TECHNICAL FIELD This invention is concerned with reinforcing/ stiffening materials, e.g. for use in the manufacture of shoe upper components.

BACKGROUND ART Such materials are known comprising a fabric layer impregnated with an impregnant which provides the desired degree of stiffness in the material. In addition, the impregnant may also, when activated, provide surface tackiness sufficient to cause a reinforcing/stiffening component cut or otherwise made from the material to adhere to and bond with another component or other components; alternatively the impregnated material may be provided with a surface coating of a suitable adhesive which is activated, e.g. when the material itself is activated.

In the case of shoe upper components, e.g. so- called toe puffs (or box toes) and counters (or heel end reinforcements) the purpose of activation is to render the component sufficiently flaccid to conform to the shape of the shoe last about which the shoe upper incorporating the ^" reinforcing/stiffening component is drawn. In addition, if the component has a surface coating or indeed incorporates an adhesive, the effect of activation is also to activate the adhesive to cause the reinforcing/stiffening component to adhere to the or each other shoe upper component juxtaposed thereagainst.

Reinforcing/stiffening materials of the aforementioned type are conventionally either heat- activated or solvent-activated.. Reinforcing/stiffening components made of heat-activatable materials are usually activated by radiant heat, e.g. so-called flash heaters, or by conducted heat, e.g. in so-called conditioning machines in which the shoe upper incorporating the reinforcing/stiffening component is subjected to a steam

treatment or is clamped between heated clamp members. In addition, it is known to immerse such reinforcing/ stiffening components in hot water which also has the effect of conditioning the material of the component thus to render it flaccid for subsequent insertion into a shoe upper. It will of course be appreciated that no chemical reaction takes place between the impregnant and the water, but rather merely the heat of the water affects the condition of the impregnant. In the case of solvent-activation, in general the solvents used are toxic and/or inflammable, so that increasingly restrictions are being applied on their use and indeed on their general handling, both during their use and also subsequently, and storage. For these and other reasons, therefore, the use of such solvents for activation purposes is becoming progressively less attractive, although in many instances, because heat necessarily requires energy (even when the heat is provided by hot water) , in many instances the substitution of heat-activated materials for solvent- activated ones is not practicable.

It is one of the objects of the present invention to provide an improved reinforcing/stiffening material activation of which can be achieved without the use of heat and without the use of a toxic and/or inflammable solvent.

DISCLOSURE OF THE INVENTION The invention provides a reinforcing/stiffening material comprising a fabric layer impregnated with an impregnant comprising a stiffening component and a water- soluble component in quantities' such that when the material is immersed in water it is rendered flaccid and hardens to a stiffening consistency when dried.

It will of course be appreciated that by using water as the solvent, the problems of the use of toxic and/or inflammable solvents is dispensed with, and in

particular the problems of disposal of the solvent after use are mitigated, if not indeed eliminated, because the water is generally innocuous.

Preferably the impregnant comprises 10 to 50% by dry weight water-soluble component and up to 60% by dry weight stiffening component. Moreover, in one embodiment the impregnant comprises not less than 30% by dry weight water-soluble component, which component additionally is rendered adhesive when immersed in water. in another embodiment, on the other hand, the impregnant comprises up to 15% by dry weight water-soluble component, in which case an adhesive surface coating may be applied to one or both sides of the material.

In the material in accordance with the invention preferably the stiffening component comprises one or a combination of the following: polyvinyl acetate or one or more copolymers thereof, polyvinyl pyrolidone, one or more acrylates, one or more methacrylates, and styrene-butadiene rubber, while the water-soluble component preferably comprises one or a combination of the following: polyvinyl alcohol, one or more soluble acrylates, one or more soluble methacrylates, starch and dextrin.

Moreover, the impregnant may further comprise a hardening component which undergoes a chemical reaction when immersed in weak acid solution whereby it is rendered flaccid when in a wetted state and dries to a hardened condition; in this latter case, the impregnant preferably comprises up to 60% by dry weight hardening component. More particularly, in such a case the hardening component undergoes a chemical reaction when immersed in a solution of citric acid or boric acid or when immersed in water in which latent acids are present. Suitable hardening components include one or more amino resins, e.g. melamine-formaldehyde resins and urea- formaldehyde resins.

The impregnant may of course also comprise a filler by which the water absorption rate of the material is enhanced, and an additive or additives for limiting the amount of water taken up by the material. It has been found that, using a reinforcing/ stiffening material in accordance with the invention, or a reinforcing/stiffening shoe upper component cut or otherwise made from such material, appropriate softening of the material can be achieved by immersion in water or, in the case of the second embodiment referred to above, in a weak acid solution, thus rendering the material or upper component sufficiently flaccid to be moulded to the shape of a former, e.g. a shoe last, and furthermore upon drying out or being force-dried the material or upper component becomes hard and thus affords a suitable reinforcing/stiffening function. Moreover, in the case in particular of the second embodiment referred to above, by reason of the presence of the hardening component a substantially irreversible hardening takes place so that subsequent immersion in water will no longer affect significantly this reinforcing/stiffening function. BEST METHOD OF CARRYING OUT THE INVENTION

There nov. ^τ follow three Examples of reinforcing/ stiffening materials in accordance with the invention. t will of course be appreciated that these Examples have been selected for description merely by way of non- limiting examples of the invention.

Example I A reinforcing/stiffening material suitable for use e.g. in the manufacture of shoe upper components, more especially a so-called toe puff material, comprised a non-woven felt weighing in the order of 220g/m ² impregnated with an impregnant of approx 550g/π-2. The thus impregnated material weighed approx 770g/m2 and had a thickness in the order of 1.55mm.

In the finished material the impregnant comprised the following constituents (in proportions by weight) :

Viking 1605 (polyvinyl acetate) 43.0%

Emulvin (surfactant/stabiliser) 0 1%

Revinex 9042 (styrene-butadiene rubber) 8.5%

Gohsenol GL03 (polyvinyl alcohol) 34.0%

Paracol 845N Wax 0.5% Speswhite Clay (China clay filler) 13.0%

In manufacturing the impregnant the various components were mixed in a mixing chamber containing water. The surfactant was diluted in a 44% dispersion and the polyvinyl alcohol in a 30% solution. The water in the mixing chamber weighed 8% of the total wet weight. A pH adjuster, in the form of an ammonia solution, was also added. The filler was in a 60% dispersion.

When the impregnant was fully mixed, the fabric was impregnated in an impregnant/fabric ratio of 2.5:1.

In use toe puffs cut from the finished material were immersed in water for a period sufficient to enable the polyvinyl alcohol, which is relatively brittle when dry, to absorb water and become soft, thus rendering the whole material flaccid. The wax served to limit the water absorption, the filler to control the rate of absorption.

When the toe puffs were suitably flaccid they were inserted into lined shoe uppers, between the lining and the outer layer, and the thus combined upper was then lasted over a shoe last to cause the toe end of the upper, incorporating the toe puff, to conform to the shape of the toe end of the last. The toe puff was then dried out while retained thus conformed and hardened to the shape when dry.

It will of course be appreciated that by

varying the relative quantities of polyvinyl acetate and styrene-butadiene rubber it is possible to vary the brittleness/flexibility of the toe puff in its hardened condition. By reason of the relatively high content of polyvinyl alcohol, moreover, and the fact that when immersed in water it becomes tacky and adhesive, in using a toe puff cut from the material its surfaces are rendered tacky and adhesive as well as its being rendered flaccid when immersed in the water.

Example II A reinforcing/stiffening material for use e.g. in the manufacture of shoe upper components, more especially a so-called toe puff material, comprised a non-woven felt, in this case weighing in the order of

180g/m2 impregnated with an impregnant of approx 450g/m2.

The impregnated material thus weighed approx 630g/m2 and had a thickness in the order of 1.40mm. in the finished material the impregnant comprised the following constituents (in proportions by weight) :

Emulvin W (surfactant/stabiliser) 0.4% BT 970 (urea-formaldehyde resin) 42.0%

Acronal S886S (hard acrylate) 10.4%

Speswhite Clay (China clay filler) 9.5%

Gohsenol GL03 (polyvinyl alcohol) 34.0%

Revinex 9042 (styrene-butadiene rubber) 3.5% Paracol 845N Wax 0.2%

When the impregnant was fully mixed the fabric was impregnated in an impregnant/fibre ratio of 2.5:1.

In use toe puffs cut from the reinforcing/ stiffening material were immersed in a weak acid solution, preferably an organic acid; a suitable acid was

citric acid. The material was immersed until rendered suitably flaccid, whereafter the toe puff was inserted between the lining and outer of a shoe upper, and the forming process was continued as described with reference to Example I.

The effect of the acid solution on the urea- formaldehyde resin was to cause cross-linking to take place whereby a much stiffer toe puff resulted than was the case of Example I.

Example III This material was generally similar to that of Example II except that the polyvinyl alcohol content was reduced. This was found to have the effect of reducing significantly the adhesiveness of the surface of cut toe puffs when immersed, which thus enabled the toe puffs to be used in conjunction with shoe uppers without linings. A bonding agent was used in this case in the form of a surface coating of adhesive applied to one surface only of the material, providing the desired adhesion to the outer shoe upper component. The surface-coated adhesive was a polycaprolactone, applied in powder form and fused, but any suitable adhesive could be used. It should be noted that the adhesive must not form a barrier coating to water absorption.

If desired, the material could be coated on both surfaces with adhesive.

The particular composition used in this Example for the impregnant comprised (in proportions by weight):

Emulvin W (surfactant/stabiliser) 0.5%

BT 970 (urea-formaldehyde resin) 57.5%

Acronal S886S (hard acrylate) 14.4%

Speswhite Clay (China clay filler) 12.9% Gohsenol GL03 (polyvinyl alcohol) 9.6%

Revinex 9042 (styrene-butadiene rubber) 4.8%

Paracol 845N Wax 0.3%