Application of Extrusion Control in Officinal Flexible Package

Transfusion product is the one of most used items in medical instruments. And there are two categories of transfusion medications including glucose and sodium chloride injecta. In developed countries in Europe and America, the using rate of soft plastic bag amounted to more than 95% while in China the figure is less than 6%. According to statistics from Chinese State Food and Drug Administration, the number of domestic companies that manufacture non PVA soft bag is 30 plus. In recent years, some Chinese manufacturers are able to make a compact and automatic production line with printing, packing, filling and sealing. This trend begins to prompt pharmaceutical factory to take non PVC soft bag as the first choice for package of transfusion injecta.

Non PVC composite membrane is co-extruded out of three layers plastics including PP, PE, PA and SEBS with different melting points under 1 million class clean-room conditions. Inner layer is made from PP and PE and it the innoxious inertia polymer with stable chemical property, free of falling off. Middle layer is composed of PP and PA and it is compacting material with water and gas proof performance. Outer layer aims to intensify mechanical strength of bag. Now soft bag sold in the market is made from PP and PA.

The currently used non PVA medical packing membranes are made through blow molding. The common feature is that multilayer coextru-lamination is adopted to composite multiplayer materials with different performance requirements. The accurate control of thickness of each layer is particularly important due to their varied applications. To control the thickness precisely, almost film blowing production line adopts weight flow control technology to control extrusion amount and measures deviation between actual and set value. Thus machine will aotu regulate screw rotate speed to change amount accordingly. Therefore, the thickness deviation between each layer and set value can be control in a very small range.

Shini-Syncro Extrusion Control system resorts to Loss-in-weight principle to fulfill precise metering and equipments include Syline Loss-in-weight hopper for handling single material and eaSYbatch Gain plus Loss- in-weight compact blender.

SYline consists of a storage hopper and a weighing hopper. Once screws start to work, two weighing sensors beneath weighing chamber begin to detect material consumption and send back signals to controllers, which will compare material consumption with extrusion throughput so that machine adjusts screw rotate speed to ensure constant extrusion amount. When material in hopper reaches low level, butterfly valve beneath storage hopper will open to allow material to load into weighing hopper, and one cycle is finished like this.

Controllers are PLC and HMI from B&R Company, convenient for updating. And butterfly valve is capable of effectively avoiding material clamp. Controllers can control extrusion throughput and weight per length (need to opt for coding wheel) to maintain a constant output of amount and weight. They also can control material loading with up to 11 stations. A central control can be achieved via Internet Interface to perform long-distance control and trouble-shooting and recipes and material consumption can be stored.

At present, there are three domestic manufacturers of transfusion membrane adopting Shini-Syncro Extrusion equipments. Namely they are Jsbest New Material Co., Ltd, Heng Tian Pharmaceutical Package Co., Ltd and Hunan FE Pharmaceutical Machinery Co., Ltd.