![<?echo $_SERVER['SERVER_NAME'];?>](/template/twentyseventeen/skin/images/header.jpg)
Fiber-grade polyurethane chips, that is, linear polyether (thermoplastic) thermoplastic polyurethane elastomer (TPU), are dried, melted, metered, spun, wound, oiled, balanced, and other processes to obtain melt spun spandex products. The main one-step process is used to produce: The diisocyanate, polyether glycol, chain extender and additives are directly added into the twin-screw reactor after being metered and polymerized. With the growing maturity of fiber-grade polyurethane chip technology and the improvement of melt spinning technology, melt-spun spandex products are comparable to dry spun spandex products.
First of all, the performance of the TPU (heat resistance, hydrolysis resistance) is improved:
Japan's Bell spinning company adopts the method of adding prepolymer in the TPU melt to improve the spinning processing conditions and the mechanical properties of the finished product. The specific method is to melt the TPU chips through a screw extruder and add a prepolymer obtained by reacting a diisocyanate with a polyester or a polyether diol at the outlet thereof, and then uniformly mixing the mixture by a static mixer before spinning. The effect of adding prepolymers on the one hand can reduce the melting temperature of the TPU chips, so that the spinning can be performed at a lower temperature; on the other hand, the isocyanate groups in the prepolymer can be in the TPU macromolecules during the fiber forming process. Chemical crosslinking occurs between the fibers to improve the mechanical properties of the fibers. The strength of the obtained fiber can reach 1.38-1.51 cN/dtex, and the elongation at break can range from 450% to 550%. The elastic recovery at 190°C can still be maintained at 40-70%. At present, this method has been widely used in spandex melt spinning.
Second, the isocyanate group-containing prepolymer has poor storage stability, that is, an extremely active NCO group easily loses its activity and thus cannot function as a chemical crosslinking agent. ways to improve:
The isocyanate groups in the prepolymer are first blocked with compounds such as phenols and alcohols. At the spinning temperature, this closed prepolymer will reactivate and act as a chemical crosslink. With aromatic diol chain extenders, the heat resistance of fiber-grade polyurethane chips can be further improved. When the chain extender was 1,4-butanediol, about 5% of a cross-linking agent was added. The cross-linking agent was an isocyanate-terminated aliphatic polyester oligomer. After chemical cross-linking treatment, the resilience of the fiber was evaluated. Can significantly improve.
First of all, the performance of the TPU (heat resistance, hydrolysis resistance) is improved:
Japan's Bell spinning company adopts the method of adding prepolymer in the TPU melt to improve the spinning processing conditions and the mechanical properties of the finished product. The specific method is to melt the TPU chips through a screw extruder and add a prepolymer obtained by reacting a diisocyanate with a polyester or a polyether diol at the outlet thereof, and then uniformly mixing the mixture by a static mixer before spinning. The effect of adding prepolymers on the one hand can reduce the melting temperature of the TPU chips, so that the spinning can be performed at a lower temperature; on the other hand, the isocyanate groups in the prepolymer can be in the TPU macromolecules during the fiber forming process. Chemical crosslinking occurs between the fibers to improve the mechanical properties of the fibers. The strength of the obtained fiber can reach 1.38-1.51 cN/dtex, and the elongation at break can range from 450% to 550%. The elastic recovery at 190°C can still be maintained at 40-70%. At present, this method has been widely used in spandex melt spinning.
Second, the isocyanate group-containing prepolymer has poor storage stability, that is, an extremely active NCO group easily loses its activity and thus cannot function as a chemical crosslinking agent. ways to improve:
The isocyanate groups in the prepolymer are first blocked with compounds such as phenols and alcohols. At the spinning temperature, this closed prepolymer will reactivate and act as a chemical crosslink. With aromatic diol chain extenders, the heat resistance of fiber-grade polyurethane chips can be further improved. When the chain extender was 1,4-butanediol, about 5% of a cross-linking agent was added. The cross-linking agent was an isocyanate-terminated aliphatic polyester oligomer. After chemical cross-linking treatment, the resilience of the fiber was evaluated. Can significantly improve.