Preparation method of high-performance raw natural rubber

Abstract

The invention discloses a preparation method of high-performance raw natural rubber. The preparation method comprises the following steps: 1) adding carbon dioxide from an inlet of a supergravity device; 2) adding fresh natural latex into a supergravity device from a material inlet; 3) the carbon dioxide and the natural latex are in effective contact on a rotor of the supergravity device; 4) collecting natural latex at a material outlet, and standing or slowly flowing and solidifying at room temperature to obtain milk white natural rubber clots; and 5) sequentially carrying out thinning, crepe pressing and drying on the rubber clots to further obtain the raw natural rubber which is milky white to yellowish. According to the invention, zero acid consumption in the natural latex solidification process, zero emission of organic acid-containing wastewater / waste gas and product quality improvement are realized. The process conditions are mild, and the solidification time is less than or equal to 1h; according to the method, continuous operation of the process can be achieved, the prepared raw rubber is good in quality, the initial plasticity value is larger than or equal to 45, the plasticity retention rate is larger than or equal to 95, and the tensile strength after vulcanization is larger than or equal to 24 MPa.

Description

Technical Field

[0001] The invention relates to the technical field of natural rubber raw rubber, in particular to a method for preparing high-performance natural rubber raw rubber. Background Art

[0002] Natural latex is a viscous milky white liquid. The rubber obtained through further processing has a wide range of applications, including aviation, automobile transportation, medical industry, daily necessities and strategic materials. The main source of natural latex is the Brazilian rubber tree, which is made into raw rubber through processes such as collection, coagulation and drying. Traditional natural rubber raw rubber usually uses the acid coagulation method. Excessive acidity will destroy the molecular chain of natural rubber. The prepared raw rubber has limited performance. A large amount of acidic latex slurry waste will also be produced in the process, causing environmental pollution. With the continuous growth of global demand for rubber, the performance of traditional natural rubber can no longer meet the increasingly complex and demanding application scenarios. Therefore, the development of more environmentally friendly and higher-performance natural rubber raw rubber has become an important research direction in the industry.

[0003] The existing natural rubber preparation process includes the steps of latex, coagulation, pressing, drying and packaging. During this process, the non-rubber components of latex (such as proteins, lipids, etc.) have an adverse effect on the performance of natural rubber. On the one hand, researchers have tried to develop new production equipment to strengthen the existing coagulation technology. For example, Chinese patent application CN109517095A discloses a natural latex coagulation device and method, which uses a DC electric field to break the potential balance of the isoelectric point of protein on the surface of rubber particles, thereby agglomerating rubber particles; Chinese patent CN216321179U discloses a centrifugal natural latex coagulation device, which is provided with a spraying mechanism to make the texture of the coagulated natural latex more uniform and high-quality, and is provided with a solid natural latex pushing and conveying mechanism. This type of technical improvement has a relatively complex device and still has certain limitations in reducing environmental pollution. On the other hand, in response to the problem of insufficient rubber performance, the existing patented technologies are mainly concentrated in the fields of chemical modification, nanofiller composite and process optimization. For example, patent CN102323456A proposes a method for improving the heat resistance of natural rubber by graft polymerization, but this method relies on a large amount of chemical reagents and has certain environmental problems. Patent CN103456789B introduces a method of filling natural rubber with nano-silicon materials, which significantly improves the mechanical properties and aging resistance of rubber. However, the high price of nano-materials and the complex process limit the feasibility of large-scale application. Therefore, it is of great practical significance to develop a method for preparing natural rubber raw rubber without excessive reliance on chemical reagents or expensive fillers.

[0004] Carbon dioxide, as a colorless, odorless, non-toxic gas, can change the pH value of latex by combining with water to form carbonic acid, thereby controlling the coagulation process of natural latex. Compared with the traditional acid coagulation method, it is more environmentally friendly, and realizes the comprehensive utilization of carbon dioxide, promoting the low-carbon transformation of industry and scientific and technological innovation. At present, the process of carbon dioxide carbonization of natural latex is realized by high pressure means. For example, Chinese patent application CN111718432A discloses a method of coagulating natural latex using high-pressure carbon dioxide. Natural latex is coagulated under the protection of carbon dioxide, the rubber component will not be damaged, and can maintain its original state, and the natural rubber product finally prepared is of good quality.

[0005] However, the above-mentioned method of coagulating natural rubber latex with high-pressure carbon dioxide still has defects: 1) it must be carried out under high pressure (10-30MPa), which places higher requirements on equipment and increases production costs and risks; 2) the closed carbon dioxide reactor cannot achieve continuous operation of the reaction and can only be operated intermittently. Summary of the invention

[0006] Based on the limitations of the prior art, the present invention provides a method for preparing high-performance natural rubber raw rubber. The method can promote the dispersion and dissolution of carbon dioxide in natural rubber latex, achieve the optimized arrangement of natural rubber molecular chains, and improve the comprehensive performance of natural rubber raw rubber; at the same time, it achieves zero acid consumption in the coagulation process of natural latex, zero discharge of organic acid wastewater / waste gas, and product quality improvement. The pressure condition required for the preparation method of the present invention is ≤4MPa, avoiding the high-pressure production environment; the process conditions of the method of the present invention are mild, and the coagulation time is ≤1h; and the continuous operation of the process can be achieved; the color of the prepared raw rubber product is milky white to slightly yellow, the quality is good, the initial plasticity value is ≥45, the plasticity retention rate is ≥95, and the tensile strength after vulcanization is ≥24MPa.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing high-performance natural rubber raw rubber comprises the following steps:

[0009] 1) Adding carbon dioxide from the inlet of the supergravity device;

[0010] 2) adding fresh natural rubber latex into the supergravity device from the material inlet;

[0011] 3) Carbon dioxide and natural rubber latex are effectively contacted on the rotor of the high gravity device;

[0012] 4) collecting the natural rubber latex at the material outlet and letting it stand or slowly flow and coagulate at room temperature to obtain a milky white natural rubber clot;

[0013] 5) The rubber clot is pressed, creped and dried in sequence to obtain natural rubber raw rubber, which is milky white to slightly yellowish in color.

[0014] Preferably, in step 1), the purity of the carbon dioxide is 10% to 99.99% by volume.

[0015] Preferably, in step 2), the fresh natural latex refers to unprocessed fresh latex flowing out from rubber-producing plants.

[0016] Preferably, in step 3), the gas-liquid volume ratio of the carbon dioxide to natural rubber latex is 0.5:1 to 16:1.

[0017] Preferably, in step 3), the rotor speed of the supergravity device is 300 to 3000 r / min.

[0018] Preferably, in step 3), the operating pressure condition is ≤4 MPa, further ≤0.3 MPa.

[0019] Preferably, in step 4), the room temperature solidification range is 10 to 45°C.

[0020] Preferably, in step 4), the solidification is carried out under static state or slow flow; the static state time is 1 to 60 minutes, and the slow flow solidification time is 10 to 60 minutes.

[0021] Preferably, in step 5), the drying includes hot air drying, vacuum drying, microwave drying and freeze drying; according to the different drying methods, the color of the sample is milky white to slightly yellow.

[0022] 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.

[0023] 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.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. Compared with the acid coagulation method used in industry, the method of the present invention realizes zero acid consumption and zero emission of wastewater / acid waste gas in the natural latex coagulation process, which conforms to the development trend of the contemporary process industry to transform into a resource-saving and environmentally friendly model.

[0026] 2. The method of the present invention can realize the continuous carbonization of natural latex, with mild process conditions and fast coagulation speed, and is expected to realize the on-site emulsification of natural latex, thereby reducing the labor cost in the latex collection process. The pressure condition required for the preparation method of the present invention is ≤4MPa, avoiding the high-pressure production environment; thereby reducing production costs and risks.

[0027] 3. The method of the present invention realizes the optimized arrangement of natural rubber molecular chains and improves the comprehensive performance of natural rubber raw rubber. The obtained natural rubber raw rubber is milky white to slightly yellow in color, has good quality, has an initial plasticity value of ≥45, a plasticity retention rate of ≥95, and a tensile strength of ≥24MPa after vulcanization.

[0028] 4. The hypergravity environment provided by the hypergravity device in the present invention can improve the color difference and non-uniformity of performance caused by uneven distribution of latex, and realize the high-quality coagulation of natural latex; on the other hand, the hypergravity device enhances the mixing of gas-liquid phases and the rapid renewal of the phase interface, reduces the amount of carbon dioxide used, and the invented method has a fast latex coagulation speed and a mild process. The present invention combines hypergravity technology with the method of coagulating natural latex with carbon dioxide, which can realize a more efficient and environmentally friendly production process of natural rubber and higher product performance, and can meet the requirements of modern industry for high-performance natural rubber materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] Figure 1 The process flow chart of the method for preparing high-performance natural rubber raw rubber of the present invention is shown;

[0031] Figure 2 The milky white natural rubber raw rubber product diagram prepared by the present invention is shown;

[0032] Figure 3 A diagram of a yellowish natural rubber raw rubber product prepared by the present invention is shown. DETAILED DESCRIPTION

[0033] 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.

[0034] As one aspect of the present invention, the present invention provides a method for preparing a high-performance natural rubber raw rubber, comprising the following steps:

[0035] 1) Adding carbon dioxide from the inlet of the supergravity device;

[0036] 2) adding fresh natural latex into the supergravity device from the material inlet;

[0037] 3) Carbon dioxide and natural rubber latex are effectively contacted on the rotor of the high gravity device;

[0038] 4) collecting natural rubber latex at the discharge port and allowing it to stand or flow slowly to solidify at room temperature to obtain a milky white natural rubber clot;

[0039] 5) The rubber clot is pressed, creped and dried in sequence to obtain natural rubber raw rubber, which is milky white to slightly yellowish in color.

[0040] According to certain embodiments of the present invention, in step 1), the purity of the carbon dioxide is 10% to 99.99% by volume.

[0041] According to some embodiments of the present invention, in step 2), the fresh natural rubber latex refers to unprocessed fresh latex discharged from rubber-producing plants.

[0042] According to some embodiments of the present invention, in step 3), the gas-liquid volume ratio of the carbon dioxide to natural rubber latex is 0.5:1 to 16:1.

[0043] According to some embodiments of the present invention, in step 3), the rotor speed of the supergravity device is 300-3000 r / min; more preferably 900-1500 r / min.

[0044] According to certain embodiments of the present invention, in step 3), the operating pressure condition is ≤4 MPa; more preferably ≤0.3 MPa.

[0045] According to some embodiments of the present invention, in step 4), the room temperature solidification range is 10-45°C.

[0046] According to some embodiments of the present invention, in step 4), the solidification is performed under static state or slow flow; the static state time is 1 to 60 minutes, and the slow flow solidification time is 10 to 60 minutes.

[0047] According to some embodiments of the present invention, in step 5), the drying includes hot air drying, vacuum drying, microwave drying, freeze drying, etc.; according to different drying methods, the color of the sample is milky white to slightly yellow. The present invention has no particular limitation on the drying temperature and time, and a natural rubber raw rubber product can be obtained according to a process well known in the art.

[0048] The supergravity device used in the present invention is a prior art, such as a supergravity device for solid-liquid separation disclosed in Chinese patent CN113413646B, a CO2 lock device based on supergravity technology disclosed in Chinese patent CN116474578A, and an integrated method and system for industrial gas carbon capture treatment and irrigation water / ammonia-containing wastewater / seawater dissolved carbon fertilization disclosed in Chinese patent CN117123045A.

[0049] Example 1

[0050] A method for preparing high-performance natural rubber raw rubber comprises the following steps:

[0051] Take 2kg of fresh natural latex, the purity of carbon dioxide is 99.99%;

[0052] First, carbon dioxide was introduced into the supergravity device from the inlet, and natural latex was fed by a peristaltic pump with a gas-liquid ratio of 1.5:1 and a rotation speed of 1200rpm. Under normal pressure and 25°C, a large amount of latex was solidified after standing for 25 minutes.

[0053] The rubber coagulate is pressed, creped and hot-air dried in sequence to obtain slightly yellow natural rubber raw rubber.

[0054] Example 2

[0055] A method for preparing high-performance natural rubber raw rubber comprises the following steps:

[0056] Take 2kg of fresh natural latex, carbon dioxide is industrial waste gas, after treatment, its purity is 60%;

[0057] First, carbon dioxide was introduced into the supergravity device from the inlet, and natural latex was fed by a peristaltic pump with a gas-liquid ratio of 5:1 and a rotation speed of 1200 rpm. Under normal pressure and 25°C, a large amount of latex was solidified after standing for 40 minutes.

[0058] The rubber coagulate is pressed, creped and hot-air dried in sequence to obtain slightly yellow natural rubber raw rubber.

[0059] Example 3

[0060] A method for preparing high-performance natural rubber raw rubber comprises the following steps:

[0061] Take 2kg of fresh natural latex, carbon dioxide is industrial waste gas, after treatment, its purity is 98%;

[0062] First, carbon dioxide was introduced into the supergravity device from the inlet, and natural latex was fed by a peristaltic pump with a gas-liquid ratio of 3:1 and a rotation speed of 1200rpm. Under normal pressure and 25℃, a large amount of latex was solidified after standing for 30 minutes.

[0063] The rubber coagulate is pressed, creped and hot-air dried in sequence to obtain slightly yellow natural rubber raw rubber.

[0064] Example 4

[0065] A high-performance natural rubber raw rubber and a preparation method thereof, comprising the following steps:

[0066] Take 2kg of fresh natural latex, the purity of carbon dioxide is 99.99%;

[0067] First, carbon dioxide was introduced into the supergravity device from the inlet, and natural latex was fed by a peristaltic pump with a gas-liquid ratio of 1.5:1 and a rotation speed of 1200rpm. Under the conditions of low pressure of 0.1MPa and 25℃, a large amount of latex was solidified after standing for 3 minutes.

[0068] The rubber clot is successively thinned, creped and microwave dried to obtain yellowish natural rubber raw rubber.

[0069] Example 5

[0070] A high-performance natural rubber raw rubber and a preparation method thereof, comprising the following steps:

[0071] Take 2kg of fresh natural latex, the purity of carbon dioxide is 99.99%;

[0072] First, carbon dioxide was introduced into the supergravity device from the inlet, and natural latex was fed by a peristaltic pump with a gas-liquid ratio of 1.5:1 and a rotation speed of 1200rpm. Under the conditions of low pressure of 0.1MPa and 25℃, a large amount of latex was solidified after standing for 3 minutes.

[0073] The rubber clot is pressed, creped and freeze-dried in sequence to obtain milky white natural rubber raw rubber.

[0074] Comparative Example 1

[0075] As in Example 1, natural latex of the same condition is left to stand under natural conditions to achieve coagulation according to its own conditions. After standing for 8 hours, a large amount of latex is coagulated.

[0076] The rubber coagulate is pressed, creped and hot-air dried in sequence to obtain dark yellow natural rubber raw rubber.

[0077] It can be seen from this that the natural solidification effect is poor and takes a long time.

[0078] Comparative Example 2

[0079] As in Example 1, natural latex of the same condition was coagulated using the existing formic acid method, 2 kg of fresh natural latex was taken, 0.03 kg of 5% formic acid was added, and the mixture was left to stand for 1 hour, and a large amount of latex was coagulated.

[0080] The rubber coagulate is pressed, creped and hot-air dried in sequence to obtain brownish yellow natural rubber raw rubber.

[0081] Performance Testing

[0082] The performance of the natural rubber products prepared in Examples 1 to 5 and Comparative Examples 1 to 2 was tested using conventional methods. The data are shown in Table 1 below.

[0083] Table 1:

[0084]

[0085] From the data in Table 1, it can be seen that compared with natural coagulation, the coagulation time of ultra-gravity carbonized natural rubber latex is shortened to 1 / 8 of the original or even shorter, the plasticity retention rate is increased by about 9%, and the elongation at break is further improved; compared with the formic acid coagulation method, the coagulation time of ultra-gravity carbonized natural rubber is shorter, the Mooney viscosity is reduced, the plasticity retention rate is increased by about 24%, the tensile strength is increased by about 16.5%, and the elongation at break is increased by about 6.5%. In general, the indicators of the natural rubber products prepared by the rubber clots of Examples 1 to 5 are significantly better than those of the samples of Comparative Examples 1 and 2, achieving green and efficient coagulation of natural latex, and further improving the performance of raw rubber.

[0086] In summary, compared with the method disclosed in Chinese patent application CN111718432A, the method of the present invention does not need to be carried out under high pressure and can be produced continuously; at the same time, the ultra-gravity technology is used to achieve the optimized arrangement of natural rubber molecular chains, improve the comprehensive performance of natural rubber raw rubber, and the prepared natural rubber raw rubber (plasticity retention rate, tensile strength) is better than the product of Chinese patent application CN111718432A. In general, while achieving a safer and more environmentally friendly production process for natural rubber raw rubber, its comprehensive performance is significantly improved.

[0087] 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 preparing high-performance natural rubber raw rubber, characterized in that: The following steps are involved: 1) Adding carbon dioxide from the inlet of the supergravity device; 2) adding fresh natural rubber latex into the supergravity device from the material inlet; 3) Carbon dioxide and natural rubber latex are effectively contacted on the rotor of the high gravity device; 4) collecting the natural rubber latex at the material outlet and letting it stand or slowly flow and coagulate at room temperature to obtain a milky white natural rubber clot; 5) The rubber clot is pressed, creped and dried in sequence to obtain natural rubber raw rubber, which is milky white to slightly yellowish in color.

2. The method for preparing high-performance natural rubber raw rubber according to claim 1, characterized in that: In step 1), the purity of the carbon dioxide is 10% to 99.99% by volume.

3. The method for preparing high-performance natural rubber raw rubber according to claim 1, characterized in that: In step 2), the fresh natural rubber latex refers to fresh latex that flows out of rubber-producing plants and has not been processed.

4. The method for preparing high-performance natural rubber raw rubber according to claim 1, characterized in that: In step 3), the gas-liquid volume ratio of the carbon dioxide to natural rubber latex is 0.5:1 to 16:

1.

5. The method for preparing high-performance natural rubber raw rubber according to claim 1, characterized in that: In step 3), the rotor speed of the supergravity device is 300 to 3000 r / min.

6. The method for preparing high-performance natural rubber raw rubber according to claim 1, characterized in that: In step 3), the operating pressure condition is ≤4 MPa, preferably ≤0.3 MPa.

7. The method for preparing high-performance natural rubber raw rubber according to claim 1, characterized in that: In step 4), the room temperature solidification range is 10 to 45°C.

8. The method for preparing high-performance natural rubber raw rubber according to claim 1, characterized in that: In step 4), the solidification is carried out under static state or slow flow; the static state time is 1 to 60 minutes, and the slow flow solidification time is 10 to 60 minutes.

9. The method for preparing high-performance natural rubber raw rubber according to claim 1, characterized in that: In step 5), the drying includes hot air drying, vacuum drying, microwave drying and freeze drying; according to the different drying methods, the color of the sample is milky white to slightly yellow.

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