Flame-retardant polyurethane rigid foam as well as preparation method and application thereof

Abstract

The invention discloses flame-retardant rigid polyurethane foam as well as a preparation method and application thereof, belongs to the technical field of flame-retardant foam, and solves the problem of low flame-retardant efficiency of rigid polyurethane foam in the prior art. The flame-retardant polyurethane rigid foam is prepared from the following components in parts by mass: 90 to 100 parts of polyester polyol, 2.5 to 4.5 parts of deionized water, 1.5 to 3.5 parts of silicone oil, 0.6 to 0.9 part of a catalyst, 10 to 15 parts of a reactive flame retardant and 110 to 130 parts of polyphenyl polyisocyanate. The flame-retardant polyurethane rigid foam plastic is prepared from the prepared reactive flame retardant and polyfunctional polyester polyol, and the problems that in the prior art, flame-retardant polyurethane rigid foam plastic is not high in flame-retardant efficiency, low in limit oxygen index and high in heat release rate are solved.

Description

Technical Field

[0001] The invention relates to the technical field of flame retardant foams, and more specifically to a flame retardant polyurethane rigid foam and a preparation method and application thereof. Background Art

[0002] Rigid polyurethane foam (RPUF) has become one of the most widely used varieties of foam plastics due to its advantages such as low cost, high compressive strength and good thermal conductivity. It is widely used in the fields of heat preservation and cold preservation, exterior wall insulation, cold chain transportation, LNG ship liquid cargo containment system and shore tank insulation system. Rigid polyurethane foam will burn quickly after ignition due to its flammable properties of organic matter and its three-dimensional pore structure, and the flame formed will spread rapidly. At present, the limiting oxygen index (LOI) of RPUF without flame retardant is about 18.5%, which seriously limits its practical application value.

[0003] At present, there are three common methods to improve the flame retardant properties of RPUF, namely, using reactive flame retardants (FRs) to react with polyurethane matrix (reactive flame retardants), using additive flame retardants (FRs) through physical blending (additive flame retardants), and applying flame retardant coatings to the surface of polyurethane foam to form flame retardant coatings (coating flame retardants). Additive flame retardants will affect the mechanical properties of foam plastics, which is not conducive to the subsequent application of materials and the durability of their effectiveness; coating flame retardants have weak interface adhesion and bonding strength, poor durability, and high labor costs. Therefore, reactive flame retardants are more commonly used in production.

[0004] Although the reactive flame retardant has good bonding with the matrix and has negligible effect on the physical properties of the foamed plastic, the existing reactive flame retardant has low flame retardant efficiency, low limiting oxygen index (<27.0%), and high heat release rate. At present, in the preparation of polyurethane rigid foam, the polyols used are mainly polyether polyols and some polyester polyols. Compared with polyether polyols, the foam material formed by polyester polyols is more effective in high and low temperature resistance, and the flame retardancy of polyester polyurethane is easier to achieve, but the functionality and viscosity of polyester polyols are difficult to meet the preparation of polyester polyurethane foam. Therefore, it is more important to prepare polyester polyurethane rigid foam with good flame retardancy. Summary of the invention

[0005] The invention provides a flame retardant polyurethane rigid foam and a preparation method and application thereof, which are used to solve the problem of low flame retardant efficiency of polyurethane rigid foam in the prior art.

[0006] In the first aspect, the present invention provides a flame retardant polyurethane rigid foam, which comprises the following components, measured by mass: 90 to 100 parts of polyester polyol, 2.5 to 4.5 parts of deionized water, 1.5 to 3.5 parts of silicone oil, 0.6 to 0.9 parts of catalyst, 10 to 15 parts of reactive flame retardant, and 110 to 130 parts of polyphenyl polyisocyanate.

[0007] As a possible implementation, the flame retardant polyurethane rigid foam includes the following components, measured by mass: 100 parts of polyester polyol, 3.0 parts of deionized water, 2.5 parts of silicone oil, 0.9 parts of catalyst, 10 parts of reactive flame retardant, and 120 parts of polyphenyl polyisocyanate.

[0008] As a possible implementation method, the polyester polyol is a PE4120 series, having a hydroxyl value of 190 to 220 mgKOH / g and a viscosity of 2500 to 4500 mPa·s at 25°C; and / or, the catalyst is any one or two of triethylenediamine, stannous octoate, and dibutyltin dilaurate; and / or, the silicone oil is any one of AK-8805, AK-8818, and AK-158.

[0009] As a possible implementation, the hydroxyl value of the polyester polyol is 200 mgKOH / g; and / or the catalyst is a triethylenediamine solution with a mass concentration of 33%; and / or the silicone oil is AK-8805.

[0010] As a possible implementation, the limiting oxygen index is 28.7% to 32.5%.

[0011] As a possible implementation, the polyester polyol has a certain degree of branching and is prepared by esterification and polycondensation of di(poly)hydric alcohol and di(poly)acid. Exemplarily, the di(poly)hydric alcohol is one or a combination of ethylene glycol, propylene glycol, trimethylolpropane, pentaerythritol, neopentyl glycol, hexylene glycol, and erythritol, and exemplarily, the di(poly)hydric alcohol is trimethylolpropane or ethylene glycol; Exemplarily, the di(poly)orthoacid is one or a combination of adipic acid, sebacic acid, trimellitic anhydride, and pyromellitic anhydride, and exemplarily, the di(poly)orthoacid is trimellitic anhydride and adipic acid.

[0012] As a possible implementation, the polyester polyol has a hydroxyl value ranging from 190 to 220 mgKOH / g and a viscosity ranging from 2500 to 4500 mPa·s.

[0013] In a second aspect, the present invention provides a method for preparing a flame retardant polyurethane rigid foam, comprising the following steps: mixing the raw material components in proportion according to the formula components contained in the flame retardant polyurethane rigid foam described in any possible implementation method of the first aspect, and preparing the flame retardant polyurethane rigid foam by a one-pot method and a full water free foaming method.

[0014] As a possible implementation method, the method comprises the following steps: according to the formula of the flame retardant polyurethane rigid foam according to any one of claims 1 to 5, except for the polyphenyl polyisocyanate, the remaining components are mixed in proportion at a speed of 1000 to 2500 r / min and a time of 2 to 4 minutes; the polyphenyl polyisocyanate is added and mixed again for 15 to 25 seconds to obtain a mixture; and the mixture is freely foamed at room temperature and then cured at room temperature for 20 to 50 hours.

[0015] As a possible implementation, the mixing treatment conditions are: a rotation speed of 1500 r / min and a duration of 3 min; and / or, the remixing duration is 20 s; and / or, the curing duration is 48 h.

[0016] In a third aspect, the present invention provides an application of the flame retardant polyurethane rigid foam described in any possible implementation of the first aspect or the flame retardant polyurethane rigid foam prepared by the preparation method described in any possible implementation of the second aspect in thermal insulation and flame retardant materials.

[0017] As a possible implementation manner, the thermal insulation and flame retardant material is used for exterior wall insulation.

[0018] The present invention adopts the reactive flame retardant (FRD) provided by patent CN116102788A, and modifies dimethyl methylphosphonate (DMMP) with bio-based carbon alcohol to prepare a highly efficient reactive flame retardant containing active hydroxyl groups. The prepared reactive flame retardant is used together with multifunctional polyester polyol to prepare a flame retardant polyurethane rigid foam plastic, so as to solve the problems of low flame retardant efficiency, low limiting oxygen index and high heat release rate of the flame retardant polyurethane rigid foam plastic in the prior art.

[0019] The present invention introduces FRD as a polyol into a polyester-type RPUF with polyester polyol as a formula component to obtain a polyester-type RPUF with a uniform closed cell structure. As a flame-retardant polyurethane rigid foam plastic, the compression strength and thermal conductivity are maintained while the limiting oxygen index and heat resistance are greatly improved, the heat release rate is significantly reduced, and the residual carbon amount is increased, thereby providing an innovative, economical and green method for producing flame-retardant thermal insulation materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0021] Figure 1 This is a vertical combustion rating test chart of the polyurethane rigid foam-A1 provided in an embodiment of the present invention.

[0022] Figure 2 This is a vertical combustion rating test chart of the polyurethane rigid foam-A2 provided in an embodiment of the present invention.

[0023] Figure 3 A vertical combustion rating test diagram of a conventional flame retardant material provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In order to solve the problem of low flame retardant efficiency of polyurethane rigid foam in the prior art, an embodiment of the present invention provides a preparation experiment and a characterization experiment of a flame retardant polyurethane rigid foam.

[0026] The present invention provides two methods for preparing polyester polyols, and the steps thereof are respectively as follows:

[0027] Method 1: Add the dibasic acid and diol into a four-necked flask respectively, heat the system to make it esterify at 150-160°C, keep the top temperature of the fractionation column at 100±2°C, add polyhydroxy compound after the initial esterification reaction is completed, continue the esterification reaction at 200-230°C, until the top temperature of the fractionation column drops to room temperature, and the esterification reaction is completed; continue to heat the system to make it condense at 230-240°C and -0.05MPa to a carboxyl value of <8mgKOH / g; add a catalyst, continue to condense at 230-240°C and -0.1MPa to a carboxyl value of <2mgKOH / g, and obtain polyester polyol. The catalyst is one or a mixture of tetrabutyl titanate, tetraisopropyl titanate, methylbenzenesulfonic acid, antimony acetate, calcium acetate, and zinc acetate.

[0028] Method 2: Put the dibasic acid and diol into a four-necked flask respectively, heat the system to make it esterify at 150-160°C, keep the top temperature of the fractionation column at 100±2°C, wait until the top temperature of the fractionation column drops to room temperature, and the esterification reaction ends; continue to heat the system to make it condense at 220-230°C and -0.05MPa to a carboxyl value of <1mgKOH / g, cool the system to 160°C, add the polyacid compound, heat the system at 200-240°C for esterification for 3-5h, keep the temperature unchanged, add the catalyst, condense at -0.05--0.1MPa to a carboxyl value of less than 2mgKOH / g, and obtain polyester polyol. Wherein, the catalyst is one or a mixture of tetrabutyl titanate, tetraisopropyl titanate, methylbenzenesulfonic acid, antimony acetate, calcium acetate, and zinc acetate. In this embodiment, tetrabutyl titanate is used.

[0029] Furthermore, the flame retardant polyurethane rigid foam prepared by the embodiment of the present invention using the prepared reactive flame retardant, polyester polyol 4120B and polyester polyol PE4120A as raw materials has an excellent limiting oxygen index, and its heat release rate and residual carbon rate have been significantly improved. Moreover, in the vertical burning test, compared with conventional flame retardant materials, the flame retardant polyurethane rigid foam provided by the embodiment of the present invention has a more excellent vertical burning grade.

[0030] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0031] Example 1

[0032] This embodiment provides an experiment for preparing a reactive flame retardant and polyester polyol.

[0033] Pour DMMP and erythritol in a mass ratio of 2:1 into a three-necked round-bottom flask, stir with a magnetic stirrer, heat to 110-130°C and keep warm until erythritol is completely melted, then continue to heat the reactants to 160-170°C, and react under condensation reflux for 6-8 hours. All the above operations are carried out under nitrogen protection. After the reaction is completed, stop nitrogen flow, heat to 175-180°C, vacuum for 2-3 hours to remove unreacted DMMP and by-products, and obtain a reactive flame retardant. Its phosphorus content is 16%-20%, and the reaction yield is 79%-82%.

[0034] 146g of adipic acid and 62g of ethylene glycol were respectively put into a four-necked flask, and the heating system was used to perform an esterification reaction at 150-160°C, and the top temperature of the fractionation column was maintained at 100±2°C. After the initial esterification reaction was completed, 121g of trimethylolpropane was added, and the esterification reaction was continued at 200-230°C until the top temperature of the fractionation column dropped to 30°C and the esterification reaction was completed; the heating system was continued to perform a reduced pressure polycondensation reaction at 230-240°C at a rate of -0.01MPa / 30min, and the polycondensation reaction was kept at -0.05MPa for 1h, and the acid value was measured to be 6.8mgKOH / g, and 0.03g of toluenesulfonic acid catalyst was added, and the reduced pressure polycondensation reaction was continued at 230-240°C at a rate of -0.01MPa / 30min until the polycondensation reaction was completed at -0.1MPa, and the acid value was measured to be 1.32mgKOH / g, and polyester polyol PE4120A was obtained. Its hydroxyl value is 201 mgKOH / g and its viscosity (25°C) is 3797 mPa·s.

[0035] 146g of adipic acid and 233g of diethylene glycol were respectively put into a four-necked flask, and the system was heated to make the esterification reaction at 150-200℃, and the top temperature of the fractionation column was maintained at 100±2℃. When the top temperature of the fractionation column dropped to 30℃, the esterification reaction was completed; the system was continued to be heated to make it perform reduced pressure polycondensation at 220-230℃ at a rate of -0.01MPa / 30min, and the polycondensation reaction was kept at -0.05MPa for 3h, and the carboxyl value was measured to be 0.9mgKO H / g, the system was cooled to 160°C, trimellitic anhydride compound was added, the system was heated at 200-240°C for esterification reaction for 3h, the temperature was kept constant, 0.03g of tetrabutyl titanate catalyst was added, and the polycondensation reaction was continued at 230-240°C at a rate of -0.01MPa / 30min until -0.1MPa was reached, the acid value was measured to be 1.78mgKOH / g, and polyester polyol PE4120B was obtained. Its hydroxyl value was 217mgKOH / g, and the viscosity (25°C) was 4374mPa·s.

[0036] Example 2

[0037] This embodiment provides an experiment for preparing a flame retardant polyurethane rigid foam.

[0038] The reactive flame retardant, polyester polyol 4120B and polyester polyol PE4120A used in this example are all from Example 1.

[0039] Add 100g of polyester polyol PE4120A, 2.5g of deionized water, 1.5g of silicone oil AK8805, 0.6g of catalyst A33 and 10g of reactive flame retardant into a plastic beaker (capacity 500mL) equipped with a magnetic stirrer and stir at a speed of 1000r / min for 2 minutes. Add 110g of PAPI (polyphenyl polyisocyanate) into the above mixture and stir for 15s to obtain a mixture. Move the mixture into a mold and foam it freely at room temperature. After foaming, cure it at room temperature for 20 to 50h to obtain flame-retardant polyurethane rigid foam-A1.

[0040] Add 100g of polyester polyol PE4120A, 2.5g of deionized water, 1.5g of silicone oil AK8805, 0.6g of catalyst A33 and 10g of reactive flame retardant into a plastic beaker (capacity 500mL) equipped with a magnetic stirrer and stir at a speed of 1000r / min for 2 minutes. Add 110g of PAPI (polyphenyl polyisocyanate) into the above mixture and stir for 15s to obtain a mixture. Move the mixture into a mold and foam it freely at room temperature. After foaming, cure it at room temperature for 20 to 50h to obtain flame-retardant polyurethane rigid foam-A1.

[0041] Add 100g of polyester polyol PE4120A, 4.5g of deionized water, 3.5g of silicone oil AK8805, 30.9g of catalyst A3 and 15g of reactive flame retardant into a plastic beaker (capacity 500mL) equipped with a magnetic stirrer and stir at a speed of 2500r / min for 4 minutes. Add 130g of PAPI (polyphenyl polyisocyanate) into the above mixture and stir for 25s to obtain a mixture. Move the mixture into a mold and foam it freely at room temperature. After foaming, cure it at room temperature for 20 to 50h to obtain flame-retardant polyurethane rigid foam-A2.

[0042] Add 100 g of polyester polyol 4120B, 2.5 g of deionized water, 1.5 g of silicone oil AK8805, 0.6 g of catalyst A33 and 10 g of reactive flame retardant into a plastic beaker (capacity of 500 mL) equipped with a magnetic stirrer, and stir at a speed of 1500 r / min for 2 minutes; add 110 g of PAPI (polyphenyl polyisocyanate) into the above mixture and stir for 15 seconds; transfer it to a mold and foam it freely at room temperature. After foaming, cure it at room temperature for 48 hours to obtain flame-retardant polyurethane rigid foam-B1.

[0043] Add 100 g of polyester polyol 4120B, 4.5 g of deionized water, 3.5 g of silicone oil AK8805, 30.9 g of catalyst A3 and 15 g of reactive flame retardant into a plastic beaker (capacity of 500 mL) equipped with a magnetic stirrer, and stir at a speed of 1500 r / min for 4 minutes; add 130 g of PAPI (polyphenyl polyisocyanate) into the above mixture and stir for 20 seconds; transfer it to a mold and foam it freely at room temperature. After foaming, cure it at room temperature for 48 hours to obtain flame-retardant polyurethane rigid foam-B2.

[0044] Example 3

[0045] This embodiment provides a performance characterization experiment of a flame retardant polyurethane rigid foam.

[0046] According to ASTM D 2863-17, the limiting oxygen index (LOI) test of the sample was carried out using the HC-2C oxygen index instrument of Nanjing Shangyuan Analytical Instrument Co., Ltd.; the size of the sample was 150mm×10mm×10mm.

[0047] According to ISO 5660 standard, the combustion behavior of the sample was evaluated using the British FTT cone calorimeter; the sample size was 100×100×25mm 3 , the external heat flux is selected as 35kW / m 2 .

[0048] The thermal stability of the rigid foam was evaluated by thermogravimetric analyzer (TG); the testing instrument was American TGA Q50, 8.0 mg of the sample was weighed for testing, and the test temperature range was 30-800°C under N2 atmosphere, and the heating rate was 10°C / min.

[0049] According to GB / T 8813-2020 standard, a universal materials testing machine (MTS CMT6103) was used to test the compressive strength of the samples; the sample size was 50mm×50mm×50mm, and the compression speed was 5mm / min.

[0050] The thermal conductivity was tested using a thermal conductivity tester (EKO Instruments) according to ASTM C518-04; the sample size was 200 mm × 200 mm × 40 mm, and the temperatures of the upper and lower plates were set to 16° C. and 34° C., respectively, to maintain an average sample temperature of 25° C.

[0051] According to ASTM D 3801-19 standard, the vertical combustion test was carried out using the HVUL-2 instrument produced by Shenzhen Neutron Measurement Instrument Co., Ltd. The size of the sample to be tested was 127 mm × 13 mm × 10 mm.

[0052] In this example, the polyurethane rigid foam-A1, polyurethane rigid foam-A2, polyurethane rigid foam-B1 and polyurethane rigid foam-B2 prepared in Example 2 were used as samples to be tested, and performance tests were carried out. The results are as follows.

[0053] The limiting oxygen index of polyurethane rigid foam-A1 is 29.1%, and the heat release rate is 344kW / m 2 Reduced to 188kW / m 2 The residual carbon rate increased from 6.2% to 14.2%, and the initial thermal decomposition temperature of the material was about 232°C. The flame-retardant polyester polyurethane rigid foam was cut into 50mm×50mm×50mm blocks. The compression strength was tested using GB / T8813-2020 and was 201KPa, which was equivalent to the blank sample. The thermal conductivity of the foam was measured using ASTM C518-04 and was approximately 0.0268W / (m·K). The vertical burning rating reached UL94 V-0 (such as Figure 1 shown).

[0054] The limiting oxygen index of polyurethane rigid foam-A2 is 32.1%, and the heat release rate is 314kW / m 2 Reduced to 169kW / m 2 The residual carbon rate increased from 6.2% to 16.1%, and the initial thermal decomposition temperature of the material was about 232°C. The obtained flame-retardant polyester polyurethane rigid foam was cut into 50mm×50mm×50mm specimens. The compression strength was tested using GB / T8813-2020 and was 215KPa, which was equivalent to the blank sample. The thermal conductivity of the foam was measured using ASTM C518-04 and was approximately 0.0273W / (m·K). The vertical burning rating reached UL94 V-0 (such as Figure 2 shown).

[0055] The limiting oxygen index of polyurethane rigid foam-B1 is 28.7%, and the heat release rate is 324kW / m 2 Reduced to 175kW / m 2 The residual carbon rate increased from 6.5% to 15.4%, and the initial thermal decomposition temperature of the material was about 262°C. The obtained flame-retardant polyester polyurethane rigid foam was cut into 50mm×50mm×50mm specimens. The compression strength was tested using GB / T8813-2020 and was 221KPa, which was equivalent to the blank sample. The thermal conductivity of the foam was measured using ASTM C518-04 and was approximately 0.0269W / (m·K). The vertical burning rating reached UL94 V-0.

[0056] The limiting oxygen index of polyurethane rigid foam-B2 is 32.5%, and the heat release rate is 298kW / m 2 Reduced to 162kW / m 2, the residual carbon rate increased from 6.7% to 15.8%, and the initial thermal decomposition temperature of the material was about 253°C. The obtained flame-retardant polyester polyurethane rigid foam was cut into 50mm×50mm×50mm specimens, and the compression strength was 225KPa tested using GB / T8813-2020, which was equivalent to the blank sample. The thermal conductivity of the foam was measured using ASTM C518-04 to be approximately 0.0271W / (m·K). The vertical burning rating reached UL94 V-0.

[0057] A conventional flame retardant product (reference for its preparation process: Jia Jiheng, Xie Jixing, Tian Shengyi, et al. Study on flame retardant polyurethane rigid foam compounded with HHPCP and DMMP [J]. Polyurethane Industry, 2015, 30(05): 22-25.) was used as the sample to be tested for vertical combustion test. The results are as follows: Figure 3 From the results shown, it can be seen that it is difficult for conventional products to achieve UL94 V-0 flame retardancy.

[0058] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0059] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A flame retardant polyurethane rigid foam, characterized in that: The invention comprises the following components in parts by mass: 90 to 100 parts of polyester polyol, 2.5 to 4.5 parts of deionized water, 1.5 to 3.5 parts of silicone oil, 0.6 to 0.9 parts of catalyst, 10 to 15 parts of reactive flame retardant and 110 to 130 parts of polyphenyl polyisocyanate.

2. The flame retardant polyurethane rigid foam according to claim 1, characterized in that: The invention comprises the following components in parts by mass: 100 parts of polyester polyol, 3.0 parts of deionized water, 2.5 parts of silicone oil, 0.9 parts of catalyst, 10 parts of reactive flame retardant and 120 parts of polyphenyl polyisocyanate.

3. The flame retardant polyurethane rigid foam according to claim 1, characterized in that: The polyester polyol is of the PE4120 series, having a hydroxyl value of 190 to 220 mgKOH / g and a viscosity of 2500 to 4500 mPa·s at 25°C; And / or, the catalyst is any one or two of triethylenediamine, stannous octoate, and dibutyltin dilaurate; And / or, the silicone oil is any one of AK-8805, AK-8818, and AK-158.

4. The flame retardant polyurethane rigid foam according to claim 3, characterized in that: The hydroxyl value of the polyester polyol is 200 mgKOH / g; And / or, the catalyst is a triethylenediamine solution with a mass concentration of 33%; And / or, the silicone oil is AK-8805.

5. The flame retardant polyurethane rigid foam according to any one of claims 1 to 4, characterized in that: Its limiting oxygen index is 28.7% to 32.5%.

6. A method for preparing a flame retardant polyurethane rigid foam, characterized in that: The steps include: The flame retardant polyurethane rigid foam is prepared by mixing the raw material components according to the formula components contained in any one of claims 1 to 5 in proportion and adopting a one-pot method and a full water free foaming method to obtain the flame retardant polyurethane rigid foam.

7. The preparation method according to claim 6, characterized in that: The steps include: According to the formula of the flame retardant polyurethane rigid foam according to any one of claims 1 to 5, except for the polyphenyl polyisocyanate, the remaining components are mixed according to proportions at a speed of 1000 to 2500 r / min and a time of 2 to 4 minutes; Add the polyphenyl polyisocyanate and mix again for 15 to 25 seconds to obtain a mixture; The mixture is allowed to foam freely at room temperature and then cured at room temperature for 20 to 50 hours.

8. The preparation method according to claim 7, characterized in that: The mixing process conditions are: rotation speed 1500r / min, duration 3min; And / or, the duration of the remixing is 20 s; And / or, the curing time is 48 hours.

9. Use of the flame-retardant polyurethane rigid foam according to any one of claims 1 to 5 or the flame-retardant polyurethane rigid foam prepared by the preparation method according to claims 6 to 8 in thermal insulation and flame-retardant materials.

10. The use according to claim 9, characterized in that: The thermal insulation and flame retardant material is used for external wall thermal insulation.

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