(19)
(11)EP 3 083 489 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
04.09.2019 Bulletin 2019/36

(21)Application number: 14871451.2

(22)Date of filing:  19.12.2014
(51)Int. Cl.: 
B82Y 40/00  (2011.01)
C08B 5/14  (2006.01)
C08B 15/00  (2006.01)
(86)International application number:
PCT/US2014/071366
(87)International publication number:
WO 2015/095641 (25.06.2015 Gazette  2015/25)

(54)

METHOD FOR PRODUCTION OF CELLULOSE NANOCRYSTALS FROM MISCANTHUS GIGANTEUS AND COMPOSITES THEREFROM

VERFAHREN ZUR HERSTELLUNG VON CELLULOSENANOKRISTALLEN AUS MISCANTHUS GIGANTEUS UND VERBUNDSTOFFE DARAUS

PROCÉDÉ DE PRODUCTION DE NANOCRISTAUX DE CELLULOSE À PARTIR DE MISCANTHUS GIGANTEUS ET COMPOSITES ASSOCIÉS


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 20.12.2013 US 201361918993 P

(43)Date of publication of application:
26.10.2016 Bulletin 2016/43

(73)Proprietor: Case Western Reserve University
Cleveland, OH 44106 (US)

(72)Inventors:
  • ROWAN, Stuart
    Cleveland Heights, Ohio 44106 (US)
  • HUNSEN, Mo
    Shaker Heights, Ohio 44120 (US)
  • WAY, Amanda
    Cleveland Heights, Ohio 44106 (US)

(74)Representative: Renkema, Jaap 
IPecunia Patents B.V. P.O. Box 593
6160 AN Geleen
6160 AN Geleen (NL)


(56)References cited: : 
WO-A1-2013/000074
US-A1- 2008 057 555
US-A1- 2013 274 350
WO-A1-2014/085730
US-A1- 2009 011 474
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    FIELD OF THE INVENTION



    [0001] The present invention relates to methods for isolating cellulose nanocrystals (CNCs) from the plant Miscanthus Giganteus (MxG). Impressive yields are obtained through a combination of processing steps including base hydrolysis, bleaching and acid hydrolysis. MxG-CNCs are produced having high aspect ratios, are biorenewable and can be used for a wide range of applications such as nanofillers in composites. MxG-CNC-containing composites are also disclosed.

    BACKGROUND OF THE INVENTION



    [0002] Cellulose nanocrystals have been isolated from various organic sources, Cellulose is found primarily In plants, but Is also present in selected marine animals such as sea tunicates, as well as algae, bacteria, and fungi for example.

    [0003] CNCs from sea tunicates, microcrystalline cellulose and cotton have been shown to provide nanocomposites possessing an interesting stimuli-responsive behavior, see U.S. Patent No. 8,344,060. The CNCs from sea tunicates have been demonstrated to have a high aspect ratio (L/D ca. 80) and their composites show superior mechanical reinforcement to other biosources. However, CNCs from sea tunicates are generally not suitable for industrial scale up.

    [0004] CNCs Isolated from plant sources, for example wood, are commercially available, but tend to have relatively low aspect ratios. Therefore, larger amounts of the CNCs need to be added into, for example, a polymer matrix in order to achieve significant reinforcement.

    [0005] Accordingly, a problem of the invention was to discover a source for cellulose nanocrystals that is renewable, relatively inexpensive, and abundant, with at least these factors being critical for any large scale production.

    [0006] A further problem of the Invention Is to provide a process for isolating cellulose nanocrystals that provides desirable yields thereof.

    SUMMARY OF THE INVENTION



    [0007] The problems of the Invention are solved by processes for isolating cellulose nanocrystals from Miscanthus Giganteus. The processes of the present invention provide excellent yields of CNCs isolated from Miscanthus Giganteus (MxG-CNCs).

    [0008] A further object of the present invention is to provide methods for isolating MxG-CNCs including a base hydrolysis step, a bleaching step and an acid hydrolysis step.

    [0009] Yet another object of the present invention is to provide MxG-CNCs possessing relatively high aspect ratios.

    [0010] Still another object of the present invention is to provide composite compositions including MxG-CNCs within a matrix composition, preferably a polymer matrix.

    [0011] A further object of the present invention Is to provide a composition Including MxG-CNCs as nanofiller.

    [0012] An additional object of the present invention is to provide MxG-CNCs having carboxyl functionality.

    [0013] Another aspect of the present Invention is a process for isolating cellulose nanocrystals from Miscanthus Giganteus, comprising the steps of performing a base hydrolysis step on a quantity of Miscanthus Giganteus; performing a bleaching step on a solid material recovered from the base hydrolysis step; performing an acid hydrolysis step on a solid material recovered from the bleaching step; and recovering cellulose nanocrystals from Miscanthus Giganteus after performing the acid hydrolysis step.

    [0014] Accordingly, another aspect of the invention is a composite composition, comprising a matrix material; and cellulose nanocrystals from Miscanthus Giganteus.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0015] The invention will be better understood and other features and advantages will become apparent by reading the detailed description of the invention, taken together with the drawings, wherein:

    Fig. 1 Is infrared spectra of Miscanthus Giganteus cellulose nanocrystals Isolated from the raw material (MxG-CNC) and after TEMPO oxidation (MxG-CNC-CO2H);

    Fig. 2(A) illustrates a wide angle x-ray diffraction image of MxG-CNCs at different hydrolysis times by 1M HCl;

    Fig. 2(B) is a graph illustrating that various ratios of amorphous to crystalline cellulose could be prepared as needed by varying the duration of the hydrolysis and that 97% crystallinity was achieved after 12 hours of hydrolysis by 1M HCL;

    Figs. 3(A) and (B) are transmission electron microscopy (TEM) images of MxG-CNC;

    Fig. 4 Illustrates a tempo oxidation reaction sequence of MxG-CNC to MxG-CNC-CO2H;

    Fig. 5 is a graph Illustrating charge density of MxG-CNC-CO2H;

    Fig. 6 is an image showing birefringence of MxG-CNC-CO2H.

    FIG 7. is a transmission electron microscopy (TEM) image of sulfonated MxG-CNC, MxG-CNC isolated using sulfuric acid; and

    FIG. 8 shows the Dynamic Mechanical Analysis (DMA) of nanocomposites of MxG-CNCs In a PVAc matrix


    DETAILED DESCRIPTION OF THE INVENTION



    [0016] Miscanthus Giganteus is a perennial, non-invasive grass hybrid that originates in Asia. It is currently being grown in different locations around the globe and has been used to make electricity, heat, and as a feed stock for biofuels. Miscanthus Giganteus gives superior yields of dry mass compared to other plants, including switch grass or com. When suitable growing conditions are achieved, more than 12 tons of dry mass per acre can be obtained from Miscanthus Giganteus, which is generally more than twice that of switch grass or corn.

    [0017] It has been discovered that cellulose nanocrystals can be isolated from Miscanthus Giganteus. The isolated Miscanthus Giganteus cellulose nanocrystals, herein MxG-CNCs, can be utilized in a wide range of compositions and have particular application as a nanofiller.

    [0018] In a first step, a desired amount of Miscanthus Giganteus is obtained. In a further step, the Miscanthus Giganteus is comminuted with appropriate equipment that is typically utilized to reduce the average particle size of solid material to a smaller average particle size, for example by grinding, milling, crushing, or the like. Various types of mills and crushers are known in the art and include, but are not limited to, blenders, ball mills, hammer mills, roller mills or presses, vibration mills, jet mills, cone crushers, hammer crushers and jaw crushers.

    [0019] After Miscanthus Giganteus particles of a desired consistency or particle size are obtained, a base hydrolysis step is performed to hydrolyze the Miscanthus Giganteus. In one embodiment, the comminuted Miscanthus Giganteus Is soaked in a basic solution having a pH of about 12 to about 14 or 16. Preferably a plurality of treatments are utilized in one embodiment, with two to four treatments desired and three treatments preferred. After the particles are immersed, soaked or otherwise wetted or contacted with the desired basic solution, the hydrolyzed particles are filtered and washed with distilled water in order to bring an end to or otherwise complete a particular base hydrolysis treatment operation.

    [0020] In one embodiment, the Miscanthus Giganteus can be placed in a 2 weight percent sodium hydroxide solution at room temperature for 24 hours followed by two treatments with 2 weight percent sodium hydroxide solution at 100 °C for 22 hours to hydrolyze the comminuted Miscanthus Giganteus. Aqueous sodium hydroxide (about 1 weight percent to about 4 weight percent), from about room temperature to about 100 °C, and from about 12 to about 72 hours could be used for the base hydrolysis step. In addition, a higher weight percent sodium hydroxide solution could also be used for the Initial base hydrolysis step. In another embodiment, a 3 weight percent sodium hydroxide solution at 100°C for 3 hours can be utilized with this step repeated a plurality of times, for example 3 times wherein the material is filtered and washed with distilled water after each soak, which reduces the total base hydrolysis duration to 12 hours total. Alternatively a more dilute sodium hydroxide solution for a prolonged duration Is another alternative. One could also use other bases such as, but not limited to, MOH (where M is a cationic counter ion) for the base hydrolysis step. After completion of the desired base hydrolysis, a solid material is filtered and washed with distilled water.

    [0021] After the base hydrolysis step has been performed, a bleaching step is initiated on the solid material recovered to remove the non-cellulose component and color. In one embodiment, one or more of sodium chlorite and/or sodium hypochlorite are utilized in a solution at a concentration of between about 0.5 and about 4 weight percent along with acetic acid at a concentration between about 0.2 and about 9 weight percent. Preferably the mixture is stirred/mixed during the bleaching step. The duration of the step ranges from about 1 to about 3 hours at a temperature of about 50 °C to about 80 °C. Alternatively, the process can be performed for about 12 to about 24 hours at room temperature. The solution is filtered and washed with distilled water to obtain the solid product.

    [0022] An acid hydrolysis step is performed on the solid material obtained from the bleaching step, The solid material is placed in an acid, such as but not limited to hydrobromic acid, phosphoric acid, sulfuric acid, and hydrochloric acid, with the concentration of acid ranging from about 0.5 molar to about 18 molar and desirably From about 9 molar to about 12 molar for a suitable period of time. In one embodiment the acid hydrolysis step is performed in a 1M HCl solution for about 0.5 to about 24 hours. A higher concentration of acid is generally used for a shorter duration or a lower amount of acid for a longer duration.

    [0023] Utilizing sulfuric acid produces sulfonated MxG-CNCs. In one embodiment 9 molar sulfuric acid at 40 °C for one hour can be utilized. FIG 7 shows the TEM of sulfonated MxG-CNCs. One could also use a higher or lower amount of sulfuric acid for shorter or longer hydrolysis times, respectively to isolate sulfated MxG-CNCs.

    [0024] The acid hydrolysis step is preferably performed under heat (70-100 °C).

    [0025] 2,2,6,6-Tetramethylpiperidine-1-oxyl (TEMPO) oxidation can also be utilized to prepare MxG-CNCs with carboxyl functionality. The MxG-CNCs (1.45 g) were dispersed in 150 mL distilled water followed by addition of TEMPO (0.123 g) and NaBr (1.23 g) and 200 wt.% (compared to mass of CNCs in solution) of NaOCl. The mixture was stirred for 4.5 hours after adjusting the pH to 10-11 with 10 M NaOH solution. NaCl (5.0 g) was then added to the mixture and stirred for 10 more minutes. The mixture was the centrifuged to decant the supernatant. The residue was then washed with 1 M NaCl (x 3) and centrifuged to decant the supernatant and then subsequently washed with 0.1 M HCl (x 3) and centrifuged to decant the supernatant. The oxidized MxG-CNCs were then dialyzed for 24 hours against distilled water and freeze-dried using a lyophilizer to yield 1.09 g of white oxidized MxG-CNC-COOH. The concentration of -COOH functional groups on the surface of the cellulose nanocrystals was determined via a conductometric analysis. A solution of 0.05 wt.% MxG-CNC-COOH was dispersed in water via a 12 hr sonication. Hydrochloric acid (12 M) was then added in 10 µl increments until the pH of the solution reached ca. 3. Titrations were then performed with a 0.01 M sodium hydroxide solution in multiples of three, yielding an average carboxylate concentration of 1,750 mmol/Kg. By controlling the amount of the reagents (TEMPO, NaOCl and NaBr) added and the time of the reaction it is possible to alter the amount of oxidation.

    [0026] As utilized herein, the term composite and/or composition including the MxG-CNCs is defined as a material including 1) the MxG-CNCs as well as 2) at least one other material that is not MxG-CNC and therefore has different physical and/or chemical properties. That said, many different types of materials can be mixed with the MxG-CNCs in order to form a composition or composite. Various materials include, but are not limited to one or more polymers, one or more liquids and one or more non-polymeric materials. The MxG-CNCs can be utilized in many different applications including, but not limited to, paper, plastics, rubber, paints, coatings, adhesives and sealants. Compositions and composites including the MxG-CNCs can include any desired amount thereof, In one nonlimiting embodiment, the MxG-CNCs are used In an amount from about 1 to about 20 parts based on 100 total parts by weight of polymer.

    [0027] Polymer nanocomposites can be prepared utilizing the MxG-CNCs as the nanoparticles in the compositions and procedures described in U.S. Patent No. 8,344,060, herein fully incorporated by reference. In additional embodiments or aspects of the invention, one or more polymers or copolymers are mixed with or otherwise combined with MxG-CNCs, with varying surface functionalities, to form polymer nanocomposites comprising MxG-CNCs. Many different polymers or copolymers can be utilized with examples including, but not limited to, various alkylene oxide polymers and copolymers such as ethylene oxide, propylene oxide, copolymers of ethylene oxide and epichlorohdrin and/or other monomers; a vinyl aromatic (co)polymer such as polystyrene and styrene copolymers; polyolefin polymers or copolymers such as polyethylene and polypropylene; diene polymers and copolymers, such as cis-polybutadiene; polyacrylates and acrylate copolymers, such as methyl methacrylate; poly(vinyl acetate); poly(vinyl alcohol); polyamides; poly(urethanes) and polyester polymers or copolymers such as polycaprolactone, poly(ethylene terephthalate) or polylactate

    [0028] In one embodiment, a the solution containing the desired (co)polymer(s) and MxG-CNCs can be mixed as desired, such as in order to obtain a substantially homogenous mixture, and then the solution can be cast or otherwise placed into a desired form and dried in order to produce a finished composite. In one embodiment the solution can be dried in a vacuum oven wherein suitable pressures, temperatures and drying times will vary depending upon the system utilized. Various additives as known to those of ordinary skill in the art can be added to the composition in any desired amounts.

    [0029] As an example, the incorporation of the MxG-CNCs into a poly(vinyl acetate) matrix (produced by mixing appropriate amounts of a dispersion of the MxG-CNCs in dimethylformamide with a solution of the polymer in dimethylformamide followed by drying In a vacuum oven) yielded films that showed a significant mechanical enhancement above the glass transition temperature of the material (FIG 8). For example, MxG-CNCs were sonicated in DMF overnight to prepare a 3 mg/mL dispersion and PVAc was dissolved by stirring in DMF to prepare a 50 mg/mL solution. Nanocomposites were then prepared by combining the PVAc solution in DMF and the dispersion of MxG-CNCs in DMF into Teflon® Petri dishes. The amounts of MxG-CNCs and PVAc was varied such that it resulted in a range of 1-20 weight percent of MxG-CNCs In the PVAc matrix after evaporation of the solvent. The dishes were placed into a vacuum oven (65 °C, 15 mbar, 5 days) to remove the solvent. The material was compression-molded in a Carver laboratory press at 87 °C and 3000 psi for 5 min to yield the nanocomposite films. The mechanical properties of the nanocomposites were then characterized by dynamic mechanical analysis.

    Examples


    Comparative Example 1



    [0030] As no procedure is believed to be known to isolate cellulose nanocrystals from Miscanthus Giganteus, a procedure for Isolating cellulose nanocrystals from wood was utilized based upon the following references: Salajkov, M.; Berglund, L. A.; Zhou, Q. J. Mater. Chem. 2012, 22, 19798-19805, Alemdar, A.; Sain, M. Comp. Sci. & Tech. 2008, 68, 557-565.

    [0031] Cellulose nanocrystals from Miscanthus Giganteus were obtained from the following procedure. The blended stalk was exposed to potassium hydroxide solution (5 wt.%) at 80 °C for 15 hours and filtered. The solid was stirred in acetic acid (0.015 mL) and sodium hypochlorite (0.03 mL) solution (30 mL DI water) until the solution became white (ca. 6 hours) and filtered. The resulting solid was then acid hydrolyzed with hydrochloric acid (12 M, 1 mg/mL) for 1,5 hr at reflux to give a yield of 1 wt.% of white solid (78% crystallinity by WAXS).

    Comparative Example 2



    [0032] In view of the poor yield and low degree of crystallinity obtained, a second attempt was made utilizing a procedure set forth in the following reference: Helbert, W.; Cavaille, J.Y.; Dufresne, A. Polymer Composites 1996, 17, 604-611.

    [0033] The blended stalk was exposed to sodium hydroxide solution (2 wt.%) at 80 °C for 4 hours and filtered, After filtration, the process of NaOH wash and filtration as above was repeated 5 more times. After the final filtration the solid was stirred in an acetic acid (7.5 %) sodium hypochlorite (1.7%), and sodium hydroxide (2.7%) solution until the solid became white (ca. 12 hours) and then was filtered. The resulting solid was then put in 1 M hydrochloric acid (1 mg solid/1 mL HCI) and refluxed for 12 hr to give a yield of 8 wt.%. WAXS analysis showed this material was ca. 97% crystalline.

    Examples of the Invention



    [0034] In view of the low yields, the following procedures were invented to produce relatively high yields of MxG-CNCs.

    Base Hydrolysis Step



    [0035] We have carried out an initial soaking of the Miscanthus stalk in 2 wt.% sodium hydroxide solution at room temperature for 24 hours followed by two treatments with 2 wt.% sodium hydroxide solution at 100 °C for 22 hours to hydrolyze the Miscanthus stalk. In addition, a higher wt.% sodium hydroxide solution could also be used for the initial base hydrolysis step. For example, we have used a 3 wt.% sodium hydroxide solution at 100 °C for 3 hours and repeating this step three times (filtering and washing with distilled water at each step) thus reducing the total base hydrolysis duration to 12 hours total (as opposed to 24 hours total in procedure attempt 2 described above). Using a more dilute sodium hydroxide solution for a prolonged duration is another alternative.

    Bleaching Step



    [0036] We have used sodium chlorite instead of sodium hypochlorite as an alternative for the bleaching step resulting in a much whiter product In a short amount of time (1-3 hr at 50-80 °C or 12-24 hr at room temperature). We have also shown that the bleaching step could be performed either before or after the hydrolysis step to yield a white product.

    Acid hydrolysis Step



    [0037] We have shown that the acid hydrolysis step using 1 M HCl for 6-15 hr gave CNCs with a higher % crystallinity. Alternatively, one can use a slightly higher concentration of HCl for shorter duration or a lower amount of HCl for a longer duration. Phosphoric acid is another viable alternative for this step. Using 9 M sulfuric acid at 40 °C for 1 hour resulted in sulfated MxG-CNCs. One could also use a higher or lower amount of sulfuric acid for a shorter or longer hydrolysis times, respectively, to isolate sulfated MxG-CNCs.

    [0038] An Example of another preferred embodiment is as follows:

    [0039] Miscanthus Giganteus stalk (16.73 g) was soaked in 300 mL of 2 wt.% sodium hydroxide solution at room temperature for 24 hours followed by two treatments with 250 mL of 2 wt.% sodium hydroxide solution at 100 °C for 22 hours, filtering and washing with distilled water at each step. Bleaching solution (225 mL) containing 2.25 g sodium chlorite and 15 drops of glacial acetic acid was then added and the mixture heated for 2 hours at 68 °C. The mixture was filtered and washed with distilled water to yield a white solid. The resulting solid was then hydrolyzed with 200 mL of 1 M hydrochloric acid at 75 °C for 15 hours to give a yield of 33.2 wt.% MxG-CNCs.

    [0040] While in accordance with the patent statutes the best mode and preferred embodiment have been set forth, the scope of the invention is not limited thereto, but rather by the scope of the attached claims.


    Claims

    1. A process for isolating cellulose nanocrystals from Miscanthus Giganteus, comprising the steps of:

    performing a base hydrolysis step on a quantity of Miscanthus Giganteus;

    performing a bleaching step on a solid material recovered from the base hydrolysis step;

    performing an acid hydrolysis step on a solid material recovered from the bleaching step; and

    recovering cellulose nanocrystals from Miscanthus Giganteus after performing the acid hydrolysis step.


     
    2. The process according to claim 1, wherein prior to performing the base hydrolysis step a quantity of Miscanthus Giganteus is obtained and comminuted to reduce an average particle size of solid material to a smaller average particle size.
     
    3. The process according to claim 1, wherein the base hydrolysis step includes contacting the Miscanthus Giganteus with a basic solution having a pH of about 13 to about 14, and wherein the base utilized has a formula of MOH, wherein M is a cationic counter ion.
     
    4. The process according to claim 3, wherein the bleaching step comprises contacting one or more of sodium chlorite and sodium hypochlorite; and also acetic acid with the solid material recovered from the base hydrolysis step, wherein the one or more of the sodium chlorite and sodium hypochlorite are present in a concentration between about 0.5 in about 4 weight percent and a concentration of acetic acid is between about 0.2 and about 9 weight percent.
     
    5. The process according to claim 4, wherein the bleaching step is performed for about 1 to about 3 hours at a temperature of about 50 °C to about 80 °C, wherein mixing is performed during at least part of the time period.
     
    6. The process according to claim 4, wherein the acid hydrolysis step comprises contacting the solid material recovered from the bleaching step with an acid having a concentration ranging from 0.5 molar to about 18 molar.
     
    7. The process according to claim 6, wherein the acid Is one or more of hydrobromic acid, phosphoric acid, sulfuric acid and hydrochloric acid.
     
    8. The process according to claim 7, wherein the acid hydrolysis step is performed for about 0.5 to about 24 hours.
     
    9. The process according to claim 1, further including the step of adding carboxyl functionality to the recovered cellulose nanocrystals.
     
    10. A composition comprising a polymer and the recovered cellulose nanocrystals according to claim 1.
     
    11. The composition comprising a polymer and the recovered cellulose nanocrystals according to claim 8.
     
    12. A composite composition, comprising:

    a matrix material; and

    cellulose nanocrystals from Miscanthus Giganteus.


     
    13. The composite composition according to claim 12, wherein the matrix material comprises one or more polymers or copolymers.
     
    14. The composite composition according to claim 13, wherein the polymers or copolymers comprise alkylene oxide (co)polymers, a vinyl aromatic (co)polymer, a polyolefin (co)polymer, a diene (co)polymer, a polyacrylate (co)polymer, polyamide, a polyester or a combination thereof.
     


    Ansprüche

    1. Verfahren zum Isolieren von Cellulose-Nanokristallen aus Miscanthus giganteus, umfassend die folgenden Schritte:

    Durchführen eines Basenhydrolyseschritts an einer Menge von Miscanthus giganteus;

    Durchführen eines Bleichungsschritts an einem Feststoff, das aus dem Basenhydrolyseschritt gewonnen wurde;

    Durchführen eines Säurehydrolyseschritts an einem aus dem Bleichungsschritt gewonnenen Feststoff; und

    Rückgewinnen von Cellulose-Nanokristallen von Miscanthus giganteus nach Durchführen des Säurehydrolyseschritts.


     
    2. Verfahren nach Anspruch 1, wobei vor dem Durchführen des Basenhydrolyseschritts eine Menge von Miscanthus giganteus erhalten und zerkleinert wird, um eine durchschnittliche Teilchengröße des Feststoffs auf eine kleinere durchschnittliche Teilchengröße zu reduzieren.
     
    3. Verfahren nach Anspruch 1, wobei der Basenhydrolyseschritt das Inkontaktbringen des Miscanthus giganteus mit einer basischen Lösung mit einem pH von ungefähr 13 bis ungefähr 14 einschließt und wobei die verwendete Base eine Formel MOH aufweist, wobei M ein kationisches Gegenion ist.
     
    4. Verfahren nach Anspruch 3, wobei der Bleichungsschritt das Inkontaktbringen von Natriumchlorit und/oder Natriumhypochlorit umfasst; und auch von Essigsäure mit dem aus dem Basenhydrolyseschritt gewonnenen Feststoff , wobei das Natriumchlorit und/oder Natriumhypochlorit in einer Konzentration zwischen ungefähr 0,5 in ungefähr 4 Gewichtsprozent vorliegen und eine Konzentration an Essigsäure zwischen ungefähr 0,2 und ungefähr 9 Gewichtsprozent liegt.
     
    5. Verfahren nach Anspruch 4, wobei der Bleichungsschritt für ungefähr 1 bis ungefähr 3 Stunden bei einer Temperatur von ungefähr 50 °C bis ungefähr 80 °C durchgeführt wird, wobei das Mischen während mindestens eines Teils des Zeitraums durchgeführt wird.
     
    6. Verfahren nach Anspruch 4, wobei der Säurehydrolyseschritt das Inkontaktbringen des aus dem Bleichungsschritt gewonnenen Feststoffs mit einer Säure mit einer Konzentration im Bereich von 0,5 bis ungefähr 18 Mol umfasst.
     
    7. Verfahren nach Anspruch 6, wobei die Säure eine oder mehrere von Bromwasserstoffsäure, Phosphorsäure, Schwefelsäure und Salzsäure ist.
     
    8. Verfahren nach Anspruch 7, wobei der Säurehydrolyseschritt ungefähr 0,5 bis ungefähr 24 Stunden lang durchgeführt wird.
     
    9. Verfahren nach Anspruch 1, ferner den Schritt des Hinzufügens einer Carboxylfunktionalität zu den rückgewonnenen Cellulose-Nanokristallen einschließend.
     
    10. Zusammensetzung, umfassend ein Polymer und die rückgewonnenen Cellulose-Nanokristalle nach Anspruch 1.
     
    11. Zusammensetzung, umfassend ein Polymer und die rückgewonnenen Cellulose-Nanokristalle nach Anspruch 8.
     
    12. Verbundzusammensetzung, umfassend:

    ein Matrixmaterial; und

    Cellulose-Nanokristalle von Miscanthus giganteus.


     
    13. Verbundzusammensetzung nach Anspruch 12, wobei das Matrixmaterial ein oder mehrere Polymere oder Copolymere umfasst.
     
    14. Verbundzusammensetzung nach Anspruch 13, wobei die Polymere oder Copolymere Alkylenoxid(co)polymere, ein aromatisches Vinyl(co)polymer, ein Polyolefin(co)polymer, ein Dien(co)polymer, ein Polyacrylat(co)polymer, Polyamid, einen Polyester oder eine Kombination davon umfassen.
     


    Revendications

    1. Procédé d'isolement de nanocristaux de cellulose de Miscanthus Giganteus, comprenant les étapes consistant à :

    effectuer une étape d'hydrolyse basique sur une quantité de Miscanthus Giganteus ;

    effectuer une étape de blanchiment sur un matériau solide récupéré de l'étape d'hydrolyse basique ;

    effectuer une étape d'hydrolyse acide sur un matériau solide récupéré de l'étape de blanchiment ; et

    récupérer les nanocristaux de cellulose de Miscanthus Giganteus après avoir effectué l'étape d'hydrolyse acide.


     
    2. Procédé selon la revendication 1, dans lequel avant d'effectuer l'étape d'hydrolyse basique une quantité de Miscanthus Giganteus est obtenue et finement divisée pour réduire une taille de particule moyenne de matériau solide à une taille de particule moyenne plus petite.
     
    3. Procédé selon la revendication 1, dans lequel l'étape d'hydrolyse basique comprend la mise en contact du Miscanthus Giganteus avec une solution basique ayant un pH d'environ 13 à environ 14, et où la base utilisée a une formule de MOH, où M est un contre ion cationique.
     
    4. Procédé selon la revendication 3, dans lequel l'étape de blanchiment comprend la mise en contact d'un ou de plusieurs du chlorite de sodium et de l'hypochlorite de sodium ; et aussi l'acide acétique avec le matériau solide récupéré de l'étape d'hydrolyse basique, où les un ou plusieurs du chlorite de sodium et de l'hypochlorite de sodium sont présents à une concentration comprise entre environ 0,5 à environ 4 pour cent en poids et une concentration d'acide acétique est comprise entre environ 0,2 et environ 9 pour cent en poids.
     
    5. Procédé selon la revendication 4, dans lequel l'étape de blanchiment est effectuée durant environ 1 à environ 3 heures à une température d'environ 50 °C à environ 80 °C, où un mélange est effectué durant au moins une partie de la période de temps.
     
    6. Procédé selon la revendication 4, dans lequel l'étape d'hydrolyse acide comprend la mise en contact du matériau solide récupéré de l'étape de blanchiment avec un acide ayant une concentration se situant dans la plage allant de 0,5 molaire à environ 18 molaires.
     
    7. Procédé selon la revendication 6, dans lequel l'acide est un ou plusieurs de l'acide bromhydrique, de l'acide phosphorique, de l'acide sulfurique et de l'acide chlorhydrique.
     
    8. Procédé selon la revendication 7, dans lequel l'étape d'hydrolyse acide est effectuée durant environ 0,5 à environ 24 heures.
     
    9. Procédé selon la revendication 1, comprenant en outre l'étape d'addition d'une fonctionnalité carboxyle aux nanocristaux de cellulose récupérés.
     
    10. Composition comprenant un polymère et les nanocristaux de cellulose récupérés selon la revendication 1.
     
    11. Composition comprenant un polymère et les nanocristaux de cellulose récupérés selon la revendication 8.
     
    12. Composition de composite, comprenant :

    un matériau de matrice ; et

    des nanocristaux de cellulose de Miscanthus Giganteus.


     
    13. Composition de composite selon la revendication 12, dans laquelle le matériau de matrice comprend un ou plusieurs polymères ou copolymères.
     
    14. Composition de composite selon la revendication 13, dans laquelle les polymères ou copolymères comprennent des (co)polymères d'oxyde d'alkylène, un (co)polymère aromatique vinylique, un (co)polymère de polyoléfine, un (co)polymère de diène, un (co)polymère de polyacrylate, un polyamide, un polyester ou une de leurs combinaisons.
     




    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description




    Non-patent literature cited in the description