Waste rubber regeneration desulfurization method

Abstract

The invention relates to the technical field of desulfurization and regeneration of waste rubber, in particular to a regeneration and desulfurization method of waste rubber, which comprises the following steps: soaking waste rubber powder in an ammonium bicarbonate solution, heating to 60 DEG C to enable waste rubber particles to form dense micropores, and adding a heterotrophic nitrification-aerobic denitrification bacteria solution to react with zinc oxide in the waste rubber so as to realize the regeneration and desulfurization of the waste rubber. Zinc oxide in waste rubber is separated through the cell surface adsorption effect, thermococcus thermophilic archaea and waste rubber powder are blended and subjected to a fermentation reaction in a closed environment at the temperature of 90-94 DEG C, a fermentation product can be broken with sulfur bonds in the waste rubber, and due to the fact that the thermococcus thermophilic archaea can survive at the higher temperature, the sulfur bonds in the waste rubber can be broken. The reaction is more violent than that of strains surviving at normal temperature, the fermentation product can better penetrate through the waste rubber particles, the fermentation product can more completely break sulfur bonds of the waste rubber particles, and the tensile strength and the elongation at break of the desulfurized rubber are greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of waste rubber desulfurization and regeneration, in particular to a waste rubber regeneration and desulfurization method. Background Art

[0002] Rubber is a high molecular polymer with a relative molecular mass between 100,000 and 1,000,000. Raw rubber has high elasticity and plasticity and can be processed into various shapes according to product requirements, but its physical and mechanical strength is poor. It will deform under external forces and cannot return to its original shape. After rubber is vulcanized, sulfur and other substances form sulfur bridges, making rubber products into irregular high molecular elastomers with three-dimensional structures. At this time, rubber products have excellent physical and mechanical properties and can be used as various rubber products.

[0003] In waste rubber products, such as rubber tires, since they have been vulcanized, if the waste rubber is to be recycled, it needs to be regenerated. The process of rubber devulcanization is to break the sulfur bridge in the vulcanized rubber, rather than removing the sulfur element. The sulfur element remains in the rubber after desulfurization. The composition of the rubber after vulcanization is very complex, and the corresponding desulfurization reaction mechanism is difficult to clearly describe. It is generally believed that rubber desulfurization is a free radical reaction process. The cross-linked network breaks under high temperature or shear force to form free radicals, which couple with the sulfur stripping agent free radicals to complete the desulfurization. The cross-linked network may have three different ways of breaking, namely, cross-link bond breakage, main chain breakage, and random breakage of cross-link bonds and main chains.

[0004] In the prior art, most of the cross-linked networks in rubber are broken by physical conditions such as high temperature, high pressure or shear force. The Chinese patent with the announcement number CN104962601B discloses a method for regenerating waste rubber by desulfurization of two kinds of microorganisms. The waste tire tread rubber powder is placed in the culture medium of Sphingomonas and Gordonia to react, and the biological enzymes produced by the two bacteria are used to selectively break the sulfur cross-linked bonds. However, this method has the following shortcomings: the two bacteria can only act on the cross-linked bonds with a thickness of about several microns on the surface of the rubber powder, and the network structure is still maintained inside the rubber particles. The rubber activator zinc oxide will prevent Sphingomonas and Gordonia from oxidizing and degrading the cross-linked sulfur bonds. The scheme can only reduce the sulfur content on the surface of the rubber powder, and cannot achieve the performance of recycling. Summary of the invention

[0005] The technical problem to be solved by the present invention is: how to improve the method for regenerating and desulfurizing waste rubber by using microorganisms to enhance the performance of the regenerated rubber.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0007] The waste rubber regeneration and desulfurization method comprises the following steps:

[0008] Step 1: crush the waste rubber to a particle size of 400-600 μm, immerse it in an ammonium bicarbonate solution, wherein the ammonium bicarbonate solution is prepared by mixing ammonium bicarbonate powder and water in a mass ratio of 1-3:10, and react at 60° C. with stirring for 1-2 days;

[0009] Prepare LB culture medium, inoculate activated heterotrophic nitrification-denitrifying bacteria into the LB culture medium, and culture at 30-40° C. for 24-30 hours to obtain heterotrophic nitrification-denitrifying bacteria liquid;

[0010] Step 2: Add the heterotrophic nitrification-denitrification bacteria solution to the ammonium bicarbonate solution at a mass ratio of 1:1, react at 30-40°C for 3-4 hours, filter out the waste rubber powder, disinfect it, and set it aside;

[0011] Step 3: Add culture medium, thermophilic archaea of ​​the genus Thermococcus and YPS culture medium into the fermentation tank, add 4-5% sodium chloride by mass ratio into YPS, control the pH at 6.5-7, the temperature at 90-94° C., the stirring speed at 400-500 rpm, the pressure at 0.1-0.2 MPa, and react for 26-30 hours;

[0012] Step 4: Put the waste rubber powder filtered out in step 2 into a closed fermentation tank, the mass ratio of waste rubber to YPS culture medium is 1:3-5, the pH is controlled at 6.5-7, the temperature is controlled at 90-94°C, the stirring speed is 400-500rpm, the pressure is 0.1-0.2MPa, and after reacting for 3-4 days, the waste rubber powder is filtered out and dried to obtain devulcanized rubber.

[0013] Furthermore, in the above waste rubber regeneration and desulfurization method, the heterotrophic nitrification-denitrifying bacteria DNF23.

[0014] Furthermore, in the above waste rubber regeneration and desulfurization method, the Thermococcus thermophilic archaeon is Thermococcus thermophilic archaeon HJ21.

[0015] Furthermore, in the above waste rubber regeneration and desulfurization method, the waste rubber is selected from waste tire tread rubber.

[0016] The present invention also protects the regenerated rubber obtained by the above waste rubber regeneration and desulfurization method.

[0017] The beneficial effects of the present invention are as follows: the present invention soaks the waste rubber powder in an ammonium bicarbonate solution, so that the ammonium bicarbonate penetrates into the waste rubber powder particles; at 60°C, the ammonium bicarbonate decomposes to produce carbon dioxide gas and ammonia gas, so that the waste rubber particles form dense micropores, and the specific surface area of ​​the waste rubber particles is increased; by adding heterotrophic nitrification-denitrification bacteria liquid, the zinc oxide present in the waste rubber can be reacted to separate the zinc oxide in the waste rubber through cell surface adsorption; the thermophilic archaea of ​​the genus Thermococcus are mixed with the waste rubber powder, and fermented at a temperature of 90-94°C in a closed environment to make the waste rubber powder have a good effect; The fermentation product can break the sulfur bonds in the waste rubber to achieve the purpose of desulfurization. Since the thermophilic archaea of ​​the genus Thermococcus can survive at higher temperatures, its reaction is more intense than that of the bacteria that survive at room temperature. The fermentation product can better penetrate the waste rubber particles. Since the waste rubber particles themselves have dense micropores after being treated with ammonium bicarbonate, 4-5% of sodium chloride is added in step 3. Its role is to promote the fermentation of the bacteria, so that the fermentation product can penetrate into the waste rubber powder, so that the fermentation product can more completely break the sulfur bonds of the waste rubber particles, and greatly increase the tensile strength and elongation at break of the desulfurized rubber. DETAILED DESCRIPTION

[0018] In order to explain the technical content, achieved objectives and effects of the present invention in detail, the following is an explanation in conjunction with the implementation modes.

[0019] The specific embodiment of the present invention relates to a waste rubber regeneration and desulfurization method, comprising the following steps:

[0020] Step 1: crush the waste rubber to a particle size of 400-600 μm, immerse it in an ammonium bicarbonate solution, wherein the ammonium bicarbonate solution is prepared by mixing ammonium bicarbonate powder and water in a mass ratio of 1-3:10, and react at 60° C. with stirring for 1-2 days;

[0021] Prepare LB culture medium, inoculate activated heterotrophic nitrification-denitrifying bacteria into the LB culture medium, and culture at 30-40° C. for 24-30 hours to obtain heterotrophic nitrification-denitrifying bacteria liquid;

[0022] Step 2: Add the heterotrophic nitrification-denitrification bacteria solution to the ammonium bicarbonate solution at a mass ratio of 1:1, react at 30-40°C for 3-4 hours, filter out the waste rubber powder, disinfect it, and set it aside;

[0023] Step 3: Add culture medium, thermophilic archaea of ​​the genus Thermococcus and YPS culture medium into the fermentation tank, add 4-5% sodium chloride by mass ratio into YPS, control the pH at 6.5-7, the temperature at 90-94° C., the stirring speed at 400-500 rpm, the pressure at 0.1-0.2 MPa, and react for 26-30 hours;

[0024] Step 4: Put the waste rubber powder filtered out in step 2 into a closed fermentation tank, the mass ratio of waste rubber to YPS culture medium is 1:3-5, the pH is controlled at 6.5-7, the temperature is controlled at 90-94°C, the stirring speed is 400-500rpm, the pressure is 0.1-0.2MPa, and after reacting for 3-4 days, the waste rubber powder is filtered out and dried to obtain devulcanized rubber.

[0025] In the above implementation manner, the disinfection treatment in step 2 is to soak the waste rubber powder in 75% alcohol for 4-6 hours and filter it out.

[0026] In the above implementation mode, by immersing the waste rubber powder in an ammonium bicarbonate solution, the ammonium bicarbonate is allowed to penetrate into the waste rubber powder particles. At 60°C, the ammonium bicarbonate decomposes to produce carbon dioxide gas and ammonia gas, so that the waste rubber particles form dense micropores, and the specific surface area of ​​the waste rubber particles is increased. By adding a heterotrophic nitrifying-denitrifying bacterial solution, it can react with the zinc oxide present in the waste rubber, and the zinc oxide in the waste rubber is separated by cell surface adsorption. The thermophilic archaea of ​​the genus Thermococcus are mixed with the waste rubber powder, and fermented at a temperature of 90-94°C in a closed environment, so that the fermentation product can break the sulfur bond in the waste rubber, thereby achieving the purpose of desulfurization. Since the thermophilic archaea of ​​the genus Thermococcus can survive at a higher temperature, its reaction is more intense than that of the bacteria that survive at room temperature, and the fermentation product can better penetrate the waste rubber particles. Moreover, since the waste rubber particles themselves have dense micropores after being treated with ammonium bicarbonate, the fermentation product can more completely break the sulfur bond of the waste rubber particles, thereby greatly increasing the tensile strength and elongation at break of the devulcanized rubber.

[0027] Preferably, the heterotrophic nitrifying-denitrifying bacteria is DNF23.

[0028] The heterotrophic nitrification-good denitrifying bacteria DNF23 was purchased from Guangdong Microbial Culture Collection Center with a collection number of GDMCC No: 60713. The strain is an existing strain and is disclosed in a Chinese patent with a publication number of CN114084957A.

[0029] Preferably, the Thermococcus thermophilic archaeon is Thermococcus thermophilic archaeon HJ21.

[0030] The thermophilic archaeon HJ21 of the genus Thermococcus was purchased from the China Center for Type Culture Collection with a collection number of CCTCC No: M207010. This strain is an existing strain and is disclosed in a Chinese patent with a publication number of CN101070527A.

[0031] Preferably, the waste rubber is selected from waste tire tread rubber.

[0032] The specific implementation manner of the present invention also relates to the regenerated rubber obtained by the above waste rubber regeneration and desulfurization method.

[0033] Example 1

[0034] A method for regenerating and desulfurizing waste rubber comprises the following steps:

[0035] Step 1: crush the waste tire tread rubber to a particle size of 500 μm, immerse it in an ammonium bicarbonate solution, wherein the ammonium bicarbonate solution is prepared by mixing ammonium bicarbonate powder and water in a mass ratio of 2:10, and react at 60° C. with stirring for 2 days;

[0036] LB culture medium was prepared, and activated heterotrophic nitrification-denitrifying bacteria DNF23 (GDMCC No: 60713) was inoculated into the LB culture medium, and cultured at 37° C. for 26 hours to obtain a heterotrophic nitrification-denitrifying bacteria liquid;

[0037] Step 2: Add the heterotrophic nitrification-denitrification bacteria solution to the ammonium bicarbonate solution at a mass ratio of 1:1, and react at 37°C for 3.5 hours, then filter out the waste rubber powder, disinfect it, and set it aside;

[0038] Step 3: Add culture medium, Thermococcus thermophilic archaea HJ21 (CCTCC No: M207010) and YPS culture medium into the fermenter, add 5% sodium chloride by mass to YPS, control the pH at 7, the temperature at 92°C, the stirring speed at 450rpm, the pressure at 0.2MPa, and react for 28h;

[0039] Step 4: The waste rubber powder filtered out in step 2 is put into a closed fermentation tank, the mass ratio of waste rubber to YPS culture medium is 1:4, the pH is controlled at 7, the temperature is controlled at 92°C, the stirring speed is 450rpm, and the pressure is 0.2MPa. After reacting for 4 days, the waste rubber powder is filtered out and dried to obtain devulcanized rubber.

[0040] Example 2

[0041] A method for regenerating and desulfurizing waste rubber comprises the following steps:

[0042] Step 1: crush the waste tire tread rubber to a particle size of 400 μm, immerse it in an ammonium bicarbonate solution, wherein the ammonium bicarbonate solution is prepared by mixing ammonium bicarbonate powder and water in a mass ratio of 1:10, and react at 60° C. with stirring for 1 day;

[0043] LB culture medium was prepared, and activated heterotrophic nitrification-denitrifying bacteria DNF23 (GDMCC No: 60713) was inoculated into the LB culture medium, and cultured at 30° C. for 24 hours to obtain a heterotrophic nitrification-denitrifying bacteria liquid;

[0044] Step 2: Add the heterotrophic nitrification-denitrification bacteria solution to the ammonium bicarbonate solution at a mass ratio of 1:1, and react at 30°C for 3 hours, then filter out the waste rubber powder, disinfect it, and set it aside;

[0045] Step 3: Add culture medium, Thermococcus thermophilic archaea HJ21 (CCTCC No: M207010) and YPS culture medium into the fermenter, add 4-5% sodium chloride by mass ratio into YPS, control the pH at 6.5, control the temperature at 90°C, stir at 400rpm, and the pressure at 0.1MPa, and react for 26h;

[0046] Step 4: The waste rubber powder filtered out in step 2 is put into a closed fermentation tank, the mass ratio of waste rubber to YPS culture medium is 1:3, the pH is controlled at 6.5, the temperature is controlled at 90°C, the stirring speed is 400rpm, and the pressure is 0.1MPa. After reacting for 3 days, the waste rubber powder is filtered out and dried to obtain devulcanized rubber.

[0047] Example 3

[0048] A method for regenerating and desulfurizing waste rubber comprises the following steps:

[0049] Step 1: crush the waste tire tread rubber to a particle size of 600 μm, immerse it in an ammonium bicarbonate solution, wherein the ammonium bicarbonate solution is prepared by mixing ammonium bicarbonate powder and water in a mass ratio of 3:10, and react at 60° C. with stirring for 2 days;

[0050] LB culture medium was prepared, and activated heterotrophic nitrification-denitrifying bacteria DNF23 (GDMCC No: 60713) was inoculated into the LB culture medium, and cultured at 40° C. for 30 hours to obtain a heterotrophic nitrification-denitrifying bacteria liquid;

[0051] Step 2: Add the heterotrophic nitrification-denitrification bacteria solution to the ammonium bicarbonate solution at a mass ratio of 1:1, and react at 40°C for 4 hours, then filter out the waste rubber powder, disinfect it, and set it aside;

[0052] Step 3: Add culture medium, Thermococcus thermophilic archaea HJ21 (CCTCC No: M207010) and YPS culture medium into the fermenter, add 4-5% sodium chloride by mass ratio into YPS, control the pH at 6.5-7, control the temperature at 94°C, stir at 500 rpm, and the pressure at 0.2 MPa, and react for 30 hours;

[0053] Step 4: Put the waste rubber powder filtered out in step 2 into a closed fermentation tank, the mass ratio of waste rubber to YPS culture medium is 1:3-5, the pH is controlled at 6.5-7, the temperature is controlled at 94°C, the stirring speed is 500rpm, and the pressure is 0.2MPa. After reacting for 4 days, the waste rubber powder is filtered out and dried to obtain devulcanized rubber.

[0054] Comparative Example 1

[0055] The method for regenerating and desulfurizing waste rubber described in Example 1 is different in that the step of mixing the waste rubber powder with the ammonium bicarbonate solution in step 1 is omitted, and the other steps remain unchanged.

[0056] Comparative Example 2

[0057] The method for regenerating and desulfurizing waste rubber described in Example 1 is different in that the step of preparing the heterotrophic nitrification-denitrifying bacterial solution in step 1 and the step of adding the heterotrophic nitrification-denitrifying bacterial solution to the ammonium bicarbonate solution in a mass ratio of 1:1 in step 2 are omitted, and the other steps remain unchanged.

[0058] Comparative Example 3

[0059] The method for regenerating and desulfurizing waste rubber described in Example 1 is different in that the bacterial species in step 3 is replaced by a mixture of Sphingomonas and Gordonia in a volume ratio of 1:2, the culture medium is replaced by: NH4Cl0.4g / L, KH2PO44g / L, K2HPO4·3H2O 4g / L, MgSO4·7H2O 0.8g / L, CaCl20.01g / L, Na2S2O4·5H2O 10g / L, peptone 1g / L, yeast powder 0.1g / L, glucose 2g / L, and the rest is water, the reaction temperature in steps 3 and 4 is 25°C, and other conditions remain unchanged.

[0060] Comparative Example 4

[0061] The method for regenerating and desulfurizing waste rubber described in Comparative Example 3 is different in that the step of mixing the waste rubber powder with the ammonium bicarbonate solution in step 1 is omitted, the step of preparing the heterotrophic nitrification-good denitrification bacterial solution in step 1 is omitted, and the step of adding the heterotrophic nitrification-good denitrification bacterial solution to the ammonium bicarbonate solution in a mass ratio of 1:1 in step 2 is omitted.

[0062] Experimental example

[0063] The same batch of waste tire treads were used as raw materials, and the waste rubber regeneration and desulfurization methods of Examples 1-3 and Comparative Examples 1-4 were respectively used to obtain corresponding desulfurized rubbers. The tensile strength and elongation at break of the corresponding desulfurized rubbers were tested. The test results are shown in Table 1:

[0064] Table 1

[0065] Tensile strength(MPa) Elongation at break (%) Example 1 17.3 429 Example 2 16.3 422 Example 3 16.6 413 Comparative Example 1 9.8 158 Comparative Example 2 11.5 187 Comparative Example 3 14.8 226 Comparative Example 4 8.5 127

[0066] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for regenerating and desulfurizing waste rubber, characterized in that: The following steps are involved: Step 1: crush the waste rubber to a particle size of 400-600 μm, immerse it in an ammonium bicarbonate solution, wherein the ammonium bicarbonate solution is prepared by mixing ammonium bicarbonate powder and water in a mass ratio of 1-3:10, and react at 60° C. with stirring for 1-2 days; Prepare LB culture medium, inoculate activated heterotrophic nitrification-denitrifying bacteria into the LB culture medium, and culture at 30-40° C. for 24-30 hours to obtain heterotrophic nitrification-denitrifying bacteria liquid; Step 2: Add the heterotrophic nitrification-denitrification bacteria solution to the ammonium bicarbonate solution at a mass ratio of 1:1, react at 30-40°C for 3-4 hours, filter out the waste rubber powder, disinfect it, and set it aside; Step 3: Add culture medium, thermophilic archaea of ​​the genus Thermococcus and YPS culture medium into the fermentation tank, add 4-5% sodium chloride by mass ratio into YPS, control the pH at 6.5-7, the temperature at 90-94° C., the stirring speed at 400-500 rpm, the pressure at 0.1-0.2 MPa, and react for 26-30 hours; Step 4: Put the waste rubber powder filtered out in step 2 into a closed fermentation tank, the mass ratio of waste rubber to YPS culture medium is 1:3-5, the pH is controlled at 6.5-7, the temperature is controlled at 90-94°C, the stirring speed is 400-500rpm, the pressure is 0.1-0.2MPa, and after reacting for 3-4 days, the waste rubber powder is filtered out and dried to obtain devulcanized rubber.

2. The method for regenerating and desulfurizing waste rubber according to claim 1, characterized in that: The heterotrophic nitrification-denitrifying bacteria DNF23.

3. The method for regenerating and desulfurizing waste rubber according to claim 1, characterized in that: The Thermococcus thermophilic archaeon is Thermococcus thermophilic archaeon HJ21.

4. The method for regenerating and desulfurizing waste rubber according to claim 1, characterized in that: The waste rubber is selected from waste tire tread rubber.

5. The regenerated rubber obtained by the waste rubber regeneration and desulfurization method according to any one of claims 1 to 4.