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The surface treatment of pearlescent pigments on plastic products
- Jun 25, 2018 -

The surface treatment of pearlescent pigments on plastic products



Pearlescent color can be used for transparent and translucent plastic resin, the use of pearlescent pigments will bring a fascinating visual effects. Pearlescent pigments are widely used in cosmetic containers, all kinds of packaging, toys, decorative materials, all kinds of film and so on plastic products.


The application of pearlescent pigments in plastics note that the pearlescent pigments have different characteristics from the processing of common pigments.


Generally to get the best pearlescent effect, you must pay attention to the following conditions:


  1.The transparency of the dyed plastic resin is good (or high brightness); 


  2. Use of transparent pigments and pearlescent pigments as much as possible;


  3. Minimize the destruction of pearlescent pigments during processing;


  4. The pearlescent pigments are fully dispersed and the pigments are parallel to the plastic surface orientation.


  In addition to the above conditions, the characteristics of plastic resins and processing methods will also affect the final product gloss properties.


The amount of pearlescent pigments in plastics is generally 0.5%-2%, and the dosage of thin film or thin-walled products should be correspondingly larger, generally 4%-5%. The coloring of the coloured thermoplastic resin of the pearlescent pigment has many kinds of methods.


One of the best pearl color masterbatch. Direct coloring is simple, but the quality is difficult to guarantee.



1. The resin powder coloring directly with the powder, simply add the pigment directly into the kneading machine mixed evenly. This kind of kneading machine has two kinds of rotary barrel and high speed type.

The use of high-speed kneading machine should be ordinary pigments and other additives added to the resin powder mixed evenly, before the end of the mixing to add pearlescent powder, this is because the pearlescent pigment in the high shear force under the action of the crystal structure is vulnerable to damage, affecting the pearlescent effect.



 2. Direct coloring of resin granular material Pearlescent pigments can not be directly added to the resin particles, but the liquid coupling agent must be used to fix it on the surface of the resin particle, so that it produces a combination of physical or chemical. These coupling agents include a variety of softener and refined mineral oil. In addition, the wetting properties of the interface are improved by adding emulsifiers or high boiling point solvents.


Under normal circumstances, the coupling agent to increase the amount of resin 0.2-0.5%, such as the need for the pearlescent pigment dispersed in the resin more evenly, can be in the pigment and resin mixture to add 1% of the low molecular weight of polyethylene powder.


This method of coloring the maximum amount of 2%, more than this dosage, because the resin surface without space to continue to adsorption, excess pigments can only be scattered out.


 3. Liquid Curing Mixing Pearlescent pigments can also be prepared in advance with solvents, additives, organic pigments mixed into liquid pigments, that is, pearlescent pulp. such as with the organic pigment pulping, the organic pigments should be ground to the specified fineness and then mixed with pearlescent pigments.


Pearl paste should pay attention to the precipitation of pearlescent pigments, preferably using the appropriate prevention agent, before the application of mixing evenly to ensure the concentration of pearlescent pigments in the uniformity of the slurry.


 4. Pearlescent Masterbatch Coloring The color Masterbatch method is the best coloring effect. Ordinary thick and thin resin powder can be used to prepare masterbatch, because the pearl powder added will cause the melt index down, so the general use of higher melt Index, more liquid molecular weight than the coloring resin of the same polymer as the carrier of pigments. The preparation of Masterbatch has two methods, continuous type and clearance type. The general industrialized production adopts the continuous production of double screw extruder.


Considerations for Preparing Pearlescent Masterbatch:



  1. In the process of mixing, the pearlescent pigments should avoid the long time effect of high shearing force, so as to avoid destroying the crystal structure of pearlescent pigments and affecting the pearlescent effect of the products.

  2.  
    Improve the back pressure to improve the mixing effect of the screwdriver, and disperse the pearlescent pigment fully.


  3.  
    Increase the temperature in the possible range, reduce the melt viscosity, reduce the structure of the pearlescent pigment damage.


  4.                                                                                                                                                                  Mold finish, mold gate design and construction of the adjustment is also very important, will cause the arrangement of pearlescent pigments disorderly, affect the product's pearlescent color.


Matters needing attention in the pearlescent thermal plastic plastics


 1.
  Polyolefin Polyolefin in the process of molding has been used to stabilize the phenolic antioxidant, because of titanium dioxide and antioxidant phenolic reaction, to make the color yellow.

For products with high aging performance requirements, please select the treated pearlescent powder to minimize the change in color when processing storage.


2.
  Pvc Pearlescent pigments can be applied to soft and hard PVC. The stabilizer should be selected to ensure that the PVC remains transparent after coloring and stabilization.

And the iron ions in the PVC formula will cause stability decline, so the use of iron-containing pearlescent pigments needs to be tested in advance for stability.


3.
  Dry before processing Pearlescent pigments generally contain about 0.5% of the adsorption water. Hygroscopic Plastics must be dried before use, so that the moisture content of the resin and pearlescent pigments is within the prescribed limits.


It is very important to dry the raw material and the final color masterbatch when preparing the color masterbatch of the hygroscopic resin.


Pearlescent pigments can be used in any kind of thermoplastic plastic.


Using any kind of molding method can have good pearlescent effect, generally used for extrusion molding and injection molding.


Pearlescent pigments for the surface treatment of plastic products surface treatment usually by painting and printing two methods to achieve decorative effect.


The best way to paint is to spray or dip, so that the chip is the best arrangement.  


Also can be used with pearlescent pigment printing inks. Pearlescent pigments can also be used in plastic laser marking technology, the production of marble color effect, latex products and casting resin.

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