阅读说明：本技术 含氟聚合物的无皂制备方法 (Soap-free preparation method of fluorine-containing polymer ) 是由 唐妮 王汉利 杜延华 吕鹏程 刘德鹏 王梦琪 于 2020-12-31 设计创作，主要内容包括：本发明涉及含氟聚合物技术领域,具体涉及一种含氟聚合物的无皂制备方法。所述的含氟聚合物的无皂制备方法,以水为溶剂,以含氟单体和全氟乙烯基醚为聚合单体,在气态链转移助剂和无机引发剂的共同作用下,反应得到含氟聚合物。本发明的含氟聚合物的无皂制备方法,获得的聚合乳液可通过物理机械方式实现固液分离,固体免除洗涤可直接烘干,获得成品,有效降低氟聚合物的制造成本并且有利于环境保护,制成的产品助剂杂质含量小于1ppm。(The invention relates to the technical field of fluorine-containing polymers, in particular to a soap-free preparation method of a fluorine-containing polymer. The soap-free preparation method of the fluorine-containing polymer takes water as a solvent, takes a fluorine-containing monomer and perfluorovinyl ether as polymerization monomers, and reacts under the combined action of a gaseous chain transfer assistant and an inorganic initiator to obtain the fluorine-containing polymer. According to the soap-free preparation method of the fluorine-containing polymer, the obtained polymerization emulsion can realize solid-liquid separation in a physical mechanical mode, the solid can be directly dried without washing, a finished product is obtained, the manufacturing cost of the fluorine-containing polymer is effectively reduced, the environment protection is facilitated, and the impurity content of the prepared product auxiliary agent is less than 1 ppm.)

1. A soap-free preparation method of a fluorine-containing polymer is characterized by comprising the following steps: the fluorine-containing polymer is obtained by reacting water as a solvent and a fluorine-containing monomer and perfluorovinyl ether as polymerization monomers under the combined action of a gaseous chain transfer aid and an inorganic initiator.

2. The soap-free process for producing a fluoropolymer according to claim 1, wherein: the method comprises the following steps:

(1) adding water into a reaction kettle to remove oxygen, adding one or more of perfluorovinyl ether and a gaseous chain transfer assistant, and uniformly stirring;

(2) and (2) heating the temperature in the reaction kettle to 65-90 ℃, adding the fluorine-containing monomer until the pressure of the reaction kettle is 3.0-6.0MPa, continuously adding the inorganic initiator to carry out polymerization reaction, continuously adding the fluorine-containing monomer in the reaction process to control the pressure of the reaction kettle to be 3.0-6.0MPa, and stopping the reaction when the reaction amount of the fluorine-containing monomer reaches the designed weight to obtain the fluorine-containing polymer.

3. The soap-free production method of a fluorine-containing polymer according to claim 1 or 2, characterized in that: the perfluorovinyl ether has the structure CF₂Wherein Rf is-CF₃，-CF₂CF₃or-CF₂CF₂CF₃。

4. The soap-free production method of a fluorine-containing polymer according to claim 1 or 2, characterized in that: the structure of the gaseous chain transfer auxiliary agent is C_nH_xF_(2n+2-x)Wherein n is an integer of 1-3, and the value of x is an integer of x being more than or equal to 1 and less than or equal to 2n + 2.

5. The soap-free production method of a fluorine-containing polymer according to claim 1 or 2, characterized in that: the inorganic initiator is persulfate.

6. The soap-free production method of a fluorine-containing polymer according to claim 1 or 2, characterized in that: the perfluorovinyl ether is used in an amount of 0.05 to 1 wt% based on the total weight of the polymerized monomers.

7. The soap-free production method of a fluorine-containing polymer according to claim 1 or 2, characterized in that: the amount of the gaseous chain transfer aid is 0.005-0.5 wt% of the total weight of the polymerized monomers.

8. The soap-free production method of a fluorine-containing polymer according to claim 1 or 2, characterized in that: the inorganic initiator is used in an amount of 0.001 to 0.5 wt% based on the total weight of the polymerized monomers.

9. The soap-free process for producing a fluoropolymer according to claim 2, wherein: in the step (1), oxygen is removed until the oxygen content is less than or equal to 20 ppm.

10. The soap-free process for producing a fluoropolymer according to claim 2, wherein: in the step (2), the initiator is continuously added for 60-90 min.

Technical Field

The invention relates to the technical field of fluorine-containing polymers, in particular to a soap-free preparation method of a fluorine-containing polymer.

Background

Fluoropolymers are polymers having a fluorinated backbone, and have been widely used in the military industry and new energy fields such as chemical industry, electronics, automobiles, aerospace and the like due to their excellent heat resistance, chemical resistance, weather resistance, ultraviolet stability and the like.

Commercial processes for the production of fluoropolymers include emulsion polymerization of one or more fluorinated monomers, containing monomers, dispersants, media and important ingredients such as initiators and chain transfer aids, which are removed by multiple washes at the end of the polymerization. Although the auxiliary agent can be mostly removed by the processes of post-treatment, multiple washing and the like, the complete removal is difficult. The inclusion of undeleted coagents can affect the polymer properties, while the addition and removal of coagents also adds complexity to the process and increases the cost of manufacture. And the frequently used fluorinated surfactants, including perfluorooctanoic acid and its salts, have caused environmental concerns, can accumulate in vivo, and are beginning to be banned globally.

In this regard, patents WO2018/167190 and CN110724222 successively select surface active auxiliaries which are environmentally friendly, and as a result, it may take a lot of time to verify the product performance and the biological effect of the auxiliaries of the new system, and the solution after washing needs further treatment to be discharged, and there is still a certain adverse effect on the environment.

The polymerization induced self-assembly (PISA) concept was proposed by Hawkett (see C.J.Ferguson, R.J.Hughes, D.Nguyen, Macromolecules,2005,38, 2191-.

The CN201310744861.6 invention adopts a soap-free mode to successfully polymerize polyvinylidene fluoride resin to be applied to the field of lithium batteries, and because various liquid phase auxiliaries are still adopted, certain waste liquid is formed, the components are complex, the separation treatment and the discharge are not easy, and the cost and the process are not obviously improved.

Disclosure of Invention

The invention aims to provide a soap-free preparation method of a fluorine-containing polymer, solid-liquid separation of a polymerization emulsion obtained by the method can be realized by a physical mechanical mode, washing of solids is avoided, direct drying can be realized, a finished product is obtained, the manufacturing cost of the fluorine-containing polymer is effectively reduced, environmental protection is facilitated, and the impurity content of an auxiliary agent of the prepared product is less than 1 ppm.

The soap-free preparation method of the fluorine-containing polymer takes water as a solvent, takes a fluorine-containing monomer and perfluorovinyl ether as polymerization monomers, and reacts under the combined action of a gaseous chain transfer assistant and an inorganic initiator to obtain the fluorine-containing polymer.

Specifically, the soap-free preparation method of the fluorine-containing polymer comprises the following steps:

(1) adding water into a reaction kettle, deoxidizing until the oxygen content is less than or equal to 20ppm, adding one or more of perfluorovinyl ether and a gaseous chain transfer assistant, and uniformly stirring;

(2) heating the temperature in the reaction kettle to 65-90 ℃, adding the fluorine-containing monomer until the pressure of the reaction kettle is 3.0-6.0MPa, continuously adding the inorganic initiator for 60-90min, carrying out polymerization reaction, continuously adding the fluorine-containing monomer during the reaction process to control the pressure of the reaction kettle to be 3.0-6.0MPa, stopping the reaction when the reaction amount of the fluorine-containing monomer reaches the designed weight, recovering the unreacted monomer, separating fluorine-containing polymer, and drying.

Wherein, the fluorine-containing monomer includes but is not limited to vinylidene fluoride, ethylene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene and hexafluoropropylene.

The perfluorovinyl ether has the structure CF₂Wherein Rf is-CF₃，-CF₂CF₃or-CF₂CF₂CF₃。

The perfluorovinyl ether is used in an amount of 0.05 to 1 wt% based on the total weight of the polymerized monomers.

The structure of the gaseous chain transfer auxiliary agent is C_nH_xF_(2n+2-x)Wherein n is an integer of 1-3, and the value of x is an integer of x being more than or equal to 1 and less than or equal to 2n + 2.

The amount of the gaseous chain transfer aid is 0.005-0.5 wt% of the total weight of the polymerized monomers.

The inorganic initiator is persulfate, preferably potassium persulfate and ammonium persulfate.

The inorganic initiator is used in an amount of 0.001 to 0.5 wt% based on the total weight of the polymerized monomers.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention firstly generates a large amount of low polymer with a certain length of hydrophobic chain segment in water phase, wherein the chain contains hydrophilic ether bond and initiator fragment-SO^4-Groups which give the oligomers themselves the function of surfactants, which when they reach a critical micelle concentration form oligomeric micelles alongside one another and solubilize the monomers, initiating the reaction and thus the nucleation;

(2) according to the invention, an inorganic initiator and a gaseous chain transfer auxiliary agent are used as a telomerization agent, the prepared emulsion is separated to obtain residual inorganic initiator and a water phase, the gaseous chain transfer auxiliary agent is recycled, and the fluorine-containing polymer can be directly dried without being washed by water;

(3) the invention has emulsification effect by introducing the polymerization monomer containing ether bond and inorganic initiator, and simultaneously adopts the gaseous chain transfer auxiliary agent, thus avoiding the defects that expensive surface active auxiliary agent must be added in the conventional suspension and emulsion polymerization and the washing process is complicated, the process operation is simple, the water consumption and production time per ton are less than the conventional mode, the process is efficient and economic, and the impurity content of the prepared product auxiliary agent is less than 1 ppm.

Detailed Description

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. Any obvious modifications or alterations to the present invention, based on the teachings of the present invention, which are obvious to those skilled in the art, should also be considered as the scope of the present invention.

Example 1

Adding 6L of deionized water into a 10L horizontal reaction kettle, and purging with nitrogen for 30min until the oxygen content in the reaction kettle is less than 20 ppm; preparing 250g of ammonium persulfate aqueous solution with the mass fraction of 2% in total for later use; adding 0.5g of perfluoroethyl vinyl ether and 5g of pentafluoroethane into a polymerization kettle, then starting stirring, raising the temperature in the reaction kettle to 65 ℃, adding a vinylidene fluoride monomer until the pressure in the reaction kettle reaches 6MPa, and adding an initiator at a constant speed by using a metering pump for 60 min. Continuously adding vinylidene fluoride monomer to maintain the pressure until the total amount of the reaction monomer reaches 1kg, stopping the reaction, and copolymerizing for 155 min. Recovering unreacted monomer, venting to normal pressure, cooling, separating the product, drying and testing.

Example 2

Adding 6L of deionized water into a 10L horizontal reaction kettle, and purging with nitrogen for 30min until the oxygen content in the reaction kettle is less than 20 ppm; preparing 250g of ammonium persulfate aqueous solution with the mass fraction of 0.4% in total for later use; adding 2.5g of perfluoroethyl vinyl ether and 0.3g of difluoroethane into a polymerization kettle, then starting stirring, raising the temperature in the reaction kettle to 82 ℃, adding a vinylidene fluoride monomer until the pressure in the reaction kettle reaches 3MPa, adding an initiator at a constant speed by using a metering pump, and adding for 75 min. Continuously adding vinylidene fluoride monomer, keeping the pressure until the total amount of the reaction monomer reaches 1kg, stopping the reaction, and copolymerizing for 187 min. Recovering unreacted monomer, venting to normal pressure, cooling, separating the product, drying and testing.

Example 3

Adding 6L of deionized water into a 10L horizontal reaction kettle, and purging with nitrogen for 30min until the oxygen content in the reaction kettle is less than 20 ppm; preparing 250g of ammonium persulfate aqueous solution with the mass fraction of 0.04% in total for later use; adding 5g of perfluoroethyl vinyl ether and 0.05g of ethane into a polymerization kettle, then starting stirring, raising the temperature in the reaction kettle to 90 ℃, adding a vinylidene fluoride monomer until the pressure in the reaction kettle reaches 3MPa, and adding an initiator at a constant speed by using a metering pump for 90 min. Continuously adding vinylidene fluoride monomer to keep pressure until the total amount of the reaction monomer reaches 1kg, stopping the reaction, and copolymerizing for 199 min. Recovering unreacted monomer, venting to normal pressure, cooling, separating the product, drying and testing.

Comparative example 1

Adding 6L of deionized water into a 10L horizontal reaction kettle, and purging with nitrogen for 30min until the oxygen content in the reaction kettle is less than 20 ppm; preparing 250g of ammonium persulfate aqueous solution with the mass fraction of 2% in total for later use; adding 10g of ammonium perfluorooctanoate dispersing agent, 0.5g of perfluoroethyl vinyl ether and 0.6g of ethyl acetate into a polymerization kettle, then starting stirring, raising the temperature in the reaction kettle to 90 ℃, adding vinylidene fluoride monomer until the pressure in the reaction kettle reaches 3MPa, adding an initiator at a constant speed by using a metering pump, and adding for 60 min. Continuously adding vinylidene fluoride monomer to maintain the pressure until the total amount of the reaction monomer reaches 1kg, stopping the reaction, and copolymerizing for 152 min. Recovering unreacted monomer, venting to normal pressure, cooling, separating the product, drying and testing.

Comparative example 2

Polymerization was carried out according to the method of comparative example 1 for 159 min. Recovering unreacted monomers, venting to normal pressure, cooling, separating products, adding 5L of pure water into a washing barrel, stirring for 20min, and centrifuging for 20min for separation; the materials are washed for 6 times in such a circulating way, dried and tested.

Comparative example 3

Adding 6L of deionized water into a 10L horizontal reaction kettle, and purging with nitrogen for 30min until the oxygen content in the reaction kettle is less than 20 ppm; preparing 250g of ammonium persulfate aqueous solution with the mass fraction of 0.4% in total for later use; adding 2.5g of perfluoroethyl vinyl ether and 0.3g of ethyl acetate into a polymerization kettle, then starting stirring, raising the temperature in the reaction kettle to 90 ℃, adding a vinylidene fluoride monomer until the pressure in the reaction kettle reaches 3MPa, adding an initiator at a constant speed by using a metering pump, and adding for 75 min. Continuously adding vinylidene fluoride monomer to maintain the pressure until the total amount of the reaction monomer reaches 1kg, stopping the reaction, and copolymerizing for 178 min. Recovering unreacted monomer, venting to normal pressure, cooling, separating the product, drying and testing.

Comparative example 4

The polymerization was carried out according to the method of comparative example 3 for 173 min. Recovering unreacted monomers, venting to normal pressure, cooling, separating products, adding 5L of pure water into a washing barrel, stirring for 20min, and centrifuging for 20min for separation; the materials are washed for 3 times in such a circulating way, dried and tested.

Reference CEN/TS 15968: 2010, using LC-MS or LC-MS-MS, the polymers prepared in examples 1-3 and comparative examples 1-4 were analyzed to determine the content of organic auxiliary. The test results are shown in table 1, wherein:

the detection limit of the method is 1 mg/kg;

ND ═ undetected (< MDL);

the water consumption of the ton product only calculates the consumption of the polymerization and post-treatment process;

the ton product time was only calculated for the polymerization and work-up process.

TABLE 1 comparison of Polymer production Process and Properties

Experiment number	Ton Water consumption (t)	Ton product time (h)	Impurity content (ppm)
				Example 1	60	2.58	ND
Example 2	60	3.12	ND
				Example 3	60	3.31	ND
Comparative example 1	60	2.53	977
				Comparative example 2	360	6.65	＜20
Comparative example 3	60	2.96	264
				Comparative example 4	210	4.88	＜20

As can be seen from Table 1, when the impurities meet the requirement of < 20ppm or less, the water consumption and the time consumption for preparing the polymer ton products of examples 1-3 are obviously reduced, and the impurity content is obviously reduced.