Patent GB-571251-A (GB)
Title: Improvements in or relating to moulded articles or methods of making the same
IPC: A43B21/20
Filed: 1943-06-24
Abstract: A method of moulding a shoe heel or other article comprises intimately mixing a preponderance of compressible resilient material such as wood flour or sawdust with solid finely-divided thermosetting resin which is highly viscous at its curing temperature, making a preform by pressing with heat insufficient to cure the resin, and then moulding and curing the preform into article shape.  The preform may be slightly larger than the finished article.  The moulding powder may comprise 5-35 parts by weight of phenol formaldehyde resin and 95-65 parts of wood flour &c.  The phenolformaldehyde resin may be made by heating together sulphuric acid water and phenol and adding formaldehyde.  When the reaction is complete, the water is removed by vacuum and an excess of calcium hydroxide is added.  The resin is finally compounded with hexamethylene tetramine and zinc stearate.  Instead of phenol-formaldehyde resin, resin made from formaldehyde and substituted phenols, ureaaldehyde resins, thiourea-aldehyde resins or mixture of the last two resins may be used.  The moulded article may comprise an outer shell of thermosetting resin, and, if the article is to be lacquered, this shell may include a substance adapted to increase the bonding power of the lacquer; such a substance may be polyvinyl acetate, shellac, ester gum, oxidised resin, butyraldehyde condensation product of polyvinyl alcohol, ethyl cellulose or cellulose acetate.  The shell may be applied by dipping the preform (prior to the final moulding) into a suspension of the thermosetting resin, which suspension may include the bond-increasing substance.  The suspension may comprise uncured phenol-formaldehyde resin, polyvinyl acetate, colloidal clay (to give a smooth surface), hexamethylene tetramine, zinc stearate and naphtha or other volatile non-solvent.  After the shell has dried it is heated to cause the resins to flow slightly and adhere to the preform, alternatively, to secure this adherence, the coating may contain a naphtha-soluble resin such as ester gum or rosin; instead of being dipped, the preform may be brushed or sprayed, and the resultant heating to drive off the solvent shortens the subsequent curing time.  The coated preform is then moulded and cured, and to the resultant article is applied a nitrocellulose lacquer containing a modified glyceryl phthalate resin, dibutylphthalate, pigment, and a thinner, the thinner consisting of ethyl acetate, butyl acetate, ethyl lactate, butanol, toluol and xylol; alternatively, the lacquer may have a basis of shellac, alkyd resin, oil-soluble phenolic resin, ethyl cellulose, polyvinyl acetate or chlorinated rubber.  Colour may be imparted to the article before the final moulding operation, by coating the preform with a composition comprising phenol-formaldehyde resin, wood flour, zinc stearate, hexamethylene tetramine, cotton flock, low-boiling naphtha and benzol and either (a) carbon black, a resin-soluble black dye and hydrated lime, or (b) a non-black resin-soluble dye, lithopone and zinc oxide.ALSO:A method of moulding a shoe heel or other article comprises intimately mixing a preponderance of compressible resilient material such as wood flour or sawdust with solid, finely-divided, thermosetting resin which is highly viscous at its curing temperature, making a preform by pressing with heat insufficient to cure the resin, and then moulding and curing the preform into article shape.  The preform may be slightly larger than the finished article.  The moulding powder may comprise 5-35 parts by weight of phenol-formaldehyde resin and 95-65 parts of wood flour &c.  The phenol-formaldehyde resin may be made by heating together sulphuric acid, water and phenol and adding formaldehyde.  When the reaction is complete, the water is removed by vacuum and an excess of calcium hydroxide is added.  The resin is finally compounded with hexamethylene tetramine and zinc stearate. Instead of phenol-formaldehyde resin, resin made from formaldehyde and substituted phenols, urea-aldehyde resins, thiourea-aldehyde resins or mixtures of the last two resins may be used.  The moulded article may comprise an outer shell of thermosetting resin, and, if the article is to be lacquered, this shell may include a substance adapted to increase the bonding power of the lacquer; such a substance may be polyvinyl acetate, shellac, ester gum, oxidized resin, butyraldehyde condensation product of polyvinyl alcohol, ethyl cellulose or cellulose acetate.  The shell may be applied by dipping the preform (prior to the final moulding) into a suspension of the thermosetting resin, which suspension may include the bond-increasing substance.  The suspension may comprise uncured phenol-formaldehyde resin, polyvinyl acetate, colloidal clay (to give a smooth surface) hexamethylene tetramine, zinc stearate and naphtha or other volatile non-solvent.  After the shell has dried, it is heated to cause the resins to flow slightly and adhere to the preform; alternatively, to secure this adherence, the coating may contain a naphtha-soluble resin such as ester gum or rosin; instead of being dipped, the preform may be brushed or sprayed, and the resultant heating to drive off the solvent shortens the subsequent curing time.  The coated preform is then moulded and cured, and to the resultant article is applied a nitrocellulose lacquer containing a modified glyceryl-phthalate resin, dibutyl phthalate, pigment, and a thinner, the thinner consisting of ethyl acetate, butyl acetate, ethyl lactate, butanol, toluol and xylol; alternatively the lacquer may have a basis of shellac, alkyd resin, oil-soluble phenolic resin, ethyl cellulose, polyvinyl acetate or chlorinated rubber.  Colour may be imparted to the article before the final moulding operation, by coating the preform with a composition comprising phenol-formaldehyde resin, wood flour, zinc stearate, hexamethylene tetramine, cotton flock, low-boiling naphtha and benzol and either (a) carbon black, a resin-soluble black dye and hydrated lime, or (b) a non-black resin-soluble dye, lithopone and zinc oxide.