JPH0229478A - Coating resin composition - Google Patents

Abstract

PURPOSE:To obtain a coating composition which is good in workability in the production of a resin and the preparation of a coating material, has a small heating loss during film baking and lowly dusts by mixing a specified alkyl- etherified amino resin with a resin curable by reaction therewith. CONSTITUTION:The title coating resin composition is obtained by mixing an alkyl-etherified amino resin (A) obtained by the addition and condensation of an amino resin material (essentially consisting of benzoguanimine which may contain an amino compound such as melamine or acetoguanamine) with formaldehyde, and the etherification of the product with an alcohol and having contents of the resin having one triazine ring in the molecule and of the resin having two triazine rings in the molecule of 10-25wt.%, respectively, and a Gardner viscosity (nonvolatiles of 60% and in n-butanol diluent) <= U and a free formaldehyde content of 1.5wt.% with a resin (B) curable by reaction with resin A. This composition is good in workability during the production of a resin and, the preparation of a coating material, has a low heating loss during film baking and lowly dusts.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a resin composition for paint containing an alkyl etherified amino resin.

(Prior Art) Thermosetting resin compositions made by combining alkyl etherified amino resins with alkyd resins, acrylic resins, epoxy resins, etc. have been used for paints. Recently, there has been a strong demand for labor-saving, resource-saving, energy-saving, work rationalization, etc. for coating paints for automobiles, industrial machinery, steel furniture, electrical appliances, buildings, etc.

To solve these problems, it is desirable to be able to cure at a low temperature of 90 to 110°C for 20 minutes, or to be able to bake for a short time at a high temperature such as 200 to 250°C.

In conventional aminoalkyd resins or aminoepoxy resins, the alkyl etherified amino resins used are:
The number average molecular weight is relatively small (the resin contains a relatively large amount of bonded formaldehyde and butyl ether groups, and it is a mixture of one to several dozen triazine nuclei in the molecule, mononuclear and Generally, the content of low molecular weight dinuclear bodies is relatively high.

Furthermore, some amino resins disclosed in JP-A-62-101666 have a proportion of mononuclear bodies and dinuclear bodies of 10% by weight or less.

[Problems to be Solved by the Invention] Paints using alkyl etherified amino resins with a high content of low molecular weight substances volatilize the low molecular weight parts together with the organic solvent during the curing reaction, and may adhere to the inside of the drying oven or dry in the oven. entrance and exit,
Dust coagulates and solidifies when it comes into contact with low-temperature atmospheres such as inside dust walls and duct leaks.

These scattered substances cause problems such as product defects and ignition of deposits due to falling onto objects to be coated at the entrance and exit of the furnace, as well as increased cleaning and management costs for furnace management.

On the other hand, alkyl etherified amino resins with a relatively low content of low molecular weight substances, as shown in JP-A-62-101666, have been improved with respect to the above-mentioned problems; It has the disadvantage of poor workability.

The present invention has good workability during resin production and paint preparation,
The present invention provides a resin composition for coatings which has a small heating loss during baking of a coating film and has few scattered substances.

[Means to solve the problem]

The present invention provides (A) amino resin raw material (benzoguanamine is an essential component, and may also contain one or more amino compounds selected from the group consisting of melamine, acetoguanamine, phthaloguanamine, dicyandiamide, or urea).
is obtained by addition condensation with formaldehyde and etherification reaction with alcohol, and the ratio of those having one triazine nucleus and those having two triazine nuclei in the molecule is 10 to 25% by weight, respectively, and the Gardner viscosity (nonvolatile content 6
0%, diluent solvent n-butanol) is less than U, free formaldehyde is less than 5% by weight, and (B) a resin that can be cured by reacting with the alkyl etherified amino resin. The present invention relates to a resin composition for a coating material.

The method for producing the alkyl etherified amino resin, component (A), used in the resin composition of the present invention is already known, and can be easily synthesized by appropriately selecting conditions. The amino resin raw material contains benzoguanamine as an essential component, but may also contain one or more amino compounds selected from the group consisting of melamine, acetoguanamine, phthaloguanamine, dicyandiamide, and urea. When other amino compounds are used in combination, the amount of benzoguanamine used is preferably 10% by weight or more based on the total amount of amino resin raw materials. It is more preferable to use 30% by weight or more. (A
The alkyl etherified amino resin which is the component () is a resin in which the ratio of one triazine nucleus and two triazine nuclei in the molecule is 10 to 25%, respectively. The proportion is more preferably 10 to 17% by weight.

If the proportion of either one or two triazine nuclei in the molecule exceeds 25% by weight,
The amount of low-molecular substances that volatilize during heat curing increases, and the proportion of substances that adhere to the inside of the drying oven increases. In addition, the content of unreacted amino compounds such as melamine and benzoguanamine, or low formaldehyde adducts such as melamine and guanamine increases, and the proportion of volatilization and adhesion also increases. Furthermore, free formaldehyde and formaldehyde released from the amino resin also have an adverse effect. On the other hand, if the proportion of either one or two triazine nuclei in the molecule is less than 10% by weight, a large amount of solvent will be required to form a paint, and the solid content of the coating will decrease. , the sharpness of the coating film is poor. In addition, the resin itself has a high viscosity before being made into a paint, making it extremely difficult to handle and reducing work efficiency.

Jiru.

The alkyl etherified amino resin of the present invention is produced by subjecting an amino resin raw material containing benzoguanamine to an addition reaction with formaldehyde in an alcohol such as butanol or methanol, followed by a condensation reaction and an alkyl etherification reaction in an acidic region. Thereafter, alcohol such as butanol or methanol is added again to perform a re-alkyl etherification reaction to lower the viscosity, and finally, the solvent can be removed to reach the desired solid content. Alternatively, after the condensation reaction and the alkyl etherification reaction, the solvent may be removed, alcohol may be added again, the alkyl etherification reaction may be performed again, the viscosity may be lowered, and the solvent may be removed to achieve the desired solid content again. good. At this time, the content of free formaldehyde is reduced to 1.5% by weight by desolventizing for 1 to 3 hours at a temperature of 125 to 150°C under reduced pressure of, for example, 300 mmHg or less.
It can be as follows. More preferable conditions are 250
The other conditions are the same under reduced pressure of mmHg or less.

In the above reaction, except for the formaldehyde addition reaction step,
It is preferable to add an acidic catalyst such as hydrochloric acid, sulfuric acid, phosphoric acid, nitric acid, phthalic acid, maleic acid, oxalic acid, or formic acid, and carry out the reaction under acidic conditions (preferably pH 4 to 6). The reaction temperature is preferably reflux temperature from the viewpoint of synthesis time, etc., and in the case of using butanol, for example, it is preferably 90 to 120''C.

In addition, the raw materials may be charged, for example, 4 to 7 moles of formaldehyde and 4 to 7 moles of alcohol to 1 mole of amino resin raw material.
It is preferable to use 8 moles of alcohol and 0.5 to 4 moles of additional alcohol, and 1.8 to 4.0 moles of formaldehyde and 2 to 5 moles of alcohol per mole of benzoguanamine.
mol, preferably from 0.5 to 4.0 mol of additional alcohol.

The molecular weight distribution of the alkyl etherified amino resin thus obtained is measured by gel permeation chromatography, and the proportion of those having one triazine nucleus and those having two triazine nuclei in the molecule is determined from the chromatogram. It can be determined by calculating the area ratio of the components.

The alkyl etherified amino resin used in the present invention is n-
Viscosity when dissolved in butanol so that the non-volatile content is 60% by weight (Gardner 25'c > is less than U. Ut rod jj & -r% palm f'lh ゞ 3゜7 In the present invention (B) Examples of resins that can be cured by reacting with the alkyl etherified amino resin used as components include acrylic resins, alkyd resins, alkyd-modified acrylic resins,
Conventionally known resins such as epoxy resins and epoxy-modified alkyd resins can be used. These preferably have a hydroxyl value of 15 to 200 in order to react with the alkyl etherified amino resin.

The alkyd resin is a resin obtained by reacting, for example, a polyhydric carboxylic acid, a polyhydric alcohol, and, if necessary, oil or fat or a fatty acid thereof. Examples of polyhydric carboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, tetrabitrophthalic acid, maleic acid, fumaric acid, succinic acid, adipic acid, sepacic acid, trimellitic acid, and pyromellitic acid.

These may be used in the form of ester-forming derivatives such as acid anhydrides and acid halides. As a polyhydric alcohol,
Ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, neopentyl glycol, ■, 4-butanediol, 16-hexanediol, trimethylene glycol, glycerin, trimethylolpropane, trimethylolethane, pentaerydrift, etc. There is. Examples of the oil include tung oil, linseed oil, soybean oil, dehydrated castor oil, 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 0°C, add the 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 is a method of reacting with C, etc.

Acrylic resins also contain α,β-ethylenically unsaturated monomers having hydroxy groups such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate. It is obtained by copolymerizing monomers and other unsaturated monomers. Other unsaturated monomers include αβ-monoethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid, methyl acrylate, ethyl acrylate, n-phthyl acrylate, and diacrylic acid. - Alkyl esters of α, β monoethylenically unsaturated carboxylic acids such as ethylhexyl, methyl methacrylate, and n-butyl methacrylate; acrylamides such as acrylamide, methacrylamide, N-methylolacrylamide, N-methylolmethacrylamide, and diacetone acrylamide; derivatives, lycidyl esters of α, β-monoethylenically saturated 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, Examples include aromatic unsaturated monomers such as vinyltoluene.

The above copolymerization can be carried out by heating to 90 to 160'C in the presence of a radical catalyst such as azobisisobutyronitrile, benzoyl peroxide, dibutyl peroxide, cumene hydroperoxide.

The alkyd resin-modified acrylic resin can be obtained by polymerizing monomers that are raw materials for the acrylic resin in the presence of the alkyd resin.

The raw material composition of the alkyd resin, acrylic resin, and alkyd resin-modified acrylic resin is preferably adjusted so that the hydroxyl value is 15 to 200. Note that if the hydroxyl value is too small, the curability tends to be poor, and if it is too large, the water resistance of the coating film tends to be poor.

In the present invention, the alkyl etherified amino resin and the resin that can be cured by reacting with the alkyl etherified amino resin are preferably blended so that the weight ratio of the former to the latter is 10/90 to 70/30. When this weight ratio is less than 10/90, the curing performance tends to be poor, and when it exceeds 70/30, the flexibility of the coating film tends to be poor.

The resin composition for paint according to the present invention includes hydrochloric acid, phosphoric acid, p
- A catalyst such as toluenesulfonic acid may be added. The amount used is preferably 1% by weight or less based on the alkyl etherified amino resin.

Furthermore, the resin composition for paint according to the present invention can be used by adjusting the solid content to an appropriate level with an organic solvent such as xylene, toluene, butyl cellosolve, ethyl cellosolve, n-butanol, isobutanol, isopropanol, or methanol. can.

Pigments such as titanium white and other additives may be added to the coating resin composition according to the present invention, depending on the purpose.

Further, as a coating method, spray painting, dipping, etc. can be adopted.

〔Example〕

Next, production examples and examples related to the present invention will be shown.

Hereinafter, "part" and "1%" refer to "part by weight" and "1%," respectively.
% by weight.

Production Example 1 Melamine 63g, benzoguanamine 93.5g, n-
370 g of butanol and 1 part of 80% paraformaldehyde
87.5 g was weighed out and an addition reaction was carried out under reflux (95°C) for 1 hour. Thereafter, p) was adjusted to 15 to 5.5 with nitric acid, heated again, and dehydrated for 3 hours under reflux. Thereafter, 144 g of n-butanol was added, and dehydration was performed for 1 hour while refluxing again. Thereafter, the flask was cooled, and solvent removal was started under reduced pressure (250 mm 11 g), and the end point of solvent removal was when the temperature of the contents of the flask reached 135°C.

The desolution time at this time was 1 hour and 30 minutes. Thereafter, it was diluted with n-butanol so that the nonvolatile content was 60%.

The Gardner viscosity (25°C) at this time was M.

Production Example 2 Using the same equipment as Production Example 1, melamine 37.8g1 benzoguanamine 130.9g, n-butanol 370g
, 150 g of 80% paraformaldehyde was weighed out and an addition reaction was carried out under reflux (95°C) for 1 hour. after that,
The pH was adjusted to 5 to 5.5 with nitric acid, heated again, and dehydrated for 3 hours under reflux.

Thereafter, the flask was cooled, and solvent removal was started under reduced pressure (220 mmHg), and the end point of solvent removal was when the temperature of the contents of the flask reached 135°C. 144 g of n-butanol was added and the etherification reaction was carried out again under reflux for 1 hour. Thereafter, the solvent was again removed under reduced pressure (250 mm) (Ig), and the temperature reached 125°C, which was defined as the end point. Thereafter, it was diluted with n-butanol so that the nonvolatile content was 60%. The Gardner viscosity (25°C) at this time was H.

Production Example 3 Using the same equipment as Production Example 1, benzoguanamine 187
296 g of n-butanol and 112.5 g of paraformaldehyde were weighed out, and an addition reaction was carried out under reflux (94°C) for 1 hour and 30 minutes. Then, adjust the pH to 4.0 with nitric acid.
Adjust to ~4.5, heat again, and dehydrate under reflux for 5
Time went. Thereafter, 144 g of n-butanol was added, and dehydration was performed for 1 hour while refluxing again. After that, it was cooled and the solvent was removed under reduced pressure (200 mm tlg).
When the temperature reached °C, it was considered as the end point of solvent removal. Thereafter, it was diluted with n-butanol so that the nonvolatile content was 60%.

The Gardner viscosity (25°C) at this time was G.

Comparative Production Example 1 Using the same equipment as Production Example 1, 126 g of melamine, n-
444g butanol and 375g paraformaldehyde
was weighed and subjected to an addition reaction at 90° C. for 1 hour, then adjusted to pH 6 to 6.5 with nitric acid, heated again, and subjected to a dehydration step for 3 hours under reflux. Thereafter, desolvation was started at the same temperature, and the end point of the desolvation was when the temperature of the contents of the flask reached 130°C. Thereafter, it was diluted with n-butanol so that the nonvolatile content was 60%. The Gardner viscosity (25°C) at this time was A.

Regarding the alkyl etherified amino resins obtained in Production Examples 1 to 3 and Production Comparative Example 1, one triazine nucleus was added in the molecule.
Table 1 shows the proportions and molecular weights of those having 1 and 2 atoms. These were determined by gel permeation chromatography under the following measurement conditions using a standard polystyrene calibration curve to determine each component corresponding to the chromatogram, and by the area ratio of the chromatogram of each component.

Measurement conditions Column: Hitachi Chemical ■Product name: Gelpak
ack) R-420, R-430, R-440, 3 trees connected in series, number of theoretical plates 17,000/wood Solvent: Tetrahydride Furan Flow rate: 1.77 ml/min Temperature: 40°C Sample concentration: 600 mg 15 m1 Injection Amount: 200μ! Detector: Differential refractometer (blank below) Table 1 Characteristics of alkyl etherified amino resin Example 1 50 parts by weight of the butyl etherified melamine resin solution of Production Example 1 and alkyd resin (Hitachi Chemical Co., Ltd. Sigma product name, Phthalkyd 804- Weigh out 40 parts by weight of 70A, solid content hydroxyl value 80, solid content 70%, and add 1
5.5 g was added to adjust the coating solid content to 55%. This paint was applied to a tin plate (10 cm x 10 cm) using a bar coater #60 after measuring its weight. This tin plate is dried at 108°C for 30 minutes, and after cooling, the weight of the coating film is measured.

After that, 20 minutes at 150°C, 10 minutes at 180°C, 2
Baking was performed separately at 00"C for 3 minutes and at 200°C for 10 minutes, and the weight was measured again after cooling. The same test was performed five times for each heat loss, and the average value was determined. 3
Shown in the table. In addition, the heating loss was calculated|required by the following formula.

Loss on heating (%) - Examples 2 to 3 and Comparative Example 1 The loss on heating was determined in the same manner as in Example 1 using the formulations shown in Table 2. The results are shown in Table 3.

Margins below [Effects of the Invention] The resin composition for paints according to the present invention has good workability during resin production or paint preparation, and also has a small heating loss and less scattering during baking of the paint film.

Table 2 Paint formulation Unit: parts Table 3 Heating loss measurement results

Claims (1)

[Claims] 1. (A) Amino resin raw material (contains benzoguanamine as an essential component, and may also contain one or more amino compounds selected from the group consisting of melamine, acetoguanamine, phthaloguanamine, dicyandiamide, or urea) ) with formaldehyde and etherification reaction with alcohol, and the ratio of those having one triazine nucleus and those having two triazine nuclei in the molecule is 10 to 10, respectively.
25% by weight, Gardner viscosity (non-volatile content 60%,
an alkyl etherified amino resin in which the dilution solvent (n-butanol) is U or less and a free formaldehyde content is 1.5% by weight or less; and (B) a resin that can be cured by reacting with the alkyl etherified amino resin. Resin composition for paint.