Preparation process of high-temperature-resistant composite knitted fabric

Abstract

This invention relates to the field of fabric preparation technology, and provides a preparation process for high-temperature resistant composite knitted fabric, solving the problems of existing high-temperature resistant fabrics being too thick, lacking softness and elasticity, and having difficulty in actively increasing the heat insulation cavity in high-temperature environments due to design defects. The invention includes the following steps: S1, weaving a heat-resistant outer layer using high-temperature resistant flame-retardant yarn; S2, providing a breathable membrane; S3, weaving an elastic inner layer using skin-friendly elastic yarn; S4, preparing an adhesive paste; S5, applying the adhesive paste to the breathable membrane in a discrete dot matrix pattern to form adhesive dots; S6, sequentially stacking and hot-pressing the heat-resistant outer layer, the breathable membrane, and the elastic inner layer; S7, curing and shaping the composite fabric. By setting adhesive dots between the breathable membrane and the elastic inner layer, the adhesive dots remain in a low-protrusion state without expansion after lamination, preventing the fabric from becoming too thick and stiff under normal temperature conditions, thus helping to maintain the fabric's softness, elasticity, and breathability.

Description

Technical Field

[0001] This invention relates to the field of fabric preparation technology, specifically to a preparation process for a high-temperature resistant composite knitted fabric. Background Technology

[0002] High-temperature resistant composite knitted fabrics are widely used in fire-fighting protective clothing, industrial heat-insulating clothing, welding protective equipment, and high-temperature work protective gear. These fabrics typically need to simultaneously possess flame retardancy, high-temperature resistance, heat insulation, waterproofing and breathability, softness and comfort, and a certain degree of elasticity to meet the protective and wearing needs of the human body in high-temperature environments.

[0003] Chinese Patent Publication No. CN114889255A discloses a sandwich-structured flame-retardant and heat-insulating fire-fighting suit fabric and its preparation method. The fabric consists of a flame-retardant heat-reflective layer, a waterproof and breathable layer, a sandwich-shaped heat insulation layer, and a comfort layer, arranged sequentially from the outside to the inside. The waterproof and breathable layer is made of expanded PTFE microporous waterproof and breathable membrane, and the sandwich-shaped heat insulation layer is formed by bonding multiple layers of needle-punched nonwoven fabric through a dot-matrix method, with air insulation cavities retained between the layers to improve the flame-retardant and heat insulation performance of the fabric.

[0004] However, the aforementioned existing technologies still primarily rely on pre-formed static insulation structures to achieve their insulation effect. Their sandwich-like insulation layers are typically composed of non-woven fabrics, aerogel materials, porous structures, or pre-reserved air layers, with the insulation cavity essentially fixed after fabric fabrication. When the fabric is at room temperature or under normal wearing conditions, this type of pre-formed insulation layer still occupies a certain thickness, easily leading to an overall thicker and stiffer fabric, affecting softness, elasticity, and comfort against the skin. When the fabric is in a high-temperature environment, the height and shape of the pre-formed air layer are difficult to actively increase according to changes in the thermal environment, limiting the potential for improving insulation performance.

[0005] Furthermore, existing multi-layer composite fabrics typically use adhesives, dot bonding, or stitching to connect the functional layers. Ordinary adhesives or dot bonding structures mainly serve an interlayer fixing function, and their function is relatively simple. Under high temperatures, they may soften, become brittle, crack, or peel, making it difficult to further transform into a stable thermal insulation support structure during heating. If the thickness of non-woven fabric layers, aerogel layers, or fixed air layers is increased to improve thermal insulation performance, it will further increase the fabric's weight and thickness, reducing moisture permeability and wearing comfort. Summary of the Invention

[0006] Therefore, in view of the above problems, the present invention provides a preparation process for high-temperature resistant composite knitted fabric, which solves the problems of existing high-temperature resistant fabrics being too thick, lacking softness and elasticity, and having difficulty in actively increasing the heat insulation cavity with high-temperature environment due to design defects.

[0007] To achieve the above objectives, the present invention is implemented through the following technical solution: A process for preparing a high-temperature resistant composite knitted fabric includes the following steps: S1. A heat-resistant outer layer is formed by weaving high-temperature resistant and flame-retardant yarn, and the heat-resistant outer layer is subjected to surface activation treatment. S2. Provide a moisture-permeable membrane and activate at least one surface of the moisture-permeable membrane; S3. An elastic inner layer is formed by weaving skin-friendly elastic yarn, and a spaced support structure is formed on the side of the elastic inner layer facing the moisture-permeable membrane. S4. Prepare the dispensing paste, wherein the dispensing paste comprises a high-temperature resistant adhesive matrix, an inorganic heat-resistant filler, and a thermally expanding filler; S5. The adhesive paste is applied in a discrete dot matrix manner to the side of the moisture-permeable membrane facing the elastic inner layer and / or the side of the elastic inner layer facing the moisture-permeable membrane to form adhesive dots; S6. The heat-resistant outer layer, the moisture-permeable membrane, and the elastic inner layer are stacked in sequence, and hot-pressed composite is performed under conditions lower than the initial expansion temperature of the thermal expansion filler, so that the adhesive dots form a low-protrusion state without expansion after hot-pressing composite, and the adhesive dots simultaneously connect the moisture-permeable membrane and the elastic inner layer. S7. The composite fabric is cured and shaped to obtain a high-temperature resistant composite knitted fabric. The adhesive dots serve as interlayer bonding units at room temperature, and expand and carbonize in situ under high temperatures of 200°C to 350°C, causing the inorganic heat-resistant filler to form a heat-resistant skeleton in the adhesive dots, thereby forming a heat-resistant porous support and creating or enlarging a heat insulation cavity between the moisture-permeable membrane and the elastic inner layer.

[0008] Furthermore, the high-temperature resistant flame-retardant yarn includes one or more of meta-aramid yarn, para-aramid yarn, polyphenylene sulfide yarn, polyimide yarn, and flame-retardant viscose yarn.

[0009] Furthermore, the heat-resistant outer layer is a weft-knitted double-sided structure, rib knit, air-layer structure, or warp-knitted structure, and the weight of the heat-resistant outer layer is 80g / m² to 260g / m².

[0010] Furthermore, the moisture-permeable membrane is an expanded polytetrafluoroethylene membrane, a polyimide microporous membrane, or a high-temperature resistant flame-retardant polyurethane microporous membrane, and the thickness of the moisture-permeable membrane is 5 μm to 50 μm, with an average pore size of 0.05 μm to 2 μm.

[0011] Furthermore, the elastic inner layer is woven from one or more of flame-retardant viscose yarn, aramid blended yarn, polyimide blended yarn, and flame-retardant elastic covering yarn, and is treated with moisture-wicking finishing to form capillary moisture-wicking channels that guide moisture from the human body side to the moisture-permeable membrane side.

[0012] Furthermore, the spacer support structure is woven together from heat-shrinkable high-temperature resistant support yarn and high-temperature resistant stable yarn. The heat-shrinkable high-temperature resistant support yarn produces a heat shrinkage rate of 12% to 20% under conditions of 220°C to 280°C, so as to pull the elastic inner layer to locally arch and cooperate with the adhesive dots to form a heat insulation cavity.

[0013] Furthermore, in step S5, the adhesive dots are arranged correspondingly or staggered with the spacer support structure, so that a continuous or intermittent water vapor channel is formed between adjacent adhesive dots.

[0014] Further, by weight, the dispensing paste comprises 100 parts of high-temperature resistant adhesive matrix, 20 to 35 parts of inorganic heat-resistant filler, 8 to 18 parts of aerogel particles, 10 to 20 parts of thermal expansion filler, 6 to 12 parts of flame retardant synergist, and 1 to 3 parts of coupling agent.

[0015] Furthermore, the high-temperature resistant adhesive matrix is ​​an organosilicon adhesive, a fluorine-modified organosilicon adhesive, a polyimide adhesive, or a high-temperature resistant flame-retardant polyurethane adhesive; the inorganic heat-resistant filler includes one or more of silica, alumina, mica powder, zinc borate, glass powder, and silicate powder; the thermally expandable filler includes one or more of expandable graphite, thermally expandable microspheres, and intumescent phosphorus-nitrogen flame-retardant systems.

[0016] Further, in step S5, the adhesive dots are formed by rotary screen printing, screen printing, gravure dispensing, or digital dispensing. The protrusion height of the adhesive dots after hot pressing is 0.02mm to 0.3mm, the diameter of the adhesive dots is 0.2mm to 3mm, the center distance between adjacent adhesive dots is 1mm to 8mm, and the area coverage of the adhesive dots is 5% to 35%. After being subjected to a high temperature of 200℃ to 350℃, the volume expansion ratio of the adhesive dots is 1.5 times to 5 times, and the height of the heat insulation cavity increases to 0.2mm to 3mm.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention combines a heat-resistant outer layer, a breathable membrane, and an elastic inner layer, and sets adhesive dots formed by dispensing adhesive paste between the breathable membrane and the elastic inner layer. These adhesive dots act as interlayer bonding units at room temperature, ensuring the strong bond between the breathable membrane and the elastic inner layer. At the same time, by hot-pressing the composite at a temperature lower than the initial expansion temperature of the thermal expansion filler, the adhesive dots remain in a low-protrusion state after composite formation, preventing the fabric from becoming too thick or stiff at room temperature and helping to maintain the fabric's softness, elasticity, and breathability.

[0018] When the fabric is exposed to a high temperature environment of 200℃ to 350℃, the adhesive dots can expand in situ and carbonize and harden, so that the inorganic heat-resistant filler forms a heat-resistant skeleton in the adhesive dots, forming a heat-resistant porous support, which promotes the formation or enlargement of the heat insulation cavity between the moisture-permeable membrane and the elastic inner layer.

[0019] This invention enables a state transition from soft and breathable at room temperature to enhanced thermal insulation at high temperature, improving the high-temperature thermal insulation performance, interlayer structure stability, and high-temperature protection reliability of the fabric without significantly increasing the initial thickness and weight of the fabric. Detailed Implementation

[0020] The following will describe in detail the implementation of the present invention with reference to specific embodiments, so that the process of how the present invention uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0021] In the following examples, "parts" refers to parts by weight.

[0022] Example 1: This example provides a preparation process for a high-temperature resistant composite knitted fabric, which specifically includes the following steps.

[0023] S1. Preparation of the heat-resistant outer layer: Meta-aramid yarn, para-aramid yarn, and flame-retardant viscose yarn were selected as high-temperature resistant and flame-retardant yarns, with a mass ratio of 60:15:25. The heat-resistant outer layer was formed by weft knitting on both sides, and the resulting heat-resistant outer layer had a basis weight of 160 g / m².

[0024] The obtained heat-resistant outer layer was subjected to desizing, washing and drying in sequence. The drying temperature was 80℃ and the drying time was 10min. Then, the side of the heat-resistant outer layer facing the moisture-permeable membrane was subjected to low-temperature plasma surface activation treatment with a treatment power of 500W and a treatment time of 60s.

[0025] S2. Treatment of the moisture-permeable membrane: An expanded polytetrafluoroethylene (ePTFE) membrane is provided as the moisture-permeable membrane, the membrane having a thickness of 18 μm and an average pore size of 0.8 μm. Both surfaces of the moisture-permeable membrane are subjected to corona activation treatment at a power of 1.2 kW and a speed of 8 m / min, giving the membrane surface suitable for composite bonding. After surface activation treatment, the surface energy of the heat-resistant outer layer or the moisture-permeable membrane is increased to no less than 38 mN / m, thereby improving the bonding stability between the heat-resistant outer layer and the moisture-permeable membrane.

[0026] S3. Preparation of the elastic inner layer: Flame-retardant viscose yarn, aramid blended yarn, and flame-retardant elastic covering yarn are selected as skin-friendly elastic yarns, with a mass ratio of 45:35:20. The elastic inner layer is formed by weft-knitted air-layer structure, and a spaced support structure is simultaneously woven on the side of the elastic inner layer facing the breathable membrane.

[0027] The spacer support structure is formed by heat-shrinkable high-temperature resistant support yarn and high-temperature resistant stabilizing yarn. The heat-shrinkable high-temperature resistant support yarn is a polyimide composite support yarn that has undergone a predetermined heat treatment, and the high-temperature resistant stabilizing yarn is an aramid stabilizing yarn. The heat shrinkage rate of the heat-shrinkable high-temperature resistant support yarn at 250°C is 16%.

[0028] The elastic inner layer is treated with moisture-wicking finishing by immersing it in a hydrophilic finishing solution with a mass concentration of 25 g / L, with a roll-off rate of 70%. Then, it is dried at 100℃ for 3 min and baked at 150℃ for 1 min to form capillary moisture-wicking channels in the elastic inner layer that guide moisture from the human body side to the moisture-permeable membrane side.

[0029] Specifically, the spacer support structure consists of convex dot-shaped or convex strip-shaped knitted support portions disposed on the side of the elastic inner layer facing the moisture-permeable membrane. These support portions are arrayed along the warp and weft directions of the fabric. Each support portion is formed by heat-shrinkable, high-temperature resistant support yarn in a floating or tucked manner, with a high-temperature resistant stabilizing yarn serving as the ground weave yarn to fix the heat-shrinkable, high-temperature resistant support yarn to the surface of the elastic inner layer. The initial height of each support portion is 0.15mm to 0.30mm, and the center-to-center distance between adjacent support portions is 3mm to 6mm. After hot-pressing, the support portions and adhesive dots are misaligned to form moisture channels. Under high temperature, the heat-shrinkable, high-temperature resistant support yarn shrinks, causing the elastic inner layer to locally arch, and together with the expanded adhesive dots, supports the heat insulation cavity between the moisture-permeable membrane and the elastic inner layer. The misalignment means that the projection of the adhesive dots in the fabric thickness direction is located between two or more adjacent support portions, and the center of the adhesive dots does not coincide with the center of any support portion.

[0030] S4. Preparation of dispensing paste: Prepare the dispensing paste. By weight, the dispensing paste includes: 100 parts of silicone adhesive, 12 parts of silica, 8 parts of alumina, 6 parts of mica powder, 12 parts of aerogel particles, 15 parts of expandable graphite, 8 parts of ammonium polyphosphate, and 2 parts of silane coupling agent.

[0031] The preparation method of the dispensing slurry is as follows: First, add the silane coupling agent to the silicone adhesive and stir for 10 minutes at 500 r / min; then add silica, alumina, mica powder and aerogel particles in sequence and stir for 20 minutes at 800 r / min; finally, add expandable graphite and ammonium polyphosphate and stir for 15 minutes at 600 r / min, and vacuum degas for 8 minutes to obtain a uniformly dispersed dispensing slurry.

[0032] S5. Dot Formation: The adhesive paste is applied to the side of the breathable membrane facing the elastic inner layer using a rotary screen printing method, forming discrete dot matrix adhesive dots. The diameter of each adhesive dot is 1.2 mm, the center-to-center distance between adjacent adhesive dots is 4 mm, and the area coverage of the adhesive dots is 18%.

[0033] The staggered arrangement of the adhesive dots and the spacer support structure on the elastic inner layer creates a continuous water vapor channel between adjacent adhesive dots, preventing the adhesive paste from blocking the micropores of the moisture-permeable membrane over a large area.

[0034] The moisture channel refers to the area between adjacent adhesive dots that is not covered by the adhesive paste. This area is connected to the microporous area of ​​the moisture-permeable membrane, allowing moisture from the human body side to be discharged to the outside through the elastic inner layer, the gap between adjacent adhesive dots, and the moisture-permeable membrane.

[0035] S6. Composite: The heat-resistant outer layer, the moisture-permeable membrane, and the elastic inner layer are sequentially stacked, with the moisture-permeable membrane located between the heat-resistant outer layer and the elastic inner layer, and the adhesive dots located between the moisture-permeable membrane and the elastic inner layer. Composite is performed using a hot-pressing method at a temperature of 130℃, a pressure of 0.18MPa, and a pressing time of 45s. The hot-pressing temperature is lower than the initial expansion temperature of expandable graphite, ensuring that the adhesive dots only bond and solidify without expanding during the composite process. "No expansion" means that the volume of the adhesive dots after hot-pressing does not exceed 50% of its volume after high-temperature treatment, preferably 20% to 40%. This percentage characterizes the volume relationship between the adhesive dots after hot-pressing and after high-temperature expansion, and does not indicate that the adhesive dots have completed 20% to 40% thermal expansion during the hot-pressing stage.

[0036] After hot-press lamination, the adhesive dots simultaneously connect the breathable membrane and the elastic inner layer. The adhesive dots are in a low-protrusion state, with a protrusion height of 0.10mm. Because the adhesive dots do not expand, the laminated fabric maintains good softness and fit.

[0037] S7. Curing and Shaping: The hot-pressed composite fabric is cured and shaped at 150℃ for 5 minutes, and after cooling, a high-temperature resistant composite knitted fabric is obtained.

[0038] High-temperature treatment test: The obtained high-temperature resistant composite knitted fabric was placed in a 250℃ hot air environment for 120 seconds. After treatment, the adhesive dots expanded in situ and carbonized and hardened. Silica, alumina, mica powder and aerogel particles formed an inorganic heat-resistant skeleton in the adhesive dots, and expandable graphite provided expansion support, transforming the adhesive dots from a low-protrusion bonding structure at room temperature into a heat-resistant porous support.

[0039] The carbonization and hardening refers to the cross-linking, decomposition, carbonization, or hardening of the adhesive matrix in the adhesive dots under high temperature, transforming the adhesive dots from a flexible adhesive state to a porous, cured state with a certain compressive support capacity. The heat-resistant skeleton refers to an inorganic filler support network formed by silica, alumina, mica powder, silicate powder, or aerogel particles remaining inside the adhesive dots after carbonization and hardening, overlapping or embedding themselves in the carbonized matrix.

[0040] Measurements showed that the volume expansion of the adhesive dots after high-temperature treatment was 3.1 times, and the height of the heat insulation cavity formed between the moisture-permeable membrane and the elastic inner layer was 1.4 mm. After the high-temperature treatment ended and the material cooled, the adhesive dots maintained their expanded porous support shape. The expansion and carbonization hardening process was irreversible.

[0041] The volume expansion ratio of adhesive dots refers to the ratio of the volume of the adhesive dots after being subjected to high temperature to the volume of the adhesive dots after hot pressing. The volume expansion ratio of adhesive dots is not the same concept as the increase in height along the fabric thickness direction; during expansion, the adhesive dots can undergo dimensional changes in both the thickness direction and the in-plane direction simultaneously. The final height of the insulation cavity is not determined solely by the height of the adhesive dots, but rather by the initial support height of the support component, the expansion height of the adhesive dots along the thickness direction, and the local arching height formed by the traction elastic inner layer after the shrinkage of the heat-shrinkable high-temperature resistant support yarn. Therefore, the final height of the insulation cavity can be greater than the increase in height of the adhesive dots themselves along the thickness direction.

[0042] The fabric obtained in Example 1 was compared with a control fabric without thermal expansion filler in terms of performance. The test method is as follows: 1. Moisture permeability test: Performed according to the method specified in GB / T 12704.1; 2. Peel strength test: Performed according to the method specified in FZ / T 01085; 3. High-temperature back surface temperature rise test: Place the outer side of the sample towards a 250℃ heat source, treat for 120s, and measure the temperature rise of the inner surface. 4. Flexibility test: The bending length is tested using the cantilever beam method; 5. Heat insulation cavity height test: The heat insulation cavity height is obtained by cooling the fabric after high-temperature treatment, embedding it in resin, slicing it along the thickness direction, observing the cross-section using an optical microscope or scanning electron microscope, and measuring the average distance between the moisture-permeable membrane and the elastic inner layer.

[0043] The test results are as follows: The fabric obtained in Example 1 has a moisture permeability of 8200 g / (m²·24h), a peel strength of 8.6 N / 25 mm, and a bending length at room temperature of 4.8 cm. After treatment at 250℃ for 120 s, the inner surface temperature rise is 38℃, and the insulation cavity height is 1.4 mm. The control fabric without thermal expansion filler, after treatment under the same conditions, has an inner surface temperature rise of 52℃ and an average interlayer spacing of 0.4 mm.

[0044] Therefore, in this embodiment, the adhesive dots mainly serve as interlayer bonding units at room temperature, and can form a heat-resistant porous support and increase the heat insulation cavity under high temperature, thereby improving high-temperature heat insulation performance while maintaining moisture permeability and flexibility.

[0045] Example 2: The difference between this example and Example 1 lies in the different compositions of the heat-resistant outer layer, the moisture-permeable membrane, and the adhesive paste.

[0046] In S1, the heat-resistant outer layer is made of a blend of polyphenylene sulfide yarn, meta-aramid yarn and flame-retardant viscose yarn, with a mass ratio of 40:40:20 and a rib structure, with a weight of 190 g / m².

[0047] In S2, the moisture-permeable membrane is a polyimide microporous membrane with a thickness of 25 μm and an average pore size of 0.5 μm. The side of the membrane facing the elastic inner layer is subjected to plasma activation treatment with a treatment power of 600 W and a treatment time of 50 s.

[0048] In S3, the elastic inner layer is woven from polyimide blended yarn, flame-retardant viscose yarn, and flame-retardant elastic covering yarn, with a mass ratio of 40:40:20. The spacer support structure is woven from heat-shrinkable high-temperature resistant support yarn and aramid stabilizing yarn. The heat-shrinkable high-temperature resistant support yarn has a heat shrinkage rate of 14% at 260℃.

[0049] In S4, by weight, the dispensing paste includes: 100 parts of fluorine-modified silicone adhesive, 10 parts of silica, 10 parts of alumina, 8 parts of silicate powder, 10 parts of aerogel particles, 12 parts of thermally expandable microspheres, 6 parts of ammonium polyphosphate, 3 parts of melamine, and 1.5 parts of silane coupling agent.

[0050] In step S5, adhesive dots are formed using screen printing. The diameter of each dot is 0.8 mm, the center-to-center distance between adjacent dots is 3 mm, and the dot area coverage is 15%. The adhesive dots are correspondingly positioned with the spacer support structure, allowing them to expand at high temperatures and jointly support the breathable membrane and elastic inner layer. "Correspondingly positioned" means that the projection of the adhesive dot in the fabric thickness direction at least partially coincides with the projection of the support portion of the spacer support structure in the fabric thickness direction. Preferably, the center of the adhesive dot coincides with the center of the support portion, or the distance between their centers is no greater than half the radius of the adhesive dot.

[0051] In S6, the hot-pressing temperature is 115℃, the hot-pressing pressure is 0.15MPa, and the hot-pressing time is 60s. This temperature is lower than the initial expansion temperature of the thermally expandable microspheres, and the adhesive dots remain unexpanded after hot pressing, with a protrusion height of 0.07mm.

[0052] In S7, the curing and setting temperature is 140℃ and the time is 6 minutes to obtain a high-temperature resistant composite knitted fabric.

[0053] The fabric obtained in Example 2 was treated in a 220°C hot air environment for 180 seconds. After high-temperature treatment, the volume expansion ratio of the adhesive dots was 2.4 times, and the height of the insulation cavity was 0.9 mm. The fabric's moisture permeability was tested to be 7900 g / (m²·24h), its peel strength was 7.9 N / 25 mm, and the temperature rise of the inner surface was 41°C.

[0054] In this embodiment, the polyimide microporous membrane improves the heat resistance stability of the breathable membrane, the fluorinated silicone adhesive improves the dimensional stability of the adhesive dots at high temperatures, and the thermally expanding microspheres enable the adhesive dots to expand controllably under relatively low temperature conditions, thus making it suitable for inner layer materials of protective clothing that require high softness and heat resistance stability.

[0055] Example 3: The difference between this example and Example 1 is that it uses an outer layer with a higher heat resistance rating and a larger adhesive dot expansion structure.

[0056] In S1, a heat-resistant outer layer is formed by weaving para-aramid yarn, polyimide yarn, and meta-aramid yarn in a mass ratio of 35:35:30. The heat-resistant outer layer is a warp-knitted structure with a weight of 230 g / m². After washing and drying, the heat-resistant outer layer undergoes plasma roughening treatment with a power of 700 W for 80 seconds.

[0057] In S2, the moisture-permeable membrane is an expanded polytetrafluoroethylene membrane with a thickness of 35 μm and an average pore size of 1.2 μm.

[0058] In S3, the elastic inner layer is woven from aramid blended yarn and flame-retardant elastic covering yarn in a mass ratio of 70:30. The spacer support structure is woven from heat-shrinkable high-temperature resistant support yarn and aramid stabilizing yarn. The heat-shrinkable high-temperature resistant support yarn has a heat shrinkage rate of 18% at 270℃.

[0059] In S4, by weight, the dispensing paste includes: 100 parts of polyimide adhesive, 15 parts of silica, 10 parts of alumina, 8 parts of mica powder, 16 parts of aerogel particles, 18 parts of expandable graphite, 10 parts of ammonium polyphosphate, 2 parts of pentaerythritol, and 2.5 parts of silane coupling agent.

[0060] In S5, a gravure dispensing method is used to apply adhesive paste to the side of the elastic inner layer facing the moisture-permeable membrane, forming adhesive dots. The diameter of the adhesive dots is 1.8 mm, the center-to-center distance between adjacent adhesive dots is 5.5 mm, and the area coverage of the adhesive dots is 25%. The adhesive dots and the spacer support structure are staggered, so that part of the support structure is located between adjacent adhesive dots, thereby forming a water vapor channel that combines continuous and intermittent flow at high temperatures.

[0061] In S6, the heat-resistant outer layer, the moisture-permeable membrane, and the elastic inner layer are sequentially stacked and hot-pressed together at 160℃ and 0.22MPa for 40s. This hot-pressing temperature is lower than the initial significant expansion temperature of expandable graphite, so that the adhesive dots remain in a low-protrusion state after hot pressing, with a protrusion height of 0.18mm.

[0062] In S7, the composite fabric is cured and set at 180℃ for 4 minutes to obtain a high-temperature resistant composite knitted fabric.

[0063] The fabric obtained in Example 3 was treated in a 320°C hot air environment for 90 seconds. After high-temperature treatment, the adhesive dots expanded significantly and carbonized and hardened, forming a heat-resistant porous support with an inorganic heat-resistant filler skeleton. Measurements showed that the volume expansion ratio of the adhesive dots was 4.2 times, and the height of the insulation cavity was 2.2 mm.

[0064] Tests showed that the fabric obtained in Example 3 had a moisture permeability of 7100 g / (m²·24h), a peel strength of 8.2 N / 25 mm, and an inner surface temperature rise of 43°C after treatment at 320°C for 90 seconds. This example is suitable for applications requiring high-temperature insulation, such as welding protective clothing, industrial high-temperature work clothes, and heat-resistant protective gear.

[0065] Comparative Example 1: This comparative example is basically the same as Example 1, except that no thermal expansion filler is added to the dispensing slurry. Specifically, it consists of 100 parts of silicone adhesive, 12 parts of silica, 8 parts of alumina, 6 parts of mica powder, 12 parts of aerogel particles, 8 parts of ammonium polyphosphate, and 2 parts of silane coupling agent.

[0066] The same process as in Example 1 was used for dispensing, laminating, and curing to obtain the comparative fabric. After the comparative fabric was placed in a 250°C hot air environment for 120 seconds, the adhesive dots did not expand significantly, the volume change of the adhesive dots was 1.1 times, the average distance between the breathable membrane and the elastic inner layer was 0.4 mm, and the temperature rise of the inner surface was 52°C.

[0067] Compared with Example 1, Comparative Example 1 did not have thermal expansion filler, so the adhesive dots could not effectively transform into heat-resistant porous supports at high temperatures, resulting in a less significant increase in the heat insulation cavity and a reduction in high-temperature heat insulation performance.

[0068] Comparative Example 2: This comparative example is basically the same as Example 1, except that the hot-pressing composite temperature is 230°C, which is higher than the initial expansion temperature of the thermal expansion filler in the adhesive paste, so that the adhesive dots expand fully during the hot-pressing composite stage.

[0069] After hot-pressing lamination, the height of the adhesive dots is 0.65mm, the fabric bending length at room temperature is 7.6cm, and the moisture permeability is 6100g / (m²·24h). A stiff feeling appears around the adhesive dots in some areas. After being treated in a 250℃ hot air environment for 120s, the volume expansion ratio of the adhesive dots is only 1.2 times, and the change in the height of the insulation cavity is not significant.

[0070] Compared with Example 1, the adhesive dots in Comparative Example 2 expand fully in advance during the composite stage, resulting in increased fabric thickness and stiffness at room temperature. At the same time, it lacks the ability to further expand in situ to form or enlarge the insulation cavity under subsequent high-temperature conditions, making it difficult to achieve a balance between room temperature softness and moisture permeability and high-temperature enhanced insulation.

[0071] As can be seen from Examples 1 to 3 and Comparative Examples 1 and 2, the present invention achieves this by hot-pressing composite under conditions lower than the initial expansion temperature of the thermal expansion filler, so that the adhesive dots remain in a low-protrusion state without expansion after hot-pressing composite. At room temperature, the adhesive dots mainly serve as interlayer bonding units between the moisture-permeable membrane and the elastic inner layer, and retain the water vapor channels between adjacent adhesive dots. When the fabric is subjected to high temperatures of 200°C to 350°C, the adhesive dots undergo irreversible in-situ expansion and carbonization hardening. The inorganic heat-resistant filler forms a heat-resistant skeleton in the carbonized adhesive dots, thereby forming a heat-resistant porous support, so that a heat insulation cavity is formed or enlarged between the moisture-permeable membrane and the elastic inner layer.

[0072] This structure can maintain the softness, moisture permeability and interlayer bonding strength of composite knitted fabrics at room temperature, and improve the thermal insulation performance and structural stability of the fabrics at high temperatures. It is suitable for protective equipment such as fire protective clothing, industrial heat-insulating clothing, welding protective equipment, high-temperature operation protective clothing, heat-resistant gloves, sleeve protectors and knee pads.

[0073] Although the invention has been specifically shown and described in conjunction with preferred embodiments, those skilled in the art should understand that various changes in form and detail may be made to the invention without departing from the spirit and scope of the invention as defined in the appended claims, all of which shall be within the scope of protection of the invention.

Claims

1. A process for the production of a high temperature resistant composite knitted fabric, characterized in that, Includes the following steps: S1. A heat-resistant outer layer is formed by weaving high-temperature resistant and flame-retardant yarn, and the heat-resistant outer layer is subjected to surface activation treatment. S2. Provide a moisture-permeable membrane and activate at least one surface of the moisture-permeable membrane; S3. An elastic inner layer is formed by weaving skin-friendly elastic yarn, and a spaced support structure is formed on the side of the elastic inner layer facing the moisture-permeable membrane. S4. Prepare the dispensing paste, wherein the dispensing paste comprises a high-temperature resistant adhesive matrix, an inorganic heat-resistant filler, and a thermally expanding filler; S5. The adhesive paste is applied in a discrete dot matrix pattern to the side of the breathable membrane facing the elastic inner layer and / or the side of the elastic inner layer facing the breathable membrane to form adhesive dots. The spacer support structure is woven together by heat-shrinkable high-temperature resistant support yarn and high-temperature resistant stable yarn. The heat-shrinkable high-temperature resistant support yarn produces a heat shrinkage rate of 12% to 20% under conditions of 220°C to 280°C, so as to pull the elastic inner layer to locally arch and cooperate with the adhesive dots to form a heat insulation cavity. S6. The heat-resistant outer layer, the moisture-permeable membrane, and the elastic inner layer are stacked in sequence, and hot-pressed composite is performed under conditions lower than the initial expansion temperature of the thermal expansion filler, so that the adhesive dots form a low-protrusion state without expansion after hot-pressing composite, and the adhesive dots simultaneously connect the moisture-permeable membrane and the elastic inner layer. S7. The composite fabric is cured and shaped to obtain a high-temperature resistant composite knitted fabric. The adhesive dots serve as interlayer bonding units at room temperature, and expand and carbonize in situ under high temperatures of 200°C to 350°C, causing the inorganic heat-resistant filler to form a heat-resistant skeleton in the adhesive dots, thereby forming a heat-resistant porous support and creating or enlarging a heat insulation cavity between the moisture-permeable membrane and the elastic inner layer.

2. A process for making high temperature resistant composite knitted fabric as claimed in claim 1 wherein: The high-temperature resistant and flame-retardant yarn includes one or more of meta-aramid yarn, para-aramid yarn, polyphenylene sulfide yarn, polyimide yarn, and flame-retardant viscose yarn.

3. A process for making high temperature resistant composite knitted fabric as claimed in claim 1 wherein: The heat-resistant outer layer is a weft-knitted double-sided structure, rib structure, air layer structure, or warp-knitted structure, and the weight of the heat-resistant outer layer is 80g / m² to 260g / m².

4. The preparation process of the high-temperature resistant composite knitted fabric according to claim 1, characterized in that: The moisture-permeable membrane is an expanded polytetrafluoroethylene membrane, a polyimide microporous membrane, or a high-temperature resistant flame-retardant polyurethane microporous membrane. The thickness of the moisture-permeable membrane is 5 μm to 50 μm, and the average pore size is 0.05 μm to 2 μm.

5. The preparation process of the high-temperature resistant composite knitted fabric according to claim 1, characterized in that: The elastic inner layer is woven from one or more of flame-retardant viscose yarn, aramid blended yarn, polyimide blended yarn, and flame-retardant elastic covering yarn, and is finished to form capillary moisture-wicking channels that guide moisture from the human body side to the moisture-permeable membrane side.

6. The preparation process of the high-temperature resistant composite knitted fabric according to claim 1, characterized in that: In step S5, the adhesive dots are arranged correspondingly or staggered with the spacer support structure, so that a continuous or intermittent water vapor channel is formed between adjacent adhesive dots.

7. The preparation process of the high-temperature resistant composite knitted fabric according to claim 1, characterized in that: By weight, the dispensing paste comprises 100 parts of high-temperature resistant adhesive matrix, 20 to 35 parts of inorganic heat-resistant filler, 8 to 18 parts of aerogel particles, 10 to 20 parts of thermal expansion filler, 6 to 12 parts of flame retardant synergist, and 1 to 3 parts of coupling agent.

8. The preparation process of the high-temperature resistant composite knitted fabric according to claim 7, characterized in that: The high-temperature resistant adhesive matrix is ​​an organosilicon adhesive, a fluorine-modified organosilicon adhesive, a polyimide adhesive, or a high-temperature resistant flame-retardant polyurethane adhesive; the inorganic heat-resistant filler includes one or more of silica, alumina, mica powder, zinc borate, glass powder, and silicate powder; the thermally expandable filler includes one or more of expandable graphite, thermally expandable microspheres, and an expandable phosphorus-nitrogen flame-retardant system.

9. The preparation process of the high-temperature resistant composite knitted fabric according to claim 1, characterized in that: In step S5, the adhesive dots are formed by rotary screen printing, screen printing, gravure dispensing, or digital dispensing. The protrusion height of the adhesive dots after hot pressing is 0.02mm to 0.3mm, the diameter of the adhesive dots is 0.2mm to 3mm, the center distance between adjacent adhesive dots is 1mm to 8mm, and the area coverage of the adhesive dots is 5% to 35%. After being subjected to a high temperature of 200℃ to 350℃, the volume expansion ratio of the adhesive dots is 1.5 times to 5 times, and the height of the heat insulation cavity increases to 0.2mm to 3mm.