EP1162307B1 - Shoe press belt for paper machines - Google Patents

Description

The invention relates to a shoe press belt for use in shoe presses of a paper machine, with a carrier and a liquid impermeable tape layer, the one inner layer and an adjacent outer layer has, wherein the outer layer is a porous Has structure and the porous structure exclusively from cavities open to the outside is formed.

Such a shoe press belt is shown in FIGS. 6 and 7 US 4,701,368. It has a liquid impermeable Band layer on the two layers with a liquid-impermeable inner layer and one to it adjacent outer layer is built up. With one The embodiment is an additional carrier in the form of a fabric, while in the other embodiment the inner layer also acts as a carrier has and thus forms the carrier. The outer layer, designed for direct attachment to the paper web is made of a closed-pore or open-pore Foam material exist, the latter case the paper web is drained via the outer layer and therefore be dispensed with a press felt can.

The known shoe press belt has the disadvantage that the Practical outer layer under the high pressure of the shoe press is completely squeezed because it just consists of the thin cell walls of the foam. Therefore at least with the open-pore version Desired drainage is insufficient or insufficient on.

US 4,552,620 discloses a shoe press belt that of a woven carrier and one or both sides applied tape layer, which is consistent with a limited number of not related to each other standing pores is provided. The pores have one Diameters from 0.019 to 0.185 mm and are said to be on the intended for installation on the outside of the paper web create a stone-like texture. This texture is said to Detachment of the paper web from the shoe press belt after Make it easier to run through the shoe press.

The shoe press belt described above has the disadvantage that the band layer because of the whole Cross-section distributing pores is very elastic and that it is therefore strongly compressed in the shoe press nip with the result that the pores are also compressed. The pores are therefore not even for the purpose to improve the drainage of the paper web and cannot do this either.

The invention has for its object a shoe press belt of the type mentioned in such a way that it is much more resistant to compression in the Press nip is and therefore effective drainage guaranteed the paper web.

This object is achieved in that the outer layer consists of a non-foamed material, so preferably made of a plastic material, where, however, there are only pores that face the outside are open. Otherwise the strip layer is homogeneous and can therefore meet the respective requirements adjusted in terms of hardness, modulus of elasticity etc. become. It has been shown that by such a way built shoe press belt an effective drainage the paper web - possibly supported by a moving Press felt - is obtained.

The inner layer is expediently impermeable to liquids trained and can be longitudinal and / or pressure elastic be trained. Preferably the specific one Carrier modulus ≤ 500 cN / tex. For the inner layer materials such as PBT, PES, PA6, PA6.6, PA6.10, PA6.12, PA11, PA12 and PTT in question, these materials are also combined with each other can.

The carrier secures - as with all belts for a paper machine - The structural strength of the shoe press belt. For this purpose, the carrier can be constructed from threads, for example in the form of a woven fabric, knitted fabric or laid scrim. But there are also appropriately trained people Non-woven fabrics, for example in impregnated or compressed form, in question, where possible should have a uniform thickness. On the website, on which the coating is applied, the Smooth surface, e.g. be ground, be trained. Around a firm connection between carrier and coating To manufacture, it is advantageous if the carrier in the Coating is at least partially embedded. Also full embedding is possible.

Natural rubber is used as the material for the inner layer or an elastomer in question. Are particularly suitable Silicone elastomer, polyester elastomer and polyurethane. Prefers the hardness of the inner layer should be between 80 and 95 Shore A.

Organic filler particles, for example TiO ₂ or clay, can also be embedded in the inner layer in order to influence their hardness. For the function of the inner layer, it is advantageous if it has a thickness tolerance of a maximum of 100 µm. To achieve such a thickness tolerance, it can be turned and sanded accordingly before the outer layer is applied.

Polyurethane and / or silicone elastomer and / or polyester elastomer are preferred as the material for the outer layer. When such or other plastic materials are used, the cavities can be produced in a manner known per se by sprinkling and storing soluble particles on them, which can be dissolved out with a solvent to which the outer layer is resistant (cf. EP-A 0 786 550). Water-soluble particles in the form of salts such as NaCl, KCl and / or CaCO ₃ are particularly suitable for this. The particles should have a diameter of 10 microns to 1500 microns, preferably between 400 microns and 1000 microns, in a random distribution in order to create correspondingly large voids.

To improve the wear resistance of the outer layer, it is proposed to provide it with a layer of nanoparticles on its surface. These particles, previously used in chemistry as pigments for color effects, cosmetics and data storage layers, whose particle sizes are in the nano range, can effectively protect the outer layer against wear, especially if the nanoparticles consist, for example, of SiO ₂ or metals and form an almost closed layer. The nanoparticles can be applied as sol, in which case the solvent - usually alcohol - is then evaporated. In some areas, the nanoparticles can be provided with fluorocarbon chains in order to give surface areas of the outer layer a hydrophobic character and thereby facilitate the detachment of the paper web from the shoe press belt.

Another alternative for the production of the outer layer is an electron beam hardened To use prepolymer emulsion. For this come in particular Silicones or polyurethanes in question in one Water-surfactant mixture are emulsified during electron beam curing is evaporated.

It is further provided according to the invention that the outer layer outside consists of materials that areas form different hydrophilicity or hydrophobicity. Both are intended to detach the paper web from the shoe press belt facilitate, the areas and the differences arranged in terms of hydrophilicity or hydrophobicity and should be trained that there is still one sufficient adhesion of the paper web in the area of lifting the press felt is secured.

The shoe press belt expediently has a hardness between 80 Shore A and 95 Shore A and a thickness tolerance of ± 50 µm.

According to the invention it is further provided that between Another layer is arranged on the outer layer and the inner layer is which is harder than the outer layer.

Finally, it is proposed according to the invention that the complete shoe press belt has a thickness tolerance of ± 100 µm.

Figur 1

einen teilweisen Längsschnitt durch ein Schuhpressenband für eine Papiermaschine;

Figur 2

einen Längsschnitt durch eine erste Ausbildung der Außenschicht des Schuhpressenbands gemäß Figur 1;

Figur 3

einen Längsschnitt durch eine zweite Ausbildung einer Außenschicht des Schuhpressenbands gemäß Figur 1 und

Figur 4

einen Längsschnitt durch eine dritte Ausführungsform einer Außenschicht des Schuhpressenbands gemäß Figur 1.

The invention is illustrated in more detail in the drawing with the aid of schematically illustrated exemplary embodiments. Show it:

Figure 1

a partial longitudinal section through a shoe press belt for a paper machine;

Figure 2

a longitudinal section through a first embodiment of the outer layer of the shoe press belt according to Figure 1;

Figure 3

a longitudinal section through a second embodiment of an outer layer of the shoe press belt according to Figure 1 and

Figure 4

2 shows a longitudinal section through a third embodiment of an outer layer of the shoe press belt according to FIG. 1.

The shoe press belt 1 shown in FIG. 1 has one Carrier 2, which in this case is made of a fabric There is use of polyamide threads. The carrier 2 has an inner layer 3 on the top and a base layer on the bottom 4, with the carrier 2 in both layers 3, 4 is embedded. Inner layer 3 and base layer 4 consist of a silicone elastomer.

On top of the inner layer 3 is an outer layer 5 applied, which has a porous structure and a has smooth surface 6. The surface 6 is for the system a paper web is provided while the bottom the base layer 4 over the rollers of a paper machine running.

In the embodiment shown in Figure 2, the outer layer 5 essentially from a cast polyurethane layer 7. To in this polyurethane layer 7 for Cavities open on the outside - designated by way of example with 8 - To be generated are in the polyurethane material before the application salt particles - designated 9 by way of example - Evenly distributed and in a variable Size distribution from 10 µm to 1500 µm has been stored. After formation of the polyurethane layer 7 on the inner layer 3 are those salt particles 9 by means of water been washed out, not completely by the Polyurethane layer 7 were enclosed, i.e. connection had to the outside. In this way, cavities 8 emerged, the depth of which was the previous depth of penetration Salt particle 9 corresponds and open to the outside are. Those salt particles 9 that are at a distance from Surface 6 were stored, are not detached been and therefore still present in the polyurethane layer 7.

The cavities 8 interrupt the surface 6. Nevertheless remain between the openings of the cavities Areas of the surface 6 which lie in one plane as well interconnected and smooth. The paper web a large investment area is thus offered, whereby a correspondingly high adhesive force is created. The Cavities 8 generate due to their expansion after passing through of the press nip a negative pressure that the liability supports the paper web on the surface 6.

In the embodiment shown in Figure 3 Outer layer 5 is also the starting material polyurethane. However, this material is in powder form applied and then sintered so that here also a polyurethane layer 10 with a smooth surface 11 has trained. In the polyurethane powder were Salt particles stored (cf. in this respect that in EP-A 0 786 550 described method), which then by a Washing process have been completely extracted so that a porous structure forming from the surface 11 open cavities - designated 12 by way of example - came into being. The effect of the polyurethane layer 10 is the same as that of the polyurethane layer 7 according to FIG Figure 2.

The embodiment shown in Figure 4 shows one Outer layer 5, which consists of an emulsion of prepolymers has been manufactured. This emulsion is on the inner layer 3 has been applied and then electron beam hardened Service. As a result, individual, with each other in Related polymer particles - exemplary with 13 designated - emerged, between which there are cavities - designated by way of example with 14 - have formed. All in all is also a porous structure with a comparatively smooth surface 15 arose.

Claims (22)

1. Shoe press belt (1) for use in shoe presses of a paper machine, having a support (2) and a liquid-impermeable belt layer (3, 5) which has an inner layer (3) and an outer layer (5), the outer layer (5) having a porous structure and the porous structure being formed exclusively from cavities (8, 12, 14) open toward the outer side, wherein the outer layer (5) is made of an unfoamed material.
2. The shoe press belt as defined in Claim 1, wherein the inner layer (3) is liquid-impermeable.
3. The shoe press belt as defined in Claim 1 or 2, wherein the inner layer (3) is of longitudinally elastic and/or compressively elastic configuration.
4. The shoe press belt as defined in one of Claims 1 through 3, wherein the support (2) has in the longitudinal direction a specific modulus of = 500 cN/tex.
5. The shoe press belt as defined in one of Claims 1 through 4, wherein the support (2) is a woven fabric, knitted fabric, thread layer, or fiber batt, or a combination thereof.
6. The shoe press belt as defined in one of Claims 1 through 5, wherein the support (2) is at least partially embedded into the inner layer (3).
7. The shoe press belt as defined in one of Claims 1 through 6, wherein the inner layer (3) is made of natural rubber or an elastomer, in particular silicone elastomer, polyurethane, and/or polyester elastomer.
8. The shoe press belt as defined in one of Claims 1 through 7, wherein the inner layer (3) has a hardness of between 80 and 95 Shore A.
9. The shoe press belt as defined in one of Claims 1 through 8, wherein the inner layer comprises inorganic filler particles.
10. The shoe press belt as defined in one of Claims 1 through 9, wherein the inner layer (3) has a thickness tolerance of max. 100 µm.
11. The shoe press belt as defined in one of Claims 1 through 10, wherein the outer layer (5) is made of polyurethane and/or silicone elastomer and/or polyester elastomer.
12. The shoe press belt as defined in one of Claims 1 through 11, wherein the cavities (8, 12, 14) in the outer layer (5) have an average diameter of 10 µm to 1500 µm.
13. The shoe press belt as defined in one of Claims 1 through 12, wherein the outer layer (5) is equipped on its surface with nanoparticles which form a partially continuous layer.
14. The shoe press belt as defined in Claim 13, wherein the nanoparticles are made at least partially of SiO₂.
15. The shoe press belt as defined in Claim 13 or 14, wherein the nanoparticles comprise fluorocarbon chains.
16. The shoe press belt as defined in one of Claims 1 through 10, wherein the outer layer (5) is made of an electron beam-cured prepolymer emulsion.
17. The shoe press belt as defined in one of Claims 1 through 16, wherein the outer layer (5) comprises, on the outer side, materials which form regions of differing hydrophilicity and hydrophobicity.
18. The shoe press belt as defined in one of Claims 1 through 17, wherein the outer layer (5) has a thickness of = 3 mm and the inner layer (3) has a thickness of 1-3 mm.
19. The shoe press belt as defined in one of Claims 1 through 18, wherein the outer layer (5) has a hardness of between 8 Shore A and 95 Shore A.
20. The shoe press belt as defined in one of Claims 1 through 19, wherein the outer layer has a thickness tolerance of ± 50 µm.
21. The shoe press belt as defined in one of Claims 1 through 20, wherein a further layer, which is harder than the outer layer (5), is arranged between the outer layer and inner layer (3).
22. The shoe press belt as defined in one of Claims 1 through 21, wherein the shoe press belt (1) as a whole has a thickness tolerance of ± 100 µm.

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