JP2622793B2 - Two-part chipping-resistant coating composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-pack type chipping-resistant paint which is applied to the outer plate of a vehicle, especially to a side sill portion, a rocker panel portion, a fender portion and the like of a vehicle body for the purpose of preventing stone splashing (anti-chipping). It relates to a composition.

[0002]

2. Description of the Related Art Conventionally, peeling of a coating film on a vehicle outer plate caused by pebbles, gravel and the like jumping from a road surface while the vehicle is running has been a problem because it causes rust and poor appearance. Paint with shock absorption is applied for the purpose of protection. In particular, a chipping-resistant paint having a film thickness of 200 μm or more is applied to a portion of the automobile body such as a side sill portion, a rocker panel portion, a fender portion, etc., which has a large impact due to a stone splash, after the topcoat paint is applied. When coating on such a completed vehicle body, a two-pack type chipping-resistant paint that does not require a large-scale drying facility is applied.

[0003]

SUMMARY OF THE INVENTION For the purpose of countermeasures against surface deterioration due to acid rain (pH 4 or less), which has recently become a social problem, and scratches at the time of car washing, various top coats having excellent weather resistance and mechanical properties have been developed. Development has increased in recent years. However,
Many of these coatings incorporate complex cross-linking using silicon-based resin or fluorine-based resin. For example, the coating composition disclosed in JP-A-2-248777 is exemplified. Although it is excellent in water repellency, solvent resistance and mechanical properties, the coating of the top-coating type chipping-resistant coating applied after the top coating has a poor adhesion. A problem that the original performance cannot be exhibited. Under such circumstances, there is a demand for the development of a two-pack type chipping-resistant paint having excellent adhesion.

[0004]

Means for Solving the Problems The inventors of the present invention have studied with the aim of developing a top-coating type chipping-resistant paint which forms a coating film having not only chipping resistance but also excellent adhesion on the above-mentioned topcoat surface. Went diligently. As a result, a coating composition containing an isocyanate group-containing compound and a polyol compound as main components, wherein the NCO / OH equivalent ratio of the isocyanate group-containing compound and the polyol compound and PWC are adjusted to specific ranges, the coating composition, By coating the side sill, rocker panel, fender, etc. of a top-coated vehicle, it was found that a coating film with excellent adhesion as well as chipping resistance was formed.

The inventors of the present invention have developed a conventional two-pack type chipping-resistant paint in developing a topcoat-type chipping-resistant paint which forms a coating film having excellent adhesion as well as chipping resistance on the above-mentioned top-coated surface. As a result of studying the effects of NCO equivalent of isocyanate group-containing compound, OH equivalent of polyol compound, amount of curing catalyst, etc. on the adhesiveness, the NCO / OH equivalent ratio was increased to improve the composition in addition to urethane bonds. It has been found that the generation of an amount of urea bonds improves the adhesion to the overcoated surface. This is presumed that when the crosslink density in the coating film was increased, the number of functional groups contributing to adhesion increased, and as a result, the adhesion was improved. In addition, it has been found that increasing the PWC also contributes to the improvement in adhesion. This can be presumed to be due to an improvement in chipping resistance due to cohesive failure of the pigment and an increase in pseudo-crosslinking density. The subject was found to be satisfied when the relationship between the NCO / OH equivalent ratio and the PWC was within a specific range. The present invention has been completed based on such findings.

That is, the present invention relates to a paint containing an isocyanate group-containing compound, a polyol compound, and a pigment as main components, wherein the NCO / OH equivalent ratio of the isocyanate group-containing compound and the polyol compound is y, and PWC is x. sometimes Characterized in that an isocyanate group-containing compound, a polyol compound and a pigment were blended so as to satisfy
The present invention relates to a liquid type chipping-resistant coating composition.

The isocyanate group-containing compound used in the present invention is a compound of trimer or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), or the above isocyanate A prepolymer of a group-containing compound can be used. In addition, two or more of the above isocyanate group-containing compounds may be used in combination, if necessary.

As the polyol compound used in the present invention, polyether polyol, polyester polyol, acrylic polyol, epoxy polyol and the like can be used. If necessary, two or more of the above polyol compounds may be used in combination.

The coating composition of the present invention must be adjusted so that the equivalent ratio of the NCO equivalent of the isocyanate group-containing compound to the OH equivalent of the polyol compound becomes 1 to 3. If the equivalent ratio is less than 1, the number of functional groups contributing to adhesion such as urea bonds and the crosslink density are insufficient, and as a result, adhesion is not improved, which is not preferable. When the equivalent ratio exceeds 3, it is necessary to increase the use amount of the isocyanate group-containing compound or use an isocyanate group-containing compound having a large NCO equivalent. The former case is not preferred because the resulting coating cost is extremely increased, and the latter case is not preferred because a highly toxic isocyanate group-containing compound is used.

[0010] In the coating composition of the present invention, it is necessary to adjust the PWC to 50 to 75 using a pigment used for a general coating. If the PWC is less than 50, the adhesion is not improved, which is not preferable. On the other hand, if the PWC is more than 75, the coating film becomes brittle and, as a result, the chipping resistance decreases, which is not preferable.

The coating composition of the present invention comprises an NCO / OH compound of the isocyanate group-containing compound and the polyol compound.
By adjusting the equivalent ratio and the PWC so that the following equation 1 is satisfied, the target performance can be secured. When y <−0.125x + 9.25, the adhesion is not improved, which is not preferable.

The main pigments used in the present invention are extender pigments, coloring pigments, and the like, and extender pigments used for general paints such as calcium carbonate, silica, kaolin, barite, and clay can be used. . As the coloring pigment, a coloring pigment used for general paints such as carbon and titanium oxide can be used. In addition, rust preventive pigments used for general paints can be used as needed.

In the coating composition of the present invention, in addition to the above-described components, other components used in ordinary solvent-based coating compositions can be used, if necessary. For example, tin-based compounds and cobalt-based compounds that are reaction accelerators, silicon-based, non-silicon-based, fluorine-based, and acrylic copolymers that are interfacial modifiers, and organic and inorganic-based viscosity modifiers. Copolymers and diluents such as toluene, xylene, hydrocarbon solvents such as mineral spirits, ethyl acetate, ester solvents such as butyl acetate, ketone solvents such as methyl ethyl ketone, alcohol solvents such as ethanol and butanol, butyl ether, Ether solvents such as ethylene glycol monomethyl ether can be used alone or in combination as appropriate.

The coating composition of the present invention is composed of a composition (base agent) using the above-mentioned polyol compound and a composition (curing agent) using the above-mentioned isocyanate group-containing compound.
It is a liquid type coating composition, in which the pigment and other components are distributed to a main agent and a curing agent, and each is mixed and dispersed for adjustment. The coating film is formed by mixing the two liquids at a predetermined ratio immediately before coating, and conventionally used coatings such as air spray coating and airless spray coating (preferably using a two-liquid mixing type coating machine). It can be painted by a machine or a painting facility, and is formed by drying at room temperature for about 1 to 5 hours.

[0015]

Next, an embodiment of the present invention will be described. All parts and percentages in the text are by weight. Curing agent A: TDI prepolymer formed by adding TDI to trimethylolpropane and solid content of isobutyl acetate 7
An isocyanate group-containing compound liquid of 5% and NCO% 13 was obtained. Curing agent B: An isocyanate group-containing compound liquid having a solid content of 75% and an NCO of 18 consisting of biuret-modified HDI produced from 3 moles of HDI and isobutyl acetate was obtained.

Main agent A: polyester polyether polyol compound (OH value 1
65) 100 parts by weight, 370 parts by weight of calcium carbonate, 5 parts by weight of carbon, 0.1 parts by weight of dibutyltin dilaurate, 100 parts by weight of isobutyl acetate,
The mixture was stirred at a high speed for 0 minutes and dispersed to obtain a coating composition. Main agent B: polyester polyether polyol compound (OH value 1
65) 100 parts by weight, 230 parts by weight of calcium carbonate, 5 parts by weight of carbon, 0.1 parts by weight of dibutyltin dilaurate, 100 parts by weight of isobutyl acetate,
The mixture was stirred at a high speed for 0 minutes and dispersed to obtain a coating composition. Main agent C: polyester polyether polyol compound (OH value 1
65) 100 parts by weight, 600 parts by weight of calcium carbonate, 5 parts by weight of carbon, 0.1 parts by weight of dibutyltin dilaurate, 250 parts by weight of isobutyl acetate,
The mixture was stirred at a high speed for 0 minutes and dispersed to obtain a coating composition. Main agent D: polyester polyether polyol compound (OH value 7
0) 100 parts by weight, 600 parts by weight of calcium carbonate, 5 parts by weight of carbon, 0.1 parts by weight of dibutyltin dilaurate, 250 parts by weight of isobutyl acetate,
The mixture was stirred at a high speed for 0 minutes and dispersed to obtain a coating composition.

Example 1 A coating composition composed of 575.1 parts by weight of a base material A and 115 parts by weight of a curing agent A and having an NCO / OH equivalent ratio of 1.21 and a PWC of 66.8 was obtained. Example 2 A coating composition composed of 575.1 parts by weight of a main agent A and 200 parts by weight of a curing agent A and having an NCO / OH equivalent ratio of 2.10 and a PWC of 60.0 was obtained. Example 3 A coating composition having a NCO / OH equivalent ratio of 2.63 and a PWC of 56.5, comprising 575.1 parts by weight of a main agent A and 250 parts by weight of a curing agent A, was obtained. Example 4: A coating composition composed of 575.1 parts by weight of a base material A and 75 parts by weight of a curing agent B and having an NCO / OH equivalent ratio of 1.09 and a PWC of 70.6 was obtained. Example 5: A coating composition having an NCO / OH equivalent ratio of 1.67 and a PWC of 66.8, comprising 575.1 parts by weight of a main agent A and 115 parts by weight of a curing agent B, was obtained. Example 6: A coating composition comprising 575.1 parts by weight of a main agent A and 200 parts by weight of a curing agent B and having an NCO / OH equivalent ratio of 2.90 and a PWC of 60.0 was obtained. Example 7: A coating composition composed of 955.1 parts by weight of a base material C and 150 parts by weight of a curing agent B and having an NCO / OH equivalent ratio of 2.18 and a PWC of 74.0 was obtained.

Comparative Example a: A coating composition comprising 575.1 parts by weight of a main agent A and 90 parts by weight of a curing agent A and having an NCO / OH equivalent ratio of 0.95 and a PWC of 69.1 was obtained. Comparative Example b: A coating composition composed of 575.1 parts by weight of a main agent A and 50 parts by weight of a curing agent B and having an NCO / OH equivalent ratio of 0.73 and a PWC of 73.2 was obtained. Comparative Example c: A coating composition composed of 435.1 parts by weight of a base material B and 90 parts by weight of a curing agent A and having an NCO / OH equivalent ratio of 0.95 and a PWC of 58.5 was obtained. Comparative Example d: A coating composition composed of 435.1 parts by weight of a base material B and 200 parts by weight of a curing agent A and having an NCO / OH equivalent ratio of 2.10 and a PWC of 48.5 was obtained. Comparative Example e: A coating composition composed of 435.1 parts by weight of a base material B and 90 parts by weight of a curing agent B and having an NCO / OH equivalent ratio of 1.31 and a PWC of 58.5 was obtained. Comparative Example f: A coating composition composed of 435.1 parts by weight of a base material B and 200 parts by weight of a curing agent B and having an NCO / OH equivalent ratio of 2.91 and a PWC of 48.5 was obtained. Comparative Example g: A coating composition having an NCO / OH equivalent ratio of 1.45 and a PWC of 77.6, comprising 955.1 parts by weight of a base material C and 100 parts by weight of a curing agent B, was obtained. Comparative Example h: A coating composition composed of 955.1 parts by weight of a base material D and 100 parts by weight of a curing agent B and having an NCO / OH equivalent ratio of 2.57 and a PWC of 77.6 was obtained.

Test Example 1: Process in which an electrodeposition coating film, an intermediate coating film, a top coating film, and a clear coating film composed of a polysiloxane resin were formed on a zinc phosphate-treated soft steel plate. The coating compositions of Examples 1 to 7 and Comparative Examples a to h were applied so as to have a dry film thickness of 200 μm, and left at room temperature for one week. An JIS-K5400-1990, 8.5.2 adhesion test was performed except that the cut width was 2 mm in order to confirm the adhesion of the obtained coating film. In addition, a gravel test was performed to confirm chipping resistance. Table 1 shows the test results.

[0020]

[Table 1]

Adhesion test evaluation: 10 indicates that each cut is thin and both sides are thin
Smooth, peel off at the intersection of cuts and squares at a glance
There is no. No. 4 has a wide width of peeling due to cuts and the area of the defect is all positive
15-35% of square area. 2 is wider than 4 due to the cut,
The area is 35-65% of the total square area. 0: Peeling area is 65% or more of the total square area. Gravelo test evaluation: JA-400 manufactured by Suga Test Instruments Co., Ltd.
Performed under the following test conditions using an LA-type stepping stone tester
Was. Type of stepping stone: No. 6 crushed stone Stepping stone amount: 500 g Air pressure: 4 kgf / cm²  Spraying distance: 350 mm Sample temperature: -20 ° C Sample holding angle: perpendicular to spraying direction Test plate area: 140 mm × 70 mm ○: No peeling of 2 mm square or more, peeling area: test plate surface
0-5% of product. △ indicates no peeling of 4 mm square or more, and the area of peeling is the surface of the test plate.
5-10% of the product. × indicates that the area of peeling is 10% or more of the area of the test plate. As is clear from the test results, each of the examples satisfying the expression 1
The coating composition has good adhesion test and gravelo test.
However, none of the coating compositions of Comparative Examples satisfying the formula 1
These tests also had poor results.

[0022]

According to the coating composition of the present invention, surface deterioration due to acid rain, which has recently become a social problem, and poor adhesion to a topcoat film developed for the purpose of preventing scratches during car washing. Since a coating film having excellent chipping resistance can be obtained without causing such a phenomenon, it is suitable as a two-pack type chipping-resistant coating composition.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the NCO / OH equivalent ratio and the adjustment range of PWC in Examples 1 to 6 and Comparative Examples a to h. Numerical values in the graph represent each example, and alphabets represent comparative examples.

Claims (1)

(57) [Claims] 1. A paint mainly comprising an isocyanate group-containing compound, a polyol compound and a pigment, wherein the isocyanate group-containing compound and the polyol compound have an NCO / OH equivalent ratio of y, and a pigment weight% per paint solid content. When the density (hereinafter PWC) is x Characterized in that an isocyanate group-containing compound, a polyol compound and a pigment were blended so as to satisfy
Liquid type chipping-resistant coating composition.