FI124748B - Paper product and method and system for preparing the mixture ratio - Google Patents

Description

A PAPER PRODUCT AND A METHOD AND A SYSTEM FOR MANUFACTURING FURNISH

Field of the Invention

This invention relates to a method and system for manufacturing a furnish for a paper product which comprises a fibril cellulose material. In addition, this invention relates to a paper product.

Background of the Invention

Cellulose, which is an Abundant natural raw material, is a polysaccharide composed of a linear chain of several hundred to ten thousand linked D-glucose units. Cellulose fibers can be refined with a refiner or a grinder to produce fibril cellulose material. Typically, the production of fibril cellulose material requires a significant amount of beating energy. Therefore, there may be an efficiency problem with said material production.

Summary of the Invention

The present invention discloses a method and system for manufacturing a pulp comprising fibril cellulose. In addition, the invention discloses a paper product comprising fibril cellulose.

The present invention is based on the use of fibril cellulose in paper furnish. The Inventory of the Present Invention Has Surprisingly Found A Way To Produce Cellulose Material With Increased Production Efficiency. Fibril cellulose as such can provide a paper product with new functional properties. Moreover, due to the present invention, it may be possible to achieve a simple fibril cellulose process with low energy consumption. The produced pulp comprising fibril cellulose may be used, for example, as a strength additive for a paper product.

According to the present invention, anionized cellulose fibers are fed together with a cellulose pulp, such as a mechanical pulp or chemical pulp, preferably together with a chemical pulp, through a beating process in a paper machine approach system.

Aspects of the Invention are characterized by what is stated in the independent claims 1, 6 and 8. Various embodiments of the invention are disclosed in the dependent claims.

In the method according to the present invention, the manufactured furnish contains a fibril cellulose material, the method advantageously comprises: introducing a first raw material to a system, introducing a first raw material to a system, which second raw material the material consists of anionized cellulose fibers that are oxidized by nitroxyl-mediated oxidation of hydroxyl groups of the cellulose, conveying the first raw material and the second raw material to the same refiner, refining and mixing the first raw material and the second raw material in the refiner in order to produce pulp comprising fibril cellulose material.

In the system according to the present invention, the manufactured furnish contains fibril cellulose material, the system comprises: first means for introducing the first raw material to the system, which first raw material comprises cellulose pulp (2), second means for introducing the second raw material material to the system, which second raw material consists of cellulose fibers that are oxidized by nitroxyl-mediated oxidation of hydroxyl groups of the cellulose, at least one conveyor to conveyed raw materials to at least one refiner (8), at least one refiner (8) to refine and to mix first raw material and second raw material in order to produce the furnish comprising fibril cellulose material (4).

Thanks to the present invention which can solve several issues of fibril cellulose utilization on a paper machine, it may be possible to achieve at least some of the advantages mentioned below: - quite simple (ie quite inexpensive) system for fibril cellulose process, - transportation low solids content fibril cellulose may be avoided, - efficient mixing of basic furnish and fibril cellulose may be guaranteed during the beating process, - paper properties may be improved without significant loss of drainage speed.

Due to the present invention, for example, a separate fibrillating process is taking place in low solids content is not necessarily needed. Therefore, the invention may significantly simplify the start-up of fibril cellulose usage, because some large investments such as installation of separate fibrillating aggregates may be avoided.

Description of the Drawings

In the following, the invention will be illustrated by drawings in which

Figs1a-1d show schematically some example embodiments of the invention, and

Figs 2-7 show results from experimental tests.

Detailed Description of the Invention

In the following Disclosure, all percentages are by dry weight, unless otherwise stated.

2 cellulose pulp, 2a chemical cellulose pulp, 3 anionized cellulose fibers, 4 fibril cellulose material, 5 chemical pre-treatment, 8 refiner, and 10 refined cellulose pulp.

Cellulose is a renewable natural polymer that can be converted to many chemical derivatives. Derivatization takes place Mostly by chemical reactions of hydroxyl groups in the β-D-glucopyranose units of the polymer. By chemical derivatization, the properties of the cellulose can be altered in comparison to the original chemical form while retaining the polymeric structure.

The term "cellulose raw material" refers to any cellulose raw material source that can be used in the production of chemically and / or mechanically treated cellulose fibers. The raw material can be based on any plant material that contains cellulose. The plant material may be wood. The wood can be from Softwood trees such as spruce, pine, fir, larch, Douglas-fir or hemlock, or from Hardwood trees such as birch, Aspen, poplar, alder, eucalyptus or acasia, or from a mixture of Softwood and Hardwood. Nonwood material can be from agricultural residues, grasses or other plant substances such as straw, leaves, bark, seeds, hulls, flowers, vegetables or fruits from cotton, corn, wheat, goat, rye, barley, rice, flax, hemp, Manila hemp, sisal hemp, jute, ramie, kenaf, bagasse, Bamboo or reed.

The term "chemical (cellulose) pulp" 2a refers to the cellulose fibers that are isolated from any cellulose raw material or any combination of cellulose raw materials by a chemical pulping process. Therefore, lignin is at least for the most part removed from the cellulose raw material. Chemical pulp 2a is preferably sulfate wood pulp. In an example, the chemical pulp is isolated from Softwood and / or from Hardwood. The used chemical pulp 2a may be unbleached or bleached. Typically, the diameter of the fibers varies from 15 to 25 pm and the length exceeds 500 pm, but the present invention is not intended to be limited to these parameters.

The term "mechanical (cellulose) pulp" refers to the cellulose fibers that are isolated from any cellulose raw material by a mechanical pulping process. The mechanical pulping process could be preceded by a chemical pretreatment, producing a chemimechanical pulp. The cellulose fibers used in this invention consist of mechanically and / or chemically and / or chemimechanically treated cellulose fibers. Herein they are referred to as "raw material pulp 2" or "cellulose pulp 2". Therefore, cellulose pulp 2 may consist of chemical cellulose pulp and / or mechanical pulp and / or chemical pulp.

The term "SEC" refers to specific energy consumption.

The term "SR" refers to the so called Schopper-Riegler freeness of pulp.

The term "WRV" refers to the value of water retention.

It is possible to use fibril cellulose 4 in mechanical pulp containing papers such as printing paper. The method according to the present invention may be used, for example, in Light Weight Coated (LWC) or Super Calendered (SC) papers. Advantageously the method according to the present invention is used in paper grades having a high chemical pulp share, i.e. in papers comprising more chemical pulp 2a than mechanical pulp. In an embodiment, at least 80% of the dry weight, more preferably at least 90% of the dry weight and most preferably at least 95% of the dry weight of the cellulose fibers used in this invention is from a chemical pulp 2a.

The term "fibril cellulose" 4 refers to a collection of isolated cellulose microfibrils or microfibril bundles derived from cellulose raw material. There are several widely used synonyms for fibril cellulose. For example: nanofibrillated cellulose (NFC), nanocellulose, microfibrillar cellulose, nanofibrillar cellulose, nano-scale fibrillated cellulose, m icrof i bri 11 ated cellulose (MFC), or cellulose microfibrils. Fibril cellulose described in this application is not the same material as so called cellulose whiskers, which are also known as: cellulose nanowhiskers, cellulose nanocrystals, cellulose nanorods, rod-like cellulose microcrystals or cellulose nanowires. In some cases, similar terminology is used for both materials, for example by Kuthcarlapati et al. (Metals Materials and Processes 20 (3): 307-314, 2008) where the studied material was called "cellulose nanofiber" although they were clearly referred to cellulose nanowhiskers. Typically, these materials do not have amorphous segments along the fibrillar structure as fibril cells, which leads to a more rigid structure. Cellulose whiskers are also shorter than fibril cellulose.

The anionization of the cellulose fibers, preferably chemical pulp, is preferably carried out by the reaction of the primary hydroxyl groups of the cellulose are oxidized catalytically by a Heterocyclic nitroxyl compound. Other Heterocyclic Nitroxyl Compounds are known to have selectivity in the oxidation of hydroxyl groups of C-6 to glucose units of cellulose can also be used. Advantageously, the primary hydroxyl groups of the cellulose are oxidized first, after which the material is refined at least partially into the fibril cellulose.

The charge (ieq / g) of the anionized cellulose fibers is preferably between -700 and -1200, for example between -900 and -1100.

The term "oxidation of cellulose" refers to the oxidation of hydroxyl groups (of cellulose) to aldehydes and / or carboxyl groups. It is preferred that the hydroxyl groups are oxidized to the carboxyl groups, i.e. the oxidation is complete, before the refining step in the refiner is implemented. "Catalytic oxidation" refers to nitroxyl-mediated (such as "TEMPO" -mediated) oxidation of hydroxyl groups. The term "TEMPO-treated" refers to a material that is treated with a so-called "TEMPO" chemical, i.e. 2,2,6,6-tetramethylpiperidinyl-1-oxy free Radical.

The "Catalytic Oxidation of Fibrous Material" in turn refers to the material containing cellulose that is oxidized by nitroxyl-mediated (such as TEMPO-mediated) oxidation of hydroxyl groups of the cellulose. In addition, the terms "anionized cellulose fibers" "and" anionized cellulose material "3 are used, referring to a material comprising at least 90 w-% (of dry weight) cellulose material, more preferably comprising cellulose material, in which cellulose is oxidized by nitroxyl-mediated (such as" TEMPO "-mediated) oxidation of hydroxyl groups of the cellulose.

Advantageously, chemical pulp 2a, which may be produced from Softwood and / or Hardwood, is extensively oxygenated in the presence of Catalytic oxidation, such as TEMPO-mediated oxidation in order to produce anionized cellulose fibers 3. The anionized cellulose fibers 3 have a high anionic charge and, thus, received anionized fibers are relatively easily fibrillated under shear forces.

Advantageously, the cellulose pulp 2 and the anionized cellulose material 3 are combined with each other before at least one refiner step in at least one refiner 8. The refiner 8 is preferably a grinder or a refiner, such as a conical refiner or a disc refiner or a. cylindrical refiner. In an aspect of the invention, at least one refiner 8 is a grinder, a homogenizer, a colloider, a friction grinder, a fluidizer, or an ultrasound sonicator.

The anionized cellulose material 3 is added to the cellulose pulp 2 which is going to a refiner 8 in a paper machine approach system. The anionized material 3, such as a tempo-treated pulp, is fibrillated due to shear forces and energy consumed during the beating process. Most preferably the cellulose pulp 2 to be refined together with the anionized cellulose material 3 comprises unbeaten chemical pulp 2a, but said cellulose pulp 2 may also comprise a beaten chemical pulp and / or mechanical pulp.

Advantageously, the furnish comprises cellulose pulp 2 and anionized cellulose material 3 to be conveyed to the refiner 8 comprised between 0.3 and 5% of dry weight, more preferably between 0.6 and 3% of dry weight, and most preferably between 1 and 2% of dry weight cellulose fibers which are oxidized by nitroxyl-mediated oxidation of hydroxyl groups of the cellulose. The cellulose pulp 2 may comprise a chemical pulp and / or a mechanical pulp. It is also possible to add some additional cellulose pulp (s) after said refiner 8.

The amount of fibril cellulose in the manufactured paper furnish is preferably between 0.1 and 5.0% of the pulp (dry weight), more preferably between 0.3 and 4% (dry weight), and most preferably between 1 and 2% (dry weight) of the manufactured furnish. The amount is calculated from the whole furnish, including the fiber and the possible filler.

The amount (sum) of the anionized cellulose material 3 and the fibril cellulose 10 in a base paper product (before any possible coating step) and / or in the furnish is preferably between 0.01-10.0% or more preferably between 0.05 and 5.0 % of dry weight and most preferably between 0.5 and 2.0% of dry weight.

Due to the chemical pre-treatment of the cellulose fibers, the charge of the cellulose fibrils increases, hence the repulsion forces between the fibrils increase. In order to achieve an efficient fibrillation process, a high oxygenation rate is required. Advantageously, the charge of the anionized cellulose fibers is between -900 and -1100 ieq / g.

According to the present invention, the chemical pre-treatment 5 of the cellulose pulp 2 (in order to produce anionized cellulose material 3) may be part of the solution for manufacturing paper furnish (as shown in Figures 1a and 1d), or the chemical pre-treatment 5 may be implemented in another process.

The cationic polyelectrolyte, such as Starch, is preferably dosed to the cellulose pulp (2) before the dosage of the fibrous cellulose material (4). The cationic polyelectrolyte can be any retention or strength polymer used in paper manufacturing, e.g. cationic Starch, cationic Polyacrylamide (CPAM) or polydimethyldiallyl ammonium chloride (PDADMAC). Also, combinations of different polyelectrolytes can be used. Preferably, the cationic polyelectrolyte is cationic Starch (CS). The cationic polyelectrolyte is added in an amount of 0.01 to 5% of the dry weight of the fibers in the furnish, preferably approximately 0.10 to 1.00% of the dry weight.

Thanks to the present invention, it is possible to mix cellulose pulp 2 with anionized chemical material 3 efficiently while at least some of the anionized cellulose material 3 is fibrillated into fibril cellulose 4 in at least one refiner 8. Therefore, fibril cellulose 4 may be mixed for example with cellulose pulp 2, such as chemical pulp 2a, without any separate mixing and fibrillating aggregates, ie an additional mixer may not be required.

According to the present invention, it is possible to avoid transportation of low solids fibril cellulose having a consistency of 5% at the most. In fibril cellulose production, the concentration of fibril cellulose in dispersion is typically very low, usually around 1-5%. Therefore, the logistic costs are typically too high to transport the material from the production site. The specific surface area of the fibril cellulose is very large due to its nanoscopic dimensions, and the concentration or drying of the fibril cellulose hydrogel is challenging. Respectively, strong water retention is natural for fibril cellulose since water is bound on the surfaces of fibers through numerous hydrogen bonds.

Thanks to the present invention, the fibril cellulose 4 may be produced in the paper mill, i.e. in on-site fibril cellulose production, even without the need for Complicated Dosing Aggregates in a paper machine approach system. According to the invention of the invention, a storage tank, dilution water and dosing pumps are needed to feed said anionized cellulose material 3 to the main pulp line going to beating. Thus, the present invention is advantageously a Simplified Fibril Cellulose Dosing Process.

The novel solution can be a cost effective way of using fibril cellulose in wet end applications. The invention may cause an effective dispersion of fibril cellulose and a proper mixing with the base furnish. The paper produced from the pulp manufactured according to the present invention may have many advantages. For example, the grammage of the paper may be decreased and / or the amount of the filler in use may be increased and / or the strength properties of the produced paper may be increased. In addition, the amount of silicone coating needed on a release paper may be reduced due to the new properties of the produced paper.

The paper comprises (at least Mostly, ie at least 60% of dry weight, more preferably at least 75% and most preferably at least 90% of dry weight) of a label laminate. The release paper is typically strongly refined, hence, the chemically treated cellulose may be refined into the fibril cellulose efficiently. Advantageously, the basis weight range for manufactured paper is between 30 and 90 g / m2, more preferably between 30 and 50 g / m2. The produced paper may be coated and / or surface sized and / or calendered.

The label laminate preferably comprises two layers which are laminated together, i.e. a release liner and a face layer are provided between the release liner and the face layer. The term "face layer" refers to the "top layer" of the label laminate, also called as the face stock.

The face layer forms at least one layer that is attached to another surface with an adhesive layer when the label laminate is used.

The term "release liner" refers to a structure comprising at least one backing material layer as a base material and at least one release coating layer on a Backing material layer. In other words, the backing material layer is usually coated with a thin layer of release agent, such as Silicone. Therefore, the release liner can be easily removed from the face layer when the label is adhered to a substrate. Herein, the term "release paper" refers to said backing material. Advantageously, the produced paper is coated with at least one Silicon coating layer in order to produce a release liner for a label laminate.

The pulp from which the handsheet is made is preferably collected from the pulp flow that is going to the headbox of a paper machine. In other words, the pulp preferably comprises every compound of the base paper to be manufactured, such as fillers, chemicals, pulps, etc., but the process parameters of the paper machine cannot have any effect on the results. Typically, the fibril cellulose added in a small amount in the paper has one, two, three or four of the following effects on the handsheet, if the handsheet is manufactured from the pulp produced according to the present invention: - Clearly lower air permeance if compared to a reference handsheets. - Improved initial wet strength if compared to reference handsheets. - Improved Scott Bond if compared to reference handsheets. - Higher SR or WRV without adjusting beating if compared to a reference handsheets.

These properties are also presented in Table 2.

Experimental tests

In experimental tests, different kinds of pulps for paper products were manufactured. The paper sheets were made from the produced Pulps and tested afterwards.

Raw materials and a trial plan

Chemical Pulps made with a conventional chemical Pulping process were used as cellulose pulp 2. The Chemical Pulps used were isolated from pine (so called "Mask Pinus" manufactured by UPM) and from birch (so called "Mask Betula" manufactured by UPM).

The trial was carried out according to the plan presented in Table 1. SEC, pulp type (Birch, Pine), amount of anionized cellulose material ("TEMPO pulp"), amount of readymade fibril cellulose (TEMPO MFC), a place where the fibril cellulose was added and the amount of Starch was varied as shown in Table 1.

Table 1. Trial shoulder. 3

The fibril cellulose material was dispersed with Bamix® - hand mixer for 2 minutes before the dispersed fibril cellulose was added to the chemical pulp. The mixture did not form fillers. Starch (Raisamyl 50021) was added to the chemical pulp. If the fibril cellulose was added before the beating step, the mixing time of the mixture comprised the fibril cellulose, chemical pulp and starch was 20 min. If the fibril cellulose was added after the beating step, the Starch and cellulose pulp were mixed with each other for a total mixing time of 15 min, after which the fibril cellulose was added to the mixture. The mixing time of the mixture consisting of Starch, chemical pulp and fibril cellulose was in this case for 5 min. A 100 mesh wire was used in the trial.

Test results

A summary of the test results is shown in Table 2, which

Internal 1: Drainage time was defined by the time until visible water disappears during sheet forming, and

Internal 2: Wet tensile strength was measured with L&W tensile tester from wet sheets. Two solids content levels were used in which solids content was between 35 and 50%, and the results were interpolated to 45% solids content

Table 2. Summary of test results.

The addition of fibril cellulose significantly increased the SR level of the pulp produced. It was not rated that SEC at about 225 kWh / t would have brought the SR level of Tempo pulp containing furnish to the level of Tempo fibrils containing furnish beaten at 200 kWh / t SEC. Examples of SR levels are shown in Figure 2.

The results showed generally higher water retention values (WRV) with pulps comprising fibril cellulose material than with reference pulps without fibril cellulose material. It was not that SEC at 225 kWh / t would have brought the WRV-level of Tempo pulp containing furnish to the level of Tempo fibrils containing furnish beaten at 200 kWh / t of SEC. Some water retention values are shown in Figure 3.

According to the Trials, increased beating energy consumption was not necessary when the Tempo-treated pulp was fibrillated during beating. The SR and WRV levels of beaten pulp were lower than in the case of ready-made Tempo-fibril addition to beaten pulp.

Sheet properties results are based on laboratory sheets. Anionized cellulose fibers added to the beating step seemed to give good paper sheet properties. In Figures 4-7, "T" refers to "Tempo treated."

Air permeability of the pulp comprised of fibril cellulose was clearly lower than air permeability of the reference pulp. In addition, the results showed lower porosity when the fibrils were added to the beaten pulp instead of the unbeaten pulp. Tempo pulp and Tempo fibrils were approximately at the same level when added to beating. Air permeability results are shown in Figure 4.

For Scott Bond, Tempo fibrils seemed to be slightly more effective than Tempo pulp. Tempo addition to unbeaten pulp seemed to be more effective than addition to unbeaten pulp. Scott Bond results are shown in Figure 5.

For the Tensile index, a good performance was shown with the Tempo pulp added to the beaten pulp. Tempo pulp and fibrils added to beating seemed to be slightly better than when fibrils were added to beaten pulp, or at least as good as when fibrils were added to beaten pulp. Tensile Indexes are shown in Figure 6.

For wet tensile strength at 45% solids content, a good performance was shown with Tempo pulp added to beating and Tempo fibrils added to beaten pulp. This is shown in Figure 7.

Drainage was comparable to reference samples but with higher strength properties. Tempo-treated fibrils and Tempo-treated pulp with higher SEC gave most dense sheet but also slowest drainage.

It can be easily seen from the refining results of the SR and WRV are increased with the refining step of the chemical pulp and Tempo pulp clearly more than the Refining step of the chemical pulp without Tempo pulp, thus, the Tempo pulp is clearly fibrillated into fibril cellulose material during the Refining step.

Thanks to the present invention, a production of fibril cellulose for paper applications can be possible with low energy consumption. One skilled in the art understands that different embodiments of the invention may have applications in environments where Optimization of a paper product comprising fibril cellulose is desired. Therefore, it is obvious that the present invention is not limited to the above-presented embodiments, but it can be modified within the scope of the appended claims.

Claims (14)

A process for preparing a blend ratio of a paper product, wherein the blend ratio comprises a nanofibrillary cellulosic material, the method comprising: introducing into the system a first raw material comprising a cellulosic pulp (2), a second raw material comprising a second raw material comprising anionized cellulose fibers; which have been catalytically oxidized by oxidation of the hydroxyl groups of the cellulose by nitroxyl transferring the first raw material and the second raw material to a refiner (8), milling and blending the first raw material and the second raw material in a refiner (8) to form a nanofibrillar cellulose (4). Process according to Claim 1, characterized in that the sum of nano-fibril cellulose (4) and anionized cellulose fibers (3) in the prepared blend ratio is 0.01 to 10.0% by weight on a dry basis. Process according to Claim 1 or 2, characterized in that the amount of nanofibril cellulose (4) in the prepared blend is from 0.1 to 5.0% by dry weight. Method according to one of the preceding claims, characterized in that the first raw material comprises a chemical pulp (2a). Method according to one of the preceding claims, characterized in that the refiner (8) is located in a paper machine approach system. Paper comprising cellulosic pulp and nanofibrillary cellulosic material, characterized in that the nanofibrillary cellulosic material is made from milled anionic cellulose fibers comprising cellulose which has been catalytically oxidized by hydroxylation of the cellulose and nitroxylated (papermaking), and nanofibril cellulose is dispersed and mixed in a basic paper blend ratio. Paper according to claim 6, characterized in that the paper has a basis weight of 30-90 g / m2, preferably 30-50 g / m2 Paper according to Claim 6 or 7, characterized in that the paper has at least one of the following: improved bond strength properties, improved web wet index, and reduced air permeability properties compared to paper made from pulp without nanofibrillar cellulose. Paper according to claim 6, 7 or 8, characterized in that the paper is a release paper for self-adhesive label. Paper according to claim 6, 7 or 8, characterized in that the paper is a sandpaper base paper. Paper according to claim 6, 7 or 8, characterized in that the paper is printing paper. Paper according to claim 6, 7 or 8, characterized in that the paper is packaging material and / or board. Paper according to one of Claims 6 to 12, characterized in that the amount of fibril cellulose (4) in the paper is 0.5 to 2.5% by weight. Use of a blend ratio for the production of paper or board wherein at least a portion of the blend ratio is made by a process according to any one of claims 1 to 5.