Pigments for Textile Printing
In textile pigment printing, the colourant is bound to the fabric surface by a polymeric binder resin rather than being fixed into the fibre structure as with reactive or vat dyes. This makes pigment printing substrate-independent — the same formulation works on cotton, polyester, nylon, and blends without requiring different application chemistry for each fibre type. Copper phthalocyanine blues and greens are the dominant pigments for blue and green shades in this segment because of their high tinctorial strength, excellent wash and light fastness, and compatibility with both aqueous binder emulsions and digital inkjet ink systems. As the industry moves rapidly toward digital pigment printing, the demand for ultra-fine, narrowly distributed CPC dispersions with particle sizes below 1 µm continues to grow, placing new demands on pigment finishing and surface treatment.
Key Performance Requirements
Wash fastness
Printed textiles must withstand repeated domestic and industrial laundering cycles without significant colour loss or staining of adjacent fabrics. In pigment printing, wash fastness is primarily a function of the binder film's integrity and adhesion to the fibre surface, but the pigment's particle size and distribution also play a role — coarse or poorly dispersed particles create weak points in the binder film that accelerate wash-off. A well-dispersed CPC pigment in a quality binder system routinely achieves ISO 105-C06 ratings of 4–5.
Crock fastness (rub resistance)
Crock fastness measures the transfer of colour from the printed fabric to a white rubbing cloth under dry and wet conditions. Poor crock fastness is a common complaint in pigment printing and is caused by inadequate binder cross-linking, excessive pigment loading, or surface pigment not encapsulated by the binder film. Optimising the pigment-to-binder ratio and ensuring a uniform binder film through proper print paste rheology and curing conditions are critical to achieving acceptable ratings.
Particle fineness
For conventional screen printing, a median particle size of 1–3 µm is sufficient, but digital inkjet printing through piezoelectric heads with nozzle diameters of 20–30 µm demands median particle sizes well below 1 µm with no particles above 5 µm to prevent nozzle clogging. Achieving this fineness while maintaining colour strength requires intensive milling, careful classification, and surfactant systems that prevent reagglomeration during storage.
Binder compatibility
Pigment printing pastes are complex formulations containing the pigment dispersion, acrylic or polyurethane binder emulsion, thickener, cross-linker, and sometimes a softener. The pigment surface chemistry must be compatible with all these components to avoid coagulation, viscosity instability, or poor film formation. CPC pigments with anionic or non-ionic surface treatments are generally compatible with the acrylic binders dominant in the industry.
Recommended Grades
| Grade | Shade | Rationale |
|---|---|---|
| PB 15:3 | Greenish blue | The standard greenish-blue pigment for rotary and flatbed screen printing on all textile substrates. Its beta crystal form provides the bright, clean cyan shade that is the starting point for most blue and blue-derived colour recipes, with reliable dispersion behaviour in conventional print paste formulations. |
| PB 15:0 | Reddish blue | Untreated alpha-form blue providing a reddish shade that is valued for navy, royal blue, and warmer tone recipes in textile printing. Its natural hydrophilic surface makes it easier to disperse in the aqueous systems used in textile print paste preparation, reducing milling time and energy consumption. |
| PG 7 | Bluish green | The standard green pigment for all textile printing methods, offering exceptional wash and light fastness. Its yellowish-green hue is the foundation for all green shade matching in the textile sector, and its high heat stability ensures no shade change during the fixation and curing step at 150–170 °C. |
Technical Considerations
- Digital pigment printing requires dispersions with a d₉₉ below 1 µm (ideally below 0.5 µm) to prevent clogging of piezoelectric print heads. Standard textile-grade CPC pigments are too coarse; specially milled and classified nano-dispersions are needed. These dispersions must also exhibit Newtonian or near-Newtonian rheology at the low shear rates (10²–10³ s⁻¹) and jetting frequencies of inkjet systems.
- Wash fastness in pigment printing depends more on the binder system than on the pigment itself. A self-cross-linking acrylic or polyurethane binder that forms a continuous, flexible film with good fibre adhesion is the primary determinant of durability. The pigment's role is to be uniformly distributed within this film so that no unencapsulated particles are exposed to the wash liquor.
- The textile industry is under increasing regulatory pressure to eliminate formaldehyde-based cross-linkers from pigment printing binders. Blocked isocyanate and carbodiimide cross-linking systems are emerging replacements, and the pigment's surface treatment must be verified for compatibility with these newer chemistries to avoid coagulation or loss of fastness performance.
- At high pigment loadings (above 8–10 % on paste weight), the dried print can feel stiff and papery — a phenomenon known as poor 'hand'. Reducing pigment loading while maintaining colour depth requires high-strength, well-dispersed CPC grades. Alternatively, soft-feel binders or silicone-based softeners can be added to the paste to restore textile hand, but these additives may slightly reduce crock fastness.
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