Preparation method and application of 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant

Abstract

The invention discloses a preparation method and application of a 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant. The specific steps are as follows: S1: synthesis of 1,3,5-tri(bromomethyl)benzene (I); S2: synthesis of 1,3,5-benzenetrimethylphosphonic acid ethyl ester (II); S3: synthesis of 1,3,5-benzenetrimethylphosphonic acid (III); S4: synthesis of 1,3,5-benzenetrimethylphosphonic acid aluminum (IV); the flame retardant compound provided by the invention has a high P content (22.77%) in the structure and a good flame retardant effect. When the addition amount is 20 parts, the limiting oxygen index of a rigid polyurethane foam can reach 29.3%, and the vertical combustion UL94 reaches the V0 level. The preparation method provided by the invention has cheap and readily available raw materials, is simple to operate, has a high yield, and is easy to industrialize.

Description

Technical Field

[0001] The invention relates to the field of flame retardants, in particular to a preparation method and application of a 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant. Background Art

[0002] Flame retardant is a functional additive that makes flammable polymers flame retardant. It is mainly designed for the flame retardancy of polymer materials. There are many types of flame retardants. According to the method of use, they are divided into additive flame retardants and reactive flame retardants. There are many types of flame retardants, especially those involving the synthesis of 1,3,5-tri(bromomethyl)benzene (Ⅰ). There are many existing synthesis methods, such as method 1 Figure 7 As shown: 1,3,5-benzenetrimethylol and hydrogen bromide / acetic acid (30%) are used as raw materials, and reflux reaction is carried out under nitrogen protection for 2 hours, then the reaction solution is cooled to room temperature, diluted with ice water, and extracted with CH2Cl2. The organic phase is washed with water and saturated NaHCO3 solution in turn, dried with magnesium sulfate, and the crude product is recrystallized with n-hexane after concentration, with a yield of 78%; this method has high raw material prices, and hydrogen bromide is highly toxic, which is not easy to industrialize; Method 2 is as shown Figure 8 As shown: add mesitylene to the reaction bottle, heat to 155°C, slowly drip liquid bromine (about 2h), then heat to 170-180°C, and then add liquid bromine in batches (about 6h). Then the reaction liquid is refluxed at 170°C for 1 hour, cooled to room temperature, filtered, and the yield is 80%; this method has a high reaction temperature and the liquid bromine is highly toxic and volatile, and is not easy to industrialize; Method 3: using mesitylene and NBS as raw materials, benzoyl peroxide as an initiator, and carbon tetrachloride as a solvent, 70°C, reacting for 12h, the yield is 95%, and the purity of the product using this method is low; for this purpose, a preparation method of 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant is provided. Summary of the invention

[0003] The purpose of the present invention is to provide a preparation method and application of 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant in view of the defects of the prior art, so as to solve the problems raised by the above background technology.

[0004] To achieve the above object, the present invention provides the following technical solution: a method for preparing a 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant, the specific steps are as follows:

[0005] S1: Synthesis of 1,3,5-tri(bromomethyl)benzene (Ⅰ);

[0006] S11: At room temperature, 1,3,5-trimethylbenzene, N-bromosuccinimide, benzoyl peroxide and benzene were added to a three-necked flask in sequence, and then slowly heated to 80°C under magnetic stirring. Initially, the reaction solution was boiled by the heat released by the reaction itself. When the solution stopped boiling spontaneously, the reaction solution was heated for about 1 hour. TLC monitoring showed that V (petroleum ether): V (ethyl acetate) = 10:1;

[0007] S12: After the reaction is completed, the mixture is cooled and filtered, and the filtrate is washed with distilled water and saturated sodium chloride in sequence, dried with anhydrous sodium sulfate, and concentrated to precipitate a light yellow block solid;

[0008] S13: The crude product was recrystallized from a mixture of ethanol and n-hexane to obtain white needle-shaped crystals Ⅰ, which were dried in vacuum with a yield of 82.3%;

[0009] S2: Synthesis of 1,3,5-benzenetrimethylphosphonic acid ethyl ester (II);

[0010] S21: At room temperature, 1,3,5-tri(bromomethyl)benzene and triethyl phosphite were added to the reaction bottle in sequence, and the resulting solution was kept at 150° C. for 12 h under nitrogen atmosphere, monitored by TLC, V (dichloromethane): V (methanol) = 15:1;

[0011] S22: After the reaction is completed, the excess triethyl phosphite is removed by cooling and decompression to obtain a colorless viscous oil II with a yield of 96.3%;

[0012] S3: Synthesis of 1,3,5-benzenetrimethylphosphonic acid (III);

[0013] S31: At room temperature, the intermediate II prepared in the previous step and concentrated hydrochloric acid were added to the reaction bottle in sequence, and the reaction was refluxed at 110° C. for 20 h. TLC monitoring showed that V (dichloromethane): V (methanol) = 8:1;

[0014] S32: After the reaction is completed, the reaction is cooled and the excess water and HCl are removed under reduced pressure to obtain a white solid, which is recrystallized from a mixture of methanol and water to obtain a large amount of white crystal blocks III, which are then vacuum dried to obtain white crystals with a yield of 82.1%;

[0015] S33: Select appropriate crystals for X-ray single crystal testing, and the results show that the synthesized compound is compound III;

[0016] S4: Synthesis of 1,3,5-benzenetrimethylphosphonic acid aluminum (IV);

[0017] S41: Dissolve intermediate III in distilled water and aluminum sulfate 18hydrate in distilled water, and transfer the two solutions into a reaction bottle;

[0018] S42: Then react at room temperature, the reaction liquid gradually changes from colorless and transparent to white emulsion. After reacting for 3 hours, stop stirring, filter, wash with distilled water, and dry in a vacuum drying oven at 60°C for 8 hours to obtain a white powder with a yield of 96%.

[0019] As a preferred technical solution of the present invention, the reaction solvent in S11 is any one of benzene, carbon tetrachloride or dichloromethane; the initiator can also be azobisisobutyronitrile.

[0020] As a preferred technical solution of the present invention, the molar ratio of 1,3,5-trimethylbenzene to N-bromosuccinimide is 1:(3-3.2).

[0021] As a preferred technical solution of the present invention, the reaction temperature in S11 is 75-85° C., and the reaction time is 0.5-1.5 h.

[0022] As a preferred technical solution of the present invention, the volume ratio of ethanol to n-hexane in S13 is 1:(1-1.5); the vacuum drying temperature is 40-50°C, and the drying time is 5-6h.

[0023] As a preferred technical solution of the present invention, the molar ratio of 1,3,5-tri(bromomethyl)benzene to triethyl phosphite in S21 is 1:(8-11).

[0024] As a preferred technical solution of the present invention, the reaction temperature in S21 is 140-155° C., and the reaction time is 10-13 h.

[0025] As a preferred technical solution of the present invention, the reaction temperature in S31 is 100-120° C., and the reaction time is 20-24 h.

[0026] As a preferred technical solution of the present invention, the volume ratio of water to methanol in S32 is 1:(5-8), the vacuum drying temperature is 50-55°C, and the drying time is 8-10h.

[0027] Application of 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant, application of 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant in rigid polyurethane foam.

[0028] The beneficial effects of the present invention are as follows: the flame retardant compound provided by the present invention has a high P content (22.77%) in its structure and a good flame retardant effect. When the addition amount is 20 parts, the limiting oxygen index of the rigid polyurethane foam can reach 29.3%, and the vertical combustion UL94 reaches the V0 level. The preparation method provided by the present invention has cheap and readily available raw materials, is simple to operate, has a high yield, and is easy to industrialize. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the equation diagram of the present invention;

[0030] Figure 2 is the synthesis formula of 1,3,5-benzenetrimethylphosphonic acid ethyl ester (II) of the present invention;

[0031] Figure 3 is the synthesis formula of 1,3,5-benzenetrimethylphosphonic acid (III) of the present invention;

[0032] Figure 4 The crystal structure diagram of 1,3,5-benzenetrimethylphosphonic acid of the present invention;

[0033] Figure 5 This is a particle size distribution diagram of 1,3,5-benzenetrimethylphosphonic acid aluminum of the present invention;

[0034] Figure 6 The nuclear magnetic hydrogen spectrum of 1,3,5-tri(bromomethyl)benzene of the present invention is

[0035] Figure 7 is the synthesis formula of method 1 in the background technology of the present invention;

[0036] Figure 8 It is the synthesis formula of method 2 in the background technology of the present invention. DETAILED DESCRIPTION

[0037] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0038] Embodiment 1:

[0039] See also Figure 1-5 The present invention provides a technical solution: a method for preparing a 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant, the specific steps are as follows:

[0040] S1: Synthesis of 1,3,5-tri(bromomethyl)benzene (Ⅰ);

[0041] At room temperature, 1,3,5-trimethylbenzene (3.61 g, 30.0 mmol), N-bromosuccinimide (16.02 g, 90 mmol), benzoyl peroxide (0.17 g, 0.7 mmol) and 100 mL of benzene were added to a 250 mL three-necked flask in sequence, and then slowly heated to reflux (80°C) under magnetic stirring. Initially, the reaction self-exothermic reaction can make the reaction solution boil. When the solution stops boiling spontaneously, the reaction solution is heated for about 1 h. TLC monitoring [V (petroleum ether): V (ethyl acetate)] The reaction solvent is carbon tetrachloride or dichloromethane; the initiator can also be azobisisobutyronitrile; after the reaction is completed, the mixture is cooled and filtered, and the filtrate is washed with distilled water and saturated sodium chloride in turn, dried over anhydrous sodium sulfate, and concentrated to precipitate a light yellow block solid; the crude product is recrystallized from a mixed solution of ethanol and n-hexane (volume ratio 1:1) to obtain white needle-shaped crystals I, which are vacuum dried (dried at 40-50°C for 5-6h) to obtain 8.81g of 1,3,5-tri(bromomethyl)benzene, with a yield of 82.3%;

[0042] S2: Synthesis of 1,3,5-benzenetrimethylphosphonic acid ethyl ester (II);

[0043] At room temperature, 1,3,5-tri(bromomethyl)benzene (7.2 g, 20.17 mmol) and triethyl phosphite (35 mL, 202 mmol) were added to a 100 mL reaction bottle in sequence, and the resulting solution was kept at 150°C for 12 h under a nitrogen atmosphere, and monitored by TLC (V(dichloromethane):V(methanol)=15:1); after the reaction was completed, the solution was cooled and the excess triethyl phosphite was removed under reduced pressure to obtain 10.26 g of colorless viscous oil II, with a yield of 96.3%;

[0044] S3: Synthesis of 1,3,5-benzenetrimethylphosphonic acid (III);

[0045] At room temperature, the intermediate II (6.34 g, 12.00 mmol) prepared in the previous step and 120 mL of concentrated hydrochloric acid were added to a 250 mL reaction bottle in sequence, and the reaction was refluxed at 110°C for 20 h, and TLC was monitored [V (dichloromethane): V (methanol) = 8: 1]. After the reaction was completed, the reaction was cooled and the excess water and HCl were removed under reduced pressure to obtain 4.01 g of a white solid, which was recrystallized from a methanol / water (volume ratio 7: 1) mixed solution to obtain a large amount of white crystal blocks III. After vacuum drying (drying at 50-55°C for 8-10 h), 3.55 g of white crystals were obtained, with a yield of 82.1%. Suitable crystals were selected for X-ray single crystal testing, and the results showed that the synthesized compound was compound III.

[0046] S4: Synthesis of 1,3,5-benzenetrimethylphosphonic acid aluminum (IV);

[0047] Dissolve intermediate III (1.80 g, 5.00 mmol) in 10 mL of distilled water, and aluminum sulfate 18hydrate (3.33 g, 5.00 mmol) in 20 mL of distilled water. Transfer the two solutions into a 100 mL reaction bottle. Then react at room temperature. The reaction solution gradually changes from colorless and transparent to a white emulsion. After reacting for 3 h, stop stirring, filter, wash with 50 mL of distilled water, and dry in a vacuum drying oven at 60°C for 8 h to obtain 1.96 g of white powder with a yield of 96%.

[0048] The present invention also conducted a nuclear magnetic resonance on the 1,3,5-tri(bromomethyl)benzene prepared in Example 1 to obtain a nuclear magnetic resonance hydrogen spectrum, and the spectrum information is as follows:

[0049] 1 H NMR (300MHz, CDCl3) δ7.38(3H,s,Ar-H), 4.48(6H,s,CH2).

[0050] Embodiment 2:

[0051] S1: Synthesis of 1,3,5-tri(bromomethyl)benzene (Ⅰ);

[0052] At room temperature, 1,3,5-trimethylbenzene (5.0 g, 41.6 mmol), N-bromosuccinimide (24.4 g, 137.3 mmol), benzoyl peroxide (0.19 g, 0.8 mmol) and 105 mL of carbon tetrachloride were added to a 250 mL three-necked flask in sequence, and then slowly heated to reflux under magnetic stirring, and the reaction was kept at constant temperature for 12 hours. TLC monitoring [V (petroleum ether) : V (ethyl acetate) = 10:1] The reaction was completed, cooled, filtered, and the filtrate was washed with distilled water and saturated sodium chloride in sequence, dried over anhydrous sodium sulfate, and concentrated to precipitate a light yellow block solid. The crude product was recrystallized from a mixture of ethanol and n-hexane (volume ratio 1:1) to obtain 11.64 g of white needle-shaped crystals Ⅰ, with a yield of 78.4%;

[0053] S2: Synthesis of 1,3,5-benzenetrimethylphosphonic acid ethyl ester (II);

[0054] At room temperature, 1,3,5-tri(bromomethyl)benzene (10.0 g, 28.02 mmol) and triethyl phosphite (43 mL, 250 mmol) were added to a 100 mL reaction bottle in sequence, and the resulting solution was kept at 150°C for 12 h under a nitrogen atmosphere. The reaction was monitored by TLC (V(dichloromethane):V(methanol)=15:1). The reaction was completed, cooled, and the excess triethyl phosphite was removed under reduced pressure to obtain 14.02 g of colorless viscous oil II, with a yield of 94.7%.

[0055] S3: Synthesis of 1,3,5-benzenetrimethylphosphonic acid (III);

[0056] At room temperature, the intermediate II (7.0 g, 13.25 mmol) prepared in the previous step and 130 mL of concentrated hydrochloric acid were added to a 250 mL reaction bottle in sequence, and the reaction was refluxed at 110°C for 20 h. The reaction was monitored by TLC (V (dichloromethane): V (methanol) = 8:1). After the reaction was completed, the product was cooled and the excess water and HCl were removed under reduced pressure to obtain 4.68 g of a white solid. The solid was recrystallized from a methanol / water (volume ratio 7:1) mixture to obtain a large amount of white crystals III. After vacuum drying (drying at 50-55°C for 8-10 h), 3.83 g of white crystals were obtained, with a yield of 80.3%.

[0057] S4: Synthesis of 1,3,5-benzenetrimethylphosphonic acid aluminum (IV);

[0058] Intermediate III (3.60 g, 10.00 mmol) was dissolved in 20 mL of distilled water, and aluminum sulfate 18hydrate (7.33 g, 11.00 mmol) was dissolved in 50 mL of distilled water. The two solutions were transferred into a 250 mL reaction bottle and then reacted at room temperature. The reaction solution gradually changed from colorless and transparent to a white emulsion. After reacting for 3 h, stirring was stopped, and the solution was filtered with suction. The solution was washed with 80 mL of distilled water and dried in a vacuum drying oven at 60 ° C for 8 h to obtain 3.94 g of white powder with a yield of 96.5%.

[0059] Embodiment 3:

[0060] S1: Synthesis of 1,3,5-tri(bromomethyl)benzene (Ⅰ);

[0061] At room temperature, 1,3,5-trimethylbenzene (10.0 g, 83.2 mmol), N-bromosuccinimide (48.8 g, 274.6 mmol), azobisisobutyronitrile (0.09 g, 0.55 mmol) and 250 mL of dichloromethane were added to a 500 mL three-necked flask in sequence, and then slowly heated to reflux under magnetic stirring, and the reaction was kept at constant temperature for 5 hours. TLC monitoring [V (petroleum ether) : V (ethyl acetate) = 10: 1] The reaction was completed, cooled, filtered, and the filtrate was washed with distilled water and saturated sodium chloride in sequence, dried over anhydrous sodium sulfate, and concentrated to precipitate a light yellow block solid. The crude product was recrystallized from a mixture of ethanol and n-hexane (volume ratio 1: 1) to obtain 7.66 g of white needle-shaped crystals Ⅰ, with a yield of 25.8%;

[0062] S2: Synthesis of 1,3,5-benzenetrimethylphosphonic acid ethyl ester (II);

[0063] At room temperature, 1,3,5-tri(bromomethyl)benzene (5.0 g, 14.01 mmol) and triethyl phosphite (20 mL, 116.30 mmol) were added to a 100 mL reaction bottle in sequence, and the resulting solution was reacted at 150 °C for 12 h under a nitrogen atmosphere. The reaction was completed under TLC monitoring [V (dichloromethane): V (methanol) = 15:1]. The reaction was cooled and the excess triethyl phosphite was removed under reduced pressure to obtain 6.87 g of colorless viscous oil II with a yield of 92.8%.

[0064] S3: Synthesis of 1,3,5-benzenetrimethylphosphonic acid (III);

[0065] At room temperature, the intermediate II (5.0 g, 9.46 mmol) prepared in the previous step and 100 mL of concentrated hydrochloric acid were added to a 250 mL reaction bottle in sequence, and the reaction was refluxed at 110°C for 20 h. The reaction was monitored by TLC (V (dichloromethane): V (methanol) = 8:1). After the reaction was completed, the product was cooled and the excess water and HCl were removed under reduced pressure to obtain 3.37 g of a white solid. The product was recrystallized from a methanol / water (volume ratio 7:1) mixture to obtain a large amount of white crystals III. After vacuum drying (drying at 50-55°C for 8-10 h), 2.70 g of white crystals were obtained, with a yield of 79.2%.

[0066] S4: Synthesis of 1,3,5-benzenetrimethylphosphonic acid aluminum (IV);

[0067] Intermediate III (2.00 g, 5.55 mmol) was dissolved in 25 mL of distilled water, and aluminum sulfate 18hydrate (7.33 g, 4.81 mmol) was dissolved in 40 mL of distilled water. The two solutions were transferred into a 250 mL reaction bottle and then reacted at a constant temperature. The reaction solution gradually changed from colorless and transparent to a white emulsion. After reacting for 3 h, stirring was stopped, the mixture was filtered, washed with 40 mL of distilled water, and dried in a vacuum drying oven at 60 ° C for 8 h to obtain 2.18 g of white powder with a yield of 96.2%.

[0068] The flame retardant compound provided by the present invention has a high P content (22.77%) in its structure and a good flame retardant effect. When the addition amount is 20 parts, the limiting oxygen index of the rigid polyurethane foam can reach 29.3%, and the vertical combustion UL94 reaches the V0 level. The preparation method provided by the present invention has cheap and readily available raw materials, is simple to operate, has a high yield, and is easy to industrialize.

[0069] The above embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims

1. The preparation method of 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant is characterized by: The specific steps are as follows: S1: Synthesis of 1,3,5-tri(bromomethyl)benzene (Ⅰ); S11: At room temperature, 1,3,5-trimethylbenzene, N-bromosuccinimide, initiator benzoyl peroxide and benzene were added to a three-necked flask in sequence, and then slowly heated to 80°C under magnetic stirring. Initially, the reaction solution was boiled by the heat released by the reaction itself. When the solution stopped boiling spontaneously, the reaction solution was heated for about 1 hour. TLC monitoring showed that V (petroleum ether): V (ethyl acetate) = 10:1; S12: After the reaction is completed, the mixture is cooled and filtered, and the filtrate is washed with distilled water and saturated sodium chloride in sequence, dried with anhydrous sodium sulfate, and concentrated to precipitate a light yellow block solid; S13: The crude product was recrystallized from a mixture of ethanol and n-hexane to obtain white needle-shaped crystals Ⅰ, which were dried in vacuum with a yield of 82.3%; S2: Synthesis of 1,3,5-benzenetrimethylphosphonic acid ethyl ester (II); S21: At room temperature, 1,3,5-tri(bromomethyl)benzene and triethyl phosphite were added to the reaction bottle in sequence, and the resulting solution was kept at 150° C. for 12 h under nitrogen atmosphere, monitored by TLC, V (dichloromethane): V (methanol) = 15:1; S22: After the reaction is completed, the excess triethyl phosphite is removed by cooling and decompression to obtain a colorless viscous oil II with a yield of 96.3%; S3: Synthesis of 1,3,5-benzenetrimethylphosphonic acid (III); S31: At room temperature, the intermediate II prepared in the previous step and concentrated hydrochloric acid were added to the reaction bottle in sequence, and the reaction was refluxed at 110°C for 20 h. TLC monitoring showed that V (dichloromethane): V (methanol) = 8:1; S32: After the reaction is completed, the reaction is cooled and the excess water and HCl are removed under reduced pressure to obtain a white solid, which is recrystallized from a mixture of methanol and water to obtain a large amount of white crystal blocks III, which are then vacuum dried to obtain white crystals with a yield of 82.1%; S33: Select appropriate crystals for X-ray single crystal testing, and the results show that the synthesized compound is compound III; S4: Synthesis of 1,3,5-benzenetrimethylphosphonic acid aluminum (IV); S41: Dissolve intermediate III in distilled water and aluminum sulfate 18hydrate in distilled water, and transfer the two solutions into a reaction bottle; S42: Then react at room temperature, the reaction liquid gradually changes from colorless and transparent to white emulsion. After reacting for 3 hours, stop stirring, filter, wash with distilled water, and dry in a vacuum drying oven at 60°C for 8 hours to obtain a white powder with a yield of 96%.

2. The method for preparing the 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant according to claim 1, characterized in that: The reaction in S11 further includes a reaction solvent, and the reaction solvent is selected from any one of benzene, carbon tetrachloride or dichloromethane; the initiator can be replaced by azobisisobutyronitrile.

3. The method for preparing the 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant according to claim 1, characterized in that: The molar ratio of 1,3,5-trimethylbenzene to N-bromosuccinimide is 1:(3-3.2).

4. The method for preparing the 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant according to claim 1, characterized in that: In the S11, the reaction temperature is 75-85° C., and the reaction time is 0.5-1.5 h.

5. The method for preparing the 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant according to claim 1, characterized in that: The volume ratio of ethanol to n-hexane in S13 is 1:(1-1.5); the temperature of the vacuum drying is 40-50° C., and the drying time is 5-6 hours.

6. The method for preparing the 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant according to claim 1, characterized in that: The molar ratio of 1,3,5-tri(bromomethyl)benzene to triethyl phosphite in S21 is 1:(8-11).

7. The method for preparing the 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant according to claim 1, characterized in that: The reaction temperature in S21 is 140-155° C., and the reaction time is 10-13 h.

8. The method for preparing the 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant according to claim 1, characterized in that: The reaction temperature in S31 is 100-120° C., and the reaction time is 20-24 h.

9. The method for preparing the 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant according to claim 1, characterized in that: The volume ratio of water to methanol in the S32 is 1:(5-8), the vacuum drying temperature is 50-55°C, and the drying time is 8-10h.

10. Application of 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant, characterized in that: Application of 1,3,5-benzenetrimethylphosphonic acid aluminum flame retardant in rigid polyurethane foam.

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