Dried non-derivatized cellulosic fiber material and process for its production

Abstract

According to one example aspect of the present application, there is provided a dried non-derivatized cellulosic fiber material comprising non-derivatized cellulosic fibers having a water retention value of at least 1.0 grams of water per gram of pulp, a curl % of less than 20%, and a curl / wide ratio of less than 1.0.

Description

Technical Field

[0001] This invention relates to cellulose fibers. In particular, this invention relates to dried, non-derived cellulose fiber materials and methods for treating cellulose fiber materials with deep eutectic solvent (DES), as well as the use of deep eutectic solvent as an additive in pulp manufacturing processes. Background Technology

[0002] Dried cowhide pulp is an excellent starting material for the production of a variety of wood fiber-based products. The drying process allows for cost-effective transportation and long shelf life. However, dried pulp fibers tend to aggregate and lose the porosity or openness of their fiber walls. This is explained, for example, by keratinization (Stone, JE; Scallan AM). The change is (partially) irreversible, with each rewetting-drying cycle leading to further fiber closure.

[0003] Mechanical refining is the most common industrial process for restoring the porosity of fiber walls. The more closed the fiber structure, the more difficult and energy-intensive the refining process. A closed fiber structure also reduces the fiber's accessibility and ability to absorb water. The accessibility of monomeric or polymeric chemicals to the fiber is also reduced due to the closed fiber structure.

[0004] Treatment with alkali (such as NaOH) causes the pulp fiber wall structure to swell because the increased osmotic pressure disrupts the hydrogen bonds between the protocellulose fibers that form the fiber wall. Simultaneously, during alkali treatment, hemicellulose, which keeps the fiber wall open due to its charge, is extracted from the fiber. The content of charged groups in hemicellulose is the dominant factor in fiber swelling behavior (Laine, J.; Stenius, P.). Therefore, removing hemicellulose from the pulp leads to increased fiber keratinization during drying, and when rewetting, the swelling of the fiber wall is significantly lower than in undried pulp or dried pulp fibers retaining hemicellulose (Lund et al.). Alkali treatment also increases the crimp of the pulp fibers, thus reducing their length.

[0005] Therefore, methods that keep the fiber structure open during the drying cycle are advantageous in many ways. Potential applications that benefit from an open fiber structure include, for example, paper and paperboard manufacturing, 3D molding, production of synthetic cellulose fibers, and synthesis of cellulose derivatives.

[0006] The objective of the embodiments of the present invention is to overcome at least some of the disadvantages of the prior art. Summary of the Invention

[0007] The objective of this invention is to provide a dry cellulose fiber material that is highly energy-efficient for refining. Another objective is to provide a dry cellulose fiber material that, when redispersed in water, exhibits straighter fibers and a more open cell wall structure compared to pulp fibers from typical pulping processes.

[0008] This invention is defined by the features of the independent claims. Specific embodiments are defined in the dependent claims.

[0009] According to a first aspect of the invention, a dried cellulose fiber material is provided, comprising non-derived cellulose fibers having a water retention value of at least 1.0 g water / g pulp, a crimp % of less than 20%, and a crimp % / width ratio of less than 1.0.

[0010] One or more implementations may include one or more features from the following list:

[0011] - The water retention value should be at least 1.5 g water / g pulp, or at least 2.0 g water / g pulp.

[0012] - Curl% / length ratio less than 11.0, such as less than 10.5

[0013] - Non-derived cellulose fibers have a length greater than 0.5 mm.

[0014] - Non-derived cellulose fibers have a width greater than 5 μm.

[0015] - Non-derived cellulose fibers have a tensile index of at least 80 Nm / g, for example, at least 130 Nm / g.

[0016] - Curl percentage is determined according to ISO 16065-2 standard.

[0017] - Non-derived cellulose fibers can be refined to a tensile index of at least 80 Nm / g according to EN ISO 5264-2:12 by 2000 revolutions.

[0018] According to a second aspect of the present invention, a method is provided, the method comprising:

[0019] - Provides cellulose fiber materials in the form of aqueous suspensions;

[0020] - Adding a certain amount of eutectic solvent to an aqueous suspension under non-derivative conditions to obtain a mixture comprising cellulose fiber material, water, and eutectic solvent; and

[0021] - The mixture obtained by drying.

[0022] One or more implementations may include one or more features from the following list:

[0023] - Cellulose fiber materials originate from pulping processes

[0024] - Cellulose fiber materials contain pulp that has never been dried.

[0025] The providing step includes suspending dried cellulose fibers or dried pulp in water to obtain an aqueous suspension.

[0026] The concentration of the aqueous suspension is at least 0.5%, such as 1 to 40%, such as 2 to 20%.

[0027] - Eutectic solvents cannot derivatize cellulose.

[0028] - The eutectic solvent consists of a non-derivative eutectic solvent.

[0029] - The eutectic solvent is preferably composed of a mixture of choline chloride and urea, choline chloride and imidazole, ammonium thiocyanate and urea, guanidine hydrochloride and urea, or choline chloride and dimethylurea.

[0030] - The resulting mixture contains at least 0.1%, such as at least 1%, for example 5 to 50% eutectic solvent, calculated by the total volume of water.

[0031] - The resulting mixture contains less than 70%, if less than 50%, or if less than 30%, of eutectic solvent by total volume of water.

[0032] - The concentration of the obtained mixture is 0.5-30%, such as 2-10%.

[0033] The method further includes, for example, dehydrating the mixture by filtration, pressing, or a combination thereof, to obtain a dehydrated mixture.

[0034] The drying is carried out at a temperature of at least 50°C, such as 50 to 100°C, preferably under ambient pressure.

[0035] The addition and drying steps are carried out at a temperature below 120°C.

[0036] - After the drying process, the water content of the mixture is less than 15 wt% based on the total weight of the mixture.

[0037] - After the drying process, the fibers are non-derivative.

[0038] - After drying and subsequent redispersement in water, the fiber's water retention value is at least 1.0 g water / g pulp, for example at least 1.2 or at least 1.5 g water / g pulp.

[0039] - After drying, the tensile index of the fiber is at least 15 Nm / g, preferably at least 20 Nm / g.

[0040] As a result of the method, the refinability of pulp fibers is improved.

[0041] As a result of the method, the fiber can be refined to a tensile index of at least 80 Nm / g by 2000 revolutions according to EN ISO 5264-2:12.

[0042] According to a third aspect of the present invention, a dry cellulose fiber material obtained by the method is provided.

[0043] According to a fourth aspect of the invention, the use of a deep eutectic solvent as an additive in a pulp manufacturing process, particularly in the drying step of the pulp manufacturing process, wherein the pulp is intended to be used as a raw material in a paperboard manufacturing process or a nanocellulose manufacturing process.

[0044] Advantages of the implementation method

[0045] Dry and open-structured fibers have the potential for use in a wide range of applications.

[0046] For example, some implementations can reduce the energy consumption required for refining fibers (typically in paperboard and tissue paper applications). At the same refining energy consumption, and limited, for example, by the number of revolutions in refining according to EN ISO 5264-2:12 in Papirindustriensforskningsinstitut (PFI), higher strength can be obtained without unduly increasing the fine fiber content or density.

[0047] The dry fiber, with its open fiber structure, can benefit subsequent chemical modification by improving the fiber's accessibility to modifying chemicals.

[0048] This dried fiber is therefore suitable for certain hygiene products that require high absorbency.

[0049] This dried fiber even makes it feasible to produce nanocellulose by using dried fiber as a starting material.

[0050] In some embodiments, the method of the present invention can open the fiber structure through internal fibril formation (measured by water retention value (WRV)). Fibers obtained by this method can even retain their open structure after drying.

[0051] The fibers obtained by the method can be straighter than untreated fibers and therefore have less kink, i.e., they have a lower crimp percentage.

[0052] The fibers obtained by the method can be straight after drying and have an open structure and good refinability. Detailed Implementation

[0053] In this context, the term "deep eutectic solvent" (DES) refers to a solution of Lewis or Brønsted acid and base that forms a deep eutectic mixture with a complex hydrogen bond network (which has hydrogen bond donors and hydrogen bond acceptors). DES is anhydrous and inert.

[0054] In this context, the term "non-derivative conditions" refers to conditions in which no chemical bonds, such as ester bonds, exist between the eutectic solvent or its components and the fiber.

[0055] In this context, the term "dry" means a material whose water content, calculated by the total weight of the material, is less than 20 wt%, preferably less than 15 wt%, and more preferably less than 10 wt%.

[0056] In this context, the term "water retention value" (WRV) refers to the ability of a sample of wood fibers or pulp blocks to retain water. The value can be determined according to ISO 23714:2014. It is the ratio of the mass (by weight) of water retained by a wet pulp sample after centrifugation under specified conditions to the dried mass (by weight) of the same pulp sample. The WRV value increases with increasing beating degree due to internal fibrillation, widening of small internal pores, and delamination, a process known as "swelling," which occurs simultaneously with the development of external fibrils, which also contribute to retaining additional water (Scandinavian Pulp, Paper and Board Testing Committee).

[0057] In this context, the term "crib%" refers to the crimp index, which is the length-weighted average percentage of fiber crimp. The crimp% of a fiber can be determined by FS5 analysis conforming to ISO 16065-2.

[0058] In this context, the term "never-dried pulp" refers to pulp that has not been dried to a dry matter content of more than 50 wt% after pulping (such as chemical cooking).

[0059] This embodiment describes the preparation of dried, non-derivative cellulose fibers with an open structure, which are treated with water containing a deep eutectic solvent prior to drying, and their potential applications.

[0060] According to one aspect, a dry, non-derived cellulose fiber material is provided, comprising non-derived cellulose fibers having a water retention value (WRV) of at least 1.0 g water / g pulp, a crimp % of less than 20%, and a crimp % / width ratio of less than 1.0.

[0061] The cellulose fiber materials of the present invention preferably have an open fiber structure. This is demonstrated by a higher WRV level compared to pulp fibers from typical pulping processes. Therefore, the fibers of the present invention can have a higher degree of internal fibrillation than pulp fibers from typical pulping processes. Consequently, the energy consumption required for refining the fibers (typically in paperboard and tissue paper applications) is reduced. At the same refining energy consumption, higher strength can be obtained without excessively increasing the fines or density. These fibers are generally straighter than pulp fibers from typical pulping processes, and therefore can have less kinking, i.e., a lower crimp percentage. Surprisingly, the openness of the fiber structure, the straightness of the fibers, and the higher refinability are not lost after drying, but rather all these characteristics can be retained simultaneously. The resulting cellulose fiber materials can provide benefits for chemical modification through improved accessibility and are suitable for certain absorbent hygiene products.

[0062] The water retention value (WRV) can be at least 1.5 g water / g pulp, such as 2.0 g water / g pulp.

[0063] Underformed cellulose fibers can have a length greater than 0.5 mm. "Length" refers to the maximum dimension of the fiber. Length can be measured, for example, by optical methods such as the FS5 fiber analyzer conforming to ISO 16065-2.

[0064] Underformed cellulose fibers can have a width greater than 5 μm. "Width" refers to the dimension perpendicular to the maximum dimension (i.e., length). Width can be measured, for example, by optical methods such as using an FS5 fiber analyzer conforming to ISO 16065-2.

[0065] The crimp % / width ratio can be determined by the crimp % of the non-derived cellulose fibers and the width of the non-derived cellulose fibers.

[0066] The curl % / length ratio can be less than 11.0, such as less than 10.5.

[0067] The crimp % / length ratio can be determined by the crimp % of the non-derived cellulose fibers and the width of the non-derived cellulose fibers.

[0068] The non-derived cellulose fibers of the dried, non-derived cellulose fiber material can have a tensile index of at least 80 Nm / g, for example, at least 130 Nm / g.

[0069] The non-derived cellulose fibers of the dried, non-derived cellulose fiber material can have a Scott Bond value of at least 80 Nm / g, such as at least 130 Nm / g.

[0070] Tensile index and Scott Bond can be measured using standard methods ISO 1924-2 and TAPPI T569.

[0071] The cellulose fibers of the dried, non-derived cellulose fiber material can be refined to a tensile index of at least 80 Nm / g by 2000 revolutions according to EN ISO 5264-2:12.

[0072] According to another aspect, a method is provided, comprising:

[0073] - Provides cellulose fiber materials in the form of aqueous suspensions;

[0074] - Adding a certain amount of eutectic solvent to an aqueous suspension under non-derivative conditions to obtain a mixture comprising cellulose fiber material, water, and eutectic solvent; and

[0075] - The mixture obtained by drying.

[0076] The method produces open and straight fibers by water-treating the fibers with a non-derivative deep eutectic solvent (DES) prior to drying. Therefore, higher strength can be achieved without excessively increasing the fineness or density of the fibers, while maintaining the same refining energy consumption. Fibers obtained by this method are generally straighter than untreated fibers and thus have less kinking, i.e., a lower crimp percentage. Surprisingly, the openness of the fiber structure, the straightness of the fibers, and the high strength are not lost after drying, but rather all these characteristics are retained simultaneously. Furthermore, the fibers produced by this method offer benefits for chemical modification through improved accessibility and are suitable on their own for certain absorbent hygiene products.

[0077] In some embodiments, the cellulose fiber material comprises cellulose fibers (such as wood) derived from perennial plants, for example from any broad-leaved tree, such as trees of the Betulaceae family, such as birch or aspen, trees of the Salicaceae family, eucalyptus, mixed tropical hardwoods or pine, or any combination thereof. Cellulose fibers may also be made from any coniferous tree (such as spruce or pine) or any combination thereof. Cellulose fibers may also be made from a combination of broad-leaved and coniferous trees.

[0078] In some embodiments, the cellulose fiber material comprises at least 80 wt%, such as at least 90 wt%, of cellulose fibers derived from wood, based on the total dry weight of the material. The cellulose fiber material may also comprise cellulose fibers derived from annual plants such as rice straw, reeds, rushes, bamboo, sugarcane, bagasse, or any other gramineous plant.

[0079] In some embodiments, the cellulose fiber material comprises pulp fibers derived from a typical pulping process.

[0080] Cellulose fiber materials can be derived from pulping processes.

[0081] Cellulose fibrous materials can originate from the process of processing wood-based materials (such as wood chips and / or sawdust) using conventional pulping processes to produce cellulose fibrous materials.

[0082] The pulping process may include cooking with a hot mixture of water, sodium hydroxide, and sodium sulfide, washing, bleaching, and optionally drying.

[0083] Cellulose cellulose materials may contain pulp such as paper-grade pulp. Cellulose cellulose materials may contain at least 50 wt%, such as at least 80 wt%, or at least 90 wt%, of pulp such as paper-grade pulp, or kraft pulp, based on the total dry weight of the material.

[0084] The pulp can be selected from the following: cowhide pulp, sulfite pulp, chemithermomechanical pulp, thermomechanical pulp, mechanical pulp, and any combination thereof.

[0085] Preferably, the cellulose fiber material comprises bovine pulp.

[0086] In one embodiment, the cellulose fiber material substantially does not contain any nanostructured or microstructured cellulose such as microfibrillated cellulose, nanofibrillated cellulose, cellulose microfibrils, and cellulose nanofibrils. In one embodiment, the cellulose fiber material contains less than 5 wt%, such as less than 1 wt%, of nanostructured or microstructured cellulose based on the total dry weight of the material.

[0087] Preferably, the cellulose fiber material may comprise undried pulp. Undried pulp is not dried during or after the pulping process and therefore has a higher water content than dried pulp. For example, undried pulp may have a water content greater than 10 wt%. In one embodiment, the cellulose fiber material comprises at least 50 wt%, such as at least 80 wt%, such as at least 90 wt%, of undried pulp based on the total dry weight of the material.

[0088] Alternatively or additionally, the cellulose fibrous material may comprise dried pulp. For example, the dried pulp may have a water content of less than 10 wt%. In one embodiment, the cellulose fibrous material comprises less than 20 wt%, such as less than 5 wt%, of dried pulp based on the total dry weight of the material.

[0089] Pulp that has never been dried or dried pulp can be softwood pulp or hardwood pulp.

[0090] The concentration of the aqueous suspension may be at least 0.5%, such as 1 to 40%, such as 2 to 20%.

[0091] In this method, the providing step may include suspending dried cellulose fibers or dried pulp in water to obtain an aqueous suspension.

[0092] This method may include adding a deep eutectic solvent (DES) as a liquid.

[0093] DES can be formed by weighing the DES components into a beaker, mixing the DES components, and generating a DES mixture from the mixed DES components. The DES mixture can be generated in an oven at 100°C. Afterward, the DES mixture can be heated. Alternatively, the DES mixture can be heated in an oil bath. Heating can be carried out at 100°C for 4 hours.

[0094] Preferably, the eutectic solvent cannot derivatize cellulose.

[0095] Preferably, the eutectic solvent is composed of a non-derivative eutectic solvent.

[0096] For example, DES can be a mixture of choline chloride and urea, choline chloride and imidazole, ammonium thiocyanate and urea, guanidine hydrochloride and urea, choline chloride and dimethylurea, or other such non-derivative DES systems.

[0097] The resulting mixture may contain at least 0.1%, such as at least 1%, for example 5 to 50% eutectic solvent, calculated by the total volume of water.

[0098] The resulting mixture contains less than 70%, less than 50%, or less than 30% of a deep eutectic solvent by total volume of water.

[0099] The concentration of the obtained mixture can be 0.5-30%, such as 2-10%.

[0100] The addition step may include mixing cellulose fiber material, water, and DES. Mixing can be performed using a pump or mixer (such as a static mixer or a dynamic mixer). The cellulose fiber material, water, and DES can be mixed, for example, for up to 30 minutes. Mixing can be performed at a temperature below 90°C.

[0101] Prior to the drying step, the method may further include dehydrating the mixture, for example, by filtration, pressing, or a combination thereof, to obtain a dehydrated mixture. "Dehydration" means removing at least a portion of the water from the mixture. Therefore, most of the water can be removed by filtration, and subsequent drying of the mixture thus takes less time.

[0102] After the dehydration and / or before drying, the cellulose fiber material can be washed with deionized water. The washing can be performed, for example, three times.

[0103] Drying can be carried out at a temperature of at least 50°C, such as 50 to 100°C, preferably under ambient pressure.

[0104] The addition and drying steps can be carried out at temperatures below 120°C.

[0105] After drying, the water content of the mixture can be less than 15 wt% based on the total weight of the mixture.

[0106] After drying, the fibers can be non-derivative.

[0107] After drying and subsequent redispersing in water, the water retention value of the fiber can be at least 1.0 g water / g pulp, for example at least 1.2 g water / g pulp or at least 1.5 g water / g pulp.

[0108] After drying, the tensile index of the fiber can be at least 15 Nm / g, preferably at least 20 Nm / g.

[0109] After drying, the Scott Bond of the fiber can be at least 80 Nm / g, such as at least 130 Nm / g.

[0110] As a result of this method, the refinability of the pulp fibers can be improved.

[0111] As a result of this method, the fiber can be refined to a tensile index of at least 80 Nm / g by 2000 revolutions according to EN ISO 5264-2:12.

[0112] The method may further include refining the fiber according to EN ISO 5264-2:12 after drying, preferably by refining at 2000 revolutions to a tensile index of at least 80 Nm / g.

[0113] According to another aspect, a dry cellulose fiber material was obtained by the method described above.

[0114] According to another aspect, the use of deep eutectic solvent as an additive in pulp manufacturing processes, particularly in the drying step of pulp manufacturing processes, is provided, wherein the pulp is intended to be used as a raw material, for example, in paperboard manufacturing processes or nanocellulose manufacturing processes.

[0115] DES can be used to improve the water retention value of pulp fibers.

[0116] Example

[0117] Example 1

[0118] In this example, undried bleached softwood kraft pulp was treated with DES consisting of choline chloride and urea in an aqueous system containing different DES-water ratios. First, the undried pulp was dispersed in water. DES was prepared by weighing choline chloride and urea (the DES component) in beakers, mixing the DES components, and generating a DES mixture in an oven at 100°C. The DES mixture was then heated in an oil bath at 100°C for 4 hours. The desired amounts of DES were added to the pulp dispersion to obtain samples with DES-water volume ratios of 10:90, 30:70, and 70:30. The samples were then mixed at 80°C for 30 minutes. A reference sample was treated similarly but without the addition of DES. The treated samples were filtered and then dried overnight at 80°C. The dried samples were dissociated (redispersed) in water according to EN ISO 5264-2:12, and the water retention value (WRV) was measured from the dissociated pulp samples, as shown in Table 1 below. FS5 analysis according to ISO 16065-2 was performed to determine the fiber crimp %.

[0119] Table 1. Water Retention Value (WRV) and Curl of Dissociated Pulp Samples.

[0120] Sample, DES: water volume ratio WRV after drying and redispersing WRV increase relative to reference paddle curly% 0:100 (reference) 1.14 - 24.77 % 10:90 1.39 22 % 19.03 % 30:70 1.52 33 % 18.23 % 70:30 1.57 38 % 16.25 %

[0121] Surprisingly, even the addition of a minimum amount of 10% choline chloride-urea DES to the aqueous pulp suspension treatment before drying significantly increased the WRV of both dried and redispersed pulp. In unrefined pulp, both fiber porosity and fine fiber content contributed to WRV. Since no increase in fine fiber content was observed in the choline chloride-urea-added pulp by FS5 analysis conforming to ISO 16065-2, it can be concluded that the fibers in these pulps were more open or less keratinized after drying compared to the reference pulp fibers.

[0122] Example 2

[0123] The pulp prepared as described in Example 1 was subjected to PFI refining, and hand-made sheets were prepared from the refined pulp according to EN ISO 5264-2:12. WRV was measured from the refined pulp. Tensile index and Scott Bond (a measure of the internal bond strength of paper) were measured from the hand-made sheets using standard methods ISO 1924-2 and TAPPI T569.

[0124] Surprisingly, the DES-treated and subsequently dried pulp was found to be easier to refine compared to the reference pulp. Achieving the same tensile index and Scott Bond level required fewer refinements (revolutions) compared to the reference pulp. A higher WRV level was maintained during refining, indicating that fiber openness was preserved.

[0125] Table 2. Water retention value (WRV) of refined pulp, and tensile index and Scott Bond of hand-made sheets.

[0126] Sample, DES: water volume ratio Pulping, rotation speed WRV, g / g Tensile index, Nm / g Scott Bond, Nm / g 0:100 (reference) 0 1.14 13.4 87 2000 1.69 64.4 341 4000 1.91 79.3 476 10:90 0 1.39 21.5 136 2000 1.93 80.8 491 4000 2.12 97.7 713 30:70 0 1.52 24.8 145 2000 1.93 88.5 562 4000 2.08 100.2 801 70:30 0 1.57 25.5 160 2000 1.84 78.3 539 4000 2.00 91.1 654

[0127] It should be understood that, as those skilled in the art will recognize, the embodiments disclosed herein are not limited to the specific structures, processes, or materials disclosed herein, but extend to their equivalents. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0128] Throughout this specification, references to "one embodiment" or "an embodiment" mean that a specific feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the invention. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout this specification do not necessarily refer to the same embodiment.

[0129] As used herein, various items, structural elements, constituent elements, and / or materials may be presented in public lists for convenience. However, these lists should be interpreted as if each member of the list were individually identified as a separate and unique member. Therefore, without indication to the contrary, any single member of such a list should not be interpreted as a de facto equivalent to any other member of the same list based solely on its presentation in the public group. Furthermore, various embodiments and examples of the invention may be mentioned herein along with alternatives to its various components. It should be understood that such embodiments, examples, and alternatives should not be construed as de facto equivalents to each other, but should be considered as separate and autonomous representations of the invention.

[0130] Furthermore, the described features, structures, or properties can be combined in one or more embodiments in any suitable manner. Numerous examples of specific details such as length, width, shape, etc., are provided in the following description to provide a thorough understanding of embodiments of the invention. However, those skilled in the art will recognize that the invention can be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0131] While the foregoing examples illustrate the principles of the invention in one or more specific applications, it will be apparent to those skilled in the art that numerous modifications can be made to the form, use, and implementation details without inventive effort and without departing from the principles and concepts of the invention. Therefore, the invention is not intended to be limited except for the claims set forth below.

[0132] The verbs “comprising” and “including” are used herein as open-ended restrictions, neither excluding nor requiring the presence of any unrecorded features. Unless otherwise expressly stated, the features recited in the dependent claims are freely combinable. Furthermore, it should be understood that the use of “an” or “a” (i.e., the singular form) throughout this document does not exclude the plural.

[0133] Industrial applicability

[0134] This invention is industrially applicable, at least in the manufacture of fiber compositions.

[0135] List of abbreviations

[0136] DES deep eutectic solvent

[0137] CCl choline chloride

[0138] WRV Water Retention Value

[0139] PFI Papirindustriens forskningsinstitut

[0140] Citation List

[0141] Stone, JE; Scallan AM The Influence of Drying on the PoreStructure of the Cell Wall. 1965. Consolidation of the Paper Web, Trans. of the IIIrd Fund. Res. Symp. Cambridge, 1965, (F. Bolam, ed.), pp 145–166, FRC, Manchester, 2018.

[0142] Joutsimo, O. 2004. Effect of Mechanical Treatment on Softwood KraftFibre Properties. Available: http: / / lib.tkk.fi / Diss / 2004 / isbn9512274450 / isbn9512274450.pdf

[0143] Scandinavian Pulp, Paper and Board Testing Committee. 2000. WaterRetention Value. SCAN-C 62:00.

[0144] Lund et al. J. Engineered Fibers and Fabrics, Vol 7, Issue 2 – 2012.

[0145] Laine, J.; Stenius, P.; Effect of charge on the fiber and paperproperties of bleached industrial kraft pulp, Paperi Puu 1997, 79, No 4, 257-266.

Claims

1. A dry, non-derived cellulose fiber material comprising non-derived cellulose fibers having a water retention value of at least 1.0 g water / g pulp, a crimp percentage of less than 20%, and a crimp percentage / width ratio of less than 1.

0.

2. The dried, non-derived cellulose fiber material according to claim 1, wherein, The water retention value is at least 1.5 g water / g pulp, such as at least 2.0 g water / g pulp.

3. The dried, non-derived cellulose fiber material according to any one of the preceding claims, wherein, The curl % / length ratio is less than 11.0, such as less than 10.

5.

4. The dried, non-derived cellulose fiber material according to any one of the preceding claims, wherein, The non-derived cellulose fibers have a length greater than 0.5 mm.

5. The dried, non-derived cellulose fiber material according to any one of the preceding claims, wherein, The non-derived cellulose fibers have a width greater than 5 μm.

6. The dried, non-derived cellulose fiber material according to any one of the preceding claims, wherein, The non-derived cellulose fiber has a tensile index of at least 80 Nm / g, such as at least 130 Nm / g.

7. The dried, non-derived cellulose fiber material according to any one of the preceding claims, wherein, The percentage of curl is determined according to ISO 16065-2 standard.

8. The dried, non-derived cellulose fiber material according to any one of the preceding claims, wherein, The non-derived cellulose fibers can be refined to a tensile index of at least 80 Nm / g by 2000 revolutions according to EN ISO 5264-2:

12.

9. A method comprising: - Provides cellulose fiber materials in the form of aqueous suspensions; - Adding a certain amount of eutectic solvent to an aqueous suspension under non-derivative conditions to obtain a mixture comprising cellulose fiber material, water, and eutectic solvent; and -Dry the obtained mixture to obtain a dry, non-derived cellulose fiber material.

10. The method according to claim 9, wherein, The cellulose fiber material is derived from the pulping process.

11. The method according to any one of claims 9 to 10, wherein, The cellulose fiber material comprises pulp that has never been dried.

12. The method according to any one of claims 9 to 11, wherein, The providing step includes suspending dried cellulose fibers or dried pulp in water to obtain an aqueous suspension.

13. The method according to any one of claims 9 to 12, wherein, The concentration of the aqueous suspension is at least 0.5%, such as 1 to 40%, such as 2 to 20%.

14. The method according to any one of claims 9 to 13, wherein, The deep eutectic solvent cannot derivatize cellulose.

15. The method according to any one of claims 9 to 14, wherein, The eutectic solvent is composed of a non-derivative eutectic solvent, preferably one of the following mixtures: choline chloride and urea, choline chloride and imidazole, ammonium thiocyanate and urea, guanidine hydrochloride and urea, and choline chloride and dimethylurea.

16. The method according to any one of claims 9 to 15, wherein, The resulting mixture contains at least 0.1%, such as at least 1%, for example 5 to 50% eutectic solvent, calculated by the total volume of water.

17. The method according to any one of claims 9 to 16, wherein, The resulting mixture contains less than 70%, such as less than 50%, such as less than 30% of a deep eutectic solvent by total volume of water.

18. The method according to any one of claims 9 to 17, wherein, The concentration of the obtained mixture is 0.5-30%, such as 2-10%.

19. The method according to any one of claims 9 to 18 further comprises, for example, dehydrating the mixture by filtration, pressing, or a combination thereof, to obtain a dehydrated mixture.

20. The method according to any one of claims 9 to 19, wherein, The drying is carried out at a temperature of at least 50°C, such as 50 to 100°C, preferably under ambient pressure.

21. The method according to any one of claims 9 to 20, wherein, The addition and drying steps are carried out at a temperature below 120°C.

22. The method according to any one of claims 9 to 21, wherein, After the drying process, the water content of the mixture is less than 15 wt% based on the total weight of the mixture.

23. The method according to any one of claims 9 to 22, wherein, After drying, the cellulose fibers are non-derivative.

24. The method according to any one of claims 9 to 23, wherein, After drying and subsequent redispersing in water, the water retention value of the cellulose fibers is at least 1.0 g water / g pulp, for example at least 1.2 or at least 1.5 g water / g pulp.

25. The method according to any one of claims 9 to 24, wherein, After drying, the tensile index of the cellulose fiber is at least 15 Nm / g, preferably at least 20 Nm / g.

26. The method according to any one of claims 9 to 25, wherein, As a result of the method, the refinability of the cellulose fibers in the pulp is improved.

27. The method according to any one of claims 9 to 26, wherein, As a result of the method, the cellulose fibers can be refined to a tensile index of at least 80 Nm / g by 2000 revolutions according to EN ISO 5264-2:

12.

28. A dried cellulose fiber material obtained by the method according to any one of claims 9 to 27.

29. The use of deep eutectic solvents as additives in pulp manufacturing processes, particularly in the drying step of pulp manufacturing processes, wherein... The pulp is intended to be used as a raw material, for example, in paperboard manufacturing processes or nanocellulose manufacturing processes.

30. The use according to claim 29, for improving the water retention value of the cellulose fibers in the pulp.