JPH07118567A - Primer for preventing yellowing of coating film on polypropylene material - Google Patents

Abstract

PURPOSE:To obtain a primer for preventing the yellowing of a coating film formed by coating a polypropylene material with a primer and with a topcoating agent. CONSTITUTION:A primer wherein the primer resin comprises a (chlorinated) polyolefin resin and the resin solid matter comprises 100 pts.wt. (chlorinated) polyolefin and 10-30wt.% epoxy resin. It can form a coating film having an elongation of 300-400% and a tensile strength of 100-200g/cm2.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a coating film yellowing prevention primer for polypropylene materials.

[0002]

2. Description of the Related Art As a conventional primer for polypropylene (PP) material, there are, for example, the followings.
A polyolefin resin or a chlorinated polyolefin resin having a similar solubility parameter (SP value) is applied to the resin of the PP material primer in order to secure the adhesion of the coating film to the PP material. Further, the polyolefin resin or the chlorinated polyolefin resin is modified with a compound having a polar group such as epoxy or maleic anhydride in order to secure the adhesion to the top coating film. As for the coating property of the primer, the elongation is 400% or more, and therefore the tensile strength of the coating is 100 g / cm ² or less.

[0003]

However, in such a conventional primer for a PP material, the PP material contains an antioxidant, an ultraviolet absorber, a light stabilizer, etc., and these additive components are used. Since it is not formulated so as to prevent the transfer to the primer, there is a problem that in the case of light-colored topcoating, the topcoating film turns yellow due to the influence of heat and the like, and the commercialability is deteriorated. Yellowing of the coating is PP
The hindered phenolic antioxidant contained in the material reacts with the chlorohydrin compound contained as a by-product of the epoxy resin used in the primer to change to a yellow substance having a quinone structure, or the antioxidant is overcoated. There is a problem in that even the top coating film turns yellow due to a yellow product formed by the reaction with the ultraviolet absorber or the light stabilizer contained in the film.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and prevents yellowing of a coating film formed by coating a polypropylene material with a primer and a topcoat paint. In the primer for preventing, the solid content of the polyolefin resin or chlorinated polyolefin resin used as the primer resin is 100
The amount of epoxy resin to be blended with respect to 10 to 30% by weight
And the elongation of the primer is 300 to 400% and the tensile strength is 100 to 200 g / cm ² , so that the yellowing of the coating film can be prevented without adding a reducing agent to the primer. Is.

[0005]

In the present invention, a polyolefin resin or a chlorinated polyolefin resin and an epoxy resin are used for the primer. In order to obtain the primer of the present invention, the coating amount can be adjusted by the following method to obtain a coating film having desired coating film physical properties. (1) In the chlorinated polyolefin resin, the bonding portion between chlorine and polyolefin is modified with a resin having a carboxyl group. The elongation rate can be changed according to the degree of metamorphism, and the elongation rate can be suppressed by increasing the degree of metamorphism. It is necessary to increase the amount of epoxy resin to be compounded as the degree of metamorphism increases. (2) The tensile strength of the coating film can be adjusted by the amount of the epoxy resin added to the polyolefin-based or chlorinated polyolefin-based resin. When the amount of the epoxy resin compounded is large, the tensile strength becomes large.

In the present invention, the degree of modification, that is, the crosslink density of the coating film is controlled by adding an epoxy resin, whereby the elongation ratio and tensile strength of the primer coating film are balanced and a tough coating film is obtained. The transfer of yellowing substances in the coating film from the PP base material is prevented. If the elongation is insufficient, the cracks in the coating film become notches and even the material is destroyed. Further, if the elongation is large, that is, the crosslink density is low, the migration of the yellowing substance in the coating film from the PP substrate cannot be prevented.

By adjusting the physical properties of the coating film by the method described above,
As the coating film physical property value of the primer of the present invention, the measurement temperature is 2
At 0 ° C, elongation is 300-400%, tensile strength is 100-
200 g / cm ² can be obtained. The primer having the coating film physical properties can prevent the antioxidant contained in the PP material from migrating to the primer, and can sufficiently exhibit the performance as the primer coating film.

The elongation is less than 300% and the tensile strength is 20.
If it is larger than 0 g / cm ^{2, the} impact resistance of the coating film is lowered. On the other hand, when the elongation is 400% and the tensile strength is 100 g / cm ² , the migration of the antioxidant to the primer cannot be prevented, and yellowing of the top coating film appears. Further, the primer resin of the present invention comprises a polyolefin resin or a chlorinated polyolefin resin and an epoxy resin as described above, and the polyolefin resin or the chlorinated polyolefin resin has a polar group such as epoxy or maleic anhydride. Modified with compound or mixed with epoxy resin. A polyolefin resin having an SP value similar to that of the PP substrate ensures adhesion to the substrate, and epoxy or maleic anhydride having a polar group ensures adhesion to the overcoat film.

[0009]

EXAMPLES The present invention will be described below with reference to examples and comparative examples. In the examples, "parts" means "parts by weight" unless otherwise specified. Creation of painted board Polypropylene (PP) base material (TX
-1180) was degreased with isopropyl alcohol. Next, a chlorinated polyolefin resin was used to prepare primers having different elongations and tensile strengths.
After coating a primer with a composition shown in (5) to a dry film thickness of 5 μm and baking and drying at 90 ° C. for 20 minutes, a topcoat paint (Soflex # 1200 B621 manufactured by Kansai Paint Co., Ltd.) has a dry film thickness of 30 μm. And then baked and dried at 120 ° C. for 20 minutes.
And the coated plate of Comparative Examples 1-5 was obtained. Table 1 also shows the results obtained by conducting a coating film performance test using the finished coated plate by the following evaluation method.

Evaluation method (1) Heat-resistant yellowing The test piece was left in a drying oven kept at 90 ° C for 240 hours,
The b value is measured 1 hour after the removal. The yellowing degree (Δd) is calculated by the following formula. Δb = (b value after heat resistance test) − (b value before heat resistance test) Measuring device: CR-200 (manufactured by Minolta Co., Ltd.) (2) Adhesion of coating film Using a cutter knife, 2 mm goggles that reach the substrate Twenty-five pieces were made, the adhesive tape was adhered to the eyelet, and one end of the tape was kept perpendicular to the effective surface and was momentarily separated at a speed of 0.5 m / s or more. Determine adhesion. (3) Impact resistance Using a DuPont impact tester, the height at which the coating film cracked was displayed. The weight of the weight was 500 g. (4) Elongation and tensile strength A universal tensile tester (UTM-4-20 manufactured by Toyo Baldwin Co., Ltd.) was used as a sample with a primer coating free film having a size of 10 × 50 mm and a thickness of 5 to 10 μm.
0), load cell is 5kg, deformation speed is 10mm / mi
The measurement conditions were n, the number of measurements 5 (average of 5 data), and chart speed 20 mm / min. From the measured data, X and Y were read, and the elongation percentage and tensile strength were determined by the following formulas.

[0011]

[Equation 1] The results of the above evaluations are shown together in Table 1.

[0012]

[Table 1]

[0013]

As described above, according to the present invention, in the primer for preventing the yellowing of the coating film formed by coating the primer and the top coating material on the polypropylene material, the resin of the primer is used. Is a polyolefin resin or a chlorinated polyolefin resin and an epoxy resin, 10 to 30% by weight of the epoxy resin is added to 100 parts of the polyolefin resin or chlorinated polyolefin resin as a resin solid content, and a primer coating film. Since the physical properties are such that the elongation rate is 300 to 400% and the tensile strength is 100 to 200 g / cm ² , (1) the yellowing of the top coat film on the polypropylene material can be prevented,
(2) It will be possible to expand the adoption of light colors,
(3) The excellent effect that the coating film performance, especially the impact resistance can be improved is obtained.

Claims (1)

[Claims] 1. A primer for preventing yellowing of a coating film formed by coating a polypropylene material with a primer and a topcoat paint, wherein the primer resin is a polyolefin resin or a chlorinated polyolefin resin and an epoxy resin. Consisting of 100 to 30% by weight of an epoxy resin based on 100 or more of a polyolefin resin or a chlorinated polyolefin resin as a resin solid content, and a coating film physical property of a primer having an elongation of 300 to 400%,
A coating film yellowing-preventing primer for polypropylene materials, which has a tensile strength of 100 to 200 g / cm ² .