Uses of compositions containing cationic biopolymers

Abstract

The present invention relates to the use of a composition comprising a cationic biopolymer as a drainage and / or dewatering agent in the production of pulp or fibrous webs containing cellulose fibers. The cationic biopolymer is selected from cationic 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. The present invention also relates to a method for increasing drainage and / or dewatering in the production of pulp or fibrous webs.

Description

[Technical Field]

[0001] The present invention relates to the use of a composition comprising a cationic biopolymer and to a method for increasing dewatering and / or drainage in the production of pulp or in the production of fibrous webs according to the preambles of the independent claims presented below. [Background technology]

[0002] Dewatering is an important aspect in both the production of pulp and the production of fibrous webs such as paper and paperboard. In pulp production, water is removed from a pulp web or pulp sheet using a dewatering press, such as a twin-wire press or a shoe press. After dewatering, the pulp web can be dried in a dryer containing multiple superimposed horizontal drying levels, cut into sheets, and packaged. Alternatively, in integrated mills, the dewatered pulp is transferred by pumping directly to the stock preparation section of the paper / board machine without intermediate drying.

[0003] In the production of fibrous webs, such as paper and paperboard, water removal from the fibrous web begins immediately after its formation in the forming section. Initial water removal, or drainage, occurs by gravity, followed by dewatering using dewatering elements such as foils. Dewatering then continues in the forming section using multiple vacuum boxes to suction water from the formed web. The vacuum boxes are arranged one after the other in the machine direction, and the vacuum, or pressure drop, generated by the vacuum boxes increases in the machine direction as the web becomes drier and water removal becomes more difficult. After the forming section, the fibrous web undergoes press dewatering by mechanically pressing the wet web in the press section. Press dewatering can be carried out using a means for press dewatering, such as a shoe press or a pair of cylinders. Press dewatering increases the density of the formed web and affects its surface structure, thereby affecting the quality of the final fibrous web. After the press section, the moisture content of the fibrous web can be approximately 30 to 60% by weight. The fibrous web is then dried in a drying section, for example using heated cylinders and / or infrared radiators, to a final dryness of about 93-95% by weight.

[0004] Dewatering is an energy-consuming part of the production of pulp and fiber webs. Furthermore, efficient water removal ensures good process runnability and helps achieve good retention and uniform formation.

[0005] The drainage and dewatering efficiency of pulp or fiber webs can be improved by using various chemicals alone or in various combinations. Drainage and dewatering chemicals are typically synthetic polymers that exhibit cationic charges. However, there is growing interest in reducing the use of petroleum-based chemicals and replacing them with more sustainable alternatives. Due to growing environmental concerns, as well as regulatory and incentive policies, it is desirable 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 comparable or better drainage and dewatering effects. Because dewatering and drying are energy-intensive processes, improved drainage and dewatering can result in significant savings in energy consumption.

[0006] One of the aims of the present invention is to minimize or even eliminate the drawbacks present in the prior art.

[0007] One of the objects of the present invention is to improve drainage and / or dewatering, especially dewatering, in the production of pulp or fibrous webs such as paper, paperboard, etc.

[0008] These objects are achieved by the invention with the features set out below in the characterising parts of the independent claims. Some preferred embodiments of the invention are set out in the dependent claims. The features set out in the dependent claims can be freely combined with one another unless expressly stated otherwise. DETAILED DESCRIPTION OF THE INVENTION

[0009] A typical use of a composition comprising a cationic biopolymer according to the present invention is as a drainage and / or dewatering agent in the production of pulp or fibrous webs comprising cellulose fibers, wherein the cationic biopolymer is selected from cationic crosslinked α-1,3-glucan polymers, cationic ester or cationic ether derivatives of graft copolymers of dextran and α-1,3-glucan, or any mixture thereof.

[0010] An exemplary method according to the present invention for increasing dewatering and / or drainage in the production of a pulp or fibrous web comprising cellulose fibers comprises: obtaining a fiber suspension comprising cellulose fibers; adding a dewatering and / or draining agent to the fiber suspension, the dewatering and / or draining agent comprising a cationic biopolymer selected from cationic crosslinked α-(1,3-glucan) polymers, cationic ester or cationic ether derivatives of graft copolymers of dextran and α-glucan, or any mixture thereof; forming a fibrous web of pulp, paper, paperboard, or the like; removing water from the fibrous web, preferably by assisted dewatering; Includes.

[0011] It has now been surprisingly discovered that cationic cross-linked α-1,3-glucan polymers and cationic ester or ether derivatives of graft copolymers of dextran and α-1,3-glucan can be used as drainage and dewatering agents in the production of pulp and fibrous cellulosic webs. It is believed that cross-linked α-1,3-glucan polymers have a three-dimensional structure that provides effective interaction with fibers in pulp or fiber suspensions. This also applies to ester and ether derivatives of graft copolymers, where the three-dimensional structure is formed by side chains grafted onto the polymer backbone. Cationic cross-linked polymers and cationic graft copolymer derivatives are not only effective drainage and / or dewatering agents, but also help achieve other desirable properties, such as effective retention during dewatering and a desired solids content in the formed web. Furthermore, dewatering efficiency is achieved without compromising formation. Cationic α-1,3-glucan polymers and cationic graft copolymer derivatives can provide dewatering and / or drainage results that are acceptable, or may be as good as or better than those obtained with conventional petroleum-based polymers such as cationic polyacrylamide, glyoxylated polyacrylamide, or polyvinylamine, whereas cationic biopolymers, when used in accordance with the present invention, can significantly improve the sustainability of the final product.

[0012] Compositions containing cationic biopolymers do not cause flocculation of pulp or fiber suspensions, which means that the compositions can provide improved drainage and / or dewatering without impairing formation.

[0013] In this context, the term "drainage" refers to the removal of water by gravity from pulp or a wet fibrous web. Drainage agents improve free drainage, i.e., the removal of water by gravity from a pulp or a wet fibrous web. Mechanical water removal elements that can be used to assist free drainage include, for example, foils, blades, forming shoes, forming rolls, or forming cylinders. Drainage therefore includes the initial removal of water by gravity, e.g., in the early stages of the forming section, until a wet line is obtained, i.e., a visual change from a wet web to a dry web is observed and air begins to pass through the wet web. Typically, water removal by drainage is completed when the wet web has a dryness of 3 to 7% by weight.

[0014] The term "dewatering" refers to assisted dewatering, i.e., the assisted removal of water from pulp or a wet fibrous web. Dewatering includes both vacuum dewatering and press dewatering. After vacuum dewatering, the dryness of the pulp or fibrous web can typically increase to 13-23% by weight, preferably 14-20% by weight, and more preferably 16-22% by weight. Vacuum dewatering is typically followed by press dewatering, in which the dryness of the pulp or fibrous web increases to 40-55% by weight, preferably 43-52% by weight, and more preferably 45-50% by weight. The use of a dewatering agent can increase the dryness after vacuum dewatering by 0-5% units compared to the situation without the agent, and can increase the dryness after press dewatering by 1-5% units. In vacuum dewatering, assisted water removal can be achieved by using a vacuum of typically 15-70 kPa. The vacuum can be achieved by using a suction element such as a blower, a vacuum box, a vacuum pump, or a couch roll. In press dewatering, assisted water removal can be achieved by using a squeeze nip between cylinders or by using other mechanical dewatering means such as a shoe press, center roll press, roll press, or twin-wire press. Dewatering also includes any combination of vacuum dewatering and press dewatering, in which water is removed by using both pressure and vacuum or suction. The dewatering agent improves dewatering, i.e., water removal from the pulp or wet fibrous web by using suction and / or pressing. For vacuum dewatering, the dewatering agent preferably has the ability to provide flocculation of the fine particles of the fiber suspension without flocculation of the fibers, thus achieving high vacuum levels for good web formation and effective drying. For press dewatering, the dewatering agent preferably has the ability to neutralize the charges of negatively charged fibers, fine particles, and colloidal materials present in the pulp or wet web. Negative charges cause repulsive forces, which increase the distance between fibers, fine particles, and colloidal materials, simultaneously creating space for water.As the charges are neutralized, the distance between fibers, fine particles and colloidal materials is minimized, reducing the water binding capacity of the pulp or wet web.

[0015] According to one embodiment of the present invention, water may be removed from the pulp or from the fibrous web by assisted dewatering using one or more of a dewatering element, a vacuum box, and a means for press dewatering.

[0016] The present invention is particularly suited to improving the dewatering of pulp or wet fibrous webs such as paper, paperboard, tissue, and the like.

[0017] In this context, the term "dextran" refers to an α-glucan containing at least 50%, preferably at least 60%, more preferably at least 70%, even more preferably at least 80% or at least 90% α-1,6-glycosidic bonds, with the remainder up to 100% typically being α-1,3-glycosidic bonds. The dextran may be substantially linear, meaning that it has 0-5% branches prior to the formation of the graft copolymer with α-1,3-glucan. Any branches present in the dextran itself are typically short, 1-3 glucose monomers in length.

[0018] In the present context, "α-1,3-glucan polymer" and "α-1,3-glucan" refer to a polymeric structure having a polysaccharide backbone comprising 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 being α-1,3-linked.

[0019] The cationic biopolymer may be a cationic cross-linked α-1,3-glucan polymer. Therefore, the cationic cross-linked α-1,3-glucan polymer used in the present invention contains a cationic substituent attached to its structure. The cationic substituent may be a substituted ammonium group, preferably a quaternary ammonium group, more preferably a trialkylammonium group. Examples of the alkyl group in the trialkylammonium group include a methyl group, a hydroxymethyl group, a hydroxyethyl group, and a hydroxypropyl group. Examples of the substituted ammonium group include a trimethylammonium group. The cationic substituent of the α-1,3-glucan polymer can interact with negatively charged fibers in a manner that results in effective drainage and / or dehydration.

[0020] Crosslinked α-1,3-glucan polymers suitable for use in the present invention can be obtained by contacting an α-1,3-glucan polymer with a crosslinking agent and a solvent, such as water. The amount of crosslinking agent used can be 20 to 5,000 ppm, preferably 100 to 5,000 ppm, calculated on the dry weight of the polymer. According to one embodiment, crosslinking agents can be used that are selected from the group including epihalohydrins, such as epichlorohydrin; epoxy compounds; 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, and adipic acid.

[0021] Alternatively, cationic biopolymers suitable for use in the present invention may be cationic ester or ether derivatives of graft copolymers of dextran and α-1,3-glucan. Suitable graft copolymer derivatives, methods for their preparation, and methods for determining their glycosidic linkage profiles are described, for example, in WO 2021 / 247810. The degree of polymerization of the α-1,3-glucan may range from 20 to 3,000, preferably from 500 to 2,000. For example, the degree of polymerization may range from 20 to 2,000 or from 55 to 1,000. The degree of polymerization herein refers to the number of glucose units contained in each side chain.

[0022] According to one embodiment of the present invention, the cationic graft copolymer can contain 10 to 70% by weight, preferably 20 to 60% by weight, and more preferably 30 to 50% by weight, of dextran, calculated based on the dry weight of the graft copolymer before ester or ether derivatization. The cationic graft copolymer can contain, for example, 30 to 90% by weight, preferably 40 to 80% by weight, and more preferably 50 to 70% by weight of α-(1,3-glucan), e.g., α-1,3-glucan side chains, calculated based on the dry weight of the graft copolymer before ester or ether derivatization.

[0023] According to one embodiment, the cationic biopolymer may be a cationic graft copolymer comprising a dextran backbone and α-1,3-glucan side chains, preferably linked to the dextran backbone via α-1,2 and / or α-1,3 and / or α-1,4 branches. The α-1,3-glucan side chains may comprise at least 70%, preferably at least 80%, more preferably at least 90% or at least 95%, and sometimes 99% or 100% α-1,3-glycosidic linkages.

[0024] The graft copolymer derivatives contain one or more cationic substituents linked to the graft copolymer via ester or ether bonds. The cationic substituents may include substituted ammonium groups, such as primary, secondary, tertiary, or quaternary ammonium groups, preferably quaternary ammonium groups, and more preferably trialkylammonium groups. The ammonium groups may be substituted with alkyl and / or aryl groups, such as C1-C4 alkyl or C6-C24 alkyl groups. One of the groups in the substituted ammonium groups contains one carbon or carbon chain in an ether or ester bond to the graft copolymer.

[0025] According to one embodiment of the present invention, the composition comprises a cationic biopolymer, which may have a degree of cationic substitution ranging from 0.05 to 1.2, preferably from 0.1 to 1.0, more preferably from 0.1 to 0.7, and even more preferably from 0.15 to 0.6 or from 0.25 to 0.6. The degree of substitution refers to the average number of hydroxyl groups substituted with cationic groups via ether or ester bonds or other bonds in each glucose unit of the graft or crosslinked copolymer. This degree of substitution has been observed to provide the biopolymer with cationic properties that result in effective dewatering, particularly in the press dewatering of wet fibrous webs such as pulp or paper or paperboard. Furthermore, high cationic properties improve the water solubility of the biopolymer, which makes press dewatering more effective. However, excessive cationic properties are preferably avoided, as they may cause ecotoxicity to aquatic organisms or undesirable flocculation. Biopolymers with excessive cationic properties may also contain impurities, limiting their suitability for, for example, food contact applications.

[0026] According to one embodiment of the present invention, the composition can comprise a cross-linked cationic graft copolymer of dextran and α-1,3-glucan. Cross-linking can be achieved using the same cross-linking agent as defined above. Cross-linking of the branched structure of the graft copolymer further modifies the three-dimensionality of the cationic biopolymer.

[0027] The cationic biopolymer may have a salt viscosity of 50 to 5,000 mPas, preferably 200 to 4,000 mPas, measured at a 2 wt% biopolymer concentration. 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 certain range, the cationic biopolymer can provide effective dewatering, particularly vacuum dewatering. The size of the cationic biopolymer is believed to enable optimal flocculation, especially with fine particles in the fiber suspension. Salt viscosity is measured in the presence of salt in water at a 2 wt% biopolymer concentration as the active substance, as follows: The cationic biopolymer is first dissolved in deionized water as a 2 wt% solution as the active biopolymer. Sodium chloride (NaCl) is then added until the solution's conductivity reaches 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. Viscosity measurements are performed at the maximum possible rotation speed.

[0028] The composition containing the biopolymer may further contain other compounds or substances, for example, a salt compound, a urea compound, or a cationic synthetic polymer such as polyvinylamine or polyethyleneimine.

[0029] The composition may comprise or consist of a mixture of two or more biopolymers selected from cationic cross-linked α-1,3-glucan polymers or cationic ester or ether derivatives of graft copolymers of dextran and α-1,3-glucan. According to one preferred embodiment, the composition consists of biopolymers.

[0030] The composition containing the cationic biopolymer may have a charge density, as measured by Mutek PCD, of 0.7 to 5.0 meq / g, preferably 0.8 to 4 meq / g, and more preferably 0.9 to 3.0 meq / g. The charge density of the composition is selected to provide effective vacuum dehydration while avoiding problems associated with excessive cationicity, such as ecotoxicity to aquatic organisms.

[0031] A composition containing a cationic biopolymer selected from cationic crosslinked α-1,3-glucan polymers, cationic ester or ether derivatives of dextran and α-glucan graft copolymers, or any mixture thereof, is added to an aqueous fiber suspension to function as a drainage or dewatering agent. According to one embodiment, the composition provides the cationic biopolymer to the fiber suspension in an amount of 0.1 to 0.8 kg / t, preferably 0.15 to 0.6 kg / t, and more preferably 0.2 to 0.4 kg / t. The amounts are given as active substance.

[0032] According to one embodiment of the present invention, a composition containing a cationic biopolymer is used to improve drainage and / or dewatering, particularly dewatering, in the production of a fibrous web, such as paper or paperboard, containing or consisting of regenerated cellulose fibers. This method results in an aqueous fibrous suspension containing regenerated cellulose fibers. The regenerated fibers may be derived from recycled paper and / or old corrugated containerboard (OCC). The fibrous suspension may contain more than 20% by weight, preferably more than 50% by weight, more preferably more than 70% by weight, and even more preferably more than 80% by weight of recycled fibers, calculated based on the total dry fiber weight of the suspension. The fibrous suspension may contain 100% by weight of recycled fibers. According to a preferred embodiment, the amount of recycled fibers in the fibrous suspension may be 50-100% by weight, preferably 80-100% by weight, and more preferably 90-100% by weight.

[0033] When the aqueous fiber suspension comprises or consists of recycled fibers, the aqueous fiber suspension 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 range from 2 to 10 mS / cm, preferably from 3 to 9 mS / cm, more preferably from 3.5 to 8 mS / cm. Compositions containing biopolymers may provide improved drainage and / or dewatering even for these fiber suspensions with high conductivity.

[0034] According to one embodiment of the present invention, a composition comprising a cationic biopolymer is used to improve drainage and / or dewatering, in particular dewatering, in the production of chemical or semi-chemical pulp or in the production of fibrous webs, such as paper or paperboard, comprising or consisting of cellulose fibers obtained by chemical or semi-chemical pulping. The composition is suitable for pulp and fiber 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).

[0035] The composition containing the cationic biopolymer can be added to a fiber suspension having a consistency ranging from 0.2 to 20% by weight, preferably from 0.3 to 4% by weight, and more preferably from 0.3 to 1.9% by weight. When the composition is used as a drainage or dewatering agent in the production of fibrous webs such as paper and paperboard, the composition can be added to low-consistency raw materials having a concentration of 19 g / L or less, preferably less than 15 g / L. Typically, the fiber suspension has a consistency ranging from 5 to 19 g / L, preferably from 5 to 15 g / L, at the time of addition of the biopolymer-containing composition. When the composition containing the biopolymer is used as a drainage or dewatering agent in the production of pulp, the composition can be added to pulp having a consistency of 0.5% by weight or more, preferably 3% by weight or more, and sometimes 6% by weight or more. Typically, the fiber suspension has a consistency ranging from 0.5 to 20% by weight, preferably 3 to 15% by weight, at the time of addition of the biopolymer-containing composition.

[0036] When the composition is used as a dewatering agent in the production of pulp, the composition may be added to a fiber suspension having a concentration in the range of 4 to 20% by weight, preferably 6 to 20% by weight, more preferably 8 to 15% by weight.

[0037] When a composition containing a cationic biopolymer is used in the production of a fibrous web, such as paper or paperboard, the composition can be used in combination with other papermaking chemicals. In one embodiment of the present invention, a retention aid system, for example, a cationic synthetic polymer, preferably a cationic polyacrylamide, can be added to a fiber suspension containing cellulose fibers to optionally provide at least partial flocculation. For example, the retention aid system can include a cationic poly(meth)acrylamide obtained by polymerizing (meth)acrylamide and 5 to 15 mole % of a cationic monomer and having a weight-average molecular weight in the range of 3,000,000 to 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. The cationic synthetic polymer is preferably added before the final shear stage before the headbox of the papermaking or paperboard machine.

[0038] According to one embodiment of the present invention, the retention aid system may further comprise microparticles, preferably selected from inorganic siliceous microparticles such as colloidal silica or bentonite. The inorganic siliceous microparticles may be selected from silica-based particles, silica microgel, colloidal silica, silica sol, silica gel, polysilicates, aluminosilicates, polyaluminosilicates, borosilicates, polyborosilicates, zeolites, and swelling clays such as bentonite. Preferably, the inorganic siliceous microparticles are selected from colloidal silica or bentonite. The microparticles are added after the addition of the cationic synthetic polymer of the retention system, preferably after the final shear stage before the headbox of a paper machine or board machine. The microparticles may provide at least partial reflocculation after the final shear stage.

[0039] According to one preferred embodiment of the present invention, the composition comprising the biopolymer may be added simultaneously with the cationic polyacrylamide, optionally followed by the addition of colloidal silica microparticles. [Example]

[0040] Some embodiments of the present invention are illustrated in the following non-limiting examples.

[0041] Example 1 In Example 1, the effect of cationic derivatives of graft copolymers of dextran and α-1,3-glucan on the press dewatering of fibrous webs containing regenerated cellulose fibers was investigated.

[0042] The performance of a cationic graft copolymer derivative, i.e., a branched polymer, with a degree of substitution (DS) of 0.4 was compared with a) a cationized linear, non-crosslinked α-1,3-glucan polymer with a DS of 0.4, and b) a polyvinylamine containing 35 mol% vinylamine and 65 mol% n-vinylformamine (MW 500,000 g / mol), which is commonly used as a drainage agent in paper and board machines.

[0043] An aqueous fiber suspension of 0.3% consistency was prepared from furnish obtained from a Southern European RCF mill. The conductivity and pH of the fiber suspension were not adjusted, with a conductivity value of 6.3 mS / cm and a pH of 6.1.

[0044] A dynamic drainage analyzer (DDA) was used to study the solids content of the fibrous web after the wire section and press section, as well as the initial drainage. The DDA parameters used were: wire with 0.25 mm opening; vacuum 200 mbar; chase time 20 seconds.

[0045] 500 mL of fiber suspension was placed in a DDA vessel and mixed at 1000 rpm. The drainage aid to be tested was added 20 seconds before the start of drainage. The tested dosages, expressed as active chemicals, are shown in Table 1. The retention systems used at each test point were 0.2 kg / t cationic polyacrylamide and 0.2 kg / t (dry basis) silica, added 10 seconds and 7 seconds before drainage, respectively.

[0046] The drainage time was measured. After drainage 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 flash dryer, and reweighed after drying. Wire and press solids values ​​were calculated. These values ​​indicate the dryness of the web after vacuum dewatering and press dewatering. The results are shown in Table 1.

[0047] [Table 1]

[0048] The results in Table 1 show that the cationic graft copolymer of dextran and α-1,3-glucan produced higher press solids and wire solids compared to the reference example. In particular, the improvement in press solids was significantly higher than that obtained with the synthetic polymer (polyvinylamine). Table 1 also shows that increasing the dosage does not necessarily produce better results, as exemplified by the results for two different levels of polyvinylamine addition. There appears to be an optimal dosage for the press dewatering aid, with higher dosages producing diminishing results.

[0049] Example 2 In Example 2, the effect of cationic derivatives of graft copolymers of dextran and α-1,3-glucan on the press dewatering of fibrous webs containing recycled cellulose fibers was further investigated by repeating Example 1 but using different fiber suspensions.

[0050] The cationic graft copolymer derivative and the cationized linear non-crosslinked α-1,3-glucan were the same as those in Example 1.

[0051] In Example 2, an aqueous fiber suspension of 0.45% consistency was prepared from furnish obtained from a Southern European RCF mill. The conductivity and pH of the fiber suspension were not adjusted from a conductivity value of 4.1 mS / cm and pH 6.1.

[0052] The tested dosages of press dewatering aid, shown as active chemicals, are shown in Table 2. The holding 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. The other procedures were the same as in Example 1. The results are shown in Table 2.

[0053] [Table 2]

[0054] The results in Table 2 show that the cationic graft copolymer of dextran and α-1,3-glucan produced higher press solids and wire solids compared to the linear reference. Again, the results obtained with the linear α-1,3-glucan reference show the effect of the optimal dosage level in Table 2.

[0055] Example 3 In Example 3, the effect of a cationic graft copolymer of dextran and α-1,3-glucan on the press dewatering of a fibrous web containing regenerated cellulose fibers was studied.

[0056] The performance of two cationic graft copolymer derivatives, i.e., branched polymers, with degrees of substitution (DS) of 0.2 and 0.4 was compared with a) the performance of two cationized linear, non-crosslinked α-1,3-glucan polymers with degrees of substitution (DS) of 0.2 and 0.4, and b) the performance of polyvinylamine, which is commonly used as a drainage agent in paper and board machines.

[0057] An aqueous fiber suspension was prepared as follows: Old corrugated containerboard (OCC) from a Central European board mill was immersed in chemical water with a pH of 6.8 at 85°C for 5 minutes at a 2.5 wt% consistency. 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 reached 3 mS / cm. After immersion, the OCC was thermally disintegrated at 30,000 rpm using a laboratory disintegrator. The resulting furnish was cooled to room temperature (approximately 23°C) and diluted with the same chemical water to a 0.7 wt% consistency before the experiment.

[0058] A dynamic drainage analyzer (DDA) was used to study the solids content of the fibrous web after the wire section and press section, as well as the initial drainage. The DDA parameters used were: wire with 0.25 mm opening; vacuum 200 mbar; chase time 20 seconds.

[0059] 500 ml of the prepared fiber suspension was placed in a DDA vessel and mixed at 1000 rpm. The drainage aid to be tested was added 20 seconds before the start of drainage. The tested dosages, expressed as active chemicals, are shown in Table 3. The retention systems used at each test point were 0.2 kg / t cationic polyacrylamide and 0.2 kg / t (dry basis) silica, added 10 seconds and 7 seconds before drainage, respectively.

[0060] The drainage time was measured. After drainage 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 flash dryer, and reweighed after drying. Wire and press solids values ​​were calculated.

[0061] Table 3 shows that the cationic graft copolymer of dextran and α-1,3-glucan significantly improves press solids, i.e., press dewatering.

[0062] [Table 3]

[0063] Example 4 In Example 4, the effect of cationic cross-linked α-1,3-glucan and cationic graft copolymer of dextran and α-1,3-glucan on press dewatering of a fibrous web containing regenerated cellulose fibers was studied.

[0064] The performance 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) was compared with that of two cationized linear cross-linked α-1,3-glucan polymers with degrees of substitution (DS) of 0.3 (salt viscosity at 2%: 900 mPas) and 0.5 (salt viscosity at 2%: 26 mPas). Cationization was performed using epoxide chemistry, such as 2,3-epoxypropyltrimethylammonium chloride (EPTAC). Cationic cross-linked α-1,3-glucan polymers were prepared from α-1,3-glucan (DP1500) by adding polyethylene glycol diglycidyl ether (EDGE) as a cross-linker during the cationization step. The amount of cross-linker was adjusted to a level that resulted in an approximately three-fold increase in the Brookfield DV1 SSA viscosity of the polymer compared to the viscosity of the starting polymer at a 3% concentration and 25°C temperature.

[0065] An aqueous fiber suspension was prepared as follows: Old corrugated cardboard (OCC) from a Central European board mill, as in Example 3, was immersed in chemical water at 85°C for 5 minutes at a consistency of 2.5% by weight. After immersion, the OCC was thermally disintegrated using a laboratory disintegrator at 30,000 rpm. The resulting furnish was cooled to room temperature (approximately 23°C) and diluted with the same chemical water to a consistency of 0.7% by weight before the experiment.

[0066] A dynamic drainage analyzer (DDA) was used to study the solids content of the fibrous web after the wire section and press section, as well as the initial drainage. The DDA parameters used were: wire with 0.25 mm opening; vacuum 300 mbar; chase time 15 seconds.

[0067] 500 ml of the prepared fiber suspension was placed in a DDA vessel and mixed at 1000 rpm. The drainage aid to be tested was added 20 seconds before the start of drainage. The tested dosages, expressed as active chemicals, are shown in Table 4. The retention systems used at each test point were 0.2 kg / t (dry weight) cationic polyacrylamide and 0.2 kg / t (dry weight) silica, added 10 seconds and 7 seconds before drainage, respectively.

[0068] The drainage time was measured. After drainage 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 flash dryer, and reweighed after drying. Wire and press solids values ​​were calculated. These values ​​indicate the dryness of the web after vacuum dewatering and press dewatering.

[0069] From Table 4, it can be seen that both the cationic cross-linked α-1,3-glucan polymer and the cationic graft copolymer of dextran and α-1,3-glucan improved press solids, i.e., press dewatering. The cationic cross-linked α-1,3-glucan polymer improved vacuum dewatering, as seen in the wire solids values. The lower dosage (0.5 kg / t) of the cationic graft copolymer improved wire solids values ​​more than the higher dosage (0.8 kg / t). This again demonstrated that microfloc formation for vacuum dewatering has an optimum dosage that depends on the polymer used and the fiber suspension used.

[0070] [Table 4]

[0071] Although the present invention has been described with reference to what are currently believed to be the most practical and preferred embodiments, it is understood that the present invention is not limited to the above-described embodiments, and the present invention is intended to encompass different modifications and equivalent technical solutions within the scope of the appended claims.

Claims

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

2. 2. Use according to claim 1, characterized in that the cationic graft copolymer comprises 10 to 70% by weight, preferably 20 to 60% by weight, more preferably 30 to 50% by weight of dextran, calculated on the dry weight of the graft copolymer before ester or ether derivatization.

3. 3. Use of the composition according to claim 1 or 2, characterized in that the cationic graft copolymer comprises 30 to 90% by weight, preferably 40 to 80% by weight, more preferably 50 to 70% by weight of α-(1,3-glucan), calculated on the dry weight of the graft copolymer before ester or ether derivatization.

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. Use according to any one of claims 1 to 4, characterized in that the cationic graft copolymer is crosslinked.

6. Use according to any one of claims 1 to 5, characterized in that the cationic crosslinked biopolymer is obtained by using a crosslinking agent selected from the group comprising epihalohydrins, epoxy compounds, diglycidyl ethers, polyvalent metals, glyoxal and polycarboxylic acids.

7. 7. Use according to any one of claims 1 to 6, characterized in that the cationic biopolymer has a salt viscosity of 50 to 5000 mPas, preferably 200 to 4000 mPas, measured at a biopolymer concentration of 2% by weight.

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

6.

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

10. Use according to any one of claims 1 to 9, characterized in that the manufacture of the fibrous web comprises regenerated cellulose fibres and / or cellulose fibres obtained by chemical pulping or semi-chemical pulping.

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

12. Use according to any one of the preceding claims, characterized in that the composition comprising the cationic biopolymer is added to a fibre suspension having a consistency ranging from 0.2 to 20% by weight, preferably from 0.3 to 4% by weight, more preferably from 0.3 to 1.9% by weight.

13. Use according to any one of claims 1 to 12, characterized in that a retention aid system, preferably comprising a cationic polyacrylamide, is added to a fibre suspension comprising cellulose fibres.

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

15. obtaining a fiber suspension comprising cellulose fibers; adding a dewatering and / or draining agent to the fiber suspension, the dewatering and / or draining agent comprising a cationic biopolymer selected from cationic crosslinked α-(1,3-glucan) polymers, cationic ester or cationic ether derivatives of graft copolymers of dextran and α-glucan, or any mixture thereof; forming a fibrous web of pulp, paper, paperboard, or the like; removing water from the fibrous web, preferably by assisted dewatering; 1. A method for increasing dewatering and / or drainage in the production of a pulp or fibrous web comprising cellulose fibers, comprising:

16. 16. The method of claim 15, wherein water is removed from the fibrous web by assisted dewatering using one or more of a dewatering element, a vacuum box, and a means for press dewatering.

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