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
1996-08-05
2002-02-12
Niland, Patrick D. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C524S501000, C526S338000, C526S340000
Reexamination Certificate
active
06346579
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire having a tread which is composed of a unique blend of latices. The tread composition exhibits improved properties which correlate to increased durability and treadwear of the pneumatic tire.
SUMMARY OF THE INVENTION
The present invention relates to a pneumatic tire having a tread containing from 50 to 100 phr of a dried rubber derived from a blend of a styrene butadiene latex and an acrylonitrile butadiene latex.
DETAILED DESCRIPTION OF THE INVENTION
There is disclosed a pneumatic tire having a tread comprised of 100 parts by weight of a first blend of rubbers, wherein said first blend comprises
(a) 50 to 100 phr of a dried rubber derived from a second blend of rubber latices, said second blend of rubber latices containing styrene-butadiene rubber latex and acrylonitrile-butadiene rubber latex and
(b) 0 to 50 phr of a dried rubber selected from the group consisting of natural rubber, synthetic cis 1,4-polyisoprene, 3,4-polyisoprene, styrene/butadiene rubber, acrylonitrile/butadiene rubber, styrene/isoprene/butadiene terpolymer rubber, cis 1,4-polybutadiene rubber, high trans 1,4-polybutadiene rubber, styrene/isoprene rubber isoprene/butadiene rubber and mixtures thereof.
A majority (from 50 to 100 phr) of the total rubber used in the tread is a dried rubber derived from a blend of two rubber latices. The first latex is a latex derived from the emulsion polymerization of styrene and butadiene monomers. The bound styrene content of the styrene butadiene rubber latex may range from 5 to 50 percent by weight. For example, conventional styrene contents in commercially available SBR generally range from 20 to 28 percent and 30 to 45 percent. The relatively higher levels of styrene are considered beneficial for enhancing traction or skid resistance of the tire tread. The solids content, also known as percent solids, of the styrene butadiene latex may vary. For example, the percent solids may range from 5 to 70 percent. Preferably, the percent solids range from 10 to 40 percent.
The other latex which is combined with the styrene butadiene latex is an acrylonitrile butadiene latex, also known as an NBR latex. The bound acrylonitrile content may range as low as 5 percent to as high as 50 percent by weight. Preferably, the acrylonitrile level ranges from 10 to 35 percent. The solids content may range from 5 to 70 percent. Preferably, the percent solids range from 10 to 40 percent.
The SBR latex and the NBR latex are prepared in accordance with conventional emulsion polymerization techniques. The principles of emulsion polymerization are discussed in references such as “Synthetic Rubber” by G. S. Whitby, Editor-in-Chief, John Wiley and Sons, 1954, particularly Chapter 8, and “Emulsion Polymerization” by F. A. Bovey et al, Vol. IX of “High Polymers,” Interscience Publishers, Inc., 1955.
Conventional free radical polymerization initiators that are used in emulsion polymerization include compounds such as t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide and paramenthane hydroperoxides and even hydrogen peroxide. These compounds perform very effectively when used in polymerization recipes containing appropriate levels of supporting ingredients. By “supporting ingredients” is meant those materials often referred to as activators in emulsion, or other systems where required. U.S. Pat. No. 3,080,334 describes some of these materials at column 5, lines 20-26. Such materials can also be referred to as catalyst activators. The term “redox polymerization” is often used where the complete initiator system includes a redox system, i.e., reducing agents and oxidizing agents in a proportion that yields polymerization initiating species. All of these initiator systems are well known in the art.
Emulsion polymerizations are normally accomplished in the range of 5° C. to 90° C. Though the activator or “redox” initiated systems are preferred for low temperature polymerizations, they are very effective at high temperatures also, normally requiring appreciably lower quantities of the various ingredients to obtain a desirable polymerization rate.
The free radical sources used in the initiator systems are those customarily used in free radical polymerizations, for example, organic initiators such as azonitriles, azo-derivatives, peroxides and hydroperoxides and inorganic initiators such as inorganic peroxy compounds. Radiation, e.g., of the ultraviolet and gamma ray type can also be used as a free radical source. Various organic initiators are described by J. Brandrup and E. H. Immergut, Polymer Handbook (John Wiley & Sons), 1965, pages II-3 to II-51. The pH of the latex emulsion generally ranges from about 7.5 to 13. Preferably, the pH ranges from about 8 to 11.
The SBR and NBR latices emulsion may also contain various conventional compounds such as surface active agents, short stop materials such as di-tertiary-butyl hydroquinone and similar compounds, all of which are present in small amounts. The surface active agents may consist of emulsifiers comprising the salts of natural acids such as potassium stearate, potassium-processed rosin, and the like, or such surface active agents may be synthetics such as alkali metal salts of alkyl aryl sulfonic acid, particularly alkylbenzene sulfonic acid, condensed naphthalene-formaldehyde sulfonic acid, and the like, or non-ionics such as polyalkylene oxide dioleates, sorbitan trioleate, alkylolamides, the condensation products of nonyl phenol with ethylene oxide or propylene oxide-ethylene oxide products. Preferably, anionic-type surfactants are used such as potassium stearate, potassium-processed rosin, and the alkali metal salts of alkylbenzene sulfonic acid.
The SBR latex and the NBR latex may be blended in a wide range of weight ratios, based on dry weight. For example, the blend of the two latices may comprise from 99 to 30 percent by weight of the styrene butadiene rubber and from 1 percent to 70 percent by weight of the NBR rubber. Preferably, the ratio will range from 95 to 35 percent by weight of the styrene butadiene rubber and from 5 to 65 percent by weight of the NBR rubber.
In addition to the SBR latex and NBR latex, additional latices may be optionally added to form the blend of latices prior to coagulation and drying. For example, natural rubber latex, polybutadiene latex and mixtures thereof may be used. Relative to the total dry weight of the SBR latex and NBR, these optional latices are added in minor amounts. For example, based on a dried weight basis, the amount of optional latex, if used, may be combined in an amount ranging from about 5 to 45 weight percent of the total weight of the SBR latex, NER latex and optional combined. Preferably, if an optional latex or latices are used, the amount ranges from 10 to 30 percent by weight based on the total weight of the SBR, NBR and optional latices combined. The solids content of the natural rubber latex and polybutadiene latex may range from about 10 to 60. Preferably, the solids content ranges from 15 to 50.
After the NBR and SBR latices have been combined and thoroughly mixed, along with any optional latex or latices, the blend of latices are coagulated to recover a dry rubber. Standard coagulation techniques, such as salt-acid coagulation procedures, can be employed.
The minority (from 0 phr to 50 phr) of the total rubber used in the tread is dried rubber(s) not derived from a blend of two or more latices. This rubber(s) may be natural rubber, synthetic cis 1,4-polyisoprene, 3,4-polyisoprene, solution polymerized or emulsion polymerized styrene/butadiene rubber, styrene/isoprene/butadiene terpolymer rubber, cis 1,4-polybutadiene, high trans 1,4-polybutadiene, styrene/isoprene rubber, isoprene/butadiene rubber and mixtures thereof. Preferably, if used, the dried rubber is natural rubber, cis-1,4-polybutadiene and mixtures thereof. The preferred amount of this component rubber is from 10 to 40 phr of the total rubber used in the tread with the balance of 90 to 60 phr being derived from the second
Miller Joseph Walter
Sandstrom Paul Harry
Smith Richard Robinson
Zanzig David John
Hendricks Bruce J.
Niland Patrick D.
The Goodyear Tire & Rubber Company
LandOfFree
Pneumatic tire having a tread compound derived from latex blend does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Pneumatic tire having a tread compound derived from latex blend, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pneumatic tire having a tread compound derived from latex blend will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2947716