Pigments for Coatings & Paints
Copper phthalocyanine pigments serve the full spectrum of coatings applications, from cost-sensitive architectural emulsion paints to the most demanding automotive OEM and aerospace finishes. Their combination of exceptional weatherfastness, chemical inertness, and high chroma makes them indispensable wherever durable blue or green colour is required. Non-flocculating grades are essential in metallic and pearlescent basecoats where any pigment agglomeration would disrupt aluminium flake orientation and destroy the flop effect. In powder coatings and coil coatings, heat stability up to 200 °C and compatibility with TGIC, HAA, and polyester–epoxy hybrid binders are baseline requirements. Formulators select among alpha and beta crystal forms, untreated and surface-stabilised variants, to optimise the balance of shade, dispersibility, flocculation resistance, and cost for each coating technology.
Key Performance Requirements
Weatherfastness
Exterior coatings must retain colour and gloss after years of exposure to UV radiation, moisture, and temperature cycling. CPC pigments are inherently among the most durable organic pigments, but performance in tints can drop significantly when photocatalytic TiO₂ grades are used. Grade selection, pigment-to-binder ratio, and choice of complementary UV absorbers and HALS stabilisers must be engineered as a system.
Non-flocculation
Flocculation — the loose, reversible aggregation of pigment particles — causes colour drift, loss of gloss, flooding and floating in mixed-pigment systems, and poor reproducibility. In automotive and industrial coatings applied by spray, curtain, or roller, any flocculation is immediately visible as a defect. Surface-treated non-flocculating grades (PB 15:2, PB 15:4) are required for these applications.
Chemical resistance
Coatings in marine, industrial maintenance, and automotive underbody applications must withstand acids, alkalis, salt spray, fuel, and hydraulic fluid without colour change or pigment migration. CPC pigments offer inherent resistance to most chemicals, but the pigment–binder interface and dispersion quality also affect the film's overall chemical durability. Proper pigment surface treatment and dispersion protocol are essential.
Heat stability
Stoving enamels, coil coatings, and powder coatings undergo curing temperatures of 160–220 °C for extended dwell times. Beta-form CPC blues and PG 7 are stable well above these temperatures, but alpha-form blues can undergo crystal growth or phase conversion to beta if not properly stabilised. Grade data sheets must be checked against the specific cure schedule of each coating line.
Recommended Grades
| Grade | Shade | Rationale |
|---|---|---|
| PB 15:3 | Greenish blue | General-purpose beta-form blue for decorative, general industrial, and marine coatings where good all-round performance and cost efficiency are the primary drivers. Delivers a clean greenish-blue shade with high tinctorial strength and good lightfastness in both full shade and tint. |
| PB 15:4 | Greenish blue | Non-flocculating beta-form blue engineered for automotive OEM, coil, and powder coatings. The stabilised surface treatment ensures flawless metallic flop, consistent colour development in thin-film coil applications, and resistance to reagglomeration during the high shear and elevated temperatures of extrusion and curing. |
| PB 15:2 | Reddish blue | Non-flocculating alpha-form blue offering a reddish shade that is preferred in automotive refinish and certain decorative applications where a warmer blue is specified. Its stabilised surface chemistry prevents solvent-induced crystal change while maintaining excellent gloss and transparency in both solid and metallic colours. |
| PB 15:1 | Reddish blue | Stabilised alpha-form blue for architectural and decorative emulsion paints. Its solvent resistance prevents shade shift during tinting with universal tinters containing glycols, and its moderate cost makes it the standard choice for the large-volume architectural segment. |
| PG 7 | Bluish green | The universal green pigment for all coating systems from architectural emulsion to aerospace topcoats. Its fully halogenated structure provides exceptional weatherfastness, heat stability to 300 °C, and broad chemical resistance, with no viable single-pigment alternative in the market. |
Technical Considerations
- In automotive OEM metallic basecoats, the pigment must be fully deflocculated to avoid disrupting aluminium or mica flake orientation. PB 15:4 with its controlled surface charge allows flakes to lie flat and parallel to the substrate, producing the desired brightness at face angle and a clean, deep flop at grazing angle. Any flocculation shows up as mottling or streaking under inspection lamps.
- Powder coatings present unique challenges: the pigment is dry-blended with resin chips before extrusion at 90–130 °C, then the extrudate is milled and electrostatically sprayed. Particle size distribution must be optimised for smooth incorporation during extrusion, and the pigment must survive the 180–200 °C cure oven without shade change. PB 15:4 and PG 7 are the standard grades for this process.
- In waterborne latex architectural paints, the pH of the millbase and letdown (typically pH 8–9) can affect the surface charge and flocculation behaviour of the pigment. Stabilised grades or grades with compatible surface treatments are preferred to maintain colour acceptance, and in-can tint strength testing should be performed after accelerated storage to verify stability.
- Coil coatings are applied at very high line speeds (60–200 m/min) as thin films (15–25 µm dry) on pre-treated aluminium or steel strip, then cured in seconds at peak metal temperatures of 220–250 °C. The pigment must develop full colour at these low film weights and short cure times, and must not bloom, migrate, or shift shade. PB 15:4 and PG 7 are the approved grades for all major coil coaters.
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