Method for low-temperature desulfurization and raw material recovery of waste rubber

Abstract

The invention provides a low-temperature desulfurization and raw material recovery method for waste rubber, and belongs to the technical field of rubber desulfurization. The method comprises the following steps: compounding chloramine and organic amine to carry out low-temperature desulfurization on the waste rubber, and separating to obtain desulfurized rubber and carbon black; the organic amine is selected from alcohol amine or tetraethylenepentamine. Through the compounding effect of chloramine and organic amine, on the premise of not damaging a C-C chain of a polymer, fracture of a cross-linking bond is promoted, the polymer is effectively separated, carbon black is released, regeneration of rubber and recycling of carbon black are achieved, and meanwhile, the performance of recycled rubber is kept and is not affected; and compared with the traditional thermal decomposition or chemical desulfurization method, the desulfurization efficiency is obviously improved.

Description

Technical Field

[0001] The invention belongs to the technical field of rubber desulfurization, and in particular relates to a method for low-temperature desulfurization of waste rubber and raw material recovery. Background Art

[0002] Waste rubber products such as tires, rubber tubes, rubber shoes, etc. are difficult to degrade in the natural environment due to their durable physical and chemical properties. Long-term accumulation not only occupies a large amount of land, but also may cause pollution to soil and water. Therefore, converting these waste rubber products into reusable resources has become an important research direction in the field of environmental protection and the rubber industry.

[0003] Traditional rubber recycling methods mainly rely on physical or chemical means, such as mechanical crushing, pyrolysis, chemical dissolution, etc., but these methods often have problems such as high energy consumption, reduced performance of recycled rubber, and environmental pollution. In recent years, with the continuous development of new material technology and environmental protection technology, rubber recycling technology has also been developing continuously.

[0004] Chinese invention patent publication number CN102775633A mentions a low-temperature desulfurization production method for recycling and reusing waste rubber. The selected waste rubber is crushed by a two-roll rubber crushing machine, and the crushed waste rubber is ground into fine powder by a grinding machine. The expansion and crushing agent and the fine powder are put into a two-roll rubber mixing mill for stirring. Under a certain temperature, pressure and time, the rubber can be desulfurized.

[0005] Chinese invention patent publication number CN117164953A mentions a low-temperature desulfurized oil-free high molecular weight reclaimed rubber, a preparation method and an application in a tire carcass. The high molecular weight reclaimed rubber is mainly subjected to a desulfurization reaction by spiral extrusion after pretreatment by mixing waste rubber powder, an activator and a modifier in a certain proportion. The oil-free high molecular weight reclaimed rubber is obtained by temperature-controlled extrusion.

[0006] Chinese invention patent publication number CN117487263A mentions a regenerated rubber prepared from waste tires and its preparation method. The waste tires are crushed into tiny particles of 40-60 mesh, and activated and desulfurized with an activator (to improve the cross-linking activity and cross-linking performance of the rubber powder, and to improve the strength after re-vulcanization). Modified white carbon black is also prepared, and its surface is oxidized to introduce anti-aging amino groups on the surface. The migration resistance of white carbon black is utilized to maintain anti-aging performance for a long time; white carbon black is treated with 2,4-pentadienoic acid to achieve the purpose of improving the strength of the rubber.

[0007] Although these rubber recycling technologies have achieved certain results, there are still some challenges and problems. For example, how to further improve the performance of recycled rubber to make it close to or reach the level of virgin rubber; how to reduce energy consumption and emissions during the recycling process to achieve true green production; and how to establish an effective waste rubber recycling and reuse system to promote the industrial application of rubber recycling technology. Summary of the invention

[0008] The present invention aims at the problems existing in the prior art and provides a method for low-temperature desulfurization of waste rubber and raw material recovery. The waste rubber is desulfurized at low temperature by using a combination of chloramine and organic amine, and unreacted waste rubber, desulfurized rubber and carbon black are obtained by separation. The regeneration of rubber and the recycling and reuse of carbon black are achieved, while the recycled rubber retains its original properties; the desulfurization efficiency is significantly improved.

[0009] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0010] The invention provides a method for low-temperature desulfurization of waste rubber and recovery of raw materials. The method adopts a compound of chloramine and organic amine to carry out low-temperature desulfurization on the waste rubber, and obtains unreacted waste rubber powder, desulfurized rubber and carbon black through separation; the organic amine is selected from alcohol amine or tetraethylenepentamine (TEPA).

[0011] Preferably, the organic amine is an alcohol amine.

[0012] Furthermore, the molar ratio of the organic amine to the chloramine is 0.3-0.6:1.

[0013] Furthermore, the chloramine is selected from one or more of monochloramine, dichloramine, trichloramine and hypochlorite.

[0014] Furthermore, the alcoholamine is selected from one or more of ethanolamine (ETA), diethanolamine (DEA) and hydroxyethylethylenediamine (AEEA).

[0015] The principle of the desulfurization process of the present invention is as follows:

[0016] The amine group in the organic amine used promotes the breaking of cross-linking bonds. The vulcanized rubber molecule contains four chemical bonds: C=C, CC, CS, and SS (the bond energy decreases in sequence). Due to the difference in bond energy, mechanical shearing will first destroy the SS bond (two types of dissociation: ① homogeneous dissociation, producing two sulfur-free free radicals; ② heterogeneous dissociation, producing positively charged -S + and negatively charged -S - ), the amine group can capture the positively charged -S + and release H + , free H + Further with -S -Combined to form -SH terminal groups, the dissociation of the cross-linking bond is completed, the molecular chain combines with the amine chain, blocking the activity of sulfur and the re-cross-linking process. TEPA contains multiple amine groups, and one molecular chain can be connected to multiple rubber molecular chains. Similarly, the amine groups of AEEA, ETA, and DEA can combine with -S + and -S - The reaction occurs and blocks its activity, the SS bond content is reduced, and hydroxyl groups are introduced into the rubber molecular chain. Alcoholamines effectively promote the breaking of crosslinking bonds during the desulfurization process; at the same time, the targeted sulfur crosslinking reaction of chloramines is combined to decompose the waste rubber powder. Without destroying the CC polymer chain, the polymer can be effectively separated, carbon black can be released, and the performance of the rubber itself can be maintained. When using an alcoholamine compound, its structure also has a hydroxyl group, which can reduce Mooney viscosity, increase plasticity, and improve desulfurization efficiency.

[0017] Furthermore, the method also includes: using a dehydrating agent and the compound chemical reagent simultaneously to perform low-temperature oxidative desulfurization treatment on the waste rubber.

[0018] Furthermore, the dehydrating agent is selected from one or more of calcium oxide, silica gel and organic solvent.

[0019] Furthermore, the organic solvent is selected from one or more of ethanol, n-butanol, acetone and dioxane.

[0020] Furthermore, the waste rubber is selected from one or more of full tire rubber, tread rubber, inner tube rubber and shoe material rubber.

[0021] Furthermore, the main components of the waste rubber include one or more of butadiene rubber, styrene-butadiene rubber, butyl rubber, chlorinated butyl rubber, brominated butyl rubber and nitrile rubber.

[0022] Furthermore, the low-temperature desulfurization and raw material recovery method specifically comprises the following steps:

[0023] (1) collecting waste rubber, grinding and sieving, and removing iron powder to obtain waste rubber powder;

[0024] (2) dissolving an organic amine and a chloramine in water respectively to obtain an organic amine aqueous solution and a chloramine aqueous solution, and mixing them to obtain a composite chemical reagent;

[0025] (3) adding a compound chemical reagent to the waste rubber powder, or adding a compound chemical reagent and a dehydrating agent to the waste rubber powder at the same time, to carry out a desulfurization reaction;

[0026] (4) After the reaction is completed, the reaction mixture is separated and treated to recover the unreacted waste rubber, devulcanized rubber and carbon black.

[0027] Furthermore, the concentration of the organic amine aqueous solution is 0.6-15 mol / L; the concentration of the chloramine aqueous solution is 3.0-30 mol / L.

[0028] Furthermore, the mass ratio of the waste rubber powder, the compound chemical reagent and the dehydrating agent is 100:0.7-4.5:0.5-4; preferably 100:0.7-2.5:0.5-0.7.

[0029] When the dehydrating agent is not used, the mass volume ratio of the waste rubber powder to the compound chemical reagent is 100:0.7-4.5, preferably 100:0.7-2.5.

[0030] Furthermore, the desulfurization reaction temperature is 50-200°C.

[0031] Furthermore, the desulfurization reaction pressure is 70-100 kPa.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The present invention uses a combination of organic amine and chloramine to desulfurize waste rubber. The synergistic effect of the two is significant. Under the premise of ensuring that the CC bond of the rubber main chain remains intact, the SS bond and the CS bond can be selectively broken, and the polymer can be effectively separated, the carbon black can be released, and the performance of the rubber itself can be maintained;

[0034] (2) Compared with traditional thermal decomposition or chemical desulfurization, the mixed reagent of alcohol amine and chloramine used in the present invention not only effectively promotes the breaking of cross-linking bonds, but also helps to reduce Mooney viscosity, improve plasticity, and effectively improve the efficiency of oxidative desulfurization;

[0035] (3) The present invention has a simple post-treatment for the reaction mixture, and can adopt a variety of separation methods or a combination thereof to effectively separate the unreacted waste rubber powder, devulcanized rubber and carbon black, and the unreacted waste rubber powder is returned to the previous step to continue the reaction. DETAILED DESCRIPTION

[0036] The embodiments of the present invention will be described in detail below in conjunction with the examples, but those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific conditions are specified in the examples, conventional conditions are used. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0037] Example 1

[0038] (1) taking waste tires (mainly composed of 61.67% polyisoprene rubber, 26.5% carbon black, steel wire and a small amount of additives), grinding them to a particle size of less than 1 mm, and removing iron powder by magnetic attraction to obtain waste rubber powder;

[0039] (2) dissolving monochloramine and hydroxyethylethylenediamine (AEEA) in water respectively to prepare a monochloramine aqueous solution with a concentration of 19.4 mol / L and a hydroxyethylethylenediamine aqueous solution with a concentration of 5.83 mol / L, and compounding the monochloramine to hydroxyethylethylenediamine (AEEA) in a molar ratio of 10:3 to obtain a compound chemical reagent;

[0040] (3) waste rubber powder, compound chemical reagent and dehydrating agent (calcium oxide) were mixed in a mass ratio of 100:2.5:0.6 and added into the reactor, and oxidative desulfurization reaction was carried out at 200°C and 85kPa for 0.5h;

[0041] (4) After the reaction is completed, the reaction liquid is firstly separated by filtering and centrifuging system. The carbon black aggregates into a paste and sinks, while the desulfurized rubber and unreacted waste rubber powder remain in the upper liquid. The paste is separated and transferred to a batch reactor and heated to 100-200 ° C for 30 minutes, and then sent to the ultrafiltration system for two-stage filtration:

[0042] ① Use a 20nm ultrafiltration membrane to filter (retain larger particles and impurities, including some unreacted waste rubber powder) to obtain filter residue 1 and filtrate 1;

[0043] ② The filtrate 1 is further filtered using a 3 nm ultrafiltration membrane (to retain smaller particles, dissolved matter and carbon black) to obtain a filter residue 2 and a filtrate 2; the filter residue 2 is concentrated for subsequent reuse; the filtrate 2 is mixed with the above-mentioned upper liquid and returned to step (1) for further processing.

[0044] Example 2

[0045] (1) taking waste tires (mainly composed of 61.67% polyisoprene rubber, 26.5% carbon black, steel wire and a small amount of additives), grinding them to a particle size of less than 750 μm, and removing iron powder by magnetic attraction to obtain waste rubber powder;

[0046] (2) dissolving dichloramine and diethanolamine (DEA) in water respectively to prepare a dichloramine aqueous solution with a concentration of 11.64 mol / L and a diethanolamine aqueous solution with a concentration of 5.24 mol / L, and compounding them according to a molar ratio of dichloramine to diethanolamine (DEA) of 20:9 to obtain a compound chemical reagent;

[0047] (3) adding the waste rubber powder and the compound chemical reagent into the reactor at a mass ratio of 100:2.5, and carrying out oxidative desulfurization reaction at 50°C and 100 kPa for 2 hours;

[0048] (4) The reaction solution was post-treated and separated according to the method of Example 1.

[0049] Example 3

[0050] (1) taking waste tires (mainly composed of 61.67% polyisoprene rubber, 26.5% carbon black, steel wire and a small amount of additives), grinding them to a particle size of less than 550 μm, and removing iron powder by magnetic attraction to obtain waste rubber powder;

[0051] (2) dissolving trichloramine and ethanolamine (ETA) in water respectively to prepare a trichloramine aqueous solution with a concentration of 8.30 mol / L and an ethanolamine aqueous solution with a concentration of 4.98 mol / L, and compounding them according to a molar ratio of trichloramine to ethanolamine (ETA) of 5:3 to obtain a compound chemical reagent;

[0052] (3) adding the waste rubber powder and the compound chemical reagent into the reactor at a mass ratio of 100:4.5, and carrying out oxidative desulfurization reaction at 50°C and 70 kPa for 12 hours;

[0053] (4) The reaction solution was post-treated and separated according to the method of Example 1.

[0054] Example 4

[0055] (1) taking waste tires (mainly composed of 61.67% polyisoprene rubber, 26.5% carbon black, steel wire and a small amount of additives), grinding them to a particle size of less than 1 mm, and removing iron powder by magnetic attraction to obtain waste rubber powder;

[0056] (2) dissolving monochloramine and tetraethylenepentamine (TEPA) in water respectively to prepare a monochloramine aqueous solution with a concentration of 9.71 mol / L and a tetraethylenepentamine aqueous solution with a concentration of 2.91 mol / L, and compounding them in a molar ratio of monochloramine to tetraethylenepentamine (TEPA) of 3:10 to obtain a compound chemical reagent;

[0057] (3) adding waste rubber powder, compound chemical reagent and dehydrating agent (calcium oxide) into the reactor at a mass ratio of 100:4.5:0.6, and carrying out oxidative desulfurization reaction at 200°C and 85kPa for 0.5h;

[0058] (4) The reaction solution was post-treated and separated according to the method of Example 1.

[0059] Comparative Example 1

[0060] The only difference from Example 1 is that a monochloramine aqueous solution with a concentration of 29.1 mol / L is used instead of the compound chemical reagent, and the mass ratio of waste rubber powder, monochloramine aqueous solution and calcium oxide is 100:2.5:0.6.

[0061] Comparative Example 2

[0062] The only difference from Example 1 is that the compound chemical reagent is replaced by an aqueous solution of hydroxyethylethylenediamine with a concentration of 8.65 mol / L, and the mass ratio of waste rubber powder, aqueous solution of hydroxyethylethylenediamine and calcium peroxide is 100:2.5:0.6.

[0063] The results of the desulfurization treatment of waste tires in various embodiments and comparative examples are shown in Table 1.

[0064] (1) Determination of sol content: Using the Soxhlet extraction method, a certain mass of sample was weighed and wrapped with filter paper. After extraction with acetone for 12 h, the sample was taken out of the vacuum drying oven and dried at 60 °C to constant weight. The mass m was obtained. 0 Then, the sample was submerged with toluene, extracted for 14 h, taken out to a vacuum drying oven, and dried at 60 °C to a constant weight. 1 ; Sol content: Sol content = [(m 0 -m 1 ) / m 1 ]×100%.

[0065] (2) Desulfurization rate determination: Determined by infrared spectroscopy, desulfurization rate = [(sulfur content before desulfurization - sulfur content after desulfurization) / sulfur content before desulfurization] × 100%. The higher the desulfurization rate, the more thoroughly the sulfur element in the rubber is removed.

[0066] Table 1 Results of desulfurization of waste rubber

[0067]

[0068]

[0069] It can be seen from the above table that: compared with Example 1, the desulfurized rubber sol content obtained by using a single chemical reagent of alcohol amine or chloramine in Comparative Examples 1 and 2 is lower than that obtained by using a compound chemical reagent, which shows that the compound chemical reagent used in the present invention has a significant effect on breaking the cross-linked bonds in the waste rubber material; at the same time, the combined use of the two also improves the desulfurization rate, and the synergistic effect is significant; in addition, compared with chloramine, the desulfurization effect of alcohol amine is more significant, which further verifies the role of hydroxyl in reducing Mooney viscosity, improving plasticity, and improving desulfurization efficiency.

[0070] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for low-temperature desulfurization of waste rubber and recovery of raw materials, characterized in that: The waste rubber is desulfurized at low temperature by using a combination of chloramine and organic amine, and unreacted waste rubber powder, desulfurized rubber and carbon black are obtained through separation; the organic amine is selected from alcoholamine or tetraethylenepentamine.

2. The low-temperature desulfurization and raw material recovery method according to claim 1, characterized in that: The molar ratio of the organic amine to the chloramine is 0.3-0.6:

1.

3. The low-temperature desulfurization and raw material recovery method according to claim 1, characterized in that: The chloramine is selected from one or more of monochloramine, dichloramine, trichloramine and hypochlorite; the alcoholamine is selected from one or more of ethanolamine, diethanolamine and hydroxyethylethylenediamine.

4. The low-temperature desulfurization and raw material recovery method according to claim 1, characterized in that: The method also includes: using a dehydrating agent together with chloramine and organic amine to perform low-temperature oxidative desulfurization treatment on the waste rubber.

5. The low-temperature desulfurization and raw material recovery method according to claim 4, characterized in that: The dehydrating agent is selected from one or more of calcium oxide, silica gel and organic solvents; wherein the organic solvent is selected from one or more of ethanol, n-butanol, acetone and dioxane.

6. The low-temperature desulfurization and raw material recovery method according to claim 1, characterized in that: The waste rubber is selected from one or more of full tire rubber, tread rubber, inner tube rubber and shoe material rubber; the main components of the waste rubber include one or more of butadiene rubber, styrene butadiene rubber, butyl rubber, chlorinated butyl rubber, brominated butyl rubber and nitrile rubber.

7. The low-temperature desulfurization and raw material recovery method according to any one of claims 1 to 6, characterized in that: The specific steps include: (1) collecting waste rubber, grinding and sieving, and removing iron powder to obtain waste rubber powder; (2) dissolving an organic amine and a chloramine in water respectively to obtain an organic amine aqueous solution and a chloramine aqueous solution, and mixing them to obtain a composite chemical reagent; (3) adding a compound chemical reagent to the waste rubber powder, or adding a compound chemical reagent and a dehydrating agent to the waste rubber powder at the same time, to carry out a desulfurization reaction; (4) After the reaction is completed, the reaction mixture is separated and treated to recover the unreacted waste rubber, devulcanized rubber and carbon black.

8. The low-temperature desulfurization and raw material recovery method according to claim 7, characterized in that: The concentration of the organic amine aqueous solution is 0.6-15.0 mol / L; the concentration of the chloramine aqueous solution is 3.0-30 mol / L.

9. The low-temperature desulfurization and raw material recovery method according to claim 7, characterized in that: The mass ratio of the waste rubber powder, the compound chemical reagent and the dehydrating agent is 100:0.7-4.5:0.5-4.

10. The low-temperature desulfurization and raw material recovery method according to claim 7, characterized in that: The desulfurization reaction temperature is 50-200°C; the desulfurization reaction pressure is 70-100kPa.

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