GB1500542A - Plasticized papers - Google Patents

Abstract

1500542 Paper prepared from plastics fibrils; papermaking machines MONTEDISON SpA 24 March 1975 [25 March 1974] 12088/75 Headings D2A and D2B A process for making paper from thermoplastic fibrils comprises forming a wet sheet of superimposed layers comprising a layer of cellulosic fibres and a layer of synthetic thermoplastic polymeric fibrils, either layer being superimposed on the other, reducing the water content of the sheet to from 30-80% by wt. by suction and/or compression, drying the sheet to a moisture content of less than 0.5%, and heating the sheet under pressure at a temperature greater than the softening temperature of the thermoplastic polymer. The latter may be a polyolefin, e.g. a low or high density polyethylene, isotactic polypropylene, or ethylene/propylene copolymer with a predominant content of propylene, a polyamide e.g. nylon 6, a vinyl polymer e.g. polyvinyl chloride, polyvinyl acetate, polyacrylonitrile, or a polyoxymethylene. Mixtures of the same polymeric fibrils but with different thermoplastic characteristics, or of different polymeric fibrils, may be used provided that they are compatible with each other and have sufficiently close softening temperatures. Cellulosic fibres may be present in the layer of thermoplastic polymeric fibrils. The cellulosic layer of the paper may be calendered, coated and/or sized. Conventional additives, e.g. dyestuffs, pigments, fillers, dispersants, anti-mildew agents, and other fibres, e.g. rayon, cellulose acetate, nylon, or polyvinyl alcohol fibres, may be added to the aqueous fibrous dispersion from which each layer is formed. Preferably, the thermoplastic polymeric fibrils are coated with a polyvinyl alcohol/aliphatic aldehyde condensate. A laminate comprising a layer of thermoplastic polymer in the form of a continuous film sandwiched between two or more sheets of paper or cardboard may be made by the process. Apparatus. The preparation of a two-layer sheet, see Fig. 1, may be carried out using cylinder machines 1, 2 for cellulosic fibrous stock and thermoplastic fibrous stock respectively. A layer of thermoplastics fibres is superimposed on a layer of cellulosic fibres and the resulting sheet is conveyed by felt 10 past suction boxes 3 and press rolls 4. The still wet sheet is conveyed over drying cylinders 5, and then through glazing unit 6, and cooling rolls 7, before being taken-up on reel 8. The preparation of a cellulosic/thermoplastic material/cellulosic-laminated sheet, (Fig. 2, not shown) may be carried out as described above, except that two cylinder machines are used for the cellulosic fibrous stock, and a Fourdrinier for the thermoplastic fibrous stock, the latter machine being located between the two cylinder machines.