DK164125B

DK164125B - Flat, liquid-permeable device and a method for production of such a device

Info

Publication number: DK164125B
Application number: DK522386A
Authority: DK
Inventors: Seppo Sorsa
Original assignee: Stowe Woodward Finland Oy
Priority date: 1985-03-01
Filing date: 1986-10-31
Publication date: 1992-05-11
Also published as: DE3674402D1; EP0250421B1; WO1986005219A1; DK164125C; AU5583086A; SU1671164A3; FI850844A0; CA1295866C; FI75893B; AU575474B2; DK522386A; FI850844L; EP0250421A1; FI75893C; BR8607073A; JPS62502347A; DK522386D0

Description

iin

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Opfindelsen angår et væskegennemtrængeligt pressef i 1 tbånd eller pressesibånd af den i krav l's indledning angivne type.The invention relates to a liquid-permeable press belt in a 1 or 1 belt press of the type specified in the preamble of claim 1.

Indretningen ifølge opfindelsen anvendes primært som en pres-5 sefilt, men kan også anvendes som f.eks. en pressevire.The device according to the invention is used primarily as a press felt, but can also be used as e.g. a press wire.

I en papirfremstillingsmaskine udtrækkes vand i tre forskellige sektioner f.eks. i viresektionen ved filtrering, i pressesektionen ved vådpresning og i tørresektionen ved fordamp-10 ning. Ud fra en økonomisk betragtning i forbindelse med papirfremstilling er det vigtigt, at banen afvandes så grundigt som muligt før den når frem til tørresektionen.In a papermaking machine, water is extracted in three different sections e.g. in the wire section by filtration, in the press section by wet pressing and in the dry section by evaporation. From the economic point of view of paper making, it is important that the web is dewatered as thoroughly as possible before reaching the drying section.

I papirfremsti 11ingsmaskinens viresektion, dvs. i formeenhe-15 den, udtrækkes så meget vand som muligt fra papirmassen ved brug af en vire. Ved en vire menes et endeløst vævet stofbånd, hvorigennem vandet filtreres fra papirmassen. Virerne er normal fremstillet af phosphor-bronce eller en syntetisk fiber.In the papermaking machine wire section, i.e. in the molding unit, as much water as possible is extracted from the pulp using a wire. By a wire is meant an endless woven fabric band through which the water is filtered from the pulp. The wires are normally made of phosphorus bronze or a synthetic fiber.

20 Den fiberbane, som er blevet tildannet i viresektionen i pa pirfremstillingsmaskinen, har stadigvæk et højt fugtighedsind-hold, som reduceres i papirfremsti 11 ingsmaskinens vådpresse ved at presse banen sammen med en eller flere pressefilte imellem valser. Vådpresningens hovedfunktion er således at af-25 vande banen, men dens virkning er også at komprimere banen og styrke den, så at den opnår tilfredsstillende vådstyrke. Banens tilstrækkelige vådstyrke er en forudsætning for, at den kan bevæges uden at gå i stykker fra pressesektionen til tørresektionen og yderligere fra den ene tørretromle til den næ-30 ste. I vådpressen er det muligt at anvende valser af forskellige typer, såsom glatte, perforerede, rillede eller belagte valser. Det er også muligt at anvende en pressevire imellem pressefilten og valseoverfladen for at forbedre afvandingsevnen og eliminere mærkning af papiret ved hjælp af valsen.The fiber web formed in the wire section of the pie making machine still has a high moisture content which is reduced in the papermaking machine's wet press by pressing the web together with one or more press felt between rollers. The main function of the wet pressing is thus to dewater the web, but its effect is also to compress the web and strengthen it so that it achieves satisfactory wet strength. The web's sufficient wet strength is a prerequisite for it to move without breaking from the press section to the drying section and further from one dryer to the next. In the wet press it is possible to use rollers of various types, such as smooth, perforated, grooved or coated rolls. It is also possible to apply a press wire between the press felt and the roller surface to improve dewatering ability and eliminate marking of the paper by the roller.

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Pressefiltens primære funktion er at optage det vand, der udtrækkes fra banen. Det er også filtens funktion af understøtteThe primary function of the press felt is to absorb the water extracted from the web. It is also the felt's function of support

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2 banen i pressen og at beskytte den over for beskadigelse heri. Pressefiltens struktur spiller en afgørende rolle for papirets endelige kvalitet. En effektivt virkende pressefilt skal nødvendigvis have god afvandingsevne, mekanisk styrke, lang 5 brugstid og evne til at bidrage til f remst i Ilingen af papir med en ensartet kvalitet uden mærker.2 the press in the press and to protect it from damage herein. The structure of the press felt plays a crucial role in the final quality of the paper. Effective press felt must necessarily have good dewatering ability, mechanical strength, long working life and ability to contribute to the production of paper of uniform quality without marks.

Generelt set anvendes nålefilte med et højt indhold af syntetiske fibre som pressefilt. Disse syntetiske fibre er typisk 10 polyamidfibre, polyesterfibre og polyacrylnitrilfibre. I de fleste filte findes der et vatteret lag, som er fastgjort til basisstoffet. Egenskaberne ved en komplet filt kan reguleres ved brug af fibre af forskellig finhed og af forskellige råmaterialer i den vat, der er nålet til filten. Det er muligt 15 at give filten de ønskede egenskaber ved at kombinere forskellige typer af vatlag. I filte af denne type er det et problem at opnå tilstrækkelig glathed. Der er blevet gjort forskellige forsøg for at forbedre filtenes glathed, f.eks. ved fastgørelse af et tyndt lag af finere fibre oven på den side af fi 1 — 20 ten, der vender ind i mod papirbanen.In general, needle felt with a high content of synthetic fibers is used as press felt. These synthetic fibers are typically 10 polyamide fibers, polyester fibers and polyacrylonitrile fibers. In most blankets there is a quilted layer which is attached to the base fabric. The properties of a complete felt can be regulated by the use of fibers of different fineness and of different raw materials in the cotton felt needle. It is possible to give the felt the desired properties by combining different types of cotton wool layers. In blankets of this type, it is a problem to obtain sufficient smoothness. Various attempts have been made to improve the smoothness of the felt, e.g. by attaching a thin layer of finer fibers on top of the side of the fi 1-20 facing into the paper web.

Pressefilten har en afgørende virkning på afvandingen, og derfor er dens kvalitet en meget vigtig faktor. Generelt set er det formålet at anvende usammentrykkelige, stive filte med en 25 åben struktur. En filt, der er for åben, kan imidlertid frembringe ugunstige mønstre i banen og en ujævn fordeling af tryk på banens fibre.The press felt has a decisive effect on the drainage and therefore its quality is a very important factor. Generally, the purpose is to use incompressible rigid blankets with an open structure. However, a felt that is too open can produce unfavorable patterns in the web and an uneven distribution of pressure on the web's fibers.

De filte der anvendes nu om dage og som helt eller delvis er 30 fremstillet af syntetiske fibre har en forholdsvis dårlig evne til at modstå sammentrykning, og som følge heraf mister de deres elasticitet og de sammenpresses, hvilket reducerer deres afvandingsevne. Også tilstoppende stoffer, såsom fibre, fremmer sammenpresningen af filten og derved forkortes den økono-35 misk egnede brugstid for filten. På grund af ovennævnte ulemper må der tages særlige hensyn til vedligeholdelsen af filtene, og de må udskiftes forholdsvis ofte. I de papirfremstil-The felt used nowadays and which are made in whole or in part of synthetic fibers has a relatively poor ability to withstand compression and, as a result, lose their elasticity and compress, reducing their dewatering ability. Also, clogging substances, such as fibers, promote the compression of the felt and thereby shorten the economically suitable useful life of the felt. Due to the aforementioned disadvantages, special care must be taken in the maintenance of the blankets and they must be replaced fairly often. In the paper making

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3 1 ingsmaskiner, der anvendes nu om dage, anvendes der kontinuerligt arbejdende filt-rengøringsanlæg, hvilke anlæg omfatter forskellige filtvedligeholdelsesindretninger, såsom tryksprøjter og sugespalter, der strækker sig hen over viren.3 1 sewing machines nowadays are used continuously operating felt cleaning systems which include various felt maintenance devices such as pressure sprays and suction slots extending across the wire.

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Fra finsk patentansøgning nr. 810884 kendes en indretning, der anvendes som en vire eller en filt. Denne indretning omfatter en filmdel, som har kanaler, der strækker igennem filmen, og som er fremstillet ved hjælp af 1 aserstrå ler, samt en foΓΙΟ stærkn i ngsdel som er kombi neret med filmdelen, og som består af stof, som omfatter stabelfibre. I en indretning af denne type kan tilstopningen af kanalerne og stofferne også udgøre et problem.Finnish patent application No. 810884 discloses a device which is used as a wire or a felt. This device comprises a film portion which has channels extending through the film and which is manufactured by means of 1 Azer beam, as well as a foil reinforcing member combined with the film portion and consisting of fabric comprising staple fibers. In a device of this type, the clogging of the ducts and fabrics can also be a problem.

15 Fra tysk patentskrift nr. 628980 kendes dannelsen af en si, som kan anvendes til afvanding af papirmasse, og som i modsætning til konventionelle metalsier fremstilles af vulkaniseret naturlig eller syntetisk gummi. Denne si har huller med voksende tværsm' tsarea 1.15 German Patent No. 628980 discloses the formation of a sieve which can be used for dewatering pulp and which, unlike conventional metal sieves, is made of vulcanized natural or synthetic rubber. This screen has holes with growing cross section 1.

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Fra europæisk patentansøgning nr. 0103376 kendes et papirtørringsbånd fortrinsvis af metal, men der er også mulighed for at fremstille det af plastdug, hvis der skal anvendes forholdsvis lave temperaturer i tørreren. Båndets perforering 25 fremstilles ved mekanisk forbehandling såsom udstansning ved hjælp af mekaniske midler eller laser. Båndets tykkelse er fra 0,1 til 0,15 mm.From European Patent Application No. 0103376, a paper drying tape is preferably known from metal, but it is also possible to make it from plastic cloth if relatively low temperatures are to be used in the dryer. The tape perforation 25 is produced by mechanical pretreatment such as punching by mechanical means or laser. The thickness of the tape is from 0.1 to 0.15 mm.

Et lignende bånd er kendt fra britisk patentskrift nr. 995620, 30 der omhandler et bånd af f.eks. syntetisk harpisk og forsynet med afvandings- eller drænåbninger.A similar belt is known from British Patent Specification No. 995620, which discloses a belt of e.g. synthetic resin and provided with drainage or drainage openings.

Formålet med opfindelsen er at tilvejebringe et væskegennem-trængeligt bånd, som er indrettet til brug især som en presse-35 filt, og som har en god afvandingsevne og en høj mekanisk styrke, og ved hjælp af hvilken der opnås en jævn fordeling af trykket ved valsespalten, og ved hjælp af hvilken ovenfor nævnte ulemper undgås. Formålet med opfindelsen er også at tilvejebringe et enkelt bånd, som er let at anvende, kræver lille vedligeholdelse og har en lang brugstid.The object of the invention is to provide a liquid-permeable belt, which is adapted for use especially as a press felt, which has a good dewatering ability and a high mechanical strength, and by which an even distribution of the pressure is obtained by the roll gap and by means of which the above mentioned disadvantages are avoided. The object of the invention is also to provide a single band which is easy to use, requires little maintenance and has a long service life.

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5 Dette opnås ved at båndet ifølge opfindelsen er ejendommeligt ved, at hvert hul tiltager i diameter fra en mikroporedannende ende ved den imod papirbanen vendende - overf 1 ader til en væsentlig større pore end mikroporen ved den modsatte overflade, at båndet er støbt af et ikke-termoplasti sk polymerisk materi-10 ale, at hullerne er samtidigt støbte huller, som er tildannet igennem båndet, og at der i båndet er tildannet tværgående båndforstærkningsmateriale, som er forbundet med båndet.This is achieved by the tape according to the invention being characterized in that each hole increases in diameter from a micropore forming end at the facing paper web - transfers to a substantially larger pore than the micropore at the opposite surface, that the tape is molded from a thermoplastic polymeric material, that the holes are simultaneously molded holes formed through the tape and that transverse tape reinforcing material formed in the tape is formed in the tape.

Båndet kan være fremstillet af støbelige ikke-termoplastiske 15 polymerer, der er velegnet til dette formål og elastomere, såsom urethangummi. Udover urethangummi er det også muligt at anvende andre gummimaterialer, såsom nitrilgummi og silicone-gummi.The tape may be made of moldable non-thermoplastic polymers suitable for this purpose and elastomers such as urethane rubber. In addition to urethane rubber, it is also possible to use other rubber materials such as nitrile rubber and silicone rubber.

20 støbelige ikke-termoplastiske polymerer, såsom urethangum mi, kan let blandes med polymeriske additiver, såsom epoxy, så at der fremstilles et ensartet støbeligt basismateriale.20 moldable non-thermoplastic polymers, such as urethane gum, may be readily mixed with polymeric additives such as epoxy to produce a uniform moldable base material.

Båndets egenskaber kan om ønsket være modificeret på forskel-25 lige måder.The properties of the tape may be modified in various ways if desired.

Således kan de mekaniske egenskaber, såsom stivhed, hårdhed og modstandsevne over for slid samt fleksibilitet reguleres ved valg af en passende ikke-termoplastisk polymer.Thus, the mechanical properties such as stiffness, hardness and resistance to abrasion as well as flexibility can be regulated by selecting an appropriate non-thermoplastic polymer.

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Styrkeegenskaberne kan være forbedret ved hjælp af forskellige forstærkningsmaterialer, såsom glasfibre, fibre der er skåret i små stykker, monofilamenter, multifi lamenter og/eller et metalnet. Det er også muligt at anvende både vævede og ikke-væ-35 vede forstærkningsmaterialer. Syntetiske fibre, såsom polyamidfibre, aromatiske polyamidfibre ("Kevlar") og polyesterfibre er typiske råmaterialer. Forstærkningsmaterialerne er fortrinsvis placeret inden i legemet.The strength properties can be enhanced by various reinforcing materials such as glass fibers, small cut fibers, monofilaments, multifilaments and / or a metal mesh. It is also possible to use both woven and nonwoven reinforcing materials. Synthetic fibers, such as polyamide fibers, aromatic polyamide fibers ("Kevlar") and polyester fibers are typical raw materials. The reinforcing materials are preferably located within the body.

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Urethangummi har gode mekaniske-dynamiske egenskaber, og derudover er det yderst reaktivt på støbestadiet, så at det er let at opnå en kemisk binding mellem urethangummiet og de fleste forstærkningsmaterialer.Urethane rubber has good mechanical-dynamic properties and, in addition, it is highly reactive at the casting stage, making it easy to obtain a chemical bond between the urethane rubber and most reinforcing materials.

5 Båndets afvandingsevne kan forbedres, og denselasticitet kan reguleres ved at tildanne hulheder og/eller porer af den i den kendetegnende del af krav 3 angivne type. Disse hulheder og porer kan være åbne eller lukkede. Den åbne porøsitet kan også 10 være sådan, at porerne er progressivt mere åbne gennem hele båndet.The dewatering ability of the tape can be improved and its elasticity can be controlled by forming cavities and / or pores of the type specified in the characterizing portion of claim 3. These cavities and pores may be open or closed. The open porosity may also be such that the pores are progressively more open throughout the band.

Båndets overfladeegenskaber i henseende til friktion og slip kan reguleres således, at der opnås de ønskede egenskaber i 15 denne henseende.The surface properties of the belt with respect to friction and slip can be adjusted so as to obtain the desired properties in this respect.

Den side af båndet, der er indrettet til at vende ind imod papirbanen, er ifølge opfindelsen meget glat og mikroporøs, og afvandingsevnen af indretningen er god. Ved hjælp af båndet 20 ifølge opfindelsen opnås et meget ensartet tryk ved valsespalten, og dette ensartede tryk bidrager til dannelsen af papir med en jævn og god kvalitet. Når båndet ifølge opfindelsen anvendes, er det endvidere ikke nødvendigt at anvende elastisk belægning af valserne.According to the invention, the side of the tape adapted to face the paper web is very smooth and microporous and the dewatering ability of the device is good. By means of the belt 20 according to the invention, a very uniform pressure is obtained at the roller slot, and this uniform pressure contributes to the formation of paper of a uniform and good quality. Furthermore, when the tape according to the invention is used, it is not necessary to use elastic coating of the rollers.

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Opfindelsen angår også en fremgangsmåde til fremstilling af et vandgennemtrængeligt bånd, især en pressefilt til brug i en papirfremstillingsmaskine af den type, der er angivet i krav 1, hvilken fremgangsmåde er ejendommelig ved, at råmater i aler-30 ne af et ikke-termoplastisk polymerisk materiale påføres et endeløst underlag, som har koniske dele, der rager i alt væsentligt vinkelret ud fra underlagets overflade, hvilken procedure efterfølges om nødvendigt med en hærdning, hvorefter båndet adskilles fra underlaget.The invention also relates to a method for producing a water-permeable belt, in particular a press felt for use in a paper-making machine of the type according to claim 1, characterized in that raw materials in the core of a non-thermoplastic polymeric material is applied to an endless substrate having conical portions projecting substantially perpendicularly from the surface of the substrate, which procedure is followed, if necessary, by curing, after which the strip is separated from the substrate.

35 Påføring af råmaterialerne på underlaget foregår fortrinsvis ved støbning, spredning eller sprøjtning. Underlaget skal ge35 The raw materials are applied to the substrate preferably by casting, spreading or spraying. The substrate must give

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6 nerelt set behandles med et smøremiddel, således at hele båndet let kan adskilles fra underlaget.6 is generally treated with a lubricant so that the entire strip can be easily separated from the substrate.

Ifølge en foretrukken udførelsesform er det endeløse underlag 5 anbragt imellem to valser.According to a preferred embodiment, the endless support 5 is arranged between two rollers.

Ifølge endnu en udførelsesform for opfindelsen er det endeløse underlag tilpasset omkring en valse med stor diameter. Den rundtgående overflade på en valse med stor diameter kan også 10 udgøre det endeløse underlag.According to yet another embodiment of the invention, the endless support is adapted around a large diameter roller. The circumferential surface of a large diameter roller may also constitute the endless support.

Opfindelsen er beskrevet mere detaljeret nedenfor under henvisning til tegningen, hvor 15 fig. 1 viser et langsgående snit igennem en udførelsesform for et bånd ifølge opfindelsen, fig. 2 det i fig. 1 viste bånd set ovenfra, 20 fig. 3 et langsgående snit igennem en anden udførelsesform for et bånd ifølge opfindelsen, fig. 4 et langsgående snit igennem en yderligere udførelsesform for et bånd ifølge opfindelsen, 25 fig. 5 et langsgående snit igennem en fjerde udførelsesform for et bånd ifølge opfindelsen, og fig. 6 et langsgående snit igennem et apparat til brug ved 30 fremstillingen af båndet ifølge opfindelsen.The invention is described in more detail below with reference to the drawing, in which FIG. 1 shows a longitudinal section through an embodiment of a belt according to the invention; FIG. 2 shows the embodiment of FIG. 1 is a top view of the tape, FIG. 3 is a longitudinal section through another embodiment of a belt according to the invention; FIG. 4 is a longitudinal section through a further embodiment of a belt according to the invention; FIG. 5 is a longitudinal section through a fourth embodiment of a belt according to the invention; and FIG. 6 is a longitudinal section through an apparatus for use in the manufacture of the belt according to the invention.

I fig. 1 er et plant legeme tildannet af støbeligt ikke-termo-plastisk polymermateriale forsynet med henvisningstallet 1. Dette legeme 1 er fortrinsvis fremstillet af urethangummi. Le-35 gemet 1 har koniske huller 2. Overfladen 3 (fig. 1 og 2) imod hvilken papirbanen skal ligge an er mikroporøs og meget glat.In FIG. 1 is a planar body formed of castable non-thermoplastic polymeric material provided with reference numeral 1. This body 1 is preferably made of urethane rubber. The layer 1 has conical holes 2. The surface 3 (Figs. 1 and 2) against which the paper web should lie is microporous and very smooth.

Den anden overflade har for dens part porer, som er tydeligtThe other surface has for its part pores, which is clear

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7 mere åbne. Som felge af denne struktur har båndet ifølge opfindelsen, når den anvendes som en pressefilt eller pressevire, en god afvandingsevne, og derudover bliver hullerne 2 ikke let tilstoppet.7 more open. As rims of this structure, the belt according to the invention, when used as a press felt or press wire, has a good dewatering ability and in addition the holes 2 are not easily clogged.

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Fig. 3 viser et bånd magen til det, der er vist i fig. 1 bortset fra, at det er forstærket med et forstærkningsmateriale 4. Forskellige syntetiske fibre, tråde og stoffer, glasfibre og metaltråde og net tilhører en gruppe at materialer, 10 som er velegnet som forstærkningsmaterialer.FIG. 3 shows a band similar to that shown in FIG. 1 except that it is reinforced with a reinforcing material 4. Various synthetic fibers, yarns and fabrics, glass fibers and metal wires and nets belong to a group of materials which are suitable as reinforcing materials.

Fig. 4 viser et bånd magen til fig. 1 bortset fra, at det har porer 5. Disse porer kan være åbne eller lukkede porer. Åbne porer gør båndet mere svampelignende, hvorved dets afvandings-15 evne forbedres. Lukkede porer til gengæld, forbedrer indretningens elastiske egenskaber.FIG. 4 shows a band similar to FIG. 1 except that it has pores 5. These pores may be open or closed pores. Open pores make the strip more mushroom-like, thereby improving its dewatering ability. Closed pores, in turn, improve the elasticity of the device.

Fig. 5 viser et bånd magen til det, der er vist i fig. 1 bortset fra, at det har hulheder 6, som forbinder hullerne og hul-20 heder, som udmunder i hullerne.FIG. 5 shows a band similar to that shown in FIG. 1 except that it has holes 6 which connect the holes and holes 20 which open into the holes.

Ovenfor er der kun beskrevet få udførelsesformer for opfindelsen. Oer kan foretages mange ændringer, uden at man herved afviger fra opfindelsens ide, idet der f.eks. kan anvendes kom-25 binationer og modifikationer af de beskrevne udførelsesformer. F.eks. kan båndet ifølge opfindelsen både være forstærket og indeholde porer.Above, only a few embodiments of the invention have been described. Many changes can be made without departing from the idea of the invention. combinations and modifications of the described embodiments may be used. Eg. For example, the tape of the invention may be both reinforced and contain pores.

Under henvisning til fig. 6 beskrives der to metoder til frem-30 stilling af et bånd ifølge opfindelsen. En båndlignende støbeform 7 er udspændt imellem to valser 9. Støbeformens overflade har koniske pigge 8, hvis form svarer til den ønskede form af hullerne i båndet. Råmaterialerne af et ikke-termoplastisk po-lymerisk materiale påføres denne "sømmåtte", så at der frem-35 bringes et bånd med den ønskede tykkelse. Dette råmateriale kan påføres ved støbning, spredning eller sprøjtning. Til den endelige hærdning af materialet anvendes der normalt en varmebehandling. Den færdige indretning adskilles fra "sømmåtten".Referring to FIG. 6, there are described two methods for making a belt according to the invention. A strip-like mold 7 is spaced between two rollers 9. The surface of the mold has conical spikes 8, the shape of which corresponds to the desired shape of the holes in the strip. The raw materials of a non-thermoplastic polymeric material are applied to this "seam" so as to produce a tape of the desired thickness. This raw material can be applied by casting, spreading or spraying. For the final curing of the material, a heat treatment is usually used. The finished device is separated from the "nail mat".

Claims

If the porosity of the strip is desired to increase, appropriate chemical materials such as volatiles or water-soluble substances are added to the non-thermoplastic polymeric material during the manufacturing process. These substances form under the influence of heat or water pores in the device. An example 10 of such water-soluble substances is common salt whose grain size determines the size of the pores. Claims. 15

A liquid-permeable press filter belt or press belt for use in press sections of a papermaking machine, comprising an endless flat strip (1) of a polymeric material, said strip having a paper 20 facing surface (3) and an opposite surface and tapered holes, extending therethrough in the thickness direction, and connecting the two surfaces and imparting liquid permeability in the thickness direction to the band (1), characterized in that each hole (2) increases in diameter from a micropore-forming end at the surface facing the paper web to a substantially larger pore than the micropore at the opposite surface, that the tape (1) is molded from a non-thermoplastic polymeric material, that the holes (2) are simultaneously molded holes (2) formed through the tape and that in the belt are formed transverse belt reinforcing material which is connected to the belt.

Tape according to claim 1, characterized in that the polymeric material is an elastomer. 35

Tape according to claim 2, characterized in that the elastomer is urethane rubber. DK 164125 B

Band according to claim 1, characterized in that the band (1) has embedded cavities (6) which extend transversely within the band in the width direction or the longitudinal direction, that at least some of the cavities (6) connect in it. at least two holes transversely by cutting them within an intermediate region thereof seen in the thickness direction of the belt, whereby the cavities (6) during use help to equalize internal hydraulic pressure in the transverse direction within the belt. Band according to claim 1, characterized in that the band (1) further has transverse closed pores (5) for controlling the elastic properties of the band, which closed pores are embedded in the band. The tape according to claim 1, characterized in that the tape further comprises transverse open pores which are embedded in the tape and serve to dewater it.

Process for producing a liquid-permeable strip, in particular a press felt for use in papermaking machines and of the type as defined in claim 1, characterized in that the raw materials of a non-thermoplastic polymeric material are applied to an endless substrate (7). ) having tapered portions (8) protruding substantially from the surface of the substrate, which procedure is followed, if necessary, by curing, after which the strip is separated from the substrate.

Method according to claim 7, characterized in that the endless support (7) is arranged between two rollers (9). 30

Process according to claim 7 or 8, characterized in that the non-thermoplastic polymeric material is an elastomer such as urethane rubber.

Method according to one or more of claims 7-9, characterized in that the application is by casting, spreading or spraying. DK 164125 B

Method according to one or more of claims 7 to 10, characterized in that the application takes place in layers.

Method according to claim 11, characterized in that a reinforcing material (4) is applied between the layers.

Process according to one or more of claims 7 to 12, characterized in that the porosity of the non-thermoplastic polymeric material is increased by the use of slightly volatile substances and / or water-soluble substances which are adapted for the manufacturing process and forming, under the influence of heat and / or water, the desired pores and voids in the form of either open cells or closed cells in the desired locations. 15

Process according to claim 13, characterized in that the water-soluble substance used is salt whose grain size determines the size of the pores and cavities. 20 25 30 35