Single-component intumescent flame retardant with layered structure and super carbonization ability and preparation method thereof

Abstract

The present application relates to a kind of single-component intumescent flame retardant with layered structure and super strong carbon formation ability and its preparation method, the method of the present application first 3,4-dihydroxybenzaldehyde and organic diamine rich in benzene ring or nitrogen heterocycle are reacted to prepare intermediate product, then intermediate product and phytic acid are organically combined, by esterification crosslinking reaction, construct macromolecular crosslinking network, prepare the single-component intumescent flame retardant with layered structure and super strong carbon formation ability finally.Compared with general ammonium phytate flame retardant, the flame retardant prepared in the present application has wash resistance, and can form super strong intumescent dense and hard carbon layer when burning.Polymer materials can be simultaneously endowed with excellent flame retardant properties and flame-retardant durability.In addition, since the flame retardant of the present application has layered structure, it can be more uniformly dispersed in polymer, and can significantly improve the mechanical properties of polymer.The preparation process of the flame retardant of the present application is simple, practical, and has very broad application prospect.

Description

Technical Field

[0001] This invention relates to the field of organic flame retardants, specifically to a single-component intumescent flame retardant with a layered structure and strong char-forming ability, and its preparation method. Background Technology

[0002] Due to their excellent comprehensive properties, polymer materials have been widely used in textiles, electronics, construction, automobiles, and other fields, becoming an indispensable basic material in national economic construction. However, polymer materials are highly flammable; once ignited, the flames are difficult to extinguish, leading to serious fires. Therefore, flame-retardant treatment of polymer materials is essential.

[0003] Intumescent flame retardants are widely used in polymer materials due to their low smoke, excellent char-forming ability, and heat-suppressing effect. During combustion, intumescent flame retardants form a dense, expanded protective layer on the surface of the polymer material, effectively slowing down or interrupting combustion. Commonly available intumescent flame retardants are mixtures of ammonium polyphosphate, pentaerythritol, and melamine. However, these flame retardants are mostly inorganic, exhibiting poor dispersibility and compatibility in organic polymer substrates, which can damage the mechanical properties of the polymer material. Furthermore, over time, the flame retardant migrates to the substrate surface, affecting flame retardant durability. On the other hand, these mixed flame retardants have poor water resistance; the flame retardant performance of the modified polymer material significantly decreases when exposed to water. Single-component intumescent flame retardants, on the other hand, incorporate multiple flame-retardant groups onto a single molecule, offering better dispersibility and compatibility.

[0004] In recent years, with the strengthening of the concept of sustainable development, bio-based materials have attracted widespread attention from scholars. Phytic acid, due to its high phosphorus content and good char-forming properties, has been used to prepare intumescent flame retardants. Currently, some scholars have used phytic acid and simple organic amine molecules to carry out acid-base neutralization reactions to prepare a series of ammonium phytate salt flame retardants. Although these flame retardants exhibit good flame retardant properties, they are all salt compounds (ionic bonds), easily soluble in water, and not resistant to washing, thus limiting their application to some extent. For example, Li et al. used phytic acid and 1,6-hexanediamine as raw materials and water as a solvent to carry out an acid-base neutralization reaction. The water solvent was removed by rotary evaporation to prepare the phytate flame retardant PA-HAD (Tough and flame-retardant poly(lactic acid) composites prepared via reactive blending with biobased ammonium phytate and in situ formed crosslinked polyurethane, composites communications, 8, 52-57). Adding 5 wt% of this type of flame retardant enabled polylactic acid to pass the UL-94V-0 rating, achieving an oxygen index of 26%. This work was also patented (CN 108047494A) and granted. From the preparation method of this scholar's phytate flame retardant, it is easy to see that the prepared flame retardant is water-soluble. Gao et al. prepared a phytic acid-piperazine salt flame retardant, PHYPI (A novel bio-based flame retardant for polypropylene from phyticacid, Polymer Degradation and Stability, 161, 298-308), using phytic acid and piperazine as raw materials and water as a solvent. This flame retardant was applied to polypropylene and achieved good flame retardant effects. However, this flame retardant is also water-soluble and therefore not resistant to washing.

[0005] Furthermore, the aforementioned phytate flame retardants are all prepared by a simple acid-base neutralization reaction using phytic acid and organic amine molecules. The organic amine molecules used are typically small molecules such as aliphatic amines, aromatic amines, melamine, piperazine, aminoethylpiperazine, and imidazole. Therefore, the resulting flame retardants have insufficient char-forming ability, resulting in the inability to form a high-strength expanded char layer and effectively protect polymers. For example, the PHYPI flame retardant prepared above has a char residue of only 34.7% under nitrogen atmosphere and at 700°C. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a single-component intumescent flame retardant with a layered structure and a strong char-forming ability, and a method for preparing the same.

[0007] To solve the above technical problems, the present invention adopts the following technical solution:

[0008] A single-component intumescent flame retardant with a layered structure and superior char-forming ability has the following structural formula:

[0009]

[0010] In the formula, R can be any of the following structures:

[0011]

[0012] A method for preparing a single-component intumescent flame retardant with a layered structure and strong char-forming ability includes the following steps:

[0013] Step 1: Mix 3,4-dihydroxybenzaldehyde and organic diamine in anhydrous ethanol, react at 25-80°C, stir for 1-6 hours, cool to room temperature, filter, wash with ethanol and dry to obtain intermediate A;

[0014] Step 2: Disperse the intermediate A obtained in Step 1 in a solvent to form a uniform suspension, then slowly add phytic acid solution, stir for 5-12 hours, and the reaction temperature is 25-100℃. After the reaction is completed, filter, wash with deionized water and dry to obtain a single-component intumescent flame retardant with a layered structure and super char-forming ability.

[0015] Furthermore, in step 1, the molar ratio of 3,4-dihydroxybenzaldehyde to organic diamine is (2-5):1.

[0016] Furthermore, the organic diamine in step 1 is any one or more of 4,4'-diaminodiphenylmethane, 4,4'-diaminophenyl sulfone, 3,5-diaminotriazole, 4,4'-diaminodiphenyl ether, 4,4'-diaminoterphenyl, 4,4'-diaminodiphenyl sulfide, and 2,2'-diamino-4,4'-bisthiazole.

[0017] Furthermore, in step 2, the molar ratio of intermediate A to phytic acid is (0.2-5):1.

[0018] Furthermore, the solvent in step 2 is any one of acetonitrile, toluene, benzene, acetone, chloroform, and water.

[0019] Compared with the prior art, the present invention, by adopting the above technical solution, has the following advantages:

[0020] 1. While existing reports of ammonium phytate flame retardants exhibit good flame retardant effects, they are all water-soluble and not water-resistant, which greatly limits their application. This invention utilizes the acidic hydroxyl groups of phytic acid and the phenolic hydroxyl groups on intermediate A molecule for esterification, and the continuous reaction and cross-linking form a large molecular network, resulting in abundant aromatic ester groups within the flame retardant molecule. This gives the flame retardant of this invention water resistance.

[0021] 2. Existing phytate flame retardants are all prepared by directly reacting phytic acid with small organic amine molecules. The resulting phytate flame retardant molecules lack sufficient carbon and gas sources to form a high-strength expanding char layer, thus failing to effectively slow down or interrupt the polymer's combustion reaction. In contrast, the phytate flame retardant prepared in this invention is synthesized using a two-step method. First, 3,4-dihydroxybenzaldehyde is reacted with an organic diamine rich in benzene rings or nitrogen heterocycles to generate intermediate A; then, intermediate A is reacted with phytic acid to obtain the final product.

[0022] Intermediate A is rich in benzene rings or nitrogen heterocycles. When heated, it exhibits good charring properties and releases a large amount of inert gas, serving as an excellent carbon and gas source. Phytic acid is also a good acid and carbon source. By organically combining phytic acid and intermediate A, a single-component intumescent flame retardant with superior charring ability is finally obtained. The flame retardant prepared by this invention can form a super-strong intumescent char layer during combustion, and this intumescent char layer is very hard, capable of withstanding a 200-gram weight. Simultaneously, the surface of the char layer is also very dense. Therefore, this hard and dense intumescent char layer can very effectively block combustion. The flame retardant prepared by this invention has higher flame retardant efficiency.

[0023] 3. In this invention, due to the cross-linking reaction between phytic acid and intermediates, a super-large cross-linked network is formed, ultimately resulting in a flame retardant with a layered structure. Because the flame retardant of this invention has a layered structure, when blended with a polymer, the polymer molecular chains can intercalate within the layered structure of the flame retardant, greatly enhancing the interfacial interaction between the flame retardant and the polymer matrix, improving dispersibility, and thus significantly improving the mechanical properties of the polymer.

[0024] 4. The preparation method of this invention is simple, easy to operate, and convenient for industrial production.

[0025] The present invention will now be described in detail with reference to the accompanying drawings and examples. Attached Figure Description

[0026] Figure 1 Here is a SEM image of the flame retardant prepared in Example 1 of this invention;

[0027] Figure 2 The infrared spectrum of the flame retardant prepared in Example 1 of this invention;

[0028] Figure 3 XPSO, which is the flame retardant prepared in Example 1 of this invention. 1s Structural diagram;

[0029] Figure 4 Thermogravimetric analysis of the flame retardant prepared in Example 1 of this invention;

[0030] Figure 5 A digital photograph of the expanded char layer formed by the flame retardant prepared in Example 1 of the present invention;

[0031] Figure 6 A graph showing the heat release rate of a polylactic acid composite material prepared in Example 1 of the present invention with 2% by weight added.

[0032] Figure 7 The tensile strength and impact strength diagrams of polylactic acid composite materials consisting of pure polylactic acid and polylactic acid with 2% by weight of the flame retardant prepared in Example 1 of the present invention. Detailed Implementation

[0033] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0034] Example 1:

[0035] (1) First, 0.2 mol of 3,4-dihydroxybenzaldehyde and 0.1 mol of 4,4'-diaminodiphenylmethane were mixed in anhydrous ethanol. The reaction temperature was 25°C, and the mixture was stirred for 1 h. After cooling to room temperature, the intermediate product was obtained by filtration, washing with ethanol and drying.

[0036] (2) Weigh 0.1 mol of the intermediate product obtained in step 1 and disperse it in acetonitrile to form a uniform suspension. Then slowly add 0.5 mol of phytic acid solution, stir for 5 h, and the reaction temperature is 25 °C. After the reaction is completed, filter, wash with deionized water and dry to obtain the final product flame retardant.

[0037] like Figure 1 The SEM image of the flame retardant prepared in Example 1 shows that the flame retardant has a layered structure with a size of 1 to 10 micrometers.

[0038] like Figure 2 The infrared spectrum of the flame retardant prepared in Example 1 shows that the flame retardant was successfully synthesized;

[0039] like Figure 3 XPSO, the flame retardant prepared in Example 1 shown 1s The structural diagram proves that the flame retardant molecule contains abundant ester bonds (PO, CO);

[0040] like Figure 4 The thermogravimetric analysis of the flame retardant prepared in Example 1 shows that the flame retardant has 69.3% char residue at a high temperature of 700℃, demonstrating its strong char-forming ability.

[0041] like Figure 5 The digital photograph of the flame retardant formed by the flame retardant in Example 1 shows that the flame retardant has a super expansion capacity, and the residual char has a hard structure.

[0042] like Figure 6 The heat release rate diagram of the polylactic acid composite material with flame retardant prepared in Example 1 shows that, compared with unmodified polylactic acid, the peak heat release rate of flame-retardant modified polylactic acid is reduced by 30%.

[0043] like Figure 7 The tensile strength and impact strength diagrams of the polylactic acid composite material with flame retardant prepared in Example 1 are shown. Compared with pure polylactic acid, the impact performance of the polylactic acid composite material with added flame retardant is improved by 101%.

[0044] Example 2:

[0045] (1) First, 0.3 mol of 3,4-dihydroxybenzaldehyde and 0.1 mol of 4,4'-diaminophenyl sulfone were mixed in anhydrous ethanol. The reaction temperature was 40℃, and the mixture was stirred for 2 h. After cooling to room temperature, the intermediate product was obtained by filtration, washing with ethanol and drying.

[0046] (2) Weigh 0.2 mol of the intermediate product obtained in step 1 and disperse it in toluene to form a uniform suspension. Then slowly add 0.4 mol of phytic acid solution, stir for 6 h, and the reaction temperature is 40 °C. After the reaction is completed, filter, wash with deionized water and dry to obtain the final product flame retardant.

[0047] Example 3:

[0048] (1) First, 0.4 mol of 3,4-dihydroxybenzaldehyde and 0.1 mol of 3,5-diaminotriazole were mixed in anhydrous ethanol. The reaction temperature was 50℃, and the mixture was stirred for 3 h. After cooling to room temperature, the intermediate product was obtained by filtration, washing with ethanol and drying.

[0049] (2) Weigh 0.2 mol of the intermediate product obtained in step 1 and disperse it in benzene to form a uniform suspension. Then slowly add 0.2 mol of phytic acid solution, stir for 7 h, and the reaction temperature is 50 °C. After the reaction is completed, filter, wash with deionized water and dry to obtain the final product flame retardant.

[0050] Example 4:

[0051] (1) First, 0.5 mol of 3,4-dihydroxybenzaldehyde and 0.1 mol of 4,4'-diaminodiphenyl ether were mixed in anhydrous ethanol. The reaction temperature was 60℃, and the mixture was stirred for 4 h. After cooling to room temperature, the intermediate product was obtained by filtration, washing with ethanol and drying.

[0052] (2) Weigh 0.4 mol of the intermediate product obtained in step 1 and disperse it in acetone to form a uniform suspension. Then slowly add 0.2 mol of phytic acid solution, stir for 8 hours, and the reaction temperature is 60℃. After the reaction is completed, filter, wash with deionized water and dry to obtain the final product flame retardant.

[0053] Example 5:

[0054] (1) First, 1 mol of 3,4-dihydroxybenzaldehyde and 0.5 mol of 4,4'-diaminoterphenyl were mixed in anhydrous ethanol. The reaction temperature was 70℃, and the mixture was stirred for 5 h. After cooling to room temperature, the intermediate product was obtained by filtration, washing with ethanol and drying.

[0055] (2) Weigh 0.3 mol of the intermediate product obtained in step 1 and disperse it in chloroform to form a uniform suspension. Then slowly add 0.1 mol of phytic acid solution, stir for 9 h, and the reaction temperature is 70 °C. After the reaction is completed, filter, wash with deionized water and dry to obtain the final product flame retardant.

[0056] Example 6:

[0057] (1) First, 3 mol of 3,4-dihydroxybenzaldehyde and 1 mol of 4,4'-diaminodiphenyl sulfide were mixed in anhydrous ethanol. The reaction temperature was 80℃, and the mixture was stirred for 6 h. After cooling to room temperature, the intermediate product was obtained by filtration, washing with ethanol and drying.

[0058] (2) Weigh 0.8 mol of the intermediate product obtained in step 1 and disperse it in water to form a uniform suspension. Then slowly add 0.2 mol of phytic acid solution, stir for 10 h, and the reaction temperature is 80℃. After the reaction is completed, filter, wash with deionized water and dry to obtain the final product flame retardant.

[0059] Example 7:

[0060] (1) First, 5 mol of 3,4-dihydroxybenzaldehyde and 1 mol of 2,2'-diamino-4,4'-bisthiazole were mixed in anhydrous ethanol. The reaction temperature was 50℃, and the mixture was stirred for 3 h. After cooling to room temperature, the intermediate product was obtained by filtration, washing with ethanol and drying.

[0061] (2) Weigh 0.5 mol of the intermediate product obtained in step 1 and disperse it in acetonitrile to form a uniform suspension. Then slowly add 0.1 mol of phytic acid solution, stir for 12 h, and the reaction temperature is 100℃. After the reaction is completed, filter, wash with deionized water and dry to obtain the final product flame retardant.

[0062] Example 8:

[0063] When the flame retardant obtained in Example 1 is used in polylactic acid, the flame retardant content is 2%, and the oxygen index of the prepared polylactic acid can reach more than 26%, the peak heat release is reduced by 30%, and the impact strength is increased by 101%.

[0064] Example 9:

[0065] When the flame retardant obtained in Example 1 is used in epoxy resin, the amount of flame retardant added is 10%. The resulting epoxy resin has an oxygen index of 35%, a heat release peak decrease of 60%, a tensile strength of 70 MPa, and an impact strength of 10 MPa.

[0066] Example 10:

[0067] When the flame retardant obtained in Example 1 was used in Lyocell fibers at a concentration of 5%, the resulting Lyocell fibers achieved an oxygen index of 30%, enabling the textiles to self-extinguish upon removal of the flame. The peak heat release decreased by 30%, and the tensile strength was 130 MPa.

[0068] Example 11:

[0069] The flame retardant obtained in Example 1 was used in carbon fiber reinforced epoxy resin composites at a dosage of 10%. The resulting carbon fiber composites achieved an oxygen index of 40%, passed the V0 rating during vertical burning, and exhibited a 40% reduction in peak heat release. The tensile strength was increased by 30% and the flexural strength by 20% compared to the unmodified carbon fiber composites.

[0070] The above description provides examples of the preferred embodiments of the present invention. Parts not detailed herein are common knowledge to those skilled in the art. The scope of protection of the present invention is determined by the claims. Any equivalent modifications based on the technical teachings of the present invention are also within the scope of protection of the present invention.

Claims

1. A method for preparing a single-component intumescent flame retardant with a layered structure and strong char-forming ability, characterized in that, Includes the following steps: Step 1: Mix 3,4-dihydroxybenzaldehyde and organic diamine in anhydrous ethanol, react at 25-80°C, stir for 1-6 hours, cool to room temperature, filter, wash with ethanol and dry to obtain intermediate A; In step 1, the molar ratio of 3,4-dihydroxybenzaldehyde to organic diamine is (2-5):1; the organic diamine in step 1 is any one or more of 4,4'-diaminodiphenylmethane, 4,4'-diaminophenyl sulfone, 3,5-diaminotriazole, 4,4'-diaminodiphenyl ether, 4,4'-diaminoterphenyl, 4,4'-diaminodiphenyl sulfide, and 2,2'-diamino-4,4'-bisthiazole. Step 2: Disperse the intermediate A obtained in Step 1 in a solvent to form a uniform suspension, then slowly add phytic acid solution, stir for 5-12 hours, and the reaction temperature is 25-100℃. After the reaction is completed, filter, wash with deionized water and dry to obtain a single-component intumescent flame retardant with a layered structure and super char-forming ability. The molar ratio of intermediate A to phytic acid in step 2 is (0.2-5):

1.

2. The preparation method of the single-component intumescent flame retardant with layered structure and strong char-forming ability according to claim 1, characterized in that, The solvent in step 2 is any one of acetonitrile, toluene, benzene, acetone, chloroform, and water.

3. A single-component intumescent flame retardant with a layered structure and superior char-forming ability, characterized in that, It is prepared by the preparation method according to any one of claims 1-2.

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