| 摘要 |
<p>The invention pertains to a process for the production of a dye preparation from plant material, in particular madder root or the areal parts of weld, which allows efficient separation of the desired compounds from the less desired compounds, and which can be carried out in the absence of organic solvents. The process comprises the steps of providing plant material to be extracted in particulate form, contacting the particulate plant material with an aqueous medium to form a first slurry of particulate plant material in the aqueous medium, holding the slurry for a period of at least 5 minutes, if the p H of the slurry after the holding step is 5 or higher, adapting the p H of the slurry to a value of below 5, optionally aging the slurry for a period of at least minutes, subjecting the optionally aged slurry to a solid-liquid separation step to form a solid plant material fraction and a first aqueous liquid fraction, contacting the solid fraction resulting from the solid-liquid separation step with an aqueous medium to form a second 2 slurry with a pH of at least 8, subjecting the second slurry to a solid-liquid separation step to form a solid plant material fraction and a dye preparation second aqueous liquid fraction.</p> |
