Preparation process of dimethyl methylphosphonate flame retardant

Abstract

The invention belongs to the technical field of preparation of organic phosphine flame retardants, and particularly relates to a preparation process of a dimethyl methylphosphonate flame retardant, which comprises the following steps: feeding liquid TMP into a rearrangement reaction kettle through a thermal insulation pipeline, carrying out Arbuzov rearrangement reaction to obtain a rearrangement synthetic liquid, transferring the rearrangement synthetic liquid to a distillation kettle, distilling out low fractions at first, and then distilling out low fractions at second, thereby obtaining the dimethyl methylphosphonate flame retardant. The low fraction returns to the rearrangement reaction kettle to circularly participate in the reaction, then a DMMP finished product is distilled out, and residual liquid obtained after reduced pressure distillation serves as a flame retardant to be sold or sent to qualified units to be incinerated; the low fraction which is not completely reacted contains a certain amount of TMP, and is recycled through a synthesis rearrangement reaction, so that the cost of the raw materials is greatly reduced, the recycling of the raw materials, the high-yield production of DMMP, the secondary utilization of the byproduct polycondensation phosphonate, or the compliance incineration treatment are realized, and the byproducts can be reasonably treated.

Description

Technical Field

[0001] This invention belongs to the field of organophosphorus flame retardant preparation technology, specifically referring to a preparation process of a dimethyl methylphosphonate flame retardant. Background Technology

[0002] Dimethyl methylphosphonate (DMMP) is one of the mainstream additive phosphine-based flame retardants on the market due to its advantages such as high flame retardant efficiency, low dosage, and good compatibility. Existing DMMP preparation processes mostly use trimethyl phosphite (TMP) as a raw material, synthesized via the Arbuzov rearrangement reaction, but they have the following core drawbacks: 1. Low raw material utilization: In traditional processes, unreacted TMP (accounting for 10% to 15% of the raw material input) is directly discarded with the low fraction, which not only accounts for more than 60% of the raw material cost, but also causes resource waste. 2. Inadequate process parameters: Most processes only set the reaction temperature range without specifying key parameters such as segmented temperature control and stirring rate, resulting in large fluctuations in reaction conversion rate (only 85%~90%). 3. Improper disposal of by-products: Polyphosphonate condensate, a by-product of the rearrangement reaction (accounting for 1% to 3% of the total product), is often directly discharged or simply incinerated, which neither achieves secondary utilization of resources nor easily causes environmental risks. 4. Poor equipment compatibility: Some processes use ordinary carbon steel reactors, which are prone to corrosion due to the weak acidity of TMP / re-drained liquid, resulting in excessive impurity content in the product (acid value > 2.0 mg KOH / g). Summary of the Invention

[0003] To address the aforementioned problems, this invention provides a preparation process for dimethyl methylphosphonate flame retardant. Unreacted TMP is recovered and recycled through distillation, significantly reducing raw material costs and enabling raw material recycling. DMMP is produced in high yield, and the byproduct polyphosphonate is reused or disposed of in accordance with regulations, thus ensuring the proper handling of byproducts.

[0004] To achieve the above functions, the technical solution adopted by the present invention is as follows: a preparation process for a dimethyl methylphosphonate flame retardant, wherein each step of the preparation process is carried out under pure nitrogen protection, and includes the following steps: (1) TMP is pumped into the high-level metering tank using a metering pump; (2) Rearrangement reaction: Trimethyl phosphite (TMP) is fed into the rearrangement reactor through a pipeline. The amount of feed is one-fifth of the volume of the rearrangement reactor. When the steam riser is found to have a backflow, the steam is turned off and the steam is stabilized. Then the remaining TMP in the high-level metering tank is slowly and uniformly added to the rearrangement reactor to ensure safe production. The Arbuzov rearrangement reaction is carried out at 110-180℃ and atmospheric pressure for 6-8 hours to obtain the rearrangement synthesis liquid. (3) Vacuum distillation and raw material recycling: The rearranged synthesis liquid is transferred to a distillation vessel and vacuum distilled at 110~180℃ and 0.06~0.095MPa. First, the low fraction is distilled off and returned to the rearranged reactor to participate in the reaction. Then, the DMMP product is distilled off. (4) By-product disposal: The residue remaining after vacuum distillation is polyphosphonate, which is sold as a flame retardant or sent to a qualified unit for incineration.

[0005] Preferably, in step (3), the rearranged synthesis solution is filtered through a 10 μm filter and then fed into a distillation vessel for staged distillation: Stage 1: Control the temperature of the distillation vessel to 110~130℃ and the vacuum degree to 0.06~0.07MPa, distill off the low fraction at 80~100℃, and return the low fraction to the rearrangement reactor in step (2) for circulation; Stage 2: Adjust the temperature of the distillation vessel to 140~180℃ and the vacuum degree to 0.08~0.095MPa to distill the DMMP product.

[0006] Preferably, the temperature of the Arbuzov rearrangement reaction in step (2) is 130-160°C and the reaction time is 7 hours.

[0007] Preferably, the main component of the low fraction in step (3) is unreacted TMP.

[0008] Compared with the prior art, the present invention achieves the following beneficial effects by adopting the above solution: 1. This invention, through the phased control of vacuum distillation, can accurately separate unreacted raw materials in the rearrangement reaction, recover them, and reintroduce them into the reaction system to participate in the reaction. This avoids the problem of unreacted raw materials remaining in the product and causing excessive odor, which affects product quality, as is the case in traditional processes. This raw material recycling mechanism not only improves the overall utilization rate of core raw materials but also reduces resource idleness and waste, which is in line with the development direction of resource-saving chemical production and reduces the raw material consumption cost in the production process from the source. 2. This invention adopts a segmented temperature-controlled rearrangement reaction mode. By combining initial heat preservation and dispersion with subsequent precise heating, it ensures a more complete and uniform reaction of raw materials, reducing the generation of impurities caused by incomplete local reactions. At the same time, multiple precision filtration processes remove trace impurities generated during the reaction and distillation, further improving product purity. Compared with traditional processes, the DMMP product prepared by this invention has a more uniform appearance, smaller fluctuations in key performance indicators, and significantly improved purity and stability. It can meet the stringent requirements of high-end polymer materials for flame retardant purity, effectively expanding the application fields and market space of the product. 3. A differentiated strategy of "graded utilization and compliant disposal" is adopted for polyphosphonate byproducts generated by vacuum distillation, which maximizes the value of byproducts, avoids the environmental risks caused by arbitrary disposal, takes into account the dual needs of resource utilization and environmental compliance, and improves the green level of the production process. Attached Figure Description

[0009] Figure 1 This is a process flow diagram of the preparation process of the dimethyl methylphosphonate flame retardant of the present invention. Detailed Implementation

[0010] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0011] This invention discloses a preparation process for a dimethyl methylphosphonate flame retardant, wherein each step of the preparation process is carried out under pure nitrogen protection, and includes the following steps: (1) 5t TMP is pumped into the high-level metering tank using a metering pump; (2) Rearrangement reaction: TMP was added dropwise to a stainless steel 316 rearrangement reactor, and the jacket was heated to 110°C and kept at that temperature for 1 hour. Then the temperature was raised to 160°C and stirred at 80 rpm for 6 hours. The TMP residue was measured to be 0.4%, and the reaction was stopped to obtain about 5 tons of rearrangement synthesis liquid. (3) Vacuum distillation: First, the distillation vessel is set at 120℃ and vacuum degree 0.065MPa to distill off about 0.2t of low fraction, which is returned to the rearrangement reactor. Then, the temperature is adjusted to 160℃ and vacuum degree 0.09MPa to distill off the DMMP product. (4) By-product disposal: The distillation residue of about 0.05t, with an acid value of 1.8mgKOH / g, is sold as a flame retardant.

[0012] Product performance test results: Appearance: Colorless transparent liquid; Phosphorus content: 25.1%; Viscosity: 1.75 cps; Acid value: 0.8 mg KOH / g; Water content: 0.04%; Relative density: 1.160.

[0013] Comparative Example 1 A conventional preparation process for a dimethyl methylphosphonate flame retardant includes the following steps: (1) Rearrangement reaction: 5t TMP was directly added to a carbon steel reactor, heated to 180℃ and stirred at 50rpm for 8h to obtain about 4.7t of rearrangement synthesis liquid; (2) Vacuum distillation: The distillation kettle is set at 180℃ and the vacuum degree is 0.07MPa. About 4.1t of DMMP product is directly distilled out, and about 0.5t of low fraction is directly discarded. (3) Product refining: After filtering the crude product, 4.0t of finished product is obtained; (4) By-product disposal: 0.1t of residual liquid is directly sent to hazardous waste disposal.

[0014] Product performance test results: Appearance: Slightly yellow liquid; Phosphorus content: 24.5%; Viscosity: 1.82 cps; Acid value: 2.2 mg KOH / g; Water content: 0.08%; Relative density: 1.158.

[0015] Comparison table of the effects of Example 1 and Comparative Example 1 index Example 1 Comparative Example 1 DMMP product yield 99.2% 91.0% TMP raw material consumption per unit (t / t-DMMP) 0.93 1.05 Product acid value (mgKOH / g) 0.8 2.0 By-product resource utilization rate 100% 0% The present invention and its embodiments have been described above. This description is not restrictive, and the embodiments shown are only one of the embodiments of the present invention, and are not actually limited thereto. In short, if those skilled in the art are inspired by this description and design similar embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A preparation process for a dimethyl methylphosphonate flame retardant, characterized in that, Each step of the preparation process is carried out under the protection of pure nitrogen, including the following steps: (1) TMP is pumped into the high-level metering tank using a metering pump; (2) Rearrangement reaction: Trimethyl phosphite (TMP) was fed into the rearrangement reactor through a pipeline and carried out the Arbuzov rearrangement reaction at 110-180°C and atmospheric pressure for 6-8 hours to obtain the rearrangement synthesis solution. (3) Vacuum distillation and raw material recycling: The rearranged synthesis liquid is transferred to a distillation vessel and vacuum distilled at 110~180℃ and 0.06~0.095MPa. First, the low fraction is distilled off and returned to the rearranged reactor to participate in the reaction. Then, the DMMP product is distilled off. (4) By-product disposal: The residue remaining after vacuum distillation is polyphosphonate, which is sold as a flame retardant or sent to a qualified unit for incineration.

2. The preparation process of the dimethyl methylphosphonate flame retardant according to claim 1, characterized in that, In step (3), the rearranged synthetic liquid is filtered through a 10μm filter and then fed into a distillation vessel for staged distillation: Stage 1: Control the temperature of the distillation vessel to 110~130℃ and the vacuum degree to 0.06~0.07MPa, distill off the low fraction at 80~100℃, and return the low fraction to the rearrangement reactor in step (2) for circulation; Stage 2: Adjust the temperature of the distillation vessel to 140~180℃ and the vacuum degree to 0.08~0.095MPa to distill out the DMMP product.

3. The preparation process of the dimethyl methylphosphonate flame retardant according to claim 1, characterized in that, The Arbuzov rearrangement reaction in step (2) is carried out at a temperature of 130–160 °C for 7 hours.

4. The preparation process of the dimethyl methylphosphonate flame retardant according to claim 2, characterized in that, The main component of the low fraction in step (3) is unreacted TMP.

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