Flame retardant thermoplastic polyurethane resin, preparation method thereof, application thereof and protective clothing

Abstract

The present invention provides a flame retardant thermoplastic polyurethane resin, wherein the polyurethane resin includes at least the following structural units: #imgabs0# wherein R1 is a polyol and R2 is an isocyanate. The polyurethane resin provided by the present invention contains a large amount of isocyanurate structures with flame retardant properties, and its flame retardant grade is greater than or equal to UL‑94 VTM‑1, and has good transparency; it is halogen-free and environmentally friendly; it does not contain phosphorus elements, and after long-term storage, the flame retardant grade will not decrease due to easy water absorption, and the material performance will not be significantly attenuated. The method for preparing a polyurethane resin provided by the present invention first adds an aliphatic diisocyanate and a phthalic anhydride polyester polyol to form a carbamate structure; then a catalyst is added, and under nitrogen protection, the excess isocyanate structure undergoes a trimerization reaction to form an isocyanurate structure, and finally the chain is extended under the action of a chain extender to form a macromolecular polyurethane resin. In this method, a plasticizer is used as a solvent for the reaction, and the softness of the polyurethane resin is adjusted at the same time.

Description

Technical Field

[0001] The invention relates to a flame retardant thermoplastic polyurethane resin, a preparation method of the flame retardant thermoplastic polyurethane resin, application of the flame retardant thermoplastic polyurethane resin in the preparation of positive pressure protective clothing, and the positive pressure protective clothing. Background Art

[0002] Existing nuclear power disposable positive pressure protective clothing products use PVC material as flame retardant fabric. PVC material itself contains halogen, which will cause great environmental pollution during waste treatment (deep burial and combustion), especially the chlorine-containing acid substances and dioxins released during combustion are highly corrosive and carcinogenic, causing environmental pollution, equipment damage and human safety problems. Currently, halogen-free flame retardant polyurethane resin (TPU) on the market mostly uses phosphorus-containing flame retardants and TPU resin particles to be blended and then calendered into film. To achieve the product flame retardant grade UL-94VTM-0, the addition ratio of flame retardant needs to exceed 20%. At the addition ratio that reaches the flame retardant grade, the calendered film usually has poor transparency or the transparency decreases after placement. In addition, phosphorus-containing flame retardants are hygroscopic, and long-term placement will cause the flame retardant grade to decrease, and the material performance will be significantly attenuated.

[0003] Invention patent content

[0004] In order to overcome the defects of the prior art, the present invention provides a polyurethane resin having flame retardant properties. The flame retardant thermoplastic polyurethane resin does not contain phosphorus and its transparency remains basically unchanged after being placed for a long time.

[0005] In one aspect, the present invention provides a flame retardant thermoplastic polyurethane resin, characterized in that the transparent flame retardant thermoplastic polyurethane resin comprises at least the following structural units:

[0006] Among them, R1 is polyol and R2 is isocyanate.

[0007] On the other hand, the present invention also provides a method for preparing a flame retardant thermoplastic polyurethane resin, characterized in that the method comprises the following steps:

[0008] a. Under stirring and nitrogen protection conditions, aliphatic diisocyanate, phthalic anhydride polyester polyol and plasticizer are mixed to obtain a mixture 1; wherein the molar number of the aliphatic diisocyanate is greater than the molar number of the phthalic anhydride polyester polyol; the mixture 1 is heated to 60-100° C. and reacted at the temperature for 10-60 minutes to obtain a reaction mixture 1;

[0009] b. Under stirring and nitrogen protection conditions, adding a catalyst to the reaction mixture 1 to obtain a mixture 2, heating the mixture 2 to 100-140 ° C, and reacting at this temperature for 10-60 minutes to obtain a mixture of an NCO-terminated isocyanurate structured polyurethane prepolymer;

[0010] c. Under stirring and nitrogen protection conditions, at 100-140° C., a chain extender is added to the mixture of the NCO-terminated isocyanurate structured polyurethane prepolymer to obtain a mixture 3, and the mixture is reacted at 100-140° C. for 40-80 minutes to obtain a flame retardant thermoplastic polyurethane resin.

[0011] The flame-retardant thermoplastic polyurethane resin provided by the present invention contains a large amount of isocyanurate structures with flame-retardant properties, and its flame-retardant grade is greater than or equal to UL-94VTM-1, and has good transparency; it does not contain halogen and is environmentally friendly; it does not contain phosphorus elements, and after long-term storage, its flame-retardant grade will not decrease due to easy water absorption, and the material performance will not be significantly attenuated.

[0012] The method for preparing a flame-retardant thermoplastic polyurethane resin provided by the present invention has good flame-retardant properties of the prepared polyurethane resin, and the properties remain stable and attenuated during the shelf life of the product. The method for preparing a flame-retardant thermoplastic polyurethane resin of the present invention first adds aliphatic diisocyanate and phthalic anhydride polyester polyol to form a carbamate structure, i.e., the main structure of the polyurethane resin; then a catalyst is added, and under the protection of nitrogen and the action of temperature, the excess isocyanate structure undergoes a trimerization reaction to form an isocyanurate structure, and finally, under the action of a chain extender, the chain is extended to form a macromolecular polyurethane resin. In addition, in the preparation method, a plasticizer is used as a solvent for the reaction, which simplifies the preparation process and adjusts the toughness of the prepared polyurethane resin, and is environmentally friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 The infrared spectrum of the flame retardant thermoplastic polyurethane resin prepared in Example 1 of the present application; wherein, at 1635-1742 cm -1 The absorption peak between is the absorption peak of isocyanurate structure. With the increase of content, the position of the absorption peak shifts and the peak intensity varies. 3310-3500cm -1 The broad peak at 1550 cm is the stretching vibration of amino (or urea) formate NH -1 NH bending vibration, 1742.24cm -1 The stretching vibration peak of C=O of amino (or urea) formate appears at 1742.24 cm-1. These three absorption peaks are characteristic peaks of amino (or urea) formate bonds, indicating that the synthesized product is indeed a polyurethane structure. -1 Instead of 1716cm -1It indicates that the polyurethane is a polyester polyurethane rather than a polyether polyurethane. DETAILED DESCRIPTION

[0014] The present invention provides a flame retardant thermoplastic polyurethane resin, characterized in that the transparent flame retardant thermoplastic polyurethane resin comprises at least the following structural units:

[0015] Among them, R1 is polyol and R2 is isocyanate.

[0016] In a preferred embodiment, R1 is one or more of polyethylene phthalate diol, polyhexanediol 1,6-phthalate diol and polyneopentyl phthalate diol.

[0017] In order to obtain better flame retardant properties, in a preferred embodiment, the molar mass of the isocyanurate in the flame retardant thermoplastic polyurethane resin is 15-35%, preferably 20-30%.

[0018] In order to obtain a flame retardant thermoplastic polyurethane resin having excellent toughness, in a preferred embodiment, the flame retardant thermoplastic polyurethane resin further contains a plasticizer.

[0019] In order to obtain better toughness, in a preferred embodiment, the plasticizer accounts for 20-50% by weight of the flame retardant thermoplastic polyurethane resin, preferably 30-40% by weight.

[0020] In a preferred embodiment, the flame retardant thermoplastic polyurethane resin is prepared by the following method:

[0021] a. mixing an aliphatic diisocyanate, a phthalic anhydride polyester polyol and a plasticizer under stirring and in a nitrogen atmosphere to obtain a mixture 1; wherein the molar ratio of the aliphatic diisocyanate to the phthalic anhydride polyester polyol is 3-6:1, and the amount of the plasticizer is 20-50% by weight of the total amount of the aliphatic diisocyanate and the phthalic anhydride polyester polyol, preferably 30-40%; heating the mixture 1 to 70-90° C. and reacting at the temperature for 20-40 minutes to obtain a reaction mixture 1;

[0022] b. Under stirring and in a nitrogen atmosphere, a catalyst is added to the reaction mixture 1 to obtain a mixture 2, the mixture 2 is heated to 110-130 ° C, and reacted at this temperature for 20-40 minutes to obtain a mixture of an NCO-terminated isocyanurate structured polyurethane prepolymer;

[0023] c. Under stirring and in a nitrogen atmosphere, at 110-130° C., a chain extender is added to the mixture of the NCO-terminated isocyanurate structured polyurethane prepolymer, wherein the molar ratio of the chain extender added to the mixture of the NCO-terminated isocyanurate structured polyurethane prepolymer is 1:0.5-1, to obtain a mixture 3, and react at 110-130° C. for 50-70 minutes to obtain a flame retardant thermoplastic polyurethane resin.

[0024] Preferably, in step a, the molar ratio of aliphatic diisocyanate to phthalic anhydride polyester polyol is 4-5:1;

[0025] Preferably, in step a, the amount of the plasticizer used is 30-40 wt % of the total amount of the aliphatic diisocyanate and the phthalic anhydride polyester polyol.

[0026] The phthalic anhydride polyester polyol may be a phthalic anhydride polyester polyol commonly used in the art; in a preferred embodiment, the phthalic anhydride polyester polyol is selected from one or more of polyethylene phthalate diol, polyhexanediol 1,6-phthalate diol and polyneopentyl phthalate diol.

[0027] In a preferred embodiment, the molecular weight of the phthalic anhydride polyester polyol is 1000-3000 Daltons, preferably 1500-2500 Daltons.

[0028] The aliphatic diisocyanate may be a commonly used aliphatic diisocyanate in the art; in a preferred embodiment, it is one or more selected from isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and 1,4-cyclohexane diisocyanate.

[0029] In the present application, the plasticizer is used to adjust the toughness of the polyurethane resin on the one hand, and is used as a solvent for the reaction of aliphatic diisocyanate and phthalic anhydride polyester polyol on the other hand.

[0030] The plasticizer may be a commonly used plasticizer in the art. In a preferred embodiment, the plasticizer is selected from one or more of dioctyl terephthalate, dimethoxyethylene glycol phthalate, tricresyl phosphate, dipropylene glycol phthalate and triethylene glycol nonanoate.

[0031] The chain extender may be a commonly used chain extender in the art, preferably a diol or a diamine.

[0032] The diol may be a diol commonly used in the art. In a preferred embodiment, the diol is selected from one or more of ethylene glycol, propylene glycol, butanediol, pentanediol and hexanediol.

[0033] The diamine may be a commonly used diamine in the art. In a preferred embodiment, the diamine is selected from one or more of ethylenediamine, propylenediamine, hexamethylenediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, and benzidine.

[0034] In a preferred embodiment, in step a, the stirring speed is 700-900 rpm; in step b, the stirring speed is 1100-1300 rpm; in step c, the stirring speed is 1900-2100 rpm.

[0035] The present application also provides a method for preparing a flame retardant thermoplastic polyurethane resin, characterized in that the method comprises the following steps:

[0036] a. mixing an aliphatic diisocyanate, a phthalic anhydride polyester polyol and a plasticizer under stirring and in a nitrogen atmosphere to obtain a mixture 1; wherein the molar number of the aliphatic diisocyanate is greater than the molar number of the phthalic anhydride polyester polyol; heating the mixture 1 to 60-100° C. and reacting at the temperature for 10-60 minutes to obtain a reaction mixture 1;

[0037] b. Under stirring and in a nitrogen atmosphere, a catalyst is added to the reaction mixture 1 to obtain a mixture 2, the mixture 2 is heated to 100-140 ° C, and reacted at this temperature for 10-60 minutes to obtain a mixture of an NCO-terminated isocyanurate structured polyurethane prepolymer;

[0038] c. Under stirring and in a nitrogen atmosphere, at 100-140° C., a chain extender is added to the mixture of the NCO-terminated isocyanurate structured polyurethane prepolymer to obtain a mixture 3, and the mixture is reacted at 100-140° C. for 40-80 minutes to obtain a flame retardant thermoplastic polyurethane resin.

[0039] In step a, the molar number of the aliphatic diisocyanate is greater than the molar number of the phthalic anhydride polyester polyol, and preferably the molar ratio is greater than 2, more preferably greater than 3.

[0040] In step a, the isocyanurate structure with flame retardant properties is formed by controlling the molar number of the aliphatic diisocyanate to be greater than the molar number of the phthalic anhydride polyester polyol without adding a catalyst, wherein the isocyanate structure and the isocyanurate structure are shown in I and II below, respectively:

[0041]

[0042] In a preferred embodiment, the method comprises the following steps:

[0043] a. Under stirring and in a nitrogen atmosphere, an aliphatic diisocyanate, a phthalic anhydride polyester polyol and a plasticizer are mixed in a molar ratio of 1:3-1:6 to obtain a mixture 1, the mixture 1 is heated to 70-90 ° C, and reacted at this temperature for 20-40 minutes to obtain a reaction mixture 1;

[0044] b. Under stirring and in a nitrogen atmosphere, a catalyst is added to the reaction mixture 1 to obtain a mixture 2, the mixture 2 is heated to 110-130 ° C, and reacted at this temperature for 20-40 minutes to obtain a mixture of an NCO-terminated isocyanurate structured polyurethane prepolymer;

[0045] c. Under stirring and in a nitrogen atmosphere, at 110-130° C., a chain extender is added to the mixture of the NCO-terminated isocyanurate structured polyurethane prepolymer, wherein the molar ratio of the chain extender added to the mixture of the NCO-terminated isocyanurate structured polyurethane prepolymer is 1:0.5-1, to obtain a mixture 3, and react at 110-130° C. for 50-70 minutes to obtain a flame retardant thermoplastic polyurethane resin.

[0046] Preferably, in step a, the molar ratio of aliphatic diisocyanate to phthalic anhydride polyester polyol is 4-5:1;

[0047] Preferably, in step a, the amount of the plasticizer used is 30-40 wt % of the total amount of the aliphatic diisocyanate and the phthalic anhydride polyester polyol.

[0048] The catalyst may be a catalyst commonly used in the art, preferably dibutyltin dilaurate, tri-n-butyltin methoxylate or stannous octoate.

[0049] Preferably, the mass ratio of the catalyst to the aliphatic diisocyanate is 0.005-0.01:1, preferably 0.008:1.

[0050] The phthalic anhydride polyester polyol may be a phthalic anhydride polyester polyol commonly used in the art; in a preferred embodiment, the phthalic anhydride polyester polyol is selected from one or more of polyethylene phthalate diol, polyhexanediol 1,6-phthalate diol and polyneopentyl phthalate diol.

[0051] In a preferred embodiment, the molecular weight of the phthalic anhydride polyester polyol is 1000-3000 Daltons, preferably 1500-2500 Daltons.

[0052] The aliphatic diisocyanate may be a commonly used aliphatic diisocyanate in the art; in a preferred embodiment, it is one or more selected from isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and 1,4-cyclohexane diisocyanate.

[0053] In the present application, the plasticizer is used to adjust the toughness of the polyurethane resin on the one hand, and is used as a solvent for the reaction of aliphatic diisocyanate and phthalic anhydride polyester polyol on the other hand.

[0054] The plasticizer may be a commonly used plasticizer in the art. In a preferred embodiment, the plasticizer is selected from one or more of dioctyl terephthalate, dimethoxyethylene glycol phthalate, tricresyl phosphate, dipropylene glycol phthalate and triethylene glycol nonanoate.

[0055] The chain extender may be a commonly used chain extender in the art, preferably a diol or a diamine.

[0056] The diol may be a diol commonly used in the art. In a preferred embodiment, the diol is selected from one or more of ethylene glycol, propylene glycol, butanediol, pentanediol and hexanediol.

[0057] The diamine may be a commonly used diamine in the art. In a preferred embodiment, the diamine is selected from one or more of ethylenediamine, propylenediamine, hexamethylenediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine, and benzidine.

[0058] In a preferred embodiment, in step a, the stirring speed is 700-900 rpm.

[0059] In a preferred embodiment, in step b, the stirring speed is 1100-1300 rpm.

[0060] In a preferred embodiment, in step c, the stirring speed is 1900-2100 rpm.

[0061] The invention also relates to the application of the flame-retardant thermoplastic polyurethane resin in the preparation of positive pressure protective clothing.

[0062] The present invention also relates to a positive pressure protective suit, the main body of which is prepared from the flame retardant thermoplastic polyurethane resin provided by the present invention; the main body of the positive pressure protective suit includes a front placket, a back, sleeves, trouser legs, a helmet, etc.

[0063] Example 1

[0064] Under nitrogen atmosphere, at a stirring speed of 800 rpm, 4,4'-dicyclohexylmethane diisocyanate (HMDI, CAS: 822-06-0) was added dropwise to a mixture of phthalic anhydride polyester polyol (DGPA, CAS: 32472-85-8) (molecular weight 3000 Dalton) and dioctyl terephthalate (DOTP); wherein the molar ratio of 4,4'-dicyclohexylmethane diisocyanate to phthalic anhydride polyester polyol was 3:1, and the amount of dioctyl terephthalate was 30% of the total weight of 4,4'-dicyclohexylmethane diisocyanate and phthalic anhydride polyester polyol. The rotation speed was maintained at 800 rpm, and the temperature was raised to 80°C for reaction for 30 minutes to obtain a reaction mixture 1;

[0065] Then, a catalyst dibutyltin dilaurate (CAS: 77-58-7, the amount of dibutyltin dilaurate used is 0.01 of the mass of 4,4'-dicyclohexylmethane diisocyanate) is added to form a mixture 2, and the mixture 2 is heated to 120° C. under N2 protection conditions, and the reaction is continued for 30 minutes at a stirring speed of 1200 rpm to obtain an isocyanurate structured polyurethane prepolymer with NCO end-capping;

[0066] At a rotation speed of 2000 rpm, a chain extender 1.4 butanediol (BD, CAS: 110-63-4) was added, and the amount of the chain extender added was such that the molar ratio of the mixture with the NCO-terminated isocyanurate structure polyurethane prepolymer was 1:0.5; the reaction was carried out at 120°C for 60 minutes to obtain TPU resin, and the flame-retardant TPU masterbatch 1 was obtained by granulation after cooling.

[0067] Example 2

[0068] Under nitrogen atmosphere, at a stirring speed of 700 rpm, isophorone diisocyanate was added dropwise to a mixture of polyethylene phthalate diol (molecular weight 2000 Dalton) and dimethoxyethylene phthalate; wherein the molar ratio of isophorone diisocyanate to phthalic anhydride polyester polyol was 6:1, and the amount of dimethoxyethylene phthalate was 50% of the total weight of isophorone diisocyanate and polyethylene phthalate diol. The rotation speed was maintained at 700 rpm, and the temperature was raised to 70°C for reaction for 40 minutes to obtain a reaction mixture 1;

[0069] Then, a catalyst tri-n-butyl methoxytin is added, the amount of tri-n-butyl methoxytin is 0.008 of the mass of isophorone diisocyanate, to form a mixture 2, and the mixture 2 is heated to 110° C. under N2 protection conditions, and the reaction is continued for 40 minutes at a stirring speed of 1100 rpm to obtain an isocyanurate structured polyurethane prepolymer with NCO end-capping;

[0070] At a speed of 1900 rpm, the chain extender ethylenediamine was added in an amount such that the molar ratio of the mixture with the NCO-terminated isocyanurate structure polyurethane prepolymer was 1:1. The reaction was carried out at 110°C for 70 minutes to obtain TPU resin, and the flame-retardant TPU masterbatch 2 was obtained by granulation after cooling.

[0071] Example 3

[0072] Under nitrogen atmosphere, at a stirring speed of 900 rpm, hexamethylene diisocyanate was added dropwise to a mixture of dipropylene glycol phthalate and poly(neopentyl phthalate) diol (molecular weight 2500 Dalton); wherein the molar ratio of hexamethylene diisocyanate to poly(neopentyl phthalate) diol was 4:1, and the amount of dipropylene glycol phthalate was 40% of the total weight of hexamethylene diisocyanate and poly(neopentyl phthalate) diol. The rotation speed was maintained at 900 rpm, and the temperature was raised to 80°C for reaction for 20 minutes to obtain a reaction mixture 1;

[0073] Then, a catalyst stannous octoate is added, and the amount of stannous octoate used is 0.005 of the mass of hexamethylene diisocyanate to form a mixture 2. The mixture 2 is heated to 130° C. under N2 protection conditions, and the reaction is continued for 20 minutes at a stirring speed of 1300 rpm to obtain an isocyanurate structured polyurethane prepolymer with NCO end-capping.

[0074] At a rotation speed of 2100 rpm, chain extender ethylene glycol is added in an amount such that the molar ratio of the mixture with the NCO-terminated isocyanurate structure polyurethane prepolymer is 1:0.8; react at 130°C for 50 minutes to obtain TPU resin, and after cooling and granulation, flame-retardant TPU masterbatch 3 can be obtained.

[0075] Performance Test:

[0076] The flame retardant TPU masterbatch 1, flame retardant TPU masterbatch 2 and flame retardant TPU masterbatch 3 prepared in Examples 1-3 were melt-cast and calendered into flame retardant films TPU-1, TPU-2 and TPU-3 with a thickness of 0.3 mm. The flame retardancy and transparency of the prepared flame retardant films TPU-1, TPU-2, TPU-3 and commercially available phosphorus-containing polyurethane flame retardant films 1 and 2 were tested according to the UL-94 standard method; and the flame retardancy and transparency were tested after being placed at 60°C and 60% relative humidity for 3 months. The test results are shown in the following table:

[0077]

[0078] It can be seen from the above table that the polyurethane resin film provided by the present invention has excellent flame retardant properties and transparency, and after being placed in an environment with high temperature and humidity for 3 months, no change in its flame retardant properties can be detected, and its transparency is slightly reduced; while the commercially available phosphorus-containing polyurethane flame retardant film has very poor transparency. After being placed in the same environment as the present invention for the same time, its flame retardant properties are significantly reduced and its transparency is further deteriorated.

Claims

1. A flame retardant thermoplastic polyurethane resin, characterized in that: The flame retardant thermoplastic polyurethane resin comprises at least the following structural units: Wherein, R1 is phthalic anhydride polyester polyol, and the phthalic anhydride polyester polyol is selected from one or more of polyethylene phthalate diol, poly(1,6-hexanediol phthalate) diol and poly(neopentyl phthalate) diol; R2 is isocyanate; wherein the flame retardant thermoplastic polyurethane resin is prepared by the following method: a. Under stirring and nitrogen protection conditions, aliphatic diisocyanate, phthalic anhydride polyester polyol and plasticizer are mixed to obtain a mixture 1; wherein the molar ratio of aliphatic diisocyanate to phthalic anhydride polyester polyol is 3-6:1, and the amount of plasticizer is 20-50% by weight of the total amount of aliphatic diisocyanate and phthalic anhydride polyester polyol; the mixture 1 is heated to 70-90°C and reacted at the temperature for 20-40 minutes to obtain a reaction mixture 1; the aliphatic diisocyanate is selected from one or more of isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and 1,4-cyclohexane diisocyanate; the plasticizer is selected from one or more of dioctyl terephthalate, dimethoxyethylene phthalate, dipropylene glycol phthalate and triethylene glycol nonanoate; b. Under stirring and nitrogen protection conditions, a catalyst is added to the reaction mixture 1 to obtain a mixture 2, the mixture 2 is heated to 110-130 ° C, and reacted at this temperature for 20-40 minutes to obtain a mixture of a polyurethane prepolymer having an NCO-terminated isocyanurate structure; c. Under stirring and nitrogen protection conditions, at 110-130° C., a chain extender is added to a mixture of an isocyanurate structure polyurethane prepolymer with an NCO end-capping structure, the molar ratio of the chain extender added to the mixture of the isocyanurate structure polyurethane prepolymer with an NCO end-capping structure is 1:0.5-1, to obtain a mixture 3, and react at 110-130° C. for 50-70 minutes to obtain a flame retardant thermoplastic polyurethane resin; the chain extender is a diol or a diamine; the isocyanurate structure accounts for 15-35% of the molar mass of the flame retardant thermoplastic polyurethane resin.

2. The flame retardant thermoplastic polyurethane resin according to claim 1, characterized in that: The molecular weight of the phthalic anhydride polyester polyol is 1000-3000 Daltons.

3. The flame retardant thermoplastic polyurethane resin according to claim 1, characterized in that: The diol is selected from one or more of ethylene glycol, propylene glycol, butylene glycol, pentanediol and hexanediol.

4. The flame retardant thermoplastic polyurethane resin according to claim 1, characterized in that: The diamine is selected from one or more of ethylenediamine, propylenediamine, hexamethylenediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine and benzidine.

5. The flame retardant thermoplastic polyurethane resin according to any one of claims 1 to 4, characterized in that: In step a, the stirring speed is 700-900 rpm; in step b, the stirring speed is 1100-1300 rpm; in step c, the stirring speed is 1900-2100 rpm.

6. A method for preparing a flame retardant thermoplastic polyurethane resin, characterized in that: The method comprises the following steps: a. Under stirring and nitrogen protection conditions, aliphatic diisocyanate, phthalic anhydride polyester polyol and plasticizer are mixed to obtain a mixture 1; wherein the molar ratio of aliphatic diisocyanate to phthalic anhydride polyester polyol is 3-6:1, and the amount of plasticizer is 20-50 weight % of the total amount of aliphatic diisocyanate and phthalic anhydride polyester polyol; the mixture 1 is heated to 70-90°C and reacted at this temperature for 20-40 minutes to obtain a reaction mixture 1; the phthalic anhydride polyester polyol is selected from polyphthalic anhydride The aliphatic diisocyanate is selected from one or more of isophorone diisocyanate, hexamethylene diisocyanate, dicyclohexylmethane diisocyanate and 1,4-cyclohexane diisocyanate; the plasticizer is selected from one or more of dioctyl terephthalate, dimethoxyethylene phthalate, dipropylene glycol phthalate and triethylene glycol nonanoate; b. Under stirring and nitrogen protection conditions, a catalyst is added to the reaction mixture 1 to obtain a mixture 2, the mixture 2 is heated to 110-130 ° C, and reacted at this temperature for 20-40 minutes to obtain a mixture of a polyurethane prepolymer having an NCO-terminated isocyanurate structure; c. Under stirring and nitrogen protection conditions, at 110-130° C., add a chain extender to the mixture of the NCO-terminated isocyanurate structure polyurethane prepolymer, the molar ratio of the chain extender added to the mixture of the NCO-terminated isocyanurate structure polyurethane prepolymer is 1:0.5-1, to obtain a mixture 3, and react at 110-130° C. for 50-70 minutes to obtain a flame retardant thermoplastic polyurethane resin. The chain extender is a diol or a diamine.

7. The method according to claim 6, characterized in that The diol is selected from one or more of ethylene glycol, propylene glycol, butylene glycol, pentanediol and hexanediol.

8. The method according to claim 6, characterized in that The diamine is selected from one or more of ethylenediamine, propylenediamine, hexamethylenediamine, p-phenylenediamine, o-phenylenediamine, m-phenylenediamine and benzidine.

9. The method according to claim 6, characterized in that In step a, the stirring speed is 700-900 rpm.

10. The method according to claim 6, characterized in that In step b, the stirring speed is 1100-1300 rpm.

11. The method according to any one of claims 6 to 10, characterized in that: In step c, the stirring speed is 1900-2100 rpm.

12. Use of the flame retardant thermoplastic polyurethane resin according to any one of claims 1 to 5 in the preparation of positive pressure protective clothing.

13. A positive pressure protective suit, characterized in that: The main body of the positive pressure protective clothing is prepared from the flame retardant thermoplastic polyurethane resin described in any one of claims 1-5.

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