Common problems and solutions of the quality of particles in thermoplastic extrusion granulation1. The length of the strip is greater than 2 times of the normal pellets are considered as strips.
The main causes are pull-on or broken bars, the direction of the bar is not straight, the bar is not suitable for immersion in water, the cutter of the pelletizer is worn or notched, etc.
1) During normal production, adjust the direction of the strip into the pelletizer and adjust the length of water soaking;
2) When the broken strip is serious during production, the extrusion process should be adjusted;
3) Pay attention to the inspection of the pelletized motorized knife, and replace the damaged moving knife in time;
4) Appropriate vibrating screen can be used to screen the long strips.
2. Two or more granules connected side by side are called continuous granules. Modified material
The main reasons for the continuous particles of modified material are the failure to divide or break the strip in time, the length of the immersion is not enough, and the temperature of the head is too high.
1) When extruding the draw bar, choose a nylon wheel with a suitable width to separate the glued strips in time;
2) Adjust the proper length of cooling and immersion to prevent overheating of the strip, which can reduce the continuous grain;
3) Properly reduce the temperature of the machine head and adjust the temperature of the strip;
4) For the occurrence of continuous grains, a vibrating sieve with appropriate mesh openings can be used for sieving.
3. Not all the cut surfaces of two or more grains of centipede strips are cut together. They are called centipede strips, which actually belong to the category of connected grains.
The main reasons are the speed when driving the bar, the speed of the twin screw extruder, the immersion length is not enough, the cutter of the pelletizer is worn, or the gap between the fixed knife and the movable knife is too large.
1) The operator should pull the strip at a uniform speed to avoid the strip being too thick;
2) Adjust the appropriate extrusion process to avoid feeding at the discharge port;
3) Adjust the appropriate length of cooling and immersion to avoid overheating of the strip;
4) Adjust the gap between the fixed knife and the movable knife, and no longer can replace the new knife.
4. Black spots There are black spot particles on or in the particles.
The main reasons for the black spots are: the pumping screw is not clean; there are black spots in the raw materials; the screw is carbonized; the environmental pollution;
1) During the screw extraction process of the conversion product, if the screw is not cleaned, re-pull the screw; the cleaning point: "three ports", the mesh plate behind the filter and the large head;
2) Strengthen incoming material inspection, especially in filled mineral powder or flame retardant, black spots and impurities are more likely to occur; for example, Z30S or T30S particles containing wood chips in the package, low-grade filled mineral powder or flame retardant; these are all Cannot be used to produce modified plastics with strict black spots;
3) Pay attention to control and adjust the barrel temperature and the residence time of materials in the barrel to prevent the processing temperature from being too high; that is, the corresponding extrusion process should be designed according to the formula of each product.
4) Pay attention to the surrounding environmental sanitation and keep the ground moist, and it is necessary to do isolation and protection between the machines that produce products of different colors.
5) The auxiliary equipment of the extrusion equipment such as water tank and pelletizer should be cleaned regularly;
6) Each time the screen is changed, the remaining material on the mobile screen and template must be cleaned up to prevent carbonization for too long;
7) Pay attention to the floor strips are strictly prohibited to enter the pelletizer, to prevent the introduction of dust;
8) Prevent the generation of plastic static electricity, static electricity is easy to attract dust;