EP0944750B1 - High-strength high-modulus polyacrylonitrile fibres, method for their production and use - Google Patents

Description

The present invention relates to fibers made from homo- or copolymers containing recurring acrylonitrile and / or methacrylonitrile units (im called PAN fibers)) high modulus and high strength, as well as a specially adapted process for their production and their use, especially as reinforcing materials or for the production of filters, Ropes or friction linings.

PAN fibers of high strength are known per se. For example, Dobrecov et al. in soviet. Contributions to fiber research and textile technology, 9, pp. 407-411 (1972) described PAN fibers of high strength and high modulus which are derived from PAN types of high molecular weight; Examples of this are molecular weights of 3.10 ⁶ .

From EP-A-0,165,372 and EP-A-0,255,109 fibers of strength are included more than 8.83 cN / dtex and processes for their production, in which PAN types of high molecular weight are also used. According to EP-A-0,255,109 become PAN types with a molecular weight of more than 500,000 (weight average) used, while according to EP-A-0,165,372 PAN types with an intrinsic viscosity of more than 2.5, which corresponds to a molecular weight of more than 210,000 (weight average).

Without exception, PAN types are unusual in the above-mentioned writings high molecular weight used. Usual molecular weight values for PAN fibers range approximately from 80,000 to 180,000 (cf. the statements by Falkai et al. in "Synthesefaser", p. 200, publisher Chemie (1981) or by Masson et al. in "Fiber Producer", June 1984, pp. 34-37).

The use of the high molecular PAN types specified in these documents also poses problems in the manufacture of these fibers. So must due to the lower solubility of the high molecular weight PAN types the concentration of spinning mass for the production of a spinning mass is reduced become. This is the case, for example, when processing PAN types lower molecular weight possible, with dope concentrations of 19 - 21% to work. In the above writings, however, is reduced Spinning mass concentrations of at most 10 - 15% worked. That means a significant loss in productivity of 25 - 70% for a Production plant. For example, according to EP-A-0,165,372 with a Spinning mass concentration worked between 6 - 12% (Examples 5 - 7). The means a loss of productivity between 45 - 70%.

Furthermore, the dwell time for loosening the PAN in the Solvent significantly with increasing molecular weight of the polymer. Here new systems have to be purchased to solve the problem in order to be effective Maintain dissolving process. So usually additional measures are required be taken to work with a higher dope concentration can. In EP-A-0,255,109 an attempt is made to add 1-10% Water to the dope to reduce the viscosity to a higher To be able to work spinning mass concentration. However, this is with a Risk of corrosion associated with the systems; also with this Measure only limited viscosity reductions possible.

PAN fibers of high strength have also been known to work with PAN types of usual molecular weight have been produced. So be for example in GB-A-1,193,170 PAN fibers, the strengths up to 17.5 g / denier. The elongation at break of the fibers described is however, with more than 15% too high for many applications.

From EP-A-0,044,534 high-strength PAN fibers of high modulus are known, which have also been produced with PAN types of conventional molecular weight. Fibers with strengths of up to 81 cN / tex are described Initial moduli up to 1989 cN / tex. PAN fibers, what strengths of more than 100 cN / tex and at the same time initial moduli of more than 15 N / tex (based on 100% stretch) are not described in this document.

From EP-A-0,645,479 PAN fibers are known whose strength is up to 100 is cN / tex and its initial modulus is a maximum of 21.5 N / tex. PAN fibers, what strengths of more than 100 cN / tex and at the same time initial moduli of have more than 15 N / tex (based on 100% elongation) Scripture not described. PAN fibers are in due to their high resistance aggressive environments, for example in strongly alkaline environments, or reinforcement materials in demand for UV radiation. For technical Applications include high strength and high initial moduli low elongation at break. There is a need for PAN fibers with one property profile of this type, in particular according to PAN fibers, by methods high productivity are available.

The present invention relates to fibers made from homo- or copolymers with a weight average molecular weight of 80,000 to 210,000, containing at least 70% by weight of recurring acrylonitrile and / or Methacrylonitrile units, characterized in that the fibers have a strength of more than 100 cN / tex and an initial module of more than 15 N / tex, based on 100% stretch.

Polymer raw materials which can be produced by the customary processes Precipitation or solution polymers are used. Depending on the Requirements for the application areas can be both homo- and Copolymers of acrylonitrile are used. With the used Monomers should be as pure as possible. As Comonomers are all unsaturated which are copolymerizable with acrylonitrite Compounds, preferably unsaturated carboxylic acids, such as acrylic acid, Methacrylic acid or itaconic acid; unsaturated sulfonic acids, such as allyl, Methallyl or styrene sulfonic acid; unsaturated carboxamides, such as Acrylamide or methacrylamide; Esters of unsaturated carboxylic acids, such as the Methyl, ethyl, propyl, butyl or octyl ester of acrylic or Methacrylic acid or polyfunctional hydroxyethyl or aminoethyl esters or their derivatives of acrylic or methacrylic acid; Esters of carboxylic acids with unsaturated alcohols or ethers based on unsaturated alcohols, such as Vinyl esters and ethers, for example vinyl acetate, vinyl stearate, vinyl butyrate, Vinyl bromoacetate, vinyl dichloroacetate or Trichloressigsäurevinylester; unsaturated aldehydes or ketones, such as acrolein or crotonaldehyde; Acid halides of unsaturated carboxylic acids such as acrylic or methacrylic acid chlorides; or other copolymerizable with acrylonitrile Monomers such as styrene, butadiene, propylene or vinyl halides, for example Vinyl chloride, vinylidene chloride or vinyl bromide.

Preferred copolymerizable monomers are acrylic esters or methacrylic esters of C ₁ -C ₂₂ alcohols, e.g. B. methyl acrylate, methyl methacrylate, butyl methacrylate, octyl methacrylate, ethyl acrylate, isobutyl acrylate, (meth) acrylic esters of perfluorinated C ₁ -C ₂₂ alcohols; Vinyl aromatics with up to 20 carbon atoms, e.g. B. styrene, vinyl toluene; the esters of maleic acid and fumaric acid with C ₁ -C ₂₂ alcohols; Vinyl chloride, vinyl acetate, ethylene and butadiene, methyl acrylate is preferred.

In addition, other functional monomers containing acrylonitrile and / or methacrylonitrile are copolymerizable. The Functional monomers can contain hydroxyl, silane or epoxy groups. Examples include vinyl trimethoxysilane, vinyl tributoxysilane, Methacryloxypropyltrimethoxysilane, vinyl-tris- (methoxyethoxy) -silane, vinyltriacetoxysilane, Hydroxyethyl methacrylate, hydroxybutyl methacrylate, Glycidyl acrylate, glycidyl methacrylate or 2-hydroxyethyl acrylate.

Other suitable acrylonitrile polymers are SAN, ABS and NBR copolymers, where also the acrylonitrile portion that described above Percentage by weight.

The polymers used preferably have a content of at least 90% by weight, in particular at least 99% by weight, of acrylonitrile units.

There are polyacrylonitrile homopolymers or copolymers used, the molecular weight (weight average) 80,000 to 210,000, preferably 175,000 to 210,000.

The strengths of the fibers according to the invention are more than 100 cN / tex, preferably 101 to 150 cN / tex.

The initial moduli, based on 100% elongation, of the invention Fibers are more than 15 N / tex, preferably 22 to 35 cN / tex, whole particularly preferably 22 to 30 cN / tex.

The tensile strength of the fibers according to the invention is more than 85 cN / tex. preferably more than 90 cN / tex, with a maximum elongation at break of 15%, preferably 7 to 9%.

Also preferred are fibers as defined above, the knot strengths of more have than 15 cN / tex, in particular from 17 to 20 cN / tex.

The individual filament titers of the fibers according to the invention move depending on Intended use - in the range 0.3 - 100 dtex, preferably 0.9 - 20 dtex. at textile applications, titers in the range from 1.0 to 3 dtex are preferred.

In the course of development, it has emerged that such high-strength PAN fibers can also be manufactured with high productivity if ~ certain procedural conditions are observed. PAN fibers in particular are of the type described above, i.e. with strengths of more than 100 cN / tex and an initial modulus of more than 15 N / tex, based on 100% elongation, available if the spinning pressure of the spinning solution at the spinneret is at least 20 bar, preferably at least 30 bar.

a) Herstellung einer Spinnlösung enthaltend ein organisches aprotisches Lösungsmittel oder eine Mischung derartiger Lösungsmittel und mindestens 15 Gew.%, bezogen auf die Spinnlösung, eines Homo- oder Copolymeren enthaltend mindestens 70 Gew.-% wiederkehrende Acrylnitril- und/oder Methacrylnitril-Einheiten

b) Verspinnen dieser Spinnlösung nach einem Naßspinnverfahren oder einem Trockendüsen-Naßspinnverfahren in ein Koagulationsbad, wobei der Spinndruck der Spinnlösung an der Düse mindestens 20 bar beträgt,

c) Koagulation der ersponnenen Fäden im Koagulationsbad und Abziehen dieser Fäden aus dem Koagulationsbad, und

d) Nachbehandeln der ersponnenen Fäden unter Durchführung einer oder mehrerer Verstreckungen, wobei der Verstreckgrad zwischen Abzugsvorrichtungen der ersponnenen Fäden aus dem Koagulationsbad und Ausgang der Nachbehandlungsstrecke mindestens 1 : 10 beträgt.

The invention therefore also relates to a method for producing high-strength fibers of a homo- or copolymer with a weight average molecular weight of 80,000 to 210,000, containing at least 70% by weight of repeating acrylonitrile and / or methacrylonitrile units, comprising the following measures:

a) Preparation of a spinning solution containing an organic aprotic solvent or a mixture of such solvents and at least 15% by weight, based on the spinning solution, of a homo- or copolymer containing at least 70% by weight of recurring acrylonitrile and / or methacrylonitrile units

b) spinning this spinning solution using a wet spinning process or a dry-jet wet spinning process in a coagulation bath, the spinning pressure of the spinning solution at the nozzle being at least 20 bar,

c) coagulation of the spun threads in the coagulation bath and removal of these threads from the coagulation bath, and

d) post-treatment of the spun threads by carrying out one or more stretching, the degree of stretching between draw-off devices of the spun threads from the coagulation bath and exit of the post-treatment section being at least 1:10.

Any organic aprotic can be used as the spinning solvent Use solvents or a mixture of such solvents. examples for such solvents are dimethyl sulfoxide (DMSO), dimethylacetamide (DMAC, N-methylpyrolidone (NMP) and especially dimethylformamide (DMF).

Classical processes and Machines are used. In the method according to the invention, the Spinning mass concentration at least 15%, preferably more than 26%, especially 29 to 38%. When using spinning mass concentrations of less than 15% may experience nozzle run problems; i.e. it irregularities in the nozzles and subsequently occur during spinning sticking can occur. Furthermore, the productivity of the Post-treatment line directly with the decrease in the spinning mass concentration from. The viscosity of the spinning solution is at least 150 Pa · s, preferably 260 to 450 Pa · s (determined at 80 ° C in DMF).

The spinning solution is usually filtered and spun before if necessary degassed. Here, gel particles and if necessary existing impurities removed. The filtration comes at The method according to the invention is of great importance since with this Measure the error rate during spinning and after-treatment can be significantly reduced. Thus, spinning defects can subsequently be found in the Contact and wet drawing of the fiber to windings on the drawing rolls to lead.

The filtration can be carried out using the known devices be, for example with filter presses in which the spinning mass through several compact fabric layers can be pressed through. For filtration is preferred a 2 or multi-stage high pressure filtration in the filter box with support tube are used (pressure> 30 bar). A measure of the filter effect represents the so-called continuity; this represents one Upper limit for those particle diameters that still have the filter happen.

In the case of spinning solutions with DMF as the solvent are preferred Filters with a continuity of 5 to 15 µm are used. This means that Particles with a diameter of less than 5 to 15 µm still filter can happen. If the filtration of the dope does not work properly, i.e. in the case of spinning solutions with DMF as solvent with a coarser one Filters that are carried out as 15 µm are subject to later production disruptions expected.

The filtration temperature is preferably in the case of DMF spinning solutions between 80 and 90 ° C.

The speed at which the threads emerge from the spinneret must be so be chosen so that the fibers themselves when immersed in the liquid practically do not bend and maintain their previous direction of movement. The spraying speed of the spinning solution can range from at least 5 m / min to 50 m / min can be changed. Spray speeds of 15 to are preferred 35 m / min.

The spraying speed S is calculated according to the following equation: S = 4 x F Z xd 2 x π

S =

Spritzgeschwindigkeit (m/min)

F =

Fördermenge (cm³/min)

Z =

Anzahl der Düsenlöcher

d =

Düsenlochdurchmesser (mm)

Mean:

S =

Spraying speed (m / min)

F =

Delivery rate (cm ³ / min)

Z =

Number of nozzle holes

d =

Nozzle hole diameter (mm)

Due to the high spraying speed and the high spinning pressure, the spun threads without noticeably changing direction in that Coagulation bath or through the surface of the coagulation bath. change the direction of the threads when immersed in the coagulation bath is essential, so with gluing the fibers together and on the Surface of the nozzle. In the coagulation bath, the Change the direction of movement of the threads.

Due to the high spraying speed and the relatively high viscosity of the highly concentrated spinning solution, a high pressure can be built up in the spinneret. This high pressure is essential to achieve high strength. Due to the high concentration, the process is again very economical to operate and has high productivity.
However, it is disadvantageous that, due to the high pressure, problems with spinning can occur. These manifest themselves, for example, in the spinneret becoming clogged, that is to say drops of the spinning mass sticking to the nozzles. It is therefore advisable to raise the temperature of the spinning solution when such problems occur before it passes through the spinneret in order to lower the viscosity of the spinning solution. In the case of DMF as a spinning solvent, it is therefore advisable to heat the spinning solution to at least 80-100 ° C shortly before it enters the nozzle.

Spinning mass temperatures of these spinning solutions below 100 ° C can cause problems described above. At spinning mass temperatures above 130 ° C with the evaporation of the DMF and with yellowing To count spinning mass. In the case of DMF, it is therefore preferable to work with Temperatures of the spinning solution in front of the spinneret from 80 to 130 ° C.

The spinning pressure of at least 20 bar given above relates to the heated spinning solution, the temperature of which ranges from 80 to 130 ° C lies.

The correct choice of the nozzle hole diameter significantly affects the clean and perfect entry of the threads into the coagulation bath. The required high spray speeds of the invention Procedures are particularly important when choosing large nozzle hole diameters difficult to realize. in these cases is having problems with spinning and a spilling nozzle. If such problems occur, then In individual cases it is advisable to reduce the nozzle diameter.

In addition, by choosing the thickness of the thread, its behavior when Pressing into the liquid of the coagulation bath can be influenced. How already mentioned the threads must be in such conditions Coagulation bath are pressed in that the fibers are immersed in the Do not bend liquid and its previous speed direction to lose. This can also be done by choosing the diameter of the nozzle holes to be influenced.

Typically, the nozzle hole diameters are less than 150 µm; nozzle hole diameters of 60 to 120 μm are preferred.

The spinning can be carried out according to the wet spinning process known per se or Dry nozzle wet spinning processes are carried out. To do this, the spinneret in the Coagulation bath are immersed or the spinneret is for Coagulation bath surface attached at a predetermined distance, whereby the spinning takes place through an air gap. The distance between the spinneret and the coagulation bath surface can be used in wide ranges be varied, preferably the distance is less than 10 millimeters, especially 1 to 10 mm.

The coagulation bath is usually an aqueous mixture containing one organic aprotic solvent - for example a solution, dispersion or suspension of this organic aprotic solvent in water. The organic aprotic solvent is preferably in the coagulation bath the selected spinning solvent.

The concentration of the organic aprotic solvent is To choose the individual case so that there is a sufficiently fast and complete Coagulation results. When working with relatively highly concentrated spinning solutions care must be taken that the concentration of the organic aprotic Solvent in the coagulation bath is not too high. Will the Concentration of the organic aprotic solvent in the coagulation bath selected high, so fiber bonding can take place on the trigger godet, since none complete coagulation of the fiber is guaranteed.

Typically one works with concentrations of the organic aprotic Solvent of less than 75% by weight, preferably less than 50% by weight, in particular 20 to 50% by weight (based on the solution in the coagulation bath).

The temperature of the coagulation bath is between 20 and 110 ° C, preferably 40 to 90 ° C, in particular 60 to 85 ° C.

The length of the coagulation bath is - depending on the Spray speed - at least 0.5 m. In any case, the length of the Coagulation bath can be chosen so that one for the subsequent After-treatment sufficient coagulation is achieved.

After the coagulation, the fiber is post-treated; this can be on a known aftertreatment system.

Surprisingly, it was found that the inventive Spinning PAN fibers are available that are stretched very high can. The spun fibers are used to produce high-strength PAN fibers Threads treated with one or more stretching, the total degree of stretching between take-off devices of the spun threads from the coagulation bath and exit of the Aftertreatment section at least 1:10, preferably 1:10 to 1:25, is.

In the aftertreatment, the fiber can, for example, be washed one or more times after leaving the coagulation bath, an additional coagulation being able to take place in these steps. The fiber is usually wet-drawn and / or softened during at least one washing step. After washing, drying is usually done. The fibers are then post-drawn in a further drawing step; this can be done by stretching in a hot air bath and / or by contact stretching, for example via heated godets, the stretching ratio being at least 1: 1.5 in the case of contact stretching. The fibers are then drawn off, preferably under tension. Furthermore, it is possible and preferred to fix the drawn fibers after the post-drawing. This is advantageously carried out by heating to temperatures of 130 to 350 ° C, preferably 150 to 250 ° C, in a normal atmosphere. This fixation stabilizes the PAN fiber and the density increases from approximately 1.18 g / cm ³ to values of more than 1.2 g / cm ³ , this increase in density being able to be accompanied by a partial loss of strength.

The fibers can then be fed to a cutting device or the Fibers are further processed as filaments, for example wound up.

Such post-treatment processes of the PAN fibers are known per se and for example in EP-A-0,044,534, EP-A-0,165,372 and EP-A-0,255,109 described.

The PAN fibers according to the invention can be used for a wide variety of purposes Applications are used. These fibers are typically used for technical purposes. Examples of this are the use as Reinforcing material for the production of composite materials, for example for the production of fiber-reinforced thermoplastic or thermosetting plastics or in particular for the production of fiber-reinforced hydraulically setting materials, for example in concrete. The PAN filaments according to the invention are preferably suitable for the Manufacture of UV-resistant ropes, lines and convertible tops of all kinds. Examples of top materials are tops, tarpaulins etc. for the automotive industry or tarpaulins to protect surfaces and objects.

Furthermore, the PAN fibers according to the invention can be used to produce Nonwovens are used, e.g. as a filter or as geotextiles Find use.

Another preferred area of application of the PAN fibers according to the invention is the production of friction linings, especially brake linings.

Claims (34)

1. Fibers of homo- or copolymers having a weight average molecular weight in the range from 80 000 to 210 000 and containing at least 70% by weight of recurring acrylonitrile and/or methacrylonitrile units, characterized in that the fibers have a tenacity of more than 100 cN/tex and an initial modulus of more than 15 N/tex, based on 100% extension.
2. Fiber according to claim 1, characterized in that the homo- or copolymer contains at least 90% by weight of acrylonitrile units.
3. Fiber according to claim 2, characterized in that the homo- or copolymer contains at least 99% by weight of acrylonitrile units.
4. Fiber according to claim 1, characterized in that the fiber has a tenacity in the range from 101 to 150 cN/tex.
5. Fiber according to claim.1, characterized in that the fiber has an initial modulus (based on 100% extension) in the range from 22 to 35 cN/tex.
6. Fiber according to claim 5, characterized in that the fiber has an initial modulus (based on 100% extension) in the range from 22 to 30 cN/tex.
7. Fiber according to claim 1, characterized in that the fiber has a breaking strength of more than 85 cN/tex.
8. Fiber according to claim 7, characterized in that the fiber has a breaking strength of more than 90 cN/tex.
9. Fiber according to claim 1, characterized in that the fiber has a breaking extension of not more than 15%.
10. Fiber according to claim 9, characterized in that the fiber has a breaking extension in the range from 7 to 9%.
11. Fiber according to claim 1, characterized in that the fiber has a single filament linear density in the range from 0.3 to 100 dtex.
12. Fiber according to claim 11, characterized in that the fiber has a single filament linear density in the range from 0.9 to 20 dtex.
13. A process for producing high strength fibers of homo- or copolymers having a weight average molecular weight in the range from 80 000 to 210 000 and containing at least 70% by weight of recurring acrylonitrile and/or methacrylonitrile units, comprising the following measures:

    a) preparing a spinning solution containing an organic aprotic solvent or a mixture of such solvents and at least 15% by weight, based on the spinning solution, of a homo- or copolymer containing at least 70% by weight of recurring acrylonitrile and/or methacrylonitrile units,

    b) spinning this spinning solution by a wet spinning process or by a dry jet-wet spinning process into a coagulation bath at a spinning pressure of the spinning solution on the die of at least 20 bar,

    c) coagulating the spun filaments in the coagulation bath and withdrawing these filaments from the coagulation bath, and

    d) aftertreating the spun filaments by performing one or more drawing steps, the draw ratio between the devices for withdrawing the spun filaments from the coagulation bath and the point of exit from the aftertreatment sector being at least 1:10.
14. A process according to claim 13, characterized in that the solvent used is dimethyl sulfoxide (DMSO), dimethylacetamide (DMAC), N-methylpyrrolidone (NMP) and especially dimethylformamide (DMF).
15. A process according to claim 13, characterized in that the spinning dope concentration is more than 26%.
16. A process according to claim 15, characterized in that the spinning dope concentration is in the range from 29 to 38%.
17. A process according to claim 13, characterized in that the viscosity of the spinning solution is at least 150 Pa·s and especially in the range from 260 to 450 Pa s (determined at 80°C in DMF).
18. A process according to claim 13, characterized in that the spinning solution is filtered through a filter of 5-15 µm permeability prior to spinning.
19. A process according to claim 13, characterized in that the temperature of the spinning solution upstream of the spinneret die is in the range from 80 to 130°C.
20. A process according to claim 13, characterized in that the die hole diameter is in the range from 60 to 150°µm.
21. A process according to claim 13, characterized in that the extrusion speed is in the range from 5 to 50 m/min.
22. A process according to claim 13, characterized in that the spinning pressure of the spinning solution on the die is at least 30 bar.
23. A process according to claim 13, characterized in that the spinning is effected by means of a dry jet-wet spinning process in which the size of the air gap between the spinneret die and the surface of the coagulation bath is in the range from 1 to 10 mm.
24. A process according to claim 13, characterized in that the coagulation bath is an aqueous mixture of the spinning solvent, the concentration of the spinning solvent being less than 75% by weight, based on the coagulation bath.
25. A process according to claim 24, characterized in that the coagulation bath is an aqueous mixture of the spinning solvent, the concentration of the spinning solvent being less than 50% by weight, based on the coagulation bath.
26. A process according to claim 25, characterized in that the coagulation bath is an aqueous mixture of the spinning solvent, the concentration of the spinning solvent being in the range from 20 to 50% by weight, based on the coagulation bath.
27. A process according to claim 13, characterized in that the temperature of the coagulation bath is in the range from 20 to 110°C, preferably in the range from 40 to 90°C and especially in the range from 60 to 85°C.
28. The use of the fibers according to claim 1 as reinforcing materials for the manufacture of composite materials.
29. The use according to claim 28, characterized in that the composite materials are fiber-reinforced hydraulically setting materials.
30. The use of the fibers according to claim 1 for manufacturing nonwovens, in particular for manufacturing filters or geotextiles.
31. The use of the fibers according to claim 1 for manufacturing friction linings.
32. The use of the fibers according to claim 1 for manufacturing ropes and lines.
33. The use of the fibers according to claim 1 for manufacturing tilt fabrics.
34. Composite material, nonwoven, friction lining, ropes, lines or tilt fabric comprising fibers according to claim 1.