CA2135592A1

CA2135592A1 - Process for preparing finely divided polyacrylonitrile

Info

Publication number: CA2135592A1
Application number: CA002135592A
Authority: CA
Inventors: Ulrich Holzinger; Wilfried Walkenhorst
Original assignee: Individual
Current assignee: Hoechst AG
Priority date: 1993-11-13
Filing date: 1994-11-10
Publication date: 1995-05-14
Also published as: DE4338878A1; EP0653444A3; EP0653444A2; JPH07188305A

Abstract

Abstract Process for preparing finely divided polyacrylonitrile The invention relates to a process for preparing finely divided homopolymers or copolymers containing at least 50 % by weight of recurring acrylonitrile and/or meth-acrylonitrile units (based on the monomers used), which comprises:
a) dissolving and/or suspending and/or emulsifying and/or dispersing the monomers in one or more liquids which are inert under the reaction condi-tions, where b) the sum of the monomer concentrations at the begin-ning and during the polymerization is less than 10 %
by weight, c) high shear forces acting on the polymerization mixture prior to and during the polymerization to that the resulting homopolymer or copolymer par-ticles have a D50 % value of less than 10 µm and d) carrying out the polymerization in a known manner by addition of a polymerization initiator.
The finely divided polyacrylonitrlle is suitable, for example, as pigmenting agent and organic filler and as pigment substitute in electrophoretic surface coatings of automobile or industrial surface coatings, as matting agent and/or colorable pigment in surface coatings, plastics, fibers, films, paper and cardboard, as adsorbent for gases and liquids, as raw material for the production of carbon microbeads as filler for liquid chromatography or ion exchange columns, as reinforcing material and/or filler for polymers and as raw material for the production of fibers, films and membranes.

Description

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Description Proce~e for preparing ~inely divided polyacrylonitrile The preeent invention relates to a process for preparing finely divided homopolymers or copolymers containing recurring acrylonitrile and/or methacrylonitrile unit~.

It is known that acrylonitrile can be polymeri~ed by various proce~ses. For acrylic fiber~, acrylonitrile is usually polymerized by solution or suspen~ion-precipi~
tation polymerization. In the su~pension-procipitation polymerization, the polymer is u~ually obtained as a finely divided suspenaion which can be filtered off, washed and dried.

The particle size of acrylonitrile polymers i~ usually characterized by a so-called D value. The diameter D(p) at the percentile point p and the median value D(50 %) is defined as follows: ~;

Starting out from the volume distribution Dmax V = J v(Di)dD

Dmin the diameter D(p) i~ given at the point where ;~
D1 = D (~
f J v(Di)dD p * V.
D1 = D(O %) V i~ the total volume of the particles Di is the diameter o~ the individual particles v(D~ the volume of the individual particles Dmin = D(O %) i8 the ~mallest particle diameter -' ' .' ~ " ~ ' ' ' .

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DmaX = D(100 %) ie the largest part~cle diameter p is the percentile value. -:..:', This determines a mean particle diameter, where the maximum particle diameter, derived from the volume distribution function, which would l~ad to X % passing a sieve ic the eo-called AX value. Thus, for example, for p - 50 % this means that all particle~ having a diameter D c D(50 %) together make up 50 % of the total volume (z median diameter). (T. Allen "Particle Size Measurement Chapman & Hall ~td., London Mal~ern Instrument~ Ltd.
"System 3601 Usermanual" Spring Lane South, Worc WR 14 1 AQ, England; p. 5.1 ff.) . . ; . ' For suspension-precipitation polymerizations carried out according to the prior art, the D50 % value of the particle size i~ usually not below 40 ~m.

Further acrylonitrile polymers known p~r ~e are t~e SAN, ABS and NBR copolymer~ which are generally prepared by emulaion poly~erization. Thi~ gives a latex which may have to first be broken for further processing. The individual particles of thi~ latex are u~ually not larger than 0.08 ~m but have an irregular particle geometry. The acrylonitrile content in the~e known copolymers i~ below 50 % by weight.
.
The proce~es hitherto known for preparing poly(meth)acrylonitrile having a particle ~ize of less than 10 ~m are compl~cated and are hardly economically ~uitable for the preparaton of relatively large to industrial amount~. Thus, JP-A-01/043531 de~cribe~ a ~;
proces~ in which a coar~ely particulate polyacrylonitrile polymelr containing more than 80 % by weight of acrylonitrile i~ dissolved in a ~uitable solvent and is ~ubsequently precipitated again. Besides this precipita-tion process, DE-A-3,940,781 de~cribels a mechanical proce~ in which a coarsely particulate polyacrylonitrile polymer is finely milled together with up to 94 % by : ~ ' ' : ~ . . :
: . .

weight of acrylonitrile in ~pacial mills, for example a fluidized-bed counter-jet mill or a ~tirred ball mill (cf. al~o Ullmann's Encyclopedia of Indu~trial ~hemietry, 5th Edition, Volume B2, 5-20 to 34, VCH-Verlag, Weinheim 1988). Both known processe~ require complicated appa-ratus.
, Experiments have shown that the particle~ of the poly-acrylonitrile milled in accordance with DE-A-3,940,781 res~hle squashed platelet~ on microecopic examination, and that the particles of the polyacrylonitrile precipi-tated in accordance with JP-A-01/043531, l~kewi~e on microscopic exam$nation, have a tattered and eplit surface structure.

JP-A-04/261404 describe~ a process $or preparing poly-acrylonitrile particles having a mean diameter of 1:10 ~m. For this purpose, the polymerization mixture comprising acrylonitrile monomer, di~persion stabilizer, a hydrophilic and a hydrophobic solvent is polymerized with ~haking at 65~.

20 JP-A-02/307909 discloses rod-shaped poly(meth)acrylo-nitrile particles. The preparation of the rod-~haped particle~ is carried out by polymerization of a suspen-sion of the monomers, previously homogenized by stirring, in a water/polyvinyl alcohol ~olvent mixture.

25 Furthermore, it i8 known from Ullmann, Volume 19, (1980), pp. 130 ff. that alteration of the stirring ~peed during the suspeneion-precipitation polymerization can influence the particle size of the polymer~ formed. By mean~ of the above-described measure, the particle ~ize~ can be varied 30 within a range from 1000 to 200 ~m. It is not po~eible to extrapolate the D50 % value of the particle sizes to below 10 ~m as a function of the ~tirring speed; particle ~ize~ below 200 ~m cannot be produced u3ing the usually achievable stirring speeds.

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It ie therefore an object of the invention to develop a ~imple and a~ economical a~ po~ i~le process for prepa-ring poly(meth)acrylonitrile, in which the polymer is obtained after polymerization directly in the form of small particle~ and in which the particle diameters have a D50 % value of les~ than 10 ~m.
. .
It has now been found that it is po~ible to prepare a poly(meth)acrylonitrile powder having a D50 % value of less than 10 ~m if in polymerization the total monomer concentration iB reduced below a range customary for the polymerization of acrylonitrile and at the same time high shear force~ act on the polymerization mixture.
, .
The invention accordingly provides a procesc for prepa-ring homopolymers or copolymer~ containing at leaRt 50 %
by weight of recurri~g acrylonitrile and/or methacrylo-nitrile unit~, which comprices:
a) dissolving and/or su~pending and/or emul~ifying and/or dispersing the monomers in one or more liquids which are inert under the reaction condi-tions, where b) the sum of the monomer concentrationc at the begin-ning and during the polymerization is less than 10 %
by weight, c) high ~hear forces acting on the polymerization mixture prior to and during the polymerization eo that the resulting homopolymer or copolymer particles have a D50 % value of le~8 than 10 ~m and d) carrying out the polymerization in a known manner by addition of a polymerization initiator.

The low monomer concentration at the beginning and during the polymerization (le~ than 10 % by weight, baaed on the polymerization mixture) is an unuQual range for those ckilled in the art of polymerization, ~ince the reaction rate in a polymerization having an initial monomer concentration of le~s than 10 % by weight is normally very low and as a re~ult only low yield~ and ~pace-time S 3 ~

conver~ions can be achieved.

A~ has been surpri~ingly found, action of high shear forces on the polymerization mixture during the polymerization and copolymerization of acrylonitrile and/or methacrylonitrile gives unexpectedly high reaction ratee and space-time yields. Furthermore, the particle size distribution can be varied and set within a wide range by the measures of the invention. The preferred D50 % value of the particle si~e of the finely divided polyacrylonitrile i~ less than 10 ~m and greater than 0.1 ~m. By mean~ of the particle size, further specific propertie~ such as, for example the rheology and the external and internal surface ar0a, can, lf desired, be influenced and altered in a targeted mann0r.

The acrylonitrile and/or methacrylonitrile polymers prepared using the proce~s of the invention preferably contain 70 % by weight of recurring acrylonitrile and/or methacrylonitrile units. Furthermore, up to 30 % by weight of one or more monomers capable of copolymerization can be added to the acrylonitrile and/or methacrylonitrile. Partlcular preference is given to poly(meth)acrylonitrile polymer~ containing at least 90 %
by weight of recurring acrylonitrile and/or methacrylo-nitrile units.

Examples of monomers capable of copolymerization are acrylic esters or methacrylic ester~ of Cl^C22-alcohols, e.g. methyl acrylate, methyl methacrylate, butyl methacrylate, octyl methacrylate, ethyl acrylate, i~obutyl acrylate, (meth)acrylic e~ters of perfluorinated Cl-C22-alcohols; vinyl aromatics having up to 20 carbon atom~, e.g. styrene, vinyltoluene; the esters of maleic acid and fumaric acid with C1-C22-alcohol~; vinyl chloride, vinyl acetate, ethylene and butadiene. Prefe-rence is given to methyl acrylate.

Furthermore, it i8 pos~ible to u~e, for example, .: .. . ~ .

`3 ~3 2 .:
un~aturated carboxylic, sulfonic and phosphonic acids and their ester~ and salts as comonomers, examples being acrylic acid, crotonic acid, itaconic acid, vinyl~ulfonic acid, (meth)acrylosulfonic acid, styrenesulfonia acid, acrylamidomethylpropanesulfonic acid, vinylpho~phonic acid and ester~ thereof.
The suitable comonomers likewi~e include unsaturated primary, secondary and/sr tertiary amines, such as dimethylaminoneopentylmethacrylate,dimethylaminomethyl-neopentyl acrylate, 2-N-morpholinoethyl methacrylate, 2-N-morpholinoethyl acrylate, or amides of acrylic or methacrylic acid, such as acrylamide, dimethyl-methacrylamide or methylbutylacrylamide.
' In addition, it is also possible to use other functional monomers which can be copolymerized with acrylonitrile and/or methacrylonitrile. The functional monomers can contain hydroxy, silane or epoxy groups. Examples of the~e are vinyltrimethoxysilane, vinyltributoxysilane, methacryloxypropyltrimethoxysilane, vinyltris(methoxy-ethoxy)silane, vinyltriacetoxysilane, hydroxyethylmethacrylate, hydroxybutyl methacrylate, glycidyl acrylate, glycidyl methacrylate or 2-hydroxyethyl acrylate.
' ' :' '~
By means of the selection of the monomer~ to be used, properties such as the glass transition temperature, hardness and brittleness can be influenced.
:' The term polymerization refer~, in particular, to preci-pitation polymerizations in which the monomers are dis~olved and/or suspended and/or emulsified and/or dispersed beforehand in one or more liquids inert in respect of the monomer and polymer. The proce~s of the invention is preferably carried out by the suspension-precipitation polymerization method.
The shear force nece~sary during polymerization i~
usually generated by one or more ~tirrers and/or other di~persing devices which generate high shear and which . .

9 ~

can be u~ed ~imultaneou~ly and/or ~uccessively. Examples of these are propeller, impeller, turbine, guide jet, inclined blade, toothed disc (di~solver) or pinned di~c (dissolver) stirrer, with and without baffles. It is likewi~e po~ible to use all types of static and dynamic mixers and also jet mixers as disper~ing devices. Jet mixers mean such mixers which mix the polymerization mixtures by passage through a nozzle. Preference is given to stirrer~ using the rotor/stator principle ~uch a~
stirrers of the Ultra-Turrax (from Janke & Runkel, Staufen, Germany) type or stirrers of the Pentax (from Bran & Lubbe, Hamburg, Germany) type.
Furthermore, the di~persion can al~o be carried out using devices built into the reactor and/or by (forced) circu-lation (inline) outside the reactor.

The polymerization reaction can be carried out batchwiee,semi-continuou~ly or continuously.
Suitable reactore for the continuous polymerization process are, for example, the continuous stirred tank reactor, a cascade comprising from 2 to 4 reactors, the tube reactor or the loop reactor or any desired combina-tion of the specified reactors.

Suitable liquids which are inert under the reaction conditions are protic and/or aprotic solvents and/or non-solvents and mixtures thereof. Suitable aprotic solventsare either nonpolar ones, such as aliphatic and aromatic hydrocarbons, or polar ones such as halogenated hydro-carbons, dimethylformamide, dimethyl sulfoxide, dimethyl-acetamide and acetonitrile. Suitable protic reaction media are, for example, water and alcohol~.

The total monomer concentration at the beginning and during the polymerization is at most 10 % by weight, preferably from 1 to 10 ~ by weight, paticularly prefe-rably from 3 to 8 % by weight.

The molecular weight of the poly(meth)acrylic pol~mers ... . .
: . . . . .. .

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can be set in a conventional manner by the selection of the radical initiator and by polymerization variables known to thoee skilled in the art, euch as initiator concentration and/or polymerization temperature. The molecular weight Mw (weight average) of the poly(meth)acrylonitrile polymere prepared by the process of the invention is ueually from 3 x 104 to 8 x 105 g~mol, preferably from 5 x 104 to 4.5 x 105 g/mol.
If deeired, the molecular weight can be regulated by meane o~ a chain regulator euch ae 2-mercaptoethanol. The molecular weight Mw ie determined by the method of Fikentscher (Makromol. Chem. 57 1962, 52) using the relationehip [~] = 1.78 x 10-4 x MW0.78 where ~ ie the viecoeity nu~ber (intrineic viecosity).

Polymerization initiatore which can be ueed are either water-eoluble compounde euch ae, for example, H2O2, potaeeium peroxodieulfate and organic azo and peroxo compounde, or compounde which are sparingly eoluble in water euch ae, for example, azobieieobutyronitrile or other azo and peroxo compounde. The particularly preferred radical initiator ie the redox eyetem potaeeium peroxodieulfate and eodium bisulfite.

An emuleifier can be additionally added to the polymerization mixture. By thie meane, the particle sizs of the polymer can be further reduced or the polymer can be given epecific propertiee such ae, for example, a particularly good euitability for cathodically depoei-table coating compoeitione.

Suitable emuleifiere are:
cationic surfactants euch ae cetylamine hydrochloride and ealte of other fatty aminee with etrong acide;
non-ionogenic emuleifiere euch as fatty alcohol ethoxy-lates and alkylphenol ethoxylatee euch ae, for example, r~

_ 9 _ : ~
the Genapol grades (Hoech~t AG); anionic ~urfactants ~uch as sodium lauryl sulfate and other alkyl sulfate~
and alkylbenzenesulfonates.

The polymerization can also be carried out using protec-tive collo$d~ as dispersants. Suitable dispersants are, for example, starch, sodium salt of carboxymethyl-cellulose, methylcellulose, polyvinyl alcohol or partially saponified polyvinyl acetate.

The reaction temperature for the polymerization is usually 30-75C, preferably 40-60C; the polymerization time is generally between 30 minutes and 5 hours and i8 dependent on the reaction procedure or polymerizatio~
temperature and also on the monomers, the solvent, the initiator substances and the polymerization procese selected in the particular case.

The polyacrylonitrile suspension obtained can be freed of monomers after polymerization, for example by distilla-tion. Before or subsequent to the removal of monomerc, the liquid phase can be mostly removed, for example by filtration or by means of a centrifuge. By waehing with water and filtering or centrifuging again, the poly~er suspen~ion can be freed of interfering salts and other residual materials. Subsequently, the finely divided poly(meth)acrylonitrile polymer ~till containing residual water can be dried, with care having to be taken to ensure that the particle~ do not agglomerate. Suitable driers are, for example, ~pray driers and rotary di~k atomization driers.

The particle surface of the almost round particles can, on microscopic examination, be described as a compara~
tively raspberry-like ~tructure in which the ~urface of the almost round polymer particle ha~ sitting on it further round polymer particles. As a re~ult, the polymer particle i~, in contrast to milled or precipitated polymer~, almost round (spherical geometry) and has a ~: .' a J 9 2 large specific surface area.

The finely divided polymer is auitable, for example, as pigmenting agent and organic filler. Particularly a~
pigment eubstitute in place of titanium dioxide in electrophoretic surface coatings of automobile or indus-trial finishe~, the polymer ha~ many possible applica-tion~. In addition, the finely di~ided polymer of the invention can be ueed as matting agent and colorable pigment in surface coating~, pla~tics, Çibers, films, paper and cardboard. The polymer haR a ~ery high internal and external sur~ace area. Depending on the particle size, it absorbs from over 5 times to over 10 times its weight of water and other liquids without losing its paste-like aggregated state in which it iR firm enough to be cut.
,:
The large surface area also offers increa~ed reactivity for chemical reactions on the polymer grain, for example gases or liquids can be adsorbed.
The good liquid absorption and ~torage capacity of the polymer can be exploited in use as adsorbent and bind~r.
It can also be used as thixotrope and thick~ner in surface coatings, plastics or the like.
In addition, the polymer can be u~ed as raw material for (carbon)microbeads, as filler for liquid chromatography or ion exchange columns, as reinforcing material and filler for polymers or as starting material for polymsr-analogou~ reaction~. Likewise, it can al~o be used as starting material for fibers, film~ and mzmbranes.

The following working example~ illustrate the present invention without limiting it.

Examples~
In the following examples, the particle size distribu-tions are mea~ured using a Malvern particle sizer model 3600. ~-~
Initiation of polymerization wa~ carried out in the .::

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~;'- '' - ' . , ' ' . ' ' " ' `' : "' ' --` hl3~i 197 examples described below by addition of the ~olutions I
and II.
Solution I wa~ prepared from 50 ml of di~tilled water and 0.72 g of pota~ium peroxodi~ulfate and solution II was prepared from 50 ml of di~tilled water and 2.88 g of sodium bi~ulfite.

Example 1 (Acrylonitrile polymerization in aqueous medium: batch-wise method) A reaction ve3sel was initially charged with:
1520 ml of distilled water, 180 g of distilled acrylonitrile, 3.6 mg of Mohr's salt, 1.3 ml of 99 % strength formic acid.
After passing through nitrogen and set~ing the tempera-ture to 55C, the polymerization wa~ initiated by addition of the solutions I and II and the reaction mixture was dispersed by means of a Ultra-Turrax stirrer at about 10,000 revolutions per minute.

After the polymerization wa~ complete, the water and unreacted monomer were separated off. Washing twice with distilled water gave a polymer suspenaion which ha~ a conductivity of le~s than 10 ~S/cm (measured ae a 10 %
strength suQpension in di~tilled water having an intrinsic conductivity of at most 0.1 ~S/cm) and who~e properties are shown in Table 1. The yield o~ polymer wa~
79.3 % of theory.

Example 2 to Example 4 The experiment~ were carried out as described in Example 1. Both the amounta u~ed and the re~ults are shown in Table 1.

Example 5 The experiment wa~ sarried out as described in Example 1.

....... . . .. . . . . .

However, the stirrer used wa~ a di3~01ver ~tirrer having a diameter of 150 mm and operating at 1500 revolution~
per minute. The results are shown in Table 1.

Example 6 The experiment was carried out a~ described in Example 1.
However, the etirrer used in the reactor was a propeller stirrer having a diameter of 80 mm and operat~ng at 500 revolutlons per minute. The reaction mixture was disper~ed by pumped circulation of the reaction mixture through a flow-through chamber ~itted with an Ultra-Turrax etirrer connected inline, the ~tirrer being operated at about 10,000 rpm. The pumped circulation rate was about 1,800 mg/min. The resulte are ehown in Table 1.

Example 7 (Semi-continous feed stream addition method) .~ ~ ;. -:
The amounts used correspond to the amounts in Example 1.
However, only half the reaction mixture was initlally .
charged and dispersed by means of an Ultra-Turrax stirrer at about 10,000 revolution~ per minute. After initiation with 25 ml of each of the solution~ I and II, the remaining solutions were simultaneously metered into the initial mixture over a period of one hour. The results are shown in Table 1.

Example 8 (Continuous polymerization) The amount~ used correspond to the amounts in Example 1.
1700 ml of the reaction mixture were initially charged and di~persed by means of an Ultra-Turrax stirrer at about 10,000 revolutions per minute. However, after initiation with 50 ml of each of solutions I and II, 50 ml/h of the solutions I and II and also 1700 g/h of the reaction mixture as was also initially charged at the beginning of the reaction were simultaneously metered into the initial mixture and a product stream of 1800 g ~135~2 per hour wae continuously taken out. After establishment of equilibrium, sampling was commenced. The results are shown in Table 1.

Example 9 The experiment was carried out as described in Example 1.
However, 5.4 g of the emulsifier Genapol GX 110 were additionally added to the reaction mixture. The reeults of the experiment axe shown in Table 1.

Example 10 A reaction vessel was initially charged with~
1500 ml of distilled water, 70 g of distilled acrylonitrile.
After passing through nitrogen and setting the tempera-ture to 70C, lnltiation was carried out uslng 1.5 g of azobieisobutyronitrile (AIBN) diesolved in 5 ml of acrylonitrlle. Durlng the entire polymerization, the reaction mlxture wa~ di~persed by mean~ of an Ultra-Turrax stlrrer at about 10,000 revolutions per mlnute.
After a reaction time of 2 hours, the partlcle dlameter (D50% value) was 5.50 ~m and the yield was 38.3 % of theory.

Comparative Example 1:

The experiment wae carried out a~ described in Example 1.
However, the stirrer used was a propeller ~tirrer (without baffles) having a diameter of 150 mm and opera~
ting at 1500 revolutions per minute. The results are ~hown in Tabls 1.

Comparative Example 2~

The experiment was carried out as described in Example 1.
Howevsr, the amount of monomer used wa~ 337.5 g. The reaction mixture was dispersed by means of an .`~ ';,' ! ' . . ' : ' ~ .

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Ultra-Turrax etirrer at about 10,000 revolutions per :
minute. The re~ults are shown in Table 1. ~ ~

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Claims

1. A process for preparing homopolymers or copolymers containing at least 50 % by weight of recurring acrylonitrile and/or methacrylonitrile units, which comprises:
a) dissolving and/or suspending and/or emulsifying and/or dispersing the monomers in one or more liquids which are inert under the reaction condi-tions, where b) the sum of the monomer concentrations at the beginning and during the polymerization is less than 10 % by weight, c) high shear forces acting on the polymerization mixture prior to and during the polymerization 80 that the resulting homopolymer or copolymer particles have a D50 % value of less than 10 µm and d) carrying out the polymerization in a known manner by addition of a polymerization initiator.

2. The process as claimed in claim 1, wherein the acrylonitrile and/or methacrylonitrile polymer contains at least 70 % by weight, preferably at least 90 % by weight, of recurring acrylonitrile and/or methacrylonitrile units.

3. The process as claimed in claim 1 or 2, wherein the D50 % value is less than 10 µm and greater than 0.1 µm.

4. The process as claimed in one or more of claims 1 to 3, wherein the sum of the monomer concentrations at the beginning and during the polymerization is between 1 and 10 % by weight, preferably between 3 and 8 % by weight.

5. The process as claimed in one or more of claims 1 to 4, wherein the polymerization temperature is between 30 and 75°C and the polymerization time is between 5 hours and 30 minutes.

6. The process as claimed in one or more of claims 1 to 5, wherein a cationic surfactant, a non-ionogenic emulsifier or an anionic surfactant or a mixture thereof is additionally added to the polymerization mixture.

7. The process as claimed in one or more of claims 1 to 6, wherein the polymerization reaction is carried out batchwise, semi-continuously or continuously.

8. A homopolymer or copolymer containing at least 50 %
by weight of recurring acrylonitrile and/or meth-acrylonitrile unite obtainable by the process as claimed in claim 1.

9. Use of the homopolymer or copolymer obtained by the process as claimed in one or more of claims 1 to 7 as pigment or organic filler or as pigment substi-tute in electrophoretic surface coatings of automo-bile or industrial finishes.

10. Use of the homopolymer or copolymer obtained by the process as claimed in one or more of claims 1 to 7 as matting agent and/or colorable pigment in surface coatings, plastics, fibers, films, paper and cardboard.

11. Use of the homopolymer or copolymer obtained by the process as claimed in one or more of claims 1 to 7 as adsorbent for gases and liquids.

12. Use of the homopolymer or copolymer obtained by the process as claimed in one or more of claims 1 to 7 as raw material for the production of carbon micro-beads as filler for liquid chromatography or ion exchange columns.

13. Use of the homopolymer or copolymer obtained by the process as claimed in one or more of claims 1 to 7 as reinforcing material and/or filler for polymers.

14. Use of the homopolymer or copolymer obtained by the process as claimed in one or more of claims 1 to 7 as raw material for the production of fibers, films and membranes.