Factors Influencing the Quality of Hard Controlled Goods
- time:
- 2019-05-13
Core Tip: Single screw extruder usually uses the plasticized granular material to form the hard pipe, so the quality of the hard pipe depends to a large extent on the plasticization degree and uniformity of the semi-product granular material. There are generally two kinds of plasticizing processes for granules: one is to plasticize kneaded and uniform powder in the extruder, while discharging round strips on the machine head, the other is to cut the kneaded materials into round granules by rotary knife; the other is to draw the kneaded materials into sheets of certain thickness and width after mixing and plasticizing on the rolling machine, roll them into rolls, and then cut them into square granules. 1. The advantages of extrusion plasticizing granulation are continuous sealing, low investment in equipment, low labor intensity and low noise. Single screw extruders often use plasticized granules to form hard tubes. Therefore, the quality of hard tubes depends largely on the plasticization degree and uniformity of semi-finished granules.
There are generally two kinds of plasticizing process routes for granular materials: one is to plasticize kneaded and uniform powder in extruder, release circular strip material on the machine head, and cut it into circular granular material by rotary knife;
The other is to draw the kneading mixture into sheets of certain thickness and width after mixing and plasticizing on the rolling machine, roll it into rolls, and then cut it into square granules.
1. Extrusion plasticizing granulation
The advantages are continuous sealing, low investment in equipment, low labor intensity and low noise. Therefore, it is the development trend of granulation technology at present. Special twin-screw pelletizing extruder, because of its good mixing degree and uniform plasticization, has received widespread attention.
But the following points must be paid attention to in production: raw materials must have enough fineness to ensure uniform mixing in kneading machine, otherwise, in the process of extrusion and granulation, particles will appear white spots, carbon black spots, and filler caking points, which will affect the quality.
The resin must be of loose type so as not to affect the continuous bursting of the granulating extruder.
The extruder body temperature must be controlled below 170 C to avoid discoloration on the outside and micro-holes on the inside. Such granular material is unstable in pipeline production and easy to decompose.
In the process of granulation, it is necessary to change the filter mesh frequently so as to avoid garbage mixing in or destroying the normal operation due to the breakdown of the mesh.
2. Internal mixing and rolling plasticizing granulation
The temperature of internal mixing plasticization and drum plasticization should not be too high. The material temperature of internal mixing plasticization should not exceed 175-180 C, and the distance of drum plasticization should not exceed 3 mm. The process of turning over and turning over at low temperature is more reasonable, and at the same time, each batch of granules requires uniform and ideal plasticization degree.
It is stated as follows: raw materials must be mixed evenly in the mixing process, otherwise in the extrusion process, tribasic lead sulfate and barium stearate are easy to precipitate, and the stability of granules is poor, easy to decompose.
In the process of internal mixing and plasticizing, if the material temperature is too high, the pipes are easy to hair and foam during extrusion.
When producing granular materials by two-way rolling plasticization without mixer, attention should be paid to the plasticization temperature should not be too low. Otherwise, the pipes are easy to be brittle and the flat test can not meet the quality requirements.
If the plasticizing temperature is too high, the pressure will be higher and the current of the main motor will increase during the extrusion process.
