Separation method of fluorine-containing polymer emulsion

Abstract

The invention belongs to the technical field of high polymer material processing, and particularly relates to a separation method of fluorine-containing polymer emulsion. According to the separation method of the fluorine-containing polymer emulsion, the fluorine-containing polymer emulsion is separated in a spray drying mode, the ammonium salt is added, polymer condensation can be prevented, unstable groups in a polymer can be replaced, the demulsification process and the drying process are completed in the spray drying process, crushing treatment is not needed, and the separation method is simple and convenient to operate. And drying to obtain dry resin. The fluorine-containing polymer emulsion is one of a fluorinated ethylene propylene resin emulsion, a polyvinylidene fluoride resin emulsion, a polytetrafluoroethylene resin emulsion and a tetrafluoroethylene-hydroxybutyl vinyl ether polymer emulsion. The solid content of the fluorine-containing polymer emulsion ranges from 20% to 30%. According to the separation method of the fluorine-containing polymer emulsion, demulsification and drying are integrated, operation steps are simple, a demulsifier is not needed, and product pollution and environmental pollution are reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of polymer material processing, and in particular relates to a method for separating a fluorine-containing polymer emulsion. Background Art

[0002] In the production process of fluoropolymer materials, the treatment of emulsion is a crucial link. Due to its unique chemical stability and physical properties, fluoropolymer emulsion is widely used in many fields such as coatings, adhesives, plastics, rubber, etc. However, the demulsification and drying of emulsion has always been one of the key factors restricting production efficiency and product quality.

[0003] The traditional mechanical stirring demulsification method mainly relies on the shear force generated by high-speed stirring to destroy the oil-water interface in the emulsion, thereby achieving water-oil separation. However, this method has many shortcomings. First, a large amount of heat is generated during the mechanical stirring process, which may cause local overheating of the emulsion and affect product quality. Secondly, the collision and aggregation of emulsion droplets during the stirring process are often not sufficient, resulting in low demulsification efficiency and easy generation of large particle agglomerates, which affects subsequent processing. In addition, the mechanical stirring demulsification method usually requires a large equipment space, low equipment utilization, and subsequent cumbersome separation and drying steps are required, which increases production costs and energy consumption.

[0004] In order to overcome the shortcomings of mechanical stirring demulsification, chemical demulsification came into being. This method changes the type and interfacial properties of the emulsion by adding a specific demulsifier to the emulsion, causing it to become unstable and demulsify. There are many choices of demulsifiers, including acid-base compounds, metal salt compounds, organic flocculants, etc. The acid-base demulsification method mainly combines the cations and anions in the emulsifier through acid-base neutralization reaction, thereby destroying the stability of the emulsifier. Metal salt compounds remove surfactants on the emulsified oil interface through their cationic part, inhibit the formation of double electric layers, and remove oil droplets through mechanisms such as coagulation and adsorption. However, the chemical demulsification method also has some problems. On the one hand, the demulsifier has a strong specificity, and different demulsifiers need to be selected for different emulsions, which increases the difficulty and cost of operation. On the other hand, the use of demulsifiers may introduce impurities, affecting the purity and safety of the product. In addition, the chemical demulsification method may also produce environmental problems such as wastewater and waste residue.

[0005] In view of the limitations of traditional demulsification methods, it is particularly important to develop a new emulsion treatment technology that is efficient, environmentally friendly and widely applicable.

[0006] In the "Proceedings of the 11th National Heterogeneous Phase Separation Academic Exchange Conference", "A Study on the Separation Process of Fluorinated Polymer Emulsion, Xu Shuhui, Du Lihong, Xu Jing'an, Wang Shiyong, (Shanghai Institute of Chemical Industry)", it was proposed that the foam separation technology will be used to enrich the fluorinated polymer emulsion, which is achieved by hanging side agitators and ventilation. Although the modification of the agitator achieves separation, it has high energy consumption, high maintenance costs, and difficult gas control. Summary of the invention

[0007] The technical problem to be solved by the present invention is to overcome the above-mentioned defects of the prior art and provide a method for separating fluorine-containing polymer emulsions, integrating the two-step process of demulsification and drying, with simple operation steps, no need for demulsifier, and reducing product pollution and environmental pollution.

[0008] The method for separating the fluorine-containing polymer emulsion of the present invention separates the fluorine-containing polymer emulsion by spray drying, demulsifies and adjusts the particle size at the same time, and the demulsification and drying processes are completed in the spray drying process without the need for further pulverization to obtain a dry resin.

[0009] The fluorine-containing polymer emulsion is one of polyperfluoroethylene-propylene resin emulsion, polyvinylidene fluoride resin emulsion, polytetrafluoroethylene resin emulsion and tetrafluoroethylene-hydroxybutyl vinyl ether polymer emulsion.

[0010] The solid content of the fluorine-containing polymer emulsion is between 20% and 30%.

[0011] During the spray drying process, an ammonium salt solution is added, wherein the ammonium salt solution includes one of ammonium carbonate, carbonamide, ammonium bicarbonate, and ammonium carbamate, and the amount of the ammonium salt is 2-5% of the solid content in the fluoropolymer emulsion. The presence of the ammonium salt can replace unstable groups in the polymer, such as carboxyl groups.

[0012] The feed temperature of the ammonium salt solution is lower than 20°C.

[0013] The high temperature treatment temperature of the spray drying is in the heating section, and the heating temperature is between 180°C and 220°C.

[0014] The length of the heating section is 10-30m.

[0015] The flow rate of the fluorine-containing polymer emulsion in the heating section is 0.1m / s-2m / s, and the residence time is 5s-300s.

[0016] The heating section is built with baffles to allow the solution to be mixed better.

[0017] The particle size of the obtained dry resin is between 10-20 μm.

[0018] The heating section is provided with a baffle plate.

[0019] Specifically, the method for separating the fluorine-containing polymer emulsion is to dissolve an ammonium salt in water to prepare an ammonium salt solution, take a fluorine-containing polymer emulsion with a solid content of 20%-30%, add the ammonium salt solution, and then send it into a spray drying process, spray drying at 180°C-220°C, allow the obtained resin particles to stay in the spray dryer for 5s~300s, and measure the resin particle size.

[0020] Compared with the prior art, the present invention has the following beneficial effects: (1) The method for separating fluorinated polymer emulsions of the present invention greatly simplifies the production process by integrating the multi-step processes of centrifugal demulsification, flash drying, and crushing granulation into an integrated operation. By adopting spray drying technology, the demulsification, particle size adjustment and drying treatment of the emulsion can be completed in the same equipment without the need for subsequent crushing steps, thereby significantly improving the production efficiency. At the same time, the use of demulsifiers in traditional demulsification methods is avoided, the production cost is reduced, the product pollution and environmental problems that may be caused by the introduction of demulsifiers are reduced, and green production is achieved.

[0021] (2) The separation method of the fluorine-containing polymer emulsion of the present invention can achieve precise control of the particle size of the obtained dried resin by precisely controlling the process parameters in the spray drying process, such as the amount of ammonium salt solution, the spray drying temperature and the residence time of the resin particles in the spray dryer, thereby ensuring that the particle size distribution is within the range of 10-20 μm. This feature enables the product to have a more uniform particle size and better physical properties, meeting the high requirements for material performance in high-end application fields.

[0022] (3) The separation method of the fluorine-containing polymer emulsion of the present invention is not only applicable to the separation of polyperfluoroethylene propylene resin emulsion, polyvinylidene fluoride resin emulsion, polytetrafluoroethylene resin emulsion, and tetrafluoroethylene-hydroxybutyl vinyl ether polymer emulsion, but also has a wide range of applicability due to its characteristic of not requiring a specific demulsifier. In addition, through the innovative application of centrifugal spray drying technology, efficient and environmentally friendly emulsion processing is achieved, providing a new idea for technological innovation in the field of polymer material processing. The method not only improves production efficiency and reduces production costs, but also has significant economic and social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the separation process of the fluorine-containing polymer emulsion of the present invention.

[0024] Figure 2 This is the infrared absorption spectrum of the resin powder prepared in Example 3. DETAILED DESCRIPTION

[0025] The present invention will be further described below in conjunction with specific embodiments.

[0026] like Figure 1 As shown, the separation process of the fluorine-containing polymer emulsion of the present invention is as follows: the ammonium salt solution and the fluorine-containing polymer emulsion are simultaneously fed into the heat exchanger / heating section, the heating section is equipped with a baffle, a high temperature reaction of 180-220°C is carried out in the heating section, and spraying is carried out in the spray chamber, the spraying uses a blower to feed air into the spray chamber, and after being heated by the air heat exchanger, the air and the compressed air compressed by the compressor enter the spray chamber together for simultaneous demulsification and drying, and after the spraying is completed, the cyclone separator is fed to obtain the dried resin powder. The spray head used in the spray chamber is an existing spray head structure, and its structure is not described in detail.

[0027] Example 1 The separation method of the polyperfluoroethylene propylene resin (FEP) emulsion is as follows: ammonium carbonate is dissolved in water to prepare a 20wt% ammonium carbonate aqueous solution, 40kg of FEP emulsion with a solid content of 20% is taken, 800g of a 20wt% ammonium carbonate aqueous solution (2%) is added, the feed temperature of the ammonium carbonate aqueous solution is 15°C, and then it is sent to a spray drying chamber for simultaneous demulsification and drying, the heating section length is 10m, the flow rate of the resin emulsion is 0.5m / s, and spray drying is performed at 200°C, the obtained resin particles stay in the heating section for 20s, and the dried resin powder is measured to have an average resin particle size of 13μm.

[0028] Example 2 The separation method of the polyvinylidene fluoride resin (PVDF) emulsion is as follows: carbon amide is dissolved in water to prepare a 20wt% carbon amide aqueous solution, 40kg of PVDF emulsion with a solid content of 20% is taken, 2kg of 20wt% carbon amide aqueous solution (5%) is added, the feeding temperature of the carbon amide aqueous solution is 10°C, and then it is sent into a spray drying chamber for simultaneous demulsification and drying, the heating section length is 20m, the flow rate of the resin emulsion is 1m / s, and spray drying is performed at 180°C, the obtained resin particles stay in the heating section for 20s, and dry resin powder is obtained, and the average particle size of the resin is measured to be 16μm.

[0029] Example 3 The separation method of polytetrafluoroethylene resin (PTFE) emulsion is as follows: ammonium bicarbonate is dissolved in water to prepare a 20wt% ammonium bicarbonate aqueous solution, 40kg of PTFE emulsion with a solid content of 30% is taken, 1.8kg of 20wt% ammonium bicarbonate aqueous solution (4%) is added, the feed temperature of the ammonium bicarbonate aqueous solution is 15°C, and then it is sent to a spray drying chamber for simultaneous demulsification and drying, the heating section length is 15m, the flow rate of the resin emulsion is 0.1m / s, and spray drying is performed at 220°C. The obtained resin particles are allowed to stay in the spray dryer for 150s to obtain a dry resin powder. The average particle size of the resin is measured to be 18μm, and its infrared absorption spectrum is as shown in Figure 2 shown.

[0030] Example 4 The separation method of tetrafluoroethylene-hydroxybutyl vinyl ether polymer emulsion comprises the following steps: dissolving ammonium carbamate in water to prepare a 20wt% ammonium carbamate aqueous solution; taking 40kg of tetrafluoroethylene-hydroxybutyl vinyl ether polymer emulsion with a solid content of 25%, adding 0.75kg of a 20wt% ammonium carbamate aqueous solution (3%), wherein the feeding temperature of the ammonium carbamate aqueous solution is 12°C; and then feeding the emulsion into a spray drying chamber for simultaneous demulsification and drying; the heating section length is 18m, the flow rate of the resin emulsion is 0.3m / s, and spray drying is performed at 200°C; the obtained resin particles are allowed to stay in the spray dryer for 60s to obtain dried resin powder; and the average particle size of the resin is measured to be 14.8μm.

[0031] Comparative Example 1 This comparative example is the same as Example 1, but 50g of 20wt% ammonium carbonate aqueous solution is removed, and 20kg of FEP emulsion with a solid content of 20% is directly sent to the spray drying process. After treatment, the average particle size of the resin is measured to be 50μm. This is because during the emulsion polymerization process, the polarity of the carboxyl group causes the molecular chains to easily aggregate, thereby forming a larger particle size.

[0032] Comparative Example 2 This comparative example is the same as Example 1, except that "spray drying at 200° C." is replaced by "spray drying at 150° C.", and after the treatment, the average particle size of the resin is measured to be 35 μm.

Claims

1. A method for separating a fluorinated polymer emulsion, characterized in that: The fluorine-containing polymer emulsion is separated by spray drying, and the emulsion is broken and the particle size is adjusted at the same time. The demulsification and drying processes are completed in the spray drying process, and no pulverization treatment is required to obtain a dry resin.

2. The method for separating a fluorinated polymer emulsion according to claim 1, characterized in that: The fluorine-containing polymer emulsion is one of polyperfluoroethylene-propylene resin emulsion, polyvinylidene fluoride resin emulsion, polytetrafluoroethylene resin emulsion and tetrafluoroethylene-hydroxybutyl vinyl ether polymer emulsion.

3. The method for separating a fluorinated polymer emulsion according to claim 1, characterized in that: The solid content of the fluorine-containing polymer emulsion is between 20% and 30%.

4. The method for separating a fluorinated polymer emulsion according to claim 3, characterized in that: An ammonium salt solution is added during the spray drying process. The ammonium salt solution includes one of ammonium carbonate, carbonamide, ammonium bicarbonate and ammonium carbamate, and the amount of the ammonium salt is 2-5% of the solid content in the fluorine-containing polymer emulsion.

5. The method for separating a fluorinated polymer emulsion according to claim 4, characterized in that: The feed temperature of the ammonium salt solution is lower than 20°C.

6. The method for separating a fluorinated polymer emulsion according to claim 1, characterized in that: The temperature of the heating section in the spray drying process is between 180°C and 220°C.

7. The method for separating a fluorinated polymer emulsion according to claim 6, characterized in that: The length of the heating section is 10-30m.

8. The method for separating a fluorinated polymer emulsion according to claim 7, characterized in that: The flow rate of the fluorine-containing polymer emulsion in the heating section is 0.1m / s-2m / s, and the residence time is 5s-300s.

9. The method for separating a fluorinated polymer emulsion according to claim 7, characterized in that: The heating section is provided with a baffle plate.

10. The method for separating a fluorinated polymer emulsion according to claim 1, characterized in that: The particle size of the obtained dry resin is between 10-20 μm.

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