FI86657C - VID PAPPERSFRAMSTAELLNING ANVAENDBAR FILT SAMT FOERFARANDE FOER DESS FRAMSTAELLNING. - Google Patents

Abstract

Process for heat-sealing a layer of pervious material (26) to a support (20) formed of interwoven threads characterized in that during the fabrication of the support (20) there are provided on one side (21) special threads having a core and a thermoplastic outer part of which the melting temperature is lower than that of the core and than those of other threads, and in that the side (21) is heated until the outer part of the special threads is melted, whereafter the layer (26) is applied to said side. The mechanical and tightness qualities of the support and of the layer have thereby been preserved. Utilization of the process for the making of paper felts and filter fabrics.

Description

86657

This invention relates to a papermaking felt comprising a layer of a permeable material attached to a support structure of interwoven yarns and a method of making the same.

One such method is described in GB-A 994914.

In this method, the support structure contains special thermoplastic yarns that are heated and melted before a permeable layer is added to it.

The disadvantage of this method is that it partially destroys the tissue structure of the support structure, as some of the special yarns melt completely. In addition, the bonding is incomplete because when the wire completely melts, the molten thermoplastic material spreads irregularly between the remaining yarns of the support structure and the permeable material layer.

The felt and method according to the invention avoid these disadvantages. The felt is characterized in that only the weft yarns on the surface of the support structure consist of single-stranded special yarns having a thermoplastic core surrounded by a cover having a lower melting temperature than that of the core and other yarns, the layer of permeable material being attached to the main layer.

The method is characterized in that the surface of the support structure containing weft yarns of single-stranded special yarns having a core surrounded by a plastic sheath having a melting temperature lower than that of the core and other yarns 2 86657 is heated to the melting point of the special yarn coating , whereby a bridge is formed between the core of the special yarns and the layer of permeable material.

When the special yarns are heated, only the outer part melts and forms a bridge between the core of the special yarns and the layer of permeable material. Thus, the support structure is not partially destroyed, and the bond between the support structure and the permeable layer is very well obtained.

The present invention is particularly advantageous in the manufacture of blankets for papermaking, wherein the permeable layer makes it possible, inter alia, to prevent the paper web from being patterned under pressure and to remove water extracted from the paper web to be made.

Papermaking felts are conventionally made by needling a layer of permeable material formed from intertwined fibers into a support structure formed by woven yarns (even if there is further gluing between the support structure and the permeable layer, as described in DE-A 1807329).

The felt made in this way has several drawbacks. First, its permeability is reduced because the fibers are introduced into the support structure.

In addition, the layer of permeable material is compacted and covered by a large number of small funnels through which the needle needles have passed.

Finally, the needles damage the support structure, thus reducing the life of the felt and contributing to its deformation.

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In addition, when connecting means (loops, spirals, etc. are joined to the support structure prior to needling to be joined by the connecting wire to form an endless loop of felt), the needling damages the connecting means. In addition, the presence of fibers in the splicing means after needling makes it difficult to pass through the splice wire required to make the splice.

The method according to the invention makes it possible to select the desired support structure, e.g. the use of yarns which are chemically resistant, and even if their strength is relatively low, it would no longer fall below acceptable values due to the needles.

For some applications, a very strong support structure may be selected to prevent deformation of the felt as it rotates or wear when it comes in contact with the rollers, without fear of its partial destruction during needling.

In the papermaking felt, the weft yarns preferably form a heated surface weft yarns, said yarns being perpendicular to the direction of movement of the felt.

In this case, the contact between the support structure and the permeable layer is good, and it is possible to keep the stresses between the permeable layer and the support structure due to the bending during the movement of the felt.

The method according to the invention is also very advantageous for the production of filter cloths, in which the purpose of the permeable layer is to filter liquid or gas and retain impurities, especially when the support structure which provides the mechanical characteristics is provided with connecting means.

It should be emphasized that the use of the invention makes it possible to dispense with the use of needling machines, which are relatively expensive.

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The invention will now be described in detail with reference to a particular embodiment shown in the accompanying drawings.

Figures 1 and 2 show the support structure and layer used in the method according to the invention; and

Figure 3 schematically shows an apparatus for carrying out the method according to the invention.

The woven backing layer 20 consists of eight groups of warp yarns 11, 2 ', 3', 4 ', 5', 6 ', 7', 8 ', and weft yarns 1, 2, 3, 4, 5, 6, 7, 8, 9 , 10, 11, 12, ...

(see Figure 1).

On the upper surface 21, which is the right side of the support structure, the weft yarns 1, 3, 4, 6, 7, 9, 10, 12 (i.e. two of each of the three yarns) are protruding, which can best be seen in section II-II (Figure 2). .

On the lower surface 22, which is the wrong side of the support structure 20, the second weft yarns 2, 5, 8, 11 (i.e. one of each of the three yarns) are arranged below the warp yarns.

The protruding weft yarns 1, 3, 4, 6, 7, 9, 10, 12 are special single-stranded bicomponent yarns. They consist of a polyester core 24 surrounded by a polyamide cover 25. The other weft yarns 2, 5, 8, 11 and warp yarns 1 ', 2', 3 ', 4', 5 ', 6', 7 ', 8' are polyester.

Two-component yarns can be made either by extrusion, weaving or further twisting.

The polyester has a melting point of 230 ° C and the polyamide has a melting point of 180 ° C.

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The support structure can be made by weaving, knitting, spiral structure, etc.

Two-component specialty yarns have a core made of a single strand or multiple strands or even a cut fiber yarn, and an outer portion surrounding the core, which exterior may be a sheath or formed from surrounding yarns, with a melting point below the melting point of the other yarns forming the core and support structure.

As a result, the special wires retain a certain part of their mechanical properties even after the outer part has melted.

Since the needle does not impose any restrictions, the layer of permeable material can be selected for the final product taking into account the desired properties.

This layer 26 may be formed of continuous or discontinuous yarns bonded together by needling, melting, resin impregnation, etc.

It can also be formed from an extruded film that is or has been made permeable to a medium.

The support layer can be terminated at both ends with connecting means (loops, spirals, etc.).

The apparatus for carrying out the invention (Fig. 3) comprises heating elements, e.g. infrared heaters 30, two rollers 31, 32, the first of which is fixed-axis and the second of which is pressed against the first, a heating cylinder 33 and transport rollers 34, 35 together with a stretching roller 36.

The permeable layer 26 is wound on the cylinder 37.

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The support structure is mounted on rollers 34, 35 and a stretching roller 36. It runs between the rollers 31, 32 and around the cylinder 33. Cylinder 33 is a drive cylinder.

The surface 21 with the special wires of the support structure (transverse to the direction of movement) passes under the heating elements 30, which heat it to a sufficiently high temperature to melt the outer part of the special wires (e.g. 200 ° C). The permeable layer 26 is brought by a roll 32 against the surface 21 on which the fused yarns are located. Leaving the rollers 31, 32, the layer 26 adheres to the surface 21, and the assembled support structure 20 and the layer 26 are wound around a cylinder 33 (layer 26 against the cylinder 33) which is heated to a low temperature (120 ° C) to improve the surface condition.

At the beginning and end, of course, precautions must be taken to prevent the ends of the permeable layer from overlapping.

It will be appreciated that both surfaces 21 and 22 of the support structure 20 could be provided with special wires, and the layer 26 bonded to each side.

In papermaking felts, it is recommended to place special yarns along the weft (perpendicular to the direction of movement), as shown in the figures.

It is also possible to place the special yarns along the warps 1 ', 2', 3 ', 4', 5 ', 6', 7 ', 8' and thus in harmony with the direction of movement of the felt.

Both placement methods reduce the bending stresses between the permeable layer 26 and the support layer 20 during the movement of the felt.

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Claims (4)

86657 l. A papermaking felt comprising a layer (26) of permeable material joined by interwoven yarns (1 ', 2', 3 ', 4', 5 ', 6', 7 ', 8', 1. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12), characterized in that the weft yarns on the surface (21) of the support structure only consist of single-stranded special yarns (1, 3, 4, 6, 7, 9, 10, 12) having a thermoplastic core (24) surrounded by a coating (25) having a lower melting point than the core (24) and other yarns (1 ', 2', 3 ', 4 ', 5', 6 ', 7', 8 ', 2, 5, 8, 11), wherein the layer (26) of permeable material is connected to the support structure by melting the special wires (1, 3, 4, 6, 7, 9, 10 , 12) cover (25). A method of making a felt according to claim 1, wherein the layer (26) of permeable material is joined by interwoven yarns (1 ', 2', 3 ', 4', 5 ', 6', 7 ', 8', 1, 2, 3 , 4, 5, 6, 7, 8, 9, 10, 11, 12), characterized in that the surface (21) of the support structure, which contains single-stranded different warp yarns (1, 3, 4, 6) as weft yarns, , 7, 9, 10, 12) having a core (24) surrounded by a plastic cover (25) having a melting point lower than that of the core (24) and other yarns (1 ', 2', 3 ', 4', 5). ', 6', 7 ', 8', 2, 5, 8, 11), is heated to the melting point of the casing (25) of the special yarns (1, 3, 4, 6, 7, 9, 10, 12), after which the permeable a layer of material (26) is placed on this surface (21), whereby a bridge is formed between the core of the special yarns and the layer of permeable material. Method according to claim 2, characterized in that the single-stranded special yarns (1, 3, 4, 6, 7, 9, 10, 12) have a polyester core (24) and an outer part consisting of a polyamide 6 coating (25), that the other yarns (! ', 2', 6 86657 3 ', 4', 6 ', 7', 8 ', 2, 5, 8, 11) are polyester, and that the special yarns (1, 3, 4, 6, 7 , 9, 10, 12) is heated to a temperature close to 200 ° C before the layer (26) is placed. Method according to Claim 2 or 3, characterized in that the support structure (20) is provided with connecting means (23) before the layer (26) is fastened. i Patentkrav: 86 657