A method for producing a thermoplastic functional polyester fiber

Abstract

The application belongs to the technical field of high polymer materials, and relates to a preparation method of thermoplastic functional polyester fiber, which comprises the following steps: melt blending a reactive modifier with thermoplastic polyester, and then melt spinning to obtain the thermoplastic functional polyester fiber; the molecular chain of the reactive modifier comprises multiple-N=C=N- segments and multiple-NR-CO-NH- segments, -R is a functional prepolymer segment, the lengths of the -R segments in the different-NR-CO-NH- segments are not completely same, and the positions of the-NR-CO-NH- segments are random; and the unsaturated double bonds in the reactive modifier react with the terminal carboxyl groups of the thermoplastic polyester in the melt blending process. The reactive modifier with the specific structure is melt blended with the thermoplastic polyester and spun, high proportion of functional components is grafted, crosslinking reaction is avoided, and the problems of low grafting proportion or loss of processability of the material in the prior art are solved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high polymer materials, and relates to a preparation method of thermoplastic functional polyester fibers. BACKGROUND

[0002] In the production of thermoplastic polyester fibers, functional modification is often needed to expand the application scenarios. Functional modification is mainly achieved in two ways: one is to blend a blending-type modifier with polyester, and to make polyester obtain functionality by physical mixing; and the other is to use a reactive modifier, and to introduce the reactive modifier into the polyester molecular chain by chemical action to realize intrinsic functional modification.

[0003] Although the first way is simple to operate, the blending-type modifier is only physically combined with the polyester molecules, and is prone to migration or loss due to external force or temperature change in the process of processing or use, resulting in functional attenuation, and when a high proportion is added, the mechanical properties and processing stability of the fiber are also affected.

[0004] The second way can solve the problems existing in the first way by chemically combining the reactive modifier with the polyester molecular chain, and therefore becomes a better choice. For example, patent application CN102875982A uses a single functional group reactive flame retardant (such as a phosphorus hetero-fused compound) to react with the end groups of the polyester molecular chain to realize in-situ modification in the melt blending process, and obtains a flame retardant system with good compatibility and convenient processing. However, the single functional group reactive modifier contains only one reaction site, and the number of end groups of the polyester after melt polycondensation is limited, resulting in a low grafting ratio.

[0005] In order to improve the grafting ratio, the industry has tried to use reactive modifiers containing multiple reaction sites, but the multiple reaction sites of such reactive modifiers are prone to react with the end groups of different polyester molecular chains at the same time or within a short period of time, forming a three-dimensional cross-linked network structure, resulting in the loss of thermoplasticity of the polyester, and the polyester cannot be processed by melt spinning and the like, seriously affecting the practicability of the material.

[0006] Therefore, there is an urgent need for a preparation method of thermoplastic polyester fibers which can realize high proportion of reactive modifier grafting and avoid cross-linking reaction. SUMMARY

[0007] The purpose of the present application is to solve the problems existing in the prior art, and to provide a preparation method of thermoplastic functional polyester fibers.

[0008] To achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0009] A preparation method of thermoplastic functional polyester fibers, which comprises the following steps: melt blending a reactive modifier with a thermoplastic polyester, and then melt spinning to obtain the thermoplastic functional polyester fibers.

[0010] The reactive modifier is prepared by reacting polycarbodiimide with a functional prepolymer;

[0011] The functional prepolymer is a flame-retardant prepolymer, or a cationic dyeable prepolymer, or a mixture of the flame-retardant prepolymer and the cationic dyeable prepolymer;

[0012] The flame-retardant prepolymer is prepared by esterification reaction and pre-polycondensation reaction of a binary acid containing a flame-retardant structural unit and a first aliphatic diol; the molar ratio of the binary acid containing a flame-retardant structural unit to the first aliphatic diol is 1:1-1.1;

[0013] The reaction equation of the flame-retardant prepolymer is shown as follows:

[0014] ;

[0015] The cationic dyeable prepolymer is prepared by esterification reaction and pre-polycondensation reaction of sodium 5-sulfonate isophthalic acid and a second aliphatic diol; the molar ratio of sodium 5-sulfonate isophthalic acid to the second aliphatic diol is 1:1-1.1;

[0016] In the preparation of the reactive modifier, the molar ratio of the functional prepolymer to the polycarbodiimide is 1:9-12, the reaction temperature is 120-160°C, the pressure is 50-80 Pa, and the reaction time is 1.5-3 h;

[0017] In the preparation of the reactive modifier, the terminal carboxyl groups in the functional prepolymer and the polycarbodiimide undergo grafting reaction and are connected through acylurea bonds, and the reaction equation is shown as follows:

[0018] ;

[0019] By adjusting the addition amount ratio of the functional prepolymer to the polycarbodiimide, the number of reaction sites in the reactive modifier can be flexibly controlled: the reaction of the terminal carboxyl groups on the molecular chain of the functional prepolymer with the unsaturated double bonds on the molecular chain of the polycarbodiimide is random, and the unreacted unsaturated double bonds are randomly distributed in the molecular chain of the modifier, and by adjusting the mass ratio of the two, the number of unreacted unsaturated double bonds can be adjusted, so as to realize grafting reaction while avoiding crosslinking reaction;

[0020] In addition, in the preparation of the reactive modifier, a plurality of functional prepolymers are reacted with the polycarbodiimide at the same time, so as to prepare a multifunctional reactive modifier, thereby avoiding the limitation of the low reaction rate of the multi-component copolymer system in the melt polycondensation process of the multifunctional copolyester;

[0021] The molecular chain of the reaction type modifier prepared by the above method comprises multiple -N=C=N- segments and multiple -NR-CO-NH- segments, -R is a functional prepolymer segment, the lengths of the -R segments in different -NR-CO-NH- segments are not completely the same, and the positions of each -NR-CO-NH- segment are random;

[0022] In the melt blending process, the unsaturated double bonds in the reaction type modifier react with the terminal carboxyl groups of the thermoplastic polyester.

[0023] The reaction type modifier of the present application contains multiple reaction sites (-N=C=N- segments), but crosslinking reaction can be avoided (if crosslinking reaction occurs, the thermoplastic polymer will exhibit the characteristics of insolubility and infusibility, and melt spinning cannot be carried out, the present application can be smoothly melt spun, and therefore it can be known that the present application does not occur crosslinking reaction), because the molecular chain of the reaction type modifier contains multiple side chains -R (functional prepolymer segments), and the lengths of these side chains -R are not completely the same, and the positions are random, which can inhibit the reaction of multiple reaction sites with the terminal groups of different polyester molecular chains at the same time or within a short period of time to some extent, so that multiple reaction sites can react with different polyester molecular chains in steps and in order, and then crosslinking network structure is avoided.

[0024] If the lengths of the side chains -R are completely the same, on the one hand, it is more difficult to synthesize because during the preparation of the functional prepolymer, while the molecular chain is lengthened by ester exchange reaction, the ester bonds in the molecular chain will also be randomly broken by ester exchange reaction, thereby forming chain segments with different lengths; on the other hand, if the lengths of the side chains -R are completely the same, the steric hindrance effect will be weakened and the risk of crosslinking will be increased: this is because the motion trends of the side chains -R with the same length are the same, and the "dynamic shielding effect" formed by the combination of long and short side chains -R is lost (the slow motion of long side chains -R can provide a stable spatial barrier, and the fast motion of short side chains -R can fill the gap and "drive away" the approaching polyester molecular chains), and the side chains -R with the same length are more regular in structure, and more likely to form a local ordered region in the molecular chain of the reaction type modifier, so that the -N=C=N- segments and the terminal groups of the polyester molecular chains are more likely to react. If the positions of the side chains -R are regular, the protection mechanism of steric hindrance will be further weakened, because the regular side chains -R will form a relatively regular channel, causing the polyester molecular chains to be more likely to react with the -N=C=N- segments from the interval between the regularly arranged side chains -R, and increasing the possibility of crosslinking reaction, and thus the material may lose the properties of thermoplasticity and melt spinning.

[0025] As a preferred technical solution:

[0026] The method for preparing the thermoplastic functional polyester fiber as described above, the polycarbodiimide is one or more of aliphatic polycarbodiimide and aromatic polycarbodiimide, the number average molecular weight of the polycarbodiimide is 1000-8000 g / mol, and the content of the carbodiimide group of the polycarbodiimide is 10-15 wt%.

[0027] The method for preparing the thermoplastic functional polyester fiber as described above, the binary acid containing the flame-retardant structural unit is one or more of DDP ([(6-oxo-6H-dibenzo-(C,E)(1,2)-oxaphosphorin-6-one)-methyl]-butanedioic acid) and CEPPA (2-carboxyethyl phenyl phosphinic acid);

[0028] The first aliphatic diol is one or more of ethylene glycol, 1,3-propanediol and 1,5-pentanediol.

[0029] The method for preparing the thermoplastic functional polyester fiber as described above, when preparing the flame-retardant prepolymer, the temperature of the esterification reaction is 180-220 °C, the pressure is 0.1-0.4 MPa, and the time is 60-90 min; the temperature of the pre-polycondensation reaction is 200-240 °C, the pressure is 50-80 Pa, and the time is 30-45 min.

[0030] The second aliphatic diol is one or more of ethylene glycol, 1,3-propanediol and 1,5-pentanediol.

[0031] The method for preparing the thermoplastic functional polyester fiber as described above, when preparing the cationic dyeable prepolymer, the temperature of the esterification reaction is 190-230 °C, the pressure is 0.1-0.4 MPa, and the time is 60-90 min; the temperature of the pre-polycondensation reaction is 210-250 °C, the pressure is 50-80 Pa, and the time is 30-45 min.

[0032] The method for preparing the thermoplastic functional polyester fiber as described above, when the functional prepolymer is the flame-retardant prepolymer, the breaking strength of the thermoplastic functional polyester fiber is ≥3.0 cN / dtex, the breaking elongation is 20%-30%, the limiting oxygen index of the fiber is ≥30.0%, the vertical burning grade reaches V-0 level, and the limiting oxygen index of the fiber or the textile made therefrom decreases by no more than 5% after 50 times of washing;

[0033] When the functional prepolymer is the cationic dyeable prepolymer, the breaking strength of the thermoplastic functional polyester fiber is ≥3.3 cN / dtex, the breaking elongation is 20%-30%, the dye uptake of the fabric made of the thermoplastic functional polyester fiber is ≥96% after dyeing with cationic dyes, and the color fastness grade is ≥4.5;

[0034] When the functional prepolymer is a mixture of the flame-retardant prepolymer and the cationic dyeable prepolymer, the mass ratio of the flame-retardant prepolymer to the cationic dyeable prepolymer is 9-9.5:1-0.5, the breaking strength of the thermoplastic functional polyester fiber is ≥3.1 cN / dtex, the breaking elongation is 20%-30%, the limiting oxygen index of the fiber is ≥30.0%, the vertical combustion level reaches V-0 level, the limiting oxygen index of the fiber or the textile made of the fiber decreases by not more than 5% after 50 times of washing, and the dyeing rate of the fabric made of the thermoplastic functional polyester fiber is ≥95% after dyeing with the cationic dye, and the color fastness level is ≥4.5 level.

[0035] Since the reactive modifier can react with the end groups of the thermoplastic polyester and form a chemical bond during the blending process, and the acylurea structure formed by the reaction of the reactive modifier with the end groups of the polyester and the unreacted unsaturated double bond have long-term hydrolysis resistance, the reactive modifier will not be lost during the textile finishing process (such as washing, soaping, high-temperature setting, wrinkle-resistant treatment, etc.), and the functional performance (such as flame-retardant performance) of the thermoplastic functional polyester fiber can be prevented from being reduced after textile finishing.

[0036] The preparation method of the thermoplastic functional polyester fiber, the thermoplastic polyester is prepared by esterification reaction and polycondensation reaction in sequence from a diacid and a third aliphatic diol; the diacid is one or more of terephthalic acid, isophthalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid and sebacic acid; and the third aliphatic diol is one or more of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol and decanediol.

[0037] The preparation method of the thermoplastic functional polyester fiber, the mass ratio of the reactive modifier to the thermoplastic polyester is 0.25-1.5:8.5-9.75, and the temperature of the melt blending is 140-260°C; during the melt spinning, the pre-oriented fiber is prepared first, and then the pre-oriented fiber is sequentially subjected to drawing, heat setting and winding to obtain the thermoplastic functional polyester fiber.

[0038] The reactive modifier used in the present application is a macromolecular reactive modifier, which has a high thermal decomposition temperature and can meet the melt processing requirements of the thermoplastic polyester. During the melt blending stage, the end groups of the thermoplastic polyester molecular chain and the end groups generated by thermal degradation can react with the reactive modifier, which can not only realize the introduction of the reactive modifier into the polyester molecular chain, but also inhibit the decrease of the molecular weight of the thermoplastic polyester during the processing, improve the melt viscosity after extrusion, and reduce the viscosity reduction of the polyester after thermal processing.

[0039] The process parameters of melt spinning include: drawing temperature 65-80℃, heat setting temperature 80-150℃, spinning speed (rotating speed of friction roller in spinning process) 2400-3600m / min, length-diameter ratio of spinneret hole 1:2-4, side blowing temperature 15-25℃.

[0040] Advantages:

[0041] The present application solves the problem of low grafting ratio of the existing monofunctional reactive modifier by using the specific structure of the reactive modifier and melt blending with the thermoplastic polyester, and then melt spinning, which can realize high proportion of reactive modifier grafted onto the polyester molecular chain by the reaction of multiple -N=C=N- segments in the reactive modifier with the terminal carboxyl group of the thermoplastic polyester, and can inhibit the reaction of multiple reaction sites with the terminal groups of different polyester molecular chains at the same time or in a short period of time by the steric hindrance effect of the -R segments with different lengths and random positions, avoid forming crosslinked network structure, and ensure that the thermoplastic polyester fiber can be normally melt spun. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 The crystallization comparison curves of the thermoplastic functional polyester fibers prepared for different embodiments and PET (Suzhou Baolide Material Science and Technology Co., Ltd., brand RPET);

[0043] Figure 2 The melting comparison curves of the thermoplastic functional polyester fibers prepared for different embodiments and PET (Suzhou Baolide Material Science and Technology Co., Ltd., brand RPET);

[0044] Figure 3 The infrared spectrum of the flame-retardant prepolymer, polycarbodiimide and reactive modifier of example A1;

[0045] Figure 4 The actual picture of the reactive modifier of example A1. DETAILED DESCRIPTION

[0046] The present application will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present application and not to limit the scope of the present application. In addition, it should be understood that after reading the content taught by the present application, those skilled in the art can make various modifications or modifications to the present application, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

[0047] The following are the test methods of the relevant performance indicators in each embodiment:

[0048] Number average molecular weight: obtained by the Shimadzu GPC-20A device test, the test process is: first, the dried sample is dissolved in chloroform at a concentration of 1 mg / mL, stirred at room temperature for 4-6 h or ultrasonic assisted dissolution at 40℃ for 2 h, then filtered with PTFE filter membrane with a thickness of 0.22 μm; during the test, the column temperature is set to 30℃, the chloroform mobile phase is pumped at a flow rate of 1.0 mL / min, the injection volume is 10 μL, and the number average molecular weight is obtained after curve integration;

[0049] Content of carbodiimide group in polycarbodiimide: weigh 0.1-0.3 g of sample and place it in a conical flask, add 25 mL of toluene to dissolve (if the sample is not soluble, heat to help dissolve); remove 20 mL of n-butylamine toluene solution with a concentration of 0.2 mol / L and add it to the conical flask, seal it and react in a 60℃ water bath for 30 min to make the carbodiimide and primary amine fully adducted to form urea; after the reaction is completed, cool to room temperature, dilute with 50 mL of distilled water, add 3-4 drops of bromocresol green indicator, then titrate with 0.1 mol / L hydrochloric acid aqueous solution until the solution changes from blue to light green and does not fade within 30 seconds, while a blank test is performed (the rest of the operation is exactly the same as the sample test except that no sample is added); calculate Y (unit: mol / g) according to the following formula, then multiply it by the molecular weight of the carbodiimide group (unit: g / mol) to obtain the grams of carbodiimide group per gram of polycarbodiimide, and then the content of carbodiimide group in polycarbodiimide (unit: wt%) can be obtained.

[0050] ;

[0051] In the formula, V0 is the volume of hydrochloric acid aqueous solution consumed by the blank test (L); V1 is the volume of hydrochloric acid aqueous solution consumed by the sample test (L); c is the actual concentration of hydrochloric acid aqueous solution (mol / L); m is the mass of the sample (g);

[0052] Breaking strength and elongation at break: tested according to the standard GB / T 14344-2022 "Chemical fibers - Filament tensile property test method";

[0053] Limiting oxygen index of fiber: tested according to the standard FZ / T 50016-2011 "Synthetic fibers - Filament combustion property test method - Oxygen index method";

[0054] Limiting oxygen index of textile made of fiber: first, the fiber is processed by a loom to obtain a textile, and then tested according to the standard GB / T 5454-2024 "Textiles - Combustion properties - Oxygen index method";

[0055] Vertical burning rating: tested according to the standard "UL 94: Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances Testing";

[0056] Dye-uptake rate and color fastness grade of the fabric made of the fiber after dyeing with cationic dyes: the fiber is first processed by a loom to obtain a fabric, then the fabric is dyed through a conventional cationic dyeing process, finally the dye-uptake rate is tested according to GB / T 23976.1-2023 "Dyes Determination of Dye-uptake Rate Curve", and the color fastness grade is tested according to GB / T 3921-2008 "Textiles Color Fastness Test Color Fastness to Soaping".

[0057] Example A1

[0058] A preparation method of a thermoplastic functional polyester fiber, the specific steps are as follows:

[0059] (1) Preparation of materials;

[0060] Dibasic acid A: DDP;

[0061] First aliphatic diol: ethylene glycol;

[0062] Polycarbodiimide: poly(4,4'-diphenylmethane carbodiimide), number average molecular weight is 1000 g / mol, and carbodiimide group content is 10 wt%;

[0063] Dibasic acid B: terephthalic acid;

[0064] Third aliphatic diol: ethylene glycol;

[0065] Catalyst: ethylene glycol antimony;

[0066] (2) Preparation of flame-retardant prepolymer;

[0067] The flame-retardant prepolymer is prepared from the dibasic acid A and the first aliphatic diol through esterification reaction and pre-polycondensation reaction in sequence; wherein the molar ratio of the dibasic acid A to the first aliphatic diol is 1:1; the esterification reaction is carried out at a temperature of 220°C, a pressure of 0.4 MPa, and for a time of 90 min; the pre-polycondensation reaction is carried out at a temperature of 240°C, a pressure of 80 Pa, and for a time of 45 min;

[0068] (3) Preparation of reactive modifier and thermoplastic polyester;

[0069] The reactive modifier is prepared by reacting the polycarbodiimide with the flame-retardant prepolymer; the molar ratio of the flame-retardant prepolymer to the polycarbodiimide is 1:9; the reaction is carried out at a temperature of 160°C, a pressure of 50 Pa, and for a time of 3 h; the molecular chain of the prepared reactive modifier comprises a plurality of -N=C=N- segments and a plurality of -NR-CO-NH- segments, -R is a flame-retardant prepolymer segment, the lengths of the -R segments in different -NR-CO-NH- segments are not completely identical, and the positions of the -NR-CO-NH- segments are random; the infrared spectra of the flame-retardant prepolymer, the polycarbodiimide, and the reactive modifier in this embodiment are shown in Figure 3 The actual object of the reactive modifier is shown in Figure 4

[0070] The thermoplastic polyester is prepared by sequentially carrying out esterification and polycondensation reactions on the dibasic acid B and the third aliphatic diol; the molar ratio of the dibasic acid B to the third aliphatic diol is 1:1.2; the esterification reaction is carried out at a temperature of 250°C, a pressure of 0.4 MPa, and for a time of 150 min; the polycondensation reaction is carried out at a temperature of 280°C, a pressure of <100 Pa, and for a time of 120 min;

[0071] When the thermoplastic polyester is prepared, a catalyst is added at the feeding stage, and the addition amount of the catalyst is 0.03 wt% of the addition amount of the dibasic acid B;

[0072] (4) Preparation of the thermoplastic functional polyester fiber;

[0073] The reactive modifier and the thermoplastic polyester are melt blended, and then melt spinning is carried out; in the melt spinning, pre-oriented fibers are first prepared, and then the pre-oriented fibers are sequentially subjected to drawing, heat setting, and winding, thereby obtaining the thermoplastic functional polyester fiber; the mass ratio of the reactive modifier to the thermoplastic polyester is 1:9, and the melt blending is carried out at a temperature of 260°C; the process parameters of the melt spinning are as follows: drawing temperature 80°C, heat setting temperature 150°C, spinning speed 3600 m / min, length-diameter ratio of the spinneret hole 1:4, and side blowing temperature 25°C.

[0074] The prepared thermoplastic functional polyester fiber has a breaking strength of 3.5 cN / dtex, an elongation at break of 20%, a limiting oxygen index of 33%, and a vertical burning level of V-0 grade; and the limiting oxygen index of the fiber or the textile product made therefrom decreases by no more than 5% after 50 times of washing.

[0075] Example A2

[0076] A method for preparing a thermoplastic functional polyester fiber, and the specific steps are as follows:

[0077] (1) Preparation of materials;

[0078] Dibasic acid A: DDP; ​

[0079] First aliphatic diol: 1,3-propanediol;

[0080] Polymeric carbodiimide: poly(diisopropylcarbodiimide) with a number average molecular weight of 3000 g / mol and a carbodiimide group content of 12 wt%;

[0081] Dibasic acid B: terephthalic acid;

[0082] Third aliphatic diol: butanediol;

[0083] Catalyst: antimony trioxide;

[0084] (2) preparing a flame-retardant prepolymer;

[0085] The flame-retardant prepolymer is prepared by esterification and pre-polycondensation of dibasic acid A and the first aliphatic diol; the molar ratio of dibasic acid A to the first aliphatic diol is 1:1.05; the esterification is carried out at a temperature of 200°C, a pressure of 0.25 MPa and for 75 min; the pre-polycondensation is carried out at a temperature of 225°C, a pressure of 75 Pa and for 40 min;

[0086] (3) preparing a reactive modifier and a thermoplastic polyester;

[0087] The reactive modifier is prepared by reacting the polymeric carbodiimide with the flame-retardant prepolymer; the molar ratio of the flame-retardant prepolymer to the polymeric carbodiimide is 1:10; the reaction is carried out at a temperature of 145°C, a pressure of 75 Pa and for 2 h; the molecular chain of the prepared reactive modifier comprises multiple -N=C=N- segments and multiple -NR-CO-NH- segments, -R is a flame-retardant prepolymer segment, the length of the -R segment in different -NR-CO-NH- segments is not exactly the same, and the position of each -NR-CO-NH- segment is random;

[0088] The thermoplastic polyester is prepared by esterification and polycondensation of dibasic acid B and the third aliphatic diol; the molar ratio of dibasic acid B to the third aliphatic diol is 1:1.25; the esterification is carried out at a temperature of 200°C, a pressure of 0.25 MPa and for 120 min; the polycondensation is carried out at a temperature of 250°C, a pressure of <100 Pa and for 180 min;

[0089] During the preparation of the thermoplastic polyester, the catalyst is added at the feeding stage, and the addition amount of the catalyst is 0.035 wt% of the addition amount of dibasic acid B;

[0090] (4) preparing a thermoplastic functional polyester fiber;

[0091] The reactive modifier is melt-blended with the thermoplastic polyester, and then melt spinning is performed. In the melt spinning, a pre-oriented fiber is first prepared, and then the pre-oriented fiber is sequentially subjected to drawing, heat setting and winding, to obtain the thermoplastic functional polyester fiber. The mass ratio of the reactive modifier to the thermoplastic polyester is 1.25:8.75, and the temperature for melt blending is 240°C. The process parameters for melt spinning are as follows: drawing temperature 70°C, heat setting temperature 120°C, spinning speed 3000 m / min, length-diameter ratio of the spinneret hole 1:3, and side-blowing temperature 20°C.

[0092] The final thermoplastic functional polyester fiber has a breaking strength of 3.2 cN / dtex, an elongation at break of 25%, a limiting oxygen index of 31%, and a vertical burning rating of V-0 level. After 50 times of washing, the limiting oxygen index of the fiber or the textile made therefrom decreases by no more than 5%.

[0093] Example A3

[0094] A method for preparing a thermoplastic functional polyester fiber, and the specific steps are as follows:

[0095] (1) Preparation of materials;

[0096] Dibasic acid A: CEPPA;

[0097] First aliphatic diol: 1,5-pentanediol;

[0098] Polycarbodiimide: poly(diisopropylcarbodiimide) with a number average molecular weight of 8000 g / mol and a carbodiimide group content of 15 wt%;

[0099] Dibasic acid B: succinic acid;

[0100] Third aliphatic diol: butanediol;

[0101] Catalyst: ethylene glycol antimony;

[0102] (2) Preparation of a flame-retardant prepolymer;

[0103] The flame-retardant prepolymer is prepared from the dibasic acid A and the first aliphatic diol through esterification and pre-polycondensation. The molar ratio of the dibasic acid A to the first aliphatic diol is 1:1.1. The esterification is performed at a temperature of 180°C, a pressure of 0.1 MPa and for a time of 60 min. The pre-polycondensation is performed at a temperature of 200°C, a pressure of 50 Pa and for a time of 30 min.

[0104] (3) Preparation of a reactive modifier and a thermoplastic polyester;

[0105] The reactive modifier is prepared by reacting polycarbodiimide with a flame-retardant prepolymer; the molar ratio of the flame-retardant prepolymer to the polycarbodiimide is 1:12; the reaction is carried out at a temperature of 120°C, a pressure of 80 Pa, and for a time of 1.5 h; the molecular chain of the prepared reactive modifier comprises a plurality of -N=C=N- segments and a plurality of -NR-CO-NH- segments, -R is a flame-retardant prepolymer segment, the lengths of the -R segments in different -NR-CO-NH- segments are not completely identical, and the positions of the -NR-CO-NH- segments are random;

[0106] The thermoplastic polyester is prepared by sequentially performing esterification and polycondensation on the binary acid B and a third aliphatic diol; the molar ratio of the binary acid B to the third aliphatic diol is 1:1.2; the esterification is carried out at a temperature of 175°C, a pressure of -0.05 MPa, and for a time of 120 min; and the polycondensation is carried out at a temperature of 230°C, a pressure of <1000 Pa, and for a time of 150 min.

[0107] In the preparation of the thermoplastic polyester, a catalyst is added at the feeding stage, and the addition amount of the catalyst is 0.03 wt% of the addition amount of the binary acid B.

[0108] (4) preparing a thermoplastic functional polyester fiber;

[0109] The reactive modifier and the thermoplastic polyester are melt blended, and then melt spinning is performed; in the melt spinning, pre-oriented fibers are first prepared, and then the pre-oriented fibers are sequentially subjected to drawing, heat setting, and winding, thereby obtaining the thermoplastic functional polyester fiber; the mass ratio of the reactive modifier to the thermoplastic polyester is 1.5:8.5, and the melt blending is carried out at a temperature of 140°C; the process parameters of the melt spinning are as follows: a drawing temperature of 65°C, a heat setting temperature of 80°C, a spinning speed of 2400 m / min, a length-diameter ratio of the spinning hole of 1:2, and a side blowing temperature of 15°C.

[0110] The thermoplastic functional polyester fiber prepared finally has a breaking strength of 3 cN / dtex, an elongation at break of 30%, a limiting oxygen index of 30%, and a vertical combustion rating of V-0 level; and the limiting oxygen index of the fiber or a textile product made therefrom decreases by no more than 5% after 50 times of washing.

[0111] Example B1

[0112] A method for preparing a thermoplastic functional polyester fiber, and the specific steps are as follows:

[0113] (1) preparation of materials;

[0114] isophthalic acid-5-sodium sulfonate;

[0115] the second aliphatic diol is ethylene glycol;

[0116] Polymeric carbodiimide: poly(4,4'-diphenylmethane carbodiimide) with a number average molecular weight of 1000 g / mol and a carbodiimide group content of 10 wt%;

[0117] Dibasic acid: terephthalic acid;

[0118] Third aliphatic diol: ethylene glycol;

[0119] Catalyst: antimony ethylene glycol;

[0120] (2) preparing a cationic dyeable prepolymer;

[0121] The cationic dyeable prepolymer is prepared from sodium 5-sulfoisophthalic acid and the second aliphatic diol through esterification and pre-polycondensation in sequence; the molar ratio of sodium 5-sulfoisophthalic acid to the second aliphatic diol is 1:1; the esterification is carried out at a temperature of 230°C, a pressure of 0.4 MPa and for 90 min; the pre-polycondensation is carried out at a temperature of 250°C, a pressure of 80 Pa and for 45 min;

[0122] (3) preparing a reactive modifier and a thermoplastic polyester;

[0123] The reactive modifier is prepared from the polymeric carbodiimide and the cationic dyeable prepolymer; the molar ratio of the cationic dyeable prepolymer to the polymeric carbodiimide is 1:9; the reaction is carried out at a temperature of 160°C, a pressure of 50 Pa and for 3 h; the molecular chain of the prepared reactive modifier comprises multiple -N=C=N- segments and multiple -NR-CO-NH- segments, -R is a cationic dyeable prepolymer segment, the length of the -R segment in different -NR-CO-NH- segments is not completely the same, and the positions of the -NR-CO-NH- segments are random;

[0124] The thermoplastic polyester is prepared from the dibasic acid and the third aliphatic diol through esterification and polycondensation in sequence; the molar ratio of the dibasic acid to the third aliphatic diol is 1:1.2; the esterification is carried out at a temperature of 250°C, a pressure of 0.4 MPa and for 150 min; the polycondensation is carried out at a temperature of 280°C, a pressure of <100 Pa and for 120 min;

[0125] In the preparation of the thermoplastic polyester, the catalyst is added at the feeding stage, and the addition amount of the catalyst is 0.03 wt% of the addition amount of the dibasic acid;

[0126] (4) preparing a thermoplastic functional polyester fiber;

[0127] The reactive modifier is melt-blended with the thermoplastic polyester, and then melt spinning is performed, in which a pre-oriented fiber is prepared first, and then the pre-oriented fiber is sequentially subjected to drawing, heat setting and winding, to obtain the thermoplastic functional polyester fiber; wherein the mass ratio of the reactive modifier to the thermoplastic polyester is 0.25:9.75, and the temperature for melt blending is 260°C; the process parameters for melt spinning are as follows: drawing temperature 80°C, heat setting temperature 150°C, spinning speed 3600m / min, length-diameter ratio of the spinneret hole 1:4, and side-blowing temperature 25°C.

[0128] The breaking strength of the finally prepared thermoplastic functional polyester fiber is 3.8cN / dtex, and the breaking elongation is 20%; after the fabric prepared from the thermoplastic functional polyester fiber is dyed with cationic dyes, the dyeing rate is 96%, and the color fastness level is 4.5.

[0129] Example B2

[0130] A preparation method of a thermoplastic functional polyester fiber, and the specific steps are as follows:

[0131] (1) Preparation of materials;

[0132] Sodium 5-sulfoisophthalate;

[0133] Second aliphatic diol: 1,3-propanediol;

[0134] Polycarbodiimide: poly(diisopropylcarbodiimide) with a number average molecular weight of 3000g / mol and a carbodiimide group content of 12wt%;

[0135] Dibasic acid: terephthalic acid;

[0136] Third aliphatic diol: butanediol;

[0137] Catalyst: ethylene glycol antimony;

[0138] (2) Preparation of cationic dyeable prepolymer;

[0139] The cationic dyeable prepolymer is prepared from sodium 5-sulfoisophthalate and the second aliphatic diol through esterification reaction and pre-polycondensation reaction in sequence; wherein the molar ratio of sodium 5-sulfoisophthalate to the second aliphatic diol is 1:1.05; the temperature for esterification reaction is 210°C, the pressure is 0.25MPa, and the time is 70min; the temperature for pre-polycondensation reaction is 230°C, the pressure is 65Pa, and the time is 40min;

[0140] (3) Preparation of reactive modifier and thermoplastic polyester;

[0141] The reactive modifier is prepared by reacting polycarbodiimide with cationic dyeable prepolymer; the molar ratio of the cationic dyeable prepolymer to the polycarbodiimide is 1:10; the reaction is carried out at a temperature of 140°C, a pressure of 70 Pa and for 2 h; the molecular chain of the prepared reactive modifier comprises multiple -N=C=N- segments and multiple -NR-CO-NH- segments, -R is a cationic dyeable prepolymer segment, the lengths of the -R segments in different -NR-CO-NH- segments are not completely the same, and the positions of the -NR-CO-NH- segments are random;

[0142] The thermoplastic polyester is prepared by sequentially performing esterification and polycondensation on a dibasic acid and a third aliphatic diol; the molar ratio of the dibasic acid to the third aliphatic diol is 1:1.25; the esterification is carried out at a temperature of 200°C, a pressure of 0.25 MPa and for 120 min; the polycondensation is carried out at a temperature of 250°C, a pressure of <100 Pa and for 180 min;

[0143] In the preparation of the thermoplastic polyester, a catalyst is added at the feeding stage, and the addition amount of the catalyst is 0.03 wt% of the addition amount of the dibasic acid;

[0144] (4) preparing a thermoplastic functional polyester fiber;

[0145] The reactive modifier and the thermoplastic polyester are melt blended, and then melt spinning is performed; in the melt spinning, pre-oriented fibers are first prepared, and then the pre-oriented fibers are sequentially subjected to drawing, heat setting and winding, thereby obtaining the thermoplastic functional polyester fiber; the mass ratio of the reactive modifier to the thermoplastic polyester is 0.35:9.65, and the melt blending is carried out at a temperature of 240°C; the process parameters of the melt spinning are as follows: a drawing temperature of 70°C, a heat setting temperature of 120°C, a spinning speed of 3000 m / min, a length-diameter ratio of the spinning hole of 1:3 and a side blowing temperature of 20°C.

[0146] The thermoplastic functional polyester fiber finally prepared has a breaking strength of 3.6 cN / dtex and an elongation at break of 26%; after a fabric prepared from the thermoplastic functional polyester fiber is dyed with a cationic dye, the fabric has a dyeing rate of 97% and a color fastness grade of 4.5.

[0147] Example B3

[0148] A method for preparing a thermoplastic functional polyester fiber, and the specific steps are as follows:

[0149] (1) preparation of materials;

[0150] sodium 5-sulfoisophthalate;

[0151] the second aliphatic diol is 1,5-pentanediol;

[0152] Polymeric carbodiimide: poly(diisopropyl carbodiimide) with a number average molecular weight of 8000 g / mol and a carbodiimide group content of 15 wt%;

[0153] Dibasic acid: succinic acid;

[0154] Third aliphatic diol: butanediol;

[0155] Catalyst: ethylene glycol antimony;

[0156] (2) preparing a cationic dyeable prepolymer;

[0157] The cationic dyeable prepolymer is prepared by esterification reaction and pre-polycondensation reaction of sodium 5-sulfoisophthalic acid and the second aliphatic diol in sequence; wherein the molar ratio of sodium 5-sulfoisophthalic acid to the second aliphatic diol is 1:1.1; the temperature of the esterification reaction is 190°C, the pressure is 0.1 MPa, and the time is 60 min; the temperature of the pre-polycondensation reaction is 210°C, the pressure is 50 Pa, and the time is 30 min;

[0158] (3) preparing a reactive modifier and a thermoplastic polyester;

[0159] The reactive modifier is prepared by reaction of the polymeric carbodiimide and the cationic dyeable prepolymer; wherein the molar ratio of the cationic dyeable prepolymer to the polymeric carbodiimide is 1:12; the temperature of the reaction is 120°C, the pressure is 80 Pa, and the time is 1.5 h; the molecular chain of the prepared reactive modifier comprises multiple -N=C=N- segments and multiple -NR-CO-NH- segments, -R is a cationic dyeable prepolymer segment, the length of the -R segment in different -NR-CO-NH- segments is not completely the same, and the positions of each -NR-CO-NH- segment are random;

[0160] The thermoplastic polyester is prepared by esterification reaction and polycondensation reaction of the dibasic acid and the third aliphatic diol in sequence; wherein the molar ratio of the dibasic acid to the third aliphatic diol is 1:1.2; the temperature of the esterification reaction is 175°C, the pressure is -0.05 MPa, and the time is 120 min; the temperature of the polycondensation reaction is 230°C, the pressure is <1000 Pa, and the time is 150 min;

[0161] In the preparation of the thermoplastic polyester, the catalyst is added at the feeding stage, and the addition amount of the catalyst is 0.035 wt% of the addition amount of the dibasic acid;

[0162] (4) preparing a thermoplastic functional polyester fiber;

[0163] The reactive modifier is melt-blended with the thermoplastic polyester, and then melt spinning is performed. In the melt spinning, a pre-oriented fiber is first prepared, and then the pre-oriented fiber is sequentially subjected to drawing, heat setting and winding, to obtain the thermoplastic functional polyester fiber. The mass ratio of the reactive modifier to the thermoplastic polyester is 0.5:9.5, and the temperature for melt blending is 140°C. The process parameters for melt spinning are as follows: drawing temperature 65°C, heat setting temperature 80°C, spinning speed 2400 m / min, length-diameter ratio of the spinning hole 1:2, and side-blowing temperature 15°C.

[0164] The breaking strength of the finally prepared thermoplastic functional polyester fiber is 3.3 cN / dtex, and the breaking elongation is 30%. After the fabric prepared from the thermoplastic functional polyester fiber is dyed with cationic dyes, the dyeing rate is 98%, and the color fastness grade is 4.5.

[0165] Example C1

[0166] A method for preparing a thermoplastic functional polyester fiber, and the specific steps are as follows:

[0167] (1) Preparation of part of materials;

[0168] Polymeric carbodiimide: poly(4,4'-diphenylmethane carbodiimide) with a number average molecular weight of 1000 g / mol and a carbodiimide group content of 10 wt%;

[0169] Dibasic acid: terephthalic acid;

[0170] Third aliphatic diol: ethylene glycol;

[0171] Catalyst: ethylene glycol antimony;

[0172] (2) Preparation of flame-retardant prepolymer and cationic dyeable prepolymer;

[0173] The preparation process of the flame-retardant prepolymer is the same as that in Example A1, and the preparation process of the cationic dyeable prepolymer is the same as that in Example B1;

[0174] (3) Preparation of reactive modifier and thermoplastic polyester;

[0175] The reactive modifier is prepared by reacting polycarbodiimide with a mixture of flame-retardant prepolymer and cationic dyeable prepolymer; wherein, the mass ratio of flame-retardant prepolymer to cationic dyeable prepolymer is 9:1, and the ratio of the total molar amount of flame-retardant prepolymer and cationic dyeable prepolymer to the molar amount of polycarbodiimide is 1:9; the reaction temperature is 160°C, the pressure is 50Pa, and the time is 3h; the molecular chain of the prepared reactive modifier includes multiple -N=C=N- segments and multiple -NR-CO-NH- segments, and -R is a cationic dyeable prepolymer segment or a flame-retardant prepolymer segment. The length of the -R segment in different -NR-CO-NH- segments is not exactly the same, and the position of each -NR-CO-NH- segment is random.

[0176] Thermoplastic polyester is prepared by sequentially esterification and polycondensation of a diacid and a third aliphatic diol; wherein the molar ratio of the diacid to the third aliphatic diol is 1:1.2; the esterification reaction is carried out at a temperature of 250°C, a pressure of 0.4 MPa, and a time of 150 min; the polycondensation reaction is carried out at a temperature of 280°C, a pressure of <100 Pa, and a time of 120 min.

[0177] When preparing thermoplastic polyester, a catalyst is added during the feeding stage, and the amount of catalyst added is 0.035 wt% of the amount of diacid added.

[0178] (4) Preparation of thermoplastic functional polyester fibers;

[0179] The reactive modifier is melt-blended with thermoplastic polyester and then melt-spun. During melt spinning, pre-oriented fibers are first prepared, and then the pre-oriented fibers are sequentially drawn, heat-set, and wound to obtain thermoplastic functional polyester fibers. The mass ratio of reactive modifier to thermoplastic polyester is 1:9, and the melt blending temperature is 260°C. The melt spinning process parameters are: drawing temperature 80°C, heat setting temperature 150°C, spinning speed 3600m / min, spinneret length-to-diameter ratio 1:4, and side blowing temperature 25°C.

[0180] The final thermoplastic functional polyester fiber has a breaking strength of 3.6 cN / dtex, a breaking elongation of 20%, a limiting oxygen index of 33%, a vertical flammability rating of V-0, and a limiting oxygen index decrease of no more than 5% after 50 washes. When fabrics made from thermoplastic functional polyester fiber are dyed with cationic dyes, the dyeing rate is 98% and the color fastness grade is 4.5.

[0181] The melt flow comparison curves and crystallization comparison curves of the final products and PET of Examples A1, B1, B2 and C1 are shown below. Figure 1 and Figure 2 As shown, from Figure 1 andFigure 2 As can be seen, the crystallization peak temperature of the final product of each embodiment is higher than that of PET, and the melting peak temperature is lower than that of PET, which indicates that the reactive modifier is grafted with the end groups of the polyester molecular chain to form a branched structure, thereby changing the crystallization and melting behavior of the polyester.

[0182] Example C2

[0183] A method for preparing a thermoplastic functional polyester fiber, the specific steps are as follows:

[0184] (1) Preparation of part of the materials;

[0185] Polycarbodiimide: poly(diisopropylcarbodiimide), number average molecular weight 3000 g / mol, carbodiimide group content 12 wt%;

[0186] Dibasic acid: terephthalic acid;

[0187] Third aliphatic diol: butanediol;

[0188] Catalyst: antimony trioxide;

[0189] (2) Preparation of flame-retardant prepolymer and cationic dyeable prepolymer;

[0190] The preparation process of the flame-retardant prepolymer is the same as that of Example A2, and the preparation process of the cationic dyeable prepolymer is the same as that of Example B2;

[0191] (3) Preparation of reactive modifier and thermoplastic polyester;

[0192] The reactive modifier is prepared by reacting polycarbodiimide with a mixture of flame-retardant prepolymer and cationic dyeable prepolymer; wherein the mass ratio of flame-retardant prepolymer to cationic dyeable prepolymer is 9.25:0.75, and the ratio of the total molar mass of flame-retardant prepolymer and cationic dyeable prepolymer to the molar mass of polycarbodiimide is 1:10; the reaction temperature is 140°C, the pressure is 70 Pa, and the time is 2 h; the molecular chain of the prepared reactive modifier includes multiple -N=C=N- segments and multiple -NR-CO-NH- segments, -R is a cationic dyeable prepolymer segment or a flame-retardant prepolymer segment, the lengths of -R segments in different -NR-CO-NH- segments are not completely the same, and the positions of each -NR-CO-NH- segment are random;

[0193] The thermoplastic polyester is prepared by esterification and polycondensation of dibasic acid and third aliphatic diol; wherein the molar ratio of dibasic acid to third aliphatic diol is 1:1.25; the esterification temperature is 200°C, the pressure is 0.25 MPa, and the time is 120 min; the polycondensation temperature is 250°C, the pressure is <100 Pa, and the time is 180 min;

[0194] The catalyst is added in the feeding stage in the preparation of the thermoplastic polyester, and the amount of the catalyst added is 0.03wt% of the amount of the dibasic acid added;

[0195] (4) preparing the thermoplastic functional polyester fiber;

[0196] The reactive modifier is melt-blended with the thermoplastic polyester, and then melt spinning is performed, and in the melt spinning, pre-oriented fibers are prepared first, and then the pre-oriented fibers are sequentially drawn, heat set and wound, to obtain the thermoplastic functional polyester fiber; wherein the mass ratio of the reactive modifier to the thermoplastic polyester is 1.25:8.75, and the temperature for melt blending is 240°C; the process parameters for melt spinning are: drawing temperature 70°C, heat setting temperature 120°C, spinning speed 3000m / min, length-diameter ratio of the spinneret hole 1:3, and side blowing temperature 20°C.

[0197] The breaking strength of the finally prepared thermoplastic functional polyester fiber is 3.3cN / dtex, the breaking elongation is 25%, the limiting oxygen index of the fiber is 31%, the vertical combustion level reaches V-0 level, and the limiting oxygen index of the fiber or the textile made therefrom decreases by no more than 5% after 50 times of washing; after the fabric made of the thermoplastic functional polyester fiber is dyed with cationic dyes, the dyeing rate is 96%, and the color fastness level is 4.5.

[0198] Example C3

[0199] A method for preparing a thermoplastic functional polyester fiber, and the specific steps are as follows:

[0200] (1) preparation of part of materials;

[0201] Polycarbodiimide: poly(diisopropylcarbodiimide) with a number average molecular weight of 8000g / mol and a carbodiimide group content of 15wt%;

[0202] Dibasic acid: succinic acid;

[0203] Third aliphatic diol: butanediol;

[0204] Catalyst: ethylene glycol antimony;

[0205] (2) preparation of flame-retardant prepolymer and cationic dyeable prepolymer;

[0206] The preparation process of the flame-retardant prepolymer is the same as that in Example A3, and the preparation process of the cationic dyeable prepolymer is the same as that in Example B3;

[0207] (3) preparation of reactive modifier and thermoplastic polyester;

[0208] The reactive modifier is prepared by reacting polycarbodiimide with a mixture of flame-retardant prepolymer and cationic dyeable prepolymer; the mass ratio of the flame-retardant prepolymer to the cationic dyeable prepolymer is 9.5:0.5, and the ratio of the total molar quantity of the flame-retardant prepolymer and the cationic dyeable prepolymer to the molar quantity of the polycarbodiimide is 1:12; the reaction is carried out at a temperature of 120°C, a pressure of 80Pa and for 1.5h; the molecular chain of the prepared reactive modifier comprises multiple -N=C=N- segments and multiple -NR-CO-NH- segments, -R is a cationic dyeable prepolymer segment or a flame-retardant prepolymer segment, the lengths of the -R segments in different -NR-CO-NH- segments are not completely the same, and the positions of the -NR-CO-NH- segments are random;

[0209] The thermoplastic polyester is prepared by esterification and polycondensation of diacid and third aliphatic diol; the molar ratio of the diacid to the third aliphatic diol is 1:1.2; the esterification is carried out at a temperature of 175°C, a pressure of -0.05MPa and for 120min; the polycondensation is carried out at a temperature of 230°C, a pressure of <1000Pa and for 150min;

[0210] In the preparation of the thermoplastic polyester, a catalyst is added at the feeding stage, and the addition amount of the catalyst is 0.03wt% of the addition amount of the diacid;

[0211] (4) preparing the thermoplastic functional polyester fiber;

[0212] The reactive modifier is melt-blended with the thermoplastic polyester, and then melt spinning is carried out; in the melt spinning, pre-oriented fibers are prepared first, and then the pre-oriented fibers are subjected to drawing, heat setting and winding in sequence, thereby obtaining the thermoplastic functional polyester fiber; the mass ratio of the reactive modifier to the thermoplastic polyester is 1.5:8.5, and the melt blending is carried out at a temperature of 140°C; the process parameters of the melt spinning are as follows: drawing temperature 65°C, heat setting temperature 80°C, spinning speed 2400m / min, length-diameter ratio of the spinning hole 1:2, and side blowing temperature 15°C.

[0213] The finally prepared thermoplastic functional polyester fiber has a breaking strength of 3.1cN / dtex, an elongation at break of 30%, a limiting oxygen index of 30%, and a vertical burning level of V-0 grade; after 50 times of washing, the limiting oxygen index of the fiber or the textile made therefrom decreases by not more than 5%; after dyeing the fabric made of the thermoplastic functional polyester fiber with cationic dye, the dyeing rate is 95%, and the color fastness level is 4.5 grade.

Claims

1. A method for preparing thermoplastic functional polyester fiber, characterized in that, Thermoplastic functional polyester fibers are obtained by melt-blending reactive modifiers with thermoplastic polyester and then melt-spinning them. The reactive modifier is prepared by reacting polycarbodiimide with a functional prepolymer; The functional prepolymer is a flame-retardant prepolymer, or a cationic dyeable prepolymer, or a mixture of a flame-retardant prepolymer and a cationic dyeable prepolymer; The flame-retardant prepolymer is prepared by sequentially esterification and pre-condensation reaction of a diacid containing flame-retardant structural units and a first aliphatic diol; the molar ratio of the diacid containing flame-retardant structural units to the first aliphatic diol is 1:1-1.1; the diacid containing flame-retardant structural units is one or more of DDP and CEPPA. The cationic dyeable prepolymer is prepared by sequentially esterification and pre-condensation reaction of sodium isophthalate-5-sulfonate and a second aliphatic diol; the molar ratio of sodium isophthalate-5-sulfonate to the second aliphatic diol is 1:1-1.

1. When preparing reactive modifiers, the molar ratio of functional prepolymer to polycarbodiimide is 1:9-12, the reaction temperature is 120-160°C, the pressure is 50-80Pa, and the time is 1.5-3h. During melt blending, the unsaturated double bonds in the reactive modifier react with the terminal carboxyl groups of the thermoplastic polyester.

2. The method for preparing a thermoplastic functional polyester fiber according to claim 1, characterized in that, The polycarbodiimide is one or more of aliphatic and aromatic polycarbodiimides, with a number-average molecular weight of 1000-8000 g / mol and a carbodiimide group content of 10-15 wt%.

3. The method for preparing a thermoplastic functional polyester fiber according to claim 1, characterized in that, The first aliphatic diol is one or more of ethylene glycol, 1,3-propanediol, and 1,5-pentanediol.

4. The method for preparing a thermoplastic functional polyester fiber according to claim 3, characterized in that, When preparing flame-retardant prepolymers, the esterification reaction temperature is 180-220°C, the pressure is 0.1-0.4MPa, and the time is 60-90min; the precondensation reaction temperature is 200-240°C, the pressure is 50-80Pa, and the time is 30-45min.

5. The method for preparing a thermoplastic functional polyester fiber according to claim 1, characterized in that, The second aliphatic diol is one or more of ethylene glycol, 1,3-propanediol, and 1,5-pentanediol.

6. The method for preparing a thermoplastic functional polyester fiber according to claim 5, characterized in that, When preparing cationic dyeable prepolymers, the esterification reaction is carried out at a temperature of 190-230°C, a pressure of 0.1-0.4 MPa, and a time of 60-90 min; the precondensation reaction is carried out at a temperature of 210-250°C, a pressure of 50-80 Pa, and a time of 30-45 min.

7. The method for preparing a thermoplastic functional polyester fiber according to claim 1, characterized in that, When the functional prepolymer is a flame-retardant prepolymer, the breaking strength of the thermoplastic functional polyester fiber is ≥3.0 cN / dtex, the breaking elongation is 20%-30%, the limiting oxygen index of the fiber is ≥30.0%, the vertical flammability rating reaches V-0, and the limiting oxygen index of the fiber or textiles made from it decreases by no more than 5% after 50 washes. When the functional prepolymer is a cationic dyeable prepolymer, the breaking strength of the thermoplastic functional polyester fiber is ≥3.3cN / dtex, the breaking elongation is 20%-30%, and the dyeing rate of the fabric made of the thermoplastic functional polyester fiber is ≥96% and the color fastness grade is ≥4.5 after dyeing with cationic dyes. When the functional prepolymer is a mixture of flame-retardant prepolymer and cationic dyeable prepolymer, the mass ratio of flame-retardant prepolymer to cationic dyeable prepolymer is 9-9.5:1-0.

5. The breaking strength of the thermoplastic functional polyester fiber is ≥3.1cN / dtex, the breaking elongation is 20%-30%, the limiting oxygen index of the fiber is ≥30.0%, the vertical flammability rating reaches V-0, and the limiting oxygen index of the fiber or textiles made from it decreases by no more than 5% after 50 washes. When the fabric made from the thermoplastic functional polyester fiber is dyed with cationic dye, the dyeing rate is ≥95% and the color fastness grade is ≥4.

5.

8. The method for preparing a thermoplastic functional polyester fiber according to claim 1, characterized in that, The thermoplastic polyester is prepared by sequentially esterification and polycondensation of a diacid and a third aliphatic diol; the diacid is one or more of terephthalic acid, isophthalic acid, succinic acid, glutaric acid, adipic acid, heptanoic acid, octanoic acid, azelaic acid, and sebacic acid; the third aliphatic diol is one or more of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, and decanediol.

9. The method for preparing a thermoplastic functional polyester fiber according to claim 8, characterized in that, The mass ratio of reactive modifier to thermoplastic polyester is 0.25-1.5:8.5-9.75, and the melt blending temperature is 140-260°C. During melt spinning, pre-oriented fibers are first prepared, and then the pre-oriented fibers are sequentially stretched, heat-set, and wound to obtain thermoplastic functional polyester fibers.

10. The method for preparing a thermoplastic functional polyester fiber according to claim 9, characterized in that, The process parameters for melt spinning include: drawing temperature 65-80℃, heat setting temperature 80-150℃, spinning speed 2400-3600m / min, spinneret length-to-diameter ratio 1:2-4, and side blowing temperature 15-25℃.

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