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Technology world: calcium carbonate masterbatch production technology introduction

Dec 25, 2017

Calcium  carbonate as the largest inorganic powder material, the direct use of  plastic can cause dust flying, seriously damaging the production  environment. At  the same time, because it is a hydrophilic material, the lipophilic  resin directly added to the dispersion is not good, so for calcium  carbonate powder, the general need to be processed into masterbatch  beforehand to provide customers, so that you can solve the production  environment and Compatibility issues. Before, Xiao Bian to introduce technology | calcium carbonate  masterbatch formula design principles, here we introduce the production  technology of calcium carbonate masterbatch.

    01, melt mixing equipment

    The choice of reciprocating single-screw extruder, symmetrical or  asymmetric twin-screw extruder, continuous or double-rotor mixer, double  extrusion unit can be, underwater pull, grinding face can be eager.

    If the carrier material is suitable, the equipment is best to use continuous mixer, but should pay attention to:

    Time - mixing time to control properly, too long can easily lead to stick pan, yellow, and even decomposition.

    Exhaust - Before mixing begins at the beginning of physical caking  of the aggregate, 3-5 venting to eliminate moisture or small molecule  volatiles and accelerate dispersion of inorganic powders.

    (1) continuous mixer

    Mixer + single-screw extruder and internal mixer + twin-screw extruder, continuous mixer can be used for PE and PBS carrier. Double rotor continuous mixer exhaust effect prominent, the realization of automatic continuous dust production.

    (2) double extrusion equipment

    Twin-screw extruder + single-screw extruder, outstanding exhaust effect, PP carrier can only be used two-stage screw extruder.

    (3) twin-screw extruder

    L / D is as high as possible, the general requirements of more than 40, PP carrier can only use twin-screw extruder. Recently, an asymmetric twin-screw extruder has been developed with the double plasticization effect of shearing and extrusion.

    02, melt mixing process

    (1) high-speed mixer

    Feeding order:

    Calcium carbonate should be added to the dehydration treatment, after the addition of other components. Add calcium carbonate mixed for about 5 minutes (expected temperature reached 60-80);

    Add about 1% coupling agent surface treatment for 5 minutes (after  the treatment of calcium carbonate in the glass all float above is  handled);

    Join PP carrier, polypropylene wax for 2 minutes;

    Add lubricant and stir for 2 minutes (high speed mixer current is  increased from 70A to 100A, low speed stirring and cooling at 40 ℃).

    Moisture control: the temperature to reach a certain height,  prolapse of water adsorbed on the surface of calcium carbonate, so that  the control of less than 0.3%.

    Static  elimination: calcium carbonate in the mixing process is likely to cause  frictional electrification, especially the obvious sheet-shaped  structure of calcium carbonate, which will cause serious aggregation of  particles into a group, affecting the dispersion effect. Masterbatch in use, will appear in the product white spots. The first solution is to add a small amount of antistatic agent in  the formula, the second is the high-speed mixing of materials left to  stand for 20 hours before use.

    (2) filter

    The filter must be set, its role is great, often overlooked. The filter can rotate the material into linear motion, the use of  strong shear operation to further plasticize the material, adjust the  melt pressure in the nose, filter impurities and decomposition of  materials.

    The filter is generally three or four layers of structure, such as 80/120/80, 100/140/100 and 100/120/140/100. Usually 1 hour for 1, disposable, do not recommend burning and then use. If the filter is too thin, it will lead to the extruder pressure increases, the current increases, reducing production.

    There are two possibilities for blocking a network:

    First, the larger particles of the powder, or the powder is too  fine to cause reunion, leaving a large number of inorganic powder after  sintering the residue of the mesh belongs to this reason;

    Second, the carrier resin or small molecule additives accumulate  in the filter, residence time is too long, resulting in thermal  decomposition, if the plugging the yellow residue, gray, black, no  residue after sintering, this is the reason.

    03, product quality control

    (1) moisture control

    Moisture  and its low molecular weight volatiles should be controlled below 0.3%,  to ensure that the blown film is not leaks, no water ripples. Specific means of inspection with a magnifying glass to observe  the masterbatch compact no obvious foam voids, so the product surface is  very bright.

    (2) Density control

    Single-screw  extruder mainly plays the role of uniform granulation and compacting  compaction, the parent material as dense as possible, can be fully ruled  out moisture or small molecules of volatile matter, so follow-up  composite filler products, the more bright the surface. Density  by single-screw extruder pelletizing head melt pressure increases, in  particular, can reduce the melt temperature, increase feed speed and so  on.