Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-11-28
2002-06-25
Nutter, Nathan M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S210000, C525S213000, C525S232000, C525S240000
Reexamination Certificate
active
06410650
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an ethylene-&agr;-olefin-non-conjugated polyene copolymer rubber, a rubber composition for sealing, a molded part for sealing and a process for producing the molded part. More particularly, it relates to techniques capable of providing a cross-linked, molded rubber part for sealing which is excellent in sealing performance as well as rolling processability, shape retention, mechanical strength properties, heat resistance, cold or low temperature resistance and compression set resistance.
BACKGROUND ART
Many sealing materials for use in automobiles and buildings comprise ethylene-propylene copolymer rubber (EPR) and ethylene-propylene-diene copolymer rubber (EPDM), which are excellent in heat resistance, weather resistance, processability and cost. EPR and EPDM have been very widely spread, especially as materials indispensable for automobile door, trunk and window seals.
As the performance has become higher and higher and the life has become longer and longer in automobiles, higher and higher performance has been required for these sealing materials. However, it has become difficult to fully satisfy all the requisite performance by conventional techniques.
Sealing performance may be affected by many factors, such as the cross-sectional shape, compression set resistance and flexibility of a sealing rubber. For example, the cross-sectional shape of a current sealing rubber has become more complex than conventional ones; lip portions thereof have become thinner and longer. Further, sealing materials to be mounted on hard-top components are now required to be larger in their cross-sectional shape and thinner in their thickness than conventional ones. Thus, a problem of “shape collapse” has been caused in the vulcanizing or foaming step in a process for preparing sealing materials; i.e., a correct cross-sectional shape cannot be obtained.
“Shape retention” is generally used as an index for the shape collapse. There is a need for sponge rubbers having good shape retention. Attempts to use two or more polyene components for the purpose of improving the shape retention of EPDM, such as ethylene-propylene-5-ethylidene-2-norbornene copolymer (EPT), have been made relatively long (see, for example, Japanese Patent Publication Nos. 44-7713 and 47-23914 and Japanese Patent Application Laying Open Nos. 49-62582, 49-62583, 56-22338 and 58-191705), but have not achieved all the aforementioned desirable performance.
For instance, in the method using the combination of 5-ethylidene-2-norbornene (ENB) and dicyclopentadiene (DCPD) as the polyene in EPDM, any of extrusion processability, vulcanizing rate and mechanical strength of vulcanized rubber does not exhibit a satisfactory value depending upon the balance between the contents of ENB and DCPD. Further, the method using both ENB and vinylnorbornene (VNB) as the polyene in EPDM is still not sufficient and is poor in manufacturing cost, though the balance between the extrusion processability, vulcanizing rate and mechanical strength of vulcanized rubber is slightly improved. Thus, no satisfactory EPDM has been obtained.
A method for providing excellent sealing performance, shape retention and sponge rubber properties by using a metallocene catalyst was found (Japanese Patent Application Laying Open No. 9-3269) but did not provide satisfactory rolling processability.
Thus, according to the aforementioned methods, no EPDM has been obtained that is capable of providing a cross-linked, molded rubber part for sealing which is excellent in sealing performance as well as rolling processability, shape retention, mechanical strength properties, heat resistance, cold resistance and compression set resistance.
Accordingly, there is a great need for a cross-linked, molded rubber part for sealing which is excellent in sealing performance as well as rolling processability, shape retention, mechanical strength properties, heat resistance, cold resistance and compression set resistance, and a process for producing the same.
DISCLOSURE OF THE INVENTION
The present invention is to solve the above mentioned problems associated with the prior art and has an object of providing an ethylene-&agr;-olefin-non-conjugated polyene copolymer rubber capable of providing a cross-linked, molded rubber part for sealing which is excellent in sealing performance as well as rolling processability, shape retention, mechanical strength properties, heat resistance, cold resistance and compression set resistance, as well as a rubber composition for sealing using said copolymer rubber, a molded part for sealing, and a process for producing the molded part.
In a first aspect, the present invention is an ethylene-&agr;-olefin-non-conjugated polyene copolymer rubber comprising ethylene, an &agr;-olefin having 3 to 20 carbon atoms and a non-conjugated polyene, characterized in that:
(i) the intrinsic viscosity [&eegr;] as measured in decalin solvent at 135° C. is 1.5 to 5.0 dl/g;
(ii) the g&eegr;
‡
or g′ value is 0.6 to 0.9, wherein the g&eegr;
‡
value is defined as a ratio of the intrinsic viscosity [&eegr;] as measured in (i) above to an intrinsic viscosity [&eegr;]
blank
as measured in decalin solvent at 135° C. of a linear ethylene-propylene copolymer having an ethylene content of 70% by mole which has the same weight average molecular weight (according to light scattering method) as the ethylene-&agr;-olefin-non-conjugated polyene copolymer rubber having the intrinsic viscosity [&eegr;] ([&eegr;]/[&eegr;]
blank
), and the g′ value is defined as a ratio of the intrinsic viscosity [&eegr;] as measured in (i) above to an intrinsic viscosity [&eegr;]
blank
′ as reduced to a linear ethylene-propylene copolymer having an ethylene content of 70% by mole, which is determined by gel permeation chromatography (140° C., o-dichlorobenzene solvent) of the ethylene-&agr;-olefin-non-conjugated polyene copolymer (g′=[&eegr;]/[&eegr;]
blank
′);
(iii) the Mw/Mn is 3.0 to 50;
(iv) the iodine value is 10 to 40;
(v) the molar ratio of ethylene to the &agr;-olefin having 3 to 20 carbon atoms is 40/60 to 95/5; and
(vi) the intensity ratio D of T&agr;&bgr; to T&agr;&agr; in
13
C-NMR spectrum (T&agr;&bgr;/T&agr;&agr;) is 0.5 or less.
The copolymer rubber of the first invention is not particularly limited as long as it has the aforementioned properties as a whole, and may be obtained by a one step polymerization reaction or may be any composition comprising copolymer rubbers having different properties.
In a second aspect, the present invention is an ethylene-&agr;-olefin-non-conjugated polyene copolymer rubber comprising ethylene, an &agr;-olefin having 3 to 20 carbon atoms and a non-conjugated polyene, which comprises:
(A) an ethylene-&agr;-olefin-non-conjugated polyene copolymer rubber, wherein the molar ratio of ethylene to the &agr;-olefin having 3 to 20 carbon atoms is 40/60 to 75/25; the intrinsic viscosity [&eegr;] as measured in decalin solvent at 135° C. is 0.5 to 2.0 dl/g; the iodine value is 15 to 50; and the g&eegr;
‡
or g′ value is 0.8 to 0.98, wherein the g&eegr;
‡
value is defined as a ratio of the intrinsic viscosity [&eegr;] as measured in the above to an intrinsic viscosity [&eegr;]
blank
as measured in decalin solvent at 135° C. of a linear ethylene-propylene copolymer having an ethylene content of 70% by mole which has the same weight average molecular weight (according to light scattering method) as the ethylene-&agr;-olefin-non-conjugated polyene copolymer rubber having the intrinsic viscosity [&eegr;] ([&eegr;]/[&eegr;]
blank
), and the g′ value is defined as a ratio of the intrinsic viscosity [&eegr;] as measured in the above to an intrinsic viscosity [&eegr;]
blank
′ as reduced to a linear ethylene-propylene copolymer having an ethylene content of 70% by mole, which is determined by gel permeatio
Kawasaki Masaaki
Koda Taku
Mitsui Chemicals INC
Nutter Nathan M.
Sherman & Shalloway
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