Patent GB-770014-A (GB)
Title: Cellulose derivative compositions and cured products prepared therefrom
IPC: C08L1/08
Filed: 1954-07-15
Abstract: A composition comprises (1) a cellulose ester or ether having free hydroxyl groups; (2) a minor proportion of a glycidyl polyether of a polyhydric alcohol or polyhydric phenol having an average of at least 1.1 epoxy groups per molecule; and (3) an epoxy-curing catalyst, preferably an organic or inorganic acid, certain salts of inorganic acids and boron trifluoride complexes. The glycidyl polyether may be obtained by reacting for several hours at 50-150 DEG  C. a dihydric phenol, such as resorcinol, catechol, hydroquinone, methyl resorcinol, bisphenol {2,2-bis-(4-hydroxyphenyl) propane}, 2,2 - bis - (4 - hydroxyphenyl) butane, 4,41 - dihydroxybenzophenone, bis - (4 - hydroxyphenyl) - ethane, or 1,5 - dihydroxynaphthalene, with an excess, e.g. 4-8 mol. excess, of, for example, epichlorohydrin in an alkaline medium.  The preferred glycidyl polyether is that prepared with bisphenol, having an average of 1.1 to 2.0 epoxy groups per molecule and a molecular weight of 200-900, especially 300-800. Other glycidyl polyethers may be obtained by reacting a polyhydric alcohol, such as glycerol, propylene glycol, ethylene glycol, diethylene glycol, butylene glycol, hexanetriol, sorbitol, mannitol, pentanetriol, pentaerythritol, di- and tripentaerythritol, polyglycerol, dulcitol, inositol, methyltrimethylol propane, 2,6-octanediol, 1,2,4,5-tetrahydroxycyclohexane, 2-ethylhexanetriol-1,2,6, glycerol methyl ether, glycerol allyl ether, polyvinyl alcohol or polyallyl alcohol, with, for example, epichlorhydrin, preferably in the presence of 0.1-5 per cent by weight of an acid-acting compound, such as hydrofluoric acid, boron trifluoride, stannic chloride or stannic acid, at about 50-125 DEG C. in the proportions of about one mol. of epichlorhydrin for every equivalent of hydroxyl group in the polyhydric alcohol.  The reaction product is then fully or partially dehydrochlorinated by heating at about 50-125 DEG  C. with a small, e.g. 10 per cent, stoichiometrical excess of a base, such as sodium aluminate.  The preferred aliphatic polyhydric alcohols are those containing 2-10 carbon atoms and 2-6 hydroxyl groups and especially the alkane polyols containing 2-8 carbon atoms and 2-6 hydroxyl groups.  The preferred glycidyl polyethers prepared from these have 1.1-4.0, particularly 1.1-3.0, epoxy groups per molecule and a molecular weight between 120 and 1000, particularly between 200 and 350. The cellulose esters or ethers used preferably contain at least one hydroxyl group for every four, and especially for every two, anhydro glucose units.  The esters include cellulose acetate, butyrate, acetate-butyrate and acetate-propionate.  The ethers include ethyl, methyl ethyl, benzyl and carboxy-methyl cellulose. There may also be used cellulose ether-esters, such as the propionate of benzyl cellulose and the butyrate of methyl cellulose.  Preferred cellulose derivatives are cellulose esters which have 20-70 per cent of the hydroxyl groups esterified with a monocarboxylic acid containing 2-12 carbon atoms, especially cellulose acetate having a combined acetic acid content of 15-50 per cent.  The epoxy-curing catalyst may be citric acid, acetic acid acetic anhydride, butyric acid, caproic acid, phthalic acid, phthalic anhydride, tartaric acid, aconitic acid, oxalic acid, succinic acid, succinic anhydride, lactic acid, maleic acid, maleic anhydride, fumaric acid, 1,2,4-butane-tricarboxylic acid, malonic acid, 1,1,5-pentanetricarboxylic acid, phosphoric acid, boric acid, sulphonic acids such as benzene sulphonic acid, perchloric acid, persulphuric acid, potassium persulphate or the boron trifluoride complexes, such as the p-cresol or the urea complex or the diethylaniline complex.  Particularly preferred curing catalysts are the organic mono- and polycarboxylic acids and their anhydrides containing not more than 16 carbon atoms, inorganic acids of the formula Ha[(X)w(Z)y] wherein X is a nonmetal having an atomic weight above 2, Z is fluorine, w is an integer, y is an integer greater than 1, and a equals the valence of the radical [(X)w(Z)y] and the salts of these acids with metals of atomic weight 24-210 in groups I to IV and VIII of the Periodic Table.  Examples of these preferred catalysts include copper and nickel sulphates, calcium phosphate, cobaltous and copper fluosilicates and copper, zinc, iron, cadmium, nickel, cobaltous, magnesium and strontium fluoborates.  The compositions of the invention may be prepared by adding the glycidyl polyethers and one or more of the curing catalysts to a 10-30 per cent solution of the cellulose ester or ether in one or more of the usual solvents and heating the mixture.  When then final product is to be a coating or in a shaped form such as a film or filament, the heating may be effected before or after the coating or shaping operation.  The preferred proportion of glycidyl polyether is 20-50 per cent of the amount of cellulose ester or ether employed.  Shaped articles composed of the compositions of the invention may be cured by heating at 90-200 DEG  C. for 1-20 minutes, the preferred curing temperature being within the range 120-190 DEG  C.  In an example 4.5 parts of a glycidyl polyether, derived from equivalent proportions of glycerol and epichlorhydrin, and 0.225 part of boron trifluoride-para-cresol complex are added to a solution of 15 parts of cellulose acetate, having 1 out of 6 hydroxyl groups unreacted, in 85 parts of aqueous acetone.  Films of this mixture are cast on glass panels which are then heated for 5 minutes at 160 DEG  C. to produce clear hard films resistant to acetone. Filaments are also prepared by dryspinning the solution, and these may be twisted into yarn and heated to 70-120 DEG  C. Specification 766,273 is referred to.