WO2015086555A1

WO2015086555A1 - Press band and the use thereof, and press roll and shoe press

Info

Publication number: WO2015086555A1
Application number: PCT/EP2014/076968
Authority: WO
Inventors: Delphine Delmas; Uwe Matuschczyk
Original assignee: Voith Patent Gmbh
Priority date: 2013-12-13
Filing date: 2014-12-09
Publication date: 2015-06-18

Abstract

The invention relates to a press band, such as a press cover for a press roll, in particular for a press roll of a shoe press for de-watering a fibrous material web, or for a transfer band for transporting a fibrous material web, in particular a paper-, paperboard-, tissue-, or pulp web, said press band comprising at least one layer, containing or made of polyurethane, in which a reinforcement is embedded. The polyurethane is formed by a prepolymer and a curing agent, wherein the prepolymer is a mixture of 1,4-phenylene diisocyanate (PPDI) and polytetramethylene ether glycol (PTMEG), and the curing agent contains the following components: (K1) between 0 and 64 mol% aromatic diamine having a molar mass greater than 300 g/mol, preferably between 20 and 64 mol%; (K2) between 0 and 20 mol% aromatic diamine having a molar mass less than 300 g/mol; (K3) between 0 and 15 mol% linear or cycloaliphatic amine having a molar mass less than 300 g/mol; (K4) between 0 and 5 mol% tertiary amine; and (K5) between 0 and 50 mol% polyol.

Description

Press belt and its use, as well as press roller and shoe press

The invention relates to a press belt and its use, a press roll and a shoe press according to the independent claims. Such press belts can be used, for example, as press jackets for a press roll of a shoe press for dewatering a fibrous web or transfer belts for transporting a fibrous web, in particular a paper, board, tissue or pulp web, for a machine for producing the same. Other applications away from the processing or transport of fibrous webs, such as industrial rollers, would be conceivable.

In a shoe press the web runs together with at least one water-permeable press belt, z. B. a press felt, by a nip, which is a press roll - also referred to as shoe press roll - and a counter-roller is formed. The shoe press roll comprises a rotating press jacket and a stationary press element, the press shoe, which is supported on a supporting yoke and which is pressed by hydraulic pressing elements against the rotating press jacket. The press cover is thereby pressed in the nip against the counter roll. The fibrous web can also pass through the nip of the shoe press between two press felts or between a press felt and a water-impermeable transfer belt.

When passing through the fibrous web through the nip water is pressed out of the web. Shoe presses are characterized by the fact that the shoe can be adapted by a concave shape to the counter roll and that thus a longer pressing zone is generated. The length of the nip is preferably more than 250 mm in the web running direction. That's why significantly more water is squeezed out with shoe presses than with normal roller presses. The water pressed out in the nip, or at least the portion of it pressed out in the direction of the press roll, must be temporarily stored in the press felt and in the press jacket during the nip passage. After leaving the nip, the water is in front of the re-entry into the nip from the press cover in jars spun or with the help of suction elements removed from the felt. In order to have the necessary storage volume for the water during the Nipdurchgangs, the press jackets are often provided with grooves or blind holes on the fibrous web facing jacket surface.

The press cover must be sufficiently flexible to allow it to pass around the shoe, it must be sufficiently stiff so that it does not deform or compress too much in the nip under the press load, and it must be sufficiently wear resistant. Press jackets may therefore comprise a single- or multi-ply polymer layer, preferably of polyurethane, in which reinforcing threads are embedded in the form of loops or woven fabrics.

The present invention relates to such generic press jackets, transfer belts or devices which comprise these.

From EP 1 087 056 A2 such a press cover is already known. Disclosed therein is a press cover, which is provided with blind holes on the lateral surface, to receive the pressed-out water.

EP 2 284 314 A1 discloses a papermaking shoe press belt which is formed from a reinforcing fiber base material and a polyurethane layer which are integrated with one another, wherein the reinforcing fiber base material is embedded in the polyurethane layer. The polyurethane layer is formed by curing a composition of a urethane prepolymer (A) and an active hydrogen group (H) -containing curing agent (B), wherein the urethane prepolymer (A) comprises reacting an isocyanate compound comprising 55 to 100 mole% of a p-phenylene diisocyanate compound , which can be obtained with a long-chain polyol and contains terminal isocyanate group (s), and wherein a curing agent (B) contains 65 to 100 mol% of one or more organic polyamine compound (s) and which has active hydrogen groups (H) and is selected from 4,4'-methylenedianiline and / or a complex of 4,4'-methylenedianiline and sodium chloride; 4,4'-methylenebis (2,6-diethyl-3-chloroaniline).

Transfer ribbons are less subject to alternating dip loads, but due to their length and weight, they also have to meet strong reinforcement with the same requirement for reliable bonding to the polymer matrix.

It is therefore an object of the invention to develop the devices known from the prior art so that the processability and the reaction rate allow a secure connection of the reinforcement to the polymer matrix by the reflowing of the reinforcement is made possible, but the mechanical and dynamic properties high level can be maintained.

The object is solved by the features of the independent claims.

According to the invention, i) the prepolymer is a reaction product of 1,4-phenylene diisocyanate (PPDI) and polytetramethylene ether glycol (PTMEG) and ii) the crosslinker contains the following components: (K1) 0% to 64% mol of aromatic diamine with a molar mass> 300 g / mol, preferably 20% mol to 64% mol; (K2) 0% mol to 20% mol of aromatic diamine with a molar mass <300 g / mol; (K3) 0% mol to 15% mol linear or cycloaliphatic amine having a molar mass of <300 g / mol; (K4) 0% to 5% mol tertiary amine; and (K5) 0% to 50% of a polyol.

It may preferably be provided in feature i) that the prepolymer contains 50% to 100% mol of PPDI. The components according to the invention, in particular K1 to K5, can, as stated in the independent claims, be selected with regard to their molar proportions such that they do not exceed 100% mol. For the purposes of the invention, by shoe press is meant a device for dewatering a fibrous web, such as a paper, board, tissue or pulp web. The shoe press comprises a shoe press roll and a counter roll, which together form or define a nip (also called press nip or shoe press nip). The shoe press roll further comprises a rotating press cover and a stationary pressing element, the so-called press shoe. The latter is supported by a supporting, likewise standing yoke. About the yoke then the press shoe can be pressed for example via hydraulic pressing elements to the rotating press cover. The press cover is thereby pressed in the nip against the counter roll. The term standing means that the pressing element does not rotate relative to the shoe press roll or the counter roll, but can move translationally - for example, toward and away from the counter roll - preferably in the radial direction - and thus relative to the counter roll. In addition to the fibrous web and the press belt, one or more circumferentially endlessly circulating felts and / or further endlessly circulating press belts can be guided through the press nip of the shoe press. Of course, such a shoe press may include more than one shoe press nip. In the context of the invention, a press belt is to be understood as meaning a belt or a sheath which is guided together with a fibrous web through the nip of a shoe press.

The press belt can be designed as a press cover of the shoe press, which is designed as a circumferentially endless, closed jacket and is held by two lateral clamping disks and rotated about the fixed press shoe to form the shoe press roll. In order to reduce the friction of the press belt on the press shoe, oil for lubrication can be applied to the inside of the press belt, ie the side facing the press shoe. Instead of the guide through the two side clamping discs, the press belt, as is the case with open shoe presses, on the press shoe and a plurality of guide rollers be guided. The surface of press jackets may be provided with grooves and / or blind holes.

The press belt can also be embodied in the sense of the invention as a transfer belt, which is guided between the fibrous web and the mantle of a mating roll as a circumferentially endless belt in order to transport the fibrous web through the shoe press nip. The fibrous web is then removed after the shoe press nip using a suction roll from the press belt, taken on another fabric and fed to the following machine group. Thus, it is advantageous if the surface of the transfer belt has sufficient adhesion to the fibrous web to guide it safely and if the surface of the transfer belt has good smoothness and low tendency to marring. On the other hand, it is also advantageous if the fibrous web can be pulled off again. Basically, transfer belts according to the invention are not limited to use in shoe presses, but can also be found outside this application. Transfer belts for conveying a fibrous web, white a paper, cardboard, tissue or pulp web can then be designed so that they preferably wrap around several rollers in operation. For the purposes of the invention, a fibrous web is to be understood as a scrim of fibers, such as wood fibers, synthetic fibers, glass fibers, carbon fibers, additives, additives or the like. Thus, the fibrous web may be formed, for example, as a paper, board or tissue web, which essentially comprise wood fibers, wherein small amounts of other fibers or additives and additives may be present.

The term reinforcement in the sense of the invention means reinforcement of at least one layer containing or consisting of polyurethane. The reinforcement is embedded in the polyurethane. In other words, the polyurethane takes over the role of the polymer matrix surrounding the reinforcement and due to adhesion or cohesion forces on the Polymer matrix binds. As reinforcement come familiar to the expert materials.

The polyurethanes thus produced are characterized by a sufficiently slow reaction rate, good mechanical and dynamic properties and improved thermal stability.

Further advantageous aspects of the invention will become apparent from the dependent claims. The component (K1) of the crosslinker MCDEA may preferably be with a molar mass of about 380 g / mol.

Preferably, the component (K2) of the crosslinker can be DETDA with a molar mass of 178 g / mol.

Further preferably, the component (K3) of the crosslinker may be 4,4'-methylenebis (cyclohexylamine) (CAS 1761-71 -3) having a molar mass of about 210 g / mol. Preferably, component (K4) of the crosslinker may be triethylenediamine (TEDA).

More preferably, component (K5) of the crosslinker may be selected from polytetramethylene ether glycol (PTMEG) or polycarbonates or polyols.

According to a particularly preferred aspect of the invention, the molar ratio between prepolymer and crosslinker may be between 0.9 and 1.1. Advantageously, the polyols may be selected from: polyester polyol, in particular polycaprolactone polyol; Polyether polyols, in particular

Polytetramethylene ether glycol (PTMEG), polypropylene glycol (PPG), polyethylene glycol (PEG) or polyhexamethylene ether glycol; polycarbonate,

Polyethercarbonate polyol, polybutadiene polyol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, polybutylene glycol, 1,4-butanediol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, 4,4'-dihydroxyphenylacetylene (DHPA), 1,4-dihydroxyethylphenyl diether (HQEE), trimethylol propane (TMP).

The molar mass of the polyols can be between 900 and 3000 g / mol.

Preferably, the amine may be selected from hydrazines, ethylenediamines, diethylenetoluenediamine (DETDA), diethylmethylbenzenediamines (DETDA), methylene-bis-orthochloroaniline (MOCA), dimethylthiotoluenediamine (DMTDA), trimethyleneglycol di (p-aminobenzoate) (TMAB), 4 , 4'-Methylenebis (2,6-diethylaniline) (MCDEA), 2,2'-methyliminodiethanol (MDEA), triisopropanolamine (TIPA).

According to one aspect of the invention, the press cover or the transfer belt may be constructed of multiple layers, wherein at least the outermost layer comprises a prepolymer mixture according to claim 1.

According to a further advantageous aspect of the invention, the prepolymer mixture according to claim 1 may be provided at least in regions, preferably in the edge regions of the outermost layer.

The invention will be explained in more detail with reference to a preferred embodiment.

Usually, press belts, that is, press jackets for shoe press rolls and transfer belts, can be constructed of a polyurethane material. In such a case, reinforcing may be embedded in the polyurethane matrix in the form of yarns. This can be a scrim or a fabric. On a detailed Description can be omitted here, since this is well known in the art.

Such a press cover may usually be made by casting the polyurethane. In this case, for example, first the reinforcement is wound onto a casting core and subsequently the polyurethane is applied from nozzles displaceable in the longitudinal direction of the casting core, while the casting core rotates under its nozzle about its longitudinal axis. As a result, the polyurethane is applied in a band-like application in which the windings abut one another, at least in abutment.

The application can be carried out in one or more layers, whereby material variations such as filler gradients in different layers are also possible. After curing of the polyurethane, the press shell is subjected to further processing steps, for example, provided with surface structures and finally withdrawn from the casting core.

Transfer belts can usually be cast on large casters, where the basic structure is suspended and coated by means of a likewise movable casting device, which usually has a casting belt and an associated support structure or two casting belts, between which the liquid polyurethane is introduced. Here too, casting is carried out on part of the total width of the transfer belt and the casting device is moved for a spiral application.

From the above methods, various demands are made on the polyurethane mixture. On the one hand, the viscosity should allow a uniform application on exit from the nozzle, on the other hand, the polyurethane should not be too thin, otherwise it runs when turning the casting core and dripping. The same applies to the production of the transfer belt. The so-called pot life, which provides information on the crosslinking of the polyurethane over time, should therefore be chosen so that the polyurethane is indeed firm enough during the application not dripping, but still reactive enough to be able to make a connection with the newly applied polyurethane composition at the next turn. However, these requirements are not absolutely necessary and depend heavily on the application of the polyurethane mixture.

In addition, it may be advantageous that the polyurethane composition is thin enough to completely penetrate the various layers of the reinforcement, the number of which may be, for example, up to three (or even more) and also include fabric layers, and to cover the yarns over the entire surface. This may be significant in that poor circulation can interfere with the bonding of the reinforcement to the polymer matrix and lead to cracking and delamination. Trapped air bubbles in turn can lead to defects in the pressure profile, which can manifest itself in markings of the fiber web. Transfer belts and press jackets of shoe press rolls are equally subject to a variety of chemical and mechanical stresses, as already briefly mentioned above. In addition to the wet environment, which in addition to water may contain, among other things, oil-containing substances and other chemicals, in particular the mechanical stress on a press cover are of importance. Due to the opposite bending movements when entering and leaving the nip, the press jackets in addition to the pressures prevailing in the nip are subject to strong, partially counteracting loads. If the material of the press jacket is weakened by chemical effects or swelling, cracks will occur which will lead to the failure of the press jacket. As a result, severe damage to the press roll or even the subsequent sections of the machine can occur, for example, when the polyurethane delaminates and peels off of the press cover. Especially with regard to the occupational safety aspects for the operating personnel, safe operation of the press jacket is of great importance here. Similar problems can occur with the long and heavy transfer belts. According to one embodiment of the invention, a press roll, such as a shoe press roll, is provided for a shoe press for dewatering a fibrous web, wherein the press roll has at least one press belt according to the invention.

According to a further embodiment of the invention, a shoe press is provided for dewatering a fibrous web, preferably a paper, board, tissue or pulp web, comprising a press roll and a counter roll, which together form or define a nip, wherein the press roll comprises a rotating press cover and the press cover is formed as a press belt according to the invention.

According to a further embodiment of the invention, a use of a press belt according to the invention in a press, such as shoe press for dewatering a fibrous web, preferably a paper, board, tissue or pulp web is provided.

A polyurethane mixture is described below which takes into account the above-mentioned requirements and permits the production of a press jacket or a transfer tape which, in addition to high mechanical and chemical resistance, has excellent dynamic properties.

The raw materials for polyurethane are mainly isocyanates, polyols and polyamines. Usually, an isocyanate prepolymer is used. An isocyanate prepolymer is formed from isocyanate monomers that have been partially reacted with a high molecular weight polyol or with a mixture of high molecular weight polyols. Diisocyanates are particularly important because they offer the best flexibility and dynamic resilience. However, a restriction to a diisocyanate is not mandatory, and other starting materials would be conceivable in principle, as far as they are suitable for the present invention. The properties of the polyurethane depend on many factors: the isocyanate monomer type, the proportion of free monomers, the ratio XH / NCO, type, functionality and molecular weight of the polyols, type, functionality and molecular weight of the polyamines, any fillers, catalysts, etc ,

Particularly suitable polyols for use in press jackets are families of polyols such as polyester polyols (e.g., polycaprolactone polyol), polyether polyols (e.g., polytetramethylene ether glycol (PTMEG), polypropylene glycol (PPG), polyethylene glycol (PEG), or polyhexamethylene ether glycol), polycarbonate polyol.

Polyethercarbonate polyol, polybutadiene polyol. Furthermore, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, polybutylene glycol, 1, 4-butanediol, 1, 3-propanediol, 1, 5-pentanediol, 1, 6-hexanediol, 4,4'-dihydroxyphenylacetylene (DHPA), 1, 4-Dihydroxyethylphenyldiether (HQEE), trimethylolpropane (TMP) or similar Find use.

The polyamines and / or polyols used as crosslinkers may be selected from hydrazines, ethylenediamines, diethylenetoluenediamine (DETDA), diethylmethylbenzenediamines, methylene-bis-orthochloroaniline (MOCA),

Dimethylthiotoluenediamine (DMTDA), trimethyleneglycol di (p-aminobenzoate) (TMAB), 4,4'-methylenebis (2,6-diethylaniline) (MCDEA), 2,2'-methyliminodiethanol (MDEA), triisopropanolamine (TIPA), etc The crosslinker may further consist partially of the polyols or contain one or more of the polyols used to make the prepolymer.

The most important mechanical properties of the polyurethane matrix for a press cover or a transfer belt are abrasion resistance, low tendency to crack formation and crack growth, low sensitivity to water, oil, acids, alkalis, solvents and a low tendency to swell in the abovementioned substances. The positive properties of PPDI-based polyurethanes are already known. PTMEG is a common polyol used in the production of "high performance" polyurethane elastomers.The disadvantage of PTMEG is its low thermooxidative stability, which reduces the life of the press jacket or conveyor belt.The dynamic properties of PTMEG-based polyurethanes are on the other hand tends to be good compared to other (polyether) polyols.

The problems with regard to the thermooxidative stability can be improved by the use of aromatic amines, in particular 4,4'-methylene-bis (3-chloro-2,6-diethylaniline) (MCDEA) in the crosslinker. The mechanical properties are also improved by the use of MCDEA.

The setting of the desired reaction rate or viscosity is carried out according to the invention by the combination of different amines in the crosslinker. The reactivity of the amines depends on their structure and molar mass. Thus, according to a rule of thumb, e.g. aliphatic amines more reactive than the aromatic amines. Among the aromatic amines, in turn, those with a higher molar mass are slower in their reaction rate (with some exceptions).

Preferred embodiment:

The Applicant has found in laboratory tests that a suitable solution is designed as follows:

Prepolymer: 0% to 100% PPDI-PTMEG, preferably 50% to 100%.

crosslinkers:

Component K1: 0% to 64% mol of aromatic diamine with a molar mass> 300 g / mol, in particular MCDEA with a molar mass of about 380 g / mol, preferably 20% to 64% mol Component K2: 0% to 20% mol of aromatic diamine with a molar mass <300 g / mol, in particular DETDA with a molar mass of 178 g / mol

Component K3: 0% to 15% mol linear or cycloaliphatic amine with a molar mass of <300 g / mol, in particular 4,4'-

Methylenebis (cyclohexylamine) with a molar mass of about 210 g / mol

- Component K4: 0% mol to 5% mol tertiary amine, in particular TEDA

Component K5: 0% to 50% of a polyol with a molar mass of 900 to 3000 g / mol, in particular PTMEG.

The components according to the invention, in particular K1 to K5, can, as indicated, be chosen in such a way with regard to their molar proportions that they do not exceed 100% mol together. Particularly preferred is a solution in which the molar ratio between prepolymer and crosslinker is between 0.9 and 1.1.

Furthermore, it is conceivable that the press cover or the transfer belt is composed of several layers. Thus, an outer layer, which comes into contact with the press felt and / or the fibrous web and thus exposed to water and other chemical substances, be particularly resistant to swelling by using the abovementioned prepolymer mixtures according to the invention, while the inner layers with Other prepolymers can be constructed. This has the advantage, inter alia, that the mechanical and chemical properties of the press jacket or of the transfer tape can be influenced separately from one another.

It is also conceivable that the abovementioned prepolymer mixtures are used only in certain areas of the press jacket or transfer tape, for example on the edge. In the edge areas, in particular of press jackets, the load is particularly high, since on the one hand the edge of the press shoe mechanically on acting on the press cover and on the other hand, the paper web edges mechanically load the edge areas by oscillations.

Claims

claims

1 . Press belt, such as press cover for a press roll, preferably for a press roll of a shoe press for dewatering a fibrous web, or transfer belt for transporting a fibrous web, preferably a paper, board, tissue or pulp web, wherein the press belt at least one, containing a polyurethane or from this existing layer, in which a reinforcement is embedded, wherein the polyurethane is formed from a prepolymer and a crosslinker, which crosslinker comprises a mixture of amines, characterized in that i) the prepolymer is a reaction product of 1, 4-phenylene diisocyanate (PPDI ) and polytetramethylene ether glycol (PTMEG) and that ii) the crosslinker contains the following components: (K1) 0% to 64% mol aromatic diamine with a molar mass> 300 g / mol, preferably 20% mol to 64% mol; (K2) 0% mol to 20% mol of aromatic diamine with a molar mass <300 g / mol; (K3) 0% mol to 15% mol linear or cycloaliphatic amine having a molar mass of <300 g / mol; (K4) 0% to 5% mol tertiary amine; and (K5) 0% to 50% of a polyol.

2. Press belt according to claim 1, characterized in that the component (K1) of the crosslinker MCDEA with a molar mass of about 380 g / mol.

3. Press belt according to claim 1 or 2, characterized in that the

Component (K2) of the crosslinker DETDA having a molecular weight of 178 g / mol.

4. Press belt according to one of claims 1 to 3, characterized in that the component (K3) of the crosslinking agent is 4,4'-methylenebis (cyclohexylamine) having a molar mass of about 210 g / mol.

5. Press belt according to one of claims 1 to 4, characterized in that the component (K4) of the crosslinking agent is triethylenediamine (TEDA).

6. Press belt according to one of claims 1 to 5, characterized in that the component (K5) of the crosslinker is selected from polytetramethylene ether glycol (PTMEG) or polycarbonates or polyols.

7. Press belt according to one of the preceding claims, characterized in that the molar ratio between prepolymer and crosslinker is between 0.9 and 1, 1.

8. Press belt according to one of the preceding claims, characterized in that the polyols are selected from: polyester polyol, in particular polycaprolactone polyol; Polyether polyols, especially polytetramethylene ether glycol (PTMEG), polypropylene glycol (PPG), polyethylene glycol (PEG) or polyhexamethylene ether glycol; Polycarbonate polyol, polyethercarbonate polyol, polybutadiene polyol, ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, polybutylene glycol, 1,4-butanediol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, 4,4'-dihydroxyphenylacetylene (DHPA ), 1,4-dihydroxyethylphenyl diether (HQEE), trimethylol propane (TMP).

9. Press belt according to claim 8, characterized in that the molar mass of the polyols is between 900 and 3000 g / mol.

10. Press belt according to one of the preceding claims, characterized in that the amine is selected from hydrazines, ethylenediamines, diethylenetoluenediamine (DETDA), diethylmethylbenzenediamine (DETDA), methylene-bis-orthochloroaniline (MOCA), dimethylthiotoluene diamine (DMTDA), trimethyleneglycol di (p-) Aminobenzoate) (TMAB), 4,4'-methylenebis (2,6-diethylaniline) (MCDEA), 2,2'-methyliminodiethanol (MDEA), triisopropanolamine (TIPA).

1 1. Press belt according to one of the preceding claims, characterized in that the press belt is composed of several layers, wherein at least the outermost layer comprises a prepolymer mixture according to claim 1.

12. Press belt according to claim 1 1, characterized in that the prepolymer mixture is provided according to claim 1 at least partially, preferably in the edge regions of the outermost layer.

13. Press roll, such as shoe press roll, for a shoe press for dewatering a fibrous web, characterized in that the press roll has at least one press belt according to one of the preceding claims.

Shoe press for dewatering a fibrous web, preferably a paper, board, tissue or pulp web, comprising a press roll and a counter roll, which together form or define a nip, wherein the press roll comprises a rotating press cover, characterized in that the press cover As a press belt according to one of claims 1 to 12 is formed.

15. Use of a press belt according to one of claims 1 to 12 for a press, such as shoe press for dewatering a fibrous web, preferably a paper, board, tissue or pulp web.