Phosphonate composite flame retardant as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of flame-retardant material preparation, and discloses a phosphonate composite flame retardant as well as a preparation method and application thereof. The preparation method of the phosphonate composite flame retardant provided by the invention comprises the following steps: under the catalytic action of a tris (2-pyridyl methyl) amine iron complex, carrying out oxidation reaction on a diethyl methylphosphonite rectification byproduct and air, and carrying out reduced pressure distillation to obtain the phosphonate composite flame retardant. The preparation method provided by the invention has the advantages of short process flow, controllable reaction, low production cost and the like, realizes comprehensive resource utilization of the diethyl methylphosphonite rectification byproduct, and has important economic benefits and environmental benefits. The prepared phosphonate composite flame retardant is excellent in flame retardance and can be used in the fields of textiles, rubber, plastics or building materials and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardant material preparation, and relates to a phosphonate composite flame retardant and a preparation method and application thereof. Background Art

[0002] Diethyl methylphosphite is an important organic chemical intermediate for pesticides, medicines and synthetic materials. It is widely used in the synthesis of organophosphorus pesticides, such as the herbicide glufosinate, alkylthiophosphate insecticides methyl parathion and fenitrothion, etc. At present, the mainstream routes for the industrial synthesis of diethyl methylphosphite include the aluminum process and the gas phase process. Regardless of the aluminum process or the gas phase process, after the esterification reaction is completed, the obtained product needs to be distilled to obtain high-purity diethyl methylphosphite. During the distillation process, a large amount of diethyl methylphosphite distillation by-products will be produced, and the distillation by-products mainly include triethyl phosphite, ethyl methyl ethyl phosphonate, diethyl phosphonate, ethyl methyl phosphonate and diethyl methyl phosphite, etc. The main component structure is as follows: .

[0003] Since the diethyl methylphosphite distillation byproduct also contains a small amount of phosphorus oxides and low-valent organic phosphorus, the distillation byproduct has poor stability. At present, the distillation byproduct is mainly disposed of as hazardous waste, which not only fails to effectively utilize resources, but also increases the processing cost. Summary of the invention

[0004] Aiming at the current situation that diethyl methylphosphite distillation by-product resources are wasted in the prior art, the present invention provides a method for preparing a phosphonate composite flame retardant by utilizing diethyl methylphosphite distillation by-products. The flame retardant has excellent flame retardant properties and can be widely used in the fields of textiles, rubber, plastics, building materials, etc.

[0005] In order to achieve the above-mentioned object of the invention, the embodiment of the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a phosphonate composite flame retardant, the preparation method comprising the following steps: Under the catalysis of tris(2-pyridylmethyl)amine iron complex, the diethyl methylphosphite distillation byproduct is oxidized with air and distilled under reduced pressure to obtain a phosphonate composite flame retardant.

[0006] The preparation method of the phosphonate composite flame retardant provided by the present invention uses diethyl methylphosphite distillation byproduct as raw material, and under the action of catalyst tris(2-pyridylmethyl)amine iron complex, the components such as triethyl phosphite are oxidized to triethyl phosphite, and the phosphonate composite flame retardant with excellent flame retardancy is obtained. Commonly used oxidants such as peroxides, ozone and the like have strong oxidizing power, and can react rapidly with phosphorus oxides and low-valent organic phosphorus in diethyl methylphosphite distillation byproducts, and the reaction is uncontrollable and the risk of spontaneous combustion and explosion is relatively high. In the present invention, air is used as an oxidant, and a stable and controllable reaction can be achieved under the action of the catalyst, thereby obtaining a phosphonate composite flame retardant, realizing the comprehensive utilization of resources of diethyl methylphosphite distillation byproducts, and the utilization rate reaches more than 70%, thereby having important economic and environmental benefits.

[0007] The preparation method of the phosphonate composite flame retardant provided by the present invention has the advantages of short process flow, controllable reaction and low production cost. The prepared phosphonate composite flame retardant has excellent flame retardant performance. When an appropriate amount of the composite flame retardant is used in polyurethane foam plastics, a product with a flame retardant grade of V-0 can be obtained. The composite flame retardant has broad application prospects.

[0008] Preferably, the tris(2-pyridylmethyl)amine iron complex comprises any one of tris(2-pyridylmethyl)amine iron (II) complex or tris(2-pyridylmethyl)amine iron (III) complex. The specific preparation method comprises: at room temperature, adding a tris(2-pyridylmethyl)amine acetonitrile solution dropwise to an aqueous solution of ferric chloride or ferrous chloride, stirring for 30 minutes, concentrating until a large amount of solid is produced, filtering, washing with ether, and obtaining a solid powder complex, namely, tris(2-pyridylmethyl)amine iron complex. In the reaction, the molar ratio of tris(2-pyridylmethyl)amine to iron ions is 1:1.

[0009] The ferric ions or ferrous ions selected for preparing the catalyst in the present invention are cheap and easy to obtain; the catalyst has a positive effect on oxidizing triethyl phosphite in the byproduct of diethyl methylphosphite distillation to triethyl phosphonate.

[0010] Preferably, the mass ratio of the tris(2-pyridylmethyl)amine iron complex to the diethyl methylphosphite by-product is 0.1:100 to 0.5:100.

[0011] Preferably, the diethyl methylphosphite distillation by-product comprises the following components in percentage by mass: 30% to 36% triethyl phosphite, 35% to 40% ethyl methyl ethyl phosphonate, 5% to 10% diethyl phosphonate, 4% to 8% ethyl methyl phosphonate, 2% to 3% diethyl methylphosphite and 7% to 15% other components.

[0012] Due to the different processes for synthesizing diethyl methylphosphite, the proportions of various components in the obtained distillation by-products are different. The diethyl methylphosphite distillation by-product described in the present invention is prepared by a gas phase process. The gas phase process uses methane, phosphorus trichloride, and carbon tetrachloride as raw materials, and obtains methyl dichlorophosphine through high temperature reaction and distillation. Methyl dichlorophosphine and ethanol and liquid ammonia are esterified and distilled to obtain diethyl methylphosphite with a content of more than 95%. In the gas phase process, since the boiling points of methyl dichlorophosphine and phosphorus trichloride are close, the distillation separation effect is poor, resulting in the increase of the content of triethyl phosphite and diethyl phosphonate in the distillation by-products of phosphonic acid esters in the process compared with the aluminum process. The specific components are described above.

[0013] Preferably, the oxidation reaction is carried out at a temperature of 80°C to 120°C and for a time of 10h to 20h.

[0014] Preferably, the air intake is 0.5 vvm~2 vvm.

[0015] The present invention uses air with weak oxidizing ability as an oxidant, and reacts under the action of the above catalyst. The reaction is safe and controllable, with low risk, easy to obtain raw materials, and easy to implement industrially. After the reaction is completed, low-valent phosphorus in the distillation by-product is converted into pentavalent phosphorus, the danger of the by-product is significantly reduced, and the flame retardant performance is improved. More than 80% of the distillation by-products can be recycled through distillation.

[0016] Preferably, when the content of triethyl phosphite in the reaction system is ≤0.2%, the oxidation reaction is terminated and vacuum distillation is performed, wherein the pressure of the vacuum distillation is 1400Pa~1600Pa and the temperature is 80°C~85°C.

[0017] In a second aspect, the present invention provides a phosphonate composite flame retardant, which is prepared by the preparation method of the phosphonate composite flame retardant provided in the first aspect.

[0018] Preferably, the sum of the mass proportions of triethyl phosphonate and ethyl methyl ethyl phosphonate in the phosphonate flame retardant is ≥ 95%.

[0019] The invention discloses a phosphonate flame retardant prepared by compounding triethyl phosphonate and ethyl methyl ethyl phosphonate, and the flame retardant has good flame retardant effect. Within the experimental range of the invention, the limiting oxygen index of the polyurethane foam plastic prepared by using the phosphonate composite flame retardant provided by the invention is 26.8% to 27.1%, and the UL94 flame retardant grade can reach V-0 grade.

[0020] In a third aspect, the present invention provides use of the phosphonate composite flame retardant provided in the second aspect in textiles, rubber, plastics or building materials.

[0021] In view of the relatively low production cost and excellent flame retardant performance of the phosphonate composite flame retardant provided by the present invention, combined with its own chemical properties, the flame retardant has broad application prospects and is suitable for preparing textiles, rubbers, plastics or building materials with certain flame retardant properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 is a gas chromatogram of reaction solution I in Example 1 of the present invention; Figure 2 is a gas chromatogram of the phosphonate composite flame retardant in Example 1 of the present invention; DETAILED DESCRIPTION In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0024] The raw materials and reagents used in the present invention, unless otherwise specified, are conventional commercially available products; the methods used in the present invention, unless otherwise specified, are conventional methods in the art.

[0025] The contents of the components in the distillation byproduct of diethyl methylphosphite and the phosphonate composite flame retardant were determined by Agilent 6820 gas chromatography. The specific determination conditions are as follows: Chromatographic column: DM-62430m*0.53mm, 3.0μm; detection wavelength: 250nm; temperature program setting: 70℃ for 1min, increase to 230℃ at a heating rate of 15℃ / min and hold for 20min; injection volume: 3μL.

[0026] Example 1 This embodiment provides a method for preparing a phosphonate composite flame retardant, the preparation method comprising the following steps: 5kg (5.1L) of diethyl methylphosphite distillation byproduct was added to a 10L glass kettle, and 5g of tris(2-pyridylmethyl)amine iron (II) complex was added, and the system was heated to 60°C. Air was introduced through the air distributor at the bottom of the kettle for oxidation reaction, wherein the air flow rate was 10L / min, the reaction temperature rose slowly, and the reaction temperature was controlled at 100°C. The reaction tail gas was condensed and the low-boiling point waste was recovered. After 20 hours of reaction, reaction liquid I was obtained; the content of triethyl phosphite in reaction liquid I was detected by gas chromatography and was 0.18%, and its gas chromatogram was as shown in the figure Figure 1 shown.

[0027] Among them, the diethyl methylphosphite distillation by-product selected in this embodiment contains the following components in mass percentage: triethyl phosphite 34.5%, ethyl methyl ethyl phosphonate 36.2%, diethyl phosphonate 9.6%, ethyl methyl phosphonate 5.9%, diethyl methyl phosphonite 2.5%, and other components totaling 11.3%; The preparation method of tris(2-pyridylmethyl)amine iron (II) complex in this embodiment is as follows: at room temperature, 1000 mL of acetonitrile solution of tris(2-pyridylmethyl)amine with a concentration of 0.1 mol / L is added dropwise to 100 mL of ferrous chloride aqueous solution with a concentration of 1 mol / L, stirred for 30 minutes, concentrated until a large amount of solid is produced, filtered, and washed with ether to obtain a solid powder complex.

[0028] The reaction solution I was distilled under reduced pressure, and the fraction at 80°C to 85°C was collected at a pressure of 1500 Pa to obtain 3.5 kg of phosphonate composite flame retardant.

[0029] The phosphonate composite flame retardant prepared in this embodiment was measured by gas chromatography, and its gas chromatogram is as follows: Figure 2 It was determined that the mass proportion of ethyl methyl ethyl phosphonate in the phosphonate composite flame retardant prepared in this embodiment was 50.5%, the mass proportion of triethyl phosphonate was 46.3%, and the total mass proportion of ethyl methyl ethyl phosphonate and triethyl phosphonate was 96.8%.

[0030] Example 2 This embodiment provides a method for preparing a phosphonate composite flame retardant, the preparation method comprising the following steps: 5kg of diethyl methylphosphite distillation byproduct was added to a 10L glass kettle, and 25g of tris(2-pyridylmethyl)amine iron (II) complex was added, and the system was heated to 60°C. Air was introduced through the air distributor at the bottom of the kettle for oxidation reaction, wherein the air flow rate was 2.5L / min, the reaction temperature rose slowly, and the reaction temperature was controlled at 120°C. The reaction tail gas was condensed and the low-boiling point waste was recovered. After 10 hours of reaction, reaction solution I was obtained; the content of triethyl phosphite in reaction solution I was 0.11% by gas chromatography.

[0031] Among them, the diethyl methylphosphite distillation by-product selected in this embodiment contains the following components in mass percentage: triethyl phosphite 34.7%, ethyl methyl ethyl phosphonate 36.8%, diethyl phosphonate 5.8%, ethyl methyl phosphonate 7.9%, diethyl methyl phosphonite 2.8%, and other components totaling 12%; The method for preparing tris(2-pyridylmethyl)amine iron (II) complex in this example is the same as that in Example 1.

[0032] The reaction solution I was distilled under reduced pressure, and the fraction at 80°C-85°C was collected at a pressure of 1400 Pa to obtain 3.55 kg of phosphonate composite flame retardant.

[0033] The phosphonate composite flame retardant prepared in this embodiment was measured by gas chromatography. According to the measurement, the mass proportion of ethyl methyl ethyl phosphonate in the phosphonate composite flame retardant prepared in this embodiment was 49.5%, the mass proportion of triethyl phosphonate was 46.0%, and the total mass proportion of ethyl methyl ethyl phosphonate and triethyl phosphonate was 95.5%.

[0034] Example 3 This embodiment provides a method for preparing a phosphonate composite flame retardant, the preparation method comprising the following steps: 5kg of diethyl methylphosphite distillation byproduct was added to a 10L glass kettle, 10g of tris(2-pyridylmethyl)amine iron (III) complex was added, and the system was heated to 80°C. Air was introduced through the air distributor at the bottom of the kettle for oxidation reaction, wherein the air flow rate was 5L / min, the reaction temperature rose slowly, and the reaction temperature was controlled at 80°C. The reaction tail gas was condensed and the low-boiling point waste was recovered. After the reaction time was 15h, the reaction solution I was obtained; the content of triethyl phosphite in the reaction solution I was detected by gas chromatography and was 0.15%.

[0035] Among them, the diethyl methylphosphite distillation by-product selected in this embodiment contains the following components in mass percentage: triethyl phosphite 34.2%, ethyl methyl ethyl phosphonate 37.3%, diethyl phosphonate 6.6%, ethyl methyl phosphonate 4.8%, diethyl methyl phosphonite 2.2%, and other components totaling 14.9%; In this embodiment, the preparation method of tris(2-pyridylmethyl)amine iron (III) complex is as follows: at room temperature, 1000 mL of acetonitrile solution of tris(2-pyridylmethyl)amine with a concentration of 1 mol / L is added dropwise to 100 mL of 1 mol / L ferric chloride aqueous solution, stirred for 30 minutes, concentrated until a large amount of solid is produced, filtered, and washed with ether to obtain a solid powder complex.

[0036] The reaction solution I was distilled under reduced pressure, and the fraction at 80°C to 85°C was collected at a pressure of 1600 Pa to obtain 3.6 kg of phosphonate composite flame retardant.

[0037] The phosphonate composite flame retardant prepared in this embodiment was measured by gas chromatography. According to the measurement, the mass proportion of ethyl methyl ethyl phosphonate in the phosphonate composite flame retardant prepared in this embodiment was 50.3%, the mass proportion of triethyl phosphonate was 46.2%, and the total mass proportion of ethyl methyl ethyl phosphonate and triethyl phosphonate was 96.5%.

[0038] Comparative Example 1 This comparative example provides a preparation method of a phosphonate composite flame retardant. The preparation method provided in this comparative example is basically the same as that in Example 1, except that no catalyst is added during the oxidation reaction, and the remaining reaction raw materials and their condition parameters are consistent with those in Example 1, specifically: 5kg of diethyl methylphosphite distillation byproduct was added to a 10L glass kettle, and the system was heated to 60°C. Air was introduced through the air distributor at the bottom of the kettle for oxidation reaction, wherein the air flow rate was 10L / min, the reaction temperature rose slowly, and the reaction temperature was controlled at 100°C. The reaction tail gas was condensed and the low-boiling point waste was recovered. After 48 hours of reaction, reaction liquid I was obtained; the content of triethyl phosphite in reaction liquid I was 8.5% by gas chromatography.

[0039] The reaction solution I was distilled under reduced pressure, and the fraction at 80°C to 85°C was collected at a pressure of 1500 Pa to obtain 2.96 kg of phosphonate composite flame retardant.

[0040] The phosphonate composite flame retardant prepared in this comparative example was measured by gas chromatography. It was determined that the mass proportion of ethyl methyl ethyl phosphonate in the phosphonate composite flame retardant prepared in this comparative example was 59.5%, the mass proportion of triethyl phosphonate was 36.8%, and the total mass proportion of ethyl methyl ethyl phosphonate and triethyl phosphonate was 96.3%.

[0041] Compared with Example 1, in this comparative example, no catalyst was added during the oxidation reaction, resulting in a very slow oxidation reaction rate of triethyl phosphite in the reactant. Even if the reaction time was as long as 48 hours, more than 35% of triethyl phosphite was not oxidized, the total amount of the flame retardant obtained was greatly reduced, and the proportion of ethyl methyl ethyl phosphonate in the flame retardant was significantly increased.

[0042] Effect example In order to investigate the flame retardant properties of the phosphonate composite flame retardant prepared in the above Examples 1 to 3 and Comparative Example 1, the present invention applies the phosphonate composite flame retardant and the commercially available conventional flame retardant triethyl phosphonate (content 99%) to prepare polyurethane foam plastics with flame retardant properties, and evaluates the flame retardant effects of the polyurethane foam plastics prepared by adding different flame retardants. The specific preparation method is as follows: Add 3g of cyclopentane, a foaming agent, 1g of a polyether silicone stabilizer, 1g of dimethylcyclohexylamine and 12.1g of a flame retardant to 20g of sucrose polyether polyol, mix evenly in a high-speed disperser to obtain a uniform milky white viscous liquid mixture, quickly pour 40g of polymethylene polyphenyl polyisocyanate into the mixture, mix and stir evenly, and when bubbles emerge and the mixture turns white, immediately pour the mixture into a mold with a mold temperature of 45°C for foaming molding, and place the foam in an oven at 85°C for drying and maturation after demoulding to obtain a polyurethane foam with flame retardant properties. Wherein, the flame retardant is a phosphonate composite flame retardant or commercially available triethyl phosphonate obtained in Examples 1 to 3 or Comparative Example 1.

[0043] The flame retardant properties of polyurethane foam plastics with flame retardant properties prepared by adding different flame retardants were tested, and their limiting oxygen index and UL94 flame retardant grade were determined. The test results are shown in Table 1 below.

[0044] Table 1 Flame retardant properties of polyurethane foams with flame retardant properties prepared by adding different flame retardants

[0045] As can be seen from Table 1, the composite flame retardant containing ethyl methyl ethyl phosphonate and triethyl phosphonate prepared by adding the composite flame retardant containing ethyl methyl ethyl phosphonate prepared by Examples 1 to 3 of the present invention has a similar limiting oxygen index as the polyurethane foam prepared by adding the same amount of conventional commercial triethyl phosphonate, and the UL94 flame retardant grade of the obtained products is the same, both of which are V-0 grade. The flame retardant properties of the phosphonate composite flame retardants prepared by Examples 1 to 3 of the present invention are better than those of Comparative Example 1.

[0046] In summary, the phosphonate composite flame retardant obtained by the preparation method provided in Examples 1 to 3 has excellent flame retardant properties, and combined with its own chemical properties, it can be further applied to the fields of textiles, rubber, plastics or building materials.

[0047] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a phosphonate composite flame retardant, characterized in that: The preparation method comprises the following steps: Under the catalysis of tris(2-pyridylmethyl)amine iron complex, the diethyl methylphosphite distillation byproduct is oxidized with air and distilled under reduced pressure to obtain a phosphonate composite flame retardant.

2. The method for preparing the phosphonate composite flame retardant according to claim 1, characterized in that: The tris(2-pyridylmethyl)amine iron complex includes any one of a tris(2-pyridylmethyl)amine iron (II) complex and a tris(2-pyridylmethyl)amine iron (III) complex.

3. The method for preparing the phosphonate composite flame retardant according to claim 1, characterized in that: The mass ratio of the tris(2-pyridylmethyl)amine iron complex to the diethyl methylphosphite byproduct is 0.1:100 to 0.5:

100.

4. The method for preparing the phosphonate composite flame retardant according to claim 1, characterized in that: The diethyl methylphosphite distillation by-product comprises the following components in percentage by mass: 30% to 36% of triethyl phosphite, 35% to 40% of ethyl methyl ethyl phosphonate, 5% to 10% of diethyl phosphonate, 4% to 8% of ethyl methyl phosphonate and 2% to 3% of diethyl methylphosphite.

5. The method for preparing the phosphonate composite flame retardant according to claim 1, characterized in that: The temperature of the oxidation reaction is 80° C. to 120° C., and the time is 10 h to 20 h.

6. The method for preparing the phosphonate composite flame retardant according to claim 1, characterized in that: The air intake is 0.5 vvm~2 vvm.

7. The method for preparing the phosphonate composite flame retardant according to claim 2, characterized in that: The pressure of the reduced pressure distillation is 1400Pa~1600Pa, and the temperature is 80℃~85℃.

8. A phosphonate composite flame retardant, characterized in that: The composite flame retardant is prepared by the method for preparing the phosphonate composite flame retardant according to any one of claims 1 to 7.

9. The phosphonate composite flame retardant according to claim 8, characterized in that: The sum of the mass proportions of triethyl phosphonate and ethyl methyl ethyl phosphonate in the phosphonate flame retardant is ≥95%.

10. Use of the phosphonate composite flame retardant according to claim 8 or 9 in textiles, rubber, plastics or building materials.

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