JPS6412310B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a curable cationic water-based epoxy resin coating composition. In recent years, paints have been gradually shifting from solvent-based to low-solvent paints, and low-solvent paints, especially water-based paints, are being developed in epoxy resin paints as well.
In order to make epoxy resin water-soluble or water-dispersible, there is a method of emulsifying the epoxy resin using a surfactant. A method that aims at solubilization by introducing polar groups into the epoxy resin skeleton. There are two methods. Due to the surfactant used in these methods, the water resistance and chemical resistance of the coating film obtained is generally inferior to that of solvent-based coatings. There are two types of methods: an anion type in which a carboxyl group is introduced as a polar group, and a cation type in which an amino group is introduced as a polar group. Since the corrosion resistance deteriorates significantly under these conditions, there has recently been a rapid shift to the cationic type, which has excellent corrosion resistance, and has been used mainly for automobiles. However, the cationic water-based epoxy resin paints that are currently in practical use are epoxy resins.
It is known to react a primary or secondary amine, neutralize it with an acidic substance, and then mix a water-soluble blocked isocyanate compound as a curing agent.
However, this easily cationic paint using a blocking isocyanate compound as a curing agent also has the problem that a high temperature of, for example, 160 to 200 DEG C. is required for baking, and a large amount of volatile matter due to the blocking agent is released during baking. However, as a result of intensive research by the present inventors,
formula (However, X is a residue obtained by removing the carboxyl group from a dibasic acid, R and R' are alkylene groups, and n is 0 or a positive integer.) Bisimidazoline compound (A) represented by: A neutralized product obtained by neutralizing the reaction product with the above epoxy resin (B) with a volatile acid so that the pH of the system becomes 4 to 8.5 is suitable as a vehicle for water-based paints or other water-based coating compositions. We have discovered that this is the case, and have completed the present invention. The reaction product of (A) and (B) above is formed by the reaction of the hydroxyl group in (A) with the epoxy group in (B) by the catalytic action of the tertiary nitrogen of the imidazoline ring in (A), resulting in an ether bond. At the same time, a new hydroxyl group is generated by cleavage of the epoxy group, and (B)
Since it is used in excess compared to (A), it seems that it mainly has a chemical structure in which a large number of free epoxy groups remain. That is, the present invention relates to a mechanism in which epoxy groups are left over and used for subsequent curing. Therefore, the curing mechanism is completely different from the conventional method described above in which an amine is added to an epoxy group and then cured with an isocyanate compound, although they belong to the same category of cationic water-based epoxy resins. The coating composition of the present invention has the following excellent effects. (1) Since it is a water-based composition, there is no risk of deterioration of the working environment or ignition like with solvent-based products. (2) Easy to handle as it is a one-component type. (3) Despite being a one-component type, it is stable and can withstand long-term storage. This is because the raw material bisimidazoline compound (A) does not have hydrogen directly bonded to the nitrogen atom, so the reaction with the epoxy group is slow at room temperature, and there is almost no reaction in the acid salt state. Due to its unique three-dimensional structure, a stable water-soluble or water-dispersible resin can be obtained even if an equivalent amount or more of epoxy groups are reacted with it.In addition, the reaction to synthesize (A) is usually at a considerably high temperature and for a long time. This is thought to be due to the fact that since the reaction is carried out under reduced pressure, there is almost no unreacted low-molecular-weight amine mixed in (A). (4) The curing reaction can be carried out at easily controllable temperatures of about 50-150°C. It can also be made into a thin film and dried at room temperature. That is, compared to the baking temperature of 160 to 200° C. for conventional cationic water-based epoxy resin paints, the baking conditions can be made gentler, which is industrially advantageous. (5) Less volatile matter is generated during baking. In conventional cationic water-based epoxy resins, the isocyanate compound blocking agent volatilizes during baking, but this does not occur in the present invention. (6) When applied to metals and other objects, the coating film is hard, has excellent chemical resistance, and corrosion resistance, and does not have the drawbacks of brittleness of epoxy resin, and has good flexibility and durability. It also has excellent impact resistance. This seems to be because the composition of the present invention is a cationic epoxy resin and the presence of dibasic acid residues in (A) helps in internal plasticization of the cured product. In the present invention, the formula A bisimidazoline compound A represented by is used. Here, X is a residue obtained by removing the carboxyl group from a dibasic acid, R and R' are alkylene groups, and n is 0 or a positive integer. Although the above-mentioned bisimidazoline compound (A) can be produced by any method, it is industrially advantageous to react a dibasic acid with a hydroxyalkyl ethylene diamine to amidate it, followed by a ring-closing reaction. In this method, hydroxyalkylethylenediamine is used in excess and the amidation reaction is
Ring-closing reaction (imidazolination reaction) at 150-200℃
It is preferable to carry out the reaction at a temperature of 180 to 260°C while gradually increasing the degree of vacuum. This reaction yields a compound where n=0 in the above formula. A compound in which n is 1 or more can be obtained by adding alkylene oxide to this. Dibasic acids include malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid,
Azelaic acid, sebacic acid, dodecadiic acid, a dibasic acid having 21 carbon atoms which is an addition reaction of oleic acid and acrylic acid, dimer acid, etc. are used, and oxyacids such as tartaric acid and malic acid can also be used. Note that a tribasic acid may be mixed as long as it is in a small proportion. As the hydroxyalkylethylenediamine, hydroxyethylethylenediamine, hydroxypropylethylenediamine, etc. are used. Examples of the alkylene oxide that may be added if necessary include ethylene oxide, propylene oxide, and butylene oxide. In the above formula, the number of carbon atoms in X is not particularly limited, but it is appropriate to set it to 1 to 40, preferably 4.
Choose from a range of ~38. The number of carbon atoms in R is usually 2 to 4, preferably 2. It is appropriate that R' has 2 to 4 carbon atoms, preferably 2 carbon atoms. n is 0 to 4 or more,
If the numerical value of n becomes large, the water resistance of the coating film tends to decrease, so preferably n is set to 0. Next, as the epoxy resin (B), an epoxy resin obtained by reacting bisphenol A or bisphenol F with epichlorohydrin or dichlorohydrin is preferably used. In addition, polyglycidyl ether of novolac resin, polyglycidyl ether of aminophenol, diglycidyl ether of resorcinol, diglycidyl ether of tetrabromobisphenol A, glycidyl ether or ester of hydroxybenzoic acid, polyglycidyl ether of polyhydric alcohol, polycarbonate. Acid polyglycidyl esters, polymethylglycidyl ethers, or esters are also used, but these have inferior coating performance compared to bisphenol A or F type epoxy resins, so bisphenol A or esters are preferable to using them alone. It is often used in combination with F-type epoxy resin. There are no particular restrictions on the molecular weight or epoxy equivalent of the epoxy resin (B), and any resin having a molecular weight of about 300 to 3,800 and an epoxy equivalent of about 150 to 3,300 can be used.
A particularly preferred range is a molecular weight of about 330 to 3,000 and an epoxy equivalent of about 170 to 2,100. The reaction ratio between the bisimidazoline compound (A) and the epoxy resin (B) has a great influence on the properties of the resulting resin. In the present invention, (B) is used in an amount equal to or more than the amount of (A). If the proportion of (B) is too small, the properties such as water resistance and chemical resistance of the coating film will be insufficient, and the stability of the resulting resin will also be poor. If the ratio of (B) is too large, water solubility or water dispersibility may be insufficient or severe conditions will be required for baking, so preferably 1.1 to 5 mol of (B) to 1 mol of (A). It is preferable to select moles, especially from the range of 1.2 to 4.5 moles. Although there are cases where it is not necessary to use a reaction solvent during the reaction between (A) and (B), in many cases it is desirable to use a solvent to avoid thickening of the system. When using a solid epoxy resin, the use of a solvent is essential. The solvent is preferably a solvent that is compatible with water, such as isopropanol, ethyl cellosolve, butyl cellosolve. These solvents can remain in the final product. The reaction temperature and time mainly depend on the epoxy resin (B).
It depends on the type of bisimidazoline compound (A), and has little to do with the type of bisimidazoline compound (A). When a bisphenol A type epoxy resin is used as (B), in general, resins with lower epoxy equivalents react more easily, so low temperatures and short times are sufficient; resins with higher epoxy equivalents are less likely to react, so high temperatures and long periods of time are sufficient. Become. After the reaction between (A) and (B), the reactants are neutralized with a volatile acid. Volatile acid refers to an acid that volatilizes at least partially, preferably substantially completely, at the baking temperature without curing, and specifically includes formic acid, acetic acid, propionic acid, butyric acid, lactic acid, Examples include organic or inorganic acids such as acrylic acid, methacrylic acid, hexahydrobenzoic acid, hydrogen fluoride, hydrochloric acid, and hydrobromic acid. Particularly preferred acids are acetic acid and lactic acid. Neutralization is preferably carried out so that the pH of the system is 4 to 8.5, particularly 5 to 8. If the pH exceeds 8 due to insufficient neutralization, sufficient hydrophilicity will not be obtained, while if the addition of acid is excessive and the pH becomes less than 4, rust will occur if the object is a metal. Simultaneously with or after this neutralization, an appropriate amount of water or a mixture of water and a water-miscible solvent such as alcohols or ketones is added to the system to adjust the desired concentration. Prior to this dilution, the reaction solvent can be recovered if necessary. The coating composition of the present invention is composed of the neutralized product obtained above as a main ingredient, and in addition, fillers, pigments, dyes, plasticizers, stabilizers, antifoaming agents, leveling agents, anti-sagging agents, etc. Known additives such as rust preventives may also be blended. Other known curing agents may also be used in combination without departing from the spirit of the present invention. The composition of the present invention is applied to the object by spraying, roller coating, brushing, dipping, curtain flow coating, electrodeposition, or any other method. Targets include a variety of materials including metal, slate boards, asbestos boards, wood boards, plywood, plastic surfaces, glass, and concrete. Curing or baking after application can be performed under relatively mild conditions of about 50 to 150°C. Of course, there is no problem even if the temperature is high. It is also possible to cure at room temperature by selecting the coating thickness, type of epoxy resin, etc. The coating composition of the present invention can be used for a wide variety of coatings such as general paints, electrodeposition paints, and printing. Next, the coating composition of the present invention will be further explained with reference to Examples. Hereinafter, "%" refers to % by weight. Example 1 280 g (0.5 mol) of dimer acid (Versadime 216 manufactured by Henkel Japan Co., Ltd.) and 156 g (1.5 mol) of hydroxyethylethylenediamine were charged into a reactor equipped with a stirrer, a thermometer, a reflux condenser tube, and a water sample tube. The reaction was carried out at 150-180°C for 3 hours. During this time, 18g of water leaked into the test tube. Then, the temperature was slowly increased from 180°C to 210°C over about 3 hours, and during this time the degree of vacuum was gradually increased from normal pressure to about 10 mmHg. This caused an additional 18 g of water and excess amine to flow out. By the above operations, the formula About 345 _g of _an amber viscous liquid of a bisimidazoline compound represented by (X is _C34H66-62 and R is _CH2CH2 ) was obtained. Next, 35g of the bisimidazoline compound obtained above
(0.05 mol) and a pre-prepared bisphenol A type solid epoxy resin (Epicoat 1001 manufactured by Yuka Ciel Epoxy Co., Ltd., epoxy equivalent 450~
500, molecular weight approximately 900) 80% butyl cellosolve solution
125 g (0.11 mol) was charged into a reactor equipped with a stirrer, a thermostat, and a reflux condenser, and heated to 60 to 80°C while stirring. As the reaction progressed, the system gradually thickened. After 30 minutes, 8 g of a 50% acetic acid aqueous solution was added for neutralization, and 188 g of water was added to obtain 356 g of a pale yellow, translucent resin liquid. The resin content of this resin liquid was 38%, the pH was 6.6, and the Gardner-Holt viscosity was H. I put this resin saliva in a container and stored it indoors, but
Even after two months, no hardening or separation occurred, and there was no change in viscosity. Also, apply this resin liquid on a steel plate using a Baker applicator, bake it at 130℃ for 30 minutes, and apply it to the steel plate for 20 minutes.
A coating film with a thickness of ±2μ was obtained and the physical properties of the coating film were measured. The above results are shown in Table 1 Example 2 35g of bisimidazoline compound obtained in Example 1
(0.05 mol) and bisphenol A type solid epoxy resin (Epicoat manufactured by Yuka Ciel Epoxy Co., Ltd.)
1004, epoxy equivalent 900-1000, molecular weight approximately 1400)
200g (0.1 mol) of 70% butyl cellosolve solution was charged into a reactor, heated to 60-70℃ for 20 minutes, and then heated to 70℃ for 20 minutes.
The mixture was allowed to react at ~80°C for 20 minutes, then neutralized by adding 7 g of a 50% aqueous acetic acid solution, and diluted by adding 218 g of water to obtain 460 g of an emulsion. The resin content of this emulsion was 38%, the pH was 6.7, and the Gardner-Holt viscosity was FG. Table 1 shows the stability of this emulsion and the physical properties of the coating film when this emulsion was applied onto a steel plate and baked at 130°C for 30 minutes. Example 3 35g of bisimidazoline compound obtained in Example 1
(0.05 mol), bisphenol F type liquid epoxy resin (Dainippon Ink & Chemicals Co., Ltd., Epiclon)
830, epoxy equivalent weight 175, molecular weight 350) and 20 g of ethyl cellosolve were placed in a reactor and heated while stirring, resulting in a temperature of 60°C.
The content mixture became clear. As heating continued at 70-80°C, the system gradually thickened. After 30 minutes, the reaction was completed, and 7 g of 50% acetic acid aqueous solution was added to neutralize it, and 130 g of water was added to dilute it, yielding 262 g of emulsion. This emulsion had a resin content of 40%, a pH of 6.7, and a Gardner-Holt viscosity of U. Table 1 shows the stability of this emulsion and the physical properties of the coating film when this emulsion was applied onto a steel plate and baked at 130°C for 30 minutes. Example 4 35g of bisimidazoline compound obtained in Example 1
(0.05 mol), bisphenol A type liquid epoxy resin (Epicoat manufactured by Yuka Ciel Epoxy Co., Ltd.)
828, epoxy equivalent weight 184-194, molecular weight approximately 380) 40g
(0.105 mol), bisphenol A type solid epoxy resin (Epicoat manufactured by Yuka Ciel Epoxy Co., Ltd.)
1001, epoxy equivalent 450-500, molecular weight approximately 900)
Charge 40 g (0.035 mol) of 80% butyl cellosolve solution and 20 g of butyl cellosolve into a reactor,
React at 70℃ for 45 minutes, then add 50% acetic acid aqueous solution 7
When the mixture was neutralized by adding 126 g of water and further diluted with 126 g of water, 268 g of a pale yellow transparent resin liquid was obtained. The resin content of this resin liquid was 40%, the pH was 6.5, and the viscosity was Gardner-Holt T. Table 1 shows the stability of this resin liquid and the physical properties of the coating film when this resin liquid was applied onto a steel plate and baked at 130°C for 30 minutes. Example 5 By reacting 176 g (0.5 mol) of an oleic acid-acrylic acid adduct (Diacid 1550 manufactured by West Baco) and 156 g (1.5 mol) of hydroxyethylethylenediamine in the same manner as in Example 1, the formula A bisimidazoline compound represented by was obtained. Next, 240g of the bisimidazoline compound obtained above
(0.05 mol), bisphenol type solid epoxy resin (Epicoat 1001 manufactured by Yuka Ciel Epoxy Co., Ltd.,
Epoxy equivalent 450-500, molecular weight approx. 900) 135g
(0.15 mol) and 30 g of butyl cellosolve were charged into a reactor, reacted at 60 to 75°C for 1 hour, and then
Neutralize by adding 7.5 g of lactic acid aqueous solution, and then add 201 g of water.
When diluted by adding g, a pale yellow transparent resin liquid was obtained.
397g was obtained. The resin content of this resin liquid is 40%,
The pH was 6.6 and the viscosity was UV according to Gardner-Holt. Table 1 shows the stability of this resin liquid and the physical properties of the coating film when this resin liquid was applied onto a steel plate and baked at 130°C for 30 minutes. Example 6 OctamethylenebisN-hydroxyethylimidazoline was synthesized by reacting 202 g (1 mol) of sebacic acid and 270 g (2.6 mol) of hydroxyethylethylenediamine in the same manner as in Example 1. Next, 10 g (0.03 mol) of octamethylene bis N-hydroxyethylimidazoline obtained above, bisphenol A type solid epoxy resin (Epicote 1001 manufactured by Yuka Ciel Chemical Co., Ltd., epoxy equivalent
450-500, molecular weight approximately 900) and 20 g of butyl cellosolve were charged into a reactor, and 55-65
℃ for 1 hour, 65-75℃ for 15 minutes, and then
Neutralize by adding 4g of 50% acetic acid aqueous solution, then add water
When diluted by adding 122g, a translucent resin liquid was obtained.
237g was obtained. The resin content of this resin liquid is 38%,
The pH was 6.6 and the viscosity was Gardner-Holt N ⁺ . Table 1 shows the stability of this resin liquid and the physical properties of the coating film when this resin liquid was applied onto a steel plate and baked at 130°C for 30 minutes. Example 7 TetramethylenebisN-hydroxyethylimidazoline was synthesized by reacting 146 g (1 mol) of adipic acid and 230 g (about 2.2 mol) of hydroxyethylethylenediamine in the same manner as in Example 1. Next, 7 g (about 0.025 mol) of tetramethylene bis N-hydroxyethylimidazoline obtained above, bisphenol A type solid epoxy resin (Epicote 1007 manufactured by Yuka Ciel Chemical Co., Ltd., epoxy equivalent 1750-2100, molecular weight about 2900) 150 g (0.031 mol) of a 60% butyl cellosolve solution and 30 g of butyl cellosolve were charged into a reactor and reacted at 80 to 105°C for 60 minutes, then neutralized by adding 3 g of a 50% aqueous acetic acid solution, and further diluted by adding 130 g of water. However,
A pale yellow transparent resin liquid was obtained. The resin content of this resin liquid was 30%, the pH was 6.5, and the Gardner-Holt viscosity was U. Table 1 shows the stability of this resin liquid and the physical properties of the coating film when this resin liquid was applied onto a steel plate and baked at 130°C for 30 minutes. Example 8 Bisphenol A type solid epoxy resin (Epicote 1001 manufactured by Yuka Ciel Chemical Co., Ltd., epoxy equivalent 450-500, molecular weight approximately 900) 270 g (0.3 mol)
was dissolved in 80 g of butyl cellosolve, and 28 g (0.1 mol) of tetramethylenebisN-hydroxyethylimidazoline obtained in Example 7 was added thereto. This mixture was reacted at 60 to 70°C for 20 minutes and at 70 to 75°C for 10 minutes, and then neutralized by adding 18 g of 50% acetic acid aqueous solution.
When diluted by further adding 40 g of water, 805 g of emulsion was obtained. This emulsion had a resin content of 37%, a pH of 7.0, and a Gardner-Holt viscosity of J. Table 1 shows the stability of this resin liquid and the physical properties of the coating film when this resin liquid was applied onto a steel plate and baked at 130°C for 30 minutes.

[Table] (Note) Stability was observed after being left indoors for 2 months. The Gobanme test is the number of scratches left after being removed by cellophane adhesive tape when a 1mm-wide scratch is made vertically and horizontally with a cutter. Pencil hardness: Mitsubishi Uni Pencil, load: 1Kg. Impact resistance was measured using a Dupont impact tester.
A 500g weight (a spherical shot-shaped tip with a diameter of 1/16 inch, etc.) was dropped from a height of 50cm, and damage to the painted surface was examined. The toluene rubbing test is determined by rubbing the coated surface 100 times with absorbent cotton soaked in toluene. Boiling water resistance is determined by immersing in boiling water for 3 hours. Alkali resistance is measured in 5% caustic soda aqueous solution.
Judgment was made after soaking at 25℃ for 48 hours. Acid resistance was determined by immersion in 5% sulfuric acid at 25°C for 48 hours. Salt spray resistance is the rust width of the crosscut after being sprayed with salt water for 150 hours. Example 9 An experiment similar to Example 7 was conducted except that 1 mole of tetramethylenebisN-hydroxyethylimidazoline obtained in Example 7 was reacted with 1 to 4 moles of ethylene oxide. The results were similar to Example 7 except that the boiling water resistance was slightly inferior to Example 7.
It was as good as in the case of . Example 10 70g of bisimidazoline compound obtained in Example 1
(0.1 mol) and bisphenol A type liquid epoxy resin (Epicoat manufactured by Yuka Ciel Chemical Co., Ltd.)
828, epoxy equivalent weight 184-194, molecular weight approximately 380) 114
g and 30 g of ethyl cellosolve were reacted at 55 to 65° C. for 50 minutes, neutralized by adding 16 g of a 50% acetic acid aqueous solution, and further diluted with 475 g of water to obtain 613 g of a pale yellow transparent resin liquid. The resin content of this resin liquid is 30%,
The pH was 6.6 and the viscosity was G according to Gardner-Holt. This resin liquid was applied to a steel plate and dried at room temperature.
The results of testing the coating film after one month were as follows. Goban test 70/100 Pencil hardness 3H Impact resistance 1/8 x 300 x 50 Bending resistance 2φ pass Toluene rubbing test No change 100 times Boiling water resistance No abnormality

Claims (1)

[Claims] 1 formula (However, X is a residue obtained by removing the carboxyl group from a dibasic acid, R and R' are alkylene groups, and n is 0 or a positive integer.) Bisimidazoline compound (A) represented by: A coating composition containing as a main ingredient a neutralized product obtained by neutralizing the reaction product with the above epoxy resin (B) with a volatile acid so that the pH of the system becomes 4 to 8.5. 2. The composition according to claim 1, wherein R is an ethylene group and n is 0. 3. The composition according to claim 1, wherein the reaction ratio of (A) and (B) is 1.1 to 5 moles of (B) per 1 mole of (A).