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What's best pigment for coloring plastic

What's best pigment for coloring plastic

Feb 26,2024

What is plastic colorant

  Plastic colorants/pigment refer to substances that can change the color of objects or dye colorless objects with color.

Performance of plastic colorants

  Plastics are mainly colored by adding inorganic pigments and organic pigments , which require high color intensity and brightness, good transparency, hiding properties, dispersion, weather resistance, thermal stability, chemical stability, and electrical properties. and environmental performance.

Types and application progress of plastic colorants/pigments

  1. Inorganic pigments

  Inorganic pigments are traditional plastic colorants. Although inorganic pigment have poor tinting power, they have excellent heat resistance, weather resistance, and migration resistance, and are cheap . Although they often contain heavy metals and their toxicity problems have limited their use, they are currently used in plastics. It still plays an important role in the field of plastic coloring. According to the chemical structure, the current inorganic colorants mainly include the following categories: metal oxides(chrome yellow,Pigment yellow 34,Pigment red 104), mainly titanium dioxide(Tio2), chromium trioxide, iron oxide(Pigment red 101,Pigment yellow 42), zinc oxide, antimony oxide, etc.; Carbon Black(Pigment black 7); metal sulfides, such as cadmium sulfide, sulfide Mercury, etc.; chromates, such as chromium yellow, chromium orange, etc.; molybdates, such as molybdenum red, etc.; others such as ultramarine blue(Pigment Blue 29), iron blue, manganese pigments, cobalt pigments and bismuth vanadate and other pigments.

  Titanium dioxide(Tio2) is currently the most widely used plastic colorant. The main direction of application research is the application of nanoscale ultra-fine titanium dioxide, which not only plays a coloring role but also has a bactericidal effect. The dispersion of titanium dioxide is poor, and organic treatment agents are generally used to treat its surface. Organic treatment agents generally include triethanolamine, sorbitol, mannitol, polyethylene glycol, polypropylene glycol, alkyl chlorosilanes, and esters. compounds, fatty acid compounds, etc.

  Carbon black is the second most commonly used plastic colorant after titanium dioxide. It is classified according to processing methods and comes in many varieties. When used as a pigment, it is generally called "pigment carbon black". There are many types of this type of carbon black, especially the development and application of gas phase silica in recent years, which has many excellent properties and has attracted much attention. Carbon black not only has a coloring function, but also has excellent weather resistance and thermal oxygen resistance; the correct selection of carbon black can also improve the conductive or insulating properties of the polymer.

  Cadmium pigments are a type of particularly stable inorganic pigments with bright colors and small coloring dosages. However, due to toxicity restrictions, the European Union and the United States have clearly restricted their use. However, due to its excellent properties, especially excellent heat resistance, it is still difficult to find suitable substitutes in some special processing applications. Currently, in the processing of engineering plastics that require high processing temperatures such as polyamide, polyformaldehyde, and polytetrafluoroethylene, Still in use.

  2. Organic pigments

  Organic pigments have become important colorants for plastics due to their wide variety, bright colors, high tinting power, and excellent application properties. According to their different structural types , pigments suitable for plastic coloring mainly include:

  Insoluble azo pigments, especially mono- and disazo pigments with relatively complex structures, contain multiple polar substituents such as methyl, nitro, halogen, amide, etc. or heterocyclic substituents such as benzimidazolinone in the molecule. Group and azo condensation pigment varieties, the chromatographic range is mainly yellow(Pigment yellow 13,Pigment yellow 83..), orange(Pigment orange 13..), red(Pigment red 57:1), etc., especially some organic pigments produced from 3,3'-dichlorobenzidine as raw materials are suitable for coloring a variety of plastics. And has good application performance.

  Lake pigments(Pigment red 53:1) are mainly a small number of naphthol sulfonate (carboxylic acid) red lake pigments. Due to their large molecular polarity, they have good thermal stability and high tinting power, and can be used for processing and molding at moderate temperatures. Resin coloring.

  Phthalocyanine pigments(Pigment blue 15:3,Pigment green 7) have excellent heat resistance, light resistance, weather resistance, high tinting strength and migration resistance, and are low in price. There are mainly two types: phthalocyanine pigment blue and phthalocyanine pigment green, with monotonous color spectrum; in addition, its use in large-scale high-density polyethylene products will cause deformation and brittleness, which deserves special attention. Heterocyclic and condensed ring ketones, these products have excellent application properties and are not only used for plastic coloring, but also for coatings , inks , etc. Due to their complex molecular structure and high cost , their comprehensive properties are excellent, and they are generally called High-end organic pigment varieties.

  Quinacridones pigment(Pigment red 122)have excellent migration resistance, light resistance and heat resistance. There are currently about 20 industrialized varieties. The main varieties are quinacridone red(Pigment red 122), purple(Pigment violet 19) red quinacridone pigments, yellow light maroon red The main production company for quinacridone pigments and bright red quinacridone pigments is the Swiss Ciba Company, and there are also a few companies in China.

  Diketopyrrolopyrrole pigments, referred to as DPP pigments(Pigment red 254), are Ciba's patented products, of which the two main products are C. I. The patents of Pigment Red 254 and 264 expired in 2003. The current global DPP pigment production reaches about 7000t/Y. The main raw materials are dialkyl succinate, p-chlorobenzonitrile and p-phenylbenzonitrile.

  Dioxazine pigments(Pigment violet 23) contain the parent structure of triphenyldioxazine in their molecular structure, mostly in the purple spectrum. They are mainly used in acrylic resin sheets and extruded low-density polyethylene products. They have been successfully developed and industrially produced in China and are commonly used. Used as a whitening and yellowing inhibitor for titanium dioxide.

  Isoindolinone pigments(Pigment yellow 110,Pigment yellow 139), the main variety is tetrachloroisoindolinone. This pigment has light resistance, solvent resistance and heat resistance. Due to its outstanding resistance to migration, it is particularly suitable for use in soft polyvinyl chloride products. Currently, it is mainly Used in automotive plastic products.

  There are also some such as carbazole, perylene(Pigment red 149,Pigment red 179), quinophthalone, anthraquinone(Pigment red 177), benzimidazolones(Pigment yellow 180), etc. Currently, the production of these high-end plastic colorants is mainly concentrated in Western Europe, and the main manufacturer is DyStar, Ciba CorporationClariant Corporation , etc.

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