Method for producing natural rubber by coupling supergravity with microwave drying

Abstract

The invention discloses a method for producing natural rubber by coupling supergravity with microwave drying. The method comprises the following steps: S1, supergravity carbon dissolving reaction; s2, standing and solidifying; s3, dehydrating and granulating; and S4, microwave drying. According to the invention, high-efficiency solidification of natural latex is realized in a short time by adopting a supergravity carbon dissolving technology, and then a working mode of natural raw rubber is formed through short-time microwave drying. Compared with the prior art, the natural raw rubber production efficiency is higher, operation is safer and more environmentally friendly, the produced natural raw rubber is more excellent in physical performance, the Mooney viscosity of the prepared raw rubber is 80-86, the plasticity retention rate is larger than or equal to 95%, the elongation at break is larger than or equal to 730%, and the tensile strength is larger than or equal to 24 MPa; and reliable technical support is provided for the field of natural rubber processing.

Description

Technical Field

[0001] The invention belongs to the field of natural rubber processing, and in particular relates to a method for producing natural rubber by ultra-gravity coupled microwave drying. Background Art

[0002] Natural rubber (NR) is considered one of the four basic industrial raw materials along with coal, steel and oil, and is the only renewable resource among the four industrial raw materials, with important strategic value. Due to its excellent high elasticity, mechanical properties, heat generation and wear resistance, as well as good insulation, sealing and adhesion, it is widely used in agriculture, industry, national defense science and technology, transportation, medical care and daily life and other fields.

[0003] China has always been a major consumer of natural rubber. Although my country's rubber industry has made significant progress, the output and supply of domestic natural rubber still cannot meet the needs of the domestic market, resulting in the need to import a large amount of rubber. In recent years, my country's natural rubber production field still has problems such as poor consistency of rubber quality, serious environmental pollution, and insufficient output of high-performance natural rubber. Therefore, we must continue to improve the existing rubber making process to improve the quality of natural rubber primary processed products to meet future development needs.

[0004] There are many factors that affect the performance of natural rubber, and the processing technology of latex is the most important, among which the coagulation and drying process is the top priority. Therefore, some scholars have conducted a lot of research on the coagulation and drying process of natural rubber latex.

[0005] At present, the coagulation process of natural rubber in my country is mainly acid coagulation, and the commonly used acids in the process are formic acid, acetic acid and sulfuric acid. Although the acid coagulation rubber making process has a fast rubber making speed and a high natural raw rubber production rate, at the same time, the acid coagulation rubber making cost is relatively high, accounting for more than 15% of the total rubber making cost, and it is highly corrosive. A large amount of clean water is required to treat the residual acid, ammonium salt, etc. in the wet rubber, which is seriously polluting the environment. Long-term production practice has proved that the physical properties of the standard rubber produced by the acid coagulation process are poor. The drying process of natural rubber mainly adopts hot air drying. This drying process uses coal, diesel, electric heat, etc. as heat sources and air as the heating medium to dry the natural rubber. However, this drying process has a long existence time, and there is aging and bonding of the rubber during the drying process, and the white core appears due to insufficient drying, resulting in the problem of unstable quality of the produced rubber. Summary of the invention

[0006] In order to solve the problems of serious environmental pollution, long production cycle, poor performance of the produced rubber, and low yield in the existing natural rubber processing process, the present invention provides a method for producing natural rubber by ultra-gravity coupled microwave drying. The method effectively improves the production efficiency of natural rubber, reduces production costs, and the production process is safe, green and pollution-free. The tensile properties and plasticity retention rate of the produced natural raw rubber are significantly improved, and it has more excellent physical properties. The present invention improves the coagulation and drying process of natural latex, which will bring important technological breakthroughs and economic benefits to the field of natural rubber processing.

[0007] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0008] A method for producing natural rubber by ultra-gravity coupled microwave drying comprises the following steps:

[0009] S1: Ultra-gravity carbon dissolution reaction

[0010] The fresh latex is pumped into the high-gravity reactor from the liquid phase inlet through a liquid delivery pump, and the carbon dioxide enters the high-gravity reactor from the gas phase inlet through a gas flow meter; the two are fully reacted and dissolved in the high-gravity reactor, and are discharged from the liquid phase outlet after the reaction and dissolution;

[0011] S2: Standing and solidifying

[0012] The latex discharged from the liquid phase outlet is transported to a static coagulation tank and allowed to stand to completely coagulate to form wet glue;

[0013] S3: Dehydration and granulation

[0014] The wet rubber is transported to an extrusion dehydrator to remove moisture and undergo granulation processing;

[0015] S4: Microwave drying

[0016] The dehydrated wet glue is conveyed to a microwave drying oven for drying to form natural dry glue.

[0017] Preferably, in step S1, the device used for the ultra-gravity carbon dissolution reaction includes an ultra-gravity reactor, a gas valve, a gas flow meter, a pressure gauge, a liquid valve, a liquid flow meter, and a liquid delivery pump.

[0018] Preferably, the ultra-gravity reactor comprises a motor, a rotating shaft, a filler, a rotating chamber, a liquid phase inlet, a liquid phase outlet, a gas phase outlet, and a gas phase inlet;

[0019] Preferably, 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.

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

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

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

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

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

[0025] Preferably, in step S2, the standing time is 30-120 min.

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

[0027] Any range described in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0028] Unless otherwise specified, all raw materials in the present invention can be purchased from the market, and the equipment used in the present invention can adopt conventional equipment in the relevant field or refer to the existing technology in the relevant field.

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

[0030] The present invention adopts ultra-gravity carbon dissolving technology to make natural rubber latex realize efficient coagulation in a short time, and then forms a working mode of natural raw rubber through short microwave drying. Compared with the prior art, the present invention effectively improves the production efficiency of natural rubber, reduces the production cost, and the production process is safer and greener. The physical properties of the produced natural raw rubber are more excellent. The Mooney viscosity of the prepared raw rubber is 80-86, the plasticity retention rate is ≥95%, the elongation at break is ≥730%, and the tensile strength is ≥24MPa; it provides reliable technical support for the field of natural rubber processing. BRIEF DESCRIPTION OF THE DRAWINGS

[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 flow chart of producing natural rubber by ultra-gravity coupled microwave drying of the present invention;

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

[0034] Figure 3It is a schematic structural diagram of the microwave drying device of the present invention. DETAILED DESCRIPTION

[0035] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. It should be understood by those skilled in the art that the following specific description is illustrative rather than restrictive, and should not be used to limit the scope of protection of the present invention.

[0036] See also Figure 1-Figure 3 As shown, as one aspect of the present invention, a method for producing natural rubber by ultra-gravity coupled microwave drying of the present invention comprises the following steps:

[0037] S1: Ultra-gravity carbon dissolution reaction

[0038] The fresh latex is pumped into the high-gravity reactor from the liquid phase inlet through a liquid delivery pump, and the carbon dioxide enters the high-gravity reactor from the gas phase inlet through a gas flow meter; the two are fully reacted and dissolved in the high-gravity reactor, and are discharged from the liquid phase outlet after the reaction and dissolution;

[0039] In the ultra-gravity carbon dissolution reaction device, CO2 dissolves in natural latex and produces carbonic acid, which can effectively reduce the pH value of natural latex and promote the coagulation process of natural latex; the ultra-gravity environment and shearing effect increase the mass transfer efficiency between phases by 1 to 3 orders of magnitude compared with the traditional tower, and the micro-mixing and mass transfer process are greatly enhanced, so that CO2 forms micro-nano bubbles in natural latex. The presence of nano-micro bubbles increases the gas-liquid contact area, strengthens the mass transfer / dissolution of the gas-liquid system, and promotes the generation of carbonic acid to a higher degree; the outlet latex pH in the ultra-gravity reactor of the present invention can be reduced to 6.01, and if the outlet latex pH after circulation exceeds 5 minutes can be reduced to 5.90;

[0040] S2: Standing and solidifying

[0041] The latex discharged from the liquid phase outlet is transported to a static coagulation tank and allowed to stand to completely coagulate to form wet glue;

[0042] S3: Dehydration

[0043] The wet rubber is transported to an extrusion dehydrator to remove moisture;

[0044] S4: Microwave drying

[0045] The dehydrated wet glue is conveyed to a microwave drying oven for drying to form natural dry glue.

[0046] In the present invention, the extrusion dehydrator can remove most of the moisture from the wet glue, and then the dehydrated wet glue is sent to the drying device for microwave drying. In microwave drying, under the action of the electromagnetic field, the polar molecules in the wet glue are changed from the original random distribution state to the polar orientation arrangement according to the electric field. Under the action of the high-frequency electromagnetic field, these oriented molecules continuously change according to the frequency of the alternating electromagnetic field. This process causes the molecules to continuously move and rub against each other, thereby generating heat. The electric field energy in this process is converted into the thermal energy of the medium, so that the temperature of the medium is continuously increased, thereby achieving the purpose of drying.

[0047] In the present invention, the inventors found that when the drying temperature is 80-120° C., the wet glue can be uniformly dried in about 30-60 minutes.

[0048] See also Figure 2 As shown, according to some embodiments of the present invention, in step S1, the device used for the ultra-gravity carbon dissolution reaction includes an ultra-gravity 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 delivery pump 7.

[0049] According to some embodiments of the present invention, the ultra-gravity reactor 1 includes a motor 11, a rotating shaft 12, a filler 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 some embodiments of the present invention, the liquid delivery 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 some embodiments of the present invention, the shell diameter of the ultra-gravity reactor is 250-5000 mm.

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

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

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

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

[0056] According to some embodiments of the present invention, in step S2, the standing 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 can be understood that the microwave drying device in the present invention is a prior art, for example, see Figure 3 As shown, the microwave drying device includes an exhaust port 21 , a material conveyor belt 22 , a microwave drying box 23 and a conveyor belt motor 24 .

[0058] Example 1

[0059] A method for producing natural rubber by ultra-gravity coupled microwave drying comprises the following steps:

[0060] First, the entire reaction device is filled with CO2, and fresh latex is fed through a peristaltic pump with a gas-liquid ratio of 1.5. The reaction is carried out at a supergravity speed of 1200rpm. The pH of the outlet latex is detected by a pH meter and is 6.01. The outlet latex is left to stand for 1-2 hours to achieve complete coagulation of the latex, and the rubber still retains its original fresh herbal smell.

[0061] After the wet rubber is dehydrated, it is subjected to microwave drying at a drying temperature of 100°C for about 40 minutes to form natural raw rubber.

[0062] The raw rubber was tested and the plasticity retention rate was 95%, the Mooney viscosity was 81.3, the elongation at break was 731.9%, and the tensile strength was 25.8 MPa.

[0063] Example 2 :

[0064] A method for producing natural rubber by ultra-gravity coupled microwave drying comprises the following steps:

[0065] First, the entire reaction device is filled with CO2, and fresh latex is fed through a peristaltic pump with a gas-liquid ratio of 1.5. The reaction is carried out at a supergravity speed of 1200rpm. The outlet latex is circulated for 5 minutes, and the outlet latex pH is detected by a pH meter to be 5.90; the outlet latex is left to stand for 0.5-1h to achieve complete coagulation of the latex, and the rubber still retains its original fresh herbal smell;

[0066] After the wet rubber is dehydrated, it is subjected to microwave drying at a drying temperature of 100°C for about 40 minutes to form natural raw rubber.

[0067] The raw rubber was tested and the plasticity retention rate was 96%, the Mooney viscosity was 82.2, the elongation at break was 730.4%, and the tensile strength was 24.9 MPa.

[0068] Comparative Example 1

Natural solidification + microwave drying

[0069] Example 1 was repeated, except that the coagulation mode of fresh latex was changed to natural coagulation. The fresh latex was allowed to stand for more than 24 hours and naturally coagulated into wet rubber. However, at this time, the latex produced a heavy sour and smelly odor due to natural fermentation. After the wet rubber was dehydrated, it was microwave dried at a drying temperature of 100° C. and a drying time of 40 minutes to form natural raw rubber.

[0070] The raw rubber was tested and the plasticity retention rate was 89%, the Mooney viscosity was 79.3, the elongation at break was 722.7%, and the tensile strength was 22.7 MPa.

[0071] It can be seen from this that:

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

[0073] 2) At the same time, by comparing this comparative example with Example 1, it can be seen that the use of an ultra-gravity reactor for treatment can significantly shorten the coagulation time;

[0074] Comparative Example 2

Ultra-gravity solidification + hot air drying

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

[0076] The raw rubber was tested and the plasticity retention rate was 91%, the Mooney viscosity was 80.2, the elongation at break was 727.2%, and the tensile strength was 22.9 MPa.

[0077] It can be seen from this that:

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

[0079] 2) At the same time, by comparing this comparative example with Example 1, it can be seen that microwave drying can significantly shorten the drying time;

[0080] 3) This comparative example and comparative example 3 do not use microwave drying or high gravity reactor for coagulation. The test results show that after high gravity and microwave drying, the plasticity retention rate, elongation at break and tensile strength of the produced glue are significantly increased.

[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, so that the latex could be coagulated into wet rubber, but this process produced a large amount of pungent odor due to the addition of formic acid; after the wet rubber was dehydrated, it was dried with hot air at a drying temperature of 70°C and a drying time of more than 24 hours to form natural raw rubber.

[0083] The raw rubber was tested and the plasticity retention rate was 78%, the Mooney viscosity was 86.5, the elongation at break was 706.0%, and the tensile strength was 21.9 MPa.

[0084] It can be seen from this that:

[0085] 1) This comparative example does not use microwave drying or high gravity reactor for coagulation, and is compared with Example 1 which uses both microwave drying and high gravity reactor for coagulation. The plasticity retention rate, elongation at break and tensile strength of the glue produced by this method are greatly reduced;

[0086] 2) This comparative example does not use microwave drying or supergravity reactor for coagulation, and is compared with comparative example 2 which does not use microwave drying but uses supergravity reactor for coagulation. It can be seen from the test results that after supergravity treatment, the plasticity retention rate, elongation at break and tensile strength of the produced glue are significantly improved.

[0087] Comparative Example 4

Ultra-gravity solidification + vacuum drying

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

[0089] The raw rubber was tested and the plasticity retention rate was 93%, the Mooney viscosity was 68.0, the elongation at break was 718.4%, and the tensile strength was 22.18 MPa.

[0090] It can be seen from this that:

[0091] 1) This comparative example uses a supergravity reactor for coagulation without microwave drying, and is compared with Example 1 which uses both microwave drying and supergravity reactor for coagulation. The plasticity retention rate, elongation at break and tensile strength of the glue produced by this method show a significant decrease;

[0092] 2) Compared with Comparative Example 3, which neither uses microwave drying nor a supergravity reactor for coagulation, the plasticity retention rate, elongation at break and tensile strength of the produced glue are significantly improved.

[0093] To sum up: It can be seen from the test results of the above embodiments and comparative examples that the time required for coagulation of natural rubber latex after ultra-gravity carbon dissolution coagulation is greatly shortened compared with natural coagulation, and the produced natural raw rubber has stronger tensile properties and plasticity retention rate; compared with the formic acid coagulation process, the tensile strength, elongation at break and plasticity retention rate of the produced natural raw rubber are significantly improved, and the operation is simpler and greener.

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

[0095] The present invention unexpectedly found that the fresh latex can be coagulated and dried by using the technology of ultra-gravity carbon dissolution coupled with microwave drying. Only by coupling the above technology can the Mooney viscosity of the prepared raw rubber be 80-86, the plasticity retention rate be ≥95%, the elongation at break be ≥730%, the tensile strength be ≥24MPa and the like.

[0096] The invention has important practical application value for natural latex processing technology. Compared with the prior art, the invention can realize the coagulation and drying of natural latex in a short time, realize the production of high-quality natural rubber to a greater extent, and the process is more environmentally friendly and simpler to operate, effectively improving the natural rubber production efficiency, and providing reliable technical support for related fields.

[0097] Obviously, the above embodiments of the present invention are merely examples for clearly explaining the present invention, and are not intended to limit the implementation methods of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is impossible to list all implementation methods here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for producing natural rubber by ultra-gravity coupled microwave drying, characterized in that: The steps include: S1: Ultra-gravity carbon dissolution reaction The fresh latex is pumped into the high-gravity reactor from the liquid phase inlet through a liquid delivery pump, and the carbon dioxide enters the high-gravity reactor from the gas phase inlet through a gas flow meter; the two are fully reacted and dissolved in the high-gravity reactor, and are discharged from the liquid phase outlet after the reaction and dissolution; S2: Standing and solidifying The latex discharged from the liquid phase outlet is transported to a static coagulation tank and allowed to stand to completely coagulate to form wet glue; S3: Dehydration and granulation The wet rubber is transported to an extrusion dehydrator to remove moisture and undergo granulation processing; S4: Microwave drying The dehydrated wet glue is conveyed to a microwave drying oven for drying to form natural dry glue.

2. The method for producing natural rubber by ultra-gravity coupled microwave drying according to claim 1, characterized in that: In step S1, the apparatus used for the ultra-gravity carbon dissolution reaction includes an ultra-gravity 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 method for producing natural rubber by ultra-gravity coupled microwave drying according to claim 2, characterized in that: The ultra-gravity reactor comprises a motor, a rotating shaft, a filler, a rotating chamber, a liquid phase inlet, a liquid phase outlet, a gas phase outlet and a gas phase inlet.

4. The method for producing natural rubber by ultra-gravity coupled 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 for producing natural rubber by ultra-gravity coupled microwave drying according to claim 2, characterized in that: The outer shell diameter of the ultra-gravity reactor is 250-5000 mm.

6. The method for producing natural rubber by ultra-gravity coupled microwave drying according to claim 2, characterized in that: The inner diameter of the rotor of the ultra-gravity 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 ultra-gravity coupled microwave drying according to claim 2, characterized in that: The filler is a metal wire mesh with an aperture of 2-5 mm.

8. The method for producing natural rubber by ultra-gravity coupled microwave drying according to claim 1, characterized in that: In step S1, the operation process is continuous liquid inlet and continuous gas inlet; the gas phase is the continuous phase and the liquid phase is the dispersed phase; Preferably, in step S1, the gas-liquid ratio of the carbon dioxide and the fresh latex is 1.3-1.

7.

9. The method for producing natural rubber by ultra-gravity coupled microwave drying according to claim 1, characterized in that: In step S2, the standing time is 30-120 min.

10. The method for producing natural rubber by ultra-gravity coupled microwave drying according to claim 1, characterized in that: 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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