JPS61218650A - Thermoplastic elastomer - Google Patents

Abstract

PURPOSE:To obtain a thermoplastic elastomer having rubber elasticity (moldable similarly to thermoplastic resin giving a molded article having rubber elasticity), by compounding a specific block copolymer with a softener comprising a polybutene having a specific molecular weight. CONSTITUTION:100pts.wt. of the block copolymer of formula (A is polymer block of monovinyl-substituted aromatic hydrocarbon; B is elastomeric polymer block of conjugated diene; n is integer of 1-5) is compounded with 70-300pts. wt. of a polybutene having an average molecular weight of 700-2,500.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to thermoplastics that are characterized by rubber elasticity and flexibility, and which are extremely excellent in mechanical strength.

(Prior art) In recent years, rubber-like soft materials that do not require a vulcanization process,
Thermoplastic elastomers (hereinafter abbreviated as TPE), which have moldability similar to that of thermoplastic resins, are attracting attention and being used in fields such as automobile parts, home appliance parts, medical and food equipment parts, electric wires, and miscellaneous goods.

Currently, various types of TPEs such as polyolefin, polycrethane, polyester, and polystyrene have been developed and are commercially available.

(Problems to be solved by the invention) However, these TPEs do not reach the level of vulcanized rubber in terms of quality in the use of vulcanized rubber, which is one of the wide application fields for rubber. Therefore, its use in the field of vulcanized rubber is extremely limited.

For example, polyolefin TPE is relatively inexpensive and has excellent heat resistance and weather resistance, but it cannot be made soft, and even the most flexible type has a JIS-A hardness (JIS K-
6301) is about 70, and the JI of general vulcanized rubber
It is still too hard compared to S-A hardness of 60. Also, JIS-
The tensile strength in the low hardness area around A hardness 70 is 25
~4 s#/y, which is considerably lower than about 100 m/- for vulcanized rubber.

Polyester TPE and polyurethane TPE are also
Even the most flexible product on the market has a JIS-A hardness of 80.
~90, it is very hard compared to vulcanized rubber and is not suitable for the field of application of vulcanized rubber.

On the other hand, styrene-butadiene-styrene block polymer (SBS) and styrene-isoprene-styrene (
Polystyrene-based TPEs such as SIS) block polymers are more flexible and have better rubber elasticity than the above-mentioned TPEs, but they do not have double bonds in the polybutadiene block or polyimprene block within the polymer. Because of this, there are problems with heat aging resistance (thermal stability) and weather resistance.

By hydrogenating the intramolecular double bonds of a block copolymer of styrene and conjugated diene, an elastomer with improved thermal stability can be obtained. The thermoplastic elastomer containing this elastomer as a rubber component is an olefin-based T
Although it is superior to PE in terms of flexibility, rubber elasticity, and strength, it has a JIS-A hardness of around 50 of 70 to c+o#/-, which is inferior to vulcanized rubber.

As a result of intensive studies aimed at developing a flexible and high-strength TPE, the present inventors discovered that a specific synthetic softener can be used as a softening agent in a thermoplastic elastomer that uses a hydrogenated derivative of sterene-butadiene polymer polymer as a rubber component. The present invention has been completed by discovering that by using a rubber agent, the rubber can be flexible and have high strength comparable to that of vulcanized rubber.

(Means for Solving the Invention) That is, the present invention provides a rubber component having the general formula A(-B-A)n [wherein A is a monovinyl-substituted aromatic hydrocarbon polymer block, B is an elastomeric polymer block of a conjugated diene, and n is an integer from 1 to 5] In a thermoplastic elastomer using a hydrogenated derivative of a block copolymer, the average molecular weight is based on ioo parts by weight of the rubber component. is 700 to 2500 polybutene 70 to 3
00 parts by weight of a thermoplastic elastomer.

(Function) The monovinyl-substituted aromatic hydrocarbon monomer constituting the polymer block A in the hydrogenated derivative of the block copolymer with the general formula A(-B-A)n of the rubber component used in the present invention is , although various ones may be mentioned, styrene and α-methylstyrene are particularly suitable. The conjugated diene monomer of polymer block B in the same formula is preferably butadiene or isoprene, and a mixture of both may be used. When butadiene is used as a single conjugated diene monomer to form polymer block B, the 1.2-microstructure in the polybutadiene microstructure is
It is preferable to adopt polymerization conditions of 0 to 50%,
Particularly suitable is one having a 1°2-microstructure of 35 to 45%. Further, the proportion of polymer block B in the copolymer is preferably at least 65% by weight.

The average molecular weight of the polymer block A is 5000 to 12
5,000, and block B is preferably in the range of 15,000 to 250,000.

The block copolymer used in the present invention is hydrogenated.

Many methods have been proposed as methods for producing hydrogenated derivatives of block copolymers having the above-mentioned general formula.
There are methods described in publications such as No. 43-6636.

In the hydrogenation during its production, at least 50%, preferably 80% or more of the olefinic double bonds in polymer block B are hydrogenated, and polymer block A
Preferably, 25% or less of the aromatic unsaturated bonds therein are hydrogenated. As such a block polymer, a commercially available polymer such as KRATON-G (trade name manufactured by Shell Chemical Co., Ltd.) can be used.

The polybutene used in the present invention is mainly composed of imbutylene, with some n-butene copolymerized, and has an average molecular weight of 700 to 2500, preferably SOO.
2000.

If the average molecular weight is less than 700, the strength and physical properties of the resulting thermoplastic elastomer will be lowered if it exceeds 2,500.

The blending ratio is 70 to 300 parts by weight, preferably ioo to 200 parts by weight, per 100 parts by weight of the aforementioned block polymer that is the rubber component.

When the blending ratio is less than 70, moldability, strength, and physical properties decrease. Moreover, if it exceeds 300 parts by weight, the strength of the obtained thermoplastic elastomer will not only decrease, but also the outer g (stickiness) of the molded product will deteriorate.

The present invention is characterized by containing a predetermined amount of these essential components when obtaining a thermoplastic elastomer. Generally, thermoplastic elastomers contain paraffin oil, paraffin oil, 100 parts by weight or less of hydrocarbon oil such as naphthenic oil; 200 parts by weight or less of polyolefin resin such as polyethylene, polycropylene, ethylene-α-olefin copolymer resin, propylene-α-olefin copolymer resin, etc.: calcium carbonate, talc 500 parts by weight or less of inorganic fillers such as mica, carbon black, etc. are blended in accordance with the target quality, and the thermoplastic elastomer of the present invention also follows this.

The method for producing the thermoplastic elastomer of the present invention can be by mechanical melt mixing. Specifically, general melt mixing machines such as Banbury Mixer 1, various types of Nigoo, and extruders can be used.

The thermoplastic elastomer of the present invention may optionally contain pigments,
Additives such as heat stabilizers, antioxidants, UV absorbers, etc. can be added.

Further, thermoplastic resin molding methods such as injection molding, extrusion molding, and blow molding are applicable.

The thermoplastic elastomer of the present invention can be used in household appliances, industrial parts such as automobile parts, foods, medical equipment parts, daily necessities, and the like.

(Example) In the Examples, the test methods used for various evaluations are as follows. However, all measurement samples were made using a 5-ounce in-line screw type injection molding machine at injection pressure s o o
It was obtained by transverse punching of a 2 trm thick sheet formed at H/d, injection temperature of 200°C, and mold temperature of 40°C.

(1) JIS-A hardness [-] JIS-6301 (2) Tensile strength [W/, [) JIS-A hardness [-] JIS-6301 (test piece No. 3) (3) Tensile elongation [%] JIS- Ni-6301 (test piece No. 3) (4) Compression set [%] JIS-6301 (70°C, 22 hours) The ingredients used in the examples are as follows.

(1) Rubber component (block polymer) Shell Chemical Co., Ltd. ! KRATON-G1651 (
Brookfield viscosity; 2000 cps in a 20% by weight toluene solution, 77 or less) (2) Polybutene component Polybutene I (V15 (average molecular weight 5) manufactured by Nippon Petrochemical Co., Ltd.
40) Same as above HVloo (average molecular weight 9
70) Same as above HV300 (average molecular weight 1
350) Same as above HV1900 (average molecular weight 2700) (3) Other polyolefin resin Mitsubishi Yuka MSPX9800 (propylene-α olefin copolymer polymer; 230'C1L16#load M
F.R.I. 09710 minutes) Paraffin oil PW90 manufactured by Idemitsu Kosan Co., Ltd. (40℃ kinematic viscosity 95゜s 4
cst) Inorganic filler calcium carbonate (average particle size 2.5 microns, higher fatty acid ester surface treatment) Example 1 Using a Banbury mixer with the formulation shown in Table 1,
The mixture was kneaded at 70° C. and 80 rpm for 10 minutes and then cut into sheets to obtain thermoplastic elastomer pellets. A sheet having a thickness of 2 cm was formed by injection molding using the pellets. The moldability was good, and the appearance of the molded product was also good.

The obtained injection molded sheet was evaluated for hardness, tensile strength, elongation, and compression set, and as shown in Table 1, the JIS-A hardness was 53-55 and the tensile strength was 110-120.
#/cd, elongation 730-790%, compression set 35-4
It was good at 0%.

Comparative examples were also examined as shown in Table 1.

As can be seen from the above Examples and Comparative Examples, it is understood that the thermoplastic elastomer of the present invention has excellent flexibility and has the strength of a vulcanized rubber group.

(Margin below)

Claims (1)

[Claims] The rubber component has the general formula A-(B-A)n [However, A in the formula is a monovinyl-substituted aromatic hydrocarbon polymer block, and B is a conjugated diene elastomeric polymer block. In a thermoplastic elastomer using a hydrogenated derivative of a block copolymer (n is an integer of 1 to 5), 70 to 3 parts of polybutene with an average molecular weight of 700 to 2,500 is added to 100 parts by weight of the rubber component.
A thermoplastic elastomer containing 0.00 parts by weight.