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
2000-12-28
2004-04-20
Mulcahy, Peter D. (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...
C524S491000, C524S505000, C524S515000
Reexamination Certificate
active
06723776
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a low modulus polymer composition and a sealant using the same. More particularly, the present invention relates to a polymer composition which exhibits a low modulus at a very wide range of temperature (i.e. excellent flexibility), less thermal deformation at high temperature and a small compression set at low temperature, and which also has tack, and a sealant which is especially suited for use in a telecommunication cable closure.
Sealants used in a telecommunication cable closure require excellent flexibility, conformability, weather resistance and aging resistance, and small compression set.
As a conventional sealant, there can be used hydrogenated thermoplastic elastomers such as hydrogenated styrene-isoprene block copolymer, hydrogenated styrene-butadiene block copolymer, hydrogenated styrene-isoprene-styrene block copolymer (SIS) [i.e. styrene-ethylene-propylene-styrene block copolymer, hereinafter referred to “as “SEPS”], and hydrogenated styrene-butadiene-styrene block copolymer (SBS) [i.e. styrene-ethylene-butylene-styrene block copolymer, herein after referred to as “SEBS”]and rubber shaving no double bond on a main chain, such as ethylene-propylene-diene rubber (EPDM).
A softener is added in the thermoplastic elastomers and rubbers to improve the flexibility. As the softener, paraffin oil having a pour point of not lower than −20° C. and particularly about −15° C. is often used.
However, a sealant composed of a rubber such as EPDM requires a vulcanizing process which takes long time to mold so that the production efficiency is low. Although recycling of a resource has recently been required in view of the environmental protection, it is scarcely possible to recycle the sealant composed of the rubber such as EPDM alone in practice. Expensive facilities and much labor, for example, use of supercritical water and decomposition by high concentration of ozone are required to dare to recycle EPDM rubber.
Various EPDM(s) are known, components of which are changed according to the purposes thereof. A sealant of a telecommunication cable closure is required to have a small compression set at a low temperature ranging from −30 to 0° C. and to be superior in flexibility. However, it is difficult that a conventionally known EPDM satisfies the properties described above. For example, a sealant using a conventionally known EPDM is likely to cause leakage as a result of deterioration of the sealing ability within a low temperature range because the compression set at −20° C. exceeds 90% and a change in hardness between room temperature and −20° C. is very large. Also there is a problem that compression required to seal can not be conducted sufficiently because the hardness increases within the above low temperature range.
On the other hand, any of the diblock copolymer, SEPS and SEBS has thermoplasticity and the sealant using them causes severe deformation at high temperature. These thermoplastic elastomers generally have such characteristics that the compression set rapidly increases within the low temperature region because oil having a high pour point is incorporated therein. A large compression set deteriorates sealing ability, thereby to cause problems such as water permeation and leakage of an inner gas.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a polymer composition wherein the problems described above have been solved. That is, an object thereof is to provide a low modulus polymer composition which can be injection-molded, and is recyclable and easy to mold and process and is also superior in flexibility (low modulus), and which shows a small compression set within a low temperature range and less deformation at high temperature and also has good mechanical strength such as tear strength and surface strength, large tensile strength and elongation at breakage, and good surface texture on molding.
Another object of the present invention is to provide a sealant which exhibits excellent flexibility and small compression set, which are particularly suited for use in a telecommunication cable closure, and also has large tensile strength and large elongation at breakage as well as tack.
To attain the objects described above, the present inventors have intensively studied, thus obtaining a low modulus polymer composition comprising a thermoplastic elastomer such as SEPS or SEBS, and EPDM, portion of which exists in the thermoplastic elastomer dispersed finely after being dynamically vulcanized, and oil having a pour point of not higher than −35° C. in the amount of not less than 200 parts by weight based on 100 parts by weight of the total amount of the thermoplastic resin and rubber (Japanese Patent Application No. 2000-6902). This material has such an advantageous feature suited for use as a sealant that it can be injection-molded and is recyclable and shows a small compression set at the temperature within a range from low temperature (−30° C.) to high temperature (70° C.) and a very low modulus.
Furthermore, the present inventors have obtained a low modulus polymer composition further comprising an olefin polymer so as to improve the brittleness, mechanical strength and extrusion texture on molding of the polymer composition while maintaining such a feature that the above low modulus polymer composition can be injection-molded and is recyclable and shows a small compression set at the temperature within a range from low temperature (−30° C.) to high temperature (70° C.) and a very low modulus (Japanese Patent Application No. 2000-92026).
Furthermore, the present inventors have succeeded in increasing the tensile strength, elongation at breakage and the tear strength by adding carbon black to the above low modulus polymer composition containing an olefin polymer.
Thus, the present invention provides the following low modulus polymer compositions and a sealant using the same.
(1) A low modulus polymer composition comprising:
(A) at least one thermoplastic elastomer selected from the group consisting of a hydrogenated styrene-isoprene-styrene block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer and a styrene-ethylene-(ethylene-propylene)-styrene block copolymer,
(B) a rubber component containing an ethylene-propylene-diene rubber, and
(C) a softener, wherein
the amount of the softener (C) is not less than 200 parts by weight based on 100 parts by weight of the total amount of the components (A) and (B) and at least portion of the component (B) is crosslinked by dynamic crosslinking.
(2) A low modulus polymer composition comprising:
(A) at least one thermoplastic elastomer selected from the group consisting of a hydrogenated styrene-isoprene-styrene block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer and a styrene-ethylene-(ethylene-propylene)-styrene block copolymer,
(a) an olefin polymer,
(B) a rubber component containing an ethylene-propylene-diene rubber, and
(C) a softener, wherein
the amount of the softener (C) is not less than 200 parts by weight based on 100 parts by weight of the total amount of the components (A), (a) and (B), and
at least portion of the rubber component (B) is crosslinked by dynamic crosslinking.
(3) A low modulus polymer composition comprising:
(A) at least one thermoplastic elastomer selected from the group consisting of a hydrogenated styrene-isoprene-styrene block copolymer, a hydrogenated styrene-butadiene-styrene block copolymer and a styrene-ethylene-ethylene-propylene-styrene block copolymer,
(a) an olefin polymer,
(B) a rubber component containing an ethylene-propylene-diene rubber,
(C) a softener, and
(D) carbon black, wherein
the amount of the softener (C) is not less than 200 parts by weight based on 100 parts by weight of the total amount of the components (A), (a) and (B), and
at least portion of the rubber component (B) is crosslinked by dynamic crosslinking.
(4) A sealant comprising the low modulus polymer composition of an
Mizoguchi Tetsuo
Sakaki Toshiaki
Mulcahy Peter D.
Sumitomo Rubber Industries Ltd.
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