CN111548532B - Biomass intumescent flame retardant, preparation method and special device thereof - Google Patents

Abstract

The invention discloses a biomass intumescent flame retardant, a preparation method and a special device thereof, and belongs to the technical field of flame retardant preparation. The flame retardant has a core-shell structure with ammonium polyphosphate as the core and aminated lignin as the shell. The cross-linked structure of melamine. The preparation method is as follows: firstly, the lignin is subjected to phenolic modification, and then the phenolic lignin is subjected to Mannich reaction with melamine and formaldehyde to obtain the phenolated-aminated lignin, and then the phenolic-aminated lignin is combined with the polyamide. The ammonium phosphate reacts to obtain the flame retardant. Its special device adopts a two-stage control system, including a lignin purification system, a lignin phenolization system, a mixture preparation system, a flame retardant synthesis system, and their respective controllers and overall controllers. The invention converts the lignin into an intumescent flame retardant with high economic benefit, and has the advantages of easy availability of raw materials, safe operation and easy reaction.

Description

Biomass intumescent flame retardant and its preparation method and special device

technical field

The invention belongs to the technical field of preparation of flame retardants, and in particular relates to a biomass intumescent flame retardant, a preparation method and a special device thereof.

Background technique

At present, most of the flame retardants used in China are halogen-based flame retardants, but they will emit hydrogen halide gas and thick smoke in the case of high temperature and open fire. According to the survey: the human body suffocation caused by the hydrogen halide gas produced by the combustion of halogen is the most direct cause of casualties in building fires. In addition, most halogen-based flame retardants (especially polybrominated phenyl ethers) can be decomposed to produce extractable organic compounds (EOX), which can be enriched in the human body in various ways, which is extremely harmful to human health. Therefore, the development of an environmentally friendly and efficient halogen-free flame retardant is imminent.

As one of the most abundant natural polymers in nature, lignin has few practical applications, while flame retardants have broad application prospects as a high value-added product of lignin. Chinese Patent No. 2011100078002, published on July 18, 2012, discloses a method for preparing a biomass-based flame retardant. The catalyst is subjected to the first contact reaction for 1 to 4 hours, and then starch is added for the second contact reaction to obtain the modified lignin; (2) at 100 to 180° C., phosphoric acid and pentaerythritol are subjected to the third contact reaction for 0.5 to 5 hours, and the Polyether polyol, ammonium polyphosphate and melamine are added to the product obtained by the third contact reaction, and the fourth contact reaction is performed at 100-180° C. for 0.5-4 hours to obtain a flame retardant. The flame retardant can bring certain flame retardant properties to the matrix, but it can only be used in polyurethane foams, and has great limitations.

Yin Weida (Molecular Construction of Intumescent Flame Retardants and Research on Flame Retardant Polylactic Acid [D]. Harbin Institute of Technology. 2018.) mentioned in the paper the method of flame retardant treatment of polylactic acid, which uses the Mannich reaction to The lignin is modified with melamine, then compounded and mixed with ammonium polyphosphate, and the mixture is melt-blended with polylactic acid to obtain a flame-retardant polylactic acid material. Liu Yun et al. (Research on MCA Synergistic Intumescent Flame Retardant LDPE Foam [J]. Modern Plastics Processing and Application, 2016, 28(4): 19-22.) Using lignin as carbon source, ammonium polyphosphate as acid source and Gas source and melamine urate are synergistic flame retardants, and low density polyethylene is used as matrix material. The intumescent flame retardant low density polyethylene foam material is prepared by blending, plasticizing and hot pressing method. Although the above-mentioned prior art has expanded the application scope of lignin-based flame retardants, ammonium polyphosphate has disadvantages such as poor compatibility with the polymer matrix, poor water resistance, and easy agglomeration, resulting in its easy precipitation in practical applications, In addition, as an additive flame retardant, each component is only physically mixed and added. It is easier to migrate when mixed, resulting in a rapid decline in the flame retardant properties and mechanical properties of the material, which greatly limits the application of the entire intumescent flame retardant system in applications with higher flame retardant performance requirements.

SUMMARY OF THE INVENTION

In view of the above problems existing in the prior art, the purpose of the present invention is to provide a biomass intumescent flame retardant, another purpose of the present invention is to provide a preparation method of the flame retardant, and another purpose of the present invention is to provide the preparation method of the flame retardant. Method specific device.

In order to solve the above problems, the technical scheme adopted in the present invention is as follows:

A biomass intumescent flame retardant has a core-shell structure with ammonium polyphosphate as the core and aminated lignin as the shell. The cross-linked structure of melamine attached to the ortho-carbon of the phenolic hydroxyl group.

A method for preparing a biomass intumescent flame retardant. First, lignin is subjected to phenolic modification to obtain phenolic lignin, and then the phenolic lignin is subjected to Mannich reaction with melamine and formaldehyde to obtain phenolated-amine. The biomass intumescent flame retardant is obtained by reacting the phenolic-aminated lignin with ammonium polyphosphate.

The specific reaction steps are:

Step 1, mix lignin and sulfuric acid solution, stir at 75-85 ° C for 1-2 h, then increase the temperature to 90-100 ° C, add phenol, stir for 1-2 h, cool, wash and dry to obtain phenolic lignin;

In step 2, the ammonium polyphosphate and the ethanol aqueous solution are mixed and stirred for 30 to 60 minutes, then melamine is added, the temperature is raised to 65 to 75° C. and stirred for 5.5 to 6.5 hours, and the mixture is washed and dried after cooling to obtain a mixture of melamine and ammonium polyphosphate;

Step 3, disperse the mixture of phenolic lignin, melamine and ammonium polyphosphate into N,N-dimethylformamide, heat up and stir, add formaldehyde solution when heated to 70～80℃, react for 2.5～3.5h, cool down After washing and drying, the biomass intumescent flame retardant is obtained.

Preferably, the mass ratio of ammonium polyphosphate to melamine is (1-1.4):1.

Preferably, the mass ratio of the phenolic lignin to the mixture of melamine and ammonium polyphosphate is 1:(4-6).

Preferably, the mass ratio of phenolic lignin to formaldehyde is 1:(0.6-0.8).

Preferably, the lignin is enzymatically hydrolyzed lignin.

Preferably, in step 1, the concentration of the sulfuric acid solution is 1.5-2.5 mol/L.

Preferably, in step 2, the volume ratio of ethanol to water in the ethanol aqueous solution is (2-3):1.

A special device for the aforementioned preparation method, comprising a lignin purification system, a lignin phenolization system, a mixture preparation system and a flame retardant synthesis system,

In the lignin purification system, the discharge ports of the enzymatic lignin storage tank and the sodium hydroxide solution storage tank are connected to the first reactor, the discharge port of the first reactor is connected to the first filter, and the hydrochloric acid is stored The discharge port of the tank, the distilled water storage tank and the first reactor is connected with the pH adjustment tank, the discharge port of the pH adjustment tank is respectively connected with the first waste storage tank and the first drying tank, and the discharge port of the first drying tank is connected with the first waste storage tank and the first drying tank. the second reactor is connected;

In the lignin phenolization system, the discharge ports of the sulfuric acid storage tank and the phenol storage tank are connected to the second reactor, the discharge ports of the second reactor and the ether storage tank are connected to the second flushing device, and the ether recovery device are respectively connected with the second washing device and the second dryer, the discharge port of the second washing device is connected with the second dryer, and the discharge port of the second dryer is connected with the third reactor;

In the mixture preparation system, the discharge ports of the melamine storage tank and the ammonium polyphosphate storage tank are connected to the fourth reactor, and the discharge ports of the ethanol aqueous solution storage tank are respectively connected to the fourth reactor and the fourth flushing device. The outlet of the fourth reactor is connected to the fourth flushing device, the outlet of the fourth flushing device is connected to the fourth filter, the outlet of the fourth filter is connected to the fourth dryer, and the feed of the ethanol recovery tank The port is connected with the fourth dryer, the discharge port is connected with the fourth filter, and the discharge port of the fourth dryer is connected with the third reactor;

In the flame retardant synthesis system, the discharge ports of the solvent storage tank, the formaldehyde storage tank and the distilled water storage tank are connected to the third reactor, the discharge port of the third reactor is connected to the third filter, and the third filter The discharge port of the dryer is connected with the third dryer, and the discharge port of the third dryer is connected with the flame retardant storage tank.

Compared with the prior art, the beneficial effects of the present invention are:

The preparation method of the invention converts the lignin into an intumescent flame retardant with high economic benefit, and has the advantages of easy availability of raw materials, safe operation and easy reaction. The obtained flame retardant has a core-shell structure, and the outer bag material plays a role in isolating and protecting the internal ammonium polyphosphate, which solves the defects of the ammonium polyphosphate itself. When used in epoxy resin, the flame retardant performance and water resistance of the material are improved. have been greatly improved.

The special intelligent equipment of the present invention has a compact structure and adopts a two-stage control system, which is conducive to the accurate control of the reaction process. The stirring equipment contains a solenoid valve, which can realize the switching between stirring and reflux stirring, which is conducive to the progress of the reaction, and the waste is stored in the waste. In the storage tank, it can be reused after further recycling, which is suitable for industrialization and application.

Description of drawings

Fig. 1 is the process flow schematic diagram of the flame retardant of the present invention;

Fig. 2 is the structural representation of the flame retardant of the present invention;

Fig. 3 (a) is the X-ray photoelectron spectrogram of melamine, and Fig. 3 (b) is the X-ray photoelectron spectrogram of the intumescent flame retardant obtained in Example 1;

Fig. 4(a) is a photograph of the morphology of ammonium polyphosphate, and Fig. 4(b) is a photograph of the morphology of the intumescent flame retardant obtained in Example 1;

Fig. 5 is the schematic diagram of the special preparation device of the flame retardant of the present invention;

In Fig. 5: 11, storage tank for enzymatic hydrolysis of lignin; 12, storage tank for sodium hydroxide solution; 13, first reactor; 14, storage tank for hydrochloric acid; 15, first filter; 16, storage tank for distilled water; 17, pH adjustment tank; 18, the first waste storage tank; 19, the first drying tank; 21, the sulfuric acid storage tank; 22, the phenol storage tank; 23, the second reactor; 24, the ether storage tank; 25, the second flushing device 26, ether recovery device; 27, second dryer; 31, solvent storage tank; 32, formaldehyde storage tank; 33, distilled water storage tank; 34, third reactor; 35, third filter; 36, third dryer; 37, flame retardant storage tank; 41, melamine storage tank; 42, ammonium polyphosphate storage tank; 43, ethanol aqueous solution storage tank; 44, fourth reactor; 45, fourth flushing device; 46, fourth Filter: 47, ethanol recovery tank; 48, fourth dryer; C1, first controller; C2, second controller; C3, third controller; C4, fourth controller; C0, overall controller.

Detailed ways

The present invention will be further described below with reference to specific embodiments.

The raw materials used in the following examples are:

Enzymatically hydrolyzed lignin was purchased from Jinzhou Lingyu Chemical Co., Ltd., and the lignin content was 70-80%;

Epoxy resin was purchased from Nantong Xingchen Synthetic Materials Co., Ltd., and its brand name is E51;

The rest of the raw materials are commercially available analytical grades.

The test instruments used are:

The XPS analysis uses an X-ray photoelectron spectrometer model AXIS Ultra DLD;

The surface morphology of the material was analyzed by a Japanese JSM-7600F field emission electron microscope;

Thermogravimetric analysis was performed using Shimadzu DTG-60AH thermogravimetric analyzer;

The flame retardant performance test adopts HC-2 oxygen index instrument;

The combustion performance test adopts the FTT2000 cone calorimeter of the British FTT Company.

Example 1

A preparation method of biomass intumescent flame retardant, with reference to Fig. 1, comprises the following steps:

(1) Purification of lignin

Mix 20 g of enzymatically hydrolyzed lignin with 200 mL of 10 wt% sodium hydroxide solution, raise the temperature to 75 °C and fully stir for 1 h, then filter to remove undissolved precipitates, and adjust the pH of the resulting solution to 3.0-4.0 by adding 10% vol hydrochloric acid dropwise to make the solution. After the lignin was completely precipitated, the precipitate was washed three times with distilled water until the washing water became neutral. The washed lignin was dried under reduced pressure at 80 °C until there was no change in weight, and the product was labeled as Lig-O.

(2) Phenolic modification of lignin

10 g of Lig-O was mixed with 70 mL of H ₂ SO ₄ solution (2 mol/L), followed by stirring at 80° C. for 1.5 h. After the stirring was completed, the temperature was raised to 95° C., and 18 g of phenol was added, followed by stirring for another 1.5 h. After the reaction was completed, after the solution was cooled to room temperature, diethyl ether and distilled water were added for washing 3 times, and then the obtained modified product was dried to constant weight, and the product was marked as Lig-pH.

(3) Preparation of ammonium polyphosphate and melamine mixture

Prepare 1L of ethanol aqueous solution (V ethanol:V water=5:2) for use. 6 g of ammonium polyphosphate (APP) and 140 mL of ethanol aqueous solution were mixed and added to a stirrer, and stirred at room temperature for 30 min. After the ammonium polyphosphate was dispersed, 5 g of melamine (MEL) was added, the temperature was raised to 70° C., and the mixture was refluxed and stirred for 6 hours. After the stirring was completed, after the solution was cooled to room temperature, 500 mL of ethanol solution was added, the solid was washed three times, filtered, and the washed solid was placed in a vacuum drying oven at 70 °C for 12 h.

(4) Synthesis of intumescent flame retardants

Add 4g phenolic lignin (Lig-pH) and a mixture of 20g melamine and ammonium polyphosphate into the reactor, and add 100mL N,N-dimethylformamide (DMF), put it in an oil bath and stir and heat . When the temperature reached 75° C., 7.5 g of formaldehyde solution (40% by mass) was added, and the mixture was stirred and refluxed for 3 h to carry out the Mannich reaction. After the reaction was completed, after the solution was cooled to room temperature, 500 mL of distilled water was added, stirred for 5 minutes, and then filtered. The obtained solid was dried in a vacuum drying box at 70° C. for 24 hours to obtain a biomass intumescent flame retardant with a yield of 54.5%.

The element composition and valence state of the prepared flame retardant were analyzed, as shown in Figure 3. Wherein, Figure 3(a) is the X-ray photoelectron spectrum of melamine, and Figure 3(b) is the X-ray photoelectron spectrum of the obtained intumescent flame retardant. The peak at 401.2 eV in the figure is the peak of NH ₄ ⁺ in APP, indicating that after the Mannich reaction, phenolated-aminated lignin may coat APP.

The samples were sprayed with gold to improve their electrical conductivity. The surface morphology of the ammonium polyphosphate and the prepared flame retardant was observed using a field emission electron microscope with an accelerating voltage of 15 kV, as shown in Figure 4. Among them, Figure 4(a) is a picture of the morphology of ammonium polyphosphate, and Figure 4(b) is a picture of the morphology of the obtained intumescent flame retardant. It can be seen from the picture that APP is a columnar structure with a size of about 10um. smooth. After the Mannich reaction, the size of the particles in the figure is about 10um, which can be concluded to be APP, but the surface has become rough, and many small particles are attached to the surface, which indicates that after the Mannich reaction, the phenolic-aminated wood The element covers the APP without changing the shape of the APP.

Combined with the topographic map and XPS map, it can be proved that APP was successfully coated by the phenolated-aminated lignin after the Mannich reaction to form a core-shell structure. The schematic diagram of the structure of the flame retardant is shown in Figure 2.

Thermogravimetric analysis of the flame retardant was carried out. The protective gas and the purging gas were nitrogen, the gas flow rate was 50 mL/min, the heating rate was 15 °C/min, and the temperature at which the maximum decomposition rate was measured was 382 °C. was 37.5%.

Apply this to epoxy, when added at 10%:

Passed the UL-94 vertical combustion test, and the test level reached V-0 level;

The spline size is 100mm×6.5mm×3.2mm, according to the ATSM D2863 standard, the limit oxygen index of the spline is 36.1%;

The size of the spline is 100mm×100mm×3.2mm. According to the ISO 5660-1 standard, the samples are placed on a cone calorimeter for testing, each sample is wrapped with aluminum foil, the heat flux is 50kW/m ² , and the total smoke emission is 9.9m ² /m ² , the total heat release is 53.1MJ/m ² .

The splines with a thickness of 3.2mm were placed in a constant temperature water bath at 70°C, taken out after 168 hours, dried at 120°C for 3 hours, cooled to room temperature, and tested for flame retardant properties. The vertical combustion test level is still V-0, and the limiting oxygen index was 33.7%.

Example 2

A preparation method of biomass intumescent flame retardant, with reference to Fig. 1, comprises the following steps:

(1) Purification of lignin

Mix 20g of enzymatically hydrolyzed lignin with 200mL of 10wt% sodium hydroxide solution, heat up to 70°C and stir well for 1.5h, then filter to remove undissolved precipitates, and the obtained solution is adjusted by dropwise addition of 10%vol hydrochloric acid to pH=3.0～4.0, After the lignin was completely precipitated, the precipitate was washed 5 times with distilled water until the washing water became neutral. The product was dried under reduced pressure at 75°C until there was no change in weight, designated Lig-O.

(2) Phenolic modification of lignin

10 g of Lig-O was mixed with 70 mL of H ₂ SO ₄ solution (2 mol/L), followed by stirring at 75° C. for 2 h. After the stirring was completed, the temperature was raised to 90° C., and 25 g of phenol was added, followed by stirring for another 1.5 h. After the reaction was completed, after the solution was cooled to room temperature, diethyl ether and distilled water were added for washing 3 times, and then the obtained modified product was dried to constant weight, which was marked as Lig-pH.

(3) Preparation of ammonium polyphosphate and melamine mixture

Prepare 1L ethanol aqueous solution (V ethanol:V water=5:2). 6 g of ammonium polyphosphate and 140 mL of ethanol aqueous solution were mixed and added to the stirrer, and stirred at room temperature for 1 h. After the ammonium polyphosphate was dispersed, 4.5 g of melamine was added, the temperature was raised to 65°C, and the mixture was refluxed and stirred for 5.5 hours. After the stirring was completed, after the solution was cooled to room temperature, 500 mL of ethanol solution was added, the solid was washed 3 times, filtered, and the washed solid was placed in a vacuum drying oven at 75 °C for 10 h.

(4) Synthesis of intumescent flame retardants

A mixture of 6 g of phenolic lignin (Lig-pH) and 25 g of melamine and ammonium polyphosphate was added to the reactor, and 150 mL of DMF was added, and the mixture was stirred and heated in an oil bath. When the temperature reached 80° C., 9 g of formaldehyde solution (mass fraction 40%) was added, and the mixture was stirred and refluxed for 2.5 h. After the reaction was completed, after the solution was cooled to room temperature, 500 mL of distilled water was added, stirred for 5 minutes, and then filtered. After repeating 3 times, the obtained solid was placed in a vacuum drying box to be dried at 75° C. for 10 hours to obtain a biomass intumescent flame retardant with a yield of 52.3%.

Thermogravimetric analysis of the flame retardant was carried out, the protective gas and purge gas were nitrogen, the gas flow rate was 50 mL/min, the heating rate was 15 °C/min, the temperature at which the maximum decomposition rate was measured was 373 °C, and the carbon residue rate at 800 °C was was 36.1%.

Apply this to epoxy, when added at 13%:

Passed the UL-94 vertical combustion test, and the test level reached V-0 level;

The spline size is 100mm×6.5mm×3.2mm, according to the ATSM D2863 standard, the measured limit oxygen index is 35.7%;

The size of the spline is 100mm×100mm×3.2mm. According to the ISO 5660-1 standard, the samples are placed on a cone calorimeter for testing, each sample is wrapped with aluminum foil, the heat flux is 50kW/m ² , and the total smoke emission is 10.3m ² /m ² , the total heat release is 54.2MJ/m ² .

The splines with a thickness of 3.2mm were placed in a constant temperature water bath at 70°C, taken out after 168 hours, dried at 120°C for 3 hours, cooled to room temperature, and tested for flame retardant properties. The vertical combustion test level is still V-0, and the limiting oxygen index was 33.5%.

Example 3

The special intelligent device using the above preparation method, as shown in Figure 5, includes a lignin purification system, a lignin phenolization system, a preparation system for ammonium polyphosphate and melamine mixture, a flame retardant synthesis system, and a first controller C1, The second controller C2, the third controller C3, the fourth controller C4 and the overall controller C0.

Wherein, the lignin purification system includes: the discharge ports of the enzymatic lignin storage tank 11 and the sodium hydroxide solution storage tank 12 are connected to the first reactor 13 , and the discharge port of the first reactor 13 is connected to the first filter 15 Connected, the discharge ports of the hydrochloric acid storage tank 14, the distilled water storage tank 16 and the first reactor 15 are connected with the pH adjustment tank 17, and the discharge ports of the pH adjustment tank 17 are respectively connected with the first waste storage tank 18 and the first drying tank 19 The outlet of the first drying tank 19 is connected to the second reactor 23 .

The lignin phenolization system includes: the discharge ports of the sulfuric acid storage tank 21 and the phenol storage tank 22 are connected with the second reactor 23, the discharge ports of the second reactor 23 and the ether storage tank 24 are connected with the second flushing device 25, The ether recovery device 26 is respectively connected with the second flushing device 25 and the second dryer 27, the outlet of the second flushing device 25 is connected with the second dryer 27, and the outlet of the second dryer 27 is connected with the third reactor 34 connected.

The ammonium polyphosphate and melamine mixture preparation system includes: the melamine storage tank 41 and the discharge port of the ammonium polyphosphate storage tank 42 are connected to the fourth reactor 44, and the discharge port of the ethanol aqueous solution storage tank 43 is respectively connected with the fourth reactor 44 and the fourth reactor 44. The fourth flushing device 45 is connected, the outlet of the fourth reactor 44 is connected to the fourth flushing device 45, the outlet of the fourth flushing device 45 is connected to the fourth filter 46, and the outlet of the fourth filter 46 is connected Connected to the fourth dryer 48, the feed port of the ethanol recovery tank 47 is connected to the fourth dryer 48, the discharge port is connected to the fourth filter 46, and the discharge port of the fourth dryer 48 is connected to the third reactor 34 connected.

The flame retardant synthesis system system includes: DMF storage tank 31, formaldehyde storage tank 32, and distilled water storage tank 33. The outlet is connected to the third reactor 34, and the outlet of the third reactor 34 is connected to the third filter 35. , the outlet of the third filter 35 is connected to the third dryer 36 , and the third dryer 36 is connected to the storage tank 37 of the flame retardant.

The main reaction of the device is carried out in each reactor, wherein the third reactor and the fourth reactor contain pipes connected by solenoid valves, which can realize free switching between stirring and reflux stirring. Each reactor and drying tank contain temperature sensors. It is beneficial to realize the temperature control with the heating device. The pH adjustment tank and the flushing tank both contain pH sensors, which are beneficial to realize the pH control. Each connecting pipeline is controlled by a solenoid valve, which is beneficial to realize the timing function. The solenoid valve and the device are connected with the controller of the corresponding system, the controllers at all levels are connected with the main controller, the operator only needs to operate the main controller, and the controllers are all PLC controllers.

The operation method of the device is as follows:

The enzymatic hydrolyzed lignin storage tank 11 and the sodium hydroxide solution storage tank 12 are extracted into the first reactor 13, the temperature is raised to 75 ° C and fully stirred for 1 hour, the product is extracted into the first filter 15 and filtered for 15 minutes, and the product after the filtration is completed Discharge into the pH adjustment tank 17, the hydrochloric acid storage tank 14 extracts the hydrochloric acid into the pH adjustment tank 17, adjusts the pH to 3-4, discharges the liquid into the first waste storage tank 18, and extracts distilled water from the distilled water storage tank 16. The remaining precipitation is washed until the pH is neutral, the liquid is discharged to the first waste storage tank 18, the solid is transported to the first drying tank 19, dried at 80°C for 30 minutes, and the solid is transported to the second reactor 23. The sulfuric acid storage tank 21 extracts sulfuric acid into the second reactor 23, and stirs it for 1.5 hours at 80 °C. After the stirring is completed, the temperature is raised to 95 °C. After that, the phenol in the phenol storage tank 22 flows into the second reactor 23, and is stirred for 1.5 hours. h, the product is discharged into the second flushing device 25, the ether is extracted from the ether storage tank 24 and the ether recovery device 26 for flushing 30min, the solution is discharged to the second dryer 27 after completion, and the liquid is recovered to the ether recovery device 26 , the solids are sent to the third reactor 34 .

The liquid in the ammonium polyphosphate storage tank 42 and the ethanol aqueous solution storage tank 43 was discharged into the fourth reactor 44, stirred at normal temperature for 30 min, and then the melamine storage tank 41 was discharged into the fourth reactor 44, the temperature was raised to 70 ° C, and the Solenoid valve, reflux stirring for 6h, after stirring, the product is discharged to the fourth flushing device 45, the ethanol aqueous solution is extracted from the ethanol aqueous solution storage tank 43 and washed for 30min, and the product is discharged to the fourth filter 46 for filtration, and the liquid is discharged into ethanol for recovery In the tank 47 , the solid is transported to the fourth dryer 48 , dried at 70° C. for 12 hours, the evaporated liquid is discharged into the ethanol recovery tank 47 for recovery, and the solid is transported to the third reactor 34 .

The solid in the second dryer 27, the fourth dryer 48 and the solution in the DMF storage tank 31 were added to the third reactor 34, heated and stirred, and when the temperature reached 75 °C, formaldehyde was extracted from the formaldehyde storage tank 32 and added to the third reactor. In the reactor 34, the solenoid valve is opened, and the reflux is stirred for 3 hours. After the reaction is completed, distilled water is drawn from the distilled water storage tank 33 and continues to be stirred for 5 minutes. After the reaction is completed, the product is discharged to the third filter 35 for filtration for 15 minutes. The third dryer 36 is dried at 70° C. for 24 hours, and the dried solids are transported to the flame retardant storage tank 37 .

Claims (7)

1. a preparation method of biomass intumescent flame retardant, is characterized in that, at first lignin is carried out phenolic modification, obtains phenolic lignin, then phenolic lignin is carried out Mannich reaction with melamine, formaldehyde , obtain phenolic-aminated lignin, and then react phenolic-aminated lignin with ammonium polyphosphate to obtain the biomass intumescent flame retardant; The specific reaction steps are: Step 1, mix lignin and sulfuric acid solution, stir at 75-85 ° C for 1-2 h, then increase the temperature to 90-100 ° C, add phenol, stir for 1-2 h, cool, wash and dry to obtain phenolic lignin; In step 2, the ammonium polyphosphate and the ethanol aqueous solution are mixed and stirred for 30 to 60 minutes, then melamine is added, the temperature is raised to 65 to 75° C. and stirred for 5.5 to 6.5 hours, and the mixture is washed and dried after cooling to obtain a mixture of melamine and ammonium polyphosphate; Step 3, disperse the mixture of phenolic lignin, melamine and ammonium polyphosphate into N,N-dimethylformamide, heat up and stir, add formaldehyde solution when heated to 70～80℃, react for 2.5～3.5h, cool down After washing and drying, the biomass intumescent flame retardant is obtained. 2 . The method for preparing a biomass intumescent flame retardant according to claim 1 , wherein the mass ratio of ammonium polyphosphate to melamine is (1-1.4):1. 3 . 3. The preparation method of biomass intumescent flame retardant according to claim 1, wherein the mass ratio of phenolic lignin to the mixture of melamine and ammonium polyphosphate is 1:(4～6). 4 . The method for preparing a biomass intumescent flame retardant according to claim 1 , wherein the mass ratio of phenolic lignin to formaldehyde is 1:(0.6-0.8). 5 . 5 . The method for preparing a biomass intumescent flame retardant according to claim 1 , wherein the lignin is enzymatically hydrolyzed lignin. 6 . 6 . The method for preparing a biomass intumescent flame retardant according to claim 1 , wherein, in step 1, the concentration of the sulfuric acid solution is 1.5-2.5 mol/L. 7 . 7 . The method for preparing a biomass intumescent flame retardant according to claim 1 , wherein in step 2, the volume ratio of ethanol to water in the ethanol aqueous solution is (2-3):1. 8 .

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