JPH04198376A - Resin composition for coating compound of electrodeposition - Google Patents

Abstract

PURPOSE:To obtain the title composition providing a cured coating film having excellent progress of electrodeposition, water resistance and flexibility, comprising a specific alkyl etherified spiroguanamine resin, a water-soluble resin, etc., in a specific ratio. CONSTITUTION:The objective composition comprising (A) 5-60 pts.wt. (solid content) alkyl etherified spiroguanamine resin which is obtained by adding an aldehyde and then alkyl etherifying with <=4C alcohol and contains >=4 bonded formaldehydes on the average and >=2 alkyl ether groups on the overage per spiroguanamine nucleus and (B) 95-40 pts.wt. (solid content) water-soluble or water-dispersible resin in amounts to give 100 pts.wt. total amounts.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a resin composition for electrodeposition paint.

[Conventional technology]

In recent years, there has been a strong demand for labor-saving and energy-saving paints for coating automobiles, industrial machinery, steel furniture, electrical appliances, etc. Furthermore, recently, in order to prevent air pollution caused by organic solvents emitted from paints, there has been a shift from conventional solvent-based paints to water-based paints. In particular, primers for automotive steel plates, aluminum sash, etc. are now being replaced by electrodeposition paints.

In electrodeposition paints containing amino resin as a curing agent,
When using hexamethoxymethylmelamine resin, which is a methyl etherified melamine resin, as the amino resin, it has little commonality with electrodeposition, so it is difficult to use hexamethoxymethylmelamine resin in long-term continuous electrodeposition coating runs. There is a problem in that methoxymethylmelamine resin accumulates in the electrodeposition bath and its resin composition changes, resulting in coating film performance that is different from the initial performance. Therefore, in order to maintain coating film performance, operations such as further adding hexamethoxymethylmelamine resin are performed so that the resin composition within the electrodeposition bath becomes constant. These operations are industrially very complex and difficult.

On the other hand, in order to solve these problems, mixed ethylated melamine resins have been developed and utilized, but these also do not exhibit sufficient co-progressivity. Furthermore, there are reports on methyl etherified guanamine resin, but due to its low water solubility, a phenomenon in which methyl etherified guanamine resin precipitates in the electrodeposition bath is observed.

Generally, after the electrodeposition paint is placed in the electrodeposition bath, it is not necessary to replace the paint (it is used continuously) for a long period of several years.Therefore, it is difficult to keep the resin composition in the electrodeposition bath constant. , is very important.

[Problem to be solved by the invention] □The present invention
It solves the problems of the conventional technology mentioned above, has excellent commonality with electrodeposition,
To provide a resin composition for electrodeposition paint that does not accumulate in an electrodeposition bath even during long-time electrodeposition coating runs, and which provides a cured coating film with excellent water resistance and flexibility. be.

[Means to solve the problem]

The present invention achieves the above object by using a specific alkyl etherified spiroguanamine resin as an amino resin. That is, the present invention provides (A)
A spiroguanamine resin to which an aldehyde is added and then alkyl etherified with an alcohol having 4 or less carbon atoms, which has an average of 4 or more formaldehyde bonds and an average of 2 or more alkyl ether groups per spiroguanamine nucleus. A battery containing 5 to 60 parts by weight (solid content) of an alkyl etherified spiroguanamine resin and 95 to 40 parts by weight (solid content) of a water-soluble or water-dispersible resin (B) in a total amount of 100 parts by weight. The present invention relates to a resin composition for paint coating.

In the present invention, the alkyl etherified spiroguanamine resin as component (A) can be easily synthesized by a known method by appropriately selecting reaction conditions.

The alkyl etherified spiroguanamine resin of component (A) is one in which an aldehyde such as formaldehyde or paraformaldehyde is added to spiroguanamine, and the number of bound formaldehydes is 4 or more on average per spiroguanamine nucleus. It is. If the number of bound formaldehydes is less than 4 on average, the stability of a coating material using the resin will be greatly reduced when it is made into a resin. The upper limit of the number of bound formaldehydes is usually eight.

The number of bound formaldehydes per spiroguanamine nucleus is preferably 5 or more on average.

The alkyl etherified hipyguanamine resin of the present invention is
Furthermore, the above adduct is alkyl etherified with an alcohol having 4 or less carbon atoms (methanol, ethanol, propatool or isopropanol, butanol), and the number of alkyl ether groups bonded by the alkyl etherification reaction is The average number of spiroguanamine nuclei is two or more per one spiroguanamine nucleus. The number of bonded alkyl ether groups is per one spiroguanamine nucleus,
If the number is less than 2, the coating stability will be poor and the co-advancement property will be reduced.

If an alcohol having 5 or more carbon atoms is used, the resulting resin will have poor water solubility or water dispersibility.

The total number of alkyl ether groups that can be bonded by the alkyl etherification reaction is at most 8 per one spiroguanamine nucleus, but in the case of poly(), since the spiroguanamine resin is partially condensed, it is less than 8. few.

In addition, spiroguanamine is 2. 4. 8. 10-
It means tetraoxaspiro(5,5)undecane-39-bis(2-ethylguanamine), and its structure is shown by the following formula. For example, this product is manufactured by Ajinomoto Mono Co., Ltd. under the trade name C.
Available as TU Guanamine.

The alkyl etherified spiroguanamine resin used in the present invention can be produced by various methods.

For example, spiroguanamine, formaldehyde and methanol are mixed to make an alkaline solution (preferably pH 9 to 11).
), then heating under acidic conditions (preferably pH 2 to 5) to cause condensation and etherification reactions; Spiguanamine, formaldehyde, and methanol or water are mixed and heated under alkaline conditions. There is a method in which the spiroguanamine resin obtained by conducting an addition reaction is isolated, methanol is added thereto, and the reaction is carried out by heating under acidic conditions. In this production method, 4 to 20% formaldehyde is added to 1 mole of spiroguanamine.
It is desirable to use alcohol in a ratio of 5 to 50 moles.

The water-soluble or water-dispersible resin that is component (B) in the present invention is not particularly limited as long as it reacts with the alkyl etherified spiroguanamine resin that is component (A). Examples include dispersible alkyd resins, water-soluble or water-dispersible acrylic resins, and the like.

The above-mentioned water-soluble or water-dispersible alkyd resin is, for example, a neutralized product of an alkyd resin obtained by reacting a polyhydric carboxylic acid, a polyhydric alcohol, and optionally an oil or a fatty acid thereof. Examples of polyvalent carboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, maleic acid, fumaric acid, succinic acid, adipic acid, sebacic acid, trimellitic acid, and pyromellitic acid. These may be used in the form of ester-forming derivatives such as acid anhydrides and methyl esters. As a polyhydric alcohol,
Ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, 1,4-butanediol, 1゜6-hexanediol, trimethylene glycol, glycerin, trimethylolpropane, trimethylolethane, pentaerylene There are tritto etc.

Oils include tung oil, linseed oil, soybean oil, dehydrated castor oil,
These include safflower oil, castor oil, coconut oil, and tall oil.

The alkyd resin can be produced by a known method, and when oil is used, the oil and polyhydric alcohol are mixed in the presence of a transesterification catalyst such as lithium hydroxide.
After reacting at 60°C, add polybasic acid and remaining polyhydric alcohol and react at 180 to 250°C. If oil is not used, mix the raw materials and heat at 180 to 250°C.
There are ways to react.

Further, the water-soluble or water-dispersible acrylic resin may include α, acrylic acid, methacrylic acid, maleic acid, itaconic acid, etc.
β-monoethylenically unsaturated carboxylic acid and acrylic acid 2-
Hydroxyethyl, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-methacrylate
- α, β with hydroxy group such as hydroxypropyl
- A neutralized acrylic resin obtained by copolymerizing an ethylenically unsaturated monomer and other unsaturated monomers.

Other unsaturated monomers include methyl acrylate, ethyl acrylate, n-butyl acrylate, diacrylate
- Alkyl esters of α, β-monoethylenically unsaturated carboxylic acids such as ethylhexyl, methyl methacrylate, n-butyl methacrylate, acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, diacetone acrylamide, etc. Acrylamide derivatives, glycidyl esters of α,β-monoethylenically unsaturated carboxylic acids such as glycidyl acrylate and glycidyl methacrylate, vinyl esters of saturated carboxylic acids such as vinyl acetate and vinyl propionate, styrene, α-methylstyrene, vinyl Examples include aromatic unsaturated monomers such as toluene.

The above copolymerization can be carried out by heating at 130 to 160°C in the presence of a radical catalyst such as azobisisobutyronitrile, benzoyl peroxide, dibutyl peroxide, cumene hydroperoxide.

The alkyd resin and acrylic resin before neutralization have an acid value of 20~
300 and a hydroxyl value of 15 to 400. Acid value 20~100 and hydroxyl value 15~
It is more preferable to adjust it so that it becomes ZOO. If the acid value is too low, water solubility or water dispersibility will be poor after neutralization,
If the acid value is too high, the coating film properties tend to deteriorate. Also,
If the hydroxyl value is too small, the curability will be poor, and if it is too large, the water resistance of the coating film will be likely to be poor.

In order to make such alkyd resins and acrylic resins water-soluble or water-dispersible before neutralization, the acid groups of the resins may be neutralized with a volatile base such as ammonia or an amine. Examples include primary, secondary and secondary compounds such as monopropylamine, monobutylamine, diethylamine, dibutylamine, triethylamine, tributylamine, monoethanolamine, ethylmonoethanolamine, monocyclohexylamine, morpholine, piperidine. Tertiary aliphatic or cycloaliphatic amines can be used. Ammonia and amine are 0 per equivalent of acid group.
．． Preferably, 3 to 1.2 moles are used.

In the present invention, the alkyl etherified spiroguanamine resin as the component (A) and the water-soluble or water-dispersible resin as the component (B) have a weight ratio (solid content ratio) of (A)/(B) of 5/
The ratio is 95 to 60/40. Outside this range, the coating properties such as curability or flexibility of the coating film will be poor.

Further, a catalyst such as an inorganic acid such as hydrochloric acid or phosphoric acid, or an organic acid such as para-toluenesulfonic acid may be added to the resin composition for electrodeposition coating of the present invention. The amount used is preferably 1 part by weight or less per 100 parts by weight of component (A) (solid content).

The resin composition for electrodeposition paint of the present invention comprises butyl cellosolve,
Dilute to an appropriate solid content with a mixed solvent of water and a water-soluble organic solvent such as ethyl cellosolve, methyl cellosolve, diacetone alcohol, 3-methoxy-3-methylbutan-1-ol, isopropanol, ethanol, or methanol. Can be used. The water-soluble organic solvent is preferably used in an amount of 5 parts by weight or more, particularly preferably 10 parts by weight or more, per 100 parts by weight of water.

Pigments and other additives may be used in the resin composition for electrodeposition paint of the present invention depending on the purpose.

〔Example〕

Next, production examples of spiroguanamine resin used in the present invention and examples of the present invention will be shown. In the example, "1 part" and "%" are
Unless otherwise specified, "parts by weight" and "% by weight" respectively.
means.

Production example 1 7-box with stirrer, reflux condenser and thermometer:
! G: 1 m, 80% paraformaldehyde (moisture 2
0%) 562.5g (15mol), methanol 6
40 g (20 moles) and 30% sodium hydroxide 2.6
Weigh out g, and add 434.2 g of spiroguanamine (
1 mol) was added and the pH was adjusted to 10.5 at reflux temperature (83°C).
The addition reaction was carried out for 4 hours. Then, add 62% nitric acid to
．． 0g was added, the pH was adjusted to 3.5, and the alkyl etherification reaction was carried out at 70°C for 10 hours. After the reaction is completed, the reaction solution is made alkaline (pH
10.0) and concentrated under reduced pressure. The amount produced at this time was about 650 g. This resin was diluted with butyl cellosolve and adjusted to a solid content of 75%, and the viscosity was Y (Gardna/25°C).

Production Example 2 Using the same apparatus as Production Example 1, 750 g (19.5 mol) of 80% rose formaldehyde and 800 g of methanol (
25 mol) and 2.6 g of 30% sodium hydroxide, and further added 434.2 g (1 mol) of spiroguanamine.
was added, the temperature was raised to 60°C, and an addition reaction was carried out at the same temperature for 4 hours. Thereafter, zOg of 62% nitric acid was added, and further 800 g of methanol was added to adjust the pH to acidic pH 3,5>, and an alkyl etherification reaction was carried out at 70° C. for 10 hours. After the reaction was completed, the reaction solution was made alkaline (pHIo, 0) with 30% sodium hydroxide, and then concentrated under reduced pressure.

The amount produced at this time was about 725 g. This resin was diluted with butyl cellosolve and adjusted to a solid content of 75%, and the viscosity was Y (Gardna/25°C).

Table 1 shows the results of analysis of the number of formaldehyde bound to one spiroguanamine nucleus and the number of alkyl ether groups in the alkyl etherified spiroguanamine resin obtained as described above.

Table 1 *1: Based on phosphoric acid decomposition method and NMR analysis.

*2: Based on NMR analysis.

Examples 1 to 2 and Comparative Examples 1 to 2 Alkyl etherified spiroguanamine resin and water-soluble acrylic resin manufactured in Production Example (manufactured by Hitachi Chemical Co., Ltd., trade name: Hytaloid 7200K, solid content 50%, solvent;
A paint was prepared by mixing water/isopropanol (1 weight ratio of 1 part water/1 part weight ratio) according to the formulation shown in Table 2.

Using this paint, the distance between poles ioam and pole ratio 1 was applied to a mild steel plate.
Electrodeposition coating was carried out under the following conditions: /1, electrodeposition bath temperature: 25° C., applied voltage: 50 ports, and current application time: 2 minutes. Table 3 shows the commonality of electrodeposition at the initial stage and after repeated turnover.

Furthermore, Table 4 shows the performance of the resulting electrodeposition coating film which was baked at 160° C. for 30 minutes.

Coating film performance was evaluated using the following test method.

In addition, the following (a) to (e) are JISK5400+:
It was evaluated accordingly.

(a) Gloss: Measurement was performed using 60 degree specular reflectance.

(b) Pencil hardness: Measured with Mitsubishi Pencil Uni.

(C) Crosscut: 100 squares were cut at 1 mm intervals on the coating surface with a cutter knife, and the number of squares remaining when peeled off with cellophane tape was evaluated.

(d) Erichsen value: Measured using an Erichsen tester.

(e) Impact value: Determined in centimeters using a DuPont impactor 1/2''-500g.

g) Boiling water resistance: After being immersed in boiling water for 1 hour, it was taken out and the condition of the painted surface was judged with the naked eye according to the following criteria.

○...no change △...slightly attacked ×...severely attacked (margins below) Table 2 Formula (Unit: 2 parts) *1: Hitachi Chemical ■, trade name Melan 523, *2: Hitachi Kasei Kogyo ■, trade name Melan 660 Table 3 Electrodeposition commonality Table 4 [Effects of the invention] The resin composition for electrodeposition coatings according to the present invention has excellent electrodeposition commonality, as well as excellent water resistance and flexibility. Produces an excellent cured coating.

Agent Patent Attorney Kunihiko Wakabayashi

Claims (1)

[Claims] 1. (A) A spiroguanamine resin to which an aldehyde is added and then alkyl etherified with an alcohol having 4 or less carbon atoms, wherein an average of 4 per spiroguanamine nucleus is obtained.
5 to 60 parts by weight (solid content) of an alkyl etherified spiroguanamine resin having at least 100 bound formaldehyde and an average of 2 or more alkyl ether groups; and (B) 95 to 40 parts by weight (solid content) of a water-soluble or water-dispersible resin. ) in a total amount of 100 parts by weight.