The present invention relates to a laminated product for use in footwear manufacturing and to a method of manufacturing an insole for a footwear.

BACKGROUND OF THE INVENTION

Different kinds of laminated products using a needling process for bonding two layers of different material are already known in footwear manufacturing. However, a drawback with those products is that they generally do not provide a good rigidity to the finished product and therefore their use is limited to articles which do not require a good rigidity. As a result, they are not very suitable as an insole for footwear.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a laminated product for use in footwear manufacturing which overcomes this drawback. More particularly, an object of the present invention is to propose a laminated product suitable for use in footwear manufacturing comprising: an upper layer made of a resilient foam material; and a bottom layer made of a fibrous mat comprising: a multiplicity of fibers, a fraction of which penetrates the foam material of the upper layer for bonding the bottom layer to the upper layer; and a stiff portion for providing stiffness to the product .

Another object of the present invention is to propose a laminated insole for a footwear comprising: an upper layer made of a resilient foam material and having an outline shaped for incorporation in the footwear; and a bottom layer made of a fibrous mat and having a shape conforming with the outline of the upper layer, the fibrous mat comprising: a multiplicity of fibers, a fraction of which penetrates the foam material of the upper layer for bonding the bottom layer to the upper layer; and a stiff portion for providing stiffness to the insole.

Preferably, the upper layer has an outer surface opposed to the bottom layer, and each of the fibers of the fraction penetrating the foam material emerges from said outer surface and thereby provides a pilosity thereon.

Preferably also, the stiff portion of the bottom layer is obtained by impregnating an outer surface of the fibrous mat with a member selected from the group consisting of a latex, a solution of thermoplastic resin and a solution of thermosetting resin.

Alternatively, the fibrous mat may comprise a plurality of constructive fibers having a given melting point and a plurality of binding fibers having a melting point smaller than the melting point of the constructive fibers,- and then the stiff portion of the fibrous mat may be obtained by subjecting an outer surface of the fibrous mat to a temperature greater than the melting point of the binding fibers and smaller than the melting point of the constructive fibers.

A further object is to propose a method of manufacturing a laminated product suitable for use in footwear manufacturing, the method comprising the steps of:

a) needling a layer made of a fibrous mat comprising a multiplicity of fibers to a layer made of a resilient foam material such that a fraction of said fibers penetrates the foam material ; and b) stiffening a portion of the fibrous mat for providing stiffness to the insole.

Advantageously, a laminated product according to the present invention is suitable for use as an insole aε well as a slip-in insole in any footwear. As can be appreciated, it takes advantage of the resilient properties of the foam and the stiffness and thermoformability of the fibrous mat and in a preferred version it also takes advantage of the comfort provided by the pilosity covering the upper layer of foam.

A non restrictive description of preferred embodiments will now be given with reference to the appended drawings .

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an insole according to a preferred embodiment of the present invention;

FIG. 2 is a side elevational cross-sectional view of the insole shown in FIG. 1; FIG. 3 is a side elevational cross-sectional view of a laminated product according to the present invention shown before the needling step of the method;

FIG. 4 is the same view as FIG. 3 showing the product after the needling step; FIG. 5 is the same view as FIG. 4 showing a layer of textile needled to the upper layer of foam,- and FIG. 6 is the same view as FIG. 5 showing the product after the impregnation of the fibrous layer with a resin.

DESCRIPTION OF PREFERRED EMBODIMENTS

Referring to FIGS. 1, 2 and also 6, the invention is generally characterized by a laminated product (2) suitable for use as an insole for a footwear. It can also be used as a slip- in insole. This product may be used flat and be cut for matching the shape of a foot. It comprises an upper layer made of a resilient foam material (4) and, if it is used as an insole as shown in FIG. 1, it also has an outline (6) εhaped for incorporation in a footwear. The product (2) further comprises a bottom layer made of a fibrous mat (10) and having a shape conforming with the outline of the upper layer (4) . The fibrous mat (10) which comprises a multiplicity of fibers (12) is needled to the upper layer (4) so that a fraction of those fibers (12) penetrates the foam material of the upper layer (4) for bonding the bottom layer (10) to the upper layer (4) . The fibrous mat (10) further comprises a stiff portion (14) for providing stiffness to the product (2) . As illustrated, the fibrous mat (10) preferably includes a non-voven mat of fibers. Each of the fibers (12) of the fraction penetrating the foam material (4) preferably emerges from the outer surface (16) of the upper layer (4) and thereby provides a pilosity (17) thereon which gives a comfortable finish to the product (2) .

Alternatively, the laminated insole (2) may further comprise a reinforcement laminate (9) embedded in the fibrous mat (10) . In other words, the fibrous mat (10) may contain in its εtructure a reinforcement fabric or laminate (9) , bonded together with the fibers during construction of the mat (10) .

The reinforcement fabric or laminate (9) may be a polypropylene scrim fabric with very small openings, or said scrim may be coated on one or both sides with a 1 to 3 mils polypropylene coating. Other coatings, scrims or films, selected

in the group of polyester, nylon, polyethylene may be used as long as they are able to resist to the temperatures found in the production process of the laminate or during production of the footwear product. An additional layer of textile (18) may also be bonded to the upper layer of foam (4) . In the embodiment illustrated in FIG. 2, the fibers (12) of the bottom layer (10) which are threaded through the upper layer (4) are used for combining this additional layer of textile (18) on the surface of the upper layer (4) . In another preferred embodiment (not illustrated) , this additional layer may also be laminated to the surface of the top layer. This additional layer (18) may comprise another nonwoven mat, a felt, a knit, a brushed cloth, synthetic fur or any other kind of textile allowing to improve the aesthetic aspect or comfort of the product.

As can be appreciated, the version of the invention illustrated in FIGS. 1, 2 and 6 takes advantage of the resilient properties of synthetic foams, the stiffness and the thermoformability of the fibrouε mat, as well as the comfort provided by the fibers needled through the foam.

These properties are obtained by having a stiff bottom layer (10) , an upper layer of a resilient synthetic foam (4) and an upper surface having a comfortable touc .

Preferably, the fibrous mat (10) comprises a plurality of fibers (12) selected in the group consisting of synthetic fibers εuch as polyester, polypropylene, nylon, etc., or artificial fibers such aε rayon, viscose, etc. , natural fibers such as wool, jute, etc., and mixtures thereof. The fibrous mat (10) may also compriεe fiberε with specific function . For example, if the fibers transferred by the needling process are electrically conductive, the product will dissipate static electricity therefrom. Advantageously, the bottom layer (10) may comprise

a small amount of electrically conductive fibers, preferably 1% to 20% in weight. These fibers have a resistivity lower than 10 ^{" 3} Ωcm and may be made of stainless steel, copper or synthetic fibers coated with a layer of nickel, silver or any other conductive metal. Carbon fibers, epitropic, or carbon coated fibers or polymeric conductive fibers can be used. For example, the fibrous mat (10) may comprise 3 to 6% of a nickel coated acrylic fibre produced for STATEX in Germany under the trademark EX-STAT. The bottom layer (10) may also comprise fibers containing agents preventing fungus or bacteria growth. These fibers will prevent any bacteria growth under the foot and are preferably selected from the group consiεting of polyester, polypropylene, acetate acrylic and the like. For example, an acetate fibre of 2 dtex manufactured by the company HOECHST under the name MICROSAFE may be suitable.

Preferably also, these fibers (12) are heat resistant. The exact composition of the fibrous mat (10) depends on the process used for stiffening the structure and the expected uεe of the multilayer product.

Preferably, the fibers (12) of the fibrous mat (10) have a size comprised between 0,7 and 25 dtex, more preferably between 1,5 and 10 dtex. Their length is preferably comprised between 25 and 150 mm, and more preferably between 38 and 100 mm. The bottom layer (10) is made by a conventional process of carding and then needling the mixture of fibers chosen. Preferably, this bottom layer (10) has a surface density compriεed between 70 and 1000 g/m ² , more preferably between 200 and 800 g/m ² . The resilient foam material of the upper layer (4) may be an opened or closed-cell synthetic foam. It preferably consists of a polymer selected from the group consisting of polyurethane,

polyester, polyether, crosε-linked polyethylene, polyvinylic chloride, and the like. Such foamε are available commercially. For example, an opened-cell polyurethane foam such as the one produced by RODGERS Co. under the trademark PORON may be used. In a first preferred embodiment, the stiff portion (14) of the bottom layer (10) is obtained by impregnating an outer surface (20) of the fibrous mat (10) with a member selected from the group consisting of a latex, a solution of thermoplastic resin and a solution of thermosetting resin. This latex or solution is then dried and cross-linked. Thiε operation gives the εtiffneεs required for an inner sole.

Preferably, the fibrous mat (10) is stiffened while keeping a good resiliency for absorbing shocks. The resin is selected in the group consiεting of acrylic, methylmethacrilate, ethylvinylacetate, polyvinyl alcohol, εtyrene butadiene resin and styrene butadiene comprising melamine formol .

The amount of resin required varies between 100 and 350 g/m ² in the dry state, preferably 150 and 250 g/m ² .

In a second preferred embodiment, the fibrous mat (10) may be stiffened by mixing constructive fibers with binder fibers. More particularly, in this case, the fibrous mat (10) comprises a plurality of constructive fibers having a given melting point and a plurality of binding fibers having a melting point smaller than the melting point of the constructive fibers. The εtiff portion (14) of the fibrous mat (10) is then obtained by subjecting the outer surface (20) of the fibrous mat (10) to a temperature greater than the melting point of the binding fibers and smaller than the melting point of the constructive fibers. By heating the fibrous mat (10) to a temperature just enough to exceed the melting point of the binding fibers, the stiffness required is obtained. Preferably, it is only the fibrouε mat (10) which is subjected to heat, while the upper part of the

structure remains at room temperature. In this way, the suppleness of the foam is kept.

The proportions of the binding fibers in the fibrous mat (10) preferably vary from 10% to 80% by weight, more preferably from 25% to 60%. These binding fibers are preferably selected from the group consisting of polyesterε or copolyesters having a low softening temperature, high or low density polyethylene, polypropylene or dual fibers of the type sheath core or side by side. For the case of sheath core fibers, the heart has a high melting point while the core comprises a polymer with a low melting point. During the heating, this core will keep the linkage between the fibers.

Referring to FIGS. 3 to 6, consecutive steps of a preferred version of a method of manufacturing a laminated product suitable for use in footwear manufacturing are illustrated. The method comprises the steps of a) , needling a layer made of a fibrous mat (10) comprising a multiplicity of fibers (12) to a layer made of a resilient foam material (4) such that a fraction of said fibers (12) penetrates the foam material (4) . FIG. 3 shows the fibrous mat (10) and the layer of foam (4) before the needling step and FIG. 4 shows the same layers after the needling step. Preferably, aε illuεtrated in FIG. 5, in step a) , the fraction of the fibers (12) which are threaded through the foam material (4) may also be used for comt ning an additional layer of textile (18) as described hereinbefore. This additional layer (18) may alεo be laminated to the product by using conventional laminating methodε. The method further comprises the step of b) , stiffening a portion of the fibrous mat for providing stiffness to the insole, as shown in FIG. 6, and then step c) , if the product is going to be used as an insole, of forming an insole having an outline εhaped for incorporation in the footwear.

The fibrous mat (10) and foam material (4) used are preferably aε the fibrouε mat and foam material described hereinbefore ,

Preferably, after stiffening the bottom portion of the laminate by methods described in the invention, an additional step of calendering may help make denser a fibrous mat (10) reinforced with a reinforcement fabric (9) in order to achieve a Frazier air permeability smaller than 5 cubic feet per minute. Such a laminate iε well suited for construction of footwear by injection molding of thermoplastic, rubber, polyurethane, or polyvinylchloride soles directly against the insole described in the invention.

As can be appreciated, the method consists in transferring a portion of the fibers (12) contained in the bottom layer (10) through the upper layer (4) by means of needles provided with barbs. The amount of transferred fibers (12) may be adjusted by controlling the number of penetrations per square centimeter and controlling the depth of the needle into the foam (4) .

Preferably, the threaded fibers emerge from the outer surface (16) of the upper layer (4) and therefore these fibers are visible on the surface of the upper layer (4) and are forming a pilosity (17) thereon.

This pilosity (17) on the surface of the upper layer (4) provides a comfortable finish to the product. It also allowε eaεy diεεipation of the perspiration and moisture therefrom. Furthermore, the fibers (12) which are threaded through the upper layer (4) improve the transfer of perspiration and moisture from the foot towards the bottom layer (10) where it could be disεipated. If the fibers (12) brought to the outer εurface (16) of the upper layer (4) are electrically conductive fibers or the fibers preventing bacteria growth, these fibers on the surface of the top layer (4) allow either to dissipate

static electricity, provide a link between the sole and the foot, or prevent bad odours due to bacteria growth.

Preferably, the stiffening of step b) comprises the steps of: - partially impregnating the fibrous mat (10) with a member selected from the group consisting of a latex, a solution of thermoplastic resin and a solution of thermosetting resin;

- heating the fibrous mat (10) to a temperature compriεed between 100°C and 200°C, preferably between 130 to 180°C and for a time εufficient to allow the evaporation of the dispersion solvent and the reticulation of the resin; and

- cooling the fibrous mat (10) .

FIG. 6 shows the laminated product (2) after it haε been made stiff by partially coating the fibrous mat (10) with a latex or a solution comprising a synthetic resin. The dispersion beforehand transformed into foam is pushed into the non woven mat (10) by means of a scrape or any other process allowing an impregnation at a predetermined depth in the non woven fibrous mat (10) . The fibrous mat (10) is then subjected to a temperature comprised between 100 to 200°C, preferably between 130 to 180°C for a time sufficient to allow the evaporation of the dispersion solvent and the reticulation of the resin. After cooling, the stiffnesε obtained iε controlled by measuring the bending reεistance of the structure. Preferably for the embodiment illustrated in FIG. 6, the upper layer (4) compriseε a foam made of polyurethane which is not deteriorated through this process .

Preferably, the fibrous mat (10) iε impregnated with a resin in an amount comprised between 100 and 350 g/m ² of fibrous mat, and more preferably between 150 and 250 g/m ² .

Alternatively, the εtiffening of step b) may be performed with a process which does not use binders in the form of

disperεion. In this case, and as described hereinbefore, the fibrous mat (10) comprises a plurality of constructive fibers having a given melting point and a plurality of binding fibers having a melting point smaller than the melting point of the constructive fibers, and wherein the stiffening of step b) compriseε the stepε of:

- εubjecting for a given time an outer surface (20) of the fibrous mat (10) to a temperature greater than the melting point of the binding fibers and smaller than the melting point of the constructive fibers; and

- cooling the fibrouε mat (10) .

As for the other preferred embodiments, the fibrouε mat

(10) may alεo comprise conductive fibers or fibers preventing bacteria growth. This embodiment is stiffened by transferring heat to the fibrous mat (10) preferably by means of a system consiεting of two continuous bands. One band is heated to a temperature sufficient for softening the binder fibers. The other band is maintained at room temperature and is kept at a distance which is equal to or slightly inferior to the width of the structure. The structure has to be maintained at the softening temperature for a time long enough for allowing heat to penetrate into the width of the fibrous mat (10) without heating or softening the upper layer (4) . Other heating techniques may be used for heating the fibrous mat (10) . For example, radiation, convection or induction techniques may be used.

A laminated product (2) according to the present invention may afterwards be thermoformed into a desired shape, aε illuεtrated in FIG. 6. Although preferred embodimentε of the invention have been described in detail herein and illustrated in the accompanying drawings, it is to be understood that the invention is not

limited to these precise embodiments and that various changes and modifications may be effected therein without departing from the scope or spirit of the invention.