DE19839925A1 - Improved inversion carbon blacks of smaller rolling resistance - Google Patents

Abstract

Furnace carbon black is incorporated into an SSBR/BR rubber compound. The carbon black has CTAB value of 20-190m<2>/g and 24M4-DBP absorption of 40-140 ml/100 g, with tan delta 0/tan delta 60 ratio which satisfies the relation tan delta 0/tan delta 60 \> 2.76-6.7 \* 10<-3> \* CTAB, where tan delta 60 is lower than the value for ASTM carbon blacks with identical CTAB surface area and 24M4-DBP absorption. The distribution curve of the particle sizes has an absolute slope of less than 400000 nm<3>. The slope is determined from formula AS = EPSILON Hi(xi-x)<3>/ EPSILON Hi(I), where both the numerator and denominator are summed from i = l to i = k. HI = frequency at which the particle diameter xI occurs; and x = particle diameter of the aggregate, whose weight corresponds to the average particle weight of the carbon black aggregate and the summation is in the range 1-3000 nm in equidistant spacing for each nanometer.

Description

The present invention relates to improved inversions and a process for their preparation.

Carbon blacks are largely used as booster carbon blacks used for the tire industry. The own The influence of the carbon blacks in connection with the Properties of the rubber compounds used Ge useful properties of the finished tires.

High abrasion resistance, low rolling resistance and good adhesion on wet roads are required. The two latter properties are significantly influenced by the viscoelastic behavior of the tread compound be. For periodic deformation, the viscoelastic behavior can be determined by the mechanical loss factor tanδ and in the case of elongation or compression by the dynamic expansion modulus | E * | to be discribed. Both sizes are strongly temperature dependent. The wet grip is commonly correlated with the loss factor tan δ ₀ at about 0 ° C and the rolling resistance with the loss factor tan δ ₆₀ at about 60 ° C. The higher the loss factor at the low temperature, the better the adhesion of the tire mix on wet roads is usually better. To reduce tion of the rolling resistance, however, a klei ner loss factor is required at the high temperature.

Abrasion resistance and viscoelastic properties the loss factor of the tread mixtures, are significantly affected by the properties of the Amplifier soot determined. The main influence is Here, the specific surface, in particular the CTAB-Ober surface, which is a measure of the rubber-effective upper  surface portions of the soot is. With increasing CTAB upper surface increase abrasion resistance and tanδ.

Other important soot parameters are the DBP absorption and the 24M4 DBP absorption as measures of the output structure, or the mechanical Beanspru the remaining soot structure, as well as the specific surface area (also BET surface area) of the carbon blacks DIN 66 132.

The soot parameters mentioned depend on the shape of the soot part from. In the production of carbon black initially form soge called primary particles with diameters between 10 and 500 nm, the solid three-dimensional aggregates together to grow. The spatial structure and the particle sizes Distribution of these aggregates is reflected in the soot parameters to be measured.

For tread mixtures, carbon blacks having CTAB surface areas between 20 and 190 ² / g and 24M4 DBP absorption values between 40 and 140 ml / 100 g are suitable.

The mean particle diameter of the carbon black aggregates is used for Classification of carbon blacks according to ASTM D-1765. It is about with a four-digit alphanumeric nomenclature, where the first letter (an N or an S) is a statement makes about the vulcanization properties, while the first digit of the following three digit number one Information about the mean particle size gives. These ASTM classification, however, is very crude. That's the way it works within one of these ASTM classification ranges significantly different viscoelastic properties of Tread mixtures come.

DE 195 21 565 describes so-called Inversionsruße, largely meet the requirements for low rolling resistance and improved adhesion. These are carbon blacks in which the ratio of tanδ ₀ / tanδ ₆₀ when processed into a SSBR / BR rubber compound of the relationship

tanδ ₀ / tanδ ₆₀ <2.76-6.7 × 10 ^-3 × CTAB,

is sufficient and the value of tanδ _{60 is} always lower than the corresponding value for ASTM carbon blacks with the same CTAB surface and 24M4-DBP absorption.

The carbon blacks according to DE 195 21 565 are according to the Furnaceruß process produced, with which today the vast majority of those used in the tire industry Carbon blacks are produced. For the production of inversions This procedure was specially modified.

The Furnaceruß process is based on the principle of oxida intensive pyrolysis, ie incomplete combustion, of carbon black raw materials in one with high refractory material lined reactor. As carbon black raw material so-called Soot oils used, but also gaseous hydrocarbons can be used alone or simultaneously with carbon black. Regardless of the specific design of the reactor can three zones in the carbon black reactor are distinguished, the three correspond to different stages of soot production. The Zo NEN lie along the reactor axis one behind the other and be flows through successively from the reaction media.

The first zone, the so-called combustion zone, comprises in essentially the combustion chamber of the reactor. Here is one hot combustor exhaust produced by a fuel, in usually hydrocarbons, with an excess of before warmed combustion air or other oxygenated Gas is burned. As fuel today becomes predominant Natural gas used, but also liquid hydrocarbons like Heating oil can be used. The burning of the Fuel is usually under excess oxygen. After the book "Carbon Black", 2nd Edition, Marcel Dekker Inc., New York 1993, page 20 is for achievement  optimal energy utilization is crucial to that as complete as possible turnover of the fuel Carbon dioxide and water takes place in the combustion chamber. The Excess air promotes the full turnover of the Fuel. The fuel is usually used by means of a or more burner lances introduced into the combustion chamber.

As measure for the identification of the excess air is often used the so-called K-factor. It is about at the K-factor the ratio of the for a stöchio metriche combustion of the fuel required amount of air to the actual amount of combustion air supplied. A K-factor of 1 means a stoichiometric Ver incineration. With excess air, the K-factor is less than 1. Üb Typically, with K-factors between 0.3 and 0.9 gear beitet.

In the second zone of the carbon black reactor, the so-called Reak tion zone, the soot formation takes place. This is the soot raw material is injected into the stream of hot exhaust gas and a mixed. Not related to those in the combustion zone completely converted amount of oxygen is in the reac tion zone introduced amount of hydrocarbons in excess. Therefore, soot formation usually starts here.

Soot oil can be injected into the reactor in various ways become. For example, an axial oil injection is suitable lance or one, or more, radial oil lances, in a plane perpendicular to the flow direction on the Scope of the reactor are arranged. A reactor can be longitudinal the flow direction several levels with radial oil lances respectively. At the head of the oil lances are either Spray or spray nozzles that allow the soot oil in the stream of the exhaust gas is mixed.

With simultaneous use of soot oil and gaseous Hydrocarbons, such as methane, as Rußroh substance, the gaseous hydrocarbons can be separated  from soot oil over its own set of gas lances in the Stream of hot exhaust gas to be injected.

In the third zone of the carbon black reactor, the so-called Ab break zone (quench zone), the soot formation by rapid Cooling of the soot-containing process gas stopped. Thereby undesirable post-reactions are avoided. Such after Reactions would lead to porous carbon blacks. The reactionab Breakage is usually achieved by spraying water by means of suitable spray nozzles. Mostly the carbon black reactor several places along the reactor for spraying Water, or "quenching", on, so that the Residence time of the carbon black in the reaction zone may vary. In a downstream heat exchanger, the residual heat the process gas used to preheat the combustion air men.

It is a variety of different reactor shapes has become known. The variants described concern all three reactor zones, with particularly many training form on the reaction zone and the arrangement of the Injek tion lances for the carbon black raw material. Modern reactors usually have several oil injection lances, both over the circumference of the reactor as well as along the reac Torachse are distributed. The auf auf up to several individual streams shared soot can be better in the out of the combustion chamber flowing stream of hot combustion gas exhaust gas mixed become. Distributed locally along the direction of flow Entry points is a time staggering of the Ölinjek possible.

The primary particle size and thus the normal easily determinable specific soot surface can by the amount of the injected into the hot exhaust gas soot oil be presented. Are the quantities and temperatures of the held in the combustion chamber exhaust gas kept constant then only the amount of carbon black for the primary particle size is or the specific soot surface responsible  Lich. Larger amounts of carbon black result in coarser particulate carbon blacks with lower specific surface areas than lower soot quantities of oil. At the same time with the change in the amount of soot än the reaction temperature is lowered: since the sprayed Soot oil lowers the temperature in the reactor, mean larger Soot oil amounts lower temperatures and vice versa. from that follows in the already cited book "Carbon Black "on page 34 describes the relationship between soot education temperature and specific Rußoberfläche berzie primary particle size.

The soot oil is applied to two different injection sites, the along the reactor axis offset from each other, up shares, so is at the first upstream location the still contained in the combustion chamber exhaust gas amount of Residual oxygen relative to the sprayed soot oil in the over shot available. The soot formation is thus at this Place at higher temperature than when compared to following soot injection sites, d. H. at the first Injection site always form finely divided carbon blacks higher specific surface than at a subsequent Injection site. Any further injection of soot oils will result to further temperature drops and soot with larger ones Primary. Thus produced carbon blacks have so a widening of the aggregate size distribution curve and show a different behavior after incorporation into gum as carbon blacks with a very narrow monomodal aggregate sizes spectrum. The wider aggregate size distribution curve leads to a lower loss factor of the rubber compound, that means a lower hysteresis, which is why you too speaks of low hysteresis soot. Carbon blacks of this type, or processes for their preparation are in Patents EP 0 315 442 and EP 0 519 988.

The conventional methods are thus able to pass through along the reactor axis offset spraying of the carbon black Blacks with a broader aggregate size distribution curve  produce after incorporation into rubber compounds this Rubber compounds give a reduced rolling resistance hen.

To prepare the inversion blacks, the furnace carbon black Modified method in another way. While the Conventional Furnaceruß process as full as possible permanent combustion of the fuel in the combustion chamber, or in the combustion zone, the process according to DE 195 21 565 is based on the manufacturer tion of inversion soot that by incomplete Combustion of fuel in the combustion zone Koh be formed with the flow of hot Exhaust gases are transported to the reaction zone and there a germ-induced soot formation with the supplied Rußroh start up the fabric. The intended incomplete Ver However, combustion of the fuel does not mean that the Fuel burned in a deficit of oxygen becomes. Rather, the method of the invention is just if there is an excess of air or oxygen Gases in the combustion chamber. It can as konven tional carbon black K factors between 0.3 and 0.9 applied become.

In order to produce soot nuclei despite the excess air, you can according to DE 195 21 565 various ways followed the. In a preferred variant of the method one goes of liquid hydrocarbons as fuel, the instead of natural gas in the combustion chamber of the reactor with egg nem excess of air or oxygen-containing gases ver be burned. Liquid hydrocarbons burn for a long time more samer than gaseous, as they are first in the gaseous form leads, that is, must be evaporated. Despite oxygen therefore, excess can be used with liquid hydrocarbons in addition to burning, carbon germs are also produced the one that - if there is enough time and the Tempe is high enough - burn again, or else  with rapid cooling to larger soot particles grow NEN. The germ-induced soot formation is based on that one in the combustion of liquid hydrocarbons nuclei formed in excess of oxygen directly the soot oil brings into contact and thus the germination passes.

Another variant of the method according to DE 195 21 565 uses natural gas as fuel. A germination is there achieved by that the outflow velocity of the Ga It's so low from the burner lances It is chosen that one consciously a bad interference of the Natural gas reaches the hot stream of combustion air. The formation of soot nuclei in poorly mixed flames men is known, where it is because of the lighting of the ge Particles also spoke of glowing flames. at This procedure is also the same as Ver combustion of liquid hydrocarbons important that the formed germs immediately after emergence with the Soot oil are brought into contact. Carried by one larger combustion chamber or combustion zone therefor, that the germs with the surplus acid present can implement material in the combustion zone, one leaves So a complete combustion in the combustion zone of the carbon black reactor, there is no germ-induced soot instead of.

Both variants described can also kom together be combined. In this case, the liquid coals hydrogen and natural gas or other gaseous fuels in suitable proportions at the same time the combustion zone supplied. As liquid hydrocarbons be be preferably oils, for example, the soot oil itself, used.

The method according to DE 195 21 565 is thus to that in the combustion zone, in which in relation to the used hydrocarbons, the oxygen in excess is present, liquid and / or gaseous hydrocarbon  fuels as fuel and ensures that for example, by an insufficient residence time of the liquid Hydrocarbons or by an insufficient Durch mixture of gaseous hydrocarbons with the Ver combustion air, form soot nuclei, which are immediately after their origin with the carbon black raw material, which related to the Oxygen level is used in excess, in the reac tion zone brings into contact, the resulting carbon black reaction gas mixture then by injecting water into the demolition zone cools and the resulting soot in the usual Way further processed.

The fuel carries according to DE 195 21 565 crucial to the formation of soot and is therefore in the following as the primary Designated carbon black. To enter the reaction zone Shedding carbon black is accordingly secondary Carbon black referred to and carries the largest amount Part of the formed soot at.

The inversion carbon black according to DE 195 21 565 impart carbon black mixtures with respect to corresponding conventional carbon blacks a reduced rolling resistance and a comparable Wet adhesion. Further, AFM investigations (AFM = Atomic Force Microscopy) found that the inversion soot a significantly rougher surface than corresponding surface Standard ASTM carbon blacks and thereby improved Connection of the rubber polymer to the soot particles ermögli (See W. Gronski et al., "NMR Relaxation - A Method Relevant for Technical Properties of Carbon Black Filled Rubbers ", International rubber conference 1997, Nuremberg, Page 107). The improved bonding of the rubber polymer leads to the reduced rolling resistance.

Investigations on the abrasion of rubber mixtures using Inversion carbon blacks have shown that these blacks produce the Rubber compounds improved under low loads To give abrasion resistance. At high loads, like them  occur in tires for trucks, this gum mimischungen increased abrasion.

The object of the present invention is therefore to improve Specify inversion soot, which in particular by characterized a reduced abrasion at high loads NEN.

This object is achieved by a Furnaceruß with CTAB values between 20 and 190 m ² / g and 24M4-DBP absorption between 40 and 140 ml / 100 g with a ratio tanδ ₀ / tanδ ₆₀ , which when incorporated into a SSBR / BR- Gum mimic the relationship

tanδ ₀ / tanδ ₆₀ <2.76-6.7 × 10 ^-3 × CTAB,

the value of tan δ _{60 is} always lower than the value for ASTM carbon blacks having the same CTAB surface area and 24M4 DBP absorption. This carbon black is characterized in that the distribution curve of the particle diameter of the carbon black aggregates has an absolute skewness of less than 400,000 nm ³ .

With regard to the ratio tanδ ₀ / tanδ _{60, the} carbon blacks according to the invention fulfill the same requirements as the known inversion blacks and therefore, when incorporated into rubber mixtures, impart reduced rolling resistance to the tires made therefrom. However, they are distinguished from the known inversion carbon blacks by a narrower aggregate size distribution. To describe the aggregate size distribution, the "absolute skewness" measure known from statistics is used (see: Lothar Sachs: "Statistical Evaluation Methods", Springer-Verlag Berlin, 3rd edition, pages 81 to 83). It is a description of the shape of the aggregate size distribution curve more appropriate to the present problem than a limitation of aggregate sizes by maximum and minimum values.

The "absolute skewness" means the deviation from a symmetric aggregate size distribution. A skewed distribution curve exists if one of the two descending branches of the distribution curve is extended. is the left part of the curve lengthens, it is called negative Leaning, that is the determination of the absolute skewness returns values below zero. Is the right corner section extended, so there is a positive skewness with values grö above zero. The well-known ASTM carbon blacks as well as the inversi Onsruße and the carbon blacks of the invention have a positive Skewness of different severity.

Surprisingly, it was found that in the state of Technique accepted view, a widened aggregate size distribution of the amplifier soot lend the chew Schukmischungen a reduced rolling resistance, none May claim universality. The at inversions reduce the rolling resistance of Rubber compounds is obviously not of breadth the aggregate size distribution depends, but is in the we sentlichen by the larger surface roughness of In version soot and the associated better connection of the Rubber polymer caused to the carbon black surface.

Compared with the known inversion with their relatively broad aggregate size distribution now Abriebwi resistor according to the invention can be improved by the fact that the width of the aggregate distribution is limited. In particular, the proportion of carbon black aggregates having large particle diameters must be reduced if the carbon blacks are to impart improved wear resistance to rubber compounds in addition to reduced rolling resistance. This is the case when the absolute skewness of the aggregate size distribution is less than 400,000, preferably less than 200,000 nm ³ . The absolute skewness of the inversion blacks known from DE 195 21 565 is above 400 000 nm ³ , while the absolute skewness of standard ASTM carbon blacks is below 100 000 nm ³ .

The absolute skewness of the aggregate size distribution of a soot can be determined with the aid of a disc centrifuge and corresponding evaluation of the measured values. The sample to be examined is dispersed in an aqueous solution and separated in a disk centrifuge according to their particle size: the larger the particles are, the greater their mass, the faster the soot particles move outwards due to the centrifugal force in the aqueous solution , They walk through a photoelectric barrier, which absorbs the extinction as a function of time. From these data, the aggregate size distribution, that is the frequency as a function of the particle diameter is calculated. From this, the absolute skewness AS can be determined as follows:

Here, H _i denotes the frequency with which the particle diameter x _i occurs. In this case, x is the particle diameter of the particles whose mass corresponds to the mean particle mass of the carbon black aggregates. x is also calculated using the aggregate size distribution. The summations in the above formula must be made in the range of 1 nm to 3000 nm at equidistant intervals of one nanometer each. Any missing measured values are calculated by linear interpolation.

The inversion blacks according to the invention can be prepared according to the in DE 195 21 565 generic methods described produce. According to this method, the inversion soot becomes produced in a carbon black reactor, which along the Reak Torachse a combustion zone, a reaction zone and a  Contains demolition zone. In the combustion zone is through Burning a primary Rußrohstoffs in oxygen ent holding a stream of hot exhaust gases generated. This hot gas flow is from the combustion zone through the Re action zone in the demolition zone passed. In the reaction Zone is a secondary Rußrohstoffe in the hot exhaust gas mixed. The soot formation is carried out in the demolition zone Spraying water stopped. This is called primary Carbon black oil, an oil / gas mixture or natural gas alone used. The combustion of the primary carbon black in The combustion zone is guided so that Rußkeime form, with which the secondary Rußrohstoff directly in Contact is brought.

In order to obtain the carbon blacks according to the invention, this process must now be carried out in such a way that the carbon black which forms has an aggregate size distribution with an absolute skewness of less than 400,000 nm ³ . This can be achieved, for example, by increasing the supply of combustion air, primary and secondary carbon black.

The method described is not specific to a Re limited actuator geometry. It can rather be different reactor types and reactor sizes. The desired nucleation in the combustion zone, the Hire a specialist through various measures. Possible Influences for optimizing nucleation in use tion of oil as fuel, the combustion air / oil Mass ratio, the type of atomizer used for the fuel and the size of the atomized oil droplets. As a fuel atomizer can both pure Druckzerstäu over (single substance atomizer) as well as two-component atomizer with internal or external mixture are used as Atomizing medium compressed air, water vapor, hydrogen, a Inert gas or a hydrocarbon gas used who that can. The combination of a So liquid with a gaseous fuel can be used for  Example by using the gaseous fuel as Sputtering medium realized for the liquid fuel become.

Preference is given to the atomization of liquid fuel Two-component atomizer used. While at Einstoffzer A change in throughput also dusts an amendment The droplet size can lead to the droplet size Batch spraying largely independent of throughput to be influenced.

The size of the atomized droplets must be adjusted so who that at the point of injection of the carbon black oil is still sufficient carbon black germs are available. The optimal droplets Size depends on the geometry of the selected Reak tors. In the reactor used in the examples have Mean droplet diameter in the range between 50 and 100 μm proven. These values were calculated using the Zer Pollution of water determined. The optimal setting of the However, atomizers are best performed empirically on the reactor under observation of the flame picture. Too fine an atomizer tion of the liquid fuel leads to the complete Combustion of droplets without nucleation. Too big a drop This leads to coke formation and an unstable flame. A good nucleation is present with a light sooting flame.

As Rußrohstoff so-called carbon black oils, that is highly aromatic and / or long-chain oils, alone or in Combination with hydrocarbon gases, esp especially natural gas. Suitable carbon black oils are pe trochemical oils (steam cracker oils, cat crackers oils), car bochemical oils (coal tar oil) and pyrolysis oils with egg BMC index greater than 130. These oils will as well in the case of liquid fuels preferably with binary material Atomize atomises.

With the method according to the invention, the entire Pa lette industrial furnace carbon black can be prepared. The person skilled in the necessary measures for this purpose, such as the adjustment of the residence time in the reaction zone and the addition of additives for influencing the carbon black structure are known. It has been found that the carbon blacks produced by the method according to the invention differ significantly from conventional carbon blacks in sliding analysis characteristics. When incorporated into SSBR / BR rubber blends, these blends impart a tanδ ₀ / tanδ ₆₀ ratio to the resultant rubber blend, which is greater than conventional carbon blacks, with the same tanδ ₆₀ below the corresponding value for ASTM carbon blacks CTAB surface area and 24M4-DBP absorption. This observation applies to carbon blacks having CTAB values between 20 and 190 m ² / g, in particular for carbon blacks having CTAB values between 60 and 140 m ² / g ₁ and 24M4 DBP absorption values between 40 and 140 ml / 100 G. In addition, in these carbon blacks by suitable process management verhin changed that the aggregate size distribution curve has particularly large proportions with large aggregate diameters.

The carbon blacks of the invention impart the SSBR / BR rubber mixtures a stronger temperature dependence of tanδ. ne ben this, in DE 195 21 565 as inversion designated effect, the carbon blacks according to the invention have a narrowed aggregate size distribution over the conventional inversion soot on. The dynamic one Expansion modulus | E * | SSBR / BR rubber compounds with the Carbon black according to the invention is generally lower at 0 ° C as the modulus of expansion using standard ASTM carbon blacks.

The germ-induced soot formation has the same effect as with the be knew inversion blacks on the structuring of the surface surface of soot particles. Through investigations with the help of Atomic Force Microscopy (AFM) found that he inventive carbon blacks have a rougher surface than Standard ASTM carbon blacks.  

The invention will now be closer by means of some examples purifies. Show it

Fig. 1 shows a longitudinal section through the use for the manufacture of the carbon blacks reactor.

Fig. 2 is a graph of the ratio tanδ ₀ / tanδ ₆₀ over the CTAB surface for various fiction, contemporary carbon blacks and conventional comparison blacks.

Fig. 3 Aggregate size distribution curve of a standard ASTM carbon black N220.

FIG. 4 shows an aggregate size distribution curve of the conventional inversion black of Example 1. FIG .

Fig. 5 Aggregate size distribution curve of erfindungsge MAESSEN Inversionsrußes of Example 2.

Fig. 6 Abriebverhalten a rubber compound using carbon black according to Example 1 relative to a reference rubber mixture

Fig. 7 Abrasion behavior of a rubber compound using carbon black according to Example 2 relative to a reference rubber compound Examples 1 and 2

In the carbon black reactor shown in FIG. 1, a conventional inversion carbon black (Example 1) and an inversion carbon black according to the invention (Example 2) were prepared.

The carbon black reactor ( 1 ) has a combustion chamber 2 , in which the hot exhaust gas for the pyrolysis of the carbon black oil is produced by burning the primary Rußrohstoffes under supply of atmospheric oxygen. The primary Rußrohstoff is introduced via the axial burner lance 3 in the combustion chamber. The burner lance can be moved to optimize the germ-induced soot formation in the axial direction.

The supply of combustion air via the opening 4 in the end wall of the combustion chamber. The combustion chamber runs ko to the constriction 5 to. After passing through the Eng the reaction gas mixture expands into the reaction chamber. 6

With A, B and C are different positions for the Injek tion of the carbon black oil in the hot process gas by means of oil 7 zen called. The oil lances have at their head appro priate spray nozzles. At each injection position, 4 injectors are distributed over the circumference of the reactor.

The combustion zone, reaction zone and demolition zone which are important for the process according to the invention are identified in FIG. 1 by the Roman numerals I to III. They can not be sharply separated. Their axial extent depends on the respective positioning of the burner lance, the oil lances and the quench water lance 8 .

The dimensions of the reactor used are shown in the following list:

Largest diameter of the combustion chamber 900 mm Length of the combustion chamber to bottleneck 1390 mm Length of the conical part of the combustion chamber 1160 mm Diameter of the bottleneck 140 mm Length of the bottleneck 230 mm Diameter of the reaction chamber 250 mm Position of oil lances ¹ ) @ A 110 mm B - 150 mm C - 320 mm Position of quench water lance (s) ¹ ) ≈ 1000-5500 mm ¹ ) measured from entry into the bottleneck (+: after admission, -: before entry).

The two carbon blacks produced in the described reactor were prior to characterization and incorporation into the Rubber compounds wet-rolled by the usual methods.

For the production of the carbon blacks were as primary and as sec The carbon black raw material is a soot oil with a BMC index of 160 used, which compiled in Table 1 egg features.

Table 1

Properties of the carbon black oil

The reactor parameters for the production of the carbon blacks are in Table 2 listed.

Table 2

Reactor parameters for the production of the carbon blacks of Example 1 (comparative carbon black) and Example 2

Determination of soot-analytical characteristics

On the carbon blacks according to the invention as well as on some commercial comparative carbon blacks, the usual soot-analytical characteristics were determined according to the following standards:
CTAB surface: ASTM D-3765
Iodine adsorption: ASTM D-1510
DBP absorption: ASTM D-2414
24M4 DBP absorption: ASTM D-3493
BET surface area: DIN 66 132.

Determination of viscoelastic properties

The determination of the viscoelastic properties of with These carbon blacks reinforced rubber compounds was according to DIN 53513 performed. In particular, the loss factors were tanδ at 0 ° C and at 60 ° C and the dynamic expansion modulus | E '* | at 0 ° C determined. The testre used for the rubber compounds zeptur is listed in Table 3.  

Table 3

SSBR / BR test formulation

The SSBR rubber component is an in Solution polymerized SBR copolymer with a styrene content of 25% by weight and a butadiene content of 75% by weight. The Vinyl content of butadiene is 67%. The copolymer contains 37.5 phr of oil and is sold under the trade name Buna VSL 5025-1 sold by Bayer AG. Its Mooney Viscosity (ML 1 + 4/100 ° C) is about 50.

The BR rubber component is a cis 1,4-polybutadiene (neodymium type) having a cis 1,4 content of 97% by weight, a trans 1,4 content of 2% by weight, a 1,2-content of 1 weight percent and a Mooney viscosity between 38 and 48. This component is sold under the trade name Buna CB 24 of of Bayer AG.

The aromatic oil used was Naftolen ZD from Chemetall det. The PPD portion of the test formulation was Vulkanox 4020 and at the CBS stake around Vulkacit CZ, both from Bayer AG. As wax was Protector G35 of the HB-Fuller GmbH used.  

The incorporation of the carbon blacks into the rubber compound was carried out in three stages according to the following tabular list:

Subsequent determination of viscoelastic properties then took place on each of five specimens from the above rubber compounds under the following conditions:

Table 4

Determination of viscoelastic properties according to DIN 53513

In each case the median value of the measurements is used on the five test specimens.

The results of the viscoelastic investigations are listed in Table 5 and shown graphically in FIG . A total of 14 commercial comparative carbon blacks, designated V1 through V14 in Table 5, and the carbon blacks of Example 1 and Example 2 were tested.

Table 5 contains for the comparative carbon blacks, as far as known, nor their ASTM classification.  

In Table 5, the carbon blacks are ordered by ascending CTAB surface. In FIG. 2, their ratio tanδ ₀ / tanδ _{60 is} plotted over the CTAB surface for these carbon blacks. The two inversion blacks show a significantly higher tanδ ratio for the same CTAB surface, ie a steeper temperature profile of the loss factor. This is especially true in comparison with the two lh carbon blacks (V3 and V6) in Table 5 , which are carbon blacks according to EP 0 315 442. In the lh carbon blacks no steeper temperature profile of the loss factor could be determined.

The region of the inversion blacks can be clearly distinguished from the conventional blacks. It lies above the boundary line shown in Fig. 2, which draw by the relationship

tanδ ₀ / tanδ ₆₀ = 2.76-6.7 × 10 ^-3 × CTAB

given is.

It is also characteristic of the inversion blacks that, with the same CTAB surface area and similar 24M4 DBP absorption as the standard ASTM carbon blacks, they lead to a lower loss factor tan δ ₆₀ and generally to a lower dynamic modulus of elasticity of the rubber blends.

Aggregate size distribution curves

To measure the aggregate size distribution curves, a Disc centrifuge BI-DCP with red light diode of the company Brookhaven used. This device has been specially designed for the Determination of aggregate size distribution curves of feintei developed from absorbance measurements and is with an automatic measuring and evaluation program equipped to determine the aggregate size distribution.

To perform the measurements was first a Disper 200 ml of ethanol, 5 drops of ammonia solution and 0.5 g of Triton X-100 and demineralized Water produced to 1000 ml. Furthermore, a Spin liquid from 0.5 g Triton X-100, 5 drops Ammonia solution and make up with demineralized water made to 1000 ml.

Thereafter, 20 mg of carbon black with 20 ml of dispersion solution Staggered and placed in a cooling bath for 4.5 minutes with 100 watts of ultrasonic power (80% pulses) in the solution suspended.

Before beginning the actual measurements, the centrifuge was operated for 30 minutes at a speed of 11 000 min ^-1. 1 ml of ethanol was injected into the rotating disc and then carefully layered with 15 ml of spin fluid. After about one minute, 250 .mu.l of the Rußsus pension were injected and started the measurement program of the device and the spin fluid in the centrifuge with 50 ul of dodecane overcoated. From each sample to be measured, a duplicate determination was made.

The evaluation of the raw data curve then took place with the Calculation program of the device taking into account the Stray light correction and with automatic baseline Adaptation.  

FIGS. 3 to 5 show the obtained unit size distribution curves, from which, as described above, the absolute skewness of the distribution curves can be calculated.

Fig. 3 is the distribution curve of a carbon black N220 (carbon black V9 in Table 5), Fig. 4 is the distribution curve of the inversion carbon black of Example 1 and Fig. 5 shows the distribution curve of the inversion carbon black of Example 2 according to the invention gives. The known inversion carbon black of example 1 shows a strong asymmetry of the distribution curve, which is caused in particular by a very large proportion of aggregate sizes above about 150 nm. This proportion of carbon black aggregates is greatly reduced in the inversion carbon black according to the invention, which is manifested by a correspondingly reduced absolute skewness.

The absolute skewness values obtained from such distribution curves are listed in Table 6 for some standard ASTM carbon blacks and the two inversion blacks. It can be seen that the standard ASTM carbon blacks have a very small absolute skew, that is, their aggregate size distribution curves are relatively symmetrical. By contrast, the known inversion carbon black of Example 1 has a very large absolute skewness of more than 400,000 nm ³ . In which
The inverse carbon black of Example 2 according to the invention is still greater than the standard carbon blacks but, compared to the known inverse carbon black, the absolute skewness is reduced to about one third.

Table 6

Absolute skewness of the aggregate size distribution curves of some blacks

abrasion tests

It was the abrasion behavior of rubber compounds under Use of the two inversion blacks and the standard black N220 were made using a special abrasion examined. This abrasion test allows a Bewer tion of the abrasion of a rubber compound relative to a Reference rubber compound for different loads and Speeds.

This abrasion test used is described in detail in the following publications:
KA Grosch, the 131 ^th ACS Rubber Div. Meeting, No97 (1987) and
KA Grosch et al., Kautsch. Rubber art st. 50, 841 (1997).

A corresponding tester is commercially available. Therefore, with respect to the details of the abrasion test refer to the above publications for this device.

The rubber compounds used for the abrasion tests were identical to the rubber compounds for the viskoela Static investigations. As a reference rubber compound was the rubber compound with the standard carbon black N220 (soot V9) used.

Figs. 6 and 7 show the results obtained. In the three-dimensional diagrams of these figures, the evaluation of the abrasion compared to the reference rubber mixture in dependence on the logarithm of the speed and the logarithm of the registered by the load in the specimen energy W is plotted. The abrasion behavior of the reference rubber compound is set equal to 100.

Fig. 6 shows the abrasion performance of a rubber compound using the inversion carbon black of Example 1. It can be seen that the rubber compound with the known Inver sionsruß at low loads and low Geschwin speeds shows a significantly reduced abrasion compared to the reference rubber mixture. At high loads, however, the abrasion deteriorates compared to the reference rubber compound.

Fig. 7 shows the abrasion behavior of a rubber compound using the inversion carbon black of Example 2 of the present invention in comparison with the reference rubber compound. The rubber compound with the inversion carbon black according to the invention shows a more balanced abrasion behavior than the known inversion carbon black. Especially at high speeds and high loads, this rubber compound still shows up to 10% improved abrasion behavior. The carbon blacks according to the invention are therefore outstandingly suitable for the preparation of rubber mixtures for tire treads and adhesive mixtures.

Claims (3)

Furnaceruß with CTAB values between 20 and 190 m ² / g and 24M4-DBP absorption between 40 and 140 ml / 100 g with a ratio tanδ ₀ / tanδ ₆₀ , which when incorporated into a SSBR / BR rubber compound of the relationship
tanδ ₀ / tanδ ₆₀ <2.76-6.7 × 10 ^-3 × CTAB,
is sufficient, wherein the value of tanδ _{60 is} always lower than the value for ASTM carbon blacks with the same CTAB surface and 24M4-DBP absorption, characterized in that the distribution curve of the particle diameter of the carbon black aggregates has an absolute skewness of less than 400,000 nm ³ , wherein the absolute skewness AS is determined according to the following formula from the measured aggregate size distribution of the soot
wherein H _i denotes the frequency at which the particle diameter x _i occurs and x is the particle diameter of those carbon black aggregates whose mass corresponds to the average mass of the carbon black aggregates and the summations in the calculation formula in the range of 1 nm to 3000 nm at equidistant intervals of a nanometer. 2. A process for the production of Furnaceruß according to claim 1 in a carbon black reactor, which along the reactor axis, a combustion zone, a reaction zone and an Ab breakage zone, by generating a stream of hot exhaust gas in the combustion zone by burning a primary Rußrohstoffes in an oxygen-containing gas and conduct the exhaust gas from the combustion zone through the reaction zone in the demolition zone, mixing a secondary Rußrohstoffes into the hot exhaust gas in the reaction zone and stopping soot formation in the demolition zone by spraying water, being used as pri märer Rußrohstoff oil, oil / gas mixture or natural gas alone and the combustion of the primary carbon black raw material is conducted so that nuclei form and the secondary carbon black raw material germinating directly with these soot is brought into contact, characterized in that the supply of combustion air, primary and se kundärem Rußrohstoff is increased in such a way in that the resulting absolute skewness of the particle size distribution curve of the forming carbon black is below 400 000 nm ³ . 3. Use of Furnaceruß according to claim 1 for the Her production of rubber compounds for the production of Tires, in particular for tire treads and tires Adhesive mixtures.