Phenolic-yellowing-resistant polypropylene staple fiber and preparation method thereof

Abstract

The invention discloses an anti-phenolic yellowing polypropylene staple fiber and a preparation method thereof, and belongs to the technical field of high-performance polypropylene, the preparation method comprises the following steps: reacting 2, 3-naphthalic anhydride with 1-methyl-1-phenylhydrazine to generate a ring-opening intermediate containing a naphthalene ring and hydrazide structure, and esterifying the ring-opening intermediate with compound fatty alcohol of hexadecanol and 2-octyldodecanol to obtain an anti-phenolic yellowing agent; the phenolic yellowing resistant agent is compounded with low-viscosity mineral white oil, caprylic capric triglyceride, polyethylene glycol fatty acid ester, polyisobutylene succinimide and lauryl phosphate monoester potassium salt to form an oil-based phenolic yellowing resistant functional agent, and the oil-based phenolic yellowing resistant functional agent is coated on the surface of a polypropylene fiber through a bundling oiling process. Compared with the prior art, the method has the advantages that double synergy of compact barrier and uniform covering is achieved, the anchoring capacity of the functional film is enhanced, the yellowing grade of the obtained polypropylene staple fiber phenol reaches 4.5 grade, the polypropylene staple fiber phenol is free of attenuation after being soaked in water, the breaking strength is larger than or equal to 4.5 cN / dtex, and the elongation at break is larger than or equal to 40%.

Description

Technical Field

[0001] This invention relates to the field of high-performance polypropylene technology, and in particular to a polypropylene staple fiber resistant to phenolic yellowing and its preparation method. Background Technology

[0002] Polypropylene staple fiber, with its advantages of low density, high mechanical strength, and excellent chemical resistance, is widely used in textile fabrics, home decoration, industrial fabrics, and automotive interiors. However, due to the lack of polar groups in the polypropylene molecular structure, the fiber is susceptible to yellowing under the influence of oxygen and nitrogen oxides in the high-temperature environment of melt spinning and during subsequent storage and use. This severely affects the quality of white and light-colored products. Therefore, resistance to phenolic yellowing has gradually become a key bottleneck restricting the upgrading of polypropylene staple fiber products.

[0003] Existing patent CN115747994A discloses an anti-phenolic yellowing polypropylene filament and its preparation method. It uses an anti-phenolic yellowing oil agent containing SOPE series emulsifiers, fatty acid polyethylene glycol esters, and sulfonated amphoteric surfactants in the oiling process, achieving a phenolic yellowing level of 4 or higher for the polypropylene filament. However, this technology is mainly applicable to continuous filament products, and its anti-yellowing function relies on the physical compounding of the oil agent components; the functional agent lacks chemical anchoring effect on the fiber substrate. Patent CN111663331A discloses a novel nylon anti-phenolic yellowing agent, which, through the compounding of isooctanol sulfate sodium salt, alcohol ether carboxylates, and other raw materials, achieves an anti-phenolic yellowing level of approximately 4.5 for the finished fabric. However, its application is limited to nylon fabrics, and this water-based finishing system cannot be directly adapted to the highly hydrophobic polypropylene fiber. The patent with publication number CN116023293A discloses a naphthalene ring nylon anti-yellowing agent, which uses 1,8-naphthalenedicarboxylic anhydride to react with unsymmetrical dimethylhydrazine to generate a ring-opening product containing carboxyl and hydrazide groups, which can effectively capture acidic yellowing substances. However, this technology is also aimed at nylon fabrics and mainly solves the problem of heat yellowing. Its water-soluble product has poor compatibility with polypropylene substrate and is difficult to form a stable adhesion on the fiber surface.

[0004] In summary, existing anti-yellowing technologies are mostly designed for nylon fabrics or polypropylene filaments, lacking a dedicated solution applicable to polypropylene staple fibers that also ensures functional durability. How to achieve a stable bond between anti-phenolic yellowing functional agents and a highly hydrophobic polypropylene substrate through molecular structure design, and to synergistically improve anti-yellowing performance and water resistance durability, is a pressing technical challenge in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to provide anti-phenolic yellowing polypropylene staple fiber and its preparation method.

[0006] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0007] A method for preparing anti-phenolic yellowing polypropylene staple fiber is as follows:

[0008] Step 1: Polypropylene chips are melt-extruded to form nascent precursor fibers; the nascent precursor fibers are cooled and solidified, and the cooled fibers are immediately bundled and oiled, the oil being an oil-based anti-phenolic yellowing functional agent;

[0009] Step 2: The nascent filaments after oiling in Step 1 are subjected to high-ratio orientation stretching and heat relaxation setting. The continuous filaments after stretching and setting are cut into short fibers, and after drying, anti-phenolic yellowing polypropylene short fibers are obtained.

[0010] The preparation method of the oil-based anti-phenolic yellowing functional agent is as follows:

[0011] Low-viscosity mineral white oil and caprylic / capric glyceride were added sequentially as base oils. While heating and stirring, an anti-phenolic yellowing agent was added. Subsequently, polyethylene glycol fatty acid ester, auxiliary surfactant, and potassium lauryl phosphate monoester were added, and the mixture was stirred continuously at a uniform speed to obtain an oil-based anti-phenolic yellowing functional agent.

[0012] The preparation method of the anti-phenolic yellowing agent is as follows:

[0013] After reacting 2,3-naphthalenedicarboxylic anhydride with 1-methyl-1-phenylhydrazine in a solvent to obtain an intermediate, the intermediate was then reacted with a fatty alcohol, and the resulting product was post-treated to obtain the anti-phenolic yellowing agent.

[0014] Preferably, the method for preparing the anti-phenolic yellowing agent is as follows:

[0015] S1. Add 2,3-naphthalenedicarboxylic anhydride and 1-methyl-1-phenylhydrazine to an aqueous ethanol solution; stir at high temperature, cool to room temperature after the reaction is complete, and remove the solvent by rotary evaporation at low temperature to obtain the intermediate;

[0016] S2. Mix the intermediate obtained in step S1 with a fatty alcohol, keep warm and stir under nitrogen protection, and after the material is completely melted into a liquid state, add p-toluenesulfonic acid, and heat up to react under nitrogen protection. Remove the water generated during the reaction. After the reaction is completed, cool and crystallize, filter and dry to obtain the anti-phenol yellowing agent.

[0017] The fatty alcohol is at least one of octadecanol, hexadecyl alcohol, docosyl alcohol, 2-octyldodecyl alcohol, 2-ethyldecyl alcohol, and oleyl alcohol.

[0018] Preferably, the fatty alcohol is composed of hexadecyl alcohol and 2-octyldodecyl alcohol in a molar ratio of 0.5-2:0.5-2.

[0019] The auxiliary surfactant is at least one of sorbitan oleate and polyisobutylene succinimide.

[0020] Preferably, the auxiliary surfactant is polyisobutylene succinimide.

[0021] A method for preparing anti-phenolic yellowing polypropylene staple fiber is as follows:

[0022] Step 1: Polypropylene chips are fed into a single-screw extruder for melt extrusion. The melt then enters a spinning box with a constant temperature and is metered and pumped to the spinneret to form nascent filaments. The extruded nascent filaments then enter a side-blowing air window system for uniform cooling and solidification. After cooling, the filaments are immediately bundled and oiled. The oil is an oil-based anti-phenolic yellowing functional agent. The oil-based anti-phenolic yellowing functional agent is preheated to 35-45℃, and the oiling rate is controlled at 1.8%-2.5%.

[0023] Step 2: The nascent filaments after oiling in Step 1 are directly introduced into a multi-stage hot roller drawing machine for drawing and setting. The continuous filaments after drawing and setting are then cut into short fibers by a cutting machine. After drying, anti-phenolic yellowing polypropylene short fibers are obtained.

[0024] The single-screw extruder precisely controls the temperature of the six temperature zones from feeding to extrusion to 220-230℃, 235-245℃, 245-255℃, 250-260℃, 245-255℃, and 245-255℃ respectively.

[0025] The temperature of the spinning box is kept constant at 240-250℃.

[0026] The side-blowing temperature of the side-blowing window system is set to 15-25℃, and the wind speed is 0.4-0.8m / s, so that the temperature of the nascent raw filament is reduced to below 65℃.

[0027] The total draw ratio of the multi-stage hot roll drawing machine is set to 3-6 times, the draw line speed is maintained at 500-2000m / min, and the temperature of the multi-stage hot rolls is set sequentially as follows: first roll 70-80℃, second roll 110-120℃, third roll 120-140℃, and shaping tail roll 120-130℃.

[0028] The anti-phenolic yellowing polypropylene staple fiber has a length of 33-42 mm and a linear density of 1.8-2.5 dtex.

[0029] The preparation method of the oil-based anti-phenolic yellowing functional agent is as follows, in parts by weight:

[0030] Prepare a mixing vessel, and sequentially add 500-800 parts of low-viscosity mineral white oil and 100-200 parts of caprylic / capric triglyceride as base oil, and heat to 50-70℃; under dispersion stirring at 200-400 r / min, add 80-120 parts of anti-phenolic yellowing agent to completely melt and dissolve it in the oil phase; then add 60-100 parts of polyethylene glycol fatty acid ester, 5-15 parts of auxiliary surfactant and 15-25 parts of potassium lauryl phosphate monoester, and continue stirring at a uniform speed for 20-50 minutes to obtain the oil-based anti-phenolic yellowing functional agent.

[0031] The preparation method of the anti-phenolic yellowing agent is as follows:

[0032] S1. Add 2,3-naphthalenedicarboxylic anhydride and 1-methyl-1-phenylhydrazine to a 40-70 wt% aqueous ethanol solution at a molar ratio of 0.5-2:0.5-2, where the total weight of the aqueous ethanol solution is 3-5 times the total weight of the monomers. Stir at 50-150 r / min for 1-3 hours at 30-50℃. After the reaction is complete, allow it to cool naturally to room temperature. Remove the solvent by rotary evaporation at 40-50℃ to obtain the intermediate.

[0033] S2. Add the intermediate obtained in step S1 and the fatty alcohol to the reactor at a molar ratio of 0.5-2:0.5-2. Under nitrogen protection, first heat to 70-85℃ and stir at 30-80 r / min. After the material is completely melted into a liquid state, add p-toluenesulfonic acid at 0.3%-0.8% of the total weight of the reactants as a catalyst. Under nitrogen protection, heat to 110-120℃ and react for 2-6 hours. During the reaction, remove the generated water in real time through a water separator. After the reaction is completed, pour the hot material into anhydrous ethanol to cool and crystallize. Filter and dry to obtain the anti-phenol yellowing agent.

[0034] The design concept of this invention first addresses the compatibility issue between the anti-phenolic yellowing functional agent and the polypropylene substrate at the molecular structure level. Polypropylene, as a strongly hydrophobic material, has a surface that is difficult to stably bond with conventional polar anti-yellowing substances. This invention uses 2,3-naphthalenedicarboxylic anhydride and 1-methyl-1-phenylhydrazine as raw materials, reacting them under mild aqueous conditions to generate an open-ring intermediate containing a naphthalene ring and an acylhydrazine structure, which possesses the ability to capture acidic yellowing substances such as nitrogen oxides. Based on this, the intermediate is esterified with a long-chain fatty alcohol, introducing a C12-C22 alkyl chain to give the anti-phenolic yellowing agent molecule a hydrophobic structure similar to polypropylene, thereby significantly improving its spreadability and anchoring strength on the fiber surface, laying the foundation for subsequent performance optimization.

[0035] Based on the selection of fatty alcohols, this invention overcomes the limitations of using single alcohols and proposes a synergistic design concept of combining straight-chain alcohols and branched-chain alcohols. Cetyl alcohol, as a straight-chain saturated alcohol, has esterification products that can form an ordered alkyl chain arrangement on the fiber surface, constructing a highly efficient physical barrier layer that effectively blocks the intrusion of external yellowing factors. 2-Octyldodecanol, as a branched-chain saturated alcohol, has esterification products that impart excellent spreadability and flexibility to the oil film, ensuring that the functional agent uniformly covers the micro-uneven structure of the fiber surface. The two are combined in an equimolar ratio, achieving a dual synergy of a dense barrier and uniform coverage, resulting in a superior anti-phenolic yellowing effect compared to either single alcohol.

[0036] Furthermore, this invention introduces a functional macromolecular dispersant at the oil-based functional agent formulation level, achieving a leap from single anti-yellowing to multifunctional synergistic effects. Based on the esterification of cetyl alcohol and 2-octyldodecyl alcohol, the traditional auxiliary surfactant, dehydrated sorbitan oleate, is replaced with polyisobutylene succinimide. This molecule, with its high molecular weight polyisobutylene long chain, exhibits high compatibility and deep entanglement with the oil-phase base oil. Simultaneously, its terminal polar succinimide head group forms a stable physical and chemical network with the fiber surface and other polar components in the oil through strong adsorption, significantly improving the functional film's resistance to peeling under water immersion conditions. This design achieves a dual improvement in anti-phenolic yellowing performance and durability, resulting in enhanced steady-state performance.

[0037] Compared with the prior art, the present invention has the following beneficial technical effects:

[0038] 1) This invention introduces alkyl long chains by esterifying the intermediate with long-chain fatty alcohols, which significantly improves the compatibility and fastness of the anti-yellowing agent with polypropylene fibers while retaining the anti-yellowing function, and overcomes the technical defects of traditional anti-yellowing agents that are easy to migrate and fall off.

[0039] 2) This invention uses a combination of hexadecyl alcohol and 2-octyldodecyl alcohol for esterification. The straight-chain alcohol forms a dense physical barrier, while the branched-chain alcohol imparts excellent spreadability. The two work synergistically to achieve a better anti-phenolic yellowing effect, which is more than 0.5 grades higher than the esterification product of a single alcohol.

[0040] 3) This invention introduces polyisobutylene succinimide into an oil-based functional agent, and utilizes the strong adsorption force between its polar succinimide head group and the residual polar sites or microporous structures on the fiber surface to achieve chemical anchoring, thereby constructing a dense cross-interface connection network, which significantly enhances the water resistance stability of the functional membrane in complex environments. Detailed Implementation

[0041] The sources or parameters of some substances are as follows:

[0042] The low-viscosity mineral white oil has a kinematic viscosity of 3.8 mm at 40°C. 2 / s.

[0043] The selected product is polyethylene glycol fatty acid ester, specifically polyethylene glycol 400 monostearate, which has a saponification value of 82 mg KOH / g.

[0044] Caprylic / capric triglyceride is a fully esterified triester (GTCC) with an HLB value of 1.0-2.0 (indicating strong lipophilicity), an acid value ≤0.1mgKOH / g, and a saponification value of 325-345mgKOH / g.

[0045] 2,3-Naphthalenedicarboxylic anhydride is made from high-purity industrial-grade or analytical-grade raw materials, with a 2,3-naphthalenedicarboxylic anhydride content ≥98.0%.

[0046] 1-Methyl-1-phenylhydrazine, using chemically pure grade with a purity ≥99.0%.

[0047] p-Toluenesulfonic acid, with an effective content of not less than 98.5%.

[0048] Polyisobutylene succinimide is selected as an industrial-grade lubricating oil dispersant with an active ingredient content of 60%-70%.

[0049] Octadecyl alcohol is made from high-purity industrial-grade or analytical-grade raw materials, with an octadecyl alcohol content of ≥98.0%.

[0050] Cetyl alcohol is made from high-quality cetyl alcohol with a purity of ≥98.5%.

[0051] Docosyl alcohol with a purity of ≥95.0% (high-purity industrial grade) is selected.

[0052] 2-Octyledododecanool, using 2-octyledododecanool with a purity ≥97.0%.

[0053] 2-Ethyldecyl alcohol, using chemically pure 2-ethyldecyl alcohol with a purity ≥98.0%.

[0054] For oleyl alcohol, select oleyl alcohol with an iodine value in the range of 80-95 gI2 / 100g and a purity of ≥85.0% (calculated as cis-9-octadecenol).

[0055] In the embodiments and comparative examples of this invention, all raw materials are commercially available products.

[0056] Example 1

[0057] A method for preparing anti-phenolic yellowing polypropylene staple fiber is as follows:

[0058] Step 1: Polypropylene chips with a moisture content of 80 ppm and an isotacticity of 98.2% are fed into a single-screw extruder for melt extrusion. The extruder's six temperature zones from feeding to extrusion are precisely controlled sequentially at 225℃, 240℃, 250℃, 255℃, 250℃, and 250℃. The melt then enters a spinning box with a constant temperature of 245℃ and is metered and pumped to the spinneret to form nascent filaments. The extruded nascent filaments then enter a side-blowing window system for uniform cooling and solidification, reducing the temperature to 60℃. The side-blowing temperature is set at 20℃ and the air velocity is 0.65 m / s. After cooling, the filaments are immediately bundled and oiled. An oil-based anti-phenolic yellowing functional agent is preheated to 40℃ and uniformly coated onto the fiber surface, with the oiling rate controlled at 2.2%.

[0059] Step 2: The nascent filament bundle after oiling in Step 1 is directly introduced into a multi-stage hot roller drawing machine for drawing and setting. The total drawing ratio of the drawing machine is set to 5.0 times, the drawing linear speed is maintained at 1500m / min, and the temperature of the multi-stage hot rollers is set sequentially as follows: 75℃ for the first roller, 115℃ for the second roller, 130℃ for the third roller, and 125℃ for the setting tail roller to fully release the internal stress of the fiber and ensure the elongation. The continuous filament bundle after drawing and setting is then cut into short fibers with a length of 38mm by a cutting machine. After the drying step, anti-phenolic yellowing polypropylene short fibers with a linear density of 2.2dtex are obtained.

[0060] The preparation method of the oil-based anti-phenolic yellowing functional agent is as follows, in parts by weight:

[0061] Prepare a mixing vessel and add 650 parts of low-viscosity mineral white oil and 150 parts of caprylic / capric triglyceride as base oils, and heat to 60°C. While dispersing and stirring at 300 r / min, add 100 parts of anti-phenolic yellowing agent and let it completely melt and dissolve in the oil phase. Then add 80 parts of polyethylene glycol fatty acid ester, 10 parts of dehydrated sorbitan oleate and 20 parts of potassium lauryl phosphate monoester, and continue stirring at a uniform speed for 40 minutes to obtain the oil-based anti-phenolic yellowing functional agent.

[0062] The preparation method of the anti-phenolic yellowing agent is as follows:

[0063] S1. 2,3-Naphthalenedicarboxylic anhydride and 1-methyl-1-phenylhydrazine were added to a 50wt% ethanol aqueous solution at a molar ratio of 1:1, and the total weight of the ethanol aqueous solution was 4 times the total weight of the monomers. The mixture was stirred at 100r / min for 2 hours at 40℃. After the reaction was completed, the mixture was naturally cooled to room temperature and the solvent was removed by rotary evaporation at 45℃ to obtain the intermediate.

[0064] S2. The intermediate obtained in step S1 and octadecyl alcohol are added to a reaction vessel at a molar ratio of 1:1.05. Under nitrogen protection, the temperature is first raised to 80°C and stirred at 50 r / min. After the material is completely melted into a liquid state, 0.5% of p-toluenesulfonic acid as a catalyst is added. Under nitrogen protection, the temperature is raised to 115°C and reacted for 4 hours. During the reaction, the water generated as a byproduct is removed in real time through a water separator. After the reaction is completed, the material is poured into anhydrous ethanol while hot to cool and crystallize. After filtration and drying, the anti-phenol yellowing agent is obtained.

[0065] Example 2

[0066] The preparation method of anti-phenolic yellowing polypropylene staple fiber is basically the same as that in Example 1, except that octadecyl alcohol is replaced with an equimolar amount of hexadecyl alcohol in the preparation method of the anti-phenolic yellowing agent.

[0067] Example 3

[0068] The preparation method of anti-phenolic yellowing polypropylene staple fiber is basically the same as that in Example 1, except that octadecyl alcohol is replaced with an equimolar amount of docosyl alcohol in the preparation method of the anti-phenolic yellowing agent.

[0069] Example 4

[0070] The preparation method of anti-phenolic yellowing polypropylene staple fiber is basically the same as that in Example 1, except that octadecyl alcohol is replaced with an equimolar amount of 2-octyldodecyl alcohol in the preparation method of the anti-phenolic yellowing agent.

[0071] Example 5

[0072] The preparation method of anti-phenolic yellowing polypropylene staple fiber is basically the same as that in Example 1, except that octadecyl alcohol is replaced with an equimolar amount of 2-ethyldecyl alcohol in the preparation method of the anti-phenolic yellowing agent.

[0073] Example 6

[0074] The preparation method of anti-phenolic yellowing polypropylene staple fiber is basically the same as that in Example 1, except that octadecyl alcohol is replaced with an equimolar amount of oleyl alcohol in the preparation method of the anti-phenolic yellowing agent.

[0075] Example 7

[0076] The preparation method of anti-phenolic yellowing polypropylene staple fiber is basically the same as that in Example 1, except that: in the preparation method of the anti-phenolic yellowing agent, octadecyl alcohol is replaced with an equimolar amount of fatty alcohol, wherein the fatty alcohol is composed of hexadecyl alcohol and 2-octyldodecyl alcohol in a molar ratio of 1:1.

[0077] Example 8

[0078] The preparation method of anti-phenolic yellowing polypropylene staple fiber is basically the same as that in Example 1, except that: in the preparation method of the anti-phenolic yellowing agent, octadecyl alcohol is replaced with an equimolar amount of fatty alcohol, wherein the fatty alcohol is composed of docosyl alcohol and oleyl alcohol in a molar ratio of 1:1.

[0079] Example 9

[0080] The preparation method of anti-phenolic yellowing polypropylene staple fiber is basically the same as that in Example 7, except that the sorbitol oleate is replaced with an equal amount of polyisobutylene succinimide in the preparation method of the oil-based anti-phenolic yellowing functional agent.

[0081] Comparative Example 1

[0082] The preparation method of the anti-phenolic yellowing polypropylene staple fiber is basically the same as that in Example 1, except that the preparation method of the anti-phenolic yellowing agent is different.

[0083] The preparation method of the anti-phenolic yellowing agent is as follows:

[0084] S1. 2,3-Naphthalenedicarboxylic anhydride and 1-methyl-1-phenylhydrazine were added to a 50wt% ethanol aqueous solution at a molar ratio of 1:1, and the total weight of the ethanol aqueous solution was 4 times the total weight of the monomers. The mixture was stirred at 100r / min for 2 hours at 40℃. After the reaction was completed, the mixture was naturally cooled to room temperature and the solvent was removed by rotary evaporation at 45℃ to obtain the anti-phenol yellowing agent.

[0085] Comparative Example 2

[0086] The preparation method of anti-phenolic yellowing polypropylene staple fiber is basically the same as that in Example 1, except that the anti-phenolic yellowing agent is replaced with an equal amount of low viscosity mineral white oil in the preparation method of the oil-based anti-phenolic yellowing functional agent.

[0087] Test Example 1

[0088] Anti-phenolic yellowing performance test:

[0089] The tests were conducted according to the national standard GB / T 29778-2013 "Textiles - Tests for Color Fastness - Evaluation of Potential Phenolic Yellowing". Polypropylene staple fiber samples prepared in each example and comparative example were sandwiched together with standard control fabric in a special test paper containing 2,6-di-tert-butyl-4-nitrophenol (BHT). After placing the paper between two glass plates and applying a fixed weight to apply the specified pressure, the entire sample was tightly sealed with a BHT-free polyethylene film. It was then placed in a constant temperature oven at 50℃±2℃ for 16 hours. After treatment, the samples were removed and cooled to room temperature. The degree of yellowing was visually evaluated using GB / T 250-2008 "Textiles - Tests for Color Fastness - Evaluation of Color Change - Gray Scale" in a standard light source box to determine the phenolic yellowing grade. Grade 5 represents no yellowing, and grade 1 represents severe yellowing. A higher grade indicates better resistance to phenolic yellowing. The test results are shown in Table 1.

[0090] Table 1

[0091]

[0092] Test Example 2

[0093] Water immersion resistance test:

[0094] Take 5g of each polypropylene short fiber sample prepared in each example and comparative example, and spread it evenly in a sample basket made of 200-mesh stainless steel wire mesh (ensuring that the fiber remains loose but does not fall apart during the soaking process). Completely immerse the sample basket in a beaker containing 250mL of distilled water (liquid ratio 1:50) and let it stand in a constant temperature water bath at 40℃±2℃ for 60 minutes. After soaking, remove the sample basket, gently turn the fiber with tweezers and rinse it with room temperature distilled water for 1 minute. Then dry the fiber sample in a forced-air drying oven at 60℃±2℃ for 2 hours until constant weight. Determine the phenolic yellowing grade of the treated sample according to the anti-phenolic yellowing performance test method described in Test Example 1, and compare it with the phenolic yellowing grade of the original sample that has not been soaked. The water resistance durability of the oil-based anti-phenolic yellowing functional agent on the fiber surface is evaluated by the phenolic yellowing grade and the degree of grade reduction of the sample after soaking. The higher the grade and the smaller the degree of reduction, the stronger the adhesion of the functional agent on the fiber surface and the better the water resistance durability of the anti-phenolic yellowing function. Each group was measured in parallel three times, and the average value was taken. The relevant test data are summarized in Table 2.

[0095] Table 2

[0096]

[0097] Test Example 3

[0098] Breaking strength and elongation at break tests:

[0099] The test was conducted in accordance with the national standard GB / T14337-2022 "Test Method for Tensile Properties of Chemical Fibers (Short Fibers)".

[0100] Test results show that the polypropylene staple fibers prepared in each embodiment and comparative example of the present invention fully meet the mechanical performance requirements, with a breaking strength ≥4.5cN / dtex and a breaking elongation ≥40%.

[0101] Examples 1-6 involved esterification reactions of intermediates with different long-chain fatty alcohols. While retaining the naphthalene ring and hydrazide functional groups, long-chain alkyl ester structures were introduced, significantly improving the compatibility and affinity between the molecules and the polypropylene substrate. This allowed the anti-phenolic yellowing agent to spread more evenly and stably and anchor to the fiber surface, resulting in a superior protective effect compared to Comparative Example 1 in the phenolic yellowing test. This verified the role of esterification modification in improving the bonding strength between the functional agent and the fiber.

[0102] Example 7, using a combination of hexadecyl alcohol and 2-octyldodecyl alcohol for esterification, exhibited a significant synergistic effect. The straight-chain saturated structure of hexadecyl alcohol ester can form an ordered alkyl chain arrangement on the fiber surface, constructing an efficient physical barrier layer; while the branched structure of 2-octyldodecyl alcohol ester endows the oil film with excellent spreadability and flexibility, ensuring that the functional agent uniformly covers the fiber surface. The complementary advantages of the two achieve a dual synergy of barrier and uniform coverage. In contrast, Example 8, using a combination of docosyl alcohol and oleyl alcohol, showed that the docosyl alcohol ester was prone to precipitation due to its excessively long carbon chain, resulting in an uneven oil film, and the unsaturated double bonds contained in oleyl alcohol were easily oxidized and degraded. The two could not form an effective synergy, thus the anti-phenolic yellowing effect was poor.

[0103] Example 9, based on Example 7, replaced dehydrated sorbitan oleate with polyisobutylene succinimide, further improving water immersion resistance. Taking advantage of the non-polar nature of polypropylene fibers, the non-polar polyisobutylene long chains of the polyisobutylene succinimide molecule have a very high structural similarity to the alkyl segments of the oil-phase base oil and fatty alcohol esters. Utilizing the principle of "like dissolves like," it deeply penetrates and embeds itself into the mixed oil film, forming an interpenetrating network structure. Meanwhile, its highly polar succinimide head groups actively orient towards the fiber surface, tightly binding to the active sites on the fiber surface through strong polar adsorption or hydrogen bonding, thereby generating a strong anchoring effect that firmly anchors the entire functional film to the fiber. This anchoring effect significantly improves the erosion resistance of the oil-based functional agent under water immersion conditions.

Claims

1. A method for preparing anti-phenolic yellowing polypropylene staple fiber, characterized in that, The method is as follows: Step 1: Polypropylene chips are melt-extruded to form nascent precursor fibers; the nascent precursor fibers are cooled and solidified, and the cooled fibers are immediately bundled and oiled, the oil being an oil-based anti-phenolic yellowing functional agent; Step 2: Stretch and heat relax the nascent filament bundles after oiling in Step 1. Cut the continuous filament bundles after stretching and setting into short fibers. After drying, anti-phenolic yellowing polypropylene short fibers are obtained. The preparation method of the oil-based anti-phenolic yellowing functional agent is as follows: Low-viscosity mineral white oil and caprylic / capric triglyceride are heated and stirred, and an anti-phenolic yellowing agent is added; then polyethylene glycol fatty acid ester, auxiliary surfactant and potassium salt of lauryl phosphate are added and stirred to obtain an oil-based anti-phenolic yellowing functional agent. The preparation method of the anti-phenolic yellowing agent is as follows: After reacting 2,3-naphthalenedicarboxylic anhydride with 1-methyl-1-phenylhydrazine in a solvent to obtain an intermediate, the intermediate was then reacted with a fatty alcohol, and the resulting product was post-treated to obtain the anti-phenolic yellowing agent. The fatty alcohol is composed of hexadecyl alcohol and 2-octyldodecyl alcohol; The auxiliary surfactant is polyisobutylene succinimide.

2. The method for preparing anti-phenolic yellowing polypropylene staple fiber as described in claim 1, characterized in that, The method is as follows: Step 1: Polypropylene chips are fed into a single-screw extruder for melt extrusion. The melt then enters a spinning box with a constant temperature and is metered and pumped to the spinneret to form nascent filaments. The extruded nascent filaments then enter a side-blowing air window system for uniform cooling and solidification. After cooling, the filaments are immediately bundled and oiled. The oil is an oil-based anti-phenolic yellowing functional agent. The oil-based anti-phenolic yellowing functional agent is preheated to 35-45℃, and the oiling rate is controlled at 1.8%-2.5%. Step 2: The nascent filaments after oiling in Step 1 are directly introduced into a multi-stage hot roller drawing machine for drawing and setting. The continuous filaments after drawing and setting are then cut into short fibers by a cutting machine. After drying, anti-phenolic yellowing polypropylene short fibers are obtained.

3. The method for preparing anti-phenolic yellowing polypropylene staple fiber as described in claim 2, characterized in that, The single-screw extruder precisely controls the temperature of the six temperature zones from feeding to extrusion to 220-230℃, 235-245℃, 245-255℃, 250-260℃, 245-255℃, and 245-255℃ respectively.

4. The method for preparing anti-phenolic yellowing polypropylene staple fiber as described in claim 2, characterized in that, The temperature of the spinning box is kept constant at 240-250℃.

5. The method for preparing anti-phenolic yellowing polypropylene staple fiber as described in claim 2, characterized in that, The side-blowing temperature of the side-blowing window system is set to 15-25℃, and the wind speed is 0.4-0.8m / s, so that the temperature of the nascent raw filament is reduced to below 65℃.

6. The method for preparing anti-phenolic yellowing polypropylene staple fiber as described in claim 2, characterized in that, The total draw ratio of the multi-stage hot roll drawing machine is set to 3-6 times, the draw line speed is maintained at 500-2000m / min, and the temperature of the multi-stage hot rolls is set sequentially as follows: first roll 70-80℃, second roll 110-120℃, third roll 120-140℃, and shaping tail roll 120-130℃.

7. The method for preparing anti-phenolic yellowing polypropylene staple fiber as described in claim 2, characterized in that, The anti-phenolic yellowing polypropylene staple fiber has a length of 33-42 mm and a linear density of 1.8-2.5 dtex.

8. The method for preparing anti-phenolic yellowing polypropylene staple fiber as described in claim 1, characterized in that, The preparation method of the oil-based anti-phenolic yellowing functional agent is as follows, in parts by weight: Prepare a mixing vessel, and sequentially add 500-800 parts of low-viscosity mineral white oil and 100-200 parts of caprylic / capric triglyceride as base oil, and heat to 50-70℃; under dispersion stirring at 200-400 r / min, add 80-120 parts of anti-phenolic yellowing agent to completely melt and dissolve it in the oil phase; then add 60-100 parts of polyethylene glycol fatty acid ester, 5-15 parts of auxiliary surfactant and 15-25 parts of potassium lauryl phosphate monoester, and continue stirring at a uniform speed for 20-50 minutes to obtain the oil-based anti-phenolic yellowing functional agent.

9. The method for preparing anti-phenolic yellowing polypropylene staple fiber as described in claim 1, characterized in that, The preparation method of the anti-phenolic yellowing agent is as follows: S1. Add 2,3-naphthalenedicarboxylic anhydride and 1-methyl-1-phenylhydrazine to a 40-70 wt% aqueous ethanol solution at a molar ratio of 0.5-2:0.5-2, where the total weight of the aqueous ethanol solution is 3-5 times the total weight of the monomers. Stir at 50-150 r / min for 1-3 hours at 30-50℃. After the reaction is complete, allow it to cool naturally to room temperature. Remove the solvent by rotary evaporation at 40-50℃ to obtain the intermediate. S2. The intermediate obtained in step S1 and the fatty alcohol are added to a reaction vessel at a molar ratio of 0.5-2:0.5-2. Under nitrogen protection, the temperature is first raised to 70-85℃ and stirred at 30-80 r / min. After the material is completely melted into a liquid state, 0.3%-0.8% of p-toluenesulfonic acid as a catalyst is added. Under nitrogen protection, the temperature is raised to 110-120℃ and reacted for 2-6 hours. During the reaction, the water generated as a byproduct is removed in real time through a water separator. After the reaction is completed, the material is poured into anhydrous ethanol while hot to cool and crystallize. After filtration and drying, the anti-phenol yellowing agent is obtained. The fatty alcohol is composed of hexadecyl alcohol and 2-octyldodecyl alcohol in a molar ratio of 0.5-2:0.5-2.

10. A polypropylene staple fiber resistant to phenolic yellowing, characterized in that, The anti-phenolic yellowing polypropylene staple fiber is prepared by the preparation method according to any one of claims 1-9, comprising a polypropylene fiber matrix and an oil-based anti-phenolic yellowing functional agent uniformly anchored on the surface of the matrix; the oil-based anti-phenolic yellowing functional agent comprises an anti-phenolic yellowing agent and an auxiliary surfactant polyisobutylene succinimide, wherein the raw materials for preparing the anti-phenolic yellowing agent comprise cetyl alcohol and 2-octyldodecyl alcohol; the anti-phenolic yellowing polypropylene staple fiber has a phenolic yellowing grade ≥ 4.5.

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