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
2001-11-15
2004-04-27
Reddick, Judy M. (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...
C524S445000, C524S492000, C524S493000
Reexamination Certificate
active
06727311
ABSTRACT:
BACKGROUND OF THE INVENTION
Tires are increasingly expected to provide higher and higher levels of performance characteristics. For instance, it is normally expected for tires to exhibit good traction characteristics on both dry and wet surfaces as well as low rolling resistance for good vehicle fuel economy. However, it has traditionally been very difficult to improve the traction characteristics of a tire without compromising its rolling resistance and treadwear. Low rolling resistance is important because good fuel economy is virtually always an important consideration. Reducing the weight of tires is also a goal of automobile and truck manufacturers because reduced weight results in improved fuel economy. Reducing the weight of tires is of particular importance in the case of aircraft tires. Good treadwear is also an important consideration because it is generally the most important factor in determining the life of the tire.
The traction, treadwear and rolling resistance of a tire is dependent to a large extent on the dynamic viscoelastic properties of the elastomers utilized in making the tire tread. In order to reduce the rolling resistance of a tire, rubbers having a high rebound have traditionally been utilized in making the tire's tread. On the other hand, in order to increase the wet skid resistance of a tire, rubbers that undergo a large energy loss have generally been utilized in the tire tread. In order to balance these two viscoelastically inconsistent properties, mixtures of various types of synthetic and natural rubber are normally utilized in tire treads. For instance, various mixtures of styrene-butadiene rubber and polybutadiene rubber are commonly used as a rubber material for automobile tire treads. However, such blends are not totally satisfactory for all purposes.
Rubbers having intermediate glass transition temperatures (−70° C. to −40° C.) compromise rolling resistance and treadwear without significantly increasing traction characteristics. For this reason, blends of rubbers having low glass transition temperatures and rubbers having high glass transition temperatures are frequently utilized to attain improved traction characteristics without significantly compromising rolling resistance or treadwear. However, such blends of rubbers having low glass transition temperatures and rubbers having high glass transition temperatures exhibit poor processability. This major disadvantage associated with such blends has greatly hampered their utilization in making tire tread compounds.
U.S. Pat. No. 2,885,381 discloses a composition of matter comprising a copolymer of a conjugated diene and a heterocyclic nitrogen containing monomer having a sole CH
2
═CH— substituent, such as 2-vinylpyridine, said copolymer having been compounded with 25-100 weight parts per 100 parts of said copolymer of a finely ground mineral pigment selected from the group consisting of silica and aluminum silicate as the sole reinforcing agent.
In recent years, there has been a trend to include silica as a filler in tire tread compounds to further improve traction characteristics. U.S. Pat. No. 5,036,133 discloses a vulcanizable rubber composition that is comprised of: (A) an uncured natural or synthetic isoprene rubber, or one or more uncured butadiene-based synthetic rubbers, or uncured blends thereof, said uncured rubbers being sulfur vulcanizable, (B) a silica filler, (C) sulfur, (D) an organic accelerator and (E) a vinylpyridine-butadiene interpolymer co-activator, said interpolymer co-activator (E) containing from about 20 percent to about 65 percent by weight of vinylpyridine units, the amount of said vinylpyridine-butadiene copolymer co-activator being from about 0.5 to 2 parts by weight per 100 parts by weight of said rubber.
Authors Wang et. al in the
Journal of Applied Polymer Science
, Vol. 78, 1879-1883 (2000) describe a process of making clay-rubber mixtures by mixing an SBR latex or a styrene-vinylpyridine-butadiene latex with the hydrophilic unmodified clay without quaternary ammonium salts. In the case of the styrene-vinylpyridene-butadiene latex and clay composite, the expansion of clay gallery in the case of styrene-vinylpyridine composite was reported to increase from 1.24 to 1.46 nm, which is not significant enough. The intercalation of the rubber was minimal and very limited exfoliation is evident from stacks of clay layers as shown in the TEM micrographs for the said composite. The limited extent of intercalation is not expected to provide substantial property enhancement in tire materials. The article does not suggest of achieving a light-weight rubber composition and a tire with improved rolling resistance. The intercalation achieved by using the organically modified modified clay with quaternary ammonium surfactant by mixing it in a solution of rubber is also described, that resulted in somewhat better intercalation or expansion of clay galleries. Nevertheless, the mixing time of 12 hours was used, which is rather long for an industrial process. The publication does not disclose a bulk thermomechanical mixing method of making rubber-clay nanocomposite with uniform dispersion and high degree of exfoliation that will result in a light weight composition and lower hysteresis.
European Patent Application EP1029823 A2 describes preparation of rubber composite materials. This European Patent Application discloses a composite clay rubber material comprising at least one material selected from the group consisting of a first composite clay material and a second composite clay material, and a rubber material; said first composite material comprising a clay mineral having interlayer section, an onium ion having 6 or more carbon atoms, bonding to said clay mineral via an ionic bond for expanding said interlayer section and rendering said interlayer section compatible with an organic molecule; a first guest molecule having a polar group therein being at least partially incorporated into said expanded interlayer section and bonded to said clay mineral through a hydrogen bonding between said clay mineral and said polar group; and a second guest molecule as said organic molecule without a polar group as said organic molecule being at least partially incorporated into said expanded interlayer section, said first guest molecule having a molecular length equal to or smaller than that of said onium ion, said second guest molecule having a molecular length equal to or larger than that of the said onium ion; said second composite clay material comprising a clay mineral having an interlayer section; an onium ion having 6 or more carbon atoms, bonding to said clay mineral via ionic bond for expanding said interlayer section and rendering said interlayer section compatible with an organic molecule; and a main guest molecule as said organic molecule having a polar group in a main chain and/or side chain thereof being at least partially incorporated into said expanded interlayer section and bonded to said clay mineral through a hydrogen bonding between said clay mineral and said polar group, said main guest molecule having a molecular length equal to or larger than that of the said organic onium ion-wherein said organic onium ion contained in at least one of said first composite clay material and said second composite clay material is crosslinked with at least one of said second guest molecule and said main guest molecule and a molecule of said rubber material.
European Patent 1029823A2 further describes that crosslinking be provided by using the onium ions with unsaturated groups for crosslinking with the guest molecule and rubber materials.
European Patent 1029823A2 also discloses the rubber materials as being selected from the group consisting of natural rubber, isoprene rubber, chloroprene rubber, styrene rubber, nitrile rubber, ethylene-propylene rubber, ethylene-propylene-diene rubber, butadiene rubber, styrene-butadiene rubber, butyl rubber, epichlorohydrin rubber, acrylic rubber, urethane rubber, fluoro rubber and silicone rubber. This European Patent also s
Ajbani Manoj
Castner Eric Sean
Halasa Adel Farhan
Hsu Wen-Liang
Lee Ginger
Reddick Judy M.
Rockhill Alvin T.
The Goodyear Tire & Rubber Company
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