Patent GB-599084-A (GB)
Title: Felted products and methods of making them
IPC: D04H1/54
Filed: 1945-06-06
Abstract: 599,084. Agglutinated fibrous sheets; compound sheet materials. SYLVANIA INDUSTRIAL CORPORATION. June 6, 1945, No. 14245. Convention date, June 8, 1944. Drawings to Specification. [Class 140] Felt-like sheet materials or shaped articles such as pipe-coverings are made by superimposing a number of layers each consisting of a mixture of thermoplastic and non- thermoplastic or less thermoplastic fibres, and heating the assembly to soften and render tacky the thermoplastic fibres, the thermoplastic fibres in the layers remote from the heating device having a lower softening temperature than those in the other layers to achieve uniform softening and bonding. The assembled layers may be heated from both sides, e.g. by calender rolls or heated platens, in which case the middle layers contain fibres with a lower softening point than the outer layers. When heated from one side only, the layer next the heating device contains thermoplastic fibres of higher softening point than the more remote layers. Hollow articles may be obtained by winding thin webs of the mixed fibres on a mandrel in the form of a cylinder, cone, or sphere in the requisite order depending upon whether heat is to be applied from the mandrel, or externally by an oven. The difference in softening point may arise from a different chemical constitution, e.g. polyvinyl chloride has a higher melting point than polyvinyl acetate, and a copolymer of vinyl chloride and vinyl acetate has a higher softening point as the proportion of vinyl chloride increases ; or it may arise from using identical resins polymerised to a different extent ; or from a different plasticiser content. The fibres may be mixed by carding, or may be mixed in an air-stream and subsequently deposited. The heating may be by contact with heated surfaces, dry hot air, steam, irradiation, or highfrequency electric field. The product may be compacted before or after heating and may be calendered, embossed, printed, or dyed. The individual thin layers may be partly activated before assembling them together. The heatactivable fibres may be plasticised cellulose esters or ethers, coumarone or indene resins, polyvinyl compounds, thermosetting resins in the thermoplastic state, e.g. phenol-, urea-, or sulphonamide-aldehyde resins or alkyd resins which may. be oil-modified, sulphur olefine resins, nylon, natural or synthetic rubber, gutta percha, balata, or mixtures of two or more substances. The non-activable fibres may be wood pulp fibres, cotton, flax, jute, kapok, silk, regenerated cellulose, cellulose esters or ethers, cellulose ether . xanthates, cellulose xanthofatty acids, cellulose thiourethanes, natural and synthetic rubber, asbestos, mineral wool, spun glass, natural and synthetic resins, fibres made by slitting and shredding films such as flock or leather dust. In examples : (1) a web containing 9 parts cotton linters to 1 part of fibres of a copolymer of vinyl acetate and vinyl chloride is interposed between two webs containing 7 parts of viscose rayon staple fibres and 3 parts of cellulose acetate fibres and placed between two surfaces heated to 275‹ F. ; (2) an assembly of webs is hot-calendered in which the two middle layers are of viscose rayon staple and low-melting polyvinyl acetate fibres, the layers next the middle are of wool flock and an after-chlorinated vinyl acetatechloride copolymer, the next layers are of cotton linters and a similar chlorinated copolymer of higher chlorine content and softening point, and the outer layers are of viscose rayon staple and cellulose acetate plasticised to soften at 285-300‹ F. ; (3) webs are wound helically in superposition on a cylindrical mandrel, the inner layers containing cotton and cellulose ether fibres, followed by a layer containing rayon staple and vinyl acetate-chloride fibres, and an outer layer of wool flock and polyvinyl acetate fibres, and made into a unitary product by applying heat through the mandrel.