DE2364367A1 - PROCESS FOR MANUFACTURING FIBERS AND FABRICS FROM POLYACRYLNITRILE - Google Patents

Description

F 73/06 Neumünster, December 19, 1973

63 PL / ho

Neumünster machine and
Apparatebau Gesellschaft mbH., Neumünster

Method of making fibers and filaments from

Polyacrylonitrile

The invention relates to a method for producing Fibers and threads of high strength from polyacrylonitrile by wet spinning, the dissolved polymer in a Coagulatxonsbad is spun and the fibers or threads are then converted and knitted.

The strength of fibers made of polyacrylonitrile, insofar as they are used for textile purposes, is in the order of magnitude between 1.7 and 2.5 g / den for most types. The usual strength values for threads are between 2.5 and 5 »0 g / den. The elongations in the two cases mentioned are a maximum of $ 35 and $ 20, respectively. The aim was to achieve these mechanical properties because they appeared to be sufficient and even particularly suitable for the intended purpose.

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For special purposes, e.g. for use in the technical field, attempts were made to achieve higher strengths. In. in the last few years, it turned out, for example, that then, if the threads are to be used as the starting product for carbon or graphite threads, particularly high strengths required are. In this case, however, the elongations should only at 8 to 12 ^ έ. lie.

Attempts have now been made in various ways to produce such high-strength fibers and threads. So you have e.g. the drawing ratios changed and increased, namely such that when subdividing into hot water and dry stretching, the stretching ratio in the Dry stretching should be much higher than at the preceding Hexßwasserverdreckung. One also has a hot water stretch and then a double Dry stretching applied. That way were Strength values of up to 8 g / den are achieved. Attempts have also been made to hot stretching in glycerine or a other oily liquid to perform. It was assumed that the heating of the thread was significant would be done more evenly. You also have the spun thread in a still moist state, i.e. without prior drying, stretched in hot glycerine. Here, too, were significantly higher strength values up to to 10 g / the received. However, it turned out that

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the strength of the fibers is high on average, but was always very uneven.

On the other hand, it was soon recognized that the properties of the polymer are also crucial Are of importance for the achieved strength of the threads. The higher the average degree of polymerization set became, the higher one also got with the strength of the "spun threads. It turned out, however, that Solutions with high degrees of polymerization as a result of their high viscosity are technically difficult to handle and spin.

As is well known, there are various solvents for Polyacrylonitrile. It is also known that, depending on the type of solvent, polymers "with quite different Spinning properties and thus also result in different strengths. You have organic and inorganic Solvent used. Organic solvents are e.g. dimethylformamide, dimethylacetamide, dimethyl sulfoxide and others more. Highly concentrated solvents have proven to be inorganic solvents. Solutions of various inorganic Salts such as zinc chloride, magnesium chloride, calcium chloride and various thiosulfates and nitrates proven, also concentrated acids. The complex salt NaZnClo has proven to be particularly suitable, its

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Aqueous solutions in a concentration between ^ h and 60 percent by weight are also able to dissolve aeropolymerizates with a high average degree of polymerization without any problems. It is also already known that very homogeneous spinning solutions are obtained even if the acrylonitrile and optionally a comonomer are polymerized in this complex salt solution itself. Finally, UV light has long been used to regulate the polymerization process in the presence of formaldehyde and hydrogen peroxide (OS 1 669 552).

The object of the invention is to provide a method of the type specified at the beginning so that fibers with previously unattained strength values, in particular from 12 to 15 g / den or higher.

This object is achieved according to the invention when proceeding according to claim 1. This instruction is due the previous opinion of experts, according to which the most homogeneous structure possible over the entire fiber cross-section was strived for, in stark contradiction, as can be seen, for example, from DT AS 1 1 ^ 3 965. The professional who works with one of the many different manufacturing processes for Polyacrylonitrile is familiar, becomes easy in the

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Be able to apply the teaching of claim 1 to realize one of the known processes by slightly modifying one of the known processes.

The measures of claims 2 and in particular 3 contribute significantly to achieving a particularly pronounced one Improvement of the mechanical properties.

A special method is given in claim Λ.

Claims 5 and 6 contain information about the composition particularly preferred salt solutions for the reaction solution.

Particularly good results were obtained with the one described in claim 7 specified combination of metal ions achieved as an additive to the reaction solution.

According to claim 8 one obtains technical spinning properties, which give the highest strength.

The range specified in claim 9 for the degree of polymerization of the spinning solution is both process engineering as well as optimal in terms of the quality of the end product.

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The feature of claim 10 brings advantages in the wet drawing process.

The aftertreatment according to claim 11 is particularly beneficial Measure to the fact that the formed on the thread surface Skin is preserved and further solidified.

Claim 12 gives a preferred use of the erfindungsgeinäß produced fibers or threads as an intermediate product for the production of an end product with excellent Strength values.

Based on one of the known manufacturing processes becomes according to the invention, for example, as follows proceeded:

A concentrated aqueous solution is prepared which contains 34 to kk% ZnCl ₂ and 15 to 25 # NaCl with the proviso that the total salt content is greater than 58 $. A salt content above 60 ^ would not significantly affect the strength of the fiber, but is undesirable in order to avoid crystallization in the pipelines. The composition expediently corresponds approximately to the stoichiometric composition of the complex NaZnCl ^,

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A total of about 8 to 9 percent by weight of acrylonitrile and methyl acrylate are dissolved in this salt solution, the added amount consisting of 90 to 99 $ acrylonitrile and 10 to 1 $ methyl acrylate. Instead of methyl acrylate, it is also possible to add other comonomers, for example methyl methyl acrylate or vinyl acetate. A pH of about is set with hydrochloric acid. After addition, ^"r required sensitizers formaldehyde and hydrogen peroxide d is introduced under UV irradiation with a wavelength of 2000 to 5000 angstroms and the polymerization performed. By adding small amounts of metal ions, e.g. 0.1 to 0.3 mg / l Cu ions, 2 -10 mg / l Fe ions or up to 80 mg / l. Mn ions, the desired high degree of polymerisation is achieved in the spinning solution, which, if the polymer concentration is sufficiently high, ensures a favorable viscosity in terms of spinning technology and thus excellent spinnability of the spinning solution and the stretchability of the resulting thread. The most suitable spinning solution is obtained if the polymerization is conducted in such a way that an average degree of polymerization of 3000 to 4200 is produced. The degree of polymerization should be determined and defined as follows:

From the spinning solution to be examined, films are produced in a known manner, which are washed completely free of salt and then need to be dried. Of these

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dissolve about 125 mg in 25 ml of dimethylformamide. It is now the viscosity of the pure solvent and

the viscosity of the solution using a capillary viscometer certainly. Then the average molecular weight is:

DMG =

C. K
C = concentration of the solution in g / l

The constant K is determined empirically:

~ ⁶

K = 1.3 ^ 6. 10

The average degree of polymerization is

DMG

DP =

Molecular weight of the monomers

In the present case, with an average degree of polymerization from 3000 to 4200 an average molecular weight from 160,000 to 220,000. By comparison, the commercially available fibers and threads have average molecular weights of 40,000 to 80,000, corresponding to degrees of polymerization between 750 and 15ΟΟ.

After filtration and deaeration, the solution becomes more customary Way through a spinneret into the precipitation bath. The precipitation bath should not contain more than $ 5 dissolving salts, whereby the quantitative ratio of the dissolving salts corresponds to the polymerization solution. The temperature of the felling bath is between about 10 and 18 ° C. The resulting threads are going at a much greater rate

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withdrawn from the precipitation bath than the theoretical exit velocity from the spinneret. This is defined on the assumption that the diameter of the individual threads is assumed to be equal to the diameter of the bores in the spinneret, i.e. the theoretical Exit speed is

_ Volume escaping per unit of time ~ Sum of the bore cross-sections.

The delay, ie the ratio between the theoretical exit speed and the take-off speed, should be in the range from 1: 3 to 1: h. It should be pointed out at this point that the theoretical exit speed is not identical to the thread length exiting per unit of time in the event of a tension-free exit. This is namely much smaller due to the shrinkage. In relation to this, the optimal distortion would be in the vicinity of 1: 7.

In this method of operation it was surprisingly found that threads or fibers are formed which have a very specific have novel oriented structure, which gives them the desired excellent strengths and other gives good properties for further processing. As is shown by scanning electron microscope images the fiber a firm and structured 'skin. Such a

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If the spinning process is continued appropriately, thread can achieve strengths of up to 16 g / den.

Further processing begins with the thread in the After the coagulation process is washed in such a way that that it is completely free of the solvent. After washing, the thread is in a known manner in stretched with hot water. The stretching ratio is 1: 2.5 or higher up to near the breaking point. Following the water drawing, the thread is dried and converted in a known manner. The conversion must be complete. The conversion is done by the thread is passed almost without tension, e.g. over heated rollers.

The converted thread is now in hot glycerin or another suitable oil-like medium stretched again. The stretching ratio here can be 1: 5 or be above. After the hot stretching, the The thread is freed from the stretching agent. Is the extender e.g. glycerine, it is washed again in cold water. It will depend on the prospect Further processing wet or dry in a known manner wound up.

Example:

In 1000 ml of a concentrated saline solution that is 39 percent by weight Zinc chloride and 19.5 percent by weight sodium

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chloride in k contains 1.5 percent by weight of water, 179 ml of acrylonitrile and 9> 5 '»1 methyl acrylate are dissolved. 10 ml of concentrated hydrochloric acid, 3 »5 ml of a '10 ^ d. gen formaldehyde solution and 2.7 ml peroxide (35 %) are added. Finally, there are also 50 mg / l manganese ions and 5 mg / l iron ions.

After the monomers have completely dissolved, the reaction solution is irradiated with UV light of 3600 Angstroms. After the start of the reaction, the temperature is maintained at 60 ° for a reaction time of about 75 minutes. Under these conditions the polymer has an average molecular weight of 185,000 with a falling ball viscosity of 180 sec / 150 mm. The spinning solution is filtered and vented in the usual way and can then be spun immediately or later. The spinning takes place with a delay of 38/1 ^ 6 cm / min in a precipitation bath which contains no more than h · * 5% of the dissolving salts and is kept at a temperature of 12 °. In the subsequent wash with clear water, the dissolving salts are completely removed, with the thread running almost completely free of tension. It is now stretched in water at 92 ° C. in a ratio of 1: 3. The thread is then passed over heated rollers at a surface temperature of 110 to 115 °, and finally dried

at 135 to 1Ί5 ⁰ the conversion process known for acrylic fibers

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subject »Here the tension should be so low that the draw ratio is at most 1; 1.1 sawn. After the conversion, the thread is in a Glycerinbadvon I65 ⁰ in a ratio of 1: 5 stretched, after stretching it is washed in the usual way, possibly dried and 'finally wound up.

The thread obtained in this way has a strength of 16 g / den. The maximum stretch is 10 ⁰ ^.

A carbon thread made from such a thread achieves a strength of 360 kgf / mm ^. The modulus of elasticity is 35,000 kg / mm ² .

A graphite thread made from such a find possibly achieves an even higher strength,

Patent claims:

BAD ORlG i _NAL

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Claims (1)

F 73/06 Neumünster, January 19-1973 Neumünster machines "- and
Apparatebau Gesellschaft mbH. , Neuinünster Claims , 1.) Method of making fibers and threads high Strength of polyacrylonitrile by wet spinning, whereby the dissolved polymer is spun in a coagulation bath and the fibers or threads are then converted and stretched, characterized in that, that during the coagulation process on the fiber surface a firm skin is formed, which is retained in the subsequent process steps and is further strengthened. 2. The method according to claim 1, characterized in that that by delay in coagulation an already oriented Structure of the skin is created. 3. The method according to claim 2, characterized in that the delay, defined by the ratio of the theoretical exit speed to the withdrawal speed, is 1: 3 to 1: k . - - 14 - 5 0 9826/0857 H. Process according to one of Claims 1 to 3, where in a highly concentrated aqueous salt solution of zinc chloride and sodium chloride, acrylonitrile is dissolved together with a gomonomer and then polymerized in the presence of formaldehyde and hydrogen peroxide under the action of UV light, the resulting solution then being polymerized is spun in a coagulating bath containing the same salts at a reduced concentration, characterized in that the salt solution, a small amount of ions of the metals copper, iron and manganese individually or in combination, and in that the coagulation bath is not more than 5 ^r ß> solvent salts contains. 5. The method according to claim h, characterized in that the weight ratio 1 trii.s of the dissolving salts to one another approximately corresponds to the stoichiometric ratio of the complex NaZnCl3. 6. The method according to claim 5, characterized in that the aqueous salt solution contains 38 to 40 $ zinc chloride and 18 to 20 "jL sodium chloride. 7. The method according to any one of claims 4 to 6, characterized in that characterized in that the aqueous saline solution as a whole 40 to 60 mg / l Manganiouen and ^ 4 to 6 mg / l iron ions contains. - I- = 5 - 509826/0857 8. The method according to any one of claims h to 7 _5, characterized in that the comonomer used is "methyl acylate. 9. The method according to any one of claims k to S ₉ thereby . '■ - ■■ characterized in that the Polyraerxsatxonsgrad of the spinning solution is set to 3000 to ^ 200. 10. The method according to any one of claims h to 9 »characterized in that the fibers are washed after coagulation. 11. The method according to any one of claims 1 to 10, characterized in that the drawing takes place in two stages, the fiber first drawn in hot water with a draw ratio of 1: 2.5 to 1: 3, then an intermediate drying and a conversion at low Subjected to tension, then stretched in hot glycerol or a similar oily liquid in a ratio of 1: k to 1 s 5 and finally washed in the usual way and optionally dried. 12. Use of the fibers produced by the process according to one of claims 1 to 11 as an intermediate product for the production of carbon> the graphite threads. 60 98 2 6 / OBB 7 '° ^R ' ^GiNAL ^ pecth,