High-strength aramid fiber textile and method of making same

Abstract

The application discloses a high-strength aramid fiber textile and a preparation method thereof, and relates to the technical field of high-performance fiber materials.The first section, the second section and the third section of the coagulation bath are arranged in a temperature and ion liquid concentration decreasing order along the direction of the spinning fine stream, so that the diffusion rate of the surface layer and the core layer of the spinning fine stream is synchronized, the skin-core heterogeneous structure of the aramid fiber is eliminated, and the homogenized aramid fiber is obtained.The fiber is used as the warp yarn and the weft yarn for three-dimensional orthogonal weaving, and the blended yarn with the homogenized aramid fiber as the core layer and the polytetrafluoroethylene film with micropores as the skin layer is introduced as the penetrating yarn in the thickness direction of the fabric, the micropores of the skin layer and the yarn gap form the capillary sweat-removal channel.Under the premise of maintaining the anti-puncture, anti-cutting and anti-tearing protection performance of the fabric, the fiber interface shear strength and the single-filament tearing strength are improved, and the air-permeability and sweat-removal performance of the fabric are improved, and the application can be used in the field of high-strength textiles such as individual protection equipment.

Description

Technical Field

[0001] This invention relates to the field of high-performance fiber materials technology, specifically to a high-strength aramid fiber textile and its preparation method. Background Technology

[0002] Aramid fibers possess ultra-high strength, high modulus, and high temperature resistance, and are widely used in protective equipment, bulletproof armor, and high-end industrial textiles.

[0003] The industry generally uses wet or dry-jet wet spinning processes to prepare aramid fibers. The aramid polymer is dissolved in a strong acid or a specific solvent to form a spinning solution. After being extruded through a spinneret, it enters a coagulation bath and solidifies into fibers by relying on the bidirectional diffusion of the solvent and coagulant.

[0004] Existing coagulation baths typically employ a single-phase constant concentration and constant temperature system. The surface layer of the spinning fine stream is in direct contact with the coagulant, and its diffusion rate is significantly higher than that of the core layer. This results in the surface layer of the fiber cross-section solidifying before the core, forming a skin-core heterogeneous structure with significant differences in orientation and crystallinity between the skin and the core layer.

[0005] When the fiber is subjected to transverse shear or tearing loads, this structure is prone to stress concentration at the core-sheath interface and sheath peeling, which limits the further improvement of fiber interface shear strength and monofilament tear strength.

[0006] In addition, protective textiles usually need to increase the warp and weft density to meet the requirements of puncture resistance, cut resistance, and tear resistance, but this will compress the gap between the warp and weft yarns, resulting in a significant decrease in the breathability and moisture permeability of the fabric.

[0007] Existing technologies do not introduce yarn structures with independent flow-guiding functions in the fabric thickness direction, making it difficult to balance high-strength protective performance with breathable and sweat-wicking comfort. There is an urgent need for a technical solution that can simultaneously improve the mechanical properties of the fiber itself and the breathability of the fabric. Summary of the Invention

[0008] The technical problem to be solved by the present invention is that in the existing wet or dry-jet wet spinning process of aramid fiber, the coagulation bath is a single-phase constant concentration and constant temperature system. The diffusion rate of the surface layer and the core layer of the spinning fine stream is inconsistent, forming a skin-core heterogeneous structure. This makes the skin layer easy to peel off when the fiber is subjected to transverse shear or tearing load, which limits the improvement of fiber interface shear strength and monofilament tear strength.

[0009] At the same time, while existing high-density woven aramid textiles meet the requirements for protective performance such as puncture resistance, cut resistance, and tear resistance, they are difficult to balance with breathability and sweat-wicking comfort.

[0010] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0011] On the one hand, a method for preparing aramid fibers is provided, including the preparation of an aramid polymer spinning solution and a coagulant composed of an ionic liquid and water;

[0012] The spinning solution is extruded through a spinneret to form a fine spinning stream;

[0013] The spinning stream is sequentially passed through a first coagulation bath, a second coagulation bath, and a third coagulation bath arranged along its direction of travel. The temperature and ionic liquid concentration of the first coagulation bath are higher than those of the second coagulation bath, and the temperature and ionic liquid concentration of the second coagulation bath are higher than those of the third coagulation bath. This ensures that the diffusion rate of the coagulant on the surface of the spinning stream is synchronized with that of the coagulant in the core layer, resulting in a homogeneous aramid fiber initial product with essentially the same solidification front for the skin and core layers.

[0014] The homogenized aramid fiber precursor is then subjected to washing, stretching and orientation, and drying and shaping to obtain the homogenized aramid fiber finished product. Based on this, the actual temperature and ionic liquid concentration of each coagulation bath section are collected in real time to calculate the ratio of the surface diffusion coefficient to the core diffusion coefficient, thus obtaining the diffusion rate matching coefficient. This matching coefficient is compared with a preset threshold range to obtain the deviation. The control quantity is calculated according to the proportional-integral-derivative control law, and the output power of the heating device and the replenishment rate of the replenishment pump in the corresponding coagulation bath section are adjusted accordingly to form a closed-loop regulation, ensuring that the diffusion rate matching coefficient continuously falls within the preset threshold range.

[0015] On the other hand, a high-strength aramid fiber textile is provided, comprising warp yarns arranged along the X direction, weft yarns arranged along the Y direction, and through yarns arranged along the Z direction. The warp yarns and the weft yarns are three-dimensionally orthogonally woven according to a preset warp and weft density to form the main skeleton of the fabric. The warp yarns and the weft yarns are all homogenized aramid fibers as described above.

[0016] The through yarn is a core-sheath type blended yarn with homogenized aramid fiber as the core layer and a sheath layer made of polytetrafluoroethylene film with microporous structure as the outer layer. The through yarn continuously interweaves and connects the interlacing points of adjacent yarn layers along the thickness direction of the fabric. The microporous structure of the sheath layer of the through yarn and the gaps between the yarns together form a capillary perspiration channel that runs through the inner and outer surfaces of the textile.

[0017] On the other hand, a method for preparing the above-mentioned high-strength aramid fiber textile is provided, which includes preparing homogenized aramid fiber using the above-mentioned aramid fiber preparation method, using the homogenized aramid fiber as X-direction warp and Y-direction weft respectively, preparing a core-sheath type blended yarn with the homogenized aramid fiber as the core layer and a sheath layer made of polytetrafluoroethylene film with microporous structure as the outer layer as the Z-direction through yarn, and then performing three-dimensional orthogonal weaving of the warp, weft and through yarn according to a preset warp and weft density and a preset spacing to obtain high-strength aramid fiber textile.

[0018] Compared with the prior art, the beneficial effects of the present invention by adopting the above technical solution are as follows:

[0019] 1. This invention actively constructs a temperature gradient and an ionic liquid concentration gradient that decrease sequentially along the direction of the spinning stream in the coagulation bath, and combines this with a dual diffusion rate matching closed-loop control to keep the diffusion rates of the surface layer and the core layer of the spinning stream synchronized. This eliminates the intrinsic skin-core heterostructure of aramid fibers, making the fibers less prone to skin peeling due to interface defects when subjected to transverse shear or tearing loads, thereby improving the interfacial shear strength and monofilament tear strength of the fiber body.

[0020] 2. In terms of fabric structure, the high-density homogenized aramid filament braided skeleton in the X and Y directions ensures the fabric's puncture, cut, and tear resistance. The microporous structure of the sheath-core type blended through yarn in the Z direction, together with the gaps between the yarns, forms a capillary perspiration channel. Without reducing the overall coverage density and protective performance of the fabric, it provides a pathway for water vapor molecules to conduct from the inner surface of the fabric to the outer surface, thereby improving the fabric's breathability, moisture permeability, and perspiration wicking performance, achieving a balance between high protective strength and wearing comfort. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the overall preparation process of high-strength aramid textiles in an embodiment of the present invention.

[0022] Figure 2 This is a flowchart of the closed-loop regulation and control of the three-stage coagulation bath in an embodiment of the present invention. Detailed Implementation

[0023] The following is in conjunction with the appendix Figure 1-2 The specific embodiments of the present invention will be further described below. It should be noted that the description of these embodiments is for the purpose of helping to understand the present invention, but does not constitute a limitation of the present invention.

[0024] The technical solution of the present invention will be further described below with reference to specific embodiments. Those skilled in the art should understand that the following embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0025] I. Specific Implementation Methods of Homogenized Gradient Coagulation Spinning Process

[0026] In this embodiment, the preparation method of aramid fiber is based on the existing wet spinning production line, and the coagulation bath is modified by segmented temperature control and dynamic concentration regulation, specifically including the following:

[0027] First, prepare the aramid polymer spinning solution by dissolving the aramid polymer in concentrated sulfuric acid to form a uniform spinning solution.

[0028] Simultaneously, a coagulant composed of ionic liquid and water at a preset concentration is prepared to form a composite coagulant system with a gradient distribution along the length of the coagulant bath.

[0029] Next, the spinning solution is extruded through a spinneret to form a spinning stream. The spinning stream then passes sequentially through a first coagulation bath, a second coagulation bath, and a third coagulation bath set along its direction of travel. The temperature and ionic liquid concentration of the first coagulation bath are higher than those of the second coagulation bath, and the temperature and ionic liquid concentration of the second coagulation bath are higher than those of the third coagulation bath. By setting a higher temperature and a higher ionic liquid concentration in the first coagulation bath, the diffusion and penetration rate of the coagulant on the surface of the spinning stream is slowed down, so that the surface diffusion rate is closer to the core diffusion rate.

[0030] The temperature and ionic liquid concentration of the second coagulation bath are between those of the first and third stages, serving as a transitional adjustment.

[0031] The third coagulation bath, by setting a relatively low temperature and a low concentration of ionic liquid, ensures that the core layer can be fully solidified. After the three-stage gradient coagulation bath treatment, the solidification front of the spinning flow surface layer and the core layer are basically consistent, resulting in a homogeneous aramid fiber primary product with uniform morphology of the skin and core layers.

[0032] The three-section coagulation bath is separated by partitions along the fiber travel direction. Each section is equipped with an independent heating and cooling jacket, a temperature sensor, and a conductivity-type ionic liquid concentration sensor, as well as a micro-liquid replenishment pump interface. The fiber bundle passes through the three sections of the bath in a horizontal direction. The sensors in each section collect the actual temperature and actual ionic liquid concentration data of the current section in real time and transmit the data to the gradient closed-loop controller.

[0033] To achieve precise matching of diffusion rates between the surface and core layers, this embodiment also provides a dual diffusion rate matching closed-loop control method, the specific implementation process of which is as follows.

[0034] First, a dynamic calculation model for the surface diffusion coefficient and core diffusion coefficient of the spinning fine stream is established. This model is based on Fick's second diffusion law:

[0035] ;

[0036] In the formula, This indicates the concentration of the coagulant at the radial position of the spinning stream;

[0037] Indicates time;

[0038] This represents the diffusion coefficient, with a value of [value missing] for the surface layer of the spinning fine stream. The core layer value is ;

[0039] This indicates the radial position coordinates of the spinning stream.

[0040] Secondly, based on the above model and combined with the actual temperature and actual ionic liquid concentration data of each coagulation bath section, the ratio of the surface diffusion coefficient to the core diffusion coefficient is calculated to obtain the diffusion rate matching coefficient. :

[0041] ;

[0042] In the formula, The matching coefficient represents the diffusion rate between the surface layer and the core layer. , The meaning is the same as before, when When the value falls within a preset threshold range, it is determined that the diffusion rates of the surface layer and the core layer are in a synchronous matching state. In this embodiment, the preset threshold range is 1.0 to 1.2.

[0043] Secondly, the closed-loop controller will use the matching coefficients calculated in real time. The deviation is obtained by comparing it with a preset threshold range. And calculate the control output according to the proportional-integral-derivative control law:

[0044] ;

[0045] In the formula, Indicates the controller at time. The output control quantity is used to adjust the power of the heating device in the corresponding coagulation bath section or the replenishment rate of the replenishment pump;

[0046] Indicates time The deviation of the matching coefficient;

[0047] , , These represent the proportional coefficient, integral coefficient, and differential coefficient, respectively.

[0048] Represents the integral variable;

[0049] This represents the rate of change of the deviation.

[0050] The controller is based on the calculated control quantity By adjusting the output power of the heating and cooling jacket of the corresponding coagulation bath section and the replenishment rate of the ionic liquid replenishment pump through the drive circuit, the actual temperature and actual concentration of the section converge to the target gradient value. The three coagulation baths are independently closed-loop regulated until the spinning fine stream passes through all three coagulation baths. At this time, the solidification front of the surface layer and the core layer advances basically synchronously, completing the skin-core homogenization solidification.

[0051] After being treated in a three-stage gradient coagulation bath, the fibers are sequentially fed into a washing unit to remove residual ionic liquids and impurities. They are then stretched and oriented in a multi-stage stretching unit and finally dried and shaped to obtain homogenized aramid fiber products. According to the test, the homogenized aramid fiber prepared in this embodiment has significantly reduced differences in the orientation and crystallinity between the skin and core layers in the cross-section. The interfacial shear strength and monofilament tear strength of the fiber are improved compared with the fiber prepared by a single-phase constant concentration and constant temperature coagulation bath.

[0052] II. Specific Implementation Methods of Bionic Micro-flow Three-dimensional Orthogonal Hybrid Fabric Structure

[0053] After obtaining homogenized aramid fibers, this embodiment further constructs high-strength aramid fiber textiles based on these fibers.

[0054] Both the X-direction warp and Y-direction weft yarns are homogenized aramid filaments produced by the above process. They are then woven in three dimensions orthogonally according to the preset warp and weft density to form a dense three-dimensional orthogonal skeleton, ensuring that the fabric as a whole has the puncture resistance, cut resistance, and tear resistance properties that meet the protection level requirements.

[0055] In the selection of the Z-direction through yarn, a core-sheath type blended yarn is adopted, which has a homogenized aramid filament as the core layer and a sheath layer made of porous polytetrafluoroethylene film with microporous structure as the outer layer. The core layer provides the main mechanical strength of the through yarn, and the sheath layer has multiple micropores distributed on it. In this embodiment, the pore size of the micropores is 0.1 micrometers to 5 micrometers and the porosity is 30% to 70%. The through yarn continuously interweaves the interlacing points of adjacent yarn layers along the fabric thickness direction at a preset interval. Under the premise of maintaining the overall density and structural integrity of the fabric, the microporous structure of the sheath layer and the yarn gaps together form a capillary perspiration channel network that runs through the inner and outer surfaces of the fabric.

[0056] The moisture-conducting driving force of this capillary channel can be described by the following capillary pressure formula:

[0057] ;

[0058] In the formula, This indicates the capillary pressure difference between the inside and outside of the microporous channel, which drives water vapor molecules to be conducted from the inner surface of the fabric to the outer surface along the microchannel;

[0059] This indicates the surface tension of water on the microporous surface of polytetrafluoroethylene;

[0060] This indicates the contact angle between water and the microporous walls of polytetrafluoroethylene (PTFE).

[0061] The equivalent radius of the micropores in the polytetrafluoroethylene (PTFE) skin is represented by... The value of is controlled within the aforementioned aperture range, which allows Maintaining a value range that is conducive to the conduction of moisture from the inner surface to the outer surface, thereby achieving the breathability and perspiration-wicking properties of the fabric without reducing the overall coverage density and the resistance to puncture, cut, and tear.

[0062] III. Overall Preparation Method of High-Strength Aramid Fiber Textiles

[0063] The method for preparing high-strength aramid fiber textiles provided in this embodiment includes: obtaining homogenized aramid fibers using the aforementioned homogenized gradient coagulation spinning process;

[0064] The homogenized aramid fiber was used as the X-direction warp and Y-direction weft, respectively.

[0065] Prepare a core-sheath type blended yarn with homogenized aramid fiber as the core layer and a sheath layer made of polytetrafluoroethylene film with microporous structure as the outer layer, as a Z-direction through yarn;

[0066] The warp yarns, weft yarns, and through yarns are woven in three dimensions orthogonally according to a preset warp and weft density and a preset spacing. The through yarns continuously interweave and connect the interlacing points of adjacent yarn layers along the fabric thickness direction, so that the microporous structure of the skin layer and the gaps between the yarns together form a capillary sweat-wicking channel that runs through the inner and outer surfaces of the fabric, ultimately resulting in a high-strength aramid fiber textile.

[0067] Testing showed that the high-strength aramid fiber textiles produced using the method of this embodiment, while maintaining the original levels of puncture resistance, cut resistance, and tear resistance, exhibited significantly improved breathability and moisture-wicking properties compared to textiles made using a single homogeneous aramid filament in a two-dimensional high-density weave without introducing a guiding yarn structure in the thickness direction.

[0068] It should be noted that in other embodiments, the coagulant may not be an ionic liquid, but instead a sulfuric acid aqueous solution of different concentrations combined with segmented temperature control to achieve a similar effect of simultaneous dual diffusion rates.

[0069] The Z-direction through yarn can also be replaced with hollow tubular polytetrafluoroethylene fiber bundles arranged at preset intervals to form a flow channel area in a local area in the fabric thickness direction. The above alternatives can all achieve the technical effects of the present invention to eliminate the heterogeneous structure of the skin and core and to balance the protective strength and breathability and sweat-wicking performance to varying degrees, and all fall within the protection scope of the present invention.

[0070] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications without departing from the spirit and scope of the present invention. Therefore, any modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for preparing aramid fiber, characterized in that, Includes the following steps: Prepare a spinning solution for aramid polymers and a coagulant composed of an ionic liquid and water. The spinning solution is extruded through a spinneret to form a fine spinning stream; The spinning stream is sequentially passed through a first coagulation bath, a second coagulation bath, and a third coagulation bath arranged along its direction of travel. The temperature and ionic liquid concentration of the first coagulation bath are higher than those of the second coagulation bath, and the temperature and ionic liquid concentration of the second coagulation bath are higher than those of the third coagulation bath. This ensures that the diffusion rate of the coagulant on the surface of the spinning stream is synchronized with the diffusion rate of the coagulant in the core layer, resulting in a homogeneous aramid fiber initial product with consistent solidification fronts of the skin and core layers. The homogenized aramid fiber precursor is sequentially washed, stretched and oriented, and dried and shaped to obtain the homogenized aramid fiber finished product.

2. The preparation method according to claim 1, characterized in that, It also includes the step of performing closed-loop regulation on the first coagulation bath, the second coagulation bath, and the third coagulation bath respectively: Real-time acquisition of the actual temperature and actual ionic liquid concentration of the current coagulation bath section; Based on the actual temperature and the actual ionic liquid concentration, the ratio of the surface diffusion coefficient to the core diffusion coefficient of the spinning microfluid is calculated to obtain the diffusion rate matching coefficient. The diffusion rate matching coefficient is compared with a preset threshold range to obtain the deviation. Based on the aforementioned deviation, the control quantity is calculated according to the proportional-integral-derivative control law; Based on the control quantity, adjust the output power of the heating device and the replenishment rate of the replenishment pump in the corresponding coagulation bath section so that the diffusion rate matching coefficient falls within the preset threshold range.

3. The preparation method according to claim 2, characterized in that, The preset threshold range is 1.0 to 1.

2.

4. A high-strength aramid fiber textile, comprising warp yarns arranged along the X-direction, weft yarns arranged along the Y-direction, and through yarns passing through along the Z-direction, wherein the warp yarns and the weft yarns are three-dimensionally orthogonally woven at a preset warp and weft density to form the main skeleton of the fabric, characterized in that, Both the warp and weft yarns are homogenized aramid fibers prepared by the preparation method described in claim 1; The through yarn is a core-sheath type blended yarn, which has homogenized aramid fiber as the core layer and a polytetrafluoroethylene film with microporous structure as the outer layer. The through yarn continuously interweaves and connects the interlacing points of adjacent yarn layers along the thickness direction of the fabric. The microporous structure of the through yarn's outer layer and the gaps between the yarns together form a capillary perspiration channel that runs through the inner and outer surfaces of the textile.

5. The high-strength aramid fiber textile according to claim 4, characterized in that, The micropores on the polytetrafluoroethylene film have a pore size of 0.1 micrometers to 5 micrometers and a porosity of 30% to 70%.

6. The high-strength aramid fiber textile according to claim 4, characterized in that, The through yarns are evenly distributed at preset intervals along the thickness direction of the fabric.

7. A method for preparing a high-strength aramid fiber textile, characterized in that, Includes the following steps: Homogenized aramid fibers were prepared using the preparation method described in claim 1. The homogenized aramid fibers are used as X-direction warp yarns and Y-direction weft yarns, respectively. A core-sheath type blended yarn is prepared as a Z-direction through yarn. The core-sheath type blended yarn has homogenized aramid fiber as the core layer and a polytetrafluoroethylene film with microporous structure as the outer layer. The X-direction warp yarn, the Y-direction weft yarn, and the Z-direction through yarn are orthogonally woven in three dimensions according to a preset warp and weft density and a preset spacing to obtain a high-strength aramid fiber textile.

8. The preparation method according to claim 7, characterized in that, The Z-direction through yarn continuously interweaves and connects the interlacing points of adjacent yarn layers along the fabric thickness direction, so that the microporous structure of the skin layer and the gaps between the yarns together form a capillary perspiration channel that runs through the inner and outer surfaces of the fabric.

Images