FI120265B - Starch etherification method - Google Patents

Description

FIELD OF THE INVENTION Field of the Invention

The present invention relates to a novel process for the preparation of starch ethers.

5 State of the art

Unlike other carbohydrates and edible polymers, starch occurs as discrete particles called starch granules. These generally consist of two types of molecules, amylose and amylopectin. Of these, amylose is a straight-chain (1,4) -aD-glucan, while amylopectin is a branched, bush-like structure containing both (1,4) -aD bonds between D-glucose residues and (1,6) -aD , Ullmann's Encyclopedia of Industrial Chemistry, vol. A25, 1994, pp. 1-18. The following formulas illustrate typical structures of amylose and amylopectin.

ch2oh ch2oh ch2oh k-0 / -0 / -0

OH OH OH

Typical structure of straight-chain amylose CH2OH CH3OH ΤΌΗ ° \ -o' — f fo. ; OH 0H | .ch2oh ch2 ch2oh J-ο J-o l-o

O

OH OH OH

Typical structure of amylopectin containing (1,6) -α-branching Conventional starches contain approximately 75% of the amylopectin molecules, the remainder being amylose. Amylopectin is a very large molecule with molecular weights ranging from one million to several million. Amylose having a straight chain structure is considerably smaller and typically has a molecular weight of 5,000 to 200,000.

2

Commercial starches are obtained from seeds, especially maize, wheat, rice, tapioca, sago and potato. Especially in Scandinavia, barley is also used as a natural starch source. These starch granules have a diameter of 1 to 100 µm. Rice starch has the smallest granules (3 to 9 µm), potato starch has 5 to 15 µm and corn starch has a size of 5 to 26 µm with an average diameter of 15 µm. In addition, wheat starch granules typically have a size of 3 to 35 µm and barley starch 5 to 35 µm, respectively. Kirk-Othmer, Encyclopedia of Chemical Technology, 1997, 4th edition, vol. 22, pp. 699-719, and Ketola H, Andersson T, Papermaking Chemistry, 1999, book 4, pp. 269-274.

10 Because of their extremely high molecular weights and the chemical composition of both amylose and, in particular, amylopectin of the shrubbery nature, these branched polysaccharides are practically insoluble in solvents other than water. And in water, the starch granules must be cooked before they release their water-soluble molecules. Generally, they do not form the correct solutions in water due to their molecular size and intracellular interactions, but rather form molecular dispersions. Most starch derivatives can be prepared from any natural starch, but due to their solubility and molecular size, they are mainly produced from potato starch and, in the United States, waxy corn starch.

Above a certain temperature, which is characteristic of each type of starch, known as the "gelatinization temperature," the starches) crack and form a gel Ci. The viscosity increases to a maximum and then decreases asymptotically to a threshold value when the dissolved polymer molecules are dispersed in water. Complete dissolution of single molecules of starch grain occurs only at temperatures above 100 ° C, TT 25 Ullmanns Encyclopedia of Industrial Chemistry, vol. A26, 1995, pp. 246-248.

TV The effect of heat treatment on starches is strongly dependent on whether it is cured in excess water, in a limited amount of water, under pressure or in extrusion cooking. With excess water, it appears that starch swelling is a two-step process consisting of initial granulation of the granules followed by dissolution of the granules. Both of these steps are irreversible. When water is scarce, thermal responses are interpreted to be due to melting of starch crystal germs. When using extrusion cooking, the starch granules are physically broken, thereby allowing water to penetrate more rapidly into the granule. In contrast to conventional gelation, starch 35 fragmentation (dextrinization) appears to be the major reaction during extrusion, Kirk-Othmer, Encyclopedia of Chemical Technology, 4th edition, 1997, vol. 22, pp. 699-719.

Dissolution of starch

U.S. Pat. No. 1,943,176 discloses a process for preparing cellulose solutions by dissolving cellulose while heating in a liquefied N-alkylpyridinium or N-benzylpyridinium chloride salt, preferably in the presence of an anhydrous nitrogenous base such as pyridine. Such salts are known as ionic liquids. The cellulose to be solubilized is preferably in the form of regenerated cellulose or bleached cellulose or liner. U.S. Pat. No. 1,943,176 also proposes separating cellulose from a cellulose solution with suitable precipitating agents, such as water or alcohol, for example to produce cellulosic fibers or films or pulps. According to US 1,943,176, cellulose solutions are suitable for various chemical reactions, such as etherification or esterification. In Example 14, triphenylchloromethane is added to a solution of cellulose in a mixture of benzylpyridinium chloride and pyridine, and then the cellulose solution is poured into methyl alcohol to separate the cellulose ether.

Other cellulose solvents are also known. For example, viscose is prepared from cellulose xanthate using sulfur carbon as both a reagent and a solvent. U.S. Patent 3,447,939 discloses the dissolution of natural or synthetic polymeric compounds such as cellulose in cyclic mono (N-methylamine-N-oxide), particularly N-methylmorpholine-N-oxide.

WO 03/029329 discloses a leaching process which is very similar to that disclosed in US 1,943,176. The main improvement is the use of microwave radiation to promote dissolution. The cellulose to be solubilized is 25 fibrous cellulose, wood pulp, linters, cotton balls or paper, i.e. cellulose in a very pure form. The inventors of WO 03/029329 have published an article (Swatloski, RP, Spear SK, Holbrey, JD, Rogers, RD Journal of the American Chemical Society, 124, pp. 4 974-4 975, 2002) which focuses on the dissolution of cellulose in ionic liquids, in particular with 1-butyl-3-methylimidazolium chloride by heating in a microwave oven. The cellulose used in the leaching tests solubilized the pulp (from the cellulose acetate, lyocell and viscose production lines), the fibrous cellulose and the filter paper, i.e. cellulose in a very pure form without significant amounts of lignin. This article also discloses the precipitation of cellulose from an ionic liquid solution by addition of water or other precipitation solutions, including ethanol and acetone.

4

ionic liquids

Several synonyms for ionic liquids are known in the literature. So far, "molten melt" is perhaps the most widely used term for ionic compounds in liquid form. However, salt salts and ionic liquids differ. Ionic liquids are salts which are liquids near room temperature (typically -100-200 ° C but can be up to 300 ° C) (Wassercheid, P., Welton, T., Ionic Liquids in Synthesis, 2003, WILEY). -VCH, pp. 1-6, 41-55 and 68-81). For this reason, these solvents are commonly referred to as RTIL (room temperature ionic liquids).

RTILs are non-flammable, non-volatile and have good heat resistance. Typically, these solvents are organic salts or mixtures of at least one organic ingredient. By changing the nature of the ions contained in the RTIL, the properties available to the RTILs can be changed. The lipophilicity of the RTIL ionic liquid is easily altered by the degree of cation substitution. Similarly, mixing with water and other protic solvents can be adjusted from complete se-mixability to near-complete immiscibility by altering the anion substitution.

All of these modifications of cations and anions can produce very high levels of ionic liquids that can be adjusted for specific applications. In addition, RTILs are relatively inexpensive and easy to manufacture. They can also be reused after regeneration.

Microwaves In the recent literature on organic synthesis, it is known that reaction times for organic reactions are significantly reduced when the energy required to effect the reaction is introduced into the system using microwave microwave radiation. The commonly used frequency for microwave energy is 2.45 GHz. There is an abundance of literature available in the field of microwave technology in organic synthesis and more and more are being published. In 1994, Mingos published an example of a short summary article on this topic (D. Michael P. Mingos; '' Microwaves in Chemical Synthesis', August 1, 1994, pp. 30,596-599). Loupy et al. have recently published a review of heterogeneous catalysis using microwave radiation (Loupy, A., Petit, A., Hamelin, J., Texier-Boullet, F., Jachault, P., Mathe, D .; free organic synthesis using a focused microwave ”in Synthesis, 1998, pp. 1 213-1 234). On request, Strauss has published another representative article in this field (C.R.

5

Strauss; A Combinatorial Approach to the Development of Environmental Benign Organic Chemical Preparations, Aust. J. Chem. 1999, 52, pp. 83-96).

Due to its ionic nature, ionic liquids are excellent media for microwave technology. Rogers et al. published in 2002 a method for dissolving pure cellulose fibers into ionic liquids in the microwave field (Swatloski, R.P., Spear, S.K., Holbrey, J.D., Rogers, R.D. Journal of the American Chemical Society, 2002,124, pp. 4,794-4,975). In addition, they regained the fibers by mixing water with this fiber-containing solution.

SUMMARY OF THE INVENTION The object of the invention is to provide a process for the preparation of starch ethers.

The invention is based on the surprising finding that the basic etherification of starch can be carried out in an ionic liquid where the reaction between starch and an etherifying agent such as chloroacetic acid / alkali metal chloroacetate proceeded quickly and smoothly and no problem was observed with the solubility of the reagents or product. The good solubility of the reagents results in efficient and economical reactions without unnecessary excess of an inorganic base such as NaOH, thus also preventing the degradation of the starch chain. The possibility of significant decomposition is further reduced by mild reaction conditions and low reaction temperatures, which are achieved either by microwave radiation or by pressure.

Because of the good solubility of all starting materials, the invention also provides the ability to readily regulate DS by the molar ratio of reagent to AGU [anhydroglucopyranose unit (ide) n]. The invention also provides the ability to prepare high or fully substituted starch ethers, and, thanks to its higher solubility, mild conditions and shorter reaction times, also provides a completely new method of preparing starch ethers of type 25. The ionic liquids can be reused after regeneration.

In the accompanying drawing, Figure 1 shows the spectrum obtained by FTIR analysis of a carboxymethyl starch sample prepared by the method of the present invention.

6

Brief Description of the Drawings 5 Detailed Description of the Invention

According to the invention there is provided a process for the preparation of a starch ether which comprises mixing the starch with an ionic liquid solvent to dissolve the starch and then treating the dissolved starch with an etherifying agent in the presence of a base to form the starch ether and .

Solubilization and etherification can be promoted using microwave radiation and / or pressure.

The pressure is preferably up to 2.0 MPa and more preferably 1.5 to 2.0 MPa.

The dissolution of the starch can be carried out at a temperature of 0-150 ° C, preferably 10-100 ° C, such as 20-85 ° C. If microwave radiation is used, heating may be performed by such radiation. The solution is stirred until complete dissolution is achieved.

No other organic solvents or cosolvents, such as nitrogen-containing bases, e.g. pyridine, are required for leaching. Organic bases are excluded in this way.

The leaching and etherification is carried out essentially without water. By "substantially water-free" is meant that no more than a few percent by weight of water is present.

Preferably, the water content is less than 1% by weight.

The solution may contain from about 1% to about 35% by weight of the solution. Preferably, the amount is from about 10% to about 25% by weight.

The etherification may be carried out at the same or a lower temperature than the leaching. Both inorganic and organic bases can be used as catalysts.

The ionic liquid solvent melts at -100-200 ° C, preferably below 170 ° C, and more preferably -50-120 ° C.

7

Preferably, the ionic solvent cation is a five or six membered heterocyclic ring optionally fused to a benzene ring and containing at least one nitrogen, oxygen or sulfur atom as heteroatoms. The heterocyclic ring may be aromatic or saturated. The cation may be any of the following: R4 R4 R * R11 ^ A ^ R5 R3J1 .5 R3 X R3 NL R4 Ä.

R1 R1 R1 R1

Pyridinium Pyridazinium Pyrimidinium Pyrazinium R4R5 R3 ^ R4 R5x / R3 r, nSn.rJ R2 ^ r5 r, nQo R3 R1 R4

Imidazolium Pyrazolium Oxazolium R4 / R3 R4 R3 R3 R2 R5v R3

AA Ati AA

r'n $% 2 r'-n $ N rA * p2 p4 1,2,3-triazolium R 1,2,4-triazolium T f,

Thiazolium R5 r4 r4 r3 rwL0 'YtY "' r7YVar9 R6'y> x - r'N'R1 R8 R1 R7 Re

Quinolinium zquinolinium r4 RS R5 R4 rAA0 ΑΝΆ R1 + R2 R1-4-R2 5 Piperidinium Pyrrolidinium 1 wherein R and R are independently C1-C6 alkyl or C2-C6 alkoxyalkyl and R3, R4, R5, R6 , R 7, R 8 and R 9 are independently hydrogen, C 1 -C 6 alkyl, C 2 -C 6 alkoxyalkyl, or C 1 -C 6 alkoxy, or halogen.

In the above formulas, R 1 and R 2 are both preferably C 1 -C 4 alkyl, and R 3 -R 9, if present, are preferably hydrogen.

8

C 1 -C 6 alkyl is methyl, ethyl, propyl, isopropyl, butyl, seobutyl, tert-butyl, pentyl, an isomer of pentyl, hexyl or an isomer of hexyl.

C 1 -C 6 alkoxy comprises the above-mentioned C 1 -C 6 alkyl bonded to an oxygen atom.

C 2 -C 6 alkoxyalkyl is an alkyl group substituted with an alkoxy group having a total carbon number of from 2 to 6.

Halogen is preferably chlorine, bromine or fluorine, especially chlorine.

Preferred cations have the following formulas: R 4 -R 5 R 3 -R 4 R 5 -R 3 «.N © lSL 7 c, .N © b

R1 Y R2 R2 N R5 R1 Y

R3 R1 R4

Imidazolium Pyrazolium Oxazolium R4 / R3 R4 R3 R3 R2 R5 R3 R'N ^ N-R2 R'-NYr <R-'Nfb 1,2,3-Triazolium R2 1,2,4-Triazolium R4

Thiazolium wherein R 1 to R 5 are as defined above.

A particularly preferred cation is the imidazolium cation of the formula: R 1 / R 5 R 1 Y R 2

Li 1 R 3 wherein R 1 -R 5 are as defined above. In this formula, preferably R 3 -R 5 are each hydrogen and R 1 and R 2 are independently C 1 -C 6 alkyl or C 2 -C 6 alkoxyalkyl. More preferably, one of R1 and R2 is methyl and the other is C1-6 alkyl. In this formula, R may also be halogen, preferably chlorine. The anion of the ionic liquid solvent may be any of the following: halogen such as chloride, bromide or iodide, pseudohalogen such as thiocyanate or cyanate, 9 perchlorate, C 1 -C 6 carboxylate such as formate, acetate, propionate, butyrate, lactate, pyruvate, maleate, nitrate, C2-C6 carboxylate substituted with at least one halogen atom, such as trifluoroacetic acid,

C 1 -C 6 alkylsulfonate substituted with at least one halogen atom, such as trifluoromethanesulfonate (triflate), tetrafluoroborate BF 4 ', or 10fb-trihexafluoride PF 6'

The above halogen substituents are preferably fluorine.

The anion of the ionic liquid solvent is preferably selected from those which provide a hydrophilic ionic liquid solvent. Such anions include halogen, pseudohalogen or C 1 -C 6 carboxylate. Halogen is preferably chloride, bromide or iodide, and pseudohalogen is preferably thiocyanate or cyanate.

If the cation is 1- (C 1 -C 6 -alkyl) -3-methylimidazolium, the anion is preferably a halide, especially chloride.

A preferred ionic liquid solvent is 1-butyl-3-methylimidazolium chloride (BMIMC1) having a melting point of about 60 ° C.

Another type of ionic liquid solvent useful in the present invention is an ionic liquid solvent wherein the cation is a quaternary ammonium salt of the formula R11 R10-N-R12 R13 wherein R10, R11, R12 and R13 are independently C1-C30 alkyl, C3-C8 or an C3 heterocyclic C8 group, and the anion is halogen, pseudohalogen, perchlorate, C (C6-carboxylate or hydroxide).

The C1-C30 alkyl group may be straight-chain or branched, and is preferably a C1-C12 alkyl group.

The C3-C8 carbocyclic group comprises cycloalkyl, cycloalkenyl, phenyl, benzyl and phenylethyl groups.

10

The C3-C8 heterocyclic group may be aromatic or saturated and contain at least one heteroatom selected from the group consisting of nitrogen, oxygen 5 and sulfur.

The inorganic base used for the etherification is preferably an alkali metal hydroxide such as lithium, sodium or potassium hydroxide. Typical organic bases include basic catalysts such as TEA (triethylamine), DIPEA (diisopropylethylamine), TMEDA (N, N, N ', N'), tetramethylethylenediamine, etc. Other organic bases may also be considered. Organic bases are typically relatively expensive reagents. Thus, organic bases are used as catalysts and catalytic volumes, i.e. they are not used in equimolar volumes or in excess.

The ether group of the starch ethers prepared by the process of the present invention may be a C 1 -C 6 alkyl, aryl or aryl C 1 -C 3 alkyl group optionally substituted with at least one functional group selected from the group consisting of: carboxyl, hydroxyl, amino, alkoxy, halogen, cyano, amide, sulfo, phosphorus, nitro and silyl.

The ether group of the starch ethers prepared by the process of the present invention may also be a silyl group substituted with three to 20 carbons or different groups selected from the group consisting of C 1 -C 8 alkyl, aryl and aryl C 1 -C 3 alkyl.

The aryl group contains phenyl and naphthyl.

An aryl-C 1 -C 3 alkyl group (also called aralkyl) is an aryl group as defined above bonded to the O-group of cellulose via an alkyl group containing 1, 2 or 3 carbon atoms. The aryl-C 1 -C 3 alkyl group includes, for example, a benzyl, diphenylmethyl, trityl and phenylethyl group.

Typical cellulose ethers prepared by the process of the present invention include: - alkylated starch 30-2-hydroxyethyl starch, 2-hydroxypropyl starch and 2-butylethyl starch - 2-aminoethyl starch 11-2-cyanoethyl starch - carboxymethyl 2-carboxymethyl starch -sulfoethyl starch - 2-phosphoromethyl starch.

Typical starch chelysilyl ethers prepared by the process of the present invention include: trimethylsilyl starch, tert-butyldimethylsilyl starch, diphenylmethylsilyl starch, triphenylsilyl starch, tribenzyl 1-ylsilyl starch, and tribenzyl 1-ylsilyl starch.

According to the present invention, starch ethers can be prepared by any of the following four reactions: a) Starch-OH + Ra-X + MOH -► Starch-O-Ra R b) Starch-OH + V Rb / + MOH - ►

Z

rc

Starch -O-CH-CH-R 1 / ZH

Ra

c) Starch-OH + Rd-CH = C (Y) Re + MOH-Starch-O-CH-CH-Y

15 Re d) Starch-OH + RfCHN2 + MOH -► Starch-0-CH2Rf

In the above reaction equations: M is Li, Na or K, X is halogen such as chloride, bromide or iodide, or sulfate,

R a is C 1 -C 6 alkyl, aryl or aryl C 1 -C 3 alkyl, said alkyl or aryl optionally substituted with at least one functional group selected from the group consisting of carboxyl, hydroxyl, amino, alkoxy, halogen, cyano, amide, sulfo, phosphorus, nitro and silyl, R 5 may also be silyl substituted with three groups selected from the group consisting of C 1 -C 8 alkyl, aryl and aryl 1 -C 1 -C 3 -alkyl, Z is O (cyclic compound which is epoxide) or NH (cyclic compound which is aziridine),

R b and R c are independently hydrogen or C 1 -C 3 alkyl optionally substituted with at least one functional group selected from the group consisting of carboxyl, hydroxyl, amino, alkoxy, halogen, cyano, amide, sulfo, phosphorus, nitro silyl, Y is an electron withdrawing substituent such as cyano (CN), amide (CONH2) or sulfo (SO3TSia +), Rd and Re are independently from each other hydrogen or C1-C3 alkyl and Rf is C1-C8 alkyl.

Aryl and arylC1-C3 alkyl groups are as defined above. The alkoxy group is preferably C 1 -C 6 alkyl-O-.

For the preparation of starch silyl ethers, the starting material Ra-X is preferably silyl chloride 20 dia.

According to the present invention, both simple substituted starch ethers having only one type of substituent and mixed starch ethers having at least two different substituents can be prepared.

The starch ether obtained after etherification can be separated from the solution by adding to it a non-solvent of starch ether to precipitate the starch ether. Non-solvent should! also be non-solvent of the ionic liquid solvent and mixed with the ionic liquid solvent. Said non-solvent is preferably an alcohol such as a C 1 -C 6 alkanol, for example methanol, ethanol, propanol or isopropanol. Other non-solvents such as ketones (e.g. acetone), acetonitrile, dichloromethane, polyglycols and ethers may also be used.

30 If the DS of starch ether is suitable, even water can be used as a non-solvent.

13

The resulting starch ether can also be separated by extraction into a suitable solvent which is a non-solvent of the ionic liquid solvent.

The main advantages of the preferred methods of the present invention for the preparation of starch ethers in ionic liquids are: 5 · excellent solubility of the reagents used • high solubility allows all natural starches to be used in derivatization • excess reagents which in turn leads to economical degradation of the starch chain • rapid and economical separation of reaction products by precipitation of the prepared product by addition of a non-solvent product and additionally a simple, energy saving product drying process • preparation of existing and also new starch ether products 15 · significantly shorter reaction times and lower reaction temperatures using microwave radiation conditions • easy control of the degree of substitution (DS) by reagent and anhydrogl mole ratio of ukopyranose unit (s) (AGU (s)) 20 · Possibility of producing high or fully substituted (DS = 3) starch ethers • Possibility of making mixed ethers • Possibility of reusing ionic liquids In this specification, percentages are by weight unless not otherwise stated.

Example carboxymethylation of starch

500 mg of starch was dissolved in ionic liquid (BMIMC1, 5 g, melting point 60 ° C) by microwave to give a 10% solution. After the addition of monochloroacetic acid (2.05 eq.), A small excess of solid NaOH (3.25 eq.) Was added. The reaction was allowed to proceed at 70 ° C for two hours, after which the product was precipitated by adding isopropanol to the reaction mixture. The precipitate was removed by filtration and the by-product salts were removed by washing the precipitate with isopropanol. The washed product, carboxymethylated starch, was dried overnight in an oven at 105 ° C and analyzed

Claims (17)

A process for the preparation of a starch ether which comprises mixing the starch with an ionic liquid solvent to dissolve the starch, and then treating the dissolved starch with an etherifying agent in the presence of a base to form the starch ether and then dissolving and starching the ether. The process of claim 1, wherein the etherifying agent is Ra-X and wherein Ra is C 1 -C 6 alkyl, aryl or aryl-C 1 -C 3 alkyl, said alkyl or aryl 10 being optionally substituted with at least one functional group selected from the group consisting of carboxyl, hydroxyl, amino, alkoxy, halogen, cyano, amide, sulfo, phosphorus, nitro and silyl, Ra may also be silyl substituted with three groups selected from the group consisting of C 1 -C 9 alkyl, aryl and aryl C 1 -C 3 alkyl, The process of claim 1, wherein the etherifying agent is N-Rb Z and wherein Z is O (cyclic compound which is epoxide) or NH (cyclic compound which is aziridine) and Rb and Rc are independently hydrogen or C]. An -C3 alkyl group optionally substituted with at least one functional group selected from the group consisting of carboxyl, hydroxyl, amino, alkoxy, halogen, cyano, amide, sulfo, phosphorus, nitro and silyl. The process of claim 1, wherein the etherifying agent is Rd-CH = C (Y) R e, wherein 25 is an electron withdrawing substituent such as cyano (CN), amide (CONH 2) or sulfo (SO 3 'Na +), and Rd and R e is independently hydrogen or C 1 -C 3 alkyl. The process of claim 1, wherein the etherifying agent is R 1 CHN 2 wherein R f is C 1 -C 5 alkyl. The method of claim 1, wherein microwave radiation is used to aid solubilization and etherification. The method of claim 1 or 6, wherein pressure is applied to aid in leaching and etherification. The process of claim 1, wherein the ionic liquid solvent melts at a temperature below 200 ° C. The method of claim 1, wherein the cation 10 of the ionic liquid solvent is selected from the group consisting of: R 1, R 6, R 6, R 6, VN, R 6, Ar 5, R 6, kAr 5, R 1, R 1, R 1, R 4, R 5, > # - r5 r-nSo R3 R1 R4 RWR3 r4wr3 r3Vn'r2 r5wr3 R'-N9S R2 R4 r5 R4 R4 R3 r6J ^ r3 R11 ^ R7VV ^ R9 R6'VAYN'R1 R8 R1 R7 R8 ',' R4 r3är5 r5 wherein R 1 and R 2 are independently C 1 -C 6 alkyl or C 2 -C 6 alkoxyalkyl, and R 3, R 4, R 5, R 6, R 7, R 8 and R 9 are independently hydrogen, C 1 -C 6 alkyl, C 2 -C 6 alkoxyalkyl or C 1 -C 6 alkoxyiryl, or halogen, and wherein the anion of the ionic solvent is halogen, pseudohalogen, perchlorate or C 1 -C 6 carboxylate. The process according to claim 9, wherein said cation is R 4 - R 5 R 5 - nSn.r 2 R 3 wherein each R 3 - R 5 is hydrogen R 1 and R 2 are the same or different and are C 1 -C 6 alkyl, and said anion is halogen, preferably chloride. The process of claim 1, wherein the cation of the ionic liquid solvent is R 11 R 10 -N-R 12 R 13 wherein R 10, R 11, R 12 and R 13 are independently C 1 -C 30 alkyl, C 3 -C 8 carbocyclic or Q-C 5 heterocyclic and the anion of the ionic solvent is a halo-10 gene, pseudohalogen, perchlorate, C 1 -C 6 carboxylate or hydroxide. The process of claim 1, wherein the inorganic base is lithium, sodium, or potassium hydroxide. A process according to any one of the preceding claims, wherein the ether group of the starch ether is a C 1 -C 6 alkyl, aryl or aryl C 1 -C 3 alkyl group optionally substituted with at least one functional group which is selected from the group consisting of; carboxyl, hydroxyl, amino, alkoxy, halogen, cyano, amide, sulfb, phosphorus, nitro and silyl. The process according to any one of claims 1 to 12, wherein the ether group of the starch ether is a silyl group substituted with three groups selected from the group consisting of C 1 -C 9 alkyl, aryl and aryl C 1 -C 3 alkyl . The method of claim 1, wherein the starch ether is separated from the solution by adding a non-solvent of starch ether to precipitate the starch ether. The process of claim 16, wherein said non-solvent is an alcohol, ketone, acetonitrile, dichloromethane, polyglycol, ether or water. The process of claim 1, wherein the starch ether is separated by extraction with a non-solvent of the ionic liquid solvent.