GB2024279A - A stiffening shoe inner material, the heel region of a shoe comprising this material, and a process for stiffening the heel region of shoes - Google Patents

Abstract

A sheet-form or piece-form, stiffening shoe inner material is adapted for the heel region of a shoe and is capable of being processed thermoplastically or by solvent action, the shoe inner material comprising a single-layer fibrous structure charged or filled with at least one plastics material having a stiffening effect at normal temperature up to about 60 DEG C in a quantity of from 0.1 to 0.9 kg per square metre of fibrous structure. The heel region of the shoe consists of only two layers (upper material and the new shoe inner material) instead of the conventional three layers (upper material, rear cap and slip strap).

Description

SPECIFICATION A stiffening shoe inner material, the heel region of a shoe comprising this material and a process for stiffening the heel region of shoes The present invention relates to a new stiffening shoe inner material and to a heel region of normal sturdy walking shoes comprising this shoe inner material. It does not relate for example to light, unlined shoes and/or to shoes without a stiffening cap in the heel region.

The heel region of normal sturdy walking shoes consists of at least three formed layers: first the shaft or shaft material (also known as the upper material), second the stiffening cap or the stiffening material (also known as the rear cap or rear capping or capping in short) and third the slip strap or slip strap material. This list does not include the usual adhesive layers.

The new shoe inner material intended for stiffening the heel region of walking shoes is best produced in sheet form and used in the form of pieces cut to size therefrom. It is thermoplastic, i.e. heatformable, or can be softened by the action of solvents. It consists of a single-layer fibrous structure, i.e. it does not have a multilayer structure, which is charged or filled with at least one plastics material having a stiffening effect at normal temperature (about 15 to 25"C) up to about 60"C in a quantity of from 200 to 800 g per square meter of the fibre structure, the charge optionally containing fillers, dyes, pigments, plasticisers, stabilisers, blowing agents, processing aids and/or known extenders in conventional quantities.The shoe inner material is advantageously fine-pored, porous and absorbent to water and solvents.

Accordingly, the present invention relates to a sheet-form or piece-form, stiffening shoe inner material adapted for the heel region of a shoe and capable of being processed thermoplastically or by solvent action, said shoe inner material comprising a single-layer fibrous structure charged or filled with at least one plastics material having a stiffening effect at normal temperature up to about 60"C in a quantity of from 0.1 to 0.9 kg per square metre of fibrous structure.

One of the large-surface sides of the sheet or cutting of shoe inner material is provided with a layer based on a plastics material capable of being tackified by the action of heat or by the action of a solvent or solvent mixture, preferably a thermoplastic plastics material. To enable the effect of the slip strap material hitherto used in the manufacture of shoes to be obtained with the new shoe inner material as well, its surface has a non-slip finish or character. Accordingly, the surface of the new material has a certain roughness which prevents the heel from slipping out or at least makes it difficult for the heel to slip out.It is particularly advantageous to provide that side of the new material which comes into contact with the heel or stocking with a velvetlike character by mechanically treating the surface in question, for example by grinding using suitable known machines (grinding rollers).

The above-described shoe inner material is incorporated into the heel of the shoe and fixed there, best by bonding. Surprisingly and contrary to the structure of conventional walking shoes, the new shoe inner material replaces both the function of the stiffening shoe capping and the function of the slip strap which is intended to prevent the heel from slipping out of the rear part of the shoe. This dual function of the new shoe inner material considerably simplifies the manufacture of shoes and reduces manufacturing costs, which would appear to be of particular advantage to show production in the developing countries. The hitherto long-established practice of using both flexible slip strap material and also stiffening capping material in the manufacture of shoes may now be surprisingly changed and considerably simplified by virtue of the present invention.The present invention eriables above all plain shoes to be more economically produced.

Accordingly, the new heel region of a shoe provided by the present invention no longer has the conventional separate rear cap and consists of the last-formed cutting of shoe inner material of the type described above and the shaft bonded thereto.

The present invention also provides a process for stiffening the heels of shoes which is characterised in that, for simultaneously stiffening the heel region and producing the slip strap effect, a suitable cutting of the new deformable shoe inner material is attached, stitched or similarly fixed to the upper edge of the inside of an unlined upper material shaft, the inside of the cutting being coated with adhesive where the shoe inner material which is not provided with a tacky layer is used, after which the assemblage is formed on the last by the action of heat and, optionally, pressure and hence is also bonded.

Where the shoe inner material has been provided on one side with a dry, i.e. non-tacky, but activatable layer of adhesive and cut to size for use, the stiffening process described above may be varied and simplified by softening the cutting of shoe inner material attached or stitched to the shaft by means of a solvent or solvent mixture and at the same time tackifying the layer of adhesive and then forming the shaft and cutting of inner material on the shoe last in the conventional way, the shaft and cutting being bonded at the same time. The solvent or solvent mixture may readily be applied, for example, using a brush, to that side of the shoe inner material which is not coated with the adhesive, after which the solvent (mixture) gradually diffuses into and through the shoe inner material, softens it and then also activates the adhesive layer.Thus, providing the solvent or solvent mixture is suitably selected, there is enough time for the softened cutting of shoe inner material to be formed with the shaft in the conventional way and at the same time bonded. The cutting of shoe inner material may also be simply immersed in the solvent (mixture) in such a way that only the cutting and not the shaft is wetted by the solvent, after which it is formed and bonded in the manner described.

The new shoe inner material shows very good strength properties both in dry form and in wet form and high dimensional stability, even after the influ ence of moisture. Its abrasion resistance, water absorption and release (comparable with the absoprtion and release of foot perspiration) and stitch uprooting resistance are also very good. The new shoe inner material also shows favourable stress-strain behaviour and low swelling and shrinkage valuers. All these valuable properties make the new material particularly suitable for use as a shoe inner material.

The fibrous structures used are woven fabrics, knitted fabrics, non-woven fabrics and, preferably, fleeces of natural or synthetic fibres, such as cotton, wool, synthetic wool, rayon and/or synthetic fibres of poiyamide, polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, polypropylene and, in particular, polyesters such as polyethylene glycol terephthalate. The fibrous structures have a weight per square metre of from 80 to 500 grams, preferably from 150 to 400 grams. In the case of fleeces, the weight per square metre is from 150 to 400 grams.

The stiffening plastics suitable for charging are, in particular, polymers of styrene and copolymers of styrene and butadiene, also polyvinyl chloride, polyvinyl acetate, polyvinylidene chloride, vinyl chloride/ vinyl acetate copolymers and similar known polymers. They are used in such a quantity that, finally, the charge amounts to from 0.1 to 0.9 kg, preferably from 0.2 to 0.7 kg per square metre of fibrous structure (dry weight without the weight of the fibrous structure). The above-mentioned plastics may also be advantageously used together with known natural resins such as colophony, or synthetic resins such as urea formaldehyde or melamine formaldehyde resins or their pre-condensates and/or with polyvinyl alcohols, above all largely to completely saponified types.

In addition, fillers such as kaolins, chalk, talcum, clays, silica fillers, siliceous chalk, kieselguhr and, optionally, titanium dioxide, carbon blacks and other pigments may also be used for charging in a quantity of from 10 to 200 parts by weight and preferably in a quantity of up to 80 parts by weight, based on 100 parts by weight of the polymer. Other auxiliaries which may additionally be present in the charge are dyes, pigments, plasticisers, stabilisers, blowing agents, processing aids and/or extenders used in the conventional quantities.The mixture intended for charging has to be selected according to the composition, the quantity of the constituents and their form, for example as a dispersion, paste or dough, in such a way that the charged or filled and dried fibrous structures are stiff-elastic and relatively hard at normal temperatures up to about 60"C. To this end, polystyrene and copolymers of styrene and butadiene having a styrene content of from 85 to 60 and from 40 to 20% by weight, the remainder being butadiene, are preferably used as the plastics material in a quantity of from 250 to 600 grams per square metre of fibrous structure. The styrene-butadiene copolymers may advantageously be so-called carboxylated types, i.e. copolymers containing carboxyl groups in the molecule. The charging mixture is best in the form of a pasty coating composition.

The solvents which soften the shoe inner material and, optinally, the adhesive layer are conventional volatile organic compounds which are liquid to thinly liquid at room temperature, for example ketones, esters, volatile hydrocarbons such as petrol and benzene, alcohols, tetrahydrofuran, ethers and mixtures thereof, particularly methyl propyl ketone, ethyl butyl ketone, methyl isobutyl ketone and methyl-n-butyl ketone. It is preferred to use methyl ethyl ketone.

The plastics material intended for the adhesive layer which is capable of being tackified by the action of heat or by solvent action is preferably a thermoplastic plastics material. Accordingly, the adhesive is based on polychlorobutadiene, polyvinyl acetate, polyacrylates, nitrile rubber or preferably on ethylene/vinyl acetate copolymers. If desired, it is possible, often advantageously to add other resins to this adhesive base, for example natural resins, phenolic resins, maleate resins, modified colophony resins or similar known resins, in the conventional quantities, The adhesives are coated onto the shoe inner material or the cutting thereof in a suitably prepared form, for example in admixture with solvents or as a dispersion. This may be done by machine immediately after production of the sheet-form material.

Alternatively, the cutting may be coated with the adhesive preparation during production ofthe shoe.

In the latter case, bonding may be carried out immediately. If the shoe inner material already has a dried adhesive layer, the adhesive may be reactivated by heat or solvent action as described above.

The fibrous structure is charged by impregnation or coating, the charging composition being accommodated in a tank through which the fibrous material is passed. Charging may also be carried out by coating, in which case the fibrous structure is placed on a rubber blanket. Alternatively, it is even possible to use a coating knife of the type normally used for coating purposes, in which case a charging composition of suitably adjusted viscosity is used. The required amount of coating is adjusted and hence the required total weight of the shoe inner material (in grams per square metre of surface area) obtained by suitable means, such as squeezing rollers or stripping blades.

The charged fibrous structure is preferably dried on heated drying rollers arranged one behind the other or in drying tunnels or drying chambers. The travelling sheet or web may be laterally guided by known needle or clip chains.

In addition to the methods described above, the layer of adhesive to be applied to one side of the charged or coated sheet may also be applied by ' melt-coating, spray-coating, knife-coating, or powder-coating, the plastics material having to be distributed in the form required for each of the abovementioned variants of the process, for example in the form of a powder, a granulate or a paste (dispersion).

In order to finish or improve the surface of the sheet, the sheet may be smoothed by treatment with a heated roller, by pressure, heat or similar known processes or, preferably, it may be prepared by a mechanical treatment, such as grinding. By grinding (preferably using abrasive paper or sand paper), the sheet is advantageously provided with a particularly uniform velvet-like surface.

After production in a sheet form, the new shoe inner material is best cut into squares measuring 1 x 1 metre for example or into suitable portions forthe shoe. The shoe manufacturer generally prefers to produce the portions from the squares himself, for example by punching according to his slip strap model.

In many cases, these cuttings are processed without trimming, i.e. without removal of the sharp edges formed by punching. The ability of the material to be trimmed without difficulty is a significant advantage because trimmed cuttings or punchings are generally required for processing because they improve the appearance and the wearing properties of the shoe. Trimming is carried out either solely along the upper line or even at the sides. The portion thus formed is then stitched into the shaft either solely along the upper line or even at the sides. It is optionally joined to the shoe inner lining as well.

This is followed by pre-forming using a so-called pre-forming machine accompanied by bonding using the heated lasts. The adhesive used is activated by the heat applied.

If no pre-forming machines are available, last forming may even be carried out by wetting the cutting with one of the above-mentioned organic solvents or with a mixture of solvents, as a result of which it becomes soft and supple, followed by shaping.

Production of the shoe is then completed in the conventional way.

The finished shoe having the new shoe inner material is distinguished by a slender heel which follows the contour of the last used for its production. The valuable advantage lies in the fact that, instead of the conventional three layers (upper material, rear cap and slip strap), only two layers (upper material and the new shoe inner material) form the heel region of the shoe.

The present invention is illustrated by the following Examples.

Examples The following mixtures were prepared as a charging composition for the subsequent coating impregnation or saturation of a fibrous structure. To this end, the individual constituents of the mixture were combined in the order indicated with slow stirring, and stirring was continued at room temperature until the mixture was completely homogeneous.

The parts quoted in the following are always parts by weight.

I 1. 75.0 parts of an aqueous dispersion of a styrene homopolymer having a dry substance content of 50% by weight and a pH-value of 11.5; the styrene polymer itself had a softening temperature of approximately 105"C and formed a continuous film at 185"C (film-forming temperature), 2. 23.0 parts of an aqueous colloidal dispersion of poly-2-chlorobutadiene having a polymer content of 58% by weight and a pH-value of 13.0; the poly-2-chlorobutadiene itself is a type having only a minimal tendency to crystallise and has a mean particle size in the dispersion of about 1 60cm, 3. 2.0 parts of a plasticiser/emulsifier mixture of 60.0 parts of dibutyl phthalate, 5.0 parts of a commercial emulsifier (OFA-emulsifier, a product of Chemische Werke Huls A.G., Marl, Germany) and 4. 35.0 parts of water.

II 1. 85.0 parts of an aqueous dispersion of a carboxylated styrene-butadiene copolymer having a dry substance content of 50% by weight and a pH-value of from 8.0 to 9.0 prepared from a copolymer having a styrene content of 81% (Dow Latex 241, a product of Dow Chemical S.A. Europe of Zurich, Switzerland) and 2. 15.0 parts of a natural, crystalline finely ground calcium carbonate (Calcipone, a product of Hans Muller, Dusseldorf, Germany).

Ill 1. 14.0 parts of an aqueous dispersion of a carboxylated styrene-butadiene copolymer (same dispersion as in 11.1).

2. 50.0 parts of an aqueous dispersion of a carboxylated styrene-butadiene copolymer having a dry substance content of 48% by weight and a pH-value of from 8.0 to 9.0 prepared from a copolymer containing 63% of butadiene (Synthomer Latex 9340, a product of Synthomer Chemie GmbH, Frankfurt-on-Main, Germany), 3. 5.8 parts of a water-containing precondensate or urea and formaldehyde (Urecoll 181, a product of BASF A.G., Ludwigshafen, Germany) having avis- cosity of from 5 to 8 Pa.s (as measured in accordance with DIN 53015 on a 4% aqueous solution), a dry substance content of 70% by weight, a density of 1.3 and a pH-value of from 8.0 to 9.0, the precondensate (as dry substance) having a nitrogen content of from 18to 19% by weight.

4. 1.2 parts of aluminium chloride and 5. 29.0 parts of a natural, crystalline, finely ground calcium carbonate (same product as in 11.2.).

a) The charging composition according to I. was applied to a travelling fleece by means of an impregnating apparatus (consisting of an impregnation tank filled with composition 1., an immersed guide roller and a pair of metering rollers on the edge of the tank). This fleece was a standard endless-fibre fleece of 3.5 dtex thick fibres of polyethylene glycol terephthalate held together by known binders and weighed approximately 180 g/m2. The charged fleece was then dried at a temperature increasing to about 130 C until constant in weight and subsequently reduced to a thickness of approximately 1.5 mm by means of a standard roll calendar. The total weight of the finished material now amounted to 750 glm2, corresponding to a charge of 570 g/m2.

The material had a pleasant uniform appearance (over its entire surface) and the required feel which proved to be non-slip and felt slightly rough.

About half the meterage of this material was then ground on one of the large-surface sides by means of a standard roller grinding machine of which the grinding rollers were lined with an emery paper having a particle size of 120 meshes.

In this way, the ground surface of the material was given a pleasant, velvet-like character. This material is best processed in such a way that the ground side, subsequently incorporated in the shoe, faces the heel or the stocking.

b) The charging composition according to II. was applied to a woven fabric of the following type and composition by means of a standard coating machine: synthetic wool cross twill roughened on both sides; weight approximately 250 g/m2; filament density 27/19 filaments per cm.; yarn count = 28/14.

The charge amounted to 500 g/m2. Final weight of the finished material 750 g/m2; thickness 0.90 mm. It is eminently suitable for use as a stiffening and slip-strap material for shoes.

c) The charging composition according to Ill. was applied to a woven cotton fabric roughened on both sides (weight 250 g/m2; filament density 17/15 filaments per cm; yarn count = 34/8; calico weave) using a standard coating machine. After drying and calendering, the fabric weighed 780 g/m2, had a thickness of 1 mm and was ideally suitable for stiffening the rear caps of shoes.

d) The charging composition according to Ill was coloured by the additional incorporation of a mixture of pigments consisting of 140 grams of brown, 120 grams of yellow and 19 grams of black (Vulcanosol pigments, products of BASF A.G., Ludwigshafen, germany) per kg of the charging composition. The composition thus coloured was applied to the above-described endless fibre fleece in such a quantity that the charged, dried material weighed 750 m2/g. Calendaring produced a thickness of approximately 1.1 mm. The material was then ground on one side, as described in a), as a result of which it became more uniform in appearance and less rough in feel.

For incorporation into the shoe, blanks were punched from the sheet cut into squares and "trimmed" on one side. These blanks were incorporated into the heel region of the shoe, providing it with a permanent heel form following the contour of the last used. At the same time, the heel was prevented from readily slipping out of the shoe.

e) The shoe inner material described above in a) being roughened on one side was coated on the other side with a layer of adhesive having the following composition: 1) 22.0 parts of an ethylene/vinyl acetate copolymer (containing 40% of vinyl acetate; melt index 2.5 [grams per 10 minutes at 190"C/2.16 kp load]; Mooney viscosity ML4 = 20), 2) 16.5 parts of a terpene-phenol resin (melting range 120-130"C; acid number 60-70, determined as milligrams of KOH per gram of solid resin), 3) 16.5 parts of a maleate resin (melting range 108-118"C, acid number 120, determined as described above) and 4) 45.0 parts oftoluene as solvent for 1) to 3).

The toluene solution was applied to the moving sheet by means of a standard knife coater and dried on a following tenter frame. After evaporation of the toluene, an increase in the weight of the sheet of approximately 100 grams per square metre was observed.

The dry adhesive layer is readily activated by the action of heat or by solvent action. During processing, the punched and trimmed blank,.which also becomes soft and formable, is formed (on the last) simultaneously with this activation of the adhesive, which represents an advantageous simplification of the production process.

Claims (11)

1. A sheet-form or piece-form, stiffening shoe inner material adapted for the heel region of a shoe and capable of being processed thermoplastically or by solvent action, said shoe inner material comprising a single-layer fibrous structure charged or filled with at least one plastics material having a stiffening effect at normal temperature up to about 60"C in a quantity of from 0.1 to 0.9 kg per square metre of fibrous structure.

2. A shoe inner material as claimed in Claim 1, wherein one of the large-surface sides of the sheet or piece cut therefrom is provided with a layer based on a plastics material capable of being tackified by the action of heat or by the action of a solvent or solvent mixture.

3. A shoe inner material as claimed in Claim 2, wherein the plastics material is thermoplastic.

4. A shoe inner material as claimed in any of Claims 1 to 3, wherein it has a non-slip surface character.

5. A shoe inner material as claimed in any of Claims 1 to 3, wherein that side of the material which is not provided with the tacky layer or which is not intended to be coated with the adhesive layer has a velvet-like surface character which is produced by a mechanical treatment.

6. A shoe inner material as claimed in any of Claims 1 to 5 which also comprises one or more fillers, dyes, pigments, plasticisers, stabilisers, blowing agents, processing aids and/or extenders in conventional quantities.

7. A shoe inner material substantially as described with particular reference to the Examples.

8. A process for stiffening the heel region of a shoe and producing the slip-strap effect which comprises securing a cutting of a deformable shoe inner material as claimed in any of Claims 1 to 7 to the upper edge of the inside of an unlined upper material shaft, and applying a layer of adhesive to the inside of the cutting directed towards the shaft where the shoe inner material is used, the assembly then being formed and bonded on the last by the action of heat and, optionally, pressure.

9. A process for stiffening the heel region of a shoe and producing the slip-strap effect which comprises securing a cutting of a deformable shoe inner material as claimed in any of claims 2 to 7, to the upper edge of the inside of an unlined upper material shaft coating the assembly with, or briefly immersing the assembly in a solvent or solvent mixture on the adhesive-free side, forming on the last after the resulting softening of the shoe inner material and the plastics layer thus takified, fixing and bonding in the form by evaporation of the solvent.

10. A process for stiffening the heel region of a shoe and producing the slip-strap effect substantially as described with particular reference to the Examples.

11. A heel region of a shoe consisting of two layers, one layer being the last-formed cutting of shoe inner material as claimed in any of claims 1 to 7, and the other layer being the shaft firmly bonded thereto.