Single Re-Pelletizing System for Multiple Types of Waste

Sikoplast is well-known for its recycling and re-pelletizing systems for plastic waste such as for film, nonwovens and PET bottles. It is now able to offer a single re-pelletizing line for a wide variety of waste which also includes textile yarn.

Sikoplast has successfully conducted trials with the following materials on the same re-pelletzing line:

• Carpet waste (PP BCF Yarn)
• Heavy duty sacks (PP)
• Meltblown nonwoven (PP)
• Artificial grass (PE)

The above materials vary greatly in terms of MFI, moisture content, and bulk density. As an example, the bulk density ranged from 24 g/L for the meltblown nonwoven to 105 g/L for the artificial grass.

The re-pelletizing line used for trials consists of the following line components:

• Sikoplast grinder (cutting mill)
• Material silo (hopper)
• Recycling extruder
• Vacuum pump
• Hydraulic screen changer
• Metering pump
• Under-Water-Granulation system (UWG pelletizer)
• Centrifugal drying system
• Vibrating unit
• Bagging station

The Sikoplast grinder is at floor level, which means it can easily be fed manually. Although the grinder is fed manually for normal operation, it can also be fed with a small conveyor belt or with pull-in rolls fro waste in roll form. The grinder does not need to be located at the recycling line. It can be located in a separate room for dust and noise protection. The  chopped material is conveyed pneumatically from the grinder to the material hopper.

The material hopper is designed to accommodate a wide range of bulk densities with its specially shaped and positioned agitators. These agitators prevent blocking or bridging of the material, and their speed and torque are adjustable. The hopper has one maximum level indicator and a number of minimum level indicators for various bulk densities. There is no thermal treatment of the material inside the hopper. The only purpose of the hopper is to maintain a constant material feed to the extruder and to provide buffer storage in the system. The hopper stores up to one-half hour of production so that the knives in the grinder can be changed without stopping the entire line.

The extruder has two degassing ports for the removal of moisture and volatiles. Sikoplast has found that sometimes only one degassing port is necessary. More than two degassing ports leads to longer screws, larger drive motors, larger water pumps, higher energy costs, and a greater chance to damage the melt. The temperature profile of the extruder is adjusted for each of the materials being processed.

Various types of screen changers can be used depending on the level of contamination of the material. They can either be one or two piston and are of Sikoplast's own design and construction. In the case of extreme contamination, an automatic screen changer can be used.

The UWG can be opened very quickly. The drive for the rotating knife is fixed and is attached to the face plate with a quick disconnect. The face plate is suspended from an overhead rail. To open the UWG, the face plate is disconnected from the drive and then slides backwards on the rail.