Controlling raw materials is the key to solve the color difference of
blow molded products. If the new materials are fully used to control the parameter temperature, it is unlikely that the color difference of the blown products will be caused by the materials. If the returned materials are increased, the color difference of the blown products will be caused by the color value of the returned materials and the uneven mixing during the mixing process due to the increased quantity. If the return material is increased in production, it is necessary to adjust the increase proportion and mixing time according to the performance of the return material to ensure the material is uniform and reduce the color difference of blow molded products.
1. For the problems of materials and color masterbatch, strengthen the inspection of raw materials warehousing when using color masterbatch; For
blow molding processing of the same product, the same manufacturer, same brand masterbatch and color masterbatch shall be selected as far as possible. If it is necessary to replace the color masterbatch manufacturer, do a good job of sample test, and start production in batches after meeting the standard.
2. The problem of uneven mixing of materials and color masterbatch The poor mixing of materials and color masterbatch will also change the color of the product. After the materials and color masterbatch are evenly mixed, when they are fed into the hopper through the lower suction, due to the electrostatic effect, the color masterbatch is separated from the masterbatch and easy to be adsorbed on the hopper wall, which is bound to cause the change of the color masterbatch amount in the blow molding cycle, and then the color difference occurs. The most effective way is not to use a suction machine, but to use a hot air dryer, and use manual feeding method to prevent color difference caused by the separation of toner and masterbatch.
3. The problem of influence of barrel temperature on color difference
During the processing of blow molded products, it is often encountered that a heating ring is damaged and invalid or the heating control part is out of control, resulting in drastic changes in the barrel temperature and then color difference. Generally, the uneven plasticization will be accompanied by the color difference when the heating ring is damaged or fails, while the uncontrolled long burning of the heating control part will be accompanied by product gas spots, severe discoloration and even coking. Therefore, it is necessary to check the heating part frequently during blow molding. If the heating part is damaged or out of control, it should be replaced and repaired in a timely manner to reduce the probability of such color difference.
4. Problems in production process adjustment When the production process adjusts the blow molding process parameters, try not to change the blow molding temperature, back pressure, blow molding cycle and the amount of color masterbatch, and observe the effect of the change of process parameters on the color.
