JPH0536466B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water-dispersible or water-soluble coating resin composition that provides a coating film with excellent low-temperature curability and excellent corrosion resistance. More particularly, the invention relates to a coating resin composition particularly suitable for electrodeposition comprising an anionic resin prepared from sorbic acid, maleic anhydride, an epoxy resin and an unsaturated fatty acid.

Conventionally, anionic electrodeposition paints have been used as primers for various coatings. However, such a paint requires a high temperature of 160 to 180°C to be sufficiently cured, which is not preferable from the viewpoint of energy saving. Although efforts have been made to develop low-temperature curing anionic electrodeposition paints in order to improve these drawbacks, the current situation is that nothing useful has yet been found.

As a result of intensive research aimed at developing a low-temperature curing resin for coatings, the present inventors discovered that a low-temperature curing resin obtained from a condensate containing sorbic acid, maleic anhydride, epoxy resin, and unsaturated fatty acids as essential components was discovered. The present inventors have discovered that it provides a coating film with excellent properties and good corrosion resistance, and is suitable as an anionic electrodeposition coating material, leading to the completion of the present invention.

That is, according to the present invention, 1 to 10% by weight of sorbic acid, 1 to 10% by weight of maleic anhydride, 1 to 30% by weight of an epoxy resin with a molecular weight of 500 or more, and 20% by weight of unsaturated fatty acids.
~60% by weight, and a number average molecular weight of 1000 to 6000, weight average molecular weight obtained by condensing 0 to 70% by weight of a mono- to trivalent organic acid and a mono- to tetravalent alcohol.
5,000 to 200,000 and an acid value of 25 to 100 is dispersed or dissolved in water by amine or alkali neutralization, and a resin composition suitable for paints, particularly electrodeposition paints, is provided.

Regarding conventional electrodepositing resin compositions, there are numerous patents and several reviews, such as "Petroleum and Petrochemistry" 18(3) , 101-105 (1974) or "Paint Technology" 1973(1) , 155. ~164 mag. However, all of these have various drawbacks; for example, in the case of the composition of Japanese Patent Publication No. 51-32655,
The drawback is that it takes 30 minutes at 170°C to dry the paint film. Also, J.oil Col, Chem.Assoc., 53 , 353
−362 (1970), “Room Temperature
"Curing Electrodeposited Coatings" describes an electrodeposition coating that cures at room temperature, but this is a two-component system, and one electrodeposition coating cannot be used for a long period of time. In contrast, the electrodeposition coating composition according to the present invention is a one-component type, is stable for a long period of time, and has sufficient hardness, corrosion resistance, and other general coating properties when dried at a low temperature of 80 to 100°C. It differs from conventional electrodeposition coating compositions in that it provides

Sorbic acid and maleic anhydride, which are raw materials for the resin composition of the present invention, may be added separately, or the sorbic acid and maleic anhydride may be added separately.
It may also be added as an alder adduct. Sorbic acid and maleic anhydride should each be used at 1 to 10% by weight. In both cases, if the amount is less than 1% by weight, the effect is small, and if it is more than 10% by weight, gelation tends to occur. Although sorbic acid and maleic anhydride do not necessarily have to be in equimolar amounts, it is effective to use 1.5 to 0.8 mol of maleic anhydride per 1 mol of sorbic acid.

The fatty acids used in the present invention include iodine value
Drying oil fatty acids of 130 or higher are suitable. Examples of such dry fatty acids include linseed oil fatty acids, eno oil fatty acids, linseed oil fatty acids, soybean oil, and the like. In addition to drying oil fatty acids, semi-drying oils with an iodine value of 100 to 130, such as cottonseed oil, rapeseed oil, rice bran oil, etc.
Alternatively, a non-drying oil with an iodine value of 100 or less, for example fatty acids such as palm oil and coconut oil, may be used. Only one type of these fatty acids may be used, or two or more types may be used. However, in order to obtain sufficient normal temperature drying properties, the resin composition of the present invention must contain 20 to 60% by weight of a fatty acid having at least one unsaturated carbon-carbon bond in the resin raw material. If it is less than 20%, sufficient room temperature drying properties cannot be obtained, and if it is more than 60%, the initial hardness is low. More preferably, the fatty acid should be contained in the resin raw material in an amount of 30 to 50% by weight. The above fatty acids may be introduced directly as fatty acids, or may be added as glycerin esters (oils and fats) of fatty acids.

As the epoxy resin used in the present invention, a diglycidyl ether type epoxy resin of bisphenol A is suitable, and the molecular weight must be 500 or more. If it is less than 500, sufficient quick-drying properties and hardness cannot be obtained. Other epoxy resins include polyglycidyl ethers such as bisphenol F, phenol novolak, and cresol novolak, which have melting points.
Can be used at temperatures above 40℃. The resin composition must contain 1 to 30% by weight of at least one of the above-mentioned epoxy resins in the raw materials. 10~ for epoxy resins with low molecular weight (500~1000)
30% by weight is desirable, with high molecular weight (2000~
In the case of epoxy resin (7000), the content is preferably 1 to 20% by weight.

In addition to the above-mentioned raw materials, the composition of the present invention may contain, as raw materials, mono- to trivalent acids and mono- to tetravalent alcohols that are used as raw materials for ordinary alkyds. Finally, the necessary amounts of one or more monovalent to trivalent acids and one or more monovalent to tetravalent alcohols are added so as to have a number average molecular weight of 1000 to 6000, a weight average molecular weight of 5000 to 200000, an acid value of 25 to 100. can be used to synthesize product (A). Examples of the mono- to trivalent acids mentioned above include various aliphatic carboxylic acids such as acetic acid, butyric acid, oleic acid, various aromatic carboxylic acids such as benzoic acid, tert-butylbenzoic acid, phthalic acid, isophthalic acid. , various other dimer acids, adducts of various fatty acids and maleic acid, trimellitic acid, and the like. 1 to 4 above
Examples of alcohols include various aliphatic alcohols such as tert-butyl alcohol, amyl alcohol, 2-ethylhexyl alcohol,
Examples include various aromatic alcohols, such as benzyl alcohol, as well as ethylene glycol, propylene glycol, neopentyl glycol, glycerol, trimethylolethane, and pentaerythritol.

The resin of the present invention can be synthesized by reacting the above raw materials all at once or in several batches. These reactions include, in addition to the Diels-Alder addition reaction, addition or condensation reactions between alcohol groups, carboxylic acid groups, carboxylic acid anhydride groups, and epoxy groups, and polymerization reactions between unsaturated fatty acids.

The Diels-Alder addition reaction is generally carried out at 50°C.
Proceed with the above. Maleic anhydride (mp53℃,
bp202℃) and sorbic acid (mp135℃, decomposition point 228
The Diels reaction (°C) is preferably carried out at 140 to 190°C. The ring-opening reaction of epoxy resin with carboxylic acid is promoted by an amine catalyst, so
It is effective to add a high boiling point amine such as dimethylbenzylamine in an amount of 1/100 to 1/1000 of the weight of the epoxy.
The esterification reaction between an alcohol group and a carboxyl group is suitably carried out at 150 to 250°C. 200℃
In the above case, the reaction of the unsaturated carbon-carbon double bonds of the unsaturated fatty acid and sorbic acid becomes significant, so it is necessary to control the reaction temperature so as not to react excessively. In particular, since oxygen in the reaction system reacts with carbon-carbon double bonds, it is necessary to proceed with the reaction in an atmosphere of inert gas (nitrogen, carbon dioxide, etc.).

The reaction is stopped by lowering the temperature or by mixing a water-soluble organic solvent or the like when a predetermined molecular weight (number average 1000 to 6000) or a corresponding viscosity or acid value is reached. The water-soluble organic solvent used is preferably alcohols such as alkanols, such as methanol, ethanol, propyl alcohol, monoalkyl ethylene glycol, monoalkyl diethylene glycol, etc., but other water-soluble solvents, such as acetone, THF, etc. ,
Dioxane etc. can also be used.

A stable aqueous solution or dispersion can be obtained by neutralizing the aqueous solvent solution of the product (A) with a neutralizing agent, for example, organic amines such as triethylamine or diethanolamine, or ammonia or sodium hydroxide, and then adding deionized water. You can get a body.

The dispersion referred to herein generally consists of a resin phase having a particle size of 10 μm or less and a continuous aqueous phase. This dispersion may be optically transparent or opaque.

When performing electrodeposition coating, a container is first filled with this aqueous solution or dispersion so as to immerse the conductive cathode and the conductive anode to be coated, and then a voltage is applied between the two electrodes. An adhesive film of the coating composition is electrodeposited onto the anode. Voltage conditions are 1~
1000V, typically 50-300V. The current density usually ranges from a maximum of 0.1 A/cm2 to zero A/ ^cm2 during the electrodeposition process.
decreases to cm ² . PH is usually set at 7-10.
Electrodeposition coating with the composition of the invention is suitable for conductive substrates such as iron, aluminum, copper, etc. Curing and drying of the adhesive film is normally carried out at 120 to 200°C, but when the composition of the present invention is used, the temperature is 60 to 120°C.
It is also possible to obtain sufficient hardness, corrosion resistance and other physical properties at ℃.

The paint according to the present invention can be applied to various objects other than metal by brush coating, spray coating, roller coating,
Although any coating method such as dip coating can be used for coating, it is most suitable for electrodeposition coating on conductive metal products such as those mentioned above.

Next, the present invention will be specifically explained using Examples and Comparative Examples. Percentages and parts are by weight.

Example 1 In a reaction vessel with _N2 substitution, linseed oil fatty acids
Heat 315 parts to 180°C. Add 200 parts of epoxy resin (Dainippon Ink KK, Epicron 1050) and 0.2 part of catalyst dimethylbenzylamine, raise the temperature to 180°C again, and keep at 180°C for 1 hour. After lowering the temperature to 150°C, 168 parts of phthalic anhydride, 200 parts of trimethylolethane, 140 parts of trimethylpentanediol, 48 parts of maleic anhydride and 53 parts of sorbic acid were added, and the temperature was gradually heated to 180°C over 3 hours. Warm up. Proceed with the condensation reaction while maintaining the temperature at 180°C, and when the acid value reaches 50 and the Gardner viscosity of the 60% butyl cellosolve solution of the resin reaches V, the temperature is immediately lowered to 80°C, and about 400 parts of isopropyl alcohol is added. Prepare a solution containing 70% non-volatile resin.

143 parts of the resin solution and titanium dioxide (Teikoku Kako)
KK, JR600E) 100 parts and isopropyl alcohol
Knead 57 parts in a sand mill, NV67%, PWC50
Prepare % mill base.

While stirring a mixture consisting of 107 parts of the resin solution, 75 parts of the millbase, and 6.5 parts of triethylamine, 811.5 parts of ion-exchanged water is gradually added to prepare 1000 parts of an aqueous electrodeposition coating dispersion.

The aqueous dispersion has a breakdown voltage of 300V and a pH of 8.4, and is electrodeposited on an iron phosphate-treated mild steel plate anode at 150V for 2 minutes and dried at 100°C for 15 minutes.
A smooth, hard and flexible coating film with a film thickness of 20 μm is obtained.
The coating film had a wearable pencil hardness of H, and the peeling width of the cellophane tape was within 3 mm on one side in a 150-hour salt water spray test.

Example 2 In a reaction vessel with _N2 substitution, tall oil fatty acid
355 parts, maleic anhydride 54 parts and sorbic acid 59 parts
and heat to 150℃. After keeping at 150℃ for 1 hour, 189 parts of phthalic anhydride, 200 parts of trimethylolethane, epoxy resin (Epicron 7050)
Add 100 parts of hydrogenated bisphenol A, 40 parts of hydrogenated bisphenol A, and 0.01 part of dimethylbenzylamine, and gradually heat.
Raise the temperature to 180℃ over 3 hours. After that, the condensation was continued while maintaining the temperature at 180 ° C. When the acid value reached 80 and the Gardner viscosity of the 60% butyl cellosolve solution of the resin reached R, the temperature was quickly lowered, and about 300 parts of isopropyl alcohol and about 100 parts of butyl cellosolve were added.
Prepare a resin solution containing 70% non-volatile resin.

A mill base is prepared in the same manner as in Example 1 using the above resin solution. After mixing 107 parts of the resin solution with 75 parts of the millbase and 11.5 parts of TEA, 806.5 parts of ion-exchanged water is gradually added to prepare an aqueous electrodeposition coating dispersion.

The aqueous dispersion has a breakdown voltage of 110V and a pH of 7.8, and is electrodeposited on an iron phosphate-treated mild steel plate anode at 70V for 2 minutes and cured at 100°C for 15 minutes.
A smooth hard flexible coating was obtained. The coating film is
Has a worn pencil hardness of H and salt spray resistance test of 150.
The peeling width of the cellophane tape over time was within 3 mm on one side.

Comparative Example 1 In a reaction vessel with _N2 substitution, linseed oil fatty acid
363 parts of phthalic anhydride, 371 parts of phthalic anhydride, 80 parts of trimethylolpropane, and 186 parts of pentaerythritol were charged and gradually heated to 190°C over 3 hours. 190
Continue the condensation reaction while maintaining the temperature at °C. When the acid value reaches 55 and the Gardner viscosity of the 60% butyl cellosolve solution of the resin reaches R, the temperature is immediately lowered to 80 °C, and approximately 400 parts of isopropyl alcohol is added to solidify the resin. Prepare a 70% resin solution.

An electrodeposition paint aqueous dispersion was prepared in the same manner as in Example 1, and further electrodeposition coating and coating film tests were conducted.

The coating film has a wearable pencil hardness of 4B or less,
The peeling width of the cellophane tape after 100 hours of salt water spray resistance test was 8 mm or more on one side.

Comparative Example 2 In a reaction vessel with _N2 substitution, linseed oil fatty acids
Heat 366 parts to 180°C. 95 parts of epoxy resin (Epiclon 4050) and catalyst dimethylbenzylamine
Add 0.1 part, raise the temperature to 180℃ again, and keep at 180℃ for 1 hour. After lowering the temperature to 150°C, 321 parts of phthalic anhydride and 218 parts of pentaerythritol are added, and the mixture is gradually heated to 190°C over 3 hours. Proceed with the condensation reaction while keeping the temperature at 190℃, and the acid value is 70, 60% of the resin.
When the Gardner viscosity of the butyl cellosolve solution reaches W, the temperature is immediately lowered to 80°C, and approximately 400 parts of isopropyl alcohol is added to prepare a resin solution with a resin solid content of 70%.

An electrodeposition paint aqueous dispersion was prepared in the same manner as in Example 1, and further electrodeposition coating and coating film tests were conducted. The coating film had a pencil hardness of F-H, and the peeling width of the cellophane tape after 100 hours of salt water spray resistance test was approximately 5 mm on each side.

Claims (1)

[Claims] 1 sorbic acid 1-10% by weight, maleic anhydride 1
~10% by weight, epoxy resin 1~ with a molecular weight of 500 or more
30% by weight, unsaturated fatty acids 20-60% by weight, and 1
~ Number average molecular weight obtained by condensing 0 to 70% by weight of a trivalent organic acid and a mono to tetravalent alcohol
1000-6000, weight average molecular weight 5000-200000, acid value
A resin composition for coatings made by dispersing or dissolving 25 to 100 products in water by neutralizing with amine or alkali.