Thermal insulation aerogel composite fiber

Abstract

The present application provides a method for preparing an all-polymer aerogel composite fiber by compositing a fibrous material with a polymeric microaerogel powder using a melting process, the method comprising the steps of: (a) weighing a material for forming an aerogel composite fiber, the material should be composed of 0.1% to 20% (w / w) of polymeric micro aerogel powder and 80% to 99.9% (w / w) of fibrous material; (a) mixing the polymeric microaerogel powder with a fibrous material to form a homogeneous composite mixture; and (b) heating the composite mixture to the melting point of the fibrous material to disperse the polymeric microaerogel throughout the molten fibrous material, and then extruding the composite mixture to form the aerogel composite fiber.

Description

Technical Field

[0001] Various embodiments of the present disclosure relate to the technical field of thermal insulation materials, and in particular, to thermal insulation aerogel composite fibers. Background Art

[0002] Thermal insulation is important for survival and comfort in cold weather regions, allowing humans to maintain body temperature regardless of the surrounding environment. Thermal insulation is found in many products such as building walls, cooling systems, engines, etc., but the most common use of thermal insulation is in clothing. Wearing the right thermally insulating clothing when the weather is cold can help us stay healthy and reduce the amount of calories we need.

[0003] Aerogel is a synthetic, porous, ultralight material with one of the lowest thermal conductivity and density of any known material. Aerogel's excellent thermal insulation properties have been widely used in cooling, construction, and aerospace applications, however, the use of aerogel in the textile industry remains limited. Aerogels are most commonly prepared in the form of large sheets and are derived from inorganic materials that have poor adhesion to conventional textile materials. In addition, commercial aerogels are usually prepared using expensive supercritical drying processes due to the large amount of pressurized gas required. For these reasons, the use of aerogels in textiles is limited to thick garments that are large enough to fit large aerogel sheets into, such as jackets, vests, or gloves. These products are also very expensive.

[0004] The present application aims to address these problems by introducing a novel low-cost method for producing aerogel-reinforced thermally insulating textile fibers that can be woven into any form of clothing, thereby facilitating the commercialization and availability of aerogel-insulated clothing to consumers. Summary of the invention

[0005] The present application provides a low-cost method for enhancing the thermal insulation of textiles by producing thermally insulating aerogel composite fibers by including micro-sized aerogels in textile fibers. Since the aerogels are integrated inside the fibers, low-cost aerogel-enhanced clothing of any shape can be produced.

[0006] Micro aerogels are prepared using a low-cost method to produce aerogels derived from a background patent (U.S. Patent No. 10,807,059). The micro aerogels are made using organic polymers and dried using a modified low-cost freeze-drying process. The resulting micro aerogels have very low thermal conductivity, good adhesion to textile fibers, the ability to withstand high temperatures during melt extrusion, are small enough to be included in fibers, and are inexpensive to produce. In addition, these polymer micro aerogels can be added to any polymer material as a thermal insulation additive.

[0007] Aerogel composite fibers are prepared by mixing micro aerogels with polyethylene terephthalate (PET) pellets in a melt extruder, where the micro aerogels are dispersed in molten PET and extruded into aerogel composite fibers. The resulting aerogel composite fibers have improved thermal insulation properties compared to the original fibers, while their mechanical properties have not changed significantly.

[0008] The porous micro-aerogel is dispersed inside the fiber material, thereby forming a porous structure inside the fiber. These pores shorten the mean free path of heat conduction inside the fiber, thereby reducing the thermal conductivity of the fiber and increasing its thermal insulation properties. In addition, since the micro-aerogel is made of organic polymer, the micro-aerogel has good adhesion to the organic fiber material and does not significantly affect its mechanical properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] In the figures of the accompanying drawings, one or more embodiments are shown by way of example and not limitation, wherein elements / modules and steps indicated by the same reference numerals represent the same elements / modules and steps throughout. Unless otherwise specified, the drawings are not drawn to scale.

[0010] Figure 1 is a diagram of a cross section of an aerogel composite fiber, illustrating how aerogel shortens the mean free path of heat conduction.

[0011] Figure 2 is a flow chart of the synthesis of polyimide (PI) based micro aerogels, which shows a PI / DMAc / ethanol mixture as a precursor.

[0012] Figure 3 is a SEM image of the PI micro-aerogel at a magnification of 10,000X, which shows the complete pore structure of the micro-aerogel.

[0013] Figure 4 It is a diagram of PI micro aerogel mixed with PET pellets and PI / PET aerogel composite fiber.

[0014] Figure 5 is a SEM image of a cross section of a PI / PET fiber at 20,000X magnification, showing the micro aerogel pores inside the fiber.

[0015] Figure 6 is a histogram showing thermal conductivity measurements of PET fibers, 1 wt% PI / PET fibers, and 2 wt% PI / PET fibers.

[0016] Figure 7is a histogram showing fiber tenacity strength measurements for PET fibers, 1 wt% PI / PET fibers, and 2 wt% PI / PET fibers. DETAILED DESCRIPTION

[0017] The present disclosure is further described with reference to some exemplary embodiments. The embodiments below are helpful for those skilled in the art to further understand the present disclosure without causing any limitation to the present disclosure. It should be noted that various changes and modifications can be derived by those skilled in the art without departing from the inventive concept of the present disclosure. Such changes and modifications should belong to the protection scope of the present disclosure.

[0018] In order to better understand the present disclosure, the present disclosure is described in detail with reference to the accompanying drawings and specific embodiments. Unless the context clearly requires otherwise, throughout the specification and claims, the technical and scientific terms used herein represent the meanings commonly understood by those skilled in the art. In addition, the terms used in the specification of the present disclosure are only used to illustrate the purpose of specific embodiments, and are not intended to limit the present disclosure. The term "and / or" used in this article to refer to a list of one or more items covers all the following interpretations of the term: any item in the list, all items in the list, and any combination of items in the list.

[0019] It should be noted that, in the absence of conflict, the embodiments of the present disclosure and the features therein may be combined, and the embodiments and features all fall within the protection scope of the present disclosure.

[0020] This application introduces a new method of using aerogel technology to enhance thermal insulation clothing. Currently, the bulky shape of aerogels and their high cost hinder the use of aerogels in the textile industry, which in turn limits the types of clothing that can be manufactured. Using this application, low-cost aerogel-enhanced thermal insulation clothing can be produced, which can be of any size and is more accessible to a wider range of consumers. The introduction of products made using this invention will encourage other textile companies to develop their own aerogel technology and inspire the next generation of aerogel applications in the industry.

[0021] According to Business Wire, the global winter clothing market is estimated to be $422.9 billion (USD) in 2020 and is forecast to reach $582.4 billion in 2027. As the most advanced aerogel-enhanced textile on the market, the present invention will be able to capture a significant market share. Textiles made using the present invention will require less thickness / material to achieve the same level of thermal insulation as traditional textiles, allowing consumers to obtain thinner, lighter and more comfortable clothing.

[0022] The term "aerogel" is also a lucrative marketing term because of its association with NASA and space technology. Many companies attempt to use the term on their products even though their products have little or no aerogel and no significant increase in thermal insulation properties. The present invention will produce clothing that properly utilizes the thermal insulation properties of aerogel and is more affordable than other aerogel clothing on the market.

[0023] like Figure 2 As shown, a suitable organic polymer material (which may be a polyimide (PI) or an aromatic polyamide) is mixed in a polar aprotic organic solvent (e.g., dimethylacetamide (DMAc), dimethylsulfoxide (DMSO), dimethylformamide (DMF) or n-methyl-2-pyrrolidone (NMP)) and stirred at 60°C until a homogeneous polymer solution is formed. The solvent is used to break the intermolecular bonds of the polymer and separate them into individual polymer chains. A suitable non-solvent (which may be water, ethanol or another organic solvent) is added to the polymer solution until it approaches the precipitation point of the solution, and then mixed together until homogeneity is achieved. The non-solvent is used to reduce the solubility of the polymer in the solvent, which will aid the gelation process and act as a porogen for the gel.

[0024] The polymer mixture is then transferred to a mold and frozen in a suitable freezer until a completely frozen wet gel is formed. The appropriate temperature of the freezer will depend on the solvent and non-solvent used for the polymer mixture; the non-solvent should remain in the liquid phase at freezing temperatures. When the solvent in the mixture freezes, the concentration of the solvent will decrease, causing the polymers to phase separate and restore their intermolecular bonds, thereby forming a physically cross-linked porous structure called a gel. Depending on the concentration of the polymer and non-solvent, the pores of the wet gel are usually nanometer or micrometer sized.

[0025] Afterwards, the frozen wet gel is removed from its mold and immersed in a non-solvent bath, which is added to the mixture and left at its freezing temperature until the solvent exchange process is complete. The frozen solvent crystals inside the wet gel will be washed away by a diffusion process using a non-solvent bath, which is done to stabilize the wet gel for further processing, thereby preventing the molten solvent from dissolving the polymer and destroying the gel structure. The resulting wet gel is brought to room temperature to break it into slightly wet gels.

[0026] In order to break the wet gel into slightly wet gel, the wet gel was placed in a planetary ball mill jar filled with zirconium oxide grinding balls and immersed in ethanol. Figure 2 As shown, the wet gel is then ball milled at 400 rpm for 1 to 3 hours, or until the desired particle size distribution is achieved. The resulting slightly wet gel suspension is then extracted from the jar and centrifuged at 10,000 rpm to separate the slightly wet gel from the liquid phase. The slightly wet gel is then washed and centrifuged at least once more, the washing liquid preferably being a suitable freeze drying agent, in this case a 25% by volume tert-butyl alcohol / water mixture.

[0027] The well-washed slightly moist gel is then resuspended in 25% by volume of tert-butyl alcohol / water and frozen at -30°C until completely frozen. It is then placed in a freeze dryer, where it is kept under the triple point pressure of the freeze dryer (in this case, the triple point pressure of tert-butyl alcohol is 3.97 kPa) until it is completely dried into a micro-aerogel. Freeze drying enables the liquid phase to be gradually extracted from the slightly moist gel, which helps prevent shrinkage and keep the pore structure intact. Wet gel drying is usually accomplished by supercritical drying that requires expensive high-pressure equipment and pure gas. Freeze drying enables the production of aerogels or micro-aerogels at a lower cost and lower risk. Figure 3 Figure 2 is a scanning electron microscope (SEM) image of PI micro-aerogel at a magnification of 10,000X, which shows the complete pore structure of the micro-aerogel. Figure 3 As shown, the size of the micro aerogels is mostly less than 60 μm, their porous structure is maintained by ball milling and freeze-drying processes, and they have an ultra-low thermal conductivity of 0.030 W / mK to 0.040 W / mK.

[0028] Figure 4 Figure 1 is a diagram of PI micro aerogel mixed with PET pellets and PI / PET aerogel composite fibers. Figure 4 As shown, to prepare aerogel composite fibers, 1 wt% to 5 wt% of micro aerogel is mixed with a fiber material, in this case PET or PLA in its original pellet form. The mixture is processed through a melt extruder at the melting temperature of the fiber material, where the micro aerogel is dispersed throughout the molten fiber material and then extruded into aerogel composite fibers. Figure 5 is a SEM image of a cross section of a PI / PET fiber at 20,000X magnification, showing the micro aerogel pores inside the fiber. Figure 1is a diagram of a cross section of an aerogel composite fiber, which shows how aerogel shortens the mean free path of heat conduction. Figure 1 As shown, the fully formed fiber contains micro-aerogel pores in its interior, which shortens the mean free path of heat conduction inside the fiber and improves its thermal insulation properties. Figure 6 is a histogram showing thermal conductivity measurements of PET fibers, 1 wt% PI / PET fibers, and 2 wt% PI / PET fibers, illustrating the reduction in thermal conductivity by the addition of micro aerogel. Figure 7 is a histogram showing the fiber toughness strength measurements for PET fiber, 1 wt% PI / PET fiber, and 2 wt% PI / PET fiber, which shows that the addition of micro aerogel does not significantly affect the fiber toughness. A 20% drop bar is added as an acceptable threshold condition for industrial garment processing. Figure 6 and Figure 7 As shown, the aerogel composite fibers show significantly reduced thermal conductivity compared to the original fibers, while the fiber toughness strength is only slightly reduced.

[0029] In some embodiments, the method for preparing aerogel composite fibers comprises the following steps:

[0030] (a) weighing a material for forming aerogel composite fibers, the material should be composed of 0.1% to 20% (w / w) polymer micro aerogel powder and 80% to 99.9% (w / w) fiber material;

[0031] (a) mixing polymer micro aerogel powder and fiber material to form a homogeneous composite mixture; and

[0032] (b) heating the composite mixture to the melting point of the fiber material to disperse the polymer micro aerogel throughout the molten fiber material, and then extruding the composite mixture to form aerogel composite fibers.

[0033] In some embodiments, the polymer micro aerogel powder has an average particle size of 0.1 μm to 100 μm, a porous structure with an average pore size of 10 nm to 2000 nm, and a thermal conductivity of 20 mW / mK to 100 mW / mK.

[0034] In some embodiments, polymer micro aerogel powder is prepared by dissolving 0.1% to 30% (w / w) of a polymer in a suitable solvent at 40°C to 80°C, then adding 0% to 30% (v / v) of a suitable non-solvent, and then freezing the mixture, gelling in a non-solvent bath, ball milling into microgels, washing, and finally freeze-drying using tert-butyl alcohol.

[0035] In some embodiments, the polymer is a polyimide or an aramid.

[0036] In some embodiments, the solvent is a chemical that is capable of dissolving 0% to 30% (w / w) of the polymeric material and can accept up to 0% to 30% of a non-solvent without precipitating the polymeric material.

[0037] In some embodiments, the non-solvent is a chemical that causes precipitation of the polymeric material when added in excess.

[0038] In some embodiments, gelation occurs in a refrigerator, freezer, or liquid nitrogen.

[0039] In some embodiments, the gel is ball-milled into a microgel within 0.1 hour to 48 hours.

[0040] In some embodiments, washing and freeze drying use a suitable solvent that can freeze and sublime at a pressure below 600 Pa.

[0041] In some embodiments, the fiber material is polyethylene terephthalate, polylactic acid, and / or nylon.

[0042] In some embodiments, the composite mixture is melted and formed into fibers by melt spinning or melt extrusion.

[0043] In some embodiments, the fiber diameter is from 10 μm to 200 μm.

[0044] In some embodiments, the fibers show a 1% to 50% reduction in thermal conductivity and a ±30% change in fiber tenacity strength compared to fibers produced using only the fiber material.

[0045] Other embodiments of the present application provide a textile comprising aerogel composite fibers manufactured by the above preparation method.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit the technical solutions of the present disclosure. Under the concept of the present disclosure, the technical features of the above embodiments or other different embodiments can be combined, the steps therein can be implemented in any order, and various changes can be obtained in different aspects of the present disclosure. For the sake of brevity, they will not be repeated here. Although the present disclosure is described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that they can still modify the technical solutions described in the above embodiments, or derive equivalent alternative forms of some technical features; however, such modifications or alternative forms will not cause the essence of the corresponding technical solution to deviate from the spirit and scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. A method for preparing an aerogel composite fiber, comprising the following steps: (a) weighing a material for forming the aerogel composite fiber, wherein the material should be composed of 0.1% to 20% (w / w) of polymer micro aerogel powder and 80% to 99.9% (w / w) of fiber material; (a) mixing the polymer micro aerogel powder with the fiber material to form a homogeneous composite mixture; and (b) heating the composite mixture to the melting point of the fiber material to disperse the polymer micro aerogel throughout the melted fiber material, and then extruding the composite mixture to form aerogel composite fibers.

2. The method for preparing aerogel composite fibers according to claim 1, wherein the polymer micro aerogel powder has an average particle size of 0.1 μm to 100 μm, a porous structure with an average pore size of 10 nm to 2000 nm, and a thermal conductivity of 20 mW / mK to 100 mW / mK.

3. The method for preparing aerogel composite fibers according to claim 1, wherein the polymer micro aerogel powder is prepared by dissolving 0.1% to 30% (w / w) of a polymer in a suitable solvent at 40°C to 80°C, then adding 0% to 30% (v / v) of a suitable non-solvent, and then freezing the mixture, gelling it in a non-solvent bath, ball milling it into microgels, washing it, and finally freeze-drying it using tert-butyl alcohol. 4 . The method for preparing aerogel composite fibers according to claim 3 , wherein the polymer is polyimide or aromatic polyamide.

5. The method for preparing aerogel composite fibers according to claim 3, wherein the solvent is a chemical capable of dissolving 0% to 30% (w / w) of a polymer material and capable of accepting up to 0% to 30% of a non-solvent without precipitating the polymer material.

6. The method for preparing aerogel composite fibers according to claim 3, wherein the non-solvent is a chemical that causes precipitation of the polymer material when added in excess.

7. The method for preparing aerogel composite fibers according to claim 3, wherein the gelation occurs in a refrigerator, a freezer or liquid nitrogen.

8. The method for preparing aerogel composite fibers according to claim 3, wherein the gel is ball-milled into microgel within 0.1 hour to 48 hours. 9 . The method for preparing aerogel composite fibers according to claim 3 , wherein the washing and the freeze-drying use a suitable solvent that can be frozen and sublimated at a pressure lower than 600 Pa.

10. The method for preparing aerogel composite fibers according to claim 1, wherein the fiber material is polyethylene terephthalate, polylactic acid and / or nylon. 11 . The method for producing aerogel composite fibers according to claim 1 , wherein the composite mixture is melted and formed into fibers by melt spinning or melt extrusion. 12 . The method for preparing aerogel composite fibers according to claim 1 , wherein the fiber diameter is 10 μm to 200 μm.

13. The method for preparing aerogel composite fibers according to claim 1, wherein the fibers show a decrease in thermal conductivity of 1% to 50% and a change in fiber toughness strength of ±30% compared to fibers produced using only the fiber material.

14. A textile product comprising the aerogel composite fiber manufactured by the preparation method according to claim 1.

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