DD156265A1 - METHOD FOR THE PRODUCTION OF FORM BODIES FROM POLYMER SOLUTIONS - Google Patents

Abstract

A process is described for the preparation of shaped bodies from polymer solutions by coagulation in which coagulation takes place under the action of ultrasonic vibrations.

Description

Process for the production of molded articles from polymer solutions

Field of application of the invention

The invention relates to a process for the preparation of molded articles from polymer solutions by coagulation of the polymers in liquid precipitation media

technical

Polymers of polymers by coagulation of polymer solutions in precipitating media are generally prepared such that the polyene solutions having a sufficiently high concentration of the polymer are introduced into liquid media, the polymer solution being conveniently formed by means of shaping devices upon entering the precipitation medium of a shape appropriate to the final product and that the polymer is thereby brought to coagulate the polymer separates in the swollen state, ie with a high proportion of precipitation, from «

The "course of the coagulation of the polymer solutions can be followed by determining the decrease in the solvent content of the coagulating moldings." This decrease is defined as the degree of coagulation (KG), where

- A - B 'r - 7 KG = -. 100 [%]

A - originally existing solvent B = s after a defined time remaining amount of solvent «

So 100% coagulation mean _s that no solvent is more in the coagulated molded body _s d "h" coagulation is finished

For the technical realization of the coagulation process to achieve a minimum value of the degree of coagulation is _nine such "B * uptake by supporting, from" location "j Deduction or guide s devices" If the requirement for mechanical handling of the koagulie "Governing molding of Coagulation level too low? the coagulating body does not have the sufficient stability for these technically necessary process steps after coagulation. "The time required to set this minimum coagulation degree thus substantially determines the speed of production of the tablets and thus the economy of the processes

On the other hand, in the coagulation process, however, the type of primary structure of the coagulating moldings is also determined to a significant degree, and thus the mechanical and other structural properties such as, for example, are determined. .B. " the gas, vapor, or dye sorption and -definition ratios in the polymer reformer bodies ₉ d * h _{0 are} generally the same. Utility value, affected.

The hitherto "known method for the production of moldings from polymer solutions by coagulation of the polymers now adheres to the lack that they set limits in the fundamental objective to combine an economically advantageous method of manufacturing the moldings with the production of favorable for the use value of the moldings structures These limits are given by the fact that, given a given polymerisation, the period of time required for achieving the minimum degree of coagulation has so far necessarily been coupled under all coagulation conditions with the formation of a very specific, otherwise non-negotiable primary structure of the coagulating shaped bodies, ie. : this structure is hitherto solely dependent on the complex interaction of polymer, solvent, precipitant, the architecture of the moldings and the precipitation bath temperature (Rogowin, SA: Man-made Fibers - Fundamentals of Chemistry and Technology, VEB Fachbuchverlag Leipzig _s 19G0, p. 439).

For example, B., B. is known that given a given polymer and solvent, the period for setting the minimum coagulation. grades can be reduced by using precipitants that lead to thermodynamic reasons to rapid coagulation. Although this one goal is achieved, however, arise in the moldings morphological structures that adversely affect die.Userauchproperties of the moldings (Grobe, V, and Meyer, K .: Faserforsch, u · Textiltechnik W (1959) 5, 214- 224T.

In addition, the production costs for the molded bodies are increased by the fact that in the technical process the recovery of the precipitates is associated with increased energy expenditure, since these precipitants, in order to retain their high precipitating power, preferably in pure form, have only a few proportions Furthermore, it is known that the mentioned period of time can be reduced by using elevated temperatures in coagulation.

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However, this also results in formations whose utility value is reduced as a result of a very loose structure apart from the increased energy expenditure, this time for heating up the precipitates (Rogowin? S "A _e ; Chemiefasern - Grundlagen der Chemie und Technologie", VEB Fachbuchverlag Leipzig, 196o _{S e} 599;? Grobe V. and man ,. G ₀ s Paserforsch "and textile technology 19 (1968) 2 _S 49-55).

The aim of the invention is it _? to accelerate the coagulation process for the production of polymer moldings and to improve the use value of the products

task

It is the object of the invention * to accelerate the setting of a degree of coagulation of polymers required for the technical realization of coagulation processes, and / or to expand the variability of the morphological structures _{9 of} the shaped bodies produced during coagulation *

Features of the invention

It was found _s that the problem is solved when the system "coagulating moldings - precipitation medium" in the coagulation of the polymer solutions energized with ultrasound "is · The effect of ultrasonic vibrations need not be immediacy after leaving the polymer solutions from the molding device.? It is also sufficient for the task to be solved if the ultrasound acts on the system after about a second. «

The action of the ultrasonic vibrations on the coagulating bodies according to the invention enables an economically advantageous acceleration of the coagulation process and / or an increase in the utility value of the resulting tablets. By selective variation of the morphological structures

The following examples are intended to explain the process according to the invention:. , _;

example 1

A 15% solution of polyacrylonitrile in dimethylformamide is applied by means of a puller to a glass plate in a 0.3 mm thick layer. Then, this glass plate is immersed for 10 seconds at 22 ⁰ C in water, which is excited by ultrasonic vibrations at a frequency of 40 KHz. It is produced by coagulation of a membrane-like polymer sheet, which still contains 327 g of dimethyl formamide per 100 g of polymer solid substance · Because 100 g of polymer solid substance dissolved solvent in 567 g at a 15% solution, this means that after 10 seconds, the coagulation level is 42% ₀

Comparative Example 1

The procedure is as in Example 1 with the difference that the coagulant Y / asser is not excited by ultrasound. The resulting polymer surface still contains 441 g of dimethylformamide per 100 g of polymer solids after a coagulation time of 10 seconds; the degree of coagulation thus has a value of only 22 % on _β

It was proceeded as in Example 1 with the difference _? that the coated with the polymer solution the glass plate before dipping in aas by Ulti-aschallschwingungen excited water for one second in v / ater immersed v / ill "that is not excited by Uitraschallschvrlngungen * The result is a lOrmkörper _ä still 309 g of dimethylformamide per 100 g contains solid substance So the degree of coagulation is 46 %

fr ·

f H U

An 18 "solution of cellulose 2 1/2 acetate in dimethylformamide wi ^ d. As in Example 1, placed on a glass plate and then coagulated under the same conditions The flat shaped body containing after a coagulation time of 10 seconds still 237 g of dimethylformamide per 100 g polymer solid subs danz »Since at an 18 $ L ₀ solution 100 g of polymer substance dissolved in 456 g of solvent. are? This means that after 10 seconds the degree of coagulation is 48 % _e

Without excitation by ultrasound, the coagulated polymer molded article still contains 328 g of dimethylformamide per 100 g of polymer solid substance after 10 seconds under otherwise identical conditions; the degree of coagulation thus has a value of 28 %,

Beisj3iel__4

An 18% solution of cellulose 2.1 / 2-acetate in dimethylacetamide (DMAc) is brought in the form described in Example 1 under the action of UItraschallschwingungen in water at 22 ⁰ C for coagulation «_For comparison, a same solution without the action of ultrasonic vibrations ₉ but otherwise under the same conditions coagulated "in water '* the resulting molded body to be compared enthalten'nach same coagulation different amounts of dimethylacetamide resulting ₉ from which different coagulation values," you are given in Table 1 "

^ jU Coagulation _s result, the strength in the coagulation of a 18% solution of cellulose-2.t / 2-acetate in DIiAc in v / ater as Fällmediura after 10 and 30 seconds

Coagulation duration

10 SQQ

with no effect under binwir of ultrasound kuna of Ul-5 chwingunge

23

trasü.hall cchv / i ng

47

Example 5

A solution of 20.7 % of an acrylonitrile copolymer in dimethylformamide is forced through the holes of a spinneret into a coagulation bath containing the water which is excited by ultrasonic vibrations. The result is filiform shaped bodies which, after removal of the solvent, become longer due to storage in water Have a source value of 384 % and show larger cavities in cross-section. "The source value Q was determined as Q = ff ~ .M» 100

where 'N =' gel thread weight

M = "weight of the dried thread"

Comparative Example 5

The procedure is as in Example 5 with the difference that the water serving as coagulation medium is not excited by ultrasonic vibrations. "The resulting molded articles have a source value of 345 % after the same type of aftertreatment. A smaller void volume can be seen in cross section in comparison to the threads produced according to the invention.

Example 6

Through the holes of a spinneret, an I5% solution of an acrylonitrile polynier in dimethylformamide is printed in a coagulation bath containing the carbon tetrachloride excited by vibratory vibrations. The moldings remain in the precipitation bath for 5 minutes; then the excitation is turned off, and the moldings remain for another 30 minutes in the precipitation medium »Es. arise threads that have a lobed cross-section, which reveals no cavities in the microscope. After 60 seconds of coagulation time, the filaments still contain 63 g of dimethylformamide per 100 g of polymer solid; the degree of coagulation is thus 89 %.

Comparative Example 8

Example 4 is used with the difference that the carbon tetrachloride serving as coagulation medium is not excited by ultrasonic vibrations. The resulting filaments have the same cross-section as in Example 6 _a. The degree of coagulation is only 76 %.

Claims (2)

invention claim 1 ♦ Process for the preparation of shaped articles from polymer solutions by coagulation after shaping of the solutions, characterized in that the coagulation takes place under the action of ultrasonic vibrations. •. φ · · 2 * Method according to item 1, characterized in that the ultrasonic oscillations act directly or with a time delay of = 1 second after the shaping of the polymer solution on the system "coagulating molding precipitate".