A kind of environmentally friendly flocculation and wet mixing method of latex based on fine rubber powder

Abstract

The present invention provides an environmentally friendly flocculation and wet mixing method for latex based on fine rubber powder. The flocculation method includes the following steps: (1) removing impurities in the fine rubber powder and treating the rubber powder to make it highly hydrophilic; (2) adding the treated fine rubber powder to natural rubber latex and mixing it to achieve homogenized mixing of the rubber powder and the latex; (3) subjecting the rubber powder-latex mixed solution to strong shearing and sufficient flocculation to remove moisture; and (4) dehydrating and drying the flocculated rubber material to obtain a flocculent gel. The wet mixing method based on the flocculation method of fine rubber powder includes the following steps: (1) uniformly mixing natural rubber latex and fine rubber powder to obtain a mixed solution 1, stirring and mixing a rubber reinforcing system and a vulcanizing agent with deionized water to obtain a mixed solution 2; (2) mixing the mixed solution 1 / 2 to obtain a mixed solution 3, adding the mixed solution 3 to a strong shearing device to flocculate it and then drying it; and (4) adding a vulcanizing agent to the dry rubber to mix and disperse it. The flocculation and wet mixing method can achieve high-value application of rubber powder while achieving acid-free flocculation of natural latex.

Description

Technical Field

[0001] The invention relates to the field of natural rubber production, and in particular to an environmentally friendly latex flocculation and wet mixing method based on fine rubber powder. Background Art

[0002] With its widespread use in transportation, military, and aerospace, natural rubber has become one of the four major industrial raw materials, along with coal, steel, and petroleum. Natural rubber is produced from natural latex through the steps of collection, coagulation, cleaning, and drying. Coagulation is a crucial step in the formation of natural rubber. Latex flocculation utilizes electrolytes or other reagents to enlarge or precipitate the particles of the latex, achieving flocculation. Currently, natural latex coagulation methods primarily include natural flocculation, microbial flocculation, acid flocculation, inorganic salt flocculation, and bioflocculation. Traditional strong acid flocculation generally uses formic acid, acetic acid, or sulfuric acid as latex flocculants. Different coagulation methods directly affect the quality of the rubber. When acid flocculants are added to natural latex, dense clots form at the coagulation point, hindering the uniform distribution of the flocculant throughout the latex and preventing the formation of uniformly structured rubber clots. This can affect the formation of macromolecular chains in the natural latex particles, adversely affecting the health of operators and corrosive to containers and equipment.

[0003] CN109485752A discloses a method for flocculating concentrated natural rubber latex. First, concentrated natural rubber latex is slowly added to a seawater-like flocculant under stirring. After the concentrated natural latex is added, stirring is continued for 20-40 minutes. The concentrated natural latex and the seawater-like flocculant are reacted under set conditions, and then naturally cooled to 15-35°C to obtain a gel block. Then, the gel block is washed with 300ml of deionized water. Finally, the gel block is sequentially placed in an open mill and a dryer for dehydration and drying, respectively, to produce natural rubber. This method generates waste liquid that consumes a lot of energy and is complex to dispose of, causing certain environmental pollution. CN114213558A discloses the use of montmorillonite as a flocculant for natural latex. The montmorillonite is added to the latex raw material when it is heated to 20°C to 60°C, and then mechanically stirred. The ratio of the latex raw material to the montmorillonite is 100:10-17. This method requires controlling the latex temperature, which increases the complexity of the process. At the same time, the distance between montmorillonite layers is small, and the affinity between montmorillonite layers and latex molecular chains is low, making it difficult for latex monomers or molecules to be easily inserted between montmorillonite layers, and the montmorillonite cannot be better dispersed in the latex.

[0004] In the past, in the rubber industry, wet rubber masterbatches were used to improve the processability and dispersibility of fillers when manufacturing rubber compositions containing fillers such as carbon black. Specifically, the filler and a dispersion solvent were pre-mixed in a certain ratio, and a slurry solution containing the filler, obtained by dispersing the filler in the dispersion solvent by mechanical force, was mixed with a rubber latex solution in the liquid phase. Then, a coagulant such as an acid was added to cause the mixture to solidify, and the coagulant was recovered and dried. When a wet rubber masterbatch is used, compared to the use of a dry rubber masterbatch obtained by mixing the filler and rubber in the solid phase, a wet masterbatch with excellent filler dispersibility and good processability is obtained. Using a wet masterbatch as a raw material, it is possible to manufacture rubber products such as pneumatic tires with reduced rolling resistance and excellent fatigue resistance.

[0005] Wet mixing is gaining popularity. For example, a method for preparing a silica wet mix (CN04212108A) involves self-emulsifying synthetic latex to make it hydrophilic, then wet-mixing silica with natural latex to produce the mix. While this method improves the mutual dispersibility between silica slurry and synthetic latex, it suffers from low production efficiency, high equipment energy consumption, and difficulty in waste liquid recovery. Wet mixing of fillers and rubber latex is a method for producing a masterbatch. CN1900149A discloses a method for preparing an organically modified clay and styrene-butadiene rubber nanocomposite. A suspension of clay and water with a layered crystal structure is mixed with styrene-butadiene latex, followed by demulsification and flocculation, drying, mixing, and vulcanization to produce the clay-styrene-butadiene rubber nanocomposite. However, this method is limited to styrene-butadiene latex and is not applicable to solution-polymerized rubber latex. Summary of the Invention

[0006] The present invention addresses the shortcomings of existing technologies and provides a method for latex flocculation based on fine rubber powder. The preparation method provided by the present invention enables acid-free flocculation and good dispersion of natural rubber latex, and enhances the interfacial bonding between the rubber powder and the rubber matrix. The resulting rubber exhibits excellent mechanical properties.

[0007] In order to achieve the above-mentioned purpose of the invention, the present invention provides the following technical solutions.

[0008] The present invention provides a flocculation method based on fine rubber powder latex, comprising the following steps:

[0009] (1) Remove impurities from fine rubber powder and process the fine rubber powder to make it highly hydrophilic;

[0010] (2) adding the treated fine rubber powder to natural rubber latex, and then mixing them in a high-speed stirrer to achieve homogenized mixing of the rubber powder and latex;

[0011] (3) The rubber powder-latex mixture is sheared and fully flocculated to remove water;

[0012] (4) Dehydrating and drying the flocculated rubber material to obtain a flocculent gel.

[0013] The content of rubber components in the natural rubber latex in the above method is 27-80%;

[0014] The fine rubber powder is one or more of truck tire rubber powder, passenger car tire rubber powder and rubber shoe rubber powder;

[0015] The fine rubber powder in the above step (1) comes from one or more of the methods of preparing rubber powder: room temperature pulverization method, low temperature pulverization method, wet method or solution method, and ultra-high pressure water jet method.

[0016] The mesh size of the fine rubber powder in the above step (1) is 40 mesh or more, preferably 120 mesh to 200 mesh;

[0017] In the above step (1), the fine rubber powder is treated with a plasma treatment device or an alkaline solution or an acidic solution to improve its hydrophilicity;

[0018] The mass ratio of natural rubber latex to fine rubber powder in the above step (2) is 167:(10-40).

[0019] In the above step (2), the stirring speed of the high-speed stirring device is 2000-10000 r / min, preferably 4000-6000 r / min, and the stirring time is 1-5 min, preferably 2-4 min;

[0020] In the above step (3), the strong shear device is one or more devices such as an extruder, an internal mixer, and a continuous mixer, and the temperature of the strong shear device is 30-70°C, preferably 40-60°C, and the screw speed is 20-60r / min, preferably 30-50r / min;

[0021] The dehydration and drying device described in the above step (4) is one or more devices such as an extruder, an internal mixer, and a dryer. The temperature of the dehydration and drying device is 80-140°C, preferably 100-120°C, and the screw speed is 30-80r / min, preferably 50-60r / min.

[0022] The present invention also provides a wet mixing method based on fine rubber powder, which uses fine rubber powder and natural rubber latex solution as raw materials and realizes wet rubber mixing through process control, comprising the following steps:

[0023] (1) mixing natural rubber latex and fine rubber powder in a high-speed stirrer to obtain a mixed solution 1, and simultaneously stirring and mixing a rubber reinforcing system and a vulcanizing agent in an appropriate proportion with deionized water in a conventional stirrer to obtain a mixed solution 2;

[0024] (2) Stirring the mixed solution 2 with a conventional stirrer, injecting the mixed solution 1 into the mixed solution 2 and mixing evenly to obtain the mixed solution 3;

[0025] (3) adding the mixed solution into a strong shear device, regulating the shear strength by process parameters to cause flocculation, and then dehydrating and drying the flocculated gel through a dehydration device;

[0026] (4) adding an appropriate proportion of vulcanizing agent to the dried rubber material in a mixing device for homogenization, dispersion and mixing to complete the wet process rubber mix preparation;

[0027] The content of rubber component in the natural rubber latex in the above step (1) is 27-80%;

[0028] The fine rubber powder is one or more of truck tire rubber powder, passenger car tire rubber powder and rubber shoe rubber powder;

[0029] The rubber reinforcing system is one or more of carbon black, white carbon black, modified kaolin, mica powder, and attapulgite-modified clay;

[0030] The carbon black is one or more of N339, N115, N375, and N326;

[0031] The fine rubber powder in the above step (1) is obtained by one or more methods of preparing rubber powder by room temperature pulverization, low temperature pulverization, wet method or solution method, or ultra-high pressure water jet method;

[0032] The mesh size of the fine rubber powder in the above step (1) is 40 mesh or more, preferably 100 mesh to 200 mesh.

[0033] In the above step (1), the stirring speed of the high-speed stirrer is 2000-10000 r / min, preferably 4000-6000 r / min, and the stirring time is 1-5 min, preferably 2-4 min. The stirring speed of the ordinary stirrer is 200-800 r / min, preferably 500-700 r / min, and the stirring time is 2-10 min, preferably 5-8 min.

[0034] In the above step (1), the mass ratio of natural rubber latex to fine rubber powder is 167:(5-30), and the mass ratio of the rubber reinforcing system and vulcanization auxiliary system to deionized water is 1:(3-5);

[0035] In the above step (2), the stirring speed of the ordinary stirrer is 200-600 r / min, preferably 400-550 r / min, and the stirring time is 1-7 min, preferably 3-5 min.

[0036] The strong shearing equipment in the above step (3) can be one of an internal mixer, an extruder, and a high-speed mixer, preferably a high-speed mixer, with a stirring speed of 4000-10000 r / min, preferably 5000-8500 r / min, and a stirring time of 20-70 s, preferably 40-50 s;

[0037] The dehydration device can be selected from a dehydration extruder, an internal mixer, a dryer and the like, preferably a dehydration extruder, with a dehydration temperature of 80-140°C, preferably 100-120°C, and a screw speed of 30-80r / min, preferably 50-60r / min.

[0038] The mixing equipment in the above step (4) can be one of an internal mixer, an open mixer, and a continuous mixer, preferably an open mixer, with a minimum roller spacing of 0.1-0.3 mm, preferably 0.1-0.25 mm, a rotation speed of 50-100 r / min, preferably 65-90 r / min, a shearing time of 3-10 min, preferably 4-8 min, and a shearing temperature of 25-80°C, preferably 33-76°C.

[0039] Based on the above steps, the mechanism of environmentally friendly flocculation and wet mixing of latex based on fine rubber powder is proposed. In natural latex, the surface of latex particles is composed of proteins and phospholipids, which can form hydrogen bonds with water molecules. At the same time, it is negatively charged, causing the latex particles to repel each other, which allows the latex particles to exist stably in water. The surface of fine rubber powder has some hydroxyl groups, which have been shown in FTIR results ( Figure 4 ) is confirmed, these hydroxyl groups can also form hydrogen bonds with the hydrophilic group on water molecule and latex particle surface, thereby improve its dispersibility in natural rubber latex.In the high-speed shear mixing process, fine rubber powder can be evenly distributed in the natural rubber latex, has improved the collision chance between latex particle and carbon black, fine rubber powder and the latex particle itself, thereby promoted latex demulsification.Afterwards, the natural rubber molecular chain will cover and be wrapped around the fine rubber powder, forms a network between the fine rubber powder that the natural rubber chain connects, has prevented contact and the reunion of carbon black in the flocculation process, thereby improved the dispersibility of carbon black in rubber composite materials. In addition, due to the irregularity and large area of ​​fine rubber powder surface, the natural rubber chain will adhere closely to the fine rubber powder surface, and the hydroxyl group on the fine rubber powder surface can be combined with the hydrophilic group in the natural rubber latex, further strengthens the bonding between the natural rubber chain and the fine rubber powder.

[0040] The present invention provides an environmentally friendly latex flocculation and wet mixing method based on fine rubber powder. This method implements a latex flocculation process and the filling application of rubber powder in rubber systems. Through hydrophilic treatment and high-speed shearing process regulation, leveraging the good compatibility of rubber powder and latex, the latex wall is broken and flocculated, while also enhancing the interfacial bonding between the rubber powder and the rubber matrix, improving its dispersibility within the rubber matrix, and leveraging the rubber powder's filler-reinforcing effect on the rubber matrix, thereby improving the quality of wet rubber mixing. While achieving high-value applications of rubber powder in rubber product systems, it also achieves acid-free flocculation of natural latex. Furthermore, the process is environmentally friendly, highly efficient, requires minimal production equipment, and generates no waste liquid. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other embodiments can be obtained based on these drawings without paying any creative work.

[0042] Figure 1: SEM image of rubber powder prepared by ultra-high pressure water jet method;

[0043] Figure 2: SEM image of ordinary wet mixed rubber;

[0044] Figure 3: SEM image of rubber powder-wet mix prepared by ultra-high pressure water jet method;

[0045] Figure 4 : FTIR images of rubber powder prepared by ultra-high pressure water jet method (WPRP) and rubber powder prepared by mechanical grinding at room temperature (MGRP);

[0046] In Figure 1, a, b, c, and d are the morphologies of the rubber powder prepared by ultrahigh pressure water jet method under 50, 100, 200, and 500 times electron microscope magnification;

[0047] In Figure 2, a, b, c, and d are the morphologies of ordinary wet-mixed rubber under an electron microscope at 50, 100, 200, and 500 times magnification;

[0048] In Figure 3, a, b, c, and d are the morphologies of the rubber powder-wet mix prepared by ultra-high pressure water jet method under an electron microscope at 50, 100, 200, and 500 times magnification; DETAILED DESCRIPTION

[0049] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only 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 making creative efforts are within the scope of protection of the present invention.

[0050] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Figure 1 shows an SEM image of rubber powder prepared by ultrahigh-pressure water jetting. The SEM reveals a highly irregular surface shape, a high specific surface area, a jagged surface structure, and numerous structural bridges. These irregularities create friction when the rubber powder contacts the rubber particles, causing intense internal friction between the rubber powder and the outer protein walls of the rubber particles, resulting in a wall-breaking effect. After the wall breaks, the macromolecular chains of the latex become entangled on the surface of the rubber powder. After vulcanization, they cross-link and bond well with the rubber matrix, eliminating the interface between the two.

[0052] Figures 2 and 3 show SEM images of a conventional wet mix and a rubber powder-wet mix prepared by ultrahigh-pressure water jetting. Figure 3(d) shows no visible pores or significant gaps between the rubber powder particles and the rubber matrix, indicating strong interfacial adhesion in the composite prepared by ultrahigh-pressure water jetting, which contributes to improved mechanical properties. The cross-sections show fewer particles and a smoother surface, indicating good compatibility between the rubber matrix and the rubber powder. The images at different magnifications in Figure 3 all show the absence of free carbon black and large carbon black aggregates in the cross-sections of the composites prepared by ultrahigh-pressure water jetting, indicating that the carbon black is well dispersed and tightly bound within the rubber matrix. Figure 2 shows the presence of large, exposed carbon black aggregates in the cross-sections of the conventional wet mix, indicating poor dispersion of the carbon black within the rubber matrix and weak bonding between the carbon black particles and the rubber. The SEM images demonstrate that the excellent dispersibility, permeability, and compatibility of the rubber powder prepared by ultrahigh-pressure water jetting contribute to the satisfactory mechanical properties of the composites.

[0053] Figure 4 The FTIR results of mechanically ground rubber powder (MGRP) and WPRP show that MGRP has a peak at 2918 cm -1 It has a sharper peak than WPRP at 2850 cm -1 Has a similar peak. WPRP at 3336cm -1 and 1096cm -2 The peak at 1537 cm is more significant than that of MGRP. -1 There is a sharp peak at 3336cm, while WPRP shows a small peak here. Considering the composition of rubber powder, -1 、2918cm -1 and 2850cm -1 The peak at 1537cm -1 and 1096cm -2The peaks at and may correspond to hydroxyl, methyl, methylene, C=C, and CO groups, respectively. These results suggest that WPRP may contain fewer methyl and C=C groups and more hydroxyl groups than MGRP. The significant differences between the two rubber powders are primarily due to the different preparation processes. The rubber powder preparation process involves the breaking of C-C, C-S, and S-S bonds. During mechanical milling, the breaking of C-C and C-S bonds generates numerous carbon radicals, which can combine with hydrogen to produce methyl groups, leading to an increase in the methyl content. During water jet milling, the high-pressure water jet destroys the rubber structure while introducing a large amount of oxygen into the rubber system. The cavitation created by the water jet creates a gas-liquid coexistence similar to that of supercritical water, providing a strong oxidizing environment that allows the oxidation and decomposition of conjugated C=C bonds to form hydroxyl-terminated structures. Furthermore, the breaking of C-C and C-S bonds generates numerous carbon and sulfur radicals, which can also be oxidized to form hydroxyl-terminated structures, reducing the methyl content. As a result, WPRP contains fewer methyl groups and conjugated C=C structures and more hydroxyl and CO structures.

[0054] [Example 1]

[0055] As a preferred embodiment of the present invention, a method for preparing a rubber compound based on flocculation of fine rubber powder latex is provided:

[0056] Example 1

[0057] Pour formic acid flocculant into a high-speed blender, along with 167g of natural rubber latex (60%). Stir the mixture at 8000 rpm for 2 minutes to complete flocculation. Place the flocculent gel in a dehydrator for drying at 100°C and a screw speed of 55 rpm. The dried sample is then added to a Hake internal mixer, small ingredients are added, and mixing continues for 5 minutes to complete the process. Finally, the sample is vulcanized in an open mill.

[0058] The weight fraction of each component in the above-mentioned rubber compound formula is:

[0059]

[0060] Example 2

[0061] The rubber powder prepared by the 120-mesh ultra-high pressure water jet method is spread on a square glass panel in a low-temperature plasma machine and placed steadily in the plasma vacuum chamber. Then, the low-temperature plasma instrument processing parameters are set, the discharge power is 250W, the processing time is 8 minutes, and the working atmosphere is air. After treatment, the rubber powder is placed in a drying oven at 60°C and dried for 3 hours.

[0062] 10g of the dried, ultra-high-pressure water jet-prepared rubber powder was weighed and poured into a high-speed blender. Simultaneously, 167g of 60% natural rubber latex was added to the blender. Both were stirred at 8000 rpm for 2 minutes to complete flocculation. The flocculated gel was then placed in a dehydrator for dehydration and drying at a temperature of 100°C and a screw speed of 55 rpm.

[0063] The dried sample was added to a Hake internal mixer, small materials were added, and internal mixing was completed for 5 minutes. Finally, the sample was vulcanized in an open mill.

[0064] The weight fractions of the components in the above-mentioned rubber compound formula are as follows:

[0065] Example 3

[0066] A rubber mix was prepared according to the method of Example 2, the difference from Example 2 being that the mesh size of the rubber powder prepared by the ultra-high pressure water jet method was 140 meshes.

[0067] Example 4

[0068] A rubber mix was prepared according to the method of Example 2, the difference from Example 2 being that the mesh size of the rubber powder prepared by the ultra-high pressure water jet method was 160 meshes.

[0069] Example 5

[0070] The rubber powder prepared by the 120-mesh ultra-high pressure water jet method is spread on a square glass panel in a low-temperature plasma machine and placed steadily in the plasma vacuum chamber. Then, the low-temperature plasma instrument processing parameters are set, the discharge power is 250W, the processing time is 8 minutes, and the working atmosphere is air. After treatment, the rubber powder is placed in a drying oven at 60°C and dried for 3 hours.

[0071] 10g of the dried, ultra-high-pressure water jet-prepared rubber powder was weighed and poured into a high-speed blender. Simultaneously, 333g of 30% natural rubber latex was added to the blender. Both were stirred at 8000 rpm for 2 minutes to complete flocculation. The flocculated gel was then placed in a dehydrator for dehydration and drying at a temperature of 100°C and a screw speed of 55 rpm.

[0072] The dried sample was added to a Hake internal mixer, small materials were added, and internal mixing was completed for 5 minutes. Finally, the sample was vulcanized in an open mill.

[0073] The weight fractions of the components in the above-mentioned rubber compound formula are as follows:

[0074] Example 6

[0075] A rubber mix was prepared according to the method of Example 2, except that the added mass of the rubber powder prepared by the ultra-high pressure water jet method was 20 g.

[0076] Example 7

[0077] The rubber powder prepared by the 120-mesh room temperature crushing method is spread on a square glass panel in a low-temperature plasma machine and placed steadily in the plasma vacuum chamber. Then, the low-temperature plasma instrument processing parameters are set, the discharge power is 250W, the processing time is 8 minutes, and the working atmosphere is air. After treatment, the rubber powder is placed in a 60°C drying oven and dried for 3 hours.

[0078] Weigh 10g of the dried, room-temperature pulverized rubber powder and pour it into a high-speed blender. Simultaneously, add 167g of 60% natural rubber latex and stir at 8000 rpm for 2 minutes to complete flocculation. The flocculated gel blocks are then placed in a dehydrator for dehydration and drying at a temperature of 100°C and a screw speed of 55 rpm.

[0079] The dried sample was added to a Hake internal mixer, small materials were added, and internal mixing was completed for 5 minutes. Finally, the sample was vulcanized in an open mill.

[0080] The weight fractions of the components in the above-mentioned rubber compound formula are as follows:

[0081]

Performance test

[0082] The hardness, tensile strength and elongation at break of the rubber obtained in Examples 1-7 were tested, and the results are shown in Table 1.

[0083] The powder was observed using a JSM-7500F scanning electron microscope produced by JEOL Ltd. The sample was fractured using liquid nitrogen and the cross section was gold-sprayed. The acceleration voltage was 5 kV, and the appropriate magnification was selected based on actual needs.

[0084] A dynamic mechanical analyzer (DMA) can obtain indicators such as the material's dynamic storage modulus, loss modulus, and loss tangent. The DMA testing principle is also based on the change in elastic modulus under different mechanical forms. During the test, the test sample is heated according to a program and a periodic oscillating force is applied to determine the material's elastic modulus. At the same time, certain characteristic points of the material, such as the glass transition temperature (Tg), are tested. DMA causes a sample of a certain geometric shape to undergo a sinusoidal deformation. In this way, the sample can withstand a controllable stress or strain. If the stress is constant, the sample will produce a certain degree of deformation. The magnitude of the deformation is related to the stiffness of the sample. The motor inside generates a sine wave and transmits it to the sample through the drive shaft. This is used to measure rolling resistance.

[0085] GB 9871-1988 Determination of aging properties of vulcanized rubber (tensile stress relaxation test), using UT-2060 tensile testing machine according to national standard GB / T 528-98 for testing.

[0086] The hardness of the rubber was tested using the LX-A hardness tester produced by Shanghai Liuling Instrument Factory in accordance with the national standard GB / T531.1-2008. The test thickness was 6mm and the temperature was room temperature. The average value was taken after multiple tests.

[0087] Tensile strength and elongation at break were tested using a UT-2060 tensile testing machine according to GB / T 528-98. Specific parameters were set at a tensile speed of 500 mm / min and room temperature. The tensile strength, stress at 100% modulus, stress at 300% modulus, and elongation at break were recorded.

[0088] Mooney viscosity: The samples were tested using a Mooney viscometer produced by Uni-Tech Co., Ltd. in accordance with the national standard GB / T1232.1-2000. Specific test conditions: test temperature 100°C, preheating time 1 minute, test time 4 minutes.

[0089] Table 1 Performance test of rubber obtained in Examples 1-7

[0090]

[0091] The physical and mechanical properties, dispersion, aging and rolling resistance test data of the rubber vulcanizate prepared by flocculation with the addition of fine rubber powder at a ratio of 10% are better than those of the rubber prepared by the traditional acid flocculation method; by comparing the test data of Examples 2-4, it can be seen that when the same ratio of fine rubber powder is added, the smaller the particle size of the rubber powder is, the better the physical properties and dynamic properties of the rubber vulcanizate prepared by flocculation; by comparing Example 2 with Example 5, it can be seen that the reduction in the rubber component content in the latex causes a slight decrease in the performance of the rubber prepared by the latex flocculation process based on fine rubber powder, but the impact is small; by comparing the test data of Example 2 with Example 7, it can be concluded that the physical and mechanical properties and dynamic properties of the rubber vulcanizate prepared by flocculation of rubber powder prepared by the ultra-high pressure water jet method are better than those of the rubber prepared by flocculation of ordinary rubber powder prepared by the room temperature pulverization method.

[0092] This method is based on the good compatibility of fine rubber powder and latex, which can improve its dispersibility in the rubber matrix. While realizing the high-value application of rubber powder in the rubber product system, it also achieves acid-free flocculation of natural latex. The process is green and environmentally friendly, has high production efficiency, low requirements for production equipment, and no waste liquid is generated.

[0093] The above embodiments are only for illustration and not for limitation of the technical solutions of the present invention. Any modification or partial replacement that does not deviate from the spirit of the present invention shall be included in the scope of the claims of the present invention.

[0094] [Example 2]

[0095] As a preferred embodiment of the present invention, a wet mixing method based on fine rubber powder is as follows:

[0096] Example 1

[0097] Stir 167g of natural rubber latex (60%) in a high-speed stirrer at 8000r / min for 2min, weigh 50g of carbon black (N330) and a vulcanizing agent into a beaker, then pour in 150g of deionized water, and stir the carbon black-vulcanizing agent aqueous solution in a stirrer at a stirring speed of 500r / min for 5min. Then pour the latex into the carbon black-vulcanizing agent aqueous solution (stirring while pouring) at a stirring speed of 500r / min for 3min. After stirring, pour it into the high-speed stirrer. Turn on the high-speed stirrer and stir for 30-50s. After completion, pour it into a glass dish and dry it in an oven.

[0098] The dried sample was added to the Hake internal mixer, the temperature was set to room temperature, and the sample was mixed for 3 minutes to obtain the treated sample. After it was completely dried, it was put back into the Hake internal mixer for mixing, sulfur was added, and the mixing was completed for 5 minutes to complete the process.

[0099] The weight fraction of each component in the above-mentioned rubber compound formula is:

[0100]

[0101] Example 2

[0102] The rubber powder prepared by the 120-mesh ultrahigh-pressure water jet method was dried in a drying oven at 60°C for 3 hours. 5g of the dried rubber powder was weighed and poured into a high-speed blender. 5g of the rubber powder and 167g of natural rubber latex (60%) were stirred in the blender at 8000 rpm for 2 minutes. 50g of carbon black (N330) and a vulcanizing agent were weighed and placed in a beaker. 150g of deionized water was then added. The carbon black-vulcanizing agent aqueous solution was stirred in a blender at 500 rpm for 5 minutes. The latex was then poured into the carbon black-vulcanizing agent aqueous solution (stirring simultaneously) at 500 rpm for 3 minutes. After stirring, the mixture was poured back into the high-speed blender. The high-speed blender was turned on and stirred for 30-50 seconds. After stirring, the mixture was poured into a glass dish and dried in an oven.

[0103] The dried sample was added to the Hake internal mixer, the temperature was set to room temperature, and the sample was mixed for 3 minutes to obtain the treated sample. After it was completely dried, it was put back into the Hake internal mixer for mixing, sulfur was added, and the mixing was completed for 5 minutes to complete the process.

[0104] The weight fractions of the components in the above-mentioned rubber compound formula are as follows:

[0105] Example 3

[0106] A rubber mix was prepared according to the method of Example 2, the difference from Example 2 being that the added mass of the rubber powder prepared by the ultra-high pressure water jet method was 10 g.

[0107] Example 4

[0108] A rubber mix was prepared according to the method of Example 2, except that the added mass of the rubber powder prepared by the ultra-high pressure water jet method was 15 g.

[0109] Example 5

[0110] A rubber mix was prepared according to the method of Example 2, except that the added mass of the rubber powder prepared by the ultra-high pressure water jet method was 20 g.

[0111] Example 6

[0112] A rubber mix was prepared according to the method of Example 2, the difference from Example 2 being that the mesh size of the rubber powder prepared by the ultra-high pressure water jet method was 100 mesh.

[0113] Example 7

[0114] A rubber mix was prepared according to the method of Example 2, the difference from Example 2 being that the mesh size of the rubber powder prepared by the ultra-high pressure water jet method was 160 meshes.

[0115] Example 8

[0116] Weigh 5g of 120-mesh rubber powder prepared by room temperature pulverization and pour it into a high-speed blender. Stir 5g of rubber powder and 167g of natural rubber latex (60%) in a high-speed blender at 8000r / min for 2min. Weigh 50g of carbon black (N330) and a vulcanizing agent into a beaker, then pour in 150g of deionized water. Stir the carbon black-vulcanizing agent aqueous solution in a blender at a speed of 500r / min for 5min. Then pour the latex into the carbon black-vulcanizing agent aqueous solution (stirring while pouring) at a speed of 500r / min for 3min. After stirring, pour it into the high-speed blender. Turn on the high-speed blender and stir for 30-50s. After stirring, pour it into a glass dish and dry it in an oven.

[0117] The dried sample was added to the Hake internal mixer, the temperature was set to room temperature, and the sample was mixed for 3 minutes to obtain the treated sample. After it was completely dried, it was put back into the Hake internal mixer for mixing, sulfur was added, and the mixing was completed for 5 minutes to complete the process.

[0118] The weight fractions of the components in the above-mentioned rubber compound formula are as follows:

[0119] Performance Testing

[0120] The hardness, tensile strength, elongation at break, etc. of the rubber obtained in Examples 1 to 9 were tested, and the results are shown in Table 1.

[0121] Hardness: The hardness of the rubber compound was tested using the LX-A hardness tester produced by Shanghai Liuling Instrument Factory. The test was carried out in accordance with the national standard GB / T 531.1-2008. The test thickness was 6mm and the temperature was room temperature. The average value was taken from multiple tests.

[0122] Tensile strength and elongation at break were tested using a UT-2060 tensile testing machine according to GB / T 528-98. Specific parameters were set at a tensile speed of 500 mm / min and room temperature. The tensile strength, stress at 100% modulus, stress at 300% modulus, and elongation at break were recorded.

[0123] Mooney viscosity: The samples were tested using a Mooney viscometer produced by Uni-Tech Co., Ltd. in accordance with the national standard GB / T1232.1-2000. Specific test conditions: test temperature 100°C, preheating time 1 minute, test time 4 minutes.

[0124] Water contact angle: Ordinary rubber powder and water-cut powder were hot-pressed into smooth flat sheets. The water contact angles of the ordinary rubber powder and water-cut powder were tested using an OCA20 contact angle meter from DataPhysics, Germany, in accordance with GB / T 30693-2014.

[0125] Rolling resistance: Determined using a dynamic mechanical analyzer (GaBOME-TER-150, Germany) in the tensile mode with a temperature sweep frequency of 10 Hz, a static strain of 5%, a static stress of 70 N, a dynamic strain of 0.25%, a dynamic stress of 60 N, a temperature range of -65 to 65°C, and a heating rate of 2°C / min.

[0126] Carbon black dispersion: Use a cutter to cut the stretched vulcanized film, place the cut surface in the observation window of the DisperGRADER carbon black dispersion instrument, and place the cut sample firmly and flat. Set the test method, select the dispersion calculation threshold of 23μm, the volume fraction of the filler as 30%, and the exposure time as 40ms.

[0127] Hot air aging performance test: After the vulcanized rubber sample is cut into dumbbell-shaped specimens according to the regulations, it is placed in a hot oven at 100°C for 72 hours. After the experiment, the mechanical properties of the aged specimens are tested.

[0128] Table 1 Performance test of rubber obtained in Examples 1 to 9

[0129]

[0130]

[0131] As can be seen from Table 1, the rubber mix obtained by the method of the present invention has low hardness, high carbon black dispersibility, and a Mooney viscosity index that exceeds the national standard. Furthermore, the water contact angles of the rubber powder prepared by the 120-mesh ultrahigh-pressure water jet method and the rubber powder prepared by the room-temperature pulverization method are 86.3 and 109.7, respectively. The rubber powder prepared by the ultrahigh-pressure water jet method has a smaller water contact angle and better hydrophilicity. The specific surface areas of Examples 2-8 show that the rubber powder prepared by the ultrahigh-pressure water jet method has a larger specific surface area and a more irregular surface shape than the rubber powder prepared by the room-temperature pulverization method. Furthermore, the higher the mesh size of the rubber powder prepared by the ultrahigh-pressure water jet method, the greater its specific surface area. The tensile strength and elongation at break of the rubber mix prepared by adding 160-mesh ultra-high-pressure water jetting rubber powder increased by 3.11 MPa and 49.26%, respectively, compared to the original rubber, demonstrating that the rubber mix prepared by adding the ultra-high-pressure water jetting rubber powder has excellent mechanical and physical properties. Furthermore, the rolling resistance and aging performance retention of the rubber mix prepared by adding the 160-mesh ultra-high-pressure water jetting rubber powder increased by 0.042 and 0.09, respectively, compared to the original rubber, demonstrating that the ultra-high-pressure water jetting rubber powder has a reinforcing effect on the performance of the rubber mix. Examples 2-5 compare different addition amounts of the same mesh size ultra-high-pressure water jetting rubber powder. It can be seen that as the addition amount increases, the performance decreases, indicating that a small amount of ultra-high-pressure water jetting rubber powder can enhance the performance of the rubber material. Comparing Example 2 with Example 8, Example 8 demonstrates that the rubber material prepared by adding the ultra-high-pressure water jetting rubber powder is superior to the rubber material prepared by adding the room-temperature pulverization method. Comparing the experimental data of Example 2 with that of Examples 6-7, it is shown that the higher the mesh size and the smaller the particle size of the rubber powder prepared by the ultra-high pressure water jet method, the better the performance of the rubber composite material prepared therefrom. Comparing the performance test data of the rubber mix prepared by Example 1 with the rubber powder prepared by the ultra-high pressure water jet method, it can be seen that the comprehensive performance of the rubber mix prepared by this method is far superior to that of the rubber mix prepared by the traditional wet method. The rubber powder prepared by the ultra-high pressure water jet method has better compatibility in the rubber matrix and eliminates the interfacial effect during the bonding process. In addition, the rubber powder prepared by the ultra-high pressure water jet method can improve the dispersibility of the reinforcing filler in the rubber matrix. While realizing the high-value application of the rubber powder in the rubber product formulation system, it also achieves acid-free flocculation of natural latex. Moreover, this process is green and environmentally friendly, with high production efficiency.

Claims

1. An environmentally friendly latex flocculation method based on fine rubber powder, characterized by: The invention relates to a preparation method for latex flocculation using fine rubber powder and natural rubber latex solution as raw materials through process control. The latex flocculation method based on fine rubber powder comprises the following steps: (1) Remove impurities from fine rubber powder and process the fine rubber powder to make it highly hydrophilic; (2) adding the treated fine rubber powder to natural rubber latex, and then mixing them in a high-speed stirrer to achieve homogenized mixing of the rubber powder and latex; (3) The rubber powder-latex mixture is sheared and fully flocculated to remove water; (4) dehydrating and drying the flocculated rubber material to obtain a flocculent gel; The fine rubber powder in step (1) is derived from rubber powder prepared by ultra-high pressure water jet method, and the rubber powder is treated by a plasma treatment device to increase the hydrophilicity of the surface of the fine rubber powder; The mesh size of the fine rubber powder in step (1) is 120 mesh to 200 mesh; The mass ratio of natural rubber latex to fine rubber powder in step (2) is 167:

10.

2. The environmentally friendly latex flocculation method based on fine rubber powder according to claim 1, characterized in that: The content of rubber component in the natural rubber latex is 27-80%; The fine rubber powder is one or more of truck tire rubber powder, passenger car tire rubber powder and rubber shoe rubber powder.

3. The environmentally friendly latex flocculation method based on fine rubber powder according to claim 1, characterized in that: The drying temperature in step (4) is 80-140°C.

4. The environmentally friendly latex flocculation method based on fine rubber powder according to claim 3, characterized in that: The drying temperature in step (4) is 100-120°C.

5. The environmentally friendly latex flocculation method based on fine rubber powder according to claim 1, characterized in that: In step (2), the stirring speed of the high-speed stirrer is 2000-10000 r / min, and the stirring time is 1-5 min.

6. The environmentally friendly latex flocculation method based on fine rubber powder according to claim 1, characterized in that: In step (2), the stirring speed of the high-speed stirring device is 4000-6000 r / min, and the stirring time is 2-4 min; The strong shear mixing device in step (3) is selected from an extruder, an internal mixer, or a continuous mixer; The dehydration and drying device described in step (4) is a kind of extruder, internal mixer and dryer.

7. The environmentally friendly latex flocculation method based on fine rubber powder according to claim 6, characterized in that: The strong shear mixing device in step (4) is an extruder, and the extruder process parameters are set as follows: temperature of 30-70° C. and screw speed of 20-60 rpm; The dehydration and drying device described in step (5) is an extruder, and the process parameters of the extruder are set as follows: the dehydration temperature is 80-140° C., and the screw speed is 30-80 rpm.

8. The environmentally friendly latex flocculation method based on fine rubber powder according to claim 7, characterized in that: In step (4), the extruder process parameters are set as follows: temperature of 40-60° C. and screw speed of 30-50 rpm; The extruder process parameters in step (5) are set as follows: dehydration temperature is 100-120° C., and screw speed is 50-60 rpm.

9. A wet mixing method based on fine rubber powder, characterized in that: The invention relates to a method for preparing wet mixed rubber using fine rubber powder and rubber latex solution as raw materials and through process control, comprising the following steps: (1) mixing natural rubber latex and fine rubber powder in a high-speed stirrer to obtain a mixed solution 1, and simultaneously stirring and mixing appropriate proportions of rubber reinforcement system and vulcanization auxiliary system materials with deionized water in a conventional stirrer to obtain a mixed solution 2; (2) Stirring the mixed solution 2 with a conventional stirrer, injecting the mixed solution 1 into the mixed solution 2 and mixing evenly to obtain the mixed solution 3; (3) adding the mixed solution into a strong shear device, regulating the shear strength by process parameters to cause flocculation, and then dehydrating and drying the flocculated gel through a dehydration device; (4) adding a certain proportion of vulcanizing agent to the dried rubber material in a mixing device for homogenization, dispersion and mixing to complete the wet process rubber mix preparation; The content of latex in the natural rubber latex in step (1) is 27-80%; The fine rubber powder is one or more of truck tire rubber powder, passenger car tire rubber powder and rubber shoe rubber powder; The rubber reinforcing system is one or more of carbon black, white carbon black, modified kaolin, mica powder, and attapulgite-modified clay; The carbon black is one or more of N339, N115, N375, and N326; The fine rubber powder in step (1) is derived from rubber powder prepared by ultra-high pressure water jet method; The mesh size of the fine rubber powder in step (1) is 100-200 mesh; In step (1), the stirring speed of the high-speed stirrer is 4000-6000 r / min, and the stirring time is 2-4 min. The stirring speed of the ordinary stirrer is 500-700 r / min, and the stirring time is 5-8 min. The mass ratio of natural rubber latex to fine rubber powder in step (1) is 167:(5-30); The mass ratio of the rubber reinforcing system and the vulcanization auxiliary system to deionized water is 1:(3-5); In step (2), the stirring speed of the ordinary stirrer is 200-600 r / min, and the stirring time is 1-7 min.

10. A wet mixing method based on fine rubber powder according to claim 9, characterized in that: In step (2), the stirring speed of the ordinary stirrer is 400-550 r / min, and the stirring time is 3-5 min; The dehydration device is selected from a dehydration extruder, an internal mixer, and a drying machine; The mixing equipment in step (4) is an open mill with a minimum roller distance of 0.1-0.25 mm; The rotation speed of the mixing equipment is 65-90r / min, the shearing time is 4-8min, and the shearing temperature is 33-76°C; The strong shearing equipment in step (3) is a high-speed stirrer with a stirring speed of 5000-8500 r / min and a stirring time of 40-50 s.

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