Fluid barrier membranes

Details Fluid barrier membranes Fluid barrier membranes

1998-12-14

2002-05-21

Dye, Rena L. (Department: 1772)

Stock material or miscellaneous articles

Hollow or container type article

Nonself-supporting tubular film or bag

C428S035500, C428S035700, C428S036800, C428S423100, C005S655300, C036S029000, C036S03500R

Reexamination Certificate

active

06391405

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to barrier membranes suitable for containing fluids and to inflated bladders made of such membranes.
BACKGROUND OF THE INVENTION
Barrier membranes and inflatable bladders formed from such membranes have been used in a variety of products such as vehicle tires, balls, accumulators used on heavy machinery, and in footwear, especially shoes, as cushioning devices. It is often desirable to use polymeric materials that are thermoplastic because thermoplastic materials may be reclaimed and reformed into new articles, thus reducing waste during manufacturing operations and promoting recycling after the life of an article. While thermoplastic barrier films may be flexed to a certain extent due to their thinness, in the past thermoplastic barrier films have generally not had sufficient elasticity for many applications. In order to overcome this shortcoming, the barrier materials were blended or layered with elastic materials. Elastic materials, or elastomers, are able to substantially recover their original shape and size after removal of a deforming force, even when the part has undergone significant deformation. Elastomeric properties are important in many applications, including inflatable bladders for footwear and hydraulic accumulators.
Footwear, and in particular shoes, usually include two major components, a shoe upper and a sole. The general purpose of the shoe upper is to snuggly and comfortably enclose the foot. Ideally, the shoe upper should be made from an attractive, highly durable, comfortable materials or combination of materials. The sole, constructed from a durable material, is designed to provide traction and to protect the foot during use. The sole also typically serves the important function of providing enhanced cushioning and shock absorption during athletic activities to protect the feet, ankles, and legs of the wearer from the considerable forces generated. The force of impact generated during running activities can amount to two or three times the body weight of the wearer, while other athletic activities such as playing basketball may generate forces of between six and ten times the body weight of the wearer. Many shoes, particularly athletic shoes, now include some type of resilient, shock-absorbent material or components to cushion the foot and body during strenuous athletic activity. These resilient, shock-absorbent materials or components are commonly referred to in the shoe manufacturing industry as the midsole. Such resilient, shock-absorbent materials or components can also be applied to the insole portion of the shoe, which is generally defined as that portion of the shoe upper directly underlying the plantar surface of the foot.
Gas-filled bladders may be used for midsoles or inserts within the soles of shoes. The gas-filled bladders are generally inflated to significant pressures in order to cushion against the forces generated on the foot during strenuous athletic activities. Such bladders typically fall into two broad categories, those that are “permanently” inflated, such as disclosed in Rudy, U.S. Pat. Nos. 4,183,156 and 4,219,945, and those using a pump and valve system, such as those disclosed in Huang, U.S. Pat. No. 4,722,131, each of which is incorporated herein by reference.
Athletic shoes of the type disclosed in U.S. Pat. No. 4,183,156 having “permanently” inflated bladders have been sold under the trademark “Air-Sole” and other trademarks by Nike, Inc. of Beaverton, Oregon. Permanently inflated bladders of such shoes are constructed using an elastomeric thermoplastic material that is inflated with a large molecule gas that has a low solubility coefficient, referred to in the industry as a “super gas.” Cases such as SF
6
, CF
4
, C
2
F
6
, C
3
F
8
, and so on have been used in this way as super gases. Super gases are costly, however, and so it is desirable to provide permanent inflation with less expensive gasses like air or nitrogen. By way of example, U.S. Pat. No. 4,340,626 entitled “Diffusion Pumping Apparatus Self-inflating Device” which issued Jul. 20, 1982, to Rudy, which is expressly incorporated herein by reference, discloses selectively permeable sheets of film that are formed into a bladder and inflated with a gas or mixture of gases to a prescribed pressure. The gas or gases utilized ideally have a relatively low diffusion rate through the selectively permeable bladder to the exterior environment while gases contained in the atmosphere, such as nitrogen, oxygen, and argon, have a relatively high diffusion rate are able to penetrate the bladder. This produces an increase in the total pressure within the bladder, by the addition of the partial pressures of the nitrogen, oxygen and argon from the atmosphere to the partial pressures of the gas or gases with which the bladder is initially inflated. This concept of a relative one-way addition of gases to enhance the total pressure of the bladder is now known as “diffusion pumping.”
Many of the earlier midsole bladders used in the footwear manufacturing industry prior to and shortly after the introduction of the Air-Sole™ athletic shoes consisted of a single layer gas barrier type film made from polyvinylidene chloride-based materials such as Saran® (which is a registered trademark of the Dow Chemical Co.) and which by their nature are rigid plastics, having relatively poor flex fatigue, heat sealability and elasticity. Composite films of two gas barrier materials have also been used. Momose, U.S. Pat. No. 5,122,322, incorporated herein by reference, describes a film of a first thermoplastic resin having a plurality of continuous tapes of a second thermoplastic resin that lie parallel to the plane of the film. The first thermoplastic resin is selected from polyolefin, polystyrene, polyacrylonitrile, polyester, polycarbonate, or polyvinyl chloride resins and modified resins. The second resin may be a polyamide, saponified ethylene vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyvinylidene chloride, or polyacrylonitrile copolymer. The film is formed by extruding the first resin from a first extruder and the second resin from a second extruder, introducing both extrudate streams simultaneously into a static mixer in which the layers (tapes) are formed. The film may have one or two outer films laminated to it. While these films are disclosed to have an oxygen permeation rate of 0.12 to 900 cc/m
2
-day-atm at 20° C., making them generally suitable for forming cushioning material for packaging and shipping material, the films are not resilient or flexible enough for cushioning bladders for footwear.
Known bladder films that are composites or laminates can also present a wide variety of problems in shoe bladders, such as layer separation, peeling, gas diffusion or capillary action at weld interfaces, low elongation leading to wrinkling of the inflated product, cloudy appearing finished bladders, reduced puncture resistance and tear strength, resistance to formation via blow-molding and/or heat-sealing and RF welding, high cost processing, and difficulty with foam encapsulation and adhesive bonding, among others. Some previously known multi-layer bladders used tie-layers or adhesives in preparing laminates in order to achieve interlayer bond strength high enough to avoid the problems mentioned. The use of such tie layers or adhesives, however, generally prevents regrinding and recycling of any waste materials created during product formation back into an usable product, making manufacturing more expensive and producing more waste. Use of adhesive also increases the cost and complexity of preparing laminates. These and other perceived short comings of the prior art are described in more extensive detail in U.S. Pat. Nos. 4,340,626; 4,936,029 and 5,042,176, each of which are hereby expressly incorporated by reference.
Besides combinations of two gas barrier layers, composites may be formed from layers of materials having very different properties. Composites of different materials are particularly useful for footwear bladders because

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