FI58184B - BEHANDLING AV FIBERMATERIAL - Google Patents

Description

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09.0U.75 England-England (GB) U3985 / 7U, 1UU75 / 75 (71) Karl Kroyer St. Anne's Limited, St. Anne's Road, Bristol BSU UAD,

England-England (GB) (72) Denis Raymond Hicklin, Bath, Brian William Attvood, Hanham Nr. The present invention relates to a process for the production of a multilayer web of cellulosic material suitable for folding into a carton, in which case a cellulosic fibrous material is dry-formed into a layer of fibrous fibrous material. then the layers are combined into a web.

In a typical method for dry forming a fibrous web, a fibrous raw material, e.g. wood cellulose defibered into individual fibers in a hammer mill, is conveyed in a to help form the fibrous web.

If it is desired to produce multilayer paper or paperboard by the method described above, it is advantageous to use a series of dispensers which, with their respective suction boxes, are arranged in succession along the strip. In this case, the successive layers land on top of each other. Each distributor is usually fed with fiber from a hammer mill connected to this distributor.

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The above method and apparatus for forming multi-ply dry-formed paper or paperboard are hereinafter referred to hereinafter as "the type described".

The method according to the invention is mainly characterized in that the combination of the following steps: a) impregnates the outer layers with a stiffener, e.g. starch, b) impregnates the inner layer (s) with a first adhesive, e.g. wax / resin adhesive which makes the inner layer (inner layer) (c) wetting the combined layers to a moisture content of about 35% by weight, d) reinforcing the wetted, combined impregnated layers by passing the web around the surface of a cylinder heated to about 110 ° C and pressing the web into contact with the surface by means of press rolls 17-1 * 1 * kp / cm.

The second adhesive is preferably selected from a rumble comprising starch, gelatin, latex compounds, polyvinyl acetate or combinations thereof, with or without a mineral such as clay.

The second adhesive may be applied to one or both sides of the web.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which Figure 1 is a schematic diagram of a machine for forming a multilayer web of fibrous material according to the invention, Figure 2 is a cross-section of a product according to the invention at an intermediate stage; + is an alternative shape to the machine shown in Figure 1.

Figure 1 shows a machine for making multilayer board from dry laid fibers. The machine comprises an endless perforated plastic strip 9 on which the dry fibers are lowered from successive manifolds 10, 11, 12 and 13 arranged along the strip. A vacuum, or suction boxes 1, are placed below the strip 9 below each manifold, thus holding the fibers on the strip. Thus, each dispenser provides one final layer of paperboard, ends 10 and 13 provide outer layers and 11 and 12 inner layers.

3,5884

Chopped fiber or a mixture of chopped fibers and other materials is fed to each manifold 10, 11, 12 and 13 from a hammer mill 15, 16, 17 and 18, respectively.

Dry wood chips from rolls 19 and 20, respectively, are fed to hammer mills 15 and 18. Approximately 8 wt.% Of dry Viseosol from dry starch is added to the pulp in hammer mill 18 from starch source 21.

The pre-torn dry wood chips are fed to hammer mills 16 and 17 from tanks 22 and 23, and before it enters the hammer mills it is sprayed with water-resistant wax / resin glue from sprayers 26 and 27, respectively. - from sources 2b and 25, respectively. As a result, the inner layers deposited on the manifolds 11 and 12 are water-resistant due to the water-resistant resin / wax adhesive they contain.

The resulting dry-laid multilayer web 8 is then moistened with a water jet 28 from its surface layer (i.e., counted by a dispenser 13) to give a moisture content of about 35% by weight. The wet web is reinforced by conveying hot steam over the surface of the heated cylinder 29 at a temperature of 110 ° C, the web being pressed into contact with the cylinder on one quarter of its circumference by compression rollers 30 at compression pressures between 17 and 1 kp / cm.

Leaving the cylinder 29, the web 8 is moistened from below (i.e. the layer calculated by the dispenser 10) with a water jet 31, which is a 5-10 # solution of Viscosol starch. The moisture content of the wetted web is 15-20% by weight. The web passes through a slot 32 formed by a steam heated cylinder and a press roll at 110 ° C for 3 to 17 kg / cm compression to reinforce the underside or rear layer. The web then passes over the rotating cylinder 33 at 110 ° C. The dried web, which typically contains 6-8 wt.% Moisture, then passes through the adhesive press rolls 3 at a compression pressure of 9 ^ / kp / cm. A solution of e.g. 80 # Viscosol starch and 20 # polyvinyl acetate is added by means of a press through nozzles 38. The adhesive-pressed web is subjected to a hot moist compression or casting step by conveying it to a steam-heated cylinder 35 at a temperature above 110 ° C and pressing it into contact with a rubber press roll 36 at a compression pressure of 3 ~ 9 kp / cm. This delivery smoothes and strengthens the surface layer of the board. A similar hot wet press delivery can be made on the opposite surface with a second heated cylinder and press roll. The web passes to the coating and finishing units generally shown in 37 · * 58184

The adhesive added to the web 8 through the nozzles 38 contains water and the amount of substance used is adjusted to ensure that the total moisture content of the bonded web leaving the adhesive press rolls is between 15-30% by weight, preferably about 25%.

An alternative method of treating a wet bonded web after it leaves the rollers 3 * + will now be described with reference to Figure 1.

The glued, moist web is conveyed after leaving the gluing press rolls 3l + around the additional guide roller 1 + 6 and is hot-pressed or hot-formed by passing through a press-fit slot formed by a large heated cylinder 1 + 5 cooperating with a press roll 1 + 7 around which the felt passes. then through a finishing compartment, which may comprise coater and calender rolls, before being rolled as a finished carton onto a storage drum.

Alternative adhesives in liquid form include gelatin, latex compounds, polyvinyl acetate, or combinations thereof, either with or without a mineral, such as clay.

The adhesive can be applied in any suitable manner. Instead of being applied to both sides of the web, it can also be applied only to the other side.

In this example, the web has a thickness of between 50 and 500 g / m and is passed through glue presses and hot press rolls at a speed of 61 m / min. Roll 1 + 5 is heated with steam to give a surface temperature between 93-20l + ° C. There are 9-1 + 1 + kp / cm between the slit press rolls 1 + 5 and 1 + 7.

Roll 1 + 5 has a smooth surface or a textured surface depending on the desired surface finish of the web. Roll 1 + 5 operates on the upper surface of the web, i.e. on a surface free of marks of the forming wire or the like.

In a variation of the invention, the web leaving the press rolls 1 + 5 and 1 + 7 is hot-pressed again, but this time the second or wire-patterned surface of the web is on a large heated roll in a second series of press rolls.

If the web leaving the press rolls 1 + 5 and 1 + 7 is not moist enough for additional hot pressing, it is re-glued to give the required moisture content before feeding to the additional press rolls. In re-gluing, each web surface can be re-glued or only the other surface is glued.

When the roll 1 + 5 has a flat surface, it has been found that the invention provides a web having an excellent surface or surfaces for subsequent printing.

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Thus, this example of Figure 1+ provides a method of treating a web made from fibrous material by a dry forming method in which, after the web is formed, made strong and dried, it is glued to give a moisture content of about 25% by weight and then glued to a wet web. hot pressing by passing it through a pressing slot formed by a heated roll which cooperates with the pressing roll.

As a result of the gluing and hot pressing shown in Figures 1 and 1+ of the outer layers of starch containing web, these outer layers stiffen and strengthen. Penetration into the middle layers is limited by the amount of water-repellent adhesive in the middle layers. Stiffeners (e.g. starch) are thus concentrated in the outer layers, which are ideal areas for improving web stiffness.

The gluing of the middle layers thus prevents the reception of stiffening chemicals, such as starch, which are applied to the outer layers.

Figure 2 shows a section of the web immediately after it has passed over the drying roll 33. The inner layers l1 and h2 contain a water-repellent adhesive and the outer layers l0 and it3 contain starch. Both surfaces are made rigid. The stiffness of the web is typically 8 Kenley units. After passing through the gluing press 3 * +, the stiffness of the web typically becomes 12 Kenley units.

Figure 3 shows a cross-section of the web after it has passed through the adhesive press 3 * + and through the hot moisture pressing (stiffening) cylinder 35. The outer layers Uo and i + 3 have gained considerably more rigidity and strength, but this has not shifted to the middle layers 1 + 1 and 1 + 2. Typically, the stiffness of the web has evolved into 15 Kenley units. In a typical example, the top and back surfaces of the finished web are cellulose with 18% Viscosol starch and 1% pvar, and the middle layer or layers are wood chips with 8% Viscosol starch and 3% glue. Normally, each layer is not homogeneous but the concentration of adhesive increases per surface.

The use of certain adhesives (e.g. wax-based) in the middle layers as such and their anti-penetration effect of stiffeners can lead to a decrease in the strength of the middle layers relative to the outer layers. Changes in the degree of reinforcement can also occur due to other factors, such as moisture content and heat. These differences, together with the water contents of the stiffeners in the different layers, provide a boundary between the inner and outer layers. This limit affects the degree of delamination between the inner and outer layers when folding and can thus improve the foldability of the web.

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The strength and stiffness of the final web is therefore concentrated in its outer layers and a boundary is formed between the middle layers and the outer layers to facilitate delamination of these layers when the board is bent.

Variations can be made to the example of the method described above.

Starch can be used less or not at all for the middle layer mass. The adhesive for the middle layers may contain a binder or crosslinking agent such as resins or hemicellulose. The starch may be added to the pulp before the first dispenser (10) or the amount of starch added to the dispenser 13 or spray unit 31 or at 28 may vary. Instead of starch, other substances such as hemicellulose or carboxymethylcellulose can be used to modify the base web to provide the desired stiffness / strength / bending properties. Slit compression and cylinder temperatures can be varied to suit individual web requirements. Different types of pulps can be used for different layers. -

The invention can be used in webs for folding boxboard molding board, corrugated board and can board.

Claims (7)

7 58184 A method of making a multilayer web of cellulosic material suitable as a collapsible carton, dry forming the cellulosic fibrous material into layers and then joining the layers into a web, characterized by a combination of the following steps: a) impregnating the outer layers with a stiffener e.g. with a wax / resin adhesive which makes the inner layer (s) impermeable to the stiffener of the outer layers, c) wetting the combined layers to a moisture content of about 35% by weight, d) reinforcing the wetted, combined impregnated layers by applying 110 °. Around the surface of a cylinder heated to C and press the web into contact with the surface by means of press rolls at a nip pressing pressure of 17 “^ U kp / cm. A method according to claim 1, characterized in that the stiffener is added to the cellulosic fibrous mass before the outer layer is formed. A method according to claim 1, characterized in that the stiffener is applied to the outer layer of the web after the formation and the web is then conveyed through an adhesive press. Method according to one of the preceding claims, characterized in that the reinforced web is further treated by applying a second adhesive to the web when it is dry or substantially dry to give the web the required moisture content and hot-pressing the surface of the glued wet web. A method according to claim H, characterized in that the hot pressing is performed by passing the web through a pressing gap between the heated roll and the pressing roll. A method according to claim 4, characterized in that the web is given a moisture content of 15-30% by weight and the hot pressing is performed at a pressure of about 110 ° C and with a pressing of about 3 ~ 9 kp / cm. Process according to Claim 1+, characterized in that the second adhesive is selected from the group consisting of starch, gelatin, latex compounds, polyvinyl acetate or combinations thereof. Method according to Claim 7, characterized in that the clay is added to the second adhesive, Method according to one of the preceding claims, characterized in that the cellulosic fibrous material is treated in a hammer mill before being layered.