Preparation method of regenerated polyester bicomponent side-by-side composite elastic fiber

Abstract

The present invention belongs to the technical field of polymer materials and relates to a preparation method of a regenerated polyester bicomponent side-by-side composite elastic fiber. Preparation method: A mixture of a polylactic acid thermoplastic elastomer and a first polylactic acid is used as the first component, and a second polylactic acid is used as the second component, and side-by-side composite spinning is carried out to obtain the regenerated polyester bicomponent side-by-side composite elastic fiber; the preparation process of the polylactic acid thermoplastic elastomer is: after mixing the reaction raw materials, pre-polycondensation reaction and final polycondensation reaction are carried out in sequence to obtain the polylactic acid thermoplastic elastomer. By selecting a polylactic acid oligomer with a specific molecular weight having double-terminal carboxyl groups, and appropriate reaction raw materials such as a dibasic acid and a polyether diol (or a polyether diamine), the present invention ensures the compatibility and fluidity of the polylactic acid thermoplastic elastomer and the second polylactic acid during the spinning process, thereby improving the stability and continuity of the spinning process, and reducing the production difficulty and cost.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer materials and relates to a method for preparing recycled polyester two-component parallel composite elastic fibers. Background Art

[0002] Polylactic acid is currently the only biodegradable polyester material derived from renewable plants, and is also regarded as the biomaterial with the broadest prospects for industrial application. Polylactic acid fiber is very suitable for the preparation of close-fitting fabrics and products due to its skin-friendly and antibacterial properties, moisture absorption and perspiration, and smooth feel. However, due to the high modulus of polylactic acid fiber, it feels hard and has poor elasticity, so the fabrics made are not close to the skin and lack elasticity, which limits its application range to a certain extent. In order to improve this situation, polylactic acid fiber is often blended with spandex to prepare elastic fiber. However, spandex and polylactic acid have poor compatibility, and hairy fibers are prone to occur when blended. In addition, the production cost of spandex is high and the process flow is long, all of which restrict the development of polylactic acid elastic fiber.

[0003] Self-crimping fiber is a fiber with an irreversible three-dimensional spiral curling structure, usually prepared by two-phase polymers with different shrinkage stresses through parallel composite spinning, drawing and heat treatment. Compared with ordinary curling fibers, self-crimping fibers not only save energy consumption, but also avoid mechanical damage to the fibers during texturing. Therefore, they are widely favored by the market and become a differentiated fiber.

[0004] The patent application with publication number CN107022804A discloses a method for preparing flame-retardant, degradable and antibacterial polylactic acid elastic fiber. The method provides elastic properties to polylactic acid by reactively blending vinyl polydimethylsilane, and the overall preparation process is simple and feasible. The patent application with publication number CN109853084A provides a polylactic acid / polyester elastomer composite elastic fiber, which is prepared by composite spinning of polylactic acid slices, polyester elastomer slices and compatibilizer in a certain proportion, giving polylactic acid fiber excellent elasticity and soft feel, improving its comfort, and making polylactic acid fiber more widely used in close-fitting fabrics. The patent with authorization announcement number CN113136638B discloses a biodegradable parallel composite elastic fiber and a preparation method thereof. The method melts and composites PB TSI copolyester and PLA in parallel, and the obtained composite elastic fiber has good compatibility and biodegradability.

[0005] Although the above patents or patent applications have made certain progress in the modification of polylactic acid fibers, they have not fully considered the compatibility and fluidity differences between the two components during the spinning process. Summary of the invention

[0006] The object of the present invention is to solve the problems existing in the prior art and provide a preparation method of regenerated polyester bicomponent side-by-side composite elastic fibers.

[0007] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A preparation method of regenerated polyester bicomponent side-by-side composite elastic fibers, using a mixture of a polylactic acid thermoplastic elastomer and a first polylactic acid as the first component, and a second polylactic acid as the second component, and performing side-by-side composite spinning to obtain the regenerated polyester bicomponent side-by-side composite elastic fibers;

[0009] The preparation process of the polylactic acid thermoplastic elastomer is: after mixing the reaction raw materials, performing a pre-polycondensation reaction and a final polycondensation reaction in sequence to obtain the polylactic acid thermoplastic elastomer;

[0010] The reaction raw materials include a dibasic acid, X, and a branching agent;

[0011] The dibasic acid is a double-end carboxyl polylactic acid oligomer, and the double-end carboxyl polylactic acid oligomer is prepared by an ester exchange reaction of waste polylactic acid and a first aliphatic dibasic acid;

[0012] Alternatively, the dibasic acid is a mixture of a double-end carboxyl polylactic acid oligomer and a second aliphatic dibasic acid;

[0013] X is a polyether diol;

[0014] Alternatively, X is a mixture of a polyether diol and a first aliphatic diol;

[0015] Alternatively, X is a polyether diamine;

[0016] Alternatively, X is a mixture of a polyether diamine and a first aliphatic diamine;

[0017] The first aliphatic dibasic acid has 4-20 carbon atoms; if the first aliphatic dibasic acid has more than 20 carbon atoms, the carbon chain of the first aliphatic dibasic acid is too long, on the one hand, it will cause the reaction activity of the terminal carboxyl group of the first aliphatic dibasic acid to be relatively low. If the time of the ester exchange reaction is not extended, the ester exchange reaction will not be thorough enough to effectively prepare the double-end carboxyl polylactic acid oligomer. If the time of the ester exchange reaction is extended, the thermal degradation of the waste polylactic acid will become serious; on the other hand, during the ester exchange reaction, the first aliphatic dibasic acid has to enter the molecular chain of the polylactic acid. The too long carbon chain of the first aliphatic dibasic acid will cause the regularity of the molecular chain of the polylactic acid to be damaged too much, thus affecting the crystallization performance of the final polylactic acid thermoplastic elastomer and further affecting the spinning process; if the carbon chain of the first aliphatic dibasic acid is too short, its thermal stability is very poor and it will volatilize at the ester exchange temperature and cannot depolymerize the waste polylactic acid;

[0018] The number-average molecular weight of the double-end carboxyl poly(lactic acid) oligomer is 2,000 - 12,000 g / mol; if the molecular weight of the double-end carboxyl poly(lactic acid) oligomer is too low, the crystallization ability of the poly(lactic acid) thermoplastic elastomer will be low, thus affecting the spinning process; if the molecular weight of the double-end carboxyl poly(lactic acid) oligomer is too high, uneven reaction will occur during the repolymerization process, ultimately resulting in too wide a molecular weight distribution of the poly(lactic acid) thermoplastic elastomer, thus affecting the spinning process;

[0019] The degree of polymerization of the double-end carboxyl poly(lactic acid) oligomer is 25 - 160;

[0020] The first poly(lactic acid) is poly(lactic acid) with an intrinsic viscosity of 1.00 - 1.40 dL / g, and the second poly(lactic acid) is poly(lactic acid) with an intrinsic viscosity of 2.00 - 4.00 dL / g.

[0021] As a preferred technical solution:

[0022] In the preparation method of a regenerated polyester bicomponent side-by-side composite elastic fiber as described above, the second aliphatic dicarboxylic acid has 4 - 6 carbon atoms;

[0023] The polyether diol is one or more of polyethylene glycol, polypropylene glycol, and polytetrahydrofuran; the relative molecular weight of the polyether diol is 400 - 6,000 g / mol;

[0024] The first aliphatic diol has 2 - 10 carbon atoms;

[0025] The polyether diamine is one or more of polyoxyethylene diamine and polyoxypropylene diamine; the relative molecular weight of the polyether diamine is 400 - 4,000 g / mol;

[0026] The first aliphatic diamine has 4 - 12 carbon atoms;

[0027] The branching agent is one or more of glycerol, trimethylolpropane, pentaerythritol, and sorbitol.

[0028] In the preparation method of a regenerated polyester bicomponent side-by-side composite elastic fiber as described above, the molar ratio of the dicarboxylic acid to X is 1:1.01 - 1.05, the content of the double-end carboxyl poly(lactic acid) oligomer in the mixture of the double-end carboxyl poly(lactic acid) oligomer and the second aliphatic dicarboxylic acid is 90 - 99 mol%, the content of the polyether diol in the mixture of the polyether diol and the first aliphatic diol is 90 - 99 mol%, the content of the polyether diamine in the mixture of the polyether diamine and the first aliphatic diamine is 90 - 99 mol%, and the molar amount of the branching agent is 0.1 - 5% of the molar amount of the dicarboxylic acid.

[0029] A preparation method of the regenerated polyester bicomponent side-by-side composite elastic fiber as described above, the pressure of the pre-polycondensation reaction is 0.01 - 0.3 MPa, the temperature is 190 - 260 °C, and the time is 1 - 3 h; the pressure of the final polycondensation reaction is 5 - 300 Pa, the temperature is 260 - 280 °C, and the time is 3 - 5 h.

[0030] A preparation method of the regenerated polyester bicomponent side-by-side composite elastic fiber as described above, during the preparation process of the polylactic acid thermoplastic elastomer, an antioxidant is also added; the antioxidant is one or more of antioxidant 1010, antioxidant 168, and antioxidant 616; the mass of the antioxidant is 100 - 500 ppm of the total mass of the reaction raw materials.

[0031] A preparation method of the regenerated polyester bicomponent side-by-side composite elastic fiber as described above, the relative molecular mass of the polylactic acid thermoplastic elastomer is 14000 - 33000 g / mol, the molecular weight distribution index is 1.5 - 3.0, and the melting point is 130 - 190 °C.

[0032] A preparation method of the regenerated polyester bicomponent side-by-side composite elastic fiber as described above, the preparation process of the double-ended carboxyl polylactic acid oligomer is: adding waste polylactic acid, the first aliphatic dicarboxylic acid, and a catalyst into a reaction kettle, and reacting at 180 - 230 °C and 0.01 - 0.5 MPa for 2 - 5 h to obtain the double-ended carboxyl polylactic acid oligomer;

[0033] Among them, the mass of the first aliphatic dicarboxylic acid , the mass of the waste polylactic acid , the relative molecular mass of the first aliphatic dicarboxylic acid , and the theoretical value of the number-average molecular weight of the double-ended carboxyl polylactic acid oligomer satisfy the following formula:

[0034] ;

[0035] In the formula, , are in the unit of g; , are in the unit of g / mol; φ is 17 g / mol;

[0036] The mass of the catalyst is 100 - 500 ppm of the mass of the waste polylactic acid; the catalyst is one or more of titanium glycolate, tetrabutyl titanate, antimony glycolate, antimony acetate, antimony oxide, stannous octoate, stannous chloride, zinc acetate, and zinc oxide;

[0037] The derivation process of the above formula is: According to the preparation process of the double-ended carboxyl polylactic acid oligomer, the structural formula of the double-ended carboxyl polylactic acid oligomer can be speculated as (wherein, R is the segment between two carboxyl groups in the first aliphatic dibasic acid, and n is the number of lactic acid repeating units);

[0038] It can be seen therefrom that it includes n lactic acid repeating units and 1 first aliphatic dibasic acid; the relative molecular mass of the lactic acid link is 72, and when capped with the first aliphatic dibasic acid, 1 -OH (molar mass is 17 g / mol, denoted as φ) will be removed. Let the theoretical value of the number-average molecular weight of the double-end carboxyl poly(lactic acid) oligomer be , then Equation 1 can be listed:

[0039] = 72n + - φ; Equation 1

[0040] Converting gives Equation 2:

[0041] n = ([[]] - + φ) / 72; Equation 2

[0042] Let the mass of the waste poly(lactic acid) added during the preparation process be , and the number of moles of lactic acid links in the waste poly(lactic acid) be n PLA , then Equation 3 can be listed:

[0043] n PLA = m / 72; Equation 3

[0044] It can be obtained that the number of lactic acid links in the waste poly(lactic acid) is n PLA / n times more than the number of lactic acid links in the designed double-end carboxyl poly(lactic acid) oligomer, and the multiple of the increase is the number of moles n COOH of the required first aliphatic dibasic acid, that is, Equation 4 is obtained:

[0045] n COOH = n PLA / n; Equation 4

[0046] Substituting Equation 3 into Equation 4, Equation 5 is obtained:

[0047] n COOH = m / (72n); Equation 5

[0048] And the relative molecular mass of the first aliphatic dibasic acid can be calculated according to Equation 6:

[0049] = n COOH × ; Equation 6

[0050] Substituting Equation 5 into Equation 6, Equation 7 is obtained:

[0051] = (m × ) / (72n); Formula 7

[0052] Finally, substituting Formula 2 into Formula 7 gives the above formula;

[0053] Tests show that the relative deviation of the number-average molecular weight of the double-ended carboxyl poly(lactic acid) oligomer does not exceed 2%. The relative deviation = (|actual value - theoretical value| / theoretical value) × 100%. The above formula can be used to guide production. After determining the target number-average molecular weight of the double-ended carboxyl poly(lactic acid) oligomer, a suitable first aliphatic dibasic acid can be selected according to the above formula, and the mass of the first aliphatic dibasic acid and the mass of the waste poly(lactic acid) can be determined.

[0054] For the preparation method of a regenerated polyester bicomponent side-by-side composite elastic fiber as described above, the content of the poly(lactic acid) thermoplastic elastomer in the first component is 60 - 90 wt%, and the mass ratio of the first component to the second component is 2:8 - 8:2.

[0055] For the preparation method of a regenerated polyester bicomponent side-by-side composite elastic fiber as described above, the process parameters of the side-by-side composite spinning include: spinning temperature 190 - 230 °C, spinning speed 1500 - 2500 m / min, cooling air temperature 15 - 25 °C, cooling air speed 0.3 - 0.6 m / s, and relative humidity of the cooling air 60% - 80%.

[0056] For the preparation method of a regenerated polyester bicomponent side-by-side composite elastic fiber as described above, the single fiber fineness of the regenerated polyester bicomponent side-by-side composite elastic fiber is 1.1 - 5.5 dtex, the breaking strength is 1.5 - 3.0 cN / dtex, the elastic recovery rate is not less than 85% at 20% fixed elongation, the crimp ratio is 50 - 70%, the crimp elastic rate is not less than 90%, and the compression resilience rate ≥ 85%.

[0057] The principle of the present invention is as follows:

[0058] The formation of the crimp structure of the bicomponent side-by-side composite fiber is jointly determined by two factors: the thermal shrinkage difference between the two components and the good interfacial structure. Starting from the design of the polymer molecular structure, the present invention first designed a dicarboxyl polylactic acid oligomer through an ester exchange reaction, and then reacted it with a polyether diol (or polyether diamine), a branching agent, etc. to prepare a polylactic acid thermoplastic elastomer. The polyether diol (or polyether diamine) enables the polylactic acid thermoplastic elastomer to have a polyether segment, thereby enabling the polylactic acid thermoplastic elastomer to have good elastic recovery, so that an unbalanced stress deviating from the fiber axis is generated due to the thermal shrinkage difference between the two components during the fiber preparation process, providing a necessary condition for the generation of the crimp structure. The branching agent enables the polylactic acid thermoplastic elastomer to have a micro-branched structure, which can enhance the crimp performance of the fiber. For the bicomponent side-by-side composite melt spinning, the fluidity between the two components is the key to successfully realizing the spinning forming. The introduction of the polyether segment will increase the fluidity of the polylactic acid thermoplastic elastomer, resulting in too large a fluidity difference between it and polylactic acid. Therefore, the present invention uses a mixture of a polylactic acid thermoplastic elastomer and a first polylactic acid as the first component, and a second polylactic acid as the second component. The presence of the first polylactic acid can serve as a physical entanglement point to reduce the fluidity of the polylactic acid thermoplastic elastomer, and at the same time can promote the compatibility between the polylactic acid thermoplastic elastomer and the second polylactic acid at the interface.

[0059] Beneficial effects:

[0060] (1) By introducing a polylactic acid thermoplastic elastomer as the first component and spinning it side by side with the second polylactic acid, the fiber prepared by the present invention has excellent elasticity and a soft hand feeling, overcomes the disadvantages of traditional polylactic acid fibers having a hard hand feeling and poor elasticity, makes the fiber more skin-friendly, and broadens the application range of polylactic acid fibers in skin-friendly fabrics.

[0061] (2) By selecting a dicarboxyl polylactic acid oligomer with a specific molecular weight and degree of polymerization, as well as suitable reaction raw materials such as a dibasic acid and a polyether diol (or polyether diamine), the present invention ensures the compatibility and fluidity between the polylactic acid thermoplastic elastomer and the second polylactic acid during the spinning process, thereby improving the stability and continuity of the spinning process, reducing the production difficulty and cost.

[0062] (3) A part of the dibasic acid in the present invention is derived from the ester exchange reaction of waste polylactic acid and a first aliphatic dibasic acid. This not only realizes the high-value utilization of waste polylactic acid, reduces environmental pollution, but also conforms to the concept of sustainable development.

[0063] (4) Compared with the traditional preparation method of polylactic acid elastic fibers, the present invention can obtain elastic fibers with a self-crimp structure without an additional texturing treatment step, thereby saving energy consumption, reducing production costs, and avoiding mechanical damage to the fibers caused by the texturing treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 1H NMR spectrum of the double - end carboxyl poly(lactic acid) oligomer prepared in Example 11;

[0065] Figure 2 Cross - section SEM image of the regenerated polyester bicomponent side - by - side composite elastic fiber of Example 6. DETAILED DESCRIPTION OF THE INVENTION

[0066] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

[0067] The following are the test methods for relevant performance indicators in each example and comparative example:

[0068] Intrinsic viscosity: It is measured using an Ubbelohde viscometer with a capillary diameter of 0.7 - 0.8 mm. Weigh 0.25 g of the sample to be tested with an electronic balance, dissolve it in a mixed solvent of phenol and tetrachloroethane with a mass ratio of 1:1 in a water bath at 60 - 70 °C to obtain a test solution with a concentration of 0.005 g / ml. Then, place the test solution in a constant temperature water bath at 25 ± 0.1 °C for 10 min, observe and record the time it takes for the test solution to flow through the upper and lower calibration lines of the Ubbelohde viscometer (set a control group at the same time, the difference from this test is only that the sample to be tested is not added). The test is carried out 3 times in parallel and the average value is taken as the final result. The calculation process is as follows:

[0069] η r = ;

[0070] η sp = ;

[0071] ;

[0072] In the formula, η r is the relative viscosity, is the flow - through time of the test solution (s), is the flow - through time of the mixed solvent of phenol and tetrachloroethane in the control group (s), η sp is the specific viscosity, is the intrinsic viscosity (dL / g).

[0073] Number-average molecular weight, relative molecular weight, relative molecular mass, molecular weight distribution index: Tested by Agilent 1260 Gel Permeation Chromatograph (GPC), with the chromatographic column being Agilent HFIP series, and the mobile phase consisting of hexafluoroisopropanol and sodium trifluoroacetate (the concentration of sodium trifluoroacetate is 0.02 mol / L), and the test temperature is 35 °C.

[0074] Degree of polymerization: Dissolve 5 - 10 mg of the sample to be tested in 0.55 - 0.6 mL of deuterated chloroform (CDCl 3 ) to obtain the solution to be tested, and test it by Avance - 600Hz Nuclear Magnetic Resonance Spectrometer (NMR); among them, the number of scans is 64 times.

[0075] Melting point: Tested with reference to "GB / T 19466.3 - 2004 Plastics - Differential Scanning Calorimetry (DSC) - Part 3: Determination of melting and crystallization temperatures and enthalpies".

[0076] Melt index: Tested according to GB / T 3682.1 - 2018.

[0077] Denier: Tested according to GB / T 14343 - 2008.

[0078] Breaking strength: Tested according to GB / T 14344 - 2008.

[0079] Elastic recovery rate at 20% fixed elongation: Tested according to FZ / T 50007 - 2012.

[0080] Coiling curvature: Tested according to GB / T 14338 - 2022.

[0081] Coiling elastic rate: Tested according to GB / T 6506 - 2017.

[0082] Compression resilience rate: Tested according to FZ / T 52010 - 2014.

[0083] Example 1

[0084] A preparation method of a regenerated polyester bicomponent side - by - side composite elastic fiber, the specific steps are as follows:

[0085] (1) Preparation of raw materials;

[0086] Waste polylactic acid: Intrinsic viscosity is 1.00 dL / g;

[0087] The first aliphatic dibasic acid: Succinic acid;

[0088] Catalyst: Tetrabutyl titanate;

[0089] X: polyethylene glycol, with a relative molecular weight of 400 g / mol;

[0090] Branching agent: glycerol;

[0091] Antioxidant: antioxidant 1010;

[0092] First polylactic acid: intrinsic viscosity is 1.00 dL / g;

[0093] Second polylactic acid: intrinsic viscosity is 2.00 dL / g;

[0094] (2) Prepare a double-ended carboxyl polylactic acid oligomer;

[0095] Add waste polylactic acid, the first aliphatic dibasic acid, and a catalyst into a reaction kettle, and react at 180 °C and 0.01 MPa for 5 h to obtain a double-ended carboxyl polylactic acid oligomer with a number average molecular weight of 2000 g / mol and a degree of polymerization of 25;

[0096] Among them, the mass ratio of waste polylactic acid to the first aliphatic dibasic acid is 16:1, and the mass of the catalyst is 100 ppm of the mass of waste polylactic acid;

[0097] (3) Prepare a polylactic acid thermoplastic elastomer;

[0098] After mixing the double-ended carboxyl polylactic acid oligomer, X, the branching agent, and the antioxidant, first perform a pre-polycondensation reaction at 0.01 MPa and 190 °C for 3 h, and then perform a final polycondensation reaction at 300 Pa and 260 °C for 5 h to obtain a polylactic acid thermoplastic elastomer with a relative molecular weight of 14000 g / mol, a molecular weight distribution index of 1.5, and a melting point of 130 °C; among them, the molar ratio of the double-ended carboxyl polylactic acid oligomer to X is 1:1.01, the molar amount of the branching agent is 0.1% of the molar amount of the double-ended carboxyl polylactic acid oligomer, and the mass of the antioxidant is 100 ppm of the total mass of the double-ended carboxyl polylactic acid oligomer, X, and the branching agent;

[0099] (4) Prepare a regenerated polyester bicomponent side-by-side composite elastic fiber;

[0100] Taking the mixture of polylactic acid thermoplastic elastomer and the first polylactic acid as the first component, and the second polylactic acid as the second component, side-by-side composite spinning is carried out to obtain the recycled polyester bicomponent side-by-side composite elastic fiber; wherein, the melt index of the first component at 190°C and 2.16 kg is 60 g / 10 min, the melt index of the second component at 190°C and 2.16 kg is 65 g / 10 min, the content of the polylactic acid thermoplastic elastomer in the first component is 60 wt%, the mass ratio of the first component to the second component is 2:8. After mixing the first component and the second component in this proportion, DSC testing is carried out, and the result shows that there is only one melting point, indicating good compatibility between the first component and the second component; the process parameters of side-by-side composite spinning include: spinning temperature 190°C, spinning speed 1500 m / min, cooling air temperature 15°C, cooling air speed 0.3 m / s, and relative humidity of cooling air 60%.

[0101] The fineness of the single filament of the finally prepared recycled polyester bicomponent side-by-side composite elastic fiber is 1.1 dtex, the breaking strength is 1.5 cN / dtex, the elastic recovery rate at 20% fixed elongation is 85%, the crimp ratio is 50%, the crimp elastic rate is 91%, and the compression resilience rate is 85%.

[0102] Comparative Example 1

[0103] A method for preparing a fiber, which is only different from Example 1 in that: in step (2), the addition amount of waste polylactic acid is adjusted, and the mass ratio of waste polylactic acid to the first aliphatic dicarboxylic acid is 8:1, which makes the number-average molecular weight of the polylactic acid oligomer with double terminal carboxyl groups 1000 g / mol and the degree of polymerization 12.

[0104] The breaking strength of the finally prepared fiber is 1.0 cN / dtex.

[0105] Compared with Example 1, the breaking strength of the fiber in Comparative Example 1 decreased significantly. This is because the number-average molecular weight of the polylactic acid oligomer with double terminal carboxyl groups in Comparative Example 1 was too low, resulting in a decrease in the crystallization ability of the polylactic acid thermoplastic elastomer, and an ordered and dense crystalline structure could not be formed during the spinning process, thereby affecting the intermolecular force and orientation arrangement inside the fiber, making the overall mechanical properties of the fiber worse, and finally showing a decrease in the breaking strength.

[0106] Example 2

[0107] A method for preparing a recycled polyester bicomponent side-by-side composite elastic fiber, the specific steps are as follows:

[0108] (1) Preparation of raw materials;

[0109] Waste polylactic acid: intrinsic viscosity is 1.10 dL / g;

[0110] First aliphatic dicarboxylic acid: succinic acid;

[0111] Catalyst: antimony glycolate;

[0112] X: polypropylene glycol, with a relative molecular weight of 6000 g / mol;

[0113] Branching agent: glycerol;

[0114] Antioxidant: antioxidant 1010;

[0115] First polylactic acid: intrinsic viscosity is 1.10 dL / g;

[0116] Second polylactic acid: intrinsic viscosity is 2.05 dL / g;

[0117] (2) Preparation of double - end carboxyl polylactic acid oligomer;

[0118] Add waste polylactic acid, first aliphatic dibasic acid, and catalyst into the reaction kettle, and react at 190 °C and 0.05 MPa for 5 h to obtain a double - end carboxyl polylactic acid oligomer with a number - average molecular weight of 4000 g / mol and a degree of polymerization of 54;

[0119] Among them, the mass ratio of waste polylactic acid to the first aliphatic dibasic acid is 33:1, and the mass of the catalyst is 100 ppm of the mass of waste polylactic acid;

[0120] (3) Preparation of polylactic acid thermoplastic elastomer;

[0121] After mixing the double - end carboxyl polylactic acid oligomer, X, branching agent, and antioxidant, first carry out a pre - polycondensation reaction at 0.02 MPa and 200 °C for 3 h, and then carry out a final polycondensation reaction at 100 Pa and 260 °C for 5 h to obtain a polylactic acid thermoplastic elastomer with a relative molecular weight of 20000 g / mol, a molecular weight distribution index of 1.5, and a melting point of 150 °C; among them, the molar ratio of the double - end carboxyl polylactic acid oligomer to X is 1:1.01, the molar amount of the branching agent is 0.2% of the molar amount of the double - end carboxyl polylactic acid oligomer, and the mass of the antioxidant is 100 ppm of the total mass of the double - end carboxyl polylactic acid oligomer, X, and branching agent;

[0122] (4) Preparation of regenerated polyester bicomponent side - by - side composite elastic fiber;

[0123] Taking the mixture of polylactic acid thermoplastic elastomer and the first polylactic acid as the first component, and the second polylactic acid as the second component, side-by-side composite spinning is carried out to obtain regenerated polyester bicomponent side-by-side composite elastic fibers; wherein, the melt index of the first component at 195 °C and 2.16 kg is 70 g / 10 min, the melt index of the second component at 195 °C and 2.16 kg is 73 g / 10 min, the content of polylactic acid thermoplastic elastomer in the first component is 60 wt%, the mass ratio of the first component to the second component is 2:8. After mixing the first component and the second component in this proportion and carrying out DSC testing, the result shows that there is only one melting point, indicating good compatibility between the first component and the second component. The process parameters of side-by-side composite spinning include: spinning temperature 195 °C, spinning speed 1500 m / min, cooling air temperature 15 °C, cooling air speed 0.3 m / s, and relative humidity of cooling air 65%.

[0124] The fineness of the single filament of the finally prepared regenerated polyester bicomponent side-by-side composite elastic fiber is 1.5 dtex, the breaking strength is 1.5 cN / dtex, the elastic recovery rate at 20% fixed elongation is 87%, the crimp ratio is 55%, the crimp elastic rate is 93%, and the compression resilience rate is 87%.

[0125] Example 3

[0126] A preparation method of regenerated polyester bicomponent side-by-side composite elastic fibers, the specific steps are as follows:

[0127] (1) Preparation of raw materials;

[0128] Waste polylactic acid: intrinsic viscosity is 1.15 dL / g;

[0129] The first aliphatic dibasic acid: adipic acid;

[0130] Catalyst: titanium glycolate;

[0131] X: polytetrahydrofuran, relative molecular weight is 1000 g / mol;

[0132] Branching agent: glycerol;

[0133] Antioxidant: antioxidant 1010;

[0134] The first polylactic acid: intrinsic viscosity is 1.15 dL / g;

[0135] The second polylactic acid: intrinsic viscosity is 2.50 dL / g;

[0136] (2) Preparation of double-end carboxyl polylactic acid oligomer;

[0137] Add waste poly(lactic acid), the first aliphatic dicarboxylic acid, and a catalyst into a reaction kettle, and react at 200 °C and 0.1 MPa for 4 h to obtain a double-ended carboxyl poly(lactic acid) oligomer with a number-average molecular weight of 5000 g / mol and a degree of polymerization of 67;

[0138] Among them, the mass ratio of waste poly(lactic acid) to the first aliphatic dicarboxylic acid is 33:1, and the mass of the catalyst is 200 ppm of the mass of waste poly(lactic acid);

[0139] (3) Prepare a poly(lactic acid) thermoplastic elastomer;

[0140] Mix the double-ended carboxyl poly(lactic acid) oligomer, X, a branching agent, and an antioxidant, first carry out a pre-polycondensation reaction at 0.04 MPa and 210 °C for 3 h, and then carry out a final polycondensation reaction at 100 Pa and 260 °C for 5 h to obtain a poly(lactic acid) thermoplastic elastomer with a relative molecular weight of 30000 g / mol, a molecular weight distribution index of 1.7, and a melting point of 190 °C; among them, the molar ratio of the double-ended carboxyl poly(lactic acid) oligomer to X is 1:1.02, the molar amount of the branching agent is 0.3% of the molar amount of the double-ended carboxyl poly(lactic acid) oligomer, and the mass of the antioxidant is 200 ppm of the total mass of the double-ended carboxyl poly(lactic acid) oligomer, X, and the branching agent;

[0141] (4)Prepare a regenerated polyester bicomponent side-by-side composite elastic fiber;

[0142] Use the mixture of the poly(lactic acid) thermoplastic elastomer and the first poly(lactic acid) as the first component, and use the second poly(lactic acid) as the second component to carry out side-by-side composite spinning to obtain a regenerated polyester bicomponent side-by-side composite elastic fiber; among them, the melt index of the first component at 200 °C and 2.16 kg is 75 g / 10 min, the melt index of the second component at 200 °C and 2.16 kg is 74 g / 10 min, the content of the poly(lactic acid) thermoplastic elastomer in the first component is 65 wt%, the mass ratio of the first component to the second component is 3:7. After mixing the first component and the second component in this proportion and carrying out a DSC test, the result shows that there is only one melting point, indicating good compatibility between the first component and the second component. The process parameters of side-by-side composite spinning include: spinning temperature 200 °C, spinning speed 1500 m / min, cooling air temperature 15 °C, cooling air speed 0.4 m / s, and relative humidity of cooling air 60%.

[0143] The single-filament fineness of the finally prepared regenerated polyester bicomponent side-by-side composite elastic fiber is 2.5 dtex, the breaking strength is 1.9 cN / dtex, the elastic recovery rate at 20% fixed elongation is 89%, the crimp ratio is 55%, the crimp elastic rate is 93%, and the compression resilience rate is 89%.

[0144] Example 4

[0145] A preparation method of regenerated polyester bicomponent side-by-side composite elastic fiber is as follows:

[0146] (1) Preparation of raw materials;

[0147] Waste polylactic acid: intrinsic viscosity is 1.20 dL / g;

[0148] The first aliphatic dibasic acid: adipic acid;

[0149] Catalyst: antimony acetate;

[0150] X: a mixture of polyethylene glycol and ethylene glycol, the relative molecular weight of polyethylene glycol is 6000 g / mol, and the content of polyethylene glycol is 90 mol%;

[0151] Branching agent: trimethylolpropane;

[0152] Antioxidant: antioxidant 168;

[0153] The first polylactic acid: intrinsic viscosity is 1.20 dL / g;

[0154] The second polylactic acid: intrinsic viscosity is 2.55 dL / g;

[0155] (2) Preparation of double-end carboxyl polylactic acid oligomer;

[0156] Add waste polylactic acid, the first aliphatic dibasic acid, and the catalyst into the reaction kettle, and react at 205 °C and 0.15 MPa for 4 h to obtain a double-end carboxyl polylactic acid oligomer with a number-average molecular weight of 6000 g / mol and a degree of polymerization of 81;

[0157] Among them, the mass ratio of waste polylactic acid to the first aliphatic dibasic acid is 40:1, and the mass of the catalyst is 200 ppm of the mass of waste polylactic acid;

[0158] (3) Preparation of polylactic acid thermoplastic elastomer;

[0159] After mixing the double-end carboxyl polylactic acid oligomer, X, the branching agent, and the antioxidant, first carry out a pre-polycondensation reaction at 0.06 MPa and 220 °C for 2 h, and then carry out a final polycondensation reaction at 100 Pa and 270 °C for 4 h to obtain a polylactic acid thermoplastic elastomer with a relative molecular weight of 33000 g / mol, a molecular weight distribution index of 1.9, and a melting point of 190 °C; among them, the molar ratio of the double-end carboxyl polylactic acid oligomer to X is 1:1.02, the molar amount of the branching agent is 0.7% of the molar amount of the double-end carboxyl polylactic acid oligomer, and the mass of the antioxidant is 300 ppm of the total mass of the double-end carboxyl polylactic acid oligomer, X, and the branching agent;

[0160] (4) Preparation of regenerated polyester bicomponent side-by-side composite elastic fiber;

[0161] A mixture of polylactic acid thermoplastic elastomer and the first polylactic acid is used as the first component, and the second polylactic acid is used as the second component. Side-by-side composite spinning is carried out to obtain regenerated polyester bicomponent side-by-side composite elastic fibers. Among them, the melt index of the first component at 205 °C and 2.16 kg is 86 g / 10 min, the melt index of the second component at 205 °C and 2.16 kg is 87 g / 10 min, the content of polylactic acid thermoplastic elastomer in the first component is 70 wt%, and the mass ratio of the first component to the second component is 3:7. After mixing the first component and the second component in this proportion, DSC testing is carried out. The results show that there is only one melting point, indicating good compatibility between the first component and the second component. The process parameters of side-by-side composite spinning include: spinning temperature 205 °C, spinning speed 2000 m / min, cooling air temperature 20 °C, cooling air speed 0.4 m / s, and relative humidity of cooling air 70%.

[0162] The fineness of the single filament of the finally obtained regenerated polyester bicomponent side-by-side composite elastic fiber is 2 dtex, the breaking strength is 1.9 cN / dtex, the elastic recovery rate at 20% fixed elongation is 89%, the crimp ratio is 70%, the crimp elasticity rate is 96%, and the compression resilience rate is 90%.

[0163] Example 5

[0164] A preparation method of regenerated polyester bicomponent side-by-side composite elastic fibers, the specific steps are as follows:

[0165] (1) Preparation of raw materials;

[0166] Waste polylactic acid: intrinsic viscosity is 1.25 dL / g;

[0167] The first aliphatic dicarboxylic acid: suberic acid;

[0168] Catalyst: antimony oxide;

[0169] X: A mixture of polyethylene glycol and decanediol, the relative molecular weight of polyethylene glycol is 1000 g / mol, and the content of polyethylene glycol is 99 mol%;

[0170] 996379 Branching agent: trimethylolpropane;

[0171] Antioxidant: antioxidant 168;

[0172] The first polylactic acid: intrinsic viscosity is 1.25 dL / g;

[0173] The second polylactic acid: intrinsic viscosity is 2.55 dL / g;

[0174] (2) Preparation of double-end carboxyl polylactic acid oligomer;

[0175] Waste poly(lactic acid), a first aliphatic dicarboxylic acid, and a catalyst were added to a reaction kettle, and the reaction was carried out at 210 °C and 0.2 MPa for 3 h to obtain a carboxyl-terminated poly(lactic acid) oligomer with a number-average molecular weight of 8000 g / mol and a degree of polymerization of 109;

[0176] Among them, the mass ratio of waste poly(lactic acid) to the first aliphatic dicarboxylic acid was 45:1, and the mass of the catalyst was 300 ppm of the mass of waste poly(lactic acid);

[0177] (3)Prepare a poly(lactic acid) thermoplastic elastomer;

[0178] After mixing the carboxyl-terminated poly(lactic acid) oligomer, X, a branching agent, and an antioxidant, a pre-polycondensation reaction was first carried out at 0.08 MPa and 240 °C for 2 h, and then a final polycondensation reaction was carried out at 80 Pa and 270 °C for 4 h to obtain a poly(lactic acid) thermoplastic elastomer with a relative molecular weight of 25000 g / mol, a molecular weight distribution index of 2.4, and a melting point of 170 °C; among them, the molar ratio of the carboxyl-terminated poly(lactic acid) oligomer to X was 1:1.03, the molar amount of the branching agent was 1.5% of the molar amount of the carboxyl-terminated poly(lactic acid) oligomer, and the mass of the antioxidant was 300 ppm of the total mass of the carboxyl-terminated poly(lactic acid) oligomer, X, and the branching agent;

[0179] (4)Prepare a regenerated polyester bicomponent side-by-side composite elastic fiber;

[0180] A mixture of the poly(lactic acid) thermoplastic elastomer and the first poly(lactic acid) was used as the first component, and the second poly(lactic acid) was used as the second component for side-by-side composite spinning to obtain a regenerated polyester bicomponent side-by-side composite elastic fiber; among them, the melt index of the first component at 210 °C and 2.16 kg was 101 g / 10 min, the melt index of the second component at 210 °C and kg was 97 g / 10 min, the content of the poly(lactic acid) thermoplastic elastomer in the first component was 70 wt%, the mass ratio of the first component to the second component was 4:6, and after mixing the first component and the second component in this proportion and performing a DSC test, the result showed that there was only one melting point, indicating good compatibility between the first component and the second component. The process parameters of side-by-side composite spinning included: spinning temperature 210 °C, spinning speed 2000 m / min, cooling air temperature 20 °C, cooling air speed 0.5 m / s, and relative humidity of cooling air 70%.

[0181] The single-filament fineness of the finally prepared regenerated polyester bicomponent side-by-side composite elastic fiber was 3 dtex, the breaking strength was 2 cN / dtex, the elastic recovery rate at 20% fixed elongation was 88%, the crimp ratio was 60%, the crimp elasticity rate was 93%, and the compression resilience rate was 89%.

[0182] Example 6

[0183] A method for preparing a regenerated polyester bicomponent side-by-side composite elastic fiber, the specific steps are as follows:

[0184] (1)Preparation of raw materials;

[0185] Waste polylactic acid: intrinsic viscosity is 1.30 dL / g;

[0186] The first aliphatic dibasic acid: suberic acid;

[0187] Catalyst: stannous octoate;

[0188] The second aliphatic dibasic acid: succinic acid;

[0189] X: polyethylene oxide diamine, relative molecular weight is 400 g / mol;

[0190] Branching agent: pentaerythritol;

[0191] Antioxidant: antioxidant 168;

[0192] The first polylactic acid: intrinsic viscosity is 1.30 dL / g;

[0193] The second polylactic acid: intrinsic viscosity is 3.0 dL / g;

[0194] (2)Preparation of double-end carboxyl polylactic acid oligomer;

[0195] Add waste polylactic acid, the first aliphatic dibasic acid, and the catalyst into the reaction kettle, react at 215 °C and 0.2 MPa for 3 h, and obtain a double-end carboxyl polylactic acid oligomer with a number average molecular weight of 9000 g / mol and a degree of polymerization of 123;

[0196] Among them, the mass ratio of waste polylactic acid to the first aliphatic dibasic acid is 51:1, and the mass of the catalyst is 300 ppm of the mass of waste polylactic acid;

[0197] (3)Preparation of polylactic acid thermoplastic elastomer;

[0198] After mixing a double - end carboxyl polylactic acid oligomer, a second aliphatic dicarboxylic acid, X, a branching agent, and an antioxidant, first carry out a prepolycondensation reaction at 0.1 MPa and 245 °C for 2 h, and then carry out a final polycondensation reaction at 80 Pa and 270 °C for 4 h to obtain a polylactic acid thermoplastic elastomer with a relative molecular mass of 25000 g / mol, a molecular weight distribution index of 2.3, and a melting point of 170 °C; wherein, the ratio of the total molar amount of the double - end carboxyl polylactic acid oligomer and the second aliphatic dicarboxylic acid to the molar amount of X is 1:1.03, the molar amount of the double - end carboxyl polylactic acid oligomer is 90% of the total molar amount of the double - end carboxyl polylactic acid oligomer and the second aliphatic dicarboxylic acid, the molar amount of the branching agent is 2.5% of the total molar amount of the double - end carboxyl polylactic acid oligomer and the second aliphatic dicarboxylic acid, and the mass of the antioxidant is 400 ppm of the total mass of the double - end carboxyl polylactic acid oligomer, the second aliphatic dicarboxylic acid, X, and the branching agent;

[0199] (4)Prepare a regenerated polyester bicomponent side - by - side composite elastic fiber;

[0200] Take the mixture of the polylactic acid thermoplastic elastomer and the first polylactic acid as the first component, and take the second polylactic acid as the second component, and carry out side - by - side composite spinning to obtain a regenerated polyester bicomponent side - by - side composite elastic fiber; wherein, the melt index of the first component at 215 °C and 2.16 kg is 105 g / 10 min, the melt index of the second component at 215 °C and 2.16 kg is 103 g / 10 min, the content of the polylactic acid thermoplastic elastomer in the first component is 80 wt%, the mass ratio of the first component to the second component is 5:5. After mixing the first component and the second component in this ratio and carrying out DSC testing, the result shows that there is only one melting point, indicating good compatibility between the first component and the second component. The process parameters of side - by - side composite spinning include: spinning temperature 215 °C, spinning speed 2000 m / min, cooling air temperature 20 °C, cooling air speed 0.5 m / s, and relative humidity of cooling air 75%.

[0201] The single - filament fineness of the finally prepared regenerated polyester bicomponent side - by - side composite elastic fiber is 3.5 dtex, the breaking strength is 2 cN / dtex, the elastic recovery rate at 20% fixed elongation is 90%, the crimp ratio is 60%, the crimp elasticity rate is 94%, the compression resilience rate is 92%, and the cross - section SEM picture is as Figure 2 shown. It can be seen from the figure that the compatibility between the first component and the second component is good, and there is no obvious separation between the two.

[0202] Example 7

[0203] A preparation method of a regenerated polyester bicomponent side - by - side composite elastic fiber, the specific steps are as follows:

[0204] (1)Preparation of raw materials;

[0205] Waste polylactic acid: intrinsic viscosity is 1.30 dL / g;

[0206] The first aliphatic dibasic acid: sebacic acid;

[0207] Catalyst: stannous chloride;

[0208] The second aliphatic dibasic acid: succinic acid;

[0209] X: polyoxypropylene diamine, relative molecular weight is 4000 g / mol;

[0210] Branching agent: pentaerythritol;

[0211] Antioxidant: antioxidant 616;

[0212] The first polylactic acid: intrinsic viscosity is 1.30 dL / g;

[0213] The second polylactic acid: intrinsic viscosity is 3.05 dL / g;

[0214] (2) Prepare a double-end carboxyl polylactic acid oligomer;

[0215] Add waste polylactic acid, the first aliphatic dibasic acid, and the catalyst into a reaction kettle, and react at 220 °C and 0.3 MPa for 2 h to obtain a double-end carboxyl polylactic acid oligomer with a number average molecular weight of 10000 g / mol and a degree of polymerization of 136;

[0216] Among them, the mass ratio of waste polylactic acid to the first aliphatic dibasic acid is 49:1, and the mass of the catalyst is 400 ppm of the mass of waste polylactic acid;

[0217] (3) Prepare a polylactic acid thermoplastic elastomer;

[0218] Mix the double-end carboxyl polylactic acid oligomer, the second aliphatic dibasic acid, X, the branching agent, and the antioxidant, first carry out a pre-polycondensation reaction at 0.15 MPa and 250 °C for 1 h, and then carry out a final polycondensation reaction at 50 Pa and 280 °C for 3 h to obtain a polylactic acid thermoplastic elastomer with a relative molecular weight of 15000 g / mol, a molecular weight distribution index of 2.2, and a melting point of 140 °C; among them, the total molar amount of the double-end carboxyl polylactic acid oligomer and the second aliphatic dibasic acid is in a ratio of 1:1.04 to the molar amount of X, the molar amount of the double-end carboxyl polylactic acid oligomer is 95% of the total molar amount of the double-end carboxyl polylactic acid oligomer and the second aliphatic dibasic acid, the molar amount of the branching agent is 3% of the total molar amount of the double-end carboxyl polylactic acid oligomer and the second aliphatic dibasic acid, and the mass of the antioxidant is 400 ppm of the total mass of the double-end carboxyl polylactic acid oligomer, the second aliphatic dibasic acid, X, and the branching agent;

[0219] (4) Prepare a regenerated polyester bicomponent side-by-side composite elastic fiber;

[0220] Using a mixture of polylactic acid thermoplastic elastomer and the first polylactic acid as the first component and the second polylactic acid as the second component, side-by-side composite spinning is carried out to obtain recycled polyester bicomponent side-by-side composite elastic fibers. Among them, the melt index of the first component at 220 °C and 2.16 kg is 120 g / 10 min, the melt index of the second component at 220 °C and 2.16 kg is 108 g / 10 min, the content of polylactic acid thermoplastic elastomer in the first component is 80 wt%, and the mass ratio of the first component to the second component is 6:4. After mixing the first component and the second component according to this ratio and performing DSC testing, the results show that there is only one melting point, indicating good compatibility between the first component and the second component. The process parameters of side-by-side composite spinning include: spinning temperature 220 °C, spinning speed 2500 m / min, cooling air temperature 25 °C, cooling air speed 0.3 m / s, and relative humidity of cooling air 80%.

[0221] The single filament fineness of the finally obtained recycled polyester bicomponent side-by-side composite elastic fibers is 4.5 dtex, the breaking strength is 2.5 cN / dtex, the elastic recovery rate at 20% fixed elongation is 87%, the crimp ratio is 55%, the crimp elasticity rate is 93%, and the compression resilience rate is 87%.

[0222] Example 8

[0223] A preparation method of recycled polyester bicomponent side-by-side composite elastic fibers, the specific steps are as follows:

[0224] (1) Preparation of raw materials;

[0225] Waste polylactic acid: intrinsic viscosity is 1.35 dL / g;

[0226] The first aliphatic dicarboxylic acid: sebacic acid;

[0227] Catalyst: zinc acetate;

[0228] The second aliphatic dicarboxylic acid: adipic acid;

[0229] X: a mixture of polyethylene oxide diamine and butanediamine, the relative molecular weight of polyethylene oxide diamine is 1000 g / mol, and the content of polyethylene oxide diamine is 90 mol%;

[0230] Branching agent: pentaerythritol;

[0231] Antioxidant: antioxidant 616;

[0232] The first polylactic acid: intrinsic viscosity is 1.35 dL / g;

[0233] The second polylactic acid: intrinsic viscosity is 3.50 dL / g;

[0234] (2) Prepare carboxyl-terminated polylactic acid oligomer;

[0235] Add waste polylactic acid, the first aliphatic dibasic acid, and a catalyst into a reaction kettle, and react at 225 °C and 0.4 MPa for 2 h to obtain a carboxyl-terminated polylactic acid oligomer with a number-average molecular weight of 11,000 g / mol and a degree of polymerization of 150;

[0236] Among them, the mass ratio of waste polylactic acid to the first aliphatic dibasic acid is 54:1, and the mass of the catalyst is 400 ppm of the mass of waste polylactic acid;

[0237] (3) Prepare polylactic acid thermoplastic elastomer;

[0238] After mixing the carboxyl-terminated polylactic acid oligomer, the second aliphatic dibasic acid, X, a branching agent, and an antioxidant, first perform a pre-polycondensation reaction at 0.2 MPa and 255 °C for 1 h, and then perform a final polycondensation reaction at 30 Pa and 280 °C for 3 h to obtain a polylactic acid thermoplastic elastomer with a relative molecular weight of 20,000 g / mol, a molecular weight distribution index of 1.8, and a melting point of 150 °C; among them, the total molar amount of the carboxyl-terminated polylactic acid oligomer and the second aliphatic dibasic acid is in a ratio of 1:1.04 to the molar amount of X, the molar amount of the carboxyl-terminated polylactic acid oligomer is 96% of the total molar amount of the carboxyl-terminated polylactic acid oligomer and the second aliphatic dibasic acid, the molar amount of the branching agent is 4% of the molar amounts of the carboxyl-terminated polylactic acid oligomer and the second aliphatic dibasic acid, and the mass of the antioxidant is 500 ppm of the total mass of the carboxyl-terminated polylactic acid oligomer, the second aliphatic dibasic acid, X, and the branching agent;

[0239] (4) Prepare regenerated polyester bicomponent side-by-side composite elastic fiber;

[0240] Use the mixture of the polylactic acid thermoplastic elastomer and the first polylactic acid as the first component, and use the second polylactic acid as the second component for side-by-side composite spinning to obtain a regenerated polyester bicomponent side-by-side composite elastic fiber; among them, the melt index of the first component at 225 °C and 2.16 kg is 125 g / 10 min, the melt index of the second component at 225 °C and 2.16 kg is 123 g / 10 min, the content of the polylactic acid thermoplastic elastomer in the first component is 90 wt%, the mass ratio of the first component to the second component is 7:3, and after mixing the first component and the second component in this ratio and performing a DSC test, the result shows that there is only one melting point, indicating good compatibility between the first component and the second component. The process parameters of side-by-side composite spinning include: spinning temperature 225 °C, spinning speed 2500 m / min, cooling air temperature 25 °C, cooling air speed 0.4 m / s, and relative humidity of cooling air 80%.

[0241] The monofilament fineness of the finally prepared regenerated polyester bicomponent side-by-side composite elastic fiber is 5 dtex, the breaking strength is 2.5 cN / dtex, the elastic recovery rate at 20% fixed elongation is 90%, the crimp ratio is 50%, the crimp elastic modulus is 90%, and the compression resilience rate is 89%.

[0242] Example 9

[0243] A preparation method of a regenerated polyester bicomponent side-by-side composite elastic fiber comprises the following specific steps:

[0244] (1) Preparation of raw materials;

[0245] Waste polylactic acid: intrinsic viscosity is 1.40 dL / g;

[0246] First aliphatic dicarboxylic acid: eicosanedioic acid;

[0247] Catalyst: zinc oxide;

[0248] Second aliphatic dicarboxylic acid: adipic acid;

[0249] X: a mixture of polyethylene oxide diamine and dodecane diamine, the relative molecular weight of polyethylene oxide diamine is 1000 g / mol, and the content of polyethylene oxide diamine is 99 mol%;

[0250] Branching agent: sorbitol;

[0251] Antioxidant: antioxidant 616;

[0252] First polylactic acid: intrinsic viscosity is 1.40 dL / g;

[0253] Second polylactic acid: intrinsic viscosity is 4.00 dL / g;

[0254] (2) Preparation of double-end carboxyl polylactic acid oligomer;

[0255] Add waste polylactic acid, first aliphatic dicarboxylic acid, and catalyst into a reaction kettle, and react at 230 °C and 0.5 MPa for 2 h to obtain a double-end carboxyl polylactic acid oligomer with a number-average molecular weight of 12000 g / mol and a degree of polymerization of 160;

[0256] Among them, the mass ratio of waste polylactic acid to first aliphatic dicarboxylic acid is 34:1, and the mass of the catalyst is 500 ppm of the mass of waste polylactic acid;

[0257] (3) Preparation of polylactic acid thermoplastic elastomer;

[0258] After mixing the double-end carboxyl polylactic acid oligomer, the second aliphatic dicarboxylic acid, X, the branching agent, and the antioxidant, first conduct a pre-polycondensation reaction at 0.3 MPa and 260 °C for 1 h, and then conduct a final polycondensation reaction at 5 Pa and 280 °C for 3 h to obtain a polylactic acid thermoplastic elastomer with a relative molecular mass of 14,000 g / mol, a molecular weight distribution index of 3, and a melting point of 140 °C; wherein, the ratio of the total molar amount of the double-end carboxyl polylactic acid oligomer and the second aliphatic dicarboxylic acid to the molar amount of X is 1:1.05, the molar amount of the double-end carboxyl polylactic acid oligomer is 99% of the total molar amount of the double-end carboxyl polylactic acid oligomer and the second aliphatic dicarboxylic acid, the molar amount of the branching agent is 5% of the total molar amount of the double-end carboxyl polylactic acid oligomer and the second aliphatic dicarboxylic acid, and the mass of the antioxidant is 500 ppm of the total mass of the double-end carboxyl polylactic acid oligomer, the second aliphatic dicarboxylic acid, X, and the branching agent;

[0259] (4)Prepare a recycled polyester bicomponent side-by-side composite elastic fiber;

[0260] Use the mixture of the polylactic acid thermoplastic elastomer and the first polylactic acid as the first component, and use the second polylactic acid as the second component for side-by-side composite spinning to obtain a recycled polyester bicomponent side-by-side composite elastic fiber; wherein, the melt index of the first component at 230 °C and 2.16 kg is 150 g / 10 min, the melt index of the second component at 230 °C and 2.16 kg is 147 g / 10 min, the content of the polylactic acid thermoplastic elastomer in the first component is 90 wt%, the mass ratio of the first component to the second component is 8:2. After mixing the first component and the second component in this proportion and conducting a DSC test, the result shows that there is only one melting point, indicating good compatibility between the first component and the second component. The process parameters of the side-by-side composite spinning include: spinning temperature 230 °C, spinning speed 2500 m / min, cooling air temperature 25 °C, cooling air speed 0.6 m / s, and relative humidity of the cooling air 80%.

[0261] The single fiber fineness of the finally prepared recycled polyester bicomponent side-by-side composite elastic fiber is 5.5 dtex, the breaking strength is 3 cN / dtex, the elastic recovery rate at 20% fixed elongation is 88%, the crimp ratio is 55%, the crimp elasticity rate is 92%, and the compression resilience rate is 89%.

[0262] Comparative Example 2

[0263] A method for preparing a fiber, which is only different from Example 9 in that: in step (2), the addition amount of the waste polylactic acid is adjusted, and the mass ratio of the waste polylactic acid to the first aliphatic dicarboxylic acid is 37:1, which makes the number average molecular weight of the double-end carboxyl polylactic acid oligomer 13,000 g / mol and the degree of polymerization 176.

[0264] The breaking strength of the finally prepared fiber is 1.1 cN / dtex.

[0265] Comparing Comparative Example 2 with Example 9, the breaking strength of the fiber decreased significantly. This is because the number-average molecular weight of the double-ended carboxyl polylactic acid oligomer in Comparative Example 2 was too high, resulting in uneven reactions during repolymerization. Eventually, the molecular weight distribution of the polylactic acid thermoplastic elastomer became too wide, causing more defects in the internal structure of the fiber. The arrangement and interaction between molecular chains became disordered. When the fiber was subjected to external forces, stress could not be evenly distributed on the molecular chains and was prone to concentration at the defect sites, leading to easier breakage of the fiber and a decrease in the breaking strength.

[0266] Comparative Example 3

[0267] A method for preparing a fiber, which is only different from Example 9 in that: the first aliphatic dibasic acid used in this comparative example is tetracosane dicarboxylic acid (CAS No. 3365-67-1).

[0268] The breaking strength of the finally prepared regenerated polyester bicomponent side-by-side composite elastic fiber was 1.3 cN / dtex.

[0269] Comparing Comparative Example 3 with Example 9, the breaking strength of the fiber decreased significantly. This is because the carbon chain of the first aliphatic dibasic acid in Comparative Example 3 was too long, resulting in a decrease in the reaction activity of the terminal carboxyl group and making it difficult to complete the transesterification reaction thoroughly. This led to insufficient preparation of the double-ended carboxyl polylactic acid oligomer and, at the same time, excessively damaged the regularity of the polylactic acid molecular chain, seriously affecting the crystallization performance of the polylactic acid thermoplastic elastomer. Eventually, a good fiber structure could not be formed during the spinning process, thus reducing the mechanical properties of the fiber.

[0270] Example 10

[0271] A method for preparing a regenerated polyester bicomponent side-by-side composite elastic fiber, which is only different from Example 1 in that: no antioxidant is added in step (3); the relative molecular weight of the polylactic acid thermoplastic elastomer is 20000 g / mol, the molecular weight distribution index is 1.6, and the melting point is 180 °C.

[0272] The single filament fineness of the finally prepared regenerated polyester bicomponent side-by-side composite elastic fiber was 1.3 dtex, the breaking strength was 2.5 cN / dtex, the elastic recovery rate at 20% fixed elongation was 87%, the crimp ratio was 60%, the crimp elasticity rate was 93%, and the compression resilience rate was 87%.

[0273] Example 11

[0274] A preparation method of regenerated polyester bicomponent side-by-side composite elastic fiber, which is only different from Example 1 in that: the intrinsic viscosity of waste polylactic acid is 1.40 dL / g, the first aliphatic dibasic acid is adipic acid, and the mass of the catalyst is 300 ppm of the mass of waste polylactic acid; when preparing the double-terminal carboxyl polylactic acid oligomer, the mass ratio of waste polylactic acid to the first aliphatic dibasic acid is 13:1, the reaction temperature is 150 °C, the reaction time is 4 h, and the number-average molecular weight of the prepared double-terminal carboxyl polylactic acid oligomer is 2000 g / mol, and the nuclear magnetic resonance spectrum is as Figure 1 shown.

[0275] The fineness of the single filament of the finally prepared regenerated polyester bicomponent side-by-side composite elastic fiber is 1.2 dtex, the breaking strength is 1.7 cN / dtex, the elastic recovery rate at 20% fixed elongation is 87%, the crimp ratio is 60%, the crimp elastic rate is 92%, and the compression resilience rate is 87%.

[0276] In the above examples, it has been verified that the relative deviation of the number-average molecular weight of the double-terminal carboxyl polylactic acid oligomer does not exceed 2%, and the relative deviation = (|actual value - theoretical value| / theoretical value) × 100%, and the calculation formula of the theoretical value is as follows:

[0277] ;

[0278] In the formula, (the mass of the first aliphatic dibasic acid), (the mass of waste polylactic acid) are in the unit of g; (the relative molecular weight of the first aliphatic dibasic acid), (the theoretical value of the number-average molecular weight of the double-terminal carboxyl polylactic acid oligomer) are in the unit of g / mol; φ is 17 g / mol.

[0279] In this article, the number-average molecular weight is defaulted to the actual value, unless the number-average molecular weight is clearly defined as the theoretical value.

Claims

1. A method for preparing a recycled polyester bicomponent parallel composite elastic fiber, characterized in that: A mixture of a polylactic acid thermoplastic elastomer and a first polylactic acid is used as a first component, and a second polylactic acid is used as a second component, and parallel composite spinning is performed to obtain a recycled polyester two-component parallel composite elastic fiber; The preparation process of polylactic acid thermoplastic elastomer is as follows: after mixing the reaction raw materials, sequentially carrying out a pre-polycondensation reaction and a final polycondensation reaction, the polylactic acid thermoplastic elastomer is obtained; The reaction raw materials include dibasic acid, X, and branching agent; The dibasic acid is a double-terminal carboxyl polylactic acid oligomer, which is prepared by an ester exchange reaction between waste polylactic acid and a first aliphatic dibasic acid; Alternatively, the dibasic acid is a mixture of a double-terminated carboxyl-containing polylactic acid oligomer and a second aliphatic dibasic acid; X is a polyether diol; Alternatively, X is a mixture of a polyether diol and a first aliphatic diol; Alternatively, X is a polyether diamine; Alternatively, X is a mixture of a polyether diamine and a first aliphatic diamine; The first aliphatic dibasic acid has 4 to 20 carbon atoms; The number average molecular weight of the double-terminated carboxyl polylactic acid oligomer is 2000-12000 g / mol; The degree of polymerization of the double-terminated carboxyl polylactic acid oligomer is 25-160; The first polylactic acid is a polylactic acid having an intrinsic viscosity of 1.00-1.40 dL / g, and the second polylactic acid is a polylactic acid having an intrinsic viscosity of 2.00-4.00 dL / g; The branching agent is one or more of glycerol, trimethylolpropane, pentaerythritol and sorbitol.

2. The method for preparing a recycled polyester bicomponent parallel composite elastic fiber according to claim 1, characterized in that: The second aliphatic dibasic acid has 4 to 6 carbon atoms; The polyether diol is one or more of polyethylene glycol, polypropylene glycol and polytetrahydrofuran; the relative molecular weight of the polyether diol is 400-6000 g / mol; The first aliphatic diol has 2 to 10 carbon atoms; The polyether diamine is one or more of polyoxyethylene diamine and polyoxypropylene diamine; the relative molecular weight of the polyether diamine is 400-4000 g / mol; The first aliphatic diamine has 4-12 carbon atoms.

3. The method for preparing a recycled polyester bicomponent parallel composite elastic fiber according to claim 2, characterized in that: The molar ratio of the dibasic acid to X is 1:1.01-1.05, the content of the double-terminal carboxyl polylactic acid oligomer in the mixture of the double-terminal carboxyl polylactic acid oligomer and the second aliphatic dibasic acid is 90-99 mol%, the content of the polyether diol in the mixture of the polyether diol and the first aliphatic diol is 90-99 mol%, the content of the polyether diamine in the mixture of the polyether diamine and the first aliphatic diamine is 90-99 mol%, and the molar amount of the branching agent is 0.1-5% of the molar amount of the dibasic acid.

4. The method for preparing a recycled polyester bicomponent parallel composite elastic fiber according to claim 1, characterized in that: The pressure of the preliminary polycondensation reaction is 0.01-0.3MPa, the temperature is 190-260°C, and the time is 1-3h; the pressure of the final polycondensation reaction is 5-300Pa, the temperature is 260-280°C, and the time is 3-5h.

5. The method for preparing a recycled polyester bicomponent parallel composite elastic fiber according to claim 1, characterized in that: During the preparation of the polylactic acid thermoplastic elastomer, an antioxidant is also added; the antioxidant is one or more of antioxidant 1010, antioxidant 168 and antioxidant 616; the mass of the antioxidant is 100-500ppm of the total mass of the reaction raw materials.

6. The method for preparing a recycled polyester bicomponent parallel composite elastic fiber according to claim 1, characterized in that: The relative molecular mass of the polylactic acid thermoplastic elastomer is 14000-33000 g / mol, the molecular weight distribution index is 1.5-3.0, and the melting point is 130-190°C.

7. The method for preparing a recycled polyester bicomponent parallel composite elastic fiber according to claim 1, characterized in that: The preparation process of the double-terminal carboxyl polylactic acid oligomer is as follows: waste polylactic acid, a first aliphatic dibasic acid and a catalyst are added into a reaction kettle, and the reaction is carried out at 180-230° C. and 0.01-0.5 MPa for 2-5 hours to obtain the double-terminal carboxyl polylactic acid oligomer; The mass of the catalyst is 100-500ppm of the mass of the waste polylactic acid; the catalyst is one or more of ethylene glycol titanium, tetrabutyl titanate, ethylene glycol antimony, antimony acetate, antimony oxide, stannous octoate, stannous chloride, zinc acetate and zinc oxide.

8. The method for preparing a recycled polyester bicomponent parallel composite elastic fiber according to claim 1, characterized in that: The content of the polylactic acid thermoplastic elastomer in the first component is 60-90wt%, and the mass ratio of the first component to the second component is 2:8-8:

2.

9. The method for preparing a recycled polyester bicomponent parallel composite elastic fiber according to claim 8, characterized in that: The process parameters of parallel composite spinning include: spinning temperature 190-230°C, spinning speed 1500-2500m / min, cooling air temperature 15-25°C, cooling air speed 0.3-0.6m / s, cooling air relative humidity 60%-80%.

10. The method for preparing a recycled polyester bicomponent parallel composite elastic fiber according to claim 9, characterized in that: The monofilament fineness of the recycled polyester two-component parallel composite elastic fiber is 1.1-5.5 dtex, the breaking strength is 1.5-3.0 cN / dtex, the elastic recovery rate is not less than 85% at a fixed elongation of 20%, the curling rate is 50-70%, the curling elasticity is not less than 90%, and the compression rebound rate is ≥85%.

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