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Introduction of dispersants for plastics
Introduction of dispersants for plastics
Dispersant is a kind of surfactant with two opposite properties of lipophilicity and hydrophilicity at the same time in the molecule. It can uniformly disperse the solid particles of inorganic and organic pigments that are difficult to dissolve in liquids, and can also prevent the sedimentation and agglomeration of solid particles to form a stable suspension.
Product Category：
1、Fatty acids, fatty amides and esters
Stearamide and higher alcohol can be used together to improve lubricity and thermal stability. The dosage (mass fraction, the same below) is 0.3%-0.8%, and it can also be used as a slip agent for polyolefins; Hexenyl bis-stearamide, also known as ethylene-based bis-stearamide, is a high melting point lubricant, the dosage is 0.5% to 2%; stearic acid monoglyceride, tristearic acid glyceride；The dosage of oleic acid acyl is 0.2%～0.5%;Hydrocarbon paraffin solid, melting point is 57～70℃, insoluble in water, soluble in organic solvent, dispersibility, compatibility and thermal stability in resin are all poor, the dosage is generally below 0.5%.
2、Paraffin
Although paraffin is an external lubricant, it is a non-polar linear hydrocarbon and cannot wet the metal surface, that is to say, it cannot prevent resins such as polyvinyl chloride from adhering to the metal wall，Only when used together with stearic acid, calcium stearate, etc., can the synergistic effect be exerted.
liquid paraffin：freezing point -15--35°C, has poor compatibility with resin during extrusion and injection molding processing. The addition amount is generally 0.3%-0.5%. If it is too much, it will make the processing performance worse.
Microcrystalline Paraffin：Obtained from petroleum refining process, its relative molecular mass is relatively large, and there are many isomers, melting point is 65-90 ℃, lubricity and thermal stability are good, but the dispersibility is poor, the dosage is generally 0.1%-0.2%,preferably used in combination with butyl stearate and higher fatty acids.
3、metal soap
The metal salts of higher fatty acids are called metal soaps. For example, barium stearate is suitable for various plastics, and the dosage is about 0.5%; zinc stearate is suitable for polyolefin, ABS, etc., and the dosage is 0.3%; Calcium stearate is suitable for general plastics, external lubrication, the dosage is 0.2%-1.5%; other stearic acid soaps such as cadmium stearate, magnesium stearate, copper stearate.
4、low molecular weight wax
Low molecular weight wax is made of various polyethylene (homopolymer or copolymer), polypropylene, polystyrene or other polymer modified products，a series of oligomers with different properties are formed by cracking and oxidation.
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, the chemical name of polyethylene wax is polyethylene glycol, and the English name PEG (Poly Ethylene Glycol) is the most commonly used.
Product Action：
1、Improve the gloss and increase the leveling effect. The gloss actually mainly depends on the scattering of light on the surface of the coating (that is, a certain level of flatness)；
2、Prevent floating color；
3、Improve tinting strength Note that tinting strength is not as high as possible in an automatic grading system；
4、Reduce viscosity, increase pigment loading；
5、This is the case to reduce flocculation, but the finer the particle, the higher the surface energy, and the dispersant with higher adsorption strength is required, but the dispersant with too high adsorption strength may cause adverse effects on the performance of the coating film；
6、Increase storage stability；
7、Increase color development, increase color saturation.
8、Increase transparency (organic pigments) or hiding power (inorganic pigments).
Purchase requirements：
1、Good dispersion performance, preventing filler particles from agglomerating with each other；
2、Appropriate compatibility with resins and fillers, good thermal stability;
3、Good fluidity during molding and does not cause color drift;
4、Does not affect the performance of the product, non-toxic and cheap;
5、The amount of dispersant is generally 5% of the mass of the masterbatch.
