Preparation method of low-molecular-weight liquid rubber containing recycled illegal cooking oil

Abstract

The invention discloses a preparation method of low-molecular-weight liquid rubber containing recycled illegal cooking oil, which comprises the following steps: adding raw rubber, recycled illegal cooking oil, auxiliaries and other raw materials into a mixing device for mixing, adding the mixed rubber into an extruder A for preheating and softening, then feeding into an extruder B for constant-temperature stabilization, then feeding into an extruder C for rapid transportation and thermal degradation, and finally feeding into an extruder D for extrusion. And finally, feeding into a cooling device for cooling, so as to obtain a liquid rubber product. According to the invention, through accurate process control, the raw rubber is rapidly degraded while the oil product is ensured not to be excessively consumed, and the obtained recycled illegal cooking oil-rubber co-degradation product has the softening effect of a small molecule oil plasticizer and the co-crosslinking effect of liquid rubber. The method has the characteristics of high efficiency, continuity and easiness in amplification and industrialization, and compared with the traditional thermal degradation process, the recycled illegal cooking oil can enhance heat transfer, and has the characteristics of energy conservation and environmental protection.

Description

Technical Field

[0001] This invention belongs to the field of liquid rubber technology, specifically relating to a method for preparing low molecular weight liquid rubber containing recycled waste cooking oil. Background Technology

[0002] Plasticizers are crucial in rubber formulations for improving processing performance and reducing product hardness. Traditional small-molecule oil-based plasticizers suffer from the drawback of easy migration and precipitation. Therefore, the industry has opted to use liquid rubbers with structures similar to the matrix rubber. Because liquid rubber molecules contain reactive functional groups or double bonds at the ends or main chains, they can co-crosslink with the rubber matrix during vulcanization, thus permanently fixing themselves within the vulcanization network and effectively preventing migration and precipitation. Therefore, a common practice that balances immediate processing performance with long-lasting properties is to use small-molecule oils and liquid rubber together, aiming to simultaneously obtain the immediate softening effect of small-molecule oils and the co-crosslinking advantages of liquid rubber.

[0003] Liquid rubber preparation methods are divided into two types: small-molecule polymerization and macromolecular degradation. Small-molecule polymerization involves complex processes and demanding conditions, resulting in high industrial production costs and limiting its large-scale industrial application. In contrast, macromolecular degradation uses raw rubber as a raw material and breaks down its molecular backbone through heat, mechanical shearing, and chemical reagents. This method has lower preparation costs and is more suitable for industrial production. In particular, using a screw extruder for degradation allows for some control over the degradation process through process parameters. However, traditional macromolecular degradation methods suffer from low degradation efficiency, high energy consumption, and uneven degradation due to the poor thermal conductivity of raw rubber. To enhance heat and mass transfer, oil is often added to accelerate the softening of the rubber under heating conditions, which also provides an opportunity to utilize renewable resources.

[0004] The composition of recycled waste cooking oil is complex, with triglycerides (over 95%) as its main component. It is a potential source of environmentally friendly plasticizers and process oils. However, triglycerides have poor thermal stability; when heated to approximately 250-300℃ under normal pressure, they decompose, oxidize, and polymerize instead of reaching a stable boiling point. Furthermore, they decompose before reaching their boiling point, posing a significant challenge to their application in high-temperature rubber processing. While screw extruders can provide a continuous and efficient mixing and reaction environment, without precise temperature control, waste cooking oil will decompose and become largely ineffective at the high temperatures required for degradation, making stable utilization impossible.

[0005] Existing technologies also include some methods for rubber regeneration using oil-assisted processes. For example, invention patent CN119307002A discloses a method for preparing high-oil-extruded liquid regenerated rubber, which involves mixing waste rubber powder with a softener and then de-crosslinking it using a screw extruder. This method focuses on breaking the crosslinking network of vulcanized rubber (waste rubber powder), and its process temperature setting needs to avoid oil decomposition, hence the temperature is relatively low. This temperature is insufficient to provide the energy required to break the main chain of raw rubber molecules, therefore this method is not suitable for preparing liquid rubber from raw rubber. Another invention patent CN119931147A uses co-pyrolysis of biomass oil and waste rubber powder followed by extrusion regeneration, but it also fails to solve the key problem of stabilizing the oil at the high temperature required for raw rubber degradation, and its process is also unsuitable for the thermal degradation preparation of oil-containing liquid rubber.

[0006] In summary, there is an urgent need for a method that integrates the heat transfer advantages and environmental value of recycled waste cooking oil based on existing technologies. This method involves using raw rubber as a raw material and employing a macromolecular degradation method to prepare liquid rubber. Through precise process control, the method can stably and efficiently utilize recycled waste cooking oil, avoiding its decomposition and failure under necessary high-temperature processing conditions. This method aims to prepare high-molecular-weight rubber into low-molecular-weight liquid rubber containing recycled waste cooking oil, thus combining the softening effect of small-molecule plasticizers with the co-crosslinking effect of liquid rubber. Summary of the Invention

[0007] To address the shortcomings of the prior art, this invention provides a method for preparing low molecular weight liquid rubber containing recycled waste cooking oil. Through precise process control, the raw rubber is rapidly degraded while ensuring that the oil is not excessively consumed. The resulting recycled waste cooking oil-rubber co-degradation product combines the softening effect of small molecule oil plasticizers with the co-crosslinking effect of liquid rubber.

[0008] To achieve the above objectives, the technical solution of this invention is as follows: A method for preparing low molecular weight liquid rubber containing recycled waste cooking oil, comprising the following steps: S1, Raw material mixing stage: The mixture of raw rubber, recycled waste cooking oil, plasticizer, free radical inhibitor, and antioxidant is mixed in a mixing device, and the discharge temperature and Mooney viscosity are controlled. S2, Heating and softening stage: The compound is fed into extruder A, and the screw speed and barrel temperature of extruder A are set to heat and soften the rubber compound. S3, Constant Temperature Heating and Stabilization Stage: The softened rubber compound is fed into extruder B, and the screw speed and constant temperature of extruder B are set to ensure that the rubber compound is heated stably. S4, Thermal Degradation and Conveying Stage: The rubber compound, after being stabilized at a constant temperature, is fed into extruder C. The screw speed and barrel temperature of extruder C are set for thermal degradation and conveying. S5, Constant Temperature Cooling Stage: The degraded rubber compound is fed into extruder D, the screw speed and constant temperature of extruder D are set, the temperature of the rubber compound is stabilized, and a vacuum device is used to evacuate at the end. S6, Cooling and Collection Stage: The vacuumed rubber compound is sent into a cooling device, the parameters of the cooling device are set, the rubber compound is cooled, and the final discharge temperature is controlled to obtain low molecular weight liquid rubber containing recycled waste oil.

[0009] Preferably, the mass ratio of the raw rubber, recycled waste cooking oil, plasticizer, free radical inhibitor and antioxidant is 100:10-40:0-10:0-10:0-5.

[0010] Preferably, the raw rubber is one or a mixture of at least two of the following: natural rubber, eucommia rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, and SBS; and the recycled waste cooking oil is a commercially available, commonly available recycled waste cooking oil product.

[0011] Preferably, the plasticizer is one or a mixture of at least two of plasticizers A82, A86, A60, and HT105; the free radical inhibitor is an alkyl disulfide, used at low dosage and low temperature to abstract free radicals during the process of rubber chain breaking and molecular weight reduction. Because the operating temperature is insufficient at this time, its own activity is insufficient, and it cannot continue to react after abstraction, thus playing an inhibitory role; the antioxidant is one or a mixture of at least two of antioxidants 4020, 4010NA, 2246, and RD.

[0012] Preferably, the mixing device in step S1 is one or two types of internal mixers and open mills used in series, the Mooney viscosity of the final discharged rubber is 70-95, and the temperature of the discharged rubber compound is 100-120℃.

[0013] Preferably, the extruder A is a twin-screw extruder, a three-screw extruder, or a planetary screw extruder with enhanced shearing action, having a length-to-diameter ratio of 35-60:1, a screw shearing element length of not less than 25% of the total length, a counter-rotating element length of not less than 10% of the total length, a rotational speed of 40-140 rpm, a barrel heating temperature of 140-180℃, and a rubber compound residence time of not less than 50 seconds.

[0014] Preferably, the extruder B is a co-rotating parallel twin-screw extruder with a length-to-diameter ratio of 60-80:1, the length of the screw kneading element is not less than 25% of the total length, the length of the shearing element is not less than 25% of the total length, the rotation speed is 35-100 rpm, the barrel heating temperature is constant at 260℃, and the rubber material residence time is not less than 80s.

[0015] Preferably, the extruder C is an anti-rotating twin-screw extruder with a length-to-diameter ratio of 50-70:1, a screw kneading element length of not less than 15% of the total length, a shearing element length of not less than 30% of the total length, a rotational speed of 40-140 rpm, a barrel heating temperature of 240-350℃, and a rubber compound residence time of not less than 40 seconds.

[0016] Preferably, the extruder D is a co-rotating parallel twin extruder with a length-to-diameter ratio of 60-80:1, a screw kneading element length of not less than 25% of the total length, a shearing element length of not less than 25% of the total length, a rotation speed of 35-100 rpm, a barrel heating temperature of 260℃, and a rubber material residence time of not less than 80s.

[0017] Preferably, the cooling device is one or two of the following: a screw extruder and a mixing tank, used in series to provide cooling effect to the rubber compound. The cooling effect is such that the discharge temperature of the rubber compound is less than 120°C within a 50s cooling time.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) In the mixing stage before the raw materials enter the extruder, the recycled waste oil has an enhancing effect on the mixing of raw rubber and various additives, especially powder additives, making the mixing more uniform; during the extruder stroke, the recycled waste oil can enhance the heat transfer of the rubber compound, improve the heat conduction efficiency, make the rubber compound more likely to reach or approach the barrel heating temperature in the extruder, reduce heat loss, and make the degradation reaction more uniform. (2) This invention uses a multi-stage temperature control process of constant temperature heating-thermal degradation conveying-constant temperature cooling to stabilize the oil temperature before and after the degradation reaction at near the boiling point of triglycerides, thereby maximizing the heat transfer effect. At the same time, the counter-parallel twin-screw extruder C can ensure conveying efficiency, so that the raw rubber can be rapidly degraded while ensuring that the oil is not excessively consumed. After passing through the thermal degradation screw, the small molecules of the decomposed oil are extracted by the vacuum equipment of the second stage constant temperature screw, reducing unnecessary oil degradation product residues and solving the limitation of the heating temperature of the thermal degradation screw on the oil decomposition. (3) The entire preparation process of the present invention is based on a multi-stage extruder unit, realizing a fully continuous operation from raw materials to products, which is easy to scale up and industrialize, and overcomes the problems of batch-specificity and low efficiency of traditional batch degradation process; (4) In the final product, recycled waste cooking oil is fixed in the system as a blending component, which is equivalent to adding some oil products. This makes the product have both the excellent softening ability of traditional small molecule oil and the co-crosslinking function of liquid rubber, avoiding migration and precipitation. At the same time, the use of recycled waste cooking oil products realizes the high added value transformation of waste resources, reflects the concept of recycling and environmental protection in the era, conforms to the overall carbon cycle strategy, and also provides a new path for the low-cost and environmentally friendly production of liquid rubber. Detailed Implementation

[0019] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0020] Example 1 (1) Raw material mixing stage: Mix 100 parts by weight of natural rubber, 10 parts by weight of recycled waste cooking oil, 2 parts by weight of plasticizer A82, 2 parts by weight of free radical inhibitor (alkyl disulfide), and 1 part by weight of antioxidant 4020 in a mixer, and control the Mooney viscosity of the discharged rubber to be 90 and the temperature of the discharged rubber compound to be 100℃. (2) Heating and softening stage: The compound is fed into the twin-screw extruder A. The screw speed of the extruder A is set to 45 rpm and the barrel temperature is 140℃. The rubber compound is heated and softened, and the residence time of the rubber compound is 50 s. (3) Constant temperature heating and stabilization stage: The heated and softened rubber compound is fed into the co-rotating parallel twin-screw extruder B. The screw speed of the extruder B is set to 70 rpm, the constant temperature is 260℃, the rubber compound is heated stably, the rubber compound temperature is stabilized, and the rubber compound residence time is 80S. (4) Thermal degradation stage: The rubber compound after being stabilized at constant temperature is fed into the counter-rotating twin-screw extruder C. The screw speed of the extruder C is set to 70 rpm and the barrel temperature is set to 280℃ for thermal degradation. The residence time of the rubber compound is 40 s. (5) Constant temperature cooling stage: The degraded rubber compound is fed into the co-rotating parallel double extruder D. The screw speed of the extruder D is set to 70 rpm and the constant temperature is 260℃ to stabilize the rubber compound temperature. The rubber compound residence time is 80S. A vacuum pump is used to evacuate the end. (6) Cooling and collection stage: The vacuumed rubber compound is sent into the cooling device, the parameters of the cooling device are set, the rubber compound is cooled by the device, and the final discharge temperature is controlled. Within 50s of cooling, the discharge temperature of the rubber compound is less than 120℃. Finally, the liquid rubber product is discharged and collected to obtain an oil-containing liquid rubber that is completely soluble in toluene with a number average molecular weight Mn of 67925.

[0021] Example 2 (1) Raw material mixing stage: 100 parts by weight of natural rubber, 15 parts by weight of recycled waste cooking oil, 2 parts by weight of plasticizer A86, 4 parts by weight of free radical inhibitor (alkyl disulfide) and 2 parts by weight of antioxidant 2246 are mixed in an open mill, and the Mooney viscosity of the discharged rubber is controlled to be 85 and the temperature of the discharged rubber compound is 105℃. (2) Heating and softening stage: The compound is fed into the three-screw extruder A. The screw speed of the extruder A is set to 60 rpm and the barrel temperature is 160℃. The rubber compound is heated and softened, and the residence time of the rubber compound is 55S. (3) Constant temperature heating and stabilization stage: The heated and softened rubber compound is fed into the co-rotating parallel twin-screw extruder B. The screw speed of the extruder B is set to 70 rpm, the constant temperature is 260℃, the rubber compound is heated stably, the rubber compound temperature is stabilized, and the rubber compound residence time is 85S. (4) Thermal degradation stage: The rubber compound after being stabilized at constant temperature is fed into the counter-rotating twin-screw extruder C. The screw speed of the extruder C is set to 85 rpm and the barrel temperature is 330℃ for thermal degradation. The residence time of the rubber compound is 45 s. (5) Constant temperature cooling stage: The degraded rubber compound is fed into the parallel double extruder D in the same direction. The screw speed of the extruder D is set to 70 rpm and the constant temperature is 260℃ to stabilize the temperature of the rubber compound. The residence time of the rubber compound is 85S. A vacuum pump is used to evacuate the end. (6) Cooling and collection stage: The vacuumed rubber compound is sent into the cooling device, the parameters of the cooling device are set, the rubber compound is cooled by the device, and the final discharge temperature is controlled. Within 50s of cooling, the discharge temperature of the rubber compound is less than 120℃. Finally, the liquid rubber product is discharged and collected to obtain an oil-containing liquid rubber that is completely soluble in toluene with a number average molecular weight Mn of 27412.

[0022] Example 3 (1) Raw material mixing stage: Mix 100 parts by weight of styrene-butadiene rubber, 15 parts by weight of recycled waste cooking oil, 2 parts by weight of plasticizer A60, 5 parts by weight of free radical inhibitor (alkyl disulfide), and 1 part by weight of antioxidant 4010NA in a mixer, and control the Mooney viscosity of the discharged rubber to be 70 and the temperature of the discharged rubber compound to be 120℃. (2) Heating and softening stage: The compound is fed into planetary screw extruder A. The screw speed of extruder A is set to 50 rpm and the barrel temperature is 200℃. The rubber compound is heated and softened, and the residence time of the rubber compound is 50 s. (3) Constant temperature heating and stabilization stage: The heated and softened rubber compound is fed into the co-rotating parallel twin-screw extruder B. The screw speed of the extruder B is set to 70 rpm, the constant temperature is 260℃, the rubber compound is heated stably, the rubber compound temperature is stabilized, and the rubber compound residence time is 80S. (4) Thermal degradation stage: The rubber compound after being stabilized at constant temperature is fed into the counter-rotating twin-screw extruder C. The screw speed of the extruder C is set to 80 rpm and the barrel temperature is 360℃ for thermal degradation. The residence time of the rubber compound is 40 s. (5) Constant temperature cooling stage: The degraded rubber compound is fed into the co-rotating parallel double extruder D. The screw speed of the extruder D is set to 70 rpm and the constant temperature is 260℃ to stabilize the rubber compound temperature. The rubber compound residence time is 80S. A vacuum pump is used to evacuate the end. (6) Cooling and collection stage: The vacuumed rubber compound is sent into the cooling device, the parameters of the cooling device are set, the rubber compound is cooled by the device, and the final discharge temperature is controlled. Within 50s of cooling, the discharge temperature of the rubber compound is less than 120℃. Finally, the liquid rubber product is discharged and collected to obtain an oil-containing liquid rubber that is completely soluble in toluene with a number average molecular weight Mn of 18489.

[0023] Example 4 (1) Raw material mixing stage: Mix 100 parts by weight of styrene-butadiene rubber, 15 parts by weight of recycled waste cooking oil, 2 parts by weight of plasticizer HT105, 4 parts by weight of free radical inhibitor (alkyl disulfide), and 2 parts by weight of antioxidant 4020 in a mixer, and control the Mooney viscosity of the discharged rubber to be 80 and the temperature of the discharged rubber compound to be 110℃. (2) Heating and softening stage: The compound is fed into the twin-screw extruder A. The screw speed of the extruder A is set to 60 rpm and the barrel temperature is 180℃. The rubber compound is heated and softened, and the residence time of the rubber compound is 55 s. (3) Constant temperature heating and stabilization stage: The heated and softened rubber compound is fed into the co-rotating parallel twin-screw extruder B. The screw speed of the extruder B is set to 70 rpm, the constant temperature is 260℃, the rubber compound is heated stably, the rubber compound temperature is stabilized, and the rubber compound residence time is 80S. (4) Thermal degradation stage: The rubber compound after being stabilized at constant temperature is fed into the counter-rotating twin-screw extruder C. The screw speed of the extruder C is set to 75 rpm and the barrel temperature is 340℃ for thermal degradation. The residence time of the rubber compound is 45 s. (5) Constant temperature cooling stage: The degraded rubber compound is fed into the co-rotating parallel double extruder D. The screw speed of the extruder D is set to 70 rpm and the constant temperature is 260℃ to stabilize the rubber compound temperature. The rubber compound residence time is 80S. A vacuum pump is used to evacuate the end. (6) Cooling and collection stage: The vacuumed rubber compound is sent into the cooling device, the parameters of the cooling device are set, the rubber compound is cooled by the device, and the final discharge temperature is controlled. Within 50s of cooling, the discharge temperature of the rubber compound is less than 120℃. Finally, the liquid rubber product is discharged and collected, and finally, an oil-containing liquid rubber with a number average molecular weight Mn of 59627 that is completely soluble in toluene is obtained.

[0024] Example 5 (1) Raw material mixing stage: Mix 100 parts by weight of butadiene rubber, 15 parts by weight of recycled waste cooking oil, 2 parts by weight of plasticizer A60, 10 parts by weight of free radical inhibitor (alkyl disulfide), and 1 part by weight of antioxidant 2246 in a mixer, and control the Mooney viscosity of the discharged rubber to be 95 and the temperature of the discharged rubber compound to be 100℃. (2) Heating and softening stage: The compound is fed into the three-screw extruder A. The screw speed of the extruder A is set to 60 rpm and the barrel temperature is 190℃. The rubber compound is heated and softened, and the residence time of the rubber compound is 50 s. (3) Constant temperature heating and stabilization stage: The heated and softened rubber compound is fed into the co-rotating parallel twin-screw extruder B. The screw speed of the extruder B is set to 70 rpm, the constant temperature is 260℃, the rubber compound is heated stably, the rubber compound temperature is stabilized, and the rubber compound residence time is 85S. (4) Thermal degradation stage: The rubber compound after being stabilized at constant temperature is fed into the counter-rotating twin-screw extruder C. The screw speed of the extruder C is set to 75 rpm and the barrel temperature is 300℃ for thermal degradation. The residence time of the rubber compound is 40 s. (5) Constant temperature cooling stage: The degraded rubber compound is fed into the parallel double extruder D in the same direction. The screw speed of the extruder D is set to 70 rpm and the constant temperature is 260℃ to stabilize the temperature of the rubber compound. The residence time of the rubber compound is 85S. A vacuum pump is used to evacuate the end. (6) Cooling and collection stage: The vacuumed rubber compound is sent into the cooling device, the parameters of the cooling device are set, the rubber compound is cooled by the device, and the final discharge temperature is controlled. Within 50s of cooling, the discharge temperature of the rubber compound is less than 120℃. Finally, the liquid rubber product is discharged and collected to obtain an oil-containing liquid rubber that is completely soluble in toluene with a number average molecular weight Mn of 14256.

[0025] Example 6 (1) Raw material mixing stage: 100 parts by weight of butadiene rubber, 15 parts by weight of recycled waste cooking oil, 2 parts by weight of plasticizer A82, 1 part by weight of free radical inhibitor (alkyl disulfide) and 1 part by weight of antioxidant 4020 are mixed in a mixing device consisting of a mixer and a milling machine connected in series, and the Mooney viscosity of the discharged rubber is controlled to be 75 and the temperature of the discharged rubber compound is 115℃. (2) Heating and softening stage: The compound is fed into the twin-screw extruder A. The screw speed of the extruder A is set to 60 rpm and the barrel temperature is 200℃. The rubber compound is heated and softened, and the residence time of the rubber compound is 60 s. (3) Constant temperature heating and stabilization stage: The heated and softened rubber compound is fed into the co-rotating parallel twin-screw extruder B. The screw speed of the extruder B is set to 70 rpm, the constant temperature is 260℃, the rubber compound is heated stably, the rubber compound temperature is stabilized, and the rubber compound residence time is 80S. (4) Thermal degradation stage: The rubber compound after being stabilized at constant temperature is fed into the counter-rotating twin-screw extruder C. The screw speed of the extruder C is set to 75 rpm and the barrel temperature is 340℃ for thermal degradation. The residence time of the rubber compound is 50 s. (5) Constant temperature cooling stage: The degraded rubber compound is fed into the co-rotating parallel double extruder D. The screw speed of the extruder D is set to 70 rpm and the constant temperature is 260℃ to stabilize the rubber compound temperature. The rubber compound residence time is 80S. A vacuum pump is used to evacuate the end. (6) Cooling and collection stage: The vacuumed rubber compound is sent into the cooling device, the parameters of the cooling device are set, the rubber compound is cooled by the device, and the final discharge temperature is controlled. Within 50s of cooling, the discharge temperature of the rubber compound is less than 120℃. Finally, the liquid rubber product is discharged and collected, and finally, an oil-containing liquid rubber with a number average molecular weight Mn of 9044 that is completely soluble in toluene is obtained.

[0026] Comparative Example 1 (1) Raw material mixing stage: Mix 100 parts by weight of natural rubber, 10 parts by weight of recycled waste cooking oil, 2 parts by weight of plasticizer A82, 2 parts by weight of free radical inhibitor (alkyl disulfide), and 1 part by weight of antioxidant 4020 in a mixer, and control the Mooney viscosity of the discharged rubber to be 90 and the temperature of the discharged rubber compound to be 100℃. (2) Heating and softening stage: The compound is fed into the twin-screw extruder A. The screw speed of the extruder A is set to 45 rpm and the barrel temperature is 180℃. The rubber compound is heated and softened, and the residence time of the rubber compound is 50 s. (3) Thermal degradation stage: The heated and softened rubber compound is fed into the counter-rotating twin-screw extruder C. The screw speed of the extruder C is set to 70 rpm and the barrel temperature is set to 280℃ for thermal degradation. The residence time of the rubber compound is 40 s. (4) Constant temperature cooling stage: The degraded rubber compound is fed into the co-rotating parallel double extruder D. The screw speed of the extruder D is set to 70 rpm and the constant temperature is 260℃ to stabilize the rubber compound temperature. The rubber compound residence time is 80 s. A vacuum pump is used to evacuate the end. (5) Cooling and collection stage: The vacuumed rubber compound is sent into the cooling device, the parameters of the cooling device are set, the rubber compound is cooled by the device, and the final discharge temperature is controlled. Within 50s of cooling, the discharge temperature of the rubber compound is less than 120℃. Finally, the liquid rubber product is discharged and collected to obtain an oil-containing liquid rubber that is completely soluble in toluene with a number average molecular weight Mn of 80341.

[0027] Comparative Example 2 (1) Raw material mixing stage: 100 parts by weight of natural rubber, 15 parts by weight of recycled waste cooking oil, 2 parts by weight of plasticizer A86, 4 parts by weight of free radical inhibitor (alkyl disulfide) and 2 parts by weight of antioxidant 2246 are mixed in an open mill, and the Mooney viscosity of the discharged rubber is controlled to be 85 and the temperature of the discharged rubber compound is 105℃. (2) Heating and softening stage: The compound is fed into the three-screw extruder A. The screw speed of the extruder A is set to 60 rpm and the barrel temperature is 160℃. The rubber compound is heated and softened, and the residence time of the rubber compound is 55S. (3) Constant temperature heating and stabilization stage: The heated and softened rubber compound is fed into the co-rotating parallel twin-screw extruder B. The screw speed of the extruder B is set to 70 rpm, the constant temperature is 260℃, the rubber compound is heated stably, the rubber compound temperature is stabilized, and the rubber compound residence time is 85S. (4) Thermal degradation stage: The rubber compound after being stabilized at constant temperature is fed into the counter-rotating twin-screw extruder C. The screw speed of the extruder C is set to 85 rpm and the barrel temperature is 330℃ for thermal degradation. The residence time of the rubber compound is 45 s. (5) Constant temperature cooling stage: The degraded rubber compound is fed into the parallel double extruder D in the same direction. The screw speed of the extruder D is set to 70 rpm and the constant temperature is 260℃ to stabilize the temperature of the rubber compound. The residence time of the rubber compound is 85S. A vacuum pump is used to evacuate the end. (6) Cooling and collection stage: The vacuumed rubber compound is sent into the cooling device, the parameters of the cooling device are set, the rubber compound is cooled by the device, and the final discharge temperature is controlled. Within 50s of cooling, the discharge temperature of the rubber compound is less than 120℃. Finally, the liquid rubber product is discharged and collected to obtain an oil-containing liquid rubber that is completely soluble in toluene with a number average molecular weight Mn of 40859.

[0028] Comparative Example 3 (1) Raw material mixing stage: Mix 100 parts by weight of styrene-butadiene rubber, 15 parts by weight of recycled waste cooking oil, 2 parts by weight of plasticizer A60, 5 parts by weight of free radical inhibitor (alkyl disulfide), and 1 part by weight of antioxidant 4010NA in a mixer, and control the Mooney viscosity of the discharged rubber to be 70 and the temperature of the discharged rubber compound to be 120℃. (2) Heating and softening stage: The compound is fed into planetary screw extruder A. The screw speed of extruder A is set to 50 rpm and the barrel temperature is 200℃. The rubber compound is heated and softened, and the residence time of the rubber compound is 50 s. (3) Thermal degradation stage: The heated and softened rubber compound is fed into the counter-rotating twin-screw extruder C. The screw speed of the extruder C is set to 80 rpm and the barrel temperature is 360℃ for thermal degradation. The residence time of the rubber compound is 40 s. (4) Constant temperature cooling stage: The degraded rubber compound is fed into the co-rotating parallel double extruder D. The screw speed of the extruder D is set to 70 rpm and the constant temperature is 260℃ to stabilize the rubber compound temperature. The rubber compound residence time is 80 s. A vacuum pump is used to evacuate the end. (5) Cooling and collection stage: The vacuumed rubber compound is sent into the cooling device, the parameters of the cooling device are set, the rubber compound is cooled by the device, and the final discharge temperature is controlled. Within 50s of cooling time, the discharge temperature of the rubber compound is less than 120℃. Finally, the liquid rubber product is discharged and collected to obtain an oil-containing liquid rubber that is completely soluble in toluene with a number average molecular weight Mn of 26527.

[0029] Table 1 Product data: molecular weight Mn Oil content (percentage by mass of recycled waste cooking oil used) (%) Example 1 67925 76 Example 2 27412 81 Example 3 18489 79 Example 4 59627 73 Example 5 14256 85 Example 6 9044 70 Comparative Example 1 80341 68 Comparative Example 2 40859 63 Comparative Example 3 26527 60 After extraction with petroleum ether at 75°C for 12 hours using acetone and a Soxhlet extractor, the oil content of the liquid rubber products from Examples 1-6 and Comparative Examples 1-3 was determined, and the results are shown in Table 1. It can be concluded that the oil extraction amount in Examples 1-6 was significantly higher than that in Comparative Examples 1-3. The difference between Comparative Examples 1-3 and Examples 1-3 is the absence of step S3 (isotropic heating stabilization stage). Therefore, the liquid rubber prepared in Examples 1-6 using the method of this invention (isotropic heating-thermal degradation and transport-isotropic cooling) has a higher oil content, reducing excessive oil consumption during degradation. Furthermore, it can be seen that by changing the process parameters, the molecular weight can be flexibly controlled, indicating that the method of this invention provides greater controllability over the molecular weight when preparing liquid rubber.

[0030] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for preparing low molecular weight liquid rubber containing recycled kitchen waste oil, characterized in that, Includes the following steps: S1, Raw material mixing stage: The mixture of raw rubber, recycled kitchen waste oil, plasticizer, free radical inhibitor, and antioxidant is mixed in the mixing device, and the discharge temperature and Mooney viscosity are controlled. S2, Heating and softening stage: The compound is fed into extruder A, and the screw speed and barrel temperature of extruder A are set to heat and soften the rubber compound. S3, Constant Temperature Heating and Stabilization Stage: The softened rubber compound is fed into extruder B, and the screw speed and constant temperature of extruder B are set to ensure that the rubber compound is heated stably. S4, Thermal Degradation and Conveying Stage: The rubber compound, after being stabilized at a constant temperature, is fed into extruder C. The screw speed and barrel temperature of extruder C are set for thermal degradation and conveying. S5, Constant Temperature Cooling Stage: The degraded rubber compound is fed into extruder D, the screw speed and constant temperature of extruder D are set, the temperature of the rubber compound is stabilized, and a vacuum device is used to evacuate at the end. S6, Cooling and Collection Stage: The vacuumed rubber compound is sent into a cooling device, the parameters of the cooling device are set, the rubber compound is cooled, and the final discharge temperature is controlled to obtain low molecular weight liquid rubber containing recycled kitchen waste oil.

2. The method for preparing low molecular weight liquid rubber containing recycled kitchen waste oil as described in claim 1, characterized in that: The mass ratio of the raw rubber, recycled kitchen waste oil, plasticizer, free radical inhibitor and antioxidant is 100:10-40:0-10:0-10:0-5.

3. The method for preparing low molecular weight liquid rubber containing recycled kitchen waste oil as described in claim 1, characterized in that: The raw rubber is one or a mixture of at least two of the following: natural rubber, eucommia rubber, isoprene rubber, butadiene rubber, styrene-butadiene rubber, nitrile rubber, and SBS. The recycled kitchen waste oil is a commercially available common recycled kitchen waste oil product.

4. The method for preparing low molecular weight liquid rubber containing recycled kitchen waste oil as described in claim 1, characterized in that: The plasticizer is one or a mixture of at least two of plasticizers A82, A86, A60, and HT105; the free radical inhibitor is an alkyl disulfide; and the antioxidant is one or a mixture of at least two of antioxidants 4020, 4010NA, 2246, and RD.

5. The method for preparing low molecular weight liquid rubber containing recycled kitchen waste oil as described in claim 1, characterized in that: The mixing device mentioned in step S1 is one or two types of internal mixers and open mills used in series, with the final Mooney viscosity of the discharged rubber being 70-95 and the temperature of the discharged rubber compound being 100-120℃.

6. The method for preparing low molecular weight liquid rubber containing recycled kitchen waste oil as described in claim 1, characterized in that: The extruder A is a twin-screw extruder, three-screw extruder, or planetary screw extruder with enhanced shearing action, having a length-to-diameter ratio of 35-60:1, a screw shearing element length of not less than 25% of the total length, a counter-rotating element length of not less than 10% of the total length, a rotation speed of 40-140 rpm, a barrel heating temperature of 140-180℃, and a rubber compound residence time of not less than 50 seconds.

7. The method for preparing low molecular weight liquid rubber containing recycled kitchen waste oil as described in claim 1, characterized in that: The extruder B is a co-rotating parallel twin-screw extruder with a length-to-diameter ratio of 60-80:

1. The length of the screw kneading element is not less than 25% of the total length, the length of the shearing element is not less than 25% of the total length, the rotation speed is 35-100 rpm, the barrel heating temperature is constant at 260℃, and the rubber material residence time is not less than 80s.

8. The method for preparing low molecular weight liquid rubber containing recycled kitchen waste oil as described in claim 1, characterized in that: The extruder C is an anti-rotating twin-screw extruder with a length-to-diameter ratio of 50-70:

1. The length of the screw kneading element is not less than 15% of the total length, the length of the shearing element is not less than 30% of the total length, the rotation speed is 40-140 rpm, the barrel heating temperature is 240-350℃, and the rubber compound residence time is not less than 40s.

9. The method for preparing low molecular weight liquid rubber containing recycled kitchen waste oil as described in claim 1, characterized in that: The extruder D is a co-rotating parallel twin extruder with a length-to-diameter ratio of 60-80:

1. The length of the screw kneading element is not less than 25% of the total length, the length of the shearing element is not less than 25% of the total length, the rotation speed is 35-100 rpm, the barrel heating temperature is constant at 260℃, and the rubber material residence time is not less than 80s.

10. The method for preparing low molecular weight liquid rubber containing recycled kitchen waste oil as described in claim 1, characterized in that: The cooling device is one or two of the following: a screw extruder and a mixing tank, used in series to provide cooling effect to the rubber compound. The cooling effect is that the discharge temperature of the rubber compound is less than 120°C within a 50-second cooling time.