Spandex and recycling method which can be recycled together with aromatic polyester fibers

Abstract

The present application provides a spandex which can be co-recycled with aromatic polyester fibers and a recycling method, the spandex contains a specific aromatic group-polyether block structure in the soft segment of the molecular structure, while ensuring the mechanical properties of the spandex, the aromatic group in the soft segment can be co-chemically recycled with the aromatic polyester fibers into terephthalic acid (PTA) or dimethyl terephthalate (DMT), the fabric made of the spandex and the aromatic polyester fibers can omit the fiber separation step and directly undergo chemical recycling, thus simplifying the recycling steps of the polyester fabric and improving the recycling efficiency and the recycling rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of chemical fiber recycling, and particularly relates to a spandex capable of being recycled together with aromatic polyester fiber and a recycling method. BACKGROUND

[0002] China is a large country of textile consumption, and a large amount of waste textiles are produced in social production and life every year. Polyester fiber fabrics made of various aromatic polyester polymers account for a large proportion, and the non-degradable polyester fiber fabrics cause an environmental problem that cannot be ignored. In addition, the aromatic polyester polymer as a raw material of polyester fiber is a recyclable material. However, the waste polyester fiber fabric is often blended with cotton, spandex and other types of fibers, and the polyester fiber is difficult to separate from the waste polyester fiber fabric, which makes recycling difficult and causes a large amount of resource waste.

[0003] The recycling of polyester materials can adopt physical recycling or chemical recycling. The physical recycling is to melt and granulate the recycled polyester materials after sorting and cleaning to obtain polyester particles. However, this method has a high requirement for the quality of the recycled materials. The waste polyester fiber fabric is often dyed and blended with other fibers, which causes difficulty in sorting. In addition, the dye in the polyester fiber has an influence on the performance of the recycled materials. Therefore, the waste polyester fiber fabric is difficult to be recycled by the method of melting and granulation. The chemical recycling is to recycle the benzene ring structure in the polyester molecule into PTA (terephthalic acid) or DMT (dimethyl terephthalate) by a chemical method, and the PTA or DMT is reused as a chemical raw material. However, other fibers such as cotton and spandex in the polyester fiber fabric still need to be separated in advance, which increases the process steps and reduces the recycling efficiency. SUMMARY

[0004] To solve the above problems, the present application provides a spandex capable of being recycled together with aromatic polyester fiber and a recycling method. The fabric made of the spandex and the aromatic polyester fiber can be recycled together by a chemical method, which saves the sorting step and improves the recycling efficiency and the recycling rate of the polyester fiber fabric. In the following, if no special description is given, the polyester fiber is the polyester fiber made of aromatic polyester polymer, and the specific scheme is as follows.

[0005] A spandex capable of being recycled together with aromatic polyester fiber, characterized in that the soft segment of the molecular structure of the spandex comprises a repeating unit represented by the following formula (1):

[0006]

[0007] wherein R1 is at least one of an aromatic ring and an aromatic heterocycle, and the mass content of R1 in the repeating unit is 4.5% to 44%; R2 is at least one of saturated alkane groups with a carbon atom number of 2 to 5; and x is 2 to 20.

[0008] The soft segment accounts for 80-97% of the polymer mass in the polymer molecules of the spandex, and the mass of the repeating unit represented by formula (1) accounts for more than 50% of the mass of the soft segment.

[0009] Optionally, R2 is at least two kinds of saturated alkane groups with 2-5 carbon atoms.

[0010] Optionally, R2 is preferably a saturated alkane group with 2 carbon atoms.

[0011] Optionally, R1 is a benzene ring.

[0012] Optionally, x in formula (1) is 3-10.

[0013] The application also provides a recycling method of a fabric made of the above-mentioned spandex and aromatic polyester fibers.

[0014] The recycling method mainly comprises the following steps:

[0015] Step one: crushing the fabric;

[0016] Step two: recycling the fabric into PAT or DMT by a chemical method.

[0017] Specifically, the chemical method for recycling the fabric in step two can adopt the following two methods, and the specific steps are as follows:

[0018] Method one:

[0019] Step 1): add 4 times the mass of the fabric of ammonia to the crushed fabric, and place it in a high-temperature and high-pressure reaction kettle, and react at 160℃ for 8h;

[0020] Step 2): reduce the temperature of the reaction product obtained in step 1) to below 35℃, filter, and filter out the polyether glycol component precipitated; then transfer it into a reduced pressure distillation device, and perform reduced pressure distillation, and recover the ammonia distilled out, and distill until the pH of the remaining solution in the device is reduced to below 7.5;

[0021] Step 3): add hydrochloric acid to the remaining solution to reduce the pH of the solution to below 5, and then perform reduced pressure distillation to collect the small molecular diol fraction;

[0022] Step 4): crude PTA is precipitated in the bottom liquid after distillation, and high-purity PTA is obtained after hot water recrystallization and drying.

[0023] Method two:

[0024] Step A): add 4 times the mass of the fabric of ethylene glycol to the crushed fabric, and add zinc acetate as a catalyst, and perform alcoholysis at 190-200℃ under reflux conditions for 5h;

[0025] Step B) distilling the system obtained in Step A) until 90% of the diol is distilled off, and stopping the distillation and lowering the temperature of the material to below 64℃;

[0026] Step C) adding methanol to the system obtained in Step B) and adding sodium methoxide as a catalyst, maintaining the temperature below 64℃, and reacting for 5h;

[0027] Step D) removing the residual ethylene glycol, methanol and amine substances by atmospheric distillation;

[0028] Step E) removing the zinc acetate and sodium methoxide by high-temperature ion exchange, and then purifying the DMT from the remaining system by vacuum distillation to obtain high-purity DMT.

[0029] Advantages:

[0030] The present application provides a spandex which can be co-recycled with aromatic polyester fibers, the soft segment of the molecular structure of the spandex contains an ester group connected aromatic group-polyether block structure, so it can participate in the alcoholysis or alkaline decomposition polyester recycling process, co-recycling to obtain PTA or DMT containing aromatic ring, the fabric made of the spandex and aromatic polyester fibers can omit the fiber separation step and directly undergo chemical recycling, simplifying the recycling steps of polyester fabric and improving the recycling efficiency and recovery rate. DETAILED DESCRIPTION

[0031] The existing chemical method of polyester fiber recycling needs to separate other fibers in the polyester fiber fabric first, and then recycle the aromatic ring group in the polyester through alcoholysis or alkaline decomposition. The separation of other fibers in this route is difficult, which affects the recycling efficiency of polyester fibers and further affects the recovery rate of polyester fibers. Most of the polyester fibers on the market are polyester fibers made of aromatic polyester polymers. Therefore, the present application provides a spandex which can be co-recycled with aromatic polyester fibers, the fabric made of the spandex and aromatic polyester fibers can be co-recycled by chemical method, which omits the fiber separation step and improves the recycling efficiency of polyester fibers. The specific scheme is as follows:

[0032] A spandex which can be co-recycled with aromatic polyester fibers, characterized in that the soft segment of the molecular structure of the spandex contains the following formula (1) repeating unit:

[0033]

[0034] wherein R1 is at least one of aromatic ring and aromatic heterocycle, and the mass content of R1 in the repeating unit is 4.5%-44%; R2 is at least one of saturated alkane groups with carbon atom number of 2-5; x is 2-20;

[0035] The soft segment in the polymer molecule of the spandex accounts for 80-97% of the mass of the polymer, and the mass of the repeating unit represented by formula (1) accounts for more than 50% of the mass of the soft segment.

[0036] For the sake of description, the aromatic ring or heteroaromatic ring represented by R1 is collectively referred to as an aromatic group hereinafter.

[0037] In the repeating unit structure represented by formula (1) above, the polyether structure is arranged in an interval with the aromatic group, and the spandex with the above structure as the soft segment of the molecular chain has excellent elastic recovery rate, elongation at break and elastic modulus, while being able to achieve mechanical properties comparable to conventional polyester-based spandex or polyether-based spandex, the aromatic diester structure is introduced into the molecular structure of the spandex, so that the chemical structure of the spandex can participate in alcoholysis or alkaline decomposition reaction, and participate in the process route of recycling PTA or DMT of aromatic polyester fibers.

[0038] In formula (1) above, when the content of the aromatic group R1 is too high, the molecular rigidity of the finally prepared spandex will be too large, which will affect the elongation at break of the spandex; and when the content of the aromatic group R1 is too low, it will adversely affect the modulus and permanent set of the spandex, therefore, in the present application, the mass content of R1 in the repeating unit is preferably 4.5%-44%. In the present application, in order to make the spandex participate in the recycling of polyester fibers, since the aromatic ring group in common polyester fibers is usually a benzene ring (such as PET, PPT, PBT, PBAT, etc. containing terephthalate structure polyester) or a furan ring (such as PEF, etc. containing furan dimethyl ester structure polyester), therefore, in the present application, R1 is preferably a benzene ring or a furan ring, and most preferably R1 is a benzene ring.

[0039] In the soft segment structure of the spandex molecular structure, in addition to the aromatic group-polyether block structure described above, there are also reaction product groups of isocyanate components and alcohol hydroxyl components, and in addition, there may be some modified structures such as aliphatic structures, but in order to ensure the resilience of the spandex, the repeating unit structure of formula (1) above is an important structure in the soft segment of the spandex, therefore, the mass of formula (1) above in the soft segment should be more than 50%, and in a preferred embodiment, the mass percentage of the repeating unit represented by formula (1) in the soft segment is greater than 70%.

[0040] In the structure of formula (1) above, (R2-O) xThe structure actually represents a polyether segment, wherein x represents the polymerization degree of the (R2-O) structure, the polymerization degree x of the polyether segment is preferably 2-20, more preferably 3-10, and the molecular weight of the polyether segment can be 100-1000, preferably 300-1000, more preferably 600-900. In fact, only when the polymerization degree and the number average molecular weight of the polyether segment are in the above range, the structure in which the polyether structure and the aromatic group structure are arranged at intervals can be used as the soft segment structure of the spandex, and the mechanical properties such as the elastic modulus, the elastic recovery rate and the elongation at break of the spandex can meet the requirements. The length of the polyether segment also affects the mass ratio of the above R1 group in the repeating unit of formula (1).

[0041] In the polyether segment, R2 is preferably a saturated alkane group with 2-5 carbon atoms. The smaller the number of carbon atoms in R2, the greater the density of ether oxygen bonds, which can enhance the interaction between the soft segment and the hard segment in the spandex molecule, thereby increasing the tensile modulus and the recovery modulus, but is not conducive to elongation. Correspondingly, the more the number of carbon atoms between the ether oxygen bonds, the weaker the interaction between the soft segment and the hard segment of the polyurethane, and the greater the elongation of the obtained spandex. The polyether segment with 2-3 carbon atoms in the monomer R2 is usually derived from polyethylene glycol and polypropylene glycol. Compared with polytetrahydrofuran with 4 carbon atoms, the polyether segment with 2-3 carbon atoms has a lower cost, and therefore, in actual production, the number of carbon atoms in R2 is preferably 2 or 3; or a polyether segment formed by copolymerization of monomers with different carbon atom numbers is preferably used, which can reduce the cost and adjust the performance, i.e. the polyether segment can be a structure in which saturated alkane groups with 2, 3 or 4 carbon atoms are arranged at intervals through ether oxygen bonds. Specifically, the polyether segment can be a mixture of at least two of polytetrahydrofuran, polypropylene glycol and polyethylene glycol, or a segment of a copolymer diol obtained by reacting at least two of tetrahydrofuran, ethylene oxide, propylene oxide, 2-methyltetrahydrofuran or 3-methyltetrahydrofuran, and the polyether segment is preferably a segment of a copolymer diol obtained by reacting tetrahydrofuran with at least one of ethylene oxide, propylene oxide, 2-methyltetrahydrofuran or 3-methyltetrahydrofuran.

[0042] In the molecular structure of the spandex described in the present application, the soft segment accounts for 80%-97% of the mass of the polymer. If the mass ratio of the soft segment in the polymer is too high, the breaking strength of the spandex will be too low, and the mechanical properties will be poor; if the mass ratio of the soft segment in the polymer is too low, the elongation of the spandex will be insufficient, and the stress will be large.

[0043] The spandex that can be co-recycled with the aromatic polyester fiber described in the present application can be prepared in the following manner:

[0044] The polyether ester polyol containing the structure of formula (1) described above is used as the soft segment raw material of the spandex, and is reacted with diisocyanate and a chain extender to prepare the spandex containing the structure of formula (1) described above by dry spinning, wet spinning or melt spinning.

[0045] wherein the above polyether ester polyol comprising the structure of formula (1) should satisfy the following characteristics:

[0046] The polyether ester polyol comprises the repeating unit shown in formula (1) and a terminal alcohol hydroxyl group:

[0047]

[0048] wherein R1 is at least one of an aromatic ring and an aromatic heterocyclic ring, and the mass content of R1 in the repeating unit is 4.5% to 44%; R2 is at least one of saturated alkane groups with carbon atom number of 2 to 5; x is 2 to 20, preferably 3 to 10;

[0049] The mass percentage of the repeating unit shown in formula (1) in the polyether ester polyol is greater than 75%;

[0050] The average functionality of the terminal alcohol hydroxyl group is 1.95 to 2.00;

[0051] The number average molecular weight of the polyether ester polyol is 1000 to 5000, preferably 1000 to 3500, more preferably 1400 to 2500, and most preferably 1500 to 2300.

[0052] The number average molecular weight of the polyether ester polyol described above should be 800 to 5000, preferably 1000 to 3500, more preferably 1400 to 2500, and most preferably 1500 to 2300. The larger the number average molecular weight of the polyether ester polyol, the larger its viscosity, and it is difficult to perform continuous operation on an industrial scale. However, if the molecular weight of the polyether ester polyol is too small, when the molecular weight of the polyurethane prepolymer is required to be consistent, more diisocyanate needs to be involved in the synthesis, resulting in a higher content of urethane groups in the prepolymer, thus the interaction between the prepolymer molecules is enhanced, the viscosity is also increased, and at the same time, the length of the soft segment in the formed polyurethane is shorter, which will affect the recovery performance of the final polyurethane fiber.

[0053] The average functionality of the terminal alcohol hydroxyl group in the polyether ester polyol described above can be 1.95 to 2.00, preferably 1.96 to 2.00, and more preferably 1.98 to 2.00, which can ensure that the polyether ester polyol can be smoothly terminated by isocyanate and then chain-extended by a small molecule amine or alcohol. The "average functionality" represents the average number of moles of alcohol hydroxyl groups per mole of polyether ester polyol that can participate in the reaction. In the present application, considering the dehydration of the terminal hydroxyl groups of the polyether diol to form double bonds, and the presence of unreacted carboxyl groups, the average functionality of the alcohol hydroxyl group can be calculated as follows:

[0054] Functionality = 2 * alcohol hydroxyl group moles / (alcohol hydroxyl group moles + carboxyl group moles + double bond moles)

[0055] The polyether ester polyols can be prepared by condensation reaction or transesterification reaction of aromatic diacid, ester or anhydride thereof with polyether diol.

[0056] The application also provides a recycling method of fabric made of the above-mentioned spandex and aromatic polyester fiber, wherein the aromatic groups in the polymer soft segment structure of the spandex and the aromatic groups in the polyester fiber are both benzene rings, and the specific method is as follows:

[0057] A recycling method of fabric made of the above-mentioned spandex and aromatic polyester fiber, comprising the following steps:

[0058] Step 1): crushing the fabric;

[0059] The fabric is made of the spandex and the aromatic polyester fiber according to the application, and the fabric can also contain other components that can participate in polyester chemical recycling, but preferably the point fabric is made of only the spandex and the aromatic polyester fiber according to the application. Among them, the aromatic polyester fiber is a polyester fiber containing aromatic groups in the molecular structure, preferably one or more of PET (polyethylene terephthalate) fiber, PPT (polytrimethylene terephthalate) fiber, PBT (polybutylene terephthalate) fiber, and PBAT (polybutylene adipate / terephthalate) fiber. To accelerate the reaction speed in the recycling process, the fabric should be crushed first, and to reduce the impact of stains on the surface of the fabric on the reaction, the stains on the surface of the fabric should be removed in advance.

[0060] Step 2): adding ammonia water not less than 4 times the mass of the fabric, placing it in a high-temperature and high-pressure reaction kettle, and reacting at 160℃ for 8h;

[0061] The ammonia water is used to hydrolyze the polyester fiber and the spandex, and the ammonia water reacts with the polyester fiber to obtain small molecular diols and ammonium terephthalate, and the ammonia water reacts with the spandex to obtain ammonium terephthalate, polyether diol, MDI derivative, small molecular amine and other by-products. In order to make the reaction fully proceed, the ammonia water should be excessive, and in the application, the addition amount of the ammonia water is preferably not less than 4 times the mass of the fabric, and the concentration of the ammonia water is 25%-28%, preferably 25%.

[0062] Step 3): reducing the temperature of the reaction product obtained in step 2) to below 35℃, filtering, and filtering out the precipitated polyether diol component; transferring into a reduced pressure distillation device, and performing reduced pressure distillation and recovering the distilled ammonia water, and distilling until the pH of the remaining solution in the device is reduced to below 7.5;

[0063] Since the boiling point of ammonia in ammonia water is low, the reaction product is first cooled to below 35°C, and distilled at low temperature, so that the excess ammonia water can be recovered and used for the decomposition of polyester. At the same time, since the melting point of the polyether glycol component is usually higher than 35°C, the precipitated polyether glycol component can be filtered out after cooling. Since the ammonia water itself is alkaline, when the pH of the remaining solution in the distillation device is reduced to below 7.5 or is neutral, it means that the excess ammonia water has been completely distilled and recovered. Among them, the pH can be detected in real time by an online pH detector.

[0064] Step 4) The remaining solution is added with hydrochloric acid to reduce the pH of the solution to below 5, and then distilled under reduced pressure to collect the small molecule diol fraction;

[0065] The system obtained in step 3) is added with hydrochloric acid to make the system acidic, and the terephthalate in the system combines with hydrogen ions to form PTA. Then the system is distilled to separate the small molecule polyol obtained by reaction from the system.

[0066] Step 5) The crude PTA is precipitated from the bottom liquid after distillation, and high-purity PTA is obtained after hot water recrystallization and drying.

[0067] The polyether component in the system has been filtered out in step 3), and the small molecule diol is also distilled out in step 4), and the remaining components in the system include ammonium chloride, PTA, MDI derivatives, etc. Among them, PTA has poor solubility, and the remaining components have good solubility under acidic conditions. Therefore, as the ethylene glycol and water in the system decrease during the distillation process, PTA will first precipitate from the system, and after filtration, crude PTA is obtained. High-purity PTA that can be used for polyester synthesis is recovered after hot water recrystallization and drying of the crude PTA. The purity of the high-purity PTA is more than 99%.

[0068] Method two:

[0069] A method for recycling a fabric made of the above spandex and aromatic polyester fiber, comprising the following steps:

[0070] Step A) crushing the fabric;

[0071] The fabric is made of spandex and aromatic polyester fiber according to the present application, and other components that can participate in polyester chemical recycling can also be included in the fabric, but preferably the fabric is made of only spandex and aromatic polyester fiber according to the present application. Among them, the aromatic polyester fiber is a polyester fiber containing aromatic groups in the molecular structure, preferably one or more of PET (polyethylene terephthalate) fiber, PPT (polytrimethylene terephthalate) fiber, PBT (polybutylene terephthalate) fiber, and PBAT (polybutylene adipate / terephthalate) fiber. To accelerate the reaction speed in the recycling process, the fabric should be first crushed, and to reduce the impact of stains on the surface of the fabric on the reaction during the reaction, the stains on the surface of the fabric should be removed in advance.

[0072] Step B) glycolysis is carried out at 190-200°C under reflux conditions by adding 4 times the mass of the fabric of ethylene glycol and adding zinc acetate as a catalyst, and the reaction is carried out for 5h;

[0073] Ethylene glycol is used for alcoholysis of aromatic polyester fiber and spandex, and ethylene glycol reacts with polyester to obtain BHET (bis-hydroxyethyl terephthalate) and small molecule diol byproducts such as ethylene glycol, propylene glycol, and butanediol, and ethylene glycol can also react with the ester bond in the soft segment of the spandex molecule to obtain BHET (bis-hydroxyethyl terephthalate) and byproducts such as polyether glycol, amine, and MDI derivatives. Preferably, 4 times the mass of the polyester fiber of ethylene glycol is added, and increasing the amount of ethylene glycol is beneficial to the yield of BHET, and will also reduce the amount of multimers formed by BHET in the alcoholysis product, which is beneficial to the subsequent process. The reflux condition means that the evaporated ethylene glycol is cooled and then falls back into the reaction system. Because the reaction temperature is too high, ethylene glycol is easily volatilized, and the reflux condition can avoid the decrease in the amount of ethylene glycol in the actual reaction system caused by excessive volatilization of ethylene glycol. The alcoholysis temperature in the present application is preferably 196°C.

[0074] Step C) distillation is carried out on the system obtained in step B), and when the amount of diol distilled reaches 90% of the theoretical value, the distillation is stopped, and the temperature of the material is reduced to below 64°C;

[0075] In this step, distillation can distill the ethylene glycol obtained by alcoholysis, small molecule diols such as butanediol, and amine substances. The theoretical value refers to the total amount of diol in the system minus the amount of ethylene glycol required to convert terephthalic acid into BHET. Generally, when the distillation head temperature begins to drop to 70°C, it can be considered that the small molecule diols have been distilled out to a small amount, reaching 90% of the theoretical value. Because methanol needs to be added in the next step for continuous reaction, the temperature should be reduced to below 64°C. The temperature here is not strictly required to be below the boiling point of methanol.

[0076] Step D) methanol is added to the system obtained in step C), and sodium methoxide is added as a catalyst, the temperature is maintained below 64°C, and the reaction is carried out for 5h;

[0077] The ester exchange reaction is carried out with excess methanol and BHET to obtain DMT and ethylene glycol.

[0078] Step E) removing residual ethylene glycol, methanol and amine substances by atmospheric distillation;

[0079] In step D) above, the excess methanol can be removed by distillation, because the boiling point of DMT is higher than that of methanol and ethylene glycol, and the ethylene glycol, methanol and amine substances in DMT can be removed.

[0080] Step F) removing zinc acetate and sodium methoxide by high-temperature ion exchange, and then purifying DMT from the remaining system by vacuum distillation to obtain high-purity DMT.

[0081] The system after the reaction still contains residual products of spandex after the reaction, so it is necessary to purify DMT. The obtained DMT is removed from the remaining system by high-temperature ion exchange to remove zinc acetate and sodium methoxide, and then purified by vacuum distillation to separate from the residual products of spandex alcoholysis, to obtain high-purity DMT with a purity higher than 99%.

[0082] The present application is described in more detail by way of examples, in which the test methods of the parameters involved are as follows:

[0083] 1. Average functionality:

[0084] Functionality = 2 * moles of alcohol hydroxyl groups / (moles of alcohol hydroxyl groups + moles of carboxyl groups + moles of double bonds).

[0085] The acid value is measured by the method described in HG / T 2708-1995, the hydroxyl value is measured by the method described in HG / T 2709 / 1995, and the unsaturation is measured by the method described in GB / T 12008.6-2010. The corresponding acid value, hydroxyl value and unsaturation are converted into the number of moles of the corresponding end groups in the polyether ester diol.

[0086] 2. Tensile 300% stress, breaking strength and breaking elongation: all according to the "Textile Industry Standard of the People's Republic of China" FZ / T 50006-2013, "Spandex filament tensile property test method".

[0087] 3. Plastic deformation test:

[0088] The prepared sample is clamped into the upper clamp holder at one end, and a pre-tension is applied at the other end to stretch the sample along the axial direction and clamp it into the lower clamp holder, and the instrument is started.

[0089] The sample is stretched from 0% elongation L0 to 300% elongation L1 at a speed of 500 mm / min, then returned to 0% elongation, and the stretching and recovery cycle is repeated four times; during the fifth stretching to 300% elongation, the force value F1 when stretched to 200% is recorded, and after a delay of 30 s, it is returned to 0% elongation, and during this process, the force value F2 when returned to 200% is recorded; after a delay of 30 s, the sixth stretching is performed, and the length L2 of the sample when stretched to the pre-tension is recorded.

[0090] The plastic deformation rate calculation formula is: (L2-L0) / L0*100%

[0091] Wherein "5LP200%" represents the stress value when the fifth stretching is to 200% elongation, i.e. F1; "5UP200%" represents the rebound stress value when the fifth stretching is returned to 200% elongation from 300% elongation, i.e. F2, which can be used to characterize the recovery modulus; "plastic deformation rate" represents the increase ratio of the length of the spandex filament after five stretchings compared to the original length.

[0092] In addition, the antioxidants mentioned in the following examples are antioxidant 245, the auxiliary dyes are DH300R or 2462B, and the light stabilizers are Tinuvin 791, all of which are commercially available materials on the market.

[0093] Example 1

[0094] 17 parts by weight of polyethylene glycol PEG200 (number average molecular weight 200) and 11 parts by weight of terephthalic acid were put into a reaction kettle, and nitrogen was passed to displace the air in the reaction kettle. The stirring in the reaction kettle was started, and the stirring speed was 150 rpm. The system was subjected to programmed temperature rise, and the temperature was raised to 150°C and maintained for 5 h; the temperature was continued to be raised to 260°C, and the temperature was maintained until the water removal rate of the system reached more than 90% of the theoretical value, and the solution became homogeneous. Tetraisopropyl titanate was added, and the vacuum was gradually extracted to 2000 Pa; when the acid value was less than 0.5 mgKOH / g, polyether ester diol with a number average molecular weight of 1500 was obtained. Test results show that the average functionality is 1.98, the viscosity at 90°C 1S -1 is 35 poise, and it is a liquid at room temperature.

[0095] 100 kg of the above prepared polyether ester diol was added to a reaction kettle which had been heated to 45°C, and the stirring was started with a stirring speed of 150 rpm. 26.5 kg of diphenylmethane diisocyanate was added, and after stirring for 5 min, the temperature was raised to 90°C. The pre-polymer was obtained by reacting at 90°C for 2 h.

[0096] The prepolymer was cooled to 50°C, and 161 kg of dimethylacetamide (DMAc) was used to dissolve the prepolymer, and then an amine solution containing 2.33 kg of ethylenediamine (EDA) and 0.28 kg of diethylamine (DEA) with a mass concentration of 3.2% was added, the stirring speed was increased to 300 rpm, and the chain extension reaction was carried out. After the completion of the chain extension reaction, the necessary antioxidants, dyeing aids and other auxiliaries were added, and aging was carried out for 30 h to obtain a spinning dope with a solid content of 35%. The above dope was dry spun to obtain a spandex PUU-1 with a denier of 40D.

[0097] Example 2

[0098] 17 parts by weight of polyethylene glycol PEG200 (number average molecular weight 200) and 11.8 parts by weight of terephthalic acid were put into a reaction kettle, nitrogen was passed to replace the air in the reaction kettle, and the stirring of the reaction kettle was started with a stirring speed of 150 rpm. The system was subjected to programmed temperature rise, and the temperature was raised to 150°C and kept for 5 h, and then the temperature was continuously raised to 260°C, and the temperature was kept until the water yield of the system reached more than 90% of the theoretical value, and the solution became homogeneous, and then titanium isopropyl titanate was added, and the vacuum was gradually extracted to 2000 Pa. When the acid value was less than 0.5 mgKOH / g, a polyether ester diol with a number average molecular weight of 2120 was obtained. Test results show that the average functionality is 1.98, the viscosity at 90°C is 25 poise, and it is a liquid at room temperature. -1

[0099] 100 kg of the above prepared polyether ester diol was added to a reaction kettle which had been kept at a constant temperature of 45°C, and the stirring was started with a stirring speed of 150 rpm. 21.3 kg of diphenylmethane diisocyanate was added, and after stirring for 5 min, the temperature was raised to 90°C; and the prepolymer was obtained by reacting at 90°C for 2 h.

[0100] The prepolymer was cooled to 50°C, and 161 kg of dimethylacetamide (DMAc) was used to dissolve the prepolymer, and then an amine solution containing 2.33 kg of ethylenediamine (EDA) and 0.28 kg of diethylamine (DEA) with a mass concentration of 3.2% was added, the stirring speed was increased to 300 rpm, and the chain extension reaction was carried out. After the completion of the chain extension reaction, the necessary antioxidants, dyeing aids and other auxiliaries were added, and aging was carried out for 30 h to obtain a spinning dope with a solid content of 35%. The above dope was dry spun to obtain a spandex PUU-1 with a denier of 40D.

[0101] Example 3

[0102] ​8.5 parts by weight of polytetramethylene glycol PTG650 (number average molecular weight 650), 8.5 parts by weight of polyethylene glycol PEG600 (number average molecular weight 600) and 3.52 parts by weight of terephthalic acid were put into a reaction kettle, and the air in the reaction kettle was replaced by nitrogen. The stirring of the reaction kettle was started, and the stirring speed was 150 rpm. The system was subjected to programmed temperature rising, and the temperature was raised to 150°C and kept for 5 h; the temperature was continuously raised to 230°C, and the temperature was kept until the water content of the system was more than 92.5% of the theoretical value, and the solution became homogeneous. Tetraisopropyl titanate was added. Vacuum was gradually applied to 2000 Pa, and the acid value was less than 0.5 mgKOH / g, to obtain a polyether ester diol with a number average molecular weight of 1800. The average functionality was 1.98, the viscosity at 90°C 1S-1 was 45 poise, and the polyether ester diol was a liquid at room temperature.

[0103] 100 kg of the polyether ester diol of Example 5 was added into a reaction kettle which had been kept at 45°C. The stirring was started, and the stirring speed was 150 rpm. 23.5 kg of diphenylmethane diisocyanate was added, and the temperature was raised to 90°C after 5 min of stirring. The pre-polymer was obtained by reacting at 90°C for 2 h.

[0104] The pre-polymer was cooled to 50°C, and the pre-polymer was dissolved in 157 kg of dimethylacetamide (DMAc). Then, an amine solution containing 2.27 kg of ethylenediamine (EDA) and 0.28 kg of diethylamine (DEA) with a mass concentration of 3.2% was added. The stirring speed was increased to 300 rpm, and the chain extension reaction was carried out. After the chain extension reaction was completed, necessary antioxidants, dyeing aids and other auxiliaries were added, and the mixture was aged for 30 h to obtain a spinning dope with a solid content of 35%. The spinning dope was subjected to dry spinning to obtain a spandex PUU-3 with a denier of 40D.

[0105] Comparative Example 1

[0106] The spandex of this comparative example was prepared by using a conventional polytetramethylene glycol ether diol as a soft segment raw material, and was used for mechanical property comparison with the spandex provided by the present application.

[0107] 100 kg of polytetramethylene glycol PTMG2000 (number average molecular weight 2000) was added into a reaction kettle which had been kept at 45°C. The stirring was started, and the stirring speed was 150 rpm. 22.2 kg of diphenylmethane diisocyanate was added, and the temperature was raised to 90°C after 5 min of stirring. The pre-polymer was obtained by reacting at 90°C for 2 h.

[0108] The prepolymer was cooled to 50°C, and 155.5 kg of dimethylacetamide (DMAc) was used to dissolve the prepolymer, then an amine solution containing 2.26 kg of ethylenediamine (EDA) and 0.28 kg of diethylamine (DEA) with a concentration of 3.2% was added, the stirring speed was increased to 300 rpm, and the chain extension reaction was carried out. After the chain extension reaction was completed, the necessary antioxidants, dyeing aids and other auxiliaries were added, and then aged for 30 h to obtain a spinning dope with a solid content of 35%. The above dope was subjected to dry spinning to obtain a spandex PUU-0 with a denier of 40D.

[0109] The mechanical property test results of the spandex prepared in Examples 1-3 and Comparative Example 1 are shown in the following table:

[0110]

[0111] As can be seen from the data in the above table, the spandex that can be co- recycled with polyester as described in the present application has mechanical properties such as tensile modulus, resilience modulus and plastic deformation resistance that exceed those of conventional polyether-based spandex; although the breaking strength and elongation at break are slightly reduced, they can still meet the requirements of conventional fabric use.

[0112] Example 5

[0113] 360 kg of spandex PUU-1 prepared in Example 1 and 1640 kg of polyester filaments were woven into a warp-knitted polyester plain fabric by warp knitting, the polyester was a commercially available 50D / 48F type polyester fiber, and the prepared fabric was a 18 / 82 specification spandex-polyester fabric.

[0114] 100 kg of the above fabric was crushed into fragments with a size of less than 1 cm, 400 kg of ammonia water with a concentration of 25% was added, and the mixed material was placed in a high-temperature and high-pressure reaction kettle and reacted at 160°C for 8 h; the temperature of the obtained reaction product was reduced to below 35°C, and then transferred into a reduced-pressure distillation device for reduced-pressure distillation, and the distilled ammonia water was recovered; when the remaining solution in the device became neutral, the remaining solution was added into hydrochloric acid to reduce the pH of the solution to below 5, and then reduced-pressure distillation was performed to collect the ethylene glycol fraction; PTA (terephthalic acid) was precipitated from the bottom liquid after distillation, and was used as a raw material for aromatic polyester diol after recrystallization from hot water. After the above recovery process, 23 kg of ethylene glycol and 72.5 kg of PTA were recovered.

[0115] Example 6

[0116] 360 kg of spandex PUU-1 prepared in Example 1 and 1640 kg of polyester filaments were woven into a warp-knitted polyester plain fabric by warp knitting, the polyester was a commercially available 50D / 48F type polyester fiber, and the prepared fabric was a 18 / 82 specification spandex-polyester fabric.

[0117] The 100 kg of the fabric is pulverized into pieces with a size less than 1 cm, 400 kg of ethylene glycol is added, and zinc acetate is added as a catalyst, alcoholysis is carried out at 196 ℃ for 5 h; distillation is carried out on the obtained system, when the amount of the distilled glycol reaches 90% of the theoretical value, the distillation is stopped, and the temperature of the material is reduced to 64 ℃; methanol is added to the obtained system, and sodium methoxide is added as a catalyst, the temperature is maintained at 64 ℃, and reaction is carried out for 5 h; ethylene glycol and methanol are removed by atmospheric distillation to obtain DMT; the obtained DMT is subjected to high-temperature ion exchange to remove zinc acetate and sodium methoxide, and then is subjected to reduced-pressure distillation to obtain DMT with high purity. After the above recovery process, 83 kg of DMT is recovered.

[0118] As can be known from the results of Examples 5-6, the spandex provided by the present application which can be co-recovered with the aromatic polyester fiber can participate in the recovery process of the polyester, and the aromatic diacid ester structure in the polyester and the spandex can be recovered by the recovery method provided by the present application and reused as a chemical raw material.

Claims

1. A method for recycling a fabric made of spandex and an aromatic polyester fiber, characterized by, The recycling method mainly comprises the following steps: Step one: crushing the fabric; Step two: recycling the fabric into terephthalic acid or dimethyl terephthalate by chemical method; The soft segment of the molecular structure of the spandex comprises repeating units shown in the following formula (1): Formula (1), wherein R1 is at least one of an aromatic ring and an aromatic heterocycle, and the mass content of R1 in the repeating unit is 4.5% to 44%; R2 is at least one of saturated alkyl groups having 2 to 5 carbon atoms; x is 2 to 20; (R2-O)x X the molecular weight of the segment is 100 to 1000; The soft segment accounts for 80%-97% of the mass of the polymer, and the mass of the repeating units shown in formula (1) accounts for more than 50% of the mass of the soft segment.

2. The recycling method according to claim 1, characterized in that, The R2 is at least two kinds of saturated alkane groups with carbon atom number of 2-5.

3. The recycling method according to claim 1, characterized in that, The R2 is a saturated alkane group with carbon atom number of 2.

4. The recycling method of claim 1, wherein, The R1 is a benzene ring.

5. The recycling method of claim 1, wherein, In formula (1), x is 3-10.

6. The recycling method of claim 1, wherein, The aromatic polyester fiber is one or several of PET fiber, PPT fiber, and PBT fiber.

7. The recycling method of claim 1, wherein, The specific steps of step two are as follows: Step 1): adding 4 times the mass of the fabric of ammonia to the crushed fabric, placing it in a high-temperature high-pressure reaction kettle, and reacting at 160℃ for 8h; Step 2): reducing the temperature of the reaction product obtained in step 1) to below 35℃, filtering, and filtering out the precipitated polyether glycol component; then transferring it into a reduced pressure distillation device, performing reduced pressure distillation, and recovering the distilled ammonia water, and distilling until the pH of the remaining solution in the device is reduced to below 7.5; Step 3) adding hydrochloric acid to the remaining solution to reduce the pH of the solution to below 5, and then performing reduced pressure distillation to collect the small molecule diol fraction; Step 4) precipitating crude PTA in the bottom liquid after distillation, recrystallizing with hot water, and drying to obtain high-purity PTA.

8. The recycling method of claim 1, wherein, The specific steps of step two are as follows: Step A) adding 4 times the mass of the fabric of ethylene glycol to the crushed fabric, and adding zinc acetate as a catalyst, and performing alcoholysis at 190-200℃ under reflux conditions for 5h; Step B) distilling the system obtained in step A), and stopping distillation when the amount of diol distilled reaches 90% of the theoretical value, and reducing the temperature of the material to below 64℃; Step C) adding methanol to the system obtained in step B), and adding sodium methoxide as a catalyst, and maintaining the temperature below 64℃, and reacting for 5h; Step D) removing residual ethylene glycol, methanol, and amine substances by normal pressure distillation; Step E) removing zinc acetate and sodium methoxide by high-temperature ion exchange, and then purifying DMT from the remaining system by reduced pressure distillation to obtain high-purity DMT.

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