Preparation method of nanocellulose reinforced and dispersed silicon flame retardant

Abstract

The invention discloses a preparation method of a nanocellulose reinforced and dispersed silicon flame retardant, which comprises the following steps: mixing calcium-based montmorillonite with deionized water to obtain a calcium-based montmorillonite suspension; taking a suspension formed by mixing carboxylated nanocellulose and deionized water as a dispersing agent, and mixing a calcium-based montmorillonite suspension and the dispersing agent to obtain a mixed solution; stirring the prepared mixed solution, then carrying out ultrasonic dispersion treatment, then carrying out centrifugal precipitation, and taking an upper-layer suspension to obtain a synergistic flame-retardant solution; mixing sodium silicate with deionized water to prepare a sodium silicate solution; and mixing the prepared synergistic flame-retardant solution with a sodium silicate solution, adding an alkali solution at the same time, carrying out an ion replacement reaction, uniformly stirring, cooling to room temperature, and carrying out sealed storage, so as to obtain the nano-cellulose reinforced and dispersed silicon-based flame retardant. The preparation method of the silicon-based flame retardant solves the technical problems of poor compatibility, low mechanical property and reduced flame retardance caused by increase of the addition amount of inorganic mineral substances in the silicon-based flame retardant in the prior art.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardants, and in particular is a method for preparing a nano-cellulose reinforced and dispersed silicon-based flame retardant. Background Art

[0002] Bamboo and wood materials are widely used in modern society, especially in home furnishings. However, bamboo and wood are inherently flammable, requiring flame retardant treatment during processing to maximize their flame retardancy. The mandatory standard "Combustion Performance Requirements and Labeling of Flame-Retardant Products and Components for Public Places" (GB20286-2006) specifies the flame retardancy ratings for decorative products and components used in public places and residences.

[0003] Conventional practice in wood and bamboo processing involves directly adding inorganic flame retardants, such as phosphorus, nitrogen, boron, silicon, and magnesium, to adhesives. Halogen flame retardants, while offering advantages such as low dosage, low cost, and good material compatibility, interfere with free radical chain reactions during combustion, leading to the production of large quantities of toxic and hazardous gases. This poses a threat to environmental protection and can also lead to the bioaccumulation of toxic substances, endangering human health. Silicon-based flame retardants, primarily based on Si-O-Si chains, are highly effective, low-toxic, drip-resistant, char-forming, and smoke-suppressing halogen-free flame retardants and have become a new trend in flame retardant development.

[0004] Existing silicone flame retardants include organosiloxanes, inorganic silicones, and organic-inorganic hybrid silicones. Organosiloxanes are linear high-molecular polymers with monovalent organic groups as pendant groups. They are divided into high-temperature and room-temperature vulcanized silicone rubbers according to their vulcanization temperature. They mainly act in the condensed phase and lack gas-phase flame retardancy, so they cannot achieve good results in heat release rate and vertical burning tests. Inorganic silicone flame retardants use silica or other inorganic silicate materials as flame retardants. Silica or other inorganic silicate materials will migrate to the surface of the melt, acting as a heat barrier and achieving a certain flame retardant effect. Inorganic-organic hybrid silicones have become one of the current research hotspots in flame retardants due to their good structural design and the combination of the respective advantages of inorganic and organic.

[0005] Inorganic silicates such as silica and montmorillonite are currently the most common flame retardant raw materials. However, excessive addition of these inorganic silicates significantly reduces their compatibility with the substrate. While researchers have introduced polypropylene for coating, this still fails to address issues such as reduced toughness and poor compatibility with wood and bamboo substrates. Therefore, silicon-based flame retardant technology for bamboo and wood materials requires further refinement and improvement. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a method for preparing a silicon-based flame retardant reinforced with nanocellulose to address the shortcomings of the above-mentioned prior art. The method for preparing a silicon-based flame retardant reinforced with nanocellulose solves the technical problems of poor compatibility, low mechanical properties and decreased flame retardancy caused by the increase in the amount of inorganic minerals added in the prior art silicon-based flame retardants.

[0007] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0008] A method for preparing a nanocellulose-enhanced dispersed silicon-based flame retardant comprises the following steps:

[0009] Step 1: Mixing calcium-montmorillonite with deionized water to obtain a calcium-montmorillonite suspension; using a suspension of carboxylated nanocellulose and deionized water as a dispersant, and mixing the calcium-montmorillonite suspension and the dispersant to obtain a mixed solution;

[0010] Step 2: Stirring the mixed solution prepared in step 1 for a certain period of time, performing ultrasonic dispersion treatment, and then performing centrifugal precipitation to obtain a synergistic flame retardant solution;

[0011] Step 3: Mix sodium silicate with deionized water to prepare a sodium silicate solution; mix the synergistic flame retardant solution prepared in step 2 with the sodium silicate solution, and add an alkali solution at the same time. After ion exchange reaction at a certain temperature for a certain time, stir evenly, cool to room temperature, seal and store, thereby obtaining a nanocellulose-reinforced dispersed silicon-based flame retardant.

[0012] As a further improved technical solution of the present invention, the step 1 specifically includes:

[0013] Calcium-based montmorillonite and deionized water are mixed in a mass ratio of 1:50-100 to obtain a calcium-based montmorillonite suspension; carboxylated nanocellulose and deionized water are mixed in a mass ratio of 1:50-100 to obtain a carboxylated nanocellulose dispersion; the calcium-based montmorillonite suspension and the carboxylated nanocellulose dispersion are stirred for 30 minutes respectively, and then the calcium-based montmorillonite suspension and the carboxylated nanocellulose dispersion are mixed in a mass ratio of 1:1, and stirred for 12 hours to obtain a mixed solution.

[0014] As a further improved technical solution of the present invention, the step 2 specifically includes:

[0015] The mixed solution prepared in step 1 is ultrasonically dispersed using an ultrasonic cell disruptor at a power of 800-1000 W for 30-60 min. The solution is then centrifuged at a speed of 9000-10000 rpm for 10-15 min to obtain a milky white gel-like upper suspension, i.e., the synergistic flame retardant solution.

[0016] As a further improved technical solution of the present invention, the step 3 specifically includes:

[0017] Sodium silicate is mixed with 60°C deionized water in a mass ratio of 0.3:1 to prepare a transparent sodium silicate solution; the synergistic flame retardant solution prepared in step 2 is mixed with the transparent sodium silicate solution in a mass ratio of 2.5-5:100, and 0.5 mol / L alkaline solution is added to adjust the pH value of the solution to greater than 10. An ion exchange reaction is carried out at 60°C for 15-30 minutes. After stirring evenly, the mixture is cooled to room temperature and sealed for storage to obtain a nanocellulose-reinforced dispersed silicon-based flame retardant.

[0018] As a further improved technical solution of the present invention, in step 3, the alkaline solution is NaOH solution or Ca(OH)2 solution.

[0019] The beneficial effects of the present invention are:

[0020] (1) The present invention utilizes the rich carboxyl and hydroxyl functional groups of carboxylated nanocellulose to uniformly and stably disperse calcium-montmorillonite in a sodium silicate solution, and combines pH control to achieve stable and long-lasting dispersion of montmorillonite flakes, while forming a "montmorillonite-calcium silicate-TOCNF" composite structure.

[0021] (2) The present invention adopts the method of ion replacement to achieve sodium modification of natural calcium-based montmorillonite, thereby improving its dispersion, suspension and water absorption and expansion properties, enhancing its adsorption capacity, and forming a more stable composite structure with bamboo and wood, thereby improving the problem of poor compatibility between existing flame retardants and the matrix.

[0022] (3) The carboxylated nanocellulose in the present invention is rich in carboxyl and hydroxyl functional groups, which can serve as a bridge between the inorganic flame retardant component and the bamboo wood matrix, thereby achieving a stable connection between the flame retardant and the matrix; after the addition of nanocellulose, the connection is more firm, the toughness is enhanced, and the mechanical properties are also strengthened.

[0023] (IV) The flame retardant prepared by the present invention can form a stable and dense inorganic layer on the surface of the body, forming a physical barrier that can inhibit oxygen diffusion and heat transfer. Sodium silicate decomposes at high temperature to form glassy SiO2, which can form a "ceramic-carbon" composite barrier layer together with the expandable porous carbon layer formed by Al2O3 and TOCNF in montmorillonite to block the release of combustible gases. In addition, the Al2O3 between the montmorillonite layers 3+ and Ca in calcium silicate 2+ It can catalyze and capture free radicals in the combustion chain reaction, inhibiting the spread of flames. The combined effect achieves excellent flame retardant properties. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention are further described below:

[0025] Example 1:

[0026] A method for preparing a nanocellulose-enhanced dispersed silicon-based flame retardant comprises the following steps:

[0027] Step 1. Mix 1g of calcium montmorillonite with 100g of deionized water to obtain a calcium montmorillonite suspension; mix 1g of carboxylated nanocellulose with 100g of deionized water to obtain a carboxylated nanocellulose dispersion; stir the calcium montmorillonite suspension and the carboxylated nanocellulose dispersion for 30 minutes respectively, and then mix the calcium montmorillonite suspension and the carboxylated nanocellulose dispersion in a mass ratio of 1:1, and stir for 12 hours to obtain a mixed solution.

[0028] Step 2: Stir the mixed solution prepared in step 1 for a certain period of time, perform ultrasonic dispersion treatment, and then perform centrifugal precipitation to obtain a synergistic flame retardant solution.

[0029] Specifically, the mixed solution prepared in step 1 was ultrasonically dispersed by an ultrasonic cell disruptor with a power of 800 W and an ultrasonic dispersion treatment time of 30 min. Thereafter, the solution was centrifuged at a speed of 9000 rpm for 10 min to obtain a milky white gel-like upper suspension, i.e., the synergistic flame retardant solution.

[0030] Step 3: Mix 30 g of sodium silicate with deionized water to prepare a sodium silicate solution; mix the synergistic flame retardant solution prepared in step 2 with the sodium silicate solution, and add an alkali solution at the same time. After ion exchange reaction at a certain temperature for a certain time, stir evenly, cool to room temperature, and seal for storage to obtain a nanocellulose-reinforced dispersed silicon-based flame retardant.

[0031] 30 g of sodium silicate was mixed with 100 g of 60° C. deionized water to prepare a transparent sodium silicate solution; 3.25 g of the synergistic flame retardant solution prepared in step 2 was mixed with 130 g of the transparent sodium silicate solution, and 0.5 mol / L of an alkaline solution was added to adjust the pH value of the solution to greater than 10. An ion exchange reaction was carried out at 60° C. for 15 minutes. After stirring evenly, the mixture was cooled to room temperature and sealed for storage to obtain a nanocellulose-reinforced dispersed silicon-based flame retardant.

[0032] In step 3, the alkaline solution is NaOH solution or Ca(OH)2 solution.

[0033] Example 2:

[0034] Step 1. Mix 1.5 g of calcium montmorillonite with 100 g of deionized water to obtain a calcium montmorillonite suspension; mix 1.5 g of carboxylated nanocellulose with 100 g of deionized water to obtain a carboxylated nanocellulose dispersion; stir the calcium montmorillonite suspension and the carboxylated nanocellulose dispersion for 30 minutes respectively, and then mix the calcium montmorillonite suspension and the carboxylated nanocellulose dispersion in a mass ratio of 1:1, and stir for 12 hours to obtain a mixed solution.

[0035] Step 2: Stir the mixed solution prepared in step 1 for a certain period of time, perform ultrasonic dispersion treatment, and then perform centrifugal precipitation to obtain a synergistic flame retardant solution.

[0036] Specifically, the mixed solution prepared in step 1 was ultrasonically dispersed by an ultrasonic cell disruptor with a power of 900 W and an ultrasonic dispersion treatment time of 40 min. Thereafter, the solution was centrifuged at a speed of 9500 rpm for 13 min to obtain a milky white gel-like upper suspension, i.e., the synergistic flame retardant solution.

[0037] Step 3: Mix 30 g of sodium silicate with deionized water to prepare a sodium silicate solution; mix the synergistic flame retardant solution prepared in step 2 with the sodium silicate solution, and add an alkali solution at the same time. After ion exchange reaction at a certain temperature for a certain time, stir evenly, cool to room temperature, and seal for storage to obtain a nanocellulose-reinforced dispersed silicon-based flame retardant.

[0038] 30 g of sodium silicate was mixed with 100 g of 60° C. deionized water to prepare a transparent sodium silicate solution; 3.25 g of the synergistic flame retardant solution prepared in step 2 was mixed with 130 g of the transparent sodium silicate solution, and 0.5 mol / L of an alkaline solution was added to adjust the pH value of the solution to greater than 10. An ion exchange reaction was carried out at 60° C. for 25 minutes. After stirring evenly, the mixture was cooled to room temperature and sealed for storage to obtain a nanocellulose-reinforced dispersed silicon-based flame retardant.

[0039] In step 3, the alkaline solution is NaOH solution or Ca(OH)2 solution.

[0040] Example 3:

[0041] Step 1. Mix 2 g of calcium montmorillonite with 100 g of deionized water to obtain a calcium montmorillonite suspension; mix 2 g of carboxylated nanocellulose with 100 g of deionized water to obtain a carboxylated nanocellulose dispersion; stir the calcium montmorillonite suspension and the carboxylated nanocellulose dispersion for 30 minutes respectively, and then mix the calcium montmorillonite suspension and the carboxylated nanocellulose dispersion in a mass ratio of 1:1, and stir for 12 hours to obtain a mixed solution.

[0042] Step 2: Stir the mixed solution prepared in step 1 for a certain period of time, perform ultrasonic dispersion treatment, and then perform centrifugal precipitation to obtain a synergistic flame retardant solution.

[0043] Specifically, the mixed solution prepared in step 1 was ultrasonically dispersed using an ultrasonic cell disruptor with a power of 1000 W and an ultrasonic dispersion treatment time of 60 min. Subsequently, the solution was centrifuged at a speed of 10,000 rpm for 15 min to obtain a milky white gel-like upper suspension, i.e., the synergistic flame retardant solution.

[0044] Step 3: Mix 30 g of sodium silicate with deionized water to prepare a sodium silicate solution; mix the synergistic flame retardant solution prepared in step 2 with the sodium silicate solution, and add an alkali solution at the same time. After ion exchange reaction at a certain temperature for a certain time, stir evenly, cool to room temperature, and seal for storage to obtain a nanocellulose-reinforced dispersed silicon-based flame retardant.

[0045] 30 g of sodium silicate was mixed with 100 g of 60° C. deionized water to prepare a transparent sodium silicate solution; 6.5 g of the synergistic flame retardant solution prepared in step 2 was mixed with 130 g of the transparent sodium silicate solution, and 0.5 mol / L of an alkaline solution was added to adjust the pH value of the solution to greater than 10. An ion exchange reaction was carried out at 60° C. for 30 minutes. After stirring evenly, the mixture was cooled to room temperature and sealed for storage to obtain a nanocellulose-reinforced dispersed silicon-based flame retardant.

[0046] In step 3, the alkaline solution is NaOH solution or Ca(OH)2 solution.

[0047] Comparative Example 1:

[0048] This comparative example provides a silicon-based flame retardant, which differs from Example 3 in that calcium-based montmorillonite and carboxylated nanocellulose are not added.

[0049] Comparative Example 2:

[0050] This comparative example provides a silicon-based flame retardant, which differs from Example 3 in that no dispersant carboxylated nanocellulose colloid is added.

[0051] Table 1 below summarizes the flame retardant performance parameters of the examples and the comparative examples. It can be seen that the flame retardant performance of the examples can reach B1 level.

[0052] Table 1:

[0053] LOI Flame retardant grade Example 1 (1.0 g) 28.40% B1 Example 2 (1.5g) 31.60% B1 Example 3 (2.0 g) 32.30% B1 Comparative Example 1 (pure sodium silicate) 24.10% B2 Control Example 2 (no carboxylated nanocellulose added) 25.90% B2

[0054] The proposed method for preparing a nanocellulose-enhanced dispersed silicon-based flame retardant significantly improves both flame retardancy and mechanical properties compared to a control. Furthermore, the method is simple to implement, low-cost, and highly effective, making it suitable for large-scale promotion.

[0055] The embodiment described above is only a preferred solution of the present invention and does not limit the present invention in any form. Other variations and modifications are possible without exceeding the technical solution described in the claims.

Claims

1. A method for preparing a nanocellulose-enhanced dispersed silicon-based flame retardant, characterized in that: The following steps are involved: Step 1: Mixing calcium-montmorillonite with deionized water to obtain a calcium-montmorillonite suspension; using a suspension of carboxylated nanocellulose and deionized water as a dispersant, and mixing the calcium-montmorillonite suspension and the dispersant to obtain a mixed solution; Step 2: Stirring the mixed solution prepared in step 1 for a certain period of time, performing ultrasonic dispersion treatment, and then performing centrifugal precipitation to obtain a synergistic flame retardant solution; Step 3: Mix sodium silicate with deionized water to prepare a sodium silicate solution; mix the synergistic flame retardant solution prepared in step 2 with the sodium silicate solution, and add an alkali solution at the same time. After ion exchange reaction at a certain temperature for a certain time, stir evenly, cool to room temperature, seal and store, thereby obtaining a nanocellulose-reinforced dispersed silicon-based flame retardant.

2. The method for preparing a nanocellulose-enhanced dispersed silicon-based flame retardant according to claim 1, characterized in that: The step 1 specifically includes: Calcium-based montmorillonite and deionized water are mixed in a mass ratio of 1:50-100 to obtain a calcium-based montmorillonite suspension; carboxylated nanocellulose and deionized water are mixed in a mass ratio of 1:50-100 to obtain a carboxylated nanocellulose dispersion; the calcium-based montmorillonite suspension and the carboxylated nanocellulose dispersion are stirred for 30 minutes respectively, and then the calcium-based montmorillonite suspension and the carboxylated nanocellulose dispersion are mixed in a mass ratio of 1:1, and stirred for 12 hours to obtain a mixed solution.

3. The method for preparing a nanocellulose-enhanced dispersed silicon-based flame retardant according to claim 1, wherein: The step 2 specifically includes: The mixed solution prepared in step 1 is ultrasonically dispersed using an ultrasonic cell disruptor at a power of 800-1000 W for 30-60 min. The solution is then centrifuged at a speed of 9000-10000 rpm for 10-15 min to obtain a milky white gel-like upper suspension, i.e., the synergistic flame retardant solution.

4. The method for preparing a nanocellulose-enhanced dispersed silicon-based flame retardant according to claim 1, wherein: The step 3 specifically includes: Sodium silicate is mixed with 60°C deionized water in a mass ratio of 0.3:1 to prepare a transparent sodium silicate solution; the synergistic flame retardant solution prepared in step 2 is mixed with the transparent sodium silicate solution in a mass ratio of 2.5-5:100, and 0.5 mol / L alkaline solution is added to adjust the pH value of the solution to greater than 10. An ion exchange reaction is carried out at 60°C for 15-30 minutes. After stirring evenly, the mixture is cooled to room temperature and sealed for storage to obtain a nanocellulose-reinforced dispersed silicon-based flame retardant.

5. The method for preparing a nanocellulose-enhanced dispersed silicon-based flame retardant according to claim 1, wherein: In step 3, the alkaline solution is NaOH solution or Ca(OH)2 solution.