Method for producing alpha-1, 3-glucan fibrid-based additive, alpha-1, 3-glucan fibrid-based additive and use thereof

Abstract

The invention relates to an additive based on alpha-1, 3-glucan fibrid, comprising a mixture of alpha-1, 3-glucan fibrid and a cationically branched polymer. In a method for preparing an additive based on alpha-1, 3-glucan fibrids, a linearly uncharged alpha-1, 3-glucan is dissolved in a basic solvent to obtain an alpha-1, 3-glucan solution, and the alpha-1, 3-glucan is precipitated under acidic conditions under shear, and at the same time at least one cationic branched polymer is mixed with the alpha-1, 3-glucan fibrids to obtain the additive based on alpha-1, 3-glucan fibrids. The present invention relates to a method for preparing an alpha-1, 3-glucan-based additive comprising mixing alpha-1, 3-glucan solution with a cationic branched polymer to prepare a suspension of an alpha-1, 3-glucan-based additive comprising a mixture of alpha-1, 3-glucan fibrids and a cationic branched polymer.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for producing an additive based on alpha-1,3-glucan coagulum fibers according to the claim. Furthermore, the present invention relates to a new additive based on alpha-1,3-glucan coagulum fibers and its use. BACKGROUND

[0002] In recent years, the demand for fiber-based packaging has been increasing worldwide due to ecological motives and the growth of online shopping. To meet the demand, it would be desirable to use higher yield pulp and lower density products. These changes would reduce the demand for raw materials and lower transportation costs by lighter products. However, the production of lighter fiber-based products requires the use of more efficient dry strength additives to meet the requirements set for them. In addition, higher yield pulp such as chemi-thermomechanical pulp (~90% yield) tends to form products with poorer strength properties compared to those made from chemical pulp such as kraft pulp (~40% yield).

[0003] Generally, dry strength additives used in paper or board manufacturing are cationic high molecular weight polymers that are able to adsorb onto anionic fibers. The most commonly used additives are starch and polyacrylamide, both of which are often modified to be cationic. In the past decade, the use of microfibrillated cellulose (MFC) to improve dry strength has also received a lot of attention. The drawback of using MFC as a strength additive is the increased density and water retention of the sheet, which has a negative effect on dewatering. However, dewatering is an important aspect in the manufacture of paper or board, as it is an energy-consuming part of the production of paper or board.

[0004] Therefore, to achieve both ecological and economic benefits, there is still a continuous need to develop better additives for strengthening in the manufacture of paper or board, in order to.

[0005] Alpha-1,3-glucan is a polysaccharide found primarily in fungal cell walls. In the past, it has not been utilized industrially due to its limited commercial availability. Recently, an enzymatically engineered production pathway has been discovered to produce alpha-1,3-glucan polymers from sucrose. Alpha-1 -3-glucan has advantages similar to those of cellulose (beta-1,4-glucan), such as renewability, biodegradability, insolubility in water, high hydrogen bonding potential, rigidity, etc., while differing from cellulose in that it can be completely dissolved in sodium hydroxide, whereas cellulose requires more harsh and more expensive chemicals to dissolve. In addition, alpha-1,3-glucan is able to be dissolved and subsequently precipitated under high shear to make a product called coagulum fiber. Coagulum fibers can be produced from alpha-1,3-glucan, for example, by the method disclosed in patent publication WO 2016 / 196022. SUMMARY

[0006] The object of the present invention is to reduce or even eliminate the above-mentioned problems occurring in the prior art.

[0007] The object of the present invention is to provide a method for producing an alpha-1,3-glucan precipitation fiber based additive. In particular, the object of the present invention is to provide a method for producing an alpha-1,3-glucan precipitation fiber based additive for use in paper or paperboard manufacturing.

[0008] Further, the object of the present invention is to provide a new alpha-1,3-glucan precipitation fiber based additive and its use. In particular, the object of the present invention is an alpha-1,3-glucan precipitation fiber based additive for use in manufacturing paper or paperboard.

[0009] These objects are achieved by the present invention having the features presented in the independent claims. Some preferred embodiments of the present invention are given in the dependent claims. The features recited in the dependent claims are combinable with each other freely, unless explicitly stated otherwise.

[0010] The embodiments and advantages mentioned herein relate equally to the method according to the present invention, the alpha-1,3-glucan precipitation fiber based additive and the use, as applicable, even if not always specifically mentioned.

[0011] A typical method for producing an alpha-1,3-glucan precipitation fiber based additive according to the present invention comprises

[0012] - dissolving linear alpha-1,3-glucan in an alkaline solvent to obtain an alpha-1,3-glucan solution, - obtaining at least one cationic branched polymer, - precipitating the alpha-1,3-glucan under shear under acidic conditions and simultaneously mixing the cationic branched polymer with the alpha-1,3-glucan solution to produce a suspension of the alpha-1,3-glucan precipitation fiber based additive comprising a mixture of alpha-1,3-glucan precipitation fibers and cationic branched polymer.

[0013] A typical alpha-1,3-glucan precipitation fiber based additive according to the present invention comprises a mixture of alpha-1,3-glucan precipitation fibers and cationic branched polymer. A typical alpha-1,3-glucan precipitation fiber based additive of the present invention is produced by a method according to the present invention.

[0014] The present invention relates to a new additive based on alpha-1,3-glucan schopper fibers. It has surprisingly been found that precipitating alpha-1,3-glucan schopper fibers in the presence of a cationically branched polymer allows to produce a schopper fiber composite comprising a mixture of alpha-1,3-glucan schopper fibers and cationically branched polymer. It has been observed that cationically branched polymers, such as cationized glyoxal polyacrylamide polymers or cationically branched water-soluble dextran polymers, can be precipitated as part of the alpha-1,3-glucan schopper fiber structure, as the performance of the alpha-1,3-glucan schopper fiber based additive produced according to the method of the present invention outperforms the reference points of adding alpha-1,3-glucan schopper fibers and GPAM separately or only premixed together.

[0015] The alpha-1,3-glucan schopper fiber based additive according to the present invention can be used for the manufacture of paper or paperboard. According to an embodiment of the present invention, the alpha-1,3-glucan schopper fiber based additive can be used as a strengthening agent in the manufacture of paper or paperboard. An improved efficiency in terms of strength properties is observed without adversely affecting the dewatering performance. In particular, an improved dry strength in the manufacture of paper or paperboard has been observed without adversely affecting the dewatering performance. The alpha-1,3-glucan schopper fiber based additive produced according to the method of the present invention provides a synergistic effect of alpha-1,3-glucan schopper fibers and cationically branched polymer. Thus, the additive according to the present invention provides an improved strength efficiency in the manufacture of paper or paperboard.

[0016] According to an embodiment of the present invention, the alpha-1,3-glucan schopper fiber based additive can be used as a strengthening agent in the manufacture of paper or paperboard. Furthermore, the use of the alpha-1,3-glucan schopper fiber based additive according to the present invention enables a reduction of the use of raw materials and the realization of lighter products, thus bringing both economic and environmental benefits in the manufacture of paper or paperboard. However, the use of the alpha-1,3-glucan schopper fiber based additive according to the present invention is not limited to this use only. BRIEF DESCRIPTION OF DRAWINGS

[0017] In the following, some embodiments of the present invention will be described in detail. The accompanying drawings are part of the present description. In the drawings, Figure 1 and Figure 2 The results of the tensile strength and Z-strength tests of Example 1 are shown. The performance of the alpha-1,3-glucan schopper fiber based additive according to the present invention ("composite") was compared to the separate addition of alpha-1,3-glucan schopper fibers and GPAM, as well as to a premix of alpha-1,3-glucan schopper fibers and GPAM.

[0018] Figure 3The relationship of the improvement in tensile index GM (%) versus the change in WRV (%) for the results of Example 1 is shown.

[0019] Figure 4 The particle size distribution of Example 2 is shown.

[0020] Figure 5 The results of the tensile strength test of Example 2 are shown.

[0021] Figure 6 The relationship of the improvement in tensile index GM (%) versus the change in WRV (%) for the results of Example 2 is shown.

[0022] Figure 7 The relationship of the improvement in z-strength (%) versus the improvement in tensile index GM (%) for the results of Example 3 is shown. DETAILED DESCRIPTION

[0023] In the context of the present invention, "alpha-1,3-glucan", "a-1,3-glucan", "alpha-1,3-glucan polymer" and "a-1,3-glucan polymer" mean a polymeric structure having a polysaccharide backbone comprising D-glucose units linked together through glycosidic bonds. At least 70%, preferably at least 80%, more preferably at least 90% or 95%, sometimes even 99% or 100% of the glycosidic bonds are a-1,3-bonds. This means that in the polysaccharide backbone, the a-D-glucose units are connected to each other through carbons 1 and 3 on adjacent a-D-glucose rings. The form of the glycosidic bond can be determined by a person of ordinary skill in the art by using methods known per se, such as HNMR. 1

[0024] Alpha-1,3-glucan has advantages similar to those of cellulose (beta-1,4-glucan). However, unlike cellulose, which requires rather harsh and expensive chemical treatment to be solubilized, alpha-1,3-glucan can be easily solubilized into an alkaline solution, such as a sodium hydroxide (NaOH) solution. This property is used in the method according to the present invention.

[0025] ​In the process for producing an alpha-1,3-glucan precipitation fiber based additive according to the present application, an alpha-1,3-glucan polymer powder, typically a microcrystalline alpha-1,3-glucan polymer powder, is first dissolved in an alkaline solvent, for example in a NaOH solution, to obtain an alpha-1,3-glucan solution, also referred to as a dope. As mentioned above, the alpha-1,3-glucan polymer to be dissolved in the alkaline solvent represents a polymeric structure containing a polysaccharide backbone comprising D-glucose units linked together through glycosidic bonds. The type of alkaline solvent for the alpha-1,3-glucan can include an aqueous alkaline solution containing sodium hydroxide, potassium hydroxide, lithium hydroxide, lithium chloride / DMAC, DMSO / lithium chloride, etc. The alkaline solvent for the alpha-1,3-glucan should be miscible with the liquid used for precipitation of the precipitation fiber. After dissolving the alpha-1,3-glucan, the alpha-1,3-glucan precipitation fiber can be precipitated under acidic conditions under shear. In the process according to the present application, the alpha-1,3-glucan precipitation fiber is precipitated in the presence of a cationic branched polymer. In embodiments according to the present application, the alpha-1,3-glucan precipitation fiber is precipitated in the presence of a cationized glyoxal polyacrylamide polymer (GPAM) and / or a cationic branched glucan polymer. When the alpha-1,3-glucan is precipitated under shear under acidic conditions, the cationic branched polymer is mixed simultaneously with the alpha-1,3-glucan solution (dope) to produce a suspension of the alpha-1,3-glucan precipitation fiber based additive comprising a mixture of alpha-1,3-glucan precipitation fibers and cationic branched polymer. Precipitation under shear means that the mixture is mixed sufficiently during precipitation to produce a fibril structure. Any type of mixer can be used for the mixing. The mixing speed and the mixing duration can be adjusted as desired. When the alkaline alpha-1,3-glucan solution is neutralized under acidic conditions, the alpha-1,3-glucan precipitation fiber is precipitated. The process according to the present application allows to control the morphology of the alpha-1,3-glucan precipitation fiber based additive by controlling and / or varying process parameters. At least one of the process parameters, which can for example be selected from the group consisting of: dope concentration (amount of alpha-1,3-glucan mixed into the solvent), type of mixer, mixing speed, mixing duration, pH during precipitation, addition rate of the solvent in which the alpha-1,3-glucan is dissolved, and amount of cationic branched polymer, can be varied. By varying the process parameters, the size of the alpha-1,3-glucan precipitation fiber or the shape of the precipitation fiber can for example be varied.

[0026] In the context of this invention, the term "precipitate fiber" refers to non-particulate, fibrous, or membrane-like particles, at least one of whose three dimensions is on the order of magnitude smaller than the largest size. The formation of α-1,3-glucan precipitate fibers in the presence of a cationic branched polymer yields a precipitate fiber composite product with better quality than the sum of its components. When α-1,3-glucan precipitate fibers are formed in the presence of a cationic branched polymer, the branched cationic polymer is better retained on the precipitate fibers compared to when α-1,3-glucan and the cationic branched polymer are simply mixed together. The cationic branched polymer may even be encapsulated within the α-1,3-glucan precipitate fibers because precipitation occurs in the presence of the cationic branched polymer. The method according to the invention enables the inclusion of a cationic branched polymer in the precipitate fiber formation. In the method according to the invention, the α-1,3-glucan polymer and the cationic branched polymer form a composite structure, which is referred herein as an α-1,3-glucan-based additive comprising a mixture of α-1,3-glucan precipitating fibers and the cationic branched polymer.

[0027] In an embodiment of the invention, based on the total weight of the solution, the α-1,3-glucan solution may contain 5%-14% by weight, preferably 10%-14% by weight, and more preferably 11%-13% by weight of α-1,3-glucan.

[0028] According to the present invention, α-1,3-glucan is a linear, uncharged α-1,3-glucan polymer dissolved in an alkaline solution to produce a spinning solution and for constructing precipitated fibers. According to embodiments of the present invention, the α-1,3-glucan used in this method comprises α-1,3-glucan with a neutral charge. This means that the α-1,3-glucan polymer does not contain any charged substituents that substitute for the hydroxyl groups in the polysaccharide backbone of the polymer. The polysaccharide backbone of the α-1,3-glucan polymer is linear, i.e., it is unbranched. According to embodiments of the present invention, the α-1,3-glucan has a molecular weight of 100,000-250,000 Da.

[0029] In an embodiment of the method according to the invention, α-1,3-glucan and cationic branched polymer are mixed in a weight ratio between 10:1 and 40:1, preferably between 10:1 and 25:1, and more preferably between 15:1 and 25:1.

[0030] In the process according to the present application, the cationic branched polymer is simultaneously mixed to the alpha-1,3-glucan when the alpha-1,3-glucan is precipitated under shear in acidic conditions. By acidic conditions is meant an acidic solution. Any suitable acid can be used. According to embodiments of the present application, the acidic solution comprises sulfuric acid. According to embodiments of the present application, the alpha-1,3-glucan and the cationic branched polymer can be added to the acidic solution using any method known to the person skilled in the art. For example, direct injection into the acidic solution can be used. In embodiments according to the present application, at least a portion of the cationic branched polymer is mixed to the alpha-1,3-glucan solution prior to being provided in contact with the acidic solution or prior to being injected into the acidic solution, preferably the cationic branched polymer is mixed to the alpha-1,3-glucan solution prior to being provided in contact with the acidic solution or prior to being injected into the acidic solution. Alternatively, the alpha-1,3-glucan solution and the cationic branched polymer are simultaneously provided in contact with the acidic solution or simultaneously injected into the acidic solution. In exemplary embodiments according to the present application, a process is carried out in a continuous manner using a flow-through reactor. In a flow-through reactor, the alpha-1,3-glucan, the cationic branched polymer and the acidic solution are continuously supplied into the reactor and the alpha-1,3-glucan based precipitation fiber based additive obtained is continuously collected at the outlet. During the addition of the alpha-1,3-glucan and the cationic branched polymer in contact with the acidic solution, their mixture is subjected to shear forces and turbulent flow so that the alpha-1,3-glucan precipitation fiber is formed by precipitation.

[0031] According to embodiments of the present application, the suspension of the alpha-1,3-glucan precipitation fiber based additive comprising a mixture of alpha-1,3-glucan precipitation fiber and cationic branched polymer has a pH in the range of 1 to 6, preferably 2 to 6 or 3 to 6.

[0032] According to the present application, the cationic branched polymer can be any kind of cationic branched water-soluble polymer. In the present disclosure, branched polymer refers to a polymer having a branched structure. Branched polymers have side chains attached to the polymer backbone. Thus, branching of a polymer material occurs by replacing some of the atoms from the polymer chain with a substituent group. The substituent group can be a short or long side chain attached to the polymer backbone. There are different types of branched polymers such as graft polymers and comb polymers.

[0033] According to the present application, the cationic branched polymer comprises at least one cationic branched polymer. According to embodiments of the present application, the cationic branched polymer comprises cationized glyoxal polyacrylamide polymer (GPAM) and / or cationic branched dextran polymer. Without being bound by any theory, it is postulated that the branched polymer has a three-dimensional structure so that the precipitation fiber flocculates to form larger complexes which can be better retained in the fiber.

[0034] In embodiments according to the application, the cationic branched polymer can comprise a cationized glyoxal polyacrylamide polymer (GPAM). By cationized glyoxal polyacrylamide polymer is meant a cationic polyacrylamide polymer having pendant glyoxalated groups. In glyoxalation, a base polymer is reacted with glyoxal. The cationic polyacrylamide base polymer can be a copolymer of acrylamide and at least one cationic monomer. According to one embodiment of the application, the polyacrylamide base polymer is prepared by polymerization of acrylamide and at least one cationic monomer. The acrylamide can be acrylamide or another primary amine containing monomer such as methacrylamide, ethyl acrylamide, N-ethyl methacrylamide, N-butyl methacrylamide or N-ethyl methacrylamide, or combinations thereof. The cationic monomer can be any suitable cationic monomer typically used for such cationic GPAMs. According to one embodiment of the application, the cationic polyacrylamide base polymer can be prepared by polymerization of acrylamide and at least one cationic monomer selected from the group consisting of diallyldimethylammonium chloride (DADMAC), [3-(acrylamido)propyl]trimethylammonium chloride (APTAC) and [3-(methacrylamido)propyl]trimethylammonium chloride (MAPTAC) and combinations thereof. The cationized glyoxal polyacrylamide can comprise only one type of cationic monomer or it can comprise more than one type of cationic monomer. In embodiments according to the application, the cationized glyoxal polyacrylamide polymer comprises at least 5 mol% of cationic monomer, preferably at least 10 mol% of cationic monomer and more preferably at least 20 mol% of cationic monomer, based on the total moles of polymerizable monomers. According to embodiments of the application, the cationized glyoxal polyacrylamide polymer comprises 5-40 mol% of cationic monomer, preferably 5-25 mol% of cationic monomer, based on the total moles of polymerizable monomers.

[0035] The molecular weight of the cationic polyacrylamide base polymer prior to glycoxidation has a major contribution to the molecular weight of the final GPAM. The weight average molecular weight of the cationic polyacrylamide base polymer in the cationized glycoxidized polyacrylamide polymer can vary. According to embodiments of the present application, the weight average molecular weight of the polyacrylamide base polymer is in the range of 10,000-200,000 Da, preferably in the range of 100,000-200,000 Da. In the present disclosure, the base polymer of the cationized glycoxidized polyacrylamide polymer refers to the backbone of the polyacrylamide polymer, which is the result of the polymerization reaction of acrylamide and cationic monomers. The backbone is a substantially linear chain, and all other chains can be considered as side chains. Methods for measuring the weight average molecular weight are well known to those skilled in the art, for example, gel permeation chromatography (GPC) or size exclusion chromatography (SEC) can be used.

[0036] The cationized glycoxidized polyacrylamide polymer is water-soluble, which means that the polymer is miscible with water. When mixed with an excess of water, the polymer is preferably completely dissolved, and the obtained polymer solution is preferably substantially free of discrete polymer particles or pellets. Excess of water means that the obtained polymer solution is not a saturated solution. According to the method of the present application, a water solution of GPAM is used. In embodiments according to the present application, the water solution of GPAM comprises 2-5 wt% or 2-3 wt% of GPAM, calculated on the total weight of the solution.

[0037] In another exemplary embodiment according to the present application, the cationic branched polymer can comprise one or more cationic branched dextran polymers. The cationic branched dextran polymer can comprise cationic cross-linked a-1,3-dextran polymers, cationic graft copolymers of dextran and a-1,3-dextran, and any mixture thereof.

[0038] The cationic cross-linked a-1,3-glucan polymer comprises cationic substituents substituted on the hydroxyl groups of the polysaccharide backbone of the polymer. The cationic substituents of the cationic a-1,3-glucan polymer can be substituted ammonium groups, preferably quaternary ammonium groups, more preferably trialkyl ammonium groups. The alkyl groups in the trialkyl ammonium groups can be, for example, methyl, hydroxymethyl, hydroxyethyl or hydroxypropyl groups. The substituted ammonium groups can be, for example, trimethyl ammonium groups. According to one preferred embodiment of the present application, the cationic a-1,3-glucan polymer can have a charge density value in the range of 0.1 -50 peq / g, preferably 0.5-30 peq / g, more preferably 1 -10 peq / g. According to one embodiment of the present application, the cationic a-1,3-glucan polymer comprising cationic substituents attached to its structure can have a degree of substitution (DS) in the range of 0.05-1, preferably 0.05-0.75, more preferably 0.1 -0.75, even more preferably 0.15-0.5. The degree of substitution refers to the average number of hydroxyl groups per D-glucose unit in the polysaccharide backbone of the a-1,3-glucan polymer that are substituted. Since there are three hydroxyl groups in each D-glucose unit, the degree of substitution cannot be higher than 3.

[0039] The cationic cross-linked a-1,3-glucan polymer can be obtained by contacting the cationic a-1,3-glucan polymer with a cross-linking agent and a solvent, such as water. The amount of the cross-linking agent used can be 20-5000 ppm, preferably 100-5000 ppm, calculated as dry weight of the polymer. According to one embodiment, a cross-linking agent selected from the group comprising epichlorohydrin, epichlorohydrin, a diallyl ether, such as a diallyl ether or an ethylene glycol diallyl ether, a polyvalent metal, such as zirconium carbonate or cyanuric chloride, glyoxal, and a polybasic carboxylic acid, such as citric acid, glutaric acid, adipic acid, can be used.

[0040] Alternatively, the cationic branched glucan polymer suitable for use in the present application can be a cationic ester derivative or ether derivative of a graft copolymer of dextran and a-1,3-glucan. Suitable graft copolymer derivatives, methods for their preparation and determination of their glycosidic linkage distribution are described, for example, in WO 2021 / 247810. The degree of polymerization of the a-1,3-glucan can be in the range of 20-3000, preferably 500-2000. For example, the degree of polymerization can be in the range of 20-2000 or 55-1000. The degree of polymerization refers herein to the number of glucose units comprised within the individual side chain.

[0041] In the context of the present invention, the term "glucan" denotes an alpha-glucan, wherein at least 50%, preferably at least 60%, more preferably at least 70%, or even at least 80% or at least 90% of the glycosidic linkages are alpha-1,6-glycosidic linkages, wherein the balance to 100% is typically alpha-1,3-glycosidic linkages. The glucan has a substantially linear structure, which means that it has 0% to 5% branching prior to forming the graft copolymer with the alpha-1,3-glucan. The possible branching in the glucan itself is typically short, with a length of 1 to 3 glucose monomers.

[0042] According to one embodiment of the present invention, the cationic graft copolymer can comprise 10 to 70 wt.%, preferably 20 to 60 wt.%, more preferably 30 to 50 wt.% of glucan, calculated from the dry weight of the graft copolymer prior to ester or ether derivatization. The cationic graft copolymer can comprise, for example, 30 to 90 wt.%, preferably 40 to 80 wt.%, more preferably 50 to 70 wt.% of alpha-1,3-glucan, for example alpha-1,3-glucan side chains, calculated from the dry weight of the graft copolymer prior to ester or ether derivatization.

[0043] According to one embodiment, the cationic graft copolymer can be a cationic graft copolymer of a glucan and an alpha-1,3-glucan comprising a glucan backbone and alpha-1,3-glucan side chains, wherein preferably the side chains are attached to the glucan backbone via alpha-1,2 and / or alpha-1,3 and / or alpha-1,4 branches. These alpha-1,3-glucan side chains can comprise at least 70%, preferably at least 80%, more preferably at least 90% or at least 95%, sometimes even 99% or 100% of alpha-1,3-glycosidic linkages.

[0044] The graft copolymer derivative comprises one or more cationic groups, which are attached to the graft copolymer via an ester or ether linkage. The cationic group can comprise a substituted ammonium group, such as a primary, secondary, tertiary or quaternary ammonium group, preferably a quaternary ammonium group, more preferably a trialkylammonium group. The ammonium group can be substituted with alkyl and / or aryl groups, for example with C1-C4 alkyl groups or C6-C24 alkyl groups. One of the groups in the substituted ammonium group comprises a carbon or carbon chain, which is attached to the graft copolymer via an ether linkage or an ester linkage.

[0045] According to one embodiment of the present invention, the composition can comprise a cross-linked cationic graft copolymer of a glucan and an alpha-1,3-glucan. The cross-linking of the branched structure of the graft copolymer further modifies the three-dimensionality of the cationic biopolymer.

[0046] In a preferred embodiment of the present invention, the method of preparing an additive based on alpha-1,3-glucan flocculating fibers comprises

[0047] - dissolving linear, uncharged alpha-1,3-glucan in an alkaline solvent to obtain an alpha-1,3-glucan solution, - obtaining at least one cationically branched polymer selected from glyoxal polyacrylamide polymers (GPAM) and / or cationically branched dextran polymers, and - precipitating the alpha-1,3-glucan under shear under acidic conditions and simultaneously mixing the cationically branched polymer with the alpha-1,3-glucan solution to produce a suspension of alpha-1,3-glucan sediment fiber based additive comprising a mixture of alpha-1,3-glucan sediment fibers and cationically branched polymer.

[0048] The alpha-1,3-glucan sediment fiber based additive according to the present invention comprises a mixture of alpha-1,3-glucan sediment fibers and cationically branched polymer. In one preferred embodiment according to the present invention, the alpha-1,3-glucan sediment fiber based additive according to the present invention comprises a mixture of alpha-1,3-glucan sediment fibers and cationically branched GPAM and / or cationically branched dextran polymer. The sediment fibers have a fiber shape with an average length of 10 pm - 1 mm and a width of 200 nm - 200 pm.

[0049] According to an embodiment of the present invention, the alpha-1,3-glucan sediment fiber based additive is produced by the method according to the present invention.

[0050] According to an embodiment of the present invention, the alpha-1,3-glucan sediment fiber based additive is a suspension comprising 1 - 4 wt-%, preferably 2 - 3 wt-% of an additive comprising a mixture of alpha-1,3-glucan sediment fibers and cationically branched polymer, such as cationically branched glyoxal polyacrylamide polymer and / or cationically branched dextran polymer.

[0051] According to an embodiment of the present invention, the alpha-1,3-glucan sediment fiber based additive is used as an additive in paper or board making. In an embodiment of the present invention, the alpha-1,3-glucan sediment fiber based additive is used as a strength enhancer, preferably a dry strength enhancer, in paper or board making.

[0052] A method for increasing strength, preferably dry strength, in the manufacture of a fibrous web comprising cellulose fibers, such as in the manufacture of paper or board, according to an embodiment of the present invention, the method comprising

[0053] - obtaining a fibrous suspension comprising cellulose fibers, - adding to the fibrous suspension an alpha-1,3-glucan sediment fiber based additive according to the present invention, and - forming a fibrous web from the fibre suspension and removing water from the fibrous web.

[0054] Experimental examples

[0055] Materials

[0056] Enzyme engineered a-1,3-glucan polymer powder was provided by IFF (DuPont Nutrition and Biosciences). The a-1,3-glucan polymer was obtained as a dry powder with a dry matter content of 90 wt%.

[0057] Bleached chemi-thermomechanical pulp BCTMP (dry matter content 87 wt%) and broke paper (dry matter content 92 wt%) were obtained from Nordic pulp and paperboard manufacturer.

[0058] Glyoxal polyacrylamides with different cationicities were used in the examples: GPAM-LOW, GPAM-MED and GPAM-HIGH provided by Kemira Oyj. The different GPAMs are described in Table 1.

[0059] Table 1. GPAM products used.

[0060]

[0061] Preparation of alpha-1,3-glucan flocculating fibers and alpha-1,3-glucan flocculating fiber based additives comprising cationic branched polymers Preparation of pulp

[0062] The a-1,3-glucan coagulated fibres were manufactured by first dissolving the a-1,3-glucan polymer powder in 4-5% NaOH to obtain an 1 1 wt% a-1,3-glucan solution. The obtained a-1,3-glucan solution, referred to as the spinning dope, was mixed with a mixer (Heidolph, RZR 2102 control) for up to 15 minutes to ensure complete dissolution. About 100 g of a 1.5 wt% sulphuric acid solution was added to the reaction vessel. An IKA T 25 digital Ultra-Turrax was placed in the reaction vessel, which was set to 25000 rpm to mix the contents of the reaction vessel. The spinning dope (20 g) was injected into the reaction vessel during 20 to 30 seconds, causing the dissolved a-1,3-glucan polymer to precipitate into coagulated fibres. The lab-prepared a-1,3-glucan coagulated fibres were used as a reference in the examples, referred to as “neutral coagulated fibres” or “reference neutral coagulated fibres”.

[0063] The additives based on alpha-1,3-glucan precipitation fibers according to the present application are produced in a similar way, but the cationic branched polymer, such as a cationized glyoxal polyacrylamide polymer or a cationic branched alpha-1,3-glucan polymer, is injected into the reaction vessel simultaneously with the spinning dope.

[0064] Sheet formation

[0065] The BCTMP was hot disintegrated using a lab disintegrator (Novifibre, 45 l) in tap water at 80°C at 3.5% solid content at 500 rpm for 5 minutes, followed by a continued treatment at 1000 rpm for 25 min. The broke paper was first torn into squares of about 25 mm x 25 mm and soaked in tap water at room temperature overnight. It was then beaten with a Valley Hollander beater at 1.57% solids for 30 minutes until a Schopper-Riegler value of 25.

[0066] Measurement

[0067] Lab sheets were prepared using a DSF (Dynamic Sheet Former, Techpap). The BCTMP and broke paper were diluted to 0.5% dry substance content and the furnish containing 75% BCTMP and 25% broke paper was mixed. In addition to the additives based on alpha-1,3-glucan precipitation fibers and alpha-1 -3-glucan precipitation fibers according to the present application, silica and polyacrylamide based retention and drainage aids and cationic starch were used to more realistically simulate the process. The target grammage of the sheets was 100 g / m 2 and adjusted by varying the amount of furnish used for each test run. The pump speed of the furnish was 950 rds / min and the speed of the drum was 1250 rpm. The drainage time was set to 40 s. The sheets were pressed twice with a press roll between felt and blotter paper with a pressure of 5 bar and subsequently dried for 10 minutes at 130°C with a lab sheet dryer oven (STFI). The dried sheets were brought to a controlled climate room for conditioning before testing. The samples were conditioned in a standard climate room according to ISO 187 standard (23°C, 50% humidity) for at least 4 hours.

[0068] Figure 1

[0069] Tensile strength of paper samples was measured using a Lorentzen & Wettre Tensile Tester model 066. The samples were prepared by punching them into 20 x 15 mm strips / sample, 10 in the machine direction and 10 in the cross direction. The measurement method was based on the ISO 1924-3 standard, but the samples were measured using a test speed of 12 mm / min.

[0070] Z-directional strength of paper samples was measured using a Lorentzen & Wettre ZD Tensile Tester, with 3M Type ST-415 tape. The method was based on the ISO 15754:2009 standard.

[0071] Water retention value (WRV) was used as a test method to approximate the effect of the a-1,3-glucan-based additive according to the application on paper wet press solids. The dry matter content after pressing, i.e. the amount of water that can be removed mechanically from the paper material, is an important feature. Removing water from the sheet mechanically is much more energy efficient than drying with heat. The method used was a modified version of the traditional WRV measurement, where 90% of bleached kraft pulp was combined with 10% of the a-1,3-glucan-based additive according to the application / a-1,3-glucan coagulant fiber / reference (without coagulant fiber). First, 9.67 g of 30.7 wt% pulp was mixed thoroughly with 16.5 grams of 2% of the a-1,3-glucan-based additive according to the application / a-1,3-glucan coagulant fiber / reference in a plastic bag. The bag was immersed in a 50°C water bath for 5 minutes before the material was portioned into 4 centrifuge tubes. Next, the centrifuge tubes were centrifuged at 3000 G for 15 minutes at 23°C. The filter cake was then removed from the centrifuge tubes and immediately weighed. Finally, the filter cake was dried at 105°C for at least 4 h before the final dry filter cake was weighed.

[0072] Particle size distribution of different samples was measured using a Malvern Mastersizer 2000. The samples were diluted in deionized water and measured using a dispersant refractive index of 1.33, a sample refractive index of 1.59 and an absorption coefficient of 0.01. Mie theory was used for describing the results.

[0073] Example 1 : Performance of the a-1,3-glucan coagulant fiber-based additive according to the application relative to separate addition of a-1,3-glucan coagulant fiber and GPAM and relative to a premix of a-1,3-glucan coagulant fiber and GPAM

[0074] The performance of the alpha-1,3-glucan precipitation fiber based additive comprising alpha-1,3-glucan precipitation fiber and cationized glyoxal polyacrylamide (GPAM) according to the present application was tested in relation to the separate addition of alpha-1,3-glucan precipitation fiber and GPAM, and in relation to their premix. In the premix, the formed alpha-1,3-glucan precipitation fiber and GPAM were premixed together in an IKA T25 digital Ultra-Turrax at 10 000 rpm for 30 seconds before addition to the pulp.

[0075] Water retention was tested by the improved WRV method. In addition, the strength performance was evaluated by preparing and testing handsheets, wherein the alpha-1,3-glucan precipitation fiber and GPAM test points given pre-mixed or separately were used as reference.

[0076] The samples used for sheet formation are introduced in Table 2. The composite refers to the alpha-1,3-glucan precipitation fiber based additive according to the present application.

[0077] Table 2. Description of the samples used.

[0078]

[0079] Sheet formation was performed with an addition of 30 kg / ton of precipitation fiber per test point. This corresponds to an addition of 3 kg / ton, 1.5 kg / ton and 0.75 kg / ton of GPAM-MED based on different precipitation fiber to GPAM ratios. Figure 2 and Figure 1 The alpha-1,3-glucan precipitation fiber based additive according to the present application (referred to as composite in Figure 3 and 2 performs best in terms of in-plane and out-of-plane strength.

[0080] In addition to performing best in strength, the composite according to the present application also performs well in the WRV test, as they do not substantially increase the water retention compared to the neutral precipitation fiber ("reference"). Figure 4 It is shown that the composite according to the present application improves the tensile strength compared to the reference material (neutral precipitation fiber as such), as well as the separate addition of GPAM and precipitation fiber and their premix, respectively, and does not adversely affect the drainage performance.

[0081] Example 2: Performance of GPAM with different cationic degrees in the alpha-1,3-glucan precipitation fiber based additive in relation to the separate addition of alpha-1,3-glucan precipitation fiber and GPAM

[0082] The influence of the cationicity of the glyoxal polyacrylamide on the strength development of the alpha-1,3-glucan precipitation fiber based additive according to the present invention was investigated. The results were compared to reference points where the precipitation fiber and the GPAM were applied to the furnish separately. The samples are described in Table 3. Composite means the alpha-1,3-glucan precipitation fiber based additive according to the present invention.

[0083] Table 3. Description of samples

[0084] The particle size distribution of the precipitation fibers prepared from different GPAM was investigated using a pre-mixed precipitation fiber / GPAM-HIGH mixture and neutral precipitation fiber (without GPAM as reference). The particle size distribution (PSD) Figure 5 ) shows that the particle size distribution of the alpha-1,3-glucan precipitation fiber based additives is very similar. Thus, the cationicity of the GPAM does not significantly influence the precipitation. However, there is a clear difference in the size distribution between the neutral precipitation fiber, the pre-mixed precipitation fiber / GPAM and the alpha-1,3-glucan precipitation fiber based additive according to the present invention. The alpha-1,3-glucan precipitation fiber based additive according to the present invention contains more particles at larger sizes compared to the reference. This can indicate that the precipitation fibers are cross-linked into larger floes.

[0085] In the tensile strength test, the highest tensile strength was obtained with GP-HIGH, which has the highest cationicity, as can be seen in Figure 6 . The tensile strength in the separately added test points decreases with increasing cationicity of the GPAM. The trend of the composites seems to be the opposite.

[0086] Although some of the separately added references are competitive in the strength results, their water retention results are significantly worse than the water retention results of the composites. Composite means the alpha-1,3-glucan precipitation fiber based additive according to the present invention. In Figure 7 , the tensile strength is plotted against the WRV to highlight the performance of GP-HIGH. The references (0-ref) were not added with precipitation fiber or composite.

[0087] Example 3: Performance of different cationic polymers in alpha-1,3-glucan precipitation fiber based additives

[0088] In this experiment, the use of different cationic polymers (linear and branched polymers) in alpha-1,3-glucan precipitation fiber based additives was investigated. The test series contains seven different cationic polymers. The polymers and their key properties are introduced in Table 4 below.

[0089] Table 4. Description of polymers.

[0090]

[0091] The DS of the B-glucan is 0.03 and it comprises 30% glucan and 70% a-1,3-glucan.

[0092] The samples were prepared in a similar manner as the a-1,3-glucan precipitated fiber based additive comprising a-1,3-glucan precipitated fiber and cationic branched polymer as described above. The polymers were injected into the reaction vessel simultaneously with the dope. The dosage of the polymers was chosen to be similar to their conventional dosage in papermaking. The polyacrylamide based retention chemical was added in a ratio of 1 :52, which corresponds to 0.6 kg / ton added to the pulp when using a dosage of 30 kg / ton of precipitated fiber. Cationic starch, GPAM and a-1,3-glucan were dosed to the precipitated fiber composite in a ratio of 1 :20, which corresponds to 1.5 kg / ton added to the pulp. Laboratory handsheets were prepared by the method introduced above to evaluate the strength properties of these composites. The results are shown in Table 2. Figure 7 Summary of results A neutral precipitated fiber is also given as a reference in Table 2.

[0093] The a-1,3-glucan precipitated fiber based additives with branched cationic polymer additives such as GPAM and B-glucan performed better than the linear counterparts in both in-plane and out-of-plane strength.

[0094] ​

[0095] The a-1,3-glucan precipitated fiber based additives prepared according to the present invention performed better than their reference counterparts. Better performance was found in both in-plane and out-of-plane strength and water retention. The a-1,3-glucan precipitated fiber based additives were prepared in the presence of cationic branched polymers such as GPAM and / or cationic branched glucan polymers.

[0096] According to the present invention, it was found that the a-1,3-glucan precipitated fiber based additives prepared with GPAM having the highest cationicity produced the highest strength handsheets. Also, the performance of the medium cationicity product was better than the reference points where the same components were given separately or premixed. Considering the machine speed and drying cost, the furnish with the a-1,3-glucan based additives according to the present invention also had the lowest water retention value, which is another desirable property of the product. Furthermore, it was observed that the cationic branched polymers performed more desirably in the a-1,3-glucan precipitated fiber based additives of the present invention compared to the linear polymers. In summary, based on these examples, the method according to the present invention can be used to produce effective dry strength agents.​

Claims

1. A method for producing an additive based on α-1,3-glucan-precipitated fibers, characterized in that, The method includes - Linear α-1,3-glucan was dissolved in an alkaline solvent to obtain an α-1,3-glucan solution. - To obtain at least one cationic branched polymer, - Precipitate α-1,3-glucan under shear conditions in acidic conditions, while simultaneously mixing the cationic branched polymer with the α-1,3-glucan solution to produce a suspension of the additive based on α-1,3-glucan precipitated fibers, the additive comprising a mixture of α-1,3-glucan precipitated fibers and the cationic branched polymer.

2. The method according to claim 1, characterized in that, Based on the total weight of the solution, the α-1,3-glucan solution contains 5-14% by weight, preferably 10-14% by weight, and more preferably 11-13% by weight of the linear α-1,3-glucan.

3. The method according to claim 1 or 2, characterized in that, The α-1,3-glucan includes α-1,3-glucan with a neutral charge.

4. The method according to any one of the preceding claims, characterized in that, The α-1,3-glucan and the cationic branched polymer are mixed in a weight ratio between 10:1 and 40:1, preferably between 10:1 and 25:1, and more preferably between 15:1 and 25:

1.

5. The method according to any one of the preceding claims, characterized in that, At least a portion of the cationic branched polymer is mixed into the α-1,3-glucan solution before being brought into contact with the acidic solution.

6. The method according to any one of the preceding claims, characterized in that, The α-1,3-glucan solution and the cationic branched polymer simultaneously provide contact with the acidic solution.

7. The method according to any one of the preceding claims, characterized in that, The suspension of the additive based on α-1,3-glucan precipitated fibers has a pH in the range of 1-6, preferably 2-6, or 3-6, and the additive comprises a mixture of the α-1,3-glucan precipitated fibers and the cationic branched polymer.

8. The method according to any one of the preceding claims, characterized in that, The cationic branched polymer comprises a cationic glyoxal polyacrylamide polymer and / or a cationic branched dextran polymer.

9. The method according to claim 8, characterized in that, Based on the total molar number of polymerizable monomers, the cationic glyoxal polyacrylamide polymer contains at least 5 mol% cationic monomers, preferably at least 10 mol% cationic monomers, and more preferably at least 20 mol% cationic monomers.

10. The method according to claim 8 or 9, characterized in that, Based on the total molar number of polymerizable monomers, the cationic glyoxal polyacrylamide polymer contains 5-40 mol% cationic monomers.

11. The method according to any one of the preceding claims, characterized in that, The cationic branched dextran polymer comprises cationic crosslinked α-1,3-glucan polymers, graft copolymers of dextran and α-1,3-glucan, and any mixture thereof.

12. An additive based on α-1,3-glucan precipitated fibers, comprising a mixture of α-1,3-glucan precipitated fibers and a cationic branched polymer.

13. The additive according to claim 12, characterized in that, The precipitation fibers have an average length between 10 µm and 1 mm and a width between 200 nm and 200 µm.

14. The additive according to claim 12 or 13, characterized in that, The α-1,3-glucan-based additive is produced by the method according to any one of claims 1 to 11.

15. Use of the α-1,3-glucan-based additive according to any one of claims 12 to 14 as a reinforcing agent in the manufacture of paper or paperboard.

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