CS265217B2 - Hardening material for shoes and process for preparing thereof - Google Patents

Abstract

The solution concerns a new kind of bracing material with melting properties footwear adhesives and parts of footwear, consisting of from a carrier material that is double-sided provided with a hot melt adhesive layer. The essential feature of the solution is that carrier material and hot melt adhesive layer They are porous flexible, leaving a melt layer adhesives consist of polycaprolactone, especially from a mixture of 60 to 95 wt. polycaprolactone with molecular weight 45 000 and 40 to 5 wt. polycaprolactone with a molecular weight of 35,000 and weight the ratio of carrier material to hot melt adhesive from 3: 1 to 1: 1, especially from 1.8: 1 to 1: 1; 2.2: 1. Carrier material and melt layers adhesives do not form a film, or only form it to a small extent and the material solidifies after processing when the hot-melt adhesive is activated.

Description

It is an object of the present invention to provide a new type of reinforcing material having hot melt adhesive properties for shoes and parts of shoes, as well as a method for producing the same.

Materials for stiffening footwear have been known for a very long time, the advantage being made in the form of a strip and the blanks made therefrom are used to stiffen the shoe part of the shoe or the toe of the shoe. The blanks may be shaped and adhered to the upper of the shoe and / or the lining material of the shoe by the action of solvents or heat. After shaping and cooling, and optionally after evaporation of the solvent, the reinforcing material is intended to ensure both the good shape of the shoe and the corresponding shape of the shoe. good product flexibility.

The reinforcing material which can be activated by means of solvents is the subject of U.S. Pat. No. 2,840,492. The reinforcing material described herein and used for many years consists of a fibrous material which is impregnated with a mixture consisting of polystyrene and styrene-butadiene copolymers. An essential feature of this material is that the styrene content of the copolymers is greater than 50% by weight. and the ratio of styrene to butadiene in the total mixture is not less than 75:25 but not more than 95: 5. Furthermore, it is important that the polymer particles deposited on the fibrous material do not form a film or make it only to a small extent, so that they do not expand or melt very little. As a result, liquid solvents can rapidly enter the reinforcing material and soften the reinforcing material rapidly.

The blanks of this kind can be softened with a liquid organic solvent and start to dissolve by their action, so that when they contain the solvent they are moldable and bondable.

A deficiency of this reinforcing material is believed to be that the optimum conditions for its activation by the solvent can hardly be prepared or only at great expense. Processing of solvent-impregnated reinforcing material is unhealthy, in many cases toxic and above all time-consuming. In addition, the holding time during pressing and gluing is critical.

In Austrian patent specification 205 887, a flexible material is proposed for stiffening the toe cap which is cured only after being shaped by the treatment with curing additives, i.e. it is stiffened. Accordingly, the material can be produced by applying, for example, a mixture of soluble, curable materials which only harden afterwards and non-curable polymers based on polyvinyl chloride, polyvinyl acetate, polystyrene, etc., onto a fibrous support on which a textile grid is arranged. Among the curable materials, natural adhesives and curable precondensates of synthetic resins, for example based on formaldehyde urea, can be mentioned.

The material thus produced is flexible and capable of being stored after drying. After painting or dipping in the curing solution, the die cut front or back sticks are placed in the shoe and cured at room temperature.

In contrast to the solvent-activated reinforcing material, the flexible material according to Austrian patent specification 205 887 has the particular advantage that the shaping into the form of a finished reinforcing product, for example the heel or the toe of the shoe, is no problem with respect to its flexibility. sculpted.

However, these reinforcing materials have not proved satisfactory in all cases, in particular, poor adhesion often occurs.

Finally, U.S. Pat. No. 3,778,251 also proposes to eliminate the difficulties that arise in the processing of reinforcing materials by activating solvents, so that only those materials which consist of a carrier impregnated with a thermoplastic material whose particles are used as reinforcing materials in the footwear industry are used. it does not form a film or produces it only to a very small extent and which is provided on at least one side with a polycaprolactone layer. Such a material is solid and non-sticky at room temperature. It can be thermally activated so that solvent activation is not required. As is known, the polycaprolactone melts at a temperature of between 60 and 182 ° C, and in particular between 79.4 and 121 ° C, and its softening point is between 60 and 82 ° C. The polycaprolactone layer forms a film.

According to a particularly preferred embodiment described in U.S. Pat. No. 3,778,251, the impregnated material is coated on both sides with a polycaprolactone layer. This should have the advantage that, during thermal activation, the stiffening material, if any, remains both flexible and gluable with the inner lining and the upper leather. The polycaprolactone layers are film-forming, in contrast to the impregnated material.

In practice, however, it has been shown that the reinforcing materials produced according to the US patent still have significant drawbacks in the manufacture of footwear. It has also been shown that blanks of this material present considerable difficulties in insertion and shaping; The polycaprolactone layers reinforce the same impregnated carrier material in many cases so much that it is necessary to exceed the melting point of the polycaprolactone already during the insertion and shaping of the billets. Another solution: the hot-melt adhesive polycaprolactone is already liquid during the insertion and during the forming process, thus gluing the reinforcing material with the inner lining and the upper leather before it is formed.

This most often leads to the formation of so-called pockets in the region of the heel arch.

Attempts to overcome the difficulties described by the use of particularly thin polycapron layers must be marked as unsuccessful. As has been shown in such cases, the amount of polycaprolactone is not sufficient to solidify (stiffen) the impregnated carrier and, moreover, to adhere to the upper material (inner lining and upper leather).

Thereby, the task was to find a reinforcing material which is hot-melt adhesive on both sides, but which would be well deformable before the hot-melt adhesive was activated and only after its hot-melt adhesive was activated would it obtain its reinforcing properties.

The solution of the given task is based on the knowledge that the described problems can be solved by finding a reinforcing material which would have a high flexibility below the hot-melt adhesive activation temperature, i.e. which would be well deformable and only after reaching the hot-melt into a carrier material which is not film-forming or is only slightly film-forming has become rigid or elastically rigid.

The new reinforcing material for footwear consists of a carrier which is provided with a double-sided layer of hot-melt adhesive. The stiffening material according to the invention is characterized in that the carrier material and the hot-melt adhesive layer are porous and flexible, the hot-melt adhesive layers consisting of polycaprolactone, in particular a mixture of 60 to 95% by weight. % polycaprolatone having a molecular weight of 45,000 and 40 to 5 wt. polycaprolactone having a molecular weight of 35,000 and a weight ratio of carrier material to hot melt adhesive is from 3: 1 to 1: 1, in particular from 1.8: 1 to 2.2: 1. It is to be noted that the present invention is not limited to the aforementioned weight ratio.

Both textile and non-woven inserts consisting of natural or man-made fibers or mixtures thereof can be used as carrier material. Impregnation of the carrier material is not absolutely necessary, but may be carried out according to one preferred embodiment of the invention. Unimpregnated carrier materials lead to particularly well-formed and manageable reinforcing materials.

The impregnation of the carrier material is carried out in a manner known per se with an aqueous dispersion of the polymer or copolymer or mixtures thereof. The solids content of the aqueous dispersions is preferably between 35 and 50% by weight. % polystyrene, styrene copolymers or vinyl acetate, in particular those consisting of 70 wt. % to 95 wt. % styrene and 30 wt. up to 5 wt. % butyl acrylate or 30 wt. % to 5 wt. butadiene. It is also possible to use copolymers of vinyl acetate and vinyl chloride, especially in admixture with polystyrene, for example a mixture of 70 to 95 wt. % polystyrene and 30 to 5 wt. copolymer of vinyl acetate and vinyl chloride.

Polycaprolactone, preferably mixtures of polycaprolactone of different molecular weights, is preferably used as the hot melt adhesive. Mixtures of 60 to 95 wt. polycaprolactone having a molecular weight of about 45,000 and 40 to 5 wt. polycaprolactone with a molecular weight of about 35,000. Of course, the invention is not limited to these mixtures. By selecting a mixture of polycaprolactone with polymer particles of different molecular weights, the melt viscosity and hence the melt temperature can be influenced, in particular it can be optimized. Furthermore, a good final bonding can be ensured in addition to good stiffening (hot melt adhesive inflow).

According to further embodiments of the invention, hot-melt adhesives may have different melt viscosities on both sides of the carrier material. This allows processing, for example by gluing, even at different temperatures on both sides of the material. Thus, for example, the side of the blank facing away from the heat source can stick together at lower temperatures. The new shoe reinforcement material is produced by first heating the carrier material to a temperature of 30 to 80 ° C, for example IR rays, and then applying a powdered hot melt adhesive to both sides. After melting and fixing of the hot-melt adhesive powder, the web of goods is smoothed while cooling. The granulometric composition of the hot melt adhesive is up to 500 µm.

The invention is further elucidated on the basis of the examples.

Example 1

A double-faced plain weave fabric consisting of a blend of cotton and poly2 ester fibers having a basis weight of 200 g / m 2 was impregnated with an aqueous dispersion of styrene-butyl acrylate copolymer (styrene content of about 90%) and dried to a dry weight of 600 g / m.

Under suitable drying conditions, in particular a drying temperature of about 100-110 [deg.] C., it has been found that the polymeric impregnating agent forms only a small film. The unstretched inner belt thus produced was coated on both sides with a powder mixture consisting of polycaprolactone having a particle size distribution of up to 500 .mu.m. The polycaprolactone consisted of a 90 wt. polycaprolactone having a molecular weight of 45,000 and 10 wt. with a molecular weight of 35,000.

The melting and smoothing of the powder was carried out in such a way as to prevent film formation of both the inner web and the powder layer. The reinforcing material produced was stamped in the shape of a toe cap and was chamfered at the upper edge. The preformed back toe was then slipped into the toe pocket of the shoe upper and molded in the heel to an aluminum mold heated to 80 ° C with a silicone protoform heated to the hand temperature for 12 seconds. In the pressure and heat treatment area stiff and glued to the upper material. The area which has not been subjected to pressure and heat treatment has not yet been glued and can be easily molded. Finally, the upper was placed on the base hoof and subjected to the usual stretching processes. Parts that had not yet been subjected to pressure and heat treatment were now solidified and glued at 120 ° C and 5 minutes as they passed through the heat curing tunnel.

Example 2

Polyester staple fiber fleece with a staple fiber length of about 40 mm and a 1.7 dtex titer was coated on both sides with a powdered polycaprolactone layer (molecular weight of about 45,000) with a granulometric composition of up to 500 µm, as in Example 1. Soft and flexible stiffening material was now sewn in the sewing workshop while sewing the shoe upper at the heel. The upper of the shoe was then mounted as if there was no rear toe cap. During curing (5 min, 130 ° C), the outer layer of polycaprolactone penetrated completely into the fleece formation and simultaneously glued the fleece with the lining and the upper leather. After cooling, the heel was elastically elastic.

Example 3

The reinforcement of the polyester woven web (stabilized - with a basis weight of about 50 g / m and a titre of about 2.5 dtex) was impregnated on a laboratory impregnation apparatus with about 50% aqueous dispersion of styrene-butadiene copolymer with butadiene content of about 10% to a total weight of 300 g / m (dry) and not fully hardened by selection of suitable drying conditions. A mixture of polycaprolactone powder and a granulometric composition of up to 500 µm was applied to the web at a temperature of about 80 ° C after passing through the drying channel, in an amount of about 1 30 g / m 2. The powder mixture consisted of 60% polycaprolactone with a molecular weight of about 45,000 and a 40% polycaprolactone with a molecular weight of about 35,000. Thus, the powder mixture sintered under the still present heat on the material web without forming a film and thereby consolidating the goods web. . The material thus treated was wound after cooling. Then, about half of the carrier material was processed by cutting the web of goods and rewinding to a second winding point and using a laminating calender on which the moving goods were now laminated, a side that had not yet been coated with a hot adhesive side . After cooling, the laminate was wound up. The underside of the goods was now separately coated with the same powder, but only in an amount of 70 g / m, following the same criteria.

After cooling, the product was rewound and then cut to form the sheets and fastened after ten.

Back sticks were punched out of the plate material using a punching knife. After the chamfers were chamfered, the back sticks thus produced were worked into the upper as in Example 1.

Claims (4)

SUBJECT OF THE INVENTION A shoe reinforcing material comprising a carrier having a hot-melt adhesive layer on both sides, characterized in that the carrier material and the hot-melt adhesive layer are porous and flexible, wherein the hot-melt adhesive layers consist of polycaprolactone, in particular a 60-95% blend wt. % polycaprolactone having a molecular weight of 45,000 and 40 to 5 wt. polycaprolactone with a molecular weight of 35,000 and a weight ratio of carrier material to hot melt adhesive of 3: 1 to 1: 1, in particular 1.8: 1 to 2.2: 1 * 2. The reinforcing material of claim 1, wherein the carrier material is impregnated with a thermoplastic. Method for producing reinforcing material for shoes according to Claims 1 and 2, characterized in that the carrier material is first heated to a temperature of 50 to 80 ° C and coated on both sides with a layer of powdered polycaprolactone, in particular powder mixtures of 60 to 95% by weight. % polycaprolactone having a molecular weight of 45,000 and 40 to 5 wt. polycaprolactone with molecular weight 35,000, and after melting and fixing the powdered hot melt adhesive, it is smoothed while cooling. 4. The method of claim 3 wherein the carrier material is impregnated with an aqueous thermoplastic dispersion prior to application of the hot melt adhesive and is dried to prevent film formation.