JPS5847413B2 - Molding resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a polypropylene resin composition with excellent paintability and printability.

More specifically, by introducing reactive active groups onto the surface of chemically inert polypropylene molded products without impairing the original physical properties of the base polypropylene, secondary processing such as painting and printing can be easily performed. The purpose of this invention is to provide a molding resin composition that can be used for molding.

Conventionally, polypropylene resin has been widely used in industry because it is cheap, easy to mold, and has excellent mechanical properties. However, polypropylene resin has polar groups or reactive active groups in its molecular structure. Moreover, it is difficult to perform secondary processing such as painting and printing because it does not have any oxidation properties and has poor solubility in solvents.

When performing secondary processing on the surface of a polypropylene molded product as described above, attempts have been made to improve the affinity of the surface of the polypropylene molded product with paints and inks by applying various surface treatments to the surface of the polypropylene molded product. There is.

For example, for printing, fire treatment and corona discharge treatment are generally performed, but these methods limit the shape of the molded product and have problems such as insufficient sustainability of the surface activity obtained. Furthermore, these surface treatment methods cannot be applied to painting because they have drawbacks such as the inks that can be used are limited.

In addition, for painting, methods such as treating the surface of polypropylene molded products with chromic acid monosulfuric acid or organic solvents such as perchlorethylene are generally known, but these methods require the use of powerful chemicals and are difficult to operate. However, it is not practical because it is complicated and expensive.

On the other hand, in terms of paints, polypropylene paints that do not require surface treatment as mentioned above have been developed, but there are two types of paints: one that uses a resinous primer for the undercoat, and one-coat paint that does not require a primer. However, the former method has the disadvantage that the primer is expensive and therefore the coating cost is high, and the adhesion between the polypropylene and the paint is insufficient, which poses a practical problem.

Also, the latter paint, which does not require a primer, is a special paint.
The problem is that the gloss of the coating film and the moisture resistance and gasoline resistance of the coating film are limited, and it is not sufficient for practical use.

In order to impart affinity to polypropylene resins, attempts have been made to copolymerize active comonomers such as acrylic acid, vinyl acetate, methyl methacrylate, etc., but molded products of these modified polypropylenes are It cannot be painted with paint, and its physical properties are significantly different from those of original polypropylene, making it unsuitable for practical use.

As described above, there is still no known method for painting the surface of a polypropylene molded article with an ordinary paint.

The object of the present invention is to obtain polypropylene molded articles having a modified surface that can be painted with ordinary paints without surface treatment.

The present inventors are currently studying various methods for surface modification of polypropylene and molded products. Conventionally, it has been thought that there is no compatibility and if the molded product is mixed and molded, the surface of the molded product will peel off, making it impossible to obtain a molded product that can be used in practical use. It was discovered that even when polypropylene and polystyrene were mixed in the presence of a styrene-butadiene copolymer, the layers did not peel off, and when a polymer with a functional group was added, the surface of the shaped product was significantly modified. , the paintability of not only thermoplastic paints but also paints containing thermosetting resins is improved, and the molded product according to the present invention can be coated without surface treatment or without the use of a primer. The present invention was achieved by discovering that the adhesion strength of the coating film was significantly improved.

That is, the paintable polypropylene resin composition according to the present invention refers to 100 parts of crystalline polypropylene resin,
For 100 parts of the polypropylene resin consisting of 3 to 20 parts of modified polypropylene grafted with a polar monomer, 3 to 20 parts of styrene-butadiene copolymer, 5 to 20 parts of styrene resin, and styrene-butadiene copolymer. 1 to 10 polymers having compatible functional groups
It is a resin composition obtained by blending and melt-kneading parts.

Crystalline polypropylene resins herein refer to propylene homopolymers obtained by polymerizing propylene alone, and essentially crystalline polypropylene resins containing propylene and ethylene or other α-olefins with a content of 20 wt% or less in the copolymer. It is a block copolymer.

Modified polypropylene is a copolymer obtained by crafting a polypropylene homopolymer or a propylene-ethylene copolymer with at least one monomer of acrylic acid or methacrylic acid and an alkyl ester thereof.

The blending amount of modified polypropylene is polypropylene resin 10
0 parts to 3 to 20 parts, preferably 5 to 10 parts.

When the amount is less than 3 parts, it is difficult to obtain the desired coating properties, and when it is more than 20 parts, there is a drawback that heat resistance and weather resistance are impaired.

Styrene-butadiene copolymer is a generally commercially available unvulcanized thermoplastic elastomer.

The amount of styrene-butadiene copolymer is 3 to 20 parts per 100 parts of modified polypropylene-containing polypropylene resin.
parts, preferably 10 to 15 parts.

If the amount is less than 3 parts, the dispersion of the styrene resin will be poor when it is blended, and delamination will occur in molded products from the mixture, making it impossible to obtain a composition that is satisfactory in the present invention.

If the amount is 20 parts or more, a composition with satisfactory dispersibility and paintability of the styrene resin can be obtained, but there is a drawback that the heat resistance properties, which are the inherent properties of polypropylene resin, are significantly impaired.

Styrenic resins include styrene homopolymer, copolymer of styrene and methylstyrene, AS resin, and ABS.
It is resin.

The blending amount of the styrene resin is 5 to 50 parts, preferably 10 to 20 parts, per 100 parts of the modified polypropylene-containing polypropylene resin.

If the amount is less than 5 parts, it will be difficult to obtain the desired paintability, and if it is more than 50 parts, the inherent heat resistance and impact resistance of the polypropylene resin will deteriorate, and delamination will occur on the surface of the molded product.

A polymer having a functional group that is compatible with styrene-butadiene copolymerization is a (meth)acrylic having at least one kind of functional group among carboxyl functional group, hydroxy functional group, amide functional group, epoxy functional group, and amino group. It is an acid ester copolymer.

For example, carboxy-functional monomers include (meth)acrylic acid, itaconic acid, maleic acid, fumaric acid, and hydroxy-functional monomers include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, and amide. Acrylamide as a functional monomer,
The epoxy functional monomer is glycidyl methacrylate, methylglycidyl (meth)acrylate, and the amino group-functional heptamer is diethylaminoethyl methacrylate or diethylaminomethyl (meth)acrylate.
It is a copolymer containing (meth)acrylic acid ester, styrene, α-methylstyrene, and acrylonitrile as other components.

For producing the novel polypropylene resin composition according to the present invention, a Banbury type mixer or a twin-screw extruder with a large kneading effect is used.

The resin composition obtained by melt-kneading can be molded by any molding method such as an injection molding machine, an extrusion molding machine, or a blow molding method.

There is no problem in adding inorganic fillers such as calcium carbonate, talc, mica powder, or wood flour to the resin compound according to the present invention, and the rigidity and heat resistance properties can be improved by adding these ingredients.

The molded product made of the polypropylene resin composition according to the present invention described in detail above can be painted without the need for complicated pretreatment unlike ordinary polypropylene resin molded products. The value is extremely large.

Specific examples will be introduced below using Examples.

Parts and percentages are by weight unless otherwise specified.

Example 1 Modified polypropylene with 5.5% acrylic acid content per 100 parts of crystalline propylene-ethylene copolymer (melt flow index 8.0) with 8.0% ethylene content
100 parts of polypropylene resin (melt flow index 20.0), 10 parts of styrene-butadiene copolymer (manufactured by Asahi Kasei Corporation, Toughprene-A), 10 parts of polystyrene (melt flow index 1.0), and 15% glycidyl methacrylate. , a functional copolymer consisting of 50% styrene, 25% methyl methacrylate, and 10% butyl (meth)acrylate.
,0 0 0) 3 parts and 2,6-ditertiarybutyl para-cresol, 4,4'thiobis(
0.15 parts of each of 6-tert-butyl-m-cresol-containing calcium stearate dilauryl thiopropionate was added to the polypropylene resin, mixed for 3 minutes with a Henschel mixer, and then heated to a temperature of 190~190°C with a twin-screw extruder. 21
It was extruded and pelletized at 0°C.

From this pellet, a test piece of 80 x 160 x 2 was formed using a screw in-line injection forming machine and painted using Kawakami Paint High Plus 150 without any special pre-treatment.The results are shown in Table 1 as a comparative example ( The results are shown in comparison with those containing no styrene-butadiene copolymer, styrene resin, or polymer having a functional group.

Example 2 In Example 1, methacrylic 5 was used as the functional copolymer.
%, 60% methyl methacrylate, and 35% 2-ethylhexyl (meth)acrylate (molecular weight Mw = 12,000), except that a test piece was prepared in the same manner as in Example 1. was molded and painted.

The peeling test of the paint film is 100/100, DuPont impact test (
-10°C) was 140 to 150 ky- on the painted surface and 60 to 70 ky- on the painted back side.

Examples 3 to 6 In Example 1, the styrene-butadiene copolymer was
The test piece was shaped and painted in the same manner as in Example 1 except as shown in 2.

Table 2 shows the bending test results and coating results for the material.

Claims (1)

[Claims] 1. For 100 parts of crystalline polypropylene resin, 3 to 20 parts of modified polypropylene resin obtained by graft polymerizing at least one monomer of acrylic acid, methacrylic acid, and their alkyl esters to polypropylene resin, 3 to 20 parts of styrene-book diene copolymer, 5 to 5 parts of styrene resin
0 part, and a (meth)acrylic acid ester having at least one functional group of carboxy functional group, hydroxy functional group, amide functional group, epoxy functional group, and amino group that is compatible with the styrene-butadiene copolymer. Polymer 1
-10 parts of a resin composition for molding.