Patent GB-630666-A (GB)
Title: Felts and methods of producing the same
IPC: D04H1/54
Filed: 1944-12-13
Abstract: 630,666. Felt; paper; compound fabrics. SYLVANIA INDUSTRIAL CORPORATION. Dec. 13, 1944, No. 24983. Convention date, Dec. 18, 1943. [Classes 42 (ii), 96 and 140] A felt or paper-like product is made containing a mixture of non-adhesive and potentially adhesive fibres and the latter " activated," i.e. rendered adhesive, in a plurality of substantially uniformly spaced areas to cause a greater adhesion between fibres in such areas than in the remaining areas, and subsequently de-activated. For activation, there may be used the local application of heat, with or without pressure, e.g. heated patterned rollers or other surfaces, hot water, steam or a blast of hot dry gas; or local treatment with a solvent or swelling agent under appropriate conditions of temperature and concentration; or a latent activating agent combined with the potentially adhesive or non-adhesive fibres, followed by local activation by chemicals, heat or irradiation. A plasticizer may be applied before, and removed after, the activation, and during activation the fibres are preferably subjected to a compacting treatment as by pressure or tension. De-activation may be accomplished by cooling, or, if the potentially adhesive fibres comprise a thermo-setting resin, by heating to a higher temperature, or by the removal of solvent or other activating agent where these are used. In Fig. 3 the felt A is treated with a fluid-activating agent by being laid on the hollow conical projections 32 on the upper surface 33 of a container 34, steam, solvent or dry hot air being pumped by a pump 35, through the orifices in projections 32. Alternatively, the felt may be passed between a pair of rollers, one or both being provided with a raised pattern, and heated by steam admitted to the interior. Such an embossing process may be followed by a similar one for the unactivated portions of the pattern, e.g. a pair of rollers, one of which is heated to form an activated pattern of squares, may be followed by an unheated pair producing alternate raised and depressed pyramidal projections in register with the squares. The resultant material may be sandwiched between paper, felt, or films, to give a self-supporting structure (Fig. 8). To improve the strength of the felt, the activated portions of the pattern are preferably spaced closer together than the average length of the fibres. The felts may be used for battery separators, heat and sound insulation, vibration damping material, gaskets, packings, wicks, and gaseous or liquid filtering media. The potentially adhesive fibres may be produced from various types of synthetic resins, cellulose derivatives, synthetic and natural rubber and substitutes therefore, and mixtures thereof. They may be mixed with non-adhesive fibres such as wood pulp fibres, cotton, flax, jute, kapok, wool, hair, and silk, and synthetic fibres of cellulose and its derivatives, natural and synthetic rubber and derivatives thereof, fibres made from alginic acid, gelatine and casein, or natural or synthetic resins not rendered tacky when the potentially adhesive fibres are activated; also mineral fibres and fibres made by slitting, cutting or shredding non-fibrous films. The potentially adhesive fibres may be pre-formed, or they may be formed simultaneously with the felt by blowing the molten or dissolved substance into a gas, by means of a spray-gun, and collecting the resultant fibres on a belt. Non-adhesive fibres may be produced simultaneously by the same method; or the felt may be deposited from a liquid suspension. Specification 547,288 is referred to.