A method for improving the coagulation effect of a fluoroelastomer emulsion

Abstract

The present application relates to a method for improving the coagulation effect of fluorine rubber emulsion, which is characterized by adding a solubilizer to the system; the steps are adding high-purity water to the emulsion, then adding a coagulant, and then adding the solubilizer to coagulate. After coagulation, the colloidal particles are loose, the conductivity and water content are low, the washing and dehydration are easy, the drying time is short, the production cost is reduced, and the product quality and production efficiency are improved.

Description

Technical Field

[0001] This invention relates to the field of synthetic rubber technology, and in particular to a method for improving the coagulation effect of fluororubber emulsions. Background Technology

[0002] Compared with other rubbers, fluororubber possesses excellent comprehensive properties such as high temperature resistance, chemical corrosion resistance, oil resistance, and weather aging resistance, making it an important sealing material and chemical conveying material in the automotive, aerospace, and chemical industries. Its outstanding characteristic is its high temperature resistance, allowing it to operate continuously in temperatures ranging from -50°C to 300°C.

[0003] Fluororubber produced by emulsion polymerization is an emulsion synthesized from three monomers—vinylidene fluoride, tetrafluoroethylene, and hexafluoropropylene—or two monomers—vinylidene fluoride and hexafluoropropylene, or vinylidene fluoride and trifluorochloroethylene—through free radical initiation. Fluororubber emulsions require coagulation before further processing. The coagulation process is essentially a demulsification process, and there are two main methods of demulsification: physical demulsification, such as freezing, and chemical demulsification, such as salting out.

[0004] The coagulation method currently used for fluororubber latex is the traditional coagulation method, which involves removing unreacted raw material monomers by nitrogen purging after the emulsion polymerization reaction is completed, and then transporting it to the coagulation unit. A coagulant is added to the coagulation kettle for coagulation, and after washing, dehydration, and vacuum drying, the fluororubber product is obtained.

[0005] Patent CN101323657A discloses a method for preparing pentonitrile rubber latex and pentonitrile rubber, including the preparation of pentonitrile rubber latex and the step of coagulating it into a rubber block. The coagulant in this invention is an inorganic acid salt, and inorganic acid salt impurity ions are easily left in the rubber block, making it difficult to clean and dry.

[0006] Patent CN102875711A discloses a coagulation and washing method for polyvinylidene fluoride (PVDF) emulsion. This method mainly involves mechanically coagulating the PVDF emulsion, allowing it to stand, and then washing it. However, since the PVDF emulsion produced by mechanical coagulation is a paste-like colloid, the separation process is time-consuming, and the average particle size of the paste-like colloid is relatively small (5-10 μm). This method is not suitable for conventional centrifugal dehydration, as the dehydration time is long, which is not conducive to industrial production.

[0007] In summary, existing methods for coagulating fluororubber emulsions have the following shortcomings:

[0008] The resulting colloid particles are dense and difficult to clean and dry; powdery or paste-like colloids are easily lost during cleaning, and filtration and dehydration are time-consuming, increasing production costs.

[0009] Impurities in residual adhesive particles can affect the appearance and performance of the product, leading to a decline in product quality; SO4 in the adhesive particles 2- Cl- NO 3- Impurity ions cause severe corrosion to post-processing metal equipment. Summary of the Invention

[0010] The purpose of this invention is to provide a method for improving the coagulation effect of fluororubber emulsions. After coagulation, the colloidal particles are loose, with low electrical conductivity and water content, making them easy to clean and dehydrate, and requiring a short drying time. This reduces production costs, improves product quality and production efficiency, and solves the problems in the background art.

[0011] To address the aforementioned technical problems, the technical solution provided by this invention for improving the coagulation effect of fluororubber emulsions is as follows:

[0012] This invention discloses a method for improving the coagulation effect of fluororubber emulsion, which uses fluororubber emulsion as raw material and is characterized by adding a solubilizer to the system. The steps are as follows: first, add high-purity water to the emulsion, then add a coagulant, and then add a solubilizer to the emulsion for coagulation.

[0013] In any of the above embodiments, it is preferred that the solubilizer comprises at least one or more combinations selected from methylcellulose, polyethylene glycol monomethyl ether, polyoxyethylene fatty acid ester, polysorbate, and PEG (polyethylene glycol).

[0014] In any of the above embodiments, it is preferred that the coagulant comprises one selected from CaCl2, MgCl2, K2SO4, NaCl, KCl, and NH4Cl.

[0015] In any of the above embodiments, it is preferred that the mass ratio of the solubilizer to the raw material is 0.08 to 0.5:100, and the raw material is based on the weight of the dry fluororubber emulsion.

[0016] In any of the above embodiments, it is preferred that the mass ratio of the coagulant, solubilizer, and raw material is 0.3-1.0:0.08-0.5:100, and the raw material is based on the weight of the dry fluororubber emulsion.

[0017] Preferably, in any of the above solutions, the method for improving the coagulation effect of fluororubber emulsion includes the following steps:

[0018] ① Preparation of coagulant solution: Dissolve 0.3 to 1.0 parts by weight of coagulant in high-purity water to prepare a 15 to 25% solution for later use;

[0019] ② Preparation of solubilizer solution: Dissolve 0.08 to 0.5 parts by weight of solubilizer in high-purity water to prepare a 10 to 15% solution for later use;

[0020] ③ Preparation of raw materials: Preheat the fluororubber emulsion equivalent to 100 parts by weight of dry rubber to 20-60℃ to remove unpolymerized monomers and set aside;

[0021] ④ Emulsion coagulation: Add the raw materials prepared in step ③ to the coagulation vessel, then add high-purity water to dilute to a solid content of 10-20%, stir at a speed of less than 500 rpm, add the coagulant solution prepared in step ① containing 0.3-1.0 parts by weight of coagulant, and stir at a speed of more than 1000 rpm for 2-5 minutes; then add the solubilizer solution prepared in step ② containing 0.08-0.5 parts by weight of solubilizer to the coagulation vessel, continue stirring for 3-8 minutes, coagulate until the rubber particles are uniform and the slurry is clear, stop stirring to obtain the demulsified fluororubber particles, wash the precipitated rubber particles, pass them through a vibrating screen, and dry them to obtain the fluororubber product.

[0022] In any of the above embodiments, it is preferred that the present invention can recycle the removed unpolymerized monomers.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] The solubilizer used in this invention has good water solubility and is environmentally friendly. By utilizing the solubilizer to solubilize the micelles of inorganic salts, it achieves a loosening, dispersing, and lubricating effect on the colloidal particles during the coagulation process. This helps to form intercellular channels within the particles, reducing particle density and agglomeration. After coagulation, the particles are spongy, with an average particle size of 0.5–2 cm, making them easy to wash and dry, reducing wastewater discharge and saving energy. Simultaneously, it reduces residual impurities within the product, improves product quality, and mitigates the corrosion of metal equipment in post-processing by inorganic acid ions. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] To better understand the above technical solution, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0027] Example 1:

[0028] The coagulation treatment of fluororubber latex was carried out according to the following steps:

[0029] ① Preparation of coagulant solution: Accurately weigh 30g of MgCl2 coagulant, dissolve it in high-purity water to prepare a 15% solution for later use;

[0030] ② Preparation of solubilizer solution: Accurately weigh 8g of PEG400 solubilizer, dissolve it in high-purity water to prepare a 10% solution for later use;

[0031] ③ Preparation of raw materials: Preheat 5 kg of fluororubber latex with a solid content of 20% (equivalent to 1 kg of dry rubber) to 30°C and set aside.

[0032] ④ Emulsion coagulation: Add the raw materials prepared in step ③ to the coagulation vessel and stir at a speed of 250 rpm. Add the coagulant solution prepared in step ① and stir at 1500 rpm for 2-5 minutes. Then add the solubilizer solution prepared in step ② to the coagulation vessel and continue stirring for 3-8 minutes until the rubber particles are uniform and the slurry is clear. After stopping stirring, the fluororubber particles precipitated from the emulsion are obtained. The precipitated rubber particles are washed 10 times, passed through a vibrating screen, and vacuum dried for 3 hours to obtain the fluororubber product.

[0033] Example 2:

[0034] The coagulation treatment of fluororubber latex was carried out according to the following steps:

[0035] ① Preparation of coagulant solution: Accurately weigh 100g of K2SO4 coagulant, dissolve it in high-purity water to prepare a 15% solution for later use;

[0036] ② Preparation of solubilizer solution: Accurately weigh 20g of PEG300 solubilizer, dissolve it in high-purity water to prepare a 10% solution for later use;

[0037] ③ Preparation of raw materials: Preheat 5 kg of fluororubber latex with a solid content of 20% (equivalent to 1 kg of dry rubber) to 30°C and set aside.

[0038] ④ Emulsion coagulation: Add the raw materials prepared in step ③ to the coagulation vessel and stir at 300 rpm. Add the coagulant solution prepared in step ① and stir at 1200 rpm for 2 minutes. Then add the solubilizer solution prepared in step ② to the coagulation vessel and continue stirring for 3 minutes until the rubber particles are uniform and the slurry is clear. After stopping stirring, the fluororubber particles precipitated from the demulsification are obtained. The precipitated rubber particles are washed 10 times, passed through a vibrating screen, and vacuum dried for 3 hours to obtain the fluororubber product.

[0039] Example 3:

[0040] The coagulation treatment of fluororubber latex was carried out according to the following steps:

[0041] ① Preparation of coagulant solution: Accurately weigh 30g of MgCl2 coagulant, dissolve it in high-purity water to prepare a 15% solution for later use;

[0042] ② Preparation of solubilizer solution: Accurately weigh 50g of PEG400 solubilizer, dissolve it in high-purity water to prepare a 10% solution for later use;

[0043] ③ Preparation of raw materials: Preheat 5 kg of fluororubber latex with a solid content of 15% and equivalent to 1 kg of dry rubber to 30°C and set aside.

[0044] ④ Emulsion coagulation: Add the raw materials prepared in step ③ to the coagulation vessel and stir at a speed of 400 rpm. Add the coagulant solution prepared in step ① and stir at 2000 rpm for 3 minutes. Then add the solubilizer solution prepared in step ② to the coagulation vessel and continue stirring for 4 minutes until the rubber particles are uniform and the slurry is clear. After stopping stirring, the fluororubber particles precipitated from the demulsification are obtained. The precipitated rubber particles are washed 10 times, passed through a vibrating screen, and vacuum dried for 3 hours to obtain the fluororubber product.

[0045] Example 4:

[0046] The coagulation treatment of fluororubber latex was carried out according to the following steps:

[0047] ① Preparation of coagulant solution: Accurately weigh 100g of MgCl2 coagulant, dissolve it in high-purity water to prepare a 15% solution for later use;

[0048] ② Preparation of solubilizer solution: Accurately weigh 5g of PEG600 solubilizer, dissolve it in high-purity water to prepare a 10% solution for later use;

[0049] ③ Preparation of raw materials: Preheat 5 kg of fluororubber latex with a solid content of 15% and equivalent to 1 kg of dry rubber to 30°C and set aside.

[0050] ④ Emulsion coagulation: Add the raw materials prepared in step ③ to the coagulation vessel and stir at 500 rpm. Add the coagulant solution prepared in step ① and stir at 2000 rpm for 4 minutes. Then add the solubilizer solution prepared in step ② to the coagulation vessel and continue stirring for 5 minutes until the rubber particles are uniform and the slurry is clear. After stopping stirring, the fluororubber particles precipitated from the emulsion are obtained. The precipitated rubber particles are washed 10 times, passed through a vibrating screen, and vacuum dried for 3 hours to obtain the fluororubber product.

[0051] Example 5:

[0052] The coagulation treatment of fluororubber latex was carried out according to the following steps:

[0053] ① Preparation of coagulant solution: Accurately weigh 10g of MgCl2 coagulant, dissolve it in high-purity water to prepare a 15% solution for later use;

[0054] ② Preparation of solubilizer solution: Accurately weigh 5g of PEG400 solubilizer, dissolve it in high-purity water to prepare a 10% solution for later use;

[0055] ③ Preparation of raw materials: Preheat 5 kg of fluororubber latex with a solid content of 10% and equivalent to 1 kg of dry rubber to 30°C for later use;

[0056] ④ Emulsion coagulation: Add the raw materials prepared in step ③ to the coagulation vessel and stir at 300 rpm. Add the coagulant solution prepared in step ① and stir at 1800 rpm for 5 minutes. Then add the solubilizer solution prepared in step ② to the coagulation vessel and continue stirring for 6 minutes until the rubber particles are uniform and the slurry is clear. After stopping stirring, the fluororubber particles precipitated from the demulsification are obtained. The precipitated rubber particles are washed 10 times, passed through a vibrating screen, and vacuum dried for 3 hours to obtain the fluororubber product.

[0057] Example 6:

[0058] The coagulation treatment of fluororubber latex was carried out according to the following steps:

[0059] ① Preparation of coagulant solution: Accurately weigh 300g of MgCl2 coagulant, dissolve it in high-purity water to prepare a 15% solution for later use;

[0060] ② Preparation of solubilizing solution: Accurately weigh 5g of polysorbate solubilizer, dissolve it in high-purity water to prepare a 10% solution for later use;

[0061] ③ Preparation of raw materials: Preheat 5 kg of fluororubber latex with a solid content of 10% and equivalent to 1 kg of dry rubber to 30°C for later use;

[0062] ④ Emulsion coagulation: Add the raw materials prepared in step ③ to the coagulation vessel and stir at a speed of 400 rpm. Add the coagulant solution prepared in step ① and stir at 1800 rpm for 2-5 minutes. Then add the solubilizer solution prepared in step ② to the coagulation vessel and continue stirring for 3-8 minutes until the rubber particles are uniform and the slurry is clear. After stopping stirring, the fluororubber particles precipitated from the demulsification are obtained. The precipitated rubber particles are washed 10 times, passed through a vibrating screen, and vacuum dried for 3 hours to obtain the fluororubber product.

[0063] Example 7:

[0064] The coagulation treatment of fluororubber latex was carried out according to the following steps:

[0065] ① Preparation of coagulant solution: Accurately weigh 10g of MgCl2 coagulant, dissolve it in high-purity water to prepare a 15% solution for later use;

[0066] ② Preparation of solubilizing solution: Accurately weigh 100g of polysorbate solubilizer, dissolve it in high-purity water to prepare a 10% solution for later use;

[0067] ③ Preparation of raw materials: Preheat 5 kg of fluororubber latex with a solid content of 10% and equivalent to 1 kg of dry rubber to 30°C for later use;

[0068] ④ Emulsion coagulation: Add the raw materials prepared in step ③ to the coagulation vessel and stir at a speed of 500 rpm. Add the coagulant solution prepared in step ① and stir at 2000 rpm for 2-5 minutes. Then add the solubilizer solution prepared in step ② to the coagulation vessel and continue stirring for 3-8 minutes until the rubber particles are uniform and the slurry is clear. After stopping stirring, the fluororubber particles precipitated from the demulsification are obtained. The precipitated rubber particles are washed 10 times, passed through a vibrating screen, and vacuum dried for 3 hours to obtain the fluororubber product.

[0069] Example 8:

[0070] The coagulation treatment of fluororubber latex was carried out according to the following steps:

[0071] ① Preparation of coagulant solution: Accurately weigh 150g of MgCl2 coagulant, dissolve it in high-purity water to prepare a 15% solution for later use;

[0072] ② Preparation of solubilizing solution: Accurately weigh 100g of polysorbate solubilizer, dissolve it in high-purity water to prepare a 10% solution for later use;

[0073] ③ Preparation of raw materials: Preheat 5 kg of fluororubber latex with a solid content of 10% and equivalent to 1 kg of dry rubber to 30°C for later use;

[0074] ④ Emulsion coagulation: Add the raw materials prepared in step ③ to the coagulation vessel and stir at 300 rpm. Add the coagulant solution prepared in step ① and stir at 1800 rpm for 2-5 minutes. Then add the solubilizer solution prepared in step ② to the coagulation vessel and continue stirring for 3-8 minutes until the rubber particles are uniform and the slurry is clear. After stopping stirring, the fluororubber particles precipitated from the emulsion are obtained. The precipitated rubber particles are washed 10 times, passed through a vibrating screen, and vacuum dried for 3 hours to obtain the fluororubber product.

[0075] Comparative Example 1:

[0076] Other conditions are the same as in Example 1, except that no solubilizer is added during the coagulation process.

[0077] Comparative Example 2:

[0078] Other conditions are the same as in Example 4, except that no solubilizer is added during the coagulation process.

[0079] Experimental Example

[0080] The products obtained from Examples 1 to 8 and Comparative Examples 1 to 2 were tested according to the following test methods, and the results are shown in Table 1.

[0081] Testing the conductivity of fluororubber washing water

[0082] 1. After the fluororubber product has been washed a certain number of times in the washing tub, fill a beaker with water from the drain outlet of the washing tub (the water level only needs to be appropriate, weighing is not required) and send it to the analysis room for testing.

[0083] 2. Due to the low conductivity of the test sample, the FE30 conductivity meter with an electrode that has a built-in temperature probe (such as the LE701 conductivity electrode) was selected.

[0084] 3. Turn on the conductivity meter;

[0085] 4. After the instrument self-test passes, fully immerse the electrode in the sample to be tested, then press the reading key to start the measurement. During the measurement, the decimal point will flash, and the display will show the conductivity value of the sample, with an "A" icon displayed on the screen. The measurement will stop when the result stabilizes, and the decimal point will stop flashing. Displayed on the screen;

[0086] 5. Test complete;

[0087] Moisture content test of fluororubber raw rubber

[0088] 1. Place the aluminum box in an oven to dry for 15 minutes;

[0089] 2. Remove the aluminum box and place it in a desiccator to cool for 30 minutes;

[0090] 3. Weigh the empty aluminum box and record the mass as m0;

[0091] 4. Weigh out more than 5g of white glue cut into granules, and record it as m1;

[0092] 5. Place the weighed white glue into an aluminum box and bake in an oven at 105℃ for 1.5 hours;

[0093] 6. After cooling for 30 minutes, weigh the white glue and aluminum box and record the mass as m2;

[0094] 7. The formula for moisture content X is:

[0095]

[0096] Fluororubber particle size testing method

[0097] 1. After being washed clean, the fluororubber is discharged into a vibrating screen for filtration to remove adsorbed moisture and for particle size analysis. The vibrating screen plate is set with four layers of different screen hole diameters from top to bottom: 2.0cm, 1.5cm, 1.0cm, and 0.5cm. After screening, it is fed into a material tray for collection via a belt.

[0098] 2. Weigh and record the percentage of the weight of the product collected on different sieve openings relative to the total product weight, and then calculate the average particle size based on this percentage.

[0099] Table 1. Experimental data for examples and comparative examples.

[0100] Example 1 100 margin 0.3 0.08 A+ 0.118 0.8cm 1.3 Example 2 100 margin 1 0.2 A+ 0.100 1.9cm 1.4 Example 3 100 margin 0.3 0.5 A 0.075 1.6cm 1.6 Example 4 100 margin 1 0.5 A 0.078 1.2cm 2.4 Example 5 100 margin 0.1 0.05 B 0.109 0.3cm 2.6 Example 6 100 margin 3 0.05 B 0.142 0.4cm 2.8 Example 7 100 margin 0.1 1 B 0.112 0.2cm 2.5 Example 8 100 margin 1.5 1 B 0.117 0.4cm 2.6 Comparative Example 1 100 margin 0.3 none C 0.229 0.1cm 16 Comparative Example 2 100 margin 1 none C 0.311 0.3cm 20

[0101] A comparative analysis of Examples 1 to 6 and Comparative Examples 1 to 2 shows that the average particle size of the gel produced using the same coagulation method with the addition of a solubilizer is larger than that without. Under the same drying time and washing cycles, the moisture content and washing water conductivity of the gel particles produced with the solubilizer are lower than those without. This method reduces water consumption and shortens drying time, resulting in a product with lower impurity content. Furthermore, the effect is even better with a specific amount of solubilizer. Within a specific range of proportions, the coagulant and solubilizer produce a synergistic effect, with the optimal effect achieved within this range.

[0102] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for improving the coagulation effect of fluororubber latex, using fluororubber latex as raw material, characterized in that... Add a solubilizer to the system; The steps are as follows: first, add high-purity water to the emulsion, then add a coagulant, and then add a solubilizer to coagulate it. The solubilizer is selected from at least one or a combination of methylcellulose, polyethylene glycol monomethyl ether, polyoxyethylene fatty acid ester, polysorbate, and PEG (polyethylene glycol).

2. The method for improving the coagulation effect of fluororubber latex according to claim 1, wherein the coagulant is selected from one of CaCl2, MgCl2, K2SO4, NaCl, KCl, and NH4Cl.

3. The method for improving the coagulation effect of fluororubber emulsion according to claim 1, wherein the mass ratio of solubilizer to raw material is 0.08-0.5:100, and the raw material is based on the weight of the dry fluororubber emulsion.

4. A method for improving the coagulation effect of fluororubber emulsion according to any one of claims 1-3, wherein the mass ratio of coagulant, solubilizer and raw material is 0.3-1.0:0.08-0.5:100, and the raw material is based on the weight of the dry rubber of the fluororubber emulsion.

5. A method for improving the coagulation effect of fluororubber emulsion according to claim 4, comprising the following steps: ① Preparation of coagulant solution: Dissolve 0.3 to 1.0 parts by weight of coagulant in high-purity water to prepare a 15 to 25% solution for later use; ② Preparation of solubilizer solution: Dissolve 0.08 to 0.5 parts by weight of solubilizer in high-purity water to prepare a 10 to 15% solution for later use; ③ Preparation of raw materials: Preheat the fluororubber emulsion equivalent to 100 parts by weight of dry rubber to 20-60℃ to remove unpolymerized monomers and set aside; ④ Emulsion coagulation: Add the raw materials prepared in step ③ to the coagulation vessel, then add high-purity water to dilute to a solid content of 10-20%, stir at a speed of less than 500 rpm, add the coagulant solution prepared in step ① containing 0.3-1.0 parts by weight of coagulant, and stir at a speed of more than 1000 rpm for 2-5 minutes; then add the solubilizer solution prepared in step ② containing 0.08-0.5 parts by weight of solubilizer to the coagulation vessel, continue stirring for 3-8 minutes, coagulate until the rubber particles are uniform and the slurry is clear, stop stirring to obtain the demulsified fluororubber particles, wash the precipitated rubber particles, pass them through a vibrating screen, and dry them to obtain the fluororubber product.

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