CN110698115A - A kind of phosphotungstic acid intercalated hydrotalcite lightweight foam insulation material and preparation method thereof - Google Patents

Abstract

The invention discloses a phosphotungstic acid intercalated hydrotalcite lightweight foam insulation material and a preparation method thereof. A Zn/Al hydrotalcite precursor is prepared by a co-precipitation method; The phosphotungstic acid-Zn/Al type hydrotalcite was prepared by dropping into the Zn/Al type hydrotalcite precursor slurry, and the Zn/Al type hydrotalcite precursor was modified; the phosphotungstic acid-Zn/Al type hydrotalcite, The nanocellulose and the binder are mixed and freeze-dried to obtain the phosphotungstic acid intercalated hydrotalcite lightweight foam insulation material. The ZnAl-LDHs modified by heteropolyphosphotungstic acid intercalation can solve the problems of large addition amount and low flame retardant efficiency when single ZnAl-LDHs are used as flame retardants. It has the characteristics of low density, high strength and green environmental protection.

Description

A kind of phosphotungstic acid intercalated hydrotalcite lightweight foam insulation material and preparation method thereof

technical field

The invention belongs to the field of biomass foam materials, and in particular relates to a hydrotalcite-like lightweight foam insulation material and a preparation method thereof.

Background technique

With the increasingly serious environmental pollution problem and the depletion of petroleum resources, the research and development of biodegradable, resource-rich, recyclable lightweight thermal insulation and fireproof thermal insulation materials has become a major problem that needs to be solved urgently in the society. Fire-resistant insulation materials can effectively reduce energy loss and improve energy utilization. Due to its excellent characteristics, it has been widely developed and applied in the fields of aviation, aerospace, chemical industry, construction, machinery, storage and energy. However, lightweight refractories have shortcomings such as low strength and poor heat resistance. Therefore, the current research on lightweight refractories at home and abroad focuses on increasing the mechanical strength of the material and improving the refractory temperature, including the addition of additives, preparation methods, etc. Research on aspects, such as adding nanoparticles, refractory fibers, etc. to enhance materials, etc.

LDHs (layered double hydroxides), is a class of layered hydroxides composed of two or more metal elements, known as layered double metal hydroxides, hydrotalcite-like or layered composite metal hydroxides thing. This type of material is composed of mutually parallel and positively charged layers, and the interlayers are composed of anions that balance the positive charge of the layers and interlayer water molecules. The properties of LDHs mainly include: exchangeability of interlayer anions, tunable denaturation of layer composition and structure, acid-base amphiphilicity, structural memory effect, and peelable layers. Due to the unique layered structure of LDHs and the tunable denaturation of layer composition and interlayer anions, by introducing new guest anions into the interlayers, the composition and properties of the materials are correspondingly changed, and the functionalities with different structures are prepared. new material. At present, the main methods for preparing LDHs modified by anion intercalation include coprecipitation, ion exchange, molecular self-assembly, calcination reduction, and backmixing precipitation.

LDHs itself not only has the spatial structure characteristics similar to molecular sieves, but also can directly serve as the rigid support of the flame-retardant intumescent layer. It is expected that by modifying LDHs, the interlayer environment of hydrotalcites can be changed, the compatibility between hydrotalcites and polymers can be improved, the interlayer spacing of LDHs can be increased, and the density of LDHs can be reduced to achieve light weight, low dosage and high flame retardancy. Efficient low-smoke, halogen-free, non-toxic, environmentally friendly flame retardant.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is to overcome the deficiencies and defects in the above background technology, and provide a hydrotalcite-like lightweight foam thermal insulation material and a preparation method thereof, so as to improve the thermal insulation and flame retardant effect.

In order to solve the above-mentioned technical problems, the technical scheme proposed by the present invention is:

A preparation method of phosphotungstic acid intercalated hydrotalcite lightweight foam insulation material, comprising the following steps:

(1) Preparation of Zn/Al hydrotalcite precursor by co-precipitation method;

(2) Using the ion exchange method, drop the phosphotungstic acid salt solution into the Zn/Al type hydrotalcite precursor slurry in step (1), and modify the Zn/Al type hydrotalcite precursor to obtain phosphotungstic acid -Zn/Al hydrotalcite;

(3) Mixing the phosphotungstic acid-Zn/Al hydrotalcite, nanocellulose, and binder obtained in step (2), and freeze-drying to obtain a phosphotungstic acid intercalated hydrotalcite lightweight foam insulation material.

Further, the coprecipitation method described in step (1) is to mix zinc salt and aluminum salt into a mixed salt solution, adjust the pH value to 6 to 9, heat up to 50-90 ° C, and obtain through vigorous stirring, crystallization and post-processing. Zn/Al hydrotalcite precursor.

Further, the zinc salt and aluminum salt in step (1) are prepared according to the mole ratio of zinc ion to aluminum ion being 2:1-3:1.

Further, in the ion exchange method described in step (2), the phosphotungstate solution is dropped into the Zn/Al hydrotalcite precursor slurry in step (1), vigorously stirred, and heated to 50-90° C., and the reaction is obtained. Phosphotungstic acid-Zn/Al hydrotalcite.

Further, in step (2), the mass ratio of the host Zn/Al hydrotalcite to the guest phosphotungstate is 1:3-3:1.

Further, the size distribution of the nanocellulose in step (3) is as follows: the nanocellulose with a fiber length of 1-100 nm accounts for 25%-60%; the nanocellulose with a fiber length of 100-1000 nm accounts for 35%-50% ; Fiber length of 1μm ~ 10mm nanocellulose accounted for 10% ~ 15%.

Further, the adhesive in step (3) is one or more of boric acid, tartaric acid, malic acid or citric acid.

Further, in step (3), the mass ratio of phosphotungstic acid-Zn/Al hydrotalcite, nanocellulose, and binder is 20-55:40-80:1-5.

Further, in step (3), one or more of a small molecular alcohol organic solvent, a macromolecular organic compound or a flame retardant auxiliary is also added.

The phosphotungstic acid intercalated hydrotalcite lightweight foam insulation material provided by the invention is prepared by the method.

The present invention adopts co-precipitation method and ion exchange method to introduce phosphotungstic acid anion into Zn/Al type hydrotalcite layered structure to prepare phosphotungstic acid intercalated Zn/Al type hydrotalcite, which is then mixed with nanocellulose, adhesive, etc. The additives are mixed evenly, and after freeze-drying, an environmentally friendly lightweight foam refractory material is made. Compared with the prior art, the beneficial effects of the present invention are:

(1) The present invention is the first to use phosphotungstic acid-Zn/Al hydrotalcite and nanocellulose to prepare a lightweight foam refractory material with a three-dimensional network structure, multiple pores, low thermal conductivity and high flame retardant effect.

Zn/Al hydrotalcite laminates contain a large amount of hydroxyl groups, CO ₃ ^2– , amorphous water and crystal water. The H ₂ O and CO ₂ released from decomposition when heated can dilute oxygen and absorb a large amount of heat, reducing the temperature of the combustion system. Therefore, it has a flame retardant effect; and LDHs are decomposed at a high temperature of 500-600 ℃ to form a composite metal oxide with porous and large specific surface area, which can absorb the smoke generated during the combustion process and play a role in smoke suppression. Zn element can promote the formation of char and smoke suppression.

Since the lamellae and the interlayer anions are connected by hydrogen bonds, the interlayer anions of LDHs are exchangeable, so phosphotungstate ions can be used to replace the interlayer anions to modify them.

In the present invention, phosphotungstic acid is inserted between the layered structures of the hydrotalcite-like structure by ion exchange, and the heteropolyacid can be made firm by the strong electrostatic force between the phosphotungstic acid and the layered metal ions of the hydrotalcite-like class. fixed on the hydrotalcite-like.

The present invention utilizes P element with good flame retardant effect and tungsten element with efficient smoke suppression effect of phosphotungstic acid molecule, [PW ₁₂ O ₄₀ ] ^3- can significantly improve the thermal stability and flame retardancy of LDHs after being introduced into the hydrotalcite-like . Phosphotungstic acid can catalyze the dehydration of cellulose into ester and solidify into carbon, which can effectively delay the pyrolysis of the material, reduce the heat and flue gas release during the combustion process, and enhance the thermal stability of the material. It realizes less addition, light weight and high efficiency.

In the present invention, the hydrotalcite-like modified by phosphotungstic acid intercalation is introduced into the nanocellulose foam material, and the foam material has excellent thermal insulation and flame retardant effect. The ZnAl-LDHs modified by heteropolyphosphotungstic acid intercalation solves the problems of large addition amount and low flame retardant efficiency when a single ZnAl-LDHs is used as a flame retardant. It has the characteristics of low density, high strength and green environmental protection.

(2) The present invention adopts nanocellulose with a certain length distribution, which can not only fully retain the quantum size effect of nanocellulose, but also give full play to the strengthening effect of nanocellulose of different lengths, and fully guarantee the mechanical effect of lightweight foam materials. .

(3) The lightweight foam material contains a variety of components such as phosphotungstic acid, hydrotalcite-like, and adhesive. Each component exerts a synergistic flame retardant effect, and gives full play to its condensed phase flame retardant mechanism and gas phase flame retardant mechanism, giving light Excellent flame retardant effect of quality foam material.

(4) In the present invention, the generation of pore size is regulated by adding organic small molecule solvent to the foam material, so that the generated cells are arranged neatly and regularly, have a layered structure, and have uniform pore size distribution. The composite of macromolecular organic matter and nanocellulose can form a similar "reinforced concrete" structure, thereby significantly improving the strength and processability of foam materials. Adding a small amount of flame retardant additives can further improve the flame retardant properties of foam materials.

Description of drawings

In order to illustrate the embodiments of the present invention or the technical solutions in the prior art more clearly, the following briefly introduces the accompanying drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are For some embodiments of the present invention, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without creative efforts.

Figure 1 is the burning photos of each sample lightweight foam insulation material under the flame of alcohol lamp at 500-600℃: a) CNF; b) CNF/50%ZnAl-NO ₃ -LDHs/2% H ₃ BO ₃ ; c ) CNF/50%ZnAl-PW ₁₂ O ₄₀ -LDHs/2% H ₃ BO ₃ ;

Figure 2 is a SEM image of the CNF/50%ZnAl-PW ₁₂ O ₄₀ -LDHs/2% H ₃ BO ₃ lightweight foam thermal insulation material.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and in detail below with reference to the accompanying drawings and preferred embodiments of the specification, but the protection scope of the present invention is not limited to the following specific embodiments.

Unless otherwise defined, all technical terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the protection scope of the present invention.

Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or can be prepared by existing methods.

A method for preparing a phosphotungstic acid intercalated Zn/Al hydrotalcite/nanocellulose lightweight foam material according to a specific embodiment of the present invention comprises the following steps:

(1) Preparation of Zn/Al hydrotalcite precursor by co-precipitation method;

(2) using ion exchange method to modify the Zn/Al type hydrotalcite precursor in step (1) to obtain phosphotungstic acid-Zn/Al type hydrotalcite;

(3) mixing the phosphotungstic acid-Zn/Al type hydrotalcite, nanocellulose, binder and other auxiliary agents obtained in step (2), and freeze-drying to obtain phosphotungstic acid intercalated Zn/Al type hydrotalcite nanocellulose Lightweight foam material.

In a preferred embodiment, the co-precipitation method is as follows: taking zinc salt and aluminum salt by weighing the ionic molar ratio of ₂ :1-3:1 to prepare a mixed salt solution, under N atmosphere, using hydrogen peroxide Adjust the pH value of sodium to 6-9, stir evenly, heat up to 50-90 ° C, and the reaction time is 6-20 hours, after vigorous stirring, crystallization, centrifugation, washing to neutrality, and drying at normal pressure to obtain Zn/Al The solid hydrotalcite-like precursor is then formulated into a Zn/Al-like hydrotalcite precursor slurry.

Preferably, the zinc salt is one or more of zinc nitrate, zinc chloride, and zinc sulfate, and the aluminum salt is one or more of aluminum nitrate, aluminum chloride, and aluminum sulfate.

In a preferred embodiment, the ion exchange method is as follows: drop the phosphotungstate solution dropwise into the Zn/Al hydrotalcite precursor slurry in step (1), stir vigorously, and heat up to 50- 90° C. and the reaction time is 5-20 hours to obtain an intercalation-modified phosphotungstic acid-Zn/Al hydrotalcite slurry. Preferably, the mass ratio of the host Zn/Al hydrotalcite to the guest phosphotungstate is 1:3-3:1. The ion exchange method utilizes the exchangeability of anions between the LDHs layers to exchange [PW ₁₂ O ₄₀ ] ^3- with the anions between the LDHs layers to obtain the target product.

Preferably, in the step (3), the size distribution of the nanocellulose is as follows: nanocellulose with a fiber length of 1-100 nm accounts for 25%-60% (wt%); nanocellulose with a fiber length of 100-1000nm Cellulose accounts for 35% to 50%; nanocellulose with a fiber length of 1 μm to 10 mm accounts for 10% to 15%. Nanocellulose with a certain length distribution can not only fully retain the quantum size effect of nanocellulose, but also give full play to the reinforcing effect of nanocellulose of different lengths, which fully guarantees the mechanical effect of lightweight foam materials.

Preferably, in the step (3), the binder is one or more of boric acid, tartaric acid, malic acid, and citric acid, and the addition of acid substances can further improve phosphotungstic acid-Zn/Al water Compatibility between talc and nanocellulose. The phosphotungstic acid intercalated Zn/Al-based hydrotalcite and nanocellulose were connected into porous foam with uniform pore size network structure through chemical bonds or electrostatic interactions. The mass ratio of the phosphotungstic acid-Zn/Al hydrotalcite, nanocellulose, and binder is 20-55:40-80:1-5.

Preferably, in the step (3), the auxiliary agent further includes one or more of a small molecular alcohol organic solvent, a macromolecular organic compound, and a flame retardant auxiliary. The small molecular organic solvent is one or more of methanol, ethanol and n-butanol; the macromolecular organic solvent is one or more of starch, xylan and soybean protein; the flame retardant auxiliary is carbon nanometer One or more of tube and graphene. The organic small molecule solvent can control the formation of ice crystals in the freeze-drying process, so as to control the pore size of the foam material, so that the generated cells are arranged in a regular, layered structure with uniform pore size distribution. The composite of macromolecular organic matter and nanocellulose can form a similar "reinforced concrete" structure, thereby significantly improving the strength and processability of foam materials. Adding a small amount of flame retardant additives can further improve the flame retardant properties of foam materials.

The method of step (3) freeze-drying first freezes the water-containing material below the freezing point, so that the water is transformed into ice, and then the ice is transformed into steam under a relatively high vacuum. The temperature-programmed control can effectively maintain the pore structure and size of the composite material, ensuring Excellent mechanical properties of foam materials.

Comparative ratio:

1. Weigh Zn(NO ₃ ) ₂ 9H ₂ O and Al(NO ₃ ) ₃ 9H ₂ O according to n(Zn ²⁺ )/n(Al ³⁺ )=3:1, adjust the pH value to 7.0, After reaction at 70℃ for 12h, ZnAl-NO ₃ -LDHs was prepared by co-precipitation method.

2. Mix the ZnAl-NO ₃ -LDHs slurry with CNF (nanocellulose fiber) according to the dry weight percentage ratio in Table 1 and stir evenly; and add a certain amount of H ₃ BO ₃ solution dropwise. The evenly mixed samples were placed horizontally in a freeze dryer and frozen at -50°C for 12 hours; then vacuum dried. Among them, the vacuum degree is 4.5pa, and the heating process is divided into five stages: the temperature of the first stage is -5 °C, and drying is 3 hours; the temperature of the second stage is 10 °C, and drying is 5 hours; the temperature of the third stage is 20 °C, and drying is 10 hours; The temperature of the fourth stage is 30°C and drying is performed for 10h; the temperature of the fifth stage is 40°C and drying is performed for 15h. The CNF/ZnAl-NO ₃ -LDHs/H ₃ BO ₃ lightweight foam thermal insulation material was prepared.

Table 1 Composition ratio of CNF/ZnAl-NO ₃ -LDHs/H ₃ BO ₃ lightweight foam thermal insulation materials

3. The obtained product is tested for fire resistance, and the obtained results are shown in Table 3.

Fire resistance test: The XC-24-K-12 thermocouple and OM-DAQ-USB-2400 data acquisition recorder produced by OMEGA Company in the United States were used to evaluate the fire resistance of the modified LDHs/nanocellulose lightweight foam insulation material performance. The lightweight foam insulation material was placed on the steel plate, the thermocouple was placed on the back of the steel plate, and the curve of the back temperature of the sample with time was recorded.

4. Carry out the combustion performance test of the obtained product, and the obtained result is shown in Figure 1.

Combustion performance test: The D7100 SLR camera produced by Nikon Corporation of Japan was used to record the combustion process of the modified LDHs/nanocellulose lightweight foam insulation material. The sample was burned in the outer flame of the alcohol lamp flame to test the combustion performance of the lightweight foam insulation material.

Thermal conductivity test: The thermal conductivity of the lightweight foam thermal insulation material was evaluated by using the Hot Disk TPS 2500S thermal conductivity meter (in the transient mode, the output power is 20mW) produced by the Swedish Hot Disk Company.

Example

(1) Weigh Zn(NO ₃ ) ₂ ·9H ₂ O and Al(NO ₃ ) ₃ ·9H ₂ O according to n(Zn ²⁺ )/n(Al ³⁺ )=3:1, and adjust the pH to 7.0 , and reacted at 70℃ for 12h to obtain ZnAl-NO ₃ -LDHs by co-precipitation method.

(2) Accurately weigh a certain mass of H ₃ PW ₁₂ O ₄₀ according to m _{main body} /m _[PW12O40]3 -=1:2, dissolve it in deionized water, and neutralize it with quantitative NaOH to obtain a sodium phosphotungstate solution. Under N ₂ atmosphere, the sodium phosphotungstate solution was added dropwise to the ZnAl-NO ₃ -LDHs main slurry at an appropriate speed, and stirred vigorously; the reaction solution was allowed to react at the set temperature of 60 °C for 14 h. After repeated washing with deionized water, and drying under normal pressure at 50°C for 24 hours, ZnAl-PW ₁₂ O ₄₀ -LDHs white solid was obtained.

(3) according to the dry weight mass percentage ratio of table 2 (CNF+ZnAl-PW ₁₂ O ₄₀ -LDHs+H ₃ BO ₃ total 100%), ZnAl-PW ₁₂ O ₄₀ -LDHs slurry and CNF are mixed and stirred uniformly; And a certain amount of boric acid solution was added dropwise. According to the vacuum drying method of the comparative example, the sample is freeze-dried to obtain it.

(4) The obtained product is tested for fire resistance, combustion performance and thermal conductivity, and the test method is the same as above.

Table 2 Composition and ratio of CNF/ZnAl-PW ₁₂ O ₄₀ -LDHs/H ₃ BO ₃ lightweight foam thermal insulation materials

Table 3 shows the fire resistance test of the lightweight foam thermal insulation materials of Comparative Examples and Examples under the thermal irradiation power of 35kW/m ² (643°C), and the temperature rise of the unfired surface of the test samples. When the backfire temperature of the defined material rises to 200°C and 250°C, the corresponding rates are v _200°C and v _250°C , and are used to evaluate the fire resistance of lightweight foam insulation materials. It can be seen from Table 3 that the backfire temperature of pure CNF and CNF/ZnAl-NO ₃ -LDHs/H ₃ BO ₃ lightweight foam thermal insulation materials increases rapidly. Compared with pure CNF foams, the CNF/ZnAl-PW ₁₂ O ₄₀ -LDHs/H ₃ BO ₃ lightweight foams prepared by ZnAl-PW ₁₂ O ₄₀ -LDHs composite CNF with H ₃ BO ₃ as the linking agent The refractory performance of thermal insulation materials is significantly enhanced. As the content of ZnAl-PW ₁₂ O ₄₀ -LDHs increases, the v _{200 °C} of the material decreases gradually.

Table 3 Test results of backfire temperature of lightweight foam thermal insulation materials of comparative examples and examples

Table 4 Temperature test results of thermal conductivity of lightweight foam thermal insulation materials of comparative examples and examples

Table 4 is the thermal conductivity temperature test results of the lightweight foam thermal insulation materials of Comparative Examples and Examples, the thermal conductivity of CNF/25%ZnAl-PW ₁₂ O ₄₀ -LDHs/2% H ₃ BO ₃ lightweight foam thermal insulation materials The coefficient is 0.04210W/(m·K), which is significantly lower than that of pure CNF, which is 0.04517W/(m·K). The results show that the composite of ZnAl-PW ₁₂ O ₄₀ -LDHs is effective The thermal conductivity of the nanocellulose lightweight foam thermal insulation material is inhibited effectively, so that the CNF/ZnAl-PW ₁₂ O ₄₀ -LDHs/H ₃ BO ₃ lightweight foam thermal insulation material exhibits good thermal insulation performance.

Figure 2 is the SEM image of the CNF/50%ZnAl-PW ₁₂ O ₄₀ -LDHs/2% H ₃ BO ₃ lightweight foam thermal insulation material. It can be seen from the figure that when the addition amount of ZnAl-PW ₁₂ O ₄₀ -LDHs is 50%, the overall structure of the CNF/ZnAl-PW ₁₂ O ₄₀ -LDHs/H ₃ BO ₃ lightweight foam insulation material is compact, the cut surface is flat, and the holes are The distribution is uniform and the shape is regular, and the pore size is about 200-300um. At the same time, the particle size of ZnAl-PW ₁₂ O ₄₀ -LDHs was uniform and dispersed evenly in the pore walls of the CNF matrix without obvious agglomeration, indicating that the dispersibility of ZnAl-PW ₁₂ O ₄₀ -LDHs has been significantly improved and can be well supported In CNF, the two have good compatibility.

Figure 1 is a photo of the combustion of each sample lightweight foam thermal insulation material under the flame of an alcohol lamp at 500-600°C. The ignition time is one of the important criteria to measure the combustion performance of the material. The ignition time of pure CNF is 1s. The open flame of the material is extinguished at 5s, and the material is out of the fire at 18s. At this time, there is only a little carbon layer left, and more white ashes are attached to the surface. During the entire combustion process, pure CNF burns rapidly and violently under the outer flame of the alcohol lamp, and the material shrinks and deforms significantly when heated. The ignition time of the CNF/ZnAl-NO ₃ -LDHs/H ₃ BO ₃ lightweight foam thermal insulation material is 3s, the open flame of the material is self-extinguishing at 6s, and the material is released from the fire at 35s. Comparing the combustion process of the two, it can be seen that compared with CNF, when the addition amount of ZnAl-NO ₃ -LDHs is 50%, the ignition time of CNF/ZnAl-NO ₃ -LDHs/H ₃ BO ₃ material is delayed, and the flame changes significantly. Small, the burning time of the open fire is shortened, the shrinkage of the shape of the material is improved when it is removed from the fire, and there is still a small amount of carbon residue on the upper side of the material, and the ash on the lower side is continuous without obvious scattering. The results show that the combustion degree of the CNF/ZnAl-NO ₃ -LDHs/H ₃ BO ₃ lightweight foam insulation material is moderated and the fire resistance is enhanced. When the addition amount of ZnAl-PW ₁₂ O ₄₀ -LDHs reaches 50%, it is observed that: CNF/ZnAl-PW ₁₂ O ₄₀ -LDHs/H ₃ BO ₃ lightweight foam insulation material is carbonized under the flame of alcohol lamp, and There is a certain shrinkage and bending deformation when heated, but it is also not ignited during the whole process of 67s. When leaving the fire at 67s, it can be clearly seen that the charcoal layer on the upper side of the material is still intact, and the charcoal layer on the lower side is covered with a small amount of ash, but it does not fall off. Compared with pure CNF and CNF/ZnAl-NO ₃ -LDHs/H ₃ BO ₃ , CNF/ZnAl-PW ₁₂ O prepared with [PW ₁₂ O ₄₀ ] ^3- intercalation modified ZnAl-NO ₃ -LDHs composite CNF The charcoal layer formed by ₄₀ -LDHs/H ₃ BO ₃ lightweight foam insulation material can be heated for a longer time, the degree of combustion resistance is significantly enhanced, and it has higher combustion performance (not easy to burn). Among them, the decomposition products of ZnAl-PW ₁₂ O ₄₀ -LDHs at high temperature can promote the instant dehydration, esterification and curing of the CNF substrate to form a protective carbon layer, thereby improving the flame retardant performance and combustion performance of the material.

The above are only preferred embodiments of the present invention, and do not limit the present invention in any form. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solutions of the present invention should fall within the protection scope of the technical solutions of the present invention.

Claims (10)

1. a preparation method of phosphotungstic acid intercalation class hydrotalcite lightweight foam insulation material, is characterized in that, comprises the following steps: (1) Preparation of Zn/Al hydrotalcite precursor by co-precipitation method; (2) Using the ion exchange method, drop the phosphotungstic acid salt solution into the Zn/Al type hydrotalcite precursor slurry in step (1), and modify the Zn/Al type hydrotalcite precursor to obtain phosphotungstic acid -Zn/Al hydrotalcite; (3) Mixing the phosphotungstic acid-Zn/Al hydrotalcite, nanocellulose, and binder obtained in step (2), and freeze-drying to obtain a phosphotungstic acid intercalated hydrotalcite lightweight foam insulation material. 2. the preparation method of phosphotungstic acid intercalated hydrotalcite light foam thermal insulation material according to claim 1, is characterized in that, the described co-precipitation method of step (1) is to mix zinc salt, aluminum salt The salt solution is reacted with a pH value of 6-9 and a temperature of 50-90° C. to obtain a Zn/Al type hydrotalcite precursor. 3. the preparation method of the phosphotungstic acid intercalation type hydrotalcite light foam thermal insulation material according to claim 2, is characterized in that, the zinc salt described in step (1), aluminium salt are according to the mole of zinc ion and aluminium ion The ratio is 2:1-3:1 formulated. 4. The preparation method of the phosphotungstic acid intercalated hydrotalcite lightweight foam insulation material according to any one of claims 1 to 3, wherein the ion exchange method in step (2) is to convert phosphotungstic acid The salt solution is dropped into the Zn/Al type hydrotalcite precursor slurry in step (1), and the reaction is carried out at a temperature of 50-90° C. to obtain phosphotungstic acid-Zn/Al type hydrotalcite. 5. The preparation method of phosphotungstic acid intercalated hydrotalcite light foam thermal insulation material according to claim 4, characterized in that in step (2), the composition of host Zn/Al hydrotalcite and guest phosphotungstate The mass ratio is 1:3-3:1. 6. The preparation method of the phosphotungstic acid intercalated hydrotalcite lightweight foam insulation material according to any one of claims 1 to 3, wherein the nanocellulose size distribution in step (3) is: Nanocellulose with fiber length of 1-100nm accounts for 25%-60%; nanocellulose with fiber length of 100-1000nm accounts for 35%-50%; nanocellulose with fiber length of 1μm-10mm accounts for 10%-15% . 7. The preparation method of the phosphotungstic acid intercalated hydrotalcite lightweight foam thermal insulation material according to any one of claims 1 to 3, wherein the adhesive in step (3) is boric acid, tartaric acid, At least one of malic acid or citric acid. 8. The preparation method of the phosphotungstic acid intercalated hydrotalcite lightweight foam thermal insulation material according to any one of claims 1 to 3, wherein in step (3), phosphotungstic acid-Zn/Al water The mass ratio of talc, nanocellulose and binder is 20-55:40-80:1-5. 9. The preparation method of the phosphotungstic acid intercalated hydrotalcite lightweight foam thermal insulation material according to any one of claims 1 to 3, characterized in that in step (3), a small molecular alcohol organic solvent, One or more of macromolecular organic compounds or flame retardant additives. 10 . A phosphotungstic acid intercalated hydrotalcite lightweight foam insulation material, characterized in that, it is prepared by the method of any one of claims 1 to 9 .

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