Note: Descriptions are shown in the official language in which they were submitted.
y
-1-
1
DESCRIPTION
TITLE OF THE TNVENTTON
Method for the Pyrolysis of Polymers
RELATED APPLTCATION
This application is a divisional of Canadian Applica-
tion Serial No. 2,058,992 filed April 10, 1991.
FIELD. OF THE INVENTION
This invention relates to a method for pyrolytically
decomposing a polymer to continuously produce a low molecular
weight polymer of quality in a simplified apparatus through
simple steps, and more particularly, to a method for producing
a pyrolytic wax by pyrolytically decomposing an olefin polymer
and effectively removing volatile components resulting from
the pyrolytic reaction from the reaction mixture using a
simplified apparatus whereby a pyrolytic wax of quality having
satisfactory hue and a minimal content of contaminants is
continuously produced in a stable manner for a long period.
BACKGROUND OF THE INVENTION
Heretofore, low molecular weight polymers, for
example, low molecular weight polyolefins such as polyethylene
and polypropylene have- been widely used as waxes in a variety
of applications, for example, such as pigment dispersants,
rubber processing aids, resin processing aids, additives to ink
and coating compositions, fiber treating agents, and electro-
statographic toners. In the recent years, the demand far such
low molecular weight polymers in these applications
72736-~4D
~.~~~'~9~
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is increasing and more strict requirements are imposed on
their quality.
Known methods for producing low molecular weight
polyolefins include telomerization of olefins, thermal
degradation of high molecular weight polymers, and separation
and purification of 'low molecular weight polymers by-produced
during the preparation of high molecular weight polymers.
However, the previously proposed processes based on
thermal degradation suffer from several problems in that the
IO size of reactor is increased when a tank type reactor is used
for batchwise mass production, and that control of reaction
conditions such as temperature is difficult when a tubular
reactor is used.
In the pyrolytic processes,~volatile components including
low molecular weight hydrocarbons are produced during
pyrolysis of polyolefins, and if such volatile components,
even in minor amounts, are left in the final product of
pyrolytic wax, the pyrolytic wax becomes deteriorated in
quality with respect to residual volatile content, smell,
2 0 flash point, molecular weight distribution and the like.
Further, the low molecular weight hydrocarbons can be oxidized
with air entrained with the polyolefin feed and air
incidentally admitted on the way of the process to thereby
produce oxygenated hydrocarbons which will adversely affect
2 5 the hue of the pyrolytic wax product, and the degree of
2~~~~~~
_3_
separation of such hydrocarbons varies among separating
techniques. It is thus necessary to effectively remove the
volatile components in the production process.
Moreover, since the thermal degradation processes
generally use severe reaction conditions, it is likely that
low molecular weight fractions of the resulting polyolefin
have poor hue due tothermal history and thermally deteriorated
contaminants are formed in the reactor, and consequently, a
continuous mode of production is difficult. To overcome this
problem, a method of carrying out pyrolysis in the presence of
steam-containing inert gas was proposed (Japanese Patent
Fublication No. 9368/1968). This method, however, imposes
substantial limitations on the protection of apparatus against
corrosion and the selection of apparatus material and adds
complexity to reaction operation, leaving practical problems.
SUMMARY OF THE TNVENTION
The present invention provides a method for the
pyrolysis of apolymer comprising the steps of: introducing
a reaction mixture resulting from pyrolytic reaction of a
polymer in a pyrolysis reactor into an evaporator connected
to the pyrolysis reactor at a high temperature, causing the
reaction mixture to evaporate in the evaporator while blowing
an inert gas into the evaporator, withdrawing volatile
components separated from the reaction mixture from the
evaporator, and withdrawing the reaction mixture from the
evaporator.
72736-64D
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The above-mentioned method of the present invention
is employed, in a preferred embodiment, for producing a
pyrolytic wax using_an olefin polymer as a starting polymer.
In a preferred embodiment, the pyrolysis of the
polymer may be conducted by feeding the polymer to an extruder -
where the polymer is melted, metering the molten polymer from
the extruder to a tubular pyrolysis reactor through metering
means connected to the extruder, and pyrolytically decomposing
the polymer in the tubularpyrolysis reactor to produce low
molecular weight polymers.
In another preferred embodiment, for producing a
pyrolytic wax, the pyrolysis of an olefin polymer may be
conducted in the presence.of a higher fatty acid and/or a
hydrochloric acid acceptor.
Preferably, an insert is disposed in the interior
of the evaporator for promoting separation of volatile
components from the reaction mixture in the evaporator
interior.
BRIEF DESCRIPTION OF THE DRAWTNGS
FIG. 1 is a view illustrating a pyrolysis reactor
that may be used in the method of the present invention.
FIG. 2 is a view illustrating an evaporator that
may be used in the method of the present invention.
BEST MODE FOR CARRYING OUT-_THE TNVENTTON
Now the method for the pyrolysis of polymers accord-
ing to the present invention is described in detail.
72736-64D
CA 02154799 2002-05-14
72736-64D
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The polymer pyrolysis method of the invention is
not limited to a certain particular type of polymer, but
applicable to all types of polymers as long as they are
pyrolytically decomposable. Examples of the polymer include
homopolymers or copolymers of a-olefins generally containing
2 to 20 carbon atoms such as ethylene, propylene, 1-butene,
isobutene, 1-pentene, 2-methyl-1-butene, 3-methyl-1-butene,
1-hexene, 3-methyl-1-pentene, 4-methyl-1-pentene, 1-heptene,
1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene,
1-octadecene, 1-eicosene, etc.; copolymers of these a-
olefins with monomers copolymerizable therewith; and
polymers of styrene, (meth)acrylic acid, (meth)acrylates,
vinyl acetate, etc. and all thermoplastic polymers excluding
vinyl halide monomers such as polyvinyl chloride and
polyvinylidene chloride, and any of these polymers can be
pyrolytically decomposed into corresponding low molecular
weight polymers.
Examples of the monomers copolymerizable with a-
olefins include acrylic acid, methacrylic acid, acrylates,
methacrylates, vinyl acetate, polybasic unsaturated
carboxylic acids such as malefic acid and anhydrides and
esters thereof, etc. The method of the invention is
particularly useful in the pyrolysis of olefin polymers, for
example, homopolymers of a-olefins such as polyethylene,
polypropylene, poly-1-butene, and poly-4-methyl-1-pentene
and polymers based on a-olefins into lower molecular weight
ones, thereby producing a pyrolytic wax consisting of low
molecular weight polymers. The invention is illustrated
below with respect to the preparation of pyrolytic wax.
-6-
Referring to FIG. l, there are illustrated an
extruder 1, a tubular pyrolysis reactor 2, heater means 3 for
heating the tubular pyrolysis reactor 2, and metering means 4.
72736-64D
_7_
In the apparatus, a polymer feed is supplied to the
extruder 1 from a hopper 5 connected to a feed inlet 11 of the
extruder 1, melted and milled in the extruder 1 at a
predetermined temperature, and extruded out of an extruder
outlet 12.
The extruder is'not particularly limited to a certain
type, but all types of extruders can be used, for example
single or twin screw type, as long as it can melt and extrude
r
a polymer feed..
For melting the polymer feed in the extruder, the
extruder is heated to a temperature which may be properly
selected in accordance with a particular type of polymer feed
to be melted.
For example, temperatures of about 200 to 350°C,
preferably about 270 to 330°C are used when olefin polymers
such as polyethylene and polypropylene are used as. the polymer
feed for preparing pyrolytic wax consisting of lower molecular
weight olefin polymers. .
The rate of extrusion of the polymer through the extruder
2 0 may be properly selected in accordance with the type, form
(pellet, powder or the like), quantity, and melting
temperature of the polymer feed used. The~diameter and length
of the extruder screw may be similarly selected. When olefin
polymers such as polyethylene and polypropylene are used as
2 5 the polymer feed for preparing pyrolytic wax consisting of
- ~ ~ ~1~='~~~
- . _8_
lower molecular weight olefin polymers, for example, a single
screw extruder with a screw having a length to diameter ratio
(L/D) of from 15 to 40 is operated at a heating temperature of
200 to 350°C and at a feed rate of about 10 kg/hr for D = 40
S mm.
On delivery of a polymer feed to the.extruder, it is
preferred to use an inert gas atmosphere as the atmosphere
extending from the feed inlet 11 through the extruder to the
w
tubular pyrolysis reactor to be described later in detail,
because such an atmosphere is effective for preventing
oxidation of the polymer feed, oxidation and coloring of the
resulting low molecular weight polymers, and formation of
carbonaceous contaminants. An inert gas atmosphere may be
established, for example, by passing an inert gas such as
nitrogen through the feed inlet 11 from the hopper S.
After the polymer feed is melted in the extruder 1 and
discharged from the extruder outlet 12 in this way, the molten
polymer feed is delivered to the tubular pyrolysis reactor 2
through a polymer flowpath 6.
In the practice of the present invention, midway the
flowpath 6 through which the molten polymer is delivered from
the extruder 1 to the tubular pyrolysis reactor 2, the
metering means 4 is preferably disposed for quantitatively
controlling the delivery of the molten polymer from the
2 5 extruder 1 to the tubular pyrolysis reactor 2 because the
_g_
controlled delivery ensures uniform progress of pyrolytic
reaction, succeeding in.obtaining homogeneous low molecular
weight polymers with a narrow molecular weight distribution
and therefore, in higher yields.
. The metering~means 9 may be a gear pump or screw pump,
for example, and any desired one may be selected in accordance
with the feed rate of molten polymer to be pumped, viscosity
of molten polymer, required precision of feed rate, operating
r
temperature and.pressure, and the like. Gear pumps are
preferred especially because of their ability to pump even ..
high viscosity molten polymers, precise feed rate, and
pressure increase capacity.
,. Then in the tubular pyrolysis reactor 2, the molten
polymer feed is heated by the heater means 3 around the
reactor whereby it is pyrolytically decomposed.
The tubular pyrolysis reactor, which is effective for
efficiently heating the reaction mixture passing therethrough
for pyrolytically decomposing the molten polymer, may be of
any desired structure including the single tube type, double
2 0 tube type having an inner tube for passage'of the reaction
mixture and an outer tube for passage of heating medium, and
mufti-tube type-having a plurality of reaction tubes for
passage of the reaction mixture. Preferably the tubular
pyrolysis reactor is longitudinally inclined such that its
2 S outlet 22 is at a higher level because gas components
CA 02154799 2002-02-14
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resulting from pyrolytic reaction of the polymer can be
smoothly discharged from within the pyrolytic reactor, the
pyrolytic reactor can be reduced in volume, and the generation
of carbonaceous contaminants can be suppressed.
~5 It is preferred to incline the tubular pyrolysis reactor
at an inclination angle of about 2 to about 10 degrees since
the apparatus can assume a normal arrangement.
If the tubular pyrolysis reactor is too long so that it
is disposed in a folded arrangement rather than a linear
IO arrangement, it is preferred for the above-mentioned reason to
arrange the pyrolysis reactor so as to uniformly elevate from
the inlet to the outlet.
Further preferably, a so-called static mixer, for
example, is disposed in the interior of the tubular pyrolysis
IS reactor in order to properly control the flow, agitation, and
mixing of the reaction mixture for achieving effective
pyroiysis of the polymer feed with concomitant advantages
including reduction of the necessary reaction volume of the
reactor, increased yields of the resulting low molecular
2 0 weight polymers, and minimized generation of carbonaceous
contaminants. The static mixer is commercially available as
the KENICS type from Kenics Co., USA, the SULZER type from
Sulzer A.G., Germany, SQUARE mixer from Sakura Seisakusho K.K,
Japan, HI-MIXER from Toray K.K., Japan, and T.K.-ROSS LDD
2 5 mixer from Dow Chemical Co., USA_
*Trade-mark
t
-11-
The tubular pyrolysis reactor is equipped with heater
means which is not particularly limited and may be of any
desired heating type including those based on an electric
heater, low frequency induction heating, and molten salt
heating medium. In particular, heating by an electric heater
is easy to precisely control the longitudinal temperature
distribution over the tubular pyrolysis reactor, thus
resulting in low molecular weight polymers of higher quality.
The heating temperature of the tubular pyrolysis reactor may
be properly selected in accordance with the polymer feed tb be
pyrolytically decomposed. For example, a temperature of about
350 to 450°C, preferably about 360 to 430°C is selected when
polyethylene is used as the polymer feed and a temperature is
selected in the same range when polypropylene is used.
Further, the residence time of the reaction mixture in
the tubular pyrolysis reactor, that is, pyrolytic time of the
polymer, the pressure, and the inner diameter of the tubular
pyrolysis reactor are generally about 10 minutes to 5 hours,
preferably from about 30 minutes to 3 hours, more preferably
2 0 from about 30 to 100 minutes, about 5 Torr to 50 kg/cm2G, more
preferably from about 500 Torr to 1.8 kg/cm2G, and from about
1/2 to 10 inches, preferably about 4 to 8 inches for single
and double tube type pyrolysis reactors and about 3/4 to 1-1/2
inches for mufti-tube type pyrolysis reactors, respectively.
~.~~~7~9
-12-
The reaction mixture containing low molecular weight
polymers resulting from pyrolysis is taken. out of the tubular
pyrolysis reactor 2 through the outlet 22 and further
processed in subsequent steps.
Also preferably, pyrolysis of polymers, especially
pyrolysis of olefin polymers into lower molecular weight
pyrolytic waxes is carried out in the presence of a higher
fatty acid and/or a hydrochloric acid acceptor.
Examples of the higher fatty acid used herein include
IO fatty acids having 10 or more carbon atoms such as capric
acid, lauric acid, myristic acid, palmitic acid, stearic acid,
oleic acid, 12-hydroxystearic acid, ricinoleic acid,
arachidinic acid, behenic acid, and montanic acid.
Examples of the hydrochloric~acid acceptor include metal
IS salts of higher fatty acids, epoxidized higher fatty acid
esters, hydrotalcite, and calcium oxide.
Exemplary of the metal salts of higher fatty acids are
metal salts of the above-mentioned higher fatty acids, with
exemplary metals being lithium, sodium, potassium, magnesium,
2 0 calcium, strontium, barium, zinc, cadmium, aluminum; tin, and
lead.
Examples of the epoxidized higher fatty acid ester
include epoxidized octyl stearate, etc.-
-13-
In the method of the invention, the higher fatty acids
and hydrochloric acid acceptors may be used alone or in
admixture of two or more.
Preferred inter alia are stearic acid, palmitic acid, and
12-hydroxystearic acid among the higher fatty acids and
calcium stearate, aluminum stearate, and magnesium stearate
among the hydrochloric acid acceptors.
In the method of the invention, the higher fatty acid
and/or'hydrochloric acid acceptor is generally used in an
amount of about 0.001 to 1 part by weight, preferably about
0.01 to 0.5 parts by weight per 100 parts~by weight of the
olefin polymer.
.. If desired, the method of the invention may utilize
thermal stabilizers, weathering stabilizers, surfactants,
lubricants, nucleating agents, and anti-blocking agents as
long as the benefits of the invention are not lost.
Examples of the thermal stabilizer used herein include
phenolic stabilizers and organic phosphorus stabilizers.
Exemplary of the phenolic stabilizers are 2,6-di-t-butyl-
2 0 4-methylphenol, 2,6-di-t-butyl-4-ethylphenol, 2,6-
dicyclohexyl-4-methylphenol, 2,6-diisopropyl-4-ethylphenol,
2,6-di-t-amyl-4-methylphenol, 2,6-di-t-octyl-4-n-propylphenol,
2,6-dicyclohexyl-4-n-octylphenol, 2-isopropyl-4-methyl-6-t-
butylphenol, 2-t-butyl-4-ethyl-6-t-octylphenol, 2-isobutyl-9-
2 5 ethyl-6-t-hexylphenol, 2-cyclohexyl-4-n-butyl-6-
. -14-
isopropylphenol, dl-Ct-tocopherol, t-butylhydroquinone, 2,2'-
methylenebis(4-methyl-6-t-butylphenol), 4,4'-butylidenebis(3-
methyl-6-t-butylphenol), 4,4'-thiobis(3-methyl-6-t-
butylphenol), 2,2'-thiobis(4-methyl-6-t-butylphenol), 4,4'-
S methylenebis(2,6-di-t-butylphenol), 2,2'-methylenebis[6-(1-
methylcyclohexyl)-p-cresol], 2,2'-ethylidenebis(2,4-di-t-
butylphenol), 2,2'-butylidenebis(2-t-butyl-4-methylphenol),
1,1,3-tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane,
,..
triethyleneglycol-bis[3-(3-t-butyl-5-methyl-4-
hydroxyphenyl)propionate], 1,6-hexanediol-bis[3-(3,5-di-t-
butyl-4-hydroxyphenyl)propionate], 2,2-thiodiethylenebis[3-
(3,5-di-t-butyl-4-hydroxyphenyl)propionate], N,N'-
hexamethylenebis(3,5-di-t-butyl-4-hydro~:y-hydrocinnamide),
3,5-di-t-butyl-4-hydroxybenzylpho~sphonate diethyl ester,
1,3,5-tris(2,6-dimethyl-3-hydroxy-4-t-
butylbenzyl)isocyanurate, 1,3,5-tris[(3,5-di-t-butyl-4-
hydroxyphenyl)propionyloxyethyl]isocyanurate, tris(4-t-butyl-
2,5-dimethyl-3-hydroxybenzyl)isocyanurate, 2,4-bis(n-
octylthio)-6-(4-hydroxy-3,5-di-t-butylanilino)-1,3,5-triazine,
2 0 tetrakisjmethylene-3-(3,5-di-t-butyl-4-hydroxy-
phenyl)propionate]methane, bis(3,5-di-t-butyl-4-hydroxybenzyl
ethyl phosphonate) calcium, bis(3,5-di-t-butyl-4-hydroxybenzyl
ethyl phosphonate) nickel, bis[3,3-bis(3-t-4-
hydroxyphenyl)butyric acid] glycol ester, r7,N'-bis[(3,5-di-t- -
2 S butyl-4-hydroxyphenyl)propionyl]hydrazine, 2,2'-oxamido-
' -15-
bisjethyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 2,2'-
methylenebis(4-methyl-6-t-butylphenol)terephthalate, 1,3,5-
trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene,
3,9-bas[1,1-dimethyl-2-{(3-t-butyl-4-hydroxy-5-
methylphenyl)propionyloxy}ethyl]-2,4,8,10-tetraoxaspiro[5,5]-
undecane, 2,2-bas[4-(2-(3,5-di-t-butyl-4-hydroxy-
hydrocinnamoyloxy))ethoxyphenyl]propane, and ~3-(3,5-di-t-
butyl.-4-hydroxyphenyl)propionic acid alkyl esters. Preferred
among these are.2,6-di-t-butyl-4-methylphenol,
tetrakis[methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)-
propionate]methane, and n-octadecyl-(3-(3,5-di-t-butyl-4-
hydroxyphenyl)propionate belonging to the ~3-(3,5-di-t-butyl-9-
hydroxyphenyl)propionic acid alkyl esters.
Exemplary of the organic phosphorus stabilizers are
1$ trioctyl phosphate, trilauryl phosphate, tridecyl phosphate,
octyl diphenyl phosphate, tris(2,4-di-t-butylphenyl)
phosphate, triphenyl phosphate, tris(butoxyethyl) phosphate,
tris(nonylphenyl) phosphate, distearyl pentaerythritol
diphosphite, tetra(trisdecyl)-1,1,3-tris(2-methyl-5-t-butyl-4-
2 0 hydroxyphenyl) butane diphosphite, tetra (C12_15 mixed alkyl) -
4,4'-isopropylidene diphenyl.diphosphite, tetra(tridecyl)-
4,4'-butylidenebis(3-methyl-6-t-butylphenol)diphosphite,
tris(3,5-di-t-butyl-4-hydroxyphenyl) phosphate, tris(mono-,
di- mixed nonylphenyl) phosphate, hydrogenated 4,4'-
2 5 isopropylidenediphenol polyphosphate,
-16-
bas(octylphenyl)~bis[9,4'-butylidenebis(3-methyl-6-t-
butylphenyl)]~1,6-hexanediol diphosphite, phenyl 4,4'-
isopropylidenediphenol pentaerythritol diphosphite, tris[4,4'-
isopropylidenebis(2-t-butylphenyl)] phosphate, phenyl
diisodecyl phosphate, di(nonylphenyl) pentaerythritol
diphosphite, tris(1,3-distearoylo>:yisopropyl) phosphate, 4,4'-
isopropylidenebis(2-t-butylphenol) di(nonylphenyl) phosphate,
9,10-dihydro-9-oxa-9-oxa-10-phosphaphenanthrene-10-oxide, and
bas(dialkylphenyl)pentaerythritol diphosphite esters.
The last-mentioned bas(dialkylphenyl)pentaerythritol
diphosphite esters include spiro and cage types of the
following formulae (1) and (2), respectively. Most often,
mixtures of isomers are used for economical reason because
conventional methods produce phosphate esters as an isomeric
mixture.
R'
O-P~OCH=~ ~ CHz'
/C\ /P O ~ C~l )
OCI-I=/ \OCH /_
F'
r,
1~
O OCH,
P-OCH, C OCH= p
R'
OCH=
O
R=
-17-
In the formulae, R1 and R2 are selected from alkyl groups
having 1 to 9 carbon atom's, preferably branched alkyl groups,
and are most preferably tert-butyl groups, and they are most
preferably attached to the phenyl group at 2-, 4- and 6-
positions.
Illustrative examples of the bis(dialkylphenyl)-
pentaerythritol diphosphite esters are bis(2,4-di-t-
butylphenyl)pentaerythritol diphosphite and bis(2,6-di-t-
...
butyl-4-methylphenyl)pentaerythritol diphosphite.
Also included in the organic phosphorus stabilizers are
phosphonites having a structure in which carbon is~directly
attached to phosphorus, for example, tetrakis(2,4-di-t-
butylphenyl)-4,4'-biphenylene diphosphonite.
Preferred among the above-mentioned organic phosphorus
stabilizers are bis(2,6-di-t-butyl-4-methylphenyl)-
pentaerythritol diphosphite and tetrakis(2,4-di-t-
butylphenyl)-4,4'-biphenylene diphosphonite.
In the embodiment of the invention wherein the thermal
stabilizer is used, the above-mentioned phenolic and organic
2 0 phosphorus stabilizers may be used alone or in admixture of
two or more.
When used, the amount of the thermal stabilizer is
generally about 0.1 to 30 parts by weight, preferably about
0:5 to 10 parts by weight per part by weight of the higher
2 5 fatty acid and/or hydrochloric acid acceptor.
_ 2~~=~'~~~
_~8_
In the method of the invention, the higher fatty acid
and/or hydrochloric acid acceptor and optionally used
additives are supplied to the pyrolytic reaction of olefin
polymers in any desired manner, for example, by incorporating
them in the olefin polymer feed during pelletization thereof;
by batchwise or continuously adding them to the olefin polymer
feed at the same time or separately when the olefin polymer
feed is admitted into the reactor; or by supplying an olefin
...
polymer feed commercially available as a blend previously
containing such higher fatty acid and/or hydrochloric acid
acceptor and optional additives.
The above-mentioned pyrolytic reaction in the pyrolysis
reactor yields a reaction mixture which generally contains
volatile components resulting from pyrolytic reaction. Often,
I5 the volatile components are mainly composed of hydrogen and
hydrocarbons having 1 to about 35 carbon atoms although the
exact composition varies with a particular type of olefin
polymer as the starting feed. Illustratively, the volatile
components are mainly composed of hydrocarbons having about 25
2 0 to 35 carbon atoms when the starting feed is polyethylene and
hydrocarbons having about 8 to 13 carbon atoms when the
starting feed is polypropylene. In addition to the
hydrocarbons, incidental impurities in the starting feed and
oxygenated hydrocarbons resulting from air incidentally
2 5 admitted during the process are present in minor amounts and
CA 02154799 2002-02-14
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_ -19-
if any, they can adversely affect the hue of the end product
or pyrolytic wax. It is to be noted that the presence of
oxygenated hydrocarbons is ascertained by subjecting all the
volatile components to silica gel fractionation and thin film
chromatography, and then to infrared absorption analysis
whereupon the presence of hydroxyl, carbonyl and carboxyl
groups is observed.
Illustrated in FIG. 2 are an evaporator 7, an inlet
8 for reaction mixture, located near a top, an inlet 9 for
inert gas, located near a bottom, an outlet 10 for volatile
components, located at the top, an outlet 13 for reaction
mixture located at the bottom
and an insert 14 disposed in the evaporator. A reaction
mixture resulting from pyrolytic reaction of an olefin polymer
in a pyrolysis reactor (not shown) as previously described is
admitted into the evaporator 7 through the inlet 8. The
evaporator 7 may be of any desired shape including tower,
tube, and tank shapes although a tower shaped evaporator is
especially preferred because of promcted contact of the
reaction mixture with inert gas, consistent degree of
decomposition of the olefin polymer feed, and stable operation.
The evaporator is adjusted to a high temperature of
about 250 to 430°C, preferably about 300 to 400°C because
volatile components do not condense or dissolve in the end
product o r
-20-
pyrolytic wax, because oxygenated hydrocarbons which would
otherwise cause coloring of the wax and be difficult to
subsequently separate from the wax do not dissolve in the wax
and are thus easy to separate, and because the reaction
S mixture can be treated at the high temperature as in the
pyrolysis reactor with saved energy. The pressure in the
evaporator is adjusted to about 500 Torr to 1.8 kg/cm2G,
preferably about 750 Torr to 0.5 kg/cm2G. These conditions
r
are advantageous in that any extra equipment such as a vacuum
pump and pressure control system is not required and stable
operation is facilitated by a simple process.
The volatile components separated from the reaction
mixture are withdrawn from the vapor outlet 10 and provided to
a condenser (not shown) where they are condensed into a liquid
1S to be discharged as waste oil while the remaining non-
condensible gases may be burned in order to prevent the smell
from spreading.
In the method of the invention, an inert gas is blown
into the evaporator 7 through the gas inlet 9 so as to provide
2 0 counterflow contact with the reaction mixture for assisting in
discharging the volatile components through the vapor outlet
10. The inert gases used herein include nitrogen gas, carbon
dioxide gas, steam and the like, with nitrogen gas being
preferred. The blowing rate of inert gas may be properly
2 S adjusted in accordance with the flow rate of the reaction
CA 02154799 2002-02-14
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- -21-
mixture incoming from the pyrolysis reactor, that is,
processing quantity, as well as the type of an olefin polymer
used and the degree of pyrolysis although the inert gas is
often used in an amount of about 0.1 to 20 mol, preferably
about 1 to 5 mol per kg of the reaction mixture.
For the evaporator of tower or tubular type, it is
preferably equipped with plates or a static mixer, loaded with
packings, or provided with wetted walls, because the contact
between the reaction mixture and inert gas is promoted and
more effective separation of volatile components from the
reaction mixture is achieved.
The plates used herein are not particularly limited and
their examples include bubble cap trays, uniflux trays,
perforated trays, valve trays (flexible trays, Natta*=loat
valve trays, ballast trays, etc.), cascade trays, Venturi*
trays, Kitter trays, recycling trays, jet trays, turbo grid
trays, ripple t rays, dual flow trays, baffle trays, and ring
and doughnut trays.
Included in the static mixer which is not particularly
2 0 limited are KENICS*type, SULZER type, SQUARE mixer, and T.K.-
ROSS LPD mixer.
The packings are generally formed of porcelain or
metallic materials capable of withstand high temperatures
prevailing in the evaporator. Since the shape is not
2 5 particularly limited, exemplary packings include spherical
*Trade-mark
CA 02154799 2002-02-14
72736-64D
_2?_
*
packings, ring type packings (Raschig rings, Lessing*rings,
spiral rings, cross partition rings, and pole rings), saddle
type packings (bevel saddles and interlocking saddles), spray
packings, Pana*packings, Goodloe*packings, Stedman packings,
Dicksori packings, MacMahon*packings, cannon protruded met31
packings, helix, tellerette, and perpendicular plate packings.
The wetted wall may be obtained by utilizing the inner
wall of the tower itself or providing a multi-tube structure.
Utilization of the tower itself offers the most simple tubular
structure because no insert is present in the evaporator
interior.
While a variety of inserts are mentioned above, the
method of the invention favors the use of perforated trays,
jet trays, ripple trays, dual flora trays, baffle trays, and
ring-and-doughnut trays among the plates, the above-mentioned
ones among the static mixers, spherical packings, ring
packings and saddle packings among the packings, and the
above-mentioned two structures among the wetted walls because
they are applicable to reaction mixtures which are highly
2 0 viscous and can contain contaminants and because of simple
structure.
Preferably, the quantity of inserts disposed in the
evaporator corresponds to about 2 or 3 theoretical stages in
view of the size of evaporator and separation capacity.
*Trade-mark
~~~~.~'~~9
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The reaction mixture exiting from the outlet 13 after
removal of volatile components in the evaporator is provided
to later stage steps where decomposition reaction is
terminated by cooling and contaminants are removed by
filtration. Finally the reaction mixture is cooled and
solidified into a solid pyrolytic wax.
EXAMPLE
Examples of the.present invention are given below by way
I 0 of illustration.
A polymer was pyrolytically decomposed in a system
constructed as shown in FIG. 1 by~using polypropylene having
an ultimate viscosity ['t'[] of 1.6 dl/g as measured in decalin
at 135°C as the polymer feed and operating an extruder and a
tubular pyrolysis reactor of the following specifications
under the following conditions.
Fxt ruder
2 0 Screw diameter: 39.85 mm
Cylinder diameter: 40.0 mm
Extruder temperature (at outlet): 300°C
Extrusion rate: 10.5 kg/hr.
Tubular ~yroly~is a or
2 5 Reactor tube diameter: 50 mm
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Heating temperature: 360°C and 902°C
Internal pressure: atmospheric
Residence time: 33 min.
(based on polymer feed rate)
Meter,'_nQ m_an (gear pump, 20 cc/revolution,
gear revolution: 13 rpm)
Feed rate: 10.5 kg/hr.
The resulting reaction mixture was subjected to gas-
liquid separation for removing volatile components, then
filtered and purified, obtaining low molecular weight
polymers. The low molecular weight polymers were evaluated or
measured for melt viscosity, volatile content, powder hue,
melt color, molecular weight distribution (Mw/Mn), and number
of terminal double bonds by the following methods. The
results are shown in Table 1.
a) Melt viscosity
A low molecular weight polymer sample was heated and
melted at 180°C and the melt viscosity was measured by means
of a Brookfield*viscometer.
0 b) Volatile content
A low molecular weight polymer sample, about 2 grams, was
kept for 2 hours in a constant temperature hot air dryer at
150°C and a loss of weight was considered as the volatile
content.
*Trade-mark
CA 02154799 2002-02-14
72736-64D
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c) Powder hue
A sample was ground into a powder having a mean particle
size of about 300 ~tm which was measured for hue by means of a
Hunter*Laboratory color difference meter.
d) Melt color
A sample was melted at 180°C and the color of the molten
sample was compared with a HAZEN colorimetric standard
solution using color comparison tubes.
e) Molecular weight distribution
1 0 Measurement was made by Gel Permeation Chromatography
(GPC) .
f) Number of terminal double bonds
An infrared absorption spectrum was measured whereby the
number of terminal double bonds was determined from the
characteristic absorption peak of double bond at 1640 cm'1
Table 1
Melt Volatile
Heating viscosity, content, Powder hue
2 ~ ~~ a t emp . . °C'. cep a 180°c' ~ L,' a h
1 360 2200 < 0.01 94.0 0.2 1.5
2 402 45 0.15 93.8 0.0 2.2
Melt Molecular weight Number of terminal
~ 5 color, distribution double bonds,
Example APHA (Mw/Mn1 /~ Ot'
1 50 2.7 0.5
2 75 2.5 2.6
*Trade-mark
-2 6-
Examples 3-5 & Comparative Example 1
Preparation of pyro~lytic wax was continued for 9 days by
means of a system shown in FIG. 1 by admitting a polymer feed
consisting of 100 parts by weight of polypropylene having an
ultimate viscosity [1'~] of 1.6 dl/g and an amount of the
additives) shown in Table 2 to the extruder 1 through the
inlet 11 and continuously delivering the feed to the tubular
pyrolysis reactor 2 equipped with the heater 3 through the
flocapath 6 under the~~following conditions. In Comparative '
Example 1, the operation was stopped on the second day.
Ext- ri~dPr
Screw diameter: 39.85 mm
Cylinder diameter: 40.0' mm
1 5 Extruder temperature (at outlet) : 300°C
Extrusion rate: 10.5 kg/hr.
Tubular py~7ysi~ r a o
Reactor tube diameter: 50 mm
Heating temperature: 402°C
2 0 Internal pressure: atmospheric
Residence time: 33 min.
(based on polymer feed rate)
The continuously outflowing reaction mixture was
subjected to gas-liquid separation for removing volatile
_ - -27-
components, obtaining pyrolytic wax. Samples were taken out
everyday over the process:
The pyrolytic wax sample obtained everyday was measured
for hue as in Example 1 and measured for contaminant content
by the following method. The results are shown in Table 2.
Content of _onaminant~
It was indirectly judged from the L value associated with
the colorimetric measurement of the powder. Larger the
r
contaminant content, the lower became the degree of whiteness
and hence, the L value.
-28-
O c-1M tn r-IN ~ M c-i
M O N O M O N ~'OM O M
O O1 O a1 n7
r1 r-i r-1
N tn c-IN O M r-i
N M O N O M O N O M O M
O al O O1 N
r1 i-1 .-i O
O N w-I O fl O O C N
t~ ~ O N O v~ O N O M O M
O Ol O 01 N N
7 .-i ,-i
_
~ N V' u~ r1 .-i tn M 01 N
3 O O
M O N M O N M O N n rt5
,~ ~ O 01 O 01 , n7
O
N N tn M r-1 O O
M O N O M O ~ J-~
O N M O M ~i
O 01 O 01 N ~1 C~
~ I
c-i ,-1 O
-r-1
.-i
~ M N O fl CD O M O
'1 O O U O C
' M O N ~ O ~ v' O M 7 N U
O dl p 61 N U i~.
U -i ~ G I O..
~ h
N N v~ O ~-iO u~ M o0 ~ ~ O
O '~ h
M M O N O ~ O N O M O N t~ -'~ ~ a
N 01 O 61 O ~ N 1-) O T3
'-'t '-1 '-a~ S~.
.C
O O ~ f-t O N O tn M ~tl~ U ~ 1
.--i
N ~ O N 00~ O N O M O N O .~ O I
O al O S-1
r-i
T5 9,
O N O O N OO O N N O r-f0 j Q
~
v' 1
r-t~ O N O v~ O ~ O v~ O N O ~ O ~ O 1
O 01 O ~ O c0I tn r-i
'-1 '--101 '-f N I
?~ --i
I
a a a a . .c?
~ ~ ~ ~o I
.~z ,~ s~ .sz
~
a) U N U -1~
x ,.C M
sa 5a ~ -~-1
sa a a ~ 1
a a~ ~ ' ~3
a~ .c .c U M
.c .c
3 3 g ~ a~
,..a'., ~ " +~ N c'i
Q. ~ ~ ~. N
E ~ ~ ~ s-~t
~~
2
.
U * ~ -x .
? u~ o o ~ .-1
. , +> >,
p O tn U
-.1 o m ~ , ~ TS
o -rt
~ 0 ~ cc~
O ~ -r-1
t(7 O +~
II U c~
II U U
to
~ I
O
U ~
1
<v
:a
'~ E ~C W
-.-~t U
w ~ .~ N
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o * *
+~ *
x
U
~
w
~~~~7~~~
-2 9-
Example 6
Using a series of an~extruder and a tubular pyrolysis
reactor, polypropylene having an ultimate viscosity of [1'~] of
1.6 dl/g was pyrolytically decomposed under the following
conditions.
Ex .r ~d .r
Screw diameter: 39.85 mm
Cylinder diameter: 40.0 mm
Extruder temperature (at outlet),: 300°C
Extrusion rate: 10.5 kg/hr.
TubL~ar ~yrol_vs~~ r a tar
Reactor tube diameter: 50 mm
Heating temperature.: 402°C
Internal pressure: atmospheric
IS Residence time: 33 min.
(based on polymer feed rate)
The resulting reaction mixture (pyrolysis reactor outlet
temperature: 400°C) was admitted into the evaporator connected
to the tubular pyrolysis reactor as outlined in FIG. 2 through
2 0 the inlet 8 schematically illustrated therein.
FVaT~oratnr
Size: tubular, inner diameter 2 inches,
length 1 mm
Insert: KENICS type static mixer
2 5 Temperature : 380°C
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At the same time, nitrogen gas was blown into the evaporator 7
through the gas inlet 9 at a flow rate of 350 N-liter/hr. for
evaporation. volatile components separated from the reaction
mixture were continuously withdrawn through the vapor outlet
10 and cooled in a subsequent step tnot shown). In turn, the
reaction mixture from which volatile components had been
separated was withdrawn through the outlet 13, rapidly cooled
to 200°C for completely terminating pyrolytic reaction,
filtered, and then cooled and solidified into a pyrolyLic wax.
The pyrolytic wax was measured for melt viscosity,
volatile content, powder hue, melt color, and ratio (Mw/Mn) of
weight average molecular weight (Mw) to number average
molecular weight (Mn) representative of molecular weight
distribution as in Example 1 and further evaluated or measured
1J for flash point and smell by the following methods. The
results are shown in Table 3.
Flash point
Measurement was made with a Pensky-Martens flash point
taster (closed type).
An organoleptic test used persons having a normal sense
of smell.
*Trade-mark
Y
-31-
Pyrolytic wax was obtained by the same procedure as in
Example 6 except that the reaction mixture exiting.from the
tubular pyrolysis reactor was not admitted into the evaporator
and instead, volatile components were separated by cooling to
200°C .
The pyrolytic wax was measured or evaluated for melt
viscosity, volatile content, flash point, powder hue, melt
color, ratio (Mw/Mn) of weight average molecular weight (Mw)
, to number average molecular weight (Mn) representative of .
molecular weight distribution, and smell as in Example 1 or 5.
The results are shown in Table 3.
C'.omparafi i.v xamp~
Pyrolytic wax was obtained by the same procedure as in
Example 6 except that no nitrogen gas was blown into the
evaporator.
The pyrolytic wax was measured or evaluated for melt
viscosity, volatile content, flash point, powder hue, melt
2 0 color, ratio (Mw/Mn) of weight average molecular weight (Mw)
to number average molecular weight (Mn) representative of
molecular weight distribution, and smell as in E:~ample 1 or 6.
The results are shown in Table 3.
2J
~~v~~v~
Comparative Example 4
Pyrolytic wax was obtained by the same procedure as
in Examgle 6 except that no insert was disposed in the
evaporator.
The pyrolytic wax was measured or evaluated for melt
viscosity, volatile~content, flash point, powder hue, melt
color, ratio (Mw/Mn) of weight average molecular weight (Mw)
to number average molecular weight (rin) representative of
molecular weight distribution, and smell as.in Example 1 or 6.
The results are shown in Table 3.
Table 3
Melt Volatile Flash
viscosity, content, point Powder
hue
Example c at 180C C L a b
6 45 0.15 220 93.8 0.0 2.2
CE2 30 6.0 <140 91.5 -0.1 5.0
CE3 40 2.0 150 92.5 -0.1 4.0
CE4 44 0.30 210 93.5 0.0 2.6
Melt Molecular weight
color, distribution
Example APHA tMw/Mn) Smell
6 75 2.5 none
CE2 200 3.8 strong
CE3 150 2.9 weak
CE4 100 2.6 none
INDUSTRIAL APPLICABILITY
The present invention provides a method capable of
continuously producing low molecular weight polymer of quality
by pyrolytically decomposing a polymer with a simplified
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apparatus in a simple step. The invention is of great
industrial value in practice because the polymer to which the
invention is applicable is not particularly limited and a
variety of polymers can be pyrolytically decomposed into~low
molecular weight polymers of quality.
The method of the invention is also of great
industrial value in practice when pyrolytic reaction is
carried out in the presence of a higher fatty acid and/or a
hydrochloric acid acceptor because there is obtained a
~ pyrolytic wax which is improved in quality with respect to hue
and contaminant
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-33-
content and preparation of such pyrolytic wax of quality can
be continued for a long period in a stable manner.
Further the third embodiment of the method of the
invention allows volatile components to be immediately and
effectively removed from the reaction mixture resulting from
pyrolysis of an olefin polymer, thus producing a pyrolytic wax
which is improved in quality with respect volatile content,
powder and melt hue, smell, flash point, molecular weight
distribution and the like. Since oxygenated hydrocarbons
which would largely detract from the hue of the end product or
pyrolytic wax among the volatile components, are prevented
from mixing with or dissolving in the end pyrolytic wax, there
is.obtained a pyrolytic wax having a minimal content of
oxygenated hydrocarbons and good flue.
According to the method of the invention, any desired
pyrolytic wax can be obtained depending on the heating
temperature in a tubular pyrolysis reactor, an olefin polymer
used and the like, and the pyrolytic wax is a homogeneous one
having a narrow molecular weight distribution and improved in
2 0 quality with respect to volatile content, hue, heat
resistance, flash point, smell, and thermal stability.
Consequently, the pyrolytic wax obtained by the method of the
invention finds a wide variety of applications including
usages as pigment dispersants requiring color (chromatic
2 5 color) clearness, copying machine toners requiring image
.. .
_" -34-
visibility and release property, resin modifiers for,_food and
medical agents requiring odorless and hygienic features, hot-
melt adhesives requiring heat~resistance and thermal
stability, heat resistant ink, and the like.
