GB1299242A - Method of making a polyurethane article having a resilient mass bonded to a rigid structure - Google Patents

Abstract

1299242 Polymethane foam article UNIVERSAL OIL PRODUCTS CO 24 March 1970 [2 April 1969] 14172/70 Heading B5A [Also in Division C3] A polyurethane article comprising a rigid foam structure bonded to a resilient foam mass, e.g. a rigid foam seat with a resilient foam cushion bonded thereto, is made by introducing into an encompassing mould a first mixture of polyols having an average molecular weight less than 725, a polymeric isocyanate, and a first blowing agent as specified below; allowing this mixture to foam and cure to a rigid structure; removing part or all of the mould; covering at least one exposed surface of the rigid structure with a further mould section to form an enclosed cavity, and introducing a second mixture of polyols having an average molecular weight greater than 3000, a polymeric isocyanate, an alcohol monomer present from 0À1% to 15% by weight of the second mixture and a second blowing agent as specified below, this second mixture being allowed to foam, cure and thereby form a resilient mass bonded to the rigid structure. The first blowing agent is either dichloro-difluoromethane, trichlorofluoromethane or trichloro-trifluoroethane present in an amount from 0À04% to 13% by weight of the first mixture and the second blowing agent is any of these flurocarbons or dichlorofluoromethane present in an amount from 0À07% to 13% by weight of the second mixture. The mould sections may be of silicone rubber, or of epoxy resin cured against a leather surface to provide a simulated grain finish, a release agent being used. A denser skin may. be provided on either of the foam surfaces either by appropriate formulation of the foam mixture, or by applying a polyurethane coating to the mould surface, e.g. by two-part spraying, before casting or by coating the finished product. A two part mould is used to cast a rigid foam seat, the upper part having vent holes and the lower part carrying a pin-mounted threaded insert which becomes embedded in the foam when cured (Fig. 7, not shown). This rigid seat, provided with a vent hole, is then used as a top mould half in combination with a further lower mould section (Fig. 8, not shown) in which the second foam mixture is foamed and cured to form a resilient cushion bonded to the rigid seat. Preferably the rigid portion is formed with a peripheral groove or other edge formation to give an improved bond with resilient mass (Figs. 3 to 6, not shown). Examples of various polyol formulations are given together with suitable amine catalysts and surfactants. The isocyanates may be e.g. polymethylene, polyphenylisocyanate or a mixture of toluene and methane diisocyanates, and the monomeric alcohol preferably comprises 1, 4 butane diol, 1. 4 cyclohexane dimethanol or 1, 6 hexane diol. A preferred polyol mixture for the first mixture comprises a polyoxypropylene derivative of pentaerythritol terminated by four secondary hydroxy groups and a copolymer of dimethylsiloxane and ethylene glycol. The polyol for the second mixture may be polyether based or a propylene oxide adduct of trimethylpropane trimethylpropane terminated with ethylene oxide. Suitable formulations for the coatings are also given.