Differential fiber is a term used in the chemical fiber industry. It is not a word with a strict definition, but generally refers to chemical fibers that are different from general conventional varieties, and generally refers to chemical fibers with certain characteristics created by technical transformation of conventional chemical fiber varieties. The concept of differentiald fiber is sometimes different from functional fiber. The former mainly improves wearability, while the latter highlights special properties such as high temperature resistance, corrosion resistance, high strength and high modulus. However, at present, the distinction between the two is gradually blurred and becomes inseparable, and functional fibers are also regarded as differentiald fibers.

There are many varieties of differentiald fibers, currently easy to dye, colored, high moisture absorption, waterproof, high shrinkage, antistatic, anti-pilling, antibacterial, flame retardant, far infrared, anti-ultraviolet, luminous, special-shaped, fine denier, ultra-fine Denier, composite, imitation silk, imitation wool and imitation hemp and other varieties.

Differentiald fibers can be prepared by chemical modification and physical modification, the main points of which are as follows.

The main method in the chemical modification method is the copolymerization method, that is, the introduction of some special genes in the basic structure of the macromolecule and copolymerization, such as when producing polyester with purified terephthalic acid (PTA) and ethylene glycol (EG) , Introduce a small amount of sodium dimethyl sulfonate isophthalate (SIPM) to prepare cationic dyeable polyester.

There is a blending method in the physical modification method, that is, a specific modifier (or additive) is mixed into the polymer melt or solution before spinning, and then spinning is performed, so that the modifier can be Blend evenly into fibers. For example, antibacterial fiber is made by adding antibacterial agent into polyester melt and then spinning. In addition, changing the macroscopic structure of fibers is also an important method of physical modification, such as passing two polymer melts or their solutions with different properties through a special distribution device, so that each fiber spun contains these two components. That is, composite fiber; it can also make the fiber microporous, shape the cross section, roughen the surface, etc.

The main varieties of differentiald fibers

The following main varieties of differentiald fibers use chemical modification or physical modification, and some use both methods. Because polyester accounts for the largest proportion of chemical fibers, it also has the most varieties of differentiald fibers.

In the production of cationic dye-friendly polyester (ECDP), in addition to the raw materials PTA and EG, if a small amount of 3,5-sodium dimethyl sulfoisophthalate (SIPM) is added as the third monomer to copolymerize, the A sulfonic acid group that can be used as a cationic dye dye seat is added to the modified molecular chain to obtain a cationic dye-dyeable polyester (CDP). However, under normal pressure boiling dyeing conditions, only ring dyeing occurs, and it is difficult for dyestuffs to enter the interior of the fiber. To obtain a better dyeing effect, high temperature and high pressure methods have to be used. Later, people added a small amount of the fourth monomer, polyethylene glycol, to obtain a cationic dye-friendly polyester (ECDP) that can be easily dyed under normal pressure conditions, and its fibers are soft to the touch and have superior performance, but are heat-resistant. The stability is greatly reduced. Under the ironing temperature of 180 ℃, the maximum strength loss is more than 30%. In further research, some researchers added 1,4-butanediol partly instead of EG, which greatly improved the heat resistance and stability of the produced fibers.

Flame-retardant fiber Fire caused by fiber products has become one of the major disasters in society. According to the survey of fire accidents in recent years, fires caused by interior decorations and textiles occupy the first place. To this end, countries around the world have formulated laws and regulations on fabric flame retardancy, and announced their implementation. my country has also formulated national standards for flame-retardant protective clothing, stipulating that employees in metallurgy, forestry chemical industry, petroleum, fire protection and other departments should use flame-retardant protective clothing, and the number of them will exceed 6 million. , my country currently needs about 930,000 tons/year. Flame-retardant polyester can be produced by methods such as copolymerization, blending, and sheath-core composite spinning. The fibers prepared by the latter two methods have permanent flame-retardant properties, but the cost is relatively high. The flame retardant used is required to have good flame retardant properties, non-toxic, good durability, no decomposition during polymerization and spinning, no side reactions, good compatibility with polymers, and good for polyester spinnability and all Fiber performance was not adversely affected. There are already 47 factories producing 167 varieties of flame retardants in the world. Relevant domestic units are also developing flame retardants containing phosphorus, sulfur, nitrogen, silicon and halogens. The above-mentioned skin-core composite fiber uses flame-retardant polyester as the core and ordinary polyester as the skin, which has a more complete flame-retardant effect.

Antibacterial fiber When people wear clothing, metabolites such as sweat, sebum and grease on the surface of the skin will adhere to the fiber, and they will produce low-level fatty acids and volatile compounds under the action of foreign microorganisms when they interact with the bacteria on the skin. It emits a bad smell, which reduces the heat retention and air permeability of the fiber. If the antibacterial agent is introduced into the fiber, the reproduction of bacteria can be inhibited. At present, there are two types of antibacterial agents. One is nano-scale silver-containing zeolite antibacterial materials developed by major Japanese companies. The antibacterial fibers produced are safe and harmless to the human body and have good durability. It has a significant impact, and its antibacterial efficiency is only 70% to 80%; the nano-scale antibacterial polyester staple fiber recently developed by Tianjin Petrochemical Chemical Fiber Factory is such a variety. The other is the organic antibacterial agent developed by Shanghai Synthetic Fiber. The AMF series antibacterial fiber produced is harmless to the human body and has a broad-spectrum antibacterial effect on Gram-negative and positive bacteria, with an antibacterial rate greater than 90%. In particular, it has good compatibility with polymers and will not have adverse effects on spinning (including fine denier spinning). Now it is widely used in polyester and polypropylene, successfully making underwear and bedding, etc. This kind of antibacterial agent is the first in China, and its antibacterial rate has reached the international advanced level.

The far-infrared fiber is infiltrated into a small amount of ceramic powder (mainly titanium, tin, zirconium, aluminum oxide and zirconium carbide, etc.) After absorbing the thermal energy radiation (infrared radiation) of the human body or the outside world, these additives release far-infrared rays with a wavelength range of 2.5 μm to 30 μm through molecular energy level transitions, among which are commonly known as reproductive wavelengths and are closely related to biological growth. Far-infrared rays in the wavelength range of 4 μm to 14 μm can cause the resonance of cell molecules on the surface of the human body, thereby activating the surface cells of the human body and promoting the blood circulation of the microvessels on the surface of the human skin, achieving the effects of keeping warm, maintaining health and promoting metabolism. Whether its effect is obvious or not is mainly reflected in the selection and ratio of metal oxides, because different metal oxides have different wavelengths of far-infrared radiation. The key technology of its preparation lies in the fineness of the particles, the selection of additives and its dispersibility in the polymer.

Anti-ultraviolet fiber In recent years, due to the serious damage of the atmospheric ozone layer, the radiation of the sun's ultraviolet rays to the earth is gradually increasing. In order to reduce the harm of ultraviolet rays to the human body, the chemical fiber industry has developed anti-ultraviolet fibers. Clothes made of this fiber are generally summer clothes, such as shirts, mountaineering suits, sun hats, etc., which can effectively reduce the damage of ultraviolet rays (wavelength 200nm ~ 400nm) in the sun to human skin, prevent dermatitis and skin damage. It can also reduce the heating caused by radiation, so that it is not only comfortable to wear, but also cool and pleasant. We are currently still following the Australian/New Zealand standards and classification methods, and the UPF value of UV-resistant textiles should be greater than 15. The anti-ultraviolet agent used is generally composed of two materials: one is benzophenone and phenolic aromatic compounds, which can absorb ultraviolet light, mainly based on them; the other is metal oxides (such as zinc oxide, titanium dioxide, etc.) And barium sulfate, etc., they have both absorption and reflection. Since a specific substance can only absorb ultraviolet rays in a certain wavelength range, the anti-ultraviolet agent should be composed of various materials. Like the far-infrared fiber, its key technology is also the choice of anti-ultraviolet agent, particle size and its dispersion in the polymer.

Antistatic fiber In a relatively dry environment, polyester fabric has static electricity, which is not only easy to absorb dust, but also often sticks to the skin, making it uncomfortable to wear. In certain occasions, the static electricity of the fabric may cause a fire. For this reason, antistatic fibers were developed. The fiber is prepared by two methods: one is blended spinning with conductive material and polymer, and the other is composite spinning technology. A certain component in the composite fiber has antistatic properties due to infiltration of conductive materials. The material is an inorganic metal compound or carbon black or the like. In addition, the antistatic agent can also use organic metal salts, such as polyether ester antistatic agent PEEM containing metal salts. It is said that the antistatic fiber made by blending antistatic agent and polyester has excellent and long-lasting antistatic performance, which is better than that of antistatic fiber made by polyether ester antistatic agent without metal salt.

Hydrophilic fibers Natural fibers such as cotton, wool, hemp, etc. are all hydrophilic fibers, while polyester, acrylic fibers and polypropylene fibers in synthetic fibers are hydrophobic fibers. When the relative temperature is 65%, the equilibrium temperature absorption rate of cotton is 6% to 9%, while that of polyester is only 0.4% to 0.7%. Polyester underwear feels itchy when worn next to the skin and feels stuffy when sweating, while cotton underwear is comfortable when worn next to the body. The moisture absorption rate of polyester and other synthetic fibers is very low, which is determined by the chemical structure of these synthetic fiber macromolecules. For example, polyester macromolecules are composed of benzene rings, methylene groups and ester groups (-COO-), which are resistant to water molecules. There is no strong attraction, but relying on the inherent surface tension of the substance to make a small amount of water adsorb on the fiber surface or internal microporous surface. Two methods can be used to enhance the hydrophilicity of polyester, one is to introduce hydrophilic genes, such as polyethylene glycol, into the fiber through the copolymerization method, and the other is to change the cross-sectional shape of the fiber to make a trilobal shape , C type, L type, etc., make the fiber have a microporous structure inside, increase the specific surface area, and use the microporous capillary action to absorb water. It can also be blended with polyester fine denier silk and hydrophilic cellulose fibers to produce textiles with excellent hydrophilicity.

The full name of luminescent fiber is light storage type self-luminous fiber. It is made by blending polyester, polypropylene or nylon polymer with luminescent agent. It can absorb light - store energy - emit light, and after absorbing natural light for 30 minutes, it can continue to emit light for 8 hours to 12 hours. The luminescent agent is composed of strontium added to phosphorus, or zinc phosphide impregnated with copper and some patented materials, or selenium soil series chemicals. Luminescent fibers are widely used in the field of clothing and decoration, for making clothing fabrics, theater carpets, aircraft interior fabrics, belts, ropes and life-saving equipment in the fishing industry.

Although the performance of fine-denier fiber polyester is superior to that of natural fibers, there are still many shortcomings in terms of hand feeling, appearance and wearing performance, so fine-denier and ultra-fine-denier polyester have emerged as the times require. At present, there is no standard definition of fine denier in various countries in the world. Usually, the single-thread fineness less than 1.1dtex (dtex is the fineness unit, when the fiber length is 10000m, the weight is 1g, called 1dtex) is called fine denier fiber, and less than 0.33dtex is called superfiber. Fine denier fibers. As the fibers become thinner, the bulkiness and coverage of the fabric are improved. Many microfibers on the surface of the fabric form a fine concave-convex structure, which increases the fine velvet feel. It is often used in imitation suede, artificial leather and imitation silk products. Furthermore, due to the wicking effect of the fine denier fiber capillary, the moisture permeability of the fabric is greatly improved, and waterproof and breathable fabrics can be made. As early as the mid-1960s, the conventional spinning method could be used to stably produce 0.4dtex-1.1dtex polyester filaments; in the 1970s, ultra-fine filaments of 0.1dtex were produced by two composite spinning methods: stripping method and sea-island method. At present, the thinnest ultra-fine denier has reached 0.001dtex. In addition, ultra-fine denier fabric has excellent cleaning function and filter performance, and is an important raw material for efficient cleaning cloth and new filter materials. Recently, porous ultra-fine denier yarns have been developed at home and abroad, so that the fabric has better hand feeling and drapability, and the appearance is gorgeous. The corresponding technology and equipment are still under development and improvement.

Three different fibers refer to fibers with different fineness, different shrinkage and different cross-sections. At present, polyester is mainly used as raw material. "Different denier" is a multi-filament composed of monofilaments with different deniers. The thicker core yarn can provide sufficient elasticity, stiffness, elasticity and crispness, and the thinner fiber can be used as the cortex to provide soft feel and bulkiness. "Different shrinkage" is to use single fibers with different shrinkage rates to make yarns. After post-processing, the fabric structure is tight, and the monofilaments with low shrinkage rates in the yarn have the effect of relaxation, fluffy and embossing; "Different shrinkage" "Cross-section" refers to the use of round, triangular, trilobal, five-lobal or hexagonal cross-sectional silk to make multifilaments, which can make the interior of the yarn stable and fluffy, and the appearance is soft and soft. Three different fibers can be produced by composite spinning or mixed fiber composite technology. It is widely used in synthetic wool-like products and is very successful. At present, the material of the three different fibers is mainly polyester.

The mixed fiber composite processing technology used to produce this yarn has a higher technical content. Examples of popular products currently on the market are as follows: ①Different shrinkage mixed fiber yarn, which is made of fine denier yarn and high shrinkage yarn mixed fiber and processed through the network. Spiral crimp, that is, with a high-shrinkage yarn as the main axis, the fine denier yarn is fluffy and curled in the shape of a rattan tree (equivalent to crepe crepe). ②Intermittent network yarn, that is, two parallel multifilament network and non-network (also known as off-network) sections are intermittent, and the gloss effect reflected on the fabric by the two is different, and its law can be specified artificially. ③Parallel interlacing yarn is to combine two sections of multifilaments with different properties, different raw materials and different colors, and then interweave, so as to obtain special effects and interlacing yarns of different colors. ④Using polyester medium-oriented yarn (MOY) or pre-oriented yarn (POY) as raw material, after two processes of stretching and false twisting, in the stretching section due to different stretching rates, the coarse details of the filaments are produced, and after the false twisting section The strands are deformed to achieve a thick and thin appearance with bulk properties, thereby producing a textured yarn with coarse details. Blended fiber composite processing technology is a new technology that is emerging, and it will become one of the most important technologies in the development of new textile fabrics.

An important trend in the development of differentiald chemical fibers at home and abroad is to make differentiald fibers have multiple functions. For example, the flame-retardant fibers developed abroad in recent years have anti-static, anti-pilling, Antibacterial and anti-mildew functions.