Preparation method of iron-silicon modified biochar flame retardant and preparation method of modified phenolic foam

Abstract

A method for preparing an iron-silicon modified biochar flame retardant and a method for preparing a modified phenolic foam thereof, belonging to the field of thermal protection technology. The scheme comprises the following steps: hydrolyzing straw powder, washing and drying to obtain biochar; mixing biochar and ferrous sulfate solution, filtering and drying to obtain iron-modified biochar; blending iron-modified biochar, organosilicon and halogen-free flame retardant to obtain iron-silicon modified biochar flame retardant. Adding an alkaline catalyst to melted phenol, stirring evenly, then adding paraformaldehyde in batches at a uniform speed, and obtaining a resol phenolic resin through a step reaction; lowering the temperature to 60-70°C, adding boric acid solution dropwise to the resol phenolic resin for constant temperature reaction, and rotary evaporation to control the resin solid content to 60%-70% to obtain a boron-modified phenolic resin; blending the boron-modified phenolic resin, the iron-silicon modified biochar flame retardant and a foaming aid, and foaming treatment to obtain a silicon-modified biochar flame-retardant phenolic foam.

Description

Technical Field

[0001] The present invention belongs to the technical field of thermal protection, and in particular relates to a method for preparing an iron-silicon modified biochar flame retardant and a method for preparing a modified phenolic foam thereof. Background Art

[0002] Traditional insulation materials like polystyrene (PS) foam are widely used in the insulation field due to their low price, excellent thermal insulation properties, low water absorption, and good impact resistance. However, the material itself has poor flame retardancy. Polyurethane (PU) foam has excellent thermal insulation properties and low water absorption, but it is expensive, has poor flame retardancy, and produces a large amount of harmful gases when burned. Therefore, the application of traditional insulation materials is limited. With the rapid development of industries such as construction, petrochemicals, and shipbuilding, lightweight, fireproof, and low-toxic materials are gradually gaining popularity. Among commonly used insulation foam materials, phenolic foam has advantages that other foam materials cannot match, making it widely used. However, phenolic foam has problems such as poor toughness, high crushing rate, and "smoldering" properties. Summary of the Invention

[0003] The present invention provides a method for preparing an iron-silicon modified biochar synergistic flame retardant and a method for preparing the modified phenolic foam. The biochar is prepared from environmentally friendly biomass raw materials and combined with organosilicon and a halogen-free flame retardant to produce a green biomass flame retardant. This flame retardant improves the dispersibility of the flame retardant in the phenolic foam, enhancing the flame retardant properties of the phenolic foam. This improves the generation of harmful gases during the flame retardant process of halogen-free flame retardants, while also increasing foam toughness and reducing crushing rate. This invention can promote the further application of biomass materials in flame retardancy and open up new avenues for flame retardant phenolic foam.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A method for preparing an iron-silicon modified biochar flame retardant comprises the following steps:

[0006] Step 1: hydrolyzing the straw powder, washing and drying it to obtain biochar;

[0007] Step 2: mixing the biochar and ferrous sulfate solution, shaking, filtering and drying to obtain iron-modified biochar;

[0008] Step 3: Blend the iron-modified biochar, organosilicon and halogen-free flame retardant to obtain an iron-silicon modified biochar flame retardant.

[0009] The mass ratio of the iron-modified biochar, the organosilicon and the halogen-free flame retardant is (1-5): (10-20): (1-10).

[0010] The straw powder is a combination of one or more of corn straw powder, wheat straw powder, furfural residue, peanut shell powder and rice straw powder.

[0011] The organosilicon is one or more of methyl vinyl silicone oil, methylphenyl silicone oil, cyanide-containing silicone oil, octamethylcyclotetrasiloxane, and dihydroxy-polydimethyldiphenylsiloxane; the halogen-free flame retardant includes one or more of triethyl phosphate, bisphenol A diphosphate, diethyl aluminum phosphinate, triphenyl phosphate, triphenol phosphate, and bisphenol A-bis(diphenyl phosphate).

[0012] A method for preparing an iron-silicon modified biochar flame retardant modified phenolic foam prepared by the preparation method comprises the following steps:

[0013] Step 1, synthesizing resol phenolic resin: adding an alkaline catalyst to melted phenol, stirring evenly, then adding paraformaldehyde in batches at a uniform rate, reacting at a temperature of 60-70° C. for 1-3 hours, then heating to 70-80° C. for 2-3 hours to obtain resol phenolic resin;

[0014] Step 2, synthesizing boron-modified phenolic resin: cooling the temperature to 60-70° C., adding boric acid solution dropwise to the resol phenolic resin, and performing constant temperature reaction for 4-8 hours by adding dropwise using a dropping funnel, and controlling the resin solid content at 60%-70% by rotary evaporation to obtain a boron-modified phenolic resin;

[0015] Step 3: Blend the boron-modified phenolic resin, the iron-silicon-modified biochar flame retardant and the foaming aid, stir at 500-1000 r / min for 1-3 minutes at room temperature, pour into a preheated foaming mold, and foam at 60-80°C for 10-120 minutes to obtain silicon-modified biochar flame-retardant phenolic foam.

[0016] Furthermore, the molar ratio of the aldehyde group in the paraformaldehyde to the phenol group in the phenol is 1:1.5 to 1:2.0.

[0017] Furthermore, the alkaline catalyst includes one or more of potassium hydroxide, sodium hydroxide, and barium hydroxide.

[0018] Furthermore, the boric acid accounts for 3-10% of the mass of the resol phenolic resin; the solvent of the boric acid solution is one or more of methanol, ethanol, and isopropanol; and the boric acid accounts for 3-10% of the mass of the solvent.

[0019] Furthermore, the foaming aid includes a foaming agent, a curing agent and a surfactant; the mass ratio of the boron-modified phenolic resin, the iron-silicon modified biochar flame retardant, the foaming agent, the curing agent and the surfactant is 100:6-10:5-20:8-20:1-8.

[0020] The surfactant includes one or more of Tween-60, Tween-80, polysiloxane or polysiloxane surfactants; the foaming agent includes one or more of petroleum ether, n-pentane, n-hexane, isopentane, cyclopentane, n-butane, and dichloromethane; the curing agent is phosphoric acid, p-toluenesulfonic acid, hydroquinone and water in a ratio of (30-20):

[0021] A mixed acid of (100~90):(20~5):(20~30).

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The silicon element in the iron-silicon modified biochar and the boron element in the boron modified phenolic resin form a glassy covering layer at high temperature. The carbon layer generated by the synergistic biochar can effectively reduce the release of various polluting gases in the phenolic foam, thereby improving the high temperature resistance and flame retardancy of the foam.

[0024] 2. The present invention uses renewable resource straw powder as raw material, and improves the high temperature resistance and flame retardancy of biochar by introducing silicon and phosphorus elements. The synergistic halogen-free flame retardant can obtain excellent flame retardant effect. Surface modification of biochar and ferrous sulfate solution can increase the specific surface area of biochar, thereby improving the biochar's adsorption capacity for pollutant gases.

[0025] 3. The use of biomass raw materials to prepare biochar reduces material costs compared to adsorption materials such as carbon nanotubes and activated carbon, providing a high value-added utilization approach for biomass raw materials.

[0026] 4. The iron-silicon modified biochar synergistic flame retardant improves the flame retardancy of the foam, reduces the slagging rate, and reduces the release of phosphorus-containing pollutants after the addition of halogen-free flame retardants and the release of pollutant gases from the foam itself; reduces production costs and makes full use of environmental resources. It can be applied to chemical companies and the construction industry. Under the premise that the country has strict requirements on the flame retardancy of thermal insulation materials, the market prospects for phenolic foam with excellent self-flame retardant properties are broad. DETAILED DESCRIPTION

[0027] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] The raw materials of the present invention are all commercially available, and unless otherwise specified in the following examples, all parts are by weight.

[0029] Straw powder, a renewable resource, can be produced as biochar through hydrothermal and pyrolysis methods. Biochar's porosity provides excellent adsorption capacity. Compared to traditional adsorption materials such as activated carbon, zeolite biosieves, and metal-organic frameworks, biochar boasts lower cost and greater availability. Therefore, biochar can be used as a cost-effective, renewable adsorption material.

[0030] Biochar is primarily prepared by hydrothermal and pyrolysis methods. Compared to pyrolysis, the hydrothermal method exhibits a higher retention rate of aromatic structures. As the heat treatment temperature increases, the content of polar groups in the biochar decreases, and its hydrophobicity increases. Compared to pyrolysis biochar, the H / C ratio is higher, and the aromatic structure retention rate is higher. The π-π EDA interaction between the electron-deficient benzene rings in the halogen-free flame retardant and the aromatic layer of the biochar increases the binding rate between the biochar and the halogen-free flame retardant, improving the dispersion of the flame retardant in the system and achieving a better flame retardant effect.

[0031] Introducing silicone into the system can optimize the viscosity of the foaming resin and the generation of bubbles, allowing the foaming agent to be dispersed throughout the emulsified system, thereby promoting bubble formation. Silicone acts as a bubble nucleating agent, reducing the free energy during nucleation and promoting the formation of foam pores. This promotes the formation of closed cells during the foaming process and improves the foam's microstructure.

[0032] The present invention utilizes boric acid-modified phenolic resin to synthesize a phenolic resin with a flexible boron-oxygen bond, and physically blends it with an iron-silicon modified biochar flame retardant to improve the surface tension of the resin; the iron-silicon modified biochar synergistic halogen-free flame retardant is added to the boron-modified phenolic resin for foaming. At high temperatures, organic silicon and boron will form a glass layer, which together with the carbon layer can effectively prevent the release of polluting gases, while reducing the foam pulverization rate and improving the flame retardancy of the foam.

[0033] Example 1

[0034] A method for preparing an iron-silicon modified biochar flame retardant comprises the following steps:

[0035] Step 1: hydrolyze the straw powder in a hydrothermal reactor at 220°C for 7 hours, filter under reduced pressure, wash with ethanol and deionized water, and dry at 80°C for 12 hours to obtain biochar;

[0036] Step 2: 1 g of biochar was mixed with 30 ml of ferrous sulfate solution (0.1 mol / L) prepared with deionized water and shaken for 6 h, filtered under reduced pressure, and dried at 105 °C for 6 h to obtain iron-modified biochar;

[0037] Step 3: Blend the iron-modified biochar, organosilicon and halogen-free flame retardant in a mass ratio of 1:10:1 to obtain an iron-silicon modified biochar flame retardant.

[0038] A method for preparing an iron-silicon modified biochar flame retardant modified phenolic foam prepared by the above method comprises the following steps:

[0039] Step 1, synthesis of resol phenolic resin: adding an alkaline catalyst to melted phenol, blending and stirring uniformly, then adding paraformaldehyde in batches at a uniform speed, reacting at a temperature of 60° C. for 3 h and at 70° C. for 2 h to obtain resol phenolic resin.

[0040] Step 2: Synthesis of boron-modified phenolic resin: Cool the temperature to 60°C, add the prepared boric acid solution (phenolic resin: boric acid: ethanol = 10:1:10) using a dropping funnel, and react at a constant temperature for 4 hours. Use rotary evaporation to control the resin solid content at 60% to obtain boron-modified phenolic resin.

[0041] Step 3: Blend 100 parts of boron phenolic resin, 10 parts of iron-silicon modified biochar flame retardant, 8 parts of n-pentane, 15 parts of curing agent, and 3 parts of surfactant by mass, and foam and cure at 60°C for 30 minutes to obtain silicon-modified biochar flame-retardant phenolic foam. The material properties are shown in Appendix 1.

[0042] Example 2

[0043] A method for preparing an iron-silicon modified biochar flame retardant comprises the following steps:

[0044] Step 1: hydrolyze the straw powder in a hydrothermal reactor at 220°C for 7 hours, filter under reduced pressure, wash with ethanol and deionized water, and dry at 80°C for 12 hours to obtain biochar;

[0045] Step 2: 1 g of biochar was mixed with 30 ml of ferrous sulfate solution (0.1 mol / L) prepared with deionized water and shaken for 6 h, filtered under reduced pressure, and dried at 105 °C for 6 h to obtain iron-modified biochar;

[0046] Step 3: Blend the iron-modified biochar, organosilicon and halogen-free flame retardant in a mass ratio of 1:10:2 to obtain an iron-silicon modified biochar flame retardant.

[0047] A method for preparing an iron-silicon modified biochar flame retardant modified phenolic foam prepared by the above method comprises the following steps:

[0048] Step 1, synthesizing resol phenolic resin: adding an alkaline catalyst to melted phenol, blending and stirring uniformly, then adding paraformaldehyde in batches at a uniform rate, reacting at a temperature of 60° C. for 3 hours and at 70° C. for 2 hours to obtain resol phenolic resin;

[0049] Step 2: Synthesis of boron-modified phenolic resin: Cool the temperature to 60°C, add the prepared boric acid solution (phenolic resin: boric acid: ethanol = 10:1:10) using a dropping funnel, and react at a constant temperature for 4 hours. Use rotary evaporation to control the resin solid content at 60% to obtain boron-modified phenolic resin.

[0050] Step 3: Blend 100 parts of boron phenolic resin, 10 parts of iron-silicon modified biochar flame retardant, 8 parts of n-pentane, 15 parts of curing agent, and 3 parts of surfactant by mass, and foam and cure at 60°C for 30 minutes to obtain silicon-modified biochar flame-retardant phenolic foam. The material properties are shown in Appendix 1.

[0051] Example 3

[0052] A method for preparing an iron-silicon modified biochar flame retardant comprises the following steps:

[0053] Step 1: hydrolyze the straw powder in a hydrothermal reactor at 220°C for 7 hours, filter under reduced pressure, wash with ethanol and deionized water, and dry at 80°C for 12 hours to obtain biochar;

[0054] Step 2: 1 g of biochar was mixed with 30 ml of ferrous sulfate solution (0.1 mol / L) prepared with deionized water and shaken for 6 h, filtered under reduced pressure, and dried at 105 °C for 6 h to obtain iron-modified biochar;

[0055] Step 3: Blend the iron-modified biochar, organosilicon and halogen-free flame retardant in a mass ratio of 1:10:3 to obtain an iron-silicon modified biochar flame retardant.

[0056] A method for preparing an iron-silicon modified biochar flame retardant modified phenolic foam prepared by the above method comprises the following steps:

[0057] Step 1, synthesizing resol phenolic resin: adding an alkaline catalyst to melted phenol, blending and stirring uniformly, then adding paraformaldehyde in batches at a uniform rate, reacting at a temperature of 60° C. for 3 hours and at 70° C. for 2 hours to obtain resol phenolic resin;

[0058] Step 2: Synthesis of boron-modified phenolic resin: Cool the temperature to 60°C, add the prepared boric acid solution (phenolic resin: boric acid: ethanol = 10:1:10) using a dropping funnel, and react at a constant temperature for 4 hours. Use rotary evaporation to control the resin solid content at 60% to obtain boron-modified phenolic resin.

[0059] Step 3: Blend 100 parts of boron phenolic resin, 10 parts of iron-silicon modified biochar flame retardant, 8 parts of n-pentane, 15 parts of curing agent, and 3 parts of surfactant by mass, and foam and cure at 60°C for 30 minutes to obtain silicon-modified biochar flame-retardant phenolic foam. The material properties are shown in Appendix 1.

[0060] Example 4

[0061] A method for preparing an iron-silicon modified biochar flame retardant comprises the following steps:

[0062] Step 1: hydrolyze the straw powder in a hydrothermal reactor at 220°C for 7 hours, filter under reduced pressure, wash with ethanol and deionized water, and dry at 80°C for 12 hours to obtain biochar;

[0063] Step 2: 1 g of biochar was mixed with 30 ml of ferrous sulfate solution (0.1 mol / L) prepared with deionized water and shaken for 6 h, filtered under reduced pressure, and dried at 105 °C for 6 h to obtain iron-modified biochar;

[0064] Step 3: Blend the iron-modified biochar, organosilicon and halogen-free flame retardant in a mass ratio of 1:10:4 to obtain an iron-silicon modified biochar flame retardant.

[0065] A method for preparing an iron-silicon modified biochar flame retardant modified phenolic foam prepared by the above method comprises the following steps:

[0066] Step 1, synthesizing resol phenolic resin: adding an alkaline catalyst to melted phenol, blending and stirring uniformly, then adding paraformaldehyde in batches at a uniform rate, reacting at a temperature of 60° C. for 3 hours and at 70° C. for 2 hours to obtain resol phenolic resin;

[0067] Step 2, synthesis of boron-modified phenolic resin: the temperature was lowered to 60°C, and a boric acid solution (phenolic resin: boric acid: ethanol = 10:1:10) was added dropwise using a dropping funnel, and the reaction was carried out at a constant temperature for 4 hours. The solid content of the resin was controlled at 60% by rotary evaporation to obtain a boron-modified phenolic resin;

[0068] Step 3: Blend 100 parts of boron phenolic resin, 10 parts of iron-silicon modified biochar flame retardant, 8 parts of n-pentane, 15 parts of curing agent, and 3 parts of surfactant by mass, and foam and cure at 60°C for 30 minutes to obtain silicon-modified biochar flame-retardant phenolic foam. The material properties are shown in Appendix 1.

[0069] Example 5

[0070] A method for preparing an iron-silicon modified biochar flame retardant comprises the following steps:

[0071] Step 1: hydrolyze the straw powder in a hydrothermal reactor at 220°C for 7 hours, filter under reduced pressure, wash with ethanol and deionized water, and dry at 80°C for 12 hours to obtain biochar;

[0072] Step 2: 1 g of biochar was mixed with 30 ml of ferrous sulfate solution (0.1 mol / L) prepared with deionized water and shaken for 6 h, filtered under reduced pressure, and dried at 105 °C for 6 h to obtain iron-modified biochar;

[0073] Step 3: Blend the iron-modified biochar, organosilicon and halogen-free flame retardant in a mass ratio of 1:10:5 to obtain an iron-silicon modified biochar flame retardant.

[0074] A method for preparing an iron-silicon modified biochar flame retardant modified phenolic foam prepared by the above method comprises the following steps:

[0075] Step 1, synthesizing resol phenolic resin: adding an alkaline catalyst to melted phenol, blending and stirring uniformly, then adding paraformaldehyde in batches at a uniform rate, reacting at a temperature of 60° C. for 3 hours and at 70° C. for 2 hours to obtain resol phenolic resin;

[0076] Step 2, synthesis of boron-modified phenolic resin: the temperature was lowered to 60°C, and a boric acid solution (phenolic resin: boric acid: ethanol = 10:1:10) was added dropwise using a dropping funnel, and the reaction was carried out at a constant temperature for 4 hours. The solid content of the resin was controlled at 60% by rotary evaporation to obtain a boron-modified phenolic resin;

[0077] Step 3: Blend 100 parts of boron phenolic resin, 10 parts of iron-silicon modified biochar flame retardant, 8 parts of n-pentane, 15 parts of curing agent, and 3 parts of surfactant by mass, and foam and cure at 60°C for 30 minutes to obtain silicon-modified biochar flame-retardant phenolic foam. The material properties are shown in Appendix 1.

[0078] Example 6

[0079] A method for preparing an iron-silicon modified biochar flame retardant comprises the following steps:

[0080] Step 1: hydrolyze the straw powder in a hydrothermal reactor at 220°C for 7 hours, filter under reduced pressure, wash with ethanol and deionized water, and dry at 80°C for 12 hours to obtain biochar;

[0081] Step 2: 1 g of biochar was mixed with 30 ml of ferrous sulfate solution (0.1 mol / L) prepared with deionized water and shaken for 6 h, filtered under reduced pressure, and dried at 105 °C for 6 h to obtain iron-modified biochar;

[0082] Step 3: Blend the iron-modified biochar, organosilicon and halogen-free flame retardant in a mass ratio of 1:10:6 to obtain an iron-silicon modified biochar flame retardant.

[0083] A method for preparing an iron-silicon modified biochar flame retardant modified phenolic foam prepared by the above method comprises the following steps:

[0084] Step 1, synthesizing resol phenolic resin: adding an alkaline catalyst to melted phenol, blending and stirring uniformly, then adding paraformaldehyde in batches at a uniform rate, reacting at a temperature of 60° C. for 3 hours and at 70° C. for 2 hours to obtain resol phenolic resin;

[0085] Step 2: Synthesis of boron-modified phenolic resin: Cool the temperature to 60°C, add the prepared boric acid solution (phenolic resin: boric acid: ethanol = 10:1:10) using a dropping funnel, and react at a constant temperature for 4 hours. Use rotary evaporation to control the resin solid content at 60% to obtain boron-modified phenolic resin.

[0086] Step 3: Blend 100 parts of boron phenolic resin, 10 parts of iron-silicon modified biochar flame retardant, 8 parts of n-pentane, 15 parts of curing agent, and 3 parts of surfactant by mass, and foam and cure at 60°C for 30 minutes to obtain silicon-modified biochar flame-retardant phenolic foam. The material properties are shown in Appendix 1.

[0087] Comparative Example 1

[0088] By mass, 100 parts of phenolic resin, 8 parts of n-pentane, 15 parts of curing agent, and 3 parts of surfactant were stirred at a rate of 1000 r / min for 3 minutes and then poured into a preheated foaming mold. The mold was foamed in an oven at 60°C for 60 minutes to obtain phenolic foam. The material properties are shown in Table 1.

[0089] Comparative Example 2

[0090] By mass, 100 parts of boron-modified phenolic resin, 8 parts of n-pentane, 15 parts of curing agent, and 3 parts of surfactant were stirred at a rate of 1000 r / min for 3 minutes and then poured into a preheated foaming mold. The mold was foamed in an oven at 60°C for 60 minutes to obtain boron phenolic foam. The material properties are shown in Table 1.

[0091] Comparative Example 3

[0092] According to mass, 100 parts of boron-modified phenolic resin, 8 parts of n-pentane, 15 parts of curing agent, 3 parts of surfactant, and 10 parts of silicone were stirred at a rate of 1000 r / min for 3 minutes and then poured into a preheated foaming mold. The mold was foamed in an oven at 60°C for 60 minutes to obtain silicon-modified boron phenolic foam. The material properties are shown in Table 1.

[0093] Comparative Example 4

[0094] By mass, 100 parts of boron-modified phenolic resin, 8 parts of n-pentane, 15 parts of curing agent, 3 parts of surfactant, 10 parts of silicone, and 4 parts of flame retardant were stirred at a rate of 1000 r / min for 3 minutes and then poured into a preheated foaming mold. The mold was foamed in an oven at 60°C for 60 minutes to obtain silicon-modified boron phenolic flame retardant foam. The material properties are shown in Table 1.

[0095] As can be seen from Appendix 1, the present invention prepares a silicon-modified biochar flame-retardant phenolic foam material with smaller pores, more uniform pore distribution, reduced slag drop rate, increased limiting oxygen index, improved flame retardancy, and improved smoke suppression.

[0096] Table 1 Properties of different formulations of silicon-modified biochar synergistically used in CR-741 flame-retardant phenolic foam

[0097]

[0098] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing an iron-silicon modified biochar flame retardant modified phenolic foam, characterized in that: The preparation method of the iron-silicon modified biochar flame retardant comprises the following steps: Step 1: hydrolyzing the straw powder, washing and drying it to obtain biochar; Step 2: mixing the biochar and ferrous sulfate solution, shaking, filtering and drying to obtain iron-modified biochar; Step 3: Blending iron-modified biochar, organosilicon and halogen-free flame retardant to obtain iron-silicon modified biochar flame retardant; the mass ratio of the iron-modified biochar, organosilicon and halogen-free flame retardant is (1-5): (10-20): (1-10); the halogen-free flame retardant includes one or more of triethyl phosphate, bisphenol A diphosphate, diethyl aluminum phosphinate, triphenyl phosphate, triphenol phosphate, and bisphenol A-bis(diphenyl phosphate); The preparation method of the iron-silicon modified biochar flame retardant modified phenolic foam comprises the following steps: Step 1: adding an alkaline catalyst to melted phenol, stirring evenly, then adding paraformaldehyde in batches at a uniform rate and reacting at a temperature of 60-70° C. for 1-3 hours, then heating to 70-80° C. and reacting for 2-3 hours to obtain a resol resin; Step 2: Cooling the temperature to 60-70° C., adding a boric acid solution dropwise to the resol phenolic resin for a constant temperature reaction for 4-8 hours, and controlling the resin solid content at 60%-70% by rotary evaporation to obtain a boron-modified phenolic resin; Step 3: blend the boron-modified phenolic resin, the iron-silicon-modified biochar flame retardant and the foaming aid, and perform foaming treatment to obtain the silicon-modified biochar flame-retardant phenolic foam.

2. The preparation method according to claim 1, wherein: The straw powder is a combination of one or more of corn straw powder, wheat straw powder, peanut shell powder and rice straw powder.

3. The preparation method according to claim 1, wherein: The organosilicon is one or more of methyl vinyl silicone oil, methyl phenyl silicone oil, cyanide-containing silicone oil, octamethylcyclotetrasiloxane, and dihydroxy-polydimethyldiphenylsiloxane.

4. The preparation method according to claim 1, wherein: The molar ratio of the aldehyde group in the paraformaldehyde to the phenol group in the phenol is 1:1.5 to 1:2.

0.

5. The preparation method according to claim 1, wherein: The alkaline catalyst includes one or more of potassium hydroxide, sodium hydroxide, and barium hydroxide.

6. The preparation method according to claim 1, wherein: The boric acid accounts for 3-10% of the mass of the resol phenolic resin; the solvent of the boric acid solution is a combination of one or more of methanol, ethanol, and isopropanol; the boric acid accounts for 3-10% of the mass of the solvent.

7. The preparation method according to claim 1, wherein: The foaming aid includes a foaming agent, a curing agent and a surfactant; the mass ratio of the boron-modified phenolic resin, the iron-silicon modified biochar flame retardant, the foaming agent, the curing agent and the surfactant is 100:6-10:5-20:8-20:1-8.

8. The preparation method according to claim 1, wherein: The temperature of the foaming treatment is 60-80° C., and the time is 10-120 minutes.

Images