How do black spots appear in the plastic granulating machines? In the process of granulation, it is a common problem to encounter the black spots of the pumped particles. How to solve this problem? Cause such a phenomenon is the problem of pelletizing machine, raw material, or other factors caused by it?

Black spot problems in the process of granulation is a common fault phenomenon, especially in color, light color products especially, tend to be at the end of the production process, found that product performance and feel the product color is no problem, but after a period of time has received customer complaints “product qualified rate is too low, have black spots, ask to return the money”, etc. At this time, the problem of why there will be black spots makes many friends have a headache.

In order to avoid the harm of carbonization to plastic products as far as possible, the most important thing is effective prevention, to minimize the loss. In order to deeply understand the nature of carbonization, but also good at using effective solutions, in the solution and prevention of plastic products carbonization of each link, we need to strictly control.

To quickly clean the carbides in the machine, it is necessary to use the hard plastic or its return material and white mineral oil to clean, and the temperature should be appropriately increased by 10~15°C. At this point, consider the small extruder plasticizing capacity of the plastic. For large and medium-sized extruders that can plasticize ultra high molecular weight plastics, ultra-high molecular weight plastics or their return material can be used to clean with white mineral oil. Because the hardness of ultra-high molecular weight plastic is good, coupled with the high temperature, the cleaning object will be softened, so as to become easy to fall off, which is conducive to the carbide being taken out of the plastic melt. During the cleaning process, the speed of the extruder is repeatedly switched between low and high-speed many times. If the motor load is left, the extruder can be stopped and restarted repeatedly during the operation to further improve the cleaning effect. When the carbide (black spots) in the melt is significantly reduced, replace the usual plastic cleaning until clean, gradually adjust to the appropriate temperature, then normal production.

In the actual production of plastic products, generally in the plastic pelletizing machine before the shutdown of the feed port, remove the extruder and plastic melt in the head, close the temperature of each area, and then shut down the power. Because the plastic melt metal, has strong adhesion, every time when stop cannot be completely ruled out absolutely, will eventually have a thin layer of plastic melt firmly adhesion on the inner wall of the extruder barrel and the head and the screw, the parking equipment after natural cooling and heating process next time long time under high-temperature condition were stranded, happen significant thermal degradation, Gradually yellow, zoom into carbide. According to the conventional shutdown method, no effective sealing measures have been taken at both ends of the die and feed mouth of the machine head, which leads to the oxidation of air entering the machine and the aggravation of thermal deterioration of the residual plastic inside the machine, providing favorable conditions for carbonization.

Because the equipment is a metal structure, its thermal expansion rate difference is larger, with plastic has the plastic to reduce the adhesion of the metal, carbide easily from the barrel inner wall of plastic granulator, head on the wall and screw off, got into the plastic melt, causing more products inside and outside wall of black spots, it’s easy to have a piercing or leakage and other quality problems, after a long downtime, heating up again, Plastic products are prone to many large and small black spots, which can not meet the quality requirements of products. These black spots are the carbide after thermal degradation of residual plastic in the machine. The washing machine is usually used to remove the plastic melt with black spots by a continuous extrusion of plastic, and the washing machine time is up to 3-5 hours. If the original ultra-high molecular weight plastic cups are carbonized and primary color products are produced, the difficulty of the washing machine will be greatly increased, the washing machine will take longer and the washing machine cost will be higher.