JPH04261450A - Polypropylene resin composition with excellent coatability - Google Patents

Abstract

PURPOSE:To provide the title composition excellent in adherability to coatings, without the need for etching treatment with the vapor of an organic solvent such as trichloroethane, plasma treatment, etc. CONSTITUTION:The objective composition can be obtained by incorporating (A) 100 pts.wt. of polypropylene with (B) 20-100 (pref. 23-60) pts.wt. of a hydrogenated styrene-isoprene triblock copolymer elastomer >=10g/10min in the melt index under a load of 2.16kg/cm<2> at 230 deg.C.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides excellent paint adhesion without the need for etching treatment using vapor of organic solvents such as trichloroethane, plasma treatment to oxidize the surface, flame treatment, etc. after molding. The present invention relates to a polypropylene resin composition.

0002

2. Description of the Related Art Polypropylene resin compositions have come to be used in place of metal materials for exterior panel materials such as bumpers and fenders of automobiles. Polypropylene has extremely poor paintability as it is, so it is usually coated after etching with organic solvent vapor such as trichloroethane, plasma treatment to oxidize the surface, flame treatment, etc. Among these treatment methods, after etching the surface with trichloroethane vapor, a primer containing chlorinated polyolefin is applied in advance, heated and dried, and then paint is applied and heated to harden. It is also the cheapest and most easily used. However, in recent years, highly volatile and chemically stable chlorine compounds such as trichloroethane are difficult to decompose even after being released into the atmosphere, and when they diffuse into the ozone layer that surrounds the earth, they can cause problems such as ultraviolet rays emitted by the sun. It is said that this destroys ozone molecules, which absorb light, and as a result, the amount of harmful ultraviolet rays that fall on the ground increases, increasing the frequency of skin cancer and other diseases. Against this background, regulations are being implemented in Western countries to reduce the amount of chlorinated organic solvents such as trichloroethane used on a global scale. However, other methods that do not use trichloroethane, such as plasma treatment, require large equipment and require a great deal of expense to construct equipment to treat large items such as automobile bumpers. If flame treatment is applied to the surface of a combustible resin, there is a risk that the thin parts will melt or catch fire, resulting in a poor yield. In addition, in the case of flame treatment, the part of the oxidizing flame that oxidizes the surface of polypropylene cannot be made very large, and if the shape of the object to be treated is complex, there will be parts where the flame does not reach sufficiently, resulting in the paint film after painting. The problem is that the adhesion strength of thermoplastic resins is abnormally low, and the shapes that can be used are limited to those that are almost flat. The advantage of being able to manufacture products is lost.

On the other hand, block copolymers of styrene and conjugated diene or hydrogenated products thereof have been proposed to be used as impact modifiers for styrene-based resins and polyolefin-based resins (for example, JP-A-58 -215446
, JP-A-60-133039, JP-A-61-0142
48, JP-A-01-174550, etc.)
. However, commonly used styrene-butadiene block copolymers, styrene-isoprene copolymers, or their hydrogenated products have high viscosity, and when they are mixed with polypropylene, mechanically kneaded, and then injection molded, the surface layer of the molded product The rubber layer exists in the polypropylene layer in a nearly spherical shape. Therefore, even if the solvent contained in the paint penetrated into the surface layer, the surface area of the rubber layer was not high, so it did not contribute much to improving the paintability.

0004

[Problem to be solved by the invention] That is, the present invention
By providing a polypropylene resin composition that provides excellent paint adhesion without the need for etching treatment using vapor of an organic solvent such as trichloroethane, plasma treatment to oxidize the surface, flame treatment, etc. after molding. be.

[0005]

[Means for Solving the Problems] As a result of intensive research in order to solve the above-mentioned problems, the present inventors have discovered that hydrogenation of a block copolymer consisting of styrene and butadiene or isoprene with a specific viscosity to polypropylene It has been found that the adhesion strength of the coating film can be sufficiently strong for practical use without etching the surface with vapors such as trichloroethane.

That is, the present invention provides polypropylene 100
A coating comprising 20 to 100 parts by weight of a hydrogenated styrene-isoprene triblock copolymer elastomer having a melt index of 10 g/10 minutes or more when measured at 230°C and a load of 2.16 kg/cm2. It is a polypropylene resin composition with excellent properties.

In the present invention, homopolypropylene and copolymers with olefin monomers such as ethylene can be used as the polypropylene, but homopolypropylene is particularly preferred because of its excellent rigidity, heat resistance, and surface brightness. Further, since the ethylene-propylene block copolymer has excellent impact strength, part or all of the homopolypropylene used may be replaced with the ethylene-propylene block copolymer, if necessary. Furthermore, other resins such as high-density polyethylene, low-density polyethylene, linear low-density polyethylene, polybutene, etc. may be blended in addition to polypropylene as long as impact strength and surface hardness are not significantly reduced.

The hydrogenated styrene-isoprene triblock copolymer elastomer used in the present invention is obtained by hydrogenating a triblock copolymer (St-Is-St) of styrene (St) and isoprene (Is), and mainly It is an elastomer in which the unsaturated bonds of the isoprene block are hydrogenated.
The melt index measured at 230°C and a load of 2.16 kg/cm2 is 10 g/10 minutes or more, preferably 15 to 70 g/10 minutes, more preferably 20 to 50
g/10 minutes. If the elastomer has a melt index of 10 g/10 minutes or less, even if it is blended with polypropylene and a molded product is obtained by a method such as injection molding, the adhesive strength will be low because the elastomer will not become fibrous or layered in the surface layer. inferior to The amount of styrene constituting the hydrogenated styrene-isoprene triblock copolymer elastomer used in the present invention is preferably 10% or more;
If the amount of styrene is less than 0%, the adhesion strength with the paint is insufficient.

The blending amount of the hydrogenated styrene-isoprene triblock copolymer elastomer used in the present invention is as follows:
The amount is 20 to 100 parts by weight, preferably 20 to 80 parts by weight, and more preferably 23 to 60 parts by weight, based on 100 parts by weight of polypropylene. If it is less than 20 parts by weight, sufficient adhesion strength of the paint cannot be obtained. , for over 100 copies,
The heat resistance of the resin composition is extremely low, and it may become deformed when heated and dried after coating.

Further, in the resin composition of the present invention, an appropriate amount of an elastomer other than the hydrogenated styrene-isoprene triblock copolymer elastomer may be used. For example, butadiene elastomer, isoprene elastomer, chloroprene elastomer, ethylene-propylene elastomer, ethylene-propylene terpolymer, butyl elastomer, acrylic elastomer, tetrafluoroethylene perfluoromethyl ether elastomer, fluorosilicone elastomer, epichlorohydrin elastomer, Polysulfide elastomer, ethylene-butene copolymer elastomer, styrene-butadiene diblock copolymer elastomer, styrene-butadiene diblock copolymer elastomer, styrene-isoprene diblock copolymer elastomer, styrene-isoprene triblock copolymer Elastomer, hydrogenated styrene-butadiene diblock copolymer elastomer, hydrogenated styrene-
Examples include butadiene diblock copolymer elastomer, hydrogenated styrene-isoprene diblock copolymer elastomer, and the like.

[0011] In addition to the resin components, additives may be added to the resin composition of the present invention, if necessary. for example,
Additives include antioxidants, dispersants, ultraviolet absorbers, antistatic agents, pigments, dyes, crystallization promoters, lubricants, flame retardants, plasticizers, and the like.

The polypropylene resin composition of the present invention is mixed in a ribbon blender, Henschel mixer, etc. in the same way as ordinary polypropylene resin compositions, and then melt-kneaded in an apparatus such as a Banbury mixer, heated roll, extruder, co-kneader, etc. After making it into pellets, it can be extruded into a sheet using an extruder, followed by secondary molding using methods such as vacuum forming, pressure forming, vacuum pressure forming, press molding, blow molding, injection molding, etc. .

[0013] In the method of the present invention, the above-mentioned processed product may be washed directly or simply with an aqueous solution of an alcohol, an acid or alkali, or an aqueous solution of a surfactant, and then painted with a paint. It may be treated with a primer and painted with paint. However, sufficient adhesive strength can be obtained without the need for etching treatment using vapors of organic solvents such as trichloroethane, plasma treatment to oxidize the surface, flame treatment, etc., which have conventionally caused problems in processes including painting.

[0014]

[Example] The present invention will be explained in detail below using Examples.

Examples 1 to 3 "Mitsui Noblen JH-G" as homopolypropylene
(manufactured by Mitsui Toatsu Chemical Co., Ltd., MI 4 g/10 minutes), hydrogenated styrene-isoprene triblock copolymer elastomer "Septon 2002" [manufactured by Kuraray Co., Ltd., MI 30 g/10 minutes, styrene amount 30% by weight] were blended in the composition ratio shown in Table 1, mixed with a Henschel mixer, and then pellets were obtained with a 35 mm twin-screw extruder.
80mm x 15 in an injection molding machine with a mold clamping pressure of 100 tons
Form a plate of 0mm x 2mm and use it as a primer.
RB-115” (manufactured by Nippon B-chemi Co., Ltd.) from 20 to
Apply it to a thickness of 50μ and dry at 80℃ for 30 minutes.
As a paint, "U-040" (alkyd paint, manufactured by Nippon Paint Co., Ltd.) was applied to a film thickness of 40 to 80 μm and heated at 120° C. for 60 minutes. After 48 hours, a checkerboard peel test was conducted to measure the adhesion strength of the coating film, and the coating film was cut into strips with a width of 10 mm and the peel strength was measured using a tensile tester. Further, a paint was applied in the same manner except that no primer was applied, and evaluation was made in the same manner. The cross-cut peel test and peel strength measurements were sufficient for practical use. The results are shown in Table-1.

Examples 4 to 6 Examples 4 to 6 except that a portion of the homopolypropylene used in Example 1 was replaced with an ethylene-propylene block copolymer (ethylene content 8%) with an MI of 8 g/10 min. A primer and a paint were applied in the same manner as in 1, and the adhesion strength of the paint film was evaluated. The cross-cut peel test and peel strength measurements were sufficient for practical use. Table 1 shows the results.
Shown below.

Comparative Example 1 A plate was formed using the homopropylene used in Example 1 in the same manner as in Example 1, and a coating was applied to the plate to evaluate the adhesion strength of the coating film. The measured values of the cross-cut peel test and peel strength were extremely low and not suitable for practical use. The blending ratio and results are shown in Table-1.

Comparative Example 2 Ethylene-propylene elastomer "EP 02P" (manufactured by Nippon Gosei Rubber Co., Ltd., MI) was used instead of the hydrogenated styrene-isoprene triblock copolymer elastomer.
A plate was molded in the same manner as in Example 1, except that 30% by weight of 3.5) was used, a paint was applied, and the adhesion strength of the paint film was evaluated. The measured values of the cross-cut peel test and peel strength were too low to withstand practical use. Table 1 shows the blending ratio and results.
Shown below.

Comparative Example 3 "Septon 2" was used instead of the hydrogenated styrene-isoprene triblock copolymer elastomer used in Example 1.
043″ (manufactured by Kuraray Co., Ltd., MI 2.7g/1
A plate was formed in the same manner as in Example 1, except that 25% by weight of styrene (styrene content: 13% by weight) was used, a coating was applied, and the adhesion strength of the coating film was evaluated. The measured values of the cross-cut peel test and peel strength were too low to withstand practical use. The blending ratio and results are shown in Table-1.

Comparative Example 4 95% by weight of homopolypropylene, hydrogenated styrene
A plate was molded in the same manner as in Example 1, except that the amount of isoprene triblock copolymer elastomer was 5% by weight, and a coating was applied to evaluate the adhesion strength of the coating. The measurements of the cross-cut peel test and peel strength showed that the amount of elastomer was insufficient and the adhesion strength of the paint was low, making it unsuitable for practical use. The blending ratio and results are shown in Table-1.

Comparative Example 5 In place of the hydrogenated styrene-isoprene triblock copolymer elastomer used in Example 1, a hydrogenated styrene-butadiene triblock copolymer elastomer was used as "Krayton G-1652" (Shell Chemical Co., Ltd.).
manufactured by MI 1.9g/10 min, styrene content 29
A plate was molded in the same manner as in Example 1 except that 25% by weight of 25% by weight was used, a paint was applied, and the adhesion strength of the paint film was evaluated. The measured values of the cross-cut peel test and peel strength were too low to withstand practical use. The blending ratio and results are shown in Table-1.

Reference Example The surface of the plate used in Comparative Example 2 was treated with trichloroethane vapor for 60 seconds, and a paint was applied in the same manner as in Example 1 to evaluate the adhesion strength of the paint film. The measured values of the grid peel test and peel strength were almost suitable for practical use. The blending ratio and results are shown in Table-1.

[0023]

[Table 1]

[0024]

Effects of the Invention The resin composition of the present invention does not require etching with vapors such as trichloroethane, plasma treatment, or flame treatment, which have been indispensable in conventional coating of molded articles made of polypropylene resin compositions. Furthermore, even without the use of a primer, adhesion strength sufficient for practical use can be obtained between the paint and the paint. Therefore, if the resin composition of the present invention is used, trichloroethane, which can destroy the ozone layer in the upper layer of the earth's atmosphere, is not used, so the coating method poses almost no problem in terms of environmental safety. Furthermore, since a method such as plasma treatment that does not require a batch-type coating process can be used, the amount of coating does not decrease and the coating cost does not increase. Furthermore, unlike flame treatment, the flexibility of molding shape inherent to thermoplastic resins is not lost.

Claims (2)

[Claims] Claim 1: 100 parts by weight of polypropylene,
Excellent paintability characterized by comprising 20 to 100 parts by weight of a hydrogenated styrene-isoprene triblock copolymer elastomer with a melt index of 10 g/10 minutes or more measured at 230°C and a load of 2.16 kg/cm2. polypropylene resin composition. 2. The polypropylene resin composition with excellent paintability according to claim 1, wherein the polypropylene is homopolypropylene.