EP4244261A1

EP4244261A1 - A method for preparing esterified cellulose and/or hemicellulose

Info

Publication number: EP4244261A1
Application number: EP21810058.4A
Authority: EP
Inventors: Janak SAPKOTA; Teemu POHJALAINEN; Pasi Virtanen; Harri Kosonen; Sakari MODIG; Matti Ristolainen
Original assignee: UPM Kymmene Oy
Current assignee: UPM Kymmene Oy
Priority date: 2020-11-11
Filing date: 2021-11-10
Publication date: 2023-09-20
Also published as: FI20206137A1; WO2022101551A1

Abstract

A method for preparing esterified cellulose and/or hemicellulose is disclosed. The method may comprise mixing an anhydride mixture and cellulose and/or hemicellulose, thereby obtaining an esterification mixture, such that the anhydride mixture esterifies the cellulose and/or hemicellulose at least partially, thereby forming the esterified cellulose and/or hemicellulose; and wherein the anhydride mixture is obtainable or obtained by reacting a fatty acid with a short-chain acid anhydride in the presence of an acid catalyst, such that an initial anhydride mixture is obtained, wherein the initial anhydride mixture comprises a mixed anhydride having a fatty acyl group and a short-chain acyl group, a portion of the short-chain acid anhydride, and a short-chain acid and optionally a fatty acid anhydride having two fatty acyl groups; and removing the short-chain acid, the short-chain acid anhydride and optionally water and/or impurities present in the initial anhydride mixture at least partially from the initial anhydride mixture, thereby obtaining the anhydride mixture.

Description

A METHOD FOR PREPARING ESTERIFIED CELLULOSE AND/OR

HEMICELLULOSE

TECHNICAL FIELD

The present disclosure relates to a method for preparing esterified cellulose and/or hemicellulose , to an esterified cellulose and/or hemicellulose and to a thermoplastic cellulose and/or hemicellulose polymer material .

BACKGROUND

Cellulose and hemicellulose are renewable raw materials well suited for producing thermoplastic materials .

Cellulose and/or hemicellulose may be homogeneously esterified e . g . using ionic liquids or solvents such as DMAC-LiCl or TBAF-DMSO, but they may be toxic and challenging to recycle , thereby making them less desirable for sustainable production in an industrial scale . Heterogeneous esterification approaches may also involve the use of solvents , such as acetic acid, which may contribute significantly to waste generated by the esterification process .

Further, efficient esterification of cellulose and/or hemicellulose using fatty acids may be challenging due to relatively low reactivity of the fatty acids , in particular long-chain fatty acids , towards hydroxyl groups of cellulose and/or hemicellulose and steric effects .

SUMMARY

A method for preparing esterified cellulose and/or hemicellulose is disclosed . The method may comprise mixing an anhydride mixture and cellulose and/or hemicellulose , thereby obtaining an esterification mixture , such that the anhydride mixture esterifies the cellulose and/or hemicellulose at least partially, thereby forming the esterified cellulose and/or hemicellulose ; and wherein the anhydride mixture is obtainable or obtained by

- reacting a fatty acid with a short-chain acid anhydride in the presence of an acid catalyst , such that an initial anhydride mixture is obtained, wherein the initial anhydride mixture comprises a mixed anhydride having a fatty acyl group and a shortchain acyl group, a portion of the short-chain acid anhydride , a short-chain acid and optionally a fatty acid anhydride having two fatty acyl groups ; and

- removing the short-chain acid, the shortchain acid anhydride and optionally water and/or impurities present in the initial anhydride mixture at least partially from the initial anhydride mixture , thereby obtaining the anhydride mixture .

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings , which are included to provide a further understanding of the embodiments and constitute a part of this specification, illustrate various embodiments . In the drawings :

Fig . 1 schematically illustrates an embodiment of the esterification process .

DETAILED DESCRIPTION

- reacting a fatty acid with a short-chain acid anhydride in the presence of an acid catalyst , such that an initial anhydride mixture is obtained, wherein the initial anhydride mixture comprises a mixed anhydride having a fatty acyl group and a shortchain acyl group, at least a portion of the shortchain acid anhydride , a short-chain acid and optionally a fatty acid anhydride having two fatty acyl groups ; and

The initial anhydride mixture may thus comprise at least a portion of the short-chain acid anhydride and/or at least a portion of the fatty acid ( s ) that have not reacted .

The reacting the fatty acid with the shortchain acid anhydride in the presence of the acid catalyst , such that the initial anhydride mixture is obtained, and the removing of the short-chain acid, the short-chain acid anhydride and optionally water and/or impurities present in the initial anhydride mixture at least partially from the initial anhydride mixture , thereby obtaining the anhydride mixture , may be referred to as production of reactive fatty acids or production of the anhydride mixture in the context of this specification . The by-products of the production of the anhydride mixture ( the short-chain acid and the short-chain acid anhydride ) may be removed from the initial anhydride mixture and reused in subsequent production of the anhydride mixture and/or valori zed as a product . In other words , the short-chain acid and/or the short-chain acid anhydride removed at least partially from the initial anhydride mixture may be reused in the method or as a separate product . Additionally or alternatively, it may be possible to extract unreacted components from the initial anhydride mixture ( or from the anhydride mixture ) . For example , the short-chain acid anhydride removed at least partially from the initial anhydride mixture may be partially reused in the method and/or partially removed from the method . I f components removed at least partially from the initial anhydride mixture are reused, they may also contain water, so that each reuse cycle may generate more water and/or other impurities in the method . Thus a part of the removed components may be directed out of the process . Any useful components may be utili zed for other suitable purposes , including those not mentioned in this specification .

An exemplary schematic of reactions occurring in the production of the anhydride mixture is shown in Scheme 1 . A fatty acid, octanoic acid in this schematic, is reacted with acetic anhydride as the short-chain acid anhydride in the presence of sulfuric acid as the acid catalyst . The initial anhydride mixture obtained comprises a mixed anhydride ( acetic octanoic anhydride ) , a portion of the short-chain acid anhydride ( acetic anhydride ) that has not reacted, a short-chain acid ( acetic acid) , a fatty acid anhydride ( octanoic anhydride ) and a portion of the fatty acid ( octanoic acid) that has not reacted . p.

Scheme 1. Synthesis products for the reaction of a fatty acid (here octanoic acid) with acetic anhydride in the presence of a catalyst. Bp. = boiling point .

As the acetic acid and acetic anhydride have significantly lower boiling points than e.g. the mixed anhydride, they may be removed or separated e.g. by vacuum distillation or by any other suitable method described in this specification to obtain the anhydride mixture that may be used for the esterification. For example, in the above scheme, distillation at a temperature of at least 140 °C (for example, at about 200 °C at normal pressure) may readily remove the acetic acid and acetic anhydride (and possibly also e.g. residual water) from the initial anhydride mixture, such that the acetic octanoic anhydride and the octanoic anhydride remain in the anhydride mixture.

Scheme 2 shows an exemplary schematic of the reaction mechanism in the esterification. Although cellulose is depicted in the scheme, a skilled person will understand that similar reaction mechanisms may apply to hemicellulose or a mixture thereof .

R=alkyl of long chain faty acids

Scheme 2 . Reaction mechanism of the mixed esterification of cellulose with fatty acids and acetic anhydride . Cell = cellulose .

The fatty acyls of the mixed anhydride may react with hydroxyl groups ( -OH) of the cellulose and/or hemicellulose , such that covalent ester bonds are formed . Likewise , the short-chain acyls of the mixed anhydride ( and optionally of the short-chain acid anhydride ) may react with hydroxyl groups of the cellulose and/or hemicellulose . However, as the removal of the short-chain acid and the short-chain acid anhydride at least partially from the initial anhydride mixture according to one or more embodiments described in this specification may increase the relative proportion of the mixed anhydride , a higher DS of the fatty acyl groups may be obtained than without it .

Thus , by the at least partial removal of the short-chain acid and/or of the short-chain acid anhydride , it is possible to affect the degree of substitution of fatty acyls in the esterified cellulose and/or hemicellulose .

It may therefore be possible to obtain mixed cellulose and/or hemicellulose esters with a desired degree of substitution of fatty acyls and possibly with a desired degree of substitution of short-chain acyls . The need to adj ust the degree ( s ) of substitution after the esterification, for example by hydrolysis , may be reduced or even obviated .

It may therefore be possible to obtain an esterified cellulose and/or hemicellulose and thermoplastic cellulose and/or hemicellulose polymer material with desired properties , such as flowability and/or tensile strength . The need to add plastici zers to the thermoplastic cellulose and/or hemicellulose polymer material may be reduced . An extrudable thermoplastic cellulose and/or hemicellulose polymer material may also be obtained .

The esterification may be performed as a one- pot reaction, i . e . in a single reactor . However, removing the short-chain acid, the short-chain acid anhydride and optionally water and/or impurities present in the initial anhydride mixture at least partially from the initial anhydride mixture , thereby obtaining the anhydride mixture , may also be performed in a separate unit , for example in a separate distillation unit .

The short-chain acid, short-chain acid anhydride , and/or the optional impurities may be at least partially removed by various different methods , including various separation and/or fractionation methods . This may enrich or increase the relative proportion of the mixed anhydride in the anhydride mixture . Thereby the degree of substitution of the fatty acyl ( s ) in the esterified cellulose and/or hemicellulose may be increased relative to the degree of substitution of the short-chain acyls .

The impurities that may be at least partially removed may include e . g . possible degradation and/or side products of chemicals used in the method, and/or impurities from the chemicals used in the method .

The short-chain acid, short-chain acid anhydride , and/or the optional impurities , which are at least partially removed, may have boiling points lower than the boiling points of the mixed anhydride and of the optional fatty acid anhydride . Thus the short-chain acid, short-chain acid anhydride , and/or the optional impurities may be removed at least partially by a method capable of separating and/or fractionating compounds based on their boiling points . Examples of such methods may include e . g . distillation, vacuum distillation, and/or vacuum evaporation . The distillation may be performed at normal pressure ( ambient atmospheric pressure ) . Other methods that may be contemplated may include e . g . separation and/or fractionation methods based on the si ze of the components , filtration, and/or chromatographic methods . Any method that may preferentially remove the short-chain acid, shortchain acid anhydride , and/or the optional impurities at least partially but preferentially retain the mixed anhydride in the anhydride mixture , i . e . to enrich or increase the relative proportion of the mixed anhydride in the anhydride mixture , may be contemplated . The short-chain acid, short-chain acid anhydride , and/or the optional impurities may be fractionated into two or more fractions .

The proportion of the short-chain acid, short-chain acid anhydride , and/or the optional impurities that may be at least partially removed may depend e.g. on the proportion of the short-chain acid anhydride and other components in the initial anhydride mixture. For example, up to about 40 %

(w/w) , or about 25-35 % (w/w) of the total components of the initial anhydride mixture may be removed. However, the proportion may vary depending on various factors .

In the context of this specification, the term "short-chain acid" may be understood as referring to a carboxylic acid having a shorter chain than the fatty acid(s) . The term "short-chain acid anhydride" may be understood as an anhydride of the short-chain acid, or of two short-chain acids, having a shorter chain than the fatty acid(s) .

Examples of suitable short-chain anhydrides may include e.g. formic anhydride (boiling point (bp) 92 °C) ; acetic formic anhydride; acetic anhydride (bp 138-140 °C) ; acetic propanoic anhydride (bp approx. 154 °C) ; propanoic anhydride (bp 167-170 °C) ; butanoic propanoic anhydride; and/or butanoic anhydride.

The short-chain acid anhydride may be represented by formula I wherein each Rx is independently selected from a C1-C4 alkyl.

In Formula I, each R¹ may be the same (for example, both Rx groups in Formula I may be Cx alkyls, C2 alkyls, C3 alkyls or C4 alkyls) or they may be different. Each Rx may thus be independently selected from a Cx alkyl, a C2 alkyl, a C3 alkyl or a C4 alkyl.

The mixed anhydride may be represented by formula II

Formula II wherein Rx is a C1-C4 alkyl, and R2 is an aliphatic chain having at least 4 carbon atoms, with the proviso that R¹ has fewer carbon atoms than R². Rx may thus be selected from a Cx alkyl, a C2 alkyl, a C3 alkyl or a C4 alkyl .

The optional fatty acid anhydride having two fatty acyl groups may be represented by formula III

Formula III wherein each R2 is independently selected from an aliphatic chain having at least 4 carbon atoms . hort-chain acid may be represented by

Formula IV wherein Rx is a Cx~C4 alkyl. Rx may thus be selected from a Cx alkyl, a C2 alkyl, a C3 alkyl or a C4 alkyl .

The fatty acid(s) and/or the fatty acyl group (s) of the mixed anhydride and of the optional fatty acid anhydride may, in principle, be any fatty acid(s) , including any aliphatic monocarboxylic acid, for example those derived from or contained in esterified form in an animal or vegetable fat, oil or wax .

The fatty acid(s) and/or the fatty acyl group (s) of the mixed anhydride and of the optional fatty acid anhydride may be linear or branched. They may be saturated or unsaturated. Branched fatty acid(s) may reduce hydrogen bonding between cellulose and/or hemicellulose strands and may thereby help in obtaining easily plasticized cellulose and/ or hemicellulose .

The term "a fatty acid" may, at least in some embodiments, refer to two or more fatty acids, and/or to a mixture of fatty acids. Therefore any references to "a fatty acid" or "the fatty acid" in this specification may, alternatively or additionally, be understood as references to two or more fatty acids, and/or to a mixture of fatty acids.

The fatty acid(s) may be derived from e.g. a vegetable oil, animal fat, and/or tall oil. Typically such sources may provide a mixture of fatty acids having various compositions. It may be possible e.g. to distil out fatty acids of certain chain lengths and/or other properties and provide such fatty acids for use in the method.

The fatty acid(s) and/or the fatty acyl group (s) of the mixed anhydride and of the optional fatty acid anhydride may each have 4 to 28 (i.e. 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, or 28) carbon atoms. In certain embodiments, they may have 6 to 20 carbon atoms, or 6 to 16 carbon atoms, or 8 to 16 carbon atoms. The number of carbon atoms may be understood as including the carbon atom of the carboxyl group of the fatty acid/fatty acyl group.

Likewise, each R2 may be independently selected from an aliphatic chain having 4 to 28 i.e. 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, or 28) carbon atoms. In certain embodiments, each R2 may be independently selected from an aliphatic chain having 6 to 20 carbon atoms, or 6 to 16 carbon atoms, or 8 to 16 carbon atoms.

Reactivity of fatty acids may decrease upon increase in the number of carbon atoms; for example, fatty acids having more than 16 carbon atoms may have a lower reactivity. However, fatty acids having longer chains may allow for producing thermoplastic cellulose and/or hemicellulose polymer materials from the esterified cellulose and/or hemicellulose, even in embodiments in which the degree of substitution (DS) is lower. A skilled person may therefore select suitable fatty acid(s) and/or number (s) of carbon atoms such that the reactivity and/or the properties of the end product are desirable.

The 4 to 28 carbon atoms, or any other number (s) of the carbon atom(s) , of the fatty acyl group (s) may be understood as including the carbon atom of the carboxyl group. In other words, the fatty acyl group (s) may then include 4 to 28 carbon atoms in total .

The short acid anhydride may, at least in some embodiments, be selected from the group of formic anhydride, acetic anhydride, propionic anhydride, acetic propionic anhydride, and any mixtures and combinations thereof. These short acid anhydrides may have boiling points and/or other properties well suited for removing them at least partially from the initial anhydride mixture.

The short acid anhydride may, at least in some embodiments, be selected from the group of acetic anhydride, propionic anhydride, acetic propionic anhydride, and any mixtures and combinations thereof.

The short acid anhydride may, at least in some embodiments, comprise or be acetic anhydride.

In the context of this specification, the term "cellulose and/or hemicellulose" may be understood as referring to cellulose; to hemicellulose; and/or to any mixture or combination thereof. For example, it may refer to a mixture or composition comprising cellulose and optionally hemicellulose, such as pulp. Such a mixture may comprise predominantly cellulose, but also an amount of hemicellulose . For example , pulp may typically contain e . g . about 10 - 25 % (w/w) of hemicellulose ; the remaining pulp may be cel lulose , although the pulp may additionally comprise impurities such as lignin residues ( typically less than 1 % (w/w) ) , extractives , and/or ash . However, hemicellulose may also be used instead of cellulose , or a mixture comprising predominantly hemicellulose and optionally cellulose . For example , hemicellulose obtainable from textile processes may be contemplated . The cellulose and/or hemicellulose may, in some embodiments , be understood as referring to a composition comprising cellulose and/or hemicellulose and optionally one or more impurities , for example one or more of the impurities mentioned above .

The cellulose and/or hemicellulose may be modified prior to the esterification . In other words , the cellulose and/or hemicellulose that is mixed with the anhydride mixture may already be modified . Various modifications may be available to cellulose and/or hemicellulose and may be compatible with the esterification according to one or more embodiments described in this specification . For example , the cellulose and/or hemicellulose may be modified so as to contain charged ( anionic, cationic, or both) groups prior to the esterification .

The cellulose and/or hemicellulose may be dry and powdered cellulose and/or hemicellulose , such as dry and powdered chemical pulp, when mixed with the anhydride mixture .

The cellulose and/or hemicellulose may be activated prior to mixing with the anhydride mixture . The activated cellulose and/or hemicellulose may optional ly be dried prior to mixing with the anhydride mixture . For example , if a chemical activation method performed using a liquid reagent is used, the cellulose and/or hemicellulose may require drying after the activation.

The cellulose and/or hemicellulose may be physically activated.

The cellulose and/or hemicellulose may be mechanically activated and optionally dried prior to mixing with the anhydride mixture. The cellulose and/or hemicellulose may, alternatively or additionally, be mechanically disintegrated and dry before it is mixed with the anhydride mixture. The mechanical activation may be done e.g. by grinding the cellulose and/or hemicellulose. The mechanical activation may comprise mechanically pre-treating the cellulose and/or hemicellulose e.g. by refining, using a hammer mill, and/or pulverizing the cellulose and/or hemicellulose e.g. by friction grinding or using a ball mill. This may increase the surface area of the cellulose and/or hemicellulose and possibly cut a portion of the fibers in the cellulose and/or hemicellulose; however, typically the polymer length is not significantly affected.

Various other activation methods may also be contemplated. The cellulose and/or hemicellulose may be chemically activated. The cellulose and/or hemicellulose may be chemically activated by using e.g. ionic liquids, hydrolysis, and/or alkaline extraction. The cellulose and/or hemicellulose may be enzymatically activated. The enzymatic activation may be done e.g. by using a lytic polysaccharide monooxygenase (LPMO) and/or an endoglucanase .

The activation may be done to improve access to hydroxyl groups of the cellulose and/or hemicellulose. The cellulose and/or hemicellulose may be prepared earlier and stored and/or obtained separately e.g. by purchasing from a supplier, or it may be mechanically or otherwise activated shortly before the esterification. It may be beneficial to use the mechanically activated cellulose and/or hemicellulose relatively shortly after the mechanical activation to optimize esterification results.

The dry cellulose and/or hemicellulose may thus be in the form of a high surface area powder.

The cellulose and/or hemicellulose may, additionally or alternatively, comprise or be Kraft pulp, for example never dried Kraft pulp. However, any chemical pulp, such as soda and/or sulfite pulp, may also be used. The cellulose and/or hemicellulose, such as pulp, may be obtainable from wood or from non-wood materials. The cellulose and/or hemicellulose may be prepared from cellulose raw material of a plant origin. The raw material may be based on any plant material that contains cellulose and/or hemicellulose. The plant material may be, for example, wood. The wood may be from a softwood tree, such as spruce, pine, fir, larch, Douglas fir or hemlock, or from a hardwood tree, such as birch, aspen, poplar, alder, eucalyptus, oak, beech or acacia, or from a mixture of a softwood and a hardwood. In an embodiment, the cellulose and/or hemicellulose is obtained from wood pulp. In an embodiment, the cellulose and/or hemicellulose is obtained from hardwood pulp. In an example, the hardwood is birch. In an embodiment, the cellulose and/or hemicellulose is obtained from softwood pulp.

Non-wood material may be derived from agricultural residues, grasses or other plant substances such as straw, leaves, bark, seeds, hulls, flowers, vegetables or fruits from cotton, corn, wheat, oat, rye, barley, rice, flax, hemp, manila hemp, sisal hemp, jute, ramie, kenaf, bagasse, bamboo or reed. Depending on the raw material source, e.g. hardwood (HW) vs. softwood (SW) pulp, different polysaccharide compositions may exist in the cellulose and/or hemicellulose. The cellulose may contain hemicelluloses and lignin in varying amounts, depending on plant source and pulping conditions . For example , bleached birch pulp has a high xylose content ( 25% by weight ) and a negligible lignin content . Pulps are typically complex mixtures of different polysaccharide structures .

The cellulose and/or hemicellulose may be formed by isolating cellulose and/or hemicellulose from a raw material that contains cellulose by chemical , mechanical , thermo-mechanical , or chemi-thermo- mechanical pulping processes , for example kraft pulping, sulfate pulping, soda pulping, organosolv pulping, and by conventional bleaching processes . The cellulose and/or hemicellulose may, in some embodiments , not contain substantial amounts of lignin, or it may contain only traces of lignin or non-detectable amounts of lignin . Thus al so the cellulose and/or hemicellulose may be essentially lignin-free .

With the method, it may be possible to esterify cellulose and/or hemicellulose without the need to use additional solvents ( i . e . without adding a solvent other than the components of the anhydride mixture ) . Thus the amount of waste generated may be reduced and the sustainability of the method improved .

In some embodiments , no additional solvents are included or added to the esterification mixture . In this context , the term "additional solvent" may be understood as a solvent added to the esterification mixture in order for the esterification reaction to proceed, apart from the short-chain acid (which may, at least in some embodiments , be considered to be a solvent and/or function as a solvent in the esterification) .

In some embodiments , the method may optionally comprise workup washing, which may include washing with a solvent . This may be done to remove the unreacted fatty acid ( s ) and/or other unwanted components from the esterified cellulose and/or hemicellulose . Such unwanted components may be removed e . g . so that they do not cause of f-flavours or migrate to the surface when the esteri fied cellulose and/or hemicellulose and/or a thermoplastic cellulose and/or hemicellulose polymer material ( for example , a film) comprising or prepared from it are in contact with food products . In such embodiments , the term "additional solvent" is not intended to include the solvent ( s ) used in the workup washing .

The acid catalyst is not particularly limited . It may comprise or be a strong acid, such as sulfuric acid and/or hydrochloric acid . However, other acids and acid catalysts may also be contemplated .

In an embodiment , the anhydride mixture may be obtained, the cellulose and/or hemicellulose and the anhydride mixture may be mixed, and the cellulose and/or hemicellulose may be esterified in a single reactor . This may simpl ify the process and/or allow for easier scalability .

The anhydride mixture and the cellulose and/or hemicellulose may be mixed and the anhydride mixture may esterify the cellulose and/or hemicellulose under mixing, for example under mechanical stirring or kneading . The mixing may result in a higher degree of substitution .

In an embodiment , the cellulose and/or hemicellulose may be optionally mechanically activated, the cellulose and/or hemicellulose and the anhydride mixture may be mixed, and the cellulose and/or hemicellulose may be esteri fied in a high consistency processing reactor . The mixing and kneading action that may be provided by the high consistency processing reactor may result in a higher degree of substitution of the esterified cellulose and/or hemicellulose ; it may thereby generate less waste than certain other approaches .

In the method, the reagents ( components ) may be circulated and reused . The esterified cellulose and/or hemicellulose obtained may be filtered and/or washed.

The esterified cellulose and/or hemicellulose obtained may be dried, for example in an oven.

The esterified cellulose and/or hemicellulose may then be used for various purposes, for example in the preparation of a thermoplastic cellulose and/or hemicellulose polymer material.

An esterified cellulose and/or hemicellulose is also disclosed.

The degree of substitution (DS) of fatty acyls in the esterified cellulose and/or hemicellulose may be greater than the DS of short-chain acyls in the esterified cellulose and/or hemicellulose.

The total DS in the esterified cellulose and/or hemicellulose may be in the range of 0.2 to 3.0, wherein the DS of fatty acyls in the esterified cellulose and/or hemicellulose may be greater than the DS of short-chain acyls in the esterified cellulose and/or hemicellulose.

The degree of substitution of fatty acyls in the esterified cellulose and/or hemicellulose may be, for example, at least 0.2, or in the range of 0.2 to 3.

The degree of substitution of short-chain acyls in the esterified cellulose and/or hemicellulose may be up to 2.8, or in the range of 0.2 to 2.8) .

The degree of substitution, either total DS or DS of fatty acyls and/or DS of short-chain acyls, may be determined e.g. by nuclear magnetic resonance (NMR) methods .

The esterified cellulose and/or hemicellulose may be obtainable by the method according to one or more embodiments described in this specification.

A thermoplastic cellulose and/or hemicellulose polymer material is also disclosed. The thermoplastic cellulose and/or hemicellulose polymer material or thermoplastic cellulose and/or hemicellulose polymer mixture may comprise or be formed from the esterified cellulose and/or hemicellulose according to one or more embodiments described in this specification.

The thermoplastic cellulose and/or hemicellulose polymer material may further comprise various additives, such as e.g. a filler (for example, inorganic fine particles and/or organic compounds) , a plasticizer, a flame retardant, an antioxidant, a colouring (for example, a colouring pigment) , a masterbatch, etc.

The thermoplastic cellulose and/or hemicellulose polymer material may comprise up to 30 %, 0.1 - 30 % (w/w) , or up to 10 %, or 0.5 - 10 % (w/w) , or up to 5 % , or 0.1 - 5 % (w/w) of plasticizer (s) .

However, the esterified cellulose and/or hemicellulose may simply be purified and optionally e.g. extruded into a desired form (such as into grains or film) without adding further additives. Any additional components or the absence thereof may depend e.g. on the exact composition of the esterified cellulose and/or hemicellulose and/or the intended use thereof or of the thermoplastic cellulose and/or hemicellulose polymer material.

The esterified cellulose and/or hemicellulose and/or the thermoplastic cellulose and/or hemicellulose polymer material may be extruded e.g. into grains, pellets, filaments, or a film or heat pressed to a film. Such films may be slightly transparent or transparent .

An article obtainable from the esterified cellulose and/or hemicellulose according to one or more embodiments disclosed in this specification or from the thermoplastic cellulose and/or hemicellulose polymer material according to one or more embodiments disclosed in this specification is also disclosed. The article may be e.g. extruded, molded or heat pressed.

The article may be e.g. a container, a casing, a packaging article, a film, a filmic label, a medical device (such as a nozzle) , a plastic or composite profile, or a 3D printing filament.

EXAMPLES

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

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

Figure 1 schematically illustrates an embodiment of the esterification process.

At 1, i.e. at production of the reactive fatty acids (production of the anhydride mixture) , acetic anhydride as the short-chain acid anhydride, fatty acids and an acid catalyst, such as sulfuric acid, are mixed so as to react the fatty acid with the acetic anhydride and to form a mixed anhydride having a fatty acyl group derived from the fatty acid and a short-chain acyl group (acetyl) derived from the short-chain acid anhydride. The resulting reactive fatty acid, i.e. initial anhydride mixture, is then subjected to a suitable separation procedure, for example distillation as shown in Scheme 1, such that at least a portion of the acetic acid and acetic anhydride remaining after the reaction are removed. They may be recycled back into the production of the reactive fatty acid at 1 as indicated by an arrow. The mixed anhydride remains in the anhydride mixture. At least a portion of impurities may also be removed in the separation procedure , as indicated by an arrow . Additionally or alternatively, water may be removed in the separation procedure (not shown in Fig . 1 ) . For example , the acetic acid anhydride removed at least partially from the initial anhydride mixture may be partially reused in the method and/or partially removed out of the process , as shown by arrows . I f components removed at least partially from the initial anhydride mixture are reused, they may also contain water, so that each reuse cycle may generate more water and/or other impurities in the method . Thus a part of the removed components may be directed out of the process .

At 2 , kraft pulp, such as never dry kraft pulp, as the cellulose and/or hemicellulose source is activated, for example by mechanical grinding, and dried . Subsequently the activated anhydride mixture containing the mixed anhydride , i . e . reactive fatty acid, from 1 is mixed with the activated cellulose and/or hemicellulose at 3 , such that the esterification reaction may proceed . When the esterification reaction has proceeded to a sufficient extent , the resulting esterified cellulose and/or hemicellulose may be filtered and washed at 4 . The resulting thermoplastic cellulose and/or hemicellulose at 5 may be e . g . dried and optionally processed further or used as such e . g . by extruding it into a film or an article .

EXAMPLE 1

567 g of acetic anhydride , 5 . 5 g of catalyst sulfuric acid and 400 g of octanoic acid were added to a reactor with mixing set to about 40 rpm and the temperature was raised to 80 ° C . The mixture was let to stand for 1 h . 150 g of dry grinded kraft birch pulp is inserted to a high consistency reactor with stirring set after the pulp addition back to 40 rpm. The reactor was held at 80 °C for 2 h, then worked up by following .

The reactor temperature was lowered to at least 60 °C by using water cooling and then 1 1 of 50 % ethanol mixture was carefully poured into the reactor. This extraction took 30 min, and then the suspension was carefully poured into a 10 1 container. The product was filtered from the dilute acetic acid mixture, mixed with 4 1 of deionized water, washed with water, the procedure being repeated until washings with water gave neutral pH suspension. Water was removed as far as possible by filtration and then the product was dried in an oven at 105 °C.

The pulp used in the examples contained, in addition to cellulose, about 25 % (w/w) of hemicellulose; less than 1 % (w/w) of lignin residues; 0.2 % (w/w) extractives; and 0.4 % (w/w) ash.

EXAMPLE 2

567 g of acetic anhydride, 5.5 g of catalyst sulfuric acid and 556 g of lauric acid were added to a reactor with mixing set to about 40 rpm and the temperature was raised to 80 °C. The mixture was let to stand for 1 h.

150 g of dry grinded kraft birch pulp was inserted to the high consistency reactor with stirring set after pulp addition back to 40 rpm. The reactor was held at 80 °C for 2 h then worked up by the following :

The reactor temperature was lowered to at least 60 °C by using water cooling and then 1 1 of 50 % ethanol mixture was carefully poured into the reactor. This extraction took 30 min, and then the suspension was carefully poured into a 10 1 bucket or similar. The product was filtered from the dilute acetic acid mixture, mixed with 4 1 of deionized water, washed with water, the procedure being repeated until washings with water gave neutral pH suspension. Water was removed as far as possible by filtration and then the product was dried in an oven at 105 °C.

EXAMPLE 3

Esterified cellulose was produced as described in Example 2, except a 6 h reaction was performed with a Juccheim reactor.

EXAMPLE 4

284 g of acetic anhydride, 0.5 g of catalyst sulfuric acid and 200 g of octanoic acid was mixed in rotary evaporator at 90 °C for 1 h. Then acetic acid and acetic anhydride were distilled away in said temperature using 50-200 mbar reduced pressure. 316 g of reactive fatty acid mixture was obtained and 138 g of distillate.

This reactive fatty acid mixture was added to a batch reactor together with 0.5 g of sulfuric acid catalyst with mixing set to about 11 Hz and the temperature was raised to 80 °C.

20 g of dry grinded kraft birch pulp was then inserted to the batch reactor. The reactor was held at 80 °C for 2 h, then worked up by the following:

The reactor temperature was lowered to at least 60 °C by using water cooling, and then 1 1 of 50 % ethanol mixture was carefully poured into the reactor. This extraction took 30 min, and then the suspension was carefully poured into a 10 1 bucket or similar. The product was filtered from the dilute acetic acid mixture, mixed with 4 1 of deionized water, washed with ethanol and water, the procedure being repeated until washings with water gave neutral pH suspension . Water was removed as far as possible by filtration and then the product was dried in an oven at 105 ° C .

EXAMPLE 5

568 g of acetic anhydride , 6 g of catalyst sodium hydrogen sulfate and 400 g of octanoic acid were mixed in rotary evaporator at 90 ° C for 1 h . Then acetic acid and acetic anhydride were distilled away using 100 -200 mbar reduced pressure . 556 g of reactive fatty acid mixture was obtained and 353 g of distillate . Reactive fatty acid mixture was thereafter filtered to remove catalyst residue .

This mixture was added to a reactor together with 1 mL of sulfuric acid catalyst with mixing set to about 40 rpm, and the temperature was raised to 80 ° C .

90 g of dry grinded kraft birch pulp was then inserted to the high consistency reactor . The reactor was held at 80 ° C for 2 h, then worked up by the following :

The reactor temperature was lowered to at least 60 ° C by us ing water cooling, and then 1 1 of 50 % ethanol mixture was carefully poured into the reactor . This extraction took 30 min, and then the suspension was carefully poured into a 10 1 bucket or similar . The product was filtered from the dilute acetic acid mixture , mixed with 4 1 of deioni zed water, washed with ethanol and water, the procedure being repeated until washings with water gave neutral pH suspension . Water was removed as far as possible by filtration and then the product was dried in an oven at 105 ° C . EXAMPLE 6

Esterified cellulose samples obtained in examples 1 -3 were analysed as shown in Table 1 .

Table 1 .

Ref . Commercial cellulose acetate internal method

* *Total degree of substitution

End products were further analyzed by NMR (nuclear magnetic resonance ) and ¹³C NMR techniques . These results (not shown) confirmed that esterification resulted in products given in Scheme 2 and that the fatty acid reactivity is different in examples 4 and 5 when compared to examples 1 -3 .

It is obvious to a person skil led in the art that with the advancement of technology, the basic idea may be implemented in various ways . The embodiments are thus not limited to the examples described above ; instead they may vary within the scope of the claims . The embodiments described hereinbefore may be used in any combination with each other . Several of the embodiments may be combined together to form a further embodiment . A method, a product , or a use , disclosed herein, may comprise at least one of the embodiments described hereinbefore . It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments . The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages . It will further be understood that reference to ' an ' item refers to one or more of those items . The term "compri sing" is used in thi s specification to mean including the feature ( s ) or act ( s ) followed thereafter, without excluding the presence of one or more additional features or acts .

Claims

27 CLAIMS

1 . A method for preparing esterified cellulose and/or hemicellulose , wherein the method comprises mixing an anhydride mixture and cellulose and/or hemicellulose , thereby obtaining an esterification mixture , such that the anhydride mixture esterifies the cellulose and/or hemicellulose at least partially, thereby forming the esterified cellulose and/or hemicellulose ; and wherein the anhydride mixture is obtainable or obtained by

2 . The method according to claim 1 , wherein the short-chain acid, short-chain acid anhydride , and/or the optional impurities , which are at least partially removed, have boiling points lower than the boiling points of the mixed anhydride and of the optional fatty acid anhydride , and wherein the shortchain acid, short-chain acid anhydride , and/or the optional impurities are removed at least partially by a method capable of separating or fractionating compounds based on their boil ing points , such as distillation and/or vacuum evaporation ; or by other separation and/or fractionation method .

3. The method according to claim 1 or 2, wherein the short-chain acid anhydride is represented by formula I

O O A R¹^CT ^R¹ Formula I wherein each Rx is independently selected from a C1-C4 alkyl; wherein the mixed anhydride is represented by Formula II wherein Rx is a Cx~C4 alkyl, and R2 is an an aliphatic chain having at least 4 carbon atoms, with the proviso that R¹ has fewer carbon atoms than R²; the optional fatty acid anhydride having two fatty acyl groups is represented by formula III

Formula III wherein each R2 is independently selected from an aliphatic chain having at least 4 carbon atoms; and/or the short-chain acid is represented by a IV wherein Rx is a Cx~C4 alkyl.

4. The method according to any one of claims

1 - 3, wherein the fatty acyl group (s) of the mixed anhydride and of the optional fatty acid anhydride each have 4 to 28 carbon atoms, or 6 to 20 carbon atoms, or 6 to 16 carbon atoms, or 8 to 16 carbon atoms .

5. The method according to any one of claims 1 - 4, wherein the short acid anhydride is selected from the group of formic anhydride, acetic anhydride, propionic anhydride, acetic propionic anhydride, and any mixtures and combinations thereof.

6. The method according to any one of claims 1 - 5, wherein the cellulose and/or hemicellulose is dry and powdered cellulose and/or hemicellulose, such as dry and powdered chemical pulp, when mixed with the anhydride mixture.

7. The method according to any one of claims 1 - 6, wherein the cellulose and/or hemicellulose is mechanically activated and dried prior to mixing with the anhydride mixture, or the cellulose and/or hemicellulose is mechanically disintegrated and dry before it is mixed with the anhydride mixture.

8. The method according to any one of claims 1 - 7, wherein no additional solvents are included or added to the esterification mixture.

9. The method according to any one of claims 1 - 8, wherein the acid catalyst comprises or is a strong acid, such as sulfuric acid and/or hydrochloric acid .

10. The method according to any one of claims 1 - 9, wherein the anhydride mixture is obtained, the cellulose and/or hemicellulose and the anhydride mixture are mixed, and the cellulose and/or hemicellulose is esterified in a single reactor.

11. The method according to any one of claims 1 - 10, wherein the cellulose and/or hemicellulose is optionally mechanically activated, the cellulose and/or hemicellulose and the anhydride mixture are mixed, and the cellulose and/or hemicellulose is esterified in a high consistency processing reactor.

12. An esterified cellulose and/or hemicellulose, wherein the total degree of substitution (DS) in the esterified cellulose and/or hemicellulose is in the range of 0 . 2 to 3 . 0 , and wherein the DS of fatty acyls in the esterified cellulose and/or hemicellulose is greater than or equal to the DS of short-chain acyl s in the esteri fied cellulose and/or hemicellulose .

13 . The esterified cellulose and/or hemicellulose according to claim 12 , wherein the esterified cellulose and/or hemicellulose is obtainable by the method according to any one of claims 1 - 11 .

14 . A thermoplastic cellulose and/or hemicellulose polymer material , wherein the thermoplastic cellulose and/or hemicellulose polymer or thermoplastic cellulose and/or hemicellulose polymer mixture comprises or is formed from the esterified cellulose and/or hemicellulose according to claim 12 or 13 .

15 . An article obtainable from the esterified cellulose and/or hemicellulose according to claim 12 or 13 or from the thermoplastic cellulose and/or hemicellulose polymer material according to claim 14 , wherein the article is optionally extruded, molded or heat pressed .

16 . The article according to claim 15 , wherein the article is a container, a casing, a packaging article , a film, a filmic label , a medical device , a plastic or composite profile , or a 3D printing filament .