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With China Plastic Machinery
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Polyvinyl chloride fiber is also called chlorinated nylon, a kind of polyvinyl chloride olefin fiber. It is a synthetic fiber made of polyvinyl chloride by wet or dry spinning. It has self-extinguishing properties, which are not possessed by general natural fibers and chemical fibers. It has good warmth retention and insulation properties, high chemical stability, and good wear resistance, but poor heat resistance, light resistance and thermal conductivity. It cannot be ironed, steam sterilized, washed with boiling water, or dyed at high temperatures, and is non-flammable.
Polyvinyl chloride (PVC) fiber is a fiber spun from polyvinyl chloride resin, referred to as chlorinated nylon in China. As early as 1913, F. Klatte produced the first batch of PVC fibers by thermoplastic extrusion, but this process was not used later. In 1930, E.Hubert, Pabst and Necht of IG Company of Germany dissolved PVC in cyclohexanone, and then used wet spinning in an aqueous solution containing 30% acetic acid to produce PVC fiber for consumption. Subsequently, production officially began under the trade name Pece Fasern. Under the technical conditions at that time, this production method was difficult, so it developed very slowly. It was not until the early 1950s that PVC fiber appeared as an industrial product.
Polyvinyl chloride fiber has the advantages of a wide source of raw materials, low price, good thermoplasticity, good elasticity, good chemical resistance, good electrical insulation, wear resistance, low cost and high strength. In particular, the fiber has good flame retardancy, is difficult to burn and self-extinguishing, and the limiting oxygen index LOI is as high as 37.1%. However, due to the poor heat resistance of polyvinyl chloride fiber, poor stability and dyeability to organic solvents, its production and development are affected. Compared with other synthetic fibers, it has always been in a backward state. In recent years, the so-called second generation of polyvinyl chloride fiber has emerged, and its heat resistance is much better than that of traditional polyvinyl chloride fiber. At the same time, with the improvement of living standards, people's safety awareness is getting stronger and stronger. Many countries have put forward flame retardant requirements for bedding, children's and elderly pajamas, interior decoration fabrics, fire-fighting supplies, aircraft, automobiles, and ship warehouse supplies. As a flame-retardant fiber material, polyvinyl chloride fiber will be widely used in special industries such as firefighting, military, aerospace, metallurgy, and petrochemicals through the improvement and improvement of raw materials and production technology.
Polyvinyl chloride fiber is harder and has a lower strength among synthetic fibers, similar to cotton.
Polyvinyl chloride has poor heat resistance and will shrink significantly when the temperature reaches 65-70¡æ. There is no obvious melting point. Its viscosity-fluidization temperature is about 170-220¡æ, and its decomposition temperature is 150-155¡æ. At this temperature, a small amount of HCl will be released, prompting it to further decompose. Therefore, an alkaline stabilizer must be added to neutralize HCl and inhibit its autocatalytic cracking reaction. Therefore, not only can polyvinyl chloride not be spun by melt spinning, but even if it is spun by thermoplastic extrusion at a lower temperature, appropriate heat stabilizers must be added.
Polyvinyl chloride is an amorphous polymer with a small amount of microcrystals. The density of polyvinyl chloride is about 1.39-1.419/cm. Polyvinyl chloride fiber has low thermal conductivity and good warmth retention, which is better than cotton and wool. Polyvinyl chloride has asymmetric factors in its macromolecular structure, so it has a strong dipole moment, which makes polyvinyl chloride fiber have certain electrostatic properties and good dust absorption. Polyvinyl chloride does not absorb water and is difficult to dissolve in general solvents. The solvents used for wet spinning are: ethylene dichloride, tetrachloroethane, chlorobenzene, cyclohexanone, tetrahydrofuran, dimethylformamide, propylene oxide and epichlorohydrin.
The unique performance of polyvinyl chloride fiber, that is, its advantage, lies in its flame retardancy. At high temperatures, polyvinyl chloride decomposes a large amount of non-flammable HCl gas, which takes away a lot of heat on the one hand, and isolates the air on the other hand to extinguish the flame. The limiting oxygen index LOI of polyvinyl chloride fiber is as high as 37.1%. It shrinks and carbonizes in an open flame, and extinguishes itself when leaving the fire source. Its products are particularly suitable for flammable places.
Polyvinyl chloride fiber has good stability to inorganic reagents. At room temperature, in most inorganic acids, alkalis, oxidants and reducing agents, the fiber strength is almost not lost or rarely reduced. Polyvinyl chloride is prone to light aging. When it is exposed to light for a long time, the macromolecules will undergo oxidative cracking.
The main disadvantage of polyvinyl chloride fiber is poor heat resistance. It is only suitable for use below 40-50¡æ. It softens at 65-70¡æ and shrinks significantly. The second is poor resistance to organic solvents and poor dyeability. Although it cannot be dissolved by most organic solvents, it can be swollen. It is difficult to color polyvinyl chloride fibers with commonly used dyes, so most of them are dyed with stock solution in production.
Chlorofilament production process includes wet spinning and dry spinning, and the products are both short fibers. The solvent (or kneading agent) used is acetone, and the process flow is as follows:
1. Wet spinning process
Polyvinyl chloride ¡ú kneading (swelling) ¡ú dissolving ¡ú filtering ¡ú temperature adjustment ¡ú spinning ¡ú bundling ¡ú washing ¡ú stretching ¡ú oiling ¡ú drying (heat setting) ¡ú curling ¡ú cutting ¡ú short fibers.
2. Dry spinning process
Polyvinyl chloride ¡ú kneading (swelling) ¡ú dissolving ¡ú filtering ¡ú temperature adjustment ¡ú spinning ¡ú bundling ¡ú stretching ¡ú heat setting ¡ú oiling ¡ú cutting ¡ú drying ¡ú short fibers.
The coagulation bath used for wet spinning of polyvinyl chloride is an acetone aqueous solution. The acetone content in the bath is controlled at 20% to 22%, the bath temperature is maintained at about 35¡ãC, the spinning speed is generally 16 to 20 m/min, and the residence time of the filaments in the coagulation bath is 10 to 12 seconds. The resulting nascent fibers are washed and then stretched.
The sleeve temperature during dry spinning of polyvinyl chloride is 80 to 120¡ãC, and the winding speed is 100 to 200 m/min. The sleeve length can be 3.5 to 6 m. The higher the winding speed, the longer the sleeve length should be. The acetone is volatilized by means of a hot air flow, and the stock solution stream is coagulated into fibers. The hot air in the spinning sleeve is drawn out and condensed or adsorbed with activated carbon to recover the acetone. In order to ensure production safety, the acetone content in the air in the sleeve must not be close to the explosion limit of acetone (2.15% to 13%, the volume fraction of acetone).
PVC fiber products include filaments, staple fibers, and bristles, with staple fibers and bristles being the main types.
In civilian applications, it is mainly used to make various knitted underwear, wool yarn, felt, and home decorative fabrics. Knitted underwear, sweaters, and woolen trousers made of PVC fibers not only have good warmth retention properties, but are also flame retardant. In addition, due to the effect of static electricity, they have a certain auxiliary effect on arthritis.
In industrial applications, PVC fibers can be used to make various filter cloths, work covers, insulating cloths, and covering materials used at room temperature. In addition, dust masks made of PVC fibers have excellent electrostatic effects and are particularly good at dust absorption. PVC bristles are mainly used to weave window screens, screens, and ropes. In addition, researchers at Teijin Corporation of Japan have found that PVC fibers will produce a large number of negative ions after friction with the human body, and they are trying to use this feature to develop health products.
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