Patent GB-560940-A (GB)
Title: Improvements in and relating to the production of resilient material having a basis of regenerated cellulose or a cellulose ester
IPC: C08L1/08
Filed: 1942-10-22
Abstract: Resilient material suitable for use in forming sealing-pads or discs for cans or bottles comprises moist particles of regenerated cellulose or of non-thermoplastic incompletely saponified cellulose ester united into a compact mass by means of a binding agent.  The binding agent may be present to the extent of about 10-20 per cent of the weight of regenerated cellulose or saponified cellulose ester particles.  Particles of the cellulosic material may be mixed with a hygroscopic substance, and the mixture is moulded under pressure so as to unite the particles and form a soft, compact, and flexible material which is very resilient.  Discs of this material, used alone or faced with a thin film or foil of a water-resistant substance, e.g. cellulose acetate or ethyl cellulose, may be used as cushion liners for closures of bottles or other containers to give gas- and liquid-tight seals.  The discs may be used with metal caps or shells which are applied to the filled bottles by a capping device and which press the resilient discs against the upper edges of the bottles. Regenerated cellulose particles may be obtained from viscose or from an organic ester of cellulose by saponification using organic or inorganic saponifying agents.  A cellulose ester in finely divided form may be treated with a volatile liquid which has a solvent or softening action when in vapour state, then subjected to heat and pressure in a closed chamber.  The pressure is suddenly released so as to cause rapid vaporisation of the liquid and expansion of the cellulose ester to a cellular mass. This material is ground and the particles are saponified.  The hygroscopic substance may be added to the regenerated cellulose before moulding, shaping, or processing. Glycerine, ethylene glycol, diethylene glycol, calcium chloride, magnesium chloride, or sodium nitrate, may be used, preferably in amount sufficient to maintain a moisture content of 25-50 per cent by weight of the regenerated cellulose.  The binding agent may be a glue, preferably waterresistant, such as casein glue, animal glue, or vegetable glue, or a cellulose acetate or other derivative, or a resin or gum, applied as a solution in a volatile solvent or as a powder which is mixed with the regenerated cellulose and then wetted with a solvent, or it may be an inorganic binding agent such as sodium silicate.  When thermosetting or thermoplastic resins are used, they may be applied as powder with the regenerated cellulose and the mixture may be subjected to moulding under heat and pressure. Phenol-formaldehyde, glycerolphthalic anhydride resins, cumaron resins, polyvinyl compounds, colophany, balsam, copaiba, dammar, elemi, and mastic, may be used.  When cellulose acetate or other ester is used as the binder, the resiliency of the material may be increased by treatment with a saponifying agent to convert the binder to regenerated cellulose. In the moulding operation pressures of 5 to 5,000 lbs per sq. in. with or without application of heat, e.g. 60-120 DEG  C. may be employed.  The material may be moulded into sheets from which the sealing-discs may be punched, or it may be moulded into a rod or cylinder from which the discs are sliced or cut.  The sheets or cylinders may be made by compression moulding, or cylinders may be obtained by extrusion through a nozzle.ALSO:Resilient material suitable for use in forming sealing-pads or discs for cans or bottles comprises moist particles of regenerated cellulose or of non-thermoplastic incompletely saponified cellulose ester united into a compact mass by means of a binding agent.  Particles of the cellulosic material may be mixed with a hygroscopic substance, and the mixture is moulded under pressure so as to unite the particles and form a soft, compact, and flexible material which is very resilient.  The hygroscopic substance may be added to the regenerated cellulose before moulding, shaping, or processing.  Glycerine, ethylene glycol, diethylene glycol, calcium chloride, magnesium chloride, or sodium nitrate, may be used. The binding agent may be a glue, preferably water-resistant, such as casein glue, animal glue, or vegetable glue, or a cellulose acetate or other derivative, or a resin or gum, applied as a solution in a volatile solvent or as a powder which is mixed with the regenerated cellulose and then wetted with a solvent, or it may be an inorganic binding agent such as sodium silicate.  When thermosetting or thermoplastic resins are used, they may be applied as powder with the regenerated cellulose and the mixture may be subjected to moulding under heat and pressure.  Phenol-formaldehyde, glycerol-phthalic anhydride resins, cumaron resins, polyvinyl compounds, colophany, balsam, copaiba, dammar, elemi, and mastic, may be used.  When cellulose acetate or other ester is used as the binder, the resiliency of the material may be increased by treatment with a saponifying agent to convert the binder to regenerated cellulose.  In the moulding operation pressures of 5 to 5,000 lbs. per sq. in. with or without application of heat, e.g. 60-120 DEG  C., may be employed. The material may be moulded into sheets from which the sealing-discs may be punched, or it may be moulded into a rod or cylinder from which the discs are sliced or cut.  The sheets or cylinders may be made by compression moulding, or cylinders may be obtained by extrusion through a nozzle.