GB1000876A - Plasticising nitrocellulose - Google Patents

Abstract

Nitrocellulose is plasticized by contacting it with a plasticizer therefor dissolved in a liquid medium which has substantially no solvent action on the nitrocellulose but which has a solvent action on the plasticizer and subsequently isolating the resultant plasticized nitrocellulose from the liquid medium. Where the nitrocellulose has been previously "damped," any damping liquid is considered to form part of the liquid medium. The liquid medium may comprise an aqueous solution of one or more organic liquids; and may comprise a mixture containing water and water-miscible organic liquid in a ratio in the range 1 : 1 to 19 : 1 by weight. Preferably, the water-miscible organic liquid is not a strong solvent for the nitrocellulose. Specified liquids include ethanol, n-propanol and isopropanol. Ethyl acetate may be present in addition to isopropanol. The plasticizer present may be completely dissolved in the liquid medium and its concentration therein preferably does not exceed 10% by weight. Nitrocellulose may be contacted with the plasticizer at an elevated temperature, suitably at or near the reflux temperature of the liquid medium. Desirably, the nitrocellulose is stirred in the liquid medium and the plasticizer is added to the mixture slowly at such a rate that the plasticizer concentration in the liquid medium does not exceed 1% by weight. The composition of the liquid medium may be altered during the time that the nitrocellulose is contacted therewith (e.g. by distilling off some of the liquid, or by addition of water), to vary the solvent action of the liquid medium on the plasticizer. Variation may be such as to bring the ratio of water to water-miscible organic liquid within the range of 1 : 1 to 19 : 1 by weight, at some stage of the process. The composition of the liquid medium may be so altered as to cause all the plasticizer to pass into the nitrocellulose, and substantially all the organic liquid may be removed from the liquid medium during said process. If desired, the plasticized nitrocellulose may be cooled while in suspension in the liquid medium. All the required quantity of plasticizer may be initially dissolved in the liquid medium or may be added thereto over a period of time at the start of the process. In plasticizing low viscosity grades of nitrocellulose, the plasticizer is added to the liquid medium over a period of time and the liquid medium is adjusted during the process so as to be comparatively rich in water-miscible organic liquid when plasticizer addition commences and comparatively weak in said liquid at the end of plasticizer addition. A major proportion of the plasticizer may be added during the time when the concentration of water-miscible organic liquid is comparatively high, the composition of the liquid changed to one having a comparatively low concentration of water-miscible organic liquid and the remaining portion of the plasticizer added slowly to the liquid medium. Specified plasticizers include dibutyl phthalate, dioctyl phthalate, dicyclohexyl phthalate, tricresyl phosphate, castor oil, butyl acetyl ricinoleate, epoxidized soya bean oil, camphor, nitroglycerine or ethylene glycol dinitrate or mixtures thereof.