CN107778396A - A kind of polytetrafluoroethylsuspending suspending resin and preparation method thereof - Google Patents

Abstract

The present invention relates to the technical field of fluorine chemical industry, in particular to a preparation method of polytetrafluoroethylene suspension resin. That is; wherein, the molecular weight accelerator is perfluorobutylethylene. The SSG range of the suspension resin produced by this method is 2.140-2.159, the average molecular weight range is 10.122 million-15.651 million, and the strength is excellent. This kind of resin can be used to process molded products with excellent performance, neatness, smoothness and high strength, which can be used in mechanical equipment, building bridges, anti-corrosion materials, etc. Simultaneously, the production process of the present invention has a stable operation process and is easy for industrialized production.

Description

A kind of polytetrafluoroethylene suspension resin and preparation method thereof

technical field

The invention relates to the technical field of fluorine chemical industry, in particular to a polytetrafluoroethylene suspension resin and a preparation method thereof.

Background technique

The excellent chemical corrosion resistance, high and low temperature resistance, aging resistance, low friction, non-stickiness, and physiological inertia of PTFE make it an indispensable special material in the fields of chemical industry, machinery, electrical, construction, and medical treatment. .

Suspension in PTFE resin (PTFE resin) is one of the main products at present. At present, most of the PTFE suspension resins in China are general-purpose molding resins, which are medium and low-grade resin products, and ammonium persulfate is generally used. (salt) thermal decomposition initiation system or ammonium persulfate (salt)-sodium bisulfite oxidation-reduction system or oxidation-reduction system catalyzed by ferrous sulfate to prepare general-purpose PTFE suspension resin. With the expansion of the use of PTFE suspension resin and the advancement of manufacturing technology, the internal quality of general-purpose PTFE suspension resin needs to be improved. The core is the insufficient molecular weight of the resin and low basic strength, which limit the high-end application of suspension PTFE resin.

Around the 1970s, companies such as DuPont and Allied developed a method for preparing modified PTFE resin by adding modified monomers during the polymerization process, and put it into production. The production of its modified PTFE resin is to add a small amount of modified monomers such as perfluoron-propyl vinyl ether (PPVE), perfluoromethyl vinyl ether (PMVE) and perfluoropropylene (HFP) to the polymerization system. Molecular design of PTFE structure, introducing side groups on its molecular main chain, reducing the crystallinity of PTFE, thereby improving its processing performance, such as effectively improving the creep resistance and weldability of PTFE suspension resin, but The molecular weight of the resin is relatively low, and there is a lot of room for improvement in terms of basic strength.

Chinese patent CN1147262A discloses a polymerization method for suspension polymerization of tetrafluoroethylene into polytetrafluoroethylene, which is characterized in that the polymerization is started at a low temperature, and the temperature is raised to a higher temperature in the process to complete the polymerization reaction, and the shrinkage characteristics of the resin are obtained. The obtained resin is equivalent, and the production efficiency is improved. In the embodiment, the SSG of the resin is 2.168, and the molecular weight level of the resin is difficult to meet the requirements of high-strength products.

CN101125900 discloses a method for preparing suspension-modified polytetrafluoroethylene by adding a second comonomer. The second comonomer used in the method is perfluoropropyl vinyl ether, and the initiator can be alkali metal or alkaline earth metal persulfate, or a redox initiation system. Among them, the addition of perfluoropropyl vinyl ether adopts the method of vacuum suction, which avoids the use of dispersants. However, there are resins with low molecular weight, poor tensile properties, and low production efficiency.

Disclosed in CN1464595A is a method for preparing high-molecular-weight tetrafluororesin in the presence of terpenes. In this patent, the method of dispersion polymerization is adopted. The SSG range of the obtained resin is 2.163-2.173. The ammonium perfluorooctanoate used in dispersion polymerization is dispersed Resin is currently restricted for use, and its emission poses a threat to the environment. The molecular weight of the resin is low, and it is difficult to meet the application in high-strength demand occasions.

In view of this, it is necessary to provide a new polytetrafluoroethylene suspension resin and a preparation method thereof.

Contents of the invention

The first object of the present invention is to provide a kind of preparation method of polytetrafluoroethylene suspension resin, and specific technical scheme is: suspension polymerization reaction of tetrafluoroethylene monomer takes place under the effect of free radical initiator, molecular weight promoter, promptly obtains ;

Wherein, the molecular weight accelerator is perfluorobutylethylene.

The preparation method of the present invention uses water as the medium, and preferably, the amount of water accounts for 50-70% of the volume of the reaction vessel. The water is preferably deionized water.

Preferably, the concentration of the molecular weight promoter relative to water is 50-250 ppm.

The purpose of adding the molecular weight accelerator in the suspension polymerization reaction of the present invention is to realize the connection between polytetrafluoroethylene molecular chains through the double bond on the molecular chain of the accelerator, so as to increase the molecular weight of the suspension resin. The ultra-high molecular weight helps to improve the intrinsic physical properties of the resin, and the products prepared from this resin have the advantages of high strength and excellent performance.

Preferably, the free radical initiator is a system consisting of an oxidizing agent and a reducing agent.

Wherein, the oxidant is selected from one or more of alkali metal persulfates, potassium permanganate, and potassium bromate. The alkali metal persulfate is selected from one or more of ammonium persulfate, sodium persulfate and potassium persulfate. Preferably, the concentration of the oxidizing agent relative to water is 10-50 ppm.

Wherein, the reducing agent is selected from one or more of ferrous sulfate, sulfite, and oxalic acid. The sulfite is selected from one or more of sodium sulfite and potassium sulfite. Preferably, the reducing agent is used in an amount of 1-5 ppm relative to water.

Most preferably, the free radical initiators used in the present invention are ammonium persulfate and sodium sulfite.

Preferably, the feeding amount of the tetrafluoroethylene monomer is 10-15% of the water consumption.

Preferably, the temperature of the suspension polymerization reaction is 18-38°C, more preferably 20-30°C.

Preferably, the pressure of the suspension polymerization reaction is 0.5-1.5 MPa, more preferably 0.8-1.2 MPa.

As a preferred technical solution of the present invention, the above-mentioned preparation method specifically includes: adding water accounting for 50-70% of the volume of the reaction vessel into the reaction vessel, and then adding an oxidizing agent, a reducing agent, and a molecular weight promoter so that the concentrations of the three relative to the water 10-50ppm, 1-5ppm, 50-250ppm respectively, exhaust the air in the system, feed tetrafluoroethylene monomer into the reaction vessel to maintain the system pressure at 0.5-1.5MPa, and carry out suspension polymerization at 18-38°C , that is.

As a better technical solution of the present invention, the above-mentioned preparation method specifically includes: adding water accounting for 50-70% of the volume of the reaction vessel into the reaction vessel, then adding ammonium persulfate, sodium sulfite, and a molecular weight accelerator therein, so that the three are relatively The concentration of water is 10-50ppm, 1-5ppm, 50-250ppm respectively, the air in the system is discharged, tetrafluoroethylene monomer is passed into the reaction vessel to maintain the system pressure at 0.8-1.2MPa, and the process is carried out at 20-30°C Suspension polymerization, that is.

Wherein, the air in the system is removed by replacing with an inert gas, preferably the oxygen content in the system is ≤20ppm.

Above-mentioned reaction also comprises the step of carrying out post-processing after reaction finishes, and described post-processing is known to those skilled in the art, and generally speaking, described post-processing comprises reclaiming unreacted tetrafluoroethylene monomer in reaction vessel, to gained resin The steps of boiling, grinding, smashing, washing, drying and pulverizing are carried out.

Wherein, preferably, the boiling temperature is 85-95° C., and the boiling time is 0.5-1.5 hours. Preferably, the drying temperature is 140-200°C. It is better to control the average particle size of the resin to be 15-300 μm in the pulverization.

In the invention, perfluorobutylethylene is added in the suspension polymerization reaction, and the SSG range of the produced suspension resin is 2.140-2.159, the average molecular weight range is 10.122-15.654 million, and the strength is excellent. This kind of resin can be used to process molded products with excellent performance, neatness, smoothness and high strength, which can be used in mechanical equipment, building bridges, anti-corrosion materials, etc. Simultaneously, the production process of the present invention has a stable operation process and is easy for industrialized production.

On the basis of conforming to common knowledge in the field, the above-mentioned preferred conditions can be combined with each other to obtain preferred embodiments of the present invention.

Detailed ways

The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. The raw materials or reagents involved in the examples are all known products, and the operations involved are conventional operations in the art unless otherwise specified.

Example 1

Add 30L of deionized water and 0.6g of ammonium persulfate to the cleaned 50L autoclave, seal the reactor, start stirring, and evacuate the reactor. When the oxygen content is less than or equal to 20ppm, it is qualified. Put tetrafluoroethylene monomer (TFE monomer) to bring the pressure in the kettle to 0.5MPa, then raise the temperature of the reactor to 20°C, add 0.075g of oxalic acid and 1.5g of perfluorobutylethylene into the reactor, and fill the tank with TFE body until the pressure in the kettle reaches 0.8MPa, and the reaction starts. During the reaction, the monomer was continuously replenished to maintain a constant pressure in the kettle. When the feeding amount of TFE monomer reaches 4kg, the reaction is finished, the stirring is stopped, the monomer in the kettle is recovered and evacuated, replaced, and emptied. And other post-processing procedures to obtain resin products with an average particle size of 30-40 μm.

Example 2

Add 35L of deionized water and 1.05g of sodium persulfate to the cleaned 50L autoclave, seal the reactor, start stirring, and evacuate the reactor, when the oxygen content is less than or equal to 20ppm, it is qualified, and then fill the reactor with Add TFE monomer so that the pressure in the kettle reaches 0.5MPa, then raise the temperature of the reactor to 22°C, add 0.12g of sodium sulfite and 8.7g of perfluorobutylethylene into the reactor, and fill in TFE monomer until the pressure in the kettle reaches 1.2 MPa, start to react. During the reaction, the monomer was continuously replenished to maintain a constant pressure in the kettle. When the feeding amount of TFE monomer reaches 4kg, the reaction is finished, the stirring is stopped, the monomer in the kettle is recovered and evacuated, replaced, and emptied. And other post-processing procedures to obtain resin products with an average particle size of 30-40 μm.

Example 3

Add 30L of deionized water and 0.7g of potassium permanganate to the cleaned 50L autoclave, seal the reactor, start stirring, and evacuate the reactor, when the oxygen content is less than or equal to 20ppm, it is qualified. Fill in TFE monomer to make the pressure in the kettle reach 0.5MPa, then raise the temperature of the reactor to 30°C, add 0.085g of potassium sulfite and 4.5g of perfluorobutylethylene into the reactor, and fill the tank with TFE monomer Pressure to 1.0MPa, start the reaction. During the reaction, the monomer was continuously replenished to maintain a constant pressure in the kettle. When the feeding amount of TFE monomer reaches 4kg, the reaction is finished, the stirring is stopped, the monomer in the kettle is recovered and evacuated, replaced, and emptied. And other post-processing procedures to obtain resin products with an average particle size of 30-40 μm.

Example 4

Add 30L of deionized water and 0.9g of potassium bromate to the cleaned 50L autoclave, seal the reactor, start stirring, and evacuate the reactor, when the oxygen content is less than or equal to 20ppm, it is qualified, and then fill the reactor with TFE The monomer makes the pressure in the kettle to 0.5MPa, then the temperature of the reactor is raised to 20°C, 0.095g of ferrous sulfate and 5.5g of perfluorobutylethylene are added to the reactor, and TFE monomer is charged until the pressure in the reactor reaches 0.8 MPa, start to react. During the reaction, the monomer was continuously replenished to maintain a constant pressure in the kettle. When the feeding amount of TFE monomer reaches 4kg, the reaction is finished, the stirring is stopped, the monomer in the kettle is recovered and evacuated, replaced, and emptied. And other post-processing procedures to obtain resin products with an average particle size of 260-300 μm.

Comparative example 1

Add 30L of deionized water and 0.7g of ammonium persulfate to the cleaned 50L autoclave, seal the reaction kettle, start stirring, and evacuate the reaction kettle. When the oxygen content is ≤ 20ppm, it is qualified. Add TFE monomer to bring the pressure in the kettle to 0.5MPa, then raise the temperature of the reactor to 20°C, add 0.085g of sodium sulfite to the reactor, fill in the TFE monomer until the pressure in the kettle reaches 1.2MPa, and start the reaction. During the reaction, the monomer was continuously replenished to maintain a constant pressure in the kettle. When the feeding amount of TFE monomer reaches 4kg, the reaction is finished, the stirring is stopped, the monomer in the kettle is recovered and evacuated, replaced, and emptied. And other post-processing procedures to obtain resin products with an average particle size of 30-40 μm.

Comparative example 2

Using the tetrafluoroethylene polymerization method disclosed in Chinese Patent Publication No. CN1147262A, the obtained tetrafluoroemulsion is subjected to post-treatment procedures such as boiling, grinding, crushing, washing, drying, and crushing to obtain an average particle size of 30 to 40 μm. Resin products.

Table 1 lists the performance parameters of the polytetrafluoroethylene prepared in Examples 1-4 and Comparative Examples 1 and 2.

Table 1: Embodiment 1-4, the product performance parameter of comparative example 1 and 2

It can be seen from the above data that the polytetrafluoroethylene suspension resin prepared by the present invention has a smaller SSG value, a larger molecular weight, and good tensile strength and elongation at break.

Although, the present invention has been described in detail with general description, specific implementation and test above, but on the basis of the present invention, some modifications or improvements can be made to it, which will be obvious to those skilled in the art . Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (10)

1. A kind of 1. preparation method of polytetrafluoroethylsuspending suspending resin, it is characterised in that：Tetrafluoroethylene monomer radical initiator, Suspension polymerization occurs in the presence of molecular weight accelerator, produces；Wherein, the molecular weight accelerator is perfluoro butyl second Alkene.
2. 2. preparation method according to claim 1, it is characterised in that：The suspension polymerization is described using water as medium Molecular weight accelerator is 50-250ppm relative to the concentration of water.
3. 3. preparation method according to claim 1 or 2, it is characterised in that：The radical initiator be by oxidant and The system of reducing agent composition.
4. 4. preparation method according to claim 3, it is characterised in that：Persulfate of the oxidant selected from alkali metal, One or more in potassium permanganate, potassium bromate；

   Preferably, the dosage of the oxidant is 10-50ppm relative to the concentration of water.
5. 5. the preparation method according to claim 3 or 4, it is characterised in that：The reducing agent is selected from ferrous sulfate, sulfurous acid One or more in salt, oxalic acid；

   Preferably, the dosage of the reducing agent is 1-5ppm relative to the concentration of water.
6. 6. preparation method according to claim 5, it is characterised in that：The radical initiator is ammonium persulfate and sulfurous Sour sodium.
7. 7. according to the preparation method described in claim 1 or 2 or 4 or 6, it is characterised in that：The temperature of the suspension polymerization For 18-38 DEG C, preferably 20-30 DEG C.
8. 8. preparation method according to claim 7, it is characterised in that：The pressure of the suspension polymerization is 0.5- 1.5MPa, preferably 0.8-1.2MPa.
9. 9. preparation method according to claim 1, it is characterised in that：Added into reaction vessel and account for reaction vessel volume 50-70% water, oxidant, reducing agent, molecular weight accelerator are then added, make three relative to the concentration of water be respectively 10- 50ppm, 1-5ppm, 50-250ppm, discharge the air in reaction system, and being passed through tetrafluoroethylene monomer into reaction vessel makes body It is that pressure maintains 0.5-1.5MPa, carries out suspension polymerization in 18-38 DEG C, produce.
10. 10. the polytetrafluoroethylsuspending suspending resin that any one of the claim 1-9 preparation methods obtain.