WO2017211798A1 - Process for the preparation of a cellulose product - Google Patents

Process for the preparation of a cellulose product Download PDF

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Publication number
WO2017211798A1
WO2017211798A1 PCT/EP2017/063675 EP2017063675W WO2017211798A1 WO 2017211798 A1 WO2017211798 A1 WO 2017211798A1 EP 2017063675 W EP2017063675 W EP 2017063675W WO 2017211798 A1 WO2017211798 A1 WO 2017211798A1
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solution
cellulose
oxide
tertiary amine
amount
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PCT/EP2017/063675
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French (fr)
Inventor
Auriane FREYBURGER
Werner Kunz
Cordt Zollfrank
Yaqing DUAN
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Universität Regensburg
Technische Universität München
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Publication of WO2017211798A1 publication Critical patent/WO2017211798A1/en

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    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F2/00—Monocomponent artificial filaments or the like of cellulose or cellulose derivatives; Manufacture thereof
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01D—MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS
    • D01D1/00—Treatment of filament-forming or like material
    • D01D1/02—Preparation of spinning solutions

Definitions

  • the present invention relates to a process which allows the fabrication of a shaped cellulose product, in particular cellulose fibers, in an efficient and sustainable manner.
  • Cellulose is a primary resource from lignocellulosics such as wood, cotton plants, and other lignified higher plants. It is the most important biomass resource on earth and has an estimated annual production of 100-150 billion tons. Because of its easy availability, cellulose is of great importance for industrial processing to produce fibers, films, and membranes, for example.
  • Lyocell- or NMMO-process is based on the dissolution and the shaping of cellulose assisted by a tertiary amine-oxide, in particular N-methylmorpholine-N-oxide (NMMO), as a solvent (e.g. US 5,589,125; US 5,698,151 ; M. Walker et al., "N-Morpholinoxid (NMMO) - Die Engineering effets Losestoffs für Industriellen architecture von Zelluiosefasern", Lenzinger Berichte 76/97).
  • NMMO N-methylmorpholine-N-oxide
  • US 4,145,532 discloses a process for the preparation of a cellulose product, comprising precipitating cellulose from a solution thereof in a solvent comprising a tertiary amine oxide, water, and an optional aprotic organic liquid co-solvent having a dipole moment greater than about 3.5 Debye.
  • the Lyocell process offers several advantages: it is non-toxic, environmentally benign, and allows the dissolution of cellulose without derivatization or pretreatment.
  • the commercial Lyocell fibers were first produced by Courtaulds (Great Britain) and are currently made by Lenzing AG (Austria) under the Tencel® trade name on an industrial scale (100 ktons/year). Solutions of cellulose in NMMO and water can also be used to prepare other types of shaped or molded products (cf. WO 01/96636 A1).
  • Lyocell fibers are made with a dry jet- wet spinning technique and different process steps.
  • the first process step consists of dissolving cellulose in NMMO in presence of water.
  • This solution is generally composed of 10-15 % cellulose, 50-60 % NM O, and 20-30 % water.
  • the excess of water is extracted at reduced pressure and high temperature until complete dissolution of cellulose is obtained (typically at 13-15 wt% of water, i.e. a percentage of water close to the one found in NMMO monohydrate).
  • this spinning dope is then extruded at elevated temperatures (90- 120°C) through an air gap into a coagulation bath. There, the extrudate is impoverished of NMMO, which allows the regeneration of the cellulose. Finally, the obtained fibers are washed and dried. At the end of the process, NMMO is recovered from the baths and recycled.
  • a remaining disadvantage of the Lyoceil process is a relatively high energy consumption due to elevated process temperatures and the reduction of the water content prior to the shaping (e.g. spinning) of the cellulose solutions which may be necessary.
  • stabilizers are generally used to prevent the thermal degradation of NMMO and cellulose, which can occur during high process temperatures.
  • the present invention provides a process for the preparation of a shaped cellulose product as defined in the annexed claims, which process comprises the steps of:
  • the addition of the lactone can decrease the melting temperature of a blend of cellulose, a tertiary amine-N-oxide, and the lactone, such that a solution can be prepared and/or brought into a predetermined shape at lower temperatures, compared to a solution of the cellulose in a solvent comprising the tertiary amine-N-oxide without the use of the lactone.
  • the solution is provided as a spinning dope, it can be spun at lower temperatures to provide cellulose fibers of good quality.
  • the thermal load on the cellulose during the process can be reduced.
  • thermal degradation is prevented, the use of chemical stabilizers can be reduced or avoided, and/or the consumption of energy during the process can be reduced.
  • the lactone selected from ⁇ -valerolactone, ⁇ -butyrolactone, and a combination thereof beneficiaiiy reduces the viscosity of the solution comprising the DCiuiose, the tertiary amine-N-oxide, and the lactone compared to a solution of the DCiuiose in a solvent comprising the tertiary amine-N-oxide without the use of the lactone.
  • This allows the concentration of the cellulose in the solution to be increased at a given temperature while maintaining the rheologicai properties of the solution, which can be of relevance for the step of shaping the solution, e.g. in a spinning step.
  • ⁇ - valerolactone and ⁇ -butyrolactone can be added in significant amounts to a tertiary amine-N- oxide, such as NMMO, without disturbing the dissolution process of cellulose and without affecting the stability of the solution.
  • a tertiary amine-N- oxide such as NMMO
  • the ratio of lactone/ tertiary amine-N-oxide in the solution provided in step a) of the process in accordance with the invention can be varied over wider ranges depending on the desired properties of the solution.
  • the process in accordance with the invention provides a shaped cellulose product, i.e. a product comprising cellulose as a main constituting material, preferably a product which essentially consists of cellulose.
  • a product comprising cellulose as a main constituting material as referred to herein preferably contains 80 wt% or more, more preferably 90 wt% or more, and even more preferably 95 wt.% or more of cellulose, based on the total weight of the product as 100 wt%.
  • a product essentially consisting of cellulose or consisting of cellulose is particularly preferred.
  • essentially consisting of cellulose refers to a product which is formed from cellulose, and which may contain remainders of substances (e.g. in an amount of not more than 3 wt%, preferably not more than 1 wt%) which are derived e.g. from the biomass source of the cellulose.
  • the shaped product prepared by the process in accordance with the invention can take various shapes, including e.g. the shape of a film, a membrane or a fiber.
  • the process is used for the preparation of a cellulose fiber as the shaped cellulose product.
  • a solution which comprises dissolved cellulose, a tertiary amine-N-oxide, a lactone selected from y- valerolactone, ⁇ -butyrolactone, and a combination thereof, and water.
  • the cellulose which is comprised by the solution provided in step a) is not particularly limited. It can be conveniently obtained from biomass resources. Depending on the intended use and the required quality of the shaped cellulose product provided by the process of the invention, cellulose material from recycled materials, such as waste paper, cardboard, other cellulose containing fiber assemblies, from agricultural waste, such as mechanically and/or chemically broken up annual plants, or from forestry material, such as wood may be included at least in part in the cellulose is dissolved in the solution provided in step a).
  • the cellulose is introduced into the solution in the form of small pieces, e.g. as a powder.
  • the cellulose is dried before it is introduced into the solution to control the water content of the solution.
  • the cellulose material may be milled and/or ground and/or dried before the solution is provided.
  • the degree of polymerization (DP) of the cellulose dissolved in the solution provided in step a) ranges from 100 to 1200, more preferably from 100 to 1000 and most preferably from 400 to 1000.
  • the degree of polymerization is indicated as the viscosity average degree of polymerization, as it may be determined from a cupriethylenediamine hydroxide solution of the cellulose using an Ubbelohde viscometer, typically at a temperature of 20°C.
  • the tertiary amine N-oxide may be, for example, at least one selected from a cyclic tertiary amine-N-oxide wherein the tertiary N atom forms part of a heterocyclic structure, and a tertiary amine oxide as defined in US 5,409,532, and having the structure:
  • each of R, and R 2 is independently an a!kyl group with 1 to 4 C-atoms
  • R 3 is selected from the group consisting of a hydrogen atom, a hydroxyi group and an alkoxy group with 1-4 C-atoms
  • m and n are whole numbers which fulfill the conditions 1 ⁇ m ⁇ 8 and 1 ⁇ n ⁇ 4, respectively.
  • the tertiary amine N-oxide is at least one selected from N,N,N-trimethylamine-N- oxide, N,N-dimethylcyclohexylamine-N-oxide, N-methylmorpholine-N-oxide, N- methylpiperidine-N-oxide, N-methylazacyclopheptane-N-oxide, N-methylpyrrolidine-N-oxide, N,N-dimethylbenzylamine-N-oxide, N,N-dimethylethanolamine-N-oxide and 2-(N,N- dimethy!aminoethoxy)-ethanol-N-oxide.
  • the tertiary amine N-oxide comprises N-methylmorpholine-N-oxide (also referred to herein as NMMO), and even further preferably the tertiary amine N-oxide is (i.e. consists of) N-methylmorpholine-N-oxide.
  • N-methylmorpholine-N-oxide can be favorably used in the form of its monohydrate (also referred to herein as NMMO mono.). Using this monohydrate, a defined water content of the solution prepared in step a) of the process in accordance with the invention can be conveniently provided.
  • the lactone contained in the solution provided in step a) of the process in accordance with the invention is selected from ⁇ -valerolactone (also referred to as gamma-valerolactone, or GVL), ⁇ -butyrolactone (also referred to as gamma-butyrolactone, or GBL), and a combination thereof.
  • ⁇ -valerolactone also referred to as gamma-valerolactone, or GBL
  • GBL gamma-butyrolactone
  • the process encompasses the provision of a solution which comprises ⁇ - vaiero!actone and is free of ⁇ -butyrolactone, a solution which comprises ⁇ -butyrolactone and is free of ⁇ -valerolactone, or a solution which contains a combination of ⁇ -valerolactone and ⁇ -butyrolactone.
  • ⁇ - valerolactone either as the only lactone or in combination with ⁇ -butyrolactone, and more preferably the solution comprises ⁇ -vaierolactone as the only lactone.
  • ⁇ -Valerolactone is of particular interest since it is not only stable under typical production conditions applied for the preparation of cellulose products, such as cellulose fibers, and non-toxic, but also conveniently obtainable from biomass, e.g. via the degradation of cellulose. Moreover, it has the most favorable toxicological profile.
  • the addition of the lactone to the solution comprising cellulose allows improving the processability of the cellulose solution, without exerting a negative effect on the quality, e.g. the surface structure, of the obtained cellulose product.
  • the content of cellulose is preferably 1 wt% or more, more preferably 5 wt% or more, even more preferably 8 wt% or more, and most preferably 10 wt% or more, based on the total weight of the solution as 100 wt%. It is preferably 30 wt% or less, more preferably 25 wt% or less, based on the total weight of the solution as 100 wt%.
  • the content may preferably be 1 to 30 wt%, more preferably 1 to 25 wt%, even more preferably 5 to 25 wt%, and most preferably 10 to 25 wt%, based on the total weight of the solution as 100 wt%.
  • the content of the tertiary amine-N-oxide, preferably of NMMO, in the solution provided in step a) of the process in accordance with the invention is preferably 40 to 85 wt%, more preferably 43 to 74 wt%, and most preferably 43 to 61 wt, based on the total weight of the solution as 100 wt%.
  • the amine- N-oxide in an amount of 43 to 56 wt% if the solution contains the cellulose in an amount of 1 to less than 10 wt%, and to use the amine-N-oxide in an amount of 55 to 74 wt%, more preferably 55 to 61 wt%, if the solution contains the cellulose in an amount of 10 wt% or more, e.g. 10 to 25 wt%. If a hydrate of the tertiary amine-N-oxide is used, the weight of the water contained in the hydrate is not included in these percentages. Rather, its weight will be taken into account as weight of water contained in the solution provided in step a).
  • the content of the lactone selected from y-valerolactone, ⁇ -butyrolactone and a combination thereof i.e the content of ⁇ -valerolactone, if used alone as the preferred embodiment, the content of ⁇ -butyrolactone if used alone, or the combined contents of ⁇ -valerolactone and of ⁇ -butyroiactone, if used in combination
  • the content of the lactone selected from y-valerolactone, ⁇ -butyrolactone and a combination thereof is typically 65 wt% or less, preferably 5 to 53 wt%, more preferably 10 to 50 wt%, even more preferably 15 to 50 wt%, based on the total weight of the solution as 100 wt%.
  • the lactone in an amount of 26 to 50 wt% if the solution contains the cellulose in an amount of 1 to less than 10 wt%, and to use the lactone in an amount of 5 to 27 wt%, more preferably 10 to 27 wt% and even more preferably 15 to 27 wt%, if the solution contains the cellulose in an amount of 10 wt% or more, e.g. 10 to 25 wt%.
  • the content of water in the solution provided in step a) of the process in accordance with the invention is preferably 5 to 13 wt%, preferably 5 to 12 wt%, more preferably 6 to 1 1 wt%, and most preferably 6 to 10 wt%, based on the total weight of the solution as 100 wt%.
  • the solution provided in step a) comprises the water in an amount of 20 wt% or less, preferably 16 wt% or less, more preferably 10 to 16 wt%, and most preferably 13 to 16 wt%, based on the sum of weights of the water and the tertiary amine-N-oxide as 100 wt%.
  • a water content in this range can be conveniently provided using the monohydrate of NMMO as the tertiary amine-N-oxide.
  • the tertiary amine-N-oxide is N-methyi morpholine oxide
  • the lactone is ⁇ -valerolactone
  • the solution in step a) comprises the cellulose in an amount of 1 to less than 10 wt%, water in an amount of 6 to 9 wt%, the N-methyi morpholine oxide in an amount of 43 to 56 wt%, and the ⁇ -vaierolactone in an amount of 28 to 50 wt%, based on the total weight of the solution as 100 wt%.
  • the tertiary amine-N-oxide is N-methyl morpholine oxide
  • the lactone is y-valerolactone
  • the solution in step a) comprises the cellulose in an amount of 10 to 25 wt%, water in an amount of 6 to 1 1 wt%, more preferably 8 to 1 1 wt%, the N-methyl morpholine oxide in an amount of 55 to 74 wt%, and the ⁇ -valerolactone in an amount of 5 to 27 wt%, more preferably 10 to 27 wt%, and most preferably 15 to 27 wt%, based on the total weight of the solution as 100 wt%.
  • the solution provided in step a) of the process in accordance with the invention may consist exclusively of dissolved cellulose, the tertiary amine-N-oxide, in particular NMMO, the lactone, in particular ⁇ -valerolactone, and water. However, it may also contain additives, e.g. stabilizers, which assist in the processing of the solution, or which provide desired properties of the final product.
  • the sum of the amounts of the dissolved cellulose, the tertiary amine-N-oxide, which is preferably NMMO, the lactone, which is preferably GVL, and water is 95 wt% or more, more preferably 97 wt% or more and even more preferably 99 wt% or more, based on the total weight of the solution as 100 wt%, and most preferably the solution provided in step a) of the process in accordance with the invention consists of dissolved cellulose, the tertiary amine-N-oxide, which is preferably NMMO, the lactone, which is preferably GVL, and water.
  • the method for the preparation of the solution provided in step a) is not particularly limited.
  • the cellulose is added to a composition comprising the tertiary amine-N-oxide, which is preferably NMMO, a lactone, which is preferably GVL, and water, and is dissolved therein.
  • the cellulose may be added to the total amount of the tertiary amine-N-oxide, the lactone, and water to be contained in the solution provided in step a), or to a first volume of the composition comprising the tertiary amine-N-oxide, the lactone, and water to prepare a suspension or a slurry, followed by the addition of the remaining amount to prepare the solution.
  • the provision of the solution in step a) may also involve milling of the cellulose with a first volume of the composition.
  • the cellulose is dissolved in the composition comprising the tertiary amine-N- oxide, the lactone, and water while the composition is heated to a temperature in the range of 50 to 120 °C, preferably 60 to 80 °C.
  • the dissolution of the cellulose in the heated composition may be accomplished by first heating the composition comprising the tertiary amine-N-oxide, the lactone, and water and subsequently adding the cellulose, or by first mixing the cellulose, the tertiary amine-N-oxide, the lactone, and water, and subsequently heating the mixture, with the latter being preferred.
  • the dissolution process is supported by agitating, e.g. stirring, the heated solvents.
  • step b) of the process in accordance with the invention is carried out following step a).
  • step b) the solution which has been provided in step a) is brought into a predetermined shape.
  • This process step thus provides a shaped intermediate product (also referred to as a shaped solution) comprising the dissolved cellulose, a tertiary amine-N-oxide, which is preferably NMMO, a lactone, which is preferably GVL, and water.
  • a shaped intermediate product also referred to as a shaped solution
  • a shaped intermediate product also referred to as a shaped solution
  • a shaped intermediate product comprising the dissolved cellulose, a tertiary amine-N-oxide, which is preferably NMMO, a lactone, which is preferably GVL, and water.
  • the predetermined shape into which the solution can be brought are a film shape, or a fiber shape.
  • the shaping of the solution may be accomplished, e.g., by a mold into which the solution is filled, such as a mold for film casting, or by a die through which the solution is extruded or discharged.
  • a die in the form of a spinneret is used to provide an intermediate product in the shape of a fiber.
  • the viscosity of the shaped intermediate product is sufficiently high that the predetermined shape is maintained while the shaped intermediate product is handled (e.g. transported or processed).
  • an intermediate product in film shape can typically be taken from a mold in which it was shaped, and can be immersed in a subsequent step in a coagulation bath, or an intermediate product in a fiber shape can typically be drawn to adjust the diameter of the fiber and/or to adjust the orientation of the cellulose molecules contained therein.
  • the shaped intermediate product can still be considered as a solution wherein the cellulose molecules are surrounded by the composition comprising the tertiary amine-N-oxide, the lactone, and water.
  • the shaping of the solution in step b) is carried out while the solution has a temperature in the range of 20 to 120 °C, more preferably in the range of 25 to 75 °C, and even more preferably in the range of 25 to 50 °C.
  • the process in accordance with the invention is a fiber spinning process wherein the solution is brought into a fiber shape in step b) by discharging it as a spinning dope through a spinneret, and wherein the shaped cellulose product is a cellulose fiber.
  • the spinning dope is discharged through the spinneret with a preferred solution temperature in the range of 20 to 120 °C, more preferably in the range of 25 to 75 °C, and even more preferably in the range of 25 to 50 °C.
  • the solution is discharged through the spinneret to provide an intermediate product in fiber shape, and that the intermediate product subsequently passes through an air gap, where it can be subjected to one or more processing steps of cooling, moistening or drawing.
  • a drawing step the desired diameter of the fiber shape can be adjusted and/or the orientation of the cellulose molecules contained in the intermediate product can be adjusted.
  • the shaping of the solution in step b) and the subsequent regeneration of the dissolved cellulose in step c) are carried out in a dry jet-wet fiber spinning apparatus.
  • Procedures and suitable devices to bring a cellulose solution into a predetermined shape, and in particular to carry out a fiber spinning process using a cellulose solution are well known in the art and described, e.g., in US 5,589,125, US 5,698,151 , US 5,948,655 or WO 01/96636).
  • step c) of the process in accordance with the invention is carried out following step b).
  • step c) the dissolved cellulose is regenerated in a coagulation bath (also referred to as a precipitation bath).
  • a coagulation bath also referred to as a precipitation bath.
  • the regeneration of the dissolved cellulose involves the immersion of the shaped intermediate product which is provided in step b), and which comprises the dissolved cellulose, the tertiary amine-N-oxide, which is preferably NMMO, the lactone, which is preferably GVL, and water, in the coagulation bath.
  • the solution is brought into a fiber shape in step b) by discharging it as a spinning dope through a spinneret, and the fiber shaped intermediate product is then injected into the coagulation bath to regenerate the dissolved cellulose.
  • the regeneration of the cellulose generally involves the extraction of tertiary amine-N-oxide and lactone from the shaped intermediate product (also referred to as shaped solution) into the coagulation bath.
  • the liquid in the coagulation bath is typically water or an aqueous solution with a water content of 70 wt% or more, more preferably 80 wt% or more, based on the total weight of the coagulation bath as 100 wt%.
  • the coagulation bath may also contain 100 wt% of water.
  • the rate at which the regeneration proceeds may be controlled by using a coagulation bath in step c) of the process in accordance with the invention containing one or more organic additives in combination with the water.
  • additives include in particular the tertiary amine-N-oxide and/or the lactone which also contained in the solution provided in step a) in accordance with the invention.
  • the concentration of the tertiary amine-N-oxide and/or the lactone, if present in the coagulation bath is lower than their concentration in the shaped intermediate product (shaped solution), such that a concentration gradient is formed when the shaped intermediate product is contacted with the coagulation bath.
  • the temperature of the coagulation bath during the regeneration of the cellulose in step c) of the process in accordance with the invention is not particularly limited, and ranges preferably from 0 °C to 30 °C, preferably from 10 °C to 25 °C.
  • a particularly preferred process in accordance with the invention is a process for the preparation of a cellulose fiber, comprising the steps of:
  • the provided shaped cellulose product may be subjected to further process steps as needed, such as a washing step and/or a drying step.
  • further process steps may be desired wherein the initial shaped product is processed.
  • one or more of the following steps may be added in the case where the shaped cellulose product is a cellulose fiber: cutting the fiber, crimping fibers, treating the fiber with a finishing agent, and weaving or providing a non-woven structure.
  • the process of the invention comprises a further step wherein the tertiary amine-N-oxide and the lactone which are dissolved in the coagulation liquid or the coagulation bath are recovered from the coagulation liquid/the coagulation bath, and can be recycled.
  • Important aspects of the present invention shall be summarized in the following items, wherein items 1 , 19 and 30 describe the invention in general terms, whereas items 2 to 18 and 20 to 29 describe preferred embodiments.
  • a process for the preparation of a shaped cellulose product comprising the steps of: a) providing a solution comprising dissolved cellulose, a tertiary amine-N-oxide, a lactone selected from ⁇ -valeroiactone, ⁇ -butyrolactone, and a combination thereof, and water;
  • tertiary amine-N-oxide is at least one selected from a cyclic tertiary amine-N-oxide, and a tertiary amine-N-oxide having the structure:
  • each of R-i and R 2 is independently an alkyl group with 1 to 4 C-atoms
  • R 3 is selected from the group consisting of a hydrogen atom, a hydroxy! group and an alkoxy group with 1-4 C-atoms
  • m and n are whole numbers which fulfill the conditions 1 ⁇ m ⁇ 8 and 1 ⁇ n ⁇ 4, respectively.
  • step a) comprises 1 to 30 wt%, more preferably 1 to 25 wt%, even more preferably 5 to 25 wt%, and most preferably 10 to 25 wt% of dissolved cellulose, based on the total weight of the solution as 100 wt%.
  • step a) comprises the tertiary amine-N-oxide in an amount of 40 to 85 wt%, more preferably 43 to 74 wt%, and most preferably 43 to 61 wt%, based on the total weight of the solution as 100 wt%.
  • the solution provided in step a) comprises the lactone in an amount of up to 65 wt%, more preferably 5 to 53 wt%, even more preferably 10 to 50 wt%, and most preferably 15 to 50 wt%, based on the total weight of the solution as 100 wt%.
  • step a) comprises the water in an amount of 5 to 13 wt%, more preferably 5 to 12 wt%, even more preferably 6 to 11 wt%, and most preferably 6 to 10 wt%, based on the total weight of the solution as 100 wt%.
  • step a) comprises the water in an amount of 20 wt% or less, more preferably 16 wt% or less, even more preferably 10 to 16 wt%, and most preferably 13 to 16 wt%, based on the sum of weights of the water and the tertiary amine-N-oxide as 100 wt%.
  • the tertiary amine-N-oxide is N-methyl morpholine oxide
  • the lactone is ⁇ -valerolactone
  • the solution provided in step a) comprises the cellulose in an amount of 10 to 25 wt%, water in an amount of 6 to 11 wt%, the N-methyl morpholine oxide in an amount of 55 to 74 wt%, and the v-valerolactone in an amount of 5 to 27 wt%, more preferably 10 to 27 wt%, and most preferably 15 to 27 wt%, based on the total weight of the solution as 100 wt%.
  • step a) comprises the tertiary amine-N-oxide and the water in the form of a hydrate of the tertiary amine-N-oxide, more preferably in the form of the monohydrate of the tertiary amine-N-oxide.
  • step a) comprises dissolving the cellulose in a composition comprising the tertiary amine-N-oxide, the lactone, and water.
  • step b) 14. The process of any of item 1 to 13, wherein the solution is brought into a predetermined shape in step b) by discharging it through a die. 15. The process of any of items 1 to 16, wherein step b) is carried out while the solution has a temperature in the range of 20 to 120 °C, more preferably in the range of 25 to 75 °C, and most preferably in the range of 25 to 50 °C.
  • a cellulose solution comprising dissolved cellulose, a tertiary amine-N-oxide, a lactone selected from y-valerolactone, ⁇ -butyrolactone, and a combination thereof, and water
  • tertiary amine-N-oxide is at least one selected from a cyclic tertiary amine-N-oxide, and a tertiary amine-N-oxide having the structure:
  • each of i and R 2 is an alkyl group with 1 to 4 C-atoms
  • R 3 is selected from the group consisting of a hydrogen atom, a hydroxyl group and an alkoxy group with 1-4 C- atoms
  • m and n are whole numbers which fulfill the conditions 1 ⁇ m ⁇ 8 and 1 ⁇ n ⁇ 4, respectively.
  • FIG. 1 shows the melting temperatures (onset temperature T on and peak maximum temperature T pm ) of NMMO mono./GVL mixtures as a function of the GVL content.
  • MCC microcrystalline cellulose
  • GCL lactones gamma-valerolactone
  • GBL gamma-hexalactone
  • GBL gamma-butyrolactone
  • DMSO dimethyl sulfoxide
  • PC propylene carbonate
  • ⁇ gas-phase dipole moment
  • D Debeye
  • the following table shows the amounts of cosolvents which lead to a clear and stable solution for the indicated amounts of cellulose upon and after dissolution at 80 °C.
  • the proportion of NMMO monohydrate in each solution can be calculated according to the following equation: 100 wt% - wt%(celiulose) - wt%(co-solvent).
  • PC turned out not to be suitable as a cosolvent, because degradation occurred during the dissolution with NMMO monohydrate (the solution turned brown and a gas was released).
  • DMSO a maximum ratio of 35 wt% could be used to dissolve 1 wt% of cellulose, and a maximum ratio of 10 wt% to dissolve 10 wt% of cellulose.
  • the solution crystallized at room temperature, so it can not be spun at low temperatures.
  • Microcrystal!ine cellulose (MCC) used in the preparation of the spinning dope was purchased from Merck (Germany).
  • the degree of polymerization (DP) of MCC in cupriethylenediamine hydroxide solution was measured with an Ubbelohde viscometer and is about 124.
  • Cellulose was dried at 70°C for 24 hours prior to use.
  • 4-Methyimorpho!ine-N-oxide monohydrate (NMMO mono.), purity >95 %) was obtained from Sigma Aldrich (Germany). Its water content was determined by coulometric Karl-Fischer-Titration (899 coulometer, Metronohm) and was around 13.3 wt%.
  • ⁇ -Valeroiactone at purity>99% was purchased from Sigma Aldrich (Germany) and dried effectively with molecular sieves prior to use.
  • the water content of GVL was determined by Karl-Fischer-titration and is less than 0.01 wt%.
  • the spinning dope was prepared by mixing desired amounts of MCC, NMMO mono, and GVL in sealed glass vials under nitrogen atmosphere to avoid water adsorption. The samples were mechanically stirred for 2 hours at 80°C to obtain a homogeneous solution. This solution was ultrasonicated for 10 minutes also at 80°C to remove bubbles. Fiber spinning
  • FIG. 2 provides a schematic illustration of this spinning set-up.
  • the solution is discharged from the dope vessel (5) through a spinneret (7) under nitrogen pressure.
  • a manometer (2) is used to check the actual pressure in the set-up.
  • Two valves (3 and 4) are connected between the dope vessel and the nitrogen pipe (1 ).
  • the dope valve allows regulating the nitrogen flow and the second valve (ventilation valve) is used to ventilate the apparatus at the end of the process.
  • the control of both valves is possible either manually or automatically with an electronic controlled system (6).
  • the temperature of the spinning dope is regulated using a sand bath (1 1).
  • the solution coagulates in a spinning bath (8) and forms a filament.
  • the resulting filament is wound on a take-off roller (9) at linear speed, which is controlled by an electronic system (10). Finally, fibers are washed and dried on the bobbin.
  • Coagulation of the fibers took place in a distilled water bath at room temperature.
  • the fibers were wound on the bobbin at linear speeds of 3.5-8.3 m/min. They were then washed with a spray of distilled water and dried at room temperature.
  • Optical microscopy (Nikon Eclipse E400) was used to characterize the surface structure of the fibers.
  • Figure 1 shows the melting temperatures (onset temperature (T on ) and peak maximum temperature (T pm )) of NMMO monohydrate/GVL mixtures as a function of the GVL weight percentage.
  • Figure 2 shows a scheme of the lab-scale spinning set-up used to produce fibers
  • Figure 3 shows microphotographs illustrating the surface structure of cellulose fibers spun from solutions of 5 wt% cellulose, 58 wt% NMMO monohydrate and 37 wt% GVL at (A) 25°C, (B) 30°C, and (C) 40°C. Spinning bath was distilled H 2 0.

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Abstract

The present invention relates to a process for the preparation of a shaped cellulose product, which uses the cellulose in the form of a solution in a mixture of a tertiary amine-N-oxide and a lactone selected from γ-valerolactone, γ-butyrolactone, and a combination thereof. The process comprises the steps of providing a solution comprising dissolved cellulose, the tertiary amine-N-oxide, the lactone, and water; bringing the solution into a predetermined shape; and regenerating the dissolved cellulose in a coagulation bath. Moreover, the invention provides a solution comprising dissolved cellulose, a tertiary amine-N-oxide, a lactone selected from y-vaierolactone, γ-butyrolactone, and a combination thereof, and water, which is used in the process.

Description

Process for the preparation of a cellulose product
The present invention relates to a process which allows the fabrication of a shaped cellulose product, in particular cellulose fibers, in an efficient and sustainable manner.
Cellulose is a primary resource from lignocellulosics such as wood, cotton plants, and other lignified higher plants. It is the most important biomass resource on earth and has an estimated annual production of 100-150 billion tons. Because of its easy availability, cellulose is of great importance for industrial processing to produce fibers, films, and membranes, for example.
In the past twenty years, an environmentally friendly and simple process for the processing or (re)shaping of cellulose has been used to replace the earlier viscose technology and to produce industrial celluiosic fibers. This process is called Lyocell- or NMMO-process and is based on the dissolution and the shaping of cellulose assisted by a tertiary amine-oxide, in particular N-methylmorpholine-N-oxide (NMMO), as a solvent (e.g. US 5,589,125; US 5,698,151 ; M. Walker et al., "N-Morpholinoxid (NMMO) - Die Entwicklung eines Losemittels zur Industriellen Produktion von Zelluiosefasern", Lenzinger Berichte 76/97). US 4,145,532 discloses a process for the preparation of a cellulose product, comprising precipitating cellulose from a solution thereof in a solvent comprising a tertiary amine oxide, water, and an optional aprotic organic liquid co-solvent having a dipole moment greater than about 3.5 Debye.
The Lyocell process offers several advantages: it is non-toxic, environmentally benign, and allows the dissolution of cellulose without derivatization or pretreatment. The commercial Lyocell fibers were first produced by Courtaulds (Great Britain) and are currently made by Lenzing AG (Austria) under the Tencel® trade name on an industrial scale (100 ktons/year). Solutions of cellulose in NMMO and water can also be used to prepare other types of shaped or molded products (cf. WO 01/96636 A1).
In the commercial process, Lyocell fibers are made with a dry jet- wet spinning technique and different process steps. The first process step consists of dissolving cellulose in NMMO in presence of water. This solution is generally composed of 10-15 % cellulose, 50-60 % NM O, and 20-30 % water. The excess of water is extracted at reduced pressure and high temperature until complete dissolution of cellulose is obtained (typically at 13-15 wt% of water, i.e. a percentage of water close to the one found in NMMO monohydrate). After filtration and outgassing, this spinning dope is then extruded at elevated temperatures (90- 120°C) through an air gap into a coagulation bath. There, the extrudate is impoverished of NMMO, which allows the regeneration of the cellulose. Finally, the obtained fibers are washed and dried. At the end of the process, NMMO is recovered from the baths and recycled.
However, a remaining disadvantage of the Lyoceil process is a relatively high energy consumption due to elevated process temperatures and the reduction of the water content prior to the shaping (e.g. spinning) of the cellulose solutions which may be necessary. Furthermore, stabilizers are generally used to prevent the thermal degradation of NMMO and cellulose, which can occur during high process temperatures.
Therefore, there is still a need for efficient processes which allow the preparation of high quality products, in particular shaped or molded products, from renewable resources such as cellulose, and which have a reduced environmental impact.
In order to solve this problem, the present invention provides a process for the preparation of a shaped cellulose product as defined in the annexed claims, which process comprises the steps of:
a) providing a solution comprising dissolved cellulose, a tertiary amine-N-oxide, a lactone selected from y-valerolactone, γ-butyrolactone, and a combination thereof, and water;
b) bringing the solution into a predetermined shape; and
c) regenerating the dissolved cellulose in a coagulation bath;
to provide the shaped cellulose product.
It has been found that the use of a lactone selected from γ-valerolactone and y- butyrolactone, and a combination thereof as a co-solvent in the solution comprising the cellulose allows improving the processability, in particular the spinnabiiity, of the cellulose solution, in addition, lactones can be obtained from renewable resources, and, in particular, γ-valerolactone is of very low toxicity and environmentally benign. Thus, the addition of the lactone can decrease the melting temperature of a blend of cellulose, a tertiary amine-N-oxide, and the lactone, such that a solution can be prepared and/or brought into a predetermined shape at lower temperatures, compared to a solution of the cellulose in a solvent comprising the tertiary amine-N-oxide without the use of the lactone. In particular, if the solution is provided as a spinning dope, it can be spun at lower temperatures to provide cellulose fibers of good quality. Thus, the thermal load on the cellulose during the process can be reduced. As a result, thermal degradation is prevented, the use of chemical stabilizers can be reduced or avoided, and/or the consumption of energy during the process can be reduced.
Moreover, the lactone selected from γ-valerolactone, γ-butyrolactone, and a combination thereof beneficiaiiy reduces the viscosity of the solution comprising the ceiiuiose, the tertiary amine-N-oxide, and the lactone compared to a solution of the ceiiuiose in a solvent comprising the tertiary amine-N-oxide without the use of the lactone. This allows the concentration of the cellulose in the solution to be increased at a given temperature while maintaining the rheologicai properties of the solution, which can be of relevance for the step of shaping the solution, e.g. in a spinning step. In this regard, it has further been found that γ- valerolactone and γ-butyrolactone can be added in significant amounts to a tertiary amine-N- oxide, such as NMMO, without disturbing the dissolution process of cellulose and without affecting the stability of the solution. Thus, the ratio of lactone/ tertiary amine-N-oxide in the solution provided in step a) of the process in accordance with the invention can be varied over wider ranges depending on the desired properties of the solution.
As set forth in the annexed claims, the process in accordance with the invention provides a shaped cellulose product, i.e. a product comprising cellulose as a main constituting material, preferably a product which essentially consists of cellulose. A product comprising cellulose as a main constituting material as referred to herein preferably contains 80 wt% or more, more preferably 90 wt% or more, and even more preferably 95 wt.% or more of cellulose, based on the total weight of the product as 100 wt%. As noted above, a product essentially consisting of cellulose or consisting of cellulose is particularly preferred. In this context, "essentially consisting of cellulose" refers to a product which is formed from cellulose, and which may contain remainders of substances (e.g. in an amount of not more than 3 wt%, preferably not more than 1 wt%) which are derived e.g. from the biomass source of the cellulose. The shaped product prepared by the process in accordance with the invention can take various shapes, including e.g. the shape of a film, a membrane or a fiber. Preferably, the process is used for the preparation of a cellulose fiber as the shaped cellulose product. In step a) of the process in accordance with the invention, a solution is provided which comprises dissolved cellulose, a tertiary amine-N-oxide, a lactone selected from y- valerolactone, γ-butyrolactone, and a combination thereof, and water.
The cellulose which is comprised by the solution provided in step a) is not particularly limited. It can be conveniently obtained from biomass resources. Depending on the intended use and the required quality of the shaped cellulose product provided by the process of the invention, cellulose material from recycled materials, such as waste paper, cardboard, other cellulose containing fiber assemblies, from agricultural waste, such as mechanically and/or chemically broken up annual plants, or from forestry material, such as wood may be included at least in part in the cellulose is dissolved in the solution provided in step a). Preferably, the cellulose is introduced into the solution in the form of small pieces, e.g. as a powder. Also, it is preferred that the cellulose is dried before it is introduced into the solution to control the water content of the solution. Thus, if necessary, the cellulose material may be milled and/or ground and/or dried before the solution is provided.
Preferably, the degree of polymerization (DP) of the cellulose dissolved in the solution provided in step a) ranges from 100 to 1200, more preferably from 100 to 1000 and most preferably from 400 to 1000. In this context, the degree of polymerization is indicated as the viscosity average degree of polymerization, as it may be determined from a cupriethylenediamine hydroxide solution of the cellulose using an Ubbelohde viscometer, typically at a temperature of 20°C.
The tertiary amine N-oxide may be, for example, at least one selected from a cyclic tertiary amine-N-oxide wherein the tertiary N atom forms part of a heterocyclic structure, and a tertiary amine oxide as defined in US 5,409,532, and having the structure:
R1R2N(0)-(CH2)m-0-(CH2)n-R3,
wherein each of R, and R2 is independently an a!kyl group with 1 to 4 C-atoms, R3 is selected from the group consisting of a hydrogen atom, a hydroxyi group and an alkoxy group with 1-4 C-atoms, and m and n are whole numbers which fulfill the conditions 1 < m < 8 and 1 < n≤ 4, respectively. Preferably, the tertiary amine N-oxide is at least one selected from N,N,N-trimethylamine-N- oxide, N,N-dimethylcyclohexylamine-N-oxide, N-methylmorpholine-N-oxide, N- methylpiperidine-N-oxide, N-methylazacyclopheptane-N-oxide, N-methylpyrrolidine-N-oxide, N,N-dimethylbenzylamine-N-oxide, N,N-dimethylethanolamine-N-oxide and 2-(N,N- dimethy!aminoethoxy)-ethanol-N-oxide. More preferably, the tertiary amine N-oxide comprises N-methylmorpholine-N-oxide (also referred to herein as NMMO), and even further preferably the tertiary amine N-oxide is (i.e. consists of) N-methylmorpholine-N-oxide. For example, the N-methylmorpholine-N-oxide can be favorably used in the form of its monohydrate (also referred to herein as NMMO mono.). Using this monohydrate, a defined water content of the solution prepared in step a) of the process in accordance with the invention can be conveniently provided.
The lactone contained in the solution provided in step a) of the process in accordance with the invention is selected from γ-valerolactone (also referred to as gamma-valerolactone, or GVL), γ-butyrolactone (also referred to as gamma-butyrolactone, or GBL), and a combination thereof. Thus, the process encompasses the provision of a solution which comprises γ- vaiero!actone and is free of γ-butyrolactone, a solution which comprises γ-butyrolactone and is free of γ-valerolactone, or a solution which contains a combination of γ-valerolactone and γ-butyrolactone. Preferred in the context of the invention are solutions containing γ- valerolactone, either as the only lactone or in combination with γ-butyrolactone, and more preferably the solution comprises γ-vaierolactone as the only lactone. γ-Valerolactone is of particular interest since it is not only stable under typical production conditions applied for the preparation of cellulose products, such as cellulose fibers, and non-toxic, but also conveniently obtainable from biomass, e.g. via the degradation of cellulose. Moreover, it has the most favorable toxicological profile.
As noted above, it has been surprisingly found that the addition of the lactone to the solution comprising cellulose allows improving the processability of the cellulose solution, without exerting a negative effect on the quality, e.g. the surface structure, of the obtained cellulose product.
In the solution provided in step a) of the process in accordance with the invention, the content of cellulose is preferably 1 wt% or more, more preferably 5 wt% or more, even more preferably 8 wt% or more, and most preferably 10 wt% or more, based on the total weight of the solution as 100 wt%. It is preferably 30 wt% or less, more preferably 25 wt% or less, based on the total weight of the solution as 100 wt%. For example, the content may preferably be 1 to 30 wt%, more preferably 1 to 25 wt%, even more preferably 5 to 25 wt%, and most preferably 10 to 25 wt%, based on the total weight of the solution as 100 wt%.
The content of the tertiary amine-N-oxide, preferably of NMMO, in the solution provided in step a) of the process in accordance with the invention is preferably 40 to 85 wt%, more preferably 43 to 74 wt%, and most preferably 43 to 61 wt, based on the total weight of the solution as 100 wt%. Within these preferred ranges, it is further preferred to use the amine- N-oxide in an amount of 43 to 56 wt% if the solution contains the cellulose in an amount of 1 to less than 10 wt%, and to use the amine-N-oxide in an amount of 55 to 74 wt%, more preferably 55 to 61 wt%, if the solution contains the cellulose in an amount of 10 wt% or more, e.g. 10 to 25 wt%. If a hydrate of the tertiary amine-N-oxide is used, the weight of the water contained in the hydrate is not included in these percentages. Rather, its weight will be taken into account as weight of water contained in the solution provided in step a). The content of the lactone selected from y-valerolactone, γ-butyrolactone and a combination thereof (i.e the content of γ-valerolactone, if used alone as the preferred embodiment, the content of γ-butyrolactone if used alone, or the combined contents of γ-valerolactone and of γ-butyroiactone, if used in combination) in the solution provided in step a) of the process in accordance with the invention is typically 65 wt% or less, preferably 5 to 53 wt%, more preferably 10 to 50 wt%, even more preferably 15 to 50 wt%, based on the total weight of the solution as 100 wt%. Within these preferred ranges, it is further preferred to use the lactone in an amount of 26 to 50 wt% if the solution contains the cellulose in an amount of 1 to less than 10 wt%, and to use the lactone in an amount of 5 to 27 wt%, more preferably 10 to 27 wt% and even more preferably 15 to 27 wt%, if the solution contains the cellulose in an amount of 10 wt% or more, e.g. 10 to 25 wt%.
The content of water in the solution provided in step a) of the process in accordance with the invention is preferably 5 to 13 wt%, preferably 5 to 12 wt%, more preferably 6 to 1 1 wt%, and most preferably 6 to 10 wt%, based on the total weight of the solution as 100 wt%.
As regards the content of water, it is preferred that the solution provided in step a) comprises the water in an amount of 20 wt% or less, preferably 16 wt% or less, more preferably 10 to 16 wt%, and most preferably 13 to 16 wt%, based on the sum of weights of the water and the tertiary amine-N-oxide as 100 wt%. For example, a water content in this range can be conveniently provided using the monohydrate of NMMO as the tertiary amine-N-oxide. Thus, in one exemplary embodiment of the process in accordance with the invention, the tertiary amine-N-oxide is N-methyi morpholine oxide, the lactone is γ-valerolactone, and the solution in step a) comprises the cellulose in an amount of 1 to less than 10 wt%, water in an amount of 6 to 9 wt%, the N-methyi morpholine oxide in an amount of 43 to 56 wt%, and the γ-vaierolactone in an amount of 28 to 50 wt%, based on the total weight of the solution as 100 wt%.
In a more preferred exemplary embodiment of the process in accordance with the invention, the tertiary amine-N-oxide is N-methyl morpholine oxide, the lactone is y-valerolactone, and the solution in step a) comprises the cellulose in an amount of 10 to 25 wt%, water in an amount of 6 to 1 1 wt%, more preferably 8 to 1 1 wt%, the N-methyl morpholine oxide in an amount of 55 to 74 wt%, and the γ-valerolactone in an amount of 5 to 27 wt%, more preferably 10 to 27 wt%, and most preferably 15 to 27 wt%, based on the total weight of the solution as 100 wt%.
The solution provided in step a) of the process in accordance with the invention may consist exclusively of dissolved cellulose, the tertiary amine-N-oxide, in particular NMMO, the lactone, in particular γ-valerolactone, and water. However, it may also contain additives, e.g. stabilizers, which assist in the processing of the solution, or which provide desired properties of the final product. Preferably, the sum of the amounts of the dissolved cellulose, the tertiary amine-N-oxide, which is preferably NMMO, the lactone, which is preferably GVL, and water is 95 wt% or more, more preferably 97 wt% or more and even more preferably 99 wt% or more, based on the total weight of the solution as 100 wt%, and most preferably the solution provided in step a) of the process in accordance with the invention consists of dissolved cellulose, the tertiary amine-N-oxide, which is preferably NMMO, the lactone, which is preferably GVL, and water.
The method for the preparation of the solution provided in step a) is not particularly limited. Typically, the cellulose is added to a composition comprising the tertiary amine-N-oxide, which is preferably NMMO, a lactone, which is preferably GVL, and water, and is dissolved therein. Following this procedure, the cellulose may be added to the total amount of the tertiary amine-N-oxide, the lactone, and water to be contained in the solution provided in step a), or to a first volume of the composition comprising the tertiary amine-N-oxide, the lactone, and water to prepare a suspension or a slurry, followed by the addition of the remaining amount to prepare the solution. The provision of the solution in step a) may also involve milling of the cellulose with a first volume of the composition. Preferably, the cellulose is dissolved in the composition comprising the tertiary amine-N- oxide, the lactone, and water while the composition is heated to a temperature in the range of 50 to 120 °C, preferably 60 to 80 °C. The dissolution of the cellulose in the heated composition may be accomplished by first heating the composition comprising the tertiary amine-N-oxide, the lactone, and water and subsequently adding the cellulose, or by first mixing the cellulose, the tertiary amine-N-oxide, the lactone, and water, and subsequently heating the mixture, with the latter being preferred. Preferably, the dissolution process is supported by agitating, e.g. stirring, the heated solvents.
As will be appreciated by the skilled reader, step b) of the process in accordance with the invention is carried out following step a). In step b), the solution which has been provided in step a) is brought into a predetermined shape. This process step thus provides a shaped intermediate product (also referred to as a shaped solution) comprising the dissolved cellulose, a tertiary amine-N-oxide, which is preferably NMMO, a lactone, which is preferably GVL, and water. Examples for the predetermined shape into which the solution can be brought are a film shape, or a fiber shape. The shaping of the solution may be accomplished, e.g., by a mold into which the solution is filled, such as a mold for film casting, or by a die through which the solution is extruded or discharged. Preferably, a die in the form of a spinneret is used to provide an intermediate product in the shape of a fiber.
Typically, the viscosity of the shaped intermediate product is sufficiently high that the predetermined shape is maintained while the shaped intermediate product is handled (e.g. transported or processed). For example, an intermediate product in film shape can typically be taken from a mold in which it was shaped, and can be immersed in a subsequent step in a coagulation bath, or an intermediate product in a fiber shape can typically be drawn to adjust the diameter of the fiber and/or to adjust the orientation of the cellulose molecules contained therein. Nevertheless, the shaped intermediate product can still be considered as a solution wherein the cellulose molecules are surrounded by the composition comprising the tertiary amine-N-oxide, the lactone, and water.
Preferably, the shaping of the solution in step b) is carried out while the solution has a temperature in the range of 20 to 120 °C, more preferably in the range of 25 to 75 °C, and even more preferably in the range of 25 to 50 °C.
In a preferred embodiment, the process in accordance with the invention is a fiber spinning process wherein the solution is brought into a fiber shape in step b) by discharging it as a spinning dope through a spinneret, and wherein the shaped cellulose product is a cellulose fiber. Also in this embodiment, the spinning dope is discharged through the spinneret with a preferred solution temperature in the range of 20 to 120 °C, more preferably in the range of 25 to 75 °C, and even more preferably in the range of 25 to 50 °C. In the fiber spinning process, it is preferred that the solution is discharged through the spinneret to provide an intermediate product in fiber shape, and that the intermediate product subsequently passes through an air gap, where it can be subjected to one or more processing steps of cooling, moistening or drawing. As noted above, in a drawing step, the desired diameter of the fiber shape can be adjusted and/or the orientation of the cellulose molecules contained in the intermediate product can be adjusted. Thus, it is particularly preferred that the shaping of the solution in step b) and the subsequent regeneration of the dissolved cellulose in step c) are carried out in a dry jet-wet fiber spinning apparatus.
Procedures and suitable devices to bring a cellulose solution into a predetermined shape, and in particular to carry out a fiber spinning process using a cellulose solution, are well known in the art and described, e.g., in US 5,589,125, US 5,698,151 , US 5,948,655 or WO 01/96636).
As will be appreciated by the skilled reader, step c) of the process in accordance with the invention is carried out following step b). In step c), the dissolved cellulose is regenerated in a coagulation bath (also referred to as a precipitation bath). Thus, a shaped cellulose product is provided.
Typically, the regeneration of the dissolved cellulose involves the immersion of the shaped intermediate product which is provided in step b), and which comprises the dissolved cellulose, the tertiary amine-N-oxide, which is preferably NMMO, the lactone, which is preferably GVL, and water, in the coagulation bath. Preferably, the solution is brought into a fiber shape in step b) by discharging it as a spinning dope through a spinneret, and the fiber shaped intermediate product is then injected into the coagulation bath to regenerate the dissolved cellulose. The regeneration of the cellulose generally involves the extraction of tertiary amine-N-oxide and lactone from the shaped intermediate product (also referred to as shaped solution) into the coagulation bath.
The liquid in the coagulation bath is typically water or an aqueous solution with a water content of 70 wt% or more, more preferably 80 wt% or more, based on the total weight of the coagulation bath as 100 wt%. The coagulation bath may also contain 100 wt% of water. If desired, the rate at which the regeneration proceeds may be controlled by using a coagulation bath in step c) of the process in accordance with the invention containing one or more organic additives in combination with the water. Such additives include in particular the tertiary amine-N-oxide and/or the lactone which also contained in the solution provided in step a) in accordance with the invention. However, as will be appreciated by the skilled reader, the concentration of the tertiary amine-N-oxide and/or the lactone, if present in the coagulation bath, is lower than their concentration in the shaped intermediate product (shaped solution), such that a concentration gradient is formed when the shaped intermediate product is contacted with the coagulation bath. The temperature of the coagulation bath during the regeneration of the cellulose in step c) of the process in accordance with the invention is not particularly limited, and ranges preferably from 0 °C to 30 °C, preferably from 10 °C to 25 °C.
From the above, it will be apparent to the skilled reader that a particularly preferred process in accordance with the invention is a process for the preparation of a cellulose fiber, comprising the steps of:
a) providing a solution comprising dissolved cellulose, N-methyl morpholine oxide, v- valerolactone and water;
b) discharging the solution as a spinning dope through a spinneret; and
c) injecting the shaped solution into a coagulation bath to regenerate the dissolved cellulose and to provide the cellulose fiber.
Once the cellulose has been regenerated in step b), the provided shaped cellulose product may be subjected to further process steps as needed, such as a washing step and/or a drying step. As will be understood by the skilled person, one or more further steps may be desired wherein the initial shaped product is processed. For example, one or more of the following steps may be added in the case where the shaped cellulose product is a cellulose fiber: cutting the fiber, crimping fibers, treating the fiber with a finishing agent, and weaving or providing a non-woven structure.
Moreover, it is preferred that the process of the invention comprises a further step wherein the tertiary amine-N-oxide and the lactone which are dissolved in the coagulation liquid or the coagulation bath are recovered from the coagulation liquid/the coagulation bath, and can be recycled. Important aspects of the present invention shall be summarized in the following items, wherein items 1 , 19 and 30 describe the invention in general terms, whereas items 2 to 18 and 20 to 29 describe preferred embodiments.
1. A process for the preparation of a shaped cellulose product, comprising the steps of: a) providing a solution comprising dissolved cellulose, a tertiary amine-N-oxide, a lactone selected from γ-valeroiactone, γ-butyrolactone, and a combination thereof, and water;
b) bringing the solution into a predetermined shape; and
c) regenerating the dissolved cellulose in a coagulation bath;
to provide the shaped cellulose product.
2. The process of item 1 , wherein the tertiary amine-N-oxide is at least one selected from a cyclic tertiary amine-N-oxide, and a tertiary amine-N-oxide having the structure:
R1R2N(0)-(CH2)m-0-(CH2)n-R3l
wherein each of R-i and R2 is independently an alkyl group with 1 to 4 C-atoms, R3 is selected from the group consisting of a hydrogen atom, a hydroxy! group and an alkoxy group with 1-4 C-atoms, and m and n are whole numbers which fulfill the conditions 1 < m≤ 8 and 1 < n≤ 4, respectively.
3. The process of item 1 or 2, wherein the tertiary amine-N-oxide comprises N-methyl morpholine oxide, more preferably wherein the tertiary amine-N-oxide is N-methyl morpholine oxide.
4. The process of any of items 1 to 3, wherein the lactone is γ-valerolactone (gamma- valerolactone).
5. The process of any of items 1 to 4, wherein the solution provided in step a) comprises 1 to 30 wt%, more preferably 1 to 25 wt%, even more preferably 5 to 25 wt%, and most preferably 10 to 25 wt% of dissolved cellulose, based on the total weight of the solution as 100 wt%.
6. The process of any of items 1 to 5, wherein the solution provided in step a) comprises the tertiary amine-N-oxide in an amount of 40 to 85 wt%, more preferably 43 to 74 wt%, and most preferably 43 to 61 wt%, based on the total weight of the solution as 100 wt%. 7. The process of any of items 1 to 6, wherein the solution provided in step a) comprises the lactone in an amount of up to 65 wt%, more preferably 5 to 53 wt%, even more preferably 10 to 50 wt%, and most preferably 15 to 50 wt%, based on the total weight of the solution as 100 wt%.
8. The process of any of items 1 to 7, wherein the solution provided in step a) comprises the water in an amount of 5 to 13 wt%, more preferably 5 to 12 wt%, even more preferably 6 to 11 wt%, and most preferably 6 to 10 wt%, based on the total weight of the solution as 100 wt%.
9. The process of any of items 1 to 8, wherein the solution provided in step a) comprises the water in an amount of 20 wt% or less, more preferably 16 wt% or less, even more preferably 10 to 16 wt%, and most preferably 13 to 16 wt%, based on the sum of weights of the water and the tertiary amine-N-oxide as 100 wt%.
10. The process of any of items 1 to 9, wherein, the tertiary amine-N-oxide is N-methyl morpholine oxide, the lactone is γ-valerolactone, and the solution provided in step a) comprises the cellulose in an amount of 10 to 25 wt%, water in an amount of 6 to 11 wt%, the N-methyl morpholine oxide in an amount of 55 to 74 wt%, and the v-valerolactone in an amount of 5 to 27 wt%, more preferably 10 to 27 wt%, and most preferably 15 to 27 wt%, based on the total weight of the solution as 100 wt%.
1 1. The process of any of items 1 to 10, wherein the solution provided in step a) comprises the tertiary amine-N-oxide and the water in the form of a hydrate of the tertiary amine-N-oxide, more preferably in the form of the monohydrate of the tertiary amine-N-oxide.
12. The process of any of items 1 to 11 , wherein step a) comprises dissolving the cellulose in a composition comprising the tertiary amine-N-oxide, the lactone, and water.
13. The process of item 12, wherein the cellulose is dissolved while the composition comprising the tertiary amine-N-oxide, the lactone, and water is heated to a temperature in the range of 50 to 120 °C, more preferably 60 to 80 °C.
14. The process of any of item 1 to 13, wherein the solution is brought into a predetermined shape in step b) by discharging it through a die. 15. The process of any of items 1 to 16, wherein step b) is carried out while the solution has a temperature in the range of 20 to 120 °C, more preferably in the range of 25 to 75 °C, and most preferably in the range of 25 to 50 °C.
16. The process of any of items 1 to 15, wherein the dissolved cellulose is regenerated in step c) by immersing a shaped intermediate product obtained in step b) in the coagulation bath.
17. The process of any of items 1 to 16 wherein the shaped cellulose product is a cellulose fiber, and wherein the solution is brought into a fiber shape in step b) by discharging it as a spinning dope through a spinneret.
18. The process of item 17, wherein the dissolved cellulose is regenerated in step c) by injecting the solution discharged in step b) into the coagulation bath.
19. A cellulose solution comprising dissolved cellulose, a tertiary amine-N-oxide, a lactone selected from y-valerolactone, γ-butyrolactone, and a combination thereof, and water
20. The solution of item 19, wherein the tertiary amine-N-oxide is at least one selected from a cyclic tertiary amine-N-oxide, and a tertiary amine-N-oxide having the structure:
R,R2N(0)-(CH?)m-0-(CH2)n-R3,
wherein each of i and R2 is an alkyl group with 1 to 4 C-atoms, R3 is selected from the group consisting of a hydrogen atom, a hydroxyl group and an alkoxy group with 1-4 C- atoms, and m and n are whole numbers which fulfill the conditions 1 < m≤ 8 and 1≤ n < 4, respectively.
21. The solution of item 19 or 20, wherein the tertiary amine-N-oxide comprises N-methyl morpholine oxide, more preferably wherein the tertiary amine-N-oxide is N-methyl morpholine oxide.
22. The solution of any of items 19 to 21 , wherein the lactone is γ-valerolactone (gamma- valerolactone).
23. The solution of any of items 19 to 22, which comprises 1 to 30 wt%, more preferably 1 to 25 wt%, even more preferably 5 to 25 wt%, and most preferably 10 to 25 wt% of dissolved cellulose, based on the total weight of the solution as 100 wt%. 24. The solution of any of items 19 to 23, which comprises the tertiary amine-N-oxide in an amount of 40 to 85 wt%, more preferably 43 to 74 wt%, and most preferably 43 to 61 wt%, based on the total weight of the solution as 100 wt%.
25. The solution of any of items 19 to 24, which comprises the lactone in an amount of up to 65 wt%, more preferably 5 to 53 wt%, even more preferably 10 to 50 wt%, and most preferably 15 to 50 wt%, based on the total weight of the solution as 100 wt%.
26. The solution of any of items 19 to 25, which comprises the water in an amount of 5 to 13 wt%, more preferably 5 to 12 wt%, even more preferably 6 to 1 1 wt%, and most preferably 6 to 10 wt%, based on the total weight of the solution as 100 wt%.
27. The solution of any of items 19 to 26, which comprises the water in an amount of 20 wt% or less, more preferably 16 wt% or less, even more preferably 10 to 16 wt%, and most preferably 13 to 16 wt%, based on the sum of weights of the water and the tertiary amine-N- oxide as 100 wt%.
28. The solution of any of items 19 to 27, wherein the tertiary amine-N-oxide is N-methyl morpholine oxide, the lactone is γ-valerolactone, and the solution comprises the cellulose in an amount of 10 to 25 wt%, water in an amount of 6 to 1 1 wt%, the N-methyl morpholine oxide in an amount of 55 to 74 wt%, and the γ-valero!actone in an amount of 5 to 27 wt%, more preferably 10 to 27 wt%, and most preferably 15 to 27 wt%, based on the total weight of the solution as 100 wt%.
29. The solution of any of items 19 to 28, which comprises the tertiary amine-N-oxide and the water in the form of a hydrate of the tertiary amine-N-oxide, preferably in the form of the monohydrate of the tertiary amine-N-oxide.
30. Use of the cellulose solution in accordance with any of items 19 to 29 as a spinning dope for the preparation of cellulose fibers.
The following examples illustrate the invention further. Examples
Influence of the lactone on the thermal characteristics of mixtures of the tertiary amine-N-oxide and the lactone
The positive effect of γ-valerolactone (GVL) on the thermal behavior of mixtures of 4-methyl morpholine-N-oxide monohydrate (NMMO mono.) and GVL was investigated with differential scanning calorimetry (DSC) measurements. Figure 1 shows the melting temperatures (onset temperature Ton and peak maximum temperature Tpm) of NMMO mono./GVL mixtures as a function of the GVL content. By adding GVL to NMMO mono., the melting temperature of the mixture decreases. That means that the heating temperature during the dissolution of cellulose in NMMO mono./GVL mixtures can be readily reduced compared to the process with only NMMO mono. For instance, 1 wt% cellulose could be dissolved at 59°C in a NMMO mono/GVL solution (weight ratio of 1 :1), instead of 80°C in exclusively NMMO mono.
Performance of γ-valerolactone and γ-butyro lactone as cosolvents of cellulose
The dissolution of different concentrations of microcrystalline cellulose (MCC) in NMMO monohydrate was observed in the presence of the lactones gamma-valerolactone (GVL), gamma-hexalactone (GHL) and gamma-butyrolactone (GBL). In addition, solutions containing dimethyl sulfoxide (DMSO) and propylene carbonate (PC) as polar cosolvents not belonging to the lactone class were prepared. Each of the cosolvents has a gas-phase dipole moment (μ) or more than 3.5 Debeye (D), as estimated by quantum mechanical, semi- empirical calculations with MOPAC (PM6).
The following table shows the amounts of cosolvents which lead to a clear and stable solution for the indicated amounts of cellulose upon and after dissolution at 80 °C. The proportion of NMMO monohydrate in each solution can be calculated according to the following equation: 100 wt% - wt%(celiulose) - wt%(co-solvent). PC turned out not to be suitable as a cosolvent, because degradation occurred during the dissolution with NMMO monohydrate (the solution turned brown and a gas was released). For DMSO, a maximum ratio of 35 wt% could be used to dissolve 1 wt% of cellulose, and a maximum ratio of 10 wt% to dissolve 10 wt% of cellulose. For higher ratios of DMSO, the solution crystallized at room temperature, so it can not be spun at low temperatures. Cellulose Cosolvent (wt%)
(wt%)
GVL GHL GBL D SO PC
(5.20 D) (5.28 D) (5.10 D) (4.71 D) (5.73 D)
1 50 35 65 35 0
5 37 25 50 - -
8 28 15 40 - -
10 27 10 30 10 -
Preparation of cellulose fibers as shaped cellulose products
Materials and preparation of the spinning dope Microcrystal!ine cellulose (MCC) used in the preparation of the spinning dope was purchased from Merck (Germany). The degree of polymerization (DP) of MCC in cupriethylenediamine hydroxide solution was measured with an Ubbelohde viscometer and is about 124. Cellulose was dried at 70°C for 24 hours prior to use. 4-Methyimorpho!ine-N-oxide monohydrate (NMMO mono.), purity >95 %) was obtained from Sigma Aldrich (Germany). Its water content was determined by coulometric Karl-Fischer-Titration (899 coulometer, Metronohm) and was around 13.3 wt%. γ-Valeroiactone (GVL) at purity>99% was purchased from Sigma Aldrich (Germany) and dried effectively with molecular sieves prior to use. The water content of GVL was determined by Karl-Fischer-titration and is less than 0.01 wt%. The spinning dope was prepared by mixing desired amounts of MCC, NMMO mono, and GVL in sealed glass vials under nitrogen atmosphere to avoid water adsorption. The samples were mechanically stirred for 2 hours at 80°C to obtain a homogeneous solution. This solution was ultrasonicated for 10 minutes also at 80°C to remove bubbles. Fiber spinning
The cellulose dope was spun by an apparatus developed in our laboratory. Figure 2 provides a schematic illustration of this spinning set-up. The solution is discharged from the dope vessel (5) through a spinneret (7) under nitrogen pressure. A manometer (2) is used to check the actual pressure in the set-up. Two valves (3 and 4) are connected between the dope vessel and the nitrogen pipe (1 ). The dope valve allows regulating the nitrogen flow and the second valve (ventilation valve) is used to ventilate the apparatus at the end of the process. The control of both valves is possible either manually or automatically with an electronic controlled system (6). The temperature of the spinning dope is regulated using a sand bath (1 1). After going through the spinneret, the solution coagulates in a spinning bath (8) and forms a filament. The resulting filament is wound on a take-off roller (9) at linear speed, which is controlled by an electronic system (10). Finally, fibers are washed and dried on the bobbin.
Cellulose solutions were spun at different temperatures using mixtures composed of 5 wt% CC, 58 wt% NMMO mono., and 37 wt% GVL. With this method, cellulose fibers could be produced at 25-40°C instead of 90-120°C required in the industrial Lyocell process. The surface structure of these fibers, spun at extrusion temperatures of 25°C (A), 30°C (B), and 40°C (C), are shown in Figure 3. As can be seen from the microphotographs, the variation of the temperature of the spinning process does not affect the fiber surface, which is smooth and exhibits thin grooves parallel to the spinning direction. Fibers were spun with an 80 μηι spinneret under 2.6 bars. Coagulation of the fibers took place in a distilled water bath at room temperature. The fibers were wound on the bobbin at linear speeds of 3.5-8.3 m/min. They were then washed with a spray of distilled water and dried at room temperature. Optical microscopy (Nikon Eclipse E400) was used to characterize the surface structure of the fibers.
Figure 1 shows the melting temperatures (onset temperature (Ton) and peak maximum temperature (Tpm)) of NMMO monohydrate/GVL mixtures as a function of the GVL weight percentage.
Figure 2 shows a scheme of the lab-scale spinning set-up used to produce fibers
Figure 3 shows microphotographs illustrating the surface structure of cellulose fibers spun from solutions of 5 wt% cellulose, 58 wt% NMMO monohydrate and 37 wt% GVL at (A) 25°C, (B) 30°C, and (C) 40°C. Spinning bath was distilled H20.

Claims

1. A process for the preparation of a shaped cellulose product, comprising the steps of: a) providing a solution comprising dissolved cellulose, a tertiary amine-N-oxide, a lactone selected from γ-valerolactone, γ-butyrolactone, and a combination thereof, and water;
b) bringing the solution into a predetermined shape; and
c) regenerating the dissolved cellulose in a coagulation bath;
to provide the shaped cellulose product.
2. The process of claim 1 , wherein the tertiary amine-N-oxide is at least one selected from a cyclic tertiary amine-N-oxide, and a tertiary amine-N-oxide having the structure:
R1R2N(0)-(CH2)m-0-(CH2)n-R3,
wherein each of R, and R2 is independently an alkyl group with 1 to 4 C-atoms, R3 is selected from the group consisting of a hydrogen atom, a hydroxyl group and an alkoxy group with 1-4 C-atoms, and m and n are whole numbers which fulfill the conditions 1≤ m < 8 and 1≤ n≤ 4, respectively.
3. The process of claim 1 or 2, wherein the tertiary amine-N-oxide comprises N-methyl morpholine oxide.
4. The process of any of claims 1 to 3, wherein the lactone is γ-valerolactone (gamma- valerolactone).
5. The process of any of claims 1 to 4, wherein the solution provided in step a) comprises 1 to 30 wt% of dissolved cellulose, based on the total weight of the solution as 100 wt%.
6. The process of any of claims 1 to 5, wherein the solution provided in step a) comprises the tertiary amine-N-oxide in an amount of 40 to 85 wt%, based on the total weight of the solution as 100 wt%.
7. The process of any of claims 1 to 6, wherein the solution provided in step a) comprises the lactone in an amount of 5 to 53 to wt%, based on the total weight of the solution as 100 wt%.
8. The process of any of claims 1 to 7, wherein the solution provided in step a) comprises the water in an amount of 5 to 13 wt% based on the total weight of the solution as 100 wt%.
9. The process of any of claims 1 to 8. wherein step b) is carried out while the solution has a temperature in the range of 25 to 75 °C.
10. The process of any of claims 1 to 9 wherein the shaped cellulose product is a cellulose fiber, and wherein the solution is brought into a fiber shape in step b) by discharging it as a spinning dope through a spinneret.
11. The process of claim 10, wherein the dissolved cellulose is regenerated in step c) by injecting the solution discharged in step b) into the coagulation bath.
12. The process of claim 1, wherein, the tertiary amine-N-oxide is N-methyl morpholine oxide, the lactone is γ-valerolactone, and the solution provided in step a) comprises the cellulose in an amount of 10 to 25 wt%, water in an amount of 6 to 11 wt%, the N-methyl morpholine oxide in an amount of 55 to 74 wt%, and the γ-valerolactone in an amount of 5 to 27 wt%, based on the total weight of the solution as 100 wt%.
13. A cellulose solution comprising dissolved cellulose, a tertiary amine-N-oxide, a lactone selected from y-valerolactone, γ-butyrolactone, and a combination thereof, and water.
14. The cellulose solution of claim 13, wherein the tertiary amine-N-oxide is at least one selected from a cyclic tertiary amine-N-oxide, and a tertiary amine-N-oxide having the structure:
R1R2N(0)-(CH2)m-0-(CH2)n-R3,
wherein each of R-, and R2 is independently an a Iky I group with 1 to 4 C-atoms, R3 is selected from the group consisting of a hydrogen atom, a hydroxyl group and an alkoxy group with 1-4 C-atoms, and m and n are whole numbers which fulfill the conditions 1≤ m≤ 8 and 1 < n < 4, respectively.
15. The cellulose solution of claim 13 or 14, wherein the tertiary amine-N-oxide comprises N-methyi morpholine oxide.
16. The cellulose solution of any of claims 13 to 15, wherein the lactone is v- valerolactone (gamma-valerolactone).
17. The cellulose solution of any of claims 13 to 16, which comprises 1 to 30 wt% of dissolved cellulose, based on the total weight of the solution as 100 wt%.
18. The cellulose solution of any of claims 13 to 17, which comprises the tertiary amine- N-oxide in an amount of 40 to 85 wt%, based on the total weight of the solution as 100 wt%.
19. The cellulose solution of any of claims 13 to 18, which comprises the lactone in an amount of 5 to 53 to wt%, based on the total weight of the solution as 100 wt%.
20. The cellulose solution of claims 13 to 19, which comprises the water in an amount of 5 to 13 wt% based on the total weight of the solution as 00 wt%.
21. The cellulose solution of claim 13, wherein the tertiary amine-N-oxide is N-methyl morpholine oxide, the lactone is γ-valerolactone, and the solution comprises the cellulose in an amount of 10 to 25 wt%, water in an amount of 6 to 1 1 wt%, the N-methyl morpholine oxide in an amount of 55 to 74 wt%, and the lactone in an amount of 5 to 27 wt%.
22. Use of the cellulose solution in accordance with any of claims 13 to 21 as a spinning dope for the preparation of cellulose fibers.
PCT/EP2017/063675 2016-06-07 2017-06-06 Process for the preparation of a cellulose product WO2017211798A1 (en)

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