| 摘要 |
965,870. Cleaning melt spinning nozzles. ONDERZOEKINGSINSTITUUT RESEARCH N.V. Feb. 12, 1963 [Feb. 16, 1962], No. 5633/63. Heading B5B. Spinning nozzles employed in the melt spinning of synthetic organic thermoplastic materials, which nozzles have been treated during the spinning process with a liquid polyorganosiloxane are treated after the spinning process with a hydrocarbon having a boiling point of at least 150‹ C., or with a mixture of hydrocarbons having an initial boiling point of at least 150‹ C., and thereafter with a molten mixture of a nitrate and a nitrite of sodium and/or potassium, e.g. 45 to 55% by weight of potassium nitrate and the remainder sodium nitrite. The temperature of the molten mixture may be within the range 200‹ C. to 600‹ C. The mixture of liquid hydrocarbons may be liquid paraffin (medicinal white oil). The polyorgano siloxane may be a polymethylsiloxane having a viscosity of 50 to 1000 centistokes at 25 ‹ C. If a solid hydrocarbon is to be used in the cleaning of the spinning nozzle, it should be melted before being applied to the nozzle. In an example, the nozzle to be cleaned is first immersed in a liquid paraffin having a viscosity of 35 centistokes at 20‹ C. and a specific gravity of 0.87. The nozzle is then removed from the oil and immersed in a melt consisting of equal parts by weight of potassium nitrate and sodium nitrite and maintained at a temperature of 450‹ C. In the other example the melt used consists of equal parts by weight of sodium nitrate and sodium nitrite maintained at a temperature of 500‹ C. In both cases the nozzle after having been treated is cooled and subsequently rinsed with warm water to remove the salts. It is found that whereas nozzles which have been used for melt spinning polyamides can be freed from adhering polyamide, whether decomposed or not, by treatment with the melt alone, polymethylsiloxane deposits are not removed as well unless the nozzle is first treated with a hydrocarbon or mixture of hydrocarbons as specified.
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