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CN-117209532-B - Method for preparing diethyl aluminum phosphinate with low byproduct content

CN117209532BCN 117209532 BCN117209532 BCN 117209532BCN-117209532-B

Abstract

The invention discloses a method for preparing aluminum diethylphosphinate with low byproduct content, which comprises the steps of dispersing aluminum phosphinate solid in an aqueous solution containing alkali metal hydroxide in a low concentration, enabling ethylene and the aluminum phosphinate solid to undergo an addition reaction under the initiation of a free radical initiator at a reaction temperature of 100-150 ℃ under a reaction pressure of 0.1-0.3 MPa, controlling the consumption of ethylene in a reaction system until the aluminum phosphinate solid fully reacts to obtain an aluminum monoethyl phosphinate solution, separating solid from liquid, collecting filtrate, introducing ethylene into the collected filtrate, enabling the aluminum monoethyl phosphinate in the filtrate and the ethylene to undergo an addition reaction under the initiation of the free radical initiator, and obtaining aluminum diethylphosphinate precipitate at a reaction temperature of 100-150 ℃ and a reaction pressure of 0.1-0.3 MPa. The invention successfully prepares the diethyl phosphinic acid aluminum product with the byproduct content of less than 0.5wt percent and even less than 0.1wt percent.

Inventors

  • LI JINZHONG
  • LEI HUA

Assignees

  • 江苏利思德新材料股份有限公司

Dates

Publication Date
20260508
Application Date
20230905

Claims (10)

  1. 1. A process for preparing aluminum diethylphosphinate having a low by-product content comprising: Dispersing aluminum hypophosphite solid in an aqueous solution containing alkali metal hydroxide in a low concentration, wherein the mass ratio of the aluminum hypophosphite solid to water is 1:20-1000, enabling ethylene and the aluminum hypophosphite solid to undergo an addition reaction under the initiation of a free radical initiator, controlling the consumption of ethylene in a reaction system until the aluminum hypophosphite solid fully reacts at the reaction temperature of 100-150 ℃ and the reaction pressure of 0.1-0.3 MPa, obtaining an aluminum monoethyl phosphinate solution, and collecting filtrate through solid-liquid separation; introducing ethylene into the collected filtrate, and enabling aluminum monoethyl phosphinate in the filtrate and the ethylene to undergo an addition reaction under the initiation of a free radical initiator, wherein the reaction temperature is 100-150 ℃, and the reaction pressure is 0.1-0.3 MPa, so as to obtain aluminum diethyl phosphinate precipitate; in the first step, the mole ratio of ethylene to aluminum hypophosphite solid is 0.1-3:1; in the second step, the mol ratio of ethylene to aluminum monoethyl phosphinate is 0.1-3:1; The total weight percentage of byproducts in the aluminum diethylphosphinate prepared by the method is lower than 0.5 percent.
  2. 2. The method according to claim 1, wherein in the first step, the preparation method of the aluminum hypophosphite solid comprises the steps of reacting hypophosphorous acid and/or soluble hypophosphite with an aluminum-containing compound in water to generate aluminum hypophosphite precipitate, and filtering and washing the precipitate to obtain the aluminum hypophosphite solid.
  3. 3. The method according to claim 2, wherein the aluminum hypophosphite solid is prepared by a process comprising: The soluble hypophosphite is an alkali metal salt; the aluminum-containing compound is at least one of aluminum sulfate, aluminum chloride, aluminum nitrate, aluminum hydroxide and aluminum acetate; the temperature of the reaction is 20-120 ℃, and the pressure of the reaction is 0.01-10 MPa.
  4. 4. The method according to claim 1, wherein in the second step, the content of the aluminum monoethyl phosphinate in the filtrate is 5wt% or less.
  5. 5. The method according to claim 1, wherein in the first and second steps, the radical initiator is independently selected from a peroxide and/or an azo compound.
  6. 6. The method of claim 5, wherein in step one and step two, the free radical initiator is independently selected from the group consisting of water-soluble peroxides.
  7. 7. The method according to claim 6, wherein in the first and second steps, the radical initiator is independently selected from at least one of hydrogen peroxide, potassium persulfate, sodium persulfate, and ammonium persulfate.
  8. 8. The method according to claim 1, wherein in step one: the alkali metal hydroxide is sodium hydroxide and/or potassium hydroxide; In the aqueous solution containing the alkali metal hydroxide, the mass ratio of the alkali metal hydroxide to water is 1:50-10000.
  9. 9. The method according to claim 1, wherein step two further comprises filtering the washed aluminum diethylphosphinate precipitate.
  10. 10. The method according to claim 1, wherein the total weight percentage of byproducts in the aluminum diethylphosphinate prepared by the method is less than 0.1%.

Description

Method for preparing diethyl aluminum phosphinate with low byproduct content Technical Field The invention relates to the technical field of preparation of aluminum diethylphosphinate, in particular to a method for preparing aluminum diethylphosphinate with low byproduct content. Background As described in the patent CN1284787C and CN1660858B, the synthesis of the existing aluminum diethylphosphinate is usually completed in two steps, namely (1) the addition reaction of water-soluble inorganic phosphinate and ethylene in an aqueous medium, so that the inorganic phosphinate is ethylated to obtain water-soluble diethyl phosphinate, and (2) the double decomposition reaction of the water-soluble diethyl phosphinate and the water-soluble aluminum salt to obtain aluminum diethylphosphinate precipitate, wherein the precipitate has high hydrophobicity and good flame retardant function. In the two-step reaction, the key is that the first-step addition reaction of ethylene and inorganic hypophosphite is a control step of the whole preparation process, and the reaction efficiency and the product quality are determined. Inorganic hypophosphites are ethylated by addition to ethylene and converted to diethyl hypophosphite. The reaction mechanism is that a water-soluble free radical Initiator (Initiator) is heated and decomposed in a water phase to generate free radicals, the free radicals firstly attack active phosphorus hydrogen bonds to break the phosphorus hydrogen bonds to generate hypophosphite free radicals, the hypophosphite free radicals attack double bonds of ethylene, the double bonds are opened and combined to form new phosphate free radicals containing ethyl, and the free radicals continue to react with the phosphorus hydrogen bonds of the hypophosphite to finish addition. The reaction formula is as follows: In the addition reaction, since ethylene is in a gas phase and hypophosphite is dissolved in a water phase, the addition reaction belongs to a gas-liquid reaction, in actual production, ethylene exists in a large amount in a reactor, in the presence of an initiator, ethyl in a diethyl phosphinate structure can be initiated by the initiator to form free radicals, and the free radicals are added with ethylene to form byproducts of ethylene overaddition, and the side reactions are as follows: Of these side reactions, the lower the probability of continuing to be initiated as the carbon chain grows. In the existing preparation process, after the first-step addition reaction is carried out, non-water-soluble aluminum diethyl phosphinate precipitate is generated by reacting with aluminum-containing compounds, and meanwhile, the byproduct dialkyl phosphinate is combined with aluminum ions to form non-water-soluble aluminum dialkyl phosphinate which can be precipitated together with the aluminum diethyl phosphinate and cannot be separated. Thus, in the existing preparation process of aluminum diethylphosphinate, the prepared aluminum diethylphosphinate generally comprises aluminum ethylbutylphosphinate, aluminum butylbutylbutylphosphinate, aluminum ethylhexyl phosphinate, aluminum butylhexylphosphinate, aluminum hexylhexylphosphinate, and the like due to the presence of side reactions. The aluminum ethylbutylphosphinate is mainly used as a byproduct, and the content of the aluminum ethylbutylphosphinate is about 2% by weight, and the byproducts cannot be separated from the aluminum diethylphosphinate, so that the aluminum diethylphosphinate flame retardant in industrial products actually comprises a certain amount of byproducts. These excessive addition forms aluminum dialkylphosphinate byproducts, as described in patent CN1660857B, can cause degradation of the polymer, reducing the mechanical properties of the polymer material. The process proposed in patent CN1660857B allows to reduce the proportion of by-products by changing the reaction medium from the organic solvent acetic acid to water, but even in the aqueous phase the content of by-products in the aluminium diethylphosphinate produced is still not low, the minimum by-products reported as in example 3, 0.9% mol of aluminium ethylbutylphosphinate, still have a higher content and the negative effects are still present. Thus, to address these negative effects, it is necessary to prepare aluminum diethylphosphinate with lower by-product content in the aqueous phase to obtain a high purity aluminum diethylphosphinate product. According to the principle of addition reaction of ethylene and inorganic hypophosphite and the characteristics of industrial production, a novel synthesis process is developed, and the purpose of the invention is to prepare the aluminum diethylphosphinate with low byproduct content, so as to solve the negative influence caused by the fact that the existing aluminum diethylphosphinate contains higher byproducts. Disclosure of Invention The invention provides a method for preparing aluminum diethylphosphinate with low byproduct content, wh