MXPA96002639A - Method and system to manufacture a fibrosaformed network in s - Google Patents

Abstract

For the manufacture of dry-formed webs of cellulose fibers there are two different ways of adhering or binding the fibers, namely, a glue application to the network surfaces and, respectively, a mixing within the fiber fiber filler. heat-activated binders, which are activated by the passage of the network through a heating zone. The last method is the best in practice, of course, particularly for liquid absorption products, but there is a problem in that the finished material becomes powder, with short unbonded fibers. According to the invention, it has been speculated that this problem can be largely avoided by the auxiliary use of the first method, modified to the effect that both surfaces of the network are concurrently subject to a supply of a very small amount of glue, foam condition, for example, only with 1 gram per square meter, whereby the surfaces remain permeable, but also sealing against the extrusion of the short fibers from the inside of the

Description

> METHOD AND SYSTEM TO MANUFACTURE A FIBROSA NETWORK FORMED IN DRY The present invention relates to a method 5 for the manufacture of a fibrous network material formed in dry, based on dry-formed cellulose fibers, with an appropriate adhesion. The arrangement or arrangement of the fibers for the formation of a current network, is usually effected by means of a paste material | A paper bin that is shredded and mixed in an air flow, which carries the loose fibers to a distributor head above a perforated, movable forming wire, below which a suction chamber is placed for downward suction of the fibers against the wire, where these are currently deposited as a network of cohesive fibrous pulp, with a desired network thickness. The products are typically used as sheets for the absorption of liquids. It is important that the dry-formed pulp web be stabilized or bonded, and in practice this is accomplished in two different ways, for example, by the application of glue or by the use of adherent binder fibers: 2 * > 1. Gluing: On a wire carrier the REF: 22688 > . The pulp network is passed through a gluing station, in which, by means of a number of nozzles, an appropriate tail, usually of the latex type, is sprayed onto the net, after which the wire is guided to the net. through a tunnel oven for drying the glue. After this the network is transferred to an overhead wire, against which it is fixed by suction from above, so that the lower side of the network is exposed, and the network is then conducted through or over another gluing station , where the brook is correspondingly sprayed against this lower side of the net. After this the network is conducted through a tunnel kiln for drying and final solidification of the tail, after which the network supports itself and can be rolled up for storage or distribution. Through this method the networks are manufacturable ^^ W in high quality sheet, but for the machinery, the method is rigorous and vulnerable to irregularities at the gluing stations. It is also a limitation that the method is not appropriate for thick-web networks, since it is difficult to achieve a high depth of penetration of the tail, with which a relatively thick layer tends to segregate in the plane central, where the adhesion is weak or missing * completely. The products will typically contain about 85% cellulose fibers and about 15% binder. The typical weights of the products can be 50-120 g / m2, since the heavier products are delaminated easily. In addition, the products are not suitable for containing superabsorbents. 2. Use of binder fibers: Through this In this method, a homogeneous mixture of heat-activated binder fibers, also referred to as heat-adhesion fibers, is produced within the cellulose fibers, whereby the dry-formed web material can be fixed only when driven to a through a heating zone. For the system and the control, this is a simpler method, by means of which thick networks are also manufacturable, since ^^^ binder fibers will be uniformly present both in the outer planes and in the planes interiors of the material. The weight of the product can typically be 40-800 g / m2, and a considerable mixture of superabsorbent agents or other additives is usable. The achievable quality is completely acceptable for many different applications, however, they occur Certain disadvantages are due to the fact that for economic reasons the mixing percentage of the thermobonding fibers typically has to be limited to approximately 15%. Normally, cellulose fibers have length ranges between 0.5 and about 5 mm, while heat-adhered fibers are often 6 mm or larger. In practice this gives a good adhesion of the longer cellulose fibers, while the shorter cellulose fibers are adhered incompletely. This means * 10 that the material can be fouled with short fibers, which is in general a profound disadvantage, and the products are therefore mainly used as insert materials in outer casings. In this way the dirt in dust can be eliminated towards outside, but when they return there are large-scale problems within the plants, where the products are handled as insert material. Here you must use systems «Powerful evacuation, which by themselves create problems, and to this must be added that the aspiration The associated "dust" implies an elimination of a considerable part of the original material, with which this part is added completely in vain and thus represents an effective waste. By means of the invention, it is desired to counteract the fiber disintegration, which naturally gives rise to speculations at a higher mixing rate of the binder fibers with different lengths. However, this is hardly any realistic possibility, and by means of the invention it is understood that a better solution will be a combined use of the two mentioned methods, albeit with the tail method in a modified form. As mentioned, by means of the gluing method an adhesion result is achieved, which will be better on the surface of the network and poorer in the central layer of the network, but if, by a combined application of the thermobonding binder fibers is only a matter of sealing against dust coming from the network, this will be achieved through the coating of the 'network with superficial tail layers, very thin. Since the cohesion in the network material will be ensured by the activation of the thermobonding binder fibers, a surface adhesive will be applicable simultaneously on both sides of the web. the already self-supporting network, and the two layers of glue applied, which can be extremely thin, will be hardenable by passing them through an additional, simple heating zone with relatively low capacity. When the surfaces of network material appear in this way with junctions *. of thin glue, a seal is made against the extrusion of the short cellulose fibers from the network material, and this is exactly the desired result. This implies that by means of the invention there will be no speculation on any increased local adhesion of the mentioned fibers, although the effect may partially depend on the occurrence of increased fiber bonds at the surface, while this is to a lesser extent a matter of effective coating of the fibers. the surface. In this way, a main characteristic of the present invention is that in the joining of the fibers use is made of the mixed thermo-adhesive fibers, while the surfaces of the network are sealed in greater or lesser degree by the addition of glue in modest quantities, without ambition of any deep penetration of the glue within the material. It is not then # decisive how the tail is applied, but for the invention, however, it is an important subaspecto Indicate how the glue can be applied in a new and very economical way to achieve the desired result. Thus, according to the invention it is a preferred possibility that the glue is applied in a condition in the form of foam, whereby this can cover surfaces with a minimum of dry matter * in it. The effect has been observed that the liquid in the settlement of the foam preferably settles in the areas of the cross-linking between the fibers, rather than by a general settling on the surfaces of the fibers, and this effect is optimal for the desired result, that is to say, that by using small amounts of liquid and dry material, a bond of the short fibers can be made on the surface, so that they remain partially or in their place, and partially help the sealing against the extrusion of the fibers. short and unbound fibers from the inner part of the network material. This remains light and porous, so that for example it will be appropriate for fabrics with impregnated moisture. 15 A good effect is achieved by mixing only 1 to 2 g of binder per m2 per side, using a binder in the form of foam, dispersed in # water, only with approximately 2 g of dry pulp per liter of foam. The foam can be generated in a conventional foaming unit, and in the volume of foam the glue may then be present in an amount of only 0.2% by volume. Correspondingly, there will be very little water to be -dried out of the product, thereby drying and The hardening of the glue can be effected with a rather low energy consumption in the hardening zone, after coupling. The application of the foam can be effected in any appropriate manner, for example by vertical, horizontal or downward feeding of the network through the coupling rollers, with controlled supply of foam to the point of attachment of the roller on both sides of the net. A process of lamination of the net gives an attractive result, since the surface fibers will be joined in stretched positions, whereby the surface obtains a smoother and firmer character. By means of the mixed wetting agents, it is possible to control the depth of Penetration - of the pre-foamed binder. If the depth of penetration is too small, the layer of adherent or thin binder on the surface, * will be scraped soon, and if the depth is too great, this will partially involve a consumption It will be unnecessarily large in binder and will partially give the product a character in the form of plastic, with slow absorption of water. As mentioned above, the glue can be dried and hardened at low energy consumption, However, this can take place at a high temperature such that the adhesion fibers can be reactivated, and as explained below, this can give the most extraordinary result that the tensile strength of the network can be increased to almost double. The invention gives significant results with respect to the planning of manufacture of products with desired qualities, without which. the qualities are altered by a successive extrusion of the short fibers from the products. Since this amount of fiber can be of a remarkable size, the associated result will be that clocaría is possible in a much better way to achieve the desired qualities of the finished product. The invention is, in a preferred embodiment, shown schematically in the drawing. In the drawing a forming wire 2 is shown, which has a transfer section 4 below a pair of distributor heads 6, to supply a mixture of loose cellulose fibers, and heat-addable fibers to section 4, on which A loose net 8 is formed in this way. The latter is compressed between the rollers 10, and then transferred to a transport wire 12 by means of an aerial transfer station 14. The wire 12 carries the network through an area of heating 16, in which the thermobonding fibers are activated for the bonding of cellulose fibers, usually at a temperature of 130 to 140 ° C. After this, the now stabilized and self-supporting network is taken through the coupling rollers 18. Conventionally the network, now as a product network, is hereinafter taken for winding in the rolls 34 of finished products. By the invention, however, a The station 20 is subsequently coupled, in which the net 22, on both sides, is provided with a binder foam, preferably by the net which is led downwards around a bypass or deflection roll 24 downwards to a unit called a scarf , consisting of a pair of rollers 26 positioned with adjustable spacing, and with upper means not illustrated, for the addition of the impregnation compound • 28 point of upper roller clamping, on both sides of the network 22 driven downwards. In this way it is possible to control the supply of impregnation compound, partly by adjusting the coupling clamping point, and partly by regulating the flow of the compound to a higher or lower level, above of the clamping point of the roller, for example inside *, of a regulation range of 2 to 20 cm. In addition, the supply can in this case be adjusted for the contents of the dry material in the binder (as an example within 5 to 15%) and by adjusting the density of the foam, for example within the range of 20 to 100 g / lt. The hardness / softness of the product can be controlled by choosing a binder with a hard or soft film, respectively, while * ,. that the hydrophilic / hydrophobic qualities of the product can be controlled by means of suitable additives or pre-foaming agents. Having passed the unit 20, the network 22 is taken on a band 30 through a tunnel of Heating 32, in which the network, preferably by means of added hot air, is heated to a rapid evaporation of the aqueous part of the foam 28, after which the network is wound on the usual distribution roller 34. Surprisingly, it has been proven that by using an appropriate high temperature, in the tunnel kiln 32, preferably 130-140 ° C, not only an efficient water evaporation is achieved, but also an improvement of the tensile strength. of the network product, from a total of 25 to 100%. This can not be explained from the very modest supply of glue on the outer sides of the network 22, but from other circumstances, however: When the network 8 passes the rollers 10, it is pressed down against the carrier wire 2, which is normally a woven grid wire made of intersecting threads, which, in the manner of associated intersections, will form local parts, projecting outwards and lowered, # 10 respectively. In the projection parts the fibers in the network will be extra-compressed when the rollers 10 pass, so that the fibers as they are here locally depressed, will be extra-sensitive to the bonding or welding effect that occurs in the area of . Heating 16. However, this condition is weakened because the network, while passing through the transfer unit 14 is slightly loosened, influenced by the weak attraction force and the movement of the network, which is necessary for remove the wire of the forming wire, and transfer it to the transfer wire, - just as a corresponding looseness will occur in the transfer from the transfer wire to the wire of the furnace. In addition, the compressed network has a certain power of Expansion, and thus the originally well-depressed fibers will not all be well defined when passing through the hardening tunnel 16. However when the network 22 passes after this by the station 20, a new compression of the network and a some increase in the cohesion in the surface layers of the network, so that during the next step through the furnace unit 32, not only the evaporation of the water from the foamed glue will be caused, but also an activation by heat, renewed, of the heat-resistant fibers, as is preferably operated at approximately the same temperature as in tunnel 16, for example about 140 ° C. In this way the tail treatment of the network will be with some type of catalyst for the achievement of a tensile strength, significantly increased, subsequent, of the network material. The immediate result of the invention, to know the union or the sealing of the "fibers in powder" Under the maintenance of an unsealed surface, it is also advantageous in still another way, since a retained amount of the fibers just inside the fixed surface layers, has a significant effect of fluid spreading, which is of great importance. importance in absorption products. In many of these products it is almost known in advance that the liquid supply during use will appear only in a sub-area of the product, and for a desired absorption capacity, a superabsorente has to be dosed in consideration of this. If the product can appear with a good distribution ability, the dosage of the superabsorbent can be minimized. There is reason to emphasize that aqueous foam can be added on both sides of a product having a central layer of a superabsorbent material, without said material having to become activated with water. For example, the product may have a lower layer of fiber of 70 g / m2, an intermediate layer of superabsorbent of 30 g / m2, and a layer fiber upper of 30 g / m2. The invention is also advantageous with respect to filter materials, where the conversion to powder, significantly reduced and the sustained content of short fibers, is of a positive effect. It is possible by the invention to use the binder foam as a carrier for coloring pigments, these being added before foaming, whereby a certain coloring of the products can be produced in a simpler manner. However, already Since the binder is normally used in very modest amounts, only the dyeing in pastel colors is achievable, unless the process is specifically adapted with respect to a stronger dyeing. By the invention it has been proved that it is possible to foam-coat an air-deposited product, thermally bonded, which only contains some small percentages of binder fibers, for example 5%, by the application of an increased amount of glue binder, by example 10%, whereby it is possible to manufacture a product predominantly "joined by latex" without the binder having to be added by the traditional spray technique. Hereby the same abrasion resistant surface is achieved, than by traditional binder spraying, but without the associated limitation of the maximum thickness of the network, e'l. which is usually between 100/120 g / m2. To such thicknesses it has been necessary to impregnate the network in order to avoid delamination of the product, but this is not necessary in the present situation, and this means, among other things, that products with rather low density can be manufactured. According to the invention, when working with a significantly reduced amount of glue, the coarse products will maintain a remarkably increased amount of cellulose fibers not covered by a film of binder, and thus will have optimum absorption capacities. From a process point of view, it is advantageous that the binder application is carried out only at one site in the system, and not at two sites as in the prior art. In addition, it is more advantageous to avoid traditional spray stations, which give rise to many problems with respect to operation and maintenance while, for example, a scarf provides a good and uniform treatment result, and is easy to maintain . However, other foam application techniques could be used, for example the so-called mesh coating. In principle, nothing prevents the binder foam from being applied to the network, before it is thermally fixed, and in that case it may be sufficient to use a simple, successive heating zone for the activation of the binding fibers and the binder. tail agent. Finally, a couple of manufacturing examples of the specific products according to the invention should be given: A. Production of a hydrophilic product, covered with foam.

A product deposited by air, of 60 g / m2, consisting of 85% of wood cellulose fibers with the highest possible content of long fibers, and 15% of heat-resistant fibers, is covered with foam in a scarf, the roller clamping which is adjusted to 0.6 mm. The pre-foamed binder is produced in the following manner: Specification of the binder mixture: 11.1% of Sarpifan WRG (Stockhausen, Denmark). 0.2% of Rohagal 10 n (Rohm GmbH, Denmark) 88.7% of Water The binder is converted to foam at a density of 20 g / l. If the foam level in the scarf is approximately 4 cm, approximately 1.5 g of binder (100% of the dry material) is added every m2 on each side of the product. After the foam coating, the "product is dried in a normal way, for example B. Manufacture of a hydrophobic product coated with foam.

The product is manufactured in the same manner as mentioned above, but with a different specification of binder mixture.

Specification of the binder mixture: 11.1% of Sarpifan WRG (Stockhausen, Denmark) 2.0% of Stokal STA (Stockhausen, Denmark) 86.9 of Water It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Having described the invention as above, property is claimed as contained in the following:

Claims (10)

1. A method for the manufacture of a dry-formed paper material, by successively laying a network of cellulose fibers on a forming wire, and treating the network to provide adhesion of the fibers thereto, characterized the method because the adhesion or agglutination of the fibers is effected by a combination of an activation of thermobonding fibers, supplied by the previous mixing in the cellulose fibers, and a binder application to the surfaces of the network, this application being conducted with a part of the material dried significantly below 15%, preferably from 0.5 to 5%, for the purpose of adhering the short cellulose fibers to the surfaces.

2. The method according to claim 1, characterized in that the binder is applied in an amount of 0.5 to 10 grams of dry material per square meter of grid surface.

3. The method according to claim 1, characterized in that the binder that is applied to the surfaces of the network after it is stabilized by thermal activation of the heat-absorbable fibers, and in the binder is hardened by a heating run of the network at such a high temperature that the adhesion fibers are reactivated.

4. The method according to claim 1, characterized in that the binder is applied in a foam condition, for example, with water / air as 10 carrier.

5. The method according to claim 4, characterized in that the network material, in spite of the application of the aqueous binder, is manufactured 15 with one or more core layers containing or consisting of superabsorbent material.

A 6. The method according to claim 1, characterized in that the binder is used in 20 mixture with pigments.

7. The method according to claim 1, characterized in that for the manufacture of a predominantly thermally adhered material, 25 makes use of a network with 10 to 25% thermo-adhesive fibers and a binder dose of 0.5 to 10 g / m: surface.

8. The method according to claim 1, characterized in that for the manufacture of a material predominantly bonded with binder, use is made of a network with 3 to 7% of heat-resistant fibers and a binder dose of 5 to 20 g / m2. Of surface .

9. A system for carrying out the method according to claim 1, comprising a device for dry laying the fibers on a forming wire, to form a fibrous network, and a device for driving the means for adhering or joining the fibers, characterized the system by the combination of the laying of the device that is of the type that operates based on fibers, with the mixed heat-absorbable fibers, whereby the driving device is a heating zone, and of the presence of a station for the application of relatively small amounts of binder to the surfaces of the network, namely, enough to make the finished network material, mainly without dusting.

10. The system according to claim 9, characterized in that the binder station comprises means such as a scarf for the application of the binder in a foam carrier. 15 20 25