A method for preparing multi-level composite fibers based on hollow microsphere soft gel

Abstract

The present invention discloses a method for preparing a multi-stage composite fiber based on hollow microsphere soft gel. The method comprises adding an appropriate amount of hollow microspheres to a certain amount of polyvinyl alcohol aqueous solution and stirring the solution at different rotation speeds to obtain a flowable gel-like soft substance. The obtained gel-like soft substance is subjected to spinning and stretching under different drawing speeds and temperature conditions to obtain polyvinyl alcohol / hollow microsphere composite fibers of different diameters. The composite fibers are then immersed in another polymer solution for a period of time, taken out and dried to obtain a multi-stage composite fiber of polyvinyl alcohol / hollow microsphere@polymer with a core-shell structure. This multi-stage composite fiber not only has excellent flexibility and tensile strength, but also has excellent properties such as lightness, softness, wearability, and impact resistance. It can well meet the needs of practical applications and has great application potential in the fields of heat insulation, fire protection, and impact resistance.

Description

Technical Field

[0001] The invention belongs to the field of synthesis and preparation of organic-inorganic hybrid materials, and relates to a method for preparing multi-level composite fibers based on hollow microsphere soft gel. Background Art

[0002] Core-shell composite fibers are functionalized composite fibers that combine the excellent properties of both the core and shell layers. They typically exhibit superior properties to those of the core and shell layers themselves, such as controlled mechanical strength and excellent thermal conductivity. Their unique structure significantly enhances the fiber's usefulness and broadens its application areas. By controlling temperature, humidity, and drafting speed, core-shell fibers can fully utilize their properties, such as small diameter, large surface area, and high porosity.

[0003] Chinese patent CN202010096276.X discloses a super-hydrophobic nanofiber membrane for oily wastewater treatment and its preparation method. Chinese patent CN201911043209.5 discloses a method for preparing a silica microsphere / glass fiber cloth composite thermal insulation membrane material. These patents all incorporate hollow microspheres with low thermal conductivity into the system as fillers, taking advantage of the filler's high internal porosity and low air content, which has a significant barrier effect on conduction and convection, and can achieve excellent thermal insulation when blended or coated. However, the hollow microspheres are prone to cracking and falling off when attached to the fiber membrane, affecting the fiber membrane's thermal insulation, thermal stability, and high temperature resistance. Summary of the Invention

[0004] The present invention provides a method for preparing multi-level composite fibers based on hollow microsphere soft gel. The soft gel material can be quickly prepared into single fibers with a large aspect ratio by simple drawing. The prepared fibers have the characteristics of excellent flexibility, high temperature resistance, heat insulation, and strong impact resistance.

[0005] The present invention provides a method for preparing a multi-level composite fiber based on hollow microsphere soft gel, comprising the following steps:

[0006] Step 1: The hollow microspheres are mixed with deionized water to obtain a uniform dispersion, and then the dispersion is added to the PVA aqueous solution and mixed and stirred to prepare a fluid gel-like soft material.

[0007] Step 2: Spinning the gel-like soft substance, drying and solidifying it to prepare a morphologically stable polyvinyl alcohol / hollow microbead composite fiber.

[0008] Step 3: Immersing the polyvinyl alcohol / hollow microbead composite fiber in a polymer solution, taking it out and drying it, thereby obtaining a core-shell structure multi-level composite fiber with a core layer of polyvinyl alcohol / hollow microbeads and a shell layer of polymer.

[0009] As the preferred technical solution:

[0010] In the first step, the stirring time for preparing the gel-like soft material can be 0-24 hours.

[0011] In the first step, the hollow microspheres refer to hollow glass microspheres with a particle size of 2-60 μm. Microspheres of different particle sizes can be mixed and used.

[0012] In the first step, the flow state means that the soft gel can slowly deform under the action of gravity and external force, the automatic deformation rate under gravity is 0.001 to 0.5 m / s, it can immediately deform under external force, and the deformation caused by the external force can slowly disappear after the external force is removed.

[0013] In the first step, the microstructure of the gel-like soft material is as follows: the PVA on the surface of the hollow microbeads encounters the boric acid diffused from the hollow microbeads themselves and locally flocculates in the area around the surface of the hollow microbeads. The PVA farther away from the hollow microbeads can still slide freely and play a lubricating role on the hollow microbead / flocculated PVA complex. This microstructure in which part of the PVA is locally flocculated and the other part can relatively slide makes the soft gel have both solid properties and a certain degree of fluidity.

[0014] In the first step, the mass ratio of glass microspheres to deionized water is 1:0.1 to 5. The PVA accounts for 1% to 20% of the total mass of the gel soft substance; the hollow microsphere dispersion accounts for 1% to 10% of the total mass of the gel soft substance.

[0015] In the first step, the PVA is one of those with an alcoholysis degree of 88% or 99%, or a mixture of two or more thereof.

[0016] In the second step, the spinning refers to stretching and spinning under the conditions of 20-55° C. and 20%-70% relative humidity, with a stretching speed of 0.1-5 m / s.

[0017] In the second step, the curing temperature is 30 to 100° C. and the maximum temperature is maintained for 12 to 48 hours to remove the solvent and obtain a stable fiber morphology.

[0018] In the third step, the polymer in the polymer solution is one or more of polyurethane, polyimide, polyamide, polyvinyl pyrrolidone, polyarylsulfone, polyacrylonitrile, polysiloxane, polyvinyl formal, and melamine formaldehyde resin.

[0019] The core and shell layers of the multi-stage composite fiber produced by the present invention are tightly connected, yet a clear interface exists between the shell and core layers. The shell layer of the core-shell multi-stage composite fiber is a continuous, unbroken layer, effectively preventing leakage of the hollow microspheres in the core layer. The PVA in the core layer prevents the free movement of the hollow microspheres, providing a damping effect.

[0020] The present invention adopts spinning technology to prepare multi-level composite fibers of polyvinyl alcohol / hollow microspheres @ polymer with a core-shell structure. The obtained single fiber inherits the high temperature resistance of silicon dioxide and has good flexibility after coating. Compared with directly blending hollow microspheres in the fiber membrane, it is easier to control and not easy to fall off. By adjusting the spinning parameters and curing process, a multi-level composite fiber of polyvinyl alcohol / hollow microspheres @ polymer with a core-shell structure is obtained. Since the surface of the single fiber is evenly coated with the polymer solution, a dense protective layer is formed, which improves the flexibility of the single fiber. In addition, hollow microspheres have the advantages of light weight, high strength, good fluidity, heat insulation, corrosion resistance, etc., and play an increasingly important role in the development of heat insulation, wear resistance, and other composite materials. Their application in new energy industry and biomaterials has achieved rapid development.

[0021] The present invention uses hollow microspheres instead of silica hollow microspheres. Because the hollow microspheres contain boric acid, when dispersed in a polyvinyl alcohol solution, the polyvinyl alcohol crosslinks with the surface of the hollow microspheres. The resulting mixture forms a flowable, transparent, soft gel-like substance with excellent biocompatibility. When stretched by external force, continuous fibers with a large aspect ratio can be produced. Hollow microspheres are readily available and simple to operate. Introducing hollow microspheres into polyvinyl alcohol fibers can help reduce their thermal conductivity and enhance their resistance to low-speed impact. Core-shell composite fibers prepared using hollow microspheres as cores have excellent mechanical strength and effectively prevent leakage of the internal hollow microspheres. These fibers can be used as lightweight thermal insulation, phase change, and low-speed impact resistant materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a SEM cross-sectional view of the multi-stage composite fiber of polyvinyl alcohol / hollow microspheres@polymer with a core-shell structure in Example 1.

[0023] Figure 2 This is a comparison chart of the stretching of the polyvinyl alcohol / hollow microsphere fiber with a core-shell structure and the polyvinyl alcohol / hollow microsphere@polymer multi-stage composite fiber in Example 1. DETAILED DESCRIPTION

[0024] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0025] Example 1

[0026] Step 1: Ultrasonic dispersion of 2.4 g of hollow microbeads (10-250 μm) with 9.6 g of deionized water was performed to obtain a uniform microbead dispersion. Separately, 3.625 g of PVA-1788 was slowly added to 25.375 g of deionized water. The mixture was magnetically stirred in an 80°C water bath for 4 hours before heating was stopped to obtain a 12.5% ​​PVA solution. The resulting PVA solution and microbead dispersion were mixed and stirred at room temperature for 12 hours to obtain a fluid, gel-like soft substance.

[0027] Step 2: The gel-like soft substance is spun into composite fibers. Spinning process parameters include a spinning temperature of 35°C, a relative humidity of 40%, and a drafting speed of 0.5 m / s. The prepared fibers are then placed in an oven for curing at 80°C, maintained at the highest temperature for 12 hours, to produce polyvinyl alcohol / hollow microsphere composite fibers.

[0028] The third step: immersing the polyvinyl alcohol / hollow microsphere composite fiber in water-based polyurethane with a solid content of 60% for a period of time, taking it out and drying it in an oven at 80°C to obtain a core-shell structure multi-level composite fiber (polyvinyl alcohol / hollow microsphere@polymer multi-level composite fiber) with a core layer of polyvinyl alcohol / hollow microsphere and a shell layer of water-based polyurethane. Figure 1 This is a SEM cross-sectional view of the multi-stage composite fiber obtained in Example 1. The fiber was subjected to a mechanical property tensile test. Figure 2 The tensile strength curves of the core-shell structured polyvinyl alcohol / hollow microsphere fiber and the polyvinyl alcohol / hollow microsphere@waterborne polyurethane multi-stage composite fiber in Example 1 are shown. Integrating the two curves, the work of rupture of the polyvinyl alcohol / hollow microsphere fiber is 0.212 J / mm. 2 The breaking energy of the multi-level composite fiber of polyvinyl alcohol / hollow microspheres@waterborne polyurethane is 0.583J / mm 2 , the latter's fracture work increased to 2.75 times.

[0029] Example 2

[0030] Step 1: Ultrasonic dispersion of 2.4 g of hollow microbeads (10-250 μm) with 9.6 g of deionized water was performed to obtain a uniform microbead dispersion. Separately, 3.625 g of PVA-1788 was slowly added to 25.375 g of deionized water. The mixture was magnetically stirred in an 80°C water bath for 4 hours before heating was stopped to obtain a 12.5% ​​PVA solution. The resulting PVA solution and microbead dispersion were mixed and stirred at room temperature for 12 hours to obtain a fluid, gel-like soft substance.

[0031] Step 2: The gel-like soft substance is spun into composite fibers. Spinning process parameters include a spinning temperature of 35°C, a relative humidity of 40%, and a drafting speed of 0.5 m / s. The prepared fibers are then placed in an oven for curing at 80°C, maintained at the highest temperature for 12 hours, to produce polyvinyl alcohol / hollow microsphere composite fibers.

[0032] Step 3: The polyvinyl alcohol / hollow microsphere composite fiber is immersed in polyimide with a solid content of 15% for a period of time. The fiber is then removed and dried in an oven at 80°C to produce a multi-stage composite fiber with a core layer of polyvinyl alcohol / hollow microspheres and a shell of polyimide. This multi-stage composite fiber does not melt when exposed to the flame of an alcohol lamp and extinguishes itself when removed from the flame. The material also exhibits a limiting oxygen index of 40%, making it difficult to burn.

[0033] Step 4: Fix the multi-level composite fiber on the workbench and perform a pendulum impact test on the fiber. Because the hollow microspheres are filled inside the single fiber, they absorb a large amount of impact energy during the impact process and are easy to break, thus enhancing the impact performance.

[0034] Example 3

[0035] Step 1: Ultrasonic dispersion of 2.4 g of hollow microspheres (10-250 μm) and 9.6 g of deionized water was performed to obtain a uniform microsphere dispersion. Separately, 3.625 g of polyvinylpyrrolidone (PVP) was slowly added to 25.375 g of deionized water and magnetically stirred for 4 hours to obtain a 12.5% ​​PVP solution. The resulting PVP solution was mixed with the microsphere dispersion and stirred at room temperature for 12 hours. A fluidized, soft gel-like substance was not obtained, but a PVP solution containing glass microspheres was obtained.

[0036] The second step was to spin the material into composite fibers. The spinning parameters were: spinning temperature 35°C, relative humidity 40%, and drafting speed 0.5 m / s. The prepared material was then placed in an oven for curing at 80°C, maintained at the highest temperature for 12 hours. However, no polyvinyl pyrrolidone / hollow microbead composite fibers were obtained.

[0037] The third step is to immerse it in water-based polyurethane with a solid content of 60%. The polyvinyl pyrrolidone / hollow microsphere composite fiber disintegrates due to the direct dissolution of polyvinyl pyrrolidone, and no multi-stage composite fiber is obtained. The above-mentioned embodiments only express several implementation methods of the present invention. The description is relatively specific and detailed, but it should not be understood as limiting the scope of the patent of the present invention. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be based on the appended claims.

Claims

1. A method for preparing multi-level composite fibers based on hollow microsphere soft gel, characterized in that: The steps include: The first step is to mix and stir the hollow microspheres with deionized water to obtain a uniform dispersion, and then add the dispersion to the PVA aqueous solution and stir to prepare a fluid gel-like soft substance. The hollow microspheres are borosilicate hollow glass microspheres with a spherical particle size ranging from 10 to 250 μm and a wall thickness of 0.1 to 0.2 times the particle size of the hollow microspheres. Microspheres of different particle sizes can be mixed and used. Step 2: Spinning the gel-like soft substance, drying and solidifying it to prepare a morphologically stable polyvinyl alcohol / hollow microbead composite fiber; Step 3: Immersing the polyvinyl alcohol / hollow microbead composite fiber in a polymer solution, taking it out and drying it, thereby obtaining a core-shell structure multi-level composite fiber with a core layer of polyvinyl alcohol / hollow microbeads and a shell layer of polymer.

2. The method for preparing a multi-stage composite fiber according to claim 1, characterized in that: In the first step, the flow state means that the soft gel can slowly deform under the action of gravity and external force, the automatic deformation rate under gravity is 0.001~0.5 m / s, it can produce immediate deformation under external force, and the deformation caused by external force can slowly disappear after the external force is removed.

3. The method for preparing a multi-stage composite fiber according to claim 1, characterized in that: In the first step, the mass ratio of the hollow microspheres to deionized water is 1:0.1-5; the PVA accounts for 1%-20% of the total mass of the gel-state soft substance; the hollow microsphere dispersion accounts for 1%-10% of the total mass of the gel-state soft substance; and the PVA is one or a mixture of two or more having an alcoholysis degree of 88% or 99%.

4. The method for preparing a multi-stage composite fiber according to claim 1, characterized in that: In the first step, the microstructure of the gel-like soft material is as follows: the PVA on the surface of the hollow microbeads encounters the boric acid diffused from the hollow microbeads themselves and produces local flocculation in the area around the surface of the hollow microbeads. The PVA farther away from the hollow microbeads can still slide freely and play a lubricating role on the hollow microbead / flocculated PVA complex. This microstructure in which part of the PVA is locally flocculated and the other part can slide relatively makes the soft gel have both solid properties and fluidity.

5. The method for preparing a multi-stage composite fiber according to claim 1, characterized in that: In the second step, the spinning refers to stretching spinning under the conditions of 20-55° C. and 20%-70% relative humidity, with a stretching speed of 0.1-5 m / s.

6. The method for preparing a multi-stage composite fiber according to claim 1, characterized in that: In the second step, the curing temperature is 30-100° C. and maintained at the highest temperature for 12-48 hours to remove the solvent and obtain a stable fiber morphology.

7. The method for preparing a multi-stage composite fiber according to claim 1, wherein: In the third step, the polymer concentration in the polymer solution is 5 wt% to 60 wt%, and the polymer is one or more of polyurethane, polyimide, polyamide, polyvinyl pyrrolidone, polyarylsulfone, polyacrylonitrile, polysiloxane, polyvinyl formal, and melamine formaldehyde resin.

8. A multi-stage composite fiber prepared by the method according to any one of claims 1 to 7, characterized in that: The core layer and the shell layer of the multi-stage composite fiber are tightly connected, but a clear interface exists between the shell layer and the core layer.

9. The multi-stage composite fiber according to claim 8, characterized in that The shell layer of the core-shell structure multi-stage composite fiber is a continuous unbroken layer, which can effectively prevent the leakage of the hollow microspheres in the core layer; the PVA in the core layer can prevent the hollow microspheres from moving freely, and has a damping effect.

Images