Pearlescent pigments for coloring plastic resins and surface treatment of plastic products

Coloring of plastic resin by pearlescent pigment

   There are many ways to color thermoplastic resins with pearlescent pigments. Among them, the pearlescent masterbatch has excellent coloring. Direct coloring is very simple, but the quality is difficult to guarantee.

      1. Directly color the resin powder. When coloring the powder, just add the pigment directly to the kneader and mix evenly. This type of kneader has two types: drum type and high-speed type. When using a high-speed kneader, ordinary pigments and other additives should be added to the resin powder and mixed uniformly, and the pearl powder should be added at the end of the mixing. This is because under the action of high shearing force, the lamella structure of pearlescent pigments will be destroyed and the pearlescent effect will be affected. Pearlescent pigments, color changing pigments, fluorescent pigments

      2. Directly color the resin particles. Pearlescent pigments cannot be directly added to the resin particles. Liquid coupling agents must be used to fix them on the surface of the resin particles to make them physically or chemically bonded. In addition, emulsifiers or high boiling point solvents can be added to improve the wettability of the interface. Generally, the amount of coupling agent added is 0.2-0.5% of the amount of resin. In order to disperse the pearlescent pigment in the resin better, 1% of low molecular weight polyethylene powder can be added to the mixture of the pigment and the resin.

       3. Mixing, pearlescent pigments are pre-mixed with solvents and auxiliary organic pigments to make liquid pigments, that is, the so-called pearlescent paste. If it is pulped with organic coloring pigments, the organic pigments should be ground to the specified fineness in advance before mixing with them. The pearlescent pigments are mixed together. The pearlescent paste should be stirred evenly during application to prevent the precipitation of the pearlescent pigments to ensure the uniformity of the concentration of the pearlescent pigments in the pearlescent paste.

4. Preparation and use of pearlescent color masterbatch When using pearlescent pigments to color thermoplastic resins, the color masterbatch method is extremely effective. Ordinary coarse and fine resin powders can be used to prepare color masterbatches, but first, use a polymer with high melt index, good fluidity, and low molecular weight as the carrier of the pigment. The preparation of color masterbatches can be continuous and intermittent. Two methods: general industrial production uses twin-screw extruders for continuous production.

      4.1 Preparation of 30% pearlescent color masterbatch Firstly, 70 parts of PE pellets are premixed with various additives such as wetting agent and dispersant. The mixing time depends on the batch size and mixing intensity, and then the pearlescent pigment is added and mixed evenly. , The mixture is slowly added to the double screw rod extruder. The temperature of the feeding zone is 140°C, and the temperature of the mouth film is 160---180°C. After extrusion, it is eagerly cut into pellets.

      4.2 Precautions for the manufacture of pearlescent pigment masterbatch: 1. The pearlescent pigment should avoid high shear and long-term action during the mixing process, so as not to damage the lamella structure of the pearlescent pigment and affect the pearlescent effect of the product; 2. Improve the mixing effect of the screw, Thereby improving the uniformity of the pearlescent pigment dispersion; 3. Using a larger L/D and adding a filter screen can improve the coloring effect of the pearlescent masterbatch; 4. Within the allowable range, increase the processing temperature and reduce the amount of pearlescent pigment flakes Destruction of the crystal structure; 5. In order to obtain a better pearlescent color, the smoothness of the mold surface and the design of the mold gate are very important. The smoother the mold, the more uniformly arranged and smooth and even pearlescent color can be obtained. It is better to choose a single gate than multiple gates. The position of the gate should usually be chosen at a thick place away from the flow barrier, and the space distance between the end of the gate and the runner system should be as small as possible.

Pearlescent pigments are used for surface treatment of plastic products

   The surface of plastic products can be treated with painting and printing methods to achieve a decorative effect. When painting with painting, an excellent method is spraying. Because the parallel arrangement of the wafer-like pigments is very good at this time.