GB815898A - Improvements in or relating to resilient materials - Google Patents

Abstract

<PICT:0815898/III/1> A method of treating a resilient sponge or foam material having intercommunicating cells in order to vary the compression-resistance characteristics thereof comprises treating the material with a natural or synthetic rubber which is applied to the material in the form of a latex so as to coat the cell walls throughout the mass of the latter and thereafter causing the rubber on the cell walls to dry and to contract so that the deposited rubber by its action on the cellular material produces a reduction in the compressive force which must be applied to the material in order to produce a predetermined partial compression of the latter within a part of the range of compression of the material. The cellular material may be that produced by the reaction of a polyester with a polyisocyanate or polyisothiocyanate or may be of natural or synthetic rubber. A coagulant for the latex may be applied simultaneously or separately, and must be employed when the cellular material is of foam or sponge rubber. A dilute acid such as acetic is suitable. Alternatively a solid salt such as calcium nitrate may be deposited on the cell walls before the latex treatment, or a heat-sensitive coagulant, such as ammonium acetate, together with a surface-active agent, may be added to the latex. The latex may be of the pre-vulcanized type, which merely requires drying or it may be partly vulcanized or unvulcanized, in which case a subsequent vulcanization is required. In an example a sheet 1 of cellular polyester/diisocyanate reaction product is passed through a bath 2 of pre-vulcanized natural or synthetic rubber latex, then between the pairs of squeeze rollers 5 and 6 (which leave latex deposited over the internal cell walls), through a bath 9 of dilute acetic acid and between squeeze-rollers 10 and 11. The sheet is then washed and dried. Specification 730,848, [Group V], is referred to.ALSO:<PICT:0815898/IV (a)/1> A method of treating a resilient sponge or foam cellular material having intercommunicating cells in order to vary the compression-resistance characteristics thereof comprises treating the material with a natural or synthetic rubber which is applied to the material in the form of an aqueous dispersion or latex so as to coat the cell walls throughout the mass of the latter and thereafter causing the rubber on the cell walls to dry and to contract so that the deposited rubber by its action on the cellular material produces a reduction in the compressive force which must be applied to the material in order to produce a predetermined partial compression of the latter within a part of the range of compression of the material. The cellular material may be that produced by the reaction of a polyester with a polyisocyanate or polyisothiocyanate or may be of natural or synthetic rubber. A coagulant for the latex may be applied simultaneously or separately, and must be employed when the cellular material is of sponge or foam rubber. A dilute acid, such as acetic is suitable. Alternatively, a solid salt, such as calcium nitrate, may be deposited on the cell walls before the latex treatment, or a heat-sensitive coagulant, such as ammonium acetate, together with a surface-active agent may be added to the latex. The latex may be of the pre-vulcanized type, which merely requires drying, or it may be partly vulcanized or unvulcanized, in which case a subsequent vulcanisation is required. In an example, a sheet of cellular polyester/diisocyanate reaction product 1 is passed through a bath of pre-vulcanized natural or synthetic rubber latex 2, through squeeze-rollers 5 and 6 (which leave latex deposited over the internal cell walls), through a bath 9 of dilute acetic acid and between squeezerollers 10 and 11. The web is then washed and dried. Specification 730,848, [Group V], is referred to.