TWI904989B - Preparation method of composite fiber, composite fiber and composite fiber mesh for agriculture - Google Patents

Abstract

A preparation method of a composite fiber is provided. The preparation method of a composite fiber includes: providing a doped zinc oxide and grinding it to form a ground doped zinc oxide; reacting the ground doped zinc oxide with a surface modifier agent to form a surface modified doped zinc oxide dispersion; providing a doped tungsten oxide and grinding it to form a ground doped tungsten oxide, and then mixing it with the surface modified doped zinc oxide dispersion to form an inorganic powder dispersion; performing a spray dry process on the inorganic powder dispersion to form an inorganic powder; dispersing the inorganic powder in a polymer to form a composite fiber composition; and subjecting the composite fiber composition to a spinning process to obtain a composite fiber. A composite fiber and a composite fiber mesh for agriculture are also provided.

Description

Preparation methods of composite fibers, composite fibers, and composite fiber webs for agricultural use.

This invention relates to a method for preparing a composite fiber, the composite fiber, and a composite fiber web for agricultural use.

Currently, most greenhouse netting used to block solar radiation and prevent overheating is colored. However, colored netting has poor visible light transmittance, which can negatively impact crop growth when applied to agricultural applications. Therefore, there is an urgent need to develop fabrics that can simultaneously achieve both light transmission and heat radiation insulation.

This invention provides a method for preparing composite fibers, which can produce composite fibers with good UV resistance, heat insulation and weather resistance, as well as composite fiber webs for agricultural use.

A method for preparing a composite fiber according to the present invention includes the following steps: providing doped zinc oxide and grinding the doped zinc oxide to form ground doped zinc oxide; reacting the ground doped zinc oxide with a surface modifier to form a surface-modified doped zinc oxide dispersion; providing doped tungsten oxide and grinding the doped tungsten oxide to form a surface-modified doped zinc oxide dispersion. Grinded tungsten oxide is mixed with a surface-modified zinc oxide dispersion to form an inorganic powder dispersion; the inorganic powder dispersion is spray-dried to form inorganic powder; the inorganic powder is dispersed in a polymer to form a composite fiber composition; the composite fiber composition is spun to obtain composite fibers.

The present invention provides a composite fiber, which is produced using the above-described method for preparing composite fibers.

This invention provides an agricultural composite fiber net, which is made using the aforementioned composite fiber.

Based on the above, the method for preparing composite fibers of the present invention disperses zinc oxide and tungsten oxide in a polymer, thereby enabling the resulting composite fibers and agricultural composite fiber webs to simultaneously block ultraviolet and near-infrared rays. Furthermore, the method utilizes a surface modifier to make the zinc oxide and tungsten oxide compatible with each other, thereby reducing the likelihood of spinneret blockage or yarn breakage during the spinning process of the composite fiber composition.

To make the above features and advantages of this invention more apparent and understandable, detailed examples are provided below.

The following are detailed embodiments of the present invention. The details presented in these embodiments are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. Anyone skilled in the art can modify or change these details as needed for the actual implementation. Furthermore, descriptions of well-known apparatus, methods, and materials may be omitted to avoid obscuring the description of the various principles of the present invention.

A range may be expressed herein as from “about” one specific value to “about” another specific value, or it may be directly expressed as one specific value and/or to another specific value. In expressing the range, another embodiment includes from that one specific value and/or to another specific value. Similarly, when a value is expressed as an approximation by using the antecedent “about,” it will be understood that the specific value forms another embodiment. It will be further understood that each endpoint of a range may be obviously related to or unrelated to another endpoint.

In this document, non-limiting terms (such as: may, can, for example, or other similar terms) refer to the implementation, inclusion, addition, or existence of something that is not necessary or optional.

Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It will also be understood that terms (such as those defined in commonly used dictionaries) shall be interpreted as having a meaning consistent with their meaning in the relevant technical context, and shall not be interpreted in an idealized or overly formal sense, unless expressly defined herein. < Method for the Preparation of Composite Fibers >

This invention provides a method for preparing a composite fiber, comprising: providing doped zinc oxide and grinding the doped zinc oxide to form ground doped zinc oxide; reacting the ground doped zinc oxide with a surface modifier to form a surface-modified doped zinc oxide dispersion; providing doped tungsten oxide and grinding the doped tungsten oxide to form a ground doped zinc oxide dispersion. Grind tungsten oxide and mix the ground tungsten oxide with a surface-modified zinc oxide dispersion to form an inorganic powder dispersion; spray-dry the inorganic powder dispersion to form inorganic powder; disperse the inorganic powder in a polymer to form a composite fiber composition; and spin the composite fiber composition to obtain composite fibers.

There are no particular limitations on the type of zinc oxide used for doping; appropriate doped zinc oxide can be selected according to requirements. In this embodiment, the doped zinc oxide may include aluminum-doped zinc oxide (Al-doped ZnO, AZO), gallium-doped zinc oxide (Ga-doped ZnO, GZO), or other suitable doped zinc oxides. The doped zinc oxide may be a single type or a combination of multiple doped zinc oxides.

The particle size of the doped zinc oxide can be from 10 nanometers to 1000 nanometers, preferably from 15 nanometers to 300 nanometers, and even more preferably from 15 nanometers to 180 nanometers. In some embodiments, the particle size of aluminum-doped zinc oxide (AZO) can be from 10 nanometers to 1000 nanometers, preferably from 40 nanometers to 180 nanometers, but this disclosure is not limited thereto. In some embodiments, the particle size of gallium-doped zinc oxide (GZO) can be from 10 nanometers to 1000 nanometers, preferably from 15 nanometers to 50 nanometers, but this disclosure is not limited thereto.

There are no particular limitations on the methods of doping zinc oxide with other elements (such as aluminum, gallium, or other suitable elements). For example, well-known element doping methods can be used, which will not be elaborated here.

There are no particular limitations on the method of grinding the doped zinc oxide particles, but physical shear dispersion or similar methods can be used, such as using a high-speed homogenizer and a bead mill, to break up the agglomerated powder so that the powder particles can be uniformly dispersed in the solvent, thereby reducing the particle size and making the particles uniformly dispersed to form a dispersion with good stability (such as the inorganic powder dispersion subsequently formed).

In this embodiment, the terminator of the surface modifier may include a hydrolyzable group and an organic functional group. The organic functional group may include vinyl, amino, epoxy, or other suitable functional groups. The hydrolyzable group may include an alkoxy or other suitable group.

For example, the hydrolyzable group and the organic functional group in the surface modifier may be located at opposite ends of the surface modifier structure. Thereby, the hydrolyzable group can chemically react with the doped zinc oxide to form a bond, and the organic functional group can generate intermolecular forces (e.g., hydrogen bonds) with the doped tungsten oxide. It is worth noting that the organic functional group and the doped tungsten oxide may approach each other but not form a bond. In this embodiment, the surface modifier may include a compound represented by the following formula (1).

(RO) ₃ -Si-(R') _m -X Formula (1),

In formula (1), R represents an alkyl group having 1 to 2 carbon atoms, preferably an ethyl group; R’ represents an alkyl group, ether group, or combination thereof having 1 to 3 carbon atoms, preferably a methylene group, propyl group, ether group, or combination thereof; m represents an integer from 0 to 3, preferably an integer from 0 to 1; X represents a vinyl group, amino group, or epoxy group.

In equation (1), the OR group can chemically react with doped zinc oxide to form a bond, and the X group can generate intermolecular forces with doped tungsten oxide.

The surface modifier may be a single surface modifier or a combination of multiple surface modifiers. In some embodiments, the surface modifier may include 3-aminopropyltriethoxysilane, vinyltriethoxysilane, 3-glycidyloxypropyltriethoxysilane, or other suitable surface modifiers. For example, the surface modifier may be Dynasylan® AMEO (trade name, manufactured by Mocon Corporation), Dynasylan® GLYMO (trade name, manufactured by Mocon Corporation), Dynasylan® VTMO (trade name, manufactured by Mocon Corporation), or other suitable surface modifiers, but this disclosure is not limited thereto.

There are no particular limitations on the doped tungsten oxide; appropriate doped tungsten oxides can be selected according to requirements. In this embodiment, the doped tungsten oxide may include cesium-doped tungsten oxide (Cs-doped _WO3 , CTO), but this disclosure is not limited thereto. The doped tungsten oxide may be a single doped tungsten oxide or a combination of multiple doped tungsten oxides.

In some embodiments, the particle size of cesium-doped tungsten oxide (CTO) can be from 10 nanometers to 1000 nanometers, preferably from 30 nanometers to 150 nanometers, but this disclosure is not limited thereto.

There are no particular limitations on the methods of doping tungsten oxide with other elements (such as cesium or other suitable elements), for example, well-known element doping methods can be used, which will not be elaborated here.

There are no particular limitations on the method for grinding doped tungsten oxide particles; an appropriate method can be selected according to the requirements. The method for grinding doped tungsten oxide particles can be the same as or different from the method for grinding doped zinc oxide particles.

There are no particular restrictions on the polymer; appropriate polymers can be selected according to requirements. In this embodiment, the polymer may include polyester, polyethylene (PE), polypropylene (PP), polyamide (PA), or other suitable polymers. The polymer may be a single polymer or a combination of multiple polymers.

For example, polyesters may include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), or other suitable polyesters. Polyamides may include nylon.

In this embodiment, in the method for preparing composite fibers, the inorganic powder dispersion can be spray-dried and then mixed with a polymer to form a composite fiber composition (i.e., fiber masterbatch). During the spray-drying process, the inorganic powder dispersion can enter a spray dryer and be spray-dried to form inorganic powder. Before collecting the inorganic powder, the temperature in the chamber where the inorganic powder is placed can be the outlet temperature. The outlet temperature is higher than the temperature at which the inorganic powder is collected (i.e., the collection temperature). The outlet temperature can be from 120°C to 160°C, and the collection temperature can be from 20°C to 50°C. For example, the outlet temperature can be 140°C, and the collection temperature can be 30°C, but this disclosure is not limited to these. In some embodiments, inorganic powder dispersions can be spray-dried, baked, and stirred before being used to produce masterbatches using a twin-screw mixer.

The composite fiber composition may include doped zinc oxide, surface modifiers, doped tungsten oxide, and polymers. In this embodiment, based on a total weight of 100 parts by weight of the composite fiber composition, the solid content of the composite fiber composition is 0.2 parts by weight to 3 parts by weight, preferably 0.6 parts by weight to 1.6 parts by weight.

The total weight of the composite fiber composition is 100 parts by weight, the amount of doped zinc oxide used is 0.1 to 2 parts by weight, preferably 0.2 to 1.1 parts by weight; the amount of surface modifier used is 0.005 to 0.05 parts by weight, preferably 0.01 to 0.03 parts by weight; the amount of doped tungsten oxide used is 0.1 to 1 part by weight, preferably 0.4 to 0.8 parts by weight; and the amount of polymer used is 90 to 99.8 parts by weight, preferably 99.37 to 99.48 parts by weight.

In this embodiment, the weight ratio of the amount of doped zinc oxide to the amount of doped tungsten oxide is 1:4 to 4:1, preferably 1:2 to 2:1.

In some embodiments, the composite fiber composition may be subjected to a pressure test before the spinning process to avoid problems such as yarn blockage or yarn breakage during subsequent spinning. The pressure test can use well-known test methods and select an appropriate pressure value as needed, which will not be elaborated here.

The spinning process of composite fiber components may include, for example, the following steps, but this disclosure is not limited thereto.

Inorganic powder particles can be dispersed in a polymer using a planetary mill. In some embodiments, the inorganic powder is dispersed in the polymer at a grinding speed of 200 rpm to 350 rpm for a grinding time of 15 hours (hr) to 28 hours, preferably 18 hours to 24 hours. For example, 10 grams of inorganic powder and 40 grams of aqueous solution (composed of 30 grams of deionized water and 10 grams of dispersant) are mixed and placed in a grinding jar, and 60 grams of 0.4 mm zirconia beads are added for grinding. A uniformly dispersed and well-suspended inorganic powder dispersion is obtained by grinding at a speed of 300 rpm for 18 hours.

In some embodiments, after dispersing inorganic powder in a polymer, a masterbatch containing 5 wt% to 10 wt% inorganic powder is prepared using a twin-screw mixer. When the inorganic powder content in the masterbatch is within this range, it facilitates the addition of the masterbatch during spinning and allows for passing pressure rise tests. Subsequently, the masterbatch containing 5 wt% to 10 wt% inorganic powder is uniformly mixed with regular particles at a weight ratio of 1:9, and then spun using a melt spinning machine (spinning temperature, for example, 240°C to 270°C or 270°C to 300°C, and spinning speed, for example, 2550 m/min to 4200 m/min) to obtain composite fibers.

If the inorganic powder particles agglomerate and are not well dispersed in the solvent during the above-mentioned process steps, or if a surface modifier is not used to make the doped zinc oxide and doped tungsten oxide compatible, the composite fiber composition may cause problems such as spinneret blockage or yarn breakage during subsequent spinning processes. Based on this, this embodiment involves grinding zinc oxide and tungsten oxide doped together, and using a surface modifier to make them more compatible. This reduces the likelihood of spinneret blockage or yarn breakage during the spinning process of the composite fiber composition. Example 1 : Preparation of aluminum-doped zinc oxide ( AZO )

A mixed solution with a concentration of 1 ml/L was prepared using zinc nitrate (purchased from Sigma-Aldrich Corporation) and aluminum chloride (purchased from Sigma-Aldrich Corporation), wherein the ratio of aluminum added to the total weight of zinc and aluminum was 1:100. This mixed solution, along with an ammonium bicarbonate solution (purchased from Sigma-Aldrich Corporation), was added dropwise to water while maintaining the temperature at 40°C and the pH at 7.0 to 7.5, and stirring vigorously. This yielded a homogeneous, white, basic zinc carbonate precipitate. The precipitate was washed, separated, and then dried to obtain a powder. The obtained powder is sintered in a mixture of hydrogen and argon at a temperature of 400°C to 700°C for 30 to 60 minutes. After sintering, aluminum-doped zinc oxide particles are obtained.

In this embodiment, the particle size of the aluminum-doped zinc oxide particles can be adjusted by changing the sintering temperature and sintering time to form particles with a size of 50 nanometers to 1000 nanometers. For example, when the sintering temperature is 400°C and the sintering time is 60 minutes, particles with a size of 50 nanometers to 150 nanometers can be obtained (more suitable for spinning processes). When the sintering temperature is 700°C and the sintering time is 30 minutes, particles with a size greater than 500 nanometers can be obtained (more suitable for coating processes).

In this embodiment, the particle size of the prepared aluminum-doped zinc oxide before and after grinding can be analyzed by scanning electron microscopy (SEM). Before grinding, the aggregated particle size of the aluminum-doped zinc oxide is approximately 5 to 20 micrometers. After grinding, no agglomeration was observed in the aluminum-doped zinc oxide, and the individual particle size is approximately 40 to 180 nanometers. Preparation Example 2 : Preparation of gallium-doped zinc oxide ( GZO )

The gallium-doped zinc oxide particles were prepared using the same steps as in Preparation Example 1, except that the aluminum chloride in Preparation Example 1 was replaced with gallium chloride.

In this embodiment, the particle size of the gallium-doped zinc oxide before and after grinding can be analyzed by scanning electron microscopy (SEM). Before grinding, the aggregated particle size of the gallium-doped zinc oxide is approximately 2 to 15 micrometers. After grinding, no agglomeration of the gallium-doped zinc oxide was observed, and the individual particle size is approximately 15 to 50 nanometers. Preparation Example 3 : Preparation of a surface-modified doped zinc oxide dispersion.

Take 50 parts by weight of ethanol and 17 parts by weight of water, add 30 parts by weight of the powder (AZO or GZO) prepared in Preparation Example 1 or Preparation Example 2, and ultrasonically vibrate for 30 minutes. Then, add 1-3 parts by weight of surface modifier affinity to adjust the pH value to 4, and vigorously stir to hydrolyze the siloxane. Maintain stirring at 60°C for 120 minutes to attach the surface modifier affinity to the AZO or GZO surface to obtain a modified powder dispersion. Preparation Example 4 : Preparation of Inorganic Powder Dispersion

The powder dispersion prepared in Example 3 by modification (6.6 parts by weight) was dissolved in 77.4 parts by weight of solvent (water or alcohol), and 16 parts by weight of a 25% dispersion of cesium tungsten powder (purchased from Senguan) was added. The mixture was stirred at room temperature for 10 minutes to obtain the inorganic powder dispersion. The weight of each powder added depends on the final powder content. It is worth noting that the inorganic powder dispersion can then be spray-dried to form inorganic powder.

In this embodiment, the particle size of the cesium-doped tungsten oxide before and after polishing can be analyzed by X-ray diffractometer (XRD) and scanning electron microscopy (SEM) (as shown in Figures 1 and 2A-2D). Before polishing, the aggregated particle size of the cesium-doped tungsten oxide is about 5 micrometers to 20 micrometers, the secondary particle size is about 300 nanometers to 650 nanometers, and the grain size is about 105 nanometers (as shown in Figure 1(a) and Figures 2A-2B). After grinding, no agglomeration was observed in the cesium-doped tungsten oxide; the individual particle size was approximately 30 to 150 nanometers, and the grain size was approximately 14 nanometers (as shown in Figure 1(b) and Figures 2C-2D). Example 1 : Method for preparing composite fibers and the composite fibers obtained therefrom.

Two parts by weight of milled aluminum-doped zinc oxide particles (40 to 180 nm in size) were reacted with 0.1 parts by weight of 3-aminopropyltriethoxysilane (purchased from Sigma-Aldrich) to form a surface-modified aluminum-doped zinc oxide dispersion. This dispersion was then mixed with four parts by weight of milled cesium-doped tungsten oxide particles (30 to 150 nm in size). The inorganic powder dispersion was subsequently spray-dried. The nozzle outlet temperature of the spray drying is set to 140°C. The inorganic powder collected after spray drying is uniformly dispersed in high-density polyethylene (HDPE) with a weight ratio of 6 parts by weight using a twin-screw mixer to prepare PE masterbatch, thereby obtaining HDPE masterbatch (i.e., composite fiber composition). It is worth noting that the detailed preparation methods of the aluminum-doped zinc oxide particles, the surface-modified zinc oxide dispersion, and the inorganic powder dispersion can be referred to in Preparation Example 1, Preparation Example 3, and Preparation Example 4, respectively, and will not be repeated here.

Next, HDPE masterbatch containing doped zinc oxide particles and cesium-doped tungsten oxide with a powder concentration of 6% is uniformly mixed with regular HDPE granules (Liansu® LH901, purchased from Taiwan Polymer Chemicals Co., Ltd.) in an appropriate weight ratio and dried (for example, 1 part by weight of HDPE masterbatch can be mixed with 9 parts by weight of regular HDPE granules to dilute the inorganic powder concentration by 10 times). Then, a spinning process is performed using a melt spinning machine (spinning temperature of 240°C to 270°C) to obtain a composite fiber with a single fiber diameter of 190 μm. The powder concentration in the fiber is 0.6% (0.2% doped zinc oxide + 0.4% cesium doped tungsten oxide). Examples 2 to 5 and Comparative Examples 1 to 11.

The methods for preparing the composite fibers of Examples 2 to 5 and Comparative Examples 1 to 11, and the composite fibers obtained therefrom, were prepared using the same steps as in Example 1, except that the raw materials and their amounts in the preparation methods were changed (as shown in Table 1). After the prepared composite fibers were pressed into films with a thickness of 0.25 mm, the UV-VIS-NIR spectral transmittance was measured using an ultraviolet-visible-infrared spectrometer (model UV-3600, manufactured by Shimadzu Corporation), and the weather resistance and tensile strength were measured using a universal testing machine (model Instron Model 4505 Universal Testing Machine, manufactured by Instron Corporation). The results are shown in Tables 1-2 and Figures 3-4.

In the embodiments and comparative examples, the composite fibers of Embodiment 2 and Comparative Example 10 were made into heat-insulating yarns by using transparent weft yarns to weave a 24-mesh agricultural net, and then pressed into a film with a thickness of 0.25 mm for evaluation. In the composite fibers of Embodiment 3 and Comparative Example 11, the composite fibers were made into heat-insulating yarns by using transparent weft yarns to weave a 32-mesh agricultural net, and then pressed into a film with a thickness of 0.25 mm for evaluation.

[Table 1] Ingredients (unit: parts by weight) Implementation Examples 1 2 3 4 5 Doped zinc oxide AZO 0.2 0.2 0.2 0.7 0.7 GZO - - - 0.3 0.4 Doped tungsten oxide CTO 0.4 0.4 0.4 0.5 0.5 Surface modifiers 3-Aminopropyltriethoxysilane 0.01 0.01 0.01 - - Vinyltriethoxysilane - - - 0.02 - 3-Glycidyloxypropyltriethoxysilane - - - - 0.03 polymer PE 99.39 99.39 99.39 - - PET (fabric) - - - 98.48 - Nylon (cloth) - - - - 98.37 Average penetration UV (240~380 nm) 13.70 27.26 21.10 4.32 0.77 VIS (380~780 nm) 61.63 73.51 68.39 11.58 8.07 NIR (780~2600 nm) 24.72 42.47 36.80 6.00 6.89

[Table 1] (Continued) Ingredients (unit: parts by weight) Comparative example 1 2 3 4 5 6 Doped zinc oxide AZO - - - - 0.2 0.4 GZO - - - - - - Doped tungsten oxide CTO - 0.2 0.4 0.8 - - Surface modifiers 3-Aminopropyltriethoxysilane - - - - - - Vinyltriethoxysilane - - - - - - 3-Glycidyloxypropyltriethoxysilane - - - - - - polymer PE 100 99.8 99.6 99.2 99.8 99.6 PET - - - - - - Nylon - - - - - - Average penetration UV (240~380 nm) 28.47 25.94 20.43 10.61 6.05 6.30 VIS (380~780 nm) 86.73 83.41 74.66 55.43 75.06 72.64 NIR (780~2600 nm) 78.45 69.71 50.26 22.05 71.99 69.38

[Table 1] (Continued) Ingredients (unit: parts by weight) Comparative example 7 8 9 10 11 Doped zinc oxide AZO 0.8 2 10 0.6 0.6 GZO - - - - - Doped tungsten oxide CTO - - - - - Surface modifiers 3-Aminopropyltriethoxysilane - - - - - Vinyltriethoxysilane - - - - - 3-Glycidyloxypropyltriethoxysilane - - - - - polymer PE 99.2 98 90 99.4 99.4 PET - - - - - Nylon - - - - - Average penetration UV (240~380 nm) 6.33 3.57 0.08 5.14 1.48 VIS (380~780 nm) 70.09 71.40 45.49 55.54 46.45 NIR (780~2600 nm) 67.16 69.47 53.84 76.07 75.53 *Comparative Examples 10 and 11 also had 0.4 parts by weight of pink pigment added to each.

[Table 2] Implementation Examples Comparative example 2 3 4 5 Tensile strength (kg/ ^cm² ) Before lighting 77 90 65 100 After light exposure 76 87 49 76 Tensile strength retention rate (%) 98.7 96.7 75.4 76.0 < Evaluation Method >

Average transmittance: The transmittance values are averaged by scanning the wavelength range at 2 nm using an ultraviolet-visible-infrared spectrometer (model UV-3600, manufactured by Shimadzu Corporation). When the average transmittance of ultraviolet (UV) light is 13%~28%, the average transmittance of visible light (VIS) light is 61%~74%, and the average transmittance of infrared light (NIR) light is 24%~43%, it is considered the transmittance acceptable for agricultural technology (i.e., the acceptable transmittance for agricultural composite fiber mesh).

Tensile strength before light exposure: According to ASTM D5035-06, the tensile strength was tested at a rate of 300 mm/min using an Instron Model 4505 Universal Testing Machine (manufactured by Instron Corporation, Inc.).

Tensile strength after irradiation: After 700 hours of irradiation using a weathering tester (Ci5000, Atlas) according to ASTM D4355-07, tensile strength was tested at a rate of 300 mm/min using a universal testing machine (Instron Model 4505 Universal Testing Machine, Shin-Nano Corporation) according to ASTM D5035-06. A tensile strength retention rate of 96%–99% is considered acceptable in agricultural technology (i.e., acceptable tensile strength for agricultural composite fiber mesh). Light source: 12000W xenon arc lamp (Atlas). Illuminance: 0.35 W/ ^m² (wavelength 340 nm). Photofilter: S-type borosilicate inner and outer tubes. Program cycle: 90 minutes of light exposure, followed by 30 minutes of simultaneous water spraying and light exposure. Black disc temperature: 65±3℃ during light exposure cycle, 40±2℃ during water spraying cycle. Dry bulb temperature: 46±3℃ during light exposure cycle, 40±2℃ during water spraying cycle. Relative humidity: 50±5% during light exposure cycle, 85±5% during water spraying cycle. Exposure time: 700 hours. < Evaluation Results >

As shown in Table 1 and Figure 3, the methods for preparing composite fibers, including mixing milled doped tungsten oxide with a surface-modified doped zinc oxide dispersion to form an inorganic powder dispersion, can be successfully used in the spinning process to obtain composite fibers with good UV resistance, visible light transmittance, and heat insulation properties, and are suitable for textiles requiring UV resistance, visible light transmittance, and heat insulation. In contrast, the methods for preparing composite fibers do not include the composite fibers obtained in Comparative Examples 1-11, which use doped zinc oxide and/or doped tungsten oxide, and have poor UV resistance and/or heat insulation properties.

Furthermore, when the composite fiber is used as the insulating yarn through transparent weft yarn, the composite fiber prepared using methods that do not use doped tungsten oxide and instead add pink pigment, as described in Comparative Examples 10-11, results in commercially available agricultural fabrics. The composite fibers obtained in Comparative Examples 10-11 can block some visible light, thus providing insulation, but they also affect the light required for plant growth. In other words, currently commercially available agricultural fabrics cannot simultaneously achieve good insulation and visible light transmittance. When the composite fiber is made into a heat-insulating yarn by means of transparent weft yarn, the composite fiber obtained in Examples 2-3 has better heat insulation and visible light transmittance than the composite fiber obtained in Comparative Examples 10-11, and can be used in textiles that have both good visible light transmittance and heat insulation (e.g., textiles used in agricultural technology).

As shown in Table 1 and Figure 4, compared to the composite fibers obtained in Examples 1-3, where the amount of zinc oxide used in the composite fiber preparation method is 0.1 to 0.5 parts by weight, the composite fibers obtained in Examples 4-5, where the amount of zinc oxide used in the composite fiber preparation method is 0.6 to 2 parts by weight, have better UV resistance and heat insulation properties. Therefore, the composite fibers obtained in Examples 4-5 are suitable for clothing textiles.

Furthermore, the composite fiber prepared using a method that does not use doped zinc oxide and doped tungsten oxide, as in Comparative Example 1, resulted in a composite fiber with high visible light (VIS) transmittance but poor thermal insulation. The composite fiber obtained in Comparative Example 1 is suitable for agricultural applications where only pest control is required.

Furthermore, in the method for preparing the composite fiber in Comparative Example 4, there is a problem of spinneret blockage during the spinning process, that is, poor spinning performance. The process must be interrupted and the spinneret blockage problem must be resolved before the spinning process can continue.

As shown in Table 2, the composite fiber prepared by the method of mixing milled doped tungsten oxide with a surface-modified doped zinc oxide dispersion exhibits good weather resistance and is suitable for agricultural applications. In contrast, the composite fiber prepared by the method of not using doped tungsten oxide, as described in the comparative example, exhibits poor weather resistance.

Furthermore, the preparation methods of composite fibers do not include Comparative Examples 2 to 11, which use surface modifiers. During the spinning process, problems such as yarn blockage or yarn breakage may occur. The spinning process must be interrupted and the problem (such as solving the yarn blockage problem) must be resolved before the spinning process can continue.

In summary, the method for preparing composite fibers of the present invention disperses zinc oxide and tungsten oxide in a polymer, thereby enabling the resulting composite fibers and agricultural composite fiber webs to achieve both high light transmittance and the ability to block ultraviolet and near-infrared rays. Furthermore, the method utilizes a surface modifier to promote the affinity between zinc oxide and tungsten oxide, thereby reducing the likelihood of spinneret blockage or yarn breakage during the spinning process. Based on this, the composite fiber prepared by the method provided by the present invention has good UV resistance, heat insulation and weather resistance, and can be used in textiles such as clothing and agricultural technology (e.g., agricultural composite fiber nets).

Although the present invention has been disclosed above by way of embodiments, it is not intended to limit the present invention. Anyone with ordinary skill in the art may make some modifications and refinements without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended patent application.

without.

Figure 1(a) shows the particle size of the cesium-doped tungsten oxide according to the present invention before polishing, analyzed by X-ray diffractometer (XRD), with the calculated 2θ full width at half maximum (FWHM) at 27–28 degrees. Figure 1(b) shows the particle size of the cesium-doped tungsten oxide according to the present invention after polishing, analyzed by X-ray diffractometer (XRD), with the calculated 2θ full width at half maximum (FWHM) at 27–28 degrees. After polishing, the FWHM of the signal peak significantly widens and the signal decreases, indicating that the grain size decreases after polishing. Figures 2A and 2B show the particle size of the cesium-doped tungsten oxide according to the present invention before polishing, analyzed by scanning electron microscopy (SEM). Figures 2C and 2D show the particle size of cesium-doped tungsten oxide after grinding according to the present invention, analyzed by scanning electron microscopy (SEM). Figure 3 shows the UV-VIS-NIR transmittance (%) of the composite fibers obtained according to the preparation methods of Examples 2-3 and Comparative Examples 10-11 of the present invention, measured by a UV-VIS-NIR spectrometer (model UV-3600, manufactured by Shimadzu Corporation). Figure 4 shows the UV-VIS-NIR transmittance (%) of the composite fibers obtained according to the preparation method of embodiments 4-5 of the present invention, measured by an ultraviolet-visible-infrared spectrometer (model UV-3600, manufactured by Shimadzu Corporation).

Claims (15)

A method for preparing a composite fiber includes: providing doped zinc oxide and milling the doped zinc oxide to form milled doped zinc oxide; reacting the milled doped zinc oxide with a surface modifier to form a surface-modified doped zinc oxide dispersion; providing doped tungsten oxide, milling the doped tungsten oxide to form milled doped tungsten oxide, and further milling the milled doped zinc oxide... Tungsten oxide is mixed with the surface-modified zinc oxide dispersion to form an inorganic powder dispersion; the inorganic powder dispersion is spray-dried to form inorganic powder; the inorganic powder is dispersed in a polymer to form a composite fiber composition; and the composite fiber composition is spun to obtain composite fibers, wherein the zinc oxide doped includes aluminum-doped zinc oxide (Al-doped ZnO, AZO), gallium-doped zinc oxide (Ga-doped ZnO, GZO), or a combination thereof. The method for preparing the composite fiber as described in claim 1, wherein the milled doped zinc oxide has a particle size of 15 nanometers to 300 nanometers. The method for preparing the composite fiber as described in claim 1, wherein the surface modifier has a hydrolyzable group and an organic functional group at its end, and the organic functional group includes vinyl, amino or epoxy groups. The method for preparing the composite fiber as described in claim 1, wherein the surface modifier comprises 3-aminopropyltriethoxysilane, 3-glycidoxypropyltriethoxysilane, vinyltriethoxysilane, or a combination thereof. The method for preparing a composite fiber as described in claim 1, wherein the doped tungsten oxide includes cesium-doped tungsten oxide. The method for preparing the composite fiber as described in claim 1, wherein the milled tungsten oxide has a particle size of 30 nanometers to 150 nanometers. The method for preparing the composite fiber as described in claim 1, wherein the total weight of the composite fiber composition is 100 parts by weight, the amount of the doped zinc oxide used is 0.1 to 2 parts by weight, and the amount of the doped tungsten oxide used is 0.1 to 1 part by weight. The method for preparing the composite fiber as described in claim 1, wherein the weight ratio of the amount of doped zinc oxide used to the amount of doped tungsten oxide used is 1:4 to 4:1. The method for preparing the composite fiber as described in claim 1, wherein the polymer includes polyester, polyethylene, polypropylene, polyamide, or combinations thereof. A composite fiber, produced using the method for preparing a composite fiber as described in any one of claims 1 to 9. An agricultural composite fiber net, made using the composite fibers as described in claim 10. The agricultural composite fiber mesh as described in claim 11, wherein the average ultraviolet (UV) transmittance of the agricultural composite fiber mesh is 13% to 28%. The agricultural composite fiber mesh as described in claim 11, wherein the average visible light (VIS) transmittance of the agricultural composite fiber mesh is 61% to 74%. The agricultural composite fiber mesh as described in claim 11, wherein the average infrared (NIR) transmittance of the agricultural composite fiber mesh is 24% to 43%. The agricultural composite fiber mesh as described in claim 11, wherein the tensile strength retention rate of the agricultural composite fiber mesh is 96%~99%.