Process for the production of black pigment from sustainable raw materials without carbon dioxide emissions and its use

Abstract

Development of a process for producing carbon black pigment that generates no carbon dioxide emissions, exhibits color strength comparable to currently available carbon black pigments, and displays a saturated black hue. The analytical data of this carbon black pigment must comply with the relevant regulations permitting its use in food packaging, printing inks, paints, and cosmetic products.

Description

[0001] The use of carbonaceous materials as black pigments is as old as humanity. In the Stone Age, charred wood was used for cave paintings. Egyptian tombs contain depictions of charcoal being ground in mortars. Early applications can also be traced back to India. The pyrolysis, or carbonization of wood in charcoal kilns through incomplete combustion, has been practiced for centuries. All of these processes produce a coarse-grained material that is unsuitable for industrialized applications as a pigment.

[0002] Demand for carbon black increased particularly in the fifteenth century with the invention of the printing press. Even today, carbon black pigment can be found in all areas of modern life. It is used in the ink of inkjet printers, as a reinforcement for natural and synthetic rubber, and as an active ingredient in electrically conductive plastics. Perhaps its broadest and best-known application is as a pigment in paints, varnishes, and plastics to create a deep black color, as it exhibits greater color strength than so-called iron black or organic pigments.

[0003] Carbon powders made from organic raw materials are available on the market. The company Werth-Metall offers powdered hemp charcoal, powdered oak charcoal, and powdered coconut charcoal. However, the particle sizes of these carbon powders are all in the micrometer range and are too large and too weak for use as pigments. Some of these materials, even when dispersed in binding agents, do not exhibit a deep black hue.

[0004] Carbon black pigments manufactured industrially using standardized processes are produced and processed in large quantities. The following industrial manufacturing processes and the cited patents are associated with carbon dioxide emissions in almost all cases.

[0005] So, in today’s understanding, they are harmful to the climate.

[0006] The combustion of coal tar distillates (1) and the deposition of the soot produced during combustion on cold surfaces produces a finely divided black pigment. This process is still used industrially today and is known under the name "lamp black process". This produces relatively large pigment agglomerates or aggregates which have a deep black hue. The pigment is less colour intensive than pigments from other processes. The disadvantages of this process are the high emissions of carbon dioxide from the combustion process and the low pigment yield. In the Degussa process (2), the pigment is additionally wet ground in a rotor ball mill to destroy aggregates and agglomerates and to improve dispersibility. The pigment suspension must then be filtered, dried, dry ground and the resulting pigment dust separated in a filter.This manufacturing process involves four additional production steps and is very cost-intensive.

[0007] These processes are harmful to the climate due to the high energy consumption and high carbon dioxide emissions.

[0008] The furnace black process is based on the thermal oxidative decomposition of aromatic oils derived from hard coal, crude oil, or natural gas. Part of the feedstock burns in an incomplete combustion process in the furnace's reaction zone. At the end of the reaction, water is sprayed in to cool the reaction mixture and prevent further combustion of the resulting pigment black (4). The resulting furnace black pigment black is collected and sent for further processing. A large number of patents exist for the furnace black process, examples of which are patents (4, 5, 6, and 7).

[0009] These processes are harmful to the climate due to the high energy consumption and high carbon dioxide emissions.

[0010] Other processes include the thermal black process and the acetylene black process. (3) These involve thermal cracking of natural gas, oil, or acetylene. The "continuous thermal process of making carbon black" is described in the patent (8). These processes are also harmful to the climate due to the large energy consumption and high carbon dioxide emissions.

[0011] WO 2021 / 223789 A1 describes a biogenic black pigment and a process for its production and use. The raw material is a carbon material produced analogously to the LignoBoost process described in DE 10 016 201 801 A1. This kraft lignin is hydrothermally treated with caustic soda and then filtered, washed in a filter press, dried, and ground. The kraft lignin is then carbonized at temperatures up to 600 °C in a drum or rotary kiln or in a fluidized-bed dryer, wet-ground with an additive, filtered, dried, and ground.

[0012] Although this process is characterized by zero carbon dioxide emissions, it is not very environmentally friendly due to the hydrothermal treatment with caustic soda. The processing of the caustic soda is complex and costly, making it uneconomical and harmful to the climate.

[0013] DE 10 2916 201 801 A1 describes a particulate carbon material made from renewable raw materials. The renewable raw material is a lignin-containing biomass, the production of which is described in DE 10 016 201 801 A1. This process is highly energy-intensive due to the hydrothermal treatment with caustic soda at high temperatures and high pressure, and is therefore harmful to the climate.

[0014] DE 3703077 describes a process for producing carbon black pigment in which the surface characteristics of the carbon black pigment are modified by treatment with an organic adsorbate. The carbon black pigment is produced using the furnace carbon black process, which emits significant amounts of carbon dioxide. This process, too, is harmful to the climate due to the high energy consumption and high carbon dioxide emissions.

[0015] DE 3141779 A1 describes a process in which an aromatic starting material is pyrolytically dissociated in an oil combustion process. Pyrolysis is carried out using combustion gases with a stoichiometric excess of oxygen. This process is also harmful to the climate due to the high energy consumption and high carbon dioxide emissions.

[0016] DE 3141779 describes a process in which a liquid hydrocarbon is pyrolytically converted into soot in a reactor using pyrolytically generated combustible gases. This process is also harmful to the climate due to the high energy consumption and high carbon dioxide emissions.

[0017] DE 28 46 405 describes the post-treatment of an oxidatively post-treated carbon black from the MCC range with a high specific surface area for use in deep black paints. Because the carbon black process requires a large amount of energy and generates high carbon dioxide emissions, this process is harmful to the climate.

[0018] The Carbonauten company's website describes pigment black materials produced from wood by pyrolysis in large, heated, cylindrical metal reactors. However, no information is provided on pigments, color strengths, analytical data, or other properties. Only highly filled plastic preparations are offered, but their application as pigments is not described.

[0019] However, it is calculated how much carbon dioxide can be saved by this process compared to burning wood.

[0020] There is a wealth of information in the literature on the production of fine-particle carbon materials.

[0021] In Römpps Chemie Lexikon (11), page 97 of volume 1 describes the production of activated carbon from plant materials by heating with zinc chloride or phosphoric acid to 500 to 900 °C or by dry distillation at 700 to 1000 °C under steam or carbon dioxide atmosphere.

[0022] On page 1737 of Volume 3 of Römpp's Chemistry Encyclopedia, the production of charcoal in large, externally heated retorts under anaerobic conditions at 350 to 400 °C is described. According to Römpp's Chemistry Encyclopedia, all coniferous and deciduous woods—except beech—are suitable for this process.

[0023] The production of activated carbon is described in detail in Winnacker-Küchler (12) on pages 327 to 331. Carbonization in a rotary kiln involves chemical activation of the organic raw materials using a zinc chloride solution or phosphoric acid. This chemical activation reduces tar formation during heating in the rotary kiln. The disadvantage of this process is that, after carbonization, the zinc chloride must be washed out of the resulting charcoal in an aqueous suspension, or the remaining phosphoric acid must be neutralized in an aqueous suspension of the charcoal, and the resulting salts must be washed out. This process consumes a lot of water and energy, which is unsustainable.

[0024] Neither book provides any information about the suitability of the charcoal produced in this way as a pigment.

[0025] The invention was based on the task of developing a process for producing pigment black that does not generate carbon dioxide emissions, has a color strength comparable to that of carbon black pigments currently on the market, and has a saturated black hue in its pure form. The analytical data for this carbon black pigment produced in this way must meet the relevant regulations that allow its use in food packaging, printing inks, colored varnishes, and cosmetic products.

[0026] In particular, the requirements for pigments according to the BfR IX regulation as of June 1, 2019, must be met at least, but preferably undercut.

[0027] The limit values ​​of the BfR IX regulation as of 01.06.2019 are: arsenic 100 ppm Lead 100 ppm cadmium 100 ppm Chromium, saturated 1000 ppm mercury 50 ppm barium 100 ppm antimony 50 ppm selenium 100 ppm chrome 100 ppm cadmium 10 ppm not exceed.

[0028] Regulation (EU) No. 10 / 2011 also applies.

[0029] in the AP(89) 1 - the following limit values ​​are also listed: Aromatic amines

[0030] The content of primary unsulfonated aromatic amines, soluble in 1M hydrochloric acid and expressed as aniline, should not exceed 500 ppm.

[0031] The content of benzidine, β-naphthylamine and 4-aminobiphenyl, individually or in total, should not exceed 10 ppm in total. Sulfonated aromatic amines

[0032] Sulfonated aromatic amines are defined as compounds that are sulfonated at all aromatic or conjugated ring structures.

[0033] The total content of sulfonated aromatic amines extracted with a suitable solvent and determined by a suitable test, expressed as anilinesulfonic acid, should not exceed 500 ppm. Pigment soot

[0034] Pigment black should meet all national requirements for food-grade materials. Furthermore, the extractable content of pigment black from toluene should never exceed 0.15%. Polychlorinated biphenyls (PCBs)

[0035] The content of extractable polychlorinated biphenyls should not exceed 25 ppm, expressed as decachlorobiphenyl.

[0036] According to the revised Cosmetics Regulation, substances with carcinogenic, mutagenic, or reproductive toxic effects, so-called CMR substances, may no longer be used in cosmetics starting in March 2023. Most polycyclic aromatic hydrocarbons (PAHs) are listed as prohibited substances in Annex II of Regulation (EC) 1223 / 2009.

[0037] The production of a carbon black pigment that meets all these requirements and can be produced sustainably is described in the following examples: Examples:Example 1:

[0038] The raw material used was beechwood chips dried and ground at 150 °C with a moisture content of 1.5% and a bulk density of 188 g / L. These beechwood chips were filled into a conical porcelain crucible with a height of 47 mm and an inner upper diameter of 57 mm. The crucible volume was 93 ml. During filling, the beechwood chips were mechanically compacted. The filling weight was 20.6 g. The crucible was tightly sealed with aluminum foil and annealed in an "efco" laboratory muffle furnace at 605 °C for 40 minutes. Pyrolization produced heavy smoke. After cooling the crucible and removing the aluminum foil, deep black carbon was obtained. The yield was 6.2 g, with some of the carbon firmly baked onto the crucible wall.The behavior of this material is not suitable for a continuous pyrolysis process in a drum or rotary kiln, as the drum becomes clogged over time due to caking on the drum wall. Example 2:

[0039] The raw material used was ground beechwood chips with a moisture content of 29.6% and a bulk density of 260 g / L. Before grinding, 2% diammonium hydrogen phosphate was added to the beechwood chips. These beechwood chips were filled into a conical porcelain crucible with a height of 47 mm and an inner upper diameter of 57 mm. The crucible volume was 93 ml. During filling, the beechwood chips were mechanically compacted. The filling weight was 30.2 g. The crucible was tightly sealed with aluminum foil and annealed in an efco laboratory muffle furnace at 605 °C for 40 minutes. Only slight smoke was generated during pyrolysis. After cooling the crucible and removing the aluminum foil, deep black carbon was obtained. The yield was 7.5 g, and no caking was observed on the crucible wall. This process is suitable for technical implementation for a carbon raw material.

[0040] The components of the black carbon from Example 2 were determined by the laboratory CTL ® GmbH, Chemical-Technological Laboratory, Krackser Straße 12, 33659 Bielefeld I, further tested for impurities. The following levels were determined: Arsenic: < 0.5 ppm Cadmium: < 0.5 ppm Chrome: 0.6 ppm Mercury: < 0.5 ppm Lead: < 0.5 ppm Antimony: < 0.5 ppm Selenium: < 2.0 ppm PAHs: (Polycyclic aromatic hydrocarbons) PAHs: (Polycyclic aromatic hydrocarbons); Quantification limit: 0.2 mg / kg Test method: AfPS GS PAH: 2019-01: 24 substances; Extraction with toluene: GC / MS analysis. 24 substances Individual assessment Test result: Benz(a)anthracene not detectable Chrysanthemums not detectable Benz(b)fluoranthen not detectable Benz(k)fluoranthen not detectable Benzo(j)fluoranthen not detectable Benzo(a)pyren not detectable Benzo(e)pyren not detectable Dibenz(a,h)anthracene not detectable Total assessment naphthalene 0.85 ppm Acenaphthylen not detectable Acenaphthene not detectable Fluoren not detectable Phenanthren 0.1 ppm Anthracene not detectable Fluoranthen not detectable Pyren not detectable Indo(1,2,3,c,d)pyren not detectable Benzo(ghi)perylen not detectable Cylopenta(c,d)pyren not detectable Dibenzo(a‚l)pyren not detectable Dibenzo(a,e)pyren not detectable Dibenzo(a,i)pyren not detectable Dibenzo(a,h)pyren not detectable 1-Methylpyren not detectable 24 PAHs / Total: 0.95 ppm This significantly exceeds the BfR IX regulation as of June 1, 2019. Example 3:

[0041] The carbonaceous material obtained according to Example 2 was further comminuted in a wet mill.

[0042] This material was processed into a pumpable suspension in a dissolver. 2 wt. % Geniosil GF 96 (Wackerchemie) and 6 wt. % Byk 9076 were added as additives. In the pilot plant of Netzsch, Selb, this suspension was milled in a "MiniCer" stirred ball mill with zirconium silicate grinding media using a recirculation process in aqueous suspension and an operating time of 60 minutes. The pigment suspension was separated from the grinding media in the mill using a sieve. The particle size was determined in aqueous suspension using the Mastersizer - v3.81. The mean particle size distribution Dv (50) was 2.49 µm (see appendixes for particle size distribution measurement and electron micrograph).

[0043] The pigment suspension is then filtered through a special filter paper (Macherey-Nagel, MN 85 / 70) in a Büchner funnel under vacuum. The pigment filter cake is dried at 80 °C in a drying cabinet and ground in a hammer mill for 4 minutes.

[0044] Coloration in polyethylene on a two-roller test according to DIN "Pigments and fillers - Dispersibility methods and assessment of dispersibility in plastics - Part 3: Determination of coloristic properties and dispersibility hardness of black and colored pigments in polyethylene by a roller test (ISO 23900-3:2015); German version EN ISO 23900-3:2018 with a pigment concentration of 1 wt% results in a deep black solid shade. Coloration in polyethylene on a two-roller test according to DIN "Pigments and fillers - Dispersibility methods and assessment of dispersibility in plastics - Part 3: Determination of coloristic properties and dispersibility hardness of black and colored pigments in polyethylene by a roller test (ISO 23900-3:2015); German version EN ISO 23900-3:2018 in the whitening with titanium dioxide in a ratio of 1:9 and a pigment concentration of one wt% results in a comparable color strength to commercially available gas black. Example 4:

[0045] A pilot plant experiment was conducted in a drum furnace manufactured by Elino, Düren. The tube diameter was approximately 300 mm, and the heated zone was approximately 3000 mm. The heating chamber temperature was set to 620 °C, and the furnace was electrically heated. The furnace had a total of three control zones. The drum speed was 1.5 revolutions per minute, and the drum furnace inclination was 1.5° and was continuously adjustable manually.

[0046] The beechwood sawdust, milled with 2% diammonium hydrogen phosphate and possessing a residual moisture content of 29%, was carbonized at a bulk density of 260 g / L and a feed rate of 25 kg / h at an internal tube temperature of 620°C. The water contained in the beechwood sawdust evaporates and renders the atmosphere inert within the rotary kiln. The water vapor is discharged from the rotary kiln in countercurrent. The resulting carbon black crude pigment was packaged hermetically in metal drums with clamping lids after leaving the cooling zone of the rotary kiln. The yield was 6.2 kg / h of pigment black. Example 5:

[0047] The resulting pigment black crude pigment was ground in a stirred ball mill as in Example 3), filtered, dried and dry ground.

[0048] Literature: (1) Industrial Coloration of Plastics, Carl Hanser Verlag, ISBN: 978-1-56990-852-5 (2) Patent DE102007026214 A1 (3) Patent CA000000090809A (4) Patent US000002967762A (5) Patent AU001984037094B2 (6) Patent WO002001072908A1 (7) Patent US 2,967,762 (8) Patent US000002773744A (9) Patent WO 2021 / 223789 A1 (10) https: / / carbonauten.com / (11) Römpps Chemistry Encyclopedia, ISBN 3-440-04510-2, 8th edition, Stuttgart 1979 (12) Winnacker-Küchler(3), Chemical Technology, 4th edition, Hanser Verlag (13) Patent: WO 2021 / 223789 A1 (14) Patent DE 10 2916 201 801 A1 (15) Patent DE 3703077 (16) Patent DE 3141779 A1 (17) Patent DE 3141779 (18) Patent DE 28 46 405 QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2021 / 223789 A1 [0011, 0048] DE 10 016 201 801 A1 [0011, 0013] DE 10 2916 201 801 A1 [0013, 0048] DE 3703077 [0014, 0048] DE 3141779 A1 [0015, 0048] DE 3141779 [0016, 0048] DE 28 46 405 [0017, 0048] DE 102007026214 A1

[0048] CA 000000090809A

[0048] US 000002967762A

[0048] AU 001984037094B2

[0048] WO 002001072908A1

[0048] US 2,967,762

[0048] US 000002773744

[0048] Cited non-patent literature

[0000] ISO 23900-3:2015

[0044] EN ISO 23900-3:2018

[0044] Industrial Coloration of Plastics, Carl Hanser Verlag, ISBN: 978-1-56990-852-5

[0048] Römpps Chemistry Encyclopedia, ISBN 3-440-04510-2, 8th edition, Stuttgart 1979

[0048] Winnacker-Küchler(3), Chemical Technology, 4th edition, Hanser Verlag

[0048]

Claims

[1] Process for the production of pigment black from sustainable shredded organic raw materials in a climate-friendly process without carbon dioxide emissions by pyrolysis of organic materials with the addition of an additive and pyrolysis in a rotary kiln or drum kiln under exclusion of air. [2] Process according to claim 1), in that ammonium phosphates, preferably diammonium hydrogen phosphate, are mixed into the beech wood chips in a mixer before pyrolysis and that the amount of diammonium hydrogen phosphate is 0.1 to 20 wt. %, preferably 1 to 5 wt. %. [3] Method according to claim 1), that the sustainable raw material consists of beech wood chips with a residual moisture content of 20 to 35%. [4] Process according to claim 1), characterized in that the mixture according to claim 3 is pyrolyzed in a drum or rotary kiln at a temperature between 601 and 800 °C under exclusion of air. [5] Process according to claim 1), in that the resulting pigment black crude pigment is suspended in water and comminuted in a wet grinding in a mill, preferably in a stirred ball mill, with grinding media of 0.1 to 3 mm diameter to an average particle size (D 50) of 0.1 to 2000 µm, preferably to 1.0 to 5.0 µm and then separated in a filter press. [6] Process according to claim 5), characterized in that the pigment black suspension is mixed with additives prior to grinding, which improve the wetting and dispersibility of pigment black in binders or plastics. [7] Process according to claim 1), in which the pigment filter cake is gently dried in a drying cabinet, a belt dryer, a spin-flash dryer, a freeze dryer, and then dry-ground. [8] Process according to claim 1), characterized in that the resulting pigment black contains heavy metal and PAH contents of less than 1 ppm. [9] Process according to claim 1), characterized in that the resulting black pigment is used for coloring plastics, lacquers, printing inks, powder coatings, leather, rubber, mineral paints, plasters, concrete and cosmetic products such as mascara, eyeliner and eyebrow dye.