A continuous coagulation process for fluoropolymer emulsions

Abstract

This invention discloses a continuous coagulation method for fluoropolymer emulsions, comprising the following steps: First, pre-coagulating a fluoropolymer emulsion with a particle size of 0.03-0.10 μm to obtain a pre-demulsified emulsion with a particle size ≥3 μm; then, performing secondary coagulation on the pre-demulsified emulsion using a horizontal stirred tank, finally obtaining fluoropolymer solids. For fluoropolymer emulsions with a particle size of 0.10-0.40 μm, traditional coagulation tanks or emulsification pumps can achieve good coagulation, but using the method of this invention, the coagulated water-solid content is lower and the equipment utilization rate is higher under the same processing time.

Description

Technical Field

[0001] This invention belongs to the field of fluorochemical technology, specifically relating to a method for coagulating fluoropolymer emulsions. Background Technology

[0002] Fluorine atoms in the main chain of fluoropolymers have a strong ability to attract and bind electrons, resulting in a high electron cloud density, low electron cloud mobility, and difficulty in polarization. The electron cloud of fluorine atoms in organic fluorine polymers provides strong shielding protection for the main chain. This special structure endows fluoropolymer products with high weather resistance, high UV resistance, high chemical resistance, high water and oil repellency, and excellent electrical properties such as low dielectric constant and high insulation. They can be used in various fields such as cables, pipes, membranes, and pump and valve linings.

[0003] Fluoropolymer emulsions generally undergo post-processing steps such as coagulation, washing, drying, and granulation. Among these, the coagulation process is a demulsification process, which disperses the emulsion from a stable homogeneous phase into two parts: a solid phase and a liquid phase.

[0004] Traditional coagulation and demulsification methods include chemical demulsification, ultrasonic demulsification, mechanical demulsification, and cryogenic demulsification. In industry, the most common coagulation method is mechanical stirring demulsification, which involves placing the emulsion in an emulsion tank and stirring it at high speed. Due to the high-speed shearing action, the latex particles collide with each other, forming larger latex particles that precipitate from the aqueous phase. This coagulation method requires a large area, has low equipment utilization, and is not conducive to fully utilizing production capacity.

[0005] Patent CN104941558 discloses a jet flash coagulation kettle for continuous preparation of hydrogenated nitrile butadiene rubber. The method achieves flash coagulation by shearing the rubber liquid through the synergistic effect of steam and circulating hot water jet. However, this method is complex, consumes a large amount of steam and water, generates a large amount of wastewater, and has high costs.

[0006] Patent CN104292369 discloses an inline emulsifier that can continuously coagulate polytetrafluoroethylene propylene emulsion. However, the solid content in the coagulated water produced by this method is too high, resulting in resin loss, high production costs, and significant environmental impact.

[0007] Patent CN109762081 discloses a pipeline emulsifier that realizes a continuous coagulation method for fluoropolymer emulsions. The fluoropolymer emulsion and water are continuously fed into the pipeline emulsifier, and shear demulsification is performed at a certain speed. This method does not completely demulsify and has strict requirements on the particle size of the emulsion. Emulsions with a particle size of less than 0.1 μm are difficult to coagulate.

[0008] It is evident that current continuous coagulation methods generally suffer from problems such as incomplete demulsification, high water-solid content during coagulation, high energy consumption, and difficulty in coagulating emulsions with particle sizes below 0.1 μm. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a continuous coagulation method for fluoropolymer emulsions, which solves the problems of difficult coagulation, high loss, and the need to add additives for low particle size emulsions.

[0010] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0011] A continuous coagulation method for fluoropolymer emulsions includes the following steps:

[0012] First, fluoropolymer emulsions with an emulsion particle size of 0.03-0.10 μm are pre-coagulated to obtain pre-demulsified emulsions with a particle size ≥3 μm.

[0013] Then, the pre-demulsified emulsion was subjected to secondary coagulation using a horizontal stirred tank to finally obtain a fluoropolymer solid.

[0014] The mass ratio of fluoropolymer emulsion to water during pre-coagulation is 1:1-2, and the mass ratio of pre-demulsified emulsion to water during secondary coagulation is 1:1-2.

[0015] Preferably, the fluoropolymer emulsion is one or more mixtures of perfluoroethylene propylene emulsion, polyvinylidene fluoride emulsion, meltable polytetrafluoroethylene emulsion, and polytetrafluoroethylene emulsion.

[0016] Preferably, the linear velocity of the impeller edge in the horizontal stirred tank is controlled to be 20-50 m / min.

[0017] Preferably, pre-coagulation is carried out using an emulsification pump or a vertical coagulation tank.

[0018] The technical solution adopted in this invention has the following beneficial effects:

[0019] The biggest difference between a horizontal stirred tank and traditional coagulation tanks and emulsification pumps is that the liquid movement in a horizontal stirred tank is irregular, while the liquid flow in a traditional coagulation tank is vortex-like, significantly reducing the collision between latex particles. Emulsification pumps break down latex particles through a shear plate, and a sufficiently high rotation speed is required to achieve good coagulation results, which places a heavy load and high demands on the equipment. Furthermore, emulsions with a particle size of less than 0.10 μm still have difficulty coagulating.

[0020] The main function of a horizontal stirred tank is to provide power to make the pre-demulsified emulsion move irregularly. The pre-demulsified emulsion can serve as the center for latex particle aggregation. During the irregular movement, the particles collide and adsorb with each other to aggregate into larger latex particles. At the same time, this collision can destroy the protective layer on the surface of the latex particles, thereby allowing the solid substances in the latex particles to precipitate out better.

[0021] The pre-demulsified emulsion contains a large amount of precipitated micro-powder, with an overall particle size generally ≥3μm. Particles smaller than this size are difficult to coagulate in a horizontal stirred tank because, due to technical limitations, the horizontal stirred tank cannot reach a high rotation speed, making it impossible to form a pre-demulsified emulsion with a larger particle size on its own. However, for pre-demulsified emulsions with a larger particle size, after stirring and coagulation in a horizontal stirred tank, a large number of latex particles and micro-powders adsorb, collide, and agglomerate with each other. Moreover, this low rotation speed ensures that the adsorbed and agglomerated solids will not be dispersed and returned to the wastewater, resulting in a significant reduction in the coagulated water solids content.

[0022] For fluoropolymer emulsions with an emulsion particle size of 0.10-0.40 μm, traditional coagulation tanks or emulsification pumps can achieve good coagulation. However, using the method of this invention, the coagulated water-solid content is lower and the equipment utilization rate is higher under the same processing time.

[0023] Therefore, the present invention solves the problems of low particle size emulsions being difficult to coagulate, having high losses, and requiring the addition of additives.

[0024] The specific technical solution of the present invention and its beneficial effects will be disclosed in detail in the following specific embodiments. Detailed Implementation

[0025] The technical solution of the present invention will be explained and described below with reference to the embodiments of the present invention. However, the following embodiments are only preferred embodiments of the present invention and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments in the implementation methods without creative effort are all within the protection scope of the present invention.

[0026] Those skilled in the art will understand that, without conflict, the features in the following embodiments and implementations can be combined with each other.

[0027] This embodiment provides a continuous coagulation method for fluoropolymer emulsions, including the following steps:

[0028] First, fluoropolymer emulsions with an emulsion particle size of 0.03-0.10 μm are pre-coagulated to obtain pre-demulsified emulsions with a particle size ≥3 μm. Then, the pre-demulsified emulsions are subjected to secondary coagulation in a horizontal stirred tank to obtain fluoropolymer solids. The mass ratio of fluoropolymer emulsion to water during pre-coagulation is 1:1-2, and the mass ratio of pre-demulsified emulsion to water during secondary coagulation is also 1:1-2.

[0029] Preferably, the edge linear velocity of the stirring blades in the horizontal stirred tank is controlled at 20-50 m / min. The fluoropolymer emulsion is one or more mixtures of perfluoroethylene propylene emulsion, polyvinylidene fluoride emulsion, meltable polytetrafluoroethylene emulsion, and polytetrafluoroethylene emulsion.

[0030] In this embodiment, pre-coagulation is carried out using an emulsification pump or a vertical coagulation tank.

[0031] The biggest difference between a horizontal stirred tank and traditional coagulation tanks and emulsification pumps lies in the irregular liquid movement within the tank, whereas in a traditional coagulation tank, the liquid flows in a vortex pattern, significantly reducing collisions between latex particles. Emulsification pumps break down latex particles using a shear plate, requiring sufficiently high rotational speeds to achieve good coagulation, which places significant loads and demands on the equipment. Furthermore, they struggle to coagulate emulsions with particle sizes below 0.10 μm. The primary function of a horizontal stirred tank is to provide the power to induce irregular movement in the pre-demulsified emulsion. This pre-demulsified emulsion acts as a center for latex particle aggregation, colliding and adsorbing with each other during this irregular movement to form larger particles. Simultaneously, these collisions disrupt the protective layer on the particle surface, allowing for better precipitation of solid substances within the latex particles.

[0032] One embodiment and comparative example show that the pre-coagulated emulsion is not coagulated well by a conventional vertical coagulation tank. This is mainly because although the conventional vertical coagulation tank can provide a higher rotation speed, the vortex flow mode cannot allow more latex particles to collide and be adsorbed. Moreover, the excessively high rotation speed will cause low-size powder to detach and return to the wastewater, increasing the solid content in the wastewater.

[0033] The pre-demulsified emulsion contains a large amount of precipitated micro-powder, with an overall particle size generally ≥3μm. Particles smaller than this size are difficult to coagulate in a horizontal stirred tank because, due to technical limitations, the horizontal stirred tank cannot reach a high rotation speed, making it impossible to form a pre-demulsified emulsion with a larger particle size on its own. However, for pre-demulsified emulsions with a larger particle size, after stirring and coagulation in a horizontal stirred tank, a large number of latex particles and micro-powders adsorb, collide, and agglomerate with each other. Moreover, this low rotation speed ensures that the adsorbed and agglomerated solids will not be dispersed and returned to the wastewater, resulting in a significant reduction in the coagulated water solids content.

[0034] For vertical coagulation tanks, at low speeds, the emulsion moves in a vortex-like, orderly motion. This reduces the collisions between the micro-powders and latex particles, making it difficult to achieve the desired adsorption into large particles and precipitation. If the speed is increased, the micro-powders adsorbed on the surface of the particles will be redispersed into the water due to centrifugation, increasing the solid content in the water and resulting in greater losses.

[0035] It is well known in the field of emulsification pumps that low speed results in poor coagulation. Although high speed can improve the coagulation effect, it means a short residence time, so there is an upper limit to the coagulation effect. Furthermore, it is difficult to coagulate fluoropolymer emulsions with a particle size of 0.03-0.10μm. This conclusion has been described in detail in patent CN109762081.

[0036] In one embodiment, it is shown that for fluoropolymer emulsions with an emulsion particle size of 0.10-0.40 μm, conventional coagulation tanks or emulsification pumps can achieve good coagulation. However, by using the method described in this invention, the coagulated water-solid content is lower and the equipment utilization rate is higher under the same processing time.

[0037] Compared with existing technologies, the present invention does not require the use of nitric acid or other additives during the coagulation process.

[0038] Example 1

[0039] 200 L of perfluoroethylene propylene emulsion with a particle size of 0.03 μm was placed in an emulsion tank, and 300 L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at 3000 rpm to obtain a pre-demulsified emulsion with a particle size of 4.7 μm. This pre-demulsified emulsion was then placed in a horizontal stirred tank and 600 L of water was added. At this point, the solid content of the wastewater was 18.9%. The horizontal stirred tank was then started, maintaining a blade edge linear velocity of 28 m / min, and coagulation was carried out for 15 minutes. The solid content of the wastewater after coagulation was tested and found to be 0.032%.

[0040] Comparative Example 1

[0041] 200L of perfluoroethylene propylene emulsion with a particle size of 0.03μm was placed in an emulsion tank, and 300L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at its maximum speed of 10,000 rpm to obtain a pre-demulsified emulsion. The demulsified emulsion was then placed in a horizontal stirred tank and 600L of water was added; no coagulation occurred. The solids content of the wastewater after coagulation was tested to be 12.6%.

[0042] Example 2

[0043] 200 L of perfluoroethylene propylene emulsion with a particle size of 0.047 μm was placed in an emulsion tank, and 300 L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at 3000 rpm to obtain a pre-demulsified emulsion with a particle size of 5.3 μm. This pre-demulsified emulsion was then placed in a horizontal stirred tank and 600 L of water was added. At this point, the solid content of the wastewater was 17.6%. The horizontal stirred tank was then started, maintaining a blade edge linear velocity of 28 m / min, and coagulation was carried out for 15 minutes. The solid content of the wastewater after coagulation was tested and found to be 0.026%.

[0044] Comparative Example 2

[0045] 200L of perfluoroethylene propylene emulsion with a particle size of 0.047μm was placed in an emulsion tank, and 300L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at its maximum speed of 10,000 rpm to obtain a pre-demulsified emulsion. The demulsified emulsion was then placed in a horizontal stirred tank and 600L of water was added; no coagulation occurred. The solid content of the wastewater after coagulation was tested and found to be 11.7%.

[0046] Example 3

[0047] 200 L of perfluoroethylene propylene emulsion with a particle size of 0.098 μm was placed in an emulsion tank, and 300 L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at 3000 rpm to obtain a pre-demulsified emulsion with a particle size of 7.5 μm. This pre-demulsified emulsion was then placed in a horizontal stirred tank and 600 L of water was added. At this point, the solid content of the wastewater was 10.6%. The horizontal stirred tank was then started, maintaining a blade edge linear velocity of 28 m / min, and coagulation was carried out for 15 minutes. The solid content of the wastewater after coagulation was tested and found to be 0.015%.

[0048] Comparative Example 3

[0049] 200L of perfluoroethylene propylene emulsion with a particle size of 0.098μm was placed in an emulsion tank, and 300L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at its maximum speed of 10,000 rpm to obtain a pre-demulsified emulsion. The demulsified emulsion was then placed in a horizontal stirred tank and 600L of water was added; no coagulation occurred. The solids content of the wastewater after coagulation was tested and found to be 7.6%.

[0050] Example 4

[0051] 200 L of perfluoroethylene propylene emulsion with a particle size of 0.098 μm was placed in an emulsion tank, diluted with 300 L of water, and then pre-coagulated in a vertical coagulation tank at 3500 rpm for 15 minutes to obtain a pre-demulsified emulsion with a particle size of 5.5 μm. This pre-demulsified emulsion was then transferred to a horizontal stirred tank with 600 L of water added, at which point the wastewater solids content was 16.6%. The horizontal stirred tank was then agitated, maintaining a blade edge linear velocity of 28 m / min, and coagulated for 15 minutes. The solids content of the wastewater after coagulation was tested to be 0.017%.

[0052] Comparative Example 4

[0053] 200L of perfluoroethylene propylene emulsion with a particle size of 0.098μm was placed in an emulsion tank, and 300L of water was added for dilution. The emulsion was then pre-coagulated in a vertical coagulation tank at its maximum speed of 10,000 rpm for 30 minutes to obtain a pre-demulsified emulsion. The demulsified emulsion was then transferred to a horizontal stirred tank with 600L of water added; no coagulation occurred. The solids content of the wastewater after coagulation was measured to be 12.6%.

[0054] Table 1: Aggregation of emulsions with particle size <0.1 μm in examples and comparative examples

[0055]

[0056]

[0057] As shown in Examples 1-3 and Comparative Examples 1-3, when the emulsion particle size is less than 1 μm, traditional emulsification pumps and vertical coagulation tanks are insufficient for efficient coagulation. However, after pre-coagulation, the emulsion undergoes coagulation in a horizontal stirred tank, resulting in a significant reduction in the water-solid content. Furthermore, when using the pre-coagulation method described in this invention, the rotation speed of the emulsification pump and coagulation tank is only about 30% of their maximum speed, reducing equipment requirements. The coagulation time in the horizontal stirred tank is also only 15 minutes, greatly saving coagulation time and improving equipment utilization. While increasing the rotation speed during pre-coagulation can improve the coagulation effect to some extent, it significantly increases equipment wear and tear.

[0058] Example 5

[0059] 200 L of perfluoroethylene propylene emulsion with a particle size of 0.124 μm was placed in an emulsion tank, and 300 L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at 2500 rpm to obtain a pre-demulsified emulsion with a particle size of 8.3 μm. This pre-demulsified emulsion was then placed in a horizontal stirred tank and 600 L of water was added. At this point, the solid content of the wastewater was 9.6%. The horizontal stirred tank was then started, maintaining a blade edge linear velocity of 28 m / min, and coagulation was carried out for 15 minutes. The solid content of the wastewater after coagulation was tested and found to be 0.017%.

[0060] Comparative Example 5

[0061] 200L of perfluoroethylene propylene emulsion with a particle size of 0.124μm was placed in an emulsion tank, and 300L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at its maximum speed of 10,000 rpm to obtain a pre-demulsified emulsion. The demulsified emulsion was then placed in a horizontal stirred tank and 600L of water was added; no coagulation occurred. The solids content of the wastewater after coagulation was tested to be 4.8%.

[0062] Example 6

[0063] 200 L of perfluoroethylene propylene emulsion with a particle size of 0.168 μm was placed in an emulsion tank, and 300 L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at 2500 rpm to obtain a pre-demulsified emulsion with a particle size of 8.9 μm. This pre-demulsified emulsion was then placed in a horizontal stirred tank and 600 L of water was added. At this point, the solid content of the wastewater was 7.2%. The horizontal stirred tank was then turned on, maintaining a blade edge linear velocity of 28 m / min, and coagulation was carried out for 15 minutes. The solid content of the wastewater after coagulation was tested and found to be 0.012%.

[0064] Comparative Example 6

[0065] 200L of perfluoroethylene propylene emulsion with a particle size of 0.168μm was placed in an emulsion tank, and 300L of water was added for dilution. The emulsion was then pre-coagulated using an emulsifying pump at its maximum speed of 10,000 rpm to obtain a pre-demulsified emulsion. The demulsified emulsion was then placed in a horizontal stirred tank and 600L of water was added; no coagulation occurred. The solids content of the wastewater after coagulation was tested and found to be 1.1%.

[0066] Example 7

[0067] 200 L of perfluoroethylene propylene emulsion with a particle size of 0.214 μm was placed in an emulsion tank, and 300 L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at 2000 rpm to obtain a pre-demulsified emulsion with a particle size of 8.9 μm. This pre-demulsified emulsion was then placed in a horizontal stirred tank and 600 L of water was added. At this point, the solid content of the wastewater was 7.2%. The horizontal stirred tank was then started, maintaining a blade edge linear velocity of 28 m / min, and coagulation was carried out for 15 minutes. The solid content of the wastewater after coagulation was tested and found to be 0.013%.

[0068] Comparative Example 7

[0069] 200L of perfluoroethylene propylene emulsion with a particle size of 0.214μm was placed in an emulsion tank, and 300L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at its maximum speed of 10,000 rpm to obtain a pre-demulsified emulsion. The demulsified emulsion was then placed in a horizontal stirred tank and 600L of water was added; no coagulation occurred. The solid content of the wastewater after coagulation was tested and found to be 0.35%.

[0070] Example 8

[0071] 200 L of perfluoroethylene propylene emulsion with a particle size of 0.296 μm was placed in an emulsion tank, and 300 L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at 1500 rpm to obtain a pre-demulsified emulsion with a particle size of 10.9 μm. This pre-demulsified emulsion was then placed in a horizontal stirred tank and 600 L of water was added. At this point, the solid content of the wastewater was 5.2%. The horizontal stirred tank was then started, maintaining a blade edge linear velocity of 28 m / min, and coagulation was carried out for 15 minutes. The solid content of the wastewater after coagulation was tested and found to be 0.011%.

[0072] Comparative Example 8

[0073] 200L of perfluoroethylene propylene emulsion with a particle size of 0.296μm was placed in an emulsion tank, and 300L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at its maximum speed of 10,000 rpm to obtain a pre-demulsified emulsion. The demulsified emulsion was then placed in a horizontal stirred tank and 600L of water was added; no coagulation occurred. The solid content of the wastewater after coagulation was tested and found to be 0.13%.

[0074] Example 9

[0075] 200 L of fusible polytetrafluoroethylene (PTFE) emulsion with a particle size of 0.182 μm was placed in an emulsion tank and diluted with 300 L of water. The emulsion was then pre-coagulated using an emulsification pump at 1500 rpm to obtain a pre-demulsified emulsion with a particle size of 7.7 μm. This pre-demulsified emulsion was then placed in a horizontal stirred tank and 600 L of water was added. At this point, the solid content of the wastewater was 4.6%. The horizontal stirred tank was then agitated, maintaining a blade edge linear velocity of 28 m / min, and coagulation was carried out for 15 minutes. The solid content of the wastewater after coagulation was tested and found to be 0.014%.

[0076] Comparative Example 9

[0077] 200L of fusible polytetrafluoroethylene (PTFE) emulsion with a particle size of 0.182μm was placed in an emulsion tank, and 300L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at its maximum speed of 10,000 rpm to obtain a pre-demulsified emulsion. The demulsified emulsion was then placed in a horizontal stirred tank and 600L of water was added; no coagulation occurred. The solid content of the wastewater after coagulation was tested and found to be 0.32%.

[0078] Example 10

[0079] 200 L of fusible polytetrafluoroethylene (PTFE) emulsion with a particle size of 0.182 μm was placed in an emulsion tank and diluted with 300 L of water. The emulsion was then pre-coagulated using an emulsification pump at 10,000 rpm to obtain a pre-demulsified emulsion with a particle size of 16.3 μm. This pre-demulsified emulsion was then placed in a horizontal stirred tank and 600 L of water was added. At this point, the solid content of the wastewater was 0.32%. The horizontal stirred tank was then agitated, maintaining a blade edge linear velocity of 28 m / min, and coagulation was carried out for 15 minutes. The solid content of the wastewater after coagulation was tested and found to be 0.011%.

[0080] Comparative Example 10

[0081] 200L of perfluoroethylene propylene emulsion with a particle size of 0.182μm was placed in an emulsion tank, and 300L of water was added for dilution. The emulsion was then pre-coagulated in a vertical coagulation tank at its maximum speed of 10,000 rpm for 30 minutes to obtain a pre-demulsified emulsion. The demulsified emulsion was then transferred to a horizontal stirred tank with 600L of water added; no coagulation occurred. The solids content of the wastewater after coagulation was measured to be 0.36%.

[0082] Table 2: Aggregation of Emulsion Particle Size > 0.1 μm in Examples and Comparative Examples

[0083]

[0084] As shown in Examples 5-9 and Comparative Examples 5-9, it is evident that using the present invention for coagulation can significantly reduce the rotational speed of the emulsification pump and the vertical coagulation tank, and the resulting coagulated water-solid content is also lower than that of traditional coagulation methods. The higher the emulsion particle size, the better the coagulation effect of traditional coagulation methods. Example 10 shows that, when combined with the horizontal stirring coagulation method of the present invention, the coagulated water-solid content can be further reduced.

[0085] Example 11

[0086] 200 L of perfluoroethylene propylene emulsion with a particle size of 0.185 μm was placed in an emulsion tank, and 300 L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at 1500 rpm to obtain a pre-demulsified emulsion with a particle size of 10.9 μm. This pre-demulsified emulsion was then placed in a horizontal stirred tank and 600 L of water was added. At this point, the solid content of the wastewater was 5.2%. The horizontal stirred tank was then started, maintaining a blade edge linear velocity of 28 m / min, and coagulation was carried out for 15 minutes. The solid content of the wastewater after coagulation was tested and found to be 0.011%.

[0087] Comparative Example 11

[0088] 200 L of perfluoroethylene propylene emulsion with a particle size of 0.185 μm was placed in an emulsion tank, and 300 L of water was added for dilution. The emulsion was then pre-coagulated using an emulsification pump at 1500 rpm to obtain a pre-demulsified emulsion with a particle size of 10.9 μm. This pre-demulsified emulsion was then placed in a vertical coagulation tank, and 600 L of water was added. At this point, the solid content of the wastewater was 5.2%. The coagulation tank was then stirred at 10000 rpm for 15 minutes. The solid content of the wastewater after coagulation was tested and found to be 1.1%.

[0089] Examples 11 and Comparative Example 11 show that even if the pre-coagulation process is the same, the effect of coagulation by stirring in a horizontal stirred tank is better than that of a traditional vertical coagulation tank.

[0090] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that the present invention includes, but is not limited to, the content described in the above specific embodiments. Any modifications that do not depart from the functional and structural principles of the present invention will be included within the scope of the claims.

Claims

1. A continuous coagulation method for fluoropolymer emulsions, characterized in that, Includes the following steps: First, fluoropolymer emulsions with an emulsion particle size of 0.03-0.10 μm are pre-coagulated to obtain pre-demulsified emulsions with a particle size ≥3 μm. Then, the pre-demulsified emulsion was subjected to secondary coagulation using a horizontal stirred tank to finally obtain a fluoropolymer solid. The mass ratio of fluoropolymer emulsion to water during pre-coagulation is 1:1-2, and the mass ratio of pre-demulsified emulsion to water during secondary coagulation is 1:1-2. Pre-coagulation is carried out using an emulsification pump or a vertical coagulation tank.

2. The continuous coagulation method for fluoropolymer emulsion according to claim 1, characterized in that, The fluoropolymer emulsion is one or more mixtures of perfluoroethylene propylene emulsion, polyvinylidene fluoride emulsion, meltable polytetrafluoroethylene emulsion, and polytetrafluoroethylene emulsion.

3. The continuous coagulation method for fluoropolymer emulsion according to claim 1, characterized in that, The linear velocity of the impeller edge in the horizontal stirred tank is controlled at 20-50 m / min.

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