Thermal insulation composite fiber and its preparation method and application

Abstract

The present invention provides a thermal insulation composite fiber and its preparation method and application. The preparation method specifically comprises: dissolving polyurethane in an organic solvent, then adding rush powder thereto, mixing, and obtaining a core layer solution of a preset concentration; then dissolving the polyurethane in a binary mixed solvent to obtain a skin layer solution of a preset concentration; and preparing the thermal insulation composite fiber by coaxial wet spinning. The present invention first uniformly disperses rush powder in the polyurethane solution to obtain a core layer solution, then prepares a skin layer polyurethane solution containing a binary mixed solvent, and prepares the thermal insulation composite fiber by coaxial wet spinning. The composition of the coagulation bath is controlled to be a mixed solvent formed by DMSO, DMAc, and water, and a suitable draft ratio is controlled. The prepared thermal insulation composite fiber has a light texture, contains a large amount of still air, has a strong thermal insulation effect, good air permeability, absorbs moisture and wicks away perspiration, and increases still air to enhance thermal insulation, windproof, and environmentally friendly effects.

Description

Technical Field

[0001] The present invention relates to the technical field of functional fibers, and in particular to a thermal insulation composite fiber and a preparation method and application thereof. Background Art

[0002] Thermal composite fibers are typically hollow or porous. Their hollow structure imparts specific properties such as excellent warmth retention and bulk. Hollow or porous fibers possess a unique luster, bulkiness, stain resistance, and pilling resistance, improving their elasticity and coverage. Currently, most of the specialized thermal fibers on the market are porous coarse-denier fibers. Coarse-denier hollow fibers consist of multiple cavities within a single coarse fiber. Due to their poor softness and mechanical properties, coarse fibers are only suitable for bedding, such as hollow thermal quilts and pillow cores, and are not suitable for producing down quilts, silk quilts, or thermal clothing.

[0003] The patent application number CN202210546809.9 discloses a passive thermal insulation multi-material microstructure fiber, a fabric and a preparation method thereof. The passive thermal insulation multi-material microstructure fiber, the core layer material includes a first polymer and a thermal insulation functional material, and the thermal insulation functional material includes hydrophilic silica aerogel particles, etc. The application adopts a coaxial wet spinning process combined with freeze-drying technology to prepare aerogel fibers, and introduces hydrophilic silica aerogel particles and other thermal insulation functional materials into the fiber core layer, making solvent exchange easier during the wet spinning process, forming many slender channels, and the cross-section of the fiber finally obtains a radial pore structure, and the pore structure of the fiber is not easy to collapse. The shortcomings of this method are: during the preparation process, the obtained as-spun fiber needs to be subjected to solvent exchange and freeze-drying treatment, which is a complicated process. At the same time, whether freeze-drying is complete will affect the thermal insulation effect of the fiber; if the aerogel in the core layer leaks, there will be a safety hazard to the human body; the performance of the obtained thermal insulation multi-material microstructure fiber needs to be improved.

[0004] In view of this, it is necessary to design an improved thermal insulation composite fiber and its preparation method and application to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a thermal insulation composite fiber and its preparation method and application. First, rush powder is evenly dispersed in a polyurethane solution to obtain a core layer solution, and then a skin layer polyurethane solution containing a binary mixed solvent is prepared. The thermal insulation composite fiber is prepared by coaxial wet spinning, and the composition of the coagulation bath is controlled to be a mixed solvent formed by DMSO, DMAc and water. At the same time, a suitable draft ratio is controlled. The prepared thermal insulation composite fiber has a light texture, contains a large amount of still air, has a strong thermal insulation effect, good air permeability, moisture absorption and perspiration removal, and the increase of still air improves the thermal insulation, windproof and environmental protection effects.

[0006] To achieve the above-mentioned object of the invention, the present invention provides a method for preparing a thermal insulation composite fiber, comprising the following steps:

[0007] S1. The polyurethane is dissolved in an organic solvent to obtain a polyurethane solution; rush powder is then added thereto and mixed to obtain a core solution of a preset concentration;

[0008] S2. dissolving the polyurethane in a binary mixed solvent to obtain a cortical solution of a preset concentration;

[0009] S3. Preparation of thermal insulation composite fibers by coaxial wet spinning.

[0010] As a further improvement of the present invention, in step S1, the organic solvent is DMF, the mass fraction of polyurethane in the polyurethane solution is 5%-10%; and the mass ratio of rush powder to polyurethane in the core layer solution is 8:2-6:4.

[0011] As a further improvement of the present invention, in step S2, the mass fraction of polyurethane in the cortex solution is 12%-18%.

[0012] As a further improvement of the present invention, in step S2, the binary mixed solvent is a mixed solvent of DMSO and DMAc; the mass ratio of DMSO to DMAc is 1:1-1:2.

[0013] As a further improvement of the present invention, step S3 is specifically: injecting the core layer solution prepared in step S1 and the skin layer solution prepared in step S2 into the coaxial spinning needle of the wet spinning equipment and extruding them through the coaxial spinning needle, then performing phase replacement in a coagulation bath, stretching, and drying to obtain the thermal insulation composite fiber.

[0014] As a further improvement of the present invention, the coagulation bath is a mixed solvent formed by DMSO, DMAc and water; the mass ratio of DMSO to DMAc is 1:1, and the total mass of DMSO and DMAc accounts for 3%-8% of the total mass of the mixed solvent.

[0015] As a further improvement of the present invention, the spinning temperature of the wet spinning is 15-30°C; the draft ratio is 1:1-1:1.5; and the drying temperature is 60-100°C.

[0016] As a further improvement of the present invention, the preparation of the core layer solution in step S1 and the preparation of the skin layer solution in step S2 are both carried out by mechanical stirring; the stirring rate of the mechanical stirring is 700-900 r / min, and the stirring time is 80-100 min.

[0017] The present invention also provides a thermal insulation composite fiber, which is prepared by using any of the above-mentioned methods for preparing the thermal insulation composite fiber and comprises a windproof skin layer and a thermal insulation core layer.

[0018] The present invention also provides an application of a thermal insulation composite fiber, wherein the thermal insulation composite fiber is applied to thermal insulation fabrics.

[0019] The beneficial effects of the present invention are:

[0020] (1) The preparation method of the thermal insulation composite fiber provided by the present invention comprises the following steps: firstly, the rush powder is uniformly dispersed in the polyurethane solution to obtain a core layer solution, and the rush powder and the polyurethane form a preliminary interaction; then, a skin layer polyurethane solution containing a binary mixed solvent is prepared, which not only makes the polyurethane dissolve better, but also can well control the coagulation speed of the fiber in the subsequent coagulation bath, and at the same time can improve the mechanical properties of the polyurethane, thereby obtaining a skin-core fiber with excellent structure, wherein the skin layer of the skin-core fiber has a better supporting and restraining effect on the core layer, and can maintain the original shape of the fiber when the skin-core fiber is squeezed by an external force (improving the mechanical properties), and at the same time increases the content of still air to enhance the thermal insulation effect; then Thermal insulation composite fibers were prepared using coaxial wet spinning. The composition of the coagulation bath was controlled to be a mixed solvent formed by DMSO, DMAc and water, so that the solvents in the core layer and the cortex layer maintained a suitable diffusion rate, thereby causing the core and cortex layers to slowly solidify. At the same time, as the solvents in the core and cortex layers diffused, the cortex and core layers further formed a porous structure. The interaction between the polyurethane in the core layer and the rush caused the structure to be fine-tuned. The long molecular chains of the polyurethane wrapped the rush, and at the same time, the different rush powders were firmly bonded together by the interaction between the polyurethane molecular chains. At the same time, the groups on the surface and inside of the rush formed hydrogen bonds with the active groups of the polyurethane, further improving stability. In addition, the polyurethane molecules in the core layer and the cortex were further cross-linked and entangled, making the core-skin structure more stable. At the same time, by drawing the fiber, at an appropriate draw ratio, the microstructure of the fiber further changed. Finally, by drying, a thermal insulation composite fiber with a stable structure and rich pores was obtained.

[0021] (2) The preparation method of the thermal insulation composite fiber provided by the present invention fully utilizes the advantages of the natural hollow three-dimensional network structure (multi-level pore structure), large porosity, small pore size, large specific surface area, and natural degradability (environmental protection) of rush. The prepared thermal insulation composite fiber has a light texture, contains a lot of still air, has a strong thermal insulation effect, good air permeability, absorbs moisture and wicks away sweat, and increases the still air to enhance the effects of thermal insulation, windproof, and environmental protection. At the same time, the arrangement of the rush powder in the core layer is different, so that the porous structure is arranged irregularly. When squeezed by external force, the air is not easily discharged, further improving the thermal insulation effect. By making full use of the rush powder and the large porosity and large specific surface area, the prepared thermal insulation composite fiber has the advantages of thermal insulation, breathability, lightness, windproof, and environmental protection.

[0022] (3) The preparation method of the thermal insulation composite fiber provided by the present invention uses recycled rush powder, which is economical and environmentally friendly. The fiber length and fineness are well controlled, and it can be widely adapted for the processing of thermal insulation fabrics. It has excellent mechanical properties and excellent thermal insulation performance. Furthermore, rush itself is harmless to the human body and is safer. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a schematic diagram of the structure of the thermal insulation composite fiber prepared by the present invention.

[0024] Reference numerals

[0025] 1- Windproof skin layer; 2- Warm core layer. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0027] It should also be noted here that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0028] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0029] The present invention provides a method for preparing a thermal insulation composite fiber, comprising the following steps:

[0030] S1. Preparation of core layer solution:

[0031] Add polyurethane (TPU) into DMF and stir mechanically at a stirring rate of 700-900 r / min for 80-100 min to fully dissolve the polyurethane to obtain a polyurethane solution having a mass fraction of 5%-10% of polyurethane in the polyurethane solution.

[0032] Next, rush powder (which retains its three-dimensional porous structure; different rush powders may have different three-dimensional porous structures) is added and mixed to form a core solution of a predetermined concentration. The mass ratio of rush powder to polyurethane in the core solution is 8:2-6:4. The rush powder particle size is 20-90 μm.

[0033] In this process, a polyurethane solution is first prepared, and then rush powder is added to it. The rush powder is evenly dispersed in the polyurethane solution. At the same time, active groups such as ester and amino groups in the polyurethane molecular chain interact with the abundant hydroxyl groups on the surface and inside the pores of the rush powder, further making the rush powder evenly and stably dispersed in the polyurethane solution.

[0034] S2. Preparation of cortical solution

[0035] Polyurethane (TPU) was added to a binary mixed solvent formed by DMSO and DMAc, and mechanically stirred at a stirring rate of 700-900 r / min for 80-100 min to fully dissolve the polyurethane and obtain a cortex solution of a preset concentration.

[0036] The mass ratio of DMSO to DMAc in the binary mixed solvent is 1:1-1:2, and the mass fraction of polyurethane in the cortex solution is 12%-18%.

[0037] In this process, a binary mixed system is used to dissolve the polyurethane, which, on the one hand, allows the polyurethane to be better dissolved, and on the other hand, can improve the subsequent coagulation speed of the fiber in the coagulation bath, thereby obtaining a fiber with excellent structure.

[0038] S3. Preparation of thermal insulation composite fiber:

[0039] The thermal insulation composite fiber is prepared by coaxial wet spinning. Specifically, the core layer solution prepared in step S1 and the sheath layer solution prepared in step S2 are injected into the coaxial spinning needle of the wet spinning equipment and extruded through the coaxial spinning needle. Then, phase replacement is carried out in a coagulation bath, and the thermal insulation composite fiber is obtained by drawing and drying.

[0040] The coagulation bath is a mixed solvent of DMSO, DMAc, and water; the mass ratio of DMSO to DMAc is 1:1, and the combined mass of DMSO and DMAc accounts for 3%-8% of the total mass of the mixed solvent. The wet spinning temperature is 15-30°C; the draft ratio is 1:1-1:1.5; and the drying temperature is 60-100°C.

[0041] In this process, coaxial spinning is used to prepare fibers with a skin-core structure. At the same time, the composition of the coagulation bath is controlled to be a mixed solvent formed by DMSO, DMAc and water, so that the solvent of the core layer and the solvent of the skin layer maintain a suitable diffusion rate, thereby causing the core layer and the skin layer to slowly solidify, avoiding the disadvantage that the core layer solvent cannot fully diffuse. As the core and skin layer solvents diffuse, the structure of the polyurethane and rush in the core layer is fine-tuned. The long molecular chain of the polyurethane wraps the rush, and at the same time, the different rush powders are firmly bonded together by the interaction between the polyurethane molecular chains. At the same time, the groups on the surface and inside of the rush are bonded to the active groups of the polyurethane, further improving stability. At the same time, the polyurethane molecules in the core layer and the polyurethane molecules in the skin layer are further entangled, making the skin-core structure more stable.

[0042] At the same time, by stretching, at a suitable stretching ratio, the microstructure of the fiber further changes, and finally through drying, a thermal insulation composite fiber with stable structure and rich pores is obtained.

[0043] The present invention also provides a thermal insulation composite fiber, which is prepared by the above-mentioned thermal insulation composite fiber preparation method. Figure 1 As shown, the thermal insulation composite fiber includes a windproof cortex 1 and a thermal insulation core layer 2. The windproof cortex 1 not only plays a windproof role, but also provides a supporting skeleton for the thermal insulation core layer 2, better restraining the thermal insulation core layer 2. At the same time, the polyurethane molecular chains of the windproof cortex 1 and the thermal insulation core layer 2 are entangled with each other, further reinforcing the structure. In addition, the rush powder in the thermal insulation core layer 2 is evenly dispersed in the core layer, and at the same time, the arrangement of different rush powders is different, making the porous structure irregularly arranged. With such an arrangement, compared with the radial pore structure, the pore structure with different arrangement modes is more likely to adsorb air in the pores without exchanging air with the outside world, further improving the thermal insulation effect; at the same time, the binary solvent system of the cortex is matched with the single solvent of the core layer, regulating the pore structure and the arrangement mode of polyurethane and rush powder, which is beneficial to improving the mechanical properties and thermal insulation performance of the composite fiber.

[0044] The present invention also provides an application of a thermal insulation composite fiber, wherein the thermal insulation composite fiber is applied to thermal insulation fabrics.

[0045] The present invention is described in detail below through specific examples.

[0046] Example 1

[0047] A method for preparing a thermal insulation composite fiber comprises the following steps:

[0048] S1. Preparation of core layer solution:

[0049] Polyurethane (TPU) was added to DMF and mechanically stirred at a stirring rate of 800 r / min for 90 min to fully dissolve the polyurethane to obtain a polyurethane solution having a mass fraction of 7.5% of polyurethane.

[0050] Then, rush powder is added thereto and mixed to obtain a core layer solution of a predetermined concentration. The mass ratio of rush powder to polyurethane in the core layer solution is 7:3.

[0051] S2. Preparation of cortical solution

[0052] Polyurethane (TPU) was added to a binary mixed solvent formed by DMSO and DMAc, and mechanically stirred at a stirring rate of 800 r / min for 90 min to fully dissolve the polyurethane to obtain a cortex solution of a preset concentration.

[0053] The mass ratio of DMSO to DMAc in the binary mixed solvent was 1:1.5, and the mass fraction of polyurethane in the cortex solution was 15%.

[0054] S3. Preparation of thermal insulation composite fiber:

[0055] The core layer solution prepared in step S1 and the skin layer solution prepared in step S2 are injected into the coaxial spinning needle of the wet spinning equipment and extruded through the coaxial spinning needle, and then phase-exchanged in a coagulation bath, stretched, and dried to obtain the thermal insulation composite fiber.

[0056] The coagulation bath was a mixed solvent of DMSO, DMAc, and water; the mass ratio of DMSO to DMAc was 1:1, and the combined mass of DMSO and DMAc accounted for 5% of the total mass of the mixed solvent. The wet spinning temperature was 25°C, the draw ratio was 1:1.25, and the drying temperature was 80°C.

[0057] Examples 2-3 and Comparative Examples 1-2

[0058] A method for preparing a thermal insulation composite fiber is different from that of Example 1 in that, in step S1, the mass fraction of polyurethane in the polyurethane solution is different. Other aspects are substantially the same as those of Example 1 and will not be described herein.

[0059] The thermal insulation composite fibers prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance tests, and the results are shown in Table 1:

[0060] Tensile strength refers to the tensile strength of thermal insulation composite fibers, tested in accordance with GB / T14344-2022 standard.

[0061] Tensile strain refers to the tensile strain of thermal insulation composite fibers, which is tested in accordance with GB / T14344-2022 standard.

[0062] Thermal conductivity refers to the thermal conductivity of the thermal insulation composite fiber, which is measured using a DRPL-II thermal conductivity tester (transient hot wire method).

[0063] The thermal conductivity of rush is 60mW / (m·K).

[0064] Table 1 Thermal insulation composite fibers prepared in Examples 1-3 and Comparative Examples 1-2

[0065]

[0066] As shown in Table 1, within a certain range, as the polyurethane mass fraction increases (Examples 1-3), the tensile strength and tensile strain of the thermal insulation composite fiber gradually increase, while the thermal conductivity first decreases and then increases. This is mainly because the change in polyurethane mass fraction affects the viscosity of the core layer solution, which in turn affects the dispersion uniformity of rush in the core layer solution and the interaction between polyurethane and rush. When the polyurethane mass fraction is relatively moderate, the pore structure in the core layer of the composite fiber is uniform, and the interaction between polyurethane and rush is uniform, resulting in better thermal insulation and mechanical properties of the composite fiber.

[0067] As the mass fraction of polyurethane further increases (Comparative Example 2), the change in the tensile strength of the thermal insulation composite fiber basically tends to be stable, while the thermal conductivity increases significantly, indicating that its thermal insulation effect is significantly poor.

[0068] When the mass fraction of polyurethane is very low (Comparative Example 1), the entanglement and continuity between polyurethane macromolecules will be hindered, greatly reducing the mechanical properties of the composite fiber.

[0069] Examples 4-5 and Comparative Examples 3-4

[0070] A method for preparing a thermal insulation composite fiber is provided. Compared with Example 1, the difference is that in step S1, the mass ratio of rush powder to polyurethane in the core layer solution is different. Other details are substantially the same as Example 1 and will not be repeated here.

[0071] The thermal insulation composite fibers prepared in Examples 4-5 and Comparative Examples 3-4 were subjected to performance tests, and the results are shown in Table 2:

[0072] Table 2 Thermal insulation composite fibers prepared in Examples 4-5 and Comparative Examples 3-4

[0073]

[0074] As shown in Table 2, within a certain range, as the rush powder content in the core layer solution increases (Examples 1, 4, and 5), the tensile strength and tensile strain of the resulting thermal composite fiber show a trend of gradually decreasing, and the corresponding thermal conductivity shows a trend of first decreasing and then increasing. This is mainly because the change in the mass ratio of rush powder to polyurethane affects the interaction between rush and polyurethane in the core layer solution, which in turn affects the structure and properties of the core layer. When the rush powder content is moderate, the overall performance of the resulting thermal composite fiber is better.

[0075] As the rush powder content in the core layer solution further increases (Comparative Example 3), the polyurethane cannot fully wrap the rush, thereby affecting the strength of the mutual bonding between different rush powders in the core layer and affecting the mechanical properties of the composite fiber.

[0076] When the content of rush is very low (Comparative Example 4), the number of multi-level pores in the composite fiber is significantly reduced, the thermal conductivity of the composite fiber is greatly increased, and the warmth-keeping effect is deteriorated.

[0077] Examples 6-7 and Comparative Examples 5-6

[0078] A method for preparing a thermal insulation composite fiber is different from that of Example 1, except that, in step S2, the mass fraction of polyurethane in the cortex solution is different. The rest is substantially the same as that of Example 1 and will not be described again.

[0079] The thermal insulation composite fibers prepared in Examples 6-7 and Comparative Examples 5-6 were subjected to performance tests, and the results are shown in Table 3:

[0080] Table 3 Warm-keeping composite fibers prepared in Examples 6-7 and Comparative Examples 5-6

[0081]

[0082] As shown in Table 3, within a certain range, as the polyurethane mass fraction in the sheath solution increases (Examples 1, 6, and 7), the tensile strength and tensile strain of the thermal insulation composite fiber show an upward trend, while the thermal conductivity shows a trend of first decreasing and then increasing. This is mainly because the change in the polyurethane mass fraction in the sheath solution affects the density of the sheath structure and the mutual entanglement of polyurethanes, which in turn affects the double diffusion between the coagulation bath and the core solution, ultimately affecting the performance of the thermal insulation composite fiber.

[0083] When the polyurethane concentration of the skin layer is too high (Comparative Example 6), the densification of the skin layer hinders the double diffusion of the coagulation bath and the core layer solution, which is not conducive to the formation of the multi-level porous structure of the core layer.

[0084] When the polyurethane concentration of the skin layer is too low (Comparative Example 5), the skin layer structure is relatively loose, which affects the binding of the core layer and the mutual entanglement of the core layer and the skin layer, resulting in poor mechanical properties.

[0085] Examples 8-9 and Comparative Examples 7-10

[0086] A method for preparing a thermal insulation composite fiber is different from that of Example 1, except that in step S2, the mass ratio of DMSO to DMAc in the binary mixed solvent is different. Other steps are substantially the same as those of Example 1 and will not be described again.

[0087] The thermal insulation composite fibers prepared in Examples 8-9 and Comparative Examples 7-10 were subjected to performance tests, and the results are shown in Table 4:

[0088] Table 4 Thermal insulation composite fibers prepared in Examples 8-9 and Comparative Examples 7-10

[0089]

[0090] Table 4 shows that an appropriate ratio of DMSO to DMAc in the binary solvent mixture facilitates the preparation of composite fibers with excellent tensile strength, tensile strain, and thermal conductivity. Using only DMSO or DMAc as a single solvent results in different arrangements of polyurethane molecular chains in the polyurethane-rich phase during the phase replacement process, resulting in an uneven pore structure in the resulting composite fibers, reducing their mechanical properties. Furthermore, the thermal conductivity increases, leading to poorer thermal insulation.

[0091] Examples 10-11 and Comparative Examples 11-12

[0092] A method for preparing a thermal insulation composite fiber is different from that of Example 1, except that in step S3, the mass of DMSO and DMAc and the proportion of the mass of the mixed solvent are different. Other details are similar to those of Example 1 and will not be repeated here.

[0093] The thermal insulation composite fibers prepared in Examples 10-11 and Comparative Examples 11-12 were subjected to performance tests, and the results are shown in Table 5:

[0094] Table 5 Thermal insulation composite fibers prepared in Examples 10-11 and Comparative Examples 11-12

[0095]

[0096]

[0097] As shown in Table 5, with increasing DMSO and DMAc content in the coagulation bath, the tensile strength and tensile strain of the composite fiber gradually increased and then stabilized, while the thermal conductivity first decreased and then increased. This is mainly because the increase in DMSO and DMAc content in the coagulation bath slowed the phase replacement rate between the polyurethane and the coagulation bath, which is more conducive to the structural regulation of the pores within the polyurethane composite fiber. However, when the content of the mixed solvent in the coagulation bath is too high, the pore distribution in the composite fiber becomes more uneven and the pore volume decreases relatively, which increases the thermal conductivity of the composite fiber and leads to a decrease in the thermal insulation effect.

[0098] Examples 12-13 and Comparative Examples 13-14

[0099] A method for preparing a thermal insulation composite fiber is different from that of Example 1 in that, in step S3, the spinning temperature is different. The rest is substantially the same as that of Example 1 and will not be described again.

[0100] The thermal insulation composite fibers prepared in Examples 12-13 and Comparative Examples 13-14 were tested, and the results are shown in Table 6:

[0101] Table 6 Thermal insulation composite fibers prepared in Examples 12-13 and Comparative Examples 13-14

[0102]

[0103] As shown in Table 6, as the spinning temperature increases, the tensile strength and tensile strain of the composite fibers first increase and then decrease, while the thermal conductivity first decreases and then increases. This is because changes in the spinning temperature affect the phase replacement process during fiber formation, which in turn affects the regulation of the pore structure within the composite fibers. Excessively high or low spinning temperatures accelerate or slow the phase replacement process during formation, both of which are detrimental to the regulation of the pore structure within the composite fibers.

[0104] Examples 14-15 and Comparative Examples 15-16

[0105] A method for preparing a thermal insulation composite fiber is different from that of Example 1 in that, in step S3, the drafting ratio is different. The rest is substantially the same as that of Example 1 and will not be described again.

[0106] The thermal insulation composite fibers prepared in Examples 14-15 and Comparative Examples 15-16 were subjected to performance tests, and the results are shown in Table 6:

[0107] Table 7 Thermal insulation composite fibers prepared in Examples 14-15 and Comparative Examples 15-16

[0108]

[0109] As shown in Table 7, with increasing draw ratios, the tensile strength of the composite fibers first increases and then decreases, the tensile strain gradually decreases, and the thermal conductivity first decreases and then increases. This is because the larger the draw ratio, the more pronounced the axial orientation of the polyurethane molecular chains and rush particles, which increases the overall tensile strength of the composite fibers and reduces the tensile strain. At the same time, the pore orientation and complex connectivity within the composite fibers decrease, increasing the thermal conductivity of the composite fibers.

[0110] Comparative Example 17

[0111] A method for preparing a thermal insulation composite fiber, compared with Example 1, differs in that, in step S1, polyurethane and rush powder are added to DMF simultaneously. The other steps are substantially the same as in Example 1 and are not described in detail here. The thermal insulation composite fiber obtained in Comparative Example 17 has a tensile strength of 6.0 MPa, a tensile strain of 402%, and a thermal conductivity of 38 mW / (m·K), which are inferior to those in Example 1. This is mainly because the rush powder may agglomerate when the polyurethane and rush powder are added to DMF simultaneously, resulting in poor uniformity of the core layer solution, which in turn affects the performance of the thermal insulation composite fiber and its fabric.

[0112] Comparative Example 18

[0113] A method for preparing a thermal insulation composite fiber, compared to Example 1, differs in that, in step S2, the binary mixed solvent is DMSO and DMF. Other steps are substantially the same as in Example 1 and are not further described here. The thermal insulation composite fiber obtained in Comparative Example 18 had a tensile strength of 6.1 MPa, a tensile strain of 397%, and a thermal conductivity of 40 mW / (m·K), which are inferior to those in Example 1.

[0114] Comparative Example 19

[0115] A method for preparing a thermal insulation composite fiber, compared with Example 1, differs in that in step S2, the binary mixed solvent is DMAc and DMF. The rest is substantially the same as in Example 1 and is not described here. The thermal insulation composite fiber obtained in Comparative Example 19 has a tensile strength of 5.9 MPa, a tensile strain of 390%, and a thermal conductivity of 39 mW / (m·K), which are inferior to those in Example 1. Comparative Examples 18-19 illustrate that only the appropriate type of binary mixed solvent system can better regulate the pore structure and the arrangement of polyurethane and rush powder, thereby improving the performance of the thermal insulation composite fiber.

[0116] Comparative Example 20

[0117] A method for preparing a thermal insulation composite fiber, compared to Example 1, differs in that in step S3, the coagulation bath is solely water. The remaining steps are substantially the same as in Example 1 and are not further described here. The thermal insulation composite fiber obtained in Comparative Example 20 had a tensile strength of 6.0 MPa, a tensile strain of 381%, and a thermal conductivity of 44 mW / (m·K), which were inferior to those in Example 1.

[0118] Comparative Example 21

[0119] A method for preparing a thermal insulation composite fiber, compared to Example 1, differs in that, in step S3, the coagulation bath is a mixed solvent of DMAc and water, with the mass of DMAc accounting for 5% of the total mass of the mixed solvent. Other conditions are substantially the same as in Example 1 and are not further described here. The thermal insulation composite fiber obtained in Comparative Example 21 had a tensile strength of 6.2 MPa, a tensile strain of 403%, and a thermal conductivity of 37 mW / (m·K), which are inferior to those in Example 1.

[0120] Comparative Example 22

[0121] A method for preparing a thermal insulation composite fiber, compared with Example 1, differs in that, in step S3, the coagulation bath is a mixed solvent of DMSO and water, the mass of DMSO accounts for 5% of the total mass of the mixed solvent, and the rest is substantially the same as Example 1 and will not be repeated here. The thermal insulation composite fiber obtained in Comparative Example 22 has a tensile strength of 6.1 MPa, a tensile strain of 394%, and a thermal conductivity of 36 mW / (m·K), which are worse than those in Example 1. Comparative Examples 20-22 illustrate that the different types of coagulation baths affect the phase replacement rate between polyurethane and the coagulation bath, thereby affecting the structural regulation of the internal pores of the polyurethane composite fiber, and ultimately affecting the performance of the thermal insulation composite fiber.

[0122] Comparative Example 23

[0123] A method for preparing a thermal insulation composite fiber, compared with Example 1, differs in that rush is replaced with hydrophilic silica aerogel, the unstretched fiber is placed in a tert-butanol solution with a mass concentration of 25%, soaked for 24 hours, then placed in a -70°C environment and frozen for 3 hours, and then placed in a freeze drying oven and freeze-dried for 24 hours to obtain a thermal insulation composite fiber; the other methods are substantially the same as Example 1 and are not described here. The thermal insulation composite fiber obtained in Comparative Example 23 has a tensile strength of 5.3 MPa, a tensile strain of 350%, and a thermal conductivity of 47 mW / (m·K), which are worse than those in Example 1. This shows that the interaction between the specially structured rush and polyurethane is more conducive to regulating the pore structure and the arrangement in the core layer and the cortex, resulting in better performance of the thermal insulation composite fiber.

[0124] Comparative Example 24

[0125] A method for preparing a thermal insulation composite fiber, compared to Example 1, differs in that a polyurethane layer is directly coated on the surface of the rush fiber, ensuring that the thickness of the core layer and the skin layer are the same as in Example 1. The thermal insulation composite fiber obtained in Comparative Example 24 has a tensile strength of 4.3 MPa, a tensile strain of 230%, and a thermal conductivity of 64 mW / (m·K), which are worse than those in Example 1. This indicates that the rush powder enriches the multi-level pore structure, thereby improving the performance of the thermal insulation composite fiber.

[0126] Comparative Example 25

[0127] A method for preparing a thermal insulation composite fiber, compared with Example 1, differs in that, in step S1, the solvent used in the core layer solution is the same as the solvent used in the cortex solution, both of which are binary mixed solvents formed by DMSO and DMAc. The rest is substantially the same as in Example 1 and will not be repeated here. The thermal insulation composite fiber obtained in Comparative Example 25 has a tensile strength of 6.4 MPa, a tensile strain of 405%, and a thermal conductivity of 69 mW / (m·K), which are worse than those in Example 1. This shows that the mutual matching of the binary solvent system of the cortex layer and the single solvent of the core layer is required to better control the pore structure and the arrangement of the polyurethane and rush powder, thereby improving the performance of the composite fiber.

[0128] In summary, the thermal insulation composite fiber provided by the present invention and its preparation method and application are as follows: first, rush powder is evenly dispersed in a polyurethane solution to obtain a core layer solution, and then a skin polyurethane solution containing a binary mixed solvent is prepared. The thermal insulation composite fiber is prepared by coaxial wet spinning, and the composition of the coagulation bath is controlled to be a mixed solvent formed by DMSO, DMAc and water. At the same time, a suitable draft ratio is controlled. The prepared thermal insulation composite fiber has a light texture, contains a lot of still air, has a strong thermal insulation effect, good air permeability, absorbs moisture and wicks away sweat, and increases still air to enhance the effects of warmth, windproof, and environmental protection. The use of recycled waste rush powder is economical and environmentally friendly, and the length and fineness of the fiber are well controllable, and can be widely adapted to the processing of thermal insulation fabrics, with excellent mechanical properties and excellent thermal insulation performance. Furthermore, rush itself is harmless to the human body and safer.

[0129] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing a thermal insulation composite fiber, characterized in that: The steps include: S1. The polyurethane is dissolved in an organic solvent to obtain a polyurethane solution; rush powder is then added thereto and mixed to obtain a core layer solution having a predetermined concentration; the organic solvent is DMF; S2. The polyurethane is dissolved in a binary mixed solvent to obtain a cortical solution of a preset concentration; the binary mixed solvent is a mixed solvent of DMSO and DMAc; the mass ratio of DMSO to DMAc is 1:1-1:2; S3. Preparation of thermal insulation composite fibers by coaxial wet spinning.

2. The method for preparing the thermal insulation composite fiber according to claim 1, characterized in that: In step S1, the mass fraction of polyurethane in the polyurethane solution is 5%-10%; the mass ratio of rush powder to polyurethane in the core layer solution is 8:2-6:

4.

3. The method for preparing the thermal insulation composite fiber according to claim 1, characterized in that: In step S2, the mass fraction of polyurethane in the cortex solution is 12%-18%.

4. The method for preparing the thermal insulation composite fiber according to claim 1, characterized in that: Step S3 is specifically as follows: injecting the core layer solution prepared in step S1 and the skin layer solution prepared in step S2 into the coaxial spinning needle of the wet spinning equipment and extruding them through the coaxial spinning needle, then performing phase replacement in a coagulation bath, stretching, and drying to obtain the thermal insulation composite fiber.

5. The method for preparing the thermal insulation composite fiber according to claim 4, characterized in that: The coagulation bath is a mixed solvent formed by DMSO, DMAc and water; the mass ratio of DMSO to DMAc is 1:1, and the mass of DMSO and DMAc accounts for 3%-8% of the total mass of the mixed solvent.

6. The method for preparing the thermal insulation composite fiber according to claim 4, characterized in that: The spinning temperature of the coaxial wet spinning is 15-30°C; the draw ratio is 1:1-1:1.5; and the drying temperature is 60-100°C.

7. The method for preparing the thermal insulation composite fiber according to claim 1, characterized in that: The preparation of the core layer solution in step S1 and the preparation of the skin layer solution in step S2 are both carried out by mechanical stirring; the stirring rate of the mechanical stirring is 700-900 r / min, and the stirring time is 80-100 min.

8. A thermal insulation composite fiber, characterized in that: The thermal insulation composite fiber is prepared by the preparation method of any one of claims 1 to 7, and comprises a windproof skin layer and a thermal insulation core layer.

9. An application of a thermal insulation composite fiber, characterized in that: The thermal insulation composite fiber prepared by the preparation method of any one of claims 1 to 7 or the thermal insulation composite fiber according to claim 8 is applied to thermal insulation fabrics.

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