JPH03181575A - High chipping-resistant aqueous dispersion type coating compound composition - Google Patents

Abstract

PURPOSE:To obtain the title composition providing coating film having excellent appearance, water-vapor resistance, etc., containing an aqueous dispersion prepared by emulsifying a water-soluble polyester resin containing a unit composed of a specific acid anhydride and a blocked polyisocyanate in a specific ratio in an aqueous medium, as a film-forming component. CONSTITUTION:The objective composition containing an aqueous dispersion prepared by emulsifying (A) a water-soluble polyester resin which comprises 5-50wt.% unit composed of an acid anhydride shown by the formula (R is 8-20C alkyl or alkenyl) and has 25-100KOHmg/g acid value, 50-200KOHmg/g hydroxyl number and 500-5,000 number-average molecular weight and (B) a blocked polyisocyanate having <=5,000 number-average molecular weight in the ratio of (50:50)-(99:1) (weight ratio) in (C) an aqueous medium, as a film-forming component.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention provides a novel highly chipping-resistant aqueous dispersion coating composition. The present invention relates to an aqueous dispersion type coating composition capable of forming a coating film having chipping properties.

[Prior Art] In recent years, water-based paints that use water as a diluent have been attracting attention from the viewpoint of preventing air pollution and saving resources, and bake-hardening water-based paints have already been developed for industrial use. In this baking-curable water-based paint, a mixture of a polyester resin having a carboxyl group and a water-soluble melamine resin is usually used as a coating film-forming component, and baking sometimes causes condensation polymerization of the polyester resin and melamine resin. By this, it is cured and a coating film is formed (for example, JP-A-61-31
Publication No. 472).

Incidentally, in automobile painting, the coating film formed is required to have the ability to protect the material from collisions with pebbles and the like, that is, to have chi-nobbing resistance. However, in conventional bake-curable water-based paints, melamine resin is usually used as a curing agent for polyester resin, and due to the hard and brittle nature of the triazine ring in the melamine resin,
It is difficult to form a coating film with sufficient chipping resistance,
Therefore, it has the disadvantage of being difficult to use for car painting, etc., and its applications are inevitably limited.

[Problems to be Solved by the Invention] The present invention overcomes the drawbacks of conventional bake-curing water-based paints, can form a coating film with particularly high chipping resistance, and has the ability to This was done with the aim of providing a water-based paint that can also satisfy other required performances.

[Means for Solving the Problem] As a result of intensive research to develop a water-based paint having the above-mentioned preferable properties, the present inventors have developed a block-forming method using a specific water-soluble polyester resin as a paint film-forming component. It was discovered that the object could be achieved by a composition containing an aqueous dispersion in which polyisocyanate and polyisocyanate were emulsified in a specific proportion in an aqueous medium, and based on this knowledge, the present invention was completed. Ta.

That is, the present invention provides a unit 5 formed from an acid anhydride represented by (A) general formula % formula % (1) (R in the formula is an alkyl group or alkenyl group having 8 to 20 carbon atoms) ~50% by weight
containing, acid value 25-10100KOH/g, hydroxyl value 5O-200KOH+mg/i+ and number average molecule ji
500~s, ooo water-soluble polyester resin, (B
) number average molecular weight s, o o.

The weight ratio of the following blocked polyisocyanate is 50:
The present invention provides a highly chipping-resistant aqueous separation-type paint composition characterized by containing an aqueous dispersion emulsified in an aqueous medium at a ratio of 5Q to 99;l as a film-forming component. .

The present invention will be explained in detail below.

(A) used as a coating film forming component in the composition of the present invention
The component water-soluble polyester resin needs to contain 5 to 50% by weight of units formed from acid anhydrides represented by the general formula (D).

The reason why the acid anhydride is used as a raw material for the polyester resin is that oil-free polyester resin has a high surface tension, so it has poor wettability to the object to be coated, and it causes coating film defects such as repelling and denting during painting. When applying multilayer coating with fatty acid-modified polyester resin, there is a risk of problems with interlayer adhesion as a physical property of the coating film.

If the content of units formed from nucleic acid anhydrides in the water-soluble polyester resin used in the present invention is less than 5% by weight, the effect of improving chipping resistance, which is the objective of the present invention, will not be sufficiently exhibited; If it exceeds , the degree of freedom in designing the quality of the paint decreases.

The alkyl group or alkenyl group in the acid anhydride is
As long as the number of carbon atoms is in the range of 8 to 201, preferably 10 to 1B, it may be linear or branched. The number of carbon atoms in the alkyl group or alkenyl group is 2
If it exceeds 0, the effect of improving chipping resistance will not be sufficiently exerted even though the carbon chain becomes long, and it will be difficult to obtain it industrially, which is inappropriate for practical use.

Examples of such acid anhydrides include octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl,
Succinic anhydride with an alkyl group such as octadecyl,
Examples include succinic anhydride having an alkenyl group such as octenyl, nonenyl, decenyl, undecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, and octadecenyl. One type of these acid anhydrides may be used, or two or more types may be used in combination.

The water-soluble polyester resin used in the present invention needs to have an acid value in the range of 25 to 100 KOHmy/y and a hydroxyl group in the range of 50 to 200 KOHmy/y. If the acid value is less than 25KOHmg/9 (
B) Component blocked polyisocyanate may not be able to be emulsified into an aqueous medium in a stable state;
If it exceeds 00 KOHn/g, there is a tendency for the alkali resistance of the coating film to decrease significantly.

In addition, the hydroxyl value is important for the solubility of the polyester resin in aqueous media and the crosslinking points, and if the hydroxyl value is less than 50KOHI19/g, the hydrophilicity will be insufficient and the crosslinking points will be too small, resulting in poor water resistance of the coating film. There is a risk that the strength will be insufficient, and if it exceeds 200 KOHrn979, there is a tendency for the water resistance of the coating film to decrease.

Furthermore, the water-soluble polyester resin needs to have a number average molecular weight in the range of 500 to s, ooo. If the number average molecular weight is less than 500, the water resistance, chipping resistance, and durability of the coating film will be poor, and the object of the present invention cannot be fully achieved. There is a tendency for the fluidity to decrease and the smoothness of the coating film to be impaired.

Such water-soluble polyester 84FW also has the effect of effectively emulsifying the hydrophobic blocked polyisocyanate of component (B) in an aqueous medium.

The water-soluble polyester resin used in the present invention uses as raw materials the above-mentioned acid anhydrides, polyhydric alcohols, polybasic acids, and oils and fats used as necessary, which are commonly used as raw materials for ordinary polyester resins. However, it can be manufactured by a known method.

Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1.3-butylene glycol, 1.4-butanediol, 1.6-hexanediol, diethylene glycol, dipropylene glycol,
Neopentyl glycol, triethylene glycol, hydrogenated bisphenol A1 glycerin, trimethylolethane, trimethylolpropane, pentaerythritol,
Examples include dipentaerythritol. These polyhydric alcohols may be used alone or in combination of two or more.

In addition, examples of polybasic acids include heptalic anhydride, isophthalic acid, terephthalic acid, succinic anhydride, adipic acid, azelaic acid, sebacic acid, maleic anhydride, fumaric acid,
Examples include itaconic acid and trimellitic anhydride. These polybasic acids may be used alone or in combination of two or more.

The water-soluble polyester resin thus obtained is usually neutralized with a basic substance. At this time, the basic substance is 40% of the carboxyl group contained in the water-soluble polyester resin.
It is preferable to use an amount necessary to neutralize ~100 mol%; if the amount used is less than 40 mol%, the polyester resin may not be water-solubilized;
Exceeding this is not preferred because the viscosity of the resulting water-soluble polyester resin liquid increases significantly, and as a result, a large amount of diluent is added during coating, resulting in a decrease in solids concentration and poor coating workability.

The blocked polyisocyanate used as component (B) in the coating film forming component in the composition of the present invention includes 1
Has two or more incyanate groups in the molecule, the molecule! 5
,000 or less, such as ethylene diisocyanate, propylene diisocyanate,
Tetraethylene diisocyanate, hexamethylene diisocyanate, decamethylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, 2.4-tolylene diisocyanate, 2.6-
) lylene diisocyanate, 1.5-7 tylene diisocyanate, 4.4', 4. -triphenylmethane triinocyanate, 4,4'-diphenylmethane diisocyanate, 3.3'-dimethyl-4,4'-diphenylene diisocyanate, m-xylylene diisocyanate, p-xylylene cyisovanoa 1-L-sophorone diisocyanate, Examples include lysine diisocyanate-1, polyol adducts of these diisocyanates, biuret compounds, incyanurate compounds, and other polyisocyanates masked with blocking agents. Among these, hexamethylene diisocyanate and this Bronk bodies of polyol adducts, biuret compounds, and incyanurate compounds are suitable.

Examples of blocking agents include phenols such as phenol and cresol, alcohols such as methanol and benzyl alcohol ether, active methylenes such as methyl acetoacetate and dimethyl malonate, amide types such as acetalinide and acetate amide, and other imides. Examples include those based on amine-based, imidazole-based, urea-based, carbamate-based, imine-based, oxime-based, mercaptan-based, Wt salt-based, and lactam-based.

The blocked polyisocyanate used in the present invention needs to have a number average molecular weight of s,ooo or less. When the number average molecular weight exceeds s,ooo, the viscosity becomes too high, the fluidity during baking tends to decrease, and the smoothness of the coating film tends to be impaired.

In the composition of the present invention, the above-mentioned (
A) component water-soluble polyester resin and (B) Ii2
One type of blocked polyisocyanate may be used, or two or more types may be used in combination,
In addition, the ratio of their use should be selected so that the weight ratio of component (A) to component (B) is in the range of 50:50 to 99:1, preferably 60:40 to 80:20. It is. If the amount of blocked polyisocyanate is less than the above range, the effect of improving chipping resistance will not be fully exhibited, and if it is more than the above range, the wettability to the coated object will decrease, and coating film defects such as repellents and dents will occur. more likely to occur.

In order to increase the curing speed, the m-acids of the present invention may include inorganic and organic metal carboxylates, tin, bismuth, zinc, lead, mercury, vanadium, balt, nickel, iron, potassium, Halide salts of metals such as copper (e.g., dibutyltin dicarboxylate, stannous octoate,
zinc octoate, bismuth octoate, etc.) and N, N',
Known urethanes such as tertiary amines (blocked and free tertiary amines) such as N'''-tris(methylaminopropyl)hexahydrotriazine, tris(dimethylaminomethyl)phenol, triethylenediamine, imidazoline, etc. A catalyst can be added, and if desired, other curing agents such as melamine resins can also be used in combination with the blocked polyisocyanate, as long as the object of the invention is not impaired.

There are no particular limitations on the method for preparing the aqueous dispersion type coating composition of the present invention, and known methods can be used. For example, first, the water-soluble polyester resin as the component (A) is neutralized in an aqueous medium using the required amount of basic substance, and then the required amount of the blocked polyisocyanate as the component (B) is added thereto to form a homogeneous mixture. to prepare an aqueous dispersion. Then, to this aqueous dispersion, a curing accelerator, other curing agents, other water-soluble resins, coating surface conditioners, etc. are added as necessary, and the mixture is mixed by known means. A desired aqueous dispersion type coating composition can be obtained by homogeneously mixing the components. In addition, when preparing a pigmented aqueous dispersion type coating composition, a pigment paste is prepared by a conventional method using a part of the polyester resin of the component (A), and this is mixed with the aqueous dispersion. It's good too,
Pigments may be incorporated directly into the aqueous mass.

The aqueous dispersion type coating composition of the present invention prepared in this way can be applied to the object to be coated using methods such as brush coating, spray coating, dip coating, and electrostatic coating, in the same way as conventional water-based coatings. Thereafter, by performing a baking treatment, a cured coating film having a high degree of chipping resistance can be formed.

[Example] Next, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited in any way by these examples.

The coating film performance was evaluated according to the following method.

(1) Chipping resistance diamond shot tester (manufactured by Suga Test Instruments Co., Ltd.,
10 diamond shots each at speeds of 90, 130, and 170 km/h were applied to the paint film cooled to -20°C using a KSS"l type), and a cellophane adhesive tape with a width of 24 mm was applied to the area. Divide the total area of the peeled film by 3, take that value as the peeled area, and calculate the percentage of the peeled film reaching the base steel plate in the salt spray test ( JIS K-54007
, 8 salt spray test) was performed for 72 hours, and was calculated from the number of rust occurrence points, and was taken as the base scratch achievement rate.

(2) 60' specular gloss Determined in accordance with JIS K-54006, 760° specular gloss.

(3) Pencil hardness: Based on JIS K-54006, 14 pencil pull test and JIS D-02028, 10 pencil scratch test method, pencil (Mitsubishi Uni, manufactured by Mitsubishi Pencil Co., Ltd.,
Cut only the wood part (product name) and angle the core at a 45° angle to the painted steel plate surface.
It is expressed as the pencil hardness just before the painted surface is scratched by contact friction at an angle of .

(4) Adhesion JIS K-54006, 15th board test, JIS
In accordance with D-02028, 12th board test method, draw 11 equally spaced 1 mm parallel lines perpendicularly to each other on the test piece using a sharp thin knife (NT canter, etc.) to create 100 1 mm squares. A cellophane adhesive tape with a width of 24 mm was adhered to it, and it was pulled upward at once, and the number of pieces remaining without peeling was expressed as χ, and the adhesion was expressed as χ/100.

(5) Humidity Resistance The appearance of the coating film was observed after it was left in a humidity tester at a temperature of 50°C and a humidity of 98% for 360 hours.

Production Example 1 Production of water-soluble polyester resin A-1 In a four-bottle flask equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas introduction tube, 20.0 parts by weight of inphthalic acid and 10.0 parts by weight of trimellitic anhydride. 9.3 parts by weight of adipic acid, 25. parts by weight of hexadecenyl succinic anhydride. O3
i parts by weight, 20.8 parts by weight of 1,4-butanediol, and 14.9 parts by weight of trimethylolpropane, heated at 220°
The esterification reaction was carried out at C for 2 hours and then at 190°C for 2 hours to obtain an acid value of 50, a hydroxyl value of 120, and a number average molecular weight of 16.
A water-soluble polyester resin of No. 00 was obtained.

The temperature of the resulting resin reaction product was lowered to 100°C, and butyl cellosolve was added thereto to obtain water-soluble polyester resin A-1 with a heating residue of 80% by weight.

Production Example 2 Production of Water-Soluble Polyester Resin A-2 In the same manner as Production Example 1, 20% of isophthalic acid was placed in a four-necked 7 flask equipped with a stirrer, a thermometer, a reflux condenser, and a nitrogen gas inlet tube. O3i parts, trimellitic anhydride 6.6 parts by weight, dodecyl succinic anhydride 30.9 parts by weight, polyethylene glycol (molecular weight 200) 15.0 parts by weight, 1,
8.7 parts by weight of 4-butanediol and 18.81 parts by weight of trimethylolpropane were charged, and an esterification reaction was carried out at 220°C for 2 hours and then at 190'O for 2 hours to obtain an acid value of 35, a hydroxyl value of 150, and a number of A water-soluble polyester resin having an average molecular weight of 1.400 was obtained.

The temperature of the resulting resin reaction product was lowered to 100°C, and butyl cellosolve was added to obtain water-soluble polyester resin A-2 with a heating residue of 80% by weight.

Examples 1 to 5 The temperature of the water-soluble polyester resins A-1 and A-2 shown in Table 1 obtained in the production examples was lowered to 60°C, and while stirring with a homodisper (manufactured by Tokushu Kika Kogyo Co., Ltd.) After uniformly neutralizing by adding dimethylethanolamine corresponding to 0.75 molar equivalent of carboxyl groups in the resin reactant, blocked polyisocyanate shown in Table @1 was added and mixed. While maintaining the same temperature, deionized water was gradually added to obtain an aqueous dispersion with a strong bluish color and a heating residue of 36% by weight.

Next, in order to produce a white aqueous dispersion paint from this aqueous dispersion, first a water-soluble polyester resin A-133,0 was prepared.
An aqueous resin solution of water-soluble polyester resin A-1 was obtained with a heating residue of 33% by weight, consisting of 8.3 parts by weight of butyl cellosolve, 2.0 parts by weight of dimethylethanolamine, and 56.7 parts by weight of deionized water. In addition, water-soluble polyester resin A-233, O3i parts, butyl cellosolve 8.3
An aqueous resin solution of water-soluble polyester resin A-2 having a heating residue of 33% by weight was prepared from 1.4 parts by weight of dimethylethanolamine and 57.3 parts by weight of deionized water, and then this A-1, Resin aqueous solution 3 for each of A-2
White pastes A-1 and A-2 were prepared by fractionating in a sand mill for 1 hour at a blending ratio of 0.0 parts by weight, 60.0 parts by weight of titanium oxide, and 10.0 parts by weight of deionized water. This white paste, the above aqueous dispersion, dibutyltin dilaurate as a curing catalyst, and an additive for water-based paints (Agitol A white aqueous dispersion paint having a weight ratio of 1:1 was obtained.

Examples 6 to 10 A white paste and an aqueous dispersion were prepared in the same manner as in Examples 1 to 5, and the white paste, aqueous dispersion, and melamine resin (
Nikaratsuku MW-30 (manufactured by Sanso Chemical Co., Ltd., trade name, solid content 100%), dibutyl tin dilaurate, and additives for water-based paints were mixed in the proportions shown in Table 1, and the pigment content and resin content were mixed. A white water-based dispersion paint was obtained in which the weight ratio was 1:1 and the weight ratio of the mixture of water-soluble polyester resin and blocked polyinsyanate to melamine resin was 85:15.

Comparative Example 1.2 A water-soluble paint containing no blocked polyisocyanate was produced using the water-soluble polyester resins A-1 and A-2 obtained in Production Example.

That is, an aqueous resin solution corresponding to the aqueous dispersion of the example was prepared without using blocked polyisocyanate, and this aqueous resin solution, white paste, melamine resin, and additives were mixed in the proportions shown in Table 1, and the pigment A water-soluble white paint having a weight ratio of 1=1 and a weight ratio of water-soluble polyester resin to melamine resin of 85:15 was obtained.

(Left below) Test example A dull steel plate with a thickness of O, Bmm treated with zinc phosphate,
Cationic electrodeposition paint (Aqua No. 4200, NOF (
Co., Ltd., trade name) to a dry film thickness of 20 μm, and baked at 175°C for 25 minutes. The diluted paint was diluted with deionized water and the viscosity was adjusted to 30 seconds at 20°C using a 7-odd cup #4, and the diluted paint was air-sprayed to a dry film thickness of 35 μm.
After setting at 20°C for IO minutes, then setting at 60°C for 5 minutes, and baking at 160°C for 30 minutes, a top coat (Melami No. 200
0, Nippon Oil & Fats Co., Ltd., product name) was air-sprayed to a dry film thickness of 35 μm, and 30
Bake for a minute. The thus obtained coating film was evaluated for chiaping resistance, external coating properties, gloss, hardness, adhesion, and moisture resistance. The results are shown in Table 2.

It is clear from Table 2 that the aqueous dispersion paint of Examples 1-10, whose film component is an aqueous fraction mainly composed of a mixture of polyester resin and blocked polyisocyanate, contains no blocked polyisocyanate. It can be seen that compared to Comparative Example 1.2 in which no coating was applied, the chipping resistance, peeling area, and scratch rate were significantly improved without impairing the coating appearance, gloss, hardness, adhesion, and moisture resistance. 〇(
(Left below) [Effects of the Invention] The highly chipping-resistant aqueous dispersion coating composition of the present invention is an aqueous dispersion in which a water-soluble polyester resin and a blocked polyisocyanate are emulsified in an aqueous medium as coating film-forming components. The cured coating film has good appearance, gloss, hardness, adhesion, and moisture resistance, and
It has particularly high chipping resistance and is suitable for use in, for example, automobile painting.

Claims (1)

[Claims] 1(A) From acid anhydrides represented by the general formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (R in the formula is an alkyl group or alkenyl group having 8 to 20 carbon atoms) Acid value 25-100 KOHm, containing 5-50% by weight of units formed
g/g, a water-soluble polyester resin with a hydroxyl value of 50 to 200 KOHmg/g and a number average molecular weight of 500 to 5,000, and (B) a blocked polyisocyanate with a number average molecular weight of 5,000 or less in a weight ratio of 50:50 to 99:1
1. A highly chipping-resistant aqueous dispersion coating composition, characterized in that it contains as a coating film-forming component an aqueous dispersion emulsified in an aqueous medium at a ratio of .