A flame retardant with a microcapsule structure, a flame-retardant fiber, and a preparation method and application thereof

Abstract

The application discloses a flame retardant with a microcapsule structure, a flame-retardant fiber and a preparation method and application thereof, the flame retardant comprises a core material and a shell covering the core material, the core material is a phosphazene flame retardant compound, and the shell is inorganic nanoparticles; the structure of the phosphazene flame retardant compound is shown as formula I: wherein, R1 is selected from R2 is selected from -OCH3, a benzene ring, and the application simultaneously introduces the elements phosphorus, nitrogen and silicon with flame retardant performance into the flame retardant compound and prepares a microcapsule structure; the outer layer has exposed hydroxyl groups, can form hydrogen bonds with hydroxyl groups on cellulose, and improves the binding force between the flame retardant and the cellulose. The flame-retardant Lyocell fiber prepared by using the flame retardant can simultaneously have excellent flame retardancy, mechanical properties and washing resistance, and the flame retardant has a small use and addition amount and a high effective incorporation rate.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of fiber preparation, and particularly relates to a flame retardant with a microcapsule structure, a flame-retardant fiber and a preparation method and application thereof. BACKGROUND

[0002] Lyocell fiber is a new type of regenerated cellulose fiber, which is prepared by dry-wet method using wood pulp as raw material and N-methyl morpholine-N-oxide (NMMO) as solvent. No waste gas and residue are generated in the whole process. The raw material can be naturally degraded, and the fabric has the excellent properties of cotton comfort, polyester strength, silk-like gloss and touch, etc., and is known as "green fiber". However, Lyocell fiber belongs to carbohydrates and burns quickly when exposed to fire. The flammable property limits its application in many fields. Therefore, an effective and reasonable flame-retardant modification method is urgently needed to improve the flame-retardant property of Lyocell fiber and expand its application range.

[0003] At present, the methods for improving the flame-retardant property of Lyocell fiber mainly include chemical modification, physical blending, fabric post-treatment, dip coating method, etc. Chemical modification is to functionalize the flame retardant and then graft it onto Lyocell fiber or combine it together by using certain interaction force with Lyocell fiber. This method not only has high effective doping rate, but also the obtained flame-retardant fiber has good durability. Physical blending is the most commonly used modification method, which refers to blending the flame retardant with flame-retardant function into the fiber spinning solution by blending and doping, and then spinning to obtain flame-retardant Lyocell fiber. This method is simple, but the obtained flame-retardant fiber has poor durability. The flame retardant is easy to fall off and agglomerate on the fiber, resulting in poor uniformity of the flame-retardant fiber, a large amount of flame retardant falling off into the coagulation bath, and the solvent being difficult to recover. The fabric post-treatment or dip coating method not only makes the obtained flame-retardant fiber have poor hand feeling and mechanical property, but also causes the solvent to be difficult to recover.

[0004] Therefore, how to research the flame-retardant Lyocell fiber with high flame retardancy, green environmental protection, high mechanical property and durability is the focus of people's pursuit and attention.

[0005] In view of this, the present application is proposed. SUMMARY

[0006] The technical problems to be solved by the present application are to overcome the deficiencies of the prior art, and to provide a flame retardant with a microcapsule structure, a flame-retardant fiber and a preparation method and application thereof.The present application simultaneously introduces the elements phosphorus, nitrogen and silicon with flame-retardant properties into a flame-retardant compound and prepares a flame-retardant microcapsule structure, and the flame-retardant Lyocell fiber prepared by using the flame retardant of the present application can simultaneously have excellent flame retardancy, mechanical properties and washing resistance, and the flame retardant has a small addition amount and a high effective incorporation rate.

[0007] To solve the above technical problems, the basic idea of the technical solution of the present application is:

[0008] The first object of the present application is to provide a flame retardant with a microcapsule structure, comprising a core material and a shell covering the core material, wherein the core material is a phosphazene flame-retardant compound, and the shell is an inorganic nanoparticle, and the structure of the phosphazene flame-retardant compound is shown in formula I:

[0009]

[0010] wherein R1 is selected from R2 is selected from -OCH3, a benzene ring,

[0011] In a further aspect, the structure of the phosphazene flame-retardant compound is shown in formula II, formula III or formula IV:

[0012] In a further aspect, the inorganic nanoparticle comprises a silicon-containing polyhydroxyl inorganic nanoparticle or a silicon-containing polyhydroxyl inorganic nanoparticle obtained after hydrolysis.

[0013] In the present application, the phosphazene flame-retardant containing the flame-retardant elements phosphorus and nitrogen is used as the core of the microcapsule, and the polyhydroxyl nanoparticle containing the flame-retardant element silicon is used as the shell, thereby forming a microcapsule structure with exposed polyhydroxyl groups. On the one hand, the core of the flame-retardant microcapsule structure belongs to the phosphorus and nitrogen flame-retardant, which can reduce the temperature of the surface layer of the fiber during the combustion of the fiber, and form an oxygen barrier layer on the surface of the fiber to prevent the combustion of the fiber; and the shell of the flame-retardant microcapsule structure belongs to the silicon flame-retardant, which can be cracked into a carbon layer when heated, thereby further improving the oxidation resistance and flame retardancy of the fiber through the carbon layer. The flame-retardant Lyocell fiber prepared by using the flame retardant of the present application contains the above three flame-retardant elements, and the flame-retardant performance of the fiber can be obviously improved when the content of the flame retardant is low, without adding other dispersants, emulsifiers and other auxiliaries. On the other hand, the large number of exposed hydroxyl groups of the microcapsule structure can interact with the hydroxyl groups on the cellulose through hydrogen bonds, thereby improving the mutual combination force between the flame retardant and the fiber, avoiding the phenomenon of the flame retardant falling off in the coagulation bath, and further improving the durability and mechanical properties of the flame-retardant Lyocell fiber.

[0014] Further, the inorganic nanoparticles are selected from one or more of ethyl silicate, hydroxyl silicone oil, and hydroxyl dimethyl silicone.

[0015] A second object of the present application is to provide a preparation method of the flame retardant with microcapsule structure according to any of the above embodiments, comprising:

[0016] (1) mixing hexachlorocyclotriphosphazene, a first catalyst, a first reaction solvent and a hydroxyl or phenolic compound to perform a nucleophilic substitution reaction to obtain a trioxyl-trichlorocyclotriphosphazene compound;

[0017] (2) mixing the trioxyl-trichlorocyclotriphosphazene compound, a hydroxyl or phenolic compound, a second catalyst and a second reaction solvent to perform a nucleophilic substitution reaction in a reaction kettle, and then performing filtration, drying and chromatographic column separation to obtain a hexacyclotriphosphazene compound;

[0018] (3) stirring and mixing the hexacyclotriphosphazene compound, ammonia water, a third reaction solvent and deionized water, performing ultrasonic treatment, then adding inorganic nanoparticles into the mixed solution and stirring; ending the reaction and performing centrifugal separation to obtain the flame retardant with microcapsule structure.

[0019] After the hexacyclotriphosphazene compound is prepared, the hexacyclotriphosphazene compound, ammonia water, a third reaction solvent and deionized water are stirred and mixed, ultrasonic treatment is performed, then inorganic nanoparticles are added into the mixed solution and stirred; the reaction is ended and centrifugal separation is performed to obtain the flame retardant with microcapsule structure. Under such conditions, the inorganic nanoparticles can form a microcapsule structure covering the phosphazene compound, and the multiple hydroxyl groups are exposed outside, which is beneficial to forming hydrogen bonds with the hydroxyl groups of cellulose, thereby improving the mutual binding force between the flame retardant and the fiber and avoiding falling off.

[0020] Further, in step (1), the molar ratio of the hexachlorocyclotriphosphazene, the hydroxyl or phenolic compound, the first catalyst and the first reaction solvent is 1:(6-10):(9-13):(8-12).

[0021] Further, the hydroxyl or phenolic compound is selected from one or more of phenol, methyl phenol, methanol and 4-phenyl phenol.

[0022] Further, the first catalyst is selected from one or more of potassium carbonate, cesium carbonate, magnesium carbonate, zinc carbonate, lithium carbonate, calcium carbonate and other carbonates.

[0023] Further, the first reaction solvent is selected from one or more of toluene, xylene, diphenyl or cumene.

[0024] Further, in step (1), the conditions of the nucleophilic substitution reaction include: first, reacting at room temperature for 30 min, then heating to 60-80℃ for 1 h, and finally heating to 100-120℃ for 8-16 h, with the heating rate being 5-10℃ / min.

[0025] Further, in step (2), the molar ratio of the trioxyl-trichlorocyclotriphosphazene compound, the hydroxyl or phenolic compound, the second catalyst and the second reaction solvent is 1:(3-5):(5-7):(15-20).

[0026] Further, the second catalyst is selected from strong basic catalysts; preferably, the second catalyst is selected from one or more of cesium fluoride, zinc fluoride, potassium fluoride, sodium fluoride, etc.

[0027] Further, the second reaction solvent is selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide or dimethyl sulfoxide.

[0028] Further, in step (2), the temperature in the nucleophilic substitution reaction kettle is 120-150℃, the pressure is 0.1-0.3Mpa, and the reaction time is 5-12 h.

[0029] Further, in step (3), the molar ratio of the hexacyclotriphosphazene compound, ammonia, the third reaction solvent, deionized water and the inorganic nanoparticles is 1:(45-50):(90-100):(60-70):(6-10).

[0030] Further, the third reaction solvent is selected from one or more of methanol, ethanol and propanol.

[0031] Further, the average particle size of the hexacyclotriphosphazene compound is 5um.

[0032] Further, the average particle size of the inorganic nanoparticles is 300-600nm; preferably, the average particle size is 300-500nm.

[0033] By controlling the average particle size of the hexacyclotriphosphazene compound and the inorganic nanoparticles, it is beneficial to obtain more uniform spinning dope, improve the mechanical properties of the flame-retardant fiber, and better combine the flame retardant and cellulose, thereby improving the flame retardancy and durability of the fiber.

[0034] Further, the temperature of the ultrasonic treatment is preferably 50-80℃, and the time is 30-60 min.

[0035] The third object of the present application is to provide the use of the flame retardant with microcapsule structure according to any one of the preceding embodiments or combinations thereof in the preparation of flame-retardant fibers; preferably, in the preparation of flame-retardant Lyocell fibers.

[0036] The fourth object of the present application is to provide a flame-retardant Lyocell fiber comprising the flame retardant with microcapsule structure according to any one of the preceding embodiments or combinations thereof and cellulose, wherein the mass ratio of the flame retardant to cellulose is 5-15:100.

[0037] The present application further mixes the flame retardant with microcapsule structure comprising phosphorus, nitrogen and silicon flame-retardant elements as described above with cellulose pulp to dissolve and spin to obtain flame-retardant Lyocell fibers. The mass ratio of the flame retardant to cellulose is 5-15:100, and a small amount of flame retardant can achieve good flame-retardant effect, has high effective incorporation rate, and does not need to add emulsifiers, dispersants and other auxiliaries, and the flame-retardant fibers have excellent flame-retardant performance, good durability and high mechanical properties.

[0038] The fifth object of the present application is to provide a preparation method of the flame-retardant Lyocell fiber as described above, comprising:

[0039] (1) mixing the flame retardant with microcapsule structure as described above with NMMO aqueous solution to obtain a first mixed solution;

[0040] (2) mixing the first mixed solution, a stabilizer and an antioxidant by vigorous stirring, and then adding cellulose pulp pieces into the system, and sequentially mixing, swelling, vacuumizing and dehydrating to obtain a spinning dope;

[0041] (3) spinning the spinning dope by dry-wet spinning, forming into a coagulation bath through a spinneret, and then extruding, coagulating, drawing, washing, cutting and drying to obtain the flame-retardant Lyocell fiber;

[0042] Preferably, in step (1), the mass ratio of the flame retardant with microcapsule structure to NMMO aqueous solution is 1:100-120;

[0043] In a further embodiment, in step (1), the concentration of NMMO in the first mixed solution is 75-80%, and the mixing and stirring time of the flame retardant with NMMO solution is 30-45 min;

[0044] In a further embodiment, in step (2), the mass ratio of the flame retardant to cellulose pulp pieces is 5-15:100;

[0045] In a further embodiment, in step (2), the mixing and stirring time of the first mixed solution, the stabilizer and the antioxidant is 10-20 min.

[0046] Further, in step (2), the dried cellulose pulp is made into small pieces of uniform size; the size of the small pieces of cellulose pulp is (0.5-2cm) x (0.5-2cm), which is beneficial for swelling and dissolving.

[0047] Further, the mass ratio of the cellulose pulp to the spinning dope is 8-20:100.

[0048] Further, in step (2), the temperature for swelling the small pieces of pulp is 70-90℃, and the swelling time is 20-50min.

[0049] Further, in step (2), the temperature of the system during vacuum dehydration is 100-110℃, and the pressure is 0.1-0.3Mpa.

[0050] Further, in step (2), the stabilizer is n-propyl gallate, and the antioxidant is hydroxylamine.

[0051] Further, in step (3), the temperature for dry-wet spinning is 85-110℃, and the pressure is 5-15KPa; the temperature of the coagulation bath is 10-30℃, and the concentration of the coagulation bath is an aqueous solution containing NMMO solvent, wherein the mass percentage of NMMO in the coagulation bath is 0-30%.

[0052] After the spinning dope is prepared, the existing spinning equipment, method and condition can be used for spinning, which is only one embodiment provided by the present application.

[0053] Compared with the prior art, the present application has the following beneficial effects:

[0054] 1. The present application uses phosphazene flame retardant containing flame-retardant elements phosphorus and nitrogen as the core of microcapsule, and multi-hydroxyl nanoparticles containing flame-retardant element silicon as the shell, thereby forming a microcapsule structure with exposed multi-hydroxyl, and provides a flame retardant with inorganic nanoparticle-coated phosphazene microcapsule structure. The flame retardant can form hydrogen bonds with the hydroxyl groups of cellulose through the hydroxyl groups, thereby improving the binding force between them and avoiding falling off, and also has excellent flame-retardant effect.

[0055] 2. The application provides a kind of flame-retardant Lyocell fiber containing inorganic nanoparticle coated phosphazene microcapsule structure;The microcapsule flame retardant with the above-mentioned phosphorus, nitrogen, silicon flame-retardant element is further mixed with cellulose pulp to be dissolved and spun to obtain flame-retardant Lyocell fiber.The flame-retardant Lyocell fiber of the application also has phosphorus, nitrogen, silicon flame-retardant element, and the large amount of hydroxyl exposed by microcapsule structure can interact with the hydroxyl on cellulose by hydrogen bond, improve the mutual binding force of flame retardant and fiber, avoid the phenomenon that flame retardant falls off in coagulation bath, and further improve the durability and mechanical properties of flame-retardant Lyocell fiber.In addition, the core of the microcapsule structure of flame retardant belongs to phosphorus, nitrogen flame retardant, which can reduce the temperature of fiber surface layer during fiber combustion, and form an oxygen barrier layer on the surface of fiber to prevent combustion of fiber;And the shell of the microcapsule structure of flame retardant belongs to silicon flame retardant, which can crack into carbon layer when heated, to further improve the oxidation resistance and flame retardancy of the fiber.The prepared flame-retardant Lyocell fiber contains the above three kinds of flame-retardant elements, which can significantly improve the flame-retardant performance of the fiber when the content of flame retardant is low.

[0056] The specific embodiments of the application will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0057] The accompanying drawings are part of the present application and serve to provide a further understanding of the present application, the schematic embodiments of the present application and their descriptions serve to explain the present application, but do not constitute undue limitation on the present application. Obviously, the drawings described below are only some embodiments, and other drawings can be obtained by those skilled in the art without creative labor. In the drawings:

[0058] Figure 1 A schematic diagram of a microcapsule structure with exposed hydroxyl groups, in which a phosphazene flame retardant containing flame-retardant elements phosphorus and nitrogen is used as the core, and a multi-hydroxyl nanoparticle containing flame-retardant element silicon is used as the shell.

[0059] Figure 2 Infrared spectrum of the flame retardant with microcapsule structure of silica-coated trimethylol-methyl-triphenylcyclotriphosphazene compound prepared in Example 1.

[0060] It should be noted that these drawings and written descriptions are not intended to limit the scope of the concept of the present application in any way, but to illustrate the concept of the present application to those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0061] In order to make the purposes, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments will be described clearly and completely below with reference to the drawings in the embodiments of the present application. The following embodiments are used to explain the present application but not to limit the scope of the present application.

[0062] In the present application, the required raw materials are all commercially available products well known in the art unless otherwise specified.

[0063] In the present application, the process or method of mixing the solution can be any process known in the art as long as the raw materials can be mixed uniformly.

[0064] In the present application, the flame retardant with microcapsule structure comprises a core material and a shell covering the core material, wherein the core material is a phosphazene flame retardant compound, and the shell is an inorganic nanoparticle.

[0065] The preparation process of the phosphazene flame retardant compound is as follows:

[0066]

[0067] R1 is selected from

[0068] R2 is selected from -OCH3, a benzene ring,

[0069] The inorganic nanoparticle is a polyhydroxyl nanoparticle containing the flame-retardant element silicon or a polyhydroxyl inorganic nanoparticle containing silicon obtained after hydrolysis.

[0070] In the present application, the preparation process of the flame retardant with microcapsule structure is as shown in Figure 1 wherein the hexacyclic triphosphazene compound is any one or several of the hexacyclic triphosphazene compounds prepared according to any one of the above schemes or a combination thereof; the inorganic nanoparticle is added into the mixed solution of the hexacyclic triphosphazene compound after ultrasonic treatment, and a flame retardant with microcapsule structure is obtained by reaction.

[0071] Embodiment 1

[0072] Preparation of trimethylphenolmethyl-trichlorohexacyclic triphosphazene compound:

[0073] Into a 2L reaction vessel purged and maintained with nitrogen, 101 g of hexachlorocyclotriphosphazene compound was taken, 1 L of solvent toluene was added and stirred for 30 minutes. Then, 1200 g of potassium carbonate was added to the above system and stirred for 30 minutes. Then, 249 g of p-cresol methyl compound was added and heated to 120 °C for 10 hours. The reaction was completed and cooled to room temperature to obtain the reaction mixture. The reaction mixture was added to deionized water to obtain the precipitate. The precipitate was kept in a vacuum tube furnace and heated to 210 °C to obtain sublimed crude product. The sublimed product was collected to obtain trimethylphenol methyl-trichlorocyclotriphosphazene compound in 82% yield. The structure of the product is shown below:

[0074]

[0075] Preparation of trimethylphenol methyl-trichlorocyclotriphosphazene compound:

[0076] Into a 1.5 L reaction vessel equipped with a mechanical stirrer, 188 g of phenol, 770 mL of N-methyl pyrrolidone, and 310 g of zinc fluoride were added and stirred for 30 minutes. Then, 282 g of trimethoxybenzene-trichlorocyclotriphosphazene compound was added and stirred for 30 minutes at room temperature under nitrogen atmosphere. The reaction vessel was pressurized to 0.2 MPa and heated to 120 °C for 8 hours. The reaction was completed and the reaction mixture was obtained by depressurizing and cooling. The reaction mixture was filtered, dried, and separated by column chromatography using a mixture of ethyl acetate and dichloromethane to obtain trimethylphenol methyl-trichlorocyclotriphosphazene compound in 78% yield. The structure of the product is shown below:

[0077]

[0078] Preparation of polyhydroxysilica coated trimethylphenol methyl-trichlorocyclotriphosphazene compound microcapsule flame retardant:

[0079] Into a reaction vessel, 74 g of trimethylphenol methyl-trichlorocyclotriphosphazene compound, 288 g of methanol solvent, and 108 g of deionized water were added and stirred to obtain a mixture. Then, 158 g of ammonia water was added to the mixture and ultrasonically treated at 50 °C for 30 minutes to obtain an ultrasonically treated mixture. Then, 128 g of tetraethyl orthosilicate was added to the mixture in portions and stirred to complete the reaction. The reaction mixture was separated by centrifugation and washed with deionized water and methanol to obtain polyhydroxysilica coated trimethylphenol methyl-trichlorocyclotriphosphazene compound microcapsule flame retardant.

[0080] Example 2

[0081] Preparation of triphenyl-trichlorocyclotriphosphazene compound:

[0082] Into a 2L reaction vessel purged and maintained with nitrogen, 140 g of hexachlorocyclotriphosphazene compound was taken, 600 mL of solvent xylene was added and stirred well for 30 minutes. Then 1303 g of cesium carbonate was added as catalyst and stirred well for 30 minutes at room temperature. Then 264 g of phenol compound was added and heated to 100 °C for 12 hours. The reaction mixture was cooled to room temperature and precipitate was separated by adding the mixture into a mixture of deionized water and ethanol. The precipitate was dried in a vacuum oven at 180 °C to get the crude product. The crude product was purified by sublimation to get the pure product triphenyl-trichlorocyclotriphosphazene compound in 87% yield. The structure of the product is given below:

[0083]

[0084] Preparation of triphenyl-trichlorocyclotriphosphazene compound:

[0085] Into a 2.5 L reaction vessel equipped with mechanical stirrer, 113 g of methanol, 704 g of cesium fluoride and 900 mL of N,N-dimethylacetamide were taken and stirred well for 30 minutes. Then 364 g of triphenyl-trichlorocyclotriphosphazene compound was added and stirred well for 30 minutes at room temperature. The reaction mixture was heated to 110 °C for 10 hours at 0.3 MPa pressure. The reaction mixture was cooled to room temperature and the precipitate was separated by adding the mixture into a mixture of deionized water and ethanol. The precipitate was dried in a vacuum oven at 180 °C to get the crude product. The crude product was purified by sublimation to get the pure product triphenyl-trichlorocyclotriphosphazene compound in 83% yield. The structure of the product is given below:

[0086]

[0087] Preparation of multi-hydroxyl silica coated triphenyl-trichlorocyclotriphosphazene compound microcapsule flame retardant:

[0088] Into a reaction vessel, 102 g of triphenyl-trichlorocyclotriphosphazene compound, 885 g of ethanol and 238 g of deionized water were taken and stirred well. Then 432 g of ammonia was added to the above mixture and sonicated for 40 minutes at 60 °C to get the sonicated mixture. Then 291 g of tetraethyl orthosilicate was added to the above mixture in small portions and stirred well. The reaction mixture was centrifuged and washed with deionized water and ethanol to get the multi-hydroxyl silica coated triphenyl-trichlorocyclotriphosphazene compound microcapsule flame retardant.

[0089] Example 3

[0090] Preparation of triphenylphenol-trichlorocyclotriphosphazene compound:

[0091] Into a 2L reaction vessel purged and maintained with nitrogen, 170 g of hexachlorocyclotriphosphazene compound was taken, 500 mL of solvent toluene was added and stirred for 30 minutes. To this, 600 g of magnesium carbonate was added as a catalyst and stirred for 20 minutes at room temperature. To this, 680 g of 4-phenyl phenol compound was added and heated to 120 °C with a hold time of 9 hours. The reaction mixture was cooled to room temperature to get the reaction mixture. To this, deionized water was added to get the precipitate. The precipitate was kept in a vacuum tube furnace and heated to 200 °C to get sublimed product. The sublimed product was collected to get the triphenyl phenol-trichlorocyclotriphosphazene compound in 83% yield. The structure of the product is given below:

[0092]

[0093] Preparation of triphenyl phenol-triphenyl cyclotriphosphazene compound:

[0094] Into a 2.5 L reaction vessel equipped with mechanical stirrer, 112 g of phenol, 63 g of sodium fluoride, 400 mL of dimethyl sulfoxide was added and stirred for 30 minutes. To this, 225 g of triphenyl phenol-trichlorocyclotriphosphazene compound was added and stirred for 30 minutes at room temperature. The reaction mixture was pressurized to 0.2 Mpa and heated to 120 °C with a hold time of 7 hours. The reaction mixture was cooled to get the reaction mixture. The reaction mixture was filtered, dried and separated by column chromatography using a mixture of petroleum ether and ethyl acetate to get the triphenyl phenol-triphenyl cyclotriphosphazene compound in 80% yield. The structure of the product is given below:

[0095]

[0096] Preparation of polyhydroxysilica coated triphenyl phenol-triphenyl cyclotriphosphazene compound microcapsule flame retardant:

[0097] Into a reaction vessel, 88 g of triphenyl phenol-triphenyl cyclotriphosphazene compound, 589 g of propanol solvent and 123 g of deionized water was added and stirred to get a homogeneous mixture. To this, 211 g of ammonia was added and sonicated for 60 minutes at 50 °C to get the sonicated mixture. To this, 170 g of tetraethyl orthosilicate was added in portions and stirred to get the reaction mixture. The reaction mixture was centrifuged and washed with deionized water and propanol to get the polyhydroxysilica coated triphenyl phenol-triphenyl cyclotriphosphazene compound microcapsule flame retardant.

[0098] Example 4

[0099] Preparation of polyhydroxysilica coated triphenyl phenol-triphenyl cyclotriphosphazene compound microcapsule flame retardant:

[0100] First, the dry Cosmo pulp was crushed into 2 cm x 2 cm pieces, 1 Kg of the crushed pulp was weighed, and then 60 g of the microcapsule flame retardant of the triphenyl-trimethylcyclotriphosphazene compound coated with polyhydroxysilica prepared in Example 1 was added to 7 Kg of an NMMO aqueous solution having a mass concentration of 76% and stirred for 1 h to obtain a uniformly mixed flame retardant solution. Then, the weighed pulp pieces were added to the uniformly mixed flame retardant solution, and hydroxylamine and n-propyl gallate were added and mixed to swell for 40 minutes, and vacuum was applied at 100°C for 5 h to prepare a spinning dope.

[0101] The spinning dope was extruded through a spinneret after being metered by a metering pump at a pressure of 6 KPa and at 95°C, passed through a 30 cm long air gap section, and introduced into a coagulation bath of an NMMO aqueous solution having a mass fraction of 10% at 20°C, and after coagulation, drawing, washing, cutting, and drying, flame-retardant Lyocell fiber I1 was obtained.

[0102] Example 5

[0103] Preparation of flame-retardant Lyocell fiber containing microcapsules of triphenyl-trimethylcyclotriphosphazene compound coated with polyhydroxysilica:

[0104] First, the dry Cosmo pulp was crushed into 2 cm x 2 cm pieces, 1 Kg of the crushed pulp was weighed, and then 60 g of the microcapsule flame retardant of the triphenyl-trimethylcyclotriphosphazene compound coated with polyhydroxysilica prepared in Example 1 was added to 7 Kg of an NMMO aqueous solution having a mass concentration of 76% and stirred for 1 h to obtain a uniformly mixed flame retardant solution. Then, the weighed pulp pieces were added to the uniformly mixed flame retardant solution, and hydroxylamine and n-propyl gallate were added and mixed to swell for 40 minutes, and vacuum was applied at 100°C for 5 h to prepare a spinning dope.

[0105] The spinning dope was extruded through a spinneret after being metered by a metering pump at a pressure of 6 KPa and at 95°C, passed through a 30 cm long air gap section, and introduced into a coagulation bath of an NMMO aqueous solution having a mass fraction of 10% at 20°C, and after coagulation, drawing, washing, cutting, and drying, flame-retardant Lyocell fiber I1 was obtained.

[0106] Example 6

[0107] Preparation of flame-retardant Lyocell fiber containing microcapsules of triphenyl-trimethylcyclotriphosphazene compound coated with polyhydroxysilica:

[0108] Firstly, the dried Cosmo pulp was crushed into 2 cm x 2 cm pieces, 1 Kg of the crushed pulp was weighed, and then 70 g of the microcapsule flame retardant of the triphenylphenol-triphenylcyclotriphosphazene compound coated with the polyhydroxy silicon dioxide prepared in Example 3 was added to 7 Kg of an aqueous NMMO solution having a mass concentration of 76% and stirred for 1 h to obtain a uniformly mixed flame retardant solution. Then, the weighed pulp pieces were added to the uniformly mixed flame retardant solution, and hydroxylamine and n-propyl gallate were added and mixed and swelled for 40 min, and vacuum was applied at 100°C for 5 h to prepare a spinning dope.

[0109] The spinning dope was extruded from a spinneret to spin under the conditions of a pressure of 6 KPa and a temperature of 95°C, passed through a 30 cm long air gap section, and then entered a coagulation bath having a temperature of 20°C and a mass fraction of 10% of an aqueous NMMO to be coagulated, drawn, washed with water, cut, and dried to obtain the flame-retardant Lyocell fiber I3.

[0110] Comparative Example 1

[0111] Firstly, the pulp dried for 12 h was crushed into 1.5 cm x 1.5 cm pieces, 0.5 Kg of the crushed pulp was weighed, and then added to 4.5 Kg of an aqueous NMMO solution having a mass concentration of 78% and stirred for 20 min, and then a mixture of hydroxylamine and n-propyl gallate uniformly mixed in advance was added to the pulp-NMMO system and stirred vigorously for 25 min, the system was heated to 90°C and maintained at this temperature for 40 min to swell, and then vacuum was applied at 105°C and a pressure of 0.2 Mpa for 30 min to obtain a spinning dope;

[0112] The spinning dope was extruded from a spinneret to spin under the conditions of a pressure of 6 KPa and a temperature of 105°C, passed through a 30 cm long air gap section, and then entered a coagulation bath having a temperature of 20°C and containing 10% of an aqueous NMMO to be coagulated, and then drawn, washed with water, and dried to obtain the Lyocell fiber I0.

[0113] Comparative Example 2

[0114] Preparation of flame-retardant Lyocell fiber containing a trimethylphenolmethyl-triphenylcyclotriphosphazene compound:

[0115] First, the dried Cosmo pulp is crushed into 2 cm x 2 cm pieces, 1 Kg of the crushed pulp is weighed, and then 60 g of the triphenyl-methyl-triphenylcyclotriphosphazene compound prepared in Example 1 is added to 7 Kg of an NMMO aqueous solution having a mass concentration of 76% and stirred for 1 h to obtain a uniformly mixed flame retardant solution. Then, the weighed pulp pieces are added to the uniformly mixed flame retardant solution, and hydroxylamine and n-propyl gallate are added and mixed to swell for 40 min, and vacuum is applied at 100°C for 5 h to prepare a spinning dope.

[0116] The spinning dope is extruded through a spinneret to spin at a pressure of 6 KPa and at 95°C, passes through a 30 cm long air gap section, and is introduced into an NMMO water coagulation bath having a mass fraction of 10% at a temperature of 20°C, and after coagulation, drawing, washing, cutting, and drying, a flame-retardant Lyocell fiber II 0 is obtained.

[0117] Comparative Example 3

[0118] Preparation of a flame-retardant Lyocell fiber containing a triphenyl- trimethylcyclotriphosphazene compound:

[0119] First, the dried Cosmo pulp is crushed into 2 cm x 2 cm pieces, 1 Kg of the crushed pulp is weighed, and then 60 g of the triphenyl- trimethylcyclotriphosphazene compound prepared in Example 2 is added to 7 Kg of an NMMO aqueous solution having a mass concentration of 76% and stirred for 1 h to obtain a uniformly mixed flame retardant solution. Then, the weighed pulp pieces are added to the uniformly mixed flame retardant solution, and hydroxylamine and n-propyl gallate are added and mixed to swell for 40 min, and vacuum is applied at 100°C for 5 h to prepare a spinning dope.

[0120] The spinning dope is extruded through a spinneret to spin at a pressure of 6 KPa and at 95°C, passes through a 30 cm long air gap section, and is introduced into an NMMO water coagulation bath having a mass fraction of 10% at a temperature of 20°C, and after coagulation, drawing, washing, cutting, and drying, a flame-retardant Lyocell fiber III 0 is obtained.

[0121] Comparative Example 4

[0122] Preparation of a flame-retardant Lyocell fiber containing a triphenyl- trimethylcyclotriphosphazene compound:

[0123] Firstly, the dried Cosmo pulp was crushed into 2cm x 2cm pieces, 1Kg of the crushed pulp was weighed, then 70g of the triphenylphenol-triphenylcyclotriphosphazene compound prepared in Example 3 was added into 7Kg of NMMO aqueous solution with a mass concentration of 76% and stirred for 1h to obtain a mixed flame retardant solution. Then the weighed pulp pieces were added into the mixed flame retardant solution, and hydroxylamine and n-propyl gallate were added and mixed and stirred for swelling for 40min, and vacuum was applied at 100°C for 5h to prepare a spinning dope.

[0124] The spinning solution was extruded from the spinneret under the action of a metering pump at a pressure of 6KPa and 95°C, passed through a 30cm air gap, and entered a NMMO aqueous coagulation bath with a mass fraction of 10% at a temperature of 20°C, and after coagulation, drawing, washing, cutting and drying, the flame-retardant Lyocell fiber IV0 was obtained.

[0125] Performance test

[0126] 1) The trihydroxy silica-coated trimethylphenyl methyl-triphenylcyclotriphosphazene compound microcapsule flame retardant prepared in Example 1 was subjected to infrared characterization, and the results are shown in Figure 2 From the spectrum, it can be seen that the P=N stretching vibration absorption peak on the phosphazene structure appears at 1255cm -1 , the P-O-C vibration absorption peak on the phosphazene structure appears at 1188cm -1 , 981cm -1 and 855cm -1 , in addition, 3362cm -1 is the asymmetric stretching vibration absorption peak of the hydroxyl group in the microcapsule structure, and the absorption peaks at 1159cm -1 and 465cm -1 belong to the asymmetric and symmetric stretching vibration absorption peaks of the Si-O-Si structure. The above results show that the flame retardant with a microcapsule structure of trihydroxy silica-coated phosphazene has been successfully prepared.

[0127] 2) The dry breaking strength (CN / dtex) of the flame-retardant Lyocell fiber prepared in Examples 4-6 was tested according to the test method for the tensile properties of staple fibers in GB / T14337;

[0128] 3) The dry breaking elongation (%) of the flame-retardant Lyocell fiber prepared in Examples 4-6 was tested according to the test method for the tensile properties of staple fibers in GB / T14337;

[0129] 4) The wet breaking strength (CN / dtex) of the flame-retardant Lyocell fiber prepared in Examples 4-6 was tested according to the test method for the tensile properties of staple fibers in GB / T14337;

[0130] 5) Wet elongation at break (%) of the flame-retardant Lyocell fiber prepared in Examples 4-6, the test method of which refers to GB / T14337 Test method for tensile properties of staple fibers;

[0131] 6) Limiting oxygen index (LOI, %) of the flame-retardant Lyocell fiber prepared in Examples 4-6, the test method of which refers to FZT50016-2011 Test method for flame-retardant properties of viscose staple fibers;

[0132] 7) The test methods of the properties of the fibers prepared in Comparative Examples 1-4 refer to the methods of 2)-6) above.

[0133] The test results of the above properties are shown in Table 1.

[0134] Table 1 Test performance indicators of the flame-retardant Lyocell fibers prepared in each example and comparative example

[0135]

[0136]

[0137] As can be seen from Table 1, since phosphorus, nitrogen, silicon and other flame-retardant elements are introduced into the fiber at the same time, even if the addition amount of the flame retardant is small, compared with the performance of the Lyocell fiber without adding the flame retardant, the obtained flame-retardant Lyocell fiber has excellent flame-retardant performance, the LOI value of which is above 32%, and as the incorporation amount of the flame retardant increases, the flame-retardant performance of the flame-retardant Lyocell fiber is obviously improved; in addition, since a large number of hydroxyl units capable of interacting with the hydroxyl groups of the fiber are introduced into the structure of the flame-retardant microcapsule, the effective incorporation of the flame retardant into the fiber is ensured, the incorporation rate of the flame retardant in the fiber is improved, and the washing resistance of the flame-retardant fiber is improved, and after 30 times of washing, the LOI value of the obtained flame-retardant Lyocell fiber is still above 30%.

[0138] Compared with Comparative Example 1, the mechanical properties of the flame-retardant Lyocell fiber prepared by the present application are not reduced too much, which is because the flame-retardant microcapsule structure has good binding fastness with the Lyocell fiber, preventing the flame retardant from simply staying on the surface of the fiber to reduce the mechanical properties of the fiber.

[0139] Compared with Comparative Examples 2-4, the LOI value of the flame-retardant Lyocell fiber of Examples 4-6 is obviously higher, and the flame-retardant effect is better, and especially after 30 times of washing, Examples 4-6 can maintain better washing resistance compared with Comparative Examples 2-4, which proves that the multi-hydroxyl microcapsule structure prepared in the present application can maintain good binding fastness with the Lyocell fiber, and plays an important role in improving the washing resistance of the flame-retardant Lyocell fiber.

[0140] The above description is only the preferred embodiment of the present application, and is not intended to limit the present application in any form. Although the present application has been disclosed as above with the preferred embodiment, it is not intended to limit the present application, and any person skilled in the art can make some changes or modifications to the above-mentioned technical content with the above-mentioned prompt without departing from the technical solution of the present application, and any simple modification, equivalent change and modification of the above-mentioned embodiment made according to the technical essence of the present application without departing from the technical solution of the present application still belongs to the scope of the present application.

Claims

1. A flame retardant having a microcapsule structure, characterized by comprising: The microcapsule structure comprises a core material and a shell covering the core material, and has a plurality of exposed hydroxyl groups; the core material is a phosphazene flame retardant compound, and the shell is an inorganic nanoparticle; the inorganic nanoparticle comprises a hydroxyl-containing inorganic nanoparticle or a hydrolyzed hydroxyl-containing inorganic nanoparticle; the phosphazene flame retardant compound has a structure as shown in formula II, III or IV:

2. The flame retardant according to claim 1, characterized in that The inorganic nanoparticle is selected from one or more of ethyl silicate, hydroxyl silicone oil and hydroxyl dimethyl silicone.

3. A process for the preparation of a flame retardant as claimed in claim 1 or 2, characterised in that, The method comprises the following steps: (1) mixing hexachlorocyclotriphosphazene, a first catalyst, a first reaction solvent and a hydroxyl or phenolic compound to perform a nucleophilic substitution reaction to obtain a trihydroxy-trichlorocyclotriphosphazene compound; (2) mixing the trihydroxy-trichlorocyclotriphosphazene compound, a hydroxyl or phenolic compound, a second catalyst and a second reaction solvent to perform a nucleophilic substitution reaction in a reaction kettle, and then performing filtration, drying and chromatographic column separation to obtain a hexacyclotriphosphazene compound; (3) stirring and mixing the hexacyclotriphosphazene compound, ammonia water, a third reaction solvent and deionized water, ultrasonicating, then adding an inorganic nanoparticle into the mixed solution and stirring; and finally centrifuging to obtain a flame retardant with a microcapsule structure.

4. The production method according to claim 3, characterized by, In step (1), the molar ratio of the hexachlorocyclotriphosphazene, the hydroxyl or phenolic compound, the first catalyst and the first reaction solvent is 1:(6-10):(9-13):(8-12).

5. The preparation method according to claim 3, characterized in that, In step (1), the hydroxyl or phenolic compound is selected from one or more of phenol, methylphenol, methanol and 4-phenylphenol.

6. The preparation method according to claim 3, characterized in that, In step (1), the first catalyst is selected from one or more of potassium carbonate, cesium carbonate, magnesium carbonate, zinc carbonate, lithium carbonate and calcium carbonate.

7. The preparation method according to claim 3, characterized in that, In step (1), the first reaction solvent is selected from one or more of toluene, xylene, diphenyl or cumene.

8. The preparation method according to claim 3, characterized in that, In step (1), the nucleophilic substitution reaction is performed at room temperature for 30 min, then the temperature is raised to 60-80 ℃ for 1 h, and finally the temperature is raised to 100-120 ℃ for 8-16 h, and the temperature rising rate is 5-10 ℃ / min.

9. The method of any one of claims 3-8, wherein, In step (2), the molar ratio of the trihydroxy-trichlorocyclotriphosphazene compound, the hydroxyl or phenolic compound, the second catalyst and the second reaction solvent is 1:(3-5):(5-7):(15-20).

10. The method of any one of claims 3-8, wherein, In step (2), the second catalyst is a strong alkaline catalyst.

11. The method of claim 10, wherein, In step (2), the second catalyst is selected from one or more of cesium fluoride, zinc fluoride, potassium fluoride and sodium fluoride.

12. The method of making according to any one of claims 3-8, wherein, In step (2), the second reaction solvent is selected from one or more of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide and dimethyl sulfoxide.

13. The method of making according to any one of claims 3-8, wherein, In step (2), the temperature in the nucleophilic substitution reaction kettle is 120-150 ℃, the pressure is 0.1-0.3 Mpa, and the reaction time is 5-12 h.

14. The method of any one of claims 3-8, wherein, In step (3), the molar ratio of the hexacyclic triphosphazene compound, ammonia, the third reaction solvent, deionized water and the inorganic nanoparticles is 1: (45-50): (90-100): (60-70): (6-10).

15. The method of making according to any one of claims 3-8, wherein, In step (3), the third reaction solvent is selected from one or more of methanol, ethanol and propanol.

16. The method of making according to any one of claims 3-8, wherein, In step (3), the average particle size of the inorganic nanoparticles is 300-600 nm.

17. The method of making according to any one of claims 3-8, wherein, In step (3), the average particle size of the inorganic nanoparticles is 300-500 nm.

18. The method of making according to any one of claims 3-8, wherein, In step (3), the ultrasonic treatment is performed at a temperature of 50-80°C for 30-60 min.

19. Use of the flame retardant with microcapsule structure according to claim 1 or 2 in the preparation of flame-retardant fibers.

20. The use according to claim 19, characterized in that, Use in the preparation of flame-retardant Lyocell fibers.

21. A flame-retardant Lyocell fiber, characterized in that, The flame retardant with microcapsule structure according to claim 1 or 2 and cellulose are mixed in a mass ratio of 5-15:

100.

22. A process for the production of flame-retardant Lyocell fibres as claimed in claim 21, characterised in that, The flame retardant with microcapsule structure according to claim 1 or 2 and cellulose are mixed in a mass ratio of 5-15:

100. (1) mixing the flame retardant with microcapsule structure according to claim 1 or 2 with an aqueous NMMO solution to obtain a first mixed solution; (2) mixing the first mixed solution, a stabilizer and an antioxidant by vigorous stirring, and then adding cellulose pulp pieces to the system, and sequentially mixing, swelling, vacuum dewatering to obtain a spinning dope; (3) spinning the spinning dope through dry-wet spinning, and forming through a spinneret into a coagulation bath, and then extruding, coagulating, drawing, washing, cutting and drying to obtain flame-retardant Lyocell fibers.

23. The preparation method according to claim 22, characterized in that, In step (1), the mass ratio of the flame retardant with microcapsule structure to the aqueous NMMO solution is 1:100-120.

24. The method of claim 22, wherein, In step (1), the concentration of NMMO in the first mixed solution is 75-80%, and the mixing and stirring time of the flame retardant with NMMO solution is 30-45 min.

25. The preparation method according to claim 22, characterized in that, In step (2), the mass ratio of the flame retardant to the cellulose pulp pieces is 5-15:

100.

26. The method of claim 22, wherein, In step (2), the mixing and stirring time of the first mixed solution, the stabilizer and the antioxidant is 10-20 min.

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