Method for producing natural rubber by supergravity coupling microwave drying

Abstract

The application discloses a method for producing natural rubber by supergravity coupling microwave drying, and comprises the following steps: S1, supergravity carbon dissolving reaction; S2, standing and solidification; S3, dehydration and granulation; and S4, microwave drying. The method adopts the supergravity carbon dissolving technology to realize efficient solidification of natural latex in a short time, and then realizes the working mode of forming natural raw rubber through short-time microwave drying. Compared with the prior art, the method has the advantages of higher efficiency, safer and greener operation, and more excellent physical properties of the produced natural raw rubber, and the Mooney viscosity of the prepared raw rubber is 80-86, the plasticity retention rate is greater than or equal to 95%, the elongation at break is greater than or equal to 730%, and the tensile strength is greater than or equal to 24 MPa, thereby providing reliable technical support for the natural rubber processing field.

Description

Technical Field

[0001] This invention belongs to the field of natural rubber processing, and in particular relates to a method for producing natural rubber by supergravity coupled microwave drying. Background Technology

[0002] Natural rubber (NR) is considered one of the four basic industrial raw materials, along with coal, steel, and petroleum. It is the only renewable resource among these four, giving it significant strategic value. Due to its excellent elasticity, mechanical properties, heat generation properties, and abrasion resistance, as well as its good insulation, sealing, and adhesive properties, it is widely used in agriculture, industry, defense technology, transportation, medical and health care, and daily life.

[0003] China has always been a major consumer of natural rubber. Despite significant progress in its rubber industry, domestic production and supply of natural rubber still cannot meet domestic market demand, necessitating substantial imports. In recent years, my country's natural rubber production sector has faced challenges such as poor consistency in rubber quality, severe environmental pollution, and insufficient production of high-performance natural rubber. Therefore, we must continuously improve existing rubber processing techniques to enhance the quality of primary processed natural rubber products and meet future development needs.

[0004] Many factors affect the properties of natural rubber, with the processing technology of latex being the most important. Among these, the coagulation and drying processes are of paramount importance. Therefore, scholars have conducted extensive research on the coagulation and drying processes of natural rubber latex.

[0005] Currently, acid coagulation is the primary method for coagulating natural rubber in my country, with formic acid, acetic acid, and sulfuric acid commonly used. While acid coagulation offers fast production speed and a high yield of raw natural rubber, it is also costly, accounting for over 15% of the total production cost. Furthermore, it is highly corrosive, requiring extensive water treatment to remove residual acids and ammonium salts from the wet rubber, resulting in significant environmental pollution. Long-term production practice has shown that the standard rubber produced by acid coagulation has poor physical properties. The drying process for natural rubber mainly employs hot air drying, using coal, diesel, or electricity as heat sources and air as the heating medium. However, this drying process is time-consuming, and problems such as rubber aging and adhesion, as well as insufficient drying leading to a white core, result in unstable rubber quality. Summary of the Invention

[0006] To address the problems of severe environmental pollution, long production cycles, poor rubber performance, and low yield in existing natural rubber processing methods, this invention provides a method for producing natural rubber using gravity-coupled microwave drying. This method effectively improves the production efficiency of natural rubber, reduces production costs, and is safe, environmentally friendly, and pollution-free. The tensile properties and plasticity retention of the produced raw natural rubber are significantly improved, resulting in superior physical properties. This invention improves the coagulation and drying processes of natural rubber latex, bringing significant technological breakthroughs and economic benefits to the natural rubber processing industry.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] A method for producing natural rubber by supergravity-coupled microwave drying includes the following steps:

[0009] S1: Hypergravity carbon dissolution reaction

[0010] Fresh latex is pumped into the hypergravity reactor through the liquid phase inlet using a liquid transfer pump, while carbon dioxide enters the hypergravity reactor through the gas phase inlet using a gas flow meter. Both react and dissolve fully in the hypergravity reactor, and are then discharged through the liquid phase outlet after reaction and dissolution.

[0011] S2: Allow to solidify

[0012] The latex discharged from the liquid phase outlet is transported to a settling and coagulation tank, where it is allowed to stand until it is completely solidified, forming a wet glue.

[0013] S3: Dehydration and Granulation

[0014] The wet adhesive is fed to an extrusion dewatering machine to remove moisture and then granulate.

[0015] S4: Microwave drying

[0016] The dehydrated wet adhesive is conveyed to a microwave drying oven for drying, forming a natural dry adhesive.

[0017] Preferably, in step S1, the apparatus used for the hypergravity carbon dissolution reaction includes a hypergravity reactor, a gas valve, a gas flow meter, a pressure gauge, a liquid valve, a liquid flow meter, and a liquid transfer pump.

[0018] Preferably, the hypergravity reactor includes a motor, a rotating shaft, packing material, a rotating chamber, a liquid phase inlet, a liquid phase outlet, a gas phase outlet, and a gas phase inlet;

[0019] Preferably, the liquid transfer pump is a peristaltic pump or a diaphragm pump; the liquid flow meter is a positive displacement flow meter or an ultrasonic flow meter.

[0020] Preferably, the outer shell of the supergravity reactor has a diameter of 250-5000 mm.

[0021] Preferably, the rotor inner diameter of the supergravity reactor is 50-1000mm, the rotor outer diameter is 150-4000mm, and the rotor speed is 100-2000rpm.

[0022] Preferably, the filler is a metal wire mesh with a mesh size of 2-5 mm.

[0023] Preferably, in step S1, the operation process involves continuous liquid and continuous gas intake; the gas phase is a continuous phase, and the liquid phase is a dispersed phase.

[0024] Preferably, in step S1, the gas-liquid ratio of carbon dioxide to fresh latex is 1.3-1.7.

[0025] Preferably, in step S2, the settling time is 30-120 minutes.

[0026] Preferably, in step S4, the temperature of the microwave drying oven is 80-120℃, and the drying time is 20-40 min.

[0027] Any range described in this invention includes the endpoint, any value between the endpoints, and any subrange consisting of the endpoint or any value between the endpoints.

[0028] Unless otherwise specified, all raw materials used in this invention can be obtained commercially, and the equipment used in this invention can be conventional equipment in the relevant field or refer to existing technology in the relevant field.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] This invention employs a high-gravity carbonization technology to achieve efficient coagulation of natural latex in a short time, followed by brief microwave drying to form natural raw rubber. Compared with existing technologies, this invention effectively improves the production efficiency of natural rubber, reduces production costs, and makes the production process safer and more environmentally friendly. The resulting natural raw rubber exhibits superior physical properties, with a Mooney viscosity of 80-86, plasticity retention ≥95%, elongation at break ≥730%, and tensile strength ≥24MPa. This provides reliable technical support for the natural rubber processing industry. Attached Figure Description

[0031] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0032] Figure 1 This is a flowchart of the process for producing natural rubber using supergravity-coupled microwave drying according to the present invention;

[0033] Figure 2 This is a schematic diagram of the supergravity reaction device of the present invention;

[0034] Figure 3This is a schematic diagram of the microwave drying device of the present invention. Detailed Implementation

[0035] To more clearly illustrate the present invention, the following description, in conjunction with preferred embodiments, further clarifies the invention. Those skilled in the art should understand that the specific descriptions below are illustrative rather than restrictive, and should not be construed as limiting the scope of protection of the present invention.

[0036] See Figures 1-3 As shown, as one aspect of the present invention, a method for producing natural rubber by supergravity-coupled microwave drying includes the following steps:

[0037] S1: Hypergravity carbon dissolution reaction

[0038] Fresh latex is pumped into the hypergravity reactor through the liquid phase inlet using a liquid transfer pump, while carbon dioxide enters the hypergravity reactor through the gas phase inlet using a gas flow meter. Both react and dissolve fully in the hypergravity reactor, and are then discharged through the liquid phase outlet after reaction and dissolution.

[0039] In the hypergravity carbon dissolution reactor, CO2 dissolves in natural latex to produce carbonic acid, which effectively reduces the pH value of the natural latex and promotes its coagulation process. The hypergravity environment and shearing action increase the mass transfer efficiency between phases by 1 to 3 orders of magnitude compared to traditional tower reactors, greatly enhancing the micro-mixing and mass transfer processes. This allows CO2 to form micro- and nano-bubbles in the natural latex. The presence of these micro- and nano-bubbles increases the gas-liquid contact area, enhances the mass transfer / dissolution of the gas-liquid system, and promotes carbonic acid production to a greater extent. The outlet pH of the latex in the hypergravity reactor of this invention can be reduced to 6.01, and if the circulation exceeds 5 minutes, the outlet pH can be reduced to 5.90.

[0040] S2: Allow to solidify

[0041] The latex discharged from the liquid phase outlet is transported to a settling and coagulation tank, where it is allowed to stand until it is completely solidified, forming a wet glue.

[0042] S3: Remove moisture

[0043] The wet rubber is fed into an extrusion dewatering machine to remove moisture;

[0044] S4: Microwave drying

[0045] The dehydrated wet adhesive is conveyed to a microwave drying oven for drying, forming a natural dry adhesive.

[0046] In this invention, the extrusion dewatering machine can remove most of the moisture from the wet adhesive, and then the dehydrated wet adhesive is sent to a drying device for microwave drying. During microwave drying, under the action of an electromagnetic field, the polar molecules in the wet adhesive change from their original random distribution state to an arrangement according to the polarity of the electric field. Under the action of a high-frequency electromagnetic field, these oriented molecules continuously change according to the frequency of the alternating electromagnetic field. This process causes continuous molecular motion and mutual friction, thereby generating heat. The electric field energy in this process is converted into the thermal energy of the medium, causing the temperature of the medium to rise continuously, thus achieving the purpose of drying.

[0047] In this invention, the inventors discovered that when the drying temperature is 80-120℃, the wet adhesive can be dried uniformly in about 30-60 minutes.

[0048] See Figure 2 As shown, according to certain embodiments of the present invention, in step S1, the apparatus used for the hypergravity carbon dissolution reaction includes a hypergravity reactor 1, a gas valve 2, a gas flow meter 3, a pressure gauge 4, a liquid valve 5, a liquid flow meter 6, and a liquid transfer pump 7.

[0049] According to certain embodiments of the present invention, the supergravity reactor 1 includes a motor 11, a rotating shaft 12, packing 13, a rotating chamber 14, a liquid phase inlet 15, a gas phase outlet 16, a liquid phase outlet 17, and a gas phase inlet 18.

[0050] According to certain embodiments of the present invention, the liquid transfer pump 15 is a peristaltic pump or a diaphragm pump; the liquid flow meter 13 is a positive displacement flow meter or an ultrasonic flow meter.

[0051] According to certain embodiments of the present invention, the outer shell of the hypergravity reactor has a diameter of 250-5000 mm.

[0052] According to certain embodiments of the present invention, the rotor inner diameter of the supergravity reactor is 50-1000 mm, the rotor outer diameter is 150-4000 mm, and the rotor speed is 100-2000 rpm.

[0053] According to certain embodiments of the present invention, the filler is a metal wire mesh with a mesh aperture of 2-5 mm.

[0054] According to certain embodiments of the present invention, in step S1, the operation process is continuous liquid feeding and continuous gas feeding; the gas phase is a continuous phase and the liquid phase is a dispersed phase.

[0055] According to certain embodiments of the present invention, in step S1, the gas-liquid ratio of the carbon dioxide and the fresh latex is 1.3-1.7.

[0056] According to some embodiments of the present invention, in step S2, the settling time is 30-120 minutes.

[0057] According to certain embodiments of the present invention, in step S4, the temperature of the microwave drying oven is 80-120°C, and the drying time is 30-60 minutes. It is understood that the microwave drying apparatus in this invention is prior art; for example, see [link to previous document]. Figure 3 As shown, the microwave drying device includes an exhaust port 21, a material conveyor belt 22, a microwave drying chamber 23, and a conveyor belt motor 24.

[0058] Example 1

[0059] A method for producing natural rubber by supergravity-coupled microwave drying includes the following steps:

[0060] First, CO2 fills the entire reaction apparatus. Fresh latex is fed through a peristaltic pump at a gas-liquid ratio of 1.5. The reaction is carried out at a supergravity speed of 1200 rpm. The pH of the outlet latex is measured to be 6.01 using a pH meter. The outlet latex is allowed to stand for 1-2 hours to achieve complete coagulation. At this time, the rubber still retains its original fresh herbal smell.

[0061] After the wet gum is dehydrated, it is microwave dried at 100℃ for about 40 minutes to form natural raw gum.

[0062] The raw rubber was tested and found to have a plasticity retention rate of 95%, a Mooney viscosity of 81.3, an elongation at break of 731.9%, and a tensile strength of 25.8 MPa.

[0063] Example 2 :

[0064] A method for producing natural rubber by supergravity-coupled microwave drying includes the following steps:

[0065] First, CO2 fills the entire reaction apparatus. Fresh latex is fed through a peristaltic pump at a gas-liquid ratio of 1.5. The reaction is carried out at a supergravity speed of 1200 rpm. The outlet latex is circulated for 5 minutes, and the pH of the outlet latex is measured to be 5.90 using a pH meter. The outlet latex is allowed to stand for 0.5-1 hours to achieve complete coagulation. At this time, the rubber still retains its original fresh herbal aroma.

[0066] After the wet gum is dehydrated, it is microwave dried at 100℃ for about 40 minutes to form natural raw gum.

[0067] The raw rubber was tested and found to have a plasticity retention rate of 96%, a Mooney viscosity of 82.2, an elongation at break of 730.4%, and a tensile strength of 24.9 MPa.

[0068] Comparative Example 1 [Natural solidification + microwave drying]

[0069] Repeat Example 1, except that the coagulation method of fresh latex is changed to natural coagulation. Fresh latex can be naturally coagulated into wet glue after standing for more than 24 hours. However, at this time, the latex produces a strong sour smell due to natural fermentation. After the wet glue is dehydrated, it is microwave dried at 100°C for 40 minutes to form natural raw glue.

[0070] The raw rubber was tested and found to have a plasticity retention rate of 89%, a Mooney viscosity of 79.3, an elongation at break of 722.7%, and a tensile strength of 22.7 MPa.

[0071] Therefore, it can be seen that:

[0072] 1) This comparative example uses microwave drying alone without using a hypergravity reactor for coagulation, compared with Example 1 which uses both microwave drying and a hypergravity reactor for coagulation. The test results show that after hypergravity treatment, the plasticity retention rate, Mooney viscosity, elongation at break, and tensile strength of the resulting adhesive are significantly improved.

[0073] 2) Meanwhile, a comparison between this comparative example and Example 1 shows that using a high-gravity reactor can significantly shorten the solidification time;

[0074] Comparative Example 2 [Supergravity solidification + hot air drying]

[0075] Repeat Example 1, except that the drying method of the raw rubber is changed to hot air drying; that is, after the wet rubber is dehydrated, it is dried with hot air at a temperature of 70°C for more than 24 hours to form natural raw rubber.

[0076] The raw rubber was tested and found to have a plasticity retention rate of 91%, a Mooney viscosity of 80.2, an elongation at break of 727.2%, and a tensile strength of 22.9 MPa.

[0077] Therefore, it can be seen that:

[0078] 1) This comparative example uses a centrifugal reactor for coagulation alone without microwave drying, and is compared with Example 1, which uses both microwave drying and a centrifugal reactor for coagulation. The test results show that the raw rubber after microwave drying has significantly improved plasticity retention, elongation at break, and tensile strength.

[0079] 2) Meanwhile, a comparison between this comparative example and Example 1 shows that microwave drying can significantly shorten the drying time;

[0080] 3) This comparative example and Comparative Example 3 were compared without microwave drying or a centrifugal reactor for coagulation. The test results show that the plasticity retention rate, elongation at break, and tensile strength of the resulting adhesive significantly increased after centrifugal and microwave drying treatments.

[0081] Comparative Example 3 [Formic acid coagulation + hot air drying]

[0082] Example 1 was repeated, except that the coagulation method of fresh latex was changed to formic acid coagulation, and the drying method of raw rubber was changed to hot air drying. A certain proportion of formic acid was added to the fresh latex and stirred for 1-2 hours to coagulate the latex into wet rubber. However, this process produces a large amount of irritating odor due to the addition of formic acid. After dehydration, the wet rubber was dried with hot air at a temperature of 70°C for more than 24 hours to form natural raw rubber.

[0083] The raw rubber was tested and found to have a plasticity retention rate of 78%, a Mooney viscosity of 86.5, an elongation at break of 706.0%, and a tensile strength of 21.9 MPa.

[0084] Therefore, it can be seen that:

[0085] 1) This comparative example uses neither microwave drying nor a high-gravity reactor for coagulation, compared to Example 1 which uses both microwave drying and a high-gravity reactor for coagulation. The plasticity retention, elongation at break, and tensile strength of the resulting adhesive are significantly reduced by this method.

[0086] 2) This comparative example did not use microwave drying or a hypergravity reactor for coagulation, and was compared with Comparative Example 2, which did not use microwave drying but used a hypergravity reactor for coagulation. The test results show that after hypergravity treatment, the plasticity retention rate, elongation at break, and tensile strength of the resulting adhesive were significantly improved.

[0087] Comparative Example 4 [Ultragravity solidification + vacuum drying]

[0088] Example 1 was repeated, except that the drying method for the raw rubber was changed to vacuum drying. After the wet rubber was dehydrated, it was vacuum dried at a temperature of 70°C, a vacuum degree of 0.2 kPa, and a drying time of 20 hours to form natural raw rubber.

[0089] The raw rubber was tested and found to have a plasticity retention rate of 93%, a Mooney viscosity of 68.0, an elongation at break of 718.4%, and a tensile strength of 22.18 MPa.

[0090] Therefore, it can be seen that:

[0091] 1) This comparative example uses a centrifugal reactor for coagulation alone, without microwave drying, in contrast to Example 1, which uses both microwave drying and a centrifugal reactor for coagulation. The plasticity retention, elongation at break, and tensile strength of the adhesive produced by this method show a significant decrease.

[0092] 2) This comparative example is compared with Comparative Example 3, which does not use microwave drying or a supergravity reactor for coagulation. The plasticity retention rate, elongation at break and tensile strength of the resulting gel are significantly improved.

[0093] In summary, the test results from the above examples and comparative examples show that the natural latex solidified by supergravity carbon dissolution has a significantly shorter solidification time compared to natural solidification, and the resulting natural raw rubber has stronger tensile properties and plasticity retention. Compared with the formic acid solidification process, the tensile strength, elongation at break, and plasticity retention of the produced natural raw rubber are significantly improved, and the operation is simpler and more environmentally friendly.

[0094] Compared with hot air drying and vacuum drying, microwave-dried natural rubber can achieve uniform drying of the rubber in a shorter time, effectively improving drying efficiency. Furthermore, the plasticity retention and tensile properties of microwave-dried natural rubber are significantly improved.

[0095] This invention unexpectedly discovered a technique for coagulating and drying fresh latex using a supergravity carbon dissolution coupled with microwave drying. Only through this coupling of techniques can the desired benefits be achieved, such as a Mooney viscosity of 80-86, plasticity retention ≥95%, elongation at break ≥730%, and tensile strength ≥24 MPa.

[0096] This invention has significant practical application value for natural latex processing technology. Compared with existing technologies, this invention can achieve the coagulation and drying of natural latex in a shorter time, enabling the production of high-quality natural rubber to a greater extent. Furthermore, the process is more environmentally friendly, simpler to operate, and effectively improves the production efficiency of natural rubber, providing reliable technical support for related fields.

[0097] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is impossible to exhaustively list all embodiments here. All obvious variations or modifications derived from the technical solutions of the present invention are still within the protection scope of the present invention.

Claims

1. A method for producing natural rubber by supergravity coupled microwave drying, characterized by, The method comprises the following steps: S1: supergravity carbon dissolving reaction Fresh latex is pumped into the supergravity reactor through the liquid inlet by a liquid delivery pump, and carbon dioxide is introduced into the supergravity reactor through the gas inlet by a gas flow meter; the two are fully reacted and dissolved in the supergravity reactor, and then discharged through the liquid outlet after reaction and dissolution; S2: standing and solidification The latex discharged from the liquid outlet is transported to a standing and solidification tank, and is completely solidified by standing to form wet rubber; S3: dewatering and granulation The wet rubber is transported to an extrusion dewatering machine to remove water and perform granulation processing; S4: microwave drying The wet rubber after dewatering is transported to a microwave drying oven for drying to form natural dry rubber.

2. The method for producing natural rubber by supergravity coupling microwave drying according to claim 1, characterized in that: In step S1, the device used for supergravity carbon dissolving reaction comprises a supergravity reactor, a gas valve, a gas flow meter, a pressure gauge, a liquid valve, a liquid flow meter, and a liquid delivery pump.

3. The process for production of natural rubber by supergravity coupled microwave drying as claimed in claim 2 wherein: The supergravity reactor comprises a motor, a rotating shaft, a filler, a rotating cavity, a liquid inlet, a liquid outlet, a gas outlet, and a gas inlet.

4. The method for producing natural rubber by supergravity coupling microwave drying according to claim 2, characterized in that: The liquid delivery pump is a peristaltic pump or a diaphragm pump; the liquid flow meter is a positive displacement flow meter or an ultrasonic flow meter.

5. The method of claim 2, wherein the supergravity coupled microwave drying of natural rubber is characterized by: The outer shell diameter of the supergravity reactor is 250-5000 mm.

6. The method of claim 2, wherein the supergravity coupled microwave drying of natural rubber is characterized by: The inner diameter of the rotor of the supergravity reactor is 50-1000 mm, the outer diameter of the rotor is 150-4000 mm, and the rotor speed is 100-2000 rpm.

7. The method for producing natural rubber by supergravity coupling microwave drying according to claim 3, characterized in that: The filler is a metal wire mesh, and the mesh aperture is 2-5 mm.

8. The method of claim 1, wherein the supergravity coupled microwave drying of natural rubber is characterized by: In step S1, the operation process is continuous liquid feeding and continuous gas feeding; the gas phase is the continuous phase, and the liquid phase is the dispersed phase.

9. The method of claim 1, wherein the supergravity coupled microwave drying of natural rubber is characterized by: In step S1, the gas-liquid ratio of carbon dioxide and fresh latex is 1.3-1.

7.

10. The process for production of natural rubber by super gravity coupled microwave drying as claimed in claim 1 wherein: In step S2, the standing time is 30-120 min.

11. The process for production of natural rubber by supergravity coupled microwave drying as claimed in claim 1 wherein: In step S4, the temperature of the microwave drying oven is 80-120°C, and the drying time is 20-40 min.

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