CA1049196A - Process for the preparation of polyalphaolefine fibrids obtained thereby - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE :
The invention relates to a process for the production of polymeric products in the from of fibrids, comprising polymeri-zing at least one compound containing at least one olefinic unsa-turation in the presence of a catalytic system comprising a redu-cing aluminium compound and a compound of a transition metal se-lected from the groups IV and VIII of the Periodic System, the aluminium compound being selected either among organometallic compounds having the general formula Al RxX3-x wherein R is an aryl, alkyl or cycloalkyl radical, X is a hydrocarbon radical or hydrogen, x is a whole or fractional number between 0 and 3 or among polymeric compounds of polyiminic nature containing repeat-ing units of the type (AlH-NR) where is R has the aforesaid mean-ing, the catalytic system having a Al Me ratio, wherein Me repre-sents the transition metal, ranging from 1 to 200 and a total concentration of the transition metal, ranging from 1 to 200 and a total concentration of the transition metal compound ranging from 0.001 to 5 mmoles/1, in a solvent selected among those ha-ving good solvent power for the monomer and low solvent power for the polymer which forms, at a temperature comprised between 0°C and -20°C, when the catalytic system comprises aluminium com-pounds AlRxX3-x and vanadium compounds, between 50°C and 90°C, when the catalytic system comprises a polyiminoalane and a tita-nium compound, and between -15°C and +90°C, when the catalytic system comprises a polyiminoalane and a vanadium compound. It is therefore possible to obtain fibrids directly during polymerisa-tion without application of shear stress. The fibrids of the pre-sent invention can be used as synthetic pulp for the production of papers.

Description

~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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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.
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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~ :.

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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-.. ..
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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-.

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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 .
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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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Claims (10)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for the production of polymeric products in the form of fibrids, comprising polymerizing at least one compound containing at least one olefinic unsaturation in the presence of a catalytic system selected in the group consisting of (a) titanium tetrachloride, as catalyst, and a polyminioalane containing repeating units of the type (AlH-NR) wherein R is an aryl, alkyl or cycloalkyl radical, as co-catalyst, at a temperature system comprised between 40°C and 90°C; (b) vanadium oxychloride 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, at a temperature system comprised between -15°C and +90°C ; and (c) vanadium halide or oxy-halide 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, at a temperature system comprised between +15°C and -20°C, said catalytic system having a Al/Me ratio, wherein Me represents titanium or vanadium, ranging from 1 to 200 and a total concentration of the titanium or vanadium compound ranging from 0.001 to 5 mmoles/l, in a solvent selected among those having good solvent power for the monomer and low solvent power for the polymer which forms.

2. Process according to claim 1, characterized in that the reaction of polymerization is carried out in presence of a solvent selected among aliphatic, aromatic, cycloaliphatic hydro-carbons and chlorine, containing hydrocarbons.

3. Process as claimed in claim 1 or 2, characterized in that the reaction of polymerization of ethylene is carried out in the presence of heptane as solvent.

4. Process as claimed in claim 1, characterized in that the reaction is carried out in presence of a catalytic system constituted by TiC14 and polyiminoalane at a Al/Ti ratio ranging from 1.2 to 80 and at a concentration of TiC14 ranging from 0.03 to 2 mmoles/1.

5. Process as claimed in claim 4, characterized in that the reaction is carried out by adding to the solvent at first polyiminoalane and then TiC14.

6. Process as claimed in claim 1, characterized in that the reaction is carried out in presence of a catalytic system constituted by VOCl3 and polyiminoalane at a Al/V ratio ranging from 2.2 to 17.5 at a concentration of VOCl3 ranging from 0.5 to 0.25 mg at/l.

7. Process as claimed in claim 1, characterized in that the reaction is carried out in presence of a catalytic system constituted by A12Et3Cl3 and VOCl3 with a Al/V ratio ranging from 1 to 60 and with a VOCl3 concentration ranging from 0.002 to 0.15 mmoles/1.

8. Process according to claim 1, characterized in that the reaction is carried out by feeding ethylene and butadiene into a reaction medium constituted by heptane.

9. Process according to claim 8, characterized in that the reaction is carried out in presence of a catalytic system constituted by AlEtCl2 and VO(O isop.)3 with a Al/V ratio equal to 17.5.

10. Process according to claim 1, wherein the reaction temperature is ranging from 0°C and -20°C when the cata-lytic system comprises the aluminium compound AlRxX3-x and vanadium halide or oxyhalide; from 50°C to 90°C when the catalytic system comprises polyiminoalane and titanium tetrachloride; and from +l5°C to +70°C when the catalytic system comprises polyimi-noalane and vanadium oxychloride.