KR100756124B1 - Low-Temperature Curable Cationic Resin Composition for Use in Electrodeposition and Paints containing the Same - Google Patents

Abstract

The present invention relates to an electrodeposition resin composition containing a blocked polyisocyanate-based curing agent, comprising a polyepoxy-amine cationic resin as a base resin; And a polyisocyanate curing agent prepared by reacting an aliphatic or aromatic isocyanate, a mono alcohol and an acrylic monomer, dihydroxy alkanoic acid, and a polyfunctional polyol, wherein the amount of the curing agent is 10 to 60 weight based on the base resin. It is characterized by being%. The composition is a low temperature curing type which partially blocks diisocyanates with mono alcohols and acrylic monomers in combination with dihydroxy alkanoic acid in the preparation of polyisocyanate-based curing agents, resulting in the use of dihydroxy alkanoic acid as a blocker for isocyanates. The fall of stability can be prevented, and the performance of the coating film formed using this is much superior to the conventional electrodeposition resin composition. In addition, the yellowing phenomenon generated when using aromatic isocyanate may be improved as well as to improve uniform coating property.

Electrodeposition Resin, Isocyanate, Hardener, Blocker, Epoxy

Description

Low-Cemperature Curable Cationic Resin Composition for Use in Electrodeposition and Paints containing the Same

The present invention relates to an electrodeposition resin composition containing a blocked polyisocyanate-based curing agent. More specifically, the present invention relates to an electrodeposition resin composition containing a polyisocyanate-based curing agent composed of a dihydroxy alkanoic acid, a monoalcohol and an acrylic monomer, a polyfunctional polyol, and a diisocyanate, which is a low-temperature dissociative blocker, and a coating material containing the same. will be.

In general, in the electrodeposition coating, the polymer having a charge moves to the electrode of the opposite charge under the action of direct current, in which the change of pH caused by electrolysis of water causes the precipitation of the polymer to form a non-conductive coating film. This electrodeposition method is of increasing importance because it provides higher paint adhesion efficiency, significant corrosion resistance and low environmental pollution compared to non-electrophoretic means. Initially, electrodeposition was carried out using the base to be coated as an anode. This is known as "anion electrodeposition" as is well known. However, in 1972, cationic electrodeposition was commercially introduced that allows for better rust resistance. Since then, cationic electrodeposition has steadily gained popularity, making it the main electrodeposition method of today. More than 80% of all cars produced worldwide are undercoat by cation electrodeposition. In the meantime, in order to satisfy various functionalities required for cationic electrodeposition, resins for dispersing pigments have been developed, and two-liquidization has been put to practical use.

Resin used for cationic electrodeposition is typically epoxy resin, and the curing agent is mixed with this epoxy resin and neutralized by acid to form an aqueous dispersion. The electrodeposited paint is obtained by adding a pigment paste, agglomeration solvent, other additives, etc. to the aqueous product thus obtained.

The hardening agent used in the above cationic electrodeposition is mainly composed of blocked isocyanates. The blocked isocyanate curing agents dissociate sobubush blockers to generate isocyanate functional groups, and the resulting isocyanates react with various reactors present in the resin skeleton. Crosslinking occurs. Therefore, the curing temperature mainly depends on the temperature at which the blocking agent is dissociated, and the selection of the isocyanate and the blocking agent can be said to be the key in preparing the curing agent suitable for the desired curing conditions. Isocyanates commonly used in the manufacture of hardeners include hexamethylene diisocyanate, 4-methyl-1,3-phenylene diisocyanate, methylene diphenyl diisocyanate, 1,4-cyclo hexane diisocyanate, isophorone diisocyanate, dianisidine diisocyanate. Isocyanate, tetramethyl xylene diisocyanate and the like. These isocyanates are blocked with various blocking agents to form electrodeposition resins together with polyepoxy resins. The blocking agents used here include alcohols, phenols, oximes, lactams, N, N-dialkylamides, esters of carboxylic acids containing α-hydroxyl groups, and the like. to be. Suitable of such blockers are disclosed in US Pat. No. 3,959,106.

On the other hand, aromatic isocyanates are known to be preferable for relatively low temperature curing than aliphatic isocyanates, and lactams, phenols, oximes and the like are particularly advantageous for low temperature curing. In this regard, Korean Patent Publication No. 90-1383 discloses that furfuryl alcohol can be used as a blocking agent for low temperature curing. However, when oxime is used as a blocking agent, the use of aromatic isocyanate as the isocyanate has a fatal effect on the stability of the resin because the dissociation temperature of the oxime is too low. Therefore, it is common to use aliphatic isocyanates when oximes are used as blocking agents.

In addition, dihydroxy alkanoic acid can be used as a blocking agent for aromatic isocyanates. In the above case, when a certain temperature is reached, dihydroxy alkanoic acid dissociates in an instant. At this time, since free acid is generated and participates in curing, it is advantageous for low temperature curing and in terms of stability of the resin. However, when the total amount of the aromatic isocyanate is blocked with dihydroxy alkanoic acid, it is difficult to obtain a uniform liquid curing agent since the dihydroxy alkanoic acid has a tendency to crystallize at room temperature. In particular, in the case of producing an aqueous dispersion by applying this as a curing agent to the electrodeposition resin composition, excessive precipitation occurs in the aqueous dispersion, resulting in very poor storage stability.

 In contrast, the present inventors overcome the problems of the prior art and block diisocyanate with dihydroxy alkanoic acid in order to prevent the deterioration of storage stability caused when dihydroxy alkanoic acid is used as a blocking agent of isocyanate. When partially blocked with a mono alcohol and acrylic monomer prior to the following, it was found that a low temperature hardening type curing agent having excellent storage stability can be prepared, by using the low temperature hardening type electrodeposition resin composition.

Accordingly, it is an object of the present invention to provide a low temperature curing type cationic electrodeposition resin composition containing a low temperature curing type curing agent having excellent storage stability.

The low temperature curable electrodeposition resin composition of the present invention for achieving the above object is a polyepoxy-amine cationic resin as a base resin; And a polyisocyanate-based curing agent prepared by reacting an aliphatic or aromatic isocyanate, a mono alcohol and an acrylic monomer, a dihydroxy alkanoic acid represented by Formula 1 below, and a polyfunctional polyol, wherein the amount of the curing agent is determined by the base resin. It is characterized by 10 to 60% by weight on the basis of:

Wherein R1 is H or an alkyl group having 1 to 3 carbon atoms, and R2 is a methylol group.

Hereinafter, the above and other objects of the present invention can be achieved by the following description.

As described above, when dihydroxy alkanoic acid is used as a blocking agent for isocyanate in the process of preparing the polyisocyanate-based curing agent used in the preparation of the electrodeposition resin composition, dihydroxy alkanoic acid cannot be prevented. What is needed is a method that can suppress the tendency of crystallization at room temperature. As the isocyanate used in the present invention, both aliphatic and aromatic isocyanates may be used. Representative examples of such isocyanates include 4,4'-methylenebis (phenylisocyanate), 4-methyl-1,3-phenylene diisocyanate, polymeric methylenediphenyl diisocyanate (polymeric MDI), hexamethylene diisocyanate (HMDI ), Xylene diisocyanate (XDI), 2,4,6, -triisopropylphenyl diisocyanate (TIDI), diphenyl ether diisocyanate, isophorone diisocyanate (IPDI), 4,4'-dicyclohexyl methane Diisocyanate (HMDI), tetramethylxylene diisocyanate (TMXDI), 2,2,4-trimethylhexamethylene diisocyanate (TMHDI), 2,2,4 (2,4,4,)-trimethylhexamethylene diisocyanate ( TMDI) etc., These can be used individually by 1 type or in mixture of 2 or more types. Preferred aromatic diisocyanates include 4,4'-methylenebis (phenylisocyanate) and 4-methyl-1,3-phenylene diisocyanate.

In the present invention, the dihydroxy alkanoic acid used as a blocker of isocyanate has a hydroxy group and a carboxylic acid coexist in the molecular structure and when used together with an alcohol group and an acrylic monomer, crystallization of the dihydroxy alkanoic acid The tendency can be suppressed to solve the storage stability problem.

Dihydroxy alkanoic acid usable in the present invention is represented by the following general formula (1):

Formula 1

In the above formula, R1 is H or an alkyl group having 1 to 3 carbon atoms, and R2 is a metyrol group.

The dihydroxy alkanoic acid preferably has a number average molecular weight of about 100 to 200. Examples of the component include dimethyrolethane noic acid, dimethyrol propionic acid, dimethyrolbutaninoic acid, dimethyrolpentanoic acid, and the like, and at least one thereof is used. The content of the dihydroxy alkanoic acid used to prepare the curing agent is preferably about 1.0 to 60%, preferably about 1.0 to 40%, based on the equivalent of isocyanate in the isocyanate.

Monoalcohol used as a blocking agent of isocyanate together with the dihydroxy alkanoic acid is a particularly useful component for inhibiting the crystallization behavior of the dihydroxy alkanoic acid, for example, methanol, ethanol, butanol, 2-butoxy ethanol. , At least one is selected from 1,2- (2-butoxy ethoxy) ethanol, 2-hexy ethanol and the like. The monoalcohol component is preferably used at about 50 to 85% by equivalent weight of isocyanate.

In addition, the acrylic monomer contains a hydroxyl group having a flexible group in its chemical structure, hydroxy ethyl (meth) acrylate, hydroxy propyl (meth) acrylate, trimetholpropane di (methyl) acryl At least one is selected from late, tri or tetrapropyl glycol mono (meth) acrylate and the like. The acrylic monomer component is preferably used at about 5-30% by weight equivalent of isocyanate.

According to the invention, one embodiment of the process for preparing the polyisocyanate-based curing agent is as follows:

The isocyanate is first reacted with a mono alcohol and an acrylic monomer to block a portion of the isocyanate and the isocyanate / (mono alcohol and acrylic monomer) intermediate thus obtained is reacted with the aforementioned dihydroxy alkanoic acid and polyfunctional polyol, the reaction being It is preferably carried out at about 50-120 ° C.

The polyfunctional polyol is reacted with the remaining isocyanate component as a result of the reaction between the aforementioned isocyanate / (mono alcohol and acrylic monomer) intermediate and dihydroxy alkanoic acid. At this time, in order to completely react with the remaining isocyanate, it is preferable to use an excess polyol (about 10-30% excess). Such polyols are difunctional, trifunctional polyols or polymeric polyols, for example trimetholol propane, polyalkylene glycols, 1,6-hexanediol, ethoxylated trimetholol propane, polycaprolactone tri At least one can be selected and used from all or the like.                     

In the case of the curing agent production reaction, a generally known catalyst can be used. For example, an organotin compound such as dibutyltin dilaurate and dibutyl tin oxide is used, and the amount of the curing agent is about 0.1 to about 0.1 isocyanate. A 5 weight percent range is preferred. In addition, the reaction is usually carried out by dilution using a solvent (organic solvent). As such a solvent, ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone, and toluene are used.

The curing agent prepared according to the present invention not only has excellent storage stability but is also advantageous for low temperature curing as compared to the curing agent blocked with alcohol as in the prior art. In particular, the yellowing phenomenon generated when using an aromatic isocyanate can be solved. In addition, when the dihydroxy alkanoic acid is mixed with a mono alcohol and an acrylic monomer as a blocking agent, excellent rust resistance and uniform coating property can be obtained as compared with the case where the alcohol alone is used.

As such, the polyisocyanate-based curing agent provided by the present invention can simultaneously achieve two purposes of storage stability and low temperature curing by using mono alcohol and acrylic monomer with dihydroxy alkanoic acid as a blocking agent.

In the low temperature hardening type electrodeposition resin composition of the present invention, the polyepoxide resin used as the base resin has various epoxide equivalents per molecule, and preferably at least one (preferably two or more) at the ends. Has a 1,2-epoxide group of. Such polyepoxides are well known in the art and are described, for example, in US Pat. Nos. 2,467,171, 2,615,007, 2,716,123, 3,053,855, 3,075,999, and the like. Representative examples of preferred polyepoxides include polyglycidyl ethers of polyphenols, polyglycidyl ethers of aromatic polyols such as bisphenol A, and the like. These polyepoxides are etherified of an aromatic polyol (polyhydric phenol) with an epihalohydrin or dihalohydrin such as epichlorohydrin or dichlorohydrin in the presence of an alkali. It can be prepared by the reaction. Still other polyepoxides can be derived from, for example, novolak resins or polyphenol resins.

On the other hand, the increase in the molecular weight of polyglycidyl ethers of polyhydric materials is the reaction of substances comprising hydroxyl groups which can react with polyglycidyl ethers and epoxide groups of aromatic diols, for example mono alcohols or polyols. It is possible by Examples of the polyol applicable in the present invention include ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, bisphenol-A, and the like. The number average molecular weight of the polyepoxide has at least 300 or more, preferably a value between 300 and 3000. Such polyepoxides are chain-extended with polyethers or polyester polyols and the like, which are disclosed in US Pat. Nos. 4,468,307 and 4,148,772. Such chain extended polyepoxides subsequently form polyamines having primary or higher amine groups, which react with the epoxy groups to form cationic salt groups. Preferred amines used here are ketimine derivatives which are blocked by ketones and have at least one secondary amine. Ketamine groups are mentioned in US Pat. No. 4,104,147, and as dispersed in water, the polyepoxide amine reactants hydrolyze into primary amine groups. In addition, secondary amines having a primary hydroxyl group can also be used, such as methyl ethanol amine, diethanol amine, and the like. The reaction of the amine with the polyepoxide occurs by mixing the polyepoxide with the amine. This reaction can be carried out without solvent and optionally solvents such as methyl isobutyl ketone, xylene, 1-methoxy-2-propanol can also be used. Since the reaction is generally exothermic, sometimes a cooling process is necessary and generally requires a temperature between about 50 to 150 ° C.

After completion of the above-mentioned polyepoxide-amine reaction, the aforementioned polyisocyanate-based curing agent is added, wherein the amount of the curing agent added is preferably about 10 to 60% by weight based on the weight of the polyepoxide-amine reactant. Do. The resin thus prepared is partially neutralized with an organic acid for application to electrodeposition to introduce cationic groups in the resin. In order to form a suitable aqueous dispersion, the organic acid is contained such that 0.01 to 1.0 milligrams of salt is present per gram of resin solids. At this time, if the content of the hydrophilic group is low, the stability of the water dispersion is lowered, too much hydrophilic group is not preferable because the resin is too water-soluble. The aqueous dispersion finally prepared as described above contains about 30 to 50% solids depending on the application and the particle size of the aqueous dispersion is preferably about 10 to 1000 nm, most preferably about 50 to 500 nm. Have It is also desirable for the curing agent to be dispersed in an aqueous medium in an amount of about 5-50% by weight.

According to another embodiment of the present invention, pigments and various additives may be included as necessary in addition to the water dispersion prepared by the above-described method. Such pigments can be introduced, for example, in the form of pastes, which include not only pigments such as cadmium yellow, cadmium red, chromium yellow, etc., but also iron oxides, talc, lead oxide, strontium chromium, carbon black, coal powder, titanium dioxide and barium sulfate. It may be a conventional type that includes. The amount of pigment is determined in consideration of the required appearance characteristics (gloss, reflectivity, etc.) of the coating film, and the typical ratio of the pigment to the binder is about 0.1: 1 to 0.3: 1. Other additives are selected from surfactants, hydrating agents, curing catalysts such as dibutyltin dilaurate, dibutyltin oxide, and the like, and are usually added to the dispersion in an amount of about 0.01 to 3% by weight based on the resin solids. .

In addition, aqueous media may contain small amounts of coalescent solvents in addition to water, which are water soluble or partially water soluble organic solvents and are well known in the art. Examples of such flocculating solvents include hydrocarbons, alcohols, esters, ethers, ketones, and the like. Preferred flocculants include alcohols, polyols and ketones. Specific flocculating solvents include isopropanol, butanol, 2-ethylhexanol, isophorone, 4-methoxy-pentanone, ethylene and propylene glycol, mono ethyl, monobutyl and monohexyl ethers of ethylene glycol, and the like. The amount of flocculant solvent is generally about 0.01 to 25% by weight, preferably about 5% by weight, based on the weight of the aqueous medium.

When the above-mentioned aqueous dispersion is used for electrodeposition, the aqueous dispersion is placed in contact with the electrically conductive cathode and the electrically conductive anode, with the surface to be painted as the cathode. The adhesive film of the coating composition becomes a cathode when sufficient voltage is given between the electrodes after contact with the aqueous dispersion. Electrodeposition conditions are generally similar to those for depositing other types of coatings. The voltage used can vary, for example, from as low as 1 volt to as high as thousands of volts, but typically from 50 to 500 volts. Current densities are usually 0.5-5 amps / ft ² and tend to decrease during electrodeposition, which means that an insulating film is formed. The coating compositions of the present invention can be used on a variety of electrically conductive substrates, in particular metals such as steel, aluminum, copper, magnesium and the like and materials coated with conductive carbon. After coating by electrodeposition, it is usually cured by heat treatment at a temperature of about 90 to 260 ° C. for about 1 to 40 minutes.

The present invention can be more clearly understood by the following examples, which are only intended to illustrate the present invention and are not intended to limit the scope of the invention.

Comparative Example 1

For comparison with the present invention, a high temperature curing type curing agent was prepared as follows in the composition of Table 1.

Reactant Parts by weight 4-methyl-1,3-phenylene diisocyanate 200.0 2-butoxy ethanol 190.0 Trimethyrol Propane 30.8 Dibutyltin dilaurate 2.0 Methyl Isobutyl Ketone 74.6

4-methyl-1,3-phenylene diisocyanate (TDI), dibutyl tin dilaurate, and methyl isobutyl ketone were inserted in the reaction container provided with the stirrer, the thermometer, and the cooler, and it heated up to 80 degreeC. Then, 2-butoxy ethanol was slowly added dropwise and then maintained for 2 hours. After the reaction of 2-butoxy ethanol with 4-methyl-1,3-phenylene diisocyanate was terminated, trimetholol propane was slowly injected. The reaction was terminated by maintaining for 3 hours after the injection of trimetholol propane, and finally the reaction was determined by checking the NCO content. By the above reaction, a liquid curing agent having a solid content ratio of 85.0 was prepared.

Comparative Example 2

For comparison with the present invention, a high temperature curing type curing agent was prepared as follows in the composition of Table 2.

Reactant Parts by weight 4-methyl-1,3-phenylene diisocyanate 180.0 2- (2-butoxyethoxy) ethanol 209.0 Trimethyrol Propane 35.0 Dibutyltin dilaurate 1.8 Methyl Isobutyl Ketone 75.2

4-methyl-1,3-phenylene diisocyanate (TDI), dibutyl tin dilaurate, and methyl isobutyl ketone were inserted in the reaction container provided with the stirrer, the thermometer, and the cooler, and it heated up to 80 degreeC. Then, 2- (2-butoxyethoxy) ethanol was slowly added dropwise and then maintained for 2 hours. After the reaction of 2- (2-butoxyethoxy) ethanol with 4-methyl-1,3-phenylene diisocyanate was terminated, trimetholol propane was slowly injected. The reaction was terminated by maintaining for 3 hours after the injection of trimetholol propane, and finally the reaction was determined by checking the NCO content. By the above reaction, a liquid curing agent having a solid content ratio of 85.0 was prepared.

Comparative Example 3

For comparison with the present invention, a curing agent was prepared as follows in the composition of Table 3.

Reactant Parts by weight 4,4'-methylene bis (phenylisocyanate) 277.5 Dimethyrol Propionic Acid 111.44 Trimethyrol Propane 18.8 Dibutyltin dilaurate 0.4 Methyl Isobutyl Ketone 71.8

4,4'-methylene bis (phenylisocyanate), dibutyl tin dilaurate, and methyl isobutyl ketone were inserted in the reaction container provided with the stirrer, the thermometer, and the cooler, and it heated up to 80 degreeC. Then, dimethyrolpropionic acid was slowly added dropwise, and then maintained for 2 hours. After confirming that the reaction of dimethyrolpropionic acid with 4,4'-methylene bis (phenylisocyanate) was terminated, trimethyrol propane was slowly injected. The reaction was terminated by holding for 3 hours after the injection of trimetholol propane and finally the reaction was determined by checking the NCO content. By the above reaction, a liquid curing agent having a solid content ratio of 85.0 was prepared.

Example 1

To the composition of Table 4 was prepared a curing agent by the following method.

Reactant Parts by weight 4-methyl-1,3-phenylene diisocyanate 250.0 Dibutyltin dilaurate 2.0 Methyl Isobutyl Ketone 102.0 Hydroxyethyl methacrylate 70.0 2- (2-butoxyethoxy) ethanol 210.0 Trimethyrol Propane 22.0 Dimethyrol Propionic Acid 39.0

4-methyl-1,3-phenylene diisocyanate, dibutyltin dilaurate, and methyl isobutyl ketone were introduced into a reaction vessel provided with a stirrer, a thermometer, and a cooler, and the temperature was raised to 60 ° C. Then, 2- (2-butoxyethoxy) ethanol and hydroxy ethyl methacrylate were slowly injected and maintained for 2 hours. Thereafter, when the reaction was terminated by checking the NCO content, trimethol propane and dimethyrolpropionic acid were injected and maintained for 2 hours, and then the final reaction termination state was confirmed. By the above reaction, a liquid curing agent having a solid content ratio of 85.0 was prepared.

Example 2

To the composition of Table 5 was prepared a curing agent by the following method.

Reactant Parts by weight 4,4'-methylene bis (phenylisocyanate) 250.0 Dibutyltin dilaurate 2.0 Methyl Isobutyl Ketone 90.4 Hydroxypropyl (meth) acrylate 58.0 2- (2-butoxyethoxy) ethanol 170.0 Trimethyrol Propane 12.0 Dimethyrol Propionic Acid 20.0

4,4'-methylene bis (phenylisocyanate), dibutyl tin dilaurate, and methyl isobutyl ketone were inserted in the reaction container provided with the stirrer, the thermometer, and the cooler, and it heated up to 80 degreeC. Then, a mixture of 2- (2-butoxyethoxy) ethanol and hydroxy propyl (meth) arc slowly was injected and then maintained for 2 hours. When the reaction between the mixture of 2- (2-butoxyethoxy) ethanol and hydroxy propyl (meth) acrylate and 4,4'-methylene bis (phenylisocyanate) is terminated, trimetholpropane and dimethyrolpropionic acid Was injected slowly. The reaction was terminated by holding for 3 hours after the injection of trimetholpropane and dimethyrolpropionic acid, and finally the reaction was determined by checking the NCO content. By the above reaction, a liquid curing agent having a solid content ratio of 85.0 was prepared.

Example 3

To the composition of Table 6 was prepared a curing agent by the following method.

Reactant Parts by weight 4,4'-methylene bis (phenylisocyanate) 250.0 Dibutyltin dilaurate 2.0 Methyl Isobutyl Ketone 88.5 Hydroxyethyl (meth) acrylate 65.0 2- (2-butoxyethoxy) ethanol 150.0 Trimethyrol Propane 10.0 Dimethyrol Propionic Acid 24.0

4,4'-methylene bis (phenylisocyanate), dibutyl tin dilaurate, and methyl isobutyl ketone were inserted in the reaction container provided with the stirrer, the thermometer, and the cooler, and it heated up to 80 degreeC. Then, a mixture of 2- (2-butoxyethoxy) ethanol and hydroxy ethyl (meth) acrylate was slowly injected and then maintained for 2 hours. When the reaction between the mixture of 2- (2-butoxyethoxy) ethanol and hydroxy ethyl (meth) acrylate and 4,4'-methylene bis (phenylisocyanate) is terminated, trimetholpropane and dimethyrolpropionic acid Was injected slowly. The reaction was terminated by holding for 3 hours after the injection of trimetholpropane and dimethyrolpropionic acid, and finally the reaction was determined by checking the NCO content. By the above reaction, a liquid curing agent having a solid content ratio of 85.0 was prepared.

Example 4

To the composition of Table 7 was prepared a curing agent by the following method.

Reactant Parts by weight 4,4'-methylene bis (phenylisocyanate) 100.0 Dibutyltin dilaurate 1.0 Methyl Isobutyl Ketone 34.6 Hydroxypropyl (meth) acrylate 29.0 2- (2-butoxyethoxy) ethanol 50.0 Trimethyrol Propane 7.0 Dimethyrolbutanoic acid 10.0

4,4'-methylene bis (phenylisocyanate), dibutyl tin dilaurate, and methyl isobutyl ketone were inserted in the reaction container provided with the stirrer, the thermometer, and the cooler, and it heated up to 80 degreeC. Then, a mixture of 2- (2-butoxyethoxy) ethanol and hydroxy propyl (meth) acrylate was slowly injected and then maintained for 2 hours. When the reaction between the mixture of 2- (2-butoxyethoxy) ethanol and hydroxy propyl (meth) acrylate and 4,4'-methylene bis (phenylisocyanate) is terminated, trimethol propane and dimethyrolbutanoic acid Was injected slowly. The reaction was terminated by maintaining for 3 hours after the injection of trimetholol propane and dimethyrolbutanoic acid, and finally the reaction was determined by checking the NCO content. By the above reaction, a liquid curing agent having a solid content ratio of 85.0 was prepared.

Example 5                     

To the composition of Table 8 was prepared a curing agent by the following method.

Reactant Parts by weight 4,4'-methylene bis (phenylisocyanate) 100.6 Dibutyltin dilaurate 1.0 Methyl Isobutyl Ketone 36.3 Hydroxypropyl (meth) acrylate 29.0 2- (2-butoxyethoxy) ethanol 50.0 Trimethyrol Propane 8.0 Dimethyrolbutanoic acid 12.0

4,4'-methylene bis (phenylisocyanate), dibutyl tin dilaurate, and methyl isobutyl ketone were inserted in the reaction container provided with the stirrer, the thermometer, and the cooler, and it heated up to 80 degreeC. A mixture of 2- (2-butoxyethoxy) ethanol and hydroxy propyl (meth) acrylate was slowly injected and then maintained for 2 hours. When the reaction between the mixture of 2- (2-butoxyethoxy) ethanol and hydroxy propyl (meth) acrylate and 4,4'-methylene bis (phenylisocyanate) is terminated, trimethol propane and dimethyrolbutanoic acid Was injected slowly. The reaction was terminated by maintaining for 3 hours after the injection of trimetholol propane and dimethyrolbutaninoic acid, and finally the reaction was determined by checking the NCO content. By the above reaction, a liquid curing agent having a solid content ratio of 85.0 was prepared.

Comparative Example 4

Using the curing agent of Comparative Example 1, a water dispersion having a polyepoxide as a base resin as a component of the electrodeposition resin composition was prepared in the composition shown in Table 9 below.

Reactant Parts by weight N80101 ¹ 650.0 N8020 ² 90.0 Tone0201 ³ 160.0 Xylene 60.0 Anchor Amine 1040 3.0 Methoxypropanol 465.0 N-methyl ethanol amine 50.0 KT-22 ⁴ 80.0 Curing agent of Comparative Example 1 430.0 Lactic acid 40.3 Deionized water 1410.0

¹ Korea Chemical Corporation: Bisphenol A type epoxy resin (molecular weight 960)

² Korea Chemical Co., Ltd.: Bisphenol A type epoxy resin (molecular weight 1300)

³ UCC: Polycaprolactone diol (molecular weight 534)

⁴ Air Product: Diketamine with diethylene triamine and methyl isobutyl ketone / methyl isobutyl ketone solution (73%).

N8010, N8020, Tone0201, 1,6-hexanediol, and xylene were introduced into a reaction vessel equipped with a stirrer, a thermometer, a cooler, and an H separator, heated to 190 ° C to reflux to remove moisture, and then an anchoramine 1040 was added thereto. After holding at 170 ° C. for about 4 hours, the epoxy equivalent value reached 1000 and then cooled. After adding methoxypropanol, N-methylethanol amine and KT-22, the reaction was maintained at 120 ° C. for 4 hours. . When the theoretical epoxy equivalent and amine number were reached, it cooled to 80 degreeC, and added the hardening | curing agent of the comparative example 1. The mixture was removed again in vacuo at 100 ° C., neutralized with lactic acid, and then dispersed with deionized water to prepare a water dispersion resin having a solid content of about 40%.

Comparative Example 5

Electrodeposited resin was prepared in a similar manner to Comparative Example 4 except for using the curing agent prepared in Comparative Example 2.

Comparative Example 6

Electrodeposited resin was prepared in a similar manner to Comparative Example 4 except for using the curing agent prepared in Comparative Example 3.

Example 6

Electrodeposited resin was prepared in a similar manner to Comparative Example 4 except for using the curing agent prepared in Example 1.

Example 7

Electrodeposited resin was prepared in a similar manner to Comparative Example 4 except for using the curing agent prepared in Example 2.

Example 8

Electrodeposited resin was prepared in a similar manner to Comparative Example 4 except for using the curing agent prepared in Example 3.

Example 9

Electrodeposited resin was prepared in a similar manner to Comparative Example 4 except for using the curing agent prepared in Example 4.

Example 10                     

Electrodeposited resin was prepared in a similar manner to Comparative Example 4 except for using the curing agent prepared in Example 5.

In order to evaluate the curing agent prepared in the present invention Comparative Examples 4-6 prepared in the same manner as described above 6 to 10 electrodeposition resins were stored in an incubator (80 incubator) at 80 ℃ for the gel state after visual observation Checked to obtain the experimental results as shown in Table 10.

Test Items Storage stability 80 ℃ × 3 days Comparative Example 4 Good Comparative Example 5 Good Comparative Example 6 Bad Example 6 Good Example 7 Good Example 8 Good Example 9 Good Example 10 Good

Example 11

To prepare a pigment paste which is a constituent of the cationic electrodeposition paint, the composition of Table 11 was prepared as follows.

Reactant Parts by weight EPONE828 ¹ 171.7 Bisphenol-A 69.5 Triton X-100 ² 28.2 Xylene 100.0 Anchor 1040 ³ 1.0 N-methyl-2-pyrrolidone 10.0 Methoxy-2-propanol 100.0 KT-22 ⁴ 95.0 Acetic acid 20.0

¹ Shell Chemicals Epoxy Resin

² Nonionic Emulsifiers of Alkyl Allyl Polyether Alcohols

³ Air Products, Trifluoroamine Catalysts

⁴ Product of Air Products, 73% solution of diethylenetriamine dissolved in methylisobutylketone as diketamine, blocked by methylisobutyl ketone.

171.7 parts by weight of EPON 828, 100 parts by weight of Triton X-100 and xylene were inserted into a reaction vessel equipped with a stirrer, a thermometer, a cooler, and a H separator, and heated to 210 ° C. About 70 parts by weight of xylene was distilled off with an H type separator while maintaining at 210 ° C. After holding for 30 minutes, the mixture was cooled to 160 ° C, and 69.2 parts by weight of 11 parts by weight of a solution of bisphenol-A and Anchor 1040 10% N-methyl-2-pyrrolidone was introduced and then heated to 180 ° C. The epoxy equivalent was 1130 when maintained at 180 ° C. for 1 hour. Then, 100 parts by weight of methoxy-2-propanol was slowly injected and then cooled to 80 ° C. And after inserting 95 weight part KT-22, it heated up and maintained at 120 degreeC. After the holding reaction, the epoxy equivalent was confirmed to terminate the reaction. The synthesized epoxy amine resin was neutralized at 20 ° C. using 20 parts by weight of acetic acid and 100 parts by weight of deionized water was added. As a clear liquid, a water-dispersible resin having a solid content of 59.1 was prepared.

Example 12

A pigment paste was prepared by dispersing titanium dioxide, carbon black, basic lead silicate and butyl tin oxide in the pigment dispersing resin prepared in Example 11 as follows in the composition of Table 12.

Reactant Parts by weight Resin of Example 11 40.0 Red silicate 17.4 Surfinol104 ¹ 5.1 Carbon black 1.2 Titanium oxide 123.0 Dibutyl tin oxide 5.8 Deionized water 60.0

¹ Emulsifier of Air Products

The components were mixed together in the order indicated and stirred well, then dispersed up to Hegman No. 6 with a Dispermet SL-703 (B Y Kay Corporation) disperser.

Example 13

Preparation of Cationic Electrodeposition Paints and Performance Evaluation of Curing Agents

The cationic electrodeposition paint is 1600.2 parts by weight of the cationic electrodeposition resin prepared in Examples 6 to 5, Comparative Examples 4 to 5, 50 parts by weight of the plasticizer paraplex WP1 available from Rohm and Haas, and 480.2 parts by weight of the pigment paste prepared in Example 12. After mixing, deionized water was added so that the total solid content would be 20% to prepare the paints of Comparative Examples 7 to 8 and Examples 11 to 15.

The electrodeposition paint liquid was prepared to have a solid content of 20% and a ratio of pigment to binder of 0.3: 1. The electrodeposition paint was filtered through a 400 mesh wire mesh and no agglomerates were collected. Electrodeposition coating was carried out at 270V for 3 minutes using the coating liquid prepared above on a cold rolled steel sheet surface-treated with a zinc phosphate treatment agent. Thereafter, the resulting coating was washed with water and baked in an oven at 150 ° C. and 155 ° C. for 30 minutes to obtain a 25 μm thick coating.

In order to evaluate the performance of the curing agent prepared according to the present invention by measuring the curing density of the cured coating film of the electrodeposition paint formed by the above method by methyl isobutyl ketone rubbing (rubbing) to obtain the experimental results as shown in Table 13.

Test Items MIBK Rubbing 155 ℃ 150 ℃ Comparative Example 7 10th 0 times Comparative Example 8 12th 0 times Example 11 50 or more times 45 or more times Example 12 50 or more times 50 or more times Example 13 50 or more times 50 or more times Example 14 50 or more times 50 or more times Example 15 50 or more times 50 or more times

* MIBK Rubbing Test

Rubbing the cloth or tissue with a solvent (methyl isobutyl ketone) until it damages the coating film, meaning '50 or more times' means rubbing for at least 50 times so that the film is cured when there is no damage. It is.

The low temperature hardening type electrodeposition resin composition of the present invention is a low temperature hardening type blocker of isocyanate by partially blocking diisocyanate with mono alcohol and acrylic monomer together with dihydroxy alkanoic acid when preparing a polyisocyanate curing agent. It can prevent the degradation of the storage stability generated when used as, the performance of the coating film formed using this is significantly superior to the conventional electrodeposition resin composition. In addition, the yellowing phenomenon generated when using aromatic isocyanate may be improved as well as to improve uniform coating property.

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific scope of the present invention will be apparent from the appended claims.

Claims (8)

Polyepoxy-amine cationic resins as base resins; And a polyisocyanate-based curing agent prepared by reacting an aliphatic or aromatic isocyanate, a mono alcohol and an acrylic monomer, a dihydroxy alkanoic acid represented by Formula 1 below, and a polyfunctional polyol, wherein the amount of the curing agent is determined by the base resin. Low temperature curable electrodeposition resin composition, characterized in that 10 to 60% by weight as a reference: Formula 1

Wherein R 1 is H or an alkyl group having 1 to 3 carbon atoms, and R 2 is a methirol group. The low temperature curable electrodeposition resin composition according to claim 1, wherein the content of the dihydroxy alkanoic acid is 1.0 to 60% based on the isocyanate equivalent weight in the aliphatic or aromatic isocyanate. The low temperature curable electrodeposition resin composition according to claim 1, wherein the dihydroxy alkanoic acid has a number average molecular weight of 100 to 200. According to claim 1, wherein the dihydroxy alkanoic acid is at least one selected from the group consisting of dimethol ethanoic acid, dimethyrol propionic acid, dimethol butanoic acid and dimethyrolpentanoic acid. Low temperature curing type electrodeposition resin composition. The low temperature curable electrodeposition resin composition according to claim 1, wherein the content of the mono alcohol is 50 to 85% based on the isocyanate equivalent weight in the aliphatic or aromatic isocyanate. The low temperature curable electrodeposition resin composition according to claim 1, wherein the content of the acrylic monomer is 5 to 30% based on the isocyanate equivalent weight in the aliphatic or aromatic isocyanate. The method of claim 1, wherein the multifunctional polyol is at least one selected from the group consisting of trimetholol propane, polyalkylene glycol, 1,6-hexanediol, ethoxylated trimetholol propane and polycaprolactone triol Low temperature hardening type electrodeposition resin composition characterized by the above-mentioned. A low temperature hardening type electrodeposition paint containing the composition according to any one of claims 1 to 7.