Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1998-04-09
2001-05-29
Mullis, Jeffrey (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S250000, C525S314000, C525S315000, C525S316000
Reexamination Certificate
active
06239218
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a hydrogenated block copolymer which has a polymer block having a specific chain length and mainly comprising hydrogenated conjugated diene monomer units as at least one of the terminal blocks thereof and which comprises a specific content of polymer blocks mainly comprising vinylaromatic hydrocarbon compound units. The present invention also relates to a composition of the block copolymer and to a molded article of the composition.
BACKGROUND OF THE INVENTION
Conjugated diene polymers, on which many proposals have conventionally been made, are widely used, e.g., in tires, belts, impact modifiers for resins, pressure-sensitive adhesives, films and containers, mainly as elastomers, thermoplastic elastomers, and special transparent resins.
Typical known conjugated diene polymers include polybutadiene, polyisoprene, butadiene/isoprene copolymers, styrene/butadiene copolymers, styrene/isoprene copolymers, &agr;-methylstyrene/butadiene copolymers, &agr;-methylstyrene/isoprene copolymers, acrylonitrile/butadiene copolymers, acrylonitrile/isoprene copolymers, butadiene/methyl methacrylate copolymers, isoprene/methyl methacrylate copolymers, and hydrogenated polymers obtained therefrom.
On the other hand, block copolymers constituted of polymer blocks having a T
g
higher than room temperature (restrained phase) at both terminals thereof, and a polymer block having a T
g
lower than room temperature (rubbery phase) (e.g., styrene/butadiene (or isoprene)/styrene block copolymers and hydrogenated polymers obtained therefrom) interposed therebetween are widely used as thermoplastic elastomers, compatibilizing agents, and modifiers in many applications including injection molding and resin modification.
Blending of the styrene/butadiene (or isoprene)/styrene block copolymers or hydrogenated polymers obtained therefrom with other polymers, such as polystyrene, polyolefins, poly(phenylene ether), styrene/butadiene diblock copolymers, and hydrogenated polymers obtained from the diblock copolymers, to produce block copolymer compositions is widely conducted in order to improve the heat resistance, flowability, tackiness properties, and other properties of the styrene/butadiene (or isoprene)/styrene block copolymers or hydrogenated polymers obtained therefrom.
However, with the recent progress in technologies, the market demand for polymeric materials having even higher performances is becoming stronger, and there has been a strong desire for the development of a styrene-based thermoplastic elastomer having improved flowability and heat resistance. Although a styrene block copolymer having an improved balance between heat resistance and flowability has been obtainable, it has the following problems concerning moldability. When the styrene block copolymer is extrusion-molded into film, film breakage is apt to occur during film formation depending on molding conditions and the kind of the block copolymer, making stable film production impossible. Furthermore, when the styrene block copolymer is melt-blended with another resin and the blend is injection-molded, the resultant moldings have flow marks and hence a significantly impaired appearance. Consequently, there has been a strong desire for a styrene-based thermoplastic elastomer having an excellent balance among heat resistance, flowability and moldability.
One of the known effective means for meeting the above desire is to employ a radial block or to link a hydrogenated polybutadiene or hydrogenated polyisoprene block to an end of a styrene/hydrogenated polybutadiene (or hydrogenated polyisoprene)/styrene triblock polymer or of a similar triblock polymer to thereby improve the flowability of the block polymer. Another means is to blend a styrene/hydrogenated polybutadiene (or hydrogenated polyisoprene)/styrene triblock polymer or a similar triblock polymer with a styrene/hydrogenated polybutadiene (or hydrogenated polyisoprene) diblock polymer.
The present invention is based on a finding that a styrene/hydrogenated conjugated diene block copolymer upon melting, which is in a two-phase state (orderly state) consisting of a rubbery phase and a restrained phase, can be made to come into a single-phase state (disordered) at a lower temperature by regulating the block copolymer so as to contain a specific content of vinylaromatic hydrocarbon compound monomer units and a specific amount of a terminal hydrogenated conjugated diene block(s), and further based on a finding that due to the single-phase state (disorderly state) which the hydrogenated block copolymer undergoes, the copolymer alone or compositions containing the same can have even better moldability and excellent flowability and heat resistance.
Phase separation in molten block copolymers is described in
Rheology Symposium Preprints,
43, p.169 (1995). It has been reported therein that styrene/hydrogenated polybutadiene/styrene block copolymers have various order-disorder transition temperatures depending on its styrene content and molecular weight. However, there is no description therein to the effect that order-disorder transition temperature is influenced by block arrangement, in particular that a block copolymer having a specific styrene content and containing a specific amount of terminal hydrogenated polybutadiene blocks has a considerably lowered order-disorder transition temperature. The present inventors have further found that hydrogenated block copolymers regulated to have a terminal hydrogenated conjugated diene block content not lower than 0.1% by weight and lower than 9.1% by weight, while maintaining the polystyrene chain length constant so as to have the same heat resistance, have a lowered order-disorder transition temperature and improved flowability, whereas hydrogenated block copolymers having a terminal hydrogenated conjugated diene block content out of the above range have an elevated order-disorder transition temperature or reduced flowability. As described above, regulating the content of vinylaromatic hydrocarbon compound monomer units to a value in a specific range and regulating the amount of terminal hydrogenated conjugated diene blocks to a value in the range of from 0.1 to 9.1%, excluding 9.1%, by weight are particularly important in the present invention from the standpoints of flowability, moldability, and heat resistance. It should however be noted that no report has so far been made on the fact that the presence of terminal hydrogenated conjugated diene blocks in a hydrogenated block copolymer in a specific amount as in the above range greatly improves the balance among flowability, heat resistance, and moldability of the copolymer.
Polyolefin resin compositions are widely used as mechanical parts, automotive parts, and the like because they are generally excellent in chemical resistance and mechanical properties. As a result of the recent trend toward size increase and wall thickness reduction in pursuit of functions and economy in various products, there is a desire for a polyolefin resin composition excellent in impact resistance, brittleness temperature, rigidity, surface hardness, and tensile elongation at break. In particular, tensile elongation at break is one of the highly desired properties. This is because polyolefin resin compositions, when used, for example, as an automotive material, are required not to break to scatter fragments upon impaction or required to deform to absorb impact, or because polyolefin resin compositions for use in the above applications are required not to break upon creep deformation.
A generally employed method for improving the impact resistance of polyolefin resins is to add an elastomer thereto. In
K{overscore (o)}bunshi Ronbun-sh{overscore (u)}
, Vol.50, No.2, pp.81-86 (Feb. 1993) are shown various properties of compositions comprising polypropylene and an ethylene/propylene rubber as an elastomer. This report shows that increasing the addition amount of the elastomer improves impact resistance and tensile elongation at break. It is also shown therein that
Kato Kiyoo
Sasaya Eiji
Sato Takashi
Yonezawa Jun
Asahi Kasei Kogyo Kabushiki Kaisha
Birch, Stewart, Kolasch and Birch LLP
Mullis Jeffrey
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