Tannic acid flame retardant using water as solvent, its preparation method and application

Abstract

The present invention discloses a tannic acid flame retardant using water as a solvent, its preparation method and application, belonging to the technical field of flame retardant materials. The present invention uses natural renewable biological resource tannic acid as a raw material and water as a solvent, and chemically grafts and modifies tannic acid with azacyclic phosphoric acid to obtain the tannic acid flame retardant. The tannic acid flame retardant prepared by the present invention does not contain halogens, has a high phosphorus and nitrogen content, excellent flame retardant performance, good compatibility with polymers such as rigid polyurethane foam, and has a simple preparation process, mild conditions, low production cost, and is green and environmentally friendly, and is suitable for industrial popularization and application.

Description

Technical Field

[0001] The present invention belongs to the technical field of flame retardant materials, and particularly relates to a tannic acid flame retardant using water as a solvent, its preparation method and application. Background Art

[0002] Rigid polyurethane foam materials are a kind of building insulation materials with excellent comprehensive properties, having advantages such as light weight, low density, low thermal conductivity, high specific strength, heat insulation, etc. However, rigid polyurethane foam materials are flammable materials. When burning, not only the flame propagation speed is fast and the heat release rate is large, but also usually accompanied by toxic smoke, posing a great threat to people's lives and property safety. Endowing rigid polyurethane foam materials with flame retardancy through flame retardants is the most commonly used approach.

[0003] Among commercial flame retardants, the market scale and application fields of halogen-containing flame retardants have long ranked first. However, halogen-containing flame retardants will release a large amount of thick smoke when burning, and produce toxic gases such as hydrogen halide and dioxins, causing secondary harm. Therefore, halogen-containing flame retardants have been gradually restricted from use. Among many halogen-free flame retardants, phosphorus-nitrogen flame retardants have the advantages of being halogen-free, low-toxic, low-smoke, and relatively high flame retardancy efficiency, and have good application prospects.

[0004] Patent CN 115612089 B discloses a nitrogen-phosphorus composite hydrolysis-resistant reactive flame retardant, its preparation method and application; Patent CN 115678103 B reports a long-chain alkane cyclotriphosphazene flame retardant, its preparation method and application; although many researchers have proposed preparation methods of phosphorus-nitrogen flame retardants, currently the synthesis of phosphorus-nitrogen flame retardants mainly relies on petrochemical raw materials, and at the same time a large amount of organic solvents such as tetrahydrofuran and N,N-dimethylformamide are required in the synthesis process, resulting in high costs and large environmental loads, which runs counter to the concept of sustainable and green development. Patent CN 109912650 B discloses a phosphorus-nitrogen-based bio-based flame retardant, its synthesis method and application. Although this method uses bio-based aldehyde or amine compounds as raw materials, a large amount of organic solvents are still used in the synthesis process. Therefore, developing a phosphorus-nitrogen flame retardant with wide and renewable raw material sources, being green and environmentally friendly, low production cost, mild reaction conditions, good compatibility with polymers, and high flame retardancy efficiency is an urgent problem to be solved by those skilled in the art.

[0005] Tannic acid is a natural plant polyphenol compound, widely distributed in the bark, shell, root, leaves and pulp of plants, such as Chinese gallnut, pomegranate peel, lacquer tree leaves, witch hazel tree, etc. Tannic acid has characteristics such as rich resources, low price, excellent water solubility, and rich in 25 phenolic hydroxyl groups in its molecular structure, which lays a foundation for the chemical grafting modification of azacyclic phosphoric acid under the condition of using water as a solvent. Summary of the Invention

[0006] To solve the problems in the prior art that phosphorus-nitrogen type flame retardants mainly rely on petrochemical raw materials, a large amount of organic solvents are required in the synthesis process, the production cost is high, the compatibility with polymers is poor, and the flame retardant effect is not ideal, the present invention provides a tannic acid flame retardant using water as a solvent, its preparation method and application.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] One of the objects of the present invention is to protect a preparation method of a tannic acid flame retardant using water as a solvent, which includes the following steps:

[0009] (1) Preparation of azacyclic phosphoric acid: Dispersing an amine compound and phosphorous acid in deionized water together, under the protection of a nitrogen atmosphere, dropping formaldehyde and then reacting to obtain azacyclic phosphoric acid; the reaction formula is as follows:

[0010] ;

[0011] (2) Preparation of tannic acid flame retardant: Dispersing tannic acid and the prepared azacyclic phosphoric acid in deionized water together, reacting under the protection of a nitrogen atmosphere, and after the reaction is completed, cooling, vacuum distillation, washing, and vacuum drying are carried out to obtain the tannic acid flame retardant; the reaction formula is as follows:

[0012] 。

[0013] In the reaction formula, only the graft modification of a single phenolic hydroxyl group is taken as an example. The tannic acid molecule structure is rich in 25 phenolic hydroxyl groups. By adjusting the molar ratio of tannic acid and azacyclic phosphoric acid, the number of modified phenolic hydroxyl groups of tannic acid can be regulated, and tannic acid flame retardants with different phosphorus and nitrogen element contents can be obtained.

[0014] Further, the amine compound in step (1) is any one of melamine, methylguanamine, piperazine, N-ethylpiperazine, N-phenylpiperazine, N-aminoethylpiperazine, 2-aminopyrimidine, 2,4,6-triaminopyrimidine, 3-aminopyridine, 4-aminopyridine, 2,6-diaminopyridine, guanine or adenine.

[0015] Further, the molar ratio of the amine compound, phosphorous acid and formaldehyde used in step (1) is 1:(1~6):(1~6).

[0016] Further, the temperature of the reaction in step (1) is 60°C~100°C, and the time is 2h~6h.

[0017] Further, the molar ratio of tannic acid and azacyclic phosphoric acid used in step (2) is 1:(5~20).

[0018] Further, the temperature of the reaction described in step (2) is 40°C to 80°C, and the time is 2 h to 6 h.

[0019] The second object of the present invention is to protect the tannic acid flame retardant prepared by the above method. The tannic acid flame retardant prepared by the present invention does not contain halogen, has a high phosphorus and nitrogen content, and is rich in benzene rings, phenolic hydroxyl groups, nitrogen heterocycles and other structures in the molecular structure, which ensures good compatibility between the tannic acid flame retardant and the polymer matrix. On the premise of ensuring the physical and chemical properties of the polymer matrix, efficient flame retardancy of various polymer materials can be achieved.

[0020] The third object of the present invention is to protect the application of the tannic acid flame retardant in the preparation of flame-retardant polymer materials, such as flame-retardant rigid polyurethane foam.

[0021] Further, 10 wt% to 20 wt% of the tannic acid flame retardant is added to the flame-retardant rigid polyurethane foam, and its limiting oxygen index is greater than 28%.

[0022] In addition to flame-retardant rigid polyurethane foam, the tannic acid flame retardant obtained in the present invention is also applicable to the preparation of other flame-retardant products.

[0023] Compared with the prior art, the significant advantages of the present invention are as follows:

[0024] (1) The tannic acid flame retardant provided by the present invention uses natural plant polyphenol tannic acid, which is rich in resources, low in price, low-carbon and environmentally friendly, and has excellent water solubility, as a raw material, uses water as a solvent, and chemically grafts azacyclic phosphoric acid through a certain ratio relationship. Its preparation process is simple, the conditions are mild, the production cost is low, and it is environmentally friendly. It improves the resource utilization degree and product added value of tannic acid, and is suitable for industrialized popularization and application.

[0025] (2) The structure and components of the tannic acid flame retardant obtained in the present invention are easy to control, do not contain halogen, have a high phosphorus and nitrogen content, and are rich in benzene rings, phenolic hydroxyl groups, nitrogen heterocycles and other structures in the molecular structure, and have good compatibility with the polymer matrix, and can be used for efficient flame retardancy of various polymer materials.

[0026] (3) The flame-retardant rigid polyurethane foam containing 10% to 20% by mass of the tannic acid flame retardant provided by the present invention has excellent flame retardant performance, does not reduce the physical and chemical properties of polyurethane itself, and can be widely popularized and applied. Description of the Drawings

[0027] Figure 1 It is a comparison chart of UL-94 vertical burning tests for the rigid polyurethane foam prepared as a comparative example and the flame-retardant rigid polyurethane foam prepared in Example 3. As Figure 1 can be seen, the flame-retardant rigid polyurethane foam prepared by the present invention has a good flame retardant effect.

[0028] Figure 2 SEM images of the rigid polyurethane foam prepared as a comparative example and the flame - retardant rigid polyurethane foam prepared in Example 8. As can be seen from Figure 2 it, the addition of the tannic acid flame retardant has no obvious effect on the morphology of the prepared rigid polyurethane foam. Detailed Description of the Invention

[0029] A tannic acid flame retardant using water as a solvent, and its preparation method includes the following steps:

[0030] (1) Preparation of azacyclic phosphoric acid: Dispersing an amine compound and phosphorous acid in deionized water together, under the protection of a nitrogen atmosphere, after dropping formaldehyde, reacting at 60 °C - 100 °C for 2 h - 6 h to obtain azacyclic phosphoric acid; the molar ratio of the used amine compound, phosphorous acid and formaldehyde is 1:(1 - 6):(1 - 6);

[0031] (2) Preparation of the tannic acid flame retardant: Dispersing tannic acid and the prepared azacyclic phosphoric acid in deionized water together according to a molar ratio of 1:(5 - 20), reacting at 40 °C - 80 °C for 2 h - 6 h under the protection of a nitrogen atmosphere, and after the reaction, cooling, distilling under reduced pressure, washing, and drying in vacuo to obtain the tannic acid flame retardant.

[0032] Among them, the amine compound is any one of melamine, methylguanamine, piperazine, N - ethylpiperazine, N - phenylpiperazine, N - aminoethylpiperazine, 2 - aminopyrimidine, 2,4,6 - triaminopyrimidine, 3 - aminopyridine, 4 - aminopyridine, 2,6 - diamino - pyridine, guanine or adenine.

[0033] To describe in detail the technical content, structural features, achieved objectives and effects of the technical solution, the following is described in detail with specific examples.

[0034] As used herein, the mention of "example" means that the specific features, structures or characteristics described in connection with the example can be included in at least one embodiment of the present application. The term "example" appearing at various positions in the specification does not necessarily refer to the same example, nor is it particularly limited to its independence or relevance to other examples. In principle, in the present application, as long as there is no technical contradiction or conflict, the technical features mentioned in each example can be combined in any way to form the corresponding implementable technical solution.

[0035] Unless otherwise defined, the meanings of the technical terms used herein are the same as those generally understood by those skilled in the technical field to which the present application belongs; the use of the relevant terms herein is only for describing specific examples and is not intended to limit the present application.

[0036] The raw material situations used in the following examples listed in the present invention are described as follows:

[0037] Tannic acid, phosphorous acid, formaldehyde, amine compounds, and raw materials for preparing rigid polyurethane foam are all from commercially available conventional products.

[0038] The determination methods for compressive properties, limiting oxygen index, and UL-94 vertical burning rating involved in the following listed examples of the present invention are specifically introduced as follows:

[0039] The test method for compressive properties follows the relevant regulations in ASTM D1621, the determination method for limiting oxygen index follows the relevant regulations in ASTM D-2863, and the determination method for UL-94 vertical burning rating follows the relevant regulations in ASTM D-3801.

[0040] Comparative Example

[0041] This comparative example provides a method for preparing rigid polyurethane foam

[0042] The rigid polyurethane foam is prepared by a one-step free-foaming process. The specific steps are as follows: 40 g of polyether polyol LY-4110, 0.3 g of water, 0.04 g of dibutyltin dilaurate, and 4 g of silicone oil are mixed evenly. Subsequently, 54 g of polyaryl polymethylene isocyanate PM-200 is added under high-speed stirring conditions. After reacting for 10 s, the product is quickly poured into a mold and cured for 24 h to obtain rigid polyurethane foam.

[0043] Example 1

[0044] This example provides a method for preparing a tannic acid flame retardant using water as a solvent and a flame-retardant rigid polyurethane foam containing the same

[0045] (1) 1.0 mol of guanine and 2.0 mol of phosphorous acid are dispersed in deionized water. 2.0 mol of formaldehyde is added dropwise under a nitrogen atmosphere. After the addition is complete, the reaction is carried out at 70 °C for 5 h to obtain azacyclic phosphoric acid;

[0046] (2) 0.1 mol of tannic acid and 1.0 mol of the prepared azacyclic phosphoric acid are dispersed in deionized water. The reaction is carried out at 60 °C for 4 h under a nitrogen atmosphere. After the reaction, it is cooled, subjected to vacuum distillation, washed, and vacuum dried to obtain the tannic acid flame retardant.

[0047] The tannic acid flame retardant is mixed evenly with polyether polyol LY-4110, water, dibutyltin dilaurate, and silicone oil, and a flame-retardant rigid polyurethane foam is prepared according to the one-step free-foaming process described in the comparative example, where the content of the tannic acid flame retardant is 10 wt%.

[0048] Example 2

[0049] This example provides a method for preparing a tannic acid flame retardant using water as a solvent and a flame-retardant rigid polyurethane foam containing the same

[0050] (1) Disperse 1.0 mol of methylguanamine and 2.0 mol of phosphorous acid in deionized water, add 2.0 mol of formaldehyde dropwise under the protection of a nitrogen atmosphere, and react at 100 °C for 2 h after the addition is complete to obtain azacyclic phosphoric acid;

[0051] (2) Disperse 0.1 mol of tannic acid and 0.5 mol of the prepared azacyclic phosphoric acid in deionized water, react at 80 °C for 3 h under the protection of a nitrogen atmosphere, and after the reaction, cool, distill under reduced pressure, wash, and dry in vacuo to obtain a tannic acid flame retardant.

[0052] Mix the tannic acid flame retardant evenly with polyether polyol LY-4110, water, dibutyltin dilaurate, and silicone oil, and prepare a flame-retardant rigid polyurethane foam according to the one-step free foaming process described in the comparative example, wherein the content of the tannic acid flame retardant is 16 wt%.

[0053] Example 3

[0054] This example provides a preparation method of a tannic acid flame retardant using water as a solvent and a flame-retardant rigid polyurethane foam containing the same

[0055] (1) Disperse 1.0 mol of N-aminoethylpiperazine and 3.0 mol of phosphorous acid in deionized water, add 3.0 mol of formaldehyde dropwise under the protection of a nitrogen atmosphere, and react at 75 °C for 6 h after the addition is complete to obtain azacyclic phosphoric acid;

[0056] (2) Disperse 0.1 mol of tannic acid and 1.2 mol of the prepared azacyclic phosphoric acid in deionized water, react at 40 °C for 6 h under the protection of a nitrogen atmosphere, and after the reaction, cool, distill under reduced pressure, wash, and dry in vacuo to obtain a tannic acid flame retardant.

[0057] Mix the tannic acid flame retardant evenly with polyether polyol LY-4110, water, dibutyltin dilaurate, and silicone oil, and prepare a flame-retardant rigid polyurethane foam according to the one-step free foaming process described in the comparative example, wherein the content of the tannic acid flame retardant is 20 wt%.

[0058] Example 4

[0059] This example provides a preparation method of a tannic acid flame retardant using water as a solvent and a flame-retardant rigid polyurethane foam containing the same

[0060] (1) Disperse 1.0 mol of piperazine and 2.0 mol of phosphorous acid in deionized water, add 2.0 mol of formaldehyde dropwise under the protection of a nitrogen atmosphere, and react at 60 °C for 2 h after the addition is complete to obtain azacyclic phosphoric acid;

[0061] (2) Disperse 0.1 mol of tannic acid and 2.0 mol of the prepared azacyclic phosphoric acid in deionized water, react at 65 °C for 3 h under the protection of a nitrogen atmosphere, and after the reaction, cool, distill under reduced pressure, wash, and dry in vacuum to obtain the tannic acid flame retardant.

[0062] Mix the tannic acid flame retardant with polyether polyol LY-4110, water, dibutyltin dilaurate, and silicone oil evenly, and prepare the flame-retardant rigid polyurethane foam by the one-step free foaming process described in the comparative example, where the content of the tannic acid flame retardant is 15 wt%.

[0063] Example 5

[0064] This example provides a preparation method of a tannic acid flame retardant using water as a solvent and a flame-retardant rigid polyurethane foam containing the same.

[0065] (1) Disperse 1.0 mol of N-ethylpiperazine and 1.0 mol of phosphorous acid in deionized water, dropwise add 1.0 mol of formaldehyde under the protection of a nitrogen atmosphere, and react at 80 °C for 5 h after the addition is complete to obtain azacyclic phosphoric acid;

[0066] (2) Disperse 0.1 mol of tannic acid and 1.5 mol of the prepared azacyclic phosphoric acid in deionized water, react at 70 °C for 5 h under the protection of a nitrogen atmosphere, and after the reaction, cool, distill under reduced pressure, wash, and dry in vacuum to obtain the tannic acid flame retardant.

[0067] Mix the tannic acid flame retardant with polyether polyol LY-4110, water, dibutyltin dilaurate, and silicone oil evenly, and prepare the flame-retardant rigid polyurethane foam by the one-step free foaming process described in the comparative example, where the content of the tannic acid flame retardant is 12 wt%.

[0068] Example 6

[0069] This example provides a preparation method of a tannic acid flame retardant using water as a solvent and a flame-retardant rigid polyurethane foam containing the same.

[0070] (1) Disperse 1.0 mol of N-phenylpiperazine and 1.0 mol of phosphorous acid in deionized water, dropwise add 1.0 mol of formaldehyde under the protection of a nitrogen atmosphere, and react at 90 °C for 4 h after the addition is complete to obtain azacyclic phosphoric acid;

[0071] (2) Disperse 0.1 mol of tannic acid and 0.8 mol of the prepared azacyclic phosphoric acid in deionized water, react at 80 °C for 2 h under the protection of a nitrogen atmosphere, and after the reaction, cool, distill under reduced pressure, wash, and dry in vacuum to obtain the tannic acid flame retardant.

[0072] Mix the tannic acid flame retardant evenly with polyether polyol LY-4110, water, dibutyltin dilaurate, and silicone oil, and prepare the flame-retardant rigid polyurethane foam according to the one-step free foaming process described in the comparative example, where the content of the tannic acid flame retardant is 15 wt%.

[0073] Example 7

[0074] This example provides a preparation method of a tannic acid flame retardant using water as a solvent and a flame-retardant rigid polyurethane foam containing the same.

[0075] (1) Disperse 1.0 mol of 2,6-diaminopyridine and 4.0 mol of phosphorous acid in deionized water, dropwise add 4.0 mol of formaldehyde under a nitrogen atmosphere protection, and react at 80 °C for 6 h after the addition is completed to obtain azacyclic phosphoric acid;

[0076] (2) Disperse 0.1 mol of tannic acid and 0.7 mol of the prepared azacyclic phosphoric acid in deionized water, react at 75 °C for 4 h under a nitrogen atmosphere protection, and after the reaction, cool, distill under reduced pressure, wash, and dry in vacuum to obtain the tannic acid flame retardant.

[0077] Mix the tannic acid flame retardant evenly with polyether polyol LY-4110, water, dibutyltin dilaurate, and silicone oil, and prepare the flame-retardant rigid polyurethane foam according to the one-step free foaming process described in the comparative example, where the content of the tannic acid flame retardant is 14 wt%.

[0078] Example 8

[0079] This example provides a preparation method of a tannic acid flame retardant using water as a solvent and a flame-retardant rigid polyurethane foam containing the same.

[0080] (1) Disperse 1.0 mol of 2,4,6-triaminopyrimidine and 6.0 mol of phosphorous acid in deionized water, dropwise add 6.0 mol of formaldehyde under a nitrogen atmosphere protection, and react at 100 °C for 5 h after the addition is completed to obtain azacyclic phosphoric acid;

[0081] (2) Disperse 0.1 mol of tannic acid and 1.0 mol of the prepared azacyclic phosphoric acid in deionized water, react at 70 °C for 6 h under a nitrogen atmosphere protection, and after the reaction, cool, distill under reduced pressure, wash, and dry in vacuum to obtain the tannic acid flame retardant.

[0082] Mix the tannic acid flame retardant evenly with polyether polyol LY-4110, water, dibutyltin dilaurate, and silicone oil, and prepare the flame-retardant rigid polyurethane foam according to the one-step free foaming process described in the comparative example, where the content of the tannic acid flame retardant is 10 wt%.

[0083] Example 9

[0084] This embodiment provides a preparation method of a tannic acid flame retardant using water as a solvent and a flame retardant rigid polyurethane foam containing the same.

[0085] (1) Disperse 1.0 mol of adenine and 3.0 mol of phosphorous acid in deionized water, add 3.0 mol of formaldehyde dropwise under a nitrogen atmosphere, and react at 65 °C for 3 h after the addition is complete to obtain azacyclic phosphoric acid.

[0086] (2) Disperse 0.1 mol of tannic acid and 1.5 mol of the prepared azacyclic phosphoric acid in deionized water, react at 50 °C for 2 h under a nitrogen atmosphere, and after the reaction, cool, distill under reduced pressure, wash, and dry in vacuo to obtain the tannic acid flame retardant.

[0087] Mix the tannic acid flame retardant evenly with polyether polyol LY-4110, water, dibutyltin dilaurate, and silicone oil, and prepare a flame retardant rigid polyurethane foam according to the one-step foaming process described in the comparative example, where the content of the tannic acid flame retardant is 13 wt%.

[0088] Statistically organize the parameters and test results of the rigid polyurethane foam products prepared in the examples and comparative examples, and the results are shown in Table 1.

[0089] Table 1 Parameters and properties of rigid polyurethane foam products prepared in examples and comparative examples

[0090]

[0091] From the results shown in Table 1, it can be seen that the tannic acid flame retardants prepared in Examples 1-9 are applied to rigid polyurethane foam, which can make their limiting oxygen indices all higher than 28%, and the vertical burning test grades are all V-0 level. At the same time, the flame retardant products have a uniform cell structure, and the compressive strength remains basically unchanged compared with pure rigid polyurethane foam, indicating that the tannic acid flame retardant provided by the present invention can be used as an excellent flame retardant for polymer materials such as rigid polyurethane foam.

[0092] It should be noted that although the above embodiments have been described in this article, the patent protection scope of the present invention is not limited thereby. Therefore, based on the innovative concept of the present invention, any changes and modifications made to the embodiments described in this article, or equivalent structural or equivalent process transformations made using the content of the specification of the present invention, directly or indirectly applying the above technical solutions to other related technical fields, are all included in the patent protection scope of the present invention.

Claims

1. A preparation method of a tannic acid flame retardant using water as a solvent, characterized in that, it comprises the following steps: (1) Preparation of azacyclic phosphoric acid: An amine compound and phosphorous acid are jointly dispersed in deionized water. Under the protection of a nitrogen atmosphere, formaldehyde is added dropwise and then reacted to obtain azacyclic phosphoric acid; (2) Preparation of tannic acid flame retardant: Tannic acid and the prepared azacyclic phosphoric acid are jointly dispersed in deionized water and reacted under the protection of a nitrogen atmosphere. After the reaction is completed, it is cooled, distilled under reduced pressure, washed, and dried in vacuo to obtain the tannic acid flame retardant; The amine compound described in step (1) is any one of melamine, methylguanamine, piperazine, N-ethylpiperazine, N-phenylpiperazine, N-aminoethylpiperazine, 2-aminopyrimidine, 2,4,6-triaminopyrimidine, 3-aminopyridine, 4-aminopyridine, 2,6-diaminopyridine, guanine or adenine; In step (2), the molar ratio of tannic acid to azacyclic phosphoric acid used is 1:(5~20); the temperature of the reaction is 40°C to 80°C, and the time is 2h to 6h.

2. The preparation method according to claim 1, characterized in that, in step (1), the molar ratio of the amine compound, phosphorous acid and formaldehyde used is 1:(1~6):(1~6).

3. The preparation method according to claim 1, characterized in that, in step (1), the temperature of the reaction is 60°C to 100°C, and the time is 2h to 6h.

4. A tannic acid flame retardant prepared by the method according to any one of claims 1-3.

5. An application of the tannic acid flame retardant according to claim 4 in the preparation of a flame-retardant polymer composite material, characterized in that, the flame-retardant polymer composite material includes flame-retardant rigid polyurethane foam.

6. The application according to claim 5, characterized in that, 10wt% to 20wt% of the tannic acid flame retardant is added to the flame-retardant rigid polyurethane foam, and its limiting oxygen index is greater than 28%.

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