KR20050061480A - Method for producing highly stable polypropylene fibres - Google Patents

Abstract

The invention relates to a method for producing highly stable polypropylene fibres with a strength in excess of 6 cN/dtex. and an elongation of less than 40 %. To obtain the highest possible fineness of fibre, the fibre strands are first spun at a low melting temperature of less than 250 °C and a relatively low drawing speed of less than 100 m/min, whilst being cooled by a gaseous medium. The fibre strands are then stretched in at least three stretching stages with an overall stretching ratio in excess of 4:1, whereby said fibre strands are partially stretched in the first stretching stage to at least 70 % of their overall stretched state. After the stretching process, the fibre strands are cut to form the polypropylene fibres.

Description

Manufacturing method of high stability polypropylene fiber {METHOD FOR PRODUCING HIGHLY STABLE POLYPROPYLENE FIBRES}

The present invention relates to a method for producing high-strength polypropylene fibers having high toughness and low elongation by successive operations of melt spinning, drawing, drawing and cutting into polypropylene fibers.

A single step process for the production of high toughness polypropylene fibers is known from DE 35 39 185.

In this known method, the fiber strands are transferred to a water bath for cooling after spinning. The fiber strands are then drawn at high draw ratios up to 10: 1 in the draw zone. As a result of cooling the fiber strands relatively quickly in the water bath, relatively high partial orientation occurs in the surface area of the individual fibers, resulting in poor draw capacity. In addition, the known method is only suitable for producing relatively coarse fibers in which each denier is greater than 3 dtex. Larger friction effects in the individual filaments produced by the water bath alone are not able to spin fibers with finer deniers.

However, with the use of such concrete reinforcing fibers, fine fibers with very high tension are required. DE 198 60 335 A1 discloses polypropylene fibers, in which the disadvantages of quenching in liquids are replaced by air cooling. This makes it possible to produce fiber strands with fine individual deniers, but has the disadvantage that the fibers have a high elongation of at least 60%. However, as found during the reinforcement of the concrete foundation body, the elongation of the reinforcing fibers should be about the same as the elongation of the foundation material to be reinforced, so that the fibers can absorb the load as soon as possible and the foundation body is not affected. It must be left unchecked. As a result, fibers with relatively high elongation are only suitable in a limited range.

The polypropylene fibers disclosed in EP 0 535 373 Al have the required fine denier with high toughness, but can only be produced in an expensive two step process.

In this process, the fibers are temporarily stored after spinning and drawing operations with additional processing by impregnation. Thereafter, in the second step, the fiber strands are wound up again, dried and cut.

1 is a schematic diagram of a first embodiment of an apparatus according to the present invention for carrying out the manufacturing method of the present invention.

2 is a schematic diagram of another embodiment of an apparatus according to the present invention for carrying out the method of the present invention.

1 schematically shows a first embodiment of an apparatus according to the present invention for single stage production of polypropylene fibers. This type of device is commonly known to the person skilled in the art as a compact spin line, which preferably produces staple fibers of polypropylene. This compact spinning line operates at spinning speeds up to 250 m / min. Because of this, high production capacities of up to 50 t per day can be reached.

The device according to the present invention corresponds to the compact spinning line and comprises a radiator 1 having a plurality of spinning positions 2.1-2.3 arranged side by side for this purpose. In the embodiment shown in FIG. 1, the number of radial positions is only an example. Each radial position 2.1-2.3 is installed identically and is described in more detail with the radial position 2.1.

In order to extrude a plurality of fiber strands, it is preferable to provide an annular spinning projection 3 having a plurality of spinning holes in the lower surface. For example, in the spinneret 3, it is preferable to arrange 120,000 spinnerets in an annular or quadrangular arrangement. This spinneret 3 is connected to a melt source (not shown), which supplies a melt flow to the spinneret 3 under constant pressure. Suitable melt sources for supplying melt flow to the spinneret 3 are basically extruders, pumps, or a combination of both. The spinneret 3 at the spin position 2.1-2.3 is arranged in the heated spinneret 15. Downstream of this spinning beam 15, the spinning position comprises a cooling device 4 arranged substantially concentrically with the spinneret 3. The cooling device 4 is an air quench system, in which cooling air flow is generated by an annular blow nozzle, thereby forming an annular sheet formed by fiber strands. Cooling air flows from the inside to the outside to cool the fiber strands. In the illustrated embodiment, the cooled air of the cooling device 4 is supplied from the top through the spinning beams 15. However, it is also possible to arrange a cooling air supply on the side adjacent to the exiting fiber strands.

In order to move and process the fiber strand indicated by reference numeral 5 " in the embodiment of Fig. 1, a plurality of processing apparatuses are arranged downstream of the spinning machine 1. As the first processing apparatus, the extraction apparatus 6 is It is directly connected with the spinning machine 1. For each spinning position, the take-out device 6 comprises means for lubricating and advancing the fiber strands 5. For example, when lubricating the lubricant is The drawing device 6 is arranged downstream of the spinning machine 1. The drawing device deflects the fiber strands 5 of the spinning positions 2.1-2.3 from the vertical path. In this operation, a plurality of fiber strands 5, also called tows, are drawn out by the first drawing system 7.1. Disposed directly adjacent to (6) .

The drawing system (7.1) is followed by a total of three additional drawing systems (7.2-7.4). These drawing systems (7.1, 7.2, 7.3 and 7.4) each form one drawing end between them. Thus, the first drawing end 9.1 is formed between the first drawing system 7.1 and the second drawing system 7.2. The second drawing end 9.2 is formed between the drawing system 7.2 and the drawing system 7.3 and the third drawing end 9.3 is formed between the drawing system 7.3 and the drawing system 7.4. Each drawing system (7.1-7.4) comprises a plurality of drawing rolls (8), the fiber strands moving over the drawing rolls in a single loop. The drawing roll 8 of the drawing system 7.1-7.4 is driven. Depending on the draw ratio required, the draw rolls 8 of the drawing systems 7.1-7.4 are operated at different circumferential speeds. For simultaneous heat treatment of the fiber strands, the draw rolls 8 of the drawing systems 7.1-7.4 have a cooled outer surface or a heated outer surface as required. In addition, for the heat treatment of the fiber strands between the first drawing system 7.1 and the second drawing system 7.2, the first drawing end 9.1 receives a heated drawing channel 10. Inside the heated draw channel 10, the fiber strand 5 is tempered to a temperature defined by hot air or hot steam. Another heated drawing channel 10 is also arranged in the second drawing end 9.2, as between the drawing system 7.2 and the drawing system 7.3.

At the end of the fiber line formed by the continuously arranged drawing system (7.1-7.4) there is provided not only a tension control device 11 but also a cutting device 12 for cutting the fiber strands into staple fibers of defined fiber length. have.

In order to carry out the manufacturing method of the present invention in the apparatus shown in FIG. 1, the polymer melt of polypropylene is passed through the spinneret 3 at the spin position 2.1-2.3 while being pressurized by the spinner 1 in a first step. Extruded into a plurality of fiber strands. The fiber strands 5 flowing out from the spinneret 3 are drawn out by the drawing system 7.1 at a drawing speed of 100 m / min or less, preferably 50 m / min or less through the drawing device 6. In this operation, the fiber strands 5 are cooled in the cooling device 4 by a mist or gaseous cooling medium flow, preferably air. Then, when leaving the take-out device 6, the fiber strands are lubricated and joined to a tow containing all the fiber strands. The drawing roll 8 of the first drawing system 7.1 is driven at the drawing speed. At the same time, the fiber strands are further cooled past the circumference of the drawing roll 8 of the first drawing system 7.1. For this purpose, the outer surface of the drawing roll 8 of the first drawing system 7.1 is cooled.

The fiber strands 5 are drawn at three different draw rates (9.1-9.3) at different draw rates. Total draw rate is greater than 4: 1. In the drawing stage, the fiber strands are drawn with different intensities. In order to obtain a high tension in particularly fine fibers, the fiber strands must be subjected to a partial draw of at least 70% of the total draw at the first drawing end (9.1). In the drawing at the first drawing end 9.1, the fiber strand 5 is heated to a temperature higher than 100 ° C., preferably by air, in the heated drawing channel 10. This fiber strand then passes over the drawing roll 8 of the second drawing system 7.2, which is also heated to a temperature higher than 100 ° C. The second partial drawing of the fiber strand 5 takes place at the second drawing end 9.2, which is likewise treated in the heated drawing channel 10. The fiber strand is drawn more partially in the third drawing system 7.3 and the partial drawing at the second drawing end 9.3 is higher than the final partial drawing at the third drawing end. The roll 8 in the third drawing system 7.3 is likewise heated to a surface temperature above 100 ° C. for uniform and continuous drawing. After the third partial drawing, the fiber strands 5 are cooled by the cooled drawing roll 8 of the fourth drawing system 7.4. The fiber strands are then cut uniformly to the defined fiber length.

With the use of commercially available polypropylene polymers, the fiber length is 6.6 mm or 13 mm in several series of tests, each denier is 0.9-1.6 dtex, toughness is 8-9 cN / dtex, elongation is 18 It was possible to produce fibers of ~ 21%. While spinning the fiber strands, the melting point was adjusted to below 250 ° C. Tens of thousands of spinning holes are annularly arranged in the spinning board.

The drawing roll of the first drawing system (7.1) is at a draw speed of 25-40 m / min, the drawing roll of the second drawing system (7.2) is at a speed of 80 to 115 m / min, and the third drawing system (7.3) The drawing roll of is operated at a speed of 100 to 140 m / min and the drawing roll of the fourth drawing system 7.4 is operated at a speed of 100 to 160 m / min. The surface temperature of the drawing roll 8 is about 30 ° C. for the first drawing system 7.1, above 100 ° C. for the second drawing system 7.2, and 100 similarly for the third drawing system 7.3. Above 30 ° C., for the fourth drawing system 7.4 is about 30 ° C. FIG. At the first drawing end 9.1, the fiber strands are tempered with hot air above 100 ° C. in the heated drawing channel 10. In the second drawing stage 9.2 the fiber strands are treated with hot steam of less than 100 ° C. In this way, the draw rates obtained for producing the fibers are from 2.8 to 3.2: 1 for the first draw end (9.1), 1.05 to 1.5: 1 for the second draw end (9.2) and 1.05 for the third draw end (9.3). ~ 1.3: 1 range. In particular, the fiber is due to a relatively low withdrawal rate with a high draw rate at the first drawing end (9.1) and a subsequent hot drawing at the second drawing end (9.2) or a low temperature subsequent drawing at the third drawing end (9.3). Slow and preferably constant polymer cryatallization occurs in the strands. This slow, constant polymer crystallization allows for high toughness with little residual stretching. In this connection, a multistage drawing process makes it possible to produce particularly fine fibers with each denier of 2 dtex or less.

2 schematically shows another embodiment of an apparatus according to the invention for carrying out the manufacturing method of the invention. In the embodiment shown in FIG. 2, the radiator 1 and the drawing device 6 are not shown. This spinning device and the drawing device are the same as in Embodiment 1, and therefore, the above description can be referred to.

In the embodiment shown in FIG. 2, the continuously arranged processing devices for the treatment of the fiber strands are drawn system (7.1-7.4), crimping device (13), drying device (14), tension It is formed as a tanning adjusting device 11 and a cutting device 12. The drawing systems 7.1-7.4 are substantially the same as in Embodiment 1 and differ only in the number of drawing rolls 8 of each drawing system. In order to process the fiber strands, each drawing system (9.1-9.3) is provided with a heated draw channel (10). The treatment of the fiber line in the heated draw channel 10 consists of hot air, preferably in the first and second draw ends 9. 2 and steam in the third draw end 9.3. However, it is also possible to treat hot air and steam in combination at each of the draw stages (9.1-9.3).

Through the embodiment shown in FIG. 2, the production of crimped polypropylene fibers having a toughness of greater than 6 cN / dtex, an elongation of less than 40%, preferably less than 30%, each denier less than 2 dtex It is possible. For this purpose, the fiber strand 5 is crimped by the crimping device 13 after the drawing operation. This crimping device 13 consists mainly of a stuffer box crimping device in which a conveying medium compresses the fiber strands into the stuffer box chamber. After the crimping operation, the fiber strands are transferred to the drying apparatus 14. Thereafter, the tension control device 11 supplies the fiber strands to the cutting device 12 under a defined tension. Usually, a tow combining device and a steaming channel (both not shown) are arranged upstream of the crimping device.

The arrangement of the embodiment of Figs. 1 and 2 of the apparatus of the present invention is exemplary in the number or selection of the processing apparatuses. Basically, additional treatments or treatment stages may be introduced, for example by incorporating a tow to control the fiber feed suitable for crimping. It is likewise possible to provide four or more consecutive draws. What is essential in the apparatus and method of the present invention is to spin at low melting points and at low draw rates and to draw fiber strands at three or more draws, taking into account the high partial draw rate at the first draw stage. In order to successfully carry out the process according to the invention, it is first necessary to give the fiber lines a slightly partially oriented molecular structure after spinning and cooling to obtain uniform and uniform crystals. Basically, however, it is also possible to process other polymers such as polyester or polyamide, for example, with the apparatus of the present invention.

<Description of main parts of drawing>

1 spinning device

2.1-2.3 Radiation Position

3 spinneret

4 cooling system

5 fiber strands

6 drawing device

7.1-7.4 Drawing System

8 drawing roll

9.1-9.3 Drawing

10 heated draw channels

11 tension control device

12 cutting device

13 crimping device

14 drying device

15 spinning beams

It is therefore an object of the present invention to provide a process for producing high toughness polypropylene fibers of the kind described at the outset, in which it is possible to produce particularly fine fibers with individual deniers of 2 dtex or less.

Another object of the present invention is to make an apparatus available for practicing this method.

According to the invention, this object can be achieved by a device having the features of claim 12 as well as by a method having the steps of claim 1.

Advantageous configurations of the present invention are illustrated by the features of each subclaim or by a combination of the features.

A feature of the present invention is, on the one hand, that the low melting point and slow withdrawal rate during spinning aid in the partial molecular orientation of the fibers and consequently the fibers have high toughness. Due to the slow withdrawal speed, significantly smaller internal tensions occur between the polymer chains in the filament in the cooling process after spinning. Considering that the fiber is already drawn at 70% of the total draw at the first draw, drawing at three successive draws allows for constant and slow polymer crystallization in the fiber, resulting in high tenacity. As well as the preparation of fibers with low residual elongation and corresponding fineness.

In order to increase the advantageous properties of the fibers, partial drawing of the fiber strands at the second draw end is done with a higher draw ratio at the subsequent third draw end. Thus, the total draw at the draw end proceeds in a direction in which each draw rate is decreased.

For possible limited partial drawing in the first drawing zone after spinning, after spinning, the fiber strands are drawn by a first drawing system having a plurality of drawing rolls whose outer surface is cooled. The fiber strand is then moved through a heated draw channel in the first draw stage and heated to a temperature above 100 ° C. for drawing.

In order to move as continuously as possible at the drawing end, the fiber strands are continuously tempered to a temperature exceeding 100 ° C. while moving over a plurality of heated drawing rolls after exiting the first drawing end until entering the third drawing end. (temper) For this purpose, the drawing rolls of the drawing system forming the second drawing step are preferably made heatable.

It is also possible to further heat-treat the fiber strands in the second draw stage by means of another heated draw channel. Inside the heated draw channel, the fiber strands can be heated by hot air or steam. It has been found to be particularly advantageous to temper the fiber strands with hot air at the first draw end and with hot steam at the second draw end.

After drawing, the fiber strand is cooled and preferably cooled while running over a plurality of cooled rolls of a fourth drawing system at the end of the third drawing end.

Another configuration of the manufacturing method of the present invention involves crimping the fiber strands after being drawn and before being cut.

It is desirable to extrude the fiber strands through annular or rectangular spinnerts with approximately 60,000 to 120,000 spin holes in order to obtain a possible high yield of 10 t or more per day.

As defined in claim 12, the device for implementing the method of the invention has a high toughness of at least 6 cN / dtex, a low elongation of less than 40% and preferably less than 20%, with a corresponding fineness at each denier. It is characterized in that it is configured and distributed to enable the production of polypropylene fibers. It is desirable to make the drawing roll of the intermediate drawing system heatable so that the fiber strands are uniformly and continuously tempered during drawing. The drawing system at the inlet and outlet of the entire drawing section preferably has a cooled drawing roll.

Hereinafter, with reference to the accompanying drawings, the manufacturing method of the present invention will be described in detail by the embodiment of the device according to the present invention.

Claims (15)

As a method for producing a high toughness polypropylene fiber having a toughness of 6 cN / dtex or more and an elongation of less than 40%, (1.1) melt spinning a plurality of fiber strands from a polypropylene melt having a melting point of 250 ° C. or less, (1.2) drawing the fiber strands at a draw rate of less than 100 m / min and cooling the fiber strands with a gaseous cooling medium; (1.3) drawing the fiber strands in at least three draw stages with a partial pull rate of at least 70% of the total draw in the first draw stage, with an overall draw rate greater than 4: 1; and (1.4) A method for producing high toughness polypropylene fibers, comprising cutting the fiber strands into polypropylene fibers of defined fiber length. The method of claim 1 wherein the partial draw at the second draw end of the fiber strand is higher than the partial draw at the third draw end. 3. A method according to claim 1 or 2, wherein after the melt spinning the fiber strands are drawn by a first drawing system having a plurality of drawing rolls each having a cooled outer surface. The method of claim 1, wherein the fiber strand is heated to a temperature above 100 ° C. while passing through the first draw through a heated draw channel. 4. The fiber strand according to any one of claims 1 to 3, wherein the fibrous strand is at a temperature in excess of 100 DEG C while moving over a plurality of heated draw rolls after exiting the first draw stage until entering the third draw stage. Method for producing a polypropylene fiber, characterized in that tempering. 5. The method of claim 4, wherein the draw roll of the draw system forming the second draw end has a surface heated to a temperature in excess of 100 &lt; 0 &gt; C. The method according to any one of the preceding claims, wherein the fiber strands in the second draw stage move through the heated draw channel and are heated in the draw channel. 8. Process according to claim 3 or 7, wherein the fiber strands are heated with hot air and / or hot steam while traveling through the heated draw channel. The method of claim 1, wherein after drawing, the fiber strand is cooled while moving to temper over a plurality of cooled drawing rolls of a fourth drawing system at the end of the third drawing end. The manufacturing method of the polypropylene fiber made into. 10. The method of any of claims 1 to 9, wherein the fiber strands are crimped after being drawn and before being cut. The method according to any one of the preceding claims, wherein the fiber strands are extruded through an annular spinneret having a plurality of spinning holes of 60,000 to 120,000. Spinner 1 for melt spinning the fiber strands 5, a plurality of processing devices 6, 7, 10, 11 for moving and processing the fiber strands 5, and cutting the fiber strands 5 Has a cutting device (12), said processing device (6, 7, 10, 11) has a plurality of drawing systems (7.1-7.4) having a plurality of drawing rolls (8) for drawing the fiber strands (5) An apparatus for performing a method according to any one of claims 1 to 11, comprising: The drawing systems (7.1-7.4) are arranged to form a total of three drawing ends (9.1-9.3), and enable the drawing rolls (8) of the drawing system (7.1-7.4) to be driven relative to each other. 9.1) an apparatus for producing polypropylene fibers, characterized in that it is at least 70% of the total drawing at a controlled rate between the drawing systems (7.1, 7.2) forming it. 13. Apparatus according to claim 12, characterized in that the drawing roll (8) forming the second drawing end (9.2) is heatable. Apparatus according to claim 12 or 13, characterized in that the drawing roll (8) of the first drawing system (7.1) is installed for cooling upstream of the first drawing end. Device according to one of the claims 12 to 14, characterized in that the drawing roll (8) of the last drawing system (7.4) is installed for cooling downstream of the third drawing end (9.3).