Patent GB-742659-A (GB)
Title: Improvements in or relating to cellulose ether compositions
IPC: C08L1/28
Filed: 1953-02-02
Abstract: A stabilized cellulose ether composition comprises a thermoplastic cellulose ether (particularly a de-ashed ethyl cellulose) and a polycyclic phenol having at least two noncondensed aromatic nuclei joined by methylene groups, each nucleus having a hydroxy group in a position adjacent to the carbon atom attached to the methylene group. The cellulose ether is in general of the type soluble in organic solvents such as acetone, benzene, toluene-alcohol, methanol, ethanol and ethyl and butyl acetate.  Ethyl cellulose of about 37-52 (preferably 43-48) per cent ethoxyl content is particularly suitable, but the ether may be thermoplastic propyl, ethyl propyl, ethyl butyl, methyl ethyl or benzyl cellulose.  The polycyclic phenol may have as substituents in the aromatic nuclei methyl, ethyl, propyl, isopropyl, butyl, secondary butyl, tertiary butyl or amyl groups. The proportion of stabilizer may be 0.1-5 per cent (preferably 0.25-1 per cent) by weight, based on the cellulose ether.  The polycyclic phenol may be 2,21 - methylene - bis - p - cresol; 2,21 - methylene - bis - 6 - tert. - butyl - p - cresol; 2,6 - bis (2 - hydroxy - 5 - methylbenzyl) - 4 - methyl - phenol; 2,21 - methylene - bis - 4 - isopropyl - phenol; 2,6 - bis (2 - hydroxy - 5 - isopropyl benzyl)-4-isopropyl phenol; 2,6-bis (2-hydroxy - 3 - isobutyl - 5 - methyl benzyl) - 4 - methyl-phenol.  In a series of examples using the above stabilizers a solution of 60 parts of ethyl cellulose in a mixture of 380 parts of ethanol and 160 parts of benzene is adjusted to a pH not exceeding 4 with hydrochloric acid, and the ethyl cellulose is precipitated by pouring the solution into an excess of vigorously stirred distilled water at 70-75 DEG  C.  The precipitated de-ashed cellulose ether is washed four times with distilled water and, while stirring in the fourth wash water, a solution of the stabilizer in ethanol, acetone, or acetone-ethanol is added dropwise to the slurry.  The cellulose ether (by which the stabilizer has been absorbed) is then filtered off and dried at 70 DEG  C. in vacuo.  In a second series of examples the slurry constituting the fourth wash is heated to 90 DEG  C. before addition of the stabilizer.  In a third series the stabilizer is added to the original benzene-ethanol solution of the ethyl cellulose before adjustment of the pH value. The proportions of stabilizer used (based on ethyl cellulose) range from 0.25 to 1.0 per cent. It is preferable to incorporate the stabilizer with the cellulose ether in order to prevent degradation of the latter during storage, but the stabilizer may also be incorporated in the product in which the cellulose ether is employed. For example, the stabilizer may be added to a finished cellulose ether lacquer, or to the lacquer solvent during or prior to the solution of the other lacquer ingredients, or it may be added to the mixture of ingredients constituting a cellulose ether moulding powder. Cellulose ether moulding powders containing the stabilizers may be moulded at temperatures of the order of 190-250 DEG  C. without excessive degradation of the cellulose ether.  The compositions may also contain the usual plasticizers, resins such as oil-soluble phenol aldehyde condensates, ester gum, hydrogenated glycerol or pentaerythritol abietate, rosin, or oil-modified alkyd resins, end waxes such as paraffin wax, microcrystalline petroleum wax, or carnauba, candelilla, montan or japan wax.