FI96228B - Paper machine blanket and process for its manufacture - Google Patents

Abstract

The invention relates to papermachine felts of improved wear resistance, which contain a nonwoven needle-punched onto a textile 2-dimensional structure and consisting wholly or partially of 3-dimensionally crimped synthetic fibres.

Description

96228

Paper machine felt and method of making the same. - Papper-maskinfilt and förfarande för dess framställning.

The invention relates to the claimed object.

In particular, the invention relates to improved paper machine blankets having at least one fibrous mat needled on a woven surface structure consisting wholly or partially of 3-dimensionally twisted synthetic fibers, and further to a method of making paper machine felts and using such nonwoven mats on paper machine felts. enable the production of paper with a smooth surface.

Paper machine blankets are usually made from the base fabric by knitting the curled fibers into fibrous mats. Such paper machine blankets are used in the press section of paper machines to remove water from the paper web. To do this, the blankets, together with the pulp, must be passed through the press rolls. In this case, the felt and paper are subjected to very high mechanical, but also chemical and possibly thermal stresses. In particular, due to the high speeds and compression pressures, • the fibers deform very strongly in a short cycle interval.

According to the state of the art, such fibers can be protected with stabilizers against thermal and chemical damage.

In order to improve the surface quality of the paper, it is prior art to make the top layer of the felt from the finest possible titer fibers. However, the low abrasion resistance of fine titer fibers is against this desire.

One of the most important properties of the fibers used in paper machine felts is 2 96228, which is abrasion resistance, which can be obtained relatively easily for single fibers. 1 by means of a scouring test.

In this test, the conditioned fibers are loaded with a prestressing load of 0.44 cN / dtex (0.5 g / den) and hung at a predetermined angle on a precisely defined wire.

The fibers are then moved back and forth a predetermined distance along the fiber axis so that they rub against the yarn. The measure of abrasion resistance is the number of abrasion movements against the wire (abrasion movements, Drahtscheuertouren "DST"), which is required until the fiber breaks.

For this experiment, at least 44 individual values from Griinewald, K.H., Lenzinger Berichte 26. (1968) S 90-109 are used to average.

The paper machine felts used in practice today are mainly made of Polyamide 6 or Polyamide 6.6 fibers. However, other fiber types are also disclosed in the literature for this purpose. Thus, EP-A 0 287 297 discloses Polyamide 12 fibers in an analogous manner and EP-A 372 769 Polyamide 11 fibers.

DE-OS 17 61 531 describes paper machine blankets having in particular a compacted surface obtained by using non-woven mats formed from blends of wadding or shrinkable yarns and fibers with different fiber thicknesses (denier) curl and polymer structure.

According to the state of the art at the time, the fibers used in paper machine felts are produced industrially by the compression chamber method (Stauchkammerverfahren) by two-dimensional curling. However, this strong mechanical buckling stress

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3 96228 damage to the fibrous structure, which is evident in the deteriorated mechanical properties, in particular the reduced abrasion resistance compared to uncurled but thus unusable fibers.

Studies have shown that the molecular weight of fibrous polymers during compression spinning decreases at buckling points as a result of mechanical damage.

The object underlying the present invention is based on the still unsatisfactory durability of paper machine felts in industrial use, which is the result of the still unsatisfactory abrasion resistance. The object of the invention is, in addition to improved felts, to provide a method for their production.

To solve this problem, paper machine blankets formed from fiber mats made of 3-dimensionally curled synthetic fibers according to the features of claim 1 or a method for producing paper machine blankets according to the features of claim 11 and fiber mats are proposed.

The claims include further developments of the invention.

In particular, in the manufacture of filaments, some methods are known in which 3-dimensional curling is formed. However, these methods are in principle also adapted to tapuli fiber production.

By way of example, the following methods are presented here: 1. Production of bicomponent fibers with the components not concentrically distributed - e.g., side by side.

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Due to the different physical properties of both components (1 coefficient of expansion, shrinkage behavior, water uptake), a 3-dimensional curl is forced on the fibers. The manufacture of such fibers has long been prior art (e.g. Koch, P.A .; Chemiefasern /

Textilind. (1979), 431-438).

It is advantageous if the two polymer components are as similar in chemical structure as possible and thus compatible with one another, otherwise there is a risk of bonding. It is particularly preferred to use different viscosities of the same polymer or to use the same polymer for both components, the other component being modified with an additive.

2. Asymmetric freezing of fibers during melt spinning. This can be achieved by means of a liquid, a sharp stream of air or also solid cooled parts which come into contact with the hot fibers on one side. Asymmetric cooling affects the structure of the polymer. This results in different physical properties of the polymer within the filament, as in bicomponent fibers.

3. Air jet or steam jet texturing.

H. Schellenberg; 3. According to Reutlinger Texturier-Kolloquium (1984), the formation of curl in an air (steam) spray process can be described as follows:

After stretching at a temperature close to the softening point, the yarn enters the texture nozzle. There, it is heated by a jet of heating gas still under pressure and led to the dam section. In it, the existing pressure is released more or less in the form of an impact by means of the unloading openings, so that the fibril joint opens and a plug is formed. However, as the pressure is not met— 11 5 96228 sin can be released, the plug gradually protrudes through the dam section. The intensity of the dam and plug movement can be controlled by the pressure drop method.

Surprisingly, it turned out that 3-dimensionally curled synthetic fibers have significantly better abrasion resistance than two-dimensionally curled fibers from the same starting material. Curling is necessary to process the fibers into fibrous mats and gives the felt a favorable volume for water transfer.

The advantages of paper machine felts made wholly or in part from 3-dimensional crimped synthetic fibers are longer and possibly for finer fiber titers than conventionally used two-dimensional compression chamber fibers. Thus, fiber titers of less than 10 dtex can also be advantageously used, and particularly preferably between 4.5 and 6.5 dtex.

The paper machine felts according to the invention are manufactured in whole or in part by needling 3-dimensionally curled synthetic fibers according to the method according to the invention in a manner known per se.

In principle, the invention is not limited to the fibers of a particular type of polymer or combination of polymers, but can advantageously affect the properties of all types of polymer used in paper machine fabrics.

Preferably, the 3-dimensionally curled synthetic fibers are made of polyamides. PA 6, PA 11, PA 12, PA 4.6, PA 6.6, PA 6.10, PA 6.12 are particularly preferred. PA 10, T, PA 12, T, PA 12.12 or copolyamide of aliphatic monomers having 4 to 12 C atoms and / or aromatic monomers having 6 to 96228 6 to 12 C atoms. Preferred monomers for such copolyamides are caprolactam, lauric-lactam, terephthalic acid and a linear Q, Q-diamine having 4 to 12 carbon atoms.

According to the invention, 3-dimensionally curled synthetic fibers can be advantageously used for the production of needled fiber mats, which fiber mats are applicable to paper machine felts because they have a clearly better abrasion resistance compared to the prior art.

Example 1:

Air-jet textured fibers were prepared by a suitable spinning method using dried PA 6 granules threaded with 0.7% Irganox 1098. The granulation 11a had a relative viscosity (measured in 96% sulfuric acid (23 ° C), 1 g / 100 ml) et al. = 3.65. The granulate was melted in an extruder and then spun. The spinning nozzle had 48 holes 0.6 mm in diameter. The total throughput was 154 g / min. at a spinning speed of 600 m / min. The fiber bundle was frozen after blowing nozzle with blown air, after which it was treated and then wound.

The spun material was stretched, textured and then wound at 1670 m / min. With Rieter's air jet texturing machine J 0/10. The filaments were then unwound from a spool, untensioned at 165 ° C and cut. The fibers have at least 100% higher abrasion resistance (DST value) than those of the corresponding polymer. with fibers produced by the chamber method.

The fibers were made into a nonwoven mat having a basis weight of 500 g / m 2 and needled onto the base fabric. Such test felts had at least a 30% longer lifespan compared to similar felts made from compression chamber molds.

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7 by 96228 (Comparative Example 1) when the fibers were subjected to an experiment corresponding to the conditions of a paper machine.

Example 2:

In analogy to Example 1, fibers were prepared and processed into felts, however, the fibers were spun stretched. These fibers also have very good abrasion resistance (DST value). The service life of the felts was about 30% longer than the fibers of the compression chamber method described in Comparative Example 1.

Example 3:

In analogy to Example 1, fibers were prepared from PA 12 and processed into felts. Abrasion resistance and felt life were substantially better than those of the corresponding reference fibers prepared by the compression-chamber method (Comparative Example 2).

Example 4:

In analogy to Example 1, fibers were prepared from PA 6.6 (eta rel. Granulate 3.4) and examined.

Example 5:

The bicomponent fibers were prepared on a suitable spinner using dried PA 6 granules threaded with 0.7% Irganox 1098. The granules differed in relative viscosity (measured in 96% sulfuric acid (23 ° C), 1 g / ml). Granulate A: eta rel. = 3.4 and granulate B: eta rel. = 3., 65. The granules were protected in two separate extruders and then spun in a spinning bundle in which the two melt streams were combined shortly before leaving the spinning nozzle 8 96228, resulting in a side-to-side arrangement of both components. The spinning nozzle has 200 holes 0.4 mm in diameter. The total throughput was 550 g / min. at a spinning speed of 770 m / min. The fiber bundle was cooled after blowing nozzle by blowing air, then treated and then wound into a vessel. The spun material was stretched in a stretch web of conventional construction at draw roll temperatures of 60-65 ° C, softened, dried and cut. The properties of the fibers are shown in Table 1. The fibers have at least 100% higher abrasion resistance (DST value) than the fibers of the compression-chamber method from the corresponding polymers.

A fibrous mat with a basis weight of 500 g / m 2 was made from the fibers, which was needled on the base fabric. Such test felts had at least a 30% longer service life compared to the corresponding felts (Comparative Example 1) prepared by the compression chamber method when subjected to experimental conditions corresponding to a paper machine.

Example 6:

In analogy to Example 5, fibers were prepared from PA 12 granulate at different viscosities (eta rel. 2.0 and 2.2 measured in m-cresol, 25 ° C, 0.5 g / 100 ml) and processed into felts. These fibers also had very good abrasion resistance (DST value). The durability of the felts was 25% longer than with the reference fibers described in Section 2.

Example 7:

In analogy to Example 1, fibers were prepared from PA 6 and copolyamide on a caprolactam / laurine lactam base and processed into felts.

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Example 8:

In analogy to Example i, fibers were prepared from PA 6 granulate (eta rel. 3.4) and PA 66 granulate (eta rel. 3.4).

3.4) and processed into felts.

Comparative Example 1:

Polyamide 6 fibers prepared by the compression chamber method were tested as comparisons. The test results are shown in Table 1.

Comparative Example 2:

Polyamide 12 fibers prepared by the compression chamber method were studied as control variants.

The characteristic values measured from the fibers of the examples are summarized in Table 1.

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Option Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Cf. See.

e.g.

1 2 DAY 6 PA 12

Titer 20.9 21.3 22.0 21.1 21.4 22.1 22.0 22.1 [dtex]

Elongation 108 100 110 87 99 112 89 105 [%]

Strength 41 40 45 39 46 53 51 52 [cN / Tex]

Arc number 11 12 11 12 12 10 14 10 [B / cm] # DST 188000 180000 240000 50000 196000 250000 57000 100000 et al. 3.9 3.9 2.20 ** 3.4 3.7 2.17 ** 4.0 2.19 **

Visc.

* Determined using Zweigle Kräuselwaage p. 160 (test instructions see device description) ** Measured in m-cresol # 3 In the case of dimensionally curled fibers, each inflection point of the fibers is calculated as an arc (in stress-free state), while in 2-dimensionally curled fibers each deflection is calculated .

Table 1 clearly shows that the three-dimensionally curled synthetic fibers compared to the corresponding two-dimensional. to dimensionally curled fibers are substantially more abrasion resistant.

Example 4 indicates that it is known from Merkblatt "Grilon" that the abrasion resistance of PA 6.6 is only about 60-70% of the abrasion resistance of PA 6.

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Claims (21)

11 96228 Paper machine blankets having - a base fabric and - at least one layer of nonwoven mat formed of thermoplastic melt-spun polymer fibers, which layer is needled on the base fabric, characterized in that the nonwoven mat is formed entirely or partially of three-dimensionally curled fibers. Paper machine felt according to Claim 1, characterized in that the three-dimensionally curled fibers are bicomponent fibers. Paper machine felt according to Claim 1, characterized in that the three-dimensionally curled fibers are asymmetrically cooled polymer fibers. Paper machine felt according to Claim 1, characterized in that the three-dimensionally curled fibers are curled by means of an air jet method. Paper machine felt according to Claim 1, characterized in that it is three-dimensionally curled. the fibers are curled by the steam jet method. Paper machine felt according to one of Claims 1 to 5, characterized in that the three-dimensionally curled fibers are formed from at least one polyamide component. Paper machine felt according to Claim 1 or 2, characterized in that the three-dimensionally curled fibers are formed from at least two polyamide components having different properties. 12 96228 Paper machine felt according to claim 6, characterized in that the polyamide component is a polyamide selected from the group consisting of Polyamide 6, Polyamide 11, Polyamide 12, Polyamide 4,6, Polyamide 6,6, Polyamide 6,10, Polyamide 6,12, Polyamide 10 , T, Polyamide 12, T, Polyamide 12,12 and copolyamide from aliphatic monomers having 4 to 12 carbon atoms and / or aromatic monomers having 6 to 12 carbon atoms. Paper machine felt according to claim 7, characterized in that at least one of the polyamide components is a polyamide selected from the group consisting of Polyamide 6, Polyamide 11, Polyamide 12, Polyamide 4.6, Polyamide 6.6, Polyamide 6.10, Polyamide 6.12, Polyamide 10, T, Polyamide 12, T, Polyamide 12,12 and copolyamide from aliphatic monomers having 4 to 12 carbon atoms and / or aromatic monomers having 6 to 12 carbon atoms. Paper machine felt according to Claim 8 or 9, characterized in that the copolyamide is formed from monomers selected from the group consisting of caprolactam, laurine lactam, terephthalic acid and linear α, Q-diamine having 4 to 12 carbon atoms. 11. A method of making a needled paper machine felt per se: in a known manner from a base fabric and at least one layer of nonwoven fabric made of thermoplastic melt-spun polymer fibers, which layer is needled on Derus fabric, characterized in that the felt is made wholly or partially knitted 3-dimensionally . Method according to Claim 11, characterized in that bicomponent fibers are used as the 3-dimensional curled fibers. Il 13 96228 Method according to Claim 11, characterized in that asymmetrically cooled polymer fibers are used as the 3-dimensional curled fibers. Method according to Claim 11, characterized in that air-curled fibers are used as the 3-dimensional curled fibers. Method according to Claim 11, characterized in that the fibers curled by the steam jet method are used as the 3-dimensional curled fibers. Method according to one of Claims 11 to 15, characterized in that the 3-dimensional crimped fibers consist of polyamide components. Method according to one of Claims 11 to 16, characterized in that the 3-dimensionally curled fibers consist of a plurality of polyamide components having different properties. Process according to Claim 16, characterized in that the polyamide component is a polyamide selected from the group consisting of Polyamide 6, Polyamide 11, Polyamide 12, Polyamide 4.6, Polyamide 6.6, Polyamide 6.10, Polyamide 6.12, Polyamide 10 , T, Polyamide 12, T, Polyamide 12,12 and copolyamide of aliphatic monomers having 4 to 12 carbon atoms and / or aromatic monomers having 6 to 12 carbon atoms. Process according to Claim 17, characterized in that the at least one polyamide component is a polyamide selected from the group consisting of Polyamide 6, Polyamide 11, Polyamide 12, Polyamide 4.6, Polyamide 6.6, Polyamide 6.10, Polyamide 6.12, Polyamide 10, T, Polyamide 12, T, Polyamide 12,12 and copolyamide from aliphatic monomers having 4 to 12 C-14 96228 atoms and / or aromatic monomers having 6 to 12 C atoms. Process according to Claim 18 or 19, characterized in that the copolyamide is formed from monomers selected from the group consisting of caprolactam, 1α-urine-lactam, terephthalic acid and linear α, 2-diamine having 4 to 12 carbon atoms. 21. Use of nonwoven mats consisting at least in part of thermoplastic melt-spun 3-dimensionally crimped polymeric fibers selected from the group consisting of bicomponent fibers, asymmetrically cooled fibers, air jet spun fibers, and steam jet fiber spinning fibers. Il 15 96228