CZ20032748A3 - Process for making a bundle of artificial porous hollow fibers by stretching - Google Patents

Abstract

Method of making a bundle of plastic porous hollows of fibers by stretching to form a skein precursor fibers which are then stretched in a controlled manner and at a controlled temperature with the next possible processing. In doing so, the precursor fibers in the skein or z at least two spaced apart places are blinded or blinded, these places are subsequently operated in by pulling devices with different pulling forces up to k achieving a selected extension of the free portions between the two after which, if necessary, further processing of a skein or bundle, the places with the fibers become degraded by strangling or gluing it off.

Description

Method for producing a bundle of plastic porous hollow fibers by drawing

Technical field

The invention relates to a method for producing a bundle of plastic porous hollow fibers by drawing, in which a skein of precursor fibers is formed, which is then drawn in the attenuator at a controlled speed and at a controlled temperature, followed by possible further processing.

BACKGROUND OF THE INVENTION

Elongated membranes are one of the types of membranes used in filtration and contactor devices. By stretching the originally non-porous plastic film, such as polypropylene or polyethylene, microscopic pores are formed in the wall through which filtration takes place or an interfacial surface is formed. The membranes are preferably manufactured as hollow fibers with microporous walls, one medium being outside the fiber and the other flowing through the fiber cavity. Thus, a large exchange surface can be placed in a small volume of filter or contactor device. The precursor of such a porous hollow fiber, called a precursor, is produced by extrusion - by extruding a circular hole provided with a central mandrel - and then adjusted to the desired diameter. The actual production of the porous hollow fiber then proceeds by stretching the precursor.

The most well-known and most widely used method of industrial precursor drawing is continuous: The precursor circulates a plurality of rotating parallel cylinders, wherein the rotational speeds of the cylinders are adjusted to achieve the desired precursor extension. The extension can be hot or cold in several steps,

• • · • ·· • · ···· ·· · • ·· · • • · • • · • • · • • · • • • · • • « • • · • · ··· • · ··· • · «· · ♦

the number of which is determined by the number of rollers used. This known method is described, for example, in U.S. Pat. Nos. 5,294,338, 5,547,756 and 4,405,688. The disadvantage of this method is the so-called hollow fiber ironing due to unwanted fiber slip on the rolls. The friction between the hollow fiber and the cylinder causes the pore orifice to be disrupted, thereby reducing the filter effect. If the precursor breaks in operation, it is necessary to put the line into operation again. At the same time, only a relatively small number of fibers can be drawn.

Another process for manufacturing a non-constant porosity hollow fiber membrane is proposed in U.S. Patent Application Publication 2003/0111407 A1. It consists of two steps: First, the precursor is wrapped around at least two supports to form a skein, whereupon the spacing of these supports increases. After this drawing, the fibers are processed in a standard manner. There are two types of mutually different sections on the fibers thus produced. The stretches that were located in the space between the supports have full desirable porosity, while the stretches that surrounded the supports have no or only limited porosity. This is because at these wrapping points, the tensile force causes friction between the fibers or between the fibers and the support, which limits the elongation. After drawing, the resulting fibers must be processed with respect to alternating porous and non-porous sections. Furthermore, the disadvantage of the described process is the relatively complicated handling, uneven fiber quality and relatively higher precursor consumption.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method of making porous hollow fibers which avoids the disadvantages of the above methods.

SUMMARY OF THE INVENTION

This object is achieved by a method of forming a bundle of plastic porous hollow fibers by drawing, in which a skein of precursor fibers is formed, which is subsequently drawn in the attenuator at a controlled speed and at a controlled temperature, followed by possible further processing. The essence of the novel method is that the precursor fibers in the skein or bundle of fibers are cut or glued at at least two spaced apart points, which are subsequently subjected to tensile forces of different directions in the attenuator until they reach · The chosen elongation of the free sections between these points, after which, if necessary, further processing of the elongated skein or bundle, the strands with the strands damaged by strangulation or gluing are removed.

The throttling is preferably effected by wrapping the skein or bundle with a tape and clamping the sleeve.

The bonding of the precursor fibers can advantageously be accomplished by fusing them.

The site where the gluing or fitting is carried out may be formed into a block for engagement with the forks of the attenuator.

To carry the tractive force, the traction cable can be clipped behind the sleeve.

To transmit the tractive force, clamping elements can be attached to the skein or bundle by means of a clamp for engaging the forks of the attenuator.

The attenuator forks can also be gripped by the block.

The pulling force can also be transmitted by the jaws of the attenuator clamping the sleeve or block.

Overview of the drawings

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side view of a two-prong alignment bench; FIG. 2 is a location for a skein of precursor fibers provided with clamping elements; FIG. Fig. 5 shows the clamping of a plurality of skeins in the attenuator by means of clamping elements and forks, and Fig. 6 shows a method of forming a clamping block at the end of a skein.

· · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ···

DETAILED DESCRIPTION OF THE INVENTION

The following examples illustrate the invention.

Example 1

The extruded hollow fiber precursor was rewound on a skein 1 with a diameter of 250 mm with 1500 windings. Alignment of the skein X was performed on the alignment bench 2 with two mandrels 3 with a diameter of 10 mm, one fixed and the other movable. In the vicinity of the mandrels 3, the skein 1 was first wrapped with a reinforced adhesive tape 4, onto which the clamping elements 5 were placed and secured with a fixation sleeve 6. The skein thus prepared was placed in the forks 7 of the Instron shredding machine. The machine is equipped with a telescopic chamber in which a constant temperature of 150 ° C is maintained during drawing. The resulting porous hollow fibers were stabilized for 8 hours in a heat chamber at 120 ° C and a 15N parallel fiber pull. The skein of stabilized porous hollow fibers was again transferred to the cutting station by means of clamping elements 5 where the ends were removed. In the final phase, the usable part was modified for functional mounting in the module.

Example 2

The precursor was rewound on a X skein with a diameter of 1 m, while a rectangular skein with a length of 100 and a height of 30 mm was created by means of a carrier. The skein X was leveled on the alignment bench 2 and its ends provided in a manner similar to Example 1. The five skirts thus prepared were inserted into the forks 7 of the attenuator, the arms of which were spaced apart by a screw mechanism. The next procedure was the same as in Example 1. The usable part of the bundle was cut to the required length and adjusted to functionally attach the 105x35x30 mm profile to the module.

Example 3

In the laboratory, a small skein containing only several tens of precursor fibers was processed. The skein X was straightened, its ends merely wrapped with a reinforced adhesive tape 4 and tightened by a fixation sleeve 6. The skein so treated was clamped at the jaws 6 by the jaws 8 of the Instron shredder and stretched. It was then wrapped around the cylinder and its ends tied together. Tempering occurred

in a laboratory thermostat at a temperature gradient of 10 ° C / h. from 120 ° C to ambient temperature. Subsequently, the ends deteriorated by the clamping means were removed.

Example 4

The skein of the same size as in Example 3 was treated analogously to Example 3 except that its attachment in the Instron shredder was carried out by means of a steel wire 9 snapped behind the fixation sleeve 6. The stretching and tempering were the same as in Example 3.

Example 5

The precursor fiber was rewound on a 1 m diameter skein 1, then straightened on a leveling bench 2 and its ends wrapped with reinforced adhesive tape 4. The treated skein ends 1 were inserted into a heated, tefloned mold 10, 11 in which the material was sintered into a monolithic The same was done at the other end of the skein 1. The five skirts thus prepared were inserted into the forks of the attenuator. The procedure was the same as in Example 2.

Example 6

The precursor fiber was wrapped on a 50 mm wide Teflon-coated coil. A metal prism with a width corresponding to half the width of the notch, coated with a layer of Teflon, was pressed against the precursor fibers at the notch position, thereby fusing them. The fibers were cut along the notch axis, the bundle thus formed was removed from the bobbins and its ends treated analogously to Example 5. Five bundles so treated were inserted into the forks 7 of the attenuator followed by the procedure of Example 1.

The examples refer to the processing of precursor fibers in a skein formed into a longitudinal shape, wherein the points where the tensile forces are applied are the ends of that shape. However, the invention also extends to the case where the skein has more than two tensile forces and to the cases where the precursor fiber bundle formed from the skein is processed, where the tensile forces are not only at the its ends, but also between its ends.

Claims (7)

PATENT CLAIMS A method for producing a bundle of plastic porous hollow fibers by drawing, wherein a skein of precursor fibers is formed, which is subsequently drawn at a controlled speed and at a controlled temperature, followed by possible further processing, characterized in that the precursor fibers are formed in the skein or bundle thereof. at least two spaced spots are cut or glued, these spots are subsequently subjected in the attenuator to tensile forces of different direction to achieve the selected elongation between the spots, and after further processing of the elongated skein or bundle of spun fibers by strangling or gluing. Method according to claim 1, characterized in that the throttling is carried out in such a way that the skein (1) or bundle is preferably wrapped around the tape (4) and clamped by the fixing sleeve (6). Method according to claim 1, characterized in that the precursor fibers are adhered together by cutting them. Method according to claim 3, characterized in that the place where the gluing or setting is carried out is formed into a block (12) for engagement with the forks (7) of the attenuator. Method according to claim 2, characterized in that the pulling cable (9) is clamped to transmit the tractive force behind the fixing sleeve (6). Method according to claim 2, characterized in that clamping elements (5) are fastened by means of the forks (7) of the attenuator to transfer the tractive force to the skein or bundle by means of a fixing sleeve (6). Method according to claim 2 or 6, characterized in that the tensile force is transmitted by the jaws (8) of the attenuator clamping the sleeve (6) or the block (12).