The dyeing process of a dye
The so-called dyeing refers to the dye shed dye solution (or other media) and transfer to the fiber and fiber dyed through the process. The dyeing process is not the same as the usual dyeing process.
The stages of the dyeing process:
1. The dye is transferred from the dye solution to the fiber interface
Diffusion boundary layer: the liquid layer mainly transferred to the fiber surface by diffusion of dye itself, known as diffusion boundary layer
One of the important ways to speed up dyeing is to strengthen the circulation of dye solution, increase the flow rate of dye solution and minimize the thickness of diffusion boundary layer. This can not only speed up the dye to the fiber surface, but also improve the uniformity of dyeing effect
2. When the dye gets close to the fiber to a certain distance in the diffusion boundary layer, the dye molecules are quickly absorbed by the fiber surface, and hydrogen bond, van der Waals or Coulomb gravitational bond occurs between the dye molecules and the fiber surface molecules.
3. When the dye is adsorbed to the surface of the fiber, a dye concentration difference is formed in and out of the fiber, which diffuses into the fiber and becomes fixed in the fiber.
Factors affecting dyeing process
Dye movement state: dye flow diffusion adsorption diffusion
Important influencing factors:
1. Dye molecular structure 1~6 same left 1~4 same left
2. Dye solution state
3. Fiber surface characteristics
4. Fiber microstructure
5. Other composition and charge in the dye
6. Chemical structure of fiber
7. The temperature
8. Bath ratio, dye flow
9. P H value
Dye common noun explanation
Dyeing balance: when dyeing reaches a certain degree, the dye adsorption and desorption rate is equal, the dye concentration on the dye solution and fiber does not change, that is, to reach the dyeing balance state.
The dyeing process is the result of the movement of a large number of dye molecules. It is a macroscopic result and is often measured by the change of dye concentration in the dye solution and fiber, rather than representing the behavior of individual dye molecules.
Dye percentage: The percentage of the amount of dye adsorbed to the fiber as a percentage of the total dye input. Equilibrium dye percentage: The percentage of the amount of dye adsorbed to the fiber as a percentage of the total amount of dye injected when equilibrium dyeing is achieved.
Dyeing rate: The rate of change of dye concentration on the fiber with respect to dyeing time.
Dyeing rate curve: The curve of dyeing rate as a function of time (or of dye concentration on the fiber as a function of time) is called dyeing rate curve.
Adsorption isotherm: The curve of the dye concentration on the fiber and the dye concentration in the dye solution at constant temperature when dyeing reaches equilibrium.
Equilibrium adsorption: the concentration of dye on the fiber when dyeing reaches equilibrium.
Dyeing saturation value: the dye concentration on the fiber does not increase with the increase of the dye concentration in the dye solution, and the dye concentration on the fiber becomes the dyeing saturation value.
Dyeing methods can be divided into immersion dyeing (or exhaustive dyeing) and pad dyeing according to the way in which the dye is applied to the dye and fixed to the fiber.
A dyeing method in which textiles are immersed in a dye solution for a certain period of time so that the dye is dyed on the fiber and fixed in the fiber.
Features: suitable for all kinds of textile dyeing; Intermittent production, low production efficiency; The device is simple and easy to operate.
Pad dyeing is a process in which the fabric is briefly impregnated in the dye solution and then rolled to squeeze the dye into the tissue space of the fabric. Excess dye is removed so that the dye is evenly distributed on the fabric. The dye dyeing is (or mainly) done later in the process of steaming or baking.
Features: continuous dyeing process, high production efficiency, suitable for large quantities of fabric dyeing, but the dyed material by large tension, usually used for woven fabric dyeing, yarn and yarn sometimes also used for pad dyeing.
Textile dyeing can be carried out at any stage, at different stages such as fibers, yarns, fabrics and garments.
1. Bulk fiber dyeing: the fiber or bulk fiber dyeing before spinning is loaded into a large dyeing VAT and dyed at an appropriate temperature. Color - spun yarns are mostly dyed by loose fibers (or by different fibers) and are often used for woolen fabrics.
2, top dyeing: this also belongs to the fiber dyeing before yarn, and the purpose of bulk fiber dyeing is the same, in order to obtain soft color mixing effect. Top dyeing is generally used for combing wool yarns and woolen fabrics.
3, yarn dyeing: yarn dyeing before weaving, generally used for colored fabrics, sweaters, or directly used yarn (sewing thread, etc.). Yarn dyeing is the basis of dyeing and weaving.
Conventional yarn dyeing can be done in three ways:
① Hank dyeing -- dipping loose Hank yarn in a special dyeing VAT is the most expensive dyeing method;
② Bobbin dyeing -- the yarn of bobbin dyeing is wound on a bobbin with holes, and then a lot of bobbin is loaded into the dyeing cylinder. The dyeing liquid circularly flows, and the fluffy effect and softness are not as good as Hank dyeing.
(3) Warp shaft dyeing -- is a large-scale roll-in dyeing. Warp shafts (warping) should be made before woven manufacturing, and the yarns of the whole warp shaft should be dyed, such as joint pulp dyeing machine and warp yarn bundle dyeing. Because it is a warp shaft, it is more suitable for tatting dyeing. However, with the advent of warp drop tube, we can turn the dyed warp yarn into bobbin yarn, which has a wider application range. For example, the reduction dyeing method mostly used in indigo dyeing can only be solved by using warp drop tube, which is difficult to achieve without warp drop tube.
4. Piece dyeing: The method for dyeing the fabric is piece dyeing. The commonly used methods are rope dyeing, jet dyeing, roll dyeing, roll dyeing (not tie-dyeing) and warp dyeing. I will not introduce them here.
5. Garment dyeing: put the garment into nylon bags, a series of bags into the dyeing VAT together, and keep stirring in the dyeing VAT (paddle dyeing machine). Garment dyeing is suitable for knitting socks, T-shirts and most of the knitted clothing, sweaters, pants, shirts and some simple garments.