CS262768B1 - A method for preparing thermally stable filter materials from chlorinated polyvinyl chloride - Google Patents

Abstract

Preparation of filter materials from a mixture of a solution of chlorinated polyvinyl chloride and a cellulose derivative and depositing the formed microfibers in an electrostatic field. The chlorinated polyvinyl chloride and the cellulose derivative dissolve separately in the same solvent. The solutions are mixed immediately prior to spinning and are fed to a spinning apparatus with stirring.

Description

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It is an object of the present invention to provide a thermally stable filter material based on chlorinated polyvinyl chloride with cellulose derivatives.

The method of preparation of filtration materials described in MS. pat. No. 127 8S7 assumes the fibrillation of homogeneous colloidal solutions. Such solutions are formed by dissolving one polymer in a suitable solvent or in a solvent mixture. The solution after filtration can be immediately spun. Preparation of filter material from a mixture of chlorinated polyvinyl chloride and cellulose derivatives as described by MS. AO 262 763, which has improved thermal stability, encounters some of the technological difficulties that result from the fact that by dissolving two polymers in a common solvent or solvent solvent, colloidal solutions are formed which are unstable and, after a short period of time, two layers each containing one polymer. From this, the solution is. cannot produce a quality product. This case occurs by dissolving a mixture of chlorinated polyvinyl chloride with cellulose derivatives such as nitrate, diacetate, triacetate or cellulose acetobutyrate, e.g., vacetone, ethyl acetate, tetrahydrofuran or methylene chloride. The stability of these solutions can be temporarily improved by DWP No. 54 546 by the addition of additional solvents which increase the surface tension value. However, this leads to difficulties in solvent recovery. Other drawbacks of the current solvent of the two polymers are their uneven dissolution rate and thus the inadequate utilization of the dissolution apparatus.

These drawbacks are avoided by separately dissolving the polymers in a common solvent or a mixture of solvents in which the two polymers are soluble. The solutions of the two polymers are separated into a filtration apparatus where they impart mechanical impurities or gel. Filtered solutions of 8.0 to 14.0 wt. % are mixed in a ratio of 1.0 to 49.0 wt. % cellulose derivatives with 51.0 to 09.0 wt. % of the chlorinated polyvinyl chloride in the mixer equipped with a stirrer. The stirring speed of the solution mixture is min. 5 rpm. The solutions are stirred for a minimum of 60 minutes to ensure that the solution is homogeneous and then the solution is fed under continuous agitation. The distance of the mixing plug from the spinning device must not be greater than 5.0 m. The advantages of the invention are best exemplified by the examples. Example 1

A solution of chlorinated polyvinyl chloride in ethyl acetate at a concentration of 10.0 wt. % was mixed with a solution of cellulose nitrate in ethyl acetate of 10.0 wt. % immediately before spinning in a ratio of 80.0 wt. % dry matter of chlorinated polyvinyl chloride and 20.0 wt. % cellulose dry solids. The mixture was homogenized for 60 min. in a mixer mixer at a mixer speed of 50 rpm. The homogenized solution of the agitated agitation proceeded to a spinning device distant from the mashing container of 4.5 m. The filter material prepared from a solution of a mixture of these polymers formed by a layer of fibers having a diameter of 1.0 to 5.0 µm changed its dimensions in water at heat. 100 ° C by 3 ° / o in both directions and preserve the properties of the water filter in this shrinkage. Example 2

A solution of chlorinated polyvinyl chloride vacetone at a concentration of 11.0 wt. % was mixed with a solution of cellulose diacetate dissolved in a mixture of 80.0 vol% acetone and 20.0 vol% eitanol at a concentration of 11.0 wt%. % immediately before spinning, at a corresponding 60.0 wt. % dry matter of chlorinated polyvinyl chloride and 40.0 wt. % cellulose diacetate dried. After homogenising the solutions for 60 min. mixing them with an arm stirrer at 40 rpm. in the blending hopper, the flow was fed to a spinning apparatus that was 3.2 m away from the blending hopper. The filter material prepared from this blend layer, having a diameter of 4.0 to 12.0 µm, had a pulse velocity. - air 100 ° C shrinkage 1% in both directions while retaining the polar filtration properties. Example 3

A solution of chlorinated polyvinyl chloride in a concentration of 9.0 wt. % Of dissolved vehicle 90.0 vol% methylene chloride and 10.0 vol. % methanol was mixed with a solution of cellulose triacetate at a concentration of 9.0 wt. % dissolved in a flat solvent mixture immediately prior to spinning. The solutions were selected to be 70.0 wt. % dry weight of chlorinated polyvinyl chloride and 30.0 wt. % Of the dry weight of cellulose triacetate. The mixture of solutions was homogenized for 60 min. in the mixing stock at an anchor stirrer speed of 20 rpm. The homogenized solution was fed to the spinning apparatus under continuous stirring. The filter material in the form of a layer prepared from fibers having a diameter of 4.0 to 10.0 µm in the steam at a temperature of 100 ° C shrinks in both directions of the 3% porous size of the porous filtering properties.

Claims (1)

SUBJECT Process for preparing thermally stable filter materials by spinning a solution comprising a mixture of chlorinated polyvinyl chloride with a cellulose derivative and depositing the formed microfibers in an electrostatic field, characterized in that the chlorinated polyvinyl chloride and cellulose derivative are dissolved separately in the same solvent for the same OF THE INVENTION the concentration and the prepared solutions are mixed immediately before spinning in a container remote from the spinning device at a maximum of 5 m, in a ratio of 1.0 to 49.0 wt. % cellulose derivative and 51.0 to 99.0 wt. % of chlorinated polyvinylchloride and, with stirring, are fed to a spinning apparatus.