Resilient tires and wheels – Tires – resilient – Pneumatic tire or inner tube
Reexamination Certificate
2002-02-08
2003-12-16
Short, Patricia A. (Department: 1712)
Resilient tires and wheels
Tires, resilient
Pneumatic tire or inner tube
C152S450000, C152S565000, C525S133000, C525S138000, C525S139000, C525S142000, C525S143000
Reexamination Certificate
active
06662840
ABSTRACT:
BACKGROUND OF THE INVENTION
“Bead” as used herein means that part of a tire comprising an annular tensile member wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim.
A frequent problem in making a tire having a bead is maintaining good adhesion between the rubber and the bead. A conventional method in promoting the adhesion between the rubber and the reinforcement in the bead is to pre-treat the reinforcing wire with a mixture of a rubber latex and a phenol-formaldehyde condensation product wherein the phenol is almost always resorcinol. This is the so-called “RFL” (resorcinol-formaldehyde-latex) method. An alternative method of promoting such adhesion is to generate the resin in-situ (in the vulcanized rubber/textile matrix) by compounding a phenol-formaldehyde condensation product (hereinafter referred to as the “in-situ method”). The components of the condensation product consist of a methylene acceptor and a methylene donor. The most common methylene donors include N-(substituted oxymethyl) melamine, hexamethylene tetramine or hexamethoxy methyl melamine. A common methylene acceptor is a dihydroxy benzene compound such as resorcinol. The in-situ method has been found to be fairly effective where the reinforcing material is steel wire since pre-treatment of the wire with the RFL system has been observed as being largely ineffective. Unfortunately, the products using the in-situ method has still fallen short of the demands of the consumer.
The purpose of the present invention is to further improve the adhesion between the wire reinforcement in the bead and its rubber environment to satisfy this shortcoming in the existing technology.
SUMMARY OF THE INVENTION
The present invention relates to rubber stocks particularly suited for bead wire compounds for use in tires. The rubber stock of the present invention is characterized by having two or more diene rubbers. At least one of the diene rubbers is a carboxylated acrylonitrile-diene rubber having an acrylonitrile content ranging from about 15 to 45 percent by weight. The rubber stock also contains a methylene acceptor and methylene donor.
In addition, there is disclosed a pneumatic tire having a pair of beads where the beads are coated with the bead wire compound of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
There is disclosed a rubber stock for bead wire compounds comprising
(A) based on 100 parts by weight of rubber
(1) from about 5 to about 40 weight percent of a carboxylated acrylonitrile-diene rubber having an acrylonitrile content ranging from about 15 to 45 percent by weight; and
(2) from about 60 to about 95 weight percent of a non-carboxylated rubber selected from the group consisting of natural rubber, polyisoprene, polybutadiene, styrene-butadiene rubber, styrene-isoprene-butadiene rubber, styrene-isoprene rubber, isoprene-butadiene rubber and mixtures thereof;
(B) from about 0.1 to about 10 phr of a methylene acceptor; and
(C) from about 0.1 to about 10 phr of a methylene donor.
One essential component contained in the present invention is a carboxylated acrylonitrile rubber. Based on 100 parts by weight of the total rubber in the rubber composition, from 5 to 40 parts by weight, is the carboxylated acrylonitrile rubber. Preferably, from 10 to 20 parts by weight is the carboxylated acrylonitrile rubber.
The present invention involves the use of a carboxylated acrylonitrile rubber or carboxylated acrylonitrile/diene polymer having an acrylonitrile content ranging from about 15 to about 45 percent by weight. Preferably, the acrylonitrile (ACN) content ranges from 18 to 35 percent by weight. The acrylonitrile/diene copolymers are intended to include acrylonitrile/butadiene copolymers and acrylonitrile/isoprene copolymers.
The carboxylated nitrile rubbers contain chain linkages derived from unsaturated carboxylic acids of the acrylic acid type (unsaturated carboxylic acid monomers). Some representative examples of unsaturated carboxylic acids of the acrylic acid type include acrylic acid, methacrylic acid, sorbic acid, &bgr;-acryloxypropanoic acid, ethacrylic acid, 2-ethyl-3-propyl acrylic acid, vinyl acrylic acid, cinnamic acid, maleic acid, fumaric acid and the like. Carboxylated nitrile rubbers generally contain from about 0.75 percent to 15 percent by weight chain linkages (repeat units) which are derived from unsaturated carboxylic acid monomers.
The carboxylic nitrile rubbers can be synthesized using any conventional polymerization technique. Emulsion polymerization of carboxylated nitrile elastomers is generally preferred and is used almost exclusively in industrial production. This type of a synthesis generally utilizes a charge composition comprising water, monomers, an initiator and an emulsifier (soap). Such polymerizations can be run over a very wide temperature range from about 0° C. to as high as 100° C. It is more preferred for these polymerizations to be run at a temperature from about 5° C. to 60° C.
The amount of carboxylic acid monomer (unsaturated carboxylic acid of the acrylic acid type) incorporated in a carboxylated nitrile rubber may be varied over a wide range. The monomer charge ratio between the carboxylic monomer and the comonomers employed in a polymerization may also be varied over a very wide range. Generally, the charge composition used in the synthesis of carboxylated nitrile rubbers will contain 60 percent to 75 percent by weight butadiene, 15 percent to 40 percent by weight of acrylonitrile and 1 percent to 15 percent by weight methacrylic acid, based upon the total monomer charge. A typical charge composition for a carboxylated nitrile rubber will contain 65 to 69 weight butadiene, 24 to 28 weight percent acrylonitrile and 5 to 9 weight percent methacrylic acid.
The emulsifiers used in the polymerization of such polymers may be charged at the outset of the polymerization or may be added incrementally or by proportioning as the reaction proceeds. Generally, anionic emulsifier systems provide good results; however, any of the general types of anionic, cationic or nonionic emulsifiers may be employed in the polymerization.
Among the anionic emulsifiers that can be employed in emulsion polymerizations are fatty acids and their alkali metal soaps such as caprylic acid, capric acid, pelargonic acid, lauric acid, undecylic acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid and the like; amine soaps of fatty acids such as those formed from ammonia, mono- and dialkyl amines, substituted hydrazines, guanidine and various low molecular weight diamines; chain-substituted derivatives of fatty acids such as those having alkyl substituents; naphthenic acids and their soaps and the like; sulfuric esters and their salts, such as the tallow alcohol sulfates, coconut alcohol sulfates, fatty alcohol sulfates, such as oleyl sulfate, sodium lauryl sulfate and the like; sterol sulfates; sulfates of alkylcyclohexanols, sulfation products of lower polymers of ethylene as C
10
to C
20
straight chain olefins, and other hydrocarbon mixtures, sulfuric esters of aliphatic and aromatic alcohols having intermediate linkages, such as ether, ester or amide groups such as alkylbenzyl (polyethyleneoxy) alcohols, the sodium salt or tridecyl ether sulfate; alkane sulfonates, esters and salts, such as alkylchlorosulfonates with the general formula RSO
2
Cl, wherein R is an alkyl group having from 1 to 20 carbon atoms, and alkylsulfonates with the general formula RSO
2
—OH, wherein R is an alkyl group having from 1 to 20 carbon atoms; sulfonates with intermediate linkages such as ester and ester-linked sulfonates such as those having the formula RCOOC
2
H
4
SO
3
H and ROOC—CH
2
—SO
3
H, wherein R is an alkyl group having from 1 to 20 carbon atoms such as dialkyl sulfosuccinates; ester salts with the general formula:
wherein R′ is an alkyl group having from 1 to 20 carbon atoms; alkaryl sulfonates in which the alkyl groups contain preferably from 10 to
Corvasce Filomeno Gennaro
Thielen Georges Marcel Victor
DeLong John D.
Short Patricia A.
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