WO2014111854A1

WO2014111854A1 - Method for the production of microfibrillated cellulose from a precursor material

Info

Publication number: WO2014111854A1
Application number: PCT/IB2014/058282
Authority: WO
Inventors: Mikael Svedman; Veli-Matti Vuorenpalo; Olli Dahl; Kari Vanhatalo
Original assignee: Stora Enso Oyj; Kemira Oyj
Priority date: 2013-01-18
Filing date: 2014-01-15
Publication date: 2014-07-24
Also published as: SE1350057A1

Abstract

In the present disclosure there is provided a method of producing a high solids content microfibrillated cellulose suspension by passing a precursor material through a homogenizer or fluidizer, thereby reducing the particle size of the precursor material, wherein the precursor material comprises a particulate microcrystalline cellulose, wherein the particles have a natural cellulose based caramelized sugar coating.

Description

METHOD FOR THE PRODUCTION OF MICROFIBRILLATED CELLULOSE FROM A PRECURSOR MATERIAL

Technical field

The present document relates method for producing a high solid contents microfibrillated cellulose suspension from a microcrystalline cellulosic precursor material.

Background

Nanocellulose or microfibrillated cellulose (MFC) is a division of renewable materials, which are constituted of a cellulosic structure typically 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. 201 1).

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

However the production process for the MFC, i.e. the delamination of wood pulps, usually results in a MFC suspension having a solid contents or concentration of about 2-4% MFC and the remaining part being water. The final production cost of MFC is relatively high, and the low dry contents together with the high estimated product price, forces the development towards a more feasible logistic procedure, e.g. by increasing the dry contents.

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

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

Conventionally these methods require the use of large amounts of energy, due to the homogenization, and together with the low dry solids content of the MFC that is produced, this is a process which is not effective from a energy and cost perspective. There is thus a need for a new improved method of producing a high solid contents MFC suspension.

Summary

It is an object of the present disclosure, to provide an improved method for the production of microfibrillated cellulose. A specific object of the present disclosure is to provide an improved method of producing MFC from a microcrystalline cellulose precursor material, by homogenization or fluidization. The invention is based on the insight that a specific

microcrystalline cellulose precursor material may provide for a way of producing 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 the following description and drawings.

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

By using this new precursor material for the production of

microfibrillated cellulose is has surprisingly been found that a way of achieving a high solids content MFC suspension may be obtained. By using this new precursor material for the production of MFC there is also provided a that method that may allow for considerable savings in energy consumption with up to 80% (2000 kW/t to 400 kW/t), mainly due to the higher end-product consistency or concentration and due to the fact the precursor material is easy 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 cellulose produce according to the methods described in the patent applications WO201 1154600, WO201 1 154601 , WO201 1 154599 or WO201 1 154597.

According to an embodiment of the first aspect of the solution, the the precursor material may be feed into the homogenizer or fluidizer at a feed consistency in the range of 0.1 - 30 % in dry solids content. Due to the improved flow characteristics of the precursor material, and the homogeneity and particle size, a higher feed consistency than with conventional microcrystalline cellulose can be used. This means that a very broad range of feed consistencies may be used, to achieve a broad range of final product, i.e. in the MFC suspension obtained through the method, dry solids concentrations.

According to another embodiment of the first aspect the solid contents of the microfibrillated cellulose suspension may be in the range of 0.1-25 % in dry solids content.

Due to the more crystalline nature of the microfibrillated cellulose it easier 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 a high solids MFC suspension.

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

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

This means that the MFC suspension may be obtained through any method in which the particle size of the precursor material is reduced by using a pressure difference. Such methods are described in the herein referenced US4 374 702 patent or in the JP59-120638 application.

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

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

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

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

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

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

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

According to a seventh aspect there is provided a use of the

microfibrillated cellulose according to the second aspect as a pharmaceutical or nutraceutical excipient. Brief Description of the Drawings

Embodiments of the present solution will now be described, by way of example, with reference to the accompanying schematic drawings.

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

Description of Embodiments

In the present disclosure there is provided a method for producing a high solids content microfibrillated cellulose.

In the method a precursor material is passed through a

homogenization or fluidization device, once or repeatedly to achieve a high solids content MFC suspension.

The precursor material is a particulate microcrystalline cellulose having natural cellulose based caramelized sugar coating, that may be produced according to the methods described in patent applications WO201 1 154600, WO201 154601 , WO201 1 154599 or WO201 154597, i.e. though a weak acid hydrolysis of cellulose.

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

The precursor material may be fed into the homogenizator or fluidizer at a input feed consistency in the range of 0.1 - 30 % by weight in dry solids content. Preferably an input feed consistency in the range of 0.5 - 9 % by weight 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 conventional type homogenizators.

In the method the new type of precursor material may be passed through a homogenizator or fluidizer where the pressure is altered, whereby the MFC may be formed by the passage through a nozzle. The precursor material is thus compressed in the homogenizator or fluidizer, such that the particle size thereof, is reduced under high pressure. The precursor material may be passed under high pressure through a nozzle, or a hole or slots in the apparatus, and thereby forming the end product, i.e. the high solids content microfibrillated cellulose suspension. Such apparatuses and methods are described in for instance US 4 374 702 and JP59-120638.

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

The high solids content microfibrillated cellulose thus obtained may be used in a variety of applications, including rheology applications as an emulsion agent, a suspension stabilizing agent, or fluid suspension agent.The rheology application may for instance of a oil drilling application, food application, pharmaceutical application and cosmetic application.

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

The MFC may even further be uses a pharmaceutical or nutraceutical excipient.

Example Equipment

A GEA Niro Soavi PandaPlus2000 laboratory homogenizer was used to evaluate the making of MFC from different raw materials. The PandaPlus 2000 is designed for 9l/hour at a maximum of 2000 bars. The flow is fixed while the pressure in the two homogenizing stages is manually adjusted.

In one setup, the material is feed directly through the homogenizer. Several passes are obtained by repeating this procedure.

In a second setup, the material that comes out from the homogenizer is fed back to the homogenizer. In this way theoretical passes can be calculated based on the running time. For example when the sample volume is 450ml and flow 91/hour, one pass is achieved every third minute.

Material

The MCC (12107) that was used had been made with acid hydrolysis , as

disclosed in WO201 1050527, and had been pressed to 45% dry solids. The sample was diluted to desired dry solids and stirred with an Ultra Thurrax

blender 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 solids

14.5%. It was diluted to the desired dry solids and stirred for some minutes

with a propeller stirrer before homogenization. Fig. 1 illustrates a 1000 times magnified SEM picture of the pre-treated pulp (12046).

Results and conclusions

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

MCC Consistency, Pressure, Time, Theoretical

Comments

12107 % and run type bar min passes

12107-1 1 ,5 % 1500-1800 1 , 2, 3, 4, 5

12107-2 3,0 % 1500-1800 1 , 2, 3, 4, 5

1 ,5 % Phase-separation during

12107-3 1500-1800 2 0,7

circulation storage

1 ,5 %

12107-4 1500-1800 4 1 ,3

circulation

1 ,5 %

12107-5 1500-1800 6

circulation

two batches made, first

1 ,5 % without problems, pressure

12107-6 1500-1800 9 3

circulation left low (1200bar) in

second

1 ,5 %

12107-8 1000 15 5

circulation

1 ,5 %

12107-9 1000 21 7 pressure only 900bar circulation

3,0 % pressure at 1300bar, starts

12107-10 1600/1300 15 5

circulation to be difficult to mix

pressure 1300max, after 7

6,0 %

12107-12 1600/1300 15 5 minutes not possible to mix circulation

due to high viscosity

12107-20 1 ,5% 1500 3, 5

12107-21 3% 1000 3, 5

Dilution after each pass to

12107-22 10% / 8% / 6% 2000 1 , 3, 5

enable feeding The MCC became brighter and more viscous in all passes, which is an indication that it is disintegrated into MFC. In test 12107-22, the material was diluted after each pass because the viscosity increased and the material would not have flowed into the homogenizer without dilution. In bigger 5 equipment with a suitable feeding pump, consistencies over 10% should be possible.

Table 2. The test oints when re-treated pulp was used.

0 It was not possible to start the homogenization at 1.5% consistency with pre- treated pulp. Instead, the homogenization was started with water to which the pre-treated pulp was slowly added to avoid high amount of fibrous material in the feed.

Substantial clogging and pressure variations occurred with the pre-treated 5 pulp, while neither occurred when MCC was used. The pre-treated pulp was difficult to run at 1.5% which can be compared to MCC at 10% still being acceptable.

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

0

Claims

1. A method of producing a high solids content microfibrillated cellulose suspension by passing a precursor material through a homogenizer or fluidizer, thereby reducing the particle size of the precursor material c h a r a c t e r i z e d in that

the precursor material comprises a particulate microcrystalline cellulose, wherein the particles have a natural cellulose based caramelized sugar coating.

2. The method as claimed in claim 1 , wherein the precursor material is feed 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 the solid contents of the microfibrillated cellulose suspension is in the range of 1-25 % in dry solids content.

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

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

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

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

8. Use of a microfibrillated cellulose as claimed in claim 7 for rheology applications 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 is any one of a oil drilling application, food application, pharmaceutical application and cosmetic application.

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

1 1. Use of the microfibrillated cellulose as claimed in claim 7 as any one of a reinforcing agent for pulp and/or paper materials, a barrier agent, a reinforcing agent for coating materials, and a composite material in paper or polymer composites.

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

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