MXPA97001709A - A method and a system for manufacturing continuous, wide, air-setted papers, containing an absorbent dust - Google Patents

Abstract

The present invention relates to a method for manufacturing continuous papers, seated with air, with a width of more than 30 cm and with a content of superabsorbent powder material, called SAP, whereby the continuous paper is formed in a wire mesh foraminous, when guided downward against this wire cloth a flow fluidized with air of cellulose fibers, from a distributor unit placed at the top, supported by an active suction effect on the underside of the wire mesh, the continuous paper of fibers, thus formed, in the moving metal fabric is subsequently established by the addition of a binder from the outside or by the action of an initially mixed binder, typically on heating for the action of the binder fibers, activated by heat, mixed , after the addition of the absorbent powder material to the continuous paper, characterized in that the powder, absorbent material is added in an intermediate layer of the distribution of the fibers, that is, after the initial formation of the fluidized flow with fiber air and before the final deposition of the fibers in the continuous forming paper, the supply of powder that is arranged such that the powder is distributed in an oblong way along the entire width of the continuous paper formed initially or over partial sections of the width thereof, after which the powder is completely distributed by the action of the air flow that operates to effect the final distribution of the paper. Fiber material in the metal forming fabric

Description

A METHOD AND A SYSTEM FOR MANUFACTURING CONTINUOUS, WIDE, AIR-SETTED PAPERS, WHICH CONTAIN AN ABSORBENT DUST The present invention relates to the production of continuous papers seated with air, which contain a superabsorbent powder of liquids. The basic material in these continuous papers is cellulose fibers, although usually with a certain content of heat-activated synthetic fibers, for the bonding of continuous, spread paper, and it is well known that this fibrous material may also contain superabsorbent fibers, evenly distributed in the continuous paper. However, in particular for economic reasons, it is desirable to use this powder, also known as SAP, in place of the absorbent fibers, but it is much more difficult to achieve a reasonably homogeneous mixing of the SAP in the web material. It is well known that with different settling techniques of the prior art it is possible to produce a continuous, absorbent paper material in a moving metal web, by passing a first distributor head to seat or REF: 24296 to extend a layer of the bottom of the web in the web. wire mesh, then passing a powder distributor that seats a layer of SAP in the bottom layer of the continuous paper, and then passing another dispensing head that operates to seat a top layer of the continuous paper from the top. However, the SAP particles do not actually bond in the web material, which is heavily powdered during further processing, while also the final absorbent products exhibit strong detachment tendencies. With this background, it is also known that instead of trying to mix the material of SAP in the fiber material, and for this purpose, it has been a natural measure to add the powder to the flow of fiber material, fluidized with air, supplied at the distributor head, usually from a hammer mill, in which a dry pulp material is disintegrated, this can result in efficient mixing, due to high turbulence in the air, but, nevertheless, it has been necessary to accept a perceptible inhomogeneity in the final product, all according to the technique of settlement with air, applied. In this way, by means of a concentrated supply of fiber / SAP / air flow down to a distributor head having a means to agitate and distribute the material on a sorting screen above the forming wire, there it can be found a higher SAP concentration below the flow supply area, than at the periphery; in the continuous paper product, this causes a strip formation with mutually different SAP concentrations, and if the SAP is dosed at a high speed, such that a desired concentration is obtained in the peripheral areas, then dusting from the more concentrated zone or zones, which is inconvenient and causes losses, and also for other reasons a high concentration can be directly undesirable. In its beginning, the invention is based on another technique of settlement with air, of which it is indicated above, that is to say, of the type described in EP-B-8, 032, 772; this is a technique that, among the experts, is highly recognized by the present applicant. It is advantageous for a high production capacity and uniformity of the formed continuous paper, but it has been pointed out that there are problems with respect to achieving a homogeneous mixture of the absorbent powder in the fiber material when it is seated in the production wire. The technique in question is particularly relevant for the production of relatively large widths of continuous paper, for example, in the range of 50-300 cm, as for the production of absorbent pad products, narrower, it is true to cut the continuous paper in strips, making this production more economical than forming individual continuous paper with the width or widths required. Nevertheless, then it is critical to obtain a high degree of uniformity of the SAP distribution across the width of the continuous paper, since the continuous paper strips will otherwise be non-uniform. The technique discussed is based on air-fluidized fibers that move in a flow of air through the forming wire, inside a cylindrical, rotating, perforated tube, and back again through another corresponding cylindrical tube. , whereby this set of cylindrical tubes constitutes a forming head, from which the fibers are placed in a space, in or through which, as is conventional, a downward flow of air is caused by the action of a suction fan connected to a suction box below the foraminous wire mesh. The flow of fibers thus leaving the cylindrical tubes will have a certain component of movement transverse to the direction of the wire mesh, but because the flow of the fibers is guided through the wire mesh in two opposite directions, the The resulting continuous paper of fibers will still be established with a sufficient and uniform layer thickness along both of its lateral edges. With appropriate adjustments, this will hold true for the fiber material, but not with the SAP material, which can be affected in a completely different way by the respective transverse and vertical air flows. In practice, it has been found that with a simple mixture of SAP in the fiber material, the powder is deposited on the metal fabric with another distribution characteristic than that of the fiber material, whereby it is very difficult or impossible to adjust the distribution to achieve a perfect result, which is a fiber continuous paper, uniformly distributed with a uniform blend of SAP powder. You can optimize one of the two, but then the other does not. With this background, with the different techniques of settlement with air, it has been required to accept compromises due to the fact that the pertinent air flows do not affect the fibers and dust in exactly the same way. With the invention, it has been recognized that it is possible to change and improve this situation by arranging a mixture of powder at a middle stage of fiber distribution, ie, after a distribution started, but before it ends, when care is taken of introducing the powder separately on at least an essential part of the width of the web, just as in connection with the first mentioned method of applying a middle layer of the SAP material. Therefore, it is achieved that the SAP powder is not noticeably affected by the influence of the initial distribution on the fiber material, whereby the distribution of the fibers can be controlled to achieve a uniform distribution profile without the special attention to the SAP material mixture, while the latter can take place with a mandatory distribution width to a final stage such that the powder will still have time to be completely mixed with the fibers while they are under the final distribution to the formation wire mesh. Therefore, it is ensured that real and current mixing of the powder in the fiber material will occur, and that the mixture can be uniform over the entire width of the web. Of course, there may be a certain commitment interval, in which the SAP material, all according to the detailed circumstances, may be added sooner or later in the course of the supply of the fibers, and correspondingly, the supply of SAP can be more or less uniform over the width of the continuous paper, if a certain inhomogeneity is acceptable. Because of these lower quality requirements, the invention will still be advantageously useful, since the supply of SAP is then particularly easy to control. Normally, to obtain the best qualities, it is necessary to choose to add the SAP to a final stage of the process, such that there is not much turbulence left in the air that leads the fibers to the continuous paper, and it may be preferable, therefore, to supply the SAP material through an operable means for actively spreading the SAP, such that the materials can still be intensively mixed together just prior to distribution to the forming wire. Through the production of narrow continuous papers, it is known to add the SAP material by injection into the fiber space in the forming head, for example, see US-A-4, 927, 582 and EP-A-520 , 798, but with these connections, the conditions are less critical, because the supply of material, is distributed in advance over a perceptible part of the width of the continuous paper, and also, it will be less important if a reduced mixing of SAP to along the lateral edges of the pieces of the individual continuous paper. The problem considered will occur through all the continuous, wide paper laying techniques, so that the invention is not limited to special settling techniques, discussed for continuous fiber paper. In the following, the invention is described in more detail with reference to the drawings, in which: Figure 1 is a perspective view and a dry forming system with a means for conventionally supplying SAP material; Figure 2 is a sectional, longitudinal view thereof; Figures 3 and 4 are corresponding views of two systems according to the invention; Figures 5 and 6 are cross-sectional views thereof; Figure 7 is a perspective view of a preferred dry forming system; Figure 8 is a sectional view thereof; Figures 9-11 are sectional views illustrating different embodiments of the invention; Y Figures 12 and 13 are sectional views illustrating yet another embodiment; Figures 1 and 2 show a dry forming system in a very schematic manner. The system comprises a perforated metal forming fabric 2, with a head forming equipment mounted above it, shown here as two forming heads 4 and 6, each receiving a flow of fiber material, fluidized with air through the supply channels 8. It is known that this material is received from a hammer mill 10, which is currently fed with a continuous paper 12 of pulp material that is defibrated in the hammer mill. Below the wire 2 a suction box 14 is mounted, from which air is sucked down through the wire mesh such that the fiber material, as it is distributed over the width of the wire mesh, inside of the forming heads, is sucked down for the formation of a light layer of continuous paper, more or less uniform, in the wire mesh. As mentioned, it is possible to obtain an incorporation of a superabsorbent powder (SAP) into the final product by supplying the powder to an air flow / fiber feed to a forming head, for example, by supplying it. through a tube 18 as shown in the dashed lines in Figure 1, or by using a powder distributor 20, from which the powder is sprayed down over the full width of the web 16 distributed from the 4 forming head, after which the other forming head 6 will seat a continuous paper 22 of the upper parts in the powder layer. However, it is sought in these two methods to be improved by the present invention. Figure 3 indicates a solution of the system according to the invention. Within the applied forming head 4 a powder distributor 20 is mounted which extends almost or completely over the width of continuous paper and which has its lower outlet end 20 located within the appropriate fiber distribution room., separated above the metal mesh 2. In this place, there may be enough air turbulence for the powder to spread, so that it mixes well with the fiber material, which, even under the condition of being fluidized by the air it is under movement with one component down towards the wire 2, but according to the invention, it is a preferred option to use a modified powder distributor such that the distributor by itself or by a separate means arranged at the mouth 20, effect an active spreading of the powder. If this spreading is carried out both in the longitudinal and transverse direction of the continuous paper, then the spreader can be formed, as shown in Figure 5, with a transverse row of mutually separated outlets 20", but it is preferred to use a slot 20, not broken in combination with a means for spreading the powder in the longitudinal direction of the web, also as mentioned below. In the embodiment shown in principle in Figure 4, a special powder distributor is used, i.e., a transverse, perforated tube 24 which extends through the forming head 4 and which houses a conveyor to supply the powder from one end of the tube, for example, a worm conveyor. Of course, even with this design it will be possible to use a means for actively spreading the SAP powder, but it will not be required in a necessary manner. In Figure 4, it is indicated that the powder is introduced at a slightly higher level than in Figure 3, that is, in an area with higher turbulence, whereby it is less important to perform the active spreading of the powder. In Figure 6, the transverse, perforated tube 24 is seen from a long side of the forming head 4, with the worm conveyor indicated at 26. The more detailed experiments with the invention have been done in a training system dry type "Dan-Web" which, according to for example, EP-B-0, 032, 772, is characterized in that the forming head 4, as shown in Figure 7, comprises a box 30 outer with narrow, opposite, skirt portions 32, between which two cylindrical, perforated, parallel pipes 34 and 36 are arranged, which at their ends are mutually connected through the curves 38 of the tubes, which, in one or both ends of the box 30, are connected with a supply tube 40 corresponding to the supply tube 8 from the hammer mill 10 in Figures 1-5. In operation, the fiber flow is thus supplied to one or both of the cylindrical tubes 34, 36 and are circulated in the system 34, 36, 38. The cylindrical tubes 34 and 36 are punctured and rotated, and as shown in Figure 8, they are preferably provided with internal needle cylinders 42 which are rotated at high speed, whereby the fibers can be unloaded from the cylindrical tubes with high capacity and with high smoothness in the metal mesh 2; a certain non-uniformity may occur due to the transverse movement of the fibers in each of the cylindrical tubes, but this will be remedied by a uniformity opposed by the movement through the other cylindrical tube. In this way, the two cylindrical tubes are a pair of drums that constitute an individual training head. According to the invention and as shown in Figure 8, a powder distributor 20 with a downflow conduit 28 can be mounted between the two cylindrical tubes 34 and 36. As shown, the conduit can be provided with a vertically movable, lower, mouth part 44, whereby the level of the outlet mouth 20 can be adjusted. With which, it is already possible to supply the SAP powder in such a way that it can be effectively mixed with the fibers by the existing turbulence, before the fibers are deposited in the metal fabric 2, but according to the invention It is still preferable to make use of a means for actively spreading the powder from the outlet mouth 20. In this way, as shown in Figure 5, a brush cylinder, rotatable along the mouth 20, can be mounted to spread the powder. Another possibility is shown in Figure 10, where a perforated air tube 48 is mounted below the outlet slot of the powder distributor, in order to spread the powder in the transverse direction of this tube and thus , produce a good mixture of powder in the fiber material, before the final descent to the wire 2.

In Figure 11, it is shown that a final result can be obtained by means of a pair of rod electrodes 50 mounted below the mouth 20, again for spreading the powder. Figures 12 and 13 show a modified embodiment of the invention, in a system of the type discussed. Here, a parallel, axial distributor tube 52 is mounted internally in one or preferably both of the cylindrical tubes, which, as indicated in FIG. 12, can be mounted in an adjustable manner. This tube is perforated on its underside, and contains a worm conveyor 54, which, from a non-illustrated supply, can be operated to carry the SAP powder through the tube, such that the powder is let out through from the bottom of the perforated tube, with adequate capacity. It must be ensured that there is sufficient dust over the entire length of the tube, also at the end opposite the feed end, and since one may also wish to adjust the capacity of the system, by changing the speed of rotation of the worm conveyor, the system it must preferably be dimensioned, such that even at low capacity, a surplus of powder is transported, whereby the final surplus can be collected at the exit end of the tube. Instead of the worm conveyor 52, it will be possible to use a drag chain, which, if desired, can run forward through the tube in one of the tube drums and return through the tube in the other tube drum.

It is noted that in relation to this date, the best method known by the applicant to carry out the present invention is that which is clear from the present description of the invention. Having described the invention as above, the content of the following is claimed as property:

Claims (6)

1. A method to manufacture continuous papers, seated with air, with a width of more than 30 cm and with a content of superabsorbent powder material, called SAP, whereby the continuous paper is formed in a foraminous metal cloth, when guiding down against this metallic fabric an air-fluidized flow of cellulose fibers, from a distribution unit placed on top, supported by an active suction effect on the underside of the metal mesh, the continuous fiber paper, thus formed, in the moving metal web it is subsequently established by the addition of a binder from the outside or by the action of an initially mixed binder, typically on heating for the action of the binder fibers, activated by heat, mixed, after the addition of the binder. material of absorbent powder to continuous paper, characterized in that the powder, absorbent material is added in an intermediate layer of the distribution of the fibers, and that is to say, after the initial formation of the fluidized flow with fiber air and before the final deposition of the fibers in the continuous forming paper, the powder supply that is arranged such that the powder is distributed in a mandatory manner to everything length of the whole width of the continuous paper formed initially or on partial sections of the width thereof, after which, the powder is completely distributed by the action of the air flow that operates to effect the final distribution of the fiber material in the wire mesh deformation.

2. A method according to claim 1, whereby a fiber distributor of the type comprising more forming heads, successively arranged in the direction of movement of the wire mesh, is used within a common formation box, characterized in that the addition of the absorbent powder is effected by driving the powder downwards through a flat duct or a number of tubes projecting downwards into the interspace between the two forming heads.

3. A method according to claim 1, characterized in that the absorbent powder is allowed to exit through a slot forming the channel, at the lower distribution end of which a means is arranged to actively produce a controlled spreading of the powder.

4. A method according to claim 1, characterized in that the absorbent powder is supplied via a perforated tube that extends through the length of the continuous paper, inside the formation space, the powder that is transported through the tube by means of a conveyor, from one end thereof, such that despite letting out the dust through the perforations, a powder passage will occur for recirculation from the other end of the tube.

5. A method according to claim 4, in which a forming head of the type having two perforated, juxtaposed tube drums, located in a common formation box, characterized in that the powder is used for the settlement of the fibers. Absorbent is supplied internally in this tube drum.

6. A system for producing a continuous paper seated with air by the method according to claim 1, with a forming head operable to spread an air stream of fluidized fibers on a forming wire moving with a width of the continuous paper of at least 30 cm, characterized in that the forming head is provided with an internal supply means for feeding powder to the area just above the formation zone, this medium has outlet outlet areas located with uniform distribution over the entire width of the continuous paper.