EP3455396A1

EP3455396A1 - Method for producing a multifilament yarn and multifilament yarn

Info

Publication number: EP3455396A1
Application number: EP16723074.7A
Authority: EP
Inventors: André Lehmann; Evgueni TARKHANOV
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2016-05-11
Filing date: 2016-05-11
Publication date: 2019-03-20
Also published as: WO2017194103A1; US20190186051A1; JP2019523833A; US11649567B2; JP6802291B2

Abstract

The present invention relates to a method for producing a multifilament yarn from a melt of a copolymer of polyacrylic nitrile. The method is characterized in that a multifilament yarn is produced by means of pressing a melt of a copolymer through a spinning nozzle and is subsequently stretched at least tenfold. The present invention further relates to a correspondingly produced multifilament yarn.

Description

Process for producing a multifilament yarn, and

multifilament yarn

The present invention relates to a process for producing a multifilament yarn from a melt of a copolymer of polyacrylonitrile. The method is characterized in that a multifilament yarn is produced by pressing a melt of a copolymer through a spinneret and then stretched at least ten times. The present invention also relates to a correspondingly produced multifilament yarn.

The industrial production and marketing of carbon fibers began in 1963. At that time, CE developed and patented. Ford and CV. Mitchell of Union Carbide describes a continuous process for the production of carbon fibers based on cellulose precursors [Ford CE, Mitchell CV, US Pat., 3,107,152, 1963]. As early as 1964, carbon fibers with the trade name »Thornel 25« with strengths of 1.25 GPa and moduli were used of 172 GPa launched in the market. Later followed the brands "Thornel 50", "Thornel 75" and "Thornel 100". The latter carbon fibers were characterized by strengths of 4.0 GPa and moduli of 690 GPa. The excellent property profile could only be achieved by a special process control. The cellulose fibers were exposed to temperatures of 2500-3000 ° C and thereby deformed (stretch graphitization). Only at these high temperatures can graphite be plastically deformed and oriented along the fiber axis, thereby achieving competitive fiber properties.

However, the manufacturing process was so costly (up to $ 1000 / kg carbon fiber) and uneconomical (carbon yield only 10-20 wt%) that in 1978 the production of carbon fibers based on cellulose precursors was almost completely stopped and currently only For

Niche applications exist. The decline of the cellulose-based carbon fiber is closely related to the development of PAN (polyacrylonitrile) based carbon fibers, which allow significantly higher carbon yields with the same property profile.

At present, polyacrylonitrile (PAN) or copolymers of polyacrylonitrile are the dominant polymers as starting material for the production of precursor filament yarns (> 95%) and carbon fibers produced therefrom. The wide range of Ex-PAN carbon fibers is complemented by the ultra-high modulus pitch-based carbon fibers. A

Overview of production capacities, chemical and physical structure and mechanical properties as well as applications of such carbon fibers is described in J.P. Donnet et al., Carbon fibers, third edition, Marcel Dekker, Inc. New York, Basle, Hong Kong.

As stated in DE 10 2014 219 707, acrylic precursor fibers have hitherto been produced exclusively by wet or dry spinning processes. For this purpose, a solution of the polymers with concentrations <20% is spun either in a coagulation bath or a hot steam atmosphere, wherein the solvent diffuses out of the fiber. In this way, high-quality precursors are produced, but the costs of the methods are comparatively high. This results on the one hand from the required solvents and their handling, on the other hand from the relatively low throughput in solution spinning process. As shown in DE 10 2014 219 707, melt-spinnable copolymers of polyacrylonitrile (PAN) have been successfully synthesized by copolymerization of acrylonitrile with an alkoxyalkyl acrylate and also continuously melt-formed into monofilaments. This demonstrates the basic processability of the claimed polymers from the melt. The titres of the monofilaments shown are> 1 tex. This filament titer is too high for conversion of the precursor, since the diffusion path for the occurring gaseous cleavage product from the filament, during the thermal treatment of the precursor to stabilize this and to carbonize, are too long. This results in an increasing internal pressure in the filament and inevitably leads to imperfections, which do not even allow a continuous conversion or in significantly low textile-physical properties of the resulting carbon fiber. Therefore, it is essential to lower the filament titer. In order to make this possible, a multifilament spinning process has been developed for the copolymers of polyacrylonitrile described in DE 10 2014 219 707.

Thus, it is an object of the present invention to provide a process for the production of a multifilament yarn with which the filament denier of

Sawed off multifilament yarns, i. can be reduced. In addition, the corresponding multifilament yarns should have the highest possible stability. Object of the present invention is also to name appropriate multifilament yarns.

This object is achieved in terms of a method for producing a multifilament yarn having the features of claim 1, with respect to a multifilament yarn having the features of claim 18. The respective dependent claims represent advantageous further development.

The invention thus relates to a process for producing a multifilament yarn in which a melt of a copolymer of polyacrylonitrile (PAN), preparable by a copolymerization of 95 to 60 mol% of acrylonitrile with at least one comonomer selected from a) 5 to 20 mol% of at least one alkoxyalkyl acrylate of the general formula I,

Formula I

with R = CnH ₂ n ₊ i and n = 1-8 and m = 1-8, in particular n = l-4 and m = l-4

0 to 10 mol% of at least one alkyl acrylate of the general formula II

Formula II

with R '= C _n H ₂ n ₊ i and n = 1-18, and

c) 0 to 10 mol% of at least one vinyl ester of the general formula III

Formula III

with R = C _n H _{2n +} i and n = 1-18,

in a melt spinning process by means of

Extrusion of a melt of the copolymer is spun through a plurality of spinning holes having spinneret to a multifilament yarn, and

the multifilament yarn is stretched at least 10-fold.

In the method according to the invention thus a melt of the aforementioned copolymer is pressed through a spinneret. The spinneret has a multiplicity of spinning holes, and when the melt of the copolymer is extruded through the spinneret, this results in one of the number of spinnerets. punch corresponding number of individual filaments. The corresponding individual filaments are bundled into multifilament yarn. The multifilament yarn is then drawn.

According to a preferred embodiment, the multifilament yarn is stretched by at least 20 times, preferably by 25 to 1000 times, in particular 150 to 400 times.

A further preferred embodiment of the method provides that the multifilament yarn is cooled before or during drawing. The cooling can be carried out in such a way that the multifilament yarn formed is supplied with gases, in particular air. The gas is preferably heated to temperatures of -50 to + 50 ° C, in particular to temperatures of 0 to 25 ° C.

Under a stretching while the first-time extension of the multifilament yarn is referred to after its formation.

After stretching, an additional extension of the multifilament yarn can take place, this is spoken of stretching. The stretching is preferably carried out at least 1.1 to 10 times, preferably 1.1 to 6 times, the length of the multifilament yarn before the stretching operation.

Both stretching and stretching can take place by means of godets, in particular heated godets, in which case the temperatures of such godets are set to at least 50 ° C., preferably 50 to 150 ° C., in particular 55 to 90 ° C.

According to a further preferred embodiment, it is provided that the multifilament yarn is drawn from the spinneret with a nozzle delay of <3000, preferably <1500 to 10, particularly preferably <500 to 30.

This embodiment relates to the individual filaments from which the multifilament is formed. The distortion is directed to the respective individual filaments immediately after exiting the nozzle. Particularly advantageous in the present invention is that hiding the multifilament can be carried out such that a degree of orientation of the crystalline regions in the filaments forming the multifilament of> 0.7, preferably from 0.75 to 0.95, particularly preferably from 0 , 8 to 0.9 resulted.

By this measure, thus, the mechanical strength of the multifilament yarn can be further increased. It is also possible that the spinneret to a temperature at least

10 K above the temperature of the melt of the copolymer is, preferably to a temperature of 10 to 80 K, in particular 15 to 45 K above the temperature of the melt of the copolymer is adjusted.

The melt of the copolymer can be at a temperature of 120 to 300 ° C, preferably 150 to 230 ° C and / or a zero shear viscosity (determined by means of a rheometer HAAKE RS 150 with plate-cone (l °) arrangement with a diameter of the measuring geometries of 20 mm and a gap opening of 0.052 mm) of <5000 Pa s, preferably 500 to 3000 Pa s, particularly preferably 1000 to 1500 Pa s are set.

In addition, it is advantageous if the individual filaments and / or the multifilament yarn formed from the individual filaments is cooled with a cooling medium, preferably a gaseous cooling medium, in particular air, nitrogen or argon, wherein the cooling medium preferably has a temperature which is at least 10 ° C below the Temperature of the melt of the copolymer is, with preferred temperatures in the range of 10 to 200, more preferably from 15 to 80 are. The multifilament yarn can be drawn off at a final take-off rate of at least 300 m / min, preferably at least 500 to 5000 m / min, in particular 750 to 2000 m / min. The final take-off speed refers to the speed with which the multifilament yarn is ultimately wound up on a roll.

The multifilament yarn may be composed of 50 to 5,000 individual filaments 500 to 4000 individual filaments, in particular 1000 to 3000 individual filaments may be formed.

The individual filaments on which the multifilament is based are preferably adjusted to a fineness of <10 dtex, preferably from 0.01 to 10 dtex, particularly preferably from 0.1 to 5 dtex.

The spinning holes may have a round, oval, Y-shaped, star-shaped or n-cornered with 8> n> 3 geometry and / or a length to diameter ratio of 1 to 20, preferably 2 to 8.

The diameter of the spinnerets is preferably in the range of 10 to 1000 μιη, preferably 50 to 750 μιη, more preferably 100 to 500 μιη.

In particular, it is advantageous if no dimethylacetamide, dimethyl sulfoxide and / or water as the plasticizing agent, in particular no plasticizing agent at all, are added to the melt of the copolymer.

More preferably, the copolymer has a weight-average molar mass (Mw) in the range of 10,000 to 150,000 g / mol, preferably 15,000 to 80,000 g / mol.

In a particularly preferred embodiment, the copolymer has from 90 to 78 mole% of acrylonitrile

8 to 12 mol% of the comonomer a),

1 to 5 mol% of the comonomer b) and / or

1 to 5 mol% of the comonomer c).

The invention further relates to a multifilament yarn consisting of a plurality of individual filaments of a copolymer of polyacrylonitrile (PAN), preparable by a copolymerization of 95 to 80 mol% of acrylonitrile with at least one comonomer selected from a) 5 to 20 mol% of at least one alkoxyalkyl acrylate of the general formula I,

Formula I

with R = C _n H _{2n +} i and n = 1-8 and m = 1-8, in particular n = l-4 and m = l-4

b) 0 to 10 mol% of at least one alkyl acrylate of the general formula II

Formula II

with R '= C _n H _{2n +} i and n = 1-18, and

c) 0 to 10 mol% of at least one vinyl ester of the general formula III

Formula III

with R = C _n H _{2n +} i and n = 1-18,

characterized by a degree of orientation of the crystalline regions in the individual filaments of> 0.7, preferably from 0.75 to 0.95, particularly preferably from 0.8 to 0.9.

The multifilament yarn according to a preferred embodiment of 50 to 5000 individual filaments, preferably 500 to 4000 individual filaments, in particular 1000 to 3000 individual filaments. A further preferred embodiment of the multifilament yarn according to the present invention provides that the individual filaments on which the multifilament yarn is based have a fineness of <10 dtex, preferably from 0.01 to 10 dtex, particularly preferably from 0.1 to 5 dtex.

For example, the inventive method can be designed such that by means of a 1-screw extruder (L / D 25), the dried granules are successively melted, supplied to the gear pump, the constant volume flow of the melt through the spinneret promoted and the exiting filaments by means of a gas is cooled and stretched many times in the subsequent stretching unit by means of temperature-controllable godets to achieve Einzelfilamenttiter of <3 dtex. It is completely dispensed with the addition of water or solvent.

The multifilament yarn according to the present invention can be produced in particular according to a further inventive method.

The present invention will be further illustrated by the following exemplary embodiments, without limiting the invention thereto.

example 1

The dried (vacuum 60 ° C./24 h) copolymer of PAN having a composition of 6.5 mol% of methoxyethyl acrylate and 93.5 mol% of acrylonitrile and an average molecular weight Mw of 43000 g / mol and a PDI of 1.3 was obtained in a 1-screw extruder (L / D 25) dosed. To avoid sticking, the feeder was cooled and then the temperature in the zones of the extruder increased from 150 ° C to 235 ° C. The produced melt of the PAN copolymer was constantly conveyed by means of a gear pump through a 32-hole spinneret with a round hole geometry, an L / D of 6 and a hole diameter of 300 μm. The exiting

Filaments were cooled by means of an injection shaft and the nozzle delay of 98 realized by means of a withdrawal godet. On the downstream stretching godet, a degree of stretching of 1.6 could be realized before the produced multifilament yarn was continuously wound on a bobbin by a winding head.

The single filament denier was 2.9 dtex and the filament had a tenacity of 20.3 cN / tex, an modulus of elasticity of 653 cN / tex and an elongation at break of 19.7% up. The degree of orientation of the crystalline phase determined by WAXS was 0.82.

Example 2

The dried (vacuum 60 ° C / 24 h) copolymer of PAN having a composition of 9.5 mol% of methoxyethyl acrylate and 90.5 mol% of acrylonitrile and an average molecular weight Mw of 55000 g / mol and a PDI of 1.2 was in a 1-screw extruder (L / D 25) dosed. The procedure was as in Example 1, the final spinning temperature was in contrast to Example 1 220 ° C. It was a 70 hole nozzle with a L / D of 4 and round hole geometry (d = 200 iim) promoted. The exiting filaments were cooled by means of an injection shaft and the nozzle delay of 82 realized by means of a take-off godet. On the downstream Reckgaletten could a max. Degree of stretching of 2.1 at a Galettentemperatur of 85 ° C before the produced multifilament yarn was wound by a winding head continuously at a speed of 1500 m / min on a spool.

The filament has a circular cross-section and the single filament titer was 2.1 dtex and the filament had a tenacity of

37.3 cN / tex, an E modulus of 853 cN / tex and an elongation at break of 13.7%. The degree of orientation of the crystalline phase determined by WAXS was 0.85. Example 3

The dried (vacuum 60 ° C / 24 h) copolymer of PAN having a composition of 9.3 mol% of methoxyethyl acrylate and 90.7 mol% of acrylonitrile and an average molecular weight Mw of 85000 g / mol and a PDI of 1.2 was in a 1-screw extruder (L / D 25) dosed. The procedure was as in Example 1, the final spinning temperature was in contrast to Example 1 220

° C. It was a 70 hole Di.ise promoted with a L / D of 4 and round hole geometry (d = 350 μιη). The emerging filaments were cooled by means of an injection shaft and the nozzle distortion of 527 was realized by means of a take-off godet. On the downstream stretching godets, a degree of stretching of 1.5 at a temperature of 95 ° C could be realized before the produced multifilament yarn was wound on a spool continuously by a winding head at a speed of 1800 m / min. The filament has a circular cross-section and the single filament denier was 1.6 dtex and the filament had a tenacity of 45.4 cN / tex, an modulus of elasticity of 920 cN / tex and an elongation at break of 11.8%. The degree of orientation of the crystalline phase determined by WAXS was 0.88.

Example 4

The coil-wound multifilament of PAN copolymer produced in Example 3 was exposed to a radiation dose of 300 kGy by means of electron beams. Unlike the non-electron beam treated sample of the multifilament yarn, the electron beam treated precursor yarn no longer exhibits melting up to a temperature of 400 ° C. The present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an exemplary structure for carrying out a method according to the invention. With this structure, the multifilament yarns according to the invention can likewise be produced.

A melt of the copolymer is extruded through a nozzle 1 having a plurality of nozzle holes. The emerging individual filaments are bundled to form a multifilament yarn. The resulting multifilament yarn is passed through a cooling channel 2 at a withdrawal speed v _A via a

Withdrawal godet 4 deducted. At 3, an optional further preparation of the multifilament yarn can be made. In the cooling channel 2, the multifilament yarn with cooling air (shown by arrows) acted upon. About the withdrawal godet 4, the stretching of the multifilament yarn can be adjusted.

By subsequent stretching godets 5 and 6, a stretching factor xi or x _{2 can take place} between the godets 4 and 5 or 5 and 6, respectively. The multifilament yarn is thus further stretched between the godets 4 and 5 and 5 and 6. The voltage applied to the multifilament yarn can be monitored by means of a voltage sensor 7. Finally, the obtained multifilament yarn is wound on a spool 8.

Claims

claims

A process for the production of a multifilament yarn in which a melt of a copolymer of polyacrylonitrile (PAN) preparable by a copolymerization of 95 to 60 mol% acrylonitrile with at least one comonomer selected from

a) 5 to 20 mol% of at least one alkoxyalkyl acrylate of the general formula I,

Formula I

with R = CnH _{2n +} i and n = 1-8 and m = 1-8, in particular n = l-4 and m = l-4

0 to 10 mol% of at least one alkyl acrylate of the general formula II

Formula II

with R '= C _n H ₂ n ₊ i and n = 1-18, and

c) 0 to 10 mol% of at least one vinyl ester of the general formula III

Formula III

with R = C _n H _{2n +} i and n = 1-18, Extrusion of a melt of the copolymer through a plurality of spinning holes having spinneret is spun to an IVlultifilamentgarn, and

the ultrafilament yarn should be stretched at least 10 times.

A method according to claim 1, characterized in that the

IVlultifilamentgarn is stretched by at least 20 times, preferably by 25 to 1000 times, in particular 150 to 400 times.

Process according to any one of the preceding claims, characterized in that the ultrafilament yarn is cooled before and / or during drawing, preferably by bombardment with gases, e.g. Air, especially at temperatures from -50 to + 50 ° C.

Method according to one of the preceding claims, characterized in that the formed ultrafilament yarn is stretched after hiding, preferably by 1.1 to 10 times, more preferably by 1.1 to 6 times.

Method according to one of the preceding claims, characterized in that the stretching and / or stretching by means of heated godets, which are set to temperatures of at least 50 ° C, preferably 50 to 150 ° C, in particular 55 to 90 ° C.

Method according to one of the preceding claims, characterized in that the IVlultifilamentgarn of the spinneret with a nozzle delay of <3000, preferably <1500 to 10, more preferably <500 to 30 is deducted.

Method according to one of the preceding claims, characterized in that the stretching of the multifilament yarn is such that a degree of orientation of the crystalline regions in the multifilament-forming individual filaments of> 0.7, preferably from 0.75 to 0.95, particularly preferably from 0 , 8 to 0.9 results.

8. The method according to any one of the preceding claims, characterized in that the spinneret to a temperature at least 10 K above the temperature of the melt of the copolymer is, preferably to a temperature of 10 to 80 K, in particular 15 to 45 K above the temperature of the melt of the copolymer is adjusted.

Method according to one of the preceding claims, characterized in that the melt of the copolymer to a temperature of 120 to 300 ° C, preferably 150 to 230 ° C and / or a zero shear viscosity (determined by means of a rheometer HAAKE RS 150 with plate-cone (l °) arrangement with a diameter of the measuring geometries of 20 mm and a gap opening of 0.052 mm) of <5000 Pa s, preferably 500 to 3000 Pa s, particularly preferably 1000 to 1500 Pa s is set.

Method according to one of the preceding claims, characterized in that the individual filaments and / or the multifilament yarn formed from the individual filaments is cooled with a cooling medium, preferably a gaseous cooling medium, in particular air, nitrogen or argon, the cooling medium preferably having a temperature, which is at least 10 ° C below the temperature of the melt of the copolymer, with preferred temperatures in the range of 10 to 200, more preferably from 15 to 80 are.

Method according to one of the preceding claims, characterized in that the multifilament yarn with a final take-off speed of at least 300 m / min, preferably at least 500 to 5000 m / min, in particular 750 to 2000 m / min is withdrawn.

Method according to one of the preceding claims, characterized in that the multifilament yarn comprises 50 to 5000 individual filaments, preferably 500 to 4000 individual filaments, in particular 1000 to 3000 individual filaments.

Method according to one of the preceding claims, characterized in that the individual filaments underlying the multifilament lamente to a fineness of <10 dtex, preferably from 0.01 to 10 dtex, more preferably 0.1 to 5 dtex set.

Method according to one of the preceding claims, characterized in that the spinning holes a round, oval, Y-shaped, star-shaped or n-shaped with 8> n> 3 geometry and / or a ratio of length to diameter of 1 to 20, preferably 2 to 8 have.

Method according to one of the preceding claims, characterized in that the diameter of the spinnerets in the range of 10 to 1000 μιη, preferably 50 to 750 μιη, more preferably 100 to 500 μιη.

Method according to one of the preceding claims, characterized in that no dimethyl acetamide, dimethyl sulfoxide and / or water as a plasticizing agent, in particular no plasticizing agent is added to the melt of the copolymer.

Method according to one of the preceding claims, characterized in that the copolymer has a weight-average molar mass (Mw) in the range of 10,000 to 150,000 g / mol, preferably 15,000 to 80,000 g / mol.

Method according to one of the preceding claims, characterized in that the copolymer

90 to 78 mol% of acrylonitrile

8 to 12 mol% of the comonomer a),

1 to 5 mol% of the comonomer b) and / or

1 to 5 mol% of the comonomer c).

Multifilament yarn, consisting of a plurality of individual filaments of a copolymer of polyacrylonitrile (PAN), preparable by copolymerization of 95 to 80 mol% of acrylonitrile with at least one comonomer selected from a) 5 to 20 mol% of at least one alkoxyalkyl acrylate of the general formula I,

Formula I

b) 0 to 10 mol% of at least one alkyl acrylate of the general formula II

Formula II

with R '= C _n H _{2n +} i and n = 1-18, and

c) 0 to 10 mol% of at least one vinyl ester of the general formula III

Formula III

with R = C _n H _{2n +} i and n = 1-18,

The ultrafilament yarn according to the preceding claim, characterized in that the ultrafilament yarn comprises 50 to 5,000 individual filaments, preferably 500 to 4,000 individual filaments, in particular 1,000 to 3,000 individual filaments. Multifilament yarn according to one of the two preceding claims, characterized in that

the individual filaments on which the multifilament yarn is based have a fineness of <10 dtex, preferably from 0.01 to 10 dtex, particularly preferably from 0.1 to 5 dtex.

Multifilament yarn according to one of Claims 19 to 21, preparable by a process according to one of Claims 1 to 18.