CN118478570B - Multilayer flame-retardant composite fabric based on pre-oxidized fiber and preparation method thereof - Google Patents

Abstract

The present invention relates to the technical field of multi-layer composite fabrics, and discloses a multi-layer flame-retardant composite fabric based on pre-oxidized silk fiber and a preparation method thereof. The preparation method comprises: blending pre-oxidized silk fiber, modified cotton fiber and aramid fiber to obtain blended yarn; using the blended yarn as warp and weft, weaving to obtain outer fabric and inner fabric respectively; coating the outer fabric and the inner fabric with flame-retardant coating material on both sides, obtaining flame-retardant outer fabric and flame-retardant inner fabric respectively after photocuring, and combining the two by composite hot pressing to obtain a multi-layer flame-retardant composite fabric based on pre-oxidized silk fiber. The composite fabric has excellent flame retardancy and good thermal insulation performance.

Description

A multi-layer flame-retardant composite fabric based on pre-oxidized silk fiber and preparation method thereof

Technical Field

The invention relates to the technical field of multi-layer composite fabrics, and in particular to a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers and a preparation method thereof.

Background Art

Polyacrylonitrile pre-oxidized fiber is a new type of high-temperature resistant organic fiber and an intermediate product in the preparation process of carbon fiber. Because of its special flame retardant properties, it can be used as an independent textile fiber in the field of high-temperature resistant and flame retardant fabrics.

Although polyacrylonitrile pre-oxidized fiber has excellent flame retardancy, it also has the disadvantages of low strength, high brittleness, and poor textile processing performance, which affects its application in flame retardant fabrics. In the prior art, polyacrylonitrile raw fiber is usually chemically pretreated during the preparation of pre-oxidized fiber to improve the comprehensive performance of pre-oxidized fiber; or polyacrylonitrile pre-oxidized fiber is blended with other functional fibers to make up for the spinnability defects of polyacrylonitrile pre-oxidized fiber and prepare high-performance flame retardant fabrics.

Existing technologies such as Chinese patent application CN109703140A disclose a production process for flame-retardant composite fabrics, in which modified acrylic fiber and acrylic pre-oxidized yarn are mixed to prepare mixed fibers, and the prepared fabric has excellent flame retardant properties. However, although the prepared flame-retardant fabric has excellent flame retardant properties, its thermal insulation properties need to be improved, which limits the application of the fabric.

Summary of the invention

The purpose of the present invention is to overcome the deficiencies of the prior art and to provide a multi-layer flame retardant composite fabric based on pre-oxidized silk fibers and a preparation method thereof, wherein the composite fabric has excellent flame retardancy and good thermal insulation performance.

In order to achieve the above object, the technical solution adopted by the present invention is as follows:

A method for preparing a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers comprises the following steps:

Step 1: blending preoxidized silk fiber, modified cotton fiber and aramid fiber to obtain blended yarn; using the blended yarn as warp and weft to weave to obtain outer fabric and inner fabric respectively;

The pre-oxidized silk fiber is prepared by the following steps:

Step (1), mixing graphene oxide, toluene-2,4-diisocyanate and N,N-dimethylformamide, ultrasonically dispersing, stirring for reaction, adding polypropylene glycol after the reaction is completed, continuing the reaction, cooling to room temperature after the reaction is completed, obtaining a reaction product, precipitating, centrifuging, filtering, washing and drying to obtain a graphene oxide-polypropylene glycol composite material;

Step (2), mixing the graphene oxide-polypropylene glycol composite material with dimethyl sulfoxide, ultrasonically dispersing, adding the polyacrylonitrile solution, stirring, and after stirring, standing and degassing to obtain a modified polyacrylonitrile spinning solution;

Wet spinning the modified polyacrylonitrile spinning solution to obtain polyacrylonitrile fiber precursor; pre-oxidizing and chopping the polyacrylonitrile precursor to obtain pre-oxidized fiber;

The modified cotton fiber is prepared by the following steps:

Cotton fiber, potassium persulfate and water are mixed and pretreated, and after the pretreatment, methacrylamide is added to react, and after the reaction, the modified cotton fiber is filtered, washed and dried to obtain the modified cotton fiber;

Step 2: Double-sided coating of the outer fabric and the inner fabric with a flame-retardant coating material to form flame-retardant coatings on both sides of the outer fabric and the inner fabric, respectively; after coating, light curing is performed to obtain a flame-retardant outer fabric and a flame-retardant inner fabric, respectively;

The flame retardant coating material is prepared by the following steps:

Step (1), mixing silica aerogel microspheres with toluene, ultrasonically dispersing, adding γ-(2,3-epoxypropoxy)propyltrimethoxysilane, reacting, filtering, washing, and drying after the reaction is completed to obtain epoxy silica aerogel microspheres;

The epoxy-based silica aerogel microspheres, DOPO and methyl ethyl ketone are mixed and reacted, and after the reaction is completed, the solvent methyl ethyl ketone is removed by rotary evaporation to obtain a reaction product, which is then washed and dried to obtain functionalized silica aerogel microspheres;

Step (2), mixing toluene-2,4-diisocyanate and hydroxyethyl acrylate, reacting, adding functionalized silica aerogel microspheres and dibutyltin dilaurate after the reaction, continuing the reaction, and obtaining a flame retardant after the reaction;

Step (3), uniformly mixing the flame retardant, polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, photoinitiator, and defoamer to obtain a flame retardant coating material;

Step three: coat one side of the flame-retardant outer fabric with adhesive, and laminate the side of the flame-retardant outer fabric coated with adhesive with the flame-retardant inner fabric, and perform hot pressing to obtain a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers.

Preferably, in step 1: the mass ratio of preoxidized silk fiber, modified cotton fiber and aramid fiber is 30-40:20-30:40; the yarn count of blended yarn is 40-60S in British standard; the weight of outer fabric is 140-160g/m ² ; the weight of inner fabric is 120-140g/m ² .

Preferably, in the preparation of the pre-oxidized silk fiber in step (1), the mass ratio of graphene oxide, toluene-2,4-diisocyanate, N,N-dimethylformamide and polypropylene glycol is 18-22:28-32:280-340:48-52; the stirring reaction conditions are: stirring the reaction in a nitrogen atmosphere at a temperature of 70-80°C for 20-26h; and the continued reaction conditions are: continuing the reaction in a nitrogen atmosphere at a temperature of 70-80°C for 22-24h.

Preferably, the precipitant in the precipitation operation comprises acetone, and the washing liquid in the washing operation comprises acetone.

Preferably, in the preparation of the pre-oxidized silk fiber in step 1, in step (2): the mass ratio of the graphene oxide-polypropylene glycol composite material, dimethylformamide, and polyacrylonitrile solution is 1.5-2:40-50:450-460, and the polyacrylonitrile solution is prepared by mixing and dissolving polyacrylonitrile and dimethyl sulfoxide in a mass ratio of 1:3.5; the stirring conditions are: stirring at a temperature of 60-70°C for 6-8h.

Preferably, in the preparation of the pre-oxidized silk fiber in step 1, in step (2): the wet spinning operation includes: spinning with a wet spinning machine, using a 40 vol% dimethyl sulfoxide aqueous solution as a coagulation bath, curing at 60°C, drawing at a draft multiple of 8-10 times, washing with a 40 vol% dimethyl sulfoxide aqueous solution, and drying at 40-50°C for 20-24 hours; the fineness of the polyacrylonitrile fiber precursor is 1.8-2D;

The pre-oxidation operation includes: in an air atmosphere, pre-oxidation treatment is carried out at 200-210°C, 220-230°C, 240-250°C, and 260-270°C in sequence, and after reaching the set temperature each time, the pre-oxidation treatment is kept warm for 15-20 minutes; the draft ratio of the pre-oxidation treatment at 200-210°C and 220-230°C is 4-6%, and the draft ratio of the pre-oxidation treatment at 240-250°C and 260-270°C is 0%; the fiber length of the pre-oxidized silk fiber is 51mm.

Preferably, in the preparation of modified cotton fiber in step 1, the mass ratio of cotton fiber, potassium persulfate, methacrylamide and water is 4-5:0.1-0.15:2-2.5:100-120; the pretreatment conditions are: pretreatment at 70-80°C for 20-30min; and the reaction conditions are: reaction at 70-80°C for 1-2h.

Preferably, in step 2: the thickness of the flame retardant coating is 0.2-0.3 mm; the light curing conditions are: light curing for 1-1.5 min under a radiation intensity of 28-36 mW/cm ² .

Preferably, in the preparation of the flame-retardant coating material in step 2, in step (1): the mass ratio of silica aerogel microspheres, toluene, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane is 2:50-60:0.8-1; when preparing epoxy silica aerogel microspheres, the reaction conditions are: reacting at a temperature of 95-105°C for 8-10h; the mass ratio of epoxy silica aerogel microspheres, DOPO, and methyl ethyl ketone is 2.6-2.8:10-10.5:250-280; when preparing functionalized silica aerogel microspheres, the reaction conditions are: reacting at a temperature of 60-70°C for 7-8h.

Preferably, in the preparation of the flame-retardant coating material in step 2, in step (2): the mass ratio of toluene-2,4-diisocyanate, hydroxyethyl acrylate, functionalized silica aerogel microspheres, and dibutyltin dilaurate is 16-17:11-12:1.5-2:0.05-0.06; the reaction conditions are: reacting in a nitrogen atmosphere at a temperature of 50-60°C for 1-2h; and the continued reaction conditions are: continuing the reaction at room temperature for 4-5h.

Preferably, in the preparation of the flame-retardant coating material in step 2, in step (3): the mass ratio of flame retardant, polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, photoinitiator, and defoaming agent is 25-30:45-50:8-10:5-8:4-5:3-4:1.

Preferably, in step three, the hot pressing conditions are: hot pressing at a pressure of 0.15-0.2 MPa and a temperature of 100-110° C. for 25-30 seconds.

Furthermore, the adhesive is a polyurethane adhesive, and the coating amount is 20 g/m ² .

Preferably, a multi-layer flame retardant composite fabric based on pre-oxidized silk fibers is prepared by the method for preparing a multi-layer flame retardant composite fabric based on pre-oxidized silk fibers as described above.

Compared with the prior art, the present invention has the following beneficial effects:

The present invention prepares outer and inner fabrics by blending preoxidized silk fiber, modified cotton fiber and aramid fiber. The outer and inner fabrics are respectively coated with flame retardant coatings with heat insulation performance. The multi-layer flame retardant composite fabric obtained after compounding has excellent flame retardancy and good heat insulation performance.

The present invention grafts toluene-2,4-diisocyanate onto graphene oxide through an esterification reaction, and the remaining isocyanate groups after the reaction continue to undergo an esterification reaction with polypropylene glycol to obtain a graphene oxide-polypropylene glycol composite material. The graphene oxide and the polypropylene glycol are connected to improve the dispersibility of the graphene oxide in a matrix. The graphene oxide-polypropylene glycol composite material is added to a polyacrylonitrile solution to obtain a modified polyacrylonitrile spinning solution. The modified polyacrylonitrile solution is wet-spun and then pre-oxidized to obtain pre-oxidized silk fibers. The polypropylene glycol is used as a plasticizer. The agent can improve the spinning performance of polyacrylonitrile; the lamellar structure of graphene oxide is conducive to the rearrangement of molecular chains in the polyacrylonitrile fiber structure, and can induce the molecular chains in the polyacrylonitrile fiber structure to be oriented along the lamellar defense line, inhibiting the deorientation of the molecular chains during the pre-oxidation process, thereby improving the mechanical properties of the pre-oxidized silk fiber; the two are compounded, and the obtained graphene oxide-polypropylene glycol composite material has hydrogen bond interaction with the polyacrylonitrile matrix, so that the composite material can be evenly dispersed in the spinning solution, thereby improving the spinning performance and mechanical properties of the pre-oxidized silk fiber;

The present invention grafts silica aerogel microspheres with a silane coupling agent containing an epoxy group to obtain epoxy-modified silica aerogel microspheres, which are subjected to a ring-opening reaction with DOPO to obtain functionalized silica aerogel microspheres having a DOPO flame-retardant structure and hydroxyl groups, and after toluene-2,4-diisocyanate is subjected to an esterification reaction with hydroxyethyl acrylate, the remaining isocyanate groups are further subjected to an esterification reaction with the hydroxyl groups of the functionalized silica aerogel microspheres to obtain a flame retardant having a carbon-carbon double bond group, which is mixed with polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, and other additives to be used as a flame-retardant coating material, which is attached to the fabric after coating and curing to improve the flame retardant properties of the fabric. Among them, the flame retardant contains three elements, namely phosphorus, nitrogen, and silicon, which can synergistically flame retardant and further improve the flame retardancy of the fabric; the silica aerogel microspheres are a spherical aerogel material that can improve the thermal insulation capacity of the fabric;

When preparing the outer layer fabric and the inner layer fabric of the present invention, cotton fiber and methacrylamide are mixed and grafted to make the surface of the modified cotton fiber grafted with amino groups. After the flame retardant coating material is coated on the fabric, the amino functional groups of the modified cotton fiber in the fabric can undergo a ring-opening reaction with the epoxy groups of glycidyl methacrylate in the coating material, thereby further improving the adhesion effect of the flame retardant coating on the fabric, and making the prepared multi-layer flame retardant composite fabric have long-lasting flame retardancy.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a process flow chart of preparing a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers in the present invention;

FIG2 is a schematic structural diagram of a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers prepared in the present invention;

3 is a bar graph of limiting oxygen index of Examples 1-5 and Comparative Examples 1-3 in performance tests of the present invention;

FIG4 is a bar graph of temperature differences in performance tests of Examples 1-5 and Comparative Examples 1-3 of the present invention;

In the figure:

1. Outer fabric; 2. Flame retardant coating; 3. Inner fabric; 4. Polyurethane adhesive; 5. Flame retardant outer fabric; 6. Flame retardant inner fabric.

DETAILED DESCRIPTION

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

Example 1

As shown in FIG. 1 , this embodiment discloses a method for preparing a multilayer flame retardant composite fabric based on pre-oxidized silk fibers, comprising the following steps:

Step 1: blending preoxidized silk fiber, modified cotton fiber and aramid fiber in a mass ratio of 30:30:40 to obtain a blended yarn with a yarn count of 40S in British standard; using the blended yarn as warp and weft for weaving to obtain an outer fabric with a gram weight of 140 g/ ^m2 and an inner fabric with a gram weight of 120 g/ ^m2 respectively;

The pre-oxidized silk fiber is prepared by the following steps:

Step (1), graphene oxide, toluene-2,4-diisocyanate, and N,N-dimethylformamide are mixed, ultrasonically dispersed for 20 minutes, stirred and reacted in a nitrogen atmosphere at 70°C for 26 hours, and after the reaction is completed, polypropylene glycol is added, and the reaction is continued in a nitrogen atmosphere at 70°C for 24 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a reaction product, and acetone twice the mass of the reaction product is added for precipitation, centrifuged, filtered, and the filter cake is taken, and acetone five times the mass of the filter cake is added for washing three times, and dried at 40°C for 28 hours to obtain a graphene oxide-polypropylene glycol composite material; the mass ratio of graphene oxide, toluene-2,4-diisocyanate, N,N-dimethylformamide, and polypropylene glycol is 18:28:280:48;

Step (2), mixing the graphene oxide-polypropylene glycol composite material with dimethyl sulfoxide, ultrasonically dispersing, adding polyacrylonitrile solution, wherein the mass ratio of the graphene oxide-polypropylene glycol composite material, dimethylformamide, and polyacrylonitrile solution is 1.5:40:450, stirring at 60° C. for 8 hours, and after stirring, standing to room temperature, degassing, and obtaining a modified polyacrylonitrile spinning solution; wherein the polyacrylonitrile solution is prepared by mixing and dissolving polyacrylonitrile and dimethyl sulfoxide in a mass ratio of 1:3.5;

The modified polyacrylonitrile spinning solution is wet-spun to obtain polyacrylonitrile fiber precursor with a fineness of 1.8D; the polyacrylonitrile precursor is pre-oxidized and chopped to obtain pre-oxidized fiber with a fiber length of 51 mm;

The wet spinning operation includes: spinning with a wet spinning machine, using a 40 vol% dimethyl sulfoxide aqueous solution as a coagulation bath, solidifying at 60° C., stretching at a draft multiple of 8 times, washing with a 40 vol% dimethyl sulfoxide aqueous solution, and drying at 40° C. for 24 hours;

The pre-oxidation operation includes: in an air atmosphere, pre-oxidation treatment is carried out at 200°C, 220°C, 240°C, and 260°C in sequence, and after reaching the set temperature each time, the pre-oxidation treatment is kept at the temperature for 20 minutes; the draft ratio of the pre-oxidation treatment at 200°C and 220°C is 4%, and the draft ratio of the pre-oxidation treatment at 240°C and 260°C is 0%;

The modified cotton fiber is prepared by the following steps:

Cotton fiber, potassium persulfate and water were mixed and pretreated at 75°C for 25 minutes. After the pretreatment, methacrylamide was added and reacted at 75°C for 1.5 hours. After the reaction, the filter was taken and the filter cake was washed with acetone 6 times the mass of the filter cake and dried at 55°C for 10 hours to obtain modified cotton fiber.

Among them, the mass ratio of cotton fiber, potassium persulfate, methacrylamide and water is 4.5:0.13:2.3:110;

Step 2: Double-sided coating of the outer fabric and the inner fabric with flame-retardant coating material, forming flame-retardant coatings on both sides of the outer fabric and the inner fabric, respectively, with a thickness of 0.2 mm. After coating, light curing is performed for 1.5 min under a radiation intensity of 28 mW/ ^cm2 to obtain flame-retardant outer fabric and flame-retardant inner fabric respectively;

The flame retardant coating material is prepared by the following steps:

Step (1), mixing silica aerogel microspheres with toluene, ultrasonically dispersing, adding γ-(2,3-epoxypropoxy)propyltrimethoxysilane, wherein the mass ratio of silica aerogel microspheres, toluene and γ-(2,3-epoxypropoxy)propyltrimethoxysilane is 2:55:0.9, reacting at 100° C. for 9 hours, filtering after the reaction, taking the filter cake, adding acetone 6 times the mass of the filter cake for washing, and drying at 70° C. for 26 hours to obtain epoxy silica aerogel microspheres;

Epoxy silica aerogel microspheres, DOPO, and methyl ethyl ketone were mixed in a mass ratio of 2.6:10:250, and reacted at 60°C for 8 hours. After the reaction, the solvent methyl ethyl ketone was removed by rotary evaporation at 70°C to obtain a reaction product, which was washed three times with acetone 5 times the mass of the reaction product, and dried at 90°C for 4 hours to obtain functionalized silica aerogel microspheres.

Step (2), mixing toluene-2,4-diisocyanate and hydroxyethyl acrylate, reacting for 2 hours in a nitrogen atmosphere at 50°C, adding functionalized silica aerogel microspheres and dibutyltin dilaurate after the reaction, reacting for 4 hours at room temperature, and obtaining a flame retardant after the reaction; the mass ratio of toluene-2,4-diisocyanate, hydroxyethyl acrylate, functionalized silica aerogel microspheres, and dibutyltin dilaurate is 16:11:1.5:0.05;

Step (3), uniformly mixing the flame retardant, polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, photoinitiator, and defoamer in a mass ratio of 25:50:8:5:4:3:1 to obtain a flame retardant coating material;

Step 3: Coat one side of the flame retardant outer fabric with a polyurethane adhesive at a coating amount of 20 g/m ² , and laminate the side of the flame retardant outer fabric coated with the polyurethane adhesive to the flame retardant inner fabric, and hot press at a pressure of 0.15 MPa and a temperature of 100° C. for 30 seconds to obtain a multi-layer flame retardant composite fabric based on pre-oxidized silk fibers;

The structural schematic diagram of the multi-layer flame retardant composite fabric based on pre-oxidized silk fiber as shown in Figure 2 includes: an outer layer fabric 1, a flame retardant coating 2, an inner layer fabric 3, a polyurethane adhesive 4, a flame retardant outer layer fabric 5, and a flame retardant inner layer fabric 6.

Example 2

This embodiment discloses a method for preparing a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers, comprising the following steps:

Step 1: blending preoxidized silk fiber, modified cotton fiber and aramid fiber in a mass ratio of 32:28:40 to obtain a blended yarn with a yarn count of 45S in British standard; using the blended yarn as warp and weft for weaving to obtain an outer fabric with a gram weight of 145 g/ ^m2 and an inner fabric with a gram weight of 125 g/ ^m2 respectively;

The pre-oxidized silk fiber is prepared by the following steps:

Step (1), mixing graphene oxide, toluene-2,4-diisocyanate and N,N-dimethylformamide, ultrasonically dispersing for 25 minutes, stirring and reacting in a nitrogen atmosphere at 75°C for 24 hours, adding polypropylene glycol after the reaction, continuing to react in a nitrogen atmosphere at 74°C for 23 hours, cooling to room temperature after the reaction, obtaining a reaction product, adding acetone 3 times the mass of the reaction product to precipitate, centrifuging, filtering, taking a filter cake, adding acetone 6 times the mass of the filter cake to wash three times, and drying at 45°C for 26 hours to obtain a graphene oxide-polypropylene glycol composite material; the mass ratio of graphene oxide, toluene-2,4-diisocyanate, N,N-dimethylformamide and polypropylene glycol is 19:29:290:49;

Step (2), mixing the graphene oxide-polypropylene glycol composite material with dimethyl sulfoxide, ultrasonically dispersing, adding polyacrylonitrile solution, wherein the mass ratio of the graphene oxide-polypropylene glycol composite material, dimethylformamide, and polyacrylonitrile solution is 1.6:43:452, stirring at 60° C. for 8 hours, and after stirring, standing to room temperature, degassing, and obtaining a modified polyacrylonitrile spinning solution; wherein the polyacrylonitrile solution is prepared by mixing and dissolving polyacrylonitrile and dimethyl sulfoxide in a mass ratio of 1:3.5;

The modified polyacrylonitrile spinning solution is wet-spun to obtain polyacrylonitrile fiber precursor with a fineness of 1.8D; the polyacrylonitrile precursor is pre-oxidized and chopped to obtain pre-oxidized fiber with a fiber length of 51 mm;

The wet spinning operation includes: spinning with a wet spinning machine, using a 40 vol% dimethyl sulfoxide aqueous solution as a coagulation bath, solidifying at 60°C, stretching at a draft multiple of 8 times, washing with a 40 vol% dimethyl sulfoxide aqueous solution, and drying at 45°C for 22 hours;

The pre-oxidation operation includes: in an air atmosphere, pre-oxidation treatment is carried out at 200°C, 220°C, 240°C, and 260°C in sequence, and after reaching the set temperature each time, the pre-oxidation treatment is kept at the temperature for 16 minutes; the draft ratio of the pre-oxidation treatment at 200°C and 220°C is 4%, and the draft ratio of the pre-oxidation treatment at 240°C and 260°C is 0%;

Wherein, the preparation of modified cotton fiber is the same as that in Example 1;

Step ² : Double-sided coating of the outer fabric and the inner fabric with flame-retardant coating material, forming flame-retardant coatings on both sides of the outer fabric and the inner fabric, respectively, with a thickness of 0.22 mm. After coating, light curing is performed for 1 min under a radiation intensity of 30 mW/cm2 to obtain flame-retardant outer fabric and flame-retardant inner fabric respectively;

The flame retardant coating material is prepared by the following steps:

Step (1), epoxy silica aerogel microspheres, DOPO, and methyl ethyl ketone are mixed in a mass ratio of 2.65:10.2:255, and reacted at 65°C for 7.5 hours. After the reaction is completed, the solvent methyl ethyl ketone is removed by rotary evaporation at 70°C to obtain a reaction product, and acetone of 5 times the mass of the reaction product is added to wash three times, and dried at 95°C for 3 hours to obtain functionalized silica aerogel microspheres; wherein the preparation of epoxy silica aerogel microspheres is the same as that in Example 1;

Step (2), mixing toluene-2,4-diisocyanate and hydroxyethyl acrylate, reacting for 2 hours in a nitrogen atmosphere at 50°C, adding functionalized silica aerogel microspheres and dibutyltin dilaurate after the reaction, reacting for 4.5 hours at room temperature, and obtaining a flame retardant after the reaction; the mass ratio of toluene-2,4-diisocyanate, hydroxyethyl acrylate, functionalized silica aerogel microspheres, and dibutyltin dilaurate is 16.3:11.3:1.6:0.05;

Step (3), uniformly mixing the flame retardant, polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, photoinitiator, and defoamer in a mass ratio of 26:49:8.5:6:4.2:3.2:1 to obtain a flame retardant coating material;

Step 3: Coat one side of the flame retardant outer fabric with polyurethane adhesive at a coating amount of 20 g/m ² , and laminate the side of the flame retardant outer fabric coated with polyurethane adhesive to the flame retardant inner fabric, and hot press at a pressure of 0.15 MPa and a temperature of 100° C. for 30 seconds to obtain a multi-layer flame retardant composite fabric based on pre-oxidized silk fibers.

Example 3

This embodiment discloses a method for preparing a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers, comprising the following steps:

Step 1: blending preoxidized silk fiber, modified cotton fiber and aramid fiber in a mass ratio of 35:25:40 to obtain a blended yarn with a yarn count of 50S in British standard; using the blended yarn as warp and weft for weaving to obtain an outer fabric with a gram weight of 150 g/ ^m2 and an inner fabric with a gram weight of 130 g/ ^m2 respectively;

The pre-oxidized silk fiber is prepared by the following steps:

Step (1), graphene oxide, toluene-2,4-diisocyanate, and N,N-dimethylformamide are mixed, ultrasonically dispersed for 25 minutes, stirred and reacted in a nitrogen atmosphere at 75°C for 24 hours, and after the reaction is completed, polypropylene glycol is added, and the reaction is continued in a nitrogen atmosphere at 74°C for 23 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a reaction product, and acetone twice the mass of the reaction product is added for precipitation, centrifuged, filtered, and the filter cake is taken, and acetone six times the mass of the filter cake is added for washing three times, and dried at 45°C for 26 hours to obtain a graphene oxide-polypropylene glycol composite material; the mass ratio of graphene oxide, toluene-2,4-diisocyanate, N,N-dimethylformamide, and polypropylene glycol is 20:30:310:50;

Step (2), mixing the graphene oxide-polypropylene glycol composite material with dimethyl sulfoxide, ultrasonically dispersing, adding polyacrylonitrile solution, wherein the mass ratio of the graphene oxide-polypropylene glycol composite material, dimethylformamide, and polyacrylonitrile solution is 1.8:45:455, stirring at 65° C. for 7 hours, and after stirring, standing to room temperature, degassing, and obtaining a modified polyacrylonitrile spinning solution; wherein the polyacrylonitrile solution is prepared by mixing and dissolving polyacrylonitrile and dimethyl sulfoxide in a mass ratio of 1:3.5;

The modified polyacrylonitrile spinning solution is wet-spun to obtain polyacrylonitrile fiber precursor with a fineness of 1.9D; the polyacrylonitrile precursor is pre-oxidized and chopped to obtain pre-oxidized fiber with a fiber length of 51 mm;

The wet spinning operation includes: spinning with a wet spinning machine, using a 40 vol% dimethyl sulfoxide aqueous solution as a coagulation bath, solidifying at 60° C., stretching at a draft multiple of 9, washing with a 40 vol% dimethyl sulfoxide aqueous solution, and drying at 45° C. for 22 hours;

The pre-oxidation operation includes: in an air atmosphere, pre-oxidation treatment is carried out at 205°C, 225°C, 245°C, and 265°C in sequence, and after reaching the set temperature each time, the pre-oxidation treatment is kept at the temperature for 18 minutes; the draft ratio of the pre-oxidation treatment at 205°C and 225°C is 5%, and the draft ratio of the pre-oxidation treatment at 245°C and 265°C is 0%;

Wherein, the preparation of modified cotton fiber is the same as that in Example 1;

Step 2: Double-sided coating of the outer fabric and the inner fabric with flame-retardant coating material, forming flame-retardant coatings on both sides of the outer fabric and the inner fabric, respectively, with a thickness of 0.25 mm. After coating, light curing is performed for 1.3 min under a radiation intensity of 32 mW/ ^cm2 to obtain flame-retardant outer fabric and flame-retardant inner fabric respectively;

The flame retardant coating material is prepared by the following steps:

Step (1), epoxy silica aerogel microspheres, DOPO, and methyl ethyl ketone are mixed in a mass ratio of 2.7:10.3:260, and reacted at 65°C for 7.5 hours. After the reaction is completed, the solvent methyl ethyl ketone is removed by rotary evaporation at 70°C to obtain a reaction product, and acetone of 6 times the mass of the reaction product is added to wash three times, and dried at 95°C for 3 hours to obtain functionalized silica aerogel microspheres; wherein the preparation of epoxy silica aerogel microspheres is the same as that in Example 1;

Step (2), mixing toluene-2,4-diisocyanate and hydroxyethyl acrylate, reacting for 1.5 hours in a nitrogen atmosphere at 55° C., adding functionalized silica aerogel microspheres and dibutyltin dilaurate after the reaction, reacting for 4.5 hours at room temperature, and obtaining a flame retardant after the reaction; the mass ratio of toluene-2,4-diisocyanate, hydroxyethyl acrylate, functionalized silica aerogel microspheres, and dibutyltin dilaurate is 16.5:11.5:1.8:0.05;

Step (3), uniformly mixing the flame retardant, polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, photoinitiator, and defoamer in a mass ratio of 28:48:9:6:4.5:3.5:1 to obtain a flame retardant coating material;

Step 3: Coat one side of the flame retardant outer fabric with a polyurethane adhesive at a coating amount of 20 g/m ² , and laminate the side of the flame retardant outer fabric coated with the polyurethane adhesive to the flame retardant inner fabric, and hot press at a pressure of 0.18 MPa and a temperature of 105° C. for 28 seconds to obtain a multi-layer flame retardant composite fabric based on pre-oxidized silk fibers.

Example 4

This embodiment discloses a method for preparing a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers, comprising the following steps:

Step 1: blending preoxidized silk fiber, modified cotton fiber and aramid fiber in a mass ratio of 38:22:40 to obtain a blended yarn with a yarn count of 55S in British standard; using the blended yarn as warp and weft for weaving to obtain an outer layer fabric with a gram weight of 155 g/ ^m2 and an inner layer fabric with a gram weight of 135 g/ ^m2 respectively;

The pre-oxidized silk fiber is prepared by the following steps:

Step (1), mixing graphene oxide, toluene-2,4-diisocyanate and N,N-dimethylformamide, ultrasonically dispersing for 25 minutes, stirring and reacting in a nitrogen atmosphere at 75°C for 24 hours, adding polypropylene glycol after the reaction, continuing to react in a nitrogen atmosphere at 75°C for 23 hours, cooling to room temperature after the reaction, obtaining a reaction product, adding acetone 3 times the mass of the reaction product for precipitation, centrifuging, filtering, taking a filter cake, adding acetone 8 times the mass of the filter cake for washing three times, and drying at 45°C for 26 hours to obtain a graphene oxide-polypropylene glycol composite material; the mass ratio of graphene oxide, toluene-2,4-diisocyanate, N,N-dimethylformamide and polypropylene glycol is 21:31:320:51;

Step (2), mixing the graphene oxide-polypropylene glycol composite material with dimethyl sulfoxide, ultrasonically dispersing, adding polyacrylonitrile solution, wherein the mass ratio of the graphene oxide-polypropylene glycol composite material, dimethylformamide, and polyacrylonitrile solution is 1.9:48:458, stirring at 70° C. for 6.5 hours, and after stirring, standing to room temperature, degassing, and obtaining a modified polyacrylonitrile spinning solution; wherein the polyacrylonitrile solution is prepared by mixing and dissolving polyacrylonitrile and dimethyl sulfoxide in a mass ratio of 1:3.5;

The modified polyacrylonitrile spinning solution is wet-spun to obtain polyacrylonitrile fiber precursor with a fineness of 2D; the polyacrylonitrile precursor is pre-oxidized and chopped to obtain pre-oxidized fiber with a fiber length of 51 mm;

The wet spinning operation includes: spinning with a wet spinning machine, using a 40 vol% dimethyl sulfoxide aqueous solution as a coagulation bath, curing at 60° C., stretching at a draft multiple of 10, washing with a 40 vol% dimethyl sulfoxide aqueous solution, and drying at 45° C. for 22 hours;

The pre-oxidation operation includes: in an air atmosphere, pre-oxidation treatment is carried out at 210°C, 230°C, 250°C, and 270°C in sequence, and after reaching the set temperature each time, the pre-oxidation treatment is kept at the temperature for 15 minutes; the draft ratio of the pre-oxidation treatment at 210°C and 230°C is 6%, and the draft ratio of the pre-oxidation treatment at 250°C and 270°C is 0%;

Wherein, the preparation of modified cotton fiber is the same as that in Example 1;

Step ² : Double-sided coating of the outer fabric and the inner fabric with flame-retardant coating material, forming flame-retardant coatings on both sides of the outer fabric and the inner fabric, respectively, with a thickness of 0.28 mm. After coating, light curing is performed for 1 min under a radiation intensity of 34 mW/cm2 to obtain flame-retardant outer fabric and flame-retardant inner fabric respectively;

The flame retardant coating material is prepared by the following steps:

Step (1), epoxy silica aerogel microspheres, DOPO, and methyl ethyl ketone are mixed in a mass ratio of 2.75:10.4:270, and reacted at 65°C for 7.5 hours. After the reaction is completed, the solvent methyl ethyl ketone is removed by rotary evaporation at 70°C to obtain a reaction product, and acetone of 8 times the mass of the reaction product is added to wash three times, and dried at 95°C for 3 hours to obtain functionalized silica aerogel microspheres; wherein the preparation of epoxy silica aerogel microspheres is the same as that in Example 1;

Step (2), mixing toluene-2,4-diisocyanate and hydroxyethyl acrylate, reacting for 1.5 hours in a nitrogen atmosphere at 55°C, adding functionalized silica aerogel microspheres and dibutyltin dilaurate after the reaction, reacting for 5 hours at room temperature, and obtaining a flame retardant after the reaction; the mass ratio of toluene-2,4-diisocyanate, hydroxyethyl acrylate, functionalized silica aerogel microspheres, and dibutyltin dilaurate is 16.8:11.8:1.9:0.06;

Step (3), uniformly mixing the flame retardant, polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, photoinitiator, and defoamer in a mass ratio of 29:46:9.5:7:4.8:3.8:1 to obtain a flame retardant coating material;

Step 3: Coat one side of the flame retardant outer fabric with a polyurethane adhesive at a coating amount of 20 g/m ² , and laminate the side of the flame retardant outer fabric coated with the polyurethane adhesive to the flame retardant inner fabric, and hot press at a pressure of 0.2 MPa and a temperature of 110° C. for 25 seconds to obtain a multi-layer flame retardant composite fabric based on pre-oxidized silk fibers.

Example 5

This embodiment discloses a method for preparing a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers, comprising the following steps:

Step 1: blending preoxidized silk fiber, modified cotton fiber and aramid fiber in a mass ratio of 40:20:40 to obtain a blended yarn with a yarn count of 60S in British standard; using the blended yarn as warp and weft for weaving to obtain an outer fabric with a gram weight of 160 g/ ^m2 and an inner fabric with a gram weight of 140 g/ ^m2 respectively;

The pre-oxidized silk fiber is prepared by the following steps:

Step (1), graphene oxide, toluene-2,4-diisocyanate and N,N-dimethylformamide are mixed, ultrasonically dispersed for 30 minutes, stirred and reacted for 20 hours in a nitrogen atmosphere at 80°C, and after the reaction is completed, polypropylene glycol is added, and the reaction is continued for 22 hours in a nitrogen atmosphere at 80°C. After the reaction is completed, the mixture is cooled to room temperature to obtain a reaction product, and acetone 3 times the mass of the reaction product is added for precipitation, centrifuged, filtered, and the filter cake is taken, and acetone 8 times the mass of the filter cake is added for washing three times, and dried at 50°C for 24 hours to obtain a graphene oxide-polypropylene glycol composite material; the mass ratio of graphene oxide, toluene-2,4-diisocyanate, N,N-dimethylformamide and polypropylene glycol is 22:32:340:52;

Step (2), mixing the graphene oxide-polypropylene glycol composite material with dimethyl sulfoxide, ultrasonically dispersing, adding polyacrylonitrile solution, wherein the mass ratio of the graphene oxide-polypropylene glycol composite material, dimethylformamide, and polyacrylonitrile solution is 2:50:460, stirring at 70° C. for 6 hours, and after stirring, standing to room temperature, degassing, and obtaining a modified polyacrylonitrile spinning solution; wherein the polyacrylonitrile solution is prepared by mixing and dissolving polyacrylonitrile and dimethyl sulfoxide in a mass ratio of 1:3.5;

The modified polyacrylonitrile spinning solution is wet-spun to obtain polyacrylonitrile fiber precursor with a fineness of 2D; the polyacrylonitrile precursor is pre-oxidized and chopped to obtain pre-oxidized fiber with a fiber length of 51 mm;

The wet spinning operation includes: spinning with a wet spinning machine, using a 40 vol% dimethyl sulfoxide aqueous solution as a coagulation bath, solidifying at 60° C., stretching at a draft multiple of 10, washing with a 40 vol% dimethyl sulfoxide aqueous solution, and drying at 50° C. for 20 hours;

The pre-oxidation operation includes: in an air atmosphere, pre-oxidation treatment is carried out at 210°C, 230°C, 250°C, and 270°C in sequence, and after reaching the set temperature each time, the pre-oxidation treatment is kept at the temperature for 15 minutes; the draft ratio of the pre-oxidation treatment at 210°C and 230°C is 6%, and the draft ratio of the pre-oxidation treatment at 250°C and 270°C is 0%;

Wherein, the preparation of modified cotton fiber is the same as that in Example 1;

Step ² : Double-sided coating of the outer fabric and the inner fabric with flame-retardant coating material, forming flame-retardant coatings on both sides of the outer fabric and the inner fabric, respectively, with a thickness of 0.3 mm. After coating, light curing is performed for 1 min under a radiation intensity of 36 mW/cm2 to obtain flame-retardant outer fabric and flame-retardant inner fabric respectively;

The flame retardant coating material is prepared by the following steps:

Step (1), epoxy silica aerogel microspheres, DOPO, and methyl ethyl ketone are mixed in a mass ratio of 2.8:10.5:280, and reacted at a temperature of 60-70°C for 7 hours. After the reaction is completed, the solvent methyl ethyl ketone is removed by rotary evaporation at a temperature of 75°C to obtain a reaction product, and acetone of 8 times the mass of the reaction product is added to wash three times, and dried at a temperature of 100°C for 2 hours to obtain functionalized silica aerogel microspheres; wherein the preparation of epoxy silica aerogel microspheres is the same as that in Example 1;

Step (2), mixing toluene-2,4-diisocyanate and hydroxyethyl acrylate, reacting in a nitrogen atmosphere at 60° C. for 1 hour, adding functionalized silica aerogel microspheres and dibutyltin dilaurate after the reaction, reacting at room temperature for 5 hours, and obtaining a flame retardant after the reaction; the mass ratio of toluene-2,4-diisocyanate, hydroxyethyl acrylate, functionalized silica aerogel microspheres, and dibutyltin dilaurate is 17:12:2:0.06;

Step (3), uniformly mixing the flame retardant, polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, photoinitiator, and defoamer in a mass ratio of 30:45:10:8:5:4:1 to obtain a flame retardant coating material;

Step 3: Coat one side of the flame retardant outer fabric with a polyurethane adhesive at a coating amount of 20 g/m ² , and laminate the side of the flame retardant outer fabric coated with the polyurethane adhesive to the flame retardant inner fabric, and hot press at a pressure of 0.2 MPa and a temperature of 110° C. for 25 seconds to obtain a multi-layer flame retardant composite fabric based on pre-oxidized silk fibers.

Comparative Example 1

This comparative example discloses a method for preparing a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers, comprising the following steps:

Step 1: blending preoxidized silk fiber, modified cotton fiber and aramid fiber in a mass ratio of 30:30:40 to obtain a blended yarn with a yarn count of 40S in British standard; using the blended yarn as warp and weft for weaving to obtain an outer fabric with a gram weight of 140 g/ ^m2 and an inner fabric with a gram weight of 120 g/ ^m2 respectively;

The pre-oxidized silk fiber is prepared by the following steps:

Step (1), graphene oxide, toluene-2,4-diisocyanate, and N,N-dimethylformamide are mixed, ultrasonically dispersed for 20 minutes, stirred and reacted in a nitrogen atmosphere at 70°C for 26 hours, and after the reaction is completed, polypropylene glycol is added, and the reaction is continued in a nitrogen atmosphere at 70°C for 24 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a reaction product, and acetone twice the mass of the reaction product is added for precipitation, centrifuged, filtered, and the filter cake is taken, and acetone five times the mass of the filter cake is added for washing three times, and dried at 40°C for 28 hours to obtain a graphene oxide-polypropylene glycol composite material; the mass ratio of graphene oxide, toluene-2,4-diisocyanate, N,N-dimethylformamide, and polypropylene glycol is 18:28:280:48;

Step (2), mixing the graphene oxide-polypropylene glycol composite material with dimethyl sulfoxide, ultrasonically dispersing, adding polyacrylonitrile solution, wherein the mass ratio of the graphene oxide-polypropylene glycol composite material, dimethylformamide, and polyacrylonitrile solution is 1.5:40:450, stirring at 60° C. for 8 hours, and after stirring, standing to room temperature, degassing, and obtaining a modified polyacrylonitrile spinning solution; wherein the polyacrylonitrile solution is prepared by mixing and dissolving polyacrylonitrile and dimethyl sulfoxide in a mass ratio of 1:3.5;

The modified polyacrylonitrile spinning solution is wet-spun to obtain polyacrylonitrile fiber precursor with a fineness of 1.8D; the polyacrylonitrile precursor is pre-oxidized and chopped to obtain pre-oxidized fiber with a fiber length of 51 mm;

The wet spinning operation includes: spinning with a wet spinning machine, using a 40 vol% dimethyl sulfoxide aqueous solution as a coagulation bath, solidifying at 60° C., stretching at a draft multiple of 8 times, washing with a 40 vol% dimethyl sulfoxide aqueous solution, and drying at 40° C. for 24 hours;

The pre-oxidation operation includes: in an air atmosphere, pre-oxidation treatment is carried out at 200°C, 220°C, 240°C, and 260°C in sequence, and after reaching the set temperature each time, the pre-oxidation treatment is kept at the temperature for 20 minutes; the draft ratio of the pre-oxidation treatment at 200°C and 220°C is 4%, and the draft ratio of the pre-oxidation treatment at 240°C and 260°C is 0%;

Wherein, the preparation of modified cotton fiber is the same as that in Example 1;

Step 2: Double-sided coating of the outer fabric and the inner fabric with flame-retardant coating material, forming flame-retardant coatings on both sides of the outer fabric and the inner fabric, respectively, with a thickness of 0.2 mm. After coating, light curing is performed for 1.5 min under a radiation intensity of 28 mW/ ^cm2 to obtain flame-retardant outer fabric and flame-retardant inner fabric respectively;

The flame retardant coating material is prepared by the following steps:

Silica aerogel microspheres, polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, a photoinitiator, and a defoamer are uniformly mixed in a mass ratio of 1.5:50:8:5:4:3:1 to obtain a flame retardant coating material;

Step 3: Coat one side of the flame retardant outer fabric with polyurethane adhesive at a coating amount of 20 g/m ² , and laminate the side of the flame retardant outer fabric coated with polyurethane adhesive to the flame retardant inner fabric, and hot press at a pressure of 0.15 MPa and a temperature of 100° C. for 30 seconds to obtain a multi-layer flame retardant composite fabric based on pre-oxidized silk fibers.

Comparative Example 2

This comparative example discloses a method for preparing a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers, comprising the following steps:

Step 1: blending preoxidized silk fiber, modified cotton fiber and aramid fiber in a mass ratio of 30:30:40 to obtain a blended yarn with a yarn count of 40S in British standard; using the blended yarn as warp and weft for weaving to obtain an outer fabric with a gram weight of 140 g/ ^m2 and an inner fabric with a gram weight of 120 g/ ^m2 respectively;

The pre-oxidized silk fiber is prepared by the following steps:

Step (1), graphene oxide, toluene-2,4-diisocyanate, and N,N-dimethylformamide are mixed, ultrasonically dispersed for 20 minutes, stirred and reacted in a nitrogen atmosphere at 70°C for 26 hours, and after the reaction is completed, polypropylene glycol is added, and the reaction is continued in a nitrogen atmosphere at 70°C for 24 hours. After the reaction is completed, the mixture is cooled to room temperature to obtain a reaction product, and acetone twice the mass of the reaction product is added for precipitation, centrifuged, filtered, and the filter cake is taken, and acetone five times the mass of the filter cake is added for washing three times, and dried at 40°C for 28 hours to obtain a graphene oxide-polypropylene glycol composite material; the mass ratio of graphene oxide, toluene-2,4-diisocyanate, N,N-dimethylformamide, and polypropylene glycol is 18:28:280:48;

Step (2), mixing the graphene oxide-polypropylene glycol composite material with dimethyl sulfoxide, ultrasonically dispersing, adding polyacrylonitrile solution, wherein the mass ratio of the graphene oxide-polypropylene glycol composite material, dimethylformamide, and polyacrylonitrile solution is 1.5:40:450, stirring at 60° C. for 8 hours, and after stirring, standing to room temperature, degassing, and obtaining a modified polyacrylonitrile spinning solution; wherein the polyacrylonitrile solution is prepared by mixing and dissolving polyacrylonitrile and dimethyl sulfoxide in a mass ratio of 1:3.5;

The modified polyacrylonitrile spinning solution is wet-spun to obtain polyacrylonitrile fiber precursor with a fineness of 1.8D; the polyacrylonitrile precursor is pre-oxidized and chopped to obtain pre-oxidized fiber with a fiber length of 51 mm;

The wet spinning operation includes: spinning with a wet spinning machine, using a 40 vol% dimethyl sulfoxide aqueous solution as a coagulation bath, solidifying at 60° C., stretching at a draft multiple of 8 times, washing with a 40 vol% dimethyl sulfoxide aqueous solution, and drying at 40° C. for 24 hours;

The pre-oxidation operation includes: in an air atmosphere, pre-oxidation treatment is carried out at 200°C, 220°C, 240°C, and 260°C in sequence, and after reaching the set temperature each time, the pre-oxidation treatment is kept at the temperature for 20 minutes; the draft ratio of the pre-oxidation treatment at 200°C and 220°C is 4%, and the draft ratio of the pre-oxidation treatment at 240°C and 260°C is 0%;

Wherein, the preparation of modified cotton fiber is the same as that in Example 1;

Step 2: Double-sided coating of the outer fabric and the inner fabric with flame-retardant coating material, forming flame-retardant coatings on both sides of the outer fabric and the inner fabric, respectively, with a thickness of 0.2 mm. After coating, light curing is performed for 1.5 min under a radiation intensity of 28 mW/ ^cm2 to obtain flame-retardant outer fabric and flame-retardant inner fabric respectively;

The flame retardant coating material is prepared by the following steps:

Step (1), γ-(2,3-epoxypropoxy)propyltrimethoxysilane, DOPO, and methyl ethyl ketone are mixed in a mass ratio of 1:10:250, and reacted at 60°C for 8 hours. After the reaction, the solvent methyl ethyl ketone is removed by rotary evaporation at 70°C to obtain a reaction product, and acetone of 5 times the mass of the reaction product is added to wash three times, and dried at 90°C for 4 hours to obtain a modified DOPO;

Step (2), mixing toluene-2,4-diisocyanate and hydroxyethyl acrylate, reacting for 2 hours in a nitrogen atmosphere at 50° C., adding modified DOPO and dibutyltin dilaurate, reacting for 4 hours at room temperature, and obtaining a flame retardant after the reaction; the mass ratio of toluene-2,4-diisocyanate, hydroxyethyl acrylate, modified DOPO, and dibutyltin dilaurate is 16:11:0.7:0.05;

Step (3), uniformly mixing the flame retardant, polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, photoinitiator, and defoamer in a mass ratio of 25:50:8:5:4:3:1 to obtain a flame retardant coating material;

Step 3: Coat one side of the flame retardant outer fabric with polyurethane adhesive at a coating amount of 20 g/m ² , and laminate the side of the flame retardant outer fabric coated with polyurethane adhesive to the flame retardant inner fabric, and hot press at a pressure of 0.15 MPa and a temperature of 100° C. for 30 seconds to obtain a multi-layer flame retardant composite fabric based on pre-oxidized silk fibers.

In the above embodiments and comparative examples: cotton fiber is Xinjiang long-staple cotton, with a fiber length of 38-39 mm; aramid fiber comes from DuPont, USA, with a product name of aramid 1313 short fiber, a fineness of 2D, and a fiber length of 30 mm; graphene oxide comes from Hubei Maidehao Chemical Co., Ltd., with a diameter of 1 μm and a thickness of 0.8 nm; polypropylene glycol comes from Sinopharm Chemical Reagent Co., Ltd., with an average molecular weight of 400, CAS number: 25322-69-4; polyacrylonitrile comes from Shanghai Aladdin Biochemical Technology Co., Ltd., with a product number of P303200, Mw=85000, CAS number: 25014-41-9; silica aerogel microspheres come from Xi'an Haoran Biotechnology Co., Ltd., with a product name of nanoporous SiO ₂ aerogel microspheres, item number: SNJ-1301; DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) is from Wuhan Kemik Biomedical Technology Co., Ltd., CAS number: 35948-25-5; polyurethane acrylate is from Guangdong Wengjiang Chemical Reagent Co., Ltd., item number PB07265; glycidyl methacrylate is from Guangdong Wengjiang Chemical Reagent Co., Ltd., CAS number: 106-91-2; photoinitiator is from Guangdong Wengjiang Chemical Reagent Co., Ltd., model photoinitiator 1173, CAS number: 7374-98-5; defoamer is from AFCONA, model defoamer AFCONA2502; polyurethane adhesive is from Qingdao Ruikos New Material Technology Co., Ltd., model PU1179.

Test example

As shown in Figures 3-4, comprehensive performance tests were conducted on the multi-layer flame retardant composite fabrics based on pre-oxidized silk fibers prepared in Examples 1-5 and Comparative Examples 1-3. Specific test results are shown in Table 1:

Table 1

Limiting oxygen index (%) Afterburning time (s) Smoldering time (s) Damaged length (mm) Temperature difference (℃) Example 1 36.7 0 0 68.1 3.8 Example 2 37.1 0 0 67.5 3.8 Example 3 37.4 0 0 66.9 3.9 Example 4 37.8 0 0 66.2 3.9 Example 5 38.1 0 0 65.5 4.0 Comparative Example 1 29.2 4.9 0 86.2 3.6 Comparative Example 2 35.8 0 0 70.1 1.2

The detection of each index in Table 1 is based on the following standards: the limiting oxygen index is measured by GB/T5454 "Textile Combustion Performance Test-Oxygen Index Method"; the afterflaming time, smoldering time and damaged length are measured by GB/T 5455 "Textile Combustion Energy Test-Vertical Method"; the test method for thermal insulation performance is: the multi-layer flame retardant composite fabric based on pre-oxidized silk fiber prepared in Examples 1-5 and Comparative Examples 1-3 is placed on the heating platform of a thermocouple thermometer, the fabric is heated to 40°C, and the temperature difference between the front and back of the fabric is tested.

The present invention grafts silica aerogel microspheres with a silane coupling agent containing an epoxy group to obtain epoxy-modified silica aerogel microspheres, which are subjected to a ring-opening reaction with DOPO to obtain functionalized silica aerogel microspheres having a DOPO flame-retardant structure and a hydroxyl group. After toluene-2,4-diisocyanate is subjected to an esterification reaction with hydroxyethyl acrylate, the remaining isocyanate groups are further subjected to an esterification reaction with the hydroxyl groups of the functionalized silica aerogel microspheres to obtain a flame retardant having a carbon-carbon double bond group, which can be mixed with polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, and other additives to be used as a flame-retardant coating material, which is attached to fabrics after coating and curing to improve the flame retardant properties of the fabrics. Among them, the flame retardant contains three elements, phosphorus, nitrogen and silicon, which can synergistically flame retardant and further improve the flame retardancy of the fabric; silica aerogel microspheres are a spherical aerogel material that can improve the thermal insulation capacity of the fabric, which is specifically reflected in the thermal insulation performance test. The side of the fabric away from the heating platform is the upper surface, and the side of the fabric in contact with the heating platform is the lower surface. During the heating process, the temperature of the upper surface of the fabric is always lower than the temperature of the lower surface of the fabric. There is a temperature difference between the two. The greater the temperature difference, the better the thermal insulation performance of the fabric. The silica aerogel microspheres in the flame-retardant coating material of Comparative Example 1 are not surface modified, and the coating does not have the three elements of phosphorus, nitrogen and silicon to synergistically flame retardant, so the flame retardancy of the fabric is reduced. At the same time, due to the decrease in the dispersibility of the silica aerogel microspheres in the coating, the thermal insulation performance is slightly reduced.

No silica aerogel microspheres are added to the flame retardant coating material of Comparative Example 2. Although other components in the flame retardant still play a flame retardant role, the flame retardant performance improvement and heat insulation effect of the silica aerogel microspheres are lacking. Therefore, the flame retardant performance of Comparative Example 2 is slightly reduced, and the heat insulation performance is lower than that of the embodiment.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims (7)

1. A method for preparing a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers, characterized in that it comprises the following steps: Step 1: blending preoxidized silk fiber, modified cotton fiber and aramid fiber to obtain blended yarn; using the blended yarn as warp and weft to weave to obtain outer fabric and inner fabric respectively; The pre-oxidized silk fiber is prepared by the following steps: The graphene oxide, toluene-2,4-diisocyanate and N,N-dimethylformamide are mixed, ultrasonically dispersed, stirred for reaction, and polypropylene glycol is added after the reaction is completed to continue the reaction. After the reaction is completed, the reaction product is cooled to room temperature to obtain a reaction product, precipitated, centrifuged, filtered, washed, and dried to obtain a graphene oxide-polypropylene glycol composite material; the mass ratio of graphene oxide, toluene-2,4-diisocyanate, N,N-dimethylformamide, and polypropylene glycol is 18-22:28-32:280-340:48-52; the stirring reaction conditions are: stirring the reaction in a nitrogen atmosphere at a temperature of 70-80°C for 20-26h; the continued reaction conditions are: continuing the reaction in a nitrogen atmosphere at a temperature of 70-80°C for 22-24h; The graphene oxide-polypropylene glycol composite material is mixed with dimethyl sulfoxide, ultrasonically dispersed, and a polyacrylonitrile solution is added, stirred, and then allowed to stand for degassing to obtain a modified polyacrylonitrile spinning solution; the modified polyacrylonitrile spinning solution is wet-spinned to obtain polyacrylonitrile fiber precursor; the polyacrylonitrile precursor is pre-oxidized and chopped to obtain pre-oxidized fiber; Wherein, the modified cotton fiber is prepared by the following steps: Cotton fiber, potassium persulfate and water are mixed and pretreated. After the pretreatment, methacrylamide is added and reacted. After the reaction, the modified cotton fiber is filtered, washed and dried to obtain the modified cotton fiber. The mass ratio of cotton fiber, potassium persulfate, methacrylamide and water is 4-5:0.1-0.15:2-2.5:100-120. The pretreatment conditions are: pretreatment at 70-80°C for 20-30 minutes. The reaction conditions are: reaction at 70-80°C for 1-2 hours. Step 2: Double-sided coating of the outer fabric and the inner fabric with a flame-retardant coating material to form flame-retardant coatings on both sides of the outer fabric and the inner fabric, respectively; after coating, light curing is performed to obtain a flame-retardant outer fabric and a flame-retardant inner fabric, respectively; The flame retardant coating material is prepared by the following steps: The silica aerogel microspheres are mixed with toluene, ultrasonically dispersed, γ-(2,3-epoxypropoxy)propyltrimethoxysilane is added, reacted, filtered, washed, and dried after the reaction is completed to obtain epoxy silica aerogel microspheres; the epoxy silica aerogel microspheres, DOPO, and methyl ethyl ketone are mixed, reacted, after the reaction is completed, the solvent methyl ethyl ketone is removed by rotary evaporation to obtain a reaction product, washed, and dried to obtain functionalized silica aerogel microspheres; The mass ratio of silica aerogel microspheres, toluene, and γ-(2,3-epoxypropoxy)propyltrimethoxysilane is 2:50-60:0.8-1; when preparing epoxy silica aerogel microspheres, the reaction conditions are: reacting at 95-105°C for 8-10h; the mass ratio of epoxy silica aerogel microspheres, DOPO, and methyl ethyl ketone is 2.6-2.8:10-10.5:250-280; when preparing functionalized silica aerogel microspheres, the reaction conditions are: reacting at 60-70°C for 7-8h; Toluene-2,4-diisocyanate and hydroxyethyl acrylate are mixed and reacted. After the reaction is completed, functionalized silica aerogel microspheres and dibutyltin dilaurate are added and the reaction is continued. After the reaction is completed, a flame retardant is obtained; The mass ratio of toluene-2,4-diisocyanate, hydroxyethyl acrylate, functionalized silica aerogel microspheres, and dibutyltin dilaurate is 16-17:11-12:1.5-2:0.05-0.06; the reaction conditions are: reacting at 50-60°C for 1-2h in a nitrogen atmosphere; the continued reaction conditions are: continuing the reaction at room temperature for 4-5h; The flame retardant, polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, a photoinitiator, and a defoamer are uniformly mixed to obtain a flame retardant coating material; Step 3: Compound the flame-retardant outer layer fabric and the flame-retardant inner layer fabric by adhesive, and perform hot pressing to obtain a multi-layer flame-retardant composite fabric based on pre-oxidized silk fibers. 2. A method for preparing a multi-layer flame-retardant composite fabric based on preoxidized silk fiber according to claim 1, characterized in that in said step 1: the mass ratio of preoxidized silk fiber, modified cotton fiber and aramid fiber is 30-40:20-30:40; the yarn count of the blended yarn is 40-60S in British system; the gram weight of the outer layer fabric is 140-160g/m ² ; the gram weight of the inner layer fabric is 120-140g/m ² . 3. A method for preparing a multilayer flame-retardant composite fabric based on pre-oxidized silk fibers according to claim 1, characterized in that in the preparation of the pre-oxidized silk fibers in step 1: the mass ratio of the graphene oxide-polypropylene glycol composite material, dimethyl sulfoxide, and polyacrylonitrile solution is 1.5-2:40-50:450-460, and the polyacrylonitrile solution is prepared by mixing and dissolving polyacrylonitrile and dimethyl sulfoxide in a mass ratio of 1:3.5; the stirring conditions are: stirring at a temperature of 60-70°C for 6-8h; The wet spinning operation includes: spinning with a wet spinning machine, using a 40 vol% dimethyl sulfoxide aqueous solution as a coagulation bath, solidifying at 60°C, drawing at a draft multiple of 8-10 times, washing with a 40 vol% dimethyl sulfoxide aqueous solution, and drying at 40-50°C for 20-24 hours; the fineness of the polyacrylonitrile fiber precursor is 1.8-2D; The pre-oxidation operation includes: in an air atmosphere, pre-oxidation treatment is carried out at temperatures of 200-210°C, 220-230°C, 240-250°C, and 260-270°C in sequence, and after reaching the set temperature each time, the pre-oxidation treatment is kept warm for 15-20 minutes; the stretching ratio of the pre-oxidation treatment at 200-210°C and 220-230°C is 4-6%, and the stretching ratio of the pre-oxidation treatment at 240-250°C and 260-270°C is 0%. 4. According to claim 1, a method for preparing a multi-layer flame-retardant composite fabric based on pre-oxidized silk fiber is characterized in that in the step 2: the thickness of the flame-retardant coating is 0.2-0.3 mm; the photocuring conditions are: photocuring for 1-1.5 min under an irradiation intensity of 28-36 mW/ ^cm2 . 5. According to the method for preparing a multi-layer flame-retardant composite fabric based on pre-oxidized silk fiber in claim 1, it is characterized in that in the preparation of the flame-retardant coating material in step 2: the mass ratio of flame retardant, polyurethane acrylate, trimethylolpropane triacrylate, glycidyl methacrylate, vinyl triethoxysilane, photoinitiator, and defoaming agent is 25-30:45-50:8-10:5-8:4-5:3-4:1. 6. The method for preparing a multi-layer flame-retardant composite fabric based on pre-oxidized silk fiber according to claim 1 is characterized in that in the step three: the hot pressing conditions are: hot pressing at a pressure of 0.15-0.2MPa and a temperature of 100-110°C for 25-30s. 7. A multi-layer flame retardant composite fabric based on pre-oxidized silk fibers prepared by the method for preparing a multi-layer flame retardant composite fabric based on pre-oxidized silk fibers as described in any one of claims 1 to 6.