JPH0693143A - Thermoplastic elastomer composition - Google Patents

Abstract

PURPOSE:To obtain a compsn. which gives an infection molded article free from surface roughness and flow mark. CONSTITUTION:100 pts.wt. polymer component comprising 10-70wt.% peroxide- decomposable polyolefin resin, 20-90wt.% peroxide-decomposable polyolefin elastomer, and 0-60wt.% block copolymer of an A-(B-A) type (wherein A is a polymer block comprising arom. vinyl units; B is a polymer block comprising diene or olefin units; and n is an integer of 1-5) and 0-50 pts.wt. mineral oil softener are melt mixed in the presence of a peroxide.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermoplastic elastomer composition containing a polyolefin elastomer as a main component.

[0002] Thermoplastic elastomers do not require a vulcanization step and can be molded by an ordinary injection molding machine, and thus have been widely used for various automobile parts, household electric appliances, shoe soles and other miscellaneous goods in recent years. Has been.

As the thermoplastic elastomer, various styrene-butadiene-styrene block copolymers, thermoplastic polyurethane rubbers, polyester thermoplastic rubbers, and various polyolefin elastomers have been proposed.

.. As the one proposed as a thermoplastic polyolefin-based elastomer, for example, a peroxide cross-linkable polyolefin-based elastomer such as ethylene-propylene rubber and a peroxide-decomposable polyolefin-based resin such as polypropylene, melted in the presence of peroxide, Some are kneaded (JP-A-57-1358)
47, JP-A-59-6236).

As another polyolefin-based thermoplastic elastomer, a peroxide-crosslinking type polyolefin-based elastomer is partially crosslinked in advance with peroxide, and this is melted and kneaded with a styrene-butadiene-styrene block copolymer or polypropylene. Some of them have been made (JP-A-59-6236).

[0006]

[Problems to be solved] These polyolefin-based thermoplastic elastomers are excellent in rubber elasticity and flexibility. However, there is a problem in that it is difficult to obtain a molded product without rough skin when injection molding or extrusion molding is performed. An object of the present invention is to solve the above-mentioned problems of conventional thermoplastic polyolefin-based elastomers. That is, the present invention is a thermoplastic polyolefin-based elastomer, which is excellent not only in tensile strength at break and tensile elongation at break but also in rubber elasticity and flexibility, and injection molding easily produces a molded article with almost no rough skin. The purpose is to provide things.

The present invention relates to a thermoplastic elastomer composition obtained by melting and kneading (a) a peroxide-decomposable polyolefin resin and (b) a peroxide-decomposable polyolefin elastomer together with peroxide. In addition to the components (a) and (b) described above, the present invention also provides (c) a hydrogenated product of an A- (BA) _n type block copolymer (where A is an aromatic vinyl compound). A polymer block, B a polymer block of a diene hydrocarbon, n is an integer of 1 to 5), and / or (d) a mineral softener together with a peroxide, It also includes a thermoplastic elastomer composition obtained by kneading.

The components (a) to (d) will be described in detail below.

The component (a), which is a peroxide-decomposable polyolefin resin, is a polyolefin-based resin in which the decomposition reaction of the main chain takes precedence over crosslinking when heated and melted in the presence of peroxide. , Polypropylene, etc. are typical. Specifically, in addition to isotactic polypropylene and syndiotactic polypropylene, ethylene / propylene block copolymer, ethylene / propylene random copolymer, propylene / 1-butene copolymer, propylene / 1-hexene copolymer A resinous polyolefin-based polymer such as propylene-4-methylpentene-1 copolymer can be used. Of these polyolefin resins, isotactic polypropylene,
Particularly preferred are ethylene-propylene block copolymers and ethylene-propylene random copolymers. However,
In the ethylene-propylene block copolymer and the ethylene-propylene random copolymer, the proportion of propylene units is preferably 90 mol% or more. or,
The melt flow index (MF) is preferably in the range of 3 to 50. These polyolefin resins may be used alone or in combination of two or more.

The component (b) is a peroxide-decomposable polyolefin elastomer, which also preferentially causes the decomposition reaction of the main chain by the peroxide.
As such a material, ethylene / propylene rubber or ethylene / propylene / diene terpolymer having a propylene unit ratio of 55 mol% or more is preferable. In addition, a copolymer of propylene and C ₄ or more α-olefin, which is elastomeric, is also used. These include propylene and 1-butene, 1-hexene, and / or 4-methylpentene-1.
An elastomer or the like obtained by copolymerizing the above with a vanadium catalyst or the like is used.

The component (c) is an A- (BA) _n type block copolymer. Here, A represents a block of a polymer of an aromatic vinyl compound such as styrene, α-methylstyrene or chlorostyrene, and B represents a polymer of a diene hydrocarbon such as butadiene or isoprene, or ethylene, propylene, 1- A block of a polymer of an olefinic hydrocarbon such as butene, 1-hexene, and 4-methylpentene-1 is shown. n shows the integer of 1-5. Among these block copolymers, hydrogenated products of styrene / butadiene / styrene block copolymers and hydrogenated products of polymers such as styrene / isoprene / styrene block copolymers are particularly preferable.

As the mineral-based softening agent as the component (d), petroleum-based softening agents used as extending oils, process oils, and processing oils in the rubber industry can be used. The petroleum-based softening agent includes paraffin-based, naphthene-based, and aromatic-based softeners, and of these, the paraffin-based softener is most preferable.

In the thermoplastic elastomer composition of the present invention, the proportions of component (a) and component (b) are as follows.

The proportion of the peroxide-decomposable polyolefin resin as the component (a) is in the range of 10 to 70% by weight, preferably 20 to 60% by weight. When the proportion of the component (a) is less than 10% by weight, only a thermoplastic elastomer composition having poor mechanical properties such as tensile strength and tensile elongation at break and a low softening temperature can be obtained. Further, even if this thermoplastic elastomer composition is injection-molded, it is difficult to obtain a molded product free from rough skin and flow marks. On the other hand, when the component (a) is more than 70% by weight, a composition having rubber-like properties cannot be obtained.

The proportion of the peroxide-decomposable polyolefin elastomer as the component (b) is in the range of 20 to 90% by weight, preferably 40 to 70% by weight. (b)
When the proportion of the components is less than 20% by weight, the decomposition reaction takes precedence over the melting and kneading in the presence of peroxide, and as a result, the thermoplastic elastomer having excellent mechanical properties and high softening temperature is obtained. No composition is obtained. Further, from such a thermoplastic elastomer composition, a molded product having no rough skin or flow marks cannot be obtained. On the other hand, when the proportion of the component (b) exceeds 90% by weight, the crosslinking reaction takes precedence over the melting and kneading in the presence of peroxide, and as a result, the thermoplastic elastomer composition is poor in fluidity. I can only get it.

When the block copolymer of the component (c) is used in addition to the components (a) and (b), the proportion thereof must be 60% by weight or less. If the ratio of the component (c) is more than 60% by weight, there is a problem that a molded product without rough skin and flow marks cannot be obtained.

When the mineral-type softener as the component (d) is added, its proportion must be 50 parts by weight or less based on 100 parts by weight of the total amount of the components (a) to (c). is there.
When the ratio of the component (d) exceeds 50% by weight, the component (d) oozes onto the surface of the molded product, which causes a problem that the surface of the molded product becomes sticky.

In addition to the above, the thermoplastic elastomer composition of the present invention contains various inorganic fillers such as carbon black, calcium carbonate, calcium silicate, clay mineral, kaolin, talc, silica, alumina, titanium oxide, rouge,
Zinc white, barium sulfate, aluminum sulfate, calcium sulfate, basic magnesium carbonate, glass powder, diatomaceous earth,
Mica powder, asbestos powder and the like may be blended as necessary.

Further, various pigments may be blended. As pigments, ultramarine, navy blue, cobalt oxide, chrome yellow, red tan, lithobon, titanium white, zinc white, yellow iron oxide,
Inorganic pigments such as red iron oxide and iron black, and organic pigments such as azo pigments, nitroso pigments, lake pigments and phthalocyanine pigments are used.

Further, if necessary, an antiaging agent, a light stabilizer and the like may be added.

The thermoplastic elastomer composition of the present invention comprises
It can be obtained by melting and kneading the above components (a) to (d) in the presence of peroxide. The components (a) to (d) and the peroxide may be melted and kneaded at once, but first,
A method in which only the components (a) to (d) are preliminarily kneaded, and then peroxide is added, and the mixture is melted and kneaded is particularly preferable.

The proportion of peroxide added during melting and kneading is 0.02 to 1.00 parts by weight per 100 parts by weight of the total amount of components (a) to (d). When the proportion of peroxide is less than 0.02 part by weight, a molded product having a clean surface cannot be obtained when the obtained thermoplastic elastomer composition is injection-molded or extrusion-molded. On the other hand, when the proportion of peroxide is more than 1.00 parts by weight, a thermoplastic elastomer composition excellent in mechanical properties such as tensile strength and elongation cannot be obtained.

Examples of the peroxide which can be used in the present invention include dicumyl peroxide, di-tert-butyl peroxide, 2,5-dimethyl-2,5-di-
(Tert-Butylpaoxy) hexane, 2,5-dimethyl-2,5-di- (tert-butylpaoxy) hexyne-3,1,3-bis (tert-butylperoxyisopropyl) benzene, 1,1-bis (tert) -Butylperoxy) -2,3,5-trimethylcyclohexane, n-butyl-4,4'-bis (tert-butylperoxy) valerate, benzoyl peroxide,
2,4-dichlorobenzoyl peroxide, tert
-Butyl peroxybenzoate, tert-butyl peroxy isopropyl carbonate, diacetyl peroxide, lauroyl peroxide, tert-butyl cumyl peroxide, etc. can be mentioned.

When melting and kneading the components (a) to (d),
Further, a peroxide crosslinking aid may be added. Examples of peroxide crosslinking aids include divinylbenzene, sulfur, p-quinonedioxime, p, p'-dibenzoylquinonedioxime, N-methyl-N, 6-dinitrosoaniline, nitrobenzene, diphenylguanidine, trimethylolpropane. -N, N'-m-phenylenedimaleimide, triallyl cyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, trimethylolpropane trimethacrylate, allyl methacrylate, vinyl butyrate, vinyl stearate, etc. are used. be able to. Divinylbenzene is particularly preferable as the peroxide crosslinking aid. The amount of the crosslinking aid added is preferably in the range of 0.02 to 2.00 parts by weight based on 100 parts by weight of the total amount of the components (a) to (d).

For melting and kneading, a kneader, a Banbury mixer, an extruder, a continuous kneader,
A kneading device usually used for kneading rubber or plastic such as a roll mill or a taper roll can be used.
The most preferable of these kneading devices is an extruder.

[0026]

INDUSTRIAL APPLICABILITY In the thermoplastic elastomer composition of the present invention, when the respective components are melt-kneaded, the crosslinking reaction and the decomposition reaction due to peroxide occur in a well-balanced manner. Therefore, unlike conventional polyolefin-based thermoplastic elastomers, problems such as roughening of the molded product and generation of flow marks hardly occur. Also, it has excellent mechanical properties such as tensile strength and tensile elongation. Further, the compression set also shows an excellent value as compared with the conventional polyolefin thermoplastic elastomer.

[0027]

EXAMPLES The present invention will be specifically described below with reference to examples.

[Injection molding] In Examples and Comparative Examples,
The thermoplastic elastomer composition was injection-molded to form a plate having a thickness of 3 mm, and this plate was examined for rough skin of the molded product and the presence or absence of flow marks. The injection molding conditions were as follows. Injection molding machine: UBE MAX 10 ounces molding conditions: injection pressure 840 kg / cm ² injection temperature 180 to 200 ° C. Mold temperature 40 ° C. Mold dimensions: 360 × 140 × 3mm ^t, side one point gate [Test Method] (1) Melt Flow rate (MFR) Temperature 230 ° C, load 21 according to ASTM D1238
It was measured under the condition of 60 g. (2) Hardness Using a plate having a thickness of 3 mm obtained by injection molding under the above conditions, the hardness was measured according to JIS K6301. (3) Tensile Strength and Tensile Elongation From the above plate, a No. 3 dumbbell-shaped test piece was punched out, and the tensile strength of this test piece was measured under the conditions of a tensile speed of 500 mm / min and an interval between marked lines of 20 mm. Measurement is JIS
It was conducted according to K6301. (4) Compression set The test piece was punched out from the above plate, and four pieces were piled up, 70
The measurement was carried out at a temperature of 22 ° C. and a deformation of 25%. Measurement is J
It was performed according to IS K6301. (5) Softening temperature It was measured according to JIS K7206 Vicat softening point temperature measuring method. The load was 198 g. (6) Appearance of molded product The appearance of a 3 mm-thick plate obtained by injection molding under the above conditions was visually observed to check for the presence of roughness and flow marks. The evaluation was performed based on the following criteria. Roughness: Visually no surface roughness is observed.- ○ Even slight surface roughness is visually observed.
× Flow mark: No flow mark was visually observed ... ○ ○ Even if a few flow marks were visually observed ...
×

Examples 1 to 8 and Comparative Examples 1 to 4 Tables 1 below show Examples and Comparative Examples. The polyolefin resins, polyolefin elastomers, hydrogenated products of block copolymers, mineral additives, peroxides, and auxiliaries used in Examples and Comparative Examples are as follows. PP: Ube Industries, Ltd. ethylene / propylene block copolymer J703H (MFR = 3 g / 10
Min, ethylene content 4 mol%) EPR-1: Mitsui Petrochemical Co., Ltd. ethylene propylene rubber, Toughmer S-4030 (MRF = 0.4 g /
10 minutes, propylene content 59 mol%) EPR-2: manufactured by Japan Synthetic Rubber Co., Ltd. ethylene propylene rubber, EPO7P (Moonie viscosity ML _{1 + 4} (100
℃) = 70, propylene content 27 mol%) Hydrogenated block copolymer: Kuraray Co., Ltd. styrene / ethylene / propylene / styrene copolymer rubber (SEPS), Septon 2005 (styrene content 20)
% By weight, number average molecular weight 190,000) Mineral softener: Idemitsu Kosan Co., Ltd. paraffin oil, Dyna Process Oil PW-90 (kinematic viscosity 95 _.
54 cSt (40 ° C., average molecular weight 539) Peroxide: manufactured by NOF CORPORATION, Perhexa 2 _.
5B Cross-linking auxiliary agent: divinylbenzene (DVB) In both Examples and Comparative Examples, all components were mixed in advance with a 50-liter tumbler blender, and then a twin-screw extruder (UME44 manufactured by Ube Industries, Ltd.) was used.
Under a condition of 00 ° C. and 200 revolutions / minute, the mixture was melted and kneaded while flowing nitrogen gas in the lower part of the hopper to obtain a thermoplastic elastomer composition. This thermoplastic elastomer composition was injection-molded under the conditions described above, and the physical properties were measured. The results are shown in Table 1.

[0030]

[Table 1]

Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C08L 53/02 LLY 7142-4J

Claims (1)

[Claims] 1. (a) Peroxide-decomposable polyolefin resin: 10 to 70% by weight (b) Peroxide-decomposable polyolefin elastomer: 20 to 90% by weight (c) A- (B -A) _n- type block copolymer: 0 to 60% by weight (where A is a block of a polymer of an aromatic vinyl compound, B is a diene-based hydrocarbon or olefin-based carbonization) It represents a polymer block of hydrogen, n is an integer of 1 to 5), and (d) a mineral-based softening agent ... (a) to (c) in a total amount of 100 parts by weight. A thermoplastic elastomer composition obtained by melting and kneading 0 to 50 parts by weight in the presence of peroxide.