Preparation method of hexafluoropropylene oxide oligomer

Abstract

The invention belongs to the field of fluorine chemical industry, and particularly relates to a preparation method of a hexafluoropropylene oxide oligomer, which comprises the following steps: adding a solvent and a catalyst into a stirring reactor with a proper length-diameter ratio, and introducing hexafluoropropylene oxide in a stirring state; a valve is arranged at the bottom of the stirring reactor, and when the fluorine phase liquid level at the bottom of the stirring reactor is increased to a certain height, the bottom valve is opened; controlling the bottom liquid outlet rate to keep the height of the reaction liquid stable; and after the reaction is finished, collecting a component flowing out of a valve at the bottom, namely the hexafluoropropylene oxide oligomer. The method has the beneficial effects that the operation is simple, the product is easy to separate from the solvent and the catalyst, and large-scale production is easy.

Description

Technical Field

[0001] The invention belongs to the field of fluorine chemical industry, and particularly relates to a method for preparing hexafluoropropylene oxide oligomer. Background Art

[0002] Hexafluoropropylene oxide oligomers primarily refer to hexafluoropropylene oxide oligomers with a degree of polymerization below 5. These polymers contain only the elements C, F, and O in their molecular chains. They are colorless, transparent liquids at room temperature. After end-group stabilization, they possess excellent properties such as thermal stability, chemical inertness, radiation resistance, and high- and low-temperature resistance. They are important fluorinated organic intermediates. For example, perfluorinated fluids synthesized from hexafluoropropylene oxide tetramers and pentamers can be used as immersion coolants and high- and low-temperature test fluids. Perfluoro-n-propyl vinyl ether synthesized from hexafluoropropylene oxide dimers is an important modifying monomer for soluble polytetrafluoroethylene, and hexafluoropropylene oxide trimers can be used to synthesize fluorocarbon surfactants. Currently, the primary method for synthesizing hexafluoropropylene oxide oligomers is anionic polymerization of hexafluoropropylene oxide. The main production process is a batch operation, in which a solvent and catalyst are added to a reactor, followed by metered introduction of hexafluoropropylene oxide. The reactor is then allowed to stand and separate to remove the hexafluoropropylene oxide oligomers, and hexafluoropropylene oxide is then introduced again, repeating this process. Intermittent operation requires more manual operations, and static liquid separation takes a long time, which will ultimately lead to increased production costs in the industrial production process. Summary of the Invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing hexafluoropropylene oxide oligomers.

[0004] To achieve the above object, the technical solution adopted by the present invention is:

[0005] A continuous preparation method for hexafluoropropylene oxide oligomers comprises the following steps: adding a solvent and a catalyst into a stirred reactor with a suitable aspect ratio, and introducing hexafluoropropylene oxide under stirring; providing a valve at the bottom of the stirred reactor, and opening the bottom valve when the fluorine phase liquid level at the bottom of the stirred reactor reaches a certain height; controlling the bottom liquid discharge rate to maintain a stable height of the reaction liquid; and after the reaction is completed, collecting the components flowing out of the bottom valve to obtain the hexafluoropropylene oxide oligomers.

[0006] The length-to-diameter ratio of the stirred reactor is 3:1-20:1, preferably 5:1-8:1.

[0007] The volume of the stirred reactor is 1-20 L, preferably 5 L.

[0008] The stirring blade in the stirred reactor is at least 25 cm away from the bottom of the reactor.

[0009] The fluorine phase liquid level rises to 10-20 cm; preferably 15 mm, open the bottom valve.

[0010] The feeding rate of hexafluoropropylene oxide is 10-100 g / h; preferably 50-65 g / h.

[0011] The catalyst is N,N,N,N,-tetramethylmethylenediamine or tetraethylammonium bromide, and the added amount of the catalyst is 0.1%-5% of the solvent mass, preferably 0.5%.

[0012] The solvent is an aprotic solvent; preferably at least one of tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether or acetonitrile.

[0013] The distance between the hexafluoropropylene oxide inlet pipe and the stirring paddle is 0.5-2 cm, preferably 1 cm.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The embodiment of the present application employs a method of adding a solvent and a catalyst to a stirred reactor with an appropriate aspect ratio, introducing hexafluoropropylene oxide (HFPO) under stirring, and controlling the outflow rate through a bottom valve to simultaneously discharge the HFPO oligomers through ring-opening polymerization of HFPO, thereby achieving a continuous HFPO polymerization process. The present invention has the advantages of simple operation, easy separation of the product from the solvent and catalyst, and ease of scale-up production. DETAILED DESCRIPTION

[0016] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention is further described in detail below with reference to the embodiments.

[0017] Example 1

[0018] This embodiment provides a method for continuously preparing hexafluoropropylene oxide oligomers. 2 L of tetraethylene glycol dimethyl ether (TTETRA) solvent was added to a 5 L stirred reactor with an aspect ratio of 8, followed by 10 mL of N,N,N,N-tetramethylmethylenediamine (N,N,N,N-tetramethylmethylenediamine) catalyst. A valve was provided at the bottom of the stirred reactor, a stirring paddle was 25 cm from the bottom, and a hexafluoropropylene oxide inlet pipe was 2 cm from the stirring paddle.

[0019] After the solvent and catalyst are evenly stirred, hexafluoropropylene oxide is introduced at a rate of 65 g / h. When the fluorine phase liquid level at the bottom of the reactor reaches 15 cm, the bottom valve of the reactor is opened and the bottom liquid discharge rate is controlled to keep the reaction liquid level stable.

[0020] After a period of reaction, the introduction of hexafluoropropylene oxide was stopped, the fluorine phase liquid in the reactor was drained, a total of 678 g of hexafluoropropylene oxide was introduced, 670 g of the fluorine phase was collected, and the obtained product was subjected to gas chromatography analysis. The distribution of the obtained hexafluoropropylene oxide oligomers is shown in Table 1;

[0021] Table 1

[0022] Degree of polymerization (n) 0 1 2 3 4 Proportion(%) 1.2 18.9 48.6 27.8 3.5

[0023] Example 2

[0024] This embodiment provides a continuous preparation method of hexafluoropropylene oxide oligomers. 2 L of diethylene glycol dimethyl ether (DME) solvent was added to a 5 L stirred reactor with an aspect ratio of 8, followed by 10 mL of N,N,N,N-tetramethylmethylenediamine (N-tetramethylmethylenediamine) catalyst. A valve was provided at the bottom of the stirred reactor, a stirring paddle was 25 cm from the bottom, and a hexafluoropropylene oxide inlet pipe was 2 cm from the stirring paddle.

[0025] After the solvent and catalyst are evenly stirred, hexafluoropropylene oxide is introduced at a rate of 65 g / h. When the fluorine phase liquid level at the bottom of the reactor reaches 15 cm, the bottom valve of the reactor is opened and the bottom liquid discharge rate is controlled to keep the reaction liquid level stable.

[0026] After a period of reaction, the introduction of hexafluoropropylene oxide was stopped, the fluorine phase liquid in the reactor was drained, a total of 324 g of hexafluoropropylene oxide was introduced, 320 g of the fluorine phase was collected, and the obtained product was subjected to gas chromatography analysis. The distribution of the obtained hexafluoropropylene oxide oligomers is shown in Table 2;

[0027] Table 2

[0028] Degree of polymerization (n) 0 1 2 3 4 Proportion(%) 3.2 48.6 28.9 16.0 0

[0029] Example 3

[0030] This embodiment provides a method for continuously preparing hexafluoropropylene oxide oligomers. 2 L of acetonitrile solvent is added to a 5 L stirred reactor with an aspect ratio of 8, and then 10 mL of N,N,N,N-tetramethylmethylenediamine catalyst is added. A valve is provided at the bottom of the stirred reactor, a stirring paddle is 25 cm away from the bottom, and a hexafluoropropylene oxide inlet pipe is 2 cm away from the stirring paddle.

[0031] After the solvent and catalyst are evenly stirred, hexafluoropropylene oxide is introduced at a rate of 65 g / h. When the fluorine phase liquid level at the bottom of the reactor reaches 15 cm, the bottom valve of the reactor is opened and the bottom liquid discharge rate is controlled to keep the reaction liquid level stable.

[0032] After a period of reaction, the introduction of hexafluoropropylene oxide was stopped, the fluorine phase liquid in the reactor was drained, a total of 342 g of hexafluoropropylene oxide was introduced, 339 g of the fluorine phase was collected, and the obtained product was subjected to gas chromatography analysis. The distribution of the obtained hexafluoropropylene oxide oligomers is shown in Table 3;

[0033] Table 3

[0034] Degree of polymerization (n) 0 1 2 3 4 Proportion(%) 9.2 82.6 8.2 0 0

[0035] Examples 1-3 use stirred reactors with the same aspect ratio. Studies have shown that under the conditions of this aspect ratio, combined with the position of the stirring paddle and the hexafluoropropylene oxide inlet pipe, the separation of the product fluorine phase can be achieved, thereby enabling continuous production. Studies have shown that separation can be achieved when the aspect ratio is 3:1-20:1, preferably 5:1-8:1. Under the conditions of a fixed aspect ratio, different solvents have a greater influence on the type of polymerization product, and the type of product can be controlled by controlling the solvent.

[0036] Example 4

[0037] This embodiment provides a continuous preparation method of hexafluoropropylene oxide oligomers. 2L of tetraethylene glycol dimethyl ether is added to a 5L stirred reactor with an aspect ratio of 8, followed by 10g of tetraethylammonium bromide. A liquid outlet is provided at the bottom of the reactor, a stirring paddle is 30cm away from the bottom, and a hexafluoropropylene oxide inlet pipe is 1cm away from the stirring paddle. After the solvent and catalyst are evenly stirred, hexafluoropropylene oxide is introduced at a rate of 65g / h. When the fluorine phase liquid level at the bottom of the reactor reaches 15cm, the bottom valve of the reactor is opened to control the bottom liquid discharge rate so that the reaction liquid level remains stable. After a period of reaction, the introduction of hexafluoropropylene oxide is stopped, the fluorine phase liquid in the reactor is drained, a total of 328g of hexafluoropropylene oxide is introduced, 325g of the fluorine phase is collected, and the obtained product is subjected to gas chromatography analysis. The distribution of the obtained hexafluoropropylene oxide oligomers is shown in Table 4.

[0038] Table 4

[0039] Degree of polymerization (n) 0 1 2 3 4 Proportion(%) 0.8 18.6 28.9 42.3 9.4

[0040] Similarly, it can be seen from Example 4 that changing factors such as the type of catalyst, the distance between the stirring blades and the position of the hexafluoropropylene oxide inlet pipe also has a certain impact on the polymer, but it can still meet the requirements of continuous production.

[0041] As can be seen from the above examples, the embodiments of the present application employ a method of adding a solvent and a catalyst to a stirred reactor with an appropriate aspect ratio, introducing hexafluoropropylene oxide under stirring, and controlling the outflow rate of a bottom valve to achieve the simultaneous ring-opening polymerization of hexafluoropropylene oxide into oligomers while discharging the hexafluoropropylene oxide oligomers, thereby achieving a continuous polymerization process of hexafluoropropylene oxide. The present invention has the advantages of simple operation, easy separation of the product from the solvent and catalyst, and ease of scale-up production.

[0042] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A continuous preparation method of hexafluoropropylene oxide oligomers, characterized in that: The method comprises the following steps: adding a solvent and a catalyst into a stirred reactor with a suitable length-to-diameter ratio, and introducing hexafluoropropylene oxide under stirring; providing a valve at the bottom of the stirred reactor, and opening the bottom valve when the fluorine phase liquid level at the bottom of the stirred reactor rises to a certain height; controlling the bottom liquid discharge rate to maintain a stable height of the reaction liquid; and after the reaction is completed, collecting the components flowing out of the bottom valve to obtain hexafluoropropylene oxide oligomers.

2. The continuous preparation method of hexafluoropropylene oxide oligomer according to claim 1, characterized in that: The length-to-diameter ratio of the stirred reactor is 3:1-20:1, preferably 5:1-8:

1.

3. The continuous preparation method of hexafluoropropylene oxide oligomer according to claim 1, characterized in that: The volume of the stirred reactor is 1-20 L, preferably 5 L.

4. The method for continuously preparing hexafluoropropylene oxide oligomers according to claim 3, wherein: The stirring blade in the stirred reactor is at least 25 cm away from the bottom of the reactor.

5. The method for continuously preparing hexafluoropropylene oxide oligomers according to claim 3, wherein: The fluorine phase liquid level rises to 10-20 cm; preferably 15 mm, open the bottom valve.

6. The method for continuously preparing hexafluoropropylene oxide oligomers according to claim 1, wherein: The feeding rate of hexafluoropropylene oxide is 10-100 g / h; preferably 50-65 g / h.

7. The continuous preparation method of hexafluoropropylene oxide oligomer according to claim 1, characterized in that: The catalyst is N,N,N,N,-tetramethylmethylenediamine or tetraethylammonium bromide, and the added amount of the catalyst is 0.1%-5% of the solvent mass, preferably 0.5%.

8. The method for continuously preparing hexafluoropropylene oxide oligomers according to claim 1, wherein: The solvent is an aprotic solvent; preferably at least one of tetraethylene glycol dimethyl ether, diethylene glycol dimethyl ether or acetonitrile.

9. The method for continuously preparing hexafluoropropylene oxide oligomers according to claim 1, wherein: The distance between the hexafluoropropylene oxide inlet pipe and the stirring paddle is 0.5-2 cm, preferably 1 cm.