric alcohol and aromatic dihydric alcohol You may use combining two or more of them.

The polyisocyanate may use aliphatic or aromatic isocyanate, preferably an aliphatic poly selected from the group consisting of tetramethylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate and isophorone diisocyanate Isocyanates; 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylene isocyanate, diphenylmethane-4,4'-diisocyanate, polymethylene polyphenyl isocyanate, triphenylmethane-4,4 ', 4 Aromatic polyisocyanates selected from the group consisting of '' -triisocyanates; And one selected from the group consisting of a mixture thereof.

According to one embodiment of the present invention, the aromatic dihydric alcohol and the polyisocyanate can be reacted with an equivalent ratio of isocyanate: hydroxy group of 1: 0.85 to 1.15 at a temperature of 50 to 100 ° C. There is an effect that can produce a composition having a uniform molecular weight within the above temperature and equivalent ratio range.

In addition, the aromatic dihydric alcohol is preferably used at 30% by weight or less based on the total weight of the blocking agent. When used in excess of 30% by weight has a disadvantage that the viscosity of the curing agent is increased and not easy to handle.

According to another embodiment of the present invention, the aliphatic dihydric alcohol and the polyisocyanate can be reacted with an equivalent ratio of isocyanate: hydroxy group of 1: 2 to 1.15 at a temperature of 50 to 100 ° C. Within the above temperature and equivalent ratio range, gelation of the composition can be prevented.

In addition, the aliphatic dihydric alcohol is preferably used at 70% by weight or less based on the total weight of the blocking agent. Use in excess of 70% by weight exposes you to the risk of becoming a composition gel. The reaction of the polyisocyanate with the aromatic dihydric alcohol, aliphatic dihydric alcohol or a mixture thereof and the polyisocyanate according to the present invention may be terminated at the time point confirmed by the infrared analysis that no unreacted isocyanate remains in the reaction.

On the other hand, the urethane curing agent according to the present invention can be used in a completely blocked form, i.e., in a form in which free isocyanate remains, in which case it is present as a two-component resin system through a blend with an epoxy main chain. The curing agent component may usually include a curing catalyst such as tin catalyst. In addition, the curing catalyst may be included in the resin or pigment part (Pigment paste) depending on the usage. Such a curing catalyst is essential to electrodeposition and is one component constituting the electrodeposition coating composition. Examples include dibutyl tin dilauryl acid and dibutyl tin oxide, and they are preferably present in a tin component in an amount of about 0.05 to 1% by weight based on the weight of the total resin solids. Here, the weight of all the resin solids means the solid content of the whole cationic electrodeposition resin containing the urethane hardening | curing agent.

In addition, the cationic electrodeposition resin composition according to the present invention is a urethane curing agent prepared by the method according to the present invention; And amine modified polyepoxy resins prepared by reacting a polyepoxy resin with an amine.

The main resin contained in the cationic electrodeposition resin composition of the present invention is an amine-modified polyepoxy resin prepared by reacting a polyepoxy resin with an amine.

The polyepoxy resins usually have an epoxy equivalent of 180 to 2000, and preferably have two or more 1,2-epoxy groups. Examples of preferred polyepoxy resins include polyglycidyl ethers of polyphenols or polyglycidyl ethers of aromatic polyols such as bisphenol-A. Such polyepoxy resins can be prepared by ether reaction of epihalohydrin or diepihalohydrin such as epichlorohydrin or dichlorohydrin with an aromatic polyol in the presence of alkali. Another example of the polyepoxy resin is a modified polyepoxy resin derived from, for example, a noblock resin or a polyphenol resin. On the other hand, by the reaction of the polyglycidyl ether of the aromatic diol with the polyol capable of reacting with the epoxy group, the molecular weight of the polyglycidyl ether of the polyhydric material can be increased. Examples of the applicable polyol include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, bisphenol-A, and the like.

According to an embodiment of the invention, polyepoxys obtained by chain extension with aliphatic polyols and bisphenol A type polyphenols are used for the preparation of the main resin, wherein the equivalent ratio of polyphenol: polyols of bisphenol A type is preferably 1 : 0.2 to 10, more preferably 1: 0.65 to 0.85.

The amines used in the production of the main resin of the present invention are primary amines or secondary amines, and may be ketimine or diketimine derived from the reaction of primary or secondary amines and ketones, respectively. The amines may be used alone or in combination. Preferably monoisopropanolamine, 2-amino-1-phenyl-1,3-propanediol, butanolamine, diethylenetriamine, tetraethylenepentaamine, diaminotoluene ethylenediamine, N-methyl ethanol amine and their What is chosen from the group which consists of a mixture can be used.

In this case, the equivalent ratio of polyepoxy resin: amine is 1: 0.6 to 1: 1.2, more preferably 1: 0.7 to 1: 1.15. Stability of the cationic electrodeposition resin within the equivalent ratio range can be ensured.

The cationic electrodeposition resin composition for electrodeposition paint of the present invention is preferably 900 to 1300 parts by weight of the urethane curing agent, and 1000 to 1500 parts by weight of the amine-modified polyepoxy resin. If the content of the hardener for the main resin is relatively less than the above amount, there is a problem of deterioration in appearance and pinhole resistance, and if there is a relatively large amount, there is a problem vulnerable to internal permeability.

Deionized water and neutralized acid are added to the cationic electrodeposition resin composition for electrodeposition paint to prepare a cationic water-dispersible electrodeposition resin for electrodeposition paint.

As the neutralized acid, organic acids such as acetic acid, lactic acid, formic acid, and inorganic acids such as methane sulfonic acid and sulfonic acid may be used. However, the present invention is not limited thereto, and in general, all kinds of organic acids and inorganic acids that may be used in the cationic electrodeposition resin may be used. At this time, the acid content is 20 to 30 molar equivalents (mole equivalent, MEQ) is appropriate based on the resin solid content. When the acid molar equivalent is more than 30, the conductivity of electrodeposition paint is increased, so that pinholes may easily occur when coating galvanized steel sheet. In general, in order to improve the internal coating property, the acid molar equivalent when dispersing is designed to improve the electrophoresis. However, in the present invention, when the acid molar equivalent exceeds the above range, the internal coating property does not tend to be significantly improved. Rather, since the pinholes are easily generated when the galvanized steel sheet is coated, the acid content is 20 to 30 moles based on the resin solids. It is desirable to maintain the equivalent. The lower the acid molar equivalent, the better the lower the stability of the water-disperse resin.

The present invention also provides an electrodeposition coating composition comprising a cationic electrodeposition resin composition, a pigment paste and deionized water according to the present invention. The pigment paste used in the present invention is not particularly limited as long as it is commonly used in cationic electrodeposition paints.

The electrodeposition coating composition to which the urethane curing agent according to the present invention is applied can reduce bake off loss, and have excellent roughness and exhibit high internal paintability, which is environmentally friendly, and requires excellent quality and reduced paint consumption. It can be used especially suitably where it is.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, these examples are only to aid the understanding of the present invention, and the present invention is not limited thereto.

Preparation of Urethane Curing Agent

Preparation Example 1 Preparation of Urethane Curing Agent Using Aromatic Dihydric Alcohol

A urethane curing agent was prepared from the mixture of ingredients shown in Table 1 below.

Table 1

ingredient	Parts by weight
PAPI2940 ¹⁾	380.8
Methyl isobutyl ketone ²⁾	199.4
Dibutyltin laurate ³⁾	One
2- (2-butoxyethoxy) ethanol ⁴⁾	298.2
Trimethylol propane	56
Bisphenol A ⁵⁾	65.6

1) PAPI2940: Polymeric methylene diphenyl polyisocyanate commercially available from Dow Chemical Co.

2) methyl isobutyl ketone: diluent

3) dibutyltin laurate: reaction catalyst

4) 2- (2-butoxyethoxy) ethanol: blocker

5) bisphenol A: aromatic dihydric alcohol

PAPI2940, methyl isobutyl ketone and dibutyltin dilaurate were fed to the reaction flask and heated to 30 ° C. under a nitrogen atmosphere. 2- (2-butoxyethoxy) ethanol was added slowly while maintaining the temperature at 60-65 ° C. When the addition was complete the reaction mixture was left at 65 ° C. for 90 minutes. Trimethylol propane was then added and the mixture heated to 110 ° C. and left at this temperature for 3 hours and bisphenol A was added. Infrared analysis was continued at 110 ° C. until no unreacted NCO remained.

Preparation Example 2 Preparation of Urethane Curing Agent Using Aromatic Dihydric Alcohol

A urethane curing agent was prepared from the mixture of ingredients shown in Table 2 below.

TABLE 2

ingredient	Parts by weight
PAPI2940 ¹⁾	375.4
Methyl isobutyl ketone	199.4
Dibutyltin laurate	One
2- (2-butoxyethoxy) ethanol	330.8
Trimethylol propane	62.1
Bisphenol A	32.3

PAPI2940, methyl isobutyl ketone and dibutyltin dilaurate were fed to the reaction flask and heated to 30 ° C. under a nitrogen atmosphere. 2- (2-butoxyethoxy) ethanol was added slowly while maintaining the temperature at 60-65 ° C. After the addition was complete, the reaction mixture was left at 65 ° C. for 90 minutes. Trimethylol propane was then added and the mixture heated to 110 ° C. and left at this temperature for 3 hours and bisphenol A was added. Infrared analysis was continued at 110 ° C. until no unreacted NCO remained.

Preparation Example 3 Preparation of Urethane Curing Agent Using Aliphatic Dihydric Alcohol

A urethane curing agent was prepared from the mixture of ingredients shown in Table 3 below.

TABLE 3

ingredient	Parts by weight
PAPI2940 ¹⁾	413
Methyl isobutyl ketone	199.6
Dibutyltin laurate	One
2- (2-butoxyethoxy) ethanol	202.2
Trimethylol propane	38
1,2-hexanediol	147.3

PAPI2940, methyl isobutyl ketone and dibutyltin dilaurate were fed to the reaction flask and heated to 30 ° C. under a nitrogen atmosphere. 2- (2-butoxyethoxy) ethanol was added slowly while maintaining the temperature at 60-65 ° C. When the addition was complete the reaction mixture was left at 65 ° C. for 90 minutes. Trimethylol propane was then added and the mixture heated to 110 ° C. and left at this temperature for 3 hours and 1,2-hexanediol was added. At this time, the NCO equivalent weight: 1,2-hexanediol equivalent = 1: 1.6. Infrared analysis was continued at 110 ° C. until no unreacted NCO remained.

Preparation Example 4 Preparation of Urethane Curing Agent Using Aliphatic Dihydric Alcohol

A urethane curing agent was prepared from the mixture of ingredients shown in Table 4 below.

Table 4

ingredient	Parts by weight
PAPI2940 ¹⁾	403.7
Methyl isobutyl ketone	199.6
Dibutyltin laurate	One
2- (2-butoxyethoxy) ethanol	197.6
Trimethylol propane	37.1
1,2-hexanediol	161.9

PAPI2940, methyl isobutyl ketone and dibutyltin dilaurate were fed to the reaction flask and heated to 30 ° C. under a nitrogen atmosphere. 2- (2-butoxyethoxy) ethanol was added slowly while maintaining the temperature at 60-65 ° C. After the addition was complete, the reaction mixture was left at 65 ° C. for 90 minutes. Trimethylol propane was then added and the mixture heated to 110 ° C. and left at this temperature for 3 hours and 1,2-hexanediol was added. At this time, the NCO equivalent weight: 1,2-hexanediol equivalent weight was 1: 1.8. Infrared analysis was continued at 110 ° C. until no unreacted NCO remained.

Preparation Example 5 Preparation of Urethane Curing Agent Using Aromatic Dihydric Alcohol and Aliphatic Dihydric Alcohol

A urethane curing agent was prepared from the mixture of ingredients shown in Table 5 below.

Table 5

ingredient	Parts by weight
PAPI2940 ¹⁾	409.9
Methyl isobutyl ketone	199.7
Dibutyltin laurate	One
2- (2-butoxyethoxy) ethanol	160.5
Trimethylol propane	30.1
Bisphenol A	35.3
1,2-hexanediol	164.4

PAPI2940, methyl isobutyl ketone and dibutyltin dilaurate were fed to the reaction flask and heated to 30 ° C. under a nitrogen atmosphere. 2- (2-butoxyethoxy) ethanol was added slowly while maintaining the temperature at 60-65 ° C. After the addition was complete, the reaction mixture was left at 65 ° C. for 90 minutes. Trimethylol propane was then added and the mixture heated to 110 ° C. and left at this temperature for 3 hours and bisphenol A was added. The mixture was heated to 110 ° C. and then left at this temperature for 2 hours and 1,2-hexanediol was added. At this time, NCO equivalent: 1,2-hexanediol equivalent = 1: 1.8 (The second -OH reaction rate in Aliphatic diol was 11%.) Continued until no unreacted NCO remained by infrared analysis. It was kept at 110 ° C.

Preparation of Cationic Water Dispersion Resin for Electrodeposit Coating

Example 1

Cationic electrodeposition resins were prepared from mixtures of the components shown in Table 6 below.

Table 6

ingredient	Parts by weight
EPON 828 ¹⁾	680.9
Bisphenol A-ethylene oxide adduct (1: 6 molar ratio)	249.9
Bisphenol A ²⁾	199.2
Methyl isobutyl ketone ³ )	59.1
Benzyldimethylamine (1 ^st )	One
^{Benzyldimethylamine} (2 ^nd )	2.7
Urethane Curing Agent of Preparation Example 1	164.4
KT-22 ⁴⁾	1194.8
N-methyl ethanol amine	65.7

1) EPON 828: Diglycidyl ether of bisphenol A with epoxy equivalent 188, commercially available from Shell Chemicla co.

2) bisphenol A: aromatic dihydric alcohol (chain extender)

3) methyl isobutyl ketone: diluent

4) KT-22: A 73% solution in which diethylenetriamine is diketimine capped by methyl isobutyl ketone as a product of Air Product, dissolved in methyl isobutyl ketone.

EPON 828, bisphenol A-ethylene oxide adduct, bisphenol A and methyl isobutyl ketone were fed to a reaction vessel and heated to 140 ° C. under a nitrogen atmosphere. The first portion of benzyldimethylamine was added and the reaction mixture was exothermic to about 185 ° C. and refluxed to remove azeotropic water. The reaction mixture was then cooled to 160 ° C. and left for 30 minutes, then further cooled to 145 ° C. and a second portion of benzyldimethylamine was added. The temperature was maintained at 145 ° C. until the epoxy equivalent reached 1100-1140. When the said epoxy equivalent was reached, the urethane hardening | curing agent of manufacture example 1, KT22, and N-methyl ethanolamine were added continuously. The mixture was exothermic and then cooled to 125 ° C.

The cationic water-dispersion resin for electrodeposition paint was prepared from the mixture of the components shown in Table 7 below.

TABLE 7

ingredient	Parts by weight
Cationic electrodeposition resin	2528.8
Deionized Water (1 ^st )	11.37
85% formic acid	68.33
Deionized Water (2 ^nd )	1407.3
Deionized Water (3 ^rd )	1866.7
Deionized Water (4 ^th )	244.5

The cationic electrodeposition resin synthesized above was slowly added to the mixture of stirring formic acid and the first deionized water with sufficient stirring to disperse. Subsequently, second, third and fourth portions of deionized water were gradually added to the dispersion to further dilute, and the organic solvent was removed by vacuum stripping to prepare a cationic water dispersion resin for electrodeposition paint having a solid content of 36%.

Example 2

The cationic water-dispersion resin for electrodeposition paint was prepared in the same manner as in Example 1 using the curing agent of Preparation Example 2.

Example 3

Cationic water-dispersion resin for electrodeposition paint was prepared in the same manner as in Example 1 using the curing agent of Preparation Example 3.

Example 4

Cationic water-dispersion resin for electrodeposition paint was prepared in the same manner as in Example 1 using the curing agent of Preparation Example 4.

Example 5

Cationic water-dispersion resin for electrodeposition paint was prepared in the same manner as in Example 1 using the curing agent of Preparation Example 5.

Comparative Example 1

A urethane curing agent was prepared using monohydric alcohol and trihydric alcohol, and a cationic water dispersion resin for electrodeposition paint was prepared using the same.

A urethane curing agent was prepared from the mixture of ingredients shown in Table 8 below.

Table 8

ingredient	Parts by weight
PAPI2940 ¹⁾	370.2
Methyl isobutyl ketone	199.3
Dibutyltin dilaurate	One
2- (2-butoxyethoxy) ethanol	362.4
Trimethylol propane	68.1

PAPI2940, methyl isobutyl ketone and dibutyltin dilaurate were fed to the reaction flask and heated to 30 ° C. under a nitrogen atmosphere. 2- (2-butoxyethoxy) ethanol was added slowly while maintaining the temperature at 60-65 ° C. After the addition was complete, the reaction mixture was left at 65 ° C. for 90 minutes. Trimethylol propane was then added and the mixture heated to 110 ° C. and left at this temperature for 3 hours. Infrared analysis was continued at 110 ° C. until no unreacted NCO remained.

Thereafter, a cationic water-dispersible resin for electrodeposition paint was prepared in the same manner as in Example 1 using the urethane curing agent of Comparative Example 1.

Examples 6 to 10 and Comparative Example 2: Preparation of Electrodeposit Coating Composition

1292 parts by weight of the aqueous dispersion resin prepared in Examples 1 to 5 and Comparative Example 1, 244 parts by weight of the pigment paste (ED3000-A) commercially available from KC Co., and 1460 parts by weight of deionized water were mixed. Cationic electrodeposition coating compositions of 10 and Comparative Example 2 were prepared, respectively.

Each of the coating compositions prepared above was subjected to electrodeposition coating at a direct current voltage of 150V to 350V for 3 minutes at a bath temperature of 28 ° C. The coated specimen was cured for 30 minutes at 170 ° C. in an oven oven. In this case, a phosphate treated steel sheet was used.

Table 9

		Comparative Example 2	Example 6	Example 7	Example 8	Example 9	Example 10
Coating voltage ¹⁾	20 ㎛	240 V	280 V	260 V	280 V	270 V	310 V
Coating voltage ¹⁾	15 μm	170 V	200 V	170 V	200 V	210 V	230 V
Roughness (Ra) ²⁾	20 ㎛	0.15	0.22	0.18	0.26	0.19	0.13
Roughness (Ra) ²⁾	15 μm	0.18	0.25	0.19	0.29	0.2	0.15
Gloss (60 ^o ) ³⁾		82	82	83	46	57	88
Bake off loss ⁴⁾		9.8	7.2	7.5	6.8	7.3	5.5
Solvent resistance ⁵⁾		○	○	○	○	○	○
T / P (4BOX) ⁶⁾	20 ㎛	61%	68%	64%	66%	63%	73%
T / P (4BOX) ⁶⁾	15 μm	45%	61%	58%	62%	55%	71%

1) Coating voltage: DC voltage required to deposit 20㎛, 15㎛ coating film on steel sheet

2) Roughness (Ra): 6 measurement averages, Taylor-Hobson Surtronic 3P (Cut off 0.8mm)

3) Gloss (60 ㅀ): 5 measurement averages, Sheen TRI-MICRO GLOSS METER (60 ㅀ)

4) Bake off loss: The amount of weight loss after curing the deposited electrodeposited film,

Bake off loss = (Weight of specimen after pre-baking-Weight of specimen after hardening) / (Weight of specimen after pre-baking-Weight of specimen before electrodeposition coating) (※ pre bake condition: 120 ℃, 1hr)

5) Solvent resistance: The dry film change was confirmed by reciprocating 10 times under a load of 1 kg with a cloth immersed in MIBK.

6) T / P (Throwing power): 4-BOX method test device (Nagoya method, 20 × 10 × 25㎝)

Calculate the ratio (%) between the G side and the A side. (Sort specimens from A to H in the order nearest to the plate.

※ How to measure

① Using four test plates, prepare box-shaped test pieces with a test plate spacing of 20 mm. The test plate shall be 150 × 70 mm and the HOLE shall be 8 mm in diameter at a height of 45 mm of the test plate.

② 4 test plates shall be fixed with adhesive tape such as GUM TAPE and the side and bottom of the box formed of 4 sheets of steel shall be completely sealed with tape.

③ Dip a box-shaped test plate into electrodeposition solution by 90mm and apply electrodeposition coating after confirming that paint is completely entered into 3 spaces divided by steel sheet. Standard conditions for electrodeposition coating were CV 20㎛, 3 minutes, 28 ℃ and electrode ratio 1: 8.

④ After washing with water, make BAKING under standard condition and measure the thickness of coating on each side of 4 sheet steel.

As can be seen in Table 9, the coating composition prepared according to the present invention is excellent in roughness, low bake off loss, and exhibits high internal coating (T / P).

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and variations without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

Claims

A method for producing a urethane curing agent for electrodeposition paint, comprising reacting a polyisocyanate with a blocking agent comprising any one or a mixture of aromatic dihydric alcohols and aliphatic dihydric alcohols.
The method of claim 1,

The aromatic dihydric alcohol is a method selected from the group consisting of bisphenol A, bisphenol F, ethoxylate bisphenol A, and benzene diol.
The method of claim 1,

The aliphatic dihydric alcohol is one selected from the group consisting of ethylene glycol, 1,2-propylene glycol, 1,4-propylene glycol, 1,5-pentanediol, 1,2-butanediol and 1,2-hexanediol The manufacturing method of the urethane hardening | curing agent for electrodeposition paint.
The method of claim 1,

The polyisocyanate is,

Aliphatic polyisocyanates selected from the group consisting of tetramethylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate and isophorone diisocyanate; 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylene isocyanate, diphenylmethane-4,4'-diisocyanate, polymethylene polyphenyl isocyanate, triphenylmethane-4,4 ', 4 Aromatic polyisocyanates selected from the group consisting of '' -triisocyanates; And it is one selected from the group which consists of a mixture of these, The manufacturing method of the urethane hardening | curing agent for electrodeposition paint characterized by the above-mentioned.
The method of claim 1,

The aromatic dihydric alcohol and the polyisocyanate are reacted with an equivalent ratio of isocyanate: hydroxy group of 1: 0.85 to 1.15 at a temperature of 50 to 100 ° C. The urethane curing agent for electrodeposition paint.
The method of claim 1,

The aromatic dihydric alcohol is a method for producing a polyurethane curing agent for electrodeposition paint, characterized in that used in less than 30% by weight based on the total weight of the blocking agent.
The method of claim 1,

The aliphatic dihydric alcohol and the polyisocyanate are reacted with an equivalent ratio of isocyanate: hydroxy group of 1: 2 to 1.15 at a temperature of 50 to 100 ° C.
The method of claim 1,

The aliphatic dihydric alcohol is a method for producing a polyurethane curing agent for electrodeposition paint, characterized in that used in less than 70% by weight based on the total weight of the blocking agent.
A urethane curing agent prepared by the method of any one of claims 1 to 8; And

A cationic electrodeposition resin composition for electrodeposition paint comprising an amine-modified polyepoxy resin prepared by reacting a polyepoxy resin with an amine.
The method of claim 9,

The amine-modified polyepoxy resin is prepared by reacting a polyepoxy resin: amine equivalent ratio of 1: 0.6 to 1: 1.2, the cationic electrodeposition resin composition for electrodeposition paint.
The method of claim 10,

The amine-modified polyepoxy resin is prepared by reacting an equivalent ratio of polyepoxy resin: amine at 1: 0.7 to 1: 1.15, wherein the cationic electrodeposition resin composition for electrodeposition paint is prepared.
The method of claim 9,

The amines are monoisopropanolamine, 2-amino-1-phenyl-1,3-propanediol, butanolamine, diethylenetriamine, tetraethylenepentaamine, diaminotoluene ethylenediamine, N-methyl ethanol amine and mixtures thereof Cationic electrodeposition resin composition for electrodeposition paint, characterized in that selected from the group consisting of.
The method of claim 9,

The amount of the urethane hardener in the cationic electrodeposition resin composition for electrodeposition paint is 900 to 1300 parts by weight, the content of the amine-modified polyepoxy resin is 1000 to 1500 parts by weight of the cationic electrodeposition resin composition for electrodeposition paint.
An electrodeposition coating composition comprising the cationic electrodeposition resin composition according to claim 9, a pigment paste and deionized water.