JPS6026428B2 - Thermoplastic elastomer composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to thermoplastic elastomeric compositions having improved properties.

More specifically, compositions with moderate hardness and improved bending resistance and tear strength are obtained by blending 1,2-polybutadiene with thermoplastic elastomers obtained by various block copolymerizations or graft copolymerizations. The present invention relates to a thermoplastic elastomer having excellent strength and rubber elasticity obtained by crosslinking this composition. Thermoplastic elastomers obtained by block copolymerization or graft copolymerization of aromatic vinyl compounds, conjugated diolefins, etc. can be molded using the same processing techniques as general thermoplastic resins. It has the advantage of not requiring any crosslinking agent formulation or heat vulcanization process, and has appropriate rubber elasticity.

However, on the other hand, the physical properties of the molded product are insufficient in hardness,
It has low tear strength and extremely poor bending resistance.
It also has drawbacks such as poor heat resistance and oil resistance.

For example, if a non-crosslinked polystyrene-polybutadiene-polystyrene flock copolymer is left in an atmosphere of 100 oo, it will soften and deform, and will not retain its original shape.
Although crosslinking is possible, there are drawbacks such as poor mechanical properties such as low tensile speed and poor heat aging resistance even if crosslinked. For this reason, these thermoplastic elastomers cannot be used, for example, when the material is subjected to repeated deformation, external force, or heat during use, and their applications have been limited to a narrow range. In order to solve these drawbacks, conventional methods include mixing and dispersing inorganic fillers such as carbon black and calcium carbonate for the purpose of adjusting hardness and reinforcing breaking strength, and methods of blending hard resins such as polystyrene, polyethylene, and polypropylene. has been taken.

However, in the case of mixing and dispersing an inorganic filler, resin molding methods such as injection molding cannot be used as is, and preliminary mixing using rolls, banburi, etc. is required before molding. Even if it is possible to enhance tensile strength and hardness to some extent by dispersing filler particles through such premixing, improvement in tear strength and bending fatigue resistance cannot be expected. In addition, in blends with high melting point polyolefins such as polystyrene, polypropylene, and polyethylene, the hard polyolefin and soft thermoplastic elastomer exhibit a phase-separated structure in minute portions due to poor compatibility between different molecules. Similar to the above-mentioned inorganic filler particle dispersion system, improvement in bending fatigue resistance cannot be expected. Further, as a method for improving the heat resistance and oil resistance of a thermoplastic elastomer, a method of crosslinking can be considered.

However, thermoplastic elastomers are difficult to crosslink, so they cannot take full advantage of their characteristic molding processes such as injection molding, and the crosslinked products can only be obtained with poor mechanical properties and poor heat resistance. do not have. In order to solve these problems, the present inventors have made various studies and found that by mixing a thermoplastic elastomer and 1,2-polybutadiene, the above-mentioned advantages of the thermoplastic elastomer are not impaired. Good moldability,
A composition with appropriate hardness, excellent bending and fatigue resistance, and excellent fluidity can be used not only in ordinary rubber molding machines, but also for ordinary resin applications such as injection molding machines and extrusion molding machines. The inventors have discovered that the crosslinked material can be produced using a molding machine, and that a composition with excellent mechanical properties and heat resistance can be obtained from the crosslinked material, and the present invention has been achieved.

That is, the present invention provides a thermoplastic elastomer made of a block copolymer of an aromatic vinyl compound and a conjugated diolefin, with a pinyl bond of 70% or more, a crystallinity of 5 to 50%,
A thermoplastic elastomer composition consisting of a mixture of 1,2-polybutadiene having an intrinsic viscosity (30 qo in toluene) of 0.7 or more.

The 1,2-polybutadiene used in the present invention is syndiotactic 1,2-polybutadiene, and has a 1,2-vinyl bond content of 70% or more, preferably 85% or more from the viewpoint of moldability and mechanical properties. In addition, the degree of crystallinity is preferably 5 to 50%, more preferably 10 to 40% from the viewpoint of tear strength and molding thermal stability.

The molecular weight can be selected over a wide range, but from the viewpoint of improving bending resistance, it is preferable to have an intrinsic viscosity of 0.7 or more, particularly 1.0 to 3.0, as measured in a toluene solution at 30 qo. In the composition of the present invention, the blending ratio of 1,2-polybutadiene is preferably 5% by weight or more in order to improve the bending resistance of the thermoplastic elastomer, and the rubbery properties, which are the characteristics of the thermoplastic elastomer, are not impaired. For this reason, it is preferably 80% by weight or less, more preferably 15 to
6% by weight.

In addition, when the composition of the present invention is used as a vulcanizate, an appropriate vulcanization time is required, and in order to obtain a vulcanizate with good heat resistance, 1,2-polyptadiene is added to 3 parts by weight. % or more. The thermoplastic elastomer mixed with 1,2-polyptadiene has a softening temperature of 50~
A temperature of 150°C is used.

Specific examples include polystyrene-polybutadiene flock copolymer, polystyrene-polybutadiene-polystyrene flock copolymer, polystyrene-poly(styrene-butadiene)-polystyrene block copolymer, polystyrene-polyisoprene-polystyrene. Examples include block copolymers, polymers of aromatic vinyl compounds and conjugated diolefins such as the above block copolymers in which part or all of styrene is replaced with Q-methylstyrene, and hydrogenated products of these block copolymers. . When molding a blend of the above-mentioned thermoplastic elastomer and 1,2-polyptadiene, it is preferable to use blends of the thermoplastic elastomer and 1,2-polyptadiene having similar softening temperatures.

Since the softening temperature of 1,2-polybutadiene increases as its crystallinity increases, it can be appropriately changed by selecting a 1,2-polybutadiene having a crystallinity within the range of 5 to 50%.

There are no particular restrictions on the method of mixing 1,2-polybutadiene and thermoplastic elastomer, and in addition to rolls, kneader Banbury mixers, screw extruders, etc. that are usually used to mix additives into resins, tumblers, Henschel mixers, etc. Mixing methods such as those described above can be used.

Both components are preferably mixed in pellet form. In the present invention, two or more of each of 1,2-polybutadiene and thermoplastic elastomer may be used.

It is also possible to add a small amount of a polymer, such as polystyrene, which is a component of the thermoplastic elastomer. Additionally, various additives used in resin molding can be blended.
The composition of the present invention thus obtained is a thermoplastic elastomer composition with good processability, moderate hardness even in a non-crosslinked state, and significantly improved tear strength and bending resistance. .

Further, the composition of the present invention can be crosslinked, and a crab bridge product having excellent heat resistance, tensile strength, weather resistance, ozone resistance, etc. can be produced.

The crosslinking method can be a normal rubber crosslinking method. In the present invention, additives such as a crosslinking agent are added to a thermoplastic elastomer, 1,2-polybutadiene, and mixed in a mixer, and the mixture is fed to a molding machine such as a straight bag extrusion molding machine or an injection molding machine. It has the advantage of making the most of the high-speed moldability inherent in thermoplastic elastomers. On the other hand, it is possible to mold and crosslink ordinary Gen-based rubber using an injection molding machine or an extrusion molding machine, and usually the rubber, filler, softener, etc. are first mixed in a Banbury mixer, pressure kneader, etc. Mixed in an internal mixer,
Open to the public. A method is used in which a crosslinking agent or a crosslinking accelerator is added using a mold, the composition is formed into a ribbon shape or a sheet pellet shape, and then the composition is fed into an injection molding machine or an extrusion molding machine.
However, in this processing method, kneading is extremely time-consuming, and since crosslinking agents and crosslinking accelerators are kneaded into the composition, uncrosslinked rubber tends to scorch, so it is difficult to knead in a short time. It is necessary to perform cross-linking molding. Furthermore, the above-mentioned ordinary rubber compositions have poor fluidity during vulcanization molding.
It has drawbacks such as the need for extremely high injection pressure, making it difficult to perform crosslinking through injection molding and other methods. On the other hand, the composition of the present invention has excellent fluidity, and as mentioned above, it can be molded with good processability in ordinary rubber molding machines and injection molding machines, and can also be heated in molds of ordinary plastic molding machines. It is an extremely excellent composition that can be easily vulcanized and molded into a mold, yielding a crosslinked product with excellent mechanical properties and heat resistance.

As the crosslinking agent used in the present invention, sulfur, a vulcanization accelerator, an organic peroxide, an azo compound, an azide compound, etc. can be used, but organic peroxides are preferred because they have high activity and can be vulcanized in a short time.

Examples of organic peroxides include dicumyl peroxide, ditertiary butyl peroxide, tertiary butyl hydro/gu oxide, and cumene hydro/gu oxide, but dicumyl peroxide is preferred in terms of molding stability and crosslinking time. is preferred. The amount of organic peroxide used can be changed as appropriate depending on the application, but it is 0.3 to 1.0 parts by weight based on 10 parts by weight of the 1,2-polybutadiene and thermoplastic elastomer mixture. About 10 parts by weight is sufficient. When a powdered crosslinking agent or the like is used during mixing, it is preferable to add a wetting agent.

Suitable wetting agents include paraffin oil, dioctyl phthalate, and other oils and plastics. Approximately equal amounts of wetting agent and crosslinking agent can be used. It is also possible to add fillers, pigments, anti-aging agents, ultraviolet absorbers, foaming agents, etc. to the composition of the present invention to impart these effects.

As mentioned above, the composition of the present invention can be molded and vulcanized using an injection molding machine for rubber or an injection molding machine for resin equipped with a heating mold, but in this case, the temperature of the cylinder is 80 to 1
It is preferable that the screw rotation speed is 40 to 100 revolutions/minute, and the injection pressure is about 1000 kg/mm or more. The temperature of the mold is 150 qo or more, preferably 160-2
00° C., and the crosslinking time is preferably about 60 to 12 inkstone steps. The crosslinked product of the composition of the present invention obtained by molding and crosslinking in this manner has excellent strength and rubber elasticity without impairing the high-speed moldability of thermoplastic rubber, and has improved heat resistance. has.

Hereinafter, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples unless the gist thereof is changed.

The structure and physical properties of 1,2-polybutadiene used in this example are shown in Table 1, and the method for measuring the physical properties is shown in Table 1.
Table 1 Characteristic values of sample 1,2-volibutadiene Note, *I
D. Infrared absorption spectroscopy (Chi
m. etlnd. , 41, 758 (1959).

*2 Measured by density method.

At this time, the density of 1,2-polybutadiene with 100% crystallinity is determined by G. Natta (J.DoIYmer.Sci.,
20, 25 (1956)), the density of 1,2-polybutadiene with a degree of crystallinity of 0% was confirmed to be amorphous by X-ray analysis. (Special Public Interest Publication 44-32
42 Fu Special Publication No. 44-32426) with a density of 0.892 was used. Table D Evaluation method of physical property values 1. Head JIS
K6301 (Type A)2. Tear strength JIS K
6301 (Type B test piece) 3. Flexibility ASTM (D
-1052)4. Permanent elongation JIS K63015.
Anti-twill elasticity JIS K6301 Example 1 Sample D shown in Table 1 was used as the 1,2-polybutadiene, and Sorprene T475 manufactured by Asahi Kasei ■, which is a styrene-butadiene flock copolymer, was used as the thermoplastic elastomer.
and Tuffprene A were mixed in various proportions to produce compositions.

Table M shows the results of measuring the physical properties of the blended composition. Table m According to the results in Table m, as the amount of 1,2-polybutadiene (crystallinity 25%) added increases, the strength increases and the tear strength increases.

However, when the blending ratio of 1,2-polybutadiene is 75%, a decrease in rubber properties such as an increase in permanent set and a decrease in rebound resilience is observed. A remarkable effect of the present invention is an improvement in bending resistance. Solprene T475 and Toughbrane A alone would be completely destroyed after 200,000 repeated deformations, but the composition of the present invention containing 1,2-polybutadiene In the case of solids, significant improvement effects are seen in both Sorprene T475 and Tuffrene A. Example 2 This example uses Sorprene T of Example 1 as a thermoplastic resin.
475, and the blending ratio of 1,2-polybutadiene was 2.
5% and 50% compositions were prepared.

Its physical properties are shown in Table W. The higher the crystallinity of the 1,2-polybutadiene, the higher the hardness and tear strength of the composition.

The bending resistance is significantly improved compared to the thermoplastic elastomer alone of Example 1. Table IV Example 3 1,2-polybutadiene A or D5 base and styrene.
Butadiene plotter copolymer (Asahi Kasei Kogyo ■Solprene 475) 5 parts and dicumyl peroxide were kneaded using an open roll, then formed into a sheet, 160q
It was vulcanized in a dark press at 1 o.

Table W shows the properties of the obtained addition product. Example 4 The 1,2-polybutadiene D pellets of Example 3, Solprene 475 pellets, dicumyl peroxide and dioctyl phthalate were mixed in a tumbler for 10 minutes at the mixing ratio shown in Table V, and the mixture was directly put into an injection molding machine. A molded vulcanizate was obtained.

The molding and vulcanization conditions at that time are shown in the table. The physical property measurement results are also shown on the surface skin. Example 5 The C or F5 base of 1,2-polybutadiene in Example 3
A portion of the block copolymer 5 used in Example 5, 0.5 part of dicumyl peroxide, and 0.5 part of dioctyl phthalate were mixed in the same manner as in Example 4, and the mixture was molded and heated.

The results of measuring the physical properties of the obtained vulcanizate are shown on the surface. Comparative example
1 100 parts of the block copolymer of Example 3, 0.5 part of dicumyl peroxide, and 0.5 part of dioctyl phthalate were mixed in the same manner as in Example 4, and molded and vulcanized.

The results of measuring the physical properties of the obtained vulcanizate are shown on the surface. Table V Compound ratio table of sample W Injection molding vulcanization conditions Note) Matsuda GI-100D-50GS injection molding machine usage table
Dish *1) 70℃ x 22 hours x 2) 100℃ x 22 hours Loss 3) 40℃, ozone concentration 50pphm, elongation ratio 20
% evaluation method o Number of cracks A: Decimal B: Many C: Innumerable o Size and depth of cracks 1. Things that cannot be seen with the naked eye but can be seen with a sound magnifying glass.

2. Something that can be confirmed with the naked eye.

3. The crack is deep and relatively large (less than one rib).

4. Those with deep and large cracks (more than 1 rib and less than 3 ribs).

5. The crack is over 3 ribs.

Comparative Example 2 Nippon Soda ■NISSO-PB as liquid 1,21 PBD
B-3000 (molecular weight 30001, 2-vinyl content 90
As the thermoplastic elastomers, Asahi Kasei Solprene T475 and Tuffrene A, which are styrene-butadiene floc copolymers, were selected and mixed in the following proportions to produce a composition.

The results of measuring various physical properties of the blended composition are shown on the surface of the skin. As mentioned above, no improvement effect on tear strength and bending resistance was observed.

Claims (1)

[Scope of Claims] 1. A thermoplastic elastomer consisting of a block copolymer of an aromatic vinyl compound and a conjugated diolefin, a vinyl bond of 70% or more, a crystallinity of 5 to 50%, and an intrinsic viscosity ([
η] 30° C., in toluene) A thermoplastic elastomer composition comprising a mixture with 1,2-polybutadiene having a temperature of 0.7 or more. 2 20-95% by weight of thermoplastic elastomer and 1,2
- 80 to 5% by weight of polybutadiene. 3. The thermoplastic elastomer is a polystyrene-polybutadiene block copolymer, a polystyrene-polybutadiene-polystyrene block copolymer, a polystyrene-poly(styrene-butadiene)-polystyrene block copolymer, a polystyrene-polyisoprene-polystyrene block copolymer, Block copolymers of aromatic vinyl compounds and conjugated diolefins, such as the above-mentioned block copolymers in which part or all of styrene has been replaced with α-methylstyrene, hydrogenated products of these block copolymers, and polyethylene-polypropylene block copolymers. The composition according to claim 1, which is at least one selected from the group of. 4 Claim 1 in which the mixture is crosslinked
The composition described in Section. 5. The composition according to claim 4, wherein the crosslinking is carried out using an injection molding machine or an extrusion molding machine. 6 20-70% by weight of thermoplastic elastomer and 1,2-
A composition according to claim 4, consisting of a mixture with 80-30% by weight of polybutadiene.