KR20080104809A - A cationic resin composition for electrodepositable coating and an electrodepositable coating composition comprising the same - Google Patents

Abstract

A cation resin composition for an electrodeposition paint, and an electrodeposition paint composition containing the resin composition are provided to make the content of a solvent to be uniform and to improve the appearance and pin-hole resistance of a coating. A cation resin composition comprises a base (main resin) which is prepared by hydrolyzing the polymer obtained by reacting ketimine to a polyepoxy resin so as to produce a primary amine, and reacting the produced primary amine with a monoepoxy; and a curing agent which contains a blocked polyisocyanate. Preferably the polyepoxy resin is a polyepoxy resin obtained by extending the chain with an aliphatic polyol and a bisphenol A type polyphenol.

Description

Cationic resin composition for electrodeposition paint and electrodeposition paint composition containing same TECHNICAL FIELD [0001] ACCATION RESIN COMPOSITION FOR ELECTRODEPOSITABLE COATING AND AN ELECTRODEPOSITABLE COATING COMPOSITION COMPRISING THE SAME

The present invention relates to a cationic resin composition for electrodeposition paint and an electrodeposition paint composition comprising the same, wherein (i) a polymer obtained by reacting ketimine with a polyepoxy resin, followed by hydrolysis, A cationic resin composition for electrodeposition paint comprising a main resin obtained by reacting an amine with monoepoxy, and (ii) a curing agent comprising a blocked polyisocyanate, and an electrodeposition coating composition comprising the same.

In general, cationic electrodeposition is the introduction of quaternary ammonium salts or sulfonium salts, which can carry a positive charge, and they move toward the cathode in a solution with an electric field, and at the same time, they are positively charged with hydroxy anions generated by electrolysis of water. Resin is precipitated as it is reduced again, and they are referred to as being coated on the negative electrode, i.

In general, a polyepoxy-amine reaction product is used to cationic the electrodeposited resin, and as the amine, ketimine or diketimine may be used. Use of ketamine has the effect of improving the dispersibility of the resin and facilitating pH adjustment to improve dispersion stability. In addition, it is effective in improving the internal permeability (Throwing Power) of the electrodeposition paint according to the conductivity. However, ketones and primary amines are generated through hydrolysis reaction between ketamine and water in the process of water dispersion resin synthesis as the amount of ketamine used increases, and the ketones generated at this time are unintentional solvents in the cationic electrodeposition coating bath Can act as an ingredient. In addition, the generated primary amines cause urea reactions with the curing agent during baking or curing, leading to problems of deterioration of the appearance of the coating film and generation of pinholes in the galvanyl specimen.

Korean Patent Laid-Open Publication No. 2002-0084272 provides a coating having little pinholes when coating a galvanized surface with a composition containing at least one sulfonamide of 0.1 to 5% by weight based on the solid resin content of the coating composition. The electrodeposition coating composition is described. In US Pat. No. 3,947,333, polyketimine derivatives of polyamines such as diethylenetriamine or triethylenetetraamine are reacted with polyepoxy. The reaction product is neutralized with acid and dispersed in water to form primary amine groups. The equivalent product is also produced when the polyepoxy is reacted with excess polyamines such as diethylenetriamine and triethylenetetraamine, and vacuum stripping of the excess polyamine from this reaction mixture. Such products are described in US Pat. Nos. 3,663,389 and 4,116,900.

Electrodeposition should be carried out at high electrodeposition voltages in order to expect the best internal permeability (Throwing Power) in substrates with various structures such as automobile bodies. Homogeneous electrodeposition is understood to mean the ability of the electrodeposition coating to be deposited in the voids of a three-dimensional substrate, which is important for effective corrosion protection.

However, coating with high electrodeposition voltages causes surface defects in the substrate. When coating a substrate having an at least partially galvanized surface, surface defects are often formed inside the deposited cationic electrodeposition coating due to the formation of fine hydrogen blisters on the substrate, and as the electrodeposition voltage increases the unit The number of pinholes per area increases, which causes significant problems.

Although a method of adding a high boiling point solvent and a plasticizer is used to compensate for such pinhole resistance and deterioration of appearance, it has disadvantages of lowering internal power and lowering voltage of the electrodeposition paint.

An object of the present invention is to solve the problems of the prior art as described above, it is possible to make the solvent content uniform, and to provide a coating composition and electrodeposition coating composition comprising the same for the electrodeposition paint with improved coating film appearance and pinhole resistance It is.

According to one aspect of the invention,

(i) a main resin obtained by hydrolyzing a polymer obtained by reacting ketimine with a polyepoxy resin and then reacting the primary amine produced as a result of hydrolysis with monoepoxy; And

(ii) curing agents comprising blocked polyisocyanates

Provided is a cationic resin composition for electrodeposition paint comprising a.

According to another aspect of the present invention, there is provided an electrodeposition paint composition comprising a cationic resin composition for electrodeposition paint according to the present invention.

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

The main resin contained in the cationic resin composition for electrodeposition paint of the present invention is obtained by hydrolyzing a polymer obtained by reacting ketimine with a polyepoxy resin, and then reacting the primary amine produced by the hydrolysis with monoepoxy. Lose.

The polyepoxy resin usually has an epoxy equivalent of 180 to 2000, and preferably has 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 polyol applicable at this time 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 one embodiment of the present invention, polyepoxy obtained by chain extension with an aliphatic polyol and a bisphenol A type polyphenol is used for the preparation of the main resin, wherein the equivalent ratio of the polyphenol: polyol of the bisphenol A type is preferably Preferably 1: 0.2 to 10, and more preferably 1: 0.65 to 0.85.

The ketimines usable in the present invention are preferably ketimines derived from the reaction of alkylamines having the structure of Formula 1-1 or alkyldiamine having the structure of Formula 1-2 with ketones, respectively. Diketimine, which may be used alone or in combination.

[Formula 1-1]

[Formula 1-2]

In Formulas 1-1 and 1-2, R ₁ to R ₄ are each independently an aliphatic hydrocarbon having 1 to 10 carbon atoms, and X is H or a hydroxy group. The molecular weight of the ketamine represented by the formula (1-1) or (1-2) is preferably 150 to 1000, more preferably 200 to 700.

US Pat. No. 4,101,147, which is incorporated herein by reference, specifically discloses ketamine for use in the present invention. Ketamine groups hydrolyze when dispersed in water to release primary amine groups.

Ketamine derived from the formula (1) is produced through the condensation reaction of the primary amine and the ketone, preferably, substitution such as diethylenetetraamine, triethylenetetraamine and the corresponding propylene, butylene and higher alkylene amine Or a primary amine group of an unsubstituted alkylene polyamine is condensed with a ketone to convert to a ketamine group. Examples of preferred ketones include methyl ethyl ketone, diethyl ketone, methyl propyl ketone, isopropyl ketone, cyclohexanone and the like. More preferably methyl isobutyl ketone is used.

The condensation reaction of the primary amine groups of the polyamines with the ketones results in the hydrolysis of the ketimines produced again to produce primary amines and ketones. Hydrolysis of ketamine is inevitable during the synthesis of the water-dispersible resin, which means that ketones are generated in the resin composition, thereby causing a change in solvent content. Usually, the content of the ketone solvent generated at this time is 0.5 to 1% by weight of the water dispersion resin solids.

In addition, the primary amines generated by hydrolysis of ketamine under water and acid catalysis conditions are pinhole-shaped due to the local arc during cationic electrodeposition coating of galvanized galvanized sheet steel (GA steel). In addition to causing this phenomenon, it also affects the appearance and water dispersibility by forming urea bonds with the blocking agent.

Accordingly, in the present invention, the hydrolysis of ketamine generated in the process of producing a water-disperse resin is performed in advance, thereby suppressing the occurrence of ketones in the bath solution, while improving the appearance by reacting the generated primary amine with monoepoxy to extend the chain. It is to obtain the physical properties of pinhole resistance.

As monoepoxy which can be used by this invention, the monoepoxy of following General formula (2) is mentioned, for example.

[Formula 2]

In Formula 2, R ₁ is hydrogen or methyl, R ₂ is hydrogen or cycloalkyl, substituted or unsubstituted alkyl (preferably C1 to C18 alkyl), substituted or unsubstituted aryl (preferably Is C6 to C18 aryl), or an alkyl or aryl substituted moiety (e.g. -CH ₂ OR ₃ or CH ₂ COOR ₃ ), where R ₃ is substituted or unsubstituted alkyl (preferably C1 to C18) Alkyl), or substituted or unsubstituted aryl (preferably C6 to C18 aryl). In Formula 2, R ₁ and / or R ₂ may be unsubstituted or substituted with a substituent that does not interfere with the reaction of the epoxy and polyoxyalkylenepolyamine, these substituents are used under conditions that do not gel the reaction mixture Or have such properties.

Examples of suitable monoepoxy include C2 to C30 alkylene oxides including 1,2-butylene oxide, 1,2-pentene oxide, 1,2-dodecene oxide, styrene oxide and glycidyl. Other suitable examples include monohydric glycidyl esters such as glycidyl acrylate, glycidyl methacrylate, glycidyl acetate, glycidyl butyrate, glycidyl palmitate, glycidyl laurate and And glycidyl ester sold under the trade name CADURA E-10 (monomer product of HEXION). Suitably CADURA E-10P may be used. The molecular weight of the said monoepoxy is 1000 or less normally, More preferably, it is 100-500. In addition, the monoepoxy is preferably 0.1 to 10% by weight, more preferably 0.5 to 5% by weight based on the weight of the resin solid in the composition.

As mentioned above, the hydrolyzed ketimines and / or diketimines are reacted with monoepoxy to inhibit the urea reaction and add a more flexible structure (using the monoepoxy structure) to provide a tacky film, low uniform electrodeposition and Problems such as gas generation of the electrode can be alleviated.

The curing agent included in the cationic resin composition for electrodeposition paint of the present invention is a polyisocyanate at least partly blocked, preferably at least partly blocked with a polyhydric alcohol, more preferably a trihydric or higher alcohol and a monovalent or dihydric alcohol Polyisocyanates blocked at least in part.

The blocked isocyanate is an organic polyisocyanate and may be a polyisocyanate wherein the isocyanate group is reacted with a blocking compound such that the blocked isocyanate group is stable to active hydrogen at room temperature but reacts with active hydrogen at high temperature.

In the preparation of the blocked polyisocyanate curing agent, aliphatic or aromatic polyisocyanates including cycloaliphatic may be used, and representative examples thereof include 2,4- or 2,6-toluene diisocyanate and mixtures thereof, p-phenylene diisocyanate, tetra Methylene or hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisosanate, isophorone diisocyanate, diphenylmethane-4,4'-diisosanate and polymethylene polyphenyl isocyanate. . Higher polyisocyanates such as triisocyanate may also be used. Alternatively triphenylmethane-4,4 ', 4 "-triisocyanate may be used. In addition, NCO-prepolymers such as reaction products of polyisocyanates with polyols such as neopentylglycol and trimethylol propane, and reaction products of polymer polyols such as polycaprolactone diols and triols may also be used.

As a protective agent for the polyisocyanate, it is desirable to reduce the weight loss as much as possible when the membrane is heated and cured, and a low molecular weight alcohol mixture is recommended for this purpose.

On the other hand, blocked polyisocyanate curing agents can be used in two ways. Firstly, it can be used in a fully blocked form, ie in the form of free free isocyanate, in which case it is present in the bicomponent resin system through a blend with the epoxy backbone. Secondly, it may be made into a one-component resin by reacting with active hydrogen groups in the epoxy polymer backbone after only a partial blockage. In terms of the stability of the resin, the latter case where the epoxy main chain and the urethane curing agent form a chemical bond may exhibit more stable dispersion stability, but the partially blocked curing agent component is highly reactive and stored for a long time in a stable state. There is also a disadvantage in that it is not easy to cause various problems in terms of production stability. On the other hand, a curing catalyst such as tin catalyst is usually present in the curing agent component. Examples include dilauryl acid dibutyl tin 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.

The cationic resin composition for electrodeposition paint of the present invention preferably comprises 1000 to 1500 parts by weight of the main resin and 900 to 1300 parts by weight of a curing agent comprising the blocked polyisocyanate. 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.

The amount of water required for the hydrolysis of ketamine is 0.2 to 10 equivalents per molecule of amine, more preferably 0.5 to 1.5 equivalents (the number of reaction groups in the molecule). Acetic acid, formic acid, lactic acid, and the like are used as the type of acid required for hydrolysis, and the amount thereof is preferably 1 to 15 milliliter equivalents (Miliequivanlence, MEQ), more preferably 3 to 10 milliliter equivalents.

The hydrolysis reaction of ketamine is carried out at a temperature (eg, about 90 ° C. to 150 ° C.) sufficient to cause a reaction under nitrogen atmosphere, and the reaction time is usually 30 minutes to 2 hours. After the completion of the hydrolysis, monoepoxy is added to proceed with the reaction of the primary amine produced by the hydrolysis with the monoepoxy. The reaction temperature is about 70 ° C to 150 ° C, and the reaction time is suitably about 30 minutes to 3 hours. While the reaction is in progress, it is checked whether the epoxy functional group remains by titration, and when the disappearance is confirmed, the reaction is terminated.

The equivalent ratio of ketimine to monoepoxy used in the present invention is preferably 1: 0.01 to 1.5 equivalents, more preferably 1: 0.05 to 0.5 equivalents.

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.

Production Example  1-Preparation of Urethane Curing Agent

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

PAPI2940, methyl isobutyl ketone and dibutyltin dilaurate were fed to the reaction flask and heated to 30 ° C. under a nitrogen atmosphere. The first portion of 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 the last portion of 2- (2-butoxyethoxy) ethanol was added. Infrared analysis was continued at 110 ° C. until no unreacted NCO remained.

Production Example  Preparation of 2-Cationic Electrodeposited Resin

Cationic electrodeposition resins were prepared from mixtures of the components shown in Table 2 below.

EPON828, 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. 145 ° C. was maintained 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.

Example  1-cation for electrodeposition paint Water dispersion  Preparation of Resin

The cationic water dispersion resin for electrodeposition paint was prepared from the mixture of the components shown in Table 3 below. The reactive hydrogen: CADURA E-10 equivalent ratio of the primary amine produced by the hydrolysis of KT-22 was 1: 0.05.

The cationic electrodeposition resin synthesized in Preparation Example 2 was cooled to 90 ° C. The first deionized water and the first 85% formic acid were added thereto and held for 30 minutes, and then CADURA E-10 was added, and the temperature was raised to 110 ° C. and maintained for 2 hours. The reaction was then left at 125 ° C. for 2 hours and then slowly added to the mixture of second formic acid and second deionized water with sufficient stirring to disperse. A third and fourth portions of deionized water were gradually added to the obtained 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-cation for electrodeposition paint Water dispersion  Preparation of Resin

The cationic water-dispersion resin for electrodeposition paint was prepared from the mixture of the components shown in Table 4 below. The reactive hydrogen: CADURA E-10 equivalent ratio of the primary amine produced by the hydrolysis of KT-22 was 1: 0.1. The preparation method was the same as in Example 1.

Example  3-cation for electrodeposition paint Water dispersion  Preparation of Resin

The cationic water-dispersion resin for electrodeposition paint was prepared from the mixture of the components shown in Table 5 below. The reactive hydrogen: CADURA E-10 equivalent ratio of the primary amine produced by the hydrolysis of KT-22 was 1: 0.2. The preparation method was the same as in Example 1.

Comparative example  One - Mono epoxy  Electrodeposited cation without addition Water dispersion  Preparation of Resin

The cationic water-dispersion resin for electrodeposition paint was prepared from the mixture of the ingredients shown in Table 6 below.

The cationic electrodeposition resin synthesized in Preparation Example 2 was slowly added to the mixture of stirring formic acid and the first deionized water with sufficient stirring to disperse. Subsequently, second and third 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%.

Comparative example  2 - Glycidyl Butylate  Added cation for electrodeposition paint Water dispersion  Preparation of Resin

The cationic water-dispersion resin for electrodeposition paint was prepared from the mixture of the components shown in Table 7 below. The reactive hydrogen to glycidyl butylate equivalent ratio of the primary amine produced by the hydrolysis of KT-22 was 1: 0.1. The preparation method was the same as in Example 1.

Example  4-6 and Comparative example  3-4-Preparation of Electrodeposition Coating Composition

1292 parts by weight of the aqueous dispersion resin prepared in Examples 1 to 3 and Comparative Examples 1 and 2, 244 parts by weight of a pigment paste (ED2800-A) commercially available from DuPont co., And 1460 parts by weight of deionized water were mixed. Thus, the cationic electrodeposition coating compositions of Examples 4 to 6 and Comparative Examples 3 to 4 were prepared, respectively.

Using each of the coating compositions prepared above, electrodeposition coating was carried out at a direct current voltage of 150V to 350V for 2 minutes at a bath temperature of 28 ℃. At this time, a phosphoric acid-treated steel sheet was used as the specimen. The coated object coated at 210 V to 300 V for 2 minutes was cured at 160 ° C. for 25 minutes. In addition, about the pinhole resistance of the galvanized car body steel (hereinafter GA steel sheet), the voltage showing the pinhole was measured at a constant Coulomb (outer film thickness of 20 to 25 µm) at 30 ° C. Various physical property values of the coating film are shown in Table 8 below.

-Pinhole: Number of pinholes per the coated area of 1m ²

-Penetration height (Throwing Power): Measured by Ford Method as a measure of uniform electrodeposition force. Immerse the 25cm specimen in the electrodeposition bath and apply the voltage to show the ability of the cationic electrodeposition paint to penetrate (all applied voltages were 270V, and all experimental conditions were the same below).

-Outer film thickness: CED coating thickness excluding thickness of pretreatment specimen

As can be seen in Table 12 and Table 13, the coating composition prepared according to the present invention was very excellent in pinhole resistance and appearance improvement while maintaining the internal permeability (Throwing Power).

As described above, according to the present invention, the solvent content can be made uniform, and the cationic resin composition for electrodeposition paint and the electrodeposition coating composition including the same can be obtained while maintaining the internal permeability and improving the coating appearance and pinhole resistance.

Claims (8)

(i) a main resin obtained by hydrolyzing a polymer obtained by reacting ketimine with a polyepoxy resin and then reacting the primary amine produced as a result of hydrolysis with monoepoxy; And (ii) curing agents comprising blocked polyisocyanates Cationic resin composition for electrodeposition paint comprising a. 2. The resin composition according to claim 1, wherein the polyepoxy resin is a polyepoxy obtained by chain extension with an aliphatic polyol and a bisphenol A type polyphenol. The resin composition according to claim 2, wherein the equivalent ratio of polyphenol: polyol of bisphenol A type is 1: 0.65 to 0.85. The method of claim 1, wherein the ketimine is derived from the reaction of the alkylamine having the structure of Formula 1-1 or the alkyldiamine having the structure of Formula 1-2 with ketones, respectively, or Ketimine (Diketimine) Or a mixture thereof. [Formula 1-1]

[Formula 1-2]

In Formulas 1-1 and 1-2, R ₁ to R ₄ are each independently an aliphatic hydrocarbon having 1 to 10 carbon atoms, and X is H or a hydroxy group. The resin composition according to claim 1, wherein the monoepoxy has a structure represented by the following Chemical Formula 2:  [Formula 2]

In Formula 2, R ₁ is hydrogen or methyl, R ₂ is hydrogen, including cycloalkyl, substituted or unsubstituted C ₁ to C ₁₈ alkyl, substituted or unsubstituted C ₆ to C ₁₈ aryl, Or a residue substituted with C ₁ to C ₁₈ alkyl or C ₆ to C ₁₈ aryl. The resin composition according to claim 1, wherein the polyisocyanate included in the curing agent is at least partially blocked by a trihydric or higher alcohol and a monovalent or dihydric alcohol. The resin composition according to claim 1, wherein the equivalent ratio of ketimine to monoepoxy is 1: 0.05 to 0.5 equivalent. An electrodeposition coating composition comprising the cationic resin composition for electrodeposition coating according to any one of claims 1 to 7.