CN-122011714-A - Supercritical CO-based2Poly (propylene carbonate) purification and modification method

Abstract

The invention discloses a method for purifying and modifying polypropylene carbonate based on supercritical CO 2 , which is characterized in that a polypropylene carbonate raw material and an amino modified nano filler accounting for 5-10wt% of the weight of the polypropylene carbonate raw material are dry-mixed, a mixed material is added into a screw extruder through a feeder, the operation temperature of the screw extruder is controlled to be 60-120 ℃, the rear end of the screw extruder is injected with supercritical CO 2 with the pressure of 8-30 MPa and the temperature of 40-120 ℃, the material treated by the screw extruder enters a falling strip devolatilizer, the cavity temperature of the falling strip devolatilizer is controlled to be 60-120 ℃, the vacuum degree is 20-80 kPa, the retention time of a sample in the falling strip devolatilizer is 10-100 s, and the purified and modified polypropylene carbonate is obtained.

Inventors

• ZHOU QI
• ZHANG YULIANG
• CHEN QIJUN
• JIN NAN
• ZHANG JIARUI
• CHENG WEI
• CUI YING
• WANG ZHIDONG
• GONG ZHIHAI
• LI QUAN
• GU XINCHUN
• LIU XINAN
• LI YAJING
• CHEN SHENGHUA
• WANG GANG
• HOU JIANLONG

Assignees

• 中国化学赛鼎宁波工程有限公司

Dates

Publication Date

20260512

Application Date

20260129

Claims (6)

1. 1. A method for purifying and modifying polypropylene carbonate based on supercritical CO 2 is characterized by comprising the following steps of dry mixing a polypropylene carbonate raw material and an amino modified nano filler accounting for 5-10wt% of the weight of the polypropylene carbonate raw material, adding the mixed material into a screw extruder through a feeder, controlling the operation temperature of the screw extruder to be 60-120 ℃, injecting supercritical CO 2 with the pressure of 8-30 MPa and the temperature of 40-120 ℃ into the rear end of the screw extruder, enabling the material treated by the screw extruder to enter a falling-strip devolatilizer, controlling the cavity temperature of the falling-strip devolatilizer to be 60-120 ℃, controlling the vacuum degree to be 20-80 kPa, and enabling the residence time of a sample in the falling-strip devolatilizer to be 10-100 s, thus obtaining the purified and modified polypropylene carbonate.
2. 2. The purification and modification method of the polypropylene carbonate based on the supercritical CO 2 , which is characterized in that the nano filler is organic montmorillonite, graphene oxide or polysilsesquioxane, and the modification method of the nano filler is as follows, and a modifier containing amino is adopted for substitution reaction.
3. 3. The method for purifying and modifying polypropylene carbonate based on supercritical CO 2 as set forth in claim 1, wherein the screw extruder is operated at a temperature of 100-110 ℃.
4. 4. The method for purifying and modifying polypropylene carbonate based on supercritical CO 2 as claimed in claim 1, wherein the injection pressure of supercritical CO 2 is 15-25 MPa and the temperature is 90-110 ℃.
5. 5. The method for purifying and modifying polypropylene carbonate based on supercritical CO 2 as claimed in claim 1, wherein the cavity temperature of the falling strip devolatilizer is 90-110 ℃ and the vacuum degree is 60-80 kPa.
6. 6. The method for purifying and modifying the polypropylene carbonate based on the supercritical CO 2 , which is characterized in that an outlet of a screw extruder is connected with an inlet of a falling strip devolatilizer, materials enter the falling strip devolatilizer through the screw extruder, the temperature in a cavity of the falling strip devolatilizer is respectively controlled through a temperature control system and pressure through a vacuum pump, the processed materials enter a receiving tank at the bottom of the falling strip devolatilizer, and finally the materials are sent to a next working section through a discharging pump to be directly discharged or circularly and repeatedly devolatilized through the screw extruder to reach the established PPC product quality index.

Description

Purification and modification method of polypropylene carbonate based on supercritical CO 2 Technical Field The invention belongs to the technical field of high polymer materials, and particularly relates to a method for purifying and modifying polypropylene carbonate based on supercritical CO 2. Background The polypropylene carbonate is also called as polymethyl ethylene carbonate, abbreviated as PPC, is a completely degradable environment-friendly plastic synthesized by taking carbon dioxide and propylene oxide as raw materials, can be applied to fresh-keeping films of meat products, degradable foam materials, plates, disposable tableware, disposable medical and food packaging materials and the like, and can also be used for being blended with PPAT (degradable plastic) to improve the toughness of the materials. The polymerization of PPC can adopt bulk polymerization of carbon dioxide and propylene oxide, but the polymerization product increases along with the molecular weight, and the strong interaction between carbonate molecules leads to the rapid increase of the viscosity of the reaction system, which is unfavorable for the full occurrence of the reaction and easy to cause the residue of catalyst and byproducts (cyclic small molecules). These residues not only impair the mechanical properties and the service life of the material, but can also pose a threat to human health. The total Volatile Organic Compound (VOC) migration in food grade plastics must not exceed 10mg/dm2, according to food safety standards. However, the polymerized monomer and the low boiling point solvent molecules are easy to remove, but the residual cyclic micromolecules have the boiling point as high as 250 ℃ and are extremely difficult to remove. PPC is unstable when heated and is easy to decompose, and the PPC is decomposed into annular small molecules when heated, so that the residue content is increased. Propylene carbonate (abbreviated as PC) is therefore both a degradation product and a synthesis by-product, and its content control is particularly critical. In the case of bulk synthesis, screw extruders are used industrially for devolatilization in order to maintain the fluidity of high viscosity PPC, but even with vacuum operation, high temperatures are required to remove high boiling point PC, which in turn causes new degradation reactions that form vicious circle. Aiming at the problems of high material viscosity, easy degradation and the like in the PPC production process, the traditional PPC post-treatment working section mainly adopts a screw extruder, the temperature of the extruder is too low, the devolatilization efficiency is poor, the temperature of the extruder is too high, the PPC degradation can be caused to produce PC, and the residual quantity of the PC is increased. The patent with publication number CN114773587A discloses an epoxypropane removing process used in the PPC production process, which comprises customizing an SCP unit consisting of an SCP horizontal self-cleaning reactor, arranging a discharging bin at the discharging end of the lower part of the SCP unit, and simultaneously connecting with a feeding port of a double-screw extruder, so that the SCP unit and the double-screw extruder are formed into the same whole to form a double-screw PO removing unit. The main purpose of the process is to remove the residual reactant PO and other low-boiling point organic solvents in the PPC process, and simultaneously simplify the PPC post-treatment process, and a specific scheme is not provided for the problems of high-temperature thermal degradation of the PPC and removal of high-boiling point byproducts. The patent with publication number CN101928387A discloses a washing, condensing and devolatilizing method for aliphatic polycarbonate and a special device thereof, and the method is mainly characterized by disclosing a washing, condensing and devolatilizing device, comprising a polymerization reaction kettle, a flash evaporation glue tank, a condensing system consisting of one washing, condensing kettle or more than two washing, condensing kettles connected in series, a solid-liquid separation system, a polymer drying system, a gear pump, a connecting pipeline and the like, and simultaneously disclosing a washing, condensing and devolatilizing method for aliphatic polycarbonate glue solution suitable for the device. Finally, the final product can be obtained through processes of refining, sedimentation, drying and the like, and the process route is long and the energy consumption is high. The prior art CN114773587A, CN101928387A and the like do not solve the fundamental contradiction between high-temperature degradation and high-boiling point byproduct removal. Although the supercritical fluid extraction technology is generally reported in the field of polymer devolatilization (for example, US 2004/016690A 1), it is mostly aimed at thermally stable materials such as polyolefin, and the process purpose is sin