GB735481A - Improved cellulose products - Google Patents

Abstract

Cellulose pulp of high alpha-cellulose content is rendered more suitable for the production of cellulose derivatives, particularly cellulose acetate and cellulose xanthate, and for the subsequent production of rayon and allied products, by incorporating in it not more than 0.5 per cent, based on the dry weight of the pulp, of a non-ionic water-soluble polypropylene oxidepolyethylene oxide polymerization product containing at least one lipophilic polypropylene oxide radical derived from a water-insoluble polypropylene oxide and at least one hydrophilic polyethylene oxide radical. Refined pulp which still contains up to 0.15 per cent of residual natural resins may be treated. The presence of the polymerization product inhibits the adverse effect of the resins on the resistance to fatigue of tyre cord filaments made from viscose derived from such pulp. The presence of the polymer in the viscose also minimizes clogging and cratering of the spinnerets. Preferably the polymer is introduced into the cellulose pulp prior to the drying of the pulp sheets. Inactivation of the cellulose due to drying, particularly towards acetylating and other esterifying agents, is thereby minimized. The polymer may be incorporated in the wet pulp before sheet formation or in the sheet at any stage prior to completion of the drying. It may be applied as an aqueous solution to refined wood pulp on the sheet-forming machine by means of sprays or a rotating roll. An aqueous solution of the polymer may be applied to already dried wood-pulp sheets in order to improve their reactivity. The non-ionic polymer may be a bis-polyethenoxy polypropylene oxide and it may be derived from a polypropylene oxide which has a specific viscosity of at least 0.129 in a 4 g./100 ml. benzene solution at 25 DEG C., which is water-insoluble and contains at least 13 propenoxy groups and has two terminal hydroxyl groups. The hydrogen atoms in these hydroxyl groups are substituted by polyethylene oxide chains of about equal length in order to render the final compound water-soluble. A proportion of 40-90 per cent of ethylene oxide in the final compound may be required in order that the compound may be water-soluble. The polymer may also be a halopolypropenoxy polyethylene oxide derived from a long chain polypropylene oxide having a specific viscosity of at least 0.129 and having one terminal halogen atom and one terminal hydroxyl group, by substitution of the hydrogen in the hydroxyl by a polyethylene oxide chain. The polymer may also be an alkoxy (or phenoxy) polypropenoxy polyethylene oxide or it may be a bis-polypropenoxy polyethylene oxide. In an example purified cellulose pulp containing 0.1 per cent of ether-extractable resin is impregnated with 0.1 per cent of a polypropylene oxide-polyethylene oxide polymerization product and converted into alkali cellulose and then into viscose. The viscose is extruded into dilute sulphuric acid containing sodium and zinc sulphates, without cratering of the spinnerets. Tyre cords made from the filaments so produced have an improved fatigue life compared with that of cords made from filaments which have been produced in the absence of the polymerization product. If desired, a polymer may be used which contains more than one polyalkenoxy chain, each of which contains as component parts one polypropenoxy chain and one polyethenoxy chain. A polypropylene oxide may be polymerized in presence of a small proportion of a polyhydric alcohol of relatively small molecular weight to provide terminal groups, and the product may then be converted into a multi-chain polypropylene oxide-polyethylene oxide polymerization product.