Such a yarn is known from DE-A-22 60 778, for example. The yarn described exhibits a melting point of at least 275.degree. C. The maximum achievable DSC melting point, measured on a sample quantity of 8.5 mg at a heating rate of 10.degree. C. per min, is according to DE-A-22 60 778 as high as 291.7.degree. C. This DSC melting point corresponds to a DSC melting point of 291.degree. C. measured on a sample quantity of 2.5 mg at a heating rate of 20.degree. C. per min. The examples demonstrate that the increase in melting point clearly is causally related to the increase in spinning speed. To achieve the previously cited highest melting point in accordance with example 15, a spinning speed of 8,000 m/min is required. At the practically achievable spinning speeds for technical yarns of at most 6,000 m/min, the DSC melting points according to DE-A-22 60 778 lie below 290.degree. C. (2.5 mg; 20.degree. C./min), corresponding to 290.5.degree. C. (8.5 mg; 10.degree. C./min). DE-A-22 60 778 thus describes only yarns for technical application with a melting point of 275.degree. to 290.degree. C.
In DE-A-21 39 854, a method is described for subsequently imparting to yarns which have been spooled after spinning a higher melting point in excess of 285.degree. C. In this case, too, despite the very costly method, only DSC melting points under 290.degree. C. are achievable. The values given in Table II of 290.3.degree., 292.0.degree., and 290.3.degree. C. at constant length correspond to DSC melting points significantly below 290.degree. C., as can easily be derived from Table I of DE-A-22 60 778, in which the corresponding values for DSC melting point and DSC melting point at constant length are given.
USPTO Backgrounds
USPTO Backgrounds