WO2011043231A1

WO2011043231A1 - Thermoplastic elastomer composition, and molded product thereof

Info

Publication number: WO2011043231A1
Application number: PCT/JP2010/066901
Authority: WO
Inventors: 良介佐野
Original assignee: 株式会社ブリヂストン
Priority date: 2009-10-09
Filing date: 2010-09-29
Publication date: 2011-04-14
Also published as: JP2011080021A

Abstract

Disclosed is a thermoplastic elastomer composition comprising: (A) 100 parts by mass of a hydrogenated block copolymer which is produced by hydrogenating a block copolymer comprising at least one polymer block mainly composed of a vinyl aromatic compound and at least one polymer block mainly composed of a conjugated diene compound and which has a weight average molecular weight of 300,000 to 450,000; (B) 170 to 270 parts by mass of a non-aromatic-rubber-softening agent which comprises (i) 30 to 80 mass% of a non-aromatic-rubber-softening agent having a kinematic viscosity of 90 mm²/sec or less at 40˚C and a Mw/Mn ratio of 1.3 or less and (ii) 70 to 20 mass% of a non-aromatic-rubber-softening agent having a kinematic viscosity of 350 to 400 mm²/sec at 40˚C and a Mw/Mn ratio of 1.3 or less; and (C) 3 to 15 parts by mass of a polypropylene. The thermoplastic elastomer composition has a Shore A harness of 4 to 12 degrees.

Description

Thermoplastic elastomer composition and molded article thereof

The present invention relates to a hydrogenated block copolymer obtained by hydrogenating a block copolymer comprising a polymer block mainly composed of a vinyl aromatic compound and a polymer block mainly composed of a conjugated diene compound, and softening for a non-aromatic rubber. The present invention relates to a thermoplastic elastomer composition containing an agent and polypropylene, and a molded article thereof.

Conventionally, an oil is added as a softening agent to a hydrogenated block copolymer obtained by hydrogenating a block copolymer composed of a polymer block mainly composed of a vinyl aromatic compound and a polymer block mainly composed of a conjugated diene compound. Many thermoplastic elastomer compositions having a predetermined hardness have been developed.
Specifically, 100 parts by mass of a hydrogenated block copolymer having a number average molecular weight of 100,000, 150 parts by mass of a non-aromatic rubber softener having a kinematic viscosity (40 ° C.) of 100 mm ² / sec or more, and polypropylene 12 A thermoplastic elastomer composition containing 5 parts by mass (see Patent Document 1), 100 parts by mass of a hydrogenated block copolymer having a weight average molecular weight of 250,000 or more, and a kinematic viscosity (40 ° C.) of 350 to 400 mm ² / sec. A thermoplastic elastomer composition comprising 60 to 170 parts by mass of a softener for non-aromatic rubber having a molecular weight distribution (Mw / Mn) of 1.8 or less and 12.5 to 20 parts by mass of polypropylene (see Patent Document 2) , the hydrogenated block copolymer 100 parts by mass, kinematic viscosity (40 ° C.) is a thermoplastic elastomer composition containing a softening agent 50-400 parts by weight of 100 ~ 600mm ² / sec ( Patent reference 3), and the like.

JP 2000-169666 A JP 2002-225303 A JP 2003-105311 A

However, the thermoplastic elastomer compositions disclosed in Patent Documents 1 and 2 have a hardness (JIS A) of 22 degrees and a high tack property, and a thermoplastic elastomer having a very low hardness (12 degrees or less) and a low tack property is Not manufactured. On the other hand, the thermoplastic elastomer composition disclosed in Patent Document 3 has a low hardness (JIS A) of 4-7. Therefore, the inventors of the present invention tried to produce a thermoplastic elastomer composition according to the example of Patent Document 3, and although it was certainly ultra-low hardness, the softener was slightly bleeded out, and It was found that the quality was not satisfactory and there was room for further improvement.

As a result of intensive investigations by paying attention to the above problems, the present inventors have a predetermined kinematic viscosity (40 ° C.) and a molecular weight distribution with respect to 100 parts by mass of a hydrogenated block copolymer having a predetermined weight average molecular weight. 170 to 270 parts by mass of a non-aromatic rubber softener comprising a combination of two kinds of predetermined ratios of non-aromatic rubber softeners (Mw / Mn) of a predetermined value or less, and 3 to 15 parts by mass of polypropylene. The thermoplastic elastomer composition contained therein achieves ultra-low hardness (Shore A hardness = 4 to 12 degrees), but does not cause bleed-out of non-aromatic rubber softener and has low tack. In addition, the present inventors have found that the compression set is small and completed the present invention.

That is, the present invention relates to the following [1] to [4].
[1] (A) Water obtained by hydrogenating a block copolymer comprising at least one polymer block mainly composed of a vinyl aromatic compound and at least one polymer block mainly composed of a conjugated diene compound 100 parts by mass of a hydrogenated block copolymer having a weight average molecular weight of 300,000 to 450,000,
(B) (i) For non-aromatic rubber having a kinematic viscosity at 40 ° C. of 90 mm ² / sec or less and a molecular weight distribution (Mw / Mn) measured by gel permeation chromatography method of 1.3 or less Softener 30 to 80% by mass and (ii) Kinematic viscosity at 40 ° C. is 350 to 400 mm ² / sec, and molecular weight distribution (Mw / Mn) measured by gel permeation chromatography is 1.3 or less. A non-aromatic rubber softener comprising 70 to 20% by mass, containing a non-aromatic rubber softener 170 to 270 parts by mass and (C) 3 to 15 parts by mass of polypropylene, and having a Shore A hardness of 4 to 12 Degree of thermoplastic elastomer composition.
[2] In the component (B), the content of the non-aromatic rubber softener as the component (i) is 50 to 70% by mass, and the content of the non-aromatic rubber softener as the component (ii) The thermoplastic elastomer composition according to the above [1], wherein the ratio is 50 to 30% by mass.
[3] The hydrogenated block copolymer as component (A) is a polystyrene-hydrogenated polybutadiene-polystyrene triblock copolymer, a polystyrene-hydrogenated polyisoprene-polystyrene triblock copolymer, and a polystyrene-hydrogenated copolymer. The thermoplastic elastomer composition according to the above [1] or [2], which is at least one selected from a butadiene / isoprene copolymer-polystyrene triblock copolymer.
[4] A molded product obtained by molding the thermoplastic elastomer composition according to any one of [1] to [3].

According to the present invention, a thermoplastic elastomer composition having a low tackiness and a small compression set, and a molded article thereof, in which bleed-out of a softener for non-aromatic rubber is suppressed despite its extremely low hardness. Can provide.

The thermoplastic elastomer composition of the present invention comprises (A) a block copolymer comprising at least one polymer block mainly composed of a vinyl aromatic compound and at least one polymer block mainly composed of a conjugated diene compound. 100 parts by weight of a hydrogenated block copolymer obtained by hydrogenation and having a weight average molecular weight of 300,000 to 450,000, and (B) (i) a kinematic viscosity at 40 ° C. of 90 mm ² / sec or less and a molecular weight distribution (Mw / Mn) measured by gel permeation chromatography is 1.3 or less, and 30 to 80% by mass of a softener for non-aromatic rubber and (ii) 40 ° C. in a kinematic viscosity of 350 ~ 400mm ² / sec, and the molecular weight distribution measured by gel permeation chromatography molecular weight distribution (Mw / Mn) .3 made of a non-aromatic softening agent for rubber 70-20% by weight or less, containing non-aromatic softening agent for rubber from 170 to 270 parts by weight, and (C) a polypropylene 3-15 parts by weight.

[(A) Hydrogenated block copolymer]
The component (A) is obtained by hydrogenating a block copolymer comprising at least one polymer block mainly composed of a vinyl aromatic compound and at least one polymer block mainly composed of a conjugated diene compound. The weight average molecular weight of the hydrogenated block copolymer needs to be 300,000 to 450,000, preferably 330,000 to 420,000, more preferably 350,000 to 400,000. When the weight average molecular weight of the component (A) is less than 300,000, it cannot withstand the blending amount of the component (B) described later, and the component (B) tends to bleed out from the thermoplastic elastomer composition. The compression set of the resulting thermoplastic elastomer composition is increased.
In addition, in this specification, a weight average molecular weight is the value calculated | required by polystyrene conversion on the basis of the monodispersed polystyrene by the gel permeation chromatography (GPC). Further, in the present specification, “mainly” means that 80% by mass or more is contained, preferably 90% by mass or more, more preferably 95% by mass or more, further preferably It shows that it consists of 100 mass% substantially.

Examples of the vinyl aromatic compound include styrene, α-methylstyrene, α-ethylstyrene, p-methylstyrene, and the like, and styrene is preferable. As a vinyl aromatic compound, 1 type of these may be sufficient and 2 or more types may be sufficient. Preferred examples of the conjugated diene compound include 1,3-butadiene and isoprene. The conjugated diene compound may be one of these or two or more.
A hydrogenated block copolymer obtained by hydrogenating a block copolymer comprising at least one polymer block mainly composed of a vinyl aromatic compound and at least one polymer block mainly composed of a conjugated diene compound. Specific examples include a polystyrene-hydrogenated polybutadiene-polystyrene triblock copolymer (hereinafter abbreviated as SEBS) and a polystyrene-hydrogenated polyisoprene-polystyrene triblock copolymer (hereinafter abbreviated as SEPS). And polystyrene-hydrogenated butadiene / isoprene copolymer-polystyrene triblock copolymer (hereinafter abbreviated as SEEPS). These may be used individually by 1 type and may use 2 or more types together.

In SEBS, the content of the polystyrene block is not particularly limited, but is preferably 10 to 70% by mass, more preferably 20 to 65% by mass. The hydrogenation rate of the polybutadiene block is not particularly limited, but is preferably 50 mol% or more, more preferably 70 to 100 mol%.
There is no restriction | limiting in particular about the manufacturing method of SEBS, A conventionally well-known method can be used. Moreover, SEBS is marketed and you may use the commercial item whose weight average molecular weight is the said range.

In SEPS, the polystyrene block content is not particularly limited, but is preferably 10 to 70% by mass, more preferably 10 to 40% by mass. The hydrogenation rate of the polyisoprene block is not particularly limited, but is preferably 50 mol% or more, more preferably 70 to 100 mol%.
There is no restriction | limiting in particular about the manufacturing method of SEPS, A conventionally well-known method can be used. Moreover, SEPS is marketed and the commercial item whose weight average molecular weight is the said range may be used.

In SEEPS, the polystyrene block content is not particularly limited, but is preferably 10 to 70% by mass, more preferably 20 to 40% by mass. The hydrogenation rate of the butadiene / isoprene copolymer block is not particularly limited, but is preferably 50 mol% or more, more preferably 70 to 100 mol%.
There is no restriction | limiting in particular about the manufacturing method of SEEPS, A conventionally well-known method can be used. Moreover, SEEPS is marketed and you may use the commercial item whose weight average molecular weight is the said range.

[(B) Non-aromatic rubber softener]
In the present invention, as the component (B), (i) the kinematic viscosity (40 ° C.) is 90 mm ² / sec or less, and the molecular weight distribution (Mw / Mn) measured by gel permeation chromatography is 1.3 or less. A non-aromatic rubber softener [hereinafter sometimes referred to as a non-aromatic rubber softener (i) or component (i). And (ii) a non-aromatic system having a kinematic viscosity (40 ° C.) of 350 to 400 mm ² / sec and a molecular weight distribution (Mw / Mn) measured by a gel permeation chromatography method of 1.3 or less Rubber softener [Hereinafter referred to as non-aromatic rubber softener (ii) or component (ii). ] In combination. The kinematic viscosity is a value measured according to JIS K2283.
The kinematic viscosity (40 ° C.) of the non-aromatic rubber softener (i) is 5 to 80 mm from the viewpoint of tackiness and non-aromatic rubber softener retention (hereinafter referred to as oil retention). ² / sec is preferable, 10 to 70 mm ² / sec is more preferable, 15 to 60 mm ² / sec is more preferable, and 20 to 50 mm ² / sec is still more preferable. Further, the kinematic viscosity of the non-aromatic rubber softener (ii) (40 ℃), from the viewpoint of tackiness and oil retaining property, preferably 360 ~ 400mm ² / sec, more preferably 370 ~ 400mm ² / sec More preferably, it is 370 to 390 mm ² / sec.
The molecular weight distribution of the non-aromatic rubber softeners (i) and (ii) is preferably 1 to 1.25, more preferably 1 to 1.2.

The ratio of the combination of the non-aromatic rubber softener (i) and the non-aromatic rubber softener (ii) is as follows: Component (ii) 70 to 20 with respect to 30 to 80% by mass From the viewpoint of tackiness and compression set, it is preferably 60 to 20% by mass of component (ii) with respect to 40 to 80% by mass of component (i), more preferably 50 to 80 of component (i). Component (ii) is 50 to 20% by mass with respect to mass%, and more preferably component (ii) is 50 to 30% by mass with respect to component (i) 50 to 70% by mass.
The thermoplastic elastomer composition obtained when the non-aromatic rubber softener (i) and the non-aromatic rubber softener (ii) having the specific kinematic viscosity and molecular weight distribution are not used in the specific ratio. The component (B) may bleed out from the product, and the tackiness will be high, and the handleability during molding and product transportation will deteriorate, and in addition, the compression set will increase. Occurs.

As the component (B) as described above, for example, paraffinic oil, naphthenic oil, silicone oil, vegetable oil, or the like can be used. Among these, paraffinic oil and silicone oil are preferable from the viewpoint of compatibility, and paraffinic oil is more preferable. These may be used alone or in combination of two or more as long as the compatibility is good.
Examples of the paraffinic oil include Diana Process Oil PW32 (trade name, manufactured by Idemitsu Kosan Co., Ltd., Mw = 400, Mw / Mn = 1.15, kinematic viscosity (40 ° C.) = 31 mm ² / S, paraffinic oil), etc. Can be used as a softener (i) for non-aromatic rubber, such as Diana Process Oil PW380 (trade name, manufactured by Idemitsu Kosan Co., Ltd., Mw = 750, Mw / Mn = 1.15, kinematic viscosity (40 ° C. ) = 380 mm ² / S, paraffinic oil) can be used as the non-aromatic rubber softener (ii).
As the silicone oil, commercially available silicone oil and modified silicone oil can be used.
Examples of plant oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, wax, pine oil, olive oil and the like.
The blending amount of the component (B) is 170 to 270 parts by mass with respect to 100 parts by mass of the component (A) from the viewpoint of suppressing bleeding out while setting the Shore A hardness of the thermoplastic elastomer composition to 4 to 12 degrees. Preferably, the amount is 180 to 270 parts by mass, more preferably 200 to 270 parts by mass, more preferably 230 to 270 parts by mass, and still more preferably 240 to 265 parts by mass.

[(C) Polypropylene]
Although there is no restriction | limiting in particular in the polypropylene of (C) component, From a viewpoint of a moldability, the melt flow rate (henceforth MFR) measured according to JISK7210 [190 degreeC, 21.18N (2.16kgf)]. However, it is preferable to use a polyolefin of 0.1 to 100 g / 10 min, and more preferable to use a polyolefin of 0.5 to 50 g / 10 min. Such polypropylene is commercially available. Examples of commercially available products include “Novatech (registered trademark) BC05B” (trade name, manufactured by Nippon Polypro Co., Ltd.), M1600 (trade name, manufactured by Sun Allomer Co., Ltd.), and the like. May be used.
The amount of component (C) must be 3 to 15 parts by weight, preferably 3.0 to 10 parts by weight, more preferably 3.5 to 8 parts by weight, per 100 parts by weight of component (A). More preferably, it is 4.5 to 8 parts by mass. (A) When it is less than 3 parts by mass with respect to 100 parts by mass of the component, when the component (B) completely blended in the thermoplastic elastomer composition is cut into the thermoplastic elastomer composition after kneading However, the moldability cannot be improved at the same time. Moreover, when it exceeds 15 mass parts with respect to 100 mass parts of (A) component, Shore A hardness will exceed 12 degree | times and a thermoplastic elastomer composition of super-low hardness cannot be obtained.

For the purpose of improving the processability and heat resistance of the thermoplastic elastomer composition, a styrene-based resin can be used in combination with the component (C) polypropylene.
As the styrene resin, those obtained by a known production method can be used, and the styrenic resin may be produced by any of a radical polymerization method and an ionic polymerization method. The weight average molecular weight of the styrene resin is preferably 5,000 to 500,000, more preferably 10,000 to 200,000, and the molecular weight distribution is preferably 5 or less.
Examples of the styrene resin include polystyrene, a styrene-butadiene block copolymer having a styrene unit content of 60% by mass or more, rubber-reinforced polystyrene, poly α-methylstyrene, polypt-butylstyrene, and the like. These may be used individually by 1 type and may use 2 or more types together.
When the component (C) and the styrene resin are used in combination, the content of the styrene resin with respect to the total of the component (C) and the styrene resin is preferably 5 to 15% by mass.

[Other ingredients]
In producing the thermoplastic elastomer composition of the present invention, in addition to the components (A) to (C), polyphenylene ether can be contained as the component (D). The polyphenylene ether has the following general formula:

(Wherein R ¹ , R ² , R ³ and R ⁴ each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 5 carbon atoms or a phenyl group.)
In the present invention, an alloy with polystyrene, polypropylene or polyamide is also included.
In the general formula, examples of the halogen atom represented by R ¹ to R ⁴ include a chlorine atom, a bromine atom, and an iodine atom. Examples of the alkyl group having 1 to 5 carbon atoms represented by R ¹ to R ⁴ include a methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, s-butyl group, t-butyl group, Examples thereof include an n-pentyl group and an isopentyl group.

As the polyphenylene ether, known ones can be used. Examples of the homopolymer include poly (2,6-dimethyl-1,4-phenylene ether) and poly (2-methyl-6-ethyl-1). , 4-phenylene ether), poly (2,6-diphenyl-1,4-phenylene ether), poly (2-methyl-6-phenyl-1,4-phenylene ether), poly (2,6-dichloro-1) , 4-phenylene ether). Examples of the copolymer include polyphenylene ether such as a copolymer of 2,6-dimethylphenol and a monovalent phenol (for example, 2,3,6-trimethylphenol or 2-methyl-6-butylphenol). A copolymer etc. are mentioned.
Polyphenylene ethers are commercially available. Examples of commercially available products include the “Zylon (registered trademark)” series manufactured by Asahi Kasei Chemicals Corporation and the “Noryl (registered trademark)” series manufactured by GE Plastics Japan. May be used.
By including such component (D), the heat resistance of the thermoplastic elastomer composition is improved. When the component (D) is contained, the content is not particularly limited, but it is preferably 5 to 100 parts by mass with respect to 100 parts by mass of the component (A).

In producing the thermoplastic elastomer composition of the present invention, other additives may be further contained in addition to the components (A) to (D) as long as the object of the present invention is not impaired.
Examples of such additives include ceramic, carbon black, amber, senna, kaolin, nickel titanium yellow, cobalt blue, plamaster gray, quinophthalone, diketopyrrolopyrrole, quinacridone, dioxazine, phthalocyanine blue, and phthalocyanine green. Flame retardant: Anti-aging agent: Antistatic agent: Antibacterial agent: Antioxidant: Inorganic hollow fillers such as talc, silica, calcium carbonate, magnesium carbonate, aluminum hydroxide, barium sulfate, glass fiber, glass powder, glass balloon, ceramic powder Inorganic fillers such as mica, organic fillers such as cork powder, wood powder and graphite: Release agents such as stearic acid: Light stabilizers: Tackifiers such as rosin derivatives (tackfire): “Rheostomer® ) B (Trade name, Riken Technos Co., Ltd.) adhesive elastomers, such as: coumarone resins, coumarone - indene resins, and phenolic terpene resins.
When the additive is contained, the content thereof is preferably 20 parts by mass or less and more preferably 5 parts by mass or less with respect to 100 parts by mass of the component (A).

Furthermore, the thermoplastic elastomer composition of the present invention can be partially crosslinked by adding a crosslinking agent or a crosslinking aid.
As a crosslinking agent, an organic peroxide is preferable. Specific examples of the organic peroxide include 2,5-dimethyl-2,5-di (t-butylperoxy) -hexane; 2,5-dimethyl-2,5-di (benzoylperoxy) -hexane; t -Butyl peroxybenzoate; dicumyl peroxide; t-butyl cumyl peroxide; diisopropyl benzohydroperoxide; 1,3-bis- (t-butylperoxyisopropyl) -benzene; benzoyl peroxide; 1,1-di And (t-butylperoxy) -3,3,5-trimethylcyclohexane.
Examples of the crosslinking aid include divinylbenzene, trimethylolpropane triacrylate, ethylene dimethacrylate, diallyl phthalate, quinone dioxime, phenylene bismaleimide, polyethylene glycol dimethacrylate, and unsaturated silane compounds.
A crosslinking agent and a crosslinking aid may be used individually by 1 type, and may use 2 or more types together, respectively.
The crosslinking agent and the crosslinking aid can be arbitrarily used in the range of 0.1 to 5 parts by mass with respect to 100 parts by weight of the thermoplastic elastomer composition, and the degree of crosslinking can be adjusted.
In addition, when an unsaturated silane compound is used as a crosslinking aid, the crosslinking can be further advanced by contacting with moisture in the presence of a silanol condensation catalyst.

(Method for preparing thermoplastic elastomer composition)
Components (A) to (C) and, if necessary, component (D) and the above additives are mixed. For example, a uniaxial kneader, a biaxial kneader, a Banbury mixer, a brabender, a kneader, a high shear mixer, etc. It is possible to obtain a thermoplastic elastomer composition by melting and kneading preferably at 100 to 300 ° C.
In particular, in order to sufficiently mix the non-aromatic rubber softener as component (B) with each component, there is no particular limitation, but for example, the following method may be used.
A twin-screw kneader having a “screw total length / cylinder diameter” of 30 or more, preferably 50 to 70, and a ratio of the length of the kneading zone to the screw total length of 30% or more, preferably 40 to 70% is prepared. In advance, a part or all of the component (B) is added to and mixed with the component (A) and the component (C) and, if necessary, the component (D) and the additive. Feeding from the polymer charging port, and if there is a remaining component (B), feed from the polymer charging port or side feed port and melt-kneading to sufficiently mix the component (B) into the composition. Get difficult pellets.
In addition, in advance, a part or all of the component (B) is not added and mixed with the component (A) and the component (C) and, if necessary, the component (D) and the additive. At the same time, it may be fed from the polymer inlet.

The thermoplastic elastomer composition thus obtained has no or very little bleed-out of component (B) despite having a Shore A hardness of 4 to 12 degrees. In the present invention, the Shore A hardness can be 4 to 11 degrees, and preferably 4 to 10 degrees, more preferably 4 to 9 degrees, and further preferably 4 to 6 degrees as necessary.
The thermoplastic elastomer composition having a Shore A hardness of 4 to 12 degrees according to the present invention has a compression set of 32% or less (30 to 32%) and a peel strength as an index of tackiness of 0.42 to 0.45 N. And has excellent oil retention. In addition, all were measured and evaluated by the method as described in an Example.

Using the thermoplastic elastomer composition obtained as described above, a molded article can be produced by a molding method and a molding apparatus generally employed for the thermoplastic elastomer composition. Specifically, a molded body can be produced by extrusion molding, injection molding, press molding, blow molding or the like.

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

<Examples 1 to 6, Comparative Examples 1 to 11>
Each component is mixed in advance in the blending amounts (unit: parts by mass) shown in Tables 1 and 2, and then a twin-screw kneader (Toshiba Machine Co., Ltd., TEM58BS type, screw total length / cylinder diameter = 62.5, screw The mixture was kneaded at 180 ° C. at a ratio of the length of the kneading zone to the total length = 62%) and cut with a cutter while extruding into a strand to obtain a pellet of a thermoplastic elastomer composition. The resulting pellets were measured and evaluated for Shore A hardness, compression set, tackiness and oil retention as follows. The results are shown in Tables 1 and 2.

(1) Shore A hardness Measured according to JIS K6253 (type A).
(2) Compression set In accordance with JIS K6262, a test piece having a diameter of 13 mm and a thickness of 6 mm was used. The compression set is preferably small.
(3) Tackiness When two sheets (8 cm × 1.3 cm × 0.2 cm) formed from a thermoplastic elastomer composition are bonded together, pressed at 50 g / cm ² for 24 hours, and then peeled off at 100 mm / min. The strength (peel strength) was measured and used as an index of tackiness. It shows that tack property is so low that peeling strength is low.
(4) Oil retention The sheet | seat (diameter 25mm, thickness 2mm) which shape | molded the thermoplastic elastomer composition was pinched | interposed into the iron plate, and it compressed at 70 degreeC for 48 hours by 50% compression. The sheet mass reduction ratio before and after compression was measured and used as an index of the retention (oil retention) of the non-aromatic rubber softener possessed by the thermoplastic elastomer composition. Evaluation was performed as follows.
○: Change rate of 3% or less.
Δ: Change rate exceeds 3% and less than 5%.
X: Change rate of 5% or more.

1): “Septon 4077”, SEEPS, Mw = 350,000, polystyrene block content 30%, manufactured by Kuraray Co., Ltd. 2): “Septon 4099”, SEEPS, Mw = 400,000, polystyrene block content 30%, Inc. Kuraray 3): “Septon 4033”, SEPS, Mw = 100,000, polystyrene block content 30%, Kuraray Co., Ltd. 4): “Tuftec H1041”, SEBS, Mw = 200,000, polystyrene block content 30%, Asahi Kasei Chemicals Corporation 5): “Diana Process Oil PW32”, paraffinic oil, Mw = 400, Mw / Mn = 1.15, kinematic viscosity (40 ° C.) = 31 mm ² / sec, Idemitsu Kosan Co., Ltd. 6) : “Diana Process Oil PW380”, paraffinic oil, Mw = 750, Mw / M = 1.15, kinematic viscosity ^{(40 ℃) = 380mm 2 /} sec, Idemitsu Kosan Co., Ltd. 7): "Diana Process Oil PW90", paraffinic oils, Mw = 530, Mw / Mn = 1.15, a kinematic viscosity (40 ° C.) = 96 mm ² / sec, manufactured by Idemitsu Kosan Co., Ltd. 8): “Polybutene HV-35”, Mw = 750, Mw / Mn = 1.94, kinematic viscosity (40 ° C.) = 330 mm ² / sec, new 9) “Lucant HC-100”, paraffinic oil, Mw = 1450, Mw / Mn = 1.4, kinematic viscosity (40 ° C.) = 1700 mm ² / sec, Mitsui Chemicals, Inc. 10) : “NOVATEC BC05B”, MFR = 50 (g / 10 min), manufactured by Nippon Polypro Co., Ltd.

As shown in Table 1, each of the thermoplastic elastomer compositions of the present invention has a Shore A hardness in the range of 4 to 12 degrees, and despite having an ultra-low hardness, the oil retention is extremely high, Compression set is also small. Furthermore, it turns out that tack property is low.
On the other hand, as shown in Comparative Example 6 in Table 2, when the blending amount of the component (C) is less than 3 parts by mass with respect to 100 parts by mass of the component (A), the oil retention becomes poor, and compression set Also increased. Further, as shown in Comparative Examples 7 and 8, when a hydrogenated block copolymer having a weight average molecular weight of less than 300,000 is used as the component (A), the oil retention is deteriorated, and the compression set and tackiness are greatly increased. Increased.
As shown in Comparative Examples 1 and 4, when only the non-aromatic rubber softening agent (i) was used as the component (B), the compression set was greatly increased. As shown in Comparative Examples 2 and 5, when only the non-aromatic rubber softener (ii) was used, tackiness was greatly increased. Moreover, as Comparative Example 3 shows, as component (B), softening for non-aromatic rubber having a kinematic viscosity at 40 ° C. of 96 mm ² / sec and a molecular weight distribution (Mw / Mn) of 1.3 or less. When only the agent was used, tackiness was greatly increased and compression set was slightly increased.
Further, as shown in Comparative Examples 9 to 11, the tackiness is increased and / or the oil retaining property other than the combination of the non-aromatic rubber softener (i) and the non-aromatic rubber softener (ii). Worsened.

The thermoplastic elastomer composition having a Shore A hardness of 4 to 12 degrees according to the present invention has characteristics such as low tackiness, small compression set, and high oil retention despite being designed for ultra-low hardness. Therefore, it can be used for a wide range of applications, such as sealing materials, gasket materials, vibration-proof materials, shock absorbing materials, cover materials, and buffer materials.

Claims

(A) A hydrogenated block copolymer obtained by hydrogenating a block copolymer comprising at least one polymer block mainly composed of a vinyl aromatic compound and at least one polymer block mainly composed of a conjugated diene compound. 100 parts by weight of a hydrogenated block copolymer having a weight average molecular weight of 300,000 to 450,000,
(B) (i) For non-aromatic rubber having a kinematic viscosity at 40 ° C. of 90 mm 2 / sec or less and a molecular weight distribution (Mw / Mn) measured by gel permeation chromatography method of 1.3 or less Softener 30 to 80% by mass and (ii) Kinematic viscosity at 40 ° C. is 350 to 400 mm 2 / sec, and molecular weight distribution (Mw / Mn) measured by gel permeation chromatography is 1.3 or less. A non-aromatic rubber softener comprising 70 to 20% by mass, containing a non-aromatic rubber softener 170 to 270 parts by mass and (C) 3 to 15 parts by mass of polypropylene, and having a Shore A hardness of 4 to 12 Degree of thermoplastic elastomer composition.
In the component (B), the content of the non-aromatic rubber softener as the component (i) is 50 to 70% by mass, and the content of the non-aromatic rubber softener as the component (ii) is 50 The thermoplastic elastomer composition according to claim 1, which is -30% by mass.
The hydrogenated block copolymer (A) is a polystyrene-hydrogenated polybutadiene-polystyrene triblock copolymer, a polystyrene-hydrogenated polyisoprene-polystyrene triblock copolymer, and a polystyrene-hydrogenated butadiene / isoprene. The thermoplastic elastomer composition according to claim 1 or 2, which is at least one selected from a copolymer-polystyrene triblock copolymer.
A molded product obtained by molding the thermoplastic elastomer composition according to any one of claims 1 to 3.