DIE CLEANING TIPS
Die cleaning is something few operators like to do. It’s hot. Your arms get tired. It’s not air-conditioned. There are a few things that can make the job easier. If available, try to use a fractional melt index LDPE to purge out with. It has been found that adding additional anti oxidant to the purge polymer before shutting down helps in removal of the polymer from the chrome surface of the die. Common coating grades of LDPE of 4 MI or higher are stickier than the fractional melt index resins, and continue to drip out of the parts left on the machine. After separating the die, use a mono and diglycerides such as Kemester 150 or Kempster124 (Figure 1) to reduce the viscosity of the polyolfins to that of about water. You can almost wipe off the polymer with a cloth. Use it by melting the powder or flake form of mono and diglycerides and pouring it into a paper cup with a wooden tongue depressor as a handle. It is affectionately called a lollipop. Apply it on the poly left on the die at temperatures of 275°F(135°C) to 300°F(149°C). At this temperature it will readily melt. As always make certain to read and follow the suppliers MSDS. With some copper mesh you can remove most of the polymer with very little elbow grease. Finish by wiping down with cheesecloth. The mono and diglycerides will not help in the removal of polyamide or polyester.
Now what do you do about the carbon that built up on the die lips? It is easily removed with copper mesh and chrome polish. The die still needs to be hot (300 - 350°F /149 -177°C) for this to work without a lot of rubbing. You need to be careful with this step as the liquids in the chrome polish can flash through you glove and scald your hand. Wrap the copper mesh around several layers of cheesecloth or other soft cotton rag to add additional protection for your hand. Apply a small amount of chrome polish to the mesh and rub on small areas at a time. The chemicals in the chrome polish seem to react with the carbon and/or boil off the carbon. This technique seems to work on carbon deposits from polyamides, polyesters, and polyolfins.