A PROCESS FOR PRODUCING CARBON BLACK AND RELATED FURNACE REACTOR

Abstract

Suggested is a process for obtaining a carbon black composition preferably of low porosity, comprising or consisting of the following steps: (A) subjecting a hydrocarbon raw material into a high temperature combustion gas stream in order to achieve thermochemical decomposition, (B) cooling the reaction gases and (C) recovering of the carbon black thus obtained, wherein said combustion gas stream consists of at least one oxidant and at least one fuel component, and at least a part of said oxidant and/or said fuel component is subjected to an electrical pre-heating step before it is introduced into the pre-combustion chamber to form a high temperature combustion gas stream.

Claims

1. A process for obtaining a carbon black composition preferably with low porosity, comprising the following steps: (A) subjecting a hydrocarbon raw material into a high temperature combustion gas stream in order to achieve thermochemical decomposition, (B) cooling the reaction gases, and (C) recovering of the carbon black thus obtained, wherein said combustion gas stream consists of at least one oxidant and at least one fuel component, (i) at least a part of said oxidant and/or said fuel component is subjected to an electrical pre-heating step before it is introduced into the pre-combustion chamber to form a high temperature combustion gas stream; (ii) said high-temperature combustion gas stream of step (i) is transferred into a choke area for combustion; and (iii) and the combustion products obtained in step (ii) are transferred into a reaction tunnel including a terminating zone to form carbon black particles to be recovered.

2. The process of claim 1, wherein said oxidants are gaseous components selected from the group consisting of oxygen, ozone, hydrogen peroxide, nitric acid, nitrogen dioxide or nitrous oxide or oxidant-containing gas stream encompassing air, oxygen-depleted or oxygen enriched air, oxygen, ozone, a gas mixture of hydrogen peroxide and air and/or nitrogen, a gas mixture of nitric acid and air and/or nitrogen, a gas mixture of nitrogen dioxide or nitrous oxide and air and/or nitrogen, and a gas mixture of combustion products of hydrocarbons and oxidants.

3. The process of claim 1, wherein said fuel components are gaseous components selected from the group consisting of hydrocarbon, hydrogen, carbon monoxide, natural gas, coal gas, petroleum gas, a petroleum type liquid fuel such as heavy oil, or a coal type liquid fuel such as creosote oil.

4. The process of claim 1, wherein said hydrocarbon raw material is selected from the group consisting of aromatic hydrocarbon encompassing anthracene, CTD (Coal Tar Distillate), ECR (Ethylene Cracker Residue) or petroleum type heavy oils encompassing FCC oil (fluidized catalytic decomposition residual oil) which also can be preheated electrically.

5. The process of claim 1, wherein the reaction is conducted in a furnace reactor comprising at least (a) a pre-combustion chamber; (b) a choke area; (c) a reaction tunnel; (d) a terminating zone; (e) at least one electrical preheating device, and optionally (f) a heat exchanger.

6. The process of claim 1, wherein the oxidant and the fuel component are introduced into the pre-combustion chamber, and said chamber is operated at a temperature ranging from about 1,000 to about 2,500° C. to produce a high temperature combustion gas stream.

7. The process of claim 1, wherein pre-heated oxidant and/or fuel component leaves the pre-heating device with a temperature ranging from about 300 to about 1,300° C.

8. The process of claim 1, wherein the formation of the car bon black takes place in the reaction tunnel, said tunnel representing or opening into a Venturi tunnel.

9. The process of claim 1, wherein the carbon black formed in the reaction tunnel is cooled in the terminating zone, effected by introducing water as quenching agent or by means of at least one heat exchanger.

10. The process of claim 1, wherein said at least part of the oxidant and/or fuel component prior to the pre-heating in the pre-heating device is warmed up by transferring thermal energy from the same or another industrial process by means of a heat exchanger.

11. The process of claim 10, wherein said at least part of the oxidant and/or fuel component prior to the pre-heating in the pre-heating device is warmed up by transferring thermal energy from the hot material stream (consisting of carbon black and tailgas) leaving the terminating zone by means of a heat exchanger.

12. A carbon black of low porosity obtained or obtainable by the process of claim 1, wherein the carbon black exhibits a STSA surface area of 130 m.sup.2/g to 350 m.sup.2/g wherein a ratio of BET surface area to STSA surface area is less than 1.1 if the STSA surface area is in the range of 130 m.sup.2/g to 150 m.sup.2/g, wherein the ratio of BET surface area to STSA surface area is less than 1.2 if the STSA surface area is greater than 150 m.sup.2/g to 180 m.sup.2/g, wherein the ratio of BET surface area to STSA surface area is less than 1.3 if the STSA surface area is greater than 180 m.sup.2/g; and wherein a content of volatiles is less than 5 wt.-percent; provided that the STSA surface area and the BET surface area are measured according to ASTM D 6556.

13. A method comprising using the carbon black according to claim 12 as an additive for pigments, polymers, particularly rubber, and tires.

14. A furnace reactor for producing carbon black preferably of low porosity comprising the following elements: (i) a pre-combustion chamber; (ii) a choke area; (iii) a reaction tunnel (iv) a terminating zone; (v) at least one electrical preheating device, and optionally (vi) a heat exchanger, wherein (a) the pre-combustion chamber contains inlets for oxidants and fuel components, is capable for producing hot combustion gases and is connected to the choke area; (b) the choke area contains at least one inlet for the hydrocarbon raw material and is connected to the reaction tunnel; (c) the reaction zone is capable of forming the carbon black aggregates and is connected to the terminating zone, (d) the terminating zone contains (d1) at least one, preferably two, three, four or a multitude of nozzles for introducing the quenching agent or (d2) is connected to at least one heat exchanger, and is capable of cooling the carbon black aggregates, (e) the outlet of the terminating zone is connected with a heat exchanger capable of transferring at least part of the thermal energy of the carbon black to the oxidant/and or fuel component to warm them up; (f) said warmed stream of oxidants and/or fuel components is introduced into a preheating device, preferably an electric pre-heating device to be heated before being introduced into the pre-combustion chamber; and optionally (g) at least one additional pre-heating device is present for pre-heating (g1) the hydrocarbon material before introduction into the choke area and/or (g2) the reaction gases after leaving the pre-combustion chamber and before entering the terminating zone; (h) preheated reaction gases introduced into the reaction tunnel, and (i) preheated reaction gases introduced into the area behind the terminating zone.

Description

DETAILED DESCRIPTION OF THE PROCESS

[0090] More particularly the present invention refers to a process, wherein the reaction is conducted in a furnace reactor comprising at least [0091] (a) a pre-combustion chamber; [0092] (b) a choke area; [0093] (c) a reaction tunnel; [0094] (d) a terminating zone, [0095] (e) an electrical preheating device, and optionally [0096] (f) a heat exchanger.

[0097] The process in its preferred embodiment(s) is characterized in that [0098] (i) at least one oxidant and at least one fuel component are introduced into the pre-combustion chamber, and said chamber is operated at a temperature ranging from about 1,000 to about 2,500° C. to produce a high temperature combustion gas stream that is transferred into the choke area; [0099] (ii) the hydrocarbon raw material is—optionally after being pre-heated to a temperature ranging from about 100 to about 600° C.—introduced into the choke area, which is preferably a cylindrical structure also called “choke area”; [0100] (iii) the formation of the carbon black takes place in the reaction tunnel, said tunnel has preferably a length of about 3 to about 20 m and preferably from about 5 to about 15 m and can be shaped as a Venturi; [0101] (iv) the carbon black formed in the reaction tunnel is cooled in the terminating zone, effected by introducing water or any other substance as quenching agent or by means of at least one heat exchanger; [0102] (v) at least a part of the oxidant and/or the fuel component is subjected to pre-heating in a pre-heating device before being introduced into the pre-combustion chamber, said pre-heating device being preferably an electric pre-heating device which is preferably operated at a temperature ranging from about 200 to about 2,400° C. releasing the pre-heated oxidant and or fuel component with a temperature from about 300 to about 1,300° C., and preferably from about 1,100 to about 1,200° C.; [0103] (vi) at least part of the oxidant and/or fuel component is warmed up by transferring thermal energy from the same or another industrial process by means of a heat exchanger before subjected to pre-heating in the pre-heating device.

[0104] Heat exchange may take place using any industrial stream, but preferably said at least part of the gas streams send to the precombustor is warmed up by transferring thermal energy from the hot carbon black leaving the terminating zone by means of a heat exchanger. By this means the stream is warmed up to a temperature ranging from about 650 to about 950° C. before entering the pre-heating device.

[0105] Basically, any pre-heating device that is capable of heating any of the process' streams within a reasonable time on temperatures to at least 1,000° C. is suitable to be used in the process of the invention. Particular useful are powder-metallurgical heating systems arranged in ceramic tubes, since they support the combustion reach the required operating temperatures of at least 2,000 up to 2,400° C. Such pre-heating devices based on tube bundle heating elements are for example disclosed in HEAT TREATMENT, p-49-51 (2016).

[0106] Since in many plants more electrical energy is produced than consumed the use of electric pre-heating devices is particularly preferred.

[0107] The process is in more detail described in the drawings. FIG. 1 depicts the process as described above, while FIG. 2 shows an alternative including more than one preheating devices. One preferable embodiment consist of an additional preheating device to be used to pre-heat oxidants introduced into the reaction tunnel

[0108] Another preferable embodiment consists of an additional preheating device to preheat reaction gases introduced into the area behind the terminating zone.

[0109] Another preferable embodiment consists of an additional preheating device to be used to pre-heat raw material introduced into the reactor.

Carbon Black and its Industrial Application

[0110] Another object of the present invention is a carbon black composition obtained or obtainable according to the process as described above, preferably when obtained from a furnace reactor also disclosed above. Porosity is expressed as the relation between BET surface area to STSA surface area of the carbon black. The carbon black obtainable or obtained according to the present invention is characterized by [0111] a STSA surface area of 130 m.sup.2/g to 350 m.sup.2/g [0112] wherein the ratio of BET surface area to STSA surface area is less than 1.1 and preferably less than 1.0 and more preferably less than 0.9 if the STSA surface area is in the range of 130 m.sup.2/g to 150 m.sup.2/g, [0113] the ratio of BET surface area to STSA surface area is less than 1.2, preferably less than 1.1 and more preferably less than 1.0 if the STSA surface area is greater than 150 m.sup.2/g to 180 m.sup.2/g, [0114] the ratio of BET surface area to STSA surface area is less than 1.3, preferably less than 1.2 and more preferably less than 1.0 if the STSA surface area is greater than 180 m.sup.2/g; and [0115] the content of volatiles is less than 5 wt.-percent,
provided that the STSA surface area and the BET surface area are measured according to ASTM D 6556.

[0116] Another object of the present invention refers to the use of the new carbon black as an additive for pigments, polymers, particularly rubbers and tires.

Pigment Applications

[0117] Another object of the present invention refers to use of the new carbon black composition as a pigment, in particular as a black pigment for various purposes such as paints and lacquers.

[0118] Carbon black represents the ideal black pigment because it is lightfast, resistant to chemical attack and shows a deep black color that makes it superior to other inorganic pigments, such as iron oxides. It is mainly used for two applications, pure black coatings, for which the jetness is the dominating parameter, and gray coatings and paints, for which the tinting strength is more important. The first category includes carbon black pigments mainly with small primary particle sizes, and the second one with medium to large particle sizes. The primary purpose of black and gray coatings is decoration and protection. In black coatings, i.e. mass tone coloration, the fine particle size blacks show a bluish undertone whereas coarse blacks exhibit a brownish undertone. Deep black coatings are predominantly demanded from the automobile and furniture industry. However, carbon blacks which exhibit a pronounced blue undertone are even more requested. This is due to the fact that a bluish black is seen to be darker than one with a brownish undertone. Up to now this could be only fulfilled by producing carbon blacks with ever more smaller sizes. Because aggregates are the smallest dispersible units the ASD also has an impact on the jetness (blackness) and particularly on the undertone (more bluish). The more narrow the ASD in particular the more symmetrical the ASD the less the amount of coarse particles (aggregates) and hence the more bluish the undertone.

[0119] As black pigments for deep colouring of plastics mainly carbon blacks of the high colour (HC) and medium colour (MC) class are used. These blacks are found in a great variety of end products such as panelling, casings, fibbers, sheeting, footwear etc., many of them being injection moulded articles. To increase the jetness of a polymer as determined by the blackness M.sub.y one can use a carbon black with smaller sizes of primary particles, low structure blacks or increase the carbon black concentration. Using the first two options the dispersion of the carbon blacks becomes more difficult and can lead to the opposite effect. The concentration of carbon blacks in polymers can be increased only to a certain amount in practice because the mechanical properties of many plastics are usually adversely affected at higher concentrations. Carbon blacks offering a narrow in particular a more symmetrical ASD lead to a higher jetness in polymers without worsen the mechanical properties or decreasing the dispersion behaviour.

[0120] In inkjet ink application the trend is towards smaller droplets, which requires print-head nozzles with diameters of just a few micrometers. Prevention of nozzle clogging and deposits on the print-head are essential to ensure long-term print reliability. Particle fineness (aggregates) of the pigment is one of the key roles to fulfil these requirements in print reliability. Especially few amounts of coarser particles influence the filtration properties as well as the printability of final pigmented inkjet inks. The more narrow the ASD the less the amount of coarse particles (aggregates) and hence the lower risk of print unreliability.

[0121] The carbon black may be present in said pigment compositions in amounts of from about 0.3 to about 45% b.w., preferably about 1 to about 25% b.w.

Additives for Polymer Compositions

[0122] Although a polymer comprising the low porous carbon blacks according to the present invention may encompass a variety of different types, such as polyethylene, polypropylene, polystyrene, polyesters, polyurethanes and the like, the preferred polymer is a synthetic or natural rubber.

[0123] Natural rubber, coming from latex of Havea brasiliensis, is mainly poly-cis-isoprene containing traces of impurities like protein, dirt etc. Although it exhibits many excellent properties in terms of mechanical performance, natural rubber is often inferior to certain synthetic rubbers, especially with respect to its thermal stability and its compatibility with petroleum products.

[0124] Synthetic rubber is made by the polymerization of a variety of petroleum-based precursors called monomers. The most prevalent synthetic rubbers are styrene-butadiene rubbers (SBR) derived from the copolymerization of styrene and 1,3-butadiene. Other synthetic rubbers are prepared from isoprene (2-methyl-1,3-butadiene), chloroprene (2-chloro-1,3-butadiene), and isobutylene (methylpropene) with a small percentage of isoprene for-cross-linking. These and other monomers can be mixed in various proportions to be copolymerized to produce products with a wide range of physical, mechanical, and chemical properties. The monomers can be produced pure and the addition of impurities or additives can be controlled by design to give optimal properties. Polymerization of pure monomers can be better controlled to give a desired proportion of cis and trans double bonds. With respect to polymers of the synthetic or natural rubber type, another object of the present invention is a method for improving wear resistance and reinforcement, and of such polymer compositions.

[0125] The invention also encompasses the use of such carbon black compositions for achieving said effect when added to a rubber composition. The amounts of carbon black to be added to a polymer in general and particularly to a rubber ranges from about 10 to about 120 phr.sup.1, preferably about 35 to about 100 phr and more preferably about 40 to 60 phr. .sup.1phr=parts per hundred parts rubber

Polymer Compositions, Rubber Compositions and Final Products

[0126] The polymers incorporating the carbon blacks according to the present invention may be selected from the group consisting of polyethylene, polypropylene, polystyrene, polyesters, polyurethanes, but preferably the polymer is either a synthetic or natural rubber. The carbon black may be present in said compositions in amounts of from about 0.3 to about 45% b.w., preferably about 1 to about 25% b.w.

[0127] In case, the polymer composition is a rubber composition that is designated to deal as a basis for tires, such compositions generally comprise elastomer compositions, reinforcing to fillers and partly silane coupling agents. The compositions may be cured using a sulphur vulcanizing agent and various processing aids, including accelerators.

Rubbers

[0128] Any conventionally used rubber compounding elastomer is potentially suitable for the rubber compositions covered by the present invention. Non-limiting examples of elastomers potentially useful in the exemplary composition include the following, individually as well as in combination, according to the desired final viscoelastic properties of the rubber compound: natural rubber, polyisoprene rubber, styrene butadiene rubber, polybutadiene rubber, butyl rubbers, halobutyl rubbers, ethylene propylene rubbers, cross linked polyethylene, neoprenes, nitrile rubbers, chlorinated polyethylene rubbers, silicone rubbers, specialty heat and oil resistant rubbers, other specialty rubbers, and thermoplastic rubbers, as such terms are employed in The Vanderbilt Rubber Handbook, Thirteenth Edition, (1990). These elastomers may contain a variety of functional groups, including, but not limited to tin, silicon, and amine containing functional groups.

[0129] The ratios of such polymer blends can range across the broadest possible range according to the final viscoelastic properties desired for the polymerized rubber compound. One skilled in the art, without undue experimentation, can readily determine which elastomers and in what relative amounts are appropriate for a resulting desired viscoelastic property range. The rubber compositions may include [0130] liquid hydroxyl terminated polyalkylenes; [0131] halogenated co-polymers of isobutylene and p-methylstyrene, or both; [0132] EPDM-based rubbers; [0133] halogenated co-polymers of isoolefin and para-alkylstyrene; [0134] styrene-butadiene rubbers, including high trans styrene-butadiene rubbers and/or [0135] high vinyl polybutadiene elastomers.

Reinforcing Fillers

[0136] Typically, the rubber compositions are compounded with reinforcing fillers, including carbon black and silica. The carbon black may be present in amounts ranging from about 10 to about 120 phr, or from about 35 to about 100 phr or from about 40 to about 60 phr. The carbon blacks may be in pelletized form or an unpelletized flocculent mass.

[0137] Examples of suitable silica reinforcing fillers include, but are not limited to, hydrated amorphous silica, precipitated amorphous silica, wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), fumed silica, calcium silicate, and the like.

Rubber Compounding Components

[0138] Processing Aids.

[0139] The rubber composition may be compounded by, for example, mixing the various sulphur-vulcanizable constituent rubbers with various commonly used additive materials such as, for example, curing aids such as sulphur, activators, retarders, and accelerators, processing additives, such as oils, resins including tackifying resins, silicas, and plasticizers, fillers, pigments, fatty acid, zinc oxide, waxes, antioxidants and antiozonants, peptizing agents, and reinforcing materials such as, for example, carbon black.

[0140] An amount of processing aids may be from about 0 to about 10 phr. Such processing aids may include, for example, aromatic, naphthenic, and/or paraffinic processing oils. Typical amounts of antioxidants may comprise from about 1 to about 5 phr. Representative antioxidants may be, for example, diphenyl-p-phenylenediamine, TMQ, and others such as, for example, those disclosed in The Vanderbilt Rubber Handbook (1978), pages 344-346. Typical amounts of antiozonants, such as N-(1,3-dimethylbutyl)-N′-phenyl-1,4-benzene diamine (6PPD), may comprise from about 1 to 5 phr. Typical amounts of fatty acids, if used, which can include stearic acid, may comprise from about 0.5 to about 3 phr. Typical amounts of zinc oxide may comprise from about 1 to about 5 phr. Typical amounts of waxes may comprise from about 1 to about 5 phr. Often microcrystalline waxes are used. Typical amounts of peptizers may comprise from about 0.1 to about 1 phr. Typical peptizers may be, for example, pentachlorothiophenol and dibenzamidodiphenyl disulphide. Process aids, such as phenolic resin (about 2 phr) and C5 aliphatic HC resin (about 5 phr) (tackifiers) may also be useful.

[0141] Vulcanization Agents.

[0142] The vulcanization may be conducted in the presence of a sulphur vulcanizing agent. Examples of suitable sulphur vulcanizing agents include elemental sulphur (free sulphur) or sulphur donating vulcanizing agents, for example, an amine disulphide, polymeric polysulphide, or sulphur olefin adducts. Sulphur vulcanizing agents may be used in an amount ranging from about 0.5 to about 8 phr.

[0143] Accelerators.

[0144] Accelerators are used to control the time and/or temperature required for vulcanization and to improve the properties of the vulcanizate. In one embodiment, a single accelerator system may be used, i.e., a primary accelerator. A primary accelerator is used in total amounts ranging from about 0.5 to about 4 phr. In another embodiment, combinations of a primary and a secondary accelerator might be used with the secondary accelerator being used in smaller amounts (of about 0.05 to about 3 phr) in order to activate and to improve the properties of the vulcanizate. In addition, delayed action accelerators may be used which are not affected by normal processing temperatures, but produce a satisfactory cure at ordinary vulcanization temperatures. Vulcanization retarders might also be used. Suitable types of accelerators that may be used are amines, disulphides, guanidines, thioureas, thiurams, sulphonamides, dithiocarbamates, xanthates, and sulphenamides. The primary accelerator may also be a thiazole, such as a benzothiazole-based accelerator. Exemplary benzothiazole-based accelerators may include N-cyclohexyl-2-benzothiazole sulphonamide (CBS), N-tert-butyl-2-benzothiazole sulphenamide (TBBS), 4-oxydiethylene-2-benzothiazole sulphenamide (OBTS), N,N′-dicyclohexyl-2-benzothiazole sulphenamide (OCBS), 2-mercaptobenzothiazole (MBT), and dibenzothiazole disulphide (MBTS), and may be present in an amount of from about 0.8 to about 1.2 phr. In one embodiment, the amount of the benzothiazole accelerator may be from about 30 to about 60% b.w. of the sulphur vulcanizing agent.

Pneumatic Tires

[0145] A final object of the present invention is directed to a pneumatic tire comprising the new carbon black composition or a rubber composition that comprises said carbon black composition as an additive. Preferably, said tire is a bus tire or a truck tire.

[0146] The pneumatic tire according to an embodiment of the invention shows improved wear resistance and low heat build-up by using the aforementioned carbon black compositions and/or rubber compositions comprising said carbon black compositions for the tire tread in a tread portion. Moreover, the pneumatic tire according to this embodiment has a conventionally known structure and is not particularly limited, and can be manufactured by the usual method. Also, as a gas filled in the pneumatic tire according to the embodiment can be used air or air having an adjusted oxygen partial pressure but also an inert gas such as nitrogen, argon, helium or the like.

[0147] As an example of the pneumatic tire is preferably mentioned a pneumatic tire comprising a pair of bead portions, a carcass torpidly extending between the bead portions, a belt hooping a crown portion of the carcass and a tread, or the like. The pneumatic tire according to the embodiment of the invention may have a radial structure or a bias structure.

[0148] The structure of the tread is not particularly limited, and may have a one layer structure or a multi-layer structure or a so-called cap-base structure constituted with an upper-layer cap portion directly contacting with a road surface and a lower-layer base portion arranged adjacent to the inner side of the cap portion in the pneumatic tire. In this embodiment, it is preferable to form at least the cap portion with the rubber composition according to the embodiment of the invention. The pneumatic tire according to the embodiment is not particularly limited in the manufacturing method and can be manufactured, for example, as follows. That is, the rubber composition according to the above embodiment is first prepared, and the resulting rubber composition attached onto an uncured base portion previously attached to a crown portion of a casing in a green pneumatic tire, and then vulcanization-built in a given mould under predetermined temperature and pressure.