JPH04366191A - Coating composition - Google Patents

Abstract

PURPOSE:To provide a coating composition which gives coating films excellent in resistance to scuffing without damaging the film hardness, film flexibility, appearance, gloss, acid resistance, weather resistance, solvent resistance and water resistance so that it is suitable for coating automobile outer panels, household appliances, fitments and constructional exterior material that demand resistance to scuffing and particularly useful for dark color coating on which scuffs are apt to be conspicuous. CONSTITUTION:A coating composition which comprises 10-50wt.% urethane polyol, which is obtained by reaction a diisocyanate compound with a caprolactone polyol and has a weight-average molecular weight of 1,500-4,000 and a hydroxyl value of 50-80mgKOH/g, 10-80wt.% vinyl polymer, which has a weight-average molecular weight of 5,000-50,000 and a hydroxyl value of 50-150mgKOH/g, and 10-40wt.% crosslinking agent.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a new coating composition, and more particularly, a coating composition that can be used as a top coat for home appliances, automobiles, etc. and provides a coating film with excellent scratch resistance. Regarding.

0002

BACKGROUND OF THE INVENTION In order to maintain the initial quality of coated products for a long period of time, it has been desired to develop paints with excellent scratch resistance. For example, top coats applied to automobile exterior panels are susceptible to scratches during car washes, etc.
Since scratches are noticeable in dark-colored paints, which have recently been in increasing demand, there is a desire to develop paints that provide a paint film that is resistant to scratches, and various studies are being carried out.

[0003] As paints with excellent scratch resistance, paints with extremely hard coatings that are difficult to scratch have been proposed;
Since the coating film has poor flexibility, impact resistance,
It has not been put into practical use because of the problem of reduced workability.

[0004]Recently, therefore, paints have been proposed in which the scratch resistance is improved by imparting rubber elasticity to the paint film to absorb external forces that cause scratches. For example, JP-A-64-40573, JP-A-64-43373, JP-A-64-40571, JP-A-64-66.
No. 274 proposes a paint in which low molecular weight polyester polyols, polyether polyols, polyacrylate polyols, etc. are mixed with high molecular compounds, but it is difficult to efficiently crosslink the low molecular weight compounds in the paints; Furthermore, these low molecular weight compounds have a problem of poor solvent resistance and water resistance due to weak intermolecular cohesive force.

[0005]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to improve the coating film hardness, flexibility, appearance, gloss, acid resistance, solvent resistance, water resistance, weather resistance, etc. An object of the present invention is to provide a coating composition that provides a coating film with excellent scratch resistance.

[0006]

[Means for Solving the Problems] According to the present invention, the weight average molecular weight of a diisocyanate compound obtained by reacting a caprolactone polyol is 1500 to 4000.
and 10 to 50% by weight of a urethane polyol having a hydroxyl value of 50 to 180 mgKOH/g, a weight average molecular weight of 5000 to 50000, and a hydroxyl value of 50 to 15
A coating composition is provided, characterized in that it contains 10 to 80% by weight of a vinyl polymer and 10 to 40% by weight of a crosslinking agent.

The present invention will be explained in more detail below.

The coating composition of the present invention is characterized by containing a specific urethane polyol, a vinyl polymer, and a crosslinking agent in specific proportions.

In the coating composition of the present invention, the specific urethane polyol used as an essential component is a compound obtained by reacting a diisocyanate compound and a caprolactone polyol.

As the diisocyanate compound used as a raw material component of the urethane polyol, aliphatic, alicyclic or aromatic diisocyanate compounds can be preferably used. Specific examples of the aliphatic diisocyanate compound include hexamethylene diisocyanate, hexamethylene diisocyanate trimer (isocyanurate, biuret, trimethylolpropane adduct type, etc.), ethylene diisocyanate, trimethylene diisocyanate, and tetramethylene diisocyanate. , lysine diisocyanate and derivatives thereof, and alicyclic diisocyanate.
Specific examples of such compounds include isophorone diisocyanate, methylcyclohexane-2,4-(or 2,6-) diisocyanate, and 4,4-methylenebis(
Preferred examples include cyclohexyl isocyanate), adducts of each of the above diisocyanates and polyhydric alcohols such as ethylene glycol and trimethylolpropane, burettes obtained by adding water to the above diisocyanates, and polymers of the above diisocyanates. can be done. Further, specific examples of the aromatic diisocyanate compound include tolylene diisocyanate, diphenylmethane diisocyanate, and derivatives thereof. Among the diisocyanate compounds, alicyclic diisocyanate compounds are particularly preferred because they provide excellent weather resistance for coating films and facilitate control of the urethane polyol synthesis reaction. Further, when used, they can be used alone or as a mixture.

Preferable examples of the caprolactone polyol used as a raw material component of the urethane polyol include polycaprolactone diol obtained by modifying ethylene glycol with ε-caprolactone, and polycaprolactone triol obtained by modifying trimethylolpropane with ε-caprolactone. , and commercially available products such as Plaxel 205, Plaxel 208, Plaxel 210
, Praxel 212, Praxel 220, Praxel 3
03, Plaxel 305, Plaxel 308, Plaxel 312, Plaxel 320, Plaxel 407 (all trade names, manufactured by Daicel Chemical Industries, Ltd.), etc. can also be used.

[0012] The blending ratio when reacting the diisocyanate compound and caprolactone polyol is as follows:
Isocyanate groups in diisocyanate compounds (NCO
) and the hydroxyl group (OH) in the caprolactone polyol (NCO/OH molar ratio) is preferably in the range of 0.3 to 0.7. The NCO/OH molar ratio is 0
．． If it is less than 3, unreacted caprolactone polyol
If the molecular weight exceeds 0.7, the molecular weight of the urethane compound produced will become too high, which is not preferable. Further, in the reaction, preferably an aromatic solvent is used as the solvent,
Using an ester solvent, a ketone solvent, etc., preferably 5
It is desirable to react at a temperature of 0 to 80°C for 1 to 4 hours. When the reaction temperature is less than 50°C, the reaction takes a long time, and when it exceeds 80°C, the reaction proceeds unevenly, which is not preferable. Further, in the reaction, a tin-based catalyst such as dibutyltin dilaurate, an acid-based catalyst such as an organic carboxylic acid, or a basic catalyst such as a tertiary amine may be used as necessary.

Furthermore, the weight average molecular weight of the urethane polyol used as an essential component in the present invention is 1500 to 4.
The range is 000. When the weight average molecular weight is less than 1500, the water resistance and solvent resistance of the coating film decreases, and
If it exceeds 000, the crosslinking density of the coating film will decrease and the scratch resistance will decrease, so it is necessary to keep it within the above range.

Furthermore, the hydroxyl value of the urethane polyol is in the range of 50 to 180 mgKOH/g. When the hydroxyl value is less than 50 mgKOH/g, the scratch resistance of the coating film decreases, and when it exceeds 180 mgKOH/g, the water resistance of the coating film decreases, so it is necessary to keep it within the above range.

The vinyl polymer used as an essential component in the coating composition of the present invention is not particularly limited as long as it is a vinyl polymer, but may include a hydroxyl group-containing vinyl monomer and other vinyl monomers. A copolymer with a polymer and the like can be preferably used.

[0016] As the hydroxyl group-containing vinyl monomer,
For example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, etc. can be preferably used, and Plaxel FA-1
Commercial products such as , Plaxel FA-4, Plaxel FM-1, and Plaxel FM-4 (all trade names, manufactured by Daicel Chemical Co., Ltd.) can also be used.

Examples of vinyl monomers other than the hydroxyl group-containing vinyl monomer include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate, butyl methacrylate, octyl acrylate, octyl methacrylate, and dodecyl. Acrylic monomers with no functional group other than unsaturated double bonds such as acrylate, dodecyl methacrylate, octadecyl acrylate, octadecyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate; carboxyl groups such as acrylic acid and methacrylic acid Acrylic monomers having an epoxy group such as glycidyl acrylate and glycidyl methacrylate; esters of maleic acid and monohydric alcohol; styrene, vinyl acetate, vinyl chloride, etc. can be preferably mentioned, When used, they can be used alone or as a mixture.

The vinyl polymer used in the present invention can be easily obtained by a solution polymerization method, etc., in which each of the above-mentioned vinyl monomers is dissolved in an organic solvent and heated in the presence of a radical polymerization initiator to undergo a polymerization reaction. can. Examples of the organic solvent include toluene, xylene, aromatic hydrocarbon solvents such as "Solvesso #100" (trade name, manufactured by Exxon Chemical Co., Ltd.); ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate, and acetic acid. Ester solvents such as propylene glycol monomethyl ether; Ketone solvents such as methyl isobutyl ketone and methyl amyl ketone; Alcohol solvents such as butyl alcohol and amyl alcohol;
Ether alcohol solvents such as ethylene glycol monobutyl ether can be preferably used, and as the radical polymerization initiator, benzoyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, azobisisobutyronitrile, etc. are preferably used. be able to. Furthermore, a chain transfer agent such as n-dodecylmercaptan or t-dodecylmercaptan may be used if necessary.

The weight average molecular weight of the vinyl polymer is 5
The range is from 000 to 50,000. Weight average molecular weight is 5
If the weight average molecular weight is less than 50,000, the weather resistance of the coating film will deteriorate, and if the weight average molecular weight exceeds 50,000, the appearance of the coating film will deteriorate, so it is necessary to keep it within the above range.

Furthermore, the hydroxyl value of the vinyl polymer is 50.
It ranges from 150 mgKOH/g. Hydroxyl value is 50
If it is less than mgKOH/g, the compatibility with the urethane polyol decreases, and the appearance of the coating film, especially the sharpness, decreases.
If it exceeds 50 mgKOH/g, the water resistance of the coating film will decrease, so it is necessary to keep it within the above range.

As the crosslinking agent used as an essential component in the present invention, for example, polyisocyanate compounds, blocked isocyanate compounds, amino resins, etc. can be preferably used. Specifically, for example, as the polyisocyanate compounds, the above-mentioned urethane Compounds specifically listed as diisocyanate compounds, which are raw material components of polyols; Blocked isocyanates include compounds obtained by blocking the above diisocyanate compounds with lower monohydric alcohols or ε-caprolactam; amino resins Preferred examples include resins obtained by adding formaldehyde to melamine, benzoguanamine, etc., and then etherifying it with a monohydric alcohol having 1 to 4 carbon atoms, which can be used alone or as a mixture.

[0022] The blending ratio of the urethane polyol, vinyl polymer, and crosslinking agent is such that the urethane polyol is
50% by weight, vinyl polymer from 10 to 80% by weight, and crosslinking agent from 10 to 40% by weight. If the amount of the urethane polyol is less than 10% by weight, the formation of a crosslinked structure that provides rubber elasticity for the coating film to exhibit scratch resistance will be insufficient, resulting in a decrease in scratch resistance. Exceeding this is not preferable because the hardness of the cured coating film decreases. Furthermore, if the vinyl polymer content is less than 10% by weight, the hardness and solvent resistance of the cured coating film will decrease, and if it exceeds 80% by weight, the scratch resistance will decrease, which is not preferable. Furthermore, if the amount of crosslinking agent is less than 10% by weight, the formation of a crosslinked structure in the cured coating film will be insufficient, resulting in decreased solvent resistance and water resistance, and if it exceeds 40% by weight, the crosslinked structure will be too dense. The coating film becomes brittle and the impact resistance decreases. Furthermore, when an amino resin is used as a crosslinking agent, if the amount exceeds 40% by weight, in addition to the above-mentioned drawbacks, the acid resistance also decreases, which is not preferable.

[0023] The coating composition of the present invention may contain, if necessary,
Additives such as pigments and leveling agents may be added.

When using the coating composition of the present invention, preferably aromatic solvents, ester solvents, ketone solvents,
It is used by applying a paint solution obtained by diluting it with a solvent such as an alcohol-based solvent by brushing, spraying, dipping, or rolling, or by electrostatic painting. be able to. Further, the curing temperature is preferably in the range of 120 to 250°C when an amino resin is used as a crosslinking agent, and 80 to 250°C when a polyisocyanate compound or a blocked isocyanate compound is used as a crosslinking agent. If it is outside the range, it is not preferable because scratch resistance, appearance, and weather resistance will deteriorate.

[0025]

[Effect of the invention] The coating composition of the present invention has excellent scratch resistance without impairing coating hardness, coating flexibility, appearance, gloss, acid resistance, weather resistance, solvent resistance, water resistance, etc. Because it provides a coating film, it is used for automobile exterior panels, home appliances, etc. that require scratch resistance.
It is suitable for painting furniture, building exterior materials, etc., and is particularly useful for dark-colored paints where scratches are easily noticeable.

[0026]

EXAMPLES Next, the present invention will be specifically explained with reference to production examples, working examples, and comparative examples, but the present invention is not limited thereto.

[0027]

[Production Example 1] (Production of urethane polyol solution) Into a flask equipped with a stirrer, a thermometer, and a dropping funnel, 50 parts by weight of cyclohexanone and 88 parts by weight of Plaxel 208 (trade name, manufactured by Daicel Chemical Industries, Ltd.) were charged. , 50℃ with stirring
The temperature rose to . Next, at the same temperature, 12 parts by weight of isophorone diisocyanate was added dropwise from the dropping funnel over 1 hour, the temperature was further raised to 80°C, the reaction was carried out for 2 hours, and then the mixture was cooled. Xylene was added to the obtained reaction solution to obtain a urethane polyol solution with a solid content concentration of 60%. The weight average molecular weight of the obtained urethane polyol solution (hereinafter referred to as solution A) was 2110, and the hydroxyl value was 54.

Urethane polyol solutions B to H were prepared in the same manner as solution A except that the compounds and charging ratios shown in Table 1 were used. The solid content concentrations of the obtained solutions were all within the range of 59.0 to 61.0%. Table 1 shows the compositions, weight average molecular weights, and hydroxyl values of urethane polyol solutions A to H.

[0029]

[Table 1]

[0030]

[Production Example 2] (Production of vinyl polymer) 50 parts by weight of xylene and 30 parts by weight of n-butanol were charged into a flask equipped with a stirrer, thermometer, reflux condenser, and dropping funnel, and while stirring, The temperature was raised to ℃. Then, at the same temperature, a monomer mixture shown below was added dropwise over 2 hours. n-butyl acrylate
40 parts n-butyl methacrylate
11 parts 2-ethylhexyl methacrylate 20 parts styrene
15 parts 2-hydroxyethyl methacrylate 12 parts acrylic acid

2 parts azobisisobutyronitrile
After completing the addition of 3 parts, the reaction was further carried out at the same temperature for 2 hours. After the reaction was completed, butyl acetate was added to the solution obtained by cooling to obtain a vinyl polymer solution (hereinafter referred to as vinyl polymer I) with a heating residue of 50%.

Vinyl polymers II to VIII were produced in the same manner as vinyl polymer I except that the compounds and blending ratios shown in Table 2 were used. Vinyl polymers I to V
Table 2 shows the composition, weight average molecular weight, and hydroxyl value of III.

[0032]

[Table 2]

[0033]

[Examples 1 to 8, Comparative Examples 1 to 15] The urethane polyol solution obtained in Production Example 1, the vinyl polymer solution obtained in Production Example 2, and the crosslinking agent were mixed in the proportions shown in Table 3. The resulting solution was poured into a Ford cup N using Solvesso #100/n-butanol mixed solution (weight ratio: 7/3).
o. 4 for 25 seconds (20° C.) to prepare a paint solution.

Next, Hi-Epico No. 1 was applied onto the steel plate. Painted with 100 black (manufactured by Nippon Oil & Fats Co., Ltd., product name), 14
Each of the obtained coating solutions was spray-coated onto the coating film cured at a temperature of 0° C. for 20 minutes, and then heated and cured at a temperature of 140° C. for 20 minutes to obtain a test piece. The physical properties of the coating film shown below were investigated for the obtained test piece. The results are shown in Table 3.

Pencil hardness: JIS-K5400 (1990
) 8.4.2 By hand scratching method. Impact resistance: JIS-K5400 (1990) 8.3.2
According to the DuPont formula. Scratch resistance: Apply a 5% aqueous solution of 8 types of test dust (manufactured by Japan Powder Technology Association) to the test piece, and observe the condition of the coated surface of the test piece after starting the car wash brush for 60 seconds. did. The evaluation criteria are as follows. ◎: No scratches were found by visual inspection. ○: Slight scratches are found, but they are minor. △: Scratches are noticeable. ×: Scratches are extremely noticeable. Gloss value: JIS-K5400 (1990) 7.6 Coating film appearance based on specular gloss: Appearance was visually observed. The evaluation criteria are as follows. ○: No abnormality observed at all. △: Stiffness is observed on the surface of the coating film. ×: Deterioration of gloss is observed. Water resistance: After immersing the test piece in a constant temperature water bath at 50°C for 10 days, check for any abnormalities such as glossy spots or blisters on the coating film.
Those with abnormalities were marked as ×, and those without were marked as ○.

Acid resistance: 0.5ml of 30% by weight sulfuric acid aqueous solution
was spotted on a test piece, left at a temperature of 20° C. for 24 hours, and then washed with water. The presence or absence of abnormalities such as glossiness and stains on the coating film was checked. Those with abnormalities were rated ×, and those without were rated ○.

Solvent resistance: After soaking gauze in xylene solvent and rubbing it back and forth 10 times while pressing it against the test piece, check for abnormalities such as glossiness or stickiness of the coating film, and mark those with abnormalities as ×, Those that are missing are marked as ○.

Weather resistance: JIS-K5400 (1900)
9.8.1 Sunshine carbon arc lamp type 20
After exposure for 00 hours, the presence or absence of abnormalities such as cracks in the coating film was confirmed, and those with abnormalities were rated ×, and those without were rated ○.

In Table 3, Yuvan SE-60 (Mitsui Toatsu (
Co., Ltd., trade name) is a butylated melamine resin, and Coronate EH (made by Nippon Polyurethane Industries Co., Ltd., trade name) is an isocyanurate of hexamethylene diisocyanate.

[0040]

[Table 3]

From the above results, the coating composition of the present invention has the following properties:
It can be seen that the scratch resistance is improved without reducing the physical properties of the coating film.

On the other hand, in Comparative Example 1, the weight average molecular weight of the urethane polyol component was less than 1,500, so the solvent resistance and water resistance of the coating film decreased, and in Comparative Example 2, the weight average molecular weight was less than 4,000. Since the scratch resistance exceeds that range, the abrasion resistance is reduced. Furthermore, in Comparative Example 3, the hydroxyl value of the urethane polyol component was less than 50 mgKOH/g, so the scratch resistance of the coating film decreased, and in Comparative Example 4, it exceeded 180 mgKOH/g, so the water resistance of the coating film decreased. are doing.

Furthermore, in Comparative Example 5, the weight average molecular weight of the vinyl polymer was less than 5,000, so the weather resistance of the coating film decreased, and in Comparative Example 6, the weight average molecular weight was less than 5,000.
Since it exceeds 0,000, the appearance of the coating film is deteriorated. Furthermore, in Comparative Example 7, the hydroxyl value of the vinyl polymer was 50.
Since it is less than mgKOH/g, the compatibility with the urethane polyol component is reduced and the appearance of the coating film is significantly reduced.In Comparative Example 8, the hydroxyl value of the vinyl polymer was 150 m
Since it exceeds gKOH/g, the water resistance of the coating film is reduced.

Furthermore, in Comparative Examples 9 to 11, the urethane polyol component was less than 10% by weight, resulting in a decrease in the scratch resistance of the coating film, whereas in Comparative Examples 12 and 13, the urethane polyol component was less than 50% by weight. % by weight, the coating film hardness has decreased.

Furthermore, in Comparative Example 13, the vinyl polymer content was less than 10% by weight, resulting in a decrease in the hardness and solvent resistance of the coating film, whereas in Comparative Example 11, the vinyl polymer content was 80% by weight. , the scratch resistance of the coating film is reduced.

Furthermore, in Comparative Example 14, the crosslinking agent was 10
Since the amount is less than % by weight, the formation of a crosslinked structure is insufficient,
Solvent resistance and water resistance decrease, and conversely in Comparative Example 15, the crosslinking agent exceeds 40% by weight, so the crosslinked structure becomes too dense and the coating film becomes brittle, resulting in a decrease in impact resistance and acid resistance. sexuality is declining.

Claims (1)

[Claims] Claim 1: A compound having a weight average molecular weight of 1500 to 4000 and a hydroxyl value of 50 to 18, obtained by reacting a diisocyanate compound and caprolactone polyol.
Urethane polyol 10-50 with 0mgKOH/g
10 to 80% by weight of a vinyl polymer having a weight average molecular weight of 5000 to 50000 and a hydroxyl value of 50 to 150 mgKOH/g, and 10 to 40% by weight of a crosslinking agent.
A paint composition characterized by containing.