JP2626024B2 - Coating composition and paint using the same - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a coating composition and a paint, and more particularly to a coating composition and a paint suitable for coating a plastic substrate.

(Prior art) In recent years, with the progress of synthetic resin and development of applications, polyurethane resin, polycarbonate, nylon resin, ABS resin,
Plastic materials such as polyester resins have become popular with metal materials. Especially in the automotive industry,
By replacing conventional steel plates with plastic materials, it is possible to reduce the weight of the vehicle body, absorb impact energy, and because there is no rust, conversion to plastic materials is being actively promoted. Accordingly, there is a need for paints suitable for coating plastic materials.

JP-A-58-111864 discloses a coating composition for a flexible substrate comprising an oil-free polyester resin and an aminoaldehyde resin. In this coating composition, a methylene long chain bond is introduced as a component to increase the intramolecular plasticizing action of the resin, and further, a good coating appearance, water resistance, chemical resistance, etc. are imparted without impairing elasticity. An aminoaldehyde resin is used in combination with a polyester resin having a low hydroxyl value into which an alicyclic polybasic acid has been introduced.

JP-A-62-101667 discloses a thermosetting coating composition comprising an oil-free alkyd resin, polycaprolactone and an amino resin.

In this coating composition, a long chain bond of methene is introduced as a component to increase the intramolecular plasticizing action of the resin, and further, the physical properties of the coating film at low temperatures are maintained, and in order to impart blocking properties and gasoline resistance, a polymer is used. Polycaprolactone is used in combination.

Further, JP-A-62-32155 discloses an acrylic resin,
A thermosetting coating composition comprising a polytetramethylene ester glycol, a block polyisocyanate and an amino resin is disclosed.

In this coating composition, polytetramethylene ether glycol is blended with acrylic resin to internally solvate and improve the low-temperature properties of the coating film. In addition, block polyisocyanate is used in combination to provide blocking and gasoline resistance. I have.

(Problems to be Solved by the Invention) A coating composition comprising an oil-free polyester resin and an aminoaldehyde resin disclosed in Japanese Patent Application Laid-Open No. 58-111864 is a coating film at a low temperature of -20 to -30 ° C. Although its physical properties are good, its hardness, blocking properties and gasoline resistance (staining and softening) are inadequate, and there is a problem in practice as a coating material for automotive plastic substrates requiring durability.

A coating composition comprising an oil-free alkyd resin, polycaprolactone and an amino resin disclosed in JP-A-62-101667 has good low-temperature properties, blocking properties, gasoline resistance, etc. It was found that the crystallinity was good and precipitated over time, and the paint stability was insufficient.

Further, the coating composition comprising an acrylic resin, a polyether polyol, a block polyisocyanate and an amino resin disclosed in JP-A-62-32155 has good low-temperature properties, gasoline resistance, blocking properties, etc. It was found that the glossiness and finished appearance of the sample were insufficient, and there was a problem in practical use.

An object of the present invention is to solve the above-mentioned problems, and to provide a coating composition excellent in clarity, finished appearance, low-temperature physical properties, gasoline resistance, blocking property and paint stability, and a paint using the same. I do.

(Means for Solving the Problems) The present invention relates to (1) (a) a fat represented by the general formula (I); HOCH _{2 n} OH (I) (where n represents an integer of 4 to 8). family dihydric alcohol 15-35 wt%, (b) .epsilon.-caprolactone 5-25%, (c) a monoepoxy compound 5-20 wt% and (d) general formula _{(II); HOOCCH 2 n '} COOH ... ( II) (wherein, n 'is an integer of 4 to 8), obtained by blending 5 to 15% by weight of an aliphatic dibasic acid and polycondensing, having a hydroxyl value of 50 to 100 and an acid value of An alkyd resin having 10 to 30; (2) a general formula (III); HOCH ₂ CH ₂ CH ₂ CH ₂ O _{n ″} H.
(III) (where n ″ represents a positive integer) and polytetramethylene ether glycol having a number average molecular weight of 650 to 1500, (3) two or more blocked isocyanate groups in one molecule The present invention relates to a coating composition containing an aliphatic block polyisocyanate having the formula (1) and (4) an amino resin, and a coating material using the same.

The alkyd resin (1) in the present invention has a hydroxyl value of solid content of 50 to 100, preferably 70 to 90. If the hydroxyl value of the solids is less than 50, the crosslink density is low, and the gasoline resistance and blocking properties are poor. If it exceeds 100, the crosslink density increases and the low-temperature properties deteriorate.

The carboxyl group in the alkyd resin serves as a latent catalyst for the reaction between the hydroxyl group of the alkyd resin and polytetramethylene ether glycol and the amino group of the amino resin or the isocyanate group of the block polyisocyanate. Accordingly, if the acid value of the solid content of the alkyd resin is appropriate, the crosslinking reaction can be carried out at a low temperature, so that the plastic serving as the base material is prevented from being thermally degraded.

For this reason, the acid value (solid content) of the alkyd resin is 10 to
30, preferably 10 to 20. When the acid value (solid content) is less than 10, the crosslinking reaction at a low temperature cannot be sufficiently promoted, and the coating film performance generally decreases, and when it exceeds 30, the paint stability decreases.

 Next, each component of the alkyd resin will be described.

Examples of the aliphatic dihydric alcohol represented by the general formula (I) of (a) include 1,6-hexanediol, 1,4-butylene glycol, 1,5-pentanediol, and the like. More than one species can be used. They are,
When the alkyd resin is produced, it is added as a component in an amount of 15 to 35% by weight, preferably 20 to 30% by weight. If it is less than 15% by weight, the low-temperature physical properties are inferior, and if it exceeds 35% by weight, the gasoline resistance and the blocking property are inferior.

The ε-caprolactone (b) is used as an ingredient in the production of the alkyd resin in an amount of 5 to 25% by weight, preferably 10 to 20% by weight.
% By weight. If it is less than 5% by weight, the low-temperature property is inferior.
If it exceeds 5% by weight, the gasoline resistance and the blocking property are inferior.

The monoepoxy compound (c) in the present invention refers to an alkyl monoepoxy compound or an alkylbenzene monoepoxy compound. Specifically, versatic acid monoglycidyl ester [for example, Cardiura E (trade name, manufactured by Ciel Chemical Co., Ltd.) and the like], p-tert-butyl benzoic acid monoglycidyl ester [for example, PES-10 (trade name, Fuso Chemical Co., Ltd.) (Made in Japan).
The monoepoxy compound is blended in an amount of 5 to 20% by weight during the production of the alkyd resin. If it is less than 5% by weight, the bright gloss and the dispersion of the pigment are inferior.

As the aliphatic dibasic acid represented by the general formula (II) of (d), there are adipic acid, azelaic acid, sebacic acid and the like, and one or more kinds can be used. The aliphatic dibasic acid is incorporated as a component in an amount of 5 to 15% by weight during the production of the alkyd resin. If it is less than 5% by weight, the low-temperature properties are inferior, and if it exceeds 15% by weight, the blocking property and the acid resistance are inferior.

The alkyd resin (1) of the present invention comprises the above (a),
It is obtained by polycondensation using (b), (c) and (d) as essential components, but other polyhydric alcohols and polybasic acids can also be used.

As other polyhydric alcohols, in addition to the aliphatic dihydric alcohol of the above (a), polyhydric alcohols used in the production of ordinary alkyd resins, for example, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, tripropylene glycol Ethylene glycol, 1,2-
Butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, neopentyl glycol, 2,5-hexanediol, esterified product of hydroxypivalic acid and neopentyl glycol, 2,2,4-trimethyl-1,3 -Pentanediol, tricyclodecane dimethanol, 1,4-
Cyclohexanedimethanol, dimethylolpropionic acid, trimethylolethane, trimethylolpropane,
One or more of glycerin, tris (2-hydroxyethyl) isocyanurate, pentaerythritol, diglycerin, dipentaerythritol, sorbit, trishydroxymethylaminoethane and the like can be used.

Other polybasic acids include phthalic anhydride, isophthalic acid, terephthalic acid, hexahydrophthalic anhydride, benzoic acid, para-tert-butylbenzoic acid, maleic anhydride, hymic acid, itaconic acid, etc. Aromatic dibasic acids are preferred from the viewpoint of coating film performance.

The alkyd resin is produced by a known production method, for example, a melting method or a solvent method.

The mixing ratio of the alcohol component (monoepoxy compound + polyhydric alcohol) and polybasic acid is equivalent ratio (total equivalent of OH)
/ Total equivalent of COOH) 1.05 to 1.40, particularly preferably 1.15 to 1.25.

In addition, ε-caprolactone is other polyhydric alcohol,
After the condensation reaction with the polybasic acid has proceeded to a predetermined level, it is preferable to carry out a ring-opening addition reaction to the hydroxyl group of the alkyd resin.

Next, the polytetramethylene ether glycol (2) represented by the general formula (III) will be described in detail.

The polytetramethylene ether glycol represented by the general formula (III) according to the present invention has a number average molecular weight of 650.
11500, preferably 850-1300. Number average molecular weight is 65
If it is less than 0, the low-temperature flexibility is poor.

If it exceeds 1500, polytetramethylene ether glycol crystallizes during storage and separates from the alkyd resin, resulting in poor low-temperature flexibility. The number average molecular weight in the present invention is a value measured by gel permeation liquid chromatography (GPC) and converted using a standard polystyrene calibration curve.

Examples of such polytetramethylene ether glycol include PTG650, PTG850, and PTG100 manufactured by Hodogaya Chemical Industry Co., Ltd.
0, PTG1300, PTG1500 and the like are commercially available and can be used in the present invention.

The polytetramethylene ether glycol is preferably used in an amount of 2 to 15 parts by weight based on 100 parts by weight of the alkyd resin. If the amount is less than 2 parts by weight, the low temperature properties tend to be inferior, and if it exceeds 15 parts by weight, the blocking properties, gasoline resistance and finished appearance tend to decrease.

Next, the aliphatic block polyisocyanate (3) will be described.

Examples of the aliphatic block polyisocyanate having two or more blocked isocyanate groups in one molecule according to the present invention include polyisocyanates such as 1,6-hexamethylene diisocyanate such as ethyl acetoacetate, methyl ethyl ketoxime, caprolactone and the like. The one that was blocked by These are commercially available as Coronate 2513, Coronate 2507, Coronate DC2717 (all manufactured by Nippon Polyurethane Co., Ltd., trade names). When a plastic is used as the base material to be coated as the aliphatic block polyisocyanate, a type in which the blocking agent dissociates at a temperature of 120 ° C. or lower is preferable in consideration of its thermal deterioration.

The aliphatic block polyisocyanate is preferably used in an amount of 2 to 15 parts by weight based on 100 parts by weight of the alkyd resin. If the amount is less than 2 parts by weight, gasoline resistance and acid resistance tend to be inferior, and if it exceeds 15 parts by weight, low-temperature properties tend to decrease.

 Finally, the amino resin (4) will be described.

The amino resin that can be used in the present invention is not particularly limited. For example, melamine, paraformaldehyde, monoalcohols such as n-butanol, i-butanol, and phthalic anhydride are methylolated at 80 to 100 ° C., and then reflux dehydration. What is obtained by etherification while using can be used.

Specific examples of commercially available amino resins include Melan 8000, Melan 220, Melan 2000, and Melan 22 manufactured by Hitachi Chemical Co., Ltd.

The ratio of the total amount of the alkyd resin and the polytetramethylene ether glycol / the solid content of the amino resin in the coating composition according to the present invention is preferably 85/15 to 70/30 (weight ratio). As the amino resin, an n-butyl alcohol-modified melamine resin having good low-temperature hardness is particularly preferred.

A solvent can be added to the coating composition according to the present invention, and usable solvents may be the same as those used in a general amino resin / alkyd resin composition. For example, aromatic solvents such as xylene and toluene, ketones such as methyl ethyl ketone and methyl isobutyl ketone, esters such as n-butyl acetate and ethyl acetate, alcohols such as methanol and n-butanol, ethyl cellosolve, butyl cellosolve, and cellosolve Use one or more of cellosolves such as acetate, carbitols such as ethyl carbitol, butyl carbitol, carbitol acetate, saturated hydrocarbons such as heptane and cyclohexane, petroleum solvents, and mineral spirits. Can be. These solvents are usually used in an amount of about 10 to 30% by weight to dilute to the coating viscosity.

The coating composition of the present invention can be blended with a general pigment, if necessary, by a general pigment dispersing method. In addition, various additives such as plasticizer, resin for reinforcing the coating film, dispersing agent, coating surface adjusting agent, fluidity adjusting agent, ultraviolet absorber, ultraviolet stabilizer, antioxidant, crosslinking reaction accelerator and the like are appropriately compounded. You can also.

The paint according to the present invention can be applied by a usual coating method conventionally used. For painting, air spray machine, airless spray machine, electrostatic painting machine, dipping,
A roll coating machine, a brush or the like can be used.

The paint according to the present invention needs to be crosslinked and cured by heating, and is generally heated at 60 to 150 ° C for 10 to 60 minutes. An appropriate heating temperature and time are appropriately selected in consideration of the heat deformation temperature of the substrate.

(Examples) Next, the present invention will be described in detail with reference to examples, but the present invention is not limited thereto.

 Hereinafter, parts means parts by weight.

Example 1 (1) Cardiura E (manufactured by Ciel Chemical Co., Ltd., monoglycidyl versatate) was placed in a reaction tank of an alkyd resin production apparatus provided with a stirrer, a thermometer, a rectification tower, a reflux apparatus, and an inert gas introduction pipe. Ester) 43.4 parts, 1,6 hexanediol
250.7 parts, 108.1 parts of trimethylolpropane and 409.7 parts of isophthalic acid are charged and heated. The reaction temperature is gradually raised to 220 ° C, and the condensed water is removed from the system through a rectification column. When the acid value (solid content) of the resin reaches 30 or less, it is cooled, charged with 78.9 parts of adipic acid, and gradually heated to 210 ° C. Next, xylol is added to the reaction tank, and the reaction is continued by a solvent reflux method. When the acid value (solid content) of the alkyd resin reaches 14, 18
The temperature is lowered to 5 ° C, 109.2 parts of ε-caprolactone is charged, reacted at the same temperature for 2 hours, and then cooled. The solid content was adjusted to 60% with xylol / butyl cellosolve = 9/1 (weight ratio) to obtain an alkyd resin. Table 1 shows the composition, the hydroxyl value (solid content) and the acid value (solid content).

(2) Using the above alkyd resin, a pigment was dispersed with a paint shaker in the following composition to prepare a white enamel paint.

[Formulation]

(Dispersion blend) Alkyd resin 50.0 parts (Solid content) Polytetramethylene ether glycol (Number average molecular weight
3.75 parts Coronate 2513 (Nippon Polyurethane Co., Ltd., trade name) 3.75 parts (solid content) Titanium white (CR-90, Ishihara Sangyo Co., Ltd., trade name) 107.5 parts Xylene 20.0 parts Butyl cellosolve 10.0 parts Disperbyk-160 (pigment dispersing agent, trade name of Bitsukemi Co., Ltd.) 2.0 parts Total 197.0 parts (post-added) 197.0 parts of the above white enamel paint Melan 8000 (n-butyl alcohol-modified melamine resin,
Hitachi Chemical Co., Ltd., trade name) 25.0 parts (solid content) Alkyd resin 25.0 parts (solid content) BYK344 (leveling agent, made by Bitsukemi Co., Ltd., trade name) 0.5 parts Total 246.25 parts White enamel paint as above Xylene / butyl cellosolve
/ n-butanol = 80/10/10 (weight ratio) mixed solvent viscosity
Diluted for 20 seconds (Ford Cup # 4, 25 ° C).

(3) Test A 3 mm thick R-RIM polyurethane plate was degreased with trichloroethane, and a one-component polyurethane primer was applied thereon so that the dry film thickness became 8 μm, and dried at 80 ° C. for 20 minutes. Was used as a substrate. The diluted enamel paints prepared in the above Examples and Comparative Examples were air-sprayed on the substrate so that the dry film thickness became 25 to 30 μm, and baked and dried at 120 ° C. for 20 minutes. Table 2 shows the results of testing the properties of the coating film samples thus obtained.

Examples 2 to 4 The compositions shown in Table 1 were used, and the same apparatus as in Example 1 (1) was used to synthesize them in the same process, and a white enamel paint was prepared in the same manner as in (2). Further, a test plate was prepared and tested in the same manner as in (3). The results are shown in Table 2.

Comparative Examples 1 and 2 Using the alkyd resin of Example 2 and coating in the same manner as in (2) and (3) of Example 1 according to the coating composition shown in Table 1, a test plate was prepared.

Comparative Example 3 Using the same apparatus as in Example 1, neopentyl glycol was used.
336.3 parts, 89.3 parts of trimethylolpropane, 486.9 parts of isophthalic acid and 87.5 parts of adipic acid are charged and heated. 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 becomes 80 ° C or less, xylene is added to the reaction tank, and the reaction is continued by a solvent reflux method. When the oxidation (solid content) of the reactor contents reaches 12, the reaction is terminated and cooled. An alkyd resin having a hydroxyl value (solid content) of 95 was obtained.

In the same manner as in (2) and (3) of Example 1, a test plate was prepared by applying paint according to the paint formulation shown in Table 1.

Comparative Example 4 Using the same apparatus as in Example 1 with the composition shown in Table 1, it was synthesized in the same manner as in (1) of Comparative Row 3, cooled at an acid value (solid content) of 7.0, and diluted with a solvent. An alkyd resin having a hydroxyl value (solid content) of 55 and an acid value (solid content) of 7.0 was obtained.

In the same manner as in (2) and (3) of Example 1, a test plate was prepared by applying paint according to the paint formulation shown in Table 1.

Comparative Example 5 Solventso 100 was placed in a two-necked flask equipped with a stirrer, a thermometer, a nitrogen gas injection tube and a reflux condenser.
150 parts of (Ciel Chemical Co., petroleum solvent) and 50 parts of n-butanol are charged and the temperature is raised to 100 to 105 ° C. Then 50 parts of styrene, 65 parts of butyl methacrylate, 300 parts of lauryl methacrylate, 75 parts of 2-hydroxyethyl methacrylate, 10 parts of methacrylic acid, 3.5 parts of 2,2'-azobisisobutyronitrile, A mixture of 1 part of tertiary butyl peroxide is added dropwise over 3 hours. After the completion of the dropwise addition, the temperature was raised to 130 ° C., the temperature was maintained until the polymerization rate became 99.5% by weight or more, and the mixture was cooled after confirming the end point.

The obtained acrylic resin has a hydroxyl value of about 66 (solid content),
It had an acid value of about 16 (solid content), a glass transition point of about -30 ° C, and a number average molecular weight of about 7,000 (standard polystyrene equivalent value by gel permeation chromatography).

In the same manner as in Examples 1 (2) and (3), a paint was prepared according to the paint formulation shown in Table 1 to prepare a test plate.

(Note) (1) The surface condition of the coating film was visually observed.

(2) The sharpness of the coating film was visually determined.

(3) The 60-degree specular reflectance was measured.

(4) The specimen was left in an atmosphere at −20 ° C. for 4 hours, bent at 180 ° with a rod having a diameter of 13 mm, and observed for cracks in the bent portion.

(5) 5% H ₂ SO ₄ was dropped on the coating film, left at 23 ° C. for 4 hours, wiped off, and examined for traces.

(6) The test piece was immersed in a commercially available Regular gasoline at 23 ° C. for 1 hour, and the degree of contamination of the coating film immediately after removal was visually determined.

(7) After immersing the sample in water at 40 ° C for 240 hours, it was examined whether or not blisters were generated in the coating film.

(8) The paint diluted at 25 ° C. for 20 seconds (Ford Cup # 4) was left at 20 ° C. for 14 days to check the condition of the paint.

(9) Gauze was placed on the coated surface, and a load of 500 g with a diameter of 40 mm was further applied and kept at 80 ° C. for 2 hours.

As is apparent from Table 2, the coating films of Examples 1 to 4 had finished appearance, sharpness, acid resistance, blocking properties, low-temperature properties,
Excellent performance in all aspects of gasoline resistance and paint stability.

On the other hand, Comparative Example 1, in which the polytetramethylene ether glycol was removed from Example 2, was inferior in low-temperature properties, and Comparative Example 2, in which the block polyisocyanate was removed from Example 2, was acid resistant. Poor properties, blocking properties, and water resistance.

Comparative Example 3 corresponds to JP-A-62-101667, but is inferior in paint stability.

Comparative Example 4 corresponds to JP-A-58-111864, but is inferior in acid resistance, water resistance and blocking property.

Comparative Example 5 corresponds to Japanese Patent Application No. 60-170395, but is inferior in the finished appearance and sharpness of the coating film.

(Effect of the Invention) The coating composition according to the present invention and a paint using the same have excellent finish appearance, sharpness, low temperature properties, blocking properties, gasoline resistance and paint stability of the coating film.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Takao Hirayama 5-1, Sunayama, Hasaki-cho, Hashima-cho, Kashima-gun, Ibaraki Pref. , A)

Claims (4)

(57) [Claims] (1) (a) General formula (I); HOCH _{2 n} O
H ... (I) (where n represents an integer of 4 to 8) 15 to 35% by weight of an aliphatic dihydric alcohol, (b) 5 to 25% by weight of ε-caprolactone, (c) monoepoxy compound 5 to 20 wt% and (d) general formula _{(II); HOOCCH 2 n '} COOH ... (II) ( where, n' is an integer of 4-8) aliphatic dibasic acids 5-15 wt represented by %, And an alkyd resin having a hydroxyl value of 50 to 100 and an acid value of 10 to 30 obtained by polycondensation. (2) General formula (III); HOCH ₂ CH ₂ CH ₂ CH _{2 On ″} H ...
(III) (where n ″ represents a positive integer) and a polytetramethylene ether glycol having a number average molecular weight of 650 to 1500, (3) two or more blocked isocyanate groups in one molecule A coating composition comprising: an aliphatic block polyisocyanate having the formula: and (4) an amino resin. 2. The coating composition according to claim 1, wherein the amount of the polytetramethylene ether glycol (2) is 2 to 15 parts by weight based on 100 parts by weight of the alkyd resin (1). 3. The amount of the aliphatic block polyisocyanate (3) is 2 to 100 parts by weight of the alkyd resin (1).
3. The coating composition according to claim 1, wherein the amount is from 15 to 15 parts by weight. 4. A coating comprising the coating composition according to claim 1, 2 or 3.