JP2014019716A - Process for producing purified cellulose fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a process for producing a purified cellulose fiber using an ionic liquid, which can suppress decomposition and deterioration or solidification of the ionic liquid and thereby enable highly efficient recycling of the ionic liquid.SOLUTION: There is provided a process for producing a purified cellulose fiber by spinning purified cellulose using a cellulose solution, the cellulose solution being formed by dissolving a cellulose raw material in a liquid containing an ionic liquid, wherein at least a portion of the production process from the dissolution step of the cellulose raw material to the fiber spinning is performed in an inert gas atmosphere.

Description

  The present invention relates to a method for producing purified cellulose fibers from a natural material-derived cellulose raw material with low energy consumption.

Conventionally, viscose rayon produced by the viscose method has been the mainstream as a cellulose fiber containing cellulose obtained from a natural material-derived cellulose raw material. However, although the cellulose raw material itself is derived from natural products and has a low environmental load, viscose rayon has a problem that carbon disulfide, which has a high environmental load, is generated in the production process.
In order to solve the above problems, a method for producing purified cellulose fibers using N-methylmorpholine-N-oxide (NMMO) as a solvent has been developed and put into practical use in recent years. When this manufacturing method is used, there is an advantage that no harmful substances are generated and the environmental load is low. On the other hand, the refined cellulose fiber produced by the production method has a problem that the strength and fatigue resistance are inferior compared to regenerated cellulose fiber such as rayon produced by the viscose method.

Therefore, recently, a method for producing a new purified cellulose fiber using an ionic liquid and a technique that can be used for the production method have been studied.
For example, Patent Document 1 describes a method for dissolving cellulose, which includes a step of mixing cellulose with a molten ionic liquid not containing a nitrogen-containing base to form a mixture, and the cation of the molten ionic liquid The part includes a nitrogen-containing aromatic cation such as an imidazolium cation, or a cation in which one or more carbon atoms forming a ring of a cyclic alkane are substituted with a nitrogen atom, and an alkyl group or an alkoxyalkyl group is bonded to the nitrogen atom Parts are disclosed, and halogen ions, perchlorate ions, and pseudohalogen ions are disclosed as anion parts.

JP 2009-079220 A

Since ionic liquids have properties of low vapor pressure and high thermal stability, they are considered to be solvents that are easy to recycle with high efficiency and have a low environmental load.
However, the present inventors have newly found a problem that the weight of the ionic liquid decreases and solidifies under atmospheric conditions in the process of producing purified cellulose fibers using the ionic liquid.

  This invention is made | formed in view of the said situation, Comprising: In the refinement | purification cellulose fiber manufacturing process using an ionic liquid, decomposition | disassembly, a change, and solidification of an ionic liquid are suppressed, and an ionic liquid can be recycled efficiently. It is an object of the present invention to provide a method for producing a purified cellulose fiber.

  As a result of diligent research to solve the above-mentioned problems, the present invention inerts the gas in contact with the solution containing the ionic liquid in a series of steps from dissolution of cellulose to spinning and recovery of the ionic liquid from the coagulation bath. It has been found that by using a gas, decomposition, alteration and solidification of the ionic liquid can be suppressed, and the present invention has been completed.

That is, this invention provides the manufacturing method of the purified cellulose fiber which has the following characteristics.
(1) A method for producing purified cellulose, in which a purified cellulose is spun using a cellulose solution obtained by dissolving a cellulose raw material in a liquid containing an ionic liquid, the process from the step of dissolving the cellulose raw material to the step of spinning. A method for producing a purified cellulose fiber, wherein at least a part thereof is performed in an atmosphere of an inert gas.
(2) The method for producing purified cellulose fiber according to (1), wherein the inert gas is nitrogen gas.
(3) The manufacturing method of the refined cellulose fiber of (1) or (2) using the ionic liquid whose decomposition start temperature of the said ionic liquid at the time of temperature rising at a rate of 10 degreeC / min is 220 degreeC or more.
(4) The method for producing a purified cellulose fiber according to any one of (1) to (3), wherein an ionic liquid having a decomposition start temperature of 230 ° C. or higher at the time of heating at a rate of 10 ° C./min is used. .
(5) The method for producing a purified cellulose fiber according to any one of (1) to (4), wherein the dissolution temperature in the step of dissolving the cellulose raw material is 30 ° C. or higher.
(6) The ionic liquid includes a cation portion and an anion portion, and the cation portion is at least one selected from the group consisting of an imidazolium ion, a pyridinium ion, an ammonium ion, and a phosphonium ion. 5) The manufacturing method of any one refine | purified cellulose fiber.
(7) The method for producing a purified cellulose fiber according to (5), wherein the cation part is an imidazolium ion represented by the following general formula (1).

[Wherein, R ¹ represents a cyano group, an alkyl group having 1 to 4 carbon atoms, or an alkenyl group having 2 to 4 carbon atoms, R ² represents a hydrogen atom or a methyl group, R ³ represents a cyano group, An alkyl group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms is shown. ]

(8) The anion moiety is chloride ion, bromide ion, formate ion, acetate ion, propionate ion, L-lactate ion, methyl carbonate ion, aminoacetate ion, aminopropionate ion, dimethylcarbamate ion, hydrogensulfur Selected from the group consisting of phosphate ion, methyl sulfate ion, ethyl sulfate ion, methane sulfonate ion, dimethyl phosphate ion, diethyl phosphate ion, methyl phosphonate ion, phosphinate ion, thiocyanate ion, and dicyanamide ion The manufacturing method of the refined cellulose fiber of (6) or (7) which is 1 or more types.
(9) The anion portion is at least one selected from the group consisting of chloride ion, bromide ion, dimethyl phosphate ion, diethyl phosphate ion, methyl phosphonate ion, phosphinate ion, thiocyanate ion, and dicyanamide ion (6 )-(8) The manufacturing method of the refinement | purification cellulose fiber any one.
(10) The method for producing a purified cellulose fiber according to any one of (6) to (9), wherein the ionic liquid is 1-ethyl-3-methylimidazolium diethyl phosphate.

According to the present invention, in a purified cellulose fiber production process using an ionic liquid, the refined cellulose fiber production is carried out in a specific gas atmosphere, so that the decomposition, alteration and solidification of the ionic liquid are suppressed, and the ionic liquid is highly efficient. Can be recycled.
Further, according to the present invention, the purified cellulose fiber can be produced without producing harmful substances such as carbon disulfide, so that the environmental load can be reduced.

It is the figure which showed the change of a state at the time of applying a 140 degreeC heat | fever to the 1-ethyl-3-methyl- imidazolium diethylphosphate in Example 1 and the comparative example 1 with the state before a heating (Original). It is the figure which showed the FT-IR spectrum of 1-ethyl-3-methyl-imidazolium diethyl phosphate before and behind heating (140 degreeC) in air | atmosphere and nitrogen atmosphere. Examples 1 to 3 and 1-ethyl-3-methyl-imidazolium diethyl phosphate in Comparative Example 1 (in nitrogen: Example 1, in air: Comparative Example 1), 1-allyl-3-methyl in Example 2 -It is the figure which showed the change of a weight when a 140 degreeC heat | fever is added to imidazolium chloride and the 1-ethyl-3-methyl- imidazolium acetate in Example 3. FIG.

In the method for producing a purified cellulose fiber of the present invention, a cellulose solution obtained by dissolving a cellulose raw material in a liquid containing an ionic liquid is used, and if necessary, the purified cellulose fiber is spun and solidified after filtration and degassing. The ionic liquid released into the tank is collected. In all or some of these steps, the gas in contact with the ionic liquid solution is an inert gas.
In the present invention, the purified cellulose fiber may contain components other than cellulose, such as hemicellulose and lignin.

In the present invention, the cellulose raw material is not particularly limited as long as it contains cellulose, and may be a plant-derived cellulose raw material, an animal-derived cellulose raw material, or a microorganism-derived cellulose raw material. Or a regenerated cellulose raw material.
Plant-derived cellulose raw materials include cellulose raw materials derived from unprocessed natural plants such as wood, cotton, hemp and other herbs, and plants derived from plants that have been processed in advance, such as pulp, wood flour, and paper products. Examples include processed cellulose raw materials.
Examples of animal-derived cellulose raw materials include squirt-derived cellulose raw materials.
Examples of the cellulose raw material derived from microorganisms include cellulose raw materials produced by microorganisms belonging to the genus Acetobacter and Agrobacterium.
Examples of the regenerated cellulose raw material include a cellulose raw material obtained by regenerating a cellulose raw material derived from plants, animals, or microorganisms as described above by a known method such as a viscose method.
Especially, as a cellulose raw material used in this invention, the pulp which melt | dissolves favorably in an ionic liquid is preferable.

  In the present invention, before the cellulose raw material is dissolved in the liquid containing the ionic liquid, the cellulose raw material can be pretreated for the purpose of improving the solubility in the ionic liquid. Specifically, the pretreatment may include a drying treatment, a physical pulverization treatment such as pulverization and grinding, a chemical modification treatment using an acid or an alkali, and the like. Any of these can be performed by a conventional method.

  In the present invention, the ionic liquid refers to a solvent that is liquid at 150 ° C. or lower (melting point is 150 ° C. or lower) and that is composed only of ions, and the cation portion or anion portion, or both are composed of organic ions. .

The ionic liquid is composed of a cation portion and an anion portion, and the cation portion of the ionic liquid is not particularly limited and may be generally used for the cation portion of the ionic liquid.
Especially, as a preferable thing of the cation part of the ionic liquid used for this invention, a nitrogen-containing aromatic cation, an ammonium ion, and a phosphonium ion are mentioned.

Specific examples of the nitrogen-containing aromatic cation include pyridinium ion, pyridazinium ion, pyrimidinium ion, pyrazinium ion, imidazolium ion, pyrazonium ion, oxazolium ion, 1,2,3-triazoli. Umum ion, 1,2,4-triazolium ion, thiazolium ion, piperidinium ion, pyrrolidinium ion and the like.
Especially, as a nitrogen-containing aromatic cation, an imidazolium ion and a pyrimidinium ion are preferable, and an imidazolium ion represented by the following general formula (C1) is more preferable.

[Wherein, R ^{4 to} R ⁵ are each independently a cyano group, an alkyl group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms, and R ^{6 to} R ⁸ are each independently A hydrogen atom or an alkyl group having 1 to 10 carbon atoms. ]

In formula (C1), R ^{4 to} R ⁵ are each independently a cyano group, an alkyl group having 1 to 10 carbon atoms, or an alkenyl group having 2 to 10 carbon atoms.
The alkyl group having 1 to 10 carbon atoms may be linear, branched or cyclic, preferably linear or branched, and more preferably linear. .
Specific examples of the linear alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, and a decyl group.
Specific examples of the branched alkyl group include 1-methylethyl group, 1,1-dimethylethyl group, 1-methylpropyl group, 2-methylpropyl group, 1,1-dimethylpropyl group, 2, Examples thereof include 2-dimethylpropyl group, 1-methylbutyl group, 2-methylbutyl group, 3-methylbutyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group and the like.
The cyclic alkyl group may be a monocyclic group or a polycyclic group. Specific examples include monocyclic groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, and cyclooctyl group; and polycyclic groups such as norbornyl group, adamantyl group, and isobornyl group.
It is preferable that carbon number of the alkyl group in R < ⁴ > -R < ⁵ > is 1-8.
Examples of the alkenyl group having 2 to 10 carbon atoms include an alkyl group having 2 to 10 carbon atoms in which one carbon-carbon single bond is substituted with a double bond. Preferred examples include a vinyl group, Examples include allyl group. The position of the double bond is not particularly limited.
The number of carbon atoms of the alkenyl group in R ^{4 to} R ⁵ is preferably 2 to 8.
R ^{4 to} R ⁵ may be the same or different from each other.

In formula (C1), R ^{6 to} R ⁸ are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.
The alkyl group having 1 to 10 carbon atoms may be linear, branched or cyclic, preferably linear or branched, and more preferably linear. . Here, examples of the linear, branched, and cyclic alkyl groups include the same alkyl groups as those described above for R ^{4 to} R ⁵ .
The number of carbon atoms of the alkyl group in R ^{6 to} R ⁸ is preferably 1 to 6, more preferably 1 to 3, and particularly preferably 1.
R ^{6 to} R ⁸ may be the same or different from each other.

  A preferred specific example of the imidazolium ion represented by the general formula (C1) is shown as the following general formula (1).

[Wherein, R ¹ represents a cyano group, an alkyl group having 1 to 4 carbon atoms, or an alkenyl group having 2 to 4 carbon atoms, R ² represents a hydrogen atom or a methyl group, R ³ represents a cyano group, An alkyl group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms is shown. ]

  Moreover, the preferable specific example of the imidazolium ion represented by General formula (1) is shown as following formula (1-1)-(1-3).

The phosphonium ion is not particularly limited as long as it has “P ⁺ ”. Specifically, the phosphonium ion is preferably a general formula “R ₄ P ⁺ (a plurality of R are independently hydrogen atoms). It is an atom or a hydrocarbon group having 1 to 30 carbon atoms.) ”.
The hydrocarbon group having 1 to 30 carbon atoms may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group.
The aliphatic hydrocarbon group is preferably a saturated hydrocarbon group (alkyl group), and the alkyl group may be linear, branched, or cyclic.
The linear alkyl group preferably has 1 to 20 carbon atoms, and more preferably 1 to 16 carbon atoms. Specifically, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group, tetradecyl group, pentadecyl group, A hexadecyl group etc. are mentioned.
The branched alkyl group has 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms, and more preferably 3 to 16 carbon atoms. Specifically, 1-methylethyl group, 1,1-dimethylethyl group, 1-methylpropyl group, 2-methylpropyl group, 1,1-dimethylpropyl group, 2,2-dimethylpropyl group, 1-methylbutyl Group, 2-methylbutyl group, 3-methylbutyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group and the like.
The cyclic alkyl group has 3 to 30 carbon atoms, preferably 3 to 20 carbon atoms, more preferably 3 to 16 carbon atoms, and even a monocyclic group, It may be a polycyclic group. Specific examples include monocyclic groups such as cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, and cyclooctyl group; and polycyclic groups such as norbornyl group, adamantyl group, and isobornyl group.
The aromatic hydrocarbon group preferably has 6 to 30 carbon atoms. Specifically, an aryl group such as a phenyl group, a 1-naphthyl group, a 2-naphthyl group, a biphenyl group, a tolyl group, or a benzyl group And arylalkyl groups such as a phenethyl group, a naphthylmethyl group, and a naphthylethyl group.
Here, the plurality of R in the general formula “R ₄ P ⁺ ” may be the same or different.

  Especially, as a phosphonium ion, the cation part represented by the following general formula (C2) is preferable.

[In formula, R < ⁹ > -R < ¹² > is a C1-C16 alkyl group each independently. ]

In general formula (C2), R < ⁹ > -R < ¹² > is a C1-C16 alkyl group each independently. The alkyl group having 1 to 16 carbon atoms may be linear, branched or cyclic, preferably linear or branched, and more preferably linear. . Here, examples of the linear, branched, and cyclic alkyl groups include those described above.
R ^{9 to} R ¹² may be the same or different from each other, but it is preferable that three or more of R ^{9 to} R ¹² are the same from the viewpoint of availability.

Of these, in the present invention, the alkyl group of R ^{9 to} R ¹² is preferably a linear or branched alkyl group having 1 to 14 carbon atoms, and is a linear or branched chain group having 1 to 10 carbon atoms. Are more preferable, linear or branched alkyl groups having 1 to 8 carbon atoms are more preferable, and linear or branched alkyl groups having 1 to 4 carbon atoms are particularly preferable.
A preferred specific example of the cation moiety represented by the general formula (C2) is shown as the following formula (C2-1).

  In the present invention, the cation moiety is more preferably at least one selected from the group consisting of imidazolium ions, pyridinium ions, ammonium ions, and phosphonium ions.

In the present invention, examples of the anion moiety include halogen ions, carboxylate ions, sulfate ions, sulfonate ions, phosphate ions, phosphonate ions, and phosphinate ions.
Examples of the halogen ion include chloride ion, bromide ion, and iodide ion, and chloride ion and bromide ion are preferable.
As the carboxylate ion, formate ion, acetate ion, propionate ion, butyrate ion, hexanoate ion, maleate ion, fumarate ion, oxalate ion, L-lactate ion, pyruvate ion, methyl carbonate Ion, aminoacetate ion, aminopropionate ion, dimethylcarbamate ion, formate ion, acetate ion, propionate ion, L-lactate ion, methyl carbonate ion, aminoacetate ion, aminopropionate ion, Dimethyl carbamate ion is preferred.
Examples of sulfate ions include hydrogen sulfate ions, methyl sulfate ions, ethyl sulfate ions, n-propyl sulfate ions, and n-butyl sulfate ions. Hydrogen sulfate ions, methyl sulfate ions, and ethyl sulfate ions are exemplified. Fate ions are preferred.
Examples of the sulfonate ion include methanesulfonate ion, toluenesulfonate ion, benzenesulfonate ion, and the like, and methanesulfonate ion is preferable.
As a phosphate ion, what is represented by the following general formula (A1) is mentioned.

[Wherein, R ¹³ and R ¹⁴ each independently represents a hydrogen atom or an alkyl group. ]

In the general formula (A1), R ¹³ and R ¹⁴ are each independently a hydrogen atom or an alkyl group, and the alkyl group may be any of linear, branched, and cyclic. A chain or branched alkyl group is preferred. R ¹³ and R ¹⁴ preferably have 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, still more preferably 1 to 4 carbon atoms, and 1 carbon atom for industrial reasons. Or an alkyl group of 2 is particularly preferred.
R ¹³ and R ¹⁴ may be the same or different.

  Of these phosphate ions, dimethyl phosphate ions and diethyl phosphate ions are preferred.

  Examples of the phosphonate ion include those represented by the following general formula (A2).

[Wherein R ¹³ is the same as defined above. ]

In formula ^{(A2), R 13} is the same as ^{R 13} in the general formula (A1).

  Of these phosphonate ions, methyl phosphonate ions are preferred.

  The phosphinate ion is represented by the following formula (A3).

In addition, pseudohalogen ions may be mentioned as other anion moieties. Pseudohalogen ions have properties similar to those of halogen ions. Pseudohalogen ions include cyanate ions, oxocyanate ions, thiocyanate ions, and selenocyanate ions.
Moreover, a dicyanamide ion is mentioned as another anion part.

  In the present invention, the anion moiety is chloride ion, bromide ion, formate ion, acetate ion, propionate ion, L-lactate ion, methyl carbonate ion, aminoacetate ion, aminopropionate ion, dimethylcarbamate ion, Selected from the group consisting of hydrogen sulfate ion, methyl sulfate ion, ethyl sulfate ion, methane sulfonate ion, dimethyl phosphate ion, diethyl phosphate ion, methyl phosphonate ion, phosphinate ion, thiocyanate ion, dicyanamide ion More preferably, it is at least one kind.

The ionic liquid in the present invention is composed of a cation portion and an anion portion as described above. The combination of the cation part and the anion part is not particularly limited, and one or more kinds capable of suitably dissolving the cellulose raw material can be selected.
Preferred ionic liquids include 1-allyl-3-methylimidazolium chloride (AmimCl), 1-ethyl-3-methylimidazolium acetate (C2mimAc), 1-ethyl-3-methylimidazolium diethylphosphate (C2mimDEP, C2mim ( EtO) ₂ PO ₂ ), 1-ethyl-3-methylimidazolium methyl phosphonate (C2mimM EP, C2mim MeOHPO ₂ ), 1-ethyl-3-methylimidazolium phosphinate (C2mim H ₂ PO ₂ ), etc. More preferred is 1-ethyl-3-methylimidazolium diethyl phosphate.
The ionic liquid used in the present invention may be one kind or two or more kinds.

In addition, the ionic liquid in the present invention preferably has a decomposition start temperature of 220 ° C. or higher, determined according to JIS K 7120 under the condition of increasing the temperature at a rate of 10 ° C./min, and is 230 ° C. or higher. More preferably, it is more preferably 250 ° C. or higher.
The higher the decomposition start temperature when the ionic liquid is heated, the higher the thermal stability of the ionic liquid. By using an ionic liquid having high thermal stability, the amount of decomposition of the ionic liquid at the time of heating is reduced, recycling with high efficiency is facilitated, and the degree of freedom in setting temperature in the purified cellulose fiber production process is increased.
Here, the decomposition start temperature can be measured according to JIS K7120 using a commercially available thermogravimetric analyzer (TGA) or the like. Specifically, the temperature of the ionic liquid is measured by increasing the temperature at a temperature increase rate of 10 ° C./min in a nitrogen (N ₂ ) atmosphere. A TGA curve is obtained in which the horizontal axis represents temperature and the vertical axis represents weight (%). The temperature corresponding to the intersection of the tangent line of the first loose weight reduction section and the tangent line where the gradient between the bending points where the weight changes suddenly becomes maximum is defined as the decomposition start temperature of the ionic liquid.

As described above, the ionic liquid in the present invention is preferably one that is not easily decomposed or denatured when subjected to a thermal history in the production process. As the weight of ionic liquid decreased, the problem that the ionic liquid solidified became clear.
On the other hand, in the method for producing purified cellulose fiber of the present invention, all or part of the process of dissolving, filtering, defoaming and spinning cellulose and recovering the ionic liquid from the coagulation tank is in contact with the ionic liquid solution. By making the inert gas into an inert gas, it is possible to suppress the decomposition, alteration and solidification of the ionic liquid, and to recycle the ionic liquid with high efficiency.
In the present invention, the reason why such an effect is obtained is not clear, but is presumed as follows.
When the ionic liquid before and after heating is analyzed by FT-IR and the spectrum is obtained, a signal corresponding to a carbonyl group that was not observed before heating is observed in the ionic liquid heated in the atmosphere. In contrast, no carbonyl signal was observed in the ionic liquid heated in a nitrogen atmosphere. Therefore, there is a possibility that the cause of alteration / solidification of the ionic liquid in the atmosphere is oxidative degradation. Since the ionic liquid is deteriorated and solidified due to oxygen in the air, the gas in contact with all or part of the ionic liquid solution may be an inert gas.
On the other hand, there are ionic liquids that have a large weight loss due to heating even in an inert gas atmosphere such as nitrogen gas not containing oxygen. In particular, a carboxylic acid anion generally well known as a dissolving solvent for cellulose has a large weight loss due to thermal decomposition even in a nitrogen atmosphere, and a recycling recovery rate is low.

The inert gas used in the present invention is preferably selected from nitrogen gas, helium gas, neon gas, argon gas, krypton gas, xenon gas, carbon dioxide gas, more preferably nitrogen gas, argon gas, particularly preferably nitrogen. Gas.
When dissolving cellulose, filtering / defoaming / spinning cellulose solution, and recycling ionic liquid after use, it is sufficient that an inert gas exists in the part in contact with the ionic liquid solution. It may or may not be in circulation.

  In the present invention, the use amount of the ionic liquid is not particularly limited, but the concentration of the cellulose raw material in the cellulose solution is preferably 3 to 30% by weight, and preferably 5 to 25% by weight. More preferably, 8 to 15% by weight is even more preferable. When the concentration of the cellulose raw material is too low, the spun cellulose is difficult to become a dense fiber. On the other hand, when the concentration of the cellulose raw material is too high, the cellulose raw material cannot be completely dissolved.

  In the present invention, the liquid for dissolving the cellulose raw material contains the ionic liquid. The liquid may or may not contain liquid components other than the ionic liquid. Specific examples of liquid components other than the ionic liquid include organic solvents.

The organic solvent is not particularly limited as long as it is other than the ionic liquid, and can be appropriately selected in consideration of compatibility with the ionic liquid, viscosity, and the like.
Among these, the organic solvent is preferably at least one selected from the group consisting of amide solvents, sulfoxide solvents, nitrile solvents, ether solvents, aromatic amine solvents, and ketone solvents.

Examples of the amide solvent include N, N-dimethylformamide, N, N-dimethylacetamide, 1-methyl-2-pyrrolidone, 1-vinyl-2-pyrrolidone and the like.
Examples of the sulfoxide solvent include dimethyl sulfoxide and hexamethylene sulfoxide.
Examples of nitrile solvents include acetonitrile, propionitrile, benzonitrile and the like.
Examples of the ether solvent include 1,3-dioxolane, tetrahydrofuran, tetrahydropyran, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, ethyl acetate and the like.
Examples of the aromatic amine solvent include pyridine.
Examples of ketone solvents include acetone and methyl ethyl ketone.

When these organic solvents are used, the blending weight ratio between the ionic liquid and the organic solvent is preferably 6: 1 to 0.1: 1, more preferably 5: 1 to 0.2: 1. More preferably, it is 4: 1 to 0.5: 1. By setting it as the said range, it can be set as the solvent which is easy to swell a cellulose raw material.
The amount of the organic solvent used is not particularly limited, but is preferably 1 to 30 parts by weight, more preferably 1 to 25 parts by weight with respect to 1 part by weight of the cellulose raw material. More preferably, it is 5 to 10 parts by weight. By setting it as the said range, it can be set as the cellulose solution of moderate viscosity.
It is preferable to use the organic solvent as described above in combination with the ionic liquid because the solubility of the cellulose raw material is further improved.

In the present invention, the method for dissolving the cellulose raw material in the liquid containing the ionic liquid is not particularly limited. For example, the liquid containing the ionic liquid and the cellulose raw material are brought into contact with each other and heated or stirred as necessary. By performing this, a cellulose solution can be obtained.
The method for bringing the liquid containing the ionic liquid into contact with the cellulose raw material is not particularly limited. For example, the cellulose raw material may be added to the liquid containing the ionic liquid, or the liquid containing the ionic liquid in the cellulose raw material. May be added.
When heating is performed during dissolution, the heating temperature is preferably 30 to 200 ° C, more preferably 70 to 180 ° C. It is preferable to perform heating because the solubility of the cellulose raw material is further improved.
As described above, in the present invention, by dissolving the cellulose raw material in an inert gas atmosphere, it is possible to suppress decomposition, alteration and solidification of the ionic liquid.
The stirring method is not particularly limited, and the liquid containing the ionic liquid and the cellulose raw material are mechanically stirred using a stirring blade, a stirring bar, a rotor, a screw, etc., for example, in a dissolution tank, a sealed mixer or an extruder. Alternatively, a liquid containing an ionic liquid and a cellulose raw material may be sealed in a sealed container and dissolved by microwaves. The stirring time is not particularly limited, and it is preferable to carry out the stirring until the cellulose raw material is suitably dissolved.

When the liquid containing the ionic liquid contains an organic solvent in addition to the ionic liquid, the organic solvent and the ionic liquid may be mixed in advance, and after mixing the ionic liquid and the cellulose raw material, the organic solvent May be added and dissolved, or after mixing the organic solvent and the cellulose raw material, the ionic liquid may be added and dissolved.
Especially, it is preferable to mix an organic solvent and an ionic liquid beforehand, and to manufacture a liquid mixture. At this time, it is preferable that the organic solvent and the ionic liquid are stirred while heating at 70 to 180 ° C. for about 5 to 30 minutes, and mixed until the liquid containing the ionic liquid becomes uniform. .
Cellulose solution using ionic liquid obtained in this way is filled with cellulose microcrystals and modified cellulose microcrystals, carbon nanotubes, clay, silica, etc., surfactants, anti-aging agents, etc. The additive may be included.
The cellulose solution using the ionic liquid thus obtained may be filtered and defoamed as necessary. At this time, in order to lower the viscosity of the solution, it is preferable that the solution is heated to 30 to 180 ° C.

The cellulose solution obtained as described above is contacted with a coagulation solution that is a liquid other than the cellulose solution to coagulate the cellulose, and purified cellulose by a known spinning method such as dry-wet spinning or wet spinning. The fiber can be spun.
Dry and wet spinning is a method of spinning cellulose by generally introducing a cellulose solution once discharged into a gas from a spinneret into a coagulation tank holding a coagulation liquid. This is a method of spinning cellulose discharged from a spinneret disposed in a coagulation tank.
The coagulation tank means a bathtub in which a coagulating liquid for coagulating cellulose is held. As such a coagulating liquid, water and a polar solvent may be used alone or in combination, and the ionic liquid described above may be further included therein.
Examples of the polar solvent include tetrahydrofuran, acetone, acetonitrile, N, N-dimethylformamide, dimethyl sulfoxide, acetic acid, formic acid, 1-heptanol, 1-butanol, 2-propanol, 1-propanol, ethanol, methanol and the like.
The ionic liquid can be recovered from the coagulation liquid in the coagulation tank after spinning by a known separation method such as distillation or membrane separation and recycled.
Examples of the distillation method include a thin film distillation method, a vacuum distillation method, an atmospheric distillation method, and a molecular distillation method.
Examples of the membrane separation method include an ultrafiltration method and a reverse osmosis membrane method.

  EXAMPLES Next, although an Example is shown and this invention is demonstrated further in detail, this invention is not limited to a following example.

[Production of cellulose fiber]
[Example 1]
A cellulose solution obtained by dissolving pulp in 1-allyl-3-methylimidazolium chloride (AmimCl) after spinning 100 times in a nitrogen atmosphere is prepared, heated to the spinning temperature, and then placed in an extruder in a nitrogen atmosphere. Then, it was extruded into a coagulation tank, and after washing and drying, cellulose fibers were obtained.
The properties of the cellulose solution and cellulose fibers were measured by the following test methods, and the results are shown in Table 1.
(1) Dope property The cellulose solution was visually confirmed.
(2) Spinnability About 0.06 ml of a cellulose solution was dropped onto a measurement dish, and a measurement piece having a diameter of 3 mm was pressed against the measurement dish.
(3) Fiber productivity The productivity of cellulose fibers was evaluated.
The judgment criteria are shown below.
X: The bobbin cannot be wound, or the fiber can be wound around the bobbin, but the amount of winding can hardly be taken.
A: There is almost no thread breakage, and a sufficient winding amount can be secured.

[Example 2]
Cellulose fibers were obtained in the same manner as in Example 8, except that the pulp was dissolved in 1-ethyl-3-methylimidazolium diethyl phosphate (C2mimDEP) after spinning 100 times in a nitrogen atmosphere.
Properties of the cellulose solution and cellulose fibers were measured by the same test method as in Example 1, and the results are shown in Table 1.

[Example 3]
A cellulose solution was prepared by dissolving pulp in 1-ethyl-3-methylimidazolium diethyl phosphate (C2mimDEP) after spinning 100 times in an argon atmosphere. After heating this to the spinning temperature, an extruder in an argon atmosphere Was extruded into a coagulation tank, and after washing and drying, cellulose fibers were obtained.
Properties of the cellulose solution and cellulose fibers were measured by the same test method as in Example 1, and the results are shown in Table 1.

[Example 4]
A cellulose solution prepared by dissolving pulp in 1-ethyl-3-methylimidazolium acetate (C2mimAc) after spinning 30 times in a nitrogen atmosphere was prepared, heated to the spinning temperature, and then placed in an extruder in a nitrogen atmosphere. Then, it was extruded into a coagulation tank, and after washing and drying, cellulose fibers were obtained.
Properties of the cellulose solution and cellulose fibers were measured by the same test method as in Example 1, and the results are shown in Table 1.

[Comparative Example 1]
A cellulose solution was prepared by dissolving the pulp in 1-ethyl-3-methylimidazolium diethyl phosphate (C2mimDEP) after spinning 48 times under atmospheric conditions, but the ionic liquid solidified and the cellulose did not dissolve.
The properties of the cellulose solution were measured by the same test method as in Example 8, and the results are shown in Table 1.

[Comparative Example 2]
A cellulose solution is prepared by dissolving pulp in 20-spinning 1-ethyl-3-methylimidazolium diethylphosphate (C2mimDEP) under atmospheric conditions. After heating the spinning solution to the spinning temperature, an extruder is used under atmospheric conditions. Was extruded into a coagulation tank, and after washing and drying, cellulose fibers were obtained.
The properties of the cellulose solution and cellulose fibers were measured by the same test method as in Example 1, and the results are shown in Table 3.

[Comparative Example 3]
A cellulose solution was prepared by dissolving pulp in 1-ethyl-3-methylimidazolium acetate (C2mimAc) after spinning 20 times under atmospheric conditions, but the ionic liquid solidified and cellulose did not dissolve.
The properties of the cellulose solution were measured by the same test method as in Example 8, and the results are shown in Table 1.

[Examination of thermal stability of ionic liquid]
[Example 5]
The thermal stability of ionic liquid was investigated.
As the ionic liquid according to the present invention, 1-ethyl-3-methylimidazolium diethyl phosphate (C2mimDEP) was used to examine thermal stability in a nitrogen atmosphere.
Specifically, with respect to 1-ethyl-3-methylimidazolium diethylphosphate, a thermogravimetric measuring device (Q600, manufactured by TA Instruments Inc.) is used and a rate of 10 ° C./min under a nitrogen atmosphere. The change in weight was measured while the temperature was raised at. The obtained results are obtained as a TGA curve in which temperature is plotted on the horizontal axis and weight (%) is plotted on the vertical axis. Table 1 shows the temperature corresponding to the intersection of the tangent line of the first loose weight reduction section and the tangential line where the gradient between the bending points where the weight changes suddenly changes thereafter is the maximum, as the decomposition start temperature.
Moreover, it heat-processed at 140 degreeC by nitrogen atmosphere using oven (made by Yamato Scientific). The change in the properties of 1-ethyl-3-methylimidazolium diethyl phosphate after the heat treatment for 100 hours is shown in FIG. Furthermore, the time-dependent weight change of 1st-6th of heat processing is shown in FIG. Table 2 shows a linear approximation of the change in weight between the first and sixth days after heat treatment excluding the initial weight loss due to the raw material impurities, and the slope of the straight line is the decomposition rate (weight (%) / day). .
The FT-IR spectrum of 1-ethyl-3-methylimidazolium diethyl phosphate heated at 140 ° C. for 4 days in a nitrogen atmosphere was determined. The result is shown in FIG. 2 together with the result of C2mimDEP before heating.

[Example 6]
As the ionic liquid according to the present invention, 1-allyl-3-methylimidazolium chloride (AmimCl) was used to examine the thermal stability in a nitrogen atmosphere. Specifically, 1-allyl-3-methylimidazolium chloride was increased at a rate of 10 ° C./min under a nitrogen atmosphere using a thermogravimetric measuring device (Q600, manufactured by TA Instruments). The change in weight was measured while warming. A TGA curve is obtained in which the horizontal axis represents temperature and the vertical axis represents weight (%). Table 2 shows the temperature corresponding to the intersection of the tangent line of the first loose weight decreasing section and the tangent line where the gradient between the bending points where the weight changes suddenly becomes maximum is the decomposition start temperature.
Moreover, 1-allyl-3-methylimidazolium chloride was heat-treated at 140 ° C. in a nitrogen atmosphere using an oven (manufactured by Yamato Scientific Co., Ltd.). FIG. 3 shows changes in weight over time from 1 day to 6 days of the heat treatment. The weight change between the first day and the sixth day after the heat treatment was approximated by a straight line, and the slope of the straight line was shown as the decomposition rate (weight (%) / day) in Table 2.

[Example 7]
As the ionic liquid according to the present invention, 1-ethyl-3-methylimidazolium acetate (C2mimAc) was used to examine thermal stability in a nitrogen atmosphere. Specifically, for 1-ethyl-3-methylimidazolium acetate, the temperature was increased at a rate of 10 ° C./min under a nitrogen atmosphere using a thermogravimetric measurement device (Q600, manufactured by TA Instruments). The change in weight was measured while warming. A TGA curve is obtained in which the horizontal axis represents temperature and the vertical axis represents weight (%). Table 2 shows the temperature corresponding to the intersection of the tangent line of the first loose weight decreasing section and the tangent line where the gradient between the bending points where the weight changes suddenly becomes maximum is the decomposition start temperature.
Moreover, 1-ethyl-3-methylimidazolium acetate was heat-processed at 140 degreeC in nitrogen atmosphere using oven (made by Yamato Scientific company). FIG. 3 shows changes in weight over time from 1 day to 6 days of the heat treatment. The weight change between the first day and the sixth day after the heat treatment was approximated by a straight line, and the slope of the straight line was shown as the decomposition rate (weight (%) / day) in Table 2.

[Comparative Example 4]
As the ionic liquid, 1-ethyl-3-methylimidazolium diethyl phosphate (C2mimDEP) was used to examine thermal stability in the atmosphere.
Specifically, 1-ethyl-3-methylimidazolium diethyl phosphate was heat-treated at 140 ° C. under atmospheric conditions using an oven (manufactured by Yamato Scientific Co., Ltd.). The change in the properties of 1-ethyl-3-methylimidazolium diethyl phosphate after the heat treatment for 100 hours is shown in FIG. Furthermore, the time-dependent weight change of 1st-6th of heat processing is shown in FIG. The weight change between 1 day and 6 days after the heat treatment was approximated by a straight line, and the slope of the straight line was shown in Table 2 as the decomposition rate (weight (%) / day).
FT-IR spectra of 1-ethyl-3-methylimidazolium diethyl phosphate heated at 140 ° C. for 2 days and 7 days under atmospheric conditions were obtained. The result is shown in FIG.

[Examination of the effect of temperature on dissolution]
[Example 8]
The effect of temperature on cellulose dissolution of ionic liquids was investigated.
As an ionic liquid according to the present invention, pulp having a final concentration of 10% is added to 1-ethyl-3-methylimidazolium diethylphosphate (C2mimDEP), and dissolved at 105 ° C. for 4 hours. The properties of the obtained Dope are It was confirmed visually. The results are shown in Table 3.

[Example 9]
The properties of the obtained Dope were visually confirmed in the same manner as in Example 8 except that the melting temperature was 80 ° C. The results are shown in Table 3.

[Example 10]
The properties of the obtained Dope were visually confirmed in the same manner as in Example 8, except that the dissolution temperature was 25 ° C. The results are shown in Table 3.

[Example 11]
As an ionic liquid according to the present invention, a pulp having a final concentration of 10% is added to 1-allyl-3-methylimidazolium chloride (AmimCl), dissolved at 105 ° C. for 4 hours, and the properties of the obtained Dope are visually observed. confirmed. The results are shown in Table 3.

[Example 12]
The properties of the obtained Dope were visually confirmed in the same manner as in Example 11 except that the melting temperature was 80 ° C. The results are shown in Table 3.

[Example 13]
The properties of the obtained Dope were visually confirmed in the same manner as in Example 11 except that the melting temperature was 25 ° C. The results are shown in Table 3.

  As summarized in Table 1, spinning was performed using the ionic liquid after recycling 100 times (C2mimAc was 30 times) by performing the natural fiber production process in an inert gas. On the other hand, when the production process was performed in the air, it became clear that the ionic liquid was not suitable for the production of purified cellulose fibers due to the solidification of the ionic liquid and the decrease in solubility as the number of recycles increased. Thus, by making the gas in contact with the ionic liquid an inert gas in the production process of the purified cellulose fiber, the ionic liquid can be efficiently recycled. By increasing the efficiency of recycling, it is possible to reduce the amount of waste generated from the process and to produce a manufacturing method with less environmental impact.

In FIG. 1, (a) shows 1-ethyl-3-methylimidazolium diethylphosphate before heat treatment, and (b) 1-ethyl-3-methylimidazolium after treatment at 140 ° C. for 100 hours in the atmosphere. Diethyl phosphate is shown, and (c) shows 1-ethyl-3-methylimidazolium diethyl phosphate after treatment at 140 ° C. for 100 hours in a nitrogen atmosphere.
From the results shown in FIG. 1, it was confirmed that the ionic liquid solidified after 140 hours at 140 ° C. in the air, while maintaining the liquid state in the nitrogen atmosphere. Since the solidified ionic liquid cannot be used for dissolving cellulose, it is not suitable for producing purified cellulose fibers. From this result, it is clear that solidification of the ionic liquid can be suppressed by using an inert gas as the gas in contact with the ionic liquid solution in the fiber manufacturing process.

FIG. 2 shows FT-IR of 1-ethyl-3-methylimidazolium diethylphosphate before heating, after heat treatment at 140 ° C. for 4 days in a nitrogen atmosphere, and after heat treatment at 140 ° C. in air for 2 days and 7 days, respectively. The spectrum is shown.
From the result of FIG. 2, in 1-ethyl-3-methylimidazolium diethyl phosphate heated in the atmosphere, a signal corresponding to a carbonyl group that was not observed before heating was observed. From this, it is clear that when 1-ethyl-3-methylimidazolium diethyl phosphate is heated in the atmosphere, an oxidation reaction occurs. On the other hand, when heated in a nitrogen atmosphere, no signal corresponding to the carbonyl group is observed, so it is clear that the oxidation reaction is suppressed. Considering together with the results of FIG. 1, it is considered that an oxidation reaction is involved in the alteration / solidification of the ionic liquid, and it is clear that the alteration / solidification of the ionic liquid can be suppressed by suppressing the oxidation reaction. It is.

FIG. 3 shows 1-ethyl-3-methylimidazolium diethyl phosphate at 140 ° C. in air and nitrogen atmosphere (in nitrogen atmosphere: Example 1, in air: Comparative Example 1), 1-allyl-3- It is the graph which showed the time-dependent change of the weight of methyl imidazolium chloride (Example 2) and 1-ethyl-3-methyl imidazolium acetate (Example 3). From the results of analysis of volatiles when heated in a nitrogen atmosphere, the weight loss of 1-ethyl-3-methylimidazolium diethyl phosphate at the beginning of heating (day 1) was due to volatilization of components contained as impurities in the ionic liquid. The main reason for this is that subsequent weight loss is believed to be due to degradation.
The decomposition rates determined from the results of FIG. When the decomposition rate of 1-ethyl-3-methylimidazolium diethylphosphate is compared in the air and in a nitrogen atmosphere, the mass loss of the ionic liquid is suppressed to one third in the nitrogen atmosphere as compared to the air. It was confirmed. In addition, 1-ethyl-3-methylimidazolium acetate has a significant weight loss even in a nitrogen atmosphere as compared with 1-ethyl-3-methylimidazolium diethylphosphate and 1-allyl-3-methylimidazolium chloride. When the heat history reaches 140 ° C. for 24 hours, it is apparent that the upper limit of the recovery rate of the ionic liquid is 94%. In the specification of Chinese Patent No. 101382626, 140 ° C. is exemplified as the spinning temperature in continuous spinning. The heat history of 140 ° C. and 24 hours corresponds to the cumulative heating time of 24 hours at the spinning temperature.

  Furthermore, as summarized in Table 2, it can be seen that there is a correlation between the decomposition start temperatures of the three ionic liquids in a nitrogen atmosphere and the weight loss rate when heated at 140 ° C. By using an ionic liquid having a decomposition start temperature of 230 ° C. or higher in a nitrogen atmosphere of the ionic liquid, even if the thermal history is 140 ° C. for 24 hours, the weight of the ionic liquid containing no impurities is 95 It is clear that% ionic liquid may be recovered. Furthermore, by using an ionic liquid having a decomposition start temperature of 250 ° C. or higher, 99% of the ionic liquid is recovered with respect to the weight of the ionic liquid not containing impurities, even if the thermal history is 140 ° C. for 24 hours. It is clear that there is a possibility that it can be done. As described above, by determining the ionic liquid decomposition start temperature in a nitrogen atmosphere, it is possible to select an ionic liquid having a low weight loss rate during heating and excellent recyclability.

  From the results in Table 3, the higher the temperature, the better the solubility of cellulose in the ionic liquid. Since the solubility is poor at a dissolution temperature of 25 ° C., it remains clear that cellulose remains undissolved even after 4 hours, which is not suitable for industrial Dope preparation.

  From the above results, according to the present invention, in the refined cellulose fiber production process using the ionic liquid, the gas that is in contact with the ionic liquid in all or part of the process is made an inert gas to decompose and alter the ionic liquid. It is clear that solidification can be suppressed and the ionic liquid can be recycled with high efficiency.

Claims (10)

  A method for producing a purified cellulose fiber in which purified cellulose is spun using a cellulose solution obtained by dissolving a cellulose raw material in a liquid containing an ionic liquid, and at least one of the steps from the step of dissolving the cellulose raw material to the spinning. A method for producing a purified cellulose fiber, wherein the part is performed in an inert gas atmosphere.   The method for producing a purified cellulose fiber according to claim 1, wherein the inert gas is nitrogen gas.   The manufacturing method of the refined cellulose fiber of Claim 1 or 2 using the ionic liquid whose decomposition start temperature of the said ionic liquid at the time of temperature rising at a rate of 10 degree-C / min is 220 degreeC or more.   The manufacturing method of the refined cellulose fiber as described in any one of Claims 1-3 using the ionic liquid whose decomposition start temperature of the said ionic liquid at the time of temperature rising at a rate of 10 degree-C / min is 230 degreeC or more.   The method for producing a purified cellulose fiber according to any one of claims 1 to 4, wherein a dissolution temperature in the step of dissolving the cellulose raw material is 30 ° C or higher.   The ionic liquid comprises a cation part and an anion part, and the cation part is one or more selected from the group consisting of imidazolium ions, pyridinium ions, ammonium ions, and phosphonium ions. A method for producing a purified cellulose fiber according to one item. The method for producing a purified cellulose fiber according to claim 6, wherein the cation moiety is an imidazolium ion represented by the following general formula (1).
[Wherein, R ¹ represents a cyano group, an alkyl group having 1 to 4 carbon atoms, or an alkenyl group having 2 to 4 carbon atoms, R ² represents a hydrogen atom or a methyl group, R ³ represents a cyano group, An alkyl group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms is shown. ]   The anion portion is chloride ion, bromide ion, formate ion, acetate ion, propionate ion, L-lactate ion, methyl carbonate ion, aminoacetate ion, aminopropionate ion, dimethylcarbamate ion, hydrogen sulfate ion, One or more selected from the group consisting of methyl sulfate ion, ethyl sulfate ion, methane sulfonate ion, dimethyl phosphate ion, diethyl phosphate ion, methyl phosphonate ion, phosphinate ion, thiocyanate ion, and dicyanamide ion A method for producing a purified cellulose fiber according to claim 6 or 7.   The anion portion is at least one selected from the group consisting of chloride ion, bromide ion, dimethyl phosphate ion, diethyl phosphate ion, methyl phosphonate ion, phosphinate ion, thiocyanate ion, and dicyanamide ion. The manufacturing method of the purified cellulose fiber as described in any one of these.   The method for producing a purified cellulose fiber according to any one of claims 6 to 9, wherein the ionic liquid is 1-ethyl-3-methylimidazolium diethyl phosphate.