Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
2002-02-01
2004-04-13
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S140000, C521S134000, C521S142000, C521S144000
Reexamination Certificate
active
06720364
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an elastomeric composition for preparing an olefinic elastomer crosslinked foam and use thereof, and more specifically, an elastomeric composition for preparing an olefinic elastomer crosslinked foam that can provide an olefinic elastomer crosslinked foam having an Asker C hardness of 20 to 80, a low specific gravity, a low compression set (CS), and an excellent tear strength and impact resilience, and to an olefinic elastomer crosslinked foam made of this.
2. Description of the Related Art
Techniques using crosslinked foams to obtain a resin having a low specific gravity, i.e. a light weight, a high flexibility and a high mechanical strength are broadly applied to interior and exterior building materials, automotive parts such as interior materials or door glass runs, wrapping materials, articles of daily use, etc. Such techniques are used because mere foaming a resin for weight reduction leads to a reduction of mechanical strength, but, in contrast, binding molecular chains by crosslinking reaction of a resin enables weight reduction by foaming while avoiding reduction of mechanical strength.
In addition, resin crosslinked foams are also used for soles (mainly, midsoles) of athletic shoes etc. This is because materials are needed that are light and have a high mechanical strength enough to avoid deformation due to long-term use and withstand harsh use conditions.
Conventionally, crosslinked foams of an ethylene/vinyl acetate copolymer are used for soles and is publicly known. However, such crosslinked foams, which are molded using an ethylene/vinyl acetate copolymer composition, have a high specific gravity and are insufficient in terms of a low compression set, and therefore when used for a sole for example, a problem arises that the sole is heavy and is compressed by long-term use, so that mechanical strength such as impact resilience is lost.
National Publication of International Patent Application No. 9-501447 and Japanese Patent Laid-Open No. 11-206406 describe a crosslinked foam using an ethylene/&agr;-olefin copolymer, and a crosslinked foam using a mixture of an ethylene/vinyl acetate copolymer and an ethylene/&agr;-olefin copolymer, respectively. Some improvements in terms of a low specific gravity and a low compression set are attained, but adequate performance has not been obtained in these inventions.
Therefore, there is a need for an elastomeric composition for preparing an olefinic elastomer crosslinked foam that can provide an olefinic elastomer crosslinked foam having an Asker C hardness of 20 to 80, a low specific gravity, a low compression set (CS) and an excellent tear strength and impact resilience, and a crosslinked foam made of this.
The present invention intends to solve the above problems accompanying the prior art, and an object of the present invention is to provide an elastomeric composition for preparing an olefinic elastomer crosslinked foam that can provide an olefinic elastomer crosslinked foam having an Asker C hardness of 20 to 80, a low specific gravity and a low compression set (CS) and furthermore having excellent tear strength and impact resilience, and a crosslinked foam made of this.
Another object of the present invention is to provide a footwear part made of the above olefinic elastomer crosslinked foam, such as a sandals and a sole, midsole, and innersole of shoes.
SUMMARY OF THE INVENTION
The elastomeric composition for preparing an olefinic elastomer crosslinked foam of the present invention comprises an ethylene/&agr;-olefin copolymer (A) having a density (ASTM D 1505) of 880 to 920 kg/m
3
, and a melt flow rate (ASTM D 1238, 190° C., 2.16 kg load), MFR
2.16
, of 0.1 to 10 g/10 min; an organic peroxide (D); a crosslinking assistant (E); a foaming agent (F); and an organic metal compound (G) which is a compound of metal selected from Groups 2 to 12 of the periodic table and having at least two groups containing unsaturated carbon bond and at least one atom selected from oxygen, sulfur and nitrogen per one molecule.
This elastomeric composition may further comprise, based on 100 parts by weight of the ethylene/&agr;-olefin copolymer (A), 5 to 100 parts by weight of a high pressure low density polyethylene (B) having a melt flow rate (ASTM D 1238, 190° C., 2.16 kg load) of 0.1 to 50 g/10 min, and/or 5 to 1,900 parts by weight of an ethylene/vinyl acetate copolymer (C) having a vinyl acetate content of 10 to 30% by weight and a melt flow rate (ASTM D 1238, 190° C., 2.16 kg load) of 0.1 to 50 g/10 min.
The &agr;-olefin in the above ethylene/&agr;-olefin copolymer (A) is usually an &agr;-olefin having 3 to 10 carbon atoms.
There may be used, as the above ethylene/&agr;-olefin copolymer (A), a mixture of two or more ethylene/&agr;-olefin copolymers having a molecular weight distribution (Mw/Mn) determined by gel permeation chromatography (GPC) of 1.5 to 4, and a ratio (MFR
10
/MFR
2.16
) of a melt flow rate (ASTM D 1238, 190° C., 2.16 kg load), MFR
2.16
to a melt flow rate (ASTM D 1238, 190° C., 10 kg load), MFR
10
, of 5 to 20.
The above mixture of two or more of the ethylene/&agr;-olefin copolymers is preferably produced by blending or multistage polymerization so that the molecular weight distribution (Mw/Mn) determined by GPC can be within a range of 2.3 to 6.
The above organic metal compound (G) generally has at least two CH
2
═CH—CO— or CH
2
═C(CH
3
)—CO—O— groups per molecule.
The above organic metal compound (G) is preferably an organic zinc compound.
The organic zinc compound is preferably zinc diacrylate or zinc dimethacrylate.
The above organic metal compound (G) is contained in the above elastomeric composition in a proportion of 0.05 to 5 parts by weight based on 100 parts by weight of the total amount of the ethylene/&agr;-olefin copolymer (A), the high pressure low density polyethylene (B) and the ethylene/vinyl acetate copolymer (C). However, since components (B) and (C) are optional components, the amount of these components may be 0 part by weight.
The olefinic elastomer crosslinked foam of the present invention is obtained by crosslinking and foaming the above elastomeric composition for preparing an olefinic elastomer crosslinked foam of the present invention.
The olefinic elastomer crosslinked foam of the present invention may be a crosslinked foam obtained by a secondary compression of the crosslinked foam of the present invention.
The secondary compression is usually performed under conditions of a temperature of 130° C. to 200° C., a load of 30 to 300 kgf/cm
2
for 5 to 60 minutes.
These crosslinked foams desirably have a specific gravity (JIS K7222 (g/cm
3
)) of 0.05 to 0.25, a surface hardness (Asker C hardness) of 20 to 80, and a gel fraction of 70% or more.
The footwear part of the present invention is made of the above olefinic elastomer crosslinked foam of the present invention.
Examples of the footwear parts include midsoles, innersoles, soles, etc.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Now, the elastomeric composition for preparing an olefinic elastomer crosslinked foam of the present invention and a use thereof are described in detail.
The elastomeric composition for preparing an olefinic elastomer crosslinked foam of the present invention is an uncrosslinked unfoamed composition which is to be crosslinked and foamed by heating, and it comprises an ethylene/&agr;-olefin copolymer (A), an organic peroxide (D), a crosslinking assistant (E), a foaming agent (F), an organic metal compound (G), and as necessary, a high pressure low density polyethylene (B) and an ethylene/vinyl acetate copolymer (C).
Ethylene/&agr;-olefin Copolymer (A)
Ethylene/&agr;-olefin copolymer (A) used in the present invention is a low crystalline random copolymer composed of ethylene and an &agr;-olefin containing 3 to 10 carbon atoms, and has a density (ASTM D 1505) of 880 to 920 kg/m
3
and a melt flow rate (ASTM D 1238, 190° C., 2.16 kg load), MFR
2.16
, of 0.1 to 10 g/10 min, preferably 0.5 to 10 g/10 min, and more prefera
Choi Kyung-Man
Sueda Takanori
Yasaka Naoto
Yoo Chong-Sun
Yoon Jeong-Sik
Foelak Morton
Mitsui Chemicals Inc.
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