Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-02-28
2004-10-12
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S515000, C524S525000, C524S528000, C524S581000
Reexamination Certificate
active
06803398
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to an olefin-based thermoplastic elastomer composition, and more specifically, to an olefin-based thermoplastic elastomer composition having excellent oil resistance.
BACKGROUND ART
Olefin-based thermoplastic elastomers are excellent in moldability, flexibility and heat resistance, and their industrial use has expanded in various fields because of such favorable properties. Olefin-based thermoplastic elastomers are also light-weighted and easy to recycle, and such features also backed their use as energy-saving, resources-saving elastomeric substitutes for vulcanized rubbers in the field of auto-parts, industrial mechanical parts, electric and electronic parts, construction materials, and the like.
Olefin-based thermoplastic elastomers, however, suffered from the problem of insufficient oil resistance, and when they are brought in contact with a non-polar solvent such as an aromatic organic solvent, gasoline and mineral oil, they undergo swelling. Such drawback resulted in their limited use.
In view of the situation as described above, an object of the present invention is to solve the problems associated with the prior art, and to provide an olefin-based thermoplastic elastomer composition which has excellent oil resistance as well as excellent moldability.
DISCLOSURE OF THE INVENTION
According to the present-invention, there is provided an olefin-based thermoplastic elastomer composition comprising
(I) 100 parts by weight of an elastomer containing
(A) 20 to 90 parts by weight of a polypropylene resin having a melt flow rate 0.1 to 5 g/10 min when the melt flow rate is measured under the load of 2.16 kg and the temperature of 230° C. in accordance with ASTM D1238, and
(C) 10 to 80 parts by weight of an olefin-based copolymer rubber ((A)+(C)=100 parts by weight), and which has been crosslinked to a gel content of at least 95%;
(D) 10 to 300 parts by weight of a polyolefin-based resin;
(E) 10 to 300 parts by weight of an olefin-based copolymer rubber; and
(F) 10 to 300 parts by weight of a softening agent; wherein weight difference (&Dgr;W) of said composition before and after immersing in liquid paraffin at 100° C. for 24 hours is up to 150%.
According to the present invention, there is also provided an olefin-based thermoplastic elastomer composition comprising
(I) 100 parts by weight of an elastomer containing
(A) 20 to 90 parts by weight of a polypropylene resin having a melt flow rate 0.1 to 5 g/10 min when the melt flow rate is measured under the load of 2.16 kg and the temperature of 230° C. in accordance with ASTM D1238,
(B) 5 to 30 parts by weight of a linear polyethylene resin having a density of 0.920 to 0.950 g/cm
3
, and
(C) 5 to 75 parts by weight of an olefin-based copolymer rubber ((A)+(B)+(C)=100 parts by weight), and
which has been crosslinked to a gel content of at least 95%;
(D) 10 to 300 parts by weight of a polyolefin-based resin;
(E) 10 to 300 parts by weight of an olefin-based copolymer rubber; and
(F) 10 to 300 parts by weight of a softening agent; wherein weight difference (&Dgr;W) of said composition before and after immersing in liquid paraffin at 100° C. for 24 hours is up to 150%.
According to a preferred embodiment of the present invention, there is also provided an olefin-based thermoplastic elastomer composition wherein the composition contains the components (A) and (C), or the components (A), (B) and (C) as the elastomer (I) which has been produced by crosslinking said components by dynamic heat treatment in the presence of an organic peroxide.
Next, the olefin-based thermoplastic elastomer composition of the present invention (hereinafter referred to as the present composition) is described in detail.
The polypropylene resin (A) which is the a critical component of the present composition is a polymer containing propylene as its main component, and exemplary such polypropylene resin (A) include:
(1) propylene homopolymer,
(2) a random copolymer of propylene with up to 10% by mole of an &agr;-olefin other than propylene, and
(3) a block copolymer of propylene with up to 30% by mole of an &agr;-olefin other than propylene.
Exemplary such &agr;-olefins other than propylene include ethylene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene, and the polymer may include such &agr;-olefin either alone or in combination of two or more. The polypropylene resin (A) may include the polymers as described above either alone or in combination of two or more. Of the polymers as described above, the preferred is the propylene homopolymer.
In view of the improved oil resistance and sufficient moldability of the resulting olefin-based thermoplastic elastomer composition, the polypropylene resin (A) is preferably the one having a melt flow rate of 0.1 to 5 g/10 min, and more preferably 0.5 to 3 g/10 min when the melt flow rate is measured under the load of 2.16 kg and at a temperature of 230° C. in accordance with ASTM D1238.
The linear polyethylene resin (B) used as a constituent of the present composition is typically a random copolymer of ethylene with an (&agr;-olefin containing 3 to 10 carbon atoms. Use of a linear polyethylene resin results in the improved compatibility between the propylene resin (A) and the olefin-based copolymer rubber (C), and in particular, in the improved extrudability of the resulting composition. Exemplary &agr;-olefins containing 3 to 10 carbon atoms include propyelene, 1-butene, 4-methyl-1-pentene, 1-hexene, and 1-octene, and the preferred among these are 4-methyl-1-pentene and 1-hexene. The random copolymer of the ethylene with such &agr;-olefin may contain either one or two or more of such an &agr;-olefin. The linear polyethylene resin is preferably an ethylene/4-methyl-1-pentene random copolymer.
The &agr;-olefin is copolymerized in the polyethylene resin (B) preferably in an amount of 1 to 8% by mole, and more preferably, in an amount of 2 to 5% by mole.
The polyethylene resin (B) has a density of 0.920 to 0.950 g/cm
3
, and preferably, a density of 0.925 to 0.945 g/cm
3
. When the density is less than 0.920 g/cm
3
, the resulting olefin-based thermoplastic elastomer composition suffers from insufficient oil resistance and the object of the present invention will not be attained. Therefore, the limitation of the density is important.
In addition, the polyethylene resin (B) may preferably have a melt flow rate (MFR) of 0.1 to 50 g/10 min, and most preferably, a melt flow rate of 1 to 30 g/10 min when evaluated in accordance with ASTM D1238 under the load of 2.16 kg and at a temperature of 190° C. The melt flow rate in excess of 50 g/10 min results in the insufficient oil resistance while the melt flow rate of less than 0.1 g/10 min results in the insufficient moldability.
The olefin-based copolymer rubber (C) which is a critical component of the present invention may be a copolymer rubber containing an &agr;-olefin as its main component. This copolymer rubber is an amorphous, random, elastic copolymer such as an &agr;-olefin copolymer comprising two or more &agr;-olefins containing 2 to 20 carbon atoms, and an &agr;-olefin
onconjugated diene copolymer comprising two or more &agr;-olefins containing 2 to 20 carbon atoms and a nonconjugated diene.
Exemplary olefin-based copolymer rubbers include:
(1) Copolymer rubber of ethylene and an &agr;-olefin other than ethylene
[Ethylene/&agr;-olefin other than ethylene (molar ratio)=90/10 to 50/50]
(2) Copolymer rubber of ethylene, an &agr;-olefin other than ethylene, and a nonconjugated diene
[Ethylene/&agr;-olefin other than ethylene (molar ratio)=90/10 to 50/50]
[Ethylene
onconjugated diene (molar ratio)=99/1 to 90/10]
(3) Copolymer rubber of propylene and an &agr;-olefin other than propylene
[Propylene/&agr;-olefin other than propylene (molar ratio)=90/10 to 50/50]
(4) Copolymer rubber of butene and an &agr;-olefin other than butene
[Butene/&agr;-olefin other than butene (molar ratio)=90/10 to 50/50]
Exemplary &agr;-o
Ito Yuichi
Kako Chika
Nishimura Hideo
Uchiyama Akira
Ukai Junzo
Birch & Stewart Kolasch & Birch, LLP
Mitsui Chemicals Inc.
Mulcahy Peter D.
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