KR101424149B1 - A cationic resin composition for electrodepositable coating and an electrodepositable coating composition comprising the same - Google Patents

Abstract

The present invention relates to (i) a main resin obtained by hydrolyzing a polymer obtained by reacting a polyepoxy resin with a ketimine, and then reacting a primary amine produced by hydrolysis with a monoepoxy, and (ii) The present invention relates to a cationic resin composition for an electrodeposition paint comprising a polyisocyanate and an electrodeposition coating composition containing the same, and more particularly, to a cationic resin composition for electrodeposition coating comprising a polyisocyanate and an electrodeposition coating composition containing the same, wherein the solvent content can be made uniform, This improved cationic resin composition for electrodeposition paints and electrodeposition coating compositions containing the same can be obtained.

Electrodeposition, paint, cation, water dispersion, resin, composition, ketimine

Description

Technical Field [0001] The present invention relates to a cationic resin composition for electrodeposition coatings and an electrodeposition coating composition containing the same. BACKGROUND ART [0002]

The present invention relates to a cationic resin composition for electrodeposition paints and an electrodeposition coating composition containing the same, which comprises: (i) hydrolyzing a polymer obtained by reacting a polyepoxy resin with ketimine, A main resin obtained by reacting an amine with a monoepoxy, and (ii) a curing agent comprising a blocked polyisocyanate, and an electrodeposition coating composition containing the cationic resin composition.

In general, cationic electrodeposition is carried out by introducing a quaternary ammonium salt or a sulfonium salt which can be positively charged to a resin and moving them to the negative electrode in a solution in which an electric field is applied. At the same time, a positive charge is generated by a hydroxy anion generated by electrolysis of water The resin is deposited again while being reduced, and these are coated on the cathode, that is, the conductor.

In general, a polyepoxy-amine reaction product is used to cationize the electrodeposited resin, and as the amine, ketimine or diketimine can be used. The use of ketimine has the effect of improving the dispersibility of the resin, facilitating the pH adjustment, and improving the dispersion stability. It is also effective in improving the penetrating power (electrodeposition) of the electrodeposition coating due to the improved conductivity. However, as the ketimine consumption increases, ketone and primary amine are generated through the hydrolysis reaction of ketimine and water in the process of water dispersion resin synthesis. The ketones generated in this process are not contained in the cationic electrodeposition coating bath liquid ≪ / RTI > In addition, the generated primary amine causes urea reaction with the curing agent during baking or curing, resulting in deterioration of the external appearance of the coating film and generation of pinholes in the galvanic test piece.

Korean Patent Publication No. 2002-0084272 discloses a coating composition containing 0.1 to 5% by weight of at least one sulfonamide based on the solid resin content of the coating composition, wherein the zinc-plated surface is coated with a pinhole-free coating ≪ / RTI > In US Pat. No. 3,947,333, a polyketimine derivative of a polyamine such as diethylenetriamine or triethylenetetramine is reacted with a polyepoxy. When this reaction product is neutralized with an acid and dispersed in water, a primary amine group is formed. An equivalent product is also produced when the polyepoxy is reacted with an excess of polyamine such as diethylenetriamine and triethylenetetramine, and vacuum stripping of excess polyamine from the reaction mixture. Such products are described in U.S. Patent Nos. 3,663,389 and 4,116,900.

Electrodeposition at a high electrodeposition voltage should be performed in order to expect the highest penetrating power (Throwing power) on a substrate having various structures such as an automobile body. The uniform soldering force is understood to mean the ability of the electrodeposition coating agent to be deposited in the pores of the three-dimensional substrate, which is important for effective corrosion prevention.

However, coating with high electrodeposition voltage causes surface defects of the substrate. When coating a substrate having an at least partially zinc plated surface, surface defects are often formed within the deposited cationic electrodeposition coating layer due to the formation of a microhydrogen blister on the substrate, and as the electrodeposition voltage increases, The number of pin-holes per area is increased, which causes considerable problems.

In order to compensate for the decrease of the pinhole property and appearance, a method of adding a high-boiling point solvent and a plasticizer is used. However, this method has disadvantages in that it causes a reduction in the internal penetration (throwing power) and a film rupture voltage drop of the electrodeposition paint.

The object of the present invention is to provide a cationic resin composition for an electrodeposition paint and an electrodeposition coating composition containing the same, which can uniformize the solvent content and improve the appearance of the coating film and the pinhole property .

According to an aspect of the present invention,

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

(ii) a curing agent comprising a blocked polyisocyanate

A cationic resin composition for an electrodeposition paint.

According to another aspect of the present invention, there is provided an electrodeposition coating composition comprising a cationic resin composition for electrodeposition paints 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 a resin obtained by reacting a polyepoxy resin with ketimine to obtain a polymer obtained by hydrolyzing a polymer obtained by reacting a primary amine produced by hydrolysis with monoepoxy Loses.

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 one embodiment 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 equivalent ratio of the bisphenol A type polyphenol: polyol is preferably Is from 1: 0.2 to 10, more preferably from 1: 0.65 to 0.85.

Ketamine which can be used in the present invention is preferably an alkylamine having the structure represented by the following formula 1-1 or a ketimine or ketamine derived from the reaction of an alkylamine having a structure represented by the following formula 1-2 with a ketone, Diketimine, which can be used singly 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 ketimine represented by formula (1-1) or (1-2) is preferably 150-1000, more preferably 200-700.

U.S. Patent No. 4,101,147, which is incorporated herein by reference, specifically discloses ketimines that can be used in the present invention. The ketimine group hydrolyzes when dispersed in water to release primary amine groups.

The ketimine derived from the above formula (1) is produced through the condensation reaction of a primary amine with a ketone, and is preferably a diethylenetetramine, a triethylenetetramine and a corresponding substitution such as propylene, butylene and higher alkylene amine Or a primary amine group of an unsubstituted alkylene polyamine is condensed with a ketone to convert it into 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.

Hydrolysis of ketamine produced by the condensation reaction of primary amine group of polyamine with ketone regenerates primary amine and ketone. Hydrolysis of ketimine is inevitable in the process of synthesizing the water dispersion resin, which means that ketone is generated in the resin composition and the solvent content changes. Generally, the content of the ketone solvent generated at this time is 0.5 to 1% by weight of the solid content of the water-dispersible resin.

In addition, the primary amine generated by the hydrolysis of ketimine under water and acid catalytic conditions is a pinhole type due to the local arc in the cation electrodeposition coating of galvannealed sheet steel (hereinafter referred to as GA steel sheet) But also forms a block agent and a urea bond, thereby affecting the appearance and water dispersibility.

Therefore, in the present invention, the hydrolysis of ketimine generated in the process of producing the water dispersion resin is precedently performed to inhibit the generation of ketones in the aqueous solution, and the generated primary amine reacts with monoepoxy to chain extension, It is intended to obtain the pinhole properties.

Examples of monoepoxy that can be used in the present invention include monoepoxy of the following formula (2).

(2)

Wherein R ₁ is hydrogen or methyl and R ₂ is selected from the group consisting of hydrogen, substituted or unsubstituted alkyl (preferably C1 to C18 alkyl), substituted or unsubstituted aryl is a C6 to C18 aryl), or substituted alkyl or aryl moiety (for example: -CH ₂ oR ₃ or CH ₂ COOR ₃₎ [where, R ₃ is a C1 to C18 substituted or unsubstituted alkyl, preferably unsubstituted ( , Or a substituted or unsubstituted aryl (preferably C6 to C18 aryl)). In the above formula (2), R ₁ and / or R ₂ may be unsubstituted or substituted with a substituent which does not interfere with the reaction of the epoxy and the polyoxyalkylene polyamine. These substituents may be used under the condition that the reaction mixture is not gelated Or have such properties.

Examples of suitable monoepoxies 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 monosaccharide 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 can be used. The molecular weight of the monoepoxy is usually 1000 or less, and more preferably 100 to 500. [ The monoepoxy is preferably contained in an amount of 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, by reacting the hydrolyzed ketimine and / or diketimine with monoepoxy, the urea reaction is inhibited and a more flexible structure (utilizing the structure of monoepoxy) is added to produce a pressure-sensitive adhesive film, a low uniform electrodepositability Problems such as gas generation of the electrode can be alleviated.

The curing agent contained in the cationic resin composition for electrodeposition paint of the present invention is a curing agent which is at least partially blocked with a polyisocyanate, preferably at least partially blocked with a polyhydric alcohol, more preferably a trihydric alcohol and a monohydric or dihydric alcohol At least a portion of the polyisocyanate is blocked.

The blocked isocyanate is an organic polyisocyanate, and the resulting blocked isocyanate group is stable to active hydrogen at room temperature, but may be a polyisocyanate obtained by reacting an isocyanate group with a blocking compound to react with active hydrogen at high temperature.

The aliphatic or aromatic polyisocyanates including alicyclic groups may be used for preparing the blocked polyisocyanate curing agent. Representative examples include 2,4- or 2,6-toluene diisocyanate and mixtures thereof, p-phenylene diisocyanate, tetra Methylene or hexamethylene diisocyanate, dicyclohexylmethane-4,4'-diisocyanate, isophorone diisocyanate, diphenylmethane-4,4'-diisocyanate and polymethylene polyphenyl isocyanate . Higher polyisocyanates such as triisocyanates may also be used. Alternatively, triphenylmethane-4,4 ', 4 " -triisocyanate may be used. Also, NCO-prepolymers such as the reaction product of a polyisocyanate with a polyol such as neopentyl glycol and trimethylol propane, and the reaction product with a polymer polyol such as polycaprolactone diol and triol may be used.

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

On the other hand, the blocked polyisocyanate curing agent can be used in two ways. Firstly, it can be used in a completely blocked form, i.e. a form in which no free isocyanate remains, in which case it is present as a two-component resin system through a blend with the epoxy backbone. Secondly, it may be prepared as a one-component resin by reacting with an active hydrogen group in the epoxy polymer backbone after only a part of it is blocked. From the standpoint of the stability of the resin, the latter case in which the epoxy main chain and the urethane curing agent chemically bond together can exhibit more stable water dispersion stability. However, the partially blocked curing agent component is very reactive and is stored for a long period of time in a stable state It is not easy to cause various problems in terms of production stability. On the other hand, a curing catalyst such as a tin catalyst is usually present in the curing agent component. 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.

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 containing the blocked polyisocyanate. 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.

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

The hydrolysis reaction of the ketimine is carried out at a temperature sufficient to cause a reaction under a nitrogen atmosphere (for example, about 90 ° C to 150 ° C), and the reaction time is usually 30 minutes to 2 hours. After completion of hydrolysis, monoepoxy is added to allow the reaction of the primary amine and monoepoxy produced as a result of the hydrolysis. The reaction temperature is about 70 ° C to 150 ° C, and the reaction time is about 30 minutes to 3 hours. While the reaction proceeds, the presence or absence of the epoxy functional group is confirmed through 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 equivalent, more preferably 1: 0.05 to 0.5 equivalent.

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.

Manufacturing example  1 - Preparation of urethane curing agent

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

PAPI2940, methyl isobutyl ketone and dibutyl tin dilaurate were fed to the reaction flask and heated to 30 DEG C under a nitrogen atmosphere. The first portion of 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 then allowed to stand at the above temperature for 3 hours, and a final amount of 2- (2-butoxyethoxy) ethanol was added. By infrared analysis, the temperature was kept at 110 DEG C until no unreacted NCO remained.

Manufacturing example  Preparation of 2-cation electrodeposited resin

A cationic electrodeposition resin was prepared from the mixture of the components shown in Table 2 below.

Epon 828, bisphenol A-ethylene oxide adduct, bisphenol A and methyl isobutyl ketone were fed to the reaction vessel and heated to 140 DEG 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.

Example  1 - Cations for electrodeposition paints Water dispersion  Manufacture of resin

A cationic water-dispersible resin for electrodeposition paints was prepared from the mixture of the components shown in Table 3 below. The active hydrogen of the primary amine produced by hydrolysis of KT-22: CADURA E-10 Equivalent ratio was 1: 0.05.

The cationic electrodeposition resin synthesized in Production Example 2 was cooled to 90 占 폚. To this was added the first deionized water and the first 85% formic acid and kept for 30 minutes, then CADURA E-10 was added and the temperature was raised to 110 < 0 > C and held for 2 hours. Then, the reaction mixture was allowed to stand at 125 DEG C for 2 hours, and the mixture of the second formic acid and the second deionized water was slowly added to the mixture while stirring sufficiently. Third and fourth amounts of deionized water were gradually added to the dispersion to gradually dilute it, 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 - Cations for electrodeposition paints Water dispersion  Manufacture of resin

A cationic water-dispersible resin for electrodeposition paints was prepared from the mixture of the components shown in Table 4 below. The active hydrogen of the primary amine produced by the hydrolysis of KT-22: CADURA E-10 Equivalent ratio was 1: 0.1. The production method was the same as in Example 1.

Example  3 - Cations for electrodeposition paints Water dispersion  Manufacture of resin

A cationic water-dispersible resin for electrodeposition paints was prepared from the mixture of the components shown in Table 5 below. The active hydrogen of the primary amine produced by hydrolysis of KT-22: CADURA E-10 Equivalent ratio was 1: 0.2. The production method was the same as in Example 1.

Comparative Example  One - Mono-epoxy  Cations for electrodeposited coatings not added Water dispersion  Manufacture of resin

A cationic water-dispersible resin for electrodeposition paint was prepared from the mixture of the components shown in Table 6 below

The cationic electrodeposition resin synthesized in Preparation Example 2 was slowly added with stirring to the mixture of formic acid and first deionized water under agitation while stirring sufficiently. Then, the second and third amounts of deionized water were gradually added to the dispersion in order and gradually diluted, 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%.

Comparative Example  2 - Glycidyl Butylate  Cation for electrodeposited paint added Water dispersion  Manufacture of resin

A cationic water-dispersible resin for electrodeposition paints was prepared from the mixture of the components shown in Table 7 below. The active hydrogen: glycidyl butyrate equivalent ratio of the primary amine produced by the hydrolysis of KT-22 was 1: 0.1. The production method was the same as in Example 1.

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

1292 parts by weight of the water dispersion resin prepared in each of Examples 1 to 3 and Comparative Examples 1 and 2, 244 parts by weight of pigment paste (ED2800-A) commercially available from DuPont Co., and 1460 parts by weight of deionized water To prepare cationic electrodeposition coating compositions of Examples 4 to 6 and Comparative Examples 3 to 4, 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 2 minutes at a bath temperature of 28 캜. At this time, a phosphoric acid treated steel sheet was used as a specimen. The substrate coated at 210 V to 300 V for 2 minutes was cured at 160 ° C for 25 minutes. The pinholes of the zinc-plated body steel (hereinafter referred to as the GA steel sheet) were measured at a constant Coulomb (outer film thickness of 20 to 25 μm) at 30 ° C. The various physical properties of the coating film are shown in Table 8 below.

- Pinhole: Number of pinholes per 1 m ^{2 of} coated area

- Throwing power: Measured by the Ford Method as a uniform soldering force measurement. A 25 cm specimen was immersed in the electrodeposition bath and voltage was applied to show the penetration ability of the cationic electrodeposition coating (the applied voltage was 270 V, all the experimental conditions were the same hereinafter).

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

As can be seen from Tables 12 and 13, the coating compositions prepared according to the present invention exhibited excellent anti-pinhole properties and improved appearance while maintaining internal penetration (throwing power).

As described above, according to the present invention, it is possible to obtain a cationic resin composition for an electrodeposition coating and an electrodeposition coating composition containing the same, wherein the solvent content can be made uniform and the external appearance and pinhole property of the coating film can be improved while maintaining the internal permeability.

Claims (8)

(i) a main resin obtained by hydrolyzing a polymer obtained by reacting a polyepoxy resin with a ketimine, and then reacting a primary amine produced by hydrolysis with a monoepoxy; And (ii) a curing agent comprising a blocked polyisocyanate, From here, The ketimine is derived from the reaction of an alkyldiamine having a structure represented by the following formula (1-2) with a ketone, The monoepoxy represents a structure represented by the following formula (2) Wherein the equivalent ratio of the ketimine: monoepoxy is 1: 0.1 to 1: 0.5 equivalent, Cationic resin composition for electrodeposition paint: [Formula 1-2]

Wherein R ₃ and R ₄ are each independently an aliphatic hydrocarbon having 1 to 10 carbon atoms; (2)

Wherein R ₁ is hydrogen and R ₂ is CH ₂ COOR ₃ , wherein R ₃ is an alkyl having 6 to 18 carbon atoms. The cationic resin composition according to claim 1, wherein the polyepoxy resin is a polyepoxy obtained by chain extension of an aliphatic polyol and a bisphenol A type polyphenol. The cationic resin composition according to claim 2, wherein the equivalent ratio of bisphenol A type polyphenol: polyol is 1: 0.65 to 0.85. 2. The cationic resin composition according to claim 1, wherein the blocked polyisocyanate contained in the curing agent is at least partially blocked with a trivalent or higher alcohol and a monovalent or divalent alcohol. The cationic resin composition for electrodeposition coating composition according to claim 1, wherein the equivalent ratio of ketimine: monoepoxy is 1: 0.1 to 1: 0.2 equivalent. An electrodeposition coating composition comprising the cationic resin composition for electrodeposition coating according to any one of claims 1 to 5. delete delete