热流道注射成型的拖曳换料

在热流道注射成型过程中，换料不彻底和费时常常影响制品的质量和生产率，在生产中，采用多次注射法或以白色材料作为换色的过渡料等方法实现快速换料．作者基于聚合物熔体的流变行为，提出了拖曳换料的概念，建立了新料熔体和旧料熔体在热流道系统中共同流动的物理模型和数学模型．结果表明该模型较好地解释了注射速度、注射压力、粘度、温度、热流道模具的结构等对拖曳换料效率的影响；当热流道模具采用分区加热、多点控温技术时，控制新、旧料熔体的粘度小，可以明显提高换料后期的换料能力，改善生产中先易后难、先快后慢的换料过程，提高整个过程的换料能力．

Drag material change in hot runner injection molding

Quick change in the color or kinds of polymer materials often occurs in the hot runner injecting molding process. The time consuming and incomplete material change often affects the quality and productivity of products. In the practical production, multi injecting and using white material as the transition material are often used to achieve quick material change. Based on the rheological behavior of new and old plastic melt, the researches into these problems are carried out. The concept of drag material change process is presented, the physical model and mathematics model of the coflow process of new and old plastic melt in hot runner are built up, and the influence of the injection speed, the injection pressure, the viscosity difference and the temperature on drag material change process are analyzed systematically. Using multi point heating and temperature controlling, and monitoring the viscosity difference of the new and old plastic melt, the ability for material change in the late process can be improved greatly, which can solve the process problems, i.e. it is easy first and then difficult, quick first and then slow for the change of materials, and improve the ability for material change in the whole material change process.