Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1997-07-10
2002-08-13
Niland, Patrick D. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C525S098000, C525S192000, C525S193000, C525S194000, C525S197000
Reexamination Certificate
active
06433062
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for the preparation of a thermoplastic elastomeric resin composition.
The present invention also relates to a thermoplastic elastomeric resin composition.
PRIOR ART
Thermoplastic elastomeric resins which are rubber-like materials, do not need a vulcanization process and have thermoplastic resin-like molding processability are attracting attention in the fields of auto parts, parts for electric appliances, electric wire insulation, footwears and general goods, and in the is field of cap sealing materials.
Various types of such thermoplastic elastomeric resins have been developed and put on sale, such as polyolefine type, polyurethane type, polyester type, polystyrene type and polyvinyl chloride type.
Among those, polystyrene type thermoplastic elastomeric resins such as styrene-butadiene block copolymers (SBS) and styrene-isoprene block copolymers (SIS) and hydrogenated resins thereof have high softness and good rubber elasticity at normal temperature. Further, thermoplastic elastomeric resin compositions obtained from these show good processability.
However, these block copolymer compositions are unsatisfactory in compression set at a high temperature, particularly at 100° C. and, moreover, tensile properties deteriorate considerably at 80° C. or more. Thus, such compositions do not meet the levels of properties required in the fields of vulcanized rubber.
Meanwhile, the thermoplastic elastomers mentioned above are also attracting attention in the fields of cap sealing materials. Particularly, polyolefin type thermoplastic elastomers are used widely because of their high sanitary reliability and cheapness. However, these polyolefin type thermoplastic elastomers are poor in softness and, therefore, exhibit poor sealing property.
Alternatively, polystyrene type thermoplastic elastomeric resins such as SBS and SIS and hydrogenated resins thereof have high softness and good rubber elasticity at normal temperature. Further, thermoplastic elastomeric resin compositions obtained from these show good processability. Accordingly, these are used widely as an alternate of vulcanized rubber. However, these polystyrene type thermoplastic elastomer compositions cannot meet the n-heptane extraction test of the tests of Notification No. 20 of the Japanese Welfare Ministry, because softening agents such as paraffinic oil are generally added to these compositions in order to control their hardness. Accordingly, it is hard to use them as a cap sealing. Alternatively, if the paraffinic oil is not used, the softness and moldability of them deteriorate.
In order to solve such a drawback, there has been proposed a composition containing polybutene or polyisobutene as a softening agent. However, the composition disclosed are poor in heat resistance at 120° C.
Another resin compositions which comprise the block copolymer used as component (a) in the present invention has been proposed in Japanese Patent Application Laid-Open Nos. Sho-53-138451/1978, 53-138453/1978, 53-138454/1978, 53-138456/1978, 53-138458/1978, 53-138460/1978 and 53-138461/1978. However, heat resistance is poor.
The composition disclosed in Japanese Patent Application Laid-Open No. 58-215446/1983 comprises isotactic polypropylene. This composition is excellent in mechanical strength and heat resistance. However, the hardness is in the D hardness area. Thus, it cannot be said that the composition is excellent in sealing property.
SUMMARY OF THE INVENTION
A purpose of the invention is to provide a process for the preparation of a thermoplastic elastomer composition which is soft and excellent in heat deformation resistance, mechanical strength, moldability and processability.
The present inventors have noticed that an organic peroxide generate radicals, which then effect crosslinking of polyethylene and molecule cutting of polypropylene, particularly effect molecule cutting of polypropylene to deteriorate the physical properties in the elastomer composition obtained. We have now found that when a smallest amount of polypropylene needed for increasing the flowability during melting is added and an amount of polyethylene for obtaining proper dispersion is used, it is possible to enhance the crosslinking of polyethylene and dispersion of rubber component and to prepare the thermoplastic elastomer composition having excellent properties. This finding leads to the present invention.
Thus, the present invention provides a process for the preparation of a thermoplastic elastomeric resin composition comprising melt kneading
(a) 100 parts by weight of a block copolymer consisting of at least two polymeric blocks (A) composed mainly of a vinyl aromatic compound and at least one polymeric block (B) composed mainly of a conjugated diene compound, and/or a hydrogenated block copolymer obtained by hydrogenating said block copolymer,
(b) 40 to 240 parts by weight of a non-aromatic softening agent for rubber,
(c) 5 to 300 parts by weight of polyethylene or a copolymer composed mainly of ethylene, and
(d) 5 to 60 parts by weight of polypropylene or a copolymer composed mainly of propylene,
characterized in that the process comprises the following steps:
(I) melt kneading the whole amounts of components (a), (b) and (d) and a part of component (c), and, at the same time or subsequently, melt kneading these with (f) an organic peroxide, and
(II) melt kneading the product obtained from step (I) with the remaining part of component (c),
and component (c) is one which has been prepared using a single site catalyst.
In a preferred embodiment, a weight ratio of the amount of component (c) used in step (I) and that in step (II) is 90:10 to 10:90.
In another preferred embodiment, component (f) is used in an amount of 0.1 to 1.5 parts by weight per 100 parts by weight of a total amount of components (a), (b), (c) and (d).
In another preferred embodiment. 0.1 to 3.5 parts by weight of a crosslinking aid per 100 parts by weight of a total amount of components (a), (b), (c) and (d) are used together with component (f) in step (I).
In another preferred embodiment, the whole amount of
(e) at most 100 parts by weight of an inorganic filler is melt meaded in the initial stage of step (I).
In another preferred embodiment, (h) at most 3.0 parts by weight of an antioxidant per 100 parts by weight of a total amount of components (a), (b), (c) and (d) are used in step (I).
In another preferred embodiment, an additional amount of component (d) is added in step (II) and melt kneaded.
Another purpose of the invention is to provide a thermoplastic elastomer composition which is soft and excellent in heat deformation resistance, mechanical strength, moldability and processability and used properly as a sealing material.
Thus the present invention provides a thermoplastic elastomeric resin composition comprising
(a) 100 parts by weight of a block copolymer consisting of at least two polymeric blocks (A) composed mainly of a vinyl aromatic compound and at least one polymeric block (B) composed mainly of a conjugated diene compound, and/or a hydrogenated block copolymer obtained by hydrogenating said block copolymer.
(c) 5 to 150 parts by weight of polyethylene or a copolymer composed mainly of ethylene, and
(d) 5 to 80 parts by weight of polypropylene or a copolymer composed mainly of propylene,
characterized in that component (c) is one which has been prepared using a single site catalyst.
In a preferred embodiment, the composition further comprises
(b) 40 to 240 parts by weight of a non-aromatic softening agent for rubber.
In another preferred embodiment, the composition further comprises
(e) 0.01 to 100 parts by weight of an inorganic filler.
PREFERRED EMBODIMENTS OF THE INVENTION
Component (a), Block Copolymer
Component (a) used in the invention is a block copolymer consisting of at least two polymeric blocks (A) composed mainly of a viny aromatic compound and at least one polymeric block (B) composed mainly of a conjugated diene compound, or a hydrogenated block copolymer obtained by hydrogenating said block c
Tamura Akihiro
Tasaka Michihisa
Niland Patrick D.
Pitney Hardin Kipp & Szuch LLP
Riken Vinyl Industry Co., Ltd.
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