REINFORCING MATERIAL FOR FOOTWEAR

Abstract: A reinforcing material suitable for use in footwear stiffeners, characterised in that the material comprises consolidated melt-spun fibres of hot-melt adhesive, e.g. polyester melting point about 60 DEG C, combined with bulk fibres, e.g. of 20 mm to 100 mm in length, in a ratio of adhesive fibres to bulk fibres between 20:80 and 80:20 by weight, said fibres having been entangled prior to consolidation under pressure and heat.

Description: REINFORCING MATERIAL FOR FOOTWEAR The present invention relates to a reinforcing material and, more particularly, to a reinforcing material suitable for use at the heel or toe end of footwear in order to provide reinforcement and shape definition. It will be understood by those skilled in the art that presentation of footwear and maintenance of shape are highly important. However, particularly with the upper components of footwear, the materials used are quite flaccid and so not necessarily conducive to shape retention, particularly when subjected to the inherent stresses and strains of everyday use. In such circumstances, it is conventional to include a counter element at the heel and a boxed-toe or toe-puff at the toe end of footwear. These elements are made of formable materials which resiliently retain their shape after such forming operation. With such counter and toe-puff elements located in respective pockets or adhered to the upper components, it will be appreciated that a formed shape is substantially retained by all the components so assembled. These counter and toe-puff elements therefore ensure good profile definition when the footwear is on display for sale and provide shape retention for the footwear especially use when subjected to crushing deformation in use. Like most producers of consumer products, footwear manufacturers must be highly cost conscious and so require adequate performance in return for minimal expenditure. Thus, these counter and toe-puff components have been made in a variety of ways. For example, the components can be preformed moulded plastic elements but it will be appreciated that individual sizing of these pre-moulded elements will therefore be necessary. To avoid this problem, the most popular form of reinforcing component for footwear comprises a component cut from a sheet of material and then, during the manufacturing process, moulded to the desired shape. This moulding procedure generally involves heating and then chilling so the reinforcing component is thermo-formable and generally a thermoplastic. Typically, footwear reinforcing materials are based on fabric impregnated with a low softening point binder or can comprise simple extrusions of thermoplastics or be reinforced or filler loaded material. It will be appreciated that reinforced or filler loaded materials are generally cheaper as the thermoplastic is the most expensive constituent. These reinforced or filler loaded materials can be made by a variety of techniques including powder deposition where, as will be appreciated from the name, component powders of the various components are mixed and deposited upon a release paper where subsequent heating of these components melts the thermoplastic in order to consolidate these constituents together and so form the desired footwear reinforcing sheet material. Impregnation does not easily allow the use of self-adhesive binders and extrusion or powder scattering do not easily allow the incorporation of long staple length fibre reinforcing materials. It is an object of the present invention to incorporate staple fibre, for example from 20mm to 100mm in length, as a reinforcing agent in self adhesive, thermoplastic sheet materials. In accordance with the present invention there is provided a reinforcing material suitable for use in footwear stiffeners, the material comprising consolidated melt-spun fibres of hot-melt adhesive combined with bulk fibres in a ratio of adhesive fibres to bulk fibres between 20:80 to 80:20, by weight, said fibres having been entangled prior to consolidation under pressure and heat. The adhesive fibres have a dual function in a preferred material in accordance with the invention, in that they act as a binder material assisting in binding the bulk fibres together in the consolidated material and contributing substantially to the stiffness of the material but also provide a hot-melt adhesive by which the reinforcing material is bonded to other shoe components in use of the reinforcing material in the manufacture of a shoe. The fibre adhesive may be provided by any suitable adhesive for example polycarprolactone but hot-melt polyester based adhesives are preferred. Whereas the preferred reinforcing materials are self-adhesive in that the materials will stick firmly to other shoe upper components under heat and pressure, an additional adhesive coating (or coatings) of hot-melt or other adhesive types may be applied if desired. Preferably, the adhesive from which the melt-spun fibres are formed is polyester based, for example Esterpow 1112AF or Esterpow 1108AF which is believed to comprise polytetramethylene adipate and which is supplied by Bostik Limited, Leicester, LE4 6BW, England. Preferably, the bulk fibres are synthethic polymeric textile fibres, suitably polyester or polypropylene (melting point about 165 °C) but are generally unaffected in a material sense by the heat and pressure applied to consolidate the reinforcing material. Conveniently, the bulk-fibres have a melting point of at least 100°C, preferably more than 105 °C. Suitably the bulk fibres are from 20mm to 100 mm in length, preferably over 25mm in length. The reinforcing material may have variable performances in different zones of the material, through, across and/or along its length by incorporation of differing proportions of melt-spun fibres. The melt-spun staple fibres suitably could have a decitex of 0.8 to 17, more preferably 1-10, and the bulk fibres may have a similar specification. However, 1-7 decitex is preferred. Further, in accordance with the present invention, there is provided a method of making a reinforcing material suitable for use in footwear stiffeners comprising, at least, the following steps:- (a) melt spinning a hot-melt adhesive to form melt-spun fibres; (b) blending and needle punch entangling these melt-spun fibres with bulk fibres to form a non-woven felt; (c) heating said non-woven felt and compressing said felt to fully melt said adhesive melt-spun fibres to form a matrix of adhesive within which the bulk fibres are embedded; and (d) cooling said matrix of adhesive and bulk fibres to form the reinforcing material required. The blending stage under step (b) may include laying webs of different proportions of melt-spun fibres in different zones of the reinforcing material. In preferred materials in accordance with the present invention adhesive polymers, which become molten and sticky at about 60 °C but are hard and stiff when cooled below 50°C, are used to provide the adhesive fibres. Such adhesive polymers have been utilised previously as self- adhesive binders in shoe stiffener materials. These adhesive polymers can be melt-spun to create staple fibres. The technique of forming staple fibres by melt spinning is well known and the decitex of those fibres is determined by the spinneret used. Typically, the melt-spun fibres will have a length of 50 millimetres, but may range between 20 and 100mm in length. The melt-spun fibres are blended with normal bulk fibres made from for example polyester, polypropylene or other synthetic or man-made fibres. These bulk fibres do not melt at such low temperatures. The melt-spun staple fibres and the bulk fibres are blended together and entangled using known techniques to form a non- woven fabric. The non-woven fabric is heated and pressed to fully melt the melt-spun adhesive polymer staple fibres and so consolidate the bulk and melt-spun fibres together to form a continuous film of adhesive polymer within which the embedded fibrous entangled reinforcing structure formed by the bulk fibres is blended. As a result of the viscous nature of the adhesive polymer when molten, it is very difficult to achieve such an intimate mixture of adhesive polymer and bulk fibre using other techniques such as powder deposition onto a felt or extruding a film onto a felt. It will be appreciated, as indicated above, that it is necessary to incorporate bulk fibres and other filler elements in order to reduce the cost of the reinforcing material. The present fibre reinforced, self-adhesive polymer film, used as a reinforcing material suitable for footwear stiffeners, has very desirable attributes. It will be appreciated by those skilled in the art that the resulting reinforcing material is both tougher and more resilient than previous sintered powder deposition type reinforcing material. Furthermore, the resultant reinforcing material in accordance with the present invention is generally lighter, less dense and more economical than previous extruded filled, i.e. fibrous or particulate filler. Examples of adhesive polymers suitable for the present invention are Esterpow 1112AF and Esterpow 1108AF supplied by Bostik Limited, Leicester, England. Both these adhesive polymers are polyester based hot-melt binder/adhesive and are supplied in a free-flowing powder form. Distinctive features of these example polymers are their relatively low fusion temperature and their ability to set in approximately 4-7 minutes, after heating above their softening point, into a rigid and tough film. Both are based on linear saturated polyester namely poly(tetramethylene adipate) and are typically supplied in a particle distribution size of 100-800 microns. However, it will be appreciated that this adhesive polymer is heated until molten and then spun to create the staple fibres necessary in accordance with the present invention. These fibres will typically have a length of 50 millimetres. The fibres, whether the spun-melt staple fibres or the bulk fibres, may have a decitex between 0.8 and 17 but 1 to 7 is preferred. Generally, the coarser the bulk fibres, the more reinforcement there will be to the reinforcing material. The most convenient technique for blending and entangling the staple adhesive polymer fibres and the bulk fibres is through carding or needle punch entanglement. In such entanglement procedures, barbed needles are arranged to penetrate a batt or web of material carded and layered prior to presentation to reciprocating needle boards. Thus, by penetration using the barbed needles, the fibres become intermeshed and entangled in order to consolidate the non-woven felt. It will be appreciated by those skilled in the art that a suitable length of the fibres is necessary in order to achieve appropriate entanglement. Fibres which are too short or too long will not card effectively but provided that the fibres can be carded, longer fibres are preferred to produce the strongest material. The bulk fibres, in accordance with the present invention, may be any fibre type that does not melt or materially alter its performance through heating to the relatively low temperatures necessary to melt the polymer adhesive fibres as described above. Thus, polyester and polypropylene textile fibres may be used. These fibres may be relatively coarse compared to the melt-spun staple adhesive polymer fibres. The essential feature of the bulk fibres is to provide reinforcement within the adhesive polymer film. In such circumstances, coarse bulk fibres will cause greater voids and greater reinforcing material whilst finer bulk fibres may have less voids but also reduced reinforcement. Those skilled in the art will appreciate that the blending and carding process associated with manufacture of non-woven fabrics and felts leads to good fibre distribution and so exceptional fibre distribution equalization throughout the reinforcing material formed by heat/pressure consolidation. Typically, the non-woven fabric is made by cross-laying or lapping several webs of carded fibres to form a batt. Normally this cross-laying is a continuous process but "insert" webs including melt-blown fibres can be introduced into a wholly bulk fibre batt, or a wholly bulk fibre web insert into a mixed staple spun-melted fibre/bulk fibre batt, can be achieved. Thus, selective performance can be introduced into the reinforcing web by such web inserts. The inserts may be stacked or discontinuous across (laterally) and/or along (longitudinally) the direction of reinforcing material manufacture. Such selective variation in the amount of spun-melt fibre across, through and along the reinforcing material may allow introduction of directional properties to the reinforcing material or a reduction in the proportion of such expensive fibres within the material whilst maintaining appropriate performance. One method of making reinforcing material embodying the invention is hereinafter described to illustrate the invention by way of example. The fibre handling techniques used are well-known to those skilled in the art. In carrying out the illustrative method a melt-spun adhesive web is intimately blended with a bulk fibre web as follows :- (1) The chosen bulk fibre is passed once through a carding machine to open it. (2) The pre-opened bulk fibre is then passed through the card a second time to produce a uniform bulk fibre web which is then collected on a lap drum after the Doffer. (3) As the bulk fibre web is rolled onto the lap drum a melt-blown web of polytetramethylene adipate) (PTMA) is fed simultaneously onto the lap-drum so building up alternate layers of bulk fibre web and melt-blown web. (4) The layers of melt-blown and bulk fibre web are then needled with 40 gauge needles, first being tacked at 45 NPD 12 PEN-! needled 100 NPD 12 PEN! ('NPD' is the number of needle punches per cm 2 . 12 PEN means 12mm of needle penetration through the bed plate on me needling machine) Eight layers each of each web were accumulated with the melt-spun web being underneath the bulk fibre each time so that needling effectively punched the top layer of bulk fibre down through the structure and out through the bottom surface leaving a superficial layer of bulk fibres on each surface of the material. (5) The needled material was then heat-fused in a platen press each surface of which is heated at 140°C with an area pressure of around 5 psi for ten seconds. This treatment melted the melt-spun web and compressed the total structure to form a flat sheet which when cool formed a stiff plastic sheet with a density between 0.7 and 1.0 g/cc. Two illustrative reinforcing materials, manufacmring conditions and properties of which are set out in Table 1 , were produced using the above method, each using polyester textile fibre as the bulk-fibre and a poly(tetramethylene-adipate) light weight melt spun web adhesive available in several grades under the trade name Estergran from Bostik Limited, Ulverscroft Road, Leicester, United Kingdom. In both examples the grade of Estergran web used is identified as PE 65-50 and has a softening point of about 55 °C. In Example I the bulk fibre web is Hoechst T290 polyester fibre of 1.7 decitex x 38mm nominal staple fibre length at a density of 25 gsm (grams per square metre). In Example II the bulk fibre web is Hoechst T290 polyester fibre of 6.7 decitex x 60mm nominal staple length at 35 gsm. In Table 1 'NPD' has the meaning indicated above. DLC means 'Dead Load Collapse' - mis is a typically mouldability and stiffness test for footwear toe-puffs and counters reinforcing materials. 'Frank Stiffness' indicates a known flexural modulus test "Karl Frank Stiffness Test". AL indicates measurements taken in the lengthwise direction of the material. AX indicates transverse measurement. Another method is to melt-spin the adhesive polymer to create staple fibre as with commodity thermoplastic fibres. The two types (or more) of staple fibre can then be blended and formed into web using standard carding techniques. This produces a more intimate blend of the fibres man laying up separate webs. As with the other method described a heating and pressing process is required to consolidate the material into sheet form for use as a stiffener. TABLE 1 'Aquiline' is a proprietary shoe lining material available from the Applicant company. The materials produced by Examples I and II exhibit very good moulding and shape retention, very good bond strength and resilience. Bending modulus is satisfactory but not quite as high as known extruded mica-filled materials of the type referred to above, but density is lower. Actual stiffness is not very high because of the relatively low weight and gauge but is suitable for lighter shoes. Thicker materials will be required for desirable performance in mens shoes. The illustrative materials can be used to provide self-adhesive counter materials which soften and become sticky (for bonding to other shoe upper components) at typical backpart moulding temperatures in shoe manufacture but nevertheless maintain a certain level of strength and minimal melt squabbing ("squabbing" is the tendency of a sheet material to spread and increase in area when subject to pressure and/or heat). The illustrative reinforcing materials provide sufficient stiffness and strength when at ambient temperatures to provide adequate counter stiffener materials for use in some types of shoe. Whereas the illustrative materials were made by pressing in a platen press, otherwise similar materials in accordance with the invention may be made by pressing using heated calendar rolls. Furthermore, the layers of melt- spun and bulk fibres may be assembled by cross-lapping techniques prior to needle punching, for convenient continuous production. In an alternative method of making a material embodying the invention a melt-spun web may be cast, as it is manufactured, directly onto a carded (or other lightweight) bulk fibre web so that it adheres (lightly) thereto before cross-lapping or other batt formation techniques are employed. The assembly ie the light weight bulk fibre web carrying the melt-spun web is then formed into a batt made up of alternate bulk fibre and melt- spun fibre layers by cross-lapping (or other suitable techniques) and the so-formed batt needle-punched and heated and pressed to consolidate it and form a further reinforcing material embodying the invention.

Claims: CLAIMS 1. A reinforcing material suitable for use in footwear stiffeners, characterised in that the material comprises consolidated melt-spun fibres of hot-melt adhesive combined with bulk fibres in a ratio of adhesive fibres to bulk fibres between 20:80 and 80:20 by weight, said fibres having been consolidated under pressure and heat, preferably having first been entangled. 2. A material according to claim 1 wherein the hot-melt adhesive has a softening point between 45 °C and 70 °C. 3. A material according to claim 2 wherein the softening point of the adhesive is between 50°C and 60°C. 4. A material according to any one of the preceding claims wherein the bulk fibres are synthetic polymeric textile fibres. 5. A material according to claim 4 wherein the bulk fibres are selected from polyester fibres and polypropylene fibres, or a blend thereof. 6. A material according to either one of claims 4 and 5 wherein the bulk fibres have a softening point of at least 100 °C. 7. A material according to any one of the preceding claims wherein both the melt-spun fibres and the bulk fibres have a decitex of 0.8 to 17. 8. A material according to claim 7 wherein the decitex of the fibres is 1 to 10. 9. A material according to any one of the preceding claims wherein the bulk fibres are staple fibres from 20mm to 100mm in length. 10. A material according to any one of the preceding claims comprising different proportions of melt-spun fibres in different zones of the material. 11. A material according to any one of the preceding claims having a density of 0.7 to lg/cc. 12. A method of making a reinforcing material suitable for use in footwear stiffeners comprising, at least, the following steps:- (a) melt spinning a hot-melt adhesive to form melt-spun fibres; (b) blending and needle punch entangling these melt-spun fibres with bulk fibres to form a non-woven felt; (c) heating said non-woven felt and compressing said felt to fully melt said adhesive melt-spun fibres to form a matrix of adhesive within which the bulk fibres are embedded; and (d) cooling said matrix of adhesive and bulk fibres to form the reinforcing material required. 13. A method according to claim 12 wherein blending under step (b) includes laying at least one web having a different proportion of melt-spun fibres to bulk fibres in at least one zone of the reinforcing material. 14. A method according to either one of claims 12 and 13 wherein the melt spun fibres are from 20mm to 100mm in length. 15. A method according to any one of claims 12 to 14 wherein the melt-spun fibres have a softening point above 50°C and become soft and sticky at a temperature below 70 °C. 16. A method of making a reinforcing material suitable for use in shoe stiffeners comprising at least the following steps :- (a) forming a bulk fibre non- woven web; (b) melt-spinning a hot-melt adhesive to form a non-woven web of hot- melt adhesives directly on the bulk fibre so that the adhesive fibre adheres lightly thereto; (c) forming a batt of a plurality of layers of the thus-formed webs; (d) heating and pressing the batt to fully melt said adhesive fibres and to consolidate the batt to form a matrix of adhesive within which the bulk fibres are embedded; and (e) cooling said matrix to form the reinforcing material. 17. A reinforcing material made by a method according to any one of claims 12 to 16.

Inventors: JOHNSON SUSAN GWYNNETH, JOHNSON, SUSAN, GWYNNETH
Applicants: JOHNSON SUSAN GWYNNETH, TEXON MATERIALES S L, TEXON UK LTD, JOHNSON, SUSAN, GWYNNETH, TEXON MATERIALES, S.L., TEXON UK LIMITED
Application year: 1998
Main classification: D04H1
IPC codes: A43B23, D04H1, D04H5, D04H13