The Origin
125 years ago, Indigo was derived from the Indigo plant, which was cultivated in huge plantations on the Indian subcontinent. The complicated extraction process and the high market demand urged for an industrial synthesis of Indigo. It took over 17 years of development and enormous financial investment – around 18 million Gold Marks, an amount exceeding the company’s share capital of the day – before the first Indigo Pure BASF was manufactured and brought into the market in July 1897.
The Highly Efficient Indigo Production Plant
The Indigo production plant in Ludwigshafen is unique. It is the oldest and yet possibly the most efficient Indigo production plant that is still in operation today. DyStar continues this great heritage of Indigo excellence in the same production facilities, where the BASF started back in 1897. Remaining the last dyestuff producer in Europe, DyStar manufactures Indigo in a way that is paved with continuous innovations and improvements. For example, the waste gas treatment plant is catalyst based and burns the carbon content in the waste gas from the aniline recovery process. With an effective energy management system, DyStar started to integrate carbon dioxide usage into their energy consumption. This is important as they continue to work on the reduction of their primary energy consumption as well as on carbon dioxide emission.
The strategic location of the Indigo plant is unique too. Today, the plant remains embedded in the functional network of supply and discharge within the BASF Site in Ludwigshafen.
Nearly all raw materials continued to be delivered by pipeline. None of the raw materials are delivered by trucks, except for Sodium being supplied by railway tankers. Operationally, this has resulted in a large reduction of the Carbon footprint. In addition, this network also guarantees a high recycling rate of waste chemicals, which are used in other plants as raw material or can be fully recycled. DyStar mainly recycles Ammonia water solution, Aniline, n-Methyl Aniline, Potassium- and Sodium hydroxide. This Sodium hydroxide recovery is a multi-effect evaporation and dewatering process, resulting in a 100% salt, which is used as a melt in further production steps.
As a site partner of the BASF, DyStar discharges wastewater into the highly sophisticated, central effluent-treatment-plant (ETP) on the same premises. This is a win-win situation for both parties. Their alkaline wastewater helps to neutralize the acid wastewater from BASF whilst BASF monitors the wastewater flow and guaranties a full protection of the environment.
Sustainability topics continue to be the fundamental basis for DyStar’s operations. Industrial automation, the integration into the BASF supply for key intermediates, loops for recycling of solvents and environmental protection facilities, integrated Energy Management System (DIN ISO 50001), the state-of-the-art waste gas treatment are some significant efforts that make DyStar the last notable manufacturer of the coveted blue dye outside of China.
The Process Based on Heumann Synthesis
The current process is similar to the process from 125 years ago. DyStar is producing according to the “Heumann Synthesis” which consists of two raw materials used as the basis for this synthesis. The first one is PGN (Phenyl-glycine-nitrile), which is delivered by BASF via pipeline, and the other one is pure sodium, delivered by railway tankers. After the first reaction steps using both raw materials, saponification of PGN, and amidation of Sodium with Ammonia, the two solid products are brought together in a melting vessel. And the Indigo production starts following an oxidation step. Next, the product goes through a filtration step. During filtration, the Indigo paste will be filtered and washed to reduce the content of alkaline and aniline. Hydrogenation is further applied to get a solution ofs 20% Indigo content. The evaporated content delivers the premium product DyStar® Indigo Vat 40 % Solution. Alternatively, the 20% solution delivers a side-product named Indigo Grain 60%, which is used for DyStar’s other production processes.
From Solid to Indigo Solution
In 1998, after almost a century of synthetic Indigo powder application, DyStar set one of the most remarkable milestones in Indigo history by introducing the first pre-reduced DyStar Indigo Vat 40% Solution to the market. A technology that transforms Indigo into its soluble Leuco form by using Hydrogen as the reducing agent instead of Hydrosulphite. This innovation made the Indigo ready to use for the dyeing process, which is more sustainable, efficient, and much safer for the workers in the Denim Mills. It also resulted in more stable dyeing processes with less shade variations.
DyStar’s recent development for the Denim Industry “Cadira® Denim” combines this pre-reduced Indigo with a new organic reducing agent. This technology represents the first salt-free Indigo dyeing process in history, by complete elimination of hydrosulphite in the application of Indigo. Furthermore, the DyStar Indigo Coat, the DyStar Indigo 4B Coll liq and the DyStar 60% Vat Grains are the results of decades of continuous innovation and Indigo chemical engineering.
Reformulated Sodium Amide to Meet Industry Needs
Another milestone reached in the history of Indigo relates to Sodium Amide, which is one of the main intermediates used from the start of the Indigo synthesis process. Sodium Amide was also reformulated for the pharmaceutical industry in 2008. The basics of how to produce Sodium Amide were known since the beginning of the Indigo process. DyStar’s core expertise is the reason that they decided to take over the production of Sodium Amide at the Ludwigshafen plant.
125 Years of Indigo Excellence
This year, DyStar celebrates the 125th Anniversary of Synthetic Indigo. Together with their Subject Matter Experts, DyStar will drive sustainability as their core competency so as to continue to enable key stakeholders, direct customers, Brand and Retailers, manufacturers, and wider supply chain to benefit from the efficient process and production.
