Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-06-28
2001-04-24
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S240000
Reexamination Certificate
active
06221963
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a thermoplastic elastomer based on olefin, a composition of thermoplastic elastomer and a process and method for producing such elastomer and composition. More specifically, the present invention relates to a thermoplastic elastomer based on olefin, which comprises a polyethylene resin and a copolymer based on ethylene/&agr;-olefin and which is superior in the rubbery elasticity, to a composition as a starting mixture therefor and to a process and method for producing such elastomer and composition.
BACKGROUND OF THE INVENTION
Wide varieties of materials have been employed heretofore for parts and portions of installations and furnishings in the automobile, machinery, electric and electronic industries and architectural field requiring rubbery elasticity. Among them, vulcanized rubber may be exemplified. Vulcanized rubber is obtained usually through laborious and expensive process steps by first preparing an unvulcanized rubber blend by kneading raw rubber together with a cross linking agent, cross linking assistant, additives and subsidiary component(s) and then processing the resulting kneaded mass by vulcanization while forming it into a contemplated formed product under heating. Vulcanized rubber products have cross-linked molecular structure and, therefore, are not able to be recycled for reclamation.
On the other hand, polyvinyl chloride resin has a rubber-resembling property, though it does not require vulcanization step. However, polyvinyl chloride resin suffers from a significant problem of evolving a noxious gas upon incineration thereof. In addition, the rubbery elasticity thereof is inferior as compared with vulcanized rubber, so that the application field thereof is limited.
There have been known thermoplastic elastomers which behave at normal temperature as a polymer material exhibiting a rubbery elasticity but can be plasticized at a high temperature and, thus, can be processed by forming or molding into formed product. As concerns this, there has been known, as a thermoplastic elastomer based on olefin, a dynamically cross-linked product made of a polypropylene and an ethylene/&agr;-olefin copolymer. However, this also suffers from similar problems as above due to incorporation of a dynamic cross linking step.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above-mentioned problems of the stand of the technique and to provide a thermoplastic elastomer based on olefin, which is superior in the rubbery elasticity and which can be obtained simply in an economical way without using cross linking agent and, thus, can permit recycled use.
Another object of the present invention is to provide a composition of thermoplastic elastomer based on olefin from which the above-mentioned thermoplastic elastomer based on olefin can be obtained.
A further object of the present invention is to provide a method for producing the above-mentioned composition of thermoplastic elastomer based on olefin in an efficient way.
A yet further object of the present invention is to provide a process for producing the above-mentioned thermoplastic elastomer based on olefin permitting recycled use, whereby the said elastomer can be produced in a simple, efficient and economical way by a single process step without using cross linking agent.
Thus, the present invention consists in the thermoplastic elastomer based on olefin, in the composition therefor and in the method and process for producing such elastomer and composition as given below:
(1) A thermoplastic elastomer based on olefin which exhibits the following characteristics
{circle around (1+L )} to
{circle around (3)} namely,
9
≦Y−
0.43
X≦
27 (1)
{circle around (1)} in which X denotes the JIS A-hardness value (a dimensionless value) of the thermoplastic elastomer based on olefin determined according to the prescription of JIS K 6301 and Y represents the permanent compressive strain value (expressed by %) of the thermoplastic elastomer based on olefin determined according to the prescription of JIS K 6301 under a condition of 70° C.×22 hours,
{circle around (2)} a tensile strength in the range from 5 to 30 MPa determined according to the prescription of JIS K 6301, and
{circle around (3)} a permanent elongation value of 18% or less determined according to the prescription of JIS K 6301.
(2) A thermoplastic elastomer based on olefin which comprises a polyethylene resin (A) and a copolymer (B) based on ethylene/&agr;-olefin and which exhibits the characteristics {circle around (1)} to {circle around (3)} described above.
(3) The thermoplastic elastomer based on olefin as defined in the above (2), which is obtained from a mixture composed of 5-60% by weight of a polyethylene resin (A) and 40-95% by weight of a copolymer (B) based on ethylene/&agr;-olefin having a Mooney viscosity ML
1+4
(100° C.) of 90-250 and an ethylene content of 70-95 mole % by subjecting this mixture to a dynamic heat treatment in the absence of cross linking agent.
(4) The thermoplastic elastomer based on olefin as defined in the above (2) or (3), which is obtained by subjecting the polyethylene resin (A) together with the copolymer (B) based on ethylene/&agr;-olefin to a dynamic heat treatment on a double-screw extruder in the absence of cross linking agent under a process condition satisfying the provision {circle around (4)} given below:
4.8<{(
T−
130)/100}+2.2 log
P
+log
Q
−log
R <
7.0 (2)
{circle around (4)} in which T represents the temperature (° C.) of the resin mixture at the die outlet, P is the screw diameter (mm) of the double screw extruder, Q is the maximum shearing velocity (sec
−1
) at which the resin mixture is kneaded in the double screw extruder and is defined by the formula Q=P×&pgr;×S/U with P being as above, S being the number of revolutions per second (r.p.s) of the screw and U being the gap (mm) between the inner face of the barrel wall and the kneading segment of the screw at the narrowest portion thereof and R is the extrusion through-put (kg/hr) of the double screw extruder.
(5) A composition of thermoplastic elastomer based on olefin comprising 5-60% by weight of a polyethylene resin (A) and 40-95% by weight of a copolymer (B) based on ethylene/&agr;-olefin having a Mooney viscosity ML
1+4
(100° C.) of 90-250 and an ethylene content of 70-95 mole %.
(6) A composition of thermoplastic elastomer based on olefin obtained from a mixture composed of 5-60% by weight of a polyethylene resin (A) and 40-95% by weight of a copolymer (B) based on ethylene/&agr;-olefin having a Mooney viscosity ML
1+4
(100° C.) of 90-250 and an ethylene content of 70-95 mole % by subjecting this mixture to a dynamic heat treatment in the absence of cross linking agent.
(7) A composition of thermoplastic elastomer based on olefin as defined in the above (5) or (6), wherein the copolymer (B) based on ethylene/&agr;-olefin consists of an ethylene/&agr;-olefin
on-conjugated polyene copolymer.
(8) The composition of thermoplastic elastomer based on olefin defined in either one of the above (5) to (7), wherein it contains 30 parts by weight or less of a polypropylene resin (C) per 100 parts by weight of the total sum of the polyethylene resin (A) plus the copolymer (B) based on ethylene/&agr;-olefin.
(9) A process for producing a composition of thermoplastic elastomer based on olefin, comprising subjecting a mixture composed of 5-60% by weight of a polyethylene resin (A) and 40-95% by weight of a copolymer (B) based on ethylene/&agr;-olefin having a Mooney viscosity ML
1+4
(100° C.) of 90-250 and an ethylene content of 70-95 mole % to a dynamic heat treatment in the absence of cross linking agent.
(10) A process for producing a thermoplastic elastomer based on olefin, comprising subjecting a composition of thermoplastic elastomer comprising a polyethylene resin (A) and a copolymer (B) based on ethylene/&agr;-olefin to a dynamic heat treatment in the absence o
Kobayashi Kyoko
Uchiyama Akira
Birch & Stewart Kolasch & Birch, LLP
Mitsui Chemicals Inc.
Nutter Nathan M.
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