Antibacterial short fiber based on saturated fatty acid silver and preparation method thereof

Abstract

The invention belongs to the technical field of functional fiber manufacturing, and particularly relates to an antibacterial short fiber based on saturated fatty acid silver and a preparation method thereof. The method comprises the following steps: firstly, compounding saturated fatty acid silver with mesoporous silica nanospheres to prepare modified saturated fatty acid silver; then carrying out melt blending on the mixture, low-density polyethylene, a dispersing aid and a composite aid prepared from SEBS-g-MAH, hydrogenated castor oil and nano boehmite according to a specific ratio to prepare antibacterial master batches; and finally, mixing the master batch with the polyolefin base slice in proportion, and carrying out melt spinning, drafting, heat setting and cutting off to obtain the antibacterial short fiber. By means of material modification and compounding of special auxiliaries, the industrial problems that a silver component is prone to agglomeration and uneven in dispersion in the spinning process are solved synergistically, and the prepared fiber not only has good spinnability and excellent mechanical strength, but also has efficient and lasting antibacterial performance and is suitable for high-end non-woven fabric products for medical treatment and public health, personal care and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of functional fiber manufacturing, and particularly relates to a kind of antibacterial staple fiber based on saturated fatty acid silver and a preparation method thereof. BACKGROUND

[0002] Silver-based antibacterial agents have become one of the most widely used inorganic antibacterial agents due to their broad-spectrum and high-efficiency antibacterial properties. Integrating them into chemical fibers to produce products with persistent antibacterial function is an important research direction in the field of functional fibers. Such antibacterial fibers have a huge market demand in non-woven products such as medical and health care, personal care, and protective filtration.

[0003] Currently, the mainstream technical path for introducing silver-based antibacterial agents into fibers mainly includes surface finishing and blending spinning.

[0004] Surface finishing is a relatively simple process, which usually involves immersing the formed fibers or fabrics in a silver nitrate solution, and then reducing the silver ions to micron-sized silver particles, which are physically attached to the surface of the fibers. Although this method is intuitive, it has significant inherent defects: the adhesion between the silver layer attached to the surface and the fiber matrix is weak, and the silver particles can easily fall off during use, especially when subjected to friction, washing, and other physical actions. This not only leads to rapid decay of antibacterial efficiency, making it difficult to meet the requirements of product durability, but also may affect product appearance and safety due to the shedding of silver.

[0005] To overcome the durability problem of surface finishing, blending spinning has emerged. This method involves blending the antibacterial agent with the polymer matrix before spinning, so that the silver component is encapsulated inside the fiber. In theory, this can provide more persistent antibacterial effect. Early attempts have focused on directly blending micron-sized or nano-sized silver powder, silver zeolite, and other inorganic powders with polyolefin (such as polyethylene, polypropylene) chips. However, this approach faces two insurmountable technical bottlenecks in actual industrialization.

[0006] Firstly, the problem of silver powder agglomeration and dispersion. Micron-sized silver powder has a very high specific surface area and surface energy, and can easily spontaneously agglomerate in the polymer melt, forming agglomerates of varying sizes. These agglomerates can severely disrupt the uniformity and flowability of the melt during spinning, leading to a sharp increase in spinning breakage and frequent occurrence of loose yarn, making continuous and stable production impossible and severely affecting spinnability. Secondly, the poor compatibility between inorganic powders and organic polymers. The rigid silver powder agglomerates act as defect points in the fiber, disrupting the continuity of the matrix and becoming a source of stress concentration, significantly degrading the mechanical properties of the fiber, such as a significant decrease in breaking strength and elongation, making it difficult to meet the basic requirements of fiber strength for subsequent non-woven processing and final application.

[0007] Therefore, although silver-based antibacterial fiber has a broad prospect, the prior art either sacrifices durability because the silver layer is located on the surface or impairs spinnability and mechanical properties because silver powder is difficult to disperse in the matrix. The industry urgently needs a new technical solution that can realize uniform and stable dispersion of silver antibacterial components in the fiber matrix without affecting the spinnability and basic properties of the fiber and ultimately endow the product with efficient and durable antibacterial function. SUMMARY

[0008] The purpose of the present application is to provide a saturated fatty acid silver-based antibacterial staple fiber and a preparation method thereof to overcome the problems of uneven dispersion of silver particles, poor spinnability and mechanical properties, and insufficient antibacterial durability in the preparation of existing silver-containing fibers.

[0009] To achieve the above-mentioned purpose, the present application provides the following technical solutions: The first aspect of the present application provides a preparation method of a saturated fatty acid silver-based antibacterial staple fiber, comprising the following steps: (1) mixing low-density polyethylene (LDPE), modified saturated fatty acid silver, dispersion aid and composite aid, then melt blending, extruding and pelletizing to prepare antibacterial masterbatch; The modified saturated fatty acid silver is obtained by microwave treatment of saturated fatty acid silver and mesoporous silica nanospheres; The composite aid is composed of styrene-ethylene-butadiene-styrene block copolymer grafted maleic anhydride (SEBS-g-MAH), hydrogenated castor oil and nanometer boehmite; (2) mixing the antibacterial masterbatch with polyolefin base chip, melting the mixture, extruding to form primary fiber sliver; (3) drawing and heat setting the primary fiber sliver; (4) crimping and cutting the heat-set fiber to obtain the antibacterial staple fiber.

[0010] Further, the mass ratio of low-density polyethylene, modified saturated fatty acid silver, dispersion aid and composite aid in step (1) is (65-75):(22-32):(1-3):(2-5).

[0011] Further, the preparation method of the modified saturated fatty acid silver is as follows: Mix the saturated fatty acid silver and mesoporous silica nanospheres, and place the mixture in a microwave reactor under a protective atmosphere at a power of 300-500 W and a temperature of 80-110℃ for 5-15 minutes.

[0012] Further, the pore size of the mesoporous silica nanospheres is 3-5 nm, and the mass ratio of the silver saturated fatty acid to the mesoporous silica nanospheres is 1:(0.1-0.3).

[0013] Further, the silver saturated fatty acid is one or more of silver laurate, silver myristate, silver palmitate, and silver stearate.

[0014] The microwave-mesoporous silica modification treatment of the silver saturated fatty acid in the application fundamentally solves the problem of dispersion stability of the silver component in the polymer melt. Although the unmodified silver saturated fatty acid powder has better compatibility with polyolefins than inorganic silver powder, it still faces the tendency of thermal agglomeration caused by the excessively high surface energy of the particles during high-shear melt blending. These micron-sized agglomerates can become defect points in the spinning process, leading to uneven melt flow, spinneret pressure fluctuations, and even blockage, which seriously affects spinnability and degrades the mechanical strength of the fiber. Through the synergistic treatment of the silver saturated fatty acid and mesoporous silica nanospheres with specific pore sizes in the microwave field, the microwave energy not only provides heat, but also efficiently promotes the specific interaction between silver ions and the surface silicon hydroxyl groups of the silica, allowing the silver saturated fatty acid molecules to be "anchored" on the large surface and pore entrances of the mesoporous silica. This structural change, on the one hand, uses rigid and harmless silica nanospheres as physical spacers to effectively prevent direct contact between silver saturated fatty acid particles, greatly inhibiting agglomeration; on the other hand, the mesoporous silica framework provides a stable "memory" and controllable "release channel" for the silver saturated fatty acid it carries. During the service life of the final fiber, moisture and other media in the environment can slowly penetrate through these nanopores, interact with the internal silver saturated fatty acid, and promote the release of silver ions at a more gentle and sustained rate. This not only avoids the initial burst release of silver ions, but also ensures that even if the silver ions on the surface of the fiber are lost due to washing or friction, the internally stored silver can continue to supplement to the surface through the pores, thereby achieving significant durability improvement in antibacterial performance.

[0015] Further, the mass ratio of the styrene-ethylene-butadiene-styrene block copolymer grafted maleic anhydride (SEBS-g-MAH), hydrogenated castor oil, and nanobohmite is 1:(1.2-2.0):(0.8-1.2).

[0016] The maleic anhydride functional group in SEBS-g-MAH in the composite auxiliary agent can form firm interface bonding with the polyolefin matrix and the modified saturated fatty acid silver, significantly improving the compatibility, and the elastomer characteristics of the silver component endow the fiber with excellent toughness and anti-fracture ability. The hydrogenated castor oil as a high-efficiency lubricating carrier can effectively reduce the melt viscosity, ensure the excellent fluidity of the high filler material in the processing, and avoid the flow fluctuation in the spinning process. The flaky structure of the nanometer boehmite plays a rigid support role in the system, which cooperates with the former two to improve the melt strength of the composite system and the thermal dimensional stability of the final fiber. The three are combined in a specific ratio, which synchronously solves the problems of compatibility, toughening and strengthening of the fiber under high addition amount without sacrificing the processability, and ensures that the final product has excellent mechanical properties and stable spinnability.

[0017] Further, the dispersing aid is one of zinc stearate, ethylene-vinyl acetate copolymer (EVA), and silane coupling agent KH-550.

[0018] Further, the mass ratio of the antibacterial master batch to the polyolefin base chip in step (2) is 1: (3-9); and the polyolefin base chip is one of high-density polyethylene (HDPE), low-density polyethylene (LDPE), and fiber-grade polypropylene (PP).

[0019] Further, the draw ratio in step (3) is controlled to be 3.0-5.5 times, and the draw temperature is 75-90°C.

[0020] The second aspect of the present application provides a saturated fatty acid silver-based antibacterial staple fiber prepared by the above method.

[0021] Compared with the prior art, the present application has the following advantages and beneficial effects: 1. Uniform dispersion and excellent spinnability: through the synergistic effect of microwave modification treatment and special composite auxiliary agent, the thermal agglomeration tendency of the saturated fatty acid silver in the melt processing is fundamentally inhibited, so that the silver component is uniformly dispersed in the polymer matrix at the micron level. This makes the melt flow stability in the spinning process very low, solves the technical bottleneck of spinneret blockage and continuous production caused by silver powder agglomeration in the traditional blending method.

[0022] 2. Mechanical properties and antibacterial function: the uniformly dispersed silver component avoids the formation of stress concentration defects in the fiber, thereby ensuring that the fiber has high breaking strength and good elongation, fully meeting the subsequent non-woven fabric processing requirements. At the same time, the silver is firmly wrapped and anchored inside the fiber, rather than just physically attached to the surface.

[0023] 3. Highly effective and long-lasting antibacterial properties: Based on the unique slow-release mechanism of saturated fatty acid silver, the fiber can continuously and stably release silver ions with antibacterial activity in the usage environment. Even after repeated washing and friction, the internal silver reserves can be continuously replenished to the surface through mesoporous channels, thus exhibiting excellent antibacterial durability, far exceeding products prepared by surface finishing methods and ordinary blending methods.

[0024] 4. Safe and environmentally friendly processing: The entire process is a physical melt blending process, which does not require the use of chemical reducing agents, solvents or the generation of silver-containing wastewater, meets the requirements of green manufacturing, and is environmentally friendly and safe. Detailed Implementation

[0025] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0026] Unless otherwise specified, all raw materials used in the embodiments are commercially available products. The following sources are illustrative examples.

[0027] Silver laurate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., D50=5μm; silver stearate was purchased from Shanghai Maclean Biochemical Technology Co., Ltd., D90=10μm; mesoporous silica nanospheres were purchased from Nanjing Xianfeng Nanomaterials Technology Co., Ltd., pore size 3-5nm; styrene-ethylene-butadiene-styrene block copolymer grafted maleic anhydride (SEBS-g-MAH) was purchased from Kraton Performance Polymers, Inc., FG1901GT; nanoboehmite was purchased from Sammer Nanotechnology GmbH, Germany, Disperal® HP14; low-density polyethylene (LDPE) was purchased from China Petroleum & Chemical Corporation, LD-100; fiber-grade polypropylene (PP) was purchased from China National Petroleum Corporation, HP552R; high-density polyethylene (HDPE) was purchased from China National Offshore Oil Corporation, HD-5502FA.

[0028] Example 1 This embodiment provides an antibacterial short fiber based on saturated fatty acid silver, the preparation method of which includes the following steps: (1) Preparation of modified silver laurate: Weigh 1000g of silver laurate powder and 150g of mesoporous silica nanospheres with a pore size of 4nm, place them together in a high-speed mixer, and dry mix at room temperature for 15 minutes until they are uniform to the naked eye. The uniformly mixed powder was transferred to a microwave reactor, sealed, and then purged with nitrogen as a protective atmosphere to replace and maintain an inert environment inside the reactor. The microwave reactor was started, and the microwave power was set to 400W and the reaction temperature to 90℃. The process was continued under these conditions for 10 minutes. After processing, the material is allowed to cool naturally to room temperature and then discharged to obtain the modified silver laurate.

[0029] Pre-formulation of compound additives: Weigh the following three components: 100g of styrene-ethylene-butadiene-styrene block copolymer grafted maleic anhydride (SEBS-g-MAH), 150g of hydrogenated castor oil, and 100g of nano-boehmite. Add the above three materials to a high-speed mixer and mix at 800 rpm for 8 minutes to obtain the composite additive, which is then sealed and stored for later use.

[0030] Weigh the raw materials according to the following mass ratio: Low-density polyethylene (LDPE): 7000g, modified silver laurate: 2700g, dispersing agent (ethylene-vinyl acetate copolymer EVA): 200g, and compounding agent: 300g. Put all the above materials into a high-speed mixer at once and mix at 1000 rpm for 10 minutes until a homogeneous blend is obtained.

[0031] The mixed materials are continuously and stably fed into a co-rotating twin-screw extruder. The temperatures of each zone of the extruder are set as follows: Zone 1 165℃, Zone 2 175℃, Zone 3 180℃, Zone 4 180℃, and Die Head 185℃; the screw speed is constantly controlled at 300 rpm. After melt blending, extrusion, water cooling, and traction, the mixture is granulated using an underwater pelletizer. The resulting granules are dried in an 80℃ forced-air drying oven for 4 hours to obtain antibacterial masterbatch.

[0032] (2) The antibacterial masterbatch and fiber-grade polypropylene (PP) base chips were mixed at a mass ratio of 1:4, and the mixture was fed into a single-screw spinning extruder. The temperatures of each zone of the extruder were set as follows: Zone 1 195℃, Zone 2 205℃, Zone 3 210℃, and Zone 4 210℃. The polymer melt was delivered to the spinneret by a precision metering pump and extruded to form nascent fiber filaments. The filaments immediately entered the side-blowing cooling channel, where the cooling air temperature was 20℃ and the wind speed was 0.5 m / s, to solidify the filaments.

[0033] (3) The cooled and solidified nascent fiber filaments are introduced into a drawing unit consisting of three pairs of hot rollers for multi-stage drawing. The specific process is as follows: the temperature of the first pair of rollers is 75℃, the temperature of the second pair of rollers is 80℃, and the temperature of the third pair of rollers is 85℃; by adjusting the speed difference between each roller, the total drawing ratio is precisely controlled to 4.2 times. The drawn fibers then enter the heat setting rollers and are subjected to relaxation heat setting at 110℃ for 20 seconds to eliminate internal stress and stabilize the supramolecular structure of the fibers.

[0034] (4) The heat-set filament bundles are passed through a mechanical crimping machine to give the fibers 3-4 three-dimensional crimps per centimeter. Finally, the continuous long filament bundles are cut into short fibers of about 51 mm in length using a cutting machine to obtain the antibacterial short fibers based on saturated fatty acid silver.

[0035] Example 2 This embodiment provides an antibacterial short fiber based on saturated fatty acid silver. The difference from Example 1 is that the silver laurate in step (1) is replaced with silver stearate to prepare modified silver stearate.

[0036] Example 3 This embodiment provides an antibacterial short fiber based on saturated fatty acid silver. The difference from Example 1 is that the masses of the three components in the composite additive are as follows: styrene-ethylene-butadiene-styrene block copolymer grafted maleic anhydride (SEBS-g-MAH): 90g, hydrogenated castor oil: 180g, and nano-boehmite: 80g.

[0037] Example 4 This embodiment provides an antibacterial short fiber based on saturated fatty acid silver. The difference from Example 1 is that the mass of each raw material in step (1) is as follows: low density polyethylene (LDPE): 6500g, modified silver laurate: 3100g, dispersing agent (ethylene-vinyl acetate copolymer EVA): 100g, composite agent: 500g.

[0038] Example 5 This embodiment provides an antibacterial short fiber based on saturated fatty acid silver. The difference from Embodiment 1 is that in step (2), the fiber-grade polypropylene (PP) base chips are replaced with high-density polyethylene (HDPE) base chips, and the mass ratio of antibacterial masterbatch to high-density polyethylene (HDPE) base chips is 1:8.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that the modified silver laurate in step (1) is replaced with an equal mass of micron-sized silver powder with a particle size of 1-3 μm.

[0040] In this comparative example, severe spinneret clogging occurred during melt spinning, resulting in an extremely high yarn breakage rate and making stable continuous production impossible.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that in step (1), the modification treatment of silver laurate was omitted, and the unmodified original silver laurate powder was used directly.

[0042] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: In step (1), the modified silver laurate is prepared by the following method: 1000g of silver laurate powder and 150g of mesoporous silica nanospheres are placed together in a planetary ball mill and ball-milled at 300 rpm for 2 hours to obtain modified silver laurate.

[0043] Comparative Example 4 The difference between this comparative example and Example 1 is that the composite additive in step (1) consists of only two components: SEBS-g-MAH and hydrogenated castor oil, with a mass ratio of 1:1.5, and the total amount of composite additive remains unchanged.

[0044] Comparative Example 5 The difference between this comparative example and Example 1 is that in the composite additive in step (1), SEBS-g-MAH is replaced with an equal mass of polyethylene wax.

[0045] Performance testing Test samples: Antibacterial short fibers prepared in Examples 1-5 and Comparative Examples 1-5.

[0046] Test method: 1. Initial antibacterial performance test Test method: Following GB / T 20944.3-2008 Evaluation of antimicrobial properties of textiles – Part 3: Shaking method, tests were conducted on Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 6538). Fiber samples were cut to the same size, shaken together with the bacterial solution for 18 hours, and then the homogenate was cultured and counted to calculate the antimicrobial rate.

[0047] The result is expressed as: antibacterial rate (%).

[0048] 2. Antibacterial durability test Test method: Following the simulated washing procedure in GB / T 12490-2014 Textiles - Tests for color fastness to household and commercial washing, the fiber samples were subjected to 50 standard washes. After washing, the antibacterial rate was determined according to the "Initial Antibacterial Performance Test" method described above.

[0049] The results indicate the antibacterial rate (%) after 50 washes.

[0050] 3. Fiber mechanical property testing Test method: Following the specifications in GB / T 14344-2008 "Test Method for Tensile Properties of Chemical Fiber Filaments", an electronic tensile testing machine was used to test individual fibers. The clamping distance was 20 mm, and the tensile speed was 20 mm / min.

[0051] The results are expressed as: fracture strength (cN / dtex) and elongation at break (%).

[0052] 4. Spinability assessment Test method: During a fixed period of spinning, the number of times the yarn breaks down due to yarn breakage is counted and converted into the "yarn breakage rate" (times / hour).

[0053] The results are expressed as: decapitation rate (times / hour).

[0054] Table 1 Performance Test Results

[0055] The performance test results above show that the antibacterial short fibers prepared in Examples 1-5 all exhibit excellent comprehensive performance. After 50 vigorous washes, the antibacterial rate of all examples remained at an extremely high level of over 99.5%, fully demonstrating the superior antibacterial durability based on the silver slow-release mechanism of saturated fatty acids. In terms of mechanical properties, the breaking strength of all fibers exceeded 3.0 cN / dtex, and the breaking elongation was also at a good level, indicating that this technical solution successfully maintained the excellent mechanical properties of the fibers while introducing highly efficient antibacterial function.

[0056] Comparative Example 1, with its severe spinneret clogging and high breakage rate, demonstrates the insurmountable agglomeration problem of micron-sized silver powder in the melt, leading to loss of spinnability. Simultaneously, the silver powder agglomerates, acting as stress concentration points, severely disrupt the continuity of the fiber structure, resulting in extremely low tensile strength and elongation at break. Comparative Example 2 shows slight deterioration in mechanical properties and antibacterial durability, indicating that the dispersion uniformity and stability of the silver component are inferior to the modified sample, with some silver species lost during processing and use due to poor dispersion. Comparative Example 3 demonstrates that simple mechanical ball mixing cannot achieve the molecular-level "anchoring" effect achieved by microwave treatment; the binding between the modifier and silver species is not strong enough, leading to a decrease in the sustained-release stability and dispersion uniformity of silver ions. Comparative Example 4 shows a decrease in tensile strength and elongation at break, demonstrating a synergistic effect between the reinforcing effect of nano-boehmite and the toughening effect of SEBS-g-MAH; the absence of either will affect the final mechanical properties. In Comparative Example 5, after replacing SEBS-g-MAH with polyethylene wax, the fiber toughness and silver-matrix interfacial bonding were significantly weakened, which was directly reflected in the decreased mechanical properties and antibacterial durability.

[0057] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing antibacterial staple fiber based on silver saturated fatty acid, comprising the following steps: (1) mixing low-density polyethylene, modified silver saturated fatty acid, dispersion aid and composite aid, then melt blending, extruding and granulating to obtain antibacterial masterbatch; the modified silver saturated fatty acid is obtained by microwave treatment of silver saturated fatty acid and mesoporous silica nanospheres; the composite aid is composed of styrene-ethylene-butadiene-styrene block copolymer grafted maleic anhydride, hydrogenated castor oil and nanometer boehmite; (2) mixing the antibacterial masterbatch with polyolefin base chip, melting and extruding the mixture to form a primary fiber tow; (3) drawing and heat setting the primary fiber tow; (4) crimping and cutting the heat set fiber to obtain the antibacterial staple fiber. In step (1), the mass ratio of low-density polyethylene, modified silver saturated fatty acid, dispersion aid and composite aid is (65-75) : (22-32) : (1-3) : (2-5). The modified silver saturated fatty acid is prepared by mixing silver saturated fatty acid and mesoporous silica nanospheres, and then treating the mixture in a microwave reactor under a protective atmosphere at a power of 300-500 W and a temperature of 80-110℃ for 5-15 minutes. The mesoporous silica nanospheres have a pore size of 3-5 nm, and the mass ratio of silver saturated fatty acid to mesoporous silica nanospheres is 1: (0.1-0.3). The silver saturated fatty acid is one or more of silver laurate, silver myristate, silver palmitate and silver stearate. The mass ratio of styrene-ethylene-butadiene-styrene block copolymer grafted maleic anhydride, hydrogenated castor oil and nanometer boehmite is 1: (1.2-2.0) : (0.8-1.2). The dispersion aid is one of zinc stearate, ethylene-vinyl acetate copolymer and silane coupling agent KH-550.

2. The production method according to claim 1, characterized by, In step (2), the mass ratio of antibacterial masterbatch to polyolefin base chip is 1: (3-9), and the polyolefin base chip is one of high-density polyethylene, low-density polyethylene and fiber-grade polypropylene.

3. The preparation method according to claim 1, characterized in that, In step (3), the draw ratio is controlled at 3.0-5.5 times, and the draw temperature is 75-90℃.

4. The production method according to claim 3, characterized by, The method is prepared according to any one of claims 1-9.

5. The preparation method according to claim 3, characterized in that, ​ 6. The method of claim 1, wherein, ​ 7. The preparation method according to claim 1, characterized in that, ​ 8. The method of claim 1, wherein, ​ 9. The method of claim 1, wherein, ​ 10. An antibacterial short fiber based on silver of saturated fatty acid, characterized by, ​

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