JPH0559250A - Polypropylene resin composition excellent in surface hardness and impact resistance - Google Patents

Abstract

PURPOSE:To prepare a polypropylene resin compsn. excellent in surface hardness and impact resistance. CONSTITUTION:A polypropylene resin compsn. is prepd. by compounding 100 pts.wt. isotactic ethylene-propylene block copolymer (A), 9-56 pts.wt.ethylene- butene-1 copolymer elastomer (B), 9-56 pts.wt. ethylene-propylene copolymer elastomer (C) having a propylene content of 15-24wt.%, and 0-50 pts.wt. inorg. filler (D), the wt. ratio of component B to component C being 7:3-3:7.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene resin composition which has excellent surface hardness and impact resistance and is suitable as an exterior material for automobiles and the like.

[0002]

2. Description of the Related Art Polypropylene resin compositions have been used in place of metal materials for exterior materials such as automobile bumpers and fenders. Since polypropylene is insufficient in impact strength as it is, ethylene-propylene elastomer (EPM, EPDM) or the like is added for improvement. To increase the flexural modulus, a plate-like or fibrous inorganic filler such as talc is added for improvement. Further, polypropylene is a crystalline resin and has a high molding shrinkage and a high linear expansion coefficient, but in order to lower it, an elastomer such as ethylene-propylene elastomer (EPM, EPDM) and a plate-like or fibrous inorganic filler such as talc are used. Is added to improve.
However, ethylene-propylene elastomer (EP
(M, EPDM) and the like are generally mixed with polypropylene, there is a drawback that the surface hardness is lowered and scratches easily occur. If the blending amount of the elastomer is reduced, the surface hardness increases but the impact strength decreases, which is unsuitable for exterior materials such as automobiles. Further, when the elastomer component is reduced, there is a drawback that the coating property is reduced, such as the adhesion to the coating is reduced. When the blending amount of inorganic filler such as talc is increased, the bending elastic modulus is increased but the surface hardness is not increased, and depending on the kind of the filler, the surface hardness may be decreased, which is not so effective in increasing the surface hardness. .. Further, when a large amount of an inorganic filler such as talc is mixed with polypropylene, there is a drawback that impact strength is lowered.

In order to improve the surface hardness of the polypropylene resin composition, a method of dispersing another hard resin in polypropylene can be considered. For example, it is possible to compound polypropylene with a styrene resin, but polypropylene and polystyrene have poor compatibility with each other, and a styrene-butadiene elastomer, a styrene-isoprene diblock elastomer, a styrene-isoprene triblock elastomer, or these elastomers are hydrogenated. It is necessary to improve the impact strength by adding a styrene-based elastomer such as an added elastomer, and various resin compositions have been proposed (for example, JP-A-58-210950 and JP-A-6-206950).
0-1333039, JP-A-01-174550, JP-B-62-34782, JP-B-62-12812, and JP-A-6-62.
3-277261). A resin composition prepared by blending polypropylene with a styrene block copolymer elastomer has also been proposed (for example, JP-A-61-124848).
etc). Further, a bumper made of polypropylene and hydrogenated styrene-butadiene elastomer (Japanese Patent Laid-Open No. 58-2
10950), a resin composition in which an ethylene-propylene elastomer and talc are used in combination with a styrene-based elastomer (Japanese Patent Laid-Open No. 61-291247), a highly crystalline homopolypropylene having excellent rigidity and a hydrogenated styrene-isoprene block. A resin composition composed of a copolymer elastomer (Japanese Patent Laid-Open No. 156842/1988) has been proposed. However, in order to obtain the impact strength required as an exterior material for automobiles by adding a styrene-based elastomer to a resin composition composed of polypropylene and polystyrene, it is necessary to add a large amount of the elastomer, and as a result, the resin composition Surface hardness is reduced.

It has also been proposed to crosslink an ethylene-α-olefin elastomer to obtain a tough resin composition. (For example, JP-A-60-173032, etc.) However, these crosslinked elastomers cannot use a resin composition excellent in surface hardness because they use a large amount of ethylene-propylene-diene elastomer (EPDM).
On the other hand, a resin composition using an ethylene-butene-1 copolymer elastomer together with an ethylene-propylene-diene copolymer is disclosed in JP-A-60-4041, but ethylene-propylene-diene copolymer is often used. Too low surface hardness. Further, the ethylene-butene-1 copolymer elastomer had a higher glass transition temperature (Tg) and was inferior in low temperature impact strength as compared with the ethylene-propylene copolymer elastomer. In order to supplement it, it is advisable to add an ethylene-propylene copolymer elastomer.
When the propylene copolymer elastomer was added to the ethylene-butene-1 copolymer elastomer, the Rockwell hardness rapidly decreased, and no one having excellent low temperature impact strength and surface hardness was obtained.

[0005]

That is, the present invention is
It is to provide a polypropylene resin composition having excellent low temperature impact strength and surface hardness.

[0006]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that an ethylene-propylene copolymer elastomer having a specific propylene content and an ethylene-butene-1 copolymer The present inventors have found that when a polymer elastomer is used in combination with isotactic polypropylene, the Rockwell hardness is less reduced and the low temperature impact strength is excellent.

That is, the present invention comprises 100 parts by weight of an isotactic ethylene-propylene block copolymer (A) and an ethylene-butene-1 copolymer elastomer (B).
9-56 parts by weight, propylene content 15-24 wt%
Ethylene-propylene copolymer elastomer (C) 9-56 parts by weight and inorganic filler (D) 0-5
A polypropylene resin, which comprises 0 parts by weight, and the ratio of the ethylene-butene-1 copolymer elastomer (B) and the ethylene-propylene copolymer elastomer (C) is in the range of 7: 3 to 3: 7. It is a composition.

In the present invention, an isotactic ethylene-propylene block copolymer obtained by a usual solvent polymerization method is particularly preferably used. Bulk polymerization method, obtained by a gas phase polymerization method, using an ethylene-propylene block copolymer has a low Rockwell hardness and may not be excellent in surface hardness.In that case, use a suitable solvent such as hexane or heptane. It can be improved by washing. In the present invention, the isotactic ethylene-propylene block copolymer has an ethylene content of 1 to 25% by weight, particularly preferably 3 to 15% by weight, when the isotactic ethylene-propylene block copolymer is used, surface hardness and impact strength are improved. Excellent and preferable.

As the isotactic ethylene-propylene block copolymer used in the method of the present invention, a commercially available product is used, and particularly, the melt index thereof is 0.5.
It is preferable that the melt index is about 40 to 100 by a so-called thermal treatment in which the melt index of 50 to 50 is heated in the presence of a peroxide. Polypropylene having a melt index of 40 or more produced by ordinary polymerization has a small tensile elongation at break, and a large amount of ethylene-propylene copolymer elastomer is required in order to obtain sufficient elongation and impact strength for molded articles such as automobile bumpers. It is necessary to add a large amount, resulting in low rigidity and hardness.

Melt index before degrading is 0.5
If the following materials are used, flow marks are likely to occur in the injection-molded product, which is not preferable. Even if 50 or more materials are thermally degraded and used, elongation and breakage do not become large. A composition using a melt index after degrading of less than 40 has poor melt flowability and is liable to have poor weld strength. When it is 100 or more, flow marks are likely to appear in an injection molded product.

The thermal degradation method can be easily carried out by a known method of heating in the presence of a peroxide, for example, the method described in JP-A-61-233047.

Further, in addition to the isotactic ethylene-propylene block copolymer, high-density polyethylene, low-density polyethylene, ultra-low-density polyethylene, ethylene-acetic acid vinyl ester can be used as long as impact strength and surface hardness are not significantly reduced. Other resins such as copolymers, ethylene-ethyl acetate copolymers, linear low-density polyethylene, and polybutene may be blended.

In the present invention, an ethylene-butene-1 copolymer elastomer is used, but in order to obtain excellent surface hardness and impact strength, an ethylene-butene-1 copolymer having a butene-1 content of 10 to 30 wt% is used. A coalesced elastomer is most suitable, and when an ethylene-butene-1 copolymer elastomer having a butene-1 content of 30 wt% or more is used, the surface hardness is remarkably reduced, which is not preferable. On the contrary, it is not preferable to use an ethylene-butene-1 copolymer elastomer having a butene-1 content of less than 10 wt% because the impact strength is remarkably reduced.

The ethylene-propylene copolymer elastomer used in the present invention has a propylene content of 15 to 24 w.
Use t%. An ethylene-propylene copolymer elastomer in this range is preferable because it has a good balance between surface hardness and impact strength. With an ethylene-propylene copolymer elastomer of 15 wt% or less, the impact strength is inferior, and 24
In the case of an ethylene-propylene copolymer elastomer of wt% or more, the surface hardness decreases when added in a large amount until the low temperature impact strength is sufficiently improved.

In the present invention, the ratio of the ethylene-butene-1 copolymer elastomer to the ethylene-propylene copolymer elastomer is 7: 3 to 3: 7, which is higher than the ethylene-propylene copolymer elastomer. And the surface hardness is greatly reduced, and if it is less than this, the low temperature impact strength is poor.

In the present invention, the added amount of the ethylene-propylene copolymer elastomer and the ethylene-butene-1 copolymer elastomer is the above-mentioned ethylene-propylene copolymer elastomer and the ethylene-butene-1 copolymer elastomer. 9 to 56 per 100 parts by weight of isotactic polypropylene in the range of the ratio of the added amount of elastomer.
Add parts by weight. Preferably, the total amount of the ethylene-propylene copolymer elastomer and the ethylene-butene-1 copolymer elastomer added is 40 to 80 parts by weight. Even if 9 parts by weight or less of any one of them is added within the range of the ratio of addition of each elastomer described above, the low temperature impact strength is low and it is unsuitable as an exterior material for automobiles.
Further, if 56 parts by weight or more of each of the elastomers is used within the range of the ratio of the addition amount of each elastomer described above, the heat resistance and the rigidity are insufficient even if a large amount of the inorganic filler is used, resulting in an automobile It is unsuitable as an exterior material.

The composition of the present invention is particularly useful as a resin for automobile bumpers. In recent years, automobile bumpers are required to have a sense of unity with the hood of a vehicle and to have a high-quality coating. If such a part has a flaw on its surface, its commercial value is reduced and it is not suitable for use. As a resin for automobile bumpers, it has a Rockwell hardness of 55 or more and an Izod impact strength of -30 ° C of 5 kg · cm / cm.
The above are materials that have a low embrittlement temperature and impact strength as compared with conventional automobile bumper materials that use only ethylene-propylene copolymer elastomer as the elastomer component, but have a higher impact hardness and surface hardness. Is obtained.
To obtain a material having such surface hardness and impact strength, isotactic ethylene-propylene block copolymer 10
It is particularly preferable to mix 35 to 45 parts by weight of each of the ethylene-propylene copolymer elastomer and the ethylene-butene-1 copolymer elastomer with 0 part by weight.

As the inorganic filler used in the present invention,
Metal powder, carbon black, graphite, carbon fiber,
Silica, alumina, titanium oxide, iron oxide, zinc oxide, magnesium oxide, tin oxide, antimony oxide, barium ferrite, strontium ferrite, aluminum hydroxide, magnesium hydroxide, calcium sulfate, barium sulfate, talc, clay, mica, calcium silicate , Glass fiber, calcium titanate, lead zirconate titanate, aluminum nitride, silicon carbide, and the like. Particularly, talc, fibrous magnesium sulfate, and calcium titanate are excellent in the smoothness of the surface of the molded article and have a flexural modulus. It is preferable to increase. In the present invention, the inorganic filler is blended in an amount of 0 to 50 parts by weight based on 100 parts by weight of isotactic polypropylene. When it is 50 parts by weight or more, the impact strength of the polypropylene resin composition is remarkably lowered, and the surface hardness is lowered in some cases.

In the present invention, when the flat plate filler and the fibrous filler are used together, particularly when talc and the magnesium sulfate whisker are used together, the tensile elongation at break, the flexural modulus, etc. are improved as compared with the case where only the flat plate filler is used. It is preferable because the rigidity and impact strength are large, and the problem of "warpage" of the molded product is less likely to occur as compared with the case where only the fibrous filler is used.

If desired, various additives may be added to the resin composition of the present invention. Examples thereof include antioxidants, dispersants, ultraviolet absorbers, antistatic agents, pigments, dyes, crystallization accelerators, lubricants, flame retardants, plasticizers and the like.

The polypropylene resin composition of the present invention is mixed by a ribbon blender, a Henschel mixer, etc., and then melt-kneaded in a device such as a Banbury mixer, a heat roll, an extruder, a cokneader to form a pellet, and then a sheet is formed by the extruder. It is possible to use a method of secondary molding, a method of blow molding, a method of injection molding or the like by extruding into a shape, vacuum molding, pressure molding, vacuum pressure molding, press molding or the like.

[0022]

Embodiments will be described in detail below with reference to embodiments. As a method of measuring surface hardness, the Rockwell hardness (R scale) was measured by the ASTM D-785 method (two circular plates having a diameter of 50 mm and a thickness of 2 mm were used as measurement test pieces in piles) to measure the impact strength. The Izod impact strength at −10 ° C. and −30 ° C. was measured by the ASTM D-785 method (a test piece with a die notch having a thickness of 3 mm and a width of 12.5 mm was used as a measurement test piece) to obtain a melt index M.
I was measured under the conditions of 230 ° C. and 2.16 kg / cm ² .

Example 1 Isotactic ethylene-propylene block copolymer (MI 8.0 g / 10 mi obtained by a solvent polymerization method)
n, ethylene content 15 wt%) 100 parts by weight, as an ethylene-butene-1 copolymer elastomer "EBM 1
041P "(manufactured by Japan Synthetic Rubber Co., Ltd., butene-1 content 15 wt%, MI 5.8 g / 10 min) 20 parts by weight," EP961SP "as ethylene-propylene copolymer elastomer (manufactured by Nippon Synthetic Rubber Co., Ltd. , Propylene content 23 wt%, MI 0.8 g / 10 mi
n) 10 parts by weight was melt-kneaded with a 50 mm extruder to obtain pellets, and a test piece for measuring physical properties was obtained with an injection molding machine having a mold clamping pressure of 100 tons. Table 1 shows the compounding ratio of resin, melt index, Rockwell hardness, and Izot impact strength.

Comparative Example 1 A test piece for measuring mechanical properties was carried out in the same manner as in Example 1 except that 100 parts by weight of an isotactic propylene homopolymer (MI 7.5 g / 10 min) obtained by the bulk polymerization method was used. Obtained and measured the physical properties. The impact strength was not so different from that of Example 1, but the Rockwell hardness was low. Table 1 shows the compounding ratio of resin, melt index, Rockwell hardness, and Izot impact strength.

Comparative Example 2 The isotactic ethylene-propylene copolymer of Example 1 was not blended with an elastomer, and a test piece for measuring mechanical properties was molded as it was, and the mechanical properties were measured. The impact strength was significantly lower than that of Example 1. Table 1 shows the compounding ratio of resin, melt index, Rockwell hardness, and Izod impact strength.

[0026]

[Table 1] Example 2 "E" as an ethylene-butene-1 copolymer elastomer
BM 1201P "(Nippon Synthetic Rubber Co., Ltd., Butene-1)
Content 16 wt%, MI 30 g / 10 min) 45
Parts by weight, "EP01P" as an ethylene-propylene copolymer elastomer (manufactured by Japan Synthetic Rubber Co., Ltd., propylene content 22 wt%, MI 3.6 g / 10 min)
After mixing 30 parts by weight of 100 parts of the same isotactic ethylene-propylene block copolymer as in Example 1 and 15 parts by weight of "CT-8" (Talc manufactured by Asada Flour Milling Co., Ltd.) as a filler with a Henschel mixer, Melt kneading with a 50 mm extruder and in the same manner as in Example 1, a test piece for measuring mechanical properties was obtained. Table 2 shows the compounding ratio of resin and filler, melt index, Rockwell hardness, Izod.
Indicates impact strength.

Examples 3 to 5 100 parts by weight of the same isotactic ethylene-propylene copolymer as in Example 1 and 20, 25, 30 of the same ethylene-butene-1 copolymer elastomer as in Example 1 were used.
Parts by weight, 30, 25, 20 parts by weight of the same ethylene-propylene copolymer elastomer as in Example 1 and 15 parts by weight of talc as in Example 2 were melt-kneaded in the same manner as in Example 1 to form a machine. A test piece for measuring physical properties was obtained. Table-2
Shows the compounding ratio of resin and filler, melt index, Rockwell hardness, and Izod impact strength.

Comparative Example 3 100 parts by weight of the same isotactic ethylene-propylene copolymer as in Example 1, 50 parts by weight of the same ethylene-butene-1 copolymer elastomer as in Example 1, and Example 2 Using 15 parts by weight of the same talc as in Example 1, melt kneading and molding were carried out in the same manner as in Example 1 to obtain a test piece for measuring mechanical properties, and physical properties were measured. Rockwell hardness is excellent,
Low temperature impact strength was low. Table 2 shows the compounding ratio of resin and filler, melt index, Rockwell hardness, Iz.
od Indicates impact strength.

Comparative Example 4 100 parts by weight of the same isotactic ethylene-propylene copolymer as in Example 1 and 50 parts by weight of the same ethylene-propylene copolymer elastomer as in Example 1 were used as in Example 2. Melt kneading and molding were carried out in the same manner as in Example 1 using 15 parts by weight of talc, and a test piece for measuring mechanical properties was obtained, and physical properties were measured. The low-temperature impact strength was excellent, but the Rockwell hardness was low. Table 2 shows the compounding ratio of resin and filler, melt index, Rockwell hardness, Iz.
od Indicates impact strength.

[0030]

[Table 2] Example 6 Ethylene-propylene block copolymer obtained by solvent polymerization method (MI 40 g / 10 min, ethylene content 15
wt%) 100 parts by weight, 25 parts by weight each of the ethylene-butene-1 copolymer elastomer and the ethylene-propylene copolymer elastomer similar to those in Example 1, and 15 parts by weight similar to talc as in Example 2 Melt kneading and molding were carried out in the same manner as in Example 1 to obtain a test piece for measuring mechanical properties.
Table 3 shows the compounding ratio of resin and filler, melt index, Rockwell hardness, and Izod impact strength.

Comparative Example 5 100 parts by weight of the same isotactic ethylene-propylene block copolymer as in Example 6, 25 parts by weight of the same ethylene-butene-1 copolymer elastomer as in Example 1, ethylene-propylene As a copolymer elastomer, 25 parts by weight of "EP07P" (manufactured by Japan Synthetic Rubber Co., Ltd., propylene content 27 wt%, MI 0.7 g / 10 min) was used, and 15 parts by weight of talc similar to Example 2 was used. Melt kneading and molding were carried out in the same manner as in 6 to obtain a test piece for measuring mechanical properties, and the physical properties were measured. Low temperature impact strength is
There was no problem, but the Rockwell hardness was low. In Table-3,
The compounding ratio of resin and filler, melt index, Rockwell hardness, and Izod impact strength are shown.

Example 7 100 parts by weight of the same isotactic ethylene-propylene block copolymer as in Example 6, and the same ethylene-butene-1 copolymer and ethylene-propylene copolymer elastomer as in Example 1 were obtained. 25% by weight of each, as high-density polyethylene "STAFLEN E750 (C)" (manufactured by Nippon Petrochemical Co., Ltd., MI (190 ° C) 5.3 g / 10 m)
in, density 0.963 g / cm) was kneaded in the same manner as in Example 6 and molded to obtain a test piece for measuring mechanical properties. Table 3 shows the compounding ratio of resin and filler, melt index, Rockwell hardness, and Izod impact strength.

[0033]

[Table 3]

[0034]

The polypropylene resin composition of the present invention is
Has the low temperature impact strength required for exterior materials such as automobiles,
Compared with conventional molding materials composed of polypropylene, ethylene-propylene elastomer and filler, it has excellent surface hardness and excellent scratch resistance. Therefore, when used as a molding material for bumpers, fenders, etc., it is less likely to be damaged than conventional materials. Further, since the amount of the ethylene-propylene copolymer elastomer that can be used in combination is large, sufficient low temperature impact strength can be obtained even with a small amount of elastomer, and the excellent rigidity originally possessed by the isotactic polypropylene obtained by the solvent polymerization method is not so much. There is no lowering.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kotaro Suzuki 1190 Kasama-cho, Sakae-ku, Yokohama-shi, Kanagawa Mitsui Toatsu Chemical Co., Ltd. (72) Hideki Todoroki 1190 Kasama-cho, Sakae-ku, Yokohama, Kanagawa Mitsui Toatsu Kagaku Within the corporation

Claims (1)

[Claims] 1. An isotactic ethylene-propylene block copolymer (A) 100 parts by weight, an ethylene-butene-1 copolymer elastomer (B) 9 to 56 parts by weight, and a propylene content of 15 to 24% by weight. An ethylene-propylene copolymer elastomer (C) of 9 to 56 parts by weight and an inorganic filler (D) of 0 to 50 parts by weight, and an ethylene-butene-1 copolymer elastomer (B) and an ethylene-propylene copolymer elastomer. The ratio of (C) is 7:
A polypropylene resin composition characterized by being in the range of 3 to 3: 7.