| 摘要 |
1,147,595. Stretching polyoxymethylene filaments and film. FARBENFABRIKEN BAYER A.G. 1 April, 1966 [1 April, 1965], No. 14637/66. Heading B5B. Filaments or fibres of a polyoxy-methylene having an "inherent viscosity" of 0À8 to 2À5 preferably 1À0 to 2À0, inclusive are stretched at a stretch ratio of at least 4: 1 for example up to 15: 1, at a temperature which is not more than 40‹ C. and is preferably 20 to 30‹ C. below the crystalline melting point of the material of the unstretched filaments or films. This property can be determined by a differential thermoanalysis of the filament or film according to the method of Morita and Rice (Analytical Chemistry 27, pages 336-339, 1955). The filaments or films may be stretched in two stages; in a first stage at a stretch ratio of 4 : 1 to 8 : 1 and at a temperature 20 to 40‹ C. below the crystalline melting point of the unstretched filaments or film followed by a second stage in which the stretched filaments or film is further stretched at a stretch ratio of 2 : 1 to 5 : 1 at a temperature 5 to 25‹ C. below the crystalline melting point of the unstretched filament or film. The polyoxymethylenes used in making the filament or film must have molecular weights of 20,000 to 125,000, preferably 30,000 to 85,000. The polymers may be obtained by polymerization of formaldehyde and subsequent stabilization of the polymers or there may be used copolymers of trioxane with dioxolane and oxthiolane. In an example a polyoxymethylene stabilized by esterification with acetic anhydride and having an inherent viscosity of 1.35 is melt spun to form filaments having a crystalline melting point of 181‹ C. The filaments are stretched over a heating coil maintained at a temperature of 160‹ C. Œ 1‹ C. at a stretch ratio of 9 : 1. In another example, a trioxane/oxthiolane copolymer stabilized by partial alkali degradation and having an oxthiolane content of 1À5% and an inherent viscosity of 1À35 is melt spun to form filaments having a crystalline melting point of 175‹ C. which are stretched at a stretch ratio of 12 : 1 over rollers heated to 150‹ C. The inherent viscosity if the polymer is derived from the relative viscosity measured with a 0À5% solution of the polymerinp-chlorophenol at 60‹ C. |
