Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-12-04
2003-02-11
Knable, Geoffrey L. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C152S209600, C152S547000, C152S510000, C156S096000, C156S129000, C156S130500, C156S135000
Reexamination Certificate
active
06517653
ABSTRACT:
BACKGROUND OF THE INVENTION
Cured adhesion of cured or precured rubber components to green “uncured” rubber stock is important in tire retreading and in the manufacture of tires containing precured components. Conventionally, the precured components are buffed to roughen up the surface and a rubber cement is applied to the surface prior to joining the roughened surface of the precured rubber to the uncured rubber surface. The precured rubber and uncured rubber is then vulcanized. Unfortunately, such process steps are time-consuming and inefficient.
SUMMARY OF THE INVENTION
The present invention relates to a process for improving the cured adhesion of a precured rubber compound to an uncured rubber compound. The process involves assembling a pneumatic tire having a precured rubber component which is in contact with an uncured rubber component. The improvement in cured adhesion after the tire is vulcanized is realized by using a precured rubber compound comprising (a) natural rubber, emulsion-polymerized styrene-butadiene rubber and mixtures thereof; (b) precipitated silica; and (c) no fatty acid, other than any fatty acid inherently present in the natural rubber or present from the emulsion polymerization reaction to produce the styrene-butadiene rubber.
DETAILED DESCRIPTION OF THE INVENTION
There is disclosed a process for improving the cured adhesion of at least two rubber components in a pneumatic tire wherein, prior to vulcanization of the tire, one of the two components is a precured rubber compound and the other component is an uncured rubber compound comprising
(A) using a precured rubber compound characterized by from 40 to 100 parts by weight of a rubber, per 100 parts by weight of total rubber in said precured rubber compound, selected from the group consisting of natural rubber, emulsion-polymerized styrene-butadiene rubber and mixtures thereof, wherein said rubber contains from 0.5 to 3 phr of a fatty acid inherently present in the natural rubber or present from the polymerization reaction to produce the styrene-butadiene rubber;
(B) from 3 to 80 phr of precipitated silica;
(C) from 0.8 to 3.5 phr of an accelerator;
(D) from 1.0 to 3.5 phr of sulfur, wherein the weight ratio of accelerator to sulfur ranges from 0.5:1 to 3.5:1;
(E) from 1 to 10 phr of zinc oxide; and
(F) 0 phr of any fatty acid other than the 0.5 to 3 phr present in said natural rubber and emulsion-polymerized styrene-butadiene rubber.
There is disclosed a process for improving the cured adhesion of a precured rubber component in a pneumatic tire to an uncured rubber component in a tire comprising
(A) assembling the tire so a precured rubber component is in contact with an uncured rubber component wherein said precured rubber component comprises
(1) from 40 to 100 parts by weight of a rubber, per 100 parts by weight of total rubber in said precured rubber compound, selected from the group consisting of natural rubber, emulsion-polymerized styrene-butadiene rubber and mixtures thereof, wherein said rubber contains from 0.5 to 3 phr of a fatty acid inherently present in the natural rubber or present from the polymerization reaction to produce the styrene-butadiene rubber;
(2) from 3 to 80 phr of precipitated silica;
(3) from 0.8 to 3.5 phr of an accelerator;
(4) from 1.0 to 3.5 phr of sulfur, wherein the weight ratio of accelerator to sulfur ranges from 0.5:1 to 3.5:1;
(5) from 1 to 10 phr of zinc oxide; and
(6) 0 phr of any fatty acid other than the 0.5 to 3 phr present in said natural rubber and emulsion-polymerized styrene-butadiene rubber; and
(B) vulcanizing the tire at a temperature ranging from 120° C. to 200° C.
The present invention is directed to solving the problem associated with adhering a precured rubber component to an uncured rubber component after vulcanization. This problem exists when 40 to 100 parts by weight of rubber per 100 parts by weight of total rubber in the precured compound is natural rubber or emulsion-polymerized styrene-butadiene rubber. It is well known that natural rubber inherently contains various levels of naturally occurring fatty acids. In addition, it is known to add fatty acids as part of the soap system during the emulsion polymerization of styrene and butadiene to make the styrene-butadiene rubber. Unfortunately, various levels of the fatty acids remain in the recovered rubber. It is believed that use of these rubbers containing anywhere from 0.5 to 3 phr of such fatty acids result in such acids or salts thereof migrating to the surface of the cured rubber and, therefore, resulting in unacceptable adhesion values. Buffing of the surface and the use of rubber cement is then required to obtain acceptable adhesion.
The present invention involves the use of from 40 to 100 parts by weight of natural rubber or emulsion-polymerized styrene-butadiene rubber containing from 0.5 to 3 phr of fatty acids. In those instances where less than 40 parts are used, the complications due to the presence of such fatty acids are minimal. In those instances where the level of fatty acid is less than 0.5 phr, the complications due to the presence of such fatty acids are also minimal. Preferably, the precured rubber component contains from 50 to 100 parts by weight of natural rubber, the above-described styrene-butadiene rubber and mixtures thereof.
In those instances where less than 100 parts by weight is the natural rubber or emulsion-polymerized styrene-butadiene rubber, the remaining 60 phr to 0 phr may be selected from the group consisting of solution polymerized styrene/butadiene copolymers, cis 1,4-polybutadiene, synthetic cis 1,4-polyisoprene, styrene/isoprene copolymers, 3,4-polyisoprene, isoprene/butadiene copolymers, medium vinyl polybutadiene (20 percent to 60 percent by weight of vinyl units), styrene/isoprene/butadiene terpolymers, butyl rubber, polychloroprene, acrylonitrile/butadiene copolymers and ethylene/propylene/diene terpolymers and mixtures thereof. Preferably, if used, from 0 to 50 phr of the additional rubber is used and the preferred rubber is cis 1,4-polybutadiene and solution-polymerized styrene/butadiene copolymers.
The rubbers used in the green or uncured rubber stock may be the same or different than the rubbers used in the precured rubber compound. Preferably, the rubbers used in the green compound, which will be adhered to the precured rubber compound, are natural rubber or a blend containing 50 phr of natural rubber.
The commonly employed precipitated siliceous pigments used in rubber compounding applications can be used as the silica in this invention. The siliceous pigments employed in this invention are precipitated silicas such as, for example, those obtained by the acidification of a soluble silicate, e.g., sodium silicate.
Such silicas might be characterized, for example, by having a BET surface area, as measured using nitrogen gas, preferably in the range of about 40 to about 600, and more usually in a range of about 50 to about 300 square meters per gram. The BET method of measuring surface area is described in the
Journal of the American Chemical Society
, Volume 60, page 304 (1930).
The silica may also be typically characterized by having a dibutylphthalate (DBP) absorption value in a range of about 100 to about 400, and more usually about 150 to about 300.
The silica might be expected to have an average ultimate particle size, for example, in the range of 0.01 to 0.05 micron as determined by the electron microscope, although the silica particles may be even smaller, or possibly larger, in size.
Various commercially available silicas may be considered for use in this invention such as, only for example herein, and without limitation, silicas commercially available from PPG Industries under the Hi-Sil trademark with designations 210, 243, etc; silicas available from Rhone-Poulenc, with, for example, designations of Z1165MP and Z165GR and silicas available from Degussa AG with, for example, designations VN2 and VN3, etc. The Rhone-Poulenc Z1165MP silica is currently preferred.
The silica is added to the compound to be used as the precured co
DeLong John D.
Hendricks Bruce J.
Knable Geoffrey L.
The Goodyear Tire & Rubber Company
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