Fast Bordeaux GP Base

Fast Bordeaux GP Base is supplied as a free aromatic amine of the azoic diazo component class, not as a finished pigment. Colour develops only after diazotization with sodium nitrite in hydrochloric acid and subsequent coupling with an alkaline Naphthol AS developer. The absence of sulphonic acid solubilising groups means the coupled chromophore is water-insoluble and remains molecularly dispersed within the cellulosic fibre or print film. Published data for this specific configuration is limited; therefore, the processing range described below is derived from general azoic diazo component practice and from standard quality-control methods applied to the class. The product is normally handled as a dry powder, presscake, or acid-pasted solution. Its colouristic function is to produce a Bordeaux shade whose exact reflectance depends on the Naphthol AS developer, coupling pH, and after-treatment. The primary amino group is converted stoichiometrically to a diazonium chloride, and the sodium nitrite demand is assessed by diazo titration. This characteristic separates the product from finished Bordeaux pigment preparations and from oil-soluble dyes, which do not require in situ formation. Storage and transport follow the safety data sheet; the material should be kept away from oxidising acids and nitrite salts to avoid premature diazotization. The chemical class is subject to REACH registration and downstream use communication under Regulation (EC) No 1907/2006. In the production environment, skin absorption and dust control are principal exposure routes; therefore, closed transfer and local exhaust ventilation are specified. The term “Fast” in the trade name refers to the intended fastness of the formed azoic dye rather than to a property of the base itself.

What Distinguishes Fast Bordeaux GP Base from Finished Bordeaux Pigment Dispersions?

The primary distinction is the stage at which colour is formed. A finished Bordeaux pigment dispersion already contains fully formed pigment particles before the application step. Fast Bordeaux GP Base remains a reactive intermediate until the user performs diazotization. In textile azoic printing, the base is applied to fabric that has been pre-treated with Naphthol AS; coupling therefore occurs inside the fibre rather than at the surface. This mechanism supports the characteristic wet fastness of azoic dyeings, although the final fastness depends on the removal of unreacted base and decomposition by-products. A second distinction is storage stability. Stabilised diazonium salts are pre-diazotised to reduce process steps, but their stability is sensitive to moisture and temperature; the free base is chemically stable until acidified and nitrosated. The trade-off is that the free base requires a diazotization vessel with accurate temperature control. In colouristic terms, Fast Bordeaux GP Base produces deeper and bluer Bordeaux shades than many Fast Red bases when coupled with the same Naphthol AS, but published reflectance data for this specific configuration is limited and converter trials are required. The resulting dye is assessed using ISO 105-B02 for light fastness, ISO 105-C06 for washing, and ISO 105-X12 for rubbing; the required minimum grades depend on end-use. Finished pigment dispersions, by contrast, are tested for dispersibility, viscosity stability, and migration behaviour before delivery rather than after a chemical coupling step.

In continuous rotary-screen printing, the process window is defined by the competition between coupling and diazonium decomposition. The Naphthol AS-impregnated fabric enters the print station with controlled residual alkalinity. Freshly diazotised Fast Bordeaux GP Base is printed through a rotary screen of 80–125 threads/cm, with the open area and squeegee pressure adjusted to a wet add-on of 0.5–1.5 L/m². The coupling bath pH is held between pH 8 and pH 10; below this range the naphtholate ion concentration is insufficient, and above this range the diazonium ion is increasingly converted to the unreactive diazo hydroxide. Temperature is maintained at 10–20 °C during the print run. At higher temperatures, diazonium decomposition accelerates and produces tar-like residues that can stain the white ground. After coupling, the fabric is rinsed at 20–30 °C and then soaped at 90–95 °C to remove loosely coupled surface colour. The thickening system is based on a cold-water swellable acrylic or starch ether at a viscosity of 1.5–3.0 Pa·s measured by rotational viscometer at 20 rpm. The base itself is dissolved as the hydrochloride salt before mixing with the thickener; the free amine is not simply dispersed into the print paste. Batch-to-batch variation in base particle size alters the dissolution rate in hydrochloric acid, and production experience shows that oversize particles lead to local stoichiometric imbalance and lower colour yield. A 100 µm pre-sieve of the diazonium solution is therefore used to remove undissolved residue before the paste is prepared.

The diazotization reaction consumes one mole of sodium nitrite per mole of primary amine in the presence of excess hydrochloric acid. The acid excess stabilises the diazonium salt once formed. The diazonium salt decomposes by first-order kinetics, and holding the diazonium solution above 5 °C for more than 60 min reduces coupling efficiency. The optimum nitrous acid concentration is controlled by slow addition of sodium nitrite solution into the acidified base; a local excess of nitrous acid can produce nitrosation by-products. The starch-iodide endpoint test is complemented by quantitative nitrite titration when high reproducibility is required. Fast Bordeaux GP Base is incompatible with amine-based thickeners that can consume the diazonium ion or alter the coupling pH. The product should therefore be formulated only with non-ionic or anionic thickener systems.

When Minimum Wet Rubbing Fastness Must Be Verified on Cotton

Wet rubbing fastness is the most sensitive indicator of incomplete coupling or poor soaping in azoic dyeings. The test is performed according to ISO 105-X12, with a wet cotton abradant and a specified number of cycles. A minimum wet rubbing grade of 3–4 is often required for apparel goods, although exact limits depend on buyer specifications. If the grade falls below this threshold, the failure usually originates from unreacted Fast Bordeaux GP Base, diazo decomposition products, or residual Naphthol AS that has not been removed. The corrective action is to reduce the base concentration in the pad liquor, increase the coupling time, or raise the soaping temperature to 90–95 °C with a non-ionic detergent. The base concentration in a typical pad application is 5–20 g/L as the free amine; the exact concentration is set by the depth required and the Naphthol AS level on the fabric. Production experience shows that a shift in base purity of more than ±2 % between batches changes the obtained Bordeaux depth enough to require a nitrite feed adjustment because the diazotization endpoint is stoichiometric. In plant trials, the diazonium solution is checked for free nitrite with starch-iodide paper; a persistent positive result indicates over-nitrosation, while a negative result before the theoretical nitrite demand suggests incomplete diazotization or side reactions with impurities. Washing fastness is separately evaluated with ISO 105-C06, and any staining of adjacent multifibre fabric is noted.

Quality control of Fast Bordeaux GP Base at incoming inspection must separate physical form from chemical reactivity. An in-house diazotization titration validated under ISO 17025 gives the usable free amine content, while sieving and extract tests detect agglomerates and water-soluble impurities. Table 1 lists the methods applied to azoic base powders and the reason each parameter is controlled. Because the supplier certificate of analysis may not include all listed methods, the user should request the batch-specific diazo value and residual moisture. If data for a specific configuration is not available, the product is tested as a class using the methods below; no universal numerical limit is assumed.

Storage, Occupational Hygiene, and REACH Compliance Data

Fast Bordeaux GP Base is stored in sealed containers at 5–30 °C and relative humidity below 60 %. The free amine is hygroscopic and acid-sensitive; exposure to atmospheric moisture or acid vapour can cause caking and reduce diazotization yield. In a warehouse, sacks are stacked on pallets with air circulation, and partially emptied containers are re-closed under dry conditions. The product is subject to REACH registration under Regulation (EC) No 1907/2006 for the applicable tonnage band, and downstream users must confirm that their process is covered in the supplier exposure scenario. The material safety data sheet defines occupational exposure limits; because aromatic amines can be absorbed through the skin, handling requires gloves, local exhaust ventilation, and respiratory protection if dust formation exceeds the workplace limit. The material must not be stored near nitrite salts, nitrous acid sources, or strong acids because premature diazotization is exothermic. Wastewater from textile printing operations contains unreacted naphthol, nitrite, and diazo decomposition products; treatment requires pH neutralisation and biological oxidation after destruction of residual diazonium compounds. Discharge limits for aromatic amines vary by jurisdiction, and the absence of published data for this specific configuration does not remove the duty to test the site effluent for colour and amine concentration.

Shade matching with Fast Bordeaux GP Base is a stoichiometric problem rather than a simple mixing operation. The final Bordeaux hue is controlled by the ratio of diazotized base to Naphthol AS, the coupling pH, the coupling temperature, and the soaping conditions. Increasing the Naphthol AS loading relative to the base shifts the coupled dye deeper and slightly bluer, up to the point where unreacted naphthol remains. Residual naphthol creates a pale yellow background that reduces chroma and can be detected by extraction and UV-visible spectrophotometry. Coupling at the upper end of pH 9–10 may increase coupling rate but also accelerates diazonium side reactions that lower brightness. Temperature should be kept below 20 °C during coupling to preserve shade clarity. When used as a shading component, Fast Bordeaux GP Base is blended with diazotized Fast Red bases to adjust the blue component of a red print. Colourimetric assessment uses a spectrophotometer with D65 illuminant and 10° observer according to ISO 11664-4; colour differences are reported as CIELAB ΔE* values. A tolerance of ΔE* ≤ 0.8 is often applied in textile colour communication, but the final limit is buyer-specific. Published data for the exact CIELAB coordinates of Fast Bordeaux GP Base is limited; therefore, a reference standard must be agreed between supplier and user for each Naphthol AS combination.