Method for producing low-melting-point renewable polyester for sheath-core polyester through glycol degradation

[0024] Example 1

[0025] 1. Preparation of recycled low-melting polyester: the mass ratio of recycled raw materials to methanol is 1:6; the mass ratio of recycled raw materials to zinc acetate is 100:0.5; the above raw materials are polymerized to produce recycled low-melting polyester after methanolysis :The degradation temperature is 190℃, the pressure is 2.5Mpa, the reaction time is 3h, the reaction is over when the pressure returns to atmospheric pressure, the reactants are filtered, the liquid obtained is rotary evaporated, and the methanol and ethylene glycol are respectively evaporated to obtain solids It is dissolved in hot ethanol and filtered, and the obtained liquid is evaporated to remove ethanol to obtain dimethyl terephthalate (DMT). The molar ratio of dimethyl terephthalate (DMT) to isophthalic acid (IPA) is 3:1; the molar ratio of dimethyl terephthalate (DMT) to neopentyl glycol (NPG) is 7:1; the molar ratio of dimethyl terephthalate (DMT) to ethylene glycol is 1:2; the molar ratio of alcohol (the sum of ethylene glycol and neopentyl glycol (NPG)) acid is 1.5:1 ; Catalyst antimony trioxide (Sb203) and cobalt acetate (Co(Ac)2) are 300ppm of the total acid in the reaction system, and then add 0.01% by weight (relative acid content) stabilizer trimethyl phosphate (TMP) . The esterification reaction is carried out under nitrogen pressure, the temperature is 220°C, the pressure is 0.15MPa, and the reaction time is 2.2h; the polycondensation reaction temperature is 275°C, the vacuum degree is 90Pa, and the reaction time is 3.5h. The obtained low melting point polyester has a melting point of 110°C, a terminal carboxyl group content of 25 mmol/kg, and an intrinsic viscosity of 0.69 dL/g.

[0026] 2. The preparation of recycled polyester: the process flow of bottle flakes after cleaning, drum drying, multi-stage filtration, and liquid phase viscosity increase. Among them, the drum drying temperature is 130°C, and the drying time is 8 hours. The steps of liquid phase thickening are as follows: 1) The melt with intrinsic viscosity of 0.55dl/g at 270℃ after being melted by the screw is sent to the vacuum separation tower by the melt transfer pump. The melt is at a vacuum of 100pa and the temperature is The intrinsic viscosity can reach 0.68dl/g after staying at 280℃ for 30min; 2) After that, the melt enters the secondary conditioning and viscosity adjustment device, and the melt temperature and vacuum in the secondary conditioning and viscosity adjustment device and the vacuum separation tower Similarly, under the action of the rotary propeller, the melt continues to advance, and the melt viscosity continues to increase. The rotation speed of the propeller is 5r/min, the residence time is 20min, and the final melt intrinsic viscosity is 0.79dl/g. The regenerated polyester has a melting point of 264°C, a terminal carboxyl group content of 16 mmol/kg, and an intrinsic viscosity of 0.79dl/g.

[0027] 3. Skin-core regenerated polyester staple fiber: the above-mentioned low-melting polyester and regenerated polyester are accurately metered into the composite spinneret assembly with 4:6 sheath-core weight respectively, and the melt sprayed from the spinneret of the composite assembly , After cooling, winding, bundling, drawing, shaping, cutting and packaging, the core-type recycled polyester staple fiber can be obtained. The drying temperature of the recycled polyester is 150℃, the drying time is 7h, and the screw temperature is 280℃; the low melting point polyester spinning pipe insulation temperature is 230℃, the recycled polyester spinning pipe insulation temperature is 275℃, and the spinning box temperature It is 280℃; the cooling wind temperature of ring blowing is 15℃, the wind speed is 2.0m/s; the spinning speed is 1100m/min; the draft ratio is 2.0, the draft temperature is 56℃, and the draft speed is 110m/min. The quality indicators of the sheath-core recycled polyester staple fiber obtained by the above production process are:

[0028] Linear density: 4.21dtex

[0029] Breaking strength: 3.14cN/dtex

[0030] Elongation at break: 40%

[0031] Cutting length: 51.2mm.

[0032] Example 2

[0033] 1. Preparation of recycled low-melting polyester: the mass ratio of recycled raw materials to water is 1:4; the mass ratio of recycled raw materials to potassium acetate is 100:0.5; the above raw materials are polymerized to prepare recycled low-melting polyester through hydrolysis: hydrolysis The temperature is 220°C, the pressure is 4.5Mpa, and the reaction time is 2.8h. When the pressure returns to atmospheric pressure at the end of the reaction, the reactants are filtered, the resulting liquid is rotary evaporated to obtain ethylene glycol, and the filtered solids are dissolved in DMF and filtered. The obtained liquid is recrystallized to obtain terephthalic acid (TPA). The molar ratio of terephthalic acid (TPA) to adipic acid (AA) is 3.5:1; the molar ratio of terephthalic acid (TPA) to hexanediol (HG) is 6:1; terephthalic acid The molar ratio of (TPA) to ethylene glycol is 1.5:1; the molar ratio of alkyd acid is 1.5:1; the catalyst antimony trioxide (Sb203) and cobalt acetate (Co(Ac)2) is the total amount of acid in the reaction system Add the stabilizer trimethyl phosphate (TMP) with a weight of 0.01% (relative acid content). The esterification reaction was carried out under nitrogen pressure, the temperature was 220°C, the pressure was 0.3MPa, and the reaction time was 2.5h; the polycondensation reaction temperature was 275°C, the vacuum degree was 80Pa, and the reaction time was 3h. The melting point of the obtained low-melting polyester was At 105°C, the terminal carboxyl group content is 28mmol/kg, and the intrinsic viscosity is 0.67dL/g.

[0034] 2. The preparation of recycled polyester: the process flow of bottle flakes after cleaning, drum drying, multi-stage filtration, and liquid phase viscosity increase. Among them, the drum drying temperature is 110°C, and the drying time is 7 hours. The steps of liquid phase thickening are as follows: 1) The melt with intrinsic viscosity of 0.55dl/g at 270℃ after being melted by the screw is sent to the vacuum separation tower by the melt transfer pump. The melt is at a vacuum of 100pa and the temperature is The intrinsic viscosity can reach 0.68dl/g after staying at 280℃ for 30min; 2) After that, the melt enters the secondary conditioning and viscosity adjustment device, and the melt temperature and vacuum degree in the secondary conditioning and viscosity adjustment device and the vacuum separation tower Similarly, under the action of the rotary propeller, the melt continues to advance, and the melt viscosity continues to increase. The propeller's rotation speed is 5r/min, the residence time is 15min, and the final melt intrinsic viscosity is 0.78dl/g. The regenerated polyester has a melting point of 269°C, a terminal carboxyl group content of 14 mmol/kg, and an intrinsic viscosity of 0.78dl/g.

[0035] 3. Skin-core regenerated polyester staple fiber: the above-mentioned low-melting polyester and regenerated polyester are accurately metered into the composite spinneret with 5:5 sheath-core weight respectively, and the melt sprayed from the spinneret of the composite component , After cooling, winding, bundling, drawing, shaping, cutting and packaging, the core-type recycled polyester staple fiber can be obtained. The drying temperature of the recycled polyester raw material is 140℃, the drying time is 7.5h, the screw temperature is 270℃; the insulation temperature of the low melting polyester spinning pipe is 220℃, the insulation temperature of the recycled polyester spinning pipe is 275℃, the spinning box The body temperature is 280°C; the circulating air cooling air temperature is 20°C, the wind speed is 3.0m/s; the spinning speed is 1000m/min; the draft ratio is 3.0, the draft temperature is 55°C, and the draft speed is 120m/min. The quality indicators of the sheath-core recycled polyester staple fiber obtained by the above production process are:

[0036] Linear density: 4.05dtex

[0037] Breaking strength: 3.22cN/dtex

[0038] Elongation at break: 42%

[0039] Cutting length: 51.6mm.

[0040] Example 3

[0041] 1. Preparation of recycled low-melting polyester: the mass ratio of recycled raw materials to ethylene glycol is 1:3.5; the mass ratio of recycled raw materials to butadiyl tin laurate is 100:0.5; the alcoholysis reaction temperature is 196°C, The pressure is 0.15MPa, the reaction time is 2h, and the intrinsic viscosity of the reaction liquid reaches 0.29dl/g. After the reaction is over, the reaction liquid is quickly hot filtered, and the filtrate is subjected to vacuum distillation to recover ethylene glycol. The liquid after vacuum distillation (solid at room temperature) is dissolved in hot alcohol, ester, chlorinated hydrocarbon, ketone and other solvents , Heat filtered to remove insolubles, and the filtrate is naturally cooled to obtain BHET and its oligomers. Add isophthalic acid (IPA), neopentyl glycol (NPG), antimony trioxide (Sb203) and cobalt acetate (Co(Ac) to the ethylene terephthalate (BHET) and its oligomers ) 2) Conduct polycondensation reaction with stabilizer trimethyl phosphate (TMP). The polycondensation reaction temperature of ethylene terephthalate (BHET) and its oligomers is 275°C, the vacuum degree is 95 Pa, and the reaction time is 3.5 h. The obtained low melting point polyester has a melting point of 115° C., a terminal carboxyl group content of 30 mmol/kg, and an intrinsic viscosity of 0.68 dL/g. The molar amount of isophthalic acid (IPA) is the mass of recycled raw material/450; the molar amount of neopentyl glycol (NPG) is the mass of recycled raw material/960; the molar ratio of alkyd is 1.4; the catalyst is antimony trioxide (Sb203) and cobalt acetate (Co(Ac)2) are 400 ppm of the total acid in the reaction system, and 0.01% by weight (relative acid content) stabilizer trimethyl phosphate (TMP) is added.

[0042] 2. The preparation of recycled polyester: the process flow of bottle flakes after cleaning, drum drying, multi-stage filtration, and liquid phase viscosity increase. Among them, the drum drying temperature is 100°C, and the drying time is 7 hours. The steps of liquid phase thickening are as follows: 1) The melt with intrinsic viscosity of 0.55dl/g at 270℃ after being melted by the screw is sent to the vacuum separation tower by the melt transfer pump. The melt is at a vacuum of 100pa and the temperature is The intrinsic viscosity can reach 0.68dl/g after staying at 280℃ for 30min; 2) After that, the melt enters the secondary conditioning and viscosity adjustment device, and the melt temperature and vacuum degree in the secondary conditioning and viscosity adjustment device and the vacuum separation tower Similarly, under the action of the rotary propeller, the melt continues to advance, and the melt viscosity continues to increase. The propeller's rotation speed is 5r/min, the residence time is 15min, and the final melt intrinsic viscosity is 0.78dl/g. The regenerated polyester has a melting point of 267°C, a terminal carboxyl group content of 16 mmol/kg, and an intrinsic viscosity of 0.78dl/g.

[0043] 3. Skin-core regenerated polyester staple fiber: the above-mentioned low-melting polyester and regenerated polyester are accurately metered into the composite spinneret with 6:4 sheath-core weight respectively, and the melt sprayed from the spinneret of the composite component , After cooling, winding, bundling, drawing, shaping, cutting and packaging, the core-type recycled polyester staple fiber can be obtained. The drying temperature of the recycled polyester raw material is 140°C, the drying time is 7h, and the screw temperature is 280°C; the low melting point polyester spinning pipe insulation temperature is 230°C, the recycled polyester spinning pipe insulation temperature is 270°C, and the spinning box body The temperature is 285℃; the cooling air temperature of the ring blowing is 22℃, the wind speed is 2.5m/s; the spinning speed is 900m/min; the draft ratio is 2.5, the draft temperature is 60℃, and the draft speed is 110m/min. The quality indicators of the sheath-core recycled polyester staple fiber obtained by the above production process are:

[0044] Linear density: 4.24 dtex

[0045] Breaking strength: 2.67 cN/dtex

[0046] Elongation at break: 47%

[0047] Cutting length: 50.8mm.