FI66934B - FOERFARANDE FOER SLAETNING AV YTAN AV EN FILT VIRA ELLER LIKNANDE AENDLOES THERMOPLASTIC BEHANDLINGSBANA SAMT ANLAEGGNING FOER TILLAEMPNING AV DETTA FOERFARANDE - Google Patents

Description

I -____-. 1 r_, NOTICE OF PUBLICATION,,, ^ ^ utlAggningsskmft 6 6 934 VSrS ^ Patent acddolat ^ ^ (51) K «Jlu / ΙΜ, Ο.3 D 21 F 7/08 FINLAND — FINLAND (11) ν * * »« Μμιι ** - ρ * · η ** · β «αιΐηι 773981 (22) HihontapMvt — Amaknlnpd» t 30.12.77 (23) AlkupUvt - GlWfh «t * d« g 30.12.77 (41) TuHuc (wndMlnf —BIhrK offaMftg gj qj ^

Patent Office Hall Itu * _ _________________ __________________

Patent- and legitterityrelsen Amttkan utlagd odi miekrMtsn pubNcarad 31.08.84 (32) (33) (31) «Oleiluin — Begird prtortut (71) Tampereen Verkatehdas Oy, Lokero 427, 33101 Tampere 10, Finland -Finland (Fl) (72) Axel Cedercreutz, Tampere, Finland-Finland (FI) (74) Oy Kolster Ab (54) Method for smoothing the surface of a felt, wire or similar endless thermoplastic treatment track and equipment for applying this method - Förfarande för slätning av ytan av en filt, vira eller liknande ändlös, The present invention relates to a method for smoothing the surface of a felt, wire or the like endless thermoplastic treatment web used in papermaking by applying a heating and pressing effect to the treatment web for softening and compressing the paper side surface.

It is previously known to finish press blankets n.s. with drying calenders in which the endless felt is tensioned, for example, between two rolls to the desired length. One of the rollers is heated by steam or circulating oil, whereby the felt is placed on the rollers so that the paper-side surface of the felt is located on the inside against the roll. As it rotates around the heated roll, the surface of the felt is subjected to heating and softens. Tightening the felt causes it to press against the heated roll to such an extent that the softened surface of the felt becomes slightly flattened and thus becomes smoother. As the blankets cannot be tightened due to the risk of elongation above 2,66934 20 kp / width cm., The compression of the felt against the hot roll remains very low and the ironing effect is small. In order to achieve a higher degree of smoothness with such a small compressive force, a stronger heating effect must be applied to the felt, which has to operate above the melting temperature of the fibers, which in turn leads to reduced permeability, since the surface easily melts impermeable.

To provide a higher compressive force, it has previously been proposed to pass the felt first through a heat field where the felt is subjected to hot air blowing and then through a pair of press rolls which compress the preheated felt. The compressive force has been forced to limit the top roll to its own weight, as the additional load causes the rolls to bend and thus uneven compression at the edges and center of the felt. Different felt widths also cause uneven compression, which also results in unsatisfactory results. Achieving a higher degree of smoothness with such a small compressive force would in this case require heating the felt close to the melting temperature of the fibers with the resulting disadvantages.

The smooth surface of the felt is intended to reduce the amount of air carried by the felt, which causes a so-called blowing, and re-wetting of the felt that occurs after the point of compression.

The surface smoothness provided by flattened fibers has recently been implemented in press felts using pre-flattened fibers in needled surfaces. However, such a method is unsatisfactory because completely flat fibers cannot be guided so that they are always located in the felt with its wide surface facing the paper, and because the flat fiber, on the other hand, makes the felt too dense.

In wet fabrics and drying fabrics, the required surface smoothness is achieved by grinding the surface of the wire evenly. Since the substance is removed from the filaments in this way, this correspondingly reduces the strength of the wire.

On a smooth surface, the aim is to reduce the marking properties of the wire in wet fabrics and to provide e.g. more even compression of the paper web against the drying cylinder.

The object of the present invention is to provide a method which eliminates the above-mentioned drawbacks and which makes it possible to achieve a high degree of smoothness and stability without deteriorating the permeability and strength. This object is achieved by the method according to the invention, characterized in that the processing path is subjected to a simultaneous tightening, heating and pressing effect on the paper side surface by passing an endless processing path around a tensioning roll and a heating roll which forms a pressing point with the pressing roll.

The process according to the invention is based on the fact that the thermoplastic fibers have a lower softening temperature than the melting temperature. Sufficient compressive force is applied to the treatment web to be smoothed when the web is heated to the softening temperature. This causes flattening of the felt fibers and the wire filaments, respectively, and also gluing of the fibers and filaments to each other at their intersections. Due to the fact that the heating and pressing of the treatment web is performed in a press formed by a pair of rollers, the pressing force is applied to the treatment web while it is still heated and thus sufficient flattening is achieved without having to heat the processing web to the melting temperature. The presented method flattens precisely those fibers or filaments which are desired to be flattened from the point of view of use, i.e. the fibers concerning the paper web.

The gluing of the fibers and filaments to each other at the junctions also increases the stability of the processing path. In this way, the needling can be left less in the needled felt, whereby the needle marking on the surface of the felt remains smaller. Less needling also lowers production costs. Hot pressing glues the fibers together better than can be achieved with current technology. In wet and drying fabrics, the required smoothness of the surface is achieved without a decrease in strength, because the cross section of the smoothed filaments remains unchanged.

The invention also relates to an apparatus for applying the method described above, which apparatus comprises rollers for controlling an endless processing path and heating means and pressing means for heating and compressing the processing path, respectively. The apparatus is characterized in that the heating roll forms with the press roll a pair of press rolls through which the processing path passes and with the tensioning roller a pair of tension rollers around which the processing path passes.

The invention will be explained in more detail below with reference to the accompanying drawing, which schematically shows an apparatus for applying the method according to the invention.

The drawing shows a needleless endless press felt 1 made of thermoplastic fibers such as polyamide, polyester or polypropylene fibers. The felt is guided around the lower roll 4 of a tension roll 2 4 66934 and a spaced apart pair of rollers 3. The upper roll 5 together with the lower roll 4 forms a pressing point 6 through which the felt passes. The lower roll 4 is formed as a circulating oil or electrically heated heating roll with a surface temperature adjustable from 20 to 260 ° C. The upper roll is formed, for example, as a Kusters-type press roll, the pressing pressure of which can be adjusted by means of pressurized oil in a manner known per se so that the pressing pressure is uniform over the entire length of the pressing point over the felt. The compression pressure can be up to 200 kp / width cm. The hot air hood 7 ensures that the felt is fixed.

As the felt rotates over the heating roll, it is subjected to a heating effect, whereby the fibers reach a softening temperature at least on the surface of the heating roll. At the pressing point of the pair of rollers, the felt is pressed, as a result of which the fibers pressed against the heating roller flatten, forming a smooth surface of the felt. In addition, the fibers adhere to each other at their intersections within the felt. The felt is then allowed to cool and removed from the rollers.

The treatment is essentially the same if the web to be treated is a wet wire or a drying wire woven from filaments instead of a press felt. In this case, too, the filaments pressing against the surface of the heating roll become flattened, so that a smooth surface is obtained on the wire, and the filaments also adhere to each other at their intersections, so that a very stable wire is obtained.

Example

A press felt 1 having dimensions of 7.5 x 26 m, a weight of 1200 g / m and a composition of 5% wool and 95% polyamide (nylon 6.6) fibers was passed as an endless web over rollers 2 and U. The felt was first treated in four heating steps at a speed of 5 m / min, whereby the felt temperature rose as follows: 1 step to 100 ° C, 2 steps to 160 ° C and 3 steps to 200 ° C and H step to 230 ° C.

The temperature of the circulating air of the hood was raised to 100 ° C in step 11 and 160 ° C in step 2 to effect felt passage. In steps 3 and> »the temperature of the circulating air was not raised because the goal was to level the surface. Gradually raising the temperature is an advantage to provide a smooth felt. Excessive temperature rise at one time will cause wrinkles on the felt or wire. The felt was then subjected to a compression effect of 5,150 kp / cm with two turns of the press roll while the temperature was still 230 ° C. The felt thus treated had a very smooth paper-side surface due to the flattening of the surface fibers and improved stability due to the adhesion of the fibers to each other. However, the permeability of the felt was good due to the fact that no melting of the fibers on the surface of the felt occurred »

The drawing and the related description are only intended to illustrate the idea of the invention. The details of the method and apparatus according to the invention can vary considerably within the scope of the claims.

Claims (3)

6 66934 A method for smoothing the surface of a felt, wire or similar endless thermoplastic treatment web (1) used in papermaking by applying a heating and pressing effect to the paper web for softening and compressing the paper side surface, characterized in that the processing web (1) is , under the influence of heating and pressing by guiding the endless processing path (1) around the tensioning roller (2) and the heating roller (4), which together with the pressing roller (5) forms a pressing point (6). Apparatus for applying the method according to claim 1, the apparatus comprising rollers (2, 4) for guiding the endless processing path (1) and heating means and pressing means for heating and compressing the processing path, respectively, characterized in that the heating roll (4) forms a pressing roll (5) with a pair of pressure rollers (3) through which the processing path (1) passes, and with the tensioning roller (2) a pair of pressure rollers (2, 4) around which the processing path passes. Apparatus according to Claim 2, characterized in that the press roll (5) is formed by a Kiisters-type roll.