Method for preparing rrp / nrl composite material by wet coating of waste rubber surface

Abstract

The application discloses a kind of methods for preparing RRP / NRL composite material by waste rubber surface wet coating, belong to waste rubber regeneration technical field, including the following steps: S1.Adjusting the temperature of improved double-screw extruder 160 DEG C, the screw speed of double-screw extruder 60rpm, add waste rubber powder, and extrude to obtain modified powder;S2.Preparing 1% calcium chloride solution;S3.Natural latex and rubber powder are flocculated in calcium chloride solution to obtain RRP / NRL masterbatch;S4.The masterbatch, white carbon black, stearic acid, zinc oxide, antioxidant 4020, rubber oil V600, silane coupling agent KH-560 are added into the internal mixer and mixed, then sulfur and vulcanization accelerator CZ are added and mixed on the open mill to obtain the mixed rubber;S5.The mixed rubber is vulcanized, and RRP / NRL composite material is obtained.The application solves the technical problems of high cost and serious environmental pollution in traditional rubber powder modification method, and is widely used in waste rubber regeneration production.

Description

Technical Field

[0001] This invention belongs to the field of waste rubber recycling technology, and particularly relates to a method for preparing RRP / NRL composite materials by wet coating of waste rubber surface. Background Technology

[0002] The production of waste rubber powder mainly involves washing and stripping steel wires and fabrics from waste tires, followed by coarse and fine crushing, then pulverizing them into rubber powder using a grinding mill. Finally, the powder undergoes grading and screening to obtain the required quality rubber powder. Waste rubber powder possesses certain chemical and physical properties and, with appropriate treatment and processing, can be reused in agricultural tires, road tires, and other fields.

[0003] Generally, rubber powder and rubber do not have good compatibility, so many problems arise when mixing or combining them. Surface modification of rubber powder is an effective way to improve the interfacial bonding between rubber powder and the rubber matrix. However, traditional rubber powder modification methods are not suitable for large-scale production and application due to high costs and serious environmental pollution.

[0004] Therefore, in the field of waste rubber recycling equipment technology, there is still a need for research and improvement on the method of preparing RRP / NRL composite materials by wet coating of waste rubber surface. This is also a research hotspot and focus in the field of waste rubber recycling technology, and it is the starting point for the completion of this invention. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to provide a method for preparing RRP / NRL composite materials by wet coating of waste rubber, so as to solve the technical problems of high cost and serious environmental pollution of traditional rubber powder modification methods.

[0006] To solve the above-mentioned technical problems, the technical solution of the present invention is: a method for preparing RRP / NRL composite materials by wet coating of waste rubber, comprising the following steps: S1. Adjusting the temperature of the improved twin-screw extruder to 160℃ and the screw speed of the twin-screw extruder to 60rpm, adding waste rubber powder, and extruding to obtain modified rubber powder; S2. Preparing a 1% calcium chloride solution; S3. Flocculating the natural latex and the rubber powder obtained in step S1 in the calcium chloride solution to obtain RRP / NRL masterbatch, and drying it for later use; S4. Adding the masterbatch, silica, stearic acid, zinc oxide, antioxidant 4020, rubber oil V600, and silane coupling agent KH-560 to a mixer and mixing for 5-10 minutes, discharging the rubber and cooling it to room temperature, then adding sulfur and vulcanization accelerator CZ and mixing on an open mill, mixing evenly, and then sheeting and cooling to obtain a compound; S5. Placing the compound into a flat vulcanizing machine for vulcanization to obtain the RRP / NRL composite material.

[0007] As an improvement, anhydrous calcium chloride and deionized water are mixed at a mass ratio of 1:100 and stirred until fully dissolved to obtain a 1% calcium chloride solution.

[0008] As a further improvement, in step S3, the ratio of natural latex to rubber powder is 1:1.

[0009] As a further improvement, in step S4, the mass parts of the masterbatch, silica, stearic acid, zinc oxide, antioxidant 4020, rubber oil V600, silane coupling agent KH-560, sulfur, and vulcanization accelerator CZ are as follows: 100 parts masterbatch, 10 parts silica, 2 parts stearic acid, 4 parts zinc oxide, 4 parts antioxidant 4020, 3 parts rubber oil V600, 2 parts silane coupling agent KH-560, 2 parts sulfur, and 1.3 parts vulcanization accelerator CZ.

[0010] As a further improvement, in step S5, the vulcanization is carried out at a temperature of 150℃, a pressure of 10MPa, and a time of 1.3×Tc90, followed by cooling at room temperature for 8-10 hours after vulcanization.

[0011] As a further improvement, the screws of the twin-screw extruder each include a feeding section, a softening section, a shearing and reduction section, a homogenizing section, and an extrusion section in sequence, with gradient elements respectively provided on the two screws at the softening section and the shearing and reduction section.

[0012] As a further improvement, the gradient element includes a column, the outer surface of which has an annular array of 2N radially protruding ridges, where N is a positive integer greater than 2. The ridges extend along the axial direction of the screw. The outer surface of the column has an annular array of N wedge-shaped surfaces, which extend from the root of the first end of a ridge to the root of the last end of an adjacent ridge. The wedge-shaped surfaces gradually rise radially in the direction of fluid flow to the same height as the ridge.

[0013] After adopting the above technical solution, the beneficial effects of the present invention are: (1) The present invention prepares RRP / NRL composite material by wet coating of waste rubber powder. Due to the shearing action of the twin screw, the polysulfide bonds and C-S bonds inside the rubber molecules are broken, which partially desulfurizes the waste rubber powder and improves the surface activity of the waste rubber powder. The modified waste rubber powder has good compatibility with the rubber molecular chain, so the interfacial interaction between RRP and NRL is improved. Therefore, the prepared RRP / NRL composite material has good mechanical properties and vulcanization characteristics.

[0014] (2) The present invention uses waste rubber powder produced from waste tires as raw material, realizing the reuse of waste materials, which meets the requirements of sustainable development.

[0015] (3) The present invention uses a twin-screw extruder to desulfurize and regenerate waste rubber powder by shearing and breaking bonds. Since the screw of the twin-screw extruder is divided into a feeding section, a softening section, a shearing reduction section, a homogenization section and an extrusion section in sequence, the regeneration conditions (temperature, speed, etc.) can be controlled more accurately, the regeneration time is shortened and the regeneration efficiency is improved.

[0016] (4) The screw of the present invention is provided with a gradient element, and multiple variable volume or narrow volume flow channels are formed between the gradient element and the barrel and between the gradient elements. During the flow process, the rubber powder is subjected to more complex mechanical shearing, physical extrusion and volume change, and has good distribution mixing and dispersion mixing ability. At the same time, the presence of the gradient element increases the pressure difference of the rubber powder in the circumferential direction, indicating that the structure of the gradient element is conducive to the establishment of a large pressure difference of the rubber powder in the circumferential direction of the screw, which enhances the mixing effect of the rubber powder. This plays a crucial role in ensuring the uniformity of the regeneration degree.

[0017] (5) This invention uses calcium chloride solution as a flocculant, which can effectively neutralize the negative charge on the surface of latex particles, weaken electrostatic repulsion, and promote the rubber particles to approach and aggregate, greatly promoting the coagulation and precipitation of rubber particles, thereby realizing the transformation from emulsion to solid rubber. Its preparation method is simple, low-cost, and environmentally friendly. Attached Figure Description

[0018] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0019] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0020] Figure 1 This is a schematic diagram of the twin screw structure of the twin screw extruder in an embodiment of the present invention; Figure 2 This is a schematic diagram of the structure of the gradient element in an embodiment of the present invention; Figure 3 This is a schematic diagram showing the strain amplitude dependence of tanδ for RRP / NRL composite materials #1-#4 in the embodiments of the present invention; Figure 4 This is a schematic diagram showing the change of loss factor (tanδ) of RRP / NRL composite materials #1-#4 with temperature in the embodiments of the present invention; Among them, 1. feeding section, 2. softening section, 3. shearing and reduction section, 4. homogenization section, 5. extrusion section, 6. gradient element, 601. column, 602. convex ridge, 603. wedge surface. Detailed Implementation

[0021] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] The terms used in this specification, such as "front," "back," "left," "right," "inner," "outer," and "middle," are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, shall also be considered within the scope of the invention.

[0023] In the following embodiments: Natural rubber (NR) is a natural polymer compound mainly composed of cis-1,4-polyisoprene. Approximately 91%–94% of its composition is rubber hydrocarbon (cis-1,4-polyisoprene), with the remainder including proteins, fatty acids, ash, sugars, and other non-rubber substances. Natural rubber is one of the most widely used general-purpose rubbers.

[0024] The main components of waste rubber powder include: 1. Rubber base material: The main component of waste rubber powder is rubber base material, which can be natural rubber (NR), styrene-butadiene rubber (SBR), butadiene rubber (BR) or other synthetic rubber. The type of base material depends on the raw materials of the waste rubber products. 2. Carbon black: As a filler, carbon black is widely used to enhance the strength, abrasion resistance and UV stability of rubber; 3. Vulcanizing agent residue: such as sulfur. Vulcanizing agents are chemicals used in the rubber vulcanization process, and waste rubber powder usually contains vulcanizing agent residues. 4. Plasticizers: Used to increase the flexibility and processability of rubber. Some plasticizers may remain in waste rubber powder; 5. Additives: These include antioxidants, anti-aging agents, etc. These chemicals are added during the rubber production process to extend the life of rubber products. Some residues will also be found in waste rubber powder. 6. Other fillers: such as calcium carbonate, silica, etc. These fillers are used to adjust the physical properties of rubber.

[0025] These components endow waste rubber powder with certain mechanical properties and chemical stability, making it suitable for various recycling applications.

[0026] This invention provides a method for preparing RRP / NRL composite materials by wet coating of waste rubber, comprising the following steps: S1. Adjusting the temperature of the improved twin-screw extruder to 160℃ and the screw speed of the twin-screw extruder to 60 rpm, adding waste rubber powder (RRP), and extruding to obtain modified rubber powder; S2. Mixing anhydrous calcium chloride and deionized water at a mass ratio of 1:100, stirring to fully dissolve, and preparing a 1% calcium chloride solution; S3. Flocculating natural rubber latex (NRL) and the rubber powder obtained in step S1 in the calcium chloride solution to obtain RRP / NRL masterbatch, drying for later use, wherein the ratio of natural rubber latex to rubber powder is 1:1; S4. Adding masterbatch, silica, stearic acid, zinc oxide, antioxidant 4020, rubber oil V600, and silane coupler... Add coupling agent KH-560 to a mixer and mix for 5-10 minutes. After draining and cooling to room temperature, add sulfur and vulcanization accelerator CZ and mix on a two-roll mill. The mass parts of masterbatch, silica, stearic acid, zinc oxide, antioxidant 4020, rubber oil V600, silane coupling agent KH-560, sulfur, and vulcanization accelerator CZ are as follows: masterbatch 100 parts, silica 10 parts, stearic acid 2 parts, zinc oxide 4 parts, antioxidant 4020, etc. 4 parts of rubber oil V600, 3 parts of silane coupling agent KH-560, 2 parts of sulfur, and 1.3 parts of vulcanization accelerator CZ are mixed evenly, then sheeted and cooled to obtain the compound; S5. The compound is placed in a flat vulcanizing machine and vulcanized at a temperature of 150℃, a pressure of 10MPa, and a time of 1.3×Tc90. After vulcanization, it is cooled to room temperature for 8-10 hours to obtain the RRP / NRL composite material.

[0027] The rubber particles in synthetic rubber latex typically carry a negative charge, which keeps them in a stable suspension in water. Calcium chloride, as a cationic coagulant, effectively neutralizes the negative charge on the surface of the latex particles, weakens electrostatic repulsion, and promotes the rubber particles to approach and aggregate, greatly facilitating the coagulation and sedimentation of the rubber particles. This achieves the transformation from emulsion to solid rubber. Furthermore, using silica instead of carbon black as a rubber filler has the following advantages: silica has higher chemical stability, which enhances the rubber's resistance to oxidation, ozone, and ultraviolet radiation; silica production generates fewer pollutants, better meeting green environmental protection requirements; in addition, its light color facilitates waste regeneration and recycling; and rubber oil V600, as a rubber softener, significantly enhances the compatibility between rubber and filler, improving the dispersion effect of the filler.

[0028] like Figure 1 As shown, the screws of the twin-screw extruder sequentially include a feeding section 1, a softening section 2, a shearing and reduction section 3, a homogenizing section 4, and an extrusion section 5. Gradient elements 6 are respectively installed on the two screws at the softening section 2 and the shearing and reduction section 3. Figure 2 As shown, the gradient element 6 includes a cylinder 601. The outer surface of the cylinder 601 has a ring array of 2N radially protruding ridges 602, where N is a positive integer greater than 2. The ridges 602 extend along the axial direction of the screw. The outer surface of the cylinder 601 also has a ring array of N wedge-shaped surfaces 603. Each wedge-shaped surface 603 extends from the root of the first end of a ridge 602 to the root of the last end of an adjacent ridge 602. The wedge-shaped surfaces 603 gradually rise radially in the direction of fluid flow until they are equal in height to the ridges 602. The height of the ridges 602 of the gradient element 6 is lower than the thread height of the twin screw, creating a small flow channel between the ridges 602 of the two screws. The ridges 602 of the corresponding two gradient elements 6 on the two screws are staggered by a 45-degree phase difference. The corresponding relationship of the wedge-shaped surfaces 603 on the two screws is as follows: Similarly, the gradient elements on the corresponding screws... The gradient element 6 is staggered by 45 degrees. Due to the wedge-shaped surface 603 on the gradient element 6, multiple variable-volume or narrow-volume flow channels are formed between the gradient element 6 and the barrel, as well as between the gradient elements 6 themselves. During the flow process, the rubber powder is subjected to more complex mechanical shearing, physical extrusion, and volume changes, resulting in good distribution and dispersion mixing capabilities. Experiments show that the gradient element 6 has a larger minimum shear rate, which is increased by 7.8%, providing better shear regeneration effect. At the same time, the presence of the gradient element 6 increases the pressure difference of the rubber powder in the circumferential direction, indicating that the structure of the gradient element 6 is conducive to establishing a larger pressure difference of the rubber powder in the circumferential direction of the screw, enhancing the mixing effect of the rubber powder. This plays a crucial role in ensuring the uniformity of the regeneration degree.

[0029] Experimental example: #2 0 cycles of twin-screw extrusion (RRP / NRL) #3 One pass through a twin-screw motor (RRP / NRL) #4 Through twin screws, 2 times / (RRP / NRL) (1) The RRP / NRL composite material prepared by this invention has good filler dispersibility. For example... Figure 3 As shown, the filler in the rubber powder that has not undergone screw surface regeneration has poor dispersibility in RRP / NRL, a strong filler network, and tanδ increases sharply with increasing strain. As the number of times the filler passes through the screw increases, the dispersibility of the filler improves, and the strain dependence of tanδ decreases.

[0030] (2) The RRP / NRL composite material prepared by this invention has good anti-slip properties and low rolling resistance. For example... Figure 4 As shown, at 0℃, the tanδ value of #3 rubber powder is the largest, indicating the best anti-slip performance; at 60℃, the tanδ value of #4 rubber powder is lower, indicating lower rolling resistance.

[0031] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing RRP / NRL composite materials by wet coating of waste rubber surface, characterized in that, Includes the following steps: S1. The temperature of the improved twin-screw extruder is adjusted to 160℃, and the screw speed is 60 rpm. Each screw of the twin-screw extruder sequentially includes a feeding section, a softening section, a shear-reduction section, a homogenizing section, and an extrusion section. Gradient elements are respectively installed on the two screws at the softening section and the shear-reduction section. Each gradient element includes a column. The outer surface of the column has a ring array of 2N radially protruding ridges, where N is a positive integer greater than 2. The ridges extend along the axial direction of the screw. The outer surface of the column also has a ring array of N wedge-shaped surfaces. The wedge-shaped surface extends from the root of the first end of a convex ridge to the root of the last end of an adjacent convex ridge. The wedge-shaped surface gradually rises radially in the direction of fluid flow to the same height as the convex ridge. Multiple variable volume or narrow volume flow channels are formed between the gradient element and the barrel, as well as between the gradient elements. During the flow process, the rubber powder is subjected to more complex mechanical shearing, physical extrusion, and volume change, resulting in good distribution mixing and dispersion mixing capabilities. At the same time, the presence of the gradient element increases the pressure difference of the rubber powder in the circumferential direction. Waste rubber powder is added, and the modified rubber powder is obtained by extrusion. S2. Prepare a 1% calcium chloride solution by mixing anhydrous calcium chloride and deionized water at a mass ratio of 1:100 and stirring until fully dissolved to obtain a 1% calcium chloride solution; S3. Flocculate the natural latex and the rubber powder obtained in step S1 in the calcium chloride solution to obtain RRP / NRL masterbatch, and dry it for later use. S4. Add the masterbatch, silica, stearic acid, zinc oxide, antioxidant 4020, rubber oil V600, and silane coupling agent KH-560 to a mixer and mix for 5-10 minutes. After discharging and cooling to room temperature, add sulfur and vulcanization accelerator CZ and mix on a two-roll mill. After mixing evenly, sheet and cool to obtain the compound. S5. Place the compound into a flat vulcanizing machine and vulcanize to obtain the RRP / NRL composite material.

2. The method for preparing RRP / NRL composite materials by wet coating of waste rubber surface according to claim 1, characterized in that, In step S3, the ratio of natural latex to rubber powder is 1:

1.

3. The method for preparing RRP / NRL composite materials by wet coating of waste rubber surface according to claim 2, characterized in that, In step S4, the mass parts of the masterbatch, silica, stearic acid, zinc oxide, antioxidant 4020, rubber oil V600, silane coupling agent KH-560, sulfur, and vulcanization accelerator CZ are as follows: masterbatch 100 parts, silica 10 parts, stearic acid 2 parts, zinc oxide 4 parts, antioxidant 4020 4 parts, rubber oil V600 3 parts, silane coupling agent KH-560 2 parts, sulfur 2 parts, and vulcanization accelerator CZ 1.3 parts.

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