SE1350057A1 - Process for manufacturing microfibrillated cellulose from a precursor material - Google Patents

Abstract

ABSTRACT in the present disclosure there is provided a method of producing a high solids content microfibriilated cellulose suspension by passing aprecursor material through a homogenizer or fluidizer, thereby reducing theparticie size of the precursor material, wherein the precursor materialcomprises a particulate microcrystaliine cellulose, wherein the particies havea natural cellulose based caramelized sugar coating. Fig for pubi. : Fig. 1

Description

AWAPATENT AB Stora Enso OYJKemira Oyj Kontor/Handläggare Ansökningsnr Vår referens Linköping/Sofia Zander Jakobsson/SZJ SE-210568641 METHOD FOR THE PRODUCTION OF MICROFIBRILLATED CELLULOSEFROM A PRECURSOR MATERIAL Technical fieldThe present document relates method for producing a high solid contentsmicrofibrillated cellulose suspension from a microcrystaliine celluiosic5 precursor material.

BackgroundNanocellulose or microfibrillated cellulose (MFC) is a division of renewabie materials, which are constituted of a celluiosic structure typically10 having a diameter of 5-60 nm and a length of several micrometers. The MFC is typically produced by delamination of wood pulp by mechanical pressure before and/or after chemical or enzymatic treatment (Klemm et al. 2011).

Various applications for MFC have been proposed and reviewed suchas composite materials, rheological agents, non-caloric food additives, and 15 transparent films (Klemm et al. 2011, and Durán et al. 2012).

However the production process for the MFC, i.e. the delamination ofwood pulps, usually results in a MFC suspension having a solid contents orconcentration of about 2-4% MFC and the remaining part being water. Thefinal production cost of MFC is relatively high, and the low dry contents 20 together with the high estimated product price, forces the developmenttowards a more feasible logistic procedure, e.g. by increasing the drycontents.

MFC may be produced by passing a liquid suspension of fibrouscellulose or microcrystaliine cellulose (MCC) through a small diameter orifice 25 such as in the method disclosed in US4374702.

Alternatively the MFC may be produced by passing MCC though ahigh-pressure homogenizer to obtain a stable gel.

Conventionally these methods require the use of large amounts ofenergy, due to the homogenization, and together with the low dry solids 30 content of the MFC that is produced, this is a process which is not effectivefrom a energy and cost perspective.

There is thus a need for a new improved method of producing a highsolid contents MFC suspension.

Summaglt is an object of the present disclosure, to provide an improved method for the production of microfibrillated cellulose. A specific object of the presentdisclosure is to provide an improved method of producing MFC from amicrocrystalline cellulose precursor material, by homogenization orfluidization. The invention is based on the insight that a specificmicrocrystalline cellulose precursor material may provide for a way ofproducing a high solids content microfibrillated cellulose.

The invention is defined by the appended independent claims.Embodiments are set forth in the appended dependent claims and in thefollowing description and drawings.

According to a first aspect, there is provided a method of producing ahigh solids content microfibrillated cellulose suspension by passing aprecursor material through a homogenizer or fluidizer, thereby reducing theparticle size of the precursor material. The precursor material comprises aparticulate microcrystalline cellulose, wherein the particles have a naturalcellulose based caramelized sugar coating.

By using this new precursor material for the production ofmicrofibrillated cellulose is has surprisingly been found that a way ofachieving a high solids content MFC suspension may be obtained. By usingthis new precursor material for the production of MFC there is also provided athat method that may allow for considerable savings in energy consumptionwith up to 80% (2000 kW/t to 400 kW/t), mainly due to the higher end-productconsistency or concentration and due to the fact the precursor material iseasy to process into MFC by homogenization or fluidization techniques.Additionally, the method requires no mechanical pretreatment before high~pressure homogenizing, due to the Characteristics of the precursor material.

The precursor material may be a particulate microcrystalline celluloseproduce according to the methods described in the patent applicationsWO2011154600, WO2011154601, WO2011154599 or WO2011154597.

According to an embodiment of the first aspect of the solution, thethe precursor material may be feed into the homogenizer or fluidizer at a feedconsistency in the range of 0.1 - 30 % in dry solids content.

Due to the improved flow Characteristics of the precursor material, andthe homogeneity and particle size, a higher feed consistency than withconventional microcrystalline cellulose can be used. This means that a verybroad range of feed consistencies may be used, to achieve a broad range offinal product, i.e. in the MFC suspension obtained through the method, drysolids concentrations.

According to another embodiment of the first aspect the solid contentsof the microfibrillated cellulose suspension may be in the range of 0.1~25 % indry solids content.

Due to the more crystalline nature of the microfibrillated cellulose iteasier to achieve a high solids content after the homogenization. This, in turn,is due to the new precursor material, which may be easily processed into ahigh solids MFC suspension.

According to yet an alternative embodiment of the first aspect the highsolids content microfibrillated cellulose may be a stable gel.

According to another embodiment the homogenization and/orfluidization is performed under the influence of a pressure difference.

This means that the MFC suspension may be obtained through anymethod in which the particle size of the precursor material is reduced by usinga pressure difference. Such methods are described in the herein referencedUS4 374 702 patent or in the JP59-120638 application.

The precursor material may further be passed through a nozzle orsmall diameter orifice.

According to a second aspect there is provided a microfibrillatedcellulose obtained by the method according to the first aspect.

According to a third aspect there is provided a use of a microfibrillatedcellulose according to the second aspect for rheology applications as any oneof an emulsion agent, a suspension stabilizing agent, or fluid suspensionagent.

The rheology application may be any one of a oil drilling application, foodapplication, pharmaceutical application and cosmetic application.

According to a fourth aspect there is provided use of a microfibrillatedcellulose as claimed in claim 7, for a pulp and/or paper applications andprocesses.

According to a fifth aspect there is provided a use of the microfibrillatedcellulose according to the second aspect as any one of a reinforcing agent for 4 pulp and/or paper materials, a barrier agent, a reinforcing agent for coatingmaterials, and a composite material in paper or polymer composites.

According to a sixth aspect there is provided a use of a microfibrillatedcellulose according to the second aspect as absorption agent in any one of asanitary application, a wound dressing, and a coating agent.

According to a seventh aspect there is provided a use of themicrofibrillated cellulose according to the second aspect as a pharmaceuticalor nutraceutical excipient.

Brief Description of the DrawinqsEmbodiments of the present solution will now be described, by way ofexample, with reference to the accompanying schematic drawings.

Fig. 1 is a SEM photograph showing a 1000 times magnified surface ofpre-treated pulp.

Description of Embodiments ln the present disclosure there is provided a method for producing ahigh solids content microfibrillated cellulose. ln the method a precursor material is passed through ahomogenization or fluidization device, once or repeatedly to achieve a highsolids content MFC suspension.

The precursor material is a particulate microcrystalline cellulose havingnatural cellulose based caramelized sugar coating, that may be producedaccording to the methods described in patent applications WO2011154600,WO2011154601, WO2011154599 or WO2011154597, i.e. though a weakacid hydrolysis of cellulose.

This precursor material has shown to have excellent properties for anenergy efficient production of MFC. This is achieved by the fact that a higherinput feed consistence may be used with this new type of precursor materialthan with e.g. the regularly used fibrous cellulose material or even other typesof microcrystalline cellulose.

The precursor material may be fed into the homogenizator or fluidizerat a input feed consistency in the range of 0.1 - 30 % by weight in dry solidscontent. Preferably an input feed consistency in the range of 0.5 - 9 % byweight in dry solids, may be used, however input feed consistencies of above 10% by weight or even above 20 % by weight may be used in conventionaltype homogenizators. ln the method the new type of precursor material may be passedthrough a homogenizator or fluidizer where the pressure is aitered, wherebythe MFC may be formed by the passage through a nozzle. The precursormaterial is thus compressed in the homogenizator or fluidizer, such that theparticle size thereof, is reduced under high pressure. The precursor materialmay be passed under high pressure through a nozzie, or a hole or slots in theapparatus, and thereby forming the end product, i.e. the high solids contentmiorofibrillated cellulose suspension. Such apparatuses and methods aredescribed in for instance US 4 374 702 and JP59-120638.

The suspension formed by the homogenization or fluidization may bein a stable gel form.

The high solids content miorofibrillated cellulose thus obtainedmay be used in a variety of applications, including rheology applications as anemulsion agent, a suspension stabilizing agent, or fluid suspension agent.Therheology application may for instance of a oil drilling application, foodapplication, pharmaceutical application and cosmetic application.

The miorofibrillated cellulose may also be used as a reinforcing agentfor pulp and/or paper materials, a barrier agent, a reinforcing agent for coatingmaterials, and a composite material in paper or polymer composites or as anabsorption agent in sanitary applications, wound dressings, or coating agents.

The MFC may even further be uses a pharmaceutical or nutraceuticalexcipient.

Example EguipmentA GEA Niro Soavi PandaP|us2000 laboratory homogenizer was used to evaluate the making of MFC from different raw materials. The PandaPlus2000 is designed for 9l/hour at a maximum of 2000 bars. The flow is fixedwhile the pressure in the two homogenizing stages is manually adjusted. ln one setup, the material is feed directly through the homogenizer. Severalpasses are obtained by repeating this procedure. ln a second setup, the material that comes out from the homogenizer is fedback to the homogenizer. ln this way theoretical passes can be calculated 6 based on the running time. For example when the sample volume is 450m|and flow 9|/hour, one pass is achieved every third minute.

Material The MCC (12107) that was used had been made with acid hydrolysis , asdisclosed in WO2011050527, and had been pressed to 45% dry solids. Thesample was diluted to desired dry solids and stirred with an Ultra Thurraxblender for some minutes. Thereafter it was fed to the homogenizer.

The pre-treated pulp (12046) was treated as disclosed in WO2007091942,with enzymes and refining. The Scopper Riegler was 83.5 and the dry solids14.5%.lt was diluted to the desired dry solids and stirred for some minuteswith a propeller stirrer before homogenization. Fig. 1 illustrates a 1000 timesmagnified SEM picture of the pre-treated pulp (12046).

Results and conclusions Table 1. Tests with laboratory homogenizer using MCC as raw material. Tests1-2 and 20-22 done without recirculation.

MCC Consistency, Pressure, Time, Theoretical12107 % and run type bar min passes Comments12107-1 1,5 % 1500-1800 1, 2, 3, 4, 512107-2 3,0 % 1500-1800 1, 2, 3, 4, 512107-s :famn 1500-1800 2 0,7 :tgïšâjeparamn 001109 1 5 %12107-4 .' . 1500-1800 4 1,3 circulation12101-5 1:5 % . 1500-1800 5 circulation two batches made, first 1,5 % without problems, pressure 121070 circulation 15001000 0 0 iefi low (1200551) insecond 12107-s 1i5 % 1000 15 5 circulation 0 12107-9 šiíu/ígtion 1000 21 7 pressure only 900bar 3,0 % pressure at 1300bar, starts1210740 circulation 100011300 10 0 io be difficult :o mix 6 0 % pressure 1300max, after 712107-12 Círclflation 1600/1300 15 5 minutes not possible to mix due to high viscosity 12107-20 1,5% 1500 3, 512107-21 3% 1000 3, 512107-22 10% / 8% / 5% 2000 1, 5, 5 00000" efter each 005510 enable feeding The MCC became brighter and more viscous in all passes, which is anindication that it is disintegrated into MFC. ln test 12107-22, the material wasdiluted after each pass because the viscosity increased and the materialwould not have flowed into the homogenizer without dilution. ln bigger 5 equi ment with a suitable feedin ump, consistencies over 10% should beP 9 Ppossible.Table 2. The test points when pre-treated pulp was used.Consistency Feedmq Hømogenlzaïlon Theroetical12046 0/ pressure time, pressure, time, passes comments' ° , bar min bar min120464 115 % :âlietâjsinëgt :igrnot work due to high12046-s 1,5 % ägg" 9 1600 6 2-3512046-4 1,5 % 500 20 ieoo 9 3/1000continuouslyblocking of12046-5 1,5 % 1000 - 1600 15 5 homogenizer,could not bedone10 lt was not possible to start the homogenization at 1.5% consistency with pre- treated pulp. lnstead, the homogenization was started with water to which thepre-treated pulp was slowly added to avoid high amount of fibrous material inthe feed.

Substantial clogging and pressure variations occurred with the pre-treatedpulp, while neither occurred when MCC was used. The pre-treated pulp wasdifficult to run at 1.5% which can be compared to MCC at 10% still beingacceptable.

The MFC-gels made were all stable, if they were treated enough in thehomogenizer. At least one pass was needed.

Claims (13)

1. A method of producing a high solids content microfibrillated cellulosesuspension by passing a precursor material through a homogenizer orfluidizer, thereby reducing the particle size of the precursor materialcharacte zedinthat the precursor material comprises a particulate microcrystallinecellulose, wherein the particles have a natural cellulose based caramelizedsugarcoaflng. r i

2. The method as claimed in claim 1, wherein the precursor material isfeed into the homogenizer or fluidizer at a feed consistency in the range of 0.1 - 30 % by weight in dry solids content.

3. The method as claimed in any one of claims 1 or 2, wherein thesolid contents of the microfibrillated cellulose suspension is in the range of1-25 % in dry solids content.

4. The method as claimed in any one of claims 1-3, wherein the highsolids content microfibrillated cellulose is a stable gel.

5. The method as claimed in any one of claims 1-4, wherein thehomogenization and/or fluidization is performed under the influence of apressure difference.

6. The method as claimed in any one of claims 1-5, wherein theprecursor material is passed through a nozzle or small diameter orifice.

7. A microfibrillated cellulose obtained by the method as claimed in anyone of claims 1-6.

8. Use of a microfibrillated cellulose as claimed in claim 7 for rheologyapplications as any one of an emulsion agent, a suspension stabilizing agent,or fluid suspension agent.

9. The use as claimed in claim 8, wherein the rheology application isany one of a oil drilling application, food application, pharmaceuticalapplication and cosmetic application.

10. Use of a microfibrillated cellulose as claimed in claim 7, for a pulpand/or paper applications and processes.

11. Use of the microfibrillated cellulose as claimed in claim 7 as anyone of a reinforcing agent for pulp and/or paper materials, a barrier agent, areinforcing agent for coating materials, and a composite material in paper orpolymer composites.

12. Use of the microfibrillated cellulose as claimed in claim 7 asabsorption agent in any one of a sanitary application, a wound dressing, anda coating agent.

13. A use of the microfibrillated cellulose as claimed in claim 7 as apharmaceutical or nutraceutical excipient.