Halogen-free low-smoke modified vermiculite flame retardant as well as preparation method and application thereof

Abstract

The invention discloses a halogen-free low-smoke modified vermiculite flame retardant as well as a preparation method and application thereof, the halogen-free low-smoke modified vermiculite flame retardant comprises the following raw materials: vermiculite, a hydroxyl-containing cationic surfactant, transition metal and organic phosphonate, in the halogen-free low-smoke modified vermiculite flame retardant prepared by the invention, the content of the hydroxyl-containing cationic surfactant in the vermiculite is reduced, and the content of the transition metal in the vermiculite is reduced. Through multiple interactions among the cationic surface active agent, the organic phosphonate and the transition metal, the prepared modified vermiculite flame retardant can synergistically exert multiple flame retardant mechanisms, the stability of a carbon layer at high temperature is remarkably improved, the reaction path of secondary combustion is blocked, and the smoke release of the material is effectively reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of flame retardant materials, and in particular to a halogen-free low-smoke modified vermiculite flame retardant and a preparation method thereof. Background Art

[0002] Epoxy resin is a thermosetting resin that plays an important role in industrial applications. Due to its excellent chemical resistance, adhesion, electrical insulation, and mechanical properties, it has been widely used in various fields such as coatings, adhesives, and composite materials. Unfortunately, like most polymer materials, epoxy resin is flammable. During combustion, it releases large amounts of heat, toxic gases, and smoke, increasing the risk of fire.

[0003] For epoxy resins, physical modification is usually used to evenly disperse flame retardants inside the matrix to achieve the purpose of flame retardancy. This method can select and adjust the type and content of flame retardants according to the material's requirements for flame retardant properties and the implementation standards of the application site. The process required for this preparation method is simple and is one of the most commonly used flame retardant technologies for preparing flame retardant epoxy resin materials. Among them, phosphorus-based flame retardants release liquid oxygen-containing phosphoric acid in situ when thermally decomposed, which can cover the surface of the substrate, promote the dehydration and esterification of the polymer matrix, and form a protective carbon layer with physical barrier properties, effectively isolating the underlying polymer from external heat, oxygen and combustible gases, thereby inhibiting further combustion of the material. However, during the processing and combustion of the polymer, it is easy to cause the dialysis and loss of phosphorus elements, and therefore, the actual flame retardant effect of the flame retardant is affected. Compared to the entire polymer to be flame-retarded, the residual carbon formed by the catalytic matrix is ​​far insufficient. The resulting carbon layer has a low degree of graphitization and is easily oxidized and cracked under the impact of flames and heat flow, reducing the degree of protection provided to the polymer matrix. This is the fundamental reason why the fire safety of the material cannot be improved. Therefore, it is necessary to further improve the catalytic carbonization efficiency of phosphorus-based flame retardants in the matrix and increase the coverage and quality of the carbon layer. This is the key to reducing the frequency of fires in polymer materials and reducing the release of toxic smoke. Summary of the Invention

[0004] The main purpose of the present invention is to propose a halogen-free low-smoke modified vermiculite flame retardant, which aims to solve the fire safety problems of epoxy resin, such as low charring rate, high heat release, and high generation of toxic smoke.

[0005] To achieve the above object, the present invention provides a halogen-free low-smoke modified vermiculite flame retardant, wherein the raw materials of the halogen-free low-smoke modified vermiculite flame retardant include vermiculite, a cationic surfactant containing hydroxyl groups, a transition metal and an organic phosphonate.

[0006] In one embodiment, the mass ratio of the vermiculite, the hydroxyl-containing cationic surfactant, the transition metal, and the organic phosphonate is 1:(0.12-0.33):(0.1-0.17):(0.2-0.53).

[0007] In one embodiment, the organic phosphonate in the organic phosphonate solution comprises at least one of aminotrimethylenephosphonic acid, triethylenetetraaminehexa(methylphosphonic acid), diethylenetriaminepenta(methylenephosphonic acid) and hexamethylenediaminetetra(methylenephosphonic acid); and / or,

[0008] The transition metal salt in the transition metal salt solution includes at least one of zinc acetate, cobalt nitrate, zirconium chloride and copper sulfate; and / or;

[0009] The cationic surfactant containing hydroxyl groups includes at least one of dodecylmethyldihydroxyethylammonium bromide, tetradecylmethyldihydroxyethylammonium bromide, hexadecylmethyldihydroxyethylammonium bromide and octadecylmethyldihydroxyethylammonium bromide; and / or,

[0010] The present invention provides a method for preparing a halogen-free low-smoke modified vermiculite flame retardant, comprising the following steps:

[0011] S10, mixing the vermiculite dispersion with the hydroxyl-containing cationic surfactant to obtain a first product mixed solution, heating, filtering, washing, and drying the first product mixed solution to obtain a first product;

[0012] S20, respectively preparing an organic phosphonate solution and a transition metal salt solution,

[0013] S30, mixing the organic phosphonate solution with the first product to obtain a second product mixed solution, heating, filtering, washing, and drying the second product mixed solution to obtain a second product;

[0014] S40, mixing the transition metal salt solution with the second product to obtain a third product mixed solution, heating, filtering, washing, and drying the third product mixed solution to obtain a halogen-free and low-smoke modified vermiculite flame retardant.

[0015] In one embodiment, step S10 includes:

[0016] S101. Providing vermiculite;

[0017] S102, mixing the vermiculite with water to obtain a vermiculite dispersion, mixing a solvent containing a hydroxyl-containing cationic surfactant with the vermiculite dispersion, heating, centrifugally filtering, and drying to obtain a first product.

[0018] In one embodiment, in step S102:

[0019] The heating temperature is 60° C. to 90° C., and the heating time is 0.5 h to 2.5 h.

[0020] In one embodiment, in step S30:

[0021] The pH value of the mixed solution is 3-6.5.

[0022] In one embodiment, in step S30:

[0023] The heating temperature is 80° C. to 100° C.; and the heating time is 5 h to 10 h.

[0024] In one embodiment, in step S40:

[0025] The pH value of the second product mixed solution is 6 to 8; and / or,

[0026] The heating temperature is 40° C. to 60° C.; and the heating time is 9 h to 16 h.

[0027] The present invention also provides a flame-retardant epoxy resin composite material, comprising epoxy resin and the halogen-free low-smoke modified vermiculite flame retardant described above or the halogen-free low-smoke modified vermiculite flame retardant prepared by any of the above methods for preparing the halogen-free low-smoke modified vermiculite flame retardant.

[0028] The technical solution provided by the present invention provides a halogen-free, low-smoke modified vermiculite flame retardant. When the ratio of the raw materials used is within the above-mentioned mass range, the phosphonic acid groups in the organic phosphonate molecules can react simultaneously with the hydroxyl groups of the surfactant and the transition metal ions, which helps to form a multi-component composite structure in the halogen-free, low-smoke modified vermiculite flame retardant, improves the dispersibility of the vermiculite in the epoxy resin matrix, and thus enhances the actual flame retardant efficiency and smoke suppression effect of the modified vermiculite flame retardant in the polymer matrix. First, a cationic surfactant containing a hydroxyl group is adsorbed on the vermiculite surface through ion exchange and chemical grafting to obtain a pretreated vermiculite with a surface modification and an interlayer intercalation structure. Subsequently, phosphorus and transition metals are sequentially bonded to the pretreated vermiculite through grafting and coordination reactions. The above modification methods effectively reduce the hydrophilicity of vermiculite and improve its compatibility with the epoxy resin matrix; at the same time, the interlayer spacing of vermiculite is improved, making it easier to expand and disperse in the matrix when heated, which is beneficial to the nano-barrier effect of inorganic silicates. The hydroxyl and phosphonic acid groups on the surface of the modified vermiculite flame retardant can form a hydrogen bond cross-linking network with the epoxy groups or hydroxyl groups in the epoxy resin, which not only improves the interfacial bonding between the inorganic material and the polymer, but also facilitates the subsequent active agent-phosphonate-transition metal multi-composite structure to exert an in-situ synergistic catalytic carbonization effect on the polymer, effectively promoting the rapid formation of a protective carbon layer and inhibiting the combustion of pyrolysis gases. In addition, the formation of this multi-composite structure further improves the thermal stability of the flame retardant in high temperature environments, and exerts flame retardant and smoke suppression effects in the gas phase and condensed phase by forming phosphoric acid substances and phosphorus-containing free radicals. Transition metals as Lewis acids and The acid catalyst not only inhibits the chain-like free radical reaction of combustion but also, together with phosphoric acid, catalyzes the crosslinking of the matrix's pyrolysis products to form a residual carbon precursor. Ultimately, the vermiculite and residual carbon precursor combine to form a ceramic-like protective layer with excellent barrier properties and mechanical strength. This protective layer effectively inhibits the transfer and diffusion of heat, oxygen, and combustible gases, thereby achieving the flame retardant's highly effective flame retardant and smoke suppression effects. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. Where the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased commercially. In addition, the meaning of "and / or" appearing in the full text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or schemes that A and B meet at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but must be based on the ability of ordinary technicians in this field to achieve. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that the combination of such technical solutions does not exist and is not within the scope of protection required by the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0030] For epoxy resins, physical modification is usually used to evenly disperse flame retardants inside the matrix to achieve the purpose of flame retardancy. This method can select and adjust the type and content of flame retardants according to the material's requirements for flame retardant properties and the implementation standards of the application site. The process required for this preparation method is simple and is one of the most commonly used flame retardant technologies for preparing flame retardant epoxy resin materials. Among them, phosphorus-based flame retardants are decomposed in situ by heat to release liquid oxygen-containing phosphoric acid, which can cover the surface of the substrate, promote the dehydration and esterification of the polymer matrix, and form a protective carbon layer with physical barrier properties, effectively isolating the bottom polymer from external heat, oxygen and combustible gases, thereby inhibiting further combustion of the material. However, during the processing and combustion of the polymer, it is easy to cause the dialysis and loss of phosphorus elements, and therefore the actual flame retardant efficiency of the flame retardant is affected. Compared to the entire polymer matrix that requires flame retardancy, the residual carbon formed by the catalytic matrix is ​​far from sufficient. Furthermore, the resulting carbon layer has a low degree of graphitization and is easily oxidized and cracked under the impact of high temperature and heat flow, reducing the degree of protection provided to the polymer matrix. This is the fundamental reason why the fire safety of the material cannot be improved. Therefore, it is necessary to further improve the catalytic carbonization efficiency of phosphorus-based flame retardants in the matrix and increase the coverage and quality of the carbon layer. This is the key to reducing the frequency of fires in polymer materials and reducing the release of toxic smoke.

[0031] In view of this, the present invention provides a halogen-free low-smoke modified vermiculite flame retardant, wherein the raw materials of the halogen-free low-smoke modified vermiculite flame retardant include vermiculite, a cationic surfactant containing hydroxyl groups, a transition metal and an organic phosphonate.

[0032] The technical solution provided by the present invention provides a halogen-free, low-smoke modified vermiculite flame retardant. The phosphonic acid groups in the organic phosphonate molecules can react simultaneously with the hydroxyl groups and transition metal ions contained in the surfactant, thereby facilitating the formation of a multi-component composite structure in the halogen-free, low-smoke modified vermiculite flame retardant, improving the dispersibility of the vermiculite in the epoxy resin matrix, and thereby enhancing the flame retardant efficiency and smoke suppression effect of the modified vermiculite flame retardant in the polymer matrix. First, a cationic surfactant containing a hydroxyl group is adsorbed on the vermiculite surface through ion exchange and chemical grafting to obtain a pretreated vermiculite with a surface modification and interlayer intercalation structure. Subsequently, phosphorus and transition metals are sequentially combined with the pretreated vermiculite through grafting and coordination reactions. The above modification methods effectively reduce the hydrophilicity of the vermiculite and improve its compatibility with the epoxy resin matrix. At the same time, the interlayer spacing of the vermiculite is increased, making it easier to expand and disperse in the matrix when heated, which is conducive to the nano-barrier effect of the inorganic silicate. The hydroxyl and phosphonic acid groups on the surface of the modified vermiculite flame retardant can form a hydrogen bond cross-linking network with the epoxy groups or hydroxyl groups in the epoxy resin, which not only improves the interfacial bonding strength between the inorganic material and the polymer, but also facilitates the subsequent active agent-phosphonate-transition metal multi-composite structure to exert in-situ synergistic catalytic carbonization on the polymer, effectively promoting the rapid formation of a protective carbon layer and inhibiting the combustion of pyrolysis gases. In addition, the formation of this multi-composite structure further improves the thermal stability of the flame retardant in high temperature environments, and by forming phosphoric acid substances and phosphorus-containing free radicals, it exerts flame retardant and smoke suppression effects in the gas phase and condensed phase. Transition metal compounds can act as Lewis acids and The acid catalyst not only inhibits the chain-like free radical reaction of combustion but also, together with phosphoric acid, catalyzes the crosslinking of the matrix's pyrolysis products to form a residual carbon precursor. Ultimately, the vermiculite and residual carbon precursor combine to form a ceramic-like protective layer with excellent barrier properties and mechanical strength. This protective layer effectively inhibits the transfer and diffusion of heat, oxygen, and combustible gases, thereby achieving the flame retardant's highly effective flame retardant and smoke suppression effects.

[0033] Furthermore, the mass ratio of the vermiculite, the hydroxyl-containing cationic surfactant, the transition metal and the organic phosphonate is 1:(0.12-0.33):(0.1-0.17):(0.2-0.53). Within the above range, the flame retardant effect of the halogen-free low-smoke modified vermiculite flame retardant is better.

[0034] In some embodiments of the present invention, the organic phosphonate in the organic phosphonate solution includes at least one of aminotrimethylenephosphonic acid, triethylenetetraaminehexa(methylphosphonic acid), diethylenetriaminepenta(methylenephosphonic acid) and hexamethylenediaminetetra(methylenephosphonic acid); the transition metal salt in the transition metal salt solution includes at least one of zinc acetate, cobalt nitrate, zirconium chloride and copper sulfate;

[0035] In an embodiment of the present invention, the organic phosphonate comprises at least one of aminotrimethylenephosphonic acid, triethylenetetraaminehexa(methylphosphonic acid), diethylenetriaminepenta(methylenephosphonic acid), and hexamethylenediaminetetra(methylenephosphonic acid). The phosphonic acid groups in the organic phosphonate chemically bond with the hydroxyl groups of the surfactant to form a stable surfactant-phosphonate composite structure. This structure helps reduce phosphorus loss during polymer processing and combustion, retaining phosphorus in the vermiculite structure to the greatest extent possible, further enhancing the efficiency of the synergistic catalytic carbonization of the polymer matrix by the vermiculite and the flame retardant element, as well as the smoke suppression effect.

[0036] It should be noted that organic phosphonates contain phosphonic acid groups that react with the hydroxyl groups on the active agents on both sides of the vermiculite to form a binary composite structure on both sides of the vermiculite sheet. This enhances structural stability while introducing new active sites, facilitating the subsequent formation of stable coordination compounds with transition metals. Vermiculite flame retardants containing this multi-component composite structure effectively catalyze the cross-linking of the polymer matrix into char, blocking heat flow and thermal erosion within the matrix, thereby inhibiting the release and combustion of pyrolysis gases, achieving highly effective flame retardancy and low smoke emission for the polymer.

[0037] In an embodiment of the present invention, the transition metal salt includes at least one of zinc acetate, cobalt nitrate, zirconium chloride and copper sulfate, and the transition metal ions (such as zinc, cobalt, zirconium or copper, etc.) are coordinated with the phosphonic acid groups of the active agent-phosphonate composite structure, thereby fixing the transition metal ions in the formed active agent-phosphonate composite structure, further enhancing the thermal stability and flame retardant efficiency of the modified vermiculite flame retardant structure.

[0038] Furthermore, the cationic surfactant containing hydroxyl groups includes at least one of dodecylmethyldihydroxyethylammonium bromide, tetradecylmethyldihydroxyethylammonium bromide, hexadecylmethyldihydroxyethylammonium bromide and octadecylmethyldihydroxyethylammonium bromide. The cationic surfactant containing hydroxyl groups has cations (quaternary nitrogen structure), and the cations of the surfactant are exchanged with the cations contained in the layered vermiculite, so that the original interlayer spacing of the vermiculite is expanded. In addition, the surfactant can also be attached to both sides of the vermiculite layer by grafting, thereby forming a stable surface / interlayer dual-modified pretreated vermiculite. The active groups contained on both sides of the pretreated vermiculite layer not only provide active sites and space for the introduction of phosphorus and transition metals, but also form a hydrogen bond cross-linked network with the epoxy groups or hydroxyl groups in the epoxy resin, giving full play to the nano flame retardant effect of the inorganic silicate material in the polymer matrix.

[0039] The present invention also provides a method for preparing a halogen-free low-smoke modified vermiculite flame retardant, comprising the following steps:

[0040] S10, mixing the vermiculite dispersion with the hydroxyl-containing cationic surfactant to obtain a first product mixed solution, heating, filtering, washing, and drying the first product mixed solution to obtain a first product;

[0041] S20, respectively preparing an organic phosphonate solution and a transition metal salt solution,

[0042] S30, mixing the organic phosphonate solution with the first product to obtain a second product mixed solution, heating, filtering, and drying the second product mixed solution to obtain a second product;

[0043] S40, mixing the transition metal salt solution and the second product to obtain a third product mixed solution, heating, filtering, and drying the third product mixed solution to obtain a halogen-free and low-smoke modified vermiculite flame retardant.

[0044] The technical solution of the present invention involves first placing vermiculite in a cationic surfactant solution containing hydroxyl groups. Ion exchange replaces the existing cations between the vermiculite layers. Because the introduced organic cations have different sizes and polarities than the existing inorganic cations between the vermiculite layers, they occupy more space and expand the interlayer spacing of the vermiculite. Furthermore, by adjusting process conditions, the surfactant reacts chemically with the hydroxyl groups on both sides of the vermiculite lamellae, resulting in a vermiculite structure that forms a hydrogen-bonded cross-linked network with the epoxy resin matrix. Next, an organic phosphonate is anchored to the remaining hydroxyl groups of the cationic surfactant. Subsequently, a coordination reaction between the transition metal and the organic phosphonate forms a stable chelate, further enhancing the thermal stability and flame retardancy of the modified vermiculite flame retardant.

[0045] In some embodiments of the present invention, step S10 includes:

[0046] S101. Providing vermiculite;

[0047] S102, mixing the vermiculite with water to obtain a vermiculite dispersion, mixing a cationic surfactant containing hydroxyl groups with the vermiculite dispersion to obtain a first product mixed solution, heating, filtering, washing, and drying the first product mixed solution to obtain a first product.

[0048] In an embodiment of the present invention, the heating temperature is 60°C to 80°C, and the heating time is 0.5h to 2.5h. When the heating temperature and the heating time are within the above-mentioned set ranges, the surfactant molecules can be effectively promoted to enter the vermiculite layers and to adhere to both sides of the vermiculite sheets, which is beneficial to the reaction between the pretreated vermiculite and the organic phosphonate, thereby improving the flame retardant properties and smoke suppression effects of the epoxy resin.

[0049] In an embodiment of the present invention, the pH value of the mixed solution is 3 to 6.5; when the pH value of the mixed solution is within the above-set range, it helps to enhance the activity of the functional groups in the surfactants on both sides of the vermiculite flakes, making it easier to react with the phosphonic acid groups in the organic phosphonate, which is beneficial to the formation of a binary composite structure on the vermiculite surface, thereby improving the flame retardant efficiency and thermal stability of the modified vermiculite flame retardant.

[0050] In an embodiment of the present invention, the heating temperature is 80°C to 100°C; the heating time is 5h to 10h. When the heating temperature and the heating time are within the above-mentioned set ranges, sufficient power can be provided to drive the organic phosphonate to react with the hydroxyl groups of the surfactant on both sides of the vermiculite sheet, resulting in the active agent-phosphonate composite structure on both sides of the vermiculite sheet bonded with the organic phosphonate being able to coordinate with the transition metal salt, which is beneficial to the formation of a halogen-free and low-smoke modified vermiculite flame retardant structure, thereby improving the flame retardant properties and smoke suppression effect of the epoxy resin.

[0051] In an embodiment of the present invention, the pH value of the second product mixed solution is 6 to 8. When the pH value of the mixed solution is within the above-mentioned set range, it helps to enhance the activity of the functional groups in the organic phosphonate bonded in the active agent-phosphonate composite structure on both sides of the vermiculite sheet layer, making it easier to react with transition metal ions, thereby improving the flame retardant efficiency and thermal stability of the halogen-free low-smoke modified vermiculite flame retardant.

[0052] In an embodiment of the present invention, the heating temperature is 40°C to 60°C, and the heating time is 9h to 16h. When the heating temperature and the heating time are within the above-mentioned set range, the completeness of the reaction is ensured, which is beneficial to improving the integrity of the active agent-phosphonate composite structure on both sides of the vermiculite sheet layer, promoting the formation of a halogen-free and low-smoke modified vermiculite flame retardant structure, and thereby improving the flame retardant properties and smoke suppression effect of the epoxy resin.

[0053] The present invention has the following beneficial effects:

[0054] (1) In the preparation method of a halogen-free low-smoke modified vermiculite flame retardant applied by the present invention, the interlayer / surface multiple modification of vermiculite is carried out in sequence by a cationic surfactant containing hydroxyl groups, an organic phosphonate and a transition metal salt. First, the interlayer spacing of the vermiculite modified by the surfactant is expanded, and the vermiculite sheets carry active groups. These active hydroxyl groups are combined with the phosphonic acid groups contained in the organic phosphonate through chemical bonds, thereby forming a binary composite structure on the vermiculite surface, which is conducive to increasing the loading amount of organic phosphine in the vermiculite structure; then, the coordination reaction between the organic phosphonate and the metal ion is used to further form an active agent-phosphonate-transition metal cross-linked composite layer on the basis of the binary composite structure existing on both sides of the vermiculite. The resulting multi-component composite structure utilizes the high thermal stability of vermiculite and the strong catalytic properties of transition metal ions to synergistically improve the flame retardant and smoke suppression effect of phosphorus-containing compounds in the polymer combustion process.

[0055] (2) In the preparation method of a halogen-free, low-smoke modified vermiculite flame retardant applied by the present invention, a structurally complete halogen-free, low-smoke modified vermiculite flame retardant is obtained by adjusting the ratio between a cationic surfactant containing a hydroxyl group, an organic phosphonate, and a transition metal salt. When heated, the phosphonic acid substances produced by the thermal decomposition of the modified vermiculite flame retardant can contact with weak bonds such as hydroxyl groups and epoxy groups contained in the epoxy resin, catalyzing the degradation of the polymer while rapidly forming carbon, effectively giving play to the advantage of the polymer itself as a carbon source. This reaction mechanism compensates for the influence of the insufficient content of carbonizing agents in traditional flame-retardant epoxy resin composite materials on the degree of combustion of the material, significantly improving the carbonization rate and flame retardant properties of the epoxy resin.

[0056] (3) In the preparation method of a halogen-free low-smoke modified vermiculite flame retardant applied by the present invention, under the induction of a surfactant, an active agent-phosphonate-transition metal multi-component composite structure can be formed on both sides of the vermiculite layer. The modified vermiculite is completely peeled off and highly dispersed in the matrix under the promotion of pyrolysis gas, thereby serving as a physical crosslinking point, and the molecular chain is interspersed therein and together with it forms a highly crosslinked aromatic ring residual carbon precursor, effectively improving the degree of graphitization of the carbon layer; the synergistic catalytic carbonization effect between quaternary nitrogen, phosphonate and transition metal can promote the crosslinking of the degradation products of epoxy resin to form a protective carbon layer, making up for the defects of low carbonization crosslinking density and poor thermal oxidation resistance of the carbon layer caused by insufficient phosphorus content, thereby effectively improving the phenomenon of the carbon layer being broken by smoke, and the fire resistance of the material is improved.

[0057] (4) In the preparation method of a halogen-free, low-smoke modified vermiculite flame retardant applied by the present invention, the transition metal ions containing empty orbitals have strong bonding ability. They can not only capture the high-energy free radicals released by the pyrolysis of the matrix and interrupt the combustion of the matrix, but also combine with phosphoric acid substances to jointly catalyze the unsaturated bonds of the epoxy resin to form a cross-linked structure. The free radicals generated by pyrolysis and gaseous products such as smoke particles are deposited on the cross-linked structure. The high-quality carbon layer finally obtained can effectively reduce the generation of gaseous products and heat release, effectively improving the flame retardant and smoke suppression capabilities of the material. In addition, the transition metal ions can also convert CO into CO2 through oxidation-reduction reactions, significantly reducing the release of toxic gases during the combustion of the matrix.

[0058] (5) During the combustion process, the multi-component composite structure constructed by cationic surfactants, organic phosphonates, and transition metal salts can exert multiple flame retardant mechanisms in the matrix: the inner layer is a phosphonate-transition metal-quaternary nitrogen structure, which can catalyze the degradation of epoxy resin to form a protective carbon layer containing phosphorus-nitrogen-transition metal, and the outer layer is a heat-insulating layer formed by the migration of vermiculite after peeling. Such multiple protective layers can significantly improve the thermal oxidation resistance and quality of the carbon layer, thereby effectively reducing the heat release and smoke generation of the material. In addition, the gas phase flame retardant effect of the quaternary nitrogen structure has a positive effect on the combustion of the interrupted material.

[0059] (6) The present invention is simple to prepare, has abundant raw material sources, low cost, and is suitable for large-scale application.

[0060] The technical solutions of the present invention are further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0061] Example 1

[0062] Provided is a method for preparing a halogen-free, low-smoke modified vermiculite flame retardant, comprising the following steps:

[0063] Step 1: Disperse 15 g of vermiculite in 135 ml of deionized water, add 123.75 ml of a 4 wt% aqueous solution of dodecylmethyldihydroxyethylammonium bromide while stirring, and stir to obtain a mixed solution. Reflux at a constant temperature of 60° C. for 1.5 h, cool the material, centrifuge, filter, and dry to obtain the first product.

[0064] Step 2: prepare 79.5 ml of an aqueous solution of aminotrimethylenephosphonic acid with a mass percentage concentration of 10 wt % and 25.5 ml of an aqueous solution of zinc acetate with a mass percentage concentration of 10 wt %.

[0065] Step 3: The aminotrimethylenephosphonic acid aqueous solution obtained in step 2 and the first product obtained in step 1 are added to a three-necked flask and stirred to obtain a mixed solution. The pH of the reaction system is adjusted to 3.5 by hydrochloric acid or sodium hydroxide solution, and the mixture is refluxed at a constant temperature of 90° C. for 8 hours. The mixture is cooled, discharged, centrifuged, filtered, washed, and dried to obtain a second product.

[0066] Step 4: The zinc acetate aqueous solution obtained in step 2 and the second product obtained in step 3 are added to a three-necked flask at the same time and stirred to obtain a third product mixed solution. The pH of the reaction system is adjusted to 6.5 by hydrochloric acid or sodium hydroxide solution, and the mixture is refluxed at a constant temperature for 12 hours at a reaction temperature of 50° C. The material is cooled, centrifuged, filtered, washed, and dried to obtain a halogen-free and low-smoke modified vermiculite flame retardant.

[0067] Example 2

[0068] Provided is a method for preparing a halogen-free, low-smoke modified vermiculite flame retardant, comprising the following steps:

[0069] Step 1: Disperse 15 g of vermiculite in 135 ml of deionized water, add 93.75 ml of a 4 wt% aqueous solution of tetradecylmethyldihydroxyethylammonium bromide while stirring, and stir to obtain a mixed solution. Reflux at a constant temperature of 60° C. for 1.5 h, cool the material, centrifuge, filter, and dry to obtain the first product.

[0070] Step 2: prepare 49.5 ml of a 10 wt % aqueous solution of triethylenetetraaminehexa(methylphosphonic acid) and 18.75 ml of a 10 wt % aqueous solution of cobalt nitrate respectively.

[0071] Step 3: Add the triethylenetetraamine hexa(methylphosphonic acid) aqueous solution obtained in step 2 and the first product obtained in step 1 into a three-necked flask at the same time, stir and obtain a mixed solution, adjust the pH of the reaction system to 3.5 with hydrochloric acid or sodium hydroxide solution, and reflux at a constant temperature of 90° C. for 8 hours, cool the material, centrifuge, filter, wash and dry to obtain a second product.

[0072] Step 4: The cobalt nitrate aqueous solution obtained in step 2 and the second product obtained in step 3 are added to a three-necked flask at the same time and stirred to obtain a third product mixed solution. The pH of the reaction system is adjusted to 6.5 by hydrochloric acid or sodium hydroxide solution, and the reaction temperature is 50 ° C. and refluxed at a constant temperature for 12 hours. The material is cooled, centrifuged, filtered, washed and dried to obtain a halogen-free and low-smoke modified vermiculite flame retardant.

[0073] Example 3

[0074] Provided is a method for preparing a halogen-free, low-smoke modified vermiculite flame retardant, comprising the following steps:

[0075] Step 1: Disperse 15 g of vermiculite in 135 ml of deionized water, add 63.75 ml of a 4 wt% aqueous solution of hexadecylmethyldihydroxyethylammonium bromide while stirring, and stir to obtain a mixed solution. Reflux at a constant temperature of 60° C. for 1.5 h, cool the material, centrifuge, filter, and dry to obtain the first product.

[0076] Step 2: prepare 37.5 ml of a 10 wt % aqueous solution of diethylenetriamine penta(methylenephosphonic acid) and 16.8 ml of a 10 wt % aqueous solution of zirconium chloride respectively.

[0077] Step 3: Add the diethylenetriamine penta (methylene phosphonic acid) aqueous solution obtained in step 2 and the first product obtained in step 1 to a three-necked flask and stir to obtain a mixed solution. Adjust the pH of the reaction system to 3.5 with hydrochloric acid or sodium hydroxide solution, and reflux at a constant temperature of 90° C. for 8 hours. Cool the material, centrifuge, filter, wash and dry to obtain a second product.

[0078] Step 4: Add the zirconium chloride aqueous solution obtained in step 2 and the second product obtained in step 3 to a three-necked flask at the same time and stir to obtain a third product mixed solution. Adjust the pH of the reaction system to 6.5 with hydrochloric acid or sodium hydroxide solution, and reflux at a constant temperature of 50° C. for 12 hours. Cool the material, centrifuge, filter, wash and dry to obtain a halogen-free and low-smoke modified vermiculite flame retardant.

[0079] Example 4

[0080] Provided is a method for preparing a halogen-free, low-smoke modified vermiculite flame retardant, comprising the following steps:

[0081] Step 1: Disperse 15 g of vermiculite in 135 ml of deionized water, add 46.875 ml of a 4 wt% aqueous solution of octadecylmethyldihydroxyethylammonium bromide while stirring, and stir to obtain a mixed solution. Reflux at a constant temperature of 60° C. for 1.5 h, cool the material, centrifuge, filter, and dry to obtain the first product.

[0082] Step 2: prepare 30 ml of a 10 wt % aqueous solution of hexamethylenediaminetetramethylenephosphonic acid and 15 ml of a 10 wt % aqueous solution of copper sulfate.

[0083] Step 3: The hexamethylenediaminetetramethylenephosphonic acid aqueous solution obtained in step 2 and the first product obtained in step 1 are added to a three-necked flask at the same time, stirred to obtain a mixed solution, the pH of the reaction system is adjusted to 3.5 by hydrochloric acid or sodium hydroxide solution, and refluxed at a constant temperature for 8 hours at a reaction temperature of 90° C., cooled, discharged, centrifuged, filtered, washed and dried to obtain a second product.

[0084] Step 4: Add the copper sulfate aqueous solution obtained in step 2 and the second product obtained in step 3 to a three-necked flask at the same time and stir to obtain a third product mixed solution. Adjust the pH of the reaction system to 6.5 with hydrochloric acid or sodium hydroxide solution, and reflux at a constant temperature of 50° C. for 12 hours. Cool the material, centrifuge, filter, wash and dry to obtain a halogen-free and low-smoke modified vermiculite flame retardant.

[0085] Example 5

[0086] Provided is a method for preparing a halogen-free, low-smoke modified vermiculite flame retardant, comprising the following steps:

[0087] Step 1: Disperse 15 g of vermiculite in 135 ml of deionized water, add 131.25 ml of a 4 wt% aqueous solution of hexadecylmethyldihydroxyethylammonium bromide while stirring, and stir to obtain a mixed solution. Reflux at a constant temperature of 60° C. for 1.5 h, cool the material, centrifuge, filter, and dry to obtain the first product.

[0088] Step 2: prepare 82.5 ml of a 10 wt % aqueous solution of diethylenetriamine penta(methylenephosphonic acid) and 30 ml of a 10 wt % aqueous solution of zirconium chloride respectively.

[0089] Step 3: Add the diethylenetriamine penta (methylene phosphonic acid) aqueous solution obtained in step 2 and the first product obtained in step 1 to a three-necked flask and stir to obtain a mixed solution. Adjust the pH of the reaction system to 3.5 with hydrochloric acid or sodium hydroxide solution, and reflux at a constant temperature of 90° C. for 8 hours. Cool the material, centrifuge, filter, wash and dry to obtain a second product.

[0090] Step 4: Add the zirconium chloride aqueous solution obtained in step 2 and the second product obtained in step 3 to a three-necked flask at the same time and stir to obtain a third product mixed solution. Adjust the pH of the reaction system to 6.5 with hydrochloric acid or sodium hydroxide solution, and reflux at a constant temperature of 50° C. for 12 hours. Cool the material, centrifuge, filter, wash and dry to obtain a halogen-free and low-smoke modified vermiculite flame retardant.

[0091] Example 6

[0092] Provided is a method for preparing a halogen-free, low-smoke modified vermiculite flame retardant, comprising the following steps:

[0093] Step 1: Disperse 15 g of vermiculite in 135 ml of deionized water, add 37.5 ml of a 4 wt% aqueous solution of hexadecylmethyldihydroxyethylammonium bromide while stirring, and stir to obtain a mixed solution. Reflux at a constant temperature of 60° C. for 1.5 h, cool the material, centrifuge, filter, and dry to obtain the first product.

[0094] Step 2: prepare 27 ml of a 10 wt % aqueous solution of diethylenetriamine penta(methylenephosphonic acid) and 12 ml of a 10 wt % aqueous solution of zirconium chloride respectively.

[0095] Step 3: Add the diethylenetriamine penta (methylene phosphonic acid) aqueous solution obtained in step 2 and the first product obtained in step 1 to a three-necked flask and stir to obtain a mixed solution. Adjust the pH of the reaction system to 3.5 with hydrochloric acid or sodium hydroxide solution, and reflux at a constant temperature of 90° C. for 8 hours. Cool the material, centrifuge, filter, wash and dry to obtain a second product.

[0096] Step 4: Add the zirconium chloride aqueous solution obtained in step 2 and the second product obtained in step 3 to a three-necked flask at the same time and stir to obtain a third product mixed solution. Adjust the pH of the reaction system to 6.5 with hydrochloric acid or sodium hydroxide solution, and reflux at a constant temperature of 50° C. for 12 hours. Cool the material, centrifuge, filter, wash and dry to obtain a halogen-free and low-smoke modified vermiculite flame retardant.

[0097] Examples 2-6 and Comparative Examples 1-4 of the present application adopt a preparation method similar to that of Example 1, and the differences are shown in Table 1.

[0098]

[0099]

[0100] Comparative Example 1

[0101] The difference from Example 3 is that the step of adding a cationic surfactant containing a hydroxyl group in step 1 is removed, and the rest is similar to Example 3.

[0102] Comparative Example 2

[0103] The difference from Example 3 is that the "transition metal" in step 3 is removed, that is, no transition metal is added, and the rest is similar to Example 3.

[0104] Comparative Example 3

[0105] The difference from Example 3 is that the “addition of organic phosphonate” in step 4 is omitted, that is, no organic phosphonate is added. The rest is similar to Example 3.

[0106] Comparative Example 4

[0107] The difference from Example 3 is that the step of “adding organic phosphonate and transition metal” in Step 3 and Step 4 is omitted, that is, organic phosphonate and transition metal are not added. The rest is similar to Example 3.

[0108] Performance Testing

[0109] The halogen-free low-smoke modified vermiculite obtained in Examples 1-6 and Comparative Examples 1-4 was used as a flame retardant for epoxy resin to prepare a flame retardant epoxy resin composite material. The preparation process is as follows:

[0110] The prepared flame retardant was added to the epoxy resin in the proportion shown in Table 1, stirred and mixed evenly at room temperature, and then the polyamide curing agent was added according to the epoxy value of the epoxy resin, and continued to stir and mix evenly at room temperature. The mixture was added to the mold and cured at 65°C for 4 hours.

[0111] The flame retardant epoxy resin composite materials obtained in Examples 1-6 and Comparative Examples 1-4 were prepared into suitable test specimens, and the flame retardant properties of the prepared specimens were tested and analyzed. The specific analysis method is as follows:

[0112] Vertical burning (UL-94) test: tested according to GB / T 2408-2021 standard;

[0113] Limiting Oxygen Index (LOI) test: Tested according to GB / T 2406.2-2009 standard;

[0114] Residual carbon rate and expansion rate test: The flame-retardant epoxy resin composite material is placed in a muffle furnace and heated to 700°C. The volume ratio and residual carbon content of the material before and after carbonization are observed.

[0115] Total smoke release (TSP) test: The flame retardant epoxy resin composite material was placed in a cone calorimeter and irradiated at an intensity of 50kW·m -2 Tested in accordance with ISO 5660-1 standard under an environment.

[0116] The test results of the test strips prepared in Example 1-6 and Comparative Example 1-2 are shown in Table 1.

[0117] Table 1 Flame retardant properties of the test specimens of Examples 1-6 and Comparative Examples 1-4

[0118]

[0119]

[0120] The following conclusions were drawn based on the test results in Table 1:

[0121] (1) Compared with Comparative Examples 1-4, when the halogen-free low-smoke modified vermiculite flame retardant proposed in Examples 1-6 is applied to epoxy resin flame retardancy, the smoke density of all composite materials is generally low, and they have higher charring and flame retardant properties.

[0122] (2) According to the test results of Examples 1-4, it can be seen that the combination of different cationic surfactants, transition metals and organic phosphonates has different effects on the flame retardant properties and smoke release of epoxy resin: among them, the addition of hexadecylmethyldihydroxyethylammonium bromide, diethylenetriaminepenta(methylenephosphonic acid) and zirconium chloride has the best effect on improving the flame retardant efficiency and smoke suppression ability of vermiculite flame retardant.

[0123] (3) According to the test results of Examples 3, 5, and 6 and Comparative Examples 1-4, when the ratio of the three raw materials, cationic surfactant, transition metal, and organic phosphonate, exceeds the range described in the claims, it is not conducive to the integrity of the active agent-phosphonate-transition metal multi-component composite structure on both sides of the vermiculite layer, thereby affecting the flame retardant properties, charring effect, and smoke release of the flame retardant epoxy resin composite material. However, when the components of the multi-component composite structure lack one of the above raw materials, it is impossible to significantly improve the flame retardant effect and smoke suppression ability of the vermiculite flame retardant in the epoxy resin matrix.

[0124] (4) According to the test results of Example 3 and Comparative Examples 1-4, it can be seen that in the flame retardant system, the main factor affecting the charring rate is the phosphorus content of the system, while the transition metal ions play a synergistic catalytic effect; the addition of surfactants is conducive to promoting the peeling and dispersion of vermiculite flakes, and giving full play to the nano flame retardant effect of the modified vermiculite flame retardant itself; in addition, the surfactants present on both sides of the vermiculite can be constructed together with organic phosphonates and transition metal ions to form a multi-component composite structure, which is conducive to further improving the flame retardant properties of the flame retardant epoxy resin composite material.

[0125] (5) According to the test results of Example 3 and Comparative Examples 1-4, the carbon residue rate, expansion rate, oxygen index and total smoke release of the test specimens prepared in Comparative Examples 1-4 are all worse than those in Example 5.

[0126] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any ordinary technician in this industry can smoothly implement the present invention as described above. However, any equivalent changes, modifications and evolutions made by technicians familiar with this profession without departing from the scope of the technical solution of the present invention using the technical content disclosed above are all equivalent embodiments of the present invention. At the same time, any equivalent changes, modifications and evolutions made to the above embodiments based on the essential technology of the present invention are still within the scope of protection of the technical solution of the present invention.

[0127] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention specification under the inventive concept of the present invention, or direct / indirect application in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A halogen-free low-smoke modified vermiculite flame retardant, characterized in that: The raw materials of the halogen-free low-smoke modified vermiculite flame retardant include vermiculite, a cationic surfactant containing a hydroxyl group, a transition metal and an organic phosphonate.

2. The halogen-free low-smoke modified vermiculite flame retardant according to claim 1, characterized in that: In parts by mass, the mass ratio of the vermiculite, the cationic surfactant containing hydroxyl groups, the transition metal and the organic phosphonate is 1: (0.12-0.33): (0.1-0.17): (0.2-0.53).

3. The halogen-free low-smoke modified vermiculite flame retardant according to claim 1, characterized in that: The organic phosphonate in the organic phosphonate solution comprises at least one of aminotrimethylenephosphonic acid, triethylenetetraaminehexa(methylphosphonic acid), diethylenetriaminepenta(methylenephosphonic acid) and hexamethylenediaminetetra(methylenephosphonic acid); and / or, The transition metal salt in the transition metal salt solution includes at least one of zinc acetate, cobalt nitrate, zirconium chloride and copper sulfate; and / or; The hydroxyl-containing cationic surfactant includes at least one of dodecylmethyldihydroxyethylammonium bromide, tetradecylmethyldihydroxyethylammonium bromide, hexadecylmethyldihydroxyethylammonium bromide and octadecylmethyldihydroxyethylammonium bromide.

4. A method for preparing a halogen-free low-smoke modified vermiculite flame retardant, characterized in that: The following steps are involved: S10, mixing the vermiculite dispersion with the solution of the cationic surfactant containing hydroxyl groups to obtain a first product mixed solution, and heating, filtering, washing, and drying the first product mixed solution to obtain a first product; S20, respectively preparing an organic phosphonate solution and a transition metal salt solution, S30, mixing the organic phosphonate solution with the first product to obtain a second product mixed solution, heating, filtering, washing, and drying the second product mixed solution to obtain a second product; S40, mixing the transition metal salt solution with the second product to obtain a third product mixed solution, heating, filtering, washing, and drying the third product mixed solution to obtain a halogen-free and low-smoke modified vermiculite flame retardant.

5. The method for preparing a halogen-free low-smoke modified vermiculite flame retardant according to claim 4, wherein: Step S10 includes: S101. Providing vermiculite; S102, mixing the vermiculite with water to obtain a vermiculite dispersion, mixing a solution of a cationic surfactant containing hydroxyl groups with the vermiculite dispersion to obtain a first product mixed solution, heating, filtering, washing, and drying the first product mixed solution to obtain a first product.

6. The method for preparing a halogen-free low-smoke modified vermiculite flame retardant according to claim 4, wherein: In step S102: the heating temperature is 60° C. to 80° C., and the heating time is 0.5 h to 2.5 h.

7. The method for preparing a halogen-free low-smoke modified vermiculite flame retardant according to claim 4, wherein: In step S30: the pH value of the mixed solution is 3-6.

5.

8. The method for preparing a halogen-free low-smoke modified vermiculite flame retardant according to claim 4, wherein: In step S30: the heating temperature is 80° C. to 100° C.; the heating time is 5 hours to 10 hours.

9. The method for preparing a halogen-free low-smoke modified vermiculite flame retardant according to claim 4, wherein: In step S40: The pH value of the second product mixed solution is 6 to 8; and / or, The heating temperature is 40° C. to 60° C.; and the heating time is 9 h to 16 h.

10. A flame retardant epoxy resin composite material, characterized in that: The invention comprises epoxy resin and the halogen-free low-smoke modified vermiculite flame retardant according to any one of claims 1 to 3 or the halogen-free low-smoke modified vermiculite flame retardant prepared by the preparation method of the halogen-free low-smoke modified vermiculite flame retardant according to any one of claims 4 to 9.

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