Flame-retardant interfacial agent and preparation method thereof

Abstract

The application discloses a kind of flame-retardant interface agent and preparation method thereof, belong to artificial board technical field.The interface agent includes by weight parts: magnesium sulfate 10-25 parts, polyvinyl alcohol 2-8 parts, magnesium chloride 30-50 parts, borax 0.1-2 parts, industrial starch 1-5 parts, magnesium oxide 80-120 parts, water 120-160 parts.Preparation method includes: polyvinyl alcohol is dissolved in water, then magnesium sulfate is obtained first preparation;Magnesium chloride, borax and industrial starch are mixed, then water is added in batches to obtain second preparation;First preparation is added to second preparation and mixed;Finally, magnesium oxide is added in batches to obtain thick paste interface agent.The application solves the problem of moisture absorption and halogen return by replacing part of magnesium chloride with magnesium sulfate, polyvinyl alcohol and borax synergistically enhance the interface bonding, and starch improves the stability of the system.The interface agent has excellent adhesion, water resistance and flame retardant performance, and is suitable for interface reinforcement between wood and magnesium oxychloride cement, solving the technical problems of insufficient interface bonding strength and easy halogen return in the prior art.

Description

Technical Field

[0001] This invention relates to the field of engineered wood products technology, specifically to a flame-retardant interface agent and its preparation method. Background Technology

[0002] Aldehyde adhesives and their products commonly used in my country's timber industry release formaldehyde during use, polluting the living environment, and have poor thermal stability and flame retardant properties. Compared with aldehyde organic adhesives, magnesium adhesives have the advantages of being non-toxic and environmentally friendly, abundant in resources, having high bonding strength, good weather resistance, and good flame retardancy.

[0003] Magnesium-based adhesives are products made from magnesium oxide, magnesium chloride (or magnesium sulfate), and water as basic chemical compounds. Depending on the application, fillers and modifiers (organic or inorganic fiber materials, fly ash, slag powder, etc.) are added in specific proportions, followed by mixing, molding, and curing processes. Magnesium-based adhesives prepared from magnesium oxide and magnesium chloride are called magnesium oxychloride adhesives.

[0004] In the preparation of magnesium oxychloride adhesives, different raw material ratios and preparation processes have a significant impact on mechanical properties, microstructure, and hydration reaction progress. Magnesium oxychloride cement is synthesized through a three-phase system of MgO-MgCl2-H2O, and the products mainly include five and / or three phases. The MgO / MgCl2 molar ratio, magnesium chloride solution concentration, curing temperature, and magnesium oxide activity all affect the performance and structure of magnesium oxychloride cement. The composition ratios of existing magnesium oxychloride adhesives lack systematic optimization; relying solely on the binary system of magnesium chloride and magnesium oxide makes it difficult to achieve a comprehensive improvement in performance, especially in terms of adhesive strength, which is less than ideal and limits its application as an interface agent.

[0005] Modifying magnesium oxychloride cement by adding modifiers is currently the most widely used improvement method. Modifiers include acids (phosphoric acid, citric acid), salts (phosphates, silicates), mineral admixtures such as fly ash, and other cementitious materials. Different types of modifiers mainly improve the water resistance of magnesium oxychloride cement by: (1) stabilizing the hydration products of the magnesium oxychloride cement system to generate more water-stable gel-like five-phase; (2) constructing a water-blocking film on the crystal surface to weaken the wetting of magnesium oxychloride cement by water; and (3) filling the internal pores of magnesium oxychloride cement to form a dense structure while preventing water molecules from directly contacting the five-phase crystals of magnesium oxychloride cement. However, these modification schemes mostly use a single type of inorganic modifier and lack systematic research on organic-inorganic composite modification. They fail to give full play to the synergistic effect of the excellent adhesive properties of organic materials and the excellent flame retardant and waterproof properties of inorganic materials, resulting in the product being difficult to achieve an ideal balance in terms of adhesion, water resistance and flame retardancy.

[0006] In addition, existing magnesium oxychloride adhesives still exhibit moisture absorption and efflorescence, meaning that the surface turns white due to chloride ion precipitation. This not only affects the appearance quality but may also corrode metal components, and the water resistance needs to be further improved.

[0007] Therefore, there is an urgent need to develop an environmentally friendly flame-retardant interface agent that significantly enhances adhesion while possessing excellent water resistance and flame retardancy to solve the aforementioned technical problems. Summary of the Invention

[0008] Based on the problems existing in the background technology, the present invention provides a flame retardant interface agent and its preparation method to solve the technical problems of existing magnesium oxychloride cement adhesive formulations that are not optimized, have poor toughness, are prone to moisture absorption and efflorescence, and have insufficient bonding strength with wood, so as to achieve the preparation of a high-strength, water-resistant, environmentally friendly flame retardant interface agent.

[0009] This invention is implemented through the following technical solutions:

[0010] The first aspect of this invention discloses a flame retardant interface agent comprising the following components in parts by weight: 10-25 parts magnesium sulfate, 2-8 parts polyvinyl alcohol, 30-50 parts magnesium chloride, 0.1-2 parts borax, 1-5 parts industrial starch, 80-120 parts magnesium oxide, and 120-160 parts water.

[0011] Further, it includes the following components in parts by weight: 15 parts magnesium sulfate, 5 parts polyvinyl alcohol, 40 parts magnesium chloride, 1 part borax, 3 parts industrial starch, 100 parts magnesium oxide, and 140 parts water.

[0012] The second aspect of this invention discloses a method for preparing the flame-retardant interface agent, comprising the following steps:

[0013] S1. Dissolve polyvinyl alcohol in water, then add magnesium sulfate and mix well to obtain the first preparation;

[0014] S2. Mix magnesium chloride, borax, and industrial starch evenly to obtain a mixture;

[0015] S3. Add the remaining water to the mixture in batches, stir well, and obtain the second preparation;

[0016] S4. Add the first formulation to the second formulation, stir well to obtain a mixed solution;

[0017] S5. Add magnesium oxide in batches to the mixed solution and mix thoroughly to obtain a thick paste-like flame retardant interface agent.

[0018] Further, in step S1, polyvinyl alcohol is dissolved in water at 80-90°C, and then magnesium sulfate is added after the temperature is lowered to below 60°C.

[0019] Polyvinyl alcohol typically dissolves at 80-90℃, and the dissolution process is relatively slow; the larger the molecular weight, the less easily it dissolves. MgSO4 ionizes at high temperatures to produce Mg... 2+ MgSO4 is a strong hydration ion that competes with polyvinyl alcohol for free water, causing it to dehydrate and shrink to form gel particles. Therefore, MgSO4 should be added after the temperature has cooled down.

[0020] The purpose of adding polyvinyl alcohol in this invention is that polyvinyl alcohol has a high elastic modulus and good interfacial adhesion. Its long chain has strong hydrogen bond interaction with wood and the good fluidity of the long chain molecules improves the binding and permeability of the system with wood.

[0021] The purpose of adding magnesium sulfate is that, in magnesium-based cementitious systems, magnesium chloride dominates the formation of the 518 phase, but Cl... - Easily soluble, reducing water resistance and causing efflorescence; replacing 20-30% magnesium chloride with magnesium sulfate reduces the total amount of soluble ions and reduces moisture absorption and efflorescence; excessive addition of magnesium sulfate will form an unstable 318 phase, affecting the performance of the hydration reaction products.

[0022] Furthermore, in step S1, water accounts for 55-60% of the total water volume, and in step S3, water accounts for 40-45% of the total water volume.

[0023] Furthermore, in step S2, the magnesium chloride, borax, and industrial starch are mixed evenly without adding water. This involves mixing the brine raw materials and fillers evenly. If water is added first to make the magnesium chloride and water brine, and then borax and starch are added later, it is easy for the mixture to clump together. Uneven mixing will affect the coagulation process of the gelling material.

[0024] The purpose of adding borax is that it is often used as a slow-release agent to delay the setting time, and it can cross-link with polyvinyl alcohol to form a network structure to enhance the mechanical properties of materials, such as elastic modulus and viscosity, making it particularly suitable for hydrogel preparation; however, excessive addition of borax may reduce compressive strength.

[0025] The purpose of adding starch is that, as a water-absorbing polymer, starch can act as a buffer in magnesium oxychloride slurry to reduce solid-liquid separation and achieve the construction of a stable system.

[0026] Furthermore, in step S3, the stirring speed is ≤20 r / min, and the stirring time is 15-30 min.

[0027] The purpose of step S3 is to ensure that the material is fully dissolved, accelerate the dissolution while minimizing air bubbles and voids in the solution. Since the dissolution of magnesium chloride is an exothermic reaction, the process of dissolving in small amounts multiple times and stirring slowly is to control the temperature from becoming too high and causing the starch to gelatinize and clump together.

[0028] Furthermore, in step S4, after the first formulation is cooled to room temperature, it is added to the second formulation, with a stirring speed ≤20 r / min and a stirring time of 8-15 min.

[0029] Furthermore, in step S5, the mixing time for adding magnesium oxide to the mixed solution is 20-30 minutes.

[0030] The initial setting time of magnesium oxide, magnesium oxide and water mixture is generally within 60 minutes. The reason for completing the mixing within 30 minutes is to keep the mixture in a thick paste or cream state so that it can be used as an interface agent later.

[0031] The third aspect of this invention discloses the application of the flame-retardant interface agent in the preparation of composite artificial boards.

[0032] Furthermore, the flame-retardant interface agent is applied between the core layer and the flame-retardant layer.

[0033] The beneficial effects of this invention are:

[0034] 1. This invention is a hybrid interface agent, which combines organic and inorganic cementing materials. It utilizes the adhesive properties of organic materials and the flame retardancy and water resistance of inorganic materials. It is mainly used to enhance the bonding strength of the organic-inorganic interface between wood and magnesium oxychloride cement. It can firmly bond the core of different density boards to the flame retardant surface layer and has environmentally friendly flame retardant and waterproof properties.

[0035] 2. The interface agent manufacturing process of this invention is simple and reasonable, making full use of the properties of different materials, simplifying the process flow, saving time, and improving production efficiency.

[0036] 3. The organic and inorganic fillers added in this invention are inexpensive, and by controlling the optimal dosage, raw material costs can be saved, making it suitable for mass production. Attached Figure Description

[0037] The accompanying drawings are provided to further explain the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0038] Figure 1 This is a schematic diagram of the structure of the composite artificial board of the present invention;

[0039] Figure 2 This is a process flow diagram for preparing the flame-retardant interface agent according to the present invention. Detailed Implementation

[0040] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0041] Examples 1-9

[0042] Examples 1-9 determine the optimal ratio for the hydration reaction of the magnesium cementitious system.

[0043] The specific preparation steps of the test samples are as follows: According to the data in Table 1, a certain weight of magnesium sulfate and 80 parts of water were used to prepare the first preparation, and a certain amount of magnesium chloride and 60 parts of water were used to prepare the second preparation. After the first and second preparations were mixed evenly, 100 parts of magnesium oxide were added in batches and stirred for 30 minutes. The mixture was then poured into a mold, sealed and cured at room temperature for 24 hours, and then cured at room temperature for another 24 hours to obtain magnesium oxychloride cement samples. The performance of the samples was analyzed, and the corresponding test standards were: GB / T 17671-2021 "Test Method for Strength of Cement Mortar"; JC / T 568-2023 "Magnesium Oxychloride Cement Slabs"; the results are shown in Tables 1 and 2.

[0044] Table 1. Effect of magnesium chloride to magnesium sulfate ratio on the performance of magnesium oxychloride cement in Examples 1-9

[0045]

[0046] Table 2. Analysis of variance of test data for groups 1-9 in Examples

[0047]

[0048] Compressive strength reflects the mechanical properties of magnesium oxychloride cement, while the softening coefficient reflects its water resistance. Data from Tables 1 and 2 show that the optimal mix ratio is 15 parts magnesium sulfate and 40 parts magnesium chloride. The initial setting time of 42 minutes is moderate, but slightly fast for actual production; it can be adjusted according to production needs. Both factors significantly affect compressive strength and softening coefficient. Replacing magnesium chloride with an appropriate amount of magnesium sulfate can significantly improve the material's water resistance; however, excessive addition of magnesium sulfate does not further improve performance but instead easily leads to a loose material structure and performance degradation. Excess magnesium chloride in magnesium oxychloride cement can cause moisture absorption, efflorescence, and frost formation on the cement surface; while excess magnesium oxide in the system will absorb moisture from the air to form Mg(OH)2, causing the magnesium oxychloride cement sample to expand and even crack.

[0049] Examples 10-18

[0050] Examples 10-18 test the effects of polyvinyl alcohol and borax on the performance of the interface agent.

[0051] The specific preparation steps of the test sample are as follows: According to the data in Table 3, a certain amount of polyvinyl alcohol was dissolved in 80 parts of water at 85℃, cooled to below 60℃, and 15 parts of magnesium sulfate were added to make the first preparation. 40 parts of magnesium chloride and a certain amount of borax were mixed evenly and then 60 parts of water were added to make the second preparation. After the first preparation and the second preparation were mixed evenly, 100 parts of magnesium oxide were added in batches and stirred for 30 minutes. The mixture was then poured into a mold, sealed and cured at room temperature for 24 hours, and then cured at room temperature for another 24 hours to obtain magnesium oxychloride cement samples (used to determine compressive strength, softening coefficient, and initial setting time).

[0052] The specific preparation steps for the composite board sample are as follows: A certain amount of polyvinyl alcohol is dissolved in 80 parts of water at 85℃. The solution is cooled to below 60℃ and 15 parts of magnesium sulfate are added to prepare the first preparation. 40 parts of magnesium chloride and a certain amount of borax are mixed evenly, and then 60 parts of water are added to prepare the second preparation. The first and second preparations are mixed evenly, and then 100 parts of magnesium oxide are added in batches and stirred for 30 minutes to obtain the interface agent. The interface agent is then applied between the wood and the fire-retardant board using a self-developed special production process and equipment. After pressing for 12 hours, the board is cured at room temperature for 24 hours to obtain the composite board sample (e.g., ...). Figure 1 As shown, this is used to determine the shear strength of the adhesive layer.

[0053] Performance analysis was performed on the samples, in accordance with the following standards: JC / T 568-2023 Magnesium Oxide Chloride Cement Boards; GB / T17671-2021 Cement Mortar Strength Test Methods; GB / T 17657-2022 Physical and Chemical Properties Test Methods for Wood-based Panels and Decorative Wood-based Panels. The final results are shown in Tables 3 and 4.

[0054] Table 3. Effects of polyvinyl alcohol and borax on the performance of interface agents in Examples 10-18

[0055]

[0056] Table 4. Analysis of variance of adhesive layer shear strength data for Examples 10-18

[0057]

[0058] The results in Tables 3 and 4 show that the two factors significantly affect the shear strength of the adhesive layer, positively impacting compressive strength and softening coefficient, although the improvement is relatively small. This is because polyvinyl alcohol (PVA) is a linear long chain containing a large number of hydroxyl groups. After combining with magnesium oxide, it exhibits numerous long dangling chains, facilitating penetration into the porous, hydrophilic wood surface. The hydroxyl groups (-OH) on the PVA fiber surface form hydrogen bonds with the cellulose / hemicellulose of the wood components, thus enhancing the interfacial bonding strength with the wood. Borax is commonly used as a retarder, but excessive addition can affect the hydration reaction and reduce compressive strength. Therefore, the optimal ratio of 5 parts PVA and 1 part borax resulted in high shear strength and good material toughness in the adhesive layer, with minimal improvement in the strength and water resistance of magnesium oxychloride cement. Due to the retarding effect of borax, the initial setting time was 60 minutes, which is within a moderate range.

[0059] Examples 19-22

[0060] Examples 19-22 test the effect of starch on the performance of the interface agent.

[0061] The specific preparation steps of the test sample are as follows: According to the data in Table 5, 5 parts of polyvinyl alcohol were dissolved in 80 parts of water at 85℃, cooled to below 60℃, and 15 parts of magnesium sulfate were added to make the first preparation. 40 parts of magnesium chloride, 1 part of borax and a certain number of parts of starch were mixed evenly and then 60 parts of water were added to make the second preparation. After the first preparation and the second preparation were mixed evenly, 100 parts of magnesium oxide were added in batches and stirred for 30 minutes. The mixture was then poured into a mold, sealed and cured at room temperature for 24 hours, and then cured at room temperature for another 24 hours to obtain magnesium oxychloride cement sample (used to determine the softening coefficient).

[0062] The specific preparation steps for the composite board sample are as follows: According to the data in Table 5, 5 parts of polyvinyl alcohol were dissolved in 80 parts of water at 85℃, cooled to below 60℃, and 15 parts of magnesium sulfate were added to prepare the first preparation. 40 parts of magnesium chloride, 1 part of borax, and a certain amount of starch were mixed evenly, and then 60 parts of water were added to prepare the second preparation. After the first and second preparations were mixed evenly, 100 parts of magnesium oxide were added in batches and stirred for 30 minutes to obtain the interface agent. The interface agent was applied between the wood and the fire-retardant board using a self-developed special production process and equipment. After pressing for 12 hours, the composite board sample was cured at room temperature for 24 hours to obtain the composite board sample (used to determine the shear strength and initial tack of the adhesive layer).

[0063] Performance analysis was performed on the samples, in accordance with the relevant standards: JC / T 568-2023 "Magnesium Oxychloride Cement Boards" and GB / T17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels"; the final results are shown in Table 5.

[0064] Table 5. Effect of starch on the performance of interfacial agents in Examples 19-22

[0065]

[0066] As shown in Table 5, the optimal starch ratio is 3 parts. An appropriate amount of starch can promote the hydration of MgO and the formation of the five phases. However, due to the hydrophilicity of starch, adding excessive starch will lead to a decrease in water resistance. Therefore, when 5 parts of starch are added, both the shear strength and softening coefficient of the interface agent decrease. Initial tack is crucial in the manufacturing process of engineered wood panels. Too low an initial tack can easily cause slippage and misalignment during the assembly process. When the addition amount is 3 parts, the initial tack of the interface agent significantly increases to 5.33 N / mm, giving it good adhesion to the wood surface and allowing the shear strength of the adhesive layer to reach its maximum value, marking the inflection point in the interface agent's performance data.

[0067] Examples 23-26

[0068] Examples 23-26 test the effects of different mixing methods on the performance of the interface agent.

[0069] The optimal ratio of magnesium sulfate (15 parts), polyvinyl alcohol (5 parts), magnesium chloride (40 parts), borax (1 part), industrial starch (3 parts), magnesium oxide (100 parts), and water (140 parts) was selected.

[0070] The sample testing procedure is as follows:

[0071] A. Polyvinyl alcohol, B. Water, C. Magnesium sulfate, D. Magnesium chloride, E. Borax, F. Industrial starch, G. Magnesium oxide.

[0072] Example 23:

[0073] Mix the materials in the order specified in this invention, such as... Figure 2 As shown, A+B+C=first formulation, D+E+F+B=second formulation, and first formulation + second formulation + G=interface agent.

[0074] Example 24:

[0075] Polyvinyl alcohol and magnesium sulfate solution are added later. A+B+C=first preparation, B+C+D+E+F=second preparation, second preparation+G=third preparation, third preparation+first preparation=interface agent.

[0076] Example 25:

[0077] In conventional magnesium oxychloride cement mixes, A+B+C+D+E+F = first agent, and first agent + G = interface agent.

[0078] Example 26:

[0079] All solid raw materials are mixed evenly, and water is added last. A+C+D+E+F+G=mixture, mixture+B=interface agent.

[0080] Performance analysis was performed on the samples, in accordance with the relevant standards: JC / T 568-2023 "Magnesium Oxychloride Cement Boards" and GB / T17657-2022 "Test Methods for Physical and Chemical Properties of Wood-based Panels and Decorative Wood-based Panels"; the final results are shown in Table 6.

[0081] Table 6. Effects of different mixing methods on the performance of the interface agent in Examples 23-26

[0082]

[0083] As can be seen from the results in Table 6, Example 23 is the best, with reasonable reactions between components, which improves the physicochemical properties of the interface agent and has the lowest dispersion, making it suitable for industrial production. Examples 24 and 25 show large fluctuations, with incorrect reaction combinations leading to insufficient reactions between components, inadequate integration of the organic-inorganic system, and high dispersion, making them unsuitable for industrial production. Example 26 is the worst, with dry material mixing causing organic and inorganic materials to clump together, severely damaging the hydration mechanism, resulting in extremely unstable product quality and making it unsuitable for industrial application.

[0084] The final test results of the interface agent of the present invention (Example 23 group) are shown in Table 7.

[0085] Table 7 Performance test results of the interface agent of the present invention

[0086]

[0087] Finally, it should be noted that the above embodiments are merely illustrative of several implementations of the present invention and are not intended to limit the scope of the invention. For those skilled in the art, any modifications, equivalent substitutions, or improvements made without departing from the concept of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A flame-retardant interface agent, characterized in that, It includes the following components in parts by weight: 10-25 parts magnesium sulfate, 2-8 parts polyvinyl alcohol, 30-50 parts magnesium chloride, 0.1-2 parts borax, 1-5 parts industrial starch, 80-120 parts magnesium oxide, and 120-160 parts water. Includes the following steps: S1. Dissolve polyvinyl alcohol in water, then add magnesium sulfate and mix well to obtain the first preparation; S2. Mix magnesium chloride, borax, and industrial starch evenly to obtain a mixture; S3. Add the remaining water to the mixture in batches, stir well, and obtain the second preparation; S4. Add the first formulation to the second formulation, stir well to obtain a mixed solution; S5. Add magnesium oxide in batches to the mixed solution and mix thoroughly to obtain a thick paste-like flame retardant interface agent.

2. The flame retardant interface agent according to claim 1, characterized in that, The product comprises the following components by weight: 15 parts magnesium sulfate, 5 parts polyvinyl alcohol, 40 parts magnesium chloride, 1 part borax, 3 parts industrial starch, 100 parts magnesium oxide, and 140 parts water.

3. The flame retardant interface agent according to claim 1, characterized in that, In step S1, polyvinyl alcohol is dissolved in water at 80-90℃, and then the temperature is lowered to below 60℃ before magnesium sulfate is added.

4. The flame retardant interface agent according to claim 1, characterized in that, In step S1, water accounts for 55-60% of the total water volume, and in step S3, water accounts for 40-45% of the total water volume.

5. The flame retardant interface agent according to claim 1, characterized in that, In step S3, the stirring speed is ≤20 r / min and the stirring time is 15-30 min.

6. The flame retardant interface agent according to claim 1, characterized in that, In step S4, after the first formulation is cooled to room temperature, it is added to the second formulation. The stirring speed is ≤20 r / min and the stirring time is 8-15 min.

7. The flame retardant interface agent according to claim 1, characterized in that, In step S5, the mixing time for adding magnesium oxide to the mixed solution is 20-30 minutes.

8. The application of the flame-retardant interface agent as described in any one of claims 1-7 in the preparation of composite engineered wood panels.

9. The application according to claim 8, characterized in that, The flame-retardant interface agent is applied between the core layer and the flame-retardant layer.

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