JP2737251B2 - Thermoplastic elastomer composition - Google Patents

Description

The present invention relates to a thermoplastic elastomer composition useful for automotive exterior parts, interior parts, light electrical parts, industrial parts, and the like, and more particularly to a polyolefin-based resin. The present invention relates to a thermoplastic elastomer composition which is useful for a low-hardness product excellent in fatigue resistance, workability, and molded appearance by combining a hydrogenated diene copolymer.

b. Conventional technology Polyolefin-based thermoplastic elastomers composed of polyolefin-based thermoplastic resin and monoolefin copolymer rubber are mainly used for automotive parts, taking advantage of their excellent heat resistance, weather resistance, cold resistance, and economics in molding. It has been used for industrial parts. However, this thermoplastic elastomer is not sufficient in fatigue resistance, and its development to a site that is repeatedly deformed is limited.

In addition, not only polyolefin-based thermoplastic elastomers, but also generally have higher hardness than ordinary vulcanized rubber-based, and it is necessary to compound a large amount of a softening agent to achieve the same hardness as vulcanized rubber. However, compared to vulcanized rubber having the same hardness, there was a large decrease in strength properties, and there was a defect that a sticky feeling due to bleeding of the softener appeared on the surface of the molded product.

Furthermore, the appearance of a molded product of a polyolefin-based thermoplastic elastomer largely depends on molding conditions, and the optimum molding condition range is narrower than other thermoplastic elastomers. Had.

c. Problems to be Solved by the Invention The present invention provides a polyolefin-based thermoplastic elastomer composition having excellent fatigue resistance, excellent mechanical properties, and excellent moldability and appearance of a molded product suitable for low hardness applications. It is intended for.

d. Means for Solving the Problems The present invention provides a random copolymer of 10 to 90 parts by weight of a polyolefin resin (A), at least a series of conjugated dienes and 50% by weight or less of a vinyl aromatic compound, and The vinyl bond content of the diene part in the polymer is 10 to 90%,
A polymer (B-1) in which at least 70% of the olefinic double bond in the copolymer is hydrogenated, the polymer (B-
1) a polymer (B-2) in which a block of a vinyl aromatic compound is bonded to the terminal, and a polymer block of a vinyl aromatic compound and a polymer block of a conjugated diene compound; The block is a block copolymer having a block having a vinyl bond structure of 30 to 70% and a block having a vinyl bond structure of less than 30%, and having the vinyl bond structure having a block of less than 30% at a terminal, and 90 to 10 parts by weight of at least one hydrogenated copolymer (B) selected from the polymer (B-3) in which at least 70% of the olefinic double bonds in the block copolymer are hydrogenated. And a thermoplastic elastomer composition obtained by melt-mixing in the presence of a crosslinking agent.

Here, the “vinyl bond” or “vinyl bond structure” is described, for example, on page 14 of “Styrene-butadiene rubber” (Synthetic rubber processing technology complete book; Umeno, Sugihara, Kanaya; Taiseisha). It means that the butadiene moiety has a 1,2 structure as it is. The vinyl bond content refers to the ratio of vinyl bonds (1,2 structure) in the butadiene portion.

The polyolefin resin (A) is a crystalline polyolefin polymer obtained by homopolymerizing or copolymerizing an α-olefin monomer such as ethylene, propylene and 1-butene, and is preferably a crystalline polypropylene. In carrying out the present invention, these polyolefin-based resins are used alone or in combination of two or more.

The amount of the polyolefin resin (A) in the thermoplastic elastomer composition of the present invention is 10 to 90% by weight, preferably 30 to 70% by weight.

If the amount of the polyolefin-based resin (A) is less than 10% by weight, the strength properties and fatigue resistance are inferior, and if it exceeds 90% by weight, the hardness becomes high and it is difficult to use as an elastomer.

The hydrogenated copolymer (B) (hereinafter referred to as the component (B)) of the present invention includes a hydrogenated random copolymer (B-1), a hydrogenated copolymer (B-2) and a hydrogenated block copolymer. It is at least one copolymer selected from (B-3).

Before hydrogenation, the hydrogenated random copolymer (B-1) is a random copolymer of at least one conjugated diene and 50% by weight or less of a vinyl aromatic compound (hereinafter, referred to as a random copolymer). These are obtained, for example, by anionic living polymerization in a hydrocarbon solvent using an organolithium initiator. A branched polymer can be obtained by adding a required amount of a coupling agent having three or more functions to the polymer at the end of the polymerization and performing a coupling reaction.

As the conjugated diene monomer used in the random copolymer, for example, 1,3-butadiene, isoprene, 1,3-
Examples thereof include pentadiene, 2,3-dimethylbutadiene, and 3-ethylbutadiene, preferably 1,3-butadiene, isoprene, and 1,3-pentadiene, and more preferably 1,3-butadiene. Further, as the vinyl aromatic compound, styrene, α-methylstyrene, p-
Examples include methylstyrene, p-ethylstyrene, vinylnaphthalene and the like, preferably styrene, p-methylstyrene and p-ethylstyrene, and more preferably styrene.

As the organic lithium initiator, n-butyl lithium,
For example, sec-butyllithium, tert-butyllithium, or the like is used. At the time of polymerization, hexane, heptane, methylcyclopentane, cyclohexane, benzene, toluene, xylene and the like are used as a hydrocarbon solvent.

To control the content of vinyl bonds such as 1,2 bonds and 3,4 bonds in the microstructure of the conjugated diene polymer, ethers, tertiary amine compounds, alkoxides of alkali metals such as sodium and potassium, phenoxides, sulfonic acids Salt is used.

The polymerization may be carried out in a batch system or a continuous system. The polymerization temperature is usually in the range of 0 to 120 ° C., and the polymerization time is 10 minutes to 3 hours.

The coupling agent is a coupling agent having three or more functions, for example, tetrachlorosilicon, butyltrichlorosilicon, tetrachlorotin, butyltrichlorotin, tetrachlorogermanium, bis (trichlorosilyl) ethane, epoxidized linseed oil, tolylene diisocyanate Nart, 1,2,4
-Benzene triisocyanate and the like.

By hydrogenating the random copolymer thus polymerized, a hydrogenated random copolymer (B-1) is obtained.

The hydrogenation ratio of the olefinically unsaturated bond of the copolymer (B-1) is 70% or more, preferably 80% or more, and more preferably 95% or more. When the degree of hydrogenation is less than 70%, the effect of improving the weather resistance and heat resistance of the polymer is insufficient, and the application is limited.

The hydrogenation reaction can be prepared by dissolving the random copolymer of the hydrocarbon solvent is carried out in the presence of a hydrogenation catalyst at ^{20~150 ℃, 1kg / cm 2 ~100kg} / cm 2 pressurized water Motoka.

Examples of hydrogenation catalysts include catalysts in which noble metals such as palladium, ruthenium, rhodium, and platinum are supported on silica, carbon, and diatomaceous earth; complex catalysts such as rhodium, ruthenium, and platinum; organic carboxylic acids such as cobalt and nickel; and organic aluminum. Or a catalyst comprising an organic lithium, titanium compound such as dicyclopentadienyl titanium dichloride, dicyclopentadienyl diphenyl titanium, dicyclopentadienyl titanium ditolyl, dicyclopentadienyl titanium dibenzyl and lithium, aluminum or magnesium A hydrogenation catalyst made of an organometallic compound is used.

Hydrogenated random copolymer (B-1) used in the present invention
In the, the vinyl bond content of the conjugated diene part of the random copolymer as the raw material and the content of the vinyl aromatic compound are important factors that determine the physical properties of the finally obtained thermoplastic elastomer composition .

Increasing the content of the vinyl aromatic compound is effective as a factor for improving the strength properties, but if it exceeds 50% by weight, the elastic modulus is improved, but the strength is reduced.

The content of vinyl bonds in the conjugated diene polymer is 10%.
9090%, preferably 20% 〜80%. When the vinyl bond content in the conjugated diene is 10% or less, the obtained hydrogenated polymer is easily crystallized, and when it is 90% or more, the glass transition temperature increases, and both deteriorate the low-temperature characteristics.

The hydrogenated random copolymer (B-1) is modified with an acid anhydride of α, β-unsaturated carboxylic acid such as maleic anhydride, itaconic anhydride, fumaric anhydride, or glycidyl (meth) acrylate. , Allyl glycidyl ether,
A modified hydrogenated block copolymer modified with an unsaturated compound having an epoxy group such as vinyl glycidyl ether is also included.

The hydrogenated copolymer (B-2), which is one of the components (B),
One in which a vinyl aromatic compound block is bonded to one end of the hydrogenated random copolymer (B-1), or one in which a vinyl aromatic compound block is bonded to both ends of the hydrogenated random copolymer (B-1) is there. The vinyl aromatic compound block may be a tapered block in which the binding content of the vinyl aromatic compound is gradually increased. Further, one end may be formed of a vinyl aromatic compound block and the other end may be formed of a tapered block. The hydrogenated random copolymer (B-2) is a hydrogenated polymer of these copolymers. Here, the monomer component (B-1), the vinyl bond amount, the hydrogenation rate, the reason for limiting the numerical values,
Preferred ranges and the like are as described above for the hydrogenated random copolymer (B-
Exactly the same as 1), but as more preferable conditions,
When the vinyl bond amount is 30 to 80%, the total vinyl aromatic compound / the total conjugated diene compound is 5 to 40/95 to 60% by weight, and the total vinyl aromatic compound in the terminal block is 25% by weight or less of the total monomer. is there. Use of the hydrogenated polymer falling within this range can provide a more excellent thermoplastic elastomer composition which is the object of the present invention.

The hydrogenated block copolymer (B-
3) is that the block copolymer before hydrogenation has the following polymer blocks a, b and c in the molecule (where a is mainly a vinyl aromatic compound containing 90% by weight or more of a vinyl aromatic compound). B is a conjugated diene polymer block having a 1,2 structure and a vinyl bond of 3,4 structure of 30 to 70%,
c is a conjugated diene polymer block having less than 30% of vinyl bonds of 1,2 structure and 3,4 structure. ), The content of the polymer block a in the block copolymer is preferably 10 to 50% by weight, the content of the polymer block b is preferably 30 to 80% by weight, It is a block copolymer having a content of preferably 5 to 30% by weight.

In the block copolymer (B-3), the block copolymer unit is bonded to a polymer unit composed of at least one polymer block of the above a, b or c via a coupling agent residue, The united molecular chain may be a linear or branched block copolymer. The block copolymer thus obtained is used as a hydrogenated block copolymer having a number average molecular weight of 40,000 to 700,000 by hydrogenating at least 70% or more of olefinically unsaturated bonds in the polymer. You.

The block copolymer before hydrogenation contains at least one of the above polymer blocks a, b, and c as essential components, and the simplest block copolymer has a structure of (abc) However, in addition to this basic arrangement, the above three types of polymer blocks (a, b,
All or a part of c) may be a block copolymer in which one or more are arranged regularly or irregularly.

In the block copolymer before hydrogenation, the above-mentioned block copolymer unit has another 1 to 3 via a coupling agent residue.
It may be one in which the polymer molecular chains are extended or branched by bonding to individual polymer blocks. The partner polymer block to be bonded is composed of at least one polymer block of the above a, b or c. Among them, the block copolymers composed of a, b and c are linked via a coupling agent residue. Combined, for example (abc) _n X
Those having a structure of (where n = 2 to 4) are subjected to block copolymerization, and then subjected to diethyl adipate, divinylbenzene, silicon tetrachloride, tin tetrachloride, dimethyldichlorosilicon, 1,2-dibromoethane, It is easily obtained by adding a coupling agent such as 4-chloromethylbenzene. However, in one block copolymer, a,
If b and c are contained, the other polymer block does not need to contain all these three components. For example, (ab)
-C) A structure such as X (ab) may be used.

Polymer block a constituting the above block copolymer
Is styrene, α-methylstyrene, vinyltoluene,
a polymer of one or more aromatic vinyl compounds selected from aromatic vinyl compounds such as p-tert-butylstyrene or a copolymer with a conjugated diene having an aromatic vinyl compound content of 90% by weight or more; More than 80% are hydrogenated polymers. If the content of the aromatic vinyl compound in the polymer block (a) is less than 90% by weight, the coatability is undesirably reduced. The content of the polymer block a in the block copolymer before hydrogenation is preferably 10 to 50% by weight, more preferably 15 to 45% by weight, and the number average molecular weight of the polymer block a is 5,000 to 70,
000. If the amount is less than 10% by weight, the coating property is insufficiently improved, and if it exceeds 50% by weight, the effect of improving the impact resistance at low temperatures is reduced.

The conjugated diene compound described above can be used as the conjugated diene compound of the polymers b and c constituting the block copolymer. In the block copolymer, the content of the polymer block b is preferably 30 to 80% by weight, more preferably 35 to 70% by weight, and the vinyl bond content of the polymer block b is 30 to 70%, preferably 40 to 70%. At 60%, the number average molecular weight is preferably 30,000-300,000, and at least 70% or more of the olefinic double bond is a hydrogenated polymer.

If the vinyl bond content of the conjugated diene polymer before hydrogenation to be the polymer block b is less than 30%, the rubbery properties are lost, and if it exceeds 70%, the rubbery properties are lost. The content of the polymer block b in the block copolymer before hydrogenation is 30.
If it is less than 80% by weight, the improving effect is lost, and if it exceeds 80% by weight, the improving effect is reduced.

The hydrogenated block copolymer (B-3) has a content of the polymer block c of 5 to 30% by weight, preferably 5 to 25% by weight,
The vinyl block content of the polymer block c is less than 30%, preferably 3 to 20%, the number average molecular weight is 10,000 to 300,000, and at least 70% or more of the olefinic double bond of the conjugated diene polymer is hydrogenated. It is a polymer.

When the vinyl bond content of the conjugated diene polymer in the polymer block c before hydrogenation exceeds 30%, the properties of the thermoplastic elastomer as the block copolymer are lost. Also,
Conjugated diene polymers having a vinyl bond content of less than 3% are difficult to produce. When the content of the polymer block c in the block copolymer before hydrogenation is less than 5% by weight, the effect of improving the impact resistance at low temperature is insufficient when blended with a resin, and the content is 30%. If the content is more than 10% by weight, the effect of improving the impact resistance at low temperatures is inferior.

The number average molecular weight of the hydrogenated block copolymer (B-3) is preferably from 40,000 to 700,000.

The hydrogenated block copolymer (B-3) needs to be hydrogenated with at least 70% or more, preferably 90% or more, more preferably more than 95% of olefinic unsaturated bonds, and less than 70%. However, the weather resistance and heat resistance are insufficient.

The molecular weight Mn of the component (B) used in the present invention is preferably 5,000 to 1,000,000, and more preferably 30,000 to 300,000.
It is 0. The improvement in strength properties and fatigue resistance expected to be less than 5,000 cannot be made. If it exceeds 1,000,000, the fluidity becomes too small, the dispersion of the component (B) in the final composition becomes poor, and the processability decreases.

In order to add the function of the conventional rubber to the composition of the present invention, as a rubber component, an existing ethylene-propylene copolymer rubber, styrene-butadiene copolymer rubber, polyisoprene rubber, acrylic rubber, acrylonitrile- Synthetic rubber such as butadiene copolymer rubber, silicone rubber, hydrogenated acrylonitrile-butadiene rubber, and natural rubber may be mixed.

As the crosslinking agent used in the present invention, a radical generator such as an organic peroxide is usually used.

As the above-mentioned organic peroxide, 2,5-dimethyl-2,5
-Di (t-butylperoxy) hexyne-3,2,5-dimethyl-2,5-di (t-butylperoxy) hexane,
2,2'-bis (t-butylperoxy) p-diisopropylbenzene, dicumyl peroxide, di-t-butyl peroxide, t-butylperoxybenzoate, 1,1-bis (t-butylperoxy) -3,3,5-trimethylcyclohexane, 2,4-dichlorobenzoyl peroxide, benzoyl peroxide, p-chlorobenzoyl peroxide and the like, more preferably those having a high decomposition temperature are selected and used. . Further, as a method of adding the organic peroxide, it is preferable to add a monoolefin copolymer rubber of the organic peroxide in a master batch in order to secure safety and stability of quality.

The amount of the organic peroxide to be added is 0.3 to 1.5 parts by weight, preferably 0.5 to 1.0 part by weight, per 100 parts by weight of the component (B).

If the amount of the organic peroxide is less than 0.3 parts by weight,
The crosslinking density of the component (B) is low, and the mechanical strength is insufficient. When the amount of the organic peroxide exceeds 1.5 parts by weight, the crosslinking density of the component (B) increases, and the elongation of the composition decreases.

In crosslinking the component (B), a bifunctional or higher functional vinyl monomer or the like can be used as a co-crosslinking agent. Examples of such a co-crosslinking agent include the following compounds.

Ethylene dimethacrylate, 1,3-butylene dimethacrylate, 1,4-butylene dimethacrylate, 1,6-hexanediol dimethacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol dimethacrylate Acrylate, 2,2'-
Bis (4-methacryloyldiethoxyphenyl) propane, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, divinylbenzene, N, N'-
Methylenebisacrylamide, p-quinonedioxime,
p, p'-dibenzoylquinone dioxime, m-phenylene bismaleimide, 4,4'-diphenylmethane bismaleimide and the like.

The thermoplastic elastomer composition of the present invention can contain conventional auxiliary additives for rubber and resin. Such auxiliary additives include the following commercially available additives.

Softeners and plasticizers for rubber, fillers such as carbon black, white carbon, clay, talc, calcium carbonate, antioxidants, heat stabilizers, ultraviolet absorbers, coloring agents, processing aids, lubricants and the like.

The composition of the present invention is produced by using a pre-heated closed kneader such as a roll mill, a Banbury mixer, or a pressure kneader, or an extruder, and using a predetermined amount of a polyolefin resin (A) and a hydrogenated copolymer (B). ) Can be carried out by melt-mixing and simultaneously reacting a crosslinking agent. A preferred production method is a polyolefin-based resin (A) in a kneader,
This is a method in which a crosslinking agent is added at the time when the hydrogenated copolymer (B) is melt-mixed, and the reaction is carried out while dispersing.

Further, in the presence of a part of the polyolefin resin (A),
After the hydrogenated copolymer (B) is partially crosslinked, the remaining polyolefin-based resin (A) may be added and kneaded.

e. Examples Hereinafter, the present invention will be described more specifically with reference to Examples, but the present invention is not limited to the following Examples as long as the gist of the present invention is not exceeded.

The components used in the following Examples and Comparative Examples are as follows.

Crystalline polypropylene: PP (I) Mitsubishi Nobrene MH-8 hydrogenated random copolymer (I) (component (B)) manufactured by Mitsubishi Yuka Co., Ltd. Styrene content 30%, butadiene content 70%, precursor vinyl content 40%, number average molecular weight 200,000 hydrogenation rate 97%, hydrogenated random copolymerization (II) (component (B)) Styrene content 10%, butadiene content 90%, precursor vinyl content 40%, number average molecular weight 20 97% hydrogenation rate, ethylene propylene copolymer rubber (EPDM): JSR EP98, manufactured by Nippon Synthetic Rubber Co., Ltd. (contains 75 phr of extension oil) The organic peroxide masterbatch used in Examples and Comparative Examples is 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3 per 100 parts by weight of propylene content (49% by weight).
Was mixed with 10 parts by weight of a 6-inch roll.

Softener: Paraffin-based process oil Diana Process Oil PW-90 manufactured by Idemitsu Kosan Co., Ltd. Examples 1 to 5 and Comparative Examples 1 to 3 According to the formulation shown in Table 1, the thermoplastic elastomer composition was prepared by the following procedure. Produced.

The polyolefin resin and the hydrogenated random copolymer shown in Table 1 were placed in a pressurized kneader (capacity 1 manufactured by Moriyama Seisakusho) previously heated to 170 ° C., and kneading was continued until the polyolefin resin was melted. After the polyolefin resin and the hydrogenated random copolymer are uniformly melted and mixed,
A predetermined amount of the organic peroxide masterbatch was added, and kneading was continued for further 10 minutes, and the added organic peroxide was allowed to act 100% to obtain a thermoplastic elastomer composition.
The obtained composition was formed into a sheet by a 6-inch roll, formed into a square pellet by a square-cut pelletizer, formed into a plate-shaped test piece by an injection molding machine, and evaluated for physical properties.

 Table 1 shows the evaluation results.

Analysis method and evaluation method 100% tensile stress, 300% tensile stress, tensile strength, elongation at break Measured using a No. 3 dumbbell-shaped test piece according to JIS K-6301.

Hardness Using a spring-type hardness tester (JIS A, Shore D), the hardness was measured by the method of JIS K-6301.

Fatigue resistance Evaluated from the bending test specified in JIS K-6301. 10 ⁴
The crack length (mm) that grows with the number of times of bending was measured.

Examples 6 to 8 Instead of the hydrogenated random polymer used in Example 1, a polystyrene block (a) -butadiene block (b)
And (c) having a polystyrene content of 30% by weight and a butadiene block of 1,2.
-Consisting of 50% of vinyl structure (b) and 8% of 1,2-vinyl structure (c), (b) is 50% by weight, (c) is 20% by weight, and number average molecular weight is 130,000 . ) Was hydrogenated to prepare a crosslinked product in the formulation shown in Table 2 using poly (styrene-ethylene-CO-butylene-ethylene), which was similarly evaluated.

The results are shown in Table 2. Examples 9 to 11 Hydrogenated random styrene block random SBR (styrene content: terminal block 15) obtained by bonding styrene blocks to both ends of the hydrogenated random SBR polymer used in Example 1 respectively. Weight%, styrene content 50% in random SBR, butadiene content 35%, vinyl bond content 80%, number average molecular weight 300,000), and a crosslinked product was prepared according to the formulation shown in Table-2. An evaluation was performed.

 Table 2 shows the results.

Comparative Example 4 Instead of the hydrogenated random SBR (I) used in Example 2, a styrene-butadiene copolymer rubber (styrene content 23.5
%, JSR SBR 1712 manufactured by Japan Synthetic Rubber Co., Ltd., extender oil 37.5p
(hr content), and the same experiment as in Example 2 was performed.

 The results are shown in Table-3.

Comparative Example 5 Instead of the hydrogenated random SBR (I) used in Example 2, an acrylonitrile-butadiene copolymer rubber (acrylonitrile content 26%, JSR NBR N240 manufactured by Nippon Synthetic Rubber Co., Ltd.)
The same experiment as in Example 2 was performed using S).

 The results are shown in Table-3.

Comparative Example 6 An experiment was performed in the same manner as in Example 4 except that the hydrogenated random SBR having a hydrogenation rate of 97% was used instead of the hydrogenated random SBR having a hydrogenation rate of 97%.

 The results are shown in Table-3.

Comparative Example 7 An experiment was conducted in the same manner as in Example 5, except that the hydrogenated random SBR having a hydrogenation rate of 97% was used in Example 4 and the hydrogenated random SBR having a hydrogenation rate of 65% was used.

 The results are shown in Table-3.

f. Effects of the Invention The thermoplastic elastomer composition using the hydrogenated polymer having a specific structure of the present invention is far superior to conventional thermoplastic elastomer compositions in bending fatigue resistance, processability, low hardness, and molded appearance. Useful as automotive parts and industrial parts.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takumi Miyachi 2--11-24 Tsukiji, Chuo-ku, Tokyo Japan Synthetic Rubber Co., Ltd. (56) References JP-A-59-226042 (JP, A)

Claims (1)

(57) [Claims] 1. A random copolymer of 10 to 90 parts by weight of a polyolefin resin (A), at least one conjugated diene and 50% by weight or less of a vinyl aromatic compound, and a diene part in the polymer. The vinyl bond content is 10-90%,
A polymer (B-1) in which at least 70% of the olefinic double bond in the copolymer is hydrogenated, the polymer (B-
A polymer (B-2) in which a block of a vinyl aromatic compound is bonded to one or both ends of 1), and a polymer block of a vinyl aromatic compound and a polymer block of a conjugated diene compound, When the compound block has a vinyl bond structure of 30 to 70% and a vinyl bond structure
Less than 30% of the blocks, and the vinyl bond structure is less than 30%.
% Of a block copolymer having at least 70% of olefinic double bonds in the block copolymer, and a polymer (B-
At least one hydrogenated copolymer (B) selected from 3)
A thermoplastic elastomer composition obtained by melt-mixing 90 to 10 parts by weight in the presence of a crosslinking agent.