A reactive cyclic phosphate flame retardant and its preparation method and application

Abstract

The invention belongs to the technical field of flame retardant finishing of textiles, and discloses a reactive cyclic phosphate flame retardant and a preparation method and application thereof. The preparation method is as follows: firstly, phosphorus oxychloride is reacted with pentaerythritol to generate pentaerythritol phosphoryl chloride; then, propylene glycol and benzyl alcohol are reacted with pentaerythritol phosphoryl chloride to generate an intermediate product capped with propylene glycol at one end and benzyl alcohol at the other end; finally, the intermediate product is reacted with phosphoric acid to generate a reactive cyclic phosphate flame retardant; the reactive cyclic phosphate flame retardant prepared by the reactive cyclic phosphate flame retardant is used for flame retardant finishing of polyester / cotton blended fabrics. The reactive cyclic phosphate flame retardant of the present invention has a strong binding force with polyester / cotton blended fabrics, and the prepared durable flame retardant polyester / cotton blended fabrics also have excellent water washing resistance and flame retardant properties.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardant finishing of textiles and relates to a reactive cyclic phosphate flame retardant and a preparation method and application thereof. Background Art

[0002] Polyester / cotton blended fabrics are widely used in clothing and home textiles because they combine the hygroscopicity of cotton and the dimensional stability of polyester. However, for safety reasons, they also need to be flame-retardant when used in most fields.

[0003] At present, the methods commonly used for flame retardant modification of polyester / cotton blended fabrics are:

[0004] The first method is to mix flame retardants for cotton and polyester and then modify the fabric to be flame retardant. For example, Reference 1 (Durable flame retardant finishing process for polyester-cotton fabrics [J]. Printing and Dyeing, 2003, 29(2): 18-19.) uses a mixture of pure cotton durable flame retardant finishing agent FK-103 and polyester durable flame retardant finishing agent FK-106, and then uses resin finishing to achieve a flame retardant effect.

[0005] The second method is to treat cotton flame retardant and polyester flame retardant by two steps. For example, Reference 2 (Flame retardant finishing of polyester-cotton 45 / 55 blended fabric [D]. Donghua University, 2006.) and Reference 3 (Flame retardant finishing of polyester-cotton blended fabric [J]. Printing and Dyeing, 2006, 32(11):5.) both use cotton flame retardant Pyrovatex CP new, polyester flame retardant DFR and its DFR-CP two-step method to finish polyester-cotton fabric.

[0006] However, both of the above two methods have the problem of poor water resistance, which is because the flame retardant for cotton and the flame retardant for polyester only act on the cotton fiber and the polyester fiber respectively, and cannot be well combined with the other fiber.

[0007] Therefore, it is necessary to develop a flame retardant that can have a strong binding effect on both fiber components in flame-retardant polyester / cotton blended fabrics. Summary of the invention

[0008] The purpose of the present invention is to solve the problems existing in the prior art and to provide a reactive cyclic phosphate flame retardant and a preparation method and application thereof.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] A reactive cyclic phosphate flame retardant, the structural formula is as follows:

[0011] .

[0012] The present invention also provides a method for preparing the above-mentioned reactive cyclic phosphate flame retardant, comprising the following steps:

[0013] (1) reacting phosphorus oxychloride with pentaerythritol to generate pentaerythritol phosphoryl chloride;

[0014] (2) reacting propylene glycol and benzyl alcohol with pentaerythritol phosphoryl chloride to generate an intermediate product capped with propylene glycol at one end and benzyl alcohol at the other end;

[0015] (3) The intermediate product is reacted with phosphoric acid to generate a reactive cyclic phosphate flame retardant.

[0016] As the preferred technical solution:

[0017] In the method described above, in steps (1) to (3), the molar ratio of phosphorus oxychloride, pentaerythritol, propylene glycol and benzyl alcohol is 2 to 2.2:1:1:1, and the molar ratio of phosphoric acid to phosphorus oxychloride is 4 to 4.4:2.

[0018] In the method as described above, in step (1), the reaction temperature is 25-30°C and the reaction time is 3-4h; in step (2), the reaction temperature is 30-35°C and the reaction time is 2-3h; in step (3), the reaction temperature is 120-140°C and the reaction time is 3-4h. Increasing the temperature helps promote the esterification reaction, but too high a temperature will result in waste.

[0019] The method described above, the specific process is as follows:

[0020] (a) dissolving phosphorus oxychloride and pentaerythritol in a solvent (dimethyl sulfoxide) and reacting to generate pentaerythritol phosphoryl chloride;

[0021] (b) adding glycerol and benzyl alcohol to the reaction system of step (a), reacting to produce an intermediate product having one end capped with glycerol and the other end capped with benzyl alcohol;

[0022] (c) adding phosphoric acid to the reaction system of step (b) to react and generate a reactive cyclic phosphate flame retardant, and purifying the product by vacuum distillation after the reaction is completed.

[0023] In the method as described above, in step (a), the mass ratio of the solvent to phosphorus oxychloride is 30-40:1.

[0024] The present invention also provides an application of the reactive cyclic phosphate flame retardant as described above for flame retardant finishing of polyester / cotton blended fabrics.

[0025] As the preferred technical solution:

[0026] The specific process of the application as described above is as follows: after the reactive cyclic phosphate flame retardant and dicyandiamide are dissolved in water to obtain a flame retardant finishing liquid, the pH value of the flame retardant finishing liquid is adjusted to 7-8 with ammonia water (the purpose is to convert the phosphate group in the reactive cyclic phosphate flame retardant into ammonium phosphate group), the polyester / cotton blended fabric is immersed in the flame retardant finishing liquid (in this process, dicyandiamide is used as a catalyst to promote the esterification grafting reaction between the ammonium phosphate group and the hydroxyl group of the cotton fiber), the polyester / cotton blended fabric is taken out, and rolling, pre-baking and baking are carried out in sequence (in this process, the molecular chain of polyester (i.e., the material of polyester fiber) is opened, and the reactive cyclic phosphate flame retardant can enter the interior of the polyester fiber and produce a combination), to obtain a durable flame retardant polyester / cotton blended fabric.

[0027] In the above application, the concentration of the reactive cyclic phosphate flame retardant in the flame retardant finishing liquid is 150~250g / L. The higher the concentration of the reactive cyclic phosphate flame retardant, the more helpful it is to improve the flame retardant properties of polyester / cotton blended fabrics. However, if the concentration is too high, it will be a waste. The concentration of dicyandiamide is 40~60g / L.

[0028] In polyester / cotton blended fabrics, the content of polyester is 20~80wt%;

[0029] The bath ratio of polyester / cotton blended fabric to flame retardant finishing liquid is 1:30~40;

[0030] The soaking temperature is 55-65°C and the soaking time is 20-30 minutes, which helps to promote the dissolution of dicyandiamide and the diffusion of the reactive cyclic phosphate flame retardant into the fiber.

[0031] The rolling margin of rolling is 90~100%;

[0032] The pre-baking temperature is 60~70℃, and the pre-baking time is 2.5~3.5min;

[0033] The baking temperature is 160~170℃ and the baking time is 3~5min.

[0034] For the application described above, the limiting oxygen index of the durable flame retardant polyester / cotton blended fabric is ≥31.2%, the damaged length is ≤8.5cm, and the damaged length is still ≤14.6cm after 55 times of washing, which meets the B1 grade standard and has excellent flame retardant and washable properties.

[0035] Principle of the invention:

[0036] One end of the reactive cyclic phosphate flame retardant of the present invention is a reactive phosphorus-containing flame retardant structure, which can be converted into an ammonium phosphate root structure, and is covalently bonded with the hydroxyl group of the cotton fiber under the catalysis of dicyandiamide, and the reaction efficiency is high. The other end is a benzene ring structure, which has good affinity with the polyester fiber and is combined according to the principle of like dissolves like. The middle is a cyclic phosphate structure, which also has good affinity with the polyester fiber and is combined according to the principle of like dissolves like. The synthetic route of the reactive cyclic phosphate flame retardant is as follows: Figure 1 As shown in the figure, the reactive cyclic phosphate flame retardant has a strong binding force with both cotton fiber and polyester fiber. During the washing process, the binding with cotton fiber and the binding with polyester fiber need to be broken at the same time to wash the flame retardant from the fabric. Therefore, the polyester / cotton blended fabric modified by it has excellent water washing resistance.

[0037] The reactive cyclic phosphate flame retardant molecular chain of the present invention contains one benzene ring structure and one cyclic phosphate structure at the same time. The binding force between the benzene ring structure and the polyester fiber is greater than that between the cyclic phosphate structure and the polyester fiber. Generally speaking, when the flame retardant molecular chain contains two structures that can bind to the polyester fiber, in order to improve the binding force between the flame retardant and the polyester fiber, those skilled in the art will design that the two structures that can bind to the polyester fiber are both benzene ring structures. However, the present invention unexpectedly finds that the binding strength between the flame retardant containing one benzene ring structure and one cyclic phosphate structure and the polyester fiber is higher than that between the flame retardant containing two benzene ring structures and the polyester fiber. It is speculated that the possible reason is that during the high-temperature baking process, the polyester molecular chain and the flame retardant molecular chain are both in a thermal motion state, and the two molecular chains Both are looking for suitable binding sites to combine with another molecular chain. The number of binding sites with benzene ring structure in polyester molecular chain is limited. Flame retardant molecular chains containing two benzene ring structures will compete with each other and combine with these binding sites, which ultimately leads to most flame retardant molecular chains having only one benzene ring structure combined with polyester molecular chain. The number of connection points between flame retardant molecular chain and polyester molecular chain is 1. Flame retardant molecular chain is suspended on polyester molecular chain, and the two cannot form a chimeric structure. When the flame retardant molecular chain contains one benzene ring structure and one cyclic phosphate structure, when the benzene ring structure is looking for a suitable binding site to combine with polyester molecular chain, the cyclic phosphate structure is also looking for a suitable binding site to combine with polyester molecular chain. The number of connection points between flame retardant molecular chain and polyester molecular chain is 2, and the two can form a chimeric structure. Therefore, the two structures with different binding forces can better chimera with the chain segments of polyester fiber in thermal motion, thereby improving the binding force with polyester fiber.

[0038] In the molecular chain of the reactive cyclic phosphate flame retardant of the present invention, there is a certain distance between the reactive phosphorus-containing flame retardant structure and the benzene ring structure and the cyclic phosphate structure. In the polyester / cotton blended fabric, there is also a certain distance between the polyester component and the cotton component. The two distances match each other. When one end of the flame retardant is covalently bonded to the cotton fiber, the group at the other end can find a suitable distance to combine with the polyester fiber during thermal motion.

[0039] The reactive cyclic phosphate flame retardant of the invention has good water solubility, is easy to use and has high reaction efficiency with cotton fibers.

[0040] Beneficial effects:

[0041] (1) The reactive cyclic phosphate flame retardant prepared by the present invention can form a strong covalent bond with cotton fibers, and also form a similar miscible bond with polyester fibers, so that the reactive cyclic phosphate flame retardant has a strong bonding force with polyester / cotton blended fabrics. Therefore, during the washing process, the flame retardant can only be washed off the fabric by breaking the bonds with the cotton fibers and the polyester fibers at the same time. It can also be seen that the durable flame retardant polyester / cotton blended fabric prepared by the present invention has excellent water washing resistance.

[0042] (2) The reactive cyclic phosphate flame retardant prepared by the present invention has good water solubility, is easy to use, and has high reaction efficiency with cotton fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The schematic diagram of the synthesis route of the reactive cyclic phosphate flame retardant of the present invention;

[0044] Figure 2 The figure is a carbon NMR spectrum of the reactive cyclic phosphate flame retardant prepared in Example 3 of the present invention; in the figure, the chemical shifts at 141.2ppm, 129.5ppm and 127.3ppm in the carbon NMR spectrum of the reactive cyclic phosphate flame retardant are caused by the benzene ring carbon elements in the benzyl alcohol structure, the chemical shifts at 66.9 and 64.5ppm are caused by the carbon elements in the glycerol structure, and the chemical shifts at 70.0 and 33.5ppm are caused by the carbon elements in the pentaerythritol structure;

[0045] Figure 3 This is a vertical burning test diagram of the durable flame retardant polyester / cotton blended fabric prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0047] The testing methods of the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0048] Limiting oxygen index of fabric: refer to GB / T 5454-1997 "Oxygen index method for textile combustion performance test" standard to test the durable flame retardant polyester / cotton blended fabric.

[0049] Damage length: The durable flame retardant polyester / cotton blended fabric was measured with reference to GB / T 5455-2014 "Determination of damage length in vertical direction, smoldering and afterflaming time of textile combustion performance" standard.

[0050] Damaged length after 55 washes: first wash the durable flame retardant polyester / cotton blended fabric for 55 times with reference to the AATCC 61-2013 "Accelerated Test for Color Fastness to Washing for Household and Commercial Use" standard, and then measure the damaged length of the durable flame retardant polyester / cotton blended fabric test fabric after washing with reference to the GB / T 5455-2014 "Determination of the Damage Length in the Vertical Direction of Burning Performance of Textiles - Smoldering and Afterflaming Time" standard.

[0051] Example 1

[0052] A method for preparing a reactive cyclic phosphate flame retardant, comprising the following steps:

[0053] (1) Preparation of raw materials;

[0054] Phosphorus oxychloride;

[0055] Pentaerythritol;

[0056] Glycerol;

[0057] Benzyl alcohol;

[0058] Phosphoric acid;

[0059] Solvent: dimethyl sulfoxide;

[0060] (2) dissolving phosphorus oxychloride and pentaerythritol in a solvent and reacting them at 25° C. for 4 hours to generate pentaerythritol phosphoryl chloride; wherein the mass ratio of the solvent to phosphorus oxychloride is 30:1;

[0061] (3) adding propylene glycol and benzyl alcohol to the reaction system of step (2), and reacting at 30° C. for 3 h to generate an intermediate product capped with propylene glycol at one end and benzyl alcohol at the other end;

[0062] (4) adding phosphoric acid to the reaction system of step (3), reacting at 120° C. for 4 h to generate a reactive cyclic phosphate flame retardant, and purifying it by vacuum distillation;

[0063] In steps (2) to (4), the molar ratio of phosphorus oxychloride, pentaerythritol, propylene glycol and benzyl alcohol is 2.1:1:1:1, and the molar ratio of phosphoric acid to phosphorus oxychloride is 4:2.

[0064] An application of a reactive cyclic phosphate flame retardant comprises the following steps:

[0065] (a) dissolving the reactive cyclic phosphate flame retardant and dicyandiamide prepared above in water to obtain a flame retardant finishing liquid, and adjusting the pH value of the flame retardant finishing liquid to 7 with aqueous ammonia; wherein the concentration of the reactive cyclic phosphate flame retardant in the flame retardant finishing liquid is 150 g / L, and the concentration of the dicyandiamide is 40 g / L;

[0066] (b) After soaking a polyester / cotton blended fabric (polyester content is 80wt%, limiting oxygen index is 20.3%, and damaged length is 30cm) in a flame retardant finishing liquid, the polyester / cotton blended fabric is taken out, and rolling, pre-baking and baking are carried out in sequence to obtain a durable flame retardant polyester / cotton blended fabric; wherein the bath ratio of the polyester / cotton blended fabric to the flame retardant finishing liquid is 1:30, the soaking temperature is 65°C, the soaking time is 20min, the rolling rate is 90%, the pre-baking temperature is 60°C, the pre-baking time is 3.5min, the baking temperature is 160°C, and the baking time is 5min.

[0067] The final durable flame-retardant polyester / cotton blended fabric had a limiting oxygen index of 31.2%, a damaged length of 8.5 cm, and a damaged length of 14.6 cm after 55 washes.

[0068] Example 2

[0069] A method for preparing a reactive cyclic phosphate flame retardant, comprising the following steps:

[0070] (1) Preparation of raw materials;

[0071] Phosphorus oxychloride;

[0072] Pentaerythritol;

[0073] Glycerol;

[0074] Benzyl alcohol;

[0075] Phosphoric acid;

[0076] Solvent: dimethyl sulfoxide;

[0077] (2) dissolving phosphorus oxychloride and pentaerythritol in a solvent and reacting them at 28° C. for 3.5 hours to generate pentaerythritol phosphoryl chloride; wherein the mass ratio of the solvent to phosphorus oxychloride is 40:1;

[0078] (3) adding propylene glycol and benzyl alcohol to the reaction system of step (2), and reacting at 33° C. for 2.5 h to generate an intermediate product capped with propylene glycol at one end and benzyl alcohol at the other end;

[0079] (4) adding phosphoric acid to the reaction system of step (3), reacting at 125° C. for 3.7 hours to generate a reactive cyclic phosphate flame retardant, and purifying it by vacuum distillation;

[0080] In steps (2) to (4), the molar ratio of phosphorus oxychloride, pentaerythritol, propylene glycol and benzyl alcohol is 2.2:1:1:1, and the molar ratio of phosphoric acid to phosphorus oxychloride is 4.2:2.

[0081] An application of a reactive cyclic phosphate flame retardant comprises the following steps:

[0082] (a) dissolving the reactive cyclic phosphate flame retardant and dicyandiamide prepared above in water to obtain a flame retardant finishing liquid, and adjusting the pH value of the flame retardant finishing liquid to 7.5 with aqueous ammonia; wherein the concentration of the reactive cyclic phosphate flame retardant in the flame retardant finishing liquid is 175 g / L, and the concentration of the dicyandiamide is 45 g / L;

[0083] (b) After soaking a polyester / cotton blended fabric (polyester content of 50wt%, limiting oxygen index of 20.1%, and damaged length of 30cm) in a flame retardant finishing liquid, the polyester / cotton blended fabric is taken out, and rolled, pre-baked, and baked in sequence to obtain a durable flame retardant polyester / cotton blended fabric; wherein the bath ratio of the polyester / cotton blended fabric to the flame retardant finishing liquid is 1:35, the soaking temperature is 60°C, the soaking time is 25min, the rolling rate is 100%, the pre-baking temperature is 63°C, the pre-baking time is 3.3min, the baking temperature is 165°C, and the baking time is 4min.

[0084] The final durable flame-retardant polyester / cotton blended fabric had a limiting oxygen index of 32.1%, a damaged length of 8.1 cm, and a damaged length of 14.1 cm after 55 washes.

[0085] Example 3

[0086] A method for preparing a reactive cyclic phosphate flame retardant, comprising the following steps:

[0087] (1) Preparation of raw materials;

[0088] Phosphorus oxychloride;

[0089] Pentaerythritol;

[0090] Glycerol;

[0091] Benzyl alcohol;

[0092] Phosphoric acid;

[0093] Solvent: dimethyl sulfoxide;

[0094] (2) dissolving phosphorus oxychloride and pentaerythritol in a solvent and reacting them at 30° C. for 3 hours to generate pentaerythritol phosphoryl chloride; wherein the mass ratio of the solvent to phosphorus oxychloride is 35:1;

[0095] (3) adding propylene glycol and benzyl alcohol to the reaction system of step (2), and reacting at 35° C. for 2 h to generate an intermediate product capped with propylene glycol at one end and benzyl alcohol at the other end;

[0096] (4) After adding phosphoric acid to the reaction system of step (3), the reaction was carried out at 130° C. for 3.5 hours to generate a reactive cyclic phosphate flame retardant, which was purified by vacuum distillation. The nuclear magnetic resonance carbon spectrum of the purified reactive cyclic phosphate flame retardant is as follows: Figure 2 As shown;

[0097] In steps (2) to (4), the molar ratio of phosphorus oxychloride, pentaerythritol, propylene glycol and benzyl alcohol is 2.1:1:1:1, and the molar ratio of phosphoric acid to phosphorus oxychloride is 4.4:2.

[0098] An application of a reactive cyclic phosphate flame retardant comprises the following steps:

[0099] (a) dissolving the reactive cyclic phosphate flame retardant and dicyandiamide prepared above in water to obtain a flame retardant finishing liquid, and adjusting the pH value of the flame retardant finishing liquid to 8 with aqueous ammonia; wherein the concentration of the reactive cyclic phosphate flame retardant in the flame retardant finishing liquid is 200 g / L, and the concentration of the dicyandiamide is 50 g / L;

[0100] (b) After soaking a polyester / cotton blended fabric (polyester content of 20wt%, limiting oxygen index of 20%, and damaged length of 30cm) in a flame retardant finishing liquid, the polyester / cotton blended fabric is taken out, and rolled, pre-baked, and baked in sequence to obtain a durable flame retardant polyester / cotton blended fabric; wherein the bath ratio of the polyester / cotton blended fabric to the flame retardant finishing liquid is 1:40, the soaking temperature is 55°C, the soaking time is 30min, the rolling rate is 95%, the pre-baking temperature is 65°C, the pre-baking time is 3min, the baking temperature is 170°C, and the baking time is 3min.

[0101] The resulting durable flame retardant polyester / cotton blended fabric has a limiting oxygen index of 32.8% and a damage length of 7.8 cm (e.g. Figure 3As shown in the figure), after 55 times of washing, the damaged length is 13.7cm.

[0102] Comparative Example 1

[0103] A flame retardant with the structural formula: ;

[0104] The preparation method of the flame retardant comprises the following steps:

[0105] (1) Phosphorus oxychloride, propylene glycol and benzyl alcohol are dissolved in a solvent and reacted at 25° C. for 3.5 hours to generate an intermediate product capped with propylene glycol at one end and benzyl alcohol at the other two ends; wherein the mass ratio of the solvent to phosphorus oxychloride is 30:1;

[0106] (2) adding phosphoric acid to the reaction system of step (1), reacting at 120° C. for 4 hours to generate the target flame retardant, and purifying it by vacuum distillation;

[0107] In steps (1) to (2), the molar ratio of phosphorus oxychloride, propylene glycol and benzyl alcohol is 1:1:2.2, and the molar ratio of phosphoric acid to phosphorus oxychloride is 2:1.

[0108] The application of a flame retardant is basically the same as that of Example 3, except that the flame retardant used is prepared in this comparative example.

[0109] The damaged length of the flame-retardant polyester / cotton blended fabric finally obtained was 8.9 cm, and the damaged length was 30 cm after 55 times of washing.

[0110] By comparing Comparative Example 1 with Example 3, it can be seen that the damage length of the flame-retardant polyester / cotton blended fabric prepared in Comparative Example 1 is increased and the water washing resistance is reduced. This is because the number of binding sites with the benzene ring structure in the polyester molecular chain is limited, and the flame retardant molecular chains containing two benzene ring structures in the flame retardant prepared in Comparative Example 1 will compete with each other, ultimately resulting in most flame retardant molecular chains having only one benzene ring structure combined with the polyester molecular chain, and unable to produce a good binding effect with polyester; in addition, the flame retardant molecular chain segment prepared in this comparative example is relatively short, and after reacting with polyester fiber or cotton fiber, its other end is difficult to react with another fiber, so the amount of both ends of the flame retardant molecular chain segment that can simultaneously react with the two fibers is limited, which also leads to reduced water washing resistance.

[0111] Example 4

[0112] A method for preparing a reactive cyclic phosphate flame retardant, comprising the following steps:

[0113] (1) Preparation of raw materials;

[0114] Phosphorus oxychloride;

[0115] Pentaerythritol;

[0116] Glycerol;

[0117] Benzyl alcohol;

[0118] Phosphoric acid;

[0119] Solvent: dimethyl sulfoxide;

[0120] (2) dissolving phosphorus oxychloride and pentaerythritol in a solvent and reacting them at 27° C. for 3.6 hours to generate pentaerythritol phosphoryl chloride; wherein the mass ratio of the solvent to phosphorus oxychloride is 40:1;

[0121] (3) adding propylene glycol and benzyl alcohol to the reaction system of step (2), and reacting at 32° C. for 2.6 h to generate an intermediate product capped with propylene glycol at one end and benzyl alcohol at the other end;

[0122] (4) adding phosphoric acid to the reaction system of step (3), reacting at 135° C. for 3.3 h to generate a reactive cyclic phosphate flame retardant, and purifying it by vacuum distillation;

[0123] In steps (2) to (4), the molar ratio of phosphorus oxychloride, pentaerythritol, propylene glycol and benzyl alcohol is 2:1:1:1, and the molar ratio of phosphoric acid to phosphorus oxychloride is 4.3:2.

[0124] An application of a reactive cyclic phosphate flame retardant comprises the following steps:

[0125] (a) dissolving the reactive cyclic phosphate flame retardant and dicyandiamide prepared above in water to obtain a flame retardant finishing liquid, and adjusting the pH value of the flame retardant finishing liquid to 7.5 with aqueous ammonia; wherein the concentration of the reactive cyclic phosphate flame retardant in the flame retardant finishing liquid is 225 g / L, and the concentration of the dicyandiamide is 55 g / L;

[0126] (b) After soaking a polyester / cotton blended fabric (polyester content of 25wt%, limiting oxygen index of 20.1%, and damaged length of 30cm) in a flame retardant finishing liquid, the polyester / cotton blended fabric is taken out, and rolling, pre-baking, and baking are performed in sequence to obtain a durable flame retardant polyester / cotton blended fabric; wherein the bath ratio of the polyester / cotton blended fabric to the flame retardant finishing liquid is 1:32, the soaking temperature is 60°C, the soaking time is 25min, the rolling rate is 100%, the pre-baking temperature is 68°C, the pre-baking time is 2.8min, the baking temperature is 165°C, and the baking time is 4min.

[0127] The final durable flame-retardant polyester / cotton blended fabric had a limiting oxygen index of 33.4%, a damaged length of 7.5 cm, and a damaged length of 13.4 cm after 55 washes.

[0128] Example 5

[0129] A method for preparing a reactive cyclic phosphate flame retardant, comprising the following steps:

[0130] (1) Preparation of raw materials;

[0131] Phosphorus oxychloride;

[0132] Pentaerythritol;

[0133] Glycerol;

[0134] Benzyl alcohol;

[0135] Phosphoric acid;

[0136] Solvent: dimethyl sulfoxide;

[0137] (2) dissolving phosphorus oxychloride and pentaerythritol in a solvent and reacting them at 25° C. for 4 hours to generate pentaerythritol phosphoryl chloride; wherein the mass ratio of the solvent to phosphorus oxychloride is 30:1;

[0138] (3) adding propylene glycol and benzyl alcohol to the reaction system of step (2), and reacting at 30° C. for 3 h to generate an intermediate product capped with propylene glycol at one end and benzyl alcohol at the other end;

[0139] (4) adding phosphoric acid to the reaction system of step (3), reacting at 140° C. for 3 h to generate a reactive cyclic phosphate flame retardant, and purifying it by vacuum distillation;

[0140] In steps (2) to (4), the molar ratio of phosphorus oxychloride, pentaerythritol, propylene glycol and benzyl alcohol is 2.1:1:1:1, and the molar ratio of phosphoric acid to phosphorus oxychloride is 4.1:2.

[0141] An application of a reactive cyclic phosphate flame retardant comprises the following steps:

[0142] (a) dissolving the reactive cyclic phosphate flame retardant and dicyandiamide prepared above in water to obtain a flame retardant finishing liquid, and adjusting the pH value of the flame retardant finishing liquid to 7 with aqueous ammonia; wherein the concentration of the reactive cyclic phosphate flame retardant in the flame retardant finishing liquid is 250 g / L, and the concentration of the dicyandiamide is 60 g / L;

[0143] (b) After soaking a polyester / cotton blended fabric (polyester content of 30wt%, limiting oxygen index of 20.2%, and damaged length of 30cm) in a flame retardant finishing liquid, the polyester / cotton blended fabric is taken out, and rolling, pre-baking, and baking are performed in sequence to obtain a durable flame retardant polyester / cotton blended fabric; wherein the bath ratio of the polyester / cotton blended fabric to the flame retardant finishing liquid is 1:30, the soaking temperature is 65°C, the soaking time is 20min, the rolling rate is 90%, the pre-baking temperature is 70°C, the pre-baking time is 2.5min, the baking temperature is 160°C, and the baking time is 5min.

[0144] The final durable flame-retardant polyester / cotton blended fabric had a limiting oxygen index of 33.9% and a damaged length of 7.2 cm. After 55 washes, the damaged length was 13.1 cm.

Claims

1. A reactive cyclic phosphate flame retardant, characterized in that: The structural formula is as follows:

2. A method for preparing a reactive cyclic phosphate flame retardant as claimed in claim 1, characterized in that: The following steps are involved: (1) reacting phosphorus oxychloride with pentaerythritol to generate pentaerythritol phosphoryl chloride; (2) reacting glycerol and benzyl alcohol with pentaerythritol phosphoryl chloride to generate an intermediate product capped with glycerol at one end and benzyl alcohol at the other end; (3) The intermediate product is reacted with phosphoric acid to generate a reactive cyclic phosphate flame retardant.

3. The method according to claim 2, characterized in that In steps (1) to (3), the molar ratio of phosphorus oxychloride, pentaerythritol, propylene glycol and benzyl alcohol is 2 to 2.2:1:1:1, and the molar ratio of phosphoric acid to phosphorus oxychloride is 4 to 4.4:

2.

4. The method according to claim 2, characterized in that: In step (1), the reaction temperature is 25-30° C. and the reaction time is 3-4 h; in step (2), the reaction temperature is 30-35° C. and the reaction time is 2-3 h; in step (3), the reaction temperature is 120-140° C. and the reaction time is 3-4 h.

5. The method according to claim 2, characterized in that: The specific process is as follows: (a) dissolving phosphorus oxychloride and pentaerythritol in a solvent, reacting to generate pentaerythritol phosphoryl chloride; (b) adding glycerol and benzyl alcohol to the reaction system of step (a), reacting to generate an intermediate product having glycerol capped at one end and benzyl alcohol capped at the other end; (c) adding phosphoric acid to the reaction system of step (b) to react and generate a reactive cyclic phosphate flame retardant.

6. The method according to claim 5, characterized in that In step (a), the mass ratio of the solvent to phosphorus oxychloride is 30 to 40:

1.

7. The use of a reactive cyclic phosphate flame retardant as claimed in claim 1, characterized in that: Used for flame retardant finishing of polyester / cotton blended fabrics.

8. The use according to claim 7, characterized in that: The specific process is: after dissolving the reactive cyclic phosphate flame retardant and dicyandiamide in water to obtain a flame retardant finishing liquid, ammonia water is used to adjust the pH value of the flame retardant finishing liquid to 7-8, the polyester / cotton blended fabric is immersed in the flame retardant finishing liquid, the polyester / cotton blended fabric is taken out, and rolling, pre-baking and baking are carried out in sequence to obtain a flame retardant polyester / cotton blended fabric.

9. The use according to claim 8, characterized in that: In the flame retardant finishing liquid, the concentration of the reactive cyclic phosphate flame retardant is 150-250 g / L, and the concentration of dicyandiamide is 40-60 g / L; In polyester / cotton blended fabrics, the content of polyester is 20-80wt%; The bath ratio of polyester / cotton blended fabric to flame retardant finishing liquid is 1:30-40; The soaking temperature is 55-65°C and the soaking time is 20-30 minutes; The rolling rate of rolling is 90-100%; The pre-baking temperature is 60-70°C and the pre-baking time is 2.5-3.5 minutes; The baking temperature is 160-170°C, and the baking time is 3-5 minutes.

10. The use according to claim 9, characterized in that: The limiting oxygen index of the flame retardant polyester / cotton blended fabric is ≥31.2%, the damaged length is ≤8.5cm, and after 55 times of washing, the damaged length is still ≤14.6cm.

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