KR20140135471A

KR20140135471A - Method for preparing urethane curing agent for electrodeposition paint, a cationic resin composition for electrodeposition paint and an electrodeposition paint composition comprising the same

Info

Publication number: KR20140135471A
Application number: KR1020130055771A
Authority: KR
Inventors: 정하택; 정만용; 고봉성; 김홍렬; 김태호; 황영준
Original assignee: 주식회사 케이씨씨
Priority date: 2013-05-16
Filing date: 2013-05-16
Publication date: 2014-11-26
Also published as: CN105378009B; CN105378009A; KR101858272B1; RU2637029C2; RU2015153429A; WO2014185726A1

Abstract

The present invention relates to a process for producing a urethane curing agent for electrodeposition paints, which comprises reacting a polyisocyanate with one selected from aromatic divalent alcohols, aliphatic divalent alcohols and mixtures thereof, and a cationic resin for electrodeposition paints containing the curing agent The electrodeposition coating composition containing the curing agent according to the present invention is capable of reducing bake off loss of a coating film during baking, has excellent roughness and excellent internal coating property.

Description

TECHNICAL FIELD The present invention relates to a method for producing a urethane curing agent for electrodeposition paints, a cationic electrodeposition resin composition for electrodeposition paints, and an electrodeposition coating composition for electrodeposition coating compositions containing the same. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrodeposition coating composition,

The present invention relates to a process for producing a urethane curing agent for electrodeposition paints, and a cationic electrodeposition coating composition and an electrodeposition coating composition for electrodeposition paints comprising the same, wherein an aromatic divalent alcohol, an aliphatic divalent alcohol or a mixture thereof is added to an isocyanate group A urethane curing agent free of glass isocyanate, and a cationic electrodeposition resin composition and electrodeposition coating composition for electrodeposition paint containing the same.

Electrodeposition coating refers to a technique in which a polymer having a charge under direct current action moves to an electrode having an opposite charge and a change in pH due to decomposition of water in the electrode induces polymer precipitation to form a nonconductive coating film. Such electrodeposition is of increasing importance because it provides higher adhesion efficiency, significant corrosion resistance, and lower environmental contamination than non-electrophoretic means.

Common curing agents for electroplating are 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 to the NCO of the polyisocyanate is 1: 1 or 1.01: 1. Since the blocked curing agent thus prepared has a relatively small molecular structure compared to the main binder of the electrodeposition resin, it is influenced by the external appearance of the electrodeposited coating film, the baking temperature and the rise of the film depending on the content of the curing agent in the electrodeposition resin composition and the molecular weight of the blocking agent .

The electrodeposition coating film is generally baked at 140 to 180 ° C. for 20 to 40 minutes to form a finished coating film. During the baking process, the alcohol which is blocked by the hardening agent dissociates from the polyisocyanate and evaporates, . In addition, when the content of the hardener is increased to lower the firing temperature, there is a problem that the inner coatability is lowered due to the rise of the film rise.

In order to compensate for this, Korean Patent Application No. 10-2009-0027370 discloses a method of reacting a secondary amine having a hydroxy group with a monoepoxy compound to prepare a tertiary amine having a hydroxyl group as a blocking agent and a blocked curing agent The present invention provides a curing agent for a cationic electrodeposition paint that reduces the loss of a coating film in a baking process and improves the internal coating property by the influence of an amine.

Korean Patent Application No. 10-2009-0027370

It is an object of the present invention to provide a process for producing a polyisocyanate by blocking an isocyanate using a polyhydric alcohol such as an aromatic divalent alcohol or an aliphatic divalent alcohol or a mixture thereof and extending a chain of the reaction product to improve internal stiffness, And a cationic electrodeposition resin composition and an electrodeposition coating composition for electrodeposition paint containing the same.

In order to achieve the above object, the present invention provides a process for producing a urethane curing agent for electrodeposition paints, which comprises the step of using any one of aromatic divalent alcohols and aliphatic dihydric alcohols or a mixture thereof as a blocking agent and reacting the polyisocyanate with the polyisocyanate &Lt; / RTI >

According to another aspect of the present invention, there is provided a urethane curing agent prepared according to the present invention; And an amine-modified polyepoxy resin prepared by reacting a polyepoxy resin with an amine are provided.

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 process for producing the urethane curing agent contained in the cationic electrodeposition resin composition for electrodeposition coating includes a step of reacting a polyisocyanate with a blocking agent comprising an aromatic divalent alcohol and an aliphatic divalent alcohol or a mixture thereof.

The blocking agent is a blocking agent for the isocyanate in the curing agent, and aliphatic, aromatic divalent alcohols and monohydric to polyhydric alcohols may all be included in the blocking agent. In the present invention, a blocking agent comprising one selected from aromatic divalent alcohols, aliphatic divalent alcohols and mixtures thereof is used. According to one embodiment of the present invention, the polyisocyanate chain may be elongated by using a dihydric alcohol among the blocking agents used in the urethane curing agent to improve the internal coating property due to the increase in the molecular weight. In addition, It is possible to reduce the loss of the coating film generated during the baking process by using the dihydric alcohol and the aliphatic dihydric alcohol in which the dissociation time difference occurs.

As a typical blocking agent for isocyanate, an aliphatic divalent alcohol having a molecular weight of 60 to 300 and a difference in reactivity of a hydroxyl group can be used. An aromatic 2 having a characteristic of not evaporating at a suitable baking temperature of 140 to 180 캜 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- And aromatic divalent alcohols may be selected from the group consisting of bisphenol A, bisphenol F, ethoxylate bisphenol A and benzene diol, and may be selected from aliphatic dihydric alcohols and aromatic dihydric alcohols May be used in combination.

The polyisocyanate may be an aliphatic or aromatic isocyanate, preferably an aliphatic polyisocyanate selected from the group consisting of tetramethylene diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate and isophorone diisocyanate. Isocyanate; 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, p-phenylene isocyanate, diphenylmethane-4,4'-diisocyanate, polymethylene polyphenyl isocyanate, triphenylmethane- &Quot;-triisocyanate; < / RTI > And a mixture thereof.

According to one embodiment of the present invention, the aromatic divalent alcohol and the polyisocyanate can be reacted at an isocyanate: hydroxyl group equivalent ratio of 1: 0.85 to 1.15 under a temperature of 50 to 100 캜. It is possible to produce a composition having a uniform molecular weight within the range of the temperature and equivalence ratio.

The aromatic divalent alcohol is preferably used in an amount of 30 wt% or less based on the total weight of the above-mentioned blocking agent. If it is used in an amount exceeding 30% by weight, the viscosity of the curing agent increases and it is not easy to handle.

According to another embodiment of the present invention, the aliphatic divalent alcohol and the polyisocyanate can be reacted at an isocyanate: hydroxyl group equivalent ratio of 1: 2 to 1.15 at a temperature of 50 to 100 캜. Gelation of the composition can be prevented within the temperature and equivalence ratio range.

The aliphatic divalent alcohol is preferably used in an amount of 70 wt% or less based on the total weight of the barrier agent. Excessive use of more than 70% by weight may expose the user to the risk of becoming a composition gel. The reaction of the aromatic dihydric alcohol, the aliphatic dihydric alcohol, or the mixture thereof with the polyisocyanate according to the present invention can be terminated at the time when it is confirmed by infrared analysis that no unreacted isocyanate remains in the reactant.

On the other hand, the urethane curing agent according to the present invention can be used in a completely blocked form, that is, in a form in which no free isocyanate is left, in which case it exists as a two-component resin system through a blend with the epoxy main chain. A curing catalyst such as a tin catalyst may be included in the curing agent component. The curing catalyst may be included in the resin or may be contained in the pigment paste according to the usage. Such a curing catalyst is used as an indispensable element for electrodeposition and is a component constituting the electrodeposition coating composition. Examples include dibutyl tin dilaurate and dibutyltin tin oxide, which are preferably present in an amount of about 0.05 to 1% by weight based on the weight of the total resin solids. Here, the weight of the entire resin solid means the solid content of the whole cationic electrodeposition resin containing the urethane curing agent.

In addition, the cationic electrodeposition resin composition according to the present invention comprises the urethane curing agent prepared by the method according to the present invention; And an amine-modified polyepoxy resin 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 resin generally has an epoxy equivalent weight of 180 to 2000, preferably 2 or more 1,2-epoxy groups. Examples of preferred polyepoxy resins include polyglycidyl ether of polyphenol or polyglycidyl ether of aromatic polyol such as bisphenol-A. Such a polyepoxy resin can be produced by an ether reaction of an epihalohydrin such as epichlorohydrin or dichlorohydrin or diepihalohydrin with an aromatic polyol in the presence of an alkali. Another example of the polyepoxy resin is a modified polyepoxy resin derived from, for example, novolac resin or polyphenol resin. On the other hand, by the reaction of the polyglycidyl ether of the aromatic diol and the polyol capable of reacting with the epoxy group, the molecular weight of the polyglycidyl ether of the polyhydric substance can be increased. Examples of the polyol applicable at this time include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol and bisphenol-A.

According to embodiments of the present invention, an aliphatic polyol and a polyepoxy obtained by chain extension of a bisphenol A type polyphenol are used in the production of the main resin, wherein the equivalence ratio of the bisphenol A type polyphenol: polyol is preferably 1 : 0.2 to 10, and more preferably 1: 0.65 to 0.85.

The amine used in the production of the main resin of the present invention is a primary amine or a secondary amine, and may be ketimine or diketimine derived from the reaction of a primary or secondary amine with a ketone, respectively. Amines may be used alone or in combination. Preferred are mono isopropanolamine, 2-amino-1-phenyl-1,3-propanediol, butanolamine, diethylenetriamine, tetraethylenepentamine, diaminotolueneethylenediamine, N-methylethanolamine, And mixtures thereof.

At this time, the equivalent ratio of the polyepoxy resin: amine is 1: 0.6 to 1: 1.2, more preferably 1: 0.7 to 1: 1.15. The stability of the cationic electrodeposition resin can be secured within the equivalence ratio range.

In the cationic electrodeposition resin composition for electrodeposition coating of the present invention, the content of the urethane curing agent is preferably 900 to 1300 parts by weight, and the content of the amine-modified polyepoxy resin is 1000 to 1500 parts by weight. If the content of the curing agent relative to the main resin is less than the above-mentioned amount, there is a problem of deterioration of appearance and pinhole resistance, and when it is relatively large, there is a problem in that it is insufficient in internal permeability.

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

The neutralized acid may be an organic acid such as acetic acid, lactic acid, formic acid, or an inorganic acid such as MSA (methane sulfonic acid) or sulfonic acid. However, the present invention is not limited thereto, and organic acids and inorganic acids of all kinds which can be generally used for the cationic electrodeposition resin can be used. In this case, the content of acid is preferably 20 to 30 molar equivalents (MEQ) based on the solid content of the resin. When the acid molar equivalent is more than 30, the electroconductivity of the electrodeposited coating increases and pinholes can easily be formed on the galvanized steel sheet. Generally, in order to improve the internal elongation, the acid molar equivalent is designed to be high in water dispersion in order to improve the electrophoretic property. However, in the present invention, when the molar equivalent is more than the above range, there is no tendency that the internal elongation is further improved. On the contrary, since the pinhole easily occurs when the galvanized steel plate is coated, the content of acid is 20-30 moles It is preferable to maintain the equivalent. The lower the acid molar equivalent at a level not lowering the stability of the water dispersion resin, the better the lower

The present invention also provides an electrodeposition coating composition comprising a cationic electrodeposition resin composition, 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 the bake off loss of the coating film at the time of baking, has excellent roughness, exhibits high internal coating property, is environmentally friendly, requires excellent quality and reduces the amount of paint consumption Particularly in the case of the < / RTI >

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, these embodiments are provided for the purpose of helping understanding of the present invention, but the present invention is not limited thereto.

Preparation of urethane curing agent

Production Example 1: Preparation of urethane curing agent using aromatic divalent alcohol

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

ingredient Weight portion PAPI2940 ¹ ⁾ 380.8 Methyl isobutyl ketone ² ⁾ 199.4 Dibutyltin laurate ³ ⁾ One 2- (2-butoxyethoxy) ethanol ⁴ ⁾ 298.2 Trimethylolpropane 56 Bisphenol A ⁵⁾ 65.6

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

2) Methylisobutyl ketone: diluting solvent

3) Dibutyltin Laurate: Reaction Catalyst

4) 2- (2-butoxyethoxy) ethanol:

5) Bisphenol A: aromatic divalent alcohol

PAPI2940, methyl isobutyl ketone and dibutyl tin dilaurate were fed to the reaction flask and heated to 30 DEG C under a nitrogen atmosphere. 2- (2-Butoxyethoxy) ethanol was slowly added while maintaining the temperature at 60-65 占 폚. When the addition was complete, the reaction mixture was allowed to stand at 65 DEG C for 90 minutes. Then, trimethylolpropane was added and the mixture was heated to 110 DEG C and left at that temperature for 3 hours, and bisphenol A was added. By infrared analysis, the temperature was kept at 110 DEG C until no unreacted NCO remained.

Production Example 2: Preparation of urethane curing agent using aromatic divalent alcohol

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

ingredient Weight portion PAPI2940 ¹ ⁾ 375.4 Methyl isobutyl ketone 199.4 Dibutyltin laurate One 2- (2-butoxyethoxy) ethanol 330.8 Trimethylolpropane 62.1 Bisphenol A 32.3

Production Example 3: Preparation of urethane curing agent using aliphatic dihydric alcohol

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

ingredient Weight portion PAPI2940 ¹ ⁾ 413 Methyl isobutyl ketone 199.6 Dibutyltin laurate One 2- (2-butoxyethoxy) ethanol 202.2 Trimethylolpropane 38 1,2-hexanediol 147.3

PAPI2940, methyl isobutyl ketone and dibutyl tin dilaurate were fed to the reaction flask and heated to 30 DEG C under a nitrogen atmosphere. 2- (2-Butoxyethoxy) ethanol was slowly added while maintaining the temperature at 60-65 占 폚. When the addition was complete, the reaction mixture was allowed to stand at 65 DEG C for 90 minutes. Trimethylolpropane was then added and the mixture was heated to 110 < 0 > C and left at this temperature for 3 hours and 1,2-hexanediol was added. At this time, the NCO equivalent: 1,2-hexanediol equivalent = 1: 1.6. By infrared analysis, the temperature was kept at 110 DEG C until no unreacted NCO remained.

Production Example 4: Preparation of urethane curing agent using aliphatic dihydric alcohol

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

ingredient Weight portion PAPI2940 ¹ ⁾ 403.7 Methyl isobutyl ketone 199.6 Dibutyltin laurate One 2- (2-butoxyethoxy) ethanol 197.6 Trimethylolpropane 37.1 1,2-hexanediol 161.9

PAPI2940, methyl isobutyl ketone and dibutyl tin dilaurate were fed to the reaction flask and heated to 30 DEG C under a nitrogen atmosphere. 2- (2-Butoxyethoxy) ethanol was slowly added while maintaining the temperature at 60-65 占 폚. When the addition was complete, the reaction mixture was allowed to stand at 65 DEG C for 90 minutes. Trimethylolpropane was then added and the mixture was heated to 110 < 0 > C and left at this temperature for 3 hours and 1,2-hexanediol was added. At this time, the NCO equivalent: 1,2-hexanediol equivalent = 1: 1.8. By infrared analysis, the temperature was kept at 110 DEG C until no unreacted NCO remained.

Production Example 5: Preparation of urethane curing agent using aromatic divalent alcohol and aliphatic divalent alcohol

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

ingredient Weight portion PAPI2940 ¹ ⁾ 409.9 Methyl isobutyl ketone 199.7 Dibutyltin laurate One 2- (2-butoxyethoxy) ethanol 160.5 Trimethylolpropane 30.1 Bisphenol A 35.3 1,2-hexanediol 164.4

PAPI2940, methyl isobutyl ketone and dibutyl tin dilaurate were fed to the reaction flask and heated to 30 DEG C under a nitrogen atmosphere. 2- (2-Butoxyethoxy) ethanol was slowly added while maintaining the temperature at 60-65 占 폚. When the addition was complete, the reaction mixture was allowed to stand at 65 DEG C for 90 minutes. Trimethylolpropane was then added and the mixture was heated to 110 < 0 > C and left at this temperature for 3 hours and bisphenol A was added. The mixture was heated to < RTI ID = 0.0 > 110 C < / RTI > and left at this temperature for 2 hours and 1,2-hexanediol was added. At this time, the NCO equivalent: 1,2-hexanediol equivalent = 1: 1.8 (in this case, the ratio of the second -OH reaction in the aliphatic diol was 11%). Infrared analysis continued until no unreacted NCO remained Gt; 110 C. < / RTI >

Cation for electrodeposition paint Water dispersion Manufacture of resin

Example 1

A cationic electrodeposition resin was prepared from the mixture of the components shown in Table 6 below.

ingredient Weight portion 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 The urethane curing agent of Production Example 1 164.4 KT-22 ⁴⁾ 1194.8 N-methylethanolamine 65.7

1) Epon 828: diglycidyl ether of bisphenol A having an epoxy equivalent of 188, commercially available from Shell Chemicla co.

2) Bisphenol A: aromatic divalent alcohol (chain extender)

3) Methyl isobutyl ketone: diluting solvent

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

Epon 828, bisphenol A-ethylene oxide adduct, bisphenol A and methyl isobutyl ketone were fed to the reaction vessel and heated to 140 ° C under a nitrogen atmosphere. The first portion of benzyldimethylamine was added and the reaction mixture was heated to about 185 < 0 > C and refluxed to azeotropically remove the water present. The reaction mixture was then cooled to 160 DEG C and allowed to stand for 30 minutes, then further cooled to 145 DEG C and a second portion of benzyldimethylamine was added. Lt; RTI ID = 0.0 > 145 C < / RTI > until the epoxy equivalent reached 1100 to 1140. When the epoxy equivalent was reached, the urethane curing agent of Preparation Example 1, KT22, and N-methylethanolamine were added successively. The mixture was allowed to exotherm and then the temperature was cooled to 125 < 0 > C.

A cationic water-dispersible resin for an electrodeposition paint was prepared from the mixture of the components shown in Table 7 below

ingredient Weight portion 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 gradually added to the mixture of formic acid and first deionized water under agitation while thoroughly stirring. Then, the dispersion was further diluted by gradually adding the second, third and fourth amounts of deionized water, and the organic solvent was removed by vacuum stripping to prepare a cationic water-dispersible resin for electrodeposition paint having a solid content of 36%.

Example 2

A cationic water-dispersible resin for electrodeposition paint was prepared in the same manner as in Example 1, using the curing agent of Production Example 2.

Example 3

A cationic water-dispersible resin for an electrodeposition paint was prepared in the same manner as in Example 1, using the curing agent of Production Example 3.

Example 4

A cationic water-dispersible resin for an electrodeposition paint was prepared in the same manner as in Example 1, using the curing agent of Production Example 4.

Example 5

A cationic water-dispersible resin for electrodeposition paint was prepared in the same manner as in Example 1, using the curing agent of Production Example 5.

Comparative Example 1

Urethane curing agents were prepared by using monohydric alcohols and trihydric alcohols, and cationic water - dispersible resins for electrodeposition paints were prepared.

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

ingredient Weight portion PAPI2940 ¹ ⁾ 370.2 Methyl isobutyl ketone 199.3 Dibutyltin dilaurate One 2- (2-butoxyethoxy) ethanol 362.4 Trimethylolpropane 68.1

PAPI2940, methyl isobutyl ketone and dibutyl tin dilaurate were fed to the reaction flask and heated to 30 DEG C under a nitrogen atmosphere. 2- (2-Butoxyethoxy) ethanol was slowly added while maintaining the temperature at 60-65 占 폚. When the addition was complete, the reaction mixture was allowed to stand at 65 DEG C for 90 minutes. Then trimethylolpropane was added and the mixture was heated to 110 < 0 > C and left at this temperature for 3 hours. By infrared analysis, the temperature was kept at 110 DEG C until no unreacted NCO remained.

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

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

1292 parts by weight of the water dispersion resin prepared in each of Examples 1 to 5 and Comparative Example 1, 244 parts by weight of a commercially available pigment paste (ED3000-A) and 1460 parts by weight of deionized water were mixed, 10 and Comparative Example 2, respectively.

Each of the coating compositions prepared above was subjected to electrodeposition coating with a direct current voltage of 150 V to 350 V for 3 minutes at a bath temperature of 28 캜. The painted specimens were cured in an oven for 30 minutes at 170 ° C. A phosphoric acid treated steel sheet was used as the specimen.

Comparative Example 2 Example 6 Example 7 Example 8 Example 9 Example 10 Painting voltage ¹ ⁾ 20 탆 240V 280V 260V 280V 270V 310V 15 탆 170V 200V 170V 200V 210V 230V Roughness (Ra) ² ⁾ 20 탆 0.15 0.22 0.18 0.26 0.19 0.13 15 탆 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 탆 61% 68% 64% 66% 63% 73% 15 탆 45% 61% 58% 62% 55% 71%

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

2) Roughness (Ra): average of 6 measurements, Taylor-Hobson Surtronic 3P (Cut off 0.8mm)

3) Gloss (60 °): 5 measurements, TRI-MICRO GLOSS METER (60 °) from Sheen

4) Bake off loss: weight loss after curing of deposited electrodeposited coating,

Bake off loss = (specimen weight after pre-bake-specimen weight after curing) / (specimen weight after pre-bake-specimen weight before electrodeposition) (※ pre bake condition: 120 ℃, 1hr)

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

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

The ratio (%) of the G-side and the A-side is calculated. (Separate the specimens A to H in the order of close to the plate.

※ How to measure

(1) Prepare a box-shaped specimen with a test plate spacing of 20 mm using four test plates. The size of the test plate is 150 × 70 mm, and the diameter of the HOLE is 45 mm from the test plate and the diameter is 8 mm.

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

③ Dip a box-shaped test plate into the electrodeposition solution by 90 mm, and confirm that the paint completely enters the three spaces divided by the steel sheet, and then perform electrodeposition coating. The standard conditions for the electrodeposition coating are CV 20 μm, 3 minutes, 28 ° C, and the total electrode ratio is 1: 8.

④ After washing with water, bake under standard conditions and measure the coating thickness of the inner and outer sides of the four steel sheets.

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

The foregoing description is merely illustrative of the technical idea of the present invention and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

Claims

A process for producing a urethane curing agent for electrodeposition paints, which comprises reacting a polyisocyanate with a blocking agent comprising an aromatic divalent alcohol and an aliphatic divalent alcohol or a mixture thereof.

The method according to claim 1,
Wherein the aromatic divalent alcohol is one selected from the group consisting of bisphenol A, bisphenol F, ethoxylate bisphenol A, and benzene diol.

The method according to claim 1,
The aliphatic dihydric alcohol may be 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- A method for producing the urethane curing agent for electrodeposition paints.

The method according to claim 1,
The polyisocyanate,
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- &Quot;-triisocyanate;< / RTI > And a mixture thereof. The method for producing a urethane curing agent for electrodeposition paints according to claim 1,

The method according to claim 1,
Wherein the aromatic divalent alcohol and the polyisocyanate are reacted at an equivalent ratio of isocyanate: hydroxyl group of 1: 0.85 to 1.15 at a temperature of 50 to 100 占 폚.

The method according to claim 1,
Wherein the aromatic divalent alcohol is used in an amount of 30 wt% or less based on the total weight of the barrier agent.

The method according to claim 1,
Wherein the aliphatic dihydric alcohol and the polyisocyanate are reacted at an equivalent ratio of isocyanate: hydroxyl group of 1: 2 to 1.15 at a temperature of 50 to 100 占 폚.

The method according to claim 1,
Wherein the aliphatic divalent alcohol is used in an amount of 70% by weight or less based on the total weight of the barrier agent.

A urethane hardener prepared by the process of any one of claims 1 to 8; And
A cationic electrodeposition resin composition for an electrodeposition paint comprising an amine-modified polyepoxy resin prepared by reacting a polyepoxy resin with an amine.

10. The method of claim 9,
Wherein the amine-modified polyepoxy resin is reacted with an equivalent ratio of polyepoxy resin: amine of 1: 0.6 to 1: 1.2.

11. The method of claim 10,
Wherein the amine-modified polyepoxy resin is reacted with an equivalent ratio of polyepoxy resin: amine of 1: 0.7 to 1: 1.15 to prepare a cationic electrodeposition resin composition.

10. The method of claim 9,
Amines include mono isopropanolamine, 2-amino-1-phenyl-1,3-propanediol, butanolamine, diethylenetriamine, tetraethylenepentamine, diaminotoluene ethylenediamine, N-methylethanolamine and mixtures thereof Wherein the cationic electrodeposition resin composition is selected from the group consisting of polyvinyl alcohol and polyvinyl alcohol.

10. The method of claim 9,
Wherein the content of the urethane curing agent in the cationic electrodeposition resin composition for electrodeposition coating is from 900 to 1300 parts by weight and the content of the amine-modified polyepoxy resin is from 1000 to 1500 parts by weight.

An electrodeposition coating composition comprising the cationic electrodeposition resin composition according to claim 9, pigment paste and deionized water.