FI57629B - FLYERSKET FIBROESA PLATTOR - Google Patents

Description

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Patent · och registorstjrralsan '' AmMcm uttagd och uti.tkriftMi public · ™ * 30.05.80 (32) (33) (31) Pjrrdettjf «uoikwif —B« | trt priority 23.08.73

England-England (GB) U007U / 73 (71) Karl Kroyer St. Anne's Limited, St. Anne's Road, Bristol BSU UAD,

Engl ant i -England (GB) (72) Brian William Attwood, Hanham, Nr. Bristol, Dennis Raymond Hicklin,

The present invention relates to a method and apparatus for forming a multilayer web of fibrous cellulosic material, comprising the steps of forming a mat of fibrous cellulosic material, Baths, England-England (GB) (7U) Oy Roister Ab (5U) Multilayer Fibrous Sheets - Flerskiktiga fibrösa plattor dry by lowering the cellulosic fibers in the dry state by means of an air stream onto the main forming belt, and forming a sheet of aqueous fibers of cellulosic material.

The addition of water to the dry formed tissue is normally performed using water jets. However, even if these are mounted across the tissue formed to move them, there is a risk of a single jet becoming inoperable for the formation of dry spots or streaks in the dry tissue, the resulting tissue not homogeneous and differing in moisture depending on the amount of moisture present during fabric reinforcement. In addition, the maintenance difficulties associated with the jets, as well as the need for conveyors to move the jets, are not pleasant in continuously operating equipment used in the paper industry. It is an object of the present invention to avoid the use of jets when introducing water into dry formed fabrics.

2 57629

The method of forming a fibrous web of the present invention is characterized in that a mat formed of dry cellulosic fibers and a sheet of aqueous cellulosic material are joined together under sufficient pressure to form a multilayer web of material by simultaneously reinforcing , by passing the combined multilayer web through at least one nip formed by at least one pressure roller and a heated cylinder, wherein the dry formed mat receives at least most of the moisture required for its strength as moisture is transferred from the aqueous sheet to the dry formed mat.

Due to the difficulties in introducing water alone in small enough amounts to provide the required and yet sufficient moisture content to the board and to prevent the film from breaking, the method preferably uses an aqueous board consisting of a relatively thick fibrous mass. Preferably, such a pulp contains 10-15% solids, but given the difficulty of forming such a pulp, which would also form a homogeneous fibrous mat when placed on a wire, it may be necessary to use e.g. a fibrous pulp having a solids content of 3-5%.

The pulp is preferably directed to a fibrous mat by means of a nozzle.

The preferred embodiment involves forming the fibrous mass into a web by a wet process with a separate manufacturing belt and then transferring it to the fibrous mat as a wet web. The dry matter content of the wet-formed layer can be on the order of 15%. The conventional wet method uses, for example, a cylinder machine, a suction press, a pressure press or other procedures suitable for handling high-density materials.

When a wet web is used to transfer water to a dry formed fibrous mat, it is preferred that the water content of the wet web is sufficient to provide all of the moisture content required to transfer water to the dry fibers to provide sufficient reinforcement in the next reinforcement device.

The use of a wet formed web has several advantages. In particular, mixing of the fibers on a dry mat is avoided. The use of water or pulp, as described above, can damage the shape and the use of a wet formed web avoids this difficulty. In addition, when using the conventional wet method, this wet web imparts strength to the layer because the strength provided by heating can be used to advantage. In addition, all adhesive and other additives can be added during the mixing step to avoid gluing and coating difficulties on the machine wire.

3,57629

Preferably, the wet web forms the inner layer of the final product and, because it has the properties of the wet process and the associated strength, it also has advantageous folding properties and other advantages of the wet web. However, the manufacture of the product does not involve drying difficulties or, in particular, the use of cumbersome equipment, as moisture is transferred to the dry fibers in the subsequent reinforcement process.

This arrangement provides a method for dry deposition of fibers, whereby moisture is added to the fibers using a wet web, thereby avoiding syringes and further achieving the benefits of the wet web when adding moisture.

According to another object of the present invention, there is provided an apparatus for forming a multilayer web of fibrous cellulosic material, wherein the dry fibrous cellulosic material is wetted and formed into a reinforced web, the apparatus having a support surface and means for dry forming the cellulosic fibrous mat thereon. Preferably, the device includes means for joining the sheet of aqueous fibrous mass to the dry formed mat and means for reinforcing the combination by subjecting it to heat and compression.

The device may include a child to guide the high solids mass onto the mat.

The apparatus may include an additional treatment belt with a conventional wet process apparatus for forming a web thereon and means for transferring the wet formed web to the fibrous mat.

The device may include heated press rollers to reinforce the wet mat.

The invention is illustrated by way of example only in the accompanying drawings, in which Figures 1 to 3 schematically show three embodiments of the device according to the present invention.

Referring to Figure 1, there is shown an endless wire 10 which is the main manufacturing wire of the manufacturing apparatus shown. Above the manufacturing wire 10, ten distribution heads 11 are placed, through which dry fibers, e.g. cellulose mixed with 5% by weight of starch binder, are guided in an air stream on the upper surface of the wire 10 by means of an air ecosystem (not shown). The press roll 12 lightly presses the nonwoven mat to compress it.

The housing 13 with the slit 1U is mounted directly above the wire 10 and directs a high solids aqueous mass on the upper surface of the nonwoven. The moistened nonwoven mat passes around the heated reinforcement cylinder 15 and is pressed against it by four pressure rollers 16. The additional pressure roller 17, which may also be heated, provides strength to the damp nonwoven mat. The reinforced web 18 moves to the surface finishing and gluing stations if these are needed for the final product.

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Slit ih is used to direct the fibrous pulp to the nonwoven and dry matter contents of the order of 10-15% are recommended, but a solid content of the order of 3-1 *% may be very optimal with currently available feed boxes and slits. The surface temperature of the cylinder 15 can be of the order of 120 ° C and each of the pressure rollers 16 can be operated at a pressure of about 10 kp / cm. The pressure roller 17 can be operated at an even higher pressure and at a higher temperature.

An apparatus that can be used to apply a high solids pulp of the order of 15% is shown in Figure 2. This apparatus uses a main manufacturing wire 10 and a reinforcing cylinder 15 similar to the nozzles 11 in Figure 1. However, to add wet pulp to a dry nonwoven wire 20, a cylindrical to form a web on the additional manufacturing wire 21, which web is transferred by means of a roll 22 to the upper surface of the dry nonwoven on the wire 10 by means of a vacuum box 23.

In a typical installation, the ten distribution nozzles 11 can each feed the fibers in an amount of 20 g / m, whereby 200 g / m of web is obtained for the wire 10. The fibers are blended with 5% starch and have a moisture content of about 10% at this point. The cylindrical transfer device 20 forms a nonwoven mat having a solids content o of 15% '· η to obtain a final web of 25 g / m.

Thus, the wet web placed on the wire 10 contains sufficient water to form a moisture content of about $ 35 »for the mixture of dry nonwoven and wet web entering the reinforcing member provided with the cylinder 15.

The parameters of the reinforcing part comprising the cylinder 15 and the pressure rollers 16, 17 may be the same as those shown in connection with Figure 1 and are discussed in more detail in UK Patent Publication 1 k2h 682,

Instead of a cylinder transfer device, other wet processing methods can be used, e.g. suction, pressure or other devices suitable for handling materials with high solids contents. The wire of the flat wire machine can be used.

Instead of placing the wet fibrous web on the dry web, it is possible to place the dry web on the wet web by appropriately changing the structure of the machine. Due to water losses through the wire, additional moisture may be required in the wet web to compensate for these losses.

Figure 3 shows a corresponding machine structure. This implementation is similar to that in Fig. 2, in that the cylinder machine 20 'is used to form a web with a high solids content, which is transferred from the additional manufacturing wire 21 by means of rollers 22'. However, in this embodiment, the web is transferred to 5 57629 reinforcement cylinders 15 before the dry formed nonwoven is transferred to it from the wire 10. Thus, the dry formed mat is effectively combined with a wet formed web already drying in the cylinder 15. However, the moisture content of the wet formed web is just sufficient when it joins the dry formed mat. to moisten the carpet before reinforcement by means of rollers 16.

As shown in Figure 3, the cylinder machine 20 'is of the pressure type and preferably uses a BRDA-St.

However, a conventional cylinder or VAT machine or, in fact, any wet former can be used.

When using the device according to Figure 2, the pulp can be ground, in which case the normal strength associated with the wet layers can be used. Sizing and coating agents can be added to the pulp in the grinding step, thus avoiding the use of sizing and coating agents in the reinforcement step.

The wet layer forms the liner of the final product and has the usual strength and refractive properties of the wet layers, these complement the properties characteristic of the dry layer, such as false refraction and direction-independent properties. In addition, the above method avoids water spray fibers to add moisture to the dry nonwoven mat, which is a considerable difficulty in the dry process.

When multilayer products are required, the two units of Figure 2 can be reciprocated, with the wet web forming the outer layers of the product and the dry web forming the inner layers of the product.

The invention can be used in the production of nonwoven corrugated or textile-like materials as well as paper or multilayer paperboard.

Claims (10)

6,57629 A method of forming a multilayer web of fibrous cellulosic material, comprising the steps of forming a fibrous cellulosic mat dry by lowering dry cellulosic fibers by air flow onto a main forming belt, and forming a sheet of aqueous cellulosic fibrous and joining together under sufficient pressure to form a multilayer web by simultaneously reinforcing the fibers of the dry mat to a strong layer by subjecting the mat to moisture, heat and pressure, passing the combined multilayer web through at least one nip formed of at least one die at least most of the moisture it needs for its strength as the moisture transfers from the aqueous sheet to the dry formed mat. A method according to claim 1, characterized in that the sheet is formed by wet technique on an additional manufacturing strip before it is joined to the mat. A method according to claim 2, characterized in that the aqueous plate is formed by a cylinder machine. k. A method according to any one of the preceding claims, characterized in that the moisture content of the board and mat combination before reinforcement is about 30% by weight. Process according to one of the preceding claims, characterized in that the aqueous cellulose sheet has a dry matter content of 10 to 15% by weight. Method according to one of the preceding claims, characterized in that the temperature of the reinforcing cylinder is at least 65 ° C and the pressure of it or of each press roll is at least 26 kg / linear cm. Method according to one of the preceding claims, characterized in that the dry-formed mat contains about 5% by weight of starch. The apparatus for performing the method of claim 1, wherein the dry-formed fibrous cellulosic material is moistened and formed into a reinforced web, the apparatus having a support surface and means for dry-forming a cellulosic fibrous mat thereon, characterized by means for forming an aqueous fibrous pulp sheet. for joining the dry-formed mat and means for strengthening the combination by subjecting it to heat and compression. Device according to Claim 8, characterized in that it has an additional forming strip, a wet-forming device for forming a plate on it and means for transferring the layer to the material web. 57629 Device according to claim 8 or 9, characterized in that the means for reinforcing the combination comprise a heated cylinder and at least one pressing roll which, together with the heated cylinder, forms at least one pressing point. 8 57629