Preparation method of low-temperature easy-to-dye regenerated polyester fiber

Abstract

The invention belongs to the technical field of regenerated polyester fibers, and particularly relates to a preparation method of low-temperature easy-to-dye regenerated polyester fibers, which specifically comprises the following steps: firstly, carrying out transesterification on waste polylactic acid and aliphatic dibasic acid to obtain a double-carboxyl-terminated polylactic acid oligomer; sequentially carrying out homogenization reaction and condensation polymerization reaction on the double-end carboxyl polylactic acid oligomer and polyether diamine to obtain modified polylactic acid, and spinning the modified polylactic acid to obtain the low-temperature easy-to-dye regenerated polyester fiber. Wherein the number of carbon atoms of the aliphatic dibasic acid is 4-20, the number-average molecular weight # imgabs0 # of the double-end carboxyl polylactic acid oligomer is 2000-12000 g / mol, and the number-average molecular weight of the polyether diamine is 600-4000 g / mol; the low-temperature easy-to-dye regenerated polyester fiber prepared by the method is high in mechanical strength, can be dyed by adopting disperse dye at 80-100 DEG C, has the dye uptake of 95% or above, and is good in color fastness.

Description

Technical Field

[0001] The invention belongs to the technical field of regenerated polyester fibers, and in particular relates to a method for preparing low-temperature easily dyeable regenerated polyester fibers. Background Art

[0002] At a time when environmental protection is prevalent, polylactic acid fiber has attracted much attention in the field of materials because it is derived from renewable resources and is biodegradable. It has great potential in sustainable development and is expected to alleviate the pressure of traditional fibers on the environment. However, the degradation of polylactic acid fiber requires specific conditions. Even if it is degraded into carbon dioxide and water, it is difficult to use it quickly and directly, resulting in a waste of resources. Therefore, from an environmental and economic perspective, recycling and reusing waste polylactic acid is of great practical significance.

[0003] Polylactic acid fiber textiles and clothing have entered the markets of the United States, Europe, Japan, etc., but they also face many challenges. Especially in colored silk products, there are more light colors and fewer dark colors, and the color brightness is not enough. This is due to its own structure, high crystallinity and lack of hydrophilic groups in the molecular main chain, making it a hydrophobic fiber that 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 needs of dark dyeing, resulting in unsatisfactory color of polylactic acid colored silk products.

[0004] In addition, the dyeing process of polylactic acid fiber is complicated. Its glass transition temperature and melting point are low, and it is sensitive to temperature and pH value. It cannot be dyed at high temperature like polyester. When it exceeds 110℃ or encounters strong alkali, the fiber will degrade, and its strength and feel will deteriorate; if the setting temperature exceeds 130℃, it will melt. At present, polylactic acid fiber is usually dyed at 110℃, but disperse dyes need high temperature to effectively enter the fiber, resulting in low dyeing rate and poor color fastness, which seriously restricts its promotion and application.

[0005] The patent with publication number CN101270551A discloses a polylactic acid fiber disperse dye dyeing accelerator, which has the effect of significantly improving the dyeing rate of polylactic acid disperse dye dyeing, can reduce the pollution of dyeing waste liquid to water resources, and has high dyeing color fastness, and has little effect on the breaking strength of polylactic acid fiber fabric; but this technology is based on the dyeing process alone, and the polymer molecular chain structure and condensed state structure have not changed, and it is impossible to achieve low-temperature easy dyeing. The patent with publication number CN109440490A provides an azo structure lactate type disperse dye for polylactic acid fiber dyeing, which can improve the dyeing rate and the boiling point of the dye, and hydrogen bonds will be formed between the dye molecules, thereby improving the sublimation fastness of the dye, so that the dye has a better dyeing effect, but the dyeing temperature of this method can reach up to 130°C, which will cause the polylactic acid fiber to degrade and break, and affect the strength and comfort of the fiber to a certain extent. The patent with publication number CN118422509A provides a low-temperature dyeing method for polylactic acid fiber, which uses nanotechnology to modify and pretreat the polylactic acid fiber, then immerses the modified polylactic acid fiber in a dye solution of a low-temperature reactive dye, applies magnetic field technology to promote the combination of the dye and the polylactic acid fiber, and uses a photocatalytic color fixing agent to fix the color, and finally uses freeze-drying technology to dry the treated polylactic acid fiber and post-treats the dried polylactic acid fiber to enhance color stability. The post-processing process of this technology is complicated and requires excess auxiliary agents for color fixing, which increases the dyeing cost.

[0006] In view of the above-mentioned shortcomings, it is necessary to improve the existing technology and propose a regenerated polyester fiber that is easy to dye at low temperature. Summary of the invention

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

[0008] In order to achieve the above object, the present invention adopts the following technical scheme:

[0009] A method for preparing low-temperature easy-to-dye regenerated polyester fiber, comprising: firstly subjecting waste polylactic acid to an ester exchange reaction with an aliphatic dibasic acid to obtain a double-terminal carboxyl polylactic acid oligomer, then subjecting the double-terminal carboxyl polylactic acid oligomer to a homogenization reaction and a polycondensation reaction with a polyether diamine in sequence to obtain a modified polylactic acid, and then subjecting the modified polylactic acid to a spinning process to obtain a low-temperature easy-to-dye regenerated polyester fiber;

[0010] The carbon number of the aliphatic dibasic acid is 4-20; if the carbon number of the aliphatic dibasic acid is greater than 20, and the carbon chain of the aliphatic dibasic acid is too long, on the one hand, the reaction activity of the terminal carboxyl group of the aliphatic dibasic acid is low, and if the time of the transesterification reaction is not extended, the transesterification reaction will not be thorough enough, and the effective preparation of the double-terminal carboxyl polylactic acid oligomer cannot be achieved. If the time of the transesterification reaction is extended, the thermal degradation of the waste polylactic acid will become serious; on the other hand, since the aliphatic dibasic acid needs to enter the molecular chain of the polylactic acid during the transesterification reaction, the excessively long carbon chain of the aliphatic dibasic acid will cause the regularity of the molecular chain of the polylactic acid to be excessively destroyed, thereby affecting the crystallization performance of the final modified polylactic acid, and further affecting the spinning process;

[0011] Number average molecular weight of double-terminated carboxyl polylactic acid oligomer The molecular weight of the double-end carboxyl polylactic acid oligomer is 2000-12000g / mol; if the molecular weight of the double-end carboxyl polylactic acid oligomer is too low, the crystallization ability of the modified polylactic acid will be low, thereby affecting the spinning process of the modified polylactic acid; if the molecular weight of the double-end carboxyl polylactic acid oligomer is too high, an uneven reaction will occur during the repolymerization process, ultimately causing the molecular weight distribution of the modified polylactic acid to be too wide, thereby affecting the spinning process; therefore, in order to realize the reuse of copolymerized functional fibers of waste polylactic acid, the molecular weight of the double-end carboxyl polylactic acid oligomer needs to be strictly controlled;

[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, and the effect of low-temperature easy dyeing cannot be achieved; the polyether diamine is used to prepare low-temperature easy-dyeing regenerated polyester fiber through an amide exchange reaction with a double-terminal carboxyl polylactic acid oligomer, and 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, the regularity of the polylactic acid molecular chain will be excessively destroyed, thereby affecting the crystallization performance of the final polylactic acid copolymer, and further affecting the spinning process;

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

[0014] ;

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

[0016] The prior art mainly relies on alcoholysis reaction to recycle waste polylactic acid, and the ultimate goal is to obtain lactide monomer, such as CN115403554B; different from the prior art, the present invention relies on ester exchange reaction to recycle waste polylactic acid, and the ultimate goal is to obtain double-terminal carboxyl polylactic acid oligomers with a specific molecular weight, so that the fiber-forming ability and crystallization ability of polylactic acid can be retained. In addition, the present invention can realize the functional reuse of waste polylactic acid. Compared with depolymerization to lactide monomer, there is no need to separate and treat the depolymerization product, which simplifies the process of polylactic acid recovery and reuse.

[0017] As the preferred technical solution:

[0018] In the method for preparing low-temperature easy-to-dye regenerated polyester fiber as described above, the characteristic viscosity of waste polylactic acid is 1.00-1.40 dL / g and the melting point is 130-240°C.

[0019] In the method for preparing low-temperature easy-to-dye regenerated polyester fiber as described above, the molecular weight distribution index of the double-terminated carboxyl polylactic acid oligomer is 1.3-2.0.

[0020] In the method for preparing the low-temperature easy-to-dye regenerated polyester fiber as described above, the polyether diamine is one or more of polyoxyethylene diamine, polyoxypropylene diamine or polysiloxane diamine.

[0021] In the method for preparing the low-temperature easy-to-dye regenerated polyester fiber as described above, 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.

[0022] In the above-mentioned method for preparing a low-temperature easy-to-dye regenerated polyester fiber, the preparation steps of the modified polylactic acid are as follows:

[0023] (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;

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

[0025] The catalyst remains in the modified polylactic acid and can act as a crystal nucleating agent to regulate the crystallization properties.

[0026] The method for preparing a low-temperature easy-to-dye regenerated polyester fiber as described above, the mass of the aliphatic dibasic acid , the quality of waste polylactic acid , Relative molecular weight of aliphatic dibasic acids , Number average molecular weight of double-terminated carboxyl polylactic acid oligomer The relationship satisfies the following formula:

[0027] ;

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

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

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

[0031] =72n+ -φ; Formula 1

[0032] Transformation to get formula 2:

[0033] n=( - +φ) / 72; Formula 2

[0034] Assume that the mass of waste polylactic acid added during the preparation process is The molar number of lactic acid segments in waste polylactic acid is n PLA , then we can list formula 3:

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

[0036] It can be obtained that the number of lactic acid chains in waste polylactic acid is n more than that in the designed double-terminal carboxyl polylactic acid oligomer. PLA / n times, the multiple is the molar number n of the required aliphatic dibasic acid COOH , we get formula 4:

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

[0038] Substituting equation 3 into equation 4, we get equation 5:

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

[0040] The relative molecular mass of aliphatic dibasic acids It can be calculated according to formula 6:

[0041] =n COOH × ; Formula 6

[0042] Substituting equation 5 into equation 6, we get equation 7:

[0043] =(m× ) / (72n); Formula 7

[0044] Finally, substitute equation 2 into equation 7 to obtain the above formula;

[0045] The test shows that the number average molecular weight of double-terminated carboxyl polylactic acid oligomers The relative deviation does not exceed 2%, 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 polylactic acid oligomer, the appropriate aliphatic dibasic acid can be selected according to the above formula, and the quality of the aliphatic dibasic acid and the quality of the waste polylactic acid can be determined.

[0046] 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;

[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] According to the method for preparing a low-temperature easy-to-dye regenerated polyester fiber as described above, 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%.

[0049] The method for preparing a low-temperature easy-to-dye regenerated polyester fiber as described above has a moisture regain of 0.60-1.20%, a breaking strength of 2.5-5.5 cN / dtex, and an elongation at break of 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.

[0050] The regenerated polyester fiber of the present invention has the property of being easy to dye at low temperature because the molecular chain thereof contains a polyether segment. On the one hand, the polyether segment is located in the amorphous region, and the amorphous region can be opened at a lower temperature, which is conducive to the entry of dyes. On the other hand, the presence of ether bonds can improve the dyeing rate. The prior art mainly introduces a polyether segment into the polylactic acid molecular chain based on the motivation of improving the solubility of polylactic acid in water. Different from the prior art, the present invention introduces a polyether segment into the polylactic acid molecular chain based on the motivation of improving the dyeing performance of polylactic acid.

[0051] The regenerated polyester fiber of the present invention has excellent mechanical properties because, on the one hand, the fiber-forming ability and crystallization ability of polylactic acid are retained by regulating the molecular weight of the double-terminal carboxyl polylactic acid oligomer, and on the other hand, the presence of amide bonds can form hydrogen bonds, thereby improving the mechanical properties of the regenerated polyester fiber.

[0052] The color fastness of the regenerated polyester fiber after dyeing is high because the molecular chain contains an amide bond, which is generated by the polycondensation reaction of the terminal amino group and the terminal carboxyl group during the repolymerization process. The hydrogen bonding between the terminal amino group and the dye molecule can improve the color fastness to a certain extent. The method of improving the color fastness of fibers or fabrics in the prior art is mainly to introduce a color fixing agent into the fibers or fabrics. The mechanism is that the color fixing agent forms a strong binding force with the dye molecules to achieve the color fixing effect. There is no method for improving the color fastness by introducing an amide bond.

[0053] Beneficial effects:

[0054] (1) The present invention uses dibasic acid hydrolysis to effectively design the molecular chain length according to the fiber performance requirements, without the need to prepare monomers, thus saving manufacturing costs and improving the resource utilization of polylactic acid;

[0055] (2) The present invention depolymerizes and repolymerizes waste polylactic acid, controls the amount of dibasic acid added, designs the length of the polylactic acid chain segment, retains the fiber-forming ability and crystallization ability of polylactic acid, and maintains the strength of the recycled polyester fiber;

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

[0057] (4) The preparation method provided by the present invention has a simple process and can be produced on existing equipment. It can be used in current industrial production and can be applied on a large scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is the nuclear magnetic resonance spectrum of the double-terminated carboxyl polylactic acid oligomer prepared in Example 1. DETAILED DESCRIPTION

[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 are not intended 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 fall within the scope limited by the appended claims of the application equally.

[0060] Testing methods for relevant performance indicators:

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

[0062] Breaking strength and breaking elongation: tested in accordance with standard GB / T 14344-2022;

[0063] Fiber moisture regain: tested in accordance with standard GB / T 6503-2017;

[0064] Dye uptake: Tested in accordance with GB / T 23976.1-2009;

[0065] Color fastness to rubbing: tested in accordance with standard GB / T 3920-2008;

[0066] Color fastness to washing: tested in accordance with standard GB / T 5713-2013;

[0067] Color fastness to soap washing: tested in accordance with standard GB / T 3921-2008.

[0068] Example 1

[0069] A method for preparing low-temperature easy-to-dye regenerated polyester fiber, as follows:

[0070] (1) Prepare the raw materials:

[0071] Waste polylactic acid: intrinsic viscosity is 1dL / g, melting point is 130℃;

[0072] Aliphatic dibasic acid: succinic acid;

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

[0074] Catalyst: Titanium glycolate;

[0075] (2) Preparation of modified polylactic acid:

[0076] (2.1) Waste polylactic acid, aliphatic dibasic acid and catalyst were added to the reactor and reacted at 160°C and 0.01 MPa for 6 h to obtain double-terminal carboxyl polylactic acid oligomers. Its nuclear magnetic resonance spectrum is shown in Figure 1 As shown;

[0077] Number average molecular weight of double-terminated carboxyl polylactic acid oligomer is 12000 g / mol, and the molecular weight distribution index is 2;

[0078] (2.2) Continue to add polyether diamine to the reactor, first react at 180°C and 500Pa for 4 hours (homogenization reaction), and then react at 200°C and 100Pa for 1 hour (condensation 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 the waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.0:1;

[0081] (3) Spinning processing:

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

[0083] The final low-temperature easy-to-dye recycled polyester fiber has a moisture regain of 1%, a breaking strength of 3cN / dtex, and an elongation at break of 30%; after dyeing with disperse dyes at 85°C, the dyeing rate is 95%, the color fastness to rubbing is level 5, the color fastness to washing is level 5, and the color fastness to soap washing is level 5.

[0084] Comparative Example 1

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

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

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

[0088] Example 2

[0089] A method for preparing low-temperature easy-to-dye regenerated polyester fiber, as follows:

[0090] (1) Prepare the raw materials:

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

[0092] Aliphatic dibasic acid: succinic acid;

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

[0094] Catalyst: tetrabutyl titanate;

[0095] (2) Preparation of modified polylactic acid:

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

[0097] Number average molecular weight of double-terminated 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 to the reactor, first react at 180°C and 1000Pa for 2h (homogenization reaction), then react at 200°C and 70Pa for 1.5h (condensation 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 the waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.0:1;

[0101] (3) Spinning processing:

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

[0103] The final low-temperature easy-to-dye recycled polyester fiber has a moisture regain of 0.8%, a breaking strength of 2.5 cN / dtex, and an elongation at break of 35%; after dyeing with disperse dyes at 100°C, the dyeing rate is 95%, the color fastness to rubbing is level 5, the color fastness to washing is level 5, and the color fastness to soaping is level 5.

[0104] Comparative Example 2

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

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

[0107] Compared with Example 2, the breaking strength of the regenerated polyester fiber prepared in Comparative Example 2 is poor. This is because the molecular weight of the double-end carboxyl polylactic acid oligomer is too low, which will cause the modified polylactic acid to have a low crystallization ability, thereby making the oriented crystallization ability of the modified polylactic acid fiber poor, and further resulting in a decrease in the breaking strength of the fiber.

[0108] Comparative Example 3

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

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

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

[0112] Example 3

[0113] A method for preparing low-temperature easy-to-dye regenerated polyester fiber, as follows:

[0114] (1) Prepare the raw materials:

[0115] Waste polylactic acid: intrinsic viscosity is 1.15dL / g, melting point is 160℃;

[0116] Aliphatic dibasic acid: adipic acid;

[0117] Polyether diamine: polysiloxane diamine, number average molecular weight is 2000g / mol;

[0118] Catalyst: Antimony glycol;

[0119] (2) Preparation of modified polylactic acid:

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

[0121] Number average molecular weight of double-terminated 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 reactor, first react at 190°C and 500Pa for 1h (homogenization reaction), and then react at 210°C and 80Pa for 1.5h (condensation 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 the waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.1:1;

[0125] (3) Spinning processing:

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

[0127] The final low-temperature easy-to-dye recycled polyester fiber has a moisture regain of 1%, a breaking strength of 3.5 cN / dtex, and an elongation at break of 25%; after dyeing with disperse dyes at 100°C, the dyeing rate is 96%, 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.

[0128] Comparative Example 4

[0129] A method for preparing regenerated polyester fiber is basically the same as 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 final recycled polyester fiber is 0.5%, and after dyeing with disperse dyes at 100°C, the dyeing rate is 80%.

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

[0132] Comparative Example 5

[0133] A method for preparing regenerated polyester fiber is basically the same as 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 regenerated polyester fiber finally produced is 1.6 cN / dtex.

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

[0136] Example 4

[0137] A method for preparing low-temperature easy-to-dye regenerated polyester fiber, as follows:

[0138] (1) Prepare the raw materials:

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

[0140] Aliphatic dibasic acid: adipic acid;

[0141] Polyether diamine: polyoxyethylene diamine, number average molecular weight 600g / 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 a reactor, react at 190°C and 0.05MPa for 4h to obtain double-terminal carboxyl polylactic acid oligomer;

[0145] Number average molecular weight of double-terminated carboxyl polylactic acid oligomer is 10000 g / mol, and the molecular weight distribution index is 1.5;

[0146] (2.2) Continue to add polyether diamine to the reactor, first react at 200°C and 600Pa for 1h (homogenization reaction), and then react at 220°C and 90Pa for 2h (condensation 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 the waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.1:1;

[0149] (3) Spinning processing:

[0150] The spinning process adopts POY process, and the process parameters include: spinning temperature 190°C, spinning speed 1500m / min, cooling air temperature 15°C, cooling air speed 0.3m / s, and cooling air relative humidity 60%.

[0151] The final low-temperature easy-to-dye recycled polyester fiber has a regain of 0.6%, a breaking strength of 5.5 cN / dtex, and an elongation at break of 10%; after dyeing with disperse dyes at 80°C, the dyeing rate is 98%, 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.

[0152] Example 5

[0153] A method for preparing low-temperature easy-to-dye regenerated polyester fiber, as follows:

[0154] (1) Prepare the raw materials:

[0155] Waste polylactic acid: intrinsic viscosity is 1.25dL / g, melting point is 190℃;

[0156] Aliphatic dibasic acid: suberic acid;

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

[0158] Catalyst: antimony oxide;

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

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

[0161] Number average molecular weight of double-terminated carboxyl polylactic acid oligomer is 8000 g / mol, and the molecular weight distribution index is 1.3;

[0162] (2.2) Continue to add polyether diamine to the reactor, first react at 210°C and 900Pa for 1h (homogenization reaction), and then react at 230°C and 50Pa for 2.5h (condensation 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 dibasic acid is 45:1, the mass of the catalyst is 100 ppm of the mass of the waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.2:1;

[0165] (3) Spinning processing:

[0166] The spinning process adopts POY process, and the process parameters include: spinning temperature 215°C, spinning speed 2000m / min, cooling air temperature 20°C, cooling air speed 0.5m / s, and cooling air relative humidity 70%.

[0167] The final low-temperature easy-to-dye recycled polyester fiber has a regain of 0.6%, a breaking strength of 4.5 cN / dtex, and an elongation at break of 20%; after dyeing with disperse dyes at 90°C, the dyeing rate is 96%, 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.

[0168] Example 6

[0169] A method for preparing low-temperature easy-to-dye regenerated polyester fiber, as follows:

[0170] (1) Prepare the raw materials:

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

[0172] Aliphatic dibasic acid: sebacic acid;

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

[0174] Catalyst: stannous octoate;

[0175] (2) Preparation of modified polylactic acid:

[0176] (2.1) Add waste polylactic acid, aliphatic dibasic acid and catalyst into a reactor, react at 210°C and 0.1 MPa for 2 h to obtain double-terminal carboxyl polylactic acid oligomer;

[0177] Number average molecular weight of double-terminated carboxyl polylactic acid oligomer is 7000 g / mol, and the molecular weight distribution index is 1.3;

[0178] (2.2) Continue to add polyether diamine to the reactor, first react at 220°C and 700Pa for 0.5h (homogenization reaction), and then react at 250°C and 40Pa for 2.5h (condensation 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 dibasic acid is 34:1, the mass of the catalyst is 100 ppm of the mass of the waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.1:1;

[0181] (3) Spinning processing:

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

[0183] The final low-temperature easy-to-dye recycled polyester fiber has a regain of 0.8%, a breaking strength of 4cN / dtex, and an elongation at break of 25%; after dyeing with disperse dyes at 90°C, the dyeing rate is 97%, 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.

[0184] Example 7

[0185] A method for preparing low-temperature easy-to-dye regenerated polyester fiber, as follows:

[0186] (1) Prepare the raw materials:

[0187] Waste polylactic acid: intrinsic viscosity is 1.3dL / g, melting point is 220℃;

[0188] Aliphatic dibasic acid: sebacic acid;

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

[0190] Catalyst: stannous chloride;

[0191] (2) Preparation of modified polylactic acid:

[0192] (2.1) Add waste polylactic acid, aliphatic dibasic acid and catalyst into a reactor, react at 220°C and 0.1 MPa for 2 h to obtain double-terminal carboxyl polylactic acid oligomer;

[0193] Number average molecular weight of double-terminated carboxyl polylactic acid oligomer is 7000 g / mol, and the molecular weight distribution index is 1.6;

[0194] (2.2) Continue to add polyether diamine to the reactor, first react at 230°C and 800Pa for 0.5h (homogenization reaction), and then react at 250°C and 30Pa for 3h (condensation 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 the waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.1:1;

[0197] (3) Spinning processing:

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

[0199] The final low-temperature easy-to-dye recycled polyester fiber 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 dyeing rate is 96%, the color fastness to rubbing is level 4, the color fastness to washing is level 4, and the color fastness to soap washing is level 4.

[0200] Example 8

[0201] A method for preparing low-temperature easy-to-dye regenerated polyester fiber, as follows:

[0202] (1) Prepare the raw materials:

[0203] Waste polylactic acid: intrinsic viscosity is 1.35dL / g, melting point is 235℃;

[0204] Aliphatic dibasic acid: suberic acid;

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

[0206] Catalyst: zinc acetate;

[0207] (2) Preparation of modified polylactic acid:

[0208] (2.1) Add waste polylactic acid, aliphatic dibasic acid and catalyst into a reactor, react at 220°C and 0.1 MPa for 2 h to obtain double-terminal carboxyl polylactic acid oligomer;

[0209] Number average molecular weight of double-terminated carboxyl polylactic acid oligomer is 5000 g / mol, and the molecular weight distribution index is 1.9;

[0210] (2.2) Continue to add polyether diamine to the reactor, first react at 230°C and 1000Pa for 0.5h (homogenization reaction), then react at 260°C and 50Pa for 4h (condensation 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 the waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.0:1;

[0213] (3) Spinning processing:

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

[0215] The final low-temperature easy-to-dye recycled polyester fiber 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 80°C, the dyeing rate is 97%, the color fastness to rubbing is level 4, the color fastness to washing is level 4, and the color fastness to soaping is level 4.

[0216] Example 9

[0217] A method for preparing low-temperature easy-to-dye regenerated polyester fiber, as follows:

[0218] (1) Prepare the raw materials:

[0219] Waste polylactic acid: intrinsic viscosity is 1.4dL / g, melting point is 240℃;

[0220] Aliphatic dibasic acid: eicosapentadicarboxylic acid;

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

[0222] Catalyst: zinc oxide;

[0223] (2) Preparation of modified polylactic acid:

[0224] (2.1) Add waste polylactic acid, aliphatic dibasic acid and catalyst into a reactor, react at 250°C and 0.3 MPa for 1 h to obtain a double-terminal carboxyl polylactic acid oligomer;

[0225] Number average molecular weight of double-terminated carboxyl polylactic acid oligomer is 2000 g / mol, and the molecular weight distribution index is 2;

[0226] (2.2) Continue to add polyether diamine to the reactor, first react at 250°C and 1000Pa for 0.2h (homogenization reaction), and then react at 260°C and 20Pa for 4.5h (condensation 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 the waste polylactic acid, and the molar ratio of waste polylactic acid to polyether diamine is 1.0:1;

[0229] (3) Spinning processing:

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

[0231] The final low-temperature easy-to-dye recycled polyester fiber has a moisture regain of 1%, a breaking strength of 3cN / dtex, and an elongation at break of 30%; after dyeing with disperse dyes at 80°C, the dyeing rate is 98%, the color fastness to rubbing is level 4, the color fastness to washing is level 4, and the color fastness to soap washing is level 4.

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

[0233] ;

[0234] In the formula, (mass of the first aliphatic dibasic acid), The unit of (mass of waste polylactic acid) is g; (Relative molecular weight of the first aliphatic dibasic acid), The unit of (number average molecular weight of double-terminated carboxyl polylactic acid oligomer) is 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; Number average molecular weight of double-terminated carboxyl polylactic acid oligomer 2000-12000 g / mol; The number average molecular weight of the polyether diamine is 600-4000 g / mol.

2. The method for preparing a low-temperature easily dyeable 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, polyoxypropylene diamine or polysiloxane 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 quality of aliphatic dibasic acids , the quality of waste polylactic acid , Relative molecular weight of aliphatic dibasic acids , Number average molecular weight of double-terminated carboxyl polylactic acid oligomer The relationship satisfies the following formula: ； In the formula, , The unit is g; , The unit of is g / mol; φ is 17g / 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 UDY process include: spinning temperature 190-240℃, spinning speed 500-1500m / min, cooling air temperature 20-30℃, cooling air speed 0.3-1m / s, cooling air relative humidity 60%-80%; the parameters of POY process include: spinning temperature 190-240℃, spinning speed 1500-2500m / min, cooling air temperature 15-30℃, cooling air speed 0.3-0.6m / s, cooling air relative humidity 60%-80%; the parameters of FDY process include: spinning temperature 190-240℃, spinning speed 2500-3500m / min, cooling air temperature 15-20℃, 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℃, 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 soap washing is level 4-5.

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