Bio-based flame retardant modified lyocell fabric and method of making the same

Abstract

The application belongs to the technical field of lyocell fabric modification, and particularly relates to an epoxy-based crosslinking agent, a bio-based flame retardant modified lyocell fabric and a preparation method and application thereof. The application designs and synthesizes a multi-arm epoxy-based crosslinking agent with a star block structure, the center of which is a ring-shaped polysiloxane, the side arms of which include hydrophobic PO segments and hydrophilic EO segments connected with the ring-shaped polysiloxane, and the last end of the side arms is an epoxy group, which is combined with lysine and phytic acid for lyocell fabric treatment. The EO segments in the multi-arm epoxy-based crosslinking agent can form a hydrogen bond network with N-H, O-H or P-OH in phytic acid or lysine as a hydrogen bond acceptor, the epoxy group can react with P-OH, -NH2 or -COOH to form a chemical bond under baking at 75 DEG C, and further firmly combine with the lysine layer or the phytic acid layer. At the same time, the multi-arm epoxy-based crosslinking agent hydrophobic region forms a barrier to reduce the penetration of water molecules during washing.

Description

Technical Field

[0001] This application relates to the field of lyocell fabric modification technology, and in particular to a lyocell fabric modified with an epoxy crosslinking agent and a bio-based flame retardant, as well as its preparation method and application. Background Technology

[0002] Lyocell fiber is a regenerated cellulose fiber that combines comfort, softness, and ease of dyeing. Its raw material, cellulose, is abundant in nature, and its production process is environmentally friendly, aligning with current green development principles. Furthermore, lyocell fiber possesses a unique microfiber structure, offering excellent moisture wicking and comfort, making it widely used in clothing and home textiles. However, lyocell fiber has a limiting oxygen index (LOI) of approximately 18%, classifying it as a flammable material and posing a significant fire hazard. Therefore, endowing lyocell fiber with flame-retardant properties is an effective way to address this issue.

[0003] In existing technologies, the main methods for flame-retardant modification of lyocell fibers include blending spinning and finishing processes. Blending spinning involves directly mixing a suitable flame retardant with the spinning solution, passing it through a spinneret into a coagulation bath, and then drawing it to prepare flame-retardant fibers. This method requires good dispersibility and compatibility of the flame retardant in the spinning solution, and the amount added must be strictly controlled; excessive amounts will degrade the fiber's mechanical properties and affect the spinnability of the spinning solution. The finishing solution in the finishing process consists of multiple components, including flame retardants, catalysts, crosslinking agents, and curing agents. To achieve durable flame retardancy, melamine-formaldehyde resin and reactive organophosphorus N-hydroxymethyldimethylphosphonopropionamide are widely used. However, these compounds easily release formaldehyde during baking and curing, posing a serious health hazard when used in the clothing and home textile industries, potentially inducing skin cancer and respiratory diseases. Using polycarboxylic acid crosslinking agents, such as citric acid, can avoid the formaldehyde release problem, but strong acidic crosslinking agents like citric acid can reduce fiber strength and affect the hand feel of lyocell fiber fabrics. Without cross-linking agents, lyocell fabrics exhibit a significant decrease in flame retardancy after repeated washing. Therefore, developing formaldehyde-free, highly efficient, and durable bio-based flame retardants specifically for lyocell fabrics is imperative. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application designs and synthesizes a multi-arm epoxy crosslinking agent with a star-shaped block structure. The center is a cyclic polysiloxane, and the side arms include hydrophobic PO segments and hydrophilic EO segments connected to the cyclic polysiloxane. The end of the side arms is an epoxy group. When used in combination with lysine and phytic acid for the treatment of Lyocell fabric, it can improve the flame retardant properties and washability of Lyocell fabric while maintaining the fabric's mechanical properties.

[0005] To achieve the above technical objectives, the technical solution adopted in this application is as follows: In a first aspect, an epoxy crosslinking agent has a molecular structure comprising a core and side arms; wherein the core is a cyclic polysiloxane, and the side chains include polyoxypropylene (PO) segments and polyoxyethylene (EO) segments, the polyoxypropylene segments being connected to the core via R1 groups, and the polyoxyethylene segments being connected to the epoxy groups at the ends of the polyoxypropylene segments and the side arms. The general structural formula of the corresponding epoxy crosslinking agent is shown below. ; The side arms are connected to the core in sequence; The number of side chains is ≥3, that is, a≥3; Preferably, the number of side chains is 3-5, i.e., a = 3-5; b≥1; c≥1; The RO group is selected from methyl or phenyl; The R1 group is selected from alkyl groups having 2-20 carbon atoms; Preferably, the R1 group is selected from alkyl groups with 2-6 carbon atoms.

[0006] Secondly, the preparation method of the epoxy crosslinking agent described above includes obtaining it by hydrosilylation reaction of the vinyl block polymer and the cyclic hydrogen-containing silane described below. The cyclic hydrogen-containing silane is selected from methylhydrocyclosiloxane or phenylhydrocyclosiloxane; Preferably, the cyclic hydrogen-containing silane is selected from at least one of 2,4,6-trimethylcyclotrisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, and 2,4,6,8,10-pentamethylcyclopentasiloxane; More preferably, the methylhydrocyclosiloxane is selected from 1,3,5,7-tetramethylcyclotetrasiloxane; The molar ratio of vinyl groups in the vinyl block polymer to Si-H groups in the cyclic hydrogen-containing silane is (1-1.2):1; The general structural formula of the vinyl block copolymer is: ; Where R2 is selected from -H or -CH3; b≥1; c≥1 Preferably, the hydrosilylation reaction uses a platinum catalyst selected from Pt-vinylsiloxane complexes (Karstedt catalysts) or Pt-cycloolefin complexes (Ashby catalysts); Preferably, the reaction temperature of the hydrosilylation reaction is 80-120°C.

[0007] Thirdly, the use of the epoxy crosslinking agent described above in the surface treatment modification of cellulose fabrics.

[0008] Fourthly, a bio-based flame retardant modified Lyocell fabric is obtained by sequentially impregnating the Lyocell fabric with an aqueous solution of lysine, an aqueous solution of phytic acid, and an aqueous solution of the epoxy crosslinking agent described above. The lysine is selected from at least one of L-lysine, D-lysine, and racemic lysine; Furthermore, the Lyocell fabric is obtained by sequentially impregnating it with an aqueous solution of lysine, an aqueous solution of phytic acid, an aqueous solution of lysine, and an aqueous solution of the epoxy crosslinking agent described above. Fifthly, the preparation method of the bio-based flame retardant modified Lyocell fabric mentioned above includes: the Lyocell fabric is sequentially impregnated with lysine aqueous solution and dried at room temperature, impregnated with phytic acid aqueous solution and dried at room temperature, and impregnated with epoxy crosslinking agent aqueous solution and baked to obtain the finished fabric. The concentration of the lysine aqueous solution is 4-10 g / L; The concentration of the phytic acid aqueous solution is 1-3 g / L; The concentration of the aqueous solution of the epoxy crosslinking agent is 10-40 g / L; The baking temperature is 60-90℃; the baking time is 1-20 minutes. Preferably, the soaking time for the lysine aqueous solution is 3-10 minutes; Preferably, the immersion time in the phytic acid aqueous solution is 0.5-2 minutes; Preferably, the immersion time in the aqueous solution of the epoxy crosslinking agent is 3-10 minutes.

[0009] Sixthly, the application of the bio-based flame retardant modified Lyocell fabrics described above in underwear, workwear, and home textiles.

[0010] The beneficial effects of the technical solution proposed above in this application are as follows: This application designs and synthesizes a multi-arm epoxy crosslinking agent with a star-shaped block structure. The center is a cyclic polysiloxane, and the side arms include hydrophobic PO segments and hydrophilic EO segments connected to the cyclic polysiloxane. The end of the side arms is an epoxy group, which is used in combination with lysine and phytic acid for the treatment of Lyocell fabrics. The EO segments in the multi-arm epoxy crosslinking agent act as hydrogen bond acceptors and can form a hydrogen bond network with NH, OH, or P-OH in phytic acid or lysine. The epoxy groups can react with P-OH, -NH2, or -COOH under baking at 75°C to form chemical bonds, further firmly binding with the lysine layer or phytic acid layer. At the same time, the hydrophobic regions of the multi-arm epoxy crosslinking agent (including the cyclic polysiloxane and PO segments) form a barrier, reducing the penetration of water molecules during washing. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application and to more completely understand this application and its beneficial effects, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 The attenuated total reflectance Fourier transform infrared spectrum of the multi-arm epoxy crosslinking agent prepared in Example 1. Detailed Implementation

[0013] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present invention. It should be noted that the terminology used herein is only for describing specific implementation methods and is not intended to limit the exemplary implementation methods according to the present invention.

[0014] Unless otherwise specified, the experimental conditions used in the examples are generally in accordance with conventional conditions in the art or the conditions recommended by the reagent company. Unless otherwise specified, the materials and reagents used in the examples can be purchased commercially.

[0015] Unless otherwise stated or in case of contradiction, the terms or phrases used herein shall have the following meanings: The terms "and / or," "or / and," and "and / or" as used herein include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. It should be noted that when at least three items are connected by at least two conjunctions selected from "and / or," "or / and," and "and / or," it should be understood that in this application, the technical solution undoubtedly includes technical solutions connected by "logical AND," and also undoubtedly includes technical solutions connected by "logical OR." For example, "A and / or B" includes three parallel solutions: A, B, and A+B. For example, the technical solution of "A, and / or, B, and / or, C, and / or, D" includes any one of A, B, C, and D (that is, a technical solution that is connected by "logical OR"), as well as any and all combinations of A, B, C, and D, that is, combinations of any two or three of A, B, C, and D, and also combinations of all four of A, B, C, and D (that is, a technical solution that is connected by "logical AND").

[0016] In this application, the terms "multiple", "various", "multiple times", "multi-dimensional", etc., unless otherwise specified, refer to a quantity greater than or equal to 2. For example, "one or more" means one or more than or equal to two.

[0017] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it means that it is selected from either "with" or "without." If there are multiple "optional" entries in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, each "optional" entry shall be independent.

[0018] In this application, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions composed of the listed features. Example 1

[0019] The multi-arm epoxy crosslinking agent was synthesized by hydrosilylation reaction using 1,3,5,7-tetramethylcyclotetrasiloxane and allyl-PO-EO-epoxy ether as raw materials.

[0020] 135g of allyl-PO-EO-epoxy ether H-300 (Hangzhou Kecheng Chemical) and 80mL of xylene were added to a three-necked flask. The mixture was heated to 95℃ with stirring, and a mixture of 24g (0.1mol) of 1,3,5,7-tetramethylcyclotetrasiloxane, 0.1g of Karstedt catalyst, and 60mL of xylene was added dropwise. The reaction temperature was controlled at 95℃, and the addition was completed over 2 hours. The reaction was then maintained at this temperature for 3 hours. The reaction was then stopped, the temperature was lowered, and the solvent was removed by vacuum distillation at 0.01MPa and 70℃. 8g of 200-mesh activated carbon powder was added, and the mixture was stirred at 60℃ for 4 hours. The filtrate was then collected as the product and dispersed in a high-speed disperser at 1200rpm. The product was diluted with deionized water to 20g / L for later use. The infrared spectrum of the multi-arm epoxy crosslinking agent is shown below. Figure 1 As shown, 2960cm -1 The vicinity is characterized by the asymmetric stretching vibration of CH in -CH3, at 2930 cm⁻¹. -1 The vicinity of 2870 cm⁻¹ shows asymmetric stretching vibrations of CH in -CH₂-, while the vicinity of 1130 cm⁻¹ shows symmetric stretching vibrations of CH in -CH₃ and -CH₂-. -1 The nearby peak is the stretching vibration peak of COC, at 1020 cm⁻¹. -1 The vicinity shows the stretching vibration peaks of Si-O-Si, 910-920 cm⁻¹. -1 The characteristic absorption peak of the epoxy group is located at 1600-1680 cm⁻¹. -1 The absence of a distinct absorption peak indicates that the double bond has undergone complete hydrosilylation reaction. Example 2

[0021] The multi-arm epoxy crosslinking agent was synthesized by hydrosilylation reaction using 1,3,5,7-tetramethylcyclotetrasiloxane and allyl-PO-EO-epoxy ether as raw materials.

[0022] 225g of allyl-PO-EO-epoxy ether H-500 (Hangzhou Kecheng Chemical) and 120mL of xylene were added to a three-necked flask. The mixture was heated to 95℃ with stirring, and a mixture of 24g (0.1mol) of 1,3,5,7-tetramethylcyclotetrasiloxane, 0.12g of Karstedt catalyst, and 60mL of xylene was added dropwise. The reaction temperature was maintained at 95℃, and the addition was completed over 2 hours. The reaction was then maintained at this temperature for 3 hours. The reaction was then stopped, the temperature was lowered, and the solvent was removed by vacuum distillation at 0.01MPa and 70℃. 12g of 200-mesh activated carbon powder was added, and the mixture was stirred at 60℃ for 4 hours. The filtrate was then collected as the product and dispersed in a high-speed disperser at 1200rpm. The product was then diluted with deionized water to 20g / L for later use. Example 3

[0023] The multi-arm epoxy crosslinking agent was synthesized by hydrosilylation reaction using 1,3,5,7-tetramethylcyclotetrasiloxane and allyl-PO-EO-epoxy ether as raw materials.

[0024] 315g of allyl-PO-EO-epoxy ether H-700 (Hangzhou Kecheng Chemical) and 160mL of xylene were added to a three-necked flask. The mixture was heated to 95℃ with stirring, and a mixture of 24g (0.1mol) of 1,3,5,7-tetramethylcyclotetrasiloxane, 0.12g of Karstedt catalyst, and 60mL of xylene was added dropwise. The reaction temperature was maintained at 95℃, and the addition was completed over 2 hours. The reaction was then maintained at this temperature for 3 hours. The reaction was then stopped, the temperature was lowered, and the solvent was removed by vacuum distillation at 0.01MPa and 70℃. 17g of 200-mesh activated carbon powder was added, and the mixture was stirred at 60℃ for 4 hours. The filtrate was then collected as the product and dispersed in a high-speed disperser at 1200rpm. The product was then diluted with deionized water to 20g / L for later use. Example 4

[0025] The desized Lyocell plain weave fabric has a specification of 30×30 English count / 93×75 threads / inch and an areal density of 140 g / m². 2Before finishing, the fabric was first soaked in deionized water at 50°C for 2 hours and then dried in a forced-air drying oven at 35°C for 24 hours. The Lyocell fabric was then soaked in L-lysine solution (6.3 g / L) for 5 minutes, gently rolled to remove excess solution, and dried at room temperature. Next, it was soaked in phytic acid solution (2.4 g / L) for 1 minute, gently rolled to remove excess solution, and dried at room temperature. Finally, it was soaked in 20 g / L of the multi-arm epoxy crosslinking agent prepared in Example 1 for 10 minutes, gently rolled to remove excess solution, and baked at 75°C for 5 minutes to obtain the flame-retardant Lyocell fabric after surface finishing. Example 5

[0026] The specifications and pretreatment method of the Lyocell fabric are the same as in Example 4. The Lyocell fabric is immersed in L-lysine solution (6.3 g / L) for 5 min, the excess solution is removed by light roller pressing and dried at room temperature, then immersed in phytic acid solution (2.4 g / L) for 1 min, the excess solution is removed by light roller pressing and dried at room temperature, the immersion in L-lysine solution (6.3 g / L) for 5 min is continued, the excess solution is removed by light roller pressing and dried at room temperature, and finally immersed in 20 g / L of the multi-arm epoxy crosslinking agent prepared in Example 1 for 10 min, the excess solution is removed by light roller pressing and baked at 75°C for 5 min to obtain the flame-retardant Lyocell fabric after surface finishing. Example 6

[0027] The treatment method is the same as in Example 4, except that the Lyocell fabric is soaked with the multi-arm epoxy crosslinking agent prepared in Example 2, and the concentration is maintained at 20 g / L. Example 7

[0028] The treatment method is the same as in Example 5, except that the Lyocell fabric is soaked with the multi-arm epoxy crosslinking agent prepared in Example 2, and the concentration is maintained at 20 g / L. Example 8

[0029] The treatment method is the same as in Example 4, except that the Lyocell fabric is soaked with the multi-arm epoxy crosslinking agent prepared in Example 3, and the concentration is maintained at 20 g / L. Example 9

[0030] The treatment method is the same as in Example 5, except that the Lyocell fabric is soaked with the multi-arm epoxy crosslinking agent prepared in Example 3, and the concentration is maintained at 20 g / L.

[0031] Comparative Example 1 The specifications and pretreatment method of the Lyocell fabric are the same as in Example 4. The Lyocell fabric is immersed in L-lysine solution (6.3 g / L) for 5 min, the excess solution is removed by light roller pressing and dried at room temperature, and finally immersed in 20 g / L of the multi-arm epoxy crosslinking agent prepared in Example 1 for 10 min, the excess solution is removed by light roller pressing and baked at 75°C for 5 min to obtain the flame-retardant Lyocell fabric after surface finishing.

[0032] Comparative Example 2 The specifications and pretreatment method of the Lyocell fabric are the same as in Example 4. The Lyocell fabric is immersed in phytic acid solution (2.4 g / L) for 1 min, the excess solution is removed by light roller pressing and dried at room temperature, and then immersed in L-lysine solution (6.3 g / L) for 5 min. The excess solution is removed by light roller pressing and dried at room temperature. Finally, it is immersed in 20 g / L of the multi-arm epoxy crosslinking agent prepared in Example 1 for 10 min, the excess solution is removed by light roller pressing and baked at 75°C for 5 min to obtain the flame-retardant Lyocell fabric after surface finishing.

[0033] Comparative Example 3 The specifications and pretreatment method of the Lyocell fabric are the same as in Example 4. The Lyocell fabric is soaked in L-lysine solution (6.3g / L) for 5 minutes, the excess solution is removed by light roller pressing and dried at room temperature, and then soaked in phytic acid solution (2.4g / L) for 1 minute. The excess solution is removed by light roller pressing and dried at room temperature. Finally, it is soaked in L-lysine solution (6.3g / L) for 5 minutes, the excess solution is removed by light roller pressing and baked at 75°C for 5 minutes to obtain the flame-retardant Lyocell fabric after surface finishing.

[0034] Test section Mechanical performance testing: The flame-retardant lyocell fabric prepared above was tested for breaking strength and elongation at break according to ASTM D5035-11 (2015) standard. The fabric was cut into strips of 100mm×25mm, with a clamping distance of 50mm and a stretching rate of 20mm / min.

[0035] Washability and flame retardancy were tested according to ISO 6330:2021, section 4A, in a horizontal drum washing machine. The flame retardancy of fabric samples was tested after no washing, 5 washes, and 15 washes. Flame retardancy was tested according to ASTM D 1230-95 (2001). Five samples were used for each example or comparative example, with the burning time and char length recorded for each sample.

[0036] The experimental data above are recorded in Table 1.

[0037] Table 1

[0038] Analysis of the data in Table 1 shows that in Examples 4, 6, and 8, Lyocell fabric was soaked in lysine, phytic acid, and the multi-arm epoxy crosslinking agent prepared in Examples 1-3 in sequence. In Examples 5, 7, and 9, Lyocell fabric was soaked in lysine, phytic acid, lysine, and the multi-arm epoxy crosslinking agent prepared in Examples 1-3 in sequence. This resulted in Lyocell fabric with excellent flame retardant properties, which can maintain excellent flame retardant effect after 5-15 washes, and also takes into account mechanical properties.

[0039] Among them, the larger the molecular weight of the side chain of the multi-arm epoxy crosslinking agent, the more flexible the fabric is, and the slightly lower the breaking strength. The secondary impregnation of lysine has basically no negative impact on mechanics and can optimize flame retardancy while maintaining the strength of lyocell fabric. Examples 4-9 use the multi-arm epoxy crosslinking agent prepared in Examples 1-3 as the final impregnation solution. It can crosslink with lysine or phytic acid itself. Lysine first adsorbs firmly onto the surface of lyocell fabric through hydrogen bonding and electrostatic interaction to form a positively charged base layer. Then, phytic acid with high negative charge content and a large number of phosphate hydroxyl groups is combined with the lysine layer through multiple hydrogen bonds and strong electrostatic attraction. Subsequently, the multi-arm epoxy crosslinking agent can be directly impregnated. Through the multiple hydrogen bonding of EO segments and the chemical bonds formed by the reaction of epoxy groups with P-OH in phytic acid, the multi-arm epoxy crosslinking agent is firmly bound to the phytic acid layer (Examples 4, 6, 8). Alternatively, after impregnating the lysine layer, the multi-arm epoxy crosslinking agent is impregnated last. The epoxy groups react with the amino or carboxyl groups in lysine and can also be firmly bound to the lysine layer (Examples 5, 7, 9). Multi-arm epoxy crosslinking agents possess a star-shaped block structure. The center is a cyclic polysiloxane, and the side arms consist of hydrophobic PO segments and hydrophilic EO segments connected to the cyclic polysiloxane. The terminal of each side arm is an epoxy group. The EO segment acts as a hydrogen bond acceptor, forming a hydrogen bond network with NH, OH, or P-OH groups in phytic acid or lysine. The epoxy group, when baked at 75°C, reacts with P-OH, -NH2, or -COOH to form chemical bonds, further strengthening the bond with the lysine or phytic acid layer. Simultaneously, the hydrophobic regions of the multi-arm epoxy crosslinking agent (including the cyclic polysiloxane and PO segments) form a barrier, reducing the penetration of water molecules during washing.

[0040] Comparative Example 1 did not use phytic acid, but used lysine and multi-arm epoxy crosslinking agent as flame retardants alone. The flame retardant combination lacked a phosphorus source, and the nitrogen source alone had weak char-forming catalytic ability, which could not efficiently promote the dehydration and carbonization of lyocell cellulose. The effect of isolating oxygen and heat was insufficient, the material was easy to ignite, and the char residue size was significantly higher.

[0041] Comparative Example 2 first brought phytic acid into contact with Lyocell fabric. Phytic acid contains multiple phosphate groups and its aqueous solution is strongly acidic. The cellulose glycosidic bonds in Lyocell fabric are sensitive to acid. Under acidic conditions, acid-catalyzed hydrolysis occurs, leading to a significant decrease in the degree of polymerization and destruction of the regular structure of the molecular chain. This is manifested as a sharp decline in breaking strength and elongation.

[0042] Comparative Example 3 used lysine, phytic acid and lysine alone to soak lyocell fabric. It lacked the multi-arm epoxy crosslinking agent prepared in Examples 1-3. There was no direct chemical bond between lysine and phytic acid. They only relied on secondary bond effects such as hydrogen bonds. During the washing process, water molecules would destroy the secondary bond forces, and the phosphorus and nitrogen flame retardant components would dissolve and fall off. The protective layer on the surface of the lyocell fabric would be gradually damaged, resulting in a significant reduction in flame retardant performance.

[0043] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of them. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention. Although the specific embodiments of the present invention have been described above, they are not intended to limit the protection scope of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. An epoxy crosslinking agent, characterized in that, The molecular structure includes a core and side arms; the core is a cyclic polysiloxane, and the side chains include polyoxypropylene (PO) segments and polyoxyethylene (EO) segments. The polyoxypropylene segments are connected to the core through R1 groups, and the polyoxyethylene segments are connected to the epoxy groups at the ends of the polyoxypropylene segments and side arms. The general structural formula of the corresponding epoxy crosslinking agent is shown below. ； The side arms are connected to the core in sequence; The number of side chains is ≥3, that is, a≥3; b≥1; c≥1; The RO group is selected from methyl or phenyl; The R1 group is selected from alkyl groups with 2 to 20 carbon atoms.

2. A method for preparing the epoxy crosslinking agent as described in claim 1, characterized in that, This includes the following: a vinyl block polymer reacted with a cyclic hydrogen-containing silane via a hydrosilylation reaction to obtain the product. The general structural formula of the vinyl block copolymer is: ; R2 is selected from -H or -CH3; b≥1; c≥1; The cyclic hydrogen-containing silane is selected from methylhydrocyclosiloxane or phenylhydrocyclosiloxane; The molar ratio of vinyl groups in the vinyl block polymer to Si-H groups in the cyclic hydrogen-containing silane is (1-1.2):

1.

3. The method for preparing the epoxy crosslinking agent according to claim 2, characterized in that, The cyclic hydrogen-containing silane is selected from at least one of 2,4,6-trimethylcyclotrisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, and 2,4,6,8,10-pentamethylcyclopentasiloxane.

4. The method for preparing the epoxy crosslinking agent according to claim 2, characterized in that, The hydrosilylation reaction uses a platinum catalyst, which is selected from Pt-vinylsiloxane complexes or Pt-cycloolefin complexes; And / or, the reaction temperature of the hydrosilylation reaction is 80-120°C.

5. The use of the epoxy crosslinking agent as described in claim 1 in the surface treatment modification of cellulose fabrics.

6. A bio-based flame retardant modified lyocell fabric, characterized in that, Lyocell fabric is obtained by sequentially impregnating it with an aqueous solution of lysine, an aqueous solution of phytic acid, and an aqueous solution of the epoxy crosslinking agent as described in claim 1. The lysine is selected from at least one of L-lysine, D-lysine, and racemic lysine.

7. The bio-based flame retardant modified Lyocell fabric according to claim 6, characterized in that, Lyocell fabric is obtained by sequentially impregnating it with an aqueous solution of lysine, an aqueous solution of phytic acid, an aqueous solution of lysine, and an aqueous solution of an epoxy crosslinking agent as described in claim 1.

8. A method for preparing lyocell fabric as described in any one of claims 6-7, characterized in that, Lyocell fabric is sequentially subjected to lysine aqueous solution padding and room temperature drying, phytic acid aqueous solution padding and room temperature drying, epoxy crosslinking agent aqueous solution padding and baking to obtain the finished fabric. The concentration of the lysine aqueous solution is 4-10 g / L; The concentration of the phytic acid aqueous solution is 1-3 g / L; The concentration of the aqueous solution of the epoxy crosslinking agent is 10-40 g / L; The baking temperature is 60-90℃; the baking time is 1-20 minutes.

9. The method for preparing the bio-based flame retardant modified Lyocell fabric according to claim 8, characterized in that, The soaking time for the lysine aqueous solution is 3-10 minutes; And / or, the soaking time in phytic acid aqueous solution is 0.5-2 min; And / or, the immersion time in the aqueous solution of the epoxy crosslinking agent is 3-10 min.

10. The use of the Lyocell fabric as described in any one of claims 6-7 in underwear, workwear, and home textiles.

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