Liu Guangkai
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Recently, elastic fiber is unique in the depressed textile industry. Become the only product that is not affected by the market boom cycle. According to ISO 2076 1 or DIN 6000 12, elastic fiber is a synthetic linear polymer, of which 85% is composed of block polyurethane. The history of opening elastic fiber can be traced back to 1937, which was discovered and patented by Germans O. Bayer, H.RINKE3 3,6 and their colleagues. The monomer composition he used was butanediol and hexamethylene diisocyanate 3-5. 1949, E.WINDEMUTH successfully spun high molecular weight polyurethane into silk 7 by chemical spinning. J Shivers 14 and his colleagues working in DuPont successfully spun the elastic fiber named "FIBER K" at 195 1. Dupont also produced the product in full at 1962, and renamed it "Lycra", and Bayer in Europe immediately followed/.
Basic structure
Since the elastic fiber is composed of more than 85% PU segments, 8, 13, PU itself is a changeable material. It can be a very hard and highly viscoelastic material, or even a very soft material with low viscoelasticity. The chemical structure of elastic fiber is just between these two extremes. Therefore, polyurethane elastomer can be regarded as a linear block polymer, as shown in figure 1. By changing the three basic components of polyol, diisocyanate and chain extender, the structures of various polymers can be obtained, and then their properties can be changed.
In short, alternating block polymers of type (A-B) can meet the basic requirements of elastic fibers. Among them, the soft segment gives the material the characteristics of easy expansion and contraction, and the hard segment provides intermolecular interaction. Because the soft segment is irregularly curled polyether or polyester, it is a continuous phase in the fiber, accounting for 65 ~ 90% of the total weight. They are in a non-anterograde state in loose fibers. Once the fibers are stretched, they will straighten and tend to be parallel. In the X-ray diffraction experiment, it is found that in the tensile state of the fiber, the soft segment forms a crystalline region caused by stress, and the stiffness and strength of the fiber in the tensile state increase due to the strengthening of the structure. When the external force is removed, it immediately retracts, the soft segment crystals disappear, and the molecules return to the curled state, so this is the charm of elastic fibers.
synthetic method
The synthesis of polyurethane can be basically completed by the reaction of chloroformate with diamine 10,11(1-kloc-0/) or carbamate with diol (1-2).
-rn H2+Cl COOR '→-RNH COOR '-+HCl( 1- 1)
-China HR, Chief Operating Officer of Roh+Z' →-Roo China HR '→-+Zoh (1-2)
But its main development depends on isocyanate chemistry. Many linear polyurethanes can be prepared by the reaction of diisocyanate and diol. 1-3, 1.4 butanediol and 1.6 polyurethane synthesized in hexamethylene diisocyanate are the representative inventions of Bayer in 1937.
HO(CH2)4OH+OCN(CH2)6 NCO→
-[O(CH2)4OO CNH(CH2)6 NH COO]-X( 1-3)
Usually, in the process of making elastic fiber, an NCO prepolymer 12 is synthesized first, and then a chain extender is added to synthesize the raw material of elastic fiber. Next, the synthesis steps of elastic fiber are briefly introduced through several simple chemical reaction equations:
Synthesis of 1 NCO prepolymer;
Polyester diol or polyether diol reacts with methyl diisocyanate to obtain the product.
N HO-r 1-OH+2n O = C = N-R2-N = C = O→
OCN-[R2- amino-cobalt-oxygen -r 1- oxygen-cobalt-amino -R2]n-NCO
NCO prepolymer
2. The chain is extended and forms a hard chain:
OCN-[R2- ammonia-cobalt-oxygen -r 1- oxygen-cobalt-ammonia -R2] nitrogen-
NCO +H2 ^^^ NH2 → ^^^ NH-CO-NH ^^^ ^^^
Elastic fiber raw material
At this stage, urea (urea) chain has strong hydrogen bonds, which are hard chains of elastic PU. When the elastic fiber is elongated at a rate of 200%, the hard connection and the soft connection are staggered. In the figure, the tight structure is a hard link and the loose structure is a soft link.
In the whole reaction process, the soft segment is usually formed by polycondensation of polybutylene ether glycol and dibasic acid obtained from tetrahydrofuran 12 (THF) in a selected proportion. However, due to the lack of commercial types of diisocyanate, the hard segment is still limited to MDI 2.6 toluene diisocyanate (TDI) and 4.4' diphenylmethane diisocyanate (MDI) as main raw materials. Table 1 lists the main components of elastic fibers produced by major companies in the world.
label
The birth of elastic fiber has brought a lot of convenience and comfort to people's daily life. Due to the appearance of elastic fibers, garments that originally needed rigidity can be replaced by elastic fibers, which can always maintain rigidity without losing comfort, such as coats and crease-resistant clothes. Traditional materials that require high elasticity, such as bras and socks, can achieve a longer service life through updated molecular structure design. The application of elastic fibers in China has gradually become common, but at present, imported elastic fibers are still the main ones. In terms of consumption, the market capacity of Taiwan Province Province is about 6,000 tons. Therefore, with the financial support of the science and technology project of the Ministry of Economic Affairs, the Institute has completed the development of melt-spun elastic fiber raw materials. It is hoped that through the completion of this plan, the domestic industry will exert its strength in this new market and look forward to injecting another stream of living water into enterprises in this depressed environment.
Table 1. Chemical composition of elastic fiber
product name
manufacturer
Use raw materials
Asilan
Korea Taiguang
Polyether ester /MDI/ diamine
Do Rastan
Bayer Fasher/Bayer AG/USA
Polyether ester /MDI/ diamine
Electrical stimulation-produced analgesia electric stimulation analgesia method
Japan dongyang textile co., ltd
Polyether ester /MDI/ diamine
Fujibao spandex
Fuji Textile Company/Japan
Polyether ester /MDI/ diamine
Global span
Global manufacturing company/Japan
Polyether ester /MDI/ diamine
Lycra
Dupont nemours/USA
Polyether ester /MDI/ diamine
Lineltex
Filatice/Italy
Polycaprolactone /MDI/ diamine
Rojka
Asahi Kasei/ Japan
Polyether ester /MDI/ diamine
reference data
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Two. Speech at the Gordon research conference. Textile Weekly July 1958,
Colby College, New London, New Hampshire