Abstract: The formation head comprises a casing of substantially rectangular configuration in plan view provided with a perforated flat bottom-screen or sieve, and with a top wall having a number of openings communicating with the atmosphere. Opening into said casing is a conduit for feeding a flow of air-fluidized disintegrated fibers. A plurality of spaced parallel, horizontal rollers are rotatably mounted close to the perforated bottom of the said head structure. The said rollers are supported so as to be translated parallely to the bottom of the said structure. The said rollers are each provided with a plurality of peripheral radial needles. At a short distance from the bottom of the casing, parallely thereto, a moving web is mounted, cooperating with an underlying vacuum chamber onto which the screened fibers are deposited in a thin layer (S).

Abstract: A continuous process for polymerizing acrylonitrile monomer or copolymerizing a mixture of acrylonitrile monomer and a further ethylenically unsaturated monomer copolymerizable therewith in an aqueous medium and in the presence of a catalytic redox system through a primary and a secondary polymerization step. The primary step is carried out in a plurality of independent distinct reaction zones connected in parallel and operated under similar conditions, in which the conversion of the monomer or mixture of monomers is maintained at a value not exceeding 70%. The secondary step is carried out in a single reaction zone connected in series with each of the primary zones. The conversion of the monomer or mixture of monomers in the secondary zone is maintained at a value not exceeding 80% with respect to the overall feed of monomer or mixture of monomers to the primary zones.

Abstract: Sulphur dioxide and unreacted monomer or mixture of monomers are separated and recovered from the polymer or copolymer slurry obtained by polymerizing acrylonitrile monomer or copolymerizing acrylonitrile monomer and a further ethylenically unsaturated monomer copolymerizable therewith in the presence of a catalytic system comprising sulphur dioxide or a sulphite, by a process comprising the steps of separately removing the sulphur dioxide and the monomer or mixture of monomers from the slurry in two distinct volatilization zones connected in series under decreasing subatmospheric pressures, scrubbing with water the sulphur dioxide vapors removed in the first zone and vapors of unreacted monomer or monomers removed in the second zone, and recycling the two resulting aqueous solutions to the polymerization or copolymerization medium.

Abstract: A copolymer suitable for making self-extinguishing fibers, containing at least 50 wt.% acrylonitrile, from 2 to 30 wt.% vinyl or vinylidene chloride, from 0 to 10 wt.% of a neutral, ethylenically unsaturated, non-halogenated monomer and from 2 to 40 wt.% of alpha-bromoacrylonitrile.

Abstract: A copolymer suitable for making self-extinguishing fibers, containing at least 50 wt.% acrylonitrile, from 2 to 30 wt.% of vinyl or vinylidene chloride, from 0 to 10 wt.% of a neutral, non-halogenated, ethylenically unsaturated monomer and from 2 to 40 wt.% of a monomer of the general formula: ##EQU1## WHEREIN R is hydrogen or methyl and n is an integer from 1 to 4.