A process for producing a partially hydrolysed cellulose material

Abstract

A process for producing a partially hydrolysed cellulose material is disclosed. The process may comprise providing a cellulose material as a suspension, partially hydrolysing the cellulose material in the presence of an acid, and simultaneously mechanically treating the cellulose material so as to break fibres of the cellulose material, thereby obtaining the partially hydrolysed cellulose material.

Description

[0001] A PROCESS FOR PRODUCING A PARTIALLY HYDROLYSED CELLULOSE MATERIAL

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a process for producing a partially hydrolysed cellulose material .

[0004] BACKGROUND

[0005] Fine and ultra- fine cellulose materials , for example microcrystalline cellulose (MCC ) and other fine cellulose grades , may be used in various end applications , including pharmaceutical , medical , and food purposes , and technical applications such as fluid management , structure formation, gelation, thickening, plastic substitution, filter aiding, and so on .

[0006] However, large-scale production of such materials may involve relatively high costs . The production of such materials may often also require large amounts of energy .

[0007] SUMMARY

[0008] A process for producing a partially hydrolysed cellulose material is disclosed . The process may comprise providing a cellulose material as a suspension, partially hydrolysing the cellulose material in the presence of an acid, and simultaneously mechanically treating the cellulose material so as to break fibres of the cellulose material , thereby obtaining the partially hydrolysed cellulose material .

[0009] BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The accompanying drawings , which are included to provide a further understanding of the embodiments and constitute a part of this speci fication, illustrate various embodiments . In the drawings : Fig . 1 illustrates an embodiment of a process for producing a partially hydrolysed cellulose material .

[0011] DETAILED DESCRIPTION

[0012] A process for producing a partially hydrolysed cellulose material is disclosed .

[0013] The process may comprise providing a cellulose material as a suspension, partially hydrolysing the cellulose material in the presence of an acid, and simultaneously mechanically treating the cellulose material so as to break fibres of the cellulose material ( at least partially) , thereby obtaining the partially hydrolysed cellulose material .

[0014] The hydrolysis , catalysed by the acid, reduces the molecular weight of the cellulose in the cellulose material by breaking p- 1 , 4-glycosidic bonds of the cellulose . Mechanisms of the acid hydrolysis are illustrated in Scheme 1 below . Scheme 1 Mechanisms of acid hydrolysis of cellulose

[0015] When cellulose fibres are hydrolysed, in many processes some of the fibres do not necessarily dissolve well and therefore may not be hydrolysed ef ficiently . In the present process , during the acid hydrolysis , cellulose fibres in the cellulose material become more fragile , and the mechanical treatment may then break down the cellulose fibres . The mechanical treatment , for example when the hydrolysing and the mechanically treating are performed simultaneously in a loop reactor comprising a pump, wherein the pump circulates the cellulose material in the loop reactor during the hydrolysing, may cause mechanical shearing . The mechanical shearing simultaneously with the acid hydrolysis may accelerate the hydrolysis and thus particularly ef ficiently lead to the partial hydrolysis of the cellulose material . Degree of polymeri zation ( DP ) of the cellulose material may decrease relatively slowly during the hydrolysis , and f ibres may be ef ficiently shortened . The decrease of the DP may be evidenced by a decrease in the CED viscosity of the cellulose material that is partially hydrolysed . Further, the mechanical shearing may improve the evenness of the hydrolysis . The reaction rate may be increased; and a more even reaction may be achieved, such that a product of more uni form quality can be obtained . The solubility of the partially hydrolysed cellulose material in subsequent processes , for example in the production o f an alkal ine cellulose dope , may improve .

[0016] With the process , it is pos sible to produce large quantities of partially hydrolysed cellulose materials in a relatively cost-ef fective manner . Thus the present process can be used at an industrial scale . By selecting suitable conditions, it is possible to adjust and even tailor the properties of the partially hydrolysed cellulose material.

[0017] The process may be a continuous or a semi- continuous process.

[0018] The process may be integrated e.g. into a pulp mill .

[0019] The acid may comprise or be an inorganic or an organic acid, or any mixture or combination thereof. Sulphuric acid, hydrochloric acid, and / or phosphoric acid could be contemplated as the inorganic acid. E.g. acetic acid and / or oxalic acid could be contemplated as the organic acid. Preferably the acid may comprise or be a strong mineral acid, e.g. sulphuric acid, hydrochloric acid, or any mixture or combination thereof .

[0020] The hydrolysing and the mechanically treating may be performed simultaneously. The hydrolysing and the mechanically treating may be performed simultaneously e.g. in a loop reactor comprising a pump, wherein the pump circulates the suspension in the loop reactor during the hydrolysing. The circulating of the suspension and of the acid in the loop reactor thereby mechanically treats the cellulose material so as to break fibres of the cellulose material (at least partially) .

[0021] The cellulose material and the acid may be fed separately or simultaneously into the loop reactor, such that the hydrolysing and the mechanically treating are performed simultaneously in the loop reactor.

[0022] The pump may be a centrifugal pump. A centrifugal pump, for example a medium-consistency centrifugal pump, may be well suited for the process and obviate the need to include a separate mixer in the loop reactor. The centrifugal pump may be e.g. a centrifugal pump comprising a fluidizer. Centrifugal pumps may also operate efficiently even if the cellulose material is fed into the loop reactor at a relatively high consistency, even at a consistency of about 15 % (w / w) or higher. A medium-consistency centrifugal pump may be suitable for pumping a suspension having a consistency of about 5 - 15 %, for example 10 - 15 % (w / w) . Such consistencies may be generally considered to be medium consistencies. For example, a centrifugal pump comprising a fluidizer may be commercially available e.g. from Andritz or Sulzer.

[0023] Centrifugal pumps may also be used to feed the acid into the loop reactor. The centrifugal pump may circulate the suspension (or the mixture of the suspension and the acid) by means of the transfer of rotational energy from an impeller. The suspension (or mixture) may enter the rotating impeller axially and be cast out by centrifugal force along the circumference of the rotating impeller. The suspension (or mixture) may gain velocity and pressure while passing through the impeller .

[0024] Some centrifugal pumps, such as some mediumconsistency pumps, may comprise a first rotor provided with blades and a second rotor provided with blades, wherein the first and second rotor are arranged concentrically with each other and configured to rotate to opposite directions in relation to each other. The suspension may be supplied through the rotors such that they are repeatedly subjected to shear forces by the effect of the blades. However, the pumping efficiency of such pumps may be reduced, if such blades are included .

[0025] The cellulose material may comprise or be e.g. pulp, such as chemical pulp. The cellulose material may be obtainable from a chemical pulping process, such as a kraft (sulphate) process, sulphite process, soda process, and / or organosolv process. The cellulose material may originate e.g. from wood, cotton, agricultural material, or any mixture or combination thereof .

[0026] The cellulose material may be pretreated prior to the hydrolysing and the mechanically treating. The cellulose material may be pretreated enzymatically and / or by refining mechanically. The pretreating may increase the reactivity of the cellulose material by e.g. opening the fiber structure of the cellulose material. The cellulose material may be refined mechanically e.g. using a high shear mixer or an impact mixer, for example an impact mixer sold under the trade name Atrex® (Megatrex Oy) . Such a high shear mixer is described in WO2019 / 158814 (e.g. page 14, line 17 - p. 15, 1. 2; p. 26, 1. 12 - p. 30, 1. 25) which is herein incorporated in its entirety. Such a high shear mixer may comprise a first rotor provided with blades and a second rotor provided with blades, wherein the first and second rotor are arranged concentrically with each other and configured to rotate in opposite directions in relation to each other, and the cellulose material is supplied through the rotors such that it is repeatedly subjected to shear forces by the effect of the blades, the effect of the blades thereby forming a zone of high shear forces and thereby pretreating the cellulose material. The rotor elements may be capable of rotating at a speed of e.g. about 500 to 5000 rpm.

[0027] The acid may be present in the suspension at a concentration of about 0.1 - 2 % (w / w) ; preferably at a concentration of about 0.2 - 0.3 % (w / w) . In general, a low amount of acid may be beneficial, as then there will be less of a need to wash remaining acid off the partially hydrolysed cellulose material. However, other conditions during the hydrolysis, such as temperature and / or pressure, may affect the concentration of the acid required to achieve a desired hydrolysis; the concentration of the acid may need to be higher at low temperatures. If the cellulose material is hydrolysed in atmospheric conditions, the acid may be present in the suspension e.g. at a concentration of about 1 % (w / w) or higher.

[0028] The hydrolysing and the mechanically treating may be performed simultaneously at a temperature of at least about 95 °C, or at a temperature in the range of about 95 - 170 °C. Preferably, the hydrolysing and the mechanically treating may be performed simultaneously at a temperature of at least about 130 °C, or at a temperature in the range of about 130 - 150 °C. At such temperatures, the hydrolysis may proceed at a relatively fast rate. At a temperature in the range of about 130 - 150 °C, the acid may be present in the suspension e.g. at a concentration of about 0.2 - 0.3 % (w / w) .

[0029] The hydrolysing and the mechanically treating may be performed simultaneously at a pressure of at least about 1 bar, or at a pressure in the range of about 1 - 5 bar; preferably at a pressure of at least about 3 bar, or in the range of about 3 - 5 bar.

[0030] The temperature and / or the pressure may accelerate the acid hydrolysis of the cellulose material .

[0031] The acid may be present in the suspension at a concentration of about 0.1 - 2 % (w / w) ; and the hydrolysing and the mechanically treating may be performed simultaneously at a temperature of at least about 95 °C, or at a temperature in the range of about 95 - 170 °C, and at a pressure in the range of about 1 - 5 bar.

[0032] For example, the acid may be present in the suspension at a concentration of about 0.2 - 0.3 % (w / w) , and the hydrolysing and the mechanically treating may be performed simultaneously at a temperature of at least about 130 °C, or at a temperature in the range of about 130 - 150 °C, and at a pressure of at least about 3 bar, or in the range of about 3 - 5 bar. At relatively high temperature and pressure , autohydrolysis of cellulose and / or hemicelluloses may occur . The acid concentration in the suspension may also be af fected to some extent by the autohydrolysis . The cellulose and / or hemicelluloses may break down, thereby forming organic acids . For example , in the autohydrolysis of hemicellulose , the high temperature and pressure may lead to in-situ autoioni zation of water, which may cause the generation of hydronium ions . Acetyl residues in xylan may firstly be hydrolyzed to produce acetic acid, which may then catalyze hydrolysis of the remaining hemicelluloses . Thus the concentration of the acid present in the suspension def ined as above may be understood as referring to the concentration of acid added to the suspension ( for example , the acid fed separately or simultaneously into the loop reactor ) . It does not necessarily include any acid produced by autohydrolysis .

[0033] The hydrolysing and the mechanically treating may be performed simultaneously such that the consistency of the cellulose material in the suspension is e . g . at least about 1 % (w / w) , or in the range of about 1 - 15 % (w / w) , preferably about 5 - 15 % (w / w) . In practice , there is no practical lower limit to the consistency; however, at low consistencies , the volume of the suspension will increase , potentially increasing e . g . the si ze of the container or reactor in which the hydrolysis is performed, associated costs , etc . Consistencies close to or higher than 15 % , on the other hand, may not be easily pumpable .

[0034] The hydrolysing and the mechanically treating may be performed simultaneously for a time period of e . g about 5 - 20 minutes , preferably about 5 - 10 minutes .

[0035] The process may further comprise washing and optionally dewatering the partially hydrolysed cellulose material . Acid present in the partially hydrolysed cellulose material may need to be removed at least partially by washing and optionally dewatering the partially hydrolysed cellulose material . Acid remaining in the partially hydrolysed cellulose material may reduce the quality of the partially hydrolysed cellulose material .

[0036] The partially hydrolysed cel lulose material may be washed and optionally dewatered using e . g . a decanter centri fuge . Decanter centri fuges are particularly well suited for this , as the process may be arranged as a continuous process and adj usted in a continuous manner . This is because the decanter centri fuge may be operated and / or controlled continuously . Material losses may also be minimi zed . However, other suitable devices for washing and optionally dewatering the partially hydrolysed cellulose material could also be contemplated .

[0037] A decanter centri fuge may be considered to increase the rate of settling through the use of continuous rotation . Thus the partially hydrolysed cellulose material can be settled in a matter of seconds using a decanter centri fuge . This form of separation enables more rapid and controllable results .

[0038] Further, the partially hydrolysed cellulose material may be further mechanically treated using a decanter centri fuge . Cellulose fibers and / or fiber fragments of the partially hydrolysed cellulose materials may further be broken using the decanter centri fuge . This may be (not to be bound by theory, though) because g- forces generated in the decanter centri fuge may cause the cellulose fibers and / or fiber fragments to collide with each other, thereby breaking them further . The partially hydrolysed cellulose material may be fed into the decanter centri fuge as a suspension .

[0039] The decanter centri fuge may comprise a bowl rotatable about its longitudinal axis for separating the suspension into two fractions , i . e . a l ighter fraction and a heavier fraction, based on at least their densities due to centri fugal force , wherein the bowl includes a cylindrical portion and a frusto- conical portion at one end; a heavier fraction discharge at one end of the bowl and a l ighter fraction discharge at the other end of the bowl ; and a screw conveyor coaxially mounted for rotation within the bowl , the screw conveyor adapted to rotate at a speed relative with respect to the bowl for conveying the heavier fraction towards the heavier fraction discharge .

[0040] The speed at which the screw conveyor may be adapted to rotate relative with respect to the bowl may be adj usted such that the amount of the partially hydrolysed material that is fed into the decanter centri fuge is such that it will not clog the decanter centri fuge .

[0041] The resulting partially hydrolysed cellulose material may comprise cellulose of di f ferent particle si zes . The cellulose of di f ferent particle si zes may have varying particle si ze distributions . There may be a need to separate the partially hydrolysed cellulose material into one or more fractions containing cellulose of di f ferent particle si ze distributions .

[0042] During the hydrolysing, the concentration of the acid, the temperature and / or pressure during the hydrolysing, and / or conditions of the mechanically treating the cellulose material may be adj usted, thereby adj usting properties of the partially hydrolysed cellulose material . The properties of the partially hydrolysed cellulose material may comprise or be at least one of degree of polymeri zation, particle si ze , particle si ze distribution, or fiber length . In other words , the concentration of the acid, the temperature during the hydrolysing, and / or the conditions of the mechanically treating the cellulose material may be adj usted, thereby adj usting at least one of degree of polymeri zation, particle si ze, particle si ze distribution, or fiber length of the partially hydrolysed cellulose material .

[0043] The conditions of the hydrolysing and the mechanically treating may be selected e . g . according to the quality of the partially hydrolysed cellulose material that is desired . I f fine particles are desired as the partially hydrolysed cellulose material , and the degree of polymerization of the partially hydrolysed cellulose material is not of high importance , then a higher temperature and / or pressure may be used, for example together with mechanically treating with high mechanical shear forces . On the other hand, i f a low degree of polymerization of the partially hydrolysed cellulose material is desired, but reducing fibre length is not of high importance , then a lower temperature and / or pressure may be used, for example together with mechanically treating with lower mechanical shear forces .

[0044] With the present process , it may be possible to achieve e . g . a low degree of polymeri zation of the partially hydrolysed cellulose material without reducing the fiber length thereof too much .

[0045] The degree of polymeri zation of the partially hydrolysed cellulose material may be estimated by measuring its CED viscosity . The partially hydrolysed cellulose material may have a CED viscosity e . g . in the range of 100 - 200 ml / g, or, for some applications , 150 - 170 ml / g . The term "CED viscosity" may be understood as referring to viscosity number in cupri- ethylenediamine ( CED) solution . Cellulose material with a relatively low CED viscosity may have better solubility and may therefore allow for obtaining an alkaline cellulose dope with a higher concentration of the dissolved cellulose in the alkaline cellulose dope and / or a more stable alkaline cellulose dope . The CED viscosity may be measured e.g. according to the standard ISO 5351:2010.

[0046] The partially hydrolysed cellulose material may have e.g. a CED viscosity e.g. in the range of 100 - 200 ml / g, or, for some applications, 150 - 170 ml / g, and an average fiber length in the range of 0.15 - 1 mm. The average fiber length may be determined using e.g. a Valmet Fiber Image Analyzer FS5. The average fiber length may be a weighted average of the length of fibers as measured using an optical measurement. The measurement using the FS5 device may automatically measure the length of fibers and produce a weighted average for these. The average fiber length may be a number average fiber length. Any references to fiber length in this specification may be understood, at least in some embodiments, as referring to number average fiber length. In some embodiments, the average fiber length may be measured according to the standard ISO 16065-2.

[0047] The degree of polymerization (DP) may be estimated from the CED viscosity value obtained according to the standard ISO 5351:2010 according to: [p] is the CED viscosity value .

[0048] The process may further comprise separating the partially hydrolysed cellulose material into one or more, for example two or more, fine and / or ultrafine cellulose fractions. This may be done e.g. using a decanter centrifuge.

[0049] Fine cellulose may be understood as referring to cellulose particles having a diameter of about 10 nm or greater, typically in the micrometer range. Fine cellulose may also be referred to as fines. It may, in some embodiments, contain residual lignin and / or hemicellulose in addition to cellulose.

[0050] Ultrafine cellulose may be understood as referring to cellulose particles having a diameter of about 5 - 10 nm. Ultrafine cellulose may, in some embodiments, contain residual hemicellulose in addition to cellulose. The ultrafine cellulose may thus be understood as cellulose particles smaller than fine cellulose .

[0051] The one or more fine and / or ultrafine cellulose fractions may comprise or be one or more of microcrystalline cellulose; nanocellulose; colloidal cellulose; fines; hemicellulose; or partially hydrolysed hemicellulose.

[0052] In the context of this specification, microcrystalline cellulose (MCC) may be understood as referring to partially depolymerized cellulose derived from a a-cellulose precursor, from which mainly crystalline regions of the cellulose have been recovered. MCC may be defined as a purified, partly depolymerized cellulose prepared by treating a- cellulose, obtained as a pulp from fibrous plant material with mineral acids. MCC may have the appearance of a fine or granular powder. MCC may typically have a degree of polymerization of about 400 or lower, or about 350 or lower. MCC may typically not contain more than 10 % of cellulose particles with a particle size smaller than 5 pm. MCC may be considered to include different MCC types of e.g. different average particle sizes.

[0053] In the context of this specification, nanocellulose (NC) may be understood as encompassing cellulose nanocrystals (CNC) , nanocrystalline cellulose (NCC) and cellulose nanofibers (CNF) . CNC / NCC is in the form of particles, ultrafine for instance, and CNF is in fibril form. NCC may be in the form of particles shorter than cellulose nanofibrils (CNF) , with lengths ranging e.g. from hundreds to thousands of nanometers. Nanocrystalline cellulose (NCC) may be understood as referring to crystalline regions of cellulose derived from cellulose microcrystals, e.g. by strong acid hydrolysis at an elevated temperature. NCC may have a low aspect ratio. NCC may have e.g. a diameter of 2- 20 nm and a length of 100-600 nm.

[0054] In the context of this specification, colloidal cellulose may be understood as referring to cellulose in a colloidal state, in which it is dispersed in a medium in the form of nanocellulose or microcrystalline cellulose, with particles having a size of e.g. approximately 1 nm - 1 pm. In this state, cellulose can exhibit properties of both a solid and a liquid, making it highly adaptable for various uses. It may be used in industrial processes where its ability to form stable suspensions is required. Examples include emulsions for food and cosmetics, biomedical applications and pharmaceuticals, and barriers.

[0055] In the context of this specification, cellulose fines may be understood as referring to a cellulose pulp fraction (particles detached from cellulose fibres) that passes through a screen with a diameter of the round holes of 76 pm (e.g. T261 cm-94 TAPPI Standard method) or through a 200 mesh screen. Cellulose fines may have a diameter of 0.2 mm or smaller.

[0056] Partially hydrolysed hemicellulose may be obtainable from partial hydrolysis of hemicellulose, for example by acidic hydrolysis of pulp containing the hemicellulose .

[0057] The process may further comprise comminuting the partially hydrolysed cellulose material and / or the one or more fine and / or ultrafine cellulose fractions, optionally by milling. For example, the comminuting may be done by jet milling. The comminuting may allow for reaching a particularly fine particle size.

[0058] The process may further comprise drying the partially hydrolysed cellulose material and / or the one or more fine and / or ultrafine cellulose fractions.

[0059] The partially hydrolysed cellulose material and / or the fine and / or ultrafine cellulose fractions may be utilized in several applications, for example in textile production, films, packaging materials, biomedical applications, composite materials, barrier materials, and / or 3D printing materials.

[0060] EXAMPLES

[0061] Reference will now be made in detail to various embodiments, an example of which is illustrated in the accompanying drawings .

[0062] The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize the embodiments based on the disclosure. Not all steps or features of the embodiments are discussed in detail, as many of the steps or features will be obvious for the person skilled in the art based on this specification.

[0063] Figure 1 illustrates an embodiment of a process for producing a partially hydrolysed cellulose material 1. A cellulose material 2, such as pulp, is provided. In this exemplary embodiment, the cellulose material 2 is provided in dry form, i.e. as dry pulp, and suspended in water to obtain a suspension 3 e.g. in a repulper 4 to which water 5 is additionally fed. Thus the cellulose material 2 is provided to further stages as the suspension 3.

[0064] An acid 6 may be added to the suspension 3 prior to partially hydrolysing the cellulose material in the presence of the acid in a loop reactor 7. Thus a mixture 10 of the acid and of the suspension 3 is obtained. The mixture 10 of the acid 6 and of the suspension 3 may then be subjected to the hydrolysis in the loop reactor 7. However, alternatively or additionally, the acid 6 and the suspension 3 could be fed into the loop reactor 7 separately, thereby mixing them in the loop reactor 7 to obtain the mixture 10.

[0065] The loop reactor 7 may comprise a tank 8 in which the acid 6 and the suspension 3, i.e. the mixture 10 thereof , may be circulated during the hydrolysing . The loop reactor 7 may further comprise a pump 9 . The pump 9 may circulate the mixture 10 of the acid 6 and of the suspension 3 in the loop reactor 7 as indicated by the circular arrow . The circulation may create shear forces within the mixture 10 of the acid 6 and o f the suspension 3 , such that during the hydrolysing, the cellulose material in the mixture 10 is simultaneously mechanically treated so as to break fibres of the cellulose material . Thus the acid 6 may catalyse the partial hydrolysis of the cellulose material 2 , and simultaneously the mechanical treatment in the loop reactor 7 may break f ibres o f the cellulose material 2 at least partially, such that the partially hydrolysed cellulose material 1 may be obtained from the loop reactor 7 . Instead of the tank 8 , the loop reactor 7 could comprise e . g . a continuous tube or pipe connecting an outlet of the pump 9 to an inlet of the pump 9 .

[0066] The pump 9 may be e . g . a centri fugal pump, for example a medium-consistency centri fugal pump . In some embodiments , the acid 6 could be fed via the pump 9 to the loop reactor 7 .

[0067] The mixture 10 may be heated directly and / or indirectly . Steam 11 may be fed to the loop reactor 7 . The steam 11 may increase the temperature and / or pressure of the mixture 10 circulating in the loop reactor . Instead of , or in addition to the steam 11 , the mixture 10 may be heated e . g . using a heat exchanger or any other suitable heating system (not illustrated herein for simplicity) .

[0068] The partially hydrolysed cellulose material 1 may then be collected from the loop reactor 7 . The process may be considered to be e . g . a semi-continuous process .

[0069] At least in some embodiments , the partially hydrolysed cellulose material 1 may be further washed and optionally dewatered using suitable equipment , for example a decanter centrifuge 12. The partially hydrolysed cellulose material 1 may be fed into the decanter centrifuge 12, which is herein illustrated schematically. In this exemplary embodiment, the decanter centrifuge 12 is a horizontal-type centrifuge; however, other types could be contemplated instead. The decanter centrifuge 12 may be adapted to separate the partially hydrolysed cellulose material 1, which may be fed as a suspension, into two fractions, i.e. a heavier fraction 13 and a lighter fraction 14, based on at least their densities due to centrifugal force. The lighter fraction 14 may contain smaller cellulose particles as well as the majority of the liquid present in the suspension containing the cellulose material 1. In particular, the lighter fraction 14 may contain an acidic solution derived from the liquid present in the suspension or mixture containing the partially hydrolysed cellulose material 1. The majority of, or all of the cellulose particles contained in the partially hydrolysed cellulose material 1 may be separated in the heavier fraction 13. As a skilled person will understand, the partially hydrolysed cellulose material 1 may also be separated into one or more, e.g. two or more, fine and / or ultrafine cellulose fractions, as depicted herein as the heavier fraction 13 and the lighter fraction 14.

[0070] In some embodiments, the cellulose material 2 may be pretreated prior to the hydrolysing and the mechanically treating using a suitable pretreatment device 15 in order to obtain a pretreated cellulose material 16. The pretreated cellulose material 16 may then be e.g. suspended into the suspension 3 e.g. in the repulper 4, or it may be fed into the loop reactor 7 or otherwise subjected to the hydrolysing. The pretreatment device 15 may comprise e.g. a mechanical refiner and / or a reactor for enzymatically treating the cellulose material 2. The mechanical refiner may be e.g. a high shear mixer.

[0071] EXAMPLE 1

[0072] Pulp was hydrolysed in a reactor at a temperature of 140 °C such that 0.5 % of acid was added to the pulp suspension. No mechanical mixing or other mechanical treatment was applied during the hydrolysis.

[0073] During the hydrolysis, a relatively fast drop in degree of polymerization, evidenced by CED viscosity, without significant shortening of the fibers was observed. CED viscosity, fiber length and the proportion of fines observed in this experiment for samples obtained at different time points are shown in Table 1. The fiber length (number average fiber length) and proportion of fines were determined using a Valmet Fiber Image Analyzer FS5.

[0074] Table 1.

[0075] EXAMPLE 2

[0076] Pulp was hydrolysed in a similar manner as in Example 1, except that a high acid concentration of 1.5 % and a lower temperature of 115 °C were used with a longer hydrolysis time. Mechanical mixing was applied during the hydrolysis. During the hydrolysis , a relatively slow drop in CED viscosity with s igni ficant shortening of the fibers was observed . CED viscosity, fiber length (number average fiber length) and the proportion of fines observed in this experiment for samples obtained at di f ferent time points are shown in Table 2 .

[0077] Table 2 .

[0078] EXAMPLE 3

[0079] Pulp was hydrolysed in a similar manner as in Example 1 , except that a low acid concentration of 0 . 2 % was used with a longer hydrolysis time . No mechanical mixing or other mechanical treatment was applied during the hydrolysis .

[0080] During the hydrolysis , a relatively slow drop in CED viscosity with relatively little fines and little shortening of the fibers was observed . CED viscosity, fiber length (number average fiber length) and the proportion of fines observed in this experiment for samples obtained at di f ferent time points are shown in Table 3 . Table 3 .

[0081] It is obvious to a person skilled in the art that with the advancement of technology, the basic idea may be implemented in various ways . The embodiments are thus not limited to the examples described above ; instead they may vary within the scope of the claims .

[0082] The embodiments described hereinbefore may be used in any combination with each other . Several of the embodiments may be combined together to form a further embodiment . A process , a product , or a use , disclosed herein, may comprise at least one of the embodiments described hereinbefore . It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments . The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages . It will further be understood that reference to ' an ' item refers to one or more of those items . The term "comprising" is used in this speci fication to mean including the feature ( s ) or act ( s ) followed thereafter, without excluding the presence of one or more additional features or acts .

Claims

CLAIMS1 . A process for producing a partially hydrolysed cellulose material , wherein the process comprises providing a cellulose material as a suspension, partially hydrolysing the cellulose material in the presence of an acid, and simultaneously mechanically treating the cellulose material so as to break fibres of the cellulose material , thereby obtaining the partially hydrolysed cellulose material .2 . The process according to claim 1 , wherein the hydrolysing and the mechanically treating are performed simultaneously in a loop reactor comprising a pump, wherein the pump circulates the suspension in the loop reactor during the hydrolysing .3 . The process according to claim 2 , wherein the cellulose material and the acid are fed separately into the loop reactor, such that the hydrolysing and the mechanically treating are performed simultaneously in the loop reactor .4 . The process according to claim 2 or 3 , wherein the pump is a centri fugal pump .5 . The process according to any one of claims 1 - 4 , wherein the cellulose material is pretreated prior to the hydrolysing and the mechanically treating, wherein the cellulose material is optionally pretreated enzymatically and / or by refining mechanically .6 . The process according to any one of claims 1 - 5 , wherein the hydrolysing and the mechanically treating are performed simultaneously at a temperature of at least about 95 ° C, or at a temperature in the range of about 95 - 170 ° C .7 . The process according to any one of claims 1 - 6 , wherein the hydrolysing and the mechanically treating are performed simultaneously at a pressure ofat least about 1 bar, or at a pressure in the range of about 1 - 5 bar.

8. The process according to any one of claims 1 - 7, wherein the hydrolysing and the mechanically treating are performed simultaneously such that the consistency of the cellulose material in the suspension is in the range of about 1 - 15 % (w / w) , preferably in the range of about 5 - 15 % (w / w) .

9. The process according to any one of claims 1 - 8, wherein the the hydrolysing and the mechanically treating are performed simultaneously for a time period of about 5 - 20 minutes, preferably about 5 - 10 minutes.

10. The process according to any one of claims 1 - 9, wherein the process further comprises washing and optionally dewatering the partially hydrolysed cellulose material.

11. The process according to claim 10, wherein the partially hydrolysed cellulose material is washed and optionally dewatered using a decanter centrifuge.

12. The process according to any one of claims 1 - 11, wherein the process further comprises separating the partially hydrolysed cellulose material into one or more fine and / or ultrafine cellulose fractions.

13. The process according to any one of claims 1 - 12, wherein the one or more fine and / or ultrafine cellulose fractions comprise or are one or more of microcrystalline cellulose; nanocellulose; colloidal cellulose; fines; hemicellulose; or partially hydrolysed hemicellulose.

14. The process according to any one of claims 1 - 13, wherein the process further comprises comminuting the partially hydrolysed cellulose material and / or the one or more fine and / or ultrafine cellulose fractions, optionally by milling.

15. The process according to any one of claims 1 - 14, wherein the concentration of the acid, the temperature during the hydrolysing, and / or theconditions of the mechanically treating the cellulose material are adjusted, thereby adjusting properties of the partially hydrolysed cellulose material.

16. The process according to claim 15, wherein the properties of the partially hydrolysed cellulose material comprise or are at least one of degree of polymerization, particle size, or fiber length.

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