Wire drawing phenomenon of PVC drainage pipe:
The design of the calcium zinc system formula for PVC drainage pipes is affected by the improper selection of lubricants and the unbalanced lubrication system. Precipitation will occur in long-term production, which is manifested in the appearance of white precipitates on the surface of the mold (internal precipitation) and the sizing sleeve (external precipitation).
The precipitation problem in the extrusion die of our company has been solved several years ago, but the precipitation of the sizing sleeve will produce white adhesive after more than two weeks of continuous production, which will affect the appearance and size of the product. Some machines will produce slight wire drawing phenomenon, which needs to be cleaned and polished regularly, affecting the qualification rate.
The figure above shows the internal condition of the sizing sleeve of PVC drainage pipe after two weeks of continuous production. There are obvious precipitates on the sizing sleeve, which causes slight wire drawing.
Lubrication system adjustment:
In order to completely solve the problem of PVC drainage pipe precipitation and wire drawing, we have adjusted the amount of lubricant added in the original system for many times. After a minimum of two weeks, there will be more or less appearance of exoskeleton, which has not been completely eradicated. Therefore, other lubricants need to be selected to replace the existing lubrication. OP530 lubricant has many advantages such as small amount of lubricant (0.05~0.2), preventing precipitation, improving product gloss, and promoting plasticization.
According to the characteristics of OP530 lubricant, OP530 lubricant (small amount added) was used to replace stearic acid and oxidized wax in the original formula for production test.
one
Select two production lines with prominent precipitation drawing problems, use new formula for continuous production without cleaning and polishing the precipitates on the surface of the sizing sleeve, and observe the adhesion of the precipitates on the surface of the sizing sleeve.
After two weeks of continuous production, it was found that the precipitates did not increase, the original precipitates were also taken out, and there was no precipitate adhesion on the surface of the sizing sleeve;
two
The new formula was used in all PVC drainage pipe production lines. After two weeks of continuous production, it was found that all machines had no precipitation and wire drawing.
Improvement effect
Use effect of OP530 lubricant in lubricating system:
1. The extrusion rate is increased, and the pipe surface gloss is improved.
2. The lubricant does not contain metal ions, effectively preventing precipitation.
3. It can delay the accumulation of friction heat, thus improving the thermal stability at high temperature.
4. The addition amount is low, and the formula cost is basically unchanged or even slightly decreased.
5. It can promote plasticization and improve the physical properties of products, and the tensile yield strength of national standard pipes is increased from 40~41MPa to 41~43MPa.
Continuous improvement
PVC electrical conduit propulsion:
The production of PVC drainage pipes has been successful, and the phenomenon of precipitation and wire drawing has been completely solved. The next step is to make corresponding adjustments in the PVC electrical pipe in 2023.