Hydrogenated block copolymer and composition of the same

A hydrogenated block copolymer comprising: at least two polymer blocks A mainly comprising vinylaromatic hydrocarbon compound monomer units; and at least two polymer blocks B mainly comprising hydrogenated conjugated diene compound monomer units, in which at least 90% of the olefinically unsaturated double bonds contained in the unhydrogenated polymer block mainly comprising the conjugated diene compound monomer units is hydrogenated, wherein at least one of the terminal blocks is a polymer block B, the proportion of the terminal polymer block B in the hydrogenated block copolymer being 0.1% by weight or higher and lower than 9.1% by weight, and wherein the content of the vinylaromatic hydrocarbon compound units in the hydrogenated block copolymer is 12% by weight or higher and lower than 25% by weight. Also disclosed are a resin composition containing the hydrogenated block copolymer, and a molded article of the resin composition.

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, .alpha.-methylstyrene/butadiene copolymers,
 .alpha.-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.sub.g higher than room temperature (restrained phase) at both terminals
 thereof, and a polymer block having a T.sub.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 Kobunshi Ronbun-shu,
 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 although reducing the molecular weight of the
 polypropylene so as to improve alloy flowability is effective in improving
 flowability, it reduces impact resistance and tensile elongation at break.
 In Kobunshi Ronbun-shu, Vol.50, No.1, pp.19-25 (Jan. 1993) is given a
 report showing that increasing the elastomer addition amount in
 compositions comprising polypropylene and an ethylene/propylene rubber
 impairs surface hardness.
 Furthermore, many reports have conventionally been made on the addition of
 a hydrogenated block copolymer as a means for improving the impact
 resistance of polyolefin resins. In Plastic Age, Vol.42, p.117, Feb.
 (1996) are given results showing that in compositions comprising
 polypropylene and a hydrogenated block copolymer, increasing the addition
 amount of a hydrogenated styrene-based thermoplastic elastomer used as the
 hydrogenated block copolymer improves impact resistance but reduces
 rigidity. There also are results therein showing that although rigidity
 (flexural modulus) is improved by using an elastomer having a high styrene
 content, brittleness temperature is impaired thereby.
 As apparent from the above, impact resistance, brittleness temperature,
 rigidity, surface hardness and tensile elongation at break are
 inconsistent with one another. It has hence been exceedingly difficult to
 obtain a highly improved balance among these properties.
 In U.S. Pat. No. 4,168,286, there is claimed a hydrogenated block copolymer
 which has the structure of either a styrene/hydrogenated conjugated
 diene/styrene/hydrogenated polybutadiene block copolymer or a
 styrene/hydrogenated polybutadiene/styrene/hydrogenated conjugated diene
 block copolymer, and in which the 1,2-bond content in the hydrogenated
 polybutadiene block is from 1 to 10 mol %. However, in the hydrogenated
 block copolymers described in the Examples given in the above reference,
 the amount of the terminal hydrogenated polybutadiene block or terminal
 hydrogenated conjugated diene block is at least 20% by weight, which is
 outside the scope of the present invention. Moreover, in the above
 reference, there is no description nor suggestion concerning the effect of
 the amount of a terminal hydrogenated polybutadiene block or terminal
 hydrogenated conjugated diene block.
 In JP-A-2-259151, there is claimed a stretchable nonwoven fabric comprising
 a styrene/hydrogenated polybutadiene/styrene/hydrogenated polybutadiene
 block copolymer. (The term "JP-A" as used herein means an "unexamined
 published Japanese patent application".) An Example given therein
 describes a styrene/hydrogenated polybutadiene/styrene/hydrogenated
 polybutadiene block copolymer in which the content of the terminal
 hydrogenated polybutadiene block is 10% by weight. However, this reference
 neither discloses a block copolymer having a terminal hydrogenated
 polybutadiene block in an amount below 10% by weight which is within the
 scope of the present invention, nor describes the effect thereof.
 In JP-A-4-96904 and JP-A-4-96905, there is claimed a method for
 hydrogenating a styrene/butadiene block copolymer: An Example given in
 this reference describes a process in which a styrene/hydrogenated
 polybutadiene/styrene/hydrogenated polybutadiene block copolymer having a
 content of the terminal hydrogenated polybutadiene block of 10% by weight
 is produced.
 In JP-A-5-038996, there is claimed an air bag cover housing comprising a
 hydrogenated conjugated diene block copolymer, a softener for rubber, and
 an olefin resin. An Example given in this reference describes an air bag
 housing material containing a styrene/hydrogenated
 polybutadiene/styrene/hydrogenated polybutadiene block copolymer in which
 the content of the terminal hydrogenated polybutadiene block is 10% by
 weight. However, the above two references each neither discloses a block
 copolymer having a terminal hydrogenated polybutadiene block in an amount
 smaller than 10% by weight, nor describes the effect thereof.
 In JP-A-61-155446, there is claimed a composition comprising a hydrogenated
 block copolymer having a specific number-average molecular weight and a
 specific styrene content and having a specific amount of a hydrogenated
 polybutadiene block at the terminal thereof and a polyolefin. The Examples
 given therein describe compositions containing styrene/hydrogenated
 polybutadiene/styrene/hydrogenated polybutadiene block copolymers or
 hydrogenated polybutadiene/styrene/hydrogenated
 polybutadiene/styrene/hydrogenated polybutadiene block copolymers
 respectively having terminal hydrogenated polybutadiene block contents of
 1.3, 2.5, 3, 5, 6.7, 10, 20, and 40% by weight. In the specification
 thereof, there is a description as to how the amount of the terminal
 hydrogenated polybutadiene block influences the mechanical strength and
 rubber elasticity of the composition. The composition claimed in this
 reference can have a styrene content of from 5 to 50% by weight, with the
 most preferred range thereof being from 10 to 40% by weight as described
 in the specification thereof. Although there is a description therein to
 the effect that the above range was employed in order to obtain desirable
 properties, there is no description nor suggestion therein concerning the
 relationship between the styrene content and a balance among impact
 resistance, brittleness temperature, rigidity, surface hardness and
 tensile elongation at break. Furthermore, the Examples given therein are
 limited to elastomer compositions having high elastomer contents, and no
 Example is given which relates to a resin composition showing a
 resin-modifying effect. In addition, there is no Example therein which
 relates to a composition produced by using a hydrogenated block copolymer
 containing a terminal hydrogenated polybutadiene block and having a
 vinylaromatic hydrocarbon content of 12% by weight or higher and lower
 than 25% by weight, which is one of the essential requirements in the
 present invention.
 In Japanese Patent No. 2,500,391, there is claimed an elastomer composition
 which comprises a hydrogenated block copolymer having a hydrogenated
 polybutadiene block at an end, a polyolefin resin, and an
 ethylene/.alpha.-olefin copolymer, and which due to these components has
 the effect of being excellent in flexibility and processability and
 reduced in anisotropy. In this reference are given Examples concerning
 compositions containing a styrene/hydrogenated
 polybutadiene/styrene/hydrogenated polybutadiene block copolymer. In this
 reference, however, there is no description concerning the amount of the
 terminal hydrogenated polybutadiene block nor description suggesting the
 fact that the terminal hydrogenated polybutadiene block greatly improves
 the balance among impact resistance, brittleness temperature, rigidity,
 surface hardness and tensile elongation at break of the composition. In
 addition, the composition obtained according to this reference has an
 unsatisfactory balance among impact resistance, brittleness temperature,
 rigidity, surface hardness and tensile elongation at break.
 Japanese Patent No. 2,529,807 discloses a composition obtained by
 compounding a polyolefin resin with a hydrogenated block copolymer and
 optionally further with an inorganic filler, for improving low-temperature
 impact strength and flowability/processability. In the Examples given
 therein are described compositions containing a hydrogenated block
 copolymer having the structure of polystyrene/hydrogenated polybutadiene
 (poly(ethylene-butylene)/polystyrene/hydrogenated polybutadiene. However,
 there is no description therein concerning an effect of the hydrogenated
 block copolymer used, although the vinyl content of the copolymer is
 shown. Furthermore, although the MFR, molecular weight, and styrene
 content of the hydrogenated block copolymer are shown in the above
 reference, there is no description therein concerning the relationship
 between these properties and tensile elongation at break. In addition,
 there is no description nor suggestion therein concerning the amount of a
 terminal hydrogenated polybutadiene chain and the effect thereof. Although
 this conventional technique is considerably effective in greatly improving
 flowability/processability, it is unsatisfactory in the improvement of
 tensile elongation at break.
 JP-A-5-51494 discloses a composition comprising a polypropylene resin and
 two hydrogenated block copolymers having different molecular weights, for
 the purpose of improving low-temperature impact resistance, appearance
 properties and flowability/processability. In this reference are given
 Examples concerning compositions comprising a combination of a
 hydrogenated block copolymer having the structure of
 polystyrene/hydrogenated polybutadiene
 (poly(ethylene-butylene))/polystyrene/hydrogenated polybutadiene and a
 hydrogenated block copolymer having another structure. Although the
 influence of the microstructures of the conjugated diene compounds in the
 hydrogenated block copolymers used on low-temperature impact strength,
 rigidity and flowability/processability is shown in the above reference,
 there is no description therein concerning tensile elongation at break and
 surface hardness, and these two properties are not on a satisfactory
 level. In addition, there is no description nor suggestion therein
 concerning the amount of a terminal hydrogenated polybutadiene chain and
 the effect thereof.
 JP-A-5-163388 discloses a composition which comprises a polypropylene resin
 and two hydrogenated block copolymers having different molecular weights
 and in which the hydrogenated block copolymer having a lower molecular
 weight is contained in a larger amount than the hydrogenated block
 copolymer having a higher molecular weight, for the purpose of improving
 the balance between low-temperature impact resistance and rigidity and
 improving flowability/processability. In this reference are given Examples
 concerning compositions containing a combination of hydrogenated block
 copolymers having the structure of polystyrene/hydrogenated polybutadiene
 (poly(ethylene-butylene)/polystyrene/hydrogenated polybutadiene and having
 different molecular weights. Although the influence of the microstructures
 of the conjugated diene compounds in the hydrogenated block copolymers
 used on low-temperature impact strength, rigidity, and
 flowability/processability is shown in the above reference, there is no
 description therein concerning tensile elongation at break and surface
 hardness and these two properties are not on a satisfactory level. In
 addition, there is no description nor suggestion therein concerning the
 amount of a terminal hydrogenated polybutadiene chain and an effect
 thereof.
 JP-A-6-32947 discloses a composition obtained by compounding a polyolefin
 resin with a combination of hydrogenated block copolymers which differ in
 the microstructure of the conjugated diene block, for the purpose of
 improving the balance among practical low-temperature impact strength,
 heat deformation resistance and rigidity. In this reference are given
 Examples concerning compositions containing a combination of hydrogenated
 block copolymers having the structure of polystyrene/hydrogenated
 polybutadiene (poly(ethylene-butylene))/polystyrene/hydrogenated
 polybutadiene and differing in the microstructure of the conjugated diene
 block. Although the influence of the vinyl bond contents of the
 hydrogenated block copolymers used on impact strength, low-temperature
 impact strength and heat deformation resistance is shown in the above
 reference, there is no description therein concerning tensile elongation
 at break and surface hardness. In addition, there is no description nor
 suggestion concerning the amount of a terminal hydrogenated polybutadiene
 chain and an effect thereof. This conventional composition is not on a
 satisfactory level.
 JP-A-7-188481 discloses a composition comprising a highly flowable
 polypropylene and a block copolymer having the structure of
 polystyrene/hydrogenated polyisoprene/polystyrene/hydrogenated
 polyisoprene, for the purpose of improving impact resistance, rigidity and
 heat deformation resistance. There is a description therein to the effect
 that by regulating the molecular weight of the terminal hydrogenated
 polyisoprene (so that the content thereof is from 9.17 to 23.1% by weight
 based on the whole block copolymer), the composition can be made to have
 excellent physical and appearance properties. Compositions in which the
 contents of the terminal hydrogenated polyisoprene block in the block
 copolymer are 11.7% by weight and 12.26% by weight are shown in Examples
 given in the above reference. However, not only the content of the
 terminal hydrogenated polyisoprene block in the block copolymer employed
 in this conventional composition is 9.17% by weight or higher, which is
 outside the scope of the present invention, but also there is no
 description therein concerning an effect which is produced when that
 content is lower than 9.17% by weight. Furthermore, there is no
 description in the above reference concerning the balance among impact
 resistance, brittleness temperature, rigidity, surface hardness and
 tensile elongation at break, and the conventional composition is
 unsatisfactory in that balance. In the Examples given therein are shown
 compositions employing a block copolymer obtained using isoprene as a
 conjugated diene compound. Although there is a description in the above
 reference to the effect that the isoprene block copolymer is more
 effective in property improvement than a butadiene block copolymer, there
 is no description nor suggestion concerning the relationship between MFR,
 microstructure, or the like and the effect of property improvement.
 JP-A-8-20684 discloses a composition which comprises crystalline
 polypropylene and two hydrogenated block copolymers differing in melt flow
 rate (MFR) and in the content of a monovinyl-substituted aromatic
 hydrocarbon, and which is intended to be excellent in rigidity, heat
 deformation resistance and impact resistance and be satisfactory in
 appearance and moldability. There is a description therein to the effect
 that the composition tends to give moldings having flow marks and a poor
 appearance if the crystalline polypropylene has an MFR lower than 7 g/10
 min or if one of the hydrogenated block copolymers has an MFR lower than 5
 g/10 min. However, there is no description in the above reference
 concerning tensile elongation at break and surface hardness, and these
 properties of the conventional composition are not on a satisfactory
 level. Furthermore, there is no description nor suggestion therein
 concerning the amount of a terminal hydrogenated polybutadiene chain and
 the effect thereof.
 JP-A-8-20690 discloses a composition obtained by compounding a
 polypropylene resin with polyethylene, an olefin elastomer, a hydrogenated
 block copolymer, and an inorganic filler, for the purpose of improving the
 balance among properties such as impact strength, injection moldability,
 rigidity, impact resistance and brittleness temperature. In this reference
 are given Examples concerning compositions containing a hydrogenated block
 copolymer having the structure of polystyrene/hydrogenated polybutadiene
 (poly(ethylene-butylene))/polystyrene/hydrogenated polybutadiene. Although
 the vinyl content of the hydrogenated block copolymer used is shown in the
 above reference, the effect thereof is not described. Furthermore, there
 is no description nor suggestion therein concerning the amount of a
 terminal hydrogenated polybutadiene chain and the effect thereof. This
 conventional technique is insufficient in the effect of improving hardness
 and tensile elongation at break, and a further improvement in this respect
 is desired.
 As described above, a polyolefin resin composition has not yet been
 obtained which has an exceedingly good balance among impact resistance,
 brittleness temperature, rigidity, surface hardness and tensile elongation
 at break.
 SUMMARY OF THE INVENTION
 Under the above-described circumstances of the conventional techniques, an
 object of the present invention is to provide a thermoplastic elastomer
 having an excellent balance among heat resistance, flowability and
 moldability.
 Another object of the present invention is to provide a polyolefin resin
 composition containing a hydrogenated block copolymer having a specific
 structure to give an excellent balance among impact resistance,
 brittleness temperature, rigidity, surface hardness and tensile elongation
 at break.
 Other objects and effects of the invention will be apparent from the
 following description.
 As a result of extensive studies made by the present inventors, they have
 found a hydrogenated block copolymer which effectively eliminates the
 above described problems in conventional.techniques, as described above.
 The present invention has been completed based on the finding.
 That is, the above described objectives of the present invention have been
 achieved by providing:
 a hydrogenated block copolymer comprising:
 at least two polymer blocks A mainly comprising vinylaromatic hydrocarbon
 compound monomer units; and
 at least two polymer blocks B mainly comprising hydrogenated conjugated
 diene compound monomer units, in which at least 90% of the olefinically
 unsaturated double bonds contained in the unhydrogenated polymer block
 mainly comprising the conjugated diene compound monomer units is
 hydrogenated,
 wherein at least one of the terminal blocks is a polymer block B, the
 proportion of the terminal polymer block B in the hydrogenated block
 copolymer being 0.1% by weight or higher and lower than 9.1% by weight,
 and
 wherein the content of the vinylaromatic hydrocarbon compound units in the
 hydrogenated block copolymer is 12% by weight or higher and lower than 25%
 by weight.
 The present invention also relates to a resin composition containing the
 hydrogenated block copolymer and to a molded article produced from the
 resin composition.

DETAILED DESCRIPTION OF THE INVENTION
 The present invention is based on the finding that a hydrogenated block
 copolymer has an order-disorder transition temperature not higher than
 practical molding temperatures, by regulating the amount (proportion) of a
 terminal polymer block(s) B to within a specific range and the content of
 vinylaromatic hydrocarbon compound units to within a specific range. For
 example, an increase in the content of vinylaromatic hydrocarbon compound
 units results in an elevated order-disorder transition temperature when
 the number-average molecular weight is constant, while an increase in
 number-average molecular weight results also in an elevated order-disorder
 transition temperature when the content of vinylaromatic hydrocarbon
 compound units is constant. The present inventors have found that there is
 an important relationship between order-disorder transition temperature
 and moldability. The term "order-disorder transition temperature" as used
 herein means the temperature at which a hydrogenated block copolymer,
 which takes a two-phase separated state of a rubbery phase and a
 restrained phase around room temperature, comes into a single-phase state.
 The term "(excellent) moldability" as used herein has the following two
 meanings besides, simply, improved flowability. The first meaning of the
 moldability in the present invention is that when a hydrogenated block
 copolymer in a single-phase state (disorderly state) is extrusion-molded
 into a film, the extrudate is less apt to break in the space between the
 die and the wind-up roll as compared with extrudates formed from a
 hydrogenated block copolymer in a two-phase state (orderly state), whereby
 stable film production is possible. A conventional technique employed
 hitherto for avoiding film breakage or the like during extrusion molding
 has been to reduce the content of vinylaromatic hydrocarbon compound units
 in the hydrogenated block copolymer to be used, or to lower the
 number-average molecular weight of the block copolymer. However, these
 techniques have a problem that the molded article obtained has a reduced
 heat resistance. Although a higher molding temperature has been used in
 some cases to cope with the film breakage, use of this technique has been
 limited, for example, because of the decomposition temperatures of the
 additives and of the block copolymer itself. There have been cases where
 block copolymers having the same melt viscosity differ in the moldability
 as explained above even when molded under the same conditions. The present
 inventors have found that this phenomenon also is attributed to a
 difference in order-disorder transition temperatures.
 Furthermore, there have been cases where moldings obtained by melt-mixing a
 hydrogenated block copolymer with another resin and injection-molding the
 melt have flow marks on the surfaces thereof and hence have an impaired
 appearance. The present inventors have found that this phenomenon is also
 eliminated when a block copolymer having a lower order-disorder transition
 temperature is used (the second meaning of the moldability).
 As described above, there is an important relationship between the
 order-disorder transition temperature of a hydrogenated block copolymer
 and the moldability thereof. It is therefore necessary to employ a method
 capable of lowering the order-disorder transition temperature without
 impairing other properties, e.g., heat resistance and flowability.
 Although the order-disorder transition temperature may be lowered by
 reducing the content of vinylaromatic hydrocarbon compound units or by
 lowering the number-average molecular weight, the hydrogenated block
 copolymer thus modified has reduced heat resistance. However, the present
 inventors have succeeded in lowering a an order-disorder transition
 temperature to within a practical molding temperature range taking into
 account the thermal stability, etc. of polymers without adversely
 influencing the heat resistance and flowability, by designing a
 hydrogenated block copolymer to have a vinylaromatic hydrocarbon content
 within a specific range and to have at least one terminal polymer block
 mainly comprising a hydrogenated conjugated diene monomer units, which
 terminal block accounts for a specific amount (proportion) in the
 molecule. For example, when a hydrogenated block copolymer having the
 structure of styrene/hydrogenated polybutadiene/styrene is compared with a
 hydrogenated block copolymer according to the present invention having the
 structure of styrene/hydrogenated polybutadiene/styrene/hydrogenated
 polybutadiene and having the same number-average molecular weight and the
 same styrene content as those of the former block copolymer, then the
 copolymer of the present invention has a lower order-disorder transition
 temperature and better moldability although the two copolymers have the
 same heat resistance due to the same number-average molecular weight and
 the same styrene content. The effect that the incorporation of a terminal
 hydrogenated polybutadiene block enables the hydrogenated block copolymer
 to be excellent in flowability, heat resistance and moldability is
 produced only when the hydrogenated block copolymer satisfies the
 requirements according to the present invention concerning the amount
 (proportion) of the terminal hydrogenated polybutadiene block and the
 vinylaromatic hydrocarbon (e.g., styrene) content.
 The "flowability" used herein for a hydrogenated block copolymer is
 impaired when the melt viscosity thereof is high, and is improved when the
 melt viscosity thereof is low. As a measure of flowability is used the
 melt flow rate (MFR) in accordance with JIS K7210. Hydrogenated block
 copolymers having a high MFR are judged to have satisfactory flowability,
 while those having a low MFR are judged to have poor flowability. If a
 hydrogenated block copolymer having a low MFR is used, there may be cases
 where melt extrusion results in a reduced ejection amount and hence in
 reduced productivity. Generally employed techniques for improving the
 flowability of a hydrogenated block copolymer include lowering the
 number-average molecular weight thereof measured by GPC and calculated
 with standard polystyrene basis, and reducing the content of vinylaromatic
 compound monomer units while maintaining the same number-average molecular
 weight. However, these techniques impair the "heat resistance" of the
 hydrogenated block copolymer.
 The "heat resistance" of a hydrogenated block copolymer can be judged based
 on a measurement of the softening temperature thereof in a temperature
 range above room temperature. Hydrogenated block copolymers having a low
 softening temperature are judged to have poor "heat resistance", while
 those having a high softening temperature are judged to have satisfactory
 "heat resistance". Softening temperature can be determined, for example,
 by dynamic viscoelasticity analysis in which the temperature dependency of
 storage modulus, loss modulus or loss tangent is examined in a temperature
 range of from 50 to 150.degree. C. In the case where the temperature
 dependency of storage modulus is examined, the inflection point
 temperature of the resultant curve can be taken as the softening
 temperature. In the case of loss modulus or loss tangent, the peak
 temperature in the curve can be taken as the softening temperature.
 The cases where a hydrogenated block copolymer or a composition thereof has
 "impaired moldability" include: the case where, even when a hydrogenated
 block copolymer has a low melt viscosity and being moldable, it causes
 breakages of a molten film-form extrudate during film formation, making
 stable molding impossible; and the case where a blend of the hydrogenated
 block copolymer with another resin, when melt-mixed and injection-molded,
 gives moldings having flow marks.
 The hydrogenated block copolymer of the present invention may be blended
 with a polyolefin resin. In this case, the proportions of the former and
 the latter ingredients each may be from 1 to 99% by weight. This blending
 has the effect of imparting the excellent moldability according to the
 present invention. Furthermore, a resin composition comprising (1) from 60
 to 99% by weight of polyolefin resin and (2) from 1 to 40% by weight of
 the hydrogenated block copolymer of the present invention is a composite
 material having an excellent balance among impact resistance, tensile
 elongation at break, brittleness temperature, surface hardness and
 rigidity. In this case, if the proportion of the hydrogenated block
 copolymer is smaller than 1% by weight, impact resistance, tensile
 elongation at break and brittleness temperature are impaired. If the
 proportion thereof exceeds 40% by weight, surface hardness and rigidity
 are impaired. The preferred range of the proportion of the hydrogenated
 block copolymer is from 2 to 20% by weight, excluding 20% by weight.
 Namely, the resin composition of the present invention is based on a
 finding that a composition comprising a polyolefin resin and a
 hydrogenated block copolymer can have an excellent balance among impact
 resistance, tensile elongation at break, brittleness temperature, surface
 hardness and rigidity, when the hydrogenated block copolymer contains
 vinylaromatic compound monomer units in an amount within a given range and
 has a specific block arrangement. The present inventors made
 investigations based on the assumption that mechanical properties
 including brittleness temperature and tensile elongation at break are
 improved by improving the interfacial adhesion between polypropylene and a
 hydrogenated block copolymer. It is can be considered that a hydrogenated
 block copolymer having an increased molecular weight shows enhanced
 entanglement with polypropylene molecular chains during melt kneading to
 attain improved interfacial adhesion. It is thought that in order for the
 hydrogenated block copolymer to show sufficient entanglement with
 polypropylene molecular chains, the molecular weight thereof should be
 increased to some degree when the polypropylene molecular chains become
 shorter. That is, when polypropylene having a high molecular weight is
 used, the hydrogenated block copolymer may have a relatively small
 molecular weight. However, in the case where polypropylene having a
 reduced molecular weight is used in order to enhance alloy flowability in
 producing composition moldings, which are becoming large-sized in recent
 years, it cause necessity to use a hydrogenated block copolymer having an
 increased molecular weight. In addition, this technique has a problem that
 the hydrogenated block copolymer having an increased molecular weight has
 poor dispersibility under ordinary melt-kneading conditions, resulting in
 composition moldings having impaired mechanical properties. As a result of
 detailed investigations, the present inventors have found the optimal
 structure of a hydrogenated block copolymer which gives a composition
 improved in impact resistance, tensile elongation at break, brittleness
 temperature, surface hardness and rigidity even when the hydrogenated
 block copolymer is used in combination with polypropylenes of wide MFR
 range.
 In a propylene block copolymer, homopolypropylene blocks constitute a
 continuous phase and ethylene/a-olefin blocks constitute a dispersed
 phase. It is presumed that when a hydrogenated block copolymer contained
 in this system is present at the interface between the propylene block
 copolymer dispersed phase and the homopolypropylene, interfacial adhesion
 is improved and, hence, tensile elongation at break and brittleness
 temperature are improved. The present inventors have found that a
 hydrogenated block copolymer having a specific structure can efficiently
 localize at the interface between the propylene block copolymer dispersed
 phase and the homopolypropylene and improve the interfacial bonding
 strength between the dispersed phase and the homopolypropylene.
 The present invention is explained in more detail below.
 The polyolefin resin (1) for use in the present invention may be any resin
 obtained by polymerizing at least one monomer selected from ethylene,
 .alpha.-olefins having 3 to 12 carbon atoms, e.g., propylene, 1-butene,
 isobutylene, and 4-methyl-1-pentene, and the like. Specific examples
 thereof include homopolymers of ethylene, butene, methylpentene, and
 propylene, propylene block copolymers, propylene random copolymers, and
 mixtures thereof. Polyolefins having different molecular weights or
 different composition may be mixed. Especially preferred are propylene
 block copolymers. Comonomers for block or random copolymers of propylene
 include ethylene and .alpha.-olefins other than propylene. Among these,
 ethylene is preferred. These copolymers desirably have a propylene content
 of at least 55 mol %. In a propylene block copolymer produced using
 ethylene or an .alpha.-olefin as a comonomer, the homopolypropylene blocks
 constitute a continuous phase and the ethylene or .alpha.-olefin blocks
 constitute a dispersed phase. The content of this dispersed phase is
 desirably from 5 to 30% by weight based on the propylene block copolymer.
 This dispersed phase may contain polyethylene. In the present invention,
 the melt flow rate (in accordance with JIS K7210, conditions L) of the
 polypropylene resin is preferably from 0.1 to 200 g/10 min, and is more
 preferably not lower than 30 g/10 min from the standpoint of rigidity. For
 producing the polyolefin resin, any of conventionally known polymerization
 methods may be used. Examples thereof include transition polymerization,
 radical polymerization and ionic polymerization.
 The hydrogenated block copolymer (2) for use in the present invention
 comprises at least two polymer blocks A each mainly comprising
 vinylaromatic hydrocarbon compound monomer units and at least two polymer
 blocks B each mainly comprising hydrogenated conjugated diene compound
 monomer units. As the vinylaromatic hydrocarbon compound monomer units,
 one or more kinds of monomers selected, for example, from styrene,
 alkylstyrenes such as a-methylstyrene, p-methylstyrene and
 p-tert-butylstyrene, p-methoxystyrene, vinylnaphthalene, and the like can
 be used. Preferred among these is styrene. The content of such
 vinylaromatic compound monomer units in the block copolymer is from 12 to
 25% by weight, excluding 25% by weight, and is preferably from 14 to 25%
 by weight, excluding 25% by weight, from the standpoints of brittleness
 temperature, surface hardness and rigidity. If the content thereof is
 lower than 12% by weight, surface hardness and rigidity are impaired. If
 the content thereof is 25% by weight or higher, it heightens the
 brittleness temperature.
 The content of vinylaromatic compound monomer units can be measured with a
 nuclear magnetic resonance spectrometer (NMR), an ultraviolet spectrometer
 (UV), etc. The words "mainly comprising" as used herein, for example, the
 words "mainly comprising vinylaromatic compound monomer units" includes
 the case where the units are composed of one or more kinds of
 vinylaromatic monomers and the case where one or more kinds of
 vinylaromatic monomers are copolymerized with one or more kinds of other
 monomers capable of undergoing living anionic polymerization therewith.
 Examples of the copolymerizable monomers include conjugated diene compound
 monomers, methacrylic esters such as methyl methacrylate and butyl
 methacrylate, cyclohexadiene, and caprolactones. The mode of
 copolymerization is not particularly limited, and may be any of random,
 alternating, taper, etc. A plurality of the polymer blocks A may differ
 from one another in composition, molecular weight, etc.
 As the conjugated diene compounds, one or more kinds of compounds selected,
 for example, from butadiene, isoprene, 1,3-cyclohexadiene, 1,3-pentadiene,
 2,3-dimethyl-1,3-butadiene, and the like can be used. Especially preferred
 among these are butadiene, isoprene, and combined use of these. The
 microstructure of the unhydrogenated polymer block mainly comprising
 conjugated diene compound monomer units may be appropriately selected. For
 example, in the case of polybutadiene blocks, the 1,2-bond content thereof
 is preferably higher than 35 mol % and lower than 90 mol %, more
 preferably not lower than 40 mol % and lower than 60 mol %, and further
 preferably higher than 50 mol % and lower than 60 mol %. If the 1,2-bond
 content thereof is lower than 40 mol %, the tensile elongation at break is
 impaired. If the 1,2-bond content thereof is 60 mol % or higher, the
 brittleness temperature is heightened. In polyisoprene blocks, the
 3,4-bond content thereof is preferably higher than 0 mol % and lower than
 40 mol %. If the 3,4-bond content thereof is 40 mol % or higher, the
 brittleness temperature is heightened. The microstructure can be
 determined with a nuclear magnetic resonance spectrometer (NMR). The term
 "mainly comprising diene compound monomer units" includes the case in
 which a conjugated diene compound is copolymerized with one or more other
 monomers capable of undergoing living anionic polymerization therewith.
 Examples of these copolymerizable monomers include vinylaromatic compound
 monomers, methacrylic esters such as methyl methacrylate and butyl
 methacrylate, cyclohexadiene, and caprolactones. The mode of
 copolymerization is not particularly limited, and may be any of random,
 alternating, taper, etc. A plurality of the polymer blocks B may differ
 from one another in composition, molecular weight, etc.
 The term "mainly comprising" as used herein for a polymer block means that
 the content of the monomer units concerned is higher than 50 mol %,
 preferably at least 70 mol %, based on the polymer block.
 In the hydrogenated block copolymer of the present invention, at least 90%
 of the olefinically unsaturated double bonds contained in the
 unhydrogenated polymer block mainly comprising the conjugated diene
 compound monomer units is hydrogenated. If the degree of hydrogenation
 thereof is lower than 90%, the interfacial adhesion between the block
 copolymer and a polyolefin is reduced, so that the resultant composition
 has reduced impact resistance and reduced tensile elongation at break and
 deteriorates by the action of heat, light, etc. to come to have impaired
 thermoplasticity. In the blocks A, up to 20% of all unsaturated double
 bonds contained in the benzene rings of the vinylaromatic compound units
 may be hydrogenated. The degree of hydrogenation can be determined with a
 nuclear magnetic resonance spectrometer (NMR).
 The hydrogenated block copolymer preferably has a melt flow rate (MFR) of
 from 1.0 to 15 g/10 min, excluding 15 g/10 min, as measured in accordance
 with JIS K7210 under the conditions of a temperature of 230.degree. C. and
 a load of 2.16 kg. The more preferred range thereof is from 3.0 to 10 g/10
 min. If the MFR thereof is lower than 1.0 g/10 min, impact resistance is
 impaired. If the MFR thereof is 15 g/10 min or higher, sufficient tensile
 elongation at break is not obtained. In the present invention, the
 hydrogenated block copolymer may have any structure such as, e.g., a
 linear, branched, radial, or comb-shaped structure. However, the
 hydrogenated block copolymer should be constituted of at least two polymer
 blocks each mainly comprising vinylaromatic hydrocarbon compound monomer
 units and at least two polymer blocks B each mainly comprising
 hydrogenated conjugated diene compound monomer units. Furthermore, at
 least one of the terminal blocks should be a polymer block B. Preferred
 examples of the block arrangement include A-B-A-B and B-A-B-A-B. In the
 case where neighboring blocks are connected by a random copolymer, this
 random copolymer may have a tapered structure in which the composition
 thereof changes gradually.
 The terminal polymer block(s) B respectively account for a proportion of
 from 0.1 to 9.1% by weight, excluding 9.1% by weight, based on the weight
 of the hydrogenated block copolymer. From the standpoints of brittleness
 temperature and tensile elongation at break, the proportion thereof is
 preferably from 0.3 to 7.5% by weight, more preferably from 3 to 5.0% by
 weight, excluding 3 and 5.0% by weight. If the proportion thereof is lower
 than 0.1% by weight, tensile elongation at break is impaired. If the
 proportion thereof is 9.1% by weight or higher, the hydrogenated block
 copolymer is impaired in brittleness temperature. For example, in the case
 where the hydrogenated block copolymer has a block arrangement of A-B-A-B,
 the proportion of the terminal polymer block B in the whole block
 copolymer should be in the range of from 0.1 to 9.1% by weight, excluding
 9.1% by weight. In the case where the hydrogenated block copolymer has a
 block arrangement of B1-A-B2-A-B3 (B1, B2, B3: polymer block mainly
 comprising hydrogenated conjugated diene compound monomer units), the
 proportion of the terminal polymer block B1 in the whole block copolymer
 should be in the range of from 0.1 to 9.1% by weight, excluding 9.1% by
 weight, and the proportion of the terminal polymer block B3 in the whole
 block copolymer should be also in the range of from 0.1 to 9.1% by weight,
 excluding 9.1% by weight.
 The order-disorder transition temperature of the hydrogenated block
 copolymer according to the present invention is preferably not higher than
 260.degree. C., more preferably not higher than 230.degree. C., from the
 standpoint of attaining satisfactory tensile elongation at break. In the
 case where the composition is molded at a temperature not lower than the
 order-disorder transition temperature of the hydrogenated block copolymer,
 the resultant composition molding has improved tensile elongation at
 break. The present inventors presume that the reasons for this effect are
 as follows. When the hydrogenated block copolymer in which phase
 separation has disappeared is melt-kneaded with a polyolefin resin,
 molecular chains of the hydrogenated block copolymer are more apt to be
 entangled with molecular chains of the polyolefin resin as compared when
 maintaining the two-phase state of the hydrogenated block copolymers
 during melting. When the molten composition in such an entangled state is
 cooled and undergo phase separation, the interfacial adhesion strength
 between the dispersed phase and the continuous phase is improved due to
 the anchoring effect of the hard domains. The present inventors have
 furthermore found that use of a propylene block copolymer is preferred in
 that the hydrogenated block copolymer can be efficiently present at the
 interface between the propylene block copolymer dispersed phase and
 homopolypropylene to improve interfacial bonding strength, whereby tensile
 elongation at break and other properties can be further improved. Since
 polyolefin resin compositions are preferably molded at a molding
 temperature of 260.degree. C. or lower, more preferably 230.degree. C. or
 lower, from the standpoint of avoiding the deterioration of the additives
 and the resin, etc., the order-disorder transition temperature of the
 hydrogenated block copolymer is preferably 260.degree. C. or lower, more
 preferably 230.degree. C. or lower, from the standpoint of obtaining
 composition moldings having improved tensile elongation at break. The
 molded articles obtained by molding the composition of the present
 invention at a temperature not lower than the order-disorder transition
 temperature of the hydrogenated block copolymer are suitable for use as
 automotive exterior materials such as bumpers and automotive interior
 materials such as instrument panels and air bag covers. The term "molding
 temperature" means the temperature at which a composition is melt-kneaded
 and formed, the temperature at which a composition obtained is formed,
 etc. The term "order-disorder transition temperature" means the
 temperature at which a two-phase separated state of a rubbery phase and a
 restrained phase which a hydrogenated block copolymer takes around room
 temperature disappears. The order-disorder transition temperature can be
 determined by small-angle X-ray scattering analysis or rheological
 analysis. In determining the order-disorder transition temperature of a
 hydrogenated block copolymer by Theological analysis, the copolymer is
 examined for dynamic storage modulus (G') and loss modulus (G") at various
 temperatures in a sufficient shear rate range, and the found values of G'
 are plotted against those of G". The order-disorder transition temperature
 can be determined from the temperature at which the resultant straight
 line comes to have the same gradient and the same intercept.
 Alternatively, the temperature dependency of G' is measured from the
 higher-temperature side at a sufficiently low frequency, e.g., 0.1 Hz or
 lower, and the order-disorder transition temperature can be determined
 from the inflection point appearing on the higher-temperature side. The
 hydrogenated block copolymer of the present invention has a number-average
 molecular weight as calculated with standard polystyrene basis of
 preferably from 35,000 to 200,000, more preferably from 40,000 to 150,000,
 excluding 150,000. If the number-average molecular weight of the
 hydrogenated block copolymer is lower than 35,000, the copolymer does not
 have the general functions of elastomers and does not give a composition
 having desired properties. If the number-average molecular weight of the
 hydrogenated block copolymer exceeds 200,000, the copolymer has an
 elevated order-disorder transition temperature, impaired moldability,
 reduced flowability, and poor handleability. The values of number-average
 molecular weight are those calculated with standard polystyrene basis in
 gel permeation chromatography (GPC) using a commercial standard
 polystyrene for GPC calibration curve drawing.
 The hydrogenated block copolymer of the present invention can be produced,
 for example, by any of the polymerization methods described, e.g., in
 JP-B-36-19286, JP-B-43-14979, and JP-B-49-36957 so as to be within the
 scope of the present invention. (The term "JP-B" as used herein means an
 "examined Japanese patent publication".) In these methods, a vinylaromatic
 monomer is block-copolymerized with butadiene monomer in a hydrocarbon
 solvent using an anionic-polymerization initiator, e.g., an organolithium
 compound, and a vinylating agent, e.g., an ether compound such as diethyl
 ether and tetrahydrofuran or a tertiary amine such as triethylamine and
 N,N,N',N'-tetramethylethylenediamine, and optionally further using as a
 coupling agent a polyfunctional compound such as, e.g., epoxidized soybean
 oil and silicon tetrachloride, whereby a block copolymer having a linear,
 branched, or radial structure is obtained. The block copolymer thus
 produced is hydrogenated by a known method, e.g., the method described in
 JP-B-42-87045, whereby the hydrogenated block copolymer of the present
 invention is obtained.
 The resin composition of the present invention can be prepared in
 accordance with the intended proportions of the individual ingredients by
 using a suitable apparatus for use in mixing ordinary polymeric
 substances. Examples of such mixing apparatuses include kneading machines
 such as a Banbury mixer, Labo Plastomill, single-screw extruder and
 twin-screw extruder. A melt-mixing method using an extruder is preferred
 from the standpoints of productivity and high kneading effect.
 In the hydrogenated block copolymer for use in the present invention, part
 or all of the molecules thereof may have been modified so as to have a
 functional group through addition reaction with an unsaturated carboxylic
 acid or a derivative thereof. The hydrogenated block copolymer may be used
 in combination with another hydrogenated block copolymer which differs
 therefrom in composition or structure, or with an olefin elastomer such
 as, e.g., an ethylene/propylene rubber, an ethylene/butylene rubber, an
 ethylene/octene rubber, another ethylene/.alpha.-olefin copolymer rubber,
 or an ethylene/propylene/unconjugated diene terpolymer rubber. The resin
 composition of the present invention comprising a polyolefin resin (1) and
 a hydrogenated block copolymer (2) can be mixed with from 1 to 30 parts by
 weight of an olefin elastomer (3) per 100 parts by weight of the resin
 composition.
 Additives such as, e.g., an inorganic filler, stabilizer, lubricant,
 colorant, silicone oil and flame retardant can be added to the composition
 of the present invention. Examples of the inorganic filler include calcium
 carbonate, talc, magnesium hydroxide, mica, barium sulfate, silica (white
 carbon), titanium oxide, and carbon black. In the present invention, the
 composition (I) comprising a polyolefin resin (1) and a hydrogenated block
 copolymer (2), or the composition (II) comprising a polyolefin resin (1),
 a hydrogenated block copolymer (2) and an olefin elastomer (3) preferably
 contains from 5 to 50 parts by weight of an inorganic filler (4) per 100
 parts by weight of the respective composition (I) or (II) from the
 standpoint of rigidity. Examples of the stabilizer include conventionally
 known stabilizers such as hindered phenol type antioxidants,
 phosphorus-based heat stabilizers, hindered amine type light stabilizers,
 and benzotriazole type UV absorbers. Examples of the lubricant include
 stearic acid, stearamide, stearic esters, metal salts and other compounds
 of stearic acid, amorphous silica, and talc.
 The present invention will be explained below in greater detail by
 reference to Examples, but the invention should not be construed as being
 limited thereto.
 The following Examples 1 to 4 and comparative Examples 1 to 5 are directed
 to hydrogenated block copolymers and compositions thereof.
 Analyses and evaluations were conducted by the following methods.
 Determination of Styrene Content in Block Copolymer
 The absorbance of a chloroform solution of a hydrogenated block copolymer
 at 254 nm was measured with an ultraviolet spectrometer. The styrene
 content of the hydrogenated block copolymer was determined from a
 calibration curve obtained beforehand by determining the relationship
 between styrene content and absorbance.
 Determination of the Content of Terminal Polymer Block B
 A polymer was sampled before and after the polymerization for incorporating
 an unhydrogenated terminal polymer block B, and the two samples were
 analyzed with an ultraviolet spectrometer to determine the styrene content
 in each polymer. From the difference in styrene content between the two
 polymer samples, the proportion of a terminal polymer block B in the
 hydrogenated block copolymer was determined.
 Molecular Weight calculated with Standard Polystyrene Basis
 The molecular weight was calculated in gel permeation chromatography (GPC)
 using a commercial standard polystyrene for GPC calibration curve drawing.
 Melt Flow Rate (MFR)
 MFR was measured in accordance with JIS K7210 under the conditions of a
 load of 2.16 kg and a temperature of 230.degree. C.
 Softening Temperature
 Measurement was made with mechanical spectrometer RMS800, manufactured by
 Rheometrics Inc., under the conditions of a frequency of 6.28 rad/sec,
 25-mm parallel plate, and a heating rate of 3.degree. C./min to determine
 the peak temperature for loss modulus in the range of from 50 to
 150.degree. C.
 Moldability into Film
 A hydrogenated block copolymer was melted in a 25-mm extruder regulated so
 as to enable the block copolymer to be ejected through a T-die at a
 temperature of 260.degree. C. or 230.degree. C. The melt was extruded with
 the T-die and wound up to form a film. At each temperature, film winding
 was conducted at a constant rate and the screw rotational speed of the
 extruder was regulated so as to result in the same polymer ejection
 amount. The polymers which could be wound up are indicated by 0, while
 those which broke in the space between the T-die and the wind-up roll are
 indicated by x.
 Appearance of Molded Article
 Using a twin-screw extruder, a hydrogenated block copolymer was melt-mixed
 with homopolypropylene (M1600, manufactured by Asahi Kasei Kogyo Kabushiki
 Kaisha, Japan) in a proportion of 80/20 (by weight) and pelletized. The
 resultant pelletized composition was introduced into an injection molding
 machine regulated so as to have a resin temperature of 230.degree. C., and
 flat plates having a thickness of 2 mm, a width of 10 mm, and a length of
 10 mm were molded under the following conditions. The molded articles
 obtained were visually examined for flow marks. The molded articles having
 a satisfactory appearance with no flow marks are indicated by o, while
 those having a poor appearance are indicated by x.
 Injection rate: low
 Mold temperature: 40.degree. C.
 Determination of Order-Disorder Transition Temperature
 Using mechanical spectrometer RMS800, manufactured by Rheometrics Inc., G'
 and G" were measured at different temperatures under the conditions of
 25-mm parallel plate and frequencies of from 0.1 rad/sec to 100 rad/sec.
 The temperature at which the gradient of the straight line obtained by
 plotting G' against G" came to change was taken as the order-disorder
 transition temperature.
 Preparation of Hydrogenation Catalyst
 Two liters of dried and purified cyclohexane was introduced into a reactor
 the atmosphere in which had been replaced with nitrogen. Therein was
 dissolved 40 mmol of bis (.eta..sup.5 -cyclopentadienyl)titanium
 di(chloride). A cyclohexane solution containing 60 mmol of n-butyllithium
 was added to the solution, and the resultant mixture was reacted at
 25.degree. C. for 5 minutes. Immediately thereafter, 40 mmol of n-butanol
 was added thereto and this mixture was stirred and stored at room
 temperature. The resultant solution is referred to as "hydrogenation
 catalyst solution a".
 Preparation of Dilithium Catalyst
 A dilithium catalyst was obtained by the method described in
 Macromolecules, Vol.29, No.19, 1996. The starting materials used were
 commercial materials having the highest purity. Prior to use, the
 dilithium catalyst was partly deactivated with water and then analyzed by
 GC-MS to ascertain that it had a degree of dilithium incorporation of
 100%.
 EXAMPLE 1
 First-Stage Polymerization
 Into a 100-L (liter) autoclave the atmosphere in which had been replaced
 with nitrogen were introduced 28.6 L of dried and purified cyclohexane,
 5.72 g of tetramethylethylenediamine, and 2.09 kg of a styrene/cyclohexane
 mixture having a styrene content of 33 wt %. After the contents were
 heated to 70.degree. C., a cyclohexane solution containing 7.7 g of
 n-butyllithium was added thereto to carry out polymerization.
 Second-Stage Polymerization
 Subsequently to completion of the styrene polymerization as the first
 stage, 16.1 kg of a 1,3-butadiene/cyclohexane mixture having a
 1,3-butadiene content of 33 wt % was added to carry out polymerization.
 Third-Stage Polymerization
 After completion of the 1,3-butadiene polymerization as the second stage,
 2.09 kg of styrene/cyclohexane mixture having a styrene content of 33 wt %
 was added to carry out polymerization.
 The polystyrene/polybutadiene/polystyrene block copolymer (SBS1) obtained
 in this stage was sampled and examined for styrene content. As a result,
 the styrene content thereof was found to be 20.6 wt %.
 Fourth-Stage Polymerization
 Subsequently, 927 g of a 1,3-butadiene/cyclohexane mixture having a
 1,3-butadiene content of 33 wt % was introduced into the autoclave to
 carry out polymerization.
 Thereafter, 2.5 g of methanol was added to obtain a
 polystyrene/polybutadiene/polystyrene/polybutadiene block copolymer
 (SBSB1) which had a styrene content of 19.7 wt % and in which the
 polybutadiene blocks had a 1,2-bond content of 41.8 mol %. A comparison in
 GPC curve between SBS1 and SBSB1 revealed that SBSB1 had a shorter elution
 time and hence had an increased molecular weight. The GPC curves for SBS1
 and SBSB1 are shown in FIG. 1. The proportion of the terminal
 polybutadiene chain was determined from the change in styrene content, and
 was found to be 4.37 wt %.
 Hydrogenation
 Cyclohexane was then introduced into the autoclave in such an amount as to
 result in a polymer concentration of 12 wt %. The atmosphere inside the
 autoclave was replaced with hydrogen to adjust the hydrogen pressure to
 0.7 MPa (gauge pressure), and the contents were heated to 70.degree. C.
 Subsequently, hydrogenation catalyst solution a was added thereto in such
 an amount that the amount of the titanium contained therein was 30 ppm of
 the polymer, and hydrogen was continuously fed for 1 hour so as to
 maintain a hydrogen pressure of 0.7 MPa (gauge pressure). Finally, an
 A-B-A-B type hydrogenated block copolymer (SEBS1) was obtained which had a
 degree of hydrogenation of 99.8% and a molecular weight calculated with
 standard polystyrene basis of 115,000. The structure, results of various
 analyses, and moldability of the hydrogenated block copolymer obtained are
 shown in Tables 1 and 3. The block copolymer obtained in Example 1 was
 examined for the temperature dependency of loss modulus, and the results
 obtained are shown in FIG. 2.
 EXAMPLE 2
 Polymerizations and hydrogenation were conducted under the same conditions
 as in Example 1, except that 1,942 g of a 1,3-butadiene/cyclohexane
 mixture having a 1,3-butadiene content of 33 wt % was added for carrying
 out the fourth-stage polymerization. Thus, a hydrogenated block copolymer
 (SEBS2) was obtained. The structure, results of various analyses, and
 moldability of the hydrogenated block copolymer obtained are shown in
 Tables 1 and 3.
 EXAMPLE 3
 First-Stage Polymerization
 Into a 100-L autoclave the atmosphere in which had been replaced with
 nitrogen were introduced 48.6 L of dried and purified cyclohexane, 5.72 g
 of tetramethylethylenediamine, and 15.2 kg of a 1,3-butadiene/cyclohexane
 mixture having a 1,3-butadiene content of 33 wt %. After the contents were
 heated to 70.degree. C., a dilithium catalyst containing 0.120 mol of
 lithium was added thereto to carry out polymerization.
 Second-Stage Polymerization
 Subsequently to completion of the 1,3-butadiene polymerization as the first
 stage, 4.18 kg of a styrene/cyclohexane mixture having a styrene content
 of 33 wt % was added to carry out polymerization. The
 polystyrene/polybutadiene/polystyrene block copolymer obtained in this
 stage was sampled and examined for styrene content. As a result, the
 styrene content thereof was found to be 21.4 wt %.
 Third-Stage Polymerization
 After completion of the styrene polymerization as the second stage, 1.85 kg
 of a 1,3-butadiene/cyclohexane mixture having a 1,3-butadiene content of
 33 wt % was added to carry out polymerization.
 Thereafter, 2.5 g of methanol was added to obtain a
 polybutadiene/polystyrene/polybutadiene/polystyrene/polybutadiene lock
 copolymer which had a styrene content of 19.4 wt % and in which the
 polybutadiene blocks had a 1,2-bond content of 41.7 mol %. Since a
 dilithium catalyst had been used for the polymerizations, the two terminal
 polybutadiene blocks had the same molecular weight. The proportion of each
 terminal polybutadiene chain was determined from the change in styrene
 content, and was found to be 4.67 wt %. (Hydrogenation)
 Thereafter, the atmosphere inside the autoclave was replaced with hydrogen
 to adjust the hydrogen pressure to 0.7 MPa (gauge pressure), and the
 contents were heated to 70.degree. C. Subsequently, hydrogenation catalyst
 solution a was added thereto in such an amount that the amount of the
 titanium contained therein was 100 ppm of the polymer, and hydrogen was
 continuously fed for 1 hour so as to maintain a hydrogen pressure of 0.7
 MPa (gauge pressure). Finally, a B-A-B-A-B type hydrogenated block
 copolymer (SEBS3) was obtained which had a degree of hydrogenation of
 99.8% and a molecular weight calculated with standard polystyrene basis of
 115,000. The structure, results of various analyses, and moldability of
 the hydrogenated block copolymer obtained are shown in Tables 1 and 3.
 EXAMPLE 4
 Polymerizations and hydrogenation were conducted under the same conditions
 as in Example 1, except that the amounts of n-butyllithium and
 tetramethylethylenediamine used in the first stage were changed. Thus, a
 hydrogenated block copolymer (SEBS4) was obtained. The structure, results
 of various analyses, and moldability of the hydrogenated block copolymer
 obtained are shown in Tables 1 and 3. A plot of storage modulus (G')
 against loss modulus (G") at different temperatures is shown in FIG. 3.
 The order-disorder transition temperature (MST) of the hydrogenated block
 copolymer was 190.degree. C.&lt;MST.ltoreq.195.degree. C.
 Comparative Example 1
 Polymerizations and hydrogenation were conducted under the same conditions
 as in Example 1, except that 3,059 g of a 1,3-butadiene/cyclohexane
 mixture having a 1,3-butadiene content of 33 wt % was added for carrying
 out the fourth-stage polymerization. Thus, a hydrogenated block copolymer
 (SEBS5) was obtained. The structure, results of various analyses, and
 moldability of the hydrogenated block copolymer obtained are shown in
 Tables 1 and 3.
 Comparative Example 2
 Polymerizations and hydrogenation were conducted under the same conditions
 as in Example 1, except that the amounts of n-butyllithium and
 tetramethylethylenediamine used in the first stage were changed. Thus, a
 hydrogenated block copolymer (SEBS6) was obtained. The structure, results
 of various analyses, and moldability of the hydrogenated block copolymer
 obtained are shown in Tables 1 and 3.
 Comparative Example 3
 Polymerizations and hydrogenation were conducted under the same conditions
 as in Example 1, except that the amounts of n-butyllithium and
 tetramethylethylenediamine used in the first stage were changed, that the
 amount of the styrene/cyclohexane mixture having a styrene content of 33
 wt % added in the first and third stages was changed to 4.14 kg, and that
 the amount of the 1,3-butadiene/cyclohexane mixture having a 1,3-butadiene
 content of 33 wt % added in the second stage was changed to 12.0 kg. Thus,
 a hydrogenated block copolymer (SEBS7) was obtained. The structure,
 results of various analyses, and moldability of the hydrogenated block
 copolymer obtained are shown in Tables 1 and 3.
 Comparative Example 4
 Polymerizations and hydrogenation were conducted under the same conditions
 as in Example 1, except that the fourth-stage polymerization was omitted.
 Thus, a hydrogenated block copolymer (SEBS8) was obtained. The structure,
 results of various analyses, and moldability of the hydrogenated block
 copolymer obtained are shown in Tables 1 and 3.
 Comparative Example 5
 Polymerizations and hydrogenation were conducted under the same conditions
 as in Comparative Example 4, except that the amounts of n-butyllithium and
 tetramethylethylenediamine used in the first stage were changed. Thus, a
 hydrogenated block copolymer (SEBS9) was obtained. The structure, results
 of various analyses, and moldability of the hydrogenated block copolymer
 obtained are shown in Tables 1 and 3.
 TABLE 1
 Content of
 one
 Order-disorder
 Kind of terminal Degree of
 Average 1,2- or transition
 conjugated polymer hydroge- Styrene
 molecular 3,4-bond temperature
 diene block B nation content weight
 MFR content (= T ODT)
 Structure (component B) (wt %) (%) (wt %)
 (/10,000) (g/10 min) (mol %) (.degree. C.)
 SEBS 1 A-B-A-B butadiene 4.37 99.8 19.7 11.5
 1.3 41.8 230.degree. C. &lt; T ODT .ltoreq. 260.degree. C.

(1,2)
 TABLE 3
 Peak temperature in
 Moldability,
 loss modulus curve (.degree. C.)
 Moldability into film Moldability,
 Hydrogenated MFR lower-temp. higher-temp. Molding
 temperature Appearance of
 block copolymer (g/10 min) side side 260.degree.
 C. 23.degree. C. molded article
 Ex. 1 SEBS1 1.3 85.6 114 .smallcircle.
 x not evaluated
 Ex. 2 SEBS2 1.0 84.5 115 .smallcircle.
 x not evaluated
 Ex. 3 SEBS3 1.4 85.5 114 .smallcircle.
 x not evaluated
 Ex. 4 SEB54 5.3 82.0 109 .smallcircle.
 .smallcircle. .smallcircle.
 Comp. Ex. 1 SEBS5 0.6 88.4 114 .smallcircle.
 x not evaluated
 Comp. Ex. 2 SEBS6 0.9 83.0 108 .smallcircle.
 x not evaluated
 Comp. Ex. 3 SEBS7 0.0 not melted not melted not moldable
 not moldable not evaluated
 Comp. Ex. 4 SEBS8 0.5 87.4 116 x
 x not evaluated
 Comp. Ex. 5 SEBS9 3.8 82.0 108 x
 x x
 Table 3 clearly shows that the hydrogenated block copolymers according to
 the present invention and the compositions thereof were excellent in heat
 resistance, flowability, and moldability.
 The following Examples 5 to 10 and comparative Examples 6 to 12 are
 directed to resin compositions comprising a hydrogenated block copolymer
 and a polyolefin resin.
 Methods used for property measurements are as follows.
 MFR: in accordance with JIS K7210, conditions L.
 Izod impact strength: in accordance with JIS K7110; notched.
 Brittleness temperature: in accordance with JIS K7216.
 Flexural modulus: in accordance with JIS K7203; bending rate, 2 mm/min.
 Surface hardness: in accordance with JIS K7202, hardness R.
 Tensile test: in accordance with JIS K6758; pulling rate, 20 mm/min.
 (I) Ingredients
 (1) Polyolefin Resins
 Propylene block copolymers PP1 (MK755H, manufactured by Japan Polyolefin
 Co., Ltd., Japan; MFR, 63 g/10 min), PP2 (MK711H, manufactured by Japan
 Polyolefin Co., Ltd.; MFR, 43 g/10 min), and PP3 (MK711, manufactured by
 Japan Polyolefin Co., Ltd.; MFR, 33 g/10 min) were used.
 (2) Hydrogenated Block Copolymers
 Styrene and butadiene were subjected to anionic block copolymerization in
 cyclohexane solvent using n-butyllithium as an initiator and
 tetrahydrofuran as a 1,2-bond content regulator to thereby obtain a
 styrene/butadiene block copolymer. The styrene/butadiene block copolymer
 obtained was hydrogenated at a hydrogen pressure of 5 kg/cm.sup.2 and a
 temperature of 50.degree. C. using bis(.eta..sup.5
 -cyclopentadienyl)titanium di(chloride) and n-butyllithium as a
 hydrogenation catalyst. The polymer structure was controlled by changing
 the feed amounts of the monomers and the sequence of monomer addition. The
 molecular weight, 1,2-bond content, and degree of hydrogenation of the
 block copolymer were controlled by changing the catalyst amount, the
 amount of the 1,2-bond content regulator, and the period of hydrogenation,
 respectively. The styrene content of the block copolymer was determined
 with an ultraviolet spectrometer (UV), and the 1,2-bond content and degree
 of hydrogenation thereof were determined with a nuclear magnetic resonance
 spectrometer (NMR). The order-disorder transition temperature (T ODT)
 thereof was determined in the following manner. Using mechanical
 spectrometer RMS800, manufactured by Rheometrics Inc., G' and G" were
 measured at different temperatures under the conditions of 25-mm parallel
 plate and frequencies of from 0.1 rad/sec to 100 rad/sec. The temperature
 at which the gradient of the straight line obtained by plotting G' against
 G" came to change was taken as the order-disorder transition temperature.
 On the other hand, styrene and isoprene were subjected to living anionic
 block copolymerization in cyclohexane solvent using sec-butyllithium as an
 initiator to thereby obtain a styrene/isoprene block copolymer. The
 styrene/isoprene block copolymer obtained was hydrogenated at a hydrogen
 pressure of 50 kg/cm.sup.2 and a temperature of 50.degree. C. using nickel
 naphthenate and triethylaluminum as a hydrogenation catalyst. The polymer
 structure was controlled by changing the feed amounts of the monomers and
 the sequence of monomer addition. The molecular weight and degree of
 hydrogenation of the block copolymer were controlled by changing the
 catalyst amount and the period of hydrogenation, respectively. The styrene
 content of the block copolymer was determined with an ultraviolet
 spectrometer (UV), and the degree of hydrogenation thereof was determined
 with a nuclear magnetic resonance spectrometer (NMR). The order-disorder
 transition temperature (T ODT) thereof was determined in the following
 manner. Using mechanical spectrometer RMS800, manufactured by Rheometrics
 Inc., G' and G" were measured at different temperatures under the
 conditions of 25-mm parallel plate and frequencies of from 0.1 rad/sec to
 100 rad/sec. The temperature at which the gradient of the straight line
 obtained by plotting G' against G" came to change was taken as the
 order-disorder transition temperature.
 The structure and results of analyses of each sample are shown in Table 2.
 TABLE 2
 Content of
 one
 Order-disorder
 Kind of terminal Degree of Average
 1,2- or transition
 conjugated polymer hydroge- Styrene molecular
 3,4-bond temperature
 diene block B nation content weight
 MFR content (= T ODT)
 Structure (component B) (wt %) (%) (wt %) (/10,000) (g/10
 min) (mol %) (.degree. C.)
 SEBS10 A-B-A-B butadiene 4.8 99.8 17.5 11.8
 6.0 51.8 T ODT .ltoreq. 230.degree. C.