JPS62297366A - Thermosetting coating composition - Google Patents

Abstract

PURPOSE:The titled composition, containing a specific oil-free alkyd resin and amino resin, having improved gloss, blocking properties, flexural properties, resistance to acid, gasoline, water, etc., of films and suitable as coating materials for automobile plastic substrates, etc. CONSTITUTION:A composition obtained by blending (A) an oil-free alkyd resin, containing (i) 0-30wt% compound expressed by the formula HO(CH2)nOH (n is 4-10) as a polyhydric alcohol, (ii) 0-20wt% compound expressed by the formula HO2(CH2)nCO2H, e.g. adipic acid, etc., as a polybasic acid, and (iii) 0-30wt% compound expressed by the formula, e.g. epsilon-caprolactone, etc., in an amount of 5-50wt% total of the components (i)-(iii) and having 5-70 hydroxyl value and 4,000-15,000 number-average molecular weight with (B) an amino resin, preferably n-butyletherified melamine resin, etc., preferably at 90/10-70/30 weight ratio of the components (A) to (B).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to thermosetting coating compositions containing certain oil-free alkyd resins and amino resins.

(Prior Art) In recent years, with the progress of synthetic resins and the development of their uses, plastic materials such as polyurethane resins, polycarbonates, nylon resins, ABS resins, and polyester resins are replacing metal materials.

In particular, in the automobile industry, replacing conventional steel plates with plastic materials makes it possible to reduce the weight of the car body, absorb impact energy, and prevent rust, so the switch to plastic materials is actively promoted. It is being Along with this, there is a demand for paints suitable for coating plastic materials.

JP-A-58-111864 discloses a coating composition for flexible substrates comprising an oil-free polyester resin and an aminoaldehyde resin. In this coating composition, methylene long chain bonds are introduced as a component that increases the intramolecular plasticizing effect of the resin, and furthermore, in order to impart good coating film appearance, water resistance, chemical resistance, etc. without impairing elasticity. A polyester resin with a low hydroxyl value into which an alicyclic polybasic acid has been introduced and an aminoaldehyde resin are used together.

(Problems to be Solved by the Invention) The coating composition comprising an oil-free polyester resin and an aminoaldehyde resin disclosed in the above publication has a -2
The physical properties of the coating film at low temperatures of 0 to -30°C are good, but the hardness, profking property, and gasoline resistance (staining and softening) are insufficient, making it suitable for automotive plastic substrates that require durability. As a covering material, there are practical problems.

The present invention solves the above-mentioned problems and provides a thermosetting coating composition that produces a coating film that is excellent in profking properties, hardness, gasoline resistance, acid resistance, water resistance, weather resistance, etc., and has excellent durability. The purpose is to provide.

(Means for Solving the Problems) The present invention solves the above problems by using an oil-free alkyd resin containing specific components.

The present invention contains an oil-free alkyd resin and an amino resin, and the oil-free alkyd resin has the formula (■) as (1) polyhydric alcohol: HO (CHx), OH (1) (in the formula, n is 4 to 4). 0 to 30% by weight of aliphatic dihydric alcohol (representing an integer of 10), (2) polybasic acid of the formula (II): HOOC (CHz), C0OH (I[) (in the formula, n is 4
0 to 2 aliphatic dibasic acids represented by (representing an integer of ~10)
0% by weight, and (3) represented by the formula (I[[): '0 (CHz)llC-'(III)=-11111'' (in the formula, n represents the above) Lacto 70～
30% by weight as components, and these (1), (2) and (
3) The total amount of the components is 5 to 50%, and the alkyd resin has a hydroxyl value of 5 to 70° and a number average molecular weight of 4.
000 to 15,000.

As the aliphatic dihydric alcohol represented by formula (1), 1
．． 4-butylene glycol, 1.5-bentanediol, 1.6-hexanediol, 1゜7-heptanediol, 1.8-octanediol, 1.9-nonanediol, 1,10-decanediol, etc. These can be used alone or in combination of two or more.

In addition to the above-mentioned aliphatic dihydric alcohols, alcohol components include polyhydric alcohols used in the production of ordinary alkyd resins, such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, 2 -Butylene glycol, 1°3-butylene glycol, 2.3-7'
tyrene glycol, neopentyl glycol, 2.5-
Hexanediol, esterified product of hydroxypivalic acid and neopentyl glycol, 2.2.4-)dimethyl-1,3-bentanediol, tricyclodecane dimetatool, 1.4-cyclohexane dimetatool, dimethylolpropionic acid , trimethylolethane, trimethylolpropane, glycerin, tris(2-hydroxyethyl)isocyanurate, pentaerydrift, diglycerin, dipentaerydrift, sorbitol, trishydroxymethylaminoethane, etc., or one or more of them are used. Glycidyl esters of zero-branched synthetic fatty acids (e.g., Cardura-E: Trademark, manufactured by Shell Chemical Co., Ltd.) 1, long-chain alkylene monoepoxides (e.g., ADE, manufactured by Daicel Corporation), etc., which can be used can also be used in the same way. can.

The aliphatic dibasic acid of formula (n) used in the present invention includes:
For example, adipic acid, pimelic acid, speric acid, azelaic acid, sebacic acid, nonane-1°9-dicarboxylic acid,
Examples include decane-1,10-dicarboxylic acid, and these can be used alone or in combination of two or more.

In addition to the above-mentioned aliphatic dibasic acids, acid components include polybasic acids commonly used in the production of alkyd resins, such as phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, and tribasic acid. Mellitic acid, pyromellitic acid, hemic acid or acid anhydrides thereof can be used. From the viewpoint of coating film properties such as gasoline resistance and blocking properties, aromatic polybasic acids such as isophthalic acid, phthalic acid, and terephthalic acid are preferred.

Examples of the lactone represented by formula (DI) include δ-valerolactone and ε-caprolactone.

In the coating composition according to the present invention, the above (1) to (
3) The total amount of the components is preferably 5 to 50% by weight based on the total raw materials of the oil-free alkyd resin. If it exceeds 50% by weight, acid resistance, gasoline resistance, hardness, and blocking resistance will be poor. .

The oil-free alkyd resin has a hydroxyl value of 5 to 70,
The number average molecular weight is designed to be 4,000 to 15,000. The resin designed in this manner has a small amount of low molecular weight components, and when formed into a coating film, it has excellent elasticity and hardness, acid resistance, gasoline resistance, and blocking properties.

When the hydroxyl value exceeds 70, low molecular weight components increase,
Desired coating properties cannot be obtained. Further, the same applies when the number average molecular weight is 4000 or less.

The oil-free alkyd resin is preferably produced by a reduced pressure polymerization condensation method. For example, after proceeding with condensation polymerization of an alcohol component, an acid component, and a lactone component at 190 to 250°C, in the presence of a catalyst such as antimony trioxide, germanium oxide, or n-butyl titanate,
After carrying out a polycondensation reaction at 250 to 300°C under a reduced pressure of 1 to 5 mmHg, for example, trimellitic acid, lomeliftic acid, or anhydride thereof, etc., a trivalent or higher polyhydric carboxylic acid and/or for example, trimethylol. A desired oil-free alkyd resin is obtained by performing transesterification using a polyhydric alcohol having a valence of 3 or more, such as ethane, trimethylolpropane, or pentaerydrift.

In the coating composition according to the present invention, an oil-free alkyd resin may be blended with an alkyd resin produced under normal pressure or an oil-free alkyd resin.

In the coating composition according to the invention, the amine resin used in combination with the alkyd resin is produced by reacting melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, etc. with an aldehyde.

As the aldehyde, formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde, etc. are used. Note that the amino resin may be alkyl etherified with alcohol such as methyl alcohol, ethyl alcohol, n-butyl alcohol, and isobutyl alcohol.

Since plastic materials are easily deformed by heat, it is preferable to bake the paint at a low temperature, and in terms of the appearance of the paint film, it is necessary to obtain a smooth paint film without repelling.

In consideration of these points, n-butyl etherified melamine resin and methyl etherified melamine resin, which have good low-temperature curability, are preferred.

Blocked isocyanate can be used in place of amino resin in an amount of 50% by weight or less (blocked isocyanate/amino resin is 1/1 or less by weight); too much blocked isocyanate may result in unreacted or unreacted substances. Functional groups tend to remain. As the blocked isocyanate, 1゜6-hexamethylene diisocyanate,
Examples include polyisocyanates such as tolylene diisocyanate blocked with phenol, ethyl acetoacetate, and the like. For example, DC2753 (Japan Polyurethane ■
(manufactured by Takeda Pharmaceutical Co., Ltd.), Takenate B815N (manufactured by Takeda Pharmaceutical Co., Ltd.), etc.

The composition of the oil-free alkyd resin and the amino resin in the coating composition according to the present invention has a solid content weight ratio of 90/
It is preferable that the ratio is 10 to 70/30; if it is less than 90/10, the hardness, blocking property, and gasoline resistance will be poor;
If it is more than 0/30, the flexibility and acid resistance at low temperatures will be poor.

Solvents that can be used in the coating composition of the present invention are the same as those for ordinary amino resin/alkyd resin compositions, such as aromatic hydrocarbon solvents such as xylene and toluene, and ketones such as methyl ethyl ketone and methyl isobutyl ketone. system,
Ester systems such as n-butyl acetate and ethyl acetate, cellosolve systems such as ethyl cellosolve, butyl cellosolve, and cellosolve acetate, carpitol systems such as ethyl carpitol, butyl carpitol, and carpitol acetate, saturated hydrocarbon systems such as heptane and cyclohexane, One or more types of petroleum solvents, mineral spirits, etc. can be used.

The coating composition of the present invention can be made into a paint by blending common pigments by a common pigment dispersion method, if necessary. In addition, plasticizers, coating film strengthening resins, dispersants, coating surface conditioners, and fluid! I! It may contain various additives such as regulators, ultraviolet absorbers, ultraviolet stabilizers, antioxidants, and crosslinking reaction promoters.

The coating composition according to the invention can be applied by conventional coating methods. For painting, an air spray machine, an airless spray machine, an electrostatic coating machine, a dipping tank, a roll coating machine, a brush, etc. can be used.

The thermosetting coating composition of the present invention needs to be crosslinked and cured by heating, and is generally heated at 90 to 180°C for 1 to 100 minutes. Appropriate heating temperature and time are
It is selected appropriately in consideration of the heat deformation temperature of the base material.

(Example) Next, the present invention will be described in detail based on Examples, but the present invention is not limited thereto. In the Examples, "parts" means "parts by weight" unless otherwise specified.

Synthesis Example 1 of Oil-Free Alkyd 12 In a reaction tank of an oil-free alkyd resin manufacturing equipment equipped with a stirrer, a thermometer, a rectification column, a reflux device, and an inert gas introduction pipe, Cardular-E (trademark: Nigel Chemical Co., Ltd. made)
100 parts, neopentyl glycol 149 parts, 1.6-
250 parts of hexanediol, 544 parts of isophthalic acid, 100 parts of adipic acid, 49.1 parts of ethylene glycol, and 0.15 parts of dibutyltin dioxide were charged, and the reaction temperature was gradually raised to 240°C, and the condensed water was passed through a rectification column. Remove from the system. When the temperature of the rectification column falls below 80℃, xylene is added to the reaction tank and the reaction is continued by the solvent reflux method. When the acid value of the contents reaches 1.5, 0.1 part of antimony dioxide is added. The temperature was raised to 280° C., the pressure inside the system was reduced to 1.0 mmHg using a vacuum pump, and the reaction was continued for 1 hour while trapping distillates such as glycol.

Next, 28 parts of trimethylolethane was added, heated at 260° C. for 30 minutes, and then cooled to obtain an oil-free alkyd resin having a number average molecular weight of 6,000 and an OH value of 40.

In the above and following descriptions, the hydroxyl value is measured by an acetylation method using acetic anhydride and pyridine, and is expressed as the number of potassium hydroxide in the same mole as the hydroxyl group contained in 1 g of resin.

Further, the number average molecular weight was calculated based on standard polystyrene after obtaining a chromatogram by liquid gel permeation chromatography using tetrahydrofuran as an eluent. In this case, the equipment is Hitachi 635 model HLC and the column is Gelpack R4.
40, R450 and R400M (all trade names of Hitachi Chemical Co., Ltd.) can be used by connecting them in series.

Synthesis Example 2 (Control) Using the same equipment as Synthesis Example 1, Cardura-8 was placed in the reaction tank.
100 parts, 149 parts of neopentyl glycol, 1. 6
- 250 parts of hexanediol, 544 parts of isophthalic acid,
100 parts of adipic acid, 28 parts of trimethylolethane, and 0.15 parts of dibutyltin dioxide are charged, and the reaction temperature is gradually raised to 240° C., and condensed water is removed from the system through a rectification column. When the temperature of the rectification column falls below 80°C, xylene is added to the reaction tank and the reaction is continued by the solvent reflux method. When the acid value of the contents reaches 1.5, it is cooled and the number average molecular weight is 3800. An oil-free alkyd resin having a valence of 08 and 40 was obtained.

Synthesis Example 3 (Comparative: Corresponding to JP-A-58-111864) Using the same apparatus as Synthesis Example 1, 245 parts of 1,6-hexanediol, 135 parts of neopentyl glycol, and 106 parts of trimethylolethane were placed in a reaction tank. , 250 parts of adipic acid, 175 parts of phthalic anhydride, and 190 parts of hexahydrophthalic anhydride are charged, and the reaction temperature is gradually raised to 220° C., and the condensed water is removed from the system through a rectification column. When the temperature of the rectification column falls below 80° C., xylene is added to the reaction tank and the reaction is continued by the solvent reflux method. When the acid value of the contents reaches 7, the reaction is terminated, cooled, and the number average molecular weight becomes 31.
00, an oil-free alkyd resin having an OH value of 55 was obtained.

Yako 111 Example The oil-free alkyd resin obtained in Synthesis Example 1 above was blended in the following proportions, and the pigment was dispersed using a paint shaker to obtain white enamel.

Oil-free alkyd resin 75 parts □ Tybake R930100 Xylene 50 Butyl cellosolve 20 Melan 287 (n-butyl etherified melamine resin manufactured by Hitachi Chemical Co., Ltd., heating residue 50%) 50 Catalyst X450 (BYK Chemi-1, total 296 parts Above white Enamel with xylene/butyl cellosolve/n-
It was diluted with a mixed solvent of butanol = 80/10/10 (weight ratio) to a viscosity of 20 seconds (Ford cup #4, 25°C).

Comparative Example 1 A white enamel was produced in the same manner as in the above example except that the oil-free alkyd resin obtained in Synthesis Example 2 was used as the oil-free alkyd resin.

Comparative Example 2 A white enamel was produced in the same manner as in the above example except that the oil-free alkyd resin obtained in Synthesis Example 3 was used as the oil-free alkyd resin.

Test Example Preparation of coating film sample A 31 m thick R-RIM polyurethane plate was degreased with trichloroethane, a one-component polyurethane primer was applied thereon to a dry film thickness of 8 μ, and the film was heated at 80°C x 20
This was dried for a few minutes and used as a base material.

The enamels produced in the Examples and Comparative Examples described above were each air-sprayed onto this base material to give a dry film thickness of 25 to 30 μm, and baked and dried at 120° C. for 20 minutes. The properties of the coating samples thus obtained were tested and the results are shown in the table below.

In addition, the blocking property was determined by placing several pieces of gauze on the coating film.
A weight with a diameter of 40 cranes and a weight of 500 g was placed on top of it, and the temperature was raised to 50°C.
After leaving it for 2 hours, gauze marks on the paint film were observed.

The bendability was determined by leaving the sample in an atmosphere at -20° C. for 4 hours, bending it 180° with a rod of 59 mm in diameter in between, and observing whether there was a crank at the bent portion.

Acid resistance was determined by dropping 0.2 ml of 5% sulfuric acid onto the coating film and
The state of the coating film was observed after being left at ℃ for 24 hours.

Furthermore, gasoline resistance was determined by observing the state of the coating film after immersion at 20° C. for 6 hours.

Water resistance was determined by observing the state after being immersed in water at 40°C for 200 hours.

(Effect of the invention) As is clear from the above results, if the coating composition of the present invention is used, all of the gloss, blocking properties, flexibility at -20°C, acid resistance, gasoline resistance, and water resistance can be achieved. A coating film having excellent performance in this respect can be obtained.

t'r 1;

Claims (1)

[Claims] The oil-free alkyd resin contains an oil-free alkyd resin and an amino resin, and the oil-free alkyd resin has the following formula (1) as a polyhydric alcohol: HO(CH_2)_nOH(I) (where n is 4 0 to 30% by weight of aliphatic dihydric alcohol (representing an integer of ~10), (2) Formula (II) as a polybasic acid: HOOC(CH_2)_nCOOH(II) (wherein n is 4 to 10 0 to 20% by weight of aliphatic dibasic acid (representing an integer of lactone 0~
30% by weight as components, and these (1), (2) and (
3) The total amount of the components is 5 to 50% by weight, and the alkyd resin has a hydroxyl value of 5 to 70 and a number average molecular weight of 4.
000 to 15,000.