Mehrschichtiger Film

摘要

1,237,687. Cellulose ester films. GEVAERTAGFA N.V. 25 July, 1968 [16 Aug., 1967], No. 37763/67. Heading B5B. [Also in Divisions B2 and G2] A composite film comprising two hydrophobic layers is produced by casting on a casting surface a first solution of a cellulose ester in a solvent or solvent mixture with a boiling point or with boiling points below 100‹ C. and thereafter casting a second solution of a cellulose ester in a solvent or solvent mixture with a boiling point or boiling points below 100‹ C. to form a layer on the layer formed from the first solution while that layer remains on said casting surface and still contains a substantial proportion of solvent, one of the said solutions having a black pigment dispersed therein and the other a white pigment dispersed therein. The black pigment may be carbon black whilst the white pigment may be titanium dioxide, barium sulphate, zinc white or lead white. The carbon black may be present in a concentration of 1-5% by weight with respect to the total weight of solid material in such layer, whilst the concentration of the white pigment may be 10-55% by weight of the solid material. Suitable cellulose esters are cellulose triacetate, cellulose diacetate, cellulose nitrate, cellulose propionate, cellulose butyrate, and mixed esters such as cellulose acetopropionate. The solution of the cellulose ester containing the white pigment may also contain as a plasticizer a low molecular weight aromatic or aliphatic polyester of (A) an aliphatic diol (C 2-10 ) or a mixture of such diols and (B) an aliphatic dicarboxylic acid containing at most 10 carbon atoms, which polyester has been modified with a diisocyanate. Preferred polyesters are obtained from ethylene glycol and adipic acid or ethylene glycol, diethanolamine and adipic acid whilst the di-isocyanate is preferably 2,4-toluene diisocyanate. The white-pigmented layer is preferably cast first on to the casting surface which may be a casting drum or an endless metal belt. The black pigmented cellulose ester layer preferably has a thickness in the range 50-100 microns, whilst the white-pigmented layer preferably has a thickness in the range 10-50 microns. The composite film may be used as a film base for photographic material (see Division G2).