US3797138A

US3797138A - Foamed sheet for making stiffening elements

Info

Publication number: US3797138A
Application number: US00337298A
Authority: US
Inventors: A Closson
Original assignee: Individual
Current assignee: Individual
Priority date: 1973-03-02
Filing date: 1973-03-02
Publication date: 1974-03-19
Anticipated expiration: 1991-03-19

Abstract

This invention relates to a novel shaped shoe counter article formed of a thermoplastic cellular foam material, a so-called stiffener used to maintain the dimensional integrity of the shoe to conform generally with the heel of a wearer as classified in Class 36, subclass 68; the novel article is formed of an elastomeric thermoplastic foam and is particularly valuable for use in a process for making molded shoes.

Description

United States Patent Closson, Jr.

[ 3,797,138 451 Mar. 19, 1974 FOAMED'Y SHEET FOR MAKING STIFFENING ELEMENTS lnventori Addison W. Closson, Jia, 30

Coolidge Ave., Cambridge, Mass.

Filed: Mar. 2, 1973 Appl. No.: 337,298

Related US. Application Data Continuation of Ser. No. 847,724, Aug. 5, 1969, abandoned.

US. Cl. 36/68, 36/77 M Int. Cl A43b 13/42 Field of Search 36/68, 77 R, 77 M;

References Cited UNITED STATES PATENTS 4/1964 Markevitch 36/45 3,264,761 8/1966 Johnson 36/3 A 3,355,535 11/1967 Hain et a1. 161/159 X 3,416,170 3/1969 Gilbert 161/161 3,616,170 10/1971 Closson..... 36/68 X 3,711,969 l/1973 Weinstein 36/68 Primary ExdminerAlfred R. Guest Attorney, Agent, or Firm-Robert A. Cesari; John F McKenna; Andrew F. Kehoe [57] ABSTRACT This invention relates to a novel shaped shoe counter article formed of a thermoplastic cellular foam material, a so-called stiffener used to maintain the dimensional integrity of the shoe to conform generally with the heel of a wearer as classified in Class 36, subclass 68; the novel article is formed of an elastomeric thermoplastic foam and is particularly valuable for use in a process for making molded shoes.

16 Claims, 2 Drawing Figures 1 FOAMED SHEET FOR MAKING STIFFENIN ELEMENTS RELATED APPLICATIONS This application is a continuation-in-part of US. Ser. No. 847,724 filed Aug. 5, 1969, by Addison W. Closson and entitled FOAMED SHEET FOR MAKING STIF F ENING ELEMENTS, now abandoned. U.S. Pat. No. 3,616,170 was issued on an earlier continuation-inpa'rt of that application and relates to a novel material which has been found particularly useful in forming the shoe frame articles claimed in the earlier parent application and in this application.

BACKGROUND OF THE INVENTION There are numerous applications in the fabrication of wearing apparel which require stiffening and support means in order to reinforce or strengthen some particular section of the apparel. Among the most important applications of such stiffening elements are those encountered in the manufacture of shoes, sneakers, pumps, slippers and other such footwear. For example, such stiffening units are especially important in the construction of an ordinary back part of a shoe. In general, it is desirable that such components be light, with stand reasonable temperatures as may be encountered in their ordinary use, and have a degree of resilience and strength which will add to the comfort of the wearer of the shoe. These advantages are preferably obtainedwithout the addition of any excessive weight to the shoe, and a reduction in weight would be desirable. 7

A shoe counter stiffener is part of the shoe frame. The counter ensures a good fit and maintains the shape of the heel portion of the shoe throughout the flexing and other motions to which a shoe is normally subjected. In some'shoes, there will be a pocket formed of the shoe upper into which a counter-stiffening element is inserted to form the counter. In other shoes, especially sneakers, the counter may be formed by fastening the stiffening element directly to the heel; the inner part of the stiffener, in such a case, contacts the wearers foot. However, even for heavy duty shoes and boots counters have been made entirely of injectionmolded thermoplastics. Polyethylene has been used. Ethylene-vinyl acetate has also been used. Thermoplastic ionomer resins such as those'sold under the trade designationSurlyn by DuPont have also been used t form counters.

Other parts of the-shoe, serving a very different purpose than the shoe frame are the insoles and cushions. The insole is usuallyasoft and comfortable material usually designed to absorb perspiration but also to reevaporate the perspiration rapidly when the shoe has been removed from the foot. Cushioning and insoles are primarily comfort-oriented features of a shoe and have been made of foam rubber and such materials as cork-based compositions for sometime. They serve substantially no structural purpose; they serve wear and comfort functions.

Inthe selection of a material of construction for forming shoe counter stiffener elements, particular care must be given to the formability of the material from which the element is to be constructed; thus the material cannot be so temperatureand pressureresistant that it is not formable into a shaped stiffening to satisfy many applications, and thus should be able to withstand temperatures of at least from 140 F. to 150 F. as encountered in a typical laundry machine. The

Vicat softening point is an appropriate criterion of the minimum heat resistance of the polymer.

Although the above considerations are generally important, they become particularly important in footwear-making operations wherein a sole is molded, by thermal injection molding techniques, to a shoe upper comprising the stiffening element therein. In such a situation, there is often an undesirable and unsightly bulge caused by pressure from the flange at the top of the mold cavity which appears where the heel and the sole meet. This bulge not only detracts from the appearance of the footwear, but also affects the merchantability of the footwear. Moreover, there has been a difficult problem of providing sufficiently heatsusceptible counter materials so that thermal molding operations are facilitated but excessive softening or melting of the stiffener is avoided.

Up until the present time, such reinforcing elements as shoe counters have been made of a number of materials, most notably calendered rubber rag stock materials orrubber-saturated textiles and fiber. These materials have generally been formed into 0.055-inch thick counters. This thickness is customary because rubber rag stock materials are not resilient enough in lesser thicknesses. However, with the advent of improved materials, this thickness has not necessarily reflected a real need in terms of reinforcing strength. Thus, present shoe manufacturing techniques utilize a considerable quantity of material'in such reinforcing applications, but this quantity of material is in fact not really required noras applicant has found in instant invention-particularly desirable.

SUMMARYOF THE INVENTION Therefore, it is a principal object of the present invention to provide an improved stiffening or reinforcing element for use in footwear.

It is a further object of the invention to provide an improved shoe counter.

Another object of the invention is to provide an improved process for making an injection molded shoe and thereby avoiding the problem of a bulge at the site where the mold cavity rings meet an upper onto which the sole is being molded.

Another object of the invention is to provide a new lightweight and resilient heel-counter stiffening element.

A further object of the invention is to provide a novel heel stiffening elementthat will shape easily under heat, but will not degrade when subjected to temperatures of F. and above in washing apparatus.

Other objects of the invention will be obvious to those skilled in the art on reading the instant specification. v

The above objects have been substantially obtained by the construction of a novel counter-stiffening structure. The structure comprises a foam sheet and a fabric sheet laminated thereon, the foam sheet accounting for the major part of the thickness of the completed element.

By' foam (Hackhs Chemical Dictionary, Fourth Edition) is meant to define a heterogeneous product in which the gaseous phase is dispersed in a non-gaseous phase,i.e. finely divided gas bubbles or "cells, suspended in another medium. Polymer foams of this general type are known to the art. For example, see US. Pat. No. 3,431,163 wherein an ethylene-vinyl acetate foam having a particular cell shape is obtained by a special extrusion technique.

Foam" is not intended herein to define either (1) porous materials of the sponge type and which imbibe and hold a large mass of water in pores; or (2) porous materials of the so-called poromeric type wherein the critical gas volume comprises a path from one wall of the material to the other to facilitate moisture transmission. Such poromeric materials are widely used in shoe construction as upper materials. So far as is known they have no utility in forming shoe frame parts. In fact and as well understood in the art, these poromeric upper materials must be easily broken in" by the wearer of a shoe and cannot be as heavy and resilient as is required of the heel stiffener products described and claimed herein.

The foam sheet is formed of a polymeric foam material. Preferred for use are thermoplastic elastomers, most advantageously, a copolymer of ethylene and vinyl acetate such as that sold under the trade name Alathon 3130 by E.l. DuPont de Nemours and Co., Inc. This material contains about 12 percent vinyl acetate units and has been found preferable to material containing over about 18 percent such units because the latter materials have undesirably low softening points. Other useful thermoplastic elastomers include styrenebutadiene rubber such as that sold under the trade name Kraton by Shell Chemical Co., polyvinylchloride, thermoplastic polyurethane elastomers, the ionomer sold under the trade designation Surlyn by E.l. DuPont de Nemours and Co., Inc, polyethylene, and the chlorinated polyethylene sold under the trade designation Tyrin by Dow Chemical Company, the chlorosulfonated polyethylene sold under the trade designation Hypalon by DuPont, blends of such materials and the like. This list will suggestto those skilled in the art the wide variety of thermoplastic polymers which may be utilized in the process of the invention, thus, the list is to be considered illustrative only and not limiting with respect to the particular materials that can be used to form the stiffening elements of the invention. It will be understood, however, the fabric which can be used in the present invention includes any fabric, woven or unwoven, natural or synthetic, which is known to the clothing industry as suitable for use in wearing apparel. The use of this fabric is partially aesthetic and, in most cases, the element would be useful for stiffening purposes of the invention even if the fabric were not utilized. Nevertheless, because the foam utilized has a somewhat improved moisture vapor transmission characteristic over the reinforcing materials known to the art, it has been found that the presence of the fabric layers plays a role in distributing, i.e. wicking, moisture over the entire surface of the foam and thereby enhances still further the moisture vapor transmission characteristics of the element and improves the comfort of the apparel being reinforced. Moreover, it has been discovered that the foamed material laminated to a fabric substrate can serve advantageously as a shoe liner surface. This is important because it means the product of the invention can be used to form integral stiffening and lining structures. For example, it can be I It is advantageous that the Bashore resiliency be above used to form a single piece serving the function of both a shoe liner and a heel stiffening element.

In general, the foam useful in the present invention will contain from about 10 to percent by volume of voids. With ethylene and vinyl acetate based polymers, the void volume will be between 20 and 60 percent, preferably between 35 and 50 percent. Lower void volumes do not have any advantage over regular plastic films; higher void volumes tend to result in materials of insufficient strength. In a typical application, a film 0.045 inches thick will be laminated to cloth 0.013 inches thick. The lamination process will usually compress the laminate being formed to a thickness of from 0.05 to 0.055 inches in thickness, leaving the foam element about 0.037 inches thick or thicker.

It will be noted that a great reduction in weight of polymer used in a given stiffener is achieved as a result of the high void volume. Moreover, when a stiffening element according to the invention is incorporated into a shoe in a hot molding process (such as, for example, that process whereby the fabric-type upper used in the manufacture of sneakers is molded to the sole or polymeric section of a sneaker), then the resilience afforded by the presence of the foam in the back part of the sneaker effectively reduces or eliminates the unsightly bulge which has formerly been a problem in sneakers and other footwear formed by this molding technique.

A number of tests are customarily used to measure resiliency of materials. The Bashore resilience is one test; it gives a result indicative of per cent of rebound of a steel ball dropped on the test specimen; such a test gives an indication of the instantaneous elasticity of a material. As is known in the art, shoe materials subject to cyclical long-term wear-induced stresses require long-term resiliency. Thus it is desirable to combine such a resiliency test of the Bashore type with a longterm test such as the Satra Flex test known to the art. The Satra Flex test is a measure of flex life and is determined by flexing a strip of material being tested on an axis through T80 anguiar'ae'grees until it breaks.

Typical results on advantageous counter-stiffener materials after formation into foamed sheets 0.045

inches thick and containing about 40 percent in volume of voids:

' 9.5% 7.5% Bashore Resiliency 30% 30% Satra Flex 242] 2l26 nominal 71. of vinyl acetate-derived units in ethylene'vinyl acetate material sold under the trade designation Alathon by El. DuPont de Nemours and Co., Inc.

about 15 and the Satra Flex life be at least 1000 cycles.

Resiliency is inherent in elastomers, i.e. as defined in Hackhs Chemical Dictionary (4th Edition). Such elastomers will have a relatively large angle of permanent deformation and the vinyl acetate-ethylene copolymers are especially advantageous in this respect. This resilience combined with the exceptionally good adhesive properties of vinyl acetate at processing temperatures make it an ideal material for use in shoe applications. It is to be noted that theionic-crosslinked polymeric materials are useful as therrnoplastics and, therefore, are useful in the process of the invention. Conventionally crosslinked or vulcanized materials like polyurethane resins and vulcanized rubbers are not preferred for forming sheets according to the invention. Polystyrene, although thermoplastic, is typical of a polymer that is insufficiently resilient and elastomeric to be of use in applications for forming sheets according to the invention.

It is particularly desirable that a polymer system be selected which provides the necessary degree of comfort and resilience without the need of plasticizers. This is true because shoe stiffeners, especially those in molded shoes like sneakers, are subjected to such varied conditions of temperature and humidity during wear and washing that plasticizers tend to be leached out-or in some way made ineffective-during the life of the shoe. Moroever, the migration of plasticizer to the outer surface of a plastic article is considerably more of a problem when that article is in the foam; This of course, because of the smaller differences the plasticizer must travel to get to a surface where it does no good. Nevertheless, external plasticizers can be used with materials, particularly poly(vinylchloride) and its copolymers, to provide an operational, although not optimal, heel stiffening article. In normal practice, a thermoplastic material, for example, the preferred copolymer of ethylene and vinyl acetate, will be extruded in a thin sheet onto a continuous web of fabric. Blowing agents will be contained in the extruded formulae which will provide the desired amount of gas release and expansion of the thermoplastic material as it comes out of the extruder die (or on the subsequent activation) and is carried along on the cloth web. Alternatively, freon gas can be introduced into the metering section of the extruder to serve as the blowing agent.

Furthermore, the product of the invention. may be made byforming an aqueous emulsion of a polymer and blowing agent, coating it on the substrate and then heating to dry the emulsion and activate the blowing agent. Other means for forming the product of the invention include the use of organisol or plastisol compositions containing gas-forming agents, coating them on the paper and subsequently heating them to activate the blowing agents and remove a suitable quantity of the plasticizing agents. Still another processing technique is to calender a thermoplastic formulation, with the resultant sheet to a substrate, and then activate a blowing agent in theformulation by subsequent heatmg. I

' It is within the scope of the invention to add such adjuvants as fillers, pigments, anti-oxidants and reinforcing agents to the polymer composition. However, the addition of such materials is not critical to the practice of the invention. In this connection, it may be noted that it is particularly advantageous to add moisturevapor-permeable tillers (such as ionomer powder, the sparingly crosslinked ionomers known to the art, modifled cellulosic powder, cork, and other such materials known to the art) to the composition in order to enhance the moisture vapor permeability thereof. But such addition should not be of such a magnitude to interfere with the practical machine washability of the shoe. Use of foam in a shoe reinforcing counter provides an improved moisture vapor transmission over the shoe reinforcing materials known to the art. This transmission is not of the order of that obtained in shoe upper materials, but is greater than that heretofore obtainable in plastic shoe counters. This improved moisture vapor transmission is believed to be desirable, but

is apparently of little or no importance to the commercial success of the invention. It is the combination of lightweight, bulge-resistance, selective compressibility of the material at high pressure-points during shoe fabrication, high resilience and washability which have caused the commercial success of the invention.

ILLUSTRATIVE WORKING EXAMPLE In order to point out more fully the nature of the present invention, the following specific example is given as an illustrative embodiment of the novel process and products of the invention.

A formulation is prepared by dry-blending, in a typical tumbling-type blender, the following ingredients:

1 by weight Blowing agent 0.6 Zinc stearate 0.6 Ethylene vinyl acetate copolymer pellets 98.8

The blowing agent is that sold under the trade designation Kempore 200 by National Polychemicals, Inc. The copolymer is that sold by DuPont under the trade designation Ala thon' 3 130.

The material so formulated is extruded from a 6-inch extruder having a rear barrel temperature of 450 F. and a die temperature of about 350 F. The extruded sheet is removed from the extruder in the form of a foamed sheet about 0.055 inches thick and 40 inches wide. The take-off speed is approximately five feet per minute. The extruded sheet has a mass of about 1.3 lbs. per square yard. About 4 inches in front of the extruder die, the aforesaid foamed sheet is wedded to a drilling fabric having a 2.7 yards per pound weight. The finished product has a thickness of about 0.055 inches.

The product, the preparation of which has been described above, is utilized to form counter-stiffening elements of a typical design, known in the art, to be useful in sneakers. These counter-stiffening elements are stitched into the backpart section of the upper, or fabric, sections of sneakers and then joined according to the well-known Desma injection molding process, to the sole section of the sneakers to form the completed shoe.

The injection molding operation is carried out at molding temperatures cycling between F and 240 F.for a 1.5-minute cycle on a Desma Werke Injection 1 Molding Machine. A commercially-available, poly(vinylchloride) base, sold composition supplied by B.F. Goodrich Co., under the trade designation, Pliovic, is utilized in this operation. Despite the use of the extra-thick counter (of 0.060 inches thickness), the sneakers formed by this process exhibit no bulge.

' When molding a shoe with prior art stiffener elements, an irregular gap usually occurs between the shoe last (which is covered with upper and the counter portions of the shoe) and heel seat mold rings. Counter stiffeners of the present invention compress between the mold rings and tend to prevent this gap allowing the spewing out of vinyl soling compound being injected during the molding operation. Thefoam also prevents the upper fabric of the stiffenertas used in sneakers etc.) from being cut by the rings.

Moreover, the combined thermoplastic nature of the stiffener together with the inherent thermal insulating qualities of the foam structure, allow a desirable localized melt softening of the stifiener which comes in contact with hot injection soling material at the base of the counter and where it is compressed by the heat and pressure as at the back seam.

When the same operation is carried out with 0.060- inch thick counter stiffeners made of conventional ragstock rubber, a noticeable and unsightly bulge results. Furthermore, 1.5 minutes of heat at 150 F. is not enough time and temperature to cure a rubber rag stock formula.

Another major advantage of the foamed thermoplastic stiffening unit is that it eliminates the back seam ridge. This ridge is formed at the place where the quarters are stitched together and is normally covered with an overlay of tape. Frequently, after washing, the tape comes loose and allows this ridge to show through the lining of the shoe. The foamed thermoplastic stiffener is compressible when hot and allows the seam ridge to embed itself in the thickness of the counter and thereby eliminate the possibility of its subsequent shadowing through the lining. This feature of the stiffener improves the looks and comfort of the shoe.

In the drawings:

FIG. 1 shows a fragmentary view of the heel portion 10 of a sneaker shoe 12 with a counter stiffener 13 which is molded into the sole material below cushion 14. FIG. 2 shows a schematic cross-section of a stiffener 13 formed of a foamed elastomeric thermoplastic 16 containing gas cells 17 and a cotton drill cover fabric 18.

It is, of course, to be understood that the foregoing example is intended to be illustrative, and that various changes can be made in the ingredients, proportions and conditions set forth therein without departing from the spirit of the invention as defined in the appended claims.

What is claimed is:

1. A resilient laminated shoe counter having selfstiffening properties, shaped and adapted to conform to the heel portion of a shoe, said counter being a laminate formed of A. a foamed, elastomeric, organic, polymeric sheet containing 10 to 80 percent by volume of voids, and

B. a sheet of fabric bonded to said polymeric sheet wherein said polymeric sheet forms the major thickness of said laminate.

2. A counter as defined in claim 1 wherein said foamed polymeric sheet is formed of a thermoplastic copolymer of ethylene and vinyl acetate and wherein said copolymer has a Vicat softening point of above 140 F.

3. A shoe counter as defined in claim 1 wherein said foamed thermoplastic sheet has a Vicat softening point of above 140 F.

4. In an article of footwear, the improvement wherein a resilient shoe counter, conforming in shape to the heel portion of said footwear, said counter being a laminate formed of A. a sheet of foamed elastomeric organic polymeric sheet containing from 10 to percent by volume, of voids, and

B. a sheet of fabric bonded to said polymeric sheet and wherein said polymeric sheet forms the major thickness of said laminate.

5. An article of footwear as defined in claim 4, said footwear being a sneaker or a slipper.

6. An article of footwear as defined in claim 5, said foamed elastomeric sheet being formed of a copolymer substantially formed of ethylene and up to 18 percent of vinyl acetate, said copolymer having a Vicat softening point of over F.

7. An article of footwear as defined in claim 6, said footwear being a sneaker or a slipper.

8. A shoe-counter, heel-shaped stiffening article formed of a sheet of a cellular foamed elastomeric thermoplastic organic polymer, said foamed sheet forming the major thickness of said article, and wherein the Vicat softening point of the foamed thermoplastic is over 140 F. I

9. An article as defined in claim 8 wherein said polymeric foam is formed of a thermoplastic copolymer of ethylene and vinyl acetate.

10. An article as defined in claim 8 wherein the void volume of said shaped foamed thermoplastic is from 20 to 60 percent of the volume of said thermoplastic.

11. In a process for forming footwear of the type wherein a lower sole member is molded onto an upper member comprising a backpart section therein, the improvement comprising the step of incorporating into said heel section a counter-stiffener article formed of a closed-cell, foamed, thermoplastic, elastomeric organic polymer.

12. A process as defined in claim 11 wherein said polymer is a copolymer of ethylene and vinyl acetate having a Vicat softening temperature of less than 140 F.

13. An improved article of footwear comprising as a counter stiffening article therein, a reinforcing article formed of a foamed thermoplastic polymer.

14. The article of claim 13 wherein said stiffening element forms an integral counter reinforcing element and at least part of the shoe lining.

15. An article defined in claim 13 wherein said footwear is a sneaker or a slipper.

16. An article as defined in claim 13 wherein said organic polymer is a copolymer of ethylene and vinyl ace- UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION patent 3, 797,138 Dated November 19, 1974 Inventor(s) Addison (31055011, Jr

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 12, line 3, "less" should read more Signed and sealed this 24th day of September 1974,

(SEAL) Attest:

McCOY M. GIBSON JR. Attesting Officer C. MARSHALL DANN Commissioner of Patents FORM r- -wso (ID-G9)- USJOMMDC I r 1 U.5 SOVERNMEN? PRINTING OFFICE Q

Claims

1. A resilient laminated shoe counter having self-stiffening properties, shaped and adapted to conform to the heel portion of a shoe, said counter being a laminate formed of A. a foamed, elastomeric, organic, polymeric sheet containing 10 to 80 percent by volume of voids, and B. a sheet of fabric bonded to said polymeric sheet wherein said polymeric sheet forms the major thickness of said laminate.

2. A counter as defined in claim 1 wherein said foamed polymeric sheet is Formed of a thermoplastic copolymer of ethylene and vinyl acetate and wherein said copolymer has a Vicat softening point of above 140* F.

3. A shoe counter as defined in claim 1 wherein said foamed thermoplastic sheet has a Vicat softening point of above 140* F.

4. In an article of footwear, the improvement wherein a resilient shoe counter, conforming in shape to the heel portion of said footwear, said counter being a laminate formed of A. a sheet of foamed elastomeric organic polymeric sheet containing from 10 to 80 percent by volume, of voids, and B. a sheet of fabric bonded to said polymeric sheet and wherein said polymeric sheet forms the major thickness of said laminate.

6. An article of footwear as defined in claim 5, said foamed elastomeric sheet being formed of a copolymer substantially formed of ethylene and up to 18 percent of vinyl acetate, said copolymer having a Vicat softening point of over 140* F.

8. A shoe-counter, heel-shaped stiffening article formed of a sheet of a cellular foamed elastomeric thermoplastic organic polymer, said foamed sheet forming the major thickness of said article, and wherein the Vicat softening point of the foamed thermoplastic is over 140* F.

12. A process as defined in claim 11 wherein said polymer is a copolymer of ethylene and vinyl acetate having a Vicat softening temperature of less than 140* F.

16. An article as defined in claim 13 wherein said organic polymer is a copolymer of ethylene and vinyl acetate.