Patent GB-402974-A (GB)
Title: Improvements in the manufacture of thermoplastic materials
IPC: B44F9/04
Filed: 1933-03-13
Abstract: 402,974. Moulding thermoplastic substances. CELLULOID CORPORATION, 290, Ferry Street, Newark, New Jersey, U.S.A. March 13, 1933, No. 7532. Convention date, March 12, 1932. [Class 87 (ii).] Relates to the manufacture of multi-coloured thermoplastic materials, particularly those made of, or containing, derivatives of cellulose, e.g. ethyl, methyl, benzyl or other cellulose ethers, and organic cellulose esters, e.g. cellulose formate, propionate, butyrate and particularly cellulose acetate but applicable also to thermoplastic materials having a basis of rubber &c., or of casein &c. or to synthetic organic thermoplastics obtainable by the polymerisation of vinyl and other unsaturated compounds, or those obtainable by condensation reactions between phenols and aldehydes or ketones, urea and aldehydes, aldehydes and amines and amines and glycerol and phthalic anhydrides ; and consists in working, in a series of stages, a number of portions of the material into a coherent mass under heat and pressure so as to distribute throughout the mass a colouring agent contained in the surface of at least one of the portions of material, of different colour from the bulk of the portion. The working may be effected by passing the several portions of material together through heated rolls, folding the resulting sheet upon itself and repeating these operations until the desired colour distribution is obtained. Various plasticisers for the material may be employed. According to one method of carrying out the invention a portion of the thermoplastic material in sheet, slab or other form 1 has the surface coloured locally as at 2, after which an unpainted slab 2 is placed on the painted face of the slab &c. 1 and the superposed slabs are worked by heated rolls. According to another method, a slab of thermoplastic material may be superficially coated with colouring agent and cut up into fragments whose edges contain the colouring matter. Similar fragments may be cut from material whose surface has not been so treated, the two series of fragments then being mixed at random and consolidated under heat and pressure. In a further method, the mottled material 3, Fig. 2, prepared by hot working the sheets 1, 2, Fig. 1, may have part of its surface treated with colour and may then be cut into fragments so that the colour appears on the edges of some of the fragments the remainder of the fragments having no applied colour. The fragments are then mixed and consolidated under heat and pressure. The slab 3 may be cut into fragments and the edges of some of the fragments (preferably those cut from the edge of the slab) are painted first with a white paint and then with a brown dye or lake which is contained in a volatile solvent or swelling agent for the cellulose acetate &c. The fragments are then consolidated as before. The resulting material is stated to simulate Brazilian onyx. The slab 3 may also be produced by passing the superposed slabs 1, 2 first through heated corrugated rolls and then through heated smooth rolls and this slab may be halved, one half being provided with a central longitudinal coating of paint, upon which the other half is superposed, the two halves then being rolled and cut into fragments some of whose edges are provided with colour, whereupon the fragments are mixed and consolidated as before. Pigment may be introduced into the material while it is being worked in the heated rolls.