DE2044935C3 - Process for increasing the spinning speed in the wet spinning of acrylonitrile polymers - Google Patents

Description

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The invention relates to a method for increasing the spinning speed during wet spinning of higher concentrations Solutions of dimethylformamide prepared by the solution polymerisation process, acrylonitrile polymers containing hydrophilic groups in aqueous coagulation solution.

It is known to spin acrylonitrile polymers produced by suspension, emulsion or solution polymerization technology from dimethylformamide solutions into aqueous dimethylformamide coagulation baths. A decisive advantage of the homogeneous solution polymerization of acrylonitrile with optionally further comonomers in the dimethylformamide is that after the polymerization has ended and the unreacted monomers have been removed, high-quality spinning solutions are obtained which can be converted into threads, fibers and the like using dry or wet spinning technology can be processed. Solution polymers obtained in this way have a significantly lower molecular weight and solubility distribution than those produced by the suspension polymerization process and, due to the carbon-transferring and thus molecular weight-regulating effect of dimethylformamide, practically no higher molecular weight fractions, so that spinning solutions of solution-polymerized acrylonitrile polymers and polymers with the same chemical composition are the same of the same average molecular weight compared to solutions of acrylic nitrile suspension polymers are characterized by higher stabilities and lower viscosities. This makes it possible to concentrate solution polymer solutions more highly in the course of the technological monomer removal after the end of the polymerization, which ultimately results in higher spinning line outputs when spinning these solutions than when using suspension polymers or when spinning solutions obtained by solution polymerization in dimethyl sulfoxide or in aqueous sodium rhodanide Solutions are obtained. The use of spinning solutions with higher polymer concentration is also advantageous in that than in the wet spinning of acrylonitrile polymers, the diffusion processes during the coagulation of the Spinnlösungskon- .icnlmüon are dependent and highly concentrated in spinning solutions are obtained threads that due to the slower and more uniform coagulation and desolvation of the spinning solution jet present as gel have significantly fewer cavities and capillaries and consequently show a more compact structure and better processing and usage properties than threads that are spun from less concentrated spinning solutions.

This in itself advantageous use of spinning solutions however, a higher polymer concentration has the great disadvantage that the higher the spinning solution concentration - the constancy of the remaining spinning solution and coagulation bath parameters is assumed - The maximum nozzle withdrawal speed of the threads, as a criterion for the spinnable wedge and Spinning security, is reduced, whereby the achievable Spinnsiraßcnleistungen in terms of spinning speed and productivity limits are set. The more concentrated when used Spinning solutions initially achievable increase in productivity is due to the lower nozzle withdrawal speed thus inevitably humiliated again. The maximum nozzle withdrawal speed is the speed defined, in the case of .Standard conditions at the spinneret or in the immediate vicinity Near the spinneret, the first two individual capillaries tear.

To improve the nozzle withdrawal speed, methods are known that can be achieved by additives such as z. B. sulfuric acid, aromatic sulfonic acids or amine salts for the spinning solution or by increasing the Spinning solution temperature achieve a reduction in viscosity to thereby improve the spinnability. However, these variants complicate the overall process in terms of technology and economy Regard, in particular, the coagulation bath recovery and reduce the quality of the obtained Threads.

The purpose of the invention is to increase the concentration when using more highly concentrated spinning solutions the spinning line capacity without complicating the manufacturing process or the quality to affect the threads obtained.

The invention has for its object to make the coagulation process so that in the Spinning of more concentrated solutions of acrylonitrile polymers reduces the maximum Nozzle withdrawal speed is avoided.

It has been found that solutions of acrylonitrile polymers prepared by solution polymerization in dimethylformamide, which contain hydrophilic, in particular sulfonate groups _{, can be spun into aqueous Ko 1} I-gulationsbader with a proportion of 40 to 65 percent by weight of dimethylformamide without a decrease in the concentration of the spinning solution increases maximum nozzle withdrawal speed occurs when the coagulation bath temperature is increased proportionally with the increase in the polymer concentration in το of the spinning solution so that the quotient of the spinning solution concentration (in percent by weight) and the coagulation bath temperature (in ⁰ C) 0.6 in the preferred spinning of 21 to 25 percent by weight solutions to 2.1, but starting from a spinning solution concentration of 21 percent by weight per percent of the increase in the spinning solution concentration, the lower limit of the coagulation bath temperature preferably increases by 5 and the upper limit by 2'C.

Spinning solution concentrations above 25 percent by weight are less to be recommended, as in addition to the Due to the higher viscosities occurring filtration difficulties also the physical textile ones and usage properties of the threads spun from it, as well as when the value falls below this value of 0.6 for the quotient of the spinning solution concentration and the coagulation bath temperature qualitatively be decreased.

In addition, it was found that the highest nozzle withdrawal speeds when spinning Polymers are obtained which, in addition to acrylonitrile, up to 15 percent by weight of acrylic or methacrylic acid esters and / or 0.5 to 1.8 percent by weight vinyl, allyl or methallylsulfonic acid or sulfoalkylacry-IaI or -methacrylal or their inorganic or organic salts and at 20 ° C in 0.5% Dimethylformamide solution have a relative viscosity of 1.95 ± 0.1. .

The inventive method is at the use of more highly concentrated spinning solutions, and thus an increase in the spinning speed the spinning line performance achieved without adversely affecting the properties of the threads obtained will.

When using higher coagulation bath temperatures known structural loosening of the coagulated threads as a result of changed diffusion processes during coagulation is caused by the simultaneous presence of higher solids concentrations in the spinning solution and the hydrophilic character of the sulfonate-containing polymers avoided.

The proportionality of the dope concentration according to the invention and coafulation bath temperature also enables energy savings through the elimination of the low coagulation bath temperatures which turn out to be necessary at lower spinning solution concentrations.

The invention will be explained below using an example:

_{By solution polymerization of acrylonitrile, methyl acrylate and sodium allyl sulfonate} , with a proportion of comonomers of 6.95 and 1. ^ percent by weight, in dimethylformamide, a polymer solution with a viscosity , jre, = 1.95 was prepared, demonomerized and worked up into spinning solutions of the following concentrations: 18.5; 19.8: 21.4; 22.4; 25.1 and 25.9%. After filtration, these solutions were spun through a nozzle (240 holes / 0.09 mm hole diameter) into an aqueous precipitation bath containing 51.8 percent by weight of dimethylformamide and drawn off at a speed of 6.2 m / min from a roller unit, in a known manner from residual solvent freed, dried for 8 minutes at 1SC and then steamed for 10 minutes at 115.degree. C. without tension. The properties of the thread obtained are shown in the table.

The dependence of the maximum nozzle withdrawal speed of the spinning solution concentration and the spinning bath represent, once a constant temperature of 21.5 ⁰ C was set in the spin bath, the other three different Fällbadtemperaturen each were selected for the different concentrations of the spinning solutions. This resulted in the in A b b. 1 and 2 shown dependencies. Like A b b. 3 further shows, with a simultaneous proportional increase in the coagulation bath temperature, the spinning solution concentration could be increased in the area of the area delimited by the points ABCD , without a decrease in the maximum nozzle withdrawal speed and a decisive change in the physical properties of the textile with the increase in the spinning solution concentration.

table

Dope
Konzcnlratiini Coagulation
badlemperalur Maximum
Nozzle trigger Tiler Tear resistance Elongation at break Snare rcilikra % ("C) In, mini (the) (p the) 1%) Ip / den) 19.8 16.2 11.4 3.21 3.13 27.6 1.73 22.9 13.1 3.32 3.16 28.1 1.34 31.4 14.9 3.19 3.02 28.9 1.19 22.4 15.8 9.3 3.34 3.24 26.9 1.68 20.8 10.9 3.17 3.17 28.3 1.72 29.6 13.7 3.25 3.23 27.2 1.59 25.1 16.9 7.1 3.40 3.19 25.9 1.67 24.3 9.0 3.26 3.31 25.3 1.46 33.1 11.4 3.27 3.20 27.3 1.52

5 2 Maximum
Nozzle trigger 044 935 tj Tear resistance 6th - (ramin) continuation (p the) Schlingenre Dope
concentration Coagulation
bath temperature 12.8
14.5
16.0 Titer 3.06
3.10
3.23 Elongation at break (p / the % ( ⁰ C) 10.2
12.0
14.8 (the) 3.18
3.24
3.30 (%) 18.3 15.4
21.0
28.0 7.5
9.1
10.8 3.14
3.25
3.30 3.24
3.18
3.12 27.4
28.5
28.8 21.4 15.8
21.8
30.8 For this 3.30
3.18
3.26 1 sheet of drawings 26.2
26.8
27.0 , 60
, 44
1.20 25.9 20.1
25.6
32.8 3.18
3.42
3.30 26.0
26.4
27.0 , 62
1.54
, 59 1.70
1.54
1.52

Claims (2)

Patent claims: 1. A method for increasing the spinning speed during wet spinning of more concentrated solutions of dimethylformamide prepared by the solution polymerization process, containing hydrophilic groups, in particular sulfonal groups, containing acrylonitrile polymers in aqueous, 40 to 65 percent by weight of dimethylformamide-containing coagulation substrates, characterized in that during the spinning of 21 to 25 ge The quotient of the spinning solution concentration (in percent by weight) and the coagulation bath temperature (in ⁰ C) amounts to 0.6 to 2.1, based on a spinning solution concentration of 21 percent by weight per percent of the increase in the spinning solution concentration, the lower limit of the coagulation bath temperature by 5 and the upper limit by 5 2 ° C. 2. The method according to claim 1, characterized in that polymers are spun which, in addition to acrylonitrile, up to 15 percent by weight of acrylic or methacrylic acid esters and or 0.5 to 1.8 percent by weight of vinyl, allyl or methallylsulfonic acid or sulfoalkyl acrylate or methacrylate or their inorganic or organic salts and sodium at 20 ⁰ C in 0.5% Dimcthylformamidlösung have a relative viscosity of 1.95 ± 0.1.