Note: Descriptions are shown in the official language in which they were submitted.
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CARBON BLACK, METHOD FOR PRADUCING CARBON BLACK AND USE OF THE SANE
The invention concerns carbon blacks, a process for the
production of these carbon blacks as well as their use, in
particular as reinforcing carbon blacks in rubber mixtures.
Carbon blacks are known from Ullmanns Enzyklopadie der
technischen Chemie, 4 th Edition (1977), Vol. 14, pp. 633 to
648.
The most important processes for producing carbon blacks
are based on the oxidative pyrolysis of carbon-containing
carbon black raw materials. In these processes the carbon
black raw materials are incompletely burnt at high
temperatures in the presence of oxygen. These carbon black
production processes include for example the furnace carbon
black process, the gas carbon black process and the flame
carbon black process. Predominantly polynuclear aromatic
carbon black oils are used as carbon black raw materials.
Carbon blacks are used as fillers and as reinforcing agents
in the preparation of rubber mixtures for the tyre
industry. Typical rubber mixtures include, in addition to
natural and/or synthetic rubber, also carbon black, mineral
oil and further auxiliaries as well as sulfur as
vulcanisation agent.
Carbon blacks influence the abrasion resistance., rolling
resistance as well as the wet skidding behaviour of tyres
produced from these rubber mixtures. For rubber mixtures
that serve as tyre treads, so-called tread mixtures, a high
abrasion resistance with at the same time as low a rolling
resistance as possible combined with a good wet skidding
behaviour are required. A low rolling resistance leads to
a low fuel consumption of the vehicle.
Rolling resistance and wet skidding properties are
influenced by the viscoelastic behaviour of the tread
mixture. With periodic deformation the viscoelastic
behaviour can be described by the mechanical loss factor
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tanS and, in the case of stretching or compression, by the
dynamic modulus of elasticity JE*J. Both quantities are
strongly temperature-dependent.
The wet skidding behaviour of the tread mixture is
correlated with the loss factor tanEio at 0 C, while the
rolling resistance is correlated with the loss factor
tanS60 at 60 C. The higher the loss factor at the low
temperature, the better usually is the wet skidding
behaviour of the tyre mixture. In order to reduce the
rolling resistance as small a loss factor as possible at
the high temperature is required however.
The abrasion resistance and the viscoelastic properties,
and thus also the loss factor of the tread mixtures, are
essentially determined by the properties of the reinforcing
carbon blacks that are used.
An important index for the rubber-active surface proportion
of the carbon black is the specific surface, in particular
the CTAB surface or STSA surface. hfith increasing CTAB
surface or STSA surface both the abrasion resistance and
tanB increase.
Further important carbon black parameters are the DBP
absorption as a quantitative measure of the initial
structure, and the 24M4-DBP absorption as a measure of the
residual structure still remaining after the carbon black
has been subjected to mechanical stress.
For tread mixtures carbon blacks are: suitable that have
CTAB surfaces between 80 and 180 m2/g and 24M4-DBP
absorption values between 80 and 140 ml/100 g.
It is known that ASTM carbon blacks are unable to influence
the temperature dependence of the loss factor tanS in such
a way that the tread mixture has a lower rolling resistance
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with the same or better wet skidding behaviour. As is
known, the desired reduction of the rolling resistance is
directly coupled to a deterioration of the wet skidding
behaviour. Carbon blacks that have a low rolling
resistance are termed so-called "lciw hysteresis" carbon
blacks.
It is furthermore known that the rolling resistance of
tyres can be reduced by replacing the carbon black by
silica (EP 0 447 066 Al). In order to bind the silica
to the polymer building blocks of the rubber, silane
coupling reactants are used. Silica-containing rubber
mixtures have a loss factor tanS60 that is reduced by up to
50%.
The object of the present invention is to provide carbon
blacks that impart to rubber mixtures of natural rubber or
synthetic rubber or mixtures thereof a reduced rolling
resistance with at the same time the same or an improved
wet skidding behaviour and abrasion resistance.
The present invention provides a carbon black that has a
STSA surface of between 20 and 180 m2/g, a 24M4-DBP
absorption of between 40 and 140 ml/100 g, a specific BET
surface of between 20 and 250 m2/g aind a content of 0.01 to
20 wtA of silicon, referred to its ~overall weight, which
is characterised in that in rubber mixtures it has a
tanSo/tanS60 ratio of greater than 3.37 - 0.0068 = STSA.
In one embodiment of the invention, the carbon black can
also contain 0.01 to 1 wtA nitrogen in addition to
silicon.
The silicon is incorporated into the carbon black
aggregates during the production process. For this purpose
silicon-containing compounds may for example be mixed into
the carbon black raw material. Suitable silicon-containing
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compounds may be organosilicon compounds such as
organosilanes, organochlorosilanes, siloxanes and
silazanes. In particular silicone oils, silicon
tetrachloride, siloxanes and silasanes may be used.
Silanes and silicone oils may preferably be used.
The starting compound has only a slight influence on the
incorporation of the silicon atoms into the carbon black
aggregates. It can be shown by X-ray photoelectron
spectrometry (XPS) and secondary ion mass spectrometry
(SIMS) that the silicon atoms are oxidically bound and
distributed in the carbon black aggregates. The oxidic
bonding consists predominantly of silicon dioxide. Other
silicon atoms form silanol groups. lahereas the silanol
groups are mainly located on the surface of the carbon
black aggregates, silicon dioxide is distributed uniformly
over the cross-section of the aggregates.
In one embodiment of the invention the silicon may be
concentrated in the sub-surface regions of the carbon black
aggregates.
The silicon-containing groups on the surface of the carbon
black aggregates influence, after incorporation into rubber
mixtures, the interaction of the fil:ler with the rubber
polymer components. To effect a covalent bonding of the
silanol groups of the carbon blacks to the mixture polymers
bifunctional silanes, for example Si159 (Bis(3-
triethoxysilylpropyl)-tetrasulfane) from Degussa, may be
added as silane coupling reagent to the rubber mixtures.
The tread mixtures produced with the silicon-containing
carbon blacks according to the invention exhibit an
increased value of tanSO and a reduced value of tan860
compared to known carbon blacks havirig the same specific
surface and structure, without the need to add a coupling
reagent. These values correspond to a substantially
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improved wet skidding behaviour combined with a
substantially reduced rolling resistance of the tread. The
rolling resistance of the rubber mixtures can be improved
still more, i.e. reduced further, by adding bifunctional
5 silanes.
The carbon blacks according to the invention may be
produced by the furnace carbon black process according to
DE 195 21 565 Al.
According to the furnace carbon black process the oxidative
pyrolysis of the carbon black raw material is carried out
in a reactor lined with highly refractory material. In
such a reactor three zones, lying one after the other along
the reactor axis and through which the reaction media flow
in succession, may be distinguished.
The first zone, the so-called combustion zone, essentially
comprises the combustion chamber of the reactor. A hot
process gas is produced in this zone by burning a fuel, as
a rule hydrocarbons, with an excess of preheated combustion
air or other oxygen-containing gases. Natural gas may be
used as fuel. Liquid hydrocarbons such as light and heavy
heating oil may also be used.
In a preferred embodiment of the invention carbon black raw
material (carbon black oil) may also be used as fuel.
The combustion of the fuel normally takes place with an
excess of oxygen. The excess air promotes the complete
conversion of the fuel and serves to control the quality of
the carbon black. The fuel is normally introduced by means
of one or more burner lances into the combustion chamber.
The formation of the carbon black takes place in the second
zone of the carbon black reactor, the so-called reaction
zone or pyrolysis zone. To this end the carbon black raw
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material, in general a so-called carbon black oil, is
injected into and mixed in with the stream of hot process
gas. The amount of hydrocarbons introduced into the
reaction zone is in excess referred to the incompletely
reacted amount of oxygen in the combustion zone. For this
reason the formation of carbon black normally takes place
here.
If the carbon black oil is also used as fuel, the formation
of carbon black may take place already in the combustion
zone. In the reaction zone further carbon black may then
be applied to the carbon black particles formed in the
combustion zone.
Carbon black oil may be injected in various ways into the
reactor. For example, an axial oil injection lance or one
or more radial oil lances, arranged on the circumference of
the reactor in a plane vertical to the flow direction, are
suitable. A reactor may contain several planes with radial
oil lances along the flow direction. Spray or injection
nozzles are arranged on the head of the oil lances, by
means of which the carbon black is mixed into the flow of
process gas.
With the simultaneous use of carbon black oil and gaseous
hydrocarbons, for example methane, as carbon black raw
material, the gaseous hydrocarbons may be injected
separately from the carbon black oil via their own set of
gas lances into the flow of the hot waste gas.
In the third zone of the carbon black reactor, the so-
called termination zone (quench zone), the carbon black
formation is terminated by rapid cooling of the carbon
black-containing process gas. In this way undesired after-
reactions are avoided. The reaction is normally terminated
by spraying in water through suitable spray nozzles. The
carbon black reactor generally includes several places
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along the reactor for spraying in water, i.e. "quenching",
so that the residence time of the carbon black in the
reaction zone may be varied. In a heat exchanger connected
downstream the residual heat of the pressure gas is
utilised to preheat the combustion aiir and the carbon black
oil.
Whereas the aim of the known furnace carbon black processes
is to achieve as complete a combustion as possible of the
fuel in the combustion chamber, or in the combustion zone,
the process according to the invention for producing carbon
black is based on the fact that carbon seeds are formed in
the combustion zone as a result of the incomplete
combustion of the fuel, which seeds are transported with
the flow of hot waste gas into the reaction zone, where
they initiate a seed-induced carbon black formation with
the added carbon black raw material. The sought-after
incomplete combustion of the fuel-does not mean however
that the fuel is burnt in a deficit of oxygen. Rather, the
process according to the invention too employs an excess of
air or oxygen-containing gases in thie combustion chamber.
K factors of between 0.3 and 1.2 may be employed as with
conventional carbon blacks. The process is preferably
operated however with K factors of between 0.6 and 0.7.
Various methods may be adopted in order to produce carbon
black seeds despite the excess air. In a preferred variant
of the process according to the invention liquid
hydrocarbons are used as fuel, which are burnt instead of
natural gas in the combustion chamber of the reactor with
an excess of air or oxygen-containing gases. Liquid
hydrocarbons burn more slowly than g'aseous hydrocarbons
since they first have to be converted into the gaseous
form, i.e. have to be evaporated. Despite the excess
oxygen, in addition to the combustion there may also be
produced with liquid hydrocarbons carbon seeds which, if
sufficient time is available and the temperature is
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sufficiently high, also continue to burn or, if rapid
cooling is effected, can grow into larger carbon black
particles. The seed-induced carbon black formation is
based on the fact that the seeds formed in the combustion
of liquid hydrocarbons with excess oxygen are brought into
contact directly with the carbon bliFLck oil and thus
initiate the seed growth.
Another variant of the process according to the invention
uses natural gas as fuel. A seed formation is achieved if
the outflow speed of the gas from the burner lance or
lances is chosen sufficiently low so as intentionally to
achieve a poor intermixing of the natural gas with the hot
flow of the combustion air. The formation of carbon black
seeds with poorly mixed flames is kriown, in which
connection on account of the glow of' the formed particles
one also speaks of glowing flames. With this procedure it
is likewise important, as with the c;ombustion of liquid
hydrocarbons, to bring the resultant: seeds immediately
after their formation into contact with the carbon black
oil. If an attempt is made by means of a larger combustion
chamber or combustion zone to react the seeds with the
oxygen present in excess in the combustion zone so as to
achieve a complete combustion in the combustion zone of the
carbon black reactor, then no seed-induced formation of
carbon black takes place.
The carbon blacks according to the invention may be
produced by mixing the aforedescribed silicon-containing
compounds into the carbon black raw materials or spraying
them separately into the combustion chamber or the
pyrolysis zone of the carbon black reactor. The mixing of
the silicon-containing compounds into the carbon black oil
may be effected in the form of a solution if the compounds
are soluble in the carbon black oil, or in the form of an
emulsion. An incorporation of the silicon atoms into the
carbon black primary particles is achieved by means of
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these measures. One or more of the oil lances normally
employed for spraying in the carbon black raw material may
be used for the separate spraying oiE the silicon-containing
compounds.into the pyrolysis zone oiE the carbon black
reactor.
The furnace carbon black process is modified for the
production of inversion carbon black. Whereas the object
of the conventional furnace carbon black processes is to
achieve as complete a combustion as possible of the fuel in
the combustion chamber or in the combustion zone, the
process according to DE 195 21 565 for producing inversion
carbon blacks is based on the fact that carbon seeds are
formed by incomplete combustion of the fuel in the
combustion zone, which seeds are transported with the flow
of hot waste gas into the reaction zone and there initiate
a seed-induced formation of carbon black with the added
carbon black raw material. The soucrht-after incomplete
combustion of the fuel does not meari however that the fuel
is burnt in a deficit of oxygen. Rather, the process
according to the invention too operates with an excess of
air or oxygen-containing gases in tt-e combustion chamber.
K factors of between 0.3 and 0.9 may be employed as with
conventional carbon black.
In order to produce carbon black seeds despite the excess
air, various measures may be adopted according to
DE 195 21 565. In a preferred variaint of the process
liquid hydrocarbons are used as fuel., which are burnt with
an excess of air or oxygen-containinig gases instead of
natural gas in the combustion chamber of the reactor.
Liquid hydrocarbons burn more slowly than gaseous
hydrocarbons since they first have t.o be converted into the
gaseous form, i.e. have to be evaporated. Despite the
excess oxygen, in addition to the combustion there may thus
also be produced with liquid hydrocarbons carbon seeds
which, if there is sufficient time and the temperature is
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sufficiently high, will also continue to burn, or if rapid
cooling is effected can grow to form larger carbon black
particles. The seed-induced formation of carbon black is
based on the fact that the seeds formed in the combustion
5 of liquid hydrocarbons with excess oxygen are brought into
contact directly with the carbon black oil and thus
initiate the seed growth.
Another variant of the process according to DE 195 21 565
10 uses natural gas as fuel. A seed formation is achieved if
the outflow speed of the gas from the burner lance or
lances is chosen sufficiently low so as intentionally to
achieve a poor intermixing'of the natural gas with the hot
flow of the combustion air. The formation of carbon black
seeds with poorly mixed flames is known, in which
connection on account of the glow of the formed particles
one also speaks of glowing flames. !With this procedure it
is likewise important, as with the combustion of liquid
hydrocarbons, to bring the resultant seeds immediately
after their formation into contact with the carbon black
oil. If an attempt is made by means of a larger combustion
chamber or combustion zone to react the seeds with the
oxygen present in excess in the combustion zone so as to
achieve a complete combustion in the combustion zone of the
carbon black reactor, then no seed-iinduced formation of
carbon black takes place.
The two aforedescribed variants may also be combined with
one another. In this case the liquid hydrocarbons and
natural gas or other gaseous fuels are added simultaneously
in suitable ratios to the combustion zone. Oils, for
example the carbon black oil itself, are preferably used as
liquid hydrocarbons.
The process according to DE 195 21 5,65 thus comprises using
in the combustion zone, in which the oxygen is present in
excess referred to the hydrocarbons 'that are used, liquid
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and/or gaseous hydrocarbons as fuel and thereby ensuring
that carbon black seeds are formed for example by an
insufficient residence time of the liquid hydrocarbons or
by an insufficient intermixing of the gaseous hydrocarbons
with the combustion air, which carbon seeds immediately
after their formation are brought into contact in the
reaction zone with the carbon black:material, which is used
in excess referred to the amount of oxygen, the resultant
carbon black/reaction gas mixture is cooled by spraying
water into the termination zone, and the carbon black that
is thus formed is worked up in the conventional way.
According to DE 195 21 565 the fuel contributes decisively
to the carbon black formation and is therefore hereinafter
termed primary carbon black raw material. The carbon black.
raw material that is to be mixed into the reaction zone is
accordingly termed secondary carbon ]black raw material and
contributes most quantitatively to tihe carbon black that is
formed.
The inversion carbon blacks according to DE 195 21 565
impart to carbon black mixtures a reduced rolling
resistance and a comparable wet adhesion compared to
corresponding conventional carbon blacks. Furthermore, it
has been found by AFM investigations (AFM = Atomic Force
Microscopy) that the inversion carbon blacks have a
significantly rougher surface than corresponding standard
ASTM carbon blacks and thereby enable an improved binding
of the rubber polymer to the carbon black particles (see W
Gronski et al. "NMR Relaxation - A Method Relevant for
Technical Properties of Carbon Black Filled Rubbers;
International rubber conference 1997, Nuremberg, p. 107).
The improved bonding of the rubber polymer leads to the
reduced rolling resistance.
Investigations on abrasion of rubber mixtures using
inversion carbon blacks have shown that these carbon blacks
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impart an improved abrasion resistance to the rubber
mixtures at low loads. At high loads, such as occur in the
case of lorry tyres, these rubber mixtures exhibit an
increased abrasion.
In one embodiment of the invention improved inversion
carbon blacks can be used that are characterised in
particular by a reduced abrasion at high loads.
Thus it is possible to use a furnace carbon black having
CTAB values of between 20 and 190 m20g and 24M4-DBP
absorption of between 40 and 140 ml/100 g with a
tanSo/tanS60 ratio which, on incorporation into a SSBR/BR
rubber mixture, satisfies the relationship
tanSo/tanS60 > 2.76 - 6.7 x 10-3 x CTAB
wherein the value of tan860 is always lower than the value
for ASTM carbon black having the same CTAB surface and
24M4-DBP absorption. This carbon black is accordingly
characterised by the fact that the d:istribution curve of
the particle diameters of the carbon black aggregates have
an absolute skewness of less than 400 000 nm3.
These carbon blacks that can be used according to the
invention satisfy the same requiremezlts as regards the
tanSp/tanS60 ratio as the known inversion carbon blacks,
and accordingly when incorporated into rubber mixtures
impart a reduced rolling resistance to the tyres produced
therefrom. However, they are characterised by a narrower
aggregate size distribution compared to the known inversion
carbon blacks. The mathematical quantity "absolute
skewness" known from statistics is used to describe the
aggregate size distribution (see: Lothar.Sachs:
"Statistische Auswertungsmethoden", Springer-Verlag Berlin,
3rd Edition, pp. 81 to 83). This quantity provides a
description of the shape of the aggregate size distribution
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curve that can be applied to the present problem in the
form of a restriction on the aggregate sizes by means of
maximum and minimum values.
The term "absolute skewness" is understood to be the
deviation from a symmetrical aggregate size distribution.
A skew distribution curve exists when one of the two
descending branches of the distribution curve is extended.
If the left-hand part of the curve is extended, one speaks
of negative skewness, i.e. the determination of the
absolute skewness provides values le:ss than zero. If the
right-hand section of the curve is extended, a positive
skewness exists with values greater than zero. The known
ASTM carbon blacks as well as the ir.iversion carbon blacks
and the carbon blacks according to the invention all have a
positive skewness of differing magnitudes.
It was surprisingly found that=the accepted opinion in the
prior art that a broader aggregate size distribution of the
reinforcing carbon black imparts a reduced rolling
resistance to the rubber mixtures does not have any general
validity. The improvement in the rolling resistance of
rubber mixtures that is observed with inversion carbon
blacks is obviously not dependent on the width of the
aggregate size distribution, but is essentially due to the
greater surface roughness of the inversion carbon blacks
and the associated better bonding of the rubber polymer to
the carbon black surface.
With regard to the known inversion carbon blacks with their
relatively broad aggregate size distribution, their
abrasion resistance can now be improved according to the
invention by restricting the width of the aggregate
distribution. In particular, the proportion of carbon
black aggregates with large particle diameters must be
reduced if the carbon blacks are to impart to the rubber
mixtures an improved abrasion resistance combined at the
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same time with a reduced rolling resistance. This is the
case if the absolute skewness of the aggregate size
distribution is less than 400 000, preferably less than 200
000 nm3. The absolute skewness of the inversion carbon
blacks known from DE 195 21 565 is above 400 000 nm3,
whereas the absolute skewness of standard ASTM carbon
blacks is below 100 000 nm3.
.The absolute skewness of the aggregate size distribution of
a carbon black can be determined by means of a disc
centrifuge and corresponding evaluation of the measurement
values. The carbon black sample to be investigated is
dispersed in an aqueous solution and separated in a disc
centrifuge according to its particle size: the larger the
particles, the greater their mass and the more rapidly the
carbon black particles move outwardly in the aqueous
solution as a result of the centrifugal force. The
particles traverse a light barrier by means of which the
extinction is recorded as a function of time. The
aggregate size distribution, in other words the frequency
as a function of the particle diameter, is calculated from
these data. The absolute skewness AS can be determined
from this distribution as follows:
k
,LHi(Xi -xy
AS
k
IHi
i=t
In the above expression Hi denotes the frequency with which
the particle size diameter Xi occurs.. x is the particle
size diameter of the particles whose mass corresponds to
the mean particle mass of the carbon black aggregates. x
is also calculated with the aid of the aggregate size
distribution. The summations in the above formula must be
performed in the range from 1 nm to 3 000 nm at equidistant
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intervals of in each case one nanometer. Any missing
measurement values are calculated by linear interpolation.
The inversion carbon blacks according to the invention can
5 be produced by the generic process described in DE 195 21
565. According to this process the inversion carbon black
is produced in a carbon black reactor that contains along
the reactor axis a combustion zone, a reaction zone and a
termination zone. In the combustion zone a stream of hot
10 waste gases is produced by combustion of a primary carbon
black raw material in oxygen-containing gases. This hot
gas stream is passed from the combustion zone through the
reaction zone to the termination zone. In the reaction
zone a secondary carbon black raw material is mixed in with
15 the hot waste gas. The formation of carbon black is
stopped in the termination zone by spraying in water. In
the above process oil, and oil/natural gas mixture or
'natural gas alone is used as primary carbon black raw
material. The combustion of the primary carbon black raw
material in the combustion zone is carried out in such a
way that carbon black seeds are formed, with which the
secondary carbon black raw material is brought into direct
contact.
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 that is formed has an aggregate
size distribution with an absolute skewness of less than
400 000 nm3. This can be achieved for example by
increasing the addition of combustion air, or primary and
secondary carbon black raw material.
The described process is not restricted to a specific
reactor geometry. Indeed, it can be adapted to various
types and sizes of reactors. The person skilled in the
art can effect the desired seed formation in the combustion
zone by various measures. Possible influencing factors for
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optimising the seed formation when using oil as fuel are the combustion
air/oil weight ratio, the type of fuel atomiser that is used, and the
size of the atomised oil droplets. Pure pressure atomisers (single-
substance atomiser) as well as two-substance atomisers with internal or
external mixing can be used as fuel atomisers, in which connection
compressed air, steam, hydrogen, an inert gas or also a hydrocarbon gas
can be used as atomising medium. The aforedescribed combination of a
liquid and a gaseous fuel can thus be realised for example by using the
gaseous fuel as atomising medium for the liquid fuel.
According to an aspect of the present invention there is provided a
carbon black with a STSA surface of between 20 and 180 m2/g, a 24M4-DBP
absorption of between 40 and 140 ml/100g and a specific BET surface of
between 20 and 250 m2/g and a content of 0.01 to 20 wt. % of silicon,
referred to its overall weight, wherein in rubber mixtures the carbon
black has a tan bo /tan 860 ratio greater than 3.37-0.0068 STSA, and
.wherein the carbon black is produced by a seed-induced carbon black
formation.
The invention is now illustrated in more detail with the aid of the
drawing, in which:
Fig. 1 is a longitudinal section through the reactor used to produce the
carbon blacks according to the invention.
Examples
A carbon black according to the invention is produced in the carbon
black reactor 1 illustrated in Fig. 1. This carbon black reactor 1 has
a combustion chamber 2 in which the hot waste gas for the pyrolyis of
the carbon black oil is generated by burning oil under the addition of
an excess of atmospheric oxygen. The fuel is added to the combustion
chamber through the axial burner lance 3. The burner lance can be
displaced axially in order to optimise the seed-induced formation of
carbon black.
The combustion air is added through the opening 4 in the front wall of
the combustion chamber. The combustion chamber tapers conically to the
constriction 5. After passing through the constriction the reaction gas
expands into the reaction chamber 6.
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Various positions for the injection of the carbon black oil
into the hot process gas by means of the oil lances 7 are
denoted by A, B and C. The oil lances are provided at
their head with suitable spray nozzles. At each injection
position four injectors are distributed over the
circumference of the reactor.
The combustion zone, reaction zone and termination zone,
which are important for the process according to the
invention, are denoted in Fig. 1 by the Roman numerals I to
III. They cannot be sharply differentiated from one
another. Their axial length depends on the relative
positions of the burner lance, oil lances and quenching
water lance 8.
The dimensions of the reactor that is used are given in the=
following list:
Largest diameter of the combustion 530 mm
chamber:
Length of the combustion chamber to the 1525 mm
constriction:
Length of the conical part of the 1160 mm
combustion chamber:
Diameter of the constriction: 140 mm
Length of the constriction: 230 mm
Diameter of the reaction chamber: 240 mm
Position of the oil lancesl) A: + 110 mm
B: - 150 mm
C: - 410 mm
Position of the quench water lance(s)1) 1: 1355 mm
2: 2900 mm
1) Measured from the entry to the constriction (+: after
entry -: before entry)
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All carbon blacks produced in the described reactor are
formed into beads according to known processes before their
characterisation and incorporation into the rubber
mixtures.
Natural gas and a carbon black oil with a carbon content of
91.4 wt.% and a hydrogen content of 6.1 wt.% are used as
fuel for producing the carbon blacks according to the
invention.
The reactor parameters for the production of the carbon
blacks according to the invention are listed in Table 1.
Carbon blacks Rl, R2 and R3 as well a-s the comparison carbon
black A4496 are produced. For the production, silicone oil
is admixed as silicon-containing com;pound with the carbon
black oil.
For the carbon blacks R1 to R3 according to the invention
the relevant quantities are metered so that the finished=
carbon black contains 5.6 wt.% of silicon.
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=
19
~
~C =
0 C) i oLn c- t-o -+ 'A Ln
o Ln o %D N M x .-q LO
N 1'- -;z N m .--1 M
U: N
.Se
U
ro ro
-n
ro ~ M
r-1 0 cL' r~
S2 p o 0 I 0 o c- %10 ~-+ -r V)
~ o td) C) lo N M x r-i tf)
N ('r) r-i M
~O u a N d= ~--1
~d
ro
U
O
~
rn
~ ~t' o C) t'- I o ~ I tt') ZS
O IrT o l0 M d M 9C r-f CV LI) d)
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O 4)
4-)
0
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O U
34 ~
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~ \ \ .~ .~ ro rtS
O -r-I M M \ \ ~ .-~ ,~ ~
+ .-1 tT -1 ~ U
~ ~ Z o 2 x '.G o
~-+ O c~= N
W ~ .C T3
9: 0 4-)
ri) ~+ -~ aG U ~
4) 41 U RJ rtf >,
a~ N tn (V r-1 >1 fa
E ~ ~2 ~ 'O ~
41
4-) c
~+ 0 C: 0 0 O =.-I
Q. ~ U ,A 0 ~ ~ O M
~4 s4 v -. s4 b ro
pr , ~ ro r, cro i u ~ :-~ +' , e .x
;-' b' U U
U
ro o -~ o 1-4 o ~ ca 0 0 0 ~ ,~
a~ w
v~ o~ ~ ~~ o o ~ ~ o ~ o 0
Qx ~ -11 4-- ro =~ .Q ~ 04 (1) .Q .q
4-J -1-J ro -rI f[f .". O -n D ::I l4 ~-1
a~ M s4 or- $4 O-~ r- =.~ ~J-- 0 ro ro
~ ~ 0 0 (1) U +J -=1 ~ r U U U
~ ro
~ ai ~.-'~, (1) ,-4 v ~ o (1) ~ a) o
~ ~ro 0 a) -14 ~ ~ ro a) -.~ 0 -~+ zt .~ -
c~ E-+ ro w ~. c.) E+ cn w o~C ~ ~ oa ~+ E+ E+
CA 02342928 2001-03-05
WO 00/14162 PCT/EP99/06365
, . ~
The analytical data of the produced carbon blacks are
determined according to the following Norms and are listed in
Table 2:
STSA surface: ASTM D--5816
5 DBP absorption: ASTM D-2414
24M4-DBP Absorption: ASTM D=-3493
BET surface: ASTM D=-4820
CTAB surface: ASTM D--3765
Table 2: Carbon black analytical data
Carbon black DHP 24M4-DSP Si STSA CTAB
[ml/100 ] [ml/100 97 [Kt.'C) [m2g] [m2/g]
N220 114 98 0 107 110
A4496 112 96 0 108 110
R1 103 94 5.6 110 121
R2 102 96 5.6 112 122
R3 118 91 5.6 103 113
Application example
The carbon blacks Ri, R2 and R3 as well as the comparison
carbon blacks N220 and A4496 are used to produce rubber
mixtures. Among other properties, the viscoelastic
properties of the rubber mixtures are determined.
The viscoelastic properties of the rubber mixtures reinforced
with these carbon blacks are determi:ned according to
DIN 53513. The loss factors tan8 at 0 C and at 60 C are in
particular determined. The test formulation used for the
rubber mixtures is itemised in Table 3.
,,.
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Table 3: SSBR/BR test formulation
Mixture components Contents
[phr ]
SSBR 96.0
BR 30.0
Carbon black 80.0
ZnO RS 3.0
Stearic acid 2.0
Aromatic oil 10.0
6 PPD 1.5
Wax 1.0
CBS 1.5
DPG 2.0
TMTD 0.2
Sulfur 1.5
Silane coupling reagent Si69 Arbitrary
The SSBR rubber component is a SBR copolymer polymerised in
solution, with a styrene content of 25 wt.% and a butadiene
content of 75 wt.%. The vinyl conte:nt of the butadiene is
67%. The copolymer contains 37.5 phr oil and is marketed
under the trade name Buna VSL 5025-1 by Bayer AG. Its Mooney
viscosity (ML 1+4/100 C) is about 50õ
The BR rubber component is a cis 1,4-polybutadiene (Neodym
type) with a cis 1,4- content of at least 96 wt.%, a trans
1,4-content of 2 wt.%, a 1,2-content of 1 wt.%, and a Mooney
viscosity of 44 5. This component is marketed under the
trade name Buna CB 24 by Bayer AG.
Naftolen ZD from Chemetall is used a-s aromatic oil. The PPD
R
component of the test formulation is Vulkanox 4020 and the
CBS component is Vulkaci CZ, DPG is Vulkacit D and TMTD is
,,.
CA 02342928 2001-03-05
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22
Vulkacit Thiuram, all from Bayer AG. Protector G35 from HB-
Fuller GmbH is used as wax. ZnO RS is a zinc oxide of the
firm Carl Ansperger GmbH & Co.
The carbon blacks are incorporated into the rubber mixture in
three stages corresponding to the following tabular
description:
Stage 1
Settings
Mixing unit Werner & Pfleiderer GK
1.5 N
Friction 1:1.11
Rotational speed 70 min-1
Plunger pressure 5.5 bar
Empty volume 1.6 1
Degree of -filling 0.73
Throughflow temperature 80 C
Mixing procedure
0 to 1 min Buna VSL 5025-1 + Buna CB
24
1 to 3 min Half carbon black + ZnO RS
+ stearic acid + Naftolen
ZD + optionally Si69
3 to 4 min Half carbon black,
Vulkanox4020 + Protector
G35
4 min Clean
4 to 6 min Mix and discharge
Batch temperature 150 - 160 C
Storage 24 hours at room
temperature
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Stage 2
Settings
Mixing unit As in stage 1, up to
Degree of filling 0.71
Flowthrough temperature 90 C
Mixing procedure
0 to 2 min Break up batch from stage
1
2 to 5 min Hold batch temperature of
160 C by varying
rotational speed
min Discharge
Batch temperature 160 C
Storage 4h/RT
CA 02342928 2001-03-05
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24
Stage 3
Settings
Mixing unit as in stage 1, up to
Degree of filling 0.69
Throughflow temperature 50 C
Rotational speed 40
Mixing procedure
0 to 2 min Batch frcim stage 2 +
Vulkaci CZ + Vulkacit D
and Vulka.ci Thiuram +
Sulfur
2 min Discharge and form rolled
sheets in, a laboratory
mixer (diameter 200 mm,
length 450 mm, throughflow
temperature 50 C)
For homogenisation:
Cut 3 times LH and 3 times
RH and fold, also
break up 8 times with
narrow roller gap (1 mm)
and 3 times with broad
roller gap (3.5 mm) and
then remove rolled sheet
CA 02342928 2001-03-05
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The subsequent determination of the rubber properties, i.e.
Shore hardness, tensile stress values M100 and M300, rebound
at 0 and 60 C as well as loss factor
tan8 at 0 and 60 C and the dynamic nnodulus of elasticity
5(E*) at 0 C, are all measured according to the specified
Norms. The measurement conditions for the viscoelastic
properties are summarised in Table 4.
Table 4: Determination of the viscoe:Lastic properties
10 according to DIN 53513
Vulcanisation of the test bodies.
Vulcanisation temperature 165 C
Vulcanisation duration T95+ 5 m:Ln (T95:DIN
53529)
Test body shape
Shape Cylindrical
Length 10 mm
Diameter 10 mm
Number 5
Testing machine
Type/Manufacturer 830/MTS
Type of stress Elongation
Mean force amplitude 50 N
Dynamic force amplitude 25 N
Test frequency 16 Hz
Test sequence Temper for 5 minutes then
dynamic ]Loading at 16 Hz
for 2 miriutes followed by
measurement
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26
In each case the median value of the measurements on the five
test bodies is used.
The results of the rubber investigations are listed in
Table 5. Compared to the comparison carbon black, the carbon
blacks according to the invention impart to the rubber
mixtures a reduced loss factor at 60 C and an increased loss
factor at 0 C without a coupling agent. The loss factor at
60 C can be reduced further by adding Si69 Tyres that are
produced from such rubber mixtures may therefore be expected
to have an improved wet skidding behaviour with at the same
time a reduced rolling resistance.
The dry beaded carbon black R3 leads to a further drop in
tanS 60 C compared to the wet beaded carbon black Ri.
The advantageous behaviour of the carbon blacks according to
the invention is shown graphically in Fig. 2.
In Fig. 2 the tanSo/tanS60 ratio is plotted against the STSA
surface for these carbon blacks. The two carbon blacks
according to the invention have a significantly larger tans
ratio for the same STSA surface, i.e. a steeper temperature
profile of the loss factors.
The region of the carbon blacks according to the invention
can be clearly demarcated from from that of the conventional
carbon blacks. It lies above the boundary straight line
shown in Fig. 2, which is given by the calculation
tanSp/tan86o = 3.37 -0.0068 = STSA.
CA 02342928 2001-03-05
WO 00/14162 PCT/EP99/06365
27
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