Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-02-09
2002-01-08
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C526S335000, C526S348200, C526S282000
Reexamination Certificate
active
06337364
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a low modulus of elasticity-rubber composition prepared by containing a softener in an ethylene-propylene-diene rubber. More particularly, the present invention relates to a low modulus of elasticity-rubber composition comprising an ethylene-propylene-diene rubber and a softener, which shows small compression set even at wide range of temperature, especially at low temperature ranging from −30 to 0° C., excellent flexibility and self-tack, and is useful as a sealant for a telecommunication cable closure.
An ethylene-propylene-diene rubber (hereinafter abbreviated to EPDM, sometimes) is a terpolymer and is utilized as a rubber composition. With respect to the ethylene-propylene-diene rubber, for example, publicly known techniques described in the following patent publications have been known.
Japanese Patent Publication (Kokoku) No. 57-24828: This publication discloses a sealing process, which comprises molding a low-temperature vulcanizable composition prepared by adding a peroxide and a redox catalyst to a rubber-like polymer containing, as a main component, an olefin terpolymer comprising ethylene, &agr;-olefin and polyene having a non-conjugated double bond, and optionally mixing an optional component such as filler and softener.
Japanese Patent Laid-open Publication (Kokai) No. 59-27931: This publication describes a rubber composition comprising an ethylene-&agr;-olefin-polyene copolymer rubber wherein a molar ratio of ethylene to &agr;-olefin having 4 or more carbon atoms is from about 80:20 to 97:3, and a diene rubber, and also describes that a softener as one of optional components to be added in the rubber composition can be mixed in the amount of about 100 parts by weight or less based on 100 parts by weight of the rubber composition, however, the strength is lowered when the softener is mixed in the amount larger than the above amount.
Japanese Patent Publication (Kokoku) No. 60-31875: This publication describes a solvent-free type unsteady sealing material prepared by adding 150 to 1000 parts by weight of a softener and 50 to 1000 parts by weight of silcas and/or short fibers to 100 parts by weight of rubbers containing an ethylene-propylene-diene rubber. By the way, any reference with respect to properties of the ethylene-propylene-diene rubber to be used is not made.
Japanese Patent Laid-Open Publication (Kokai) No. 60-92380: This publication describes a porous sealing agent comprising ethylene, &agr;-olefin and diolefin as a monomer component, wherein 100 parts of a copolymer having a Mooney viscosity (100° C.) of 5 to 30 and 30 to 150 parts by weight of a softener are contained.
Japanese Patent Laid-Open Publication (Kokai) No. 4-65447: This publication describes a rubber composition for seal parts, which is prepared by adding 20 to 50 parts of a naphthenic or paraffinic process oil as a softener and an antioxidant to an ethylene-&agr;-olefin-diolefin copolymer composition defined by 55 to 70 mol % of an ethylene content, 50 to 100 of a Mooney viscosity (121° C.) and 5 to 24 of an iodine value.
Japanese Patent Laid-Open Publication (Kokai) No. 6-136207: This publication discloses an oil-bleeding chlorinated ethylene-&agr;-olefin copolymer composition comprising 100 parts by weight of a chlorinated ethylene-&agr;-olefin copolymer rubber having a Mooney viscosity at 121° C. of 10 to 190 and 10 to 60 parts by weight of an paraffinic process oil, wherein the chlorine content is from 20 to 40% by weight, and also describes that this composition can be used as a polymer for molding a connector, a packing and a housing of an electric circuit.
As described above, various EPDM rubber composition containing different components for various purposes have been known and, as a matter of course, required characteristics vary depending on the purposes.
When using the EPDM rubber composition for sealing in the field of a telecommunication cable closure, it is required that the composition shows small compression set even at wide range of temperature, especially at low temperature ranging from −30 to 0° C., and excellent flexibility. The “closure” used herein means a container for branching and connecting an electric wire and an optical fiber.
However, it is difficult to provide the previously known EPDM composition for sealing in low temperature range in view of characteristics. In case of a conventional composition, since the compression set at −20° C. exceeds 90% and a change in hardness between room temperature and −20° C. is very large, there is a fear that the sealability at low temperature such as −20° C. is lowered to cause leakage. There is also a problem that compression required for sealing can not be conducted sufficiently as a result of an increase in hardness. In case of almost all of compositions, it is difficult to compress because of poor flexibility and to closely contact with the cable because of poor tack.
In order to solve the problems described above, the present inventors have studied intensively to improve the EPDM rubber composition. As a result, they have found that a rubber composition, which shows small compression set even at low temperature and excellent flexibility, can be obtained by containing a combination of EPDM having specific properties and a softener having specific properties in a specific ratio. Thus, the present invention has been completed by studying furthermore.
SUMMARY OF THE INVENTION
That is, the present invention provides:
1) a low modulus of elasticity-rubber composition comprising an ethylene-propylene-diene rubber and a softener, wherein
(1) the ethylene-propylene-diene rubber has the following properties:
(a) a Mooney viscosity at 100° C. is from 90 to 130,
(b) a diene is ethylidenenorbornene,
(c) an iodine value is not more than 20, and
(d) the amount of ethylene is not more than 55% based on the total amount of ethylene and propylene;
(2) the softener has the following properties:
(a) a pour point is not higher than −40° C., and
(b) a SP value is from 6 to 8; and
the softener is contained in the amount of 300 to 700 parts by weight based on 100 parts by weight of the ethylene-propylene-diene rubber, and
2) the low modulus of elasticity-rubber composition according to the term 1), which is vulcanized.
The low modulus of elasticity-rubber composition of the present invention is suited for use as a seal material of a telecommunication cable closure because it shows flexibility, small compression set even at low temperature range, and excellent tack.
DETAILED DESCRIPTION OF THE INVENTION
EPDM used in the rubber composition of the present invention has properties specified by the terms (a), (b) and (d), as described above. With such a composition, the rubber composition shows low elasticity and the JIS A hardness is usually not more than 10. Herein, JIS is abbreviation of Japanese Industrial Standard.
The Mooney viscosity is an index of the molecular weight of EPDM. The higher the molecular weight, the higher the viscosity becomes. To the contrary, the lower the molecular weight, the lower the viscosity becomes. In the present invention, EPDM having the Mooney viscosity at 100° C. within a range from 90 to 130, preferably from 100 to 120, is used. When the molecular weight of EPDM is high, there is a merit of increased strength. On the other hand, it becomes difficult to fill with a large amount of softener and tack of the rubber after vulcanization becomes poor. A high-molecular weight EPDM having the Mooney viscosity of higher than 130 is not preferred for the reasons described above. On the other hand, when the Mooney viscosity is lower than 90, it is possible to fill with a large amount of softener such as oil and the tack is good, however, the vulcanized article is scarcely fit to use because of drastic reduction in strength. EPDM having the Mooney viscosity of about 100 to 120 is preferably used.
The iodine value of EPDM is an index of the amount of the diene component in this rubber, that is, the larger the iodine value, the l
Mizoguchi Tetsuo
Sakaki Toshiaki
Birch & Stewart Kolasch & Birch, LLP
Cheung William
Sumitomo Rubber Industries Ltd.
Wu David W.
LandOfFree
Low modulus of elasticity-rubber composition does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Low modulus of elasticity-rubber composition, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low modulus of elasticity-rubber composition will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2853418