AU768703B2

AU768703B2 - Method for producing a twisted thread for technical fabric and paper machine fabric

Info

Publication number: AU768703B2
Application number: AU52168/00A
Authority: AU
Inventors: Dieter Brokmeier; Jurgen Budenbender
Original assignee: Bayer Faser GmbH
Current assignee: Asahi Kasei Spandex Europe GmbH
Priority date: 1999-06-07
Filing date: 2000-05-26
Publication date: 2004-01-08
Anticipated expiration: 2020-05-26
Also published as: WO2000075407A1; BR0011366A; TW487746B; PL352277A1; AU5216800A; EP1190128A1; JP2003501561A

Description

WO 00/75407 PCT/EP00/04805 -1- Process for the production of a yarn for industrial fabric and paper machine fabric The invention relates to industrial fabric, especially improved paper machine fabric, based on a yam of synthetic polymers, and to a process for the production of a yarn for industrial fabric.

The process of producing paper is known in principle to the person skilled in the art.

In order to produce paper from suitable mixtures of cellulose fibres, pigments and chemical additives, a dispersion of the mixture in water is applied to a fabric of metal or synthetic wires and the liquid is removed by means of gravity and/or by suction until a self-supporting moist paper "sheet" has formed.

In order further to remove the liquid until the desired residual amount is reached, the sheet is subsequently transported through the so-called pressing section and drying section of the paper machine.

In the pressing section, the paper sheet, which is still very moist and is sensitive to mechanical processing, is placed on a so-called paper machine felt (PMF) and guided, together with the felt, through rollers which press against each other. At the point of contact of the rollers, the "nip", the paper sheet, together with the paper machine felt, is compressed and further water is squeezed out of the paper sheet.

Finally, in the drying section which then follows, the remaining liquid still present is removed from the sheet, which has solidified further, by evaporation under the action of heat, until the desired content of liquid in the paper is achieved.

The paper machine felt used in the pressing section to squeeze out the liquid generally consists of polyamide fibres and polyamide monofilaments, which are brought together by known processes to form "felts" of the desired structure and are usually needled with one another. Typical felts consist of a base fabric of polyamide WO 00/75407 PCT/EP00/04805 -2monofilaments, which is joined on one side or on both sides to a needle-punched nonwoven ofpolyamide staple fibres.

The base fabric is a single-layer or multi-layer fabric of polyamide monofilaments, the monofilaments being processed to fabrics by processes which are known in principle. The monofilaments themselves usually have a diameter of from 0.08 mm to 0.60 mm, in rare cases up to 1.20 mm.

While the thicker monofilaments having diameters of from 0.25 to 0.60 mm are generally processed in the form of single monofilaments, manufacturers of paper machine felts use the finer monofilaments of from 0.08 mm to 0.25 mm predominantly in the form of yams.

These yams consist of from 3 to 40 monofilaments and are produced in two stages.

In the first stage, a so-called preliminary yam is produced on conventional twisting machines, in which preliminary yam from two to eight monofilaments, preferably two or three monofilaments, are twisted together in one direction, for example the S direction, with from 150 to 400 revolutions per metre. This preliminary yam is unstable owing to its strong tendency to twist and cannot be processed to form a fabric.

In order to eliminate the tendency to twist, there is produced from the preliminary yam, in a second processing step, a final yam in which from two to five preliminary yars are twisted together in the opposite direction in the Z direction in the example given above. In order to produce a "stabilised" yam, that is to say a yar without a tendency to twist, the number of revolutions of the final yam is less than the number of revolutions of the preliminary yam. Typically, the preliminary yam has from 200 to 350 revolutions per metre (in the S direction, for example) and the final yam, by contrast, has from 150 to 250 revolutions per metre (in the Z direction).

WO 00/75407 PCT/EP00/04805 -3- The yam produced in two stages is stabilised against twisting and can therefore be processed without great difficulty. However, some problems that arise during further processing to fabrics cannot be solved or eliminated completely with the mentioned yams and require further complex processing steps.

For example, the differences in twist within a yam or from yam spool to yam spool, which occur for technical reasons and arise during production of the yam, cause differences in tension and variations in shrinkage in the fabric after weaving, which must be eliminated by complex subsequent heat setting processes or can only be lessened under higher fabric tension. The variations may in some cases be so great that the fabrics remain uneven after heat setting and are no longer usable for the intended purpose.

Surprisingly, it has now been found that the disadvantages of the known fabric producing processes can be eliminated if there are used for producing paper machine felts, instead of the known yams produced in two stages, yams that have been produced in one stage, that is to say twisted in only one twist direction the S or Z direction). In order to eliminate the tendency of the yams to twist, the yams according to the invention are heat set, after the preliminary twisting process, in a heat setting apparatus, which operates continuously, at temperatures of from 70'C to 240"C, under a definite tension, and the yams so treated are processed further to industrial fabric, especially for paper machine felts.

The invention provides a process for the production of a yam for industrial fabric, especially for paper machine coverings and fabric, characterised in that a yam, twisted in one twist direction (S or Z direction), of monofilaments of synthetic polymer, especially of polyamide, having a diameter of the monofilaments of from 0.06 mm to 0.60 mm, preferably from 0.08 mm to 0.25 mm, is heat set at a temperature of from 70C to 240 0 C in order to stabilise it against twisting.

WO 00/75407 PCT/EP00/04805 -4- The monofilaments consist especially of the class of the polyamides, especially selected from the group polyamide 6, polyamide 6.6, polyamide 6.9, polyamide 6.10, polyamide 6.12, polyamide 11, polyamide 12, or mixtures of the mentioned polyamides, or copolyamides of the starting monomers of those polyamides.

Heat transfer to the monofilaments during the heat setting is effected by a heating medium, especially hot air, water or steam, or by the action of heat radiation.

The heat setting may be carried out either in a stationary manner or continuously.

In particular, the heat setting is carried out continuously between two delivery arrangements each having at least two rollers having different speeds of rotation of the delivery arrangements, the speed of rotation of the first pair of rollers especially being higher than that of the second pair of rollers, and delivery to the first delivery arrangement of the heat setting being carried out under slight tension, especially from 50 to 200 g.

The heat setting preferably takes place over a period of from 0.5 second to 20 minutes, especially from 1 second to 15 minutes.

The invention also provides yam of monofilaments of synthetic polymers, obtainable by the process according to the invention.

The invention also provides industrial fabric, especially paper machine fabric for pressing felts, containing the yams according to the invention.

In a preferred industrial fabric, the warp and/or the weft of the fabric is produced from yam according to the invention.

WO 00/75407 PCT/EP00/04805 The medium used for transporting the heat energy for the heat setting is either air or water, which may be liquid or in the form of steam. The pressure of the surrounding medium may be from 1 to 5 bar, preferably from 1 to 3 bar. The duration of the action of heat is connected with the absolute level of the temperature of the medium and may be from 2 seconds to 20 minutes.

Figure 1 shows the process sequence in principle.

The process according to the invention has a number of advantages in comparison with the processes known hitherto.

After heat setting, the yams have a precisely defined shrinkage, which can be adjusted exactly to the demands of the further processing. As a result, uniform industrial fabrics can be produced, which do not require such intensive afterprocessing and whose reject rate is lower.

The industrial fabrics obtainable from the yarns according to the invention have a width and length which can better be controlled, because the differences in shrinkage of the yams are practically eliminated and the processor does not have to overcompensate for the irregularities of the fabric by a higher heat setting temperature.

Because the yarns are heat set before weaving, the industrial fabrics obtainable from the yarns according to the invention are more flexible, that is to say softer and easier to process in the subsequent processing steps, especially by the paper makers on introduction into the paper machine.

The fabrics have a more even surface, as a result of which marking of the paper machine felt in the paper is reduced.

WO 00/75407 PCT/EP00/04805 The advantage of the process according to the invention as regards its lower energy consumption and its simplicity should not be ignored either.

While the process for producing the final yarn must be carried out very slowly and with high energy consumption by the twisting machines, heat setting requires only a fraction of the energy necessary for twisting.

Further preferred embodiments of the invention, unless mentioned above, will be found in the dependent claims.

The invention is explained in greater detail with reference to Figure 1.

Figure 1 shows a process diagram for illustrating the process according to the invention.

The examples which follow serve to illustrate the invention in greater detail without limiting it. Unless indicated otherwise, percentage data relate to weight.

WO 00/75407 PCT/EP00/04805 -7- Examples Example 1: Four commercial monofilaments of polyamide 6, type X 201, diameter 0.20 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempten, to a yam having 260 revolutions per metre.

The yarn has a pronounced twist in the relaxed state and can be oriented in one direction only if placed under tension.

The yarn so produced is stabilised against twisting in a suitable heat setting device which operates continuously. To that end, the yarn 5 is guided, under slight tension (from 100 to 120 from the yarn spool 1, via a delivery device 2 consisting of five rollers (delivery device through an aqueous heat setting bath 3 having a length of 3 m and a temperature of 96°C, and is discharged by a discharge device likewise having five rollers (delivery device guided via a suction device (not shown) for removing the water that is present on the yam, and wound onto flanged spools in a winding device 4. The discharge speed of the delivery device 2 is 50 m/minute, that of the delivery device 6 is 45.5 m/minute.

Determination of shrinkage under boiling The heat set yam has no twist in the relaxed state. In order to determine the shrinkage under boiling, the yam was first conditioned for two days at 20 0 C and 65% relative humidity. After marking the length, the samples were placed, without tension, in boiling water under atmospheric pressure for five minutes and then conditioned again for 48 hours at 20 0 C and 65 relative humidity. The shortening of the yam is 3.0 based on the original length of the already set yarn.

WO 00/75407 PCT/EP00/04805 -8- The resulting shrinkage can be adjusted to any value desired for the further processing to industrial fabric of from 0 to 15 by the level of the setting temperature of the heating air, by the residence time in the heat setting medium and by the relative speed of the discharge device in comparison with the delivery device during setting.

Example 2: Six commercial monofilaments of polyamide 6, type X 201, diameter 0.20 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempten, to a yam having 240 revolutions per metre.

The yam has a pronounced twist in the relaxed state and carL be oriented in one direction only if placed under tension.

The yam so produced is stabilised against twisting in a suitable heat setting device which operates continuously. To that end, the yam is guided, under slight tension (from 100 to 120 from the yam spool, via a delivery device consisting of five rollers (delivery device through an aqueous heat setting bath 3 having a length of 3 m and a temperature of 96'C, and is discharged by a discharge device likewise having five rollers (delivery device guided via a suction device for removing the water that is present on the yam, and wound onto flanged spools in a winding device 4. The discharge speed of the delivery device 2 is 50 m/minute, that of the delivery device 6 is 45.5 m/minute.

The heat set yam has no twist in the relaxed state. The shrinkage is 3.5 determined by the method described in Example 1.

WO 00/75407 PCT/EP00/04805 -9- Example 3: 32 commercial monofilaments of polyamide 6, type X 201, diameter 0.10 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempten, to a yam having 220 revolutions per metre.

The yam has a pronounced twist in the relaxed state and can be oriented in one direction only if placed under tension.

The yam so produced is stabilised against twisting in a suitable heat setting device which operates continuously. To that end, the yarn is guided, under slight tension (from 100 to 120 from the yar spool, via a delivery device consisting of five rollers (delivery device through an aqueous heat setting bath 3 having a length of 3 m and a temperature of 96 0 C, and is discharged by a discharge device likewise having five rollers (delivery device guided via a suction device for removing the water that is present on the yam, and wound onto flanged spools in a winding device 4. The discharge speed of the delivery device 2 is 50 m/minute, that of the delivery device 6 is 45.5 m/minute.

The heat set yam has no twist in the relaxed state. The shrinkage is 2.7 determined by the method described in Example 1.

Example 4: Four commercial monofilaments of polyamide 6, type X 201, diameter 0.20 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempten, to a yam having 260 revolutions per metre.

WO 00/75407 PCT/EP00/04805 The yam so produced is stabilised against twisting in a suitable heat setting device which operates continuously. To that end, the yam is guided, under slight tension (from 100 to 120 from the yam spool, via a delivery device consisting of five rollers (delivery device through a hot-air oven having a length of 6 m and a temperature of 180°C, and is discharged by a discharge device likewise having five rollers (delivery device 6) and wound onto flanged spools in a winding device 4. The discharge speed of the delivery device 2 is 50 m/minute, that of the delivery device 6 is 45.5 m/minute.

The heat set yam has no twist in the relaxed state. The shrinkage is 3.8 determined by the method described in Example 1.

Example Six commercial monofilaments of polyamide 6, type X 201, diameter 0.20 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempten, to a yamrn having 240 revolutions per metre.

The yam so produced is stabilised against twisting in a suitable heat setting device which operates continuously. To that end, the yam is guided, under slight tension (from 100 to 120 from the yam spool, via a delivery device consisting of five rollers (delivery device through an aqueous heat setting bath 3 having a length of 3 m and a temperature of 96°C, and is discharged by a discharge device likewise having five rollers (delivery device guided via a suction device for removing the water that is present on the yam, and wound onto flanged spools in a winding device 4. The discharge speed of the delivery device 2 is 50 m/minute, that of the delivery device 6 is 45.5 m/minute.

WO 00/75407 PCT/EP00/04805 11 The heat set yam has no twist in the relaxed state. The shrinkage is 4.1 determined by the method described in Example 1.

Example 6: Four commercial monofilaments of polyamide 6, type X 201, diameter 0.20 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempten, to a yam having 260 revolutions per metre.

The yam so produced is stabilised against twisting in a suitable heat setting device which operates continuously. To that end, the yam is guided, under slight tension (from 100 to 120 from the yam spool, via a delivery device consisting of five rollers (delivery device through a heat setting oven having a steam atmosphere of 100 0 C, and is discharged by a discharge device likewise having five rollers (delivery device guided via a suction device for removing the water that is present on the yam, and wound onto flanged spools in a winding device 4. The discharge speed of the delivery device 2 is 50 m/minute, that of the delivery device 6 is 45.5 m/minute.

The heat set yam has no twist in the relaxed state. The shrinkage is 3.1 determined by the method described in Example 1.

Example 7: Four commercial monofilaments of polyamide 6, type X 201, diameter 0.20 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempten, to a yarn having 260 revolutions per metre.

WO 00/75407 PCT/EP00/04805 -12- The yam so produced is stabilised against twisting in a suitable heat setting device which operates continuously. To that end, the yam is guided, under slight tension (from 100 to 120 from the yam spool, via a delivery device consisting of five rollers (delivery device through a heat setting oven having a steam atmosphere of 100*C, and is discharged by a discharge device likewise having five rollers (delivery device guided via a suction device for removing the water that is present on the yam, and wound onto flanged spools in a winding device 4. The discharge speed of the delivery device 2 is 50 m/minute, that of the delivery device 6 is 50 m/minute.

The heat set yam has no twist in the relaxed state. The shrinkage is 8.5 determined by the method described in Example 1.

Example 8: Four commercial monofilaments of polyamide 6, type X 201, diameter 0.20 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempten, to a yarn having 260 revolutions per metre.

The yam so produced is stabilised against twisting in a suitable heat setting device which operates continuously. To that end, the yam is guided, under slight tension (from 100 to 120 from the yarn spool, via a delivery device consisting of five rollers (delivery device through a heat setting oven having a steam atmosphere of 100 0 C, and is discharged by a discharge device likewise having five rollers (delivery device guided via a suction device for removing the water that is present on the yam, and wound onto flanged spools in a winding device 4. The discharge speed of the delivery device 2 is 50 m/minute, that of the delivery device 6 is 42 m/minute.

WO 00/75407 PCT/EP00/04805 -13- The heat set yam has no twist in the relaxed state. The shrinkage is 1.5 determined by the method described in Example 1.

Example 9: Four commercial monofilaments of polyamide 6.6, type ATF 2366, diameter 0.20 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempten, to a yam having 260 revolutions per metre. The yam has a pronounced twist in the relaxed state and can be oriented in one direction only if placed under tension.

The heat set yam has no twist in the relaxed state. The shrinkage is 4.2 determined by the method described in Example 1.

Example Four commercial monofilaments of polyamide 6.10, type ATF 2311, diameter 0.20 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempten, to a yam having 260 revolutions per metre. The yam has a pronounced twist in the relaxed state and can be oriented in one direction only if placed under tension.

WO 00/75407 PCT/EPOO/04805 -14- The yam so produced is stabilised against twisting in a suitable heat setting device which operates continuously. To that end, the yarn is guided, under slight tension (from 100 to 120 from the yam spool, via a delivery device consisting of five rollers (delivery device through a heat setting oven having a steam atmosphere of 100°C, and is discharged by a discharge device likewise having five rollers (delivery device guided via a suction device for removing the water that is present on the yam, and wound onto flanged spools in a winding device 4. The discharge speed of the delivery device 2 is 50 m/minute, that of the delivery device 6 is 45.5 m/minute.

The heat set yam has no twist in the relaxed state. The shrinkage is 2.8 determined by the method described in Example 1.

Example 11: Four commercial monofilaments of copolyamide 6/6.6, type X 130, diameter 0.20 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempten, to a yam having 260 revolutions per metre.

The yam so produced is stabilised against twisting in a suitable heat setting device which operates continuously. To that end, the yam is guided, under slight tension (from 100 to 120 from the yam spool, via a delivery device consisting of five rollers (delivery device through a heat setting oven having a steam atmosphere of 100°C, and is discharged by a discharge device likewise having five rollers (delivery device guided via a suction device for removing the water that is present on the yam, and wound onto flanged spools in a winding device 4. The discharge speed of the delivery device 2 is 50 m/minute, that of the delivery device 6 is 45.5 m/minute.

WO 00/75407 PCT/EP00/04805 The heat set yam has no twist in the relaxed state. The shrinkage is 3.6 determined by the method described in Example 1.

Comparison Example Four commercial monofilaments of polyamide 6, X 201, diameter 0.20 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempen, in a two-stage process to a yam having the structure 0.20 mm x 2 x 2, 300 S-twists/220 Z-twists. This means that two monofilaments are first twisted according to known processes to form a "preliminary yam" having the structure 0.20 x 2 with 300 S-twists per metre. The preliminary yam has a pronounced tendency to twist and cannot be straightened out without being placed under tension.

In the second stage, two preliminary yam spools are processed on the same twisting machine, by a process which is likewise known, to form the "final yam" having 220 S-twists.

The yam of four monofilaments so produced exhibits no tendency to twist at all and can be straightened out in the untensioned state without difficulty.

In order to determine the shrinkage, the yam is first conditioned for two days at 0 C and 65 relative humidity. After marking the length, the samples are placed in boiling water under atmospheric pressure for five minutes and then conditioned again for 48 hours at 20 0 C and 65 relative humidity. The shortening is 9.9 based on the original length.

WO 00/75407 PCT/EPOO/04805 -16- Example 12: In a manner known per se, fabrics are produced in a 1/3 twill weave from singletwist yarns according to Example 1 and conventionally prepared yarns according to the above-mentioned Comparison Example.

The warp contains nine twist threads per centimetre, the weft contains ten threads per centimetre. Both fabrics have a fault-free surface.

In order to test the dimensional stability of the fabric, one square meter of the fabric in question is clamped weftwise at the opposing edges of the fabric in a steel frame between two metal plates and is exposed to a temperature of 160°C for 10 minutes in a hot-air oven.

The fabric produced from the comparison yams has shrunk by 6 in the warp direction and is markedly uneven.

The fabric produced from the yams according to the invention, by contrast, has shrunk by only 0.5 and remains completely smooth.

Example 13: Four commercial monofilaments of polyamide 6, type X 201, diameter 0.20 mm (manufactured by Bayer Faser GmbH), are processed on an AZB-T 200 twisting machine from Allma-Saurer, Kempten, to a yam having 260 revolutions per metre.

The yam so produced is stabilised against twisting in a suitable heat setting device which operates continuously. To that end, the yam is guided, under slight tension IF f -17- (from 100 to 120 from the yarn spool, via a delivery device consisting of-five rollers (delivery device through a heat setting oven (length 2 m) having a steam atmosphere of 100°C, and is discharged by a discharge device likewise having five rollers (delivery device guided via a suction device for removing the water that is present on the yam, and wound onto flanged spools in a winding device 4. The discharge speed of the delivery device 2 is 100 m/minute, that of the delivery device 6 is 100 m/minute.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art in this specification is not, and should not be taken as, S. an acknowledgment or any form of suggestion that the prior art forms part of the common general knowledge in Australia.

••oo

Claims

1. Process for the production of a yar for industrial fabric, especially for paper machine coverings and fabric, characterised in that a yam, twisted in one direction (S or Z direction), of monofilaments of synthetic polymer, especially of polyamide, having a diameter of the monofilaments of from 0.06 mm to 0.60 mm, preferably form 0.08 mm to 0.25 mm, is heat set at a temperature of from 70°C to 240°C in order to stabilise it against twisting, wherein the heat setting is carried out continuously between two delivery arrangements having at least two rollers having different speeds of rotation of the delivery arrangements, the speed of rotation of the first pair of rollers especially being higher than that of the second pair of rollers, and delivery to the first delivery arrangement of the heat setting being carried out under slight tension.

2. Process according to claim 1, characterised in that the monofilaments consist of the class of the polyamides, preferably selected from the group polyamide polyamide 6.6, polyamide 6.9, polyamide 6.10, polyamide 6.12, polyamide 11, polyamide 12, or mixtures of the mentioned polyamides, or copolyamides of the starting monomers of those polyamides.

3. Process according to claim 1 or 2, characterised in that the transfer of heat to the monofilaments during the heat setting is effected by a heating medium, especially hot air, water or steam, or by the action of heat radiation.

4. Process according to any one of claims 1 to 3, characterised in that the heat setting is carried out in a stationary manner or continuously.

5. Process according to any one of claims 1 to 4, characterised in that the tension is from 50 to 200g. -19-

6. Process according to any one of claims 1 to 5, characterised in that the-heat setting is carried out under a pressure of from 1 to 5 bar, preferably from 1 to 3 bar.

7. Process according to any one of claims 1 to 6, characterised in that the heat setting is carried out over a period of from 0.5 second to 20 minutes, preferably from 1 second to 15 minutes.

8. Yam of monofilaments of synthetic polymers, obtainable by a process according to any one of claims 1 to 7.

9. Industrial fabric, especially paper machine fabric for pressing felts, containing yarns according to claim 8.

10. Industrial fabric according to claim 9, characterised in that the warp of the fabric consists of yars according to claim 8.

11. Industrial fabric according to claim 9, characterised in that the weft of the fabric consists of yarns according to claim 8.

12. Process for the production of a yar for industrial fabric substantially as hereinbefore described with reference to the examples. DATED THIS 21st day of October, 2003. BAYER FASER GMBH By Its Patent Attorneys DAVIES COLLISON CAVE