GB539816A - Improvements in the manufacture of continuous sheets of thermoplastic material by extrusion - Google Patents

Abstract

539,816. Films; cellulose-derivative compositions. MONSANTO CHEMICAL CO. Feb. 16, 1940, No. 3015. Convention date, Feb. 16, 1939. [Class 2 (ii)] [Also in Group V] In processes for moulding sheets of cellulose esters or ethers of the kind in which a plastic colloidal gel of the material in a volatile solvent is extruded to form a sheet which is capable of sustaining itself and from which part of the solvent is subsequently removed, the amount of solvent used is slightly more than sufficient to maintain complete dispersion of the material in the form of a colloidal solution and to prevent mechanical fractures of the sheet and separation of the basic material and solvent during or after extrusion, but is insufficient to prevent formation of a self-sustaining sheet. The sheets may be moulded by the apparatus described in Specification 539,663. Examples of mixes are (1) cellulose acetate 100, methyl phthalyl ethyl glycollate 12, di-ethyl phthalate 12, acetone 15, denatured alcohol (5 to 6 per cent water) 24 and ethyl acetate 24 parts ; (2) cellulose acetate 100, triphenyl phosphate 17.5, diethyl phthalate 15, dimethyl phthalate 5, acetone 15, ethyl alcohol 24 and ethyl acetate 24 parts ; (3) ethyl cellulose 100, dibutyl phthalate 15, toluene 30, ethyl alcohol 10 and lactol spirits 5 parts ; (4) cellulose acetobutyrate 100, diamyl phthalate 25, ethyl alcohol 24, acetone 15 and ethyl acetate 24 parts. Specification 354,339 is referred to.