METHOD FOR PRODUCE SOLICIUM FROM WASTE

Description

[0001] The invention relates to a method for producing carbon black from waste, carbon black produced according to the method, a rubber compound and a vehicle tire containing the carbon black.

[0002] There is an ever-increasing need for suitable recycling processes in order to reuse the materials of products such as vehicle tires, especially used tires, as completely as possible and thus solve the disposal problem.

[0003] Firstly, the recycling process itself should be optimized as ecologically and economically as possible.

[0004] Secondly, the recycled product should have properties that come as close as possible to those of comparable raw materials.

[0005] It is known that vehicle tires, especially used tires, can be disposed of by means of pyrolysis under oxygen-free conditions. This process produces, among other things, pyrolysis soot, pyrolysis oil, and pyrolysis gases, with pyrolysis soot being particularly suitable as a filler for fresh rubber compounds.

[0006] However, the use of pyrolysis carbon blacks in rubber compounds for new tires is limited by the properties of the carbon blacks obtained, as they differ from ASTM carbon blacks such as N660. This leads, in particular, to a lower reinforcing effect in rubber compounds, which can result in undesirable physical properties.

[0007] WO 2013184074 A1 discloses a plasma pyrolysis process in which waste tires are crushed into a powder and the powder is transferred by means of a carrier gas into an induction thermal processor ("induction thermal processor") in order to be converted into gas ("syngas") and soot as a by-product.

[0008] US patent 3843457 discloses a process for microwave pyrolysis of shredded waste at temperatures below 200 °C in the presence of a gas stream. The use of reducing gases, such as hydrogen (H₂), is intended to reduce gases produced during microwave pyrolysis, such as carbon monoxide (CO) and carbon dioxide (CO₂). In particular, the resulting gas mixture is recovered as the process product, while the resulting solids are disposed of.

[0009] In the article Adrian M. Cunliffe and Paul T. Williams, 1999, "Influence of Process Conditions on the Rate of Activation of Chars from Pyrolysis of used tires", Energy & Fuels, Vol. 13, No. 1, 1999, pp. 166-175, a process for the subsequent activation of char with nitrogen or nitrogen and carbon dioxide at temperatures of 835 °C or more is disclosed, wherein the char was previously obtained by means of pyrolysis in a static bed reactor.

[0010] EP 3173251 A1 discloses a rubber compound which contains, among other things, recycled carbon black from pyrolysis, bearing hydroxy and / or carboxy groups on its surface. These groups are produced by oxidizing the surface under acidic conditions using an acid.

[0011] US 7,101,464 B1 relates to microwave pyrolysis of whole used tires, using an apparatus that has a preheating chamber, an irradiation chamber and a cooling chamber arranged vertically.

[0012] CN 11093845 A concerns thermal cracking of waste tires in the absence of oxygen and protective gases.

[0013] US 2011 / 0198207 A concerns a molecular distillation of used tires using a combination of ultrasound and microwaves.

[0014] The present invention is based on the objective of providing a process for producing carbon black from waste materials, which yields carbon black with improved properties compared to known pyrolysis carbon blacks. In particular, a greater strengthening effect of the surrounding matrix is ​​to be achieved when the carbon black is used in mixtures for technical rubber products and other plastics.

[0015] This is intended to make the resulting soot accessible for a wider range of applications than pyrolysis soots known in the prior art. The process should also be as economical and environmentally efficient as possible.

[0016] The problem is solved by ensuring that the procedure includes at least the following procedural steps: A) Provision of waste; B) Optional preheating of the waste to a temperature of 50 to 200 °C; C) Pyrolysis of the waste using microwaves and in the absence of oxygen in a reaction chamber at a temperature of 400 to 800 °C, producing soot and pyrolysis gas as products, wherein the pyrolysis gas is removed from the reaction chamber so that it is not available in step D); D) Cooling of the soot, wherein in step D) a gas is passed over the waste or soot at a temperature of 100 to 300°C and wherein the gas comprises at least one substance selected from the group consisting of carbon oxides, such as in particular carbon monoxide (CO) and carbon dioxide (CO₂). 2 ), sulfur oxides, in particular sulfur monoxide (SO₄), sulfur dioxide (SO₂) 2 ), sulfur trioxide (SO₄) 3 ) and sulfur tetraoxide (SO₄) 4 ), nitrogen oxides, in particular nitric oxide (NO), nitrous trioxide (N 2 O 3 ), nitrogen dioxide (NO₂) 2 ), water (H 2 O) and oxygen (O 2 ).

[0017] By passing at least one of the aforementioned substances, also referred to here as "reaction gases", over the cooled soot, its surface is activated by reaction with the substance in the gas, whereby active chemical groups are formed on the surface, such as hydroxy groups (-OH), amino groups (-NH 2 ), sulfur dioxide groups (-SO 2 ) and / or carboxy groups (-COOH).

[0018] This results in a carbon black with surface properties that cause greater reinforcement in a surrounding matrix, such as a rubber compound for vehicle tires or other technical rubber articles.

[0019] At the same time, the process is as efficient as possible due to the few process steps. In particular, the temperature of the resulting soot is lowered by cooling, and the gas is passed over the soot, so that the residual heat of the soot is utilized and a separate heating step is unnecessary.

[0020] Furthermore, the process avoids substances requiring special handling, particularly non-gaseous acids. This makes the process more environmentally friendly and optimized with regard to health aspects compared to the state of the art.

[0021] The invention is further explained below, and further advantageous embodiments are described. Unless otherwise stated, different embodiments can also be combined with one another. Furthermore, the invention also encompasses features resulting from the combination of two or more features of different hierarchical levels of preference.

[0022] The soot produced according to the present invention is also referred to as pyrolysis soot, since it is the product of pyrolysis under anaerobic conditions. When pyrolysis soots from the prior art are mentioned, this also refers to soots produced as recycling products from the pyrolysis of waste materials, such as used tires, under anaerobic conditions.

[0023] The waste in step A) preferably comprises plastics, preferably vehicle tires and / or other technical rubber articles. For the purposes of this step A), the articles referred to as "waste" include, in particular, used articles such as old tires, but also new articles such as rejects generated during the production process.

[0024] Within the scope of the present invention, vehicle tires are understood to mean pneumatic vehicle tires and solid rubber tires, including tires for industrial and construction vehicles, truck, car and two-wheeler tires.

[0025] Vehicle tires with a comparatively low proportion of silica (silicate-containing) fillers are preferred, as this also results in a lower ash content in the produced carbon black.

[0026] Preferably, vehicle tires are used that have a total silica content of 0 to 15% by weight based on the total weight of the tire. According to advantageous embodiments of the invention, vehicle tires are used that have a total silica content of 2 to 6% by weight based on the total weight of the tire. These are, in particular, commercial vehicle tires, which generally have a lower silica content compared to passenger car tires.

[0027] The waste is optionally shredded.

[0028] According to preferred embodiments, however, the unshredded waste, such as whole tires, can also be used. The subsequent pyrolysis is microwave pyrolysis, which eliminates the need for the additional shredding step.

[0029] According to step B), the waste is optionally preheated.

[0030] Preheating to temperatures of 50 to 200 °C has the advantage that microwave pyrolysis, especially of unshredded waste, can take place faster and more evenly, so that the resulting soot is also more homogeneous.

[0031] For this purpose, they can be transferred beforehand to a separate preheating chamber or directly into the microwave pyrolysis chamber.

[0032] Transferring the product directly into the microwave chamber has the advantage that a separate preheating chamber is no longer necessary.

[0033] Preheating in a separate preheating chamber has the advantage that while a first item, such as a used tire, is being pyrolyzed, a second item can be preheated simultaneously. This enables a semi-continuous process.

[0034] Pyrolysis in step C) takes place under exclusion of oxygen.

[0035] It is preferred that the pyrolysis in step C) takes place at a temperature of 400 to 700°C, particularly preferably 500 to 650°C.

[0036] At excessively low temperatures, complete pyrolysis is not guaranteed, resulting in residual contaminants remaining on the surface of the carbon black particles. This leads to impaired properties, particularly in rubber compounds containing these carbon blacks.

[0037] At excessively high temperatures, coking can occur on the surface of the resulting soot particles, which also leads to a reduction in the reinforcing properties of the obtained pyrolysis soot in the rubber mixture.

[0038] The optimal temperature range is therefore particularly between 500 and 650 °C; in this range it is especially well ensured that complete conversion takes place and, on the other hand, no coking occurs on the surface.

[0039] Preferably, the pyrolysis in step C) takes place over a period of 0.1 seconds to 10 hours, preferably up to 4 hours, and particularly preferably up to 1 hour. The longer the pyrolysis lasts, the higher the energy input into the material and the greater the extent of coking on the soot surface, which leads to a reduction in surface activity and thus counteracts the advantage achieved with the invention.

[0040] According to advantageous embodiments of the invention, the duration of pyrolysis is 0.1 to 20 seconds and is a so-called rapid pyrolysis ("flash pyrolysis"). It is advantageous to use shredded waste to ensure continuous pyrolysis.

[0041] According to further advantageous embodiments of the invention, the duration of pyrolysis is 30 minutes to 10 hours, preferably up to 4 hours, and particularly preferably up to 1 hour. This allows the use of unshredded waste, thus eliminating the need for a separate shredding step.

[0042] Preferably, the pyrolysis in step C) takes place at a pressure of 1.013 bar or less, such as at a pressure of 0.9 bar.

[0043] At such lower pressures, the resulting volatile compounds are carried away from the reaction chamber more quickly and therefore cannot condense again on the surface of the resulting or formed pyrolysis soot to form a carbonaceous residue.

[0044] Another product of pyrolysis in step C) is pyrolysis gas ("syngas"), which is removed from the reaction chamber immediately after its formation and thus removed from the process. This pyrolysis gas is largely composed of hydrogen (H₂) and, due to its rapid removal, is not available for activating the surface of the resulting soot particles.

[0045] The gas passed over the waste or soot in step D) comprises at least one substance selected from the group consisting of carbon oxides, such as in particular carbon monoxide (CO) and carbon dioxide (CO2), sulfur oxides, such as in particular sulfur monoxide (SO), sulfur dioxide (SO2), sulfur trioxide (SO3) and sulfur tetraoxide (SO4), nitrogen oxides, such as in particular nitric oxide (NO), dinitrogen trioxide (N2O3), nitrogen dioxide (NO2), water (H2O) and oxygen (O2).

[0046] The at least one substance present in the gas is intended to cause a reaction on the surface of the soot produced, so that the gas is also referred to as "reaction gas" within the scope of the present invention.

[0047] The gas stream in step D) preferably does not contain any additional carrier gas, so that it is preferably composed of 100 wt.% or 100 volume.% (vol.%) reaction gas.

[0048] It is preferred that the reaction gas is passed over the soot particles in amounts of 1 to 50 wt.%, preferably 1 to 25 wt.%, based on the amount of soot produced. Thus, in the case of 100 kg of soot produced, 1 to 50 kg, preferably 1 to 25 kg, of reaction gas is passed over the soot.

[0049] The gas comprising at least one of the aforementioned substances is introduced in step D) at a temperature of 100 to 300 °C. Particularly preferably, the temperature is 200 to 300 °C.

[0050] This provides the necessary activation energy to initiate a reaction between the reaction gas and the pyrolysis soot, allowing active groups to form on the surface. At the same time, the temperature is not too high, thus preventing unwanted side reactions.

[0051] Another subject of the present text is a soot produced according to the inventive method including all described embodiments and preferred features.

[0052] Due to surface activation, the carbon black has the advantage of producing a comparatively high reinforcing effect, e.g. in a rubber compound, thus offering an adequate replacement for a wide range of standard ASTM carbon blacks.

[0053] Another subject of the present text is a rubber mixture containing at least one rubber and at least one carbon black according to this text.

[0054] Another subject of this text is a vehicle tire which, in at least one component, contains at least one carbon black according to this text and / or at least one rubber compound according to this text.

[0055] Another subject of this text is the use of carbon black in plastics, paints, varnishes and / or electronic components.

Claims

1. Process for producing carbon black from wastes comprising at least the following process steps: A) providing wastes; B) optionally preheating the wastes to a temperature of 50°C to 200°C; C) pyrolyzing the wastes by means of microwaves and with exclusion of oxygen in a reaction chamber at a temperature of 400°C to 800°C to obtain carbon black and pyrolysis gas as the product, wherein the pyrolysis gas is discharged from the reaction chamber so that it is not present in step D); D) cooling the carbon black; wherein in step D) a gas is passed over the wastes / the carbon black at a temperature of 100°C to 300°C and wherein the gas comprises at least one substance selected from the group consisting of carbon oxides, such as especially carbon monoxide (CO) and carbon dioxide (CO2), sulfur oxides, such as especially sulfur monoxide (SO), sulfur dioxide (SO2), sulfur trioxide (SO3) and sulfur tetroxide (SO4), nitrogen oxides, such as especially nitrogen monoxide (NO), dinitrogen trioxide (N2O3), nitrogen dioxide (NO2), water (H2O) and oxygen (O2).

2. Process according to any of the preceding claims, characterized in that the pyrolysis in step C) is carried out at a temperature of 500°C to 650°C.

3. Process according to any of the preceding claims, characterized in that the pyrolysis in step C) is carried out over a period of 0.1 seconds to 10 hours, preferably up to 4 hours, particularly preferably up to 1 hour.

4. Process according to any of the preceding claims, characterized in that the pyrolysis in step C) is carried out at a pressure of 1.013 bar or less.

5. Process according to any of the preceding claims, characterized in that in step D) the gas is introduced at a temperature of 200°C to 300°C.

6. Process according to any of the preceding claims, characterized in that the wastes comprise plastics, preferably vehicle tyres and / or other technical rubber articles.