Патент USA US2407419код для вставки
Patented Sept. 10, ‘194.6 2,407,419 UNITED‘ STATES PATENT OFFICE STABILIZATION OF TETRAFLUORO ETHYLENE William Edward Hanford, Easton, Pa., assignor to E. I. du Pont de Nemours & Company, Wil I mington, Del., a corporation of Delaware No Drawing. Application February 15, 1943, Serial No. 476,025 10 Claims. 1 (C1. 260-652.5) . - 2 . . This invention relates to new compositions of matter and more particularly to compositions comprising ?uoroethylenes which are stabilized a total of 6.5 months, during which time essen tially no more polymerization takes. place. against spontaneous polymerization. Tetra?uoroethylene polymerizes after standing lar conditions without the addition of ammonia, the tetra?uoroethylene is completely ‘polymerized a few days at room temperature under super in less than one week. . Ina control experiment carried out under simi . - atmospheric pressure in accordance with the Example II teaching of U. S. Patent 2,230,654. This spon To a glass tube similar toy that employed in taneous polymerization of tetra?uoroethylene is acutely undesirable since it necessitates costly 10 Example I is added about 0.1 part of p-pheneti and time-consuming precautions for the safe dine, and the tube is then immersed in a bath of liquid ethylene and ?lled about half full of tetra storing of tetra?uoroethylene. Thus prior to the ?uoroethylene (about 20 parts) by condensation. present invention it has been an accepted prac The tube is then transferred to a bath of liquid tice to store tetra?uoroethylene at the tempera ture of solid carbon dioxide since only in this 15 nitrogen, and after freezing, it is sealed. The tube is then allowed to stand at roomrtempera way could polymerization be prevented and tetra ture, under which conditions the tetrafluoro ?uoroethylene stored in an appreciable quantity ethylene is a liquid under its own vapor pressure. over a period of time. This invention has as an object the produc After standing for 12' days there is formed only tion of stabilized ?uoroethylenes which can be 20 a trace of polymer, corresponding to less than. 1% of the total tetra?uoroethylene vpresent. I stored at normal temperature and superatmos pheric pressure for an inde?nite period of time Under similar conditions a control experiment without undergoing spontaneous polymerization. containing no stabilizer is completely polymerized in less. than one week. . . . Other objects will appear hereinafter. I havediscovered that this polymerization of 25 Example III , ?uoroethylene compounds can be prevented by Example II is repeated employing di-n-butyl incorporating therewith a small proportion of a amine instead of p-phenetidine as stabilizer. A compound containing amine nitrogen and that very small amount of polymer is formed in the the stabilized product thus obtained can be stored at normal temperature and superatmospheric 30 ?rst week of standing at room temperature, and thereafter no further polymerization occurs for pressure for an inde?nite period of time without six months. The total quantity of ‘polymer undergoing polymerization. For example, tetra formed corresponds to less than 1% by weight ?uoroethylene to which is added about 0.1% to of the total tetra?uoroethylene present. 1% by weight of tributylamine undergoes no spontaneous polymerization whatever on storage Example IV under its own vapor pressure at 25° 0., whereas unstabilized tetra?uoroethylene undergoes ap preciable polymerization in a few days under such conditions. ' The invention is further illustrated by the fol lowing examples: Example I 85 Example II is repeated employing tri-n-butyl amine in place of p-phenetidine as stabilizer. No polymerization whatever occurs under these con 40 ditions after the tube has stood at room tempera ture for 6.25 months. Example V A thick walled glass tube is ?lled about half Tetra?uoroethylene stored in the absence of its full of liquid tetra?uoroethylene by condensing 45 liquid phase under 200 lbs/sq. in. pressure at the tetra?uoroethylene while the tube is im mersed in a bath of liquid ethylene. The free space in the tube is then ?lled with ammonia room temperature in a steel container undergoes some spontaneous polymerization after standing for about a month. However, the addition of gas, the tube isv placed in liquid nitrogen to freeze 0.5% by weight of tributylamine to the storage the tetrafluoroethylene and it is sealed. The tube 50 container effectively and completely prevents this is then allowed to stand at room temperature, polymerization over a period of more than six under which conditions the liquid tetra?uoro months. ethylene is under its own vapor pressure. After one week but a trace of polymer has formed in The ?uoroethylene compounds referred to here I in are halogenated ethylene compounds contain the glass tube. The tube is allowed to stand for 55 ing at least one ?uorine atom. Examples of these 2,407,419 4 scrubbing with an acid solution or by passing the compounds are vinyl ?uoride, 1,1-di?uoroethyl ene, l-?uoro-l-bromoethylene, l-?uoro-Z-chloro gas over an absorbent for the stabilizer. As many apparently widely different embodi ments of this invention may be made without de parting from the spirit and scope thereof, it is to chloroethylene and tetra?uoroethylene. The be understood that I do not limit myself to the process of this invention is particularly suitable speci?c embodiments thereof except as de?ned in for the stabilization of poly?uoroethylenes, i. e., the appended claims. those containing more than one ?uorine atom. I claim: The amino compounds, in addition to those dis 1. A process for treating tetrafluoroethylene closed in the examples, which can be used as the which substantially reduces its tendency to spon polymerization stabilizers include a large number taneous polymerization at normal temperature of available compounds, examples of which are and superatmospheric pressure, said process com primary aliphatic amines, such as ethylamine and prising mixing with said tetrafluoroethylene a butylamine; secondary aliphatic amines, such as dihexylamine and methylbutylamine; tertiary ali 15 small amount of tertiary hydrocarbon amine. 2. A process for treating tetra?uoroethylene phatic amines, such as trimethylamine and tri which substantially reduces its tendency to spon e'thylamine; primary aromatic amines, such as taneous polymerization at normal temperature beta-naphthylamine' and aniline; secondary aro and superatmospheric pressure, said process com matic amines, such as diphenylamine and phenyl prising mixing with the tetra?uoroethylene a 20 alpha-naphthylamine; tertiary aromatic amines, small amount of a tertiary aliphatic hydrocarbon such as triphenylamine; mixed secondary amines, amine. ‘ such as N-monomethyl aniline and N-propyl ani~ 3. A process for treating tetra?uoroethylene line; and mixed tertiary amines, such as N-di— which substantially reduces its tendency to spon methyl aniline and N-butyl diphenylamine. The taneous polymerization at normal temperature stabilizers of this invention may be further ohar~ and superatmospheric pressure, said process com— acterized in that they are basic compounds con prising mixing with said tetra?uoroethylene a taining amino nitrogen, i. e., they include am small amount of tributyl amine. monia and substituted ammonias in Which one or ll. Tetra?uoroethylene stabilized with sufficient more of the hydrogen atoms is replaced by alkyl, I ' tertiary hydrocarbon amine to prevent polymeri alkaryl, aralkyl, or aryl hydrocarbon radicals. zation of the tetra?uoroethylene at 25° C. and The stabilizer is to be employed in amounts superatmospheric pressure. ranging from about 0.001% to about 5%, based 5. Tetra?uoroethylene stabilized with sufficient ethylene, 1,Z-di?uoro-1,2-dich1oroethylene, 1,1 di?uoro - 2,2-dichloroethylene, 1,1,2-tri?uoro-2 on the monomer. In general, however, it is pre ferred to employ the stabilizers in amounts rang ing from about 0.01% to about 1%, based on the amount of monomer. Fluoroethylene compounds which are stabilized according to the method given in this invention can be stored inde?nitely without danger of poly merization. On the contrary, the unstabilized compound'polymerizes on standing, either com tertiary aliphatic hydrocarbon amine to prevent polymerization of the tetra?uoroethylene at 25° C. and superatmospheric pressure. 6. Tetra?uoroethylene stabilized with su?icient tributylamine to prevent polymerization of the tetra?uoroethylene at 25° pheric pressure. 7. The process set forth said tertiary hydrocarbon amount of from 0.001% to pletely ?lling the container with solid polymer or ?lling the exit valves, so that the removal of the remainder of the unpolymerized material is im possible. undesirable but also dangerous, it is of great ad vantage to be able to store fluoroethylenes in and by means of stabilizers which are readily re moved from the monomer. It is not essential that in claim 1 in Which amine is added in 5% by Weight of the tetra?uoroethylene. Since such circumstances are not only ' de?nitely without danger of such polymerization C. and superatmos 8. Tetra?uoroethylenestabilized with tertiary hydrocarbon amine in amount of from 0.001% to 5% by weight of the tetra?uoroethylene. 9. Tetra?uoroethylene stabilized with tertiary aliphatic hydrocarbon amine in amount of from 50" 0.001% to 5% by weight of the tetra?uoroethyl the stabilizers of this invention be removed prior ene. to catalytic polymerization of the ?uoroethylene. 10. Tetra?uoroethylene stabilized with tribu tylami’ne in amount of from 0.001% to 5% by However, if desired this removal can be accom weight of the tetra?uoroethylene. plished, for example, by fractional distillation, by 55. WILLIAM EDWARD HANFORD.