Pearlescent Pigments for Plastic Applications

OUTLINE 1. 2. 3. 4. Introduction Raw Materials Manufacturing Process Issues and Solutions 1. 2. 3. 4.

3 INTRODUCTION Forty years ago, anything made of plastic was considered "cheap“. However with the development of high quality plastics this is not true today. Plastics are used in thousands of products ranging from computers, automobile parts and important medical equipment, to toys, cookware, sports equipment, and even clothes.

Plastic Products Packaging: Products: Personal care products Electronics Automotive Household Films Toys Sports Packaging: Personal care products Food Household Sanitary Toys

5 Plastic Applications

Plastics Raw Materials PE LDPE / MDPE / HDPE / LLDPE PVC hard PVC / soft PVC PP Homo Polymer / Copolymer EVA ABS semi transparent ABS/transparent ABS TPU PS HIPS / GPPS TPE PC PEEK PA PA6 / PA66 / PA46 PPS PBT PI PET PMMA POM

Plastic Properties Density Transparency Gloss Elongation Flexibility Impact Melt Flow Deflection temperature Molding Temperature Acid and alkali resistance Flammability Electronic properties

MANUFACTURING FLOW Pearl Forming Colorant Master batch Pumping tablet Color paste Forming

Extrusion Molding Extrusion is the most common processes used to form plastics. A heated plastic compound is forced continuously through a forming die made in the desired shape, like squeezing toothpaste from a tube, producing a long, usually narrow, continuous product. The formed plastic cools under blown air or in a water bath and hardens on a moving belt. Rods, tubes, pipes and toys such as Slinkys. Sheet and thin films (such as food wraps) are extruded then coiled or cut to desired lengths.

Extrusion Molding Machine parameters for best results with pearlescent pigments… Masterbatches or compounds are usually used to color the molten mass with effect pigments. For a satisfactory result in plastic extrusion with effect pigments, a balanced ratio must be maintained between the mixture energy and pigments which are as undamaged as possible. Excessive shear from mixing sections or inappropriate screws or filters destroy effect pigments and dramatically decrease the pearl luster effect. The orientation of the pigments is a requirement for an even effect. This has to be ensured in the process through a corresponding engineering and design of the machinery.

Injection Molding Injection moulding Is the second most widely used process to form plastics. The plastic compound, heated to a semi fluid state which is injected into a mould under great pressure and cools and hardens quickly. The mould is opened and the part is released. This process can be repeated as many times as necessary and is particularly suited to mass production methods. Injection moulding is used for a wide variety of plastic products, from small cups and toys to large objects weighing or more.

Injection Molding For best results with pearlescent pigments… In injection molding, flow processes in the molten mass cause the orientation of pigment platelets. By a technically well engineered tool construction the Effect pigments can orientate perfectly and showing nearly no flowline or welding effects. Another point to optimize the effect appearance is the position of the injection gate. Circular, centralized and edge minimized forms are perfectly suited for Effect pigments. In cases, where this is not possible we recommend, using our Diamond Effect pigment series in a low concentration. It shows a strong sparkling effect and decreases the optical perception of irregularities.

Blow Molding Blow molding is where gas pressure is used to form hollow objects, such as the soda pop bottles, in a direct or indirect method. For direct blow-molding, a partially shaped, heated plastic form is inserted into a mold. Air is blown into the form, forcing it to expand to the shape of the mold. For indirect blow-moulding, a plastic sheet or special shape is heated then clamped between a die and a cover. Air is forced between the plastic and the cover and presses the material into the shape of the die. In this process Effect pigments develop their full optical effect.

Blow Molding For best results with pearlescent pigments… Effect pigments are excellently suited to the extrusion blow molding process, since the extrusion process guarantees that platelet-shaped effect pigments are aligned evenly to the surface so they can develop their full optical effect. Co-extrusion is an efficient option for combining high coverage and good effects. Strong pearl luster and other effects can be achieved with a thin outer layer, while the desired opacity is created by the covering inner layer.

Blow Molding Phenomenon of Effect pigments and the interesting Frost Effect. Due to the soft heating during the blow molding process, its elasticity is not very high. Effect pigments are now elastic anyway due to their inorganic composition. The stretches form voids between the stretched polymer and the unstretchable effect pigments. The larger the pigments and the higher the stretching ratio, the more obviously the vacuoles are. Effect pigments can be used at stretching ratios of up to 3:1. In addition, 1-level or 1.5-level processes are more suitable, because the plastic is still in a semi-viscous state. In general this void effect is broadly used for the so-called frost effect in PET bottles. This frost effect gives the surface an appearance like it comes directly out of the fridge.

Manufacturing Equipment Twin-screw machine Single Screw Machine Injection molding machine Blow Molding Machine Trombone Mixer

Factors Affecting Pigment Effects Plastic resins transparency and gloss Brightness of the forming die Product surface treatment Product size and structure Pearlescent pigment quality Pearlescent pigment dispersion The extent of damage of pearl during the manufacturing process Effect from Enhancer and filler Pearl dosage

COMMON ISSUES PEARLESCENT PLASTIC Color changing / stability Black spots /pearly spots Flow lines Weld lines Yellowing Poor pearlescent effects Crazes Bubbles

Effect Issue Analysis Formula Raw material Equipment Pearlescent pigment

Issue Investigation What is the raw material used Pearlescent Pigments dosage in Master Batch Dispersion used Equipment Used Manufacturing reference such as pressure, temperature, etc. Timing If the issue is regular Pearlescent pigment coating is single layer or dual layer? The thickness of the layer Pearl total dosage Final product structure and size

Issue Reasons and Solutions Black Spots Solutions: Reduce pearl dosage in master batch Improve dispersion Reduce grinding damage Clean the equipment Use pre-dispersed pigments Use proper filtering Choose correct pearlescent pigments Possible Reasons: Poor dispersion Damage caused by grinding Impurities Accumulation Incorrect choice of pearlescent pigments

Problems and Solutions Yellowing Possible Reasons: Non-yellowing resistant pearlescent pigments The yellow resistant coating layer is damaged during grinding Chemical damage of the yellow resistant coating layer Solutions: Choose proper yellow resistant pearlescent pigments Mix the pearls properly, do not grind which destroys the yellowing resistant coating layer

Yellowing Is an reaction between Titanium and Phenol antioxidant. Occurs without humidity or lights. Is a Reversible chemical process. The speed and strength of this reaction depends on the activity of Phenol group, such as BHT. Temperature affects its speed and strength. When pearlescent pigments are used with polycarbonates yellowing issues may occur Specially treated Yellow Resistant pearlescent pigments are recommended for polycarbonates

Flow Lines Solutions: Possible Reasons: Dispersion improvement Poor master batch dispersion Equipment problems “Waves” created by moisture Processing temperature too low Mold temperature too low Solutions: Dispersion improvement Adjust manufacturing references such as temperature, speed and pressure Increase the processing and mold temperature temperature Dry raw material

Weld Lines Possible Reasons: Solution: Mold structure Pearlescent pigment and its dosage Solution: Weld lines are not avoidable but can reduced Improve the mold structure

Cautions Pearlescent pigments need to be dispersed first, except to mix into directly with PVC power plastic Plastic pieces require wetting with 0.2-0.5% adhesive first then mixed in with pearlescent pigments. Polyolefin. when it used with titanium power, reacts with phenols and may cause yellowing. PVC requires all transparent ingredients with pearlescent pigments mixed in at the last step. When Gold and Iron pearlescent pigments are used with PVC a lab test is required PMMA, PC, PA: requiring drying first before use. Exterior applications Only yellowing / weather resistant products are recommended.