Process for the preparation of a leach resistant flame retardant for finishing of fibre textiles

Abstract

The application belongs to the technical field of flame retardant synthesis for fiber textiles, and more particularly relates to a preparation method of a precipitation-resistant flame retardant for fiber textile finishing. A small-molecule water-soluble phosphate and a polyhydroxy compound are used for ester exchange reaction, and by controlling process parameters in the ester exchange reaction process, including raw material dosage ratio, reaction temperature, reaction time, removal of by-products by distillation, re-introduction of a nitrogen-containing alkaline compound and adjustment of solution pH, a finishing flame retardant with excellent flame retardant performance, precipitation resistance and washing resistance is prepared, which is particularly suitable for finishing processes such as padding and baking, impregnation and drying. The raw materials used in the preparation method are environmentally friendly and safe, the reaction is more gentle and controllable, the reaction period is short, and the efficiency is high; the precipitation-resistant flame retardant for fiber textile finishing prepared by the above method has the advantages of wide application range, high flame retardant efficiency, semi-durability, little effect on fabric hand feeling and no precipitation.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant synthesis technology for fiber textiles, and more specifically, relates to a method for preparing a flame retardant resistant to exudation for finishing fiber textiles. Background Technology

[0002] The main component of fiber textiles is high molecular polymer, which is inherently flammable, burns rapidly, and is difficult to extinguish once ignited. There are many different ways to classify flame retardant fiber fabrics. Here, we simply divide them into two types: flame retardant fibers and flame retardant finishing. The main advantage of the former is its long-lasting flame retardancy, but the disadvantage is that flame retardant fibers usually have worse mechanical properties and are more expensive than ordinary fibers. The latter involves surface treatment of textiles during the finishing process, that is, fixing flame retardants onto the fabric through adsorption deposition, chemical bonding, non-polar van der Waals forces, and adhesion, thereby achieving a flame retardant effect.

[0003] Flame retardant finishing methods include pad-drying, immersion drying, coating, spraying, and organic solvent methods. Flame retardants suitable for flame retardant finishing are divided into inorganic and organic flame retardants. Inorganic flame retardants include various phosphates, aminosulfonates, melamine salts, borates, and hydrated oxides, etc., usually used alone or in combination. Their main advantages are high flame retardant efficiency and low price; the biggest problem is poor water resistance, usually lacking wash resistance, and there is a risk of white spots appearing on the surface of dark-colored fabrics treated with flame retardant. Organic flame retardants include: Proban flame retardants, etc. Organophosphorus compounds, various phosphate ester compounds, decabromodiphenyl ethane, and a small number of halogenated flame retardants are still in use. The main advantage of organic flame retardants is that they have better flame retardant durability and do not have the problem of precipitation. Their biggest problems are: they require special processing technology (such as the ammonia fumigation process for Proban flame retardant), some organophosphorus compounds contain free formaldehyde, and halogenated flame retardants are not environmentally friendly enough. Among organic flame retardants, only phosphate ester flame retardants do not require special processes and are relatively environmentally friendly, but their preparation process usually requires the use of acyl chloride reagents (hazardous chemicals), and their preparation cost is also relatively high. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide a method for preparing a flame retardant resistant to exudation for finishing fiber fabrics, thereby solving the technical problems of existing flame retardants for finishing, such as poor water resistance, risk of white spots exudation, need for special treatment processes, and the need to use hazardous chemicals in the preparation process.

[0005] To achieve the above objectives, the present invention provides a method for preparing an efflorescence-resistant flame retardant for finishing fiber textiles, comprising the following steps:

[0006] (1) The small molecule water-soluble phosphate ester, the polyhydroxy compound and the catalyst are mixed and stirred to obtain a raw material mixture; the catalyst is used to catalyze the transesterification reaction of the small molecule water-soluble phosphate ester and the polyhydroxy compound;

[0007] (2) Nitrogen gas is introduced into the raw material mixture for protection, and the mixture is heated to allow the small molecule water-soluble phosphate ester and polyhydroxy compound to undergo an ester exchange reaction to obtain a transparent and clear solution, while ensuring that the heating temperature does not exceed the boiling point or decomposition temperature of the small molecule water-soluble phosphate ester and polyhydroxy compound.

[0008] (3) The transparent and clear solution described in step (2) is continuously heated to distill it, so that the by-products generated during the reaction and the unreacted raw materials are removed by distillation, and then the heating is stopped.

[0009] (4) After the temperature drops, dilute with water and add a nitrogen-containing alkaline compound to adjust the pH of the solution to weakly acidic, thus obtaining the flame retardant for finishing fiber textiles.

[0010] Preferably, the molar ratio of the small molecule water-soluble phosphate ester and the polyhydroxy compound in step (1) is 3:1 to 1:2, and the amount of catalyst added is 1 to 5% of the mass of the polyhydroxy compound.

[0011] Preferably, the small molecule water-soluble phosphate ester in step (1) is one or more of trimethyl phosphate, triethyl phosphate and dimethyl methyl phosphate.

[0012] Preferably, the polyhydroxy compound is one or more selected from pentaerythritol, dipentaerythritol, 1,3-propanediol, and trimethylolpropane.

[0013] Preferably, the catalyst is one or more of sodium hydroxide, potassium hydroxide, N,N-dimethylaniline, diethylamine, triethylamine, and pyridine.

[0014] Preferably, the heating in step (2) is performed at a temperature of 150 to 200°C.

[0015] Preferably, step (3) includes the following sub-steps:

[0016] (3-1) The transparent and clear solution described in step (2) is continuously heated and nitrogen gas is continuously introduced to carry out atmospheric distillation reaction for 3 to 10 hours;

[0017] (3-2) The byproducts and unreacted raw materials are distilled off by vacuum distillation, and then heating is stopped.

[0018] More preferably, the vacuum distillation in step (3-2) is carried out under vacuum conditions greater than 0.085 MPa for 2-4 hours.

[0019] Preferably, in step (4), when the temperature drops to 50°C or below, water is added to dilute the solution to obtain a transparent solution, and then a nitrogen-containing alkaline compound is added to the transparent solution to adjust the pH of the solution to 5-6.

[0020] Preferably, the nitrogen-containing basic compound in step (4) is one or more of ammonia, triethylamine, diammonium hydrogen phosphate, guanidine dihydrogen phosphate, and guanidine aminosulfonate.

[0021] In summary, compared with the prior art, the above-described technical solutions conceived by this invention have the following advantages:

[0022] Beneficial effects:

[0023] (1) The present invention proposes a method for preparing a flame retardant for finishing fiber fabrics that is resistant to precipitation. The flame retardant is prepared by transesterification reaction of small molecule water-soluble phosphate ester and polyhydroxy compound. By controlling the process parameters in the transesterification reaction, including the ratio of raw materials, reaction temperature, reaction time, distillation removal of by-products, and pH of flame retardant, a flame retardant for finishing with excellent flame retardant properties, precipitation resistance and washability is prepared. It is especially suitable for finishing processes such as pad-baking method and dip-drying method.

[0024] (2) The flame retardant for finishing fiber fabrics prepared by this invention has the advantages of wide applicability to a wide range of fabrics, high flame retardant efficiency, semi-durability, minimal impact on fabric feel, and no exudation. Specifically, this flame retardant integrates an acid source (small molecule water-soluble phosphate ester), a carbon source (polyhydroxy compound), and a gas source (introducing nitrogen-containing alkaline compound), thus possessing excellent flame retardant and char-forming effects. This makes it suitable not only for cellulose fabrics that are easy to char, such as cotton and viscose fibers, but also for polyester fibers that are less prone to char formation. In addition, when this flame retardant is applied to dark-colored fabrics for padding or spraying, the fabric has a good feel after drying and no obvious stickiness. Furthermore, when the treated fabric is placed in a high-temperature and high-humidity environment, no white spots will appear on the fabric surface after several days. Fabrics treated with flame retardant, especially cellulose and polyester fibers, can still have a certain flame retardant effect after 3 to 5 washes.

[0025] (3) The preparation method of the flame retardant for finishing fiber fabrics proposed in this invention is simple, has no hazardous chemical raw materials, has low production cost, and can realize large-scale industrial production. Attached Figure Description

[0026] Figure 1 This is a flowchart illustrating the preparation method of the flame retardant resistant to exudation for finishing fiber textiles according to the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0028] Existing flame retardants for finishing fiber textiles are generally only phosphorus-containing flame retardants, utilizing the carbon source of the fiber textile itself to achieve a char-forming flame retardant effect. However, except for textiles containing cellulose, such as polyester or polypropylene, the carbon in these fibers cannot effectively form graphite carbon during combustion, failing to exert the carbon source effect, resulting in poor flame retardant performance. This invention aims to propose a flame retardant for fiber textiles suitable for finishing processes such as pad-drying and impregnation-drying. This flame retardant integrates phosphorus, carbon, and gas sources, achieving its flame retardant effect based on an intumescent flame retardant mechanism, thereby improving the flame retardant performance of existing fiber textiles. Currently, intumescent flame retardant systems are commonly used in plastics, coatings, or other fields, where the hydrophilicity of the flame retardant is not required, making it relatively easy to construct an intumescent flame retardant system integrating phosphorus, carbon, and gas sources. The key technical problem to be solved by this invention is how to construct an expansion flame retardant system for fiber textiles that has good hydrophilicity for use in padding and baking and immersion drying finishing processes, and that integrates phosphorus source, carbon source and gas source.

[0029] Therefore, the present invention provides a method for preparing an anti-expansion flame retardant for finishing fiber textiles, such as... Figure 1 As shown, it includes the following steps:

[0030] (1) The small molecule water-soluble phosphate ester, the polyhydroxy compound and the catalyst are mixed and stirred to obtain a raw material mixture; the catalyst is used to catalyze the transesterification reaction of the small molecule water-soluble phosphate ester and the polyhydroxy compound;

[0031] (2) Nitrogen gas is introduced into the raw material mixture for protection, and the mixture is heated to allow the small molecule water-soluble phosphate ester and polyhydroxy compound to undergo an ester exchange reaction to obtain a transparent and clear solution. The heating temperature is ensured not to exceed the boiling point or decomposition temperature of the small molecule water-soluble phosphate ester and polyhydroxy compound. This reaction is a common ester exchange reaction. Compared with the reaction of highly toxic and dangerous chlorination reagents or acylation reagents with hydroxy compounds to obtain phosphate esters, the raw materials used in this ester exchange reaction are more environmentally friendly and safer, and the reaction is more mild and controllable. In addition, the water-soluble phosphate ester itself contains the flame-retardant element phosphorus. The phosphate ester compound obtained by reacting this phosphate ester with the carbon-rich polyhydroxy compound contains both acid source and carbon source, making it easier to achieve solidified phase flame retardancy, thereby giving the flame retardant itself a better flame retardant effect.

[0032] (3) The transparent and clear solution described in step (2) is continuously heated to distill it, so that the by-products generated during the reaction and the unreacted raw materials are removed by distillation, and then the heating is stopped.

[0033] (4) After the temperature drops, dilute with water and add a nitrogen-containing alkaline compound to adjust the pH of the solution to weakly acidic, thus obtaining the flame retardant for finishing fiber textiles.

[0034] In some embodiments, the molar ratio of the small molecule water-soluble phosphate ester and the polyhydroxy compound in step (1) is 3:1 to 1:2, preferably 1:1 to 3; the amount of catalyst added is 1 to 5% of the mass of the polyhydroxy compound, preferably 1 to 2%. To improve the hydrophilicity of the obtained flame retardant, the present invention uses a small molecule water-soluble phosphate ester. The small molecule water-soluble phosphate ester includes, but is not limited to, one or more of trimethyl phosphate, triethyl phosphate, and dimethyl methyl phosphate. The polyhydroxy compound is one or more of pentaerythritol, dipentaerythritol, 1,3-propanediol, and trimethylolpropane. The catalyst is one or more of sodium hydroxide, potassium hydroxide, N,N-dimethylaniline, diethylamine, triethylamine, and pyridine.

[0035] In some embodiments, the heating in step (2) is at a temperature of 150–200°C. Nitrogen gas is introduced into the reactor for protection, and the mixture is continuously heated to 150–200°C until it becomes a transparent and clear solution. The esters generated during this transesterification reaction are unstable and easily oxidized by oxygen, so nitrogen gas protection is required. The higher the reaction temperature, the faster the transesterification reaction rate, which is more conducive to the evaporation and removal of lower alcohols. However, the temperature cannot exceed the boiling point or decomposition temperature of the reactants.

[0036] In some embodiments, step (3) includes the following sub-steps: (3-1) continuously heating and continuously purging nitrogen gas onto the transparent and clear solution described in step (2) to carry out atmospheric distillation for 3-10 hours; (3-2) observing that the distilled byproduct lower alcohol reaches or exceeds 90% of the theoretical yield, the reaction is considered to be basically complete, and then distilling off the byproduct and unreacted raw materials by vacuum distillation, and then stopping the heating. After the transesterification reaction is carried out at atmospheric pressure, nitrogen gas is continuously purged at atmospheric pressure for protection, and the reaction is carried out for 3-10 hours. Here, the reaction time includes the transesterification reaction time and the time for removing the reaction byproduct lower alcohol by atmospheric distillation; the reaction time may vary depending on the reaction raw materials. The specific judgment method is to observe that the distilled lower alcohol reaches or exceeds 90% of the theoretical yield, the transesterification reaction is considered to be basically complete, then stop purging nitrogen gas, and distill off the byproduct and unreacted raw materials by vacuum distillation.

[0037] In some embodiments, the vacuum distillation in step (3-2) is a vacuum distillation reaction for 2-4 hours under a vacuum degree greater than 0.085 MPa.

[0038] In some embodiments, in step (4), when the temperature drops to 50°C or below, water is added to dilute the solution to obtain a transparent solution, and then a nitrogen-containing alkaline compound is added to the transparent solution to adjust the pH of the solution to 5-6. The nitrogen-containing alkaline compound is one or more of ammonia, triethylamine, diammonium hydrogen phosphate, guanidine dihydrogen phosphate, and guanidine aminosulfonate. When the temperature of the reactants drops to 50°C, water is added to dilute the solution to obtain a completely transparent solution; since the new ester generated by the transesterification reaction has a high viscosity, it is inconvenient to use and needs to be diluted to a liquid with a lower viscosity; dilution with water at 50°C will not cause the water to boil locally; then an alkaline nitrogen-containing compound is added to the transparent and clear solution to adjust the pH of the solution to between 5 and 6; the new ester generated by the transesterification reaction has a high acid value, making it unsuitable for use in acid-sensitive fiber fabrics, so an alkaline compound is used to adjust the pH of the solution to expand its applicable range. On the other hand, the nitrogen-containing alkaline compound also introduces N elements with gas-phase flame retardant effect into the product, so that the flame retardant produces ammonia gas during thermal decomposition, thereby diluting the oxygen in the air and exerting a flame retardant effect.

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0040] Example 1

[0041] An environmentally friendly preparation method for an eluting flame retardant used in finishing fiber fabrics:

[0042] (1) Add dimethyl methyl phosphate and pentaerythritol to a reaction vessel at a mass ratio of 1:1, stir and heat; (2) Add triethylamine as a catalyst, the mass of triethylamine being 2% of the mass of pentaerythritol; (3) Purge the mixture with nitrogen for protection and continue heating to 170°C until the mixture becomes a transparent and clear solution; (4) Distill the reaction under normal pressure for 5 hours; (5) Distill the reaction under reduced pressure with a vacuum degree greater than 0.085 MPa for 2 hours to obtain a viscous product; (6) When the temperature drops to 50°C, add water and stir to dilute to a 40% transparent solution (i.e., the mass ratio of viscous product to water is 40:60); (7) Add triethylamine to the transparent solution to adjust the pH of the solution to 5-6 to obtain a liquid flame retardant.

[0043] Example 2

[0044] An environmentally friendly preparation method for an eluting flame retardant used in finishing fiber fabrics:

[0045] (1) Add dimethyl methyl phosphate and pentaerythritol to a reaction vessel at a mass ratio of 2:1, stir and heat; (2) Add sodium hydroxide as a catalyst, the mass of sodium hydroxide being 1% of the mass of pentaerythritol; (3) Purge the mixture with nitrogen gas for protection and continue heating to 180°C until the mixture becomes a transparent and clear solution; (4) Distill the reaction under normal pressure for 6 hours; (5) Distill the reaction under reduced pressure with a vacuum degree greater than 0.085 MPa for 3 hours to obtain a viscous product; (6) Dilute the solution with water to a 40% content transparent solution when the temperature drops to 50°C; (7) Add ammonia water to the transparent solution to adjust the pH of the solution to 5-6 to obtain a liquid flame retardant.

[0046] Example 3

[0047] An environmentally friendly preparation method for an eluting flame retardant used in finishing fiber fabrics:

[0048] (1) Add trimethyl phosphate and dipentaerythritol to a reaction vessel at a mass ratio of 3:1, stir and heat; (2) Add N,N-dimethylaniline as a catalyst, the mass of which is 2% of the mass of dipentaerythritol; (3) Purge the mixture with nitrogen gas for protection and continue heating to 190°C until the mixture becomes a transparent and clear solution; (4) Distill the reaction under normal pressure for 8 hours; (5) Distill the reaction under reduced pressure with a vacuum degree greater than 0.085 MPa for 4 hours to obtain a viscous product; (6) Dilute the solution with water to a 40% content transparent solution when the temperature drops to 50°C; (7) Add diamine hydrogen phosphate to the transparent solution to adjust the pH of the solution to 5-6 to obtain a liquid flame retardant.

[0049] Example 4

[0050] An environmentally friendly preparation method for an eluting flame retardant used in finishing fiber fabrics:

[0051] (1) Add trimethyl phosphate and 1,3-propanediol to a reaction vessel at a mass ratio of 1:2, stir and heat; (2) Add pyridine as a catalyst, the mass of which is 1% of the mass of 1,3-propanediol; (3) Purge the mixture with nitrogen gas for protection and continue heating to 160°C until the mixture becomes a transparent and clear solution; (4) Distill the reaction under normal pressure for 6 hours; (5) Distill the reaction under reduced pressure with a vacuum degree greater than 0.085 MPa for 3 hours to obtain a viscous product; (6) Dilute the solution with water to a 40% content transparent solution when the temperature drops to 50°C; (7) Add dihydroguanidine phosphate to the transparent solution to adjust the pH of the solution to 5-6 to obtain a liquid flame retardant.

[0052] Example 5

[0053] An environmentally friendly preparation method for an eluting flame retardant used in finishing fiber fabrics:

[0054] (1) Add triethyl phosphate and trimethylolpropane to a reaction vessel at a mass ratio of 1:1, stir and heat; (2) Add diethylamine as a catalyst, the mass of which is 4% of the mass of trimethylolpropane; (3) Purge the mixture with nitrogen gas for protection and continue heating to 150°C until the mixture becomes a transparent and clear solution; (4) Distill the reaction under normal pressure for 10 hours; (5) Distill the reaction under reduced pressure with a vacuum degree greater than 0.085 MPa for 4 hours to obtain a viscous product; (6) Dilute the solution with water to a 40% content transparent solution when the temperature drops to 50°C; (7) Add guanidine aminosulfonate to the transparent solution to adjust the pH of the solution to 5-6 to obtain a liquid flame retardant.

[0055] Comparative Example 1

[0056] An environmentally friendly preparation method for an eluting flame retardant used in finishing fiber fabrics:

[0057] (1) Add dimethyl methyl phosphate and pentaerythritol to a reaction vessel at a mass ratio of 1:3, stir and heat; (2) Add triethylamine as a catalyst, the mass of triethylamine being 2% of the mass of pentaerythritol; (3) Purge the mixture with nitrogen gas for protection and continue heating to 170°C for reaction; (4) Distill the reaction under normal pressure for 5 hours; (5) Distill the reaction under reduced pressure with a vacuum degree greater than 0.085 MPa for 2 hours to obtain a viscous product; (6) Dilute the solution with water to a 40% content when the temperature drops to 50°C; (7) Add triethylamine to the solution to adjust the pH of the solution to 5-6 to obtain a liquid flame retardant.

[0058] Comparative Example 2

[0059] An environmentally friendly preparation method for an eluting flame retardant used in finishing fiber fabrics:

[0060] (1) Add dimethyl methyl phosphate and pentaerythritol to a reaction vessel at a mass ratio of 2:1, stir and heat; (2) Add sodium hydroxide as a catalyst, the mass of sodium hydroxide being 1% of the mass of pentaerythritol; (3) Purge the mixture with nitrogen gas for protection and continue heating to 210℃ for reaction; (4) Distill the reaction under normal pressure for 6 hours; (5) Distill the reaction under reduced pressure with a vacuum degree greater than 0.085MPa for 3 hours; (6) When the temperature drops to 50℃, dilute with water to obtain a 40% solution; (7) Add ammonia to the solution to adjust the pH to 5-6 to obtain a liquid flame retardant.

[0061] Comparative Example 3

[0062] An environmentally friendly preparation method for an eluting flame retardant used in finishing fiber fabrics:

[0063] (1) Add trimethyl phosphate and dipentaerythritol to a reaction vessel at a mass ratio of 3:1, stir and heat; (2) Add N,N-dimethylaniline as a catalyst, the mass of which is 2% of the mass of dipentaerythritol; (3) Purge the mixture with nitrogen gas for protection and continue heating to 190°C for reaction; (4) Distill the reaction under normal pressure for 8 hours; (5) Distill the reaction under reduced pressure with a vacuum degree greater than 0.085 MPa for 4 hours; (6) When the temperature drops to 50°C, dilute with water to obtain a 40% solution; (7) Add diamine hydrogen phosphate to the solution to adjust the pH of the solution to 8-9 to obtain a liquid flame retardant.

[0064] Comparative Example 4

[0065] An environmentally friendly preparation method for an eluting flame retardant used in finishing fiber fabrics:

[0066] (1) Add trimethyl phosphate and 1,3-propanediol to a reaction vessel at a mass ratio of 1:2, stir and heat; (2) Add pyridine as a catalyst, the mass of which is 6% of the mass of 1,3-propanediol; (3) Purge the mixture with nitrogen gas for protection and continue heating to 160℃ for reaction; (4) Distill the reaction under normal pressure for 6 hours; (5) Distill the reaction under reduced pressure with a vacuum degree greater than 0.085MPa for 3 hours; (6) After the temperature drops to 50℃, dilute with water to obtain a 40% solution; (7) Add guanidine dihydrogen phosphate to the solution to adjust the pH of the solution to 5-6 to obtain a liquid flame retardant;

[0067] Comparative Example 5

[0068] An environmentally friendly preparation method for an eluting flame retardant used in finishing fiber fabrics:

[0069] (1) Add triethyl phosphate and trimethylolpropane to a reaction vessel at a mass ratio of 1:1, stir and heat; (2) Add diethylamine as a catalyst, the mass of which is 4% of the mass of trimethylolpropane; (3) Purge the mixture with nitrogen gas for protection and continue heating to 150°C for reaction; (4) Distill the reaction under normal pressure for 12 hours; (5) Distill the reaction under reduced pressure with a vacuum degree greater than 0.085 MPa for 4 hours; (6) When the temperature drops to 50°C, dilute with water to obtain a 40% solution; (7) Add guanidine aminosulfonate to the solution to adjust the pH of the solution to 5-6 to obtain a liquid flame retardant.

[0070] Experimental Example 1

[0071] The flame retardants for finishing fiber fabrics prepared in Examples 1-5 and Comparative Examples 1-5 were designated as experimental groups 1-10. Two commercially available flame retardants were designated as experimental groups 11-12 (commercially available group 1 is an organophosphorus flame retardant, and commercially available group 2 is a mixture of an inorganic phosphorus-nitrogen flame retardant and an organophosphorus flame retardant). Equal amounts of samples from experimental groups 1-12 were subjected to the following tests:

[0072] Flame retardant finishing: The flame retardant was prepared into a 25% working solution and applied to cotton fabric (45g / m²) using an impregnation-pad-bake method. 2 ), viscose fiber (50-70g / m 2 ), polyester fiber (80-110g / m 2 ), polyester-viscose fiber (50-70g / m 2 ).

[0073] Routine indicator tests: Clarity and color were observed visually; pH ​​value was tested using a pH meter; Solid content was tested in a forced-air drying oven at 105°C for 3 hours; Test results are shown in Table 1.

[0074] Flame retardant test:

[0075] Vertical burning test: Tested according to GB / T5455—2014 "Determination of vertical damage length, smoldering and afterflame time of textiles". Each sample was measured 5 times, and the average value was taken. Rating was conducted with reference to GB / T17591—2006 "Flame-retardant fabrics".

[0076] Limiting oxygen index test: Tested according to GB / T 5454—1997 "Test for flammability of textiles - Oxygen index method"; flame retardant test results are shown in Tables 2.1 to 2.4.

[0077] Water fastness test: According to AATCC 61—2013 "Color fastness to washing", the water fastness of the samples was determined using an SW-12A color fastness tester. Each sample was tested 5 times, and the average value was taken. The results of the water fastness test are shown in Tables 3.1 and 3.2.

[0078] Exposure resistance test: constant temperature and humidity chamber, temperature 35±2℃, humidity ≥85%, place time 72h, observe whether white spots are exuded on the surface of black fabric; the results of the exudation resistance test are shown in Table 4.

[0079] Table 1 Comparison of test results for routine indicators in experimental groups 1-12

[0080]

[0081]

[0082] Table 2.1 Comparison of flame retardant test results of cotton fabrics in experimental groups 1-12

[0083]

[0084] Table 2.2 Comparison of flame retardant test results of viscose fiber fabrics in experimental groups 1-12

[0085]

[0086] Table 2.3 Comparison of flame retardant test results of polyester fiber fabrics in experimental groups 1-12

[0087]

[0088]

[0089] Table 2.4 Comparison of flame retardant test results of polyester-viscose fiber fabrics in experimental groups 1-12

[0090]

[0091] Table 3.1 Comparison of flame retardancy test results of viscose fibers in experimental groups 1-12 after 5 washes.

[0092]

[0093]

[0094] Table 3.2 Comparison of flame retardancy test results of polyester fibers 1-12 in experimental groups after 5 washes (5 times)

[0095]

[0096]

[0097] Table 8 Comparison of precipitation resistance test results for experimental groups 1-12

[0098] sample Experimental group number Does it produce white spots? Example 1 1 no Example 2 2 no Example 3 3 no Example 4 4 no Example 5 5 no Comparative Example 1 6 yes Comparative Example 2 7 no Comparative Example 3 8 yes Comparative Example 4 9 no Comparative Example 5 10 no Commercially available 1 11 yes Commercially available 2 12 no

[0099] In Tables 2.3 and 3.2, "-" indicates complete combustion and no rating. It is clear from the tables that the flame retardants prepared in Examples 1 to 5 exhibited superior performance compared to the comparative examples and commercially available flame retardants in conventional index testing, exudation resistance testing, and flame retardant performance testing for different fabrics, especially the flame retardant samples prepared in Examples 1 to 3. Compared to Comparative Examples 1 to 3, which adjusted the ratio of small molecule water-soluble phosphate esters and polyhydroxy compounds, the transesterification reaction temperature, and the pH of the final flame retardant, Comparative Examples 4 and 5, which adjusted the amount of transesterification reaction catalyst to 6% and the atmospheric distillation reaction to 12 hours, showed a significant decrease in the flame retardant performance.

[0100] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A process for the preparation of a leach resistant flame retardant for use in the finishing of cellulosic textile goods, characterised in that, Includes the following steps: (1) A mixture of a small molecule water-soluble phosphate ester, a polyhydroxy compound, and a catalyst is stirred to obtain a raw material mixture; the catalyst is used to catalyze the transesterification reaction of the small molecule water-soluble phosphate ester and the polyhydroxy compound; the catalyst is one or more of sodium hydroxide, potassium hydroxide, N,N-dimethylaniline, diethylamine, triethylamine, and pyridine; the molar ratio of the small molecule water-soluble phosphate ester to the polyhydroxy compound is 3:1 to 1:2; the small molecule water-soluble phosphate ester is one or more of trimethyl phosphate, triethyl phosphate, and dimethyl methyl phosphate; the polyhydroxy compound is one or more of pentaerythritol, dipentaerythritol, 1,3-propanediol, and trimethylolpropane. (2) Nitrogen gas is introduced into the raw material mixture for protection, and the mixture is heated to allow the small molecule water-soluble phosphate ester and polyhydroxy compound to undergo an ester exchange reaction to obtain a transparent and clear solution, and the heating temperature is ensured not to exceed the boiling point or decomposition temperature of the small molecule water-soluble phosphate ester and polyhydroxy compound; the heating temperature is 150~200℃. (3) The transparent and clear solution described in step (2) is continuously heated and nitrogen gas is continuously introduced to carry out atmospheric distillation reaction for 3 to 10 hours; then the by-products and unreacted raw materials are distilled off by vacuum distillation, and then the heating is stopped; wherein the vacuum distillation is vacuum distillation reaction under vacuum conditions greater than 0.085 MPa for 2 to 4 hours. (4) When the temperature drops to 50°C or below, dilute with water to obtain a transparent solution, and then add a nitrogen-containing alkaline compound to the transparent solution to adjust the pH of the solution to 5-6, thereby obtaining a flame retardant for finishing fiber textiles; the nitrogen-containing alkaline compound is one or more of ammonia, triethylamine, diammonium hydrogen phosphate, guanidine dihydrogen phosphate and guanidine aminosulfonate.

2. The production method according to claim 1, wherein The amount of catalyst added in step (1) is 1 to 5% of the mass of the polyhydroxy compound.

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