Fire-fighting and outdoor protection knitted fabric capable of being added with shape memory material and knitting process thereof

Abstract

The invention relates to a knitted fabric for fire protection and outdoor protection and a knitting process thereof, and belongs to the technical field of textiles. The knitted fabric sequentially comprises an inner layer, a first connecting layer, a second connecting layer and an outer layer from inside to outside. The inner layer and the outer layer are respectively and independently in weft plain stitch or single-face jacquard weave, the connecting layers are all in double rib stitch, the other connecting layer is connected with the inner layer or the outer layer through coils of the connecting layers, and the inner layer and the outer layer are connected through tuck stitch. The knitted fabric is excellent in structural elasticity; the connecting layer adopts interlaced double rib stitches, so that the thickness of the fabric is increased, a static air layer is provided while the light weight of the fabric is ensured, and the warm keeping effect and the heat insulation effect of the fabric are improved; a shape memory material is fed into the connecting layer, so that the interval between the inner layer and the outer layer can be enlarged, and the content of still air is further increased.

Description

Technical Field

[0001] The present invention relates to a shape memory aramid knitted fabric for fire protection and outdoor protection and its knitting process, belonging to the technical field of textiles. Background Art

[0002] With the improvement of people's living standards, the requirements for clothing are also getting higher and higher. Knitted products are favored because of their excellent elasticity, hand feeling and wearing comfort, and more and more fields begin to use knitted fabrics. For many years, fire safety has always been a major issue attracting attention. During the process of fire fighting and rescue, firefighters often face different types of dangerous heat exposure environments such as low heat radiation and hot surface contact. As a safety barrier for firefighters in fire rescue tasks, the heat protection performance of fire suits is crucial for ensuring the life safety of firefighters. Generally, it is considered that increasing the thickness of the fabric combination of fire suits is an effective method to improve their heat protection performance. However, this will also increase the movement load of the wearer. The fire suits put into use on the market include a flame-retardant outer layer, a waterproof and breathable layer, a heat-insulating layer and a comfort layer. In the face of severe fire, the heat insulation effect is difficult to ensure the life safety of firefighters. At present, the requirements for fire suits are comfortable wearing, lightweight clothing and strong heat insulation performance, and improve their heat protection performance without increasing the human load.

[0003] Keeping warm is a key factor in maintaining health in cold environments. Lightweight cold-proof clothing can provide effective warmth protection for mountaineers, scientific research personnel, polar explorers, etc. working in extremely cold environments, and can also significantly improve people's living comfort in cold seasons, without feeling inconvenient due to the restraint of heavy clothes.

[0004] The thermal conductivity of air is very low, and it is a poor conductor of heat. When air is in a static state, the molecules inside it hardly produce large-scale directional movement, and thus no heat convection phenomenon will be caused, which is conducive to reducing heat loss. In the field of textiles, static air can build a lightweight heat insulation barrier. In the design of some high-end outdoor clothing and warm home textile products, a static air layer can be added between the fiber structures of textiles or between different fabric layers to improve the heat preservation and insulation performance of textiles. Setting an air layer in fire suits or cold-proof clothing can reduce the transfer of external heat to the human body or reduce the loss of human heat to the outside without increasing the weight of the clothing. Summary of the Invention

[0005]

Technical Problem

[0006] Ordinary fire suits have insufficient heat insulation effect and comfort. Knitted fabrics are soft and elastic, which endows them with excellent wearing comfort. It is necessary to develop a lightweight knitted fabric with heat insulation and heat preservation performance for use as fire suits and cold-proof clothing to improve their wearing comfort.

[0007]

Technical Solution

[0008] In view of the above problems, the present invention uses a rib stitch as the connecting layer to prepare a four-layer knitted fabric, endowing the knitted fabric with a still air layer and improving its heat insulation and warmth retention effects. Shape memory alloy (SMA) is a new type of material that generates displacement and force through the phase change of the internal crystal structure. For temperature-induced memory alloys, their shape memory effect can be triggered only by controlling the temperature to the phase change temperature. By adding a temperature-responsive shape memory material SMA to the connecting layer, the SMA in the clothing is activated at low temperatures, the air gap between adjacent layers of the clothing increases, and the content of still air increases, thereby improving the heat insulation performance of the cold-proof clothing.

[0009] The first object of the present invention is to provide a four-layer knitted fabric, which from the inside to the outside is successively: an inner layer, a first connecting layer, a second connecting layer and an outer layer;

[0010] The inner layer and the outer layer are respectively independently a plain weft knitted fabric or a single-sided jacquard fabric;

[0011] The connecting layers are all rib stitches;

[0012] The coils of the connecting layer connect another connecting layer and the inner layer or the outer layer; a tuck stitch is used to connect the inner layer and the outer layer.

[0013] When worn, the inner layer of the four-layer knitted fabric is closer to the skin, and the outer layer is relatively farther from the skin.

[0014] In an embodiment of the present invention, the rib stitch is an m×n rib stitch knitted with one stitch skipped; m is 1 to 10, and n is 1 to 10.

[0015] In an embodiment of the present invention, when the first connecting layer and the second connecting layer are knitted, shape memory material fibers are intermittently woven in; the length of each section of the rib stitch containing shape memory material fibers in the first connecting layer and the second connecting layer is 3 to 50 coils; the weftwise length of each section of the rib stitch without shape memory material fibers in the first connecting layer and the second connecting layer is 0.5 to 5 cm.

[0016] In an embodiment of the present invention, the shape memory material is selected from one or more of shape memory alloy, shape memory polyurethane, polynorbornene, styrene-butadiene copolymer; the diameter of the shape memory material is 0.1 to 5 mm.

[0017] The connecting layer of the fabricated fabric uses a rib stitch with one stitch skipped. The knitting method of one stitch skipped can enable the rib stitch to hold more still air, has strong warmth retention, and is beneficial to fire protection heat insulation or low-temperature warmth retention. By feeding a shape memory material into the connecting layer, the interval between the inner layer and the outer layer can be enlarged, and the content of still air can be increased.

[0018] In an embodiment of the present invention, the inner layer, the outer layer, the first connecting layer, and the second connecting layer are all made of flame-retardant fibers, and the tuck stitch is made of the same yarn as the outer layer, the inner layer, or the connecting layer. The fabric thus produced has good warmth retention and heat insulation effects and has flame-retardant properties.

[0019] In an embodiment of the present invention, the flame-retardant fiber is one or more of aramid fiber, flame-retardant viscose, polyphenylene sulfide fiber, and polyimide fiber.

[0020] In an embodiment of the present invention, the aramid fiber is selected from one or more of aramid 1313, aramid 1414, and meta-aramid.

[0021] In an embodiment of the present invention, 4-38s / 1 aramid 1313 is used for the outer layer, the first connecting layer, and the second connecting layer, 4-38s / 1 flame-retardant viscose and aramid 1313 are used for the inner layer, and shape memory material fibers are fed in every 0.5-5 cm in the first and second connecting layers. The inner layer is made of viscose, and the fabric thus produced is more comfortable while ensuring heat insulation and flame retardancy.

[0022] In an embodiment of the present invention, the inner layer is made of flame-retardant fibers, the outer layer is made of ultra-high molecular weight polyethylene fibers, the first and second connecting layers are independently made of one or more of aramid fibers, high-strength polyester filaments, and ultra-high molecular weight polyethylene fibers, and the tuck stitch is made of the same yarn as the outer layer, the inner layer, or the connecting layer. The fabric thus produced is lighter while ensuring protective performance, and is convenient to carry and wear.

[0023] In an embodiment of the present invention, the molecular weight of the ultra-high molecular weight polyethylene fiber is 2 million to 6 million.

[0024] In an embodiment of the present invention, the tensile strength of the high-strength polyester filament is higher than 5 cN / dtex.

[0025] In an embodiment of the present invention, 300-800D ultra-high molecular weight polyethylene fiber is used for the outer layer, 38-4s / 1 aramid 1414 and flame-retardant viscose are used for the inner layer, and 300-800D high-strength polyester filaments are used for the first and second connecting layers. The fabric thus produced is lightweight, comfortable, and has excellent protective performance.

[0026] In an embodiment of the present invention, the inner layer is made of one or more of wool fiber, hollow polyester fiber, and acrylic fiber, the first and second connecting layers are independently made of one or more of polyester fiber, aramid fiber, and nylon fiber, the outer layer is made of one or more of polyester fiber, aramid fiber, nylon fiber, and ultra-high molecular weight polyethylene fiber, and the tuck stitch is made of the same yarn as the outer layer, the inner layer, or the connecting layer. The fabric thus produced is stiff, beautiful, warm, and comfortable.

[0027] In an embodiment of the present invention, polyamide fiber with a denier of 30 - 150D is used for the outer layer, wool fiber with a denier of 2.5 - 30D is used for the inner layer, and PET fiber with a denier of 100 - 400D is used for the connecting layer. In the first and second connecting layers, a shape memory material is fed in every 0.5 - 5 cm. The fabricated fabric is warm, comfortable, has a certain ultraviolet resistance, and is suitable for outdoor wear.

[0028] The second object of the present invention is to provide a preparation method for the above four - layer - structure knitted fabric, which is knitted by a four - bed flat knitting machine and includes the following steps:

[0029] S1. The first yarn feeder feeds yarn to knit loops on the front lower needle bed, the second yarn feeder feeds yarn to knit loops on the rear lower needle bed, and the third yarn feeder feeds yarn to knit floats on the front lower needle bed; the floats are used to connect the inner and outer layers of the fabric.

[0030] S2. The fourth yarn feeder feeds yarn to knit loops on the front lower needle bed and the rear lower needle bed, knitting one stitch and skipping one stitch to form a double rib structure of m×n, and then the third yarn feeder feeds yarn to form floats on the rear lower needle bed; m is 1 - 10, and n is 1 - 10; at this time, there are knitted double rib structures on both the front lower needle bed and the rear lower needle bed.

[0031] S3. Use the purl action to turn the double rib structure on the rear lower needle bed to the front upper needle bed, and then the second yarn feeder feeds yarn to knit loops on the rear lower needle bed.

[0032] S4. Turn the double rib structure that is turned from the rear lower needle bed to the front upper needle bed in step S3 back to the rear lower needle bed, then turn the double rib structure on the front lower needle bed to the rear upper needle bed, and then the first yarn feeder feeds yarn to knit loops on the front lower needle bed.

[0033] S5. Turn the double rib structure that is turned from the front lower needle bed to the rear lower needle bed in step S4 back to the front lower needle bed.

[0034] S6. Repeat steps S1 - S5.

[0035] In an embodiment of the present invention, in steps S1, S3, and S4, the yarns fed by the first yarn feeder and the second yarn feeder knit plain weft knitting or single - side jacquard. The yarns fed by the first yarn feeder and the second yarn feeder respectively knit the inner layer and the outer layer of the four - layer - structure knitted fabric. The inner layer or the outer layer is distinguished by the material.

[0036] In an embodiment of the present invention, in step S2, when knitting the double rib structure, the fifth yarn feeder intermittently feeds the shape memory material; each time the shape memory material is fed, 3 - 50 loops are knitted; the weft - wise length of the double rib structure without the shape memory material knitted between every two feedings of the shape memory material is 0.5 - 5 cm.

[0037] The first yarn nozzle, the second yarn nozzle, the third yarn nozzle, the fourth yarn nozzle, and the fifth yarn nozzle are only used to distinguish different yarn nozzles and do not have the meaning of sorting.

[0038] The knitting flowchart of the preparation method is as Figure 1 shown. Figure 1 Among them, the magenta yarn represents the yarn of the inner layer or the outer layer, the green yarn represents the yarn forming the tuck (only the tucks knitted on the front lower needle bed are shown, and the tucks knitted on the back lower needle bed are omitted), the dark blue yarn represents the yarn of the connecting layer, and the light blue yarn represents the yarn of the inner layer or the outer layer in the next cycle. Figure 3 It is the knitting diagram of the four-layer structure knitted fabric. Figure 4 It is the knitting simulation diagram of the four-layer structure knitted fabric. Figure 4 Among them, the magenta yarn represents the yarn of the inner layer or the outer layer, the green yarn represents the yarn forming the tuck, and the dark blue yarn represents the yarn of the connecting layer.

[0039] The third object of the present invention is the application of the above four-layer structure knitted fabric in the field of textiles.

[0040] In an embodiment of the present invention, the application includes applications in warm textiles, heat-insulating textiles, and flame-retardant textiles.

[0041] Beneficial effects:

[0042] (1) The connecting layer of the four-layer structure fabric prepared by the present invention adopts a rib stitch with one needle in every other needle, which increases the fabric thickness and the air gap, provides a static air layer while ensuring the lightness of the fabric, and improves the heat preservation effect and heat insulation effect of the fabric. A shape memory material is fed into the connecting layer, which can expand the interval between the inner layer and the outer layer, and further increase the content of static air.

[0043] (2) The fabric of the present invention is knitted by tucking on the basis of the plain stitch. By arranging the tuck units in the plain weft and using yarns of different colors and properties, patterns, flashing colors, and various structural color effects can be knitted on the surface.

[0044] (3) The fully formed fabric woven by the present invention is automatically produced through computer control, which significantly improves the production efficiency; the four-layer structure has excellent elasticity, and can be woven according to the body curve by local knitting, making the clothing fit the body more closely and improving the wearing comfort. Description of the drawings

[0045] Figure 1 It is the knitting flowchart of the four-layer structure knitted fabric.

[0046] Figure 2 It is the knitting physical diagram of the four-layer structure knitted fabric.

[0047] Figure 3 This is the weaving pattern of a four-layer knitted fabric.

[0048] Figure 4 This is a weaving simulation diagram of a four-layer knitted fabric. DETAILED DESCRIPTION

[0049] Example 1

[0050] A shape memory aramid knitted fabric used in fire-fighting uniforms, the raw materials and composition are:

[0051] Inner layer: 32S / 1 (50 / 50) (flame retardant viscose / aramid 1313), accounting for 10%

[0052] First connection layer, second connection layer: 32S / 1 aramid 1313, accounting for 63.8%; shape memory alloy (SMA), accounting for 2.0%

[0053] Outer layer: 32S / 1 Aramid 1313, accounting for 24.2%

[0054] The design process is:

[0055] The data of the protective clothing is obtained through a three-dimensional scanning system, the size of the two-dimensional paper pattern of the protective clothing is determined, and the process parameters are substituted into the size of the two-dimensional paper pattern to obtain the overall knitting process model of the protective clothing, which is then woven using a SHIMASEIKI four-needle bed fully-formed flat knitting machine.

[0056] The weaving process includes the following steps:

[0057] S1, the No. 1 yarn mouth feeds the blended yarn of flame-retardant viscose and aramid 1313 to knit the plain weft stitch on the front lower needle bed, the No. 2 yarn feeds the aramid 1313 yarn to knit the plain weft stitch on the rear lower needle bed, and then the No. 3 yarn mouth feeds the aramid 1313 yarn to knit the tuck loop on the front lower needle bed; the tuck loop is used to connect the inner and outer layers of fabric;

[0058] S2, the No. 4 yarn mouth feeds the aramid 1313 yarn from the left side of the front lower needle bed to the right side of the rear lower needle bed to weave the loop, and then feeds the yarn from the right side of the front lower needle bed to the left side of the rear lower needle bed to weave the loop, weaving one needle at a time to form a 3×3 double rib structure, and then the No. 3 yarn mouth feeds the aramid 1313 yarn on the rear lower needle bed to form a tuck loop; when weaving the double rib structure, the No. 5 yarn mouth feeds SMA intermittently; each time the shape memory material is fed, 10 loops are weaved; the weft length of the double rib structure without SMA knitted between every two feedings of SMA is 1 cm; at this time, both the front lower needle bed and the rear lower needle bed have knitted double rib structures;

[0059] S3, turn the double rib structure loop of the rear lower needle bed to the front upper needle bed by needle transfer action, and then feed the aramid 1313 yarn from the No. 2 yarn mouth to knit the weft plain needle structure on the rear lower needle bed;

[0060] S4. Turn the rib stitch coils that were transferred from the back lower needle bed to the front upper needle bed in step S3 back to the back lower needle bed, then turn the original rib stitch coils on the front lower needle bed to the back upper needle bed. Subsequently, feed a blended yarn of flame-retardant viscose and aramid 1313 from the first yarn feeder to knit plain stitch on the front lower needle bed.

[0061] S5. Turn the coils that were transferred from the front lower needle bed to the back lower needle bed in step S4 back to the front lower needle bed.

[0062] S6. Repeat steps S1 - S5.

[0063] The inner layer fabric is a blend of viscose fiber and aramid fiber. The viscose fiber fabric has good hygroscopicity and breathability, greatly improving the contact comfort of the fabric. The middle layer selects aramid fiber, and is knitted with a 1x1 rib stitch and fed with shape memory material. It has a large amount of static air, making it have strong warmth retention and good heat insulation effect. The outer layer uses aramid fiber, and aramid has excellent high-temperature resistance, and the fabric made is suitable for use as a fire-fighting suit. Figure 2 Figure [0000140] is a physical diagram of the four-layer knitted fabric made. The white yarn is pure aramid, and the blue yarn is a blended yarn of aramid and viscose.

[0064] Example 2

[0065] An aramid knitted fabric applied to military stab-proof clothing, with raw materials and compositions as follows:

[0066] Inner layer: 38S / 1 (50 / 50) (flame-retardant viscose / aramid 1414), accounting for 9.6%

[0067] The first connection layer and the second connection layer: 500D high-strength polyester filament, accounting for 63.6%

[0068] Outer layer: 500D ultra-high molecular weight polyethylene, accounting for 26.8%

[0069] Its design process is as follows:

[0070] Obtain the data of the protective clothing through a three-dimensional scanning system, determine the two-dimensional paper pattern size of the protective clothing, substitute the process parameters into the size in the two-dimensional paper pattern to obtain the overall knitting process model of the protective clothing, and then weave it with a SHIMASEIKI four-needle bed fully-fashioned flat knitting machine.

[0071] The weaving process includes the steps:

[0072] S1. Feed ultra-high molecular weight polyethylene yarn from the first yarn feeder to knit single-sided jacquard on the front lower needle bed, feed a blended yarn of flame-retardant viscose and aramid 1313 from the second yarn feeder to knit plain stitch on the back lower needle bed, and then feed high-strength polyester filament from the third yarn feeder to knit floats on the front lower and back lower needle beds; the floats are used to connect the inner and outer layers of the fabric.

[0073] S2. The high-strength polyester filament yarn is fed by the fourth yarn guide from the left side of the front lower needle bed. The yarn is knitted into loops towards the right side of the rear lower needle bed, and then the yarn is fed from the right side of the front lower needle bed and knitted into loops towards the left side of the rear lower needle bed. Knitting is done one stitch apart, forming a 4×4 rib stitch. Then, the high-strength polyester filament yarn is fed by the third yarn guide on the rear lower needle bed to form floats; at this time, rib stitches are knitted on both the front lower needle bed and the rear lower needle bed.

[0074] S3. The rib stitch on the rear lower needle bed is turned over to the front upper needle bed by a purl action. Then, a blended yarn of flame-retardant viscose and aramid 1313 is fed by the second yarn guide and plain stitch is knitted on the rear lower needle bed.

[0075] S4. The loops turned from the rear lower needle bed to the front upper needle bed in step S3 are turned back to the rear lower needle bed, and the original loops on the front lower needle bed are turned to the rear upper needle bed. Subsequently, ultra-high molecular weight polyethylene yarn is fed by the first yarn guide and single-sided jacquard stitch is knitted on the front lower needle bed.

[0076] S5. The loops turned from the front lower needle bed to the rear lower needle bed in step S4 are turned back to the front lower needle bed.

[0077] S6. Repeat steps S1 - S5.

[0078] For the inner layer fabric, a blend of viscose fiber and aramid fiber is selected. The viscose fiber fabric has good moisture absorption and breathability, greatly improving the contact comfort of the fabric. For the middle layer, high-strength polyester filament is selected. The heat resistance of high-strength polyester filament is about 200°C and it has excellent acid and alkali resistance, with good stability. For the outer layer, ultra-high molecular weight polyethylene is used. Ultra-high molecular weight polyethylene has the characteristics of high strength, high modulus, low density and impact resistance. This enables the made stab-proof clothing to be lightweight while ensuring the protective performance, facilitating carrying and wearing; ultra-high molecular weight polyethylene has a small density, high specific strength and specific modulus, which means that under the same strength, the ultra-high molecular weight polyethylene stab-proof clothing is lighter than traditional materials and is suitable for long-term wearing and performing tasks; moreover, ultra-high molecular weight polyethylene has excellent corrosion and wear resistance, as well as a relatively high thermal conductivity and excellent insulation performance. The fabricated fabric is applicable to harsh environments. The fabric can be impregnated with resin to enhance the protection effect.

[0079] Example 3

[0080] A shape memory knitted fabric applied to cold-proof clothing, with raw materials and compositions as follows:

[0081] Inner layer: 15D wool fiber, accounting for 27.9%

[0082] First connection layer, second connection layer: 150D PET fiber, accounting for 46.0%; shape memory alloy (SMA), accounting for 1.5%

[0083] Outer layer: 78D polyamide fiber, accounting for 24.6%

[0084] Its design process is as follows:

[0085] Obtain the data of the protective clothing through a 3D scanning system, determine the two-dimensional pattern size of the protective clothing, substitute the process parameters into the size in the two-dimensional pattern to obtain the overall knitting process model of the protective clothing, and then weave it with a SHIMASEIKI four-bed full-fashioned flat knitting machine.

[0086] The weaving process includes the steps:

[0087] S1. The first yarn feeder feeds wool yarn, and plain stitch is knitted on the front lower needle bed. The second yarn feeder feeds polyamide yarn and plain stitch is knitted on the rear lower needle bed. Then the third yarn feeder feeds polyamide yarn and tuck stitch is knitted on the front lower needle bed; the tuck stitch is used to connect the inner and outer layers of the fabric;

[0088] S2. The fourth yarn feeder feeds PET yarn and feeds the yarn from the left side of the front lower needle bed to knit loops towards the right side of the rear lower needle bed, and then feeds the yarn from the right side of the front lower needle bed to knit loops towards the left side of the rear lower needle bed, knitting one stitch and skipping one stitch to form a 5×5 rib stitch. Then the third yarn feeder feeds polyamide yarn on the rear lower needle bed to form tuck stitches; when knitting the rib stitch, the fifth yarn feeder intermittently feeds SMA; 50 loops are knitted each time the shape memory material is fed; the weft length of the rib stitch without SMA knitted during each two feedings of SMA is 2 cm; at this time, the front lower needle bed and the rear lower needle bed both have knitted rib stitches;

[0089] S3. Use the purl stitch action to turn the rib stitch on the rear lower needle bed to the front upper needle bed, and then the second yarn feeder feeds polyamide yarn and plain stitch is knitted on the rear lower needle bed;

[0090] S4. Turn the loops that are turned from the rear lower needle bed to the front upper needle bed in step S3 back to the rear lower needle bed, and then turn the original loops on the front lower needle bed to the rear upper needle bed. Subsequently, the first yarn feeder feeds wool yarn and plain stitch is knitted on the front lower needle bed;

[0091] S5. Turn the loops that are turned from the front lower needle bed to the rear lower needle bed in step S4 back to the front lower needle bed;

[0092] S6. Repeat steps S1 - S5.

[0093] The inner layer is made of wool fiber, which contains a lot of air and has good thermal insulation performance. It has a soft touch and good air permeability, can discharge excess heat and moisture, keep the skin dry and comfortable to wear. The middle layer is made of polyester fiber, which is woven with 1-in-1 double rib. Polyester has high strength and elastic recovery ability, and can make the fabric more straight and wide, improve the aesthetic effect, and feed shape memory material to significantly improve the thermal insulation effect. The outer layer uses nylon fiber, which has high strength and high wear resistance, strong elastic recovery, and certain UV resistance. The fabric is suitable for outdoor wear.

[0094] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A four-layer knitted fabric, characterized in that: From inside to outside, they are: inner layer, first connection layer, second connection layer and outer layer; The inner layer and the outer layer are independently made of plain weft stitch or single jacquard weave; The first connecting layer and the second connecting layer are both double rib structures; The loops of the connecting layer connect another connecting layer and the inner layer or the outer layer, and the inner layer and the outer layer are connected by a tuck structure.

2. The four-layer knitted fabric according to claim 1, characterized in that: The double rib structure is an m×n double rib knitted with one stitch every other; m is 1 to 10, and n is 1 to 10.

3. The four-layer knitted fabric according to claim 1, characterized in that: The inner layer, the outer layer, the first connecting layer and the second connecting layer are all made of flame-retardant fibers; the tuck structure uses the same yarn as the outer layer, the inner layer or the connecting layer; the flame-retardant fibers are one or more of aramid fibers and flame-retardant viscose, polyphenylene sulfide fibers, and polyimide fibers; the aramid fibers are one or more of aramid 1313, aramid 1414, and aramid sulfone fibers.

4. The four-layer knitted fabric according to claim 1, characterized in that: The inner layer is made of flame-retardant fiber; the outer layer is made of ultra-high molecular weight polyethylene fiber; the first connecting layer and the second connecting layer are independently made of one or more of aramid fiber, high-strength polyester yarn, and ultra-high molecular weight polyethylene fiber; the tuck structure uses the same yarn as the outer layer, inner layer or connecting layer.

5. The four-layer knitted fabric according to claim 1, characterized in that: The inner layer adopts one or more of wool fiber, hollow polyester fiber, and acrylic fiber; the first connecting layer and the second connecting layer independently adopt one or more of polyester fiber, aramid fiber, and nylon fiber; the outer layer adopts one or more of polyester fiber, aramid fiber, nylon fiber, and ultra-high molecular weight polyethylene fiber; the tuck structure adopts the same yarn as the outer layer, inner layer or connecting layer.

6. The four-layer knitted fabric according to claim 1, characterized in that: The first connecting layer and the second connecting layer are continuously woven with shape memory material fibers during weaving; the length of each section of the double rib structure containing shape memory material fibers in the first connecting layer and the second connecting layer is 3 to 50 loops; the weft length of each section of the double rib structure without shape memory material fibers in the first connecting layer and the second connecting layer is 0.5 to 5 cm.

7. The four-layer knitted fabric according to claim 6, characterized in that: The shape memory material fiber is selected from one or more of shape memory alloy, shape memory polyurethane, polynorbornene, and styrene-butadiene copolymer; the diameter of the shape memory material fiber is 0.1-5 mm.

8. The method for preparing the four-layer knitted fabric according to claim 1, characterized in that: The knitting process is carried out using a four-needle bed fully formed computerized flat knitting machine, including the following steps: S1, the yarn feeder No. 1 is used to weave the coils on the front lower needle bed, the yarn feeder No. 2 is used to weave the coils on the rear lower needle bed, and the yarn feeder No. 3 is used to weave the tuck loops on the front lower needle bed; the tuck loops are used to connect the inner and outer layers of fabric; S2, the yarn feeder No. 4 is used to knit the loops on the front lower needle bed and the back lower needle bed, and the loops are knitted one needle at a time to form an m×n double rib structure, and then the yarn feeder No. 3 is used to form a tuck loop on the back lower needle bed; m is 1 to 10, and n is 1 to 10; at this time, the front lower needle bed and the back lower needle bed have knitted double rib structures; S3, turn the double rib structure of the rear lower needle bed to the front upper needle bed by the needle transfer action, and then feed the yarn from the No. 2 yarn mouth to weave the loop on the rear lower needle bed; S4, transferring the interlocking rib structure from the rear lower needle bed to the front upper needle bed in step S3, and then transferring the interlocking rib structure from the front lower needle bed to the rear upper needle bed, and then feeding the yarn from the No. 1 yarn mouth to knit the loops on the front lower needle bed; S5, transferring the double rib structure from the front lower needle bed to the rear lower needle bed in step S4 and then transferring the double rib structure to the front lower needle bed; S6. Repeat steps S1 to S5.

9. The preparation method according to claim 8, characterized in that: In step S2, shape memory material fibers are fed intermittently from a No. 5 yarn feeder when knitting the interlocking rib structure; 3 to 50 loops are knitted each time the shape memory material is fed; and the weft length of the interlocking rib structure without shape memory material knitted between every two feedings of the shape memory material is 0.5 to 5 cm.

10. Application of the four-layer knitted fabric according to claim 1 in the field of textiles.

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