How polyester fiber is synthesized

Update: 07-09-2020
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The polyester film fiber process of polyester includes […]

The polyester film fiber process of polyester includes two parts: polyester melt synthesis and melt spinning. The raw materials of synthetic polyester are polyethylene terephthalic acid and ethylene glycol, which are mainly obtained from petroleum cracking, but also from coal and natural gas. Petroleum is heated and cracked to obtain toluene, xylene and ethylene. After chemical processing, terephthalic acid or dimethyl terephthalate and ethylene glycol can be obtained. In the early polyester production, dimethyl terephthalate and ethylene glycol were used as raw materials because terephthalic acid was not easy to refine. In 1965, the refining of terephthalic acid was successful, which reduced the production process and cost of polyester. Polyester produced with terephthalic acid and ethylene glycol as raw materials has increased year by year. Polycondensation: Transesterification of dimethyl terephthalate and ethylene glycol, the resulting diethylene terephthalate oligomer, polycondensation at 280~290℃ and vacuum conditions to obtain polyterephthalic acid Ethylene glycol ester; or directly esterify terephthalic acid and ethylene glycol, and then polycondensate ethylene terephthalate to obtain a polyester melt.

 

30% wool yarn

 

Polyester melt can be used to prepare polyester chips and melt direct spinning. Polyester chips are obtained by casting polyester melt through tape and pelletizing. Spinning. After drying and melting, the polyester chips can be used for spinning, preparing polyester films, polyester bottles, etc. During the melting process, the moisture contained in the chips can hydrolyze the polyester and affect the spinning performance and fiber quality. Therefore, it must be dried before spinning to reduce the moisture content of the chips to below 0.01%. In chip spinning, the dried polyester chips are heated and melted in a screw, extruded and sent to each spinning position of the spinning box. After being accurately metered and filtered by a metering pump, they are sprayed from the spinneret hole Out. The diameter of the spinneret hole is generally 0.15 to 0.30 mm.

 

The sprayed melt stream is cooled and solidified into filaments by the cooling airflow. The cooled thread is divided into polyester filament and polyester staple fiber (or polyester staple fiber) according to different processing techniques. Short polyester yarn. When spinning short fibers, multiple strands are gathered together, and after being wet and oiled, they fall into the silk barrel. Then, the finished product is obtained through processes such as bundling, stretching, crimping, heat setting, and cutting. If after stretching, undergo a tension heat setting at about 180°C, a high-strength, low-elongation short fiber with a strength of 6cN/dtex or more and an elongation of 30% or less can be obtained. Polyester staple fiber is divided into cotton type staple fiber, which is used for blending with cotton fiber and wool. Polyester filament.

 

When spinning filaments, the solidified filaments are wet and oiled, and are wound on the bobbin at a speed of about 3500 m/min to obtain pre-oriented filaments, which cannot be directly used for weaving. POY is stretched and shaped , Stretched or twisted to obtain stretched yarn. Stretched textured yarn or twisted yarn can be directly used for weaving or deformed into textured yarn. After solidification, the thread is oiled and directly stretched and wound at 4500-5000m/min to obtain a fully drawn thread, which can be used for weaving. The American commodity kodel is another polyester fiber that has been industrially produced. It is spun from a high polymer obtained by polycondensation of terephthalic acid and 1,4-cyclohexanedimethanol. Compared with polyester, it has stronger resistance to decomposition and slightly lower fiber strength and elongation. It is suitable for blending with cotton, wool, etc. The fabric made has good elasticity, hand feeling, wrinkle resistance and anti-pilling performance, but the strength and wear resistance are poor.

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