Method for preparing high-value carbon black from waste rubber

Abstract

The invention relates to the technical field of waste rubber treatment, and discloses a method for preparing high-value carbon black from waste rubber. According to the method, the waste rubber is soaked in the ice-water mixture containing ice water, calcium chloride and SDS, and a rubber cross-linked structure is destroyed through swelling and freezing effects, so that the waste rubber is embrittled, the viscoelasticity of the waste rubber is inhibited, and the waste rubber is easy to break; and further, crushing to obtain rubber micro-powder, and pyrolyzing the rubber micro-powder to obtain carbon black, thereby completing the recovery treatment of the waste rubber. The carbon black prepared by the method provided by the invention is doped into natural rubber to prepare a rubber product, and compared with a rubber product prepared from carbon black prepared by directly treating and crushing rubber at a dry ice temperature or at a low temperature of-196 to-150 DEG C, the tensile strength can be improved by 20%-50%.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of waste rubber processing, and particularly relates to a method for preparing carbon black by crushing waste rubber and pyrolysis. BACKGROUND

[0002] Rubber products are widely used in industry or life, and the waste rubber products taking synthetic rubber as the main material will be more and more. The waste rubber is composed of three parts: one part is waste tires, accounting for about 60% to 70% of the total amount of waste rubber; one part is waste rubber belts, waste rubber pipes, waste rubber shoes and other waste rubber products; and the other part is the leftover materials and scrap products generated in the production process of rubber products. The treatment of waste rubber is one of the problems faced by people today.

[0003] For the treatment of waste rubber, in the prior art, various waste rubber is depolymerized by using the principle of mechanochemistry, adopting a reducing agent and a double-screw solid-phase shearing method under low-temperature conditions, and through adjustment of the arrangement combination and cooling system of double-screw extrusion, the waste rubber is recycled. The process of this method needs to be controlled at a relatively low temperature, and has large energy consumption and poor depolymerization effect, and the rubber regeneration rate is low. Regenerated rubber refers to waste vulcanized rubber that is changed from an elastic state to a plastic and viscous state through physical and chemical processes such as crushing, heating and mechanical treatment, and can be re-vulcanized.

[0004] For example, a Chinese patent with the application publication number CN115847665A discloses a crushing process for recycling perfluoroether rubber, which crushes the perfluoroether rubber to be recycled by a liquid nitrogen freezing crusher to obtain micro powder, and then adds raw rubber, vulcanizing agent and crosslinking agent to the micro powder to prepare high-value products by mixing again. The method of the patent has the following problems: 1. In the crushing process, the temperature needs to be controlled at -196 to -150℃ by a liquid nitrogen freezing crusher, which will generate large energy consumption; 2. The rubber regeneration rate of the recycling process is low, and a large amount of raw rubber needs to be matched to mix the perfluoroether rubber micro powder. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a method for preparing high-value carbon black from waste rubber.

[0006] The specific technical scheme of the present application is as follows: In a first aspect, the present application provides a method for preparing high-value carbon black from waste rubber, which comprises the following steps: (S.1) Soaking waste rubber in an ice water mixture for 6 to 72 hours, wherein the ice water mixture comprises ice water, calcium chloride and SDS (sodium dodecyl sulfate), so as to change the crosslinking network structure of the waste rubber; (S.2) crushing the waste rubber after soaking to obtain rubber micro powder; (S.3) pyrolyzing the rubber micro powder to obtain carbon black.

[0007] The existing waste rubber recycling process needs to be crushed at a low temperature, which consumes a large amount of energy, and the depolymerization reduction effect of the rubber powder is poor, and the rubber regeneration rate is low. The existing technology needs to crush the rubber at a low temperature. The main reason is that the rubber viscoelasticity is inhibited at a low temperature, such as dry ice temperature and extremely low temperature of-196 to-150℃, and the hardness is improved, so that it is easy to crush and depolymerize the structure.

[0008] The present application is soaked in ice water containing ice water, calcium chloride and SDS, the crosslinked structure of the waste rubber is destroyed by swelling and freezing effect, so that the waste rubber is brittle, so that the viscoelasticity of the waste rubber is inhibited and it is easy to break; further, the rubber micro powder is obtained by crushing, and is pyrolyzed to obtain carbon black, so as to complete the recycling of the waste rubber. The carbon black prepared by the method provided by the present application is mixed into natural rubber to prepare rubber products. Compared with the carbon black prepared by directly crushing the rubber at a dry ice temperature or a low temperature of-196 to-150℃, the tensile strength of the rubber product prepared by the carbon black can be increased by 20% to 50%.

[0009] In the process of soaking the waste rubber in the present application, ice water and calcium chloride can enter the rubber structure, so that the rubber structure is swollen and frozen, and the viscoelasticity is inhibited, and SDS can promote the entry of ice water and calcium chloride into the rubber structure, and promote the ice water brittle effect.

[0010] As a preferred method, in (S.2), the mass ratio of ice water, calcium chloride and SDS is 100:(8-16):(0.1-0.5).

[0011] As a preferred method, in (S.2), the crushing operation is carried out at-20℃ to 5℃.

[0012] As a preferred method, in (S.2), the crushing speed of the crushing operation is 120-250 rpm.

[0013] As a preferred method, in (S.2), the particle size of the rubber micro powder is 0.1-0.9 mm.

[0014] As a preferred method, the pyrolysis treatment is: Under an inert atmosphere, the temperature is raised to 650-750℃ at a rate of 5-20℃ / min.

[0015] Further preferably, the pyrolysis treatment is: temperature to 150-300℃ at a rate of 5-20℃ / min, and the mass loss rate of the rubber micro-powder is 4-6%; temperature to 350-500℃ at a rate of 5-20℃ / min, and the mass loss rate of the rubber micro-powder is 40-50%; temperature to 650-750℃ at a rate of 5-20℃ / min, and the mass loss rate of the rubber micro-powder is 45-60%.

[0016] By the pyrolysis treatment method, the rubber micro-powder is prepared into high-value carbon black by step pyrolysis. Specifically, the plasticizer is removed by devolatilization at 150-300℃ with a weight loss control of 4-6%; then the rubber is directionally cracked by main decomposition at 350-500℃ with a weight loss control in the range of 40-50%; finally, the graphitization structure is formed by stabilizing the residual carbon at 650-750℃ with a total weight loss control in the range of 45-60%. Thus, by the three-stage temperature rising pyrolysis at 5-20℃ / min to 150-300℃, 350-500℃ and 650-750℃, the high-value carbon black is finally prepared.

[0017] In a second aspect, based on the above method, the application provides a high-value carbon black.

[0018] In a third aspect, based on the above method, the application provides an application of the carbon black in preparing rubber products.

[0019] As a preferred scheme of the application, the application method comprises the following steps: the carbon black prepared by the above method is mixed into natural rubber at a mass ratio of 20-50:100 to prepare rubber products.

[0020] The rubber products include tires, seals or shock pads.

[0021] Compared with the prior art, the application has the following technical effects: (1) The application swells and freezes the waste rubber by immersing the waste rubber in an ice water mixture containing ice water, calcium chloride and SDS, destroys the cross-linking structure of the rubber by freezing effect, and makes the waste rubber brittle, so that the viscoelasticity of the waste rubber is inhibited and the waste rubber is easily broken; further, the rubber micro-powder is obtained by breaking, and the carbon black is obtained by pyrolysis treatment, thereby completing the recycling of the waste rubber. The carbon black prepared by the method provided by the application is mixed into natural rubber to prepare rubber products, and the tensile strength of the rubber products prepared by the carbon black prepared by directly pulverizing the rubber at a dry ice temperature or at a low temperature of-196 to-150℃ can be increased by 20%-50% compared with the rubber products prepared by the carbon black.

[0022] (2) In the process of soaking the waste rubber in the present application, the ice water mixture containing ice water, calcium chloride and SDS can enter the rubber structure, so that the rubber structure swells and freezes, inhibiting its viscoelasticity, while SDS can promote the entry of ice water and calcium chloride into the rubber structure, promoting the ice water embrittlement effect. The present application provides an ice water mixture that can make the rubber brittle at around 0℃, avoiding the problem of treating rubber at extremely low temperatures of-196 to-150℃, and the energy consumption is relatively small. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 TG-DTG curves of waste rubber micro powder at different heating rates. DETAILED DESCRIPTION

[0024] The present application will be further described below in conjunction with examples. Those skilled in the art will be able to implement the present application based on these descriptions. In addition, the examples of the present application involved in the following description are generally only a part of the examples of the present application, not all examples. Therefore, based on the examples in the present application, all other examples obtained by those skilled in the art without creative labor shall fall within the scope of protection of the present application.

[0025] The existing waste rubber recycling process needs to be controlled at a lower temperature for crushing, which consumes a lot of energy, and the subsequent depolymerization effect of the rubber powder is poor, and the rubber regeneration rate is low. The existing technology needs to crush the rubber at a lower temperature, the main reason is that the rubber is inhibited at a lower temperature, for example, at dry ice temperature, and at extremely low temperatures of-196 to-150℃, the hardness of the rubber is improved, so it is easy to crush and depolymerize its structure.

[0026] Therefore, in order to solve the defects existing in the prior art, in an embodiment, the present application provides a method for preparing high-value carbon black from waste rubber, which comprises the following steps: (S.1) Soak the waste rubber in an ice water mixture for 6-72 hours, the ice water mixture containing ice water, calcium chloride and SDS (sodium dodecyl sulfate), so as to change the crosslinked network structure of the waste rubber; (S.2) Crush the soaked waste rubber to obtain rubber micro powder; (S.3) Pyrolysis treatment of the rubber micro powder to obtain carbon black.

[0027] The present embodiment can make the waste rubber brittle by soaking the waste rubber in the ice water mixture containing ice water, calcium chloride and SDS, destroying the cross-linking structure of the rubber through swelling and freezing effect, thereby inhibiting the viscoelasticity of the waste rubber and making it easy to break; further, the rubber micro-powder is obtained by crushing, and the carbon black is obtained by pyrolysis treatment, thereby completing the recycling treatment of the waste rubber. The carbon black prepared by the method provided in the present embodiment is mixed into natural rubber to prepare rubber products, and the tensile strength of the rubber products prepared by the carbon black can be increased by 20%~50% compared with the rubber products prepared by directly crushing the rubber at dry ice temperature or-196 to-150℃ low temperature.

[0028] In the process of soaking the waste rubber in the present embodiment, ice water and calcium chloride can enter the rubber structure, making the rubber structure swell and freeze, and inhibiting its viscoelasticity, and SDS can promote the entry of ice water and calcium chloride into the rubber structure and promote the ice water brittleness effect.

[0029] In an embodiment, a waste tire is used for mechanical property experiment. The waste tire material is subjected to tensile experiment at room temperature, and has viscoelasticity, and the stress fluctuates in the tensile experiment, and the average value of the maximum stress is 1618 kN / m 2 Due to the elastic characteristics of the waste tire rubber, the strain of the sample rupture is large. After the waste tire material is subjected to the soaking treatment of step (S.1) of the present application, i.e., soaked in the ice water mixture containing ice water, calcium chloride and SDS overnight for 12 hours, and then subjected to tensile experiment at 0℃, it is found that the viscoelasticity of the rubber at dry ice temperature is inhibited and the hardness is strengthened, and the maximum stress value is 2362 kN / m 2 , which is about 1.5 times larger than the maximum stress under room temperature without soaking treatment, and the maximum breaking strain is 0.54, and the strain is almost halved, and the plastic deformation of the sample after breaking is small. Therefore, the soaking treatment of step (S.1) can significantly reduce the power consumption of tensile rupture compared with room temperature.

[0030] As a preferred embodiment of the above embodiment, in (S.2), the mass ratio of ice water, calcium chloride and SDS is 100:(8~16):(0.1~0.5).

[0031] As a preferred embodiment of the above embodiment, in (S.2), the crushing operation is carried out at-20℃ to 5℃.

[0032] As a preferred embodiment of the above embodiment, in (S.2), the crushing speed of the crushing operation is 120~250 rpm.

[0033] As a preferred embodiment of the above embodiment, in (S.2), the particle size of the rubber micro-powder is 0.1~0.9 mm.

[0034] As a preferred embodiment of the above embodiment, the pyrolysis treatment is: Under an inert atmosphere, the temperature is increased to 650-750℃ at a rate of 5-20℃ / min.

[0035] Rubber micropowder was prepared from the aforementioned waste tires through steps (S.1) and (S.2), and then subjected to pyrolysis treatment at different heating rates. The TG-DTG curves are shown below. Figure 1 .Depend on Figure 1 The results show that the first weight loss stage occurs between 150 and 300 °C, with a mass loss of approximately 6.71 wt.%, mainly caused by the release of moisture, oil, plasticizers, and additives from the rubber powder. The second weight loss stage occurs between 300 and 500 °C, with a mass loss of approximately 50.25 wt.%. The main cause of weight loss in this stage is the decomposition of natural and synthetic rubbers (butadiene rubber and styrene-butadiene rubber) in the rubber powder. The peak at approximately 375 °C is mainly attributed to the decomposition of natural rubber, while the peak at 420 °C is mainly attributed to the decomposition of butadiene rubber and styrene-butadiene rubber. The third weight loss stage occurs between 500 and 700 °C, with a weight loss rate of approximately 6.34 wt.%, mainly caused by the decomposition of certain inorganic substances in the rubber powder. After 700 °C, the TG curve becomes smooth and the DTG curve no longer fluctuates, indicating that the pyrolysis reaction is complete. Different heating rates did not significantly affect the overall trend of the pyrolysis process, but as the heating rate increases, the TG and DTG curves gradually shift towards the higher temperature region, which may be due to thermal hysteresis.

[0036] As another preferred embodiment of the above, the pyrolysis treatment is as follows: The temperature is increased to 150-300℃ at a rate of 5-20℃ / min, while the mass loss rate of the rubber powder is 4-6%. Then, the temperature is increased to 350-500℃ at a rate of 5-20℃ / min, and the mass loss rate of the rubber powder is 40-50%. Then, the temperature is increased to 650-750℃ at a rate of 5-20℃ / min, and the mass loss rate of the rubber powder is 45-60%.

[0037] High-value carbon black is prepared by stepwise pyrolysis of rubber micropowder using the above-described pyrolysis method. Specifically, devolatilization is carried out at 150-300℃, with weight loss controlled at 4-6%, to remove plasticizers; then, main decomposition is performed at 350-500℃, with weight loss controlled at 40-50%, to induce directional pyrolysis of the rubber; finally, residual carbon is stabilized at 650-750℃, with total weight loss controlled at 45-60%, to form a graphitized structure. Thus, high-value carbon black is finally prepared by the three-stage pyrolysis method of increasing the temperature at 5-20℃ / min to 150-300℃, 350-500℃, and 650-750℃.

[0038] In another embodiment, the present application provides the carbon black prepared by the above method for preparing rubber products.

[0039] Specifically, the carbon black prepared by the above method is mixed into natural rubber at a mass ratio of 20-50:100, and the tensile strength of the prepared rubber product can be increased by 20-50%.

[0040] Example 1 A method for preparing high-value carbon black from waste rubber, comprising the following steps: (S.1) Soak the waste rubber in an ice water mixture for 12 hours, wherein the ice water mixture is obtained by mixing ice water, calcium chloride and SDS at a mass ratio of 100:15:0.3; and the mixing amount of the waste rubber and the ice water mixture is preferably submerged; (S.2) After soaking, the waste rubber is washed with cold water for 3 times, and then is crushed by double screw shearing at a speed of 150 rpm at -5℃ to obtain rubber powder with an average particle size of 0.5 mm; (S.3) Increase the temperature of the rubber powder to 300℃ at a rate of 10℃ / min, and make the mass loss rate of the rubber powder be 6%; then increase the temperature to 400℃ at a rate of 10℃ / min, and make the mass loss rate of the rubber powder be 50%; then increase the temperature to 700℃ at a rate of 10℃ / min, and make the mass loss rate of the rubber powder be 56%, i.e. the pyrolysis treatment is completed, to obtain a carbon black.

[0041] Example 2 A method for preparing high-value carbon black from waste rubber, comprising the following steps: (S.1) Soak the waste rubber in an ice water mixture for 72 hours, wherein the ice water mixture is obtained by mixing ice water, calcium chloride and SDS at a mass ratio of 100:8:0.5; and the mixing amount of the waste rubber and the ice water mixture is preferably submerged; (S.2) After soaking, the waste rubber is washed with cold water for 3 times, and then is crushed by double screw shearing at a speed of 120 rpm at -20℃ to obtain rubber powder with an average particle size of 0.5 mm; (S.3) Increase the temperature of the rubber powder to 300℃ at a rate of 10℃ / min, and make the mass loss rate of the rubber powder be 6%; then increase the temperature to 400℃ at a rate of 10℃ / min, and make the mass loss rate of the rubber powder be 50%; then increase the temperature to 700℃ at a rate of 10℃ / min, and make the mass loss rate of the rubber powder be 56%, i.e. the pyrolysis treatment is completed, to obtain a carbon black.

[0042] Example 3 A method for preparing high-value carbon black from waste rubber, comprising the following steps: (S.1) Waste rubber is soaked in an ice water mixture for 6 hours, the ice water mixture is obtained by mixing ice water, calcium chloride and SDS according to a mass ratio of 100:16:0.1; the mixing amount of waste rubber and ice water mixture is preferably submerged; (S.2) After soaking, the waste rubber is washed with cold water for 3 times, and then is crushed by double screw shearing at a speed of 250 rpm at 5℃ to obtain rubber powder with an average particle size of 0.5 mm; (S.3) The temperature of the rubber powder is raised to 300℃ at a rate of 10℃ / min, and the mass loss rate of the rubber powder is 6%; then the temperature is raised to 400℃ at a rate of 10℃ / min, and the mass loss rate of the rubber powder is 50%; then the temperature is raised to 700℃ at a rate of 10℃ / min, and the mass loss rate of the rubber powder is 56%, that is, the pyrolysis treatment is completed, and a carbon black is obtained.

[0043] Comparative Example 1 A method for preparing carbon black from waste rubber is provided, which comprises the following steps: (S.1) Waste rubber is crushed by a liquid nitrogen crusher at -150℃ to obtain rubber powder with an average particle size of 0.5 mm; (S.2) The temperature of the rubber powder is raised to 300℃ at a rate of 10℃ / min, and the mass loss rate of the rubber powder is 6%; then the temperature is raised to 400℃ at a rate of 10℃ / min, and the mass loss rate of the rubber powder is 50%; then the temperature is raised to 700℃ at a rate of 10℃ / min, and the mass loss rate of the rubber powder is 56%, that is, the pyrolysis treatment is completed, and a carbon black is obtained.

[0044] Comparative Example 2 A method for preparing carbon black from waste rubber is provided, which is different from Example 1 in that the ice water mixture of step (S.1) only contains ice water. The other steps are the same as Example 1.

[0045] The (S.2) crushing of this comparative example obtains rubber powder with an average particle size of 1.7 mm.

[0046] Comparative Example 3 A method for preparing carbon black from waste rubber is provided, which is different from Example 1 in that the ice water mixture of step (S.1) is obtained by mixing ice water, calcium chloride and SDS according to a mass ratio of 100:20:0.3. The other steps are the same as Example 1.

[0047] Comparative Example 4 A method for preparing carbon black by using waste rubber is provided, compared with example 1, the difference lies in that the ice water mixture of step (S.1) is obtained by mixing ice water, calcium chloride and SDS according to the mass ratio of 100:5:0.3. Other steps are the same as example 1.

[0048] Comparative example 5 A method for preparing carbon black by using waste rubber is provided, compared with example 1, the difference lies in that the ice water mixture of step (S.1) is obtained by mixing ice water, calcium chloride and SDS according to the mass ratio of 100:5:0.3. Other steps are the same as example 1.

[0049] Comparative example 6 A method for preparing carbon black by using waste rubber is provided, compared with example 1, the difference lies in that the ice water mixture of step (S.1) is obtained by mixing ice water, calcium chloride and SDS according to the mass ratio of 100:5:0.3. Other steps are the same as example 1.

[0050] Application example The carbon black obtained in examples 1 to 3 and comparative examples 1 to 6 is added to natural rubber as a filler to prepare a rubber product, and the tensile strength and hardness performance of the rubber product are tested, and the results are shown in Table 1. The formula for preparing the rubber product is (mass parts): natural rubber 100 parts, zinc oxide 5 parts, stearic acid 3 parts, accelerator M 0.6 parts, sulfur 2.5 parts, carbon black 30 parts. A Labtech Engineering double roller mill LRM-S-150 and a flat plate vulcanizing machine LP-S-80 are used to prepare carbon black reinforced rubber (thickness of 2mm), and the tensile strength and hardness performance of the carbon black reinforced rubber are tested according to the national standard.

[0051] Table 1 Group Maximum tensile stress (MPa) Hardness Example 1 14.224 49.3 Example 2 13.239 48.0 Example 3 12.423 47.6 Comparative Example 1 10.231 48.2 Comparative Example 2 7.123 34.3 Comparative Example 3 9.778 38.8 Comparative Example 4 7.563 34.1 Comparative Example 5 8.654 36.4 Comparative Example 6 7.147 35.9 Data analysis: (1) From the test data of the reinforced rubber prepared in Table 1, it can be seen that by soaking the waste rubber in the ice water mixture containing ice water, calcium chloride and SDS, the crosslinked structure of the waste rubber is destroyed by swelling and freezing effect, so that the waste rubber is brittle, thereby inhibiting the viscoelasticity of the waste rubber and making it easy to break; further, the rubber micro powder is obtained by crushing, and is pyrolyzed to obtain carbon black, which is mixed into natural rubber to prepare a rubber product. Compared with the rubber product prepared by directly low-temperature treating and crushing the rubber at-150℃ (compared with comparative example 1), the tensile strength can be increased by 20%~50%.

[0052] (2) By comparing examples 2 to 6 with example 1, it is shown that the ice water mixture containing ice water, calcium chloride and SDS has an effect on the preparation of high-value carbon black in the process of soaking the waste rubber according to the application. The ice water mixture containing ice water, calcium chloride and SDS provided by the application is beneficial to the preparation of high-value carbon black after soaking the rubber, and the carbon black can realize the reinforcement of natural rubber.

[0053] The raw materials and equipment used in the application are conventional raw materials and equipment in the art unless otherwise specified; the methods used in the application are conventional methods in the art unless otherwise specified.

[0054] The above is only a preferred embodiment of the application, and does not limit the application in any way. Any simple modification, change and equivalent transformation of the above embodiment according to the technical essence of the application still falls within the protection scope of the technical solution of the application.

Claims

1. A method for preparing high-value carbon black from waste rubber, characterized by: Includes the following steps: (S.1) Soak the waste rubber in an ice-water mixture for 6 to 72 hours, wherein the ice-water mixture comprises ice water, calcium chloride and SDS; (S.2) Crush and soak the waste rubber to obtain rubber powder; (S.3) The rubber powder is subjected to pyrolysis to obtain carbon black.

2. The method of claim 1, wherein the method is characterized by: In (S.2), the mass ratio of ice water, calcium chloride and SDS is 100:(8~16):(0.1~0.5).

3. The method of claim 1, wherein the method is characterized by: In (S.2), the pulverization operation is carried out at -20°C to +5°C.

4. The method of claim 1, wherein the method is characterized by: In (S.2), the grinding speed of the grinding operation is 120~250 rpm.

5. The method for preparing high-value carbon black from waste rubber according to claim 1 or 4, characterized in that: In (S.2), the particle size of the rubber powder is 0.1~0.9 mm.

6. The method of claim 1, wherein the method is characterized by: The pyrolysis treatment is as follows: under an inert atmosphere, the temperature is increased to 650~750℃ at a rate of 5~20℃ / min.

7. The method for preparing high-value carbon black from waste rubber according to claim 1 or 6, characterized in that: The pyrolysis treatment is as follows: The temperature is increased to 150-300℃ at a rate of 5-20℃ / min, while the mass loss rate of the rubber powder is 4-6%. Then, the temperature is increased to 350-500℃ at a rate of 5-20℃ / min, and the mass loss rate of the rubber powder is 40-50%. Then, the temperature is increased to 650-750℃ at a rate of 5-20℃ / min, and the mass loss rate of the rubber powder is 45-60%.

8. Carbon black prepared by the method according to any one of claims 1 to 7.

9. The use of carbon black as described in claim 8 in the preparation of rubber products.

10. Use according to claim 9, wherein: The carbon black described in claim 8 is incorporated into natural rubber at a mass ratio of 20-50:100 to prepare rubber products.

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