It will be understood that stiffener materials are used in a wide range of environments in order to provide reinforcement and support. For example, stiffener materials may be used as reinforcing toe puff or heel counter elements within shoe constructions. The stiffener material must be quite resilient in order to provide the reinforcement necessary but also must be produced relatively cheaply.

Typically, stiffener materials within the shoe industry have fallen into two groups namely a suitably impregnated fused non-woven material or an extruded sheet of mouldable composition. Typically the mouldable impregnant or component of the extruded sheet is a polymeric composition including styrene butadiene, ionomer, ethylene vinyl acetate, polyolefins, low-melting copolyesters and polycaprolactone, polytetramethylene adipate and polyurethanes It will be appreciated that it is most convenient if the moulding of the stiffener material can be conducted at relatively low temperatures, i. e. below 100°C, in order to suit the shoe-making process.

In counter materials for shoe constructions and other situations it will be appreciated that there will be additional coatings to the stiffener material in order to perform function. For example, it may be necessary to add an adhesive to stick a shoe heel counter to the other upper components of the footwear.

It will be appreciated that copolyesters, polyurethanes, polytetramethylene adipate and polycaprolactone thermoplastic materials are quite expensive and thus extruded stiffener materials can greatly add to the cost of a product utilising them. Furthermore, fused non-woven fabrics impregnated with thermoplastic mouldable compositions can involve costly impregnation steps and also include quite expensive components.

It is an objective of the present invention to provide through an alternative wet-laid process copolyesters or polycaprolactone stiffener materials having improved technical performance and/or reduced cost compared to extruded sheet versions.

In accordance with the present invention there is provided a stiffener material of the wet-laid type, the material including at least 20% by weight of binder support fibrous material and at least 30% adhesive binder in the form of powder or fibre, said fibrous material comprising entangled fibres in order to support said adhesive binder within interstices between said fibres to provide the stiffener material through adhesion of said adhesive binder to said fibrous material and to provide an adhesive surface to said stiffener material This fibrous material may be formed from organic, i. e. cellulosic fibres such as using wood pulp. These fibrous material fibres may have a length up to 12 mm. and be up to 30 decitex. For example polyamide or polyester mini-fibres of 7 mm. length 2 decitex would appropriate.

The adhesive binder may be any low-melting temperature polymer or polymer/resin blend including polycaprolactone, polytetramethylene adipate, polyurethanes, polyester based materials, ethylene vinyl acetate, low-melting point polyamide or other hot-melt adhesives in either powder or short staple fibre form.

The remainder of the stiffener material may be auxiliary filler up to 20% by weight.

Suitable auxiliary fillers would be calcium carbonate or china clay.

To improve adhesion in the shoe-making process, the surfaces of the stiffener material may be coated with between 20 gsm. and 300 gsm. of adhesive binder Further in accordance with the present invention there is provided a method of making a stiffener material comprising the steps of at least: (a) mixing into a pulp at least 20% by weight binder support fibrous material and at least 30% by weight of adhesive binder in powder or fibre entangled with said fibrous material with sufficient liquid carrier; (b) depositing said pulp as a mat by separation of solids within the pulp from the liquid carrier; (c) compressing and drying said mat in order to remove said liquid carrier; (d) fusing said mat by heating and pressing in order to activate said adhesive binder to consolidate said mat; and (e) coating the surfaces of said mat with between 20 gsm. and 300 gsm. of adhesive binder to improve adhesion in the shoe-making process.

An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which Figure 1 is a schematic illustration of a method of making a stiffener material and Figure 2 is a schematic part cross-section through the stiffener material.

Figure 1 shows in schematic fashion the manufacturing steps in order to produce a stiffener material in accordance with the present invention.

A hopper 1 is arranged to contain a water slurry of pulp 2 comprising at least 30% adhesive binder and at least 20% adhesive binder fibrous support material arranged to support the adhesive binder as a dispersion in water. The remainder of the matter in the pulp 2 includes auxiliary fillers. It will be appreciated that differences in the relative density between the adhesive binder, the adhesive binder support fibrous material and the auxiliary fillers require that to ensure adequate randomisation and mixing constant agitation is necessary through a paddle 3.

In the pulp 2 the adhesive binder is either in a powder or a short staple fibre form.

Types of binder adhesive material that may be used are any low-melting temperature polymer or polymer/resin blend including for example polycaprolactone, polytetramethylene adipate, polyurethanes, polyester based materials, ethylene vinyl acetate, low-melt polyamides or other hot-melt adhesives. As indicated above it is more important that the binder adhesive material is activated at acceptable shoe manufacturing temperatures, i. e. 50-100°C, and furthermore as will be discussed below that the fibre or powder size is configured to enable appropriate support within the binder support fibrous material as deposited.

The adhesive binder support fibrous materials include cellulose wood pulp or short staple fibre of a staple nature including polyamide mini-fibres. It is in accordance with the present invention that these fibres of the adhesive binder support material become entangled during a wet-lay process similar to that used in paper making in order that interstices are created to accommodate and support the adhesive binder whether it be a powder or a fibre. Thus, the fibres of the adhesive binder support material must be configured in order to create such entanglement upon wet laid deposition. It has been found that fibres up to staple length of approximately 12 mm. and a decitex up to 30 are appropriate. Furthermore, for example, with polyamide mini-fibres a staple length of 6 mm. and 2 decitex, have provided adequate results.

In terms of manufacture of the stiffener material the appropriately agitated pulp 2 is wet laid onto a support mesh 4 designed to advance in the direction of arrow A. The mesh 4 may also support a lightweight, i. e. less than 20gsm/m2 fabric upon which the pulp may be deposited in order to aid processing. In any event the liquid carrier i. e. water in the pulp 2 is designed to pass through the mesh 4 or otherwise be driven off to a substantial extent as the laid pulp 2a travels along with the mesh 4.

The laid pulp 2a as the liquid carrier, i. e. water, is removed becomes substantially condensed such that the fibres of the support material become entangled encapsulating the adhesive binder within interstices between said fibres in order to support them and create a sheet of consolidated form. Although the deposited pulp 2a still retains significant amounts of water it will be appreciated that as the fibres of the binder support material become entangled so that the position of adhesive and auxiliary fillers within the pulp 2a is substantially fixed after capture at the interstices between entangled fibres. However, the relative densities of the binder, the auxiliary filler and the fibres of the binder support material may result in localised concentration of one component within the pulp 2a. This stratification may have advantageous features within the eventual stiffener material, for example, if the adhesive binder is concentrated along the bottom surface then evidently in the eventual stiffener material the bond strength presented upon activation of the stiffener material will be enhanced at this surface. Furthermore, by combination of two layers of stiffener material it may be possible by combining top surfaces of two deposited layers of pulp 2a through lamination or whilst still wet simple combination to improve enhanced adhesive binder at both surfaces of the eventual stiffener material. In any event as adhesive binder is provided throughout the pulp 2a the eventual stiffener material will provide some adhesive at least at both surfaces of that stiffener material. This can be supplemented with an additional coating of adhesive binder onto the surfaces.

The condensed pulp 2a is next squeezed and heated to further remove the liquid carrier water and so condense the pulp into a more acceptable stiffener prerequisite web 5.

This squeezing and heating of the initial deposited pulp 2a is conducted by rollers 6 which compress the pulp 2a and may be heated in order to drive off the water carrier from the pulp 2a. Alternatively, fan heat may be used. The prerequisite stiff web 5 should after the squeezing and heating operation be essentially dry and be a solid. This solid web 5 comprises entangled fibres which constitute the fibrous binder support material within which the adhesive binder and any auxiliary filler are encapsulated.

The prerequisite web 5 evidently comprises a mat of fibrous and powder materials in a reasonably compressed and entangled solid. The various components of the web 5 are held together by mechanical entanglement and thermal bonding and are still mainly distinct. Thus, the web 5 is not as yet suitable as a stiffener material and would probably fragment if attempts are made to mould it. The web 5 must be consolidated in order to fuse the material prior to use in shoe making counter or toe puff components. This consolidation stage requires heating the web 5 to activate the binder adhesive whether it be powder or in fibre form in order to at least partially melt it and consolidating by pressing and so effectively bind the various constituents of the web 5 to form a consolidated stiffener material 6. This stiffener material 6 is a relatively stiff board sheet which may be cut and subsequently moulded to form shoe toe puff or heel counters of appropriate shape and may then be moulded through further heat activation of the adhesive binder to the configuration required. Furthermore, the adhesive binder element at the surface of the stiffener material 6 which could be supplemented with an additional coating of binder will adhere the stiffener material to other upper components within the shoe.

It will be appreciated that a practical stiffener material may be constructed of several layers or laminations of pulp or a single deposited layer and that stiffener material performance may be affected accordingly. Furthermore, a practical stiffener material may be made of several layers of wet laid pulp 2, each layer having different performance criteria dependent upon the composition and relative proportions of binder, support materials and auxiliary fillers. Thus, for example, a central core layer highly charged with relatively cheap auxiliary fillers may be sandwiched between outer layers of material having a higher adhesive binder content with the result that a relatively inexpensive stiffener material is provided with costly binder adhesive concentrated at the outer surfaces. As the method of manufacturing the stiffener material in accordance with the present invention is essentially a wet-laid process these various layers of pulp 2 may be deposited at the early wet stage and thus the squeezing effect of roller 6 will achieve the binding of the layers as required. This combination could be achieved by having several hoppers 1 arranged to be in series with regard to the grating 4 such that the respective pulp deposition is upon each other. The water used to deposit the binder and fibres must be completely dried off by heat before consolidation can be carried out.

The consolidation stage essentially comprises heating the web 5 most usually with radiant heat or possibly hot air in order to activate the adhesive binder as described followed by consolidation by pressing between, for example, rollers, platens or belts. The heaters 7 are arranged to provide this heat activation of the binder adhesive either as illustrated by non-contact. However, the heaters may be in contact with the web 5 and furthermore include further compression for consolidation of the material 6 in the consolidation stage.

After consolidation a further coating of adhesive binder may be applied to the surfaces-typically using hot-melt adhesive application processes such as extrusion coating, roller coating or sintered powder coating.

Figure 2 is a schematic illustration of a section of web 5 prior to consolidation as illustrated in Figure 1.

The web 5 comprises entangled fibres 8 which create interstices encapsulating adhesive binder 9 in powder form and auxiliary filler 10. However, it will be appreciated that the adhesive binder could also be in fibre form. It is the cost of the auxiliary filler 10 which determines whether it is in fibre or powder form.

As the fibres 8 are randomly entangled and as these fibres 8 settle about and with regard to the binder 9 and auxiliary filler 10 during the deposition stage the size of the interstices 11 vary. Furthermore, Figure 2 is a schematic illustration and thus component dimensions almost certainly will be relatively different. It will be appreciated that the pulp deposition step and water carrier removal in effect settles the solid material components 8, 9,10 out and that these components orientate themselves to ensure tight packing especially under compression from rollers 6 (Figure 1). The fibres 8 in effect provide a scaffold within which the adhesive binder 9 and any auxiliary filler 10 become encapsulated. The fibres become entangled around these components 9,10 in order to provide an integrated web 5.

In the consolidation stage the heat activated adhesive binder 9 in effect melts and spreads about the mat 5. Thus, the adhesive binder 9 binds the elements of the mat together to produce a practical stiffener material 6. The consolidation stage is irreversible and once conducted the mat 5 is a fused material. Typically, at room temperature the stiffener material will be substantially rigid whilst if heated by air or in a water bath the material becomes more flaccid and mouldable such that on subsequent cooling the material again becomes rigid in the moulded shape.

An example of the stiffener material in accordance with the present invention would be 50% of polytetramethylene adipate binder material in powder form with 50% of filler/binder support materials. This 50% of binder support materials may be up to 100% sulphate wood pulp or up to 100% nylon mini-fibres of 2 decitex 6 mm. staple length. This filler/binder support material can comprise several types of fibre or filler powder. The greater proportion of cellulose pulp to other fibres within the filler/binder support material the more uniform the product can be produced. If the filler/binder support material consists of a greater proportion of fibre other than cellulose pulp then a less uniform product is produced but it may have a slightly better adhesive bonding ability and not require an additional coating of adhesive binder.

A practical stiffener material composition is as follows : 70% by weight HM5584 BOSTIK polyester adhesive with 30% hardwood pulp. It has been found that this stiffener material provides a bond strength with known shoe lining material of approximately 8.1 Newtons/cm. However, by suitable adaptation of stiffener material composition it has been found that bond strengths up to 13 Newtons/cm. can be obtained and these are sufficient for toe puff and counter material in shoe constructions.

It will be appreciated that as adhesive binder is located throughout the present stiffener material the bond between shoe upper components and the reinforcing toe puff or counter is presented through a broader depth of the stiffener material than merely the surface and as such the possibility of component separation failure is reduced.

It will be understood that in accordance with the present invention the performance of the stiffener material can be closely related to the components used in its fabrication.