1. Selection of Dispersant An excellent dispersant should meet the following requirements: good dispersion performance, prevent accumulation of filler particles; proper compatibility with resin and filler; good thermal stability; fluidity during molding processing Good; does not cause color drift; does not affect the performance of the product; non-toxic, inexpensive.
The amount of dispersant is generally 5% by mass of the masterbatch.
2. Types of dispersing agents (1) Fatty acid, aliphatic amides and ester stearyl amides can be used in combination with higher alcohols to improve lubricity and thermal stability. The amount (mass fraction, the same below) is 0.3%-0. .8%, can also be used as a lubricant for polyolefin; hexenyl bis stearamide, also known as ethylene bis stearamide (EBS), is a high melting point lubricant, the amount is 0.5% ~ 2%; stearic acid monoglyceride (GMS), glyceryl tristearate (HTG); oleic acid acyl acid dosage 0.2% to 0.5%; hydrocarbon paraffin solid, melting point 57-70 ° C, insoluble In water, soluble in organic solvents, the dispersibility, compatibility and thermal stability of the resin are poor, and the dosage is generally below 0.5%.
(2) Paraffin wax Although paraffin wax is an external lubricant, it is a non-polar linear hydrocarbon and cannot wet the metal surface, that is, it cannot prevent the resin such as polyvinyl chloride from sticking to the metal wall, only with stearic acid and stearic acid. When calcium is used in combination, synergy can be exerted.
Liquid paraffin: solidification point -15 ~ -35 ° C, in the extrusion and injection molding process, the compatibility with the resin is poor, the addition amount is generally 0.3% -0.5%, when too much, the processing performance It is getting worse.
Microcrystalline paraffin: obtained from petroleum refining process, its relative molecular mass is large, and there are many isomers, melting point 65-90 ° C, good lubricity and thermal stability, but poor dispersion, the dosage is generally 0 .1%-0.2%, preferably used in combination with butyl stearate and higher fatty acids.
(3) Metal soaps Metal salts of higher fatty acids, called metal soaps, such as barium stearate (BaSt) is suitable for a variety of plastics, the amount is about 0.5%; zinc stearate (ZnSt) is suitable for polymerization Olefin, ABS, etc., the dosage is 0.3%; calcium stearate (CaSt) is suitable for general purpose plastics, for external lubrication, the dosage is 0.2% to 1.5%; other stearic acid soaps such as cadmium stearate ( CdSt), magnesium stearate (MgSt), copper stearate (CuSt).
(4) Low molecular waxes Low molecular weight waxes are a series of polyethylene (homopolymer or copolymer), polypropylene, polystyrene or other polymer modified materials, which are cracked and oxidized. Oligomers with different properties.
Its main products are: homopolymer, oxidized homopolymer, ethylene-acrylic acid copolymer, ethylene-vinyl acetate copolymer, low molecular ionomer and other five categories. Among them, polyethylene wax is most commonly used.
Commonly used polyethylene wax has an average relative molecular mass of 1500-4000 and a softening point of 102 ° C; other specifications of polyethylene wax have an average molecular weight of 10,000 to 20,000, and a softening point of 106 ° C; long chain of oxidized polyethylene wax The molecule has a certain amount of ester group or soap base, so the internal and external lubrication effects of PVC, PE, PP and ABS are relatively balanced, and the effect is good, and the transparency is also good.
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