Production method of low molecular weight tetrafluoro ethylene resin

Abstract

This invention discloses a preparation of low molecular weight teflon, it adopts emulsion polymerization method, utilizing deionized water as polymerization medium, utilizing Perfluorooctanoic acid as dispering agent, utilizing dichlormethane as chain transfer agent, tetafluoroethylene metamer is polymerized by utilizing persulfate as initiator. Low molecular weight Teflon is gained by agglomerating and continuously drying polymerization solution, this invention can prepare low molecular weight PTFE resin which is water-galact typus and excellent constance, it is completely suitable for follow-up manipulation and continuous operation. it can be extently enlarged, spray drying technology is energy saving and save time, directly obtained particle is thin and uniform and spherical, molecular weight distributes between 4-8*103, it has a good dispersibility for other composition, it can completely be suitable to prepare composite of low molecular weight PTFE resin whose specification is that every composition is easy to be mixed uniformly and permanent.

Description

technical field [0001] The invention relates to a method for producing low-molecular-weight polytetrafluoroethylene resin, more precisely, it relates to a method for preparing low-molecular-weight polytetrafluoroethylene resin by isothermally polymerizing under water medium conditions with dichloromethane as a chain transfer agent. Background technique [0002] Polytetrafluoroethylene resin (PTFE) is known as the "King of Plastics" by the synthetic material industry due to its good mechanical properties, electrical properties, chemical resistance, weather resistance, non-stickiness and lubricity. The molecular weight of low molecular weight polytetrafluoroethylene (also known as PTFE micropowder, commonly known as wax powder) is generally one percent of that of commonly used high molecular weight PTFE, generally 3000-10000, the average particle size is 1-20μm, and the melting point is 315-320℃ , because it has the same chemical structure as high mol...

AI Technical Summary

Problems solved by technology

The defect of this process is the intermittent operation mode of the follow-up process, which not only consumes energy but also takes time; when coagulating, concentrated hydrochloric acid is added, the operating environment is poor, the corrosion is strong, and a large amount of low-concentration hydrochloric acid waste liquid is produced, which is difficult to handle, and the polymerization liquid coagulates Equipment material requirements are strict

[0008] It should be noted that in the 16th page of the fourth issue of "Organic Fluorine Industry" in 2003, it is disclosed that foreign countries use dichloromethane and monochloromethane as chain transfer agents in the preparation of low-molecular-weight polytetrafluoroethylene resins. It clearly states that Because the reactivity of monochloromethane and dichloromethane is larger than that of difluorochloromethane, they will remain in the emulsion, which will bring troubles to the recovery and coagulation of TFE after polymerization. If the polymerization recovery monomer process does not take effective According to the technical measures, the chain transfer agent is recovered together with the gas phase monomer, which will affect the purity of TFE monomer, affect the next low molecular weight TFE polymerization, and also affect the quality of the product

[0009] It can be seen that the organic solvent-based low-molecular-weight PTFE resin polymer suspension in the above-mentioned US005,789,504A forms a paste-like colloid in a solvent, the primary particles are ultra-fine, the viscosity is high, and the fluidity is poor, and it becomes fog in the spray drying equipment Poor performance, sprayed droplet size and shape are uneven, so the obtained secondary particles of low molecular weight PTFE resin are also different in thickness and large in dispersion, which affects the application, and the solvent recovery is difficult and the environment is polluted; while Fu Chenggang et al. 1. Ammonium persulfate-initiated polymerization system, using difluorochloromethane as molecular weight regulator, to obtain low molecular weight PTFE resin polymerization liquid, poor stability, only coagulation, intermittent operation of washing and drying is completed

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