A compounded flame retardant modified lyocell fiber and a preparation method thereof

Abstract

The application discloses a kind of compound flame retardant modified Lyocell fiber and preparation method thereof.Compound flame retardant modified Lyocell fiber uses cellulose fiber as matrix material, and there is flame retardant and synergistic additive uniformly dispersed inside, the mass of flame retardant accounts for 40%-80% of the mass of cellulose in fiber, the mass of synergistic additive accounts for 1-20% of the mass of cellulose in fiber;The particle size of the flame retardant and synergistic additive satisfies fiber <0.1.The flame retardant is nitrogen-based flame retardant;Synergistic additive is selected from one or several of organic phosphorus compound, metal oxide, boron-containing compound or non-water-soluble silicate.The application uses compound flame retardant to modify Lyocell fiber, by controlling particle size, both can guarantee that fiber spinning process is smooth, also can uniformly disperse compound flame retardant inside fiber, so that the flame resistance of fiber is obviously improved, washable, excellent flame-retardant durability, and low cost, zero emission, green and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of fiber manufacturing, specifically, it relates to a Lyocell fiber modified with a compound flame retardant and its preparation method. Background Technology

[0002] Lyocell fiber is a novel regenerated cellulose fiber prepared by a solvent method, using N-methylmarine-N-oxide (NMMO) as a solvent and a dry-jet wet-spinning process. Waste generated during Lyocell fiber production is biodegradable, and the NMMO solvent used can be recovered at a high efficiency of 99.5%, and is non-toxic and does not pollute the environment. Lyocell fiber possesses excellent moisture absorption and breathability, a pleasant hand feel, comfortable wear, and excellent mechanical properties, thus finding wide application in the apparel industry.

[0003] However, Lyocell fiber is a flammable fiber and is extremely easy to burn. To expand the application of Lyocell fiber, researchers have carried out flame-retardant modification. Existing flame-retardant modification technologies for Lyocell fiber are mainly based on blending and finishing processes. Finishing processes involve attaching flame retardants to fibers or fabrics through impregnation, baking, coating, spraying, etc. This method does not have high requirements for flame retardants, but the finished fabric has a poor hand feel and is not resistant to washing. Blending processes involve adding flame retardants to slurry or spinning solution to spin flame-retardant fibers. This method is simple, but it usually faces problems such as large and wide particle size range of flame retardants, easy agglomeration of flame retardant particles, significant loss of mechanical properties, and poor wash resistance of modified fibers. In addition, the existing multi-system flame retardant compounds have high preparation costs and are prone to environmental pollution during the preparation process.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and provide a method for preparing Lyocell fiber modified with a compound flame retardant. This invention modifies Lyocell fiber using a compound flame retardant. By controlling the particle size, it ensures smooth fiber spinning and achieves uniform dispersion of the compound flame retardant within the fiber, significantly improving the fiber's flame retardancy, washability, and flame-retardant durability. Furthermore, it is low-cost, emission-free, and environmentally friendly.

[0006] To solve the above-mentioned technical problems, the basic concept of the technical solution adopted by the present invention is as follows:

[0007] The first objective of this invention is to provide a Lyocell fiber modified with a compound flame retardant, using cellulose fibers as the matrix material, with flame retardants and synergistic additives uniformly dispersed internally. The flame retardant accounts for 40%-80% of the mass of cellulose in the fiber, and the synergistic additive accounts for 1-20% of the mass of cellulose in the fiber; the particle size of the flame retardant and synergistic additive meets the following requirements.

[0008] In a further embodiment, the flame retardant accounts for 60%-80% of the cellulose mass in the fiber, and the synergistic agent accounts for 5-15% of the cellulose mass in the fiber; the particle size of the flame retardant and synergistic agent meets the following requirements. In this invention, D 90 "Less than a certain value" means that 90% of the particles are smaller than a certain particle size value.

[0009] Preferably, the particle size of the flame retardant and synergistic additive meets the following requirements:

[0010] This invention uses a compound of finished flame retardants and synergistic additives, and controls the particle size of the flame retardants and synergistic additives to achieve the desired particle size. This invention ensures smooth fiber spinning while simultaneously allowing for the addition of flame retardants within the fiber. On one hand, by modifying Loycell fibers with a compounded flame retardant and controlled particle size, flame retardancy is significantly improved, with the limiting oxygen index (LOI) increasing from 17% to over 27%. Even after washing, the fibers maintain a high LOI value, demonstrating excellent flame retardant durability. On the other hand, this invention uses pre-prepared flame retardants and synergistic additives in a compound formulation. Compared to multi-component flame retardants such as nitrogen and phosphorus, this approach offers greater flexibility, eliminates the need for synthesis, reduces costs, and is more environmentally friendly, producing no pollutants. By controlling the proportion and particle size of the flame retardant and synergistic additives, a superior flame-retardant effect is achieved. The particle size reaches [a specific value, likely related to particle size or particle size]. At this time, the impact on fiber strength is lower, and the flame retardant durability is better.

[0011] In this invention, the cross-sectional diameter of the flame-retardant fiber is about 17 micrometers. If the particle size of the flame retardant and synergistic agent is too large, firstly, the flame retardant and synergistic agent are easy to precipitate on the fiber surface, which reduces the effective addition amount, worsens the blending effect, and reduces the wash resistance and other properties; secondly, the strength of the modified fiber will be greatly reduced.

[0012] In a further embodiment, the flame retardant is a nitrogen-based flame retardant;

[0013] Preferably, the flame retardant is selected from one or more of melamine, dicyandiamide, guanidine phosphate and their derivatives;

[0014] Preferably, the initial particle size D of the flame retardant particles is...90 <50um.

[0015] In a further embodiment, the synergistic agent is selected from one or more of organophosphorus compounds, metal oxides, boron-containing compounds, or water-insoluble silicates;

[0016] Preferably, the organophosphorus compound is selected from one or more of phosphate esters, tetrahydroxymethylphosphorus chloride, tetrahydroxymethylphosphorus chloride urea condensate, tetrahydroxymethylphosphorus sulfate, and tetrahydroxymethylphosphorus sulfate urea condensate;

[0017] The metal oxide is selected from one or more of antimony trioxide, zirconium oxide, titanium oxide, magnesium oxide, calcium oxide, aluminum hydroxide, and calcium hydroxide;

[0018] The boron-containing compound is selected from zinc borate;

[0019] The non-water-soluble silicates are selected from one or more of calcium silicate, magnesium silicate, and aluminum silicate;

[0020] Preferably, the initial particle size D of the synergistic adjuvant particles is... 90 <50um.

[0021] As a preferred option, the flame retardant is melamine cyanuric acid and the synergistic additive is zinc borate; or, the flame retardant is melamine cyanuric acid and the synergistic additive is zinc oxide.

[0022] A further approach involves compounding flame retardant-modified Lyocell fibers. 15g of the fiber is placed in a laundry bag and washed once in a standard 38-minute cycle using tap water in a regular top-loading washing machine (XQN35-188). After washing, the fibers are dried in an oven at 80℃. This process is repeated 11 to 12 times to maintain the flame retardancy rating, with a LOI value > 27%.

[0023] The flame-retardant Lyocell fiber of this invention has excellent flame-retardant properties, good water resistance, and maintains excellent flame-retardant durability. The flame retardant and cellulose are evenly blended and tightly bonded, resulting in good mechanical properties and hand feel.

[0024] A second objective of this invention is to provide a method for preparing Lyocell fibers modified with a compound flame retardant, comprising:

[0025] (1) The flame retardant and synergist are premixed with an NMMO solution to obtain a first mixture, wherein the particle size of the flame retardant and synergist in the first mixture is [specific value missing].

[0026] (2) The first mixture is premixed, stirred and swollen with cellulose pulp in sequence to obtain a second mixture that is fully swollen; wherein the flame retardant accounts for 40-80% of the dry weight of the cellulose pulp and the synergistic agent accounts for 1-20% of the dry weight of the cellulose pulp.

[0027] (3) After the second mixture is dehydrated, the cellulose fibers are completely dissolved to obtain a spinning solution; the spinning solution is spun to obtain Lyocell fiber modified with compound flame retardant.

[0028] In a further embodiment, the flame retardant accounts for 60%-80% of the cellulose mass in the fiber, and the synergistic agent accounts for 5-15% of the cellulose mass in the fiber; the particle size of the flame retardant and synergistic agent meets the following requirements.

[0029] In a further embodiment, the flame retardant is a nitrogen-based flame retardant;

[0030] Preferably, the flame retardant is selected from one or more of melamine, dicyandiamide, guanidine phosphate and their derivatives;

[0031] Preferably, the initial particle size D of the flame retardant particles is... 90 <50um.

[0032] In a further embodiment, the synergistic agent is selected from one or more of organophosphorus compounds, metal oxides, boron-containing compounds, or water-insoluble silicates;

[0033] Preferably, the synergistic agent is selected from one or more of the following: phosphate ester, antimony trioxide, zirconium oxide, titanium oxide, magnesium oxide, calcium oxide, aluminum hydroxide, calcium hydroxide, zinc borate, calcium silicate, magnesium silicate, aluminum silicate, tetrahydroxymethyl phosphorus chloride, tetrahydroxymethyl phosphorus chloride urea condensate, tetrahydroxymethyl phosphorus sulfate, and tetrahydroxymethyl phosphorus sulfate urea condensate.

[0034] Preferably, the initial particle size D of the synergistic adjuvant particles is... 90 <50um.

[0035] In a further embodiment, in step (1), the flame retardant and synergistic additive are first prepared into a flame retardant dispersion, and then premixed with an NMMO solution to obtain a first mixture. The preparation method of the flame retardant dispersion includes:

[0036] A flame-retardant dispersion is prepared by grinding the dispersion medium, emulsifier, dispersant, defoamer, flame retardant, and synergistic additives.

[0037] Preferably, the grinding equipment is selected from one or more of the following: ball mill, homogenizer, and sand mill, and the grinding beads are selected from one or more of the following: stainless steel beads, zirconia beads, and tungsten carbide beads.

[0038] As a specific approach, zirconia beads are used for grinding in a sand mill at a speed of 1100-1300 r / min for a grinding time of 1-6 h.

[0039] In a further embodiment, the mass fractions of each component in the flame-retardant dispersion include:

[0040] Flame retardant: 10-50 parts

[0041] Synergistic adjuvant: 1-20 parts

[0042] Emulsifier: 0.2-20 parts

[0043] Dispersant: 0.2-20 parts;

[0044] Defoamer: 1-5 parts;

[0045] The remainder is a dispersion medium, wherein the dispersion medium is selected from water or an aqueous solution of NMMO.

[0046] In a further embodiment, the emulsifier is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecyl sulfonate, polyoxyethylene ether compounds, styrene-maleic anhydride copolymer, polyoxyethylene dehydrated sorbitan monooleate, and polyoxyethylene sorbitan trioleate.

[0047] Preferably, the dispersant is selected from one or more of sodium polyacrylate, sodium ethylene bis(naphthalene) sulfonate, fatty alcohol polyoxyethylene ether, sodium α-olefin polyoxyethylene sulfonate, and sodium maleate.

[0048] Preferably, the defoamer is selected from one or more of polyether-modified polysiloxane, polyether siloxane copolymer, and water-based acrylic defoamer.

[0049] In a further embodiment, in step (2), the stirring temperature is 30℃-100℃ and the swelling duration is 5min-60min;

[0050] Preferably, the pulp in the second mixture is in a uniform, fine, microfiber-free porridge state.

[0051] In a further step, in step (3), a dry-jet wet spinning process is adopted. The spinning solution is successively extruded through a spinneret, solidified, drawn, washed, cut and dried to obtain Lyocell fiber modified with a compound flame retardant.

[0052] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art.

[0053] 1. This invention uses a compound of finished flame retardants and synergistic additives, and controls the particle size of the flame retardants and synergistic additives to achieve the required particle size. This method not only ensures smooth fiber spinning but also allows for the addition of flame retardants within the fiber. By modifying Loycell fiber with a compound flame retardant that controls particle size, the flame retardancy is significantly improved, with the limiting oxygen index (LOI) increasing from 17% to over 27%. The fiber maintains a high LOI value even after washing, demonstrating good flame retardant durability.

[0054] 2. This invention uses pre-prepared flame retardants and synergistic additives in a compound formulation. Compared with multi-compound flame retardants such as nitrogen and phosphorus, the formulation is more flexible, requires no synthesis, is lower in cost, more environmentally friendly, and does not generate pollutants. By controlling the addition ratio and particle size of the flame retardant and synergistic additives, excellent flame retardant effects are achieved. Experiments revealed that different compound systems affect fiber strength and flame retardancy; with different compound types, the initial LOI value of the fibers is consistently higher than 27%. The melamine cyanuric acid and zinc oxide compound system showed the best results.

[0055] 3. The method of this invention can prepare a flame retardant dispersion with excellent stability. The particle size remains stable during the standing process, exhibiting excellent compatibility with NMMO solution. The production process is zero-emission and environmentally friendly. The resulting flame-retardant Lyocell fiber exhibits excellent flame retardant properties, good washability, and excellent flame retardant durability. The flame retardant and cellulose are uniformly blended and tightly bonded, resulting in good mechanical properties and a pleasant hand feel. The specific embodiments of this invention will be described in further detail below with reference to the accompanying drawings. Attached Figure Description

[0056] The accompanying drawings, as part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation of the invention. Obviously, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without creative effort. In the drawings:

[0057] Figure 1 This is a schematic diagram showing the dispersion and distribution of flame retardant and synergistic additives in the flame retardant dispersion of the present invention.

[0058] Figure 2 This is a microscope image of the flame-retardant fiber spinning solution in this invention.

[0059] Figure 3 The particle size D of the dispersion in this invention 90 Surface morphology of modified Lyocell fibers at 1.84 μm;

[0060] Figure 4 The particle size D of the dispersion in this invention90 Surface morphology of modified Lyocell fibers at 1.4 μm;

[0061] Figure 5 The particle size D of the dispersion in this invention 90 The surface morphology of modified Lyocell fibers at a density of 0.7 μm.

[0062] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0063] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0064] It should be noted that, unless otherwise specified, all reagents used in this invention are commercially available.

[0065] The washing method includes: taking 15g of fiber, putting it into a laundry bag, using a regular top-loading washing machine (XQN35-188), using tap water, and a standard 38-minute washing program as one wash, followed by drying in an oven at 80℃. Repeat the washing process up to 12 times.

[0066] Preparation of flame retardant dispersion

[0067] Example 1: Preparation of Flame-Retardant Dispersion

[0068] Three parts by weight of sodium dodecyl sulfate, five parts by weight of sodium ethyl naphthalene sulfonate, two parts by weight of polyether siloxane copolymer, and 75 parts by weight of water were stirred in a dispersion tank. Then, under shear stirring at 4-6 m / s, 26.1 parts by weight of melamine cyanuric acid and 2.2 parts by weight of zinc borate were gradually added. After stirring evenly, the mixture was transferred to a sand mill and ground with zirconia beads at 1200 r / min for 2 h. The dispersion was then filtered to obtain a flame retardant dispersion with an effective flame retardant content of 25%.

[0069] The active ingredients are flame retardants and synergistic additives. The weight percentage of the active ingredients is calculated as: weight of active ingredients / total amount of ingredients × 100%.

[0070] Example 2: Preparation of Flame-Retardant Dispersion

[0071] Four parts by weight of sodium dodecylbenzenesulfonate, seven parts by weight of fatty alcohol polyoxyethylene ether, one part by weight of polyether-modified polysiloxane, and 148 parts by weight of water were stirred in a dispersion tank. Then, under shear stirring at 4-6 m / s, 24.1 parts by weight of melamine, 2.2 parts by weight of zinc oxide, and 2 parts by weight of antimony trioxide were gradually added. After stirring evenly, the mixture was transferred to a sand mill and ground with zirconia beads at 1200 r / min for 2 h. The dispersion was then filtered to obtain a flame retardant dispersion with an effective flame retardant content of 15%.

[0072] Example 3: Preparation of Flame-Retardant Dispersion

[0073] 0.2 parts by weight of sodium dodecyl sulfonate, 0.5 parts by weight of sodium α-olefin polyoxyethylene sulfonate, 1 part by weight of polyether-modified polysiloxane, and 87.5 parts by weight of water were stirred in a dispersion tank. Then, under shear stirring at 4-6 m / s, 19.1 parts by weight of melamine cyanuric acid, 2.2 parts by weight of magnesium silicate, and 1 part by weight of zinc borate were gradually added. After stirring evenly, the mixture was transferred to a sand mill and ground with zirconia beads at 1200 r / min for 2 h. The dispersion was then filtered to obtain a flame retardant dispersion with an effective flame retardant content of 20%.

[0074] Example 4: Preparation of Flame-Retardant Dispersion

[0075] Five parts by weight of sodium dodecyl sulfonate, five parts by weight of sodium dodecyl sulfate, ten parts by weight of sodium α-olefin polyoxyethylene sulfonate, five parts by weight of polyether-modified polysiloxane, and 201 parts by weight of water were stirred in a dispersion tank. Then, under shear stirring at 4-6 m / s, 19.1 parts by weight of melamine cyanuric acid, 2.5 parts by weight of calcium silicate, and 1 part by weight of antimony trioxide were gradually added. After stirring until homogeneous, the mixture was transferred to a sand mill and ground with zirconia beads at 1200 r / min for 2 h. The dispersion was then filtered to obtain a flame retardant dispersion with an effective flame retardant content of 10%.

[0076] Examples and comparative examples of Lyocell fiber preparation

[0077] Example 5

[0078] A flame retardant dispersion with 25% wt of active ingredient was prepared according to the method in Example 1. The D content was measured using a laser particle size analyzer. 90 <1.2um. Figure 1 The figure shows the dispersion state of particulate matter (flame retardant and synergistic additive) in NMMO, and it can be seen that the dispersion is uniform.

[0079] Cellulose pulp and a mixture of NMMO aqueous solution and flame retardant dispersion were added sequentially to a reactor. The total amount of flame retardant and synergistic additives accounted for 75% of the oven-dry weight of the pulp (of which the flame retardant accounted for approximately 69% and the synergistic additives accounted for approximately 6%). The temperature was 75℃, and the mixture was stirred and swollen for 25 minutes. Then, the temperature was raised to 106℃, and a vacuum was drawn to 0.095 MPa. Vacuum dehydration was carried out for 40-60 minutes until the cellulose was completely dissolved, forming the spinning solution. Figure 2 The image shows a microscope image of the flame-retardant fiber spinning solution, which shows that the particles in the spinning solution are very evenly distributed.

[0080] The spinning solution was extruded from a spinneret with 0.09 mm / 27000 orifices at a rate of 50 ml / min using a metering pump, and then drawn in an air gap of 25 mm. The fibers were then coagulated and precipitated in a 20% NMMO coagulation bath at 25 °C. The fibers were then washed with an ultrasonic cleaner for 30 min to remove residual NMMO, and then dried at 105 °C.

[0081] The obtained fibers were processed by taking 15g of fiber, placing it in a laundry bag, and washing it once in a standard 38-minute cycle using tap water in a regular top-loading washing machine (XQN35-188). After washing, the fibers were dried in an oven at 80℃. This process was repeated 11 to 12 times. The oxygen index of the fibers before and after washing was tested according to the method specified in FZT 50016-2011. The LOI values ​​before and after washing were 34.6% and 33.2%, respectively; the fiber fineness was 2.2 dtex, and the dry breaking strength was 2.25 CN / dtex.

[0082] Example 6

[0083] A flame retardant dispersion with 15% wt of active ingredient was prepared according to the method in Example 2. The D content was measured using a laser particle size analyzer. 90 <1µm. Cellulose pulp and a mixture of NMMO aqueous solution and flame retardant dispersion were added sequentially to the reactor. The total amount of flame retardant and synergistic additives accounted for 65% of the oven-dry weight of the pulp (approximately 55.4% flame retardant and 9.6% synergistic additives). The mixture was stirred and swollen at 80℃ for 20 min, then heated to 105℃, and vacuumed to 0.095 MPa for 40-60 min until the cellulose was completely dissolved. The spinning solution was extruded from a spinneret with 0.075 mm / 2000 orifices using a metering pump at a rate of 50 ml / min, drawn in a 25 mm long air gap, and then coagulated to precipitate fibers in a 25℃, 20% NMMO coagulation bath. The fibers were then washed with an ultrasonic cleaner for 30 min to remove residual NMMO, and finally dried at 105℃.

[0084] The obtained fibers were processed by taking 15g of fiber, placing it in a laundry bag, and washing it once in a standard 38-minute cycle using tap water in a regular top-loading washing machine (XQN35-188). After washing, the fibers were dried in an oven at 80℃. This process was repeated 11 to 12 times. The washed fibers were then tested for limiting oxygen index (LOI) according to the method specified in FZ / T 50016-2011. The LOI values ​​before and after washing were 31.5% and 30.4%, respectively; the fiber fineness was 2.2 dtex, and the dry breaking strength was 3.12 CN / dtex.

[0085] Example 7

[0086] A flame retardant dispersion with 20% wt of active ingredient was prepared according to the method in Example 3. The D content was measured using a laser particle size analyzer. 90 <1µm. Cellulose pulp and a mixture of NMMO aqueous solution and flame retardant dispersion were added sequentially to the reactor. The flame retardant and synergistic agent accounted for 55% of the oven-dry weight of the pulp (approximately 47% flame retardant and 8% synergistic agent). The temperature was 72℃, and the mixture was stirred and swollen for 28 min. Then, the temperature was raised to 108℃, and a vacuum of 0.095 MPa was applied for dehydration for 40-60 min until the cellulose was completely dissolved. The spinning solution was extruded from a spinneret with 0.09 mm / 27000 orifices using a metering pump at a rate of 50 ml / min. The fibers were drawn in a 25 mm long air gap and then coagulated in a 20% NMMO coagulation bath at 25℃ to precipitate fibers. The fibers were then washed with an ultrasonic cleaner for 30 min to remove residual NMMO, and finally dried at 105℃.

[0087] The fiber was tested for oxygen index according to the method specified in FZ / T 50016-2011. The LOI values ​​before and after washing were 30.2% and 29.8%, respectively. The fiber fineness was 2.2 dtex and the dry breaking strength was 3.25 CN / dtex.

[0088] Example 8

[0089] A flame retardant dispersion with 10% wt of active ingredient was prepared according to the method in Example 4. The D content was measured using a laser particle size analyzer. 90<1µm. Cellulose pulp and a mixed solution of NMMO aqueous solution and flame retardant dispersion were added sequentially to the reactor. The flame retardant and synergistic agent accounted for 45% of the oven-dry weight of the pulp (approximately 38% flame retardant and 7% synergistic agent). The temperature was 85℃, and the mixture was stirred and swollen for 15 min. Then, the temperature was raised to 102℃, and a vacuum of 0.095 MPa was applied for dehydration for 40-60 min until the cellulose was completely dissolved. The spinning solution was extruded from a spinneret with 0.09 mm / 27000 orifices using a metering pump at a rate of 50 ml / min. The fibers were drawn in a 25 mm long air gap and then coagulated in a 20% NMMO coagulation bath at 25℃ to precipitate fibers. The fibers were then washed with an ultrasonic cleaner for 30 min to remove residual NMMO, and finally dried at 105℃.

[0090] The fiber was tested for oxygen index according to the method specified in FZ / T 50016-2011. The LOI values ​​before and after washing were 27.5% and 27%, respectively. The fiber fineness was 2.2 dtex and the dry breaking strength was 3.19 CN / dtex.

[0091] Comparative Example 1

[0092] The spinning solution was extruded from a spinneret with 0.09 mm / 27,000 orifices at a rate of 50 ml / min using a metering pump. The fibers were then drawn in a 25 mm long air gap and coagulated in a 20% NMMO coagulation bath at 25 °C to precipitate fibers. The resulting fibers were tested for oxygen index according to the method specified in FZ / T 50016-2011, with an LOI value of 17%; fiber fineness was 2.2 dtex, and dry breaking strength was 3.89 cN / dtex.

[0093] The strength and oxygen index test results of the fibers of Examples 5-8 and Comparative Example 1 are shown in Tables 1 and 2.

[0094] Table 1. Strength of modified fibers with different flame retardant contents

[0095]

[0096]

[0097] The difference in strength values ​​between Comparative Example 1 and Examples 5-8 shows that the dry breaking strength of the fibers in the system of the present invention is significantly reduced due to the addition of compound flame retardants. Furthermore, as the amount of compound flame retardant added increases, the probability of stress defects being generated inside the fiber increases, and the decrease in dry strength is also greater.

[0098] Table 2 Limiting Oxygen Index (LOI) values ​​of modified fibers with different flame retardant contents

[0099] Comparative Example 1 17 17 Example 5 34.6 33.2 Example 6 31.5 30.4 Example 7 30.2 29.8 Example 8 27.5 27

[0100] As can be seen from Examples 5-8 and Comparative Example 1, the compound flame retardant of the present invention still has good flame retardant properties on Lyocell fibers after 12 washes with water. When the flame retardant and synergistic additives account for more than 45% of the oven-dry weight of the pulp, the flame retardant LOI of the fiber is higher than 27%, reaching the flame-retardant level. The limiting oxygen index (LOI) value increases with the increase of the amount of compound flame retardant and synergistic additives.

[0101] Effect of different particle sizes on flame retardants and synergistic additives in Comparative Example 2

[0102] Referring to the components and methods of Example 1, different grinding conditions were used for each group to control the particle size. The dispersion was then filtered to obtain a flame retardant dispersion with an effective flame retardant content of 25%. The particle size distribution was measured using a laser particle size analyzer. 90 Then, fibers were prepared according to the steps and methods of Example 5, and their performance was tested. The distinguishing conditions and performance testing parameters are shown in the table below.

[0103] Table 3

[0104]

[0105] Results analysis: By extending the grinding time, flame-retardant dispersions with different particle sizes were prepared. The different particle sizes have an impact on the mechanical properties and flame-retardant properties of the fibers, especially on the flame-retardant and wash-resistant properties. Reducing the particle size helps to alleviate the damage to the mechanical properties of the fibers caused by flame retardants, while improving the flame-retardant and wash-resistant properties.

[0106] Specifically, fiber fineness has a certain impact on its strength. High-fineness fibers have lower draw and affect the degree of orientation (higher orientation results in better mechanical properties). In this case, high fineness should correspond to a lower degree of orientation, and theoretically, lower mechanical strength. However, in Table 3, as fineness increases, strength also increases, which deviates somewhat from the theory. This is due to the change in particle size. Therefore, the comparison in Table 3 shows that reducing particle size can reduce the damage to fiber mechanical properties caused by flame retardants and synergistic additives.

[0107] Figure 3 The figure shows the particle size D in the flame retardant dispersion. 90 Surface morphology of modified Lyocell fibers at 1.84 μm; Figure 4 The figure shows the particle size D in the flame retardant dispersion. 90 Surface morphology of modified Lyocell fibers at 1.4 μm; Figure 5 The figure shows the particle size D in the flame retardant dispersion. 90 The surface morphology of modified Lyocell fibers at 0.7 μm is shown in the attached image. Figure 3 , attached Figure 4 , attached Figure 5 Electron microscopy morphology of fiber surfaces prepared with flame retardant dispersions of different particle sizes shows that the reduction in particle size can prevent the accumulation and adhesion of particulate matter on the fiber surface, improve the LOI value, and enhance the washability.

[0108] When the particle size in the flame retardant dispersion If the particle size of the flame retardant and synergistic additive is too large, firstly, the flame retardant and synergistic additive are prone to precipitation on the fiber surface, reducing their effective addition amount, worsening the blending effect, and reducing properties such as wash resistance; secondly, the strength of the modified fiber will be greatly reduced.

[0109] Comparative Example 3: Effects of Different Flame Retardant and Synergistic Additive Types

[0110] Referring to the components, proportions, and methods of Example 1, different types of flame retardants and synergistic additives were used in each group, and D was detected using a laser particle size analyzer. 90 <1μm, and then this dispersion was filtered to obtain a flame retardant dispersion with an effective flame retardant content of 25%. Then, fibers were prepared according to the steps and methods of Example 5, and their performance was tested. The distinguishing conditions and performance test parameters are shown in the table below.

[0111] Table 4

[0112]

[0113]

[0114] Results Analysis: A comprehensive analysis of the effects of different compound systems on fiber strength and flame retardancy showed that the initial LOI value of the fibers was higher than 27% for all different compound types, but the reduction after washing varied. Group 5 performed better. Therefore, the compound system of Group 5, namely the compound system of melamine cyanuric acid and zinc borate, was further optimized, resulting in higher fiber strength and better flame retardancy and water resistance.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A Lyocell fiber modified with a compound flame retardant, characterized in that, Using cellulose fibers as the matrix material, flame retardants and synergistic additives are uniformly dispersed within the fibers. The flame retardant accounts for 40%-80% of the mass of cellulose in the fibers, and the synergistic additives account for 1-20% of the mass of cellulose in the fibers. The particle size of the flame retardant and synergistic additives meets the following requirement: D 90 / φ fiber < 0.08; The particle size of the flame retardant and synergistic additives satisfies D 90 <1.2 μm; The flame retardant is selected from one or two of melamine and melamine cyanuric acid; The synergistic agent is selected from one or more of organophosphorus compounds, metal oxides, boron-containing compounds, or water-insoluble silicates; the organophosphorus compounds are selected from one or more of phosphate esters, tetramethylphosphorus chloride, tetramethylphosphorus chloride urea condensate, tetramethylphosphorus sulfate, and tetramethylphosphorus sulfate urea condensate; the metal oxides are selected from one or more of antimony trioxide, zirconium oxide, titanium oxide, magnesium oxide, calcium oxide, aluminum hydroxide, and calcium hydroxide; the boron-containing compounds are selected from zinc borate; and the water-insoluble silicates are selected from one or more of calcium silicate, magnesium silicate, and aluminum silicate.

2. The Lyocell fiber modified with the compound flame retardant according to claim 1, characterized in that, Flame retardants account for 60%-80% of the cellulose mass in the fiber, while synergistic additives account for 5-15% of the cellulose mass in the fiber.

3. The Lyocell fiber modified with the compound flame retardant according to claim 1, characterized in that, Initial particle size D of flame retardant particles 90 <50um.

4. The Lyocell fiber modified with a compound flame retardant according to any one of claims 1-3, characterized in that, Initial particle size D of synergistic adjuvant particles 90 <50um.

5. A method for preparing Lyocell fiber modified with a compound flame retardant as described in any one of claims 1-4, characterized in that, include: (1) The flame retardant and synergist are premixed with NMMO solution to obtain a first mixture, wherein the particle size D of the flame retardant and synergist in the first mixture is... 90 / φ fiber < 0.08; (2) The first mixture is premixed, stirred and swollen with cellulose pulp in sequence to obtain a second mixture that is fully swollen; wherein the flame retardant accounts for 40-80% of the dry weight of the cellulose pulp and the synergistic agent accounts for 1-20% of the dry weight of the cellulose pulp. (3) After the second mixture is dehydrated, the cellulose fibers are completely dissolved to obtain a spinning solution; the spinning solution is spun to obtain Lyocell fiber modified with compound flame retardant.

6. The preparation method according to claim 5, characterized in that, In step (1), the flame retardant and synergistic additive are first prepared into a flame retardant dispersion, and then premixed with an NMMO solution to obtain a first mixture. The preparation method of the flame retardant dispersion includes: A flame-retardant dispersion is prepared by grinding the dispersion medium, emulsifier, dispersant, defoamer, flame retardant, and synergistic additives.

7. The preparation method according to claim 6, characterized in that, In step (1), the grinding equipment is selected from one or more of the following: ball mill, homogenizer, sand mill, and a combination of the two. The grinding beads are selected from one or more of the following: stainless steel beads, zirconia beads, and tungsten carbide beads.

8. The preparation method according to claim 6, characterized in that, The mass fractions of each component in the flame-retardant dispersion include: Flame retardant: 10-50 parts Synergistic adjuvant: 1-20 parts Emulsifier: 0.2-20 parts Dispersant: 0.2-20 parts; Defoamer: 1-5 parts; The remainder is a dispersion medium, wherein the dispersion medium is selected from water or an aqueous solution of NMMO.

9. The preparation method according to claim 8, characterized in that, The emulsifier is selected from one or more of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecyl sulfonate, polyoxyethylene ether compounds, styrene-maleic anhydride copolymer, polyoxyethylene dehydrated sorbitan monooleate, and polyoxyethylene sorbitan trioleate.

10. The preparation method according to claim 8, characterized in that, The dispersant is selected from one or more of sodium polyacrylate, sodium ethyl bis(naphthalene) sulfonate fatty alcohol polyoxyethylene ether, sodium α-olefin polyoxyethylene sulfonate, and sodium maleate.

11. The preparation method according to claim 8, characterized in that, The defoamer is selected from one or more of polyether-modified polysiloxane, polyether siloxane copolymer, and water-based acrylic defoamer.

12. The preparation method according to any one of claims 5-11, characterized in that, In step (2), the stirring temperature is 30℃-100℃ and the swelling time is 5min-60min.

13. The preparation method according to any one of claims 5-11, characterized in that, In step (2), the pulp in the second mixture is in a uniform, fine, microfiber-free porridge state.

14. The preparation method according to any one of claims 5-11, characterized in that, In step (3), a dry-jet wet spinning process is adopted. The spinning solution is successively extruded through a spinneret, solidified, drawn, washed, cut and dried to obtain Lyocell fiber modified with compound flame retardant.

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