Both dispersants and lubricants are commonly used additives in plastic color matching. If these additives are added to the raw materials of the product, they need to be added to the resin raw materials in the same proportion in the color matching proofing, so as to avoid color difference in the subsequent production.
The types of dispersants are: fatty acid polyureas, base stearate, polyurethane, oligomeric soap, etc. The most commonly used dispersants in the industry are lubricants. Lubricants have good dispersion properties, and can also improve the fluidity and mold release properties of plastics during molding.
Lubricants are divided into internal lubricants and external lubricants. Internal lubricants have a certain compatibility with resins, which can reduce the cohesion between resin molecular chains, reduce melt viscosity, and improve fluidity. The compatibility between the external lubricant and the resin, it adheres to the surface of the molten resin to form a lubricating molecular layer, thereby reducing the friction between the resin and the processing equipment. Lubricants are mainly divided into the following categories according to their chemical structure:
(1)) Burning class such as paraffin, polyethylene wax, polypropylene wax, micronized wax, etc.
(2) Fatty acids such as stearic acid and base stearic acid.
(3) Fatty acid amides, esters such as vinyl bis-stearamide, butyl stearate, oleic acid amide, etc. It is mainly used for dispersing, in which bis-stearamide is used for all thermoplastics and thermosetting plastics, and has a lubricating effect.
(4) Metal soaps such as stearic acid, zinc stearate, calcium stearate, pot stearate, magnesium stearate, lead stearate, etc. have both thermal stabilization and lubricating effects.
(5) Lubricants that play a role in mold release, such as polydimethylsiloxane (methyl silicone oil), polymethylphenylsiloxane (phenylmethyl silicone oil), polydiethylsiloxane (ethyl silicone oil) etc.
In the injection molding process, when dry coloring is used, surface treatment agents such as white mineral oil and diffusion oil are generally added during mixing to play the role of adsorption, lubrication, diffusion and mold release. When coloring, the raw materials should also be added in proportion medium deployment. First add the surface treatment agent and spread evenly, then add the toner and spread evenly.
When selecting, the temperature resistance of the dispersant should be determined according to the molding temperature of the plastic raw material. From the perspective of cost, in principle, the dispersant that can be used at medium and low temperature should not be selected for high temperature resistance. The high temperature dispersant needs to be resistant to above 250℃.
References:
[1] Zhong Shuheng. Color Composition. Beijing: China Art Publishing House, 1994.
[2] Song Zhuoyi et al. Plastic raw materials and additives. Beijing: Science and Technology Literature Publishing House, 2006.
[3] Wu Lifeng et al. Masterbatch User Manual. Beijing: Chemical Industry Press, 2011.
[4] Yu Wenjie et al. Plastic Additives and Formulation Design Technology. 3rd Edition. Beijing: Chemical Industry Press, 2010.
[5] Wu Lifeng. Plastic Coloring Formulation Design. 2nd Edition. Beijing: Chemical Industry Press, 2009
Post time: Jun-25-2022