SE535014C2 - A paper or paperboard product and a process for manufacturing a paper or paperboard product - Google Patents

Abstract

11 Abstract The present invention relates to a paper or paperboard productcomprising a furnish wherein said furnish comprises starch andmicrofibrillated cellulose. The invention further relates to a process for theproduction of said product.

Description

535,014 When large amounts of cationic starch are added to a papermaking stock to obtain high paper strength, two major problems arise. The first year that cationic molecules tend to saturate the anionic charge on the cellulose fi brema and thus set a limit on how much cationic starch can be added to the stock. If an excess of cationic starch is added, only a portion of the added starch will remain in the sheet and the remainder will circulate in the backwater system of the paper or board machine. A second problem is that the cations that have been made cationic by the addition of an excess of cationic starch will not be able to absorb other cationic additives which are usually added to a slurry containing pulp, such as sizing agents and retention aids. In addition, large amounts of starch often cause problems with runnability, microbiology and foaming during the manufacturing process.

It has recently been found that the addition of micro-brilliant cellulose to a paper or board will increase the strength of the product, presumably due to the improved bonding.

However, there is still a need for a cost-effective product with good strength properties.

Summary of the Invention One object of the present invention is to provide a paper or board having improved strength and density.

Another object of the present invention is to provide a process which in a simple and cost-effective manner will be able to manufacture a paper or board with improved strength and density.

These objects and other advantages are obtained by the paper or board product according to claim 1. The present invention relates to a paper or board product containing a stock containing starch and micro-coated cellulose wherein the stock contains starch in an amount of 2-15% by weight. It has been found that the strength of a product containing both starch and micro-β-glass cellulose (MFC) increases as the amount of starch can be increased without increasing the density of the paper or board product. The stock preferably contains cellulose fibers which may be fibers from deciduous and / or banana trees.

It is preferred that the stock contain 1-15% by weight of microfibrillated cellulose. The amount of starch or MFC in the product depends on the end use and the desired product properties. Large amounts of starch will increase the strength of the product and it has been shown that the combination of MFC and starch makes it possible for the product to retain larger amounts of starch.

The paper or board product is preferably a multilayer product containing at least two layers. It may be preferable that the product contains at least three layers and that the layer in the middle of the product contains stock containing starch and micro-glass cellulose.

The present invention further relates to a process for the manufacture of a paper or board product, the process comprising the steps of providing a stock containing fibers, preferably cellulose fibers, adding starch to the stock, adding micro-glazed cellulose to the stock and passing the stock to a wire to form a wire. .

It is preferred that 2-15% by weight of starch and 1-15% by weight of micro fi glass cellulose be added to the stock.

Starch and MFC can be added separately to the stock or as a mixture.

It may also be possible to boil the mixture of starch and MFC before adding to the stock. In this way, the increase in MFC is reduced.

Detailed Description The invention relates to a paper or board product containing a stock containing starch and micro-glass cellulose.

The stock contains starch in an amount of 2-15% by weight, preferably between 3-5% by weight. Accordingly, the product contains starch in an amount of 2-15% by weight, preferably between 3-5% by weight. 5 15 20 25 30 35 535 014 The stock preferably contains cellulose fibers. The cellulose branches can be leaves from deciduous and / or coniferous trees. The cellulose fibers can be mechanically, chemically, mechanically and / or chemically treated. The fibers can also be bleached or unbleached.

It has been shown that the addition of starch and micro-glass cellulose (MFC) to a stock has a very good effect on the strength of the paper or board product. Products containing both starch in large quantities and MFC make it possible for the product to retain a larger amount of starch. It has surprisingly been found that starch is added in large quantities and MFC does not increase the density of the product. The combination of MFC and starch thus has a synergistic effect in increasing the strength of the paper or board product without increasing the density of the product to the same degree. It is thus possible to reduce the density of the paper or board product but still be able to produce a strong product. In this way, a much cheaper product can be manufactured as the product fi ber content can be reduced and the strength can be maintained (compared to products manufactured according to the state of the art). In addition, the weight of the product can be reduced, which reduces transportation costs and handling costs.

Micro-spectacle cellulose (MFC) (also known as nanocellulose) is a material made from wood cellulose fibers, where the individual micro-glasses have been partially or completely separated from each other. MFC is normally very thin (~ 20 nm) and the length is usually between 100 nm to 1 μm. However, the micro-glasses can be longer, for example between 10-100 μm, but lengths up to 200 μm can also be used. Fibers that have been glazed and have micro-glasses on the surface and micro-glasses that are separated and located in an aqueous phase of a slurry are included in the MFC section.

MFC can be produced in a number of different ways. It is possible to mechanically treat cellulose glasses so that micro-glasses are formed. The production of nanocellulose or microbialized cellulose with bacteria is another option. It is also possible to manufacture micro-glasses from cellulose with the help of various chemicals and / or enzymes that will break down or dissolve the brema. An example of the manufacture of MFC is shown in WO2007091942 which describes the manufacture of MFC by means of milling in combination with the addition of enzyme.

It is also possible to modify the micro-glazed cellulose before adding it to the stock. In this way, it is possible to change the interaction and affinity for other substances. By introducing more anionic charges to the MFC, for example, the stability between the glasses and the unit consisting of glasses increases in the MFC. How the modification takes place depends, for example, on other components present in the stock.

The stock contains 2-15% by weight of starch, preferably between 3-5% by weight, and it is agreed that the stock also contains MFC in an amount of 1-15% by weight. The selected amount of starch or MFC added to the stock depends on the finished product being manufactured and the desired properties of the product. Larger amounts of starch will increase the strength of the product. However, it is not possible to increase the amount of starch too much as other problems may occur. The amount of MFC must also be regulated based on the amount of starch and of course also depending on the end use of the product. Too large amounts of MFC can cause problems with dewatering as MFC is a very thin material that easily absorbs water and increased amount will make it more difficult to dewater the product.

The paper or board product is preferably a multilayer product containing at least two layers. It may be preferable that the product contains at least three layers and that the layer placed in the middle of the product contains stock containing starch and micro-glass cellulose. It is also possible that at least one outer layer of the product or even all layers of the product contain stock containing starch and MFC. In this way it is possible to increase the strength and / or bulk of this layer. Depending on the end use of the product, it is consequently decided which and how many of the layers will contain stock containing starch and MFC.

It is not necessary that the entire stock in a layer of paper or board product contain starch and MFC, but it is preferred that starch and MFC be added to the greater part of the stock by a layer. The layers l0 l5 20 25 30 35 535 Ü'l4 may, however, contain other components such as pulp of non-starchy extracts and MFC.

The stock can also contain different amounts of fillers to increase, for example, the runnability and cost-effectiveness of the process and the manufactured substrate. Other common additives used in the manufacture of paper or board can also be added.

The carton product is preferably a high quality carton product. such as liquid packaging board, greek board or food board The paper product is preferably a high quality paper, such as copy paper of Class A or B, greek paper, LWC, SC or newsprint for high speed printing machines.

The present invention also relates to a process for the manufacture of a paper or board product, the process comprising the steps of providing a stock containing fibers, adding starch to the stock, adding micro-glass cellulose to the stock and passing the stock to a wire to form a web. The addition of starch and MFC preferably takes place in the machine vessel or before the mixing pump. It is also possible that the addition takes place to the circulating water which is eventually added to the stock. However, all practically possible sites for the addition of starch and MFC can be used as long as the residence time and mixing of the starch and MFC with the stock before it is transferred to the wire is sufficient.

The starch and MFC can be added separately, ie the starch can first be added followed by the addition of MFC or vice versa, ie MFC can first be added to the stock followed by starch. It is also possible to mix starch and MFC before adding to the stock. It is possible to mix starch and MFC before adding to the mold by boiling the mixture of starch and MFC, preferably by using a jet cooker. It has been found that by boiling the mixture of starch and MFC, MFC shows less tendency to increase. In addition, by changing the charge and the charge density of eg starch, different degrees of increase can be obtained and it is then possible to neutralize the charge of the MFC. This can affect the dewatering and retention of the fibers and any fillers in the product. It may also be possible to add a layer of starch to the MFC and then add this mixture to the stock, ie a multilayer effect can be formed.

Example Material: Bleached chemothermomechanical pulp (BCTMP) with 570 CSF.

Micro-brilliant cellulose (MFC) was prepared by refining bleached pulpwood of deciduous trees with a consistency of 4% with an edge load of 2 Wslm to 28 SR. The pulp was then enzymatically treated with Endoglucanase (Novozym 476) with an activity of 0.85 ECU / g. The enzymes were dosed into the mass which was then treated at 50 ° C for 2 hours at pH 7. After the enzymatic treatment, the mass was washed and the enzymes were deactivated at 80 ° C for 30 minutes. The pulp was then refined once more to 90-95 SR and the refined pulp was oxidized (Mlcro fl uidizer, Microfuidics corp.) By passing the pulp with a consistency of 3% through a chamber of 400 μm followed by a chamber of 100 μm, the MFC which was used was formed.

The starch used was cationic starch, Raisamyl 70021, Ciba (now BASF).

The C-PAM used was Percol 292 NS, Ciba (now BASF).

The BMA used was Eka NP495, Eka Chemicals.

Method: The dried BCTMP was soaked in water overnight and then dispersed in hot water. The suspension containing BCTMP was then diluted to a concentration of 0.3%.

The manufactured MFC was diluted to a concentration of 0.3% and dispersed using a kitchen mixer. 5 15 20 25 535 014 A shaped sheet former was used to shape the sheets used for the tests. The sheets were removed according to the following procedure; pulp suspension to make a 150 gsm sheet was added to the stock tank. While stirring, starch, if used, and MFC, if used, were added. After 30 seconds, 500 g / h C-PAM was added and after another 30 seconds, 300 g / h BMA was added to the stock and the sheet formation was then started.

The resulting sheet was wet pressed and dried while limiting shrinkage. The dried sheet was tested for structural density according to SCAN P 88:01, z-strength according to SCAN P 80:88 and tensile index according to ISO 1924-3.

Table 1: Results of styme and density tests.

Sample Structural z-strength Tensile strength index density (kPa) Geometric (kg / m3) mean (Nm / g) Reference 57OCSF 388 103 27 Addition of 5% MFC 459 218 40 Addition of 5% Starch 396 142 32 Addition of 5% MFC and 436 240 44 2.5% Starch Addition of 5% MFC and 426 256 47 5% Starch 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. The densification of the sheets also decreases compared to if only MFC was added.

Given the detailed description above of the present invention, other modifications and variations may become apparent to those skilled in the art. However, it is obvious that such other modifications and variations may occur without departing from the spirit and scope of the invention.

Claims (9)

Claims

1. A paper or paperboard product comprising a furnish whichcomprises starch and microfibrillated cellulose characterized in that thefurnish comprises an amount of starch of 2-15% by weight.

2. The paper or paperboard product according to claim 1 characterizedin that the furnish comprises celluiosic fibers.

3. The paper or paperboard product according any of the precedingclaims characterized in that the furnish comprises 1-15% by weight ofmicrofibrillated cellulose.

4. The paper or paperboard product according to any of the precedingclaims characterized in that the product is a multilayer product comprising atleast two layers.

5. The paper or paperboard according to clairn 4 characterized in thatthe product comprises at least three layers and that the layer located in themiddle of the product comprises furnish comprising starch and microfibrillatedcellulose.

6. A process for producing a paper or paperboard product whichprocess comprises the steps of: -providing a furnish comprising fibers, -adding starch to the furnish, -adding microfibrillated cellulose to the furnish, -conducting the furnish to a wire in order to form a web.

7. The process to claim 1 characterized in that 245% by weight ofstarch and 1-15% by weight of microfibrillated cellulose is added.

8. The process according to claims 6-7 characterized in that starch andMFC is added separately to the furnish.

9. The process according to any of ciaims 6~7 characterized in thatstarch and MFC is mixed before being added to the furnish. 10 The process according to ciaim 9 characterized in that starch and5 MFC is cooked before being added to the furnish.