| 摘要 |
<p>1,173,000. Treating polytetrafluoroethylene. FARBWERKE HOECHST A.G. 30 Dec., 1966 [30 Dec., 1965], No. 58328/66. Heading C3P. Polytetrafluoroethylene granular powder is manufactured by stirring a polytetrafluoroethylene powder at a temperature in the range of from 20‹ to 300‹ C. in the presence of a dispersing agent consisting of an alkane carrying at least two hydroxy and/or amino groups and/or a compound which can be derived from these alkanes by combining them by means of the hydroxy and/or amino groups or mixtures of these compounds. Polytetrafluoroethylenes: (1) an unsintered polytetrafluoroethylene obtained by polymerization of tetrafluoroethylene in an aqueous dispersion and pulverizing the polymerization product, and (2) the product obtained by polymerization of tetrafluoroethylene in the presence of a small quantity of another perfluoro-olefine, e.g. 0.05 to 0.1% of perfluoropropene. Dispersing agents ethylene glycol, propane - diol - (1.2), propane - diol - (1.3), butane-diol-(1.3), butane-diol-(1.4), a pentane diol or triol, glycerol, di-ethylene glycol, triethylene glycol, ethanolamine, propanolamine, diethanolamine, ethylenediamine and propylenediamine. The proportion between the polytetrafluoroethylene and the dispersing agent is in the range of from 1:1 to 1:10. The polytetrafluoroethylene is preferably degassed by vacuum prior to the addition of the dispersing agent. The stirring may be carried out in the presence of a liquid which is inert under the reaction conditions, viz., alcohols, esters, nitriles, ketones, aromatic or aliphatic hydrocarbons, or water containing specified wetting agents. According to an example, a four-necked flask having a capacity of 4 litres, provided with a stirrer, a cooler and a sump theremometer, was filled with 2 litres of ethylene glycol. 150 ml. of a 20% aqueous dispersion of polytetrafluoroethylene were first added and then 360 g. of screened polytetrafluoroethylene - suspension polymer powder while stirring moderately. The number of rotations was then increased to 300-400 r.p.m. and the mixture was slowly heated. After a short time and at a temperature slightly above 30‹ C., an agglomeration of the particles was observed. At the same time, the dispersion disintegrated and its solid portions also precipitated on the suspended polytetrafluoroethylene particles, favouring agglomeration. The mixture was heated to a temperature in the range of from 40‹ to 50‹ C. for 1 hour, then cooled. The polytetrafluoroethylene granules obtained were separated, washed and dried.</p> |
