Note: Descriptions are shown in the official language in which they were submitted.
PCT/EP92/02724
- 2~16~0
~-9017
MATERIAL COMPOSED OF CARBON COMPOUNDS
The invention relates to a material composed of carbon compounds
and processable with all known plastic processing machines to molded articles,
plates, panels, pipes, sheets, films etc..
Aside from the numerous, different, pure plastics, such as polyvinyl
chloride, polyethylene (low and high density), polypropylene, polystyrene,
nylons, etc., plastic-filler combinations have, in part, also for reasons of costs, ~ -
achieved special importance in the market. To cover special market
requirements, combinations of very fine-grained carbon powders, coke powders
and oil coke powders, embedded in a matrix of thermoplastic polymers, have
become known. In some cases, the very fine-grained powders of carbon, coke
or oil coke were not regarded in the usual sense as filler, but more or less
also as an integral component of the thermoplastic polymers~ which has a
decisive effect on the properties of this plastic.
A method for the procluction of plastically deformable compositions
of polyethylene and finely powdered fillers of coke, have also become known.
In said compositions, the polyethylene matrix is admixed with at least one
fourth of its weight, but preferably with the same amount or more of finely
powdered cokes in a known manner (German Auslegeschrift 1 056 607).
2 PCT/EP92/02724
21~ ~ g~O
In the plastically deformable compositions, the carbon or coke
powders did not have the material-deteriorating properties of the fillers mostly
used. Instead, they surprisingly led to improved physical properties of the
molding compound (improved tensile strength, bending tensile strength, stress-
strain and resistance to becoming brittle); the molding compounds could be
molded readily. Coke from bituminous coal~ oil or pitch proved to be
particularly suitable for filling the po]yethylene matrix. Good elastic panels
could be molded particularly from equal parts of low-ash bituminous coal
coke and polyethylene. In contrast ts~ filling the polyethylene mat~Lx with
other fillers such as slate flour, these panels showed good stability in the
bending test. At the same mL~ng ratio of slate flour to polyethylene, the ~ - `;
panels broke after only a few bending stresses.
In the known method, the coke powders are prepared by grinding
in the usual manner. Not only very fine powders (~,400 mesh cm2~, but also
powders with a coarser structure (900 mesh cm2) can be used for high-grade
molding compounds.
Cross-linking agents, lubricants and other known additives, such as
UV stabilizers, heat stabilizers, etc. can also be added to the mixtures of
polyethylenes and coke powders.
The good fusabili~ of the molded articles produced from the
known molding compounds is particularly emphasized.
3 PCT/EP92/02724
0
Molding compounds containing finely divided coke with a diameter
of less than 60 ,um have also become known. The compounds consist of
polyethylene, polypropylene, polybutylene, ethylenepropylene, ethylene-butylene
or propylene-butylene in copolymers and, ~or 100 parts of polyrner, contain
200 to 400 parts of finely divided petroleum coke, a~ least 80% of which has
an average particle size between 0.75 and 50 ,um (German Allslegeschrift
1,259,095). These moldin~ compounds are based on the realization that the
size distributiorl of the petroleum coke particles is critical for achieving
structural strengths in the end product. It vvas practically impossible to add
more than 150 to 200 parts of petroleum coke particles, the diameter of
which on the average was more than 50 ~m, to such polymers (I!). In
addition, these products did not have the necessary high impact-tension and
bending strength. In a surprising manner, it turned out that, if petroleum
coke is comminuted and particles with a particle size between 0.75 and 50
,um are mixed with the polymers, very advantageous physical properties were
achieved.
Any conventional, commercial polyolefin or copolyolefins with a
melt coefficient between about 10 and 0.2 and a molecular weight between
about 50,000 and 700,000 can be used for the production of the ~iown
rnolding compositions.
The comminution and calibration of the petroleum coke before it
is used in the known molding compositions can be attained by grinding in a
4 PCT/EP92/02724
2 ~
ball mill, rod mill, hammer mill, by tossing the coke particles by blowing with
steam or air against a surface, by the centrifugal action of rotor wings
(Pallmann pulverizing apparatus), by ultrasound oscillations or by the use of
steel rollers Iying opposi~e one another at a distance of 0.0254 cm or less.
Since the hardness of oil coke, particularly if the ash contçnt is
. relatively high, can be appreciable, for example, 7.5 to 8 on the Moh's
hardness scale, a comminution of ~he oil coke of one of the aforen entioned
~pes leads to rapid wear of the comminuting equipment and consequently to
metal, iron or steel residues in the milled material, which either must be
removed laboriously and cost intensively or leads to properties of the molding
compounds, which are not acceptable in all areas of application.
A method has also become lcnown for. producing specially ground ~ ~ :
carbons as fillers for plastics. For this method a bituminous coal, such as ~ :
anthracite, is comminuted in a nonoxidizing atmosphere in such a manner,
that the average particles sizes are not more than 2.5 ,um and so that, in
particular, the particle size distribution is such, that at least 90% of the
particles are smaller than S ,um (&erman Offenlegungschrift 1 592 914).
These known ~orms of carbon are generally obtained by
comminuting or grinding conventional carbons, preferably in autogenous
comminuting mills. In particular, mills working with flow agents, which are
ge~erally known under the name of "hurricane mills" are used. These.mills
PCT/EP92/02724
~1~16~0
contain no air or no free oxygen during the comminution, as otherwise the
flow agent would have a disadvantageous effect on the ground carbons, which
are used, for example, in rubber and other polymers. The nonoxidizing
atmosphere for the known milling of carbons is necessary because, during the
disintegration of coke, particles of very high reactivity are formed, possibly
because of the rupturing of bonds. This can occur during the grinding with
the consequence, that such ruptured bonds react with oxygen from the air and
thereby lose their reactivity. If, however, sufficient protection is provided for
the ruptured bonds, these bonds can react with other components of the
polymers and lead to polyrners or rubbers with physical properties, which are
excellent.
The effect of oxygen is prevented during comminution by an inert
gas atmosphere and during classiiiying, on the other hand, by spraying the
particles with about 0.1 to 1% zinc stearate, based on the weight of the
product. The particles are coated individually with zinc stearate, until a
relatively uniform coating is obtained. The coatiIlg melts, when the coke
powder, so protected, is added to the natural rubber, vulcanizing it.
Aside from being used as an additive for natural rubber, the coke,
prepared by the known method, can also be used as a filler ~or conventional
plastics.
6 PCT/EP92/02724
21~16~ 0
Further methods for the preparation of coke mixtures, such as that
of the German Offenlegungsschrift 1 719 517, have become known. These
methods result in a high surface enlargement of the milled particles, which
are used for admixing with plastic. Plastics for the manufacture of pipes,
panels, plates, disks and other molded objects by extrusion and injection
molding, in which the plastic, due to the admixture of electrically conducting
carbon materials, has an~istatic properties (German Offenlegungsschrift 2 017
41û), as well as modified plastics, which contain oleophilic graphite, which is
prepared by grinding a natural or synthetic graphite in an organic liquid with
the exclusion of air.
All of these materials have the disadvantage that the preparation
of the carbon or the coke is expensive, as a result of which the price per unit
weight of the finished material increases to such an extent, that with all
advantages, which these material have, their use has remained within narrow
limits because of the costs.
The more or less slightly developed abili~ of these plastics or
plastic-filler combinations to be recycled is a further disability. Rather, with
the previously known plastic-filler combinations, there are usually appreciable
losses in quality, with the consequence that already recycled plastics can
frequently be used further only in conjunction with primary plastics or, if not
mixed with these, can be used only for the manufacture of inferior molded
articles.
,
", .
7 PCT/EP92/02724
21~16aO
In addition, considerable problems arise out of the fact that such
materials can be eliminated and, particularly, disposed of only at great
expense, if at all. The materials hardly decompose, for example, in garbage
dumps and evolve pollutants in the waste gases when combusted. These
disadvan~ages become all the more important, because the use of plastics is
increasing steadily. For example, in the year 1990, far in excess of 9 million
tons of plastics were processed in the Federal ~epublic of Germany alone,
without taking into consideration the newly additional East German states, but
including the chemical fiber. At the official growth rate of 8% per year of
the plastic market, the consumption of plastic would grow in the area of the
former Federal Republic of Germany to 19 million tons per year by the year
2000. This alone could confront the realization, for example, of the targets of
the Packaging Regulation adopted by the Government, with insoluble tasks
already in 1996, since the disposal of scrap plastics from industry and
households is unsolved until now and the recycling rate in West Germany is
only about 7%. As against this, the recycling rates of aluminum, pape~r and
glass are 38.3~o, 40.7% and 43.2% respectively. If plastics, which are not
biologically degradable, would simply be deposited on garbage dumps, dumps
would result which, in the long run, would have an uncertain fate and, as a
result of material conversion, would emit into the air and water.
Buming most plastic.s, for example, in garbage incinerators, would
also create appreciable difficulties because the installations would be burdened
. . .
8 PCT/EPg2/02724
~101~
by large amounts of ash due to the fillers and ~he flue gases would be
contamina~ed by toxic dioxins or other material formed during the combustion.
Such toxicologically critical groups of materials are released during the
combustion when the temperature passes through regions between 250C and
400C and reach the atmosphere jD this way in the vicinity of the earth by
way of the flue gas. Because of such fears, it is politically impossible to
construct special garbage incinerators for toxic waste at the present time.
Particularly cost intensive is the sorting by type of packaging
materia]s and plastic household objects, such as ballpoint pens, films, sheets,
containers, canisters, toys and synthetic textiles from mixed household garbage.
All of these plastics consist of primary materials or secondary materials, that
is, those plastics, which have already been recycled at least once. Because of
exposure to heat and radiation, as well as due to the melting and
regranulation in the recycling process, these plastics show appreciable losses in
quality compared to primary plastics. If, as a result of deficient separating
possibilities, plastics are not recycled by type (polyethylene, polypropylene,
polystyrene, polycarbonate, polyester, nylon, etc.) or primary plastics and
secondary plastics are recycled together or if plastics, particularly in their first
use, contain pigments, stabilizers, plasticizers or other additives, there are
additional quality losses, which prevent reuse of such plastics for economic
reasons. There~ore only a small portion of plastics turning up are recycled.
Recycling without loss in quality worth mentioning results only if the plastics
in question are recycled by type. However, even these pure-type plastics
9 PCT/EP92/02724
2101~0
differ largely depending on the type of filler or pigment used, so that, for this
reason, quality losses are unavoidable.
Even with the support of the "dual system", which is being built up,
for example, in Germany, it will be difficult, in the future, to lay hold of even
only 8 to 10% of the total primary plastics production largely in pure form
(such as polyethylene), a further 10 tn 13%1argely of similar types and about
10% mixed and impure.
Because of their necessarily reduced quality, their deficient design
and fimsh and because of their excessively bigh price, recycled plastics do no~
fin~l the neeessary market acceptance. In addition, there are legal standards
and DIN regulations, which greatly limit the use of secondary plastics.
On the basis of all of the above, it can be assumed that the high
costs of collecting, separating, working up, granulating and transporting, as
well as the new selling costs will limit the recycling of plastics to a minimum.
In addition, as a result of the obligation of the manufacturer or the
merchant to take back the plastic products that have served their purpose,
the market prices for primary plastics will rise between 25 and 30%, in order
to cover the considerable charges arising from collecting and classifying and
the costs, which result therefrom for the disposal of these materials.
3'CT/EP~2/02724
:~` 21~1650
The previous way of re~cling plastics will result sooner or later in
a mountain of former recycled plastics, which can no longer be recycled and
are also no longer usable for thermal destruction.
Asi against this, the object of the invention is to provide materials,
which can be produced inexpensively and can be processed on almost all
plasitics processing mac~ines and ins~allations, are composed of carbon
compolmds, which not only have good mechanical, physical and processing
properties comparable with the properties of known materials composed of
carbon compounds, but also, in addition, can be reused without devaluating
quality losses and disposed of without problems and without contaminating the
environment.
It has now been found that this objective can be accomplished
simply owing to the fact that the carbo~ compounds, aside from low-polluting
and low-ash bituminous coal, bituminous coal coke or oil coke, which has
been disintegrated at very high impact speeds to very fine carbon powders,
also contain thermoplastic polymers of the hydrocarbon group, which are
combined chemically with the very fine particles of the carbon powder, due to
the bonding energy released by the high-speed impact comminution in the
closed system of material processing installations, without further addi~ives to
a material, which can be recycled repeatedly without any devaluating loss in
quality and with a calorific value of more than 37,sob kJ/kg.
1 1 l'CT/EP92/02724
~1~16~0
With the invention, it is possible to furnish solid fuels, such as
carbon in the form of coke, coal, bituminous coal, oil coke and particularly
anthracite, before they are used as thermal energy (combustion) for numerous
novel and different possible uses, provided that these fuels contain little in the
way of pollutants and ash and have been processed at very high impact
speeds to very finely grained carbon powders. It was found that these very
~me particles of the c~rbon powders, during their high-speed impact
comminution in a closed system of material processing plants, release bonding
energies, as a result of which they bond chemically without further additives
to thermoplas~ic polymers to form materials. These materials and the
products manufactured from them have physical and technological properties,
which are appreciably improve~ over those of previously used polymers. The
surprising thing is, however, that these new materials can be recycled
repeatedly without devaluating losses in quality and finally converted with a
high calorific value by combustion into thermal energy without burdening the
combustion chambers or the flue gases resulting from the combustion ~,vith
pollutants beyond the permissible measure. rhe new materials being cycled
represent an environmentally friendly, appreciable energy reserve.
. ~ , . . ..
Thanks to the invention, the conversion of this energy reserve into
thermal energy can still take place, even after repeated rec~cling, in an
environmentally friendly and almost cost-neutral manner, without resorting to
garbage dumps or gar~age incinerators.
12 PCT/EP92/02724
~lS~O
Basically, the fuels can be comminuted in comminuting installations
suitable for high-speed impact comminution. It has, however, turned out that
a particularly advantageous and, above all, economic and inexpensive
comminution is achieved in turbulent flow disintegrators of the German patent
38 02 260 I)2. Such turbulent flow disintegrators operate with
countercurrently rotating, radially consecutive blade rings in such a manner,
that zones of turbulence are formed in the annular spaces between the blade
rings. The fuel particles strike one another at high speed in these zones of
turbulence without any interfering metal abrasion taking place. As it passes
through the radially consecutive zones of turbulence, each fuel particle, on the
average, experiences eight collisions with other particles. Impact velocities
close to the velocity of sound occur particularly in the last turbulence zone
between the last but one and the outermost blade rings, but also beyond this
zone.
The comminuting time within a turbulent flow disintegrator has
been measured to be 0.5 seconds. Compared to the comminuting time of
fuels, for example, in a ball mill or in other comminuting equipment, this time
is exceptionally short. As a result, not only is the comminution more
inexpensive than in other mills, but there is also a significant chemical
engineering advantage, since the bond energies released (predominantly ions
or electrons? cannot be dissipated so quickly over the rnetal construction of
the preparation installation into the ground.
13 PCT/EP92/0272~1
2101~a~
7`he material comminution in a turbulent flow disintegrator of the
aforementioned type thus has a further, significant advantage over other types
of comminution. As a result of the high impact velocities during the
comminution and particularly because the fuel particles impact on one
another and are not flung by centrifugal forces against a wall or the like and
are not consolidated at the surface by the balls in a ball mill, high bond
energies are released and largely maintained. When the fuel particles are
brought together with the hydrocarbon of the polymers in the extruder, these
bond energies are available alrnost completely for improving the quality of the
inventive materials. Contrary to the situation in the case of comminution by
shearing or tearing as disclosed, for example, in the German
Offenlegungsschrift 1 592 914, the weakest bond energies disintegrate first in
the high-speed impact comminution described. Only the weakest bond
energies of the fuel particles are released during ~he high-speed impact
comminution described, so that the fuel disintegrates into many stable
microparticles. What is thus formed as a micropowder has strong bonding
quality in its particles and enters into chemical bonds with the respective
polymer, which lead to the outstanding properties of the new material.
The high-speed impact comminution supplies excitation energy for
the hydrogen ions/electrons and the carbon electrons, which thus can have
free orbitals and also a higher energy level. This process is temperature
dependent. Pursuant to the invention therefore, the high-speed impact
comminution and also the mrxing of the activated carbon powder with the
14 1'CT/E3~92l0272a~
2l0l6~a
polymers is carried out in the extruder while supplying heat and partly in an
inert gas atmosphere, in order to prevent interaction between the bond
energies released and the o~ygen of the air. In addition, by supplying heat,
the reactivity of the carbon powders is increased before and in the extruder.
It was found that the best processing temperature of the carbon powders with
the polymers to a bonded material in the extruder lies between 240 and
300C. If this temperature is loweFed greatly, the high-grade material
properties of the new materials, including the good electrical conductivity, are
not attained.
The above-described preparation method with high-speed impact
comminution at almost the speed of sound leads in the case of anthracite to
a surface change with formation of pores less than 3.6 ,um in diameter in the
particle structure, with the resul~ that the surface area of the particles is
greater by a factor of more than 10 than that of anthracite prepared in ball
mills or vibration grinding mills (particle size screened off at 40 ,um). The
surface area at high-speed impact comminution was 28 m2/g instead of 2.6
m2/g and 2.8 m2/g for preparations with the ball mill or the vibration grinding
mill. The pores are formed owing to the fact that, during the high-speed
impact comminution near the sound barrier, temperatures up to about 300C
result briefly during the impact processes and, as a result, volatile components
of the anthracite are set free. Particular attention must therefore be paid to ~;
ensuring that these micropores make the anthracite hygroscopic (with a water ~;
absorption up to 6%, partly also from the surrounding air). The ability of
PCT/EP92/02724
21016~0
liquids to penetrate into these micropores and to entrench themselves there is
due to the molecular StruGture of the respective liquid. H+ ions or at least
H+ dipoles occupy appropriate places in the pores, so that OH- ions or OH-
dipoles can no longer be adsorbed there (this process is time dependent). A
change in the storage time of the anthracite before it is processed further in
the extruder correspondingly reduces the absorbability of molecules with an
OH- group. This process plays an important ro]e in bringing together carbon
powders, preferably anthracite powder~ with the polymers by extrusion and
must therefore be taken into consideration.
From the "preference" of, for example, the disintegrated anthracite
for H+ ions, which can be demonstrated by absorption experimen~s with water
or phenol, it can be concluded that, in the case of the inventive material, the `
hydrogen of the -CH2-CH2- chains of the polymer combines chemically with
the carbon chains of the anthracite -C-(:~-C-.
Pursuant to the invention, polyethylenes or polypropylenes, which
are as pure as possible are used as`polymers. They are melted at 240 to ~ ;~
300C, for example, m a double-screw extruder with screws rotating in the
same direction. The prepared carbon powders, preferably the vely finely ~ ~ ~
particulate, disintegrated anthracite heated to 200 to 300C, is metered ~;;
continuously into the melt. The anthracite proportion varies from granulate
type to granulate type between 40 - 80 M %. The resulting extrudate is
granulated, so that it remains storable without reduction in quality and can be
:
16 PCT/EP92/02724
2 1 ~ 0
processed on practically all known plastic processing machines or installations
into marketable products (such as molded articles, plates, panels, pipes,
sheets, films and, because of its resistance to chemicals and UV, also into
containers, tanks, vats and canisters for disposing of chemical waste and
hazardous waste).
Anthracite, with approximately the following analytical values and
low in ash and sulfur, is particular suitable as carbon powder prepared in
finely particulate form:
Carbon Content above 94%
Ash Content below 3.5%
Sulfur Content below 1.5%
Volatile Components below 2.5%
Calorific Value above 35,500 kJ/kg
This material consists to the extent of 70% by weight of powdered
anthracite and 30% by weight of polyethylene.
Pursuant to the invention, this anthracite powder, prepared in : ~
finely particulate form, combines chemically with the polyethylene to form a ~;
new material. In comparison with polyethylene, the new material has the
following performance values:
17 PC'r/EP92/02724
21~1~aO
Value DIN P~lyethylene New Material
(Standard rype)
Tensile Strength 53 455 25 N/mm2 35 N/mm2
Stress-strain 53 455 6% 2%
Bending Strength 53 452 18 N/mm2 44 N/mm2
Modulus of 53 457 840 N/mmZ 246û N/mm2
IElasticity
Impact Strength 53 453 without without
breakage breakage
Softening ISO 306 78C 107C
Temperature Vicat
Electrical 2x10/4 Q 1X106 Q
Conductivity
Cold Impact Strength without without
breakage breakage
Further data and comparisons can be taken from the graphical
representations.
These performance data are better than the performance data of
most materials, which have become known through the state of the art. In
weathering tests, the tensile strength of the new material does not decrease as
much as it does in the case of pure polyethylene. The impact strength is `
fully retained even after 500 hours.
Pursuant to the invention, the very finely particulate carbon
powders are disintegrated and screened to particle sizes between 10 ,um and
90 ,um, depending on the use to which the material is to be put. They
constitute 20 to 70% by weight of the new material, the difference from
100% by weight consisting of polymers.
18 PCT/~EP92/02724
~ 1 6 ~ 0
Particularly important is the fact that the calorific value of the new
material lies above that of conventional fuels, as is shown by the following
table:
MateFial Calorific ~Inlue
Bituminous coal 21- 33 lcJ/g
Natural Gas 37 kJ/g
New Material up to 38.5 kJ/g
(depending on the proportion by
weight of the polymers)
Consequently, the new material can be disposed of without
difficulties, even after repeated recyclings, by combustion in power plants,
cement plants, lime plants, etc. or in garbage incinerators for obtaining
eIlvironment-friendly thermal energy. Previously, it was necessary to pay an
amount of up to DM 400.00 per ton for burning plastics in special garbage ;~
incinerators. In contrast to this, payment of the high calorific value can be
made to the supplier of power plants, cement plants, lime plants, etc.!
Because of the high carbon content of more than 90%, such material waste ;s ;
also of interest to the s~eel industry ~or improving steel qualities! There is no
contamination of the furnace installations and no burdening of the flue gases
with pollutants beyond the permissible amounts.
Processable special qualities of material granulates or material
powders with high strength, high temperature resistance and high elect~ical
conductivity result when the materials are prepared in an inert gas
19 PCT/EPg2/02724
~`" 2101~0
atmosphere in a system, which is completely closed off from the surrounding
air or in an inert gas atmosphere with a residual oxygen content of up to 3%
and, until they are processed further, are stored in a gas-tigh~ container out
of contact with the air.
Low-polluting disposal is achieved owing to the fact that the
thermoplastic polymers added contain, as additives, stabilizers, electrical
conductors s~r pigments, only those materials which, upon combustion of the
material or of the products produced therefrom, do not burden the flue gas
with substances with toxic activity or with pollutants beyond the permissible
extent.
It has now been found that a material, which consists, for example, ;
of 70% by weight of powdered anthracite and 30% by weight of polyethylene,
is not attacked by chemical reagents and is resistant to UV at normal
environmental temperatures up to 37C (test time of 2000 hours, anthracite
powder with an upper particle limit of 60 ,um).
:.
By cross-linking the inventive material with an electron accelerator,
the s~rength and thermal load~carrying abili~ of the products produced
therefrom are increased appreciably further (for example, in the case of pipes,
containers, vats, molded articles, etc.). The thermoplastic properties, however,
decrease with the increasing degree of cross-linking. Extensively cross-linked
materials are no longer suitable for recycling, but do not lose their important
.~. ~ . . - . . - , .
.: . . :
- ; 20 PCT/EP92/02724
2101~0
advantages for an environmentally friendly disposal as a low polluting fuel
with a high calorific value.
Important properties of the new materials are described in the
following by means of graphic representations, taking parameters into
consideration.
:~ :
Figure 1 shows how the tensile strength (= s~ress at the yield
point) of the inventive materials as the proportion of anthracite with a ~ -
particle slze of 60 ,um increases. Pure polyethylene (PE) serves as a
comparison basis with 100%. The analytical values of the anthracite ;
correspond to those, which are characterized in claim 2. As the particle size ;
of the anthracite powder becomes smaller, the tensile strength increases only
slightly.
Figure 2 shows the increase in strength of the new materials as a
function of the proportion by weight of anthracite. Pure polyethylene with
25.2 N/mm2 and pure polypropylene with 32.5 N/mm2 serve as a basis. The
anthracite once again has a particle size of 60 ~m. It is interesting that a
material with polyethylene as a polymer component has a clearly higher
tensile strength than a material that contains polypropylene as polymer
component. Evidently, the anthracite preipared pursuant to the invention
reacts more stably with polyethylene than with polypropylene. In the case of
SUBSTl'rUTE PAr~E
21 PC l/EP92/02724
2 1 ~
both materials, the tensile strength increases differently with increasing
anthracite contents.
Figure 3 shows the impact strength of the new materials as :
function of different degrees of fineness of the anthracite in the material.
Basically, if the particle size of the anthracite powder is 90 ,um, the impact
strength is fully maintained up to an anthracite content of 30% by ~eight.
As the anthracite content increases, the impact strength decreases and reaches
a lower value of 20% at an anthracite content of 60~o by we;ght. The
materials, in which the anthracite powder has particle sizes of 60 ,um, 30 ,um
and 10 ,~rn behave similarly. If the impact strength of new material with a
high anthracite content is important, it is advisable to select smaller particle ~ ;~
sizes.
According to Pigure 4, the impact strength of the inventive
materials is not changed by weathering. On the other hand, polyethylene
becomes brittle already after 250 hours. In industry, this disadvantage of
polyethylene usually is compensated for by the addition of stabilizers. The
inventive material makes do without these additives.
According to Figure 5, the proportion by weight of anthracite also
has an effect on the electrical conductivity, which reaches a maximum at 60%
by weight of anthracite (this corresponds to a minimum in the surface
resistance).
SUBSTITUTE P~GE
- 22 PC'r/EP92/V2724
-:: 21016~0
According to Figure 6, the tensile strength of the material is
retained practically completely after repeated recycling. The stress-strain
increases. Only after the third recycling does the impact strength of the
material ~all to S0%. The notched impact strength also decreases with the
number of recycling cycles. For many products however, both values are still
completely adequate after five recyclings. The softening temperature
decreases only slightly. The calorific value of the ne~ materials remains
unchanged, lmaffected by the recycling cycles.
As shown by Figure 7, the proportion by weight of anthracite also
affects the softening temperature of the new materials. Startîng from a
softening temperature of 78C of the pure polyethylene, which is given a
value of 100%, the softening temperature of the material with 70% by weight
of anthracite having a particle size of 60 ,um is at about 137% that is, about
170C.
SUBSTITUTE rAGE
