Preparation method of hollow fiber membrane composite thermal insulation material

Abstract

The application relates to a preparation method of a hollow fiber membrane composite thermal insulation material, which comprises the following steps: adding 18-22% of polyurethane, 4-8% of polyethylene glycol 2000 and 72-76% of N,N-dimethylacetamide into a spinning reaction kettle to mix, stir and defoam to prepare homogeneous casting solution; based on a non-solvent induced phase separation method, the homogeneous casting solution is coated on the surface of a polyester braided tube through a spinneret by adopting a concentric circle composite spinning technology, is gathered on a spinning wheel after a coagulation bath to form a reinforced polyurethane hollow fiber membrane assembly which is arranged in parallel and obliquely crosses and is mutually bonded, and the fiber membrane assembly is hot-pressed to prepare the hollow fiber membrane composite thermal insulation material under the conditions of a temperature of 60-150 DEG C and a pressure of 120-470 MPa. Since the coating layer and the braided tube are both through porous structures, the prepared composite material has good air permeability.

Description

Technical Field

[0001] This invention relates to the field of fabric preparation, specifically a method for preparing a hollow fiber membrane composite thermal insulation material. Background Technology

[0002] Traditional passive insulation materials can be divided into three categories based on their raw material composition: 1. Natural fiber insulation materials: mainly represented by natural cellulose and protein fibers such as cotton fiber, wool, rabbit hair, cashmere, camel hair, down, and silk. 2. Synthetic fiber insulation materials: represented by fluffy nonwoven materials made from pure synthetic fibers, such as hot-melt cotton wadding, spray-bonded cotton wadding, meltblown cotton wadding, needle-punched and spunlace wadding, etc. 3. Composite insulation materials: based on various natural fibers, synthetic fibers, or functional fiber materials, these are multi-layered or multi-component insulation materials prepared using methods such as interface bonding and mechanical reinforcement, such as space cotton, Antarctic cotton, and solar fleece.

[0003] With the continuous improvement of textile fiber processing technology, some new types of fibers, such as hollow fibers and microfibers, are widely used in the field of thermal insulation materials due to their excellent structural properties. Among them, hollow fibers are fibers with fine tubular cavities along the axis. The cavities can trap a large amount of still air, preventing convection and reducing heat loss, making them one of the ideal materials for preparing lightweight thermal insulation fabrics.

[0004] Reinforced hollow fiber membranes, a novel membrane technology product resulting from the intersection of functional fiber materials and separation membrane technology, possess a three-layer composite structure consisting of a polymer separation layer (surface layer with controllable porosity), a fiber braided tube (middle layer), and a cavity (inner layer). Belonging to the category of hollow porous fibers, they exhibit significant application advantages in filtration and sound-absorbing materials. Compared to traditional hollow fibers, reinforced hollow fiber membranes, due to their high-porosity separation layer, three-dimensional network fiber aggregate, and large cavity, offer a new perspective for application in thermal insulation materials. However, their development in thermal insulation materials remains largely unreported. Therefore, how to effectively process reinforced hollow fiber membranes of a certain diameter into effective product forms has become a pressing issue to be addressed in the development of thermal insulation materials.

[0005] Reinforced hollow fiber membranes have attracted increasing research attention in the water treatment field due to their advantages such as high packing density per unit volume, large filtration area, small footprint, relatively low cost, and long service life. However, the inherently large fiber diameter (millimeter level) of the membrane fibers results in poor reprocessing performance, which seriously hinders their practical application in the thermal insulation field. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a method for preparing a hollow fiber membrane composite thermal insulation material. The technical problem to be solved by this invention is achieved through the following technical solution:

[0007] To achieve the above objectives, this invention uses polyurethane (PU) as the polymer material. First, an incompletely phase-separated reinforced hollow fiber membrane is prepared using dry / wet spinning technology. Then, a composite material is obtained using a hot pressing method. The effects of different hot pressing temperatures on the structure and thermal insulation performance of the composite material are studied. Finally, a novel hollow fiber membrane composite thermal insulation material is prepared.

[0008] A method for preparing a hollow fiber membrane composite thermal insulation material, the method comprising the following steps:

[0009] Step 1: Take 18% to 22% polyurethane, 4% to 8% polyethylene glycol 2000 and 72% to 76% N,N-dimethylacetamide by mass and add them to the spinning reactor. Mix, stir and degas to prepare a homogeneous casting solution.

[0010] Step 2: Based on the non-solvent induced phase separation method, the concentric circle composite spinning technology is used to coat the homogeneous casting liquid on the surface of the polyester braided tube through the spinneret. After passing through the coagulation bath, the liquid is aggregated on the winding wheel to form a parallel, obliquely cross-configured, and mutually bonded reinforced polyurethane hollow fiber membrane assembly.

[0011] Step 3: Hot pressing the fiber membrane assembly to produce hollow fiber membrane composite thermal insulation material by hot pressing at a temperature of 60-150℃ and a pressure of 120-470MPa.

[0012] Polyurethane, polyethylene glycol, and N,N-dimethylacetamide need to be stirred in a spinning reactor at a constant temperature of 45-90℃ for 12 hours to fully dissolve the polymer, and then allowed to stand for 12 hours to remove bubbles to obtain a homogeneous casting solution.

[0013] In the first step, the homogeneous casting solution is transparent and has a viscosity range of 1500-15000 mPa·s.

[0014] In the second step, the polyester braided tube has an outer diameter of less than 1.55 mm.

[0015] In the second step, the reinforced polyurethane hollow fiber membrane is not completely phase-separated and cured. From the outside to the inside, it consists of a polyurethane porous coating, a polyester braided tube, and a cavity, with an outer diameter of less than 1.95 mm.

[0016] The third step involves a hollow fiber membrane composite insulation material, which is composed of reinforced polyurethane hollow fiber membranes arranged in parallel and oblique cross directions to form a double-layer structure.

[0017] The beneficial effects of this invention are: a multilayer composite material is prepared by bonding incompletely phase-separated reinforced polyurethane hollow fiber membranes through a hot-pressing process. This not only utilizes the porous polyurethane coating, three-dimensional network of polyester braided tubes, and large cavity structure of the reinforced polyurethane hollow fiber membrane, but also allows the three bonded membrane fibers to form an irregular cavity, thus providing space to store a large amount of air and giving the composite material excellent thermal insulation properties.

[0018] Due to the parallel and obliquely intersecting arrangement of the membrane filaments, the longitudinal mechanical properties of the composite material are mainly determined by the properties of the polyester braided tube, while the transverse mechanical properties are mainly determined by the adhesive strength between the polyurethane coatings. The prepared composite material exhibits significant differences in longitudinal and transverse breaking strength and elongation at break, demonstrating obvious anisotropy.

[0019] Since both the coating and the braided tube have a through-hole structure, the prepared composite material has good air permeability.

[0020] The prepared composite material has a high-porosity porous structure of polyurethane, a three-dimensional network structure of polyester braided tube, an inherent hollow cavity structure, and a constructed irregular cavity structure. It effectively combines a porous material with a high peak sound absorption coefficient with a resonant structure with a low peak sound absorption frequency to form a composite sound absorption structure. This novel composite structure can, to a certain extent, take into account both low-frequency and broadband sound absorption. It is expected to overcome the bottleneck problem faced in the preparation and application of sound absorption materials, namely, "poor sound absorption materials have poor sound absorption effect on low-frequency noise, and resonant sound absorption materials have a narrow sound absorption bandwidth". It has important academic and practical application value.

[0021] The technical solution of this invention is based on dry / method spinning technology and hot pressing technology. The equipment technology is relatively mature and has the advantage of large-scale application. Attached Figure Description

[0022] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0023] Figure 1 This is a schematic diagram of the reinforced polyurethane hollow fiber membrane structure of the present invention;

[0024] Figure 2 This is a schematic diagram of the hollow fiber membrane composite thermal insulation material structure of the present invention;

[0025] Figure 3 This is a SEM image of the hollow fiber membrane composite thermal insulation material of the present invention;

[0026] Figure 4 The thickness of the composite material at different hot-pressing temperatures according to the present invention;

[0027] Figure 5 The fracture strength of the composite material at different hot-pressing temperatures of the present invention;

[0028] Figure 6 The elongation at break of the composite material at different hot-pressing temperatures of the present invention;

[0029] Figure 7 The air permeability of the composite material at different hot-pressing temperatures of the present invention;

[0030] Figure 8 The thermal insulation rate of the composite material under different hot-pressing temperatures of the present invention;

[0031] Figure 9 The full-frequency sound absorption coefficient of the composite material at different hot-pressing temperatures of this invention;

[0032] Figure 10 The average sound absorption coefficient of the composite material at different hot-pressing temperatures according to the present invention;

[0033] Figure 11 The results are the test results of the performance indicators of Embodiments 1 to 5 of the present invention. Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be described more clearly and completely below with reference to the accompanying drawings in the embodiments. Of course, the described embodiments are only a part of the present invention and not all of it. Based on this embodiment, other embodiments obtained by those skilled in the art without creative effort are all within the protection scope of the present invention.

[0035] like Figures 1 to 11 As shown, a method for preparing a hollow fiber membrane composite thermal insulation material includes the following steps:

[0036] Step 1: Take 18% to 22% polyurethane, 4% to 8% polyethylene glycol 2000 and 72% to 76% N,N-dimethylacetamide by mass and add them to the spinning reactor. Mix, stir and degas to prepare a homogeneous casting solution.

[0037] Step 2: Based on the non-solvent induced phase separation method, the concentric circle composite spinning technology is used to coat the homogeneous casting liquid on the surface of the polyester braided tube through the spinneret. After passing through the coagulation bath, the liquid is aggregated on the winding wheel to form a parallel, obliquely cross-configured, and mutually bonded reinforced polyurethane hollow fiber membrane assembly.

[0038] Step 3: Hot pressing the fiber membrane assembly to produce hollow fiber membrane composite thermal insulation material by hot pressing at a temperature of 60-150℃ and a pressure of 120-470MPa.

[0039] Polyurethane, polyethylene glycol, and N,N-dimethylacetamide need to be stirred in a spinning reactor at a constant temperature of 45-90℃ for 12 hours to fully dissolve the polymer, and then allowed to stand for 12 hours to remove bubbles to obtain a homogeneous casting solution.

[0040] In the first step, the homogeneous casting solution is transparent and has a viscosity range of 1500-15000 mPa·s.

[0041] In the second step, the polyester braided tube has an outer diameter of less than 1.55 mm.

[0042] In the second step, the reinforced polyurethane hollow fiber membrane, not fully phase-separated and cured, consists of a polyurethane porous coating, a polyester braided tube, and a cavity, arranged sequentially from the outside to the inside, with an outer diameter less than 1.95 mm; (e.g., ...) Figure 1 As shown: 1 is a polyurethane coating; 2 is a polyester braided tube; 3 is a cavity.

[0043] The third step involves a hollow fiber membrane composite insulation material, which is composed of reinforced polyurethane hollow fiber membranes arranged in parallel and oblique cross directions to form a double-layer structure.

[0044] Using the above method, the following examples were prepared.

[0045] Example 1

[0046] First, 20% polyurethane, 6% polyethylene glycol 2000 and 74% N,N-dimethylacetamide by mass fraction were added to a spinning reactor (heating temperature was 50°C) and mixed (the feeding principle was solvent (37% N,N-dimethylacetamide) - powder (20% polyurethane, 6% polyethylene glycol 2000) - solvent (37% N,N-dimethylacetamide)), stirred (12h) and degassed (12h) to prepare a homogeneous casting solution. Then, based on the solvent-inducing phase separation method, concentric circle composite spinning technology was used to coat the homogeneous casting solution onto the surface of a polyester braided tube (outer diameter 1.55 mm) through a spinneret. After passing through a coagulation bath (water, temperature 50℃), the mixture was aggregated on a winding wheel (winding speed between 50.40 m / min) to form a parallel, obliquely crossed, and mutually bonded reinforced polyurethane hollow fiber membrane assembly. Finally, the fiber membrane assembly was hot-pressed, and by changing the hot-pressing temperature (80℃) and pressure (150 MPa), a hollow fiber membrane composite thermal insulation material was produced. A schematic diagram of the reinforced polyurethane hollow fiber membrane structure is shown below. Figure 1 As shown in the diagram, the hollow fiber membrane composite thermal insulation material structure is as follows: Figure 2 As shown.

[0047] Example 2

[0048] First, 20% polyurethane, 6% polyethylene glycol 2000 and 74% N,N-dimethylacetamide by mass fraction were added to a spinning reactor (heating temperature was 50°C) and mixed (the feeding principle was solvent (37% N,N-dimethylacetamide) - powder (20% polyurethane, 6% polyethylene glycol 2000) - solvent (37% N,N-dimethylacetamide)), stirred (12h) and degassed (12h) to prepare a homogeneous casting solution. Then, based on the solvent-inducing phase separation method, concentric circle composite spinning technology was used to coat the homogeneous casting solution onto the surface of a polyester braided tube (outer diameter 1.55 mm) through a spinneret. After passing through a coagulation bath (water, temperature 50℃), the mixture was aggregated on a winding wheel (winding speed between 50.40 m / min) to form a parallel, obliquely crossed, and mutually bonded reinforced polyurethane hollow fiber membrane assembly. Finally, the fiber membrane assembly was hot-pressed, and by changing the hot-pressing temperature (90℃) and pressure (150 MPa), a hollow fiber membrane composite thermal insulation material was produced. A schematic diagram of the reinforced polyurethane hollow fiber membrane structure is shown below. Figure 1 As shown in the diagram, the hollow fiber membrane composite thermal insulation material structure is as follows: Figure 2 As shown.

[0049] Example 3

[0050] First, 20% polyurethane, 6% polyethylene glycol 2000 and 74% N,N-dimethylacetamide by mass fraction were added to a spinning reactor (heating temperature was 50°C) and mixed (the feeding principle was solvent (37% N,N-dimethylacetamide) - powder (20% polyurethane, 6% polyethylene glycol 2000) - solvent (37% N,N-dimethylacetamide)), stirred (12h) and degassed (12h) to prepare a homogeneous casting solution. Then, based on the solvent-inducing phase separation method, concentric circle composite spinning technology was used to coat the homogeneous casting solution onto the surface of a polyester braided tube (outer diameter 1.55 mm) through a spinneret. After passing through a coagulation bath (water, temperature 50℃), the mixture was aggregated on a winding wheel (winding speed between 50.40 m / min) to form a parallel, obliquely crossed, and mutually bonded reinforced polyurethane hollow fiber membrane assembly. Finally, the fiber membrane assembly was hot-pressed, and by changing the hot-pressing temperature (100℃) and pressure (150 MPa), a hollow fiber membrane composite thermal insulation material was produced. A schematic diagram of the reinforced polyurethane hollow fiber membrane structure is shown below. Figure 1 As shown in the diagram, the hollow fiber membrane composite thermal insulation material structure is as follows: Figure 2 As shown.

[0051] Example 4

[0052] First, 20% polyurethane, 6% polyethylene glycol 2000 and 74% N,N-dimethylacetamide by mass fraction were added to a spinning reactor (heating temperature was 50°C) and mixed (the feeding principle was solvent (37% N,N-dimethylacetamide) - powder (20% polyurethane, 6% polyethylene glycol 2000) - solvent (37% N,N-dimethylacetamide)), stirred (12h) and degassed (12h) to prepare a homogeneous casting solution. Then, based on the solvent-inducing phase separation method, concentric circle composite spinning technology was used to coat the homogeneous casting solution onto the surface of a polyester braided tube (outer diameter 1.55 mm) through a spinneret. After passing through a coagulation bath (water, temperature 50℃), the solution was aggregated on a winding wheel (winding speed between 50.40 m / min) to form a parallel, obliquely crossed, and mutually bonded reinforced polyurethane hollow fiber membrane assembly. Finally, the fiber membrane assembly was hot-pressed, and by changing the hot-pressing temperature (110℃) and pressure (150 MPa), a hollow fiber membrane composite thermal insulation material was produced. A schematic diagram of the reinforced polyurethane hollow fiber membrane structure is shown below. Figure 1 As shown in the diagram, the hollow fiber membrane composite thermal insulation material structure is as follows: Figure 2 As shown.

[0053] Example 5

[0054] First, 20% polyurethane, 6% polyethylene glycol 2000 and 74% N,N-dimethylacetamide by mass fraction were added to a spinning reactor (heating temperature was 50°C) and mixed (the feeding principle was solvent (37% N,N-dimethylacetamide) - powder (20% polyurethane, 6% polyethylene glycol 2000) - solvent (37% N,N-dimethylacetamide)), stirred (12h) and degassed (12h) to prepare a homogeneous casting solution. Then, based on the solvent-inducing phase separation method, concentric circle composite spinning technology was used to coat the homogeneous casting solution onto the surface of a polyester braided tube (outer diameter 1.55 mm) through a spinneret. After passing through a coagulation bath (water, temperature 50℃), the mixture was aggregated on a winding wheel (winding speed between 50.40 m / min) to form a parallel, obliquely crossed, and mutually bonded reinforced polyurethane hollow fiber membrane assembly. Finally, the fiber membrane assembly was hot-pressed, and by changing the hot-pressing temperature (120℃) and pressure (150 MPa), a hollow fiber membrane composite thermal insulation material was produced. A schematic diagram of the reinforced polyurethane hollow fiber membrane structure is shown below. Figure 1 As shown, the schematic diagram, physical image, and SEM image of the hollow fiber membrane composite thermal insulation material are respectively as follows: Figure 2 , Figure 3 , Figure 4 As shown.

[0055] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely prisms of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claims. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a hollow fiber membrane composite thermal insulation material, characterized in that: The method includes the following steps: Step 1: Take 18% to 22% polyurethane, 4% to 8% polyethylene glycol 2000 and 72% to 76% N,N-dimethylacetamide by mass and add them to the spinning reactor. Mix, stir and degas to prepare a homogeneous casting solution. Step 2: Based on the non-solvent induced phase separation method, the concentric circle composite spinning technology is used to coat the homogeneous casting liquid on the surface of the polyester braided tube through the spinneret. After passing through the coagulation bath, the liquid is aggregated on the winding wheel to form a parallel, obliquely cross-configured, and mutually bonded reinforced polyurethane hollow fiber membrane assembly. Step 3: Hot pressing the fiber membrane assembly to produce hollow fiber membrane composite thermal insulation material by hot pressing at a temperature of 60-150℃ and a pressure of 120-470MPa. In the second step, the reinforced polyurethane hollow fiber membrane is not completely phase-separated and cured. From the outside to the inside, it consists of a polyurethane porous coating, a polyester braided tube, and a cavity, with an outer diameter of less than 1.95 mm. In the third step, the hollow fiber membrane composite insulation material is composed of reinforced polyurethane hollow fiber membranes arranged in parallel and oblique cross directions to form a double-layer structure.

2. The method for preparing a hollow fiber membrane composite thermal insulation material according to claim 1, characterized in that: Polyurethane, polyethylene glycol, and N,N-dimethylacetamide need to be stirred in a spinning reactor at a constant temperature of 45-90℃ for 12 hours to fully dissolve the polymer, and then allowed to stand for 12 hours to remove bubbles to obtain a homogeneous casting solution.

3. The method for preparing a hollow fiber membrane composite thermal insulation material according to claim 1, characterized in that: In the first step, the homogeneous casting solution is transparent and has a viscosity range of 1500-15000 mPa·s.

4. The method for preparing a hollow fiber membrane composite thermal insulation material according to claim 1, characterized in that: In the second step, the polyester braided tube has an outer diameter of less than 1.55 mm.

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