JPS6142735B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for obtaining a coated polyolefin molded article that has good paintability, that is, the coating film adheres well to the molded article.

As is well known, polyolefins are widely used due to their excellent physical properties and relatively low cost.
Because there is no polar group in the molecule, the adhesiveness of the coating film is poor.
It was significantly worse than ABS resin, etc., and had the disadvantage that practical adhesive strength could not be obtained.

Conventionally, methods for improving the adhesion of polyolefin include treating the surface of polyolefin molded products with flame, corona treatment, immersion treatment with chromic acid, exposure to solvent vapor, washing with solvent, or There are surface treatment methods such as wiping, but since they require an extra step, they are not only expensive, but flame treatment can also be difficult to achieve uniformly depending on the shape of the molded product, and may impair the surface appearance. In addition, there are various practical disadvantages such as hygienic problems when using solvents.

The inventors of the present invention have conducted extensive research to overcome these drawbacks, and have thus arrived at the present invention.

The present invention uses glycidyl (meth)acrylate as 10
A coating characterized by applying a paint to a polyolefin resin molded product comprising 3 to 15 parts by weight of an ethylene-glycidyl (meth)acrylate copolymer containing ~30% by weight and 97 to 85 parts by weight of a polyolefin resin. The present invention relates to a method for manufacturing polyolefin molded products.

The polyolefin resin referred to herein is a homopolymer of α-olefin such as ethylene or propylene, a copolymer thereof, a copolymer of α-olefin and another monomer, or a mixture of these polymers. Furthermore, it also includes blends with appropriate amounts of fillers such as talc and calcium carbonate, and elastomers.

The ethylene-glycidyl (meth)acrylate copolymer as used in the present invention refers to an ethylene-glycidyl acrylate copolymer and an ethylene-glycidyl methacrylate copolymer.

The ethylene-glycidyl (meth)acrylate copolymer is produced, for example, by a known high-pressure radical polymerization method.

In the present invention, ethylene-glycidyl (meth)
If the glycidyl (meth)acrylate content in the acrylate copolymer is less than 10% by weight, the effect on paintability will be insufficient, and if it exceeds 30% by weight, the compatibility with the polyolefin resin will deteriorate. Undesirable.

Furthermore, if the amount of the ethylene-glycidyl (meth)acrylate copolymer in the composition is less than 3 parts by weight, the coating performance will be insufficient, and if it exceeds 15 parts by weight, the heat resistance will deteriorate, which is undesirable. Using the molding resin thus obtained, a molded article is obtained by a conventional molding method suitable for the desired molded article, such as injection molding, extrusion molding, or blow molding.

Next, the molded article is coated with a desired coating, which can also be done in the usual manner using conventional methods such as spray coating or brush coating.

In the present invention, since the above resin is used as the molding resin, the adhesion of the coating film is good, so it has good water resistance,
Polyester-based, acrylic-based, special olefin-based paints, etc., which have good oil resistance, weather resistance, etc., can be used, and products coated with these coatings not only have initial adhesion, but also water resistance, oil resistance, and weather resistance. It is possible to obtain a coated molded product with good durability such as hardness.

This will be explained in detail below using examples.

Example 1 97% by weight of polypropylene resin copolymerized with ethylene having a melt index of 15, 20% by weight of glycidyl methacrylate and 20% by weight of a copolymer of glycidyl methacrylate and ethylene.
This was mixed with 3 parts by weight of a copolymer containing 80% by weight and having a melt index of 50, and passed through an extruder to obtain a molding resin. A plate with a thickness of 2 mm was then molded by injection molding, and without any surface treatment, the acrylic paint Micron #3000 manufactured by Kasyu Co., Ltd. was spray-painted with a spray gun and heated at 80℃. Baking was performed for 30 minutes. Use a sharp blade to make cuts in the shape of a substrate at intervals of 2 mm vertically and horizontally, and apply 24 mm cellophane tape made by Nichiban with your fingertips, and peel it off rapidly to check the adhesion of the paint film to the molded product. Examined. The coating film on the molded product was not removed by the cellophane tape at all, and the residual rate on the molded product was 100%.

Comparative Example 1 In Example 1, a plate was molded only from a polypropylene resin copolymerized with ethylene with a melt index of 15, painted in the same manner, and a sellotape peel test was performed. teeth
It was 92%.

Example 2 Homopolypropylene 80 with melt index 8
Polypropylene consisting of 20% by weight and talc
90 parts by weight and 10 parts by weight of a copolymer of ethylene and glycidyl methacrylate, consisting of 82% by weight of ethylene and 18% of glycidyl methacrylate and having a melt index of 50, were mixed and the mixture was passed through an extruder. A molding resin was obtained. A plate with a thickness of 2 mm was then molded by injection molding.

The molded product was not subjected to any surface treatment, and a special olefin paint PP-11 manufactured by Origin Electric Co., Ltd. was spray-painted on the surface as it was using a spray gun, and baked at 60° C. for 30 minutes.

The coated product was immersed in warm water at 40° C. for 70 hours, and then subjected to the cellophane tape peeling test in the same manner as in the above example. The residual rate was 100% in all peel tests.
There was no peeling at all with the Sellotape tape, and the coating adhered extremely well to the molded article.

Comparative Example 2 A plate was molded only from polypropylene in Example 2, painted in the same manner, and subjected to a cellophane tape peeling test. The remaining rate when not immersed in hot water is
60%, and 15% after soaking.

Example 3 85 parts by weight of high-density polyethylene with a melt index of 8.0 and a density of 0.955 and 15 parts by weight of the ethylene and glycidyl methacrylate copolymer used in Example 1 were blended and molded into a plate using an injection molding machine. Painting was carried out in the same manner as in 1 and a peel test was carried out, and the adhesion was good and the residual rate was 100%.

Comparative Example 3 In Example 3, a molded article was made only from high-density polyethylene, painted in the same manner, and subjected to a peel test, and the residual rate was 60%.

Claims (1)

[Claims] 1. Paint is applied to a polyolefin resin molded product consisting of 3 to 15 parts by weight of an ethylene-glycidyl (meth)acrylate copolymer containing 10 to 30% by weight of glycidyl (meth)acrylate and 97 to 85 parts by weight of a polyolein resin. A method for producing a painted polyolefin molded product, characterized by: