Note: Descriptions are shown in the official language in which they were submitted.
~9~6
The present invention relates to a process for the pre-
paration of fibrids of olefinically unsaturated compounds and to
the fibrids obtained thereby. It is well known that the ethyle-
ne polymerization is carried out either at high at lower pressures
or at room pressure.
In the first case low density polymer is obtained while
in the second case, being the reaction carried out in presence of
coordinate catalytic complexes, a higher densit~ polymer is obtained.
It is also known that alphaolefin polymers can advantageously be
transformed into fibres.
For instance fibers can be obtained by dissolving the
polymer in a suitable solvent at h;gh temperature and passing the
solution through suitable spinnerets.
In this way continuous filaments are obtained which can
be easily transformed into staple or other analogous material which
finds large use in the textile industry.
Particularly as to polyethylene or polypropylene, very
advantageous has been the use of the melt spinning.
It has been moreover found in recent years that polyal-
phaolefines can be used in the fibrids field for a partial or to-
tal substitution of the wood pulp for the manufacture of paper.
By fibrid we mean in general a hydrid morphology between a film
and a fiber. By such a term we refer to an aggregation state of
the polymeric material having a very high surface area per unit
of weight; we could for instance def~ne the fibrids as colloids
in dry state formed by filaments and small strips, since the spe
cific areas are of the same magnitude order as the ones measured
in the case of typical colloidal suspensions as silica, aluminium
or black carbon.
The preparation of fibrids via polymer is also known,
being for instance disclosed in U.S. patents No. 2,999,788 issued '~
on September 12, 1961 and assigned to E.I. du Pont de Nemours and
Co., Wilmington, Delaware; No. 2,988,782 issued on June 20, 1961;
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- ~49~
and No. 2,708,617 issued on May 17, 1955 to the same assignee.
According to the mentioned disclosure, the process is carried
out in two steps, in the first of which the polymeric material
is prepared and separated from the reaction medium in form of
powder. In a second step the polymer, in form of chips, is
heated above the melting point and then extruded through suitable
spinnerets.
The second step can be carried out also by dissolving
the polymer in a suitable solvent and from the collected solu
tion, fibrids are obtained by cooling or by quick evaporation of
the solvent.
The above mentioned process presents drawbacks as to,
for instance, the number of intermediate steps necessary for its
realization and the fact that the polymer molecular weight can-
not overcome a certain limit beyond which it is impossible to
work since the viscosity of the solution or melted polymer becomes
too high.
In more recent years, processes were developed for
producing polyethylene fibrids directly during polymerization,
said processes being the ones according to which ethylene is po-
lymerized in presence of anionic co-ordinate catalysts of the
Ziegler-Natta type; the reaction is carried out at pressures
higher than the atmospheric pressure and with a stirring which
provides a high shear stress. We have found that it is possible
to obtain fibrids of olefinically unsaturated compounds directly
during polymerization without application of shear stress, but
simply with a normal stirring, sufficient to remove the heat of
polymerization by heat exchange through the reactor walls, provi-
ding that the conditions are such that there is a high velocity
of formation of the solid polymer per unit of volume and a high
velocity of crystallization of the polymer which precipitates in
the reaction medium.
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The process for the preparatlon of fibrids according
to the present invention is carried out by polymerizing at least
one unsaturated compound containing at least one olefinic
unsaturation in presence of a catalytic system constituted by a
~itanium or vanadium compound and by an aluminium compound, the
alwnin.Lum/titanium or vanadium ratio ranging from 1 to 200,
preferably between 1 to 60 and the total amount of the titanium
or vanadium compound ranging from 0.001 to 5 mmoles/1, preferably
between 0.002 to 0.15 mmoles/l, in a solvent selected among those
having good solvent power for the monomer and low solvent
power for the polymer which forms.
In accordance with the present invention, the
catalytic sys-tem is selected in the group consisting of
(a) titanium tetrachloride, as catalyst, and a polyiminoalane,
containing repeating units of the type (AlH-NR) wherein R is an
aryl, alkyl or cycloalkyl radical, as co-catalyst the reaction
being carried out at a temperature comprised between ~15C and
-20C; (b) vanadium halide or oxyhalide as catalyst, and a poly-
minoalane containing repeating units of the type (AlH-NR) wherein
R is an aryl, alkyl or cycloalkyl radical, as co-catalyst, the
reaction being carried out at a temperature comprised between
-15 C and ~90C; and~(c) vanadium halide or oxyhalide as
catalyst, and an aluminium compound of the general formula
Al RXX3 x wherein R is an aryl, alkyl or cycloalkyl radical, X is
a hydrocarbon radical, hydrogen or halogen atom, and x is a whole
or fractional number between 0 and 3, as co-catalyst, the reaction
being carried out at a temperature comprised between 40C and
90C .
The catalyst can be preformed
9~36
or formed in situ.
It has been found -that in any case it is preferable
to -ollow the second system (formation in situ) for obtaining a
better fibrids structure. The polymerization temperature ranges
from low temperatures up to the room temperature and also to
temperatures higher than room temperature and also to temperatu-
res higher than room temperature; particularly, it ijs possible
to work at a temperature ranging from ~30C to 100C and the
temperature is chosen in function of the used catalytic couple. ~ ;
By a means of a series of tests, wherein the monomer
pressure, the stirring method, the reaction liquid, the catalyst
concentration and type were maintained constant and only the
polymerization temperature was changed, we surprisingly found
that the formation of fibrids well separated from each other
and from the reaction medium occurs within a temperature critical
zone.
Such a critical zone variable according to the reaction
medium and particularly variable according to the catalytic
system, determinates a better separation of the fibrids from the
reaction medium, or, in o-ther words, these fibrids separate with
a less amount of englobed liquid. It has been found that with the
catalytic system based on vanadium halides and/or oxyhalides and
aluminium alkyl hadlides, such critical range is tl5 C to -~0C,
while when the catalytic complex TiC14 +polyiminoalane (PIA) is
used, such range is-t40C to ~90C.
What it was said above can be explained by admitting
that in the critical temperature zone there is the best equili-
brium between -the polymerization and the cristalliza-tion. This
is a very interesting feature of the process according to the
present invention which makes the same very easy to be carried
out because it is possible to control the temperature much
better and to proportion the catalyst amount.
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1~4~96
It has been found that pressure is not an essen-tial
parameter for carrying out the process according to the present
invention. In fact it is possible to work suitably at room
pressure but the use of higher or higher or slightly lower
pressures is not prejudicial to the formation of fibrids.
The polymerization reaction according to the invention
is carried out in a solvent which can be selected within
a large range of classes: generally an aliphatic, aromatic,
cycloaliphatic hydrocarbon or an halogenated hydrocarbon is used.
However, the solvent is in any case an important parame-ter of
the process according to the invention when one considers
that, by using a reaction liquid scarcely solvent for the poly-
mer, it i9 possible to obtain fibrids well separated from each
other also with a very high polymerization velocity because
temporaneously a high crystallization velocity is permitted.
In the present description reference is made
essentially to the production of fibrids, obtained from ethylene,
because of the specific interest of the applicant for the same,
but it is obvious that what said for ethylene can be easily
applied for r
1al4~L9~
other olefine monomers or to mixture of ~ifferent olefines or to
mixture of olefines and diole~ines9 for obtaining always bo~ning
polymer fibrids according to the most general meani.ng ~lich is
accepted for this type of morphology.
The following examples will be still limited to the
production of ~ibrids of polyethylene and of copolymers ethylene-
butadiene bu-t it will be easy for a skilled in the art to obtain
fibxids starting from whatsoever olefinic mo.nomer on the basis of
what abovesaid and without going out the scope of the inventio.n~ -
Examples 1 - 4
To a flange reactor made of glass having a capacity o~
2 l, provided with thermostatic jacket, thermo.nomer, ethylene .
feeding tube, stirrer9 condenser, tap for venting the gases and
fun.nel for feeding the reagents, we fed, a~ter havi.ng removed
all traces of moisture and oxygen, 1 1 of anhydrous heptane.
~he raactor was thermostated at the temperatuLe select-
ed for the test and at room pressure, under stirring the reaction
medium was saturated with ethylene fed for 20 minutes at .a rate
of 120 l/h. The the necessary quantity of PIA (polyimino alane)
was diluted.i.n the ~eedi.ng fu~nel in 25 cc o~ anhydrous heptane,
said PIA being immediately fed to the reactor, taki.ng caxe of
wa~hing the reactor with 25 cc o~ solvent. The operatio.ns ~or
TiCl4 were analogous.
Polymerization started quickly and because of i-ts e~o-
thermic character there was a tempexature increase which was li-
mited by means of the thermostatic fluid. After a prefixed time
the polymerizatlon ~ras stopped by disactivating the cata.lytic
complex with 15 cc o~ methyl.alcohol. The polyethylene fibrids
were discharged from the reactor9 separated by decantation ~rom
reaction medium.
3~ The ob-tai.ned results for a polymerization carried out
for 35 minutes are repoxted in table 1.
"
~ 5 -
.
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- ~493~96
. In the foregoing e,{amp.les and in the next ones,'~ (mea- :
sured in dl/g) is the intrinsic viscosity o~ thè polymer and was
determined by dissolving polyethylene in decahydro.naphtallne at.
a concentration of 0.02 g/about 100, and working at a temperatu-
I re of 1~5C Moreover by R we mean the ratio betwee.n ~he volume
o~ the dry polymer and the volume of the polymer, containing sol-
vent, and was estimated, being ~lown density, by filtering the
material and weighing the s~me before and after evaporatio.n o~
the liquid at 70C at reduced pressure.
E~amples 5 - 10
The procedure of the foregoing examples was repeated
but the ~l/Ti ratio was changed. The pol~Jmerization was c æ ried
out ~or 35 minutes, at 50C, in presence of 1,1 l o~ anhydrous ~.
heptane as reactio.n medium. The results are reported o.n table 2.
From the examples of tables 1 and 2, it ~s possible to
~ote that ~ibrid~ form, wi~h ~he cata~ytic system PIA ~ TiCl4,
beyond 20C as polymeri~ation temperature, and beyond the value
2 o~ the ~l/Ti ratio~ The polymer in the form o~ fibrids englo-
bes a 1esser quantity of liquid than the polymer in the ~orm o~
powder, QS it iS e~ident from the highest valuqs of R,
Example 11
. ...._ . . . .
~y working aocording to the same procedure as i.n the
~oregoing examples, we fedto the reactor 1 1 o~ anhyarous hep-tane
which was saturated under stirrin~ with ethylene at atmospheric
pressure and temperature of 50C for 20 minutes at a rate of 120 .:
l/h. Then we fed 0.66 mmoles of TiCl4 diluted in a.small quanti
ty of solvent and subsequently 1.8 c~3 of an hexane solutio.n of
PIA containing 1.457 mg. at./cm3 of Alo The reaction started im
mediately and a temper~ture i.ncrease was noted. A~ter 35 mi.nu-
tes the catalytic complex was disactivated with 15 cc of methyl
alcohol and the polymer in the form o~ ~ibrids mixed with small
gran~es wa~ separated by decantatio~ 7 g of polyethyl0ne ha- .
ving a L~= 13.3 ~Jere obtained~ :.
: - 6 -
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~04~96
. The examination of this example allows to point out
the importance of the sequence according to which the two compo-
nents of the catalytic system are added: by introducing~i.n fact
at first TiCl~ and then PI~ a product is obtained constitllted by
.
fibrids mixed ~ith smkall granules and the separation is generally
di~ficult and expe.nsive.
am~le 12
~y usi.ng the already described apparatus, 1 1 of hepta-
ne ~ras fed in inert atmosphere and thermostated at the temperatu-
re of 50C. A stream of ethylene was i.ntroduced for 20 mi.nu-tes
at a ~ate of 120 l/h in order to saturate the reactio.n medium
which was kept under stirri.ng. At the same time i~ a 250 cc
flask pxovided with ma~ne~ic stirrer and lateral tap for feeding ;:
nitrogen ~re put 100 cc of anhydrous heptane and then, after ha-
vi.ng to a temperature of 50C we i.ntroduced 0.66 mmoles of ~iCl4
and subsequently 1.8 cm3 of an hexane solution o~ PIA containi.ng
1.457 mg. at./cm3 of Al.
. . All the comEo.nents in order to react were stirred for
- 10 minutes and the.n by means of a siphon was transferred in inert
atmosphere in-tothe polymerization reactor. The reaction started
immediately and after 35 minutes was stopped by introducing 15 cc ; ...
of methyl alcohol. We obtained 11 g o~ polyethylene in the form :~
- - of small granules having a r~= 21.70
From the examinatio.n of this example it is evident how
i-t is important, for the me.ntioned catalytic couple, the prepa-
ration in situ of the catalytic system.
~xa~ples 13
Analogously to ~hat aforesaid, ethyle.ne was polymeri- :
~ed by using a catalytic system co~stituted by VOCl3 and PIA. .:.
Conditions and results are reported in table 3.
It is possiblc to note that, with this catalytic sys-
tem, fibrids form in a wider -temperature ran~e; fibride englobe
lesser amounts of so~vent ,of polymeriæation ~arried o~lt at a tem-
.. ..
- .
:
9~L96
perature ranging from +15C to 70C. ~
Exa~les ?5 ~ 26
We used the same catalytic system as the one of the
foregoing examples (13 - 2~) and worked according to what descri-
bed by comparing the results obtained at di~fere.nt pressures.
Co.nditions and results are reported i.n table 4.
E~c~mp.l~ 27
. ~.8 l of anhydrous.n-heptane ~rere fed into a jac~eted
autoclave having a capacity of 5 l provided with a ~tirrer, mano-
meter, thermometric probe and valve for the introduction of the
ga~eous mo.nomer and of the catalyst, after having removed every
trace of oxygen and moistureO
~ he.n the autoclave was thermostated at 0C and under
stirring the reactor medium was saturated with ethyle.ne at a
pressure cf 0.5 kg/cm20 ~hen by means of a metering pump 2.85
mmoles o~ A12Et3C13 diluted in 100 cc of heptane and subseque.ntly
0.0~5 mmoles of VOCl3 were fed.
. ~he reactio~ started immediately and after 10 minutes
was stopped by adding 40 cc of mèth~l alcohol~ Well separated
fibrids were obtai.ned Laving a r~= 16 and R = 0.0690 The noti~
ce polymerization velocity was 0.8 g/l minute.
Examples 28 - 31 :
- - 2 1 of anhydrous .n-heptane were put i.nto a flanged re~
actor having a capacity of 5 l, provided with thermometer, pipe .
~or the introductio.n of ethylene, stirrer and drip~ after having
removed eYery trace of oxygen and moisture. Then the whole was
thermostated at the temperature selected for the test in ~tmosphe- .
re of dry nitro~en. ~Iighly pure ethylene at atmospheric pressure ..
was int~oduced in order to saturate the reaction medium which was
kept under stirring. In the drip we put 20 cc o~ anhydrous .n~
` 30 h~ptane in which 2 mmoles of ~l2Et~Cl~ were diluted. .
In a nitrogen atmosphere they were fed to the reàctor;
the drip was wash~d with 20 cc of n-heptane ~ .ich were transfer-
.
, . . . .
.
93L96 ~:
red into the reactor. According to the same procedure ~,15 mmo-
les of VOCl3 wexe introduced. ~he polymerization started imme-
diately and because of the reaction heat a quick increa~e~of the `~
temperature occurred. After a ~ixed time the polymeri~ation was
stopp2d by disac-tivating the catalytic system with 20 cc o~ me-
th~l alcohol. In table 5 we report -the obtained results.
. A3 it is possible to see9 ~ell separated fibrids are
obtained by working in the temperature range between O and -20C.
Outside these temperatures we obtained either po~der which englo-
bed much liquid (low R value) or compact masses (high R value)
because of a too high polymerization velocity.
Examples 32 - 34
700 cc of dlchloromethane were fed in inert atmosphere
into a flanged reactor made of glass having a capacity of 1 l,
provided with thermometer, ethylen0 feeding pipe, drip funnel and
high rota-tion velocity stirrer. The reaction medium was tnermos-
tated at the temperature selected for the test and saturated under
stirring with ethylene at atmospheric pressure. Then we introdu-
ced Q.7 mmoles of ~l2~t3Cl3 diluted in a small amount of dichlo-
romethane (10 cc) and subsequently 2.45 0 10-2 mmoles of VOCl3.
~he polymerization started quickly and after a prefixed time the
reaction was stopped by disactivating the catalytic complex with
20 cc of methyl alcoholO In table 6 the results are reported.
Prom the results it appears that by using a reaction
li~uid having less solvent power it is possible, also with a ver~ -
high polymerization velocity, to obtain fibrids well separated
if the nature of the medium permits a high crystallization velo-
city.
Example 35
Into the apparatus described in example 27? after ha-
ving removed any trace of oxygen and moisture, we ~ed in inert
atmosphere 3 l of anhydrous n-heptane and 12 g of butadiene. Then
the apparatus ~as thermostated at 0C and satur~ted under stirring
.
_ g _ .~
. :
9196
. .. .
ith ethylene ot a pres,sure of 8 Kg/cm2. Suitably diluted ln n-
heptane continuously and in the time of 20 minutes, 0.4 mmoles of
VO (O isop.)3 and 7 mmoles of AlEtC12 were introduced into the
reactor! The polymeri~ation started after 5 minutes; the tempe-
1 rature ~ras re~ulatcd by forced circulation o~ a refrigerating
mixture, Ethylene was continously fed for keeping unchanged the
total pressure of the system.
After 30 minutes from the starting of the addition ofthe catalyst, the polymeriza-tion was stopped by intro~ucing 30 cc
of butyl alcohol. 19.6 g of fibrids well separated from the re-
action medium ~rere obtained. By means of IR spectroscopy from
the absorbance values, at 10.35 ~u (unsaturation'trans) and at ;,
13.90 lu (metilenic groups) the content of diene units in the co-
polymer is 0.6$ by molesO
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