JPH055080A - Urethane coating composition - Google Patents

Abstract

PURPOSE:To obtain the title composition for use in intercoating capable of reducing surface tension, doing away with repelling phenomenon through raising coating viscosity and smoothing coating-film surface, by incorporating a polyurethane resinous matter with a specified amount of cellulose acetate butyrate. CONSTITUTION:The objective composition can be obtained by incorporating (A) a coating film-forming component consisting of a resinous matter predominant in polyurethane with (B) 0.1-1.5wt.% of cellulose acetate butyrate (CAB). The solvent for dissolving the CAB is e.g. a mixed solvent comprising (1) 20wt.% of a cellulose ester, (2) 72wt.% of acetone and (3) 8wt.% of ethanol.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in urethane coating compositions, particularly those for intermediate coating.

[0002]

2. Description of the Related Art Generally, for example, for coating outer panels of automobiles,
Primed, mid-coated and top-coated. Among them, as the coating material for the intermediate coating, polyester-melamine-based coating materials have been more often used than before, but it is effective to use a urethane coating material to improve the pitting resistance as the coating performance of the intermediate coating. It has become clear recently.

[0003]

However, since the urethane paint uses an isocyanate having a high polarity as a curing agent, the surface tension of the paint immediately after painting becomes high, and the urethane paint has a higher surface tension than the conventional polyester-melamine paint. There is a problem that the surface of the coating film does not conform to the surface easily and the smoothness is impaired.

By the way, it has been conventionally practiced to add a surface conditioner as a method for lowering the surface tension of the paint. For example, in a polyester-melamine type intermediate paint, an acrylic surface conditioner is used as a polyester or an acrylic. −
Silicon-based surface conditioners are used in the melamine-based top coatings.

Therefore, it is conceivable to add an acrylic surface modifier or a silicone surface modifier to the urethane coating for intermediate coating to lower the surface tension. However, the acrylic surface modifier has a surface tension of polyester-melamine. Even if it is used in a urethane coating which is higher than a coating based on it, it is not so effective. On the other hand, a silicone surface control agent cannot be adopted because the adhesion to the top coating layer is deteriorated. It has been empirically known that the repellency phenomenon decreases as the viscosity of the paint increases.

The present invention has been made in view of the above points, and an object thereof is to add an appropriate amount of an appropriate additive to a film-forming element of a resinous material containing polyurethane as a main component. The purpose is to lower the surface tension and quickly increase the viscosity of the paint to eliminate the repellency phenomenon, improve the conformability of the skin on the surface of the coating film made of urethane paint, and ensure the smoothness.

[0007]

Means for Solving the Problems In order to achieve the above object, a solution means of the present invention is to provide a urethane coating composition used as an intermediate coating composition, which is a coating film forming element of a resinous substance containing polyurethane as a main component. That is, 0.1 to 1.5 wt% of cellulose acetate butyrate was added therein.

[0008]

With the above structure, in the present invention, 0.1 to 1.5 wt% of cellulose acetate butyrate is added to the coating film-forming element of the resinous material containing polyurethane as the main component. Cellulose acetate
Due to the properties of butyrate, the surface tension of the coating film forming element (paint) becomes low, and the solvent in the coating film forming element evaporates rapidly to increase the viscosity and eliminate the repellency phenomenon. The smoothness of the skin is improved and smoothness is secured.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

The urethane coating composition according to the embodiment of the present invention is used as a coating material for an intermediate coating among an undercoat, an intermediate coating and an overcoat applied to the exterior coating of an automobile, for example, a polyurethane is mainly used. Cellulose acetate butyrate (hereinafter abbreviated as CAB in Examples) is contained in the coating film-forming element of the resinous material as the component.
1 to 1.5 wt% is added. CAB is added to the film-forming element so that CAB lowers the surface tension of the film-forming element (paint) and evaporates the solvent in the film-forming element to rapidly increase the viscosity and eliminate the repellency phenomenon. By virtue of this, it is possible to improve the conformability of the skin on the surface of the coating film made of the urethane paint and to ensure the smoothness.
Further, the reason why the amount of CAB added is set in the range of 0.1 to 1.5 wt% is that the above effect cannot be expected if it is less than 0.1 wt%, while the viscosity of the coating film forming element is more than 1.5 wt%. Is too high, which rather deteriorates the conformability of the coating film surface to the skin.

Next, in order to prove this, CAB
Table 1 and FIG. 1 show the experimental data obtained by changing the addition amount of the. In the additive type column of Table 1, the "butylation degree" means the degree of butylation in order to improve the compatibility with the CAB coating film-forming element, and the "viscosity" means the cellulose ester (20 %), Acetone (72%), ethyl alcohol (8%) in a solution of CAB, BALL-
The value measured by the DROP method (unit: poise),
"Tg" is a glass transition temperature (unit: ° C). Also, in the "compatibility" in the results column, "OK" means that the mixed state of CAB with respect to the coating film forming element is good.
Means that CAB aggregates into a gel, and the mixing state of CAB with respect to the coating film forming element is poor. Further, in the "Skin" in the results column, "OK" means that the viscosity rapidly increases immediately after spraying and the repellency disappears, and that the skin conformability of the coating film surface is good. It means that since the temperature rises too much, the compatibility of the skin on the surface of the coating film deteriorates. In the “determination” column of the results column, “O” means that both compatibility and skin are good, and “X” means that at least one of compatibility and skin is bad. In addition,
For reference, the lowermost row of Table 1 shows experimental data of an acrylic surface conditioner as a comparative example. In addition, in FIG.
The numbers enclosed by marks correspond to the numbers in the No. column of Table 1. Furthermore, the thick solid line indicates that the amount of CAB added is 1.5 wt.
% Of the pass / fail line, the one-dot chain line is the guideline of the pass / fail line when the amount of CAB added is 1.0 wt%, and the broken line is C
The pass / fail line is a guideline when the amount of AB added is 0.5 wt%, and the two-dot chain line is a guideline for the pass / fail line when the amount of CAB added is 0.1 wt%. The upper side of each line indicates that the surface properties of the coating film are good. Represent.

As is clear from the experimental data, the result of the judgment is that the compatibility and the skin are good.
No.4, 7-9, 12-
No.15, No.8, 9, when the amount of CAB added is 0.5 wt%
13-15, No. 1 when the amount of CAB added is 1.0 wt%
No. 1 when the addition amount of 4, 15 and CAB is 1.5 wt%
It was 4,15. By the way, the amount of CAB added is 1.0w
Taking the case of t% as an example, the viscosity is 0.7 p in FIG.
By using the CAB in the region below oise (on the left side of the thin solid line) and the degree of butylation above the one-dot chain line, that is, the shaded region, a coating film having good surface properties can be obtained. In the acrylic surface conditioner, CAB was 0.
Even if 1 to 1.5 wt% was added, a repellency phenomenon occurred in all cases, and the coating film surface properties were poor.

[0013]

[Table 1]

As described above, in the present embodiment, since 0.1 to 1.5 wt% of CAB is added to the coating film-forming element of the resinous material containing polyurethane as the main component, this CA is used.
Due to the property of B, the surface tension of the coating film-forming element (paint) can be lowered, and the solvent in the coating film-forming element can be evaporated to rapidly increase the viscosity to eliminate the cissing phenomenon. As a result, the conformability of the skin on the surface of the coating film made of urethane paint can be improved and the smoothness can be secured.

[0015]

As described above, according to the present invention,
A urethane coating composition used as an intermediate coating composition is prepared by adding cellulose acetate butyrate in a film-forming element of a resinous material containing polyurethane as a main component in an amount of 0.1 to 1.
Since it is composed by adding 5 wt%, coating film forming element (paint)
It is possible to lower the surface tension and eliminate the repellency phenomenon, improve the conformability of the skin on the surface of the coating film made of the urethane paint, and ensure the smoothness.

[Brief description of drawings]

FIG. 1 is data showing the relationship between the degree of butylation and viscosity of cellulose acetate butyrate and the amount added.

Claims (1)

Claim: What is claimed is: 1. A urethane coating composition used as an intermediate coating composition, wherein cellulose acetate butyrate is 0.1 in a film-forming element of a resinous material containing polyurethane as a main component. The urethane coating composition is characterized by being added at up to 1.5 wt%.