SE512776C2 - Paperboard laminate for use as a packaging material comprises a bulk-promoting layer, in combination with a secondary layer - Google Patents

Abstract

Fibers with a freeness of 550 - 950 ml CSF are incorporated in a bulk-promoting layer of a paper or paperboard laminate, in combination with a secondary layer on one or both sides of the bulk layer. A paper or paperboard laminate (1) comprises at least one bulk-promoting layer (2), in combination with a secondary layer (3) on one or both sides of (2). (2) and (3) are joint together directly or indirectly by their surfaces facing one another. 40 - 95% of (1) consists of cellulose fibers with a freeness of 550 - 950 ml CSF. (3) is denser than (2), and (1) has a bending stiffness index higher than 2.5 Nm7/kg3, but less than 14 Nm7/kg3, calculated as a geometric mean value for machine and transverse direction. An Independent claim is also included for the production of (1) which comprises production of (2) and joining at least on its one side directly or indirectly (3).

Description

5127762 three-layer larnate whereby all HBA was added to the middle layer.

WO95 / 26441 also describes the use of a chemically cross-linked paper laminate with two or two layers. The purpose of the use of the cross-linked fi bem (HBA) is to achieve a construction with increased bulk and with maintained tensile strength. Paper material with low density (high bulk) normally gives lower tensile strengths. To reduce this negative effect of low density, it is proposed to use water-based binders such as starch, modified starch, polyvinyl acetate and polyvinyl alcohol, etc.

These binders are proposed to be used in contents between 0.1 and 6% of the weight of the material.

Achieved flexural stiffness is expressed in Taber units. If the same method is used for recalculation of stiffness as described below under test methods, the result in WO95 / 26441, Example S, corresponds to a flexural stiffness index of approx. 1.6 Nm7 / kg3.

Dry cleaning in the production of paper has been described in the literature in a large number of articles and patents. Among other things, Swenson describes in “An introduction to dry formulation of paper”, Tappi, 1978, pp. 3-6 different techniques for forming a web using air as a dispersing medium for wood. Here are examples of products that are med made with dry forming, e.g. soft towels, stiff cardboard and masonite.

GB 1,43 0,760 and GB 1,435,703 describe forming techniques for the production of paper materials with fl layers. Among other things, it is proposed to combine dry and wet-shaped layers with each other. It is proposed to consolidate the sheet (consisting of several layers) using binder, moisture and pressing at high temperature. Product properties for dried products are characterized by high bulk, squareness (i.e. equal properties in the different directions of the sheet in the plane) and good dimensional stability. Furthermore, it is considered possible to achieve product properties similar to conventionally shaped board. Manufacturing technology is considered to reduce investment costs, water and energy consumption.

Haas describes in “Where research pays oñ”, PPI, March 1977, pp. 42-26 certain important product properties for conventional wet-formed and dry-formed cardboard. Haas describes P1322 l5 2512776 3 Pl322 the properties of the dry-formed sheets as that they have a smooth surface with the absence of fi lt and wire markings and an approved tear strength. Stiffness is reported with numerical values for the different production techniques, but is not commented on in text. The toned fl layer materials have not resulted in increased stiffness. Here, when interpreting the text, it has been assumed that “stiffness%” and “stiffness X” respectively refer to the stiffness of the sheets in the transverse and longitudinal directions, respectively (TR and MR). When recalculating, for better comparison between different materials, the flexural stiffness index can be calculated as the geometric mean of MR and TR (the square root of MR * TR), whereby a maximum achieved flexural stiffness index according to the values reported by Haas is about 1.2 Nm7 / kg3. It is thus understood that the dry forming technique as it has been applied has not contributed to an increased flexural stiffness. Haas further reports the basis weight and thickness of the various paper structures, with 550 kg / m3 appearing to be the lowest density that has been produced for the completely or partially dry-formed structures.

Attwood reports in "Dry forrning of paperboard: a look at its history and technology", Pulp and Paper, 54, 198024, pp. 120-123 experiments with paper constructions that combine dry-formed and wet-formed layers. The results reported regarding stiffness and thickness (at the same basis weight) show large differences in stiffness in machine (MR) and transverse machine direction (TR). The highest stiffness calculated as the square root from the stiffness MR * TR was obtained for materials which had been produced with wet-formed outer layers and dry-shaped center layers, whereby, however, values not exceeding 1 Nm7 / kg3 were not achieved. Attwood also presents various proposals for ways to design a process that combines dry-formed middle layers with wet-shaped outer layers. Attwood also reports the basis weight and thickness of the various paper structures, with about 600 kg / m3 appearing to be the lowest density produced for the fully or partially dry-formed structures.

US 4,9l4,773 discloses ways of making rigid cardboard material using dry exposed fi bres with a freeness of 500 CSF. The fibers to be formed into the middle layer of a sheet should be dispersed in foam. This is to prevent them from being wetted with water too much. Addition of various types of adhesives such as latex, starch, gums, etc. are mentioned as necessary conditions for obtaining a sufficient strength of the sheet. When reported flexural stiffnesses are recalculated, it appears that the maximum achieved flexural stiffness index is approximately 1.8 Nm7 / kg3.

DESCRIPTION OF THE INVENTION It has surprisingly been found that by using fi ber with a freeness of 550-950 rnl CSF, preferably fi ber with a freeness value higher than 600 m] CSF, suitably higher than 650 but less than 850 ml CSF, and most preferably higher than 700 ml of CSF, in a bulk-giving layer in the larnate, hereinafter referred to as bulk layer, in combination with a side layer on one or both sides of the bulk layer, can obtain a larnate which exhibits very high rigidity. This also has the advantage that the larnate has a lower density, and thus lower material consumption compared to previously known cardboard larnates intended for the same type of use as the larnate according to the invention, such as materials for packaging of surface and solid foods and also for packaging and packaging of industrial goods and other goods, or as an intermediate product for the production of such materials or other end products. The invention presents a paper or board laminate with a flexural stiffness index greater than 2.5 and lower than 14 Nm7 / kg3, which is more than 2-7 times higher flexural stiffness index compared with today's conventionally produced multilayer board. At the same time, the larninate has sufficient strength of the bulk layer, which normally forms the middle layer of the laminate, to enable crimping and subsequent folding of the material. A special advantage of the invention is that one of the creases can be folded unhindered both towards and away from the crease.

The bulk layer has a very low density, 50-300 kg / m 3, preferably 70-200 kg / m 3, suitably 100-180 kg / m 3 and a basis weight of 30-300 g / m 2. According to a possible embodiment, it has a basis weight of 40-80 g / m 2, according to another embodiment a basis weight of 70-120 kg / m 2. According to another aspect of the invention, the bulk layer has a thickness of 0.1-6 mm, preferably 02-1.0 mm, preferably 0.3-0.7 mm.

Said side layer has a substantially greater density and tensile strength than the bulk layer, for example a density which is at least twice as large, preferably at least three times as large and most preferably at least four times as large as the density of the bulk layer. Thus, the side layer may have a P1322 512776; P1322 density of 300-1500 kg / ma, preferably 400-850 kg / ma. Typically, the average thickness of the side layer (s) is only 3-20%, preferably a maximum of 15%, preferably a maximum of 10% of the thickness of the bulk layer.

A larnate according to the invention consisting of a bulk layer and a side layer on at least one side of the bulk layer, preferably on both its sides, has a basis weight of between 50 and 500 g / m 2. Within the said range, a laminate composed according to the invention can have a basis weight which depends on the mutual relations between the thicknesses and densities of the bulk layer and the side layers. Thus, when the bulk layer is relatively thick, the laminate may have a basis weight of 75-400 g / m 2, preferably 100-350 g / m 2, preferably 100-250 g / m 2 or 90-200 g / m 2. On the other hand, if the bulk layer is relatively thin, the laminate may have a basis weight of 300-500 g / m 2, preferably 350-450 g / m 2. In this case, in other words, the side layer / side layers dominate in terms of weight. An intermediate case is also conceivable, since the laminate consisting of said layer has a basis weight of 200-400 g / m 2, preferably 250-350 g / m 2. The drag index of the larnate according to the invention can amount to 25-150 Nm / g, preferably 50-100 Nm / g.

During manufacture, the bulk layer is laminated using adhesive and with controllable pressure and time together with said side layer with high tensile strength to form a laminate according to the invention. The laminating can advantageously be carried out at the same time as the bulk layer is consolidated. However, this is not a prerequisite, but it is equally possible to first shape and consolidate the bulk layer by drying, which is then laminated to the desired side layers.

Said bulk layers with low density can advantageously be produced by dry forming or by wet forming of kernitermomechanical pulp (CTMP) or other “mechanical” mass based on needles, eg TMP, with high freeness. Tone shaping is from one aspect preferred, any known technique being used for this, but regardless of the shaping technique, the freeness of the pulp should be higher than 550 CSF, preferably higher than 600 CSF and even more preferably higher than 650 CSF, most preferably higher than 700 CSF. A high freeness of the fi-bearing material to said first layer ensures that the sheet can be pressed during dewatering and 512776 P132 consolidation of the sheet without the density increasing to an undesired extent. Other raw materials with high wet re-weathering can also be included in the bulk layer to a certain extent, eg chemically cross-linked fi bristles, which do not have a low dewatering resistance and high re-re-drying or wet pressing, but are not preferable for at least cost reasons.

Additional possible fi raw materials are synthetic fi fibers, such as polyester, polyethylene and polypropylene fi fibers, which also have a low dewatering resistance and high re-weathering in the wet state. In a preferred embodiment, the raw material is selected for the low density layer for the bulk layer, which should normally form the middle layer in the larnate, wholly or mainly of mechanically produced, so-called high-yield pulps, ie pulps with at least 75%, preferably at least 80% wood surface yield. CTMP and TMP pulps were based mainly on webs, provided that the pulps have the above-mentioned freeness values.

Up to 40% of dry weight can also be fed to the bulk layer. Committees are hereby som niered as a declassified product of the paper or cardboard laminate, which has been broken up into pulp and with mainly exposed fi boards.

The larninate according to the invention is in a preferred embodiment built up of three layers, although two or more than three layers are conceivable, said bulk layer preferably being laminated together with side layers on both sides. However, it is conceivable that a side layer is present only on one side of the larnate. This / these side layers can advantageously be manufactured in the same plant as the bulk layer, but can also be produced separately for laminating to the bulk layer in a separate plant.

The term "side layer" shall not have a restrictive meaning. On the outside of the side layer / layers, or between some side layer and the bulk layer, additional layers can thus be found, for example barrier layers. It should also be appreciated that the side layers / surface layers; the side layer / surface layer can be coated / coated to improve printability. Typically, the preferably coated layers are in turn coated with a plastic layer or are intended to be coated with plastic, in case the laminate constitutes an intermediate product, in order to make the laminate waterproof and heat-sealable in a manner known per se for use in liquid sealing. Pl322 gaskets. The side layers / surface layers can thus in combination with the bulk layer have their functions, such as making the larnate tight against liquid and water vapor, heat-sealable and giving the desired tensile strength and flexural strength.

According to one aspect of the invention, at least one side layer of the larnate is perneable to water vapor, this side layer being formed by a stock with a drainage resistance higher than 20 ° SR, preferably higher than 25 ° SK but not higher than 65 ° SR, preferably not higher than 40 ° SK to ensure removal of water during thermal drying.

It is assumed that the laminate on this side of the bulk layer also does not contain any other layer which is not permeable to water vapor during the drying process. Suitably, the permeable surface layer (s) is made of wet-form paper with a lurking "Gurley" greater than 2 μm / Pa * s, which is preferably produced as a chemical pulp of softwood and / or hardwood.

In order to achieve the required strength in the thickness direction (z-direction) and with respect to flexural stiffness, adhesives, preferably latex adhesives, are added in an amount of 5-30% by weight of the laminate, preferably 7-30% and even more preferably 10-20%, calculated as dry weights. These polymeric binders can be added dissolved and / or dispersed in water using spray directly to the bulk layer and / or to the side layers to be transferred to and penetrate the bulk layer. Different types of coating plants can also be used to add adhesive to the side layers. Coating can then be performed with a blade coater, directly or indirectly with a roller coater.

Suitably latex is used as the binder in the bulk layer in the above-mentioned content and other binder, for example starch, carboxymethylcellulose or gum, to effect bonding between the side layer and the bulk layer.

Suitable binders for penetrating the bulk layer are dilutable in water, i.e. soluble or dispersible in water and are preferably selected from the group consisting of water-soluble polymers, or aqueous dispersions of polymers, such as polyvinyl acetate, polyvinyl alcohol, polyacrylates, polyacrylic acid, polyethylene, acrylamide, polystyrene and maleic acid derivatives in the former P1322 of homopolymers and copolymers of said polymers or optionally from the group consisting of starch, carboxymethylcellulose and gums, the latter group being particularly suitable for use with the purpose of effecting bonding between different base-based layers.

Furthermore, the different layers with fi brers may contain hydrophobic additives such as AKD glue (alkyl ketene dimer glue), resin glue, silicone-based and orer uorating substances, etc., in an amount corresponding to a maximum of 2% of each layer weight.

According to one aspect of the invention, at least one of the side layers may have been formed and pressed in a separate (a) step before it is laminated to the bulk layer. The aim is to increase the dry content and increase the tensile strength of the surface layers separately without pressing said bulk layer to such an extent that its low density is lost. Consolidation of the multilayer laminate with the assistance of adhesives can thus be done with conditions during pressing that are not determined by the side layers' need for pressing for consolidation. Optionally, drying steps with heat can be info-gas to adjust the dry content to the desired level before assembling and joining the different layers.

In order to distribute the binder in the bulk layer, which normally constitutes the middle layer, the material is suitably pressed into one or more press nips before drying. The pressing is carried out in such a way that the density of the bulk layer does not exceed the limits laid down above drying. The pressing during lamination can advantageously be carried out between rollers or strips without removing water. The amount of water to be wiped off using heat can also be reduced using a press section of the type used in conventional paper machines, or as a combination. However, if water is removed during the pressing operation, there may be a risk of binder being lost, which is an environmental and economic disadvantage.

After pressing, the laminate is dried in conventional drying equipment such as cylinder dryer with or without drying wire / l, dryer, metal strip, etc. After drying or during a suitable interruption in the drying process, the material can be coated. Alternatively, side layers with one or two coated surfaces were used. Pl322 Layers, which may form surface layers or intermediate layers, and which form barrier layers in the form of polymers of different polymers, polyethylene, polypropylene, polybutene, polyester, polyvinyl and / or vinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol copolymers, ethylene-vinyl acetate copolymers and cellulose esters in one or more layers or aluminum foil or metallized polymer m lm can complement the larnate to further enhance the properties as a packaging material. Said barrier layer can also be laid directly against the porous bulk layer, the binder in that case contributing to giving the final larnate the required strength. In such a case, however, the larnate on one side of the bulk layer must be permeable to water vapor to ensure removal of water vapor. In case the barrier layers are intended to be laminated directly to the bulk layer, it is also required that it does not have a melting point which is lower than the surface temperature of the drying cylinders, usually 130-180 ° C.

The laminate according to the invention is preferably used for food packaging or packaging for consumer products of various kinds, etc. Furthermore, laminates of the type mentioned should serve well as protection during storage and transport of goods for industrial use.

The new paper laminate has a great advantage in that it reduces the consumption of raw materials in order to achieve a certain level of rigidity of a packaging material. This entails reduced costs and / or a reduced environmental impact in connection with transports of wood raw material and end product. This reduces the total energy consumption in the production of the paper laminate according to the invention compared with conventional board production. Furthermore, the consumption of electrical energy in the production of TMP or CTMP raw material with desired properties decreases. Furthermore, these raw materials are significantly cheaper to produce than chemically crosslinked beers and chemically produced softwood pulps according to the sulphate or sulphate processes.

Further aspects and characteristics of the laminate according to the invention and the method of producing the laminate appear from the following claims and from the following description of some possible ways of producing the laminate and a number of possible embodiments of the laminate together with experiments performed. BRIEF DESCRIPTION OF THE DRAWINGS In the following description reference will be made to the accompanying drawings, of which Fig. 1 schematically shows a pilot plant according to a first conceivable embodiment for producing a carton larnate according to the invention, Fig. 1B schematically shows a variant of the first embodiment according to the invention. Fig. 2 schematically shows a pilot plant according to another conceivable embodiment for producing the laminate according to the invention, Fig. 3 schematically shows a laminate in section according to a first possible embodiment according to the invention, Fig. 4 schematically shows a larnate in Fig. 5 schematically shows a cross-sectional linerate according to a third conceivable embodiment according to the invention, Fig. 6 schematically shows a cross-sectional larnate according to a fourth possible embodiment according to the invention, Fig. 7 schematically shows a larnate in cross-section according to a fifth t conceivable embodiment according to the invention, and Fig. 8 is an image made from a photograph of a beaded portion of a laminate according to the invention and shows what the laminate looks like to have been beaded and folded 90 ° with permanent defomiation of the bulk layer but without to delaminate and without cracks in the side layers.

DESCRIPTION OF METHODS AND DEVICES FOR MANUFACTURING THE LAMINATE The bulk layer (bulk layer), which in the drawing fi gures is denoted 1 and has a very low density, is laminated together with dry or wet-shaped side layers with a significantly higher density. These side layers have been designated 2, 2a and 2b in the drawings. They can advantageously be manufactured in the same plant, but can also be manufactured separately for laminating to the low-density bulk layer in the device according to the invention. Thus, according to one aspect of the invention, at least one of the side layers has been formed and pressed in separate (a) steps before being laminated to the bulk layer 1. The purpose is to increase the dry content and increase the tensile strength of the side layers separately without pressing the bulk layer in such to the extent that its low density is lost.

Consolidation of the multilayer laminate with the assistance of adhesive can thus be done under conditions of pressing that are not determined by the side layers' need for pressing for consolidation. Optionally, drying steps with heat can be inserted to adjust the dry content to the desired level for aggregation and joining of the different layers.

In order to achieve the required strength in the thickness direction (z-direction) and with respect to bending stiffness, polymeric binders which are dissolved and / or dispersed, ie dilutable, in water are added directly to the bulk layer and / or the side layer. The amount of binder should amount to 5-30% of the weight of the structure, preferably 7-30% and even more preferably 10-20%. Said binder solution and / or dispersion can be added using spray directly to the bulk layer and / or to the side layers. However, other techniques for applying adhesives are also conceivable, in particular for applying adhesives to the side layers, such as different types of coating plants. Thus, coating is judged to be possible to perform with blade coaters, directly and indirectly with roller coaters. It is considered suitable to use latex binder for penetration into the bulk layer and other binder, for example starch, carboxymethylcellulose and gums to effect bonding between different fiber-based layers, including between bulk layer I and said side layers 2, 2a, 2b.

Suitable binders for penetration into the bulk layer are, in addition to latex binders, other water-soluble polymers, or aqueous dispersions of polymers, which are selected from the group consisting of polyvinyl acetate, polyvinyl alcohol, polyacrylates, polyacrylic acid, polyethylene acrylamide, polystyrene and maleic acid redirate said polymers. Together with the binder or binders, wetting agents can also be applied, for example sodium dodecyl sulphate, hydrophobing agents and any additional, desirable ingredients.

In order to cause the polymeric binder to penetrate and to be distributed in the bulk layer, the material is suitably pressed into one or two of its press nips before drying. The pressing is carried out in such a way that the density of said bulk layer or drying does not exceed the limits laid down above. For example, the pressing during the lamination can advantageously be carried out between rollers or strips without substantially removing water. The amount of water to be wiped off with heat can also be reduced by using a press section of the type used in conventional paper machines, or as a combination. However, if water is removed during the pressing operation, there may be a risk of binder being lost, which is an environmental and economic disadvantage. Pressing during lamination, however, has the advantage that it helps to distribute the adhesive in the z-direction of the sheet.

After pressing, the larnate is dried in conventional drying equipment, such as cylinder dryer with or without drying wire /, lt, luñ dryer, metal strip, etc. After drying or during a suitable interruption in the drying process, the larnate can be coated. Alternatively, side layers are used which are pre-coated on one or both sides. The larninate can finally be coated with various polymers to further enhance the properties as a packaging material. Such coating layers or surface layers, which have little or no permeability to water, water vapor, carbon dioxide and oxygen and thus form barrier layers for such surfaces, may consist of films of different polymers, such as polyethylene, polypropylene, polybutene, polyester, polyvinyl and / or vinylidene chloride, polyvinyl alcohol, polyethylene-vinyl alcohol copolymers, ethylene vinyl acetate copolymers and cellulose esters in one or more layers or aluminum foil or metallized polymer m lm. Said barrier layer can also be laid directly against the porous bulk layer, the adhesive in this case helping to give the final laminate the required strength. In such a case, however, the side layer and any additional layers on the opposite side of the laminate must be permeable to water vapor to ensure water vapor removal. . In the case where the barrier layers are laminated directly to the bulk layer 1, it is also required that it does not have a melting point which is lower than the external temperature of the drying cylinders, which is usually 130-180 ° C.

Referring now to Fig. 1, a planar wire in a pilot plant is denoted by the number 10.

A supply line 11 supplies a stock of the CTMP pulp to a headbox 12. The CTMP pulp has the degree of freeness characteristic of the invention which has been stated in the foregoing and which is also stated in the following claims, which has been achieved by adjusting the temperature and energy input at the pulp preparation according to per se known technology, for example according to the principles reported in the said Swedish non-completed patent application 9000515-8. The CTMP stock is led from the headbox 12 onto the wire 10. The first side layer 2a fi is sprayed with water by means of a spray unit 14 on the side to be facing the bulk layer to be formed by the stock on the wire 10, to prevent curl. According to the embodiment, the side layer 2a consists of paper made mainly of softwood according to a chemical pulping method, preferably the sulphate cellulose method. The paper 2a can be manufactured in a separate plant and also delivered from a completely different manufacturer and in this case unwound from a first supply roll 20. Alternatively, the paper 2a can be manufactured in a machine integrated with the device according to the invention for producing the laminate according to the invention in line, as in a corrugated board factory, the side layer 2a corresponding to a liner. Incidentally, the side layers 2a, 2b may very well consist of paper with the same character as the liner in corrugated board.

The moistened side layer 2a and the bulk layer 1 formed on the wire are joined face to face between a gusset roll 15 and a press roll 16. The gusset roll 15 and the first press roll 16 form a first press nip 22. The two joined layers 1, 2a then pass a second press nip 17 in a simple salted press with dewatering consisting of roller 18 and roller 19. In this case, water is transferred through the side layers 2a to the press salt, which in turn is dewatered with salt suction boxes of a conventional type. To the layers, on the bulk layer side 1, latex or other polymeric binder as above is applied as an aqueous dispersion / solution via a spray unit 13.

A second side layer 2b may be of the same type as the first layer 2a and produced in a separate plant, in which case it is unwound from a second supply roll 21, or produced in line, as described for the first layer 2a above. However, materials of another type in said second side layer 2b are also conceivable, for example plastic foil. However, in this case it is assumed that the side layer 2b also consists of a paper layer, preferably paper made of chemical pulp. The side layer 2b is then moistened by means of a third water spray unit 23 on the side to be turned towards the bulk layer 1 on the opposite side relative to the side layer 2a. In this case, the side layer 2b is provided on the same side with adhesive in a coating unit 24, which may consist of a spray unit or coating unit, for example a blade coater with direct coating on the layer 2b or via roller (roller coater). Suitably starch is used as the P1322 binder in the coating unit 24 or other suitable binder, for example carboxymethylcellulose and / or gum, to effect bonding between the side layer 2b and the bulk layer 1.

The three layers 2a, 1 and 2b are then joined together in a third press nip 26 between two press rollers 27 and 28 under little or no dewatering but under such high pressure that the distribution and penetration of the initially added binder in the bulk layer 1 is stimulated. The thus consolidated larnate, consisting of the three layers 2a, 1 and 2b, is then led to a drying unit generally designated 30 to finally be wound on roll 31. The laminate 31 can then be provided with an outer barrier layer in a separate plant. Alternatively, this can be done in line with the dryer 30 for rolling on a roll or cutting into sheets.

It is also possible to apply a barrier layer consisting of an aluminum foil 3, or metallized plastic foil between the bulk layer 1 and the side layer 2b, which is made between said second press nip 17 and said third press nip 26. In this case adhesive is applied to said foil / barrier layer 3 on the side to be facing the bulk layer 1 via a fifth spray or coating unit (not shown). This binder can be of the same character as is applied to the side layer 2b in the unit 24. It is understood that in this case the drying of the bulk layer 1 in the drying unit 30 takes place via the side layer 2a on the opposite side of the bulk layer 1 relative to the barrier layer 3. of the mold described above with reference to Fig. 1. Also in this case the forming is performed wet, but the bulk layer 1 is dewatered in press 17 before joining with the side layers 2a and 2b. Binder is applied to the side layers in the units 13 and 24, respectively, on the sides to be facing the bulk layer 1. Even in these cases, the binder can be added by spraying or coating.

The described methods of producing the larnate according to the invention, including wet forming of the bulk layer 1, undoubtedly have certain advantages, not least from a cost point of view. However, the invention also offers a method of producing the laminate, comprising P322 comprising dry removal of the bulk layer 1. Referring to Fig. 2, which also shows a pilot plant, a hammer chamber 2 is denoted by the number 40. To this is fed dry CTMP. fluff, which is processed in the hammer chamber so that fi brema fi is added. The CTMP pulp has been selected or produced in a separate process in such a way that the degree of freeness typical of the invention is obtained in said pulp, if this is dissolved in water. Regarding the freeness of the pulp which is to form the bulk layer, reference is made to the foregoing and to the appended claims, and with regard to the method of manufacturing such a pulp, reference is also made to what has been said above. The thus processed fluff pulp is transported via a tube conveyor 41 to a forming hood 42, from which the dry pulp is formed into a sheet on the wire 10. Latex or other polymeric binder as above is supplied to the CTMP sheet on the wire as above as water dispersion / solution via a first spray unit 13 Other parts of the method of manufacturing the laminate are substantially the same as in the embodiment according to Fig. 1. However, adhesive is also applied to the first side layer 2a in a ventilated adhesive applicator 43 on the side to be facing the bulk layer 1. The adhesive applicator 43 may be of the same type as the ventilated binder applicator 24, and also the binder or adhesives supplied by the binder applicator 43 may be of the same type as supplied by the binder applicator 24. A difference from the previous embodiment is further that no dewatering is required between the presses 22 and 26. the equipment and the procedure in general, reference is made to the above description construction of the plant according to Fig. 1.

Regardless of the manufacturing technique, a basic principle of the inventive method is to create a high bulk layer, which should normally form the middle layer of the laminate, to combine this bulk layer with one or more side layers, which are themselves consolidated in the laminating, and that the lamination then is carried out in such a way (low compression pressure in combination with high re-curing and dewatering of the bulk layer) that the bulk in the bulk layer is not substantially lost.

It should also be understood here that all layers to be included in the laminate can be manufactured and prepared separately, including also the bulk layer, and then laminated together by P132 512776 m laminating. In this process, the bulk layer has sufficient strength through the applied adhesive to be able to be wound up on a roll, unrolled, guided, etc., and joined to the side layers by laminating.

EMBODIMENT OF THE LAMINATE ACCORDING TO THE INVENTION Fig. 3-Fig. 7 shows a number of possible embodiments of the larnate according to the invention. It should be understood that the embodiments shown are only a number of illustrative examples and that a number of other embodiments are conceivable within the scope of the invention. Thus, for example, the number, character and location of the various layers can be varied and supplemented without departing from the basic principles of the invention, as these are expressed in the following patent claims.

EXAMPLE 1 - Fig. 3 The larninate L1 according to the embodiment consists of only two layers, namely a bulk layer 1 with the typically low density and high degree of freeness for the invention and a side layer 2. The side layer 2 typically consists of a paper layer but can in principle also consist of of a non-breast layer, for example a plastic foil, with a substantially higher density than the bulk layer 1 and otherwise selected and combined with the bulk layer 1 so that the consolidated laminate obtains the properties characteristic of the laminate according to the invention. The larninate L1 need not be an end product but preferably constitutes an intermediate product.

EXAMPLE 2 - Fig. 4 Starting from the laminate L1, Fig. 3, a barrier layer 3 has been added in the laminate L2, which abuts against the bulk layer 1 and which can consist, for example, of an aluminum foil and partly a pair of surface layers 4a and 4b, respectively. of a plastic foil.

EXAMPLE 3 - Fig. 5 This example illustrates a cardboard material, for which the invention is primarily intended to be used. This laminate L3 is made up of a thick but light, bulk-giving middle layer of fibers with said degree of unity and on either side thereof a side layer Za and 2b, respectively, consisting of, normally, a paper layer with a substantially higher density and tensile strength than the bulk layer. 1, preferably paper layers, which are much thinner than the bulk layer 1 and produced by a chemical pulping method.

EXAMPLE 4 - Fig. 6 The difference with respect to the previous Example 3 is that the bulk layer 1 in the laminate L4 is relatively thin, while the two side layers are thicker or at least have a substantial thickness in relation to the bulk layer.

EXAMPLE 5 - Fig. 7 The laminate L5 consists of a core of bulking material according to the invention and ultimately plastic foils 4a and 4b, respectively. Closest to the bulk layer 1 there is on one side a barrier layer 3 of aluminum foil and between the aluminum foil 3 and the surface layer 4a of plastic there is a paper layer 2a made of chemical pulp. On the other side, between the bulk layer 1 and the surface layer 4b of plastic, there is a side layer 2b of paper, which may be of the same type as the layer 2a.

Typically, the surface layers 4a and 4b in all of the above embodiments normally have a thickness of 0.02-0.3 mm, and in cases where a barrier layer 3 of aluminum foil is present, this has a thickness of 3-150 hours, normally greater than 10 μm. , preferably a maximum of 40 μm.

REPORT OF PERFORMANCES EXPERIMENTS Preparation of laboratory sheets Laboratory sheets were prepared with a bulk yielding middle layer consisting of CTMP or TMP pulp with very high freeness and low density and containing latex binder and, on either side of this middle layer, strong side layers of paper with significantly higher bulk density. . Both dry forming and wet forming of the bulk layer were tested. Various commercial papers of chemical sulphate cellulose pulp produced from bleached chemical softwood and / or leaf sulphate pulp or paper grades of chemical pulp produced on experimental paper machines were used as side layers.

Pl322 512776 w Dry casting of bulk layers CTMP ff uffniassa fi was brewed in Kama's H01 hammer mill with 6 mm sieve at 4500 rpm.

Formation of the bulk layer is accomplished by dispersing the fi loaded fi in air and forming fi bern on a 100 mesh metal wire with a diameter of 25 cm.

Wet formulation of bulk layers CTMP or TMP fi ber is dispersed in water at 0.6% concentration. Sheets were found in sheet form in A4 format. The sheets were rubbed against blotting paper, whereby the dry content increased to about -25%. The sheets were then dried clamped with a dryer against a cylinder with a surface temperature of 70 ° C before applying binder and lamination to the side layer.

Laminerin Latex binder containing 0.2 vil sodium dodecyl sulfate (wetting agent) was applied to the dry or wet bulk layers using spray. The dry content of the binder by spray can be varied within wide limits, but unless otherwise stated, the dry content has been about 10%.

The side layers fi were iced with water and / or sprayed with binder on the side intended to be laid against the bulk layer to avoid curl. Thereafter, the side layers were joined together with the bulk layer and 75 μm of polyethylene film was applied to each side to prevent water / binder migration. The polyethylene film was used only here as an aid in handling the samples and was thus not made to adhere to them. The composite material was pressed there at a pressure and time which was adjusted to reach the desired density, normally between 0.1 and 3 bar, and between 2 and 10 s, respectively.

Drying The laminated sheets were dried clamped under a dryer against the surface of a cylinder dryer with a surface temperature of 70 ° C. 512776 19 Pl322 TEST METHODS AND DEFINITIONS In the following, a number of product properties are described to describe the properties of the composite materials in terms of basis weight, thickness, density, tensile strength + index, z-strength, flexural stiffness + index. All properties are measured in a standardized climate, 23 C and 50% RH, and using the following standardized SCAN methods. Unless otherwise stated with respect to MR (machine direction) and TR (bidirectional direction) concerning the strength and elongation properties of the materials, the mean geometric mean value for machine and transverse direction is always meant.

Surface weight SCAN P 6:75 Thickness - density SCAN P 7:75 Tensile strength - elongation, tensile strength SCAN P 67:93 Bending resistance SCAN P 29:95 Z-strength SCAN P 80:98 Lu fi resistance, permeability Gurley SCAN P 19:78 Surface roughness, PPS SCAN P 76:95 Freeness SCAN C 21:65 Shopper - Riegler, SR SCAN C 19:65 Bending stiffness index is calculated from the following formulas: Wm7 / ks3) For belt length 50 mm width 38 mm and angle l5 °, s' == FB * o applies , os37 (mNm) FB = Bending fi (mN) Bending stiffness index = Sb / w3 Stiffness according to Kenley and Taber is determined by a geometric design of sample and clamping that corresponds to the strip length used here 50 mm with a width of 38 mm and an angle of l5 °. 512776 P1322 For conversion of Kenley stiffness to bending crane, Iggesund carton information (1979) states: Kenley bending crane fi (g) = 0.1 * LoW (mN) which gives: Bending stiffness index = Kemey * o, oss7 / o, 1 / basis weight3 (Nmvkgñ For conversion of Taber stiffness to bending force, Stiffness conversion slide from Finnboard (1979) states: Taber (gem) = 0.465 * LoW (mN) which gives: Bending stiffness index = Taber * 0.0837 / 0.465 / basis weight3 (Nm7 / kg3) LoW = Lorentzen & Wettre flexural stiffness meter (SCAN P29: 95) EXPERIMENT 1 To illustrate the importance of using a fre berr raw material with high freeness in said bulk layers, illustrative experiments have been performed with TMP and CTMP with different freeness.

Table 1 shows that the density of the sheets prepared by wet molding, see above, decreases with increasing freeness. It is also known that the strength of aterialber material is generally low at low densities. Nevertheless, as a pulp to produce a high bulk layer according to the invention, a freeness is preferably greater than 600 ml CSF, suitably greater than 650 ml CSF and most preferably at least 700 ml CSF, Table 1 Pulp type CTMP CTMP TMP Freeness (ml CSF) 697 743 798 Dry content after gusk (%) 19.5 21.0 22.9 Dry content after 1st press (%) 43.4 40.6 50.2 Dry content after 2nd press (%) 51.0 47.3 55.1 Surface weight (g / m 2) 102 102 100 Thickness (mm) 0.51 0.64 0.70 Density (kg / m3) 199 159 143 Pressure = 5 min and 2 min respectively at sheet pressure 1.1 kg / cmz 21 Pl322 EXPERIMENT 2 The effect of different basis weights and qualities of the side layers was investigated by laminating together a middle, dry shaped bulk layer with different side layers. The fiber raw material for the bulk-forming cut layer was STORA Fluff CTMP 70HD with a freeness of 697 CSF. The dry content after addition of binder and linerinization of the side layers to the bulk-giving middle layer was about 30%, before the drying process was started.

The name, composition and properties of the different side layers are reported in Table 2. 512776 22 Table 2 - Different layers 1 2 3 4 S Side layers, name: X749: 10 X749: 20 X749: 30 X749: 40 Interleaving HT Side layers, composition: , Norrland 4 29.0 SR% 60 60 Norrland 4 26.0 SR% 60 60 Stora 61 33.0 SR% 40 40 Stora 61 28.0 SR% 40 40 Interleaving HT% 100 Ymkt g / m2 52 42 53 42 39 Thickness pm 96 79 94 80 59 Density kg / m3 545 535 566 518 651 Tensile strength MR kN / m 5.2 4.3 5.8 4.0 4.5 Tensile strength TR kN / m 2.0 1.5 1.9 1.4 2.7 Tensile index IvIR Nm / g 100 l0l 109 96 115 Tensile index TR Nm / g 38 35 35 33 69 Tensile stiffness MR kN / m 562 486 633 466 436 Tensile stiffness TR kN / m 194 154 207 160 264 Tensile stiffness index MR kNrn / g 10.7 11.5 11.9 11.2 11.3 Tensile strength index TR kNm / g 3.7 3.7 3.9 3.8 6.8 Elongation MR% 2.4 2.2 2.3 2, 0 2.4 clearance TR% 5.3 4.3 4.4 3.3 2.9 Air permeability Gurley pm / Pa * s 5.0 5.7 7.2 11.4 3.2 Air resistance Gurley s 25.4 22.6 17.7 11.2 39.4 Surface roughness PPS S 1.0 Mpa S1 pm 7.4 7.8 7.3 7.1 2.9 Surface roughness PPS S 2.0 Mpa S1 um 6.5 7.1 6.4 6.0 _ 2.7 X749: 10-40 = Different paper qualities produced for 45 cm wide experimental paper machine of masses of type Norrland 4 and Stora 61 Norrland 4 = Commercial bleached chemical coniferous sulphate pulp from Stora Cell Stora 61 = Commercial bleached chemical leaf sulphate pulp from Stora Cell Interleaving HT = Commercial paper quality of bleached chemical coniferous and leaf sulphate pulp from STORA Gnivon MR = Machine direction TR = Transverse direction Table 3 shows the properties of the laminate laminates with a raw material consisting of STORA Fluff CTMP 70 HD with a freeness of 697 CSF and with different side layers according to Table 2. In column 1, results of a material consisting only of the bulk-yielding middle layer, ie without side layers, are reported.

P1322 I 512776 Table 3 - Larninate with bulk-bearing middle layer and different side layers slaosklkt (according to table 2): 1 2 3 4 5 6 No lmer- x749: 10 x749; 20 x749; 30 x749; 40 leaving HT Side layer Ylvigt g / mZ 39 52 42 53 42 Thickness hour 59 96 79 94 80 Density kg / m3 651 545, 535 566 518 Binder: Apprmn 0540 s% 25.0 14.1 11.9 13.6 12.1 13.4 Weight, total g / m2 107 177 201 185 207 180 Thickness am 672 840 843 863 820 757 Density kg / m3 160 211 238 214 253 237 Tensile strength kN / m 2.4 6.9 5.4 4.4 5.7 4.7 Tensile index Nrn / g 23 39 27 24 27 26 Tensile stiffness kN / m 245 614 541 436 546 479 Tensile stiffness index kNm / g 2.3 3.5 2.7 2.4 2.6 2.7 Elongation% 1.7 3.4 3.8 3 .7 4.0 3.2 Bejmotslånd 50 mm 15 ° mN 94 485 470 454 478 381 Bojmolsråndsindex 50 mm Nm6 / kg3 75,5 87.1 58.2 71.9 53.6 66 ° Böjsiyvllelslndex 50 mm Nm7 / kg3 5 , 97 6,89 4,60 5,69 4,24 5,21 ° z-sryrka kN / m2 152 59 46 36 61 56 Lu fi penneans Gurley tim / Pax 1524 1,3 2,4 1,8 3,6 6, 1 Air resistance Gurley s 0.1 100 54.0 _ 72.2 36.0 20.9 Appretan 0540 S is the trade name for a binder dispersion from Hoechst Perstorp, containing polyvinyl acetate as active binder.

Of the side layers evaluated in Table 3, No. 5, Interleaving HT from STORA Gruvön is the best choice. The side layer Interleaving HT thus, in combination with the bulk-yielding average layer of STORA Fluff CTMP 70 HD and with the addition of latex binder, which was penetrated and distributed in the bulk layer in the manner described above, gave a flexural stiffness index of 6.89 Nm7 / kg3. Other paper grades made from chemical pulp based on hardwood and / or coniferous wood also appear to be well suited to be used as a side layer on the bulk layer; also side layers of materials which have been produced on P1322 512776 24 P1322 an experimental paper machine (Nos. 3-6 in Table 3), in that they in combination with the binder impregnated bulk layer gave a significantly higher bending stiffness index than hitherto known commercial board materials.

EXPERIMENT 3 A series of adhesives were evaluated for suitable properties to maximize the stiffness of a larnate according to the invention using a dry-shaped bulk layer as the middle layer. The fiber raw material was also in this case STORA Fluiï 'CTMP 7OHD with a freeness of 697 m1 csF. Interim / ing HT 40 g / m2 from sroRA Gruvön was a side layer on both sides. The paper properties of this side layer have previously been reported in Table 3, No. 5.

The dry content after addition of binder and lamination of side layers was about 30% before the drying process. The results are shown in Table 4. “.. w.. . ä 3 _... NN. N22. 2: a- .. .äN ..N. “.“. “2.“ .. “. N ... ä .N ... N“ wëNsz .. “. e ... .. “.au = .æu..åw ... m ä N .. 3.“ ä NN ... N ä “wëäez _.“. E ... .. “.a .. =. Æ2.> ... w ... m ää EN ... N ... N N ... NNN ä .. za ..“. e ..... "" ......... ss .... ". ä ... .. “NN w ... N ... 3 .ä ä ... N: oo 52> æ owåiouuëv wEE.o._.

“.N ... N ... N ... N ... N SN .. wšz ..,. ° ..._.... §.å“ .. eo å .. Nä ä .. ... ä NN .. ““ “ä“ šz .. Éåêao å ä ä ä “N NN ä ... sz .a .. = .... eo ...“ .ä .. “... ä ... ““ ä Nä Ez .. Ébmwßä. ä ... “. ä. NN. NN. ON. ä. “šä -., - .ëæso ä Nä ä ä ä ä. ä. Neu ... se ..ë .... a .. = .. ä ... âšå .š ... äëe .. .year 6 äN “NN äN äN ..“ N ... N äN Nea .. .ëæso 7 ... N äN äN NN .. ää åN “ä a .. ... ÉP 7. ä. Nä. ä. ä. Nä. ON. NN. Ne ... 2.2. » 2 u 9.2 .... u fi uzzzë ... 1 “N“ N “N“ N “N“ N “N ä.: ..... = .. =.“. U ..... E. .... =. “. .b m9 ..... ..>> mÉuS / n. 2.3.2. .Näää zmêoš .. .x u <> .. BS .. QSK. ... såå Éëš .... “ä.o ..“ “82-8. OQQÉ. .... “..-....“ “82 .... ........- o ..... .aowoä. “Das .... e.“ E.w_> _. .. “ä N .z .z u .. Es. ä ä .. “o. .N äN äN u ... NN u »... GE u“ ..u = ö = öu.: M ää m ONNN: SPEEN = S2NE <: SUEQJN: SoENÉ cåuhïa. = m.u.ma <äÉaNF .. uuuoëuuim: _ ä N ä .. N N. .2æ = æ ....... ... åo E ... HE w =.>. Æ ..... a. à 2.3 .... .ä ä .. .e Nä šcoe. .NES ... åu ä ... 5.0.5 ä ... väte% s.>. W .. = .. à 2.3.3 .. ass ... - .. ... ææN NNME mm 512776 26 TG = Glass conversion temperature MPT = Minimum forming lm forming temperature * Broolcñeld viscometer RVT, spindle 2; 20 min '1 for TH 210 S, (according to data sheet) TA 2270 S and TA 2370 S., spindle 3; 20 min-l for os4o s ooh rs. , spindle s; 20 nun-l for DM z ooh 9606. ** content calculated on the weight of the middle layer.

Appretane = Trade name for binder dispersions from Hoechst Perstorp PVAC = Polyvinyl acetate PS = Polystyrene PACR = Polyacrylate PMACR = Polymethyl methacrylate PE = Polyethylene PVOH = Polyvinyl alcohol DBM = Dibutylmaleinate Table 4 shows that all tested binders are of the latex type. The basic technical reasons for the variations can be fl era. For example, the viscosity and surface tension of the adhesive can affect the distribution and action of the adhesive in the laminate.

Furthermore, properties of the polymers, such as mechanical strength and adhesion to the bone materials, should affect the final properties of the laminate. A low viscosity promotes good penetration into the thick, bulk-yielding ridge layer. On the other hand, a low viscosity in the boundary layer to the side layers can promote good adhesion and thus good consolidation of the laminate. The highest flexural stiffness index has been achieved with Appretan 0540 S and Appretan TS as binder, columns 1 and 2 in Table 4, which have a medium viscosity. Irrespective of the basic causes, Table 4 shows that the flexural stiffness index has been achieved with the inventive laminate, which substantially exceeds the current level of flexural stiffness of commercial materials. For example, Triplex (trade name) cardboard from STORA Skoghall, which is used to a very large extent for liquid packaging, has a flexural stiffness index of 1.3 Nm7 / kg3. Furthermore, Fellers and Norman in Paper Technology, third edition l996, pp. 315-318, mention that paper materials usually have a flexural stiffness index between 0.5 and 2 Nm7 / kg3.

The flexural stiffness index according to the invention also substantially exceeds the values known in the literature for materials made by dry forging. This is probably caused by the choice of high-freeness raw material, which is combined with a process (mainly in conjunction with press and drying) which means that the density of the laminate can be kept low.

The preferred binders for use in larnate according to the invention should have a glass transition temperature higher than 0 ° C, the polymers should also have been prepared by polymerizing ethylene, propylene, butene, vinyl chloride, vinyl acetate, acrylates such as methyl methacrylate. ethyl methacrylate, etc. and as copolymers. As additives, these latex binders can also use both surfactants and e.g. polyvinyl alcohol and carboxymethylcellulose to stabilize the dispersion of polymers in the water. These and similar substances, such as starch, also serve as binders.

EXPERIMENTS 4 In order to investigate the effect of density and content of binder in the laminate, a series of experiments were carried out, in which these variables were varied. As the middle layer, dry-formed bulk layers were used, the raw material being the STORA Fluff CTMP 70 HD with a friness of 697 CSF. The side layers consisted of Interleaving HT 40 g / mz from STORA Gruvön, paper properties according to Table 2, column 5. Appretan 54OS was used as binder, which was added to the middle layer. The dry matter content after adding binder and varnishing the surface layer was about 30% before the drying process was started. The results are shown in Table 5. 512776 Table 5 - Varying density and amount of binder in the larnate, consisting of dry-formed bulk layer, freeness 697 ml CSF with side layer of Interleaving HT 1 2 g 3 4 5 6 Binder amount *% 25 25 35 35 30 20 Birraerrreaeisrrrrrgt fl * % 14.6 14.5 19.7 19.7 17.1 11.8 Density bulk-yielding middle layer, guide value kg / rrß 160 220 160 220 200 160 Density bulk donor middle layer (calculated) itg / rrrß 160 227 180 236 206 175 Surface weight, bulky rnit layer layer tet. (ber) g / rrr2 98 96 101 101 104 100 Properties of the laminate: Ytvrirt g / rrt2 168 166 179 179 182 170 rjeeitiek rrrrr 73 1 540 705 574 648 690 Density itg / rrß 229 307 253 3 12 280 246 Tensile strength kN / m 7.5 7.8 7.4 8.5 8.1 7.2 Tensile strength Nrrt / g 45 47 42 47 45 43 Tensile stiffness irN / rrr 642 658 642 749 703 592 Tensile stiffness index kNm / g 3.8 4.0 3, 6 4.2 3.9 3.5 Tejrrrrrg% 3.7 3.9 3.4 3.6 3.6 3.9 Bejrrretstårrd 50 rrrrrr 15 ° rrrN 446 346 502 495 521 443 Bejrrretstårrasrrrriex 50 rrrrrt Nrrr6 / 1rg3 95 76 88 86 87 91 ° Bej stiffnessrrtiex 50 rrrrrr 15 ° Nrrt7 / 1rg3 7.49 6.03 6.97 6.8 6.88 7.18 z-styrite itN / rrrl 65 140 63 168 158 47 * content calculated on the bulk-yielding rnit layer. weight, ** content calculated on the weight of that laminate.

Table 5 shows that an increasing density gives lower bending stiffness but increased z-strength, ie strength in the thickness direction of the larnate. The table indicates that the content of binder can be varied within relatively wide limits in order to, together with the density of the product, constitute an essential control variable for the properties of the laminate. At all evaluated densities and binder contents, the flexural stiffness index of the larnate substantially exceeds previously known commercial materials.

EXPERIMENT 5 A TMP mass (thermomechanical mass) with freeness 798 ml CSF and a CTMP mass (chemithermomecharic mass) with freeness 743 ml CSF were formed wet or dispersed by the fibers in water to form bulking middle layers in laminates according to the invention.

The TMP pulp contained 10% chemical pulp ground to w 27 ° SR mixed with 90% TlV [P pulp with freeness 798 ml CSF. The addition of chemical pulp reduced freeness slightly, 512776 pulp with freeness 798 ml CSF. The addition of chemical pulp decreased fi eeness slightly, but the result was still a bulk layer with a high freeness value according to the invention.

The middle layers were laminated to side layers which consisted of the above-mentioned paper layers of quality Interleaving HT from STORA Gruvön with paper properties according to Table 2, column 5. For lamination, binder Appretan 540S was added to the bulk layer. The dry matter content after adding binder and laminating the surface layer was about 30% before the drying process was started. The results are shown in Table 6.

Table 6 - Wet-formed bulk layers, double-sided laminated with machine-smoothed paper 1 2 s Pulp 1 reflective layer nv flfl * TW ”GIMP Adhesive quantity *% 12.6 11.9 11.1 Side layers * # 1 IIHI * # 3 * Ywikt bnikgivsnde ininskiki mi. (ber) g / m2 96 78 82 Density bulk-yielding middle layer (ber) kgJm3 152 150 159 Properties of the laminate: Ywila g / ml 175 158 162 Tjeekiek pm 735 630 619 Density kg / nß 239 251 261 Tensile strength kN / m 1 1 8 12 Tensile index Nm / g 60 51 76 Density stiffness kN / m 878 751 1033 Tensile stiffness index kNm / g 5.0 4.8 6.4 clearance% 3.2 3.1 2.8 ßejmetståna 50 mm 15 ° inN 480 472 '449 Bojrnetstanasinaex 50 nnn 15 ° Nrn fi / kgï '89 119 107 Bejstyvnetsindex 50 nnn 15 ° N1n7 / kg3 7.0 10.0 8.9 s-smka kN / 1n2 89 74 107 * content calculated on the entire weight of the sheet “TNEP with 10% ground core mass (80% St.32,20% St.6l) ground to z26 ° SR *** Interleaving HT 136 110-1 Table 6 shows that the flexural stiffness index even for larnate with wet-form, bulk-giving middle layer with low density significantly exceeds currently known commercial materials . 512776 EXPERIMENT 6 The initial dry matter content for thermal drying has in the previous experiment been relatively low, about 30%.

As part of developing the process for producing the larnate on a commercial scale, Experiment 6 aims to increase the dry content of latex binder in spray application to the bulk layer and thereby reduce the amount of water in the laminate during pressing. Tone-shaped CTMP fl uff was used as the bulk-yielding cut layer and the side layers consisted of 40 g, Interleaving HT made from bleached chemical softwood and leaf sulphate pulp. The 15% binder was applied by spraying to the bulk-yielding middle layer before lamination with the side layers. The results are shown in Table 7.

Table 7 - Experiments with higher dry content in the larnate before drying Binder content * Q% 14.0 14.0 Dry content before drying, tot. % 35 40 Density, guide value; Bulking medium layer kg / m3 200 200 Properties of the laminate: Ywiin, bnikgivande niinsieiki mi. ig / in * 103 102 Density, bnikgivnnae niinekiki (bei) 'iig / niß 204 191 Ywiin g / in ”182 181 Tjeemek inn 609 638 Density» kg / ina 300 284 niagsiyiknw * ï kN / in 12,6 10,9 Dragindex Nm / g 69 60 Tensile stiffness in kN / m 1026 928 Tensile stiffness index kNm / g 5.6 5.1 clearance V% 3.1 - 2.9 'Bending moon 50 inside 15 ° i niN 425 394 Bending resistance index 50 mm l5 ° Nm5 / kg3 70 66 Bending strength index 50 niin 15 ° _ Nnf / kg * 5.9 5.5 z-eiyrkn in kN / inl 184 NA *** * Content calculated on total basis weight ** Tensile strength only tested in the machine direction, MR *** NA. = not analyzed The results in Table 7 show that even at 35 and 40% dry matter, a material with a very high flexural stiffness index is obtained, which significantly exceeds the flexural stiffness index of currently known commercial materials, 512776 TRY 7 Conversion properties of a packaging material, ie the material's suitability to be reshaped to packaging in machines that work at a high pace, o fi a continuously, are difficult to evaluate on the basis of small amounts of material that has been produced in a laboratory. However, bending and foldability are essential properties of packaging material and are possible to study. even when only small amounts of material are available. To evaluate these properties, a material according to the invention has been studied, more specifically the laminate prepared in Experiment 3 above, Table 4, column 1. The material was beaded and then folded 90 ° in the bead line. Fig. 8 shows the crimped material. The picture shows that it is possible to fold the material 90 ° towards the bead indentation without it delaminating or cracks appearing. However, it is still possible to fold the material in the other direction unhindered, ie from the big press. The low density of the bulk-giving middle layer 1 enables a permanent deformation of the middle layer to be achieved. The side layers 2a and 2b have sunk into the middle layer 1, so that shear deformation at the side of the fold is avoided.

Such shear deformations manifest themselves in a conventional laminate as bulges, which cause delamination and / or material displacement in the bulk layer, alternatively cracking in the side layer, in subsequent conversion operations. The permanent thickness reduction of the larninate during bending is at least 10%, preferably at least 20%.

The invention is not limited to the above-reported embodiments and is not limited by reported experiments but can be varied within the scope of the patent claims.

Claims (41)

10 15 20 25 30 512776 32 PATENT REQUIREMENTS A paper or paperboard laminate composed of at least one bulk-giving layer, herein referred to as a bulk layer, and on at least one side of the bulk layer at least one side layer, the side layers and bulk layers being joined together directly or indirectly over substantially their entire facing facing surfaces, characterized in that the bulk layer to 40-95% consists of cellulose fibers with a freeness of 550-950 ml CSF, that the side layer / s has a greater density than the bulk layer, and that the laminate has a flexural stiffness index higher than 2.5 Nm7 / kg3, but less than 14 Nm7 / kg3, calculated as a geometric mean for machine and transverse direction. Paper or cardboard laminate according to Claim 1, characterized in that the bulk layer consists at least 60% of fibers with a freeness value higher than 600 ml CSF, and that the laminate has a flexural stiffness index higher than 3.0 Nm7 / kg3. Paper or board laminate according to Claim 2, characterized in that the bulk layer consists of at least 60% of fibers with a freeness value higher than 650, most preferably at least 700, but less than 850 rn CSF, and that the laminate has a flexural stiffness index higher than 4.0 Nm7 / kg3_ Paper or paperboard laminate according to Claim 3, characterized in that the laminate has a bending stiffness index higher than 5.0 Nm7 / kg ”calculated as a geometric mean value for machine and transverse direction. Paper or cardboard laminate according to claim 1, characterized in that the bulk layer has a density of 50-300 kg / mB, preferably 70-200 kg / m 3, preferably 100-180 kg / m 3. Paper or cardboard laminate according to claim 1, characterized in that said side layer has a density which is at least twice as large, preferably at least three times as large and most preferably at least four times as large as the density of the bulk layer. 10 15 20 25 30 512776 33 Paper or cardboard laminate according to claim 5, characterized in that said side layer has a density of 300-1500 kg / m 3, preferably 400-850 kg / m 3. Paper or cardboard laminate according to either of Claims 5 and 7, characterized in that the larnate has a density of 100-500 kg / m 3, preferably a maximum of 400 kg / m 3, preferably 125-350 kg / m 2, preferably 150-250. kg / ma. Paper or cardboard laminate according to any one of claims 5-7, characterized in that the larnate has a density of 200-400 kg / m 3, preferably 250-350 kg / m 3. Paper or cardboard laminate according to any one of claims 5-7, characterized in that the laminate has a density of 300-500 kg / m 3, preferably 350-450 kg / m 3. Paper or paperboard laminate according to Claim 1, characterized in that the cellulose fibers in the bulk layer mainly consist of cellulose fibers produced by a per-mechanical mechanical, thermomecharical or chemithermomechanical pulp production method, preferably with a wood yield> 75%. 80%. Paper or paperboard laminate according to claim 11, characterized in that the cellulose fibers in the bulk layer mainly consist of fibers of TMP and / or CTMP pulp with said freeness value. Paper or paperboard laminate according to Claim 12, characterized in that the bulk layer, in addition to spreads of at least TMP and / or CTMP high yield pulp, contains a total of a maximum of 40%, calculated on dry weight, chemical pulp and / or folded up, mainly dried. fi asks from the paper or cardboard laminate. Paper or paperboard laminate according to Claim 12 or 13, characterized in that the bristles in the bulk layer, in addition to the bristles of at least TMP and / or CTMP high yield pulp, comprise a maximum of 30% by weight of resilient synthetic berry, preferably berth of Any polymer belonging to the group of polymers comprising polyethylene, polypropylene and polyester, and / or not more than 30% of chemically crosslinked softwood fibers. Paper or paperboard garnishes according to claim 1, characterized in that at least one of said side layers consists mainly of bleached or unbleached core sulphate, sulphate or organosolve cellulose pulp. Paper or paperboard laminate according to claim 15, characterized in that said side layer consists mainly of bleached or unbleached chemical cellulose pulp made from a cellulosic raw material consisting mainly of softwood and / or hardwood. Paper or paperboard laminate according to claim 1, characterized in that the laminate, at least on one side of the bulk layer, has a side layer which consists of a water-vapor perneable paper material formed by a stock with a drainage resistance higher than 20 ° SR but less than 65 ° SK preferably higher than 25 ° SR but not higher than 40 ° SR, and that the larnate on the opposite side of the bulk layer has at least a third layer consisting of a material which is substantially much less permeable to water vapor. than said side layer of water vapor perneable paper material formed by a stock with said dewatering resistor. Paper or paperboard laminate according to any one of the preceding claims, characterized in that at least one of said side layers consists of a paper material which has been formed and pressed in one or more separate steps before being joined to the bulk layer. Paper or cardboard laminate according to claim 17, characterized in that said at least a third layer consists of a polymer film, metal foil, preferably aluminum foil, or metallized polymer film. Paper or paperboard garnishes according to claim 19, characterized in that said third layer consists of a polymer film of a polymer selected from the group consisting of polyethylene, polypropylene, polybutene, polyester, polyvinyl chloride and / or polyvinylidene chloride. Polyvinyl alcohol, polyethylene vinyl alcohol copolymer, ethylene vinyl acetate copolymer or cellulose esters. Paper or paperboard laminate according to claim 20, characterized in that said third layer consists of a polymer film which has a melting point exceeding 130 ° C, wherein laminating of the polymer film is performed directly against the bulk layer. Paper or paperboard laminate according to claim 1, characterized in that the bulk layer has a basis weight of 30-300 g / m 2, that said at least one side layer has a basis weight of 30- 150 g / m 2, and that the laminate has a basis weight of 50-500 g / mz. Paper or cardboard laminate according to claim 22, characterized in that the bulk layer has a basis weight of 40-80 g / m 2. Paper or cardboard laminate according to claim 22, characterized in that the bulk layer has a basis weight of 70-120 g / m 2. Paper or cardboard laminate according to claim 22, characterized in that the bulk layer has a thickness of 01-6 mm, preferably 0.2-1.0 mm, preferably 0.3-0.7 mm. Paper or board laminate according to claim 22, characterized in that the larnate has a basis weight of 50-500 g / m 2, preferably 90-200 g / m 2. Paper or board laminate according to any one of the preceding claims, characterized in that it has a tensile index of 25-150 Nm / g, preferably 50-100 Nm / g. Paper or cardboard laminate according to any one of claims I-27, characterized in that said at least one side layer has a thickness amounting to 5-20%, preferably at most 15%, preferably at most 10% of the thickness of the bulk layer. 10 20 30 512776 Paper or board laminate according to any one of the preceding claims, characterized in that the bulk layer is joined to the other layer (s) included in the larnate during pressing, this pressing being performed so that the bulk layer maintains or obtains a density within said density limits. for the bulk layer. Paper or cardboard laminate according to one of the preceding claims, characterized in that the bulk layer is formed by means of dry forming. 31. Paper or cardboard laminate according to any one of claims 1-29, characterized in that the bulk layer is formed by wet forming. Paper or paperboard laminate according to any one of the preceding claims, characterized in that the bulk layer also comprises at least one binder, preferably a latex binder, in a content of 5-30%, preferably 7-30% and even more preferably -20% of the weight of the larnate, calculated as dry weights. Paper or cardboard laminate according to any one of the preceding claims, characterized in that the laminate is consolidated by adding binder to the mainly bulk layer at a content of 5-30%, preferably 7-30% and even more preferably 10-20% of the weight of the laminate, calculated on dry weights, followed by pressing and drying. Paper or paperboard laminate according to either of Claims 32 and 33, characterized in that said binder comprises at least one binder selected from the group consisting of water-soluble or water-dispersed polymers, preferably polyvinyl acetate, polyvinyl alcohol, polyacrylates, polyacrylic acid, polyethylene , polyacrylamide, polystyrene and maleic acid derivatives in the form of homopolymers and copolymers of said polymers, or from the group consisting of starch, carboxymethylcellulose and gums. Paper or paperboard laminate according to claim 34, characterized in that said binder from the group consisting of starch, carboxymethylcellulose and gum forms adhesives between the bulk layer and the adjacent at least one side layer. 10 15 20 25 30 512776 37 Paper or paperboard laminate according to any one of the preceding claims, characterized in that the laminate or bending has a permanent thickness reduction of at least 10%, preferably at least 20% in the bulk layer in the area of the bending, which facilitates folding without significant delamination occurring. between the layers or that cracks occur in the outermost layers adjacent to the bee. A method of making a paper or paperboard laminate composed of at least one bulk-giving layer, herein referred to as a bulk layer, and on at least one side of the bulk layer at least one side layer, the side layers and bulk layers being joined together directly or indirectly over substantially their entire facing surfaces, characterized in that as a bulk layer (1) a layer is selected or produced which to 40-95% by weight consists of cellulose fibers with a freeness of 550-950 ml CSF, which bulk layer is joined at least on one side directly or indirectly with a side layer (2a, 2b) having a higher density than the bulk layer to create a larnate with a flexural stiffness index higher than 2.5 Nm7 / kg3, but less than 14 Nm7 / kg3, calculated as a geometric mean direction. A method according to claim 37, characterized in that said cellulose fibers in the bulk layer have a freeness value higher than 600 ml CSF, preferably higher than 650 and most preferably at least 700 ml CSF but less than 850 ml CSF. 39. A method according to claim 37 or 38, characterized in that a paper material with a density which is at least twice as large, preferably at least three times as large and most preferably at least four times as large as the density of the bulk layer is selected as at least some side layer. - tet. 40. A method according to claim 37, characterized in that the bulk layer in the lamination with the side layers to form a consolidated laminate is only compressed to such an extent and / or caused to resurface to such an extent that the density of the bulk layer in the laminate after drying kept at so-soo kg / mß, rofl-.träflesvls vo-zoo kg / mt, preferably loo-lso kg / mß, 512776 38 41. A method according to any one of claims 37-40, characterized in that binder is added to the bulk layer and / or to the side layer (s) in an amount of 5-30%, preferably 7-30% and even more preferably -20% of the weight of the laminate, calculated as dry weights, at the latest before the layers are joined together, the main part of said adhesive being caused to penetrate and distributed in the bulk layer