GB922669A - Improvements in or relating to polypropylene fibers - Google Patents

Abstract

Colourless chlorosulphonated polypropylene fibres capable of being dyed and possessing good tensile strength may be prepared by subjecting the fibres in the solid state to irradiation capable of inducing active centres in polypropylene and to the action of sulphur dioxide and chlorine gases, before, during or after the irradiation of the fibres, to chlorsulphonate the irradiated fibres with the gases. The fibres are preferably initially saturated with the gases for several minutes, then irradiated, and thereafter held in an atmosphere of the gases to complete the radiation-induced reaction. To increase the heat-stability of the chlorosulphonated fibres they can be reacted with ammonia or an amine at about 15 DEG C. to about 150 DEG C. The fibre material preferably has a molecular weight of about 100,000 to about 500,000, particularly about 350,000 to about 450,000. The radiation utilized may be particulate radiation, such as alpha-particles and beta-radiation (that is, electrons), obtained from radio-active nuclei or high-energy electrons from machine sources; electro-magnetic radiation, such as gamma rays, X-rays, ultra-violet light or visible light. A preferred source of radiation is a beam of high-energy electrons (e.g. from about 0,5 to 3 million electron-volt electrons). For ionizing radiation the total dose may be 10,000 to 50 million rads., preferably 75,000 to 1,200,000 rads. Sufficient of the gases should be present to introduce into the fibres about 0,1 to 5,0%, preferably 1,5 to 2,5%, sulphur and 0,3 to 20%, preferably 3,5 to 10% chlorine. Preferably 1 to 50 parts by weight of each gas per part of fibres per hour are used. The mol. ratio of sulphur dioxide to chlorine may be 1-10 to 3-1. Ionizing radiation in the form of high-energy electrons is preferred, since the fibres need only be subjected to such radiation for 0,06 to 0,6 second. X-rays usually require 10 to 15 minutes exposure, and visible light 20 to 60 minutes. The temperatures used may be 20 DEG to 100 DEG C., and the pressure atmospheric. It is preferred to saturate the fibres with the gases for about 4 to 8 minutes or longer prior to the irradiation step. A list is given of amines which may be used to heat-stabilize the chlorsulphonated fibres. In examples diethanolamine, aniline, ethylene diamine and tetraethylene pentamine are used. An amine may be used either in solution or not. One and preferably two mols. or more of ammonia or an amine are preferably used per mol. of chlorosulphonyl groups introduced into the fibres. The fibres thus treated may be dyed with a variety of basic dyestuffs.