Patent GB-711714-A (GB)
Title: Improvements relating to the extrusion of cellulose acetate compositions
Inventor: ALLAN JOHN
IPC: B29C48/05
Filed: 1951-12-05
Abstract: A composition, suitable for making rigid rods, tubes, and other articles to predetermined shape and dimensions by solventless extrusion, comprises plasticized cellulose acetate containing 1 to 5 per cent., on the weight of cellulose acetate, of ricinoleic acid. The cellulose acetate may contain 52.5-55.5 per cent. of combined acetic acid and it may be such that a 6 per cent. solution in acetone has a viscosity of 30-60 centipoises at 25 DEG C. p  The cellulose acetate may be plasticized with 40-50 per cent. of its weight of diethyl phthalate or a mixture of dimethyl phthalate and triphenyl phosphate.  Other plasticizers which may be used are di(methoxy ethyl) phthalate, methyl phthalyl ethyl glycolate, acetyl triethyl citrate, tri(monochlorethyl) phosphate, tricresyl phosphate and the N-ethyl toluene sulphonamides.  Tubes or rods of circular, elliptical, square, rectangular, or other cross-section, including bars of L, U, V, T, and H section, may be obtained.  The composition may be fed, in particulate form, into a heated chamber, and may be forced through the chamber and through an appropriately shaped orifice into the air, a temperature gradient being maintained along the path of the composition up to the extrusion point so that complete coalescence of the particles occurs before reaching that point, while at that point the extruded material is sufficiently cool to emerge as a self-supporting article that, apart from thermal contraction, retains the dimensions imparted by the orifice. Preferably the temperature of the composition in the course of its travel gradually reaches a maximum from which it declines rapidly. The composition may be fed into the barrel of a ram-extruder from which it is extruded through a tube-die: the temperature of the barrel may be 50-70 DEG C., at the feeding-point, 90-110 DEG C. at the middle, and 100-110 DEG C. at the front, and the temperature of the die may be 90-100 DEG C. at the rear end, and substantially atmospheric temperature (e.g. 20-30 DEG C.) at the front end.  The use of oleic acid, instead of ricinoleic acid, is stated to be unsatisfactory.  Specification 563,121, [Group V] and U.S.A. Specification 2,491,589 are referred to.  The Provisional Specification describes also compositions containing other cellulose derivatives.ALSO:A plasticized cellulose acetate composition containing 1-5 per cent. of ricinoleic acid, based on the weight of the cellulose acetate, is formed into rigid rods, tubes, and other articles by a solventless extrusion process.  The inclusion of ricinoleic acid in the composition within the stated range of proportions enables the temperature of extrusion to be reduced to a point at which the extruded product emerges from the die at a temperature below its heat-softening point.  Tubes or rods of circular, elliptical, square, rectangular, or other cross-section, including bars of L, U, V, T, and H section, may be obtained.  The composition may be fed, in particulate form, into a heated chamber, and may be forced through the chamber and through an appropriately shaped orifice into the air, a temperature gradient being maintained along the path of the composition up to the extrusion point so that coalescence of the particles occurs before reaching that point, while at that point the extruded material is sufficiently cool to emerge as a self-supporting article that, apart from thermal contraction, retains the dimensions imparted by the orifice. Preferably, the temperature of the composition in the course of its travel gradually reaches a maximum from which it declines rapidly.  The composition may be fed into the barrel of a ram-extruder from which it is extruded through a tube-die.  The temperature of the barrel may be 50-70 DEG C. at the feeding point, 90-110 DEG C. at the middle, and 100-110 DEG C. at the front, and the temperature of the die may be 90-100 DEG C. at the rear end, and substantially atmospheric temperature (e.g. 20-30 DEG C.) at the front end.  Specification 563,121, and U.S.A. Specification 2,491,589, are referred to.  The Provisional Specification refers also to the use of compositions containing other cellulose derivatives.