JP2008063365A - Styrene elastomer composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transparent elastomer composition useful as an antislip material. <P>SOLUTION: The transparent elastomer composition having moderate tackiness is produced by adding 120-500 pts.mass of a mineral oil-based softening agent having a kinetic viscosity of 30-150 cSt to 100 pts.mass of a styrene elastomer having a mass-average molecular weight of 100,000-200,000. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a styrene-based elastomer composition that is flexible, transparent, and has an appropriate tackiness.

Transparent sandproof elastomer compositions are used for sandals, mules, pumps, pen grips and the like.
Conventionally, the composition which added the softening agent to the styrene-type elastomer is provided as this kind of composition.
The styrene elastomer composition is soft because the styrene elastomer as a raw material has rubber elasticity and low hardness, and is widely used as a rubber material.
Furthermore, styrene elastomers have good compatibility with polyolefins and rubber softeners, and are widely used as compositions containing these.
There is a need for a transparent and lower hardness material of a styrene elastomer composition.
When mineral oil softener is added to styrene elastomer, hardness decreases and flexibility increases, but when used in large quantities, the mineral oil softener bleeds out and feels when touched by hand or touching the foot. When a large amount of a mineral oil softener is added to the styrene elastomer, the styrene elastomer is dispersed in an unmelted state, resulting in poor transparency.
Addition of polyolefin to this composition improves the dispersion of the styrene-based elastomer in an unmelted state, but increases the hardness and is not suitable for reducing the hardness. Moreover, transparency is also deteriorated by adding polyolefin.
In adding a polyolefin and a rubber softener to a styrene elastomer, a mixture of a crystalline propylene resin and an amorphous propylene-α-olefin copolymer in a predetermined ratio and an ethylene having a predetermined physical property are added. A translucent elastomer composition in which bleeding out of a softener for rubber is suppressed by blending an -α-olefin copolymer has been proposed.

JP 2001-220513 A

  However, this composition is high in hardness and translucent, and is not suitable for applications requiring a transparent material with low hardness and high flexibility.

  The inventors of the present invention have completed the present invention by paying attention to the fact that the kinematic viscosity of the mineral oil softener is high and the stickiness is low when the kinematic viscosity is low. That is, as a means for solving the above-described conventional problems, the present invention includes 120 to 500 parts by mass of a mineral oil softener having a kinematic viscosity of 30 to 150 cSt to 100 parts by mass of a styrene elastomer having a mass average molecular weight of 100,000 to 200,000. The present invention provides a styrenic elastomer composition characterized by being added.

[Action]
A styrene elastomer having a mass average molecular weight of 100,000 or less has poor mechanical properties such as tensile strength at break and tensile elongation at break, and a styrene elastomer having a mass average molecular weight of 200,000 or more has poor transparency.
When a mineral oil softener with a kinematic viscosity of 30 cSt (centistokes) or less is used, the bleedout of the mineral oil softener to the elastomer surface becomes significant, and the mineral oil softener volatilizes and softens when a high temperature is applied. And slipperiness deteriorate.
When a mineral oil softener having a kinematic viscosity of 150 cSt or more is used, the stickiness of the elastomer becomes remarkable.
When the amount of the mineral oil softener is 120 parts by mass or less, the amount of the mineral oil softener absorbed by the styrenic elastomer is reduced, and it becomes difficult to gel, resulting in poor moldability. The stickiness of the elastomer becomes remarkable, and the bleed-out of the mineral oil softener becomes remarkable.

〔effect〕
In the present invention, there is provided an elastomer composition having a high transparency and a good anti-slip property, and having a good surface feeling and a low surface stickiness.

The present invention is described in detail below.
[Styrene elastomer]
The styrene-based elastomer has a polystyrene block that is a hard segment and a conjugated diene polymer block that is a soft segment, and exhibits vulcanized rubber-like properties at a low temperature and heat-melts in a heated state to exhibit fluidity. Examples of the styrene elastomer include styrene-butadiene-styrene block copolymer (SBS), styrene-isoprene-styrene block copolymer (SIS), styrene-ethylene / butylene-styrene block copolymer (SEBS), styrene- Ethylene / propylene-styrene block copolymer (SEPS), partially hydrogenated styrene-ethylene / butylene-styrene block copolymer (partially hydrogenated SEBS), styrene / (ethylene-ethylene / propylene) -styrene block copolymer ( SEEPS) and the like. Desirable styrenic elastomers are SEBS and SEEPS. When SEBS or SEEPS is used, transparency is improved and excellent slip resistance is obtained.
The mass average molecular weight of the styrenic elastomer must be in the range of 100,000 to 200,000. When the mass average molecular weight is less than 100,000, mechanical strength such as tensile strength and tensile elongation at break is deteriorated. When the mass average molecular weight exceeds 200,000, transparency is deteriorated.

[Mineral oil softener]
As the mineral oil softener used in the present invention, paraffinic oil, naphthenic oil and the like are used, but it is desirable to use paraffinic oil having good compatibility with the styrene elastomer.
The mineral oil softener must have a kinematic viscosity at 40 ° C. of 30 cSt or more and 150 cSt or less. When the kinematic viscosity at 40 ° C. is less than 30 cSt, the bleed-out of the mineral oil softener on the surface of the molded article becomes remarkable. When the kinematic viscosity at 40 ° C. exceeds 150 cSt, the mineral oil-based softener on the surface of the molded article When the bleeds out, the feeling of stickiness becomes remarkable.

[Other resins]
A desirable resin is polypropylene. As polypropylene, in addition to propylene homopolymer, copolymers of propylene and other α-olefins are also used. However, in order to make it transparent, the addition amount of 5 parts by mass or less is preferable with respect to 100 parts by mass of the styrene elastomer.

[Other ingredients]
In addition to the above components, for example, fillers such as silica, pigments, dyes, heat stabilizers, light stabilizers, plasticizers, antioxidants, antistatic agents, flame retardants, flame retardants, insecticides, antiseptics One type or two or more types of additives such as an agent, an anti-aging agent, and an ultraviolet absorber may be mixed.

[Combination]
In the present invention, the proportion of the mineral oil softener in the styrene elastomer must be in the range of 120 to 500 parts by mass of the mineral oil softener with respect to 100 parts by mass of the styrene elastomer. If it is less than 120 parts by mass, the amount of absorption of the mineral oil-based softening agent is reduced, gelation becomes difficult and moldability becomes poor, and if it exceeds 500 parts by mass, the stickiness of the molded product becomes significant, and The bleed-out of mineral oil softener is also remarkable.
The styrenic elastomer composition must have a haze value of 10% or less. If it exceeds 10%, the transparency is impaired. The hardness is preferably in the range of JIS hardness E10 or more and JIS hardness A30 or less. If the JIS hardness is less than E10, the stickiness of the molded product becomes remarkable, and the bleed-out of the mineral oil softener becomes remarkable. When it exceeds JIS hardness A30, the flexibility of the molded product is impaired.
The said composition is mixed using well-known stirring mixers, such as a Banbury mixer and a Henschel mixer, for example.
The above composition is usually pelletized by an extrusion molding machine, and the resulting pellet is formed by a known molding method such as injection molding, extrusion molding, stamping molding or hot press molding.

〔Example〕
The blends having the compositions shown in Tables 1 and 2 were prepared by mixing with a Henschel mixer, and the blend was pelletized with a twin screw extruder and then 2 mm thick, 125 mm long, and horizontal width by injection molding. A 125 mm sample was prepared.

Table 3 shows the physical properties of the styrene elastomer and paraffin oil used.

The numerical values of the composition of Tables 1 and 2 indicate parts by mass.
〔Measuring method〕
Molecular weight Gel permeation chromatography (GPC), Column used: Two Shodex KF-806M used, Solvent used: Tetrahydrofuran, Injection volume: 100 μL (0.2 w / v%), Flow rate: 1.0 mL / min, Oven temperature : Measured with 40 ° C., polystyrene standard, RI (suggested refractometer).
Transparency Evaluated by haze value when viewed with a 2 mm thick sheet produced by injection molding. The haze value was measured based on JIS K 7136 using a Nippon Denshoku Industries Co., Ltd. haze meter NDH2000.
Formability Relative evaluation of formability when a 2mm thick sheet is created with Inj.
Place the 50 mm × 50 mm × 6 mm thick injection sheet on the tackiness iron plate was allowed to stand for 1 hour a load over 100 g / cm ^2, when turned over an iron plate, evaluated visually peeling degree of the sheet.
Stickiness Relative evaluation of the feel when the injection sheet is touched by hand.
Tensile breaking strength Tensile breaking strength (MPa) according to JIS K 6251.
Tensile elongation at break Tensile elongation at break according to JIS K 6251 (%).
Volatility of mineral oil softener Evaluates the presence or absence of oil volatilization when left in a 70 ° C oven for 24 hours. The mass change rate was 1% or less, and 5% or more was rated as x.

[Physical property evaluation criteria]
Transparency ○: Haze of 10% or less ×: Over haze of 10% Moldability ○: Moldable ×: Difficult or impossible to form Tackiness ○: Sheet does not peel off from iron plate
×: The sheet peels off naturally from the iron plate. ◎: Feels uncomfortable with a smooth touch.
○: Hand feels slightly sticky, but no discomfort
Δ: Hand feels sticky and uncomfortable
×: Sticks firmly to hand and requires force to peel off Oil volatility ○: No or little volatilization ×: Volatilization

In Table 2, Comparative Example 1 using a styrene elastomer having a mass average molecular weight of 200,000 or more (247,000) is inferior in tackiness, transparency and molding processability, and has a mass average molecular weight of 100,000 or less (85560,000). Comparative Example 2 using the styrene-based elastomer is inferior in moldability and produces a slightly sticky feeling.
In Comparative Example 3 using an oil having a kinematic viscosity of 150 cSt or more (383.4 cSt), a sticky feeling was generated, molding workability was slightly inferior, and an oil having a kinematic viscosity of 30 cSt or less (11 cSt) was used. In Comparative Example 4, the volatilization of oil is large, and the tackiness and molding processability are slightly inferior.
The comparative example 5 which made the addition amount of oil 500 mass parts or more (550 mass parts) is inferior to moldability, and a sticky feeling also generate | occur | produces. Moreover, the comparative example 6 which made the addition amount of oil 120 mass parts or less (100 mass parts) is inferior to tackiness and a moldability, and is also inferior to transparency a little.
On the other hand, as shown in Table 1, the samples of Examples 1 to 5 of the present invention all have good transparency and tackiness, are less sticky and have good moldability.

Styrenic elastomer compositions that are transparent and less sticky include anti-slip sheets used for footwear sandals, mules, pumps, etc. and the difficulty of walking because these footwear sizes do not match. There are sheets and pen grips to eliminate.
Transparency is required so as not to stand out in footwear.
Pen grips are required to be transparent with a focus on design.
In any case, the touch feeling is not sticky, the feeling of fitting to the feet and fingers is emphasized, and a material with extremely low hardness is required.
Since the elastomer composition of the present invention has good anti-slip properties (tackiness), little stickiness, and excellent transparency, it is extremely useful for use and can be used industrially.

Claims (2)

  A styrene elastomer composition comprising 120 to 500 parts by mass of a mineral oil softener having a kinematic viscosity of 30 to 150 cSt added to 100 parts by mass of a styrene elastomer having a mass average molecular weight of 100,000 to 200,000. The styrene elastomer composition according to claim 1, wherein the styrene elastomer is a styrene- (ethylene-ethylene / propylene) -styrene block copolymer.