JP2013513037A - Method for manufacturing paper or paperboard products - Google Patents

Abstract

  The present invention includes a step of supplying a furnish containing fiber, a step of adding starch to the furnish, a step of adding microfibrillated cellulose to the furnish, and the furnish to wire to form a web. A method for producing a paper or paperboard product comprising a leading step, wherein starch and microfibrillated cellulose are added separately to the furnish.

Description

  The present invention relates to a method for producing a paper or paperboard product comprising a furnish comprising starch and microfibrillated cellulose.

  There is a continuing interest in papermaking methods to find ways to produce paper or paperboard at a reduced cost without compromising product properties, for example, without reducing product strength.

  One way to reduce the cost is to increase the filler content of the paper or paperboard product and thus reduce the amount of fibers in the paper or paperboard. In addition to being economically beneficial, the filler also improves the opacity and printability of the product. However, a large amount of filler in the product reduces the strength. Thus, there is a balance between the possible amount of filler added and the required strength of the paper or paperboard produced.

  Furthermore, there is a desire to produce strong but low density products during the manufacture of paperboard. Increasing the strength of the paperboard usually increases its density. Thus, there is a balance between the desired strength and density of the paperboard product.

  For example, compensating for the drop in strength caused by the addition of a large amount of filler or by increasing the bulk improves the fiber bonding properties between the fibers in the paper or paperboard, thereby maintaining strength. Is possible. A powerful treatment to improve the strength of paper or paperboard, especially the dry strength, has heretofore been to add an enhancer, preferably a cationic starch, to the furnish prior to the sheet forming operation. Cationic starch molecules added to the furnish naturally adhere to the anionic pulp fibers by electrostatic attraction and can therefore be retained in the wet fiber mat and remain intact on the final paper or paperboard.

  In order to obtain the resulting high paper strength, two main problems arise when large amounts of cationic starch are added to the papermaking furnish. The first is that the cationic starch molecules tend to saturate the anionic charge on the cellulosic fiber, thus limiting the amount of cationic starch that can be added to the slurry. When excess cationic starch is added, only a portion of the added starch is retained in the sheet, and the remainder circulates in the white water system of the paper or paperboard machine. The second problem is that fibers made cationic by adding excess cationic starch can adsorb other cationic additives, such as sizing agents and retention aids, which are typically added to the pulp slurry. Disappear. In addition, large amounts of starch often cause operability, microbiology and foaming problems during the manufacturing process.

  It has recently been found that the addition of microfibrillated cellulose to paper or paperboard increases the strength of the product, possibly due to improved fiber bonding.

International Publication No. 2007091942

  However, there remains a need for cost-effective products with good strength properties.

  It is an object of the present invention to provide a method by which paper or paperboard having improved strength and density can be produced in an easy and cost effective manner.

  These objects and other advantages are achieved by the paper or board product according to claim 1. The present invention provides a process for supplying a furnish containing fibers, a process for adding starch to the furnish, a process for adding microfibrillated cellulose to the furnish, and a furnish to wire to form a web. A method for producing a paper or paperboard product comprising a leading step, wherein starch and microfibrillated cellulose are added separately to the furnish. Since the amount of starch can be increased without increasing the density of the paper or paperboard product, a product comprising both starch and microfibrillated cellulose (MFC) has been shown to increase the strength of the product.

  It is preferred that the furnish comprises 2-15% starch and 1-15% microfibrillated cellulose. The amount of product starch or MFC depends on the end use and the corresponding desired properties of the product. Large amounts of starch increase the strength of the product and the combination of MFC and starch has been shown to allow the product to retain a greater amount of starch.

  The web formed from said furnish comprising starch and microfibrillated cellulose preferably forms a layer of paper or paperboard products. The paper or paperboard product is preferably a multilayer product comprising at least two layers. The product comprises at least three layers, and the middle layer of the product comprises a furnish comprising starch and microfibrillated cellulose, i.e. formed of a furnish comprising starch and MFC. It may be preferred that the web forms an intermediate layer of paper or paperboard.

  The present invention relates to a method for producing a paper or paperboard product comprising a furnish comprising starch and microfibrillated cellulose. The furnish comprises starch in an amount of 2-15% by weight, preferably 3-5% by weight. As a result, the product thus contains starch in an amount of 2-15% by weight, preferably 3-5% by weight.

  The furnish preferably contains cellulose fibers. The cellulose fibers may be hardwood and / or softwood fibers. Cellulose fibers can be mechanically, chemomechanically and / or chemically treated. The fiber may also be bleached or unbleached.

  It has been found that the addition of starch and microfibrillated cellulose (MFC) to the furnish has a very good effect on the strength of the paper or board. Products containing both large amounts of starch and MFC allow the product to retain higher amounts of starch. Surprisingly, it was also found that the addition of large amounts of both starch and MFC did not increase the densification of the product. Thus, the combination of MFC and starch has a synergistic effect with respect to increasing the strength of a paper or paperboard product without increasing the density of the product to the same extent. Thus, while it is possible to reduce the density of paper or paperboard products, it is still possible to produce strong products. In this way, the fiber content of the product can be reduced and the strength can be left as it is so that a very cheap product can be manufactured (compared to products manufactured by the prior art). . In addition, the weight of the product is reduced, which reduces costs during shipping and handling.

  Microfibrillated cellulose (MFC) (also known as nanocellulose) is a material made from wood cellulose fibers, where individual microfibrils are partially or totally separated from one another. MFCs are usually very thin (about 20 nm) and their length is often from 100 nm to 10 μm. However, microfibrils may be longer (eg, 10-100 μm), but lengths up to 200 μm can be used. Fibers that are fibrillated and have microfibrils on the surface, and microfibrils that are separated and in the aqueous phase of the slurry, are included in the definition of MFC.

  The MFC can be manufactured in several different ways. Cellulose fibers can be mechanically processed so that microfibrils are formed. The production of nanocellulose or microfibrillated cellulose by bacteria is another option. It is also possible to produce microfibrils from cellulose using various chemicals and / or enzymes that subdivide or dissolve the fibers.

  An example of the production of MFC is given in WO20077091942, which describes the production of MFC using purification in combination with the addition of enzymes.

  It is also possible to modify the microfibrillated cellulose prior to addition to the furnish. In this way, it is possible to change its interaction and affinity for other substances. For example, introducing an anionic charge with MFC increases the stability of the fibrils and fibril assemblies of MFC. How the modification of the microfibrillated fibers takes place depends, for example, on other components present in the furnish.

  It is preferred that the furnish comprises 2-15 wt% starch, preferably 3-5 wt% starch, and the furnish further comprises MFC in an amount of 1-15 wt%. The selected amount of starch or MFC added to the furnish depends on the final product being manufactured and the desired properties of the product. The higher the amount of starch, the greater the strength of the product. However, it is not possible to increase the amount of starch excessively, in which case other problems may arise. Also, the amount of MFC must be adjusted based on the amount of starch and, of course, the end use of the product. Too much MFC can cause dehydration problems because MFC is a very fine material that readily absorbs water, and the increased content makes it more difficult to dehydrate the product.

  The paper or paperboard product is preferably a multilayer product comprising at least two layers. It may be preferred that the product comprises at least three layers and that the layer located in the middle of the product comprises a furnish comprising starch and microfibrillated cellulose. However, it is also possible for at least one outer layer or even all layers of a product to contain a furnish containing starch and MFC. For some products, it may be advantageous that at least one of the outer layers comprises a furnish comprising starch and MFC. In this way, it is possible to increase the strength and / or bulk of this layer. As a result, depending on the end use of the product, it is determined which and how many of the layers contain a furnish containing starch and MFC.

  Although it is not necessary for the entire furnish in the layer of paper or paperboard product to contain starch and MFC, it is preferred that starch and MFC be added to the bulk of the furnish of the layer. However, the layer may comprise waste paper pulp that does not contain other ingredients such as starch and MFC.

  The furnish can also contain various amounts of fillers, for example, to increase the process and cost effectiveness of the manufactured substrate. Other commonly used additives used in the manufacture of paper or paperboard can also be added.

  The paperboard product is preferably a high quality paperboard product, for example a liquid packaging board, a graphic board or a school board. The paper product is preferably high quality paper, such as grade A or B copy paper, graphic paper, LWC, SC or newspaper for high speed printers.

  A method of manufacturing a paper or paperboard product, the method comprising supplying a furnish comprising fibers, adding starch to the furnish, adding microfibrillated cellulose to the furnish, and Leading the furnish to a wire to form a web. The starch and MFC addition is preferably done in a mechanical chest or before the fan pump. It may also be possible to add to the circulating water which is added later to the furnish. However, all practical conditions of addition for starch and MFC can be used as long as the time and mixing of starch and MFC and furnish are sufficient before being led into the wire.

  Starch and MFC are added separately. It is preferred to add starch first, followed by MFC. It may be possible to mix starch and MFC prior to addition to the furnish, but in that case the result is not as good as when starch and MFC are added separately. Furthermore, starch and MFC can be mixed by cooking them, preferably by a jet digester, before addition to the furnish. By cooking a mixture of starch and MFC, the MFC tends to less clump. In addition, varying degrees of aggregation can be obtained, for example, by changing the charge and charge density of the starch, thus making it possible to neutralize the charge of the MFC. This can affect the dehydration and retention of the fibers and the final filler in the product. It may also be possible to add a layer of starch on the MFC and then add this mixture to the furnish, i.e. create a layering effect.

Materials used:
Bleached chemical thermomechanical pulp (BCTMP) at 570 CSF.

  Microfibrillated cellulose (MFC) was prepared by refining 4% consistency bleached hardwood sulfite pulp to 28SR with an edge load of 2 Ws / m. The pulp was then enzymatically treated with Endoglucanase (Novozym 476) having an activity of 0.85 ECU / g. The enzyme was administered to the pulp, which was then treated at pH 7 for 2 hours at 50 ° C. After enzymatic treatment, the pulp was washed and the enzyme was inactivated at 80 ° C. for 30 minutes. Thereafter, the pulp is once again refined to 90-95SR, and the refined pulp is then fluidized by passing the 3% consistency pulp through a 400 μm chamber followed by a 100 μm chamber (Microfluidizer, Microfluidics corp. ), Where the MFC used was formed.

  The starches used were cationized starch, Raisamyl 70021, Chiba (now BASF).

  The C-PAM used was Percol 292 NS, Chiba (currently BASF).

  The BMA used was Eka NP495, Eka Chemicals.

  Dry BCTMP was immersed in water overnight and then dispersed in hot water. The BCTMP suspension was then diluted to a concentration of 0.3%.

  The prepared MFC was also diluted to a concentration of 0.3% and dispersed using a kitchen mixer.

  Test sheets were prepared using a formette sheet former. The sheet was prepared according to the following procedure: The pulp suspension measured to make a 150 gsm sheet was added to the feed tank. During stirring, starch was added when used and MFC when used. After 30 seconds, 500 g / t of C-PAM was added to the raw material, and after 30 seconds, 300 g / t of BMA was added to the raw material.

  The formed sheet was wet-pressed and dried in a state where shrinkage was suppressed. The dried sheets were tested for structural density according to SCAN P 88:01, z-strength according to SCAN P 80:88 and tensile strength index according to ISO 1924-3.

  As can be seen from Table 1 above, it is clear that the addition of the combination of MFC and starch greatly increases the strength (both z-strength and tensile index). Furthermore, the densification of the sheet decreased compared to the case where only MFC was added.

  Both MFC and cationic starch were also tested when premixed or added separately to the ingredients.

  When premixed, the MFC and cationic starch were mixed well into the raw material before addition. When added separately, the cationic starch was added first and mixed well with the ingredients for 5 minutes, followed by the MFC.

  An amount of 25 kg / t MFC and an amount of 20 kg / t cationic starch were added to both samples (both premixed and added separately).

  After adding MFC and cationic starch to the raw material, a formette sheet former was used as described in Example 1.

  As a reference, a raw material without MFC and cationic starch was used.

  Scott Bond was measured according to TAPPI UM-403.

  As can be seen from Table 2, both z-strength and Scottbond increase when cationic starch and MFC are added separately to the raw material.

  Other modifications and variations will be apparent to those skilled in the art in view of the above detailed description of the invention. However, it should be apparent that other such modifications and variations can be made without departing from the spirit and scope of the invention.

Claims (4)

Supplying a paper furnish containing fiber,
Adding starch to the furnish,
Adding microfibrillated cellulose to the furnish,
A method of manufacturing a paper or paperboard product comprising the step of directing a furnish to a wire to form a web comprising:
Process as described above, wherein starch and microfibrillated cellulose are added separately to the furnish.   2. Process according to claim 1, characterized in that 2 to 15% by weight of starch and 1 to 15% by weight of microfibrillated cellulose are added.   3. A method according to claim 1 or 2, characterized in that the web formed with the furnish comprising starch and microfibrillated cellulose forms a layer of paper or paperboard products.   4. A method according to claim 3, characterized in that the web forms an intermediate layer of paper or paperboard product.