JP3305472B2 - Pigment dispersion resin for electrodeposition paint and pigment dispersion paste containing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cationic resin which can be suitably used as a pigment-dispersing resin in an electrodeposition paint and a pigment-dispersing paste containing the same.

[0002]

2. Description of the Related Art Electrodeposition coating is a method in which a coating is carried out by filling a water-based coating material in a tank, electrophoresing the coating components on an object to be coated in the same bath, and electrodepositing the components on the surface to be coated. This coating method is mainly used for anticorrosion coating of an automobile body and is industrially important.

In general, a pigment and a pigment dispersant are contained in an electrodeposition paint. Before introducing the pigment into the paint,
A pigment dispersion paste in which a pigment is dispersed in an aqueous medium at a high concentration is used as an intermediate composition. A dispersant is used to impart sufficient storage stability to the pigment-dispersed paste. This dispersant is required to have the property of increasing the dispersion stability of the pigment dispersion paste and the ability to keep the paint stable for a long period of time when the pigment dispersion paste is diluted with an aqueous medium into an electrodeposition paint. You. In recent years, cationic resins have been generally used as pigment dispersants for electrodeposition paints.

For example, JP-B-53-47143 and JP-B-54-497
No. 8 discloses a cationic resin used as a dispersant for an electrodeposition paint. JP-A-1-182377 discloses a cationic resin which also functions as a catalyst in a curing reaction between an α, β-unsaturated carbonyl group and a hydroxyl group. Here, a cationic resin having a tertiary sulfonium salt as a cationic resin having an inhibitory effect in a moderately basic and corrosive environment for catalytic activity is disclosed.

Japanese Patent Application Laid-Open No. 63-23919 discloses a sulfonium resin useful as a pigment pulverizing vehicle. The most preferred example is a sulfonium resin derived from thiodiethanol.
Cationic resins having graded sulfonium salts are mentioned.

However, the pigment-dispersed resin disclosed herein is inferior in pigment dispersibility under long-term storage, and thus has a problem that a pigment-dispersed paste and an electrodeposition paint having excellent storage stability cannot be obtained.

[0007]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and an object of the present invention is to provide a pigment having excellent stability over time and excellent pigment dispersibility and high corrosion resistance. An object of the present invention is to provide a pigment-dispersed resin capable of preparing an electrodeposition paint, and a pigment-dispersed paste containing this resin and having excellent temporal stability.

[0008]

SUMMARY OF THE INVENTION The present invention provides an

[0009]

Embedded image

Wherein Ep is a residue of an epoxy resin having an epoxy equivalent of 150 to 2000, and R ¹ is hydroxymethyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 4-hydroxybutyl Or a 2,3-dihydroxypropyl group, A ^- is a counter anion, and m is a number from 0.1 to 4.0. And the above-mentioned object is achieved.

The pigment-dispersed resin of the present invention has a content of 30 to 500, especially 5
It preferably has a tertiary sulfonium value of 0 to 150.
If the tertiary sulfonium value exceeds 500, the corrosion resistance decreases,
This is because if it is less than 0, dispersion will be poor. The tertiary sulfonium value in the present invention is represented by the milliequivalent of the sulfonium group in 100 g of the resin.

Preferably, the pigment-dispersed resin of the present invention is prepared by reacting an epoxy resin with a sulfide corresponding to the tertiary sulfonium group. This reaction is
Generally, the reaction is carried out at a reaction temperature of 50 to 80 ° C, preferably 60 to 75 ° C, by mixing and stirring the epoxy resin, sulfide, acid and deionized water. The preferred reaction ratio is 1 to 4 equivalents of sulfide based on the epoxy group of the epoxy resin, and the equivalent of acid is equivalent to epoxy. As the acid,
Any substance that can be a counter anion of sulfonium can be used. Examples thereof include formic acid, lactic acid, acetic acid, propionic acid, butyric acid, dimethylolpropionic acid, boric acid, phosphoric acid, hydrochloric acid, and sulfuric acid.However, when an inorganic acid is used, a halogen compound that leads to a reduction in corrosion resistance is used. Carboxylic acids such as formic acid, lactic acid, acetic acid, propionic acid, butyric acid, and dimethylolpropionic acid are preferred because of the possibility of contamination.

The epoxy resin which can be used in the present invention is a so-called polyepoxide having an average of one or more 1,2-epoxy groups in one molecule. The epoxy equivalent of these epoxy resins is preferably 150 to 2000, more preferably 4 to 2000.
00 to 1500. When the epoxy equivalent is less than 150, a film cannot be formed at the time of electrodeposition because a film cannot be formed, and when it exceeds 2,000, the amount of cationic groups per molecule is insufficient, and sufficient water solubility cannot be obtained. The epoxy resin has a number average molecular weight of 300 to 10,000, preferably 800 to 5,000. When the number average molecular weight exceeds 10,000, dispersion becomes poor due to high viscosity, and when the number average molecular weight is less than 300, corrosion resistance is reduced.

Examples of such epoxy resins include polyglycidyl ethers of polyphenols and acrylic polymers having 1,2-epoxy groups as pendant groups.

[0015] The polyglycidyl ether of polyphenol is generally obtained by reacting polyphenol with epichlorohydrin or dichlorohydrin in the presence of an alkali. Examples of polyphenols include bis (4-hydroxyphenyl) -2,2-propane, 4,4-dihydroxybenzophenone, bis (4-hydroxyphenyl)-
1,1-ethane and the like can be mentioned. Acrylic polymer having a 1,2-epoxy group as a pendant group,
Generally, it can be obtained by copolymerizing an acrylic monomer having a 1,2-epoxy group, for example, glycidyl methacrylate alone or with another acrylic monomer.

The sulfide which can be used in the present invention has the formula R ¹ SCH ₂ CH (OH) CH ₂ OH, wherein R ¹ is as defined above. ]. Such a sulfide is generally obtained by reacting a thiol with an epoxy compound.

Specific examples of the sulfide which can be used in the present invention include 1- (2-hydroxyethylthio) -2,3-methanediol, 1- (2-hydroxyethylthio) -2,3-ethanediol, -(2-hydroxyethylthio) -2,3-propanediol, 1- (2-hydroxyethylthio) -2,3-butanediol, 2,2′-thiobis (2,3-propanediol), 1- (2-hydroxypropylthio) -2,3-propanediol and the like.

The pigment dispersion resin of the present invention thus obtained and the pigment are mixed in a weight ratio of 1: 0.05 to 1:10, preferably 1: 0.1 to 1: 0.5, by a method well known to those skilled in the art. The pigment dispersion paste of the present invention can be prepared by blending with the above.

The pigment is not particularly limited as long as it is commonly used, and examples thereof include iron oxide, strontium chromate, carbon black, titanium dioxide, talc, barium sulfate, cadmium yellow, cadmium red, chromic yellow, and phosphomolybdenum. Aluminum acid, zinc phosphomolybdate and combinations thereof.

The obtained pigment-dispersed paste is mixed with deionized water and a cationic resin, and further, as an auxiliary, other resins, solvents, antioxidants, surfactants, and other additives used in the electrodeposition step. The electrodeposition coating is obtained by adding additives known to those skilled in the art, such as auxiliaries.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, “parts” are based on weight.

Preparation Example 1 Preparation of Polyurethane Crosslinking Agent Hexamethylene diisocyanurate was placed in a reaction vessel equipped with a stirrer, a cooling pipe, a nitrogen introduction pipe, and a thermometer.
1 part, diluted with 31.6 parts of methyl isobutyl ketone (hereinafter, abbreviated as MIBK), dibutyltin dilaurate 0.2
Parts were added. After heating to 50 ° C, methyl ethyl ketoxime
87 parts were added dropwise with stirring in a dry nitrogen atmosphere, and the reaction temperature was maintained at 50 ° C. Maintain at 70 ° C. until the isocyanate group disappears by the infrared absorption spectrum.
And 4.0 parts of n-butanol to obtain a polyurethane crosslinking agent.

Preparation Example 2 Preparation of Aminated Epoxy Resin A reaction vessel equipped with a stirrer, a cooling pipe, a nitrogen introduction pipe and a thermometer was charged with Epicoat 1001 (a bisphenol A type epoxy resin having an epoxy equivalent of 475, manufactured by Yuka Shell Epoxy). ) 99.8 parts, Epicoat 1004 (Yuika Shell Epoxy,
(A bisphenol A type epoxy resin with an epoxy equivalent of 950) 85
0.2 part, 55 parts of nonylphenol, 193.3 parts of MIBK and 4.5 g of benzyldimethylamine were added, and 140 ° C.
For 4 hours to obtain a resin having an epoxy equivalent of 1175. Here, ethylene glycol n-hexyl ether 69.1
35.4 parts of a MIBK solution (solid content 78% by weight) of MIBK ketimine compound of 2-aminoethylethanolamine, 26.5 parts of N-methylethanolamine and 37.1 parts of diethanolamine were added. This was reacted at 120 ° C. for 2 hours to obtain a desired resin.

Example 1 Preparation of half-blocked diisocyanate In a reaction vessel equipped with a stirrer, a nitrogen inlet tube and a cooling tube, 222.2 parts of isophorone diisocyanate (hereinafter abbreviated as IPDI) were placed, and methyl isobutyl ketone (hereinafter abbreviated as MIBK) was placed. ) After dilution with 39.1 parts, 0.2 parts of dibutyltin dilaurate was added. After the temperature was raised to 50 ° C., 131.5 parts of 2-ethylhexanol was dropped and reacted in a dry nitrogen atmosphere over 2 hours while stirring. The reaction temperature was maintained at 50 ° C. to obtain 2-ethylhexanol half-blocked IPDI (solid content: 90%).

Preparation of Pigment-Dispersed Resin Epon
828 (Shell Chemical Co., Ltd. epoxy resin, epoxy equivalent: 190)
351.6 parts and 99.2 parts of bisphenol A were charged and heated to 130 ° C. in a nitrogen atmosphere to give benzyldimethylamine 1.4
By adding 1 part and reacting at 170 ° C. for about 1 hour,
A bisphenol type epoxy resin having an epoxy equivalent of 445 was obtained. Next, after cooling to 140 ° C., 218.3 parts (solid content: 196.5 parts) of 2-ethylhexanol half-blocked IPDI prepared above was added and reacted.

After maintaining this at 140 ° C. for 1 hour, 172.3 parts of dipropylene glycol monobutyl ether was added for dilution, and the reaction mixture was cooled to 100 ° C. and 1- (2-hydroxyethylthio) -2,3 -408.0 parts of propanediol (136.0 parts of solid content), 134.0 parts of dimethylolpropionic acid and 144.0 parts of deionized water were added. The acid value is 2.0 at 70-75 ° C.
The reaction was continued until the content became as follows, to obtain a pigment dispersion resin having a tertiary sulfonium conversion rate of 72%. This was diluted with 324.8 parts of dipropylene glycol monobutyl ether to obtain a pigment-dispersed resin (resin solid content: 50%).

Example 2 In Example 1, 408.0 parts of 1- (2-hydroxyethylthio) -2,3-propanediol (solid content: 182.0 parts) was replaced with 2,2'-thiobis
(2,3-Propanediol) The reaction was carried out in the same manner except that the amount was changed to 546.0 parts to obtain a pigment-dispersed resin having a tertiary sulfonium conversion of 82%. This was diluted with 324.8 parts of dipropylene glycol monobutyl ether to obtain a pigment-dispersed resin (resin solid content: 50%).

Example 3 In Example 1, 408.0 parts of 1- (2-hydroxyethylthio) -2,3-propanediol was added to 1- (2-hydroxypropylthio) 2,3
The reaction was carried out in the same manner except that the amount of propanediol was changed to 498.0 parts (solid content: 166.0 parts) to obtain a pigment-dispersed resin having a tertiary sulfonium conversion of 70%. This was diluted with 324.8 parts of dipropylene glycol monobutyl ether to obtain a pigment-dispersed resin (resin solid content: 50%).

Example 4 500 parts of ethylene glycol monobutyl ether was charged into a reactor equipped with a stirrer, a nitrogen inlet tube and a cooling tube, and heated to 120 ° C. with stirring. A mixture of 285.0 parts of glycidyl methacrylate, 205.0 parts of styrene, 250.0 parts of 2-hydroxyethyl methacrylate, 250.0 parts of n-butyl acrylate and 28.0 parts of t-butyl peroxyoctoate was added dropwise over 3 hours. Thereafter, 210 parts of ethylene glycol monobutyl ether, 500 parts of 1- (2-hydroxyethylthio) -2,3-propanediol and 134.0 parts of dimethylolpropionic acid were added, and further reacted at 70 ° C. Then, dipropylene glycol monobutyl ether 324.8
The resulting mixture was diluted with 1 part to obtain a pigment-dispersed resin (resin solid content: 50%).

Comparative Example 1 Preparation of Pigment Dispersion Resin Obtained from Thiodiethanol Epon was placed in a reaction vessel equipped with a stirrer, a nitrogen inlet tube, and a cooling tube.
828 533.2 parts, bisphenol A 199.6 parts and nonylphenol 19.2 parts were charged and heated to 130 ° C. under a nitrogen atmosphere. Here, ethyltriphenylphosphonium iodide 0.
By adding 75 parts and reacting at 170 ° C. for about 1 hour, a bisphenol A type epoxy resin having an epoxy equivalent of 490 was obtained. Then, after cooling to 140 ° C., 2-ethylhexanol half-blocked isophorone diisocyanate 198.4
(Solid content: 178.6 parts) and kept at 140 ° C. for 1 hour. The epoxy resin thus obtained was diluted by adding 161.8 parts of ethylene glycol monobutyl ether, cooled to 100 ° C., 122.1 parts of 2,2′-thiobis (ethanol), 134.0 parts of dimethylolpropionic acid and 144.0 parts of deionized water were added. added. The mixture was reacted at 70 to 75 ° C. until the acid value reached 5.0 to obtain a resin having a tertiary sulfonium conversion of 82%. Subsequently, the mixture was diluted with 353.5 parts of ethylene glycol monobutyl ether to obtain a pigment-dispersed resin (resin solid content: 50%).

Comparative Example 2 Preparation of quaternizing agent 174.0 parts of tolylene diisocyanate (hereinafter abbreviated as TDI) was placed in a reaction vessel equipped with a stirrer, a nitrogen inlet tube, and a cooling tube.
After diluting with MIBK 33.9 parts dibutyltin dilaurate 0.
Two parts were added. After heating to 50 ° C, 2-ethylhexanol 13
While stirring 1.5 parts, a dropping reaction was performed in a dry nitrogen atmosphere over 2 hours. The reaction temperature was maintained at 50 ° C. to obtain 2-ethylhexanol half-blocked TDI. 320.0 parts of this 2-ethylhexanol half-blocked TDI (solid content 30
4.0 parts) was added to 87.2 parts of dimethylethanolamine at room temperature, and exotherm was observed. This was stirred at 80 ° C. for 1 hour, 117.6 parts of a 75% lactic acid aqueous solution (solid content 88.2 parts) was added, and ethylene glycol monobutyl ether 39.2 was added.
Parts were added. The reaction mixture was stirred at 65 ° C. for about half an hour to obtain a quaternizing agent.

Preparation of Pigment Dispersion Resin Having Quaternary Ammonium Group Eponne was placed in a reaction vessel equipped with a stirrer, a nitrogen inlet tube, and a cooling tube.
828 (Yusuka Shell Co., Ltd. Bisphenol A with an epoxy equivalent of 190
681.2 parts and bisphenol A 289.6 parts
Then, the mixture was reacted under a nitrogen atmosphere at 150 to 160 ° C. for about 1 hour, and then cooled to 120 ° C., and then 406.4 parts of 2-ethylhexanol half-blocked TDI (solid content 386.1 parts) was added.
It is then cooled to 85-95 ° C., homogenized and furthermore the quaternizing agent prepared above, 496.3 parts (solids 421.9 parts) and deionized water
71.2 parts were added. The reaction mixture until the acid value is less than 1
The mixture was maintained at 80 to 85 ° C. and diluted with 85.6 parts of ethylene glycol monobutyl ether to obtain a pigment-dispersed resin.

Example 5 Preparation 1 of Pigment Dispersion Paste 30.0 parts (solid content: 15.0 parts) of the pigment dispersion resin prepared in Example 1
Parts), 75.4 parts of deionized water, titanium dioxide R-900P 68.9
, 14.4 parts of kaolin, 15.0 parts of aluminum phosphomolybdate and 1.7 parts of carbon black were dispersed in a sand grind mill to prepare a pigment dispersion paste ground to a particle size of 10 μm or less. This pigment dispersion paste has a total solid content of 56.0
%, Resin solid content 7.3%, and pigment solid content 48.7%.

Example 6 Preparation of Pigment Dispersion Paste A pigment dispersion paste was prepared in the same manner as in Example 5 except that the pigment dispersion resin of Example 2 was used instead of the pigment dispersion resin of Example 1.

Example 7 Preparation of Pigment Dispersion Paste A pigment dispersion paste was prepared in the same manner as in Example 5 except that the pigment dispersion resin of Example 3 was used instead of the pigment dispersion resin of Example 1.

Comparative Example 3 Preparation of Pigment Dispersion Paste A pigment dispersion paste was prepared in the same manner as in Example 5 except that the pigment dispersion resin of Comparative Example 1 was used instead of the pigment dispersion resin of Example 1.

Comparative Example 4 Preparation of Pigment Dispersion Paste A pigment dispersion paste was prepared in the same manner as in Example 5 except that the pigment dispersion resin of Comparative Example 2 was used instead of the pigment dispersion resin of Example 1.

Example 8 Evaluation of Dispersion Stability of Pigment-Dispersed Paste The pigment-dispersed pastes prepared in Examples 5 to 7 and Comparative Examples 3 and 4 were allowed to stand at 40.degree. By observing and measuring the yield value, the dispersion stability of the pigment dispersion paste was evaluated. Table 1 shows the results of these evaluations.

[0039]

[Table 1] Example No. Sedimentation state ¹⁾ Change in viscosity ²⁾ Example 5 ○ ○ Example 6 ○ ○ Example 7 ○ ○ Comparative example 3 △ × Comparative example 4 △ ○ 1) Store at 40 ° C for 2 weeks. After the temperature decreased, the sedimentation state of the paste was visually evaluated according to the following evaluation criteria. ：: no sedimentation △: soft sedimentation ×: hard sedimentation 2) After standing and storing at 40 ° C. for 2 weeks, the change in viscosity of the paste was visually evaluated according to the following evaluation criteria. ：: no thickening Δ: slight thickening ×: markedly thickened

Example 9 Preparation 1 of a cationic electrodeposition coating composition 331.9 parts of the polyurethane crosslinking agent obtained in Preparation Example 1 and 576.0 parts of the aminated epoxy resin obtained in Preparation Example 2 were n-
It was mixed with 30.3 parts of hexyl cellosolve, neutralized with 12.3 parts of glacial acetic acid, and then slowly diluted with 1067.0 parts of deionized water. Then, the organic solvent was removed under reduced pressure until the solid content became 36.0%. To this, 546.8 parts of the pigment dispersion paste prepared in Example 5 was added and mixed uniformly, and 2598.2 parts of deionized water was added to obtain a cationic electrodeposition paint having a solid content of 20.0%.

Example 10 Preparation of cationic electrodeposition paint 2 The pigment dispersion paste prepared in Example 5 was used in Example 6
A cationic electrodeposition paint was obtained in the same manner as in Example 9 except that the preparation was carried out in the same manner as in Example 9.

Example 11 Preparation of cationic electrodeposition paint 3 The pigment dispersion paste prepared in Example 5 was used in Example 7
A cationic electrodeposition paint was obtained in the same manner as in Example 9 except that the preparation was carried out in the same manner as in Example 9.

Comparative Example 5 Preparation of cationic electrodeposition coating material 4 A pigment dispersion paste prepared in Example 5 was used as a reference example 3.
A cationic electrodeposition paint was obtained in the same manner as in Example 9 except that the preparation was carried out in the same manner as in Example 9.

Comparative Example 6 Preparation of cationic electrodeposition paint 5 Reference example 4 was prepared by preparing a pigment dispersion paste in Example 5.
A cationic electrodeposition paint was obtained in the same manner as in Example 9 except that the preparation was carried out in the same manner as in Example 9.

Example 12 Evaluation of Stability of Cationic Electrodeposition Coating over Time The cationic electrocoatings obtained in Examples 9 to 11 and Comparative Examples 5 and 6 were stored at 40 ° C. for 4 weeks with stirring and then stored for 380 days. The stability over time was evaluated by evaluating the mesh network filterability and the amount of residue. Table 2 shows the results.

Evaluation of salt water corrosion resistance of cationic electrodeposition paint Each of the above cationic electrodeposition paints was electrodeposited on a cold-rolled steel sheet (without zinc phosphate treatment) at a film thickness of 10 μm and baked at 160 ° C. for 10 minutes. Make a cross cut and then run a salt spray test (SST)
We went for 20 hours. A 2.4 cm wide adhesive tape (Nichiban, product name "Cellotape") was firmly attached to the sample after this test with a finger, then the adhesive tape was rapidly peeled off, and the peeling width of the coating film from the steel plate was measured. In this way, the salt water corrosion resistance of the electrodeposition paint was evaluated. Table 2 shows the results.

[0047]

[Table 2] Example No. Stability with time ¹⁾ Corrosion and corrosion resistance ²⁾ Example 9 ○ (3 mg) ○ Example 10 ○ (5 mg) ○ Example 11 ○ (5 mg) ○ Comparative Example 5 △ (48 mg) ○ Comparison Example 6 Δ (35 mg) ○ 1) The aging stability of the paint was evaluated according to the following criteria based on the filterability of 380 mesh net and the amount of residue after storing the electrodeposited paint at 40 ° C. for 4 weeks with stirring. The figures in parentheses indicate the amount of the filtration residue. ：: Passes well △: Difficult to pass ×: Does not pass through 2) Evaluation criteria for saltwater corrosion protection ○: Peel width less than 2 mm △: Peel width 2-3 mm ×: Peel width 3 mm or more

[0048]

The pigment-dispersed resin of the present invention has a larger number of hydroxyl groups bonded to the sulfonium group than the conventional one, and the hydrophilicity of the resin is increased. As a result, it was possible to provide a pigment-dispersed resin having excellent stability over time and having good pigment dispersibility and high anticorrosion properties.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-53-86735 (JP, A) JP-A-63-179983 (JP, A) JP-A-2-11668 (JP, A) 128351 (JP, A) JP-A-6-157711 (JP, A) JP-A-6-329758 (JP, A) JP-A-7-33848 (JP, A) JP-A-7-206969 (JP, A) JP-A-7-206968 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08G 59/14 C09D 5/44 C09D 17/00 CA (STN) REGISTRY (STN)

Claims (4)

(57) [Claims] (1) Formula (1) Wherein Ep is the residue of an epoxy resin having an epoxy equivalent of 150-2000, and R ¹ is hydroxymethyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 4-hydroxybutyl or 2, A 3-dihydroxypropyl group, A ^- is a counter anion, and m is 0.1-4.
Numeric value of 0. ] A pigment dispersion resin for electrodeposition paint represented by the formula: 2. An epoxy resin having an epoxy equivalent of 150 to 2000 and a compound represented by the formula R ¹ SCH ₂ CH (OH) CH ₂ OH wherein R ¹ is as defined above. The pigment-dispersed resin for an electrodeposition paint according to claim 1, which is obtained by reacting a sulfide represented by the formula [1] with an acid in the presence of an acid. 3. The pigment-dispersed resin according to claim 1, which has a tertiary sulfonium value of 30 to 500. 4. A pigment dispersion paste for an electrodeposition paint, comprising the pigment dispersion resin according to claim 1 in a ratio of 0.05 to 10 based on the weight of the pigment.