Permanent Red 169 is the commercial designation applied to C.I. Pigment Red 169 (CAS 12237-63-7), a high-molecular-mass disazo condensation pigment used primarily in polyolefin masterbatch, rigid and plasticized PVC, engineering thermoplastics, and industrial coatings. The pigment is supplied in standard powder, low-dusting granule, and aqueous presscake forms; particle-size distribution and surface treatment are adjusted at the finishing stage to control opacity, dispersibility, and migration behaviour in specific end-use matrices. In masterbatch and compounding, dry powder grades are preferred when high pigment loadings and short wetting cycles are required. Granular grades reduce workplace dust but can require an additional dispersive mixing zone to achieve equivalent fineness of grind. Aqueous presscake is used where rub-out performance and washability in water-based coating or latex manufacture justify the handling requirement. Manufacturers typically specify colour strength against a reference standard at 95%–105% by ISO 787-24, with tinting strength and shade controlled through the drying and milling sequence. Because the pigment is a condensation product with low solubility in common solvents, it occupies a fastness position above classical azo lakes such as C.I. Pigment Red 48:2 and C.I. Pigment Red 57:1, and below certain DPP chemistries in chroma. It is not a single universal grade: batch-to-batch variance in primary particle size and surface acidity can affect filter-pressure values in plastics processing, and incoming inspection should include sieve residue and moisture content where high-speed extrusion is intended.

Specification Ranges and Standard Test Methods for C.I. Pigment Red 169

Representative manufacturer-published limits for standard powder grades of Permanent Red 169 are assembled in the following table. The values are not a procurement specification unless a supplier’s certificate of analysis matches the stated method. Density is measured by pyknometer according to ISO 787-10; oil absorption uses the Gardner-Coleman method of ISO 787-5. Volatile matter is determined at 105 °C by ISO 787-2, and sieve residue is assessed on a 45 µm sieve under ISO 787-7. Colouristic properties are relative to a supplier master standard and are commonly controlled by ISO 787-24 and ISO 787-1. Oil absorption is an indirect measure of pigment surface area and binder demand. A powder lot at the upper end of the cited range will require additional plasticizer or dispersant to reach the same flow state in PVC plastisols as a lot at the lower end. In alkyd systems, the same shift can increase mill-base viscosity if the formulation is not adjusted. pH variations above 8.5 can disrupt acid-catalysed thermoset coatings, while acidic values below 6.5 may accelerate container corrosion in water-based formulations. Sieve residue at 45 µm is not a direct measure of primary dispersion but is used to guard against large, brittle agglomerates that can survive low-shear extrusion. BET specific surface area is not universally specified for this grade; where reported, it is typically evaluated by nitrogen adsorption according to ISO 9277, with values in the approximate range of 20–60 m²/g. Lower surface-area grades are generally easier to disperse in non-polar polymers, but they may reduce tinting strength.

How Does Permanent Red 169 Disperse in Polyolefin Masterbatch on Co-Rotating Twin-Screw Extruders?

Dispersion quality is governed by primary particle size, surface treatment, and the specific mechanical energy input of the compounding line. In single-pigment polyolefin masterbatches at 40–50 wt% loading, a common industrial configuration is a co-rotating twin-screw extruder with L/D 44:1, vacuum venting at −0.08 MPa, and a screen pack of 200/400/200 mesh upstream of the die. The pigment is fed through a side feeder after the polymer melt seal to minimise pre-gelation and dusting. Melt-temperature set points of 180–230 °C are typical for LDPE and LLDPE carriers; excessive temperatures above 260 °C do not usually degrade the chromophore but can reduce melt viscosity and lower shear transfer, leaving coarse agglomerates. In a 25 mm co-rotating twin-screw extruder, screw speeds of 400–800 rpm and throughputs of 5–20 kg/h are representative for high-loaded organic pigment masterbatch, with specific mechanical energy input of 0.15–0.35 kWh/kg.

Filter-pressure values determined by EN 13900-5 are used to reject batches with poor dispersibility. In thin-gauge film letdowns below 0.1 wt% final pigment loading, a rapid increase in filter pressure indicates that the masterbatch’s pigment agglomerates have not been fully wetted or shear-fractured. Production records from high-speed blown-film lines show that pre-wetting Permanent Red 169 in a low-molecular-weight polyethylene wax or rheologically matched LDPE carrier before main extrusion reduces the incidence of screen-pack plugging and die-lip buildup. Where aqueous presscake is used, residual moisture must be below 1.0 wt% before side feeding; higher moisture levels generate melt fracture and surface porosity in cast film. Published acceptance limits are set by the converter rather than by a universal standard, because the critical pressure rise depends on filter geometry, melt viscosity, and extrusion throughput.

If Processing Temperatures Exceed 300 °C in High-Speed Thin-Wall Injection Moulding, Does Permanent Red 169 Retain Colouristic Stability?

In high-speed thin-wall injection moulding of polypropylene, melt temperatures are usually 220–260 °C, providing a distinct thermal margin below the pigment’s typical 300 °C short-term rating in polyolefins under EN 12877-2. If cycle-severity gradients force hot-runner temperatures above 300 °C, residence time becomes the controlling variable. Published data for hold times beyond 5 min in these specific configurations is limited; industrial practice is to test production-compounded material at the upper barrel and hot-tip set point using a staircase temperature profile and compare CIELAB ΔE* against a pressed or injection-moulded standard over 5 min, 10 min, and 20 min dwells. Colour drifts above 2.0 CIELAB ΔE* that persist after cooling generally indicate local hot spots or carrier-polymer degradation rather than pigment decomposition alone.

Permanent Red 169 is not recommended for polymers that require sustained processing above 320 °C, such as polysulfone, polyetherimide, or PEEK. In those matrices, the condensation chromophore can undergo progressive darkening and molecular-mass breakdown, and available supplier data are scarce. This is a deliberate operational boundary: the pigment’s fastness profile is strongest in polyolefins, styrenics, and vinyl thermoplastics processed below 300 °C.

In flexible PVC compounds, Permanent Red 169 is typically pre-dispersed at 20–30 wt% in a phthalate or trimellitate plasticizer before addition to the dry blend. The paste is charged during the hot-mix stage or through a side stream on a planetary mixer; processing temperatures of 120–160 °C are sufficient to incorporate the pigment into the PVC matrix without thermal degradation. Contact-bleeding tests in plasticized PVC are rated on a 1–5 grey scale under DIN 53775; manufacturer datasheets commonly assign a rating of 5 at 80 °C for 24 h when the pigment is fully dispersed, but the result depends on plasticizer type and PVC molecular weight. In solvent-based industrial coatings, Permanent Red 169 is milled into alkyd-melamine or thermoplastic acrylic resin systems on a bead mill or three-roll mill. Solvent fastness against methyl ethyl ketone, ethyl acetate, and ethanol is typically 4–5 on the 1–5 grey scale described in ISO 105-A03. Water-based coating formulations require pH adjustment to 7.0–8.5 and the use of non-ionic or anionically compatible dispersants to prevent pigmentation shock and viscosity instability.

Printing ink applications are primarily lamination inks for flexible packaging where solvent-retention resistance and low extractable content are required. The condensation structure of Permanent Red 169 reduces bleed into adhesive layers in solvent-based lamination systems; however, it is usually co-milled with 0.2–0.5 wt% of a hindered-amine light stabilizer in UV-curable inkjet formulations to control surface chalking. In thermoset polyester/TGIC powder coatings, the pigment is compounded on a twin-screw extruder at 90–110 °C and ground to median particle sizes near 35–40 µm; overbake resistance in tests at 200 °C for 10 min and 20 min is adequate, while gloss preservation depends on dispersion and co-additives. In sulfur-cured elastomer goods, Permanent Red 169 is used at 1–2 phr for technical products requiring heat resistance. The pigment is added with the filler batch in an internal mixer; the high-molecular-mass structure does not usually interfere with sulfur-accelerated vulcanization at 150–170 °C. Contact-bleeding tests in nitrile rubber gaskets at 70 °C for 24 h show no visible staining when the pigment is fully dispersed. Published data for digital inkjet use are limited, and printhead compatibility must be confirmed with the specific ink manufacturer.

Migration Behaviour in Polyolefin Film Layers Is Governed by Molecular Diffusion Coefficients

In monolayer polyolefin film, Permanent Red 169 shows low migration tendency because its high molecular mass and extended aromatic system reduce diffusion through the amorphous regions of polyethylene and polypropylene. Migration testing under EN 1186-1:2002 food-contact simulation with 3% w/v acetic acid, 10% v/v ethanol, and vegetable oil simulants generally yields specific migration values below the limit of detection when the pigment is fully dispersed and no soluble impurities are present. However, EN 1186-1 is a total-simulant method for finished articles, not a pigment specification; colouring-material compliance must be assessed by the final packaging converter using the actual layer structure and additive package. In multilayer blown film, the pigment is often placed in a core layer to limit surface contact, particularly in films intended for fatty food contact where oil-soluble impurities or low-molecular-weight surface coatings could affect organoleptic performance.

The diffusion-limited profile of Permanent Red 169 differs from that of low-molecular-weight monoazo pigments, which migrate readily under heat and in contact with non-polar liquids. Published diffusion data for this exact structure are limited; however, the molecular-weight dependence of migration is well established in polymer packaging literature. Pigment lots containing residual intermediate concentrations above the supplier’s specified limit can exhibit observable surface bloom in low-density polyethylene even when the main chromophore remains immobile. This property is a primary reason that Permanent Red 169 is selected for opaque red packaging films where bleed resistance outweighs maximum chroma.

A Comparative Matrix of Heat and Migration Properties Across Red Organic Pigments

The following matrix positions Permanent Red 169 relative to common red organic pigments used in plastics and coatings. Heat stability is reported for HDPE or PP injection-moulded plaques under EN 12877-2 at 5 min dwell; migration is a plasticized-PVC contact-bleeding rating on the 1–5 scale, where 5 denotes no visible bleeding. Lightfastness is blue wool scale under ISO 105-B02.

The practical difference between Permanent Red 169 and C.I. Pigment Red 254 is most visible in opaque polyolefin film: PR169 is generally lower in tinting strength per ISO 787-24, but its larger effective particle size after finishing can produce higher hiding at equal film thickness when measured by contrast ratio according to ISO 6504-3. Conversely, C.I. Pigment Red 254 is selected where maximum chroma and coloristic efficiency are required at low loadings. Against classical azo lakes, Permanent Red 169 provides substantial gains in heat resistance and bleeding resistance but at a higher purchase price and with lower tinting strength than some lake pigments. When replacing C.I. Pigment Red 48:2 in polypropylene, a colour-strength correction is usually required because PR169 is often weaker; laboratory letdowns under ISO 787-24 are used to establish the correct pigment loading. Compared with C.I. Pigment Red 170, Permanent Red 169 offers higher heat stability in thick-section PP but is less blue-shaded. In formulations where a distinct blue-red hue is required, C.I. Pigment Red 170 or C.I. Pigment Red 254 is typically blended at 5–20 wt% of the total pigment loading to shift hue without sacrificing overall fastness.