Microfiber Nonwoven

At present, more and more differentiated fibers have been successfully developed and applied to non-woven products, which has greatly improved the quality of spunlace non-woven products, and even leaped forward, and also expanded the application field of non-woven fabrics. It can almost be said that the emergence of differentiated fibers has given non-woven fabrics a new concept. Microfiber fibers are one of them. Microfiber fibers are called typical representatives of new synthetic fibers that chemical fibers are developing in the direction of high technology and high simulation. Therefore, the application of microfiber fibers in spunlace non-woven fabrics can also be regarded as an important sign that spunlace non-woven fabrics are on the road of high technology and high simulation.

Since the development of spunlace non-woven technology has not been long, the application of microfiber fibers in spunlace non-woven technology has just started, but people have become more and more aware of the advantages of the combination of spunlace technology and microfiber fibers. First, with the help of high-pressure water power of spunlace, the split microfiber fibers can be split online, thereby simplifying the subsequent alkali reduction process; secondly, microfiber fibers can enhance the inherent softness, breathability, and textile style of spunlace fabrics. Furthermore, it can produce nonwoven fabrics with lighter weight and higher strength, thereby reducing fiber costs. At present, microfiber fibers are mainly used in two categories of products on spunlace nonwoven fabrics: one is synthetic leather base fabrics, mainly artificial suede; the second is wiping cloth, especially high-end wiping cloth; the third is filter materials, such as air and liquid filter materials. The market demand for these three types of products is constantly increasing.

Because of the good development prospects of microfiber fiber spunlace nonwoven fabrics, Weston has been committed to the research of this product in recent years. A variety of microfiber fibers from home and abroad have been selected, and after repeated experiments, several microfiber fiber spunlace products have been developed and put on the market.

 

 

1.1 Classification of split microfiber fibers

The composite forms of split microfiber fibers are various, and their cross-sectional shapes include orange-peel type, parallel type, skin-core type, etc. The orange-peel type is divided into 36 petals, 24 petals, 16 petals, 6 petals, etc. Some types are also divided into hollow and non-hollow. There are also several types of component composition, the more common ones are PET/NYLON, PET/PP and PE/PP. They have been used in spunlace nonwovens. Different types of split fibers have different degrees of splitting, single filament fineness and requirements for spunlace technology. Take 16-petal PET/NYLON microfiber fibers as an example. The 2D fiber is split by the high-pressure water force of the spunlace, and becomes 16 single-filament microfiber fibers with a fineness of about 0.13D, and more than 70% of the fibers are completely split (also called fiber opening). Such a high degree of fiber opening allows products for certain purposes to be used directly without further reduction treatment. For some products with high requirements for fiber opening, the subsequent reduction process can be greatly shortened. PET/NYLON type microfiber fibers are suitable for products such as artificial suede and precision wiping cloths. PET/PP type fibers, because the PP component accounts for more than 50%, the product has good water repellency and is suitable for wiping cloths for electronic products. PP/PE type fibers have good hydrophobicity and chemical resistance and are suitable for products such as battery separator paper.

 

1.2 Characteristics of split microfiber fibers

Microfiber fibers have very small diameters, so their bending stiffness is very small, and the fibers feel particularly soft;

Microfiber fibers have a large specific surface area, so the use of microfiber fibers to make spunlace nonwovens has significantly improved coverage, fluffiness and warmth retention. Moreover, due to the large specific surface area, the fiber comes into contact with dust or oil more often, and the oil has more opportunities to penetrate through the gaps between the fiber surfaces, so it has a strong cleaning function;

Microfiber fibers can also be used to make high-density nonwoven fabrics, and the gaps between the fibers are between the diameter of water droplets and the diameter of water vapor droplets, so it has a waterproof and breathable effect;

Microfiber fibers have many fine pores between the microfibers, forming a capillary structure. If processed into towel products that can be wetted by water, they have high water absorption. Washed hair can quickly absorb water with such towels, making the hair dry quickly;

Because microfiber fibers have the above characteristics, they can be made into suede-like and high-density products, opening up new ways in the field of spunlace nonwovens. Its main application areas are high-end clothing leather, artificial suede, high-performance wipes, gas and liquid filtration materials, etc.

The development speed of microfiber fibers is very fast, and new varieties are constantly coming out. Japan, South Korea and Taiwan are in a leading position in this regard. The general development trend is that the fibers are getting thinner and thinner, and it is easier to open the fibers. This is good news for spunlace nonwoven fabric companies.

 

 

2 Production process of microfiber fiber spunlace fabric

Spunlace is the most effective method to split split bicomponent fibers into single-component microfiber fibers using high-pressure water needles. There are other ways to split bicomponent fibers, which can be separated by heat shrinkage or dissolved by chemical treatment. Spunlace is a more economical method to split fibers, which has more advantages than other methods. When the component dissolution method is used, about 20% of the polymer will be wasted, and the heat shrinkage method cannot fully separate the two components.

Microfiber fiber spunlace fabric

 

2.1 Selection of microfiber fibers

Due to the needs of spinning, the oil types used in microfiber fibers are different from conventional chemical fibers such as polyester and nylon, and the oil content is higher. This makes some types of microfiber fibers have greater static electricity and cannot be combed into a web, or it is easy to cause a large amount of foam in the water, affecting the spunlace effect. Therefore, before production, the microfiber fibers must be tested for specific resistance and oil foam. The appropriate specific resistance range is 107~108Ωocm, and the oil test needs to show that there is no obvious foam.

 

2.2 Design of the carding machine process

The denier of the microfiber fiber before splitting is large and long, so there should be no problem in carding. However, some microfiber fibers will be partially opened under the strong combing action of the carding machine needle cloth due to the weak bonding force between the components. The extremely fine fibers are entangled on the needle cloth, which damages the quality of the fiber web. In severe cases, there is even no fiber web output. Therefore, when producing microfiber fibers, the speed of the carding machine cylinder, working roller and stripping roller should be properly controlled. The principle is that the speed of these rollers should be as low as possible without affecting the uniformity of the fiber web.

 

2.3 Design of the spunlace process

For microfiber fibers, spunlace is a key process. In this process, the water column clamps the fibers to reorient and entangle them, so that the fiber web can be compressed and reinforced, and the split fibers are separated into single fibers. Therefore, for the entanglement and opening of the fibers, the setting of the spunlace process parameters is particularly important. The opening rate of microfiber fibers (the proportion of the part split into monofilaments to the total fiber) has a great influence on the performance of the product. If the opening rate is high (greater than 60%), the product will be soft, delicate, uniform, dense and strong; if the opening rate is low, it will not only fail to achieve the characteristics of microfiber fibers, but also affect the uniformity of subsequent dyeing. If it is made into artificial suede, the writability and imitation leather properties are poor.

Used for synthetic leather, especially artificial suede, the microfiber fiber spunlace fabric has strict requirements on the appearance quality, requiring good surface flatness and few and fine water needle marks. Otherwise, the quality of subsequent sanding and dyeing will be affected. Therefore, before production, the water circulation system should be cleaned more thoroughly, and an appropriate amount of antibacterial agent can be added if necessary to improve the water quality. In addition, a newer water needle plate should be selected, and all water needle plates should be carefully rinsed. Taking these measures can effectively prevent the formation of water needle marks on the cloth surface.

In the design of spunlace process parameters, the difference between microfiber fibers and conventional chemical fibers is that the fibers must be well entangled with each other, without surface fuzzing and intermediate delamination, and the fibers must be fully opened. It is difficult to achieve the unity of the two. According to the characteristics of spunlace equipment, fiber entanglement and opening are usually completed in the first three spunlaces, especially for high-quantity products above 120gsm. Therefore, the setting of the pressure of the first three spunlaces is the most critical, especially the first spunlace. If the pressure of the first spunlace is set too low, it will greatly affect the final fiber entanglement and opening effect. On the contrary, if it is set too high, it will cause the fibers to open too early, forming a denser layer on the surface of the product, thereby weakening the effect of the second and third spunlaces, resulting in the phenomenon of "half-cooked rice" in the product. This phenomenon is more obvious when producing products with a quantitative of more than 180gsm. According to practical experience, it is best to set the pressure of the first spunlace at 70%~80% of the design value, and the pressure of the second and third spunlaces will increase successively to reach the design value. At the same time, when producing microfiber fiber products, the spunlace mesh and water needle plate models should be reasonably selected to achieve the best spunlace effect.

The cross-section, components and manufacturers of microfiber fibers are different, and the difficulty of fiber entanglement and fiber opening is different, so the requirements for spunlace are also different. When designing the process, they should be treated differently. For example, under the condition that other spunlace processes are roughly the same, some microfiber fibers can be fully opened at 50 bar spunlace pressure, but some require a pressure of about 100 bar to open the fibers well, and the pressure difference between the two is half.

 

2.4 Design of drying process

After spunlace fiber opening, microfiber fibers form a large number of capillaries in the cotton layer, and the water absorption and moisture content of the cotton layer are greatly improved. In addition, the dense structure of microfiber fiber spunlace cloth affects the penetration of heat in the dryer, making microfiber fiber products more difficult to dry than ordinary polyester and nylon products, especially high-quantity products above 180gsm. Therefore, the drying temperature of microfiber fibers should be set 10~15℃ higher than that of ordinary polyester and nylon products of the same quantity.

 

 

3 Performance characteristics and applications of microfiber fiber spunlace fabrics

3.1 Application of microfiber fiber spunlace fabrics in synthetic leather

The goal of developing synthetic leather is to obtain fibers and structures corresponding to the mesh-like interlaced structure of collagen fibers in natural leather, that is, animal skin. Collagen fibers are composed of very fine fiber bundles, and their structure is unique. Microfiber fibers form a denser and more chaotic three-dimensional structure in spunlace nonwoven fabrics than ordinary synthetic fibers. After being made into leather, this structure can be realistically imitated to the extent that it is indistinguishable from the real thing. In addition, the strength of microfiber fiber spunlace fabrics is significantly higher than that of spunlace fabrics made only of conventional fibers, and the longitudinal and transverse strengths are closer. After being made into leather, the performance advantages of the leather are more prominent.

The performance comparison of PU leather made of the same quantitative microfiber fiber spunlace fabric and conventional synthetic fiber spunlace fabric is shown in the figure below. Both are Luxian "Double Circle" brand spunlace fabrics, manufactured in the same synthetic leather factory.

As can be seen from the above table, the PU leather made of microfiber spunlace fabric has excellent physical properties, large elongation and high strength. In addition, through the electron microscope photo, the microfiber spunlace fabric PU leather has a dense microstructure and a cross section similar to natural leather, which is not available in leather made of conventional fiber spunlace fabric.

Especially when used on artificial suede, the microfiber spunlace fabric highlights its superior performance. During the production process, the microfiber spunlace fabric must first be impregnated with polyurethane resin. Then it is treated with a coagulation liquid composed of DMF and water to solidify the polyurethane resin and form a continuous open-cell microporous structure. At the same time, its mechanical and physical properties, feel and elasticity are further optimized. Afterwards, after a series of post-finishing, such as dyeing, sanding, weight reduction, and brushing, the final product is obtained.

Artificial suede using microfiber spunlace fabric as the base fabric has excellent performance. Its performance comparison with traditional products is as follows:

Weston has been committed to developing microfiber artificial suede base fabrics, and some products have been put into use. The performance indicators of artificial suede made of our factory's 200gsm microfiber spunlace fabric.

 

3.2 Application of microfiber spunlace fabric in high-end clothing leather

Although the application of microfiber spunlace fabric in high-end clothing leather started late, it has a strong development momentum and has a dominant trend. Clothing leather made of microfiber spunlace fabric has excellent comprehensive wearing performance, which is reflected in: ① It feels highly soft and is lighter than genuine leather; ② It has good drape; ③ It has good breathability and moisture permeability, and is comfortable to wear; ④ The color is bright and diverse, and the fluff is plump and uniform, which is conducive to design and cutting. In addition, compared with genuine leather, microfiber spunlace clothing leather can be washed with water, will not mold or be eaten by insects, and makes maintenance very easy. It has completely changed the shortcomings of hard board, creases, and airtightness of traditional artificial leather in terms of appearance and internal performance, and has completely reached or even exceeded the characteristics of genuine leather. It has replaced genuine leather for clothing products in large quantities abroad.

 

3.3 Application of Microfiber Fiber Spunlace Cloth in High-grade Wiping Cloth

After being spunlace, the microfiber fiber forms microfiber or micro-denier fibers, giving the product a larger specific surface area. For example, the surface area can be increased to 3 times by using 6-petal split fibers, and to nearly 7 times by using 16-petal split fibers. The greatly increased surface area greatly improves the product's adsorption of dust particles and its absorption rate of water. In addition, the microfiber fiber feels extremely soft and causes almost no damage to the surface being wiped. It is particularly suitable for scratch-free cleaning cloths used in medical clinics, high-precision fields, and high-quality household use.

The following table is a performance comparison between microfiber spunlace wipes and traditional wipes:

Due to the above characteristics of microfiber spunlace wipes, its main application range is: ① High-grade mirror cloth: used for wiping optical lenses, coatings, resin lenses, glass, etc., as well as CDs, recording heads, TV screens, etc.; ② Precision wipes: used for precision machining, electronic product production, high-grade mirror production, etc.; ③ High-grade household wipes: high-grade furniture, electrical appliances, high-grade cars, jewelry, etc.

 

3.4 Application of microfiber spunlace cloth in filter materials

After spunlace, the fineness of microfibers can reach more than 70%. The microfiber denier or micro-denier fibers, which account for the vast majority of the total fiber volume, form a more dense and messy three-dimensional structure in the spunlace nonwoven fabric than ordinary synthetic fibers, with more fine gaps, which greatly increases the capillaries in the nonwoven fabric, making the product's air permeability and moisture permeability fundamentally improved. Taking advantage of these advantages, we have developed microfiber fiber filter materials, which have been widely used in the filtration of air, blood, wastewater, etc., with a filtration efficiency of up to 99.9%.

 

3.5 New uses of microfiber fiber spunlace fabrics

In order to meet the needs of the market, we are trying to develop new types of microfiber fiber spunlace fabrics to expand their application areas. For example, we have initially developed microfiber fiber absorbent materials that can be used in diapers, incontinence pads, etc. I believe that with the development of the fiber and non-woven fabric industry, the use of microfiber fiber spunlace fabrics will become more and more extensive and more and more high-end.

 

 

4 Summary

Microfiber fiber spunlace fabrics are high-performance, high-value-added products. The use of microfiber fibers to produce high-quality spunlace non-woven fabrics is an inevitable trend in the development of non-woven fabrics in the world. In the development and application of microfiber fibers, Japan, South Korea and Taiwan are at the forefront, while China is far behind. At present, most of the microfiber fibers used in China rely on imports, and the domestic microfiber fibers are of a single variety and poor quality, which cannot meet the requirements of high-end products. In addition, the processing and finishing technology of microfiber fiber products is not yet mature, and some problems cannot be solved for the time being. For example, because the microfiber fiber is too thin, the fiber has good light transmittance, which makes it difficult to dye deeply. Although darker colors can be dyed by using high concentrations of dyes, the color fastness is relatively poor. The deep dyeing and color fastness of microfiber fibers have become the biggest bottleneck in the research and development of domestic artificial suede manufacturers, and have greatly restricted the development of microfiber fiber nonwovens.

Due to the development and progress of high-tech, the chemical fiber industry has produced a lot of differentiated fibers and functional fibers, which has greatly enriched the fiber raw materials of spunlace products and accelerated the development of spunlace process technology. As a manufacturer dedicated to the development of microfiber fiber spunlace nonwovens, we call on the upstream and downstream manufacturers of domestic microfiber fibers to work together to break through the difficulties encountered in the manufacturing, processing and deep processing of microfiber fibers and their products. We look forward to the mutual promotion and improvement of the spunlace industry and the fiber making industry in the future development path, so as to push my country's microfiber fiber industry to a higher level.

 

The microfiber nonwoven we produce is by filament of 70% polyester and 30% polyamide. This extremely fine filament makes quite soft hand feel which is quite good for sensitive surface cleaning. Its unique orange segment’s similar structure enables the fabric can highly absorb oil, grease and dust. Now we can dye the fabric into most color you can find on Pantone code books. You can use different color to make different cleaning area. Its high strength and softness also make it good as package material for valuable and vulnerable items such as portable computers, phones, jewelries, diamonds, delicate tools, medical devices, etc. It is also good to for painting since it is friendly to any inks or colorants and its high strength can keep the artwork long time. The color would not fade for tens of years. Application: critical cleaning, electronic cleaning, sensitive surface cleaning, SMT cleaning, etc.