Use of composition comprising cationic biopolymer

Abstract

The present invention relates to the use of a composition comprising a cationic biopolymer as a drainage agent and / or dewatering agent in the manufacture of paper pulp or a fibrous web comprising cellulosic fibers. The cationic biopolymer is selected from the group consisting of a cationically crosslinked alpha-(1, 3-glucan) polymer, a cationic ester-or ether-derivative of a graft copolymer of dextran and alpha-1, 3-glucan, or a mixture of any thereof. The invention also relates to a method for improving dehydration and / or drainage in the manufacture of a pulp or web.

Description

Technical Field

[0001] The present invention relates to the use of compositions comprising cationic biopolymers, and to a method for increasing dewatering and / or drainage in the manufacture of pulp or in the manufacture of a fibrous web as described in the foregoing part of the independent claims provided herewith. Background Art

[0002] Dewatering is an important aspect in the manufacture of pulp and in the manufacture of fibrous webs such as paper, cardboard, etc. In the manufacture of pulp, water is removed from the pulp web or pulp board by using press dewatering, such as a twin wire press or a shoe press. After dewatering, the pulp web can be dried in a dryer comprising a plurality of stacked horizontal drying levels, cut into sheets and packaged. Alternatively, in an integrated mill, the dewatered pulp is directly transferred by pumping to the stock preparation of a paper / cardboard machine without intermediate drying.

[0003] In the manufacture of fibrous webs such as paper and cardboard, water removal from the fibrous web starts immediately after its formation in the forming section. Initial water removal, i.e., drainage, is carried out by gravity, and then dewatering is carried out using dewatering elements such as foils. Then, dewatering in the forming section is continued by means of a plurality of vacuum boxes which remove moisture from the formed web by suction. The vacuum boxes are placed one after another in the machine direction, and the vacuum (i.e., pressure drop) generated by the vacuum boxes increases in the machine direction because water removal becomes more difficult as the dryness of the web increases. After the forming section, the fibrous web is press dewatered by mechanically pressing the wet web in a press section. For example, press dewatering is carried out by using a press dewatering device such as a shoe press or a roll pair. Press dewatering also affects the quality of the final fibrous web because it increases the density of the formed web and affects its surface structure. After the press section, the water content of the fibrous web can be about 30 wt%-60 wt%. Then, in the drying section, the fibrous web is dried to a final dryness of about 93 wt%-95 wt% by using, for example, heated drums and / or infrared radiators.

[0004] Dewatering is an energy-consuming part in the production of pulp and fibrous webs. In addition, efficient water removal ensures good operation of the process and contributes to achieving sufficient retention and uniform formation.

[0005] The drainage and dehydration efficiency of pulp or fiber webs can be improved by using different chemicals, either alone or in various combinations. Drainage and dehydration chemicals are typically synthetic polymers with a cationic charge. However, there is a growing concern about reducing the use of petroleum-based chemicals and replacing them with more sustainable alternatives. Due to the increasing environmental concerns and the increasing legislative restrictions and incentives, there is a desire to find new additives made from bio-based renewable resources. Preferably, the new additives are biodegradable and do not leave toxic residues. At the same time, the new additives should still provide similar or better drainage and dehydration effects. Since dehydration and drying are high-energy processes, significant energy consumption savings can be achieved when drainage and dehydration are improved. Summary of the Invention

[0006] The object of the present invention is to minimize or even eliminate the drawbacks existing in the prior art.

[0007] The object of the present invention is to improve drainage and / or dehydration, particularly dehydration, in the manufacture of pulp or fiber webs such as paper, cardboard, etc.

[0008] These objects are achieved by the present invention, which has the features provided in the characterizing part of the independent claims. Some preferred embodiments of the present invention are given in the dependent claims. Unless otherwise explicitly stated, the features recited in the dependent claims can be freely combined with each other.

[0009] According to the present invention, a typical use of a composition comprising a cationic biopolymer is as a drainage agent and / or dehydrating agent in the manufacture of pulp or a fiber web comprising cellulose fibers, wherein the cationic biopolymer is selected from cationically crosslinked α-1,3-glucan polymers, cationic ester- or ether-derivatives of graft copolymers of dextran and α-1,3-glucan, or any mixture thereof.

[0010] Typical methods according to the present invention for improving dehydration and / or drainage in the manufacture of pulp or a fiber web comprising cellulose fibers include

[0011] - obtaining a fiber suspension comprising cellulose fibers,

[0012] - adding a dehydrating agent and / or drainage agent comprising a cationic biopolymer to the fiber suspension, the cationic biopolymer being selected from cationically crosslinked α-1,3-glucan polymers, cationic ester- or ether-derivatives of graft copolymers of dextran and α-1,3-glucan, or any mixture thereof,

[0013] - forming a fiber web of pulp, paper, cardboard, etc.,

[0014] - removing water from the fiber web, preferably by assisted dehydration.

[0015] Now, unexpectedly, it has been found that cationically crosslinked α-1,3-glucan polymers and cationic ester- or ether-derivatives of dextran-grafted copolymers with α-1,3-glucan can be used as drainage and dewatering agents in the manufacture of pulp and in the manufacture of fibrous cellulose webs. It is assumed that the crosslinked α-1,3-glucan polymers have a three-dimensional structure, which results in effective interaction with the fibers in the pulp or in the fiber suspension. The same applies to the ester- and ether-derivatives of the graft copolymers, where the three-dimensional structure is formed by side chains grafted onto the polymer backbone. The cationically crosslinked polymers and cationic graft copolymer derivatives are not only effective drainage and / or dewatering agents, but also contribute to achieving other desired properties, such as effective retention during dewatering and the desired solids content of the formed web. In addition, dewatering efficiency is obtained without loss of formation. The cationic α-1,3-glucan polymers and cationic graft copolymer derivatives can provide acceptable dewatering and / or drainage effects, sometimes as good as or even better than those obtained with conventional petroleum-based polymers such as cationic polyacrylamide, acetylated polyacrylamide or polyvinylamine. However, when used according to the present invention, the cationic biopolymer can significantly improve the sustainability of the final product.

[0016] Compositions comprising the cationic biopolymer do not cause flocculation of the pulp or fiber suspension. This means that the composition can provide improved drainage and / or dewatering without loss of formation.

[0017] In the context of the present application, the term "drainage" refers to the removal of water from pulp or a wet fiber web by gravity. Drainage agents improve free drainage, i.e., the removal of water from pulp or a wet fiber web by gravity. Mechanical water removal elements that can be used to assist free drainage are, for example, foils, blades, forming boots, forming rolls or forming cylinders. Thus, drainage encompasses, for example, initial water removal by gravity at the start of the forming section until the wet line is reached, i.e., the point at which a change from the wet web to the dry web can be observed with the naked eye and air begins to pass through the wet web. Generally, water removal by drainage ends when the wet web has a dryness of 3 wt% - 7 wt%.

[0018] The term "dewatering" refers to assisted dewatering, i.e., the assisted removal of water from pulp or a wet fiber web. Dewatering encompasses vacuum dewatering and press dewatering. After vacuum dewatering, the dryness of the pulp or fiber web can typically be increased to a dryness of 13 wt% - 23 wt%, preferably 14 wt% - 20 wt%, more preferably 16 wt% - 22 wt%. Press dewatering is typically carried out after vacuum dewatering, where the dryness of the pulp or fiber web is increased to a dryness of 40 wt% - 55 wt%, preferably 43 wt% - 52 wt%, more preferably 45 wt% - 50 wt%. Compared with the case where no dewatering agent is used, by using a dewatering agent, the dryness after vacuum dewatering can be increased by 0 - 5 percentage units, and the dryness after press dewatering is increased by 1 - 5 percentage units. In vacuum dewatering, assisted water removal can be achieved by using a vacuum, typically 15 - 70 kPa. The vacuum can be achieved by using a blower, a suction element such as a vacuum box, a vacuum pump or a couch roll. In press dewatering, assisted water removal can be achieved by using a press nip between rollers, or by using other mechanical dewatering devices such as a shoe press, a center roll press, a roll press or a twinwire press, etc. Dewatering also encompasses any combination of vacuum dewatering and press dewatering, where water is removed by using pressing and vacuum or suction. The dewatering agent improves dewatering, i.e., water is removed from the pulp or wet fiber web by using suction and / or by pressing. For vacuum dewatering, the dewatering agent preferably has the ability to provide flocculation of fines in the fiber suspension without flocculation of the fibers, thus achieving good web formation and a high vacuum level for efficient drying. For press dewatering, the dewatering agent preferably has the ability to neutralize the charges of negatively charged fibers, fines and colloidal materials present in the pulp or wet web. The negative charge creates a repulsive force, which increases the distance between the fibers, fines and colloidal materials, while creating space for water. When the charge is neutralized, the distance between the fibers, fines and colloidal materials is minimized, and the water-binding capacity of the pulp or wet web is reduced.

[0019] According to one embodiment of the present invention, water can be removed from pulp or a fiber web by using assisted dewatering with one or more of the following: a dewatering element, a vacuum box and a press dewatering device.

[0020] The present invention is particularly applicable to improving the dewatering of pulp or a wet fiber web (such as paper, cardboard, paper towels, etc.).

[0021] In the context of the present application, the term "dextran" refers to an α-glucan comprising at least 50%, preferably at least 60%, more preferably at least 70%, even more preferably at least 80% or at least 90% of α-1,6-glycosidic bonds, wherein the balance relative to 100% is usually α-1,3-glycosidic bonds. The dextran can be substantially linear, which means that it has 0-5% branching prior to forming a graft copolymer with α-1,3-glucan. The possible branches of the dextran itself are usually short, with a length of one to three glucose monomers.

[0022] In the context of the present application, "α-1,3-glucan polymer" and "α-1,3-glucan" refer to a polymeric structure having a polysaccharide backbone that comprises D-glucose units linked together by glycosidic bonds. At least 70%, preferably at least 80%, more preferably at least 90% or 95%, and sometimes even 99% or 100% of the glycosidic bonds are α-1,3-bonds.

[0023] The cationic biopolymer can be a cationic crosslinked α-1,3-glucan polymer. Thus, the cationic crosslinked α-1,3-glucan polymer used in the present invention comprises cationic substitution groups attached to its structure. The cationic substituents can be substituted ammonium groups, preferably quaternary ammonium groups, more preferably trialkylammonium groups. The alkyl groups in the trialkylammonium group can be, for example, methyl, hydroxymethyl, hydroxyethyl or hydroxypropyl. The substituted ammonium group can be, for example, trimethylammonium group. The cationic substituents of the α-1,3-glucan polymer are capable of interacting with negatively charged fibers in a manner that results in effective drainage and / or dehydration.

[0024] The crosslinked α-1,3-glucan polymer suitable for the present invention can be obtained by contacting the α-1,3-glucan polymer with a crosslinking agent and a solvent such as water. The amount of the crosslinking agent can be 20-5000 ppm, preferably 100-5000 ppm, based on the dry weight of the polymer. According to one embodiment, a crosslinking agent selected from the group consisting of: epihalohydrins such as epichlorohydrin; epoxides; diglycidyl ethers such as diglycidyl ether or ethylene glycol diglycidyl ether; polyvalent metals such as zirconium carbonate or cyanuric chloride; glyoxal; and polycarboxylic acids such as citric acid, glutaric acid, adipic acid can be used.

[0025] Alternatively, the cationic biopolymer applicable to the present invention may be a cationic ester- or ether-derivative of a graft copolymer of dextran and α-1,3-glucan. For example, suitable graft copolymer derivatives, their preparation methods, and the determination of their glycosidic bond spectra are described in WO 2021 / 247810. The degree of polymerization of α-1,3-glucan may be in the range of 20 - 3000, preferably 500 - 2000. For example, the degree of polymerization may be in the range of 20 - 2000 or 55 - 1000. The degree of polymerization herein refers to the number of glucose units contained in each side chain.

[0026] According to one embodiment of the present invention, calculated based on the dry weight of the graft copolymer before ester or ether derivatization, the cationic graft copolymer may contain 10 wt% - 70 wt%, preferably 20 wt% - 60 wt%, more preferably 30 wt% - 50 wt% of dextran. Calculated based on the dry weight of the graft copolymer before ester or ether derivatization, the cationic graft copolymer may contain, for example, 30 wt% - 90 wt%, preferably 40 wt% - 80 wt%, more preferably 50 wt% - 70 wt% of α-(1,3-glucan), such as α-1,3-glucan side chains.

[0027] According to one embodiment, the cationic biopolymer may be a cationic graft copolymer comprising a dextran backbone and α-1,3-glucan side chains, wherein preferably the side chains are linked to the dextran backbone through α-1,2 and / or α-1,3 and / or α-1,4 branches. The α-1,3-glucan side chains may contain at least 70%, preferably at least 80%, more preferably at least 90% or at least 95%, and sometimes even 99% or 100% of α-1,3-glycosidic bonds.

[0028] The graft copolymer derivative contains one or more cationic groups linked to the graft copolymer through an ester- or ether-bond. The cationic groups may include substituted ammonium groups, such as primary, secondary, tertiary, or quaternary ammonium groups, preferably quaternary ammonium groups, more preferably trialkylammonium groups. The ammonium groups may be substituted by alkyl and / or aryl groups, for example, by C1-C4 alkyl or C6-C24 alkyl groups. One of the groups in the substituted ammonium group contains a carbon or a carbon chain that forms an ether bond or an ester bond with the graft copolymer.

[0029] According to one embodiment of the present invention, the composition comprises a cationic biopolymer which may have a degree of cationic substitution in the range of 0.05 - 1.2, preferably 0.1 - 1.0, more preferably 0.1 - 0.7, even more preferably 0.15 - 0.6 or 0.25 - 0.6. The degree of substitution refers to the average number of hydroxyl groups in each glucose unit of a graft copolymer or a crosslinked copolymer that are substituted by cationic groups via ether bonds or ester bonds or via other bonds. It has been observed that such a degree of substitution provides cationicity to the biopolymer, thereby producing an effective dewatering effect, especially in the pulp of paper, cardboard, etc., or in the press dewatering of a wet fiber web. In addition, high cationicity improves the water solubility of the biopolymer, which makes the press dewatering more effective. However, an excessive cationicity is preferably avoided because it may cause ecotoxicity to aquatic organisms or lead to unwanted flocculation. Biopolymers with excessive cationicity may also contain impurities, which limit their suitability, for example, in food contact applications.

[0030] According to one embodiment of the present invention, the composition may comprise a crosslinked dextran and a cationic graft copolymer of α-1,3-glucan. Crosslinking can be carried out by using the same crosslinking agent as described above. The crosslinking of the branched structure of the graft copolymer further alters the three-dimensional structure of the cationic biopolymer.

[0031] Measured at a biopolymer concentration of 2 wt%, the salt viscosity of the cationic biopolymer is 50 - 5000 mPas, preferably 200 - 4000 mPas. This viscosity can be used to measure or estimate the molecular size of the biopolymer. It has been observed that when the viscosity of the cationic biopolymer is within a given range, the cationic biopolymer can provide an effective dewatering effect, especially a vacuum dewatering effect. It is assumed that the size of the cationic biopolymer enables optimal floc formation, especially floc formation with the fines of the fiber suspension. As described below, the salt viscosity is determined at a biopolymer concentration of 2 wt% in water in the presence of salt. The cationic biopolymer is first dissolved in deionized water as a 2 wt% solution as the active biopolymer. Then sodium chloride (NaCl) is added until the conductivity of the solution is 13 mS / cm. The salt viscosity of the resulting solution is measured at 25 °C using a Brookfield DV1 viscometer with a small sample adapter. The viscosity measurement is carried out using the maximum possible rotational speed.

[0032] The composition comprising the biopolymer may further comprise other compounds or substances. For example, the composition may include salt compounds, urea compounds, cationic synthetic polymers such as polyvinylamine or polyvinylimine.

[0033] The composition may comprise or consist of a mixture of two or more biopolymers selected from cationically crosslinked α-1,3-glucan polymers, cationic ester- or ether-derivatives of dextran-grafted copolymers of dextran and α-1,3-glucan. According to a preferred embodiment, the composition consists of a biopolymer.

[0034] The composition comprising the cationic biopolymer may have a charge density of 0.7 - 5.0 meq / g, preferably 0.8 - 4 meq / g, more preferably 0.9 - 3.0 meq / g as measured by Mütek PCD. The charge density of the composition is selected to provide effective vacuum dewatering while avoiding problems associated with cationic overdosage such as ecotoxicity to aquatic organisms.

[0035] The composition comprising the cationic biopolymer is added to an aqueous fiber suspension, said cationic biopolymer being selected from cationically crosslinked α-1,3-glucan polymers, cationic ester- or ether-derivatives of dextran-grafted copolymers of dextran and α-glucan or any mixture thereof, where it acts as a drainage or dewatering agent. According to one embodiment, the composition may be used in an amount to provide 0.1 - 0.8 kg / t, preferably 0.15 - 0.6 kg / t, more preferably 0.2 - 0.4 kg / t of the cationic biopolymer to the fiber suspension. These values are provided as active substance.

[0036] According to one embodiment of the present invention, the composition comprising the cationic biopolymer is used in the manufacture of a fibrous web such as paper or board for improving drainage and / or dewatering, in particular dewatering, said fibrous web comprising recycled cellulose fibers or consisting thereof. In this method, an aqueous fiber suspension comprising recycled cellulose fibers is obtained. The recycled fibers may be sourced from recycled paper and / or old corrugated containers (OCC). Calculated on the total dry fiber weight of the suspension, the fiber suspension may comprise >20 wt%, preferably >50 wt%, more preferably >70 wt%, even more preferably >80 wt% of recycled fibers. The fiber suspension may even comprise 100 wt% of recycled fibers. According to a preferred embodiment, the amount of recycled fibers in the fiber suspension may be 50 wt% - 100 wt%, preferably 80 wt% - 100 wt%, more preferably 90 wt% - 100 wt%.

[0037] When the aqueous fiber suspension comprises recycled fibers or consists thereof, it may have a conductivity of at least 2 mS / cm, preferably at least 3 mS / cm, more preferably at least 3.5 mS / cm. The conductivity may be in the range of 2 - 10 mS / cm, preferably 3 - 9 mS / cm, more preferably 3.5 - 8 mS / cm. Even for these fiber suspensions with high conductivity, the composition comprising the biopolymer can improve drainage and / or dewatering.

[0038] According to one embodiment of the invention, the composition comprising the cationic biopolymer is used for improving drainage and / or dewatering, especially dewatering, in the manufacture of chemical or semi - chemical pulp or in the manufacture of a fibrous web such as paper or board, said fibrous web comprising or consisting of cellulose fibers obtained by chemical pulping or semi - chemical pulping. The composition is suitable for pulp and fibers derived from chemical and semi - chemical pulping such as kraft pulping, sulfite pulping, neutral sulfite semi - chemical (NSSC) pulping, soda pulping or chemi - thermomechanical pulping (CTMP).

[0039] The composition comprising the cationic biopolymer can be added to a fiber suspension having a consistency in the range of 0.2 wt% - 20 wt%, preferably 0.3 wt% - 4 wt%, more preferably 0.3 wt% - 1.9 wt%. When the composition is used as a drainage or dewatering agent in the manufacture of a fibrous web such as paper, board, etc., the composition can be added to a thin stock having a consistency ≤ 19 g / L, preferably less than 15 g / L. Generally, when adding the composition comprising the biopolymer, the fiber suspension can have a consistency in the range of 5 - 19 g / L, preferably 5 - 15 g / L. When the composition comprising the biopolymer is used as a drainage or dewatering agent in the manufacture of pulp, the composition can be added to a pulp having a consistency ≥ 0.5 wt%, preferably ≥ 3 wt%, sometimes even ≥ 6 wt%. Generally, when adding the composition comprising the biopolymer, the fiber suspension can have a consistency in the range of 0.5 wt% - 20 wt%, preferably 3 wt% - 15 wt%.

[0040] When the composition is used as a dewatering agent in the manufacture of pulp, the composition can be added to a fiber suspension having a consistency in the range of 4 wt% - 20 wt%, preferably 6 wt% - 20 wt%, more preferably 8 wt% - 15 wt%.

[0041] When a composition containing the cationic biopolymer is used in the manufacture of fibrous webs such as paper, cardboard, etc., it can be used in combination with other papermaking chemicals. According to one embodiment of the present invention, a retention aid system, for example, a retention aid system containing a cationic synthetic polymer, preferably cationic polyacrylamide, can be added to a fiber suspension containing cellulose fibers, optionally providing at least partial flocculation. For example, the retention aid system can contain a cationic poly(meth)acrylamide, which is obtained by polymerizing (meth)acrylamide and 5 mol% - 15 mol% of a cationic monomer and has a weight average molecular weight in the range of 3,000,000 - 15,000,000 g / mol. The cationic synthetic polymer of the retention aid system can be added to the aqueous fiber suspension before, after, or simultaneously with the addition of the composition containing the cationic biopolymer. Preferably, the cationic synthetic polymer is added as close as possible to the addition of the composition containing the cationic biopolymer. Preferably, the cationic synthetic polymer is added before the last shearing stage before the headbox of a paper machine or a cardboard machine.

[0042] According to one embodiment of the present invention, the retention aid system can further include microparticles, preferably the microparticles are selected from inorganic siliceous microparticles such as colloidal silica or bentonite. The inorganic siliceous microparticles can be selected from silica-based particles, silica microgels, colloidal silica, silica sols, silica gels, polysilicates, aluminosilicates, polyaluminosilicates, borosilicates, polyborosilicates, zeolites, and swellable clays such as bentonite. Preferably, the inorganic siliceous microparticles are selected from colloidal silica or bentonite. After adding the cationic synthetic polymer of the retention system, and preferably after the last shearing stage before the headbox of a paper machine or a cardboard machine, etc., the microparticles are added. The microparticles can provide at least partial reflocculation after the last shearing stage.

[0043] According to a preferred embodiment of the present invention, the composition containing the biopolymer can be added simultaneously with cationic polyacrylamide, and optionally colloidal silica microparticles are added subsequently. Detailed Embodiments

[0044] Experiments

[0045] Some embodiments of the present invention are described in the following non-limiting examples.

[0046] Example 1

[0047] In Example 1, the effect of the cationic derivative of the graft copolymer of dextran and α-1,3-glucan on the press dewatering of a fibrous web containing recycled cellulose fibers was studied.

[0048] The properties of a cationic graft copolymer derivative with a degree of substitution DS of 0.4 (i.e., a branched polymer) were compared with a) the properties of a cationized linear non-crosslinked α-1,3-glucan polymer with a degree of substitution DS of 0.4 and b) the properties of polyvinylamine (the polyvinylamine contains 35 mol% of vinylamine and 65 mol% of N-vinylformamide, MW is 500,000 g / mol, and is commonly used as a dehydrating agent in paper machines and board machines).

[0049] An aqueous fiber suspension with a consistency of 0.3% was made from the furnish obtained from the RCF mill in southern Europe. The conductivity and pH of the fiber suspension were not adjusted from the conductivity value of 6.3 mS / cm and pH of 6.1.

[0050] The solids content of the fiber mat after the wire section and press section and during initial drainage was studied using a Dynamic Drainage Analyzer (DDA). The DDA parameters used were: a wire with a 0.25 mm opening; a vacuum of 200 mbar; a follow-up time of 20 s.

[0051] 500 mL of the fiber suspension was placed in a DDA container and mixed at 1000 rpm. The dehydrating aid to be tested was added 20 seconds before the start of drainage. Table 1 gives the test addition levels provided as active chemicals. At each test point, the retention system used was 0.2 kg / t of cationic polyacrylamide and 0.2 kg / t of silica (dry), and the addition times were 10 seconds and 7 seconds before drainage, respectively.

[0052] The drainage time was measured. After draining from the DDA, the wet sheet was removed, weighed, and then wet pressed at 4 bar for 1 minute. After wet pressing, the sheet was weighed, dried in a rapid dryer, and reweighed after drying. The wire section and press section solids content values were calculated. These values represent the dryness of the wire after vacuum dehydration and press dehydration. The results are shown in Table 1.

[0053] Table 1. Results of Example 1.

[0054]

[0055] From the results in Table 1, it can be seen that compared with the reference, the cationic graft copolymer of dextran and α-1,3-glucan produced higher press section solids content and wire section solids content. In particular, the improvement in the press section solids content was significant and even higher than the improvement achievable with the synthetic polymer (polyvinylamine). As can be seen from Table 1, an increase in dosage does not necessarily provide better results, as shown by the results of adding polyvinylamine at two different levels. There seems to be an optimal dosage level for the press dehydrating aid, where a higher dosage will reduce the effect obtained.

[0056] Example 2

[0057] In Example 2, by repeating Example 1 but using different fiber suspensions, the effect of cationic derivatives of dextran and α-1,3-glucan graft copolymers on the press dewatering of a fiber mat containing recycled cellulose fibers was further investigated.

[0058] The cationic graft copolymer derivative and the cationized linear uncrosslinked α-1,3-glucan were the same as in Example 1.

[0059] In Example 2, an aqueous fiber suspension with a consistency of 0.45% was made from the furnish obtained from a Central European RCF mill. The conductivity and pH of the fiber suspension were not adjusted from the conductivity value of 4.1 mS / cm and pH 6.1.

[0060] Table 2 gives the test addition levels of the press dewatering aids provided as active chemicals. The retention system was the same as in Example 1. After removal from the DDA, the wet sheet was wet pressed at 3.5 bar for 1 minute. Otherwise, the procedure was the same as in Example 1. The results are shown in Table 2.

[0061] Table 2. Results of Example 2.

[0062]

[0063]

[0064] From the results in Table 2, it can be seen that the cationic graft copolymer of dextran and α-1,3-glucan produced higher press solids content and wire solids content compared to the linear reference. Also, the effect of the optimum dosage level can be seen from the results obtained from the linear α-1,3-glucan reference in Table 2.

[0065] Example 3

[0066] In Example 3, the effect of the cationic graft copolymer of dextran and α-1,3-glucan on the press dewatering of a fiber mat containing recycled cellulose fibers was investigated.

[0067] The performance of two cationic graft copolymer derivatives (i.e., branched polymers) with degrees of substitution DS 0.2 and 0.4 was compared with a) the performance of two cationized linear uncrosslinked α-1.3-glucan polymers with degrees of substitution DS 0.2 and 0.4 and b) the performance of polyvinylamine commonly used as a dehydrating agent in paper and board machines.

[0068] The preparation of the aqueous fiber suspension is as follows. Old corrugated container board (OCC) from a Central European paper mill was soaked in chemical water at 85 °C at a consistency of 2.5 wt% for 5 minutes at pH 6.8. The chemical water was prepared by dissolving a salt mixture containing 70 wt% calcium acetate, 20 wt% sodium sulfate, and 10 wt% sodium bicarbonate in deionized water until the conductivity was 3 mS / cm. After soaking, the OCC was thermally decomposed with a laboratory disintegrator at 30,000 revolutions per minute. Before the experiment, the obtained formulation was cooled to room temperature (about 23 °C) and diluted to a consistency of 0.7 wt% with the same chemical water.

[0069] The solids content of the fiber mat after the forming section and the press section and the initial drainage was studied using a dynamic drainage analyzer (DDA). The DDA parameters used were: a wire with an opening of 0.25 mm; a vacuum of 200 mbar; and a subsequent time of 20 s.

[0070] 500 mL of the prepared fiber suspension was placed in a DDA container and mixed at 1000 rpm. The dewatering aid to be tested was added 20 seconds before the start of drainage. Table 3 gives the test addition levels provided as active chemicals. At each test point, the retention system used was 0.2 kg / t cationic polyacrylamide and 0.2 kg / t (dry) silica, and the addition times were 10 seconds and 7 seconds before drainage, respectively.

[0071] The drainage time was measured. After draining from the DDA, the wet sheet was taken out, weighed, and then wet pressed at 4 bar for 1 minute. After wet pressing, the sheet was weighed, dried in a rapid dryer, and reweighed after drying. The solids content values for the forming section and the press section were calculated.

[0072] It can be seen from Table 3 that the cationic graft copolymer of dextran and α-1,3-glucan significantly improved the solids content in the press section, i.e., press dewatering.

[0073] Table 3. Results of Example 3.

[0074]

[0075]

[0076] Example 4

[0077] In Example 4, the effects of cationic crosslinked α-1,3-glucan and the cationic graft copolymer of dextran and α-1,3-glucan on the press dewatering of a fiber mat containing recycled cellulose fibers were studied.

[0078] The properties of a cationic graft copolymer derivative (i.e., a branched polymer) with a degree of substitution DS of 0.3 (salt viscosity at 2%: 178 mPas) were compared with those of two cationized linear crosslinked α-1,3-glucan polymers with a degree of substitution DS of 0.3 (salt viscosity at 2% of 900 mPas) and with DS of 0.5 (salt viscosity at 2% of 26 mPas). Cationization was carried out using epoxy chemistry such as 2,3-epoxypropyltrimethylammonium chloride (EPTAC). Cationic crosslinked α-1,3-glucan polymers were prepared from α-1,3-glucan DP 1500 by adding polyethylene glycol diglycidyl ether (EDGE) as a crosslinking agent to the cationization step. The amount of the crosslinking agent was adjusted to a certain level where, at a concentration of 3% and a temperature of 25 °C, the Brookfield DV1 SSA viscosity of the polymer increased by about 3 times compared to the viscosity of the starting polymer.

[0079] The aqueous fiber suspension was prepared as follows. As shown in Example 3, old corrugated containerboard (OCC) from a Central European paper mill was soaked in chemical water at 85 °C at a consistency of 2.5 wt% for 5 minutes. After soaking, the OCC was thermally decomposed with a laboratory disintegrator at 30,000 revolutions per minute. Before the experiment, the obtained furnish was cooled to room temperature (about 23 °C) and diluted with the same chemical water to a consistency of 0.7 wt%.

[0080] The solids content of the fiber mat after the wire section and press section and during initial drainage was studied using a dynamic drainage analyzer (DDA). The DDA parameters used were: a wire with an opening of 0.25 mm; a vacuum of 300 mbar; and a subsequent time of 15 s.

[0081] 500 mL of the prepared fiber suspension was placed in a DDA container and mixed at 1000 rpm. The dewatering aid to be tested was added 20 seconds before the start of drainage. Table 4 gives the test addition levels provided as active chemicals. At each test point, the retention system used was 0.2 kg / t (dry) of cationic polyacrylamide and 0.2 kg / t (dry) of silica, and the addition times were 10 seconds and 7 seconds before drainage, respectively.

[0082] The drainage time was measured. After draining from the DDA, the wet sheet was removed, weighed, and then wet pressed at 4 bar for 1 minute. After wet pressing, the sheet was weighed, dried in a rapid dryer, and reweighed after drying. The wire section and press section solids content values were calculated. These values represent the dryness of the mat after vacuum dewatering and press dewatering.

[0083] As can be seen from Table 4, both the cationic crosslinked α-1,3-glucan polymer and the dextran and cationic graft copolymer of α-1,3-glucan with α-1,3-glucan improved the press section solids content, i.e., press dewatering. The cationic crosslinked α-1,3-glucan copolymer improved the vacuum dewatering, which was visible in the wire section solids content values. The low dose (0.5 kg / t) of the cationic graft copolymer improved the wire section solids content value more than the high dose (0.8 kg / t). This again indicates that there is an optimum dose for microflocculation for vacuum dewatering, which depends on the polymer used and the fiber suspension used.

[0084] Table 4. Results of Example 4.

[0085]

[0086]

[0087] Even if the present invention has been described with reference to what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not to be limited to the above-described embodiments, but rather the invention is intended to cover various modifications and equivalent technical solutions within the scope of the appended claims.

Claims

1. Use of a composition comprising a cationic biopolymer as a drainage agent and / or a dehydrating agent in the manufacture of pulp or a fibrous web comprising cellulose fibers, wherein the cationic biopolymer is selected from cationic crosslinked α-(1,3)-glucan polymers, cationic ester derivatives or ether derivatives of graft copolymers of dextran and α-1,3-glucan, or any mixture thereof.

2. The use according to claim 1, characterized in that Calculated on the dry weight of the graft copolymer before ester or ether derivatization, the cationic graft copolymer contains 10 wt% - 70 wt%, preferably 20 wt% - 60 wt%, more preferably 30 wt% - 50 wt% of dextran.

3. The use according to claim 1 or 2, characterized in that Calculated on the dry weight of the graft copolymer before ester or ether derivatization, the cationic graft copolymer contains 30 wt% - 90 wt%, preferably 40 wt% - 80 wt%, more preferably 50 wt% - 70 wt% of α-(1,3)-glucan.

4. The use according to claim 1, 2 or 3, characterized in that The cationic biopolymer is a cationic graft copolymer comprising a dextran backbone and α-(1,3)-glucan side chains.

5. The use according to any one of the preceding claims 1 - 4, characterized in that The cationic graft copolymer is crosslinked.

6. The use according to any one of the preceding claims 1 - 5, characterized in that The cationic crosslinked biopolymer is obtained by using a crosslinking agent selected from the group consisting of epihalohydrin, epoxide, diglycidyl ether, polyvalent metal, glyoxal, and polycarboxylic acid.

7. The use according to any one of the preceding claims 1 - 6, characterized in that Measured at a biopolymer concentration of 2 wt%, the cationic biopolymer has a salt viscosity of 50 - 5000 mPas, preferably 200 - 4000 mPas.

8. The use according to any one of the preceding claims 1 - 7, characterized in that The cationic biopolymer has a degree of cationic substitution of 0.05 - 1.2, preferably 0.1 - 1.0, more preferably 0.1 - 0.7, even more preferably 0.15 - 0.

6.

9. The use according to any one of the preceding claims 1 - 8, characterized in that The composition comprising the cationic biopolymer has a charge density of 0.7 - 5.0 meq / g, preferably 0.8 - 4 meq / g, more preferably 0.9 - 3.0 meq / g.

10. The use according to any one of the preceding claims 1 - 9, characterized in that The manufacture of the fibrous web includes recycling cellulose fibers and / or cellulose fibers obtained by chemical pulping or semi-chemical pulping.

11. The use according to any one of the preceding claims 1 - 10, characterized in that The composition is used in an amount of the cationic biopolymer in an amount to provide 0.1 - 0.8 kg / t, preferably 0.15 - 0.6 kg / t, more preferably 0.2 - 0.4 kg / t.

12. The use according to any one of the preceding claims 1 - 11, characterized in that The composition comprising the cationic biopolymer is added to a fiber suspension having a consistency in the range of 0.2 wt% - 20 wt%, preferably 0.3 wt% - 4 wt%, more preferably 0.3 wt% - 1.9 wt%.

13. The use according to any one of the preceding claims 1 - 12, characterized in that A retention aid system, preferably a retention aid system comprising cationic polyacrylamide, is added to the fiber suspension comprising cellulose fibers.

14. The use according to claim 13, characterized in that The retention aid system includes fine particles such as colloidal silica.

15. A method for improving dehydration and / or drainage in the manufacture of pulp or a fibrous web comprising cellulose fibers, the method comprising - obtaining a fiber suspension comprising cellulose fibers, - Adding a dehydrating agent and / or a drainage agent to the fiber suspension, the dehydrating agent and / or the drainage agent comprising a cationic biopolymer selected from cationic crosslinked α-(1,3-glucan) polymers, cationic ester derivatives or ether derivatives of dextran-grafted copolymers with α-glucan or any mixture thereof, - Forming a fiber web of pulp, paper, cardboard, etc., - Removing water from the fiber web, preferably by assisted dehydration.

16. The method according to claim 15, wherein, Water is removed from the fibrous web by assisted dewatering using one or more of the following: dewatering elements, suction boxes, and devices for press dewatering.

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