HK1034490B - Barrier membranes including a barrier layer employing polyester polyols - Google Patents

Description

Barrier membrane comprising a barrier layer using polyester polyol

The present application is a divisional application entitled "barrier membrane comprising a barrier layer using polyester polyol" filed 5/29/1996 under application No. 96111033.3.

The present invention relates to a barrier membrane, and more particularly to a barrier membrane that is used in certain implementations to selectively control the diffusion of gases through the membrane. In addition, in some implementations, the membrane not only selectively controls the diffusion of gases through the membrane, but may also be used to provide controlled diffusion of gases normally contained in the atmosphere.

For a further understanding of the scope of the present invention, reference may be made to U.S. patent application Ser. No.08/299,287 entitled "cushioning device with improved elastic barrier membrane" filed on 8/31/1994 U.S. patent application Ser. No.08/299,286 entitled "laminated elastically flexible barrier membrane" filed on 8/31/1994; and U.S. patent application Ser. No. 08/475276, commonly owned and assigned concurrently with the present application entitled "Barrier Membrane having a Barrier layer Using an aliphatic thermoplastic polyurethane". Each of the above patent applications is expressly incorporated herein by reference.

Very useful barrier membranes for the preservation of fluids, including liquids and/or gases, in a controlled manner have been used for many years in a wide variety of different articles ranging from very useful bladders for inflatable objects, including, for example, vehicle tires and sporting products, to accumulators for heavy machinery and cushioning devices very useful in footwear articles. Regardless of the intended use, the desired barrier membrane must generally be elastic, resistant to environmental degradation, and have excellent control over gas transfer. Often, however, materials exhibiting acceptable elasticity tend to have unacceptable low levels of gas permeation resistance. Conversely, materials that exhibit acceptable gas permeation resistance tend to have unacceptable poor elasticity.

In order to allow for both elasticity and gas permeation resistance, an elastic diaphragm suitable for use in a gas-water accumulator is described in U.S. patent No 5036110 to Moreaux, issued 6/30 1991. According to Moreaux' 110, a separator is disclosed that includes a film formed from a graft polymer that is the reaction product of an aromatic thermoplastic polyurethane and a copolymer of ethylene and vinyl alcohol, the film being positioned between two layers of thermoplastic polyurethane to form a laminate. While Moreaux' 110 attempted to raise concerns in the area relating to elasticity and resistance to gas permeation, a significant disadvantage of Moreaux was that the films could not be processed using conventional sheet extrusion techniques. Thus, the present invention is directed to barrier membranes having elasticity, good resistance to gas transmission, and in some implementations can be processed into laminates using conventional sheet extrusion techniques having high resistance to delamination.

However, it will be appreciated by those skilled in the art after considering the following specification and claims that the barrier films of the present invention have a wide range of applications including, but not limited to, bladders for inflatable objects such as soccer balls, basketball balls, soccer balls and inner tubes; films for food wrapping; and the production of fuel lines and fuel storage tanks, other applications may be enumerated. For example, a highly desirable application for the barrier diaphragm of the present invention includes for forming an accumulator that operates in a high pressure environment, such as a hydraulic accumulator discussed in detail below.

For convenience, but without limitation, the barrier membrane of the present invention is described below primarily in terms of either an accumulator or another desired application, namely cushioning devices for footwear. In order to fully discuss the utility of the barrier membrane in relation to the cushioning device of an article of footwear, it is believed necessary to describe the article of footwear in general.

Footwear articles, or more precisely, shoes, generally comprise two main parts, namely an upper and a sole. The main function of the upper is to warm and comfortably wrap the foot. Ideally, the upper should be made of an attractive, highly durable but comfortable material or composite. The sole, which may also be made of one or more durable materials, is designed primarily to pull on the ground during use, protect the user's foot and body, and to conform to the design of the shoe. The large forces generated during athletic activities require the sole of the athletic shoe to provide greater protection and shock absorption for the foot, ankle, and leg of the wearer. For example, the impact generated during running can generate as much as 2-3 times the weight of the human body. While other sports such as basketball are known to produce forces as much as about 6-10 times the weight of the human body. Thus, many shoes, and particularly many athletic shoes, now employ some type of resilience, impact absorbing material or impact absorbing assembly to provide cushioning during strenuous athletic activities by the user. Such resilient, impact-absorbing materials or components are now beginning to be used as midsole in the footwear industry.

Efforts have therefore been made to design a midsole that achieves an effective impact response including adequate shock absorption and resilience in proper consideration for the footwear industry. Such resilient, impact-attracting materials or components may also be used in the footbed portion, which is generally defined as the portion of the upper surface of the shoe directly beneath the plantar surface of the foot.

A particular focus of the footwear industry is the attempt to design midsole or sandwich structures that are suitable for containing fluids, either in a liquid state or a gaseous state, or both. An example of an inflatable structure for use in a footwear sole is shown in U.S. patent No 900867 to Miller, entitled "footwear article cushioning," entitled "article of footwear," 10/13 1908; no 1069001 by Guy, entitled "cushioning sole and heel for footwear", entitled "shoe," entitled "cushioning sole and heel for footwear", 29/7/1913; spinney No 1304915 entitled "inflatable insole" entitled "at 5/27/1919; no 1514468 by Schopf entitled "Arch buffer" entitled at 11/4/1924; no2080469, entitled "inflatable foot support," by Gilbert, granted 5 months and 18 days in 1937; towne's No 2645865 entitled "cushioning insole for footwear" entitled Town shoe, 21/7/1953; no2677906 by Reed, entitled "cushioning insole for footwear and method of making" granted 5/11/1954; rudy's No 4183156 entitled "insole construction for footwear article", granted on 15.1.1980; no 4219945 entitled "footwear article" by Rudy, entitled "article of footwear" at 9/2/1980; huang's Nos 4722131 entitled "sole air cushion" granted on 2.2.1988; and Horovitz' No 4864738 entitled "sole construction for footwear article" entitled "footwear article on 9/12 1989. Those skilled in the art will recognize that such inflatable structures are commonly referred to in the footwear industry as "bladders," which generally fall into two broad categories, namely (1) "permanent" inflation systems, such as those disclosed in U.S. patent nos. 4183156 and 4219945, and (2) pump and valve regulation systems, such as those illustrated in U.S. patent No. 4722131. As another example, athletic footwear of the type disclosed in U.S. Pat. No. 4182156, including "permanent" inflatable bladders, is successfully marketed under the trademark "Air Sole" and other trademarks by Nick corporation, Reaverton, Oregon. To date, millions of pairs of such athletic shoes have been sold throughout the united states and the world.

Permanent inflatable bladders are typically made by using an elastomeric thermoplastic material and inflating it with a macromolecular low solubility coefficient gas known in the industry as "super gas" such as SF 6. As an example, U.S. patent No.4340626 to Rudy, entitled "diffusion pumping device self-inflating apparatus", issued on 20.7.1982, is expressly incorporated herein by reference. It discloses a pair of elastic selectively permeable sheets of membrane which form a bladder into which a gas or mixture of gases is then introduced up to a predetermined pressure preferably above atmospheric pressure. The gases utilized desirably have a low diffusivity and diffuse through the selected permeable bladder to the external environment, while gases contained in the atmosphere having a high diffusivity, such as nitrogen, oxygen and argon, are able to permeate into the bladder. This increases the total pressure within the bladder by increasing the partial pressure of nitrogen, oxygen and argon from the atmosphere to the partial pressure of the retained gas initially injected into the bladder. This unidirectional addition of gas to expand the overall pressure of the bladder is now referred to as "diffusion pumping".

In diffusion pumping systems, there is a period of time before a steady state of internal pressure is reached, which is determined by the bladder material used and the containment gas selected. For example, oxygen tends to diffuse into the bladder very quickly, with the effect of an increase in internal gas pressure of about 2.5 psi (17.225 kpa, 6.89 kpa to 1 psi, the same below). In contrast, over a period of many weeks, the gradual diffusion of nitrogen into the bladder results in an increase in pressure to about 12 psig. The gradual increase in bladder pressure generally causes an increase in the tension in the bladder walls, resulting in an increase in volume due to stretching. This effect is commonly referred to in the industry as "tensile relaxation" or "creep". Thus, it is extremely important to select the materials used for the bladder and to select the containment air mixture that is to be first filled into the bladder so as to obtain a soft outer layer that is substantially permanently inflated at the desired internal air pressure and maintains the desired internal air pressure for the desired period of time.

Just promoting Airsole^TMFor this set of systems to be used inside the footwear industry, both before and shortly after the sport footwear, many midsole bladders comprise only a single layer of gas-barrier type membrane made of polyvinylidene chloride based material, such as Saran^(Dow chemistryA registered trademark of limited corporation) is hard plastic in nature, and has poor flex fatigue, heat sealability and elasticity. Moreover, bladder films made by, for example, lamination and coating techniques, which include one or more layers of barrier material in combination with a resilient bladder material (e.g., a different thermoplastic) potentially present a number of problems to be solved. These difficulties with composite structures include delamination, peeling, gas diffusion or capillary action at the weld interface, low elongation resulting in wrinkling of the inflated article, hazy finish bladder appearance, low puncture and tear strength, resistance to forming by blow molding and/or heat sealing and R-F welding, high production costs, and difficulties with foam encapsulation and bonding, among others.

Yet another problem with previously known bladders is the use of adhesive layers or adhesives in preparing the laminate. The use of such adhesive layers or adhesives generally prevents any scrap material from being re-shredded and recycled during the recycling of the article into useful articles, thus also resulting in increased manufacturing costs and relative waste. These and other drawbacks of the prior art are disclosed in U.S. patents NOS 4340626; 4936029 and 5042176. All of which are expressly incorporated herein by reference.

With some articles, e.g. Air Sole^TMWith the widespread commercial success of footwear, consumers have enjoyed articles that have a longer service life, greater impact absorption and resilience, reasonable cost, and inflation stability, without the aid of pumps and valves. Thus, significant market acceptance and success has been achieved through the use of long-term useable inflatable bladders, and advances and developments in the art relating to these articles are highly desirable. It is therefore an object to provide a resilient, "permanently" inflated, gas-filled footwear cushioning assembly that achieves, and desirably exceeds, the Air Sole, for example, offered by Nack corporation^TMThe article of athletic footwear has characteristics.

One key aspect of potential advancement comes from the recognition that macromolecules, low solubility coefficients "super air", not used in the ' 156 ', 945 and ' 738 patents "Can be replaced by a less expensive and potentially more environmentally friendly gas. For example, U.S. Pat. nos. 4936029 and 5,042,176 propose in particular a method for producing an elastic bladder membrane which substantially maintains a permanent inflation by using nitrogen as the trapped air. Further description is provided in U.S. patent No.4906502, also incorporated herein by reference. Many of the significant problems set forth in the '029 and' 176 patents have been addressed by the addition of crystalline materials having a mechanical barrier to elastic materials such as fabrics, filaments, scrims and webs. Using the technique described in the' 502 patent under the trademark TensiiLAir by Nack^TMFootwear products are also sold with great commercial success. The bladder used therein generally comprises a thermoplastic polyurethane laminated to a nylon fabric in which the core fabric is a three-dimensional two-bar Raschel knit, SF₆Is taken into the soft shell as sealed air.

By way of example, following the procedure specified in ASTM D-1434-82, an acceptable method for measuring the relative permeability, permeability and diffusion of different membrane materials is presented. According to ASTM D-1434-82, the permeation, permeability and diffusion were calculated as follows:

penetration of

Permeability rate of penetration

Diffusion

By using the formulas listed above, gas transmissibility in combination with pressure differential and film thickness can be used to define the movement of the gas under specific conditions. In this regard, in athletic shoe components that seek to meet the stringent requirements for fatigue resistance due to severe and repeated impacts, the preferred Gas Transmission Rate (GTR) value for the bladder is about 10.0 or less than 10, and most preferably a GTR value of 2.0 or less, with the average thickness of the bladder being about 508 microns.

In addition to the foregoing, the '029 and' 176 patents also discuss one of the aforementioned problems encountered with previous, co-laminated blends that attempted to use plastic materials for the oxygen barrier layer. In this regard, a major concern is the lack of fatigue resistance of the barrier layer. Polyvinylidene chloride (e.g., Saran) as described in the' 176 patent^) Good co-laminates with polyurethane elastomers require an intermediate adhesive. In this configuration, relatively complex and expensive process controls such as strict time-temperature relationships and the use of hot platens and pressure are required in combination with cold pressing under pressure to consolidate the materials together. In addition, the layers are bonded using a binder or a crystalline component is added to the elastic film at a sufficiently high content so that the gas transmission rate reaches or falls below 10 and the elasticity of the film is reduced.

Cushioning devices specifically eliminating the adhesive layer are known to be particularly prone to separation or delamination along seams and edges. As such, the development of cushioning devices that do not use an adhesive layer, thereby desirably reducing or eliminating the occurrence of delamination, is the latest focus of the industry. In this regard, the cushioning devices disclosed in co-pending U.S. patent applications NO 08/299286 and 08/299287 eliminate the need for an adhesive layer by providing a diaphragm comprising a first layer of thermoplastic polyurethane and a second layer comprising a copolymer of ethylene and vinyl alcohol where hydrogen bonding occurs at a segment between the first and second layers of the diaphragm. While the cushioning device disclosed in U.S. patent application No.08/299287 and the laminated elastomeric barrier membrane disclosed in U.S. patent application No. 08/299286 are believed to represent a significant advance in the art, still further advances have been made in accordance with the teachings of the present invention.

It is therefore a primary object of the present invention to provide a barrier membrane having improved elasticity, durability and resistance to the undesirable transmission of fluids through the membrane.

It is a further object of the present invention to provide a barrier membrane that is substantially permanently filled with nitrogen or other environmentally suitable gas or gas mixture, where the barrier membrane has a gas transmission rate of 10 or less than 10 at an average thickness of 508 microns.

It is a further object of the present invention to provide a barrier membrane and in particular a barrier membrane for use as a cushioning device having improved permeability and density.

It is another object of the present invention to provide a barrier membrane that can be formed into a laminate such as a cushion or accumulator and which is resistant to delamination without the need for an adhesive layer between the barrier layer and the elastic layer.

It is a further object of the invention to provide a barrier layer that is reworkable.

It is another object of the present invention to provide a barrier membrane that is formed using various techniques including, but not limited to, processes such as blow molding, tube molding, sheet extrusion, vacuum forming, heat sealing and RF welding.

It is a further object of the present invention to provide a barrier membrane that prevents gas from escaping along the interfaces of the layers of a laminated embodiment, particularly along the seams through capillary action.

It is a further object of the present invention to provide a barrier membrane that facilitates the implementation of common footwear manufacturing processes, such as encapsulation within a formable material.

The foregoing objects provide guidance for possible applications of the barrier membranes of the present invention, and one of ordinary skill in the art will recognize that the listed objects are not intended to be exhaustive or limiting.

To achieve the above objects, the present invention provides a barrier membrane having (1) a suitable degree of elasticity (or rigidity); (2) a suitable degree of resistance to moisture-induced aging and (3) acceptable resistance to penetration by liquids, which liquids are determined to be in the form of a gas, a liquid, or both, depending primarily on the intended use of the article; and (4) high peel resistance when used in multilayer structures. Regardless of the barrier membrane embodiment, each barrier membrane in accordance with the teachings of the present invention includes a barrier layer that at least partially includes a blend of at least one polyurethane formed from a polyester polyol made from a combination of linear dicarboxylic acids and diols, where the total number of carbon atoms of the dicarboxylic acid and diol compound is 8 or less, and at least one copolymer of ethylene and vinyl alcohol.

The polyester polyol polyurethanes used, if not commercially available, are generally formed from the reaction product of (a) one or more linear dicarboxylic acids and one or more diols; (b) at least one difunctional extender (c) at least one isocyanate and/or diisocyanate; and (d) optionally one or more processing aids.

The designation "linear dicarboxylic acid" as used herein preferably refers to a carboxylic acid having no more than 6 carbon atoms when reacted with a diol, where the total number of atoms in the reaction product of the dicarboxylic acid and the diol is no more than 8.

The term "diol" as used herein is intended to refer preferentially to polyester diols having not more than 6 carbon atoms when reacted with linear dicarboxylic acids. The reaction product of the dicarboxylic acid and the diol here has not more than 8 carbon atoms.

The term "polyester diol" as used herein is intended to refer preferentially to polyester diols having a molecular weight in the range of about 300 to about 4000, preferably from about 400 to about 2000, and most preferably between about 500 to about 1500.

The term "thermoplastic" as used herein preferably refers to a material that is capable of being softened by heat and hardened by cooling within a characteristic temperature range and that, in the softened state, can be formed into a variety of articles using a variety of techniques.

The designation "difunctional extender" is intended to be understood by those of ordinary skill in the art to mean only conventional and includes diols, diamines, aminoalcohols, etc., which generally have a molecular weight in the range of from about 60 to about 300.

Ideally, the elastomeric barrier materials used in accordance with the teachings of the present invention should be capable of retaining trapped air for extended periods of time. In a preferred embodiment, for example, the barrier membrane should not lose more than 20% of the initial inflation pressure over a two year period. In other words, an article initially inflated to a steady state pressure of 20 to 22 psi should maintain a pressure in the range of about 16 to 18 psi.

In addition, the barrier membranes used should be resilient, relatively compliant, highly resistant to fatigue and capable of being welded to form effective seams, typically by RF welding or heat sealing. The barrier material should also be able to withstand cyclic loading without breakage, particularly when a barrier membrane having a thickness of 5 mils to about 50 mils is used. Another important characteristic of barrier membranes is that they can be manufactured in different shapes using mass production techniques. Techniques known in the art are extrusion, blow molding, injection molding, vacuum molding, rotational molding, die casting and pressure forming. The barrier membranes of the present invention should preferably be formed by extrusion techniques. Such as by tube extrusion or sheet extrusion, including extrusion blow molding, particularly at sufficiently high temperatures to achieve suitable "bonding" or "chemical" bonding as will be described in detail below. These aforementioned production processes should produce articles with variable cross-sectional dimensions.

As previously mentioned, a significant feature of the barrier membrane of the present invention is that in embodiments that form articles intended to be inflated (e.g., cushioning devices for footwear), it has the ability to control the diffusion of free gases through the membrane and to maintain trapped gases within the membrane. According to the invention, not only supergases but also nitrogen can be used as containment air due to the properties of the barrier layer. Providing a barrier membrane with a blanket gas of nitrogen has a significant practical effect on protecting the earth's ozone layer and preventing earth warming.

In the present invention, if the barrier membrane forms an article such as a cushioning device, the membrane may be first inflated with nitrogen or a mixture of nitrogen and one or more super gases or inflated with air. If nitrogen or a mixture of nitrogen and one or more super gases is injected, the increase in pressure increase results from the faster diffusion of oxygen into the membrane, since the trapped gas is substantially retained within the membrane. This is effectively equivalent to an increase in pressure of no more than 2.5 psi over the initial inflation pressure and produces a modest increase in diaphragm volume of between 1 and 5%, the increase being dependent on the initial pressure. However, if air is used as the seal gas, oxygen tends to diffuse out of the membrane, while nitrogen remains as the seal gas. In this case, oxygen diffusion out of the membrane and entrapment of trapped air results in a decrease in steady state pressure increase based on the initial inflation pressure.

Another feature of the present invention is to enhance the bond created between adjacent layers, thus eliminating the adhesive layer. This is generally accomplished by laminating the first and second layers together using conventional techniques, such that the laminated barrier separator of the present invention is characterized by significant hydrogen bonding between the first layer formed from a blend of at least one aliphatic polyester polyol polyurethane and a copolymer of ethylene and vinyl alcohol and the second layer of thermoplastic polyurethane. In addition to creating hydrogen bonding, particularly when a relatively small amount of ethylene and vinyl alcohol copolymer is used for the first layer and the thermoplastic polyurethane of the first and second layers have the same functionality, there is generally a certain number of covalent bonds between the first and second layers in theory.

Another feature of the present invention is that a single-layer barrier separator using a blend of at least one polyester polyol polyurethane and a copolymer of ethylene and vinyl alcohol has excellent gas transmission rate.

The invention also provides many other more distinct advantages in view of its many forms and embodiments. Furthermore, the embodiments in the drawings are only illustrations of embodiments utilizing the barrier membranes of the present invention, it being understood that the barrier membranes have the potential for broader applications and that many examples will be described in detail below for the purpose of illustrating the general principles of the present invention and should not be considered as a descriptive matter in a limiting sense.

FIG. 1 is a side view of an athletic shoe according to the present invention with a portion of the midsole cut away to expose a cross-section;

FIG. 2 is a bottom view of the bottom surface of the athletic shoe of FIG. 1, with another cross-section partially cut away;

FIG. 3 is a cross-sectional view taken along line 13-3 of FIG. 13;

FIG. 4 is a partial side perspective view of one embodiment of a tubular two-layer cushioning device according to the present invention;

FIG. 5 is a cross-sectional view taken along line 4-4 of FIG. 4;

FIG. 6 is a partial side perspective view of a second embodiment of a tubular triple layer cushioning device according to the present invention;

FIG. 7 is a cross-sectional view taken along line 6-6 of FIG. 6;

FIG. 8 is a perspective view of an alternative septum embodiment according to the present invention

FIG. 9 is a side view of the diaphragm of FIG. 8;

FIG. 10 is a perspective view of an alternative membrane embodiment according to the present invention;

FIG. 11 is a side view of an athletic shoe having an alternative membrane embodiment in accordance with the present invention;

FIG. 12 is a perspective view of the diaphragm of FIG. 11;

FIG. 13 is a top view of the diaphragm of FIGS. 11 and 12;

FIG. 14 is a side view of an athletic shoe having another alternative membrane embodiment in accordance with the present invention;

FIG. 15 is a perspective view of the septum of FIG. 14;

FIG. 16 is a top view of the diaphragm of FIGS. 14 and 15;

figure 17 is a perspective view of an alternative septum embodiment in accordance with the teachings of the present invention;

FIG. 18 is a side view of the septum of FIG. 17;

FIG. 19 is a perspective view of an article formed from a laminated separator in accordance with the teachings of the present invention;

FIG. 20 is a perspective view of yet another article formed from a laminated separator in accordance with the teachings of the present invention;

FIG. 21 is a side view of a sheet co-extrusion apparatus;

FIG. 22 is a cross-sectional view of a plenum portion of the sheet coextrusion apparatus of FIG. 21; and is

FIG. 23 is a side view and a tube coextrusion apparatus.

Referring to fig. 1-5, an athletic shoe is shown that includes a sole structure and a cushioning device, which are examples of barrier membranes that may be used in accordance with the teachings of the present invention. Footwear 10 includes an upper 12 connected to a sole 14. Upper 12 is formed from a variety of conventional materials including, but not limited to, materials such as leather, vinyl, nylon, and other conventional textile fiber materials. In general, the upper 12 is provided with a reinforcement layer located around the toe portion 16, the lacing holes 18, the toe portion 20, and along the heel region 22. As with most athletic shoes, the sole 14 extends generally from the toe region 16, through the arch region 24, and back to the heel region 22, over the entire length of the shoe 10.

Sole structure 14 may include one or more selectively permeable barrier membranes 28, preferably disposed in a medial layer of the sole structure in an H-shape, in accordance with the present invention. According to an embodiment, the barrier membrane 28 of the present invention is formed as a tube that may have a different geometry, such as a plurality of spaced apart arrangements, parallel to one another in the heel region 22 of the midsole 26, as shown in FIGS. 1-5. The tubing is sealed to contain the injected containment air. In particular, each barrier membrane 28 is formed to include a barrier layer that allows diffusion of free gases therethrough, but resists or prevents diffusion of trapped air. These predetermined diffusion characteristics of the membrane 28 are provided by an inner barrier layer 30 located along the inner surface of a thermoplastic outer layer 32. These two layers of the membrane are best seen in figures 4 and 5. As previously mentioned, barrier membranes 28 of the present invention may be formed in different profiles or shapesAnd (4) forming. For example, an alternative membrane 28B may be formed in the shape of a heel cushion as shown in fig. 8 and 9. The sports shoe with heel cushion shown in figures 8 and 9 has been sold under the trademark Air health walker Plus by nike corporation of berlington (Beaverton), oregon^TMAre used commercially and sold. The heel cushion profile of fig. 8 and 9 is recorded in U.S. design patent application NO 007934, filed on 20/4/1933. Similarly, a heel cushion having substantially the same shape as septum embodiment 28C shown in FIG. 10 has been manufactured by Nack corporation under the trademark Airstructure II^TMUsed in sports shoes and sold. The heel cushion profile of fig. 10 has been recorded in U.S. design patent NO 343504 issued on 25/1 of 1994. By way of further example, an alternative diaphragm 28D as shown in FIGS. 11-13 is also owned by Nack and sold under the trademark Air Max^2TMAnd Air Max²CB^TMFor use in athletic shoes and for sale, the membranes may also be formed in accordance with the teachings of the present invention. The diaphragm profile is also recorded in U.S. design patent NO 349804 issued on 8/23 1994 and U.S. design patent NO 350016 issued on 8/30 1994. While another alternative diaphragm 28E is shown in fig. 14-16. Diaphragm 28E is manufactured by Nack corporation under the trade designation AirMax^TMAre commonly used in athletic shoes and sold. This membrane profile is described in U.S. design patent application NO 897966 filed on 12.6.1992. Still other diaphragm profiles designated by reference numeral 28F are shown in figures 17 and 18. It should be understood in this regard that the barrier membrane profile of the present invention (whether tubular, elongated pad-shaped, or other similar shape) may be wholly or partially encapsulated within the midsole or outer layer of the sole of an article of footwear.

Referring again to fig. 1-5, a barrier diaphragm 28 in accordance with the teachings of the present invention is provided in the form of a cushioning device, and as illustrated, the diaphragm 28 has a composite structure including an outer layer 32 of a pliable, resilient material capable of resisting expansion of the diaphragm beyond a predetermined maximum volume when subjected to gas pressure, and an inner layer 30 of a barrier material that facilitates controlled diffusion pumping or self pressurization.

Outer layer 32 is preferably formed of a material or combination of materials that provide strong heat sealability, flexural fatigue resistance, suitable modulus of elasticity, tensile and tear strength, and abrasion resistance. Thermoplastic elastomers of the polyurethane type, here thermoplastic polyurethanes or simply TPUs, are found in the prior art materials having these properties as the best materials, because of their good processability.

Of the large amount of thermoplastic polyurethane used to form outer layer 32, polyurethane such as PELLETHANE^TM2355-85ATP and 2355-95AE (trade mark of Dow chemical Co., Midland, Michigan), ELASTOLLAN^(registered trademark of BASF Corp.) and ESTANE^(registered trademark of b.f. goodrich corporation). All of the above products, whether ester-based or ether-based, have proven to be quite effective. Other polyester, polyether, polycaprolactone, polypropylene oxide and polycarbonate thermoplastic polyurethanes may be used. Typically, the thermoplastic polyurethane used to form outer layer 32 is aromatic in nature.

Inner layer 30 is the primary barrier component primarily responsible for controlling air permeation and is made from a blend or combination of one or more thermoplastic polyurethanes made from polyester polyols and one or more copolymers of ethylene and vinyl alcohol. The polyester polyol-based thermoplastic polyurethanes used in the inner barrier layer, if not commercially available, are generally prepared from the reaction product of at least one of the following: (a) a polyester polyol; (b) a difunctional extender, (c) an isocyanate and/or a diisocyanate; and (d) optionally a processing aid. As previously mentioned, desirably, the polyester polyol formed is the reaction product of a linear dicarboxylic acid and a diol, where the total number of carbon atoms of the reaction product of the dicarboxylic acid and the diol is less than or equal to eight. In a preferred embodiment, the polyester polyols used in forming the barrier layer of the laminated membrane are aliphatic in nature.

Among the linear dicarboxylic acids which are considered to be very useful in forming the polyester polyol polyurethanes of the present invention, for example, adipic acid, glutaric acid, succinic acid, malonic acid and oxalic acid are particularly useful.

Of the diols which are considered to be very useful in forming the polyester polyol polyurethanes according to the invention, such as 1, 2-ethanediol, propanediol, butanediol, pentanediol and hexanediol are considered to be particularly useful.

In a preferred embodiment, the polyester polyol-based thermoplastic polyurethane used in forming the barrier layer using either single layer or multilayer lamination in accordance with the teachings of the present invention comprises ethylene adipate. In this regard, certain commercially available ethylene glycol adipates such as FOMREZ available from Witco Chemical^22-112 and 22-225 are considered useful.

The difunctional extenders useful in accordance with the principles of the present invention are generally selected from a group of extenders including 1, 2-ethanediol, 1, 3-propanediol, 1, 2-propanediol, 1, 4-butanediol, 1, 2-hexanediol, neopentyl glycol, and the like, as well as bis (2-hydroxyethyl) ethers of dihydroxyalkylated aromatic compounds such as hydroquinone; bis (2-hydroxyethyl) ether of resorcinol; alpha-alpha' terephthalyl alcohol; bis (2-hydroxyethyl) ether of α, α' -terephthalyl alcohol; alpha-alpha' -m-xylene glycol and its bis (2-hydroxyethyl) ether. Representative of the diamine extender are aromatic diamines such as p-phenylenediamine, m-phenylenediamine, benzidine, 4, 4 '-methylenedianiline, 4, 4' -methylenebis (2-chloroaniline) and the like. Representative of aminoalcohols are ethanolamine, propanolamine, butanolamine and the like.

Preferred extenders include 1, 2-ethanediol, 1, 3-propanediol, 1, 4-butanediol, 1, 2-hexanediol, and the like

Generally, the ratio of polyester polyol (i.e., ethylene adipate) to extender can vary over a wide range depending primarily on the desired hardness of the final polyurethane elastomer. Thus, the equivalent ratio of polyester polyol to extender should be in the range of from 1: 1 to 1: 12, especially from 1: 1 to 1: 8.

Among the isocyanates, particularly useful for use in accordance with the present invention are isophorone diisocyanate (IPDI), methylene bis 4-cyclohexyl isocyanate, cyclohexyl diisocyanate (CHDI), Hexamethylene Diisocyanate (HDI), tetramethyl m-xylene diisocyanate (m-TMXDI), tetramethyl p-xylene diisocyanate (p-TMXDI), and Xylylene Diisocyanate (XDI), among others, methylene bisphenyl isocyanate is considered to be particularly useful. Generally, the isocyanate is dosed such that the overall ratio of equivalents of isocyanate to equivalents of active hydrogen-containing material is in the range of 0.95: 1 to 1.10: 1, and preferably in the range of 0.98: 1 to 1.04: 1.

The blend barrier layer 30 typically includes up to 50% by weight of a polyester polyol based thermoplastic polyurethane, but preferably includes between about 1% and about 30% by weight of a polyester polyol based thermoplastic polyurethane. In a preferred embodiment, the polyester polyol-based thermoplastic polyurethane comprising the barrier layer 30 is between about 5% to about 25% by weight.

Among the copolymers of ethylene and vinyl alcohol used in the blend for forming barrier layer 30, commercially available products such as SOARNOL available from Nippon Gohsei, Inc. of New York^TMAnd EVAL obtained from Eval company of America, Lisle, Illinois^Prove useful. Best commercially available copolymers of ethylene and vinyl alcohol such as EVAL^LCF101A typically has an average ethylene mole percent content of between about 25% and about 48%. In general, higher ethylene content results in stronger adhesion between the layers of thermoplastic polyurethane and ethylene vinyl alcohol copolymer.

With regard to the use of so-called processing aids, small amounts of prior art antioxidants, UV stabilizers, mold release agents and tack-free agents are used, where the total content of such processing aids is generally less than 3% by weight.

To prepare the compositions of the present invention, it may be desirable to also include a catalyst in the reaction mixture. Any catalyst conventionally used in the art to promote the reaction of isocyanates with active hydrogen-containing compounds may be used for this purpose. See, e.g., Saunder et al, Polyurethanes, Chemistry and Technology, first part, Interscience, New York, 1963, pages 228-; see also, Britain et al, J.applied Polymer Science, 4, 207-. These catalysts include inorganic and organic acid salts of bismuth, lead, tin, iron, antimony, uranium, cadmium, cobalt, thorium, aluminum, mercury, zinc, nickel, cerium, molybdenum, vanadium, copper, manganese, zirconium and organometallic derivatives thereof, as well as phosphine and tertiary organic amines. Typical organotin catalysts are stannous octoate, stannous oleate, dibutyltin dioctoate, dibutyltin dilaurate and the like. Typical tertiary organic amine catalysts are triethylamine, triethylenediamine, N, N, N ', N' -tetramethylethylenediamine, N, N, N ', N' -tetraethylethylenediamine, N-methylmorpholine, N-ethylmorpholine, N, N, N ', N' -tetramethylguanidine and N, N, N ', N' -tetramethyl-1, 3-butanediamine.

Whether or not a catalyst is used, if used, the weight percent of such material is less than 0.5% of the total weight of the polyester polyol-based thermoplastic polyurethane reaction mixture.

For certain embodiments, it may also be useful to include a small amount of at least one aromatic thermoplastic polyurethane as a viscosity modifier in the blend barrier layer 30. In those instances where at least one aromatic thermoplastic polyurethane is used, the total amount thereof is generally 3% by weight or less based on 100% of the barrier layer composition. As such, the composition incorporating the barrier layer may be summarized as including: (1) at least one copolymer of ethylene and vinyl alcohol in a weight percent of 50% to about 97% (2) at least one aliphatic thermoplastic polyurethane in a weight percent of 3% to about 50%, and (3) up to about 3% by weight of one or more aromatic thermoplastic polyurethanes, where the total weight of the total components of the barrier layer is equal to one hundred percent. The aromatic thermoplastic polyurethane may also be selected from the group consisting of polyester, polyether, polycaprolactone, polypropylene oxide and polycarbonate polyglycol-type materials and mixtures thereof.

As previously mentioned, the barrier membranes disclosed herein may be formed by various processing techniques including, but not limited to, extrusion, blow molding, injection molding, vacuum molding and heat sealing or RF welding of tube and sheet extruded film materials. Preferably, and as described more fully below, the separator of the present invention is made from a film formed by co-extruding a thermoplastic polyurethane material of the outer layer with a blend of a polyester polyol based thermoplastic polyurethane and a copolymer of ethylene and vinyl alcohol of the inner layer to effectively produce a multi-layer film material from which the final barrier separator is made. Next, after the multilayer film material is made, the film material is heat sealed or RF welded to form an inflatable barrier membrane with high elasticity and diffusion pumping ability.

Referring to fig. 6 and 7, an alternative barrier membrane embodiment 28A in the form of an elongated tube of a multilayer composition is shown. The modified barrier membrane 28A is substantially identical to the compositional structure shown in fig. 1-5, except that a third layer 34 is disposed adjacent to and along the inner layer surface of the barrier layer 30, such that the barrier layer 30 is sandwiched between the outer layer 32 and the innermost layer 34. The innermost layer 34 is preferably made of a thermoplastic polyurethane material to provide increased protection against hydrolysis of the barrier layer 30 due to moisture. In addition to helping to enhance protection against aging of barrier layer 30, layer 34 also helps to provide a high quality weld that creates a three-dimensional shape to the cushioning device.

The cushioning devices shown in fig. 1-7 are preferably made from a multi-layer extruded tube. The coextruded tube is coiled to a length in the range of one foot (0.03 meters) to at most five feet (1.52 meters), and is inflated to the desired initial inflation pressure in the range of 0 psi to 100 psi, preferably in the range of 5 to 50 psi, where the trapped air is preferably nitrogen. The segmented tube is RF welded or heat sealed to the desired length. The individual buffer devices are manufactured to be separated by cutting at the welded regions between the adjacent buffer devices. It should also be noted that the damping device may also be manufactured by the well-known so-called extrusion blow moulding tube method, whereby the inner shape is fused into the tube.

Since the blended first layer comprising one or more polyester polyol polyurethanes and one or more copolymers of ethylene and vinyl alcohol and the second layer comprising thermoplastic polyurethane flow through separate flow passages to the outlet end of the extruder, once they are near the extruder head, the melt streams are mixed and generally float in layers, forming a laminar flow as they enter the die body. Desirably, these materials are bonded at a temperature of between 300 degrees fahrenheit to about 450 degrees fahrenheit (148.9 to about 223.3 degrees c, 5/9 degrees c (F-32 degrees c), the same applies below) and a pressure of at least about 200 pounds per square inch to achieve optimum wetting so that the bonding between adjacent portions of the layers 30, 32, and 34 is maximized. Furthermore, for multilayer laminates, the polyester polyols used in forming the barrier layer are preferably aliphatic in nature, as it has been found that aliphatic polyurethanes can be readily processed using conventional sheet extrusion techniques.

As will be explained in more detail with reference to fig. 6 and 7, the diaphragm 28A, according to fig. 6 and 7, includes three layers, a first layer of barrier material 30 sandwiched between a second layer 32 and a third layer 34 of thermoplastic polyurethane.

In a preferred embodiment, the two thermoplastic polyurethane layers and the blended barrier layer are co-extruded at a temperature that causes a contact reaction in the form of hydrogen bonding at least along a predetermined segment of the barrier membrane, such that no intermediate adhesive or bonding layer is required.

For this purpose, it is considered that the extremely strong bonding is caused by the reason that the effective hydrogen molecules are supplied through the vinyl alcohol groups and hydroxyl groups of the ethylene-vinyl alcohol copolymer and the urethane carboxyl groups or only the effective polar groups of the urethane along the length direction of the laminated separator.

The preferred compositions and methods of the present invention rely solely on the inherent characteristics of the second and third layers of thermoplastic polyurethane and the blended barrier layer comprising polyester polyol-type thermoplastic polyurethane and one or more copolymers of ethylene and vinyl alcohol when brought into contact for bonding according to the methods of the present invention.

The theoretical chemical reaction of surface bonding between layers 32 and 34 and layer 30 that occurs across substantially the entire intended contact surface area of separator 28A may be summarized as follows:

where R is

And R' is a short chain diol such as (CH)₂)₄

In addition to the foregoing theoretical hydrogen bonding, to a more limited extent, it is believed that a certain amount of covalent bonds are formed between the second and third layers 32 and 34, respectively, with the first barrier layer 30. But also other factors such as orientation and induction forces, in other words the well-known van der waals forces, which are caused by dispersion forces existing between any two molecules and dipole-dipole forces existing between polar molecules, can have an effect on the bonding energy between the thermoplastic polyurethane and the adjacent layers of the primary barrier layer.

The hydrogen bonding between the thermoplastic polyurethane layer and the barrier layer of the present invention is in contrast to prior art embodiments, where tie layer adhesives such as Bynel are typically used^To improve and maintain adhesion between the various layers of thermoplastic polyurethane and ethylene vinyl alcohol without recognizing the presence and/or potential of such bonds.

It should also be noted that fillers such as non-polar polymeric materials and inorganic fillers or extenders such as talc, silica, mica, and the like also have a tendency to negatively affect the bonding of the thermoplastic polyurethane to the blended layer comprising a polyester polyol polyurethane and at least a copolymer of ethylene and vinyl alcohol. Thus, in processing layers 30, 32 and 34, the use of fillers, if used, must be severely limited.

Referring to fig. 12-16, a barrier membrane in the form of an air bag, also referred to herein as a cushioning device, is shown made by blow molding. To form the air bag, a two layer parison or, preferably, a three layer film is first coextruded as shown in FIGS. 21-23 and then blown to form the parison by employing conventional blow molding techniques, and then the finished air bag best shown in FIGS. 12 and 15 is inflated with the desired trapped air to the preferred initial inflation pressure and the inflation ports (e.g., inflation port 38) are sealed by RF welding.

Figures 8-10 illustrate another bladder embodiment formed from a barrier membrane. Two coextruded sheets or films, or preferably three films, are first formed, the thickness of the coextruded sheets or films typically ranging from 12.7 to 254 microns for the barrier layer 30 and from 127 to 2540 microns for the thermoplastic polyurethane layers 32 and 34. Two sheets of the multilayer film are laminated to each other and welded together at selected locations using conventional heat sealing techniques or RF welding techniques. The uninflated bladder is inflated through a shaped inflation port to a desired initial inflation pressure in the range of from 0 psi to 100 psi, preferably from 5 to 50 psi. As previously mentioned, the preferred trapped air is nitrogen.

Figures 17 and 18 illustrate yet another bladder embodiment formed from a barrier membrane of the present invention. The balloon is made by two and three layer tubing techniques forming a coextrusion of the layers, the thickness of the wall of the coextruded tube obtained by transecting the layers ranges between 12.7 and 254 microns for the barrier layer 30 and 127 and 2540 microns for the thermoplastic polyurethane layers 32 and 34, the tube is pressed to a flat configuration and the opposing walls are welded together at selected locations and at each end of the tube using conventional thermal welding techniques or RF welding. The bladder is then inflated through the shaped inflation port 38 to a desired inflation pressure ranging from about 0 psi to 100 psi, preferably from 5 to 50 psi, preferably with the trapped air being nitrogen.

The different product designs described and illustrated in the figures are intended for use as the midsoles of footwear articles, particularly athletic shoes. In the present application, the inflatable membrane may be used in any of the various embodiments that (1) are completely encapsulated in a suitable midsole foam, (2) are only encapsulated at the top of the cells to fill and even out uneven surfaces to add comfort under the foot, (3) are encapsulated at the bottom to facilitate connection to the outside of the sole, (4) are encapsulated at the top and bottom but expose the perimeter for aesthetic and market reasons, (5) are encapsulated at the top and bottom but expose only selected portions of the sides of the cells, (6) are encapsulated at the top by a molded "footbed," and (7) are used with any foam, not encapsulated.

As mentioned above, in addition to the use of the barrier membrane of the present invention as a cushion or bladder, another highly desirable application of the barrier membrane of the present invention is in an accumulator as shown in fig. 19 and 20.

Referring to fig. 19 and 20, two alternative accumulator embodiments formed from the barrier membrane material of the present invention are shown. According to fig. 19, a hose casing in the form of a hydraulic accumulator is shown, which is used in a vehicle suspension system, a vehicle brake system, an industrial hydraulic accumulator or any accumulator having a different pressure between two possible different liquid media. The bladder 124 divides the hydraulic accumulator into two chambers or compartments, one of which is filled with air, e.g., nitrogen, and the other of which is filled with a liquid. Bladder 124 includes an annular collar 126 and a flexible partition wall 128. Annular collar 126 is adapted to be peripherally secured to the inner surface of the ball accumulator such that partition wall 128 divides the accumulator into two separate chambers. The resilient spacing 128 moves generally diametrically within the ball accumulator and its position at any given time is determined by the gas pressure on one side and the liquid pressure on the opposite side.

According to yet another example, FIG. 20 shows a product made using a combination of barrier membranes 110 including a barrier layer 114 formed of a thermoplastic polyurethane formed of one or more polyester polyols and one or more compositions or blends of copolymers of ethylene and vinyl alcohol and an outer layer 116 formed of a thermoplastic polyurethane. It is desirable to be able to utilize these so-called discontinuous configurations where the tendency to delamination along certain sections of the article is generally high. One such arrangement is an annular collar 128 along the bladder or diaphragm for the hydraulic accumulator. As such, it should be appreciated that the barrier membrane 110 described herein may include segments that do not include one or more layers of ethylene vinyl alcohol copolymer.

Preferably, the polyester polyol-based thermoplastic polyurethane and ethylene vinyl alcohol copolymer are not modified, nor are any tie layers or adhesives used, in an effort to produce cross-linking or ordinary covalent bonding between the two layers. When the method according to the present invention results in a contact reaction, the preferred composition and method of the present invention rely solely on the inherent characteristics of the polyester polyol-based thermoplastic polyurethane and the copolymer of ethylene and vinyl alcohol, i.e., maximization and fundamental reliance on the presence of hydrogen bonding between the layers.

Barrier membrane 110 formed in accordance with the teachings of the present invention may be used in a number of different processes including, but not limited to, co-extrusion blow molding such as co-extrusion using continuous extrusion, intermittent extrusion using (1) reciprocating screw delivery systems (2) piston-type accumulator systems (3) and accumulator ram systems, co-injection stretch blow molding, or co-extrusion of sheets, blown films, tubes or multiple profiles. It has been found that multilayer production processes such as tube, sheet, film extrusion, blow molding using co-extrusion, appear to demonstrate significant hydrogen bonding between the individual thermoplastic polyurethane layers and the layer comprising a blend of polyester polyol based thermoplastic polyurethane and a copolymer of ethylene and vinyl alcohol.

For example, to produce articles such as hydraulic accumulator bladders or diaphragms, for example blow molded articles, by a multi-layer production process in accordance with the teachings of the present invention, the following steps are generally followed using any of a number of commercially available blow molding machines such as Bekum BM502 with a coextrusion head model NO BKB95-3B1 (not shown) or Krup KEB-5 with a coextrusion head model No VW60/35 (not shown).

The multilayer production process technology will now be mainly described. First, the resin material comprising the thermoplastic polyurethane and the barrier material comprising a blend of at least one preferably aliphatic polyester polyol based thermoplastic polyurethane and at least one copolymer of ethylene and vinyl alcohol are first dried (if necessary) according to the manufacturer's specifications and fed into an extruder. Typically, the material is fed into the extruder in a sequence where the layers are laid out, for example, TPU is outside the extruder, a blend of a polyester polyol type TPU and EVOH is in the middle of the extruder, and TPU is inside the extruder. The extruder is adjusted in heat profile for optimal treatment of the individual materials. However, it is recommended that the temperature difference at the exit of each extruder not exceed 20 degrees Fahrenheit. The heat profile is adjusted to obtain the optimum melt mass as the material is forced forward into each extruder. The heat profile is generally adjusted between 300 to about 450 degrees fahrenheit, the feed zone is the lowest set point and all other set points are gradually increased in 10 degree fahrenheit increments until the desired melt is obtained. Once exiting the extruder, a length of tubing is sometimes used to direct the material to the strand lay-up head (i.e., a three or more layer head). Any differential adjustments are made at this point. The pumping action of the extruder not only forces the material into the individual head channels or flow paths but also determines the thickness of each layer. For example, if the first extruder is 60mm in diameter, the second extruder is 35 mm in diameter, and the third extruder is 35 mm in diameter, if it is desired to produce 1.3 liters of bladder or membrane in a predetermined cycle time of 26 seconds, at a speed where the outer layer of TPU is required to be 2 mm thick, the barrier layer is required to be 76.2 microns thick, and the inner layer of TPU is required to be 2 mm thick, then the first extruder has a screw speed of 10 rpm, the second extruder speed is about 5 rpm, and for the third extruder the speed is about 30 rpm. Once in the head channel or flow path, the heat is generally held constant or reduced to adjust the melt strength of the material. Separate head channels or flow paths maintain isolation between the melts as they are directed down into the parison mold.

Just prior to entering the lower die or bushing and lower core, the material head channels or flow paths are brought together by the pressure created by the now integral runner surface area, the gap between the lower bushing and core and the pressure exerted on the cell layers by the extruders. This pressure must be at least 200 psig and can typically exceed 800 psig under the conditions described. At the location where the materials come together, a parison is formed which is a laminate of three layers comprising a layer of thermoplastic polyurethane, the first layer comprising a blend of at least one polyester polyol based thermoplastic polyurethane and at least one copolymer of ethylene and vinyl alcohol, and the second and third layers of thermoplastic polyurethane being located along opposite sides of the first layer. The upper limit of the pressure is limited substantially only by the physical strength of the indenter. After leaving the ram, the laminate is sealed at each end by the two mold halves and a gas, such as air, is injected into the mold to blow the laminate parison against the mold and hold it until sufficient cooling has occurred (i.e., about 16 seconds for the previous full pattern) at which time the gas is vented. The part is then removed from the mold and further cooled for a sufficient period of time to allow the part to be trimmed or may be further processed when needed for some parts. It will now be understood to those of ordinary skill that the layers must be kept separate until completely melted and preformed to form a hollow tube, at which time they are chemically bonded as described herein, under the heat and pressure conditions described herein.

Those skilled in the molding industry will recognize that the three main components of a blow-molding machine, namely the extruder, die and clamp, are of many different sizes and configurations to accommodate the customer's productivity plan and size requirements.

Known sheet extrusion multi-layer production processes include extrusion techniques in which two or more polymers are extruded simultaneously through a single die, where the polymers are joined together to form a single extruded article having distinct, well-bonded layers, and according to the present invention, a typical layer structure is defined as follows:

A-B

comprising two different layers of two resins.

A-B-A

Three different layers comprising two or three resins.

A-B-A-B-A

Five different layers comprising two, three, four or five resins.

Wherein A is a layer of thermoplastic polyurethane and B is at least one layer formed from a resin comprising a blend of at least one polyester polyol based thermoplastic polyurethane and at least one copolymer of ethylene and vinyl alcohol.

The equipment required to make the coextruded sheets includes an extruder for each type of resin, which is connected to a coextrusion feed apparatus as shown in FIGS. 21 and 23, which is available from many different commercial sources including Cloron corporation of Orange, Tex, and Production Components, Inc., of ear Claire, Wisconsin, among others.

The co-extrusion feed device 150 comprises three sections. The first section 152 is a feed inlet section that is connected to a separate extruder and directs a round strip of resin flow to a program section 154. Block 154 then shapes each resin stream into a rectangle and its size is proportional to the desired individual layer thickness. The transition section 156 combines the separate individual rectangular layers into a square mouth, the melting temperature of the TPU a layer should be about 300 degrees to about 450 degrees fahrenheit, and to optimize the adhesion between the TPU a layer and the B layer of the blended polyester polyol-type TPU and EVOH copolymers, the actual temperature of each melt stream should be adjusted to nearly match the viscosity of each melt stream. The intermixed layer melt stream is then molded into a single rectangular extruded melt in a sheet die 158, preferably designed with a "jacket support" as is common in the molding industry as shown in FIG. 22. The extrudate is then cooled and formed into a rigid sheet by a casting or calendering process using rollers 160.

Similar to sheet extrusion, the equipment required to make coextruded tubes includes an extruder for each form of resin and connected to a common manifold die. The polymer melt flows from each extruder into a manifold die such as that shown in fig. 23, available from Canterberry engineering, inc, of great asia atlanta, Genca, inc, and others, and into separate annular flow channels 172A and 172B, respectively, for the thermoplastic polyurethane and blended polyester polyol-based thermoplastic polyurethane and copolymer of ethylene and vinyl alcohol. The flow channel is annular in shape and has a dimension proportional to the desired thickness of each layer. The individual melts are then mixed to form a common melt stream just prior to the die inlet 174. The melt stream then passes through a channel 176 formed by an annulus between the exterior surface 178 of the cylindrical core 180 and the interior surface 182 of the cylindrical form 184. The tubular extrudate exits the die casing and is then cooled to a tubular shape by a number of common tube standard methods. Figure 23 shows two composite tubes, and it will be understood by those skilled in the art that additional layers may be added through the individual flow channels.

Regardless of the plastic forming process used, it is most important to achieve the extensive range of hydrogen bonded compatible melts required between layers over the desired length or section of the laminate, which refers to a melt of thermoplastic polyurethane resin and blended polyester polyol based thermoplastic polyurethane and ethylene vinyl alcohol copolymer. Thus, the multilayer production process used should be performed at a holding temperature of from about 300 degrees to about 450 degrees fahrenheit for blends of thermoplastic polyurethane and polyester polyol-based thermoplastic polyurethane and ethylene vinyl alcohol copolymer. Furthermore, it is important to maintain sufficient pressure of at least 200 psi where the layers engage and maintain a sufficient amount of hydrogen bonding.

As previously mentioned, in addition to the excellent bonding obtained by the laminated barrier membrane of the invention, another object is to provide a barrier membrane capable of retaining the trapped gas for the desired general time, in particular with respect to barrier membranes used as cushioning means for footwear. In general, a barrier membrane having a gas transmission rate value of 10 or less, as measured according to the procedure specified in ASTM D-1434-82, for a thickness of 508 microns, is an acceptable choice for a desired lifetime. This is due in this respect to the excellent properties of the blends of polyester polyol polyurethanes and copolymers of ethylene and vinyl alcohol in terms of elasticity, in particular resistance to ageing caused by moisture and to poor gas transmission. The barrier membranes of the present invention can be used either as a multilayer laminate or as a monolayer construction made of the barrier materials described above.

To prepare commercially unavailable samples for analysis of gas transmission properties as set forth in table I, the hydroxyl component was first prepared by adding one or more of the following ingredients to a 2000 ml reaction flask: (1) polyester polyols (i.e., technical products or reaction products of said linear dicarboxylic acids and diols); (2) a difunctional extender; and (3) processing aids such as waxes and antioxidants. The hydroxyl component is then heated to between about 95 c and 115 c (depending on the composition) and stirred to dissolve the ingredients uniformly. Next, a vacuum of less than 0.2 mm hg was applied with continued stirring to control foaming. After the end of foaming, the gas in the bottle was vented for about 30 minutes until virtually the entire foaming was terminated.

Next, the isocyanate component was prepared by placing the diisocyanate in a 250ml polypropylene beaker and heating the diisocyanate on an oven to between about 50-65 ℃. After the temperature has reached between about 50 and 65 ℃, the desired amount of isocyanate is weighed and added to the isocyanate component with constant stirring, if any catalyst.

Once the catalyst is added and thoroughly stirred, a predetermined amount of the hydroxyl component is added to the isocyanate component to effect polymerization. When the viscosity increases at the start of the polymerization (generally about 7-12 seconds after addition), the reaction is poured into a pan coated with the desired release agent and allowed to cool sufficiently.

After cooling, the newly formed polymer is cut into small particles and dried at between 85-100 ℃ for about 2-4 hours. The different samples set forth in table 1 were then cast into sheets for analysis relating to gas transfer properties.

As shown in Table 2, the results of gas transmission rates of any of samples 1 to 8 were confirmed to be better than those of comparative samples 9 to 10 each formed of a commercially available thermoplastic polyurethane resin, and samples 2 to 8, which relate to the polyethylene glycol adipate polyurethane, were confirmed to have gas transmission rate values better than those of the polybutylene adipate polyurethane of sample 1.

Since the use of a blend of a copolymer of ethylene and vinyl alcohol and a polyester polyol based thermoplastic polyurethane theoretically has a lower gas transmission rate than the polyester polyol based thermoplastic polyurethane, samples 2-8 show that it is an excellent choice for both single layer and multilayer barrier membranes because the gas transmission rate values apparently meet or approach the target value of 10 or less.

Having described preferred embodiments of the present invention in detail, it is to be understood that the invention is susceptible to modification, variation and change without departing from the scope and spirit of the appended claims.

TABLE I^*Gas transmission rate of single layer product

Composition of	Sample 1	Sample 2	Sample 3	Sample No.4	Sample No. 5	Sample No. 6	Sample 7	Sample 8	Sample 9	Sample 10
											Polybutylene adipate (a)2000m.w.1	43.12
(b)700m.w.2	15.09
											Ethylene adipate (a)1000m.w.3		61.11	62.29	49.18	60.63	49.60	30.26	16.39
(b)500m.w.4		61.11	62.29	49.18	60.63		22.69	32.77
											1, 2-ethanediol			4.25
Dipropylene glycol	0.58
											Butyl carbitol	0.21
1, 4-butanediol	7.37	6.05		9.96	6.00	8.93	6.81	7.37
											H12MDI5						41.07	39.84
MDI6	33.04	32.5		40.52				43.15
											MDI/liq.MDI7			33.12		33.03
Irganaox 10108	0.125	0.15	0.15	0.15	0.15	0.15	0.15	0.15
											Advawax 2809	0.125	0.15	0.15	0.15	0.15	0.15	0.15	0.15
Wax10	0.30
											Catalyst and process for preparing same11	0.04	0.04	0.04	0.04	0.04	0.10	0.10	0.02
Pellethane 2355-85 ATP12									100.0
											Pellethane 2355-95 AE13										100.0
Total weight percent	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0	100.0

^*All values in Table 1 are in weight percent (WT%)

1.FOMREZ^TM44-56 from Witco chemical

2.FOMREZ^TM44-160 from Witco chemical

3.FOMREZ^TM22-112 from Witco chemical

4.FOMREZ^TM22-225 from Witco chemical

DESMUDAR W (m.w 262), from BAYER AG (USA)

6.ISONATE^TM125M from Dow chemical Co., Ltd

7.80% IONATE^TM125M and 20% IONATE^TM143L of a blend from Dow chemical Co.

8.IRGANOX^TM1010 from Ciba-Gigy chemical Co

9.ADVAWAX^TM280 from

Montan fatty waxes

11.50% blend of stannous octoate and 50% dioctyl phthalate

12.PELLETHANE^TM2355-85ATP from Dow chemical

13.PELLETHANE^TM2355-95AE from Dow chemical

TABLE II

Sample number	Average thickness	GTR(cc/m2Atmospheric pressure sky)	GTR(cc/m2Atmospheric pressure day) to 20 mils thickness
				1	16.25 mil	30.95	25.15
2	15.2 mil	11.71	8.9
				3	17.13 mils	9.13	7.82
4	18.49 mils	6.58	6.08
				5	17.54 mils	7.07	6.19
6	19.93 mil	9.22	9.19
				7	19.93 mil	6.19	6.17
8	18.31 mil	1.20	1.10
				9	19.95 mil	36.42	36.33
10	18.25 mil	24.12	22.01

Claims (24)

1. A shoe comprising at least one layer of a membrane sealed and inflated with a gas, wherein the membrane has a gas transmission rate of 10 or less than 10 to the inflated gas, and wherein the membrane comprises a first layer comprising a blend of at least one copolymer of ethylene and vinyl alcohol and at least one thermoplastic polyurethane formed from a polyester polyol, and wherein the polyester polyol is formed from the reaction of a linear dicarboxylic acid having no more than six carbon atoms and a diol having no more than six carbon atoms, wherein the resulting polyester units have no more than eight carbon atoms.

2. The shoe of claim 1, wherein the dicarboxylic acid is adipic acid, glutaric acid, succinic acid, malonic acid, oxalic acid, or a combination of two or more thereof.

3. The shoe of claim 1, wherein the glycol is ethylene glycol, propylene glycol, butylene glycol, pentylene glycol, hexylene glycol, or a combination of two or more thereof.

4. The shoe of claim 1, wherein the polyurethane is formed from ethylene adipate.

5. The shoe of claim 1, wherein the polyester polyol has a molecular weight of 300 to 4000.

6. The shoe of claim 1, wherein the first layer comprises no more than 50% by weight of thermoplastic polyurethane.

7. The shoe of claim 1, wherein the first layer comprises 1% to 30% by weight of the thermoplastic polyurethane.

8. The shoe of claim 1, wherein the first layer comprises 5% to 25% by weight of the thermoplastic polyurethane.

9. The shoe of claim 1, wherein the first layer comprises no more than 3% by weight of an aromatic thermoplastic polyurethane.

10. The shoe of claim 1, wherein the copolymer of ethylene and vinyl alcohol has an average ethylene content of 25 mol% to 48 mol%.

11. The shoe of claim 1, wherein the first layer comprises:

(a) 50% to 97% by weight of at least one copolymer of ethylene and vinyl alcohol;

(b) 3% to 50% by weight of at least one aliphatic thermoplastic polyurethane formed from a polyester polyol; and

(c) not more than 3% by weight of one or more aromatic thermoplastic polyurethanes.

12. The shoe of claim 1, wherein the membrane has a second layer comprising thermoplastic polyurethane, the second layer being attached to at least a segment of the first layer, wherein the first layer is hydrogen bonded to the second layer.

13. The shoe of claim 12, wherein the thermoplastic polyurethane of the second layer is formed from a material selected from the group consisting of: polyesters, polyethers, polycaprolactones, polyoxypropylenes, polycarbonate polyglycols, and mixtures thereof.

14. The shoe of claim 1, wherein the first layer has an average thickness of 0.5 to 10 mils.

15. The shoe of claim 12, wherein the first layer has an average thickness of 0.5 to 10 mils and the second layer has an average thickness of 5 to 100 mils.

16. The shoe of claim 1, wherein the gas comprises nitrogen.

17. The shoe of claim 1, comprising more than one layer of membrane.

18. The shoe of claim 1, comprising a multi-layer membrane, wherein the membrane is a tubular membrane.

19. The shoe of claim 1 having at least one membrane disposed in the mid-sole.

20. The shoe of claim 1 having at least one membrane disposed in a heel region of the mid-sole.

21. The shoe of claim 1, wherein the at least one membrane is in the shape of a heel pad.

22. The shoe of claim 1 having at least one membrane completely enclosed by the mid-sole region.

23. The shoe of claim 1 having at least one membrane partially enclosed by the mid-sole region.

24. The shoe of claim 1 having at least one membrane at least partially surrounded by an outer region of the sole.