CN110734578A

CN110734578A - Method for separating and obtaining regenerated polyester from waste polyester raw materials

Info

Publication number: CN110734578A
Application number: CN201911107860.4A
Authority: CN
Inventors: 钱军; 马哲峰; 顾君; 郭学伟; 杜国强; 王秀华; 王勇
Original assignee: Ningbo Dafa Chemical Fiber Co Ltd
Current assignee: Ningbo Dafa New Material Co ltd
Priority date: 2019-11-13
Filing date: 2019-11-13
Publication date: 2020-01-31
Anticipated expiration: 2039-11-13
Also published as: CN110734578B

Abstract

The application belongs to the field of waste polyester recycling, and particularly relates to a method for separating waste polyester raw materials to obtain regenerated polyester, wherein the method for separating waste polyester raw materials to obtain regenerated polyester comprises the following steps of 1) preparing foam materials by recycling classified polyester, 2) carrying out melt granulation in a double-screw extruder, introducing a physical or chemical foaming agent in the granulation process, forming micro holes on the surfaces and in the waste polyester particles after passing through a cooling water tank to obtain waste polyester particles containing micropores, 3) separating the waste polyester particles containing the micropores by using a dissolving agent to separate out spandex and chinlon soluble impurities in the waste polyester particles, 4) carrying out depolymerization by using a proportion and ethylene glycol under the action of a catalyst to obtain high-purity waste polyester depolymerized liquid, and 5) finally sending the prepared depolymerized substance to a polycondensation kettle for pre-polycondensation, and carrying out final polycondensation to form a finished product.

Description

Method for separating and obtaining regenerated polyester from waste polyester raw materials

Technical Field

The application belongs to the field of waste polyester recycling, and particularly relates to a method for separating waste polyester raw materials to obtain regenerated polyester.

Background

Although is widely applied to the fields of textile clothing, decoration, food packaging and the like due to good physical and chemical stability, processability and the like, PET has extremely strong chemical inertness under natural conditions and is difficult to biodegrade, and a large amount of waste polyester causes huge pressure on the environment, so that waste polyester products are recycled, the effective recycling of resources is realized, the environmental pollution is reduced, and the method becomes an important subject of the polyester industry.

At present, the recycling of polyester waste materials mainly comprises a physical method and a chemical method. The physical method is mainly to make the waste polyester and the products thereof into regenerated chips through the processes of cutting, crushing, mixing, granulating and the like, and then reuse the regenerated chips, but the quality fluctuation of the regenerated chips is large, so that the preparation and the quality of the fibers are greatly influenced. The chemical method is mainly to depolymerize the waste polyester into raw materials or intermediates for producing the polyester by a chemical treatment method, such as a hydrolysis method, a methanol alcoholysis method, an ethylene glycol alcoholysis method and the like, and obtain high-quality raw material monomers by the procedures of purification, impurity removal and the like. At present, the pretreatment of materials before depolymerization mainly comprises the following steps: the waste silk and waste textile are cut or sheared and put into a depolymerization kettle, for example, the method of the 'pretreatment system of waste fiber and products' disclosed in the publication No. CN 105690600A. However, the bulk density of the waste is low, so that the waste is not easy to be soaked by a solvent, the liquid-solid ratio is increased, and the energy consumption and the material consumption are increased. In addition, waste silk and waste textile are made into foam materials by a friction granulation method, and then are put into a depolymerization kettle for depolymerization, for example, the method of 'recycling process of waste textile containing polyester' disclosed in the publication No. CN 105803585A. However, the rate of depolymerization is significantly reduced due to the larger size of the foam particles.

In addition, the Chinese invention patents (such as the publication numbers CN106283227A, CN106283226A, CN106279757A and the like) applied by Ningbo Dafa chemical fiber Limited company disclose methods for preparing high-quality melt by taking waste polyester textiles as raw materials, the method comprises the steps of adding alcohol with the mass of 1-8% of the raw materials into the raw materials, feeding the raw materials into a screw extruder for blending, melting and extruding, wherein the melt viscosity of the melt discharged from the screw extruder is 0.40-0.50 dl/g, then feeding the material into a thermal and viscosity adjusting device, and the melt viscosity of the melt discharged from the thermal and viscosity adjusting device is 0.620 dl/g-0.685 dl/g.

Therefore, how to overcome the above-mentioned problem that exists in the waste polyester depolymerization edulcoration process, realize effectively not only can effectively to waste polyester depolymerization product edulcoration purification, can ensure filter equipment can last stable operation again, and it is the key of this application to prepare high-quality regeneration polyester.

Disclosure of Invention

In order to solve the technical problems, the invention aims to provide a method for separating waste polyester raw materials to obtain regenerated polyester, wherein the method utilizes the waste polyester containing micropores prepared by a foaming technology to carry out high-efficiency depolymerization, then prepares high-quality regenerated polyester, and realizes high-valued recycling of the waste polyester.

In order to achieve the above object, the present application adopts the following technical solutions:

A method for separating and obtaining recycled polyester from waste polyester raw materials, which comprises the following steps:

1) sorting the recycled sorted polyester;

2) then carrying out melt granulation in a double-screw extruder, introducing a physical or chemical foaming agent in the granulation process, and forming micro holes on the surface and inside of the waste polyester granules after passing through a cooling water tank to obtain waste polyester granules containing micropores;

3) firstly, utilizing a dissolving agent to separate spandex and chinlon soluble impurities from the waste polyester granules containing micropores;

4) then depolymerizing the mixture and glycol in proportion under the action of a catalyst, and filtering to obtain high-purity waste polyester depolymerization liquid;

5) and finally, sending the prepared depolymerization product to a polycondensation kettle for pre-polycondensation, and performing final polycondensation to form a finished product.

Preferably, the recycled and classified polyester comprises or more of recycled polyester bottle chips, polyester pulp blocks, polyester fiber products and polyester waste filaments, wherein the polyester film or polyester fiber products are densified through a hot friction forming process to prepare foam materials, the temperature of the preferred hot friction forming process is 150-260 ℃, the pressure is 0.1-10 MPa, and the time is 5-15 min, and the polyester bottle chips or polyester pulp blocks are cleaned and dried.

Preferably, the average cell diameter of the waste polyester pellets of step 2) is 30 to 200 μm, and the relative density is 0.3 to 0.7.

Preferably, the physical foaming agent in the step 2) is or more of nitrogen, carbon dioxide, inert gas and the like, the chemical foaming agent is or more of foaming agent AC (azodicarbonamide), foaming agent DPT (N, N-dinitrosopentamethylenetetramine), foaming agent ABIN (azodiisobutyronitrile), foaming agent OBSH (4, 4-disulfonylhydrazonodiphenyl ether) and foaming agent NTA (N, N-dimethyl-N, N-diterephthalamide), and the foaming agent DPT is preferably selected.

Preferably, the temperature of the double-screw granulator is 220-320 ℃, the feeding percentage is 5-15%, the rotating speed of the screw is 40-80rpm, and the pressure is 70-100 Mpa; the gas introduction amount is 0.05-0.3L/min, and the ratio of the foaming agent to the waste polyester material is 1: 100-500.

Preferably, the twin-screw granulator is added with filtering devices before the die head, and the filtering devices are regulated to be 100-200 meshes.

Preferably, the dissolving agent in the step 3) is or a combination of a plurality of components selected from dimethylacetamide, N-N dimethylformamide, dimethyl sulfoxide, diethyl ether, xylene, N-butanol, formic acid, m-cresol, triethylene glycol, tetrahydrofuran, 1-ethyl-3-methylimidazole bromide salt, trifluoroethanol, benzenediol, o-dichlorobenzene, cyclohexanone, cyclopentanone, acetone and N-methylpyrrolidone, preferably N-N dimethylformamide, dimethyl sulfoxide and formic acid, the dissolving temperature is 20-180 ℃, and the dissolving time is 10-40 min.

Preferably, zinc acetate is preferably used as the depolymerization catalyst in the step 4).

Preferably, the depolymerization reaction in step 4) is carried out according to the ratio of the waste polyester repeating unit: putting the ethylene glycol into a depolymerization kettle according to the molar percentage of 1: 1-6, wherein the depolymerization kettle contains ethylene terephthalate and oligomers which account for 10-30% by mass of the total amount of the waste polyester, and a depolymerization catalyst is added; controlling the depolymerization reaction temperature to be 190-210 ℃, the reaction time to be 30 minutes-5 hours and the pressure to be 0.1-0.3 Mpa; multistage filtration is arranged between the polycondensation kettles of the depolymerization kettles, and the filtration precision is sequentially improved; obtain the depolymerization product containing the glycol terephthalate and the oligomer.

Preferably, the pre-polycondensation in the step 5) is performed by two steps, namely, condensation polymerization and condensation polymerization II, wherein the reaction temperature of condensation polymerization is 230-250 ℃, the vacuum degree is 5-30 KPa, the residence time is 1-3 hours, the reaction temperature of condensation polymerization II is 250-280 ℃, the vacuum degree is 1-5 KPa, the residence time is 1-3 hours, the final condensation polymerization reaction temperature is 275-290 ℃, the vacuum degree is 0.05-1 KPa, and the reaction time is 1-5 hours.

Preferably, the filtration is set to two stages, times of filtration is carried out after depolymerization is finished, and the first and second times of filtration are finished after pre-polycondensation, wherein the filtration precision is both 100-200 meshes, and the precision of the two times of filtration is sequentially improved.

Preferably, the polycondensation reaction needs to add a stabilizer in a pre-polycondensation stage, the stabilizer is triphenyl phosphate, triphenyl phosphite, trimethyl phosphate and the like, and triphenyl phosphate is preferred.

, carrying out precipitation adsorption treatment and magnetic fluid sedimentation treatment on the waste polyester depolymerization liquid obtained in the step 4) to obtain high-purity waste polyester depolymerization liquid, and introducing all contents of Chinese patent application numbers 2019110064695, 2019110065132 and 2019110065113 into the application.

[ l1] preferably, the precipitating agent for precipitation removal comprises the following components:

4-12 parts of nano calcium oxide

2-10 parts of diatomite

5-15 parts of nano aluminum oxide

1-6 parts of potassium hydroxide

2-10 parts of calcium carbonate

1-5 parts of hydroxyethyl cellulose sodium

2-10 parts of polyacrylamide.

As a further preference, the precipitant consists of:

6-8 parts of nano calcium oxide

3-5 parts of diatomite

8-10 parts of nano aluminum oxide

2-4 parts of potassium hydroxide

4-6 parts of calcium carbonate

2-3 parts of hydroxyethyl cellulose sodium

3-4 parts of polyacrylamide.

The application also discloses a preparation method of the precipitator, which comprises the steps of adding nano calcium oxide, diatomite, nano aluminum oxide, calcium carbonate, hydroxyethyl cellulose sodium and polyacrylamide into a grinder for grinding, sieving by a 100-mesh sieve, adding potassium hydroxide, mixing, adding into a stirring kettle for fully stirring at a stirring speed of 600 revolutions per minute for 50 minutes, and thus obtaining the precipitator.

improvement, the impurity removing method further comprises removing impurities by magnetic fluid adsorption, precipitating to remove impurities, adding the filtrate into the magnetic fluid impurity remover to make FeO magnetic fluid and the filtrate rotate and mix in the impurity remover, then disconnecting the magnetic base of the impurity remover to make it become permanent magnetic field, after 10-20 minutes, the magnetic particles deposit downwards to delaminate, filtering to remove nylon, spandex, delustering agent, titanium dioxide, etc., preferably, the FeO magnetic fluid is prepared by alcohol-water co-heating method, and according to Fe, the FeO magnetic fluid is prepared by alcohol-water co-heating method³⁺And Fe²⁺Fe in a molar ratio of 1-3:1₂(SO₄)₃Solution and FeSO₄Mixing the solutions, heating to 60-70 deg.C, maintaining constant temperature, adding NaOH solution dropwise, stirring thoroughly to adjust pH to 10-12, stirring and adding anhydrous ethanol, standing for 20-30 min, adjusting pH, increasing temperature, stirring rapidly and adding 0.4-0.8 times of Fe²⁺The coating was carried out with the amount of sodium oleate surfactant, and then the formation of black magnetic particles was observed.

The method has the advantages that 1) the contact surface of waste polyester granules containing micropores and ethylene glycol is increased, so that the depolymerization reaction rate is accelerated, the yield of depolymerized products is improved, the energy consumption and the production cost are reduced, 2) quantitative mother liquor is reserved in an alcoholysis kettle, the depolymerization efficiency can be improved, and the quality of depolymerized products can be stabilized, 3) the waste polyester granules containing micropores have high specific surface area, so that the dissolution of residual foaming agent and contained spandex and nylon is facilitated, 4) the depolymerization, the esterification and the polycondensation are carried out at lower reaction temperature, and a stabilizer is added, so that the generation of depolymerizable high polymers can be effectively reduced, and 5) the final polycondensation-formed finished product has the intrinsic viscosity of 0.60-0.70 dl/g, the melting point of 210-230 ℃, the ash content of less than or equal to 0.06%, and the number of aggregated particles of less than or equal to 1/mg.

Drawings

FIG. 1 is a graph showing the effects of the waste polyester granules containing fine pores prepared in example 1.

Detailed Description

Example 1

And cleaning and drying the recycled and classified Polyester (PET) bottle chips and Polyester (PET) pulp blocks, and then carrying out melt granulation in a double-screw extruder. Heating temperatures of all zones of the double-screw extruder are respectively 250 ℃, 260 ℃, 270 ℃, 280 ℃, 275 ℃, 270 ℃, feeding percentage of the screw is 15%, rotating speed is 50rpm, pressure is 3Mpa, foaming agent AC is selectively added to a micropore forming substance, the mass ratio of the foaming agent to the waste polyester is 1:200, the foaming agent is introduced into a fourth heating zone of the screw, and micropores are stably formed after granulation passes through a cooling water tank.

The waste polyester granules containing micropores prepared by the above-mentioned granulating step of microporous waste polyester have an average cell diameter of 85 μm and a relative density of 0.35. Average cell diameter test, the average of 100 average cell diameters was continuously measured as the diameter of the cells using an optical microscope. The method for testing the relative density of the microporous waste polyester refers to the GB1033-86 plastic density and relative density test method.

Putting the waste Polyester (PET) granules containing micropores into a dissolving agent containing N-N dimethylformamide and formic acid in a ratio of 1:1, heating to 120 ℃, fully soaking for 20min, performing solid-liquid separation, rinsing the waste Polyester (PET) granules containing micropores in a purified water cleaning pool, and finally drying at 150 ℃ to prepare the waste polyester granules containing micropores to be subjected to alcoholysis.

The prepared waste polyester (repeating unit) granules containing micropores and ethylene glycol are put into a depolymerization reaction kettle according to the proportion of 1:3 in mole percent, and depolymerization reaction is carried out for 1.5 hours at 196 ℃ under the catalysis of 0.2MPa and 0.2% w of zinc acetate, thus preparing the depolymerization product containing the ethylene glycol terephthalate. The prepared depolymerized liquid passes through a 100-mesh filtering device, and impurities and insoluble substances in the depolymerized liquid are filtered out primarily. Obtaining high-purity depolymerization liquid.

In the depolymerization solution after the depolymerization impurity removal step, the content of chinlon is less than 0.03 percent, the content of spandex is less than 0.05 percent, and the alcoholysis rate of PET is 99.2 percent.

Feeding the depolymerized liquid and a stabilizer after impurity removal into a pre-polycondensation kettle, starting two times of low-vacuum pre-polycondensation reaction under the condition of negative pressure, smoothly pumping pre-polycondensation from normal pressure to about 24Kpa absolute pressure, controlling the temperature at 270 ℃ and the reaction time at 30min, filtering by using a filter screen with the specification of 150 meshes after pre-polycondensation is completed, carrying out second pre-polycondensation reaction on the filtrate to reduce the reaction pressure to 4Kpa absolute pressure and the reaction temperature at 275 ℃ and the reaction time at 30min, then continuing to pump vacuum, carrying out high-vacuum stage polycondensation reaction to reduce the reaction pressure to 0.2Kpa absolute pressure and the reaction temperature at 285 ℃ and the reaction time at 3 h, and obtaining the high-quality regenerated polyester.

The prepared regenerated polyester has the intrinsic viscosity value of 0.61dl/g, the melting point of 244 ℃, the ash content of less than or equal to 0.05 percent and the number of agglomerated particles of less than or equal to 1/mg.

Example 2

The recycled and classified Polyester (PET) film and Polyester (PET) fiber products (curtains, carpets, clothes and the like) are densified by a hot friction forming process under the conditions of 220 ℃ of temperature, 3MPa of pressure and 10min of time to prepare the foam material. And then melting and granulating the foam material in a double-screw extruder. Heating temperatures of all zones of the double-screw extruder are 265 ℃, 270 ℃, 275 ℃, 280 ℃, 275 ℃, 270 ℃ and 270 ℃, feeding percentage of the screw is 30%, rotating speed of the screw is 65rpm, pressure is 6Mpa, foaming agent ABIN is selected as a micropore forming substance, the mass ratio of the foaming agent to the waste polyester is 1:250, the foaming agent is mixed in a fourth heating zone of the screw, and micropores are stably formed after the granulation is finished and pass through a cooling water tank.

The waste polyester pellets containing fine pores prepared by the above-mentioned fine pore waste polyester pelletizing step had an average cell diameter of 82 μm and a relative density of 0.55.

The prepared waste polyester (repeating unit) granules containing micropores and ethylene glycol are put into a depolymerization reaction kettle according to the proportion of 1:3 in mole percent, and depolymerization reaction is carried out for 1.5 hours at 196 ℃ under the catalysis of 0.2MPa and 0.2% w of zinc acetate, thus preparing the depolymerization product containing the ethylene glycol terephthalate. The prepared depolymerized liquid passes through a 100-mesh filtering device, and impurities and infusible matters in the depolymerized liquid are filtered out primarily. Obtaining high-purity depolymerization liquid.

In the depolymerization solution after the depolymerization impurity removal step, the content of the chinlon is less than 0.04 percent, the content of the spandex is less than 0.05 percent, and the alcoholysis rate of the PET is 99.2 percent.

The prepared regenerated polyester has the intrinsic viscosity value of 0.60dl/g, the melting point of 248 ℃, the ash content of less than or equal to 0.05 percent and the number of agglomerated particles of less than or equal to 1/mg.

Example 3

And cleaning and drying the recycled and classified Polyester (PET) bottle chips and Polyester (PET) pulp blocks, and then carrying out melt granulation in a double-screw extruder. Heating temperatures of all zones of the double-screw extruder are respectively 260 ℃, 270 ℃, 280 ℃, 285 ℃, 275 ℃, 270 ℃ and 270 ℃, screw feeding percentage is 45%, rotation speed is 45rpm, pressure is 75Mpa, screw feeding percentage is 45%, screw rotation speed is 65rpm, pressure is 8.5Mpa, foaming agent DPT and foaming agent ADC are selected as micropore forming substances, the ratio is 1:1, the mass ratio of the foaming agent to the waste polyester is 1:500, the foaming agent is mixed in a fourth heating zone of the screw in a feeding mode, and after granulation is finished, micropores are stably formed after passing through a cooling water tank.

The waste polyester pellets containing fine pores prepared by the above-mentioned fine pore waste polyester pelletizing step had an average cell diameter of 75 μm and a relative density of 0.68.

In the depolymerization solution after the depolymerization impurity removal step, the content of chinlon is less than 0.03 percent, the content of spandex is less than 0.05 percent, and the alcoholysis rate of PET is 99.5 percent.

The prepared regenerated polyester has the intrinsic viscosity value of 0.62dl/g, the melting point of 249 ℃, the ash content of less than or equal to 0.05 percent and the number of agglomerated particles of less than or equal to 1/mg.

Example 4

Adding recycled Polyester (PET) bottle flakes, Polyester (PET) slurry blocks and the like into a screw granulator, introducing nitrogen to perform melt granulation, wherein the heating temperature of each zone of the screw granulator is 250 ℃, 260 ℃, 270 ℃, 280 ℃, 275 ℃, 270 ℃, the screw feeding percentage is 15%, the rotating speed is 45rpm, the pressure is 75Mpa, the gas introduction amount is 0.1L/min, the filtration specification is 100 meshes, introducing nitrogen is selected for micropore formation, the gas introduction amount is 0.1L/min, the introduction position is a fourth heating zone of the screw, and the extruded material belt passes through a cooling water tank, is subjected to micropore formation stability, and is finally cut into granules.

The waste polyester pellets containing fine pores prepared by the above waste polyester granulation step had an average cell diameter of 115 μm and a relative density of 0.70.

In the depolymerization solution after the depolymerization impurity removal step, the content of chinlon is less than 0.03 percent, the content of spandex is less than 0.05 percent, and the alcoholysis rate of PET is 99.4 percent.

The prepared regenerated polyester has the intrinsic viscosity value of 0.62dl/g, the melting point of 253 ℃, the ash content of less than or equal to 0.04 percent and the number of agglomerated particles of less than or equal to 1/mg.

Example 5

The recycled and classified Polyester (PET) film and Polyester (PET) fiber products (curtains, carpets, clothes and the like) are densified by a hot friction forming process under the conditions of 220 ℃ of temperature, 3MPa of pressure and 10min of time to prepare foam materials, and then the foam materials are melted and granulated in a double-screw extruder. The heating temperature of each zone of the double-screw extruder is 265 ℃, 270 ℃, 275 ℃, 280 ℃, 275 ℃, 270 ℃ and 270 ℃, the screw feeding percentage is 30 percent, the screw rotating speed is 60rpm, the pressure is 4.5Mpa, and the specification of the filtering device is 200 meshes. Selective introduction of CO for micropore formation₂The gas introduction amount is 0.3L/min, the introduction position is a fourth heating area of the screw, and the micropore forming is stable after the granulation is finished and passes through the cooling water tank.

The waste polyester granules containing micropores prepared by the above-mentioned granulating step of microporous waste polyester have cells of 110 μm and a relative density of 0.68.

In the depolymerization solution after the depolymerization impurity removal step, the content of the chinlon is less than 0.04 percent, the content of the spandex is less than 0.05 percent, and the alcoholysis rate of the PET is 99.3 percent.

The prepared regenerated polyester has the intrinsic viscosity value of 0.62dl/g, the melting point of 255 ℃, the ash content of less than or equal to 0.03 percent and the number of agglomerated particles of less than or equal to 1/mg.

Example 6

And cleaning and drying the recycled and classified Polyester (PET) bottle chips and Polyester (PET) pulp blocks, and then carrying out melt granulation in a double-screw extruder. The heating temperature of each zone of the double-screw extruder is 260 ℃, 270 ℃, 280 ℃, 285 ℃, 275 ℃, 270 ℃ and 270 ℃, the screw feeding percentage is 45 percent, the rotating speed is 80rpm, the pressure is 75Mpa, the screw feeding percentage is 12 percent, the rotating speed is 65rpm, the pressure is 7.5Mpa, and the specification of the filtering device is 100 meshes. Selective introduction of N into the pore former₂：CO₂The mixed gas is 1:1, the gas is introduced into the fourth heating zone of the screw in a way of introducing the mixed gas with the gas at the introduction amount of 0.5L/min, and the mixed gas passes through a cooling water tank after granulation is finished and then is stably formed by micropores.

The waste polyester pellets containing fine pores prepared by the above-mentioned fine pore waste polyester pelletizing step had an average cell diameter of 113 μm and a relative density of 0.60. Average cell diameter test, the average of 100 average cell diameters was continuously measured as the diameter of the cells using an optical microscope. The method for testing the relative density of the microporous waste polyester refers to the GB1033-86 plastic density and relative density test method.

The prepared regenerated polyester has the intrinsic viscosity value of 0.63dl/g, the melting point of 246 ℃, the ash content of less than or equal to 0.03 percent and the number of agglomerated particles of less than or equal to 1/mg.

Comparative example 1

The recycled and classified Polyester (PET) bottle chips and Polyester (PET) pulp blocks are washed and dried, and then are subjected to melt granulation in a screw extruder. The heating temperature of each zone of the double-screw extruder is respectively 250 ℃, 260 ℃, 270 ℃, 280 ℃, 275 ℃, 270 ℃, the screw feeding percentage is 20 percent, the rotating speed is 50rpm, the pressure is 5.5Mpa, and the specification of the filtering device is 200 meshes. The extruded material belt passes through a cooling water tank and is cut into granules.

The relative density of the waste polyester pellets prepared through the above waste polyester granulation step was 1.27.

The dissolving agent is selected from N-N dimethylformamide and formic acid according to the ratio of 1:1, the dipping time is controlled to be 30min, the dipping temperature is 110 ℃, the waste polyester (repeating unit) and ethylene glycol are in a molar percentage of 1:3, the depolymerization reaction temperature is 200 ℃, the pressure is 0.2MPa, and the depolymerization time is 2.5 hours, so that the final depolymerized liquid contains 0.10% of chinlon, 0.08% of spandex and 98.2% of PET alcoholysis rate.

The prepared regenerated polyester has the intrinsic viscosity value of 0.60dl/g, the melting point of 248 ℃, the ash content of less than or equal to 0.15 percent and the number of agglomerated particles of less than or equal to 5/mg.

The foregoing is a description of embodiments of the present application which will enable one skilled in the art to make or use the present application, and many modifications of these embodiments will be apparent to those skilled in the art the general principles of defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application.

Claims

The method for separating and obtaining the recycled polyester from the waste polyester raw material of types is characterized by comprising the following steps:

1) sorting the recycled sorted polyester;

2) then carrying out melt granulation in a double-screw extruder, introducing a physical or chemical foaming agent in the granulation process, and forming micro holes on the surface and inside of the waste polyester granules after passing through a cooling water tank to obtain waste polyester granules containing micropores;

3) firstly, utilizing a dissolving agent to separate spandex and chinlon soluble impurities from the waste polyester granules containing micropores;

4) then depolymerizing the mixture and glycol in proportion under the action of a catalyst, and filtering to obtain high-purity waste polyester depolymerization liquid;

5) and finally, sending the prepared depolymerization product to a polycondensation kettle for pre-polycondensation, and performing final polycondensation to form a finished product.
2. The method for separating and obtaining the recycled polyester from waste polyester raw materials according to claim 1, wherein the recycled and classified polyester comprises or more of recycled polyester bottle chips, polyester pulp blocks, polyester fiber products and polyester waste filaments, wherein the polyester film or polyester fiber products are firstly densified to form foam through a thermal friction forming process, the temperature of the preferred thermal friction forming process is 150-260 ℃, the pressure is 0.1-10 MPa, and the time is 5-15 min, and the polyester bottle chips or polyester pulp blocks are cleaned and dried.
3. The method for separating and obtaining recycled polyester from waste polyester raw materials, as claimed in claim 1, wherein the average cell diameter of the waste polyester pellets in step 2) is 30-200 μm and the relative density is 0.3-0.7.
4. The method for separating and obtaining recycled polyester from waste polyester raw materials according to claim 1, wherein in step 2), the physical foaming agent in step 2) is or more of nitrogen, carbon dioxide and inert gas, the chemical foaming agent is or more of foaming agent AC, foaming agent DPT, foaming agent ABIN, foaming agent OBSH and foaming agent NTA, the twin-screw extruder temperature is 220-.
5. The method for separating and obtaining recycled polyester from waste polyester raw materials, as claimed in claim 1, wherein the twin-screw pelletizer has filtering devices before the die head, and the filtering devices are regulated to 100-200 mesh.
6. The method for separating and obtaining the regenerated polyester from waste polyester raw materials according to claim 1, wherein the dissolving agent in step 3) is a combination of or more of dimethylacetamide, N-N dimethylformamide, dimethyl sulfoxide, diethyl ether, xylene, N-butanol, formic acid, m-cresol, triethylene glycol, tetrahydrofuran, 1-ethyl-3-methylimidazolium bromide, trifluoroethanol, benzenediol, o-dichlorobenzene, cyclohexanone, cyclopentanone, acetone, and N-methylpyrrolidone, preferably N-N dimethylformamide, dimethyl sulfoxide, and formic acid, preferably the dissolving temperature is 20-180 ℃ and the dissolving time is 10-40 min.
7. The method for separating and obtaining the regenerated polyester from waste polyester raw materials according to claim 1, wherein the depolymerization catalyst of step 4) is preferably zinc acetate.
8. The method for separating and obtaining the regenerated polyester from waste polyester raw materials according to claim 1, wherein the depolymerization reaction of step 4) is carried out by feeding the waste polyester repeating units and ethylene glycol into a depolymerization kettle in a molar percentage of 1: 1-6, wherein the depolymerization kettle contains ethylene terephthalate and oligomers in an amount of 10-30% by mass of the total amount of the waste polyester, and adding a depolymerization catalyst, the depolymerization reaction temperature is controlled at 190-210 ℃, the reaction time is controlled at 30 min-5 h, and the pressure is controlled at 0.1-0.3MPa, multistage filtration is arranged between the polycondensation kettles of the depolymerization kettle, and the filtration precision is sequentially improved, thereby obtaining the depolymerization product containing ethylene terephthalate and oligomers.
9. The method for separating and obtaining the recycled polyester from waste polyester raw materials according to claim 1, wherein the precondensation in step 5) comprises condensation and polycondensation two, the reaction temperature of the polycondensation is 230-250 ℃, the vacuum degree is 5-30 KPa, the residence time is 1-3 hours, the reaction temperature of the polycondensation two is 250-280 ℃, the vacuum degree is 1-5 KPa, the residence time is 1-3 hours, the reaction temperature of the final polycondensation is 275-290 ℃, the vacuum degree is 0.05-1 KPa, and the reaction time is 1-5 hours.
10. The method for separating and obtaining recycled polyester from waste polyester raw materials as claimed in claim 1, wherein the filtration is set in two stages, the filtration is performed after the depolymerization is completed, the second filtration is performed after the pre-polycondensation, the filtration precision is all 100-200 meshes, and the two precisions are sequentially improved.