Cool-feeling polypropylene fiber and method for producing the same

Abstract

The application discloses a cool-feeling polypropylene fiber and a preparation method thereof, and relates to the technical field of clothing materials. The preparation method of the cool-feeling polypropylene fiber comprises the following steps: S1, after polypropylene 75-88 parts, polyethylene 10-15 parts, a cool-feeling additive 13-21 parts, a dispersing agent 0.8-2.5 parts, a reinforcing agent 2-3 parts and an antioxidant 0.5-1 part are mixed, the mixture is melt-blended and extruded, and then the yarn is obtained after cooling; and S2, the yarn is subjected to multi-stage drafting and relaxation heat setting to obtain the cool-feeling polypropylene fiber. By adding the antioxidant and the reinforcing agent, the oxidation resistance and the mechanical strength of the fiber are effectively improved, the service life of the cool-feeling additive is prolonged, and the overall compactness and the tensile resistance of the fiber are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of clothing materials, in particular to a cool polypropylene fiber and a preparation method thereof. BACKGROUND

[0002] With the improvement of people's living standards, the functional demand of textiles is also increasing, among which the cool fiber has attracted widespread attention because it can instantly transmit a cool feeling when it contacts the skin. Polypropylene fiber is widely used in the clothing field due to its light weight, water resistance and other advantages, but its thermal conductivity is poor, and traditional polypropylene fiber cannot provide a significant cool experience when it contacts the skin, which is difficult to meet the demand for cool clothing in summer or high-temperature environment.

[0003] In the prior art, the cool feeling of the cool fiber is usually composed of inorganic or organic materials. Although these additives can improve the thermal conductivity and cooling effect of the fiber to some extent, their stability in the fiber is poor and they are easily oxidized, light aged or heat aged. In addition, polypropylene fiber has good flexibility and processability, but its heat resistance and oxidation resistance are weak, which can affect the performance of the fiber due to degradation during long-term use. Therefore, how to prolong the service life of the cool fiber and maintain the durability of the cool performance has become a key challenge in the current technical field.

[0004] In addition, the preparation process of traditional cool fiber is complex and requires additional post-processing steps, which not only increases the production cost but also reduces the production efficiency. Therefore, under the premise of not affecting the basic performance of the fiber, it is a key challenge in the current technical field to develop a cool polypropylene fiber with long-acting cool and antibacterial properties while simplifying the preparation process. SUMMARY

[0005] In view of the problems of poor thermal conductivity of polypropylene fiber in the prior art, inability to provide significant cool experience, poor stability of cool additives and easy failure, a cool polypropylene fiber and a preparation method thereof are provided. Through the synergistic effect of inorganic coolants and organic coolants, the fiber is given basic cool and enhanced thermal conductivity, and the addition of anti-aging agents and reinforcing agents improves the aging resistance and mechanical strength of the fiber. The preparation process is simple and efficient, which is conducive to realizing the long-term stability of the cool performance.

[0006] To achieve the above purpose, the technical solution adopted by the present application is: a preparation method of a cool polypropylene fiber, comprising the following steps:

[0007] S1, mixing polypropylene 75-88 parts, polyethylene 10-15 parts, cool additive 13-21 parts, dispersing agent 0.8-2.5 parts, reinforcing agent 2-3 parts and anti-aging agent 0.5-1 parts, then melt blending and extruding, and cooling to obtain a silk thread;

[0008] S2, the yarn is subjected to multi-stage drafting and relaxation heat setting to obtain the cool polypropylene fiber;

[0009] The cool auxiliary agent comprises nano mica powder, modified zinc oxide and peppermint microcapsule.

[0010] The mass ratio of the nano mica powder, the modified zinc oxide and the peppermint microcapsule in the cool auxiliary agent is (8-12):(3-5):(2-4).

[0011] The structure of the anti-aging agent is shown in formula 1.

[0012] Formula 1: ;

[0013] R1 in formula 1 is a substituent, and R1 is selected from any one of a methyl group, a carboxyl group, an amino group, a methoxy group and a nitro group.

[0014] Further, the anti-aging agent is any one of the compounds shown in the following structures:

[0015] 、

[0016] 、

[0017] 、

[0018] .

[0019] Further, the melt index of the polypropylene is 20-30 g / 10min.

[0020] Further, the polyethylene is linear low-density polyethylene.

[0021] Further, the preparation method of the modified zinc oxide comprises the following steps:

[0022] (1) The nano zinc oxide powder is cleaned with deionized water or ethanol to remove surface impurities, and is dried at 60-80℃ for standby;

[0023] (2) The silane coupling agent KH-570 is diluted with ethanol to a mass fraction of 1%-5%, and the pH is adjusted to 4-6;

[0024] (3) The pretreated zinc oxide is added to the coupling agent solution, stirred at 50-70℃ for 1-2 hours, and assisted with ultrasonic dispersion (power 300-500W) to ensure uniform coating of the coupling agent;

[0025] (4) The coupling agent-coated zinc oxide is filtered and vacuum dried at 80-100℃ to obtain the modified zinc oxide.

[0026] Further, the preparation method of the peppermint microcapsule comprises the following steps:

[0027] (1) Mix peppermint oil and Tween 80 in proportion, add deionized water; emulsify with a high-speed homogenizer or ultrasonic equipment to form a stable water-in-oil emulsion;

[0028] (2) Select wall material gelatin and gum arabic mixed in a mass ratio of 1:1, dissolve them in deionized water, and stir until completely transparent; slowly drop the above emulsion into the wall material solution, adjust the pH value of the system to 3-5, heat to 50-70℃, and keep stirring for 1-3h to make the wall material in-situ polymerize on the surface of the core material particles to form a capsule wall;

[0029] (3) Heat to 80-90℃, add 10% formaldehyde solution, continue stirring for 1-2h to crosslink and solidify the capsule wall; stop heating, cool to room temperature, repeatedly centrifuge the microcapsule with deionized water to remove unreacted wall material and emulsifier, and place the washed microcapsule in an oven to dry at 40-60℃ to obtain peppermint microcapsule.

[0030] Further, the dispersant comprises polyethylene wax and titanate coupling agent, and the mass ratio of the polyethylene wax and the titanate coupling agent is (0.5~1.5):(0.3~0.8).

[0031] Further, the reinforcing agent comprises fumed nanosilica.

[0032] Further, the process parameters of melt blending extrusion are as follows: the temperature of the first screw zone is 210~220℃, the temperature of the second screw zone is 220~230℃, the temperature of the third screw zone is 230~250℃, the temperature of the fourth screw zone is 250~260℃, the temperature of the fifth screw zone is 250~260℃, and the temperature of the sixth screw zone is 240~250℃.

[0033] Further, the screw rotation speed is 60~80rpm.

[0034] Further, the cooling condition is as follows: the side blowing temperature is 20~25℃, the relative humidity is 60%~70%, and the wind speed is 0.8~1.2m / s.

[0035] Further, the multi-stage drafting comprises primary drafting and secondary drafting, the drafting multiple of the primary drafting is 2.0~2.5 times, and the temperature is 85~95℃, the drafting multiple of the secondary drafting is 1.5~1.8 times, and the temperature is 90~100℃.

[0036] Further, the relaxation heat setting condition is as follows: hot air treatment at 120~130℃ for 5~10min.

[0037] A cool feeling polypropylene fiber is prepared by the above preparation method.

[0038] The core mechanism of the anti-aging agent molecule described in the present application is to act as an antioxidant, delay the thermal oxidative degradation of polypropylene fibers by capturing and eliminating free radicals, thereby ensuring the durability of the cool feeling effect and prolonging the service life of the fibers. The essence of the aging of polypropylene fibers is free radical chain reaction. During processing or use, the molecular chain is easily broken to generate active free radicals, which continuously attack adjacent molecular chains, resulting in a decrease in the mechanical properties of the fibers and the failure of the cool feeling aid. The anti-aging agent molecule contains a key active group, a phenolic hydroxyl group,

[0039] The hydrogen atom in the phenolic hydroxyl group is easily taken by active free radicals to generate stable phenolic oxygen radicals. The captured active free radicals are converted into stable neutral molecules, directly interrupting the transmission of the free radical chain reaction and inhibiting the degradation of the fiber molecular chain from the source. During the aging of polypropylene, peroxide is an important inducer of secondary aging. Peroxide is easily decomposed under the action of heat / light to generate new active free radicals. The anti-aging agent can react with peroxide through a hydrogen transfer reaction. The phenolic hydroxyl group of the anti-aging agent molecule provides hydrogen atoms to peroxide, reducing it to a stable alcohol compound, while itself being regenerated as a phenolic oxygen radical to continue to participate in free radical capture, avoid the decomposition of peroxide to generate new free radicals, block the aging cycle, and further enhance the anti-aging durability of the fibers.

[0040] The present application realizes the goal of long-acting and stable cooling through a delicate synergistic mechanism. The synergy within the cooling aid system: the cooling aid is compounded by nano-mica powder, modified zinc oxide, and peppermint microcapsules in a specific ratio, forming a multi-level and multi-mechanism cooling system. Nano-mica powder, as the basic cooling material, can quickly absorb the heat on the surface of the skin and dissipate it due to its excellent thermal conductivity, providing immediate and physically stable heat conduction cooling. Peppermint microcapsules enhance the cooling effect. When the fiber contacts the skin, the microcapsules rupture and release menthol oil, which volatilizes and carries away heat, while activating the skin's cold receptors, producing a significant instantaneous cooling sensation. Modified zinc oxide plays a dual role in this system. On the one hand, as a good heat-conducting material, it assists mica powder in enhancing the overall fiber's thermal conductivity; on the other hand, it can provide antibacterial properties, inhibiting bacterial growth and providing a clean and stable internal environment for the cooling aid, indirectly ensuring the durability of the cooling effect. The synergy between the base resin and the aid system: the addition of polyethylene, blended with polypropylene, improves the flexibility and processability of polypropylene. This ensures that the melt still has good flowability even with a high proportion of cooling aid, allowing the aid to be more evenly dispersed in the fiber, avoiding hot spots or performance defects caused by uneven dispersion. The specific dispersant directly acts on the cooling aid, especially the inorganic filler, preventing its agglomeration and ensuring its nanoscale dispersion in the hydrophobic polypropylene matrix, thereby maximizing its thermal conductivity and functional effect. The synergy between functional additives and the overall structure: antioxidants are one of the core components of long-acting cooling. Polypropylene fibers are prone to thermal oxidative degradation during processing and use, leading to molecular chain breakage, reduced fiber strength, and failure of the embedded cooling aid due to matrix damage. Antioxidants effectively delay the aging of the polypropylene matrix by capturing free radicals and decomposing peroxides, ensuring the durability of the fiber structure carrying the cooling aid, allowing the cooling effect to be maintained for a long time. The reinforcing agent not only improves the mechanical strength of the fiber but also, to some extent, improves the dispersion stability of the cooling filler and enhances the overall density of the fiber, reducing the migration and loss of the aid.

[0041] Compared with the prior art, the present application has the following advantages:

[0042] 1. Significantly improve cooling performance: through the synergistic effect of inorganic and organic cooling agents, a more significant and lasting cooling experience can be provided. The inorganic cooling agent improves the thermal conductivity of the fiber, while the organic cooling agent further enhances the cooling effect by releasing menthol oil.

[0043] 2. Significantly enhance fiber stability and aging resistance: By adding anti-aging agents and reinforcing agents, the antioxidant performance and mechanical strength of the fiber are effectively improved, and the service life of the fiber is prolonged. Anti-aging agents can effectively inhibit the degradation of fiber molecular chains and prolong the service life of cooling aids, while reinforcing agents improve the overall density and tensile properties of the fiber, making it more suitable for long-term use. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions of the present application, the drawings used in the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0045] Figure 1 The nuclear magnetic chart of the anti-aging agent 1 described in the present application. DETAILED DESCRIPTION

[0046] The embodiments of the technical solutions of the present application will be described in detail below with reference to the drawings. The following examples are only used to more clearly illustrate the technical solutions of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0047] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the specification and claims of the present application and the above description of drawings are intended to cover non-exclusive inclusion.

[0048] Synthesis Example 1

[0049] Synthesis of anti-aging agent 1:

[0050] ;

[0051] First step: under nitrogen atmosphere, 10.00 g of compound 1, 7.49 g of compound 2, 7.38 g of sodium tert-butoxide, 0.35 g of tris (dibenzylideneacetone) dipalladium, 0.39 g of tri-tert-butyl phosphine and 150 ml of toluene solution were added into the reaction system, stirred uniformly, heated to 120℃, refluxed for 12 h; after the reaction was completed, the temperature was slightly lowered, diatomite was used for filtration to remove the salt and catalyst, the filtrate was cooled to room temperature, washed with water for three times, the organic phase was reserved, the water phase was extracted with ethyl acetate, the combined organic phase was dried with anhydrous magnesium sulfate, and the solvent was removed using a rotary evaporator; rotary evaporation, column chromatography, using petroleum ether and ethyl acetate mixture as eluent, rotary evaporation, 10.59 g of compound 3 was obtained. Mass spectrum MS [M+H] of compound 3: + : 375.

[0052] ;

[0053] Second step: under nitrogen atmosphere, 10.59 g of compound 3, 8.93 g of compound 4 and 150 mL of dioxane / diisopropylamine (100 mL / 50 mL) mixed solvent were added into the reaction system, stirred until uniformly dispersed, 0.06 g of palladium acetate, 0.28 g of tri-tert-butyl phosphine and 0.27 g of CuI were added, heated to 90℃, stirred for 6 h, the solvent was rotary evaporated, and column chromatography was performed on silica gel (using petroleum ether and ethyl acetate mixture as eluent), rotary evaporation, 12.89 g of antioxidant 1 was obtained. Mass spectrum MS [M+H] of antioxidant 1: + : 654, the nuclear magnetic resonance of antioxidant 1 is shown in Figure 1 .

[0054] Synthesis examples 2-4

[0055] Antioxidants 2-4 were synthesized in synthesis examples 2-4 in turn, referring to the synthesis method of synthesis example 1, compound 2 therein was replaced, and the rest was the same as synthesis example 1. The specific is shown in table 1.

[0056] Table 1.

[0057]

[0058] Example 1

[0059] Preparation of a cool feeling polypropylene fiber:

[0060] 1. Preparation of modified zinc oxide:

[0061] (1) The nano zinc oxide powder was washed with deionized water for three times to remove the surface impurities, and then dried in a 70℃ oven for standby use;

[0062] (2) Silane coupling agent KH-570 was diluted with ethanol to a mass fraction of 3%, and acetic acid was used to adjust the pH to 5.0;

[0063] (3) The pretreated zinc oxide was added to the coupling agent solution, stirred at 60°C for 1.5 hours, and assisted with ultrasonic dispersion (power 400W) to ensure uniform coating of the coupling agent;

[0064] (4) The coupling agent-coated zinc oxide was filtered and vacuum dried at 90°C for 6 hours to obtain modified zinc oxide.

[0065] 2. Preparation of peppermint microcapsules:

[0066] (1) Peppermint oil and Tween 80 were mixed at a mass ratio of 10:1, deionized water was added, and a high-speed homogenizer (10000 rpm) was used for emulsification for 10 minutes to form a stable water-in-oil emulsion;

[0067] (2) Gelatin and gum arabic were mixed at a mass ratio of 1:1 and dissolved in deionized water, and stirred until completely transparent; the above emulsion was slowly added to the wall material solution, the pH of the system was adjusted to 4.0, and the temperature was raised to 60°C, and stirred for 2 hours to allow the wall material to polymerize in situ on the surface of the core material particles to form a capsule wall;

[0068] (3) The temperature was raised to 85°C, 10% formaldehyde solution was added, and stirring was continued for 1.5 hours to allow the capsule wall to crosslink and solidify; the heating was stopped, and the temperature was cooled to room temperature; the microcapsules were washed repeatedly by centrifugation (centrifugal speed 3000 rpm, 5 minutes each time) three times with deionized water to remove unreacted wall material and emulsifiers, and then the microcapsules were dried in an oven at 50°C for 6 hours to obtain peppermint microcapsules.

[0069] 3. Preparation of cool-feeling polypropylene fibers:

[0070] 3.1. Raw material formula:

[0071] Polypropylene: 80 parts, purchased from Tianjin Xinsisheng Biotechnology Co., Ltd.;

[0072] Polyethylene: 12 parts, which is linear low-density polyethylene, purchased from Guangzhou Jinfeng Biological Technology Co., Ltd.;

[0073] Cooling aid: 17 parts, including 10 parts of nano-mica powder (purchased from Wuhan Jiyesheng Chemical Co., Ltd.), 4 parts of modified zinc oxide, and 3 parts of peppermint microcapsules;

[0074] Dispersing agent: 1.5 parts, including 1.0 part of polyethylene wax (purchased from Guangdong Taili New Material Technology Co., Ltd.) and 0.5 part of titanate coupling agent (purchased from Shenzhen Xingkeyue Biological Technology Co., Ltd.);

[0075] Reinforcing agent: 2.5 parts, fumed nano-silica, purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0076] Anti-aging agent: 0.8 parts, anti-aging agent 1 synthesized in Synthesis Example 1.

[0077] 3.2, Preparation method:

[0078] S1, the polypropylene, polyethylene, cool auxiliary agent, dispersing agent, reinforcing agent and anti-aging agent are premixed, then added into a twin-screw extruder for melt blending and extrusion, the extrusion process parameters are: screw first zone temperature 215℃, screw second zone temperature 225℃, screw third zone temperature 240℃, screw fourth zone temperature 255℃, screw fifth zone temperature 255℃, screw sixth zone temperature 245℃; the screw rotation speed is 70 rpm; after extrusion, the filaments are cooled by a cooling device, the cooling conditions are: side blowing temperature 23℃, relative humidity 65%, air speed 1.0 m / s, to obtain filaments;

[0079] S2, the filaments are subjected to multi-stage drawing and relaxation heat setting, first-stage drawing: drawing multiple 2.2 times, temperature 90℃; second-stage drawing: drawing multiple 1.6 times, temperature 95℃; relaxation heat setting: hot air treatment at 125℃ for 7 minutes, to obtain a cool polypropylene fiber.

[0080] Examples 2-4

[0081] In Examples 2-4, a cool polypropylene fiber is prepared in turn, referring to the preparation method of Example 1, the anti-aging agent 1 therein is replaced by anti-aging agents 2-4 in turn, and the rest remains the same as Example 1.

[0082] Comparative Example 1

[0083] A cool polypropylene fiber is prepared, referring to the preparation method of Example 1, the anti-aging agent therein is replaced by anti-aging agent DTPD, and the rest remains the same as Example 1.

[0084] Comparative Example 2

[0085] A cool polypropylene fiber is prepared, referring to the preparation method of Example 1, the anti-aging agent therein is replaced by , CAS: 34579-90-3, and the rest remains the same as Example 1.

[0086] Comparative Example 3

[0087] A cool polypropylene fiber is prepared, referring to the preparation method of Example 1, without adding the anti-aging agent therein, and the rest remains the same as Example 1.

[0088] Comparative Example 4

[0089] The preparation of a cooling polypropylene fiber is carried out according to the preparation method of Example 1, except that the dispersant is not added, and the rest is the same as in Example 1.

[0090] Comparative Example 5

[0091] The preparation of a cooling polypropylene fiber is carried out according to the preparation method of Example 1, without the addition of the reinforcing agent, and otherwise remains the same as in Example 1.

[0092] Performance testing:

[0093] 1. Instant cooling sensation test upon contact:

[0094] According to GB / T 35263-2017 "Test and Evaluation Standard for Instant Cooling Performance of Textiles Upon Contact", the instant cooling performance of each group of samples was tested. The results are shown in Table 2.

[0095] 2. Fracture strength test:

[0096] The tensile strength of each group of samples was tested according to GB / T 14344-2022 "Test Method for Tensile Properties of Chemical Fiber Filaments". The results are shown in Table 2.

[0097] 3. Elongation at break test:

[0098] The elongation at break of each group of samples was tested according to GB / T 14344-2022 "Test Method for Tensile Properties of Chemical Fiber Filaments". The results are shown in Table 2.

[0099] 4. Aging resistance test:

[0100] According to GB / T 8427-2019 "Textiles - Tests for color fastness to artificial light: Xenon arc", aging tests were conducted on each group of samples. Then, the retention rate of breaking strength (breaking strength after aging / breaking strength before aging × 100%) was tested according to GB / T 14344-2022 standard. The results are shown in Table 2.

[0101] Aging treatment: The fiber fabric was placed in a xenon lamp aging chamber under the following conditions: irradiance 0.89 W / (m²). 2 ·nm) (340nm), blackboard temperature 42℃, relative humidity 65%, aging time 2000h.

[0102] Table 2.

[0103]

[0104] According to the data trends in Table 2, the cool-feeling polypropylene fibers in the examples employing the specific antioxidant and auxiliary system of the present application show stable improvement in cool-feeling durability, antibacterial performance and fiber mechanical strength compared to the comparative examples. In contrast, the samples in the comparative examples omitting key ingredients (such as antioxidants, dispersants or reinforcing agents) or replacing them with conventional auxiliaries show a faster decay of cool-feeling effect, a decline in antibacterial performance and a weakening of fiber durability. In addition, the synergistic effect of the examples ensures uniform dispersion of the cool-feeling auxiliary and stability of the fiber structure, while the comparative examples show uneven performance or accelerated aging due to missing ingredients or improper collocation. Overall, the present application shows a positive trend in maintaining long-acting cool feeling and comprehensive performance.

[0105] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exerting the same effects within the scope of the technical solution of the present application are all included in the technical scope of the present application. Furthermore, within the scope of the gist of the present application, other modes obtained by applying various modifications that can be thought of by those skilled in the art to the embodiments or by combining part of the constituent elements of the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing a cooling polypropylene fiber, characterized in that, Includes the following steps: S1. Mix 75-88 parts of polypropylene, 10-15 parts of polyethylene, 13-21 parts of cooling agent, 0.8-2.5 parts of dispersant, 2-3 parts of reinforcing agent and 0.5-1 parts of antioxidant, then melt-blend and extrude, and obtain filaments after cooling; S2. Cool-feeling polypropylene fiber is obtained by subjecting the filaments to multi-stage stretching and relaxation heat setting. The cooling aids include nano-mica powder, modified zinc oxide, and menthol microcapsules; The mass ratio of nano-mica powder, modified zinc oxide, and menthol microcapsules in the cooling agent is (8~12):(3~5):(2~4); The structure of the antioxidant is shown in Formula 1: Formula 1: ; R1 in Formula 1 is a substituent, and R1 is selected from any one of methyl, carboxyl, amino, and methoxy groups.

2. The method for preparing a cooling polypropylene fiber according to claim 1, characterized in that, The antioxidant is any one of the compounds shown in the following structures: 、 、 、 。 3. The method for preparing a cooling polypropylene fiber according to claim 1, characterized in that, The melt index of the polypropylene is 20~30 g / 10min; The polyethylene is linear low-density polyethylene.

4. The method for preparing a cooling polypropylene fiber according to claim 1, characterized in that, The method for preparing the modified zinc oxide includes the following steps: (1) Clean the nano zinc oxide powder with deionized water or ethanol to remove surface impurities, and dry it at 60~80℃ for later use. (2) Dilute the silane coupling agent KH-570 with ethanol to a mass fraction of 1%~5% and adjust the pH to 4~6; (3) Add the pretreated zinc oxide to the coupling agent solution and stir at 50~70℃ for 1~2 hours, and assist in ultrasonic dispersion to ensure uniform coating of the coupling agent; (4) The zinc oxide coated with coupling agent is filtered and vacuum dried at 80~100℃ to obtain modified zinc oxide.

5. The method for preparing a cooling polypropylene fiber according to claim 1, characterized in that, The preparation method of the peppermint microcapsules includes the following steps: (1) Mix peppermint oil and Tween 80 in a certain proportion, add deionized water; emulsify with a high-speed homogenizer or ultrasonic equipment to form a stable water-in-oil emulsion; (2) Select wall material gelatin and gum arabic in a mass ratio of 1:1, dissolve them in deionized water, and stir until completely transparent; slowly drip the above emulsion into the wall material solution, adjust the pH value of the system to 3-5, raise the temperature to 50-70℃, keep warm and stir for 1-3 hours, so that the wall material is polymerized in situ on the surface of the core material particles to form the capsule wall. (3) Heat to 80-90℃, add 10% formaldehyde solution, continue stirring for 1-2 hours to allow the capsule wall to crosslink and solidify; stop heating, cool to room temperature, repeatedly centrifuge and wash the microcapsules with deionized water to remove unreacted wall material and emulsifier, put the washed microcapsules into an oven and dry at 40-60℃ to obtain peppermint microcapsules.

6. The method for preparing a cooling polypropylene fiber according to claim 1, characterized in that, The dispersant comprises polyethylene wax and titanate coupling agent, wherein the mass ratio of polyethylene wax to titanate coupling agent is (0.5~1.5):(0.3~0.8); The reinforcing agent includes fumed nano-silica.

7. The method for preparing a cooling polypropylene fiber according to claim 1, characterized in that, The process parameters for the melt blending extrusion are as follows: the temperature of the first screw zone is 210~220℃, the temperature of the second screw zone is 220~230℃, the temperature of the third screw zone is 230~250℃, the temperature of the fourth screw zone is 250~260℃, the temperature of the fifth screw zone is 250~260℃, and the temperature of the sixth screw zone is 240~250℃. The screw speed is 60~80 rpm.

8. The method for preparing a cooling polypropylene fiber according to claim 1, characterized in that, The cooling conditions are: side-blowing air temperature 20~25℃, relative humidity 60%~70%, and wind speed 0.8~1.2 m / s.

9. The method for preparing a cooling polypropylene fiber according to claim 1, characterized in that, The multi-stage drawing includes primary drawing and secondary drawing. The primary drawing has a drawing ratio of 2.0 to 2.5 times and a temperature of 85 to 95°C. The secondary drawing has a drawing ratio of 1.5 to 1.8 times and a temperature of 90 to 100°C. The relaxation heat setting conditions are: hot air treatment at 120~130℃ for 5~10 minutes.

10. A cooling polypropylene fiber, characterized in that, It is prepared by any one of the preparation methods described in claims 1 to 9.

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