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CN-122010839-A - Preparation method of aromatic isocyanate dimer

CN122010839ACN 122010839 ACN122010839 ACN 122010839ACN-122010839-A

Abstract

The invention discloses a preparation method of aromatic isocyanate dimer, which is prepared by reacting aromatic diisocyanate in the presence of tertiary phosphine catalyst, controlling the grain diameter of the crystal to be 10 mu m or less, preferably 0.5-10 mu m by high-speed shearing and stirring after the crystal is separated out from a reaction system, adding a terminator to terminate the reaction when the monomer concentration of the aromatic diisocyanate is reduced to 20-80%, preferably 30-70%, filtering to obtain solid, and drying in vacuum to remove free monomers and solvents in the solid, thus obtaining the aromatic isocyanate dimer. The process allows for a rapid achievement of products with high uretdione content and advantageously reduced levels of polymers.

Inventors

  • ZHU ZHICHENG
  • Kou Mengcun
  • BIAN KAI
  • LIN CHENGDONG
  • JIANG LIANG
  • SHI BIN
  • SHANG YONGHUA

Assignees

  • 万华化学集团股份有限公司

Dates

Publication Date
20260512
Application Date
20241112

Claims (10)

  1. 1. A preparation method of aromatic isocyanate dimer is characterized by comprising the step of reacting aromatic diisocyanate in the presence of tertiary phosphine catalyst; When the content of the aromatic diisocyanate monomer is reduced to 20-80% of the initial content, preferably 30-70%, adding a terminator to terminate the reaction; filtration gives a solid which is dried in vacuo to remove free monomer and optionally solvent from the solid to produce aromatic isocyanate dimer.
  2. 2. The method for producing an aromatic isocyanate dimer according to claim 1, wherein the aromatic diisocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, m-xylylene isocyanate, and dimethylbiphenyl diisocyanate.
  3. 3. The method for preparing aromatic isocyanate dimer according to claim 1, wherein the tertiary phosphine catalyst is one or more of trimethylphosphine, triethylphosphine, tripropylphosphine, tris (dimethylamino) phosphine, triisopropylphosphine, tri-n-butylphosphine, tri-tertiary-butylphosphine, dicyclopentylphosphine, tripentylphosphine, tricyclopentylphosphine, trihexylphosphine, triphenylphosphine, tribenzylphosphine, benzyldimethylphosphine, tricyclohexylphosphine, tri-n-octylphosphine; Preferably, the tertiary phosphine catalyst is used in an amount of 0.001 to 0.1wt%, preferably 0.002 to 0.05wt% based on the mass of the aromatic diisocyanate.
  4. 4. The process for the preparation of aromatic isocyanate dimers according to any of claims 1 to 3, wherein the reaction is carried out in the presence of optionally an alcohol promoter which is a monohydric or polyhydric alcohol having a relative molecular weight of 32 to 200, preferably one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-hexanol, octanol, 2-ethyl-1-hexanol, ethylene glycol, propylene glycol, isomeric butanediols, pentanediol, neopentyl glycol, hexanediol, octanediol, diethylene glycol, 2-ethyl-1, 3-hexanediol, 2, 4-trimethyl-1, 3-pentanediol, glycerol, trimethylolpropane; Preferably, the alcohol cocatalyst and the tertiary phosphine catalyst are added into the reaction system together after being compounded into a solution, and the alcohol cocatalyst is used in an amount such that the mass concentration of the tertiary phosphine catalyst in the solution is 5-20wt%.
  5. 5. The process for producing aromatic isocyanate dimer according to any one of claims 1 to 4, wherein said solvent is one or more of a reaction-inert aromatic hydrocarbon, aliphatic hydrocarbon or their halogenated compound, ketone, ester, amide-based solvent, preferably one or more of benzene, toluene, xylene, chlorobenzene, o-dichlorobenzene, ethyl acetate, butyl acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate, dimethylformamide, dimethylacetamide, acetone, methyl butyl ketone, methyl isobutyl ketone, cyclohexanone.
  6. 6. The process for the preparation of aromatic isocyanate dimers according to any of claims 1 to 5, wherein said terminators are selected from the group consisting of alkylating agents, acylating agents, organic acids, preferably one or more of dimethyl sulfate, methyl p-toluenesulfonate, benzoyl chloride, p-toluenesulfonyl chloride, phosphoric acid esters, sulfonic acid esters; preferably, the terminator is used in an amount of 80 to 150mol% based on the molar amount of the tertiary phosphine catalyst.
  7. 7. The process for preparing aromatic isocyanate dimers according to any one of claims 1 to 6, wherein the reaction temperature is 0 to 30 ℃.
  8. 8. The method for producing an aromatic isocyanate dimer according to any one of claims 1 to 7, wherein in the production method, a self-priming high-speed mixing shearing apparatus for materials is used to control the crystal particle size to 10 μm or less; preferably, the self-priming high speed mixing shear device is selected from IKA DIGITIAL T, IKA DIGITIALT, 50 or Yekeey ZJR-5/10.
  9. 9. The process for preparing aromatic isocyanate dimers according to any one of claims 1 to 8, wherein the process parameters of vacuum drying are 30 to 120 ℃ and 10 to 500Pa of vacuum.
  10. 10. The process for the preparation of aromatic isocyanate dimers according to any of claims 1 to 9, wherein aromatic isocyanate dimers are obtained having a diisocyanate monomer content of < 0.5% by weight, a solvent content of < 0.5% by weight and a polymer content of < 2% by weight.

Description

Preparation method of aromatic isocyanate dimer Technical Field The invention relates to an isocyanate dimer, in particular to a preparation method of an aromatic isocyanate dimer. Background The polyisocyanate prepared by polymerizing the diisocyanate monomer can effectively reduce the harm of the volatile isocyanate monomer through the self polymerization of the isocyanate, such as uretdione, trimer, iminooxadiazinedione and the like. The polyisocyanate composition is useful in a variety of applications such as curing aids, textile accelerators, and coatings, adhesives, and the like. In the free state, they are extremely reactive, sensitive to water and are prone to polymerization. One useful method of using these materials has been found to be to first convert them into dimeric compounds of isocyanate, aromatic and aliphatic isocyanate dimers having specific applications in different fields, respectively, due to differences in reactivity. Methods for producing uretdione by catalyzing the reaction of two isocyanate groups using dimerization catalysts (e.g., tertiary phosphines) are known, but in many cases higher polymerization products (hereinafter collectively referred to as "polymers") of more isocyanate groups are also formed, reducing uretdione production. Especially when aromatic uretdiones are rapidly removed from the reaction medium (e.g. by precipitation) due to their physical form, the uretdione product is contaminated with more polymer and monomer, which affects the product purity. Patent US2671082a converts isocyanates to addition products containing two isocyanate groups in good yields by contacting the aromatic isocyanates with a catalytic amount of a mixed aromatic-aliphatic tertiary phosphine catalyst at a temperature of from 0 to 60 ℃, which does not require careful control to prevent the formation of undesirable by-products such as isocyanurates. However, the obtained product still needs secondary recrystallization purification, which increases the process difficulty and the production investment. Disclosure of Invention In order to solve the technical problems, the invention provides a preparation method of aromatic isocyanate dimer, which can rapidly obtain products with high uretdione content and favorably reduce the polymer level. In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: the preparation method of aromatic isocyanate dimer comprises the steps of reacting aromatic diisocyanate in the presence of tertiary phosphine catalyst; When the content of the aromatic diisocyanate monomer is reduced to 20-80% of the initial content, preferably 30-70%, adding a terminator to terminate the reaction; filtration gives a solid which is dried in vacuo to remove free monomer and optionally solvent from the solid to produce aromatic isocyanate dimer. The invention controls the grain diameter of the crystal in the reaction system by high-speed shearing and stirring, and adjusts the conversion rate of the aromatic diisocyanate monomer at the same time, thus being beneficial to reducing the level of polymer in the product and obviously improving the purity of the uretdione. As some preferred examples of the present invention, the aromatic diisocyanate is one or more of Toluene Diisocyanate (TDI), diphenylmethane diisocyanate (MDI), m-xylylene isocyanate (XDI), dimethylbiphenyl diisocyanate (TODI). As some preferred examples of the present invention, the tertiary phosphine catalyst is one or more of trimethylphosphine, triethylphosphine, tripropylphosphine, tris (dimethylamino) phosphine, triisopropylphosphine, tri-n-butylphosphine, tri-t-butylphosphine, dicyclopentylphosphine, tripentylphosphine, tricyclopentylphosphine, trihexylphosphine, triphenylphosphine, tribenzylphosphine, benzyldimethylphosphine, tricyclohexylphosphine, tri-n-octylphosphine, more preferably tributylphosphine and/or tri-n-octylphosphine; Preferably, the tertiary phosphine catalyst is used in an amount of 0.001 to 0.1wt%, preferably 0.002 to 0.05wt% based on the mass of the aromatic diisocyanate. If the tertiary phosphine catalyst is used in an amount of more than 0.1wt%, the catalytic reaction rate is faster, more polymer formation is easily promoted and the catalyst is packed in precipitated crystals to reduce the uretdione content, whereas when the catalyst concentration is less than 0.001wt%, it is difficult to produce a solid which can be precipitated or non-reacted during the reaction. As some preferred examples of the present invention, the reaction is carried out in the optional presence of an alcohol co-catalyst which is a monohydric or polyhydric alcohol having a relative molecular weight of 32 to 200, preferably one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, isobutanol, n-hexanol, octanol, 2-ethyl-1-hexanol, ethylene glycol, propylene glycol, isomerised butylene glycol, pentylene glycol, neopentyl glycol, hexylene glycol, octylene glycol, diethy