FI126699B

FI126699B - Process for making paperboard

Info

Publication number: FI126699B
Application number: FI20145442A
Authority: FI
Inventors: Karita Kinnunen; Tuomo Hjelt
Original assignee: Metsä Board Oyj
Priority date: 2014-05-15
Filing date: 2014-05-15
Publication date: 2017-04-13
Also published as: SE1651631A1; WO2015173474A1; CN106715794A; SE540579C2; FI20145442A

Description

Method of Producing Boards

Technical Field

The present invention relates to a method of producing a paperboard (in the following also “fibrous web”) by foam forming. The method is suitable for forming various products of paperboard material, in particular it is suitable for the production of high bulk cartonboard products, such as folding box board or white lined chipboard. The invention also concerns paperboards thus obtained.

Background

Fibrous webs can be produced by foam forming which gives many advantages. In a foam, the fibres do not flocculate. When a web is made from such a fibrous foam is dewatered, for example by applying suction to the foam through a wire, the fibres will retain their non-flocculated state and form a web with good formation. The structural pressure that the foam applies to the structure when water is removed by suction is much smaller than the pressure exerted by conventional removal of water from fiber slush. The technology gives rise to a high bulk in the products.

Foam forming on a foraminous wire to yield a non-woven fibrous web is disclosed in a number of patent documents, including GB 1129757, GB 1329409, GB 1395757, GB 1397378, GB 1431603 and US 4944843, all assigned to Wiggins Teape (Radfoam).

In addition, US 3,326,745 teaches that formation of a paper web can take place between a foraminous forming fabric and a felt, with the forming fabric and felt being carried by two adjacent turning rolls, the arrangement being such that the forming fabric and felt are brought substantially into contact along web formation areas thereof lying along one or both of these rolls. After dewatering in the formation areas, the formed web follows and is carried by the felt, and subsequent dewatering and transference to steam heated driers occurs as the web travels with the felt. US 6,413,368 B1 discloses an apparatus and process for producing foam formed fibrous web in which the furnish is made up by mixing a thin water slurry of fibers at a consistency in the range of from about 0.5 to about 7 weight percent fibers with sufficient aqueous foam containing a surfactant and having an air content in the range of from about 55 to about 80 percent by volume to form a foamed fiber furnish containing from about 0.1 to about 3 weight percent fibers which is supplied directly to the forming felt or wire of a twin wire papermaking machine, adding makeup surfactant and discarding excess aqueous foam from the process as required to maintain the desired volume of foamed liquid therein.

Furthermore US 2005/0039870 A1 teaches a method and apparatus for foam forming, wherein fibrous foam suspension is introduced from a head box of a production machine to the web forming section thereof. At least one solid material is mixed into the foam in the head box. The method and the apparatus are suitable for manufacturing various web-like products of cellulose, glass fiber, aramide, sisal or other corresponding fiber material.

Paperboards comprise layers of high bulk. Although the formation of fibrous non-woven layers by foam formation having high bulk is, as such, taught in the art, the internal strength properties of such layers is still unsatisfactory for applications in which strength in the z-direction of the layer is of considerable importance, such as paperboards. GB 1431603 discloses a method of increasing internal strength by grinding, by use of reinforcing chemicals and by wet pressing, but while some improvement has been obtained in the art, bulk has been lost simultaneously.

Summary of Invention

Technical Problem

The present invention relates to the production of paperboard products which contain layers having a high bulk. In particular, the present invention addresses the issue of manufacturing paperboard products wherein layers of high bulk are needed which simultaneously exhibit properties of good internal strength, as evidenced by at least one of improved Scott Bond and improved strength in z-direction.

An aim of the present invention is to provide for the production of multilayered paperboards, such as folding box boards and white lined chipboards, where high-bulk layer are arranged as middle layers of the paperboard product. A third aim of the present invention is to manufacture fibrous layers having surface weights of generally 110 to 750 g/m2, wherein at least a part of the products exhibit in combination high bulk and good internal strength, in particular exhibiting minimum target values of the exemplary middle layer of cartonboard of a) bulk >1.8 g/m3 and b) Scott Bond > 100 J/m3. A fourth object of the present invention is to provide a method of producing, by foam forming on a foraminous wire, paperboards which meets the aforementioned target values.

Furthermore the present invention also aims at paperboards having one or a plurality of layers of which at least one meets the afore-mentioned target values.

These and other objects are achieved by the present invention, as hereinafter described and claimed.

Solution to Problem

In one aspect, the invention concerns a method for producing a paperboard, wherein at least one foamed fibrous layer is provided, and said at least one foamed fibrous layer is dewatered on the wire of a paperboard machine to form a web, wherein a water-soluble or dispersible foaming polymeric agent is used as a foaming agent. More specifically, the polymeric foaming agent is selected from the group of water-soluble or dispersible glycans, in particular polysaccharides and derivatives thereof, and other hydrophilic polymers and copolymers, such as poly(vinyl alcohol) and poly(vinyl acetate) and copolymers thereof.

Such foaming agent have been found to be capable of efficiently bonding to the fibres during foam formation to produce a web with good formation, which upon dewatering gives a fibrous matrix having high bulk and excellent internal strength properties.

Disclosed herein is also an arrangement for producing a paperboard. Comprised therein are preferably one or several of the following: At least one foam generator for production of fibrous foam from fibrous slush, water and at least one hydrophilic polymer; a web former for producing a web from the fibrous foam; a dewatering unit for the web; and means for drying of the dewatered fibrous web.

The invention also concerns a paperboard with at least one dried foamed fibrous layer, wherein the at least one foamed fibrous layer is made from a mixture of fibrous slush with foam formed from water and at least one hydrophilic polymer.

More specifically, the method according to the present invention is characterized by what is stated in the characterizing part of claim 1. A board according to the present invention is characterized by what is stated in the characterizing part of claim 10.

Advantageous Effects of Invention

Considerable advantages are obtained by means of the invention. The use of a hydrophilic polymer as a foaming agent enhances the internal strength of a foam formed layer. Hand sheet tests have showed that by the use of a hydrophilic polymeric foaming agent, such as poly(vinyl alcohol), a folding boxboard middle layer produced from chemithermo-mechanical pulp (CTMP) without starch or retention agents has a Scott Bond value of 123 J/m3 and bulk value of 3.71 g/m3. In addition, the layer retains the high bulk provided by foam forming.

The results show that it is possible to produce a high bulk middle layer of folding boxboard having advantageous strength properties with hydrophilic polymers as foam forming agents.

This also shows the possibility of forming the middle layer of folding boxboard from less refined CTMP pulp and with polyvinyl alcohol use to reach the needed strength properties.

In the tests referred to above, the samples were wet pressed.

The present invention also enables the use of less refined fiber material in high bulk fiber web.

The economical and the ecological influences of the present invention are for example savings in chemical consumptions. No other strength chemicals, such as starch or retention aids, are needed and using coarser CTMP pulp enables savings in refining energy.

Using foam forming it is also typically possible to remarkably reduce production costs and simultaneously improve properties of current products. The present invention will retain the benefits obtained by foam formation. For example, compared to water forming technology the forming consistency may be increased substantially with foam. Foam forming technology requires significantly less water than conventional paper and paperboard manufacturing which leads to minimization of the amount of raw water intake and the amount of waste water to be treated in treatment plants. Pulp contains large amounts of air, providing better opportunities for influencing the properties of the end-product. Foam forming technology reduces energy consumption, while saving on raw materials, and also widens remarkably the raw material choice.

Foam forming technology applied to paperboard manufacture using hydrophilic polymers as foaming agents further introduces new opportunities for fiber based products. Thus, it is possible to improve the properties of existing packaging, cartonboard, and the manufacture of different types of highly porous, light-weight and smooth products, such as hygiene products, insulators and filters. Foam forming technology may also be the solution for printed intelligence and electronics and microcellulose applications.

The results show that, for example in a high bulk middle layer of folding boxboard, the required strength properties can be obtained with polyvinyl alcohol. When using polyvinyl alcohol as a foaming agent especially good Scott Bond values are obtained. By contrast, with sodium lauryl sulfate and non-ionic forming agents, foaming is achieved but no particular improvement of internal strength.

Brief Description of Drawings

For a more complete understanding of particular embodiments, reference is now made to the following descriptions, taken in conjunction with the accompanying drawings. In the drawings,

Figure 1 illustrates a schematic view of a typical papermaking machine line to explain the steps of producing cartonboard;

Figure 2 shows the various types of boards included in the concept of “paperboard”;

Figure 3 shows a table with values of a middle layer of folding boxboard according to tests of the present invention in a laboratory; and

Figure 4 depicts in a schematic fashion the structure of a multilayered product.

Description of Embodiments

As discussed above, the present technology basically concerns a method for producing a board, comprising the steps of - producing a fibrous foam from cellulosic or lignocellulosic fibres, water and a foaming agent; - forming the fibrous foam on a foraminous wire into a foamed layer; - dewatering the fibrous foam layer on the foraminous wire, for example by suction, to form a dewatered web; and - drying the web thus obtained is dried to give a foamed fibrous web.

Optionally, the fibrous web can be formed as a stand-alone layer or it can be formed as part of a multilayered product for example by combining the above web forming procedure with the simultaneous formation of 2 to 5 webs.

The terms “paperboard” or “cartonboard” are used for designating fibrous web or fibrous layer which is provided by the present invention. Figure 2 shows the various boards types included in the general concept of “paperboard”. Thus, included are cartonboards, other paper boards and containerboards.

The foam forming of the at least one fibrous layer is preferably carried out by mixing the fibrous slush with foam formed from water and the foaming agent so as to provide a foamed fibrous slush which is fed onto a wire to form the fibrous layer. The preferred consistency of the fibrous slush is 0.6 % to 7 % by weight.

The water and foaming agent are preferably used for forming the foam having an air content of 40 % to 80 %, e.g. 55 % to 75 %, by volume. The concentration of the foaming agents is preferably 100 to 5000 ppm, in particular 150 ppm - 1000 ppm, calculated from the total weight of the liquid.

The at least one foamed fibrous layer is preferably wet pressed. Then the at least one foamed fibrous layer is dried to form a dried web or board, for example by cylinder drying. Drying can also be carried out as air drying by suction air through the web.

The web is preferably cartonboard made up of multiple layers of pulp. The top and/or bottom layers are preferably of bleached chemical pulp and may be coated with pigments. Mechanical pulp, semi-chemical pulp, chemical pulp, thermomechanical pulp or chemithermomechanical pulp or recycled pulp can be contained in the middle layer of the cartonboard.

In the present technology, foam formation, in particular on a paperboard machine, is carried out with the use of a foaming agent capable of acting as a surface active agent while simultaneously acting as a binder in the formed structure.

Generally, the foaming agent is selected from anionic, cationic, non-ionic and amphoteric surface active agents and surfactants, including polyvinyl alcohol and foamable starches, proteins, and combinations thereof.

Optionally at least one additional binder is used in an amount of 0.005-10 % by weight, preferably 0.05-0.5 % by weight, particularly preferably 1-2 % by weight.

In a preferred embodiment, the foaming agent is polymeric and selected from the group of hydrophilic polymers of natural or synthetic origin which are capable of achieving both foaming and binding. Typically, suitable polymers are of a kind which are soluble or at least readily dispersible in water. The polymers contain suitable polar groups attached directly to the main chain of the polymer or via side groups to the main chain.

Suitable natural and seminatural polymers are exemplied by glycans, in particular polysaccharides and physical and chemical derivatives thereof. Examples include finely divided cellulose or cellulose derivatives, biopolymers such as binders based on starch derivatives, natural gum latexes, alginates, guar gum, hemicellulose derivatives, chitin, chitosan, pectin, agar, xanthan, amylose, amylopectin, alteman, gellan, mutan, dextran, pullulan, fructan, locust bean gum, carrageenan, glycogen, glycosaminoglycans, murein, bacterial capsular polysaccharides, and the like.

Naturally, mixtures of polymeric compounds can also be used.

Other hydrophilic polymers and copolymers, are represented by hydroxyl-substituted synthetic polymers and copolymers thereof, such as polyvinyl alcohols, polyvinyl acetate dispersions, ethyl vinyl alcohol dispersions, polyurethane dispersions, acrylic latexes, styrene butadiene dispersions.

One particularly preferred foaming agent is polyvinyl alcohol. The structure of partially hydrolyzed polyvinyl alcohol is given below:

wherein R = H or COCH3

Polyvinyl alcohol used as a foaming agent according to the present invention has preferably a degree of hydrolysis from 80 % up to 99 %, preferably between 85 % and 99 %.

Polyvinyl alcohol used as foaming agent according to the present invention has a molecular weight between 10000 g/mol and 50000 g/mol, in particular between 15000 g/mol and 40000 g/mol, preferably between 20000 g/mol and 35000 g/mol.

Turning now to the embodiment illustrated in the drawings, Figure 1 depicts a conventional process of producing cartonboard with a board machine line can be subdivided into the steps of pulping, stock preparation, short circulation, forming, pressing, drying, coating, calendering, and reeling. Figure 1 illustrates a 3-ply cartonboard line, but the invention can be used in 1 to multiply board machines.

Mechanical Pulping is for example used to manufacture fibrous products such as printing and writing papers, paperboard, newsprint or tissue. Mechanical pulp provides high bulk and good opacity. Mechanical Pulp can be combined with chemical pulps to produce a mixture of properties and characteristics. Chemical pulp is pulp which is prepared from cooked wood chips. Hybrid pulping methods, e.g. chemithermo-mechanical pulping (CTMP), use a combination of chemical and thermal treatment. Chemothermomechanical pulp is a preferred raw material in the process and products of the present invention, in particular less refined CTMP. In multilayered products, one or more layer can be of this CTMP, while other layers may be produced from other types of pulp.

The pulp may be for example made from any broad-leaved tree such as a tree from the betulaceae family, e.g. birch or aspen, from the salicaceae family, from eucalyptus, mixed tropical hardwood or pines or from any combination of the aforementioned. The pulp may be also for example made from any conifer such as spruce or pine or from any combination thereof. The pulp may be also made from a combination of broad-leaved trees and conifers.

The percentage of conifers in the pulp may reach for example from 20 % to 100 %, in particular from 50 % to 100 % and preferably from 75 % to 100 %.

The pulp may be also for example made from any annual such as straw, common reed, reed canary grass, bamboo, sugarcane or any grass plant.

Stock preparation systems modify the raw materials in such a way that the stock supplied to the board machine line suits the requirements of the board machine line. The quality of the stock supplied to the board machine line influences the quality of the cartonboard. Additives such as binders, fillers, sizing agents, retention agents or other chemicals may be added to the stock. Binder may be starch, which can be modified or unmodified starch, preferably starch derived from wheat, potato, rice, com or cassava.

According to the present invention a board is produced by forming at least one foamed fibrous layer, wherein a hydrophilic polymer is used as a foaming agent in contacting foam forming, and drying said at least one foamed fibrous layer to form said web.

The foam forming of the at least one fibrous layer is preferably carried out by mixing a fibrous slush with foam formed from water and the foaming agent so as to provide a foamed fibrous slush which is fed onto a wire and dewatered to form the web which is then dried to form the board. The preferred consistency of the fibrous slush is 0.6 % to 7 % by weight. The water and foaming agent are used for forming the foam, preferably, having an air content of 40 % to 80 %, e.g. 55 % to 75 %, by volume. The concentration of the foaming agents is typically 150 ppm-1000 ppm, calculated from the total weight of the liquid, in particular the liquid phase of the slush. The size of the bubbles can vary. Typically, bubble diameters are typically between 10 pm and 300 pm, in particular between 20 pm and 200 pm and normally between 20 pm and 80 pm.

In the invention the hydrophilic polymer is mixed with pulp either in a stock preparation or short circulation in one or several paperboard ply(s). Typically the hydrophilic polymer can be added into chests or directly to the approaching pipe in the short circulation. After the addition or simultaneously therewith, air is mixed with the pulp. Air can be generated for example in a normal pulper with a mixing rotor or pumping high pressure air into approaching pipe before the headbox. A foamed fibrous slush is thus created.

The foamed fibrous slush is conducted from one or several headbox(es) 1 onto one or several wire section(s). On the wire section foamed fibrous slush is drained typically with foils, foilboxes, vacuum boxes or vacuum rolls. As a result, a board web is formed. After the wire section the dry content of the web is typically between 18 and 30 %, calculated from the total weight of the web.

From the wire section the web is conducted to the press section, where dewatering is carried out in roll nips. The dry content is increased up to 40 to 50 % in the press section.

After the press section, the web is directed onto the drier section. On the drier section, typically hot cylinders are used for evaporating water from the web.

After the drier section the board machine typically has coating and calendaring units where the final surface of the paper board is made.

Examples

The present invention has been tested at laboratory conditions. Figure 2 contains a table with bulk values and Scott Bond values of a middle layer of folding boxboard according to the tests.

According to preferred embodiments for manufacturing the board of the present invention, fiber material and nanocellulose mixture is mixed with prefabricated foam produced using polyvinyl alcohol. The foam generally has an air content of about 60 % to 70 %. The web is made from this fiber foam for example by suction of the foam through the wire. An excellent formation is reached because in stable foam the distances between particles remain and no flocculation takes place. After the web forming the fiber web is dried, for example by suction air through the web, e.g. using a suction slit.

Tests of different embodiments of the present invention using different polyvinyl alcohol grades as foaming agents in order to maximize the benefits of polyvinyl alcohol have showed that in laboratory scale it is for example possible to produce a middle layer of folding boxboard with CTMP pulp containing 10 % nanofibrillated cellulose (NFC) having a bulk value of 2.99 g/m3 and Scott Bond value of 153 J/m2 when using a first polyvinyl alcohol grade and foam forming.

Tests of a second embodiment of the present invention have showed that in laboratory scale it is possible to produce a middle layer of folding boxboard with CTMP pulp containing 10 % NFC having a bulk value of 2.60 g/m3 and Scott Bond value of 281 J/m2 when using a second polyvinyl alcohol grade and foam forming.

The tests of a third embodiment of the present invention have showed that in laboratory scale it is possible to produce a middle layer of folding boxboard with CTMP pulp containing 10 % NFC having a bulk value of 2.68 g/m3 and Scott Bond value of 314 J/m2 when using the second polyvinyl alcohol grade and foam forming.

Tests of a fourth embodiment of the present invention have showed that in laboratory scale it is also possible to produce a middle layer of folding boxboard using coarser CTMP pulp (574 CSF) without NFC, starch and retention aid additions having a bulk value of 3.71 g/m3 and Scott Bond value of 123 J/m2 when using the second polyvinyl alcohol grade and foam forming.

The reference values of a middle layer of folding boxboard containing 10 % NFC with sodium lauryl sulfate (SDS) as a foaming agent instead of polyvinyl alcohol are for example 3.11 g/m3 and 136 J/m2, respectively.

The reference values (bulk value and Scott Bond value) of a middle layer of folding boxboard containing 10 % NFC with a non-ionic foaming agent instead of polyvinyl alcohol are for example 3.15 g/m3 and 137 J/m2, respectively.

As can be seen from the table, use of polyvinyl alcohol as a foaming agent offers the possibility to achieve middle layers of folding boxboard with a bulk value of at least up to 3.90 g/m3. Using sodium lauryl sulfate as a foaming agent instead of polyvinyl alcohol middle layers of folding boxboard with a bulk value between 2.45 g/m3 and 3.11 g/m3 can be achieved. Use of a non-ionic foaming agent instead of polyvinyl alcohol can lead to middle layers of folding boxboard with a bulk value between 3.15 g/m3 and 3.45 g/m3.

As can be also seen from the table, use of polyvinyl alcohol as a foaming agent offers the possibility to achieve middle layers of folding boxboard with a Scott Bond value between 105 J/m2 and 314 J/m2. Using sodium lauryl sulfate as a foaming agent instead of polyvinyl alcohol middle layers of folding boxboard with a Scott Bond value between 70 J/m2 and 149 J/m2 can be achieved. Use of a non-ionic foaming agent instead of polyvinyl alcohol can lead to middle layers of folding boxboard with a Scott Bond value between 112 J/m2 and 137 J/m2.

Tests of a fifth embodiment of the present invention have showed that in laboratory scale it is possible to produce a middle layer of folding boxboard using coarser CTMP pulp (574 CSF) without NFC, starch and retention aid additions, which suits the aforementioned target values, when using a polyvinyl alcohol with a degree of hydrolysis of 88.0 %. The polyvinyl alcohol may have another degree of hydrolysis, eg. a degree of hydrolysis of 87.0 % or 89.0 %.

Tests of a sixth embodiment of the present invention have showed that in laboratory scale it is possible to produce a middle layer of folding boxboard using coarser CTMP pulp (574 CSF) without NFC, starch and retention aid additions, which suits the aforementioned target values, when using a polyvinyl alcohol with a molecular weight of 27000 g/mol. The polyvinyl alcohol may have another molecular weight, e.g. a molecular weight of 25000 g/mol or 35000 g/mol.

In Figure 3, a multilayered product produced according to the present invention is shown schematically. The product may be for example folding boxboard consisting of a middle layer arranged between a top layer and a lower layer. The top layer and the lower layer may be for example from bleached or unbleached chemical pulp. The middle layer on the other hand may be of chemithermomechanical pulp. The top layer and/or the lower layer may be further coated with an optional pigment coating which is not shown in Fig. 3.

The board exhibits generally a grammage (surface weight) of about 50 to 750 g/ m2. A middle layer of folding boxboard according to the present invention may be of any weight, in particular the weight may be between 10 g/m2 and 300 g/m2. Tests of a seventh embodiment of the present invention have showed that in laboratory scale it is possible to produce a middle layer of folding boxboard using coarser CTMP pulp (574 CSF) without NFC, starch and retention aid additions, which suits the aforementioned target values and has a weight of 200 g/m2. The middle layer of folding boxboard may have another weight, e.g. a weight of 100 g/m2 or 300 g/m2.

Any other layer, e.g. a first other layer, a second other layer, a lower layer or a top layer, may be produced using the method of the present invention or any other method. The first other layer may be the lower layer and the second other layer may be the top layer. The number of layers in a multilayered product according to the invention is at least two. Folding boxboard according to the invention can for example also consist of five layers, i.e. a middle layer, a first other layer, a second other layer, a top layer and a lower layer.

In case of multilayered products any other layer, e.g. a first other layer, a second other layer, a lower layer or a top layer, may be according to the invention of any weight. In particular the weight of any other layer may be between 10 g/m2 and 100 g/m2. Tests of an eighth embodiment of the present invention have showed that in laboratory scale it is possible to produce a middle layer of folding boxboard using coarser CTMP pulp (574 CSF) without NFC, starch and retention aid additions, which suits the aforementioned target values and is connected to a top layer which has a weight of 50 g/m2. The top layer of folding boxboard may have another weight, e.g. a weight of 20 g/m2 or 80 g/m2. It is further possible to produce a middle layer of folding boxboard using coarser CTMP pulp (574 CSF) without NFC, starch and retention aid additions, which suits the aforementioned target values and is connected to a lower layer which has a weight of 50 g/m2. The lower layer of folding boxboard may have another weight, e.g. a weight of 20 g/m2 or 80 g/m2.

Although the present invention has been described in detail for the purpose of illustration, various changes and modifications can be made within the scope of the claims. Different polyvinyl alcohol grades, different NFC percentages, starch and retention aid additions and use of other pulp than (coarser) CTMP pulp can for example lead to other embodiments with other characteristics. In addition, it is to be understood that the present disclosure contemplates that, to the extent possible, one or more features of any embodiment may be combined with one or more features of any other embodiment.

Industrial Applicability

The fiber web according to the invention may be used in a broad range of paperboards. Within the scope of the invention, the following paperboards may be mentioned: Duplex Wallpaper Base, Gypsum liners and boards and Core board. The containerbords include liners, such as kraftliners and testliners, and fluting and mediums, such as semi chemical fluting and recycled mediums.

In the present context, particularly interesting are, however, the cartonboards, which include folding box boards, white lined chipboards, greyboards, liquid packaging boards and food service boards, as well as solid bleached boards and coated unbleached boards and carrier boards. Thus, the fiber web can be a middle layer of folding boxboard, a cardboard product, a packaging, a hygiene product, an insulator, or a filter.

Citation List

Patent Documents US 3,326,745 US 6,413,368 US 2005/0039870 GB 1129757 GB 1329409 GB 1395757 GB 1397378 GB 1431603 US 4944843

Claims

1. Menetelmä kartongin tuottamiseksi, joka menetelmä käsittää vähintään yhden kuitupitoisen rainan, jossa menetelmässä on jäljestetty kuitupitoinen vaahto, joka mainittu kuitupitoinen vaahto muodostetaan vaahdotetuksi kuitupitoiseksi kerrokseksi, josta poistetaan vesi ja joka kuivataan muodostamaan mainittu raina, jolloin mainitun kuitupitoisen vaahdon muodostamiseksi käytetään vaahdotusaineena hydrofiilistä polymeeriä, tunnettu siitä, että saadaan aikaan kuitupitoinen kerros, jossa yhdistyvät a) massatilavuus >1,8 g/m3 ja b) Scott-sidos > 100 J/m3.A process for producing paperboard comprising at least one fibrous web, the method comprising a sequenced fibrous foam, forming said fibrous foam into a foamed dewatering layer which is dehydrated to form said fibrous foam to form a foamed foam, characterized in that a fibrous layer is obtained which combines (a) a bulk volume of> 1.8 g / m3 and (b) a Scott dressing of> 100 J / m3.

2. Patenttivaatimuksen 1 mukainen menetelmä, jossa vaahdon muodostaminen tehdään sekoittamalla kuitupitoista lietettä vedestä ja vaahdotusaineesta muodostettuun vaahtoon vaahdotetun kuitupitoisen lietteen muodostamiseksi, joka liete johdetaan viiralle muodostamaan vaahdotettu kuitupitoinen kerros.The method of claim 1, wherein forming the foam is accomplished by mixing a fibrous slurry with a foam formed from water and a blowing agent to form a foamed fibrous slurry, which slurry is passed onto a wire to form a foamed fibrous layer.

3. Patenttivaatimuksen 1 tai 2 mukainen menetelmä, jossa kuitupitoisen lietteen sakeus on 0,6 - 7 % painon mukaan.The process according to claim 1 or 2, wherein the consistency of the fibrous slurry is 0.6 to 7% by weight.

4. Jonkin edellä olevan patenttivaatimuksen mukainen menetelmä, jossa käytetään vaahtoa, jonka ilmapitoisuus on 40 - 80 %, esimerkiksi 55 - 75 % tilavuudesta.A method according to any one of the preceding claims wherein a foam having an air content of 40 to 80%, for example 55 to 75% by volume, is used.

5. Jonkin edellä olevan patenttivaatimuksen mukainen menetelmä, jossa vaahdotusaineen konsentraatio on noin 150 - 1000 ppm laskettuna nesteen kokonaispainosta.The method of any one of the preceding claims, wherein the concentration of the blowing agent is about 150 to 1000 ppm based on the total weight of the liquid.

6. Jonkin edellä olevan patenttivaatimuksen mukainen menetelmä, jossa vähintään yksi vaahdotettu kuitupitoinen kerros puristetaan märkänä vedenpoiston jälkeen.A method according to any one of the preceding claims, wherein the at least one foamed fibrous layer is pressed wet after dewatering.

7. Jonkin edellä olevan patenttivaatimuksen mukainen menetelmä, jossa vaahdotusaineet valitaan vesiliukoisesta ja di spergoi tuvasta vaahtoavasta polymeerisestä aineesta, erityisesti vesiliukoisista tai di spergoi tuvista glykaaneista, erityisesti polysakkarideista ja niiden johdannaisista.The process according to any one of the preceding claims, wherein the blowing agents are selected from a water-soluble and a di-sparging foamable polymeric substance, in particular a water-soluble or a di-sparging glycan, in particular polysaccharides and their derivatives.

8. Jonkin edellä olevan patenttivaatimuksen mukainen menetelmä Jossa vaahdotusaineet valitaan vesiliukoisesta ja di spergoi tuvasta vaahtoavasta polymeerisestä aineesta, erityisesti vesiliukoisista tai dispergoituvista hydrofiilisistä polymeereistä ja kopolymeereistä, kuten poly(vinyylialkoholista) ja poly(vinyyliasetaatista) ja niiden kopolymeereistä.The process according to any one of the preceding claims, wherein the blowing agents are selected from a water-soluble and di-spherical foaming polymeric material, in particular water-soluble or dispersible hydrophilic polymers and copolymers such as poly (vinyl alcohol) and poly (vinyl acetate) and their copolymers.

9. Jonkin edellä olevan patenttivaatimuksen mukainen menetelmä, jossa hydrofiilistä polymeeriä käytetään vaahdotusaineena tehokkaana määränä tilavuuspainoltaan suuren kuitupitoisen kerroksen tuottamiseen, jonka kerroksen ominaisuuksia ovat hyvä sisäinen lujuus, joita kuvaavat vähintään joko parempi Scott-sidos tai parempi lujuus Z-suunnassa.The method according to any one of the preceding claims, wherein the hydrophilic polymer is used as a blowing agent in an effective amount to produce a high bulk fiber layer having good internal strength, characterized by at least either improved Scott bonding or improved Z-strength.

10. Levytuote, jossa on vähintään yksi kuivattu vaahdotettu kuitupitoinen kerros, joka sisältää flokkuloimattomia kuituja ja joka on käsitelty vedestä ja vaahdotusaineena käytetystä hydrofiilisestä polymeeristä muodostetulla vaahdolla, tunnettu siitä, että kuitupitoisessa kerroksessa on yhdistelmänä suuri tilavuuspainoja hyvä sisäinen lujuus, joka mainittu tilavuuspaino on >1,8 g/m3 ja mainittu Scott-sidos on > 100 J/m3.10. A sheet product having at least one dried foamed fibrous layer containing non-flocculated fibers treated with a foam formed from water and a hydrophilic polymer used as a foaming agent, characterized in that the fibrous layer has a high bulk density of> 1% by weight, , 8 g / m3 and said Scott dressing is> 100 J / m3.

11. Patenttivaatimuksen 10 mukainen levytuote, jossa vähintään yksi kuivattu vaahdotettu kuitupitoinen kerros on järjestetty ensimmäisen muun kerroksen ja toisen muun kerroksen väliin.The sheet product of claim 10, wherein the at least one dried foamed fiber-containing layer is disposed between the first other layer and the second other layer.

12. Patenttivaatimuksen 10 tai 11 mukainen levytuote, joka sisältää mekaanista massaa, puolikemiallista massaa, kemiallista massaa, termomekaanista massaa, kemitermomekaanista massaa tai kierrätysmassaa.A sheet product according to claim 10 or 11 comprising mechanical pulp, semi-chemical pulp, chemical pulp, thermomechanical pulp, chemo-thermomechanical pulp or recycled pulp.

13. Jonkin patenttivaatimuksen 10-12 mukainen levytuote, jossa raina on kartonki, joka muodostuu useista massan kerroksista.A sheet product according to any one of claims 10 to 12, wherein the web is a paperboard consisting of a plurality of layers of pulp.

14. Patenttivaatimuksen 13 mukainen levytuote, jossa ylin ja/tai alin kerros on valkaistua kemiallista massaa.The sheet product of claim 13, wherein the top and / or bottom layer is a bleached chemical pulp.

15. Patenttivaatimuksen 14 mukainen levytuote, jossa ylin ja/tai alin kerros on pinnoitettu pigmenteillä.The sheet product of claim 14, wherein the top and / or bottom layers are coated with pigments.

16. Jonkin patenttivaatimuksen 10-15 mukainen levytuote, jossa levytuote on kartonkituote tai sen osa.A sheet product according to any one of claims 10 to 15, wherein the sheet product is a cardboard product or part thereof.

17. Jonkin patenttivaatimuksen 10-16 mukainen levytuote, jossa levytuote on kartonki, erityisesti kartonki, joka valitaan taivekartongeista, valkopintaisista uusiokuitukartongeista, nestepakkausten kartongeista, ruokapalvelukartongeista, umpinaisista valkaistuista kartongeista, pinnoitetuista valkaisemattomista kartongeista ja valkaisemattomista sellukartongeista.A sheet product according to any one of claims 10 to 16, wherein the sheet product is paperboard, in particular cardboard selected from folding boxboard, white-coated recycled paperboard, liquid packaging board, food service board, solid bleached board, coated unbleached board and board.

18. Jonkin patenttivaatimuksen 10-17 mukainen levytuote, jossa vaahdotusaine valitaan vesiliukoisesta ja di spergoi tuvasta vaahtoavasta polymeerisestä aineesta, erityisesti vesiliukoisista tai di spergoi tuvista glykaaneista, erityisesti polysakkarideista ja niiden johdannaisista.A sheet product according to any one of claims 10 to 17, wherein the blowing agent is selected from a water-soluble and di-sparging foamable polymeric material, in particular water-soluble or di-sparging glycans, in particular polysaccharides and their derivatives.

19. Jonkin patenttivaatimuksen 10-17 mukainen levytuote, jossa vaahdotusaine valitaan vesiliukoisesta ja di spergoi tuvasta vaahtoavasta polymeerisestä aineesta, erityisesti vesiliukoisista tai dispergoituvista hydrofiilisistä polymeereistä ja kopolymeereistä, kuten poly(vinyylialkoholista) ja poly(vinyyliasetaatista) ja niiden kopolymeereistä.A sheet product according to any one of claims 10 to 17, wherein the blowing agent is selected from a water-soluble and di-spherical foaming polymeric material, in particular water-soluble or dispersible hydrophilic polymers and copolymers such as poly (vinyl alcohol) and poly (vinyl acetate).

20. Jonkin patenttivaatimuksen 10-19 mukainen levytuote, jossa levyn paino on 110 - 750 g/m3 ja jossa vähintään osalla tuotteista on yhdistelmänä a) tilavuuspaino > 1,8 g/m3 ja b) Scott-sidos >100 J/m3.A sheet product according to any one of claims 10 to 19, wherein the sheet weight is 110 to 750 g / m3 and wherein at least a portion of the articles have a) a bulk density of> 1.8 g / m3 and b) a Scott dressing of> 100 J / m3.