Fluffy soft polyester fiber and preparation method thereof

Abstract

The invention belongs to the field of functional fiber materials. The invention relates to a fluffy and soft polyester fiber and a preparation method thereof. The fluffy and soft polyester fiber is prepared from the following raw materials in parts by weight: 100 parts of PET (Polyethylene Terephthalate) slices, 5.0-10.0 parts of a functional aid, 0.2-1.0 part of an antioxidant, 0.2-0.5 part of a lubricant and 0.35-2.0 parts of a fiber treating agent, the preparation method comprises the following steps: drying the raw materials, and mixing; performing melt extrusion and pressurization; performing spinning; post-processing is conducted; curling, loosening and shaping; and cutting off the tows, and packaging. The fluffy and soft polyester fiber effectively solves the problems that polyester fibers in the prior art are hard and prone to pilling, and meanwhile the fluffy and soft polyester fiber has excellent antibacterial and antistatic properties.

Description

Technical Field

[0001] The invention relates to a fluffy and soft polyester fiber and a preparation method thereof. The invention belongs to the field of functional fiber materials. Background Art

[0002] Polyester (polyethylene terephthalate, PET) fiber has excellent comprehensive properties, such as good strength, good elasticity, not easy to deform, corrosion resistance, insulation, smooth and crisp, easy to wash and dry, etc. Its application areas include clothing fabrics, home textiles, sporting goods, industrial textiles, etc. It is currently the synthetic fiber with the largest production output and the widest application range. Polyester fiber fabrics have excellent wrinkle resistance, drape and dimensional stability, but have many shortcomings such as poor moisture absorption, poor air permeability, difficulty in dyeing, easy to generate static electricity, easy to pilling, and poor hardness.

[0003] When fabrics are subjected to external friction, the fiber ends are easily pulled out of the fabric to form fluff. The fluff is tangled into small balls during repeated extension and retraction. If the small balls are not easily broken and fall off, they will further tangle to form larger balls. Polyester fabrics are prone to pilling after being rubbed, which seriously affects the appearance of the fabric and hinders the application of polyester fibers in high-end fabrics. At the same time, static electricity generated by friction is also a concern for people in wearing experience. With the improvement of consumption level, people prefer new products that are comfortable, beautiful and functional, which puts forward an urgent demand for the anti-pilling problem of polyester fiber products.

[0004] At present, the main methods to reduce pilling of polyester fabrics are: (1) coating the surface of the fabric with a modified finishing agent as a protective layer when the surface of the fabric is rubbed, adhering the fiber ends to the fiber body, and reducing the slippage between fibers. However, after repeated washing, the surface coating fails and the anti-pilling ability decreases; at the same time, the softness and comfort are lost. (2) Although the fabric's pilling resistance can be improved by blending natural fibers with polyester fibers, it still cannot meet the requirements of high-end fabrics. (3) By adding a modifier to reduce the breaking strength and elongation at the same time, the pilling can be quickly removed, thereby achieving the anti-pilling effect. However, reducing the breaking strength and elongation at the same time will inevitably deteriorate the material performance, and the same hard texture and other problems will cause poor physical feel. Summary of the invention

[0005] The purpose of the present invention is to provide a fluffy and soft polyester fiber and a preparation method thereof in view of the problem that polyester fiber is hard and easy to pill in the prior art. The functional additives made by molecular design are added to PET slices through formula design, and melt extrusion, spinning, pulling, shaping and other processes are carried out to prepare the fiber. While solving the problem, the fiber has excellent antibacterial and antistatic properties. The technical solution adopted by the present invention to solve the technical problem is: The present invention provides a fluffy and soft polyester fiber, comprising the following raw materials in parts by weight: PET slices 100 pieces; Functional additives 5.0-10.0 parts; Antioxidant 0.2-1.0 part; Lubricant 0.2-0.5 parts; Fiber treatment agent 0.35-2.0 parts; The functional additive and its preparation method include the following steps: S11, performing a silylation coupling reaction on nano-titanium and an epoxy silane coupling agent to obtain an intermediate product I; The dosage ratio of the nano titanium to the epoxy silane coupling agent is 1g:0.1-0.5g; S12, subjecting the intermediate product I to a ring-opening reaction with a dibasic acid A to obtain an intermediate product II; The intermediate product I and the dibasic acid A are added in a molar ratio of epoxy group to carboxyl group of 1:2; S13, subjecting the dibasic acid B and the diol to a condensation polymerization reaction under the action of a catalyst to obtain an intermediate product III; The molar ratio of the dibasic acid B to the diol is 1:1.

[0006] S14, adding the intermediate product II to the intermediate product III for esterification reaction to obtain the target product, i.e., the functional additive; The intermediate product II and the intermediate product III are added in a molar ratio of carboxyl to hydroxyl of 1:1.

[0007] Furthermore, the dibasic acid A is a fatty acid containing a side group.

[0008] Further, The dibasic acid B is a fatty acid containing a side group and an aromatic acid containing a side group, which are added in a molar ratio of 0.3-0.5:0.5-0.7; as well as The diols are small molecular diols containing side groups, polyether diols, and polyester diols, which are added in a molar ratio of 0.5-0.7: 0.2-0.4: 0-0.2.

[0009] Furthermore, the side group is methyl, ethyl or butyl.

[0010] Furthermore, the average polymerization degree of the intermediate product III is 20-28.

[0011] Furthermore, the intrinsic viscosity of the PET chips ranges from 0.65 to 0.90 dL / g, and the melting point is 245 to 255°C.

[0012] Furthermore, the fiber treating agent is sodium phosphate.

[0013] Another object of the present invention is to provide a method for preparing fluffy and soft polyester fibers, comprising the following steps: S21: drying and mixing of raw materials; S22: melt extrusion, pressurization; S23: spinning to obtain nascent fibers; S24: post-processing, i.e., drawing and heat setting; S25: Curly, loose styling; S26: The tow is cut and packaged to obtain fluffy and soft polyester fibers.

[0014] Further, For the melt extrusion, the temperature of each zone of the twin-screw extruder is: 250-260°C in zone 1, 260-270°C in zone 2, 270-275°C in zone 3, 275-280°C in zone 4, and 275-280°C in zone 5; In the post-processing process, the traction stretching ratio is 3.0-5.0; and The relaxation setting temperature is 115-120°C.

[0015] Beneficial effects of the present invention: (1) The present invention provides a fluffy and soft polyester fiber, which is added with a self-made functional additive. The fiber is a hyperbranched structure with nano-titanium as the nucleation center and a polyester structure embedded therein, wherein the polyester structure contains multiple side-group structural units and a polyether structure. First, the functional additive is a hyperbranched structure, which has a lower molecular weight and a higher degree of branching than the chemical structure of the PET structure, and can effectively reduce the glass transition temperature of the polyester fiber and improve the softness of the fiber; and the presence of multiple side-group structural units is similar to block copolymerization, which can increase the friction between the fibers, reduce the probability of pilling, and improve the pilling resistance; second, the polyester-type hyperbranched structure has excellent compatibility with the main PET and has a good dispersion effect; at the same time, it can destroy the regularity of the PET structure and reduce the crystallinity of the fiber, thereby appropriately reducing the tensile strength of the fiber, accelerating the shedding of pills, and further improving the pilling resistance; third, the polyester structure contains multiple side-group structural units and a polyether structure, It has excellent flexibility and can form a high curl after heat treatment to provide fluffiness; fourth, the polyether structure and other heteroatoms containing lone pair electrons in the polyester structure and nano-titanium can form an electron pathway, which can efficiently transfer electrons and has antistatic properties; fifth, the nano-titanium structure is photocatalytic and can form active oxygen species under light, which can destroy the cell walls of bacteria and has excellent broad-spectrum antibacterial effects; sixth, during the melt extrusion process, the PET polyester structure is accompanied by esterification polymerization and depolymerization. The end of the functional additive is a carboxyl structure, which can react and bond to the PET structure, which can slow down the degradation of the material and improve the processability; at the same time, it has long-term internal toughening, anti-pilling, anti-static and other functions.

[0016] (2) The present invention provides a fluffy and soft polyester fiber, which is added with a sodium phosphate fiber treatment agent by a direct addition method. First, the sodium phosphate itself has a high whiteness; second, the sodium phosphate can effectively remove the acid generated during the processing of the fiber material, prevent the further decomposition of the material, and has durability. DETAILED DESCRIPTION

[0017] The present invention is described in detail below with reference to the examples. However, it should be understood that the following examples are only illustrative of the embodiments of the present invention, and are not intended to limit the scope of the present invention.

[0018] The purpose of the present invention is to develop a fluffy and soft polyester fiber to solve the problem that polyester fiber is hard and easy to pilling. The design idea is: to improve the fluffiness and softness of polyester fiber to solve the problem of hardness, and at the same time, block copolymerization and appropriately reduce the breaking strength of the fiber to accelerate the falling of the pilling to improve the anti-pilling property. Considering the crystallinity of PET, a flexible auxiliary agent that can reduce the crystallinity is made by itself. Appropriately reducing the crystallinity of PET can solve the above problems to a certain extent. Concept scheme: Considering the chemical structure of PET, the auxiliary agent is a flexible structure, and a hyperbranched structure containing a flexible polyester chain can be made by itself, which can effectively curl into a fluffy shape during the spinning heat relaxation setting process, and the hyperbranched structure can effectively destroy the crystallinity of the matrix and reduce the breaking strength. At the same time, considering that nano-titanium has photocatalytic antibacterial properties and the conductive properties of nano-titanium, combined with the polyether diol structure, the problem of antibacterial and antistatic can also be solved. The flexible polyester chain in the above is flexible in design, and a multi-side group structure and an asymmetric dibasic aromatic acid can be used for molecular structure design to achieve the block copolymerization effect. The theoretical basis for the realization is: first, epoxy silane coupling reaction is carried out with nano-titanium; then the dibasic acid is subjected to ring-opening reaction to form a carboxyl-terminated structure; then the dibasic acid diol is subjected to esterification reaction to prepare a hyperbranched structure. Finally, after formula design, the above-mentioned self-made ingredients are added to the various raw material components for blending and extrusion; while taking the spinning process into consideration, a fluffy and soft polyester fiber with effectively improved properties is obtained, and the various components work synergistically with each other to effectively improve the mechanical properties, etc. The embodiments of the present invention are as follows: The embodiment of the present invention provides a fluffy and soft polyester fiber, comprising the following raw materials in parts by weight: PET slices 100 pieces; Functional additives 5.0-10.0 parts; Antioxidant 0.2-1.0 part; Lubricant 0.2-0.5 parts; Fiber treatment agent 0.35-2.0 parts; The functional additive and its preparation method include the following steps: S11, adding nano titanium and deionized water A to anhydrous ethanol, after ultrasonic dispersion for 1 hour, adding glacial acetic acid to adjust the pH value to 3.5-5.5, adding epoxy silane coupling agent, stirring and ultrasonicating for 0.5 hour, heating to 60-80°C and reflux for 2-4 hours; after the reaction is completed, filtering, taking the insoluble matter, rinsing with deionized water B, vacuum drying at 40°C to constant weight, grinding, and obtaining intermediate product I.

[0019] The dosage ratio of the nano titanium, deionized water A, anhydrous ethanol, epoxy silane coupling agent, and deionized water B is 1g: 2g: 18g: 0.1-0.5g: 30g; The average particle size of the nano titanium is 10-20 nm. The epoxy silane coupling agent may be silane coupling agent KH560, silane coupling agent KH561, silane coupling agent KH577, silane coupling agent KH578, etc., and preferably silane coupling agent KH560.

[0020] S12, adding the intermediate product I to N,N-dimethylformamide A, ultrasonicating, and dripping into the reaction kettle containing dibasic acid A, catalyst, and N,N-dimethylformamide B through a peristaltic pump, slowly dripping, stirring at 100-105°C, and continuing to stir for 4-8h after the completion of the dripping, cooling to room temperature, distilling under reduced pressure, and vacuum drying at 60°C for 6h to obtain the intermediate product II.

[0021] The intermediate product I and the dibasic acid A are added in a molar ratio of epoxy group to carboxyl group of 1:2; The dosage ratio of the N,N-dimethylformamide A, the dibasic acid A, and the N,N-dimethylformamide B is 100mL:0.1mol:200mL; The amount of the catalyst used is 0.4% of the total mass of the reactants; The catalyst may be triphenylphosphine or the like; The dibasic acid A is a fatty acid containing a side group; The side groups are methyl, ethyl, and butyl; The dibasic acid A with a methyl side group can be 3-methyladipic acid; 2-methylsuccinic acid; 2,2-dimethylsuccinic acid, etc.; and preferably 2,2-dimethylsuccinic acid; The dibasic acid A with an ethyl side group may be 3-methyl-3-ethylglutaric acid, etc.; The dibasic acid A having a butyl side group may be 2-butylsuccinic acid, 3-tert-butyladipic acid, etc., and 3-tert-butyladipic acid is preferred.

[0022] S13, N2 protection, add dibasic acid B, diol and catalyst into xylene, stir and heat to reflux, calculate the mass of water separated as the reaction end point; obtain a solution containing intermediate product III.

[0023] The usage ratio of the dibasic acid B, diol and xylene is 0.1 mol: 0.1 mol: 100 mL.

[0024] The dibasic acid B is a fatty acid containing a side group and an aromatic acid containing a side group, which are added in a molar ratio of 0.3-0.5:0.5-0.7; The diols are small molecular diols containing side groups, polyether diols, and polyester diols, which are added in a molar ratio of 0.5-0.7: 0.2-0.4: 0-0.2.

[0025] The side groups are methyl, ethyl, and butyl; The fatty acid with a methyl side group may be 3-methyladipic acid; 2-methylsuccinic acid; 2,2-dimethylsuccinic acid, etc.; and preferably 2,2-dimethylsuccinic acid; The fatty acid with an ethyl side group may be 3-methyl-3-ethylglutaric acid, etc. The fatty acid with a butyl side group may be 2-butylsuccinic acid, 3-tert-butyladipic acid, etc., and 3-tert-butyladipic acid is preferred.

[0026] The aromatic acid with a methyl side group may be 1-methyl-3,5-phthalic acid, etc.; The fatty acid with ethyl side groups can be 4-ethylbenzene-1,3-dicarboxylic acid, etc. The small molecule divalent fatty alcohol with a methyl side group may be 1,3-butanediol, 2,4-pentanediol, 1,3-pentanediol, 1,4-pentanediol, etc.; The polyether diol may be PPG-200, PPG-400, PPG-600, PPG-700, PPG-1000, PPG-2000, or a mixture thereof; and, the polyether diol in the following embodiments of the present invention is a mixture of PPG-400 and PPG-1000; The polyester diol may be polycaprolactone diol with a molecular weight of 530, 830 or 1000, etc., and preferably has a molecular weight of 530.

[0027] The catalyst is tetrabutyl titanate; The amount of tetrabutyl titanate used is 1.0wt% of the total mass of the reactants.

[0028] The average polymerization degree of the intermediate product III is 16-28; since the esterification polymerization of the dibasic acid and the diol belongs to a dehydration condensation reaction, the molecular weight and polymerization degree of the polyester can be rationally controlled by the molar ratio of the added dibasic acid to the diol and the quality of the separated water. When the average polymerization degree is less than 16, the molecular weight is low, the degree of flexibility is not high, and the anti-fiber crystallization is poor, which affects the anti-pilling property and the fluffy effect; when the average polymerization degree is greater than 28, the molecular chain is longer, the chain entanglement degree is high, and there will be a chain extension enhancement effect that is not conducive to the fiber softening and anti-pilling property.

[0029] S14, N2 protection, add the intermediate product II to the solution containing the intermediate product III, stir and heat until the reaction water mass is constant; filter, take the filtrate, distill under reduced pressure, and vacuum dry at 60°C for 6h to obtain the target product, i.e., the functional additive; The intermediate product II and the intermediate product III are added in a molar ratio of carboxyl to hydroxyl of 1:1.

[0030] Since there is a certain negative correlation between elongation at break and tensile strength, a higher elongation at break will increase the fluffiness, but it will have a certain reverse effect on the anti-pilling effect. This is because the higher the elongation at break, the less likely it is to fall off and form large pills. Generally speaking, the fluffier the fabric, the easier it is to pill, and a certain fluffiness can improve the softness of polyester fibers and solve the problem of hardness.

[0031] The functional additives in the present invention are combined with the molecular structure design to form a hyperbranched structure using a molecular chain containing a side group structure. First, the presence of the side group structure is similar to the block copolymers formed with different structural units, which can improve the friction between fibers, fundamentally reduce slippage, and improve anti-pilling properties; and then the shedding of fiber pills is accelerated by appropriately reducing the tensile strength, thereby improving the anti-pilling effect. In this way, the purpose of "prevention" to "treatment" is achieved.

[0032] The intrinsic viscosity of the PET chips is in the range of 0.65 to 0.90 dL / g, and the melting point is 245 to 255° C.; and the PET chips described in the present invention are brand CH 610, purchased from Wuxi Suboshi Plastic Chemical Co., Ltd.

[0033] The antioxidant described in the present invention is a combination of hindered phenols and phosphites. The hindered phenol antioxidants may be antioxidant 1010, antioxidant 1076, antioxidant 264, antioxidant 2246, etc.; and antioxidant 1010 is preferred. The phosphite antioxidants may be antioxidant 168, antioxidant 242, antioxidant TPP, etc.; and antioxidant 168 is preferred. In the following embodiments of the present invention, the antioxidants are antioxidant 1010 and antioxidant 168 added in a mass ratio of 1:2.

[0034] The lubricant may be erucamide, oleamide, ethylene bisstearamide, etc.; and, the lubricant described in the following embodiments of the present invention is erucamide and ethylene bisstearamide mixed and added in a mass ratio of 2:1.

[0035] The fiber treatment agent is a sodium phosphate salt; it may include sodium pyrophosphate, sodium tripolyphosphate, sodium tetrapolyphosphate, sodium pentapolyphosphate, sodium hexametaphosphate, or a mixture thereof; and the sodium phosphate salts described in the following embodiments of the present invention are all sodium pyrophosphate.

[0036] Another object of the embodiment of the present invention is to provide a method for preparing fluffy and soft polyester fibers, comprising the following steps: S21: drying and mixing of raw materials; i.e. Weigh the raw materials according to their weight components, mix them, and dry them at 80°C for 24 hours; S22: melt extrusion, pressurization; i.e. The dried raw material is placed in a screw extruder, melted and filtered at a temperature of 250-280°C, and then pumped to a liquid phase conditioning and viscosity adjustment reactor through a melt pump. The melt stays in the reactor for 30 minutes, and the intrinsic viscosity of the final polyester melt is 0.610.70 dL / g. For the melt extrusion, the temperature of each zone of the twin-screw extruder is: 250-260°C in zone 1, 260-270°C in zone 2, 270-275°C in zone 3, 275-280°C in zone 4, and 275-280°C in zone 5; S23: Spinning to obtain primary fibers; i.e. The melt is pumped to the secondary filter, and the filtered melt enters the spinning box after passing through the static mixer set in the pipeline, and is cooled under the action of the triangular hollow spinneret to obtain the primary fiber with high vacuum degree; S24: post-processing, i.e., drawing and heat setting; i.e. After balancing, the nascent fiber is sequentially drawn and heat-set, wherein the primary oil bath drawing temperature is 60-70°C, the secondary steam drawing temperature is 100-120°C, and the heat-set temperature is 185-210°C; In the post-processing process, the traction stretching ratio is 3.0-5.0; S25: Curly, relaxed styling; i.e. The stretched fibers enter the crimping machine, where they are crimped with high density. They are then sent to the J-shaped box for arrangement by a reciprocating trolley. The arranged fibers enter the relaxation heat setting machine for setting. The temperature of the crimping machine is 90-110°C, the main pressure is 160-180 kPa, and the back pressure is 180-210 kPa. The relaxation setting temperature is 115-120°C, and the setting time is 0.5 1h; S26: The tow is cut and packaged to obtain fluffy and soft polyester fibers.

[0037] In order to further understand the present invention, a fluffy and soft polyester fiber and a preparation method thereof provided by the present invention are described in detail below in conjunction with specific embodiments. The protection scope of the present invention is not limited by the following embodiments.

[0038] Example 1 A fluffy and soft polyester fiber, comprising the following raw materials in parts by weight: PET slices 100 pieces; Functional additives 8.0 parts; 0.6 parts of antioxidant; 0.35 parts of lubricant; 1.2 parts of fiber treatment agent; The functional additive and its preparation method include the following steps: S11, add nano titanium and deionized water A to anhydrous ethanol, ultrasonically disperse for 1 hour, add glacial acetic acid to adjust the pH value to 4.5, add silane coupling agent KH560, stir and ultrasonicate for 0.5 hour, heat to 70°C and reflux for 2.5 hours; after the reaction is completed, filter, take the insoluble matter, rinse with deionized water B, vacuum dry at 40°C to constant weight, grind to obtain intermediate product I.

[0039] The usage ratio of the nano titanium, deionized water A, anhydrous ethanol, silane coupling agent KH560, and deionized water B is 1g:2g:18g:0.35g:30g.

[0040] Its infrared data are as follows: 3396cm -1 :-OH exists and weakens; 1265cm -1 、898cm -1 、825cm -1 : Epoxy groups are present; 1109 cm -1 、801cm -1 :-Si-O- exists.

[0041] S12, add the intermediate product I to N,N-dimethylformamide A, ultrasonicate, and drip it into a reaction kettle containing 3-tert-butyl adipic acid, triphenylphosphine, and N,N-dimethylformamide B through a peristaltic pump, slowly drip it, and stir it at 105°C. After the dripping is completed, continue stirring for 4 hours, cool to room temperature, distill under reduced pressure, and vacuum dry it at 60°C for 6 hours to obtain the intermediate product II.

[0042] The intermediate product I and 3-tert-butyl adipic acid are added in a molar ratio of epoxy group to carboxyl group of 1:2; The dosage ratio of the N,N-dimethylformamide A, 3-tert-butyl adipic acid, and N,N-dimethylformamide B is 100 mL: 0.1 mol: 200 mL; The amount of triphenylphosphine used is 0.4% of the total mass of the reactants.

[0043] Its infrared data is as follows: 3422cm -1 :-OH exists; 1760cm -1 :-C=O (carboxyl) exists and weakens; 1735cm -1 :-C=O (ester) exists; 1265cm -1 、898cm -1 、825cm -1 :Epoxy group does not exist; 1109 cm -1 、801cm -1 :-Si-O- exists.

[0044] S13, N2 protection, add dibasic acid B, diol, and tetrabutyl titanate into xylene, stir and heat to reflux, calculate the mass of water separated as the reaction end point; obtain a solution containing the intermediate product III.

[0045] The usage ratio of the dibasic acid B, diol and xylene is 0.1 mol: 0.1 mol: 100 mL.

[0046] The dibasic acid B is 3-tert-butyl adipic acid and 1-methyl-3,5-phthalic acid added in a molar ratio of 0.4:0.6; The diols are 1,4-pentanediol, polyether diol, and polycaprolactone diol (molecular weight 530) added in a molar ratio of 0.6:0.3:0.1; The polyether diols are PPG-400 and PPG-1000, which are mixed in a molar ratio of 3:1.

[0047] The amount of tetrabutyl titanate used is 1.0wt% of the total mass of the reactants.

[0048] The average degree of polymerization of the intermediate product III is 21.3.

[0049] Its infrared data are as follows: 3430cm -1 :-OH exists; 3011cm -1 、1595cm -1 、1498cm -1 : benzene ring exists; 1760cm -1 :-C=O (carboxyl) exists; 1735cm -1 :-C=O (ester) exists and enhances.

[0050] S14, N2 protection, add the intermediate product II to the solution containing the intermediate product III, stir and heat until the reaction water mass is constant; filter, take the filtrate, distill under reduced pressure, and vacuum dry at 60°C for 6h to obtain the target product, i.e., the functional additive; The intermediate product II and the intermediate product III are added in a molar ratio of carboxyl to hydroxyl of 1:1.

[0051] Its infrared data is as follows: 3422cm -1 :-OH exists and is enhanced; 3011cm -1 、1595cm -1 、1498cm -1 : benzene ring exists; 1760cm -1 :-C=O (carboxyl) exists and weakens; 1735cm -1 :-C=O (ester) exists and is enhanced; 1109 cm -1 、801cm -1:-Si-O- exists.

[0052] Another object of the embodiment of the present invention is to provide a method for preparing fluffy and soft polyester fibers, comprising the following steps: S21: drying and mixing of raw materials; i.e. Weigh the raw materials according to their weight components, mix them, and dry them at 80°C for 24 hours; S22: melt extrusion, pressurization; i.e. The dried raw material is placed in a screw extruder, melt-filtered, and then pumped to a liquid phase conditioning and viscosity adjustment reactor via a melt pump. The melt stays in the reactor for 30 minutes, and the intrinsic viscosity of the final polyester melt is 0.66 dL / g. For the melt extrusion, the temperature of each zone of the twin-screw extruder is: 255°C in zone 1, 265°C in zone 2, 272°C in zone 3, 277°C in zone 4, and 277°C in zone 5; S23: Spinning to obtain primary fibers; i.e. The melt is pumped to the secondary filter, and the filtered melt enters the spinning box after passing through the static mixer set in the pipeline, and is cooled under the action of the triangular hollow spinneret to obtain the primary fiber with high vacuum degree; S24: post-processing, i.e., drawing and heat setting; i.e. After balancing, the nascent fiber is sequentially drawn and heat-set, wherein the first-stage oil bath drawing temperature is 65°C, the second-stage steam drawing temperature is 110°C, and the heat-set temperature is 200°C; In the post-processing process, the traction stretching ratio is 4.0; S25: Curly, relaxed styling; i.e. The stretched fibers enter the crimping machine, where they are crimped with high density. They are then sent to the J-shaped box for arrangement by a reciprocating trolley. The arranged fibers enter the relaxation heat setting machine for setting. The temperature of the crimping machine is 100°C, the main pressure is 175kPa, and the back pressure is 200kPa. The relaxation setting temperature is 120°C and the setting time is 0.5h; S26: The tow is cut and packaged to obtain fluffy and soft polyester fibers.

[0053] Example 2 A fluffy and soft polyester fiber, comprising the following raw materials in parts by weight: PET slices 100 pieces; Functional additives 5.0 parts; 0.2 parts of antioxidant; 0.5 parts of lubricant; 2.0 parts of fiber treatment agent; The functional additive and its preparation method include the following steps: S11, add nano titanium and deionized water A to anhydrous ethanol, ultrasonically disperse for 1 hour, add glacial acetic acid to adjust the pH value to 3.5, add silane coupling agent KH560, stir and ultrasonicate for 0.5 hour, heat to 60°C and reflux for 4 hours; after the reaction is completed, filter, take the insoluble matter, rinse with deionized water B, vacuum dry at 40°C to constant weight, grind to obtain intermediate product I.

[0054] The usage ratio of the nano titanium, deionized water A, anhydrous ethanol, silane coupling agent KH560, and deionized water B is 1g:2g:18g:0.5g:30g.

[0055] S12, add the intermediate product I to N,N-dimethylformamide A, ultrasonicate, and drip it into a reaction kettle containing 3-tert-butyl adipic acid, triphenylphosphine, and N,N-dimethylformamide B through a peristaltic pump, slowly drip it, and stir it at 100°C. After the dripping is completed, continue stirring for 8 hours, cool to room temperature, distill under reduced pressure, and vacuum dry it at 60°C for 6 hours to obtain the intermediate product II.

[0056] The intermediate product I and 3-tert-butyl adipic acid are added in a molar ratio of epoxy group to carboxyl group of 1:2; The dosage ratio of the N,N-dimethylformamide A, 3-tert-butyl adipic acid, and N,N-dimethylformamide B is 100 mL: 0.1 mol: 200 mL; The amount of triphenylphosphine used is 0.4% of the total mass of the reactants.

[0057] S13, N2 protection, add dibasic acid B, diol, and tetrabutyl titanate into xylene, stir and heat to reflux, calculate the mass of water separated as the reaction end point; obtain a solution containing the intermediate product III.

[0058] The usage ratio of the dibasic acid B, diol and xylene is 0.1 mol: 0.1 mol: 100 mL.

[0059] The dibasic acid B is 3-tert-butyl adipic acid and 1-methyl-3,5-phthalic acid added in a molar ratio of 0.5:0.5; The diols are 1,4-pentanediol, polyether diol, and polycaprolactone diol (molecular weight 530) added in a molar ratio of 0.6:0.4:0; The polyether diols are PPG-400 and PPG-1000, which are mixed in a molar ratio of 3:1.

[0060] The amount of tetrabutyl titanate used is 1.0wt% of the total mass of the reactants.

[0061] The average degree of polymerization of the intermediate product III is 21.5.

[0062] S14, N2 protection, add the intermediate product II to the solution containing the intermediate product III, stir and heat until the reaction water mass is constant; filter, take the filtrate, distill under reduced pressure, and vacuum dry at 60°C for 6h to obtain the target product, i.e., the functional additive; The intermediate product II and the intermediate product III are added in a molar ratio of carboxyl to hydroxyl of 1:1.

[0063] Another object of the embodiment of the present invention is to provide a method for preparing fluffy and soft polyester fibers, comprising the following steps: S21: drying and mixing of raw materials; i.e. Weigh the raw materials according to their weight components, mix them, and dry them at 80°C for 24 hours; S22: melt extrusion, pressurization; i.e. The dried raw material is placed in a screw extruder, melt-filtered, and then pumped to a liquid phase conditioning and viscosity adjustment reactor via a melt pump. The melt stays in the reactor for 30 minutes, and the intrinsic viscosity of the final polyester melt is 0.70 dL / g. For the melt extrusion, the temperature of each zone of the twin-screw extruder is: 260°C in zone 1, 270°C in zone 2, 275°C in zone 3, 280°C in zone 4, and 280°C in zone 5; S23: Spinning to obtain primary fibers; i.e. The melt is pumped to the secondary filter, and the filtered melt enters the spinning box after passing through the static mixer set in the pipeline, and is cooled under the action of the triangular hollow spinneret to obtain the primary fiber with high vacuum degree; S24: post-processing, i.e., drawing and heat setting; i.e. After balancing, the nascent fiber is sequentially drawn and heat-set, wherein the first-stage oil bath drawing temperature is 70°C, the second-stage steam drawing temperature is 120°C, and the heat-set temperature is 210°C; In the post-processing process, the traction stretching ratio is 5.0; S25: Curly, relaxed styling; i.e. The stretched fibers enter the crimping machine, where they form high-density crimped fibers. They are then sent to the J-shaped box for arrangement by a reciprocating trolley. The arranged fibers enter the relaxation heat setting machine for setting. The temperature of the crimping machine is 110°C, the main pressure is 180kPa, and the back pressure is 210kPa. The relaxation setting temperature is 120°C and the setting time is 0.5h; S26: The tow is cut and packaged to obtain fluffy and soft polyester fibers.

[0064] Example 3 A fluffy and soft polyester fiber, comprising the following raw materials in parts by weight: PET slices 100 pieces; 10.0 parts of functional additives; 1.0 part of antioxidant; 0.2 parts of lubricant; 0.35 parts of fiber treatment agent; The functional additive and its preparation method include the following steps: S11, add nano titanium and deionized water A to anhydrous ethanol, ultrasonically disperse for 1 hour, add glacial acetic acid to adjust the pH value to 5.5, add silane coupling agent KH560, stir and ultrasonicate for 0.5 hour, heat to 80°C and reflux for 2 hours; after the reaction is completed, filter, take the insoluble matter, rinse with deionized water B, vacuum dry at 40°C to constant weight, grind to obtain intermediate product I.

[0065] The usage ratio of the nano titanium, deionized water A, anhydrous ethanol, silane coupling agent KH560, and deionized water B is 1g:2g:18g:0.1g:30g.

[0066] S12, add the intermediate product I to N,N-dimethylformamide A, ultrasonicate, and drip it into a reaction kettle containing 3-tert-butyl adipic acid, triphenylphosphine, and N,N-dimethylformamide B through a peristaltic pump, slowly drip it, and stir it at 105°C. After the dripping is completed, continue stirring for 6 hours, cool to room temperature, distill under reduced pressure, and vacuum dry it at 60°C for 6 hours to obtain the intermediate product II.

[0067] The intermediate product I and 3-tert-butyl adipic acid are added in a molar ratio of epoxy group to carboxyl group of 1:2; The dosage ratio of the N,N-dimethylformamide A, 3-tert-butyl adipic acid, and N,N-dimethylformamide B is 100 mL: 0.1 mol: 200 mL; The amount of triphenylphosphine used is 0.4% of the total mass of the reactants.

[0068] S13, N2 protection, add dibasic acid B, diol, and tetrabutyl titanate into xylene, stir and heat to reflux, calculate the mass of water separated as the reaction end point; obtain a solution containing the intermediate product III.

[0069] The usage ratio of the dibasic acid B, diol and xylene is 0.1 mol: 0.1 mol: 100 mL.

[0070] The dibasic acid B is 3-tert-butyl adipic acid and 1-methyl-3,5-phthalic acid added in a molar ratio of 0.3:0.7; The diols are 1,4-pentanediol, polyether diol, and polycaprolactone diol (molecular weight 530) added in a molar ratio of 0.6:0.2:0.2; The polyether diols are PPG-400 and PPG-1000, which are mixed in a molar ratio of 3:1.

[0071] The amount of tetrabutyl titanate used is 1.0wt% of the total mass of the reactants.

[0072] The average degree of polymerization of the intermediate product III is 21.2.

[0073] S14, N2 protection, add the intermediate product II to the solution containing the intermediate product III, stir and heat until the reaction water mass is constant; filter, take the filtrate, distill under reduced pressure, and vacuum dry at 60°C for 6h to obtain the target product, i.e., the functional additive; The intermediate product II and the intermediate product III are added in a molar ratio of carboxyl to hydroxyl of 1:1.

[0074] Another object of the embodiment of the present invention is to provide a method for preparing fluffy and soft polyester fibers, comprising the following steps: S21: drying and mixing of raw materials; i.e. Weigh the raw materials according to their weight components, mix them, and dry them at 80°C for 24 hours; S22: melt extrusion, pressurization; i.e. The dried raw material is placed in a screw extruder, melt-filtered, and then pumped to a liquid phase conditioning and viscosity adjustment reactor via a melt pump. The melt stays in the reactor for 30 minutes, and the intrinsic viscosity of the final polyester melt is 0.61 dL / g. For the melt extrusion, the temperature of each zone of the twin-screw extruder is: 250°C in zone 1, 262°C in zone 2, 270°C in zone 3, 275°C in zone 4, and 275°C in zone 5; S23: Spinning to obtain primary fibers; i.e. The melt is pumped to the secondary filter, and the filtered melt enters the spinning box after passing through the static mixer set in the pipeline, and is cooled under the action of the triangular hollow spinneret to obtain the primary fiber with high vacuum degree; S24: post-processing, i.e., drawing and heat setting; i.e. After balancing, the nascent fiber is sequentially drawn and heat-set, wherein the first-stage oil bath drawing temperature is 60°C, the second-stage steam drawing temperature is 100°C, and the heat-set temperature is 185°C; In the post-processing process, the traction stretching ratio is 3.0; S25: Curly, relaxed styling; i.e. The stretched fibers enter the crimping machine, where they are crimped with high density. They are then sent to the J-shaped box for arrangement by a reciprocating trolley. The arranged fibers enter the relaxation heat setting machine for setting. The temperature of the crimping machine is 90°C, the main pressure is 160kPa, and the back pressure is 180kPa. The relaxation setting temperature is 115°C and the setting time is 1h; S26: The tow is cut and packaged to obtain fluffy and soft polyester fibers.

[0075] Example 4 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber, comprising the following raw materials in parts by weight: PET slices 100 pieces; Functional additives 6.0 parts; 0.6 parts of antioxidant; 0.35 parts of lubricant; 1.2 parts of fiber treatment agent.

[0076] Example 5 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber, comprising the following raw materials in parts by weight: PET slices 100 pieces; Functional additives 9.0 parts; 0.6 parts of antioxidant; 0.35 parts of lubricant; 1.2 parts of fiber treatment agent.

[0077] Example 6 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S12 and S13, The 3-tert-butyladipic acid was replaced with 2,2-dimethylsuccinic acid.

[0078] Example 7 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S12 and S13, The 3-tert-butyladipic acid was replaced with 3-methyl-3-ethylglutaric acid.

[0079] Example 8 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The 1-methyl-3,5-benzenedicarboxylic acid was replaced with 4-ethylbenzene-1,3-dicarboxylic acid.

[0080] Example 9 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The 1,4-pentanediol was replaced with 2,4-pentanediol.

[0081] Example 10 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The 1,4-pentanediol was replaced with 1,3-butanediol.

[0082] Embodiment 11 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The polyether diol is a mixture of PPG-400 and PPG-1000 in a molar ratio of 2:1.

[0083] Example 12 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The polyether diol is a mixture of PPG-400 and PPG-1000 in a molar ratio of 4:1.

[0084] Embodiment 13 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The diols are 1,4-pentanediol, polyether diol, and polycaprolactone diol (molecular weight 530), which are added in a molar ratio of 0.5:0.3:0.2.

[0085] Embodiment 14 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The diols are 1,4-pentanediol, polyether diol, and polycaprolactone diol (molecular weight 530), which are added in a molar ratio of 0.7:0.3:0; that is, polycaprolactone diol is not added.

[0086] Embodiment 15 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The average degree of polymerization of the intermediate product III is 16.2.

[0087] Example 16 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The average degree of polymerization of the intermediate product III is 27.9.

[0088] The following comparative examples are compared with Example 1: Comparative Example 1 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber formula without added functional additives.

[0089] Comparative Example 2 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S12, The intermediate product I is replaced by tetraglycidyl ether tetraphenylethane.

[0090] Comparative Example 3 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S11, The nano-titanium is replaced by nano-silicon.

[0091] Comparative Example 4 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The dibasic acid A and dibasic acid B have no side group structure, that is, 3-tert-butyl adipic acid is replaced by adipic acid, and 1-methyl-3,5-phthalic acid is replaced by isophthalic acid.

[0092] Comparative Example 5 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The 1-methyl-3,5-benzenedicarboxylic acid was replaced with 3-tert-butyladipic acid.

[0093] Comparative Example 6 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The 3-tert-butyladipic acid was replaced by 1-methyl-3,5-benzenedicarboxylic acid.

[0094] Comparative Example 7 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The 1-methyl-3,5-benzenedicarboxylic acid was replaced with 2-methyl-1,4-benzenedicarboxylic acid.

[0095] Comparative Example 8 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The diols are 1,4-pentanediol, polyether diol, and polycaprolactone diol (molecular weight 530) added in a molar ratio of 0:0.3:0.1; that is, 1,4-pentanediol is not added.

[0096] Comparative Example 9 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The diols are 1,4-pentanediol, polyether diol, and polycaprolactone diol (molecular weight 530) added in a molar ratio of 0.6:0:0.1; that is, no polyether diol is added.

[0097] Comparative Example 10 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The average degree of polymerization of the intermediate product III is 14.8.

[0098] Comparative Example 11 The rest is the same as in Example 1, except that: A fluffy and soft polyester fiber. The functional additive, and the preparation method thereof, in S13, The average degree of polymerization of the intermediate product III is 29.4.

[0099] The physical properties of the polyester fibers prepared in the embodiments of the present invention and the comparative examples were measured respectively, and the results are shown in Table 1.

[0100] Table 1 Physical test performance of each embodiment Example Tensile strength (cN / dtex) Elongation at break (%) Curl shrinkage Softness Anti-pilling grade Antibacterial activity (%) Staphylococcus aureus Antibacterial activity (%) Escherichia coli Volume resistivity (Ω▪cm) Example 1 3.4 80.1 23.5 soft 4 95.9 94.8 2.5×10 10 Example 2 4.0 70.8 20.3 soft 3.5 95.1 94.2 8.7×10 10 Example 3 3.6 74.8 21.9 soft 4 96.2 94.8 1.4×10 10 Example 4 3.9 71.0 20.8 soft 4 95.3 94.4 6.5×10 10 Example 5 3.4 79.3 23.2 soft 4 95.9 94.7 2.1×10 10 Example 6 3.7 72.4 21.4 soft 4 95.6 94.7 2.9×10 10 Example 7 3.6 75.9 22.1 soft 4 95.8 94.6 2.8×10 10 Example 8 3.5 84.7 24.2 soft 4 96.1 94.5 2.6×10 10 Example 9 3.6 74.5 21.3 soft 4 95.5 94.5 3.0×10 10 Example 10 3.7 69.1 20.1 soft 4 95.3 94.2 3.2×10 10 Embodiment 11 3.6 94.3 26.9 soft 3.5 96.0 94.8 1.1×10 10 Example 12 3.7 65.8 21.0 soft 4 95.2 94.4 3.6×10 10 Embodiment 13 3.8 81.4 23.9 soft 4 95.6 94.5 2.6×10 10 Embodiment 14 4.0 63.3 19.4 Moderate 3.5 95.8 94.2 2.7×10 10 Embodiment 15 4.5 62.5 17.5 Moderate 3.5 95.2 94.3 3.8×10 10 Example 16 4.4 104.7 27.8 soft 3.5 95.7 94.8 2.2×10 10 Comparative Example 1 4.6 58.6 6.2 Harder 2 24.5 16.9 4.2×10 13 Comparative Example 2 4.1 67.3 10.5 Moderate 2.5 26.6 16.5 5.3×10 11 Comparative Example 3 3.8 79.3 23.1 soft 3.5 26.4 17.8 3.7×10 11 Comparative Example 4 3.9 66.4 12.9 Moderate 2.5 94.2 93.6 6.4×10 10 Comparative Example 5 3.3 97.5 27.7 soft 3 93.9 92.4 8.9×10 10 Comparative Example 6 4.2 64.6 12.5 Moderate 3 94.1 92.2 6.1×10 10 Comparative Example 7 4.3 63.7 12.3 Moderate 2.5 94.0 92.5 5.6×10 10 Comparative Example 8 4.4 116.7 16.5 Moderate 3 94.3 92.8 9.1×10 9 Comparative Example 9 4.5 72.6 13.1 Moderate 3 94.2 92.3 2.8×10 11 Comparative Example 10 4.6 59.9 13.8 Moderate 3 93.8 92.0 4.4×10 10 Comparative Example 11 4.6 122.9 17.6 Moderate 2.5 94.0 92.6 2.0×10 10 First, it can be concluded from Examples 1-16 in Table 1 that the fluffy and soft polyester fiber of the present invention has excellent fluffiness, softness, and anti-pilling properties, as well as excellent antibacterial and antistatic properties.

[0101] Second, it can be observed from Example 1 and Comparative Examples 1-3 that the fluffy and soft polyester fiber of the present invention has excellent fluffiness, which is reflected in higher curl shrinkage, softness, and anti-pilling property; at the same time, it can be observed that the hyperbranched structure has a more excellent effect, and nano-titanium also has an excellent antibacterial effect; It can be observed from Example 1 and Comparative Examples 4-7 that the fluffy and soft polyester fiber of the present invention, the side group structure and the main chain structure of the dibasic acid and diol in the functional additives have a positive effect on the curl shrinkage and softness; It can be observed from Example 1 and comparative examples 8-9 that the fluffy and soft polyester fiber of the present invention has a positive effect on softness, fluffiness, anti-pilling and antistatic effects due to the appropriate ratio of diol raw materials in its functional additives; in comparative example 8, due to the absence of small molecule units at the same degree of polymerization, its average molecular weight will increase significantly, thereby improving the tensile strength; and in comparative example 9, the flexible structure without polyether will also improve the comprehensive mechanical strength.

[0102] It can be observed from Example 1 and Comparative Examples 10-11 that the appropriate degree of polymerization in the functional additives of the fluffy and soft polyester fiber of the present invention has an important influence on various properties including pilling resistance; It can be observed from Example 1 and Comparative Examples 1-3 and 9 that nano-titanium and polyether structure have a synergistic effect on the antistatic effect.

[0103] In summary, the fluffy and soft polyester fiber provided by the present invention is prepared through molecular design, self-made functional additives and formula design, and has excellent fluffiness, softness, anti-pilling properties, and also has excellent antibacterial and antistatic properties.

[0104] The test method is as follows: (1) Tensile strength: Tested according to the method described in GB / T 14337-2008.

[0105] (2) Elongation at break: Tested according to the method described in GB 9997-88.

[0106] (3) Curl shrinkage: Tested according to the method described in GB / T 6506-2017.

[0107] (4) Softness: The pendulum method is used to evaluate softness. The softness is expressed by qualitative analysis and is divided into "soft", "moderate" and "hard".

[0108] (5) Anti-pilling grade: in accordance with standard GB / T 4802.2 2008 "Determination of pilling properties of textile fabrics".

[0109] (6) Antibacterial property: After exposure to light, the standard GB / T 20944.3 2008 "Evaluation of antibacterial properties of textiles" was adopted.

[0110] (7) Volume resistivity: Tested in accordance with the method described in GB / T 14342-2015.

[0111] Based on the above ideal embodiments of the present invention, the relevant staff can make various changes and modifications without departing from the technical concept of the present invention through the above description. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A fluffy and soft polyester fiber, characterized in that: The invention comprises the following raw materials in parts by weight: PET slices 100 pieces; Functional additives 5.0-10.0 parts; Antioxidant 0.2-1.0 part; Lubricant 0.2-0.5 parts; Fiber treatment agent 0.35-2.0 parts; The functional additive and its preparation method include the following steps: S11, performing a silylation coupling reaction on nano-titanium and an epoxy silane coupling agent to obtain an intermediate product I; The dosage ratio of the nano titanium to the epoxy silane coupling agent is 1g:0.1-0.5g; S12, subjecting the intermediate product I to a ring-opening reaction with a dibasic acid A to obtain an intermediate product II; The intermediate product I and the dibasic acid A are added in a molar ratio of epoxy group to carboxyl group of 1:2; S13, subjecting the dibasic acid B and the diol to a polycondensation reaction under the action of a catalyst to obtain an intermediate product III; The molar ratio of the dibasic acid B to the diol is 1:1; S14, adding the intermediate product II to the intermediate product III for esterification reaction to obtain the target product, i.e., the functional additive; The intermediate product II and the intermediate product III are added in a molar ratio of carboxyl to hydroxyl of 1:

1.

2. The fluffy and soft polyester fiber according to claim 1, characterized in that: The dibasic acid A is a fatty acid containing a side group.

3. The fluffy and soft polyester fiber according to claim 1, characterized in that: The dibasic acid B is a fatty acid containing a side group and an aromatic acid containing a side group, which are added in a molar ratio of 0.3-0.5:0.5-0.7; as well as The diols are small molecular diols containing side groups, polyether diols, and polyester diols, which are added in a molar ratio of 0.5-0.7: 0.2-0.4: 0-0.

2.

4. A fluffy and soft polyester fiber according to claim 2 or 3, characterized in that: The side groups are methyl, ethyl and butyl.

5. The fluffy and soft polyester fiber according to claim 1, characterized in that: The average polymerization degree of the intermediate product III is 20-28.

6. The fluffy and soft polyester fiber according to claim 1, characterized in that: The intrinsic viscosity of the PET chips ranges from 0.65 to 0.90 dL / g, and the melting point ranges from 245 to 255°C.

7. The fluffy and soft polyester fiber according to claim 1, characterized in that: The fiber treating agent is sodium phosphate.

8. A method for preparing fluffy and soft polyester fiber, characterized in that: The following steps are involved: S21: drying and mixing of raw materials; S22: melt extrusion, pressurization; S23: spinning to obtain nascent fibers; S24: post-processing, i.e., drawing and heat setting; S25: Curly, loose styling; S26: The tow is cut and packaged to obtain fluffy and soft polyester fibers.

9. The method for preparing fluffy and soft polyester fiber according to claim 8, characterized in that: For the melt extrusion, the temperature of each zone of the twin-screw extruder is: 250-260°C in zone 1, 260-270°C in zone 2, 270-275°C in zone 3, 275-280°C in zone 4, and 275-280°C in zone 5; In the post-processing process, the traction stretching ratio is 3.0-5.0; and The relaxation setting temperature is 115-120°C.