A dendritic structure flame retardant and preparation method thereof

Abstract

This invention discloses a dendritic flame retardant and its preparation method. The preparation method includes the following steps: S1, adding a hydroxyl-terminated unsaturated olefin to a solution containing phenylphosphonic dichloride and an organic base, and reacting to obtain a solution containing a compound with a phosphonic dichloride structure; S2, adding a tannic acid solution to the solution after step S1, and reacting to obtain the dendritic flame retardant. This invention utilizes green and renewable tannic acid as a raw material to prepare a dendritic flame retardant. This flame retardant employs multiple flame-retardant structures, exhibits excellent flame-retardant effects, and has good compatibility with commonly used non-polar rubbers. Furthermore, this flame retardant can participate in the vulcanization of rubber, preventing the migration and precipitation of the flame retardant during storage and use.

Description

Technical Field

[0001] The invention relates to a flame retardant for rubber materials, in particular to a dendritic structure flame retardant and a preparation method thereof. Background Art

[0002] Rubber materials are generally polymer chains composed of carbon and hydrogen elements. Since carbon and hydrogen elements are easy to burn in the air at high temperatures, most traditional rubber materials are flammable. Rubber product combustion accidents cause serious casualties and property losses to human society every year. Therefore, the preparation of rubber with flame retardant properties is a goal that the industry and industrial sectors are constantly pursuing.

[0003] There are two traditional flame retardant strategies for rubber materials. One is to prepare polymer materials with intrinsic flame retardancy; the other is to introduce flame retardants containing specific flame retardant elements such as halogens, phosphorus, nitrogen, boron, silicon, etc. into polymer materials. The most common and economical solution is to prepare high-efficiency flame retardants and add them to polymer materials. Flame retardants usually use the following mechanisms to achieve flame retardancy in polymer materials: (1) Flame retardants decompose to produce relatively inert free radicals to terminate the active free radicals produced by the combustion chain reaction; (2) Flame retardants decompose to produce inert gases (such as carbon dioxide and ammonia), which suffocate the flame by diluting the oxygen concentration; (3) Flame retardants decompose to produce strong dehydrating agents (such as polyphosphoric acid) to catalyze the dehydrogenation of rubber polymer chains to form a protective carbon layer to extinguish the flame; (4) Flame retardants decompose to absorb the heat of the material to reduce the temperature of the combustion area of ​​the material, thereby stopping the combustion reaction. However, traditional flame retardants are generally polar substances. In order to obtain ideal flame retardant properties, a large amount of flame retardants are often needed to be added, which will inevitably deteriorate the mechanical properties of the material. At the same time, due to the phase separation of flame retardants in rubber materials, the flame retardant properties of the material are also continuously reduced. Therefore, seeking to prepare flame retardants that have good compatibility with rubber materials, can maintain the mechanical properties of the material itself, and have excellent flame retardant properties is an important direction for the development of rubber flame retardant technology. Summary of the invention

[0004] In view of the problem that existing flame retardants have poor compatibility with rubber materials, the present invention provides a dendritic structure flame retardant and a preparation method thereof. The flame retardant has good compatibility with currently common non-polar rubbers and can effectively improve the flame retardant properties of non-polar rubbers.

[0005] In order to achieve the above object, the present invention provides a method for preparing a dendritic flame retardant, which comprises the following steps:

[0006] S1, adding a hydroxyl-terminated unsaturated olefin to a solution containing phenylphosphonyl dichloride and an organic base, and obtaining a solution in which a phosphonyl chloride-terminated compound is dissolved after the reaction;

[0007] S2, adding tannic acid solution to the solution after the reaction in step S1, and reacting to obtain the dendritic structure flame retardant.

[0008] In the rubber matrix, tannic acid is easy to aggregate due to its strong hydrogen bonding. If tannic acid is directly used as a flame retardant for rubber, it will not only have little effect on improving the flame retardant performance, but also deteriorate the basic mechanical properties of the rubber. Therefore, single tannic acid is not suitable as a flame retardant for rubber. The present invention improves the dispersibility of tannic acid-based flame retardants and improves the flame retardancy of rubber materials by designing and adjusting the molecular structure of the flame retardant.

[0009] The present invention uses green and renewable tannic acid as a synthetic raw material, and prepares a dendritic flame retardant through a simple reaction. The remaining polar groups (hydroxyl groups) in the synthetic flame retardant structure are in the molecular core of the dendritic flame retardant, and the outer structural units of the dendritic flame retardant molecules contain non-polar isoprene structural units similar to the natural rubber structure, so the flame retardant has good compatibility with non-polar rubber. The dendritic flame retardant structure contains classic phosphorus elements, and achieves flame retardancy by eliminating the highly active free radical mechanism generated during combustion; at the same time, tannic acid is an acidic substance and rich in aromatic benzene ring structure, and it is easy to form a dense carbon layer during combustion, which has the function of isolating oxygen in the surrounding air and bidirectional transmission of fuel gas generated by thermal decomposition of rubber, and thus has excellent flame retardant effect. The present invention achieves a balance between the flame retardancy of the flame retardant and the compatibility with the material through the reasonable design of the molecular structure of the flame retardant. At the same time, during the rubber vulcanization process, the flame retardant and rubber will also undergo a vulcanization reaction to form covalent bonds and cross-link, which promotes the improvement of the dispersibility and flame retardancy of the flame retardant and expands the application of tannic acid-based flame retardants in the field of flame retardant rubber.

[0010] Preferably, in step S1, the molar ratio of phenylphosphonic dichloride to the organic base is 1:(5-10).

[0011] Preferably, in step S1, the organic base catalyst is one or more of triethylamine, tripropylamine and tributylamine.

[0012] Preferably, in step S1, the hydroxyl-terminated unsaturated olefin is one or more of farnesol, geraniol, nerol and geranylgeraniol, each of which has the following structure:

[0013]

[0014] Preferably, in step S1, the molar ratio of the phenylphosphonic dichloride to the hydroxyl-terminated unsaturated olefin is 1:1.

[0015] Preferably, in step S1, the hydroxyl-terminated unsaturated olefin is added dropwise to a solution containing phenylphosphonyl dichloride and an organic base, the reaction conditions are 20° C. to 40° C., and the reaction time is 4 h to 10 h.

[0016] Preferably, in step S2, the molar ratio of the tannic acid to the capping compound having a phosphonyl chloride structure is 1:(10-20).

[0017] Preferably, in step S2, the reaction conditions are to react at room temperature for 1 h to 1.5 h, then raise the temperature of the system to 50° C. to 60° C., and then react for 12 h to 36 h. The low temperature reaction speed is slow, which can reduce side reactions; in the later stage, as the number of reactive groups decreases, side reactions are also reduced. By raising the temperature, the reaction rate is increased to ensure complete reaction.

[0018] The second aspect of the present invention provides a dendritic structure flame retardant prepared by the above preparation method.

[0019] Through the above technical solution, the present invention achieves the following beneficial effects:

[0020] 1. Compared with traditional flame retardants, the present invention uses green and renewable tannic acid as a raw material to prepare a flame retardant with a dendritic structure. The flame retardant composite adopts a multiple flame retardant structure, has excellent flame retardant effect, and has good compatibility with currently common non-polar rubbers. At the same time, the flame retardant can participate in the vulcanization of rubber, avoiding the migration and precipitation of the flame retardant during storage and use.

[0021] 2. The preparation method of the dendritic structure flame retardant proposed in the present invention is convenient and easy. The prepared flame retardant has excellent flame retardant properties and is in line with the development direction of green chemistry. At the same time, the flame retardant has good compatibility with rubber, and the application scenarios of the flame retardant are more extensive. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a reaction route diagram of the dendritic flame retardant in the embodiment of the present invention. DETAILED DESCRIPTION

[0023] The specific implementation of the present invention is described in detail below in conjunction with the examples. It should be understood that the specific implementation described herein is only used to illustrate and explain the present invention, and is not used to limit the present invention.

[0024] Unless otherwise specified, the reagents used in the following examples are all commercially available products.

[0025] Example 1

[0026] The preparation method of the dendritic structure flame retardant comprises:

[0027] (1) 2.28 g of phenylphosphonyl dichloride and 10.4 g of triethylamine were dissolved in 30 ml of DMSO, and then 1.81 g of geraniol was added dropwise to the above solution under stirring conditions, and the stirring was continued to react at 20° C. for 10 h. After the reaction, a solution 1 containing a phosphonyl chloride structure-capped compound was obtained;

[0028] (2) Dissolve 1 g of tannic acid in 100 ml of DMSO to obtain solution 2; add solution 1 dropwise into solution 2 under stirring conditions to react. The reaction conditions are: stir the reaction at room temperature for 1 hour, then heat the system to 60° C., and then react for 24 hours;

[0029] (3) The solvent is removed by rotary evaporation to obtain a dendritic flame retardant material.

[0030] Example 2

[0031] The preparation method of the dendritic flame retardant comprises:

[0032] (1) 1.14 g of phenylphosphonyl dichloride and 5.7 g of triethylamine were dissolved in 30 ml of DMSO, and then 0.92 g of geraniol was added dropwise to the above solution under stirring conditions, and the stirring was continued to react at 40° C. for 4 h. After the reaction, a solution 1 containing a phosphonyl chloride structure-capped compound was obtained;

[0033] (2) Dissolve 1 g of tannic acid in 100 ml of DMSO to obtain solution 2; add solution 1 dropwise into solution 2 under stirring conditions to carry out a reaction. The reaction conditions are: stir the reaction at room temperature for 1 hour, then heat the system to 60° C., and then react for 12 hours.

[0034] (3) The solvent is removed by rotary evaporation to obtain a dendritic flame retardant material.

[0035] Example 3

[0036] The preparation method of the dendritic flame retardant comprises:

[0037] (1) 1.71 g of phenylphosphonyl dichloride and 8.55 g of tripropylamine were dissolved in 30 ml of DMSO, and then 1.35 g of geraniol was added dropwise to the above solution under stirring conditions, and the stirring was continued to react at 30° C. for 8 h. After the reaction, a solution 1 containing a phosphonyl chloride structure-capped compound was obtained;

[0038] (2) Dissolve 1 g of tannic acid in 100 ml of DMSO to obtain solution 2; add solution 1 dropwise into solution 2 under stirring conditions to carry out a reaction. The reaction conditions are: stir the reaction at room temperature for 1 hour, then heat the system to 60° C., and then react for 36 hours.

[0039] (3) The solvent is removed by rotary evaporation to obtain a dendritic flame retardant material.

[0040] Example 4

[0041] like Figure 1 As shown, the preparation method of the dendritic structure flame retardant is:

[0042] (1) 2.28 g of phenylphosphonyl dichloride and 10.4 g of triethylamine were dissolved in 30 ml of DMSO, and then 2.6 g of farnesol was added dropwise to the above solution under stirring conditions, and the stirring was continued to react at 20° C. for 4 h. After the reaction, a solution 1 containing a phosphonyl chloride structure-capped compound was obtained;

[0043] (2) Dissolve 1 g of tannic acid in 100 ml of DMSO to obtain solution 2; add solution 1 dropwise into solution 2 under stirring conditions to carry out a reaction. The reaction conditions are: stir the reaction at room temperature for 1.5 h, then heat the system to 60° C., and then react for 24 h.

[0044] (3) The solvent is removed by rotary evaporation to obtain a dendritic flame retardant material.

[0045] Example 5

[0046] The preparation method of the dendritic structure flame retardant comprises:

[0047] (1) 1.14 g of phenylphosphonyl dichloride and 5.7 g of triethylamine were dissolved in 30 ml of DMSO, and then 1.3 g of farnesol was added dropwise to the above solution under stirring conditions, and the stirring was continued to react at 40° C. for 8 h. After the reaction, a solution 1 containing a phosphonyl chloride structure-capped compound was obtained;

[0048] (2) Dissolve 1 g of tannic acid in 100 ml of DMSO to obtain solution 2; add solution 1 dropwise into solution 2 under stirring conditions to carry out a reaction. The reaction conditions are: stir the reaction at room temperature for 1 hour, then heat the system to 60° C., and then react for 16 hours.

[0049] (3) The solvent is removed by rotary evaporation to obtain a dendritic flame retardant material.

[0050] Example 6

[0051] The preparation method of the dendritic structure flame retardant comprises:

[0052] (1) 1.71 g of phenylphosphonyl dichloride and 8.55 g of tributylamine were dissolved in 30 ml of DMSO, and then 1.94 g of farnesol was added dropwise to the above solution under stirring conditions, and the stirring was continued to react at 30° C. for 8 h. After the reaction, a solution 1 containing a phosphonyl chloride structure-capped compound was obtained;

[0053] (2) Dissolve 1 g of tannic acid in 100 ml of DMSO to obtain solution 2; add solution 1 dropwise into solution 2 under stirring conditions to carry out a reaction. The reaction conditions are: stir the reaction at room temperature for 1 hour, then heat the system to 60° C., and then react for 30 hours.

[0054] (3) The solvent is removed by rotary evaporation to obtain a dendritic flame retardant material.

[0055] Example 7

[0056] The preparation method of the dendritic structure flame retardant comprises:

[0057] (1) 2.28 g of phenylphosphonyl dichloride and 10.4 g of triethylamine were dissolved in 30 ml of DMSO, and then 1.82 g of nerol was added dropwise to the above solution under stirring conditions, and the stirring was continued to react at 25° C. for 10 h. After the reaction, a solution 1 containing a phosphonyl chloride structure-capped compound was obtained;

[0058] (2) Dissolve 1 g of tannic acid in 100 ml of DMSO to obtain solution 2; add solution 1 dropwise into solution 2 under stirring conditions to carry out a reaction. The reaction conditions are: stir the reaction at room temperature for 1 hour, then heat the system to 50° C., and then react for 36 hours.

[0059] (3) The solvent is removed by rotary evaporation to obtain a dendritic flame retardant material.

[0060] Example 8

[0061] The preparation method of the dendritic structure flame retardant comprises:

[0062] (1) 1.14 g of phenylphosphonyl dichloride and 5.7 g of triethylamine were dissolved in 30 ml of DMSO, and then 0.92 g of nerol was added dropwise to the above solution under stirring conditions, and the stirring was continued to react at 35° C. for 6 h. After the reaction, a solution 1 containing a phosphonyl chloride structure-capped compound was obtained;

[0063] (2) Dissolve 1 g of tannic acid in 100 ml of DMSO to obtain solution 2; add solution 1 dropwise into solution 2 under stirring conditions to carry out a reaction. The reaction conditions are: stir the reaction at room temperature for 1 hour, then heat the system to 60° C., and then react for 24 hours.

[0064] (3) The solvent is removed by rotary evaporation to obtain a dendritic flame retardant material.

[0065] Example 9

[0066] The preparation method of the dendritic flame retardant comprises:

[0067] (1) 1.71 g of phenylphosphonyl dichloride and 8.55 g of triethylamine were dissolved in 30 ml of DMSO, and then 1.35 g of nerol was added dropwise to the above solution under stirring conditions, and the stirring was continued to react at 30° C. for 8 h. After the reaction, a solution 1 containing a phosphonyl chloride structure-capped compound was obtained;

[0068] (2) Dissolve 1 g of tannic acid in 100 ml of DMSO to obtain solution 2; add solution 1 dropwise into solution 2 under stirring conditions to carry out a reaction. The reaction conditions are: stir the reaction at room temperature for 1 hour, then heat the system to 60° C., and then react for 32 hours.

[0069] (3) The solvent is removed by rotary evaporation to obtain a dendritic flame retardant material.

[0070] Example 10

[0071] The preparation method of the dendritic flame retardant comprises:

[0072] (1) 2.28 g of phenylphosphonyl dichloride and 10.4 g of triethylamine were dissolved in 30 ml of DMSO, and then 3.39 g of geranylgeraniol was added dropwise to the above solution under stirring conditions, and the stirring was continued to react at 25° C. for 8 h. After the reaction, a solution 1 containing a phosphonyl chloride structure-capped compound was obtained;

[0073] (2) Dissolve 1 g of tannic acid in 100 ml of DMSO to obtain solution 2; add solution 1 dropwise into solution 2 under stirring conditions to carry out a reaction. The reaction conditions are: stir the reaction at room temperature for 1 hour, then heat the system to 60° C., and then react for 32 hours.

[0074] (3) The solvent is removed by rotary evaporation to obtain a dendritic flame retardant material.

[0075] Embodiment 11

[0076] The preparation method of the dendritic flame retardant comprises:

[0077] (1) 1.14 g of phenylphosphonyl dichloride and 5.7 g of triethylamine were dissolved in 30 ml of DMSO, and then 1.69 g of geranylgeraniol was added dropwise to the above solution under stirring conditions, and the stirring was continued to react at 30° C. for 7 h. After the reaction, a solution 1 containing a phosphonyl chloride structure-capped compound was obtained;

[0078] (2) Dissolve 1 g of tannic acid in 100 ml of DMSO to obtain solution 2; add solution 1 dropwise into solution 2 under stirring conditions to carry out a reaction. The reaction conditions are: stir the reaction at room temperature for 1 hour, then heat the system to 60° C., and then react for 24 hours.

[0079] (3) The solvent is removed by rotary evaporation to obtain a dendritic flame retardant material.

[0080] Example 12

[0081] The preparation method of the dendritic structure flame retardant comprises:

[0082] (1) 1.71 g of phenylphosphonyl dichloride and 8.55 g of triethylamine were dissolved in 30 ml of DMSO, and then 2.54 g of geranylgeraniol was added dropwise to the above solution under stirring conditions, and the stirring was continued to react at 30° C. for 8 h. After the reaction, a solution 1 containing a phosphonyl chloride structure-capped compound was obtained;

[0083] (2) Dissolve 1 g of tannic acid in 100 ml of DMSO to obtain solution 2; add solution 1 dropwise into solution 2 under stirring conditions to carry out a reaction. The reaction conditions are: stir the reaction at room temperature for 1 hour, then heat the system to 50° C., and then react for 32 hours.

[0084] (3) The solvent is removed by rotary evaporation to obtain a dendritic flame retardant material.

[0085] Performance Testing

[0086] The flame retardant natural rubber formula is shown in the following table, and the materials are added according to the mass parts.

[0087] Table 1 Flame retardant natural rubber formula

[0088]

[0089]

[0090] Use an open mill to mix the rubber, the roller temperature is 50℃, and the cooling water needs to be turned on during the mixing process. First, plasticize the natural rubber several times, then add carbon black, stearic acid, zinc oxide, flame retardant, accelerator, vulcanizer, etc. into the rubber, turn over and roll, and finally make triangle packages and thin passes 4 times before making sheets. After parking for one day, turn over the sample three times on the open mill, and make sheets. Use a flat plate tablet press at 146℃×20MPa×(t 90 +2min) to obtain a flame retardant natural rubber sample.

[0091] The limiting oxygen index (LOI) of the flame retardant natural rubber vulcanized sample was measured according to the ASTM-D2863 standard, and the size of the sample was 120mm×6.5mm×3.0mm. The mechanical properties of the rubber sample were tested according to the GB / T528-1998 standard.

[0092] The flame retardant performance test results of the samples are shown in Table 2.

[0093] Table 2 Flame retardant properties of natural rubber with different formulations

[0094]

[0095] The mechanical properties test results of the samples are shown in Table 3.

[0096] Table 3 Test results of mechanical properties of flame retardant natural rubber

[0097] Sample A00 A01 A1 A2 A3 Tensile strength / MPa 22.1 16.2 21.9 22.2 21.7 Elongation at break / % 580 412 572 595 578

[0098] As can be seen from Table 2, by adding the dendritic structure flame retardants prepared in Examples 1 to 12, the flame retardant properties of natural rubber are significantly improved.

[0099] As can be seen from Table 3, compared with the sample without adding flame retardant, after adding traditional APP flame retardant, the tensile strength of the material decreased significantly by about 26.6%, and the elongation at break decreased by 28.9%; while the mechanical properties did not decrease significantly after adding dendritic structure flame retardant, and the flame retardant properties of rubber were significantly improved. The reduction in mechanical properties of the sample with traditional flame retardant is due to the poor compatibility between the polar ammonium polyphosphate flame retardant and the non-polar natural rubber. The dendritic structure flame retardant molecules prepared by the present invention have low polarity and good compatibility with natural rubber. At the same time, the flame retardant molecules also participate in the vulcanization of rubber, which further improves the compatibility between the flame retardant and natural rubber. While improving the flame retardant properties of the sample, the mechanical properties do not decrease significantly.

[0100] The preferred implementation modes of the present invention are described in detail above in combination with the embodiments; however, the present invention is not limited to the specific details in the above implementation modes. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical scheme of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0101] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0102] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a dendritic flame retardant, characterized in that: The steps include: S1, adding a hydroxyl-terminated unsaturated olefin to a solution containing phenylphosphonyl dichloride and an organic base, and obtaining a solution in which a phosphonyl chloride-terminated compound is dissolved after the reaction, wherein the hydroxyl-terminated unsaturated olefin is one or more of farnesol, geraniol, nerol and geranylgeraniol; S2, adding tannic acid solution to the solution after the reaction in step S1, and reacting to obtain the dendritic structure flame retardant.

2. The preparation method according to claim 1, characterized in that: In step S1, the molar ratio of phenylphosphonyl dichloride to the organic base is 1:(5-10).

3. The preparation method according to claim 1, characterized in that: In step S1, the organic base catalyst is one or more of triethylamine, tripropylamine and tributylamine.

4. The preparation method according to claim 1, characterized in that: In step S1, the molar ratio of the phenylphosphonic dichloride to the hydroxyl-terminated unsaturated olefin is 1:

1.

5. The preparation method according to claim 1, characterized in that: In step S1, the hydroxyl-terminated unsaturated olefin is added dropwise to a solution containing phenylphosphonyl dichloride and an organic base, the reaction conditions are 20° C. to 40° C., and the reaction time is 4 h to 10 h.

6. The preparation method according to claim 1, characterized in that: In step S2, the molar ratio of the tannic acid to the capping compound having a phosphonyl chloride structure is 1:(10-20).

7. The preparation method according to any one of claims 1 to 6, characterized in that In step S2, the reaction conditions are to react at room temperature for 1 h to 1.5 h, then raise the temperature of the system to 50° C. to 60° C., and then react for 12 h to 36 h.

8. The dendritic structure flame retardant prepared by the preparation method according to any one of claims 1 to 7.

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