Patent GB-1350622-A (GB)
Title: Stiffener materials
IPC: A43D11/00
Filed: 1971-04-19
Abstract: 1350622 Boots &c BRITISH UNITED SHOE MACHINERY CO Ltd 19 April 1971 [6 Feb 1970] 21003/71 Heading A3B [Also in Divisions B2 and B5] Material suitable for use in stiffening a shoe upper comprises a sheet comprising polyurethane made by polymerisation of mutually reactive compounds including at least one organic compound and having at least two NCO groups and at least one organic compound having at least 2 active hydrogens and a layer of heat-activatable adhesive on the surface of the sheet, the polyurethane having a glass transition temperature of 140F to 250F and the adhesive being activatable by heating to at least said glass transition temperature, and the sheet being pliable and conformable but not flowable on application of pressure at temperatures above said glass transition temperature. The shoe upper may be stiffened to hold it in a desired shape by disposing in engagement with the shoe upper, the stiffener material, heating the stiffener material to a temperature above the glass transition temperature, shaping the shoe upper and stiffener material to a desired shape and pressing together the stiffener material and shoe upper so that the materials adhere on cooling firmly together and cooling or allowing cooling of the stiffener material while the stiffener material and the shoe upper are maintained in the desired shape. The polyurethane may be the product of condensation and polymerisation of materials comprising (a) NCO terminated prepolymer made by condensation of mutually reactive materials including at least one compound having at least two active hydrogen groups and at least one compound having at least two isocyanate groups in proportion to provide at least two equivalents of isocyanate for each equivalent of active hyrogen, (b) additional polyisocyanate, and (c) chain extender organic compound having at least two active hydrogens. The ratio of the sum of isocyanate groups from the prepolymer and isocyanate groups from the additional polyisocyanate to the active hydrogen of the chain extender being in excess of 1:1. Preferably from 15-100% of the active hydrogen compound (a) comprises a trifunotional compound, the ratio of NCO to OH being 2-1 to 9-2. Preferably the prepolymer has a molecular weight of less than 500. The additional polyisocyanate (b) may be tolylene diisocyanate or polyarylene polyisocyanate. The chain extender may comprise 5 mole percent-50 mole percent of aromatic diamine, e.g. methylene bis-orthochloroaniline, and the balance a polyol, e.g. the product of a condensation of caprolactone with a low molecular weight diol or triol. The sheet may also comprise a filler, e.g. glass fibres. One or both faces of the sheet may be provided with the heat-activatable adhesive applied, e.g. as a solution, powder with heating either at the time of application or subsequently to fuse the powder to the sheet, melt, or as a film with subsequent heating to cause the film to adhere to the sheet. The adhesive may be continuous or applied as a network or as dots or lines. Suitable adhesives include ethylene-vinyl acetate copolymers, thermo plastic urethanes, polyesters and mixtures thereof or with other thermoplastic resins, plasticisers, tackifiers, fillers. The stiffener materials may be used for the stiffening of counter regions, toes, eyelet strips. In an Example a prepolymer is prepared by reaction of 22 parts by weight polypropylene glycol ether triol having a molecular weight 4,000, three parts by weight of a trimethylol propane and 15 parts by weight tolylene diisoycyanate. Ninety parts by weight of the prepolymer were combined with 13 parts by weight tolylene diisocyanate, 63 parts by weight of an aromatic diol having an equivalent weight of 245, from condensation of methylene bis phenol with propylene oxide, 8.5 parts by weight of methylene-bis-orthochloro aniline and 0.17 parts by weight of Z 2-ethylhexoate. The mixture was spread on a sheet and heated. The resulting sheet was stripped from the casting surface and a coating of adhesive comprising a mixture of equal parts ethylene-vinyl acetate copolymer and a terpene phenolic resin applied by transfer from a release paper. As shown in Figs. 3 and 4, a stiffener blank 9 cut from the stiffener material was flexed and inserted between a counter pocket piece 14 and a shoe upper 16 and the shoe upper 16 placed on a convex mould part 18 of a back part moulding machine 20 where it was heated to above the glass transition temperature. Convex mould part 18 had an exterior surface corresponding to the desired shape of the heel end of a shoe and was provided with inferior chamber 22 into which steam was supplied through conduit 24 and from which steam was emitted through holes 26. An electric heating cartridge 28 was mounted in the lower portion of mould part 18 to supply additional heat. An end embracing band 30 was then brought down to force the shoe 16 into intimate contact with a heated mould part 18 and when the shoe part had been shaped the band 30 was loosened and the shaped shoe part removed.