Quality Influencing Factors And Control Of Dyed Products

There are many factors that affect the quality of dyed products, which are mainly equipment, dyestuff, process (process, formulation, condition), operation and other factors. Dyeing defects sometimes happen occasionally. Therefore, when analyzing the causes of the quality problems of dyed products, we should consider and analyze them from all aspects to find out the real causes of the problems, so as to solve the problems and avoid quality problems again, and control the quality of products on the basis of summing up experience.

First, the influence factors of color light on sample and levelling property.

In order to obtain high-quality dyed products, equipment and dyeing equipment should be adapted in accordance with the different dyeing processes of different fibers and fabrics. With the continuous development of production and the continuous improvement of the level of science and technology, dyeing machinery is becoming more and more advanced, but the quality problems caused by equipment can not be completely avoided.

The impact of equipment on the color light is mainly the driving stability of the equipment, such as speed, drying conditions, temperature rise and fall speed, pressure control and so on. With stable process control, the equipment can ensure the stability of dyeing and light and ensure reproducibility.

For the effect of levelling, the equipment factor is more important. In order to ensure levelness, the following requirements are put forward for equipment.

Technology adaptability is strong. It is necessary to meet the requirements of levelling, such as the temperature, pressure, speed and processing time of the equipment, as well as the adjustment of the chemical medium such as dyestuff and so on, so that the dyeing and finishing equipment is compatible with the new technology and new technology, so as to ensure the levelness and other quality requirements of the dyed fabric.

(2) high degree of automation. As far as possible, the main process parameters can be automatically detected and adjusted automatically, so as to achieve precise control, reduce leveling defects caused by human causes, meet the requirements of repeatability of the process, and ensure the stability of quality.

One machine is multi-purpose to meet the processing requirements of many varieties. The equipment of printing and dyeing plant is always limited, and the dyeing and finishing products are changing with the market demand. Therefore, if we want to enhance the adaptability of the equipment, we must ensure that the equipment can meet the levelling and other quality requirements of different kinds of fabric dyeing and finishing under the premise of reducing the investment of equipment.

Fabric in low tension or loose operation in the equipment. Tension is one of the factors that affect levelling. Tension or unevenness can easily cause leveling quality. Therefore, it is necessary to operate as loosely as possible or operate under low tension and uniform tension in the operation of equipment.

The dyeing and finishing of dyed products are closely related to dyeing and finishing equipment, except for the process and operation. The selected dyeing and finishing equipment must meet the requirements of dyeing and finishing process, be able to meet the requirements of many varieties of dyeing, and can produce high-quality products. The equipment is safe, durable, economical, high-speed, efficient, continuous, automatic, and low energy consumption, and can prevent public hazards. In a word, the equipment must ensure the quality of dyeing and finishing products.

The formulation of formulation is directly related to the quality of dyeing, and the main basis for formulating the formulation is:

Fiber properties and fabric structure and specifications. Different kinds of fibers have different structures and properties, and the dyes used are different. For example, cotton fibers are suitable for dyeing with dyes such as reactive, direct, reductive, vulcanizing, etc. The performance of polyester fiber is different. To develop polyester / cotton blended fabric dyeing process, we must consider the performance of two kinds of fibers. The same fabric should be changed in different specifications.

2. Color and dyeing.

The performance of dyes and chemicals.

Equipment performance and product adaptability.

Dyeing and finishing methods.

Quality requirements and cost requirements for dyeing and finishing.

Whether the processing formula is reasonable will directly affect whether the processed products can meet the quality requirements. If we use acrylic dyes to dye acrylic fibers, if we do not consider the compatibility of cationic dyes and the saturation value of acrylic dyes, the formulation is unreasonable, so we can not dye the necessary luster and meet the requirements of shade and leveling. If the formulation is unreasonable, it must be adjusted according to the specific requirements of production.

Process conditions are important factors affecting the color and levelness of dyed products, such as temperature, time, pH value, etc. each condition directly affects the quality of the product.

Temperature: the temperature is related to the degree of expansion of the fiber, which is related to the performance of the dye (solubility, dispersion, dyeing rate, dye uptake, color and so on), which is related to the performance of the auxiliaries. Each fiber product, each dye has its own optimum dyeing temperature. The improper control of temperature or heating rate will seriously affect the color and levelness of dyed products. Such as weak acid black BR dyed wool, the highest dyeing temperature is 80-95 degrees, while acid Tibet blue GGR highest dye temperature is 95 - 1OO degrees. For example, cationic dyes can be used to dye acrylic fibers. The heating rate must be strictly controlled.

(2) time: the determination of dyeing time is related to the diffusion and combination of dyes on the fibers. Dyeing must have enough time to dye the dye sufficiently, spread and fix it, so as to achieve the dye balance and get the proper color. When the time is too short, the dye is not completely dyed, and can not get the proper color and color. In case of dyeing, there is not enough time to dye the dye on the fiber to achieve uniform dyeing. Of course, the determination of the dyeing time is appropriate and the time is too long. Sometimes, the fabric will change with the temperature and the time of the action of chemicals.

3. PH value: pH value is also an important factor affecting dyeing color and levelness. If the disperse dyes are used to dyed polyester, it is suitable to be carried out under acidic conditions. If the pH value of these dyes is fixed to alkalinity, the color of dyes will change. If it is dyed with acid blue GGR, the pH value should not be greater than 3, otherwise the color will be obviously red. When the same dye dyes the same fiber, when the pH value changes, the color and light will change, and will affect the levelness. If the wool is dyed with acid dyes, the lower the pH value is, the more positive the electric charge of the wool is, which will accelerate the dye uptake of the negative electricity and increase the possibility of dyeing. The pH value also affects the reactivity and hydrolysis properties of dyes, such as the hydrolysis and reactivity of reactive dyes are related to the pH value. PH also affects the properties of fibers and the properties of auxiliaries, and ultimately affects the dyeing and leveling properties.

Two. Influencing factors of penetrability

The penetrability of dyes and auxiliaries is closely related to the properties of dyes and auxiliaries. Dye diffusion is the most important factor affecting dye penetration. If the dye uptake rate is fast, but the diffusivity is poor and the diffusion rate is low, it is easy to cause uneven distribution of dyes inside and outside the fiber, resulting in ring dyeing and poor penetrability. Any factors that affect the diffusion rate of dyes will affect the penetration effect of fibers and fabrics.

Auxiliaries also affect the penetrability. Adding auxiliaries such as osmosis agent, cosolvent, dispersant and fiber expanding agent to dye diffusion will be beneficial to dye penetrant fiber, but if the auxiliaries are added to the dye boat, the dye diffusion will be slowed down, and the dye penetration will be affected, and even serious dyeing will be caused.

The influence of temperature and time on the diffusion of dyestuffs into fibers is enhanced, which is helpful to improve the dyeability of dyes with poor diffusivity. However, if the dyeing temperature is high, the initial dye uptake rate of dyes will be accelerated, which will bring negative effects on levelness and penetrability. Dyeing temperature is too high, sometimes it will cause the dye to agglomerate or dye the surface of the fiber quickly, blocking the dye to further infiltrate into the inner surface, and creating a poor dye penetration. The determination of temperature depends on the properties of dyes and dyes.

Prolonging the dyeing time makes the dye diffuse sufficiently from the fiber surface to the inside of the fiber, which is conducive to enhancing the penetrability.

Three. Influence factors and control of color fastness

There are many factors that affect the color fastness of dyed products, but mainly depend on the chemical structure of dyes, the physical state of dyes on fibers, the degree of dispersion of dyes, and the combination with fibers. The dye concentration, dyeing methods and technological conditions also have a great influence on the fastness of dyes. The relationship between fiber properties and dyeing fastness is also very large. The same dye often has different fastness on different fibers, such as indigo on cotton fiber, and its fastness to sunlight is not high, but it is very high on wool.

(1) influencing factors and control of soaping fastness

Soaping fastness refers to the degree of color fading of the dyed products in soaping liquid under the prescribed conditions. It includes two items: the original sample is faded and the white cloth is stained. The fading of the original color refers to the fading of the dyed fabric before and after soaping. The white cloth stain is the way that the white cloth and the dyed fabric are stitched together in a certain way, and after being soaped, the color of the white cloth is turned off because of the fading of the dyed fabric. The soaping and fading of dyed products is the effect of external dyes and detergents on dyes on fabrics. It destroys the combination of dyes and fibers and causes dye to fade and fade from the fabric.

The fastness to soaping is related to the chemical structure of dyes. The water fastness of water-soluble dyes containing hydrophilic groups is lower than that of dyes without hydrophilic groups. For example, acid dyes and direct dyes contain more water soluble groups, and their soaping fastness is lower. The dyes with no water soluble groups such as reducing, vulcanizing, and insoluble azo dyes have higher fastness to soaping.

Soaping fastness is also related to the combination of dyes and fibers. Such as acid mordant dyes and direct copper salt dyes, due to the integration of dyes and metals, the dye molecules increase, water solubility decreases, and soaping fastness increases. The reactive dyes and fibers can covalently bond, so soaping fastness is better.

The soaping fastness of the same dye on different fibers is different. For example, the washing fastness of disperse dyes on polyester is higher than that on nylon. This is because the structure of polyester is stronger than that of nylon, and its hydrophobicity is strong.

Soaping fastness is closely related to dyeing process. Dyestuff is dyed uneasily, easy to fall off from fiber, soaping fastness is poor, washing after washing is not clean, floating color has remnant, also can cause soaping fastness decline; soaping liquid temperature, pH value and stirring condition have influence on soaping fastness; dyeing concentration has little effect on soaping fastness, but dye concentration is high, dye and fiber are supersaturated, and dye is easy to fall off by external force, which also affects soaping fastness.

In order to improve the fastness to soaping, different fibers should be selected according to the requirements of soaping fastness, and different dyes should be selected, and a reasonable dyeing process should be worked out. The dye and fiber should be fully combined and strictly washed according to the technological operation. After washing, the floating color will be washed and the appropriate fixing agent can be added to fix the color when necessary, so as to improve the soaping fastness.

(two) influencing factors and control of rubbing fastness

The rubbing fastness of dyed products is divided into two types: dry rubbing fastness and wet rubbing fastness. The former is to use dry white cloth to rub dyed products, observe the sticky color of white cloth; the latter is to use water 100% of white cloth to rub dyeing products, observe the situation of white cloth staining. The frictional fading of fabric is caused by the drop of the dye under the action of friction. Besides the external force, the wet friction also has the function of water. Therefore, the wet friction is generally about 1 degrees lower than the dry rubbing fastness.

The rubbing fastness of fabrics depends on the number of floating colors and the molecular weight of dyes, the combination of dyes and fibers, the uniformity of dye penetration, and the particle size of dyes on the fabric surface. For example, reactive dyes, dyes and fibers are fully bonded with covalent bonds, and their rubbing fastness is high; while insoluble azo dyes, when the dyeing process is not good, some of the dyes are insoluble, and they are mechanically attached to the surface of the fiber, and their rubbing fastness is low, such as floating color removal is not clean. Rubbing fastness is lower. Dye molecules are large (such as sulphur black), dyed dyes tend to form large particle dyes floating on the fiber surface, and the dye concentration is generally large, so that the rubbing fastness is reduced; especially the binding force of most dyes and fibers is easier to be destroyed in the presence of moisture, so the wet rubbing fastness is lower than that of dry rubbing fastness.

In order to ensure the rubbing fastness, suitable dyes should be selected and reasonable processes should be made to ensure that the dye can be fully bonded with fibers and penetrate into the fibers so that they will not aggregate on the surface of the fibers. It is necessary to add smooth and solid cross-linking agent when necessary, so as to make the dye and fiber more firmly combined, reduce the friction force on the surface of the fabric, and form a soft film coated with dye on the surface of the fiber, so that the dye will not fall off easily and the rubbing fastness will be enhanced.

(three) influence factors and control of sunlight fastness

The fading and discoloration of dyed products after sun is a complicated process. Under the action of sunlight, the dye absorbs light energy and molecules are in an intense state. It is unstable. The energy must be released in different forms in order to become stable. One of the forms is that dyes directly decompose after receiving light energy, while the dye producing system is destroyed and changed, while some dye molecules are oxidized or reduced by light. For example, azo dyes fade on cellulose fibers are oxidation processes, while fading on protein fibers is the result of reduction.

The fastness of the same dye to different fibers is quite different. The fastness of disperse dyes on Polyacrylonitrile and polyester fibers is higher than that on acetate fibers, and other dyes are similar. The fastness of dyes to cotton and viscose fibers is different from that of dyes on the same concentration, and the fastness to sunlight on viscose fibers is higher than that on cotton. For example, vat dyes have good fastness on cellulose fibers, but they are very poor on polyamide fibers. This is because the physical state of dye on different fibers and the fastness to fiber are different.

The fastness of dyes to dye is also related to its molecular structure. For example, the fastness of indigo dyes in reducing dyes is relatively poor, and the fastness of anthraquinone dyes is mostly excellent. In other dyes, the color fastness to dyes of anthraquinone, phthalocyanine and metal complex is generally high, and the fastness of insoluble azo dyes is quite different. For example, the structure of the dye molecule contains more amino and hydroxyl groups, which will make the dye absorb light energy and oxidize and fade. Its sunlight fastness is low, and the introduction of nitro and halogen groups will not fade easily, and make the sunlight fastness increase.

The fastness of sunlight also varies with dyeing concentration. When the same dye is dyed on the same fiber, the low light fastness is generally lower than that of high concentration.

Dyestuffs of different fastness of sunlight can sometimes affect the fastness of sunlight, some reduce the fastness to sunlight, and some improve the fastness to sunlight.

Some auxiliaries added to dyed fabrics will affect the fastness of the dyed products. For example, some fixative dyes can easily absorb light energy and fade, reduce sunlight fastness, and UV shielding agents make dye products not easy to absorb light energy, and can improve the fastness of sunlight.

Fastness to sunlight is also related to the bonding state between fiber and dye. For example, reactive dyes, bonded with fiber bonds are stable to sunlight, fastness to sunlight, while fiber contains more hydrolyzed dyes, and the fastness to sunlight is low.

The dye with good diffusion and uniform penetration in the fiber has good sunlight fastness.

In addition, fastness to sunlight is also related to the shades of colors, the physical state of dyes on fibers, and some external factors (including air humidity, air pollution and moisture content of samples).

To ensure that the products have good fastness to sunlight, the key is to choose dyes from the structure, and then develop a reasonable dyeing process to dye the specific fabric. In dyeing after finishing, the additives should be selected to ensure that the additives will not at least have a negative effect on the fastness to sunlight.

(four) other fastness

The degree of sweat fastness, chlorine bleaching fastness and sublimation fastness mainly depend on the structure of the dye itself, such as reactive dyes, some of the bonds between dyes and fibers are easy to break under acidic conditions, and the sweat fastness is poor. The reactive dyes with pyrazolone as the parent have poor oxygen resistance and bleaching fastness. The structure of phthalocyanine is better, and the reactive dyes of bromine acid structure are easy to produce fume fading. Fastness is also closely related to the structure of dyes and fibers, the concentration of dyes, the physical state of dyes on fibers, dyeing process and fiber properties.