Lyocell fiber (meaning soluble fiber ) is known as the green fiber of the 21st century. It uses N -methylmorpholine -N- oxide ( NMMO ) as a solvent and is used for wet spinning of regenerated cellulose fiber. The waste can be degraded naturally, and the amine oxide solvent in the production process can be 99% . 5 % is recycled and reused. " Very low toxicity, and does not pollute the environment ."

In 1980 , the German Akzo-Nobel company first obtained the process and product patents. In 1989 , it was officially named by the International Committee of Man-made Fibers and Synthetic Fibers. At present, the world's production capacity is about 120,000 tons, distributed in the United States, Britain, Austria, Germany, India, South Korea and Taiwan.

A. Lyocell fiber is used in clothing with its excellent wearability. It can be spun purely or blended with cotton, linen, silk, wool, synthetic fiber and viscose fiber to improve the performance of other fibers. The fabric woven by its yarn is rich in luster, soft and smooth, natural hand feel, excellent drape, good air permeability and wearing comfort. Pure Lyocell fabric has a pearl-like luster, and the inherent fluidity makes the fabric look light and thin with good drape. Different styles of pure Lyocell fabrics and blended fabrics can be woven through different weaving and knitting processes , which are used in high-end denim, ladies' underwear, fashion and men's high-end shirts, casual wear and casual wear, etc. The newly developed fine denier and super fine Denier Lyocell fiber makes it play a better role in the development of high-end products. At present, Lyocell products are becoming increasingly popular in Japan, Western Europe and the United States, and sales are increasing.

B. In industrial use, Lyocell fiber has higher strength, the dry strength is close to polyester, much higher than cotton, and its wet strength is almost 90% of the dry strength , which is unmatched by other cellulose fibers. It has been widely used in non-woven fabrics, industrial filter cloths, industrial yarns and special papers. Lyocell fiber can be made into non-woven fabrics with various properties by needle punching, spunlacing, wet laying, dry laying and hot bonding, which is better than viscose fiber products. Several companies in Europe are studying the application of Lyocell fiber in sewing thread, work clothes, protective clothing, diapers, medical clothing, etc., and Japanese paper manufacturers are also developing the use of Lyocell fiber in specialty paper .

In the wet state, Lyocell fiber products will produce obvious fibrillation through mechanical external friction. This phenomenon is manifested in the longitudinal separation of finer fibrils on the surface of the yarn, which produces hairiness. The reason for fibrillation is that Lyocell fiber has a high degree of axial orientation, and the transverse bonding force between microfibrils is weak. The high expansion of the fiber in the wet state weakens this bonding force. The weakening causes the skin fibers to fall off under the friction of the fiber itself or the metal, and the remaining skin fibers are longitudinally cracked to form longer and uneven fibrillar hairs.

The characteristics of Lyocell fibrillation make the finished style of this fiber fabric have two types. One is to use the fibrillation characteristics of the fiber to produce peach skin style through primary fibrillation, enzyme treatment and secondary fibrillation. The other product is to produce a clean surface with a clean surface without performing secondary fibrillation after the enzyme treatment. Although the easy fibrillation performance of Lyocell fiber brings convenience to the production of non-woven fabrics, filter materials and jeanette style fabrics, it brings troubles to the production and use of smooth fabrics, such as the control of processing techniques in production, The selection of equipment and auxiliaries ; the fabric is easy to fluff and pilling during use, and the color and light will change. In addition , clothing made of Lyocell fabric is severely fibrillated after many daily washings, giving the clothing a strong sense of old age.

Performance of Lyocell fiber

The main composition of Lyocell fiber is cellulose like cotton or viscose. Its molecular weight and crystallinity are between cotton and viscose.

Degree of polymerization and crystallinity of Lyocell fiber, cotton and viscose fiber

Fiber cotton Lyocell fiber viscose

Degree of polymerization 10000 500-550 250-300

Crystallinity ( % ) 70 50 30

It is precisely because of the unique degree of polymerization and crystallinity of Lyocell fiber that it has three major characteristics, namely high strength, its strength is close to polyester; rapid water absorption, its water absorption speed is close to twice that of cotton, and its moisture regain is better than cotton. Self-fibrillation produces peach skin effect.

Principles of Fibrillation

Easily fibrillated is one of the characteristics of ordinary Lyocell fibers . Fibrillation refers to the splitting of fine microfibers ( 1-4um in diameter ) on the surface of the fiber . Generally speaking, during the first fibrillation, the fibrils produced are relatively large, usually 1mm or even longer, and can be entangled into balls. If not disposed of, it will affect the wearing and look.

The fibrillation index F is used to characterize the degree of fibrillation . The I . ( I.e. Fibrillation Index ), generally divided into 0-10 levels, the higher the level, the greater the degree of fibrillation. Generally, when the degree of fibrillation is greater than 2 , the appearance of the fabric is already unsightly.

Factors Affecting Fibrillation of Lyocell Fabric

Mainly the following aspects (take 100% Lyocell , 21×16 110×60 , 63 ″ fabric as an example):

a , temperature

The higher the temperature, the greater the fibrillation index. Therefore, in order to achieve sufficient fibrillation in actual production, a higher temperature is used to improve production efficiency.

b . PH value

The increase of the pH value of the aqueous solution will help the swelling of Lyocell fiber, which is also beneficial to its fibrillation. Therefore, in order to improve the efficiency of fibrillation, the pH value of the aqueous solution should be increased as much as possible within the possible range .

c , time

Before the treatment time 90 minutes, the fabric fibrillation index has a linear relationship with the treatment time, that is, as the treatment time increases, the fibrillation index increases, and after 90 minutes, the fibrillation index increases very slowly. Therefore, it can be considered that a fibrillation time of 90 minutes should be sufficient for this fabric under the processing conditions .

Secondary fibrillation

The style of Lyocell fabric is to produce peach skin itself. Therefore, the dyed Lyocell fabric needs to use a secondary fibrillation process to produce secondary fibrils. The fibrils produced here should be much thinner and shorter than the fibrils produced for the first time. It is a dense layer of short fleece (commonly known as peach skin).

If we fibrillate the Lyocell fabric for the first time and polish sufficiently with biological enzymes, then the second fibrillation can produce the ideal peach skin, and the peach skin produced at this time should be retained.

Lyocell fiber is a new generation of regenerated cellulose fiber obtained by dissolving wood pulp in NMMO solvent system without chemical reaction and using dry spray wet process. German first by Akzo Nobel company in 1978 made in the patent, by the British after the Courtaulds Company ( later incorporated into Accordis company ) and the Austrian company Lenzing (Lenzing) successfully commercialized, the market around the world. To 2004 Nian 5 Yue, Lenzing company fully acquired LYocell fiber ( including filament and staple fiber ) production business, once monopolized the global market. LYocell fiber in the 20 century, 90 mid-decade to enter the Chinese market, Chinese trade names "Tencel," wood fiber ", etc., led to our Lyocell fiber products research and development production boom.

Because Lyocell fiber production technology once fully mastered in the hands of foreign companies, so the price has been high, Chinese 2005 imports Lyocell fiber 9795t , customs statistics import price for the 2616 Meiyuan / t , higher than the domestic price of cotton, polyester, More than 50% of conventional fibers such as viscose , the import price has reached 3 in the past few years . Above 50,000 yuan /t . Due to cost factors, the price of subsequent textile products of China's Lyocell fiber remains high.

Since 20 Century 90 since late years, Donghua University, Shanghai Textile Holding Group and other units of a long-term study, and a research institute in Germany and conduct joint research, and achieved success. 2006 years 2 months, the first bundle of domestic Lyocell fiber in Shanghai Rio Development Enterprises Ltd. smooth output, 1 000t / year production line officially put into operation, breaking the existing monopoly of foreign companies. Is expected in 2010 after years of domestic Lyocell production of fibers will exceed 1 Wan t / year scale. It can be predicted that with the successful localization of the fiber and the continuous expansion of output, the market price of China's Lyocell fiber will continue to fall.

Since the dry and wet strength of Lyocell fiber is excellent, the dry strength is close to that of polyester fiber, and the wet strength drop is small, about 85% of the dry strength , which makes Lyocell fiber strong in resistance to mechanical and chemical treatment; the breaking elongation of Lyocell fiber The change in the wet state is also very small, and the elongation in the wet state is about 17% , which makes its products have good dimensional stability. These advantages make up for the shortcomings of conventional viscose fiber. At the same time , the low energy consumption and pollution-free advantages of the Lyocell fiber production process are unmatched by conventional viscose fiber, and it is a truly green fiber. Global Lyocell fiber producing energy in 1992 than in 2 Wan t , has now expanded to 15 Wan t / year, estimated to 2010 will reach 45 Wan t / year Lyocell market share and influence fibers regenerated cellulose fiber family Strength will continue to improve.

Runteks Lyocell Series