Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2001-11-13
2003-09-09
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S134000, C521S144000
Reexamination Certificate
active
06617366
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a crosslinked olefin elastomer foam and an elastomer composition therefor. More particularly, the present invention is concerned with a crosslinked olefin elastomer foam which realizes a soft touch, exhibits a low compression set and is excellent in tear strength property and heat resistance, and is concerned with an elastomer composition for the crosslinked foam.
BACKGROUND OF THE INVENTION
A wide variety of foams are commonly produced on a commercial scale and marketed. Foams of vulcanized rubbers and soft olefin plastics can be mentioned as typical examples of such foams.
However, the conventional vulcanized rubbers, although having excellent flexibility and elasticity, inevitably require a time-consuming crosslinking or vulcanization step for realizing these properties, which incurs high cost. On the other hand, it is known to use soft olefin plastics, for example, thermoplastic resins such as ethylene/vinyl acetate copolymer (EVA) and low-density polyethylene in the formation of foams. These soft olefin plastics are basically inferior in heat resistance to the vulcanized rubbers. Thus, they encounter problems such that the applicability of obtained foams is extremely limited and that defoaming is likely to occur because of poor tension at melting to thereby render the expansion ratio low, which defoaming results in apparent surface roughening. Further, in the use of EVA, an increase of vinyl acetate content enhances the tear strength and adherence thereof but deteriorates the abrasion resistance, surface hardness and cell denseness. Therefore, the balance of properties is difficult with the use of EVA. Still further, the specific gravity of EVA itself is high, so that there occurs a problem such that foams of desirably low specific gravity cannot necessarily be obtained.
Therefore, there is a demand for the development of a crosslinked olefin elastomer foam which has a high expansion ratio, is free from surface roughening attributed to defoaming, realizes a soft touch, exhibits a low compression set and is excellent in tear strength property and heat resistance, and the development of an elastomer composition for such a crosslinked foam.
OBJECT OF THE INVENTION
The present invention has been made with a view toward solving the above problems of the prior art. It is an object of the present invention to provide a crosslinked olefin elastomer foam which has a high expansion ratio, is free from surface roughening attributed to defoaming, realizes a soft touch, exhibits a low compression set and is excellent in tear strength property and heat resistance. It is another object of the present invention to provide an elastomer composition for such a crosslinked foam.
SUMMARY OF THE INVENTION
The first crosslinked olefin elastomer foam of the present invention has a specific gravity of 0.05 to 0.2, an expansion ratio of 8 to 15, a compression set of 30 to 60% and a tear strength of 1.5 to 2.5 kg/cm.
Another crosslinked olefin elastomer foam of the present invention has a specific gravity of 0.1 to 0.2, a compression set of 20 to 60% and a tear strength of 2.0 to 4.0 kg/cm. This crosslinked foam is a secondarily compressed crosslinked foam obtained by subjecting the first crosslinked olefin elastomer foam of the present invention to further compression molding.
The first crosslinked olefin elastomer foam of the present invention can be a crosslinked foam obtained by heating an olefin elastomer composition, the olefin elastomer composition comprising:
an ethylene/&agr;-olefin copolymer (A) having a density of 0.88 to 0.92 g/cm
3
and a melt flow rate (measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238) of 0.1 to 10 g/10 min;
an organic peroxide (D);
a crosslinking auxiliary (E); and
a foaming agent (F).
The above ethylene/&agr;-olefin copolymer (A) preferably has a molecular weight distribution (Mw/Mn), as measured by gel permeation chromatography (GPC), of 2.3 to 4.0.
The first crosslinked olefin elastomer foam of the present invention is preferably produced from a composition wherein the ethylene/&agr;-olefin copolymer (A) comprises a mixture of:
5 to 95 parts by weight of an ethylene/&agr;-olefin copolymer (A1) having a density of greater than 0.88 g/cm
3
but not greater than 0.90 g/cm
3
and a melt flow rate (measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238) of 0.1 to 50 g/10 min; and
5 to 95 parts by weight of an ethylene/&agr;-olefin copolymer (A2) having a density of (0.90 to 0.93 g/cm
3
and a melt flow rate (measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238) of 0.1 to 50 g/10 min, provided that the sum of ethylene/&agr;-olefin copolymer (A1) and ethylene/&agr;-olefin copolymer (A2) is 100 parts by weight,
the mixture having a melt flow rate (measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238) of 0.5 to 10 g/10 min.
The first crosslinked olefin elastomer foam of the present invention is also preferably produced from a composition wherein the ethylene/&agr;-olefin copolymer (A) comprises a mixture of:
5 to 95 parts by weight of an ethylene/&agr;-olefin copolymer (A3) having a density of 0.88 to less than 0.91 g/cm
3
and a melt flow rate (measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238) of 0.1 to 50 g/10 min; and
5 to 95 parts by weight of an ethylene/&agr;-olefin copolymer (A4) having a density of 0.91 to 0.93 g/cm
3
and a melt flow rate (measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238) of 0.1 to 50 g/10 min, provided that the sum of ethylene/&agr;-olefin copolymer (A3) and ethylene/&agr;-olefin copolymer (A4) is 100 parts by weight,
the mixture having a melt flow rate (measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238) of 0.5 to 10 g/10 min.
The &agr;-olefin for forming the ethylene/&agr;-olefin copolymers (A), (A1), (A2), (A3) and (A4) is preferably at least one member selected from the group consisting of propylene, 1-butene, 1-hexene and 1-octene.
The crosslinking auxiliary (E) for use in this invention is preferably triallyl isocyanurate (TAIC) or triallyl cyanurate (TAC).
In this invention, it is preferred that the crosslinking auxiliary (E) and the organic peroxide (D) be used in a weight ratio ((E)/(D)) of 1/8 to 3/1.
An organic or inorganic heat decomposable foaming agent is preferably used as the above foaming agent (F).
The first elastomer composition for crosslinked olefin elastomer foam according to the present invention comprises:
an ethylene/&agr;-olefin copolymer (A) having a density of 0.88 to 0.92 g/cm
3
and a melt flow rate (measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238) of 0.1 to 10 g/10 min;
an organic peroxide (D);
a crosslinking auxiliary (E); and
a foaming agent (F).
It is preferred that the ethylene/&agr;-olefin copolymer (A) have a molecular weight distribution (Mw/Mn), as measured by gel permeation chromatography (GPC), of 2.3 to 4.0.
The first elastomer composition for crosslinked olefin elastomer foam according to the present invention is preferably a composition comprising:
an ethylene/&agr;-olefin copolymer (A) having a density of 0.88 to 0.92 g/cm
3
and a melt flow rate (measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238) of 0.1 to 10 g/10 min;
an organic peroxide (D);
a crosslinking auxiliary (E); and
a foaming agent (F),
wherein the ethylene/&agr;-olefin copolymer (A) comprises a mixture of:
5 to 95 parts by weight of an ethylene/&agr;-olefin copolymer (A1) having a density of greater than 0.88 g/cm
3
but not greater than 0.90 g/cm
3
and a melt flow rate (measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238) of 0.1 to 50 g/10 min; and
5 to 95 parts by weight of an ethylene/&agr;-olefin copolymer (A2) having a density of 0.90 to 0.93 g/cm
3
and a melt flow rate (measured at 190° C. under a load of 2.16 kg in accordance with ASTM D 1238) of 0.1 to 50 g/10 min, provided that the sum of ethylene/&agr;-olefin copolymer (A1) and ethylen
Choi Kyung-Man
Lee Kwon-Ik
Sueda Takanori
Yasaka Naoto
Yoo Chong-Sun
Bissett Melanie
Burns Doane , Swecker, Mathis LLP
Mitsui Chemicals Inc.
Seidleck James J.
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