A high-strength antibacterial polypropylene staple fiber and preparation method thereof

Abstract

This application discloses a high-strength antibacterial polypropylene staple fiber and its preparation method. The polypropylene staple fiber contains the following raw materials in parts by mass: 100 parts of polypropylene and 1 to 3.5 parts of modified nano-titanium dioxide; the raw materials of the modified nano-titanium dioxide include nano-titanium dioxide, vinyl silane compound, double-end hydrogenated silicone oil and styrene in a mass ratio of 100:3 to 5:10 to 30:2 to 5, and the double-end hydrogenated silicone oil has two silicon-hydrogen end groups; the nano-titanium dioxide is surface-treated with a vinyl silane compound and then reacts with the double-end hydrogenated silicone oil and styrene in the presence of a platinum catalyst for a silicon-hydrogen addition reaction. This application achieves a balance of various properties of the polypropylene staple fiber, such as mechanical strength, antibacterial efficacy and softness, by introducing polysiloxane chain segments with reinforcing, plasticizing and broad-spectrum antibacterial effects to graft nano-titanium dioxide.

Description

Technical Field

[0001] The present application relates to the field of polypropylene materials, and in particular to a high-strength antibacterial polypropylene staple fiber and a preparation method thereof. Background Art

[0002] As a lightweight, corrosion-resistant, chemically stable, and low-cost synthetic fiber, polypropylene staple fiber is widely used in packaging, building materials, home furnishings, and healthcare. In the medical field in particular, its non-hygroscopicity, low allergenicity, and easy disinfection make it a key material for products such as medical masks, surgical gowns, disposable bed sheets, and bandages. As medical health standards improve, the market's performance requirements for polypropylene staple fiber are becoming increasingly stringent. On the one hand, medical protective products must withstand frequent mechanical stress (such as the stretching and friction of surgical gowns during wear), requiring the fiber to possess higher breaking strength and fatigue resistance. On the other hand, medical textiles that come into close contact with the human body must effectively inhibit bacterial growth to avoid the risk of cross-infection.

[0003] Traditional methods for increasing fiber strength often involve introducing rigid inorganic fillers (such as glass fiber and calcium carbonate). For example, patent application CN116356444A achieves both strength and antibacterial properties by introducing graphene. The resulting polypropylene fibers exhibit excellent mechanical properties and broad-spectrum antibacterial activity.

[0004] However, while the introduction of such inorganic fillers can improve functionality, it significantly increases the rigidity of the fiber, resulting in a stiff feel and a tendency to cause friction discomfort when in contact with the skin. This problem is particularly prominent in applications such as medical dressings, sanitary napkin surfaces, and baby diapers, where both softness and functionality must be taken into account. Excessively hard materials not only reduce wearing comfort but may also cause skin sensitivity or even damage with long-term use. In existing technologies, balancing the mechanical strength, antibacterial efficacy, and softness of the fiber has become a key bottleneck restricting the development of high-end medical polypropylene staple fibers. Summary of the Invention

[0005] In order to achieve a balance between the mechanical strength, antibacterial efficacy and softness of polypropylene fibers, the present application provides a high-strength antibacterial polypropylene staple fiber and a preparation method thereof. By introducing polysiloxane chain segments grafted with nano-titanium dioxide with reinforcing, plasticizing and broad-spectrum antibacterial effects into the polypropylene matrix, a significant balance of multiple properties is achieved.

[0006] In the first aspect, the present application provides a high-strength antibacterial polypropylene staple fiber, comprising the following raw materials in parts by mass: 100 parts of polypropylene and 1 to 3.5 parts of modified nano-titanium dioxide; the raw materials of the modified nano-titanium dioxide comprise nano-titanium dioxide, vinyl silane compounds, double-ended hydrogenated silicone oil and styrene in a mass ratio of 100:3 to 5:10 to 30:2 to 5, and the double-ended hydrogenated silicone oil has two silicon-hydrogen end-capping groups; the nano-titanium dioxide is surface-treated with a vinyl silane compound, and then undergoes a silicon-hydrogen addition reaction with the double-ended hydrogenated silicone oil and styrene under a platinum catalyst.

[0007] This application uses modified nano-titanium dioxide to achieve a synergistic effect of antibacterial, strengthening, and toughening. Specifically, nano-titanium dioxide itself has broad-spectrum photocatalytic antibacterial properties, improving antibacterial efficiency. As rigid nanoparticles, after surface modification, nano-titanium dioxide is evenly dispersed in the polypropylene matrix. When the material is subjected to stress, these particles can hinder crack propagation, absorb and disperse stress, delay fracture, and hinder crack propagation to absorb stress, thereby enhancing the tensile strength of the fiber.

[0008] More importantly, bifunctional hydrogenated silicone oil is introduced onto the surface of the nano-titanium dioxide particles via silanol grafting, forming flexible polysiloxane segments. These polysiloxane-grafted nano-titanium dioxide segments act as internal lubricants within the PP matrix, reducing friction between the filler and the matrix and facilitating PP chain slippage, thereby reducing rigidity and increasing softness. Furthermore, these long polysiloxane chains insert themselves between the polypropylene chains, weakening interchain van der Waals forces and entanglement density, increasing free volume, and enhancing segment mobility, significantly improving the material's flexibility. In contrast, traditional silane coupling agents only improve interfacial bonding through chemical bonding and are unable to introduce flexible segments. Furthermore, the role of styrene not only serves to deplete the active hydrogen at the other end, enhancing system stability, but also improves the compatibility of the modified nano-titanium dioxide with the polypropylene matrix.

[0009] It is worth noting that if end-side hydrogen-containing silicone oil (both the double end groups and the side chains have active hydrogen) is introduced for modification, it is easy to cause particle cross-linking and agglomeration, and the reinforcement and toughening effect is poor; while if side hydrogen-containing silicone oil (only the side chain contains active hydrogen) is introduced for modification, the steric hindrance is large, the chain segment extensibility is poor, and the plasticization effect is poor.

[0010] The molecular structure of the double-ended hydrogen-containing silicone oil is shown below, wherein Me is a methyl group.

[0011]

[0012] The molecular structure of the terminal hydrogen-containing silicone oil is shown below, where Me is a methyl group.

[0013]

[0014] The molecular structure of the above-mentioned side hydrogen-containing silicone oil is shown below, wherein Me is a methyl group.

[0015]

[0016] In one embodiment, the hydrogen content of the hydrogen-containing silicone oil is 0.04-0.19%.

[0017] In one embodiment, the viscosity of the hydrogenated silicone oil is 5 to 100 mm 2 / s.

[0018] The viscosity should be controlled within the above range so that the hydrogenated silicone oil has an appropriate molecular chain length and has a good toughening effect after being grafted onto the surface of nano-titanium dioxide particles, which is beneficial to improving the flexibility of polypropylene fibers. The increase in its viscosity has a positive effect on improving flexibility.

[0019] This hydrogen content ensures sufficient chain segment flexibility. When the hydrogen content is too low (<0.04%), there are insufficient silicon-hydrogen active sites, resulting in low efficiency of the addition reaction with vinyl nano-titanium dioxide, poor toughening effect, and easy precipitation of unreacted silicone oil residue, affecting material stability. Double-terminal hydrogen-containing silicone oil products with higher hydrogen content are not available.

[0020] In one embodiment, the vinylsilane compound is selected from one or more of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, and vinylmethyldimethoxysilane.

[0021] In one embodiment, the median particle size of the nano-titanium dioxide is 20-200 nm.

[0022] The particle size selection of nano titanium dioxide directly affects its plasticizing and modification effect. When the particle size is less than 20nm, the specific surface area of the particles increases sharply, resulting in excessively high surface energy. During the grafting and modification process, it is easy to agglomerate due to intermolecular forces, reducing the grafting efficiency of vinyl silane and double-ended hydrogen silicone oil, and unable to form continuous flexible chain segments, and the plasticizing and lubricating effect is significantly weakened. When the particle size exceeds 200nm, the particle size is close to or larger than the winding spacing of the polypropylene molecular chain, making it difficult to effectively embed into the polymer network, resulting in the flexible polysiloxane chain unable to fully stretch to weaken the interchain force, and the plasticizing ability is limited. This application precisely controls the particle size of nano titanium dioxide within the range of 20 to 200nm, ensuring that the particles have sufficient specific surface area to efficiently graft flexible segments, and making their size adapt to the spacing of polypropylene molecular chains, thereby synergistically reducing the rigidity of the material through the lubrication effect of the polysiloxane chain and the free volume effect, and achieving an excellent balance of strengthening and toughening. It is worth noting that titanium dioxide larger than 1 micron basically cannot achieve plasticizing effect.

[0023] In one embodiment, the polypropylene has a melt index (MFI) of 15 to 35 g / 10 min (230° C. / 2.16 kg).

[0024] In one embodiment, the raw material of the polypropylene staple fibers contains 10 to 20 parts of nitrogen-containing heterocyclic grafted polypropylene, and the oiling agent used for oiling the polypropylene staple fibers contains 1 to 5 wt % of copper salt.

[0025] In one embodiment, the nitrogen-containing heterocycle grafted polypropylene is prepared by melt grafting reaction of components comprising the following parts by mass: 100 parts of polypropylene, 1-5 parts of vinyl nitrogen-containing heterocycle, 0.5-1.5 parts of initiator, and 0.1-0.5 parts of antioxidant.

[0026] In one embodiment, the vinyl nitrogen-containing heterocycle is selected from one or more of vinyl imidazole, vinyl pyridine, and vinyl pyrrolidone.

[0027] In one embodiment, the preparation method of the nitrogen-containing heterocycle grafted polypropylene is as follows: vinyl nitrogen-containing heterocycle, initiator, antioxidant and polypropylene are uniformly mixed, added into a screw extruder, melt-extruded at 170-185°C, pelletized, extracted with boiling acetone to remove homopolymer, and dried to obtain a grafted product.

[0028] In one embodiment, the screw extruder has a screw speed of 50 to 100 rpm and a residence time of 2 to 5 minutes.

[0029] In one embodiment, the initiator is dicumyl peroxide.

[0030] In one embodiment, the oil agent is a diluent oil emulsion, which contains 40-60 wt% spinning oil, 1-5 wt% copper salt, and the balance is water.

[0031] In one embodiment, the copper salt is a water-soluble copper salt.

[0032] In one embodiment, the copper salt is selected from at least one of copper chloride, copper nitrate, copper sulfate, and copper acetate.

[0033] Nano-titanium dioxide produces active oxygen through photocatalysis, which has broad-spectrum antibacterial and long-lasting properties. However, its light response depends on ultraviolet excitation and its activity in dark environments is insufficient, which limits its application in medical scenarios. This application introduces nitrogen-containing heterocycles into the polypropylene chain segment to give the fiber surface rich coordination sites. In the oiling process, the Cu in the oil 2+ It forms a complex with the nitrogen-containing heterocyclic ring on the fiber surface through coordination bonds, achieving immediate antibacterial effect. More importantly, in the high temperature stage of the subsequent stretching process, the molecular chain movement ability of the polypropylene amorphous region is enhanced, and Cu 2+It diffuses into the fiber interior along the gaps between molecular chains and forms a stable chelate structure with the inner nitrogen-containing heterocyclic ring. 2+ It can release and kill to achieve a short-term high antibacterial rate, and can also provide long-term antibacterial protection through the sustained release effect of the inner layer complex, so that the material can still maintain excellent antibacterial activity under light-restricted conditions.

[0034] In one embodiment, the preparation method of the modified nano titanium dioxide is:

[0035] Vinylation: Mix the vinyl silane coupling agent with ethanol and deionized water, adjust the pH to 4-5, stir and hydrolyze at room temperature, add nano-titanium dioxide, reflux reaction, centrifuge, wash and dry to obtain vinyl TiO2;

[0036] Grafting reaction: disperse vinylated TiO2 in a solvent, add double-ended hydrogenated silicone oil and platinum catalyst, heat to 90-120°C under nitrogen protection, and stir to react for 4-6 hours; add vinyl nitrogen-containing heterocycle and continue to react for 2-3 hours; after cooling, centrifuge, wash and dry to obtain.

[0037] In one embodiment, the amount of the platinum catalyst used is 0.005 to 0.01 wt % of the amount of the double-ended hydrogenated silicone oil as the raw material.

[0038] In a second aspect, the present application provides a method for preparing high-strength antibacterial polypropylene staple fibers, comprising: blending and melting the raw materials according to any of the above-mentioned raw material ratios of the polypropylene staple fibers to obtain a melt, and subjecting the melt to spinning, cooling, oiling, stretching, curling, heat setting, and cutting.

[0039] In one embodiment, the cooling comprises:

[0040] First stage cooling: the distance from the spinneret is 10-50 cm, and the wind speed is 1.1-1.6 m / s;

[0041] Second stage cooling: the distance from the spinneret is 50-100 cm, and the wind speed is 0.5-0.9 m / s.

[0042] In one embodiment, the cooling is circulating air cooling, the cooling temperature is 15-20° C., and the relative humidity is 40%-60%.

[0043] This application uses a segmented cooling process. When one segment is cold, the polypropylene fiber is rapidly cooled at high wind speeds, creating a temperature gradient between the fiber interior and surface. The fiber surface condenses quickly and has a higher degree of orientation than the fiber interior, causing surface crystal defects and stress concentration, which in turn form microcracks. These crystal defects and microcracks facilitate the diffusion of copper ions into the fiber interior during the oiling process, where they form stable complexes with nitrogen-containing heterocycles in the polypropylene segments, resulting in a more uniform and efficient antibacterial effect.

[0044] To achieve the above-mentioned segmented cooling process, the original annular static pressure chamber can be divided into three independent annular air zones along the fiber extrusion direction, corresponding to the first and second segment static pressure chambers respectively. Each static pressure chamber is equipped with an independent air valve, and the air intake of each segment is controlled by adjusting the valve opening to achieve wind speed classification. The main air duct is divided into two groups of independent air ducts, which are connected to different static pressure chambers respectively. Each static pressure chamber is equipped with an air pressure sensor interface to monitor and feedback the pressure data to the control system in real time, and dynamically adjust the air valve opening. The cooling air is centrally processed by the central air-conditioning system to ensure that the air temperature and humidity of each static pressure chamber are constant within the preset range.

[0045] In one embodiment, the stretching ratio is 3.5 to 4.5 times, which is carried out in two stages: the primary stretching temperature is 60 to 80°C, the stretching ratio is 1.5 to 2.0 times, to achieve preliminary orientation of the molecular chains; the secondary stretching temperature is 120 to 140°C, the stretching ratio is 2.0 to 2.5 times, to complete high-multiple thermal stretching and crystalline structure stabilization.

[0046] In one embodiment, in the oiling process, the oiling rate is controlled to be 0.3% to 0.8%.

[0047] In one embodiment, the heat setting temperature is 110-130°C.

[0048] In one embodiment, the cutting length is 38-65 mm.

[0049] In summary, this application has the following beneficial effects:

[0050] This application uses nano-titanium dioxide as the core to construct a core-shell structure. The rigid TiO2 core improves the fiber strength through heterogeneous nucleation and crack pinning effects; the surface-grafted polysiloxane flexible chain segments are inserted between the polypropylene molecular chains, giving the material a soft touch by reducing the entanglement density and interfacial friction. At the same time, the nitrogen-containing heterocycles introduced on the polypropylene molecular chain and the Cu in the oil 2+ Forming a gradient coordination system, that is, the surface Cu 2+It rapidly kills pathogens on contact, while the internal amorphous complex continuously releases antimicrobial components, combining with the photocatalytic activity of TiO2 to create a multi-pronged antimicrobial mechanism. The staple fibers in this application exhibit high breaking strength, an antimicrobial rate of >99.9% against Escherichia coli and Staphylococcus aureus for 24 hours, and a 40-60% reduction in bending stiffness. This material meets the stringent requirements for mechanical strength, antimicrobial properties, and wear comfort required of medical materials, making it particularly suitable for use in medical applications such as highly sensitive skin dressings. DETAILED DESCRIPTION

[0051] Preparation Example

[0052] Preparation Example 1: A modified nano-titanium dioxide, the raw material ratio is as follows:

[0053] Nano titanium dioxide (median particle size 50nm) 100g, vinyl trimethoxysilane 4g, double-ended hydrogenated silicone oil (model RH-H45, hydrogen content 0.12%, viscosity 17-22mm 2 / s) 20 g, styrene 3.5 g, platinum catalyst (chloroplatinic acid isopropanol solution, Pt content 0.5 wt%) 0.1 g, anhydrous ethanol 200 mL, deionized water 50 mL.

[0054] The preparation steps are as follows:

[0055] Vinylation: Mix vinyltrimethoxysilane with 40 mL of ethanol and 10 mL of water, adjust the pH to 4.5 with acetic acid, and hydrolyze at room temperature with stirring for 30 minutes. Add nano-titanium dioxide, reflux at 80°C for 6 hours, centrifuge, wash three times with ethanol, and vacuum dry at 80°C for 12 hours to obtain vinylated TiO2.

[0056] Hydrosilylation Grafting: Disperse vinylated TiO2 in toluene (solid-to-liquid ratio 1:5), add bifunctional hydrogenated silicone oil and platinum catalyst, heat to 100°C under nitrogen, and stir at 200 rpm for 5 hours. Add styrene and continue the reaction for 2.5 hours. Cool to room temperature, centrifuge, wash three times with toluene, and dry at 80°C to obtain the modified TiO2.

[0057] Preparation Example 2: A modified nano-titanium dioxide, the raw material ratio is as follows:

[0058] Nano titanium dioxide (median particle size 20nm) 100g, vinyl trimethoxysilane 5g, double-ended hydrogenated silicone oil (model RH-H518, hydrogen content 0.18%, viscosity 8-12mm 2 / s) 30 g, styrene 5 g, platinum catalyst (chloroplatinic acid isopropanol solution, Pt content 0.5 wt%) 0.1 g, anhydrous ethanol 200 mL, deionized water 50 mL.

[0059] The preparation steps are as follows:

[0060] Vinylation: Mix vinyltrimethoxysilane with 50 mL of ethanol and 10 mL of water, adjust the pH to 4 with acetic acid, and hydrolyze at room temperature with stirring for 30 minutes. Add nano-titanium dioxide, reflux at 80°C for 6 hours, centrifuge, wash three times with ethanol, and vacuum dry at 80°C for 12 hours to obtain vinylated TiO2.

[0061] Hydrosilylation Grafting: Disperse vinylated TiO2 in toluene (solid-to-liquid ratio 1:5), add bifunctional hydrogenated silicone oil and platinum catalyst, heat to 110°C under nitrogen, and stir at 200 rpm for 4 hours. Add styrene and continue the reaction for 3 hours. Cool to room temperature, centrifuge, wash three times with toluene, and dry at 80°C to obtain the modified TiO2.

[0062] Preparation Example 3, a modified nano-titanium dioxide, the raw material ratio is as follows:

[0063] Nano titanium dioxide (median particle size 200nm) 100g, vinyl trimethoxysilane 3g, double-ended hydrogenated silicone oil (model RH-DH04, hydrogen content 0.05%, viscosity 60-70mm 2 / s) 10 g, styrene 2.2 g, platinum catalyst (chloroplatinic acid isopropanol solution, Pt content 0.5 wt%) 0.1 g, anhydrous ethanol 200 mL, and deionized water 50 mL.

[0064] The preparation steps are as follows:

[0065] Vinylation: Mix vinyltrimethoxysilane with 40 mL of ethanol and 10 mL of water, adjust the pH to 4.5 with acetic acid, and hydrolyze at room temperature with stirring for 30 minutes. Add nano-titanium dioxide, reflux at 90°C for 6 hours, centrifuge, wash three times with ethanol, and vacuum dry at 80°C for 12 hours to obtain vinylated TiO2.

[0066] Hydrosilylation Grafting: Disperse vinylated TiO2 in toluene (solid-to-liquid ratio 1:4), add bifunctional hydrogenated silicone oil and platinum catalyst, heat to 90°C under nitrogen, and stir at 200 rpm for 6 hours. Add styrene and continue the reaction for 2 hours. Cool to room temperature, centrifuge, wash three times with toluene, and dry at 80°C to obtain the modified TiO2.

[0067] Preparation Example 4, a modified nano-titanium dioxide, differs from Preparation Example 1 in that the double-terminal hydrogen-containing silicone oil with a hydrogen content of 0.11% is replaced by a double-terminal hydrogen-containing silicone oil with a hydrogen content of 0.032% by mass.

[0068] Preparation Example 5, a modified nano-titanium dioxide, differs from Preparation Example 1 in that nano-titanium dioxide with a median particle size of 50 nm is replaced by nano-titanium dioxide with an equal mass and a median particle size of 300 nm.

[0069] Preparation Example 6, a modified nano-titanium dioxide, differs from Preparation Example 1 in that the nano-titanium dioxide with a median particle size of 50 nm is replaced by nano-titanium dioxide with an equal mass and a median particle size of 10 nm.

[0070] Preparation Example 7, a modified nano-titanium dioxide, differs from Preparation Example 1 in that no styrene is added to the raw materials. In the hydrosilylation grafting step, vinylated TiO2 is dispersed in toluene (solid-to-liquid ratio 1:5), bifunctional hydrogenated silicone oil and platinum catalyst are added, and the temperature is raised to 100°C under nitrogen, with stirring at 200 rpm for 5 hours. The mixture is cooled to room temperature, centrifuged, washed three times with toluene, and dried at 80°C to obtain the modified TiO2.

[0071] Preparation Example 8, a modified nano-titanium dioxide, the difference from Preparation Example 1 is that the same mass of double-ended hydrogenated silicone oil (model RH-H518, hydrogen content 0.18%, viscosity 8-12mm 2 / s) to replace double-ended hydrogenated silicone oil (hydrogen content 0.12%, viscosity 17-22mm 2 / s).

[0072] Preparation Example 9, a modified nano titanium dioxide, the difference from Preparation Example 1 is that the same mass of double-ended hydrogenated silicone oil (model RH-H6, hydrogen content 0.11%, viscosity 20-25mm 2 / s) to replace the double-ended hydrogen silicone oil (model RH-H45, hydrogen content 0.12%, viscosity 17-22mm 2 / s).

[0073] Preparation Example 10, a modified nano-titanium dioxide, the difference from Preparation Example 1 is that the same mass of end-side hydrogen-containing silicone oil (model RH-LHC-3, hydrogen content 0.8%, viscosity 30-40mm 2 / s) to replace the double-ended hydrogen silicone oil (model RH-H45, hydrogen content 0.12%, viscosity 17-22mm 2 / s).

[0074] Preparation Example 11, a modified nano titanium dioxide, the difference from Preparation Example 1 is that the same mass of hydrogenated silicone oil (model RH-H57, hydrogen content 0.13%, viscosity 30-40mm 2 / s) to replace the double-ended hydrogen silicone oil (model RH-H45, hydrogen content 0.12%, viscosity 17-22mm 2 / s).

[0075] Preparation Example 12, a modified nano-titanium dioxide, differs from Preparation Example 1 in that only vinylation treatment is performed, without subsequent hydrosilylation and styrene grafting. The specific preparation steps are as follows: Vinylation Treatment: Mix 4g of vinyltrimethoxysilane with 40mL of ethanol and 10mL of water, adjust the pH to 4.5 with acetic acid, and hydrolyze at room temperature with stirring for 30 minutes. Add 100g of nano-titanium dioxide (median particle size 3μm), reflux at 80°C for 6 hours, centrifuge, wash three times with ethanol, and vacuum dry at 80°C for 12 hours to obtain modified TiO2.

[0076] Preparation Example a: A nitrogen-containing heterocyclic grafted polypropylene was prepared as follows: 30 g of 1-vinylimidazole, 10 g of dicumyl peroxide, 4 g of antioxidant 1010, and 1000 g of polypropylene (copolymer PP, brand ExxonMobil Achieve 3854) were uniformly mixed, introduced into a twin-screw extruder, and melt-extruded at 170-185°C. The extrudate was pelletized and extracted with boiling acetone for 24 hours to remove the homopolymer. The grafted product was then dried.

[0077] Preparation Example b: A nitrogen-containing heterocyclic grafted polypropylene was prepared as follows: 10 g of vinyl pyridine, 5 g of dicumyl peroxide, 3 g of the antioxidant BHT, and 1000 g of polypropylene (homopolymer PP, brand Basell Pro-fax 6301) were uniformly mixed, introduced into a twin-screw extruder, and melt-extruded at 170-185°C. The extrudate was pelletized and extracted with boiling acetone for 24 hours to remove the homopolymer. The grafted product was then dried.

[0078] Preparation Example C: A nitrogen-containing heterocyclic grafted polypropylene was prepared as follows: 50 g of vinyl pyrrolidone, 15 g of dicumyl peroxide, 5 g of antioxidant 1010, and 1000 g of polypropylene (copolymer PP, ExxonMobil Achieve 3854) were uniformly mixed, introduced into a twin-screw extruder, and melt-extruded at 170-185°C. The extrudate was pelletized and extracted with boiling acetone for 24 hours to remove the homopolymer. The grafted product was then dried.

[0079] Example

[0080] Example 1: A high-strength antibacterial polypropylene staple fiber is prepared according to the following steps:

[0081] Melting: 5 kg of polypropylene (Maoming Petrochemical Z30S0, MFI = 25 g / 10 min), 0.75 kg of nitrogen-containing heterocyclic grafted polypropylene (Preparation Example a), and 0.15 kg of modified nano-titanium dioxide (Preparation Example 1) were premixed and added to a twin-screw extruder (L / D = 40). The temperature settings of each zone were: 180 ° C for zone 1, 200 ° C for zone 2, 210 ° C for zone 3, and 205 ° C for zone 4. The screw speed was 200 rpm and the melt pressure was 12 MPa.

[0082] Melt spinning: The melt is delivered to the spinneret (aperture 0.25 mm × 108 holes) via a metering pump, and the melt temperature is 205 °C.

[0083] Cooling molding: adopt ring air cooling (temperature 18±2℃, humidity 50%); first stage cooling: distance from the spinneret is 10~50cm, wind speed is 1.4m / s; second stage cooling: distance from the spinneret is 50~100cm, wind speed is 0.7m / s.

[0084] Oiling: The oiling rate is 0.5%, and the oil contains 50wt% Hengrun TAB-314, 3wt% copper sulfate, and 47wt% deionized water.

[0085] Stretching: primary stretching (70℃, 1.8 times), secondary stretching (130℃, 2.3 times).

[0086] Curling: Steam temperature 100℃.

[0087] Heat setting: 125℃ hot air treatment for 4 minutes.

[0088] Cutting: Fiber length 65mm.

[0089] Example 2, a high-strength antibacterial polypropylene staple fiber, is prepared according to the following steps:

[0090] Melting: 5 kg of polypropylene (Zhongjing Petrochemical H30S, MFI = 20 g / 10 min), 0.5 kg of nitrogen-containing heterocyclic grafted polypropylene (Preparation Example b), and 0.175 kg of modified nano-titanium dioxide (Preparation Example 2) were premixed and added to a twin-screw extruder (L / D = 40). The temperature settings of each zone were: 180 ° C for zone 1, 195 ° C for zone 2, 205 ° C for zone 3, and 200 ° C for zone 4. The screw speed was 200 rpm and the melt pressure was 12 MPa.

[0091] Melt spinning: The melt is delivered to the spinneret (aperture 0.25 mm × 108 holes) via a metering pump, and the melt temperature is 200 °C.

[0092] Cooling molding: adopt ring air cooling (temperature 18±2℃, humidity 60%); first stage cooling: distance from the spinneret is 10~50cm, wind speed is 1.2m / s; second stage cooling: distance from the spinneret is 50~100cm, wind speed is 0.5m / s.

[0093] Oiling: The oiling rate is 0.7%, and the oil contains 60wt% Hengrun TAB-314, 1.5wt% copper chloride, and 38.5wt% deionized water.

[0094] Stretching: primary stretching (80℃, 2.0 times), secondary stretching (120℃, 2.2 times).

[0095] Curling: Steam temperature 100℃.

[0096] Heat setting: 130℃ hot air treatment for 3 minutes.

[0097] Cutting: Fiber length 51mm.

[0098] Example 3, a high-strength antibacterial polypropylene staple fiber, is prepared according to the following steps:

[0099] Melting: 5 kg of polypropylene (Pureman HP561S, MFI = 33 g / 10 min), 1 kg of nitrogen-containing heterocyclic grafted polypropylene (Preparation Example c), and 0.075 kg of modified nano-titanium dioxide (Preparation Example 3) were premixed and added to a twin-screw extruder (L / D = 40). The temperature settings of each zone were: 190 ° C for zone 1, 205 ° C for zone 2, 210 ° C for zone 3, and 205 ° C for zone 4. The screw speed was 200 rpm and the melt pressure was 12 MPa.

[0100] Melt spinning: The melt is delivered to the spinneret (aperture 0.25 mm × 108 holes) via a metering pump, and the melt temperature is 205 °C.

[0101] Cooling molding: adopt ring air cooling (temperature 18±2℃, humidity 40%); first stage cooling: distance from the spinneret is 10~50cm, wind speed is 1.6m / s; second stage cooling: distance from the spinneret is 50~100cm, wind speed is 0.9m / s.

[0102] Oiling: The oiling rate is 0.4%, and the oil contains 40wt% Hengrun TAB-314, 5wt% copper sulfate, and 55wt% deionized water.

[0103] Stretching: primary stretching (70℃, 1.5 times), secondary stretching (140℃, 2.5 times).

[0104] Curling: Steam temperature 100℃.

[0105] Heat setting: 125℃ hot air treatment for 3 minutes.

[0106] Cutting: Fiber length 45mm.

[0107] Example 4, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the modified nano-titanium dioxide of Preparation Example 1 is replaced by the modified nano-titanium dioxide of Preparation Example 4 with an equal mass.

[0108] Example 5, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the modified nano-titanium dioxide of Preparation Example 1 is replaced by the modified nano-titanium dioxide of Preparation Example 5 with an equal mass.

[0109] Example 6, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the modified nano-titanium dioxide of Preparation Example 1 is replaced by the modified nano-titanium dioxide of Preparation Example 6 with an equal mass.

[0110] Example 7, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the modified nano-titanium dioxide of Preparation Example 1 is replaced by the modified nano-titanium dioxide of Preparation Example 7 with an equal mass.

[0111] Example 8, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the modified nano-titanium dioxide of Preparation Example 1 is replaced by the modified nano-titanium dioxide of Preparation Example 8 with an equal mass.

[0112] Example 9, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the modified nano-titanium dioxide of Preparation Example 1 is replaced by the modified nano-titanium dioxide of Preparation Example 9 with an equal mass.

[0113] Example 10, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the nitrogen-containing heterocyclic grafted polypropylene of Preparation Example a is replaced by an equal mass of polypropylene (copolymer PP, brand ExxonMobil Achieve 3854).

[0114] Example 11, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the oil used for oiling is replaced with an equal mass of Hengrun TAB-314 instead of copper sulfate.

[0115] Example 12, a high-strength antibacterial polypropylene staple fiber, differs from Example 10 in that the oil used for oiling is replaced with an equal mass of Hengrun TAB-314 instead of copper sulfate.

[0116] Example 13, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the cooling molding process is different, specifically: circular air cooling (temperature 18±2°C, humidity 50%) is adopted; the cooling wind speed is 1.4m / s, and the cold zone is the interval of 10 to 100cm from the spinneret.

[0117] Example 14, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the cooling molding process is different, specifically: circular air cooling (temperature 18±2°C, humidity 50%) is adopted; the cooling wind speed is 0.7m / s, and the cold zone is the interval of 10 to 100cm from the spinneret.

[0118] Comparative Example

[0119] Comparative Example 1, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the modified nano-titanium dioxide of Preparation Example 1 is replaced by the modified nano-titanium dioxide of Preparation Example 10 of equal mass.

[0120] Comparative Example 2, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the modified nano-titanium dioxide of Preparation Example 1 is replaced by the modified nano-titanium dioxide of Preparation Example 11 of equal mass.

[0121] Comparative Example 3, a high-strength antibacterial polypropylene staple fiber, differs from Example 1 in that the modified nano-titanium dioxide of Preparation Example 1 is replaced by the modified nano-titanium dioxide of Preparation Example 12 of equal mass.

[0122] Performance testing

[0123] 1. Antibacterial (short-term) performance test

[0124] Test method: Refer to GB / T 20944.3-2008 “Evaluation of Antimicrobial Properties of Textiles” for testing. The test bacteria are Escherichia coli (ATCC8739) and Staphylococcus aureus (ATCC6538).

[0125] Sample preparation: 1 g of the staple fibers prepared in the examples and comparative examples was cut into 1 mm length segments and dispersed in 10 mL of sterile physiological saline to prepare a suspension.

[0126] Test steps: Mix 0.2 mL of bacterial solution (concentration 1×106 CFU / mL) with the sample suspension and incubate at 37°C with shaking for 24 hours. After dilution, spread on an agar plate and incubate at 37°C for 24 hours. Count the colonies. Calculate the antibacterial rate (short-term effect) using the following formula:

[0127] Antibacterial rate (%) = (AB) / A×100%

[0128] Among them, A: the number of colonies in the blank control group, B: the number of colonies in the sample group.

[0129] 2. Long-term antibacterial performance test

[0130] Test method: Determined in accordance with ISO 20743:2021 “Determination of antimicrobial activity of textiles”.

[0131] Sample preparation: 5 g of fiber sample was immersed in 50 mL of simulated sweat (pH 5.5, the preparation of artificial sweat complies with ISO 105 E04:2013 standard - Test method for color fastness to perspiration) and kept at 37°C with shaking. Samples were collected after 7 days.

[0132] Long-term antibacterial rate: After soaking the sample in artificial sweat for 7 days, the long-term antibacterial rate was tested according to the above short-term antibacterial rate test method, and the antibacterial rate decrease (%) was calculated as follows: short-term antibacterial rate - long-term antibacterial rate.

[0133] 3. Tensile performance test

[0134] Test method: Refer to ASTM D3822 / D3822M-14 "Textile Monofilament Tensile Properties Test" to measure the breaking strength (MPa) and elongation (%) of the short fiber sample.

[0135] Sample preparation: 50 polypropylene staple fibers were randomly selected and pre-humidified (temperature 20°C, humidity 65% RH, 24 hours).

[0136] Test conditions: tensile speed 10 mm / min, clamping distance 20 mm, and the average value of 50 tests.

[0137] 4. Polypropylene fabric rigidity and flexibility test

[0138] Sample preparation: Polypropylene staple fibers were made into non-woven fabric (weight 50 g / m²), with a thickness of 0.3 ± 0.05 mm. Five specimens (250 mm × 25 mm) were cut along the warp and weft directions and equilibrated at 20°C ± 2°C and 65% ± 5% relative humidity for 24 hours.

[0139] Test method: Referring to GB / T 18318.1-2009 “Determination of flexural properties of textiles - Part 1: Inclined plane method”, a fabric stiffness tester (LLY-01B electronic stiffness tester) was used to measure the flexural stiffness (cN·cm) of the sample.

[0140] Table 1. Performance test results

[0141]

[0142] Analysis of test results:

[0143] 1. Antibacterial performance analysis

[0144] The short-term antibacterial rates of Examples 1-3 were greater than 99.9%, and the long-term antibacterial rates decreased by only 8.13-9.55%. However, in Examples 10-12 (without grafting nitrogen-containing heterocycles or adding copper salts), the short-term antibacterial rates or the long-term antibacterial rates decreased sharply, demonstrating the stabilizing effect of nitrogen-containing heterocycle coordination anchoring on copper ions.

[0145] Furthermore, while excessively rapid fiber cooling after extrusion (Example 13) promotes the formation of microcracks and crystal defects, it also results in a decrease in mechanical properties. Simultaneously, excessively rapid temperature drop results in insufficient fiber stretching, reduced orientation and crystallinity, resulting in lower breaking strength and elongation, and an overall decrease in softness. Conversely, excessively slow fiber cooling (Example 14) makes it difficult to form microcracks and crystal defects, resulting in a decrease in copper ion infiltration and complexation, and reduced long-term antimicrobial performance.

[0146] 2. Analysis of mechanical properties and softness

[0147] Breaking Strength: Examples 1-3 exhibited strengths of 630-670 MPa and elongations of 35-40%. However, the strength of the sample using a large particle size (Example 5) dropped to 530 MPa and the elongation to 28%, indicating that inorganic fillers with excessively large particle sizes have poor reinforcement and toughening effects. The strength of the sample using a small particle size (Example 6) increased to 600 MPa, but the elongation dropped to 30%, indicating that nano-titanium dioxide with excessively small particle size improves fiber rigidity but negatively impacts toughening and softness. Example 8 (decreased viscosity) exhibited decreased flexibility, while Example 9 (increased viscosity) exhibited increased flexibility. Since bihydrogenated silicone oils only have two terminal hydrogen groups, the difference lies solely in the increase or decrease in viscosity. This indicates that, all other conditions remaining the same, increased viscosity improves fiber toughening.

[0148] Furthermore, the sample using end-side hydrogenated silicone oil (Comparative Example 1) showed a significant decrease in both strength and elongation. This may be because end-side hydrogenated silicone oil has more than three active hydrogen atoms, which easily causes cross-linking and agglomeration of nano-titanium dioxide, making it difficult for the nano-titanium dioxide to effectively disperse and effectively fill and plasticize. This results in increased rigidity but a decrease in breaking strength. The decrease in elongation and softness caused by the use of end-side hydrogenated silicone oil (Comparative Example 2) may be due to the high number of active hydrogen atoms in the end-side hydrogenated silicone oil molecular chain, which significantly promotes product strength and degrades its plasticizing ability.

[0149] This specific embodiment is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the present embodiment as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A high-strength antibacterial polypropylene staple fiber, characterized in that: The invention comprises the following raw materials in parts by weight: 100 parts of polypropylene, 10-20 parts of nitrogen-containing heterocyclic grafted polypropylene, and 1-3.5 parts of modified nano-titanium dioxide; the raw materials of the modified nano-titanium dioxide comprise nano-titanium dioxide, vinyl silane compound, double-end hydrogenated silicone oil, and styrene in a mass ratio of 100:3-5:10-30:2-5, wherein the double-end hydrogenated silicone oil has two silyl end-capping groups; the nano-titanium dioxide is surface-treated with a vinyl silane compound, and then undergoes a hydrosilylation reaction with the double-end hydrogenated silicone oil and styrene in the presence of a platinum catalyst; the nitrogen-containing heterocyclic grafted polypropylene is prepared by melt grafting reaction of components comprising the following raw materials in parts by weight: 100 parts of polypropylene, 1-5 parts of vinyl nitrogen-containing heterocyclic, 0.5-1.5 parts of an initiator, and 0.1-0.5 parts of an antioxidant; and the oil used for oiling the polypropylene staple fibers contains 1-5 wt% of a copper salt.

2. The polypropylene staple fiber according to claim 1, characterized in that The hydrogen content of the hydrogen-containing silicone oil is 0.04-0.19%.

3. The polypropylene staple fiber according to claim 1, characterized in that The median particle size of the nano titanium dioxide is 20 to 200 nm.

4. The polypropylene staple fiber according to claim 1, characterized in that The vinyl nitrogen-containing heterocycle is selected from one or more of vinyl imidazole, vinyl pyridine and vinyl pyrrolidone.

5. The polypropylene staple fiber according to claim 1, characterized in that The preparation method of the nitrogen-containing heterocyclic grafted polypropylene comprises the following steps: uniformly mixing 1-vinylimidazole, an initiator, an antioxidant and polypropylene, adding the mixture into a screw extruder, and melt-extruding the mixture at 170-185° C., pelletizing the extrudate, extracting the homopolymer with boiling acetone, and drying the mixture to obtain a grafted product.

6. The polypropylene staple fiber according to claim 1, characterized in that The preparation method of the modified nano titanium dioxide is: Vinylation: Mix the vinyl silane coupling agent with ethanol and deionized water, adjust the pH to 4-5, stir and hydrolyze at room temperature, add nano-titanium dioxide, reflux reaction, centrifuge, wash and dry to obtain vinyl TiO2; Grafting reaction: disperse vinylated TiO2 in a solvent, add double-ended hydrogenated silicone oil and platinum catalyst, heat to 90-120°C under nitrogen protection, stir and react for 4-6 hours; add styrene and continue to react for 2-3 hours; after cooling, centrifuge, wash and dry to obtain the product.

7. A method for preparing high-strength antibacterial polypropylene staple fibers, characterized in that: include: According to the raw material ratio of the polypropylene staple fiber according to any one of claims 1 to 6, the raw materials are blended and melted to obtain a melt, and the melt is subjected to spinning, cooling, oiling, stretching, curling, heat setting and cutting to obtain the product.

8. The preparation method according to claim 7, characterized in that The cooling comprises: First stage cooling: the distance from the spinneret is 10-50 cm, and the wind speed is 1.1-1.6 m / s; Second stage cooling: the distance from the spinneret is 50-100 cm, and the wind speed is 0.5-0.9 m / s.

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