Method for regenerating waste rubber through cooperation of stirring and twin-screw extrusion

Abstract

The invention discloses a method for regenerating waste rubber through cooperation of stirring and twin-screw extrusion, and belongs to the technical field of waste rubber regeneration, and the method comprises the following steps: S1, adjusting the temperature of a stirrer to be 200 DEG C and the rotating speed to be 1200 rpm; s2, adding waste rubber powder and a softening agent, and mixing for 5 minutes, so as to obtain rubber powder subjected to preliminary desulfurization and regeneration; s3, adjusting the temperature of the double-screw extruder to 100 DEG C and the rotating speed of a main machine screw to 30 rpm; s4, adding the rubber powder in the step S2, and extruding to obtain regenerated rubber powder; s5, the rubber powder is subjected to thin-passing batch-off on an open mill, and unvulcanized reclaimed rubber is obtained; s6, mixing the unvulcanized reclaimed rubber in the step S5 with TBBS, zinc oxide, stearic acid and sulfur, mixing in an open mill, batching out, and cooling; and S7, vulcanizing the rubber compound in a vulcanizing machine to obtain the vulcanized reclaimed rubber. The invention solves the technical problems of limitation on material shape and low production rate of waste rubber powder regenerated by a single twin-screw extruder, and is widely applied to waste rubber regeneration production.

Description

Technical Field

[0001] The invention belongs to the technical field of waste rubber regeneration, and in particular relates to a waste rubber regeneration method by stirring and coordinating twin-screw extrusion. Background Art

[0002] As the world's largest rubber consumer, my country produces more than 10 million tons of waste rubber each year, including a large number of waste tires. In 2022, the amount of waste tires produced nationwide reached more than 350 million, about 12.28 million tons, which has become a veritable "black pollution". Therefore, recycling waste tires and regenerating waste rubber is an important and noteworthy efficient application to alleviate the accumulation and pollution of a large number of waste tires, both from the perspective of economic value and environmental protection.

[0003] The production process of waste rubber powder mainly includes the following steps: first, clean and remove the steel wire and fabric in the tire, then carry out coarse and fine crushing, then grind it into rubber powder through a grinder, and finally classify and screen it to obtain rubber powder that meets the requirements. These waste rubber powders have certain chemical and physical properties, and through proper treatment and processing, they can be used again in agricultural tires, roads and other fields.

[0004] The regeneration methods of waste rubber powder mainly include physical method, chemical method and biological method. The physical method combines waste rubber powder with new materials by heating or mechanical mixing to prepare recycled rubber; the chemical method uses desulfurization or dissolution technology to restore the rubber properties in waste rubber powder and produce high-quality recycled rubber; the biological method achieves environmentally friendly regeneration through microbial degradation, but it is currently less used.

[0005] The twin-screw extruder technology for recycling waste rubber powder is a process widely used in the field of waste rubber recycling. The waste rubber powder is efficiently processed by a twin-screw extruder. This technology relies on the high shear force and high temperature of the twin-screw extruder to fully mix the waste rubber powder with specific additives and deeply modify it during the melting and plasticizing process. The entire process includes precise feeding of materials, uniform mixing, high-temperature melting and extrusion molding, but there are still limitations on the shape of the material and low productivity.

[0006] Therefore, in the technical field of waste rubber recycling equipment, there is still a need for research and improvement on the waste rubber recycling method of stirring coordinated twin-screw extrusion. This is also a research hotspot and focus in the current field of waste rubber recycling technology, and it is also the starting point for the completion of the present invention. Summary of the invention

[0007] Therefore, the technical problem to be solved by the present invention is to provide a waste rubber regeneration method with stirring and coordinated twin-screw extrusion to solve the technical problems of limitation of material shape and low productivity of waste rubber powder regenerated by a single twin-screw extruder.

[0008] In order to solve the above technical problems, the technical solution of the present invention is: a method for regenerating waste rubber by stirring and coordinating twin-screw extrusion, comprising the following steps: S1. adjusting the temperature of the mixer to 200°C and the rotation speed to 1200rpm; S2. adding waste rubber powder and softener into the mixer and mixing for 5min to obtain preliminary desulfurized and regenerated rubber powder; S3. adjusting the temperature of the twin-screw extruder to 100°C and the main screw speed to 30rpm; S4. adding the rubber powder in step S2 into the twin-screw extruder, and obtaining the regenerated rubber powder after extrusion; S5. passing the rubber powder in step S4 through a thin sheet on an open mill to obtain unvulcanized regenerated rubber; S6. mixing the unvulcanized regenerated rubber in step S5 with TBBS, zinc oxide, stearic acid and sulfur on an open mill, mixing evenly, and cooling the sheet; S7. putting the mixed rubber obtained in step S6 into a vulcanizer for vulcanization to obtain vulcanized regenerated rubber.

[0009] As an improvement, the softener in step S2 is vegetable oil.

[0010] As a further improvement, in step S5, the roller distance of the mixing mill is set to 1.5±0.1 mm, and the roller temperature is 30°C.

[0011] As a further improvement, the mass fractions of the unvulcanized reclaimed rubber, TBBS, zinc oxide, stearic acid, and sulfur in step S6 are: 300 g of reclaimed rubber, 2.4 g of TBBS, 7.5 g of zinc oxide, 1 g of stearic acid, and 3.5 g of sulfur.

[0012] As a further improvement, the mixing step of the rubber material in step S6 includes: weighing 300g of the plasticized recycled rubber sample and putting it into the open mixing mill, repeatedly performing the 3 / 4 cutting, folding the lower sheet and then passing the roller action to wrap the sample on the roller, and gradually adding the prepared compounding agents. Each time a compounding agent is added, the 3 / 4 cutting is repeated alternately, and the compounding agents spilled on the ground plate are recovered into the accumulated rubber within the interval of 20s allowed by the continuous cutting. When there is no obvious free powder on the surface of the accumulated rubber or the roller, a full cut is performed and the lower sheet is folded. The folded sample is used to scrub and absorb the compounding agents scattered on the bottom plate of the open mixing mill, and then it is vertically put into the rubber mixer. After the compounding agents are mixed evenly, thin passes are made and sheets are taken out.

[0013] As a further improvement, the vulcanizing press is a flat plate vulcanizing press.

[0014] As a further improvement, the vulcanization in step S7 is performed at a temperature of 145° C., a pressure of 10 MPa, and a time of 1.3×Tc90, and after the vulcanization is completed, the vulcanization is cooled at room temperature for 8-10 hours.

[0015] After adopting the above technical solution, the beneficial effects of the present invention are:

[0016] (1) The present invention performs shear desulfurization on waste rubber powder under high temperature and high shear force environment. First, under the action of high shear force, the waste rubber powder is fully mixed with additives to destroy the cross-linked network of rubber molecules and promote the uniform dispersion of components. Then, the rubber melts at high temperature, and the molecular chain segments obtain sufficient degrees of freedom, rearrange and react chemically with the additives, such as cross-linking and desulfurization. These reactions significantly optimize the molecular structure of the recycled rubber and improve its mechanical properties, elastic modulus and durability. The entire process achieves efficient regeneration and modification of waste rubber powder through continuous mixing, plasticization and extrusion molding, and produces recycled rubber materials with excellent physical and chemical properties.

[0017] (2) Since the present invention uses a high-speed mixer to achieve preliminary regeneration of the waste rubber powder, it can achieve efficient mixing and dispersion in a short time, solving the problem of uneven distribution that is easily produced by a twin-screw extruder when processing high-viscosity or high-filling materials.

[0018] (3) Since the present invention uses a high-speed mixer to achieve preliminary regeneration of waste rubber powder, it is applicable to a variety of material forms, such as powder, granules or liquids, and is not dependent on a specific material form or viscosity, so it has higher flexibility and higher productivity.

[0019] (4) The present invention uses waste rubber powder produced from waste tires as raw material, thereby achieving the recycling of waste materials and meeting the requirements of sustainable development.

[0020] (5) The present invention mainly uses an open mixing mill to complete the preparation of reclaimed rubber, and the preparation method is simple, low-cost, and environmentally friendly.

[0021] (6) The present invention uses green and environmentally friendly vegetable oil to replace traditional highly polluting aromatic oil, thereby achieving higher tensile strength while meeting green and environmental protection requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the implementation methods of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for the implementation methods or the description of the prior art. Obviously, the drawings in the following description are only exemplary, and for ordinary technicians in this field, other implementation drawings can be derived from the provided drawings without creative work.

[0023] The structures, proportions, sizes, etc. illustrated in this specification are only used to match the contents disclosed in the specification so as to facilitate understanding and reading by persons familiar with the technology. They are not used to limit the conditions under which the present invention can be implemented, and therefore have no substantial technical significance. Any structural modification, change in proportion or adjustment of size shall still fall within the scope of the technical contents disclosed in the present invention without affecting the effects and purposes that can be achieved by the present invention.

[0024] Figure 1 Schematic diagram of the tensile strength of #1-#9 recycled rubber under different experimental conditions in the embodiment of the present invention. DETAILED DESCRIPTION

[0025] The following is a description of the implementation of the present invention by specific embodiments. People familiar with the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] The terms such as "front", "back", "left", "right", "inside", "outside", "middle", etc. cited in this specification are only for the convenience of description and are not intended to limit the scope of implementation of the present invention. Changes or adjustments to their relative relationships should be regarded as within the scope of implementation of the present invention without substantially changing the technical content.

[0027] In this embodiment, the main components of the waste rubber powder include:

[0028] 1. Rubber substrate: The main component of waste rubber powder is rubber substrate, which can be natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR) or other synthetic rubbers. The type of substrate depends on the raw material of the waste rubber products.

[0029] 2. Carbon black: As a filler, carbon black is widely used to enhance the strength, wear resistance and UV stability of rubber.

[0030] 3. Vulcanizing agent residues: such as sulfur. Vulcanizing agents are chemicals used in the rubber vulcanization process. Waste rubber powder usually contains vulcanizing agent residues.

[0031] 4. Plasticizer: used to increase the flexibility and processability of rubber. Some plasticizer may remain in the waste rubber powder.

[0032] 5. Additives: including antioxidants, anti-aging agents, etc. These chemicals are added during the production process of rubber to extend the life of rubber products. There will also be certain residues in the waste rubber powder.

[0033] 6. Other fillers: such as calcium carbonate, white carbon black, etc. These fillers are used to adjust the physical properties of rubber.

[0034] These components give waste rubber powder certain mechanical properties and chemical stability, making it useful in a variety of recycling applications.

[0035] The invention provides a waste rubber regeneration method by stirring and cooperating with twin-screw extrusion, comprising the following steps: S1. adjusting the temperature of the stirrer to 200°C and the rotation speed to 1200rpm; S2. when the equipment reaches the corresponding working conditions, adding waste rubber powder and a softener into the stirrer and mixing for 5min to obtain the rubber powder for preliminary desulfurization and regeneration; S3. adjusting the temperature of the twin-screw extruder to 100°C and the main screw rotation speed to 30rpm; S4. when the equipment reaches the corresponding working conditions, adding the rubber powder in step S2 into the twin-screw extruder, and obtaining the regenerated rubber powder after stable extrusion; S5. thinly passing the rubber powder in step S4 on an open mill to obtain unvulcanized regenerated rubber, and setting the roller distance of the open mill to 100°C; The thickness of the unvulcanized reclaimed rubber in step S5 is set to 1.5±0.1mm, and the roller temperature is 30°C; S6. The unvulcanized reclaimed rubber in step S5 is mixed with TBBS, zinc oxide, stearic acid and sulfur and mixed on an open mixing mill, wherein the mass fractions of the unvulcanized reclaimed rubber, TBBS, zinc oxide, stearic acid and sulfur are: 300g reclaimed rubber, 2.4g TBBS, 7.5g zinc oxide, 1g stearic acid and 3.5g sulfur. After mixing evenly, the lower sheet is cooled; S7. The mixed rubber obtained in step S6 is placed in a flat vulcanizer for vulcanization to obtain the vulcanized reclaimed rubber. The vulcanization temperature is 145°C, the pressure is 10MPa, and the time is 1.3×Tc90. After the vulcanization is completed, it is cooled at room temperature for 8-10h.

[0036] The softener in step S2 is vegetable oil, specifically, a biomass softener such as soybean oil, castor oil or sunflower oil. Those skilled in the art can choose to use it as needed, and this is not limited here.

[0037] The mixing step of the rubber material in step S6 includes: weighing 300g of the regenerated rubber sample after plasticization and putting it into the open mill, repeatedly performing the 3 / 4 cutting knife, folding the lower sheet and then passing the roller, so that the sample is evenly distributed and wrapped on the roller, and gradually adding the prepared compounding agent, and repeatedly performing the 3 / 4 cutting knife for each compounding agent, and recovering the compounding agent spilled on the ground plate into the accumulated rubber within the interval of 20s allowed by the continuous cutting knife, and when there is no obvious free powder on the surface of the accumulated rubber or the roller, perform full cutting and folding the lower sheet, and use the folded sample to scrub and absorb the compounding agent scattered on the bottom plate of the open mill, and then vertically put it into the rubber mixer, and after the compounding agent is evenly mixed, thin pass and sheet out. The order of adding the compounding agent, the roller spacing requirements, the number of folding the lower sheet, and the duration of rubber mixing are shown in the following table:

[0038]

[0039] #1-#9 recycled rubbers were obtained under different experimental conditions. The experimental conditions are shown in the following table:

[0040] serial number Screw speed rpm Regeneration temperature Softener quantity #1 30 100 8 #2 30 130 16 #3 30 160 12 #4 40 100 16 #5 40 130 12 #6 40 160 8 #7 50 100 12 #8 50 130 8 #9 50 160 16

[0041] refer to Figure 1 It can be seen that the tensile strength under experimental conditions #1 reached a relatively high level, as high as 9.33Mpa. It can be seen that the recycled rubber produced by this method has excellent physical and chemical properties and fully meets the performance requirements of recycled rubber.

[0042] The present invention performs shear desulfurization on waste rubber powder under high temperature and high shear force environment. First, under the action of high shear force, the waste rubber powder is fully mixed with additives to destroy the cross-linking network of rubber molecules and promote the uniform dispersion of components. Then, the rubber melts at high temperature, and the molecular chain segments obtain sufficient degrees of freedom, rearrange and react chemically with the additives, such as cross-linking and desulfurization. These reactions significantly optimize the molecular structure of the recycled rubber and improve its mechanical properties, elastic modulus and durability. The entire process realizes efficient regeneration and modification of waste rubber powder through continuous mixing, plasticization and extrusion molding, and produces recycled rubber materials with excellent physical and chemical properties.

[0043] Although the present invention has been described in detail above by general description and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements can be made to the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all belong to the scope of protection claimed by the present invention.

Claims

1. A method for recycling waste rubber by stirring and cooperating with twin-screw extrusion, characterized in that: The following steps are involved: S1. Adjust the temperature of the mixer to 200°C and the speed to 1200rpm; S2. Add waste rubber powder and softener into the mixer and mix for 5min to obtain preliminarily desulfurized and regenerated rubber powder; S3. Adjust the temperature of the twin-screw extruder to 100°C and the main screw speed to 30rpm; S4. Add the rubber powder in step S2 into the twin-screw extruder and obtain the regenerated rubber powder after extrusion; S5. Thinly pass the rubber powder in step S4 on an open mill to obtain unvulcanized regenerated rubber; S6. Mix the unvulcanized regenerated rubber in step S5 with TBBS, zinc oxide, stearic acid and sulfur on an open mill, mix well, and cool the mixture; S7. Put the mixed rubber obtained in step S6 into a vulcanizer for vulcanization to obtain vulcanized regenerated rubber.

2. The method for recycling waste rubber by stirring coordinated twin-screw extrusion according to claim 1, characterized in that: The softener in step S2 is vegetable oil.

3. The method for recycling waste rubber by stirring coordinated twin-screw extrusion according to claim 1, characterized in that: In step S5, the roller distance of the mixing mill is set to 1.5±0.1 mm, and the roller temperature is 30°C.

4. The method for recycling waste rubber by stirring coordinated twin-screw extrusion according to claim 1, characterized in that: The mass fractions of the unvulcanized regenerated rubber, TBBS, zinc oxide, stearic acid, and sulfur in step S6 are: 300 g of regenerated rubber, 2.4 g of TBBS, 7.5 g of zinc oxide, 1 g of stearic acid, and 3.5 g of sulfur.

5. The method for recycling waste rubber by stirring coordinated twin-screw extrusion according to claim 1, characterized in that: The mixing step of the rubber material in step S6 includes: weighing 300g of the plasticized recycled rubber sample and putting it into the open mixing mill, repeatedly performing 3 / 4 cutting, folding the lower sheet and then passing the roller to wrap the sample on the roller, gradually adding the prepared compounding agents, repeatedly performing 3 / 4 cutting for each compounding agent, and recovering the compounding agents spilled on the ground plate into the accumulated rubber within the interval of 20s allowed by the continuous cutting, when there is no obvious free powder on the surface of the accumulated rubber or the roller, performing full cutting and folding the lower sheet, using the folded sample to scrub and absorb the compounding agents scattered on the bottom plate of the open mixing mill, and then vertically putting it into the rubber mixing mill, and after the compounding agents are mixed evenly, thinning and discharging the sheets.

6. The method for recycling waste rubber by stirring coordinated twin-screw extrusion according to claim 1, characterized in that: The vulcanizing machine is a flat plate vulcanizing machine.

7. The method for recycling waste rubber by stirring coordinated twin-screw extrusion according to claim 6, characterized in that: The vulcanization in step S7 is performed at a temperature of 145° C., a pressure of 10 MPa, and a time of 1.3×Tc90. After the vulcanization is completed, the vulcanization is cooled at room temperature for 8-10 hours.

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