JPS6053071B2 - Method for producing aqueous coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a cold-curing or forced-drying aqueous coating composition.

In the field of room-temperature-curing or forced-drying coating compositions, from the standpoint of air pollution prevention, like other coating compositions, water is used as a diluent instead of conventional solvent systems that use organic solvents as diluents. Conversion to water-based systems is underway.

Among these, room-temperature-curing water-based coating compositions that undergo oxidative polymerization in the atmosphere to form a polymer film contain large amounts of highly unsaturated oils or fatty acids, such as drying oils and semi-drying oils. Water-based alkyd resins (hereinafter referred to as water-based alkyds), which are made by neutralizing so-called long oil-based high acid value alkyd resins with bases,
Water-based polybutadiene resins (hereinafter referred to as water-based polybutadiene) are produced by introducing carboxyl groups into polybutadiene and neutralizing this with a base. Water-based alkyds have a faster curing speed than water-based polybutadiene, but because the resin skeleton has a polyester structure, they lack alkali resistance and suffer from stability problems such as hydrolysis during storage, loss of water solubility, and coagulation. Also, the coating film is inferior in alkali resistance and water resistance compared to conventional solvent-based coatings. On the other hand, water-based polybutadiene is produced by introducing carboxyl groups into polybutadiene, which is a single or mixture of 1,2-vinyl, 1,4-trans or 1,4-cis structural units, by maleation or other methods. is neutralized with a base,
The resin skeleton is composed of carbon-carbon bonds, so it is not subject to hydrolysis and has excellent stability. In addition, when formed into a coating film, it exhibits excellent alkali resistance, water resistance, and oil resistance if a sufficient crosslinking density is reached after painting, but the unsaturated bonds of polybutadiene are more resistant to oxygen than the conjugated diene and divinylmethane structures of drying oils. It has poor polymerization reactivity with. For this reason, the curing properties after coating were poor, and it took a considerable amount of time to reach a hardness that could be used as a coating film. For this reason, several attempts have been made to improve curability. There is a method of mixing a water-based alkyd with a water-based polybutadiene, and a method of mixing or partially crosslinking a water-based polybutadiene with a water-soluble or water-dispersible hard resin obtained by copolymerizing an ethylenically unsaturated monomer. The method of improving initial curing properties by mixing water-based alkyds is actually ineffective unless a considerable amount is mixed, and since it is merely mixed, water-based alkyds, including the stability described above, are not effective. cannot avoid the disadvantages of On the other hand, the method of improving curability by mixing a hard resin obtained by copolymerizing ethylenically unsaturated monomers greatly improves the initial curability, but
Since this is polymerization through a crosslinking reaction, oil resistance, alkali resistance, and water resistance do not improve. Furthermore, even in a coating film in which crosslinking of the aqueous polybutadiene has progressed after a sufficient period of time has passed after coating, the mixed hard resin remains in a mere mixed state, so it swells when it comes into contact with oil or organic solvent. In addition, this hard resin has a high glass transition point, so if crosslinking of the aqueous polybutadiene progresses after coating, the coating film becomes too hard and loses its flexibility and adhesion. Although water-based polybutadiene has excellent properties as described above, no polybutadiene with satisfactory initial curing properties has been obtained.

The present inventors have arrived at the present invention as a result of intensive studies on a method for modifying water-based polybutadiene.

That is, the present invention involves adding 5 to 3 weight parts of maleic anhydride to 10 weight parts of polybutadiene having a number average molecular weight of 300 to 20,000, and then ring-opening the maleated polybutadiene with water and/or alcohol to form a long chain. This is a method for producing an aqueous coating composition, which comprises esterifying with 20 to 100 parts by weight of an unsaturated fatty acid glycidyl ester, further neutralizing with a base, and adding an organic acid salt of a metal. Polybutadiene in the present invention is 1,2-vinyl type, 1,4
- having a trans type or 1,4-cis type structure, or a mixture thereof, with a number average molecular weight of 300 to 20,000, preferably 500 to 10
,000. When the number average molecular weight is 300 or less, the resulting coating film has a . Curability and water resistance are poor, and if the number average molecular weight is 20,000 or more, the clay content becomes high and the maleation reaction becomes difficult, both of which are unfavorable. In addition, polybutadiene having carboxyl groups at both ends of the molecule can also be used. Maleation of the present invention. Polybutadiene is obtained by adding maleic anhydride to polybutadiene and ring-opening this with water and/or alcohol. 10 parts by weight of polybutadiene and 5 to 3 parts by weight of maleic anhydride are reacted at 140 to 230°C to give the esterified product of the present invention an acid value in the range of 20 to .150. If the amount of maleic anhydride is less than 5 parts by weight, it is difficult to introduce the unsaturated fatty acid glycidyl ester, and if the amount of maleic anhydride is more than 3 parts by weight, the insoluble matter during the reaction will carbonize and contaminate the reaction product.
Moreover, the clay content becomes extremely high, which is not preferable. In order to open the ring of polybutadiene anhydride to which maleic anhydride has been added and generate a free carboxyl group, one or more of water, a monohydric alcohol, and a dihydric alcohol are reacted. Ring opening with water yields two carboxyl groups from one anhydride, and ring opening with alcohol yields one carboxyl group. By using water and alcohol in combination, it is possible to freely change the number of carboxyl groups. Moreover, if the ring is opened with a dihydric alcohol, a hydroxyl group can be introduced, making it possible to polymerize maleated polybutadiene. Ring-opening of this anhydride is carried out by adding water or alcohol and heating to 50 to 150° C. with stirring under normal pressure or increased pressure. When ring-opening is carried out using only water, water in excess of the theoretical amount required for ring-opening is added, and after the reaction, excess water is removed under reduced pressure. When water and alcohol are used together, maleated polybutadiene can be obtained by first reacting with the alcohol, then further reacting with excess water, and finally removing unreacted water under reduced pressure. The reaction between maleated polybutadiene and long chain unsaturated fatty acid glycidyl ester can be carried out by mixing both components and heating to 80 to 15 (mega) while stirring. The amount added is the former 1
The latter is preferably in the range of 0 to 10 ruts compared to 0 ruts. The reason for this is that if the long-chain unsaturated fatty acid glycidyl ester is less than 2 parts by weight, the modification effect is insufficient, resulting in poor curability and flexibility when formed into a coating, and if it is more than 10 parts by weight, there are many fatty acid groups. If this occurs too much, the oil resistance and coating hardness, which are characteristics of polybutadiene, will decrease. The residual carboxyl groups of the reaction product of maleated polybutadiene and long-chain unsaturated fatty acid glycidyl ester (hereinafter referred to as esterified product) are neutralized with an alkali to make it water-soluble or water-dispersible, and a curing accelerator consisting of a metal organic acid salt is further added. It adds

The monohydric alcohol used in the present invention has a carbon number of 1
~18 saturated or unsaturated, straight-chain or branched alcohols, cyclohexanol, benzyl alcohol,
Examples include cyclic alcohols such as furfuryl alcohol, and ether alcohols such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, and diethylene glycol monobutyl ether. Examples of dihydric alcohols include ethylene glycol, propylene glycol, neopentyl glycol, hexylene glycol, 1,3-propanediol, 1,3-butanediol, and 1,4-butanediol having 1 to 1 carbon atoms.
8, there are straight chain or branched diols. Next, the long-chain unsaturated fatty acid glycidyl ester used in the present invention can be obtained from a mixture of long-chain unsaturated fatty acids obtained from natural drying oils or semi-drying oils, or only from specific components with a high degree of unsaturation. The extracted product is reacted with epichlorohydrin to form glycidyl ester.

Drying oils used for this purpose include tung oil, linseed oil, tall oil, soybean oil, bran oil, and safflower oil. Specific components with a high degree of unsaturation include eleostearic acid, linoleic acid, linoleic acid, dehydrated castor oil fatty acid, oleic acid, and the like alone or in mixtures. In the present invention, the base used to neutralize the esterified product is ammonia, a low boiling point alkylamine such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, or monoethanolamine, N-methylethanolamine, N-dimethyl These include low-boiling point alkanolamines such as ethanolamine and monoisopropanolamine.

In addition, the organic acid salts of metals used as hardening accelerators include one or a mixture of two or more organic acid salts such as lead, calcium, cobalt, manganese, and zirconium, which are commonly used in general oil-based paints. .

In addition, if necessary, pigments and organic solvents such as alcohols, ethers, esters, amide, and ketones having an affinity for water can be added to the esterified product.

The water-based coating composition of the present invention is characterized by the fact that the skeleton of the esterified product is composed of carbon-carbon bonds derived from polybutadiene, so it is extremely stable without being hydrolyzed during long-term storage, and because this skeleton has a hydrophobic structure. The coating film obtained from this has excellent water resistance and alkali resistance.

Furthermore, all long-chain unsaturated fatty acids are bonded to the polybutadiene skeleton via glycidyl groups and are uniformly distributed within the molecule, resulting in significantly faster curing compared to conventional water-based polybutadiene, and the long-chain unsaturated fatty acid component In addition to the crosslinking of the polybutadiene skeleton, the crosslinked structure of the polybutadiene skeleton overlaps closely, so the resulting coating film is robust and has excellent oil and solvent resistance.
Also, due to its flexible long-chain unsaturated fatty acid component, the paint film has excellent stretchability and adhesion to materials. The present invention will be explained in more detail with reference to Examples below.

In addition, in the examples, all % and parts represent weight % and parts by weight. Example 1 10% polybutadiene with a structure of 89% 1,2-vinyl type and 11% 1,4-trans type, number average molecular weight 1050, 20 parts maleic anhydride, polymerization inhibitor 2,6-ditertiarybutyl 0.2 parts of 4-methylphenol was placed in a flask, purged with nitrogen gas, and heated at 180 to 19 (range) for about 6 hours with stirring.Then, the temperature of the contents was lowered to 80°C, and the entire amount of maleic anhydride was ring-opened. Add 10.5 parts of deionized water, which is equivalent to 3 times the amount of water required for
The mixture was heated for 1 hour, and then heated at 100 to 12 (range) for 2 hours.

Excess water was then removed under reduced pressure while maintaining the content temperature at 80-100°C. To 1 (1) part of the maleated polybutadiene thus obtained, 65 parts of soybean oil fatty acid glycidyl ester was added and heated to 130 to 140'C with stirring.
After esterification for 3 hours, the contents were cooled to 70'C and diluted by adding part of isopropyl alcohol and 16 parts of butyl cellosolve to obtain an esterified product with a solid content of 80% and an acid value of 48. To 100 parts of this esterified product, cobalt naphthenate, lead naphthenate, and calcium naphthenate were added in amounts of 0.06 parts, 0.6 parts, and 0.2 parts in terms of metal, respectively, and further, 95% of the carboxyl groups of the esterified product 6.6 parts of triethylamine, sufficient to neutralize the moles, was added and thoroughly mixed, and this was diluted with 175 parts of deionized water to yield a clear water-based coating composition with a solids content of 28%.

When this was applied onto a glass plate using a "doctor plate" so that the dry coating film was 20 microns and left at room temperature, it was dry to the touch with 3 powders, reached a pencil hardness of HB after 1 day, and after 2 days It reached a pencil hardness of F, and had superior curing properties compared to commercially available water-based alkyds.After 10 days of painting, this coating film was immersed in warm water at 50°C for 3 days, but no defects such as whitening or prister appeared. This aqueous coating composition was placed in a tightly closed container and left at 30°C for 6 months, but there was no change in appearance or performance and it had excellent storage stability.Example 2 1, 2- 70% vinyl type, 15% 1,4-trans type,
15% 1,4-cis structure, number average molecular weight 1200
polybutadiene 100W), maleic anhydride 23.4
After filling an autoclave with 5 parts of xylene and thoroughly purging with nitrogen gas, the autoclave was heated to 170 to 180°C for 7 hours with stirring. Ta.

Next, xylene was removed under reduced pressure, the content temperature was adjusted to 80°C, 4.1 parts of deionized water was added, and the mixture was heated at 100 to 110°C for 4 hours to ring-open all the anhydride. 1 (1) part of the maleated polybutadiene thus obtained was placed in a flask,
To this was added 8 parts of linoleic acid glycidyl ester having an epoxy equivalent of 340, and the mixture was heated at 130 to 140° C. for 3 hours with constant stirring for esterification. This was cooled to 70°C and diluted with (low) parts of isopropyl alcohol, 30 parts of butyl alcohol, and 16.5 parts of butyl cellosolve to give a solid content of 70%.
An esterified product with an acid value of 32 was obtained. This esterified product 10
Cobalt naphthenate, lead naphthenate, and calcium naphthenate are added to 0 parts in metal equivalent values of 0.05 parts and 0.5 parts, respectively.
Furthermore, 3.8 parts of triethylamine was added and mixed, and this was diluted with deionized water to obtain a milky white aqueous coating composition with a solids content of 36%. This was applied to a mild steel plate treated with zinc phosphate so that the dry coating film was 30 microns, and force-dried at 100 to 120°C for 3 days. The pencil hardness of the paint film immediately after forced drying was HB-F, but when it was left at room temperature, the pencil hardness became H after 1 day.
So, after 2 weeks, the pencil hardness? It showed excellent curability reaching . This coated plate, which had been left at room temperature for one month, was immersed in a 1% aqueous solution of caustic soda for 24 hours, but showed no defects such as softening, blistering, fading, or peeling, and had excellent alkali resistance. Furthermore, when this coated board was left at room temperature for 2 weeks and then left under conditions of 100% relative humidity for 5 days to examine its moisture resistance, no abnormalities were observed even after 5 days. Furthermore, this painted board that had been left at room temperature for two weeks was immersed in gasoline and gear oil for two days at room temperature, but no softening, fading, or peeling was observed, and it had excellent oil and solvent resistance. . Example 3 Polybutadiene NlSSO-PBC-1 having a structure of 1.2-vinyl type and 12% of 1,4-trans type, number average molecular weight of 1480, and carboxyl groups at both ends of the molecule
000 (product of Nippon Soda Co., Ltd.) 10 parts of maleic anhydride, 21 parts of maleic anhydride, and 0.2 parts of 2,6-di-tert-butyl-4-methylphenol were placed in a flask, and after purging with nitrogen gas, the mixture was heated to 170 to 170% while stirring. Heated at 190°C for 6 hours, then cooled the content temperature to 100°C, then added 17.6 parts of benzyl alcohol equivalent to the number of moles of effectively added maleic anhydride, and heated to 130-140°C. The mixture was heated for 5 hours.

Claims (1)

[Claims] 1 Add 5 to 30 parts by weight of maleic anhydride to 100 parts by weight of polybutadiene having a number average molecular weight of 300 to 20,000, and then add 100 parts by weight of maleated polybutadiene, which is ring-opened with water and/or alcohol, to 20 parts by weight of long-chain unsaturated fatty acid glycidyl ester. Esterified with ~100 parts by weight,
A method for producing an aqueous coating composition, which further comprises neutralizing with a base and adding an organic acid salt of a metal.