Preparation method of flame-retardant viscose fiber with antibacterial function

Abstract

The invention discloses a preparation method of a flame-retardant viscose fiber with an antibacterial function, which comprises the following steps: (1) under sufficient stirring, sequentially adding a phosphorus flame retardant, a dispersant and graphene oxide into deionized water with an alkaline pH value, and stirring and ball-milling to obtain a flame retardant dispersion liquid; (2) preparing a spinning stock solution by taking cellulose pulp as a raw material, and adding the flame retardant dispersion liquid into the spinning stock solution by adopting a pre-spinning injection method to prepare a blended spinning stock solution; (3) spinning the blended spinning stock solution in a coagulating bath, and reducing the blended spinning stock solution in an oxidation-reduction bath to obtain a formed tow; and after drafting, carrying out a post-treatment process to obtain the flame-retardant viscose fiber with the antibacterial function. The production process is optimized from multiple aspects such as selection of raw materials for preparing the flame retardant, oxidation reduction and the like, and the prepared flame-retardant viscose fiber has excellent flame retardance, good physical and mechanical properties and antibacterial properties and good wearability.

Description

Technical Field

[0001] The invention relates to the technical field of regenerated cellulose fibers, and in particular to a modified flame-retardant viscose fiber. Background Art

[0002] Viscose fiber is widely used in the textile and clothing fields due to its excellent hygroscopicity and air permeability. However, due to its molecular structure similar to cotton, it is mainly composed of cellulose, does not melt at high temperatures, but burns directly, and its limiting oxygen index (LOI) is only 17%, which is a flammable material. In recent years, the flame retardant fiber and textile market has shown a steady growth trend, and the market demand for flame retardant fiber functions has also increased. Traditional flame retardant fibers and textiles have been difficult to meet new requirements. For example, curtains, bedding, carpets, decorative fabrics, military equipment, transportation, etc., not only need to have flame retardant properties, but also need to meet a variety of requirements such as hygroscopicity, antibacterial, and environmental protection.

[0003] Chinese patent CN201310514536.0 discloses a method for antibacterial finishing of cellulose fiber-containing textiles, in which microcapsule antibacterial agents are treated on the surface of textiles by a post-finishing method. The antibacterial fabrics produced by this method have poor durability and washing resistance, and the antibacterial agent is seriously lost during use. Patent CN202010221111.0 discloses an antibacterial flame-retardant fiber and a preparation method thereof, in which metal ions are implanted into the fiber surface by an impregnation method to form nanoparticles with antibacterial activity on the fiber surface, thereby obtaining a fiber material with both flame retardant and antibacterial functions. The fiber produced by this method has a poor hand feel and the durability of the flame retardant and antibacterial effect cannot be guaranteed. Patent CN201911317271.9 discloses a method for preparing antibacterial flame-retardant fibers and fabrics thereof, in which inorganic metal silver or zinc is used as a flame retardant and antibacterial agent, which has potential hazards to the environment and human body, and is easily oxidized, and will cause a large amount of flame retardant and antibacterial agent loss during production and downstream processing, resulting in poor fiber functionality.

[0004] Through the summary and analysis of the above related existing technologies, the development of antibacterial flame retardant fibers generally achieves its flame retardant properties through post-finishing technology or blending and adding. However, the flame retardant effect of the post-finishing technology has poor durability and will affect the feel of the fiber or textile. In the blending and adding technology, a better flame retardant effect is achieved, and the amount of flame retardant added is often large, which will inevitably lead to a decrease in fiber strength. In particular, phosphorus-based flame retardants are generally used in the existing technology to modify the flame retardant properties. Although phosphorus-based flame retardants have better flame retardant effects, textiles made of phosphorus-based flame retardants emit a large amount of smoke during the combustion process, thereby reducing the environmental performance.

[0005] Therefore, in order to achieve the flame retardant and antibacterial properties of textiles and meet various clothing needs such as civilian, industrial, military and police use, it is of great significance to invent a flame retardant viscose fiber with a small amount of flame retardant added, high fiber strength and good flame retardant effect. Summary of the invention

[0006] The technical problem to be solved by the present invention is: in view of the shortcomings of the prior art, a method for preparing a flame retardant viscose fiber with antibacterial function is provided. The method can achieve excellent flame retardant effect by adding a small amount of flame retardant, and the fiber has high strength, good physical and mechanical properties, and antibacterial properties.

[0007] In order to solve the above technical problems, the technical solution of the present invention is:

[0008] A method for preparing a flame-retardant viscose fiber with antibacterial function comprises the following steps:

[0009] (1) preparing a flame retardant dispersion: adding a phosphorus flame retardant, a dispersant, and graphene oxide to deionized water with an alkaline pH value in sequence under sufficient stirring, and then dispersing the mixture in a stirring ball mill at a speed of 1500 to 3000 r / min for 3 to 6 hours to obtain the flame retardant dispersion;

[0010] (2) Preparation of a blended spinning solution: a spinning solution is prepared using cellulose pulp as a raw material, and the flame retardant dispersion is added to the spinning solution by a pre-spinning injection method to obtain a blended spinning solution of flame-retardant viscose fiber with antibacterial function; the effective content of the flame retardant dispersion is 10 to 15 wt% relative to the amount of cellulose methyl ester added in the blended spinning solution, and the amount of graphene oxide added relative to the amount of cellulose methyl ester in the blended spinning solution is 2.0 to 4.0 wt%;

[0011] (3) Spinning and post-treatment: the blended spinning solution is placed in a coagulation bath for spinning, and then reduced in an oxidation-reduction bath to obtain a shaped filament bundle; the shaped filament bundle is stretched and subjected to a post-treatment process to obtain a flame-retardant viscose fiber with antibacterial function.

[0012] As an improved technical solution, the added amounts of the phosphorus-based flame retardant, dispersant, and graphene oxide in step (1) are 10-25wt%, 0.5-2wt%, and 3-5wt%, respectively; and the pH value of the flame retardant dispersion is 8-12.

[0013] The effective content in the flame retardant dispersion is the total content of the phosphorus-based flame retardant and graphene oxide.

[0014] As an improved technical solution, the phosphorus-based flame retardant is dithiopyrophosphate.

[0015] As an improved technical solution, the dispersant is one or more of sodium hexametaphosphate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, carboxymethyl cellulose, and hydroxyethyl cellulose.

[0016] As an improved technical solution, the particle size D90 of the flame retardant dispersion is ≤1.2 μm.

[0017] As an improved technical solution, the spinning solution contains 8-11wt% methyl cellulose and 5-8wt% alkali; the viscosity of the spinning solution (falling ball method) is 45-60s, the maturity (10% NH 4 Cl)12~18ml.

[0018] As an improved technical solution, the coagulation bath composition is 90-110 g / l sulfuric acid, 25-40 g / l zinc sulfate, and 260-320 g / l sodium sulfate; the coagulation bath temperature is 40-50°C.

[0019] As an improved technical solution, the redox bath is an aqueous solution of one or more of the reducing agents citric acid, ascorbic acid, and tea polyphenols; the reducing agent content in the redox bath is 3 to 8 g / l.

[0020] As an improved technical solution, the oxidation-reduction bath temperature is 92-98° C., and the oxidation-reduction time is 5-8 min.

[0021] As an improved technical solution, the post-processing process includes the following steps: cutting, washing, desulfurization, washing, oiling, opening, and drying:

[0022] The desulfurization process uses a sodium sulfite desulfurization bath; the Na 2 SO 3 The content is 5.0-8.0 g / L; the desulfurization bath temperature is 55-65°C;

[0023] The oil bath concentration of the oil application is 2.0-3.0 g / L, and the oil bath temperature is 45-55° C.;

[0024] The drying temperature of the drying is 95-125°C.

[0025] As a preferred technical solution, the steps for preparing the spinning solution are:

[0026] The pulp is reacted with alkali solution to generate alkali cellulose, which is then squeezed to remove excess alkali solution in the alkali cellulose and then enters a crusher. The crushed alkali cellulose is aged. After the aging is completed, the alkali cellulose that reaches a certain viscosity is measured and then enters a yellowing machine to react with carbon disulfide to generate cellulose sulfonate, which is then dissolved, mixed, filtered, degassed, and matured to prepare a spinning solution for spinning.

[0027] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0028] The method for preparing flame-retardant viscose fiber with antibacterial function of the present invention uses graphene oxide and phosphorus flame retardant as synergistic flame retardants in the flame retardant dispersion liquid used for modification. The graphene structure of the prior art is regular, the surface is hydrophobic, and the dispersion performance is poor. If it is used as a flame retardant, it is difficult to disperse evenly in the viscose stock solution. The graphene oxide surface selected by the present invention contains a large number of oxygen-containing functional groups such as hydroxyl, aldehyde, and carboxyl, which can form hydrogen bonds with cellulose hydroxyl in viscose, forming a stable dispersion system in the viscose stock solution, increasing the spinnability of the fiber, so that the defect content of the finished fiber is reduced, thereby increasing the mechanical strength. On the one hand, the stability of spinning is increased, and on the other hand, the amount of phosphorus flame retardant added can be greatly reduced, so that the smoke amount of the flame-retardant fiber during combustion is reduced, and the environmental protection performance is improved. At the same time, during spinning, the graphene oxide can be evenly distributed inside and outside the fiber, giving the fiber a good antibacterial function.

[0029] The preparation method of the flame-retardant viscose fiber with antibacterial function of the present invention, the blended spinning solution is spun through a coagulation bath and then passed through an oxidation-reduction bath to obtain a formed tow, the oxidation-reduction process reduces the graphene oxide in the fiber to graphene, and the thermal conductivity of the graphene contained in the fiber is better than that of graphene oxide, so that it can disperse heat more effectively than graphene oxide during combustion and slow down the fire; in addition, the two-dimensional sheet structure of graphene can be superimposed layer by layer, and a dense physical isolation layer is quickly formed during combustion to block the continuous combustion conditions, so it can play a synergistic flame-retardant role with a phosphorus-based flame retardant, and further improve the flame retardant performance. And the reducing agent selected by the present invention has mild reaction conditions, is green and environmentally friendly, and is simple to operate, and is suitable for large-scale production.

[0030] The invention optimizes the production process from multiple aspects such as the selection of raw materials for preparing flame retardants, oxidation and reduction, and gives the fiber excellent spinnability, mechanical properties and functionality. The flame retardant viscose fiber with antibacterial function prepared by the invention has good physical and mechanical properties and antibacterial properties in addition to excellent flame retardant properties, good wearing performance, fiber dry breaking strength>2.3cN / dtex, wet breaking strength>1.2cN / dtex, LOI value>30.0%, inhibition rate of Staphylococcus aureus>95.0%, inhibition rate of Escherichia coli>96.0%, inhibition rate of Candida albicans>92.0% (GB / T20944.3-2008 "Evaluation of Antibacterial Properties of Textiles" Part 3: Oscillation Method), and the antibacterial property is higher than the national standard. Moreover, the fiber prepared by the invention has long-lasting flame retardant and antibacterial properties, and there is no obvious fluctuation in functionality after 50 washings, and it can still maintain a good flame retardant effect and strong antibacterial properties. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only intended to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0032] Example 1

[0033] (1) Preparation of flame retardant dispersion: Under sufficient stirring, dithiopyrophosphate, dispersant (sodium hexametaphosphate and carboxymethyl cellulose in a mass ratio of 1:1), and graphene oxide were added in amounts of 13.5 wt%, 0.8 wt%, and 4.5 wt%, respectively, to deionized water with a pH value of 8.5, and then dispersed in a stirred ball mill at a speed of 1800 r / min for 6 h to obtain a flame retardant dispersion with a particle size D90 ≤ 1.15 μm.

[0034] (2) Preparation of blended spinning solution: A spinning solution was prepared using cellulose pulp as a raw material. The spinning solution contained 9.2 wt% methyl cellulose and 5.6 wt% alkali. The viscosity of the spinning solution (falling ball method) was 48 s, and the degree of maturity (10% NH 4 Cl)13.3ml.

[0035] The flame retardant dispersion is added to the spinning solution by a pre-spinning injection method to obtain a blended spinning solution of flame-retardant viscose fiber with antibacterial function; the effective content of the flame retardant is 10wt% relative to the amount of methyl cellulose added in the blended spinning solution, and the amount of the graphene oxide added relative to the amount of methyl cellulose in the blended spinning solution is 4.0wt%.

[0036] (3) Spinning and post-treatment: The blended spinning solution is placed into a coagulation bath for spinning. The coagulation bath composition is 98 g / l sulfuric acid, 28 g / l zinc sulfate, and 275 g / l sodium sulfate. The coagulation bath temperature is 50°C.

[0037] Then, the filaments are reduced in an oxidation-reduction bath with citric acid as the reducing agent, the citric acid concentration is 7.5 g / l, the solvent is deionized water, the oxidation-reduction bath temperature is 92.5°C, and the oxidation-reduction is carried out for 5.5 min to obtain a shaped filament bundle; after the shaped filament bundle is drawn, it is successively subjected to post-treatment steps such as cutting, washing, desulfurization, washing, oiling, opening, and drying. 2 SO 3 The concentration is 8.0g / L, the temperature is 55°C; the oiling concentration is 2.0g / L, the temperature is 45°C; the drying temperature is 95°C in zone one, 122°C in zone two, and 106°C in zone three, to obtain a flame-retardant viscose fiber with antibacterial function.

[0038] Example 2

[0039] (1) Preparation of flame retardant dispersion: Under sufficient stirring, dithiopyrophosphate, dispersant (sodium dodecylbenzene sulfonate and hydroxyethyl cellulose in a mass ratio of 1:1), and graphene oxide were added in amounts of 20 wt%, 1.2 wt%, and 4.0 wt%, respectively, to deionized water with a pH value of 10, and then dispersed in a stirred ball mill at a speed of 2200 r / min for 4 h to obtain a flame retardant dispersion with a particle size D90 ≤ 1.2 μm.

[0040] (2) Preparation of blended spinning solution: A spinning solution was prepared using cellulose pulp as a raw material. The spinning solution contained 10.4 wt% methyl cellulose and 6.4 wt% alkali. The viscosity of the spinning solution (falling ball method) was 52 s, and the degree of maturity (10% NH 4 Cl)15.6ml.

[0041] The flame retardant dispersion is added to the spinning solution by a pre-spinning injection method to obtain a blended spinning solution of flame-retardant viscose fiber with antibacterial function; the effective content of the flame retardant is 13wt% relative to the amount of methyl cellulose added in the blended spinning solution, and the amount of the graphene oxide added relative to the amount of methyl cellulose in the blended spinning solution is 3.0wt%.

[0042] (3) Spinning and post-treatment: The blended spinning solution is placed into a coagulation bath for spinning. The coagulation bath composition is 105 g / l sulfuric acid, 33 g / l zinc sulfate, and 305 g / l sodium sulfate. The coagulation bath temperature is 45°C.

[0043] Then, the filaments are reduced in an oxidation-reduction bath with ascorbic acid as a reducing agent, the ascorbic acid concentration is 5 g / l, the temperature is 95°C, and the oxidation-reduction is performed for 7 minutes to obtain a formed filament bundle; after the formed filament bundle is stretched, it is successively subjected to post-treatment steps such as cutting, washing, desulfurization, washing, oiling, opening, and drying to obtain a flame-retardant viscose fiber with antibacterial function.

[0044] The desulfurization process uses a sodium sulfite desulfurization bath; the Na 2 SO 3 The content is 6.8g / L, and the desulfurization bath temperature is 62°C; the oil bath concentration of the oiling is 2.8g / L, and the oil bath temperature is 50°C; the drying temperatures of the drying zone are 98°C in zone one, 115°C in zone two, and 108°C in zone three.

[0045] Example 3

[0046] (1) Preparation of flame retardant dispersion: Under sufficient stirring, dithiopyrophosphate, dispersant (sodium dodecyl sulfate and carboxymethyl cellulose in a mass ratio of 1:1), and graphene oxide were added in amounts of 22.5 wt%, 1.8 wt%, and 3.5 wt%, respectively, to deionized water with a pH value of 11, and then dispersed in a stirred ball mill at a speed of 2500 r / min for 4 h to obtain a flame retardant dispersion with a particle size D90 ≤ 1.1 μm.

[0047] (2) Preparation of blended spinning solution: A spinning solution was prepared using cellulose pulp as a raw material. The spinning solution contained 10.8 wt% methyl cellulose and 7.6 wt% alkali. The viscosity of the spinning solution (falling ball method) was 56 s, and the maturity (10% NH 4 Cl)17.8ml.

[0048] The flame retardant dispersion is added to the spinning solution by a pre-spinning injection method to obtain a blended spinning solution of flame-retardant viscose fiber with antibacterial function; the effective content of the flame retardant is 14.5wt% relative to the amount of methyl cellulose added in the blended spinning solution, and the amount of the graphene oxide added relative to the amount of methyl cellulose in the blended spinning solution is 2.2wt%.

[0049] (3) Spinning and post-treatment: The blended spinning solution is placed into a coagulation bath for spinning. The coagulation bath composition is 108 g / l sulfuric acid, 35 g / l zinc sulfate, and 300 g / l sodium sulfate. The coagulation bath temperature is 46°C.

[0050] Then, the filaments are reduced in an oxidation-reduction bath with tea polyphenols as a reducing agent, the concentration of the tea polyphenols is 6 g / l, the temperature is 96°C, and the oxidation-reduction is performed for 6 minutes to obtain a formed filament bundle; after the formed filament bundle is stretched, it is successively subjected to post-treatment steps such as cutting, washing, desulfurization, washing, oiling, opening, and drying to obtain a flame-retardant viscose fiber with antibacterial function.

[0051] The desulfurization process uses a sodium sulfite desulfurization bath; the Na 2 SO 3 The content is 7.0g / L, and the desulfurization bath temperature is 62°C; the oil bath concentration of the oiling is 2.5g / L, and the oil bath temperature is 52°C; the drying temperatures of the drying zone are 105°C in zone one, 125°C in zone two, and 96°C in zone three.

[0052] Comparative Example 1

[0053] Comparative Example 1 is exactly the same as step (1) and step (2) of Example 3, except that in step (3), after the blended spinning solution enters the coagulation bath for spinning, it does not undergo an oxidation-reduction step, but instead passes through a plasticizing bath of the same temperature and the same time (passing through a water bath at a temperature of 96°C for 6 minutes), and then undergoes a post-treatment step that is exactly the same as step (3) of Example 3 to obtain a flame-retardant viscose fiber.

[0054] Comparative Example 2

[0055] The difference between Comparative Example 2 and Example 3 is that in step (1), the flame retardants used are dithiopyrophosphate and graphene: under sufficient stirring, dithiopyrophosphate, dispersant (sodium dodecyl sulfate and carboxymethyl cellulose in a mass ratio of 1:1), and graphene are added in deionized water with a pH value of 11 in an amount of 22.5wt%, 1.8wt%, and 3.5wt%, respectively, and then dispersed in a stirred ball mill at a speed of 2500r / min for 4h to obtain a flame retardant dispersion with a particle size D90≤1.1μm.

[0056] Step (2) and step (3) are exactly the same as those in Example 3 to obtain flame-retardant viscose fiber.

[0057] Comparative Example 3

[0058] Comparative Example 3 is different from Example 3 in that in step (1), the flame retardant used is dithiopyrophosphate: under sufficient stirring, dithiopyrophosphate and a dispersant (sodium dodecyl sulfate and carboxymethyl cellulose in a mass ratio of 1:1) are added in an amount of 26.0wt% and 1.8wt% respectively to deionized water with a pH value of 11, and then dispersed in a stirred ball mill at a speed of 2500r / min for 4h to obtain a flame retardant dispersion with a particle size D90≤1.1μm.

[0059] Step (2) and step (3) are exactly the same as those in Example 3 to obtain flame-retardant viscose fiber.

[0060] Comparative Example 4

[0061] Comparative Example 4 is different from Example 3 in that in step (1), the flame retardant used is graphene oxide: under sufficient stirring, graphene oxide and a dispersant (sodium dodecyl sulfate and carboxymethyl cellulose in a mass ratio of 1:1) are added in amounts of 26.0wt% and 1.8wt%, respectively, to deionized water with a pH value of 11, and then dispersed in a stirred ball mill at a speed of 2500r / min for 4h to obtain a flame retardant dispersion with a particle size D90≤1.1μm.

[0062] Step (2) and step (3) are exactly the same as those in Example 3 to obtain flame-retardant viscose fiber.

[0063] The flame retardant viscose fibers prepared in the above Examples 1 to 3 and Comparative Examples 1 to 4 were sampled and their properties were tested. The results are shown in Table 1.

[0064] Table 1

[0065]

[0066] It can be seen from the experimental data in Table 1 that the present invention uses phosphorus-based flame retardants and graphene oxide for synergistic flame retardancy. Under the premise of a very low amount of phosphorus-based flame retardants, it not only has a good flame retardant effect, but also has a fiber LOI value of more than 30%, and the fiber has good physical and mechanical properties, high strength, and good antibacterial properties. In Comparative Example 1, due to the absence of an oxidation-reduction step, graphene oxide is not reduced to graphene, resulting in a decrease in LOI value and antibacterial effect. In Comparative Example 2, due to the use of graphene and phosphorus-based flame retardants as flame retardants, graphene is difficult to disperse evenly in the viscose stock solution, which not only leads to poor spinnability, but also deteriorates the physical and mechanical properties of the product after spinning, and at the same time, the flame retardant effect and antibacterial properties are also affected to a certain extent. In Comparative Example 3, no graphene oxide was added, and only phosphorus flame retardant was used. Although the total amount of flame retardant added was the same as that in Example 3, the flame retardant properties of the fiber were greatly affected due to the lack of synergistic effect, and according to GB / T20944.3-2008 "Evaluation of Antibacterial Properties of Textiles" Part 3: Oscillation Method, the antibacterial effect was low. In Comparative Example 4, no phosphorus flame retardant was added, and only graphene oxide was used. However, due to the lack of synergistic effect, the flame retardant properties of the fiber were greatly affected.

Claims

1. A method for preparing flame-retardant viscose fiber with antibacterial function, characterized in that The following steps are involved: (1) preparing a flame retardant dispersion: adding a phosphorus flame retardant, a dispersant, and graphene oxide to deionized water with an alkaline pH value in sequence under sufficient stirring, and then dispersing the mixture in a stirring ball mill at a speed of 1500 to 3000 r / min for 3 to 6 hours to obtain the flame retardant dispersion; (2) Preparation of a blended spinning solution: a spinning solution is prepared using cellulose pulp as a raw material, and the flame retardant dispersion is added to the spinning solution by a pre-spinning injection method to obtain a blended spinning solution of flame-retardant viscose fiber with antibacterial function; the effective content of the flame retardant dispersion is 10 to 15 wt% relative to the amount of cellulose methyl ester added in the blended spinning solution, and the amount of graphene oxide added relative to the amount of cellulose methyl ester in the blended spinning solution is 2.0 to 4.0 wt%; (3) Spinning and post-treatment: the blended spinning solution is placed in a coagulation bath for spinning, and then reduced in an oxidation-reduction bath to obtain a shaped filament bundle; the shaped filament bundle is stretched and subjected to a post-treatment process to obtain a flame-retardant viscose fiber with antibacterial function.

2. The method for preparing the flame-retardant viscose fiber with antibacterial function according to claim 1, characterized in that: The amounts of the phosphorus-based flame retardant, dispersant and graphene oxide added in step (1) are 10-25wt%, 0.5-2wt% and 3-5wt% respectively; the pH value of the flame retardant dispersion is 8-12.

3. The method for preparing the flame-retardant viscose fiber with antibacterial function according to claim 2, characterized in that: The phosphorus-based flame retardant is dithiopyrophosphate.

4. The method for preparing the flame-retardant viscose fiber with antibacterial function according to claim 2, characterized in that: The dispersant is one or more of sodium hexametaphosphate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, carboxymethyl cellulose and hydroxyethyl cellulose.

5. The method for preparing the flame-retardant viscose fiber with antibacterial function according to claim 2, characterized in that: The particle size D90 of the flame retardant dispersion is ≤1.2 μm.

6. The method for preparing the flame-retardant viscose fiber with antibacterial function according to claim 1, characterized in that: The spinning solution contains 8-11 wt% methyl cellulose and 5-8 wt% alkali; the viscosity of the spinning solution is 45-60s, and the degree of maturity is 12-18ml.

7. The method for preparing the flame-retardant viscose fiber with antibacterial function according to claim 1, characterized in that: The coagulation bath comprises 90-110 g / l of sulfuric acid, 25-40 g / l of zinc sulfate, and 260-320 g / l of sodium sulfate; The coagulation bath temperature is 40-50°C.

8. The method for preparing the flame-retardant viscose fiber with antibacterial function according to any one of claims 1 to 7, characterized in that: The redox bath is an aqueous solution of one or more of the reducing agents citric acid, ascorbic acid and tea polyphenols; the reducing agent content in the redox bath is 3-8 g / l.

9. The method for preparing flame-retardant viscose fiber with antibacterial function according to claim 8, characterized in that: The temperature of the oxidation-reduction bath is 92-98° C., and the oxidation-reduction time is 5-8 minutes.

10. The method for preparing flame-retardant viscose fiber with antibacterial function according to claim 1, characterized in that The post-processing process includes the following steps: cutting, washing, desulfurization, washing, oiling, opening, and drying: The desulfurization is carried out using a sodium sulfite desulfurization bath; the Na2SO3 content in the desulfurization bath is 5.0-8.0 g / L; The desulfurization bath temperature is 55-65°C; The oil bath concentration of the oil application is 2.0-3.0 g / L, and the oil bath temperature is 45-55° C.; The drying temperature of the drying is 95-125°C.

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