Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2000-12-13
2003-09-30
Knable, Geoffrey L. (Department: 1733)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S510000
Reexamination Certificate
active
06626219
ABSTRACT:
FIELD OF INVENTION
The present invention relates to tire inner tubes made from isobutylene-co-paramethylstyrene, elastomers, and blends thereof
BACKGROUND OF THE INVENTION
Tire inner tubes are ordinarily made from butyl rubber cross-linked or vulcanized to form a tube having good heat stability and physical properties. However, high temperatures and extreme conditions of use cause repeated expansion and contraction of the tire inner tubes. As a result, inner tubes made from these polymers have a limited useful life. For example, in many developing nations having bad roads and tropical and sub-tropical conditions, inner tubes are still used within tires. Inner tubes comprised of isobutylene based rubbers, such as butyl rubber, and chlorobutyl rubber, and EPDM rubber, do not have the proper properties to survive severe conditions of overloading and high temperatures. The inner tubes degrade, lose air, and become sticky, adhering to the tire. The inner tube cannot be removed from the tire, the tire cannot be retreaded, and thus the tire must be scrapped. These deficiencies in current inner tube compositions lead to excessive waste of tire composition and added cost of replacing a tire.
Most present day inner tube compositions lack the superior heat aging properties needed to produce a reliable, improved air impermeable tire inner tube capable of performing in severe service applications such as high speed, bumpy roads and overloading situations, which all may cause rapid deformation.
Inner tubes comprising butyl rubber are superior in barrier properties to inner tubes formed from any other rubber. However, certain applications require improved heat resistance which is normally obtained by blending Ethylene-Propylene (EP) or EPDM rubber with butyl in inner tube compounds. However, blending of EP or EPDM rubbers increases the air permeability of the rubbers.
U.S. Pat. No. 5,698,640 teaches isobutylene-co-brominated paramethylstyrene (EXXPRO™ ExxonMobil Chemical Company) bladders made from a low-bromine formulation. However, this low-bromine formulation does not possess proper cure properties needed for the production of inner tubes. The low bromine polymer will not develop the tensile and modulus strength needed for inner tubes. The cure system disclosed in U.S. Pat. No. 5,698,640 is considered to be too “scorchy” for inner tube processing.
U.S. Pat. No. 5,576,373 teaches the use of layered silicates in inner tubes while WO 9422680 includes a laundry list of rubbers that may be used for a variety of applications.
U.S. Pat. No. 5,650,454 discloses an elastomer composition comprising an isobutylene-paramethylstyrene copolymer rubber that may be used in inner tubes. The composition must contain an additive comprising a cross-linked fatty acid and a starch. The additive is said to increase tear resistance, but there is no suggestion that the compositions formed have enhanced thermal stability.
It has been known to use 1,6-hexamethylene-bis(sodium thiosulfate) (HTS, Flexsys Corp.) as a stabilizing agent, more specifically as a reversion inhibitor, in sulfur-vulcanized master batches of high diene rubber. See U.S. Pat. Nos. 4,417,012; 4,520,154; and 4,587,296 to Moniotte; and U.S. Pat. No. 5,508,354 to Talma et al. herein incorporated by reference for purposes of U.S. patent practice.
There is a need for an inner tube that will have enhanced thermal stability and physical properties under severe temperature and operating conditions.
SUMMARY OF THE INVENTION
It has been found that halogenated isobutylene-co-paramethylstyrene copolymer, preferably brominated isobutylene-co-paramethylstyrene copolymer, can be effectively used as a composition suitable for severe duties such as tire inner tubes.
Accordingly, in one aspect of the present disclosure, inner tubes comprising halogenated isobutylene-co-paramethylstyrene polymer, preferably brominated isobutylene-co-paramethylstyrene polymer (BIMS) exhibit improved heat resistance while retaining the superior barrier properties of butyl inner tubes.
In another aspect, the present invention provides an inner tube comprising a blend of a halogenated isobutylene-co-paramethylstyrene polymer, preferably brominated isobutylene-co-paramethylstyrene polymer, and a second isobutylene based rubber.
In another aspect, the present invention provides a composition that is heat resistant and thermostable and may be used in articles of manufacture that require such properties, such as high temperature hoses, gaskets, seals, and belts.
DETAILED DESCRIPTION OF THE INVENTION
Tire inner tubes are generally defined as inflatable air containers or bladders that are usually positioned between a tire carcass and a tire rim or wheel. Tire inner tubes can be employed in a variety of tires, such as bicycle tires, automobile, and truck tires. Although most automobile and truck tires in the industrialized world are tubeless, many developing nations, such as India, China, Indonesia, and African nations still use tires with inner tubes. In these developing nations, high temperatures, bad roads and extreme conditions of use cause repeated expansion and contraction of the tire inner tubes. As a result, inner tubes made from these polymers have a limited useful life.
In the present invention, compositions comprising halogenated isobutylene-co-paramethylstyrene polymers, preferably brominated isobutylene-co-paramethylstyrene polymers and blends of a second isobutylene based rubber and BIMS, exhibit improved heat resistance while retaining the superior barrier properties of butyl rubber inner tubes. The inner tube may comprise halogenated isobutylene-co-paramethylstyrene polymer, preferably brominated isobutylene-co-paramethylstyrene polymer or a blend comprising a second isobutylene based rubber and BIMS. The inner tube comprising the BIMS alone or the blend comprising at least 15 parts per hundred rubber halogenated isobutylene-co-paramethylstyrene in one embodiment, at least 25 parts per hundred rubber halogenated isobutylene-co-paramethylstyrene in another embodiment, and at least 40 parts per hundred rubber halogenated isobutylene-co-paramethylstyrene in yet another embodiment. As previously stated, the halogenated isobutylene-co-paramethylstyrene polymers are preferably brominated isobutylene-co-paramethylstyrene polymers (BIMS). The term parts per hundred rubber or “phr” is well understood in the art.
Isobutylene based polymers, particularly halogenated isobutylene based polymers, and more particularly halogenated butyl rubber are the primary compositions of most tire liners, heat resistant tubes, and other commercially known products such as pharmaceutical ware. The term “butyl rubber” as employed herein is intended to refer to a vulcanizable rubbery copolymer containing, by weight, from about 85% to about 99.5% combined isoolefin having from 4 to 8 carbon atoms, such as a copolymer of isobutylene/isoprene. Such copolymers and their preparation are well known to one skilled in the art. A preferred butyl rubber is shown in the following examples and is commercially available from ExxonMobil Chemical Company as Exxon® Butyl 268 rubber (hereinafter referred to as “Butyl 268” rubber).
Brominated isobutylene-co-paramethylstyrene polymer is well known in the art. The preparation of C
4
-C
7
isoolefin/paralkylstyrene copolymers is generally disclosed, for example, in U.S. Pat. No. 5,162,445 to Powers et al. and U.S. S.I.R H1475 by Newman et al. both of which are incorporated herein by reference for purposes of U.S. patent practice. BIMS with a relatively low level of bromine, at least 0.5 moles percent benzylic bromine relative to the total amount of copolymer present, is commercially available from ExxonMobil Chemical Company as EXXPRO™ elastomer.
According to the one embodiment of the invention, the BIMS has a relatively low bromination level, from 0.1 to 3.0 mol % benzylic bromine (relative to the total amount of copolymer) in one embodiment, and 0.25 to 2.0 mol % in another embodiment, and 0.60 to 1.5 mol % benzylic bromine in yet another embodiment. Below this range, the c
Duvdevani Ilan
Parente Arthur E.
Paul Utpal
Takeda Takashi
Tracey Donald S.
Arechederra Leandro
ExxonMobil Chemical Patents Inc.
Knable Geoffrey L.
LandOfFree
Inner tube compositions having improved heat resistance... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Inner tube compositions having improved heat resistance..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Inner tube compositions having improved heat resistance... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3038708