Shoe comprising a sole of a thermoplastic material and a method for use in manufacturing such a shoe

Abstract

The present invention pertains to a new shoe comprising a sole of a thermoplastic material adhered to an upper shoe with a hot melt adhesive that is applied between the sole and the upper shoe, wherein the hot melt adhesive is fused with the thermoplastic material. Advantageously, the fusion is brought about by heating the hot melt adhesive to a temperature THM such that it softens, heating the second body such that the thermoplastic material that has a melting temperature TM obtains a temperature TSUB below TM while making sure that (THM+TSUB) / 2 is equal to or higher than (TM−10° C.).

Description

GENERAL FIELD OF THE INVENTION[0001]The present invention pertains to shoes and the manufacturing thereof. More particularly the invention pertains to shoes with a sole of a thermoplastic material and a method for making a workpiece that can be used in the manufacturing of such shoes.BACKGROUND OF THE INVENTION[0002]Contemporary shoes comprise the same basic parts. All shoes have a sole, which is the bottom of a shoe, in contact with the ground. Soles can be made from a variety of materials, although most modern shoes have soles made from natural rubber, polyurethane, polyvinyl chloride (PVC) or ethylene-vinyl acetate copolymer (EVA). Soles can be simple, a single material in a single layer, but most often they are more complex, with multiple structures or layers and materials. When various layers are used, soles may consist of an insole (also known as a sock liner), a midsole, and an outsole (i.e. the layer in direct contact with the ground). The midsole is the layer in between the...

AI Technical Summary

Benefits of technology

The invention relates to a method for adhering a hot melt adhesive to a thermoplastic material, even if the thermoplastic material has a smooth surface. The method involves melting a portion of the thermoplastic material to create a bridge between the hot melt adhesive and the thermoplastic material. The use of a specific hot melt adhesive, called a thermoplastic copolyester elastomer, and a specific soft segment, called polytetramethylene oxide, results in a foam with lower density. Plasticizers can also be added to the composition to decrease hardness and increase flexibility. The invention also includes a method for adhering a textile material to a shoe sole using a hot melt adhesive. This allows for easy recycling of the shoe and sole assembly.

Problems solved by technology

Soles can be simple, a single material in a single layer, but most often they are more complex, with multiple structures or layers and materials.

Although solvent-based adhesives are relatively expensive, inherently require a long processing time and also, despite the fact that special care may need to be taken to prevent environmental damage and deleterious health effects (caused by many non-aqueous solvents), such adhesives are preferred over hot melt adhesives.

Hot melt adhesives have the advantage of being (almost) solvent free and allowing very short processing times without any foaming tendency during processing, but the adhering properties on the relatively smooth soles are relatively bad.

Still, due to the difficulty of gluing an upper shoe to a thermoplastic sole, EVA is still the polymer of choice, using solvent based adhesives to adhere the upper shoe.

The problem of low quality adherence of an upper shoe to a thermoplastic sole, especially when using a hot melt adhesive, has been known since decades.

Such compounds however are associated with health hazards.

N-Ethyl-P-tolylsulphonamide is toxic and highly irritating.

This increases process time and still may not provide adequate bonding, in particular when adhering to a thermoplastic sole.

U.S. Pat. No. 3,212,115 (filed 1959, published 1965) confirms that the use of hot melt adhesives in the manufacturing of shoes leads to several disadvantages, not the least of which is failure of the bond at temperatures involved in the treatment or use of the bonded structures in practice.

GB 2048897 (filed 1979, published 1980) states (page 1, lines 14-16) that it is known that the receptiveness of elastomeric soling material towards adhesives and to thermoplastic materials is often unsatisfactory.

These primers are toxic, irritating and environmentally unfriendly.

U.S. Pat. No. 6,497,786 (filed 1997, published 2002) describes the potential advantages of using solvent less adhesives, but indicates that the need to heat the adhesives to be able and apply them is a disadvantage, in particular since present-day sole materials may deform at high temperatures.

The solution however needs a very complicated device for specifically heating the adhesive.

Next to this, the problem of inadequate adherence when using a hot melt adhesive is neither addressed nor solved.

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