Patent GB-413806-A (GB)
Title: Improvements in the manufacture of articles from thermoplastic materials
IPC: B29C45/06
Filed: 1933-03-09
Abstract: 413,806. Moulding cellulose etc.; cellulose derivative compositions. CELLULOID CORPORATION, 290, Ferry Street, Newark, New Jersey, U.S.A. March 9, 1933, No. 7244. Convention date, March 9, 1932. [Classes 70 and 87 (ii).] Thermoplastic materials, particularly compositions containing organic derivatives of cellulose, are moulded by extruding the material under pressure from a heated space into a relatively cool mould, the temperature of the material in the heating space and the pressure applied thereto being such that the material is extruded into the mould at a rapid rate so that when the mould is full substantially every part of the material therein is still plastic. As shown in Fig. 2 a number of heating-chambers 26 are mounted on a rotary table 25 intermittently actuated by a Geneva mechanism. The supply hopper is stationary and provided with a sliding gate which is operated in synchronism with the heating- chambers. The heating-chambers are positioned in succession beneath the pressing plunger 41, the valve controlling lever 40 being actuated automatically. As shown, a number of moulds 43, one for each heating-chamber, are shown, which are retained in the operative position by a cam rail 45<a> and drop about their pivots 44<a> to eject the moulded article. One mould only may however be provided, in which case the mould would be permanently aligned with the pressing plunger. The materials which may be moulded are organic esters of cellulose, e.g. cellulose formate, cellulose propionate, cellulose butyrate, and particularly cellulose acetate and cellulose ethers, e.g. ethyl cellulose, methyl cellulose and benzyl cellulose. Plasticizers used are dimethyl phthalate, diethyl phthalte, di(methoxy ethyl) phthalate, diethyl tartrate, dibutyl tartrate, triacetin, triphenyl phosphate, or mixtures of two or more of these. Examples of moulding- compositions are : (1) Cellulose acetate 100 parts by weight, triphenyl phosphate 12À5 parts, dimethyl phthalate 12À5 parts, and mixture of ortho -and para-ethyl toluene sulphonamide 20 parts. (2) Cellulose acetate 100 parts by weight, mixture of triphenyl phosphate and tricresyl phosphate 15 parts, the phthalate of mono-methyl ether of ethylene glycol (dimethoxyethyl phthalate) 30 parts. The heating temperature specified is 160-170‹ C. and extruding pressure 5000-50000 lbs. per square inch. Specifications 215,823 and 249,600, [both in Class 70], are referred to. The Specification as open to inspection under Sect. 91 comprises also the construction shown in Fig. 1 (Cancelled). The material in granular or flaky form is fed from a hopper 1 into the chamber 3 which is surrounded by heaters 4. The piston 6, which is fluid-actuated and controlled by a valve 10, is connected to the plunger 5. The capacity of the chamber 3 is not substantially greater than that of the mould 14 so that the heating chamber is emptied at each pressing operation. After extrusion the mould part 13 is moved towards the stop 21 whereby the ejector 18 positively removes the article from the mould. This subject-matter does not appear in the Specification as accepted.