DE19902257A1 - Fourdrinier for a papermaking machine has wefts of melt spun monofilaments with structured polyamide blends to give a fourdrinier with high abrasion resistance and a low water absorbency and a reduced edge curling tendency - Google Patents

Abstract

The fourdrinier for a papermaking machine is composed of synthetic monofilaments, where at least part of the wefts are melt spun monofilaments in a mixture of polyamide (PA) 6 or PA 66 with PA 69, PA 610, PA 612, PA 11, PA 12 or hydrophobic copolyamides with a melting point of at least 150 deg C. The material has a ratio of the methylene units to the amide groups of at least 6.5 per mol. At least part of the wefts are monofilaments composed of 30-95 wt% PA 6 and 70-5 wt% PA 69, or 30-95 wt% PA 6 and 70-5 wt% PA 610, 30-95 wt% PA 6 and 70-5 wt% PA 612, or 30-95 wt% PA 6 and 70-5 wt% PA 11, or 30-95 wt% PA 6 and 70-5 wt% PA 12, or 30-95 wt% PA 6 and 70-5 wt% of a hydrophobic copolyamide with a melting point of at least 150 deg C and a ratio of methylene units to amide groups of at least 6.5 per mol., or 30-95 wt% PA 66 and 70-5 wt% PA 69, or 30-95 wt% PA 66 and 70-5 wt% PA 610, or 30-95 wt% PA 66 and 70-5 wt% PA 612, or 30-95 wt% PA 66 and 70-5 wt% PA 11, or 30-95 wt% PA 66 and 70-5 wt% PA 12, or 30-95 wt% PA 66 and 70-5 wt% of a hydrophobic copolyamide with a melting point of at least 150 deg C and a ratio of methylene units to amide groups of at least 6.5 per mol. The proportion of monofilaments with a polyamide blend in the lower wefts can be 10-100%. The warps are of polyester (polyethyleneterephthalate).

Description

The invention relates to formation sieves for the Papierher position made of synthetic monofilaments.

A continuous paper web is produced in paper machines sets by dispersing cellulose fibers in water running sieve belt are brought. This also as a forma The sieve belt designated as tion sieve dewaters the cellulose fiber dispersion so far that it has a certain cohesion owns and continues to press and dry part of the paper machine can be transported. The Formation screens are mainly made of polyester monofi laments made because of a good dimensional stability of the sieve can be guaranteed.

To ensure the best possible drainage of the fiber dispersion the formation sieve usually runs over so-called Foils and vacuum suction boxes that drain water through the strainer Suck the dispersion. These vacuum suction boxes lead to the Underside of screen (running side) for massive abrasion. For this  The reason for formation sieves in deficit (shot filaments on the running side of the sieve) partly polyamide 6 (PA 6) or polyamide 66 (PA 66) monofilament woven, because this a far better abrasion resistance than Possess polyester monofilaments. The high water absorption of PA 6 or PA 66 also leads to problems such as wise for the deformation of the sieve fabric with changes in moisture, what z. B. by raising the edges of the screen fabric can express (edge curling). This superscript is extreme disadvantageous because it is the maximum achievable path width of the paper machine and on the other hand the current ones properties of the formation sieve negatively affected.

Various variants have been proposed to overcome this problem suggested. In EP-A-0 387 395 as an alternative to PA 6 and PA 66 monofilaments made of polyester / polyurethane blends suggested. The abrasion resistance of seven which a corresponding proportion of PA 6 or PA 66 monofilaments included, but cannot be achieved in this way. Therefore, in this patent application, the invention stressed monofilaments made of PES / PUR for all wefts monofilaments used in the formation sieve. This formation sieves are then made with polyamide monofilaments Formation sieves compared, in which differ in the deficit PES and PA 66 monofilaments were woven in.

Also the use of polyamides with less water like polyamide 69 (PA 69, polyamide 610 (PA 610) and Polyamide 612 (PA 612) has been tested, but also here Reduced abrasion resistance become.

The use of polyamide 11 (PA 11) and polyamide 12 (PA 12) enables the prevention of the edge curling effect and gives excellent abrasion resistance, the deep Melting point of these polyamides of 187 and 179 ° C allowed not the fixing pe necessary for polyester monofilaments  temperatures of over 170 ° C. Such constructions are therefore only suitable to a limited extent.

The task has now been solved by using monofilaments made of polya mid blends were used, with the following combinations possible are: PA 6 / PA 69, PA 66 / PA 69, PA 6 / PA 610, PA 66 / PA 610, PA 6 / PA 612, PA 66 / PA 612, PA 6 / PA 11, PA 66 / PA 11, PA 6 / PA 12, PA 66 / PA 12. The proportion of PA 6 or PA 66 in the blend should be at least 30% by weight and a maximum of 95% by weight.

Monofilaments made of polyamide blends are, for example, in DE 36 01 565 describes, here small amounts of PA 6 to PA 66 are added to round void-free monofilaments for To be able to produce spiral sieves. In the GDR patent 76 767 are monofilaments made of PA 6 / PA 610 blends for bristles described, the aim of which is that of such Bristles made of monofilaments are slotted as much as possible (slightly splicing).

Surprisingly, it has now been shown that formation sieves, the Monofilaments from the PA blends PA 6 / PA 69, PA 66 / PA 69, PA 6 / PA 610, PA 66 / PA 610, PA 6 / PA 612, PA 66 / PA 612, PA 6 / PA 11, PA 66 / PA 11, PA 6 / PA 12, PA 66 / PA 12, PA 6 / hydrophobic copoly amide with a melting point of at least 150 ° C and a Ratio of methylene units to amide groups per molecule of at least 6.5 or PA 66 / hydrophobic copolyamide with a Melting point of at least 150 ° C and a ratio of Methylene units to amide groups per molecule of at least 6.5, included, regarding conventional abrasion resistance Formation sieves containing PA 6 or PA 66 monofilaments are equal (with the same proportion of polyamide monofilaments the same construction), the edge curling effect can however, be significantly reduced.

This improvement is both when using the monofilaments to achieve 100% deficit from the above-mentioned PA blends as if only part of the deficit from above  mentioned monofilaments (which is more common in practice the case is). The abrasion resistance is of course all the more be higher, the greater the proportion of the above monofilament is in deficit.

The copolyamides mentioned above should not be more hydrophilic than PA 69. Since the hydrophilicity essentially depends on the amide group concentration in the polymer molecule, it can be very well defined by the ratio of methylene units (CH ₂ units) / amide groups. The larger this ratio, the more hydrophobic the polyamide will be. The value for PA 69 is 6.5 (6 + 7 CH ₂ units and 2 amide groups per basic unit, ie (6 + 7) / 2 = 6.5). In the case of co polyamides which can be used according to the invention, this value should be at least 6.5.

Abrasion tests

The abrasion tests were carried out after the Schödel abrasion test Formation sieves (monofilament fabrics) carried out. The one there used device is exhibited in the TH Darmstadt and is in the essay "Practical abrasion tests on paper machines nenbespannungen "in the magazine" Das Papier ", October 1964 described.

In this test, the sieve runs at 1000 m / min and one sieve tension of 6 kN / m on four vacuum cups (vacuum 2 m water column) in an aqueous calcium carbonate dispersion (conc. 4 g / l; Type Millicarb 45 OG from Omya; Inlet 500 l / h). To The remaining thickness of the sieve is measured 20,000 cycles and used to assess abrasion (mean in each case from two measurements).

Assessment edge curling

To assess the edge curling effect, patterns with a size of 270 mm × 190 mm (length in warp direction × length in weft direction) were cut out of the respective formation sieves and treated as follows:

• A) Storage of the samples at 23 ° C; 50% rel. Humidity for at least 3 days.
• B) Subsequent storage of the samples at 23 ° C in deminerali water for at least 3 days.
• C) Drying these samples at 100 ° C in a convection oven and on closing storage at 23 ° C; 50% rel. Humidity for at least 3 days.
• D) Repeated storage of the samples at 23 ° C in the demineralizer tem water for at least 3 days.

After each step, the shape change is done as follows measure: the sieve pattern is placed on a flat table and at each corner, the distance of the corner becomes perpendicular to the table plate measured. Bend the corners to the barrel side of the Siebes, so the values with a negative sign provided, the corners bend to the paper side of the screen (Sieve top), the values with a positive Sign. The sum of these four values is for the Deformation assessment used.

The smaller the amount of this sum, the less that is Edge curling.

Table 1 below shows the measurements according to individual steps only with A, B, C and D.

Examples

All screens were made with the same construction:
double layer fabric with
Chain: 60.0 / cm 0.17 mm diameter polyester (polyethylene terephthalate) and
Weft: 23.5 / cm 0.20 mm diameter above 23.5 / cm 0.24 mm diameter below (interchangeable weft polyethylene terephthalate, test material)

example 1 (Comparative example)

A formation screen was made according to the above construction represents, in the weft below polyethylene terephthalate monofila elements were used 100%.

The results regarding abrasion resistance and edge curling are shown in Table 1.

Example 2 (Comparative example)

A formation screen was made according to the above construction represents, in the weft below polyethylene terephthalate monofila elements in alternating weft with PA 6 monofilaments were used (50% each).

The results regarding abrasion resistance and edge curling are shown in Table 1.

Example 3 (Comparative example)

A formation screen was made according to the above construction represents, in the weft below polyethylene terephthalate monofila elements used alternately with PA 610 monofilaments were (50% each).

The results regarding abrasion resistance and edge curling are shown in Table 1.

Example 4

A formation screen was made according to the above construction represents, in the weft below polyethylene terephthalate monofila elements in alternating weft with monofilaments, consisting of a Mixture of 50% PA 6 and 50% PA 610 were used (50% each).

The PA 6 / PA 610 monofilament was manufactured as follows:
50% by weight of PA 6 granules and PA 610 granules are mixed together and melted in an extruder at 290 ° C. and extruded into a water bath using a 40-hole nozzle. The spun material is drawn continuously from this spinning bath in a ratio of 1: 4.2, fixed in a hot air oven and then wound up in a tension-controlled manner.

The results regarding abrasion resistance and edge curling are shown in Table 1.

Example 5

A formation screen was made according to the above construction represents, in the weft below polyethylene terephthalate monofila elements in alternating weft with monofilaments, consisting of a Mixture of 35% PA 6 and 65% PA 610 were used (50% each).

The PA 6 / PA 610 monofilament was manufactured as follows:
35% by weight of PA 6 granules and 65% by weight of PA 610 granules are mixed together and melted in an extruder at 290 ° C. and extruded into a water bath using a 40-hole nozzle. The spun material is drawn continuously from this spinning bath in a ratio of 1: 4.2, fixed in a hot air oven and then wound up in a tension-controlled manner.

The results regarding abrasion resistance and edge curling are shown in Table 1.

Example 6

A formation screen was made according to the above construction represents, in the weft below polyethylene terephthalate monofila elements in alternating weft with monofilaments, consisting of a Mixture of 65% PA 6 and 35% PA 610 were used (50% each).

The PA 6 / PA 610 monofilament was manufactured as follows:
65% by weight of PA 6 granules and 35% by weight of PA 610 granules are mixed together and melted in an extruder at 290 ° C. and extruded into a water bath using a 40-hole nozzle. The spun material is drawn continuously from this spinning bath in a ratio of 1: 4.2, fixed in a hot air oven and then wound up in a tension-controlled manner.

The results regarding abrasion resistance and edge curling are shown in Table 1.

Example 7

A formation screen was made according to the above construction represents, in the weft below polyethylene terephthalate monofila elements in alternating weft with monofilaments, consisting of a Mixture of 50% PA 66 and 50% PA 610 were used (50% each).

The PA 66 / PA 610 monofilament was made as follows represents: 50% by weight of PA 66 granules and 50% by weight of PA 610 granules are mixed together and in an extruder at 295 ° C melted and with a 40 hole nozzle in a water bath extruded. The spinning material is continuously from this Spin bath drawn in a ratio of 1: 4.3, stretched in Hot air oven fixed and then voltage controlled spooled.

The results regarding abrasion resistance and edge curling are shown in Table 1.

Example 8

A formation screen was made according to the above construction represents, in the weft below polyethylene terephthalate monofila elements in alternating weft with monofilaments, consisting of a Mixture of 50% PA 6 and 50% PA 612 were used (50% each).

The PA 6 / PA 612 monofilament was manufactured as follows:
50% by weight of PA 6 granules and 50% by weight of PA 612 granules are mixed together and melted in an extruder at 290 ° C. and extruded into a water bath using a 40-hole nozzle. The spun material is drawn continuously from this spinning bath in a ratio of 1: 4.2, fixed in a hot air oven and then wound up in a tension-controlled manner. The results regarding abrasion resistance and edge curling are shown in Table 1.

Example 9

A formation screen was made according to the above construction represents, in the weft below polyethylene terephthalate monofila elements in alternating weft with monofilaments, consisting of a Mixture of 50% PA 6 and 50% PA 12 were used (each 50%).

The PA 6 / PA 12 monofilament was manufactured as follows:
50% by weight of PA 6 granules and 50% by weight of PA 12 granules are mixed together and melted in an extruder at 290 ° C. and extruded into a water bath using a 40-hole nozzle. The spun material is drawn continuously from this spinning bath in a ratio of 1: 4.2, fixed in a hot air oven and then wound up in a tension-controlled manner.

The results regarding abrasion resistance and edge curling are shown in Table 1.

Example 10

A formation screen was made according to the above construction represents, in the weft below polyethylene terephthalate monofila elements in alternating weft with monofilaments, consisting of a Mixture of 50% PA 6 and 50% of a copolyamide used were (50% each). The copolyamide was made from 70 mol% of Salt of sebacic acid and hexamethylenediamine, 10 mol% Laurolactam and 20 mol% of the salt from adipic acid and Hexamethylenediamine in an autoclave at temperatures of 300 ° C manufactured. The copolyamide had a melting point of 195 ° C and a ratio of methylene units to amide groups per molecule of 6.79.  

The PA 6 / copolyamide monofilament was produced as follows represents: 50 wt .-% PA 6 granules and 50 wt .-% of the above Copolyamide granules are mixed together and in one Extruder melted at 290 ° C and with a 40 hole nozzle extruded into a water bath. The spinning material becomes continuous withdrawn from this spinning bath in a ratio of 1: 4.2 stretches, fixed in a hot air oven and then tension controlled spooled.

The results regarding abrasion resistance and edge curling are shown in Table 1.  

Table 1

While the abrasion in the variants according to the invention (Decrease in sieve thickness) corresponds approximately to comparative example 2 (PA 6 monofilaments), lie when using PA 610- Monofilaments the abrasion values significantly higher (ver same example 3).

The edge curling effect can surprisingly be caused by the Use of monofilaments made from PA blends according to the invention the seven of Examples 3 to 9 clearly compared to Ver same example 2 are reduced and is only unwe considerably worse than with sieves made of 100% polyester (Ver same example 1).

Claims (14)

1. Formation sieve for paper machines consisting of syntheti monofilaments in which at least a part of the Weft yarns are melt-spun monofilaments that are made from a mixture of PA 6 or PA 66 with PA 69, PA 610, PA 612, PA 11, PA 12 or hydrophobic copolyamides with a Melting point of at least 150 ° C and a ratio Methylene units to amide groups per molecule of min at least 6.5 were produced. 2. formation screen according to claim 1, wherein at least a part of the weft yarns are monofilaments, the 30-95 wt .-% PA 6 and 70-5 wt .-% PA 69 contain. 3. formation screen according to claim 1, wherein at least a part of the weft yarns are monofilaments, the 30-95 wt .-% PA 6 and contain 70-5% by weight of PA 610. 4. formation screen according to claim 1, wherein at least a part of the weft yarns are monofilaments, the 30-95 wt .-% PA 6 and 70-5 wt .-% PA 612 contain. 5. formation screen according to claim 1, wherein at least a part of the weft yarns are monofilaments, the 30-95 wt .-% PA 6 and 70-5 wt .-% PA 11 contain .. 6. formation screen according to claim 1, wherein at least a part of the weft yarns are monofilaments, the 30-95 wt .-% PA 6 and 70-5 wt .-% PA 12 contain. 7. formation screen according to claim 1, wherein at least a part of the weft yarns are monofilaments, the 30-95 wt .-% PA 6 and 70-5% by weight of a hydrophobic copolyamide with a  Melting point of at least 150 ° C and a ratio of Methylene units to amide groups per molecule of min at least 6.5 included. 8. formation screen according to claim 1, wherein at least a part of the weft yarns are monofilaments, the 30-95 wt .-% PA 66th and 70-5 wt .-% PA 69 contain. 9. formation screen according to claim 1, wherein at least a part of the weft yarns are monofilaments, the 30-95 wt .-% PA 66th and contain 70-5% by weight of PA 610. 10. formation screen according to claim 1, wherein at least a part of the weft yarns are monofilaments, the 30-95 wt .-% PA 66th and 70-5 wt .-% PA 612 contain. 11. formation screen according to claim 1, wherein at least a part of the weft yarns are monofilaments, the 30-95 wt .-% PA 66th and 70-5 wt .-% PA 11 contain. 12. formation screen according to claim 1, wherein at least a part of the weft yarns are monofilaments, the 30-95 wt .-% PA 66th and 70-5 wt .-% PA 12 contain. 13. formation screen according to claim 1, wherein at least a part of the weft yarns are monofilaments, the 30-95 wt .-% PA 66th and 70-5% by weight of a hydrophobic copolyamide with a Melting point of at least 150 ° C and a ratio of Methylene units to amide groups per molecule of min at least 6.5 included. 14. formation sieves according to claim 1 to 13, wherein the portion that of the monofilaments made of polyamide blends in deficit can be between 10 and 100%.