Flame-retardant Lyocell fiber and preparation method thereof

Abstract

The invention provides a flame-retardant Lyocell fiber and a preparation method thereof, and belongs to the technical field of fiber manufacturing. The fiber comprises a fiber base material and a flame retardant, the flame retardant is uniformly distributed in the fiber base material, and the mass of the flame retardant is 40-80% of the mass of the fiber base material. The preparation method of the fiber comprises the following steps: preparing dispersion liquid of the flame retardant; the dispersion liquid of the flame retardant and cellulose fiber pulp are subjected to blending, swelling and vacuum dehydration, a flame retardant solution is obtained, and the mass of the flame retardant accounts for 200%-500% of the absolutely dry mass of the cellulose fiber pulp in the flame retardant solution; the flame retardant melt and the dissolving solution are mixed, the flame-retardant dissolving solution for spinning is obtained, and the mass of the flame retardant accounts for 60%-80% of the mass of cellulose in the flame-retardant dissolving solution; the flame-retardant dissolving solution for spinning is subjected to spinning, the flame-retardant Lyocell fiber is obtained, and the mass of the flame retardant accounts for 40%-80% of the mass of the fiber base material. The flame retardance of the fiber can be obviously improved, the production cost is lower, and the fiber is green and environment-friendly.

Description

Technical Field

[0001] The invention relates to the technical field of fiber manufacturing, in particular to a flame-retardant Lyocell fiber and a preparation method thereof. Background Art

[0002] Lyocell fiber is a biodegradable regenerated cellulose fiber produced by a new solvent process. It is non-toxic during the production process, and both the fiber itself and the waste produced during the production process are biodegradable. Lyocell fiber itself has excellent strength, moisture absorption and breathability, and good wearability. However, it is a flammable fiber. Although the research on flame retardant modification has been increasing in recent years, there is still a lack of application products in the field of flame retardant functionality. Summary of the invention

[0003] In view of this, the present invention provides a flame-retardant Lyocell fiber and a preparation method thereof, which can significantly improve the flame retardancy of the fiber, have a low production cost and are environmentally friendly, and are therefore more suitable for practical use.

[0004] In order to achieve the above first purpose, the technical solution of the flame retardant Lyocell fiber provided by the present invention is as follows:

[0005] The flame-retardant Lyocell fiber provided by the present invention comprises a fiber base material and a flame retardant.

[0006] The flame retardant is evenly distributed inside the fiber substrate, wherein the mass of the flame retardant is 40%-80% of the mass of the fiber substrate.

[0007] The flame-retardant Lyocell fiber provided by the present invention can be further realized by adopting the following technical measures.

[0008] Preferably, the fiber substrate is cellulose fiber.

[0009] Preferably, the ratio between the particle size of the flame retardant and the diameter of the fiber is D 90 / φ 纤维 <0.1.

[0010] Preferably, the flame retardant is a nitrogen-based flame retardant, and the initial particle size D of the flame retardant particles is 90 <50μm.

[0011] Preferably, the nitrogen-based flame retardant is 6,6'-piperazine-bis(1,3,5-triazine-2,4-diamine).

[0012] In order to achieve the above second purpose, the technical scheme of the method for preparing the flame-retardant Lyocell fiber provided by the present invention is as follows:

[0013] The method for preparing the flame-retardant Lyocell fiber provided by the present invention comprises the following steps:

[0014] preparing a dispersion of a flame retardant;

[0015] The flame retardant dispersion is mixed with cellulose fiber pulp, swollen, and vacuum-dehydrated to obtain a flame retardant solution, wherein the mass of the flame retardant accounts for 200%-500% of the absolute dry mass percentage of the cellulose pulp in the flame retardant solution;

[0016] The flame retardant melt is mixed with a dissolving liquid to obtain a flame retardant dissolving liquid for spinning, wherein the mass of the flame retardant accounts for 60% to 80% of the mass of the cellulose in the flame retardant dissolving liquid;

[0017] The flame-retardant dissolving liquid for spinning is spun to obtain the flame-retardant Lyocell fiber, wherein the mass of the flame retardant is 40%-80% of the mass of the fiber substrate.

[0018] The method for preparing the flame-retardant Lyocell fiber provided by the present invention can also be further implemented by adopting the following technical measures.

[0019] Preferably, the step of preparing the flame retardant dispersion is specifically to premix the NMMO aqueous solution of the flame retardant, and obtain the flame retardant dispersion by a grinding process, wherein the ratio of the particle size of the flame retardant to the fiber diameter is D 90 / φ 纤维 <0.1.

[0020] Preferably, the flame retardant dispersion is blended with cellulose fiber pulp, swelled, and vacuum dehydrated to obtain a flame retardant solution. Specifically, the flame retardant dispersion is mixed with an NMMO aqueous solution having a solute mass percentage of 76%-85%, and then blended with cellulose fiber pulp, swelled, and vacuum dehydrated to obtain a flame retardant solution.

[0021] Preferably, the step of mixing the flame retardant dispersion with the NMMO aqueous solution having a solute mass percentage of 76%-85% is achieved by using a static mixer.

[0022] As a preference,

[0023] In the step of mixing the flame retardant dispersion with a NMMO aqueous solution having a solute mass percentage of 76%-85%, the mixing temperature is 80° C.-85° C. and the mixing time is 10 min-15 min;

[0024] In the step of mixing the flame retardant dispersion with an NMMO aqueous solution having a solute mass percentage of 76%-85% and then blending with the cellulose fiber pulp for swelling, the swelling temperature is 90° C.-95° C., the swelling time is 30 min-45 min, and the concentration of the NMMO aqueous solution in the pre-dissolved solution after swelling is 77%-79%;

[0025] The flame retardant dispersion is mixed with a NMMO aqueous solution having a solute mass percentage of 76%-85%, and then blended with cellulose fiber pulp, swollen, and then vacuum dehydrated at a temperature of 100°C-105°C.

[0026] Preferably, the flame retardant melt is mixed with a dissolving liquid to obtain a flame retardant dissolving liquid for spinning. The specific steps are as follows: the flame retardant melt and the ordinary dissolving liquid are metered and pumped into a twin-screw extruder, and then extruded through the twin-screw extruder into a static mixer for re-mixing to obtain a flame retardant dissolving liquid for spinning.

[0027] Preferably, in the step of spinning the flame-retardant solvent to obtain the flame-retardant Lyocell fiber, the spinning process is a dry-jet wet spinning process.

[0028] Preferably, the dry-jet wet spinning process uses a coagulation bath containing 0-20% by mass NMMO aqueous solution, a coagulation bath temperature of 10° C.-25° C., and a humidity of 45%-65%.

[0029] Preferably, the mass proportions of the components in the flame retardant dispersion include: flame retardant: 10 parts to 50 parts, emulsifier: 0.2 parts to 10 parts, dispersant: 0.2 parts to 10 parts, defoamer: 1 part to 5 parts, and the balance is dispersion medium, wherein the dispersion medium is selected from water or an aqueous solution of NMMO with a mass percentage of solute of 20% to 55%.

[0030] Preferably, the emulsifier is selected from one or more of sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium dodecyl sulfonate, and polyoxyethylene ether compounds.

[0031] Preferably, the dispersant is selected from one or more of sodium polyacrylate, sodium ethylene bis naphthalene sulfonate, sodium α-olefin sulfonate, and sodium maleate.

[0032] Preferably, the defoamer is selected from one or more of polyether-modified polysiloxane, polyether-siloxane copolymer, and water-based acrylic defoamer.

[0033] Preferably, the method for preparing the flame retardant dispersion comprises the following steps:

[0034] Adding an emulsifier and a dispersant into a dispersion medium and stirring the mixture evenly to obtain a first intermediate product;

[0035] Adding an appropriate amount of defoaming agent to the first intermediate product to eliminate bubbles, thereby obtaining a second intermediate product;

[0036] Adding flame retardant powder to the second intermediate product, continuously stirring and adding a defoaming agent to obtain a third intermediate product;

[0037] The third intermediate product is filtered to remove particulate matter to obtain a fourth intermediate product;

[0038] The fourth intermediate product is ground and dispersed, so that the emulsifier and the dispersant are completely adsorbed on the surface of the flame retardant particles to obtain the flame retardant dispersion, wherein the flame retardant dispersion is a stable suspension.

[0039] Preferably, in the step of filtering the third intermediate product to remove particulate matter to obtain the fourth intermediate product, the pore size of the filter is 50 μm.

[0040] The flame-retardant Lyocell fiber and preparation method provided by the present invention use flame retardants to modify Lyocell fibers, control particle size, ensure smooth fiber spinning process, and achieve uniform distribution of flame retardants inside the fibers by mixing flame retardant solution and common solution successively, thereby improving the stability of flame retardant particle size, avoiding pipeline and tank cleaning problems caused by blending multiple materials, and reducing costs. The flame retardancy of the fibers is significantly improved, the production cost is low, and the fibers are environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0042] Attached Figure 1 A flow chart of the steps of the method for preparing the flame-retardant Lyocell fiber provided for the implementation of the present invention;

[0043] Attached Figure 2 A flow chart of the steps of preparing a flame retardant dispersion liquid involved in the method for preparing a flame retardant Lyocell fiber provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0044] In view of this, the present invention provides a flame-retardant Lyocell fiber and a preparation method thereof, which can significantly improve the flame retardancy of the fiber, have a low production cost and are environmentally friendly, and are therefore more suitable for practical use.

[0045] The existing flame retardant modification technology of Lyocell fiber is mainly based on the blending process and the finishing process. The finishing process is a method of attaching the flame retardant to the fiber or fabric by means of impregnation, baking, coating, spraying, etc. This method does not have high requirements for the flame retardant, but the fabric after finishing has a poor feel, the process is complicated and not environmentally friendly. The blending process is a method of adding the flame retardant to the slurry or spinning solution to spin the flame retardant fiber. This method is simple in process, but usually faces the problems of large flame retardant particle size, flame retardant precipitation and attachment on the fiber surface, some types of flame retardants are easily soluble (or hydrolyzed) in the high concentration NMMO system, the modified fiber has no obvious flame retardancy, and the flame retardant fiber production pipeline has high cleaning costs and pollution. In addition, the various flame retardant compounds currently developed have high preparation costs and cause serious environmental pollution during the preparation process.

[0046] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the flame-retardant Lyocell fiber and its preparation method proposed by the present invention, its specific implementation, structure, characteristics and effects are described in detail below in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0047] The term "and / or" in this article is merely a description of the association relationship of associated objects, indicating that three relationships may exist, for example, A and / or B. Specifically, it is understood that: A and B may be included at the same time, A may exist alone, or B may exist alone, and any of the above three situations may be met.

[0048] Flame retardant Lyocell fiber

[0049] The flame-retardant Lyocell fiber provided by the present invention comprises a fiber base material and a flame retardant. The flame retardant is evenly distributed inside the fiber base material, wherein the mass of the flame retardant is 40%-80% of the mass of the fiber base material.

[0050] The fiber substrate is cellulose fiber.

[0051] The ratio between the particle size of the flame retardant and the diameter of the fiber is D90 / φfiber<0.1. D90 being less than a certain value means that 90% of the particle sizes are less than a certain value.

[0052] The flame retardant is a nitrogen-based flame retardant, and the initial particle size D90 of the flame retardant particles is less than 50 μm.

[0053] Among them, the nitrogen flame retardant is 6,6'piperazine-bis(1,3,5-triazine-2,4-diamine). Among them, (6,6'piperazine-bis(1,3,5-triazine-2,4-diamine), the particle size of the flame retardant is controlled to achieve a particle size of D90 / Fiber <0.1, which can ensure the smooth fiber spinning process and achieve the purpose of adding flame retardants inside the fiber. On the one hand, the flame retardancy of the flame-retardant modified Loycell fiber is significantly improved, and the limiting oxygen index (LOI) is increased from 17% to more than 25%. On the other hand, the finished flame retardant used in the present invention is a commercially available product with a wide source, a high degree of commercialization, and few environmental protection and industrialization problems. The cross-sectional diameter of the flame-retardant fiber is about 17 microns. If the particle size of the flame retardant is too large, firstly, the flame retardant is easy to precipitate on the fiber surface, so that its effective addition amount is reduced and the flame retardant function is weakened; secondly, the blending and compounding effect of the modified fiber is deteriorated. It has obvious advantages in chemical stability in the Lyocell fiber production process, which is different from most flame retardant products on the market. For example, ammonium polyphosphate produces a pungent amine smell at 80°C in an 81% NMMO aqueous solution; NLD-02 (dithiopyrophosphate), a flame retardant for viscose, is significantly degraded in an 86.7% NMMO aqueous solution; MPP (melamine polyphosphate) is dissolved in the Lyocell fiber production process, and is related to the residence time of the solution process, and there is obvious diffusion precipitation in the coagulation bath; DOPO, CEPPA, phenoxyphosphite, diethyl hypophosphite, etc. have a significantly higher solubility in an 86.7% NMMO aqueous solution, and the loss is large with the solvent diffusion during the fiber forming process, and they cannot play a flame retardant effect, and affect the recovery of NMMO solvent. 6,6'piperazine-bis (1,3,5-triazine-2,4-diamine) has good chemical stability in the Lyocell spinning solution system and high fiber bonding, which can avoid the loss caused by diffusion of NMMO during the coagulation bath forming process. In addition, the grinding process can control the particle size of the flame retardant. By adjusting the composition of the dispersion liquid with emulsifiers and dispersants, the particle size of the flame retardant particles can be kept stable. The particle size can reach D90 / The fiber is less than 0.06, ensuring the smoothness of the fiber spinning process. The flame retardant modified Loycell fiber with 6,6'piperazine-bis(1,3,5-triazine-2,4-diamine) has significantly improved flame retardancy, and the limiting oxygen index (LOI) has been increased from 17% to more than 25%.

[0054] The flame retardant Lyocell fiber provided by the embodiment of the present invention uses a finished flame retardant as a commercial product, which has a wide source, a high degree of commercialization, a lower industrial application cost, is more environmentally friendly, and does not produce pollutants. By controlling the addition ratio of the flame retardant, a good flame retardant effect is achieved.

[0055] According to the preparation method of flame-retardant Lyocell fiber provided by the present invention, the flame retardant dispersion is fed into the feed mode: by metering mixing before swelling and blending (the flame retardant dispersion and NMMO solution are metered and mixed in a static mixer and merged into one flow), which is different from other similar patents in which the flame retardant dispersion and NMMO are pre-mixed in advance. This method can shorten the high-temperature storage time of the flame retardant, improve the stability of the particle size, and avoid the pipeline and tank cleaning problems caused by the blending of multiple materials, thereby reducing costs.

[0056] The method for preparing the flame-retardant Lyocell fiber provided in an embodiment of the present invention adopts a blending process of a flame-retardant solution and a common solution through a twin-screw extruder and a static mixer to prepare a flame-retardant spinning solution. The process method has good flexibility, significantly improves the uniform distribution of the flame retardant inside the fiber, improves the blending effect, and improves the pipeline switching cleaning efficiency.

[0057] Preparation method of flame retardant Lyocell fiber

[0058] See attached Figure 1 The method for preparing the flame-retardant Lyocell fiber provided by the present invention comprises the following steps:

[0059] Step S1: preparing a dispersion of a flame retardant;

[0060] Step S2: blending the flame retardant dispersion with the cellulose fiber pulp, swelling, and vacuum dehydrating to obtain a flame retardant solution, wherein the mass of the flame retardant accounts for 200%-500% of the absolute dry mass percentage of the cellulose pulp in the flame retardant solution;

[0061] Step S3: mixing the flame retardant melt with the dissolving liquid to obtain a flame retardant dissolving liquid for spinning, wherein the mass of the flame retardant accounts for 60%-80% of the mass of the cellulose in the flame retardant dissolving liquid;

[0062] Step S4: The flame retardant solution for spinning is spun to obtain flame retardant Lyocell fiber, wherein the mass of the flame retardant is 40%-80% of the mass of the fiber base material.

[0063] The step of preparing the flame retardant dispersion is specifically to premix the NMMO aqueous solution of the flame retardant, and obtain the flame retardant dispersion by a grinding process, wherein the ratio of the particle size of the flame retardant to the fiber diameter is D 90 / φ 纤维 <0.1.

[0064] The steps of blending the flame retardant dispersion with cellulose fiber pulp, swelling, and vacuum dehydrating to obtain the flame retardant solution are as follows: mixing the flame retardant dispersion with an NMMO aqueous solution having a solute mass percentage of 76%-85%, and then blending, swelling, and vacuum dehydrating with the cellulose fiber pulp to obtain the flame retardant solution.

[0065] The step of mixing the flame retardant dispersion with the NMMO aqueous solution having a solute mass percentage of 76%-85% is achieved by using a static mixer.

[0066] Among them, in the step of mixing the flame retardant dispersion with the NMMO aqueous solution with a solute mass percentage of 76%-85%, the mixing temperature is 80°C-85°C, and the mixing time is 10min-15min; in the step of mixing the flame retardant dispersion with the NMMO aqueous solution with a solute mass percentage of 76%-85% and then blending and swelling with cellulose fiber pulp, the swelling temperature is 90°C-95°C, the swelling time is 30min-45min, and the concentration of NMMO aqueous solution in the pre-dissolved liquid after swelling is 77%-79%; in the step of vacuum dehydration after mixing the flame retardant dispersion with the NMMO aqueous solution with a solute mass percentage of 76%-85%, blending and swelling with cellulose fiber pulp, the temperature is 100°C-105°C.

[0067] The specific steps of mixing the flame retardant melt with the solvent to obtain the flame retardant solvent for spinning are as follows: the flame retardant melt and the ordinary solvent are metered and pumped into a twin-screw extruder, and then extruded through the twin-screw extruder into a static mixer for re-mixing to obtain the flame retardant solvent for spinning.

[0068] Among them, in the step of spinning the flame-retardant solution for spinning to obtain the flame-retardant Lyocell fiber, the spinning process is a dry-jet wet spinning process.

[0069] The dry-jet wet spinning process uses a coagulation bath containing a 0-20% by mass NMMO aqueous solution, a coagulation bath temperature of 10° C.-25° C., and a humidity of 45%-65%.

[0070] The mass proportions of the components in the flame retardant dispersion include: flame retardant: 10-50 parts, emulsifier: 0.2-10 parts, dispersant: 0.2-10 parts, defoamer: 1-5 parts, and the balance is dispersion medium, wherein the dispersion medium is selected from water or an aqueous solution of NMMO with a mass percentage of 20%-55% of the solute.

[0071] Wherein, the emulsifier is selected from one or more of sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium dodecyl sulfonate, and polyoxyethylene ether compounds.

[0072] Wherein, the dispersant is selected from one or more of sodium polyacrylate, sodium ethylene bis naphthalene sulfonate, sodium α-olefin-sulfonate, and sodium maleate.

[0073] The defoamer is selected from one or more of polyether-modified polysiloxane, polyether-siloxane copolymer, and water-based acrylic defoamer.

[0074] The method for preparing the flame retardant dispersion comprises the following steps:

[0075] Step S101: adding an emulsifier and a dispersant into a dispersion medium and stirring the mixture to obtain a first intermediate product;

[0076] Step S102: adding an appropriate amount of defoaming agent to the first intermediate product to eliminate bubbles, thereby obtaining a second intermediate product;

[0077] Step S103: adding flame retardant powder to the second intermediate product, continuously stirring and adding a defoaming agent to obtain a third intermediate product;

[0078] Step S104: The third intermediate product is filtered to remove particulate matter to obtain a fourth intermediate product; in the present invention, the filter is a Y-type filter.

[0079] Step S105: The fourth intermediate product is ground and dispersed, so that the emulsifier and the dispersant are completely adsorbed on the surface of the flame retardant particles to obtain a flame retardant dispersion, wherein the flame retardant dispersion is a stable suspension. The grinding equipment is preferably a pin-type sand mill, the grinding beads are preferably 95# zirconium oxide beads, the rotation speed is 1100r / min, and the grinding time is 5h.

[0080] In the step of filtering the third intermediate product to remove particulate matter and obtain the fourth intermediate product, the pore size of the filter is 50 μm. In this case, the initial particle size D of the flame retardant particles can be achieved. 90 <50μm.

[0081] Example Preparation Example of Flame Retardant Dispersion

[0082] Example 1 Preparation of flame retardant dispersion

[0083] 4 parts by weight of sodium dodecylbenzene sulfonate, 4 parts by weight of sodium α-olefin polyoxyethylene sulfonate, 2 parts by weight of polyether modified polysiloxane, and 75 parts by weight of water are stirred in a dispersion tank, and then 28.3 parts by weight of (6,6' piperazinyl-bis (1,3,5-triazine-2,4-diamine) are gradually added under the action of shear stirring at 4-6m / s. After stirring evenly, the mixture is transferred to a sand mill and ground with zirconium oxide beads at 1100r / min for 5h. The dispersion is then filtered to obtain a flame retardant dispersion having a flame retardant active ingredient of 25%.

[0084] Wherein, the effective component is a flame retardant, and the weight percentage of the effective component=weight of the effective component / total amount of the total components×100%.

[0085] Example 2 Preparation of flame retardant dispersion

[0086] 5 parts by weight of sodium dodecyl sulfate, 5 parts by weight of sodium ethylenebisnaphthalene sulfonate, 2 parts by weight of polyether-modified polysiloxane, and 148 parts by weight of water are stirred in a dispersion tank, and then 28.3 parts by weight of (6,6'-piperazine-bis(1,3,5-triazine-2,4-diamine) are gradually added under the action of shear stirring at 4-6 m / s. After stirring evenly, the mixture is transferred to a sand mill and ground with zirconium oxide beads at 1100 r / min for 5 hours. The dispersion is then filtered to obtain a flame retardant dispersion having a flame retardant active ingredient of 15%.

[0087] Lyocell fiber preparation example and comparative example

[0088] Example 3

[0089] According to the method of Example 1, a flame retardant dispersion with an active ingredient of 25% wt was prepared, and the D 90 <1μm.

[0090] Step 1: After the flame retardant dispersion and the NMMO solution are metered and mixed in a static mixer and merged into one flow, they are swollen and blended with the cellulose pulp in a blending device. The flame retardant accounts for 200% of the absolute dry weight of the pulp. After vacuum dehydration, a flame retardant solution is obtained, in which the flame retardant accounts for 18 parts, the cellulose accounts for 9 parts, and the NMMO aqueous solution and the additives account for a total of 91 parts.

[0091] Step 2, according to the mass ratio of flame retardant solution: ordinary solution = 15.66:16.26, pumped into a twin-screw extruder through a metering pump, and then into a static mixer to obtain a flame retardant solution for spinning. The ordinary solution is composed of 12 parts of cellulose and 88 parts of NMMO aqueous solution and additives. The flame retardant solvent liquid is composed of 9.77 parts of cellulose, 7.33 parts of flame retardant, 82.9 parts of NMMO aqueous solution and others, that is, the flame retardant accounts for 75% of cellulose.

[0092] Step 3, the flame retardant solution is extruded from a spinneret with a hole size of 0.09 mm / 27000 at a speed of 50 ml / min by a metering pump, stretched in an air gap of 25 mm, and then coagulated and precipitated into fibers in a 20% NMMO coagulation bath at 25°C; the residual NMMO in the fibers is washed with an ultrasonic cleaner for 30 minutes, and then the fibers are dried at 105°C.

[0093] The obtained fiber was tested for limiting oxygen index according to the method specified in FZ / T 50016-2011, and the LOI value was 26.5±0.2%;

[0094] Example 4

[0095] According to the method of Example 1, a flame retardant dispersion with an active ingredient of 25% wt was prepared, and the D 90 <1μm.

[0096] Step 1: After the flame retardant dispersion and the NMMO solution are metered and mixed in a static mixer and merged into one flow, they are swollen and blended with the cellulose pulp in a blending device. The flame retardant accounts for 200% of the absolute dry weight of the pulp. After vacuum dehydration, a flame retardant solution is obtained, in which the flame retardant is 18 parts, the cellulose is 9 parts, and the NMMO aqueous solution and the additives account for a total of 91 parts.

[0097] Step 2, according to the mass ratio of flame retardant solution: ordinary solution = 12.57:16.26, pumped into a twin-screw extruder through a metering pump, and then into a static mixer to obtain a flame retardant solution for spinning. The ordinary solution is composed of 12 parts of cellulose and 88 parts of NMMO aqueous solution and additives. The flame retardant solvent liquid is composed of 10.02 parts of cellulose, 6.51 parts of flame retardant, 83.47 parts of NMMO aqueous solution and others, that is, the flame retardant accounts for 65% of cellulose.

[0098] Step 3, the flame retardant solution is extruded from a spinneret with a hole size of 0.09 mm / 27000 at a speed of 50 ml / min by a metering pump, stretched in an air gap of 25 mm, and then coagulated and precipitated into fibers in a 20% NMMO coagulation bath at 25°C; the residual NMMO in the fibers is washed with an ultrasonic cleaner for 30 minutes, and then the fibers are dried at 105°C.

[0099] The obtained fibers were tested for oxygen index according to the method specified in FZT 50016-2011, and the LOI values ​​were 26 ± 0.2%;

[0100] Example 5

[0101] According to the method of Example 1, a flame retardant dispersion with an active ingredient of 25% wt was prepared, and the D 90 <1μm.

[0102] Step 1: After the flame retardant dispersion and the NMMO solution are metered and mixed in a static mixer and merged into one flow, they are swollen and blended with the cellulose pulp in a blending device. The flame retardant accounts for 200% of the absolute dry weight of the pulp. After vacuum dehydration, a flame retardant solution is obtained, in which the flame retardant is 18 parts, the cellulose is 9 parts, and the NMMO aqueous solution and the additives account for a total of 91 parts.

[0103] Step 2, according to the mass ratio of flame retardant solution: ordinary solution = 9.9:16.26, it is metered into a twin-screw extruder and then enters a static mixer to obtain a flame retardant solution for spinning. The ordinary solution is composed of 12 parts of cellulose and 88 parts of NMMO aqueous solution and additives. The flame retardant solvent liquid is composed of 10.28 parts of cellulose, 5.65 parts of flame retardant, 84.07 parts of NMMO aqueous solution and others, that is, the flame retardant accounts for 55% of cellulose.

[0104] Step 3, the flame retardant solution is extruded from a spinneret with a hole size of 0.09 mm / 27000 at a speed of 50 ml / min by a metering pump, stretched in an air gap of 25 mm, and then coagulated and precipitated into fibers in a 20% NMMO coagulation bath at 25°C; the residual NMMO in the fibers is washed with an ultrasonic cleaner for 30 minutes, and then the fibers are dried at 105°C.

[0105] The fiber was tested for oxygen index according to the method specified in FZ / T 50016-2011, and the LOI value was 25.6±0.2%

[0106] Example 6

[0107] According to the method of Example 1, a flame retardant dispersion with an active ingredient of 25% wt was prepared, and the D 90 <1μm.

[0108] Step 1: After the flame retardant dispersion and the NMMO solution are metered and mixed in a static mixer and merged into one flow, they are swollen and blended with the cellulose pulp in a blending device. The flame retardant accounts for 300% of the absolute dry weight of the pulp. After vacuum dehydration, a flame retardant solution is obtained, in which the flame retardant accounts for 27 parts, the cellulose accounts for 9 parts, and the NMMO aqueous solution and the additives account for a total of 91 parts.

[0109] Step 2, according to the mass ratio of flame retardant solution: ordinary solution = 5.06:16.26, pumped into a twin-screw extruder through a metering pump, and then into a static mixer to obtain a flame retardant solution for spinning. The ordinary solution is composed of 12 parts of cellulose and 88 parts of NMMO aqueous solution and additives. The flame retardant solvent liquid is composed of 10.76 parts of cellulose, 4.84 parts of flame retardant, 84.4 parts of NMMO aqueous solution and others, that is, the flame retardant accounts for 45% of cellulose.

[0110] Step 3, the flame retardant solution is extruded from a spinneret with a hole size of 0.09 mm / 27000 at a speed of 50 ml / min by a metering pump, stretched in an air gap of 25 mm, and then coagulated and precipitated into fibers in a 20% NMMO coagulation bath at 25°C; the residual NMMO in the fibers is washed with an ultrasonic cleaner for 30 minutes, and then the fibers are dried at 105°C.

[0111] The fiber was tested for oxygen index according to the method specified in FZ / T 50016-2011, and the LOI value was 25.2±0.2%

[0112] Comparative Example 1

[0113] The spinning solution was extruded from a spinneret with a hole size of 0.09 mm / 27000 by a metering pump at a speed of 50 ml / min, drawn in an air gap of 25 mm, and then coagulated and precipitated into fibers in a 20% NMMO coagulation bath at 25°C. The obtained fibers were tested for oxygen index according to the method specified in FZ / T 50016-2011, and the LOI value was 17.0±0.2%;

[0114] The oxygen index test results of the fibers of Examples 3-6 and Comparative Example 1 are shown in Table 1.

[0115] Table 1 Limiting oxygen index (LOI) values ​​of modified fibers with different flame retardant contents

[0116]

[0117] Through Examples 3-6 and Comparative Example 1, it can be seen that the flame retardant used in the present invention has good flame retardant properties for Lyocell fiber. When the flame retardant accounts for more than 45% of the absolute dry weight of the pulp, the fiber flame retardant LOI is higher than 25%; the limiting oxygen index LOI value increases with the increase of the amount of flame retardant added.

[0118] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0119] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A flame retardant Lyocell fiber, It is characterized in that Including fiber base material and flame retardant, The flame retardant is evenly distributed inside the fiber substrate, wherein the mass of the flame retardant is 40%-80% of the mass of the fiber substrate.

2. The flame retardant Lyocell fiber according to claim 1, It is characterized in that The fiber substrate is cellulose fiber.

3. The flame-retardant Lyocell fiber according to claim 1, It is characterized in that The ratio between the particle size of the flame retardant and the diameter of the fiber is D 90 / φ 纤维 <0.

1.

4. The flame retardant Lyocell fiber according to claim 1, It is characterized in that The flame retardant is a nitrogen-based flame retardant, and the initial particle size D of the flame retardant particles is 90 <50μm.

5. The flame retardant Lyocell fiber according to claim 4, It is characterized in that The nitrogen-based flame retardant is 6,6'-piperazine-bis(1,3,5-triazine-2,4-diamine).

6. A method for preparing the flame-retardant Lyocell fiber according to any one of claims 1 to 5, It is characterized in that The following steps are involved: preparing a dispersion of a flame retardant; The flame retardant dispersion is mixed with cellulose fiber pulp, swollen, and vacuum-dehydrated to obtain a flame retardant solution, wherein the mass of the flame retardant accounts for 200%-500% of the absolute dry mass percentage of the cellulose pulp in the flame retardant solution; The flame retardant melt is mixed with a dissolving liquid to obtain a flame retardant dissolving liquid for spinning, wherein the mass of the flame retardant accounts for 60% to 80% of the mass of the cellulose in the flame retardant dissolving liquid; The flame-retardant dissolving liquid for spinning is spun to obtain the flame-retardant Lyocell fiber, wherein the mass of the flame retardant is 40%-80% of the mass of the fiber substrate.

7. The method for preparing the flame-retardant Lyocell fiber according to claim 6, It is characterized in that The step of preparing the flame retardant dispersion is specifically to premix the NMMO aqueous solution of the flame retardant, and obtain the flame retardant dispersion by a grinding process, wherein the ratio of the particle size of the flame retardant to the fiber diameter is D 90 / φ 纤维 <0.

1.

8. The method for preparing the flame-retardant Lyocell fiber according to claim 6, It is characterized in that The step of blending the flame retardant dispersion with cellulose fiber pulp, swelling, and vacuum dehydrating to obtain a flame retardant solution is specifically as follows: the flame retardant dispersion is mixed with an NMMO aqueous solution having a solute mass percentage of 76%-85%, and then blended with cellulose fiber pulp, swelling, and vacuum dehydrating to obtain a flame retardant solution.

9. The method for preparing the flame-retardant Lyocell fiber according to claim 8, It is characterized in that The step of mixing the flame retardant dispersion with the NMMO aqueous solution having a solute mass percentage of 76%-85% is achieved by using a static mixer.

10. The method for preparing the flame-retardant Lyocell fiber according to claim 8, It is characterized in that In the step of mixing the flame retardant dispersion with a NMMO aqueous solution having a solute mass percentage of 76%-85%, the mixing temperature is 80° C.-85° C. and the mixing time is 10 min-15 min; In the step of mixing the flame retardant dispersion with an NMMO aqueous solution having a solute mass percentage of 76%-85% and then blending with the cellulose fiber pulp for swelling, the swelling temperature is 90° C.-95° C., the swelling time is 30 min-45 min, and the concentration of the NMMO aqueous solution in the pre-dissolved solution after swelling is 77%-79%; The flame retardant dispersion is mixed with a NMMO aqueous solution having a solute mass percentage of 76%-85%, and then blended with the cellulose fiber pulp, swelled, and then vacuum-dehydrated at a temperature of 100° C.-105° C.; Preferably, the flame retardant melt and the dissolving liquid are mixed to obtain the flame retardant dissolving liquid for spinning, and the specific steps are: the flame retardant dissolving liquid and the ordinary dissolving liquid are metered and pumped into a twin-screw extruder, and then extruded into a static mixer through the twin-screw extruder for re-mixing to obtain the flame retardant dissolving liquid for spinning; Preferably, in the step of spinning the flame-retardant solution to obtain the flame-retardant Lyocell fiber, the spinning process is a dry-jet wet spinning process; Preferably, the dry-jet wet spinning process uses a coagulation bath containing a 0-20% by mass NMMO aqueous solution, a coagulation bath temperature of 10°C-25°C, and a humidity of 45%-65%; Preferably, the mass proportions of the components in the flame retardant dispersion include: flame retardant: 10 parts to 50 parts, emulsifier: 0.2 parts to 10 parts, dispersant: 0.2 parts to 10 parts, defoamer: 1 part to 5 parts, and the balance is dispersion medium, wherein the dispersion medium is selected from water or an aqueous solution of NMMO with a mass percentage of 20% to 55% of the solute; Preferably, the emulsifier is selected from one or more of sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium dodecyl sulfonate, and polyoxyethylene ether compounds; Preferably, the dispersant is selected from one or more of sodium polyacrylate, sodium ethylene bis naphthalene sulfonate, sodium α-olefin-sulfonate, and sodium maleate; Preferably, the defoamer is selected from one or more of polyether-modified polysiloxane, polyether-siloxane copolymer, and water-based acrylic defoamer; Preferably, the method for preparing the flame retardant dispersion comprises the following steps: Adding an emulsifier and a dispersant into a dispersion medium and stirring the mixture evenly to obtain a first intermediate product; Adding an appropriate amount of defoaming agent to the first intermediate product to eliminate bubbles, thereby obtaining a second intermediate product; Adding flame retardant powder to the second intermediate product, continuously stirring and adding a defoaming agent to obtain a third intermediate product; The third intermediate product is filtered to remove particulate matter to obtain a fourth intermediate product; The fourth intermediate product is ground and dispersed, so that the emulsifier and the dispersant are completely adsorbed on the surface of the flame retardant particles to obtain the flame retardant dispersion, wherein the flame retardant dispersion is a stable suspension; Preferably, in the step of filtering the third intermediate product to remove particulate matter to obtain the fourth intermediate product, the pore size of the filter is 50 μm.

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