Method for treating trace perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether

Abstract

The invention belongs to the technical field of fluorine chemical industry, and particularly relates to a method for treating trace perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether, which comprises the following steps: treating perfluoropolyether containing trace perfluoropolyether carboxylic acid and / or perfluoropolyether acyl fluoride by using a metal compound, converting the perfluoropolyether carboxylic acid and / or perfluoropolyether acyl fluoride into perfluoropolyether carboxylate, and heating and decomposing the perfluoropolyether carboxylate to form trace olefin; and reacting the fluorinating agent diluted by the protective gas with the formed trace olefin to convert the trace olefin into the perfluoropolyether oil. Compared with the prior art, the method solves the problems that in the prior art, a trace amount of perfluoropolyether acyl fluoride and perfluoropolyether carboxylic acid in perfluoropolyether cannot be fully removed, so that an existing product contains acid and is subjected to acid regurgitation in the using process; according to the scheme, complete decomposition and conversion of perfluoropolyether carboxylic acid can be achieved, meanwhile, olefin is prevented from being formed, and the problems that the product contains acid and the acid regurgitation phenomenon in the follow-up using process is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of fluorine chemical industry, and in particular relates to a method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether. Background Art

[0002] Perfluoropolyether is a colorless and transparent perfluoropolymer material. Perfluoropolyether basically contains only CF bonds but no CH bonds. The fluorine atoms with stronger negative charge make the attraction between molecules smaller, so perfluoropolyether has smaller surface tension and also has excellent heat resistance, corrosion resistance, low volatility, high flame retardancy, compatibility, etc. Therefore, it is widely used in chemical, electronic, electrical, mechanical, aerospace and other fields.

[0003] The synthesis process of perfluoropolyether is a complicated process. First, it is necessary to make perfluoroalkylene oxide or perfluoroalkylene oxide undergo polymerization reaction (such as anionic polymerization or photo-oxidative polymerization). The resulting polymerization reaction will inevitably form perfluoropolyether acyl fluoride compounds containing fluoroacyl groups. The process of removing the fluoroacyl groups is to hydrolyze the perfluoropolyether acyl fluoride compounds to obtain perfluoropolyether carboxylic acid, and then the perfluoropolyether carboxylic acid is subjected to fluorination reaction to obtain a stable perfluoropolyether.

[0004] At present, there are two main methods for fluorination of perfluoropolyether carboxylic acid in production. One is an intermittent kettle reaction, in which perfluoropolyether carboxylic acid is fluorinated with a gaseous fluorinating agent (such as fluorine nitrogen gas, sulfur tetrafluoride). The problem with this method is that the utilization rate of the fluorinating agent is low, and an excessive amount of gaseous fluorinating agent is required to participate in the reaction, which is time-consuming and laborious. The other is a continuous flow reaction, which mainly uses microchannels, tubular reactors or supergravity reactors for gas-liquid mixed fluorination. This method increases the utilization efficiency of fluorine gas, and the degree of fluorination of a single reaction is higher. The purpose of the above processes is to improve the utilization rate of fluorine and increase the degree of fluorination of the product, but the products shipped still have trace amounts of perfluoropolyether carboxylic acid and / or acyl fluoride, and generally require less than 0.03 mg KOH / g, which makes the product quality unstable and substandard.

[0005] CN110092901A discloses a fluorination process for unstable end groups of perfluoropolyether, comprising the following steps: step 1: after the bubbling tower fluorination reactor is evacuated, the raw materials of perfluoropolyether acyl fluoride and / or perfluoropolyether carboxylic acid are added into the reactor from the upper end of the bubbling tower fluorination reactor; then the bubbling tower fluorination reactor is heated to 130-170°C; step 2: adjusting the pressure in the bubbling tower fluorination reactor; step 3: introducing fluorinating agent gas, reacting for 45-90 minutes, and then heating to the set reaction temperature; step 4: after reacting for 4-48 hours, the reaction is terminated, the introduction of raw materials is stopped, nitrogen is purged, and the material temperature is reduced to below 40°C, and the material is discharged. It mainly uses fluorine gas to fluorinate the end groups of perfluoropolyether acyl fluoride and / or perfluoropolyether carboxylic acid, and requires additional excess fluorine gas to effectively achieve the claimed effect, resulting in a significant increase in cost.

[0006] CN117362627A discloses a method for hydrolyzing and decarboxylating a perfluoropolyether acyl fluoride compound, the method comprising the following steps: providing a starting material containing a perfluoropolyether acyl fluoride compound; contacting the starting material containing the perfluoropolyether acyl fluoride compound with water under alkaline conditions to perform a hydrolysis reaction; contacting the starting material containing the perfluoropolyether acyl fluoride compound with water to perform a hydrolysis reaction, removing the acyl group, and generating a corresponding perfluoropolyether carboxylate compound. In this scheme, the fluoropolyether hydrogen-terminated compound is actually converted by heating, and no perfluoropolyether is formed.

[0007] It can be seen that the existing technology is still unable to fully remove the trace perfluoropolyether acyl fluoride and perfluoropolyether carboxylic acid in perfluoropolyether. In order to solve the above problems, the inventors of the present application have successfully developed a new path for removing the trace perfluoropolyether carboxylic acid and / or acyl fluoride in perfluoropolyether after a lot of in-depth research. This method successfully solves the problem of acid and acid regurgitation in the existing products during use. Summary of the invention

[0008] The purpose of the present invention is to provide a method for treating trace perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether in order to solve at least one of the above problems, so as to solve the problem that the prior art still cannot fully remove trace perfluoropolyether acyl fluoride and perfluoropolyether carboxylic acid in perfluoropolyether, resulting in the problem that the existing products contain acid and acid regurgitation during use; the present scheme utilizes perfluoropolyether acyl fluoride and / or carboxylic acid under excess alkaline conditions to achieve complete decomposition and conversion of perfluoropolyether carboxylic acid, while avoiding the formation of olefins, thereby solving the problem of product acid content and acid regurgitation during subsequent use.

[0009] The purpose of the present invention is achieved through the following technical solutions:

[0010] A method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether comprises the following steps:

[0011] Step A: treating a perfluoropolyether containing a trace amount of perfluoropolyether carboxylic acid and / or perfluoropolyether acyl fluoride with an alkaline metal compound to convert the perfluoropolyether carboxylic acid and / or perfluoropolyether acyl fluoride into a perfluoropolyether carboxylate, and heating and decomposing the perfluoropolyether carboxylate to form a trace amount of olefin;

[0012] Step B: using a fluorinating agent diluted with a protective gas to carry out an addition reaction with the trace olefin formed in step A to convert the trace olefin into a perfluoropolyether oil.

[0013] Preferably, the perfluoropolyether treated by the treatment method includes K type, Y type, Z type and D type.

[0014] Preferably, the molecular weight distribution of the perfluoropolyether treated by the treatment method is 200 to 15,000.

[0015] Preferably, in step A, the metal compound is a solid compound of an oxide, hydroxide or carbonate compound of a metal element of Group I, Group II or Group II.

[0016] Preferably, step A is carried out at a temperature of 100-200°C.

[0017] Preferably, step A is a batch reaction in a kettle or a continuous reaction in a fixed bed.

[0018] Preferably, in step B, the protective gas is nitrogen or argon; and the fluorinating agent is selected from one or more of fluorine, sulfur tetrafluoride, sulfur hexafluoride and boron trifluoride.

[0019] Preferably, in step B, the fluorine content in the fluorinating agent diluted with the protective gas is 20%.

[0020] Preferably, step B is carried out at a temperature of 20-200° C. Within this range, the reaction temperature can be appropriately increased to reduce the kinematic viscosity of the perfluoropolyether and increase the mixing effect.

[0021] Preferably, step B is a batch reaction or a continuous flow reaction.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The method of the present application can completely decompose and convert the residual perfluoropolyether carboxylic acid and / or acyl fluoride in the perfluoropolyether oil into perfluoropolyether olefin, and then completely convert it into perfluoropolyether oil by adding fluorine element, thereby solving the problem of acid content in the product and acid reflux during subsequent use. DETAILED DESCRIPTION

[0024] The present invention is described in detail below with reference to specific embodiments, but this is by no means a limitation of the present invention.

[0025] In the following description, unless otherwise specified, the reagents used are conventional commercially available products, and the methods used are well known in the art.

[0026] The present application provides a method for treating a perfluoropolyether containing trace amounts of perfluoropolyether carboxylic acid and / or acyl fluoride, the method comprising:

[0027] Step A: treating the perfluoropolyether with an alkali metal compound or an ammonia compound at a certain temperature, so that a trace amount of perfluoropolyether carboxylic acid and / or acyl fluoride therein forms a perfluoropolyether carboxylate, and then decomposes by heating to form a trace amount of olefin;

[0028] Step B: A trace amount of olefin is converted into perfluoropolyether oil using a fluorination agent diluted with an inert gas.

[0029] According to the method described in the present application, the treatment method is suitable for K-type, Y-type, Z-type and D-type perfluoropolyethers with a molecular weight distribution of 200 to 15,000 and containing trace amounts of perfluoropolyether carboxylic acid and / or acyl fluoride.

[0030] According to the method described in the present application, in step A, the alkali metal compound can be a solid compound of an oxide, hydroxide or carbonate compound of a metal element of the main group I, the main group II or the sub-group, and the temperature at which the solid compound is mixed with the perfluoropolyether and decarboxylated is 100-200°C.

[0031] According to the method described in the present application, in step B, the inert gas is nitrogen or argon; the fluorinating agent is selected from one or more of the following: fluorine, sulfur tetrafluoride, sulfur hexafluoride, and boron trifluoride.

[0032] According to the method described in the present application, in step A, the reaction form can be a batch reaction in a kettle or a continuous reaction in a fixed bed.

[0033] According to the method described in the present application, in step B, the fluorine gas reaction temperature is between 20°C and 200°C, and the temperature can be appropriately increased within this range to reduce the kinematic viscosity of the perfluoropolyether and increase the mixing effect.

[0034] Example 1

[0035] A fixed bed reaction system is used, 300 kg of sodium carbonate particles are loaded into a fixed bed reactor, and after nitrogen is purged into the system, the temperature of the reactor is raised to 150° C., and a preheated 100° C. perfluoropolyether oil (average molecular weight 4800, acidity 0.05 mg KOH / g) is passed through a 130° C. preheater at a speed of 60 kg / h, and then enters the reactor, and the liquid material after the reaction passes through an intermediate tank and is introduced into a tubular reactor in parallel with fluorine / nitrogen gas with a fluorine content of 20%, the liquid material flow rate is maintained at 60 kg / h, the fluorine / nitrogen flow rate is 10 standard L / h (NL / h), and the reactor temperature is maintained at 100° C. After the reaction is completed, the fluorine gas and hydrogen fluoride are removed by reduced pressure at 100° C. to obtain the final product.

[0036] The acidity of the product was tested by acid-base neutralization method, and the result was 0 mg KOH / g.

[0037] Example 2

[0038] A 1 cubic kettle intermittent reaction system was used, and 1000 kg of perfluoropolyether oil (average molecular weight 4800, acidity 0.05 mg KOH / g) and 5 kg of potassium hydroxide powder were added to the reactor in sequence. Under closed stirring, the reactor temperature was raised from room temperature to 160°C, stirring was continued for 5 hours, and the pressure was slowly released to evacuate; fluorine / nitrogen gas with a fluorine content of 20% was slowly introduced into the reactor, and the pressure was maintained at 0.4 MPa, the reactor temperature was maintained at 160°C, and stirring was continued for 5 hours. The fluorine gas and trace amounts of hydrogen fluoride and other gases in the reactor were evacuated and replaced with nitrogen, and the temperature was lowered to 60°C. After filtering, the final product of perfluoropolyether oil was obtained.

[0039] The acidity of the product was tested by acid-base neutralization method, and the result was 0 mg KOH / g.

[0040] Example 3

[0041] A fixed bed reaction system is used, 300 kg of potassium carbonate particles are loaded into a fixed bed reactor, and after nitrogen is purged into the system, the reactor temperature is raised to 150°C, and the preheated 100°C perfluoropolyether oil (average molecular weight 500, acidity 0.02 mg KOH / g) passes through a 130°C preheater at a speed of 60 kg / h, and then enters the reactor, and the reactor pressure is maintained at 0.3 MPa. After the reaction, the liquid material passes through the intermediate tank and is introduced into the tubular reactor in parallel with the fluorine / nitrogen gas with a fluorine content of 20%, the liquid material flow rate is maintained at 60 kg / h, the fluorine / nitrogen flow rate is 10 standard L / h, the reactor temperature is maintained at 100°C, and the pressure is maintained at 0.3 MPa. After the reaction is completed, the product is distilled to remove the fluorine gas and hydrogen fluoride to obtain the final product.

[0042] The acidity of the product was tested by acid-base neutralization method, and the result was 0 mg KOH / g.

[0043] Example 4

[0044] A fixed bed reaction system is used, 300 kg of potassium carbonate particles are loaded into a fixed bed reactor, and after nitrogen is purged into the system, the reactor temperature is raised to 150°C, and the preheated 100°C perfluoropolyether oil (average molecular weight 7000, acidity 0.006 mg KOH / g) is passed through a 130°C preheater at a speed of 60 kg / h, and then enters the reactor, and the reactor pressure is maintained at 0.3 MPa. After the reaction, the liquid material passes through the intermediate tank and is introduced into the tubular reactor in parallel with fluorine / nitrogen gas with a fluorine content of 20%, the liquid material flow rate is maintained at 60 kg / h, the fluorine / nitrogen flow rate is 10 standard L / h, the reactor temperature is maintained at 100°C, and the pressure is maintained at 0.3 MPa. After the reaction is completed, the product is vacuumed and replaced with nitrogen to remove fluorine and hydrogen fluoride to obtain the final product.

[0045] The acidity of the product was tested by acid-base neutralization method, and the result was 0 mg KOH / g.

[0046] Example 5

[0047] This embodiment is basically the same as the embodiment 1, the main difference being that sulfur tetrafluoride is used to replace the fluorine gas (the fluorine gas part in the fluorine / nitrogen gas), and the rest remain the same.

[0048] The acidity of the product was tested by acid-base neutralization method, and the result was 0 mg KOH / g.

[0049] Example 6

[0050] This embodiment is basically the same as the embodiment 1, the main difference being that sulfur hexafluoride is used to replace the fluorine gas (the fluorine gas part in the fluorine / nitrogen gas), and the rest remain the same.

[0051] The acidity of the product was tested by acid-base neutralization method, and the result was 0 mg KOH / g.

[0052] Example 7

[0053] This embodiment is basically the same as the embodiment 1, the main difference being that boron trifluoride is used to replace the fluorine gas (the fluorine gas part in the fluorine / nitrogen gas), and the rest remain the same.

[0054] The acidity of the product was tested by acid-base neutralization method, and the result was 0 mg KOH / g.

[0055] The above description of the embodiments is to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the present invention should be within the scope of protection of the present invention.

Claims

1. A method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether, characterized in that: The steps include: Step A: treating a perfluoropolyether containing a trace amount of perfluoropolyether carboxylic acid and / or perfluoropolyether acyl fluoride with an alkaline metal compound to convert the perfluoropolyether carboxylic acid and / or perfluoropolyether acyl fluoride into a perfluoropolyether carboxylate, and heating and decomposing the perfluoropolyether carboxylate to form a trace amount of olefin; Step B: using a fluorinating agent diluted with a protective gas to carry out an addition reaction with the trace olefin formed in step A to convert the trace olefin into a perfluoropolyether oil.

2. The method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether according to claim 1, characterized in that: The perfluoropolyether treated by the treatment method includes K type, Y type, Z type and D type.

3. The method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether according to claim 1, characterized in that: The molecular weight distribution of the perfluoropolyether treated by the treatment method is 200 to 15000.

4. The method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether according to claim 1, characterized in that: In step A, the metal compound is a solid compound of an oxide, hydroxide or carbonate compound of a metal element of Group I, Group II or Group II.

5. The method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether according to claim 1, characterized in that: Step A is carried out at a temperature of 100-200°C.

6. The method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether according to claim 1, characterized in that: Step A is a batch reaction in a kettle or a continuous reaction in a fixed bed.

7. The method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether according to claim 1, characterized in that: In step B, the protective gas is nitrogen or argon; the fluorinating agent is selected from one or more of fluorine, sulfur tetrafluoride, sulfur hexafluoride and boron trifluoride.

8. The method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether according to claim 1, characterized in that: In step B, the fluorine content in the fluorinating agent diluted by the protective gas is 20%.

9. The method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether according to claim 1, characterized in that: Step B is carried out at a temperature of 20-200°C.

10. The method for treating trace amounts of perfluoropolyether carboxylic acid and perfluoropolyether acyl fluoride in perfluoropolyether according to claim 1, characterized in that: Step B is a batch reaction or a continuous flow reaction.