PU is polyurethane. Polyurethane leather has excellent properties. In this regard, Bayer, BASF and Huntsman have world-class production capacity, while textile fiber suppliers represented by Toray and Xu Xu have high product technology. In foreign countries, due to the influence of the Animal Protection Association and the development of technology, the performance and application of polyurethane synthetic leather surpassed that of natural leather.
After adding superfine fiber, the toughness, air permeability and wear resistance of polyurethane are further strengthened. There is no doubt that such a finished product has excellent performance.
The carboxyl and glycosidic bonds of microfiber macromolecules have good chemical activity, and various chemical reactions can occur when they meet acids, bases and oxidants, thus obtaining denatured microfibers with different properties.
Finishing of sea-island superfine fiber artificial leather
I. Introduction
Due to the increasing shortage of natural leather resources, the gradual enhancement of people's awareness of environmental protection, and the continuous progress of industrial technology, spinning raw materials and spinning technology, tanning technology and dyeing and finishing technology have developed rapidly, and a new product, bundle of ultra-fine fiber artificial leather, which is superior to leather and completely imitates leather, has emerged.
Second, the basic production of polyurethane leather.
(a) production of sea-island fibers
At present, there are two production methods of sea-island superfine fiber. One is the island-fixing method: it is made by two-component composite spinning technology, and its fiber cross section is surrounded by another component in a finely dispersed state, much like an island in the sea, and its island and sea components are continuously and densely distributed along the fiber length. The number of islands is fixed and the fineness is consistent, which can only reach 0.05 denier. After spinning, it exists in conventional denier. Only when the sea component is dissolved with solvent in post-processing, the tow of superfine fiber can be really obtained. At present, it is mostly used in filament.
The second method is the indefinite island method: it is made by two-component miscible spinning technology, and the cross section of its fiber is surrounded by another component in a finely dispersed state. The islands in a single fiber are uncontrollable in microscopic view, and are distributed discontinuously and densely in the length direction of the fiber, so it is more realistic with the actual islands. The number of islands is not fixed, and the fineness is different, but the fiber is finer, which can reach 0.000 1 denier, and its leather-like performance is stronger. After spinning, it also exists in conventional size. Only by dissolving the sea component with solvent in the post-treatment can the superfine fiber bundle be truly obtained. Because the sea-island part is stretched to form superfine fibers, filaments can not be produced at present, and only short fibers can be produced.
(2) Production of non-woven fabrics
There are two main methods to produce base fabric by using sea-island fiber: acupuncture and spunlace. The front of the fabric is fed with fibers, which are opened, carded and laid to form a fiber layer with a certain thickness, and then the fibers are entangled with each other with needles or high-pressure water jets to make a base fabric with a certain thickness and corresponding density.
(3) Leather processing
After passing the base cloth through a certain concentration of PU resin, rolling and washing, a leather-like bass is formed.
(4) dissolution, separation and processing
The perch processed in the tanning process is put into alkaline solution (toluene), and after repeated rolling at a certain temperature and time, the "sea" component is dissolved to complete fiber opening, forming a PU resin sponge completely composed of superfine fiber bundles and networks, so that artificial leather really has a dermal structure.
(5) Post-processing of polyurethane leather.
Semi-finished products obtained by dissolution and separation process need a series of finishing, such as softening, dyeing and sanding, in order to get final products with different uses and styles.
Three. Dyeing of sea-island superfine fiber artificial leather
(A) the main factors affecting dyeing
Influence of 1. fiber: Because the fineness of nylon fiber in superfine fiber leather is only 0.000 1-0.00 1 denier, the dye adsorption speed is very fast, and the levelness is poor, and the finer the fiber, the worse the levelness is; At the same time, the finer the fiber, the larger the specific surface area and the worse the color rendering; The finer the fiber, the easier it is for the dye in the fiber to migrate to the surface of the fiber, and the worse the dyeing fastness. At the same time, the finer the fiber, the more dyes will be used, and the washing fastness and rubbing fastness will be worse. Therefore, the dyeing of superfine fiber artificial leather has become a worldwide problem.
2. Influence of non-woven fabric: If the thickness of non-woven fabric is uneven and the fiber distribution is uneven in superfine fiber leather, it will also affect the dyeing effect.
3. Influence of PU resin: If PU resin is unevenly distributed in superfine fiber leather, it will also affect the dyeing effect, and the dyeing properties of different resins will also affect the dyeing effect.
4. Influence of dyes, auxiliaries and dyeing process: Different dyes, auxiliaries and dyeing process will affect the dyeing effect.
(2) dyeing mechanism
1. dyeing mechanism of nylon fiber: nylon fiber is an amphoteric fiber, which can absorb hydrogen ions in dye solution with positive charges and hydroxyl ions in dye solution with negative charges, so it can be dyed with ionic dyes. For example, acid dyes, neutral dyes, reactive dyes, direct dyes and basic dyes can be used.
2. Dyeing of 2.PU resin: The macromolecules in polyurethane contain amide groups, which can be combined with acid and neutral dyes to meet the dyeing requirements.
(3) Dyeing process
Sea-island superfine fiber artificial leather is composed of superfine nylon fiber and polyurethane. However, superfine nylon fiber is very difficult to dye because of its fast dyeing speed, poor levelness, poor dyeing depth, large amount of dyes and low dyeing fastness, and different affinity between polyurethane and fiber for dyes. Therefore, our company has done a lot of experiments on dyes, auxiliaries and dyeing process, optimized the appropriate dyes and auxiliaries, and determined the appropriate dyeing process, which achieved the purpose of uniform dyeing, deep dyeing, thorough dyeing and high color fastness, and made our products widely praised by users.
(1) Determination of dyes: Whether the product can be dyed evenly, thoroughly, without color difference and with good fastness mainly depends on the dyes. In addition, the choice of dyes should first consider the good dyeing properties of fibers and polyurethane. With the cooperation of related companies and the guidance of university professors, we have carried out a lot of experiments, mainly using acid dyes and some neutral and disperse dyes to dye the island superfine fiber artificial leather, and achieved success.
Dyes should have the following properties: good lifting, high dye uptake and easy to dye dark colors; Good levelness and reproducibility; Good migration and coverage; Good compatibility; Good fastness to sunlight, sublimation and dry and wet; Low thermal mobility.
(2) Control of PH value: pH value directly affects dye uptake, dye uptake speed, levelness and permeability, and also affects the strength of leather. The lower the PH value, the faster the dye uptake, which is beneficial to improve the dye uptake, but it will affect the levelness and permeability. The PH value should be determined according to the performance of dyes, the dosage of dyes, auxiliaries and equipment. The selection range of PH value is 4 ~ 8.5, which is generally adjusted by acid release agent.
(3) Control of dyeing temperature: The starting temperature of dyeing is generally 35℃, and the highest holding temperature is generally100-10℃. Low dyeing temperature will reduce the dye uptake, and then affect the levelness and permeability; High dyeing temperature is beneficial to level dyeing and through dyeing, but it will affect the feel of leather. In addition, the heating speed also affects the levelness and penetrability, and the heating dyeing is fast, so it is not easy to dye evenly and thoroughly.
(4) Setting of dyeing time: The dyeing time depends on the dyeing depth, which is generally 40- 120 minutes, and the deeper the depth, the longer the time.
(5) Selection of dyeing auxiliaries: different auxiliaries such as leveler, penetrant, lubricant and deacidification agent are used in dyeing. Choosing suitable auxiliaries is beneficial to dyeing effect and can improve the levelness and permeability of dyes. Leveling agent can achieve the purpose of leveling and penetration dyeing by reducing the dyeing speed or improving the dye migration. Penetrant is to accelerate the penetration of dyes into leather, so as to achieve the purpose of leveling and penetrating dyeing. Acid releaser is used to stabilize and control PH value, thus controlling dyeing speed and improving levelness.
(6) Post-dyeing treatment: the sea-island superfine fiber artificial leather contains superfine nylon fiber and polyurethane with many micropores. Therefore, after dyeing, there are many adsorbed residual dyes on the fiber surface and micropores, which directly affect the color fastness and must be removed. Generally, it is washed with water. If necessary, fixing agents should be used to improve the color fastness. Generally speaking, light color is directly washed with water, medium color is washed with detergent, and dark color is treated with fixing agent.
(7) Pretreatment: There are various impurities in the sea-island superfine fiber artificial leather, which affect the dye uptake and are not conducive to uniform and thorough dyeing. Therefore, pretreatment must be carried out to remove impurities.
(8) General dyeing process: Adjust the PH value to 4-8.5 with leveler 1-3%, penetrant 1-3 g/L and acid releaser, add necessary dyes, and then raise the temperature to 40℃ and 70℃ at 1℃/ min and 0.3℃.
Four, other finishing of island superfine fiber artificial leather
In order to obtain high quality and various styles of sea-island microfiber suede leather, it is necessary to finish it with sanding, antibacterial, flame retardant and ultraviolet protection. With the improvement of people's requirements and the progress of technology, new post-treatment methods will appear to make the products more distinctive.
1. Sanding: We use a multi-roller sander, and carry out sanding treatment according to the process that the number of sandpaper is gradually increased from front to back and the speed of sanding roller is gradually increased, so that the product can reach full and delicate fluff and appropriate length.
2. Antibacterial, flame-retardant and ultraviolet-resistant finishing: according to different product uses and different user requirements, the products are finished with antibacterial, flame-retardant and ultraviolet-resistant finishing. In order to maintain the necessary performance of products and meet the needs of foreign sales, we mainly choose foreign additives, and set appropriate drying temperature and time through impregnation to achieve the required antibacterial, flame retardant, anti-ultraviolet and other finishing effects.
Verb (abbreviation of verb) conclusion
Island superfine fiber artificial leather is a high-tech product with high added value. Its processing procedures are many, the process is long, the technology is difficult, and the benefits and risks coexist. The finishing of sea-island superfine fiber artificial leather needs high-performance dyes and auxiliaries, high-quality technicians, multi-variety, small batch and fast delivery production management mechanism and good equipment to produce products that satisfy the market.
Sea-island superfine fiber artificial leather is made into superfine fiber with fineness of 0.003-0.000 1D due to the dissolution of "sea" component. It completely simulates the structure of dermis, and has bundle collagen microfiber and microporous reticulated polyurethane elastic sponge with the same amide group as dermis, which not only has the characteristics of dermis, but also has high strength, good bending resistance, good drape, good air permeability, water resistance and elastic sponge that dermis lacks. The dyed sea-island superfine fiber artificial leather has bright color, diverse varieties, full and fine fluff, good color fastness, high utilization rate and easy processing, and is the first choice to replace leather.
Island microfiber artificial leather is widely used in shoes, clothing, sofas, gloves, bags and other fields.
Our company has been developing and producing island microfiber artificial leather for nearly ten years, and has the only national invention patent of microfiber artificial leather in China and the title of famous brand product in China. At present, the largest island superfine fiber artificial leather production base in China has been built, ranking first in the country in terms of production capacity, quality and variety development. We will continue to cooperate extensively with universities, scientific research institutions and powerful companies at home and abroad to develop more and more competitive new products to meet the higher requirements of the future market.