DE102011079892A1 - Press cover for shoe press used for dewatering of fibrous web e.g. paper and cardboard, has layer(s) containing crosslinked fluorinated polyurethane and/or fluorinated elastomer - Google Patents

Abstract

A press cover has at least one layer containing crosslinked fluorinated polyurethane and/or fluorinated elastomer.

Description

The present invention relates to a press cover for a press roll, in particular for a press roll of a shoe press for dewatering a fibrous web, in particular a paper, board, tissue or pulp web, which comprises at least one layer containing crosslinked polyurethane and / or elastomer. In addition, the present invention relates to a conveyor belt, in particular for a machine for producing or treating a fibrous web, in particular paper, board or Tissuemaschine, which comprises at least one crosslinked polyurethane and / or elastomer-containing layer. Furthermore, the present invention relates to a press roll comprising such a press jacket, a shoe press comprising such a press roll for dewatering a fibrous web, in particular a paper, board, tissue or pulp web, and a machine for producing or treating a press comprising such a press belt Fiber web, in particular paper, board or tissue machine.

Press rolls are used in a variety of presses and, for example, in the form of shoe rolls in shoe presses, which in turn are used in particular for dewatering fibrous webs, such as paper webs. Such shoe presses are constructed of a shoe roll and a counter roll with a press nip formed therebetween. Shoe rollers consist of a stationary, d. H. non-rotating, pressing element, namely the shoe, and from a circulating the shoe flexible press cover. Usually, the shoe is supported by a yoke carrying this and pressed by hydraulic pressing elements on this rotating press cover. As a rule, an oil film is built up between the shoe and the press cover for lubrication. Due to the concave configuration of the shoe on its opposite side of the backing roll results in a comparatively long press nip, which is about 20 times longer than that of conventional, consisting of two rotating rollers presses.

During operation of the shoe press, a fibrous web is passed through the press nip together with one or two press felts, the liquid emerging from the fibrous web due to the pressure exerted on the fibrous web in the press nip, which contains dissolved and undissolved compounds besides water, such as, for example Fibers, fiber fragments, fillers and / or additives, is temporarily absorbed by the press felt and provided in the press shell surface recesses. After leaving the press nip, the liquid picked up by the press cover is thrown off the press cover before the press cover re-enters the press nip. In addition, the water taken up by the press felt is removed after leaving the press nip with suction elements. Due to the comparatively long press nip because of the concave configuration of the shoe, a substantially better dewatering of the fibrous web is achieved with such a shoe press compared to a press consisting of two rotating rolls, so that the subsequent thermal drying can be correspondingly shorter. In this way, a particularly gentle dewatering of the fibrous web is achieved.

A press cover of such a shoe press must ideally meet a variety of requirements in order to achieve optimum results. On the one hand, such a press cover must be sufficiently flexible to be able to be guided around the shoe. At the same time, the press cover has to be sufficiently stiff so as not to be excessively deformed and deformed under the press load prevailing in the press nip. In addition, a press cover must have high wear resistance, good abrasion resistance, high cracking resistance, good crack growth resistance and high resistance to chemicals, especially water, oil, acids, bases and solvents.

In order to meet these diverse requirements at least partially, such press sleeves are usually constructed of fiber-reinforced polyurethane, ie of a composite material in which a fiber layer or fiber fabric is embedded in a matrix of crosslinked polyurethane. Both single-layer and corresponding multi-layer press jackets are known.

From the EP 2 284 314 A1 a press sheath for a shoe press is known, which is composed of one or more layers of cross-linked polyurethane, is embedded in the fiber fabric, composed. In this case, the crosslinked polyurethane is the reaction product of a prepolymer prepared from a 55 to 100 mole percent p-phenylene diisocyanate-containing isocyanate component and a polyol, and a crosslinker component containing 65 to 100 mole percent of one or more particular polyamines.

In the EP 2 248 944 A1 is described a press cover for a shoe press, which is composed of a layer of cross-linked polyurethane, is embedded in the fiber fabric. The crosslinked polyurethane is the reaction product of a prepolymer consisting of 55 to 100 mol% of p-phenylene diisocyanate, 4,4'-methylene diphenyl diisocyanate or tolylene diisocyanate and a crosslinking component comprising 75 to 99.9 mol% of an aliphatic diol compound having a molecular weight between 62 and 1000, hydroquinone bis-β-hydroxyethyl ether or an organic polyamine compound having a molecular weight between 108 and 1300 and 25 to 0.1 mol% of an aliphatic triol compound having a molecular weight between 92 and 134. In addition, this document discloses a corresponding press cover, for the production of a crosslinking component is used, which 60 to 99.8 mol% of an aliphatic diol compound having a molecular weight between 62 and 1000 or hydroquinone-bis-β-hydroxyethyl ether, 0.1 to 15 mol % of an organic polyamine compound having a molecular weight between 108 and 1300 and 25 to 0.1 mol% of an aliphatic triol compound having a molecular weight between 92 and 134.

Although the above press sleeves have sufficient flexibility and rigidity at the same time, their chemical resistance to water and oil, their abrasion resistance, cracking resistance, crack growth resistance, swelling behavior and resistance to corrosion and hydrolysis are in need of improvement. Particularly important for a press cover is the highest possible chemical resistance, otherwise there is a risk that the polyurethane contained in the press cover is partially depolymerized, which leads to a reduction in mechanical properties with increasing operating time.

Conveyor belts are used inter alia in machines for producing or treating a fibrous web, for example in the press section, to transport the fibrous web through the press nip and then to a transfer point at which the fibrous web is transferred to the subsequent dryer section. Such conveyor belts generally comprise at least one polymer coating providing the paper side of the belt, in which a load-absorbing textile fabric is embedded. Such conveyor belts are for example in the DE 10 2007 055 864 A1 described. In these too, the chemical resistance, in particular to water and oil, the abrasion resistance, the cracking resistance, the crack growth resistance, the swelling behavior, and the resistance to corrosion and hydrolysis, require improvement.

The object of the present invention is therefore to provide a press jacket for a press roll of a shoe press or conveyor belt, wherein the press cover or the conveyor belt high wear resistance, good abrasion resistance, excellent resistance to corrosion and hydrolysis, low friction coefficient, high cracking resistance , a good crack growth resistance, low swelling and a high resistance to chemicals, in particular water, oil, acids, bases and solvents, while being characterized by a sufficiently high flexibility and rigidity.

According to the invention, this object is achieved by providing a press jacket for a press roll, in particular for a press roll of a shoe press for dewatering a fibrous web, in particular a paper, board, tissue or pulp web, or a conveyor belt, in particular for a machine for manufacturing or Treatment of a fibrous web, in particular paper, board or tissue machine, wherein the press cover or the conveyor belt comprises at least one layer containing at least one crosslinked fluorinated polyurethane and / or fluorinated elastomer.

This solution is based on the surprising finding that a press cover or conveyor belt of at least one layer based on crosslinked fluorinated polyurethane and / or fluorinated elastomer not only - in the case of a press jacket - a sufficient flexibility for its use in a shoe press and sufficient at the same time high rigidity, high wear resistance, excellent crack growth resistance and high resistance to cracking, and is characterized in particular by excellent abrasion resistance, low friction, low swelling and high chemical resistance, especially against water, oil, acids, bases and solvents why this / this - in the case of a press jacket - excellent for use in a press roll, in particular in a press roll of a shoe press for dewatering a fibrous web, in particular a paper, cardboard, Tiss ue or pulp web, or - in the case of a conveyor belt - excellent for use, for example, in the press section of a machine for producing or treating a fibrous web, in particular paper, board or Tissuemaschine suitable. Due to the low surface tension, low coefficient of friction, good biological resistance, excellent resistance to corrosion or hydrolysis, low solubility in both polar and non-polar solvents, and high thermal stability of fluoropolymers, the fluorinated polyurethane or fluorinated elastomer content favors the above-mentioned, for Use in a press cover for a press roll a shoe press or conveyor belt advantageous properties.

In principle, all crosslinked fluorinated polyurethanes or fluorinated elastomers can be used as crosslinked fluorinated polyurethane and / or fluorinated elastomer, with good results, in particular with crosslinked fluorinated polyurethanes, being obtained.

In this case, the crosslinked fluorinated polyurethane according to a first particularly preferred embodiment of the present invention is obtainable by a process in which a prepolymer, which is the reaction product of an isocyanate component containing at least one diisocyanate and a polyol component containing at least one polyol, is reacted with at least one fluoropolymer and the reaction product thus obtained is then reacted with a crosslinking component.

According to a second particularly preferred embodiment of the present invention, the crosslinked fluorinated polyurethane is obtainable by a process comprising a prepolymer which is the reaction product of an isocyanate component containing at least one diisocyanate and a polyol component containing at least one polyol with a crosslinking component which contains at least one Crosslinking agent contains at least one fluoropolymer is reacted.

Furthermore, according to another embodiment of the present invention, it is also possible that the crosslinked fluorinated polyurethane is obtainable by a process in which a prepolymer which is the reaction product of at least one diisocyanate-containing isocyanate component and a polyol component containing at least one polyol is at least one Fluoropolymer is reacted and the reaction product thus obtained is then reacted with a crosslinking component which contains in addition to at least one crosslinking agent at least one fluoropolymer.

In all three embodiments mentioned above, it is necessary for the at least one fluoropolymer to contain one, two or more reactive groups. In this context, a reactive group is understood to mean a group which can react with the prepolymer or the at least one crosslinker. Suitable reactive functional groups are in particular hydroxyl groups, but also other reactive functional groups, for example alkoxylated and in particular ethoxylated alcohol groups, carboxylic acid groups, sulfonic acid groups, amine groups, in particular primary, but also secondary amine groups, amide groups, phosphonic acid groups and the like. In this case, the reactive functional groups are or are preferably arranged at the or the terminal ends of the fluoropolymer. Equally well, though less preferably, the fluoropolymer may have one or more than two reactive functional groups, that is, monofunctional or polyfunctional. Regardless of whether the fluoropolymer has one, two or more reactive functional groups, it is particularly preferably a perfluoropolymer.

Preferably, the at least one fluoropolymer is a difunctional fluoropolymer, which for the purposes of the present invention refers to a fluoropolymer containing two reactive functional groups. Most preferably, the fluoropolymer is a difunctional perfluoropolymer.

In a further development of the inventive concept, it is proposed that the at least one fluoropolymer is a fluoropolyether. As stated above, the fluoropolyether may contain one, two or more reactive functional groups. In particular, hydroxyl groups are considered as reactive functional groups, but also other functional groups, such as, for example, carboxylic acid groups, sulfonic acid groups, amine groups, amide groups, phosphonic acid groups and the like. Regardless of whether the fluoropolyether has one, two or more reactive functional groups, it is particularly preferably a perfluoropolyether. The at least one fluoropolymer is very particularly preferably a (per) fluoropolyether terminated with alkoxylated and in particular ethoxylated dialcohol groups or a dihydroxy-terminated (per) fluoropolyether. Surprisingly, the above advantageous properties, in particular an excellent abrasion resistance, a low coefficient of friction, low swelling and a high resistance to chemicals, in particular to water, oil, acids, bases and solvents, can be achieved to a particularly high degree, if the press cover or the conveyor belt a crosslinked fluorinated polyurethane and / or fluorinated elastomer and in particular a fluorinated polyurethane having (per) fluoropolyethergruppen.

Good results are obtained in this embodiment, in particular, when the fluoropolymer is a (per) fluoropolyether according to the following formula (I): R ¹ -QR ² (I), wherein
R ¹ and R ² , independently of one another, are selected from the group consisting of hydrogen, halogens, in particular fluorine, C ₁ -C ₂₀ -alkyl groups, halogenated, in particular fluorinated, C ₁ -C ₂₀ -alkyl groups, halogenated, in particular fluorinated, C ₁ -C ₂₀ perfluoroalkyl groups, COR ³ with R ³ = H, C ₁ -C ₂₀ -alkyl, halogenated C ₁ -C ₂₀ -alkyl or C ₁ -C ₂₀ perfluoroalkyl and preferably H, C ₁ -C ₆ -alkyl, halogenated C ₁ -C ₆ -alkyl or C ₁ -C ₆ -perfluoroalkyl, CO ₂ R ³ with R ³ = H, C ₁ - C ₂₀ alkyl, halogenated C ₁ -C ₂₀ alkyl or C ₁ -C ₂₀ perfluoroalkyl and preferably H, C ₁ -C ₆ alkyl, halogenated C ₁ -C ₆ alkyl or C ₁ -C ₆ perfluoroalkyl, CONR ³ R ⁴ in which R ³ and R ⁴ independently of one another are H, C ₁ -C ₂₀ -alkyl, halogenated C ₁ -C ₂₀ -alkyl or C ₁ -C ₂₀ -perfluoroalkyl and preferably H, C ₁ -C ₆ -alkyl, halogenated C ₁ -C ₆ -alkyl or C ₁ -C ₆ -perfluoroalkyl, SO ₂ R ³ with R ³ = H, C ₁ -C ₂₀ -alkyl, halogenated C ₁ -C ₂₀ -alkyl or C ₁ -C ₂₀ Perfluoroalkyl and preferably H, C ₁ -C ₆ alkyl, halogenated C ₁ -C ₆ alkyl or C ₁ -C ₆ perfluoroalkyl, hydroxy group, alcohol groups, alkoxylated and in particular ethoxylated alcohol groups, primary amine groups, secondary amine groups, preferably CH ₂ NHR ³ in which R ^{3 is} H, C ₁ -C ₂₀ -alkyl, halogenated C ₁ -C ₂₀ -alkyl or C ₁ -C ₂₀ -perfluoroalkyl and preferably H, C ₁ C ₆ alkyl, halogenated C ₁ -C ₆ alkyl or C ₁ -C ₆ perfluoroalkyl, tertiary amine groups preferably CH ₂ NR ³ R ⁴ wherein R ³ and R ^{4 are} independently H, C ₁ -C ₂₀ alkyl , halogenated C ₁ -C ₂₀ alkyl or C ₁ -C ₂₀ perfluoroalkyl and preferably H, C ₁ -C ₆ alkyl, halogenated C ₁ -C ₆ alkyl or C ₁ -C ₆ perfluoroalkyl, carboxylic acid groups, sulfonic acid groups , Phosphonic acid groups and any mixtures of two or more of the foregoing groups, wherein at least one of R ¹ and R ² is selected from the group consisting of hydroxy, alcohol, alkoxylated and especially ethoxylated alcohol groups, primary amine groups, secondary amine groups preferably CH ₂ NHR ³ wherein R ^{3 is} H, C ₁ -C ₂₀ alkyl, ha halogenated C ₁ -C ₂₀ alkyl or C ₁ -C ₂₀ perfluoroalkyl and preferably H, C ₁ -C ₆ alkyl, halogenated C ₁ -C ₆ alkyl or C ₁ -C ₆ perfluoroalkyl, carboxylic acid groups, sulfonic acid groups, Phosphonic acid groups and any mixtures of two or more of the aforementioned groups, and
Q is a fluoropolyether or perfluoropolyether group.

The above (per) fluoropolyether may be a monofunctional or difunctional (per) fluoropolyether. When the (per) fluoropolyether is monofunctional, it has a reactive end group and a non-functional end group, the non-functional end group being preferably selected from the group consisting of hydrogen, halogens, in particular fluoro, C ₁ -C ₂₀ alkyl groups , halogenated, especially fluorinated, C ₁ -C ₂₀ alkyl groups and C ₁ -C ₂₀ perfluoroalkyl groups. However, in this embodiment it is particularly preferred that the (per) fluoropolyether is bifunctional, that is to say has two reactive functional groups and in particular two of the abovementioned reactive functional terminal groups.

• i) Gruppen der allgemeinen Formel (II): -CF₂O-(CF₂CF₂O)_m(CF₂O)_p-CF₂- (II), worin die (CF₂CF₂O)- und die (CF₂O)-Einheiten statistisch entlang der Kette verteilt sind und m/p = 0,2 bis 4 beträgt,
• ii) Gruppen der allgemeinen Formel (III): -CF₂CH₂-(OCF₂CF₂CH₂)_r-OR⁵O-(CH₂CF₂CF₂O)_s-CH₂CF₂- (III), worin R⁵ eine Fluoralkylengruppe mit 1 bis 10 Kohlenstoffatomen ist und r/s = 0,8 bis 1,2 beträgt,
• iii) Gruppen der allgemeinen Formel (IV): -CF₂-(CF₂CF(CF₃)O)_t-(CF₂CF₂O)_u-(CFXO)_vCF₂- (IV), worin die (CF₂CF(CF₃)O)-, (CF₂CF₂O)- und (CFXO)- Einheiten statistisch entlang der Kette verteilt sind, X = F oder CH₃ ist, t/u = 0,6 bis 2,0 beträgt und u/v größer als 10 beträgt
• iv) Gruppen der allgemeinen Formel (V): -CF(CF₃)-(OCF₂CF(CF₃)O))_c-OCF₂-R⁶-CF₂O-(CF(CF₃)CF₂O)_f-CF(CF₃)- (V), worin R⁶ eine Perfluoralkylengruppe mit 1 bis 10 Kohlenstoffatomen ist und c/f = 0,8 bis 1,2 beträgt und
• v) Gruppen der allgemeinen Formel (VI): -(CFR⁷-O)_w- (VI), worin R⁷ eine Alkylen- oder Fluoralkylengruppe mit 1 bis 10 Kohlenstoffatomen ist und w eine ganze Zahl zwischen 1 und 200, bevorzugt zwischen 2 und 100 und besonders bevorzugt zwischen 5 und 30 ist.

The fluorinated radical Q in the general formula (I) is preferably a radical selected from the group consisting of:

• i) Groups of the general formula (II): -CF ₂ O- (CF ₂ CF ₂ O) _m (CF ₂ O) _p -CF ₂ - (II), wherein the (CF ₂ CF ₂ O) and (CF ₂ O) units are randomly distributed along the chain and m / p = 0.2 to 4,
• ii) Groups of the general formula (III): -CF ₂ CH ₂ - (OCF ₂ CF ₂ CH ₂ ) _r -OR ⁵ O- (CH ₂ CF ₂ CF ₂ O) _s -CH ₂ CF ₂ - (III), wherein R ^{5 is} a fluoroalkylene group having 1 to 10 carbon atoms and r / s = 0.8 to 1.2,
• iii) Groups of the general formula (IV): -CF ₂ - (CF ₂ CF (CF ₃ ) O) _t - (CF ₂ CF ₂ O) _u - (CFXO) _v CF ₂ - (IV) wherein the (CF ₂ CF (CF ₃ ) O), (CF ₂ CF ₂ O) and (CFXO) units are randomly distributed along the chain, X = F or CH ₃ , t / u = 0.6 is up to 2.0 and u / v is greater than 10
• iv) Groups of the general formula (V): -CF (CF ₃ ) - (OCF ₂ CF (CF ₃ ) O)) _c -OCF ₂ -R ⁶ -CF ₂ O- (CF (CF ₃ ) CF ₂ O) _f -CF (CF ₃ ) - (V ) wherein R ^{6 is} a perfluoroalkylene group having 1 to 10 carbon atoms and c / f = 0.8 to 1.2, and
• v) Groups of the general formula (VI): - (CFR ⁷ -O) _w - (VI), wherein R ^{7 is} an alkylene or fluoroalkylene group having 1 to 10 carbon atoms and w is an integer between 1 and 200, preferably between 2 and 100 and more preferably between 5 and 30.

In particular, good results are obtained when in the general formula (I) at least one of the radicals R ¹ and R ^{2 is} a radical according to the general formula (VI): HO (R ⁸ O) _n -CH ₂ - (VI), wherein
R ^{8 is} a C ₁ -C ₁₀ -alkyl group, preferably a C ₁ -C ₅ -alkyl group, more preferably a C ₁ -C ₃ -alkyl group and most preferably CH ₂ CH ₂ - and
- n is an integer between 0 and 5.

These fluoropolyethers are therefore those with two terminal reactive functional groups.

In a further development of the inventive concept, it is proposed that the at least one fluoropolymer is a (per) fluoropolyether according to the general formula (I), in which:
R ¹ and R ^{2 are} each HO (CH ₂ CH ₂ O) _n -CH ₂ - and
Q is a group according to the general formula (II), where m / p = 1 to 3 and n is an integer between 1 and 5, or according to the general formula (VI), where w is an integer between 5 and 30 is.

In a further development of the inventive concept, it is proposed that the fluoropolymer has a fluorine content of between 1 and 99% by weight, preferably between 50 and 70% by weight and particularly preferably between 55 and 65% by weight.

Further, it is preferable that the fluoropolymer has a weight average molecular weight between 100 and 5,000 g / mol, and preferably between 1,000 and 2,000 g / mol.

Basically, the present invention is not particularly limited in the amount of the fluoropolymer contained in the crosslinked fluorinated polyurethane. However, the abovementioned properties of the pressed casing according to the invention are achieved to a high degree if the crosslinked fluorinated polyurethane contains 0.1 to 30% by weight, preferably 0.1 to 10% by weight and more preferably 0.1 to 2% by weight. Contains% fluoropolymer.

As isocyanate component, the at least one crosslinked fluorinated polyurethane may contain, for example, a compound selected from among methylenediphenyl diisocyanate (MDI), polymeric diphenylmethane diisocyanate (PMDI), tolylene diisocyanate (TDI), naphthylene diisocyanate (NDI), hexamethylene diisocyanate (HDI), p-phenylene diisocyanate (PDI). , Isophorone diisocyanate (IPDI), 4,4'-diisocyanatodicyclohexylmethane (H12MDI) and any combination of two or more of the above compounds.

Further, in the at least one crosslinked fluorinated polyurethane as the polyol component, for example, a compound selected from the group consisting of polyester polyols, polyether polyols, polycarbonate polyols, polyether carbonate polyols, polyalkylene glycols, polybutadiene polyols, and any combination of two or more of the above compounds may be used.

In addition, all crosslinkers known for this purpose, in particular polyol and amine crosslinkers, can be used as crosslinkers.

Examples of suitable amine crosslinkers are those selected from the group consisting of 4,4'-methylenebis (2,6-diethyl-3-chloroaniline), 4,4'-methylenebis (2-chloroaniline ), 4,4'-methylenebis (2-ethylbenzylamine), 4,4'-methylenebis (2,6-diethylaniline), 4,4'-methylenebis (cyclohexylamine), diethylmethylbenzenediamine, 4 , 4'-Diaminodicyclohexylmethane, 4,4'-diamino-3,3'-dimethyl-dicyclohexylmethane, 4,4'-diaminodiphenylmethane, 3,5-dimethylthio-tolyl-diamine, 3,5-dimethyltolyl-2,4-diamine , 3,5-Dimethyltolyl-2,6-diamine, polytetramethylene oxide di-p-aminobenzoate, poly (tetramethylene-3-methyltetramethylene ether) glycol bis (4-aminobenzoate), trimethylene-bis (4-aminobenzoate), isobutyl 4-chloro-3,5-diaminobenzoate, tetramethylammonium bromide, ethylenediamine, hydrazine, hexamethylenediamine, o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, 1,4-diaminocyclohexane, 1,2-diaminocyclohexane, isophoronediamine, diethyltoluenediamine, 3.5 Dimethylthio-2,4-toluenediamine, 3,5-dimethylthio-2,6-toluene iamin and any mixtures of two or more of the aforementioned compounds.

In addition to the amine crosslinker or in place of the amine crosslinker, the crosslinker component used to crosslink the HDI prepolymer may contain at least one polyol crosslinker. In particular, good results are obtained when the at least one polyol is selected from the group consisting of ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, polybutylene glycol, 1,4-butanediol, 1,3-propanediol, 1,5-pentanediol, 1,6-hexanediol, polyethylene glycol, N-N'-bis (2-hydroxypropylaniline), di- (8-hydroxyethyl) ether, bis (2-hydroxyethyl) ether, triols, polytetrahydrofurans, and any mixtures of two or more consists of the above compounds.

In order to initiate the crosslinking reaction, it is further preferred that the crosslinker component used for crosslinking the prepolymer contains at least one catalyst in addition to the polyol crosslinker and / or amine crosslinker. In principle, all can be used as catalyst for initiating the crosslinking reaction between a prepolymer an isocyanate and a polyol and a crosslinker suitable catalysts are used, such as organometallic compounds and / or tertiary amines. For example, organometallic compounds of zinc, cobalt, bismuth, mercury, cadmium or potassium are particularly suitable for this purpose.

In a further development of the inventive idea, it is proposed that the crosslinking component used for crosslinking the prepolymer contains, in addition to the polyol having a weight-average molecular weight of more than 1000 g / mol and the optional amine crosslinker, at least one catalyst selected from the group consisting of dibutyltin dilaurate, Stannous octoate, dioctyltin diacetate, dibutyltin mercaptide, dibutyltin oxide, dimethyltin mercaptide, dioctyltin mercaptide, dimethyltin carboxylate, bis (2-dimethylaminoethyl) ether, alkylmorpholines, 1,4-diazabicyclooctane, N, N-alkylbenzylamine, 1,2-dimethylimidazole, N, N-dimethylcyclohexylamine, triethylenediamine , N, N, N ', N'-tetramethylenediamine, dioctyldicarboxylate, dioctyltin dimercaptide and any mixtures of two or more of the foregoing.

According to a further preferred embodiment of the present invention, the prepolymer has an isocyanate content of between 4 and 20% by weight and more preferably between 5 and 14% by weight.

In principle, all elastomers can be used as elastomer in the press cover or conveyor belt according to the invention, such as preferably an epoxy elastomer.

Furthermore, it is preferred that in the at least one previously described crosslinked fluorinated polyurethane and / or fluorinated elastomer-containing layer of the press jacket according to the invention or of the conveyor belt according to the invention a reinforcing fiber structure, preferably in the form of a fiber fabric or a fiber fabric is included. In this case, the at least one crosslinked fluorinated polyurethane and / or fluorinated elastomer forms the matrix in which the fiber fabric or fiber fabric is embedded.

In principle, it is also possible that at least part of the polymer matrix consists of foam.

The press jacket according to the invention can be designed as a single-layer or multilayer. When the press cover is made multi-layered, it is preferable that at least the outer layer is composed as described above. Alternatively, it is also possible that the composition composed as described above is contained only in individual regions of the press jacket, such as at the shoe edge.

Another object of the present invention is a press roll, in particular shoe roll, which comprises a press cover described above.

In addition, the present invention relates to a shoe press, in particular for dewatering a fibrous web, in particular a paper, board, tissue or pulp web, which comprises a shoe roll described above.

Furthermore, the present invention relates to a machine for producing or treating a fibrous web, in particular paper, board or tissue machine, which comprises a conveyor belt described above. Preferably, the conveyor belt comprises a polymer coating of the above-described crosslinked polyurethane, in which a load-absorbing textile fabric is embedded. In addition to the conveyor belt, the machine for producing or treating a fibrous web, in particular paper, cardboard or Tissuemaschine, of course, include a shoe press for dewatering a fibrous web, which comprises a shoe roll described above.

Hereinafter, the present invention will be described purely by way of example with reference to advantageous embodiments and with reference to the accompanying drawings.

Showing:

1 a schematic view of a shoe press with a press cover according to an embodiment of the present invention and

2 a schematic view of a press shoe comprising a shoe press and a conveyor belt press section of a paper machine according to an embodiment of the present invention.

In the 1 is a shoe press 10 shown which a shoe roll 12 and a counter roll 14 includes. While the counter roll 14 consists of a rotating cylindrically shaped roller is the shoe roll 12 from a shoe 16 , a standing yoke carrying it 18 and a press cover 20 composed. This is the shoe 16 through the yoke 18 supported and hydraulic pressing elements (not shown) on this rotating press cover 20 pressed. Due to the concave design of the shoe 16 at its counter-roller 14 opposite side results in a comparatively long press nip 22 ,

The shoe press 10 is particularly suitable for dewatering fibrous webs 24 like paper webs. In the operation of the shoe press is a fibrous web 24 with one or two press films 26 . 26 ' through the press nip 22 led, which due to the in the press nip 22 on the fibrous web 24 applied pressure from the fibrous web 24 leaking liquid, which in addition to water dissolved and undissolved compounds, such as fibers, fiber fragments, fillers and / or additives contains, of the or the press felts 26 . 26 ' and temporarily received by depressions (not shown) provided in the press shell surface. After leaving the press nip 22 becomes that of the press cover 20 absorbed liquid from the press cover 20 thrown off before the press cover 20 again in the press gap 22 entry. In addition, that of the press felt 26 . 26 ' absorbed water after leaving the press nip 22 removed with suction elements.

Because of the concave design of the shoe 16 at its counter-roller 14 opposite side comparatively long press nip 22 is with such a shoe press 10 Compared to a press consisting of two rotating rollers, a considerably better dewatering of the fibrous web 24 achieved, so that the subsequent thermal drying can be correspondingly shorter. In this way, a particularly gentle drainage of the fibrous web 24 reached.

In the 2 a section of a press section of a paper machine is shown, which is a shoe press 10 includes. This includes the shoe press 10 as well as in the 1 illustrated embodiment, a press cover 20 and a pressing element or shoe 16 having shoe roll 12 and a counter roll 14 , being between the shoe 16 and the counter roll 14 a press nip is formed. In addition, this part of the paper machine comprises two suction rolls 28 . 28 ' and two guide rollers 30 . 30 ' , In the operation of the paper machine, a through the suction rollers 28 . 28 ' led felt 26 that is at the suction roller 28 the fibrous web 24 receives, led by the press nip. In addition, below the fibrous web 24 leading felt 26 a through the guide rollers 30 . 30 ' Guided conveyor belt or transfer belt 32 passed through the press nip, the transfer belt 32 in the press nip the fibrous web 24 from the felt 26 takes over and over the guide roller 30 ' removed from the press nip. Because of in the press nip on the fibrous web 24 pressure exerted out of the fibrous web liquid, which in addition to water dissolved and undissolved compounds, such as fibers, fiber fragments, fillers and / or additives, which contains the felt 26 and is temporarily received by depressions provided in the press shell surface. After leaving the press nip that of the press cover 20 absorbed liquid from the press cover 20 thrown off before the press cover 20 again enters the press nip. In addition, that of the felt 26 absorbed water after leaving the press nip with on the suction roll 28 ' intended suction elements removed. Because of the concave design of the shoe 16 comparatively long press nip is compared with a press consisting of two rotating rollers a much better drainage of the fibrous web with such a shoe press 24 achieved, so that the subsequent thermal drying can be correspondingly shorter. In this way, a particularly gentle drainage of the fibrous web 24 reached.

Hereinafter, the present invention will be explained with reference to the present invention illustrative, but not limiting examples and a comparative example.

example 1

• Der so hergestellte Pressmantel wies die nachfolgenden Eigenschaften auf:
• Shore A-Härte: 94,5,
• Abrieb vor Wasserlagerung: 25 mm³,
• Abrieb nach 150 Stunden Wasserlagerung bei 95°C: 32 mm³,
• Shore A-Härte nach 150 Stunden Wasserlagerung bei 95°C: 91,
• Risswachstum bei 1. Mio. Belastungen in Biegewechselmaschine: 0,2 mm,
• Quellung in Wasser nach 72 Stunden bei 80°C: 2,8 %.

A 5 mm thick pressmold was prepared by using a prepolymer of MDI and PTMEG (polytetramethylene ether glycol) having a weight average molecular weight of about 1,300 g / mol with a crosslinker mixture consisting of 20 wt% of a mixture of PTMEG with a weight average Molecular weight of about 2,000 g / mol and perfluoropolyether having ethoxylated alcohol end groups and 80 wt .-% 1,4-butanediol consisted crosslinked. The ratio was 1.0. In addition, the amount of ethoxylated alcohol perfluoropolyethers based on the total amount of the reaction mixture was 0.5% by weight.

• The pressed shell produced in this way had the following properties:
• Shore A hardness: 94.5,
• Abrasion before water storage: 25 mm ³ ,
• Abrasion after 150 hours of water storage at 95 ° C: 32 mm ³ ,
• Shore A hardness after 150 hours of water storage at 95 ° C: 91,
• Crack growth at 1. million loads in bending machine: 0.2 mm,
• Swelling in water after 72 hours at 80 ° C: 2.8%.

Example 2

A press cover 5 mm thick was prepared as described in Example 1 except that the reaction mixture contained 1.0% by weight of ethoxylated alcohol-terminated perfluoropolyethers based on the total amount of the reaction mixture.

• Shore A-Härte: 94,5,
• Abrieb vor Wasserlagerung: 23 mm³,
• Abrieb nach 150 Stunden Wasserlagerung bei 95°C: 27 mm³,
• Shore A-Härte nach 150 Stunden Wasserlagerung bei 95°C: 91,
• Risswachstum bei 1. Mio. Belastungen in Biegewechselmaschine: 0,5 mm,
• Quellung in Wasser nach 72 Stunden bei 80°C: 2,6 %.

The pressed shell produced in this way had the following properties:

• Shore A hardness: 94.5,
• Abrasion before water storage: 23 mm ³ ,
• Abrasion after 150 hours of water storage at 95 ° C: 27 mm ³ ,
• Shore A hardness after 150 hours of water storage at 95 ° C: 91,
• Crack growth at 1. million loads in bending machine: 0.5 mm,
• Swelling in water after 72 hours at 80 ° C: 2.6%.

Comparative example

A press cover with a thickness of 5 mm was prepared as described in Example 1, except that the crosslinker mixture contained no perfluoropolyether having ethoxylated alcohol end groups.

• Shore A-Härte: 93,5,
• Abrieb vor Wasserlagerung: 28 mm³,
• Abrieb nach 150 Stunden Wasserlagerung bei 95°C: 43 mm³,
• Shore A-Härte nach 150 Stunden Wasserlagerung bei 95°C: 90,
• Risswachstum bei 1. Mio. Belastungen in Biegewechselmaschine: 0,2 mm,
• Quellung in Wasser nach 72 Stunden bei 80°C: 2,6 %.

The pressed shell produced in this way had the following properties:

• Shore A hardness: 93.5,
• Abrasion before water storage: 28 mm ³ ,
• Abrasion after 150 hours of water storage at 95 ° C: 43 mm ³ ,
• Shore A hardness after 150 hours of water storage at 95 ° C: 90,
• Crack growth at 1. million loads in bending machine: 0.2 mm,
• Swelling in water after 72 hours at 80 ° C: 2.6%.

LIST OF REFERENCE NUMBERS

10

 shoe press

12

 shoe roll

14

 backing roll

16

 Shoe / compression member

18

 standing yoke

20

 press cover

22

 press nip

24

 Fibrous web

26, 26 '

 press felt

28, 28 '

 suction rolls

30, 30 '

 deflection rollers

32

 Conveyor / transfer belt

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2284314 A1 [0006]
• EP 2248944 A1 [0007]
• DE 102007055864 A1 [0009]

Claims (16)

Press cover for a press roll, in particular for a press roll of a shoe press for dewatering a fibrous web, in particular a paper, board, tissue or pulp web, or conveyor belt, in particular for a machine for producing or treating a fibrous web, in particular paper, cardboard or Tissue machine, wherein the press cover or the conveyor belt comprises at least one layer containing at least one crosslinked fluorinated polyurethane and / or fluorinated elastomer. Press cover or conveyor belt according to claim 1, characterized in that the crosslinked fluorinated polyurethane is obtainable by a process in which a prepolymer, which is the reaction product of at least one diisocyanate-containing isocyanate component and a polyol component containing at least one polyol, is reacted with at least one fluoropolymer and then reacting the resulting reaction product with a crosslinker component. Press cover or conveyor belt according to claim 1, characterized in that the crosslinked fluorinated polyurethane is obtainable by a process in which a prepolymer, which is the reaction product of an isocyanate component containing at least one diisocyanate and a polyol component containing at least one polyol, with a crosslinking component, which in addition at least one crosslinker contains at least one fluoropolymer is reacted. Press cover or conveyor belt according to claim 2 or 3, characterized in that the at least one fluoropolymer contains one, two or more reactive groups, which are preferably selected from the group consisting of hydroxyl groups, alkoxylated and preferably ethoxylated alcohol groups, carboxylic acid groups, sulfonic acid groups, amine groups, Amide groups, phosphonic acid groups and mixtures of two or more of the aforementioned groups. Press cover or conveyor belt according to claim 4, characterized in that the at least one fluoropolymer is a bifunctional perfluoropolymer. Press cover or conveyor belt according to at least one of claims 2 to 5, characterized in that the at least one fluoropolymer is a (per) fluoropolyether and according to the general formula (I): R ¹ -QR ² (I), wherein R ¹ and R ² , independently of one another, are selected from the group consisting of hydrogen, halogens, in particular fluorine, C ₁ -C ₂₀ -alkyl groups, halogenated, in particular fluorinated, C ₁ -C ₂₀ -alkyl groups, halogenated, in particular fluorinated, C ₁ -C ₂₀ perfluoroalkyl, COR ³ with R ³ = H, C ₁ -C ₂₀ alkyl, halogenated C ₁ -C ₂₀ alkyl or C ₁ -C ₂₀ perfluoroalkyl and preferably H, C ₁ -C _6- alkyl, halogenated C ₁ -C ₆ -alkyl or C ₁ -C ₆ -perfluoroalkyl, CO ₂ R ³ with R ³ = H, C ₁ -C ₂₀ -alkyl, halogenated C ₁ -C ₂₀ -alkyl or C ₁ -C ₂₀ perfluoroalkyl and preferably H, C ₁ -C ₆ alkyl, halogenated C ₁ -C ₆ alkyl or C ₁ -C ₆ perfluoroalkyl, CONR ³ R ⁴ wherein R ³ and R ^{4 are} independently H, C ₁ C ₂₀ alkyl, halogenated C ₁ -C ₂₀ alkyl or C ₁ -C ₂₀ perfluoroalkyl and preferably H, C ₁ -C ₆ alkyl, halogenated C ₁ -C ₆ alkyl or C ₁ -C ₆ perfluoroalkyl are SO ₂ R ³ with R ³ = H, C ₁ -C ₂₀ alkyl, halogenated C ₁ -C ₂₀ alkyl or C ₁ -C ₂₀ perfluoroalkyl and preferably H, C ₁ -C ₆ alkyl, halogenated C ₁ -C ₆ alkyl or C ₁ -C ₆ perfluoroalkyl, hydroxy group, alcohol groups, alkoxylated and in particular ethoxylated alcohol groups, primary amine groups, secondary amine groups preferably CH ₂ NHR ³ in which R ^{3 is} H, C ₁ -C ₂₀ -alkyl, halogenated C ₁ -C ₂₀ -alkyl or C ₁ -C ₂₀ -perfluoroalkyl and preferably H, C ₁ -C ₆ -alkyl, halogenated C ₁ - C ₆ alkyl or C ₁ -C ₆ perfluoroalkyl, tertiary amine groups preferably CH ₂ NR ³ R ⁴ wherein R ³ and R ^{4 are} independently H, C ₁ -C ₂₀ alkyl, halogenated C ₁ -C ₂₀ alkyl or C ₁ -C ₂₀ perfluoroalkyl and preferably H, C ₁ -C ₆ alkyl, halogenated C ₁ -C ₆ alkyl or C ₁ -C ₆ perfluoroalkyl, carboxylic acid groups, sulfonic acid groups, phosphonic acid groups and any mixtures of two or more of wherein at least one of R ¹ and R ² is selected from the group consisting of hydroxy group, alcohol groups, alkoxylated and in particular ethoxylated alcohol groups, primary amine groups, secondary amine groups preferably CH ₂ NHR ³ in which R ^{3 is} H, C ₁ -C ₂₀ -alkyl, halogenated C ₁ -C ₂₀ -alkyl or C ₁ -C ₂₀ -perfluoroalkyl and preferably H, C C ₁ -C ₆ alkyl, halogenated C ₁ -C ₆ alkyl or C ₁ -C ₆ perfluoroalkyl, carboxylic acid groups, sulfonic acid groups, phosphonic acid groups and any mixtures of two or more of the foregoing groups, and Q is a fluoropolyether or perfluoropolyether group. Press cover or conveyor belt according to claim 6, characterized in that in the general formula (I) the radical Q is selected from the group consisting of i) groups of the general formula (II) -CF ₂ O- (CF ₂ CF ₂ O) _m (CF ₂ O) _p -CF ₂ - (II) wherein the (CF ₂ CF ₂ O) and (CF ₂ O) units are randomly distributed along the chain and m / p = 0.2 to 4, ii) groups of the general formula (III) -CF ₂ CH ₂ - (OCF ₂ CF ₂ CH ₂ ) _r -OR ⁵ O- (CH ₂ CF ₂ CF ₂ O) _s -CH ₂ CF ₂ - (III) wherein R ^{5 is} a fluoroalkylene group having 1 to 10 carbon atoms and r / s = 0.8 to 1.2, iii) groups of the general formula (IV) -CF ₂ - (CF ₂ CF (CF ₃ ) O) _t - (CF ₂ CF ₂ O) _u - (CFXO) _v CF ₂ - (IV) wherein the (CF ₂ CF (CF ₃ ) O), (CF ₂ CF ₂ O) and (CFXO) units are randomly distributed along the chain, X = F or CH ₃ , t / u = 0.6 is up to 2.0 and u / v is greater than 10 iv) groups of general formula (V) -CF (CF ₃ ) - (OCF ₂ CF (CF ₃ ) O)) _c -OCF ₂ -R ⁶ -CF ₂ O- (CF (CF ₃ ) CF ₂ O) _f -CF (CF ₃ ) - (V ) wherein R ^{6 is} a perfluoroalkylene group having 1 to 10 carbon atoms and c / f = 0.8 to 1.2 and v) groups of the general formula (VI) - (CFR ⁷ -O) _w - (VI) wherein R ^{7 is} an alkylene or fluoroalkylene group having 1 to 10 carbon atoms and w is an integer between 1 and 200, preferably between 2 and 100 and more preferably between 5 and 30. Press cover or conveyor belt according to claim 6 or 7, characterized in that in the general formula (I) at least one of the radicals R ¹ and R ^{2 is} a radical according to the general formula (VI): HO (R ⁸ O) _n -CH ₂ - (VI), wherein R ^{8 is} a C ₁ -C ₁₀ alkyl group, preferably a C ₁ -C ₅ alkyl group, more preferably a C ₁ -C ₃ alkyl group and most preferably CH ₂ CH ₂ - and n is an integer between 0 and 5 is. Press cover or conveyor belt according to at least one of Claims 6 to 8, characterized in that the at least one fluoropolymer is a (per) fluoropolyether according to the general formula (I) in which: R ¹ and R ^{2 are} each HO (CH ₂ CH ₂ O) _{n is} -CH ₂ - and Q is a group according to the general formula (II), wherein m / p = 1 to 3 and n is an integer between 1 and 5, or according to the general formula (VI), where w is a integer between 5 and 30 is. Press cover or conveyor belt according to at least one of claims 2 to 9, characterized in that the fluoropolymer has a fluorine content between 1 and 99 wt .-%, preferably between 50 and 70 wt .-% and particularly preferably between 55 and 65 wt .-% , Press cover or conveyor belt according to at least one of claims 2 to 10, characterized in that the fluoropolymer has a weight average molecular weight between 100 and 5,000 g / mol and preferably between 1,000 and 2,000 g / mol. Press cover or conveyor belt according to at least one of claims 2 to 11, characterized in that the crosslinked fluorinated polyurethane 0.1 to 30 wt .-%, preferably 0.1 to 10 wt .-% and particularly preferably 0.1 to 2 wt. - contains% fluoropolymer. Press cover or conveyor belt according to at least one of claims 2 to 12, characterized in that the isocyanate component contains a compound which is selected from the group consisting of methylenediphenyl diisocyanate, polymeric diphenylmethane diisocyanate, tolylene diisocyanate, naphthylene diisocyanate, hexamethylene diisocyanate, p-phenylene diisocyanate, isophorone diisocyanate, 4, 4'-diisocyanatodicyclohexylmethane and any combination of two or more of the above compounds, and the polyol component contains a compound selected from the group consisting of polyester polyols, polyether polyols, polycarbonate polyols, polyethercarbonate polyols, polyalkylene glycols, polybutadiene polyols, and any combinations of two or more consists of the above compounds. Press cover or conveyor belt according to at least one of the preceding claims, characterized in that in the at least one layer, the at least one crosslinked fluorinated polyurethane and / or fluorinated elastomer forms the matrix in which a fiber fabric or a fiber fabric is embedded. Shoe press for dewatering a fibrous web, in particular a paper, board, tissue or pulp web, which has a Press cover according to at least one of the preceding claims comprising press roller. Machine for producing or treating a fibrous web, in particular a paper, board or tissue machine, which comprises a conveyor belt according to at least one of claims 1 to 14.

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