JP4236254B2 - Method for producing a novel cationic electrodeposition coating - Google Patents

Description

【００２９】
（注）貯蔵安定性は４０℃にて沈降を生じるまでの期間を示す。また、製法において本願発明による方法を新製法と記し、従来法によるものを従来法と記した。
【００３０】
【発明の効果】
本発明の製造方法によって、塗料中の有機溶剤の含有量を大幅に低減でき、かつ従来のカチオン塗料と同等の特性を持つ塗料を得ることができる。樹脂が構造的に嵩高く従来製法ではエマルション化困難であった基剤樹脂も容易にエマルション化およびエマルションの安定化が可能となる。また、脱溶剤およびエマルション化とそれに続くエマルションの安定化の工程を同時に行うことにより製造工程が簡素化され、省資源化、環境保護をはかることが可能である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a cationic electrodeposition paint having a very low solvent content.
[0002]
[Prior art]
Conventionally, the preparation of a cationic electrodeposition coating has been carried out by the following method. (1) Synthesis of resin for cationic electrodeposition coating → removal of organic solvent from the resin mixture → emulsification by adding the solvent mixture removed to a mixture of water and neutralizing acid, or (2) resin for cationic electrodeposition coating → Neutralization treatment of resin Emulsification by adding water → Removal of organic solvent. (For example, Patent Document 1)
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-328639 (page 7, right first row to 10th row)
[0004]
An organic solvent is blended in the coating composition so that this neutralization treatment or emulsification can be easily performed. When combined with the organic solvent used as the reaction solvent when preparing the coating resin, the amount of the organic solvent in the coating composition is 30 to 55 parts by weight with respect to 100 parts by weight of the produced resin. Some of these organic solvents have been removed at an appropriate time in the cationic electrodeposition coating production process.
[0005]
[Problems to be solved by the invention]
If this amount of organic solvent can be reduced, it can contribute to resource saving, environmental protection, and simplification of the manufacturing process. However, the reduction in the amount of organic solvent makes emulsification inadequate and decreases the storage stability of electrodeposition paints. May cause. Considering recent trends in environmental regulations, it is preferable that the amount of the organic solvent in the paint is as small as possible. However, the reduction of the solvent involves the above problems. An object of the present invention is to provide an electrodeposition coating composition having an extremely low solvent content and excellent storage stability.
[0006]
[Means for Solving the Problems]
As a result of intensive studies on a method for producing an emulsion having a composition equivalent to that of a conventional paint in an ultra-low solvent amount composition, a means capable of achieving the above object has been found. In a method for producing a cationic electrodeposition paint from a resin composition for a cationic paint comprising a base resin, a curing agent, an additive, and an organic solvent, a method for producing a cationic electrodeposition paint characterized by performing the following treatment: ( 1) Add additives during water dispersion and desolvation. (2) When neutralization is complete, add deionized water and start depressurization, and simultaneously perform the steps of water dispersion and desolvation under reduced pressure.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail together with embodiments thereof.
The cationic electrodeposition resin in the present invention comprises a base resin having a cationic group and a curing agent for curing the base resin. As the base resin, a cationic epoxy resin in which an active hydrogen compound such as an amine is reacted with the epoxy group of the epoxy resin, the epoxy group is opened, and a cationic group is introduced is used. A blocked polyisocyanate with blocked isocyanate groups is used.
[0008]
The cationic epoxy resin is typically produced by ring-opening with an active hydrogen compound capable of introducing a cationic group into all of the epoxy groups of the bisphenol type epoxy resin. Examples of commercially available epoxy resins include Epicoat 828 (manufactured by Yuka Shell Epoxy, epoxy equivalent of 180 to 190), Epicoat 1001 (same as above, epoxy equivalent of 450 to 500), Epicoat 1010 (same as above, epoxy equivalent of 3000 to 4000), and the like. .
[0009]
Since the fluidity of the coating film at the time of film formation becomes insufficient due to the reduction in the amount of organic solvent, the smoothness of the coating film may be lowered. Therefore, the above-mentioned bisphenol type epoxy resin contains polyester polyol, polyether polyol, hydroxyl group. Flexibility is imparted by reacting with a plastic modifier such as polybutadiene, or an epoxy having flexibility, such as an epoxy group-containing polyol (Adeka Resin EP-4058, manufactured by Asahi Denka Kogyo Co., Ltd.) is used. You may do it. In addition, these epoxy resins can be chain-extended using a reaction between an epoxy group and a diol or dicarboxylic acid.
[0010]
These epoxy resins are active hydrogen compounds such that primary amino groups occupy 5 to 50% of them, so that an amine equivalent of 0.3 to 4.0 meq / g is obtained after ring opening. It is desirable to open the ring.
[0011]
Examples of the cationizing agent include those capable of introducing a cationic group into the base resin, for example, primary amines such as aliphatic, alicyclic, and aromatic, secondary amines, tertiary amine acid salts, and secondary sulfide acids. Examples include salts.
Specific examples include butylamine, octylamine, diethylamine, dibutylamine, methylbutylamine, monoethanolamine, diethanolamine, N-methylethanolamine, triethylamine hydrochloride, N, N-dimethylethanolamine acetate, diethyl disulfide / acetic acid mixture, etc. In addition, there are secondary amines in which primary amines such as aminoethylethanolamine ketimine and diethylenetriamine diketimine are blocked. A plurality of amines may be used in combination.
[0012]
As the curing agent, various known block isocyanate type curing agents can be used. The polyisocyanate may be, for example, any of aliphatic, alicyclic, aromatic and aromatic-aliphatic. Adducts or prepolymers obtained by reacting polyisocyanates with polyhydric alcohols such as ethylene glycol, propylene glycol, trimethylolpropane and hexanetriol at an NCO / OH ratio of 2 or more may also be used as the block isocyanate curing agent. As the blocking agent, those usually used such as ε-caprolactam and butyl cellosolve can be used.
[0013]
These base resins and curing agents are synthesized in the presence of a solvent that can be azeotroped with water in consideration of removing the solvent in a later step. Since most of the organic solvent is removed, the solvent content during the reaction is not particularly limited, but is preferably about 15 to 35% for ease of handling the resin and shortening the time required for the solvent removal step.
[0014]
Next, a resin composition for cationic electrodeposition coating is prepared. After the base resin, the curing agent and the additive are mixed and neutralized, it is diluted with water so that the solid content of the coating resin composition is 30 to 40%. Immediately after dilution, pressure reduction is started to remove the solvent in the composition. Naturally, the dispersion of the resin composition in water is insufficient when water is added, but the paint particles are stabilized in water even with a small amount of solvent by sufficient mixing in the azeotropic desolvation.
[0015]
Examples of the nonionic surfactant having HLB 13 to 18 include polyoxyethylenealkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene alkylallyl ether, polyoxyethylene alkylamine ether and the like. The amount of the nonionic surfactant is preferably 0.2 to 3.0%. If the amount of the activator is less than 0.2%, the emulsifying power is insufficient and the running stability of the diluted paint is reduced. Absent.
On the other hand, when the activator has an HLB of less than 13, the emulsifying power becomes insufficient, and when it exceeds 18, various performances of the obtained electrodeposition coating film are deteriorated.
[0016]
The neutralizing agent used for the neutralization treatment is not particularly limited as long as it can neutralize the cationic epoxy resin, but organic acids such as formic acid, acetic acid, lactic acid and sulfamic acid are preferable. The base resin is used at a concentration as low as possible so that it can be uniformly neutralized, and is 10 to 30 milliequivalents, preferably 15 to 25 milliequivalents per 100 g of resin solids. If the amount of the neutralized acid is less than 10 milliequivalents, the affinity for water is insufficient and the dispersion in water cannot be performed or the stability is extremely poor. The viscosity of the composition becomes very high, and it takes time for the solvent-removal process, and the amount of electricity required for deposition during electrodeposition coating increases, causing problems such as a decrease in the precipitation of paint solids.
[0017]
【Example】
Hereinafter, the features of the present invention will be clarified by showing production examples, examples and comparative examples, but the present invention is not limited thereto. “Part” and “%” indicate “part by weight” and “% by weight”, respectively.
[0018]
[Production Example 1]
Production of resin for cationic electrodeposition coating (base resin A1) Epicote 1004 (bisphenol A type glycidyl ether with epoxy equivalent of 950; manufactured by Yuka Shell Co., Ltd.) equipped with a thermometer, stirrer, and reflux condenser. 950 parts and 371 parts of methyl isobutyl ketone are charged. After heating and dissolving the epoxy resin, add 74 parts of diethanolamine at 70 ° C., and then add 76 parts of amine A (methyl isobutyl keto diketimine / methyl isobutyl ketone solution of 20% diethylenetriamine of active ingredient) and react at 100 ° C. for 2 hours. Thereafter, it was further diluted with 21 parts of deionized water. A cationic amine-modified epoxy resin having a resin solid content of 70% and a tertiary amine value of 0.86 milliequivalent (/ g solid content) was obtained.
[0019]
[Production Example 2]
Production of resin for cationic electrodeposition coating (base resin A2) A reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser, 190 parts of Adeka Resin EP4058 (epoxy equivalent 520-540, manufactured by Asahi Denka Kogyo Co., Ltd.), bisphenol A242 parts and 29 parts of methyl isobutyl ketone were charged and kept at 150 ° C. When the epoxy equivalent reached 0, 518 parts of bisphenol A-type glycidyl ether having an epoxy equivalent of 180 was added, and the mixture was kept at 150 ° C. until the epoxy equivalent reached 950. Thereafter, the mixture was cooled to 110 ° C. and diluted with 341 parts of methyl isobutyl ketone.
[0020]
To the obtained reaction product, 74 parts of diethanolamine and 76 parts of amine A (methyl isobutyl keto diketimine / methyl isobutyl ketone solution of 20% active ingredient diethylenetriamine) were added and reacted at 100 ° C. for 2 hours. Diluted in portions. A cationic amine-modified epoxy resin having a resin solid content of 70% and a tertiary amine value of 0.86 milliequivalent (/ g solid content) was obtained.
[0021]
[Production Example 3]
Preparation of resin for cationic electrodeposition paint (curing agent B) A reaction vessel equipped with a thermometer, stirrer, and reflux condenser was charged with 222 parts of isophorone diisocyanate and 87 parts of methyl isobutyl ketone, while maintaining the reaction temperature at 40 ° C. 174 parts of methyl ethyl ketoxime was gradually added dropwise to react. The NCO content was measured from the first hour of the reaction, and when the NCO content reached 0.5% or less, it was diluted with 12 parts of ethylene glycol monobutyl ether. A block polyisocyanate curing agent having a resin solid content of 80% was obtained.
[0022]
[Example 1]
Preparation of cationic electrodeposition paint 93 parts of base resin (A-1) obtained in Production Example 1, 31 parts of curing agent B obtained in Production Example 3, HN-120 (synthetic alcohol-based nonionic surfactant, HLB14.2) 1 part, manufactured by Sanyo Chemical Co., Ltd.) was charged into a reaction vessel equipped with a stirrer, thermometer, cooler and decompression device. After sufficiently mixing, 3.7 parts of 50% lactic acid diluted with deionized water was added and stirred at 40 to 70 ° C. for 30 minutes to carry out neutralization treatment. Next, 135 parts of deionized water was added with stirring, and a predetermined amount of solvent was removed and emulsified at about 70 ° C. under a pressure of 300 to 500 mmHg (gauge pressure). Thereafter, 55 parts of deionized water was added to adjust the solid content to obtain a 31.5% emulsion. The properties of the emulsion are shown in Table 1.
[0023]
[Example 2]
It carried out similarly to Example 1 except having used the base resin (A-2) obtained by manufacture example 2 instead of base resin (A-1) of Example 1. FIG. The properties of the emulsion are shown in Table 1.
[0024]
[Comparative Example 1]
The coating composition having the same composition as in Example 1 was neutralized in the same manner as in Example 1, and 190 parts of deionized water was gradually added dropwise with vigorous stirring to obtain an emulsion having a solid content of 28.3%. Subsequently, a predetermined amount of solvent was removed under a pressure of about 70 ° C. and 300 to 500 mmHg (gauge pressure) to obtain an emulsion having a solid content of 31.5%. The properties of the emulsion are shown in Table 1.
[0025]
[Comparative Example 2]
Table 1 shows the properties of the emulsion obtained by neutralizing the coating composition having the same composition as in Example 2 and then emulsifying and removing the solvent in the same manner as in Comparative Example 1.
[0026]
[Comparative Example 3]
The same procedure as in Example 2 was performed except that HN-70 (synthetic alcohol-based nonionic surfactant, HLB 11.7, manufactured by Sanyo Chemical Co., Ltd.) was used instead of the surfactant HN-120 of Example 2. It was. Table 1 shows the properties of the emulsion.
[0027]
[Comparative Example 4]
The same procedure as in Example 2 was performed except that 15 parts of ethylene glycol monobutyl ether was added instead of 1 part of HN-120 of Example 2 and 121 parts of deionized water was added. The properties of the emulsion are shown in Table 1.
[0028]
[Table 1]

[0029]
(Note) Storage stability indicates the period until sedimentation occurs at 40 ° C. Further, in the production method, the method according to the present invention is referred to as a new production method, and the method according to the conventional method is referred to as a conventional method.
[0030]
【The invention's effect】
By the production method of the present invention, the content of the organic solvent in the paint can be greatly reduced, and a paint having the same characteristics as those of the conventional cationic paint can be obtained. The base resin, which is bulky in structure and difficult to emulsify in the conventional manufacturing method, can be easily emulsified and stabilized. Further, by simultaneously performing the steps of solvent removal and emulsion formation and subsequent emulsion stabilization, the production process can be simplified, and resource saving and environmental protection can be achieved.

Claims (2)

  In a method for producing a cationic electrodeposition paint from a resin composition for a cationic paint comprising a base resin, a curing agent, a nonionic surfactant having HLB 13 to 18 and an organic solvent, a cation characterized by performing the following treatment: Electrodeposition coating production method: (1) Mixing nonionic surfactant having HLB13-18 and then entering neutralization step, (2) Deionized water is added after neutralization is completed, and reduced pressure And simultaneously perform the steps of water dispersion and vacuum desolvation.   The base resin is a cationic amine-modified epoxy resin obtained by cationizing an amine-modified resin obtained by reacting an amine with a polyepoxy resin containing a glycidyl ether of polyphenol and / or an epoxy group-containing polyol. Production method.