Preparation method of low-temperature dyeable regenerated polyester fiber

Abstract

The present invention belongs to the technical field of regenerated polyester fibers, and specifically relates to a preparation method of regenerated polyester fibers that are easily dyed at low temperatures. Specifically, waste polylactic acid is first subjected to a transesterification reaction with an aliphatic dicarboxylic acid to obtain a polylactic acid oligomer with carboxyl groups at both ends. Then, the polylactic acid oligomer with carboxyl groups at both ends and a polyether diamine are successively subjected to a homogenization reaction and a polycondensation reaction to obtain a modified polylactic acid. Subsequently, the modified polylactic acid is subjected to spinning to obtain regenerated polyester fibers that are easily dyed at low temperatures. Among them, the aliphatic dicarboxylic acid has 4-20 carbon atoms, the number-average molecular weight of the polylactic acid oligomer with carboxyl groups at both ends is 2000-12000 g / mol, and the number-average molecular weight of the polyether diamine is 600-4000 g / mol. The regenerated polyester fibers that are easily dyed at low temperatures prepared by the present invention have high mechanical strength, can be dyed with disperse dyes at 80-100 °C, the dye uptake rate reaches more than 95%, and the color fastness is good.

Description

Technical Field

[0001] The present invention belongs to the technical field of regenerated polyester fibers, and particularly relates to a preparation method of regenerated polyester fibers that are easily dyed at low temperatures. Background Art

[0002] At present, when the concept of environmental protection prevails, polylactic acid fibers have attracted much attention in the material field because they are derived from renewable resources and are biodegradable. They have great potential in sustainable development and are expected to relieve the environmental pressure of traditional fibers. However, the degradation of polylactic acid fibers requires specific conditions. Even if they are degraded into carbon dioxide and water, it is difficult to utilize them quickly and directly, resulting in a waste of resources. Therefore, from the perspectives of environmental protection and economy, it is of great practical significance to recycle and reuse waste polylactic acid.

[0003] Polylactic acid fiber textiles and garments have entered the markets of the United States, Europe, Japan, etc., but they also face many challenges. Especially in the case of colored silk products, there are more light colors and fewer dark colors, and the color brightness is insufficient. This is due to its own structure. The high crystallinity and the molecular main chain lacking hydrophilic groups make it a hydrophobic fiber, and it can only be dyed with disperse dyes. However, the coloring effect of disperse dyes on polylactic acid fibers is limited, and it is difficult to meet the requirements of dark color dyeing, resulting in unsatisfactory colors of polylactic acid colored silk products.

[0004] In addition, the dyeing process of polylactic acid fibers is complex. Its glass transition temperature and melting point are low, and it is sensitive to temperature and pH value, and it cannot be dyed at high temperatures like polyester. When the temperature exceeds 110°C or it encounters strong alkali, the fiber will degrade, and the strength and hand feel will become worse; when the setting temperature exceeds 130°C, it will melt. At present, polylactic acid fibers are usually dyed at 110°C, but disperse dyes need high temperatures to effectively enter the fibers, resulting in low dye uptake rate and poor color fastness, which seriously restricts its popularization and application.

[0005] The patent with the publication number CN101270551A discloses a dyeing promoter for polylactic acid fibers with disperse dyes, which can significantly improve the dye uptake rate in the disperse dyeing of polylactic acid, reduce the pollution of dyeing waste liquid to water resources, and has relatively high dyeing fastness and little impact on the breaking strength of polylactic acid fiber fabrics. However, this technology only starts from the dyeing process, and the molecular chain structure and condensed state structure of the polymer do not change, so it cannot achieve easy dyeing at low temperatures. The patent with the publication number CN109440490A provides an azo-structured lactate-based disperse dye for dyeing polylactic acid fibers, which can improve the dye uptake rate of the dye and increase the boiling point of the dye. Hydrogen bonds will form between dye molecules, thereby improving the sublimation fastness of the dye, making the dye have a good dyeing effect. However, the highest dyeing temperature of this method can reach 130°C, which will cause the degradation and fracture of polylactic acid fibers, and to a certain extent, affect the strength and use comfort of the fibers. The patent with the publication number CN118422509A provides a low-temperature dyeing method for polylactic acid fibers. The polylactic acid fibers are pretreated by using nanotechnology modification, and then the modified polylactic acid fibers are immersed in a dye solution of low-temperature reactive dyes. The magnetic field technology is applied to promote the combination between the dye and the polylactic acid fibers and a photocatalytic fixing agent is used to fix the color. Finally, the freeze-drying technology is applied to dry the treated polylactic acid fibers and post-treatment is carried out on the dried polylactic acid fibers to enhance the color stability. The post-treatment process of this technology is complex and requires additional auxiliaries for color fixation, increasing the dyeing cost.

[0006] In view of the above deficiencies, it is necessary to improve the existing technology and propose a regenerated polyester fiber that is easy to dye at low temperatures. Summary of the Invention

[0007] The purpose of the present invention is to solve the problems existing in the prior art and provide a regenerated polyester fiber that is easy to dye at low temperatures.

[0008] To achieve the above purpose, the present invention adopts the following technical solutions:

[0009] A preparation method of a regenerated polyester fiber that is easy to dye at low temperatures. First, the waste polylactic acid is subjected to an ester exchange reaction with an aliphatic dicarboxylic acid to obtain a polylactic acid oligomer with double-terminal carboxyl groups. Then, the polylactic acid oligomer with double-terminal carboxyl groups and a polyether diamine are subjected to a homogenization reaction and a polycondensation reaction in sequence to obtain a modified polylactic acid. Then, the modified polylactic acid is subjected to spinning processing to obtain a regenerated polyester fiber that is easy to dye at low temperatures;

[0010] The aliphatic dibasic acid has 4-20 carbon atoms; if the number of carbon atoms of the aliphatic dibasic acid is greater than 20, the carbon chain of the aliphatic dibasic acid is too long. On the one hand, it will lead to relatively low reactivity of the terminal carboxyl groups of the aliphatic dibasic acid. If the transesterification reaction time is not extended, the transesterification reaction will not be thorough enough to effectively prepare the double-terminal carboxyl polylactic acid oligomer. If the transesterification reaction time is extended, the thermal degradation of waste polylactic acid will become serious. On the other hand, during the transesterification reaction, the aliphatic dibasic acid has to enter the molecular chain of polylactic acid. The too-long carbon chain of the aliphatic dibasic acid will cause excessive damage to the regularity of the molecular chain of polylactic acid, thus affecting the crystallization performance of the final modified polylactic acid and further affecting the spinning process;

[0011] The number-average molecular weight of the double-terminal carboxyl polylactic acid oligomer is 2000-12000 g / mol; if the molecular weight of the double-terminal carboxyl polylactic acid oligomer is too low, the crystallization ability of the modified polylactic acid will be relatively low, thus affecting the spinning process of the modified polylactic acid; if the molecular weight of the double-terminal carboxyl polylactic acid oligomer is too high, uneven reaction will occur during the repolymerization process, ultimately resulting in too wide a molecular weight distribution of the modified polylactic acid, thus affecting the spinning process. Therefore, to realize the reuse of waste polylactic acid as copolymer functionalized fibers, it is necessary to strictly control the molecular weight of the double-terminal carboxyl polylactic acid oligomer;

[0012] The number-average molecular weight of the polyether diamine is 600-4000 g / mol; for modified polylactic acid with the same number-average molecular weight, if the molecular chain of the polyether diamine is too short, the content of ether bonds in the molecular chain of the modified polylactic acid will be too small to achieve the effect of easy dyeing at low temperature. The polyether diamine is used to prepare the low-temperature easy-dyeing regenerated polyester fiber through an amide exchange reaction with the double-terminal carboxyl polylactic acid oligomer. At this time, the polyether diamine will enter the molecular chain of the modified polylactic acid. If the carbon chain of the polyether diamine is too long, it will cause excessive damage to the regularity of the polylactic acid molecular chain, thus affecting the crystallization performance of the final polylactic acid copolymer and further affecting the spinning process;

[0013] The structural formula of the modified polylactic acid is as follows:

[0014] ;

[0015] In the formula, x is an integer in the range of [20, 200], -R 1 - is the chain segment between the two carboxyl groups in the aliphatic dibasic acid, -R 2 - is the chain segment between the two amino groups in the polyether diamine.

[0016] The prior art for recycling waste poly(lactic acid) mainly relies on alcoholysis reaction, and the ultimate goal is to obtain lactide monomers, such as CN115403554B; different from the prior art, the present invention recycles waste poly(lactic acid) by transesterification reaction, and the ultimate goal is to obtain a double-terminal carboxyl poly(lactic acid) oligomer with a specific molecular weight, so that the fiber-forming ability and crystallization ability of poly(lactic acid) can be retained. In addition, the present invention can realize the functional reuse of waste poly(lactic acid). Compared with depolymerizing to lactide monomers, there is no need to separate the depolymerization products, which simplifies the process of recycling and reusing poly(lactic acid).

[0017] As a preferred technical solution:

[0018] For the preparation method of a low-temperature dyeable regenerated polyester fiber as described above, the intrinsic viscosity of the waste poly(lactic acid) is 1.00 - 1.40 dL / g, and the melting point is 130 - 240 °C.

[0019] For the preparation method of a low-temperature dyeable regenerated polyester fiber as described above, the molecular weight distribution index of the double-terminal carboxyl poly(lactic acid) oligomer is 1.3 - 2.0.

[0020] For the preparation method of a low-temperature dyeable regenerated polyester fiber as described above, the polyether diamine is one or more of polyethylene oxide diamine, polypropylene oxide diamine or polysiloxane diamine.

[0021] For the preparation method of a low-temperature dyeable regenerated polyester fiber as described above, the number-average molecular weight of the modified poly(lactic acid) is 13000 - 45000 g / mol, and the molecular weight distribution index is 1.5 - 2.6.

[0022] For the preparation method of a low-temperature dyeable regenerated polyester fiber as described above, the preparation steps of the modified poly(lactic acid) are as follows:

[0023] (a) Add waste poly(lactic acid), aliphatic dicarboxylic acid and catalyst to the reaction kettle, and react at 160 - 250 °C and 0.01 - 0.3 MPa for 1 - 6 h to obtain a double-terminal carboxyl poly(lactic acid) oligomer;

[0024] (b) Continue to add polyether diamine to the reaction kettle, first react at 180 - 250 °C and 500 - 1000 Pa for 0.2 - 4 h, and then react at 200 - 260 °C and ≤100 Pa for 1.0 - 4.5 h to obtain the modified poly(lactic acid);

[0025] The catalyst remains in the modified poly(lactic acid) and can be used as a crystallization nucleating agent to regulate the crystallization performance.

[0026] For the preparation method of a low-temperature dyeable regenerated polyester fiber as described above, the mass of the aliphatic dicarboxylic acid , the mass of the waste poly(lactic acid) , the relative molecular mass of the aliphatic dicarboxylic acid The number-average molecular weight of the double-end carboxyl poly(lactic acid) oligomer and

[0027] satisfy the following formula:

[0028] In the formula, and are in the unit of g; and are in the unit of g / mol; φ is 17 g / mol;

[0029] The derivation process of the above formula is as follows: According to the preparation process of the double-end carboxyl poly(lactic acid) oligomer, the structural formula of the double-end carboxyl poly(lactic acid) oligomer can be speculated as: , (wherein, R is the chain segment between two carboxyl groups in the aliphatic dibasic acid, and n is the number of lactic acid repeating units);

[0030] It can be seen therefrom that it includes n lactic acid repeating units and 1 aliphatic dibasic acid; the relative molecular weight of the lactic acid chain segment is 72, and 1 -OH (molar mass is 17 g / mol, denoted as φ) will be removed when capped with the aliphatic dibasic acid. Let the number-average molecular weight of the double-end carboxyl poly(lactic acid) oligomer be , then Equation 1 can be listed as:

[0031] = 72n + - φ; Equation 1

[0032] Converted to Equation 2:

[0033] n = ( - + φ) / 72; Equation 2

[0034] Let the mass of the waste poly(lactic acid) added in the preparation process be , and the number of moles of lactic acid chain segments in the waste poly(lactic acid) is n PLA , then Equation 3 can be listed as:

[0035] n PLA = m / 72; Equation 3

[0036] It can be obtained that the number of lactic acid chain segments in the waste poly(lactic acid) is n PLA / n times more than the number of lactic acid chain segments 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 aliphatic dibasic acid, that is, Equation 4 is obtained:

[0037] n COOH = n PLA / n; Equation 4

[0038] Substituting Equation 3 into Equation 4, Equation 5 is obtained:

[0039] n COOH = m / (72n); Equation 5

[0040] The relative molecular mass of the aliphatic dibasic acid can be calculated according to Equation 6:

[0041] = n COOH × ; Equation 6

[0042] Substituting Equation 5 into Equation 6 gives Equation 7:

[0043] = (m × ) / (72n); Equation 7

[0044] Finally, substituting Equation 2 into Equation 7 gives the above formula;

[0045] Tests show that the number-average molecular weight of the double-end carboxyl poly(lactic acid) oligomer has a relative deviation of no more than 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-end carboxyl poly(lactic acid) oligomer, the appropriate aliphatic dibasic acid can be selected according to the above formula, and the mass of the aliphatic dibasic acid and the mass of the waste poly(lactic acid) can be determined.

[0046] The mass of the catalyst is 100 - 1000 ppm of the mass of the waste poly(lactic acid), and the molar ratio of the waste poly(lactic acid) to the polyether diamine is 1.0 - 1.2:1;

[0047] 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.

[0048] For the preparation method of a low-temperature dyeing regenerated polyester fiber as described above, the spinning process uses the UDY, POY, or FDY process; the parameters of the UDY process include: spinning temperature 190 - 240 °C, spinning speed 500 - 1500 m / min, cooling air temperature 20 - 30 °C, cooling air speed 0.3 - 1 m / s, and relative humidity of the cooling air 60% - 80%; the parameters of the POY process include: spinning temperature 190 - 240 °C, spinning speed 1500 - 2500 m / min, cooling air temperature 15 - 30 °C, cooling air speed 0.3 - 0.6 m / s, and relative humidity of the cooling air 60% - 80%; the parameters of the FDY process include: spinning temperature 190 - 240 °C, spinning speed 2500 - 3500 m / min, cooling air temperature 15 - 20 °C, cooling air speed 0.3 - 0.6 m / s, and relative humidity of the cooling air 70% - 85%.

[0049] A preparation method of a regenerated polyester fiber that is easily dyed at low temperature as described above. The moisture regain of the regenerated polyester fiber that is easily dyed at low temperature is 0.60 - 1.20%, the breaking strength is 2.5 - 5.5 cN / dtex, and the elongation at break is 10 - 40%. After dyeing with disperse dyes at 80 - 100 °C, the dye uptake rate is more than 95%, the rubbing color fastness is 4 - 5 grades, the wash color fastness is 4 - 5 grades, and the soaping color fastness is 4 - 5 grades.

[0050] The regenerated polyester fiber of the present invention has the characteristic of being easily dyed at low temperature because its molecular chain contains a polyether segment. On the one hand, the polyether segment is located in the amorphous region and can open the amorphous region at a lower temperature, which is beneficial for the entry of dyes. On the other hand, the presence of ether bonds can increase the dye uptake rate. The prior art mainly introduces polyether segments into the poly(lactic acid) molecular chain based on the motivation of improving the solubility of poly(lactic acid) in water. Different from the prior art, the present invention introduces polyether segments into the poly(lactic acid) molecular chain based on the motivation of improving the dyeing performance of poly(lactic acid).

[0051] The regenerated polyester fiber of the present invention has excellent mechanical properties because, on the one hand, the present invention retains the fiber-forming ability and crystallization ability of poly(lactic acid) by regulating the molecular weight of the double-end carboxyl poly(lactic acid) oligomer, and on the other hand, the presence of amide bonds can form hydrogen bond interactions, thereby improving the mechanical properties of the regenerated polyester fiber.

[0052] The regenerated polyester fiber of the present invention has a relatively high color fastness after dyeing because its molecular chain contains amide bonds, which are formed by the polycondensation reaction of terminal amino groups and terminal carboxyl groups during the repolymerization process. The hydrogen bond interaction between it and dye molecules will improve the color fastness to a certain extent. In the prior art, the methods for improving the color fastness of fibers or fabrics mainly introduce color fixatives into the fibers or fabrics, and their mechanism is to form a strong binding force between the color fixatives and dye molecules to achieve the color fixation effect. There is no method for improving the color fastness by introducing amide bonds yet.

[0053] Beneficial effects:

[0054] (1) Through the acidolysis of dibasic acids, the present invention can effectively design the molecular chain length according to the fiber property requirements without preparing to monomers, saving the manufacturing cost and improving the resource utilization rate of poly(lactic acid).

[0055] (2) The present invention depolymerizes and repolymerizes waste poly(lactic acid). By controlling the addition amount of dibasic acids and designing the length of the poly(lactic acid) segment, the fiber-forming ability and crystallization ability of poly(lactic acid) are retained, and the strength of the regenerated polyester fiber is maintained.

[0056] (3) The present invention provides a modified polylactic acid fiber. The addition of polyetheramine, on the one hand, improves the hand feeling of the fiber, reduces the dyeing temperature, and reduces the degradation of polylactic acid fiber during the dyeing and finishing process. On the other hand, the hydrogen bonds formed between amide bonds compensate for the reduction in color fastness caused by ether bonds and improve the strength of polylactic acid fiber.

[0057] (4) The preparation method provided by the present invention has a simple process, can be produced on existing equipment, can be used in current industrial production, and can be applied on a large scale. Brief Description of the Drawings

[0058] Figure 1 It is the nuclear magnetic resonance spectrum of the double-end carboxyl polylactic acid oligomer prepared in Example 1. Specific Embodiments

[0059] 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.

[0060] Detection methods for relevant performance indicators:

[0061] Number-average molecular weight, molecular weight distribution index: Tested by gel permeation chromatography (GPC). The instrument is Agilent 1260 gel chromatograph, the chromatographic column is Agilent HFIP series, the mobile phase is hexafluoroisopropanol, and a part of sodium trifluoroacetate is added. The concentration of sodium trifluoroacetate is 0.02 mol / L, and the test temperature is 35 °C.

[0062] Tensile strength, elongation at break: Tested with reference to Standard GB / T 14344-2022.

[0063] Moisture regain of the fiber: Tested with reference to Standard GB / T 6503-2017.

[0064] Dye uptake rate: Tested with reference to Standard GB / T 23976.1-2009.

[0065] Color fastness to rubbing: Tested with reference to Standard GB / T 3920-2008.

[0066] Color fastness to washing: Tested with reference to Standard GB / T 5713-2013.

[0067] Color fastness to soaping: Tested with reference to Standard GB / T 3921-2008.

[0068] Example 1

[0069] A preparation method of a low-temperature easily dyeable regenerated polyester fiber is as follows:

[0070] (1)Prepare raw materials:

[0071] Waste polylactic acid: The intrinsic viscosity is 1 dL / g, and the melting point is 130 °C;

[0072] Aliphatic dibasic acid: Succinic acid;

[0073] Polyether diamine: Polyoxyethylene diamine, the number-average molecular weight is 2000 g / mol;

[0074] Catalyst: Titanium glycolate;

[0075] (2)Prepare modified polylactic acid:

[0076] (2.1)Add waste polylactic acid, aliphatic dibasic acid, and catalyst to the reaction kettle, react at 160 °C and 0.01 MPa for 6 h to obtain a polylactic acid oligomer with double-terminal carboxyl groups, and its nuclear magnetic resonance spectrum is as Figure 1 shown;

[0077] The number-average molecular weight of the polylactic acid oligomer with double-terminal carboxyl groups is 12000 g / mol, and the molecular weight distribution index is 2;

[0078] (2.2)Continue to add polyether diamine to the reaction kettle, first react at 180 °C and 500 Pa for 4 h (homogenization reaction), and then react at 200 °C and 100 Pa for 1 h (polycondensation reaction) to obtain modified polylactic acid;

[0079] The number-average molecular weight of the modified polylactic acid is 30000 g / mol, and the molecular weight distribution index is 1.5;

[0080] In steps (2.1) to (2.2), the mass ratio of waste polylactic acid to aliphatic dibasic acid is 101:1, the mass of the catalyst is 1000 ppm of the mass of waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.0:1;

[0081] (3)Spinning process:

[0082] The spinning process uses the UDY process, and the process parameters include: spinning temperature 190 °C, spinning speed 500 m / min, cooling air temperature 20 °C, cooling air speed 0.3 m / s, and relative humidity of cooling air 60%.

[0083] The finally obtained low-temperature easily dyeable regenerated polyester fiber has a moisture regain of 1%, a breaking strength of 3 cN / dtex, and an elongation at break of 30%; after dyeing with disperse dyes at 85 °C, the dye uptake rate is 95%, the rubbing color fastness is grade 5, the wash color fastness is grade 5, and the soaping color fastness is grade 5.

[0084] Comparative Example 1

[0085] A preparation method of regenerated polyester fiber is basically the same as that of Example 1, except that: the aliphatic dibasic acid used in this comparative example is dimer fatty acid.

[0086] The breaking strength of the finally prepared regenerated polyester fiber is 1.5 cN / dtex.

[0087] Compared with Example 1, the breaking strength of the regenerated polyester fiber prepared in Comparative Example 1 decreases. This is because the too-long aliphatic dibasic acid will excessively damage the regularity of the polylactic acid molecular chain, thus affecting the crystallization performance of the modified polylactic acid and ultimately having an adverse effect on the spinning process.

[0088] Example 2

[0089] A preparation method of low-temperature dyeable regenerated polyester fiber is as follows:

[0090] (1) Prepare raw materials:

[0091] Waste polylactic acid: intrinsic viscosity is 1.1 dL / g, melting point is 145 °C;

[0092] Aliphatic dibasic acid: succinic acid;

[0093] Polyether diamine: polyoxypropylene diamine, number average molecular weight is 1000 g / mol;

[0094] Catalyst: tetrabutyl titanate;

[0095] (2) Prepare modified polylactic acid:

[0096] (2.1) Add waste polylactic acid, aliphatic dibasic acid, and catalyst into the reaction kettle, react at 170 °C and 0.02 MPa for 5 h to obtain a double-terminal carboxyl polylactic acid oligomer;

[0097] The number average molecular weight of the double-terminal carboxyl polylactic acid oligomer is 12000 g / mol, and the molecular weight distribution index is 1.8;

[0098] (2.2) Continue to add polyether diamine into the reaction kettle, first react at 180 °C and 1000 Pa for 2 h (homogenization reaction), and then react at 200 °C and 70 Pa for 1.5 h (polycondensation reaction) to obtain modified polylactic acid;

[0099] The number average molecular weight of the modified polylactic acid is 40000 g / mol, and the molecular weight distribution index is 1.8;

[0100] In steps (2.1) to (2.2), the mass ratio of waste polylactic acid to aliphatic dibasic acid is 101:1, the mass of the catalyst is 300 ppm of the mass of waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.0:1;

[0101] (3) Spinning process:

[0102] The UDY process is used for spinning, and the process parameters include: spinning temperature 210 °C, spinning speed 1000 m / min, cooling air temperature 25 °C, cooling air speed 0.6 m / s, and relative humidity of cooling air 70%.

[0103] The moisture regain of the finally prepared regenerated polyester fiber with low-temperature dyeability is 0.8%, the breaking strength is 2.5 cN / dtex, and the elongation at break is 35%; after dyeing with disperse dyes at 100 °C, the dye uptake rate is 95%, the rubbing fastness is grade 5, the wash fastness is grade 5, and the soaping fastness is grade 5.

[0104] Comparative Example 2

[0105] A preparation method of regenerated polyester fiber is basically the same as that of Example 2, except that: in step (2.1) of this comparative example, the addition amount of waste polylactic acid is 1000 g, and the addition amount of succinic acid is 167 g, and the number-average molecular weight of the obtained polylactic acid oligomer with double-terminal carboxyl groups is 1000 g / mol.

[0106] The breaking strength of the finally prepared regenerated polyester fiber is 1.3 cN / dtex.

[0107] Compared with Example 2, the breaking strength of the regenerated polyester fiber prepared in Comparative Example 2 is worse, because the molecular weight of the polylactic acid oligomer with double-terminal carboxyl groups is too low, which will result in a lower crystallization ability of the modified polylactic acid, thereby making the orientation crystallization ability of the modified polylactic acid fiber worse, and further leading to a decrease in the breaking strength of the fiber.

[0108] Comparative Example 3

[0109] A preparation method of regenerated polyester fiber is basically the same as that of Example 2, except that: in step (2.1) of this comparative example, the addition amount of waste polylactic acid is 1000 g, and the addition amount of succinic acid is 11 g, and the number-average molecular weight of the obtained polylactic acid oligomer with double-terminal carboxyl groups is 13000 g / mol.

[0110] The breaking strength of the finally prepared regenerated polyester fiber is 2.0 cN / dtex, and after dyeing with disperse dyes at 100 °C, the dye uptake rate is 65%.

[0111] Compared with Example 2, the breaking strength and dye uptake rate of the regenerated polyester fiber prepared in Comparative Example 3 are worse. This is because the molecular weight of the double-terminal carboxyl polylactic acid oligomer is too high, resulting in uneven reaction during the repolymerization process, ultimately causing a too wide molecular weight distribution of the modified polylactic acid, thus affecting the spinning process and further affecting the breaking strength of the modified polylactic acid fiber. In addition, too high a number-average molecular weight of the double-terminal carboxyl polylactic acid oligomer will lead to a decrease in the content of polyether diamine, and the dye uptake rate will also decrease in a low-temperature environment.

[0112] Example 3

[0113] A preparation method of a regenerated polyester fiber that is easily dyed at low temperature is as follows:

[0114] (1)Prepare raw materials:

[0115] Waste polylactic acid: The intrinsic viscosity is 1.15 dL / g, and the melting point is 160 °C;

[0116] Aliphatic dibasic acid: Adipic acid;

[0117] Polyether diamine: Polysiloxane diamine, with a number-average molecular weight of 2000 g / mol;

[0118] Catalyst: Antimony glycolate;

[0119] (2)Prepare modified polylactic acid:

[0120] (2.1)Add waste polylactic acid, aliphatic dibasic acid, and catalyst to the reaction kettle, and react at 180 °C and 0.03 MPa for 4 h to obtain a double-terminal carboxyl polylactic acid oligomer;

[0121] The number-average molecular weight of the double-terminal carboxyl polylactic acid oligomer is 11000 g / mol, and the molecular weight distribution index is 1.7;

[0122] (2.2)Continue to add polyether diamine to the reaction kettle, first react at 190 °C and 500 Pa for 1 h (homogenization reaction), and then react at 210 °C and 80 Pa for 1.5 h (polycondensation reaction) to obtain modified polylactic acid;

[0123] The number-average molecular weight of the modified polylactic acid is 25000 g / mol, and the molecular weight distribution index is 2.3;

[0124] In steps (2.1) to (2.2), the mass ratio of waste polylactic acid to aliphatic dibasic acid is 74:1, the mass of the catalyst is 300 ppm of the mass of waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.1:1;

[0125] (3)Spinning process:

[0126] The spinning process uses the UDY process, and the process parameters include: spinning temperature 240 °C, spinning speed 1500 m / min, cooling air temperature 30 °C, cooling air speed 1 m / s, and relative humidity of cooling air 80%.

[0127] The moisture regain of the finally obtained regenerated polyester fiber with low-temperature dyeability is 1%, the breaking strength is 3.5 cN / dtex, and the elongation at break is 25%; after dyeing with disperse dyes at 100 °C, the dye uptake rate is 96%, the rubbing color fastness is 4.5 levels, the wash color fastness is 4.5 levels, and the soaping color fastness is 4.5 levels.

[0128] Comparative Example 4

[0129] A preparation method of regenerated polyester fiber is basically the same as that of Example 3, except that: the number average molecular weight of the polyether diamine used in this comparative example is 400 g / mol.

[0130] The moisture regain of the finally obtained regenerated polyester fiber is 0.5%, and after dyeing with disperse dyes at 100 °C, the dye uptake rate is 80%.

[0131] Compared with Example 3, the moisture regain and dye uptake rate of the regenerated polyester fiber prepared in Comparative Example 4 are worse, because the number average molecular weight of the polyetheramine is too small, resulting in too low an ether bond content, the water absorption capacity of the prepared regenerated polyester fiber is reduced and low-temperature dyeability cannot be achieved.

[0132] Comparative Example 5

[0133] A preparation method of regenerated polyester fiber is basically the same as that of Example 3, except that: the number average molecular weight of the polyether diamine used in this comparative example is 6000 g / mol.

[0134] The breaking strength of the finally obtained regenerated polyester fiber is 1.6 cN / dtex.

[0135] Compared with Example 3, the breaking strength of the regenerated polyester fiber prepared in Comparative Example 5 has decreased, because the carbon chain of the polyether diamine is too long, which will cause too much damage to the regularity of the polylactic acid molecular chain, thus affecting the crystallization performance of the final polylactic acid copolymer. The decrease in crystallization performance further has an adverse effect on the spinning process, ultimately resulting in a decrease in the fiber breaking strength.

[0136] Example 4

[0137] A preparation method of regenerated polyester fiber with low-temperature dyeability is as follows:

[0138] (1) Prepare raw materials:

[0139] Waste polylactic acid: intrinsic viscosity is 1.2 dL / g, melting point is 175 °C;

[0140] Aliphatic dibasic acid: adipic acid;

[0141] Polyether diamine: polyoxyethylene diamine, number average molecular weight is 600 g / mol;

[0142] Catalyst: antimony acetate;

[0143] (2)Preparation of modified polylactic acid:

[0144] (2.1)Add waste polylactic acid, aliphatic dibasic acid, and catalyst into the reaction kettle, react at 190 °C and 0.05 MPa for 4 h to obtain a polylactic acid oligomer with carboxyl groups at both ends;

[0145] The number average molecular weight of the polylactic acid oligomer with carboxyl groups at both ends is 10000 g / mol, and the molecular weight distribution index is 1.5;

[0146] (2.2)Continue to add polyether diamine into the reaction kettle, first react at 200 °C and 600 Pa for 1 h (homogenization reaction), and then react at 220 °C and 90 Pa for 2 h (polycondensation reaction) to obtain modified polylactic acid;

[0147] The number average molecular weight of the modified polylactic acid is 35000 g / mol, and the molecular weight distribution index is 1.7;

[0148] In steps (2.1) to (2.2), the mass ratio of waste polylactic acid to aliphatic dibasic acid is 68:1, the mass of the catalyst is 200 ppm of the mass of waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.1:1;

[0149] (3)Spinning process:

[0150] The spinning process uses the POY process, and the process parameters 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%.

[0151] The moisture regain of the finally prepared regenerated polyester fiber with low-temperature dyeability is 0.6%, the breaking strength is 5.5 cN / dtex, and the elongation at break is 10%; after dyeing with disperse dyes at 80 °C, the dye uptake rate is 98%, the rubbing color fastness is 4.5 levels, the washing color fastness is 4.5 levels, and the soaping color fastness is 4.5 levels.

[0152] Example 5

[0153] A preparation method of a regenerated polyester fiber with low-temperature dyeability is as follows:

[0154] (1)Prepare raw materials:

[0155] Waste polylactic acid: Intrinsic viscosity is 1.25 dL / g, melting point is 190 °C;

[0156] Aliphatic dicarboxylic acid: Suberic acid;

[0157] Polyether diamine: Polyoxypropylene diamine, number average molecular weight is 600 g / mol;

[0158] Catalyst: Antimony oxide;

[0159] (2) Preparation of modified polylactic acid:

[0160] (2.1) Add waste polylactic acid, aliphatic dicarboxylic acid, and catalyst into a reaction kettle, react at 200 °C and 0.08 MPa for 4 h to obtain a polylactic acid oligomer with double-terminal carboxyl groups;

[0161] The number average molecular weight of the polylactic acid oligomer with double-terminal carboxyl groups is 8000 g / mol, and the molecular weight distribution index is 1.3;

[0162] (2.2) Continue to add polyether diamine into the reaction kettle, first react at 210 °C and 900 Pa for 1 h (homogenization reaction), and then react at 230 °C and 50 Pa for 2.5 h (polycondensation reaction) to obtain modified polylactic acid;

[0163] The number average molecular weight of the modified polylactic acid is 45000 g / mol, and the molecular weight distribution index is 1.8;

[0164] In steps (2.1) to (2.2), the mass ratio of waste polylactic acid to aliphatic dicarboxylic acid is 45:1, the mass of the catalyst is 100 ppm of the mass of waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.2:1;

[0165] (3) Spinning process:

[0166] The spinning process uses the POY process, and the process parameters 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 70%.

[0167] The moisture regain of the finally prepared low-temperature easily dyeable regenerated polyester fiber is 0.6%, the breaking strength is 4.5 cN / dtex, and the elongation at break is 20%; after dyeing with disperse dyes at 90 °C, the dye uptake rate is 96%, the rubbing color fastness is 4.5 levels, the wash color fastness is 4.5 levels, and the soaping color fastness is 4.5 levels.

[0168] Example 6

[0169] A preparation method of low-temperature easily dyeable regenerated polyester fiber is as follows:

[0170] (1) Prepare raw materials:

[0171] Waste polylactic acid: intrinsic viscosity is 1.3 dL / g, melting point is 205 °C;

[0172] Aliphatic dicarboxylic acid: sebacic acid;

[0173] Polyether diamine: polysiloxane diamine, number average molecular weight is 1000 g / mol;

[0174] Catalyst: stannous octanoate;

[0175] (2) Prepare modified polylactic acid:

[0176] (2.1) Add waste polylactic acid, aliphatic dicarboxylic acid, and catalyst into the reaction kettle, react at 210 °C and 0.1 MPa for 2 h to obtain a low molecular weight polylactic acid oligomer with double-terminal carboxyl groups;

[0177] The number average molecular weight of the low molecular weight polylactic acid oligomer with double-terminal carboxyl groups is 7000 g / mol, and the molecular weight distribution index is 1.3;

[0178] (2.2) Continue to add polyether diamine into the reaction kettle, first react at 220 °C and 700 Pa for 0.5 h (homogenization reaction), and then react at 250 °C and 40 Pa for 2.5 h (polycondensation reaction) to obtain modified polylactic acid;

[0179] The number average molecular weight of the modified polylactic acid is 20000 g / mol, and the molecular weight distribution index is 2;

[0180] In steps (2.1) to (2.2), the mass ratio of waste polylactic acid to aliphatic dicarboxylic acid is 34:1, the mass of the catalyst is 100 ppm of the mass of waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.1:1;

[0181] (3) Spinning process:

[0182] The spinning process uses the POY process, and the process parameters include: spinning temperature 240 °C, spinning speed 2500 m / min, cooling air temperature 30 °C, cooling air speed 0.6 m / s, and relative humidity of cooling air 80%.

[0183] The moisture regain of the finally prepared regenerated polyester fiber with easy dyeing at low temperature is 0.8%, the breaking strength is 4 cN / dtex, and the elongation at break is 25%; after dyeing with disperse dyes at 90 °C, the dye uptake rate is 97%, the color fastness to rubbing is 4.5 levels, the color fastness to washing is 4.5 levels, and the color fastness to soaping is 4.5 levels.

[0184] Example 7

[0185] A preparation method of a low-temperature dyeable regenerated polyester fiber is as follows:

[0186] (1) Prepare raw materials:

[0187] Waste polylactic acid: The intrinsic viscosity is 1.3 dL / g, and the melting point is 220 °C;

[0188] Aliphatic dibasic acid: Sebacic acid;

[0189] Polyether diamine: Polyoxyethylene diamine, the number-average molecular weight is 4000 g / mol;

[0190] Catalyst: Stannous chloride;

[0191] (2) Prepare modified polylactic acid:

[0192] (2.1) Add waste polylactic acid, aliphatic dibasic acid, and catalyst into the reaction kettle, react at 220 °C and 0.1 MPa for 2 h to obtain a low molecular weight polylactic acid oligomer with double terminal carboxyl groups;

[0193] The number-average molecular weight of the low molecular weight polylactic acid oligomer with double terminal carboxyl groups is 7000 g / mol, and the molecular weight distribution index is 1.6;

[0194] (2.2) Continue to add polyether diamine into the reaction kettle, first react at 230 °C and 800 Pa for 0.5 h (homogenization reaction), and then react at 250 °C and 30 Pa for 3 h (polycondensation reaction) to obtain modified polylactic acid;

[0195] The number-average molecular weight of the modified polylactic acid is 20000 g / mol, and the molecular weight distribution index is 2.2;

[0196] In steps (2.1) to (2.2), the mass ratio of waste polylactic acid to aliphatic dibasic acid is 34:1, the mass of the catalyst is 500 ppm of the mass of waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.1:1;

[0197] (3) Spinning process:

[0198] The spinning process uses the FDY process, and the process parameters include: spinning temperature 190 °C, spinning speed 2500 m / min, cooling air temperature 15 °C, cooling air speed 0.3 m / s, and relative humidity of cooling air 70%.

[0199] The final low-temperature dyeable regenerated polyester fiber obtained has a moisture regain of 1.2%, a breaking strength of 2.5 cN / dtex, and an elongation at break of 40%; after dyeing with disperse dyes at 95 °C, the dye uptake rate is 96%, the rubbing fastness is 4 levels, the washing fastness is 4 levels, and the soaping fastness is 4 levels.

[0200] Example 8

[0201] A preparation method of low-temperature dyeable recycled polyester fiber is as follows:

[0202] (1)Prepare raw materials:

[0203] Waste polylactic acid: The intrinsic viscosity is 1.35 dL / g, and the melting point is 235 °C;

[0204] Aliphatic dibasic acid: Suberic acid;

[0205] Polyether diamine: Polyoxypropylene diamine, the number-average molecular weight is 4000 g / mol;

[0206] Catalyst: Zinc acetate;

[0207] (2)Prepare modified polylactic acid:

[0208] (2.1)Add waste polylactic acid, aliphatic dibasic acid, and catalyst into the reaction kettle, react at 220 °C and 0.1 MPa for 2 h to obtain a low molecular weight polylactic acid oligomer with double-terminal carboxyl groups;

[0209] The number-average molecular weight of the low molecular weight polylactic acid oligomer with double-terminal carboxyl groups is 5000 g / mol, and the molecular weight distribution index is 1.9;

[0210] (2.2)Continue to add polyether diamine into the reaction kettle, first react at 230 °C and 1000 Pa for 0.5 h (homogenization reaction), and then react at 260 °C and 50 Pa for 4 h (polycondensation reaction) to obtain modified polylactic acid;

[0211] The number-average molecular weight of the modified polylactic acid is 16000 g / mol, and the molecular weight distribution index is 2.1;

[0212] In steps (2.1) to (2.2), the mass ratio of waste polylactic acid to aliphatic dibasic acid is 28:1, the mass of the catalyst is 600 ppm of the mass of waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.0:1;

[0213] (3)Spinning process:

[0214] The spinning process adopts the FDY process, and the process parameters include: spinning temperature 210 °C, spinning speed 3000 m / min, cooling air temperature 15 °C, cooling air speed 0.4 m / s, and relative humidity of cooling air 75%.

[0215] The moisture regain of the finally obtained regenerated polyester fiber with easy dyeing at low temperature is 1.2%, the breaking strength is 2.5 cN / dtex, and the elongation at break is 40%; after dyeing with disperse dyes at 80 °C, the dye uptake rate is 97%, the rubbing fastness is level 4, the washing fastness is level 4, and the soaping fastness is level 4.

[0216] Example 9

[0217] A preparation method of regenerated polyester fiber with easy dyeing at low temperature is as follows:

[0218] (1) Prepare raw materials:

[0219] Waste polylactic acid: The intrinsic viscosity is 1.4 dL / g, and the melting point is 240 °C;

[0220] Aliphatic dibasic acid: Eicosanedioic acid;

[0221] Polyether diamine: A mixture of polyoxypropylene diamine and polysiloxane diamine with a mass ratio of 1:1, and the number average molecular weight is 2000 g / mol;

[0222] Catalyst: Zinc oxide;

[0223] (2) Prepare modified polylactic acid:

[0224] (2.1) Add waste polylactic acid, aliphatic dibasic acid, and catalyst to the reaction kettle, and react at 250 °C and 0.3 MPa for 1 h to obtain a low molecular weight polylactic acid oligomer with carboxyl groups at both ends;

[0225] The number average molecular weight of the low molecular weight polylactic acid oligomer with carboxyl groups at both ends is 2000 g / mol, and the molecular weight distribution index is 2;

[0226] (2.2) Continue to add polyether diamine to the reaction kettle, first react at 250 °C and 1000 Pa for 0.2 h (homogenization reaction), and then react at 260 °C and 20 Pa for 4.5 h (polycondensation reaction) to obtain modified polylactic acid;

[0227] The number average molecular weight of the modified polylactic acid is 13000 g / mol, and the molecular weight distribution index is 2.6;

[0228] In steps (2.1) to (2.2), the mass ratio of waste polylactic acid to aliphatic dibasic acid is 5:1, the mass of the catalyst is 500 ppm of the mass of waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.0:1;

[0229] (3) Spinning process:

[0230] The spinning process uses the FDY process, and the process parameters include: spinning temperature 240 °C, spinning speed 3500 m / min, cooling air temperature 20 °C, cooling air speed 0.6 m / s, and relative humidity of cooling air 85%.

[0231] The moisture regain of the finally obtained regenerated polyester fiber with low-temperature dyeability is 1%, the breaking strength is 3 cN / dtex, and the elongation at break is 30%; after dyeing with disperse dyes at 80 °C, the dye uptake rate is 98%, the rubbing color fastness is grade 4, the wash color fastness is grade 4, and the soaping color fastness is grade 4.

[0232] Each of the above examples has been verified, and the number-average molecular weight of the di-carboxyl-terminated polylactic acid oligomer The relative deviation does not exceed 2%, and the relative deviation = (|actual value - theoretical value| / theoretical value) × 100%. The calculation formula for the theoretical value is as follows:

[0233] ;

[0234] In the formula, (mass of the first aliphatic dicarboxylic acid), (mass of waste polylactic acid) are in g; (relative molecular mass of the first aliphatic dicarboxylic acid), (number-average molecular weight of the di-carboxyl-terminated polylactic acid oligomer) are in g / mol; φ is 17 g / mol.

Claims

1. A method for preparing low-temperature easy-to-dye regenerated polyester fiber, characterized in that: First, waste polylactic acid and aliphatic dibasic acid are subjected to ester exchange reaction to obtain double-terminal carboxyl polylactic acid oligomers, and then the double-terminal carboxyl polylactic acid oligomers and polyether diamines are subjected to homogenization reaction and polycondensation reaction in sequence to obtain modified polylactic acid, and then the modified polylactic acid is spun to obtain low-temperature easy-to-dye recycled polyester fibers; Aliphatic dibasic acids have 4-20 carbon atoms; The number average molecular weight M of the double-terminated carboxyl polylactic acid oligomer n 2000-12000 g / mol; The number average molecular weight of the polyether diamine is 600-4000 g / mol.

2. The method for preparing low-temperature easy-to-dye regenerated polyester fiber according to claim 1, characterized in that: The intrinsic viscosity of waste polylactic acid is 1.00-1.40dL / g and the melting point is 130-240℃.

3. The method for preparing a low-temperature easily dyeable regenerated polyester fiber according to claim 1, characterized in that: The molecular weight distribution index of the double-terminal carboxyl polylactic acid oligomer is 1.3-2.

0.

4. The method for preparing a low-temperature easily dyeable regenerated polyester fiber according to claim 1, characterized in that: The polyether diamine is one or more of polyoxyethylene diamine and polyoxypropylene diamine.

5. The method for preparing low-temperature easy-to-dye regenerated polyester fiber according to claim 1, characterized in that: The number average molecular weight of the modified polylactic acid is 13000-45000 g / mol, and the molecular weight distribution index is 1.5-2.

6.

6. The method for preparing low-temperature easily dyeable regenerated polyester fiber according to claim 1, characterized in that: The preparation steps of modified polylactic acid are as follows: (a) adding waste polylactic acid, aliphatic dibasic acid and a catalyst into a reaction kettle, reacting at 160-250° C. and 0.01-0.3 MPa for 1-6 hours to obtain a double-terminal carboxyl polylactic acid oligomer; (b) Continue to add polyether diamine into the reaction kettle, first react at 180-250° C. and 500-1000 Pa for 0.2-4 h, and then react at 200-260° C. and ≤100 Pa for 1.0-4.5 h to obtain modified polylactic acid.

7. The method for preparing low-temperature easily dyeable regenerated polyester fiber according to claim 6, characterized in that: The mass m of aliphatic dibasic acid COOH , the mass m of waste polylactic acid, the relative molecular mass M of aliphatic dibasic acid nCOOH , the number average molecular weight M of the double-terminated carboxyl polylactic acid oligomer n The relationship satisfies the following formula: In the formula, m COOH The unit of ,m is g; M nCOOH 、M n The unit is g / mol; 17 g / mol; The mass of the catalyst is 100-1000ppm of the mass of the waste polylactic acid, and the molar ratio of the waste polylactic acid to the polyether diamine is 1.0-1.2:1; 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.

8. The method for preparing low-temperature easily dyeable regenerated polyester fiber according to claim 1, characterized in that: The spinning process adopts UDY, POY or FDY process; the parameters of the UDY process include: spinning temperature 190-240°C, spinning speed 500-1500m / min, cooling air temperature 20-30°C, cooling air speed 0.3-1m / s, cooling air relative humidity 60%-80%; the parameters of the POY process include: spinning temperature 190-240°C, spinning speed 1500-2500m / min, cooling air temperature 15-30°C, cooling air speed 0.3-0.6m / s, cooling air relative humidity 60%-80%; the parameters of the FDY process include: spinning temperature 190-240°C, spinning speed 2500-3500m / min, cooling air temperature 15-20°C, cooling air speed 0.3-0.6m / s, cooling air relative humidity 70%-85%.

9. The method for preparing low-temperature easily dyeable regenerated polyester fiber according to claim 8, characterized in that: The moisture regain of low-temperature easy-to-dye recycled polyester fiber is 0.60-1.20%, the breaking strength is 2.5-5.5cN / dtex, and the breaking elongation is 10-40%; after dyeing with disperse dyes at 80-100°C, the dyeing rate is more than 95%, the color fastness to rubbing is level 4-5, the color fastness to washing is level 4-5, and the color fastness to soaping is level 4-5.

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