PRIMARY JOURNAL FOR THE COATINGS MARKET IN ASIA & THE PACIFIC RIM

VOL 33 • NO 5 OCTOBER 2020

Inside: Construction Coatings

Inside: Pigments & Dispersions

Protecting the planet The latest sustainable developments in the coatings industry

ADHESIVES • EXTENDERS & FILLERS • PAKISTAN • SINGAPORE

October cover.indd 1 21/09/2020 12:06 PIGMENTS & DISPERSIONS

Curtis Ross, DCL, explains how formulators can find alternatives to lead chrome and moly orange pigments when regulatory restrictions prohibit their use Lead chrome and moly orange alternatives in the APAC region

lobal consumption of lead chromate Property Standard lead chromate Standard organic pigment pigments (PY.34 & PR.104) has Gdeclined over the last decade due Cost Economic More expensive to increased regulatory requirements. Colour Weaker Strong They continue to be used in the coatings Hiding Opaque More transparent and plastic industries due to the fact that Dispersion Easy More difficult they are the best value for performance in many applications. Lightfastness Excellent Varies Lead chromate pigments have the Weatherfastness Generally good Varies following key performance characteristics Resistance Standard inorganic Standard organic that make them extremely challenging Solvent Excellent Varies to replace: • Shade functionality – a very broad Heat Excellent (select grades) Varies breadth of shade from green shade to Chemical Good-excellent Varies mid and red shade yellows, continuing to bright oranges. Table 1. Inorganic vs organic characteristics • Chroma – high cleanliness of shade. • Durability/weatherfastness – colours performance and costs. Organic pigments • End-use application (ie outdoor do not fade or change colour upon have advantages in chroma and tint vs indoor). exposure to weather, both sunlight and strength but are inferior in opacity and • Colour, strength, opacity, heat stability, rain, hence coatings need to be re- weatherfastness. Table 1 summarises solvent/polymer compatibility and other applied less frequently. some key differences between a standard application requirements. • Opacity – the pigments are very organic pigment versus a standard lead In addition to the above, formulators opaque and, thus, hide the substrate chromate pigment. need to understand that lead chromate underneath, resulting in fewer coats of pigments exhibit much lower oil paint being required. nnHOW TO SELECT THE absorptions and as such, the pigment • Solvent resistance – the pigments APPROPRIATE LCA concentration used in a formula is do not dissolve in the solvents used much higher compared to an organic in coatings. When selecting an LCA, many factors are pigment. In addition, formulators must • No metamerism – the pigments exhibit to be considered by the formulators before take into account that dispersing lead the same colours under different light they can select the best replacement. chromate pigments is easier versus sources, for example in daylight and As this can be very challenging, DCL is organic pigments. under fluorescent lights. committed to helping the formulators This may all sound very challenging to • Heat stability – selected grades of these understand the different pigment the formulator, however, to bridge this gap pigments do not change colour under chemistries and will provide the technical DCL has created specific LCA pigments high processing temperatures. expertise required for the formulator to that target specific applications and their • Dispersibility – the pigments disperse in make excellent decisions. end-use requirements. This allows the the paint very easily and, thus, require This is particularly important with formulators to reduce costs and at the less energy and time. regard to weatherfastness, which is only same time, maintain key performance • Cost – very economical in use (about apparent after the coating is applied to properties. DCL will guide you through the 4-10 times cheaper than alternatives). an outdoor surface. Weatherfastness in process and help you understand how to general is an area where brand owners select the correct LCA. nnLEAD CHROME are unwilling to make sacrifices, as ALTERNATIVES (LCA) durability deficiencies can translate nnLCAS AVAILABLE AT DCL into expensive claims against There is no 1:1 replacement for lead the manufacturers. The key advantages of DCL LCA’s: chromate pigments, only alternatives that For formulators, the following are • Replacements for lead chromate and require some technical compromises. key performance criteria and must moly oranges – application specific. Organic pigment alternatives and lead be considered when selecting the • Ease of use – match for masstone chromate pigments differ greatly in appropriate LCA: colour and opacity.

50 APCJ • October 2020 www.coatingsgroup.com

DCL.indd 1 21/09/2020 11:37 PIGMENTS & DISPERSIONS

• Stronger tint strength. • Minimal formulation required. Vivid pigments Exterior: n Oregon State University chemistry CYMO DCL Weatherfastness Application researcher who made history a product code 1 = Severe colour change I – Industrial coatings A decade ago with the accidental 5 = No colour change PC – Powder coatings discovery of the first new blue inorganic D – Decorative/architectural pigment in more than two centuries is again A – Automotive pushing forward the science of colour. Masstone Tint Analysing the crystal structure of Lemon shade 4630 5 4 I, PC pigments based on hibonite, a mineral chrome yellow 4654 4-5 4-5 I, PC, D, A found in meteorites, Mas Subramanian of the OSU College of Science has paved the Medium shade 4632 5 5 I, PC, D chrome yellow 3RLM 4-5 5 I, PC, D, A way toward designing more pigments that 3RLX 4 4-5 I, PC, D, A are stable, durable and non-toxic with vivid hues. Findings from the study, supported Red shade 5RLM 4-5 5 I, PC, D, A chrome yellow 5RLX 4 4-5 I, PC, D, A by the National Science Foundation, were published in the American Chemical Yellow shade 4754 4-5 5 I, PC, D, A Society journal, ACS OMEGA. moly orange Subramanian and his team discovered Blue shade moly 4606 5 5 I, PC, D YInMn blue in 2009 when they were orange experimenting with new materials that could be used in electronics applications. Interior: Before YInMn blue, the last blue discovery was cobalt aluminum oxide-based blue, CYMO DCL Weatherfastness Application synthesised by a French chemist in product code 1 = Severe colour change I – Industrial coatings 1802. Cobalt blue remains a dominant 5 = No colour change PC – Powder coatings commercial pigment because of its D – Decorative/architectural intensity of colour, ease of synthesis and A – Automotive wide applicability. Its production, however, Masstone Tint requires a significant amount of a cobalt ion, Co +, that’s hazardous to both humans Lemon shade 4526 3 1 I, PC, D 2 chrome yellow 4527 4-5 3-4 I, PC, D and the environment. By analysing the structure of hibonite- Medium shade 4503 3 1 I, PC, D chrome yellow based blue pigments, Subramanian has developed a way to match or surpass Red shade 4504 3 2 I, PC, D cobalt blue’s vividness while using much chrome yellow 4507 3-4 2-3 I, PC, D less of the harmful carcinogenic cobalt ion, Yellow shade 4510 3 1 I, PC, D or replacing it entirely. The hibonite-based moly orange pigments are more thermally stable than Blue shade moly 4511 3 1 I, PC, D cobalt blue due to their higher preparation orange 4540 4 2 I, PC, D temperature and remain unaltered structurally and optically upon exposure to strong acid and alkali. nnCONCLUDING REMARKS The researchers report that an oxide containing calcium, aluminium, titanium While there is not one single replacement along with cobalt or nickel can crystallise available for lead chromate and moly into a structure similar to hibonite that orange in all applications, DCL offers a allows for a series of blue colours. range of LCA’s for each specific application Compared to traditional cobalt blue, to make reformulating easier. The best the new blue can be “tuned” by adjusting

product for any application is available how much cobalt (Co2+), nickel (Ni2+) and

in an easy to use powder, which can titanium (Ti4+) are placed into the hibonite be substituted into the formulation with structure’s three possible “chromophore” minimal additional work. n environments; those are the parts of a molecule that determine colour by reflecting some wavelengths of light while absorbing others. This study shows the presence of chromophores in a “trigonal bipyramidal- shaped crystal environment” – essentially Author: Curtis Ross, Technical Service consisting of two triangular-base Manager DCL pyramids joined base-to-base – is critical Website: www.pigments.com for colour enhancement. n

51 APCJ • October 2020 www.coatingsgroup.com

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