Cationic dye dyeable regenerated polyester fiber and preparation method thereof

Abstract

The invention discloses a cationic dye dyeable regenerated polyester fiber and a preparation method thereof, and relates to the technical field of polyester fibers, the cationic dye dyeable regenerated polyester fiber comprises the following components: waste polyester, sodium bis (2-hydroxyethyl) isophthalate-5-sulfonate and long-chain dihydric alcohol, the method comprises the following steps: mixing waste polyester, sodium bis (hydroxyethyl) isophthalate-5-sulfonate and long-chain dihydric alcohol according to a certain mass ratio, extruding the mixture in a twin-screw extruder, carrying out semi-depolymerization on the waste polyester by using the sodium bis (hydroxyethyl) isophthalate-5-sulfonate and the long-chain dihydric alcohol to obtain a semi-depolymerization product which is low-molecular-weight polyester with a hydroxyl-terminated structure, feeding the low-molecular-weight polyester into a polycondensation reactor, and carrying out condensation polymerization on the low-molecular-weight polyester with the hydroxyl-terminated structure to obtain the low-molecular-weight polyester with the hydroxyl-terminated structure. The prepared modified polyester can be directly spun or spun after being diced, and the prepared polyester fiber has a cationic dye normal-pressure dyeable effect, can remarkably reduce dyeing energy consumption and material consumption, has good hygroscopicity, improves wearing comfort and can be widely applied to the fields of clothes, home textiles and the like.

Description

Technical Field

[0001] The invention relates to the technical field of polyester fibers, in particular to a cationic dye-dyable regenerated polyester fiber and a preparation method thereof. Background Art

[0002] Polyester is an important variety of synthetic polymers. Polyester fiber is the basic raw material for textiles. In 2022, China's total output exceeded 50 million tons, which plays a pivotal role. How to recycle waste polyester resources is an important direction related to the sustainable development of the industry.

[0003] Chinese invention patent CN102605456B discloses a method for preparing polyester filaments using waste polyester raw materials. The waste polyester bottle flakes are sorted, cleaned, crushed and dried, and then conveyed to a reactive exhaust screw extruder after drying. Phenyldioxazoline and N,N'-carbonyl dicaprolactam polyester chain extender are added at 0.5% to 3% of the mass of the polyester bottle flakes. The polyester bottle flakes and the polyester chain extender are conveyed together to the reactive exhaust screw extruder. After melting and mixing, the melt is metered and conveyed to the spinning unit to prepare polyester filaments.

[0004] Chinese invention patent CN109134244A discloses a method for degrading waste polyester, wherein the polyester is subjected to preliminary alcoholysis with a diol, and then the preliminary alcoholysis product is subjected to deep alcoholysis and ester exchange with a mixture of diol and methanol to obtain dimethyl terephthalate, wherein the diol is the same as or different from the diol required for synthesizing the polyester, the diol in the mixture of diol and methanol is the diol remaining after the preliminary alcoholysis reaction, the depolymerization rate of the polyester after the preliminary alcoholysis is 20% to 60%, the depolymerization rate of the polyester after the deep alcoholysis is 90% to 100%, the mass content of diol terephthalate in the preliminary alcoholysis product is 30% to 60%, the purity of the obtained dimethyl terephthalate is 98% to 99.8%, and the yield is 85% to 96%.

[0005] Chinese invention patent CN105237752A discloses a method for preparing polyols from waste polyester bottles. After alcoholysis of the waste polyester bottles, flame-retardant phthalic anhydride is introduced and esterified with the alcoholysis product. After removing the small molecule alcohol and water, polyether triol with a pH value between 8 and 11 is added for further esterification and condensation, and the acid value of the obtained polyester polyol is adjusted, thereby preparing low-cost polyester polyol with excellent flame retardancy and physical and mechanical properties.

[0006] Chinese invention patent CN109467743A discloses a chemical regeneration method for waste polyester textiles, recycled polyester and polyester hot melt yarn, wherein the pretreated polyester textiles are subjected to a mixed polyol alcoholysis reaction, wherein the mixed polyol includes at least two of ethylene glycol, 1,3-propylene glycol and butanediol; the product after the alcoholysis reaction is subjected to a repolymerization reaction to obtain recycled polyester. This application achieves the purpose of generating recycled polyester from waste polyester textiles by using mixed polyols, without removing the self-condensation byproducts of alcohol, and directly performs a regeneration copolymerization reaction, thereby simplifying the process and reducing costs.

[0007] Chinese invention patent CN109467743A discloses a method for producing regenerated colored polyester staple fibers by a chemical method using waste polyester foam, comprising collecting waste polyester products, washing and drying the waste polyester products, crushing the dried waste polyester products in a crusher, and then performing vacuum drying treatment, mixing part of new polyester into the waste polyester products, depolymerizing the mixed waste polyester products, filtering to obtain a waste polyester depolymerization liquid, performing an esterification reaction on the waste polyester depolymerization liquid, performing a polycondensation reaction on the system after the esterification reaction, and then preparing a regenerated polyester masterbatch through an extrusion granulation device, feeding the regenerated polyester masterbatch mixed with a color masterbatch into a screw extruder and performing melt extrusion, and introducing the extruded melt into a spinning box to produce regenerated colored polyester staple fibers.

[0008] Chinese invention patent CN114031756B discloses a closed-loop method for recycling waste polyester to prepare recycled polyester with typical green and low-carbon characteristics. It includes selecting a specific depolymerization catalyst to depolymerize waste polyester under microwave conditions; removing the polyol solvent from the depolymerization product, purifying and removing by-products to obtain a depolymerized monomer; mixing the depolymerized monomer with a dibasic acid, a polyol, a polymerization catalyst and a chain extender to carry out an esterification reaction, and then adding a stabilizer and a catalyst for polycondensation to obtain recycled polyester.

[0009] Chinese invention patent CN102532591B provides a method for depolymerizing waste polyester bottles. Waste polyester bottles, ethylene glycol, sodium bicarbonate and distilled water are added into a high-temperature and high-pressure reactor in a certain proportion, and then reacted at 170-200°C for 15-40 minutes. The waste polyester bottles are depolymerized to generate sodium terephthalate and ethylene glycol and other by-products; then, the waste polyester bottles are decolorized by activated carbon adsorption, acidified with hydrochloric acid, cooled and crystallized with ice water, filtered, washed and dried to obtain terephthalic acid; the filtrate is subjected to rotary evaporation to obtain ethylene glycol which can be reused.

[0010] Judging from the above disclosed technologies, there are currently two main methods for recycling polyester: physical method and chemical method.

[0011] (1) The physical method is to melt the waste polyester, filter it, and then extrude it into a shape. It can be used as plastic or fiber. When used as fiber, it is mainly short fiber due to the decrease in molecular weight after regeneration. The molecular weight of polyester can be increased by introducing a chain extender during the melting process, but the molecular weight distribution coefficient of the thickened polyester prepared by the chain extension reaction will become wider, resulting in a decrease in spinnability. Although the physical method is relatively simple and easy to operate, it is difficult to modify polyester and the product is single. Most of the polyester used is bottle flakes for melt extrusion.

[0012] (2) Chemical recycling is to deeply depolymerize waste polyester in a small molecule depolymerizer into monomers or other types of small molecule substances, and then re-esterify and polycondense them after purification. Copolymer-modified components can be introduced during the process. Although the quality and added value of recycled polyester are improved, the process is long and the process is complicated.

[0013] In view of the above problems, an improved cationic dye-dyable regenerated polyester fiber and a preparation method thereof are now designed. Summary of the invention

[0014] The object of the present invention is to provide a cationic dyeable regenerated polyester fiber and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0015] To achieve the above object, the present invention provides the following technical solutions:

[0016] A cationic dye-dyable regenerated polyester fiber comprises the following components: waste polyester, sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long-chain diols, wherein the mass fraction of the waste polyester is more than 90%, the sodium bis(hydroxyethyl)isophthalate-5-sulfonate is 1-5% of the mass fraction of the waste polyester, and the long-chain diols are 0.5-5% of the mass fraction of the waste polyester.

[0017] As a further solution of the present invention: the waste polyester is mainly made of polyethylene terephthalate, has an intrinsic viscosity of 0.60-0.85 dL / g, and a melting point of 235-255°C.

[0018] As a further solution of the present invention: the waste polyester is a raw material composed of one or more of oil-free polyester waste silk in the spinning process, waste polyester white cloth, and waste polyester bottles.

[0019] As a further solution of the present invention: the long-chain diol is polytetrahydrofuran or polyethylene glycol, and the relative number average molecular weight is 200-4000 g / mol.

[0020] A method for preparing cationic dye-dyable regenerated polyester fiber comprises the following steps:

[0021] Step 1: Mix waste polyester, sodium bis(hydroxyethyl)isophthalate-5-sulfonate, and long-chain diols in a certain mass ratio and feed them into a twin-screw extruder, and semi-depolymerize the waste polyester using sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long-chain diols to obtain a semi-depolymerized product, which is a low molecular weight polyester with a hydroxyl-terminated structure.

[0022] Step 2: adding the semi-depolymerized product obtained in step 1 to a polycondensation reactor for pre-polycondensation and final polycondensation to finally prepare a modified polyester.

[0023] Step 3: Melting the modified polyester obtained in step 2, and then directly spinning the melt or pelletizing and spinning it, so as to prepare cationic dyeable regenerated polyester fiber.

[0024] As a further solution of the present invention: in step 1, the waste polyester needs to be dried before entering the twin-screw extruder to control the moisture content of the polyester within 100 ppm.

[0025] As a further solution of the present invention: in step 1, the extrusion temperature of the twin screw is 260-280° C., the number average molecular weight of the semi-depolymerized product is 5000-12000 g / mol, and the molecular weight distribution coefficient PDI is 1.2-2.0.

[0026] As a further solution of the present invention: in step 2, the pre-condensation temperature is 250-265°C, the reaction time is 0.25-1.0h, the reaction pressure is controlled at 500-1000Pa, the final condensation reaction temperature is 255-275°C, the reaction time is 1.5-4.5h, and the reaction pressure is controlled within 100Pa.

[0027] As a further solution of the present invention: in step 2, the number average molecular weight of the modified polyester is 18000-30000 g / mol, and the molecular weight distribution coefficient is 1.8-2.5.

[0028] As a further solution of the present invention: in step three, the cationic dyeable regenerated polyester fiber has a dyeing rate of more than 85% using cationic dyes under 95-100° C., the fiber strength is ≥3.5 cN / dtex, the fiber regain is 0.8-2.5%, and the fiber modulus is reduced by 20-40% compared with polyester fibers of the same specifications, and the comfort is significant.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention semi-depolymerizes and then polycondenses waste polyester, which can achieve homogeneous mixing of complex polyester raw materials at low molecular weight in the screw, increase the source range of raw materials for recycling waste polyester, and has stronger adaptability. Compared with the existing chemical deep depolymerization, the energy consumption and material consumption are lower. Moreover, the semi-depolymerized product can achieve efficient polycondensation and viscosity increase, and the reuse efficiency is higher.

[0031] The invention introduces a specific modified component to semi-depolymerize the waste polyester, and then prepares the modified polyester through a polycondensation reaction. The modified component plays a dual role of semi-depolymerization and functional modification of the waste polyester, and the invention significantly increases the added value of the waste polyester.

[0032] The present invention is different from the existing physical and chemical methods for recycling waste polyester. The waste polyester is depolymerized into low molecular weight polyester, and the molecular weight of the depolymerized product is regulated by controlling the content of sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long carbon chain diols. Polyester has good stability at room temperature, but a large number of ester bonds contained in the polyester are very likely to undergo ester exchange under high temperature conditions to form hydroxyl-terminated polyesters with a specific viscosity. On the one hand, the problem of the existing chemical method requiring a large amount of depolymerizing agent and energy consumption for deep depolymerization is solved, and on the other hand, the hydroxyl-terminated segments can be repolymerized.

[0033] In the present invention, waste polyester, sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long-chain diol are mixed in proportion and then enter the screw for depolymerization. Sodium bis(hydroxyethyl)isophthalate-5-sulfonate is an esterification product terminated by ethylene glycol. When blending with waste polyester in the screw, sodium bis(hydroxyethyl)isophthalate-5-sulfonate acts as diol to depolymerize polyester; the long-chain diol part depolymerizes polyester, and because the carbon chain is relatively long, it can promote the flow of polyester and reduce the residence time at high temperature. The depolymerization product enters the polycondensation reactor for co-polycondensation reaction, and the prepared modified polyester is spun to obtain fibers with the advantages of normal pressure boiling dyeing, softness and lifting.

[0034] The depolymerized product of the present invention includes polyester with a certain molecular weight, sodium bis(hydroxyethyl)isophthalate-5-sulfonate, and long-chain diols, and then enters a polycondensation reactor for pre-polycondensation and final polycondensation. The two stages are designed mainly because the vacuum degree in the pre-polycondensation stage is relatively mild, and while ensuring that sodium bis(hydroxyethyl)isophthalate-5-sulfonate, long-chain diols and polyester with a certain low molecular weight undergo polycondensation, sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long-chain diols are taken out of the vacuum system, thereby greatly avoiding the waste of modified components. When sodium bis(hydroxyethyl)isophthalate-5-sulfonate, long-chain diols and polyester with a low molecular weight form a substance with a higher molecular weight in the pre-polycondensation stage, the final polycondensation is carried out, and the vacuum degree is high at this time, so that the molecular weight can be further increased, but the modified substance will not be extracted. DETAILED DESCRIPTION

[0035] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0036] Example 1

[0037] A method for preparing cationic dye-dyable regenerated polyester fiber comprises the following steps:

[0038] Step 1: Use waste polyester as polyethylene terephthalate as the main material, with a mass fraction of 90.0%, a characteristic viscosity of 0.85dL / g, and a melting point of 255°C; before the waste polyester enters the screw for depolymerization, the moisture content of the polyester is controlled to be 65ppm by drying. Use sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long-chain diols to depolymerize the waste polyester. Among them, sodium bis(hydroxyethyl)isophthalate-5-sulfonate is added to 5.0% of the mass fraction of the waste polyester; polyethylene glycol is added as a long-chain diol, and the addition amount is 5.0% of the mass fraction of the waste polyester, and the relative number average molecular weight of polyethylene glycol is 4000g / mol; during the depolymerization process, the screw extrusion temperature is 280°C, the depolymerization reaction time is 1.0h, the number average molecular weight of the depolymerization product is 5000g / mol, and the molecular weight distribution coefficient PDI is 2.00.

[0039] Step 2: The product of the waste polyester after depolymerization in the screw enters the polycondensation reactor for pre-polycondensation and final polycondensation. The pre-polycondensation temperature is 265°C, the reaction time is 1.00h, and the reaction pressure is controlled at 1000Pa; the final polycondensation temperature is 275°C, the reaction time is 4.50h, and the reaction pressure is controlled within 100Pa. After the final polycondensation reaction of the waste polyester is completed, the number average molecular weight of the prepared modified polyester is 30,000g / mol and the molecular weight distribution coefficient is 2.50.

[0040] Step 3: Melting the modified polyester obtained in step 2, and then directly spinning the melt or pelletizing and spinning it, so as to prepare cationic dyeable regenerated polyester fiber.

[0041] Tests show that the cationic dye-dyable regenerated polyester fiber produced can achieve a dyeing rate of 95% using cationic dyes under 95-100°C conditions, the fiber strength is 3.90cN / dtex, the fiber regain is 2.5%, and the fiber modulus is 40% lower than that of polyester fibers of the same specifications.

[0042] Comparative Example 1

[0043] A method for preparing cationic dyeable regenerated polyester fiber is basically the same as that in Example 1, except that only sodium bis(hydroxyethyl)isophthalate-5-sulfonate is added to depolymerize waste polyester.

[0044] Tests show that the cationic dye-dyable regenerated polyester fiber produced can achieve a dyeing rate of 95% using cationic dyes under 95-100°C conditions, the fiber strength is 3.50cN / dtex, the fiber regain is 0.5%, and the fiber modulus is 15% lower than that of polyester fibers of the same specifications.

[0045] This is because in Comparative Example 1, only sodium bis(hydroxyethyl)isophthalate-5-sulfonate was added for depolymerization and repolymerization, and the long-chain diol component was lacking, which reduced the melt fluidity, resulting in the spinning temperature of the modified polyester being slightly higher than that of Example 1. Affected by thermal degradation during the spinning process, the fiber strength decreased, and the fiber modulus decreased only slightly.

[0046] Comparative Example 2

[0047] A method for preparing cationic dye-dyable regenerated polyester fiber is basically the same as that in Example 1, except that only long carbon chain diol is added to depolymerize waste polyester.

[0048] Tests show that the cationic dye-dyable regenerated polyester fiber produced can achieve a dyeing rate of 70% using cationic dyes under 95-100°C conditions, the fiber strength is 3.80cN / dtex, the fiber regain is 2.0%, and the fiber modulus is 30% lower than that of polyester fibers of the same specifications.

[0049] This is because in Comparative Example 1, only long carbon chain diols are added for depolymerization and repolymerization, and the sodium dihydroxyethyl isophthalate-5-sulfonate component is lacking. The cationic dye cannot form an ionic bond with the modified polyester molecular chain, resulting in the modified polyester dyeing rate being lower than that in Example 1, and failing to meet the cationic dyeing requirements.

[0050] Example 2

[0051] A method for preparing cationic dye-dyable regenerated polyester fiber comprises the following steps:

[0052] Step 1: Use waste polyester as polyethylene terephthalate as the main material, with a mass fraction of 91.5%, a characteristic viscosity of 0.81dL / g, and a melting point of 250°C; before the waste polyester enters the screw for depolymerization, the moisture content of the polyester is controlled to 70ppm by drying. Use sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long-chain diols to depolymerize the waste polyester. Among them, sodium bis(hydroxyethyl)isophthalate-5-sulfonate is added as 4.5% of the mass fraction of the waste polyester; polyethylene glycol is added as a long-chain diol, and the addition amount is 4.0% of the mass fraction of the waste polyester, and the relative number average molecular weight of polyethylene glycol is 3500g / mol; during the depolymerization process, the screw extrusion temperature is 275°C, the depolymerization reaction time is 0.75h, the number average molecular weight of the depolymerization product is 6500g / mol, and the molecular weight distribution coefficient PDI is 1.85.

[0053] Step 2: The product of the waste polyester after depolymerization in the screw enters the polycondensation reactor for pre-polycondensation and final polycondensation. The pre-polycondensation temperature is 262°C, the reaction time is 0.85h, and the reaction pressure is controlled at 800Pa; the final polycondensation temperature is 272°C, the reaction time is 3.50h, and the reaction pressure is controlled within 90Pa. After the final polycondensation reaction of the waste polyester is completed, the number average molecular weight of the prepared modified polyester is 28000g / mol, and the molecular weight distribution coefficient is 2.40.

[0054] Step 3: Melting the modified polyester obtained in step 2, and then directly spinning the melt or pelletizing and spinning it, so as to prepare cationic dyeable regenerated polyester fiber.

[0055] Tests show that the cationic dye-dyable regenerated polyester fiber produced can achieve a dyeing rate of 93% using cationic dyes under 95-100°C conditions, the fiber strength is 3.90cN / dtex, the fiber regain is 2.0%, and the fiber modulus is 35% lower than that of polyester fibers of the same specifications.

[0056] Example 3

[0057] A method for preparing cationic dye-dyable regenerated polyester fiber comprises the following steps:

[0058] Step 1: Use waste polyester as polyethylene terephthalate as the main material, with a mass fraction of 92.5%, a characteristic viscosity of 0.78dL / g, and a melting point of 248°C; before entering the screw for depolymerization, the waste polyester is dried to control the moisture content of the polyester to 74ppm. Use sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long-chain diols to depolymerize the waste polyester. Among them, sodium bis(hydroxyethyl)isophthalate-5-sulfonate is added as 4.0% of the mass fraction of the waste polyester; polyethylene glycol is added as a long-chain diol, and the addition amount is 3.5% of the mass fraction of the waste polyester, and the relative number average molecular weight of polyethylene glycol is 3000g / mol; during the depolymerization process, the screw extrusion temperature is 270°C, the depolymerization reaction time is 0.65h, the number average molecular weight of the depolymerization product is 7500g / mol, and the molecular weight distribution coefficient PDI is 1.75.

[0059] Step 2: The product of the waste polyester after depolymerization in the screw enters the polycondensation reactor for pre-polycondensation and final polycondensation. The pre-polycondensation temperature is 260°C, the reaction time is 0.75h, and the reaction pressure is controlled at 650Pa; the final polycondensation temperature is 270°C, the reaction time is 3.00h, and the reaction pressure is controlled within 80Pa. After the final polycondensation reaction of the waste polyester is completed, the number average molecular weight of the prepared modified polyester is 25000g / mol, and the molecular weight distribution coefficient is 2.30.

[0060] Step 3: Melting the modified polyester obtained in step 2, and then directly spinning the melt or pelletizing and spinning it, so as to prepare cationic dyeable regenerated polyester fiber.

[0061] Tests show that the cationic dye-dyable regenerated polyester fiber produced can achieve a dyeing rate of 91% using cationic dyes under 95-100°C conditions, the fiber strength is 3.80cN / dtex, the fiber regain is 1.8%, and the fiber modulus is 32% lower than that of polyester fibers of the same specifications.

[0062] Example 4

[0063] A method for preparing cationic dye-dyable regenerated polyester fiber comprises the following steps:

[0064] Step 1: Use waste polyester as polyethylene terephthalate as the main material, with a mass fraction of 95.0%, a characteristic viscosity of 0.75dL / g, and a melting point of 245°C; before entering the screw for depolymerization, the waste polyester is dried to control the moisture content of the polyester to 77ppm. Use sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long-chain diols to depolymerize the waste polyester. Among them, sodium bis(hydroxyethyl)isophthalate-5-sulfonate is added as 3.0% of the mass fraction of the waste polyester; polytetrahydrofuran is added as a long-chain diol, and the addition amount is 2.0% of the mass fraction of the waste polyester, and the relative number average molecular weight of polytetrahydrofuran is 2000g / mol; during the depolymerization process, the screw extrusion temperature is 268°C, the depolymerization reaction time is 0.50h, the number average molecular weight of the depolymerization product is 9500g / mol, and the molecular weight distribution coefficient PDI is 1.50.

[0065] Step 2: The product of the waste polyester after depolymerization in the screw enters the polycondensation reactor for pre-polycondensation and final polycondensation. The pre-polycondensation temperature is 257°C, the reaction time is 0.5h, and the reaction pressure is controlled at 600Pa; the final polycondensation temperature is 265°C, the reaction time is 2.25h, and the reaction pressure is controlled within 70Pa. After the final polycondensation reaction of the waste polyester is completed, the number average molecular weight of the prepared modified polyester is 22000g / mol, and the molecular weight distribution coefficient is 2.15.

[0066] Step 3: Melting the modified polyester obtained in step 2, and then directly spinning the melt or pelletizing and spinning it, so as to prepare cationic dyeable regenerated polyester fiber.

[0067] Tests show that the cationic dye-dyable regenerated polyester fiber produced can achieve a dyeing rate of 89% using cationic dyes at 95-100°C, the fiber strength is 3.75cN / dtex, the fiber regain is 1.5%, and the fiber modulus is 28% lower than that of polyester fibers of the same specifications.

[0068] Example 5

[0069] A method for preparing cationic dye-dyable regenerated polyester fiber comprises the following steps:

[0070] Step 1: Use waste polyester as polyethylene terephthalate as the main material, with a mass fraction of 96.5%, a characteristic viscosity of 0.67dL / g, and a melting point of 240°C; before entering the screw for depolymerization, the waste polyester is dried to control the moisture content of the polyester to 80ppm. Use sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long-chain diols to depolymerize the waste polyester. Among them, sodium bis(hydroxyethyl)isophthalate-5-sulfonate is added to 2.0% of the mass fraction of the waste polyester; polytetrahydrofuran is added as a long-chain diol, and the addition amount is 1.5% of the mass fraction of the waste polyester, and the relative number average molecular weight of polytetrahydrofuran is 1000g / mol; during the depolymerization process, the screw extrusion temperature is 265°C, the depolymerization reaction time is 0.35h, the number average molecular weight of the depolymerization product is 10500g / mol, and the molecular weight distribution coefficient PDI is 1.35.

[0071] Step 2: The product of the depolymerization of the waste polyester in the screw enters the polycondensation reactor for pre-polycondensation and final polycondensation. The pre-polycondensation temperature is 254°C, the reaction time is 0.35h, and the reaction pressure is controlled at 550Pa; the final polycondensation temperature is 260°C, the reaction time is 2.0h, and the reaction pressure is controlled within 60Pa. After the final polycondensation reaction of the waste polyester is completed, the number average molecular weight of the prepared modified polyester is 20,000g / mol, and the molecular weight distribution coefficient is 1.95.

[0072] Step 3: Melting the modified polyester obtained in step 2, and then directly spinning the melt or pelletizing and spinning it, so as to prepare cationic dyeable regenerated polyester fiber.

[0073] Tests show that the cationic dye-dyable regenerated polyester fiber produced can achieve a dyeing rate of 87% using cationic dyes at 95-100°C, the fiber strength is 3.55cN / dtex, the fiber regain is 1.2%, and the fiber modulus is 25% lower than that of polyester fibers of the same specifications.

[0074] Example 6

[0075] A method for preparing cationic dye-dyable regenerated polyester fiber comprises the following steps:

[0076] Step 1: Use waste polyester as polyethylene terephthalate as the main material, with a mass fraction of 98.5%, a characteristic viscosity of 0.60dL / g, and a melting point of 235°C; before entering the screw for depolymerization, the waste polyester is dried to control the moisture content of the polyester to 85ppm. Use sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long-chain diols to depolymerize the waste polyester. Among them, sodium bis(hydroxyethyl)isophthalate-5-sulfonate is added as 1.0% of the mass fraction of the waste polyester; polytetrahydrofuran is added as a long-chain diol, and the addition amount is 0.5% of the mass fraction of the waste polyester, and the relative number average molecular weight of polytetrahydrofuran is 200g / mol; during the depolymerization process, the screw extrusion temperature is 260°C, the depolymerization reaction time is 0.25h, the number average molecular weight of the depolymerization product is 12000g / mol, and the molecular weight distribution coefficient PDI is 1.2.

[0077] Step 2: The product of the waste polyester after depolymerization in the screw enters the polycondensation reactor for pre-polycondensation and final polycondensation. The pre-polycondensation temperature is 250°C, the reaction time is 0.25h, and the reaction pressure is controlled at 500Pa; the final polycondensation temperature is 255°C, the reaction time is 1.5h, and the reaction pressure is controlled within 50Pa. After the final polycondensation reaction of the waste polyester is completed, the number average molecular weight of the prepared modified polyester is 18000g / mol, and the molecular weight distribution coefficient is 1.80.

[0078] Step 3: Melting the modified polyester obtained in step 2, and then directly spinning the melt or pelletizing and spinning it, so as to prepare cationic dyeable regenerated polyester fiber.

[0079] Tests show that the cationic dye-dyable regenerated polyester fiber produced can achieve a dyeing rate of 85% using cationic dyes at 95-100°C, the fiber strength is 3.5cN / dtex, the fiber regain is 0.8%, and the fiber modulus is 20% lower than that of polyester fibers of the same specifications.

[0080]

[0081]

[0082] It is obvious to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

Claims

1. A cationic dye-dyable regenerated polyester fiber, characterized in that: The invention comprises the following components: waste polyester, sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long-chain diols, wherein the mass fraction of the waste polyester is more than 90%, the sodium bis(hydroxyethyl)isophthalate-5-sulfonate is 1%-5% of the mass fraction of the waste polyester, and the long-chain diols are 0.5%-5% of the mass fraction of the waste polyester.

2. The cationic dye-dyable regenerated polyester fiber according to claim 1, characterized in that: Waste polyester is mainly made of polyethylene terephthalate, with an intrinsic viscosity of 0.60-0.85dL / g and a melting point of 235-255℃.

3. The cationic dye-dyable regenerated polyester fiber according to claim 1, characterized in that: Waste polyester is a raw material composed of one or more of waste oil-free polyester yarn in the spinning process, waste polyester white cloth, and waste polyester bottles.

4. The cationic dye-dyable regenerated polyester fiber according to claim 1, characterized in that: The long-chain diol is polytetrahydrofuran or polyethylene glycol, and the relative number average molecular weight is 200-4000 g / mol.

5. A method for preparing a cationic dye-dyable regenerated polyester fiber according to any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: waste polyester, sodium bis(hydroxyethyl)isophthalate-5-sulfonate, and long-chain diols are mixed in a certain mass ratio and put into a twin-screw extruder, and the waste polyester is semi-depolymerized by sodium bis(hydroxyethyl)isophthalate-5-sulfonate and long-chain diols, so as to obtain a semi-depolymerized product, which is a low molecular weight polyester with a hydroxyl-terminated structure; Step 2: adding the semi-depolymerized product obtained in step 1 to a polycondensation reactor for pre-polycondensation and final polycondensation to finally prepare a modified polyester; Step 3: Melting the modified polyester obtained in step 2, and then directly spinning the melt or pelletizing and spinning it, so as to prepare cationic dyeable regenerated polyester fiber.

6. The method for preparing a cationic dye-dyable regenerated polyester fiber according to claim 5, characterized in that: In step 1, the waste polyester needs to be dried before entering the twin-screw to control the moisture content of the polyester within 100 ppm.

7. The method for preparing a cationic dye-dyable regenerated polyester fiber according to claim 5, characterized in that: In step 1, the extrusion temperature of the twin screw is 260-280° C., the number average molecular weight of the semi-depolymerized product is 5000-12000 g / mol, and the molecular weight distribution coefficient PDI is 1.2-2.

0.

8. The method for preparing a cationic dye-dyable regenerated polyester fiber according to claim 5, characterized in that: In step 2, the pre-polycondensation temperature is 250-265°C, the reaction time is 0.25-1.0h, the reaction pressure is controlled at 500-1000Pa, the final polycondensation temperature is 255-275°C, the reaction time is 1.5-4.5h, and the reaction pressure is controlled within 100Pa.

9. The method for preparing a cationic dye-dyable regenerated polyester fiber according to claim 5, characterized in that: In step 2, the number average molecular weight of the modified polyester is 18000-30000 g / mol, and the molecular weight distribution coefficient is 1.8-2.

5.

10. The method for preparing a cationic dye-dyable regenerated polyester fiber according to claim 5, characterized in that: In step three, the cationic dyeable regenerated polyester fiber has a dyeing rate of more than 85% using cationic dyes at 95-100° C., a fiber strength of ≥3.5 cN / dtex, a fiber regain of 0.8%-2.5%, and a fiber modulus reduced by 20-40% compared with polyester fibers of the same specification.

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