Anti-tack bladder

Details Anti-tack bladder Anti-tack bladder

1999-02-02

2002-04-02

Knable, Geoffrey L. (Department: 1733)

Adhesive bonding and miscellaneous chemical manufacture

Surface bonding means and/or assembly means therefor

Tire body building type

C156S394100

Reexamination Certificate

active

06363989

ABSTRACT:

FIELD OF THE INVENTION
The invention relates primarily to an anti-tack bladder made with an anti-tack rubber for use with an apparatus for manufacturing pneumatic vehicle tires, more specifically with inflatable rubber bladders conventionally used to turn ply ends over a tire bead ring and against tire plies on a tire building mandrel. Methods for making and using an anti-tack bladder and an anti-tack rubber are provided.
BACKGROUND OF THE INVENTION
Tire building or assembly machines (TAMS) conventionally use rolling inflatable rubber bladders to turn up plies of rubber material that have been wrapped around a tire building mandrel, a type of rotating collapsible drum. The bladder is known as a turn-up bladder and serves to turn up the plies over a bead formed from wire cables embedded in a tough hard rubber. The rubber ply material is tacky by nature to allow the turned up plies to stick together to form the side wall of the tire. The turn-up bladders are conventionally made of various elastomeric materials such as vulcanized rubber, natural (cis-1,4-polyisoprene) and/or synthetic rubber (i.e., styrene-butadiene) or mixtures thereof. The turn-up bladders will often stick to the uncured or partially cured plies when they are rolled over the beads to form part of the tire as they are inflated, typically, with compressed air. This adhesion slows the turn-up process by impeding the retraction of the deflated turn-up bladder and also results in decreased turn-up bladder life due to erosion caused by such adhesion to the plies.
U.S. Pat. No. 4,381,331 (Johnson) discloses a solution to the above tacking problem by having a ply turn-up bladder with at least a portion of its outer surface comprising a fabric layer of spaced cords calendered, (i.e., rolling a rubber compound into the fabric on multi-roll calender machines) with a coating of unvulcanized, uncured rubbery polymer partially embedded in the rubbery polymer surface. The spaces between such cords are free of the polymer so the cords can project above this polymer surface. This arrangement allows the polymer-free cords to contact the tacky plies, thereby reducing its adhesion to the turn-up bladder. The disadvantage of this solution are the complex finishing steps associated with preparing this outer fabric layer, such as a separate heating step to additionally cure a separately applied coating, and abrading the surface of the cords to remove some of the cured polymer to expose them. Consequently the Johnson bladder is costly to make.
U.S. Pat. No. 5,213,823 (Hunt) discloses a turn-up bladder made with a high release outside layer bonded to a core sulfur-cured rubber base, wherein the outside layer is cured in a conventional manner. The high release layer is formed from a mixture or blend of polyvinyl chloride and acrylonitrile-butadiene rubber, with a plasticizer and conventional rubber compounding ingredients. One example of a polyvinyl chloride and acrylonitrile-butadiene rubber blend that has been used is “Paracil OZO” 50, manufactured by Uniroyal, Inc. of Middlebury, Conn., USA, further described in U.S. Pat. No. 3,993,607 (Florence).
Yet another solution to the ply end tacking problem is to apply a coating to the turn-up bladder itself, such as a spray coat disclosed in U.S. Pat. No. 4,359,350 (Comper). The described coating is an aqueous lubricant containing polydimethylsiloxane, a silane, a surfactant, and optionally, a metal salt of an organic acid.
U.S. Pat. No. 5,104,477 (Williams) discloses a method to apply a surface coating of controlled release characteristics to a turn-up bladder comprising the steps of applying a releasing composition, removing a vehicle to form an adhering film, and curing the film to form the exposed release coating. The composition of the release coating is disclosed as comprising a chlorosulfonated polymer, a reinforcing filler, a green tack agent, and inert volatile solvent/diluent viscosity reducing vehicles. HYPALON, chlorosulfonated polyethylene, manufactured by E.I. duPont de Nemours and Co., of Wilmington, Del. is disclosed as a suitable chlorosulfonated polymer. Typical reinforcing fillers are carbon black, silica, fumed silica, silica dioxide and various clays known in the art, which can be used to reinforce the elastomer compositions. The green (referring to uncured, unvulcanized rubber or elastomer, not color) tack agent is typically a resin such as alkaphenol/formaldyhyde, chlorinated paraffin resins, poly(beta) terpene resins, and other resins disclosed in U.S. Pat. No. 5,104,477. Chemical curing systems are also added to the releasing composition and include sulphur-based systems containing conventional amounts of nitrogen-containing accelerator and activators known in the art. Additionally, metallic oxides such as litharge, magnesia, and sulphur bearing organic compounds and epoxy resins can be used. Typical inert, viscosity-reducing solvent/diluent vehicles are composed of organic liquids having a normal boiling point between 20-200 deg. C. These solvent vehicles function to solublize or disperse the releasing composition to enable its application as a thin film on the turn-up bladder.
One problem to be solved is that of designing an anti-tack bladder avoiding the need to coat an anti-tack material onto the surface of an already formed bladder, which would comprise an additional and more complex preparation step in manufacturing the bladder. In particular, the problem to be solved is that of departing from the use of a thin film composite to cover the bladder surface: as a matter of fact, the film(s) must be uniform and able to withstand fractures, while at the same time providing sufficient flexibility, with good adhesion to the bladder and with the ability to properly control adhesion to the ply. The production of such a film is problematic and furthermore, the curing of a film of this kind on a bladder surface is a very complex step.
Yet another problem to be solved is that of avoiding the use of the additional hazardous materials and solvents which are involved in forming a vehicle to apply the coating; such materials can in fact, pose increased environmental processing costs, as well as storage and handling safety risks.
What is desired, therefore, is an inflatable bladder with reduced adhesion to a ply, improved flexibility, better fracture resistance, all without the need to form such a material with an involved multi-step process requiring abrading, applying a separate coating material (such as a liquid, paste, or gel-like material), removal of a solvent vehicle, or depositing a final uniform coating to form the bladder's anti-tack properties.
What is also desired, therefore, is an inflatable bladder with suitable curing and anti-tack properties for use with an apparatus for manufacturing pneumatic tires. Suitable anti-tack properties in tire manufacturing allow for quick, unimpeded release of green, cured and partially cured rubber from elastomeric structures such as flexible bladders, bags, diaphragms, sleeves, and the like. Suitable curing properties of rubber used in a bladder include high durability, good cut resistance and rebound suitable for repeated inflation and deflation cycles characteristic in pneumatic tire manufacturing. The inflatable bladder should exhibit suitable curing and anti-tack properties without any visible cracking, peeling or erosion of the anti-tack bladder body under operating conditions and parameters associated with pneumatic tire manufacturing, such as capacity, bladder life, operating pressure and/or cycle time. When a rubber material is provided with such anti-tack and curing properties the bladder can be directly manufactured from, this allows a bladder to be formed without the need of additional processing steps to impart such anti-tack properties thereby simplifying production while reducing the potential for tire manufacturing down time.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the invention to provide an inflatable bladder with suitable anti-tack properties for use in pneumatic tire manufacturing which is

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