Patent GB-768562-A (GB)
Title: Improvements in or relating to foamed plastics
IPC: C08J9/30
Filed: 1954-03-15
Abstract: A urea-formaldehyde foam of fine structure is continously formed by converting a foamforming liquid into a coarse foam by pneumatic means, converting the coarse foam to a fine one by mechanical means, and admixing a ureaformaldehyde condensate with the fine foam, the original foam-forming liquid containing a curing catalyst for the urea-formaldehyde condensate so that the separate fine foam lamellae are solidified to yield a hardened foamy resin of fine structure.  A foam-forming liquid is an aqueous solution containing 35 per cent of alkyl-aryl sulphonates derived from a wax-free fraction of Scottish shale oil.  Curing catalysts mentioned are organic or inorganic acids, e.g. sulphuric acid.  The initial foam is formed by passing a stream of gas, e.g. compressed air or a gas such as ozonized air which will prevent odour in or will preserve the final product, through a fine-mesh screen beneath the surface of the foam-forming liquid.  The coarse foam is fed continuously into one end of an elongated container, fresh foam-forming liquid being supplied in replacement. Mechanical means in the elongated container convert the coarse foam to one with at least 105 pores per cu. cm.  The urea-formaldehyde condensate is then mechanically mixed with the fine foam, hardens under the influence of the catalyst and the semihardened fine foam is removed from the container by means of mechanical conveyers.  Hardening continues until completion.  The whole process can be carried out at normal temperature and pressure. By suitably adjusting the amount of catalyst, and the rates of supply of foam-forming liquid and of gas, the structure and bulk density of the foam can be controlled and a practically neutral foam with no excess catalyst can be produced.ALSO:A urea-formaldehyde foam of fine structure is continuously formed by converting a foam-forming liquid into a coarse foam by pneumatic means, converting the coarse foam to a fine one by mechanical means, and admixing a urea-formaldehyde condensate with the fine foam, the original foam-forming liquid containing a curing catalyst for the urea-formaldehyde condensate so that the separate fine foam lamellae are solidified to yield a hardened foamy resin of fine structure.  A foam-forming liquid is an aqueous solution containing 35 per cent of alkyl-aryl sulphonates derived from a wax-free fraction of Scottish shale oil.  Curing catalysts mentioned are organic or inorganic acids, e.g. sulphuric acid.  The initial foam is formed by passing a stream of gas e.g. compressed air, or a gas such as ozonized air which will prevent odour in or will preserve the final product, through a fine mesh sieve beneath the surface of the foam-forming liquid.  The coarse foam is fed continuously into one end of an elongated container, fresh foam-forming liquid being supplied in replacement. Mechanical means in the elongated container convert the coarse foam to one with at least 105 pores per cu. cm.  The urea-formaldehyde condensate is then mechanically mixed with the fine foam, hardens under the influence of the catalyst and the semi-hardened fine foam is removed from the container by means of mechanical conveyers.  Hardening continues until completion.  The whole process can be carried out at normal temperature and pressure.  By suitably adjusting the amount of catalyst, and the rates of supply of foam-forming liquid and of gas, the structure and bulk density of the foam can be controlled and a practically neutral foam with no excess catalyst can be produced.