Process for the continuous preparation of homogeneous solutions of high molecular polymers

A continuous process is described wherein suspensions of high molecular weight polymers are readily transformed into solutions thereof for extrusion, to make gel filaments, tapes, tubes and films, by use of an extruder having alternate mixing and transporting sections and operating at mechanical shear rates of from 30 to 2,000 sec..sup.-1, and with relatively short residence times therein.

This invention relates to a novel process for the continuous preparation of 
homogeneous solutions of high-molecular weight polymers and of homogeneous 
gel articles therefrom from suspensions of finely divided high-molecular 
weight polymer in a suitable solvent, and at up to relatively high 
concentrations and in relatively very short required times. 
BACKGROUND OF THE INVENTION 
The production of polymer articles, particularly filaments and ribbons, 
having very high tensile strength and modulus, from solutions of high 
molecular weight polymers, specifically high molecular weight linear 
polyethylene, has now been described in a number of patents. See, for 
instance, U.S. Pat. Nos. 4,344,908; 4,411,845; 4,422,993; 4,430,383; and 
4,436,689. Also see U.S. Pat No. 4,137,394. 
Generally speaking, in these known processes, a solution having a 
concentration of at most about 20 wt.% of a high molecular weight polymer 
is spun or extruded through an aperture, either round or slit-shaped, to 
form a filament or ribbon. This filament or ribbon can be subsequently 
converted to form a gel-state filament or ribbon by cooling to a 
temperature below the gel point. Thereafter, such gel filament or ribbon 
may be stretched or drawn at an elevated temperature, either with or 
without first removing all or part of the solvent. 
It has also been recognized that in such techniques it is very important 
that the polymer solutions used be homogeneous; in the absence of a high 
level of homogeneity the quality of the filaments or ribbons, and the 
drawability or stretchability in the gel state, will be seriously 
adversely affected, and indeed will be erratic over the length of the 
formed material. 
Typically, in the past, such solutions of the polymer have been prepared by 
stirring the high molecular weight polymer in a suitable solvent to form 
the solution. It has been recognized, however, that to form such solutions 
is not an easy task, and becomes rather time-consuming. This is partially 
due to the fact that when working with the very high molecular weight 
polymer materials involved (for instance, polyethylene having a weight 
average molecular weight of at least 4.times.10.sup.5, or especially above 
about 8.times.10.sup.5) the mechanical forces applied during the stirring 
operation tend to elongate the normally coiled polymer molecules. As a 
result of this effect a retractive force is created by which the molecule 
seeks to retract itself into a coil again. The ultimate observed result in 
the practice of the conventional stirring techniques is that the high 
molecular weight polymer molecules will tend to gather around the center 
of the stirring rod, or other device, and to climb up against the stirring 
rod or device itself. This has been described in the literature as the 
so-called Weissenberg effect. 
This effect, which is indigenous to the ordinary stirring of these high 
molecular weight polymers thus creates a major problem in attempting to 
form homogeneous solutions thereof. The Weissenberg effect is enhanced as 
the solutions are more vigorously or rapidly stirred, and as the polymer 
concentration is increased and as the molecular weight of the polymer in 
increased. It will be understood that under conditions such that the 
Weissenberg effect manifests itself, non-homogeneous polymer solutions 
result, with deleterious effects on the properties of the gel spun 
filaments, ribbons, or films. 
Effectively, homogeneous solutions can only be prepared by these techniques 
if very slow stirring rates are employed, and if relatively dilute 
solutions of the polymer are used. It will also be appreciated that as the 
solution concentration increases, the solutions take on extremely high 
viscosity characteristics. Under these circumstances, stirring becomes 
more arduous and moreover it becomes increasingly difficult thereafter to 
feed and deliver the highly viscous solutions to a spinning head or to a 
conventional extrusion device to form the gel filament or tape. 
A further disadvantage is that as the time for stirring increases, which is 
required when slow stirring speeds must be employed, the difficulty occurs 
that degradation of the polymer molecules will result unless extreme 
precautions are taken to exclude the presence of oxygen. 
Further, because of the corresponding effect of a viscosity increase the 
process also becomes increasingly difficult as the molecular weight of the 
plymer molecules increases. 
These problems have variously been recognized in the prior art as is 
illustrated by U.S. Pat. No. 4,137,394 which effectively discusses the 
slow rate of crystallization and consequently the slow rate of stirring 
required, for that process. Further, in U.S. Pat. No. 4,413,110, there is 
described a process for suspending high molecular weight polyolefins in 
paraffinic oil, wherein it is indicated that the suspension must be slowly 
stirred at elevated temperatures for many hours. These are precisely the 
conditions under which degradation of the polymer, and also segregation of 
polymer molecules of differing molecular weights, may occur, absent 
special precautions, so that, again, homogeneous solutions are not readily 
obtained. 
There are, accordingly, numerous disadvantages to the presently known 
procedures for preparing these high molecular weight solutions and with 
respect to their spinning or extrusion through an orifice or aperture. The 
problems are such that high costs are involved, particularly when the 
fundamental process is attempted to be applied on a large, commercial 
scale, and it also becomes extremely difficult to carry out the known 
processes in a continuous, as opposed to a batch, procedure. 
SUMMARY OF THE INVENTION 
The present invention now provides an improved novel process wherein, and 
surprisingly so in view of the teachings appearing in the prior art, a 
technique has been found whereby homogeneous solutions of high molecular 
weight polymers may readily be obtained while substantially avoiding the 
above-discussed problems, and in relatively short times such that hardly 
any, if any at all, polymer degradation or segregation occurs, and by 
which it is also possible to prepare and handle relatively highly 
concentrated solutions of such polymers, and even with high molecular 
weight polymers. 
In summary, this invention provides a novel process for the continuous 
preparation of homogeneous solutions of high molecular weight polymers, 
particularly polyethylene wherein a suspension of the finely divided high 
molecular weight polymer is formed in a suitable solvent or mixture of 
solvents which solvent(s) is (are) liquid at room temperature, and wherein 
the resulting suspension is passed through a extruder device equipped with 
both mixing and conveying parts or sections, preferably alternating, and 
operating at rotational speeds from about 30 to about 300 revolutions per 
minute, within such periods of time (t) that (t) expressed in minutes is 
at most 0.3 D, wherein D denotes the diameter of the extruder in 
millimeters, and at temperatures from above the dissolution temperature of 
said polymer in said solvents(s) up to about to boiling point of the 
solvent(s) (at the prevailing operating pressure), and with a mixing 
treatment providing a mechanical shear rate of between 30 and 2000 
sec..sup.-1, the desired homogeneous high molecular weight polymer 
solutions are formed which can then be readily extruded through an 
aperture to form filaments, ribbons, tapes, and film-dimensioned or even 
tubular extrudates. 
This novel process is surprisingly effective, and is contrary to existing 
teaching in the prior art. For instance, recent European patent 
application No. 0115192, of Mitsui Petrochemicals Industries Limited, 
states at page 3 that continuous extrusion spinning from a screw extruder 
is `practically impossible`, particularly where a suspension of solvent 
and powdered polyethylene are employed. The reason given is the 
excessively great difference in viscosity between the solvent and the 
polymer powder. Moreover, the same text indicates at page 3, lines 23-27, 
that even if extrusion can be effected with the polymer in a liquid (at 
operating conditions) paraffin solvent: the extrudate (e.g. filament, tape 
or film) cannot be stretched at all because it is not a uniform mixture. 
Further, it is impossible to perform melt extrusion spinning continuously 
by a screw extruder." 
As demonstrated below, however, the process of the present invention rather 
remarkably achieves exactly the result which the art believed to be 
"impossible". 
Moreover, it has been found in the present invention that the feed to the 
extruder may be either an already formed suspension of the polymer powders 
in the solvent, or, alternatively, separate feed streams of the solvent on 
the one hand and polymer powder on the other hand may be used with the 
formation of the suspension, followed by its transformation into a 
homogeneous solution, all actually occuring within the twin-screw extruder 
device itself. 
Even though very high rotational speeds are used in the extruder in the 
practice of this invention, the above-discussed "Weissenberg effect" is 
nonetheless effectively controlled, so that homogeneous solutions result 
and the same may now be readily extruded through an aperture or orifice of 
the desired shape and dimensions at the exit end of the extruder to yield 
useful, readily drawable extrudates of desirably uniform characteristics. 
DETAILED DESCRIPTION OF THE INVENTION 
The present process can in principle be generally applied for the 
preparation of solutions of a variety of high-molecular weight polymers, 
such as polyolefins, polyamides, polyvinylalcohol, polyacrylonitrile or 
mixtures of these. 
The process is particularly suitable for the preparation of homogeneous 
solutions of linear polyethylene having a weight-average molecular weight 
of at least 4.times.10.sup.5, preferably of at least 5.times.10.sup.5 and 
most preferably of at least 8.times.10.sup.5. High-molecular weight linear 
polyethylene is here understood to mean polyethylene that may contain 
minor amounts, preferably at most 5 mol %, of one or more other alkenes 
copolymerized therewith, such as propylene, butylene, pentene, hexene, 
4-methylpentene, octene, etc., with at least 100 linear chain carbon atoms 
and preferably at least 300 linear chain carbon atoms between any side 
chains, especially side chains having more than one carbon atom. The 
polyethylene may contain minor amounts, preferably at most 25 wt %, of one 
or more other polymers, in particular an alkene-1-polymer such as 
polypropylene, polybutylene or a copolymer of propylene with a minor 
amount of ethylene. 
The polyethylene may also contain substantial amounts of fillers as 
described in U.S. Pat. No. 4,411,854. It may also be an advantage to use a 
polyethylene whose weight-average/number-average molecular weight ratio is 
below 5, as described in U.S. Pat. No. 4,436,689. 
Since even in this present process the viscosity of the solution formed 
increases as the molecular weight of the polyethylene increases, so that 
the solutions become more difficult to process, generally polyethylene 
with molecular weights of more than 15.times.10.sup.6 will not be used, 
although indeed the present process is operable with such and even high 
molecular weights. The weight-average molecular weights referred to herein 
can be determined according to already known methods such as gel 
permeation chromatography and light scattering. 
This process is also very suitable for preparing homogeneous solutions of 
high-molecular weight polypropylene, particularly of polypropylene with a 
weight-average molecular weight of more than 25.times.10.sup.4, and 
preferably of at least 5.times.10.sup.5. 
The present process can also be used for preparing solutions of 
high-molecular weight polyamides, such as are prepared from lactams, 
particularly caprolactam, by anionic polymerization, having a 
weight-average molecular weight of at least 2.times.10.sup.5 and also 
high-molecular weight polyvinylalcohol, particularly having a 
weight-average molecular weight of at least 0.5.times.10.sup.5. 
The process is further particularly suitable for preparing homogeneous 
solutions of polyacrylonitrile having a weight-average molecular weight of 
at least 3.times.10.sup.5, specifically of 5.times.10.sup.5 to 
5.times.10.sup.6. Such a polyacrylonitrile can be obtained in a manner 
already known per se, for instance by free radical polymerization in 
emulsion or in solution. When here and elsewhere in the present 
application the term polyacrylonitrile is used, it is understood to refer 
to homopolymers of acrylonitrile as well as a copolymer of acrylonitrile 
with minor amounts, for instance up to 15 wt.%, of monomers compatible 
therewith, such a methacrylates, acrylates, vinylacetate. 
The concentration of polymer in the solution may vary, depending in part on 
the nature of the solvent, the molecular weight and type of the polymer 
and the desired use of the prepared solution. For the preparation of 
filaments and ribbons via the so-called gel-spinning method solutions with 
concentrations between 1 and 40 wt.%, specifically from 2 to 30 wt.%, will 
generally be used, while for other uses solutions having concentrations up 
to 50 wt.% may be desirable. 
The choice of the solvent is itself not critical. Any suitable solvent 
which is liquid at room temperature and in which the polymer is readily 
soluble at higher temperatures, preferably temperatures above the 
dissolution temperature, can be used. Of course, a mixture of suitable 
solvents can be applied too. In the preparation of solutions of 
polyolefins, particularly polyethylene, generally a halogenated or 
non-halogenated hydrocarbon will be used, such as paraffins, toluene, 
xylene, monochlorobenzene, nonane, decane, undecane, dodecane, tetralin, 
decalin or petroleum fractions with corresponding boiling ranges. In the 
preparation of solutions of polyacrylonitrile the solvents used will 
generally be substances capable of eliminating intermolecular 
dipole-dipole ineractions, such as dimethylformamide, dimethylacetamide, 
dimethylsulfoxide or ethylenecarbonate. In preparing solutions of 
polyamides the solvent used may be, inter alia, benzylalcohol, while it is 
an advantage to use dimethylsulfoxide, glycol or glycerol as solvent for 
high-molecular polyvinylalcohol. 
In the present invention the transformation of the polymer suspension into 
a homogeneous solution should take place at above about a minimum 
temperature generally equal to the so-called dissolution temperature 
(whereat a clear solution will be observed) for the particular 
polymer-solvent combination used, e.g. at least about 90.degree. C. in the 
case of polyethylene. This temperature must, however, be lower than the 
temperature at which substantial thermal decomposition of the polymer 
occurs. The selected temperature will generally also be below the boiling 
point of the solvent at the prevailing operating pressure in the 
equipment. In particular, a temperature between about 140.degree. and 
220.degree. C. may generally be employed, depending on the solvent used. 
In the process according to this invention the suspension is subjected to a 
mixing and kneading treatment at high mechanical shear rates in the mixing 
sections of the extruder employed, i.e. the suspension is exposed to the 
action of a mixing section in an extruder, provided with one ore more 
screws. Preference is given to the use of a twin-screw extruder provided 
with alternate conveying and mixing sections. However, it is also possible 
to use single-screw extruders if the same are provided with both mixing 
and conveying sections and which preferably have a grooved wall and 
conveying pins. 
In order to achieve a high shear rate and a short residence time, the 
rotational speed of the extruder screws must be rather high. With a 
twin-screw extruder this must generally be more than 30, for instance 
about 150-300, and preferably about 200, revolutions per minute. The speed 
of rotation should be such that mechanical shear rates of between 30 and 
2,000 sec.sup.-1, advantageously from 100 to 300 sec.sup.-1 are achieved. 
In the practice of the present invention it has also been found that 
effective production of homogeneous solutions can be achieved with very 
short mixing times. The time required for the transformation from 
suspension to homogeneous solution will be less than (0.3 D) minutes, 
wherein D denotes the diameter of said extruder in millimeters. Preferably 
said time is less than (0.2 D) minutes and even below (0.1 D) minutes. 
Generally said time will be less than 60 minutes, advantageously less than 
30 minutes and specifically 20 minutes at most, this for a (semi) 
commercial extruder. 
Within the stated principles and parameters for this invention, a person 
skilled in the art will now be able to select an appropriately designed 
and dimensional twin- or single-screw extruder to practice this process. 
The solutions thus obtained by this invention can be used for various 
purposes. In particular they are suitable to be processed via 
thermo-reversible gelling and stretching into ultrastrong polymer 
articles, such as fibers, ribbons, bands, tapes, and films etc. In so 
doing, it is highly advantageous to install a gear pump at the exit end of 
the extruder for purposes of metering the flow therefrom to the aperture 
or orifice of the spinning head, or equivalent device. 
The invention will now be further elucidated in the following examples 
without, however, being limited thereto.

EXAMPLE I 
A high-molecular weight polyethylene of the grade Hifax-1900 (Hercules) 
with a weight-average molecular weight M.sub.w of about 2.times.10.sup.6 
(.eta. decalin, 135.degree. C.-18.5.degree.; Fliesswert N/mm.sup.2 -0.32) 
was suspended in decalin to a nominal concentration of 5 wt.% at room 
temperature. After deaeration and washing with nitrogen and addition of a 
stabilizer composition the suspension was fed to an extruder while being 
stirred continuously (in order to prevent settling of the suspension). A 
co-rotating twin screw-extruder of the ZSK type of the firm of Werner and 
Pfleiderer was used; diameter 30 mm; L/D ratio=27. This extruder had 
2.times.30 mm screws composed of alternating conveying and mixing 
elements. The suspension was supplied at room temperature to the feed 
zone, the thermostat temperature of which was set to about 80.degree. C. 
The suspension of polyethylene in decalin was then extruded at about 
180.degree. C. (head temperature) at a screw speed of 200 rpm 
corresponding with an overall residence time in the extruder of about 3 
minutes. 
Under the above conditions the process produced a clear solution free of 
suspended particles, having a constant homogeneous composition and 
concentration. 
EXAMPLE II 
In the same way as in example I, a 3 wt.% suspension of Hifax-1900 in 
paraffin was extruded at 180.degree. C., a screw speed of 140 rpm and a 
residence time of about 4 minutes. 
A homogeneous, clear solution was obtained. 
EXAMPLE III 
In the same way as in example I a 15 wt.% suspension of a high-molecular 
weight polyethylene of the grade Hostalen GUR 412 (Ruhrchemie/Hoechst) 
with a weight-average molecular weight of about 1.5.times.10.sup.6 (.eta. 
decalin, 135.degree. C.=15: Fliesswert=0.24 N/mm.sup.2) in decalin was 
extruded at 180.degree. C., a screw speed of 180 rpm and an extruder 
residence time of about 3 minutes. 
A homogeneous, clear solution was obtained. 
EXAMPLES IV-XXX 
In the same way as in Example I, various suspensions of high-molecular 
weight polyethylenes in solvents were transformed into homogeneous clear 
solutions. The results are summarized in Table 1. (Hizex 240 M is a type 
of polyethylene of the firm Mitsui Petrochemicals with a weight-average 
molecular weight of about 1.9.times.10.sup.6 (.eta. decalin, 135.degree. 
C.=15.5, Fliesswert=0.30 N/mm.sup.2).) 
TABLE 1 
__________________________________________________________________________ 
Concentration 
Extruder 
Extruder 
Example of solution 
Temperature 
Speed 
No. Polymer Solvent 
wt. % .degree.C. 
r.p.m. 
__________________________________________________________________________ 
I Hifax-1900 
Decalin 
5 180 200 
II Hifax-1900 
Paraffin 
3 180 140 
III Hostalen GUR 412 
Decalin 
15 180 180 
IV Hifax-1900 
Decalin 
10 200 210 
VI Hifax-1900 
Decalin 
15 195 160 
VII Hifax-1900 
Decalin 
20 200 170 
VIII Hifax-1900 
Decalin 
10 190 100 
IX Hifax-1900 
Paraffin 
8 185 60 
X Hostalen GUR 412 
Paraffin 
5 200 50 
XI Hostalen GUR 412 
Paraffin 
5 200 35 
XII Hostalen GUR 412 
Paraffin 
3 200 100 
XIII Hostalen GUR 412 
Paraffin 
3 200 300 
XIV Hostalen GUR 412 
Decalin 
3 180 250 
XV Hostalen GUR 412 
Decalin 
3 180 300 
XVI Hostalen GUR 412 
Decalin 
3 180 100 
XVII Hostalen GUR 412 
Decalin 
3 180 30 
XVIII 
Hizex 240 M 
Paraffin 
7 200 150 
XIX Hizex 240 M 
Paraffin 
7 200 200 
XX Hizex 240 M 
Decalin 
5 180 100 
XXI Hizex 240 M 
Decalin 
5 180 220 
XXII Hizex 240 M 
Decalin 
7 180 180 
XXIII 
Hizex 240 M 
Decalin 
3 250 280 
XXIV Hizex 240 M 
Paraffin 
5 200 60 
XXV Hizex 240 M 
Paraffin 
5 200 100 
XXVI Hizex 240 M 
Paraffin 
5 200 200 
XXVII 
Hostalen GUR 412 
Decalin 
15 180 150 
XXVIII 
Hifax-1900 
Decalin 
20 200 80 
XXIX Hifax-1900 
Decalin 
20 200 100 
XXX Hifax-1900 
Decalin 
20 200 200 
__________________________________________________________________________ 
EXAMPLES XXXI-XXXV 
A number of solutions obtained according to the invention were transformed 
into filaments by processing the solution through a spinning aperture (1 
mm), quenching with water and extraction with dichloromethane, followed by 
single step stretching or drawing at 120.degree. C. In that process gel 
filaments of very high stretchability and product filaments having very 
high modulus and tensile strength were obtained. The results are 
summarized in Table II which clearly demonstrates the excellent 
homogeneity of the solutions according to the invention. 
The transporting behaviour, the mixing and the kneading of the material, 
the viscosity of which increases (difference in viscosity between the 
suspension and the solution is e.g. in the magnitude of a factor 
1000)depends inter alia on the polymer and the solvent used, the 
concentration applied, the screw design and the speed of the extruder. 
Particularly for filament production, it is advantageous to insert between 
the extruder and the shaping or spinning head a gear pump, which 
guarantees a continuous yield of adjusting the residence time 
independently of the selected polymer, solvent, concentration, screw 
design and speed (r.p.m.) of the extruder. 
TABLE II 
__________________________________________________________________________ 
Residence 
Concen- Speed 
time in 
Draw Tensile 
Example tration Extruder 
extruder 
ratio 
strength 
Modulus 
No. Polymer 
Solution 
Solvent 
in r.p.m. 
in min. 
120.degree. C. 
in GPa 
in GPa 
__________________________________________________________________________ 
XXXI Hostalen 
3% Decalin 
30 18 40 1.2-1.5 
30-37 
GUR 412 
XXXII 
Hostalen 
3% Decalin 
100 7 60 2.1-2.4 
50-55 
GUR 412 
XXXIII 
Hostalen 
3% Decalin 
200 3 60 2.4-2.8 
70-80 
GUR 412 
XXXIV 
Hostalen 
3% Decalin 
300 3 45 3.1-2.4 
60-70 
GUR 412 
XXXV Hifax-1900 
3% Paraffine 
200 9 67 2.0-2.2 
60-70 
__________________________________________________________________________ 
EXAMPLES XXXVI-LXXXII 
A number of solutions obtained according to the invention were transformed 
into filaments in the manner described in Examples XXXI-XXXV except that 
between the extruder and aperture a gear pump was installed, of type 
Feinpruf 2.times.0.9. The gel filaments thereby obtained show very high 
drawability and the product show very high drawability and the product 
filaments possess very high modulus and strength properties even after 
only a one step drawing, this over a very broad range of speed and with 
very short residence times. The results are summarized in Table III. 
TABLE III 
__________________________________________________________________________ 
Concen- Residence 
tration Speed 
time in 
Draw 
Tensile 
Example of solution 
Extruder 
extruder 
ratio 
strength 
Modulus 
No. Polymer 
in wt. % 
Solvent 
in r.p.m. 
in min. 
120.degree. C. 
in GPa 
in GPa 
__________________________________________________________________________ 
XXXVI Hizex 240 M 
3 Decalin 
30 12 48 2.2 97 
XXXVII 
" 100 12 46 2.3 85 
XXXVIII 
" 200 12 50 2.3 95 
XXXIX " 300 12 43 2.6 80 
XL Hizex 240 M 
3 Decalin 
30 6 60 2.4 80 
" 100 6 50 2.7 95 
" 200 6 52 2.6 90 
" 300 6 50 2.4 80 
XLIV Hizex 240 M 
3 Decalin 
30 3,3 40 2.1 85 
XLV " 100 3,3 55 2.6 85 
XLVI " 200 3,3 55 2.7 90 
XLVII " 300 3,3 58 2.4 90 
XLVIII 
Hizex 240 M 
3 Decalin 
100 2,1 52 2.3 90 
XLIX " 200 2,1 55 2.6 95 
L " 300 2,1 52 3.2 95 
LI Hifax 1900 
3 Decalin 
100 12 35 1.7 75 
LII IV = 18 200 12 55 2.4 80 
LIII " 300 12 57 2.7 85 
LIV Hifax 1900 
3 Decalin 
30 6 52 2.7 90 
LV " 100 6 52 2.7 85 
LVI " 300 6 49 2.5 80 
LVII Hifax 1900 
3 Decalin 
30 3,3 55 2.1 80 
LVIII " 100 3,3 43 2.3 75 
LIX " 300 3,3 50 2.2 75 
LX Hifax 1900 
3 Decalin 
100 2,1 64 1.4 80 
LXI " 200 2,1 52 2.1 75 
LXII " 300 2,1 43 1.9 85 
LXIII Hizex 240 M 
5 Decalin 
30 12 41 2.9 65 
LXIX " 100 12 45 2.5 80 
300 12 47 1.9 75 
LXXII Hizex 240 M 
5 Decalin 
30 6 44 1.7 50 
LXXIII 
" 100 6 42 2.0 50 
LXXIV " 200 6 40 1.4 65 
LXXV " 300 6 40 1.9 45 
LXXVI Hizex 240 M 
5 Decalin 
30 3,3 45 1.9 60 
LXXVII 
" 100 3,3 44 1.8 60 
LXXVIII 
" 200 3,3 43 2.3 50 
LXXIX " 300 3,3 48 2.0 65 
LXXX Hizex 240 M 
5 Decalin 
100 2,1 48 1.7 60 
LXXXI " 200 2,1 37 1.9 35 
LXXXII 
" 300 2,1 38 1.7 40 
__________________________________________________________________________ 
EXAMPLE LXXXIII 
To the feed zone of a co-rotating twin-screw extruder, the thermostated 
temperature of which zone was set at 80.degree. C., a finely divided 
(.delta..sub.50 =90 .mu.m), high-molecular polyethylene of the Hostalen 
GUR 412 grade (of the firm Ruhrchemie/Hoechst) with a weight-average 
molecular weight of about 1.5.times.10.sup.6 and decalin were supplied at 
a polyethylene: decalin weight ratio of about 1:30. The extruder used was 
of the ZSK type, of the firm of Werner and Pfleiderer, L/D=27, provided 
with 2.times.30 mm screws composed of alternate conveying and mixing 
elements. The temperature in the extruder was 170.degree.-180.degree. C., 
the speed was about 220 revolutions per minute. 
After a residence time of 2.7 minutes the mixture obtained was carried off 
via an aperture (diameter 1 mm) at the other end of the extruder and into 
a water bath, by which operation a solvent-containing gel filament was 
obtained having a homogeneous structure, which gel filament was found to 
be extremely suitable to be transformed via ultra-high drawing 
(single-step, 60.times.) to form a filament with a very high modulus (80 
GPa) and tensile strength (2.8 GPa). 
EXAMPLE LXXXIV 
The process of example XXXVI was repeated, however using extruder speeds of 
30, 100 and 300 revolutions per minute and residence times of, 
respectively, 18, 7 and 3 minutes. The gel filaments thereby obtained were 
of a very homogeneous structure and could be converted via stretching at 
high draw ratios (40.times. to 60.times.) into filaments with high tensile 
strengths (1.5 to 2.4 GPa) and moduli (37-70 GPa). 
EXAMPLE LXXXV 
The process of example XXXVI was repeated using an approximately 3 wt.% 
suspension of Hostalen GUR 412 in decalin prepared in a stirring flask and 
being metered to the feed zone of the extruder. 
The results were the same as those of Example I. 
EXAMPLE LXXXVI 
In the same way as in example XXXVIII a 3 wt.% suspension of a polyethylene 
of the Hifax-1900 grade (of the firm of Hercules), with a weight-average 
molecular weight of about 2.times.10.sup.6, in paraffin was fed to the 
extruder operating at a speed of 200 revolutions per minute and a 
residence time of 9 minutes. 
After quenching in a water bath a very homogeneous gel filament was 
obtained. The filament was passed through an extraction bath of 
dichloromethane and was found to be capable of being subjected to 
ultra-high stretching (about 54.times.), from which stretching operation 
filaments having a tensile strength of about 2.1 GPa and a modulus of 
about 70 GPa were obtained. 
EXAMPLE LXXXVII 
The process of example XXXIX was repeated except that this time the outlet 
of the extruder was a slit (2.times.20 mm). 
After quenching a ribbon-shaped gel was obtained, which could be stretched 
after extraction (draw ratio&gt;60.times.) to form an extremely thin (&lt;0.5 
mm), very strong ribbon (tensile strength and modulus about 2.0-2.2 GPa, 
and 60-70 GPa respectively). 
EXAMPLE LXXXVIII-LXXXIX 
The process of example LXXXVII was repeated, except that suspensions of 
Hifax-1900 in decalin were used with concentrations of 10, 15 and 20 wt.%, 
respectively, a temperature of 200.degree. C. being maintained in the 
extruder. 
After quenching, gel ribbons were obtained having a very homogeneous gel 
structure, which ribbons could be subjected to ultra-high stretching 
(40-70.times.). 
EXAMPLE LXXXX 
The process of example LXXXIX was repeated with a suspension of Hifax-1900 
in decalin at 15 wt.%. The mixture leaving the extruder was then poured 
out onto a cooling roll to form a gel film having a thickness of 2 mm and 
a width of 100 mm. This film was found to have a very homogeneous gel 
structure and could be transformed via stretching (about 25.times.) into 
an extremely thin, very strong film. 
EXAMPLE LXXXXI 
The process of example LXXXX was repeated, except that a finely divided 
(.delta..sub.50 =120 .mu.m) suspension of Hifax-1900 in decalin, at a 
weight ratio of 1:4 was fed to the feed zone of the extruder. 
The results were equivalent to those of example LXXXX. 
EXAMPLES LXXXXII-LXXXXVI 
A number of solutions obtained according to the invention were transformed 
into filaments in the manner described in examples XXXVI-LXXXII, except 
that a two-step stretching at 120.degree. C. and 140.degree. C. was 
applied. 
The polymer used (Hizex 145 M) is a polyethylene of the firm Mitsui 
Petrochemicals with a weight-average molecular weight of 
1.06.times.10.sup.6 and an intrinsic viscosity of about 8.2. As solvent 
use was made of decaline. The rotational speed of the extruder was about 
160 rpm; the residence time in the extruder amounted to about 3 minutes. 
The results are summarized in Table IV. 
TABLE IV 
______________________________________ 
Concentration of 
Tensile 
solution strength Modulus titer 
Example (wt. %) (GPa) (GPa) (dtex) 
______________________________________ 
LXXXXII 3.3 1.7 85 6 
LXXXXIII 
6.4 2.0 65 20 
LXXXXIV 10.3 1.9 60 30-200 
LXXXXV 25.6 2.3 70 6 
LXXXXVI 31.5 2.3 70 6-50 
______________________________________ 
EXAMPLES LXXXXVII-C 
A number of solutions obtained according to the invention were transformed 
into filaments via a two-step stretching as described in Examples 
LXXXXII-LXXXXVI. The solvent used was decaline. 
The results are summarized in Table V. 
TABLE V 
__________________________________________________________________________ 
Concentration 
Extruder 
Residence time 
tensile strength 
modulus 
tensile 
modulush 
solution speed 
in extruder 
(after 1st stretching) 
(after 2nd stretching) 
Example 
Polymer 
wt. % rpm min. GPa GPa GPa GPa 
__________________________________________________________________________ 
LXXXXVII 
Hifax 1900 
5 200 6 1.7 75 2.7 
(IV 18) 
LXXXXVIII 
Hifax 1900 
3 30 12 1.8 70 2.8 140 
(IV 30) 
IC Hifax 1900 
3 100 12 2.0 75 2.9 125 
(IV 30) 
C Hifax 1900 
3 200 6 2.0 90 3.0 140 
(IV 30) 
__________________________________________________________________________ 
COMATIVE EXAMPLE A 
20 liters of a 5 wt.% suspension of Hostalen GUR 412 in decalin was metered 
into a glass flask. The suspension was deaerated and flushed with 
nitrogen, after which a stabilizer was added. The suspension was slowly 
stirred at 160.degree. C. (&lt;30 rpm) for about 2 hours. Subsequently, 
without stirring, the suspension was subjected to ageing at 160.degree. C. 
for 2 hours. 
The resulting solution was clearly non-homogeneous. In the processing of 
this solution via spinning (spinning aperture 1 mm), quenching in water, 
extraction with dichloromethane and stretching at 120.degree. C., 
filaments were obtained which varied widely as to thickness, 
strechability, tensile strength and modulus. 
COMATIVE EXAMPLE B 
The process of example A was repeated, but now at a suspension volume of 
only 0.8 liters. The resulting solution was macroscopically homogeneous 
and could be transformed via the method described in example A into gel 
filaments with reasonable stretchability (max. 30.times.), upon which 
filaments with a tensile strength of 1-1.5 GPa and a modulus of 40-50 GPa 
were obtained. 
These two comparative examples A and B show that on a larger scale, the 
production of homogeneous solutions via the customary stirring method is 
extremely difficult. 
COMATIVE EXAMPLE C 
A 5%-(wt) suspension of Hostalen GUR 412 in decalin was metered to a 
single-screw extruder type Gottfert GFT 015-1-01/04 with a diameter of 20 
mm, an L/D ratio of 22, and having no intermediate mixing sections. 
Therein the suspension was transformed at 160.degree.-170.degree. C. at a 
speed of 30 rpm, to obtain an optically homogeneous solution. 
However, the filaments thereby obtained via the spinning method described 
in Example A were extremely non-homogeneous and broke during stretching. 
COMATIVE EXAMPLE D 
The process of example C was repeated, however this time the solution from 
the extruder was subjected to an ageing process of 2-15 hours at 
160.degree. C. The stretchability of the gel filaments was now at most 
40.times., while the filaments obatined had a tensile strength of about 2 
GPa and a modulus of about 60 GPa. 
These two comparative examples C and D show that the production of a really 
homogeneous solution in an extruder not provided with both mixing and 
conveying parts is possible only by use of non-economic prolonged 
after-ageing stage. 
As indicated by the foregoing examples according to this invention, the 
extruded products may be passed directly into a gaseous or liquid 
quenching medium, wherein the same are cooled almost instantaneously to 
below the gelling temperature. By this operation the extrudate is 
converted into the gel-state, and can then be further converted via 
stretching or drawing at high and even ultra-high stretch ratios, whether 
or not after removal of all or part of the solvent. Articles having a high 
tensile strength and modulus are thereby formed, for instance filaments, 
ribbons, bands, tapes, films, tubes, etc. It is, of course, also possible 
for the extrudate to be carried out directly from the extruder so as to be 
spread directly onto a solid cooled surface, for instance, a cooling roll, 
to thereby form, especially, a film-shaped gel article. Films may also be 
formed from extruded gel tubes by blowing the same, with mono- and/or 
bi-axial stretching. 
The gel articles obtained in the present process can thus especially be 
used for conversion into filaments, fibers, bands, ribbons, tapes, films, 
tubes, etc. with a high tensile strength and a high modulus via stretching 
at preferably elevated temperature, whether or not after removal of all or 
part of the solvent. 
It may also be an advantage for the gel products produced by the process of 
this invention to be subjected to irradiation, particularly electron 
radiation, before or during the stretching or drawing procedure, by which 
irradiation process improved novel products, especially having reduced 
creep and fibrillation characteristics are obtained.