JP6504161B2 - Method for producing cellulose solution - Google Patents

Description

  The present invention relates to a cellulose solution used for spinning regenerated cellulose fibers, in particular, a method for producing a cellulose solution suitable for spinning regenerated cellulose fibers by dissolving cellulose in an ionic liquid; The present invention relates to a cellulose dispersion to be used.

  Cellulose is the most abundant organic compound in nature, and is said to account for one-third of all plant matter. The regenerated cellulose fiber made from cellulose, which is a non-petroleum natural material, not only uses cellulose, which is the most abundant biomass present on the earth, but also has the advantage of low environmental impact during disposal. is there.

  However, since cellulose has very poor solubility in solvents, regardless of whether it is aqueous or organic, it is limited like regenerated cellulose fibers such as rayon fibers, cupra fibers and lyocell fibers currently produced industrially. It is only dissolved and regenerated by the above method.

  In addition, all of the above-mentioned methods for producing regenerated cellulose fiber have a risk of using a highly toxic solvent or a solvent having a high risk of explosion or the like. Therefore, it is desirable to develop a method for producing a regenerated cellulose fiber having high safety and productivity and good spinnability.

  On the other hand, in recent years, it has been reported that cellulose dissolves in an ionic liquid (Patent Document 1, Non-Patent Document 1). For example, as a method for producing regenerated cellulose fiber with high safety and productivity, a method of dissolving cellulose in an ionic liquid and spinning the regenerated cellulose fiber using the obtained solution is disclosed (for example, patent documents 2, 3).

Japanese Patent Application Publication No. 2005-506401 JP, 2009-203467, A Unexamined-Japanese-Patent No. 2012-21048

Swatloski, R.P., et al., J. Am. Chem. Soc. 2002, Vol. 124 (18), pp. 4974-4975

  However, when cellulose is dissolved in the ionic liquid by the above-mentioned conventional dissolution method, aggregates and gel lumps composed of undissolved cellulose are easily generated, and there is a problem that the spinnability and mechanical properties of the obtained fiber are reduced. is there. These lumps, once formed, need to be subjected to additional treatments such as heating and shearing, and it is difficult to completely dissolve them even if such treatments are applied, and the molecular weight of cellulose is lowered. cause.

  In addition, the aggregates and gel lumps can not be completely removed even by filtration, which causes problems such as frequent yarn breakage during spinning. In addition, even if thread breakage does not occur, in the fibers obtained by spinning, these lumps also affect the tensile strength and the elastic modulus to cause defects.

  Therefore, the present invention provides a method for producing a cellulose solution which can dissolve cellulose homogeneously in an ionic liquid and can obtain a cellulose solution having good spinnability industrially, and a cellulose decomposition solution used therefor. The purpose is

  In order to achieve such an object, the present invention is a method for producing a cellulose solution used to spin regenerated cellulose fibers, wherein cellulose having a volume average particle diameter of 20 μm to 150 μm is dispersed in an ionic liquid, It is characterized by comprising a dispersion step of preparing a cellulose dispersion, and a dissolution step of dissolving the cellulose in the ionic liquid by heating the cellulose dispersion to obtain a cellulose solution.

  In the production method of the present invention, cellulose is first dispersed in the ionic liquid in the dispersion step to prepare a cellulose dispersion.

  At this time, when the volume average particle diameter of the cellulose is less than 20 μm, the particles aggregate to form agglomerates, so that a homogeneous cellulose dispersion can not be obtained. In addition, when the volume average particle diameter of the cellulose is larger than 150 μm, the ionic liquid does not sufficiently penetrate to the center of the particles, and a gel mass is formed, so that a homogeneous cellulose dispersion can not be obtained. Then, in order to obtain a homogeneous cellulose dispersion liquid, the cellulose needs to have a volume average particle diameter of 20 μm or more and 150 μm or less, and preferably 20 μm or more and 50 μm or less.

  In the production method of the present invention, the cellulose dispersion is then heated in the dissolution step to dissolve the cellulose in the ionic liquid to obtain a cellulose solution.

  According to the production method of the present invention, by doing as described above, cellulose can be homogeneously dissolved in an ionic liquid, and a cellulose solution having good spinnability industrially can be obtained.

  In the production method of the present invention, for example, 1-ethyl-3-methylimidazolium acetate can be used as the ionic liquid.

  In the production method of the present invention, the viscosity of the ionic liquid used in the dispersing step is preferably 10,000 mPa · s or less, and cellulose can be easily dispersed in the ionic liquid. The viscosity of the ionic liquid is more preferably 6,000 mPa · s or less, still more preferably 1,000 mPa · s or less, most preferably 500 mPa · s or less, in order to easily disperse cellulose in the ionic liquid. It is.

  The viscosity of the ionic liquid can be adjusted by controlling the temperature or adding a protic solvent to the ionic liquid.

  Then, it is preferable that the liquid temperature of the ionic liquid used in the said dispersion | distribution process is -30 degreeC or more and 25 degrees C or less. By setting the liquid temperature of the ionic liquid in the above-mentioned range, it is possible to prevent the formation of agglomerates of cellulose and to prevent the viscosity of the ionic liquid from becoming high enough to prevent the dispersion of cellulose.

  Moreover, it is preferable that the ionic liquid used in the said dispersion | distribution process contains a protic solvent of 2.0 wt% or more and 7.0 wt% or less. The ionic liquid does not have a high viscosity even at low temperatures by containing a protic solvent in the above range, so that the dispersion speed of the cellulose particles can be increased, and a dispersion having good dispersibility can be prepared. . In order to prevent the viscosity of the ionic liquid from increasing at a low temperature, the ionic liquid preferably contains 4.0 wt% or more and 6.0 wt% or less of a protic solvent, and more preferably 5.3 wt% or more More preferably, it contains 5.7 wt% or less of a protic solvent. As the protic solvent, for example, water or ethanol can be used.

  Moreover, in the manufacturing method of this invention, the pulp sheet of a cotton linter can be used as said cellulose, for example. The cellulose preferably has an average degree of polymerization of 500 or more and 5,000 or less, and can impart tensile strength and an elastic modulus suitable for processing to regenerated cellulose fibers spun using the cellulose solution.

  The cellulose dispersion of the present invention is a cellulose dispersion used for producing a cellulose solution used to spin regenerated cellulose fibers, and is characterized by being prepared by the above-mentioned dispersion step.

  The method for spinning regenerated cellulose fibers of the present invention is a method for spinning regenerated cellulose fibers, and is characterized by spinning using the cellulose solution of the present invention.

The flowchart which shows typically the process of melt | dissolving cellulose and spinning it using an ionic liquid. The cellulose particle is disperse | distributed to an ionic liquid, and the photograph which shows the state of the solution after heat dissolution is shown. The photograph which shows the state of the solution after mixing ethanol with an ionic liquid as a protic solvent, and heat-dissolving.

  The present inventors have found that it is necessary to produce a homogeneous cellulose solution with few undissolved substances in order to spin industrially regenerated regenerated cellulose fibers using an ionic liquid with high productivity. Did. As a result, in order to prepare a homogeneous cellulose solution having good spinnability, it is important to disperse cellulose in an ionic liquid and to make the dispersion uniform when dispersing it, which is why cellulose It revealed that the particle size and the liquid temperature of the ionic liquid were very important.

First, the ionic liquid used and cellulose will be described.
«Ionic liquid»
As the ionic liquid, an imidazolium-based, pyridinium-based, or pyrimidinium-based ionic liquid can be used. Preferably, it is an imidazolium-based ionic liquid.

  The imidazolium-based ionic liquid has a relatively lower melting point than other ionic liquids, so the temperature range in which the liquid is present is wide, and it is fluid even at low temperatures. It is suitable for dispersing cellulose particles and is suitable for obtaining a homogeneous cellulose solution, since it has fluidity even in a low temperature range capable of suppressing adhesion of cellulose particles.

  As an imidazolium-based ionic liquid, 1-ethyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium formate, 1-allyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazo Lithium dimethyl phosphate, 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride, 1-ethyl-3-methylimidazolium diethyl phosphate, 1,3-dimethylimidazolium acetate, 1-ethyl -3- methyl imidazolium propionate etc. can be mentioned.

  By using these ionic liquids, cellulose raw materials having a relatively large degree of polymerization of 1,000 or more can be easily dissolved.

  Here, 1-ethyl-3-imidazolium acetate (hereinafter referred to as [Emim] [Ac]) was used. Moreover, when mixing with a protic solvent, the protic solvent and [Emim] [Ac] were mixed in advance at a desired ratio and used. Here, as the protic solvent, water (ion-exchanged water, distilled water, etc.) or ethanol is usually used, but if the viscosity of the ionic liquid can be adjusted, a mixture of other protic solvents or protic solvents A liquid may be added. Examples of other protic solvents include lower alcohols such as methanol, ethanol and 1-propanol, amines, acid amides and carboxylic acids. The protic solvent is preferably water from the viewpoint of securing the safety of the operation, cost and reducing the environmental load. Further, the ionic liquid was previously adjusted to a predetermined liquid temperature, and the liquid temperature was kept constant even when mixed with cellulose.

As used herein, the term "ionic liquid" refers to an ionic liquid not containing water or the like, or an ionic liquid containing a protic solvent represented by water. In addition, the solvent containing water and an ionic liquid is called mixed solvent.
«Cellulose»
Basically, any raw material may be used as a cellulose raw material used for spinning, for example, natural cellulose such as cotton, cotton linter, hemp, bamboo, abaca, bacterial cellulose, wood pulp and non-wood pulp obtained by purifying them, paper etc. Can be used. Regenerated cellulose such as rayon, cupra or lyocell, or paper or clothes made of them may be reused. When the cellulose content of the cellulose raw material is high, there are few impurities such as fats and oils, lignin and hemicellulose, and the processability, solubility and spinnability at the time of pulverization are not inhibited. Moreover, 500 or more are preferable and, as for the average degree of polymerization of a cellulose raw material, 5,000 or less are desirable from solubility. Within this range, the spun regenerated cellulose fiber can have a tensile strength and modulus suitable for processing.

  Here, a cotton linter pulp sheet is selected as having high cellulose purity and capable of obtaining uniform particles, and a sample having the same volume average particle diameter is prepared as follows, solubilities of cellulose, The spinnability was examined.

The pulp sheet was finely cut and made into particles using a grinder. The particles obtained were sieved to obtain cellulose particles having a volume average particle diameter of 10 μm, 24 μm, 30 μm, 37 μm, 50 μm, 100 μm, 150 μm and 200 μm. In addition, the grinding method can be based on the method using the existing apparatuses, such as a cutter mill, a ball mill, a jet mill, for example.
«Particle size measurement method»
The volume average particle size of the cellulose particles was measured as follows. A dispersion medium was prepared by adding a surfactant to water using a laser scattering / diffraction type particle size distribution measuring apparatus (type 1064 manufactured by CILAS). The particle size distribution based on volume was measured, and the particle diameter at which the cumulative volume ratio was 50% was defined as the volume average particle diameter (D50).
«Method of preparing solution and spinning method»
A method of dissolving cellulose in an ionic liquid and spinning it will be described. First, as shown in FIG. 1, cellulose particles are added little by little while stirring to a mixed solvent containing an ionic liquid or a protic solvent in a predetermined ratio to prepare a cellulose dispersion. The cellulose concentration is preferably 1 wt% or more from the viewpoint of spinnability, and is preferably 30 wt% or less so that the load when stirring the dispersion and the solution does not become too high.

  At this time, the ionic liquid or the mixed solvent is previously adjusted to a predetermined temperature of −40 ° C. or more and 30 ° C. or less, and dispersed while being maintained at a predetermined temperature.

  Next, the cellulose is dissolved by heating the cellulose dispersion to obtain a cellulose solution. The heating may be performed using any known heating method such as microwave heating. The heating temperature is preferably 40 ° C. or more from the viewpoint of shortening the dissolution time, and is preferably 140 ° C. or less from the viewpoint of preventing the deterioration of the ionic liquid.

The obtained cellulose solution can be spun at a temperature of 60 ° C. and water as a coagulating solution to obtain regenerated cellulose fibers. The cellulose solution is preferably subjected to pretreatment such as vacuum degassing to remove air bubbles.
«Study of particle size»
The relationship between the cellulose particle size and the dispersibility was examined. The dispersibility was confirmed using cellulose particles having a volume average particle diameter of 10 μm or more and 200 μm or less.

  While stirring 97.0 g of [Emim] [Ac] at a liquid temperature of 5 ° C. at 300 rpm, 3.0 g of cellulose particles were added little by little and stirred for 30 seconds after addition of the cellulose particles to prepare a cellulose dispersion. In addition, the cellulose dispersion was heated by microwave (2.45 GHz) at 500 W for 10 seconds using a microwave, stirred for 15 seconds, further heated for 10 seconds, and then stirred to obtain a cellulose solution. The results are shown in Table 1.

  The dispersibility was evaluated by visually stirring the prepared cellulose dispersion at 300 rpm for 5 minutes. Specifically, when cellulose particles are uniformly dispersed and no clumps of cellulose particles are visible in the cellulose dispersion, ○, clumps of cellulose particles or gel-like clumps appear locally in the cellulose dispersion The thing of (triangle | delta) and the aggregate of cellulose particle | grains or gel-like lumps which made the whole visible in a cellulose dispersion liquid was made into x.

  In addition, the solubility was evaluated by measuring a cellulose undissolved content (residue amount). Specifically, first, the obtained cellulose solution was kept at 60 ° C., two PTFE membrane filters with a pore size of 10 μm of known weight were stacked and set on a Buchner funnel, and each cellulose solution was suction filtered. After filtration, the membrane was further washed with an ionic liquid to completely replace the cellulose solution remaining in the filter with the ionic liquid, and then only the filter on the upper surface was taken out and immersed in ion exchanged water. After removing the ionic liquid from the filter while changing the ion exchange water several times, it was dried at 100 ° C. for 6 hours, and the weight was measured. A value obtained by subtracting the original filter weight is used as an indicator of solubility as a cellulose undissolved matter (residue amount).

  When cellulose particles having a volume average particle diameter of 10 μm are formed into a cellulose dispersion, the cellulose particles are aggregated to form agglomerates. Therefore, even when heated to form a cellulose solution, many aggregates remain without being dissolved, and the amount of residue after filtration is large.

  In addition, since cellulose particles having a volume average particle diameter of 200 μm have a particle diameter too large, the ionic liquid does not sufficiently penetrate to the central part of the cellulose particles, and gel lumps are formed in other parts. Furthermore, dispersibility is poor due to adhesion of the lumps, and as a result, even if it is heated, the central part becomes undissolved, and a large amount of gel-like undissolved remains, making it impossible to produce a homogeneous cellulose solution , Could not be filtered.

  From the above, it can be seen that when cellulose particles having a volume average particle diameter of 10 μm or 200 μm are used, a homogeneous cellulose solution can not be prepared because there are many undissolved substances. A cellulose solution prepared using cellulose particles having a volume average particle diameter of 10 μm or 200 μm is likely to cause thread breakage when spinning, and the resulting fiber also contains undissolved matter, so tensile strength and elasticity are obtained. Affect the rate.

  The photograph of the state of a cellulose solution is shown in FIG. In the case of using cellulose particles having a volume average particle diameter of 10 μm and having poor dispersibility when producing a cellulose dispersion, there are undissolved materials that can be visually confirmed after heat dissolution. On the other hand, in the cellulose solution prepared using cellulose having a volume average particle diameter of 24 μm, 37 μm, and 100 μm, in which the dispersibility was good when the cellulose dispersion was prepared, no undissolved matter was visually recognizable.

  In addition, a cellulose solution prepared using cellulose particles having a volume average particle diameter of 200 μm is transparent, and at first glance it seems that all the cellulose particles are dissolved, but a large gel mass is present. Therefore, filtration can not be performed as described above.

  As a result of the above examination, if the volume average particle diameter of cellulose is 20 μm or more and 150 μm or less, the dispersibility is good, and a homogeneous cellulose solution can be obtained after heat treatment, and as a result, the spinnability is also improved. I understand. In addition, the volume average particle diameter of cellulose is preferably 20 μm or more and 100 μm or less, and is 20 μm or more and 50 μm or less, from the viewpoint of ease of pulverization, a viewpoint of industrial development, and a small amount of residue of cellulose solution. Is more preferred.

In addition, in the case of cellulose particles having a particle size of more than 150 μm, and in particular having a particle size of 200 μm or more, they not only remain as undissolved substances themselves, but they cause large gel mass formation, which adversely affects dispersibility and solubility Exert. Therefore, regardless of the volume average particle size, classification is preferably performed by a sieve or the like in order to remove cellulose particles having a particle size of 200 μm or more.
«Study of liquid temperature of ionic liquid»
The present inventors have found that the dispersibility varies depending on the liquid temperature of the ionic liquid when mixing the cellulose and the ionic liquid. Then, the liquid temperature of the ionic liquid at the time of mixing was examined. The liquid temperature of the ionic liquid was changed from -40 ° C to 30 ° C to study the dispersibility and solubility of the cellulose particles. In addition, using the cellulose particle of volume average particle diameter 37 micrometers, and using the ionic liquid which changed liquid temperature from -40 ° C to 30 ° C, on the same conditions as the case of examination of the above-mentioned particle diameter, A cellulose dispersion and a cellulose solution were prepared. The results are shown in Table 2.

  The dispersibility and the amount of residue were evaluated in the same manner as in Table 1, respectively, and the amount of residue on the filter after heat treatment and filtration was measured.

  When the temperature of the ionic liquid exceeds 25 ° C., the cellulose particles easily adhere to each other. As a result, undissolved matter remains in the cellulose solution, and the amount of residue in the cellulose solution is increased. When the temperature is 25 ° C. or less, the cellulose particles can be uniformly dispersed without adhering to each other, and as a result, no undissolved matter is generated.

  On the other hand, when the liquid temperature of the ionic liquid is −40 ° C., although the dispersibility is good, the viscosity of the ionic liquid is high, and it takes a long time to uniformly disperse the cellulose particles.

  Therefore, the liquid temperature of the ionic liquid to be mixed with cellulose is preferably in the range of -30 ° C to 25 ° C, and a cellulose dispersion in which the cellulose is uniformly dispersed in a short time can be obtained -20 ° C to 25 ° C Is more preferable. The temperature of the ionic liquid is more preferably −10 ° C. or more and 20 ° C. or less, and a temperature of −10 ° C. or more is preferable because a homogeneous cellulose solution having good spinnability and little energy for cooling the ionic liquid can be obtained. The range of 10 ° C. or less is most preferable.

In addition, since the viscosity of the ionic liquid changes dramatically depending on the temperature, it is preferable that the ionic liquid used be adjusted to a viscosity suitable for dispersion in the range of -30 ° C to 25 ° C. The viscosity of the ionic liquid is preferably as low as possible in consideration of the energy required for cooling and stirring the ionic liquid and the actual dispersibility. However, the liquid temperature is preferably 25 ° C. or less, more preferably 20 ° C. or less, and still more preferably 10 ° C. or less, because the cellulose particles do not adhere to each other.
«Study of ionic liquid viscosity»
Next, the temperature of the ionic liquid was adjusted to prepare ionic liquids having different viscosities, and the dispersibility and dispersion speed of cellulose particles having a volume average particle diameter of 37 μm were examined. The viscosity was measured using a vibrating viscometer (VM-100A manufactured by Seconik Co., Ltd.) while keeping the ionic liquid at a predetermined temperature. The cellulose dispersion is the same as the case of the study of the particle diameter except that cellulose particles having a volume average particle diameter of 37 μm are used and an ionic liquid whose liquid temperature is changed from −40 ° C. to 25 ° C. is used. It manufactured on condition. The results are shown in Table 3.

  The dispersibility was evaluated in the same manner as in Table 1. For dispersion speed, ◎ for time to disperse uniformly less than 2 minutes も の, 2 for 2 minutes or more and less than 3 minutes ○, も の for 3 minutes to less than 4 minutes △, 4 minutes or more Some were indicated by x.

  Here, the result of adjusting the viscosity by changing only the temperature while maintaining the moisture content at 0.0% is shown, but even when the viscosity is adjusted by changing the moisture content, the dispersibility is lowered by the decrease in viscosity. And the dispersion speed is good.

The upper limit of the viscosity of the ionic liquid suitable for dispersion is 10,000 mPa · s or less, preferably 6,000 mPa · s or less at −40 ° C. because it takes a considerable time to disperse because the viscosity is too large. More preferably, it is 1,000 mPa * s or less, More preferably, it is 500 mPa * s or less.
«Study of ionic liquid moisture content»
From the above results, it was clarified that the viscosity of the ionic liquid affects the dispersibility of the cellulose particles, and the dispersibility affects the solubility. By keeping the ionic liquid at a low temperature, a dispersion having good dispersibility can be prepared, while the low temperature ionic liquid has a very high viscosity, so it takes time to uniformly disperse the cellulose particles. Since the viscosity of the ionic liquid is lowered by increasing the water content of the ionic liquid, the ionic liquid water content, the dispersibility of the cellulose particles, the dispersion speed, the solubility, and the spinnability were examined.

  The cellulose dispersion and the cellulose solution are cellulose particles having a volume average particle diameter of 37 μm, and a mixed solvent in which ion exchange water is added to the ionic liquid in a ratio of 0.0 wt% to 8.0 wt%. Were prepared under the same conditions as in the case of the examination of the particle diameter except that the above was used. The results are shown in Table 4.

  The water content indicates the ratio of ion exchanged water contained in the solvent ionic liquid. Spinning was performed by extruding at a flow rate of 0.5 mL / min from a 1-hole nozzle with a hole diameter of 0.1 mm with an air gap distance of 25 mm, a spinning solution temperature of 60 ° C., and a coagulating solution of water. The maximum speed at which yarn breakage did not occur on the roll immediately below the nozzle was recorded as the spinning speed. The dispersibility was evaluated in the same manner as in Table 1 and the dispersion speed in Table 3. The solubility was evaluated by visual observation of the cellulose solution after preparation, and the one having a transparent cellulose solution was regarded as ○, and one having a white turbidity was regarded as Δ. The evaluation of the solubility Δ was also completely dissolved by further heating for a long time, and the cellulose solution became transparent.

  As the water content of the ionic liquid increases, not only the dispersibility of the cellulose particles in the mixed solvent becomes good, but also the dispersion speed becomes faster, and in particular if the water content is 4.0 wt% or more, the dispersion speed is very high. fast. However, when the water content is 7.5 wt% or more, the solubility of cellulose is reduced, the cellulose particles are not completely dissolved, and a transparent homogeneous cellulose solution can not be obtained.

  In addition, as shown in Table 4, with respect to dispersibility, dispersion speed, and solubility, the moisture content is 4.0 wt% or more and 7.0 wt% or less, all good (○), very good (◎), and good (○) As for the spinning speed, it was shown that it is possible to spin at a very high speed with a moisture content of 5.5 wt% or more and 5.7 wt% or less. However, if the spinning speed is about 120 m / min, there is no problem from the viewpoint of industrial productivity, so the moisture content is preferably 2.0 wt% or more and 7.0 wt% or less, more preferably 4.0 wt% It is not less than 6.0 wt%, more preferably not less than 5.3 wt% and not more than 5.7 wt%, and most preferably not less than 5.5 wt% and not more than 5.7 wt%.

  Focusing only on the viscosity of the ionic liquid, there is no problem if the mixed solvent has fluidity in the temperature range of -30 ° C to 25 ° C in order to disperse the cellulose particles uniformly. However, when the viscosity of the ionic liquid is too high, it is necessary to devise treatment conditions such as increasing the dispersion time and increasing the number of revolutions at the time of stirring.

  The viscosity of the ionic liquid is 650 mPa · s at a moisture content of 0.0 wt%, 220 mPa · s at a moisture content of 5.0 wt%, and 180 mPa · s at a moisture content of 8.0 wt% at a liquid temperature of 5 ° C. shown in Table 4. It is. Even when the liquid temperature of the ionic liquid is lowered, by adjusting the water content, it is possible to obtain a uniform cellulose dispersion having high dispersion speed and good dispersibility, and as a result, homogeneity with good spinnability. Cellulose solution can be obtained.

  Similar to the case where water is used as the protic solvent, a homogeneous solution can be obtained by adding another protic solvent such as ethanol to the ionic liquid. In FIG. 3, 3.0 wt% of cellulose particles having a volume average particle diameter of 37 μm was added to the mixed solvent using a mixed solvent in which ethanol was added to 5.0 wt% of the ionic liquid, Show a picture. The ionic liquid was adjusted to 5 ° C. and used. As shown in FIG. 3, even when a protic solvent other than water is used, a cellulose solution having good spinnability can be obtained.

  In order to bring the viscosity of the ionic liquid into a range suitable for dispersion, adjustment of liquid temperature and water content can be performed. Table 5 shows the results of evaluation of the dispersion rate based on the water content of the ionic liquid and the liquid temperature. The cellulose dispersion was prepared under the same conditions as in the study of the viscosity of the ionic liquid except that a mixed solvent in which ion exchange water was added to the ionic liquid to a ratio of 2.0 wt% to 8.0 wt% was used. Made.

  The dispersion speed was evaluated in the same manner as in Table 3. When water is added to the ionic liquid, the viscosity in the low temperature range can be reduced, so that the dispersion speed of the cellulose particles can be shortened. Moreover, the effect becomes remarkable, so that the moisture content of an ionic liquid is large.

  Even when the evaluation of the dispersion speed is not preferable (×, Δ), a cellulose dispersion having good dispersibility can be obtained by stirring over time. A high dispersion speed is advantageous for industrially spinning cellulose fibers.

  From the above results, it can be seen that in order to obtain a cellulose solution having good spinnability, cellulose having a volume average particle diameter of 20 μm or more and 150 μm or less may be used. Furthermore, it is understood that by adjusting the water content and the liquid temperature, the viscosity of the ionic liquid can be adjusted to an appropriate range, and a cellulose solution as a spinning solution with high industrial productivity can be produced.

Claims (15)

A method for producing a cellulose solution used to spin regenerated cellulose fibers, comprising:
Dispersing the cellulose having a volume average particle diameter of 20 μm or more and 150 μm or less in the ionic liquid to prepare a cellulose dispersion;
And C. dissolving the cellulose in the ionic liquid by heating the cellulose dispersion to obtain a cellulose solution. In the method for producing a cellulose solution according to claim 1,
The method for producing a cellulose solution, wherein the ionic liquid is 1-ethyl-3-methylimidazolium acetate. In the method for producing a cellulose solution according to claim 1,
The viscosity of the ionic liquid used in the said dispersion | distribution process is 10,000 mPa * s or less, The manufacturing method of the cellulose solution characterized by the above-mentioned. In the method for producing a cellulose solution according to claim 3,
The viscosity of the ionic liquid used in the said dispersion | distribution process is 6,000 mPa * s or less, The manufacturing method of the cellulose solution characterized by the above-mentioned. In the method for producing a cellulose solution according to claim 3,
The viscosity of the ionic liquid used in the said dispersion | distribution process is 1,000 mPa * s or less, The manufacturing method of the cellulose solution characterized by the above-mentioned. In the method for producing a cellulose solution according to claim 3,
The viscosity of the ionic liquid used in the said dispersion | distribution process is 500 mPa * s or less, The manufacturing method of the cellulose solution characterized by the above-mentioned. In the method for producing a cellulose solution according to claim 1,
The liquid temperature of the ionic liquid used in the said dispersion | distribution process is -30 degreeC or more and 25 degrees C or less, The manufacturing method of the cellulose solution characterized by the above-mentioned. In the method for producing a cellulose solution according to claim 1,
The method for producing a cellulose solution, wherein the ionic liquid used in the dispersion step contains 2.0 wt% or more and 7.0 wt% or less of a protic solvent. In the method for producing a cellulose solution according to claim 8,
The method for producing a cellulose solution, wherein the ionic liquid used in the dispersion step contains 4.0 wt% or more and 6.0 wt% or less of a protic solvent. In the method for producing a cellulose solution according to claim 8,
The method for producing a cellulose solution, wherein the ionic liquid used in the dispersion step contains 5.3 wt% or more and 5.7 wt% or less of a protic solvent. In the method for producing a cellulose solution according to claim 8,
The method for producing a cellulose solution, wherein the protic solvent is water or ethanol. In the method for producing a cellulose solution according to claim 1,
The cellulose is a pulp sheet of cotton linter, and the method for producing a cellulose solution. In the method for producing a cellulose solution according to claim 1,
The method for producing a cellulose solution, wherein the cellulose has an average degree of polymerization of 500 or more and 5,000 or less. A cellulose dispersion used to make a cellulose solution used to spin regenerated cellulose fibers,
A cellulose dispersion liquid, wherein cellulose having a volume average particle diameter of 20 μm to 150 μm is dispersed in an ionic liquid. A method of spinning regenerated cellulose fibers,
A cellulose solution is prepared by dispersing cellulose having a volume average particle diameter of 20 μm to 150 μm in an ionic liquid to prepare a cellulose dispersion, and heating the cellulose dispersion to dissolve the cellulose in the ionic liquid. A spinning method of regenerated cellulose fiber characterized by spinning using.