FAQs Phthalocyanine Pigments

What is a phthalocyanine pigment?

A phthalocyanine pigment is an organic pigment based on the phthalocyanine molecule a large, ring-shaped structure made of four linked isoindole units, usually with a metal atom (most commonly copper) held at the centre. Phthalocyanine pigments are prized for their intense, clean blue and green shades, exceptional tinting strength, and outstanding resistance to light, heat, acids, alkalis, and solvents. First commercialised in the 1930s, they remain the most important class of blue and green organic pigments in the world today.

Copper phthalocyanine (CPC) is the workhorse blue colourant of modern industry. It is used in printing inks (offset, gravure, flexo, and inkjet), paints and coatings (decorative, automotive, and industrial), plastics (masterbatches, PVC, polyolefins, engineering polymers), textiles (pigment printing), rubber, paper, artists’ colours, stationery, and even specialty applications such as colour filters for LCD displays. CPC is also the chemical starting point for Pigment Green 7 and Green 36, produced by halogenating the CPC molecule.

Copper phthalocyanine has the molecular formula C₃₂H₁₆CuN₈ and a molecular weight of about 576. The molecule consists of four isoindole (benzopyrrole) units joined by nitrogen bridges into a flat, highly symmetrical macrocyclic ring, with a single copper ion coordinated at the centre. This planar, fully conjugated 18-π-electron system is what gives the pigment its intense blue colour and its remarkable thermal and chemical stability. CPC exists in several crystal forms, the most important commercially being the alpha form (reddish blue) and the beta form (greenish blue).

Pigment Blue 15 (C.I. 74160) is the Colour Index name for copper phthalocyanine blue they are the same chemistry. The suffixes denote different crystal modifications and stabilisation levels:

  • PB 15:0 – alpha form, unstabilised, reddish blue
  • PB 15:1 – alpha form, phthalimidomethyl/chlorine stabilised against flocculation and crystallisation
  • PB 15:2 – stabilised alpha form, non-flocculating grade
  • PB 15:3 – beta form, greenish blue; the highest-volume grade, dominant in inks
  • PB 15:4 – stabilised beta form, non-flocculating, preferred for solvent-based systems
  • PB 15:6 – epsilon form, the reddest shade of the family

Choosing the right suffix for the application system is one of the most important formulation decisions.

Pigment Green 7 (C.I. 74260) is polychlorinated copper phthalocyanine a CPC molecule in which 14–15 of the 16 peripheral hydrogen atoms have been replaced by chlorine. Chlorination shifts the colour from blue to a brilliant bluish green. PG 7 is by far the most widely used green pigment in the world, offering the same outstanding fastness profile as its blue parent: excellent lightfastness, weather resistance, heat stability, and resistance to acids, alkalis, and solvents. It is used across paints, plastics, inks, textiles, and rubber. (Its bromine-containing cousin, Pigment Green 36, gives a yellower green shade.)

CPC blue offers a combination of properties that no other blue pigment matches at its price point: very high tinting strength (a little pigment goes a long way), a clean and brilliant hue, excellent lightfastness and weatherfastness, heat stability typically up to 200 °C or higher depending on grade, insolubility in water and most solvents, resistance to acids and alkalis, and non-toxicity in normal use. It is also manufactured from relatively inexpensive raw materials at a large industrial scale, making it highly cost-effective. This balance of performance and economy is why it accounts for the large majority of all blue organic pigment consumed globally.

Commercially, CPC is produced by one of two routes:

Phthalic anhydride/urea process (most common, especially in India): Phthalic anhydride, urea, and a copper source (copper chloride) are heated together at 180–250 °C with a catalyst (typically ammonium molybdate), either in a high-boiling solvent or by a dry bake process. The reaction yields crude CPC.

Phthalonitrile process: Phthalonitrile is reacted directly with copper or a copper salt at elevated temperature, giving a very pure crude with fewer by-products.

The crude CPC is then purified (acid pasting or acid swelling) and finished conditioned by milling, kneading, or solvent treatment to develop the desired crystal form, particle size, and surface characteristics. Finishing is where much of the value is added, since it determines shade, strength, dispersibility, and application performance.

  • Printing inks – the largest consumer; publication gravure, offset, flexographic, packaging, and inkjet inks
  • Paints and coatings – decorative/architectural paints, automotive OEM and refinish, industrial and powder coatings
  • Plastics – masterbatch, PVC, polyolefins, engineering plastics, fibres
  • Textiles – pigment printing and dyeing
  • Paper – coloured and coated papers
  • Rubber – coloured rubber goods
  • Specialty uses – artists’ colours, stationery, cosmetics-adjacent items, seed coatings, colour filters for displays, and CD-R recording layers (dye derivatives)

Compared with alternatives such as ultramarine blue, Prussian (iron) blue, indanthrone blue, or Victoria blue toners:

  • Tinting strength: CPC is far stronger than ultramarine or Prussian blue, so less pigment is needed per unit of colour.
  • Fastness: Superior lightfastness and chemical resistance to Prussian blue and basic-dye toners; ultramarine fails in acids, while CPC does not.
  • Heat stability: Suitable for most plastics processing temperatures, unlike many organic blues.
  • Cost-performance: Indanthrone blue offers comparable fastness but at several times the price; CPC delivers premium performance at a commodity price.
  • Versatility: With multiple crystal forms and stabilised grades, CPC can be tailored to virtually any application system.

Yes chemical resistance is one of CPC’s defining strengths. It is insoluble in water, resistant to dilute acids and alkalis, and unaffected by most organic solvents at room temperature. It does not bleed in most application media and withstands soap, detergent, and bleach exposure well, which is why it is the standard blue for textile printing and detergent packaging. Its limits: it dissolves in very strong acids such as concentrated sulphuric acid (this property is actually used in its purification), and unstabilised alpha grades can change crystal form in strong aromatic solvents. For aggressive solvent systems, stabilised grades (PB 15:1, 15:2, 15:4) should be specified.

Prices vary with grade, crystal form, treatment level, order quantity, and raw material markets. As a broad indication, Indian market prices for phthalocyanine blue typically range from roughly ₹350–₹450 per kg for standard crude-based beta blue grades up to ₹500–₹700+ per kg for high-performance, surface-treated, or specialty grades (such as PB 15:4 for solvent inks or plastics-grade material). Crude CPC trades lower than finished pigment. Because prices move with copper, phthalic anhydride, and solvent costs, we recommend contacting us directly for a current quotation based on your grade and volume requirements.

Yes, generally. PG 7 is made from copper phthalocyanine blue by an additional chlorination step, which adds raw material (chlorine), processing time, and effluent-treatment costs. As a result, PG 7 typically sells at a meaningful premium over standard PB 15 grades often in the range of 30–60% higher on a per-kg basis, depending on grade and market conditions. However, because both pigments have very high tinting strength, the cost per unit of colour delivered remains highly competitive against alternative green pigments, most of which are either weaker or far more expensive.

Poor dispersion usually traces back to one or more of these causes:

  • Wrong grade for the system – e.g., an untreated aqueous grade used in a solvent-based ink. Match the grade (and its surface treatment) to your vehicle.
  • Inadequate wetting – insufficient or incompatible wetting/dispersing agent; the resin solution may not be wetting the pigment surface.
  • Insufficient milling energy or time – hard agglomerates need adequate shear; check bead size, loading, and residence time.
  • Flocculation after grinding – common with unstabilised grades in solvent systems; switch to a non-flocculating grade (PB 15:2 or 15:4) or add an anti-flocculant.
  • Pigment shock – adding letdown resin or solvent too quickly, causing the dispersion to crash.
  • Moisture pickup – pigment stored in humid conditions can form hard lumps.

If you share your ink system details with our technical team, we can recommend the correct grade and dispersion procedure.

In dilute acids, phthalocyanine pigments are essentially inert no colour change or bleeding. In concentrated strong acids (notably concentrated sulphuric acid), copper phthalocyanine dissolves by protonation to form a yellowish-green to olive solution. When this solution is poured into water, the pigment re-precipitates unchanged this “acid pasting” behaviour is actually exploited industrially to purify crude CPC and control particle size. Prolonged exposure to hot, oxidising acid mixtures can eventually degrade the molecule, but under any realistic end-use condition, acid attack is not a practical concern. Pigment Green 7 is even more acid-resistant due to its chlorinated structure.

  • Using an ink-grade or untreated pigment in plastics – leads to poor dispersion, specks, and filter-pressure problems in masterbatch.
  • Ignoring warpage – phthalocyanine blues and greens act as nucleating agents in semi-crystalline polymers (HDPE, PP), causing shrinkage and warpage in mouldings. Low-warpage grades or shade adjustment may be needed.
  • Exceeding heat stability limits – unstabilised alpha grades can shift shade at high processing temperatures; specify heat-stable grades for engineering plastics.
  • Poor let-down practice – inadequate mixing of masterbatch into virgin polymer gives streaks and colour variation.
  • Overlooking pre-drying – moisture on the pigment or masterbatch causes lacing and surface defects.
  • Wrong dispersant/carrier choice – the carrier resin must be compatible with the final polymer.

CPC pigment is chemically very stable, so storage is straightforward:

  • Keep in the original sealed packaging until use to prevent moisture pickup and contamination.
  • Store in a cool, dry, well-ventilated area away from direct sunlight and heat sources.
  • Keep bags off the floor on pallets, away from damp walls.
  • Avoid stacking excessive weight on powder bags compaction can create hard lumps.
  • Reseal partially used bags tightly.
  • Practise FIFO (first in, first out) stock rotation.

Under these conditions, phthalocyanine pigments retain full colouristic performance for several years. As with any fine organic powder, treat it as a combustible dust: avoid dust clouds near ignition sources and maintain good housekeeping.

Common treatments and additives applied during finishing include:

  • Rosin/resin treatment – coating pigment particles with rosin derivatives improves wetting and gloss, especially in publication and offset inks.
  • Phthalocyanine derivatives – sulphonated CPC, CPC-amine salts, or phthalimidomethyl-CPC deposited on the pigment surface act as anti-flocculants and crystal-growth inhibitors (the basis of PB 15:1, 15:2, and 15:4 stabilisation).
  • Amine/fatty amine treatment – improves dispersion in solvent-based and oil-based systems.
  • Surfactant treatments – anionic or non-ionic surfactants for aqueous systems (emulsion paints, water-based inks, textile printing).
  • Polymeric dispersant coatings – for high-end coatings and inkjet applications requiring fine, stable dispersions.

The right treatment depends entirely on the application medium which is why grade selection in consultation with your pigment supplier matters.

First, a clarification: phthalocyanine pigments are organic pigments the comparison is really between phthalocyanines and other colourant options in the blue-green space. Framed that way:

  • Versus inorganic blues/greens (ultramarine, Prussian blue, chrome green, cobalt blue): phthalocyanines offer far higher tinting strength, cleaner and more brilliant shades, and better acid/alkali resistance, usually at lower cost-in-use. Cobalt blue exceeds CPC only in extreme-temperature applications.
  • Versus other organic blues (indanthrone, Victoria blue toners): phthalocyanines deliver equal or better durability at a fraction of indanthrone’s price, and vastly better fastness than toner pigments.

For virtually all decorative, industrial, and automotive coating applications requiring blue or green, phthalocyanine pigments are the industry-standard choice the question is usually not whether to use them, but which grade to use. Our technical team can help you select the optimal grade for your coating system.

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