Resilient tires and wheels – Tires – resilient – Anti-skid devices
Reexamination Certificate
2000-01-12
2002-06-04
Lee, Katarzyna Wyrozebski (Department: 1714)
Resilient tires and wheels
Tires, resilient
Anti-skid devices
C152S565000, C152S532000, C156S096000, C156S128100, C156S128600
Reexamination Certificate
active
06397910
ABSTRACT:
FIELD
A retreaded tire comprised of a tread and carcass with an intervening rubber layer, conventionally referred to as a cushion, wherein the tread has an oil rich rubber-based adhesive on its inner surface at the interface between said tread and cushion. Said oil rich rubber based adhesive is free, or substantially free, of volatile organic compounds, particularly volatile organic solvents. Alternately, the oil-rich rubber-based adhesive may contain oil and volatile organic solvent wherein oil is the major component insofar as the oil and solvent is concerned.
BACKGROUND OF THE INVENTION
Historically, a rubber tire is retreaded by first abrading away its tread and buffing a surface of the remaining rubber carcass.
A strip of sulfur vulcanizable, unvulcanized rubber composition is then applied onto and circumferentially around the periphery of the buffed, cured rubber tire carcass.
Such rubber composition strip is conventionally referred as a “cushion”.
Over the cushion may then be applied a pre-cured, shaped rubber tread, to which a vulcanizable or unvulcanizable, and preferably a sulfur vulcanizable, unvulcanized rubber-based adhesive has been applied to the inner surface of the tread to enhance the interfacial adhesion between the tread and aforesaid cushion.
The resulting tire assembly is then conventionally encased in a cured butyl rubber envelope, a vacuum drawn on the envelope, and the enveloped tire assembly inserted in an autoclave and the assembly vulcanized therein at a temperature of, for example, about 130° C. to produce the retreaded tire.
Such method of tire retreading with a pre-cured tread and vulcanizable cushion over an abraded tire carcass is well known to those having skill in such art.
Historically the aforesaid rubber-based adhesive may be applied to the tread stock as a volatile organic solvent solution of the adhesive and then allowed to dry prior to application of the tread to the aforesaid cushion.
However, it is sometimes desired to provide such adhesive, and the accompanying application of the adhesive to a pre-cured tire tread, in a retreading operation without volatile organic compounds, or at least substantially free of volatile organic compounds, which may sometimes be referred to as “VOC's”.
In the description of this invention, the term “phr” as used herein, and according to conventional practice, refers to “parts of a respective material per 100 parts by weight of rubber elastomer”. In the description of this invention, the terms “rubber” and “elastomer” can be used interchangeably, unless otherwise distinguished.
The terms “rubber composition”, “compounded rubber” and “rubber compound” can be used interchangeably to refer to “rubber which has been blended or mixed with various ingredients and materials” and the terms “cure” and “vulcanize” may also be used interchangeably herein, unless otherwise noted and such terms are well known to those having skill in the rubber mixing or rubber compounding art.
SUMMARY AND PRACTICE OF THE INVENTION
In a pneumatic tire retreading operation where a tire carcass is obtained, preferably an abraded vulcanized rubber tire carcass prepared by abrading away its tread and buffing the peripheral surface of the remaining cured tire carcass, to which a strip of a sulfur vulcanizable, unvulcanized rubber composition, or cushion, is circumferentially applied to the abraded peripheral surface of said tire carcass, and to which a pre-cured rubber tread strip, which has a vulcanizable or unvulcanizable, but preferably a sulfur vulcanizable, unvulcanized rubber based adhesive on its inner surface, is applied to said cushion, wherein said rubber based adhesive is located at the interface between said cushion and said tread stock, and wherein the resulting assembly is vulcanized at an elevated temperature to form a retreaded tire; an improvement wherein said adhesive is comprised of an oil rich rubber composition
(i) which contains from about 150 to about 1400, alternately about 400 to about 1000, phr of rubber processing oil and is exclusive of volatile organic compounds; or
(ii) which contains from about 150 to about 1400, alternatively about 400 to about 1000, phr combination of rubber processing oil and volatile organic solvent wherein the weight ratio of said oil to said solvent is in a range of about 1/0.05 to about 1/0.66, preferably about 1/0.05 to about 1/0.33; wherein said solvent is evaporated from said adhesive layer prior to application of said pre-cured tread strip to said cushion layer.
Accordingly, in one aspect of this invention, a retreaded tire is provided as a concentric circular laminate comprised of:
(a) a cured rubber tire casing, or carcass, having an abraded, or buffed, circumferential peripheral surface;
(b) a concentric, circular, unvulcanized rubber cushion layer having an inner surface and outer surface, wherein the inner surface of said cushion layer is positioned on said outer peripheral surface of said tire casing; and
(c) a pre-cured rubber tire tread strip having an inner surface and an outer surface, wherein said inner tread surface contains an unvulcanized oil-rich rubber-based adhesive layer thereon and wherein said pre-cured tread strip is circumferentially positioned on the outer surface of said positioned cushion layer with said adhesive layer therebetween to create a tire assembly, wherein said adhesive layer is comprised of an oil-rich rubber-based composition:
(i) which contains from about 150 to about 1400, alternately about 400 to about 1000, phr of rubber processing oil and is exclusive of volatile organic compounds; or
(ii) which contains from about 150 to about 1400, alternatively about 400 to about 1000, phr combination of rubber processing oil and volatile organic solvent wherein the weight ratio of said oil to said solvent is in a range of about 1/0.05 to about 1/0.66, preferably about 1/0.05 to about 1/0.33; wherein said solvent is evaporated from said adhesive layer prior to application of said pre-cured tread strip to said cushion layer.
A retreaded tire is then provided by heating the said tire assembly to an elevated temperature to vulcanized said adhesive cushion layers.
Usually an elevated temperature in a range of about 100° C. to about 150° C. is used for such vulcanization.
The oil-rich, rubber-based, adhesive layer is the oil-rich adhesive provided by this invention.
A significant aspect of the invention is the use of a substantial amount of oil which, in the adhesive, is a rubber processing oil and is therefore compatible with the elastomer composition of the cured elastomer of the tread and unvulcanized elastomer composition of the cushion and with the cured elastomer composition of the tire carcass casing to which the tire tread is applied.
This aspect of the invention relies upon the high level of oil content to provide for solubilizing the rubber of the adhesive to permit application of the adhesive to the inner surface of the pre-cure tread and, after sufficient migration of the oil into the cured tread strip, to also provide protection from premature oxidation of the inner tread surface from the atmosphere and impart a tacky surface to the associated surface tread prior to the actual application of the tread to the cushion.
Suitable oils for this adhesive composition are typical rubber processing oils of viscosities (ASTM D 2161, at 99° C.) ranging from about 30 to about 70 SUS and preferably 30 to 45 SUS; of clay bed analyses (ASTM D 2007) ranging from about 10 to about 90 wt % aromatics, preferably 20 to 50 wt % aromatics; and saturates ranging from about 90 to about 10 wt % saturates, preferably 80% to 50% saturates; aniline point (ASTM D 611) ranging from about 11 to about 121° C. and preferably 15 to 82° C.
Where a volatile organic solvent is used in the oil rich adhesive of this invention, representative solvents are, for example, hexane, heptane and mixtures of liquid hydrocarbons containing from 6 to and including 7 carbon atoms. Preferably, such solvents have a boiling point at atmospheric pressure in a range of about 30° C. to about 130
D'Sidocky Richard Michael
Hopper Roger John
Losey Cheryl Ann
Magee Arthur Webster
Lee Katarzyna Wyrozebski
The Goodyear Tire & Rubber Company
Young, Jr. Henry C.
LandOfFree
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