Polymer PI fiber thermal insulation cotton and preparation method thereof

Abstract

The invention discloses polymer PI fiber heat preservation cotton and a preparation method thereof.The heat preservation cotton comprises an inner layer, a middle layer and an outer layer, the inner layer comprises PI fibers and polyvinyl alcohol fibers, the middle layer comprises the PI fibers and skin-core composite fibers, and the outer layer comprises the PI fibers, aramid fibers and low-melting-point fibers; the middle layer PI fiber is a modified PI fiber, and the preparation of the modified PI fiber comprises the following steps: under a nitrogen protection atmosphere, polymerizing pyromellitic dianhydride and 4, 4 '-diaminodiphenyl ether in N, N-dimethylacetamide to obtain a polyamide acid solution; adding phenylacetylene-terminated hyperbranched polysiloxane, fluorinated graphene oxide, a surfactant and a pore-forming agent into the polyamide acid solution, and reacting to obtain a modified polyamide acid spinning solution; and carrying out dry spinning and thermal forming treatment on the modified polyamide acid spinning solution to obtain the modified PI fiber. The obtained heat preservation cotton has the characteristics of heat preservation, washing resistance and comfort.

Description

Technical Field

[0001] This application relates to the field of thermal insulation cotton materials technology, and in particular to a high molecular weight PI fiber thermal insulation cotton and its preparation method. Background Technology

[0002] As a core filling material for clothing, thermal insulation cotton's heat insulation performance and safety reliability directly determine the quality and application range of the final product. Currently, common thermal insulation cotton materials mainly include traditional natural or chemical fibers such as polyester fiber, down, wool, and cotton, as well as high-performance synthetic fibers that have gained increasing attention in recent years. With the development of materials science, some new thermal insulation cottons are beginning to adopt composite structures or finishing processes, aiming to improve their thermal resistance, durability, or lightweighting to a certain extent. Among them, polyimide (PI) fiber, due to its inherent high-temperature resistance and flame retardant properties, is also being explored for application in the field of thermal insulation cotton, attempting to provide solutions that balance heat insulation and safety in special environments.

[0003] However, PI fiber insulation has shortcomings in terms of thermal insulation performance, washability, and comfort. PI fiber itself has a relatively high thermal conductivity, and its fiber morphology and aggregate structure are difficult to maintain stable loft over a long period, resulting in limited static air retention and insufficient heat insulation effect. Heat loss is particularly noticeable in humid or pressurized environments. Furthermore, after repeated washing, PI fiber is prone to fiber breakage, clumping, or overall structural collapse, which not only drastically reduces its thermal insulation performance but also affects the product's shape retention and lifespan. In terms of wearing or contact comfort, PI fiber usually feels stiff and lacks softness and resilience, affecting its application experience in close-fitting textiles. Summary of the Invention

[0004] To address the shortcomings of PI fiber insulation in terms of thermal insulation performance, water resistance, and comfort, a high-polymer PI fiber thermal insulation cotton and its preparation method are provided.

[0005] The first inventive objective of this invention is achieved through the following technical solution: A type of high-polymer PI fiber thermal insulation cotton includes an inner layer, a middle layer, and an outer layer. The inner layer consists of PI fiber and polyvinyl alcohol fiber, with a mass ratio of PI fiber to polyvinyl alcohol fiber of (25:75)-(20:80). The middle layer consists of PI fibers and core-sheath composite fibers, with a mass ratio of PI fibers to core-sheath composite fibers of (70:30)-(80:20). The outer layer consists of PI fiber, aramid fiber and low melting point fiber, with a mass ratio of PI fiber, aramid fiber and low melting point fiber of 50:(30-35):(15-20); The intermediate layer PI fiber is a modified PI fiber. The preparation of the modified PI fiber includes the following steps: under a nitrogen protective atmosphere, pyromellitic dianhydride and 4,4'-diaminodiphenyl ether are polymerized in N,N-dimethylacetamide to obtain a polyamic acid solution; phenylacetylene-terminated hyperbranched polysiloxane, fluorinated graphene oxide, surfactant, and pore-forming agent are added to the polyamic acid solution, and the reaction is carried out to obtain a modified polyamic acid spinning solution; the modified polyamic acid spinning solution is subjected to dry spinning and thermoforming treatment to obtain modified PI fiber.

[0006] By adopting the above technical solutions, PI fiber, as a polyimide material, has intrinsically low thermal conductivity, which can effectively block heat conduction. Its rigid molecular structure provides good resilience and thermal stability. Polyvinyl alcohol fiber has hydrophilicity and softness, and microporous structure can be introduced into the fiber network to improve air permeability and softness to the touch. The intermediate layer is mainly composed of PI fiber and core-sheath composite fiber. PI fiber, as the main body, provides the main thermal insulation performance. Its porous and fine denier structure can effectively store still air and reduce heat convection and conduction. The sheath of the core-sheath composite fiber can melt and bond the surrounding fibers after being heated to form a three-dimensional network structure, thereby fixing the position between the fibers and preventing the insulation layer thickness from decreasing due to fiber displacement during use. Therefore, the intermediate layer improves the long-term stability of the structure while ensuring high thermal insulation performance. The outer layer is composed of PI fiber, aramid fiber and low melting point fiber. PI fiber provides thermal insulation performance, while the high strength, high modulus and heat resistance of aramid fiber give the outer layer excellent tensile strength. The low melting point fiber melts and bonds under heat, solidifying the fiber network to improve the overall structural integrity and improve the water resistance of the insulation cotton. The inner layer focuses on skin-friendly comfort, the middle layer focuses on efficient heat preservation and structural stability, and the outer layer focuses on durable protection. The fibers of each layer are bonded together by low melting point components to form a continuous interface, which improves the structural integrity of the multi-layer composite, thereby enhancing the long-term heat preservation efficiency, water resistance stability and breathable and resilient comfort of the insulation cotton. Phenylacetylene-terminated hyperbranched polysiloxanes, as organic-inorganic hybrid modifiers, possess a highly branched three-dimensional spherical structure with numerous cavities within the molecule and a surface rich in organic groups. This allows them to physically entangle and interact with linear polyamic acid molecular chains, playing a toughening role in spinning solutions. The terminal phenylacetylene groups are key active groups; during subsequent thermal imidization and heat treatment, the phenylacetylene groups undergo thermal crosslinking reactions, forming stable chemical bonds between the polysiloxane and polyimide matrix, thereby enhancing flexibility and low temperature resistance. The silicone segments with modulus are chemically anchored to the rigid polyimide backbone, improving the flexibility and fatigue resistance of the final PI fiber. The introduction of silicone components effectively reduces the rigid modulus of the fiber, making the fiber easier to bend and less brittle. This directly improves the soft touch and flexibility of the insulation cotton made from this fiber, enhancing comfort. Furthermore, the chemical cross-linking network enhances the integrity of the fiber structure, enabling it to maintain stable performance under long-term repeated stress. The polysiloxane itself has excellent low surface energy, which also helps improve the overall water resistance of the fiber. Fluorinated graphene oxide is a fluorinated graphene derivative nanomaterial. In polyamic acid spinning solutions, fluorinated graphene oxide sheets can be uniformly dispersed. The oxygen-containing functional groups (such as carboxyl and hydroxyl groups) on its surface can form strong hydrogen bonds or electrostatic interactions with the polar groups on the polyamic acid chains, thereby effectively improving interfacial bonding and preventing the nanosheets from agglomerating in the fiber. The CF bonds introduced by the fluorination treatment endow it with hydrophobic and oleophobic properties. During the fiber formation process, the nanosheets are solidified in the PI matrix, playing a nano-reinforcing role. Its two-dimensional layered structure can effectively hinder the slippage of molecular chains and the propagation of microcracks, improve the tensile strength, modulus and tear resistance of fibers, thereby enhancing the resilience of thermal insulation cotton and enhancing the hydrophobic properties of fibers. The low surface energy characteristics of fluorinated graphene oxide make it evenly distributed on the surface and inside of fibers, forming a micro-rough hydrophobic structure, making fibers less susceptible to being wetted by liquid water. This helps thermal insulation cotton maintain a dry feel in humid environments, improves user comfort, and reduces the decrease in thermal insulation performance and structural damage caused by water absorption. Surfactants reduce solid-liquid interfacial tension. They contain both lipophilic and hydrophilic groups. The lipophilic end can be directionally adsorbed onto the surface of nano-additives, while the hydrophilic end extends into the continuous phase of the polar polyamic acid solution. This reduces the driving force for agglomeration and forms a solvation layer with steric hindrance on the particle surface, preventing close proximity and agglomeration. This allows the nano-additives to be uniformly and stably dispersed in the spinning solution as primary or micro-agglomerates, facilitating the uniform expression of nanofunctionality in the final fiber and reducing stress concentration or performance inhomogeneity caused by agglomeration. Pore-forming agents are a class of agents that can undergo thermal decomposition at specific temperatures and produce… During the thermoforming process of polyamic acid to polyimide, gaseous compounds decompose under heat when the polymer matrix is ​​not fully cured but has a suitable viscosity, releasing gases that nucleate and grow within the polymer matrix, forming numerous tiny, discrete pores. As the heat treatment is completed and the polymer matrix is ​​fully cured, these pores are permanently fixed inside the fiber, forming a porous microstructure. The pores trap still air, reducing the effective thermal conductivity of the fiber and enhancing its heat insulation effect. At the same time, the porous structure reduces the fiber density, helping to obtain lighter products and improving the compression resilience and fluffiness of the fiber assembly.

[0007] Optionally, the surfactant is a fatty alcohol polyoxyethylene ether.

[0008] By adopting the above technical solution, fatty alcohol polyoxyethylene ether is non-ionic. The hydrophilic and lipophilic segments in its molecular structure can reduce the surface tension of the spinning solution, allowing the hydrophobic fluorinated graphene oxide and hyperbranched polysiloxane to be more uniformly dispersed in the polyamic acid solution, reducing the aggregation of nano-components, and ensuring the uniform distribution of the modifier in the fiber matrix. This helps to form a uniform microporous structure and interfacial bonding, thereby improving the consistency of the thermal insulation performance and structural stability of the modified PI fiber, and enhancing the overall washability of the thermal insulation cotton.

[0009] Optionally, the pore-forming agent is 4,4'-oxobisbenzenesulfonylhydrazine.

[0010] By adopting the above technical solution, 4,4'-oxobisbenzenesulfonyl hydrazine decomposes under heat during thermoforming, releasing gases such as nitrogen, which form uniform closed or semi-closed micropores inside the fiber. The micropores increase the specific surface area and air content of the fiber. The presence of the static air layer effectively reduces heat conduction and convection, improving the fiber's heat insulation capacity. Furthermore, the microporous structure can increase the fiber's lightness and compression resilience, which is beneficial for improving the comfort and heat insulation performance of the insulation cotton.

[0011] Optionally, the low-melting-point fiber is ES fiber.

[0012] By adopting the above technical solution, ES fiber is a composite fiber with a core-sheath structure. When the outer layer is heated, the sheath melts and flows to the intersection of PI fiber and aramid fiber to form bonding points. After cooling, it solidifies and fixes the fiber network. The core layer maintains the fiber shape, provides stiffness to maintain porosity, and enhances the bonding strength between the outer layer fibers. This makes the insulation cotton less prone to delamination or deformation under repeated washing and mechanical action, thereby improving the durability of water resistance and insulation performance. Moreover, the introduction of ES fiber does not significantly affect air permeability.

[0013] Optionally, the core layer of the core-sheath composite fiber is polyethylene terephthalate, and the sheath layer is copolyamide.

[0014] By adopting the above technical solution, in the intermediate layer, the skin layer copolyamide has a low melting temperature, which melts and wets the PI fiber surface during hot rolling to form bonding bridges; the core layer polyethylene terephthalate has a high melting point and modulus, which maintains the fiber shape after bonding and provides rigid support to resist compression. In addition, the hydrophobic properties of polyethylene terephthalate help reduce the moisture absorption of the fiber, while the flexible segments of the copolyamide improve the toughness of the bonding phase. The two work together to make the intermediate layer form a strong and fluffy network after heat setting, effectively maintaining the static air content, thereby optimizing the thermal insulation efficiency and resilience performance.

[0015] Optionally, the mass ratio of copolyamide to polyethylene terephthalate is (2:8)-(3:7).

[0016] By adopting the above technical solution, sufficient but not excessive bonding points are formed within this range, which helps to reduce pore collapse caused by excessive melting. Polyethylene terephthalate can maintain the stiffness and elastic recovery of the fiber network, enabling the intermediate layer to obtain high porosity and high strength bonding. During long-term use, it maintains a low thermal conductivity and good compression resilience, which is conducive to the stability of thermal insulation performance and the maintenance of comfort.

[0017] Optionally, the PI fiber used in the inner layer has a fineness of 1.0-1.5D, and the PI fiber used in the outer layer has a fineness of 3.0-5.0D.

[0018] By adopting the above technical solution, the inner layer uses finer PI fibers, which can increase the number of fibers and specific surface area per unit volume, forming a finer fiber web, improving the amount of still air retention and the softness to the touch, while enhancing breathability. The outer layer uses coarser PI fibers, whose higher bending stiffness enhances the outer layer's resistance to deformation and abrasion. At the same time, the pores formed by the coarse fibers help moisture to escape. The gradual change in fineness from the inside to the outside improves the comfort, heat retention and durability of the insulation cotton.

[0019] The second objective of this invention is achieved through the following technical solution: The preparation method of the above-mentioned high-polymer PI fiber thermal insulation cotton includes the following steps: The fiber raw materials of the inner layer, middle layer and outer layer are mixed, opened and combed into a web to obtain the inner layer fiber web, the middle layer fiber web and the outer layer fiber web. They are laid up in the order of outer layer fiber web-middle layer fiber web-outer layer fiber web and hot rolled to obtain thermal insulation cotton.

[0020] By employing the above technical solution, the open mixing process ensures uniform dispersion of fiber components in each layer, preventing aggregation; the carding process forms a randomly oriented fiber network, constructing a porous basic structure. Following a symmetrical stacking sequence of outer layer-middle layer-inner layer-middle layer-outer layer, the functional gradient and stress distribution between layers are optimized. During hot rolling, heat activates the sheath melting of the outer layer low-melting-point fibers and the middle layer core-sheath composite fibers. The melt flows and penetrates to the intersections of adjacent fibers, forming bonding nodes upon cooling, integrating the three-layer fiber network into one. This thermal bonding mechanism fixes the fiber structure without excessive compression, ensuring the overall bulkiness and pore continuity of the insulation cotton. This macroscopically achieves a synergistic effect of high insulation performance, washability, and breathable resilience, while the manufacturing process ensures the uniformity and stability of the product structure.

[0021] In summary, this application has at least the following beneficial effects: (1) The inner layer focuses on skin-friendly comfort and uses soft fibers to provide a good touch; the middle layer is mainly composed of polyimide fibers, which store still air through its porous structure to achieve efficient heat preservation. At the same time, the core-skin composite fibers are melted and bonded by heat to fix the fiber network and enhance structural stability. (2) The outer layer is composed of polyimide fiber, aramid fiber and low melting point fiber, which combines heat insulation, mechanical strength and structural integration. Aramid provides high strength and heat resistance, and low melting point fiber melt bonding improves the overall water washability. (3) The fibers of each layer are bonded together by low melting point components to form a continuous interface, ensuring the structural integrity of the multilayer composite and helping to improve the long-term heat preservation efficiency, water resistance stability and breathable and resilient comfort of the insulation cotton. Detailed Implementation

[0022] raw material PI fiber, model SOT, specifications 1D×38mm, 1.2D×38mm, 1.5D×38mm, 3.0D×38mm, 4.0D×38mm, 5.0D×38mm, all purchased from Jiangsu Xiannuo New Material Technology Co., Ltd. Polyvinyl alcohol fiber, 38μm in diameter, 12mm in length, density 1.28g / cm³ 3 Purchased from Beijing Zhongfangxianjian Technology Co., Ltd.; Aramid fiber, 1.5D fineness, 51mm length, purchased from Suzhou Hengsian Protective Technology Co., Ltd. ES fiber, 1.5D fineness, 38mm length, purchased from Hubei Botao Synthetic Fiber Co., Ltd. Polyethylene fiber, 1.6D fineness, 38mm length, purchased from Jiangsu Jingbang New Material Co., Ltd. Pyromellitic dianhydride (96wt% purity), 4,4'-diaminodiphenyl ether (98wt% purity), sodium dodecyl sulfate (99wt% purity), polyethylene glycol (average molecular weight 4000), dibutyltin dilaurate (95wt% purity), N,N-dimethylacetamide (99.8wt% purity), and polyethylene terephthalate were all purchased from Shanghai Maclean Biochemical Technology Co., Ltd. Copolyamide, model DS2406, purchased from Shenzhen Dongsheng Plastic Products Co., Ltd. Fatty alcohol polyoxyethylene ether, with an average molecular weight of 315, was purchased from Shanghai Maclean Biochemical Technology Co., Ltd. γ-aminopropyltriethoxysilane was purchased from Hangzhou Jessica Chemical Co., Ltd. Sodium bicarbonate, anhydrous ethanol, and toluene are all commercially available.

[0023] Preparation Example 1 A phenylacetylene-terminated hyperbranched polysiloxane, the preparation method of which is as follows: 20 kg of toluene and 5.82 kg of phenylethynyltrimethoxysilane were added to a reaction vessel and stirred at 60 rpm for 15 min. The temperature was raised to 80 °C, and 7.8 g of dibutyltin dilaurate catalyst was added. The mixture was stirred at 100 rpm for 10 min and kept at 80 °C. 1.24 kg of methyldimethoxysilane was continuously added at a rate of 0.5 mL / s while stirring at 80 rpm. After the addition was complete, the temperature was raised to 100 °C and refluxed at this temperature for 24 h. The temperature was then lowered to 40 °C, and 0.9 kg of deionized water was added while stirring at 80 rpm. After the addition was complete, the mixture was stirred at 80 rpm at 40 °C for 4 h. 25 g of sodium bicarbonate was added and stirred at 80 rpm for 1 h. The solvent was evaporated at a vacuum of -0.095 MPa and a temperature of 60 °C for 12 h to obtain phenylethynyl-terminated hyperbranched polysiloxane.

[0024] Preparation Example 2 A modified PI fiber, the preparation method of which is as follows: Under a nitrogen atmosphere, 2.0 kg of pyromellitic dianhydride and 2.2 kg of 4,4'-diaminodiphenyl ether were added to 20 kg of N,N-dimethylacetamide, and the mixture was stirred and polymerized at 200 rpm for 4 hours at 0-5°C to obtain a polyamic acid solution with a solid content of 15%. Then, 0.5 kg of phenylethynyl-terminated hyperbranched polysiloxane, 0.1 kg of fluorinated graphene oxide, 0.05 kg of fatty alcohol polyoxyethylene ether, and 0.2 kg of 4,4'-oxobisbenzenesulfonyl hydrazine were added to the polyamic acid solution, and the mixture was stirred at 300 rpm for 2 hours to obtain a modified polyamic acid spinning solution. The modified polyamic acid spinning solution was then dry-spun at a spinning speed of 100 rpm. The spinning speed was m / min, the pore size of the spinning plate was 0.01 mm, the spinning temperature was 80℃, and then the temperature was raised to 300℃ at 5℃ / min under nitrogen atmosphere for 1 hour for thermal imidization treatment to obtain modified PI fiber.

[0025] Preparation Example 3 A modified PI fiber, which differs from Preparation Example 2 in that: no phenylethynyl-terminated hyperbranched polysiloxane is added; the rest is the same as Preparation Example 2.

[0026] Preparation Example 4 A modified PI fiber, which differs from Preparation Example 2 in that sodium dodecyl sulfate is used in place of fatty alcohol polyoxyethylene ether by an equal mass; the rest is the same as Preparation Example 2.

[0027] Preparation Example 5 A modified PI fiber, which differs from Preparation Example 2 in that polyethylene glycol is used in place of 4,4'-oxobisbenzenesulfonyl hydrazine by mass; the rest is the same as Preparation Example 2.

[0028] Preparation Example 6 A core-sheath composite fiber, the preparation method of which is as follows: 22.5 kg of polyethylene terephthalate (PET) was added to a twin-screw extruder and extruded at 280°C to obtain PET melt. 7.5 kg of copolyamide was added to a twin-screw extruder and extruded at 205°C to obtain copolyamide melt. Both the PET melt and copolyamide melt were fed into a composite spinning assembly, using PET as the core layer and copolyamide as the skin layer. The core layer pump speed was 10 rpm, and the skin layer pump speed was 15 rpm. The spinneret has an rpm of 0.15 mm orifice diameter, an aspect ratio of 2:1, 200 orifices, and a chamber temperature of 270℃. The composite spinning process yields nascent fibers, which are then cooled to room temperature (25℃) by a ring blower at a temperature of 10℃, a speed of 0.5 m / s, and a cooling distance of 1.5 m. After bundling and oiling, fiber bundles are obtained. These bundles undergo two stages of traction: the first stage has a traction ratio of 1.2, and the second stage has a temperature of 80℃ and a traction ratio of 1.5. After heat setting at 130℃ for 30 seconds, the fibers are wound and cut to obtain core-sheath composite fibers at a winding speed of 2500 m / min and a cutting length of 38 mm.

[0029] Preparation Example 7 A core-sheath composite fiber, which differs from Preparation Example 6 in that: polypropylene is used in place of polyethylene terephthalate by an equal mass; the rest is the same as Preparation Example 6.

[0030] Preparation Example 8 A core-sheath composite fiber differs from Preparation Example 6 in that it uses polyethylene of equal mass instead of copolyamide; the rest is the same as Preparation Example 6.

[0031] Preparation Example 9 A core-sheath composite fiber differs from Preparation Example 6 in that: the amount of polyethylene terephthalate is 21 kg and the amount of polyethylene terephthalate is 9 kg; the rest is the same as Preparation Example 6.

[0032] Preparation Example 10 A core-sheath composite fiber differs from Preparation Example 6 in that: polyethylene terephthalate is 24 kg and copolyamide is 6 kg; the rest is the same as Preparation Example 6.

[0033] Preparation Example 11 A core-sheath composite fiber differs from Preparation Example 6 in that: polyethylene terephthalate is 20 kg and copolyamide is 10 kg; the rest is the same as Preparation Example 6.

[0034] Preparation Example 12 A core-sheath composite fiber differs from Preparation Example 6 in that: polyethylene terephthalate is 25 kg and copolyamide is 5 kg; the rest is the same as Preparation Example 6.

[0035] Example 1 A high-polymer PI fiber thermal insulation cotton is prepared by layering an inner layer, a middle layer and an outer layer. The inner layer is prepared by PI fiber and polyvinyl alcohol fiber, and the fineness of the PI fiber used in the inner layer is 1.2D. The middle layer is prepared by modified PI fiber and core-sheath composite fiber, and the fineness of the PI fiber in the middle layer is 2.0D. The modified PI fiber is derived from preparation example 2 and the core-sheath composite fiber is derived from preparation example 6. The outer layer is prepared by PI fiber, aramid fiber and ES fiber, and the fineness of the PI fiber used in the outer layer is 4.0D.

[0036] Its preparation method is as follows: 28 kg of 1.2D PI fiber and 72 kg of polyvinyl alcohol fiber were fed into an A035 type blending and opening machine for opening. The A035 type blending and opening machine had a corner nailing curtain speed of 60 m / min, a leveling roller speed of 220 rpm, a stripping roller speed of 400 rpm, and an opening roller speed of 600 rpm. After opening, the fibers were blended in a FA022 type multi-bin blending machine. The FA022 type multi-bin blending machine had 6 bins, a blending time of 8 minutes, and an output speed of 0.9 m / min. After blending, the fibers were carded into a web by a TC11 carding machine to obtain the inner layer. The TC11 carding machine had a feed plate-feed roller gap of 0.3 mm, a feed roller speed of 0.6 rpm, a fiber basis weight of 450 g / m, a cylinder speed of 380 rpm, and a licker-in roller speed of 850 rpm. The rotation speeds are as follows: rpm; licker-in roller-cylinder spacing is 0.18 mm; cylinder-doffer spacing is 0.12 mm; cylinder-flat plate spacing is 0.25 mm, 0.22 mm, 0.20 mm, 0.22 mm, and 0.25 mm; doffer speed is 25 rpm; stripping roller speed is 30 rpm; web exit speed is 15 m / min; and fiber web density is 70 ± 3 g / m². 2 ; 75 kg of 2.0D PI fiber and 25 kg of core-sheath composite fiber were fed into an A035 type blending and opening machine for opening. The A035 blending and opening machine had a corner nailing curtain speed of 70 m / min, a leveling roller speed of 240 rpm, a stripping roller speed of 420 rpm, and an opening roller speed of 650 rpm. After opening, the fibers were fed into an FA022 type multi-bin blending machine for blending. The blending time was 6 minutes, and the output speed was 1.0 m / min. After blending, the fibers were fed into a TC11 carding machine to form a web and obtain the intermediate layer. The TC11 carding machine had a feed plate-feed roller gap of 0.35 mm, a feed roller speed of 0.7 rpm, a fiber basis weight of 480 g / m, a cylinder speed of 400 rpm, and a licker-in roller speed of 900 rpm. The rotation speed is rpm, the gap between the licker-in roller and the cylinder is 0.2 mm, the gap between the cylinder and the doffer is 0.15 mm, the gap between the cylinder cover plate and the cylinder cover plate is 0.28 mm, 0.25 mm, 0.22 mm, 0.25 mm, and 0.28 mm, the doffer speed is 28 rpm, the stripping roller speed is 35 rpm, and the fiber web density is 75 ± 3 g / m². 2 ; 50 kg of 4.0D PI fiber, 32 kg of aramid fiber, and 18 kg of ES fiber are fed into an A035 type blending and opening machine for opening. The A035 type blending and opening machine has a pinning curtain speed of 65 m / min, a leveling roller speed of 200 rpm, a stripping roller speed of 380 rpm, and an opening roller speed of 580 rpm. After opening, the fibers are fed into a FA022 type multi-bin blending machine for blending. The FA022 type multi-bin blending machine has 6 bins, a blending time of 10 minutes, and an output speed of 0.8 m / min. After blending, the fibers are fed into a TC11 carding machine for carding to form a web to obtain the outer layer. The TC11 carding machine has a feed plate-feed roller spacing of 0.40 mm, a feed roller speed of 0.5 rpm, a fiber basis weight of 500 g / m, a cylinder speed of 350 rpm, and a licker-in roller speed of 800 rpm. The rotation speeds are as follows: rpm; licker-in roller-cylinder spacing is 0.22 mm; cylinder-doffer spacing is 0.18 mm; cylinder-flatbed spacing is 0.30 mm, 0.28 mm, 0.25 mm, 0.28 mm, and 0.30 mm; doffer speed is 22 rpm; stripping roller speed is 25 rpm; web exit speed is 12 m / min; and fiber web density is 80 ± 3 g / m². 2 ; The insulation cotton is laid out in the order of inner layer-middle layer-outer layer, and then hot-rolled at 150℃ using a two-roll hot rolling mill to obtain a thickness of 23.5mm and a total areal density of 225g / m³. 2 The roll speed is 5m / min and the rolling point width is 5mm.

[0037] Comparative Example 1 A type of high-polymer PI fiber thermal insulation cotton differs from Example 1 in that: the middle layer does not contain a core-sheath composite fiber; the rest is the same as Example 1.

[0038] Comparative Example 2 A high-polymer PI fiber thermal insulation cotton, which differs from Example 1 in that the modified PI fiber is derived from Preparation Example 3; the rest is the same as Example 1.

[0039] Example 2 A type of high-polymer PI fiber thermal insulation cotton differs from Example 1 in that it uses polyethylene fiber of equal mass instead of ES fiber; the rest is the same as Example 1.

[0040] Example 3 A type of high-polymer PI fiber thermal insulation cotton, which differs from Example 1 in that: the core-sheath composite fiber is derived from Preparation Example 7; the rest is the same as Example 1.

[0041] Example 4 A type of high-polymer PI fiber thermal insulation cotton, which differs from Example 1 in that: the core-sheath composite fiber is derived from Preparation Example 8; the rest is the same as Example 1.

[0042] Example 5 A type of high-polymer PI fiber thermal insulation cotton, which differs from Example 1 in that: the core-sheath composite fiber is derived from Preparation Example 9; the rest is the same as Example 1.

[0043] Example 6 A type of high-polymer PI fiber thermal insulation cotton, which differs from Example 1 in that: the core-sheath composite fiber is derived from Preparation Example 10; the rest is the same as Example 1.

[0044] Example 7 A type of high-polymer PI fiber thermal insulation cotton, which differs from Example 1 in that: the core-sheath composite fiber is derived from Preparation Example 11; the rest is the same as Example 1.

[0045] Example 8 A type of high-polymer PI fiber thermal insulation cotton, which differs from Example 1 in that: the core-sheath composite fiber is derived from Preparation Example 12; the rest is the same as Example 1.

[0046] Example 9 A type of high-molecular-weight PI fiber thermal insulation cotton, which differs from Example 1 in that the modified PI fiber is derived from Preparation Example 4; the rest is the same as Example 1.

[0047] Example 10 A type of high-polymer PI fiber thermal insulation cotton, which differs from Example 1 in that the modified PI fiber is derived from Preparation Example 5; the rest is the same as Example 1.

[0048] Example 11 A type of high-polymer PI fiber thermal insulation cotton differs from Example 1 in that: the fineness of the PI fiber used in the inner layer is 1.0D, the inner layer PI fiber is 25kg, and the polyvinyl alcohol fiber is 75kg; the middle layer modified PI fiber is 70kg, and the core-sheath composite fiber is 30kg; the fineness of the PI fiber used in the outer layer is 3.0D, the outer layer aramid fiber is 30kg, and the ES fiber is 20kg; the rest is the same as in Example 1.

[0049] Example 12 A type of high-polymer PI fiber thermal insulation cotton differs from Example 1 in that: the fineness of the PI fiber used in the inner layer is 1.5D, the inner layer PI fiber is 20kg and the polyvinyl alcohol fiber is 80kg; the middle layer modified PI fiber is 80kg and the core-sheath composite fiber is 20kg; the fineness of the PI fiber used in the outer layer is 5.0D, the outer layer aramid fiber is 35kg and the ES fiber is 15kg; the rest is the same as in Example 1.

[0050] The performance of Examples 1-12 and Comparative Examples 1-2 was tested as follows: 1. Thermal insulation The thermal insulation performance was tested according to GB / T 35762-2017 "Test Method for Heat Transfer Properties of Textiles - Plate Method". The sample size was 30mm×30mm. The test results are shown in Table 1. 2. Washability Referring to GB / T 8629-2017 "Test Procedures for Home Washing and Drying of Textiles", a mild procedure simulating home washing was adopted. The samples were placed in a neutral detergent solution (pH 7±0.2) and washed 20 times at 40°C. The sample size was 20cm×20cm. The samples were laid flat to dry. The mass loss rate and thickness retention rate were calculated. The test results are shown in Table 1. 3. Comfort The air permeability test was conducted in accordance with GB / T 5453-1997 "Textiles - Determination of air permeability of fabrics". The test sample was a circular sample with a radius of 2.5 cm. The test results are shown in Table 2. Referring to Appendix A of FZ / T64003-2021, the loft, compression ratio and recovery rate were tested. The higher the loft, the looser the structure. The higher the compression ratio and recovery rate, the better the elasticity and the more comfortable the product. The test results are shown in Table 2.

[0051] Table 1. Test results of thermal insulation and water resistance of Examples 1-12 and Comparative Examples 1-2

[0052] Table 2. Comfort test results of Examples 1-12 and Comparative Example 1

[0053] Based on Tables 1 and 2, the test results are analyzed as follows: Compared with Comparative Example 1, Example 1 exhibits superior insulation, washability, and comfort compared to Comparative Example 1. Compared to Comparative Example 1, Example 1 incorporates a core-sheath composite fiber. The sheath of the core-sheath composite fiber, after melting upon heating, can bond with surrounding fibers, forming a stable three-dimensional network structure. This effectively fixes the relative positions between fibers, reducing the thinning of the insulation layer due to fiber displacement, thereby maintaining high-efficiency insulation performance while enhancing the long-term stability of the material structure. Therefore, incorporating a core-sheath composite fiber helps improve the insulation, washability, and comfort of the insulation cotton.

[0054] Compared with Comparative Example 1 and Comparative Example 2, Example 1 exhibits superior insulation, washability, and comfort compared to Comparative Example 2. Compared to Comparative Example 2, the modified PI fiber in Example 1 incorporates phenylacetylene-terminated hyperbranched polysiloxane. Due to its highly branched three-dimensional structure and internal cavities, the phenylacetylene-terminated hyperbranched polysiloxane can physically entangle with the polyamic acid molecular chains, thus providing toughening. The terminal phenylacetylene groups undergo thermal cross-linking during thermal imidization, chemically anchoring the flexible siloxane segments to the polyimide backbone, thereby enhancing the fiber's flexibility, fatigue resistance, and water resistance, and improving the soft touch and comfort of the final insulation material. Therefore, the addition of phenylacetylene-terminated hyperbranched polysiloxane to the modified PI fiber helps improve the insulation, washability, and comfort of the insulation material.

[0055] Comparing Examples 1 and 2, Example 1 demonstrates superior insulation, washability, and comfort compared to Example 2. Compared to Example 2, Example 1 uses ES fiber as a low-melting-point fiber. When heated, the outer layer of the ES fiber melts and forms bonding points at fiber intersections. After cooling, the fiber network is fixed, while the core layer maintains its fiber morphology and pore structure. This helps improve overall rigidity and enhances the bonding strength of the insulation cotton, making it less prone to deformation under repeated washing and mechanical action, thereby improving washability and insulation durability. Therefore, ES fiber, as a low-melting-point fiber, helps improve the insulation cotton's insulation, washability, and comfort.

[0056] Comparing Examples 1 and 3-4, Example 1 exhibits superior insulation, washability, and comfort compared to Examples 3-4. In Example 1, the sheath material of the core-sheath composite fiber is a copolyamide, and the core material is polyethylene terephthalate (PET). The intermediate layer uses a core-sheath composite fiber, where the copolyamide in the sheath melts and wets the PI fiber surface to form bonding bridges, while the PET in the core layer maintains its fiber shape due to its higher melting point and modulus, providing rigid support. The synergy of both contributes to forming a strong and fluffy network structure. Therefore, the use of copolyamide as the sheath material and PET as the core material in the core-sheath composite fiber helps improve the insulation, washability, and comfort of the insulation cotton.

[0057] Comparing Examples 1 and 5-8, Example 1 exhibits superior thermal insulation, washability, and comfort compared to Examples 5-8. Compared to Examples 5-8, Example 1 has a polyethylene terephthalate (PET) to copolyamide mass ratio of (2:8) to (3:7). Within this range, pore collapse due to excessive melting is reduced, while the PET material helps maintain the stiffness and elasticity of the fiber network, enabling the intermediate layer to achieve high porosity and high structural strength. This results in a low thermal conductivity and good compression resilience during long-term use, contributing to stable thermal insulation performance and maintaining comfort. Therefore, a PET to copolyamide mass ratio of (2:8) to (3:7) helps improve the thermal insulation, washability, and comfort of the insulation cotton.

[0058] Comparing Examples 1 and 9, Example 1 exhibits superior thermal insulation, washability, and comfort compared to Example 9. Compared to Example 9, the surfactant used in the modified PI fiber of Example 1 is fatty alcohol polyoxyethylene ether. The hydrophilic and lipophilic segments in the fatty alcohol polyoxyethylene ether molecule effectively reduce the surface tension of the spinning solution, promote the uniform dispersion of hydrophobic fluorinated graphene oxide and hyperbranched polysiloxane in the polyamic acid solution, reduce the aggregation of nano-components, and contribute to the formation of a uniform microporous structure and stable interfacial bonding, thereby improving the thermal insulation and washability of the modified PI fiber. Therefore, the use of fatty alcohol polyoxyethylene ether as a surfactant in the modified PI fiber helps improve the thermal insulation, washability, and comfort of the insulation cotton.

[0059] Comparing Example 1 and Example 10, Example 1 exhibits superior thermal insulation, washability, and comfort compared to Example 10. Compared to Example 10, Example 1 uses 4,4'-oxobisbenzenesulfonyl hydrazine as a pore-forming agent in its modified PI fiber. 4,4'-oxobisbenzenesulfonyl hydrazine releases gas upon thermal decomposition, forming a uniform microporous structure within the fiber. This increases the static air content within the fiber, effectively hindering heat conduction and thus improving thermal insulation performance. It also helps improve the material's lightness and compression resilience, enhancing the overall comfort of the insulation material. Therefore, using 4,4'-oxobisbenzenesulfonyl hydrazine as a pore-forming agent in the modified PI fiber helps improve the thermal insulation, washability, and comfort of the insulation material.

[0060] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of protection claimed in this application.

Claims

1. A high-polymer PI fiber thermal insulation cotton, characterized in that, Includes inner layer, middle layer and outer layer, The inner layer comprises PI fibers and polyvinyl alcohol fibers, wherein the mass ratio of PI fibers to polyvinyl alcohol fibers is (25:75)-(20:80). The intermediate layer comprises PI fibers and core-sheath composite fibers, wherein the mass ratio of the PI fibers to the core-sheath composite fibers is (70:30)-(80:20). The outer layer comprises PI fiber, aramid fiber and low melting point fiber, wherein the mass ratio of PI fiber, aramid fiber and low melting point fiber is 50:(30-35):(15-20); The intermediate layer PI fiber is a modified PI fiber. The preparation of the modified PI fiber includes the following steps: under a nitrogen protective atmosphere, pyromellitic dianhydride and 4,4'-diaminodiphenyl ether are polymerized in N,N-dimethylacetamide to obtain a polyamic acid solution; phenylacetylene-terminated hyperbranched polysiloxane, fluorinated graphene oxide, surfactant, and pore-forming agent are added to the polyamic acid solution, and the reaction is carried out to obtain a modified polyamic acid spinning solution; the modified polyamic acid spinning solution is subjected to dry spinning and thermoforming treatment to obtain modified PI fiber.

2. The high-polymer PI fiber thermal insulation cotton according to claim 1, characterized in that, The surfactant is a fatty alcohol polyoxyethylene ether.

3. The high-polymer PI fiber thermal insulation cotton according to claim 1, characterized in that, The pore-forming agent is 4,4'-oxobis(benzenesulfonylhydrazine).

4. The high-polymer PI fiber thermal insulation cotton according to claim 1, characterized in that, The low-melting-point fiber is ES fiber.

5. The high-polymer PI fiber thermal insulation cotton according to claim 1, characterized in that, The core layer of the core-sheath composite fiber is polyethylene terephthalate, and the sheath layer is copolyamide.

6. The high-polymer PI fiber thermal insulation cotton according to claim 5, characterized in that, The mass ratio of the copolyamide to polyethylene terephthalate is (2:8)-(3:7).

7. The high-polymer PI fiber thermal insulation cotton according to claim 1, characterized in that, The inner layer uses PI fibers with a fineness of 1.0-1.5D, and the outer layer uses PI fibers with a fineness of 3.0-5.0D.

8. A method for preparing the high-polymer PI fiber thermal insulation cotton according to any one of claims 1-7, characterized in that, Includes the following steps: The fiber raw materials of the inner layer, middle layer and outer layer are opened, mixed and combed into a web to obtain the inner layer, middle layer and outer layer. They are then laid in the order of inner layer-middle layer-outer layer and hot-rolled to obtain thermal insulation cotton.

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