Vulcanized solid rubber

Details Vulcanized solid rubber Vulcanized solid rubber

2002-04-02

2004-04-06

Harlan, Robert Deshon (Department: 1713)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Mixing of two or more solid polymers; mixing of solid...

C526S336000, C526S348600, C526S916000, C521S140000

Reexamination Certificate

active

06716931

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to vulcanized solid rubber, which is superior in its long-term compressive permanent strain; sealing efficiency; low-temperature characteristics; fatigue durability; processability such as kneadability, extrudability and shape-retaining property; and its appearance. The “solid rubber” means rubber having substantially no cell, and it is different from cellular rubber or sponge.
BACKGROUND OF THE INVENTION
Most of vulcanized solid rubber used for applications such as a car have been produced by vulcanizing ethylene-&agr;-olefin-non-conjugated diene copolymer rubber superior in its heat resistance, weather resistance, processability and cost. However, such vulcanized solid rubber cannot satisfy the following requirements recently required for vulcanized solid rubber.
A problem such that a sound such as engine sound, wind-cutting sound around doors and creaking sound of tires comes into a room during high-speed run of a car, and a problem of rain-leaking depend largely upon sealing performance of doors and windows. Therefore, vulcanized solid rubber having much more superior sealing efficiency has been desired. Particularly, materials such as a door-sealing material, a window-sealing material and an engine mount are used under compressed conditions for a long period of time, and therefore, vulcanized solid rubber having little compressive permanent strain has been desired.
The compressive permanent strain can be improved by using such an ethylene-&agr;-olefin-non-conjugated diene copolymer rubber having a high Mooney viscosity as a blend of 100 parts by weight of the ethylene-&agr;-olefin-non-conjugated diene copolymer rubber and 20 parts by weight of an extender oil exceeds 100 of Mooney viscosity (ML
1+4
(121° C.)). However, vulcanized solid rubber obtained using such an ethylene-&agr;-olefin-non-conjugated diene copolymer rubber has problems of poor kneadability, formation of carbon aggregation lumps, surface roughening and edge cutting of extrusion molded products, and surface roughening of die molded products.
Further, it is important that car doors and car windows can be opened and shut smoothly in a wide temperature range of from a low temperature to a high temperature. Therefore, vulcanized solid rubber capable of maintaining sufficient flexibility in a wide temperature range has been desired.
SUMMARY OF THE INVENTION
An object of the present invention is to provide vulcanized solid rubber, which is superior in its long-term compressive permanent strain; sealing efficiency; low-temperature characteristics; fatigue durability; processability such as kneadability, extrudability and shape-retaining property; and its appearance.
The present inventors have undertaken extensive studies of vulcanized solid rubber. As a result, it has been fond that the above-mentioned object can be accomplished by using a combination of an ethylene-&agr;-olefin-non-conjugated diene copolymer having a high Mooney viscosity and an extender oil. Thereby, the present invention has been obtained.
The present invention provides vulcanized solid rubber, which comprises a vulcanized product of an oil-extended copolymer comprising:
(i) 100 parts by weight of an ethylene-&agr;-olefin-non-conjugated diene copolymer satisfying the following requirements (1) to (4), and
(ii) 10 to 90 parts by weight of an extender oil:
(1) a weight ratio of an ethylene unit to an &agr;-olefin unit in the ethylene-&agr;-olefin-non-conjugated diene copolymer is from 73/27 to 40/60,
(2) an iodine value of the ethylene-&agr;-olefin-non-conjugated diene copolymer is from 20 to 36,
(3) Mooney viscosity (ML
1−4
(121° C.)) measured according to JIS-K-6300 of a blend containing 100 parts by weight of the ethylene-&agr;-olefin-non-conjugated diene copolymer and 20 parts by weight of an extender oil is from 100 to 180, and
(4) a ratio of weight average molecular chain length
umber average molecular chain length measured by gel permeation chromatography of the ethylene-&agr;-olefin-non-conjugated diene copolymer is from 3 to 5.
DETAILED DESCRIPTION OF THE INVENTION
Examples of the &agr;-olefin of the ethylene-&agr;-olefin-non-conjugated diene copolymer contained in the oil-extended copolymer used in the present invention are propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-octene and 1-decene. Of these, propylene and 1-butene are preferred.
A weight ratio of an ethylene unit and an &agr;-olefin unit, namely, ethylene unit/&agr;-olefin unit, in said copolymer is from 73/27 to 40/60, and preferably from 67/33 to 45/55. Here, the “unit” means a polymerized monomer unit. For example, the “ethylene unit” means a polymerized ethylene unit. When the ethylene unit exceeds 73 parts by weight, the vulcanized solid rubber obtained may extremely deteriorate its compressive permanent strain at a low temperature. When the ethylene unit is less than 40, dispersion of a reinforcing agent such as carbon black and inorganic fillers in the vulcanized solid rubber obtained may be insufficient, thereby roughening a surface of the solid rubber.
In the present invention, the “non-conjugated diene” of said copolymer means not only a non-conjugated diene but also a non-conjugated polyene such as a non-conjugated triene. Examples of such compounds are linear non-conjugated dienes such as 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene and 7-methyl-1,6-octadiene; cyclic non-conjugated dienes such as cyclohexadiene, dicyclopentadiene, methyltetraindene, 5-vinylnorbornene, 5-ethylidene-2-norbornene and 6-chloromethyl-5-isopropenyl-2-norbornene; trienes such as 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,2-norbornadiene, 1,3,7-octatriene and 1,4,9-decatriene; 5-vinyl-2-norbornene; 5-(2-propenyl)-2-norbornene; 5-(3-butenyl)-2-norbornene; 5-(4-pentenyl)-2-norbornene; 5-(5-hexenyl)-2-norbornene; 5-(5-heptenyl)-2-norbornene; 5-(7-octenyl)-2-norbornene; 5-methylene-2-norbornene; 6,10-dimethyl-1,5,9-undecatriene; 5,9-dimethyl-1,4,8-decatriene; 4-ethylidene-8-methyl-1,7-nonadiene; 13-ethyl-9-methyl-1,9,12-pentadecatriene; 5,9,13-trimethyl-1,4,8,12-tetradecadiene; 8,14,16-trimethyl-1,7,14-hexadecatriene and 4-ethylidene-12-methyl-1,11-pentadecadiene. These compounds may be used singly or in combination of two or more. A preferred compound is 5-ethylidene-2-norbornene or dicyclopentadiene or a combination of both.
An iodine value of the ethylene-&agr;-olefin-non-conjugated diene copolymer contained in the oil-extended copolymer is from 20 to 36, and preferably from 22 to 32. When the iodine value is less than 20, the vulcanized solid rubber obtained may deteriorate its compressive permanent strain, or decrease its vulcanization speed. In this regard, when a large amount of a vulcanization accelerator is used in order to increase the vulcanization speed, the vulcanized solid rubber obtained may have blooming. When the iodine value exceeds 36, flexibility of the vulcanized solid rubber obtained may be insufficient.
Mooney viscosity of the ethylene-&agr;-olefin-non-conjugated diene copolymer contained in the oil-extended copolymer satisfies a requirement that Mooney viscosity (ML
1+4
(121° C.)) measured according to JIS-K-6300 of a blend containing 100 parts by weight of said copolymer and 20 parts by weight of an extender oil is from 100 to 180, and preferably from 110 to 170. Here, the reason why the Mooney viscosity is expressed not by the Mooney viscosity of said copolymer itself but by that of the above-mentioned blend is as follows. In measuring Mooney viscosity of a copolymer having Mooney viscosity as high as 200 or more, an inconvenience such as a slip occurs between a torque-detecting rotor and the copolymer. Occurrence of such an inconvenience is unavoidable from a structural viewpoint of a Mooney viscosity measurement apparatus. As a result, it may be difficult to measure an accurate Mooney viscosity. When the Mooney viscosity is less than 100, it may be difficult to obtain vulcanized solid rubber havi

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