JPH0152406B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an oil-free polyester/aminoaldehyde resin-based top coating composition. BACKGROUND ART Conventionally, aminoalkyd resin-based, aminoacrylic resin-based, acrylic lacquer-based paints, etc., have been used as top coat paints for automobile bodies and the like.
Amino alkyd resin paints are easy to apply,
It has features such as excellent finished appearance (gloss, texture of the paint film) and excellent weather resistance (gloss retention) in areas with high pigment concentration, but it has low pigment concentration and color in the pigment. So-called dark-colored paint films containing a large amount of pigment have problems in that they tend to be scratched or blurred when waxed, and the rags are markedly colored, resulting in poor waxing resistance. This waxing resistance is a performance required for paint films immediately after painting and for paint films after exposure to the outdoors, but it is difficult to satisfy this property with aminoalkyd resin topcoat paints. Aminoacrylic resin topcoat paints have fairly good weather resistance in areas with low pigment concentrations (below 40 to 30 PHR), but waxing resistance before exposure is not necessarily good. In particular, the performance required for top coating of automobile bodies is non-sand interlayer adhesion (adhesion between coatings when the same paint is applied once again for repair coating on a coating that has been baked once and is baked); It is difficult to satisfy requirements such as the Erichsen test, impact resistance, and finished appearance (gloss, texture). The acrylic lacquer type has a disadvantage that the solid content concentration during coating is extremely low and requires a large number of coating steps. In contrast to the above paints, oil-free polyester/aminoaldehyde resin paints have features such as weather resistance, mechanical properties of the paint film (Erichsen test, impact resistance), interlayer adhesion, and high solid content concentration during painting. However, due to reasons such as difficulty in painting (e.g., easy to generate repellency), the surface of the paint film has a so-called blurred feeling and poor gloss, and poor compatibility with amino resins, In particular, it was considered difficult to apply it to the top coating of automobile bodies. Therefore, the purpose of the present invention is to maintain the advantages of conventional oil-free polyester/amino resin paints, while improving the drawbacks such as difficulty in painting, dullness of the paint film, and poor compatibility with amino resins. An object of the present invention is to provide an oil-free polyester/aminoaldehyde resin topcoat composition. A more specific object of the present invention is to provide an oil-free polyester/aminoaldehyde resin coating composition suitable for automotive topcoating. The object of the present invention is to provide an oil-free polyester top coating composition containing as essential components a binder component consisting of an oil-free polyester (A) and an aminoaldehyde resin (B), and a pigment (C). At least 75 mol% of the acid component of the free polyester (A) consists of a saturated alicyclic polybasic acid or a saturated alicyclic polybasic acid and an aromatic polybasic acid, and the aromatic polybasic acid is a saturated alicyclic polybasic acid. (ii) The oil-free polyester (A) has a hydroxyl value of
(iii) the weight ratio of oil-free polyester (A) to aminoaldehyde resin (B) is from 60:40 to 90:10; and (iv) the pigment (C) is in a proportion of 3 to 50 PHR. This is achieved by an oil-free polyester topcoat composition characterized by containing: The oil-free polyester (A) used in the present invention contains a saturated alicyclic polybasic acid (a) or a saturated alicyclic polybasic acid (a) and an aromatic polybasic acid (b) as its acid components. It is characterized in that it is contained in an amount of at least 75 mol%, preferably at least 80 mol% of the total acid components. The amount of the aromatic polybasic acid (b) is up to 6 mol, preferably within the range of 4 to 1 mol, per 4 mol of the aromatic alicyclic polybasic acid. The remainder of the polybasic acid unit can be a saturated dibasic acid represented by the general formula HOOC( _CH2 )nCOOH (n is an integer from 1 to 12). The total amount of the polybasic acid components of (a) and (b) above is 75 mol%
If it is less than 20%, weather resistance and acid resistance will decrease. Furthermore, if the content of (b) exceeds the above limit, the compatibility between the oil-free polyester and the aminoaldehyde resin, which is a crosslinking agent, will deteriorate, causing defects in the coating surface condition (lack of gloss), and causing repellency during coating. This results in exposing the drawbacks of so-called oil-free polyesters, such as being more likely to generate polyester, or becoming less soluble in aromatic solvents. The hydroxyl value of the above oil-free polyester is 60.
Should be in the range ~150, preferably ~80
The range is 130. If it is less than 60, the coating film will be insufficiently cured, while if it is more than 150, the dispersibility of the pigment and the compatibility with the crosslinking agent will be poor. Examples of the saturated alicyclic polybasic acid (a) that forms the oil-free polyester used in the present invention include hexahydrophthalic acid and its acid anhydride, hexahydrotrimellitic acid and its acid anhydride, and hexahydrophthalic acid and its acid anhydride. -Methyl trimellitic acid and its acid anhydride. Examples of the aromatic polybasic acid (b) include phthalic acid and its acid anhydride, isophthalic acid, terephthalic acid, dimethylisophthalic acid, dimethylterephthalic acid, trimellitic acid and its acid anhydride, pyromellitic acid and its acid anhydride. Examples include. Also, the general formula
Examples of saturated dibasic acids represented by HOOC(CH ₂ )nCOOH include succinic acid (and its anhydrides),
Examples include adipic acid, pimelic acid, azelaic acid, sebacic acid, and brassic acid. On the other hand, the alcohol component of the oil-free polyester is not particularly limited and can be comprised of those conventionally used in the formation of polyester, such as ethylene glycol, diethylene glycol, propylene glycol, neobentyl glycol, 1,2 -butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol,
1,6-hexanediol, 1,5-pentanediol, 1,6-hexanediol, 2,5-hexanediol, trimethylolethane, trimethylolpropane, glycerin, pentaerythritol, dipentaerythritol, diglycerin, sorbitol, Examples include Ester Diol 204 (product of Union Carbide (USA)), tricyclodecane dimethanol, 1,4-cyclohexanedimethanol, and the like. The oil-free polyester is prepared according to a conventional method.
Produced by condensation polymerization of a saturated alicyclic polybasic acid (a) and an aromatic polybasic acid (b) with at least one of the alcohols exemplified above, along with a saturated dibasic acid if necessary. In this case, the molecular weight may be adjusted by using, for example, benzoic acid, pt-butylbenzoic acid, benzoic acid methyl ester, etc. as an end-capping agent. The reaction ratio between the polybasic acid component and the alcohol component is adjusted so that the resulting oil-free polyester has a hydroxyl value of 60 to 150, preferably 80 to 130. The aminoaldehyde resin used in the present invention includes melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, etc. as amino components, and most aminoaldehyde resins commonly used in paints can be used.
Among them, melamine formaldehyde resin is most preferred from the viewpoint of weather resistance. Although the oil-free polyester of the present invention is compatible with most melamine resins, it may have poor compatibility with high molecular weight melamine resins, so it is preferable to use a relatively low molecular weight melamine resin. Hexamethoxymethylmelamine and some of its methoxy groups
When using melamine resins substituted with _C4 or higher alcohols, it is preferred to add a conventional curing catalyst such as para-toluenesulfonic acid. By replacing a part of the aminoaldehyde resin used as a crosslinking agent in the present invention with a block type polyisocyanate in an amount of 50% by weight or less, preferably 25% by weight or less, the finish of the painted surface can be improved. Ease of application and chemical resistance can be further improved. If the amount of block polyisocyanate exceeds the above range, the baking temperature will be
If the temperature is below 130℃, curing is likely to be insufficient,
There is a possibility that the above effects cannot be obtained. The above-mentioned blocked polyisocyanate is a non-yellowing polyisocyanate made into a block polyisocyanate using a commonly used blocking agent such as an aliphatic or aromatic monoalcohol, such as Takenate B-815N (Takeda Pharmaceutical Co., Ltd. (KK)
product), Takenate B-840N (Takeda Pharmaceutical Co., Ltd. product),
Adduct B1065 (Veba Chemie (Germany)),
ADDITOL VXL-80 (Hoechst Japan Co., Ltd. product)
and so on. When these blocked polyisocyanates are used, a catalyst that promotes the dissociation of the blocking agent is added if necessary. The composition of the binder component in the coating composition of the present invention is such that the weight ratio of oil-free polyester/aminoaldehyde resin or a mixture of aminoaldehyde resin and block polyisocyanate is 90/10 to 60/
Must be in the 40 range. If the crosslinking agent aminoaldehyde resin and block type polyisocyanate are less than this range, curing will be insufficient, resulting in poor weather resistance and
Coating film hardness, solvent resistance, etc. decrease, and if the amount of crosslinking agent is greater than this range, the coating film becomes brittle. The pigment concentration in the coating composition of the present invention is from 3 to
It should be in the range of 50 PHR, preferably between 3 and 40 PHR. If it is less than 3 PHR, it will be difficult to completely hide it in the base with the thickness of the top coat (approx. 20 to 50 μ) for ordinary automobile bodies, etc. On the other hand, if it is more than 50 PHR, the weather resistance will be the same as amino alkyd resin top coat. The advantages of the invention diminish as the invention becomes more difficult. Furthermore, the waxing resistance before and after exposure, which is one of the major features of the coating composition of the present invention, is very excellent for coatings containing a large amount of colored pigments, and the pigment components include colored pigments other than white/titanium. The weight ratio of the white pigment is 100/0 to 30/70, preferably 100/
The effect of the present invention is particularly remarkable when the ratio is in the range of 0 to 60/40. In order to paint an automobile body using the coating composition of the present invention, first, a binder component consisting of oil-free polyester (A) and aminoaldehyde resin (B) is mixed with a commonly used coloring pigment and, if necessary, additives. A paint is made in the usual way, and this is diluted with a diluting solvent to reduce the paint viscosity.
Adjust to 20-30 seconds at No. 4 (20℃). Then, this is applied onto the coating material on which the undercoat and intermediate coat have been formed, so that the dry film thickness is about 30 to 40 μm. Painting methods include regular air spray, airless spray, and electrostatic painting. Next, the mixture is allowed to stand at room temperature for several minutes and then heated at 140 to 150°C for 20 to 40 minutes to obtain the top coat film of the present invention. The oil-free polyester topcoat composition of the present invention meets various requirements for topcoating on automobiles, such as ease of painting, appearance of the coating, mechanical properties of the coating, chemical resistance, and solvent resistance. etc. have the same performance as aminoalkyd resin paints, which are most commonly used as top coats for automobiles. ), the waxing resistance before and after exposure is far superior to aminoalkyd resin systems. Also, it is superior to amino alkyd resin paints in terms of interlayer adhesion. Furthermore, in the range of pigment concentration of 50 PHR or less in white color paints, compared to amino alkyd resin paints, they have superior weather resistance (glossy retention), interlayer adhesion, and mechanical properties of the paint film. In particular, it has excellent waxing resistance before and after exposure on coatings with highly saturated colors such as dark green, dark maroon, and dark blue that contain a large amount of colored pigments. The present invention will be explained in more detail below with reference to Examples. Parts and percentages in the examples are by weight unless otherwise specified. [Production example of resin] Production example 1 Production of oil-free polyester resin solution A 73.9 parts of hexahydrophthalic anhydride ( 0.48 mol), isophthalic acid 53.1 parts (0.32 mol), adipic acid 14.6 parts (0.1
mol), trimethylolpropane 40.8 parts (0.3 mol) and neopentyl glycol 73.5 parts (0.7 mol)
mol) and heat. Once the raw materials have melted and stirring is possible, start stirring and raise the reactor temperature to 230°C.
Raise the temperature to ℃. However, the temperature is raised uniformly from 160°C to 230°C over 3 hours. The condensed water produced is distilled out of the system. Once the temperature reaches 230°C, keep the temperature constant and continue stirring for 2 hours. Thereafter, xylene is added into the reaction tank, and the reaction is continued by switching to condensation in the presence of a solvent. When the acid value reaches 7, the reaction is terminated and the mixture is cooled. Xylol 83 after cooling
1 part, and 62 parts of isobutanol were added to prepare an oil-free polyester resin solution A. The solid content concentration of oil-free polyester resin solution A is 60.1
%, the varnish viscosity (Gardner viscosity at 25°C) was M, the acid value of the resin was 7.1, and the hydroxyl value was 115. Production Examples 2 to 10 Production of Oil-Free Polyester Resin Solutions B to J Oil-free polyester resin solutions B to J were produced in the same manner as Production Example 1 based on the resin compositions shown in Table-1. Table 1 shows the special values of those varnishes.
Shown below. Resin solutions A to F are used in Examples of the present invention, and G to J are used in Comparative Examples.

【table】

[Preparation of painting materials]

Apply polybutadiene-based electrodeposition paint to zinc phosphate-treated automobile body door parts using the electrodeposition coating method to a dry film thickness of 20μ, and bake at 170℃ for 20 minutes. Next, after sanding the painted surface with #400 sandpaper, wipe the painted surface with gauze moistened with petroleum benzene to degrease it. Then, apply amino alkyd resin-based automotive intermediate paint to a dry film thickness of 25 μm and bake at 140°C for 30 minutes. The coated surface was then water-sanded with #400 sandpaper, drained and dried, and the coated surface was wiped with petroleum benzine to obtain coating materials for the examples and comparative examples of the present invention. Example 1 Using the polyester resin solution A obtained in Production Example 1, a maroon top coating was prepared by ball mill dispersion with the following formulation. 60% polyester resin solution A 117 parts 60% Yuban 28SE (Note 1) 50 Perindo Maroon R 6422 (Note 2) 10 Todacolor KN-0 (Note 3) 1 NeO Spectra Beads AG (Note 4) 0.3 (Note 1) Melamine resin manufactured by Mitsui Toatsu Chemical Co., Ltd. (Note 2) Maroon organic pigment manufactured by Bayer (Germany) (Note 3) Red iron (Note 4) manufactured by Toda Kogyo Co., Ltd. Carbon black manufactured by Columbia Carbon Co., Ltd. (USA) For paints Modaflow (Monsanto Co., Ltd. product) 0.05PHR and silicone oil KP- were used as paint surface conditioners.
323 (product of Shin-Etsu Chemical Co., Ltd.) 0.01 PHR was added. The obtained paint was mixed with Sucsol #1500/xylol/butyl acetate/n-butanol = 30/20/30/
20 mixed solvent with a viscosity of 25 seconds (Food cup #4,
diluted to 20℃). The diluted paint was air-sprayed onto the previously prepared coating material to a dry film thickness of 30μ, left at room temperature for 10 minutes, and then baked in an electric hot air dryer at a temperature of 140℃ for 30 minutes. .
The test results of the obtained coated plates are shown in Table 3. Examples 2 to 9, Comparative Examples 1 to 7 Using the various polyesters obtained in the above production examples, paints were prepared in the same manner as in Example 1 based on the paint formulation shown in Table 2, and painted on the coating material. . The results of each test are shown in Table 3.

【table】

【table】

【table】

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[Table] Examples 1 to 9 are oil-free polyester top coating compositions of the present invention, and exhibit excellent properties in each test. Comparative Example 1 is an example in which a polyester resin containing too much aromatic polybasic acid (isophthalic acid) was used, and there were defects in the coating surface condition such as lack of gloss on the coating surface and occurrence of repelling. Comparative Example 2 is an example using a polyester resin in which the sum of saturated alicyclic polybasic acid and aromatic polybasic acid among the polybasic acid raw materials for polyester is 75 mol% or less, and the It has poor gloss retention and acid resistance. Comparative Example 3 is an example in which the hydroxyl value of the polyester resin is too low, resulting in insufficient hardness due to insufficient curing, and inferior gasoline wiping resistance, waxing resistance, etc. Comparative Example 4 is an example in which a polyester with an excessively high hydroxyl value was used, and the coated surface lacked gloss, which may be due to insufficient pigment dispersibility or compatibility.
Comparative Example 5 and Comparative Example 6 are examples using alkyd resins, and the waxing resistance before and after exposure, interlayer adhesion, gloss retention during accelerated weathering, etc. are compared with oil-free polyester resins. and inferior. Comparative example 7 is an example using acrylic resin,
The painted surface lacks texture, and wax resistance and interlayer adhesion are poor. From the above results, it can be seen that the oil-free polyester top coating composition of the present invention has very excellent performance.

Claims (1)

[Claims] 1. Binder component and pigment consisting of oil-free polyester (A) and aminoaldehyde resin (B)
In the oil-free polyester top coating composition containing (C) as an essential component, (i) the oil-free polyester (A) is such that at least 75 mol% of the acid component is a saturated alicyclic polybasic acid or a saturated alicyclic polybasic acid. (ii) an oil-free polyester consisting of a group polybasic acid and an aromatic polybasic acid, and the aromatic polybasic acid can be present in a ratio of up to 6 moles per 4 moles of the saturated alicyclic polybasic acid; (ii) oil-free polyester; (A) has a hydroxyl value of
(iii) the weight ratio of oil-free polyester (A) to aminoaldehyde resin (B) is from 60:40 to 90:10; and (iv) the pigment (C) is in a proportion of 3 to 50 PHR. An oil-free polyester topcoat composition comprising: 2. The composition according to claim 1, wherein a part of the aminoaldehyde resin (B) is replaced by a blocked polyisocyanate. 3. The composition according to claim 2, which contains the blocked polyisocyanate in a proportion equal to or less than the weight of the aminoaldehyde resin.