JPH07118569A - Automotive yellowing-preventing primer composition - Google Patents

Abstract

PURPOSE:To obtain the title composition which prevents the coating film on a polyolefin substrate from yellowing. CONSTITUTION:The composition is one to be used when a polypropylene substrate is coated with a primer and then with a topcoating material to form a coating film thereon. The resin component of the primer comprises a (chlorinated) polyolefin resin and an epoxy resin, and the yellowing-preventing component comprises desirably 0.5-20wt.%, based on the resin solids of the primer, tin compound of the formula (R1 and R2 are each alkyl; and R3 and R4 are each a laurate group, a maleate group or a mercaptide group).

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a non-yellowing primer composition for automobiles.

[0002]

2. Description of the Related Art As a conventional primer for polypropylene (PP) base material, there is, for example, the following one.
A polyolefin resin or a chlorinated polyolefin resin having a similar solubility parameter (SP value) is applied to the resin of the primer for PP base material in order to secure the adhesion of the coating film to the PP base 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, or an epoxy resin is mixed, in order to secure the adhesion with the top coating film.

[0003]

However, in such a conventional primer for a PP base material, the PP resin used as the base material contains an antioxidant, an ultraviolet absorber, a light stabilizer and the like. However, since it is not formulated to prevent migration of these additive components to the primer, in the case of light-colored top-coating, the top-coating film turns yellow due to the influence of heat, etc. There was a problem.
The yellowing of the coating film is caused by the hindered phenolic antioxidant contained in the PP base resin reacting with the chlorohydrin compound contained as a by-product of the epoxy resin used in the primer to increase the yellowing degree. Hydrogen chloride generated by the dehydrochlorination reaction is a light stabilizer contained in the top coating film,
For example

[Chemical 2] It further reacts with the terminal N group of the 6-membered ring compound and is further yellowed.

[0004]

SUMMARY OF THE INVENTION The present invention has been made by paying attention to such conventional problems as described above, and in a primer composition used for coating a primer and a topcoat paint on a polypropylene substrate, a resin component is used. As a polyolefin resin or a chlorinated polyolefin resin and an epoxy resin, the following formula

[Chemical 3] A yellowing-free primer composition for automobiles, characterized in that it contains a tin compound represented by the formula (R ₁ and R ₂ are alkyl groups and R ₃ and R ₄ are laurate, malate or mercaptide groups). It is about things.

[0005]

In the primer composition of the present invention, a polyolefin resin or a chlorinated polyolefin resin and an epoxy resin are used as resin components. The cause of yellowing of the coating film is caused by reacting with a chlorhydrin compound contained as a by-product of the epoxy resin used for the primer and a hindered phenolic antioxidant contained in the PP base material to form a quinone structure, It further reacts with the terminal N groups of the light stabilizer (six-membered ring compound) contained in the top-coating film to further turn yellow. In the present invention, by incorporating the tin compound represented by [Chemical Formula 3] into the primer, the tin in the compound is used for the hindered phenolic antioxidant contained in the PP base resin and the primer. During the reaction with the chlorohydrin form contained as a by-product of the epoxy resin, it reacts first with the chlorhydrin form, so that the above-mentioned antioxidant does not produce the quinone structure that causes yellowing. Further, tin in the primer reacts with chlorine (Cl) to become SnCl ₂ , so that generation of hydrogen chloride can be prevented. Therefore, it is possible to prevent the reaction between various additives contained in the top coating film and hydrogen chloride.

As the tin compound of [Chemical Formula 3] used in the present invention,
For dinormal octyl tin dilaurate, dinorma
Luoctyl tin malate type, dibutyl tin dilaurate type,
Dibutyltin malate-based, dinormal octyltin dimerca
Ptide, octyltin mercaptide, dibutyltin
Examples include mercaptide series. Also, R in [Chemical 3] ₁
And R₂As normal octyl, R₃And R_Four
For this, laurate, malate, mercaptide, etc. are preferred.
It is used well.

A primer containing a polyolefin resin or a chlorinated polyolefin resin and an epoxy resin as a resin component contains a tin compound represented by [Chemical Formula 3] in an amount of 0.5 to 30% by weight based on the solid content of the primer resin. Is preferred. When the amount of the tin compound added is less than 0.5% by weight, the amount of tin is small and the reaction with the chlorohydrin body and chlorine is not sufficiently performed, so that the effect of preventing yellowing of the coating film is small. If it exceeds 30% by weight, blisters (coating swelling) occur in the coating film after the water resistance test and the adhesion of the coating film decreases.

Further, the primer resin used in the present invention comprises a polyolefin resin or a chlorinated polyolefin resin and an epoxy resin, and preferably 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.

Examples 1 to 5 and Comparative Examples 1 to 3 have the following formulas as tin compounds.

[Chemical 4] The dinormaloctyltin malate represented by (Adecastap OT-9, manufactured by Asahi Denka Co., Ltd.) was used to prepare the primers of Examples 1 to 5 and Comparative Examples 1 to 3 with the formulations shown in Table 1. Next, polypropylene (P
P) Eight base materials (TX-1180) were degreased using isopropyl alcohol. Apply each of the above primers onto each substrate so that the dry film thickness is 5 μm,
After baking and drying at 90 ° C. for 20 minutes, a urethane-modified melamine acrylic topcoat paint was applied to give a dry film thickness of 30 μm, and baking and drying at 120 ° C. for 20 minutes to obtain a coated plate. Using these finished coated plates, a coating film performance test was conducted by the following evaluation method.

Evaluation method (1) Heat-resistant yellowing test piece was left for 240 hours in a drying oven kept at 90 ° C.,
The b value is measured 1 hour after the removal. Yellowing degree (Δb) is
It 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 A 2 mm Goban that reaches the substrate using a cutter knife. Make 100 squares (10 x 10), adhere the adhesive tape to the eyes of the bag, keep one end of the tape perpendicular to the effective surface, and instantaneously separate it at a speed of 0.5 m / s or more. Determine the adhesion of the coating film to the substrate. (3) Water resistance A test piece is immersed in deionized water or distilled water. Put in a constant temperature water bath kept at 40 ° C. for 240 hours. The film is taken out and then allowed to stand at room temperature for 1 hour, after which the coating film is tested for adhesion. The adhesion test of the coating film is in accordance with (2) above.

Table 1 shows the above evaluation results together.

[Table 1]

[0013]

As described above, according to the present invention, the composition is used as a primer in a primer composition used for forming a coating film by coating a primer and a top coat on a polypropylene base material. Since the tin compound represented by [Chemical Formula 3] is preferably added in an amount of 0.5 to 30% by weight based on the solid content of the primer resin, (1) yellowing of the coating film on the polypropylene base material can be prevented, (2) It is possible to increase the use of light colors, (3) it is possible to divert inexpensive additives, and it is possible to reduce the cost of the polypropylene base material.

Claims (2)

[Claims] 1. A primer composition used for forming a coating film by coating a primer and a topcoat paint on a polypropylene substrate, which contains a polyolefin resin or a chlorinated polyolefin resin and an epoxy resin as resin components. , And the following formula A yellowing-free primer composition for automobiles, characterized in that it contains a tin compound represented by the formula (R ₁ and R ₂ are alkyl groups and R ₃ and R ₄ are laurate, malate or mercaptide groups). object. 2. The non-yellowing for automobile according to claim 1, wherein the tin compound represented by [Chemical formula 1] is contained in an amount of 0.5 to 30% by weight based on the solid content of the primer resin. Primer composition.