Preparation Method and Application of Boron-Containing Ammonium Polyphosphate

Abstract

The present invention provides a preparation method and application of boron-containing ammonium polyphosphate. The method includes: preparing a phosphorus-boron compound: first adding polyphosphoric acid, adding boric acid while stirring, continuing to stir after heating until the material is uniform, evacuating, continuing to heat, and continuing to react for 0.5h-10h to obtain a phosphorus-boron compound; preparing a boron-containing ammonium polyphosphate preproduct: adding phosphorus pentoxide and diammonium hydrogen phosphate to a kneader, stirring evenly and then starting heating, setting the heating temperature to 150℃-240℃, passing ammonia for 0.5h-2h, then stopping ammonia, adding a phosphorus-boron compound and stirring for 0.5h-1h, and then continuing to pass ammonia for 1h-6h; then reducing the amount of ammonia and continuing the reaction for 0.5h-3h, with the amount of ammonia passed for every 100 kg of reactants being 0.2m 3 / hour‑1m 3 / hour, cooling and crushing to obtain a boron-containing ammonium polyphosphate preproduct; preparation of boron-containing ammonium polyphosphate: heating the cooled and crushed boron-containing ammonium polyphosphate preproduct and passing ammonia through it in two steps to obtain boron-containing ammonium polyphosphate.

Description

Technical Field

[0001] The present invention relates to the technical field of ammonium polyphosphate modification, in particular to a preparation method of boron-containing ammonium polyphosphate and application thereof. Background Art

[0002] Ultra-thin intumescent fire-retardant coatings, primarily composed of polymer resins and fire-retardant additives, offer thermal insulation and fire-resistant properties. Furthermore, the coating must withstand external physical impact, explosion shock, seismic shock, and cracking to meet application requirements. In the rail transit sector, lightweighting the vehicle body is crucial for energy conservation and consumption reduction. Therefore, aluminum profiles and polymer composites are commonly used for their structure and materials. In this application area, ultra-thin intumescent fire-retardant coatings are primarily applied to the aluminum alloy underframe of rail transit vehicles, ensuring the load-bearing stability and integrity of the chassis structure for a specified period after a fire.

[0003] However, compared to steel, the yield strength of aluminum drops to almost zero at 375°C, which is much lower than the 550°C of steel. Therefore, the fire protection of aluminum needs to meet the requirements of rapid thermal insulation, so as to reduce heat conduction and protect the stability of the material.

[0004] Among them, ammonium polyphosphate (APP) is an important component of ultra-thin intumescent fire retardant coatings and the most important component for acid source carbonization in the intumescent system. However, the reaction and expansion temperature of ammonium polyphosphate is about 300℃.

[0005] -450℃, which cannot meet the requirements of ultra-thin intumescent fire-retardant coatings for aluminum and other materials to expand rapidly and at a high rate at lower temperatures to form a thermal insulation layer.

[0006] Currently, the main methods for reducing the decomposition temperature of APP and improving the thermal insulation of the carbon layer are to add low-polymerization phosphorus-nitrogen compounds and use intercalation materials to composite ammonium polyphosphate. For example, the following two methods:

[0007] Method 1: Layered filler compounding. Patent publication CN104552514 mentions dispersing layered zirconium phosphate and ammonium polyphosphate in water at a ratio of 1:2 to produce a composite flame retardant. The layered zirconium phosphate can act as a thermal barrier. However, this method uses a liquid phase process, which is not suitable for industrial production. Furthermore, the intercalation of APP into the layered zirconium phosphate requires a release process, which interferes with the bonding of the intumescent flame retardant's acid source, carbon source, and gas source, reducing the expansion effect of the carbon layer.

[0008] Method 2 involves adding low-polymerization phosphorus-nitrogen compounds. These use water-soluble phosphorus-nitrogen compounds, such as APP, which have a relatively high nitrogen content and rapidly generate gas and expand. However, these products exhibit poor reaction sustainability, hindering the formation of a dense carbon layer. Furthermore, their high water solubility can easily lead to salting out after the coating dries and can corrode aluminum. Summary of the Invention

[0009] The object of the present invention is to provide a method for preparing boron-containing ammonium polyphosphate. The prepared boron-containing ammonium polyphosphate has the characteristics of rapid expansion at a relatively low temperature and a dense carbon layer in an ultra-thin intumescent fire-retardant coating. The boron-containing ammonium polyphosphate can be applied to ultra-thin intumescent fire-retardant coatings made of lightweight materials such as aluminum, thereby solving at least one problem of ammonium polyphosphate in ultra-thin intumescent fire-retardant coatings, namely, the high temperature required for high-rate expansion and the poor density of the carbon layer.

[0010] In order to solve at least any of the above technical problems, the present invention provides a method for preparing boron-containing ammonium polyphosphate, comprising: preparing a phosphorus-boron compound: first adding polyphosphoric acid to a reactor, adding boric acid while stirring, heating to 80-120°C and continuing to stir until the material is uniform, evacuating, and controlling the vacuum degree at 0.03MPa-0.04MPa, then heating to 120°C-200°C, and continuing the reaction for 0.5h-10h to obtain a phosphorus-boron compound; preparing a boron-containing ammonium polyphosphate preproduct: adding phosphorus pentoxide and diammonium hydrogen phosphate to a kneader, stirring evenly and then starting heating, setting the heating temperature to 150°C-240°C, passing ammonia for 0.5h-2h, stopping ammonia, adding a phosphorus-boron compound and stirring for 0.5h-1h, and continuing the ammonia reaction for 1h-6h; wherein the ratio of the amount of ammonia passed to the reactant in the two ammonia reactions is 1m3 / 100 kg of the reactant. 3 / hour-3m 3 / hour; then reduce the ammonia flow rate and continue the reaction for 0.5h-3h, with ammonia flow rate of 0.2m per 100kg of reactants 3 / hour-1m 3 / hour, cooling and crushing to obtain a boron-containing ammonium polyphosphate preproduct; preparation of boron-containing ammonium polyphosphate: the boron-containing ammonium polyphosphate preproduct after cooling and crushing is reacted with phosphorus pentoxide and diammonium hydrogen phosphate through heating and two steps of ammonia to obtain boron-containing ammonium polyphosphate.

[0011] Optionally, the final cooling in the preparation step of the boron-containing ammonium polyphosphate pre-product only requires cooling the pre-product to about 150 degrees, and the order is cooling first and then crushing.

[0012] Optionally, in the preparation step of the phosphorus-boron compound, the mixture is heated to 80°C to 120°C and stirred until the mixture is uniformly stirred for 0.45 to 0.55 hours. The temperature in the phrase "controlling the vacuum degree at 0.03 MPa to 0.04 MPa, then raising the temperature to 120°C to 200°C and continuing the reaction for 0.5 to 10 hours" is preferably 130°C to 150°C, and the reaction time is preferably 2 to 4 hours.

[0013] Optionally, the molar ratio of phosphorus to boron in the preparation step of the phosphorus-boron compound is 1:(0.1-1). Preferably, the molar ratio of phosphorus to boron in the preparation step of the phosphorus-boron compound is 1:(0.2-0.6). Excessive boron will not react completely with phosphorus, and boric acid may self-polymerize. Furthermore, flame retardancy mainly depends on phosphorus, with boron playing a supporting role. Excessive boron will cause the acid value of ammonium polyphosphate to increase, which is not conducive to the storage stability of the coating.

[0014] Optionally, in the step of preparing the boron polyphosphate ammonium pre-product, the phosphorus-boron compound is added and stirred for 0.5 h to 1 h, and then ammonia is continued to react for 1 h to 6 h. The ammonia reaction time is preferably continued for 2 h to 4 h.

[0015] Optionally, in the step of preparing the boron-containing ammonium polyphosphate pre-product, the molar ratio of phosphorus pentoxide to diammonium hydrogen phosphate is 1:(1.05-0.95), preferably 1:(1.02-0.98).

[0016] Optionally, in the preparation step of the boron-containing ammonium polyphosphate preproduct, the mass ratio of the phosphorus-boron compound to the sum of phosphorus pentoxide and diammonium hydrogen phosphate is (0.1-10):100, preferably (2-6):100. If there is too much boron, the reaction with phosphorus will not be complete, and boric acid will self-polymerize. In addition, flame retardancy mainly depends on phosphorus, and boron plays an auxiliary role. If there is too much boron, the acid value of ammonium polyphosphate will be high, which is not conducive to the storage stability of the coating.

[0017] Optionally, the preparation of boron-containing ammonium polyphosphate includes: heating the cooled and crushed boron-containing ammonium polyphosphate pre-product, setting the heating temperature to 180°C-320°C, preferably 220°C-280°C, stirring and passing ammonia, and passing ammonia at a rate of 0.2m3 per 100 kg of material. 3 / hour -0.5m 3 / hour, the material temperature is heated to 160℃ to adjust the ammonia flow rate, and the ammonia flow rate for every 100 kg of material is 0.5m 3 / hour-2m 3 / hour, and after passing ammonia for reaction for 0.5h-2h, stop passing ammonia and heating, and continue stirring and reacting for 0.5h-2h to obtain boron-containing ammonium polyphosphate.

[0018] Optionally, the preparation of boron-containing ammonium polyphosphate further includes: absorbing excess ammonia in the preparation step of the boron-containing ammonium polyphosphate preproduct and the preparation step of the boron-containing ammonium polyphosphate by phosphoric acid to prepare diammonium hydrogen phosphate, which can be used as a raw material for the preparation step of the boron-containing ammonium polyphosphate preproduct.

[0019] Optionally, the phosphorus content in the boron-containing ammonium polyphosphate is ≥31%, the boron content ranges from 0.01% to 1%, and the preferred boron content is 0.05% to 0.3%.

[0020] Optionally, the average degree of polyphosphoric acid in the preparation step of the phosphorus-boron compound is in the range of 1.2-10, preferably 1.6-4. On the one hand, there is no industrial product with a degree of polymerization of polyphosphoric acid greater than 4, and on the other hand, a large degree of polymerization has low reaction activity. In the preparation step of the boron-containing ammonium polyphosphate pre-product, the content of phosphorus pentoxide is ≥99.5%, the activity R value is ≥1.7, and the proportion of reducing substances is ≤0.005%.

[0021] The present application also provides an application of boron-containing ammonium polyphosphate prepared by any of the above methods for preparing boron-containing ammonium polyphosphate, that is, applying boron-containing ammonium polyphosphate to intumescent fire-retardant coatings for materials with lower thermal yield strength temperatures, where lower thermal yield strength materials refer to materials such as aluminum that have a thermal yield strength lower than that of steel.

[0022] Alternatively, boron-containing ammonium polyphosphate, high-molecular polymer resin, and additives can be applied to ultra-thin intumescent fire retardant coatings. Ultra-thin is an industry consensus, relative to cement mortar.

[0023] In summary, the boron-containing ammonium polyphosphate salt prepared by the non-surface modification method of the present invention has a low decomposition temperature, and the 2% thermal decomposition temperature is less than 270°C. Not only can the fire-retardant coating expand rapidly at a lower temperature, but the boron element is also conducive to the formation of a denser glassy expanded carbon layer surface. By introducing the boron element to lower the thermal decomposition temperature of ammonium polyphosphate, it has synergistic flame retardancy with phosphorus, thereby improving the density of the expanded carbon layer formed by the fire-retardant coating.

[0024] Aluminum's yield strength drops to a very low level, almost to zero, at 375°C, far below the 550°C yield temperature of steel structures. The intumescent flame-retardant system of ultra-thin intumescent fire-retardant coatings protects aluminum and other materials by forming a dense carbon layer with a high expansion ratio at relatively low temperatures. This flame retardancy requires the synergy of multiple flame-retardant elements. Boron contributes to a denser surface of the intumescent carbon layer, while phosphorus, as the primary flame-retardant element, exhibits a synergistic flame-retardant effect with boron. These two approaches work together to address the problem of ultra-thin intumescent fire-retardant coatings for aluminum and other materials rapidly expanding at high rates at relatively low temperatures to form a thermal insulation layer, meeting the needs of rail transit.

[0025] The inventors also tried to use borates (such as ammonium salts) to prepare boron ammonium polyphosphate pre-products, but borates contain crystal water, which is not conducive to the shrinkage reaction; other boric acid metal salts or esters have low reactivity with polyphosphoric acid, and the shrinkage reaction cannot proceed.

[0026] The inventors also attempted to eliminate the phosphorus-boron compound preparation step and directly add polyphosphoric acid and boric acid to the boron-containing ammonium polyphosphate pre-product, adjusting the heating time and temperature accordingly. However, polyphosphoric acid reacts more quickly with phosphorus pentoxide, and the boric acid is more likely to self-condense. Furthermore, the dehydration reaction between boric acid and polyphosphoric acid significantly affects the synthesis and polymerization of APP. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the infrared spectrum of boron-containing ammonium polyphosphate according to Example 1 provided in the examples of the present invention;

[0028] Figure 2 This is the infrared spectrum of the boron-containing ammonium polyphosphate of Comparative Example 2 provided in the Examples of the present invention;

[0029] Figure 3 This is the infrared spectrum of commercially available ammonium polyphosphate in Comparative Example 1 provided in the embodiments of the present invention;

[0030] Figure 4 This is a TGA diagram of boron-containing ammonium polyphosphate in Example 1 provided in the examples of the present invention;

[0031] Figure 5 This is a TGA graph of boron-containing ammonium polyphosphate in Comparative Example 2 provided in the embodiments of the present invention;

[0032] Figure 6 This is the TGA chart of commercially available ammonium polyphosphate in Comparative Example 1 provided in the Examples of the present invention. DETAILED DESCRIPTION

[0033] The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0034] Example 1

[0035] (1) Preparation of phosphorus-boron compounds

[0036] First, 100 kg of polyphosphoric acid (average degree of polymerization of 2) was added to the reactor, and 34.7 kg of boric acid was added under stirring. The mixture was heated to 120°C and stirred for about 0.5 hours. The materials were uniformly mixed and vacuumed with the vacuum degree controlled at 0.03 MPa-0.04 MPa. The temperature was then raised to 130°C and the reaction was continued for 4 hours to obtain a phosphorus-boron compound.

[0037] (2) Preparation of boron-containing ammonium polyphosphate pre-product

[0038] 100 kg of phosphorus pentoxide (phosphorus pentoxide content ≥ 99.5%, active R value ≥ 1.7, reducing matter ratio ≤ 0.005%) and 93 kg of diammonium hydrogen phosphate were added to the kneader. After stirring evenly, the temperature of the heat transfer oil in the reactor was set at 200°C. Ammonia was allowed to react for 2 hours and then stopped. 3.86 kg of phosphorus-boron compound was added and stirred for 0.5 hours. The ammonia was continued to react for 4 hours. The ratio of ammonia to reactant was 3 m3 / 100 kg of reactant. 3 / hour. Reduce the amount of ammonia and continue the reaction for 2 hours. The amount of ammonia per 100 kg of reactants is 1m 3 / hour, cooling and crushing to obtain the boron-containing ammonium polyphosphate pre-product.

[0039] (3) Preparation of boron-containing ammonium polyphosphate

[0040] The reactor temperature was set at 280°C, and ammonia was introduced with stirring at a rate of 0.5 m3 / 100 kg of material. 3 / hour, the material temperature reaches 160℃, adjust the ammonia flow rate, and the ammonia flow rate for every 100 kg of material is 2m 3 / hour, and then the ammonia was passed through for 0.5 hour, and then the ammonia and heating were stopped. The reaction was continued with stirring for 2 hours to obtain boron-containing ammonium polyphosphate.

[0041] (4) The excess ammonia in the above steps 2 and 3 is absorbed by phosphoric acid to prepare diammonium hydrogen phosphate, which can be used as the raw material of the above step 2.

[0042] Example 2

[0043] (1) Preparation of phosphorus-boron compounds

[0044] First, add 100 kg of polyphosphoric acid (average degree of polymerization of 4) to the reactor, add 14.64 kg of boric acid while stirring, heat to 80 ° C and continue stirring for about 0.5 hours. The materials are uniform, evacuate, and control the vacuum degree at 0.03-0.04 MPa. Then, heat to 150 ° C and continue the reaction for 4 hours to obtain a phosphorus-boron compound;

[0045] (2) Preparation of boron-containing ammonium polyphosphate pre-product

[0046] 100 kg of phosphorus pentoxide (phosphorus pentoxide content ≥ 99.5%, active R value ≥ 1.7, reducing matter ratio ≤ 0.005%) and 93.5 kg of diammonium hydrogen phosphate were added to the kneader, stirred evenly, the temperature of the heat transfer oil in the reactor was set at 240°C, ammonia was allowed to react for 1 hour, and then ammonia was stopped. 7.74 kg of phosphorus boron compound was added, stirred for 1 hour, and then ammonia was continued for 2 hours. The ratio of ammonia to reactant was 1m3 / 100 kg of reactant. 3 / hour. Reduce the amount of ammonia and continue the reaction for 3 hours. The amount of ammonia per 100 kg of reactants is 0.5m 3 / hour, cooling and crushing to obtain the boron-containing ammonium polyphosphate pre-product.

[0047] (3) Preparation of boron-containing ammonium polyphosphate

[0048] The reactor temperature was set at 260°C, and ammonia was introduced with stirring at a rate of 0.5 m3 / 100 kg of material. 3 / hour, the material temperature reaches 160℃, adjust the ammonia flow rate, and the ammonia flow rate for every 100 kg of material is 0.5m 3 / hour, and then the ammonia was passed through for 2 hours, and then the ammonia and heating were stopped, and the reaction was continued with stirring for 0.5 hours to obtain boron-containing ammonium polyphosphate.

[0049] (4) The excess ammonia in the above steps 2 and 3 is absorbed by phosphoric acid to prepare diammonium hydrogen phosphate, which can be used as the raw material of the above step 2.

[0050] Example 3

[0051] (1) Preparation of phosphorus-boron compounds

[0052] First, 100 kg of polyphosphoric acid (average degree of polymerization of 1.6) was added to the reactor, and 40.65 kg of boric acid was added under stirring. The mixture was heated to 120°C and stirred for about 0.5 hours. The materials were homogenized and vacuumed with the vacuum degree controlled at 0.03-0.04 MPa. The temperature was then raised to 140°C and the reaction was continued for 4 hours to obtain a phosphorus-boron compound.

[0053] (2) Preparation of boron-containing ammonium polyphosphate pre-product

[0054] 100 kg of phosphorus pentoxide (phosphorus pentoxide content ≥ 99.5%, active R value ≥ 1.7, reducing matter ratio ≤ 0.005%) and 93.5 kg of diammonium hydrogen phosphate were added to the kneader. After stirring evenly, the temperature of the heat transfer oil in the reactor was set at 240°C. Ammonia was allowed to react for 0.5 hours, and then the ammonia was stopped. 11.61 kg of phosphorus-boron compound was added, stirred for 1 hour, and then the ammonia was continued for 2 hours. The ratio of ammonia to reactant was 2 m3 / 100 kg of reactant. 3 / hour. Reduce the amount of ammonia and continue the reaction for 0.5 hours. The amount of ammonia per 100 kg of reactants is 1m 3 / hour, cooling and crushing to obtain the boron-containing ammonium polyphosphate pre-product.

[0055] (3) Preparation of boron-containing ammonium polyphosphate

[0056] The reactor temperature was set at 250°C, and ammonia was introduced with stirring at a rate of 0.4 m3 / 100 kg of material. 3 / hour, the material temperature reaches 160℃, adjust the ammonia flow rate, and the ammonia flow rate for every 100 kg of material is 1m 3 / hour, and then the ammonia was passed through for 1 hour, and then the ammonia was stopped and the heating was stopped. The reaction was continued with stirring for 1 hour to obtain boron-containing ammonium polyphosphate.

[0057] (4) The excess ammonia in the above steps 2 and 3 is absorbed by phosphoric acid to prepare diammonium hydrogen phosphate, which can be used as the raw material of the above step 2.

[0058] Example 4

[0059] (1) Preparation of phosphorus-boron compounds

[0060] First, add 100 kg of polyphosphoric acid (average degree of polymerization is 2) into the reactor, add 18.06 kg of boric acid while stirring, heat to 110 ° C and continue stirring for about 0.5 hours. The materials are uniform, evacuate, and control the vacuum degree at 0.03-0.04 MPa. Then, heat to 140 ° C and continue the reaction for 2 hours to obtain a phosphorus-boron compound;

[0061] (2) Preparation of boron-containing ammonium polyphosphate pre-product

[0062] 100 kg of phosphorus pentoxide (phosphorus pentoxide content ≥ 99.5%, active R value ≥ 1.7, reducing matter ratio ≤ 0.005%) and 94 kg of diammonium hydrogen phosphate were added to the kneader, stirred evenly, and the temperature of the heat transfer oil in the reactor was set at 220°C. Ammonia was allowed to react for 1 hour, and then the ammonia was stopped. 3.88 kg of phosphorus-boron compound was added, stirred for 1 hour, and then the ammonia was continued for 3 hours. The ratio of ammonia to reactant was 2 m3 / 100 kg of reactant. 3 / hour. Reduce the amount of ammonia and continue the reaction for 1.5 hours. The amount of ammonia per 100 kg of reactants is 1m 3 / hour, cooling and crushing to obtain the boron-containing ammonium polyphosphate pre-product.

[0063] (3) Preparation of boron-containing ammonium polyphosphate

[0064] The reactor temperature was set at 220°C, and ammonia was introduced with stirring at a rate of 0.2 m3 per 100 kg of material. 3 / hour, the material temperature reaches 160℃, adjust the ammonia flow rate, and the ammonia flow rate for every 100 kg of material is 1m 3 / hour, and then the ammonia was passed through for 1 hour, and then the ammonia was stopped and the heating was stopped. The reaction was continued with stirring for 1 hour to obtain boron-containing ammonium polyphosphate.

[0065] (4) The excess ammonia in the above steps 2 and 3 is absorbed by phosphoric acid to prepare diammonium hydrogen phosphate, which can be used as the raw material of the above step 2.

[0066] Example 5

[0067] (1) Preparation of phosphorus-boron compounds

[0068] First, add 100 kg of polyphosphoric acid (average degree of polymerization of 2) to the reactor, add 34.74 kg of boric acid while stirring, heat to 100 ° C and continue stirring for about 0.5 hours. The materials are uniform, evacuate, and control the vacuum degree at 0.03-0.04 MPa. Then, heat to 140 ° C and continue the reaction for 3 hours to obtain a phosphorus-boron compound;

[0069] (2) Preparation of boron-containing ammonium polyphosphate pre-product

[0070] 100 kg of phosphorus pentoxide (phosphorus pentoxide content ≥ 99.5%, active R value ≥ 1.7, reducing matter ratio ≤ 0.005%) and 93 kg of diammonium hydrogen phosphate were added to the kneader. After stirring evenly, the temperature of the heat transfer oil in the reactor was set at 150°C. Ammonia was allowed to react for 2 hours, and then the ammonia was stopped. 9.65 kg of phosphorus-boron compound was added and stirred for 0.5 hours. The ammonia was continued to react for 3 hours. The ratio of ammonia to reactant was 2 m3 / 100 kg of reactant. 3 / hour. Reduce the amount of ammonia and continue the reaction for 1.5 hours. The amount of ammonia per 100 kg of reactants is 1m 3 / hour, cooling and crushing to obtain the boron-containing ammonium polyphosphate pre-product.

[0071] (3) Preparation of boron-containing ammonium polyphosphate

[0072] The reactor temperature was set at 280°C, and ammonia was introduced with stirring at a rate of 0.4 m3 / 100 kg of material. 3 / hour, the material temperature reaches 160℃, adjust the ammonia flow rate, and the ammonia flow rate for every 100 kg of material is 2m 3 / hour, and then the ammonia was passed through for 1 hour, and then the ammonia was stopped and the heating was stopped. The reaction was continued with stirring for 1 hour to obtain boron-containing ammonium polyphosphate.

[0073] (4) The excess ammonia in the above steps 2 and 3 is absorbed by phosphoric acid to prepare diammonium hydrogen phosphate, which can be used as the raw material of the above step 2.

[0074] Comparative Example 1

[0075] Commercially available type II ammonium polyphosphate.

[0076] Comparative Example 2

[0077] 200 kg of commercially available type II ammonium polyphosphate was added with 3.4 kg of boric acid. The reactor temperature was set at 220°C and stirred with ammonia. The ammonia flow rate was 0.5 m3 per 100 kg of material. 3 / hour, the material temperature reaches 160℃, adjust the ammonia flow rate, and the ammonia flow rate for every 100 kg of material is 2m 3 / hour, and after passing ammonia for 0.5 hour, the passing of ammonia and heating were stopped, and the reaction was continued with stirring for 2 hours to obtain boron-containing ammonium polyphosphate.

[0078] Comparative Example 3

[0079] 100 kg of commercially available type II ammonium polyphosphate was added to a high-speed mixer, and 5 kg of polyborosiloxane was added under stirring at 300 rpm. After the addition, the mixture was stirred evenly at 3000 rpm, dried, and sieved through 150 mesh to obtain polyborosiloxane-modified ammonium polyphosphate.

[0080] Polyborosiloxane was prepared by the following method: 12.37 kg of boric acid and 29.65 kg of vinyltrimethoxysilane were added to 42.02 kg of diethylene glycol dimethyl ether and stirred and dispersed, hydrochloric acid solution was added dropwise to adjust the pH to 3, the temperature was raised to 80° C., the reaction was carried out for 6 hours, and the volatilization was carried out under reduced pressure to obtain a viscous polyborosilane containing approximately 8% of diethylene glycol dimethyl ether.

[0081] Comparative Example 4

[0082] (1) Preparation of phosphorus-boron compounds

[0083] First, add 100 kg of polyphosphoric acid (average degree of polymerization is 2) into the reactor, add 76.42 kg of boric acid while stirring, heat to 120 ° C and continue stirring for about 0.5 hours. The materials are uniform, evacuate, and control the vacuum degree at 0.03-0.04 MPa. Then, heat to 130 ° C and continue the reaction for 10 hours to obtain a phosphorus-boron compound;

[0084] (2) Preparation of boron-containing ammonium polyphosphate pre-product

[0085] 100 kg of phosphorus pentoxide (phosphorus pentoxide content ≥ 99.5%, active R value ≥ 1.7, reducing matter ratio ≤ 0.005%) and 93 kg of diammonium hydrogen phosphate were added to the kneader. After stirring evenly, the temperature of the heat transfer oil in the reactor was set at 220°C. After ammonia was passed through the kneader for 1 hour, the ammonia was stopped. 28.95 kg of phosphorus-boron compound was added and stirred for 0.5 hours. The ammonia was continued to pass through the kneader for 6 hours. The ratio of ammonia to reactant was 2 m3 / 100 kg of reactant. 3 The ammonia flow rate was reduced and the reaction was continued for 2 hours, with the ammonia flow rate being 0.5 m3 / hour per 100 kg of reactants, and the product was cooled and crushed to obtain a boron-containing ammonium polyphosphate pre-product.

[0086] Other details are the same as in Example 1.

[0087] The detection methods of the above embodiments and comparative examples are as follows:

[0088] 1. pH: Prepare a 1% aqueous solution, soak in a water bath at room temperature for 30 minutes, and test with a pH meter;

[0089] 2. Viscosity: Prepare a 10% aqueous solution, soak in a water bath at room temperature for half an hour, and test with NDJ-79;

[0090] 3. Acid value: Weigh 5g ± 0.2g of sample, add 80mL of anhydrous ethanol, and stir in a 25°C constant temperature water bath for 20 minutes. Filter and rinse with a small amount of anhydrous ethanol, then combine the filtrates. Add 3 drops of phenolphthalein indicator to the filtrate and titrate with potassium hydroxide-ethanol standard titrant (the endpoint is when the solution changes from colorless to light red).

[0091] Table 1: Performance indicators of boron-containing ammonium polyphosphate in the examples and comparative examples

[0092]

[0093]

[0094] Application Examples 1-9

[0095] Examples 1-5 and Comparative Examples 1-4 were applied to the ultra-thin intumescent fire retardant coatings corresponding to Examples 1-9, respectively. The basic formula is as follows (mass percentage):

[0096]

[0097] The test was conducted using a rapid fire performance test device for intumescent coatings according to the ISO 834 temperature rise curve. The aluminum plate sample size was 40mm*80mm*1mm, and the coating dry film thickness was 1.0mm. The back panel temperature after 45 minutes of testing was as shown in Table 2.

[0098] Table 2: Application Examples 1-9

[0099] serial number Ammonium polyphosphate Back-fire surface temperature, ℃ 10-minute expansion height, cm Application Example 1 Example 1 285 2.7 Application Example 2 Example 2 289 3.1 Application Example 3 Example 3 307 2.9 Application Example 4 Example 4 291 2.6 Application Example 5 Example 5 319 2.4 Application Comparative Example 1 Comparative Example 1 410 1.5 Application Comparative Example 2 Comparative Example 2 <![CDATA[>500 1 ]]> 2.4 Application Comparative Example 3 Comparative Example 3 <![CDATA[427 2 ]]> 2.9 Application Comparative Example 4 Comparative Example 4 387 2.8

[0100] Note: 1. The surface of the carbon layer is cracked, the aluminum plate is severely deformed and melted, and the thermocouple temperature measurement fails.

[0101] 2. The surface of the carbon layer is not dense and loose.

[0102] refer to Figures 1 to 6 As can be seen from the data in Tables 1 and 2, it is found from infrared spectra and TGA analysis that polyphosphoric acid, boron-containing polyphosphoric acid and the boron-containing ammonium polyphosphate in this application are significantly different in infrared spectra. The boron-containing polyphosphoric acid prepared by the method of this application is not a simple mixture, which changes the thermodynamic decomposition properties of ammonium polyphosphate. Although ammonium polyphosphate and boric acid in Comparative Example 2 are also subjected to high-temperature treatment, the thermodynamic properties do not change much. It is better to have a low temperature on the back-fire surface for a specified time. From the application examples, the fire resistance of ultra-thin intumescent fire-retardant coatings depends on the expansion height and quality of the carbon layer, and the two complement each other. In the application of Comparative Example 2, it was found that the simple addition of boric acid not only did not improve the fire resistance, but also the presence of boric acid made the surface of the intumescent carbon layer of the prepared ultra-thin intumescent fire-retardant coating easy to crack, and the fire resistance dropped sharply. In the application of Comparative Example 3, a white powdery substance was produced on the surface of the carbon layer during the combustion process. It was silicon dioxide generated after the combustion of organosilicon. The carbon layer was loose, resulting in a decrease in fireproof performance. In the comparative example 4, it was found that the height of the carbon layer reached its highest value at 5-6 minutes, and then decreased in the later period. The carbon layer with high boron content was easily melted, resulting in a decrease in the expansion height. At the same time, due to the melting of the carbon layer with high boron content, the thermal insulation effect decreased, and small cracks appeared on the surface of the carbon layer.

[0103] Moreover, since the addition of boron will reduce the stability of APP, it is very unfavorable in water-based coatings. Currently, it can only be used in solvent-based systems. Generally, aluminum adopts solvent-based systems (such as water-based fire retardant coatings for aluminum, APP has a certain acidity, and the aluminum surface will be corroded to a certain extent. This is why boric acid must first shrink with polyphosphoric acid. At the same time, if boric acid is added directly, it will dehydrate at around 300 degrees Celsius, which will cause the carbon layer to crack. This is why Comparative Example 2 is so poor. The expansion flame retardant is a process in which polyphosphoric acid captures the polymer and the carbon-forming agent to dehydrate. Trace moisture will cause the collapse and rupture of the bubbles during the expansion process).

[0104] Although the present invention has been disclosed above by means of preferred embodiments, this is not intended to limit the present invention. Anyone skilled in the art may make slight changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be determined by the scope of protection required by the claims.

Claims

1. A method for preparing boron-containing ammonium polyphosphate, characterized in that: include: Preparation of phosphorus-boron compound: First, add polyphosphoric acid to the reactor, then add boric acid while stirring, heat to 80-120°C and continue stirring until the materials are uniform, evacuate, and control the vacuum degree at 0.03 MPa-0.04 MPa, then heat to 120-200°C, and continue the reaction for 0.5-10 hours to obtain the phosphorus-boron compound; Preparation of a boron-containing ammonium polyphosphate pre-product: adding phosphorus pentoxide and diammonium hydrogen phosphate to a kneader, stirring evenly and then starting heating, the heating temperature being set at 150°C-240°C, reacting with ammonia for 0.5-2 hours, then stopping the ammonia, adding a phosphorus-boron compound and stirring for 0.5-1 hour, and then continuing the ammonia reaction for 1-6 hours; wherein the ratio of the amount of ammonia passed to the reactant in the two ammonia reactions is 1 m³ / hour-3 m³ / hour per 100 kg of reactant; then reducing the amount of ammonia passed and continuing the reaction for 0.5-3 hours, and the amount of ammonia passed is 0.2 m³ / hour-1 m³ / hour per 100 kg of reactant, cooling and pulverizing to obtain a boron-containing ammonium polyphosphate pre-product; and Preparation of boron-containing ammonium polyphosphate: The cooled and crushed boron-containing ammonium polyphosphate pre-product is reacted with phosphorus pentoxide and diammonium hydrogen phosphate in a two-step ammonia reaction under heating to obtain boron-containing ammonium polyphosphate; In the preparation step of the phosphorus-boron compound, the molar ratio of phosphorus element to boron element is 1:(0.1-1).

2. The method for preparing boron-containing ammonium polyphosphate according to claim 1, wherein In the preparation step of the phosphorus-boron compound, the molar ratio of phosphorus element to boron element is 1:(0.2-0.6).

3. The method for preparing boron-containing ammonium polyphosphate according to claim 1, wherein In the preparation step of the boron-containing ammonium polyphosphate pre-product, the molar ratio of phosphorus pentoxide to diammonium hydrogen phosphate is 1:(1.05-0.95).

4. The method for preparing boron-containing ammonium polyphosphate according to claim 1, wherein In the step of preparing the boron-containing ammonium polyphosphate pre-product, the mass ratio of the phosphorus-boron compound to the sum of phosphorus pentoxide and diammonium hydrogen phosphate is (0.1-10):

100.

5. The method for preparing the boron-containing ammonium polyphosphate according to any one of claims 1 to 4, characterized in that: The preparation of the boron-containing ammonium polyphosphate includes: heating a cooled and crushed boron-containing ammonium polyphosphate preproduct, setting the heating temperature to 180° C.-320° C., stirring and passing ammonia, passing ammonia at a rate of 0.2 m³ / hour-0.5 m³ / hour per 100 kg of material, heating the material temperature to 160° C. to adjust the ammonia rate, passing ammonia at a rate of 0.5 m³ / hour-2 m³ / hour per 100 kg of material, allowing the ammonia to react for 0.5 h-2 h, stopping the ammonia passing and heating, and continuing the stirring reaction for 0.5 h-2 h to obtain the boron-containing ammonium polyphosphate.

6. The method for preparing the boron-containing ammonium polyphosphate according to any one of claims 1 to 4, characterized in that: The phosphorus content in the boron-containing ammonium polyphosphate is ≥31%, and the boron content ranges from 0.01% to 1%.

7. The method for preparing the boron-containing ammonium polyphosphate according to any one of claims 1 to 4, characterized in that: The average polymerization degree of polyphosphoric acid in the preparation step of the phosphorus-boron compound is in the range of 1.2-10, and the content of phosphorus pentoxide in the preparation step of the boron-containing ammonium polyphosphate pre-product is ≥99.5%, the activity R value is ≥1.7, and the reducing material ratio is ≤0.005%.

8. Use of the boron-containing ammonium polyphosphate prepared by the method for preparing boron-containing ammonium polyphosphate according to any one of claims 1 to 7, characterized in that: The boron-containing ammonium polyphosphate is applied to an intumescent fire-retardant coating for materials with relatively low thermal yield strength. The materials with relatively low thermal yield strength refer to materials with a thermal yield strength lower than that of steel, and the materials with relatively low thermal yield strength include aluminum.

9. The use of boron-containing ammonium polyphosphate according to claim 8, characterized in that: The boron-containing ammonium polyphosphate, high molecular polymer resin and auxiliary agents are applied to an ultra-thin intumescent fire-retardant coating.

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