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CN-122011239-A - Preparation method of liquid epoxidized natural rubber, prepared rubber and application

CN122011239ACN 122011239 ACN122011239 ACN 122011239ACN-122011239-A

Abstract

The invention discloses a preparation method of liquid epoxidized natural rubber, the prepared rubber and application thereof, and relates to the technical field of polymer chemical industry, the preparation method of the liquid epoxidized natural rubber comprises the following steps: after the epoxidized natural rubber latex is synthesized by an in-situ method, the prepared epoxidized natural rubber latex is degraded by utilizing the residual hydrogen peroxide and sodium nitrite in the latex to form an oxidation-reduction degradation system, so that the liquid epoxidized natural rubber is prepared. Compared with the hydrogen peroxide-sodium nitrite system in the prior art, the hydrogen peroxide in the invention is the rest part in the synthetic ENR system after the epoxy natural rubber is synthesized by the in-situ method for the first time, and the method has the advantages of no need of additional addition, low cost and simple process. And simultaneously adding quantitative sodium nitrite for degradation to obtain the viscous liquid epoxidized natural rubber with lower molecular weight. Can be used as processing aids such as adhesive, compatilizer, plasticizer and the like.

Inventors

  • SHI YAN
  • ZHAO SHUMAN
  • Hao Yuanbo

Assignees

  • 北京化工大学

Dates

Publication Date
20260512
Application Date
20260204

Claims (10)

  1. 1. A process for the preparation of a liquid epoxidized natural rubber, said process comprising: After the epoxidized natural rubber latex is synthesized by an in-situ method, the prepared epoxidized natural rubber latex is degraded by utilizing the residual hydrogen peroxide and sodium nitrite in the latex to form an oxidation-reduction degradation system, so that the liquid epoxidized natural rubber is prepared.
  2. 2. A method according to claim 1, characterized in that the method comprises: (1) Adding an emulsifying agent into the natural latex; (2) Adding formic acid and hydrogen peroxide under stirring, and heating to perform epoxidation reaction; (3) After the reaction is finished, adjusting the pH value of the latex to obtain epoxidized natural rubber latex; (4) Measuring the hydrogen peroxide content in the epoxidized natural rubber latex, and preparing a sodium nitrite solution according to the measured hydrogen peroxide content; (5) Adding the sodium nitrite solution for degradation reaction; (6) And after the reaction is finished, carrying out post-treatment to obtain the liquid epoxidized natural rubber.
  3. 3. The method according to claim 2, characterized in that: The emulsifier is used in an amount of 0.5 to 5 parts by weight, preferably 0.5 to 3 parts by weight, the formic acid is used in an amount of 1 to 60 parts by weight, preferably 2 to 30 parts by weight, the hydrogen peroxide is used in an amount of 15 to 100 parts by weight, preferably 20 to 80 parts by weight, and/or, The molar ratio of sodium nitrite to hydrogen peroxide determined in step (4) is (0.1-5.0): 1, preferably (0.1-2.0): 1, and/or, The concentration of the sodium nitrite solution is 1wt% to 30wt%, preferably 1wt% to 20wt%.
  4. 4. The method according to claim 2, characterized in that: The hydrogen peroxide content of the epoxidized natural rubber latex in step (4) is titrated with a modified indirect potassium dichromate process comprising: In the mixed solution medium of phosphoric acid and sulfuric acid, ferrous ion standard solution is used as a reducing agent, sodium diphenylamine sulfonate is used as an indicator, potassium dichromate is used for titration, and the hydrogen peroxide content in the epoxidized natural rubber latex is calculated after the titration end point is reached.
  5. 5. The method according to claim 4, wherein the modified indirect potassium dichromate process comprises: (a) Mixing ferrous ion standard solution with mixed solution of phosphoric acid and sulfuric acid, dripping epoxidized natural rubber latex, mixing and standing; (b) Optionally adding an organic solvent, standing and swelling; (c) Adding sodium diphenylamine sulfonate solution, mixing, and then titrating with potassium dichromate; (d) After the titration end point is reached, the hydrogen peroxide content in the latex is calculated according to the amount of potassium dichromate.
  6. 6. The method according to claim 5, wherein: In step (a): the concentration of the ferrous ion standard solution is 0.01-3.00mol/L, preferably 0.01-2.00mol/L, and/or, The concentration of phosphoric acid in the mixed solution of phosphoric acid and sulfuric acid is 5wt% to 50wt%, preferably 10wt% to 40wt%, and/or the concentration of sulfuric acid is 5wt% to 50wt%, preferably 10wt% to 40wt%, and/or, The ferrous ion standard solution is ferrous ammonium sulfate hexahydrate solution and/or ferrous chloride solution, and/or, In step (b): the weight ratio of the organic solvent to the epoxidized natural rubber latex is (0 to 7): 1, preferably (1 to 5): 1, and/or, The organic solvent is acetone and/or toluene, and/or, The rest time is 1-10min, preferably 2-8min, and/or, In step (c): the mass fraction of the sodium diphenylaminesulfonate solution is 0.05-10wt%, preferably 0.1-5wt%, and/or, The sodium diphenylamine sulfonate solution is used in an amount of 5-15mL, preferably 5-10mL, and/or, In step (d): The titration endpoint was a change from green to purple in solution.
  7. 7. The method according to claim 2, characterized in that: The natural latex is concentrated latex and/or fresh latex, and/or, The concentration of the formic acid is 60-90wt%, and/or, The hydrogen peroxide has a concentration of 20-50wt%, and/or, The concentration of the ammonia water is 20-30wt%, and/or, The epoxidized natural rubber latex has an epoxy degree of 5 to 60%, preferably 5 to 50%, and/or, The emulsifier may be a cationic emulsifier and/or a nonionic emulsifier, preferably, The cationic emulsifier is at least one of octadecyl trimethyl ammonium chloride, hexadecyl trimethyl ammonium bromide, dodecyl ammonium chloride, lignin amine emulsifier, tallow alkyl propylene diamine, pentamethyl ammonium chloride, octadecyl amine polyoxyethylene ether biquaternary ammonium salt and dodecyl dimethyl benzyl ammonium chloride, and/or, The nonionic emulsifier is at least one of nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene polyoxypropylene ether, alkylamine polyoxyethylene ether and fatty amide polyoxyethylene ether.
  8. 8. The method according to claim 2, characterized in that: In step (1): when the natural latex is a concentrated latex, the concentrated latex is diluted with deionized water to a solids content of 10 to 50wt%, preferably 20 to 50wt%, and/or, In the step (2): the epoxidation reaction is carried out at a reaction temperature of 30 to 80C, preferably 40 to 60C, and/or for a reaction time of 1 to 20h, preferably 1 to 15h, and/or, In the step (3): adjusting the pH value of the latex by ammonia water, and/or, The pH value is 3-11, preferably 4-10, and/or, In the step (6): The degradation reaction has a reaction temperature of 20-90 ℃, preferably 30-80 ℃, and/or a reaction time of 0.5-15 hours, preferably 1-10 hours, and/or, In the step (7): The post-treatment includes flocculation, soaking, washing with water and drying, preferably, The flocculation includes pouring the reacted latex into hot water for flocculation, more preferably, the hot water has a temperature of 70-100 ℃, and/or, The soaking comprises soaking the filtrate reacted under acidic conditions in an alkaline solution, more preferably, the concentration of the alkaline solution is 1-10wt%, and/or the soaking time is 2-12h, and/or, The water washing comprises washing with deionized water for 2-10 times, and/or, The drying temperature is 40-120 ℃ and/or the drying time is 5-48h.
  9. 9. A liquid epoxidized natural rubber produced by the process for producing a liquid epoxidized natural rubber according to any of claims 1 to 8, preferably, The liquid epoxidized natural rubber has an epoxy degree of 5 to 60%, preferably 10 to 50%, and/or a number average molecular weight of (0.2 to 4.0). Times.10 4 g/mol, preferably (0.5 to 3.0). Times.10 4 g/mol.
  10. 10. A process as claimed in claim 9, wherein the liquid epoxidized natural rubber is used as a processing aid, preferably, The processing aid is at least one of an adhesive, a compatilizer and a plasticizer.

Description

Preparation method of liquid epoxidized natural rubber, prepared rubber and application Technical Field The invention relates to the technical field of high molecular chemical industry, in particular to a preparation method of liquid epoxidized natural rubber, the prepared rubber and application. Background The Epoxidized Natural Rubber (ENR) is obtained by epoxidation modification of a Natural Rubber (NR) main chain, namely, an epoxy group (-C-O-C-) is introduced to the natural rubber main chain, and is novel bio-based high-performance rubber. The epoxy bond endows the epoxidized natural rubber with polarity and reactivity, and compared with the natural rubber, the epoxidized natural rubber has better damping property, air tightness, oil resistance, wet skid resistance, wear resistance and the like. The epoxidized natural rubber can be widely used in various fields of transportation, medical equipment, aerospace, building industry and the like due to good performance, such as automobile tires, medical gloves, interface modifiers and the like. Degradation of epoxidized natural rubber results in Liquid Epoxidized Natural Rubber (LENR). The degraded liquid epoxidized natural rubber maintains part of the performance of the epoxidized natural rubber, has lower molecular weight, and can have functional groups at the tail end, thereby improving the application and reworkability of the epoxidized natural rubber. The liquid epoxidized natural rubber can be used for rubber compatilizers, plasticizers, adhesives and the like, and has wide application market. In the prior art, the epoxidation reaction is carried out by adopting an in situ method (in situ) with milder reaction conditions and simpler and more convenient preparation of peroxyacid, namely, formic acid and hydrogen peroxide are directly added into a reaction system, and double bonds are subjected to epoxidation modification by utilizing peroxyformic acid generated in situ in the system. After the reaction, the peroxyformic acid generates formic acid with the same mole number, and the formic acid in the system acts as a catalyst. "Yang Keke, li Ruixia, wu Dacheng. Synthesis and characterization of epoxidized Natural rubber. University of Sichuan university (Nature science edition), 2001,38 (1): 82-86", yang Keke et al explored a more suitable reaction condition for the synthesis of epoxidized Natural rubber using a hydrogen peroxide-formic acid system, a 30℃reaction temperature, a molar ratio of carbon-carbon double bonds/H 2O2/HCOOH=1/1/0.55, a system latex solids content of 30%, and an initial pH of 2.0. The preparation reaction condition of the epoxidized natural rubber is mild, but the epoxidation reaction rate is slower, the efficiency is low, and the epoxidation degree of the reaction is only 25% after 8 hours under the reaction condition. Meanwhile, hydrogen peroxide is used as inflammable and explosive products, the mass of the hydrogen peroxide in a latex system is about 12%, and the consumption is large. There is no report on the decomposition of hydrogen peroxide and the residual content found in previous epoxidation studies, and from literature data, the hydrogen peroxide is generally fed in large excess, mainly to increase the rate of epoxidation modification. The residual hydrogen peroxide in the latex has an influence on the subsequent treatment and safety of the latex, so that the method has very important significance for measuring the hydrogen peroxide content in the latex. The hydrogen peroxide determination method mainly comprises an instrument analysis method and a chemical titration method, and the instrument method mainly comprises a spectrophotometry method, a high performance liquid chromatography method and the like. The chemical titration method is generally redox titration method, and mainly comprises potassium permanganate method, iodine method, cerium method, etc. Optimization study of measurement of hydrogen peroxide by ceric sulfate spectrophotometry [ J ]. Environmental science and management, 2023,48 (06): 126-131", sun Peiying et al, applied ceric sulfate spectrophotometry, and measured hydrogen peroxide content under conditions of 316nm wavelength, 0.002 mol.L -1 ceric sulfate concentration, pH=0.4, and reaction time of 6 min. Wherein Ce 4+ is reduced to Ce 3+, the solution system turns orange to colorless. "Hu Junming, dan Wenpeng, lin Shaobin. Method for measuring hydrogen peroxide in cosmetics by high performance liquid chromatography" J. Chinese J health, 2003, (05): 593-596", hu Junming et al derivatize hydrogen peroxide in a test solution with 0.02mol/L triphenylphosphine acetonitrile solution to give triphenylphosphine oxide, and measuring the concentration of triphenylphosphine oxide by aqueous liquid chromatography to give hydrogen peroxide concentration. The high performance liquid chromatography has the advantages of simplicity, rapidness, high accuracy, high sensitivity and the like, but the liquid chromatogra