Patent GB-541371-A (GB)
Title: A process for the production of hollow structures from cellulose derivatives
IPC: B29C49/00
Filed: 1940-05-22
Abstract: 541,371. Cellulose derivative bags, tubes and other hollow structures ; films. BECKER, O. W., HAGANDER, J., AHRENS, R., FRUEDENBERG, R., and LEUBE, K. May 22, 1940, No. 9096. Convention date, March 20, 1939. [Class 2 (ii)] [Also in Groups V and XVII] A hollow structure of cylindrical, spherical, conical, bladder-shaped, ellipsoidal, or other form is obtained from a correspondingly shaped flat structure of an organic cellulose ester or nitrocellulose by subjecting it to a partial saponification and at the same time to swelling, in such manner that its resistance to severing decreases from the outside to the inside, and severing, or hollowing out, the treated and thus weakened or split flat structure, e.g. by the introduction of liquids or gases, with formation of the hollow structure. The cellulose ester may be an acetate, formate, propionate, butyrate, tolyl sulphonate, nitrate, nitro-formate, or aceto-butyrate. The cellulose esters preferably contain softeners such as diethyl phthalate, dibutyl phthalate, dimethyl glycol phthalate, castor oil, paraffin oil, or triphenyl or tricresyl phosphate. The treatment of the flat structure may be such that the inner layer actually dissolves in the treating agent or one of its constituents. The saponifying agent may be a solution of sodium, potassium, ammonium, or calcium hydroxide, sodium carbonate, sulphuric acid, hydrochloric acid, or nitric acid. The swelling agent may be methyl, ethyl, or isopropyl alcohol, or a stronger swelling agent diluted with a non-solvent. As strong swelling agent there may be used glacial acetic acid, chloroform, methylene chloride, acetone, methyl ethyl ketone, dioxane, pyridine, furfural, and other liquids depending on the particular cellulose derivative used. If the mixture of saponifying agent, swelling agent, and, if desired, non-solvent tends to separate into layers, a further solvent may be added to homogenize the mixture. During the treatment, the swelling agent or solvent penetrates to the inside of the flat structure at a greater velocity than the saponifying agent or the non-solvent: The inside of the structure thus becomes highly swollen or dissolved whereas the outer layers are not so highly swollen. Severing of the structure along the internal line or surface of greatest weakness can be effected by a sliding movement of the outer layers over each other, e.g. by wringing or by passing the structure between squeezing rollers. The flat structure may be hollowed out by leading through liquids or blowing with gases. Liquids or gases may be introduced into one end of the split or opened flat structure. Gases may be evolved in the inside of the treated flat structure by adding to the treatment liquid a low-boiling liquid which on subsequent heating is converted to the gaseous form. From band-shaped flat structures there may be obtained tubes suitable for use as artificial sausage skins or fuel pipes. From circular or round flat structures there may be obtained bladder-shaped or spherical hollow structures suitable as air balloon covers. Seamless bags or pouches suitable as food containers, and also fingerstalls and gloves may be obtained. In an example, cellulose acetate strips are saponified with a solution of caustic soda, methylene chloride, ethyl and methyl alcohol. The strips are then heated to vaporize methylene chloride in the interior and the strips become blown up to cylindrical or ellipsoidal hollow bodies. In another example, discs of cellulose triacetate foil are treated with a solution of caustic soda, methylene chloride, ethyl and methyl alcohol, and then with hot water. The flat discs become inflated and form hollow tubs or containers suitable for holding meat goods. Rectangular cuttings of cellulose nitrate foil are treated with alcohol, ether, plasticizer, and aqueous sodium sulphide solution until the inner but not the outer layers are strongly swollen. The cuttings are then placed in a hot air current whereby the ether vaporizes and by blowing up the materials produces bag-like structures. These may be cut open at one side and provided with strips of adhesive or other closures. They may be used as explosion bags. The Specification as open to inspection under Sect. 91 comprises also the production of hollow structures of cellulose ethers. This subjectmatter does not appear in the Specification as accepted.