活性染料染纤维工艺流程英语
    Reactive Dyeing Process for Cellulose Fibers.
    Introduction.
    Reactive dyeing is a widely used method for imparting color to cellulose fibers such as cotton, viscose rayon, and lyocell. This process involves the covalent bonding of dye molecules to the hydroxyl groups present in the cellulose structure. Reactive dyes offer excellent wash fastness, lightfastness, and vibrant colors, making them suitable for a wide range of textile applications.
    Process Flow.
    The reactive dyeing process typically consists of the following steps:
    1. Preparation.
    The fabric is scoured to remove impurities and improve dye uptake.
    The fabric is bleached to achieve the desired whiteness.
    2. Dyeing.
    The reactive dye is dissolved in water and applied to the fabric using a dyeing machine.
    The dye solution is heated to a specific temperature to activate the dye and promote reaction with the cellulose fibers.
    The fabric is held at the dyeing temperature for an appropriate time to ensure complete dye fixation.
    3. Fixation.
    After dyeing, the fabric is treated with a fixing agent to strengthen the bond between the dye and the cellulose fibers.
    The most commonly used fixing agents are alkali (e.g., sodium carbonate) and urea.
    4. Washing.
    The dyed fabric is thoroughly washed to remove unfixed dye and residual chemicals.
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    5. Drying.
    The fabric is dried using a dryer or other suitable method.
    Dye Chemistry.
    Reactive dyes are typically bifunctional molecules, containing both a dye chromophore and a reactive group capable of covalently bonding to cellulose. The most common reactive groups include:
    Monochlorotriazinyl (MCT)。
    Dichlorotriazinyl (DCT)。
    Vinyl sulfone (VS)。
    Dyeing Conditions.
    The dyeing conditions, such as temperature, pH, and salt concentration, play a crucial role in the success of the reactive dyeing process.
    Temperature: The dyeing temperature is typically maintained between 60°C and 80°C to activate the reactive dye and promote dye fixation.
    pH: The pH of the dye bath is usually kept between 9 and 11 to ensure optimal dye solubility and reactivity.
    Salt Concentration: The addition of salt (e.g., sodium chloride) to the dye bath helps to suppress the electrostatic repulsion between the dye and cellulose fibers, promoting dye uptake.
    Advantages of Reactive Dyeing.
    Excellent wash fastness and lightfastness.
    Wide range of vibrant colors.

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