Determination of micro grit

Abstract

The present invention relates a method for vacuum sieving carbon black containing grit and carbon black having a low grit content.

Description

[0001] DETERMINATION OF MICRO GRIT

[0002] TECHNICAL FIELD

[0003]

[0001] The present invention relates to a method for vacuum sieving carbon black containing grit and carbon black having a low grit content.

[0004] TECHNICAL BACKGROUND

[0005]

[0002] Carbon blacks have numerous uses such as a reinforcing agent or filler for the rubber and tire industries. Moreover, carbon black has seen increased use in other areas such as coloring agents and reprographic toners for copying machines. The various applications of carbon black necessitate a diverse range of carbon black characteristics such as particle size, structure, yield, surface area, and stain.

[0006]

[0003] Carbon black can be manufactured using many different processes such as furnace process, gas black process, acetylene black process, thermal black process or lamp black process. Carbon black produced from e.g. a standard hydrocarbon feedstock such as oil, is often called virgin carbon black (vCB).

[0007]

[0004] However, carbon black comprises impurities or residues due to the method of manufacturing. For example, the carbon black often comprises components derived from the refractory lining. Furthermore, the carbon black can comprise several further residues such as coke or rust.

[0008]

[0005] Recycled blacks are carbon blacks typically obtained from end-of-life products containing carbon black, such as scrap tires (waste tires), and obtained by recycling processes. Production of recycled blacks typically involves 1 to 3 processes. Firstly, a pyrolysis step is deployed to decompose organic components such as rubbers or plastics. Secondly, an optional demineralization step is deployed to dissolve inorganic additives or impurities. Thirdly, the resulting material is milled to produce a controlled particle size distribution.

[0009]

[0006] Tire pyrolysis of end-of-life products containing carbon black is usually carried out at low temperatures and produces a liquid, gaseous and solid fraction. The liquid fraction can then be used to produce new or virgin carbon black in an entrained flow reactor such as a furnace reactor. US 2002 / 0117388 A1 relates to the pyrolysis of waste rubber materials, including scrap tires. The obtained carbon black is generally referred to as "recovered carbon black" (rCB).

[0010]

[0007] rCB is a complex mixture resulting from the compounds used in pyrolysis. The compounds used in the pyrolysis process may contain various components (i.e. ash) other than carbon black, such as inorganic additives and fillers (e.g., zinc oxide, silicon oxide, sulphur compounds and calcium carbonate) and traces of steel. However, the performance of rCB is generally poor compared to carbon black produced from e.g. a standard hydrocarbon feedstock such as oil. It is believed that rCB generally comprises a high content of coke, ash or further residues such as rust, or refractory lining particles.

[0008] The aforementioned residues in carbon black, such as virgin carbon black (vCB) and / or recovered carbon black (rCB), is called grit, such as micro grit.

[0011]

[0009] It is desired to provide a method in order to remove and / or determine the aforementioned grit in carbon black.

[0012]

[0010] It has been surprisingly found that grit can be removed / determined by providing carbon black containing grit that is first dispersed and then vacuum sieved. Additionally, carbon black can be provided having a low grit content.

[0013] SUMMARY OF THE INVENTION

[0014]

[0011] The present invention relates to a method for vacuum sieving carbon black containing grit comprising: (i) dispersing the carbon black containing grit in a liquid in order to obtain a dispersion of the carbon black and the grit, (ii) adding the dispersion of the carbon black and grit on top of filtration means, and (iii) applying a vacuum below the filtration means, so that the carbon black passes through the filtration means and grit that has a particle size above the size of the openings of the filtration means remains on the surface of the filtration means.

[0015]

[0012] Moreover, the carbon black is provided having (I) a STSA surface area of 90 to 105 m2 / g, an oil absorption number of 90 to 115 mL / 100g, and less than 400 ppm grit, wherein the STSA surface area is measured according to ASTM D6556-21, the oil absorption number is measured according to ASTM D2414-19 using paraffinic oil, the grit is measured according to the method mentioned in the specification; and / or (II) a STSA surface area of 95 to 115 m2 / g, an oil absorption number of 95 to 120 mL / 100g, and less than 400 ppm grit, wherein the STSA surface area is measured according to ASTM D6556-21, the oil absorption number is measured according to ASTM D2414-19 using paraffinic oil, the grit is measured according to the method mentioned in the specification; and / or (III) a STSA surface area of 105 to 125 m2 / g, an oil absorption number of 75 to 95 mL / 100g, and less than 400 ppm grit, wherein the STSA surface area is measured according to ASTM D6556-21 , the oil absorption number is measured according to ASTM D2414-19 using paraffinic oil, the grit is measured according to the method mentioned in the specification. DRAWINGS

[0016] FIG. 1 : Image of grit of Example 6

[0017] DETAILED DESCRIPTION

[0018]

[0013] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless the context clearly dictates otherwise.

[0019]

[0014] As used herein, the term "comprising" is understood to be open-ended and to not exclude the presence of additional undescribed or unrecited elements, materials, ingredients or method steps etc. The terms "including", "containing" and like terms are understood to be synonymous with "comprising". As used herein, the term "consisting of" is understood to exclude the presence of any unspecified element, ingredient or method step etc. Open-ended terms such as comprising can be further limited with the term “consisting of”.

[0020]

[0015] Unless indicated to the contrary, the numerical parameters and ranges set forth in the following specification and appended claims are approximations. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical values, however, contain errors necessarily resulting from the standard deviation in their respective measurement.

[0021]

[0016] Also, it should be understood that any numerical range recited herein is intended to include all subranges subsumed therein. For example, a range of “1 to 10” is intended to include any and all sub-ranges between and including the recited minimum value of 1 and the recited maximum value of 10, that is, all subranges beginning with a minimum value equal to or greater than 1 and ending with a maximum value equal to or less than 10, and all subranges in between, e.g., 1 to 6.3, or 5.5 to 10, or 2.7 to 6.1.

[0022]

[0017] All parts, amounts, concentrations etc. referred to herein are by weight, unless specified otherwise. If no basis for parts, amounts, concentrations etc. are indicated, the parts, amounts, concentrations etc. are based on the respective composition / atmosphere / gas in which the respective material / parameter etc. is present.

[0018] The present invention relates to a method for vacuum sieving carbon black containing grit comprising: (i) dispersing the carbon black containing grit in a liquid in order to obtain a dispersion of the carbon black and the grit, (ii) adding the dispersion of the carbon black and grit on top of filtration means, and (iii) applying a vacuum below the filtration means, so that the carbon black passes through the filtration means and grit that has a particle size above the size of the openings of the filtration means remains on the surface of the filtration means.

[0023]

[0019] Furthermore, the present invention can relate to a method for vacuum sieving carbon black containing grit comprising: (i) dispersing the carbon black containing grit in a liquid in order to obtain a dispersion of the carbon black and the grit, (ii) adding the dispersion of the carbon black and grit on top of a sieve, and (iii) applying a vacuum below the sieve, so that the carbon black passes through the sieve and grit that has a particle size above the size of the openings of the filtration means remains on the surface of the sieve.

[0024]

[0020] “Carbon black” as referred to herein means a material composed substantially, e.g. to more than 50 wt.%, or more than 70 wt.% or more than 80 wt.%, based on its total weight of carbon that is produced by pyrolysis or radical driven abstraction of not carbon atoms of a carbon black feedstock. Different industrial processes are known for the production of carbon blacks such as the furnace process, gas black process, acetylene black process, thermal black process or lamp black process. The production of carbon blacks is per se well known in the art and for example outlined in J.-B. Donnet et al., “Carbon Black:Science and Technology”, 2ndedition, therefore being not described herein in more detail. However, it is possible that “carbon black” comprises impurities as mentioned further below.

[0025]

[0021] rCB is a complex mixture resulting from the compounds used in pyrolysis. The compounds used in the pyrolysis process may contain various components (i.e. ash) other than carbon black, such as inorganic additives and fillers (e.g., zinc oxide, silicon oxide, sulphur compounds and calcium carbonate) and traces of steel.

[0026]

[0022] Recovered carbon black (rCB) - in comparison to virgin carbon black (vCB) - comprises ash (ash components) that is typically embedded in the carbon of the rCB, attached to the carbon of the rCB, attached on the surface of the carbon of the rCB, and / or associated in the carbon of the rCB.

[0027]

[0023] Ash typically comprise metal, metal compounds, silicon, oxygen, sulphur and / or silica, preferably metal comprises zinc, silicon, calcium, cobalt, manganese, potassium, aluminium, and / or iron. The ash content is typically determined according to ASTM D 1506-15 at 550 °C, 16 h.

[0028]

[0024] rCB is typically derived (or recovered) from the pyrolysis of a particulate carbon- black containing feedstock, such as rubber granulate, plastic granulate, and / or biomassbased granulate, preferably rubber granulate.

[0029]

[0025] The recovered carbon black can be derived from the pyrolysis of rubber granulate, plastic granulate, and / or biomass-based granulate, preferably rubber granulate. The recovered carbon black can be derived from the pyrolysis of a tire, preferably a pneumatic tire, a tire tread, a tire belt, a tire belt reinforcement, a tire carcass, a tire carcass reinforcement, a tire sidewall, tire inner liner, tire apex, tire shoulder, tire hump strip, tire chafer, a tire bead filler. The recovered carbon black can be derived from the pyrolysis of a cable sheath, a tube, a drive belt, a conveyor belt, a roll covering, a shoe sole, a hose, a sealing member, a profile, a damping element, a coating or a colored or printed article.

[0030]

[0026] The pyrolysis of rubber articles generally involves heating the rubber articles to temperatures, e.g., of at least 300 °C in the absence of oxygen in order to volatilize and decompose the rubber articles, producing oil, gas (pyrolysis gas), and char (such as recovered carbon black).

[0031]

[0027] As used herein, the term “rubber articles” refers to articles composed of rubber, e.g., composed of at least 40 wt.-% of rubber, based on the total weight of the rubber article. Examples of rubber articles include, but are not limited to, tires, conveyer belts, gaskets, such as door gaskets, drive belts, floor mats, shoe soles, belts, cable sheaths, hoses, and the like. Preferred rubber articles include tires. The term “rubber” includes both natural and synthetic rubbers or mixtures thereof. Natural rubber (polyisoprene) may be obtained from rubber trees (Helvea brasiliensis), guayule, and dandelion. Synthetic rubber may comprise styrene-butadiene rubber such as emulsion-styrene-butadiene rubber and solution-styrene-butadiene rubber, polybutadiene, polyisoprene, ethylene- propylene-diene rubber, ethylene-propylene rubber, butyl rubber, halogenated butyl rubber, chlorinated polyethylene, chlorosulfonated polyethylene, acrylonitrile-butadiene rubber, hydrogenated acrylonitrile-butadiene rubber, polychloroprene, acrylate rubber, ethylene-vinylacetate rubber, ethylene-acrylic rubber, epichlorohydrin rubber, silicone rubber, fluorosilicone rubber, fluorocarbon rubber or mixture of combinations of any of the foregoing.

[0032]

[0028] Virgin carbon black is usually carbon black that is not derived (or recovered) from the pyrolysis of a particulate carbon-black containing feedstock, such as rubber granulate, plastic granulate, and / or biomass-based granulate, preferably rubber granulate. Virgin carbon black is usually obtained from a furnace process, gas black process, acetylene black process, thermal black process or lamp black process by utilizing a fuel oil feedstock, preferably a feedstock that does not comprise carbon black. Thus, no carbon black that is generally present in a feedstock is recovered to produce virgin carbon black.

[0033]

[0029] In general, carbon black can be recovered carbon black, virgin carbon black or a combination thereof. It is desired that carbon black comprises 1 to 100 wt.-% rCB, preferably 10 to 95 wt.-% rCB, more preferably 20 to 80 wt.-%, most preferably 30 to 50 wt.-% rCB, based on the total weight of the carbon black. It is desired that carbon black comprises 1 to 100 wt.-% vCB, preferably 10 to 95 wt.-% vCB, more preferably 20 to 80 wt.-%, most preferably 30 to 50 wt.-% vCB, based on the total weight of the carbon black.

[0030] Carbon black (as well as rCB and vCB) can comprise residues other can carbon black itself. According to the present invention, the carbon black, such as used in the inventive method in step (i), contains (or comprises) grit.

[0034]

[0031] Grit is usually the retained material obtained after the vacuum sieving according to the inventive method. Particularly, grit is usually the retained material obtained after the vacuum sieving according to the inventive method utilizing the filtration means comprising a sieve having openings with a size of 1 to 20 pm, preferably 3 to 15 pm, more preferably

[0035] 5 to 12 pm, and most preferably 6 to 10 pm, and / or wherein the sieve has openings with an average openings size of less than the particle size of the grit, preferably less than the particle size of the grit and between 1 to 20 pm, preferably 2 to 10 pm, more preferably 6 to 10 pm, most preferably 8 to 10 pm, and / or wherein the sieve has 10 pm openings, 7 pm openings and / or 5 pm openings.

[0036]

[0032] Grit can comprise refractory lining material, coke, steel, rust, ash, or combinations thereof, preferably grit comprises refractory lining material and coke. If rCB is used, it is preferred that grit comprises ash.

[0037]

[0033] Grit can have a particle size that is higher than the particle size of the carbon black such as the dispersed carbon black. Grit can have a particle size of more than the size of the openings of the filtration means.

[0038]

[0034] Grit can be micro grit. Grit can have a particle size of more than 5 pm, more than

[0039] 6 pm, more than 7 pm, more than 8 pm, more than 9 pm, more than 10 pm, more than 11 pm, more than 12 pm, more than 13 pm, more than 14 pm, more than 15 pm, more than 16 pm, more than 17 pm, more than 18 pm, more than 19 pm, or more than 20 pm. Grit can have a particle size of no more than 1000 pm, no more than 100 pm, or no more than 50 pm. The grit can have a volume average particle size of more than 5 pm, preferably more than 7 pm, more preferably more than 10 pm, and most preferably more than 11 pm.

[0040]

[0035] The particle size of the carbon black can be less than the particle size of the grit, wherein the particle size of the carbon black is preferably measured as described in the specification by using laser diffraction after dry dispersion.

[0041]

[0036] According to step (I), the carbon black containing grit is dispersed in a liquid. For dispersing the carbon black containing grit in a liquid, an ultrasonic dispersion apparatus, Ultraschall Desintegrator Vibracell 72412 or Ultraturrax® can be used. For the Ultraturrax®, the speed can be 7000 rpm / min for 20 min. For the Ultraschall Desintegrator Vibracell 72412, the settings can be 3x5 min, 9 / 6 sec, Amplitude 70 %. It is desired that the carbon black is dispersed so that the carbon black passes through the sieve.

[0042]

[0037] The dispersing step (i) can include ultrasonic treatment of the dispersion.

[0043]

[0038] The dispersing step (i) can further include to reduce the particle size of the carbon black, preferably to reduce the particle size of the carbon black so that the carbon black passes through the filtration means (or sieve). Generally, the particle size of the grit is not reduced due to the dispersing step.

[0044]

[0039] The concentration of the carbon black in the dispersion can be between 1 to 30 wt.-%, preferably 1 to 25 wt.-%, more preferably 1 to 20 wt.-%, even more preferably 1 to 15 and most preferably 3 to 10 wt.-%, based total weight of the dispersion. The inventive method allows to sieve a high concentrated carbon black dispersion.

[0045]

[0040] The liquid can comprise water or is water. It is preferred that the dispersion comprises 1 to 99 wt.-% water, preferably 10 to 98 wt.-% water, more preferably 30 to 90 wt.-% water, even more preferably 50 to 85 wt.-% water, most preferably 60 to 80 wt.-% water, based on the total weight of the dispersion.

[0046]

[0041] The dispersion can comprise a wetting agent, wherein the wetting agent is preferably fatty alcohol ethoxylate, ammonium salt of acrylic copolymers, potassium and ammonium salt acrylic copolymer, ammonium salt of styrene-acrylic copolymers, and / or potassium and ammonium salt acrylic copolymer. Examples of suitable wetting agents are Hydropalat 3065 and Joncryl HPD 296 KOH.

[0047]

[0042] The wetting agent can be present in an amount of 1 to 20 mol-%, preferably 1 to 15 mol.-%, most preferably 2 to 10 mol.-%, based on the total moles of the dispersion.

[0048] The wetting agent can be present in an amount of 1 to 20 wt-%, preferably 1 to 15 wt-%, most preferably 2 to 10 wt-%, based on the total weight of the dispersion.

[0049]

[0043] The filtration means can comprise a sieve. The sieve can be a woven mesh, net or perforated sheet material. Preferably, the filtration means comprises a one-layer sieve cloth, preferably Dutch twilled weave.

[0050]

[0044] The filtration means can comprise a sieve have openings with a size of 1 to 20 pm, preferably 3 to 15 pm, more preferably 5 to 12 pm, and most preferably 6 to 10 pm.

[0045] The sieve can have openings with an average openings size of less than the particle size of the grit, preferably less than the particle size of the grit and between 1 to 20 pm, preferably 2 to 10 pm, more preferably 6 to 10 pm, most preferably 8 to 10 pm.

[0046] The sieve can have 10 pm openings, 7 pm openings and / or 5 pm openings.

[0051]

[0047] The method further comprises step (iii) applying a vacuum below the filtration means, so that the carbon black passes through the filtration means and grit that has a particle size above the size of the openings of the filtration means remains on the surface of the filtration means.

[0048] It is particularly desired that the vacuum is applied below the filtration means. It is not desired (but possible) that additional pressure is applied on top of the sieve.

[0052]

[0049] The pressure of the vacuum can be from 10 to 700 mbar, preferably from 10 to 400 mbar, more preferably from 50 to 200 mbar. Accordingly, it is desired that the pressure below the sieve is lower than the pressure above the sieve. It is particularly desired that the pressure above the sieve is 1 atm. Accordingly, the pressure below the sieve can be 10 to 700 mbar, preferably from 10 to 400 mbar, more preferably from 50 to 200 mbar.

[0053]

[0050] The carbon black used in step (i) can be milled before dispersing. For instance, mechanical (impact) milling, jet milling, ultrasonic milling and / or electrical arc milling, preferably ultrasonic milling.

[0054]

[0051] The expression “x50” or “x(number)” means a percentile of an average distribution (alternatively the expression “D50” or “D(number) can be used). Accordingly, x50 = 100 pm means that 50% of the sample is smaller than the indicated value 100 pm.

[0055]

[0052] The (i) volume average particle size x50 of the carbon black used in step (i) can be from 50 to 800 pm preferably 80 to 500 pm, more preferably 100 to 400 pm, and most preferably 130 to 250 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction, and / or (ii) the volume average particle size x90 of the carbon black used in step (i) can be from 50 to 400 pm preferably 80 to 350 pm, more preferably 110 to 300 pm, and most preferably 140 to 240 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction, and / or (iii) the volume average particle size x95 of the carbon black used in step (i) can be from 80 to 300 pm preferably 100 to 350 pm, more preferably 120 to 300 pm, and most preferably 180 to 250 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction, and / or (iv) the volume average particle size x99 of the carbon black used in step (i) can be from 100 to 250 pm preferably 130 to 240 pm, more preferably 160 to 230 pm, and most preferably 180 to 220 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction.

[0053] The (i) volume average particle size x50 of the carbon black used in step (i) can be from 40 to 400 pm preferably 50 to 300 pm, more preferably 60 to 200 pm, and most preferably 80 to 200 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction, and / or (ii) the volume average particle size x90 of the carbon black used in step (i) can be from 40 to 300 pm preferably 80 to 250 pm, more preferably 120 to 200 pm, and most preferably 150 to 190 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction, and / or (iii) the volume average particle size x95 of the carbon black used in step (i) can be from 70 to 250 pm preferably 80 to 200 pm, more preferably 90 to 190 pm, and most preferably 90 to 180 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction, and / or (iv) the volume average particle size x99 of the carbon black used in step (i) can be from 70 to 250 pm preferably 80 to 200 pm, more preferably 90 to 190 pm, and most preferably 90 to 180 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction.

[0054] The (i) volume average particle size x50 of the carbon black used in step (i) can be from 10 to 200 pm preferably 20 to 120 pm, more preferably 30 to 100 pm, and most preferably 40 to 80 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction, and / or (ii) the volume average particle size x90 of the carbon black used in step (i) can be from 10 to 200 pm preferably 20 to 120 pm, more preferably 30 to 100 pm, and most preferably 40 to 80 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction, and / or (iii) the volume average particle size x95 of the carbon black used in step (i) can be from 10 to 200 pm preferably 20 to 120 pm, more preferably 30 to 100 pm, and most preferably 40 to 80 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction, and / or (iv) the volume average particle size x99 of the carbon black used in step (i) can be from 10 to 200 pm preferably 20 to 120 pm, more preferably 30 to 100 pm, and most preferably 50 to 70 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction.

[0056]

[0055] The (i) volume average particle size x50 of the carbon black used in step (i) can be from 0.1 to 50 pm preferably 1 to 40 pm, more preferably 2 to 30 pm, and most preferably 3 to 20 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction, and / or (ii) the volume average particle size x90 of the carbon black used in step (i) can be from 0.1 to 50 pm preferably 1 to 40 pm, more preferably 2 to 30 pm, and most preferably 3 to 20 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction, and / or (iii) the volume average particle size x95 of the carbon black used in step (i) can be from 0.1 to 50 pm preferably 1 to 40 pm, more preferably 2 to 30 pm, and most preferably 3 to 20 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction, and / or (iv) the volume average particle size x99 of the carbon black used in step (i) can be from 0.1 to 50 pm preferably 1 to 40 pm, more preferably 2 to 30 pm, and most preferably 3 to 20 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction.

[0057]

[0056] The particle size distribution can be determined by dry measurement with the measurement system from Sympatec GmbH (Germany) consisting of VI BRI: conveyor unit (by vibration); RODOS: compressed air dispersion; and HELOS BR: measuring unit, laser diffraction. As sample preparation, 0.5 g of the dried material is filled into the funnel. During the measurement, the sample is fed with the VI BRI unit to the compressed air dispersion unit RODOS by vibration. Measurement is accomplished in HELOS BR unit using laser diffraction. OPTICAL concentration (Copt) was automatically filtered between 5- 15% during the measurement. Three separate measurements of 10 sec using each 0.5 g of the material are recorded. Before each measurement, a background measurement of 15 seconds is recorded to minimize noise. The obscuration range is controlled by the feeding rate with automatic adjustment and the hopper gap in the range of 5-15% using an integral factor of 0.2. The dispersing air pressure is set to 3 bar. Reported values (volume distribution) represent the average of three measurements after the data analysis using a standard analysis model in the instrument software.

[0058]

[0057] The aforementioned particle sizes can refer to the carbon black used in step (i). Dispersing of the carbon black can further reduce the particle size.

[0059]

[0058] As mentioned above, the carbon black used in step (i) can comprise (or can be) recovered carbon black.

[0060]

[0059] The recovered carbon black used in step (i) can comprise 1 to 50 wt.-% coke, preferably 5 to 40 wt.-% coke, more preferably 6 to 35 wt.-% coke, and most preferably 10 to 30 wt.-% coke, based on the total weight of the recovered carbon black used in step (i).

[0061]

[0060] Usually, the recovered carbon black used in step (i) comprises ash, wherein ash comprise metal, metal compounds, silicon, oxygen, sulphur and / or silica, preferably metal comprises zinc, silicon, calcium, cobalt, manganese, potassium, aluminum, and / or iron. The aforementioned ash components are typically residues of a particulate carbon blackcontaining feedstock after the pyrolysis. Waste tires often comprise the aforementioned components as additives or catalysts. However, the aforementioned components negatively affect the properties of the recovered carbon black as well as the properties of a rubber articles, such as a tire, comprising said recovered carbon black.

[0062]

[0061] The recovered carbon black used in step (i) can have an ash content in a range of from 5 to 30 wt.-%, preferably from 8 to 25 wt.-%, more preferably from 11 to 22 wt.-%, most preferably from 15 to 20 wt.-%, wherein the wt.-% is based on the total weight of the recovered carbon black used in step (i) and wherein the ash content is determined according to ASTM D 1506-15 at 550 °C, 16 h.

[0063]

[0062] Generally, ash (or ash components) is embedded in the carbon black of the recovered carbon black, attached to the carbon black of the recovered carbon black, attached on the surface of the carbon black of the recovered carbon black, and / or associated in the carbon black of the recovered carbon black. Generally, ash (or ash components) is embedded in the carbon of the recovered carbon black, attached to the carbon of the recovered carbon black, attached on the surface of the carbon of the recovered carbon black, and / or associated in the carbon of the recovered carbon black.

[0063] The recovered carbon black used in step (i) can comprise zinc, preferably zinc oxide. The recovered carbon black used in step (i) can have a zinc content in a range of from 2.0 to 6.0 wt.-%, preferably from 2.5 to 5.5 wt.-%, more preferably from 3.0 to 5.0 wt.-%, most preferably from 3.5 to 4.5 wt.-%, wherein the zinc content is based on the total weight of the recovered carbon black used in step (i) and wherein the zinc content is preferably determined according to Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), more preferably the zinc content is determined as described in the specification.

[0064]

[0064] The analysis of the Zn content can be conducted following method A in ASTM D8371-20 using an ICP-OES (Spectro Arcos III) from SPECTRO Analytical Instruments GmbH (Germany) and a microwave (turboWAVE inert) from MLS Mikrowellen-Labor- Systeme GmbH (Germany). For the sample preparation, 0.3-0.4 g of the material was weighed into a microwave tube with a capacity of 15 cm3and wetted with 1 ml of pure water (<0.055 pS / cm). Afterward, 10 cm3of concentrated nitric acid (>65 %) was added to the tube and treated in the microwave. The sample was then measured with ICP-OES.

[0065] The recovered carbon black used in step (i) can have a silicon (Si) content in a range of from 1.0 to 5.0 wt.-%, preferably from 1.8 to 4.5 wt.-%, more preferably from 2.0 to 4.0 wt.-%, most preferably from 2.2 to 4.0 wt.-%, wherein the wt.-% is based on the total weight of the recovered carbon black used in step (i) and wherein the silicon content is preferably determined by to Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), more preferably the silicon content is determined as described in the specification.

[0065]

[0066] The analysis of the Si content was conducted using an ICP-OES (iCAP 6300) from Thermo Fisher (USA) and a microwave (turboWAVE inert) from MLS Mikrowellen- Labor-Systeme GmbH (Germany). For the analysis of the Si content method A in ASTM D8371-20 was followed. However, a combination of concentrated nitric acid (>65 %) and concentrated hydrofluoric acid (~ 49%) (usually in a volume ratio of 1:1) with microwave treatment was used to completely digest the sample with microwave treatment. The digested sample is diluted with distilled water to a suitable concentration. The sample was measured with ICP-OES, whereby the device is equipped with a sample introduction kit suitable for HF. In ICP-OES, silicon can be measured with two wavelengths of 288.158 nm and 251.611 nm, preferably measured at 288.158 nm. A standard, such as a commercial standard solution (1 ,000 g / L Si in nitric acid (1 mol / L) with 2wt.-% HF commercially available from Bernd kraft GmbH (Germany) is measured for calibration. For the measurement of a rubber containing material, the ash obtained according to ASTM D 1506-15 at 550 °C, 16 h is used for the analysis of the Si content.

[0066]

[0067] Silica (or silicon in form of silica) can be embedded in the carbon black of the recovered carbon black, attached to the carbon black of the recovered carbon black, attached on the surface of the carbon black of the recovered carbon black, and / or associated in the carbon black of the recovered carbon black. Silica (or silicon in form of silica) can be embedded in the carbon of the recovered carbon black, attached to the carbon of the recovered carbon black, attached on the surface of the carbon of the recovered carbon black, and / or associated in the carbon of the recovered carbon black.

[0068] The recovered carbon black used in step (i) can have a C (carbon) content of at least 50 wt.-%, preferably at least 50 to 80 wt.-%, more preferably 55 to 75 wt.-%, even more preferably 60 wt.-% to 72 wt.-%, and most preferably 62 to 70 wt.-%, wherein the wt.-% is based on the total weight of the recovered carbon black used in step (i) and wherein the carbon content is determined by elemental analysis as described in the specification.

[0067]

[0069] The carbon black used in step (i) can have a BET surface area determined according to ASTM D6556-17 in a range from 15 to 500 m2 / g, preferably from 30 to 300 m2 / g, more preferably from 40 to 250 m2 / g, even more preferably from 50 to 200 m2 / g, most preferably from 60 to 150 m2 / g.

[0068]

[0070] The carbon black used in step (i) can have a compressed oil absorption number (COAN) measured according to ASTM D3493-16 in a range from 30 to 200 mL / 100 g, preferably from 40 to 150 mL / 100 g, more preferably from 50 to 120 mL / 100 g, even more preferably from 55 to 110 mL / 100 g, most preferably from 60 to 90 mL / 100 g.

[0069]

[0071] The carbon black used in step (i) can have (a) a BET surface area determined according to ASTM D6556-17 in a range from 40 to 100 m2 / g, preferably from 50 to 80 m2 / g, more preferably 55 to 70 m2 / g, and a compressed oil absorption number (COAN) measured according to ASTM D3493-16 in a range from 30 to 200 mL / 100 g, preferably from 40 to 150 mL / 100 g, more preferably from 50 to 120 mL / 100 g, even more preferably from 55 to 110 mL / 100 g, most preferably from 60 to 90 mL / 100 g, and / or (b) a BET surface area determined according to ASTM D6556-17 in a range from 10 to 100 m2 / g, preferably from 20 to 90 m2 / g, more preferably 25 to 80 m2 / g, and a compressed oil absorption number (COAN) measured according to ASTM D3493-16 in a range from 30 to 200 mL / 100 g, preferably from 40 to 150 mL / 100 g, more preferably from 50 to 120 mL / 100 g, even more preferably from 55 to 110 mL / 100 g, most preferably from 60 to 90 mL / 100 g, and / or (c) a BET surface area determined according to ASTM D6556-17 in a range from 200 to 600 m2 / g, preferably from 250 to 500 m2 / g, more preferably 300 to 450 m2 / g, and a compressed oil absorption number (COAN) measured according to ASTM D3493-16 in a range from 30 to 200 mL / 100 g, preferably from 40 to 150 mL / 100 g, more preferably from 50 to 120 mL / 100 g, even more preferably from 55 to 110 mL / 100 g, most preferably from 60 to 90 mL / 100 g.

[0070]

[0072] The carbon black used in step (i) can have a statistical thickness surface area (STSA) determined according to ASTM D6556-17 in a range from 15 to 500 m2 / g, preferably from 20 to 400 m2 / g, more preferably from 30 to 300 m2 / g, even more preferably from 40 to 200 m2 / g, most preferably from 50 to 150 m2 / g.

[0071]

[0073] The carbon black used in step (i) can have a volatile content measured at 950°C of 0.5 to 20 wt.-%, such as 1 to 10 wt.-%, 1.5 to 10 wt.-%, 1 to 5 wt.-%, 2 to 10 wt.-%, 2 to 15 wt.-%, 2.5 to 10 wt.-%, 3 to 7 wt.-%, or 3.5 to 7 wt.-%. The volatile content can be measured as described in the specification.

[0072]

[0074] It is desired that the carbon black used in step (i) has a transmittance of at least 20 %, preferably at least 30 %, more preferably at least 40 %, even more preferably at least 60 %, most preferably at least 80 % wherein the transmittance at 425 nm in toluene is measured according to ASTM D 1618-18 against toluene, and / or (ii) has a transmittance of at least 20 %, preferably at least 30 %, more preferably at least 40 %, even more preferably at least 60 %, most preferably at least 80 % wherein the transmittance at 355 nm in toluene is measured according to ASTM D 1618-18 against toluene, wherein the transmittance is measured at 355 nm instead of 425 nm, and / or (iii) has a transmittance of at least 20 %, preferably at least 30 %, more preferably at least 40 %, even more preferably at least 60 %, most preferably at least 80 % wherein the transmittance at 300 nm in toluene is measured according to ASTM D 1618-18 against toluene, wherein the transmittance is measured at 300 nm instead of 425 nm.

[0073]

[0075] The carbon black used in step (i) can have an oxygen content in a range of from 1.0 to 3.0 wt.-%, preferably from 1.5 to 3.0 wt.-%, more preferably from 1.5 to 2.5 wt.-%, wherein the wt.-% is based on the total weight of the carbon black used in step (i) and wherein the oxygen content is determined by elemental analysis as described in the specification.

[0074]

[0076] The carbon black used in step (i) can have a sulfur content in a range of from 1.0 to 4.0 wt.-%, preferably from 2.0 to 4.0 wt.-%, more preferably from 2.0 to 3.0 wt.-%, wherein the wt.-% is based on the total weight of the carbon black used in step (i) and wherein the sulfur content is determined by elemental analysis as described in the specification.

[0075]

[0077] The carbon black used in step (i) can (a) comprise at least 50 wt.-% carbon black, preferably at least 60 wt.-% carbon black, more preferably at least 70 wt.-% carbon black, even more preferably at least 80 wt.-% carbon black, and most preferably at least 90 wt.- % carbon black, based on the total weight of the carbon black used in step (i), and / or can (b) comprise 50 to 95 wt.-% carbon black, preferably 50 to 90 wt.-% carbon black, more preferably 65 to 87 wt.-% carbon black, more preferably 70 to 85 wt.-% carbon black, and most preferably 75 to 80 wt.-% carbon black, based on the total weight of the carbon black used in step (i).

[0076]

[0078] The method can further comprise the step of (iv) removing the filtration means containing the grit on the surface of the filtration means and (v) collecting the grit that is present on the surface of the filtration means, preferably the method further comprises the step of (vi) measuring the amount of grit that is collected in step (v).

[0077]

[0079] The method can further comprise the step of (iv) removing the sieve containing the grit on the surface of the sieve and (v) collecting the grit that is present on the surface of the sieve, preferably the method further comprises the step of (vi) measuring the amount of grit that is collected in step (v).

[0078]

[0080] Furthermore, carbon black is provided (provided carbon black) having (I) a STSA surface area of 90 to 105 m2 / g, an oil absorption number of 90 to 115 mL / 100g, and less than 400 ppm grit, wherein the STSA surface area is measured according to ASTM D6556-21, the oil absorption number is measured according to ASTM D2414-19 using paraffinic oil, the grit is measured according to the method mentioned in the specification; and / or (II) a STSA surface area of 95 to 115 m2 / g, an oil absorption number of 95 to 120 mL / 100g, and less than 400 ppm grit, wherein the STSA surface area is measured according to ASTM D6556-21 , the oil absorption number is measured according to ASTM D2414-19 using paraffinic oil, the grit is measured according to the method mentioned in the specification; and / or (III) a STSA surface area of 105 to 125 m2 / g, an oil absorption number of 75 to 95 mL / 100g, and less than 400 ppm grit, wherein the STSA surface area is measured according to ASTM D6556-21, the oil absorption number is measured according to ASTM D2414-19 using paraffinic oil, the grit is measured according to the method mentioned in the specification.

[0079]

[0081] The carbon black (provided carbon black) can comprise less than 200 ppm grit, preferably less than 150 ppm grit, more preferably less than 100 ppm grit, even more preferably less than 50 ppm grit, and most preferably less than 10 ppm grit, and / or wherein the carbon black (provided carbon black) comprises more than 20 ppm grit, preferably more than 10 ppm grit, most preferably more than 1 ppm grit, and / or wherein the carbon black comprises 1 to 400 ppm grit, preferably 10 to 200 ppm grit, most preferably 20 to 100 ppm grit. The grit is preferably determined according to the inventive method. The grit is preferably determined according to the method of the specification.

[0080]

[0082] Carbon black (I) can have a STSA surface area of 92 to 103 m2 / g, preferably 94 to 102 m2 / g, more preferably 96 to 101 m2 / g, and most preferably 98 to 100 m2 / g, and / or an oil absorption number of 92 to 112 mL / 100g, preferably 95 to 110 mL / 100g, more preferably 97 to 107 mL / 100g, and most preferably 98 to 105 mL / 100g.

[0081]

[0083] Carbon black (II) can have a STSA surface area of 97 to 112 m2 / g, preferably 98 to 110 m2 / g, more preferably 99 to 108 m2 / g, and most preferably 100 to 105 m2 / g, and / or an oil absorption number of 95 to 120 mL / 100g, preferably 97 to 115 mL / 100g, more preferably 98 to 110 mL / 100g, and most preferably 99 to 108 mL / 100g.

[0082]

[0084] Carbon black (III) can have a STSA surface area of 108 to 122 m2 / g, preferably 109 to 120 m2 / g, more preferably 110 to 119 m2 / g, and most preferably 112 to 118 m2 / g, and / or an oil absorption number of 78 to 93 mL / 100g, preferably 79 to 90 mL / 100g, more preferably 80 to 88 mL / 100g, and most preferably 81 to 87 mL / 100g.

[0083]

[0085] The carbon black (provided carbon black) can have a coke content below 5 wt.-%, preferably below 2 wt.-%, more preferably below 3 wt.-%, and most preferably below 1 wt.-%, based on the total weight of the carbon black.

[0084]

[0086] The carbon black (provided carbon black) can comprise 65 to 100 wt.-% carbon, preferably 70 to 99 wt.-%, more preferably 80 to 95 wt.-%, even more preferably 82 to 90 wt.-%, and most preferably 85 to 88 wt.-%, based on the total weight of the carbon black, as measured as described in the specification.

[0085]

[0087] The carbon black (provided carbon black) can have a C (carbon) content of at least 60 wt.-%, preferably at least 63 wt.-%, more preferably 65 to 90 wt.-%, even more preferably 70 wt.-% to 88 wt.-%, and most preferably 75 to 87 wt.-%, wherein the wt.-% is based on the total weight of the carbon black and wherein the carbon content is determined by elemental analysis as described in the specification.

[0086]

[0088] The carbon black (provided carbon black) can have an ash content in a range of from 1 to 25 wt.-%, preferably from 2 to 20 wt.-%, more preferably from 5 to 18 wt.-%, most preferably from 10 to 15 wt.-%, wherein the wt.-% is based on the total weight of the carbon black and wherein the ash content is determined according to ASTM D 1506-15 at 550 °C, 16 h.

[0087]

[0089] The carbon black (provided carbon black) can have an iodine adsorption number of 30 to 80 mg / g, preferably 40 to 70 mg / g, more preferably 45 to 65 mg / g, the iodine adsorption number is measured according to ASTM D1510-17.

[0088]

[0090] The carbon black (provided carbon black) can have a BET surface area determined according to ASTM D6556-17 in a range from 15 to 500 m2 / g, preferably from 30 to 300 m2 / g, more preferably from 40 to 250 m2 / g, even more preferably from 50 to 200 m2 / g, most preferably from 60 to 150 m2 / g.

[0089]

[0091] The carbon black (provided carbon black) can have a compressed oil absorption number (COAN) measured according to ASTM D3493-16 in a range from 30 to 200 mL / 100 g, preferably from 40 to 150 mL / 100 g, more preferably from 50 to 120 mL / 100 g, even more preferably from 55 to 110 mL / 100 g, most preferably from 60 to 90 mL / 100 g.

[0092] The carbon black (provided carbon black) can have

[0090] (a) a BET surface area determined according to ASTM D6556-17 in a range from 40 to 100 m2 / g, preferably from 50 to 80 m2 / g, more preferably 55 to 70 m2 / g, and a compressed oil absorption number (COAN) measured according to ASTM D3493-16 in a range from 30 to 200 mL / 100 g, preferably from 40 to 150 mL / 100 g, more preferably from 50 to 120 mL / 100 g, even more preferably from 55 to 110 mL / 100 g, most preferably from 60 to 90 mL / 100 g,

[0091] (b) a BET surface area determined according to ASTM D6556-17 in a range from 10 to 100 m2 / g, preferably from 20 to 90 m2 / g, more preferably 25 to 80 m2 / g, and a compressed oil absorption number (COAN) measured according to ASTM D3493-16 in a range from 30 to 200 mL / 100 g, preferably from 40 to 150 mL / 100 g, more preferably from 50 to 120 mL / 100 g, even more preferably from 55 to 110 mL / 100 g, most preferably from 60 to 90 mL / 100 g, and / or

[0092] (c) a BET surface area determined according to ASTM D6556-17 in a range from 200 to 600 m2 / g, preferably from 250 to 500 m2 / g, more preferably 300 to 450 m2 / g, and a compressed oil absorption number (COAN) measured according to ASTM D3493-16 in a range from 30 to 200 mL / 100 g, preferably from 40 to 150 mL / 100 g, more preferably from 50 to 120 mL / 100 g, even more preferably from 55 to 110 mL / 100 g, most preferably from 60 to 90 mL / 100 g.

[0093]

[0093] The carbon black (provided carbon black) can have a volatile content measured at 950°C of 0.01 to 10 wt.-%, such as 0.3 to 10 wt.-%, 0.5 to 10 wt.-%, 0.7 to 5 wt.-%, 0.8 to 4 wt.-%, 0.9 to 3 wt.-%, 1 to 2.5 wt.-%, 1.1 to 2.3 wt.-%, 1.2 to 2.2 wt.-%, 1.3 to 2.1 wt.-%, 1.4 to 2 wt.-%, 1.5 to 1.9 wt.-%, or 1.6 to 1.8 wt.-%. The volatile content can be measured as described in the specification.

[0094]

[0094] The carbon black (provided carbon black) can have a transmittance of at least 80 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 %, most preferably at least 98 % wherein the transmittance at 425 nm in toluene is measured according to ASTM D 1618-18 against toluene, and / or can have a transmittance of at least 80 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 %, most preferably at least 98 % wherein the transmittance at 355 nm in toluene is measured according to ASTM D 1618-18 against toluene, wherein the transmittance is measured at 355 nm instead of 425 nm, and / or can have a transmittance of at least 80 %, preferably at least 85 %, more preferably at least 90 %, even more preferably at least 95 %, most preferably at least 98 % wherein the transmittance at 300 nm in toluene is measured according to ASTM D 1618-18 against toluene, wherein the transmittance is measured at 300 nm instead of 425 nm.

[0095]

[0095] The volume average particle size x50 of the carbon black (provided carbon black) can be from 0.3 to 40 pm preferably 0.5 to 30 pm, more preferably 0.8 to 10 pm, and most preferably 1 to 9 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction.

[0096] The volume average particle size x90 of the carbon black (provided carbon black) can be from 0.3 to 40 pm preferably 0.5 to 30 pm, more preferably 0.8 to 10 pm, and most preferably 1 to 9 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction.

[0097] The volume average particle size x95 of the carbon black (provided carbon black) can be from 0.3 to 40 pm preferably 0.5 to 30 pm, more preferably 0.8 to 10 pm, and most preferably 1 to 9 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction.

[0098] The volume average particle size x99 of the carbon black (provided carbon black) can be from 0.3 to 40 pm preferably 0.5 to 30 pm, more preferably 0.8 to 10 pm, and most preferably 1 to 9 pm, wherein the volume average particle size is preferably measured as described in the specification by dry measurement using laser diffraction.

[0099] CHNS content determination by means of elemental analyzer

[0096] The carbon mass fraction, hydrogen mass fraction, nitrogen mass fraction and sulfur mass fraction (i.e. carbon weight fraction, hydrogen weight fraction, nitrogen weight fraction and sulfur weight fraction) are measured using an elemental analyser with thermal conductivity and infrared detector. The analyser is a device for the fully automatic and quantitative analysis of the above elements. The combustion tube is brought to a temperature of 1100 °C and the reduction tube to 850 °C. First, a blank measurement is conducted. The carbon peak area should have a value < 50, the hydrogen peak area a value < 300, the nitrogen peak area a value < 50 and the sulphur peak area a value < 350. Otherwise, the individual adsorption columns are heated and then empty measurements are started again. The blank measurement is calculated as follows: wherein b is the blank measurement, bj is the peak area of the respective blank measurement, n is the number of blank measurements, i is an index of 1 to n.

[0100] The compensation of the blank measurement is calculated as follows, acomp. = a - b, wherein acomp. Is the compensated peak area, a is the measured peak area, and b is the blank measurement value.

[0097]

[0101] Next, the daily factor is measured. For this purpose, 3 mg of sulphanilamide and 3 mg of low-level standard (e.g. carbon black standard) are weighed into each of 8 tin capsules. After weighing out the respective sample, it is placed in the capsule press, overlaid with helium for 35 s and then cold-sealed. Subtracting the blank value, the known theoretical element concentration of the standard samples is put in relation to the actually calculated element concentration. This results in the daily factor, which must be between 0.9 - 1.1. If this is not the case, these measurements should be repeated with newly opened standards. Otherwise, a new calibration must be carried out according to the manufacturer's instructions.

[0098]

[0102] The daily factor is calculated as follows, f > Ctheor

[0099] Cact wherein f is the daily factor, Ctheor. is the theoretical factor, cact. is the actual calculated elemental concentration.

[0100]

[0103] Then, 8 tin capsules each containing 5 mg ±1 mg of the desired measured component, such as rubber granulate, are weighed. After weighing the respective samples, they are placed in the capsule press, covered with helium for 35 s and then cold welded.

[0101]

[0104] For the measurement, the combustion tube is enriched with O2. The elements C, H, N and S burn to form CO2, H2O, NOx, SO2 and SO3. Halogen bound in the sample reacts to form volatile halogen compounds. In addition, there are WO3 granules in the combustion tube that provide further O2 as a catalyst, prevent the formation of nonvolatile sulphates and bind interfering alkali and alkaline earth elements. The carrier gas stream is fed into the reduction tube with Cu filling. Nitrogen oxides (NOx) are completely reduced to N2 at the copper contact. SO3 is reduced to SO2. Volatile halogen compounds are bound to the silver wool.

[0102]

[0105] N2 is not adsorbed and enters the thermal conductivity detector as the first measuring component, CO2, H2O and SO2 are adsorbed on the respective adsorption columns.

[0103]

[0106] Then, one after the other, the adsorption columns are brought to desorption temperature, so that CO2, then H2O as carrier gas enters the thermal conductivity detector and SO2 enters the infrared detector. Depending on the type and concentration of the components, the detector delivers an electrical signal which is digitised and integrated. The measurement signal is recorded as a function of time and displayed as an integral value. The absolute element content of the sample is calculated from this integral value of the individual measurement peaks and the calibration factors.

[0104]

[0107] The element concentration is calculated according to the following equation a *100*f c = - w wherein c is the elemental concentration (in %), a is the absolute element content (in mg), f is the daily factor, and w is the actual amount of the sample.

[0105]

[0108] O content determination by means of elemental analyser

[0106]

[0109] Depending on the oxygen concentration, an electrical signal is transmitted from the thermal conductivity detector (WLD) of the elemental analyser to a micro controller and then displayed as an integral value. From the integral value of the measurement peaks and the calibration factor, the absolute element content of the sample is concluded.

[0107]

[0110] The pyrolysis tube is heated to a temperature of 1050°C. First, a blank measurement is conducted. The oxygen peak area should have a maximum value of 200. If the blank value is not below 200, CO adsorption column should be heated up (260 °C, CO desorption 150 °C). After the blank values have been successfully measured, the mean value of the blank value areas is calculated.

[0108]

[0111] The blank measurement is calculated as follows: wherein b is the blank measurement, bj is the peak area of the respective blank measurement, n is the number of blank measurements, i is an index of 1 to n.

[0109]

[0112] Next, the daily factor is measured. For this purpose, 3 mg of acetanilide are weighed into each of 8 tin capsules. After weighing out the respective sample, it is placed in the capsule press, overlaid with helium for 35 s and then cold-sealed. Subtracting the blank value, the known theoretical element concentration of the standard samples is put in relation to the actually calculated element concentration. This results in the daily factor, which must be between 0.9 - 1.1. If this is not the case, these measurements should be repeated with newly opened standards. Otherwise, a new calibration must be carried out according to the manufacturer's instructions.

[0110]

[0113] The daily factor is calculated as follows, f > Ctheor Cact wherein f is the daily factor, Ctheor. is the theoretical factor, cact. is the actual calculated elemental concentration.

[0114] Then, 8 tin capsules each containing 5 mg ±1 mg of the desired measured component, such as rubber granulate, are weighed. After weighing the respective samples, they are placed in the capsule press, covered with helium for 35 s and then cold welded. The samples are then measured.

[0111]

[0115] The element concentration is calculated according to the following equation a*100*f c = - w wherein c is the elemental concentration (in %), a is the absolute element content (in mg), f is the daily factor, and w is the actual amount of the sample.

[0112]

[0116] Determined particle size distribution

[0113] The particle size distribution is determined by dry measurement with the measurement system from Sympatec GmbH (Germany) consisting of VIBRI: conveyor unit (by vibration); RODOS: compressed air dispersion; and HELOS BR: measuring unit, laser diffraction. As sample preparation, 0.5 g of the dried material was filled into the funnel. During the measurement, the sample is fed with the VIBRI unit to the compressed air dispersion unit RODOS by vibration. Measurement is accomplished in HELOS BR unit using laser diffraction. OPTICAL concentration (Copt) was automatically filtered between 5- 15% during the measurement. Three separate measurements of 10 sec using each 0.5 g of the material were recorded. Before each measurement, a background measurement of 15 sec was recorded to minimize noise. The obscuration range was controlled by the feeding rate with automatic adjustment and the hopper gap in the range of 5-15% using an integral factor of 0.2. The dispersing air pressure was set to 3 bar. Reported values (volume distribution) represent the average of three measurements after the data analysis using a standard analysis model in the instrument software.

[0114]

[0117] Volatiles at 950°C

[0115] Volatiles at 950°C were measured using a thermogravimetric instrument of Fa. LECO Instrumente GmbH (TGA-701) according to the following protocol: Pans were dried at 650°C for 30 min. The carbon black materials were stored in a desiccator equipped with desiccant prior to measurements. Baked-out pans were loaded in the instrument, fared and filled with between 0.5 g to 10 g carbon black material. Then, the oven of the TGA instrument loaded with the sample-filled pans was gradually heated up to 105°C (heating rate 20°C / min) by automated software control and the samples were dried until a constant mass was achieved. Subsequently, the pans were closed by lids, the oven was purged with nitrogen (99.9 vol% grade) and heated up to 950°C (heating rate 20°C / min). The oven temperature was kept at 950°C for 7 min. The content of volatiles at 950°C was calculated using the following equation:

[0116] EXAMPLES

[0117]

[0118] In table 1 , three carbon blacks containing grit are shown that are used in the vacuum sieving method. The carbon blacks were produced in a furnace process.

[0118]

[0119] Table 1 : Properties of the carbon black used in the vacuum sieving method.

[0119] 1STSA surface area was measured according to ASTM D6556-21.

[0120] 2Oil absorption (OAN) number was measured according to ASTM D2414-19 (using paraffinic oil)3lodine adsorption number was measured according to ASTM D1510-21.

[0121]

[0120] Carbon blacks 1 to 3 were dispersed to a particle size smaller than the sieve openings used in each example as indicated below.

[0122]

[0121] The CB was mixed with water and a wetting agent and subsequently dispersed using an ultrasonic dispersion apparatus. Ultraschall Desintegrator Vibracell 72412 or Ultraturrax® can be used. For the Ultraturrax®, the speed can be 7000 rpm / min for 20 min. For the Ultraschall Desintegrator Vibracell 72412, the settings can be 3x5 min, 9 / 6 sec, Amplitude 70 %. In table 2, the dispersing conditions are summarized.

[0123]

[0122] Table 2: Dispersion of the carbon black.

[0124]

[0123] A dutch twilled weave sieve with the desired opening width is weighted and installed in a sieve holder, which is connected to a system of two collection vessels and a vacuum pump. The pump creates a continuous under pressure below the sieve. Different types of sieve can be used. However, from a practical standpoint one-layer sieve cloth (e.g. dutch twilled weave) was found to be best. The carbon black dispersion is slowly added on top of the sieve and the sieving is facilitated due to the pressure difference.

[0125]

[0124] After the dispersion is sieved the sieve is weighted again and the grit that remained on the surface of the sieve was measured. The conditions of the vacuum sieving as well as the amount of grit is shown in table 3.

[0126]

[0125] The grit was also analyzed by a microscope. Figure 1 is an image of the grit of example 6. It is believed that the grit is derived from the refractory lining of the furnace process as well as coke and rust.

[0127]

[0126] Table 3: Conditions of the vacuum sieving.

[0128] 427] As can be seen from table 3, it was possible to remove the grit from the carbon black sample.

[0129]

[0128] It will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principle of the invention.

Claims

Claims1. A method for vacuum sieving carbon black containing grit comprising:(i) dispersing the carbon black containing grit in a liquid in order to obtain a dispersion of the carbon black and the grit,(ii) adding the dispersion of the carbon black and grit on top of filtration means, and(iii) applying a vacuum below the filtration means, so that the carbon black passes through the filtration means and grit that has a particle size above the size of the openings of the filtration means remains on the surface of the filtration means.

2. The method according to claim 1, wherein the carbon black is recovered carbon black, virgin carbon black or a combination thereof.

3. The method according to any of claims 1 or 2, wherein the filtration means comprises a sieve have openings with a size of 1 to 20 pm, preferably 3 to 15 pm, more preferably 5 to 12 pm, and most preferably 6 to 10 pm, and / or wherein the sieve has openings with an average openings size of less than the particle size of the grit, preferably less than the particle size of the grit and between 1 to 20 pm, preferably 2 to 10 pm, more preferably 6 to 10 pm, most preferably 8 to 10 pm, and / or wherein the sieve has 10 pm openings, 7 pm openings and / or 5 pm openings.

4. The process according to any of the preceding claims, wherein the particle size of the carbon black is less than the particle size of the grit, and / or wherein the carbon black is dispersed so that the carbon black passes through the sieve.

5. The process according to any of the preceding claims, wherein the concentration of the carbon black in the dispersion is between 1 to 30 wt.-%, preferably 1 to 20 wt.-%, more preferably 1 to 15 wt.-%, and most preferably 3 to 10 wt.-%, based total weight of the dispersion.

6. The process according to any of the preceding claims, wherein the filtration means comprises a sieve and the sieve is a one-layer sieve cloth, preferably Dutch twilled weave.

7. The process according to any of the preceding claims, wherein the grit has a particle size of more than 5 pm, preferably more than 7 pm, more preferably more than 10 pm, and most preferably more than 11 pm, and / or wherein the grit has a volume average particle size of more than 5 pm, preferably more than 7 pm, more preferably more than 10 pm, and most preferably more than 11 pm.

8. The process according to any of the preceding claims, wherein the dispersion comprises water and a wetting agent, wherein the wetting agent is preferably a fatty alcohol ethoxylate, ammonium salt of acrylic copolymers, potassium and ammonium salt acrylic copolymer, ammonium salt of styrene-acrylic copolymers, and / or potassium and ammonium salt acrylic copolymer.

9. The process according to any of the preceding claims, wherein the dispersion comprises a wetting agent and the wetting agent is present in an amount of 1 to 20 mol-%, preferably 1 to 15 mol.-%, most preferably 2 to 10 mol.-%, based on the total moles of the dispersion.

10. The process according to any of the preceding claims, wherein the dispersing step (i) includes ultrasonic treatment of the dispersion.

11. The process according to any of the preceding claims, wherein the method further comprises the step of (iv) removing the filtration means containing the grit on the surface of the filtration means and (v) collecting the grit that is present on the surface of the filtration means, preferably the method further comprises the step of (vi) measuring the amount of grit that is collected in step (v).

12. The process according to any of the preceding claims, wherein the pressure of the vacuum is from 10 to 700 mbar, preferably from 10 to 400 mbar, more preferably from 50 to 200 mbar.

13. Carbon black having(I) a STSA surface area of 90 to 105 m2 / g, an oil absorption number of 90 to 115 mL / 100g, and less than 400 ppm grit, wherein the STSA surface area is measured according to ASTM D6556-21 , the oil absorption number is measured according to ASTM D2414-19 using paraffinic oil, the grit is measured according to the method mentioned in the specification; and / or(II) a STSA surface area of 95 to 115 m2 / g, an oil absorption number of 95 to 120 mL / 100g, and less than 400 ppm grit, wherein the STSA surface area is measured according to ASTM D6556-21 , the oil absorption number is measured according to ASTM D2414-19 using paraffinic oil, the grit is measured according to the method mentioned in the specification; and / or(III) a STSA surface area of 105 to 125 m2 / g, an oil absorption number of 75 to 95 mL / 100g, and less than 400 ppm grit, wherein the STSA surface area is measured according to ASTM D6556-21 , the oil absorption number is measured according to ASTM D2414-19 using paraffinic oil, the grit is measured according to the method mentioned in the specification.

14. The carbon black according to claim 13, wherein the carbon black comprises less than 200 ppm grit, preferably less than 150 ppm grit, more preferably less than 100 ppm grit, even more preferably less than 50 ppm grit, and most preferably less than 10 ppm grit, and / or wherein the carbon black comprises more than 20 ppm grit, preferably more than 10 ppm grit, most preferably more than 1 ppm grit, and / or wherein the carbon black comprises 1 to 400 ppm grit, preferably 10 to 200 ppm grit, most preferably 20 to 100 ppm grit.

15. The carbon black according to any one of claims 13 or 14, wherein carbon black (I) has a STSA surface area of 92 to 103 m2 / g, preferably 94 to 102 m2 / g, more preferably 96 to 101 m2 / g, and most preferably 98 to 100 m2 / g, and / or an oil absorption number of 92 to 112 mL / 100g, preferably 95 to 110 mL / 100g, more preferably 97 to 107 mL / 100g, and most preferably 98 to 105 mL / 100g; and / or carbon black (II) has a STSA surface area of 97 to 112 m2 / g, preferably 98 to 110 m2 / g, more preferably 99 to 108 m2 / g, and most preferably 100 to 105 m2 / g, and / or an oil absorption number of 95 to 120 mL / 100g, preferably 97 to 115 mL / 100g, more preferably 98 to 110 mL / 100g, and most preferably 99 to 108 mL / 100g; and / orcarbon black (III) has a STSA surface area of 108 to 122 m2 / g, preferably 109 to 120 m2 / g, more preferably 110 to 119 m2 / g, and most preferably 112 to 118 m2 / g, and / or an oil absorption number of 78 to 93 mL / 100g, preferably 79 to 90 mL / 100g, more preferably 80 to 88 mL / 100g, and most preferably 81 to 87 mL / 100g.

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