CS262763B1 - Thermally still materials of chlorinated polyvinyl chloride - Google Patents

Abstract

Thermally stable filtration material consisting of a layer of unicellular fibers from a mixture of 51 to 99 wt. % chlorinated polyvinyl chloride and 1 to 49 wt. % cellulose derivatives, which are cellulose nitrate, cellulose acetates and cellulose acetobutyrate.

Description

The subject of the invention is a thermally stable chlorinated polyvinyl chloride filter material.

Filter materials prepared in the form of a filter layer of fibers or strips of the stage of Czechoslovakia. pat. 127 887 have excellent filtering properties and are used with success: to filter air with high demands on its purity, such as e.g. operating theaters in hospitals, computer technology, production of pharmaceuticals and photographic material and microelectronics, possibly as personal protective equipment in dusty environments such as coal mine, cement plant and processing of some substances that cause pneuconiosis. Their wider application is hampered by their relatively low thermal stability, so that they can be used at temperatures of max. 70 degrees Celsius.

When filtering oils in grouting engines, hydraulic mechanisms, the thermal stability of the filter material is 100-120 ° C, and when used in the biotechnology industry up to 140 ° C. Up to now, mainly cellulose-based filter materials have been used in these applications, but they have low flow rates due to high resistance and are relatively brittle, so that they become rapidly clogged by impurities and rupture.

To improve the thermal stability of the polyvinyl chloride, thermal stabilizers such as e.g. organic tin compounds, but these stabilize the ip polymer for a short time during its heat treatment. A disadvantage of low molecular weight additives is also their migration to the surface of the product, thereby eliminating their stabilizing ability. In addition, there is a risk of leaching of these stabilizers, e.g. oil filtration and thus the possibility of deteriorating lubricating ability of oils.

The above-mentioned drawbacks are eliminated by a thermally stable filter material of fibers or tapes from a mixture of chlorinated polyvinyl chloride with 1.0 to 49.0 wt. % high molecular weight cellulose derivatives such as cellulose nitrate, cellulose diacetate and triacetate and cellulose acetobutyrate. Fiber or strip filter materials from cellulose derivatives alone do not have as good filtration properties as chlorinated polyvinyl chloride.

By mixing the solutions of polyvinyl chloride and cellulose derivatives in the desired ratio, a mixture is obtained from which fibers are prepared which are stored pneumatically or in an electrostatic field according to U.S. Pat. No. 120,503 to a homogeneous filter layer, optionally prepared by extrusion from a slit-shaped die onto the surface of the film roll from which the tapes are fibrillated and further processed into the filter layer in the aforementioned processes.

In order to maintain the nature of the chlorinated polyvinyl chloride filter material, the proportion of cellulose derivatives in the mixture must be less than that of chlorinated polyvinyl chloride. The condition is that the cellulose derivatives are soluble in a common solvent or a common solvent mixture. This requirement is met by cellulose nitrate, diacetate, triacetate and acetobutyrate. Suitable solvents are:

acetone, ethyl acetate, butyl acetate, amyl acetate, isopropyl acetate, tetrahydrofuran, methylene chloride, chloroform and other volatile solvents.

The distribution of the cellulose derivatives mixed with chlorinated polyvinyl chloride is parallel in the direction of the fiber or tape axis. This is not a staggered distribution of the two polymers, as evidenced by the fact that the filter layer of this polymer. the combination has a shrinkage of 2.0 to 3.0 percent at 100 ° C in both directions, while shrinkage of the polyvinyl chloride filter layer under the same conditions is up to 50%.

The advantages of the present invention best exemplify the above examples.

Example 1

The filter material was prepared with a mixture of 8 wt. % of chlorinated polyvinyl chloride and 2 wt. A portion of cellulose nitrate in ethyl acetate, composed of fibers with a diameter of 1.0 to 5.0 µm. This material changed its dimensions in water at 100 ° C by 3% in both directions and retained the filtration properties of this flood shrinkage.

Example 2

The filter material was prepared from a 6 wt. % of chlorinated polyvinyl chloride and 4 wt. % of cellulose diaceltate dissolved in a mixture of 8 wt. % acetone and 2 wt. of ethanol. A foil was prepared from the prepared solution by casting and tapes with a cross-sectional dimension of 4.0 to 12.0 µm were prepared from it by fibrillation. The filter layer prepared by the pneumatic method had a 1% shrinkage in air at 100 ° C in both directions while maintaining the original filtering properties.

Example 3

The filter material was prepared from a 7 wt. parts of chlorinated polyvinyl chloride and 3 wt. cellulose triacetate components dissolved in a 9 wt. parts by weight of methylene chloride 1 wt. part of methanol by passing the prepared solution through the capillary tubes of a 0.4 mm diameter spinneret into the air stream to form fibers with a diameter of 4 to 10

The filter material thus prepared had a shrinkage of 3% of the flood dimension in both directions at a temperature of 100 ° C, while retaining the original filtering properties.

Claims (1)

5 26 2 76 3 (which were deposited in the filter layer in an electrostatic field. The filter material thus prepared had shrinkage in both directions of 3% of the initial dimension in steam at 100 ° C while maintaining the downstream filtration properties. chlorinated polyvinyl chloride base fiber filter material, characterized in that it comprises a mixture of 51 to 99% by weight of chlorinated ipolyvinyl chloride and 1.0 to 49.0% by weight of cellulose derivatives, which are cellulose nitrate and acetone. cellulose butyrate.