High-strength polypropylene short fiber for cool cloth and preparation method of high-strength polypropylene short fiber

Abstract

The invention discloses a high-strength polypropylene fiber short fiber for cool cloth and a preparation method of the high-strength polypropylene fiber short fiber, and relates to the technical field of polymer artificial filaments and analogues. The high-strength polypropylene short fiber is prepared from the following raw materials in parts by mass: 100 parts of polypropylene resin, 0.1-1 part of a nucleating agent, 0.2-0.8 part of an inorganic filler, 0.5-2 parts of a processing aid, 3-6 parts of a plasticizer, 1-5 parts of a lubricant and 0.5-2 parts of a weather-resistant flame retardant. Compared with the prior art that the polypropylene fiber short fiber is easy to age and fast in performance attenuation in a complex environment, the polypropylene fiber short fiber prepared by the invention has the advantages that the weather-resistant stability is obviously improved, and the performance reduction trend caused by aging after long-term use is obviously slowed down.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of polymer artificial filaments and the like, in particular to a high-strength polypropylene staple fiber for cool cloth and a preparation method thereof. BACKGROUND

[0002] Polypropylene staple fiber has become one of the core raw materials for cool cloth preparation due to its advantages of light weight, high breaking strength, good chemical stability, and controllable cost, and is widely used in outdoor sunshade cool cloth, indoor decorative cool cloth, industrial filter cool cloth, and vehicle interior trim cool cloth scenes. However, as the application environment of cool cloth becomes more complex, the shortcomings of existing polypropylene staple fibers in weather resistance and long-term flame retardance are increasingly prominent, becoming a key bottleneck restricting their performance upgrade.

[0003] From the perspective of weather resistance, polypropylene molecular chains do not contain anti-aging functional groups, and are prone to thermal oxidative aging and photo-oxidative degradation under outdoor ultraviolet radiation, high temperature and humidity, or alternating cold and hot environments, resulting in fiber molecular chain breakage and decreased crystallinity. Specifically, during the use of cool cloth, problems such as yellowing of the cloth surface, fiber embrittlement, and tear strength attenuation occur, for example, after 1-2 years of natural exposure, the breaking strength of outdoor sunshade cool cloth often loses more than 30%, and the cloth surface is prone to damage, making it unable to continue to play a protective role. Even decorative cool cloth used indoors is prone to fiber relaxation and cloth surface deformation due to insufficient weather resistance in a long-term air conditioning cold and hot cycle environment.

[0004] In terms of flame retardance, existing polypropylene staple fibers for cool cloth mostly rely on traditional added flame retardants, which can temporarily meet basic flame retardance standards, but have significant long-term performance defects: such flame retardants have poor compatibility with the polypropylene matrix, and are prone to migration and precipitation from the fiber interior over time with changes in temperature and humidity, resulting in gradual degradation of flame retardant effect, for example, the limiting oxygen index of industrial filter cool cloth often decreases after 6 months of continuous use, failing to meet the requirement for continuous flame retardance. At the same time, some flame retardants also have an antagonistic effect with weather resistance additives, making it difficult to synergistically improve performance after addition, and possibly accelerating fiber aging and further deteriorating weather resistance stability.

[0005] Currently, as cool cloth develops towards high-end and multifunctionalization, such as outdoor durability decoration, rail transit interior trim, and other scenes, higher requirements are placed on the weathering life and long-term flame retardance of the material, and existing polypropylene staple fibers cannot meet these requirements. Therefore, developing polypropylene staple fibers for cool cloth with excellent weather resistance and long-term flame retardance has become a technical problem that needs to be solved in the field. SUMMARY

[0006] The present application aims to solve the problems of poor weather resistance, insufficient long-term flame retardancy of polypropylene staple fiber for cool cloth in the prior art, poor compatibility of traditional flame retardants with polypropylene matrix, easy migration, and possible antagonism with weather resistance additives, and provides a high-strength polypropylene staple fiber for cool cloth with excellent weather resistance, long-term flame retardancy and high strength, which can adapt to multiple scenes of cool cloth and meet the high-end demand of cool cloth.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is: a high-strength polypropylene staple fiber for cool cloth, which is prepared from raw materials including the following components by mass: polypropylene resin 100 parts, nucleating agent 0.1-1 part, inorganic filler 0.2-0.8 part, processing aid 0.5-2 part, plasticizer 3-6 part, lubricant 1-5 part, weather-resistant flame retardant 0.5-2 part; The weather-resistant flame retardant is a compound represented by formula 1: The structure of formula 1 is: ; R1 in formula 1 is a substituent, and R1 is selected from any one of hydrogen, methyl, ethyl, methoxy, and cyano.

[0008] Further, the nucleating agent is selected from any one of dibenzyl sorbitol, p-methyl dibenzyl sorbitol, 2,4-di(3,4-dimethyl)benzyl sorbitol, and N,N'-dicyclohexyl-2,6-naphthalene dicarboxamide.

[0009] Further, the inorganic filler is selected from silicon dioxide.

[0010] Further, the processing aid is selected from any one of calcium stearate, zinc stearate, ethylene bis-stearamide, and stearic acid amide.

[0011] Further, the plasticizer is selected from any one of phthalate, epoxy soybean oil, citrate, and phosphate.

[0012] Further, the lubricant is selected from any one of ethylene wax and polyethylene wax.

[0013] Further, the weather-resistant flame retardant is selected from any one of the compounds represented by the following structures: ; ; .

[0014] Further, the weather-resistant flame retardant has the dual functions of weather resistance and flame retardancy.

[0015] Further, the high-strength polypropylene staple fiber for cool cloth can further add polyimide.

[0016] The application discloses a preparation method of high-strength polypropylene short fiber for cool cloth, which comprises the following steps: S1. Mixing: the polypropylene resin, nucleating agent, inorganic filler, processing aid, plasticizer, lubricant and weather-resistant flame retardant are added into a high-speed mixer and mixed for 15-40 minutes to obtain a mixture; S2. Melt extrusion granulation: the mixture is melt blended, extruded, cooled and granulated through a double-screw extruder to obtain polypropylene masterbatch; S3. Spinning: the polypropylene masterbatch is conveyed to a spinning machine for melt spinning, and primary fibers are formed through metering and spinneret extrusion; S4. Drafting and setting: the primary fibers are subjected to multi-stage hot drafting and relaxation heat setting to obtain the high-strength polypropylene short fiber for cool cloth.

[0017] Further, the processing temperature of the double-screw extruder is 180-250 DEG C.

[0018] Further, the spinning temperature is 230-265 DEG C.

[0019] Further, the S1 is carried out under a nitrogen atmosphere.

[0020] Further, the multi-stage hot drafting in the S4 is specifically as follows: First-stage drafting: carried out in a 40-60 DEG C water bath, and the drafting multiple is 2.5-3.5 times; Second-stage drafting: carried out in 95-105 DEG C hot air or steam, and the drafting multiple is 1.5-2.0 times; The total drafting multiple is controlled to be 4.0-6.0 times.

[0021] Further, the relaxation heat setting in the S4 is carried out at a temperature of 110-130 DEG C for 5-15 minutes.

[0022] The design core of the weather-resistant flame retardant molecule is to integrate the weather-resistant function and the flame-retardant function in a single molecule through chemical bonds, and the synergistic mechanism is as follows: as the main antioxidant, the phenolic hydroxyl group -OH efficiently captures and terminates the alkyl peroxide free radical ROO· generated by thermal oxidative aging by providing hydrogen atoms, and converts it into stable hydroperoxide ROOH, and the aryl oxygen free radical generated by itself is highly stable due to the electron delocalization effect of the adjacent large conjugate structure, thereby effectively interrupting the oxidative chain reaction of the polymer, and imparting excellent thermal oxidative aging resistance to the material; the large conjugate structure simultaneously acts as an ultraviolet light absorbing group, absorbs ultraviolet light energy and converts it into harmless heat energy, provides light aging protection for polypropylene fibers, and significantly enhances the thermal stability and structural rigidity of the whole molecule, reduces volatilization and migration, and ensures the long-acting nature of the efficacy; and the phosphonate diethyl group acts as a flame-retardant functional center, which decomposes to produce strong dehydrating phosphorus-containing species when heated, catalyzes polypropylene to dehydrate and carbonize in the condensed phase, forms a dense carbon layer with heat and oxygen insulation effect, thereby physically retarding the combustion process, and partially generates PO· free radicals in the gas phase to capture highly active H· and OH· free radicals, assisting in interrupting the combustion chain reaction. This integrated design in the molecule fundamentally avoids the problems of poor compatibility, mutual antagonism and easy migration and precipitation of physical blending additives, so that the weather-resistant component can continuously protect the integrity of the polypropylene molecular chain during processing and long-term use, lay the foundation for forming a solid carbon layer in the early stage of fire, and the flame-retardant component provides immediate fire protection, ultimately achieving the unity of high strength, long-acting weather resistance and persistent flame retardance of the polypropylene short fiber.

[0023] The present application successfully solves the three technical problems of poor weather resistance of polypropylene fiber, difficult to maintain flame retardancy and easy migration of traditional flame retardant and mutual antagonism with weathering aid through the systematic solution of "core function integration and multi-component synergy": the core innovation is to use a specially designed weather-resistant flame retardant, which is not a physical blend, but a single molecule integrating the phenolic hydroxyl group / big conjugated structure (weathering function) and phosphonate group (flame retardant function) that promotes carbonization through chemical bonds, which fundamentally inhibits component migration and precipitation, ensuring the long-term effectiveness of flame retardancy and weather resistance, and avoiding the common functional antagonism problem in physical blending; nucleating agents synergistically improve fiber strength by refining grain size, and inorganic fillers act as reinforcing agents and synergistically form a dense carbon layer with weather-resistant flame retardants in the condensed phase, further enhancing flame retardant efficiency and mechanical properties; and processing aids / lubricants and plasticizers ensure the processing flowability and fiber flexibility under high filling system; in addition, on the polypropylene resin matrix, through nitrogen protection mixing, precise control of extrusion spinning temperature, and multi-stage heat stretching and relaxation heat setting process, the structural integrity of the functional components and their uniform dispersion and directional crystallization in the fiber are ensured, ultimately preparing high-end polypropylene staple fibers with high strength, excellent long-term weather resistance and persistent flame retardancy.

[0024] Compared with the prior art, the present application has the following advantages: 1. Better weather stability: compared with the polypropylene staple fiber in the prior art which is prone to aging and performance degradation in complex environments, the weather stability of the polypropylene staple fiber prepared by the present application is significantly improved, and the performance decline trend due to aging after long-term use is significantly slowed down.

[0025] 2. Better long-term flame retardancy: the present application overcomes the defects of traditional flame retardants in the prior art, such as easy migration, flame retardant effect decay with use time, and possible antagonism with weathering aids, and the flame retardant effect of the polypropylene staple fiber of the present application can be maintained for a long time without mutual interference between flame retardant and weather resistance performance.

[0026] 3. Strength performance is more guaranteed: the present application avoids the problem that the addition of multiple aids in the prior art may have a negative impact on the strength of the fiber, and at the same time realizes excellent weather resistance and long-term flame retardancy, and can stably maintain or even improve the strength performance of the polypropylene staple fiber, meeting the use demand of high strength of denim. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is the nuclear magnetic chart of the weather-resistant flame retardant 1 of the present application.

[0028] Figure 2 It is the nuclear magnetic chart of the weather-resistant flame retardant 4 of the present application. DETAILED DESCRIPTION

[0029] The technical solutions of the present application will be clearly and completely described below with reference to the drawings in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of the present application.

[0030] Preparation Example 1 Preparation of weather-resistant flame retardant 1: ; Under the protection of nitrogen, 10 g of compound 1, 16.81 g of compound 2, 9.85 g of sodium tert-butyl alcohol and 140 ml of toluene were sequentially added into the reaction system, and after being stirred uniformly, 2.35 g of tris(dibenzylideneacetone) palladium and 0.51 g of tri-tert-butyl phosphine were added, and after being stirred uniformly, the temperature was increased to 110°C and refluxed for 10 h; after the reaction was completed, hot silica gel soil was used for filtration, anhydrous magnesium sulfate was used for drying, a rotary evaporator was used for removing the solvent, and silica gel column chromatography was used for purification, and a mixture of petroleum ether and ethyl acetate was used as an eluent to obtain 15.68 g of compound 3, and the mass spectrum M / Z MS+1 of compound 3 was 388.

[0031] ; Under the protection of nitrogen, 15.68 g of compound 3, 9.07 g of compound 4, 11.18 g of anhydrous potassium carbonate and 200 ml of toluene were sequentially added into the reaction system, and after being stirred uniformly, nitrogen was replaced twice, and under the protection of nitrogen, 2.34 g of tetrakis(triphenylphosphine)palladium was added into the system, and nitrogen was replaced twice, and heated to 105°C and refluxed for 10 h, and after the reaction was completed, filtration was performed, a rotary evaporator was used for removing the solvent, and silica gel column chromatography was used for purification, and a mixture of petroleum ether and ethyl acetate was used as an eluent to obtain 16.03 g of weather-resistant flame retardant 1, and the mass spectrum M / Z MS+1 of weather-resistant flame retardant 1 was 494, and the nuclear magnetic resonance was as follows: Figure 1 .

[0032] Preparation Example 2-Preparation Example 5 Weather-resistant flame retardants 2-5 were sequentially prepared in Preparation Examples 2-5, and the preparation method of Preparation Example 1 was referred to, and compound 4 therein was replaced, and the rest was the same as Preparation Example 1, and specific reference was made to Table 1.

[0033] Table 1.

[0034] Example 1

[0035] Preparation of a high-strength polypropylene short fiber for cool cloth: 1. Raw material components: Polypropylene resin: 100 parts, purchased from: China Petroleum Chemical Corporation, relative density is 0.90-0.91; Nucleating agent: 0.5 parts, selected from: dibenzyl benzyl sorbitol, purchased from: Shanghai Maikelin Biochemical Technology Co., Ltd.; Inorganic filler: 0.5 parts, selected from: silicon dioxide, purchased from: Jiangsu Puleisi Biological Technology Co., Ltd.; Processing aid: 1 part, selected from: calcium stearate, purchased from: Wuhan Jixin Yibang Biological Technology Co., Ltd.; Plasticizer: 4.5 parts, selected from: phthalate, purchased from: Shaanxi Liedu New Material Co., Ltd.; Lubricant: 3 parts, selected from: polyethylene wax, purchased from: Qingdao Bouni Chemical Co., Ltd., product model: Bouni ® 501; Weather-resistant flame retardant: 1 part, selected from: weather-resistant flame retardant 1.

[0036] 2. Preparation method: S1. Mixing: the above-mentioned polypropylene resin, nucleating agent, inorganic filler, processing aid, plasticizer, lubricant and weather-resistant flame retardant are added into a high-speed mixer, mixed for 30 minutes under the protection of nitrogen atmosphere, the mixing temperature is 45℃, to obtain a mixture; S2. Melt extrusion granulation: the mixture is put into the feeding hopper of a double screw extruder, and the extruder is started to melt blend. The temperature of each section of the double screw extruder is set as follows: feeding section 190℃, compression section 220℃, homogenization section 240℃, die head temperature 245℃, and the screw rotation speed is controlled at 180r / min; after the mixture is melt blended in the extruder for 15 minutes, a continuous strip-shaped melt is extruded from the die head; the strip-shaped melt is immediately cooled to room temperature in a normal temperature water bath (water temperature 25℃), and then conveyed to a granulator to cut into particles with a particle size of 2-3mm and a length of 2-2.5mm, i.e. a polypropylene master batch is obtained; S3. Spinning: the polypropylene master batch is first sent to a hot air dryer for pretreatment, the drying temperature is 90℃, the drying time is 3 hours, and the water adsorbed in the master batch is removed (moisture content ≤0.1%); the dried polypropylene master batch is conveyed to the hopper of a spinning machine, and the temperature of each section of the hopper is set according to the process requirements: feeding section 235℃, melting section 250℃, metering section 260℃, and spinneret temperature 262℃; after the master batch is melted in the hopper, the melt delivery amount is accurately controlled by a metering pump (rotation speed 25r / min), the melt is extruded through a spinneret (spinneret hole number 80, hole diameter 0.3mm) to form a continuous melt stream; the melt stream is immediately solidified by side blowing cooling (cooling air temperature 23℃, air speed 0.8m / s), and then wound up at a speed of 650m / min to obtain a nascent fiber; S4. Drafting setting: the as-spun fiber is subjected to multi-stage heat drafting and relaxation heat setting, the specific steps are as follows: first stage drafting: the as-spun fiber is introduced into a 50℃ water bath, and is subjected to drafting at a speed of 120 m / min under the action of a drafting machine, the drafting multiple is controlled to be 3.0 times, so as to preliminarily orient the fiber molecular chain; second stage drafting: the fiber subjected to the first stage drafting is sent into a hot air oven (the temperature is set to be 100℃), and is subjected to secondary drafting at a speed of 216 m / min, the drafting multiple is 1.8 times, the total drafting multiple reaches 5.4 times, so as to further improve the orientation degree and crystallinity of the fiber; relaxation heat setting: the fiber subjected to the multi-stage drafting is sent into a hot air setting machine, and is kept at a temperature of 120℃ for 10 minutes, during which the fiber relaxation rate is controlled to be 3%-5%, so as to eliminate the internal stress generated in the drafting process; after setting, the fiber is naturally cooled to room temperature, and finally is cut into staple fibers, so as to obtain the high-strength polypropylene staple fiber for cool cloth.

[0037] Examples 2-5 The preparation of the high-strength polypropylene staple fiber for cool cloth, referring to the preparation method of Example 1, the weather-resistant flame retardant 1 therein is sequentially replaced by weather-resistant flame retardants 2-5, and the rest remains the same as Example 1.

[0038] Comparative Example 1 The preparation of the high-strength polypropylene staple fiber for cool cloth, referring to the preparation method of Example 1, the weather-resistant flame retardant 1 therein is replaced by: tricresyl phosphate, and the rest remains the same as Example 1.

[0039] Comparative Example 2 The preparation of the high-strength polypropylene staple fiber for cool cloth, referring to the preparation method of Example 1, the weather-resistant flame retardant 1 therein is replaced by: antioxidant 1010, and the rest remains the same as Example 1.

[0040] Comparative Example 3 The preparation of the high-strength polypropylene staple fiber for cool cloth, referring to the preparation method of Example 1, the weather-resistant flame retardant 1 therein is replaced by: 0.5 parts of tricresyl phosphate + 0.5 parts of antioxidant 1010, and the rest remains the same as Example 1.

[0041] Comparative Example 4 The preparation of the high-strength polypropylene staple fiber for cool cloth, referring to the preparation method of Example 1, the weather-resistant flame retardant 1 therein is replaced by: 0.5 parts of tricresyl phosphate + 0.5 parts of antioxidant 1010, and the rest remains the same as Example 1.

[0042] Comparative Example 5 The preparation of the high-strength polypropylene staple fiber for cool cloth, referring to the preparation method of Example 1, the weather-resistant flame retardant 1 therein is not added, and the rest remains the same as Example 1.

[0043] Comparative Example 6 A high-strength polypropylene staple fiber for cool cloth was prepared according to the preparation method of Example 1, but without adding the nucleating agent therein, and the rest was kept the same as Example 1.

[0044] Performance test: Test sample: a high-strength polypropylene staple fiber for cool cloth prepared in the examples and comparative examples.

[0045] 1. Breaking strength: the breaking strength of the test sample was tested according to the test method of GB / T 14344-2008 “Chemical fiber-Test method for tensile properties of staple fibers”, and the data is shown in Table 2.

[0046] 2. Limiting oxygen index (LOI): the limiting oxygen index of the test sample was tested according to GB / T 2406.2-2009 “Plastics-Determination of the burning behavior in an oxygen environment-Part 2: Guidance on the test method at room temperature”, and the data is shown in Table 2.

[0047] 3. Weather resistance test: the test sample was placed in a fluorescent ultraviolet aging test box (equipped with a UVA-340 lamp tube, irradiation intensity 0.71 W / m 2 2. Limiting oxygen index (LOI): the limiting oxygen index of the test sample was tested according to GB / T 2406.2-2009 “Plastics-Determination of the burning behavior in an oxygen environment-Part 2: Guidance on the test method at room temperature”, and the data is shown in Table 2.

[0048] Table 2.

[0049] Breaking strength (cN / dtex) Limiting oxygen index (LOI, %) Breaking strength retention (%) Limiting oxygen index after aging (LOI, %) Example 1 5.3 30 96 30 Example 2 5.2 29 95 28 Example 3 5.4 31 97 31 Example 4 5.3 30 96 28 Example 5 5.2 29 95 29 Comparative Example 1 4.5 26 60 22 Comparative Example 2 4.3 19 76 13 Comparative Example 3 4.4 25 70 21 Comparative Example 4 4.6 27 73 22 Comparative Example 5 4.2 18 56 10 Comparative Example 6 3.6 30 92 28 The polypropylene staple fibers prepared in the examples using weather-resistant flame retardants (weather-resistant flame retardants 1-5) of different structures showed stable overall performance in the four core indicators of breaking strength, initial limiting oxygen index, breaking strength retention rate after aging, and limiting oxygen index after aging, without significant fluctuations. Compared with the comparative examples, the breaking strength of the examples was significantly better than that of the comparative examples using traditional flame retardants, single antioxidants, traditional flame retardants and antioxidants, and no weather-resistant flame retardants. Only the breaking strength of the comparative example without adding nucleating agent was slightly close to that of the example. The initial limiting oxygen index of the example was higher than that of the comparative examples using single antioxidants and no weather-resistant flame retardants, and was also better than that of the comparative examples using traditional flame retardants or their combination with antioxidants. The initial limiting oxygen index of the comparative example without adding nucleating agent was comparable to that of the example. The breaking strength retention rate of the example after aging was much higher than that of all the comparative examples. The limiting oxygen index of the example after aging basically maintained the initial level, while the limiting oxygen index of all the comparative examples after aging decreased to varying degrees, among which the comparative examples using single antioxidants and no weather-resistant flame retardants decreased significantly.

[0050] While embodiments of the application have been shown and described, it is to be understood that the embodiments described are merely exemplary of the principles and application of the present application. Numerous modifications and adaptions can be effected without departing from the spirit and scope of the present application, which is not limited to the exact construction and arrangement described. It is intended, therefore, to cover all modifications and adaptions that fall within the scope of the claims and their equivalents.

Claims

1. A high-strength polypropylene staple fiber for cool fabrics, characterized in that, It is prepared from raw materials containing the following parts by weight: 100 parts polypropylene resin, 0.1-1 parts nucleating agent, 0.2-0.8 parts inorganic filler, 0.5-2 parts processing aid, 3-6 parts plasticizer, 1-5 parts lubricant, and 0.5-2 parts weather-resistant flame retardant; The weather-resistant flame retardant is a compound represented by Formula 1: The structure of Equation 1 is as follows: ; In Formula 1, R1 is a substituent, and R1 is selected from any one of hydrogen, methyl, ethyl, methoxy, and cyano.

2. The high-strength polypropylene staple fiber for cool fabric as described in claim 1, characterized in that, The nucleating agent is selected from any one of the following: dibenzyl sorbitol, p-methyl dibenzyl sorbitol, 2,4-di(3,4-dimethyl)benzyl sorbitol, and N,N'-dicyclohexyl-2,6-naphthalenediamide.

3. The high-strength polypropylene staple fiber for cool fabric as described in claim 1, characterized in that, The inorganic filler is selected from silicon dioxide.

4. The high-strength polypropylene staple fiber for cool fabric as described in claim 1, characterized in that, The processing aid is selected from any one of the following: calcium stearate, zinc stearate, ethylene bis-stearamide, and stearamide.

5. The high-strength polypropylene staple fiber for cool fabric as described in claim 1, characterized in that, The plasticizer is selected from any one of the following: phthalates, epoxidized soybean oil, citrate, and phosphate esters.

6. The high-strength polypropylene staple fiber for cool fabric according to claim 1, characterized in that, The lubricant is selected from either ethylene wax or polyethylene wax.

7. The high-strength polypropylene staple fiber for cool fabric according to claim 1, characterized in that, The weather-resistant flame retardant is selected from any one of the compounds shown in the following structures: ； ； 。 8. A method for preparing a high-strength polypropylene staple fiber for cool fabric according to any one of claims 1-7, characterized in that, Includes the following steps: S1. Mixing: Add the polypropylene resin, nucleating agent, inorganic filler, processing aid, plasticizer, lubricant and weather-resistant flame retardant to a high-speed mixer and mix for 15-40 minutes to obtain a mixture; S2. Melt extrusion granulation: The mixture is melt-blended, extruded, cooled, and pelletized using a twin-screw extruder to obtain polypropylene masterbatch; S3. Spinning: The polypropylene masterbatch is fed to a spinning machine for melt spinning, and the nascent fibers are formed by metering and extrusion through a spinneret. S4. Stretching and setting: The nascent fiber is subjected to multi-stage hot stretching and relaxation heat setting to obtain the high-strength polypropylene short fiber for the fabric. The processing temperature of the twin-screw extruder is 180-250℃; The spinning temperature is 230-265℃; S1 is performed under a nitrogen atmosphere.

9. The method for preparing high-strength polypropylene staple fiber for cool fabric according to claim 8, characterized in that, The multi-stage thermal stretching mentioned in S4 specifically refers to: First stage of stretching: carried out in a warm water bath at 40-60℃, with a stretching ratio of 2.5-3.5 times; Second-stage drawing: carried out in hot air or steam at 95-105℃, with a drawing ratio of 1.5-2.0 times; The total draw ratio should be controlled between 4.0 and 6.

0.

10. The method for preparing high-strength polypropylene staple fiber for cool fabric according to claim 8, characterized in that, The relaxation heat setting temperature in S4 is 110-130℃, and the time is 5-15 minutes.

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