JPH0539459A - Chipping-resistant interlaminar paint for automobile - Google Patents

Abstract

PURPOSE:To provide a chipping resistant paint giving a chipping resistant coating film without forming pinholes on the coating film in drying. CONSTITUTION:The objective interlaminar chipping-resistant paint is produced by compounding 100 pts.wt. of a blocked isocyanate resin with 10-18 pts.wt. of a polyol resin, 80-95 pts.wt. of calcium carbonate, 15-30 pts.wt. of talc and proper amounts of a solvent and, as necessary, a conventional additive, wherein 60-75wt.% of the total calcium carbonate is surface-treated with a resin acid. The overall specific gravity of the paint composition is 1.2-1.4.

Description

Detailed Description of the Invention

The present invention relates to an interlayer anti-chipping coating material for automobiles, that is, a coating material applied between an undercoat layer and an intermediate coating layer as a countermeasure against chipping.

[0002]

2. Description of the Related Art Chipping is a phenomenon in which a coating film is peeled off when a small stone on the road surface hit by a wheel or the like collides with a vehicle body, which is a major cause of rusting and corrosion of the vehicle body. ing. The occurrence of rust due to chipping,
By chemical conversion treatment of the steel plate surface or painting method or undercoat / intermediate coating /
Even if it is attempted to prevent it by devising each coating composition of the top coat, problems occur in workability, economical efficiency, appearance quality (smoothness, sharpness), and the like. Therefore, at present, it is general to provide a dedicated chipping-resistant layer between the electrodeposition layer (undercoat layer) and the intermediate coating layer.

The chipping resistance of the coating film tends to be higher as it is a relatively soft layer, contains a large amount of pigments and fillers, and is formed thicker. Therefore, conventionally, as an interlayer chipping resistant coating, a polyester resin and a melamine resin, or a polyester resin and a blocked isocyanate compound as a main component, titanium dioxide, carbon black, zinc white, silica, cuprous oxide, basic sulfate, zinc dust Paints in which pigments such as barium carbonate, talc, and bentonite are dispersed in high concentration have been used. Recently, a chipping-resistant paint (JP-A-63-43967) has been proposed which comprises a specific polyurethane polymer, a blocked isocyanate compound and a hydroxyl group-containing resin as main components, and a filler such as titanium oxide and barium sulfate. ing.

In any chipping resistant paint, the specific gravity of the inorganic pigments / fillers added to the paint in order to improve the chipping resistance is high, and since they are added in relatively large amounts, the specific gravity of the chipping resistant paint is high. It is usually over 1.5. The interlayer anti-chipping paint is usually applied by a spray method, which is good in finish and easy to apply thickly.

[0005]

However, the chipping resistant coating using the above conventional coating has a problem that so-called pinholes are likely to occur in the dried coating film. This pinhole is a trace that the air bubbles trapped in the coating film expanded and broke through the coating film surface, and the occurrence of pinholes is attributed to the high specific gravity filler often mixed in the chipping resistant coating. It is considered. That is, during coating, when finely divided paint collides with the coating surface at the tip of the coating machine nozzle, a crown ring is generated on the surface of the object to be coated, and when this ring is crushed, air is trapped in the overlapping portion with the surrounding ring. The trapped air expands and foams during baking and drying to form pinholes.

Therefore, in chipping-resistant coating, in order to prevent the occurrence of pinholes, the rate of temperature rise during forced drying is slowed down, spray coating is divided into 3 to 4 times, and sufficient flash time is taken. It requires careful control of coating conditions or extra operations, such as water-polishing with 400-600 sandpaper or filling pinholes with putty and repainting. The present invention has been made in view of the above problems, the problem to be solved is a chipping-resistant layer exhibiting sufficient anticorrosion ability, without generating pinholes by a general spray coating method. An object is to provide an interlayer chipping-resistant paint that can be provided.

[0007]

The chipping resistant coating composition of the present invention comprises 10 to 18 parts by weight of a polyol resin, 80 to 95 parts by weight of calcium carbonate, 15 to 30 parts by weight of talc, and 100 parts by weight of a blocked isocyanate resin. A paint comprising a solvent and, if necessary, a conventional additive in an appropriate amount, wherein 60 to 75% by weight of the total calcium carbonate is surface-treated with a resin acid, and the specific gravity of the entire coating composition is 1 .2 to 1.4 or less.

In the present invention, large and heavy particles in the filler component contribute to the generation of pinholes; talc is a filler that does not generate pinholes in the coating film; If so, pinholes are less likely to occur; and by adding a specific amount of calcium carbonate surface-treated with resin acid, chipping resistance is enhanced, and as a result, even if the content of the filler is reduced, excellent resistance to It has been completed based on the new knowledge that the chipping property can be maintained.

As the polyol resin used in the coating material of the present invention, polyester polyol, polyether polyol, polyurethane polyol, acrylic polyol, nitrogen-containing polyol (amine polyol), castor oil derivative, tall oil derivative, polybutadiene polyol, butyral resin. , Alkyd resins, epoxy resins and the like. These may be used alone or in combination of two or more.

As the polyester polyol, adipic acid, phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, trimellitic acid, succinic acid, azelaic acid, pimelic acid, sebacic acid, fumaric acid, hexahydrophthalic acid, methylhexahexyl A compound having a polybasic acid such as hydrophthalic acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and dimer acid, and a compound having at least two or more hydroxyl groups in one molecule (for example, ethylene glycol, diethylene glycol, propylene glycol,
Butylene glycol, neopentyl glycol, hydrogenated bisphenol A, glycerin, butanediol,
1,3-pentanediol, hexanediol, trimethylpentanediol, hexanetriol, trimethylolethane, trimethylolpropane, pentaerythritol, etc.) can be used in a conventional manner.

As the polyether polyol, polyoxyethylene glycol, polyoxypropylene glycol, polyoxybutylene glycol, polyoxypropylene triol, polyoxypropylene quadrol and the like can be used. As a polyurethane polyol,
A compound having a terminal hydroxy group obtained from a polyhydroxy compound and a polyvalent isocyanate compound is used.

The acrylic polyols include hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, trimethylolpropane acrylic acid monoesters, their corresponding methacrylic acid derivatives, and hydroxyl groups such as polyhydroxyalkyl maleate and fumarate. Contained monomers and acrylic monomers such as acrylic acid or methacrylic acid methyl, ethyl, butyl, propyl, hexyl, 2-ethylhexyl, hydroxyethyl ester, etc., or α, β-ethylenic monomers such as styrene, vinyltoluene, vinyl acetate, etc. Examples thereof include those obtained by copolymerization with a monomer having a saturated double bond. As the castor oil derivative, triglyceride of ricinoleic acid or the like can be used, and as the polybutadiene polyol, those having a terminal hydroxy type such as 1,2-polybutadiene and 1,4-polybutadiene can be used.

As the blocked isocyanate resin, diisocyanate compounds (for example, ethylene diisocyanate, propylene diisocyanate, hexamethylene diisocyanate, tolylene diisocyanate, isophorone diisocyanate, lysine diisocyanate, dicyclohexylpropane diisocyanate, metaphenylene diisocyanate, naphthylene diisocyanate,
Triphenylmethane triisocyanate, trimethylpentane diisocyanate and the like), one of the isocyanate groups, polyester having a hydroxyl group, polyether, acryl, epoxy or the like is reacted in advance, the remaining isocyanate group a compound having active hydrogen (for example, methanol,
Aliphatic primary and secondary alcohols such as ethanol, cyclic alcohols such as phenol, benzyl alcohol, cresol and cyclohexanol, hydroxyl group-containing ethers such as ethylene glycol monomethyl ether and ethylene glycol monobutyl ether, methyl lactate, ethyl lactate, amyl lactate , Hydroxyl group-containing esters such as butyl lactate, hydroxyl group-containing ketones such as diacetone alcohol, acetoxime, ketoxime, methyl ethyl ketone oxime,
Oxime such as methyl isobutyl ketone oxime, ε-
Lactams such as caprolactam and β-propiolactam, active methylenes such as diethyl malonate and methyl acetoacetate, butyl mercaptan, hexyl mercaptan,
mercaptans such as t-butyl mercaptan, acid amides such as acetanilide, acrylamide, acetic acid amide,
Imides such as succinimide and phthalimide, amines such as diphenylamine phenylnaphthylamine, imidazoles such as imidazole and 2-ethylimidazole, ureas, imines, sulfites, etc.) Can be mentioned. By blocking and deactivating, it can be mixed with the above-mentioned polyol compound to form one liquid.

As described above, 60 to 75% by weight of the total calcium carbonate to be blended must be surface-treated with a resin acid, but resin acids for surface treatment of calcium carbonate include rosin acid, lignic acid and abieticin. Any known resin acid such as acid, d-pimaric acid and cinnamic acid may be used. The surface treatment can be carried out, for example, by the method described in JP-A-60-13864, whereby the aggregation of calcium carbonate is prevented.

The chipping-resistant paint of the present invention contains 80 to 95 parts by weight of calcium carbonate and 15 to 30 parts by weight of talc with respect to 100 parts by weight of a blocked isocyanate resin, and 60 to 75% by weight of calcium carbonate is a resin acid. It is indispensable that the surface is treated with. Calcium carbonate is 9
When 5 parts by weight or talc is blended in excess of 30 parts by weight, the specific gravity of the paint exceeds 1.4, and there is a risk that pinholes cannot be prevented. When the amount of calcium carbonate is less than 80 parts by weight or the amount of talc is less than 30 parts by weight,
The coating material has a specific gravity of less than 1.2, which may result in failure to obtain a thick film required for chipping resistance. Further, since the resin component accounts for a large amount in the total amount of the coating material and the viscosity becomes higher than the appropriate viscosity, the atomization property at the time of coating may be deteriorated, and pinholes may be likely to occur. Furthermore, among the calcium carbonate, the one treated with the surface resin acid is 60% of the total calcium carbonate.
Must be 75% by weight. By controlling the blending amount within this range, the chipping resistance will be excellent.

The conventional chipping-resistant paint of the present invention may contain other conventional additives as long as the specific gravity of the entire paint is not more than 1.4. For example, as a filler other than talc and calcium carbonate, clay, alumina, silica, flint,
White clay can be added. Barium sulfate, which imparts water resistance to the coating film, increases the specific gravity of the coating material, so the amount added should be taken into consideration when used. Others, titanium oxide, carbon black, red iron oxide, oxide yellow,
Additives such as coloring pigments such as phthalocyanine blue and phthalocyanine green, cissing inhibitors, leveling improvers, defoamers, surfactants, curing accelerators, antistatic agents, pigment dispersants, anti-sagging agents, thickeners, etc. You may mix. It is also possible to use a catalyst such as an organic metal compound such as zinc octylate or tin octylate or a tertiary amine compound such as triethylenediamine or triethylamine, which is usually used for promoting dissociation of the blocked urethane prepolymer. It is possible.

In order to prepare the interlayer anti-chipping paint for automobiles of the present invention, each component in the above mixing ratio is used together with a solvent in a disperser, three rolls, ball mill, pot mill, steel mill, pebble mill, attritor, sand mill, sand grinder, It may be charged in a mixing and dispersing machine such as a roll mill or a high-speed stirrer with blades to uniformly mix and disperse.

Examples of usable solvent components include hydrocarbons such as xylene and solvent naphtha, ketones such as methyl isobutyl ketone and cyclohexanone, esters of acetic acid and ethylene glycol monoethyl ether or diethylene glycol monoethyl ether, and acetic acid. Examples thereof include esters such as 3-methoxybutyl and dibasic acid esters. They may be used alone or in a mixture of two or more and generally 30% of all coating ingredients are used.
It is blended so as to occupy 40% by weight.

The coating of the car body is performed on a desired portion of the steel plate surface which has been subjected to chemical conversion treatment and electrodeposited with a primer. As a coating method, a spraying method such as a normal air spray, an electrostatic air spray, an airless spray, a hot airless spray can be adopted. The chipping-resistant paint of the present invention sprayed on the vehicle body is baked and dried at a temperature of 100 to 160 ° C for about 5 to 15 minutes. The dry film thickness is preferably about 50 to 200 μm.

[0020]

In the anti-chipping coating material of the present invention, calcium carbonate maintains the structural viscosity of the coating material and enables thickening of the coating film. Talc improves chipping resistance. Moreover,
These calcium carbonate and talc reduce the specific gravity of the entire paint by being used so as to occupy most of the filler. As a result, the generation of crown rings caused by the collision of the coating particles with the coating surface during coating is prevented, and no air is entrapped in the coating film, so no pinholes are formed in the chipping-resistant coating film. The above composition of the coating material of the present invention is
It does not act to reduce the current level of chipping resistance.

[0021]

EXAMPLES In order to understand the present invention, examples will be described below. Needless to say, the present invention is not limited to the examples below.

Example 1 12 parts by weight of a polyol resin, 31 parts by weight of calcium carbonate, 100 parts by weight of a blocked isocyanate resin,
Surface rosin acid treated calcium carbonate 53 parts by weight, talc 2
0 parts by weight and 115 parts by weight of solvent were blended to obtain a chipping resistant coating 1. The specific gravity of this anti-chipping paint 1 is 1.35.
Met.

Example 2 15 parts by weight of a polyol resin, 25 parts by weight of calcium carbonate, 100 parts by weight of a blocked isocyanate resin,
65 parts by weight of calcium carbonate treated with surface lignic acid, 20 parts by weight of talc and 115 parts by weight of solvent were blended to obtain a chipping resistant coating 2. The specific gravity of this anti-chipping paint 2 is 1.2.
It was 5.

Comparative Example 1 15 parts by weight of a polyol resin, 35 parts by weight of calcium carbonate, 100 parts by weight of a blocked isocyanate resin,
85 parts by weight of calcium carbonate treated with surface lignic acid, 35 parts by weight of talc, and 115 parts by weight of solvent were mixed to obtain a chipping resistant coating 3. The specific gravity of this anti-chipping paint 3 is 1.4.
It was 3.

Comparative Example 2 15 parts by weight of a polyol resin, 50 parts by weight of calcium carbonate, 100 parts by weight of a blocked isocyanate resin,
10 parts by weight of talc and 115 parts by weight of solvent were blended to obtain a chipping resistant coating 4. The specific gravity of this anti-chipping paint 4 was 1.19.

Comparative Example 3 15 parts by weight of a polyol resin, 124 parts by weight of barium sulfate, and 100 parts by weight of a blocked isocyanate resin,
14 parts by weight of talc and 115 parts by weight of solvent were mixed to obtain a chipping resistant coating 5. The specific gravity of this anti-chipping paint 5 was 1.55.

Test Example 1 Each of the chipping resistant paints 1 to 5 obtained in Examples 1 and 2 and Comparative Examples 1 to 3 was airlessly applied to a glass plate from a distance of 40 cm, and baked and dried at 110 ° C. for 10 minutes. After doing
The state of each coating film surface was visually observed. As a result, no pinholes were generated in both coating films formed with the coating materials 1 and 2 of the example, but the coating materials 3 to 5 of the comparative example.
Each coating film formed in 1 had a pinhole on one surface.

Test Example 2 Each of the above chipping-resistant paints 1 to 5 was airlessly coated on an electrodeposition plate (a steel plate on which a primer was electrodeposition-coated), and baked and dried at 110 ° C. for about 10 minutes to obtain a chipping-resistant layer having a film thickness of 90 μm. After that, an intermediate coating was applied, and after drying at 140 ° C. for 20 minutes, a top coating was applied and drying at 140 ° C. for 20 minutes. The thicknesses of the intermediate coating layer and the top coating layer after drying are both 30 μm. On each test plate manufactured by painting in this way, 3 types M4 specified in JIS B1181
Shaped brass hexagon nuts were dropped from a height of 2 m in order from the smallest weight, and the weight of the falling nut until the scratches of the coating film generated at that time reached the electrodeposition coated surface was examined. As a result, the weight of the nut is 1 on any painted surface.
It became 2 kg. From this, the above chipping resistant coating 1
It was revealed that all of the above-mentioned Nos. 5 to 5 have excellent chipping resistance.

Test Example 3 Each of the above chipping resistant coatings 1 to 5 was airlessly coated on an electrodeposition plate (a steel plate coated with a primer by electrodeposition), and baked and dried at 110 ° C. for about 10 minutes to obtain a chipping resistance layer having a film thickness of 90 μm. After that, an intermediate coating was applied, and after drying at 140 ° C. for 20 minutes, a top coating was applied and drying at 140 ° C. for 20 minutes. The thicknesses of the intermediate coating layer and the top coating layer after drying are both 30 μm. Each of the test plates manufactured by coating as described above is provided with a stepping stone tester [Suga Tester Co., Ltd., JA-
400 type] sample holder was mounted vertically, and 500 g of crushed stone No. 6 was directed to this test plate by the pressure gauge of the same tester.
It was jetted at an air pressure of kg / cm ² , and the crushed stone was made to collide with the test plate at a right angle. Next, the test plate was washed with water, dried, and after the coating film that had been lifted up by chipping was removed with an adhesive tape, the degree of peeling damage was evaluated on a five-grade scale from good (⊚) to poor (x). As a result, it was revealed that all the coated surfaces were ⊚, and that all of the chipping resistant coatings 1 to 5 had excellent anti-chipping performance.

[0030]

According to the chipping-resistant coating material of the present invention, a chipping-resistant layer free from pinholes can be provided, so that the work for countermeasures against pinholes can be omitted and the coating efficiency can be improved. Further, since the pinholes left in the chipping-resistant layer do not cause unevenness in the overcoat layer, the appearance is further improved.

Claims (1)

[Claims] 1. To 100 parts by weight of a blocked isocyanate resin, 10 to 18 parts by weight of a polyol resin, 80 to 95 parts by weight of calcium carbonate, 15 to 30 parts by weight of talc,
A paint comprising an appropriate amount of a solvent and, if necessary, a conventional additive, which is 60 to 75% by weight of the total calcium carbonate.
Which is surface-treated with a resin acid, and the specific gravity of the entire coating composition is 1.2 to 1.4 or less.