Cellulose composite waterproof flame retardant and preparation method thereof

Abstract

The present application relates to the field of flame retardant preparation, in particular to a cellulose composite waterproof flame retardant and a preparation method thereof, which solves the problem of poor flame-retardant effect of the existing waterproof flame retardant with low content, and the problem of the destruction of the cellulose fiber interlaced network of paper by the capsule wall material in the high content waterproof flame retardant, resulting in the mechanical strength of paper being reduced, and comprises the preparation of modified calcium borate, ultrasonic modification of nano calcium borate in anhydrous ethanol, surface grafting of the calcium borate, obtaining pre-grafted calcium borate, placing the pre-grafted calcium borate and acrylamide monomers in an aqueous solution of ethanol, adding AIBN reagent for reaction, obtaining a calcium borate grafted compound, and then compounding carbon nanotubes, the calcium borate grafted compound and silanized ammonium polyphosphate microcapsules to obtain the flame retardant. The present application can realize high content addition, and the paper has high tensile strength and flame-retardant performance at the same time.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of flame retardant preparation, in particular to a cellulose composite waterproof flame retardant and a preparation method thereof. BACKGROUND

[0002] Cellulose material is widely used in paper, which is derived from wood, cotton, straw, hemp, reed and the like, wherein the cellulose content is about 40% or more, but the cellulose material has the disadvantage of being easy to burn, and is further limited in use and development, so that the flame retardation of cellulose has been researched since last century, from the beginning of impregnation and coating of inorganic substances to the present adding flame retardants into cellulose liquid stock pulp, so that the flame retardant components are combined with the cellulose material before the material is formed, and then the flame-retardant cellulose is obtained, which can effectively improve the flame retardation performance of the cellulose material; another disadvantage of natural cellulose is high hygroscopicity, which can absorb water in a humid environment. Not only the mechanical strength of the material is reduced and easy to deform, but also the combination of the flame retardant and the cellulose is reduced, so that the flame retardant reaches the surface of the cellulose material, and the flame-retardant paper does not have flame-retardant durability, and the paper can only achieve the surface flame-retardant effect. Therefore, the existing flame retardant is coated with a hydrophobic capsule wall material before being combined with the cellulose, so as to solve the waterproof problem.

[0003] However, it is found in use that the tensile strength of the paper is reduced to a considerable extent with the use of the above waterproof flame retardant, for example, the traditional flame retardant ammonium polyphosphate APP must be doubled in amount after being encapsulated to achieve the same limiting oxygen index, and the non-flame-retardant components exist in the weight, which reduces the play of the flame retardant, and increasing the amount of encapsulated flame retardant will cause the strength of the paper to decrease, wherein the capsule material will destroy the hydrogen bond network of the fiber and occupy the crosslinking site of the original hydrogen bond of the fiber. In summary, in order to prepare high-quality waterproof flame-retardant paper, the amount of encapsulated flame retardant must be increased, and increasing the amount of flame retardant will reduce the mechanical strength and tensile strength of the paper. SUMMARY

[0004] In order to solve the problem that the existing waterproof flame retardant has good waterproof performance after being encapsulated, and the capsule wall material in the high-content waterproof flame retardant destroys the crosslinking network of the cellulose fiber of the paper, causing the mechanical strength of the paper to decrease, the present application provides a cellulose composite waterproof flame retardant and a preparation method thereof.

[0005] The technical scheme adopted by the present application is as follows:

[0006] Firstly, the present application provides a preparation method of a cellulose composite waterproof flame retardant, comprising the following specific preparation steps:

[0007] S1, preparation of modified calcium borate, nanometer calcium borate is placed in anhydrous ethanol for ultrasonic treatment, then a modification reagent is added for reaction, and then separation and washing are performed to obtain modified calcium borate;

[0008] S2, surface grafting of calcium borate, the modified calcium borate is dispersed in anhydrous toluene to form a modified calcium borate dispersion liquid, a RAFT reagent and a DCC catalyst are uniformly mixed in the modified calcium borate dispersion liquid to obtain pre-grafted calcium borate;

[0009] The pre-grafted calcium borate and acrylamide monomers are placed in an ethanol aqueous solution, and an AIBN reagent is added for reaction, and after the reaction is completed, post-treatment is performed to obtain a calcium borate grafted composite;

[0010] S3, preparation of a flame retardant, carbon nanotubes are placed in sodium dodecylbenzenesulfonate for ultrasonic treatment to form a CNT dispersion liquid, then ammonium polyphosphate microcapsules are dispersed in an ethanol solution, a silane coupling agent is added for reaction to form silanized ammonium polyphosphate microcapsules, the calcium borate grafted composite is dispersed in deionized water, then the silanized ammonium polyphosphate microcapsules are added, and high-speed centrifugal homogenization is performed to obtain a homogeneous composite liquid, the CNT dispersion liquid is slowly added to the homogeneous composite liquid and simultaneously ultrasonic treatment is performed, and after the treatment is completed, rotary evaporation is performed to obtain a flame retardant.

[0011] The application uses nanometer calcium borate as a flame-retardant covering layer for insulating oxygen and heat to protect the underlying substrate. However, simply adding nanometer calcium borate cannot improve the tensile strength of paper, but due to the lamellar structure of nanometer calcium borate, the tensile strength of paper may decrease. The combination sites between fibers are occupied by the lamellar structure material, and the existence of the lamellar material makes the paper become a stress concentration point under external force, causing cracks to occur. The lamellar material changes the pore distribution of the paper, and the stress is concentrated on the edge of the lamellar material under stress, causing uneven stress on the fibers, which easily breaks. Therefore, the surface of calcium borate is modified and grafted, and a polymer is used as a bridge to graft calcium borate and connect to the fibers of the pulp. The acrylamide monomer polymer has good film-forming and adhesion properties, and can easily form hydrogen bonds with the fibers to increase the combination area and bonding force between the fibers. After the modification of nanometer calcium borate, the agglomeration of nanometer particles can be effectively prevented. Through grafting of the polymer, the solubility and dispersibility of the polymer can be utilized to make the nanometer material more uniformly dispersed in the pulp suspension and the paper structure.

[0012] Secondly, the carbon nanotubes are added in the preparation process of the flame retardant, and the presence of the carbon nanotubes improves the compression strength of the expanded carbon layer formed at high temperature and reduces the risk of carbon layer fracture, wherein the carbon nanotubes prolong the path of gas diffusion and do not allow the combustible gas to directly pass through the cracks, thereby enhancing the flame retardant effect and quickly dissipating heat laterally to avoid local overheating and carbon layer fracture, thereby protecting the matrix material from high-temperature thermal degradation.

[0013] Preferably, the preparation step of the nano calcium borate in the step S1 is as follows:

[0014] The calcium chloride dihydrate is dissolved in anhydrous ethanol to form a calcium chloride solution, then the borax is stirred in deionized water to form a borax solution, the borax solution is added dropwise to the calcium chloride solution for reaction at elevated temperature, and after the reaction is completed, the precipitate is washed with deionized water and filtered to obtain the nano calcium borate.

[0015] Preferably, the molar ratio of the calcium chloride dihydrate to the borax in the reaction is 2:1, the reaction temperature is 70-80℃, and the reaction time is 6-8h.

[0016] Preferably, the modification reagent in the step S1 is γ-aminopropyl triethoxysilane, the solid-liquid ratio of the nano calcium borate to the modification reagent is 1-3g:10mL, the modification reaction temperature is 70-90℃, the modification reaction time is 12h, and the modification environment is a nitrogen atmosphere.

[0017] Preferably, in the step S2, the mass ratio of the modified calcium borate to the RAFT reagent and the DCC catalyst is 4-6:1-3:1, the pre-grafting reaction temperature is room temperature, and the reaction time is 24h.

[0018] The mass ratio of the pre-grafted calcium borate to the acrylamide monomer is 1:10-20, the addition amount of the AIBN reagent is 1%-5% of the pre-grafted calcium borate, the grafting reaction temperature is 60-80℃, and the reaction time is 6h.

[0019] Preferably, the preparation step of the ammonium polyphosphate microcapsule in the step S3 is as follows:

[0020] The ethyl cellulose is dissolved in ethyl acetate to form a pre-polymer solution, the ammonium polyphosphate and the emulsifier are added to the pre-polymer solution to form a mixed solution, then the TDI is dissolved in ethyl acetate to form a TDI solution, the TDI solution is added dropwise to the mixed solution for reaction, and the ammonium polyphosphate microcapsule is obtained.

[0021] Preferably, the mass ratio of the ethyl cellulose, the ammonium polyphosphate and the TDI is 2-10:100:5-10, the emulsifier is dodecyl phenol polyoxyethylene ether, the addition amount of the emulsifier is 0.1-0.5% of the mass of the ammonium polyphosphate, the temperature for the reaction in the mixed solution is 70-90 DEG C, and the reaction time is 5-8h.

[0022] Preferably, the mass ratio of the calcium borate grafting compound, the silanized ammonium polyphosphate microcapsule and the CNT in the step S3 is 25-40:20:1-5, and the concentration of the CNT dispersion liquid is 0.5wt%.

[0023] Preferably, the solid-liquid ratio of the calcium borate grafting compound dispersed in the deionized water is 25-40g:500mL, the rotation speed of the high-speed centrifugal homogenization is 2000rpm, the homogenization time is 15min-30min, the dropping speed of the CNT dispersion liquid is 1mL / min, and the ultrasonic treatment power is 200W.

[0024] Secondly, the cellulose composite waterproof flame retardant prepared by the preparation method of the cellulose composite waterproof flame retardant provided in the application has an addition amount of 8-15% in paper pulp, and can be used in excess without reducing the mechanical strength and tensile strength of paper.

[0025] The application has the following beneficial effects:

[0026] In the flame retardant, the calcium borate sheet layer material is combined with the acrylamide monomer by in-situ synthesis, so that the inorganic nanosheet layer material is connected by the organic long chain, the flame retardant has good flame retardant effect in paper, and the long chain rigidity can enhance the tensile strength of paper; the use of CNT can promote the formation of carbon layer and form a unique three-dimensional structure in the carbon layer, further enhancing the flame retardant property, and the silanization of the ammonium polyphosphate can also enhance the waterproof effect of the ammonium polyphosphate, prolong the storage time, and has better moisture-proof effect; the glassy substance generated by the decomposition of the grafted PAM calcium borate during combustion can also absorb free radicals generated during combustion, so as to interrupt the chain reaction, and the flame retardant of the application not only has good flame retardant effect, but also has the effect of enhancing the crosslinking of the internal fibers of paper, and can also improve or maintain the tensile strength and mechanical properties of paper when used in large quantities. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The data graph of the limiting oxygen index of the examples and comparative examples of the application.

[0028] Figure 2 The data graph of the tensile strength of paper of the examples and comparative examples of the application. DETAILED DESCRIPTION

[0029] The application will be described below with reference to the accompanying drawings in which Figure 1 to the accompanying drawings Figure 2 Detailed description of the embodiments of the present application will be given. It should be understood by those skilled in the art that the embodiments are only used to explain the technical principles of the present application and are not intended to limit the protection scope of the present application.

[0030] Preparation Example 1

[0031] Preparation of nano calcium borate

[0032] 0.050 mol of calcium chloride dihydrate was placed in 30 mL of anhydrous ethanol, and was stirred to dissolve at 75°C to form a calcium chloride solution. Then, 0.025 mol of borax was placed in 200 mL of deionized water to form a borax solution, which was added dropwise to the calcium chloride solution while maintaining the temperature at 75°C, and reacted for 7 h. After the reaction was completed, the precipitate was washed with deionized water, and filtered to obtain nano calcium borate.

[0033] Preparation Example 2

[0034] Preparation of nano calcium borate

[0035] The difference between the present preparation example and Preparation Example 1 is that the calcium chloride solution is stirred to dissolve at 70°C, and the reaction is performed at 70°C for 6 h. The remaining steps are the same as those of Preparation Example 1.

[0036] Preparation Example 3

[0037] Preparation of nano calcium borate

[0038] The difference between the present preparation example and Preparation Example 1 is that the calcium chloride solution is stirred to dissolve at 80°C, and the reaction is performed at 80°C for 8 h. The remaining steps are the same as those of Preparation Example 1.

[0039] Preparation Example 4

[0040] Preparation of ammonium polyphosphate microcapsules

[0041] 6 g of ethyl cellulose was dissolved in 200 mL of ethyl acetate to form a prepolymer solution, 100 g of ammonium polyphosphate and 0.3 g of emulsifier were added to the prepolymer solution to form a mixed solution, and then 8 g of TDI was dissolved in 30 mL of ethyl acetate to form a TDI solution. The TDI solution was added dropwise to the mixed solution, and the temperature was raised to 80°C to react for 6.5 h. After cooling, the ammonium polyphosphate microcapsules were obtained by filtration and grinding.

[0042] Preparation Example 5

[0043] Preparation of ammonium polyphosphate microcapsules

[0044] Dissolve 2 g of ethyl cellulose in 200 mL of ethyl acetate to form a prepolymer solution, add 100 g of ammonium polyphosphate and 0.1 g of emulsifier to the prepolymer solution to form a mixture, then dissolve 5 g of TDI in 30 mL of ethyl acetate to form a TDI solution, drop the TDI solution into the mixture, and react at 70°C for 5 h. After cooling, filter and grind to obtain ammonium polyphosphate microcapsules.

[0045] Preparation Example 6

[0046] Preparation of ammonium polyphosphate microcapsules

[0047] Dissolve 10 g of ethyl cellulose in 200 mL of ethyl acetate to form a prepolymer solution, add 100 g of ammonium polyphosphate and 0.5 g of emulsifier to the prepolymer solution to form a mixture, then dissolve 10 g of TDI in 30 mL of ethyl acetate to form a TDI solution, drop the TDI solution into the mixture, and react at 90°C for 8 h. After cooling, filter and grind to obtain ammonium polyphosphate microcapsules.

[0048] Example 1

[0049] Preparation of cellulose composite waterproof flame retardant

[0050] S1, disperse the calcium borate nanoparticles prepared in Preparation Example 1 in anhydrous ethanol at a solid-liquid ratio of 1 g:100 mL, ultrasonic treat for 30 min, then add γ-aminopropyltriethoxysilane at a solid-liquid ratio of 2 g:10 mL based on the calcium borate nanoparticles, reflux react at 80°C in a nitrogen environment for 12 h, then centrifuge, wash with ethanol, and vacuum dry to obtain modified calcium borate;

[0051] S2, disperse the modified calcium borate in anhydrous toluene at a solid-liquid ratio of 1 g:100 mL to form a modified calcium borate dispersion, add a RAFT reagent and a DCC catalyst to the modified calcium borate dispersion and mix uniformly, the mass ratio of the modified calcium borate to the RAFT reagent and the DCC catalyst is 5:2:1, react at room temperature for 24 h, centrifuge and filter the precipitate, wash with toluene and ethanol alternately, and dry to obtain a pre-grafted calcium borate;

[0052] Disperse the pre-grafted calcium borate and acrylamide monomers in an ethanol aqueous solution (water:ethanol=1:1) at a solid-liquid ratio of 1 g:15 g:130 mL, and add an AIBN reagent, the addition amount of the AIBN reagent is 3% of the pre-grafted calcium borate, react at 70°C for 6 h, then perform MWCO 10 kDa dialysis post-treatment to remove free PAM, and freeze-dry to obtain a calcium borate grafted composite;

[0053] S3, preparation of the flame retardant, carbon nanotubes were placed in 1 wt% sodium dodecylbenzenesulfonate with a solid-liquid ratio of 1 g:200 mL and ultrasonically treated for 1 h, the ultrasonic treatment power was 500 W, and the frequency was 20 kHz, to form a CNT dispersion liquid, the concentration of the CNT dispersion liquid was 0.5 wt%, then the ammonium polyphosphate microcapsules prepared in preparation example 4 were dispersed in an ethanol solution with a solid-liquid ratio of 1 g:5 mL, then silane coupling agent γ-methacryloyloxypropyltrimethoxysilane was added, the addition amount of the γ-methacryloyloxypropyltrimethoxysilane was 20% of the mass of the ammonium polyphosphate microcapsules, to form silanized ammonium polyphosphate microcapsules, the calcium borate grafting compound was dispersed in deionized water with a solid-liquid ratio of 30 g:500 mL, then the silanized ammonium polyphosphate microcapsules were added, the mass ratio of the calcium borate grafting compound to the silanized ammonium polyphosphate microcapsules and CNT was 30:20:3, a centrifugal speed of 2000 rpm was used for homogenization for 20 min, to obtain a homogenized composite liquid, the CNT dispersion liquid was added dropwise to the homogenized composite liquid at a speed of 1 mL / min and ultrasonically treated synchronously, the ultrasonic treatment power was 200 W, after the end of the ultrasonic treatment, rotary evaporation was performed to obtain the flame retardant.

[0054] Example 2

[0055] Preparation of cellulose composite waterproof flame retardant

[0056] S1, the nano calcium borate prepared in preparation example 2 was ultrasonically treated in anhydrous ethanol with a solid-liquid ratio of 1 g:100 mL for 30 min, then γ-aminopropyltriethoxysilane was added with a solid-liquid ratio of 1 g:10 mL based on the nano calcium borate, reflux reaction was performed at 70°C in a nitrogen environment for 12 h, then centrifugal separation was performed, ethanol was used for washing, and vacuum drying was performed, to obtain modified calcium borate;

[0057] S2, the modified calcium borate was dispersed in anhydrous toluene with a solid-liquid ratio of 1 g:100 mL to form a modified calcium borate dispersion liquid, a RAFT reagent was added to the modified calcium borate dispersion liquid and mixed uniformly with a DCC catalyst, the mass ratio of the modified calcium borate to the RAFT reagent and the DCC catalyst was 4:1:1, reaction was performed at room temperature for 24 h, the precipitate was centrifugally filtered, washed with toluene and ethanol alternately, and dried, to obtain pre-grafted calcium borate;

[0058] The pre-grafted calcium borate and acrylamide monomers were placed in an aqueous ethanol solution (water:ethanol=1:1) with a solid-liquid ratio of 1 g:10 g:130 mL, and AIBN reagent was added, the addition amount of the AIBN reagent was 1% of the pre-grafted calcium borate, after reaction at an elevated temperature of 60°C for 6 h, free PAM was removed through MWCO 10 kDa dialysis post-treatment, and freeze-drying was performed, to obtain a calcium borate grafting compound;

[0059] S3, preparation of the flame retardant, carbon nanotubes were placed in 1 wt% sodium dodecylbenzenesulfonate with a solid-liquid ratio of 1 g:200 mL and ultrasonically treated for 1 h, the ultrasonic treatment power was 500 W, and the frequency was 20 kHz, to form a CNT dispersion liquid, the concentration of the CNT dispersion liquid was 0.5 wt%, then the ammonium polyphosphate microcapsules prepared in preparation example 5 were dispersed in an ethanol solution with a solid-liquid ratio of 1 g:5 mL, then silane coupling agent γ-methacryloyloxypropyltrimethoxysilane was added, the addition amount of the γ-methacryloyloxypropyltrimethoxysilane was 20% of the mass of the ammonium polyphosphate microcapsules, to form silanized ammonium polyphosphate microcapsules, the calcium borate grafting compound was dispersed in deionized water with a solid-liquid ratio of 25 g:500 mL, then the silanized ammonium polyphosphate microcapsules were added, the mass ratio of the calcium borate grafting compound to the silanized ammonium polyphosphate microcapsules and CNT was 25:20:1, a centrifugal speed of 2000 rpm was used for homogenization for 15 min, to obtain a homogenized composite liquid, the CNT dispersion liquid was added dropwise to the homogenized composite liquid at a speed of 1 mL / min and ultrasonically treated synchronously, the ultrasonic treatment power was 200 W, after the end, rotary evaporation was performed to obtain the flame retardant.

[0060] Example 3

[0061] Preparation of cellulose composite waterproof flame retardant

[0062] S1, the nano calcium borate prepared in preparation example 3 was ultrasonically treated in anhydrous ethanol with a solid-liquid ratio of 1 g:100 mL for 30 min, then γ-aminopropyltriethoxysilane was added with a solid-liquid ratio of 3 g:10 mL based on the nano calcium borate, reflux reaction was carried out at 90°C in a nitrogen environment for 12 h, then centrifugal separation was carried out, ethanol was used for washing, and vacuum drying was carried out, to obtain modified calcium borate;

[0063] S2, the modified calcium borate was dispersed in anhydrous toluene with a solid-liquid ratio of 1 g:100 mL to form a modified calcium borate dispersion liquid, a RAFT reagent was added and mixed uniformly with a DCC catalyst in the modified calcium borate dispersion liquid, the mass ratio of the modified calcium borate to the RAFT reagent and the DCC catalyst was 6:3:1, reaction was carried out at room temperature for 24 h, the precipitate was centrifugally filtered, washed with toluene and ethanol alternately, and dried, to obtain a pre-grafted calcium borate;

[0064] The pre-grafted calcium borate and acrylamide monomers were placed in an aqueous ethanol solution (water:ethanol=1:1) with a solid-liquid ratio of 1 g:20 g:130 mL, and AIBN reagent was added for reaction, the addition amount of the AIBN reagent was 5% of the pre-grafted calcium borate, after reaction at an elevated temperature of 80°C for 6 h, free PAM was removed through MWCO 10 kDa dialysis post-treatment, and freeze-drying was carried out, to obtain a calcium borate grafting compound;

[0065] S3, Preparation of the flame retardant, carbon nanotubes were ultrasonically treated in 1 wt% sodium dodecylbenzenesulfonate at a solid-liquid ratio of 1 g:200 mL for 1 h, the ultrasonic treatment power was 500 W, and the frequency was 20 kHz to form a CNT dispersion liquid, the concentration of the CNT dispersion liquid was 0.5 wt%, then the ammonium polyphosphate microcapsules prepared in Preparation Example 6 were dispersed in an ethanol solution at a solid-liquid ratio of 1 g:5 mL, then silane coupling agent γ-methacryloyloxypropyltrimethoxysilane was added, the addition amount of the γ-methacryloyloxypropyltrimethoxysilane was 20% of the mass of the ammonium polyphosphate microcapsules, to form silanized ammonium polyphosphate microcapsules, the calcium borate grafting compound was dispersed in deionized water at a solid-liquid ratio of 40 g:500 mL, then the silanized ammonium polyphosphate microcapsules were added, the mass ratio of the calcium borate grafting compound to the silanized ammonium polyphosphate microcapsules and CNT was 40:20:5, a centrifugal speed of 2000 rpm was used for homogenization for 30 min to obtain a homogenized composite liquid, the CNT dispersion liquid was added dropwise to the homogenized composite liquid at a speed of 1 mL / min and ultrasonically treated synchronously, the ultrasonic treatment power was 200 W, and after the treatment was completed, rotary evaporation was performed to obtain the flame retardant.

[0066] Comparative Example 1 - No nano calcium borate was used

[0067] Preparation of a cellulose composite waterproof flame retardant

[0068] S1, silica was dispersed in anhydrous toluene at a solid-liquid ratio of 1 g:100 mL to form a silica dispersion liquid, a RAFT reagent and a DCC catalyst were added to the silica dispersion liquid and uniformly mixed, the mass ratio of the silica to the RAFT reagent and the DCC catalyst was 5:2:1, and the reaction was performed at room temperature for 24 h, the precipitate was centrifugally filtered, washed with toluene and ethanol alternately, and dried to obtain pre-grafted silica;

[0069] The pre-grafted silica and acrylamide monomers were placed in an aqueous ethanol solution (water:ethanol=1:1) at a solid-liquid ratio of 1 g:15 g:130 mL, and AIBN reagent was added, the addition amount of the AIBN reagent was 3% of the pre-grafted silica, the temperature was raised to 70°C, and the reaction was performed for 6 h, then MWCO 10 kDa dialysis post-treatment was performed to remove free PAM, and freeze-drying was performed to obtain a silica grafting compound;

[0070] S3, preparation of the flame retardant, carbon nanotubes were placed in 1 wt% sodium dodecylbenzenesulfonate with a solid-liquid ratio of 1 g:200 mL and ultrasonic treated for 1 h, the ultrasonic treatment power was 500 W, the frequency was 20 kHz, to form a CNT dispersion liquid, the concentration of the CNT dispersion liquid was 0.5 wt%, then the ammonium polyphosphate microcapsules prepared in preparation example 4 were dispersed in an ethanol solution with a solid-liquid ratio of 1 g:5 mL, then silane coupling agent γ-methacryloxypropyltrimethoxysilane was added, the addition amount of γ-methacryloxypropyltrimethoxysilane was 20% of the mass of the ammonium polyphosphate microcapsules, to form silanized ammonium polyphosphate microcapsules, the silica grafting compound was dispersed in deionized water with a solid-liquid ratio of 30 g:500 mL, then the silanized ammonium polyphosphate microcapsules were added, the mass ratio of the silica grafting compound, the silanized ammonium polyphosphate microcapsules and CNT was 30:20:3, homogenized for 20 min at a centrifugal speed of 2000 rpm, to obtain a homogenized composite liquid, the CNT dispersion liquid was added dropwise to the homogenized composite liquid at a speed of 1 mL / min and ultrasonic treated synchronously, the ultrasonic treatment power was 200 W, after the end, rotary evaporation was performed to obtain the flame retardant.

[0071] Comparative example 2 - direct addition of PAM long chain in the flame retardant

[0072] Preparation of cellulose composite waterproof flame retardant

[0073] S1, the nano calcium borate prepared in preparation example 1 was mixed with polyacrylamide at a weight ratio of 1:12, grinding was performed to form a mixed powder;

[0074] S2, preparation of the flame retardant, carbon nanotubes were placed in 1 wt% sodium dodecylbenzenesulfonate with a solid-liquid ratio of 1 g:200 mL and ultrasonic treated for 1 h, the ultrasonic treatment power was 500 W, the frequency was 20 kHz, to form a CNT dispersion liquid, the concentration of the CNT dispersion liquid was 0.5 wt%, then the ammonium polyphosphate microcapsules prepared in preparation example 4 were dispersed in an ethanol solution with a solid-liquid ratio of 1 g:5 mL, then silane coupling agent γ-methacryloxypropyltrimethoxysilane was added, the addition amount of γ-methacryloxypropyltrimethoxysilane was 20% of the mass of the ammonium polyphosphate microcapsules, to form silanized ammonium polyphosphate microcapsules, the silica grafting compound was dispersed in deionized water with a solid-liquid ratio of 30 g:500 mL, then the silanized ammonium polyphosphate microcapsules were added, the mass ratio of the silica grafting compound, the silanized ammonium polyphosphate microcapsules and CNT was 30:20:3, homogenized for 20 min at a centrifugal speed of 2000 rpm, to obtain a homogenized composite liquid, the CNT dispersion liquid was added dropwise to the homogenized composite liquid at a speed of 1 mL / min and ultrasonic treated synchronously, the ultrasonic treatment power was 200 W, after the end, rotary evaporation was performed to obtain the flame retardant.

[0075] Comparative Example 3 - nanometer calcium borate is not grafted with acrylamide monomer

[0076] Preparation of cellulose composite waterproof flame retardant

[0077] S1, nanometer calcium borate prepared in Preparation Example 1 was placed in anhydrous ethanol with a solid-liquid ratio of 1 g:100 mL and ultrasonically treated for 30 min, then γ-aminopropyl triethoxysilane was added with a solid-liquid ratio of 2 g:10 mL based on nanometer calcium borate, and refluxed at 80°C in a nitrogen environment for 12 h, followed by centrifugal separation, washing with ethanol, and vacuum drying to obtain modified calcium borate;

[0078] S2, the preparation of the flame retardant, carbon nanotubes were ultrasonically treated in 1 wt% sodium dodecylbenzenesulfonate with a solid-liquid ratio of 1 g:200 mL for 1 h, the ultrasonic treatment power was 500 W and the frequency was 20 kHz to form a CNT dispersion liquid, the concentration of the CNT dispersion liquid was 0.5 wt%, then the polyammonium phosphate microcapsules prepared in Preparation Example 4 were dispersed in an ethanol solution with a solid-liquid ratio of 1 g:5 mL, then silane coupling agent γ-methacryloyloxypropyl trimethoxysilane was added, the addition amount of γ-methacryloyloxypropyl trimethoxysilane was 20% of the mass of the polyammonium phosphate microcapsules, to form silanized polyammonium phosphate microcapsules, the modified calcium borate was dispersed in deionized water with a solid-liquid ratio of 30 g:500 mL, then the silanized polyammonium phosphate microcapsules were added, the complex mass ratio of the modified calcium borate, the silanized polyammonium phosphate microcapsules and CNT was 30:20:3, the homogeneous liquid was obtained by homogenizing at a centrifugal speed of 2000 rpm for 20 min, the CNT dispersion liquid was added to the homogeneous liquid at a speed of 1 mL / min and ultrasonically treated synchronously, the ultrasonic treatment power was 200 W, and the flame retardant was obtained by rotary evaporation after the treatment was completed.

[0079] Comparative Example 4 - flame retardant is prepared without using carbon nanotubes for compounding

[0080] Preparation of cellulose composite waterproof flame retardant

[0081] In this comparative example, step S1 and step S2 are the same as steps S1 and S2 of Preparation Example 1;

[0082] S3, Preparation of the flame retardant, ammonium polyphosphate microcapsules prepared in Preparation Example 4 were dispersed in ethanol solution at a solid-liquid ratio of 1 g:5 mL, then silane coupling agent γ-methacryloxypropyltrimethoxysilane was added, the amount of γ-methacryloxypropyltrimethoxysilane added was 20% of the mass of the ammonium polyphosphate microcapsules, to form silanized ammonium polyphosphate microcapsules, the calcium borate grafting compound was dispersed in deionized water at a solid-liquid ratio of 30 g:500 mL, then the silanized ammonium polyphosphate microcapsules were added, the mass ratio of the calcium borate grafting compound to the silanized ammonium polyphosphate microcapsules was 30:20, homogenization was performed at a centrifugal speed of 2000 rpm for 20 min to obtain a homogeneous composite liquid, and rotary evaporation was performed to obtain the flame retardant.

[0083] Comparative Example 5 - ammonium polyphosphate microcapsules were not reacted with a silane coupling agent to form silanized

[0084] Preparation of a cellulose composite waterproof flame retardant

[0085] S3, Preparation of the flame retardant, carbon nanotubes were ultrasonically treated in 1 wt% sodium dodecylbenzenesulfonate at a solid-liquid ratio of 1 g:200 mL for 1 h, the ultrasonic treatment power was 500 W and the frequency was 20 kHz, to form a CNT dispersion liquid, the concentration of the CNT dispersion liquid was 0.5 wt%, the calcium borate grafting compound was dispersed in deionized water at a solid-liquid ratio of 30 g:500 mL, then the ammonium polyphosphate microcapsules prepared in Preparation Example 4 were added, the mass ratio of the calcium borate grafting compound to the ammonium polyphosphate microcapsules and CNTs was 30:20:3, homogenization was performed at a centrifugal speed of 2000 rpm for 20 min to obtain a homogeneous composite liquid, the CNT dispersion liquid was added dropwise to the homogeneous composite liquid at a speed of 1 mL / min and ultrasonic treatment was performed synchronously, the ultrasonic treatment power was 200 W, and rotary evaporation was performed after completion to obtain the flame retardant.

[0086] The remaining steps were the same as those of Example 1.

[0087] Experiments and data

[0088] The flame retardant prepared in each of the above examples and comparative examples was used to prepare a flame-retardant paper, and the preparation method was as follows:

[0089] The paper pulp was diluted to 1%, the pH value was adjusted to 7.0, 10% of the dry pulp weight was added to the flame retardant, ultrasonic dispersion was performed for 30 min, then 0.05% of the dry pulp weight of cationic polyacrylamide was added, stirring was performed, and standard paper industry molding was performed, the weight of the paper was about 60 g / m 2 , and the flame-retardant paper was dried at 105°C.

[0090] The above flame-retardant paper was subjected to water contact angle and the following performance tests, and the specific test standards were as follows:

[0091] Tensile strength: tested according to the method of GB / T 12914-2018, unit: kN / m. The tensile strength of the blank control (paper without flame retardant) is 1.79 kN / m.

[0092] Limiting oxygen index: tested according to the method of GB / T 2406.2-2009, unit: %.

[0093] The specific data are shown in Table 1 below:

[0094]

[0095] According to the limiting oxygen index and the tensile strength of the paper in Table 1, a line graph is drawn as shown in Figure 1 and Figure 2 .

[0096] Analysis

[0097] According to the data in Table 1, the data of Examples 1-3 show that the use of the flame retardant prepared in the present application can make the paper not only have a high water contact angle, a good waterproof effect, and a very high limiting oxygen index, but also have a tensile strength of 2.86 or higher, combining the flame retardant effect and the tensile strength.

[0098] According to the data in Table 1, the experimental data of Comparative Example 1 show that the limiting oxygen index is very poor, and the tensile strength is good. The difference between Comparative Example 1 and Example 1 is that no nano calcium borate is used, so it can be proved that the presence of nano calcium borate can greatly improve the flame retardant effect.

[0099] According to the data in Table 1, the experimental data of Comparative Example 2 show that the water contact angle becomes smaller, and the limiting oxygen index decreases to a large extent, while the tensile strength is high. The difference between Comparative Example 2 and Example 1 is that PAM is not chemically grafted with nano calcium borate, but PAM is directly added, so it can be confirmed that the in-situ polymerization method can greatly increase the uniformity of the distribution of nano calcium borate, thereby improving the flame retardant effect and slightly affecting the waterproof performance.

[0100] According to the data in Table 1, the experimental data of Comparative Example 3 show that the limiting oxygen index decreases slightly, while the tensile strength decreases greatly. The difference between Comparative Example 3 and Example 1 is that the nano calcium borate is not grafted with acrylamide monomer, and no PAM long-chain substance is added, so it can be confirmed that the presence of PAM can strengthen the tensile strength of the paper, and slightly affect the play of the flame retardant component.

[0101] According to the data in Table 1, the experimental data of Comparative Example 4 shows that the limiting oxygen index has a small decrease, and the water contact angle and the paper tensile strength are unchanged, and the difference between Comparative Example 4 and Example 1 is that no carbon nanotubes are used to prepare the flame retardant, so it can be confirmed that the use of carbon nanotubes can slightly improve the limiting oxygen index, thereby improving the flame retardant effect.

[0102] According to the data in Table 1, the experimental data of Comparative Example 5 shows that the limiting oxygen index and the paper tensile strength also have a small decrease, and the difference between Comparative Example 5 and Example 1 is that the ammonium polyphosphate microcapsules are not reacted with the silane coupling agent to form silanization, so it can be confirmed that the silanization of the ammonium polyphosphate microcapsules can slightly improve the dispersion effect and the cross-linking degree, thereby improving the flame retardant effect and the mechanical strength of the paper.

[0103] So far, the technical solutions of the present application have been described in combination with the preferred embodiments shown in the drawings, but those skilled in the art can easily understand that the protection scope of the present application is obviously not limited to these specific embodiments. Those skilled in the art can make equivalent changes or replacements to the related technical features without departing from the principles of the present application, and the technical solutions after these changes or replacements will fall within the protection scope of the present application.

Claims

1. A flame-retardant paper prepared from a cellulose composite waterproof flame retardant, characterized in that: The preparation method is as follows: The pulp was diluted to 1%, the pH value was adjusted to 7.0, and a flame retardant was added according to 10% of the dry pulp weight. Ultrasonic dispersion was performed for 30 minutes, and then 0.05% of the dry pulp weight of cationic polyacrylamide was added. After stirring, the paper was formed. The weight of the paper was 60g / m 2 , drying at 105°C to obtain flame retardant paper; The preparation method of the cellulose composite waterproof flame retardant comprises the following specific preparation steps: S1, dispersing nano calcium borate in an organic solvent, and then adding a modifying reagent to react to obtain modified calcium borate; S2, mixing modified calcium borate, a chain transfer agent, and a catalyst to obtain pre-grafted calcium borate, and then reacting the pre-grafted calcium borate, acrylamide monomer, and an AIBN reagent in an organic solvent to obtain a calcium borate grafted complex; S3, preparing carbon nanotubes into a CNT dispersion, then reacting ammonium polyphosphate microcapsules with a silane coupling agent to form silylated ammonium polyphosphate microcapsules, homogenizing the calcium borate grafted composite and the silylated ammonium polyphosphate microcapsules by high-speed centrifugation to obtain a homogeneous composite liquid, and then slowly adding the CNT dispersion dropwise to the homogeneous composite liquid and simultaneously ultrasonicating it to obtain a flame retardant; The preparation steps of nano calcium borate in step S1 are as follows: Calcium chloride dihydrate is dissolved in anhydrous ethanol to form a calcium chloride solution, and then borax is placed in deionized water and stirred to form a borax solution. The borax solution is added dropwise to the calcium chloride solution and heated to react. After the reaction is completed, the precipitate is washed with deionized water and filtered to obtain nano calcium borate; The molar ratio of calcium chloride dihydrate to borax is 2:1, the reaction temperature is 70-80°C, and the reaction time is 6-8h; The preparation steps of the ammonium polyphosphate microcapsules in step S3 are as follows: Ethyl cellulose is dissolved in ethyl acetate to form a prepolymer solution, ammonium polyphosphate and an emulsifier are added to the prepolymer solution and stirred to form a mixed solution, and then TDI is dissolved in ethyl acetate to form a TDI solution, and the TDI solution is added dropwise to the mixed solution to react to obtain ammonium polyphosphate microcapsules; The mass ratio of ethyl cellulose to ammonium polyphosphate and TDI is 2-10:100:5-10, the emulsifier is dodecylphenol polyoxyethylene ether, and the amount of the emulsifier added is 0.1-0.5% of the mass of ammonium polyphosphate. The reaction temperature in the mixed solution is 70-90° C., and the reaction time is 5-8 hours. The modification reagent in step S1 is γ-aminopropyltriethoxysilane, the solid-liquid ratio of the nano-calcium borate to the modification reagent is 1-3g:10mL, the modification reaction temperature is 70-90°C, the modification reaction time is 12h, and the modification environment is a nitrogen atmosphere; In step S2, the mass ratio of modified calcium borate to chain transfer agent and catalyst is 4-6:1-3:1, the reaction temperature of the mixing is room temperature, and the mixing time is 24 hours; The mass ratio of the pre-grafted calcium borate to the acrylamide monomer is 1:10-20, the amount of the AIBN reagent added is 1%-5% of the pre-grafted calcium borate, the grafting reaction temperature is 60-80°C, and the reaction time is 6 hours; In step S3, the composite mass ratio of the calcium borate grafted composite to the silanized ammonium polyphosphate microcapsules and CNTs is 25-40:20:1-5; The calcium borate grafted composite is dispersed in the solvent at a solid-liquid ratio of 25-40 g:500 mL.

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